[ RadSafe ] Measuring alphas with GM? Re: Survey MDAs vs. ScanMDAs

[JGinniver at aol.com]

Hmmm,
pancake GMs are not as bad as many people think at detecting Alphas.
 
Thermo quote 0.9 cps per Bq per cm2 for Pu-238 for the 900EP15  
(contamination monitor)  see 
_http://www.thermo.com/com/cda/product/detail/1,1055,21854,00.html_ (http://www.thermo.com/com/cda/product/detail/1,1055,21854,00.html)  , 
this  is generally fitted with an LND pancake GM e.g. 7311, 7312, 7313 or 7314  
(depending on the connectors required and operating voltage).
 
Ludlum quotes 15% (4pi) efficiency for Pu-239 for the 44-9, as this and  
other similar probes (e.g. Eberline HP260, Bicron PGM, Tech Assoc P15) all use a  
15.5 cm2 pancake geiger similar to those listed above from LND (e.g. Canberra, 
 St Gobain etc.) the performance for alpha monitoring will be broadly  
similar.
 
Regards,
    Julian