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Production of 1 Tesla Field for Penning Trap?

  1. Mar 10, 2014 #1
    Hi, I'm a 2nd year undergraduate student at The University of Liverpool. I'm part of a team looking to create a novel Penning trap for a project. The short run down is that my team and myself have schematics and large quantities of information on an ion trap we're trying to build.

    We've collected together most of the components for the vacuum chambers and have found access to a vacuum pump so they're two hurdles overcome. We've even found some funding through sponsorship and through our department.

    We have however come to another obstacle in that we're a bit unsure on how we are to produce the magnetics field for our trap. We've been looking heavily into the prospect of using a solenoid in order to get the uniform field necessary but are struggling to find useful information relating to small solenoids being used in vacuum to create 1 Tesla magnetic fields. We're mostly concerned about what sort of cooling system and set-up we might require to achieve this set-up.

    If anybody has any thoughts on this or know where we can find information on the topic it would be greatly appreciated!

    I understand that without the trap being described it's difficult to know what will/won't work so please if you think you might be able to help, get in contact and I can send you some more information.

  2. jcsd
  3. Mar 11, 2014 #2
    You can get permanent magnets that produce a reasonably uniform 1T field.

    For electromagnets you are looking at a lot of power. I have seen modified welding power supplies hooked up to
    coils wound from hollow copper microwave waveguides that also serve as cooling channels for a lot of water.

    In any case it should be a lot easier to fit a small vacuum chamber inside an in-air magnet than the other way around.
  4. Mar 11, 2014 #3
    In my final year of my undergraduate degree I was part of a team which built a penning trap.

    We were able to convince the department to let us use some of the student lab apparatus. High vacuum, cryogenics experiments are quite common at our school for upper year physics. This particular apparatus was normally used to demonstrate the quantum hall effect. Was comprised of a vacuum flask, cooled by liquid nitrogen, vacuum flask filled liquid helium, vacuum chamber with the magnet and our penning trap in it. From my memory the superconducting magnet was the most dangerous part of the whole experiment because it has a significant amount of stored energy (large inductor, can only change the currently slowly). The concern was that if we saturated the superconductor it would stop superconducting and heat rapidly due to the resistive heating. This could then cause the helium pressure to rise. We never had an issue though.

    I don't want to be the bearer of bad news, but we found it very difficult to get working even for a group of 6 4th year students (only a few of us worked very hard on it). There were a number of challenges. Obviously a penning trap needs a very high vacuum beyond that produced by a simple mechanical pump, we used a turbo pump + mechanical roughing pump. We had many issues with leaks, particularly feed throughs, but also were the apparatus could be disassembled. The next biggest problem was developing an ion source. The charge to mass ratio determines the frequency particles in the trap will ossilate, this means heavy ions are easier to detect. We used a lightbulb filaments covered some potassium coating. Finally detecting the oscillation is extremely difficult - you need a very low noise high gain amplifier with a band pass filter.

    We tried to operate the system a couple of times but never did manage to detect the signal we were looking for before running out of time. We learned a lot about experimentation though.
  5. Mar 23, 2014 #4
    Yeah, we did notice that that was a big danger in using such strong magnets. We have changed to a Paul trap now in order to avoid the massive magnet field!

    Thanks a lot for all your advice.
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