Emission and emittance measurements of electron beams generated from Cu and diamond photocathodes

We report on the electron emission from Cu and diamond film cathodes irradiated with two ultraviolet excimer laser beams working at 308 nm XeCl, and 222 nm KrCl. The beam emittance measurements were performed using a new experimental setup composed of two movable slit arrays. The electron beam phase space areas were determined by splitting the beam in small beamlets and measuring the beamlet direction spread via small cups and slits. The highest emission was obtained at the lowest laser wavelength. With a 4 mm2 beam spot and 0.5 mJ laser energy the maximum currents from the Cu and diamond film cathode were 370 and 410 mA, respectively, and the corresponding emittances were 18 and 27 (π mm mrad). From these values the normalized beam brightness was estimated to be 4.6×109 A(π m rad)−2 for the Cu cathode and 2.3×109 A(π m rad)−2 for the diamond cathode. By increasing the laser energy and the spot beam the maximum extracted current was 16.4 A from the Cu cathode with the KrCl laser.