[Cuga] **Reminder to RSVP**Pizza Seminar Series- Wednesday, July 20, 2011- A message from Hari Areti

[Lorelei Carlson]

Please RSVP by COB on Monday, July 18, 2011 to: lcarlson at jlab.org

Wednesday, July 20, 2011
****CC F113****
12:00-1:30pm

*Photocathode Development at Jefferson Lab***


*Russell Mammei***

Thomas Jefferson National Accelerator Facility


Abstract:

In the past decade, there has been con­sid­er­able in­ter­est in the 
gen­er­a­tion of tens of mA av­er­age electron cur­rent in a 
pho­toin­jec­tor for use in current and future accelerator 
applications.  Some applications include Free Electron Lasers and the 
proposed Electron Ion Collider.  Two photocathodes are frequently 
considered for generating high average current electron beams and/or 
beams with high brightness: GaAs:Cs and CsK_2 Sb.  Each photocathode has 
advantages and disadvantages, although some attributes are based on 
assumptions and not demonstrated performance at "production" accelerator 
facilities.  Until recently, the GaAs:Cs photocathode has been tested 
extensively in a DC field and CsK_2 Sb in an RF field.  To make a 
well-informed choice for new accelerators, the performance of both 
photocathodes should be measured under identical conditions.  To this 
end the Polarized Source Group at JLab has partnered with the 
instrumentation group at Brookhaven National Lab (BNL) to evaluate CsK_2 
Sb in the same DC field that has been used to study GaAs:Cs.  In March 
of 2011, a CsK_2 Sb photocathode was grown at BNL and successfully 
transported in vacuum to the Injector Test Stand electron gun at JLab. 
 Since then the quantum efficiency has been monitored, e.g. photocathode 
lifetime, under average currents ranging from 1mA-20mA, with different 
laser wavelengths.  An introduction to the Injector Test Stand electron 
gun and our current results will be presented.


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