RF characterization of a tunable, high-gradient, X-band photoinjector

Highly accurate measurements of an X-band (8.548 GHz) radio frequency (RF) gun, designed to produce short (<1 ps), relativistic (5 MeV), low-emittance (<1 /spl pi/-mm/mrad, at 0.1 nC) electron bunches, have been performed at medium-power levels (1 kW, 6 /spl mu/s, 30 Hz). Balanced (within 3%), high-Q (4274), /spl pi/-mode excitation at critical coupling (S/sub 11/ < -80 dB) has been demonstrated by performing in situ phase measurements. A new tuning method to accurately adjust the coupling has been successfully implemented, which complements the independent tuning of the half and full cells, and the precise (-136 kHz//spl deg/C) temperature tuning of the gun. Finally, preliminary photoelectron results are also outlined.