The key to the geiger counter is a reduced pressure gas taken near its electrical breakdown point with a high field emission component.
Gas isn't critical if you just want functionality or to demo concept.
For the basics.....
Take a tube of metal. Copper will do. Plug one end with a piece of reynolds warp Al foil stretched tight over the end. It should be in electrical contact with the copper.
(1" copper water pipe section ~4" long would be OK)
Next, plug the other end with some form of gas tight stopper which has a very straight length of stiff, but tiny diameter wire protruding into the center of the copper tube to about 1/2" from the Al window. Note, it is normal to place an insulating ball on the end of this wire near the foil. A well cured bead of epoxy ought to do. (reduced field of the pointed tip) This plug should also have a vacuum port or pipe in it, although soldering the pipe to the side of the copper tube near the wire stoppered plug is OK.
You are now done with the physical assembly.
You will need a vacumm gauge of the Boudin type. (regular old needled vacuum guage. Pump the system down with a pump until the gauge gets near its lower limit. The ideal pressure for an air filled geiger counter would be in the 5-20cm range (50-200 torr). You will have to experiment with applied voltage and pressure. Voltages with air are usually in the 1000 volt range or higher. You would use a standard 3meg dropping resistor to the supply and capacitor coupling to a simple audio amp like the Radio Shack amplified speaker. I detail the basic geiger circuit in my video on Radiation, where I assemble a basic counter using a factory geiger tube.
It is all simplicity itself.
The problems will be a low counter rate and a very narrow, (voltage critical), geiger plateau. The optimum voltage will only allow about a plus or minus 20 volt range of geiger action. A really well behaved variable HV supply is a must. (easy to assemble with a variac controlled bridge and capacitor off of a microwave oven transformer. (lethal)).
As this simple tube is not chemically quenched, the count rate will be limited to a few thousand counts/minute.
If you have a TIG welder with the mandatory Argon bottle, backfilling the tube with argon to the required pressure will make a much improved counter tube. Actually, any old cylinder of noble gas you have laying about the house or in the back of a closet will do famously.
If you want to really move out on this effort, make a little gas/vacuum manifold with valved and gauged argon port and an alcohol port (Pure ethanol vapor for quenching) and you can seal tubes off that will rival anything you can buy!
The level of pefection can be tailored to your needs. (note: long term functional sealed tubes must be meticulously cleaned)
All of this data and info on finely detailed geiger tube construction and quenching can be had in Korff's superlative, never to be equalled, text mentioned in the BOOKS AND REFS forum. Or, better still, just search under the single word "Korff" to see all this site has to say about him and his works.
Richard Hull
Roll Your Own Geiger Counter Tubes
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Richard Hull
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Roll Your Own Geiger Counter Tubes
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Re: Roll Your Own Geiger Counter Tubes
Thanks Richard, I've got a pair of homemade geiger board's
tested and awaiting some mail order 5979 tubes. I'll play around
with some homemade tubes and see what I can get.
tested and awaiting some mail order 5979 tubes. I'll play around
with some homemade tubes and see what I can get.
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Richard Hull
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- Joined: Fri Jun 15, 2001 9:44 am
- Real name: Richard Hull
Re: Roll Your Own Geiger Counter Tubes
The 5979 is a great tube. Anton labs made some of the best. They were used in many mil spec. government geiger counters in the 50's and 60's. I have about 30 on hand here and use them casually in a number of apps.
They tend to, generally, after all these years, have degraded to the point where the base count or background is rather high and the good geiger plateau is rather narrow. This is due to the chemical reaction of the halogen quencher with the tube's metal casing, thereby, making the tubes not quench all that well any more.
In some cases, I have found good specimens that will work well from about 650 volts all the way up to 800 volts. Even bad 5979's will be serviceable enough to act as fine radiation detectors, even if not accurate or fast.
Richard Hull
They tend to, generally, after all these years, have degraded to the point where the base count or background is rather high and the good geiger plateau is rather narrow. This is due to the chemical reaction of the halogen quencher with the tube's metal casing, thereby, making the tubes not quench all that well any more.
In some cases, I have found good specimens that will work well from about 650 volts all the way up to 800 volts. Even bad 5979's will be serviceable enough to act as fine radiation detectors, even if not accurate or fast.
Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Re: Roll Your Own Geiger Counter Tubes
Actually they showed up yesterday and are Anton Electric units
I wonder if baking them may release some halogen from the
walls, you'd have to avoid melting the plastic and what looks like
the epoxy glue seals. The circuit I'm using for HV is a real dog,
I'll have to make another circuit to stop the oscillation
breakthrough to the speaker circuit.
I wonder if baking them may release some halogen from the
walls, you'd have to avoid melting the plastic and what looks like
the epoxy glue seals. The circuit I'm using for HV is a real dog,
I'll have to make another circuit to stop the oscillation
breakthrough to the speaker circuit.
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Richard Hull
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Re: Roll Your Own Geiger Counter Tubes
There is no plastic in the tubes. The front clear aperture is covered with mica so thin that the concussion of door slamming fast in a well sealed room can implode the mica. Mica windowed geiger tubes are pressure-wave sensitive. Those apertures make tissue paper look like a bank vault door.
You can't heat the tubes and get the halogens back. The bromine has actually entered into a chemical reaction and not just been absorbed into the metal walls. Heating will definitely ruin the tube.
I could never over-emphasize the delicacy and fragility of a good mica windowed geiger tube. The mica's thickness is never expressed in mils or microns, but in milligrams/sq cm! All of this is to allow the alpha particles to pass into the tube without being absorbed in the end window.
The best mica windowed tubes are all of the pancake form and cost well over $150.00 each, new.
Richard Hull
You can't heat the tubes and get the halogens back. The bromine has actually entered into a chemical reaction and not just been absorbed into the metal walls. Heating will definitely ruin the tube.
I could never over-emphasize the delicacy and fragility of a good mica windowed geiger tube. The mica's thickness is never expressed in mils or microns, but in milligrams/sq cm! All of this is to allow the alpha particles to pass into the tube without being absorbed in the end window.
The best mica windowed tubes are all of the pancake form and cost well over $150.00 each, new.
Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Re: Roll Your Own Geiger Counter Tubes
I had a closer look at my 5979's, it's glazing on ceramic not
epoxy on plastic as I first thought!!!. I'll have to get a copy of
Korff's book once I get a bit more cashed up again and read up
on tube construction techniques, I have the gear to grind and
polish thin crystalline materials, possibly starting with a mica
heatsink washer.
epoxy on plastic as I first thought!!!. I'll have to get a copy of
Korff's book once I get a bit more cashed up again and read up
on tube construction techniques, I have the gear to grind and
polish thin crystalline materials, possibly starting with a mica
heatsink washer.
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Richard Hull
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Re: Roll Your Own Geiger Counter Tubes
Mica is mined in "books". Mica is associated with pegmatite and feldspar minerals and is layed down in layers. The mica is always skeeved out of the mined books with a special razor knife. There is practically no limit to the thinness to which mica can be skeeved. Therefore, the mica windows in a GMT are not polished, they are naturally skeeved layers of desired thickness. I have personally skeeved mica so thin that it falls like a piece of goose down.
Again, the mica is not CUT to desired thickness it is literally spearated out in a natural plane by mere separation. The knife blade just assists in overcoming the rather considerable surface tension forces found at the parallel crystaline layers. There is no effective adhesion in mica layers.
Richard Hull
Again, the mica is not CUT to desired thickness it is literally spearated out in a natural plane by mere separation. The knife blade just assists in overcoming the rather considerable surface tension forces found at the parallel crystaline layers. There is no effective adhesion in mica layers.
Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Re: Roll Your Own Geiger Counter Tubes
It's amazing the esoteric information I've picked up on this forum
over the years!. I find I'm having to focus on the fusor project
first and then on all the subsidary technology afterwards. While I
think of it: a BF3 tube would be just as easy to make as a GM
tube wouldn't it?. That is assuming you could buy BF3 gas off
the shelf.
over the years!. I find I'm having to focus on the fusor project
first and then on all the subsidary technology afterwards. While I
think of it: a BF3 tube would be just as easy to make as a GM
tube wouldn't it?. That is assuming you could buy BF3 gas off
the shelf.
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AllenWallace
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- Real name:
Re: Roll Your Own Geiger Counter Tubes
This link http://www.sas.org/E-Bulletin/2003-05-2 ... /body.html contains a long discussion of gas detectors. The title is "An Interview with John De Armond About Neon Glow Tube Radiation Detectors".