Plasma focus/Z pinch as an amateur fusion approach

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Dan Knapp
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Plasma focus/Z pinch as an amateur fusion approach

Post by Dan Knapp » Fri Mar 31, 2017 10:03 pm

I've just attended the 23rd International Atomic Energy Agency Technical Meeting on Research Using Small Fusion Devices in Santiago. The program is posted at https://nucleus.iaea.org/sites/fusionpo ... ation.aspx. I'll post the link to the presentations when they're available. The RUFSD group is made up of investigators from all over the world about equally divided between small tokamak people and plasma focus people, with a few "miscellaneous" like me. Plasma focus approaches are the primary tools of people in developing countries with limited resources, not unlike the typical amateur fusion enthusiast. Years ago there were discussions by a few people pursuing plasma focus as an amateur fusion method, but I haven't seen anything In this area posted for quite some time. The necessary apparatus can be home built, basically consisting of a big capacitor (which can be home built), a HV power supply to charge it (no absolute current requirement; smaller current supply just takes longer to charge), a vacuum chamber with only a rough pump (typical operation is around 1Torr), and an electrode assembly. Neutron detection can be with a bubble detector or neutron activation. This approach would warrant further notice by the amateur community, especially those who would like to pursue the p-B11 holy grail (although proving accomplishment of p-B11 fusion remains a significant technical challenge).

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Richard Hull
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Re: Plasma focus/Z pinch as an amateur fusion approach

Post by Richard Hull » Fri Mar 31, 2017 11:03 pm

Thanks Dan for the update and bringing plasma focus discussions back to fusor. net. We had a couple of boosters long ago but they were just boosters, not doers. The effort always sounded interesting, but no one picked up the mantle and took to the doing. Maybe someone will take that tack in the future.

As you note, only activation and bubble detectors need apply in this type of fusion. My guess would be the bubble detector would be the way to go and not activation at the amateur level.

No real possibility of fusion energy here, of course, yet like this forums says, another form of fusion.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Dennis P Brown
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Re: Plasma focus/Z pinch as an amateur fusion approach

Post by Dennis P Brown » Fri Apr 07, 2017 4:29 pm

I considered this route some years ago and even picked up a 50 kV, 0.1 mFd capacitor (rather large, oil filled affair to say the least.) I, of course, have bottled D2, two excellent high vacuums (a turbo and DP) and three very high voltage supply systems (a pulsed 65 kV voltage multiplier system of my own design, a moderate current Glassman: 10 ma 40 kV supply; and my fusor's very high current 30 kV supply (on loan).)

However, as I learned the hard way, neutron detection is a big issue.

After finally putting together a working BF3 system and getting neutrons (yeah!) issues quickly over took my efforts; sadly, an over voltage damaged the system so, once again, I am struggling to put a working system together. The issue of neutron detection had side tracked me for years prior to my recent success so I am extremely unhappy about the new events... . As such, I am debating whether to continue that research idea relative to plasma self focus.

After reading this post, I am not sure the approach is worth the effort if a std detector isn't gonna cut it! That is not something I had considered. I was in the process of building a scintillation detector (have the neutron sensitive plastic, HV photo-detector tube, special power supply and now just need to assemble all that and hook it up to a counter. ) I was planning to check the new detector with my current fusor. But if that class of detector won't work with a focus system I have to abandon that project for certain. I will not use activation (don't trust it) and am not buying a bubble detector now after all I've invested in regular detectors ... .

Dan Knapp
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Re: Plasma focus/Z pinch as an amateur fusion approach

Post by Dan Knapp » Fri May 05, 2017 11:44 am

The presentations from the Santiago meeting are now posted at:
https://nucleus.iaea.org/sites/fusionpo ... ation.aspx

Dan Knapp
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Re: Plasma focus/Z pinch as an amateur fusion approach

Post by Dan Knapp » Sun Aug 27, 2017 2:55 pm

The Santiago group just published a paper on what might be the smallest plasma focus fusion device: Evidence of nuclear fusion neutrons in an extremely small plasma focus device operating at 0.1 joules, Physics of Plasmas 24:082703, 2017. This paper can be downloaded free at http://aip.scitation.org/doi/pdf/10.1063/1.4989845. The reported device would be well within the scope of what a hobbyist could build, but detecting the neutrons could be challenging. It might be possible with a bubble detector by firing multiple shots.

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Richard Hull
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Re: Plasma focus/Z pinch as an amateur fusion approach

Post by Richard Hull » Sun Aug 27, 2017 5:26 pm

Bubble detectors are the only way that any amateur of our ilk can effecively determine if fusion is taking place where any form of putt-putt boat fusion is involved. Electronic methods either fail in the hands of the amateur or are highly suspect due to failure to understand and apply correct technique. In cases where this type of fusion is quite energetic on a per pulse basis and the duty cycle is extreme, activation techniques might be applied. This however would require very large and freqent pulsed energies.

Many well designed putt-putt boat fusion pulsed systems can typically release hoards of fusion neutrons on a per pulse basis. However, on a time averaged basis they tend to fall far short of the net neutron capabilities of the well made fusor consuming similar net energies.

Such systems rely on stored energy in a capacitor. The more energy stored per shot, the more fusion neutrons can be produced. Unfortunately, the recharge time on the capacitor limits the duty cycle severely, thus, the time averaged fusion is usually quite dismal. In fusion systems of extreme energy delivery per pulse, not only is the rep rate, (duty cycle), severely limited, but the mechanical or physical nature of the device is typically savaged in the extreme, limiting the operational, long term delivery of fusion energy. (not a suitable long term energy delivbery system)

Such sytems are more akin to trying to capture lighting strokes to power a community. The only difference is the lightning is delivered at a user controlled regular time frame, but at a vastly reduced energy content. The loses, as in all fusion schemes, make any hope of useful energy extracted from the process a lost cause.

A 0.1 joule per pulse system can easily attain rep rates on the order of thousands of pulses per second using a hydrogen thyratron switch or even a system that uses the fusion chamber device itself as a relaxation oscillator component. Again, the time ordered average energy versus the net fusion delivery is in question.

I would challenge a competent, (key word here "competent"), amateur among this group to actually do this; preferably one who has already done fusion in a fusor and can compare results. This assumes such a person is actually interested in doing this pulsed work in the first place and has the gear and background to take a run at this.

Of course all of the above has been noted over the 19 odd years this site has been in operation, but not one person has done more that yapped about how great this pulsed fusion might be. As always, when it comes to gathering, creating and doing, demurring is usually the ticket that gets punched.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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