On 7/3/2011 2:21 PM, Fuqua, Bill L wrote:
> X-rays are produced when high energy electrons or protons strike certain
> materials.
> Actually any elements will produce x-rays if the electrons or protons have
> enough energy.
> X-ray tubes use metalic anodes that produce the X-rays at farly at much
> slower electrons than
> many of the other elements. Protons are usually used for elemental analysis
> Google PIXIE.
> The point is there is a reason for the vacuum in an X-ray tube. That is,
> the electrons must not
> strike any gas molecules before they get to the anode. Otherwise they loose
> energy and don't
> produce the X-rays. An arc is produced becasue the mean-free path distance
> is just long enough
> for the electron to be accelerated to enough to strike a molecule and either
> doubly ionize it or produce an extra electron and you have
We used a pair of 4-400As in a rather muscular Tesla coil to develop an
arc to evaporate the metallic or semiconductor sample, then the ions
which were charged positive were accelerated between a pair of curved,
charged, plates which happened to be located between the poles of one
monster magnet. If it started to take a wrench away from you, you let it
have it as the thing would smash your hand flat even with a small
wrench. Couple of times we had to shut it down to get wrenches back.
That was not considered desirable as this thing ran at a vacuum of 10^-7
Torr. It used mechanical roughing pumps (rotary vane) to get down to
10^-1 so the diffusion pumps could be started. We used liquid N2 in the
cold traps on those. After the diffusion pumps did all they could we
switched to ion pumps also with liquid N2. I think on occasion they
used liquid He2.
At-any-rate, the combination of electrostatic charged plates and magnet
would curve the charged ions so by the time they hit the target they
were spread our according to mass. Just as in going around a corner,
the heavy stuff didn't curve as much as the lighter *stuff*. Just as
light is spread out in to it's spectral components in a prism here the
elemental ions were spread into a spectrum according to their atomic
mass allowing purity measurements into the fractions of a part per billion.
That was a Tesla coil that was really fun to play with.<:-)) OTOH the
really big stuff would create a plasma that just floated around.
I've seen an electron beam that could turn the entire end of a 8" rod
into a molten blob. I don't know just how large a rod it could have
melted and that was 30 years ago.
I have a plasma torch that can cut through about 10" of nearly 3/4 inch
steel plate per minute. We had one torch that made mine look like a
cigarette lighter.
73
Roger (K8RI)
> a sort of chain reaction (avalanche). One electron produces two and two
> produce four etc.
> The energy required to do this is much less than that required to produce
> X-rays.
> Each time an electron strikes a molecule or atom the acceleration process
> starts over again.
> 73
> Bill wa4lav
>
>
> ________________________________________
> From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf Of
> Ron Youvan [ka4inm@tampabay.rr.com]
> Sent: Sunday, July 03, 2011 8:58 AM
> To: amps
> Subject: Re: [Amps] Risks from continuous discharge of high voltage ??
>
> Dr. David Kirkby wrote:
>
>> There's an ebay auction for a 100 kV transformer from an x-ray set.
>> http://www.ebay.co.uk/itm/190544288962
>> I mentioned to the seller he should warn people of possible production of
>> x-rays. He does not think this possible and I must admit I'm not sure if its
>> possible without a vacuum. But I've also suggested that it could produce UV
>> and
>> ozone.
> The production of X-rays requires something that does not exist in a
> transformer or the
> transformers would be lined with lead sheeting. Which is: "a high velocity
> stream of electrons that
> changes speed abruptly."
>
>> It's clearly being sold as a fun experiment:
>> "Dangerous but great fun and ideal for lots of interesting experiments."
>> But at 100 kV, I'm wondering what dangers there are apart from the obvious
>> one
>> of electrocution.
> Like setting the house on fire.
>
>> Somehow I would not want to be playing around too much with 100 kV and
>> drawing
>> big arcs, but perhaps I'm over reacting.
> I think a Van de Graaff generator would be at least 10,000 times safer.
>
>> I've suggested he ads a note that there may be other dangers other than
>> electrocution.
> --
> Ron KA4INM - Madam, there's no such thing as a tough child -- if you
> parboil them
> first for seven hours, they always come out tender. -- W.
> C. Fields
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