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From: email@example.com (Murat Ozer)
Subject: Re: In Need of a 50-KV Electron-Gun
Date: 23 Oct 2002 18:13:58 -0700
References: <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
NNTP-Posting-Date: 24 Oct 2002 01:13:58 GMT
email@example.com (N. Thornton) wrote in message news:...
> Alan wrote...
> > In normal operation the HV is applied only to the conductive coating
> >on the inside of the glass bulb. The highest voltage on the actual
> >of color tubes is the approx. 5 kV focus voltage.
> OK. So how about running it on its usual 5kV plus adding a separate
> 50kV accelerating electrode? This is after all sort of how the CRT gun
> is designed 2b used. A ring shaped trode would presumably be suitable,
> at sufficient distance to avoid arcing. I may be off track... but if
> so can you tell me why?
> > Instead of trying to remove the gun from an existing CRT, why not buy
> >a replacement gun from a CRT rebuilder who rebuilds monochrome tubes?
> > Unless the target is very well insulated the gun will have to be run
> >at -50kV, which presents major insulation problems for the gun and
> >voltage power supplies.
> > Regards, Alan.
> Presumably either the target is at +50kV, or the gun assembly is at
> -50kV, or possibly a grid near to the target is at +50kV but the
> target isn't. Either way, its not going 2b substantially different
> with a CRT gun than with a more specialist gun. Bear in mind many of
> the electrodes would be irrelevant on a CRT gun and could simply be
> electrically tied.
Murat: The target is required to be at 0 V. The electrons need to be
accelerated to +50 KV. So, would applying +50 KV to the accelerating
anode while applying no voltage to the cathode do the job?
> firstname.lastname@example.org (Rich Grise) wrote in message news:
> > email@example.com (Murat Ozer) wrote in message news:
> > > firstname.lastname@example.org (N. Thornton) wrote in message news:
> > > > email@example.com (Murat Ozer) wrote in message news:
> > > > > Hello,
> > > > > A friend of mine from Mt. Vernon, Washington is preparing a vacuum
> > > > > scattering experiment. He has the vacuum chamber, the pump and
> > > > > everything else. The 50-KV electron-gun needed in the experiment was
> > > > > lent to him by another friend; but it does not seem to be working. We
> > > > > have searched the Internet to find e-gun manufacturers. The guns of
> > > > > Kimballphysics are too sophisticated and has astronomical prices. We
> > > > > need a simple gun (like those used in oscilloscopes) that will work at
> > > > > 50 KV and less (anode-cathode)voltages capable of producing a spot
> > > > > (1-2 mm diameter) on a phosphor screen at distances from 30-75 cms. No
> > > > > varying current or other functions are necessary. It should have a
> > > > > flange with screws to mount it on the vacuum chamber.
> > > > > We need your help...
> > The only real shortcoming I can think of in using an existing
> > electron gun from a TV or scope tube is, well, a couple of them,
> > actually - breaking the glass and somehow attaching the glass
> > shards to your experiment; pumping it down to a really, really
> > hard vacuum after the gun's been in air, and the glass is welded;
> Perhaps we can get those 2 in one move. How about...
> Attach tubing to the CRT's seal nipple, evacuate the tubing, connect
> tubing to a protective gas container (ie no oxygen or water vapour).
> Now break the CRT nipple, and CRT fills with protective gas.
> Now one can weld glass onto the neck using a piece of glass from
> another CRT and a blowtorch / bunsen / etc.
> Finally the thing can be cut and handled however a 50kV gun is usually
> > driving it with the right voltages, including your makeshift
> > ultor;
> Really its the focus voltage one would need to supply. Most of the
> other trodes can be tied. When the control electrodes arent being
> given negative voltage, it would probably be poss for other control
> trodes to be tied to 0v instead of +. That often works. If not, a
> +400v supply is not so tough.
> > designing focusing coils and an ion trap -
> Electrostatic focussing is already built in. Focus Vs on modern TVs
> are typ a few kV for colour or a few 100s of V for B&W. Nothing
> Ion trap is already built in and working.
> > in other words,
> > it's doable, but an incredible pain in the ass. Either way, whether
> > you buy, build, or salvage.
> I think its easier than you say - but whatever approach one uses is
> going to be a fair amount of work, TV gun or specialist microscope
> Now, praps someone can tell me where I've gone hopelessly wrong :)
> Regards, NT
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