The Cornell University Energy Recovery Linac (ERL) photoinjector has recently demonstrated operation at 20 mA for approximately 8 hours, utilizing a multialkali photocathode deposited on a Si substrate. We describe the recipe for photocathode deposition, and will detail the parameters of the run. Post-run analysis of the photocathode indicates the presence of significant damage to the substrate, perhaps due to ion back-bombardment from the residual beamline gas. While the exact cause of the substrate damage remains unknown, we describe multiple surface characterization techniques (X-ray fluorescence spectroscopy, X-ray diffraction, atomic force and scanning electron microscopy) used to study the interesting morphological and crystallographic features of the photocathode surface after its use for high current beam production. Finally, we present a simple model of crystal damage due to ion back-bombardment, which agrees qualitatively with the distribution of damage on the substrate surface.
@article{arxiv.1110.3529,
title = {Photocathode Behavior During High Current Running in the Cornell ERL Photoinjector},
author = {Luca Cultrera and Jared Maxson and Ivan Bazarov and Sergey Belomestnykh and John Dobbins and Bruce Dunham and Siddharth Karkare and Roger Kaplan and Vaclav Kostroun and Yulin Li and Xianghong Liu and Florian Löhl and Karl Smolenski and Zhi Zhao and David Rice and Peter Quigley and Maury Tigner and Vadim Veshcherevich and Kenneth Finkelstein and Darren Dale and Benjamin Pichler},
journal= {arXiv preprint arXiv:1110.3529},
year = {2015}
}