A source of highly spin-polarised slow electrons based on the 'Fano effect' on caesium atoms

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Abstract
The source of spin-polarised electrons recently used in a 'triple-scattering experiment' in Munster is described in detail. The polarised electrons are generated by the photoionisation of caesium atoms with circularly polarised UV radiation from a high-pressure mercury discharge lamp (Fano effect). Electron intensities of 5 nA with polarisation of 84% have been routinely obtained during continuous runs of up to 200 hours in the kinetic energy range between 17 and 500 eV with an energy spread of <or=1.5 eV. The polarisation and intensity fluctuation was +or-1% and +or-10% in 10 hours, respectively.