Reduction of γ-ray background in the use of 32 keV X-rays from 137Cs sources by a gating method with a thin plastic scintillation detector

In the use of 32 keV K X-rays from 137Cs sources for the calibration of low energy photon spectrometers, a new method was developed to reduce remarkably the background continuum due to 662 keV γ-rays. This method is based upon a gating technique by the use of a 4π detector composed of thin plastic scintillator sheets which sandwich the 137Cs source. Since all X-rays from the 137Cs source are coincident with monoenergetic internal conversion electrons, the X-ray response of the photon spectrometer remains unchanged, whereas γ-ray signals are rejected by gating. This method was tested successfully for three different photon spectrometers.