Accelerator tube construction

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John Futter
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Accelerator tube construction

Post by John Futter » Tue Jul 06, 2010 9:34 pm

Ok
Here are a few pics showing two tubes. The short tube is from a 600kV accelerator. the metal plates are titanium with cast glass rings as insulators the down tube pic is the view looking from the ion source down the tube. The glass insulators are protected from being sputtered/ plated by the downturn on each plate. the other two pics of the short tube are self explanitory.
the final pic is of a well used tube from our 3MV machine kept as an emergency spare.
Note the extensive radiation damage to the glass the further down the tube the ions go.
In this tube the plates are stainless steel. HVEC did not use this for long in these tubes because of the stainless had a huge x-ray output.
Early tubes used aluminium for the metal plates. these didn't last long --around 2 years of continuous running --hence the stainless experiment you see the pic of below --these lasted much longer but the x-ray problem because of the higher Z material made using them a pain due to the extra shielding required.

All the modern tubes are made from titanium heavier in Z than Al but much lower than SS

So if you want to build an accelerator tube I would suggest water jet cut glass rings with aluminium plates (easy to make a tool to form necessary shape) all joined together with synthetic latex (carpet glue)
PS it is important to have the glass rings annealed after the water jet cutting to relieve stress.
As for how vacuum tight these tubes are the big tube sits at 2 by ten to minus 7 millibar pumped by a 500L/s diffstack (this is about the limit for a diffstack without coldtrap). So there are hundreds of glue joints and just to make sure that a leak is obvious we put 300psi of N2 Co2 mix around the outside of the tube as insulating gas.

the small tube above was insulated on the outside by 80psi SF6
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down_tube.jpg
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up_tube.jpg
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dbrown
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Re: Accelerator tube construction

Post by dbrown » Tue Jul 06, 2010 9:43 pm

Nice - I take it the steel has not been activated?

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Mark Rowley
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Re: Accelerator tube construction

Post by Mark Rowley » Tue Jul 06, 2010 10:15 pm

John,
Looks like the tube pictured on top has 12 plates. What operating voltage is that one designed for? Also, how tall is the tube and what is the spacing between the plates?

Do you have a picture of the cooresponding gun for that tube?

Mark Rowley

John Futter
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Re: Accelerator tube construction

Post by John Futter » Tue Jul 06, 2010 10:36 pm

Mark

tube =323mm high
glass rings = 110mm od 90mm id
hole down middle of metal plates 50mm
glass thickness 16.5mm
metal thickness 2mm

tube designed for 500kV operating 600kV conditioning

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Doug Coulter
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Re: Accelerator tube construction

Post by Doug Coulter » Tue Jul 06, 2010 11:23 pm

Count on John for the good stuff in this area. I liked all the little bolt spark/corona gaps as a safety/equalizer in the big tube side view in these pix.
Why guess when you can know? Measure!

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Steven Sesselmann
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Re: Accelerator tube construction

Post by Steven Sesselmann » Thu Jul 08, 2010 12:34 pm

John,

Thanks for posting this information...

I really need one of these tubes for my next experiment

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG

lutzhoffman
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Re: Accelerator tube construction

Post by lutzhoffman » Fri Jul 09, 2010 1:41 am

Thanks John:

Hydro-jet cutting, so that's how they do it now days, thank you for that tip!!! I just never thought about using it to cut glass. I have seen it cut SS like butter, but you are correct in that it will cut just about anything, even rubber in the other extreme . This would be a great way to make difficult parts out of Alumina, Quartz, or Pyrex.

Man the radiation must be fierce, the interesting thing is that you can see its progressive, with increasing energy along the length of the tube, causing more and more brown color to develope in the glass. To bad its not soda-lime, then it would be a pretty shade of purple : )

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