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@ARTICLE{Bazyl:643478,
author = {Bazyl, Dmitry and Floettmann, Klaus and Vogel, Elmar and
Zagorodnov, Igor},
title = {{M}ultiphysics {A}nalysis of {C}ryogenically {C}ooled
{P}hotocathode in a {CW} {SRF} {I}njector cavity},
reportid = {PUBDB-2026-00225, arXiv:2508.11764},
year = {2025},
abstract = {The paper evaluates the thermal regime of a cryogenically
cooled copper photocathode integrated into a continuous-wave
superconducting radio-frequency injector cavity with direct
thermal contact. Such a photoinjector layout is being
developed at DESY and has recently demonstrated a
record-high 50 MV/m axial electric field in radio-frequency
tests, marking an important milestone. To address the
thermal effect of the picosecond excitation laser, we first
develop a two-temperature model to describe the temperature
of the emitting surface at cryogenic temperatures and solve
it numerically. Subsequently, we present a one-temperature
model of the bulk photocathode coupled with an
electromagnetic model of the injector cavity. For the
current injector design, we predict a negligible impact of
the laser on the intrinsic quality factor of the cavity,
identifying instead the cryogenic stability of the copper
cathode as the primary operational limit. To overcome
cooling challenges, we propose an improved configuration of
the cathode plug. For the proposed geometry, the
multiphysics analysis confirms stable performance at a
nominal 2 W laser power, sufficient for 100 pC beams at 1
MHz under optimistic quantum efficiency assumptions.
Operation at higher laser loads will benefit from further
dedicated cryogenic analysis.},
cin = {MSL},
ddc = {530},
cid = {I:(DE-H253)MSL-20170609},
pnm = {621 - Accelerator Research and Development (POF4-621) /
6G13 - Accelerator of European XFEL (POF4-6G13)},
pid = {G:(DE-HGF)POF4-621 / G:(DE-HGF)POF4-6G13},
experiment = {EXP:(DE-H253)XFEL(machine)-20150101},
typ = {PUB:(DE-HGF)25},
eprint = {2508.11764},
howpublished = {arXiv:2508.11764},
archivePrefix = {arXiv},
SLACcitation = {$\%\%CITATION$ = $arXiv:2508.11764;\%\%$},
doi = {10.3204/PUBDB-2026-00225},
url = {https://bib-pubdb1.desy.de/record/643478},
}