The clicking of a Geiger counter is well enough known as a signifier of radioactive materials, due to it providing the menacing sound effect any time a film or TV show deals with radiation. What we’re hearing is the electronic detection of an ionization event in a Geiger-Muller tube due to alpha or beta radiation, which is great, but we’re not detecting gamma radiation.
For that a scintillation detector is required, but these are so sensitive to background radiation as to make the clicking effect relatively useless as an indicator to human ears. Could a microcontroller analyse the click rate and produce an audible indication? This is the basis of [maurycyz]’s project, adding a small processor board to a Ludlum radiation meter.
When everything sounds like a lot of clicks, an easy fix might be to use a divider to halve the number and make concentrations of clicks sound more obvious. It’s a strategy with merit, but one that results in weaker finds being subsumed. Instead the approach here is to take a long-term background reading, and compare the instantaneous time between clicks with it. Ths any immediate click densities can be highlighted, and those which match the background can be ignored. SO in goes an AVR128 for which the code can be found at the above link.
The result is intended for rock prospecting, a situation where it’s much more desirable to listen to the clicks than look at the meter as you scan the lumps of dirt. It’s not the first project in this line we’ve brought you, another one looked at the scintillation probe itself.
This was covered by Dan back in September.
I think you got that wrong my love. Alpha is helium atoms, beta is electrons and gamma is photons – and only photons pass through glass of GM tube. Scintilatsiya detectors are the ones used for alpha and beta. Next time less youtube more book friend.
A pancake probe can detect alpha, beta, and gamma.
Depends on the pancake probe. They are not all alike.
Complete rubbish. GM tubes will happily detect alpha particles. Here’s mine detecting an Americium-241 source: https://www.youtube.com/watch?v=-F4gvk5Edz0
The article says G-M tubes detect alpha particles right in the first paragraph.
Most GM tubes do not detect Alpha. Some GM tubes will detect the associated Gamma from the Alpha decay and Beta/Gamma decay of daughter products in the decay chain.
Simply showing a meter detects something near an Alpha source doesn’t mean it is detecting the Alpha.
/Senior Radcon tech with experience with BWR and Graphite Production reactors, Chem reprocessing, and Nuclear Demolition.
Complete rubbish. Am-241 produces a 60 keV gamma ray, much more readily detectable by a G-M tube than its alphas.
The alpha particles are readily detected by a suitable pancake probe. What are you using to measure a sample of Am-241?
“suitable” being the key. Most do not have the thin and fragile window required for alpha detection.
And even a good mica-windowed tube won’t detect them until you’re right on top: less than 3 cm away, because air is a pretty good absorber of alphas.
An ion chamber makes a good detector for alphas too, with the same proviso wrt range. Doesn’t give the dramatic clicking sound though.
Those 60 keV gammas though — they’ll go many meters in air.
An Alpha sensitive probe has to have a window with a lower density thickness (thinner walls). The fact that Alpha particles can be stopped by a piece of paper means the detection efficiency is usually much lower than Gamma.
Please correct this article. GM tubes always detect gamma radiation and will detect alphas and betas if the tube has a thin window, such as mylar, built into it, where those particles can pass through.
Dearest Jenny,
Most GMs only detect Beta and Gamma radiation. A few can detect Alpha. All detect Gamma. All of this is determined by the density thickness of the GM tube walls. Very thin walled tubes can detect Alpha. Slightly thicker tube walls will block Alpha and allow the more penetrating Beta and Gama pass. Other tubes have walls thick enough to exclude all but Gamma. Some tubes have a movable shield allowing the user to block one or more of the weaker penetrating radiations so it can be determined how much of each type contributed to the unshielded total reading.
The main point is all GM tubes measure Gamma radiation.
Thank you so much! After reading the first few lines of the article, I initially thought that the history of physics would have to be rewritten for hackaday ;-)
As others have said, the summary is rubbish. It’s a repost of the confidently incorrect information from the builders website.
I don’t really understand the point of the project if I’m honest. The assertion that the background makes the click rate useless is nonsense. I have used them in high background (~tens of uSv / hour environments). Set the scale appropriately and have at it.
I’m confused about the goal too. Unless they are using a scintillation probe like a sodium iodide probe on a GM body which would produce a lot more detection events. In this case you would usually just read the dial but I guess they want audio.
It has a point.
With the large detector head on this meter, normal background is many thousands of counts per minute: It’s just white noise, nearly useless for surveying for hot spots. You have to read the meter.
Reducing the click rate to something slower lets you take your eyes off the meter, as stated in the premise.