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RE: vacuum tube construction. (fwd)
---------- Forwarded message ----------
Date: Tue, 14 Aug 2007 20:51:12 +0000
From: nancylavoie@xxxxxxxxxxx
To: Tesla list <tesla@xxxxxxxxxx>
Subject: RE: vacuum tube construction. (fwd)
Look up "An Inexpensive X-Ray Machine" Should come up with a reprint of an old Scientific American article that pretty much sums it all up.Was going to try this myself with a few UV201A tubes I think (can't remember any other reason why I'd buy them).Seems easy enough to do! Be careful. Wyatt
-------------- Original message --------------
From: "Tesla list" <tesla@xxxxxxxxxx>
>
> ---------- Forwarded message ----------
> Date: Mon, 13 Aug 2007 22:06:39 -0700
> From: Anthony R. Mollner
> To: Tesla list
> Subject: RE: vacuum tube construction. (fwd)
>
> I would be interested in seeing that article.
> Tony
>
> -----Original Message-----
> From: Tesla list [mailto:tesla@xxxxxxxxxx]
> Sent: Monday, August 13, 2007 7:45 PM
> To: tesla@xxxxxxxxxx
> Subject: RE: vacuum tube construction. (fwd)
>
>
>
> ---------- Forwarded message ----------
> Date: Mon, 13 Aug 2007 16:23:27 -0700
> From: Frank
> To: Tesla list
> Subject: RE: vacuum tube construction. (fwd)
>
> Hi,
> X ray production begins with voltages above 20KV, a tube running at
> 600 V as stated will not produce any X rays.
> X rays at the lower level are called soft X rays and will easily pass
> thru soft tissue. This level is radiation is not as dangerous as
> harder X rays but one still has to pay attention to it!
>
> For sure, if you have a vacuum system good enough to overcome leaks,
> you can get to an X ray vacuum, a Lenard's tube is a good example of this.
>
> If a tube does not have X ray element construction, it will generate
> X rays but they are so diffused and scattered it is very hard to get
> any serious exposure from them.
> A Maltese cross tube was the first unfocused X ray tube and very
> difficult to obtain useable results.
> After Jackson made the focus tube, X rays then became a useable
> medical tool. Even the Coolidge tube is a focus type tube.
>
> A Tesla type X ray tube is a single element tubes that generates X
> rays in an unfocused manner much like a Maltese tube.
>
> Believe it or not, an old radio tube can be turned into an X ray tube.
> If anyone likes, I can send then an antique article on making an X
> ray machine. It uses a high frequency Tesla coil to excite a radio
> tube and there are complete instructions on how to make the HF coil.
>
> Frank
>
>
>
> At 03:33 PM 8/13/2007 -0600, you wrote:
>
> >---------- Forwarded message ----------
> >Date: Mon, 13 Aug 2007 14:21:12 -0700
> >From: Jim Lux
> >To: Tesla list
> >Subject: RE: vacuum tube construction. (fwd)
> >
> >At 12:28 PM 8/13/2007, you wrote:
> >
> > >---------- Forwarded message ----------
> > >Date: Mon, 13 Aug 2007 12:13:06 -0700
> > >From: Frank
> > >To: Tesla list
> > >Subject: RE: vacuum tube construction. (fwd)
> > >
> > >All this tube is is a simple Geissler tube.
> > >The vacuum levels are not high enough to ever generate X rays.
> >
> >Not entirely true.. More if the mean free path is greater than the
> >distance from electron source to electron target, and the voltage is
> >high enough, you can get x-rays.
> >
> >There's also soft x-ray sources using fast rising edges that I think
> >can tolerate higher pressures. An example might be a z-pinch device
> >
> >
> > >You need a hard vacuum and a diffusion or turbine pump along with a
> > >scavenging method to pump the tube down hard enough to be able to
> > >generate X rays.
> >
> >Or a sorption pump (you only have to pump once, and then you getter it).
> >
> >
> > > Tubes that can be taken apart for cleaning will not
> > >have seals good enough to hold an X ray vacuum.
> >
> >Not precisely true.. There are continuously pumped tubes that are
> >dismantleable.
> >
> >
> >
> >
> > >Large mercury arc rectifiers will work as a switch with some
> > >additional circuitry but are not available anymore. Those were used
> > >on some of the early wireless transmitters.
> >
> >They were used far more recenly than that in high voltage DC converters.
> >
> >As recently as 2005, they completed an upgrade of the Sylmar
> >Converter station at the southern end of the Pacific HVDC Intertie ,
> >replacing the mercury arc valves with thyristors.
> >
> >They normally serviced the mercury arc valves on a 7 year cycle,
> >however the 1994 Northridge earthquake interrupted the service cycle,
> >and encouraged replacement with more modern thyristors.
> >
> >Interestingly, the mercury arc based converters work just fine, it's
> >just that they require a larger maintenance crew and require more
> >servicing, so they have an availability of 92% as opposed to 98% for
> >thyristors. There's also the environmental hazard of a system with
> >many pounds of mercury.
> >
> >
> > >Dosimeters are a device to measure radiation over time, basically a
> > >charged capacitor that is discharged by radiation. Usually they are
> > >calibrated in REMS and if they ever register, the amount of radiation
> > >is enormous and you better run!
> > >
> > >A CD Geiger counter, Model CDV 700-XX is a good counter to measure
> > >radiation in small amounts and can be used to detect X rays. These
> > >are on Ebay all the time.
> >
> >I've been given to understand that CD type geiger counters have a
> >severe failing in that they don't detect low energy soft x-rays very
> >well (ones that can't penetrate the GM tube envelope). If you're
> >working at lowish voltages (tens of kV), one could have a fairly high
> >X-ray flux that wouldn't register.
> >
> >I'm not a X-ray dosimetry expert by any means, but it's probably
> >worth consulting someone who is, and, in particular, someone who's
> >familiar with low energies.
> >
> >
> > >Frank
> > >
> > > >Quoting Tesla list :
> > > >
> > > > >
> > > > > ---------- Forwarded message ----------
> > > > > Date: Mon, 13 Aug 2007 07:52:30 -0400
>
>
>
>