Large Proportional Counter Spectrometer for the Study of Radioactive Samples with Low Specific Activity

Abstract

The design and construction of a cylindrical proportional counter 36 in. long, 12 in. i.d. is described, and its performance as a spectrometer for studying soft radiations from radioactive samples of low specific activity is given. The counter tank is operated in an axial magnetic field of 2500 gauss to constrain beta rays to helical paths. A line width of 3.4% (ΔE/E) is obtained for 625-kev electrons from a Cs137 source mounted on a thin film placed within the tank. Simple theory would predict 2.2%. Beta spectra are readily obtained with sources having total activities less than 10 mμC.