XLZD 2026 Collaboration meeting

29 Jun 2026, 09:30 → 3 Jul 2026, 18:00 Europe/Zurich

Zürich

XLZD 2026 Collaboration meeting

The  2026 XLZD Collaboration meeting will be hosted by the University of Zürich. We will meet from Monday, Jun 29 to Wednesday July 1, 2026. The early-bird registration will be 160 CHF, late registration 220 CHF (including VAT). Please see the registration menu line for more details. 

After the collaboration meeting, we have reserved rooms for further work.
In particular, on Thursday there will be dedicated discussion on siting considerations and TPC construction, with further details TBA. There will also be a science/sensitivity focussed workshop on Thursday and Friday. This will include some tutorials for those new to XLZD or our software frameworks, featuring both Geant4 simulations and sensitivity/stats tools, as well as time to work collaboratively on some specific goals. If you already do or would like to contribute to WG1's efforts, please consider staying until at least Friday lunchtime to take part in the workshop.

 

For more info contact the local organiser team: 

• laura.baudis@physik.uzh.ch
• bjoern.penning@uzh.ch
• nicolas.angelides@uzh.ch 
• chiara.capelli@physik.uzh.ch
• jose.cuenca@physik.uzh.ch
• knut.moraa@physik.uzh.ch

Monday 29 June

09:30 Breakfast

Collab Meeting: Monday Morning

Convener: M. Patrick Decowski (Nikhef / University of Amsterdam)

1 Welcome

Speakers: Björn Penning, Laura Baudis

2 Spokespersons Report

Speakers: Daniel Akerib, Henrique Araujo, Prof. Marc Schumann (University of Freiburg (DE))

3 IB Chair Report

Speaker: Ran Budnik

4 Speakers Office

Speakers: Dr Alexandre Lindote, Teresa Marrodán Undagoitia

5 Path to CDR

Speakers: Henrique Araujo, Kevin Lesko

12:00 Lunch

Collab Meeting

Convener: Prof. Chamkaur Ghag

6 Siting Process

Speaker: Hugh Lippincott (UCSB)

7 Status Dark Matter

Speaker: Theresa Fruth (University of Sydney)

8 Status Double Beta Decay

Speakers: Brian Mong (SLAC), Thomas Brunner (McGill University)

9 XLZD Awards

Speakers: Prof. Kimberly Palladino (University of Oxford), Laura Baudis

15:30 Coffee Break

Collab Meeting

Convener: Teresa Marrodán Undagoitia

10 Requirements

Speakers: Daniel Tovey (University of Sheffield (GB)), Tom Shutt, Prof. Uwe Gerd Oberlack (Johannes Gutenberg University Mainz)

11 Requirements: Discussion

12 1.02 Xenon Acquisition

13 1.05 Cryostat

Poster Session: Apero & Poster Session

14 Cross Calibration Campaign for HPGe screeining

I have been running a cross calibration campaign involving several sites accross the collaboration to prep the screening facilities and prove that the results are accurate and reliable for use in XLZD. I hope here to present the first results of the study.

Speaker: Andrew Stevens (Universität Freiburg)

15 Status of Digital SiPM Development

Digital SiPM photo detectors offer several benefits over PMTs and SiPMs. They are radio-pure, allow for mechanically simple detector planes (low number of feedthroughs, low power), they deliver position and time of each photon with high granularity and may be cost effective. The challenges to address are the quality of the SPADs (dark counts, PDE) and the demonstration of a readout scheme suited for the application in XLZD. After the successful design and characterisation of a 1st generation digital SiPM chip using the IMS 350nm technology, we have designed a 2nd iteration for the XFAB 180nm technology with, for instance, a more versatile readout protocol, a much larger local hit buffer, precise time stamping and reduced power consumption. In the presentation, we want to summarise the status of the digital SiPM approach.

Speaker: Prof. Peter Fischer (Heidelberg University)

16 XLZD cryostat

We will present the updates on the design of the XLZD cryostat and the material searches.

Speaker: Dr Pawel Majewski (STFC/Rutherford Appleton Laboratory)

17 A large-diameter, dual-phase liquid xenon TPC in the unshielded PANCAKE facility

In this talk, I will provide an introduction to the Freiburg PANCAKE LXe platform, highlighting its capabilities for XLZD-related R&D. Then, I will present results from operating a 1.5-meter-diameter, 3-centimeter-deep, dual-phase TPC in this unshielded platform. Measurements of various detector- and LXe-specific quantities demonstrate that operating a large-diameter TPC is feasible in this high-background environment. These quantities include the electron lifetime dependent on purity and the electron drift velocity dependent on electric field.

Speaker: Sebastian Lindemann (University of Freiburg)

18 Quantifying the sensitivity of XLZD to low mass WIMPs using the Migdal effect

A small collaboration between The University of Melbourne and Subatech has been working to quantify the sensitivity of XLZD to low mass WIMPs in the presence of the Migdal effect. We present preliminary results from this work, showing the exclusion and discovery power of XLZD at different milestones of operation under the 40 t to 60 t "French press" detector filling strategy. These projections utilise state-of-the-art atomic calculations for the Migdal effect in liquid xenon developed in collaboration with theorists at The University of Melbourne. We use a background model comprised of standard physics backgrounds under detector performance assumptions established in the 2025 Requirements Taskforce, in addition to the latest empirical model of accidental coincidences (ACs) developed by Nikhef. This latest version incorporates updates from the XLZD AC Taskforce, including new spectra from current-generation experiments and improvements to the scalings of different components with detector geometry. It also uses newly created light collection efficiency maps for the 40 t and 60 t geometries, generated using the ray tracing software ANTS2.

Speaker: Robert James (The University of Melbourne)

19 HV delivery in XLZD

In this talk, I aim to discuss different designs for HV delivery in XLZD, in view of the target electric field, and various ideas for manufacturing and testing HV components. I plan to cover the ideas for the assembly and disassembly of such components, as well as the potential problems that may be encountered.

Speaker: Yanina Biondi (Karlruhe Institute for Technology)

20 Sustainable XLZD

We present an overview of the work being done within the XLZD-UK project for a sustainable future. We outline the framework we are using to establish the environmental footprint of the UK project and our plans to build on this to minimise the environmental impact of the project while delivering its scientific goals.

Speaker: Asher Cunningham Kaboth (University of London (GB))

21 Boulby Site Computing Infrastructure

A poster outlining the current computing infrastructure at Boulby Underground Laboratory and the improvements that are planned over the coming years to underpin the expansion of the laboratory.

Speaker: Philip Garrad

22 Cryostat Lifting and Handling

A brief overview of the challenges and current solutions on transporting, lifting, handling and maneuvering the cryostat with a focus on Boulby.

Speaker: Anmol Goyal (STFC, UKRI)

23 Xenoscope

The XLZD (XENON-LZ-DARWIN) collaboration is developing the next-generation observatory for dark matter, neutrino and rare-event physics. The detector will use a dual-phase xenon time projection chamber (TPC) with 60 tonnes of active xenon in a volume of approximately 3 meters in both height and diameter.

Xenoscope, at the University of Zurich, is a vertical demonstrator built to address the technical challenges associated with the large scaling up with respect to current experiments. The facility hosts a 2.6m tall TPC to study electron drift, diffusion, and light propagation in liquid xenon. It also serves as a test bench for hardware R&D such as characterising different coating materials or photosensor technologies.

This poster presents the Xenoscope facility and the results from the commissioning of the TPC and its first two science runs, including the observation of correlated S1–S2 signals from cosmic muons.

Speakers: Rebecca Hampp (UZH), Sana Ouahada (UZH)

24 Status of the MainzTPC Upgrade for Precision Low-Energy Recoil Measurements in Liquid Xenon

The MainzTPC is a dual-phase xenon time projection chamber (TPC) containing roughly 300 g of liquid xenon (LXe). It is dedicated to the study of scintillation and ionization processes in LXe for low-energy electronic and nuclear recoils. The detector has been designed to be the primary target in Compton and neutron scattering experiments to measure recoil energies in LXe down to 1 keV.

To improve position resolution in $x$ and $y$, the MainzTPC was redesigned to accommodate an array of 36 individually read-out silicon photomultipliers (SiPMs) in place of its monolithic top photomultiplier tube (PMT) and eight avalanche photodiodes. A primary goal of this upgrade is to enable sensitive measurements of low-energy nuclear recoils in LXe, in particular of the Migdal effect.

For this purpose, dedicated simulations of the detector response were performed. Additionally, a cryogenic amplifier board housing the SiPM array was developed and built. To address known instabilities in the liquid level, we rebuilt the level meters and level control based on camera observations of the liquid-gas interface. We report on the status of this work.

Speaker: Prof. Uwe Gerd Oberlack (Johannes Gutenberg University Mainz)

25 XLZD@Boulby - Rn Reduced Labs

An overview of the Rn Reduced spaces currently being proposed for XLZD@Boulby. Covers background information on their different purposes, their potential structural design, and their different configurations.

Speaker: Alex Jones (STFC-UKRI)

26 Photoluminescent detector materials as a potential source of delayed photon background in XLZD

Delayed photon signals remain an insufficiently constrained instrumental background in liquid xenon TPCs. One possible origin is nuisance photoluminescence (PL): absorption of 175 nm xenon scintillation photons by detector materials or surface contaminants, followed by delayed re-emission at near-UV and visible wavelengths. Recent studies at Nikhef R&D lab for Xe TPCs suggest that materials passing standard radiopurity and outgassing requirements may still fail optical-background requirements.

One of the materials that we have shown to PL is solder flux residue [https://arxiv.org/abs/2605.16845]. Resin- and rosin-based fluxes used in detector construction can leave behind PAH-containing residues after soldering and cleaning, producing measurable photoluminescence. These residues may remain as stains on soldered connections, dissolve into the bulk Xe volume, or exist in the detector as um-mm-sized flakes made during thermal cycling. Another detector material we have identified as photoluminescent is PEEK. Despite being widely considered a detector-safe structural polymer, its aromatic backbone is capable of producing PL emission under VUV excitation.

These studies motivate broader material screening and guidelines for material cleaning and handling for XLZD. Delayed photon backgrounds may originate not only from materials but also from contamination introduced by material preparation, cleaning and handling during assembly. We present examples of materials observed to photoluminesce under UV and VUV illumination and make suggestions for future XLZD cleanliness and screening strategies.

Speaker: Anna Hurhina (Nikhef)

27 XLZD@Boulby - Underground Transportation Strategies

An overview of the strategies being implemented at Boulby for underground conveyance both through the mine and labs. Primarily focussed on the types of parts we are expecting in terms of their size and weight along with how we hope to transport them through various cleanliness levels on carts.

Speaker: Mr Martin McBrinn (STFC-UKRI)

28 Options Analysis for the LXe Skin Detector

The LXe skin detector acts as an important veto system for the TPC as well as providing electrical insulation, thermal decoupling, and radiation shielding between the TPC and the ICV. In this poster we report on the ongoing early studies on instrumentation options for the skin detector: PMTs, SiPMs, WLS fibres and an ionisation-based readout.

Speaker: Ricardo Peres (Imperial College London)

29 XLZD TPC Maintenance Challenges

TPC maintenance may be a large driver for the design of several systems within the experiment. As with all engineering endevours, there is an ideal to aim for when pursuing simple and easy maintenance of a given assembly. XLZD poses quite the challenge for easy access to the full TPC for major maintenance, e.g. 40 t to 80 t detector upgrade. This poster will lay out some of the major challenges posed and possible solutions.

Speaker: Harry Byrne (STFC - RAL)

30 Novel Purity Sensors in Liquid Xenon Time Projection Chambers

The XLZD observatory will be a next-generation, multi-tonne xenon detector capable of probing dark matter and neutrino physics at unprecedented sensitivity.

Reaching the anticipated sensitivities requires extremely pure xenon, so that rare-event ionisation signals are not degraded by capture in electronegative impurities diffusing in the liquid. Achieving this purity relies on advanced purification techniques, continuous recirculation, and dedicated purity monitoring systems.

Conventional LXe purity monitoring modules are bulky and must be placed outside the sensitive detector volume. A novel approach with minimal footprint and scalability is the use of carbon nanotube-based sensors that can be placed directly in the instrumented volume.

In this poster, I will present the current R&D efforts at KIT on developing purity sensors based on single-layer carbon nanotubes, along with the status of their design and production, as a step towards novel purity-sensing technologies for future LXe-TPCs.

Speaker: Tom Sonius (Karlsruhe Institute of Technology)

31 Studies of dielectric breakdown in liquid xenon with the MOTION detector

Liquid xenon (LXe) is predicted to sustain bulk electric fields approaching 1 MV/cm; however, experiments consistently observe dielectric breakdown at much lower field strengths, comparable to the operating fields ($\mathcal{O}$(10--100) kV) anticipated for the future XLZD detector.

The MOTION detector, an $\sim$70~kg LXe setup at the Karlsruhe Institute of Technology, is used to study dielectric breakdown in LXe. We investigate how local field enhancement at electrode asperities and stressed electrode areas affect breakdown using various diagnostic methods. This poster will highlight recent advances in electrode-surface scanning and the development of experimental instrumentation to support these studies.

Speaker: Keyu Ding (Karlsruhe Institute of Technology)

32 Copper–Kapton Flex Cables for the XLZD Photosensor Readout

Copper–Kapton flex cables remain a promising alternative to coaxial cables for the XLZD photosensor readout. Detailed measurements of a 2-layer prototype, together with ongoing tests of a representative 3-layer "stripline" prototype, indicate that signal transmission over the required cable lengths is feasible with acceptable attenuation for a 100 MS/s DAQ. In particular, tests and simulations suggest that the flex-cable performance is suitable for both the Skin detector and the TPC readout and may negate the need for cold pre-amplification at the source.

We will present the latest prototype measurements, a preliminary discussion of the cabling design, and the fabrication status of a 20-m flex cable representative of the XLZD cabling requirements for further validation. These results strengthen the case for flex cables as a practical readout solution for XLZD and will inform the next steps in the system design.

Speaker: Arindam Roy (Imperial College London)

33 Improved WIMP Limits with a Focussed Test Statistic

The likelihood ratio test statistic is guaranteed to be optimal only for simple vs. simple hypotheses. For setting limits, however, we usually deal with compound hypotheses, in which case no such guarantee exists. I apply a focused test statistic to the WIMP limits of the XENONnT SR0 dataset, concentrating the statistical power around a WIMP rate of zero. The resulting limits improve on those from the likelihood ratio by 20–30% across the 20–300 GeV/c² WIMP mass range.

Speaker: Torben Flehmke (Stockholm University)

34 XLZD – TPC Installation and Maintenance Strategies

A site agnostic approach to installation of the Time Projection Chamber (TPC) into its final position within the XLZD detector - looking at different potential options for the detector design to simplify assembly staging and enable TPC maintenance access. Many of the options presented will have impacts on detector design requirements but should all hold a solution to the problem of gaining full access to the TPC without de-cabling the top and bottom PMT arrays.

Speakers: Alex Jones (STFC-UKRI), Mr Harry Byrne

35 Development and First Results of a Cryogenic Heat Pump Demonstrator for High-Flow Radon Distillation in XLZD

One of the biggest challenges for XLZD will be the mitigation of ²²²Rn to a level ten times lower than the solar pp neutrino background. While cryogenic distillation has been proven to be a suitable tool to reduce the radon background in current-generation LXe TPCs, XLZD will require a purification flow approximately 200 times larger. This high flow necessitates the development of new technologies to provide the required cooling and heating power associated with the cryogenic distillation process.

In this poster, we present our first results from a small-scale cryogenic heat pump demonstrator, which serves as a proof of concept for such a technology. The demonstrator achieved cooling and heating powers of about 120 W each while consuming 386 W of electrical power. This is sufficient to operate a small distillation system with a purification mass flow of about 3.1 kg/h. The results of this demonstrator are put into perspective for the XLZD experiment using a simplified scaling model, showing that a radon distillation system with a total mass flow of 1600 kg/h and total required cooling and heating powers of about 60 kW each will be needed to achieve the ambitious goals of the experiment.

The project is financed through the ERC AdG "LowRad" project number 101055063.

Speaker: Daniel Wenz

36 Field Cage Design Concepts for XLZD

Within the UK pre-construction project, the Oxford XLZD team is leading the design of the field cage, an integral component of the delicate inner detector. The field cage encapsulates the liquid xenon target, maximises light collection, and creates a homogeneous electric field to enable particle identification and three-dimensional event reconstruction. In light of XLZD's increased size and stringent requirements, we are evaluating traditional scaled-up design options based on previous detectors, as well as promising novel design concepts. This talk will introduce the collaboration to the designs under consideration and provide an overview of the ongoing options analysis that will form the basis for the CDR input.

Speaker: Kevin Thieme (University of Oxford)

37 Low-activity-stem PMTs for XLZD: towards ultra-low backgrounds

The next-generation liquid xenon experiment XLZD will probe the WIMP parameter space down to the irreducible neutrino background. It also aims to achieve excellent sensitivity to neutrinoless double beta decay of $^{136}$Xe, as well as to neutrinos from the atmosphere, the Sun, and supernovae. Achieving such sensitivities requires a detailed understanding and mitigation of background contributions.
In particular for the search for the neutrinoless double beta decay of $^{136}$Xe, special care must be taken to minimize the activity of $^{214}$Bi, a daughter isotope of $^{226}$Ra. The main contribution to this background arises from detector materials, primarily the PMTs and the cryostat. Significant effort is therefore devoted to the selection and development of low-radioactivity PMTs, with a strong focus on reducing $^{226}$Ra contamination.
This work presents the screening results of 16 Hamamatsu R17317 PMTs with low-activity stems. The measurements were performed using the Gator facility, a low-background, high-purity germanium (HPGe) gamma-ray spectrometer operated by the University of Zurich at the Gran Sasso National Laboratory (LNGS).
A $^{226}$Ra activity of (0.21 $\pm$ 0.02) mBq/PMT was measured, corresponding to a reduction by more than a factor of two compared to the PMTs employed in XENONnT.

Speaker: Margherita Noia (University of Zurich)

38 Precision Characterization of Internal Radioactive Background for XLZD

With the projected background reductions through cryogenic distillation systems and material selection, the XLZD detector aims for an internal radioactive isotope background an order of magnitude lower than the solar $pp$ neutrino-electron scattering rate. Given a target mass of $O(10)\,$tonnes of liquid xenon (LXe), XLZD will have sufficient statistics to measure the solar $pp$ flux with sub-percent accuracy. To realize this potential, a dedicated effort to characterize the measurement uncertainties for each radioactive background component is just as critical.

This DFG-funded project focuses on investigating, improving, and standardizing the measurement sensitivities for krypton ($^{85}\mathrm{Kr}$), radon ($^{222}\mathrm{Rn}$ and $^{220}\mathrm{Rn}$), and detector-material-induced backgrounds. For krypton, the project introduces the Xenon Filter for Krypton detection Enhancement (XeFKrE) system. Integrated into the LowRAD krypton distillation column and utilizing the Automatic Rare Gas Mass Spectrometer (Auto-RGMS), XeFKrE is designed to produce a well-defined $^{\mathrm{nat}}\mathrm{Kr}$ calibration source at the $O(10)\,$ppq level with better than 10% accuracy. For radon, the project plans to establish a full decay-chain analysis framework to constrain the rates of the beta-emitting progeny, $^{214}\mathrm{Pb}$ and $^{212}\mathrm{Pb}$, to within 1%. This framework leverages existing data from $^{222}\mathrm{Rn}$ and $^{220}\mathrm{Rn}$ calibrations, incorporating continuous source injection, algebraic Bateman equations for decay chains, and empirical modeling of loss mechanisms such as the plate-out effect. Finally, for material backgrounds, the project explores machine learning techniques that optimize the Monte Carlo simulation performance in the solar $pp$ region of interest (ROI). The ultimate goal of this work is to provide a realistic error budget reference for the electron-recoil detection channel in XLZD.

This work is supported by DFG under project number 565663248 and ERC AdG LowRad under project number 101055063.

Speaker: Ying-Ting Lin (University of Münster, Institute for Nuclear physics)

39 The Bedretto Underground Lab as R&D Facility for XLZD

Swiss research groups deliver leading contributions to particle, astroparticle, and gravitational-wave physics at major international facilities such as SURF, LNGS, and Boulby. To facilitate next-generation, large-scale projects, the Bedretto Underground Laboratory for Physics (Bedrettolab) is being developed as a premier low-background R&D facility. Located in Ticino, just two hours from Zurich via public transport, the laboratory features horizontal access and a 4000 m.w.e. overburden. Recent characterisation measurements by the University of Zürich establish low muon, gamma, neutron, and radon backgrounds, alongside minimal ambient vibration and electromagnetic noise. 

A primary goal is to utilise Bedrettolab as a flexible development and systematics testbed for the XLZD liquid xenon experiment, enabling underground R&D of hardware, rare background processes and systematic studies in a well-shielded environment. The project will take place in two stages: First, the installation of underground clean-lab infrastructure to host dark matter, neutrino, and quantum sensing experiments, including XLZD demonstrators. Then, establish a dedicated gravitational-wave testbed. Bedrettolab’s proximity to leading European institutions and management structure will allow for fast and efficient R&D operations and greatly enhance our ability to perform necessary R&D for XLZD.

Speakers: Björn Penning, Nicolas Angelides (University of Zurich)

40 Enabling XLZD at Boulby: Underground Infrastructure and Site Services

The Boulby Underground Laboratory provides a deep, low-background environment for next-generation rare-event physics experiments, including XLZD. Located at approximately 1100 m depth within a working mine, the site offers intrinsically low gamma and neutron backgrounds and low radon levels. These characteristics make it highly suitable for ultra-sensitive dark matter and neutrino detection experiments.

The proposed facility adopts a phased development strategy. An initial core laboratory supports detector assembly, integration, and commissioning within controlled clean environments, followed by the construction of a dedicated large-scale experimental hall tailored to XLZD. This approach enables early underground access while reducing technical and schedule risk.

Integrated site services—including resilient power distribution, HEPA-filtered ventilation, chilled-water cooling, low-radon air systems, on-site cryogenic generation, and high-bandwidth data connectivity—are designed to support both deployment and long-term operation. Leveraging Boulby’s established infrastructure and operational experience, this concept delivers a scalable, lab aligned with the full lifecycle requirements of XLZD.

Speaker: Jon Elmer (STFC)

41 The XLZD Assay Database & Background Calculator

XLZD will operate at an unprecedented scale. New sensitivity requirements combined with the scale-up in detector mass demand significantly stricter radiopurity requirements and far more rigorous tracking and analysis of background contributions from detector construction materials. Existing tools from predecessor experiments require significant updating to manage the logistical demands of XLZD.
This poster will present the XLZD material screening database and background budget calculator - a centralised system designed to manage the full scope of radiopurity screening data. The database stores material properties and assay results, tracks sample locations and states for radon plate-out calculations, and links detector components to Geant4 simulations for background activity scaling. We demonstrate the full pipeline using existing assay results and preliminary XLZD simulations, quantifying the contribution of each component to the total background budget. The system is live on King’s College London servers and, through an intuitive interface, acts as a searchable database for assay results and sample status, directly informing procurement and design decisions. Together, these tools give XLZD the logistical and analytical infrastructure needed to meet the background requirements for the next generation of rare event observatories.

Speaker: Bram Miles (University College London)

42 Preliminary studies of the LCE of the XLZD Outer Detector

In the framework of the XLZD collaboration, we present preliminary Monte Carlo simulation studies focused on the design and optimization of the Outer Detector (OD) system. This work evaluates a baseline, XENON-like Neutron Veto configuration based on gadolinium-doped water without an integrated metallic inner vessel.
We investigate the Light Collection Efficiency (LCE) of the system by varying the total number and spatial distribution of the 8-inch PMTs. Furthermore, we assess the impact of implementing Winston cones as light concentrators to increase the effective coverage per channel, as well as the implications in terms of LCE of introducing liquid scintillator (LAB) within the water volume.
Further Monte Carlo studies are ongoing aiming to systematically define the optimal detector dimensions and PMT number required to maximize neutron tagging efficiency, providing key inputs for a configuration that could be adopted during the initial phase of the XLZD experiment.

Speakers: Filippo Campanini, Marco Selvi (INFN Bologna), Pietro Di Gangi

Tuesday 30 June

Collab Meeting

Convener: Jonathan Hays (University of London (GB))

43 1.03/04 Cryogenics+Purification

44 Recovery Strategy

45 1.06 Xe Detector

Speakers: Prof. Kimberly Palladino (University of Oxford), Prof. Marc Schumann (University of Freiburg (DE)), Tom Shutt

46 1.07 Outer Detector

Speakers: Pietro Di Gangi, Sergey Burdin (University of Liverpool (GB))

10:30 Coffee Break

Collab Meeting

Convener: Marco Selvi (INFN Bologna)

47 1.08 Calibration

48 1.09 DAQ, Electronics

49 1.10 Controls

12:30 Lunch

Collab Meeting

Convener: Masaki Yamashita (Nagoya University)

50 Overview of Rn backgrounds and Assay Techniques

I will describe the 222Rn backgrounds in XLZD, try to come up with a bottom up estimate as I see it. I will also like to talk about Rn assay techniques.

Speaker: Brian Mong (SLAC)

51 Low radon and low internal radioactivity (LowRad) for XLZD

Next generation liquid noble gas detectors for the search of weakly interacting massive particles (WIMPs), such as XLZD, aim to increase their sensitivity down to the neutrino fog. This ambitious goal can only be achieved by further reducing the detector backgrounds dominated by LXe intrinsic isotopes of $^{85}$Kr and $^{222}$Rn to a factor ten below the unshieldable solar and atmospheric neutrino background.
It could be shown for XENONnT that cryogenic distillation is a suitable method for reducing these backgrounds, paired with stringent material selections and specialized detector designs. XLZD will require an approximately 20-times higher radon purification flow, which necessitates the development of new technologies to provide the required cooling and heating power associated with the cryogenic distillation process while meeting the requirements of the various underground laboratories.

In the ERC Advanced Grand project LowRad the technical foundations for the next generation cryogenic krypton and radon removal systems are developed. This includes among other things a krypton concentrator and a radon removal system including a cryogenic heat pump. The concentrator aims to reduce the krypton enriched xenon off-gas losses during cryogenic distillation by another factor 1000 (to 6 g/day) making a continuous online distillation during regular detector operation feasible. The cryogenic heat pump of the radon removal system is necessary to address the heating and cooling power demands of 60 kW each (equivalent to 125 kW electrical power) of future radon removal systems (XLZD-sized, 1600 kg/h), which is required to reduce the $^{222}$Rn background to less than 0.1 µBq/kg, or less than 1 atom in 100 mol xenon. This talk will present the working principles and design choices of each system, show the status of both demonstrators currently developed in Münster, and outlines the prospects for the next steps towards the final systems for XLZD.

The project is financed through the ERC AdG "LowRad" project number 101055063.

Speaker: Lutz Althüser (University of Münster)

52 CVD Nickel as a Structural Material for Next Generation Low-Background Physics Detectors

The construction of next generation low-background detectors requires, material that balances radiopurity with superior mechanical properties. While electroformed copper is currently known to have the best radiopurity levels, however it is constrained by slow depositions rate, limited structural strength and complex manufacturing requirements. The talk introduces chemical vapour deposition (CVD) nickel as an alternative, evaluating its potential to surpass current standards. CVD nickel exhibits significant advantage over electroformed copper, offering faster deposition rates, robust mechanical properties and superior weldability. Essential for developing thinner, complex and more efficient produced detector geometries. Despite the promising attributes, there are some critical unknown gaps regarding contamination free fabrication and welding processes.

The talk outlines the initial phase of a systematic research program designed to validate CVD Ni as a viable material choice for detectors. Our current efforts focus on establishing a foundational understanding of the material’s performance through evaluation of existing literature and plan the program to include the shortcomings of the prior research. We are developing a close collaboration with the world’s two primary CVD Ni suppliers as well as the potential pressure vessel fabricators to define the construction code requirements and material constraints. Conduct material test to establish a baseline assessment of material properties as well as exploring different welding techniques. This work will form the basis of an upcoming experimental campaign, which will characterize the radiopurity and mechanical properties and, inform the development of code compliant fabrication for pressure vessel applications.

A central focus of this research is the development of validatory methods for fabrication and welding process suitable for implementation within underground laboratory environments while maintaining the radiopurity requirements. By addressing these challenges, this work aims to provide the research community with a more suitable material for future research requirements. The research provides a foundational framework for the use of CVD Ni in low-background physics experiments. By bridging the gap between the material innovation, radiopurity requirements and construction constraints to address the demands of future physics experiments.

Speaker: Naman Walia

53 Exploring concepts for ReStoX at SNOLAB

The ReStoX concept is, in itself, simple: a pressure vessel with cryopumping capability, able to safely recover and store high-pressure xenon at room temperature. Beyond this concept lie complex, site-dependent engineering challenges that influence the design with aspects such as laboratory accessibility, on-site vs. off-site construction, cooling power requirements, operational complexity and cost. This talk will discuss the baseline ReStoX concepts for SNOLAB and explore alternative approaches that could significantly lower the costs and complexity of the SNOLAB Xenon Storage.

Speaker: Frédéric Girard (McGill University)

54 XLZD – Installation Planning and Schedule

An overview of the existing XLZD@Boulby schedule and how it might be adjusted to suit a site agnostic installation timeline in advance of the XLZD Concept Design Review (CDR). The current schedule covers key components from the Work Breakdown Structure (WBS) from completion of the XLZD CDR through to commissioning of the XLZD detector, identifying potential critical paths, and estimating lead times for each component.

Speaker: Alex Jones (STFC-UKRI)

55 One TPC to Rule Them All: A Unified LXe Observatory for DM and Neutrinoless Double Beta Decay

The two research communities of Neutrinoless Double Beta Decay ($0\nu2\beta$) and dark matter Weakly Interacting Massive Particle (WIMP) searches have had a large technological overlap in their use of the Liquid Xenon (LXe) Time Projection Chamber (TPC). As detectors get larger and more complex, the possibility of combining their efforts into one mutually beneficial experiment becomes important to explore. We present a detector design for a dual-phase, dual-chamber TPC whereby an inner hermetic sapphire vessel acts as a separate volume containing about 5 tonnes of active LXe enriched in $^{136}$Xe for $0\nu2\beta$ searches, embedded within the larger TPC with a now depleted active LXe volume of about 60 tonnes, optimised for WIMP searches. Our projected sensitivities for the $0\nu2\beta$ half life and the spin-independent WIMP-nucleon cross section at 50 GeV/c$^2$ are $2 \times 10^{28}$ years and $2 \times 10^{-49}$ cm$^2$, respectively. The practical challenges in incorporating such a second volume in a TPC are discussed, together with opportunities for more ambitious scenarios.

Speaker: Nadav Hargittai (Weizmann Institute of Science)

16:00 Coffee

Collab Meeting: L2 Breakout Time

56 L2 Breakout Time

18:30 Workshop Dinner - Zunfthaus zur Zimmerleuten (starts with Apero)

Zunfthaus zur Zimmerleuten
Limmatquai 40, 8001 Zürich, Schweiz

https://zunfthaus-zimmerleuten.ch/en/

Wednesday 1 July

Collab Meeting

Convener: Thomas Brunner (McGill University)

57 WIMP sensitivity

Rory

58 Accidentals

59 0nubb sensitivity

60 Simulations

61 Overview and Discussion

Speakers: Adam Softley-Brown (University of Sheffield), Jelle Aalbers (University of Amsterdam / Nikhef)

10:30 Coffee

Collab Meeting

Convener: Kathrin Valerius

62 1.11 Computing

63 1.12 Screening

64 1.13 Interfaces and Integration (I&I)

12:30 Lunch

Collab Meeting

Convener: Dr Alexandre Lindote

65 R&D Needs - Discussion

Speakers: Daniel Tovey (University of Sheffield (GB)), Tom Shutt, Prof. Uwe Gerd Oberlack (Johannes Gutenberg University Mainz)

66 XLZD Project Structure

Speaker: Henrique Araujo

67 Outreach Planning

Speakers: Erica Caden (SNOLAB), Nicolas Angelides (University of Zurich)

68 Farewell

Speakers: Björn Penning, Laura Baudis

Thursday 2 July

Thursday discussion sessions: Outer Detector discussion

Post-meeting discussion sessions

Conveners: Pietro Di Gangi, Sergey Burdin (University of Liverpool (GB))

Thursday discussion sessions: Siting Discussion

Post-meeting discussion sessions

Convener: Hugh Lippincott (UCSB)

Thursday discussion sessions: Xe detector WG meeting

Post-meeting discussion sessions

Conveners: Prof. Kimberly Palladino (University of Oxford), Prof. Marc Schumann (University of Freiburg (DE))

Analysis Workshop: WG1 Workshop introduction and talks

Workshop for analysis
leads: Jelle and Adam

Conveners: Adam Softley-Brown (University of Sheffield), Jelle Aalbers (University of Amsterdam / Nikhef), Knut Dundas Morå (Universität Zürich)

Analysis Workshop: WG1: Introduction to sensitivity tools

Workshop for analysis
leads: Jelle and Adam

Conveners: Adam Softley-Brown (University of Sheffield), Jelle Aalbers (University of Amsterdam / Nikhef)

Analysis Workshop: WG1: Introduction to simulation tools

Workshop for analysis
leads: Jelle and Adam

Conveners: Adam Softley-Brown (University of Sheffield), Jelle Aalbers (University of Amsterdam / Nikhef)

Analysis Workshop: WG1: Variance reduction/ importance boosting in simulations

Workshop for analysis
leads: Jelle and Adam

Conveners: Adam Softley-Brown (University of Sheffield), Jelle Aalbers (University of Amsterdam / Nikhef)

Friday 3 July

Analysis Workshop: WG1: Flash talks

Workshop for analysis
leads: Jelle and Adam

Conveners: Adam Softley-Brown (University of Sheffield), Jelle Aalbers (University of Amsterdam / Nikhef), Knut Dundas Morå (Universität Zürich)

Analysis Workshop: WG1: Introduction to sensitivity tools

Workshop for analysis
leads: Jelle and Adam

Conveners: Adam Softley-Brown (University of Sheffield), Jelle Aalbers (University of Amsterdam / Nikhef)

Analysis Workshop: WG1: Introduction to simulation tools

Workshop for analysis
leads: Jelle and Adam

Conveners: Adam Softley-Brown (University of Sheffield), Jelle Aalbers (University of Amsterdam / Nikhef)

Analysis Workshop: WG1: Variance reduction/ importance boosting in simulations

Workshop for analysis
leads: Jelle and Adam

Conveners: Adam Softley-Brown (University of Sheffield), Jelle Aalbers (University of Amsterdam / Nikhef)

Analysis Workshop: WG1: Close out of formal program, farewell + lunch

Workshop for analysis
leads: Jelle and Adam

Conveners: Adam Softley-Brown (University of Sheffield), Jelle Aalbers (University of Amsterdam / Nikhef), Knut Dundas Morå (Universität Zürich)

Analysis Workshop: WG1: Free room for further work

Workshop for analysis
leads: Jelle and Adam

Convener: Knut Dundas Morå (Universität Zürich)