The March 03 issue of Nuts & Volts magazine describes a radiation detector, similar to a Geiger counter, but uses a common neon bulb. The claim is that the device can detect beta and gamma radiation, alphas being blocked by the glass. The article references another article at http://www.elecdesign.com/ under the 'Ideas for Design" section, March 18 2002, titled "Simple Geiger Detector Uses Neon Glow Lamp". This circuit runs from the ac main instead of using a power inverter, so it's quite a bit simpler. I put this circuit together and I seem to be able to bias the bulb just before its ignition point as described in the article.
I set my scope up to detect the negative edge of a the voltage drop I expect for an ionization event. I found that in a darkened room, I could occasionally get a trigger by shining a very bright led keychain flashlight directly on the bulb, so I used that to get my trigger condition more or less set. I found that once set up, I didn't see ANY triggers over the span of several minutes.
Questions:
At roughly what rate should I expect to detect background particles, assuming that I'm in a simple wood-frame house with not shielded by any obstructions?
From searching though the archives on this site, I see that Americium used in a smoke detector is an Alpha emitter, so I wouldn't expect to detect anything from that source. How about lantern mantels?
The sensitivity to light as I flashed the led flashlight seemed to come and go. It kind of seemed like the sensitivity would decrease, then build back up over time if I stopped flashing the light. Based on the observations from my scope, I don't think this was due to variations in the supply voltage. Is there some property of the gas that could account for this?
