Columbus-I Pinch Tube Build

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Mark Rowley
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Columbus-I Pinch Tube Build

Post by Mark Rowley » Thu Apr 04, 2019 11:33 pm

Hello all,
It’s been a few years since my last post but retirement finally arrived last summer so now it’s time to resume mothballed projects. Immediate plans are to begin working on a new Fusor and continuing with the Columbus I pinch device (thanks to Robert Tubbs for the suggestion). Being that I had most of the parts on hand, I decided to move forward with the pinch tube first. The tube is based off of an early Project Sherwood device from around 1952 (shown below). It’s nothing more than a simple gas discharge tube with a copper return conductor. Capacitance used during the original project varied but luckily centered along the value of my pulse capacitor (14uf at 30-40kV). Deuterium backfill pressures during the pinch are generally in the 200-300 mTorr range.

The deuterium will be supplied by a PEM cell system similar to the arrangements built by others here on the forum. All the parts have been bought so it’s just a matter of assembly now.

As discussed before, neutron detection will be a tough nut to crack. I’m going to start off with silver/indium activation and a pancake version of the 1B85/indium detector. I have a large compliment of scintillation detectors so I may try using a Ludlum 44-3 with indium or silver foil over the face. But ultimately it all boils down to the cyclic rate of the “putt putt” engine.

Shown are a couple pics of what I’ve assembled so far. Nothing is permanent as I’m still shifting things around and re-designing. As of now it’s incorporating a Pyrex tube while I get everything fine tuned. I have several fused quartz tubes (2”x17”) I’ll be swapping in a bit later.
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Richard Hull
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Re: Columbus-I Pinch Tube Build

Post by Richard Hull » Fri Apr 05, 2019 5:08 am

Excellent post and device. I am glad you are looking at activation as proof of fusion since no electronic detector tube would be suitable proof in what is sure to be EMP pulses from hell. Only a decent cyclic blast of neutrons activating material that is radioactive well after shutdown would be acceptable proof of D-D fusion in this type of putt-putt system.

Best of luck with this interesting poke at doing 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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Re: Columbus-I Pinch Tube Build

Post by Robert Dwyer » Sat Apr 06, 2019 12:55 am

This looks like a really interesting project. I noticed there isn't a current diagnostic mentioned or in the drawing. One way to look at and better diagnose the dynamics of the pinch is to use a rogowski coil to measure your current waveforms. The changes in current may help you better speculate what instabilities are dominating the pinch, and help you better see how to optimize your pinch.

The BTI bubble dosimeters work great for pulsed environments, and may be easier to use than foil activation (at first). At fluxes greater than 1e5 n/shot, I doubt you would even need to rep-rate the device if you get the really sensitive dosimeters. They may even work at lower pulses, but I can't back that up. Just my two-cents.

Good luck with his project! It will be interesting to see an amatuer pulsed-power effort!
If we throw more money at it, it will have to work... right?

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Mark Rowley
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Re: Columbus-I Pinch Tube Build

Post by Mark Rowley » Sat Apr 06, 2019 6:58 pm

Thanks Richard. If a group purchase of bubble detectors happens anytime soon, count me in.

Robert, a Rogowski coil is in the works. A spacing issue between the bottom electrode and the bottom of the return conductor makes coil placement tricky. I may have to wait till I can install the longer quartz tube. The thought of a arc-over hitting the coil seems catastrophic.

Shown are a couple photos of the system loosely pieced together for fit testing. The spark-gap, inductor, crowbar, damping resistor, etc have yet to be installed.
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Patrick Lindecker
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Re: Columbus-I Pinch Tube Build

Post by Patrick Lindecker » Sun Apr 07, 2019 9:38 am

Hello Mark,

Have you a WEB link about a description of this pinch tube device, at least to understand the posts.

Thanks
Patrick

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Re: Columbus-I Pinch Tube Build

Post by Mark Rowley » Sun Apr 07, 2019 9:04 pm

Hi Patrick,
I have the PDF and would be willing to directly email it to you. I cant locate a non-pay link to the document and the pdf file size exceeds the limits of the forum.

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Re: Columbus-I Pinch Tube Build

Post by Patrick Lindecker » Sun Apr 07, 2019 10:01 pm

Mark,

>I cant locate a non-pay link to the document and the pdf file size exceeds the limits of the forum.
Anyway thanks. It is not that important. If, possibly, you have some abstract (of limited size), here is my email: f6cte at free.fr

Patrick

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Re: Columbus-I Pinch Tube Build

Post by Rex Allers » Sun Apr 07, 2019 10:23 pm

Mark,

Using your reference to Project Sherwood in the first post of this thread, I searched for that and quickly found this page:
https://archive.org/details/bishop_projectsherwood

Title: Project Sherwood: The U.S. Program in Controlled Fusion
by Bishop, Amasa S.
1958

In a right-hand column there is a list of links to various forms of the document.
I clicked PDF and was surprized to see it start to download.

It was very big -- about 70 MB -- as the pdf document is all images of the original pages.

Not sure if this is the same document you described, but it is interesting stuff and allowed me to basically understand what you've been describing. (and the history from the early 50's)
Rex Allers

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Re: Columbus-I Pinch Tube Build

Post by Richard Hull » Mon Apr 08, 2019 3:50 am

I have two first edition copies of Project Sherwood and bought most online for reference over the years for under $10.00 each. It is a must read for all who would see where fusion was in its early years long before the first hundred million was spent nation-wide. That small sum supported many early research fusion projects far beyond the operational period of Project Sherwood.

Sherwood was a good early start towards today's multi-billion dollar, continuously failing, "boondoggles".

Of note, the author, Amasa Bishop, was the main opponent of the Farnsworth fusor, following its demonstration before the AEC in 1967 by Robert Hirsch and Gene Meeks. Bishop kept the AEC from picking up the meager funding for the fusor project as AT&T wanted the AEC to take it over and develop it.

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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Mark Rowley
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Re: Columbus-I Pinch Tube Build

Post by Mark Rowley » Mon Apr 08, 2019 7:32 am

This particular publication is from the Journal of Applied Physics. Written in 1958, its specific to Columbus 1 and was written by R. E. Dunway and J. A. Phillips from Los Alamos.

Here's the link to the abstract:

https://aip.scitation.org/doi/abs/10.1063/1.1723390

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