Fusor V construction - the process long running

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Jim Kovalchick
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Re: Fusor V construction - the process long running

Post by Jim Kovalchick »

With my cross, the xrays are where you might imagine, the view port and feedthrough. At higher voltages, the cross tubes become transparent. The conflat fittings have some bulk them so that helps except out the beam target ends. I have now wrapped the cross tubes with a double layer of lead for a total of about 1/8" inch. I have a piece of thick lead on each beam end and a piece over my view port. Not much I can do about my feedthrough, but I have it facing to the back. I would like to do something different with my camera situation, but that's what I have for now. I dont have to spend time near my fusor except to take a neutron reading with a PNC and placing a neutron oven target. I am less than 1 mrem/he generally about 1 foot out at 40 kV now that I shielded.
I am working on permanent mounting of neutron detection to eliminate that dose as well.
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Richard Hull
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Re: Fusor V construction - the process long running

Post by Richard Hull »

I was thinking more in the line of a single total shield. I think, at first, I'll just do a "shadow cone" shield for myself if it gets intense. Thanks for the input. Lead wrap of the tube portion is a good idea.

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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Re: Fusor V construction - the process long running

Post by Richard Hull »

Well, take a good look at what is the finished fusor V. It may be the last time you see it!

I ran the system most of the evening and did fusion, but only a tiny amount. Extremely disappointing. Running at 29kv, 10ma and 23 microns. I got only 100 counts on the He3 counters in a minute on my best run.
I am ready to tear it down and put fusor IV back up in modified form. Boy, am I ready! However, I might try one of two more things in the effort before going back to fusor IV. It will keep me busy, at least.

I find that the heating is an issue and in spite of the additional fuel pressure, I did not see much to my satisfaction.

I am convinced it is all about the uniform huge surface area of the sphere that is the winner and 6-inch hemispheres are ideal up to about 60-70 kv.

For those with these systems, have any of you measured a favored direction for neutron emission, like the target conflats? I will probably try to cobble up and test a BC-720 system that is reliable and compact.

Richard Hull
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Fusor V 4.4 (2).JPG
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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Jim Kovalchick
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Re: Fusor V construction - the process long running

Post by Jim Kovalchick »

I sit my pnc on top of one of my beam end blanks. At 40 kV and 10 mA I get about 750 cpm. The same BF3 tube measured 400 cpm held against your fusor IV doing a million n/sec. I'm sure my total neutrons are less, but the effective neutron flux I can get close to seems higher.

I think Jon R said that small grid size differences changed his numbers a lot. I would try different grids before giving up.

I'm also concerned about grid and chamber heating. I perceive my neutron numbers flattening as I raise voltage and current as things heat up. I really need to connect my tube to a scaler to really understand it.

I am also toying with the idea of putting metal inserts on my cross ends to bring it all closer in. If you look at Jon's cube, his blanks are closer to the grid than a 6 way cross brings it.

Just some thoughts,
Jim K
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Richard Hull
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Re: Fusor V construction - the process long running

Post by Richard Hull »

As I see it, the grid in the cross systems are electron emitters, located where we do not want them. We want electron emitters at the blanks/targets where they can ionized the deuterium. To this end I hope to try a couple of things to save fusor V. Tungsten needles embeded in a circle way from the center of the flange might help. I attach a diagram here.

Also, some electrostatic ion guns might help if attached to both facing flanges. Another diagram here Note: the more current you can pour into the gun, the better. 10-20 ma is fine. The supply being positive is a snap to build.

Richard Hull
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Electrostatic Ion gun.jpg
W needle ionizer.jpg
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
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Scott Moroch
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Re: Fusor V construction - the process long running

Post by Scott Moroch »

I am curious why the tungsten needle in your ion source is at a negative bias with respect to the shell?

I would also suggest a single hole or group of holes around the center axis, rather than many perforations.

I have attached a picture of a successful deuterium ion source I have built. 1.2 kV across the glass, followed by a 20kV accelerating gap (in this case you would just use the grid).
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Deuteron Ion Source.jpg
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Richard Hull
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Re: Fusor V construction - the process long running

Post by Richard Hull »

In the gun, I did get the polarity backwards. Sorry 'bout that. I have corrected it, now, in the above original post. the bias on the needle makes it an electron high field emissive source to ionize the gas and the grounded (now negative) perforated plate attracts the deuterons some, as canal rays will go through the plate and see the huge attractive negative grid electrode. The patterned hole plate is a very inefficient positive HV extractor.

I did not mean to shotgun blast holes. Look at the nicely patterned electrostatic guns in the photos of Farnsworth's team......holes like that...

I repost the image here from my Farnsowrth history group. note the rather large radial circular holes and a rather tiny central hole




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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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Maciek Szymanski
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Re: Fusor V construction - the process long running

Post by Maciek Szymanski »

That’s very interesting idea. I’m looking forward for the results.
The peripheral holes in the cathode makes sense for me. As the most of the ionization in the discharge is done in the cathode region by the secondary electrons the central solid portion works as a target for ions and secondary electron generation. Of course these ions will be lost for the fusor, but the anode-cathode discharge current is the “engine” producing ions. some of them will pass through the holes and will be extracted by the main fusor cathode. For other hand I doubt if the needle type anode will do any help. The main function of the anode is collecting electrons and repelling ions in the positive column so to my humble opinion the flat plate may perform better. But as always the experiment will give the answer.
Also looking at the photo of those electrostatic ion guns I’m wondering if the black rings are the ferrite magnets for improving ionization?
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Dan Knapp
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Re: Fusor V construction - the process long running

Post by Dan Knapp »

If you need a way to make really sharp tungsten tips, I suggest using the electrochemical etching method used to make scanning tunneling microscopy probes. I used this approach when I tried to make a sharp focus cold cathode electron source. I wasn't able to get the electron current I was seeking, but I did manage to make some very fine points. The method is the following:
I used 0.020 inch tungsten welding electrodes with 2% cerium. The points were electrochemically etched in 2 molar sodium hydroxide solution using 4.0 VDC at about 20 mA. The tungsten rod is the anode, and a carbon rod is used for the cathode. The trick is make the etching occur only at the water air interface. You insulate the end of the tungsten rod (I used teflon insulation stripped from insulated wire) and then support the rod hanging into the etching solution with only about a millimeter of the rod above the insulation wetted. The etching takes place at the air solution interface until the bottom insulated section of tungsten drops off. You have to watch it and immediately turn off the current when the tungsten end falls off; contineed etching will eat away your point. The photo below shows one of these tips.
W tip.JPG
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Richard Hull
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Re: Fusor V construction - the process long running

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The second drawing ( circles) is not related to the ion gun at all.. it is a totally separate idea for field emission ionization at the two conflat end plates to create local ionization in that desired region.

The first drawing is the gun by itself. Yes, a magnet (premanent or coil) could be slipped over the gun to aid ionization. There is nothing to prevent a filament replacing the needle in the gun. Tests would be needed to show any results. These are the only reasons I am giving the cross any chance at all in my future.

I did just about quadruple my fusion rate to over 500 counts per minute last night as I approached 30 kV, but arcing stem-to-sharp edge of the cross juncture to ball stem foiled any increase. I will have to alumina tube the thing, I guess to see if that improves things. I would typically get 50,000 cpm at the mega n/s mark with fusor IV using the identical 3He system.

Finally, hyper fine points would be ablated away instantly as they would become incandescent due to the current and round off, to become a W deposition source.

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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Re: Fusor V construction - the process long running

Post by Richard Hull »

At some point I will institute a new fusor V construction effort based on a spherical system. This fusor effort is now terminated the kludged fusor III in 2000 did far better at 150kn/s. I'll go with "easy", working the laws of physics to my total advantage. Smooth, even field distribution over a never arcing distance with plenty of absorbing and de-sorbing surface area.

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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Jim Kovalchick
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Re: Fusor V construction - the process long running

Post by Jim Kovalchick »

Richard,
I'm sorry to hear about the fruits and lack there of, if your efforts. My numbers are bad now, but they started out fairly good. My original numbers were higher on my pnc than they were when I held it against your Fusor IV doing a million per second. I was originally bolstered and remain so by Jon Rosenstiel's cube fusor success. He stated that his grid size was important, and I will try some more to find the right size and material.

I experienced a lot of the clearance issues you did and sacrificed three Harbor Freight meters, a mini convectron, and a vacuum instrument controller to sustained arcs. It would start with normal grid cleaning type of stuff at new, higher voltages, and occasionally some of little bursts managed to strike continuous arcs. In my previous fusors, the only time this happened was within the path my stem followed from my feedthrough before it entered the open space of the chamber. The good news for me is that all this has pretty much stopped now. Of course it will all start again when I pop my chamber to look into what's going on with my lowering numbers and install a new grid.

I think I will endeavor on a little more. I want to find a grid that wont go to near melting at 400 W. I may look at blanking off my beam ends differently and or try cooling.
Call me stubborn, but I'm not done yet.

Regards,
Jim K
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Dennis P Brown
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Re: Fusor V construction - the process long running

Post by Dennis P Brown »

I looked into this issue of "smaller" chamber size some time ago and posted the results here in the forum - now, what I mean by smaller chamber wasn't my building a actual smaller chamber but rather (and this is the key) creating a smaller grounding grid. That is, rather then my larger volume chamber walls being the grounding plane, I installed a wire cage inside my existing chamber to create an equivalent "smaller volume".

What I discovered and reported here was that chamber size wasn't the key effect nor was the design of the high voltage supply grid (I used both the same HV grid and chamber.) Rather, when I created a half volume grounding wire cage (reducing my volume by 50%) within the existing chamber, I most certainly did see a 50% increase in neutron counts (measured via a bubble counter so I know it was real.)

The key difference between the two systems (large volume vs. "small" volume) wasn't just a simple volume reduction but rather my chamber operating pressure went from 5 microns (for a stable plasma) to 12-15 microns. My operating voltage/current were also the exact same for both systems. This smaller grounding cage system allowed my deuterium pressure to be greater. Hence, this provided a greater number of available deuterons within the chamber while maintaining the exact same plasma wattage (current & voltage.) The higher deuterium pressure appears to be the key as my experiment clearly showed.

Getting a greater neutron count for identical plasma energy isn't a function of chamber size itself but rather the greater operating pressure one can then create using the identical wattage (voltage and current.) The goal people need to go after is greater deuterium pressure not just a simple smaller volume. If one can raise the chamber pressure for the same energy (voltage/current) than the neutron production will be increased.

(aside; original experiential post: viewtopic.php?f=13&t=12048)
Last edited by Dennis P Brown on Thu Apr 09, 2020 10:31 am, edited 1 time in total.
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Jim Kovalchick
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Re: Fusor V construction - the process long running

Post by Jim Kovalchick »

Easier said than done Dennis.
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Richard Hull
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Re: Fusor V construction - the process long running

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The interesting part of starting over is how do I assemble the new system so that I need not ever touch the fabulous work I did on the entire vacuum system. I want to just remove the cross and plug in the new system. I am so glad I doubled the surface area of the fusor level table. I think the next "new" Thread might be entitled "Fusor V Redux".

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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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Re: Fusor V construction - the process long running

Post by Maciek Szymanski »

That's a pity Richard. I was looking forward to your results with the electrostatic ion guns. I was expecting reputable data from a well conducted experiment, as all your efforts. I hope you are planning those with your new V.
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Re: Fusor V construction - the process long running

Post by Richard Hull »

Well, I went one arcing scenario too far. I apparently blew out the turbo controller in some fashion. I have the manual with the troubleshooting guide and have verified that all 4 fuses are OK. I also had the 45 volts between the two points noted. I measured at X3 the 15 volts but not the 5 volts and 2volts. As those seem to be triggered in a feedback loop from the pump by a selector '0NE OF FOUR" in a 74c42 which is fed AB from The pump via two J FET CA081 op-amp outputs. I suspected the 74C42. (CMOS blows easy) I pulled it and put in on my lab's bread board system and ran it through the AB sequence and the 0,1,2,3 outputs worked just fine. I sure wish I had a nice schematic of the electronics in the TCP40....

I hope I haven't blown a winding. There was nothing special about the arc. It has happened about twenty or more times while struggling with the fusor V. The pump drops off line normally. I have to hit reset to get the pump start button to work again, and it always has spun right back up. I guess this one broke the camel's back.

When plugged in, the panel lights up the buttons as per normal. I hit reset then the pump on button...It lit perfectly.... the crtical K2 latching relay pulled in then dropped out....no spin up. $%#@*&

I'll keep everyone in the loop. I can see, in the distance, a restoration of the reliable old diff pump and a modified fusor IV back in biz. The turbo has been a joy until it wasn't... I will give it a fair shot and look for a circuit diagram. Anyone here have one??

It is now 10:30 AM here and I haven't slept yet. I'll get some shut-eye.

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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Re: Fusor V construction - the process long running

Post by John Futter »

It will not be the windings
this from a shelf of US (unervicible) nt 10, nt 13, nt20 etc with a few Edwards turbo controllers thrown in
All from arcs in the early days from the ion source or accel stage system development.
lots of ferrite and TVS diodes later we do not sacrifice to the gods of high vacuum so often!!
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Richard Hull
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Re: Fusor V construction - the process long running

Post by Richard Hull »

John, thanks. It is nice to hear I am not just another VCIW. (now ancient term used by Don Lancaster years ago.....Voice Crying In the Wilderness.)

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
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Dennis P Brown
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Re: Fusor V construction - the process long running

Post by Dennis P Brown »

Sorry to hear about the turbo - that is just really not fair; as I posted in another thread about turbo vs. DP I'm even more glad I used a DP instead of my turbo for orginal fusor operation. Never suspected that would occur to a turbo but obviously, it does.

While I used the trubo only for my deuterium project (still sidelined but maybe i'll reconsider if I get my nerve up ... as well as the new facility building I started.)

I use a screen to protect my turbo from stuff falling into it. Now I see that would offer other benifits as wll. So, might be a good idea to always use a screen over a turbo so to act as a Fraday shield. Besides protecting it from objects, should protect it from arcs. I did screen my thermocouple for that very reason and it stopped all arc issues I had with that instrument.
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Richard Hull
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Re: Fusor V construction - the process long running

Post by Richard Hull »

I have a great naturally supplied screen in the throat of the turbo which is no where near the fusor. Look at my images! The fusor's vacuum port looks into the gravitationally down, flat metal valve face. From there it takes a right angle to an 18" long "S" bend of SS flex hose cable into the CF to KF adapter into the screen in the throat of the turbo.

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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Re: Fusor V construction - the process long running

Post by John Futter »

Dennis
The mode of destruction is not through the throat of the turbo. The major cause of failure is the use of coax high voltage leads that increase the capacity on the output high voltage this then causes higher dI/dt events causing ground bounce. yes star grounding in evidence much as possible. Not only is it dI/dt but dV/dt as well ie wires radiating into control wires. Even target current electrometers Kiethley were not immune I have a boxfull of dead front end ones that will get repaired one day.
so protection of sensitive inputs used those expensive metal cased diodes for electrometer inputs "PAD" something from memory. then all inputs protected with TVS diodes including turbo phase outputs. All High voltage coaxes RG213) protected with clipon ferrites (3) at each end this slows the dI/DT and dV/dt artifacts when an arc occurs.
Other stuff closer to the ion source potential also protected with strings of GDT tubes (Gas discharge tubes).
All wiring run parallel ie earth return and coaxes all together to limit current loop area. same again for control cables physically seperated from the high voltage but again with their own earth returns
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Richard Hull
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Re: Fusor V construction - the process long running

Post by Richard Hull »

Alas, the week before last was devoted to a probing in the dark at the turbo controller electronic issues. Had the controller been made in a 3R, 19" rack structure, it would be much easier to probe around in, electronically. I guess I poured in about 7-10 hours and just gave up. Last week, I didn't even go into the lab except to shoot my 22 target rifle with the "Silent 22" cartridges just released by CCI.

I went back out yesterday to disconnect the turbo and run the system with just the mechanical pump. #@$(*%^. The arc also took out the LED readout to the Baratron gauge. So I spent the rest of the day replacing its display assembly, de-soldering about 25 connection and then re-soldering after mechanically adapting the new display block to the old case.

More hassles....I remember the old bumper stickers on cars here in Virginia during the Kennedy administration. They said, "Gee, I wish Ike was back....Hell, I wish Harry was back!" To this I now add "Gee, I wish fusor IV was back.....Hell, I wish fusor III was back." At least fusor III did 200K n/s!

The beat (up) goes on.

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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Re: Fusor V construction - the process long running

Post by Dennis P Brown »

So very sorry to hear how extensive the damage was and possibly via cross talk along grounding wires?!

While I have used seperate grounds (differnt wall outlet circuits rather than a star) for my fusor vs. my detectors, never supected that a star system could kill a turbo controller.

When I get the new facility built (may just order a pre-cut building for assembly by me ...ugh, still a lot of work), I will be extra careful to use a seperate ground wire for electronics and another for the fusor (I have a water well I use as a master ground for the house but I can sepeate this and my house power company supplied ground. The well would be very useful for a low noise ground, anway.)

Again, I am extremely sorry to hear this and thanks for these posts - this will certainly help others prevent similar issues.
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Re: Fusor V construction - the process long running

Post by Richard Hull »

I never had a single arc in any fusor I have ever built!! Arcs do this routinely. I got away with 6 or 7 OK in fusor 5, but there is always that straw that breaks the camel's back.

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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