125kV Fusor

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Joe Gayo
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125kV Fusor

Post by Joe Gayo »

I have a Glassman PS/WR100N2.5XY6, which is actually built with a 125N2.5 multiplier and limited by the control board. I don't have the exact schematics but Glassman supplies of this form factor are all pretty much the same (the reference designators are different which is annoying). I modified the feedback for the voltage and current follower amplifiers to output 125kV @ 3mA max, when set to 100kV @ 2.5mA. (I also purchased wire from Dielectric Sciences and made a more robust high voltage cable)

I ran this with my ion source cube today and the results are stunning. There is a 60% improvement in output between 100 and 125kV (with the same cathode current). I'm rapidly closing in on the 1E+8 n/sec goal.

P.S. My feedthrough works like a champ at 125kV.
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Richard Hull
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Re: 125kV Fusor

Post by Richard Hull »

Fabulous! I am glad you modified the system to be more usable. It is nice to be able to noodle stuff like that out. After a lifetime in Electronics I am fortunate until I hit 128 pin SM MPUs that are shot. I often turn such systems into old time kludges without all the bells and whistles offered by computer control, but only if I feel it is worth the effort. If a schematic is available I can usually make short order of a fix.

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: 125kV Fusor

Post by Jim Kovalchick »

I wonder if hitting those kind of neutron numbers emitted from a small chamber like that would allow low resolution neutron radiography. I think high res requires 10⁹ n/cm²-sec, but maybe an accumulated exposure could be done on a gadox screen and a properly shielded camera with the numbers you are heading for Joe. You may also be able to do some low grade activation analysis not just activation for the sake of activation.
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Joe Gayo
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Re: 125kV Fusor

Post by Joe Gayo »

@Jim

Great minds think alike. I have a lead shielded dark box with a GOS screen and a low light camera specifically for that purpose! I'll post more under a separate heading once the results are worth sharing.

I'm currently dealing with some non-ideal performance at 125kV. The output really should increase by a factor of 2, but I've yet to convincingly achieve that repeatedly. I had a brief glimpse of 2x performance vs 100kV today and recorded 1.3E6 CPM.
JoeBallantyne
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Re: 125kV Fusor

Post by JoeBallantyne »

So that would be 5.3E7 n/sec total based on multipliers you used in the other thread.

Correct?

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Re: 125kV Fusor

Post by JoeBallantyne »

Those cpm counts are pretty high. Have you considered moving your neutron detection tube so it is 2x, 4x or 10x further away from your source, so that you reduce your cpm by a factor of 4, 16 or 100?

At some point you may compromise the accuracy of your numbers because the count rate is so high.

(A very good problem to have...)

Joe.
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Richard Hull
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Re: 125kV Fusor

Post by Richard Hull »

The resolving time of a BF3 and the associated electronic ripple through to the counter is no real issue here as with a GM tube.

Scintillators (PMT), and BFe and 3He detctors just don't have issues in the CPM range. 200kCPM is bridge too far for most GM tubes (3300 cps) or 300usec reporting if perfectly spaced, but is not good for a GM tube as the randomness of any radiation is never evenly spaced. Faced with a combined dead time and resolving time of a GM counter tube and electronics being in the region of 100-200 usec., the average GM is limited to 100kCPM without significant calibrated resolving time correction factors in hand.

The others counting neutrons or scintillations are in the 10us or less range and even randomly spaced will not place a burden on truth in counting.

Still, just a 2 x greater distance would be nice probably until, at that new range, a 700kcpm count might herald a "till death do us part" count...without neutron shielding. Joe is probably already at the neutron shielding level for regular, repeated local operator presence or is certainly getting there. It is to be remembered that fast neutrons, as in D-D fusion, carry a 10-20X Q factor in destroying human beings over other radiations.

The average fusioneer, like me, who runs his fusor in the 500k to 1mega range a total of 40 runs per year needs no neutron shielding while present, local to the run. The dose per run is definitely not an acute dose which might be of concern, it doesn't even approach the more serious chronic dose level due to the spotty or infrequent operation.

Neutron shielding is needed for the 10e8 acute local operation and absolutely demanded for the guy operating daily at that level to avoid a chronic danger level.

Again, x-rays at or above 30kv applied is pretty much a must have shielding situation and is easily tackled with a small lead, "shadow cone" shield for the intermediately strong, regular, operators. Such a shield is demanded if large audiences are to be expected out of an abundance of caution. Remember, in all situations, the x-radiation will always be the killer radiation to be concerned about. You can fail at doing fusion,(making neutrons), and still get nicely x-rayed!

The upshot is know your radiation detector's strengths and weaknesses and your radiation of all types that will be present in any experimental or operational situation. Besides reading the excellent FAQs here on radiation, a good deal of "self-directed" reading and educational effort is demanded on the part of the noob and continuing education on the part of the "old boy"....We should never stop the learning process.

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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Joe Gayo
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Re: 125kV Fusor

Post by Joe Gayo »

Bubble dosimeters arrived today.

I've performed 5 runs at 80-125kV and have confirmation that my previous calibration (using my calibrated REM ball) was accurate within 10%!

I have a new device coming on-line within 30 days that should put the numbers over the top.

As a side note, it's pretty neat to see a dosimeter register 42 bubbles at a distance of 3ft from the cathode in 60 seconds (with everything redlined).
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Richard Hull
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Re: 125kV Fusor

Post by Richard Hull »

One statement.......WOW!

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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Bob Reite
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Re: 125kV Fusor

Post by Bob Reite »

Don't know the calibration factor of his detector but those numbers sound like he is in the 5xe07 range. May be close to a record for our group.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
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Joe Gayo
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Re: 125kV Fusor

Post by Joe Gayo »

28bub/mrem =)
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Richard Hull
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Re: 125kV Fusor

Post by Richard Hull »

42/28 = 1.5 mrem absorbed dose at 3 feet.....X 60 minutes = 90mrem/hr rate of fast-neutron radiation at 3 feet. (NASTY!)
At 1.5 feet 360mrem/hr and at 9-inches 1.44 rem/hour!!!! To hot to be around! Assumes point source and flawless isotropic emission.
Key factor assumes I did the math right in my head.
I dare not guess at the x-radiation.........
Git yerself sum shieldin', boy! Assumes you have none of significance related to fast-neutrons now.

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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Bob Reite
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Re: 125kV Fusor

Post by Bob Reite »

I calculate that he is doing 7.35E+07 N/S isotropic! WOW! That breaks Jon Rosenstiel's record of 1.2E+07 n/s. But not too surprising if he is running 100 KV.

I'd advise going to remote control operation. Inverse square law is your friend. Not only because of the dangers from X-rays and neutrons, but at 100 KV, high voltage gets "strange". It will not follow the shortest path in air from the HV source to ground, the air ionizes unevenly. Other experimenters have reported any arcing taking the "long way around" to a grounded object.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
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Richard Hull
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Re: 125kV Fusor

Post by Richard Hull »

Yes, so many folks do not know about insidious leakage surface currents, Trichel pulses, unseen corona and heated air ionizing at gradient points can cause unexpected havoc. While these unusual phenomena are not often seen in the 30 kv range, at very high voltages in air such arcing and flashover are very common.

https://www.researchgate.net/publicatio ... _formation

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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