Geiger counter options

[Tishers]

Here are a few other sources of low level radioactive materials;
)
Old, glow in the dark watch and clock faces. Typically these were painted with (Radium 226)
Old valves (tubes) from radios and televisions. Usually the high voltage regulator tube had a radioactive source to create an ionization trail so the tube could start conducting.
Smoke detectors (Americium 241)

I have a home-made sealed source of Radium 226 from an old clock face. It creates thousands of counts per second and is at least a beta/gamma emitter. I do not want to un-seal it (it is sandwiched between two layers of copper foil) as it would be a real contamination hazard.

Ms. Tisha

[trash]

Hehe ... you're a bit late to the show Tishers.
Some of us are bit hard core on collecting everything radioactive.

So the history of glow in the dark paint is that Radium was used up until about the 1950's.
Promethium was used in the 1960's and 70's and Tritium has been used since about the 1980's.

Yes, smoke detectors are Am241, though a lot these days are not, they use optical sensors.

Valves - actually no. None of the valves in old radios or TV's are "Thoriated". Thorium 232 is the isotope used in valves that have it.
The high voltage thermonic power diodes weren't Thoriated. The most common kind of tube that does have thorium are RF transmitter valves like a 4CX1000.

Thorium is also found most commonly in old gas lantern mantels. It's also in Thoriated welding rods and some of the high refraction index camera lenses and some gemstones like Ekanite.

Uranium is easy to find in antique shops. The green Uranium glass is very common and glows nicely under UV light. Brewdog and I tend to agree that the better a source glows under UV light the more radioactive it is.
It's a good general rule but there are some exceptions. Uranium glass is typically green, but some is yellow, blue and even pink.
There are also plenty of Uranium glazes. They're typically bright orange, a translucent yellow (which also fluoresces), brown and occasionally green.


Sealed your Radium. Oh that's a shame. Yes the secondary beta/gamma is nice, but Radium is an alpha emitter and so are the majority of it's daughters. Though the 7.7MeV alpha from Po214 has enough energy to penetrate the copper foil.
Pretty much all of the beta emissions will be absorbed by the copper foil. Which leaves only the gamma, most of which will penetrate the copper foil but the amount of gamma radiation is rather pitiful.

Your fears of Radium contamination from a poor old clock face are .... umm... a little excessive. The radium is pretty safely locked up in the zinc suphide crystal and glue.
So take it out of it's copper prison and let the alpha particles be free. It's really not going to hurt you unless you feel the need to lick it, and even then the radium is pretty safe from you

[mitaux8030]

Finished building the kit recently, and have been looking for sources to test it out with.
The ionising smoke detectors with Americium-241 in them only produces a weak reaction - but definitely noticeable. Think it must be the secondary gamma that's setting it off.
A lump of granite produced something barely above background.
My tritium illuminated bedside clock (about $100 of H3 tubes!) doesn't even tickle the SBM-20 as you'd expect. It also makes me feel a little better that my skull isn't being pounded by radioactive particles 8 hours a day. Life's a risk, isn't it?

Visited an antique shop today, and found a half dozen examples of uranium glass. One piece in particular was stunning in it's optical clarity and quite deep green colour (for uranium glass, anyway) but at $150 it stayed on the display stand. None of the pieces produced a count above twice the background... is that about normal for uranium glass? Thought I was going to get some weird looks by the shop owner, waving the Geiger counter around his establishment, but after talking with him he came out with "oh, so YOU'RE the guy looking at radioactive wares." Word gets around fast in these parts!

Have yet to go visit any of the abandoned uranium mines here... not gotten over that way yet, but hoping there's some torbernite in my near future. Wonder if I can get away with that without a prospectors' licence

[Bluedog]

Torbernite is very good, Auternite better and both can be bought from Peter or from rock and gems shows.
Do some research on old mining areas too, as we found 2 good sites within 2 hours drive of my home. Toongi and Carcoar, and we found great samples by the bucketfull.
The collection here in the doghouse is getting very large now, and Brewdog came home with some nice florenze and Scott glazed pottery pieces recently from an auction.
Places to hunt are basically every op-shop, vinnies, salvos etc, the tip shop, even a paint store in town has some nice uranium glass pieces. try small town op-shops as the gulgong op-shop had an extremely hot franscianware orange glazed bowl that was detectable as you walked into the room!!! the SBM20 counter rose noticably and goes into flatline overload when within 6 inches of the bowl.
Mineral samples are now into their third cardboard box with lots of wartime dials and radio equipment as well. One Australian made military radio stays out in the shed well away from the house as its front panel is detectable from 4 metres away. The radium paint is applied directly to the faceplate of the frequency dial and associated controls so the glowing radio could be operated in the jungles without using a torch to see the controls.
Re geiger counters ; the digital display kit versions from ebay are excellent and i have made lots of kits up for people to use. typically i use 4 SBM20 tubes all wired in parallel in a black plastic box, 9 volt powered with 2 line lcd display. The kit will happily drive 6 tubes in parallel too, and i have a supersniffer with digital display made from 6 in a box run from a couple of 18650 rechargable cells. you get a long runtime with lithium ion cells scrounged from old laptop battery packs.
I took a 4 tube one on a flight to Tasmania a while ago and observed the great increase in counts at full altitude compared to ground level counts. nearly a factor of 10 increase.
It freaked out the lady doing the carry-on luggage inspections , she put the blue rubber gloves on and went thru the bag finding the geiger counter. Good fun explaining about it.
Have fun hunting targets, so many places to check out, even your friends places when you go and visit them. Parents and grandparents places are always good
Cheers from the doghouse.

[Uncle Fester]

As I mentioned in post #3, I ordered the SBT-11A (small pancake) and it is more sensitive than my old Russian made counter with 2x SBM-20 tubes.
It is also very simple to mount on a small opening in the enclosure, just glued in with it's flat surfaces also allowing to get very close to the test object.
I highly recommend that kit, but do yourself a favour and ask for the SBT-11A (with socket) with it so you can also detect alpha. I think it is only $10-15 more than the SBM-20.
However I would not recommend this kit for the absolute beginner in soldering.

I use 3xAA Alkalines instead of the 9V block battery that I hate and removed the 5V regulator. Only do this after you checked everything works with the 9V and regulator.
The regulator limits the current if you made a soldering error, unregulated Alkalines can deliver several Amps. I used a 100mA polyswitch fuse.
I adjusted the pots to run and display well between 4.1 and 4.7V and a switch to cut the processor with display power so I can run around in the field for days just listening to the beeps.
Also can switch off the beeper for use in shops with out attracting too much attention. I could build the device pretty small (thanks to the SBT-11A).
Don't wan't the price to suddenly go up because everybody knows I found some interesting
However I haven't gone to the OP shops with it yet because if they have anything that looks like Vaseline glass or Fiesta ware, they already charge an arm and a leg for it.
Same on Sunday markets, it seems everybody knows these days that radio-active hunters are around.

[trash]

I'm not too sure where everybody is so I'm not sure what local areas you guys are searching.
Brewdog, Bluedog and I have overlapping turf. My local auction has some Uranium glass this weekend and some other Uranium glazes.
They sometimes call me to verify Uranium glass if they're not sure.

The ionising smoke detectors with Americium-241 in them only produces a weak reaction - but definitely noticeable. Think it must be the secondary gamma that's setting it off.

That's correct. Am241 is a very good Alpha source, but a lousy source of anything else.
The decay series is almost entirely Alpha radiation. The beta decay comes from Pa233.
The rest of the radiation is either secondary gamma from alpha emissions, but most of it actually comes from (spontaneous) nuclear fission.
Gamma, Neurons and high energy beta radiation from the fission products.

A lump of granite produced something barely above background.

Yep, it's not real interesting stuff. Standing in a granite road cutting is a bit more active, but even then it's a bit of a disappointment.

My tritium illuminated bedside clock (about $100 of H3 tubes!) doesn't even tickle the SBM-20 as you'd expect.

Actually no. Tritium might be very radioactive, but there is only a tiny amount of it in your tubes and the kicker is that it's 18.5KeV.
Your old colour TV CRT emits harder radiation.

None of the pieces produced a count above twice the background... is that about normal for uranium glass?

Yes, that's normal. Some pieces are better than others. Most of it is fairly dull, but you will find some pieces that are pretty hot.

Word gets around fast in these parts!

Which parts?

Have yet to go visit any of the abandoned uranium mines here...

That depends on on where "here" is.

Wonder if I can get away with that without a prospectors' licence

Nobody cares. Technically it is illegal in some states to prospect for Uranium. NSW recently changed that.
Though really nobody is going to kick your arse for wandering around measuring the background radiation for your son's university thesis

[mitaux8030]

"Here" is Tassie. Commercially unviable but still interesting finds of uranium (up to 0.15% UO3) have been found in the north-east of the state, so that's going to be the next place I have a poke around. Probably the abandoned Royal George tin mine to start off with - rumour has it that it was closed after high levels of radon was found gathering in the first stope.
Had a little bit of time to kill today and visited an antique shop. A display of about a dozen uranium glass items in the front window had the detector picking up elevated counts from the street front, and one piece was registering about 200CPM. I guess that's about as hot as uranium glass gets. It may come home to sit under some UV LEDs at a future date.

Speaking of which, what is the optimum wavelength to illuminate uranium glass etc. to make it fluoresce?

[trash]

There's a couple of choices for UV light. That's going to be your next purchase
You can buy an older style UV black light, they work fine. They're cheap and easy to find.

If you go to a lapidary show they have small hand held type UV fluro tubes. You want the ones which have a switch for "long and short wavelength UV light".
I don't know how the difference is achieved in the tubes but different minerals will fluoresce under different light. Calcite for example will only light up under short UV.

You can get UV LED torches, both Brewdog and I have found that the Ultrafire LED torches are best, but there is some variation in them.
I've found that if you're buying them off ebay etc, look for the sellers that have pictures showing the brightest target glowing and the least purple light. (UV is invisible - purple light is an indication of poor shorter wavelength UV).

LED strips, are longwave and produce a lot of visible light too, but they're cheap and can light up a display cheaply.
But they won't light up shortwave objects properly.

This is an example of the LED strip I use. You can see that it lights up Uranium glass quite well. Though some types of glass light up better than others under long wave, where as under shorter wavelengths they pretty much all light up. You can see objects like the dark five sided stone. It's a ruby and glows pink under shortwave UV.

There is also an ultrashort UV. These kinds of tubes are found in germicidal and Eprom erasers etc. They're clear pyrex fluro lamps.
They're dangerous to look at and be exposed to. But they do make some minerals glow that don't under short or long wave UV. Azurite (A Blue Copper mineral) glows purple under ultra short UV.


The best and cheapest choice for your first UV lamp should be an Ultrafire LED torch, broadband UV. You can't go wrong.
I also have UV lasers which are shortwave UV and great for searching long distance through shop windows at night.

[trash]

[mitaux8030]

Had an afternoon to myself, so ventured down to the abandoned tin/uranium mine, didn't stay all that long because of the rain and slippery descent, but the counter certainly got excited: 300-400CPS in some spots (about 20 times background), presumably from radon gas leeching out of the rocks. Didn't find anything worth bringing home, perhaps another time.

[trash]

nar, the Radon gas won't be responsible for that. If that were the case, you'd be dead from the primary radiation by now.
The background radiation is just gamma radiation from the ground.

This is one of the advantages of using multiple tubes. You can set up three of them as a coincidence detector.
When a gamma ray passes through all three tubes at the same time the detector registers a click. If any radiation only passes through one or two tubes it's ignored.
Set up properly you can easily determine which way radiation is coming from, the ground or the sky.

In your case you're just going to have to try an be a little more discriminating. When Bluedog and I went for a walk out to Toongi, it took us some time wandering around looking for higher and higher radiation levels until we could narrow it down to individual boulders and rocks and minerals on those rocks.

This is a video I made up at Rum Jungle last year.