REDUCTION OF GAMMA-RAY BACKGROUND IN THE USE OF 32 KEV X-RAYS FROM CS-137 SOURCES BY A GATING METHOD WITH A THIN PLASTIC SCINTILLATION DETECTOR

In the use of 32 keV K X-rays from Cs-137 sources for the calibration of low energy photon spectrometers, a new method was developed to redu ce remarkably the background continuum due to 662 keV gamma-rays. This method is based upon a gating technique by the use of a 4 pi detector composed of thin plastic scintillator sheets which sandwich the Cs-13 7 source. Since all X-rays from the Cs-137 source are coincident with monoenergetic internal conversion electrons, the X-ray response of the photon spectrometer remains unchanged, whereas gamma-ray signals are rejected by gating. This method was tested successfully for three diff erent photon spectrometers.