[ RadSafe ] Thermo Fisher CM-11

JGinniver at aol.com JGinniver at aol.com
Thu Jan 24 14:33:50 CST 2008

You don't specify what model you ae interested in.  The CM11-F use a  gas 
flow proportional probe and so probably ins't suitable for your  application.  
The CM11-E use a standard scintillation type 100cm2 alpha and  beta 
contamination probe.  The version on the CM11E is listed as the DP6DD  which has a thinner 
foil for improved efficiency, however my experience with  thinner aluminised 
mylar foils is that they are more light sensitive and so  aren't really 
suitable for outdoor/bright sunlight applications.  Thermo  used to do a version of 
the DP6 which they termed Endura which was designed to  be more robust for 
outddor/agressive working environments, although they had  prodution problems 
(the aluminium light tight coating was applied directly to  the 
scintillator/phosphor).  I'm assuming that as you are interested in the  Radon rejection 
function that you are interestd in monitoring for alpha and beta  emitting 
radionuclides?  If not the CM-11 can be configured to monitor for  beta only, but I 
can't remember what model this would be.
I can't really comment on the radon rejection function as we are interested  
in monitoring for alphas and consequnetly take radon probelms (static  
actraaction to clothing and hard hats as an occupational hazard)  We try  and 
discourage the wearing of man made fibres in area where we may have a  potential 
radon probelm. And any items 'contaminated' with alpha. are  removed bagged and 
rechecked after a period of hours to confirm whether it was a  Radon problem or 
a genuine contamination event.
Before I forget, they are not what I would term portable, they are really  
deisgned for wall mounting, although we have mounted them on 'sack trolleys' for 
 use at temporary controlled areas.  They are however mains powered (or at  
least I've never seen a battery powered version).
Hope this helps,


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