Energy calibration of a BC501A liquid scintillator using a γ-γ coincidence technique

An accurate energy calibration of a BC501A liquid scintillator by means of Compton scattering of γ-rays is described.The energy resolution and the position of the Compton edge have been precisely determined using a γ-γ coincidence technique and fitting the coincidence spectrum with a Gaussian function superimposed on a quadratic polynomial for the background.The position of the Compton edge relative to the position of the maximum and the half height of the distribution in dependence on the relevant energy resolution is discussed in detail.The results indicate that the maximum energy of the recoil Compton electron does not occur at the half height distribution but at 0.90±0.05 of the maximum height in the energy range considered.The energy resolution varies from 15.6% to 8.02% for electrons in the energy region from 0.5 MeV to 3 MeV.     

Search for Double γ-Vibrational Bands in Neutron-Rich 105Mo Nucleus

Levels in the neutron-rich ^105Mo nucleus have been investigated by observing prompt γ-rays following the spontaneous fission fragments of^252 Cf with the Gammasphere detector array. The yrast band has been confirmed and updated. The other two collective bands with the band head levels at 870.5 and 1534.6 keV are newly observed, and they are suggested as the candidates for one-phonon K= 9/2 and two-phonon K = 13/2 double γ-vibrational bands, respectively. Systematic characteristics of these bands have been discussed.     

Optimum condition of efficiency functions for HPGe γ-ray detectors in the 121-1408 keV energy range

The optimum condition of three commonly used functions in the Genie 2000 γ spectra analysis software have been studied in the 121-1408 keV energy range. The three functions are applied for fitting the full-energy peak efficiency of the HPGe gamma-ray detector. A detailed procedure to obtain the optimum condition is described. The HPGe detector is calibrated at 11 cm by three radioactive sources of point form （^152Eu, ^137Cs, ^60Co） providing 11 energy peaks. After data processing, results shows that the three functions used in the Genie 2000 gamma spectra analysis software fit best at orders 3-5. Lastly the standard radioactive source 133Ba is chosen to validate the results. Differences between the standard activity of 133Ba and the result obtained from the fitting functions are below 1.5%. Therefore the optimum orders of the three functions used in the Genie 2000 3, spectra analysis software are 3-5 with the 11 energy peaks.