Floor monitor - background increasing

[Cehn@AOL.COM]

Thanks for your reponses to my post (see below).  The cause of the increasing 

background appears to be a temperature effect on the detector.  Ludlum admits 

that for these gas filled proportionals, efficiency goes up with temperature. 

 


I would have guessed it would go down, based on the decreasing density of the 

counting gas with increasing temperature.  But other factors (not yet 

revealed) are at work.


The lesson is choose your high voltage carefully.  If you're on a flat 

plateau, temperature effects should be minimal.


Oringinal post:

"I have a Ludlum 43-37 floor monitor surveying a large concrete pad - 

outdoors.  On very hot days (>105), the instrument background goes up.  We 

take it into a cool trailer, cool it down, and background stays up.  Any 

ideas? 


My favorite theory so far is radon coming off the concrete in the heat, and 

the daughters sticking to the detector.  That would also account for the 

backgrounds returning to normal the next morning."


Joel I. Cehn, CHP 

cehn@aol.com 

Oakland, CA