RE: Thoriated Tungsten vs Pure

To: "'tesla-at-pupman-dot-com'" <tesla-at-pupman-dot-com>
Subject: RE: Thoriated Tungsten vs Pure
From: Dan Gowin <gowin-at-epic-1.nwscc.sea06.navy.mil>
Date: Tue, 1 Oct 1996 08:44:27 -0000


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From: 	Tesla List[SMTP:tesla-at-poodle.pupman-dot-com]
Sent: 	Saturday, September 28, 1996 11:25 AM
To: 	Tesla-list-subscribers-at-poodle.pupman-dot-com
Subject: 	Re: Thoriated Tungsten vs Pure

> Subject: Re: Thoriated Tungsten vs Pure

>From bturner-at-apc-dot-netSat Sep 28 10:17:05 1996
Date: Sat, 28 Sep 1996 02:02:08 -0700
From: open_minded <bturner-at-apc-dot-net>
To: tesla-at-pupman-dot-com
Subject: Re: Thoriated Tungsten vs Pure

Tesla List wrote:
> 
> >From bert.hickman-at-aquila-dot-comFri Sep 27 22:07:52 1996
> Date: Fri, 27 Sep 1996 06:31:06 -0700
> From: Bert Hickman <bert.hickman-at-aquila-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Thoriated Tungsten vs Pure
> 
> All,
> 
> I've heard three reasons for NOT using thoriated tungsten rods in a
> rotary spark gap:
> 
> 1. The thoriated kind are somewhat more expensive
> 
> 2. The doping material (Thorium) is radioactive, and when in use will
> generate particles of radioactive material that can be inhaled, etc.
> However, it must not be very radioactive, or there must not be very much
> of it in the rods since I've never seen any warning labels.
> 
> 3. Thoriating makes the rod easier to use when TIG welding since it
> helps stabilize the arc. This may be related to why thoriated tungsten
> filaments are used in high power transmitting tubes. However, if we want
> to quench the arc, wouldn't pure tungsten rods be the better choice?
> 
> I'm designing my rotary now, and need to make a materials decision.
> Thanks in advance!
> 
> -- Bert --


Bert -

I just *got* 2% thoriated rod today to try in a gap that I am
modifying. (Using 1/8") Will let you know what happens when I get
it all done and light the coil up with it. I *do* know Bill Wysock
uses thoriated tunsgten tips in his gaps, and things appear to
quench just fine with them. Remember that in a rotary gap, the thing's
gonna quench eventually anyway as the electrodes pull away from each
other. You can further enhance quenching by adding additional fixed-gaps
in series with the rotary. (I plan to do just that, BTW.) The purpose
of the thoria is to enhance electron emission - hence, it's easier to
strike the arc. In filaments/cathodes, electron emission is helped
by heating the element. Adding the thoria helps all the more.

As far as the radiation thing goes, guys in the welding shops take these
rods to the bench grinder all the time. While I certainly wouldn't want
to inhale any of the particles, I doubt that there is any significant
radiation to get excited about. Maybe if you went around with the rods
stuffed in your ears for months, or something like that... The rods are
specifically designed *not* to wear away or ablate easily. The amount
of radioactive debris that *might* get thrown around would, in my
estimation, be darn near indistiguishable from the normal background
radiation.

- Brent  (who *isn't* glowing yet.)



Brent,
	Just for informational purposes, Thorium is a biproduct of phosphate
mining. And in fact, if an individual were to do a radiation measurement on
a bag of fertilizer, I'm sure they would be surprized. And even more surprized
if they did measurements in there home, considering that most older smoke
detectors contain Americium 239. A substance I quote from the Websters
dictionary "a radioactive metallic element produced by bombardment of
plutonium with high-energy neutrons". Nasty stuff, and much more hazardous
than Thorium.

I've rambled. Now I will go.
D. Gowin
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