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Hydrogen Supply (via electrolysis)

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Noah Hoppis

Tue Mar 26 2013, 12:29AM

Registered Member #10072 Joined: Thu Feb 14 2013, 05:12AM
Location: seattle wa
Posts: 21

I need a reasonable amount of hydrogen for ionization, I was thinking about a electrolysis cell but online there isn't much to do about a pure hydrogen source, because most of what I see is for HHO torches where isolation is not so big. My biggest concern is isolation, an unspecified particle in a cyclotron might provide unfavorable results

. I was wondering if two flasks could be used then a line between the two with meg ohms of resistance to stop O from leaking into the other flask. My biggest concern is whether it would do exactly that, and If so, any other good designs?

Forty

Tue Mar 26 2013, 12:52AM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

The setup I've seen used at college looks like an H made out of glass tubing. Valves are at the top of either side to let out the gas, and the electrodes are at the bottom of each side. I suppose you could pack some cotton into the cross bar if you're worried about oxygen bubbling over. It's basically just a glorified salt bridge setup

Ash Small

Tue Mar 26 2013, 11:35AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

If you are using electrolysis, you'll need to dry the hydrogen. There are various ways to do this. I think also, for purity, you will need something like platinum electrodes (other types may be suitable, it's a while since I read up on it) There is some useful information on fusor.net, but you may need to 'dig' for it.

Daedronus

Tue Mar 26 2013, 12:10PM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
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I would just get a pressurized gas bottle, 1L bottle (or something) at the flow rates you will need it will last forever.
The guys at fusor.net did a lot or work/research into gas feeding and handling, you might want to check it out.

Edit: Another aspect you should keep in mind is that you gas lines should be metal and metal seals only, like Swagelok, elastomers are incredibly permeable at micron and sub micron pressures.

For a cyclotron I assume you are looking at 10^-6 or lower base pressure, basically you should exclude from the start any kind of elastomer seals anywhere.

Noah Hoppis

Tue Mar 26 2013, 02:45PM

Registered Member #10072 Joined: Thu Feb 14 2013, 05:12AM
Location: seattle wa
Posts: 21

OK The permeability of Viton though might be a problem as the two main seals on the device are Viton! the Drying process should be achieved by the worm which is placed in dry ice to act as a cold trap.

Ash Small

Tue Mar 26 2013, 04:32PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

A cold trap should be ok for removing moisture. There is another common method used, possibly slaked lime, but I'd need to check.

Purging your supply system will possibly not be as straightforward as if you had a pressurized supply. I'm sure it's possible, though, but, for the quantities required, it may make more sense to buy some than to produce your own.

Daedronus

Tue Mar 26 2013, 04:46PM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
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Noah Hoppis wrote ...

OK The permeability of Viton though might be a problem as the two main seals on the device are Viton! the Drying process should be achieved by the worm which is placed in dry ice to act as a cold trap.

Viton is permeable like hell, I got about 700micron/24hour rise in pressure in my system.
Initially I though it's a leak, then I run the numbers and for (my) 110 inches of viton and the volume I have this is close to the theoretical diffusion rate.

I'm considering replacing at least some of them with indium o-rings.

Ash Small

Tue Mar 26 2013, 05:42PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

You will want to eliminate as much viton from the system as possible at these pressures.

Any large seals should be the copper/knife edge type.

It's going to be problematic enough using diff. pumps (not impossible, though) without pumping outgassing viton as well.

Ideally, the gas feed line should be all stainless steel, as copper and brass can also be problematic here (again, I'd need to check before going into much detail)

Noah Hoppis

Tue Mar 26 2013, 11:12PM

Registered Member #10072 Joined: Thu Feb 14 2013, 05:12AM
Location: seattle wa
Posts: 21

Well I guess indium it is, though it's so d*mn expensive, and hard to find! The setup has changed to a more conventional H design design, though the Vacuum is not on the electrolysis setup, it is separated by a hypodermic needle and about 3ft of capillary tube so the permeability of the rubber in the H generator is not of concern. what kind of electrolyte & electrode materials should I use?

Shrad

Wed Mar 27 2013, 07:37AM

Registered Member #3215 Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780

if anyone uses indium seals, I can help them dispose of used ones as it fits my laser needs quite well.. I would laminate and make foils for my vanadates

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