Charakterisierung und Optimierung von Wienfilter und Doppel-Mott-Polarimeter an der Testquelle spinpolarisierter Elektronen Photo-CATCH
Characterization and optimization of the Wien filter and Double-Mott polarimeter at the test source of spin-polarized Photo-CATCH
The test source Photo-CATCH is the new source of spin-polarized electrons at the “Institute for Nuclear Physics” in Darmstadt. The longitudinal spin-polarized electron beam is produced from a Laser-driven GaAs cathode. The aim of the present bachelor thesis is the characterisation and optimization of the Wienfiter and polarimeter to manipulate and analyize the electron-spin polarization at Photo-CATCH. To rotate the electron-spin into the transversal plane, which is strictly neccesary for a polarization measurement based on Mott scattering, the magnetic ?field of the Wienfiter has been measured on ?five different axes with a Hall-effect magnetometer. This yields the linear relationship B(I) = 0.8088 x I – 0.0224 (central axis) between the generated magnetic ?field B and the coil current I. Further, the permeability of nickel used for shielding could be simulated to ?r = 50. Finally the Wienfiter was assembled and installed into the beamline. The energy resolution of the semi-conductor detectors in the polarimeter for the detection of the scattering asymmetry was determined to be 17 keV based on an 241Am-alpha-source. Finally a temperature dependence was detected, but could not quantified because of a nonexistent temperature stabilisation. Because of the missing vacuum-chamber, the polarimeter has not been assembled and installed into the beamline yet.