Effect of Backscattering on the Helicity ofβRadiation

Experimental investigation has been carried out on the dependence on the energy of the average longitudinal polarization of $\beta$ particles of ${}_{}{}^{90}{}_{}{}^{}\mathrm{Sr}$+${}_{}{}^{90}{}_{}{}^{}\mathrm{Y}$, backscattered by a lead target. The ratio of the polarization of backscattered to incident electrons was obtained in the energy ranges 0.3-0.8, 0.55-1.2, and 0.75-2.0 MeV with respective results of 0.657±0.192, 0.503±0.284, 0.650±0.369. The effect of a perturbing magnetic field on helicity was also studied. The results are discussed with reference to the mechanism of the backscattering process.