[Test-Equipment] Radioactive Tube Stamp (was: re: Nixie project)

[Mike Manes]

Coleman lantern mantles are made from Thorium wire, and can serve as
a pretty fair gamma source.  Vacuum tube cathodes contain Thorium oxide
(thoriated) to help free up electrons off the surface.

On 7/3/2010 13:53, WA5CAB at cs.com wrote:
> I was reading an article in Analog recently with some bearing on the
> subject.  One could say that the problem is that refining processes, by and large,
> are isotope insensitive.  If the refining process for Thorium could be
> easily set to extract only Thoium-232, there would be essentially no problem, as
> it has a half-life of some 14 billion years.  However, Thorium-230 (AKA
> Ionium) has a half-life of 7700 years.  And Thorium-228 (AKA Radiothorium) a
> half-life of under two years.
>
> FWIW, Th-230 is in the decay chain of U-238, not Th-232.
>
> In a message dated 7/3/2010 2:26:25 PM Central Daylight Time,
> dickburk at ix.netcom.com writes:
>>       There are a lot of tubes with thoriated tungsten
>> filaments, I think most of the Eimac triode and tetrode
>> transmitting tubes have them.
>>       Thorium was used in some types of optical glass
>> especially for aerial photography lenses during WW-2. Some
>> of these had enough radiation to cause "browning" of the
>> glass over a period of many years. Thorium lends some
>> desirable optical qualities to the glass but it was
>> discontinued after the degree of radiation was discovered.
>> Some sources claim that the thorium was an accidental
>> ingredient, included as an impurity particularly to
>> lanthanum, but that is not the case: thorium was delibrately
>> used and is included in the formulas shown in the patents
>> issued to the National Bureau of Standards, where rare-earth
>> optical glass was developed. Even some high-performance
>> lenses for domestic rather than military use contained some
>> thorium elements. I don't know what the radiation levels of
>> these lenses are but I understand that the decay products of
>> thorium may be more hazardous than the thorium.
>>
>
> Robert Downs - Houston
> wa5cab dot com (Web Store)
> MVPA 9480
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-- 
Mike Manes    mrmanes at gmail.com     Tel: 303-979-4899
"Things should be made as simple as possible, but not more so."
A. Einstein