Effect of incident electron energy of beta emitter on the formation of bremsstrahlung spectra in the photon energy region of 1-5Â keV

The effect of incident electron energy of beta emitter 204Tl (end-point energy = 765 keV) and 90Sr (end-point energy = 546 keV), on the formation of total bremsstrahlung spectra in thick targets, was investigated in the photon energy region of 1-5 keV. Theoretical bremsstrahlung spectra were obtained from theory that describes ordinary bremsstrahlung (OB) and the theoretical model, which includes the contribution of polarization bremsstrahlung (PB) in OB in stripping approximation. The theoretical and experimental bremsstrahlung spectra were modified by applying corrections due to the range of beta particles, self-absorption of photons in target, absorption of photons in detector compounds, and backscattering of beta particle. It was observed that the experimental results were 10-15% higher than that of the theoretical model, which includes the contribution of PB in OB in stripping approximation, particularly for medium and high Z elements. The contribution of PB in OB was suppressed with the increase in the end-point energy of the beta emitters. The results reported here clearly indicate the inadequacy of stripping approximation and the need to include the term of interference of OB and PB while describing the total bremsstrahlung spectra.