We have measured impurity levels of radioactive isotopes, especially 137Cs and 134Cs , in various
cesium compounds using HPGe detectors for the rst time. The 137Cs contamination levels of
cesium iodide (CsI) powder samples that are commercially avai...
We have measured impurity levels of radioactive isotopes, especially 137Cs and 134Cs , in various
cesium compounds using HPGe detectors for the rst time. The 137Cs contamination levels of
cesium iodide (CsI) powder samples that are commercially available were between 9.7 mBq/kg and
80 mBq/kg. With these levels of the contamination, 137Cs will be the most serious background
source in the low energy region E < 100 keV for CsI crystal. An upper limit of the 137Cs contamination
level in pollucite powder, from which CsI powders are extracted, was set to be 5.8
mBq/kg at a 90 % condence level. It should be possible to fabricate the CsI crystal with much
less 137Cs contamination than the currently available CsI crystal.