Re: ED underresponse in pulsed x-ray fields

[tdc@ehssun.lbl.gov (Ted M. de Castro)]

>>However, I have heard from someone at LBL (I think, it's been a while) who
>>used the same dosimeter in a Mega-rad/hr (instantaneous) field (pulsed as
>>well) and they responded admirably.

Well maybe not mega-rad/hr - then again...... 

We exposed to the highest fields we could find around the ALS - a few 10's 
of mREM/hr.  With the EXTREME duty cycle - around 10E6 : 1 - I guess that IS 
megarad!!

Anyhow - we did a very simple test - exposed the Siemens EPD along side a 
high rate ion chamber instrument - the HPI 1030.  They both tracked 
relatively well and there is no reason at all to assume that they would have 
even similar rate responses - thus it is reasonable to assume that both 
indeed tracked the field.

We didn't try any others.


>>This surprised me because the PD-3 is a GM tube.

Well ..... if the response is such that the probability of a count is << 1 
per machine pulse, then there is little chance of dead time losses and on a 
statistical basis it will track fairly well BUT when the probability of a 
count starts to get within a couple of orders of magnitude of 1 per pulse - 
then you'll start getting losses. 

Ted de Castro
tdc@ehssun.lbl.gov
University of California Lawrence Berkeley Laboratory
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