Ionization energy in an HPGe semiconductor detector

We report measurements of the relative pulse heights produced simultaneously by alpha particles with energies in the range 3.2-5.8 MeV and gamma rays in an hyperpure Ge detector at T=80 K. From these data, we conclude that the mean energy to create electron-hole pairs is smaller for α's than for γ's i.e. εα<ε0 contrary to earlier conclusions. Specifically, εα/ε0=0.9914± 0.0010 at Eα=5486 keV. The deviation in the ratio element ofα/element of0 from unity increases with decreasing α energy. (orig.)