Columbus-I Pinch Tube Build

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Mark Rowley
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Re: Columbus-I Pinch Tube Build

Post by Mark Rowley »

It’s been awhile since I updated my progress so here’s the latest. Following a very generous offer from Jon Rosenstiel, I was able to upgrade the capacitance of my system from 14uF at 40kV to 56uF at 40kV. Its present configuration stands at 42uF.

In addition to the capacitance, I upgraded the electrodes with a 0.25” stainless steel cap to reduce wear and tear. After about 25 shots they seem to be holding up well except for a dark sputter buildup. The quartz tube doesn’t seem to be getting sputter buildup....yet.

Another upgrade included the addition of a quick change post for the circuit inductor. This allows for some basic adjustments to the discharge waveform. Monitoring the waveform is still a work-in-progress. I hope to have some pictures in the near future.

Results...
After discovering the ultraviolet interference with the BTI bubble detectors, I have since blocked the UV by wrapping the detectors in thin lead sheet and placing them along the tube opposite of the spark gap. They are also insulated from mechanical shock, although there really is none to speak of.

As of today I am registering on average 1 bubble per shot with the shielded detectors approximately 7cm from the plasma column. Results are consistent regardless of where the detector is placed along the tube. Deuterium pressure averages 275mTorr and voltages have been between 17kV and 22kV. Circuit inductance is ~0.14uH. Increasing inductance past 0.30uH results in a neutron yield too low to detect.

Future work will be to replace the quartz tube with one from a more reliable supplier of pure quartz. The one I’m currently using is from an eBay source who stated the origin was from China. I’m not totally confident of its purity or if it has boron content. Im also assembling a Rogowski coil for diagnostics. In the meantime I’ll experiment with the operating parameters in hopes of increasing the neutron yield.

Mark Rowley
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Richard Hull
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Re: Columbus-I Pinch Tube Build

Post by Richard Hull »

I am glad to see you are back at it and in the game. Very nice set up, indeed!

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
Jon Rosenstiel
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Re: Columbus-I Pinch Tube Build

Post by Jon Rosenstiel »

Mark,
Great to see these caps finally getting some use. Nice work.

Jon Rosenstiel
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Mark Rowley
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Re: Columbus-I Pinch Tube Build

Post by Mark Rowley »

Over the past couple weeks I swapped out the pinch tube with certified fused quartz from a reputable supplier. I also machined two new electrodes to accommodate the slightly different tube size as well as to move the D2 inlet to the bottom electrode.
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After vacuum testing the entire arrangement I was pleased to see the 1402 pull an 8 mTorr vacuum after about 10 minutes of pump time.

I conducted a total of 6 shots (two sets of 3) with no neutron detection from the UV shielded bubble detectors. The first set used a small 1” Drierite column in line with the PEM cell D2 reservoir. I ran the shots at exactly the same parameters which on average had previously yielded 1 bubble per shot. That being 20kV, 42uF, 300mTorr of D2. Since the Drierite column has proven to be somewhat inconsistent, I decided to test this exact same D2 input configuration with the Fusor. Interestingly, the Fusor could barely get the neutron detector to register over 150cpm. After removing the Drierite, my neutron detection shot up to almost 5k, which is essentially normal operation. Drierite was just not going to work this time. I’m still thinking the stuff is just too porous and filled with air to keep the D2 purity at its maximum level. As with the previous forum post about Drierite, I also dumped about 32mL D2 into the tube as an attempt to purge it of air. No obvious leaks; it just wasn’t going to work.

The second set of 3 shots used straight PEM cell deuterium from the reservoir. Still no bubs but I noticed a couple other factors which may be at play. Firstly, the stainless steel electrode caps tend to quickly load up with a quartz deposition layer. The layer is thick enough where surface conductivity is nil. This wasn’t the case when I was using aluminum. But the aluminum tended to wear out quicker so I tried stainless this time. Physically, stainless holds up well but the quartz buildup is a significant problem; especially if it gets bad after 6 shots. Fwiw, none of the original machines at Livermore or Los Alamos used stainless steel. Seemed that it was almost always aluminum. I’m also wondering if the chromium, nickel, and carbon content in the SS is somehow poisoning the pinch.

Another negative issue I noticed was with the plastic spacer / stabilizer ring I had between the quartz tube and the copper return conductor. In the below picture, it’s clear there is a plasma buildup in that region has caused a darkening of the glass. Undoubtedly this is negatively affecting the pinch and I’ll be removing it for future shots.
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This picture is the lower electrode after 6 shots. Note the brownish glass-like material deposited on the stainless steel. Also of note is the ablation strike mark near one of the stainless anchoring screws.
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The upper electrode shown here has a nice centrally located ablation mark. There’s practically no evidence of the plasma pinch column anchoring at any other place on the electrode. The main difference between this electrode and the lower is that it’s totally contained within the copper return conductor pipe. The bottom electrode extends several inches below the return conductor. The non-centrally located strike mark on the bottom conductor may be due to the plastic ring disrupting the linearity of the plasma column possibly by some sort of capacitive effect.
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After making these adjustments I may add a two loop pre-ionizer as shown in this illustration. The old Livermore team insists preionization is required before any significant neutron yield is realized. Other teams tend to disagree.
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Eventually the spark gap will be replaced with a nitrogen trigatron. Unfortunately, by the time that’s done my bubble detectors may be long expired. :/

Mark Rowley
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Richard Hull
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Re: Columbus-I Pinch Tube Build

Post by Richard Hull »

Nice continuing effort. First rate. Sorry about no neuts. You would think that there would be some at such peak pulsed powers. This would be thermal fusion, I would think, due to the density and plasma heating.

Keep up the effort. Too bad about the life span of the BTI bubble detector.

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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Mark Rowley
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Re: Columbus-I Pinch Tube Build

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Just a quick update...
The tube is being completely reconfigured to a 4” diameter system with tungsten electrodes and an RF pre-ionizer. Spark gap triggering is being addressed and refined as well.

I’ve already taken delivery on the 4” diameter fused quartz tubing and aluminum round stock for the tungsten electrodes.

My current lagging factor is the Covid19 closure of our local hamfest. I can’t bring myself to using my good ham gear for the pre-ionizer so the plan is to buy a sacrificial linear amp at the swap meet. In the meantime I’m slowly machining and piecing this together. Doubtful it’ll see its first test shot before October.

As a side note, I’m machining a version of Jon R’s and Joe Gayo’s cube Fusor. I’ll post more about that in a different thread once more progress is made.

Mark Rowley
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Richard Hull
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Re: Columbus-I Pinch Tube Build

Post by Richard Hull »

Mark you are the leader!... er..the only one deeply into this pinch fusion here. The key thing is you are sticking with the effort. That is what usually wins the day. I love reading your well done reports and wish you well in the effort. I am sure it can be done and you seem determined to make it work.

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
Richard Hester
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Re: Columbus-I Pinch Tube Build

Post by Richard Hester »

When I was working on an ArF excimer laser system at Cornell during my brief fling with grad school, I tried pressurizing my spark gap switches (trigatron) with N2 and got dirty results. Pressurized air worked much better. I suspect that pressurized Freon would be even better for purposes of voltage holdoff (we had a 1MEV electron gun that used a 3-stage Marx generator with pressurized SF6 speak gaps), but I would be somewhat leery of the Freon decomposition products.

One possible use for the 60kV, 2uF cap currently cluttering my basement might be a similar pinch system.
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Richard Hull
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Re: Columbus-I Pinch Tube Build

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With Richard Hester's resurrection post I could not help but notice that this work took place just prior to the covid nightmare and continued into it in 2020. I re-read all of the posts in this long thread. Did covid affect the work? Maybe Mark can answer that or did it just sort of drop off his radar.
I have dropped a lot of projects due to lack of interest or having them go slower than I had hoped.

I have found that during retirement and as I have aged what I thought would be a time of great activity and freedom, other stuff often takes priority.

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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Mark Rowley
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Re: Columbus-I Pinch Tube Build

Post by Mark Rowley »

Hi all,
It’s been awhile since posting but here’s a few updates…

Covid, luckily, played no part with this project going dormant. I actually had three projects going simultaneously at the time, the Fusor, the Columbus pincher, and a BOT.

The pincher was eating up electrodes right and left and to get consistent neutrons, it would’ve been required to make a thyratron based trigger capable of creating a very specific wave form. It’s a important factor that’s highlighted in both the archival 1950’s Livermore and Soviet publications. Regular spark gaps or triggered gaps provide very intermittent and low neutron yields. A pulse formatter isn’t a super difficult endeavor but it would’ve been costly. Instead, I mothballed it and put full effort and funds into a beam on target system that was based off Carl Willis’s arrangement from about a decade ago. Good progress was made with that including a special high temp furnace for making deuterated targets. Still a lot of work to do and that’s where I’ll be resuming when time permits.

Tbh, not sure if I'll resume the pincher as it'll require another costly purchase of BTI bubble detectors. Due to the intense electrical interference, there's just no other way of reliably proving neutron production. Activation is only viable if a pinch is making enough neuts to do so. So its of little to no help when tuning and dealing with low initial yields.

As of now, I’m working on a long term classic car restoration project which started in early 2022. Since then, everything has been carefully set aside until it’s complete. Richard, if memory serves, you restored a few Thunderbirds a couple decades back?

The car project has about another year or two before I can focus again on making neuts. Until then, I’m in active reader mode and check in here 2-3 times a week.

Mark Rowley
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Re: Columbus-I Pinch Tube Build

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I had but one T-bird project, a 1966 convertible with a 427 and 3 dueces. My 70-80's were loaded with 23 different Lincoln Continental restoration efforts. These consisted of 2 1960s and all the rest 1963-1965 suicide door jobs. All mounted the 430 cu. in. high torque Ford dump truck engine used in all Lincolns from 1958 to 1968. I did restore a 1969 Mark III Continental which I loved. (460, 375 hp right out of the factory.) I had almost as many lady friends who loved to cruise on Friday and Saturday nights to the many old car gatherings at barbeque joints and burger stands in my beautiful land yachts.

Driving one of these monsters was a joy to experience. All of my continentals were used and the most I ever paid for any one was $1200. Most were picked up for well under $1000. They were easy to work on and repair. With all that power, on the highway, they would pass anything on the road except a gas station. Typical of these 2.5 ton monsters with the 430 and 4 thirty barrels, city mileage averaged 8-10 mpg and on the road between 15-17mpg. All owners manuals said the gas should be 101 octane ore better!

Alas, when gas went unleaded to 90 octane and $1.00/gal. in the early 90's. I turned to Japanese "rice rockets". Oh how the mighty hath fallen.
Still, those little cars are well built and get fabulous gas mileage. I hope to never own or drive an electric car in the years I have left. I currently have 6 cars, all bought used and my best on road mileage is my 1987 Toyota Celica with 196,000 miles on the odometer at 41-45mpg! The newest car I ever owned was 12 years old at time of purchase.

As in my bio here of fusor.net, I was never exclusively a Continental drivin' freak. I had many, many hobbies and scientific endeavors. Having a good job and refusing every advancement made work a joy and supplied enough cash and spare time after work to really spread my wings. Letting go of the car fetish in 1990 really opened up vast amounts of time and cash.

Good luck on your restoration. You will have a blast in drive experience, I am sure. I do miss my Lincolns.

Fusion proved to be as big a cash outlay in time and money as the cars were. I will admit I spent a lot of money in the early fusion days (1997-2010) rather uselessly in upgrading to one thing after another. I figure I am about $30,000 into fusion since 1997. But hey, your can't take it with you! No one gets out of this life alive.

Richard Hull
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Tina, one of my lady friends, by the Mark III circa 1991.  This car, a two door, was a light-weight at 4,300 lbs., was fast and nimble.  Got my only two speeding tickets in this baby.  She wanted to fly.
Tina, one of my lady friends, by the Mark III circa 1991. This car, a two door, was a light-weight at 4,300 lbs., was fast and nimble. Got my only two speeding tickets in this baby. She wanted to fly.
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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Liam David
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Re: Columbus-I Pinch Tube Build

Post by Liam David »

Glad to hear you're doing well Mark, and best of luck on the car. The guy who so graciously lets me access his lathe and mill works on old cars... a 60's Porsche is his current project, if my non-car-guy brain serves me right.

I'd be interested in seeing your deuterating furnace build, if you've got time to share. Something like that is in my not-too-distant future.
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Re: Columbus-I Pinch Tube Build

Post by Richard Hester »

That Lincoln is quire the boat...
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