Mystery metal

Mine takes 2 or 3 9-volt batteries. Came from England. I was working on nuclear imaging cameras over there, we moved the operation here, and all the tooling and equipment got boxed up and sent over. This one wasn't type-certified in the US, so it had to be made to go away. I took care of that aspect of it.

A year ago or so I did a survey of household items and their radiation levels, it was kinda surprising. Ah, here it is: (thanks google) Radiation survey of everyday objects:

Background radiation, 4 sites inside house: 1.5 Counts per Second (CPS) Background radiation, 4 sites outside house: 1.5 CPS

4 over-ripe bananas, sensor in contact with skin: 3 CPS Clean diapers: 1.5 CPS (no detectable radiation; same as background) Dirty diapers, measured at top of diaper pail: 2 CPS (suspect banana involvement) 6 month old kid: 1.5 CPS plus drool and two giggles "First Alert" smoke detector, with Americium goodness: 50 CPS on surface 10 year old Trijicon (Tritium) gunsights on Glock 19: 1.5 CPS Granite boulder, roughly 1 meter in diameter. Pink: 4 CPS Black: 3 CPS Blue/black boulder of unknown ignious type: 1.5 CPS Garden soil: 1.5 CPS

Obviously this is only a slightly scientific survey, but shows some interesting non-background results.

Reply to
Dave Hinz
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Anybody know how these work? Is there a solid-state replacement for a GM tube that works on low voltage?

Reply to
Don Foreman

A special version of static RAM will do that. RAM is usually passivated and also shielded by a glass layer that's supposed to suppress "cosmic ray" hits that destroy the contents of cells. Without the shielding, the contents will dump proportionally to the amount of radiation received.

I _don't_ know if any commercial devices are built on this principle, though.

LLoyd

Reply to
Lloyd E. Sponenburgh

I recall pocket dosimeters which had a thin conducting vane in them which, when charged to a moderately high voltage got repelled from a like charged stationary vane and sprang away from it. The dosimeter module was transparent so you could see the vanes and was filled with a gas similar to a geiger counter tube. When ionizing radiation made the gas conductive the charge on the vanes was leaked off and they moved closer together. How close they got was a measure of the total radiation received since they'd been given a "full charge". (Thus, they were fail safe if the charge leaked off through defective insulation or moisture.)

Back in the "Duck and cover" days, circa 1950, I remember building a radiation monitor which was nothing more than an NE-51 neon bulb biased at just below it's firing voltage. Radiation would make it discharge and produce "clicks" in a pair of high impedance headphones connected to it. I could set it off with an old wind up alarm clock which had a "radium" dial and hands.

Jeff

Reply to
Jeff Wisnia

Start here...

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then here

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Also note this..

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If you like building things..
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btw...if stocking a "radiation pill" stock potassium IODATE rather than potassium Iodide. The latter is nasty nasty nasty tasting..you will not be sure which dose is worse....

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

Reply to
Gunner

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Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

Reply to
Gunner

According to Don Foreman :

[ ... Geiger counters ... ]

Essentially, it is a cylindrical metal electrode surrounding a central electrode, in a low pressure (near vacuum) gas (argon, possibly?)

A high voltage is applied across it, somewhat below the level at which it will conduct on its own across the gap between the outer electrode and the central one.

When an energetic particle (radiation) enters the zone between the electrodes, it ionizes the gas to shorten the path, and a momentary arc jumps across. The current which it represents is amplified to the headphones (if any) plus integrated for the meter.

Note that the better tubes have a very thin window of quartz to let the electrons through (beta particles, IIRC). The Alpha particles and others can penetrate the metal side walls. My fancy Geiger counter has a window which flips aside from the probe for that use. The probe is used on the two most sensitive ranges. The other two ranges use a much smaller Geiger tube with a known thickness of metal housing between it and the outside (there is a special dent marking that spot for high level measurements).

Well ... a scintillation counter uses a crystal which emits tiny flashes of light whenever struck by an energetic particle, and those flashes are detected and amplified by a photomultipler tube (still needs high voltage, though not as high). It *might* (these days) be possible to use a solid state photosensor and amplifier -- I'm not sure whether the light levels are sufficient for those, however. And I *think* that the cost of the crystal is higher than the cost of the photomultiplier tube and the associated electronics.

I hope that this helps.

Enjoy, DoN.

Reply to
DoN. Nichols

Nope. GM tubes cannot detect alpha particles, even though an alpha can cause ionization. An alpha particle is capable of being stopped by a 5-mil thickness of ordinary paper. Any alpha particles detected by a GM tube originate inside the tube.

The "alpha hits" that memory chips used to be subject to were from alpha particles generated inside the IC package as secondary radiation from gamma hits.

LLoyd

Reply to
Lloyd E. Sponenburgh

The crystals are like $15 on ebay

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

Reply to
Gunner

According to Gunner :

O.K. So much for what I thought.

Thanks, DoN.

Reply to
DoN. Nichols

The ones I have worked on at PSU had a DC to DC converter to make the high voltage required for a GM tube. ...lew...

Reply to
Lew Hartswick

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Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

Reply to
Gunner

According to Gunner :

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Thanks. Now all I have to do is decide whether I really want to build one before the auctions close.

Or perhaps I should leave them for the one who asked the original questions,

Enjoy, DoN.

Reply to
DoN. Nichols

My CD V-720 Fallout Detection Meter - Yellow with meter and cool reverse handle - uses two D's for the Ion chamber - and is capable of 0-5, 0-50, 0-500 R/h. Oak Ridge called it a CDV-720 Ion Chamber survey meter -

It is powered up and in standby in the shop. Routinely scan bulk metal that I get because it might come from anywhere - and the scrap for it from anywhere. Some from China. So far so good. Not that I'm really worried - it is just nice to have a toy like this since I was in Physics myself.

Martin

Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder

Gunner wrote:

Reply to
Martin H. Eastburn

Sounds like a survey around here is overdue.

One thing I did test was the Naval bronze Port holes from a ship that was at Bikini - It was rather clean as I recall. I'll have to make a table and check out the odd ball stuff - Telescope and camera lenses - rare earth - and hum - how do I do myself - Binocs looking at meter at a distance - then get up close and see if there is an step up. Hum - worked and lived in a stones throw of blue pool coolant pond. But then I was young...

Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder

Dave H>

Reply to
Martin H. Eastburn

Mine is 3 volt. Doesn't look like much of a HF osc IIRC.

Martin

Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder

D> >

Reply to
Martin H. Eastburn

Close - not glass layer - it is a emulsion that is spun onto the surface of the whole wafer at a time. It is a sponge to alpha particles in ceramic packages and while it is nice to think a cosmic ray can be held back by anything - they zing through anything. Alpha hits are fixed but random high energy particles are not. Martin - former semiconductor debug and alpha hit test expert consultant to IBM Test in Bordeaux France.

Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder

Lloyd E. Sp>

Reply to
Martin H. Eastburn

According to Martin H. Eastburn :

I know that some of the lenses used in the manufacture of the Starlight Scopes (Night Vision scopes) for the Army were mildly radioactive.

Enjoy, DoN.

Reply to
DoN. Nichols

I think Tim May did something similar at Intel

Gunner

Reply to
Gunner

You have a War meter, it is not sensitive enough for the task. You need a survey meter to read lower levels.

Reply to
Nick Hull

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