ISSN:
1432-0630
Keywords:
PACS79.60
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Abstract. Strained layer GaAs $_{.95}$ P $_{.05}$ 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 P $^2 \times $ QE = 2.3 $\times 10^{-3}$ is comparable to that of the best strained layer cathodes reported in literature. The optimum wavelength of irradiating light around $830\;{\rm nm}$ is in convenient reach of Ti:sapphire lasers or diode lasers respectively. The cathodes are produced using MOCVD-techniques. AaAs $_{.55}$ P $_{.45}$ –GaAs $_{.85}$ P $_{.15}$ superlattice structure prevents the migration of dislocations from the substrate and bottom layers to the strained overlayer. The surface is protected by anarsenic layer so that no chemical cleaning is necessary before installation into vacuum. The source of polarized electrons attached to the Mainz race track microtron MAMI works with such cathodes now. More than 1000 hours beamtime have been performed successfully.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01567651