Seeking design suggestions for SAFIRE analog experiment

    Hello,


    I'm working on a SAFIRE analog experiment. Components:

    - Large glass bell jar with steel baseplate and gasket. Evacuated with backing pump, and turbomolecular pump as needed.

    - There will be a gas tube to feed hydrogen to a hollow anode. Pressure: on the order of 1 atm. The simplest anode will be the gas tube capped by a nickel or nickel alloy flat plate. I will also use hollow sphere anodes.

    - The electrode will be surrounded by a cathode.

    - Voltage difference: up to 1000 V and 200 mA, or 600V and 4A.
    - I hope to heat the anode to ~1000C or higher using trace plasma in the vacuum chamber to exponentially increase hydrogen diffusion through the anode shell. Is this likely to work?


    Questions:

    1) What metals should be used for different anodes? Pure nickel for sure, but I also want a nickel alloy. IIRC SAFIRE said to use at least 10% nickel content.

    2) I want a "plug and play" type setup for plugging in different anodes. Each hollow anode will be welded to a metal gas tube. How would you suggest I connect this gas tube to the base plate and vacuum/H2 feed system? This is basically a vacuum/gas feed plumbing and connector question and it's the biggest question I have right now.


    If I can get this system working and doing something interesting I will graduate to an all-metal chamber with additional instrumentation such as a langmuir probe.

    Background info:

    https://safireproject.com/ewEx…SAFIRE-Project-Report.pdf

    • Official Post

    Hi Arun.


    It's not too difficult to make the 'plug and play' electrode system. I have a version of it in my own plasma rig which I suspect is similar to yours. The electrodes here are on threaded rods -if they were bored internally they would also act as a gas feed - the white things on the silver colour anode (stainless steel 6% Ni 2%Cr) are merely alumina insulation beads as used in pottery kilns. This rig is due an upgrade soon...new Pirani Gauge, new Vacuum pump and valves. The driver for this btw is a large 15kV Neon transformer fed via the red Auto transformer you can see in the picture. The Autotransformer gives up to 300V output btw, so I could in theory overdrive the Neon transformer to 20kV (unlikely) There's also a high voltage diode network for DC as required. 12kV high power Microwave diodes are very cheap on Ebay.





    It is necessary to supply the temperature above 200-300 atmospheres, this will not work, you will get a ball lightning at the end ... While it is spinning, we will get a lot of energy!

    Нефть - это кровь планеты, надо сделать модель планеты и мы получим генератор Тарасенко, эта энергия покорит вселенную! :lenr:

    So, your metal electrodes are attached to metal threaded rods, and those are threaded directly into female threaded holes in the acrylic walls? It sounds like it would be leaky. Do you use teflon tape with it? Any special choice of threads per inch (or mm...) for this application?


    • Official Post

    Hi again. There are no threads on the entry points where solid or tube connections pass through the 25mm thick polycarbonate (Lexan) base-plate, The polycarbonate is bored to make the vacuum-greased feed throughs a 'tap-in' fit then the externals are de-greased with isopropanol and sealed both sides with clear epoxy. The plain 'empty' hole in this photo is for one of the locating bolts outside the vacuum zone and the white ring is the main seal to the bell-jar which is 1mm thick approx silicone rubber. This took a long while to degas but got there in the end.. I used a polymer base-plate rather than a metal one to reduce complications with electrical insulation of feed-throughs - which in my experience can be a potent source of leaks.


    So your method is somewhat plug and play because you only have to chip away/drill out the epoxy that is on the surface if you want to put a different electrode there.


    I think a more plug-and-play method might be an "airlock" type connection. For example, a KF-16 "full nipple" could be welded to a steel baseplate or epoxied to an acrylic wall. Then, the gas tube could be welded or vacuum-epoxied to a half nipple. This half nipple can then be attached to the KF-16 full nipple airlock in true plug and play style with a KF clamp that is inside the vacuum chamber. On the non-vacuum side of the baseplate, a gas tube could be welded/epoxied to a KF-16 half nipple which can be connected to the airlock.


    I hope there is a simpler way.


    The gas fed anode being positive, a separate insulated high voltage feedthrough for the cathode is necessary. I have a commercial feedthrough for this, probably will vac epoxy it to the baseplate.


    Quote from Alan Smith

    Hi again. There are no threads on the entry points where solid or tube connections pass through the 25mm thick polycarbonate (Lexan) base-plate, The polycarbonate is bored to make the vacuum-greased feed throughs a 'tap-in' fit then the externals are de-greased with isopropanol and sealed both sides with clear epoxy. The plain 'empty' hole in this photo is for one of the locating bolts outside the vacuum zone and the white ring is the main seal to the bell-jar which is 1mm thick approx silicone rubber. This took a long while to degas but got there in the end.. I used a polymer base-plate rather than a metal one to reduce complications with electrical insulation of feed-throughs - which in my experience can be a potent source of leaks.


    • Official Post
    Quote from Arun Luthra

    So your method is somewhat plug and play because you only have to chip away/drill out the epoxy that is on the surface if you want to put a different electrode there


    Npt quite. No need to disturb the feed-throughs to change electrodes. That is why they are fitted onto the end of the feed-throughs via a threaded rod. Everything is interchangeable- electrode material spacing type etc. And gas feeds are also easy to arrange- there is a capillary gas-feed through the baseplate that could provide an gas supply for the electrodes. You can see the capillary in the center of this shot.


    So actually there are all kinds of commerical gas feedthroughs that exist and my real problem is lack of knowledge and comfort with VCO, VCR, swagelok, etc. tube connections. I probably want to weld a tube to my anode that can be VCR-connected (or similar) to a gas feedthrough that has a VCR-ended tube on the vacuum side.

    • Official Post
    Quote from Arun Luthra

    So actually there are all kinds of commerical gas feedthroughs that exist and my real problem is lack of knowledge and comfort with VCO, VCR, swagelok, etc. tube connections


    There are indeed many types - best to standardise on one- I try to always use 1/4 in VCR when I have to go there. My main objection to using commercial feed-throughs is the price.

    • Official Post
    Quote from Alan Smith

    There are indeed many types - best to standardise on one- I try to always use 1/4 in VCR when I have to go there. My main objection to using commercial feed-throughs is the price.

    I wholeheartedly agree, one can always find exactly what one needs, but the budget can go high, and in a experimental reactor that might have to be scrapped entirely to start over, anything you purchase needs to be either very re usable or ultra cheap, within the technical constraints.


    Ours is a field of research where we have got used to try to do all we can with very scarce resources, and Alan Smith has a lot of good ideas to get more bang from each buck spent.