Generation and characterization of high intensity electron beams generatedfrom rough photocathodes

In this work, the generation and the characterization of high current elect ron beams from rough photocathodes induced by an ultraviolet excimer laser are reported. The cathodes were rough Cu disks. In order to study the influ ence of the cathode surface, the electron emission from different surface r oughnesses was investigated. To establish the electromagnetic and geometric parameters a Rogowski coil and a new slit-slit emittance meter were used. The laser beam utilized was obtained by a mixture of Kr and Cl which genera ted coherent light at 222 nm. Fixing the laser energy at 0.5 mJ and the las er spot into 4 mm(2), the maximum current as well as the maximum emittance value were obtained with the cathode that had the highest surface roughness which resulted in 1 A and 46 pi mm mrad, respectively. A low current and a low emittance were obtained with the cathode that had the lowest roughness , namely, 410 mA and 19 pi mm mrad, respectively. A quantum efficiency valu e of 1.2 x 10(-4) was reached with the cathode with the highest amount of r oughness. (C) 1999 American Institute of Physics. [S0034-6748(99)04011-3].