Mystery metal

Index of refraction. more power in a flatter lenses or even more in a curved one. Size (diameter) is light gathering ability. Focal length determines
magnification. They wanted more magnification without getting larger.
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 IHMSA and NRA Metallic Silhouette maker & member
xray wrote:

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Thorium oxide based glasses have a very different combination of refractive index and dispersion than other glasses available at the time, allowing better correction of optical abberations.
Thorium is only very slightly radioactive, and the health problems were psychosomatic, not physical, for users of the resulting optical systems. Manufacturers had to be more careful, as they were exposed to the dust resulting from grinding lenses.
Joe Gwinn
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Not so sure - as it is a high Alpha emitter - used in Vacuum tubes for massive currents - with a very long lifetime. TH 232 is close to the famous U 238 isolated by 1 element called Protactinium. By the way - U is an alpha source also.
The Alpha emitters can cause eye damage. You state it was all a mental illness. I think that was bad science running rough shod over victims. Just like agent orange and .....
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 IHMSA and NRA Metallic Silhouette maker & member
Joseph Gwinn wrote:

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wrote in message wrote:

How can alpha emitters cause any damage unless they are ingested? A piece of paper will stop an alpha particle as they are pretty low in energy.
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And big in size
but Alphas causing eye damage is just about the only spot they possibly could because as you say a sheet of paper stops them On Wed, 29 Mar 2006 19:05:36 +1100, "Tom Miller"

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Alpha emitters can cloud and kill eye tissue that is right next to the glass. I heard it was more than alpha in the first place. And transversing to the retina via the carrier fluid.
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 IHMSA and NRA Metallic Silhouette maker & member
Tom Miller wrote:

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Thorium is (perhaps was?) also found in gas mantles, for those camping lamps.
Dave
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wrote:

Still is as of 5 years ago or so; I tested a new one and it's detectable.
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I have some - gave off more white light. Now they don't use it.
Thorium is the reason why soft coal power plant is more radioactive than a Nuke plant. Thorium is found in soft coal.
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 IHMSA and NRA Metallic Silhouette maker & member
snipped-for-privacy@yahoo.com wrote:

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wrote in message

Also in most clay bricks.
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Just don't visit the mountains - more than alpha is in the rocks there!
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 IHMSA and NRA Metallic Silhouette maker & member
Tom Miller wrote:

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The half-life of Thorium is something like ten billion years, so the radiation is very dilute -- every so often, a thorium nucleus goes POP.

I don't know how one would achieve eye damage with thorium-bearing glass. I suppose one could hold the lens against one's eye for a million years. But the thorium-bearing lenses were typically used only within the optical system, because this glass was too easily scratched.
Cosmic rays are by far the larger radiation source. If one flys from LA to NYC, being above most of the atmosphere and its shielding, one gets a 100 milliREM dose, about the same as from a dental X-Ray.
Fear of radiation from thorium-bearing glass lenses in an optical instrument is therefore a mental issue.
The real danger was that people grinding lenses from thorium-bearing glass for a living would ingest a lot of the dust, and would be irradiated from within. Even that danger wasn't very large, as the dust passes right through largely unaffected. But there are many reasons to avoid ingesting glass dust.
Lens grinding is always done wet (using water), which already controls the dust. One can still use thorium-bearing glass, but the required manufacturing safety precautions and swarf disposal regulations are such that people use other kinds of glass these days, kinds of glass that were not available back when. I don't know if one can still buy the thorium-bearing glass in the West. The Russians probably still make it.
Joe Gwinn

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wrote:

Anybody know how these work? Is there a solid-state replacement for a GM tube that works on low voltage?
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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
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On Tue, 21 Mar 2006 16:50:00 GMT, "Lloyd E. Sponenburgh"

http://www.ird-inc.com /
Gunner
"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences." - Proverbs 22:3
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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. Sponenburgh wrote:

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On Tue, 21 Mar 2006 21:37:45 -0600, "Martin H. Eastburn"

I think Tim May did something similar at Intel
Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences." - Proverbs 22:3
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Don Foreman wrote:

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
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Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)
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On Tue, 21 Mar 2006 10:28:09 -0600, Don Foreman

Start here...
http://www.radmeters4u.com /
Then go here
http://www.nukalert.com /
then here
http://www.nextag.com/buyer/outpdir.jsp ;jsessionidD5216493D3DDD9A6683E600A538E1C?nxtg"690a1c0519-8B9AFCBBB7FF96ED&search=radiation+detector
http://cgi.ebay.com/RADIATION-DETECTOR-METER-GEIGER-COUNTER-DOSIMETER-NEW_W0QQitemZ7599151127QQcategoryZ11900QQrdZ1QQcmdZViewItem
Also note this..
http://www.sciencekit.com/category.asp_Q_c_E_435698_A_pn_E_6385000 http://www.gdr.org/spiderwortdefon.htm
If you like building things.. http://www.blackcatsystems.com/science/radiation.html http://www.nfinity.com/~exile/electro.htm http://www.techlib.com/science/ion.html http://cgi.ebay.com/Scintillation-Radiation-Detector-Plastic-Nuclear-Round_W0QQitemZ6262886286QQcategoryZ413QQrdZ1QQcmdZViewItem
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
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    [ ... 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.
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