Particle accelerator (Where to get the glass tube?)

[Nussi]

Hello there!

I study communications engineering and got really fascinated by magnetic fields. I started to do my own bit of "research" or "further understanding" how magnets work, how the field is influenced and what can the field influence.

After doing so I got fascinated by particle accelerators and especially the quadrupole magnets to adjust and focus the beam. Now I'd like to do some research on those magnets. The only way to get a direct visual feedback is to build a small particle accelerator with a low pressure hydrogen atmosphere to make the beam visible like in the "Fadenstrahlröhre" (Sorry, I don't know the english word for it: Wikipedia Picture). So what I thought I'd do is accelerating the electrons with about 200 to 400 Volt.

To achieve the visibility of the beam, I need a tube that won't break when evacuated. I could do that by myself but I have no oven that big to reduce the tension after sealing the tube. So I need to buy a presealed tube that has already been tempered. I have found many stores but theynever had a tube longer than 1 meter that could withstand a vacuum (these had been designed to be filled with inert gases). Anyone know a source?

 

[litup]

What is the diameter of the glass tube? I work in the semiconductor business and we don't even use glass most of the time. A lot of plastic tubing is plenty strong enough to hold back vacuum, if it is on the order of a cm or so diameter. Even bigger plastic pipe is used in vacuum pumps which have a spiral metal wire internal bracing system that prevents collapse of the tube. In your case, if you got that kind of tubing, just make sure the metal is non-magnetic and it won't interfere with the focus magnets. BTW, I used to work at Varian on ion implanters and they use, among other techniques, magnetic quadrupole focus technology, you might find pictures and maybe more details at Varian.com. Here is a wiki about quadrupole's:
http://en.wikipedia.org/wiki/Quadrupole_magnet

You can find such tubing at companies like Kurt Lesker or RS Crum. There are thick walled plastic tubing that can easily take the inward pressures of vacuum. Remember, there is very little difference in the actual inward force from say, 1 torr, to say, 1 microtorr. If you plan to conduct electrons you will need a high vacuum pump, like a diffusion pump, you can get those on the used market like a company called Bid Service or another one Carravagio brothers or Dove Bid. Other high vacuum pumps are much cleaner in terms of organics in the resulting vacuum line but are prohibitively expensive for a student project unless your lab already has access to say, a turbo molecular pump or a cryo pump. A bit overkill if you ask me but they do produce great uncontaminated vacuum. Your project would probably work just fine with a very small diffusion pump. It would pump really fast since your chamber would be only a few cubic cm most likely. Maybe a bit more since you have to include the electron source in the system. A nice electron generator that goes in a straight line by definition is the electron gun in an old CRT. If you can get it out without destroying it you won't need quadrupole magnets since it is focused electrically. You just need to commander an old tv set or old CRT computer monitor. The hard part would be exposing the electron gun GENTLY to atmosphere and then getting it glued in place in your system. You wouldn't even need the scanning electronics since all you want is a straight beam of electrons. Good luck with your project! Come back with results!