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Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
You don't tell us about the type of GM tube, so only a general answer is possibe.
GM tubes will detect energetic UV photons, which is why most, but not all, glass tubes are painted or coated black.
The glass seals on some metal tubes may be sufficient to admit light of sufficient intentsity.
If there is no way light could be getting into the tube, then we must suspect EMP/EMI from the capacitor discharge through the xenon tube.. Only tiny currents are involved in tube operation, and a small EMP or EMI pulse may be sufficient to push the tube far enough up the plateau of the Geiger Region to cause a misfire.
If the GM counter has an audio circuit, it may simply be picking up EMI by so-called 'direct detection' if it be only poorly screened.
Remember that all tubes have a percentage of spurious counts, and the more sensitive the tube, the more easily it is triggered falsely by undesired signals.
If you were to give us some GM tube data, and describe the mounting/housing of the tube, what its case is made of, whether mains or battery powered etc, I would be able to give a much better answer.
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040
It is most likely the EMI/EMP generated from the flash, especially via the trigger transformer (but just as likely the cap's e through the flash tube)
However, as I have been researching a little on the side, there is the POTENTIAL, meaning possibility though in this case not too likely, that the flash tube puts out a very small quantity of xrays, but as mentioned before: this is an unlikely scenario, since the gas inside the flash tube should be at a higher pressure than can accomadate xrays...
Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
The only thing that comes to mind is to find a way to strike an arc across a flash tube continually, probably using a flyback. Get the arc going and measure to see if there are any emissions.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
I understand that if you open the plastic case of DRSB-88 that the guts are very light sensitive, and the instrument will click in proportion to the ambient light intensity!
There is a pea neon in series with the tube in this device (the light that blinks when counting is not an LED!) and this would allow bright light from a flash to enter the case, as well as being photosensitive itself!
Moreover, the case is plastic, and so provides no EMI shielding from any RFI/EMI pulse radiated by the flash discharge.
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Strange Behavior of Geiger Counter vs Xenon Flash Lamp
