RE: Q:film badges and filter patterns

["Sandy Perle" <sandyfl@earthlink.net>]

Per Melissa, I will provide Rob Gunter's private E-Mail with some 
technical thoughts on film, filter and energy issues. This was sent 
in private so not to be construed as "advertising".

> As far as the problem I posted goes, I received a possible answer 
> via private e-mail, so I am not sure that the individual wants to be
> identified (he can do so himself if he wishes) or that he wants me to
> give too much data away as it appears to be preliminary, but in general
> terms...  

Melissa,

Greetings, I have been a subscriber of radsafe for a while and must 
say I appreciate your sponsorship and maintenance of this service. 
Thank you.  Regarding film dosimeters, I am the resident film guy 
for ICN.  My background has been in TLD, but I find the film area to 
be both interesting and challenging compared to the linear 
(booooringgggg) aspects of most TLD materials.

We have generated a lot of response curves, but I don't yet have 
data for the energies between about 150 keV to 662 keV.  I expect 
to get some data from the ISO NS250 beam (about 208 keV 
energy) in a month  or two as we are performing some calibration 
shots.  If you are interested in receiving some results, let me know.

In the mean time I will leave you with the following URL, and some 
knowledge.  The URL shows the response of Kodak type AA film.  
Most providers use the Kodak type 2 film which is a little different 
but the following should approximate the numbers.

physics.nist.gov/PhysRefData/XrayMassCoef/ComTab/kodak.html

Comparing the graph with other attenuation materials (Cu, Pb+Sn) 
will give you an idea of what to expect.  There is a slight pattern 
with Cs (662), though relatively insignificant when compared to the 
X-rays.  A slightly more pronounced pattern is visible under the Pb 
filter with NIST beam H150 (117 keV), more so with M150(80 keV) 
and so on. It looks like the distinction goes away (relatively) at 
around 200 keV, but I can't verify this with out data (yet).  Check 
out the readings under the Pb element and ask for the actual 
numbers, or even ask to have a look at the films themselves.  

One other thing to consider is this, the film pattern that can be 
seen with Cs is very slight and usually produced with a single
exposure at 90 degrees incidence on a phantom or other aparatus.  
If the real exposure occurs in the real world, the 
isotropic exposure of the dosimeter will not leave such a distinct 
pattern.  It may be that the pattern is so slight that it is not 
considered significant.  Of course, exposure to heat and humidity 
will raise the level of dose indicated, though the numbers 
you indicate are high and probably represent dose, especially the 
1+ rem.

Let me know if I can be of further assistance.

Yours,

Rob

--------------------------------------------------------------------------
------------------- RobertJ. Gunter		Tel: (714) 545-0100 
Sr.Technical
Specialist		Tel: (800) 548-5100 Ext. 2414 
ICNBiomedicals, Inc.		Fax: (714)
668-3149 DosimetryDivision		Email: 
rjgunter@icnpharm.com 3300Hyland Avenue
Costa Mesa, CA  92626

------------------
Sandy Perle
Technical Director
ICN Dosimetry Division
ICN Plaza
3300 Hyland Avenue
Costa Mesa, CA 92626
Office: (800) 548-5100 x2306 
Fax:    (714) 668-3149
  
sandyfl@earthlink.net
sperle@icnpharm.com

ICN Dosimetry Website:
http://www.dosimetry.com

Personal Website:
http://www.geocities.com/CapeCanaveral/1205

"The object of opening the mind, as of opening 
the mouth, is to close it again on something solid"
              - G. K. Chesterton -

The opinions expressed are solely, absolutely, positively, definitely those of the author, and NOT my employer
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