From: "Tim May" <timcmay@got.net>
I certainly never implied in any way that a simple G-M tube would be useful for this. Implicit in my radioistope mapping comment was that a gamma ray spectrometer would be used.
The rest of the assembly, even 20 years ago, was mostly portable: the germanium detector head, some preamps and pulse-height analyzers, and a multichannel analyzer. Most of this stuff is now done on laptops, the MCA and analysis software part. Without researching this on the Net, I would thus conjecture the entire gamma ray spectrometer could fit in a small carry-on case, using a small dewar.
http://www.giscogeo.com/pages/radgf260.html DIMENSIONS AND WEIGHT: 27x13x18 cm, 2.8 kg There's a bunch more http://www.alltheweb.com/search?cat=web&cs=utf-8&type=phrase&q=portable%20gamma%20ray%20spectrometer%20