Observations on the background spectra of four LaCl3(Ce) scintillation detectors

Our laboratory has purchased four LaCl3(Ce) scintillation crystals over the course of the last year for evaluation as part of an environmental management research and development project. In addition to the expected content of naturally radioactive 138La, we have found that all four of these detectors are contaminated to various degrees with alpha particle emitting nuclides that we have determined to be 227Ac and its daughters. The impact of these radionuclides on the background spectra and, thus, on the detection sensitivity of these detectors is presented and discussed.