[ RadSafe ] Low Level Readings using probes

[Robert J Gunter]

I have attached one of my favorite curves illustrating the energy response
of a film dosimeter with various filters over it.  It was generated by the
dosimeters used by Miron and with their permission.  It is a favorite
because you can see the effects of PEE, CS, and to a lesser extent Pair
production which leads to the non-linear responses we see in a lot of
instruments.  In my CHP Review classes, I like to point out you could
probably base a CHP test on only this curve.....

There are plenty of meters out there that will work with most any probe.
What you want to do is be able to adjust threshold, and high volts among
other things.  Older scalers are good for this and inexpensive.

Yours,

Rob

Robert J. Gunter, MSc, CHP
CHP Consultants/CHP Dosimetry
www.chpconsultants.com
www.chpdosimetry.com
Toll Free: (888) 766-4833
Fax:  (866) 491-9913 
Cel:  (865) 387-0028
rjgunter at chpconsultants.com


-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Matt Sargent
Sent: Tuesday, May 15, 2012 12:50 PM
To: radsafe at health.phys.iit.edu
Subject: [ RadSafe ] Low Level Readings using probes

Low Level Readings using probes

One thing I've read that I am trying to understand, is it sounds like the
response output is only linear up to a certain point on certain detectors,
after that readings become non-linear, this leads me into wondering about
how well various products deal with this, from what I can tell any given
meter/software solution had best be tied to a specific probe's
characteristic, not only in the high voltage power supply requirement, but
also to linearize the respond at various source levels which could
potentially confront the detector. Is this something worth worrying about?
I've yet to see any plots of how non-linear the response gets.

Up to this point in time, I have been comparing relatively small counts, if
that was all I cared about, why spend a great deal more, get a really good
detector and hook it up to just about any old meter/power supply and take
the readings. Kind of what I've been thinking. However, if I want to have
accurate comparable numbers from higher intensity levels, I have better make
sure my detector probe model is supported (and it's non-linearity corrected)
by whatever measurement meter/software solution we're using.

If that makes sense?

I have an old CDV-700 model meter and I am trying to decide if it is
worthwhile to get an alpha, beta, gamma probe for it or upgrade completely
to something new?  I am looking at the RDS-31 with the GMP-11 probe.  As I a
very familiar with the RDS family I have a bunch of the RDS-30's on the Job
Site.

One other question I have pondered is the degrading effect that Radiation
has on electronics how does the new digital equipment shield itself from
this?  Not that one is high rate areas all the time but how will they last
over time?

Can any one point me to some papers or studies that can possibly give me
some answers or make some recommendations?

Kindly,

Matt Sargent
Safety Compliance Officer

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