Performance evaluation of a beta-spectrometer comprising a plastic scintillator and multi-wire chamber using a coincidence method

This paper describes an experimental setup developed to measure the beta-ray energy spectrum as well as a Geant4 simulation study conducted to characterize the properties of a beta-spectrometer. The beta-spectrometer comprises a multi-wire chamber to generate signals to indicate the incidence of beta rays and a plastic scintillation detector to measure its energy. The coincidence method of the detector signals was used to remove high gamma-ray interference. To evaluate the performance of the developed spectrometer, the energy spectra were measured with the radionuclide sources ( 137Cs and 207Bi) emitting internal conversion electrons and gamma rays. The gamma-ray interference removal rate of the spectrometer using the coincidence method was 99.12 ± 0.09%. To reconstruct the beta spectrum from the measured spectrum, Monte Carlo simulations using the Geant4 toolkit were performed to calculate the coefficient related to the effect of gamma rays. The obtained spectrum confirmed that the energy resolution and intrinsic internal conversion peak detection efficiency of the beta-spectrometer were 10.2% at 1 MeV and 91.6%, respectively.