RE: GM Counters in High Backgrounds

[Bob Flood <bflood@SLAC.Stanford.EDU>]

At 09:13 AM 10/13/1999 -0500, you wrote:
>It's a standing joke in Containment during Outages
>when a person gets a 12kdpm/100cm2 count in a 10kdpm background and calls it
>"2k" that the individual is stuck with that name for the whole Outage until
>he/she counts the smear in a much lower background and find it reading
>between 12k and 15kdpm/100cm2.

I have to admit to some confusion over units in this discussion. In the
above example, background is compared in units of dpm to a smear exhibiting
radioactivity in dpm/100cm2. Hopefully the background count rate isn't due
to beta-emitting contamination inside the HP-210 probe. It would be due to
the incident photon field, and thus should not be converted to dpm. The
conversion that was made assumes some efficiency not given.

Can we see this case again where we deal only in insrument readings in cpm?
Are we dealing with a 1,000 cpm background or a 10,000 cpm background? And
what is the gross reading on the 15,000 DPM smear? If the GM isn't giving
you what you consider an accurate assessment of the activity on the smear,
how did you arrive at the 15,000 value?

===================================
Bob Flood
Dosimetry Group Leader
Stanford Linear Accelerator Center
(650) 926-3793
bflood@slac.stanford.edu
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