Diffusion Pump


Introduction: Diffusion Pump

As an intern (for steve) I tend to get all the sucky jobs, sweeping floors on fridays, welding frames,gutting and re-designing the internals of an EDM, designing and building a hydrogen glow brazing rig that might use a diffusion pump salvaged from a rubbish bin IF it works, fixing the pump if it doesn't work, ask Instructables for help on the pump, etc. Wait, most of those are pretty fun and everyone else sweeps on fridays too, hmm, and yet I'm an "intern".

Anyway, I need the physics peoples help. I have a diffusion pump that steve found in a dumpster somewhere. No idea how well it works or even if it works at all, I need to know how to hook it up to see if it even runs and then I can proceed with more science!
 And drudgery, given that I'm a lowly intern who nobody listens to, although there was this one time I saved us and perhaps even made us a bunch of money when I was browsing ebay....



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    You do know not to start the diffusion pump above a minimal pressure or
    kiss, kiss, goodby to something someone already trashed ! ! ?


    3 replies

    Yes, but I'm no longer on that project(back stateside for over a year now). Steveastrouk was under the impression it might be in working order when he acquired it.

    Optimistic, id he ;-)

    He's an Englishman, theres not a drop of optimism in his blood.


    The Ideanator, looks like you didn't get much help here. Any progress on your own? It takes a fair amount of work to test out your diffusion pump! You'll need to fill it with diffusion pump oil, attach a roughing pump, hook up its heaters to power, attach main inlet to a chamber (or put a blanking plate over it), hook up air or power to your valves, run cooling water to it from a recirculating chiller, attach your vacuum gauges to a controller, etc....then you get to start checking for vacuum leaks. Its a daunting task until you get used to high vac systems but once you do it's pretty straightforward!

    1 reply

    This project was for Steveastrouk (since all of this stuff is his) but I would certainly like to build something similar over here in the US if its in my budget and I can find a place to put it.
    It had a silicone oil in it already and since steve builds viscometers for a living, there wouldn't be any issues with oils. Roughing pump was available id it was plenty sucky enough, so no problems there. Power and water were taken care of (we were just going to stick it up to a water tap and a drain when it was running, saves us a pump and heatsink setup). Valves all work, gauges available, and manual/computer control. The only thing I was having trouble with were the gauges, never did figure them out.
    It seemed fairly straightforward to do really. Would have gotten further if we didn't bust that tool whilst milling the plate, in the end that was my biggest holdup.

    Now, if I do a similar thing over here, I will likely face those issues and more seeing as I was to do electron deposition of Niobium. I *can* do it with titanium, but having an exotic metal thrown in there just sounds cooler, but also because Nb is so damn hard to work with.

    this may be a stupid question, but what do people use diffusion pumps for?

    and if you havent figured it out yet, the "magnetic switch" seems to me to be a solenoid that pulls a valve or something, i'd love to be of more help but i honestly have no clue on how a diffusion pump works..

    1 reply

    They are used to achieve a high vacuum with no moving parts in the pump itself. These won't remove much air at all, but its supposed to, and after this there are molecular, turbomolecular, and cryo pumps to suck nothing in and condense it into nothing and spit it out the back. The need for any of these is to have a very tight control over the atmosphere inside a chamber.

    In my case I'm essentially making a hydrogen lightbulb to melt solder with.

    Nice picture, and excellent work picking apart the design. Its a lot clearer to me now how it all works.

    Well done.


    3 replies

    Yes, you may take a breather for the next 5 seconds, then resume cleaning the floor with your tongue.

    Where's the brush to scrape off all the swarf live?

    And drudgery, given that I'm a lowly intern who nobody listens to,

    Who said that ?