RE: GM Response (formerly Respect) -Reply

[Craig Reed <CReed@novoste.com>]

Another static problem for reliable counting... Specific field
applications of window-less long range alpha detectors (LRAD) yielded
unreliable quantitative results when alpha induced ions/electron clouds
were collected and neutralized by static on the non-conducting surfaces
being surveyed rather than on the collection electrodes of the detector.


Craig Reed
creed@novoste.com

> -----Original Message-----
> From:	LIPTONW@dteenergy.com [SMTP:LIPTONW@dteenergy.com]
> Sent:	Friday, September 04, 1998 1:10 PM
> To:	Multiple recipients of list
> Subject:	Re: GM Response (formerly Respect) -Reply
> 
> I made that statement thinking it was a moot point, not realizing that
> 
> windowless counters are still in use.  I ran into this at Argonne
> National 
> Lab, where we sometimes used a windowless internal proportional
> counter.  
> Nonconducting materials, such as paper, build up static charges.  This
> charge 
> may be strong enough to alter the electric field lines within the
> detector, 
> and, hence, the counting efficiency.  Since the static charge
> distribution 
> changes from sample to sample, this leads to nonreproducible results.
> I
> know 
> of 3 ways to overcome this:  (1) use a windowed counter, if feasible;
> (2)
> use 
> a conducting sample - I've seen carbon-impregnated smears; (3) put a
> material, 
> such as mylar, over the sample, essentially making this a windowed
> counter. 
>  
> The opinions expressed are strictly mine. 
> It's not about dose, it's about trust. 
>  
> Bill Lipton 
> dteenergy.com 
>  
> You wrote: 
>  
> <Bill, would you please elaborate on your statement below?  This is 
> <an issue we are susceptible to with our usual met. conditions (i.e., 
> <high and dry!).  Thanks! 
>  
> <Michael 
> <mford@pantex.com 
> >>>>>>>>>>>>>>>>>>>>>>> 
> <One final point and I'll leave you alone. Use a great deal of caution
> 
> <if you use a windowless counter for assaying nonconducting 
> <sources, such as smears or air samples.  Static charge buildup 
> <may lead to nonreproducible results.... 
>  
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