34th Annual Symposium of the Hellenic Nuclear Physics Society, HNPS2026
Library Amphitheatre
Lamia, University of Thessaly, Physics Department
HNPS2026 is the 34th of the Hellenic Nuclear Physics Society (HNPS) series of Symposia that take place since 1990. This year, the Symposium is organized by the Department of Physics of the University of Thessaly and will be held in person on June 5 – 6, 2026, at the Library and Information Centre of the University of Thessaly in Lamia, Greece.
The HNPS Symposium aims to bring together leading academic scientists, researchers and research scholars to exchange and share their experiences and research results on various aspects of Theoretical and Experimental Nuclear Physics. The scientific program is expected to include the most recent advances in the field, covering the following topics:
- Nuclear Structure
- Nuclear Reactions
- Nuclear Astrophysics
- Nuclear Physics Applications
- Accelerator Physics & Instrumentation
Registration and abstract submission will be handled online at the Symposium website. Official language for all HNPS2026 presentations (oral and poster) is English.
A limited number of accommodation grants are available for MSc and PhD students. Accommodation will be arranged by the organizers in reserved double rooms at designated hotels for two nights (June 4–6, 2026). Applicants must present a contribution at the symposium. Applications (including a CV and one letter of recommendation) and requests for further information should be sent to: vprassa@uth.gr
A number of hotels are available in Lamia. Special accommodation rates have been negotiated with selected hotels for symposium participants. Attendees are kindly requested to contact the hotels directly (by phone or email) and mention the Symposium Name in order to benefit from the discounted rates. For further details, please see the Accommodation section.
Please note that HNPS2026 is primarily planned as an in-person event in Lamia. A dedicated session of online talks (remote presentations) will be included in the scientific program and will be available exclusively to HNPS members affiliated with institutions abroad who are unable to attend in person. Eligible participants will be able to indicate their preference for online presentation during the abstract submission process.
The proceedings of HNPS2026 will be published as open-access articles after peer-review in the HNPS Advances in Nuclear Physics conference journal, supported by the National Documentation Centre (EKT) ePublishing Service, offering DOI and Scopus indexing.
Continuing the tradition of the Hellenic Nuclear Physics Society Symposia as a forum for collaboration and for showcasing the work of young researchers, the Organizing Committee invites you to participate in HNPS2026 and looks forward to welcoming you to the University of Thessaly in Lamia in June 2026.
Local Organizing Committee:
- V. Prassa (chair)
- A. Ioannidou
- K. Bachas
- D. Vavougios
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Registration
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Welcome adresses
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Honorary Nomination
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Invited LectureConvener: V. Prassa
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Microscopic Studies of Fission Dynamics 30m
The process of spontaneous or induced fission presents an example of large-amplitude collective motion in self-bound mesoscopic systems, exhibiting an interplay between classical and quantum effects. A wealth of experimental results has been accumulated, and a basic understanding of fission mechanism gained. In recent years, major progress has been achieved in the development of time-dependent microscopic approaches that offer a more comprehensive and predictive description of the fission process. These advances encompass the calculation of fission fragment yields [1], the characterization of energy dissipation mechanisms and total kinetic energy distributions [2,3], the study of neck formation and rupture dynamics [4], the treatment of quantum fluctuations and symmetry restoration [5], the microscopic origin of fragment angular momentum, and the analysis of quantum entanglement between the emerging fragments [6].
References
[1] Z. X. Ren, J. Zhao, D. Vretenar, T. Nikšić, P. W. Zhao, and J. Meng, Phys. Rev. C 105, 044313 (2022).
[2] J. Zhao, T. Nikšić, and D. Vretenar, Phys. Rev. 105, 054604 (2022), Phys. Rev. C 106, 054609 (2022).
[3] B. Li et al., Phys. Rev. C 107, 014303 (2023).
[4] Z. X. Ren et al., Phys. Rev. Lett. 128, 172501 (2022).
[5] B. Li et al., Phys. Rev. C 108, 014321 (2023), Phys. Rev. C 111, L051302 (2025).
[6] B. Li et al., Rev. C 110, 034302 (2024).Speaker: Prof. Dario Vretenar (University of Zagreb)
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Nuclear Structure: Models and MethodsConvener: D. Vretenar
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The B4/2 anomaly: Observation and theoretical interpretation 15m
emphasized textThe term $B_{4/2}$ anomaly is used in relation to even-even nuclei in which the ratio of the B(E2) transition rates $B_{4/2} = B(E2; 4_1^+\to 2_1^+)/ B(E2; 2_1^+\to 0_1^+)$ is less than unity, a value contrary to the predictions of all collective models. A few experimental examples have been found over the last years, the best known ones being $^{166}$W [1], $^{168,170}$Os [2,3], $^{172}$Pt [4]. From the phenomenological point of view, it has been shown that the effect can be accommodated within the Interacting Boson Model-1 (IBM-1), in which no distinction between valence protons and neutrons is made, through the inclusion of 3-body and 4-body interactions [5,6]. Alternatively, it can be interpreted [7] within the SU(3)* dynamical symmetry of IBM-2, in nuclei in which the valence protons correspond to holes and the valence neutrons to particles, or vice versa. Ongoing efforts [8] for the first microscopic interpretation of the effect, within covariant density functional theory employing the DDME2 energy density functional, will be reported.
[1] B. Saygi et al., Phys. Rev. C 96, 021301(R) (2017).
[2] T. Grahn et al., Phys. Rev. C 94, 044327 (2016).
[3] A. Goasduff et al., Phys. Rev. C 100, 034302 (2019).
[4] B. Cederwall et al., Phys. Rev. Lett. 121, 022502 (2018).
[5] Y.-X. Cheng, D.-H. Zhao, Y.-Y. Shao, L. Gong, T. Wang and X.-S. Kang,
Chin. Phys. C 49, 104105 (2025).[6] Y. Zhang and W. Teng, Phys. Rev. C 111, 014324 (2025).
[7] W. Teng, Y. Zhang, S.-N. Wang, F. Pan, C. Qi, and J. P. Draayer,
Phys. Lett. B 865, 139487 (2025).[8] D. Bonatsos, K. E. Karakatsanis, and P. Vasileiou, in preparation.
*Speaker: Dennis Bonatsos (Institute of Nuclear and Particle Physics, NCSR Demokritos, Athens, Greece) -
10:30
Evidence of triaxiality in Mo and Ru nuclei 15m
In the present work [1] we investigate the presence of triaxial deformation in Mo and Ru isotopes. We present experimental indicators of triaxiality and address the distinction between the two extremes of $\gamma$-soft [2] and $\gamma$-rigid [3] triaxial behavior. Quantitative results for the nuclei under study are obtained by means of the Algebraic Collective Model [4], as well as Hartree-Fock-Bogoliubov calculations with six representative parametrizations of the effective Skyrme interaction [5].
References
[1] Accepted for publication in Phys. Rev. C
[2] L. Wilets and M. Jean, Phys. Rev. 102, 788 (1956).
[3] A. S. Davydov and G. F. Filippov, Nucl. Phys. 8, 237 (1958).
[4] D. J. Rowe, T. A. Welsh, and M. A. Caprio, Phys. Rev. C 79, 054304 (2009).
[5] M. Bender, P.-H. Heenen, and P.-G. Reinhard, Rev. Mod. Phys. 75, 121 (2003).Speaker: Dimitrios Petrellis (Aristotle University of Thessaloniki) -
10:45
High-K isomers in the N \approx 116 shape-transition region and in oblate nuclei within the Relativistic Hartree-Bogoliubov theory 15m
K-isomers are metastable nuclear excitations of predominant single-particle character, arising in well-deformed nuclei where the projection of the total angular momentum onto the symmetry axis, K, is an approximately good quantum number. When quasiparticles align their angular momentum projections along the symmetry axis, the resulting multi-quasiparticle configuration acquires a large K value, and decay to lower-lying states is strongly suppressed by the K-selection rule, leading to half-lives orders of magnitude longer than those of non-isomeric states at comparable excitation energies [1,2]. This makes K-isomers sensitive fingerprints of the single-particle structure near the Fermi surface [3], with additional interest in applied contexts ranging from nuclear medicine to proposals for high-density nuclear energy storage [4,5].
Within the Relativistic Hartree-Bogoliubov (RHB) framework, K-isomers are described as blocked multi-quasiparticle excitations within the Equal Filling Approximation, with full self-consistent readjustment of the mean field and pairing under blocking [6,7,8,9]. We present RHB calculations of high-K states in two regimes poorly explored at the covariant mean-field level: the N ≈ 116 shape-transition region (W–Os isotopic chains), where rapid structural evolution from prolate toward γ-soft shapes produces a rich and theoretically demanding landscape of competing configurations [10,11]; and oblate nuclei, where the reversed Nilsson level ordering leads to qualitatively different high-K structures compared to the well-studied prolate case. Excitation energies and configurations are compared with available data, and candidates for unobserved isomers are proposed.
References
[1] P. Walker and G. Dracoulis, Nature 399, 35 (1999)
[2] G. Dracoulis, P. Walker and F. Kondev, Rep. Prog. Phys. 79, 076301 (2016)
[3] A.K. Jain, B. Maheshwari and A. Goel, Nuclear Isomers: A Primer (Springer, 2021)
[4] C.J. Chiara and J.P. Carroll, Nature 556, 323 (2018)
[5] D. Belic et al., Phys. Rev. Lett. 83, 5242 (1999)
[6] S. Perez-Martin and L.M. Robledo, Phys. Rev. C 78, 014304 (2008)
[7] J. Xiang et al., Phys. Rev. C 102, 034311 (2020)
[8] K.E. Karakatsanis, G.A. Lalazissis, V. Prassa and P. Ring, Phys. Rev. C 102, 034311 (2020)
[9] V. Prassa, T. Nikšić, G.A. Lalazissis and D. Vretenar, Phys. Rev. C 86, 024317 (2012)
[10] Z.P. Li, T. Nikšić et al., Phys. Rev. C 84, 054304 (2011)
[11] H.L. Liu, F.R. Xu, P.M. Walker and C.A. Bertulani, Phys. Rev. C 83, 011303(R) (2011)Speaker: Konstantinos Karakatsanis (Institute of Nuclear and Particle Physics, NCSR Demokritos, Athens, Greece) -
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Exploring Triaxial Features in Quadrupole Collective Bands of Even-Even Yb Isotopes 15m
Following a number of successful applications to the neighboring rare-earth isotopic chains, this work employs an IBM-1 Hamiltonian derived from self-consistent mean-field calculations, incorporating intrinsic triaxial deformation obtained from fermionic proxy-SU(3) irreducible representations (irreps), to investigate energy spectra and B(E2) transition strengths in the low-lying quadrupole bands of even-even $^{162-182}$Yb isotopes. For the first time, proxy-SU(3) next-highest-weight irreps are included in the calculations, resulting in substantially better agreement with available experimental data compared both to axially symmetric calculations and to triaxial calculations that include only highest-weight irreps.
Speaker: Polytimos Vasileiou (Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH)) -
11:15
Ground-state properties of finite nuclei with astrophysical interest in extreme magnetic fields, via covariant density functional theory 15m
Magnetars and the environments of core-collapse supernovae host some of the most extreme magnetic fields in the universe, reaching intensities of $10^{18}$ G. Under these conditions, the fundamental quantum structure of matter is severely altered. In this work, we investigate the ground-state properties of finite nuclei of astrophysical interest, specifically focusing on waiting-point nuclei in r- and rp-process nucleosynthesis. We employ Covariant Density Functional Theory (CDFT) to calculate bulk properties including the total binding energy, the radius, and the deformation ($\beta_2$). To rigorously assess theoretical uncertainties and model dependency, the self-consistent calculations are performed using two distinct effective interactions: the density-dependent DD-ME2 and the non-linear NL3* parameter sets within a constrained relativistic mean-field framework. Our calculations reveal that the breaking of time-reversal symmetry and the destruction of Kramer's degeneracy induce profound structural phase transitions. As the magnetic field strength increases, we observe a spontaneous rearrangement of single-particle energy levels, with critical crossings at the Fermi surface emerging at $B \approx 10^{17}-10^{18}$ G. This microscopic rearrangement forces a macroscopic phase transition, driving transitional nuclei from spherical configurations into oblate or prolate ground states. Concurrently, we observe a substantial increase in the total binding energy of the nuclei, primarily driven by the strong spin-alignment of protons and Landau orbital coupling. Both parameter sets consistently confirm these magnetically induced changes in the bulk properties of the nuclei. These structural modifications are expected to fundamentally alter the dynamics of stellar weak interaction rates governing nucleosynthesis, highlighting the necessity of robust microscopic modeling in astrophysical simulations.
Speaker: Ioannis Mavroudis (Department of Physics, Aristotle University of Thessaloniki) -
11:30
Physics-Informed Neural Networks for Solving the Three-Dimensional Schrödinger Equation in Woods–Saxon Nuclear Potential 15m
Physics-Informed Neural Networks (PINNs) provide a flexible framework for solving differential equations by embedding the governing physical laws directly into the training process. In this work, we investigate the use of PINNs for the solution of the three-dimensional time-independent Schrödinger equation in spherical coordinates, focusing on nuclear single-particle states described by Woods–Saxon type potentials.
The proposed approach is based on a separable representation of the wavefunction in radial and angular components. The nuclear mean-field potential includes the central Woods–Saxon term, the spin–orbit interaction, and the isospin-dependent Lane contribution. This allows the method to describe neutron and proton single-particle states in representative doubly-magic nuclei, including 16O, 40Ca, 48Ca, and 56Ni.
The PINN is trained by minimizing a composite physics-informed loss function that combines the Schrödinger equation residual, boundary conditions, normalization constraints, energy minimization, and orthogonality conditions for excited states. The computed energy spectra and probability densities are compared against an independently developed finite-difference solver and reference single-particle spectra from the literature.
The results show that the PINN framework accurately reproduces bound-state energy levels, preserves the correct level ordering, and captures characteristic nuclear-structure features such as spin–orbit splittings. The learned radial probability densities exhibit physically consistent localization inside the nuclear region and exponential decay at large distances. Although the PINN approach is computationally more demanding than the finite-difference baseline, it offers a continuous, differentiable, and physics-consistent representation of the nuclear wavefunction.
Overall, this work demonstrates that Physics-Informed Neural Networks can provide a promising alternative numerical framework for nuclear Schrödinger eigenvalue problems and may serve as a basis for future extensions toward inverse problems, parameter estimation, and more complex nuclear mean-field models.
Speaker: Mr Iraklis Spyrou (NCSR DEMOKRITOS)
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Coffee break 30m
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Nuclear Reactions and Experimental MethodsConvener: Th. Mertzimekis
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Neutron spectrum deconvolution by Bayesian methods 15m
The accurate and robust reconstruction of neutron spectra is essential for various nuclear applications, ranging from reactor environments to other neutron fields [1,2]. Unlike gamma-ray spectroscopy, the deconvolution of a neutron spectrum relies on solving a complex inverse problem, which is generally addressed by using various unfolding algorithms [3,4,5]. Such algorithms often require some prior (or reference) spectrum as input, usually determined by simulation. In recent years, Bayesian approaches have been proposed as alternative methods in order to solve the deconvolution problem [6,7], while recent studies have implemented some of these approaches and have shown promising results even without the use of a reference spectrum [8]. Thus, the main objective of this work is to explore and apply Bayesian methodologies [6,8] in the unfolding procedure within the context of activation foil measurements. The performance and the limits of these methods in the field of reactor applications and most importantly, their ability to evaluate the reconstructed spectrum without a prior reference spectrum will be evaluated. A comparative evaluation of their performance against classical methods [5, 9] will also be carried out.
[1] Vladimir Radulović et al., Nature Scientific Reports 14, 28604 (2024)
[2] E. Belfiore et al., Nuc. Sci. And Eng. (accepted, 2026)
[3] K. Mikszuta-Michalik et al., Fusion Engineering and Design 173, 112934 (2021)
[4] S.P. Tripathy et al., Nuc. Inst. Meth. Sec A. 583, 421 (2007)
[5] G. Grégoire et al., EPJ Web of Conf. 106, 07006 (2016)
[6] G. D’Agostini, arXiv:1010.0632v1 [physics.data-an] (2010)
[7] G. Chouladakis, arXiv:1201.4612v4 (2012)
[8] A. Pérez de Rada Fiol et al., Radiation Physics and Chemistry 226, 112243 (2025)
[9] M. Reginatto et al., Nuc. Inst. Meth. Sec. A. 476, 242 (2002)Speaker: Achment Chalil (CEA) -
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Advancing Beam Diagnostics on ESS Neutron Beamlines: Simulation and Validation of Ionization Chamber Monitors 15m
The European Spallation Source (ESS), expected to start its scientific program in 2027, will be the world's most powerful neutron source. This facility demands advanced systems for accurate beam monitoring and diagnostics. To meet these requirements, dedicated Ionization chamber Beam Monitors (I-BMs) have been developed, specifically designed to operate at ESS. This work will present both detailed simulation studies and experimental data obtained from test beam campaigns to evaluate the performance of the I-BMs.
The simulation framework presented includes modeling the complete signal formation process, from initial neutron-converter interactions to the final electronics output. Neutron transport and interactions are simulated in Geant4, with resulting energy deposition used as input to Garfield++ to calculate the induced current. The I-BM’s front-end electronics are emulated in LTspice to produce the final output signal. This framework provides a detailed description of the detector response and enables a systematic study of signal formation and detector performance. Experimental data acquired during test runs at the ISIS Neutron and Muon Source facility using I-BMs will also be presented.
Speaker: E. Samouilidis (Aristotle University of Thessaloniki) -
12:45
Differential cross-section measurements and R-matrix calculations for the elastic scattering of low energy protons on 19F, suitable for IBA purposes 15m
Fluorine, one of the lightest elements in nature, is a chemically reactive element that is used in many technological and industrial applications. Natural fluorine is monoisotopic, with one stable isotope, 19F. It can be found in a wide variety of materials such as batteries, metals, polymers, ceramics, geological and biological samples. These characteristics render fluorine especially important for detection and depth profile determination via Ion Beam Analysis (IBA) techniques.
The most appropriate of such techniques, in analyzing the majority of light elements, is the proton-Elastic Backscattering Spectroscopy (p-EBS), since protons can reach greater depths than other ion beams for the same energy/nucleon values. In order to achieve greater sensitivity to the near-surface layers of a sample, the p-EBS technique is implemented at Ep,lab=100 keV-300 keV (Medium Energy Ion Scattering – MEIS), due to the increase of the corresponding stopping power values. Adding to this, the fact that the differential cross section of the proton elastic scattering on 19F presents resonances even below 1 MeV, further increases the detection limits of the isotope and offers higher accuracy of the corresponding concentration depth profile. Consequently, in order to apply the p-EBS technique, in the medium energy range, reliable differential cross sections are needed. The experimental cross-section data are also of significant importance for the extension of the theoretically evaluated datasets well below 0.5 MeV.
The experiment took place at the 4 MV Dynamitron Tandem Laboratory of the Central Unit for Ion and Radionuclides (RUBION) of the Ruhr University Bochum in Germany. A 500 kV single-stage accelerator and a 4 MV Dynamitron Tandem accelerator were used for the measurements, which provided protons of Ep,lab=100 keV-340 keV and Ep,lab=300 keV-1000 keV, respectively. The 19F(p,p0)19F elastic scattering was studied at five backscattering detection angles. The obtained cross-section data were followed by R-matrix calculations [1], for the reproduction of the experimental values. The final results are compared to the existing datasets from the literature as well as the current evaluation [2].[1] R. E. Azuma et al., “AZURE: An 𝑅-matrix code for nuclear astrophysics,” Phys. Rev. C, vol. 81, no. 4, p. 045805, Apr. 2010, doi: 10.1103/PhysRevC.81.045805.
[2] A. F. Gurbich, “SigmaCalc recent development and present status of the evaluated cross-sections for IBA,” Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms, vol. 371, pp. 27–32, Mar. 2016, doi: 10.1016/j.nimb.2015.09.035.Speaker: Evangelia Taimpiri (NCSR "Demokritos", NTUA) -
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Differential cross-section measurements for 3He-induced reactions and elastic scattering on 16O 15m
Ion Beam Analysis (IBA) is a group of least-destructive techniques employing MeV ion beams to determine the composition and depth profile of materials. Particularly $^3$He beams come up with certain advantages. The most crucial ones are that the Q-values of $^3$He-induced reactions on most light isotopes are very high and that no special radiation safety precautions are required. In addition, $^3$He is the most suitable beam for the analysis of deuterium inside materials, rendering $^3$He-IBA essential in fusion energy research. Nevertheless, the application of $^3$He-IBA is hindered by the lack of suitable differential cross sections, which in the case of $^{16}$O are almost nonexistent.
In the present work, the differential cross sections of the $^{16}$O($^3$He, p$_0$)$^{18}$F, $^{16}$O($^3$He, p$_1$)$^{18}$F and $^{16}$O($^3$He, $\alpha_0$)$^{15}$O nuclear reactions, along with the $^{nat}O(^3$He, $^3$He$_0$) elastic scattering, were determined for the first time at five detection angles ranging from $130^{\circ}$ to $170^{\circ}$ over a beam energy range of 2.2 to 5 MeV. The obtained differential cross-section data were validated through a benchmarking experiment. All measurements took place at the 4 MV Dynamitron Tandem Laboratory of the Central Unit for Ion Beams and Radionuclides of the Ruhr University Bochum in Germany.
Speaker: Vasileios Stefanidis Toulkeridis (University of Ioannina) -
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Measurement of the 18O(d,α0-3)16N reaction cross sections for NRA purposes 15m
The $^{18}$O(d,α$_{0-3}$)$^{16}$N reactions were studied by measuring the differential cross sections over the deuteron beam energy range E$_{d,lab}$=1470–2160 keV, at backward detection angles of 120° to 170° with a 10° step. The target used was a thin Ta$_{2}$O$_{5}$ layer (areal density 326×10$^{15}$ at/cm$^{2}$), highly enriched in $^{18}$O, produced by controlled progressive anodization of tantalum foil. Layer’s total areal density, $^{18}$O enrichment, and carbon content were determined in situ through a combination of Nuclear Reaction Analysis (NRA) and Rutherford Backscattering Spectrometry (RBS), and were independently cross-checked. The measured differential cross sections range from 0.07 to 2.28 mb/sr, in close agreement with the only dataset available in the literature (Amsel, 1964 [1]) which spans from 824 to 2007 keV and refers to only one angle (165°). Differential cross sections for energies above E$_{d,lab}$ = 2007 keV and the full angular range 120°–170° are reported for the first time in this work. These new data are of direct relevance to ion beam analysis techniques and to applications in materials science, stable isotope tracing, and biological research.
[1] G.Amsel(1964), Jour. Annales de Physique (Paris), Vol.9, p.297
Speaker: Stavros Karachristos (National Technical University of Athens / Tandem Accelerator Laboratory, Institute of Nuclear and Particle Physics, N.C.S.R. “Demokritos”) -
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Development of a Gas Ionisation Detector for the ToF-ERDA setup at NCSR “Demokritos” 15m
One of the primary Ion Beam Analysis (IBA) techniques employed for the determination of sample composition and depth profile analysis is Time of Flight – Elastic Recoil Detection Analysis (ToF – ERDA). The silicon-based detectors (SSB) are used to conventionally record the energy of the recoiled particles that are analyzed following the implementation of the specific technique. The quality of the measurement can be considerably impacted by the SSB detector's low depth and mass resolution capabilities [1][2]. In the specific technique, the detection of heavy particles requires high energy, depth, and mass resolution, as well as the ability to withstand radiation damage. Consequently, it is essential to replace the silicon energy detector with a Gas Ionisation Detector (GID) in the ToF – ERDA spectrometer at N.C.S.R. "Demokritos."
The new GID is a custom-built in-house assembly. The technical attributes of the detector are in accordance with the requirements of the ToF-ERDA technique. The anode and cathode electrodes are two parallel copper plates, separated by a Frisch grid to shield the anode from the active volume of the detector. The electromagnetic field between the various components was estimated through the completion of related simulations. The properties and quality of the detector's performance were determined using dedicated measurements with a variety of configurations and settings. The outcome of employing various gas types under varying pressure conditions was also evaluated. The associated findings of the initial evaluation exams will be presented and discussed.[1] Z. Siketić, N. Skukan, and I. Bogdanović Radović, “A gas ionisation detector in the axial (Bragg) geometry used for the time-of-flight elastic recoil detection analysis,” Rev. Sci. Instrum., vol. 86, no. 8, Aug. 2015, doi: 10.1063/1.4927605/357185.
[2] J. Julin, M. Laitinen, and T. Sajavaara, “Time-of-flight ERD with a 200 mm2 Si3N4 window gas ionization chamber energy detector,” Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms, vol. 332, pp. 271–274, Aug. 2014, doi: 10.1016/J.NIMB.2014.02.076.Speaker: Anastasia Ziagkova -
13:45
177, 178Yb ground-state lifetimes 15m
The study of half-lives in the region of isotopes around A=180 is of particular importance, as nuclei in this mass region provide opportunities for investigating both fundamental and applied properties of nuclear matter. The isotopes examined in the present work are the unstable isotopes of ytterbium with A=177 and A=178, which undergo β-decay to the corresponding lutetium isobars (177,178Lu). The currently adopted half-life values of 177,178Yb originate from outdated studies, making their re-measurement using modern techniques and experimental setups necessary. Along these lines two experiments were carried out with the activation method. The first experiment was carried out at IFIN–HH, where the ROSPHERE experimental setup was employed. A proton-transfer reaction 176Yb(9Be,8 Be)177Yb was used to study the decay of 177Yb. The second experiment was conducted at IKP Köln, where the CATHEDRAL spectrometer was used to record the de-excitation γ-rays from a 2n-transfer reaction, 176Yb(18O,16O)178Yb. The results of the analysis from both experiments provide updated half-life values for the ground states of 177Yb and 178Yb and are in good agreement with the values reported in the existing literature.
- This work is supported by EURO-LABS (EU Horizon Europe Project No. 101057511) and the German Research Foundation under the grant 539757749.
† Present address: Horia Hulubei NIPNE, Strada Reactorului 30, POB MG6, RO-077125 Bucharest-Magurele, Romania.
Speaker: Margarita Efstathiou (National and Kapodistrian University of Athens)
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Conference Photo and Lunch Break 45m
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Poster session
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Application of Gaussian Process Regression for Total Kinetic Energy in Neutron-Induced Fission 1m
This study investigates the prediction of Total Kinetic Energy in neutron-induced fission using Gaussian Process Regression, a non-parametric method for probabilistic regression. Due to the computational cost of theoretical calculations and the limited availability of experimental data, it is of interest to investigate machine learning methods. Training data are obtained from the General Description of Fission Observables simulation. The GPR model is trained on selected isotopes and incident energies and evaluated on unseen cases. The results show that the model captures the overall behavior of TKE within the range of the training features.
Speaker: Martha Papadopoulou -
14:56
Predicting Fragment Kinetic Energy Distributions in Nuclear Fission using a Bayesian Mixture Density Network 1m
In this work, a modern computational method was developed with the goal to predict the total kinetic energy of neutron-induced fission fragments across a wide range of nuclei. This data-driven approach was trained on a large-scale, simulated dataset generated by the semi-empirical GEF code, which provides a comprehensive baseline of fission observables. The methodology was employed with a Bayesian neural network (BNN) architecture, augmented with a mixture-density output layer, in order to showcase accordingly the probabilistic, multimodal nature of fission, while also allowing the network to separate and quantify the aleatoric uncertainty inherent in the stochastic fission process from the epistemic uncertainty associated with the model's parameters and the training data. By enabling principled uncertainty quantifications, the model aims in increasing the conclusion capabilities in nuclear data products, clarifying the credibility of predictions derived from model-generated data and providing a flexible tool for future theoretical, experimental and applied investigations into fission phenomena.
Speaker: Christos Bompotas (Aristotle University of Thessaloniki) -
14:57
Evaluating Neutron-Induced Fission Yields using Gaussian Process Regression 1m
Accurate knowledge of fission product yields (FPY) is fundamental for nuclear reactor physics, waste management, and the understanding of nuclear structure. However, experimental data for neutron-induced fission are often sparse, especially across wide incident energy ranges. This work explores the application of Machine Learning techniques, specifically Gaussian Process Regression (GPR), to evaluate independent fission charge yields and investigate their energy dependence.
The methodology focuses on two distinct approaches. First, the GPR model is trained on evaluated data from the JENDL-5 library to establish a robust baseline for predicting charge distributions in regions where experimental measurements are missing. Second, comprehensive simulations are performed using the GEF (General-purpose Fission-model) code to generate synthetic datasets for a wide range of isotopes, from Thorium to Fermium. These simulations provide a theoretical framework for comparative analysis and allow the GPR model to learn complex physical patterns, such as odd-even staggering and the filling of the symmetry valley at higher energies.
Different covariance functions (kernels), including Radial Basis Function (RBF), Matern, and Rational Quadratic, are benchmarked using Automatic Relevance Determination (ARD) to identify the most influential physical features, such as the atomic number ($Z$) and the incident neutron energy ($E_n$). Special attention is given to the impact of noise modeling through the integration of White Noise kernels to account for aleatoric uncertainties in the data.
The results demonstrate that the GPR framework effectively reproduces the charge yield distributions and generalizes well to unseen systems, such as $^{235}$U. Furthermore, the sensitivity analysis reveals the importance of balancing local structural details with global energy trends. This study aims to provide an automated, uncertainty-aware computational tool for nuclear data evaluation, contributing to the development of more reliable fission models for both fundamental research and industrial applications.
Speaker: Konstantinos Stergiou (Department of Physics, Aristotle University of Thessaloniki) -
14:58
Reconstructing Compact Objects Equation of State (EoS) via Machine and Deep Learning 1m
A fundamental challenge in nuclear physics is the determination of the equation of state (EoS) of dense nuclear matter, which directly impacts our understanding of the structure and composition of compact astrophysical objects, such as neutron and quark stars. Traditionally, this problem has been approached through theoretical modeling, based on nuclear and particle physics, followed by validation against experimental data from heavy-ion collisions and, increasingly, astrophysical observations. In recent years, hybrid methodologies, combining theoretical predictions with observational information, have emerged, incorporating advanced statistical techniques, such as Bayesian inference alongside machine learning and deep learning frameworks. These approaches provide powerful tools for the interpretation and constraining of the EoS. In this work, we employ machine and deep learning regression techniques to infer the underlying equation of state from mass–radius relations of compact objects. The analysis is based on an extensive dataset of physically consistent equations of state, constructed using multimodal descriptions for neutron stars, as well as corresponding models for quark stars. By leveraging these data, the proposed framework enables the reconstruction of the EoS directly from observable properties, offering a complementary pathway to traditional approaches.
Speaker: Ioannis Stergakis (School of Physics, Aristotle University of Thessaloniki) -
14:59
Machine Learning and Neural Network Approaches for the Classification of Compact Stars 1m
Compact stars provide a unique probe of matter under extreme density conditions, yet their
internal composition remains uncertain. In particular, hadronic neutron stars and quark stars
may exhibit overlapping mass–radius relations, making their distinction challenging through
conventional observables alone. In this work, we apply machine learning and neural-network
methods to classify these two compact-star families using stellar mass, radius, tidal deformability, Love number, and central pressure. A dataset of 39,920 stellar configurations was generated
from 3,992 equations of state, including 2,048 hadronic models and 1,944 quark-matter models
based on the MIT bag and Color–Flavor-Locked frameworks. Several supervised classifiers,
namely Random Forest, XGBoost, Decision Tree, and Support Vector Machine, were evaluated together with a feedforward neural network. In the noise-free case, the models achieved
near-perfect classification performance, with XGBoost, SVM, and the neural network reaching
accuracy, F1-score, and AUC values close to unity. Feature-selection and ablation analyses
showed that the Love number is particularly important, highlighting the role of tidal-response
quantities in distinguishing between the two classes. To assess robustness under realistic observational conditions, synthetic datasets were generated by adding Gaussian uncertainties to mass
and radius, while tidal deformability was reconstructed through a compactness–deformability
relation with intrinsic scatter. Although observational uncertainties reduced the performance
of some models, XGBoost and the neural network remained highly robust. Overall, this study
demonstrates that machine learning can effectively support the classification of compact stars
and emphasizes the importance of precise tidal-response measurements for constraining the
dense-matter equation of state.Speaker: Despoina Neraki (Aristotle University of Thessaloniki) -
15:00
On the Nature of the Central Compact Object in HESS J1731-347 within Hadronic and Kaon-Condensed Frameworks 1m
One of the most important subjects in nuclear physics is the study of the nature of astrophysical compact objects. A quite intriguing scenario when examining the composition of nuclear stellar matter in compact star cores is the presence of exotic constituents such as kaon condensates. In the present conference contribution, we focus our attention on the central compact object (CCO) in the HESS J1731-347 supernova remnant. The CCO’s mass and radius have been estimated equal to M = $0.77 ^{+0.20} _{-0.17}$ $M_{\odot}$ and R = $10.4^{+0.86} _{-0.78}$ km (at the 1$\sigma$ level), while its redshifted surface temperature has been calculated equal to $153 ^{+4} _{-2}$ keV at an age of 2-6 kyrs. We attempt to explain not only its mass and radius but also its redshifted surface temperature for the previous time frame via considering two different stellar configurations. The first one dictates a fully hadronic neutron star, while the second one predicts the presence of kaon condensate in the star’s core.
Speaker: Dimitrios Nanopoulos (Aristotle University of Thessaloniki) -
15:01
Simulation studies of a MPGD-based Neutron Beam Monitoring system for ESS 1m
In modern neutron facilities such as the European Spallation Source (ESS), accurate beam monitoring is critical for ensuring robust diagnostics and data reliability. In this work, a Geant4-based simulation has been developed to support the design and optimization of ESS beam monitors, focusing on MPGDs with a B₄C conversion layer.
The detector’s response was evaluated by modeling energy deposition from neutron products in the drift gap for multiple gas mixtures and geometries. A systematic study of the B₄C layer thickness was performed to evaluate neutron interaction efficiency under monoenergetic and uniform neutron spectra. Additionally spatial resolution was investigated using a simplified strip readout model, giving insight into how various detector parameters affect spatial resolution. Finally, dosimetry studies were performed with a simplified electronics geometry to estimate radiation-induced energy deposition.
Speaker: Alexandros Gardikiotis (Aristotle University of Thessaloniki) -
15:02
Investigation of α-Cluster Transfer in Peripheral Collisions of $^{40}$Ca at 12.3 MeV/nucleon 1m
The investigation of α-clustering is pivotal for elucidating nuclear structure and reaction dynamics within light and medium-mass systems. In this study, we present a preliminary analysis of experimental data derived from the reaction of a $^{40}$Ca beam (12.3 MeV/nucleon) on $^{27}$Al and $^{124}$Sn targets, conducted at the Cyclotron Institute of Texas A&M University using the MARS recoil separator. Our primary objective is the identification of projectile-like fragments (PLFs) resulting from α-cluster transfer mechanisms.
Event-by-event particle identification encompassing atomic number (Z), ionic charge (q), and mass number (A), was achieved utilizing a two-element silicon detector telescope (ΔE, Er) at the MARS focal plane. This was facilitated by applying calibrated correlations of energy loss, residual energy, and magnetic rigidity. For the $^{40}$Ca + $^{27}$Al reaction, we focus on the extracted isotopic yields, momentum (p/A) distributions, and excitation energy spectra. These experimental observables are compared with theoretical calculations from the Deep Inelastic Transfer (DIT) model to evaluate the prevalence of direct transfer processes and the impact of the $^{40}$Ca cluster substructure.
Furthermore, we present a preliminary analysis of the $^{40}$Ca + $^{124}$Sn reaction, where the utilization of a heavier target enables a systematic examination of the effects of target mass and neutron-to-proton (N/Z) ratios on clustering dynamics. Collectively, this research provides significant insights into multinucleon dynamics during the transition from the Coulomb barrier to the Fermi energy regime.Speaker: Chrysi Giannitsa (National and Kapodistrian University of Athens) -
15:03
Multinucleon Transfer and Incomplete Fusion at 15 MeV/nucleon for the 86Kr + 27Al System 1m
We present an investigation of the mass-asymmetric collision of a ⁸⁶Kr beam with a ²⁷Al target at an incident energy of 15 MeV/nucleon. The primary goal is to characterize the mass, angular, and momentum distributions of projectile-like fragments emerging from this reaction. The experimental data utilized here were acquired with the MARS spectrometer at the Texas A&M University Cyclotron Institute during earlier work by our group [1]. These data are compared with theoretical predictions from two approaches: the phenomenological Deep-Inelastic Transfer (DIT) model, that describes the reaction dynamics, [2] and the microscopic Constrained Molecular Dynamics (CoMD) model [3]. In both cases, the statistical decay code GEMINI [4] is employed to describe the de-excitation of primary fragments. A comparison between the measured observables and the model outcomes offers meaningful insight into the contributing reaction mechanisms. The DIT model successfully captures the multinucleon transfer (MNT) processes. The CoMD model, while also reproducing the MNT features, additionally accounts for an incomplete fusion component in this light target. It is worth noting that the MNT mechanism is responsible for generating neutron-rich nuclides in this mass region [5–9]. We anticipate that the study of this mass-asymmetric system will enhance our understanding of heavy-ion reaction mechanisms below the Fermi energy regime (15–35 MeV/nucleon).
References
[1] G.A. Souliotis et al., Phys. Rev. C 84, 064607 (2011)
[2] L. Tassan-Got et al., Nucl. Phys. A 524, 121 (1991)
[3] M. Papa et al., Phys. Rev. C 64, 024612 (2001)
[4] R.J. Charity et al., Nucl. Phys. A 483, 371 (1988)
[5] O. Fasoula et al., Phys. Rev. C 113, 034621 (2026)
[6] S. Koulouris et al., Phys. Rev. C 108, 044612 (2023)
[7] Ch. Giannitsa et al., HNPS Advances in Nuclear Physics Vol. 32, 101 (2025)
[8] K. Gkatzogias et al., HNPS Advances in Nuclear Physics Vol. 32, 183 (2025)
[9] K. Palli et al., EPJ Web of Conferences 252, 07002 (2021)Speaker: Konstantinos Gkatzogias (Laboratory of Physical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens) -
15:05
Astrophysical S-factors for alpha reactions with 130,132,134Ba 1m
Cosmic nucleosynthesis presents a relatively good understanding of the production of light elements up to iron; however, the origin and abundances of heavier nuclei (A > 56) remain an open problem. Among the proposed nucleosynthesis mechanisms, reactions induced by charged particles, such as α particles, play a significant role in the production of p-nuclei in extreme astrophysical environments.
In the present study, the focus is on the theoretical investigation of reactions between alpha particles and 130,132,134Ba isotopes at energies of astrophysical interest. Due to the limited or even complete lack of experimental cross-section data in the relevant energy range (the Gamow window), the Hauser–Feshbach statistical model is employed to calculate reaction cross sections, as well as the corresponding astrophysical S-factor.
The calculations are performed using the TALYS nuclear reaction code, exploring different combinations of nuclear input parameters, such as optical model potentials, nuclear level densities, and γ-ray strength functions. The main objective of this work is two-fold: first, to provide reliable theoretical predictions that can guide future experimental studies at low energies, where measurements are particularly challenging due to the Coulomb barrier; and second, to contribute to a better understanding of the role of α-induced reactions in the nucleosynthesis of heavy elements and the production of p-nuclei in astrophysical environments, especially at energy ranges where access by contemporary experimental is next to impossible.Speaker: George Paparigas (National Kapodistrian University Athens) -
15:06
Gamma-ray spectroscopy of 184Os studied via the 176Yb(12C,4n)184Os fusion-evaporation reaction* 1m
Moving past the $N=104$ midshell and approaching the $Z=82$ shell closure presents several opportunities to study nuclear structure as single-particle degrees of freedom compete with collective phenomena to determine several of the spectroscopic properties observed. The Os ($Z=76$) isotopic family presents a compelling study case among the rare-earth nuclei, as it exhibits a variety of deformation and transition phenomena. $^{184}$Os ($N=108$) presents an especially interesting case among Os isotopes, featuring a rotational ground-state band, but also several other collective states, such as high-$K$ isomers, $\beta$- and $\gamma$-bands, where only scattered experimental information is known. The proxy-SU(3) model also predicts the presence of shape-coexistence in this nucleus.
$\quad$To investigate its nuclear structure, a fusion-evaporation reaction experiment was performed. Excited states in $^{184}$Os were populated via the $^{176}$Yb($^{12}$C,4n)$^{184}$Os reaction using a highly enriched (isotopic) metallic $^{176}$Yb target and a $^{12}$C beam at 60 MeV. The de-excitation $\gamma$-rays were detected using the ROSPHERE array. The current work focuses on consolidating the structure of low-energy states in $^{184}$Os, especially weakly-populated states in side bands. The present results expand existing spectroscopy information and include new measurements of several branching ratios.* This work is supported by EURO-LABS (EU Horizon Europe Project No. 101057511) and the German Research Foundation under the grant 539757749.
Speaker: Vasilis Gkionis (National and Kapodistrian University of Athens) -
15:07
Assessment of 161Tb Production from Natural Gadolinium Using Laser-Generated Fast Neutrons at ELI-ALPS 1m
Studies in the efficacy of 161Tb production through the neutron activation of 160Gd are especially important, as 161Tb is a well-known alternative to 177Lu, and is often considered superior [1] in battling CRPC (castration-resistant prostate cancer). However, there are many difficulties associated with the procurement of an enriched 160Gd2O3 target, thus necessitating a study regarding the feasibility of 161Tb production through the neutron capture process on natural gadolinium. Natural gadolinium neutron activation poses a significant challenge; there are seven stable isotopes of gadolinium, two of which (155Gd and 157Gd) have exceptionally high cross sections in the thermal neutron region. A way to bypass this problem is explored in this study, by activating natural gadolinium with fast instead of slow neutrons.
The experiment took place at the Extreme Light Infrastructure (ELI-ALPS) Research Institute in Szeged, Hungary. These facilities have the capability of accelerating deuterons with lasers, hitting a deuterated plastic target and therefore producing fast neutrons through the D-D reaction. A sample of metallic natural gadolinium (diameter ~5 mm) was irradiated using neutrons of average energy of approximately 3.05 MeV. Since 161Tb decays through β- emission, producing only low energy gamma rays, the highest of which is 74.6 keV with 10.2% intensity, it was of the outmost importance that the irradiated sample be placed in front of a HPGe detector with a very thin window, inside lead shielding which guarantees a low radiation background. The γ-spectra were acquired and analyzed, the peaks identified and the counts of the relevant photopeaks determined. Theoretical calculations were performed in conjunction with simulations utilizing MCNP to estimate the activity of the natural gadolinium sample. The findings indicate that the production of 161Tb is feasible though in small quantities.References
[1] Müller, C., Umbricht, C.A., Gracheva, N. et al. Terbium-161 for PSMA-targeted radionuclide therapy of prostate cancer. Eur J Nucl Med Mol Imaging 46, 1919–1930 (2019). https://doi.org/10.1007/s00259-019-04345-0Speaker: Nikoletta Giannakou (Vilnius University) -
15:09
Evaluation of different materials as potential trigger foils for MCP detectors 1m
One of the primary Ion Beam Analysis (IBA) techniques employed for the determination of sample composition and the performance of in-depth analysis is Time of Flight – Elastic Recoil Detection Analysis (ToF – ERDA). The technique's unique advantage is its ability to detect and distinguish light elements, including hydrogen, deuteron, and lithium (up to aluminum or higher), in a variety of samples. Additionally, it can be used to estimate the isotopic concentrations of elements. Two Multichannel Plate (MCP) detectors are employed to accurately determine the time of flight between various ions. When an ion passes through a very thin carbon foil, which is affixed in a Busch configuration with the microchannel plates, these detectors are triggered. The energy loss of the ion as it passes through the foil has a significant impact on the number of emitted electrons. Nevertheless, the energy loss at the energies of interest is relatively low for hydrogen, resulting in a decrease in the overall detection efficiency of the ToF-ERDA setup.
LiF and Al2O3 have been employed as coatings on carbon foils in order to enhance the number of emitted electrons in a variety of ToF-ERDA setups [1] [2]. The objective of this study is to examine the feasibility of substituting these materials with more appropriate alternatives. The evaporation technique was employed to construct a variety of foils in the accelerator laboratory of N.C.S.R. "Demokritos." The Dual Microprobe setup of the Laboratory for Ion Beam Interaction at Ruđer Bošković Institute (RBI) was utilized to completely characterize them through the application of complementary IBA techniques. Furthermore, the single ion impact detection set-up [3] was used at the end station of the Ion Microprobe in the same laboratory to evaluate their efficiency as potential trigger foils. The secondary electron emission was determined and contrasted among the various foils using this method. The analysis's findings will be presented and discussed.[1] Z. Siketić, I. B. Radović, and M. Jakšić, “Development of a time-of-flight spectrometer at the Ruder Bošković Institute in Zagreb,” Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms, vol. 266, no. 8, pp. 1328–1332, Apr. 2008, doi: 10.1016/J.NIMB.2007.12.070.
[2] M. Laitinen, M. Rossi, J. Julin, and T. Sajavaara, “Time-of-flight – Energy spectrometer for elemental depth profiling – Jyväskylä design,” Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms, vol. 337, pp. 55–61, Oct. 2014, doi: 10.1016/J.NIMB.2014.07.001.
[3] R. W. Smith, M. Karlušić, and M. Jakšić, “Single ion hit detection set-up for the Zagreb ion microprobe,” Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms, vol. 277, pp. 140–144, Apr. 2012, doi: 10.1016/J.NIMB.2011.12.036.Speaker: Anastasia Ziagkova -
15:10
Quantifying C profiles in heavy ion irradiated Fe(50nm)/SiO2(300nm)/Si stacks by ion beam analysis techniques 1m
E. Mitsi1,2, P.Tsavalas2, S. Pantousa2, M. Axiotis2, A. Lagoyannis 2, K. Mergia2, G. Apostolopoulos2
1 Department of Physics, National Technical University of Athens, Athens, Greece
2 National Centre for Scientific Research “Demokritos”, Agia Paraskevi, GreecePresenting author email: elmitsi@ipta.demokritos.gr
Accelerator-based ion irradiation is widely employed to investigate radiation effects in solids. In fusion materials research, it is particularly valuable as a surrogate approach for studying neu-tron-induced damage. For ion irradiation to serve as a reliable tool for radiation damage studies, extrinsic effects such as impurity incorporation during the irradiation process must be mini-mized.
Ion beam-induced carbon uptake is a notable concern, particularly in studies of Fe-based ferrit-ic/martensitic steels, which are considered candidate structural materials for future fusion power plants. Carbon can influence microstructural evolution and irradiation response through its strong interaction with irradiation-induced point defects. Since the extent of carbon contamina-tion depends on the specific experimental conditions, it is important for ion irradiation studies on steels to verify whether carbon uptake has occurred and, where possible, to quantify it.
In the present study, carbon depth profiles of irradiated pure Fe films were acquired by combined Rutherford Backscattering Spectrometry (RBS) and Nuclear Reaction Analysis (NRA). The 50 nm Fe films were deposited by DC magnetron sputtering onto Si substrates capped with a 300 nm thermally grown SiO2 layer. The thickness and structure of the films were confirmed by X-ray reflectivity and grazing incidence X-ray diffraction. Specimens were irradiated with 4 MeV O²⁺ ions to a damage dose of 0.25 displacements per atom (dpa) and with 5 MeV Cu³⁺ ions to 1 dpa. The RBS/NRA measurements were performed using a 1.4 MeV deuterium beam and a surface barrier detector positioned at a scattering angle of 170o. Spectra were acquired from irradiated specimens, unirradiated reference samples, and the pristine Si/SiO2 substrate. All irradiations were conducted at the 5.5 MV Tandem accelerator of NCSR “Demokritos”. Carbon was detected via the 12C(d,p0)13C reaction. The carbon signal comprised a high-energy peak, attributed to a surface layer typically formed under high-vacuum conditions by hydrocarbon deposition, and a low-energy tail, associated with carbon distributed throughout the sample volume. Carbon profiles were quantified by simulating the RBS/NRA spectra with the SIMNRA code. For the given experimental conditions, the detection limit for the carbon volume concentration was ~ 2 · 1019 at./cm3. Carbon was identified in all specimens, exhibiting a characteristic near-surface enrichment and extending to a depth of approximately 4 μm. The irradiated specimens showed substantially higher carbon concentrations than the reference sample, consistent with ion-beam-induced carbon uptake. Quantitatively, the near-surface carbon concentration increased by 1.2(2) · 1020 at./cm3 and 2.4(2) · 1020 at./cm3 for the 0.25 dpa and 1 dpa specimens, respectively, demonstrating a dose-dependent enhancement of carbon incorporation.Speaker: Eleni Mitsi (Department of Physics, National Technical University of Athens, Athens, Greece) -
15:11
Monte Carlo Characterization of a Neutron Irradiation System for Radiobiological Experiments 1m
A neutron irradiation system for radiobiological cell experiments was characterized using Monte Carlo simulations to assess the mixed neutron–gamma radiation field and its suitability for biological applications. The irradiator consists of two ²³⁹Pu(α,n)⁹Be neutron sources with a total ²³⁹Pu activity of 444 GBq. The sources are housed in a graphite collimator and surrounded by lead and boron-doped polyethylene shielding to optimize beam characteristics and minimize radiation levels in the surrounding area. An irradiation channel enables the placement of biological samples at different distances from the sources, allowing irradiations under varying neutron fluence rate conditions.
The characterization study was performed using the MCNP6 code [1]. A detailed computational model of the neutron sources, collimator geometry, shielding configuration, irradiation channel, and cell culture plates was developed. Neutron and gamma fluence distributions, absorbed dose, and linear energy transfer (LET) spectra within the biological samples were calculated to evaluate the radiation field characteristics relevant to radiobiological investigations. Simulations enabled the assessment of dose contributions from neutron and gamma components, spatial dose distributions, and irradiation conditions suitable for low dose-rate biological exposures.
Although radionuclide neutron sources cannot achieve the high fluence rates available at research reactors or accelerator-based facilities, they provide a simple, reliable, and cost-effective approach for fast neutron irradiation under stable and reproducible low dose-rate conditions. The present characterization provides essential dosimetric parameters for the interpretation of future radiobiological studies investigating DNA damage responses and biological effects induced by mixed neutron–gamma radiation fields.[1] T. Goorley et al., 2012, Initial MCNP6 Release Overview. Nucl. Technol. 180, 298–315.
Speaker: Apospori Eirini (INRASTES, National Center of Scientific Research «Demokritos», Aghia Paraskevi, 15310 Athens, Greece/ DNA Damage Laboratory, Department of Physics, School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Zografou, 15780 Athens, Greece) -
15:12
Development of a Methodology for Gamma-Spectrometric Analysis of Neutron Irradiated Metallic Samples 1m
The present work describes the development and implementation of a
methodology for the gamma-spectrometric characterization of metallic samples
irradiated in different neutron fields with energies ranging from 2.4 up to 14 MeV.
The samples studied consisted of a set of disc-shaped metallic elements manufactured
from high-purity materials, including silver, tantalum, cobalt, and nickel. Following
neutron irradiation, the samples were measured using High-Purity Germanium
(HPGe) detectors, while spectral analysis was carried out with dedicated gamma
spectrometry software.
Correction factors were applied on the spectrometric data to account for true
coincidence summing effects and photon self-attenuation within the sample volume.
The activity induced in each sample was then determined from the corrected gamma
spectrometric measurements, enabling a quantitative evaluation of the activation of
the specific metallic elements under the corresponding irradiation conditions.
The developed methodology demonstrates a reliable and reproducible
approach for the quantitative gamma-spectrometric analysis of irradiated metallic
samples. Furthermore, it contributes to the optimization of experimental procedures,
correction protocols, and data-analysis practices employed in neutron-activation
measurements and spectrometry laboratory operations.Speaker: Vasileia Saridaki (INRASTES, National Center of Scientific Research “Demokritos”, Aghia Paraskevi, 15310 Athens, Greece , Department of Physics, National Technical University of Athens, Zografou, 15780 Athens, Greece) -
15:13
Comparative Analysis of Turbine Leading and Reactor Leading Operating Modes in an iPWR Simulator under Load-Following Conditions 1m
The urgent need for carbon-free energy production has established Small Modular Reactors (SMRs) as a vital component of the clean energy transition. Characterized by an electrical output of 10 to 300 MWe, SMRs offer significant versatility, operating in base-load mode for grid stability or in load-following mode to compensate for intermittent Renewable Energy Sources (RES). A key advantage over conventional reactors is their enhanced safety, relying on passive systems that operate without external power or human intervention. To ensure safe deployment, high-fidelity simulation tools are essential for educational purposes and for studying reactor behavior during normal and malfunction scenarios. This study investigates the operational behavior of an integral Pressurized Water Reactor (iPWR) using the IAEA-TECNATOM simulator. The tool models a generic 150 MWth (45 MWe) iPWR with a 4.95% enriched UO2 fuel core, integrating comprehensive primary, secondary, safety, and control systems. Specifically, we examine the dynamic response of the iPWR under a 10% load maneuvering scenario (100% to 90% power reduction and subsequent restoration), comparing two distinct plant operating modes: Turbine Leading and Reactor Leading. In the Turbine Leading mode, electrical output is regulated directly by the turbine control valve, with the control rods modulating core thermal power to match secondary side demand. Conversely, the Reactor Leading mode drives electrical output indirectly via core thermal power regulation using control rods and boron concentration modifications. The results demonstrate that the Turbine Leading mode provides superior precision and faster dynamics. The Turbine Leading mode completes the power decrease in 11 minutes and recovery in 19 minutes. In contrast, the Reactor Leading mode requires 25 minutes for power reduction and 33 minutes for recovery due to indirect neutronic and reactivity feedback. Consequently, the Turbine Leading strategy proves more effective for the high-RES penetration grids and flexible nuclear operations characterizing modern and future power systems.
Speaker: Ioannis Kaissas (Nuclear Technology Laboratory, School of Electrical & Computer Engineering, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, Greece) -
15:14
Neutron Flux at the Boundaries of Rectangular Subcritical Piles with a Point Am-Be Neutron Source at their Mass Centers for Various Moderation Scenarios 1m
This study investigates the qualitative and quantitative properties of the neutron flux near the geometry boundary of the neutron subcritical piles of the Nuclear Engineering Laboratory of NTUA (NEL-NTUA) using the freely available OpenMC Code. The Laboratory operates two subcritical piles. The first one has a cubic geometry tank of 1 m3 volume. A fast neutron Am-Be source with nominal radioactivity of 10 Ci is placed at the mass center of the tank. The tank is filled with water. The second pile has a cubic geometry box of 0.2 m3 volume. A fast neutron Am-Be source with nominal radioactivity of 5 Ci is placed at its mass center. The box is filled with solid paraffin. The properties of these neutron sources inside the subcritical piles (dimensions, composition, radioactivity etc.) were prepared in detail in order to be used as input to the OpenMC code. The neutronic analysis for the water pile and the paraffin pile followed. The results showed that the neutron leakage spectrum includes thermal neutrons (assumed to have energy ranging from 0 eV to 0.5 eV), but also epithermal (assumed to have energy ranging from 0.5 eV to 0.1 MeV) and fast neutrons (assumed to have energy ranging from 0.1 MeV to infinity). In the case of the water pile, the percentages were estimated to be ~37, 11 and 52% respectively. In the case of paraffin, the percentages were estimated to be ~45, 11 and 44% respectively. The overall neutron flux in the water pile was estimated to be 3-4 neutrons cm2s-1 in the least favorable part of the tank external surface. The overall neutron flux in the paraffin pile was estimated to be 25-30 neutrons cm2s-1 in the least favorable part of the of the box external surface. Results were brutally verified with some portable instruments available in the Lab and with neutron flux results coming from the Greek Regulator's dosimetry services. After that, a series of several neutron moderators/absorbers for the water subcritical pile were computationally examined in order to test the possibility of replacing the water of the first pile with a different moderating material, not prone to leakage in case of small tank breaches. It was found that the most suitable materials for the substitution of the water are organic polymers (i.e. plastics) in the form of small diameter granules, with density slightly greater than that of water and also borax decahydrate as well as mixtures of sodium polyacrylate with water.
Speaker: N.P. Petropoulos (Nuclear Engineering Laboratory National Technical University of Athens)
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14:55
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15:30
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17:15
Nuclear Astrophysics, Dense Matter and Compact StarsConvener: A. Martinou
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15:30
Multi-Strangeness non-linear potentials & the hyperon-puzzle in neutron stars 15m
Hyperons are baryons with strangeness degrees of freedom. They play a significant role in modern nuclear physics and astrophysics due to their experimental accessibility and significant impact on the high-density equation of state. In-medium hyperons can be produced inside highly compressed matter in reactions or in neutron star cores only due to high energy production thresholds. However, the presence of the hadronic medium modifies largely the strangeness threshold conditions. The hyperon in-medium potentials manifest a non-linear behavior in density and, in particular, in single-particle momentum. These non-linear features reveal interesting novel effects in compressed matter and in neutron star matter. They provide a potential solution to the long-standing hyperon-puzzle in neutron stars. Here we discuss the hyperon non-linear potentials and present applications related to compressed matter and neutron star cores.
Speaker: Theodoros Gaitanos (Aristotle University of Thessaloniki) -
15:45
Estimating neutron-capture rate uncertainties for iron isotopes using shell-model-based level densities in TALYS 15m
Nuclear level densities (NLDs) and $\gamma$-ray strength functions ($\gamma$SFs) are key ingredients in the statistical description of compound nuclear reactions. Despite decades of development, significant uncertainties remain in their modeling. In this work, we study the impact of NLDs and $\gamma$SFs on $(n,\gamma)$ cross sections and Maxwellian-averaged reaction rates for nuclei in the iron region. NLDs are calculated using the Moments Method (MM), a shell-model-based statistical approach, and implemented in the TALYS reaction code. To enable their use in reaction calculations, the MM level densities are extended to higher excitation energies and supplemented with a phenomenological treatment of opposite-parity states. A systematic exploration of model combinations within TALYS is performed to quantify the sensitivity of calculated observables to both NLD and $\gamma$SF inputs. Comparisons with evaluated nuclear data and astrophysical databases show that the MM-based calculations reproduce the overall trends of the cross sections and reaction rates. The results indicate that, while variations in the NLD contribute to the overall uncertainty, the $\gamma$SF constitutes the dominant source of variation in the predicted observables.
Acknowledgement - This material is based upon work supported by the National Science Foundation under Award No. 2412851.
Speaker: Sofia Karampagia (Grand Valley State University) -
16:00
Nuclear Imprints on Neutron-Star Properties: A Universal-Relation Perspective 15m
Information on neutron-star matter can be encoded in low-energy nuclear observables, particularly those sensitive to the isovector sector of the nuclear interaction. In this contribution, we investigate how the electric dipole polarizability of neutron-rich nuclei can be used to constrain macroscopic properties of canonical neutron stars within a universal-relation framework. The analysis is built around the dimensionless quantity $\zeta = \beta_{1.4}\tilde{L}^{-1}$, which combines the compactness $\beta_{1.4}$ of a $1.4~M_{\odot}$ neutron star with the slope of the nuclear symmetry energy at saturation density. The correlation between $\zeta$ and the dipole polarizability $\alpha_D$ is studied across a diverse set of relativistic and non-relativistic nuclear energy density functionals, including point-coupling and meson-exchange interactions, as well as Skyrme functionals. The resulting systematics reveal a pronounced exponential dependence that persists across the considered models, supporting the use of $\alpha_D$ as a nuclear imprint of neutron-star compactness. By confronting the universal correlation with available experimental dipole polarizability data, intervals for $\zeta$ are obtained. These intervals are subsequently used to infer limits on the neutron-star radius $R_{1.4}$ and the symmetry-energy slope parameter $L$, thereby highlighting finite-nucleus dipole polarizability as a laboratory probe of neutron-star matter.
Speaker: Dr Polychronis Koliogiannis (University of Zagreb) -
16:15
Neutron star dissipative tidal deformation originated by the bulk viscosity of npe matter 15m
In this study we examine the effects of the bulk viscosity of dense matter containing neutrons, protons, and electrons in the environment of neutron stars. Our approach considers the bulk viscosity to be driven by the direct Urca mechanism which tries to restore the chemical equilibrium in a neutron star core for small perturbations of the baryon density. The bulk-viscous dissipation leads to heating and on a macroscopic scale the bulk viscosity is imprinted in the dissipative tidal deformability. The latter encodes information about the dynamical processes of neutron star interiors and their effect on the macroscopic features of neutron stars, especially in the late phase of an inspiraling binary neutron star system. The ability to measure parameters encoded in the tidal dissipative deformability by the advanced LIGO gravitational wave detectors can offer a new extra tool for examining the behavior of dense nuclear matter and imposing qualitative constraints on it. In our preliminary results we show the qualitative behavior of the dissipative tidal deformability for a phenomenological nuclear model.
Speaker: Alkiviadis Kanakis-Pegios (Aristotle University of Thessaloniki) -
16:30
Thermal effects on hadron-quark phase transition and the structure of proto-compact stars 15m
One of the most interesting subjects related to the physics of dense matter is the accurate finite temperature description of the nuclear equation of state. In the present conference contribution, we discuss the properties of hot equations of state which involve a first order phase transition from hadronic to deconfined strange quark matter. For the description of the hadronic phase we utilize a Skyrme effective interaction, while for quark matter a widely used Bag model is employed. The study focuses on the investigation of sharp phase transitions modelled via the Maxwell construction. The main goal is to examine the possibility of quark deconfinement in proto-neutron stars and its impact on their bulk properties. Apart from the effects of finite temperature, we also discuss the role of neutrino trapping on the possible occurrence of hadron-quark phase transition.
Speaker: Pavlos Laskos-Patkos (Aristotle University of Thessaloniki) -
16:45
Dark Neutron decay in Neutron Stars 15m
One of the unsolved mysteries in the particle physics is the "neutron decay puzzle". Discrepancies between the neutron lifetime measured in beam and bottle experiments suggest that exotic decay channels and/or the involvement of dark matter may be in play. Recent measurements of the compact star XTE J1814-338, with a mass of $M=1.2_{-0.05}^{+0.05}\ M_{\odot}$ and a radius of $R=7_{-0.4}^{+0.4} \ {\ Km}$ alongside those of HESS J1731-347, which has a mass of $M=0.77_{-0.17}^{+0.20}\ M_{\odot}$ and a radius of $R=10.4_{-0.78}^{+0.86} \ {\ Km}$, provide compelling evidence for the potential existence of exotic matter in neutron star cores. These observations offer important insights into the equation of state of dense nuclear matter. The proposed dark decay of the neutron may explain the existence of objects as a product of the mixing of neutron stars with dark matter, over a wide range that includes objects with small mass and radius as well as those in the mass gap region. This hypothesis can more generally explain other compact objects with both small masses and radii that are to the left and below the classical M-R diagrams. In particular we consider the case of neutron decay into a dark particle of mass $m_{\chi}=939$ MeV according to the hypothesis formulated by Fornal and Grinstein. We consider this dark matter to interact both with itself and with neutrons thus defining the equation of state of the neutron and dark matter mixture. In this study we found that with the appropriate combination of interaction parameters both masses larger than 2 solar masses can be simultaneously predicted and at the same time the compact objects XTE J1814-338 and HESS J1731-347 can be reproduced in a self-consistent way. More information can be found at our work Ref. [1]
[1] M. Vikiaris, V. Petousis, M. Veselsky, Ch.C. Moustakidis, Neutron Dark Decay and Exotic Compact Objects, eprint arXiv:2602.04477
Speaker: Dr Michail Vikiaris (Aristotle University of Thessaloniki) -
17:00
Modeling the transition from Hadron Gas to deconfined Quark Matter via the Albright-Kapusta-Young switch function. 15m
This work aims to investigate the bulk properties of hybrid stars. The transition from hadronic matter to deconfined quark matter is modeled by a switching function introduced by Albright, Kapusta and Welle. This function has an exponential form, given by: $S(\mu)\,=\,exp[-(\mu_0/\mu)^r]$ and combines the two states of the matter smoothly, in contrast with Maxwell and Gibbs transition.
Speaker: Mr Giorgos Tsalis (Aristotle University of Thessaloniki)
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Coffee Break 30m
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Online SessionConvener: A. Lagoyannis
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Statistical Evidence for Oscillatory Components in Neutron-Capture Cross Sections 15m
This work presents evidence for statistically significant oscillations in neutron-capture cross sections within the resolved-resonance region, challenging the conventional assumption that fluctuations are entirely random as predicted by random matrix theory (RMT). Using autocorrelation and cosine-fitting techniques, neutron-capture data for 21 nuclides were analyzed over a broad range of resonance energies. Highly significant oscillatory behavior was observed in 13 of the 21 cases studied, with nine exhibiting significance levels greater than 5σ. The oscillations account for an average of 10.9% of the reduced neutron-capture cross section and display periods ranging from approximately 68 to 2380 eV. These results suggest that deviations from RMT are not isolated anomalies, but instead reflect a widespread physical mechanism absent from current descriptions of neutron-induced reactions. The study was motivated in part by observations from previous DICER (Device for Indirect Capture Experiments on Radionuclides) measurements at the Los Alamos Neutron Science Center, where unexpected resonance structures and correlations in neutron transmission data hinted at nonrandom behavior in neutron-capture processes. DICER’s unique capability to perform high-resolution neutron transmission measurements on small and radioactive samples provided critical insight into resonance phenomena that inspired the present investigation. By extending these observations to a large body of neutron-capture data, the present work demonstrates that oscillatory structure appears across a wide mass range and in both capture and fission reactions. The existence of these oscillations has important implications for nuclear statistical models, evaluated nuclear data libraries, and applications in nuclear astrophysics, reactor physics, and national security. Overall, the results indicate that neutron-induced reaction cross sections contain previously unrecognized systematic structure that warrants both theoretical explanation and further experimental investigation.
Speaker: Thanos Stamatopoulos (Los Alamos National Laboratory) -
18:00
Probing Explosive Nucleosynthesis through (α,n) and (p,n) Reactions Using SECAR 15m
The synthesis of heavy elements in explosive stellar environments, such as core-collapse supernovae, is influenced by key nuclear reactions involving unstable nuclei. In neutron-rich conditions, the α-process -a sequence of (α,xn) reactions- plays a significant part in nucleosynthesis, whereas (p,n) reactions influence element formation in proton-rich conditions, during explosive silicon burning and the νp-process. However, experimental data on such reactions remain scarce, introducing significant uncertainties in astrophysical models.
A new technique has been developed for direct measurements of both (α,n) and (p,n) reactions in inverse kinematics with SECAR (SEparator for CApture Reactions). Despite it being primarily designed for capture reactions, the development of machine learning-assisted ion-optics rendered the study of (p,n) reactions using a separator feasible, and a
$^{58}$Fe(p,n) measurement served as proof-of-principle for the method. Additionally, SECAR’s capabilities have been expanded to include (α,n) reaction measurements, as demonstrated in an initial case study of the $^{86}$Kr(α,n) reaction, which influences α-process nucleosynthesis and the elemental abundances observed in metal-poor stars.In this talk, I will present recent (α,n) and (p,n) reaction measurements with SECAR, highlighting the experimental advancements that enabled these studies along with their astrophysical significance. These reaction studies pave the way for future direct reaction rate measurements on short-lived nuclei, which are essential for improving our understanding of heavy-element nucleosynthesis.
Speaker: Pelagia Tsintari (Facility for Rare Isotope Beams at Michigan State University) -
18:15
Probing nuclear interactions à la Rutherford: insights on 4He from α scattering 15m
The light nuclei attract the interest of the nuclear physics community for decades, however, we are still far away from their complete understanding. A notable example is the $^4$He, a simple and very stable nucleus constituted by two protons and two neutrons. Until a description of nuclei directly from the fundamental theory of quarks and gluons becomes computationally feasible, an effective way to proceed is to assume composite particles like protons and neutrons and the interactions among them as the basic degrees of freedom. Successful reparametrizations and models of these interactions have been developed in the last decades, which are able to accurately reproduce all the known data of proton and neutron scatterings, as well as the properties of few-body nuclear systems. However, recent electron scattering results focusing on the first excited resonant state of $^4$He nucleus, reveal a puzzling situation suggesting potential gaps in our understanding of nuclear phenomenology. Into this context, we performed new measurements of the $^4$He(0$^+_2$) resonance by $^4$He + $^4$He scattering at the MAGNEX facility of INFN – Laboratori Nazionali del Sud, featuring data of unprecedented sensitivity and state-of-art analyses of the spectral line shape together with a phenomenological reaction modeling based on a two coupled-channel system that incorporates the same ab-initio nuclear densities employed in electron-scattering studies.
Speaker: Vasileios Soukeras (Università di Catania, Italy) -
18:30
First results of the neutron induced fission cross section measurement of Uranium-236 at n_TOF facility 15m
First results of the neutron induced fission cross section measurement of Uranium-236 at n_TOF facility
Z. Eleme1, A. Tsinganis2, M. Patronis1, M. Bacak3, N. Colonna4, M. Diakaki5, P. Dimitriou6, V. Foteinou1,S. Goula1,7, J. Heyse2, M. Kokkoris5, N. Kyritsis5, V. Michalopoulou5, A. Musumarra8, D. Papanikolaou8, M.G. Pellegriti8, M. Peoviti1, M.E. Stamati1,7, P. Schillebeeckx2, G. Tagliente4, R. Vlastou5 and the n_TOF Collaboration
1 University of Ioannina, Ioannina, Greece
2 European Commission, Joint Research Centre (JRC), Geel, Belgium
3 University of Vienna, Faculty of Physics, Vienna, Austria
4 Instituto Nazionale di Fisica Nucleare, Sezione di Bari, Italy
5 National Technical University of Athens, Athens, Greece
6 International Atomic Energy Agency (IAEA), Vienna, Austria
7 European Organization for Nuclear Research (CERN), Switzerland
8 Instituto Nazionale di Fisica Nucleare, Sezione di Catania, ItalyHigh-accuracy cross section data for neutron induced reactions are essential over a wide energy range to support the design, feasibility and sensitivity studies on advanced nuclear systems [1, 2]. 236U (T1/2= 2.342x107 years) is a long-lived isotope with high specific activity, making it a major contributor to the radioactivity of reprocessed uranium. In U/Pu reactors 236U is produced through neutron capture on 235U, affecting both the neutron balance and fuel composition, while it also accumulates in the Th/U fuel cycle. Therefore, accurate knowledge of its fission cross section, within 5%, is required for the development of fast nuclear reactors and accelerator-driven-systems (ADS) [3].
For the 236U(n,f) reaction cross section, evaluated nuclear data libraries show large discrepancies in the thermal neutron region, reaching up to two orders of magnitude. Among them, only JENDL-5 [4] and JEFF-4.0 [5] reasonably reproduce the limited experimental data reported by Wagemans et al. [6,7]. Above 500 keV, existing measurements differ by up to 15%, while beyond 40 MeV only three data sets extend to several hundred MeV [8–10]. This high energy region is particularly important for constraining theoretical models of the fission process.
In this work, the 236U(n,f) cross section was measured at the n_TOF facility at CERN using Micromegas detectors and the time-of-flight technique. For the measurement, two high-purity 236U samples were employed, together with 235U, 238U, and 10B reference samples for neutron flux monitoring [11]. This contribution provides an overview of the experimental setup and presents preliminary results covering the neutron energies from meV to 400 MeV, compared with previous measurements and evaluated nuclear data libraries.REFERENCES
[1] A. Stanculescu, Annals of Nuclear Energy 62, 607-612 (2013)
[2] Generation-IV International Forum, www.gen-4.org/
[3] INDC International Nuclear Data Committee,Summary Report of the Consultants’
Meeting on Assessment of Nuclear Data Needs for Thorium and other Advanced Cycles, INDC(NDS)-408 (IAEA, Vienna, 1999).
[4] O. Iwamoto et al., Journal of Nuclear Science and Technology 60(1), 1-60 (2023)
[5] https://databank.io.oecd-nea.org/data/jeff/40/
[6] C. Wagemans et al., Nucl. Sci. Eng. 136, 415 (2000)
[7] C. Wagemans et al., Nucl. Sci. Eng. 160, 200 (2008)
[8] F. Tovesson et al., Nucl. Sci. Eng. 178, 57 (2014)
[9] Z. Ren et al., Eur. Phys. J. A 59, 5 (2023)
[10] A. S. Vorobyev et al., Phys. Rev. C 108, 014621 (2023)
[11] Z. Eleme et al., CERN-INTC-2024-029;INTC-P-700Speaker: Zinovia Eleme (University of Ioannina, Greece) -
18:45
Charged-particle discrimination using an NTD silicon detector at n_TOF/CERN 15m
Neutron-induced reactions in which at least one of the reaction products is a light charged particle are of prime importance in a variety of fields: fundamental research, medical physics, nuclear applications, i.e., fusion reactors. In fusion reactors, special efforts are ongoing to determine threshold reactions of structural materials. These materials are exposed to extreme irradiation conditions, which can lead to the formation of helium or gas within them, altering their properties. In particular, for several commonly used structural materials of fusion reactors, these data sets are urgently needed.
This contribution is about the “proof-of-principle” of a novel charged particle detector setup by taking advantage of the unique characteristics of the neutron Time-Of-Flight facility at CERN. The setup consists of a silicon wafer with a CD shape, segmented on both sides into strips and sectors, offering position-sensitive measurements [4,5]. The silicon wafer has undergone the neutron transmutation doping technique, providing a uniform electric field inside the silicon wafer. The NTD feature allows the application of an in-house Pulse Shape Analysis (PSA) algorithm for discrimination by using Machine Learning (ML) algorithms.
Within this contribution, the characterization of the detector’s response and the experimental configuration will be presented along with the experimental results.Speaker: Styliani Goula (University of Ioannina (GR), CERN)
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General Assembly of HNPS
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Plateia Ageiou Louka, 35100 Lamia
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Radiation Measurements, Dosimetry, Environmental Radioactivity and ApplicationsConveners: I. Stamatelatos, A. Ioannidou
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Geological Analysis of Radon Exhalation on Cephalonia Island with In Situ Measurements 15m
Cephalonia Island, located in western Greece, is characterized by complex geological and tectonic conditions associated with the active Cephalonia Transform Fault Zone (CTFZ), and lies at the boundary between the Paxos (Pre-Apulian) Zone and the Ionian Zone (Lekkas, 1996). The Paxos Zone is mainly characterized by relatively undeformed carbonate platform formations consisting predominantly of limestones and dolomites, whereas the Ionian Zone includes carbonate sequences overlain by flysch deposits and affected by intense folding and thrusting (Zoumpoulis et al., 2010). The tectonic regime of Cephalonia is controlled by active fault systems associated with regional strike-slip deformation and the Ionian thrust front, resulting in extensive faulting and fracturing across the island (Brooks et al., 1984). These structural discontinuities significantly enhance rock permeability and facilitate radon migration through fault zones and fracture networks from the subsurface to the atmosphere (Su et al., 2021). The present study investigates the spatial variability of soil radon exhalation rates across Cephalonia Island and examines their relationship with lithology and tectonic structures.
Ιn situ radon exhalation measurements were conducted at selected locations representing different geological formations and structural settings. The accumulation chamber method was applied using AlphaGUARD, a portable radon detector (Ouzounis, Kaissas, 2024). Radon concentration was recorded with a sampling interval of 10 minutes, over a total duration of 2 hours. The exhalation rates were derived from the linear fitting of concentration’s raise versus time. The quality of each measurement was assessed using the coefficient of determination (R²) of the linear fit.
The measured radon exhalation rates show significant spatial variability across the study area. The lowest value was recorded at Lixouri (61 Bq m⁻² h⁻¹), while the highest value was observed at Chavdata (664 Bq m⁻² h⁻¹). Elevated radon exhalation rates were mainly associated with fractured carbonate formations and areas located near active fault zones. Intermediate values were measured in locations characterized by compact limestones or partial sedimentary cover. The high R² values obtained for most measurements indicate a good linear fit and reliable estimation of exhalation rates. The study provides preliminary data for radon potential assessment on Cephalonia Island and contributes to a better understanding of radon behavior in relation to lithology and structural features. Such information is important for environmental monitoring and for evaluating radon-related hazards in seismically active regions.Lekkas, E. (1996). Neotectonic map of Cephalonia and Ithaca. National and Kapodistrian University of Athens
Zoumpoulis, E., Pomoni-Papaioannou, F., & Zelilidis, A. (2010). Studying in the Paxos Zone the carbonate depositional environment changes during Upper Cretaceous, in Sami area of Kefallinia Island, Greece. Bulletin of the Geological Society of Greece, XLIII(2), 793–801
Su, C., et al. (2021). Radon migration in fault zones and its relationship with tectonic activity. Journal of Environmental Radioactivity
Ouzounis, A. & Kaissas, I. (2025). A Review of Methodologies for Measuring Geogenic Rn Exhalation. HNPS Advances in Nuclear Physics, Vol.31
Speaker: Ioannis Kaissas (Nuclear Technology Laboratory, School of Electrical & Computer Engineering, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, Greece) -
09:45
Assessment of Occupational Radiation Exposure in DEMO Maintenance Operations: Application to the ECRH System 15m
Occupational radiation exposure (ORE) assessments are initiated from the earliest stages of nuclear facility design in order to identify high-dose operations, support dose optimization, and guide the selection of appropriate design solutions. Maintenance activities on plant systems may contribute significantly to both individual and collective doses to personnel. Consequently, ORE evaluations for maintenance activities are an essential element of the iterative application of the ALARA principle, as they can inform design modifications and optimization strategies aimed at reducing occupational exposure.
This work presents the methodology developed for the assessment of ORE associated with maintenance activities in DEMO, with particular focus on the operational radiological exposure analysis of maintenance activities for the DEMO Electron Cyclotron Resonance Heating (ECRH) system. The analysis is based on radiation field characterization, estimated dose rates, maintenance procedures, intervention frequency, the use of personnel protective equipment and associated work effort to estimate collective dose to workers, taking into account contributions from both external and internal exposure pathways.
Although the current level of design maturity does not yet allow for highly detailed ORE assessments, the present estimations give an envelope evaluation of collective dose to personnel due to preventive ECRH maintenance operations, concluding that Remote Handling Tools are required in order to perform the maintenance of the ECRH system. These results are provided to system designers to support the optimization and integration of plant systems and components from a radiological protection perspective.
The outcomes of this work provide input to the DEMO Generic Site Safety Report Volume 4 (GSSR-4), which addresses the occupational radiological hazards anticipated in DEMO and defines the measures required for worker protection [1]. The study therefore contributes to the development and safety-oriented design optimization of future fusion facilities, such as the EU Fusion Pilot Plant (FPP) and subsequent First-Of-A-Kind (FOAK) fusion plant.- This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 — EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them.
[1] DEMO Generic Site Safety Report, Volume 4 v.3.1, Occupational Safety, EFDA_D_2PMKPL_v.3.1, 2024
Speaker: Theodora Vasilopoulou (INRASTES, NCSR 'Demokritos') -
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Preliminary results of radon exhalation measurements in Northern Greece 15m
Since 2023 radon exhalation measurements were carried out by our research team in northerneastern Greece. Measured values vary from 3.62 to 432 Bq•m⁻²•h⁻¹ (Fig. 1). Exhalation rates were measured by using a diffusion accumulator [1]. While the importance of lithology on radon exhalation has been recognized [2], lithology itself does not solely govern radon exhalation. The role of structural features such as faults and fissures as well as meteorological parameters has also been proven significant [3]. In order to examine the impact of the aforementioned factors a spatial database of measured radon exhalation rates, rock lithological types [4], fault distribution [5] and meteorological parameters was compiled. Comparative statistical analysis was conducted to check whether rock lithologies, i.e. fractured, massive and mylonitized rock, and sediment lithologies, i.e. topsoil, saprolite and thick sediment deposits present the same radon exhalation behavior. No significant differences were found. Further statistical analysis of the generalized lithological units of the research area and their radon exhalation rates showed that there is no clear correlation between them. Higher exhalation rates were measured nearer to fault lines within the same lithological units. The findings show that radon emission are dependent on tectonic structures and daily weather conditions rather solely on rock types. Radon exhalation thus may be used as an indicator of hidden faults if meteorological conditions are taken into account
References.[1] A. Ouzounis and I. Kaissas, HNPS Adv. Nucl. Phys., vol. 31, pp. 90–95, 2025.
[2] H. Nan, et al., Atmosphere, vol. 17, no. 3, p. 289, Mar. 2026.
[3] P. S. Miklyaev, et al., Geochem. Int., vol. 59, no. 4, pp. 435–447, Apr. 2021.
[4] Institute of Geology and Mineral Exploration (IGME), 2015.
[5] J. Begg, et al., Scientific Data, 12:1853, 2025.Speaker: Athanasios Ouzounis (Nuclear Technology Laboratory, School of Electrical & Computer Engineering, Aristotle University of Thessaloniki, University Campus, 54124 Thessaloniki, Greece) -
10:15
Evaluation of 210Pb-based radiochronology models at four deep basins in Aegean Sea 15m
Deep marine basin sediments serve as repositories of information on physicochemical processes and the transport behavior of tracers in aquatic environments. The vertical profiles of radionuclides in the water column combined with radiochronological models in the seabed cores can provide new information in terms of geological and radiological processes. The activity concentration data of four sediment cores from different sites in the Aegean Sea were utilized to evaluate sedimentation rates and dating using the $^{210} Pb$ (CF:CS, CIC, CRS/PF) and $^{137} Cs$ models for the sediment cores sampled at the Lemnos, North Skyros, Athos and Cretan basins. The use of multiple dating approaches enables a more comprehensive reconstruction of sediment accumulation history, as well as a better understanding of the use of the models according to each marine ecosystem. The activity distributions of radionuclides provide baseline information on system stability and potential disturbances. In the sediment cores from the Skyros, Athos and Cretan basin, discrepancies in $^{210} Pb_{ex}$ are observed due to rapid changes of the activity concentration of natural radionuclides with the core depth. These are attributed to possible seismic or flooding events, or other episodic processes that resulted in the deposition of additional sediment material. Specifically, in the Athos and Cretan basins, the sediment accumulation rate (SAR), calculated using the CRS and PF models, increases at depths where higher activity concentrations are recorded. In contrast, the sediment cores from the Lemnos and Skyros basins indicate that the sedimentation and accumulation processes are characterized by relatively constant sediment deposition, taking into account the riverine and gravity-flow inputs from the North Aegean region. Consequently, the SAR is approximately two times higher compared to the CF:CS model during the last 20–30 years.
Keywords: $^{210} Pb$ dating models, deep basins, accumulation/sedimentation rate
Acknowledgements
This work was supported by the MARRE project through National Strategic Reference Framework (NSRF) 2014–2020 co-financed by Greece and the European Union (European Social Fund ESF). The authors would also want to acknowledge the crew of the research vessel R/V AEGEAO for the sampling using the box corer during the cruise in the frame of MARRE project. The HCMR group would like also to acknowledge IAEA (RER7015 project) due to know-how transfer in terms of reconstruction of environmental magnitudes as well as the EU Horizon project with the acronym CONTRAST supporting updated tools for interpreting signatures from anthropogenic and natural processes using sediment cores.Speaker: Zoi Maniati (Hellenic Centre for Marine Research, National Technical University of Athens) -
10:30
The experimental set up and the application of a marine mini gamma-ray spectrometer for the identification of radioactive objects 15m
The understanding and protection of human’s due to the consequences of nuclear incidences has become an increasingly important scientific and technological challenge. This research focuses on quantification methods of underwater gamma-ray spectrometers to identify radioactive objects in aquatic systems. The work addresses the critical need for rapid, accurate, and non-invasive monitoring methods capable of identifying gamma-ray emitters that may be caused by various nuclear incidences. Previously, continuous monitoring activities have been conducted in the marine environment using low and medium resolution underwater gamma-ray spectrometers, such as the KATERINA and GeoMAREA detection systems. The experimental set up and the applications of a compact nuclear detection system with small dimensions is employed by its integration into robotic vehicles to collect data in controlled aquatic environments. The system utilizes a 2''×2'' NaI (Tl) scintillation crystal coupled with a Silicon Photomultiplier, aiming to reduce size and weight while improving underwater maneuverability. The integrated system (sensor and drone) is applied in nuclear security needs identifying radioactive materials beneath ship hulls. An initial performance assessment was conducted in a water tank to investigate detection capabilities as a function of source-to-detector distance. Subsequently, field measurements were carried out in a marine environment to determine limits of detection using known radioactive simulant housed in a dedicated enclosure. Finally, an automated identification algorithm was also applied to detect potential threats originating from suspicious objects/sources and to generate corresponding alerts based on type of radioactivity (natural or anthropogenic).
Key Words: Nuclear maritime security, nuclear incidences, underwater gamma-ray spectrometer, radionuclide identification
Acknowledgements
The authors would like to thank the UnderSec HORIZON EU project for supporting the development of the hardware system.Speaker: Ioanna Kora (Hellenic Centre for Marine Research, Institute of Oceanography ,National Technical University of Athens) -
10:45
Proton dosimetry at Oslo Cyclotron Laboratory for radiobiological experiments* 15m
Accurate dosimetry in radiobiological experiments using proton beams requires high resolution, energy-dependent characterization of the Bragg peak, which is essential for understanding variations in Linear Energy Transfer (LET) and the corresponding radiobiological effects along the proton track. Proton beam dosimetry is typically performed using parallel-plate ionization chambers with small sensitive volumes to ensure adequate spatial resolution in regions of steep dose gradients. Monte Carlo simulations are often combined with experimental measurements to enable reconstruction of three-dimensional dose distributions, particularly in specialized setups for in vitro cell irradiation studies.
In this work, proton dosimetry of the MC-35 Scanditronix AB beam at the Oslo Cyclotron Laboratory (OCL), Norway, is presented in support of radiobiological applications. Measurements were conducted using a calibrated Advanced Markus chamber at multiple distances from the beam exit in order to experimentally resolve the Bragg peak profile of the OCL proton beam. Furthermore, Monte Carlo simulations were carried out using the MCNP 6.2 transport code to characterize beam quality parameters and to derive irradiation geometry correction factors necessary for the determination of absorbed dose to water, as well as dose deposition within cellular mono-layers in irradiated culture plates. Independent determination of the absolute proton fluence was achieved using activation foil measurements. The absorbed dose values determined from activation analysis were found to be in good agreement with those obtained via ionization chamber dosimetry, within experimental uncertainties.
The results of this study contribute to the development of a novel, multidisciplinary therapeutic technique that integrates proton therapy with proton-induced sensitizer activation, with the objective of enhancing the selective destruction of Glioblastoma Multiforme cells under controlled proton irradiation conditions.
* This work has received funding from the European Innovation Council (EIC) under grant agreement No. 101130209. The EIC receives support from the European Union’s Horizon Europe research and innovation programme.
Speaker: Antigoni Kalamara (NCSR "Demokritos") -
11:00
Patient-Level SPECT Myocardial Perfusion Classification Using Tracer-Aware Deep Learning 15m
Single-photon emission computed tomography myocardial perfusion imaging is widely used for the non-invasive assessment of coronary artery disease. Although deep learning has shown promise for automated SPECT myocardial perfusion interpretation, most previous approaches have focused on single-tracer datasets and have not explicitly considered tracer-dependent variability. This study aimed to evaluate a tracer-aware deep learning framework for patient-level classification using SPECT myocardial perfusion polar maps.
A retrospective cohort of 640 patients was included, comprising 274 technetium-99m and 366 thallium-201 studies. For technetium-99m imaging, the task was normal versus abnormal perfusion classification, whereas for thallium-201 imaging, the task was low-risk versus intermediate/high-risk classification. Polar maps were processed as RGB images and resized to 224×224 pixels. A ResNet-18 model pretrained on ImageNet was used as a shared feature encoder with tracer-specific classification heads. Stress-only, rest-only, and dual-input stress-rest configurations were evaluated using repeated patient-stratified cross-validation and an independent held-out test set. Performance was assessed using AUC and balanced accuracy.
For technetium-99m studies, the stress-only model achieved a cross-validation AUC of 0.88±0.067 and test AUC of 0.88 [0.67-0.99], with balanced accuracy values of 0.75±0.061 and 0.87 [0.70-0.98], respectively. Although the dual-input model achieved a slightly higher test AUC of 0.91 [0.79-0.99], it did not consistently outperform the stress-only configuration. For thallium-201 studies, the stress-only model achieved a cross-validation AUC of 0.88 ± 0.051 and test AUC of 0.80 [0.71-0.89], with balanced accuracy values of 0.78 ± 0.083 and 0.80 [0.68-0.89]. Rest-only models showed lower and less consistent performance across both tracers.
These findings suggest that stress-phase polar maps contain the dominant discriminative information for patient-level SPECT myocardial perfusion classification. The proposed tracer-aware framework demonstrated stable performance across clinically distinct tracers, while rest information did not consistently improve classification. Stress-focused, tracer-aware deep learning may provide an efficient approach for automated SPECT myocardial perfusion analysis, although further external validation is required.Speaker: Mr Dimitrios Samaras (Medical Informatics and Biomedical Imaging Laboratory, Faculty of Medicine, University of Thessaly, 41500 Larissa, Greece) -
11:15
Combined Photopeak and Compton Analysis for Radiological Characterization of Activated Steel in Nuclear Reactor Decommissioning 15m
The radiological characterization of activated nuclear reactor components, resulting from neutron-induced reactions, which frequently also exhibit surface contamination, is essential for decision-making regarding their management during decommissioning. Prior to the dismantling and segmentation of reactor components, the selection of an appropriate cutting technology, aimed at minimizing of secondary radioactive waste production and reducing personnel radiation exposure, depends on accurate radiological characterization of radionuclides distributed both within the material volume and on their surfaces as contamination. Following dismantling and segmentation, accurate radiological characterization of radionuclides within the materials and on their surfaces is necessary to assess the effectiveness of decontamination, to select the appropriate decontamination and clearance procedures, as well as to establish appropriate management for the remaining radioactive waste.
In activated reactor components, certain radionuclides are embedded within the material matrix (activation products), others are present as surface contamination (fission products), while some may be present simultaneously both within the volume and on the surface. As an example, ⁹⁴Nb is highly insoluble, in contrast to ⁶⁰Co, which is soluble, although both are activation products. Consequently, ⁹⁴Nb is typically not observed as surface contamination, whereas the presence of ⁶⁰Co on surfaces is significant. In contrast, ¹³⁷Cs, a typical fission product, is predominantly found as surface contamination and only rarely within the material volume.
A non-destructive technique (NDT), based on a single gamma spectrometry measurement and Monte Carlo simulations using MCNP code, for the concurrent quantitative determination of activation within the materials and on their surfaces was developed at NCSRD in the frame of the EU PREDIS project.
For the discrimination and quantification of radioactivity on the surface and within the volume, two alternative and equivalent, accurate methods based on the analysis of the photopeak and the Compton edge were developed. The first method is based on the net counts of the detector in the photopeak and the Compton edge region arising from activities distributed both within the volume and on the surface of steel samples. The second method relies on the correlation between the Compton-to-photopeak ratio (C/P) and the absolute photopeak efficiency, as derived from simulated gamma-ray spectra. This relationship was subsequently utilized for the concurrent determination of both the activities.
Both methodologies produced consistent results, while the agreement between the nominal activities and the experimentally determined values remained within the 1σ to 2σ uncertainty range, confirming the reliability of the proposed approaches for the concurrent determination of surface and volume activities in steel using a single experimental gamma-ray spectrum of an unknown sample.Speaker: Angelos Markopoulos (National Center for scientific Research "Demokritos") -
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Preliminary Study of Radiation Exposure Following a Nuclear Weapon Test 15m
The Greek Atomic Energy Commission (EEAE), as the national regulatory authority, is responsible for ensuring radiological protection and nuclear safety. To this end, EEAE focuses on the assessment of nuclear or radiological emergencies, which may entail radiological risk for the country. In this context, a series of hypothetical nuclear detonation tests were simulated and studied, using atmospheric dispersion software HYSPLIT [1].
This work initially focuses on reproducing the 1957 Operation Plumbbob “Smoky” test in Nevada. The results, in terms of dose and dose rate, were compared with historical measurements and previous studies [2]. Following satisfactory agreement, a series of nuclear detonation scenarios were simulated across selected regions of interest in Europe. The detonations were reproduced with varying yield values. The resulting dose rates and projected public doses were evaluated and linked to corresponding protective actions.References
[1] Draxler, R. R., and G. D. Hess, An overview of the HYSPLIT_4 modeling system for trajectories, dispersion, and deposition. Aust. Meteor. Mag., 47, 295–308 (1998)[2] Rolph, Ngan, Draxler. Modeling the Fallout from Stabilized Nuclear Clouds Using the HYSPLIT Atmospheric Dispersion Model. Journal of Environmental Radioactivity, Vol136, pp. 41-55 (2014)
[3] Moroz, Brian E., Beck, Harold L., Bouville, André. Predictions of Dispersion and Deposition of Fallout from Nuclear Testing Using the NOAA-HYSPLIT Meteorological Model. Health Physics. Aug;99(2):252-69 (2010)
Speaker: Dr Nikos Salpadimos (Greek Atomic Energy Commission)
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Coffee Break 30m
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Neutron Physics, Facilities and Cross-Section MeasurementsConvener: M. Diakaki
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Measuring detector efficiency in γ spectroscopy: comparison of Monte Carlo simulations with experimental measurements 15m
Determining detector efficiency in $\gamma$ spectroscopy often relies on expensive and time-consuming experimental calibrations. This study presents a validated Monte Carlo simulation approach as a flexible and cost-effective alternative. Using RayXpert$^{®}$, we modeled the complex interactions of $\gamma$ photons with HPGe and NaI(Tl) detectors, accounting for intrinsic detector properties such as dead layer thickness and Gaussian energy broadening. For HPGe detectors, the deviation between simulated and experimental efficiency curves was maintained below 5%. A case study involving a bread roll sample spiked with $^{134}$Cs and $^{137}$Cs, scanned using photogrammetry, demonstrated the method’s applicability to irregular geometries. However, unaccounted True Coincidence Summing (TCS) effects introduced biases for cascade-emitting isotopes. For NaI(Tl) detectors, simulations incorporated user-defined spectra to address the poorer energy resolution, yielding results within $\pm$10% accuracy, suitable for routine quality control or environmental monitoring. The simulations were complemented by high-resolution CT scans of the detectors to identify discrepancies between real and simulated geometries.
This work underscores the potential of Monte Carlo simulations to reduce calibration costs and improve accessibility for laboratories, while highlighting key limitations, such as TCS and geometric mismatches, that warrant further investigation.
Speaker: Dr Anastasios Kanellakopoulos (University of Applied Sciences and Arts Western Switzerland) -
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Neutron induced cross-sections on Zr isotopes in the energy range 16-18 MeV 15m
Zr is a ductile metal, with exceptional resistance to corrosion and heat, properties which make it essential in nuclear reactors, chemical and medical applications and other. On top of that, Zr has a very low absorption rate of the neutrons released by nuclear fission reactions, making it an ideal cladding material for nuclear fuel rods. Therefore, neutron cross-section data must be available for a wide energy range.
In this context, natural Zr targets were irradiated in the neutron energy range 16-18 MeV at the Van de Graaff Tandem accelerator of NCSR “Demokritos”. The irradiated Zr targets, as well as reference Al and Au were measured at HPGe detectors, where γ-rays from various (n,x) channels were detected. The cross-sections of the (n,2n), (n,p) and (n,α) reactions on $^{90}$Zr, the isotope with the highest abundance (51.46%) of natural Zr, leading to $^{89}$Ζr, and metastable states of $^{90m}$Y and $^{87m}$Sr, respectively, have been deduced using the activation technique and will be presented here.
Speaker: Veatriki Michalopoulou (National Technical Univ. of Athens (GR)) -
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Determination of 14N(n,p)14C MACS using activation measurements and AMS 15m
Neutron capture cross sections are essential inputs for modeling stellar nucleosynthesis, particularly
for the slow neutron-capture (s-process.) The 14N(n,p)14C reaction is of particular interest, as it acts
both as a neutron poison and as a source of delayed neutrons through subsequent reaction chains.
An accurate determination of its Maxwellian Average Cross Section (MACS) is therefore essential
for reliable astrophysical models. However, the two most recent measurements exhibit non-
negligible discrepancies [1,2] and the precision achievable with time-of-flight measurements
remains limited, thus motivating the development of complementary approaches.
In this contribution, we present a new measurement, combining neutron activation and
Accelerator Mass Spectrometry (AMS) technique to investigate the 14N(n,p) 14C cross section with
high sensitivity and accuracy [3]. Several nitrogen-rich target materials have been irradiated with
quasi-Maxwellian neutron spectra at the n_TOF NEAR station, using different filter configurations
to probe the energy range relevant to s-process nucleosynthesis. Complementary irradiations at
LNL-INFN [4] are planned to further validate and benchmark the method. Following irradiation,
the freshly produced 14C atoms will be quantified at the CIRCE AMS facility [5], allowing
extraction of the corresponding MACS values.Speaker: Ioanna Goula (University of Campania L. Vanvitelli / INFN Napoli) -
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Development of a high-resolution neutron transmission station at the GELINA facility 15m
A new high-resolution neutron transmission station is being developed at the GELINA time-of-flight facility of the European Commission’s Joint Research Centre in Geel. The station is installed at flight path 3, employing an extended geometry with the sample positioned at approximately 200 m and the detection system at 400 m from the neutron producing target. This geometry enables significantly improved energy resolution for fast neutron measurements and is extending the capabilities of GELINA in the MeV energy region.
The setup is currently in the commissioning phase and features a flexible detection system based on an organic liquid scintillator with pulse-shape discrimination capabilities for efficient neutron-gamma separation. First test measurements have been performed using carbon samples to benchmark the total cross section and to evaluate the performance and stability of the system. In parallel, dedicated measurements are being carried out to investigate background components, including contributions from scattered neutrons and room-return effect, which are particularly relevant at extended flight paths.
The initial results demonstrate the potential of the new station for ultra-high-resolution transmission measurement and provide a solid basis for future total cross section studies. Once the commissioning phase is completed, systematic measurements of structural materials and light elements, of particular importance for both fission and fusion applications, can be carried out, contributing to the improvement and validation of current nuclear data evaluations.Speaker: Georgios Gkatis (EC-JRC) -
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Upgrade of the ELISA setup at the GELINA facility for neutron scattering experiments from 500 keV to 8 MeV 15m
ELISA (Elastic and Inelastic Scattering Array) is a unique experimental setup in Europe, located at the GELINA (Geel Electron Linear Accelerator) facility of the EC-JRC (European Commission - Joint Research Centre), in Geel, Belgium. The setup has been developed for measuring neutron scattering differential cross sections in time-of-flight (ToF) experiments [1, 2].
The original ELISA spectrometer consists of 32 organic liquid scintillators for the detection of the scattered neutrons, from which half of the detectors have EJ301 (NE-213 equivalent) as scintillation liquid, while the rest have EJ315 (C6D6). A 235U fission chamber is used for the measurement of the incoming neutron flux. As of recently, an additional arm with eight 6Li-glass detectors has been added, in an effort to expand the low-energy neutron detection limit below 1 MeV.
To test and validate the normal operation of the new components of the ELISA setup, new measurements with a natural carbon target are being performed. The performance of the 6Li-glass detectors with respect to gamma and neutron detection will be presented, together with a first estimation of the upgrade.
Speaker: Ms Anna Karakaxi (CEA Cadarache / NTUA) -
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Study of a New Liquid Scintillator Array for Neutron Scattering Cross Section Measurements at NCSR "Demokritos" 15m
In this work, three novel EJ-309-type liquid organic scintillators and one BC-501A scintillator were optimized for measurements of neutron elastic scattering $(n,\mathrm{el})$ and inelastic scattering $(n,\mathrm{inl})$ at NCSR "Demokritos". These four liquid scintillators were arranged in a new configuration at eight representative Legendre angles, specifically at $16.2^\circ$, $37.2^\circ$, $58.3^\circ$, $79.4^\circ$, $100.6^\circ$, $121.7^\circ$, $142.8^\circ$, and $163.8^\circ$. The total elastic cross section can be accurately determined by measuring the differential elastic cross section at these angles. The array was designed taking into account detector shielding requirements, minimizing detector cross-talk, and reducing scattering angle uncertainty, while ensuring maximum possible statistics. For accurate elastic cross-section measurements, pulse shape analysis (PSA) was initially performed to discriminate neutrons from gamma rays over a broad energy range. For this purpose, a semi-digital unit, MPD-4 from Mesytec, was used to carry out the PSA and to optimize the parameters for neutron--gamma $(n$--$\gamma)$ discrimination, using an $Am-Be$ $n/\gamma$ source, along with a set of $^{137}\mathrm{Cs}$, $^{54}\mathrm{Mn}$, and $^{60}\mathrm{Co}$ gamma-ray sources. To assess the detector efficiency over a wide neutron energy range, particularly between 1 and 6 MeV, GEANT4 simulations are currently in progress. In the coming months, the validity of the procedure will be evaluated by reproducing the well-established total cross-section value of $^{12}\mathrm{C}(n,\mathrm{el})$ scattering.
Speaker: Lamprianos Amanatidis (National Technical Univ. of Athens (GR)) -
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Neutron Flux Measurement with a Diamond Detector System in Harsh Environmental Conditions 15m
Numerous areas of nuclear physics, including fusion research, space-related technologies, and medical applications, require neutron detectors that maintain reliable performance under difficult environmental conditions. Among the available detection technologies, diamond-based detectors are regarded as particularly promising for radiation measurements in such environments, due to their exceptional electrical and physical properties [1]. In this work a diamond detector system was developed by the CIVIDEC Instrumentation [2] along with the necessary electronics. The detector consists of a single-crystal diamond sensor, produced by Chemical Vapour Deposition (CVD), with dimensions of 4 mm × 4 mm and a thickness of 50 μm. In addition, a 1.8 μm 6LiF foil was used as a neutron converter in order to enhance the detection efficiency for neutrons with energies below 1 MeV.
The detector was installed at the NEAR station of the n_TOF facility at CERN, where a white neutron beam is produced via spallation reactions induced by a pulsed proton beam, producing a mixed-field neutron environment. With a flight path of only 2.5 m from the spallation target, the NEAR station is characterized by a high instantaneous neutron flux (~1010 n/cm2/proton pulse) and is therefore considered a very challenging environment for active measurements. These demanding conditions offer an excellent opportunity to assess the performance of the diamond detector under high-rate irradiation. An experimental campaign was carried out using the 50 μm diamond detector at the NEAR station, during which the neutron flux was measured. The preliminary results of this campaign will be presented and discussed.- This project has received funding from the HORIZON-EURATOM-2023-NRT-01-06 call under grant agreement No 101164596. This project has received funding from the Euratom research and training program 2014-2018 under grant agreement No 847594 (ARIEL). Also, this project received some funding for transnational access via EURO-LABS CERN Transnational Access. This work was funded by CIVIDEC-Instrumentation GmbH
References
[1] T.Shimaoka, et al. (2021) Recent progress in diamond radiation detectors Functional Diamond,1:1, 205
220, DOI:10.1080/26941112.2021.2017758[2] CIVIDEC Instrumentation, https://cividec.at/
Speaker: Kalliopi Kaperoni (National Technical Univ. of Athens (GR)) -
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Activation cross section measurements of short-lived reaction products on Mo isotopes induced by 16 to 20 MeV neutrons 15m
The study of neutron-induced reaction cross sections for Mo isotopes is crucial for both research and applications in the nuclear industry, while they are vital for reactor safety. Neutron activation is a quite efficient technique for cross-section measurements; however, measurements involving short-lived products remain challenging. In this work, neutron capture cross-section measurements of reactions leading to short-lived products have been performed to improve data accuracy for stable $^{97}$Mo and $^{98}$Mo isotopes, which are currently limited by significant uncertainties. The activation measurements were carried out at the 3.5~MeV Tandem Van de Graaff accelerator at the ``MONNET'' facility of JRC-Geel in Belgium, while the $^{3}$H(d,n)$^{4}$He reaction was used to produce neutron beams with energies above 15~MeV. Thin metallic foils of enriched Mo, provided by the CERN n_TOF collaboration, were utilized. Reference samples of Al were used, and specifically the reference reaction $^{27}$Al(n,p)$^{27}$Mg, in the determination of the neutron flux at the target position. A newly installed automated pneumatic system was used for sample irradiation, transport, and radioactivity measurements to limit the decay of the radioactive products between irradiation and measurement. After the completion of each irradiation, the activity of the Mo targets and the reference foils was measured using a HPGe detector. The cross sections of the reactions $^{97}$Mo(n,p)$^{97\mathrm{m1}}$Nb and $^{98}$Mo(n,p)$^{98}$Nb, with half-lives of 58.7s and 2.86s, respectively, could be measured via the activation technique and were accurately determined, since the implementation of isotopically enriched targets prevents contamination from reactions of neighboring isotopes which produce the same residual nucleus. The new data are expected to reduce the discrepancies among existing data in the literature as well as evaluated nuclear data libraries and improve the reliability in applications requiring accurate neutron-induced reaction cross sections.
Speaker: Zoi Bari (National Technical University of Athens) -
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The 243Am(n,f) cross-section measurement at the EAR2 of the CERN n_TOF facility 15m
The fission reaction cross-section of 243Am is a quantity of interest for both the nuclear technology sector and basic nuclear physics research. The experimental datasets available however have significant deficiencies, especially at low energies, with no comprehensive measurement of the resonances of 243Am(n,f) reaction. Two measurements of the 243Am(n,f) cross-section were performed at the neutron time of flight facility n_TOF at CERN, at the experimental areas 1 and 2 (EAR1, EAR2) to provide a high-accuracy and high-resolution dataset covering a broad neutron energy range from thermal up to hundreds of MeV. In these measurements a Micromegas detector setup and high-purity actinide samples, especially prepared and provided by the EC-JRC Geel target laboratory, were used. The measurement in EAR2 was especially optimized to measure below the threshold of 243Am at the thermal and the resonance region.
In this work, a detailed overview of the measurement at EAR2 will be given, with a focus on the measurement at the resonances of 243Am. An overview of the experimental setup and the actinide samples will be given, along with preliminary resultsSpeaker: Nikolaos Kyritsis (National Technical Univ. of Athens (GR))
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Poster Prizes
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CLOSING REMARKS HNPS2026
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