Effect of Absorbers on Alpha Spectral Measurements

An analytical expression for the response function of an alpha particle detecting system is described in this paper. The spectral spread has been assumed to be due to detector resolution and absorber between the source and detector. The counts in channel E' are given by C(E') = integral(F(E)g(E->E'))dE where g(E->E') is the gaussian distribution due to detector resolution. F(E), the spectrum of alpha particles incident on the detector after traversing a distance ro, is obtained from the expression: 1−(ro/R)=(E/E0)eta where R is the range and E0 initial energy of the particles. Eta is not too sensitive a function of energy. Experimental spectra for 234U and 241Am obtained with a surface barrier detector are compared with the spectra computed with the above response function. It is observed that eta = 1.60 gives good agreement between theory and experiment for 234U and eta = 1.68 for 241Am.