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

Abstract

In this work the electron beam current and beam emittance measured for an Al and a diamond film cathode irradiated with two different UV excimer lasers, XeCl and KrCl, are presented. The output current was measured with a fast Rogowski coil while the emittance was determined with a new diagnostic setup composed by two movable slit arrays and an array of small cups. The phase space area occupied by the electrons at the output was determined by the current measured with the cups and by the position of the slits. With a 4 mm2 beam spot the maximum current from an Al cathode was 740 mA and from a diamond cathode was 560 mA with the KrCl laser. The corresponding emittance values were 130 and 50 for the Al and the diamond cathode, respectively. From these values the normalized beam brightness were estimated to be 0.18 X 109 A((pi) m rad)-2 for Al cathode and 0.92 X 109 A((pi) mrad)-2 for diamond cathode.