Millimeter-wave photoinjector-driven chirped-pulse free-electron laser

Summary form only given, as follows. A compact, high repetition rate (2.142 GHz in burst mode), relativistic (5 MeV) photoinjector facility is currently under construction at the UC Davis Department of Applied Science, on the LLNL site. Photoelectron bunches are produced by irradiating a high quantum efficiency Cs/sub 2/Te (Cesium Telluride) photocathode with a train of 100 UV (210 nm), ultrashort (250 fs) laser pulses. These bunches are accelerated in a 1-1/2 cell /spl pi/-mode X-band RF structure energized by a 20 MW, 8.568 GHz SLAC klystron. The peak current is 0.25 kA (0.25 nC, 1 ps bunches), with a normalized beam emittance /spl epsi/<5 /spl pi/ mm-mrad. This prebunched electron beam is then transversally accelerated in a cylindrical waveguide by a 30-mm period, 10 period long helical wiggler. The peak wiggler field is adjusted to 8.5 kG, so that the group velocity of the radiated electromagnetic waves matches the axial velocity of the electron bunch (grazing condition). Chirped output pulses in excess of 2 MW power are produced with an instantaneous bandwidth extending from 125 GHz to 225 GHz and a pulse duration of 15 ps (HWHM).