0000000000855011
AUTHOR
H. Trautner
2.45 GHz synchronised polarised electron injection at MAMI
Abstract A semiconductor modelocked diode laser has been used to produce picosecond spin-polarised electron bunches from strained GaAsP photocathodes and inject them into MAMI, synchronised to the 2.45 GHz accelerating field. The laser meets the operational requirements of MAMI producing stable electron beams, with a polarisation purity of 72% and a transmission efficiency of 52% at an accelerated beam current of 10.1 μA.
Photoemission of spinpolarized electrons from strained GaAsP
Strained layer GaAs.95P.05 photo cathodes are presented, which emit electron beams spinpolarized to a degree of P = 75% typically. Quantum yields around QE = 0.4% are observed routinely. The figure of merit P2 × QE = 2.3 × 10−3 is comparable to that of the best strained layer cathodes reported in literature. The optimum wavelength of irradiating light around 830 nm is in convenient reach of Ti:sapphire lasers or diode lasers respectively. The cathodes are produced using MOCVD-techniques. A GaAs.55P.45-GaAs.85P.15 superlattice structure prevents the migration of dislocations from the substrate and bottom layers to the strained overlayer. The surface is protected by an arsenic layer so that n…