Joe Frisch: Synchrotron radiation sources and free ... - Conferences
Joe Frisch: Synchrotron radiation sources and free ... - Conferences
Joe Frisch: Synchrotron radiation sources and free ... - Conferences
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Electron Guns<br />
RF guns used at SLAC <strong>and</strong> most proposed XFELs<br />
RF cavities can support very high fields (120MV/M for LCLS)<br />
Short pulse (~picosecond) laser to generate photo-electrons<br />
Low repetition machines (LCLS 120Hz) typically use copper<br />
cathodes, low QE (3x10 -5 @260nm), but high gradient<br />
High repetition rate superconducting machines may use<br />
higher QE (Cs 2Te, ~10% at 260nm) cathodes to reduce laser<br />
power (may require reduced gradient)<br />
RF GUN: 0.5 πmm-mr measured at 250pC<br />
Pulsed DC (500kV, 3us, 10MV/M) gun used at SCCS <strong>and</strong> SACLA<br />
at Spring-8.<br />
Thermal emission from heated cathode to produce beam.<br />
0.7πmm-mr measured at 300pC<br />
NOTE: emittance measurements not directly<br />
comparable due to different bunch lengths!<br />
Maesaka et. Al.<br />
SCCS, Spring-8<br />
D. Dowell et al<br />
3mm<br />
15
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