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 2.GQ Geiger Muller Counter
 X-ray xhrcount

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ninocarlos Posted - 09/07/2018 : 09:22:04

I use xhrcount in my work and would like to know if there are x-ray leaks. Which Geiger Counter to control?
thank you
Excuse me for my english translated!
5   L A T E S T    R E P L I E S    (Newest First)
ninocarlos Posted - 09/08/2018 : 04:19:16
I don't know anything about radioactivity but your answers have been very instructive.
The xhrcount seems secure so the geiger counter may not be necessary.
Thank you.
ullix Posted - 09/08/2018 : 00:05:05
Indeed, should be Gray, not Sievert. Let's hope the company's understanding of technology is better than their understanding of physics.

But, with X-rays the factor between the units is 1, so numerically it does not matter. I'll stay with the wrong unit ÁSv for now.

The machine seems to irradiate the test objects with 1.25ÁSv within a cycle of 10 seconds. Hence the dose rate is at least 1.25ÁSv/10sec or 450ÁSv/h.

With our M4011 tube calibration factor of 0.0065ÁSv/h/CPM it would mean CPM=69000, or CPS=115 for up to 10 seconds.

But since you are looking for leaks, you will surely get much less than that. It might be too close for background to draw any conclusions.

Next problem is the ability of the M4011 tube to detect the low energy X-rays. Spec sheets - if they can be taken seriously at all - talk about a lower detection limit of 100keV, while your x-rays may be 20...50keV, i.e. are undetectable if the specs are correct.

In your case, given the time and effort you will have to go through, I would choose the largest tube available to get a higher sensitivity, and one with a Mica window for a better chance to see the low-enery x-rays.

At GMC the only option seems to be the GMC-600 counter with the LND7317 tube.

ikerrg Posted - 09/07/2018 : 13:19:57
It is strange. The absorbed dose for objects should be given in Grays (Gy), not Sv.

X-rays at normal energies are ionizing radiation, they cannot change the nuclei and therefore they cannot activate components.
ninocarlos Posted - 09/07/2018 : 11:14:28
I read on this site : Exposure of components <1.25 #956;Sv.

What does it mean? Do the components become radioactive?
ikerrg Posted - 09/07/2018 : 09:49:37
Depending on the energy of the X-rays (they might not be detectable at very low energies) and the intensity, but in principle the GMC-320+ would be the most cost effective option if the energy is at least 30 keV. Someone else could confirm the detection energy of the M4011 tubes vs. the pancake types, just in case the GMC-6XX series is better suited.

As a reference, my GMC-500+ is able to detect the X-rays in an old colour CRT TV (about 50 keV X-rays?), but to be fair, the count rate is not massively bigger than background (about 40 CPM), most probably due to the lead content in the screen glass. The TV is one of the latest models of the CRT type, and the shielding was improved on the last years of the colour CRT technology. What it is clearly measurable is a burst of Xrays when the screen is switched on and off, although I suspect that some of them are also electrons built up on the screen surface.

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