so...this is a sample of NA(CI) sodium encapsulating Cesium 137, or if not with the sample with the photomultipler tube (already posted ..) all you need is :put Nuclespot grill with table salt (NaCl), contain the salt with a piece of packing tape across the face of the source, and place the salted source in front of an HPGe detector for a few hours.....

https://carlwillis.wordpress.com/tag/nuclespot/