Re: Gas Proportional Counters

[John Harvey <harveyj@mcmail.CIS.McMaster.CA>]

We have an old Nuclear Chicago 2 inch windowless proportional counter. 
For energetic betas, such as from P-32, our efficiency is 0.68. For 
infinite backing of aluminum, the theoretical efficiency is 0.669 for 2 
pi geometry. Yes, you can get efficiencies greater than 50% for 2 pi 
geometry because of backscatter.


=======================================================================
John Harvey                            | McMaster University
Senior Health Physicist                | NRB-110
(905) 525-9140 ext 24226               | 1280 Main St. W.
harveyj@mcmail.cis.mcmaster.ca         | Hamilton, Ont Canada L8S 4K1

On Fri, 18 Apr 1997 radgovwa@sage.wt.com.au wrote:

> Hi Radsafers
> 
> We were having a discussion at morning tea/coffee about the efficiency of gas proportional 
> detectors in 2 pi geometry. I mantain that the max efficiency in 2 pi 
> should be between 40% to 45% and can't go above 50%  for 
> alpha detection. For beta detection the figure should be between 30% 
> to 40%. The sources we use for calibration are Am-214 and Sr-90.
> 
> What are your thoughts??
> 
> Rex Breheny
> radgovwa@saga.wt.com.au
>