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 Q_β-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 Q_β measurement of the 2 ^- isomer of ¹⁴⁶La; the Q_β-value was obtained to be 6580(60) keV.