RE: Portable gamma spectroscopy

[Dimiter Popoff <tgi@cit.bg>]

>.... We have compared it's performance to that 

>of our Canberra HPGe System and have found it to perform

>very favorably (although you are accepting many tradeoffs

>in the process). ...



I believe the first thing to decide is whether HPGe will be

needed or will some scintillation based detector be sufficient.

HPGe costs much more and needs liquid nitrogen (even with

the small Dewars you'll hardly call a system handheld).



 On the other hand, HPGe with its resolution makes nuclide

identification far less ambiguous than with scintilation based

detectors. Todays digital (DSP based) MCAs (like ours or 

those - somewhat less digital - of our US competitors) have practically

no warmup time and no drift, which makes them really

well suited for outdoors use. Some (well, ours :-) even need just

a single point energy calibration (offset zero is always zero).



The way Rick Edwards put his question, HPGe sounds on the one hand

like overkill (he needs not too low MDA, nor quantitative analysis);

on the other hand, for less trained personell to be able to do the

analyses, the instrument might be better off with the HPGe spectrum

data. If an identification error is acceptable (seems so, after all it can

be corrected with subsequent lab analysis), I believe most of the 

NaI portables will do - and I would not pay much attention at their

automated analytical capabilities, how long does it take to teach

someone that 137Cs is at 661.6 keV and 60Co is at 1173.2 and 1332.5...

Many NaI systems have a stabilizer (PM tubes drift a lot over temp),

but this may produce more confusion than results with an inexperienced

operator.



Dimiter





--------------------------------------------------------------------

Dimiter Popoff

Transgalactic Instruments, Gourko Str. 25 b, 1000 Sofia, Bulgaria

http://transgalactic.freeyellow.com





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