January 1, 2010.
Quantum efficiency of the electron gun at the Stanford Synchrotron Radiation Laboratory can be increased by using laser-induced photo-emission.1 The gun cathode is normally heated to ~1000 C for electron emission and injection into the synchrotron light source. In these experiments, the cathode is cooled down and irradiated with ultra-violet laser radiation to produce emission with higher quantum efficiency. The result is an increase in shot-to-shot electron emission rate and better control over the electron beam size. During my time at SLAC, two laser systems were commissioned to provide sources of ultra-violet radiation that irradiate a pair of electron guns in the photo-emission mode. The first laser system features an infrared Nd:glass laser frequency doubled to green light with a BBO crystal and doubled again to UV radiation with a second BBO crystal. The UV laser beam was then directed to the gun cathode using a visible, collinear HeNe laser beam. The second laser system features a ‘JEDI’ frequency doubled Nd:YAG laser borrowed from LCLS. In this case, the green output beam was doubled with a BBO crystal to produce UV radiation and again aligned to the gun cathode using a collinear HeNe laser beam. Because of my previous career as an engineer working at Hughes Aircraft Company and the Jet Propulsion Laboratory in the field of lasers, I was able to take laser safety classes at SLAC which enabled me to become a QLO – Qualified Laser Operator and work with both of these laser sources and transport systems during my summer internship.
SLAC National Accelerator Laboratory (SLAC)