Jim Kovalchick -My attempt at smaller fusor

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Jim Kovalchick
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick » Sat Apr 25, 2020 4:57 pm

I got rid of the alumina. Unfortunately, the problem I added the alumina for in the first place is back. At 38 kV I am hearing nasty arcing back at the connection of my feedthrough. I may just be at it's limit.

More bad news: Better symmetry has bought me a prolonged occurence of an electron beam orthogonal to the axis of my grid openings directly at the center of my view port. I have seen this before but it only showed at much lower voltages and higher pressures. In the attached picture there is a small dot where the electrons are fluorescencing the glass. Note there are two spots in the picture. There is a smaller, well defined spot and a bigger more ghostly one near it. I am more afraid of the small one. The glass was hot to the touch but because I could keep my finger on it, I am guessing below 115 F on the outside. I held a strong magnet near the dot, and the dot does not move. The only effect of the magnet was some flickering of the lighter fluorescence across the face of the glass.

In better news: At 35 kV and 6.6 mA, before I hit the arc wall at 38 kV, I measured neutron numbers that I wont report yet because they startled me. I pulled the tube from the moderator to make sure I wasn't seeing noise, and watched my indications go nearly to bottom of scale. Suffice to say, if these numbers are real, the tweaking of my grid positioning made a big difference in the fusion rate, as several have predicted.
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Jon Rosenstiel
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jon Rosenstiel » Sat Apr 25, 2020 5:20 pm

I keep confusing CF with KF, sorry. So the 2.75” CF cross has an ID of 1.44”… wow, that’s pretty darn tight, makes for a real “high-tension” environment.

With my 6" spherical fusor the alumina tubes seemed to be a positive, not so with the cube.

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Richard Hull
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Richard Hull » Sat Apr 25, 2020 11:50 pm

Have you recently checked the x-rays at that dot on the window at that voltage?

Richard Hull
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Jim Kovalchick
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick » Sun Apr 26, 2020 1:38 am

The xrays at the window are not trivial. I limit my exposure with remote camera pics, distance, and a lead flap that usually hangs over the view port. I'm not sure I want to publish a number. My ion chamber is not calibrated and the desiccant is pink right now so it will significantly over report.
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I'm not sure the xrays from the electron beam on the window will be as significant as those on the beam ends. The electron beam doesnt seem to be making near as much plasma because the beam is invisible other than the dot.
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This evening I did another run in the low to mid 30 kV range. I stayed away from higher voltages, but I also found that st 35 kV I had to keep current low otherwise grid to wall arcs start. I think I found this fusor's upper range.
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I also recorded a new personal high neutron count rate. Using rate indication only, not a scaler, the peak rate match the number from earlier today of 1200 cpm.
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Next steps will be to establish stable operation standards including applying final shielding installation, operation duration limits, and a workable neutron oven.

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Frank Sanns
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Frank Sanns » Sun Apr 26, 2020 2:25 pm

Looks like you are make good progress Jim.

You won't see an electron beam in a Fusor. The pressure is too low. The mean free path is multiple km so there is no significant interaction of electrons with the plasma. As you have noted though, you will see the fluorescence of the electron beam impinging upon surfaces.

All of the visible plasma in the fusor is excited by ions and fast neutrals alone.

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Jim Kovalchick
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick » Sun Apr 26, 2020 3:35 pm

I agree Frank. The electron beams can only be inferred from plasma which I don't see with this secondary beam.

Also as I understand it, we don't see plasma either. Only the photons released when it cools.

Jim K

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Frank Sanns
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Frank Sanns » Sun Apr 26, 2020 5:06 pm

Yes, and will all that is going on in there it has to be down to around 3 eV before we see it! Talk about energy loss.

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Jim Kovalchick
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Jim Kovalchick » Mon Apr 27, 2020 12:55 am

Conditioning is really helping my fusor performance. Tonight I operated at 38 kV and 8 mA. My neutron numbers are up 20 percent.

Attached is a picture of why you shouldn't look into an unshielded view port of a serious fusor. This gadox coated xray intensifier screen at the viewport photographed in the dark with my cell phone. Some of the light is from the plasma, but the green color is from the gadox reaction to xrays.
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Mark Rowley
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Re: Jim Kovalchick -My attempt at smaller fusor

Post by Mark Rowley » Mon Apr 27, 2020 3:33 am

Jim,
I know you don’t want to provide official numbers but could you provide a ballpark figure (on the low side) of where you think you’re at?

Mark Rowley

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Re: Jim Kovalchick -My attempt at smaller fusor

Post by John Futter » Mon Apr 27, 2020 4:59 am

Jim
just put a neodynium magnet against the fusor side of your viewport, this should pull the electron beam away from the glass

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