A precise method of Qβ determination with small HPGe detector in an energy range of 1–9 MeV

The present paper describes a method to obtain accurate β±-ray maximum energies with small HPGe detector. In order to unfold β±-ray spectrum observed, response functions for monoenergetic electrons and positrons were experimentally determined for four different sizes of HPGe detectors with diameters of 16–50 mm and with thicknesses of 10–13 mm. The reliability of the unfolding procedure was confirmed by a comparison between the experimental and its well-evaluated Qβ-value. The systematic error is estimated to be 20 keV in an endpoint energy range of 1–4 MeV, and 30 keV in 4–9 MeV. The present method was applied for the Qβ measurement of the 2− isomer of 146La; the Qβ-value was obtained to be 6580(60) keV.