Calibration of a Mott detector using circularly polarized impact radiation from helium

The conventional methods of determining the analyzing power of a Mott detector for electron-polarization measurement are not very accurate. That is why alternative methods have recently been discussed. The present paper shows how a Mott detector can be calibrated with an uncertainty of +-1% using the circular polarization of impact radiation from helium atoms that are excited by polarized electrons. The retarding-field-type Mott analyzer, its performance, and the calibration procedure are described in detail. Accurate data of the circular light polarization that may be used for absolute electron polarimetry are given at electron energies of 23.3 and 26 eV