Small Experimental Fusor

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Dennis P Brown
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Small Experimental Fusor

Post by Dennis P Brown »

I have put together a small fusor to test two different power supply configurations. See the first photo of the complete system less power supplies. The total cost including both power supplies, mechanical pump, DP w/gate valve,the main vacuum chamber/cover/adapters (self machined) and all vacuum sensors/read outs was under $650 (vac connector & plastic/steel tubing on hand); so not too much invested. Milk crates form the "rack" for the fusor system. As such, this is just an experiment to test out two surplus and very low cost power supplies and try a novel configuration for the anode and cathode within the chamber.

One of the power supplies (see the second image of both supplies in a enclosed rack mounting system) is a standard Glassman 40 kV negative supply and can be pushed to 400 watts; which isn't too good. Maybe a bit more but not too likely. The other power supply is a surplus laser supply (CO2 TEA) that can reach up to 30 kV but will supply 2200 watts continuous power. The issue is for this high current supply is that its output is positive. This incorrect polarity supply got me thinking on how to exploit it in a fusor. As pointed out by Richard, one does not energize the main vacuum chamber walls directly of a fusor for many reasons but not the least of all, for safety considerations.

To get around the issue with a positive supply I designed the fusor to handle either polarity. That is I designed the cathode and anode to be fully independent of the larger surrounding vacuum system and mostly isolated from the main vacuum chamber (steel and which is fully grounded, of course, for safety.) The two electrodes (sections out in air) each will be surrounded by a plastic tube filled with oil so arc over will be suppressed. This has not been installed yet for the electrodes and the experiment will wait for that to be done.

To address the use of either polarity supply I will have two cylindrical wire mesh grids (steel mesh coated with palladium; see pic three) acting as electrodes that do not directly couple to the main chamber walls. The cathode wire grid is much smaller and fully inside the anode wire grid. The cathode and anode each have their own connector through a thick glass plate. Both the larger cylindrical anode and a smaller cylindrical cathode will be "housed" in a glass jar (forming a "sub chamber") within the larger metal vacuum chamber. This glass jar will partly shield the vacuum walls from direct ion interaction (but of course, a lot of power will be lost to the grounded metal walls of the main chamber but for the positive supply, I have power to spare.) See the third photo of the wire mesh anode/cathodes mounted to the port window via electrode feed through's and sitting in the glass "sub-chamber". This unit is out of the chamber (image) for clarity. The picture does not show that the two wire meshs do not make contact and have a large separation between them in all dimensions.

The two feed through's (brass rods) go through my glass viewing port window (8 inch diameter and 3/4 inch thick. See pic four.) Since the ions only see the field in the sub chamber, using this wire mesh geometry for the cathode and anode, I think this should enable either supply to be used in order to ionize the deuterium gas in the sub-chamber. If I just want highest voltage but have a lower current, the standard fusor configuration can be obtained by exciting the center cylinder mess with negative 40 kV. If I want more massive current, I will install the 30 kV positive supply to my outer wire mesh (anode.) With either configuration the ions will see the exact same "field" regardless of the supply polarity used - so, in the configuration with the positive supply connected to the anode the fusor will still work as if it was being driven by a regular negative supply on the cathode as far as the ions are concerned. This should allow me to exploit a very high current positive supply to do fusion (also, it was cheap) ... or so, I hope ... .

As some are oft to say here, if one has an idea, build it.

So, I have now done that - testing can soon be carried out once I install the oil filled resistor system and submerge the electrodes under oil. As I stated before, the goal of this experiment is that I really wanted to exploit a positive power supply, while still having the ability to use my regular negative supply if desired (not simultaneously, of course.)

Comments?

Aside: still working on the deuterium gun (linear accelerator) but will post details on that soon. Progress has been made there after a long delay. THis is more a backup project but I had most all the parts on hand so decided to do the required machine work and assemble it. Finished the cathode/anode grid system and drilled the holes in the glass plate this morning ... .
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Fusor less Power Supplies
Fusor less Power Supplies
Positive and Negative Power Supplies in rack
Positive and Negative Power Supplies in rack
Outer and inner anode and cathode Mesh mounted to viewing port plate and in glass "jar"
Outer and inner anode and cathode Mesh mounted to viewing port plate and in glass "jar"
Top of fusor looking through view port plate (no electrodes)
Top of fusor looking through view port plate (no electrodes)
Last edited by Dennis P Brown on Mon Jun 29, 2015 10:51 am, edited 1 time in total.
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Richard Hull
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Re: Small Experimental Fusor

Post by Richard Hull »

As we note here often, fusion is easy....... You seem to have done this right and I see no reason why this might not work with either supply as you have taken special precautions. As long as your insulation doesn't fail and you have a good detector, I think you can do fusion. Hopefully, the grids will not melt under bombardment before you detect fusion, but that is part of the art in operting a fusor for anyone. Good luck.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Dennis P Brown
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Re: Small Experimental Fusor

Post by Dennis P Brown »

Added the new electrode feed-through's to the future fusor and did a vacuum test. The system quickly went down to 1.9 * 10 ^-5 torr (no cold trap for the DP.) A nice feature of my DP is I also have a separate water cooling line for the internal oil. Inthis manner, I can shut the heater off; open another water valve, and the DP is completely cold in under 10 minutes. Very nice for testing different vacuum gauges and adding/removing vacuum parts and not waiting for the oil to cool ... .

So, I am starting on the power cable connections (with a 50 kV capacitor and resistor system (70 K ohms) under oil.) My primary goal is making it safe - no exposure to the HV and everything grounded (including the entire vacuum system/chamber.) Photo's of the very simple (and low cost!) 40 kV feed through's are included. Aside: the electrodes on the viewing port will be filled with DP oil. If the electrodes get too hot and the epoxy partly fails, at least only DP oil will leak into the DP!

After finishing the HV cabling I will assemble my experimental neutron detector. The whole point of these devices - besides the fun of learning to assemble these monsters - was to test an idea I have for a extremely simple, cheap and easy to build neutron detector for under $100 that will provide a good level of signal from a fusor ... maybe. That is why it is science and an experiment. If it works (????) I'll post its physics and construction. If it fails ... what else is new (lol.) I'll still have the fusor and accelerator.
Attachments
0701150801.jpg
Electrodes for cathode and anode (plastic puipes will be filled with oil to prevent arc over.)
Electrodes for cathode and anode (plastic puipes will be filled with oil to prevent arc over.)
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Dennis P Brown
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Re: Small Experimental Fusor

Post by Dennis P Brown »

Completed the high voltage wiring which includes the system 50 k ohm resistor; also, added a capacitor to the power supply system for the small fusor.
The main supply cable shorted up nearly five inches of insulator to reach its outer grounding shield; apparently, the sealant (silicon) wasn't fully cured. Hopefully, just burnt insulation sealant and the PS is ok. Have to reinstall the cable before I can test the PS to see if it was damaged. Including some pictures to lighten the post.
Attachments
Complete system - fusor (right) & power supply (left)
Complete system - fusor (right) & power supply (left)
Looking down into the PS; oil tray with cap bleed res & system 50 k ohm res. Cap to the left
Looking down into the PS; oil tray with cap bleed res & system 50 k ohm res. Cap to the left
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Dennis P Brown
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Re: Small Experimental Fusor

Post by Dennis P Brown »

Update on system testing: the basic plasma using a positive power supply worked great in the 6-8 micron range using deuterium. The system lite up with a beautiful plasma and was providing a few milli-amps. unfortunately, my 50 K resistor shorted through the oil to a nearby ground and needs to be replaced (the cap was grounded and isolated but I didn't realize how close that section of the ceramic resistor was to that system.) Also, later that day, while turned off, my glass view port broke - I had the flange too tight. Mistakes, stupid ones and errors in design once again get the novice but these will be fixed and the unit further upgraded. Just will create delays. The basic system appears to work (the double floating anode/cathode system in a grounded vacuum chamber) using a positive power supply.
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Dennis P Brown
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Re: Small Experimental Fusor

Post by Dennis P Brown »

Minor update: received my replacement "fusor" ballast resister. Got smart and put a thick plastic sheath around all the resistors besides covering them, the HV lines and connection points under oil. Doubled checked that no "low voltage or ground points" are anywhere near any high voltage sections (that was a previous oversight!) When the new viewing port glass arrives, I will drill it out and install the electrodes. Looks like this unit is coming together again (at least until I discover a new failure mode (lol).) Agree that the best way to monitor current for a "positive" power supply is to "float" a meter above the fusor so it "see's" the full 30 kV but has no significant voltage drop to contend with. Will mount the meter behind a plexi-glass sheet to remind me not to touch said meter ... which will be at lethal voltages/current levels. Once re-assembled, will post a pic and the test results.
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Dennis P Brown
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Re: Small Experimental Fusor

Post by Dennis P Brown »

Update - some progress for my deuterium filled demo fusor ...

Well, after a lot of delay, built the new cover plate (on the cheap - steel plate with a 2.5 inch plastic window) to replace my all glass unit. The electrode needs to be installed but the fusor project moves forward (again, after two steps back.) Will use my 40 kV negative Glassman power supply since I should be able to squeeze enough power out of the under sized unit to make it worthwhile ... maybe 15 ma in the 22-25 kV range (added a large fan to the power supply case to be on the safe side.) The high current positive supply has an issue (of course) so that gets pulled and allowed to collect dust.

Still, better to stay with a grounded case, anyway and do things the normal way since that has been shown to work (strange how that works ... .) The fusor system, after being open to air for many months (especially the diffusion pump oil!) fired up quickly, out gassed in minutes and pumped down to 5 * 10^-5 torr in twenty minutes (total time from atm.) Diffusion pumps - what they lack in complexity, and cost makes using turbo's look almost pointless (I have a turbo system.) As a quick test, closed the main gate valve to test for leaks, and the ion gauge very slowly moved upwards; so, I guess the vac system and chamber are all still healthy.

Still, need time to run some dummy D2 tests on the system (with some HV) and add a better current meter to the HV supply. Still, something to do until I get the last part I need for the new VdG so the deuterium accelerator can be fired up and tested, as well. Since I have no neutron detectors, more just a "plasma" light show (even with D2 at voltage/current) then a serious attempt for fusion. Do need to repair my Geiger counter to check for x-rays - not too keen on electronic's repair.

But progress is progress so figured a post was in order even if it is slow ... I think a snail just passed me.
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Richard Hull
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Re: Small Experimental Fusor

Post by Richard Hull »

Keep at it and you will get there. All the best on this effort. It took me three years to get the Fusor IV on line from fusor III. Fusor V is yet, still a dream and I am retired!

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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