SBM-20 and X-Rays

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vtanner
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SBM-20 and X-Rays

Post by vtanner »

While wandering around with my recently completed Geiger kit I held it in front of a CRT based TV (Sony Trinitron 27" flat screen). With the TV on there is a definite increase in counts. Turning the TV off returns the count to normal background instantly. I was assuming that any X-Rays from the CRT would be too low in energy to trigger the SBM-20, but that might not be the case. Putting a few inches of distance between the face of the tube and the counter also reduces the count to background levels.

Am I actually picking up X-Rays with the SBM-20 or is this perhaps static charge or interference from the CRT that is confusing the counter?

- vic
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mightyohm
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Re: SBM-20 and X-Rays

Post by mightyohm »

Geiger-Muller tubes can detect x-rays, so it seems plausible that your TV is putting out some ionizing radiation.

Does the count change if you put a piece of shielding material in between the TV and the geiger counter? Maybe a thin sheet of metal?

Also, do you get any readings from behind or next to the TV?
vtanner
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Re: SBM-20 and X-Rays

Post by vtanner »

mightyohm wrote:Does the count change if you put a piece of shielding material in between the TV and the geiger counter? Maybe a thin sheet of metal?
I've tried hand holding (not grounded) a large sheet of thin aluminium (approx 15" square). It stops the count. The static charge on the face of the tube was strong enough to pull the metal towards the face of the tube when I wasn't expecting it.

I've been intending to try aluminium foil but not got around to it yet. Grounding the foil might demonstrate that it's static charge rather than X-Rays. Since just a few inches (approx 6-8 inches) of air is enough to eliminate the count I've not been convinced the X-Rays would make it through the foil though. An antistatic bag was another thought, but I don't have one big enough yet.
mightyohm wrote:Also, do you get any readings from behind or next to the TV?
No readings come from anywhere else on the TV. In fact, the maximum count is obtained in the centre of the front face of the picture tube. As I move toward the edge of the screen the count noticeably declines.

- vic
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mightyohm
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Re: SBM-20 and X-Rays

Post by mightyohm »

Then I suspect that you are, in fact, measuring x-rays. If I can find a CRT I will have to check this out.

Apparently it is normal for CRT TV's to emit a small amount of x-rays:

http://en.wikipedia.org/wiki/Cathode_ra ... _radiation
Jagnag
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Re: SBM-20 and X-Rays

Post by Jagnag »

Just posted in another thread on this site that I had the same experience detecting presumably x-rays from a Sony Trinitron CRT. In other news, this is what the mighty on Geiger kit looks like with a really good dose of x-rays
X-ray image
X-ray image
Image credit to my X-ray tech wife)
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mightyohm
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Re: SBM-20 and X-Rays

Post by mightyohm »

that is awesome, thanks for sharing! :shock:
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