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Registered Member #61858
Joined: Thu Oct 26 2017, 10:31PM
Location:
Posts: 1
I am writing to inquire about the use of GM tubes for the detection of x-rays. I understand there is some expertise on this forum in this matter. My question is outlined below, and any insight would be much appreciated!
I work in a medical office situated directly behind a diagnosic x-ray facility. My desk is 1-2 metres behind the x-ray machine's tube, but the beam usually faces either the opposite direction, or straight down (i.e either 180 or 90 degrees from my position). There is a drywall separation between the x-ray room and my office, and I'm told there is the usual requisite lead in the wall. I'm also told the beam is collimated, and stray doses should be negligible.
Because of the above proximity, I employ standard optical dosimeters, but these do not provide real-time data. In an effort to get some sense of whether there is "scatter" or "leakage" radiation exposure, I positioned a cheap "Radex One" SBM-20-based geiger counter on my desk. My concern is that this device goes berserk every time the x-ray is used, numerous times throughout each workday.
I have read some posts regarding geiger counter "over-response" in the diagnostic energy range, and wonder whether my readings could reflect that. Whenever the x-ray machine goes off, I see large spikes on the instrument. The reported doses averaged over time approximate 2-3 times the background rates. On an average day, I may see an "accumulated dose" of 1-2 uSv on the instrument, but I recognize that this is a very unreliable figure.
How can one reconcile the "over-response" of the instrument, versus the low sensitivity of the geiger counter to x-rays. Is there a way to know whether the obtained values represent an overestimate or underestimate of the true value?
I do not have access to an ionization chamber, and am hoping the above data can be interpreted in a meaningful way.
Any thoughts or insight you may be able to share would be very helpful!
Registered Member #65
Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155
xkcd dosage graph:
Borrow a calibrated scintillation detector with a seconds logging mode, as it can estimate events and particle energy.
If the counter is estimating >2 uSv from a short-burst event asymmetrically distributed over some long time frame, than there may be cause to check if the GMT may have saturated in the burst.
I keep a few Betta fish in every office for their calming company, and the fact they are easier to care for than canaries. Cheers,
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X-rays and GM Detectors (sensitivity and dosimetry)
