Quantum efficiency measurements of a copper photocathode in an RF electron gun

A 4.5 MeV photocathode RF gun has been commissioned at UCLA. A photo-injector drive laser produces sub 2 ps pulses of UV (/spl lambda/=266 nm) light with up to 200 /spl mu/J/pulse, and illuminates a copper cathode. The photoelectrons are accelerated to an energy of 3.5 MeV within the gun. The electron beam charge is measured as a function of laser energy using an integrating current transformer (ICT). We present measurements of quantum efficiency as a function of laser polarization for injection angles of 2/spl deg/ and 70/spl deg/ with respect to the cathode normal. At 70/spl deg/ incidence a 50% enhancement in quantum efficiency (>10/sup -4/) is observed for p-polarized light over s-polarized light.<
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