Re: Beam Correction Factors

[Michael Williamson <m.williamson@mailbox.uq.edu.au>]

Kathy Brock asked:

>When monitoring with a portable neutron remmeter, is it appropriate when
>measuring a small collimated beam to correct for the size of the detector
>(sphere) volume in the same manner that the dose rate is corrected when
>measuring a gamma beam with an ion chamber?  Is there a good reference
>available?
>

My 2c worth (BTW I'm quite willing to be corrected by people who are more
learned in these matters, but seeing  no-one else has replied I'd like to
give my own empirical view of the issue):

The reason we are able to apply a volume correction with an ion chamber or
scintillation crystal has to do with the relative uniformity of the
detector volume, i.e. one bit of the detector has much the same response to
radiation as any other bit.

The insides of an Anderson Braun rem counter are rather non-uniform and it
might be difficult to ensure that the volume that you irradiate has the
same response characteristics as the complete detector system.  Have a look
at the diagrams in Knoll or Cember and you'll see what I mean.


Regards

Mike

Michael Williamson				ph +61 7 3365 4504
University Radiation Protection Adviser		fax +61 7 3365 1577
The University of Queensland			m.williamson@mailbox.uq.edu.au
Brisbane 4072
Australia

Any advice or information given in this posting is the opinion of the
writer alone and other than where explicitly stated, does not represent the
views or policies of the University.


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