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RE: Thinking About A Geiger Counter

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 04:44 PM 11/6/2005, Tesla list wrote: 
Original poster: Skip Malley <skip@xxxxxxxxxxxxxxx>

I am familiar with the original thread. I was responding to one coiler's mistaken assumption that a Geiger counter could measure X-rays.


I very well know that high voltages striking objects is something that creates X-RAYS. My intended meaning is that Geiger counters count particles, not x-rays or other radiated energy.

Xrays ARE particles that can be counted by a Geiger counter. They are photons with sufficient energy to ionize a gas (hence, the term "ionizing radiation" to distinguish things like X-rays and such from RF, which is non-ionizing). The boundary line is probably somewhere in the UV.. although one might argue that the photoelectric effect is the result of ionizing the metal upon which the photon falls. For a Geiger-Muller tube, you're also counting on the avalanche that occurs, and that presumably requires a bit more energy than some stray photoelectron. Strong's book has a nice drawing of a huge GM tube loaded with Argon.

RF can be considered as photos, just that they have awfully low energy: below the activation energy of any known reaction, so claims of things such as genetic damage or cancer from RF exposure must be from mechanisms other than classical "radiation damage". The vast majority of effects of RF can be explained by thermal effects, but there ARE some athermal effects (auditory clicks from high power microwave pulses, for instance), and there is some work ongoing to try and understand them (perhaps instantaneous field).

I will admit that a geiger counter would be useless for such low energy photons as might be encoutered even with millimeter waves.

The challenge in detecting low energy xrays from a spark using a Geiger Muller type tube would be in figuring out what to make the tube of that didn't absorb the xrays. Many GM tubes for these sorts of applications have a window of something like thin mica (or perhaps Kapton or mylar?) that is rugged enough and still transparent to the low energy photons.




Skip

At 01:10 PM 11/6/2005, you wrote: 
Unnhhh... Skip -- the original question was brought about by the very
interesting: "Lab Sparks make X-Rays" thread.
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