We report on the experimental results of a niobium photocathode illuminated by two different wavelength lasers operating at 308 and 222nm.The output current was recorded by a fast Rogowski coil while the beam angular distributions by small Faraday cups placed in front the beam. For λ=308nm the quantum efficiencies were 1.0×10-6 and 2.1×10-6 for p and s-polarisation, respectively. When the 222nm light was used they were 1.6×10-5 for p-polarisation and 5.3×10-5 for s-polarisation. In both cases the s-polarisation got efficiency higher. The maximum output current was 1.25A, τ=10ns; this value was obtained utilising the shortest wavelength laser, 4.9 mJ and 20 kV accelerating voltage. By the electron beam angular divergence, we determined the upper limit normalised emittance. The shortest value found of upper limit emittance was 7 [π mm mrad], achieved by the s- polarised radiation, at λ=308nm.
Electron emission from niobium photocathode
NASSISI, Vincenzo;DONATEO, Antonio;MARTINA, Luigi;
2000-01-01
Abstract
We report on the experimental results of a niobium photocathode illuminated by two different wavelength lasers operating at 308 and 222nm.The output current was recorded by a fast Rogowski coil while the beam angular distributions by small Faraday cups placed in front the beam. For λ=308nm the quantum efficiencies were 1.0×10-6 and 2.1×10-6 for p and s-polarisation, respectively. When the 222nm light was used they were 1.6×10-5 for p-polarisation and 5.3×10-5 for s-polarisation. In both cases the s-polarisation got efficiency higher. The maximum output current was 1.25A, τ=10ns; this value was obtained utilising the shortest wavelength laser, 4.9 mJ and 20 kV accelerating voltage. By the electron beam angular divergence, we determined the upper limit normalised emittance. The shortest value found of upper limit emittance was 7 [π mm mrad], achieved by the s- polarised radiation, at λ=308nm.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
