X-ray performance of a 1242 cm3 LaCl3:Ce scintillation spectrometer

We present the results of gamma-ray measurements on a large 4 '' x 6 '' LaCl3:Ce crystal, characterized using radioactive sources over the range 14-3220 keV. The response of the crystal was found to be largely linear over the upper 90% of its dynamic range-the deviations at lower energies can be attributed to the shortcomings of the photomultiplier tube (PMT) and is in fact a generic problem when using high-gain PMTs with lanthanum halide scintillators. At 662 keV, a measured energy resolution of 4.1% FWHM was recorded at room temperature. In comparison to earlier generations of LaCl3 detectors, the internal background spectrum shows significantly less X-ray, beta, gamma-ray and alpha contamination. The integral background count rate in the energy region 20 keV-3 MeV was determined to be 1.8 cm(-3) s(-1) of which most (1.5 cm(-3) s(-1)) can be attributed to the beta continuum from La-138 and only similar to 0.04 cm(-3) s(-1) to the alpha complex from Ac-227 and daughters. Using these data, we have determined the light output of alpha particles relative to the equivalent energy electrons (or alternately gamma-rays) to be, alpha/gamma = 0.35 +/- 0.02. (c) 2007 Elsevier B.V. All rights reserved.