Dependence of the circular polarization of external bremsstrahlung on electric and magnetic fields

Abstract

A set of measurements is reported on the degree of circular polarization of external bremsstrahlung (EB) as a function of static magnetic and electric fields. Sources of 90 Y and 32 P were used; Ag and PbO were selected for targets. 1. a) Magnetic field effect : The degree of EB circular polarization does not depend on the field when this points backward to the momentum of the radiating electron beam. On the contrary it decreases with increasing field when this points forward to the momentum. The dependence on the field was investigated up to 20 000 G where a decrease of about 35 % was attained and found to be different in the two targets. 2. b) Electric field effect : The degree of EB circular polarization in PbO decreases with increasing field, but no difference was observed between forward and backward field direction. A polarization decrease of about 15% was attained at 20 kV·cm −1 . A detailed discussion shows that the observed phenomena cannot be attributed to any spurious effects of instrumental nature.