From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: X-Rays in the garage?
References: <email@example.com> <3D9A3B2E.firstname.lastname@example.org>
Date: Wed, 02 Oct 2002 01:35:06 GMT
NNTP-Posting-Date: Tue, 01 Oct 2002 18:35:06 PDT
"Christopher R. Carlen" wrote:
> James Meyer wrote:
> > On Tue, 01 Oct 2002 23:01:45 GMT, NightRunner
> > wrote:
> >>Along those lines... I had noticed once some time ago when I was into
> >>collecting tubes, that I had some tv diode tubes marked with warnings
> >>about x-rays. Could one simply drive the holy hell out of a diode at
> >>very high voltages and achieve a reasonable result? That would be
> >>easiest to implement since the diodes have just a cathode and anode
> >>complete with a handy terminal on top :-)
> > The old 1B3 color TV rectifier tubes -will- produce X-rays. Unless you
> > get one of the late model versions which were built with glass in which a large
> > percentage of lead was added. Your wife would probably cherish "lead crystal"
> > glassware, but for your purposes lead loaded glass would be something to avoid.
> > In order to get much in the way of X-rays out of a 1B3, you will need to
> > feed it with at least 30,000 volts on the plate.
> > Jim
> But those tubes were for rectifying CRT HV, which was only a few mA,
> thus you will have trouble getting many X rays with only a few mA, and
> at that current anyway, the voltage drop across the tube probably won't
> be anywhere close to that, but rather something like a few hV to a few
> kV. To get the 30kV across the tube, you'd force massive current
> through it. The tube wouldn't survive this continuous mode, but it
> might be able to do it with very narrow pulses.
> But then the cathode wasn't designed for high current anyway, so even
> low duty high current pulses would probably tear it up in short order.
It is really hard to get much current through a 1B3. The 1B3 might be
fine with a duty cycle such that the anode just started to glow and then
allowed to cool for a somewhat longer time. The times might be seconds
with a large heat sink on the anode cap.
> I'd think one would have not too much trouble building an X ray tube, if
> they had a decent vacuum cleaner.
Too much air left for a filament to survive. An interesting vacuum pump
can be made with bits of sheet metal. In this design, a fast stream of
water passes through a small chamber to an outlet tube. The air is
pumped out of the chamber. The vacuum that is attained is the vapor
pressure of the water used for pumping. The vacuum can be moderately
improved with a dry ice cold trap since most of the air is gon and
replaced by water vapor. I believe that this is called an aspirator
pump. Such pumps can be built with hand tools, a propane torch and some
bits of metal including brass tubing, copper tubing, sheet brass or
copper and solder.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons email@example.com