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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 
> 
> 
> 
>