Electron beam and rf characterization of a low-emittance X-band photoinjector

Detailed experimental studies of the first operation of an X-band (8.547 GH z) rf photoinjector are reported. The rf characteristics of the device are first described, as well as the tuning technique used to ensure operation o f the 1 1/2-cell rf gun in the balanced pi -mode. The characterization of t he photoelectron beam produced by the rf gun includes: measurements of the bunch charge as a function of the laser injection phase, yielding informati on about the quantum efficiency of the Cu photocathode (2 x 10(-5) for a su rface field of 100 MV/m); measurements of the beam energy (1.5-2 MeV) and r elative energy spread (Delta gamma/gamma (o) = 1.8 +/- 0.2%) using a magnet ic spectrometer; measurements of the beam 90% normalized emittance, which i s found to be epsilon (n) = 1.65 pi mm mrad for a charge of 25 pC; and meas urements of the bunch duration (<2 ps). Coherent synchrotron radiation expe riments at Ku-band and Ka-band confirm the extremely short duration of the photoelectron bunch and a peak power scaling quadratically with the bunch c harge.