Re: x-ray calibrations

[photcoef <photcoef@tiac.net>]

Response curves (output vs. energy) of ion chambers and other detectors with
outputs that are proportional to the deposite energy, can be calculated
easily and rapidly with PHOTCOEF. PHOTCOEF can also be used for the
calculation of dose in the skin and body, versus emergy.

Look up the PHOTCOEF Manual at

http://www.photcoef.com

Paul Kehler
AIC SOFTWARE, Inc.
P.O. Box 544
Grafton, MA 01519
Tel: 508-839-6779
Fax: 508-839-4853



At 12:52 PM 8/16/96 -0500, you wrote:
>>On the subject of calibrating survey equipment for analytical x-ray
>>machines:
>>
>>>  could you specify what type of analytical equipment, such an electron
>>> microscope?
>>
>>Unfortunately, both electron microscopes and x-ray diffraction units.
>>Double-unfortunately, as we are a research university, current/voltage/target
>>material in the XRDs is quite varied.  Triple-unfortunately, I also have
>>amusing things such as accelerators, experimental fusion devices and the
>>like to survey around. :-)  However, for the purposes of the question of
>>calibration appropriateness, let's say the equipment consists of EMs and
>>XRDs.  The XRDs are for the most part in interlocked, shielded enclosures.
>
>A committee of x-ray "experts" met at Livermore last month and concluded:
>
>A thin walled GM detector should be used to detect leakage.
>
>An ion chamber should be used to measure dose rates.
>
>At Los Alamos, we use ion chambers calibrated with Cs-137 to measure
>leakage dose rates, and integrating ion chambers calibrated according to
>NIST x-ray protocol to measure the main beam.  But I wonder if we are
>making this more complicated than we need to.
>
>As I understand it, a concern is that ion chambers show a decreased
>response to lower energy photons (below 10 keV) and so calibration with low
>energy photons might be appropriate.
>
>I think the key questions are:
>a. What causes this decreased response at low energies?
>b. Is there a similar decreased response in the skin of the body?
>If the skin response is similar to the ion chamber response then there is
>no problem, and the ion chamber will give an accurate result.
>
>I don't know the answers to questions a and b, and (as usual) I am eager to
>learn.
>
>"Shlala gashle" (Zulu greeting, meaning "Stay safe")
>mike (mcnaught@LANL.GOV)
>
>
>