Ionization Effects - February 12, 2019

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Meeting Info

We will meet Tuesday February 12 at 11:00 am EST in TL 2236.

For those calling in we'll use the Blue Jeans [1] audio conference system.

Meeting ID: 366850636# 
Moderator Passcode: 2864
Meeting URL (for video and/or audio call in):
Phone number (for audio call in): 1-888-240-2560


Background Material
PRAB (lifetime studies w/ bulk GaAs) media:high current lifetime_in print.pdf
PSTP17 (lifetime study w/ GaAs/GaAsP) media:PSTP2017_Grames_v1.pptx media:PSTP2017_Grames_Final.pdf

Paper Outline

Motivation for high polarization at high current
Requires useful long operating lifetime (e.g. 2mA is 1200C/week)
QE uniformity important for beam quality, especially parity violation experiments
Applications: Electron Ion Collider (>50 mA), Polarized Positron Source (>10mA) or Moller Standard Model test (>0.2 mA)
Experimental Conditions (GaAs/GaAsP, tee shape electrode w/ grounded anode, rf pulsed IR laser)
Injector Test Facility (anode + vacuum) => first 1 and 4 mA demos (in proceedings, unpublished)
CEBAF (anode + vacuum + radiation + apertures + polarimetry) => CEBAF performance, laser scaling (in proceedings, unpublished)
Injector Test Stand Results => 1mA and 4mA studies w/o polarimetry
CEBAF QWeak performance applying laser scaling, then operating 1-2 years @ 0.2mA w/ online Compton polarimetry vs. QE
CEBAF Scaling Experiment to achieve longest lifetime (>1000C) at >1 mA
CEBAF Polarization Experiment to measure polarization up to 1mA
Simulation Studies (IBSimu, GPT, Simion)
Ion impact distribution at photocathode (#, energy, position) for CEBAF gun/geometry => show scaling depends upon optics
Electron beam distribution and losses => validate radiation loss & vacuum load, useful to compare IBSimu w/ GPT model
Ionization and secondaries distribution and total contribution to ions reaching cathode/anode gap
Outlook & Conclusions

Background Material

Ion impact degradation of GaAs photocathodes
2018 Experiment to exploit increase of laser area to achieve >100C at >1mA from high polarization photocathodes