Author/Authors :
A. Aboubacar، نويسنده , , E. Aussoleil، نويسنده , , H. Bergeret، نويسنده , , A. Chbihi، نويسنده , , M. Dupont، نويسنده , , J. Gardès، نويسنده , , Z. Jaber، نويسنده , , M. Laguna، نويسنده , , Jane B. LeBlond، نويسنده , , D. Marie، نويسنده , , M. Querrou، نويسنده ,
Abstract :
Photo-injectors for linear accelerators and free electron laser need a high brightness photocathode with a dark current lower than 10 mA. Silicon with array of tips shows a photofield emission current with a continuous argon laser with a quantum yield of 1%. The ratio η between photofield and field emission (dark) current is 20 near the threshold of field emission. With a pulsed Nd-YAG laser (λ = 1.02 μm pulses of 35 ps duration) we observe a pure photoemission charge (70 pC) with harmonic 4 (ℏ ω4 = 4.68 eV) and a photofield charge above the threshold which is 700 pC with harmonic 2 (ℏ ω2 = 2.34 eV). We calculate for the photo-injector CANDELA the dark current following the method of Loew and Wang, starting from the experimental Fowler-Nordheim curve and we find a dark current which is 1 μA at 3 GHz at Emax = 30 MV/m.
