Speaker
Description
Advanced particle accelerator facilities with ultrafast beams require high spatial and temporal resolution beam diagnostics to work at their full potential. Conventional non-destructive beam-position monitors (BPM) are not sufficient for ultrafast beams, as rapidly varying temporal beam characteristics (ps-scale or faster) are obscured by ns-scale detector response times.
RadiaBeam Technologies and University of Colorado, Boulder are developing a single-shot nondestructive 3D BPM, measuring two transverse spatial dimensions and the temporal dimension. 3D beam position monitoring is especially critical for applications with multiple ultrashort electron bunches, including plasma wakefield acceleration (PWFA) [1] or ion channel laser [2]. In PWFA, for example, the optimal bunch spacing is approximately 100-150 um (300-450 fs), depending on plasma parameters, and the trailing (witness) beam acceleration is strongly dependent on the relative temporal spacing and transverse misalignment of the two beams.
The 3D BPM is based on the electro-optic sampling method: a laser pulse passing through a nonlinear crystal interacts with the strong transverse electric fields of a relativistic charged particle beam, experiencing polarization rotation via the Pockels effect when the fields are overlapped in time [3-5]. Ultrafast time resolution is obtained via pulse front tilt, encoding the temporal axis onto a spatial axis of the laser beam. This method has been demonstrated in our prototype device at SLAC FACET-II for 2D operation (time and one transverse spatial dimension) [6]. Our upgraded design is based on axicon focusing that, under ideal conditions, can resolve 10 fs-scale beam separations and 10 um-scale transverse beam position. The device has been installed at SLAC FACET-II and is currently being commissioned.
In this presentation, the operating principles and design of the 3D BPM will be reviewed, including preliminary experimental results. Time of arrival measurements confirm the high temporal resolution, and BPM measurements are under way. Potential applications of this design outside of two bunch experiments will be discussed.
Acknowledgements
This work is supported by the US Department of Energy under the SBIR award DE-SC0023977.
[1] C. Joshi et al., Plasma Phys. Control. Fusion 60, 034001 (2018).
[2] M. Litos et al., in 2018 IEEE Advanced Accelerator Concepts Workshop (AAC), Breckenridge, CO, USA, Aug. 2018, pp. 1-5.
[3] A. L. Cavalieri et al., PRL 94, 114801 (2005).
[4] S. Casalbuoni et al., PRSTAB 11, 072802 (2018).
[5] K. Hunt-Stone et al., NIM-A 999, 165210 (2021).
[6] C. Hansel et al., manuscript in preparation.
| Working group | WG5 |
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