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FICS II Planning and construction

Posted: Sat Nov 28, 2015 3:37 am
by Steven Sesselmann
Here we go again, this is the last one I promise (fingers crossed).

Starting a new thread for my next build called FICS II. FICS stands for Fusion Induced Charge Separation, more later. FICS II is in the very early planning stages and I estimate it might take at least a year to build. As you will soon see there are some complex engineering challenges I need to be overcome, and some of the parts are not cheap, so it will happen slowly.

The oldies in this group know my fascination with hollow cathode reactors, but for the new members I summarise a brief history of my past successes and failures.

--------- History of Steven's Hollow Cathode Reactors 2005-2015 -----------

STAR-1 was my first build, it looked like a fusor but was not a standard fusor, inside the spherical chamber was a hollow cathode with diametrically opposing ceramic tubes (seen protruding from the top), the cavity between the outer shell and the inner shell was filled with dielectric oil. Although it produced a small amount of fusion in the 1 x 10^5 or there about, it soon failed due to leaks between the ceramic accelerator tubes and the nylon Swagelok fittings I used, so this design needed a rethink. At least I learned a lot about high voltage and vacuum technology with this one.
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STAR-2, also a hollow cathode reactor had a number of improvements, first it was built in a transparent oil tank with a cage replacing the anode, it solved the leak issue by replacing the ceramic tubes with glass tubes, the glass tubes were custom made to fit a standard KF25 flange and O ring. In addition to the improved accelerator tubes this version was fitted with a negative ion source (seen on top). STAR-2 was quite successful it produced neutrons in the 2.5 x 10^5 range but it was temperamental and used to spit fire like an angry dragon. I believe was caused by fast ions going to ground causing a build up of negative charge on the cathode, this charge would be released up the tube causing s sudden flash with more ionisation. This one also blew up my PSU twice, even though it had a ballast resistor and overload protection, I believe it may have been negative charge build up on the cathode which led to this. Eventual failure on this one was again a brown conductive build up inside the glass tubes which I learnt was due to sputtering.
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STAR-3, was an attempt at focusing the beam using some copper dynodes and longer glass tubes, it was a disaster and I don't recall ever measuring any neutrons from it. Anyhow it had a different geometry with a smaller anode and used less oil so it was a better design.
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STAR-4, by the time I got around to building STAR-4, I had already made a lot of the obvious mistakes, it was a more compact build and was designed to be easy to open and service. Again it was a hollow cathode with glass tubes and ion source fitted to the top. With this reactor we had some good neutron runs and we also observed a very strange phenomenon where the reactor would keep running ie. visible plasma, neutron counts and x-rays, after the HV power was switched off, not for a couple of seconds, but up to 10 minutes or more providing the negative ion source was left on. This may be the first over unity ever constructed, who knows, in any case it has been the subject of my thoughts for a long time, as I really wanted to understand what crazy stuff was going on.
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FICS-1, after pondering about the strange run on effect with STAR 4, I eventually started to understand what was going on, the deuterium ions would fuse and send the positively charged He particle to ground, thereby leaving a negative charge on the hollow cathode, this tiny amount of charge exchange was enough to maintain several tens of kV on the cathode, especially since the cathode was under oil with minimal current leakage, even a few micro coulomb can charge a tiny spherical cathode with a capacitance in the pico Farad range. So I designed a reactor to take advantage of this effect, and called it FICS. In the image below you can see the reactor running with a nice plasma inside. FICS-1 was a single ended hollow cathode reactor constructed from glass and aluminium discs. It had a hollow tungsten cathode with the deuterium supply floating at cathode potential (very important for the charge exchange process). This was a very nice build, the glass and aluminium construction method was a great success, and everything looked quite promising. I did a couple of runs, and measured plenty of neutrons, but unfortunately it soon became evident when I reached a certain voltage, it would emit a huge amount of x-rays, so I had to stop running it. I took it apart to investigate where the electrons where coming from and I discovered a brown burn mark on the steel flange at ground potential where the electrons had taken an unexpected shortcut to ground. These are the risks you take when doing stuff others haven't done before, which is why one should impose double safety measures when treading an unknown path.
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FICS-2, is my next project, I confidently think I have it all worked out (tongue in cheek), this one is going to be the first reactor to run on it's own power. It will be a double ended hollow cathode reactor constructed using the previously used glass and aluminium disc method. Aluminium has been chosen as the optimum material in both the cathode and the dynode discs both for it's price, ease of machining and low Z. Once again the gas supply will be floating at cathode potential and fed directly into the cathode. The only source of ionisation will paschen breakdown and ions traversing through the hollow cathode, and once some fusion reactions start there will be more ionisation caused by the heat. I believe I have now solved the problem of charge build up on the cathode, the electrons will have an escape to ground via an array of zener diodes when/if the cathode voltage exceeds a given threshold. Negative high voltage will not be supplied directly to the cathode but will be applied to dynode 9, so some ions will be accelerated from GND to D9 where they will be injected into the cathode cavity and cause more ionisation and the occasional fusion reaction inside the cathode, the reactions which take place inside the cathode will cause an alpha particle to either hit the inside wall and generate secondary electrons or pass through the hole and go to ground. Every alpha particle going to ground contributes to a negative charge on the cathode. Given enough alpha particles make it to ground, the reactor will self sustain.
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Problems solved in FICS-II

Laminating the discs together with Latex is a tricky and time consuming job, and does not leave much room for mistakes, but it worked in FICS-1 and I hope it works again now.

Each aluminium disc will be machined on a CNC lathe so it overlaps the adjoining discs without touching, this prevents the ions in the tube from hitting the inside of the glass disc.

Firstly the use of Aluminium with low Z reduces the energy of the x-rays, in addition to this the electrons generated inside the cathode will not be able to enter the tube, as dynode 9 will be stepped down to a lower voltage than the zener escape.

Possible new problems in FICS-II

Floating the deuterium gas and regulator
This will be a challenge because any kind of mass flow controller or regulator needs power, which will have to be supplied by a floating battery.

Remote control
For safety reasons this reactor needs to be operated remotely, this involves building a control panel which not only controls the power but also the pressure and the gas. Controlling a floating mass flow controller is going to require some kind of servo or fibre optic control, something I have no current experience with.

This is already looking like the most expensive build so far, and one can only take so much out of the household budget these days, so I hope the Gammaspectacular business will continue funding my fusion research as it has been doing, so far so good.

Intellectual Property Protection
Yes if it works someone will copy the idea and run with it, but unfortunately copying is going to happen regardless of weather you have a patent or not, the only difference is you have the right to sue, and you have to ask yourself if you want to spend your life in the lab or in a court room. I wasted tens of thousands of dollars on patent protection in the past, and it's a mugs game, the legal costs and challenges start long before a patent is granted. My hollow cathode concept has already been copied once, by a company developing a neutron source, I feel privileged and take it as a complement my design was worth copying.

More to follow...

As this project matures I will append the progress reports to this thread, and if anyone has any advise or suggestions please let me know.

Re: FICS II Planning and construction

Posted: Sat Nov 28, 2015 10:39 pm
by Richard Hull
As always, all the best in your efforts. We look forward to updates as you move along in the process.

Richard Hull

Re: FICS II Planning and construction

Posted: Thu Dec 03, 2015 5:09 am
by Steven Sesselmann
Slowly moving forward here...

After thinking some more about hollow cathode reactors in therms of GPT, it became obvious that the cathode walls are a major source of loss. Ions striking the cathode wall collide with atoms in the wall which changes their velocity. Either slowing down or speeding up depending on which side of the fence you are on. Fortunately scaling up the size of the hollow cathode works in our favour.

Volume = (4(pi)r^3)/3
Surface area = 4(pi)r^2

s/v = 3/r
s = v(3/r)

So the wall effect diminishes rapidly with increasing radius and in addition to this the mean free path increases and therefore also the probability of fusion. With this in mind I have decided to maximise the size of the reaction chamber in FICS II, increasing it to 164 mm (6.5")
FICS II Assembly
Going for simple KF25 connections for easy of experimenting, with only two connections I don't think there will be a problem with vacuum, providing I get good seal between the glass and metal along the stack. Might stick a tiny KF25 viewport in one end so the plasma can be observed.

Wondering if constructing the chamber from low Z Al will increase or decrease the wall effect, how will an ion colliding with the wall change it's velocity, so lets apply GPT...
We know the cathode as a whole stands still with respect to ground potential, this means the nuclei must be jiggling around at some velocity as a function of their potential (GPT law).
How fast are the 27-Al nuclei jiggling?

∆v = c[∆ø/Ø]

∆v = c((930.6-930)/938) = 127,843 m/s (actually only 135,537 meters per second when all the decimals considered)

Al is clearly not such a good choice, as deuterons interacting with the wall will eventually take on this temperature.
What about 56-Fe ?

∆v = c((930.6-930.6))/938 = 0 (actually 3878 meters per second when all decimals are accounted for)

Clearly a much better choice, as we don't want our deuterons to gain energy, we want them to remain still with respect to ground potential. The optimum cathode material would be 62-Ni but it's too hard to work with, so stainless steel is I guess the next best choice. Nickel plating the inside of the cathode might be an option.
Confused about GPT ? Feel free to send me a PM with your questions.


Re: FICS II Planning and construction

Posted: Wed Dec 16, 2015 9:31 am
by Steven Sesselmann
Planning to move the project forward by a few steps over Christmas, as I will have a bit of time on my hands during the break.
Thinking of building a custom rack for FICS-II and gradually build in the components as they become available.
I already have the essential components from previous experiments, such as HV PSU, Rotary pump, Turbo Pump with controller, ISO-100 flanges, Gate valve, Pirani gauges, KF25 flex ss hoses etc..
Building the rack is trivial, but enjoyable work, The challenge will be to make the fusion chamber and tube, parts need to be made on a CNC lathe from a 190 mm Aluminium billet and won't be cheap.

One of the enhancements I am planning is to have a vacuum connection at both ends of the accelerator tube, ducting in to one 100 mm tube, I hope this will equalise the pressure at the two ends of the chamber and solve the problem of paschen breakdown on one side only.
Fics Rack

Re: FICS II Planning and construction

Posted: Wed Dec 16, 2015 2:57 pm
by Dennis P Brown
I am a bit concerned in your design by having a metal tube so close to the accelerator Einzel lens assemblies; the electric field will be drawn down/disrupted by the conduction of this very large metal cylinder so close to your field lens. Not convinced that your concern about breakdown within the accelerator column is worth the effort of two vacuum ports - at a few microns pressure within the chamber, it is highly unlikely that large volume will support even a measurable pressure gradient across your accelerator.

Re: FICS II Planning and construction

Posted: Wed Dec 16, 2015 10:42 pm
by Steven Sesselmann

Unlike the magnetic field, the electrostatic field won't affect ions through glass and metal. Ions are only electrostatically attracted to surfaces they can physically reach, nature is not silly it doesn't waste energy on a wild goose chase.

If I attach the turbo directly to one end of the double ended accelerator and flow the gas into the cathode, there would definitely be a substantial pressure differential between one end and the other, this would cause a plasma to burn on one side only, I witnessed this with the old STAR reactors.

The vacuum duct connecting the two ends doesn't need to be 100 mm diameter, it only needs to be about twice the diameter of the KF25 tubes leading into the reactor, but I thought an ISO100 flange would fit straight onto my gate valve. Still early days and a lot can change as I start building this monster.

Re: FICS II Planning and construction

Posted: Fri Jan 01, 2016 8:39 am
by Steven Sesselmann
Slowly moving forward here, my Christmas break was an opportunity to practice my stick welding skills, so I bought myself a small inverter welder and armed myself with some steel tube and figured it would be an easy job. Unfortunately it's about 30 years since I last did stick welding and my first few welds looked like bird droppings, but as the job progressed I seemed to get more confident with the stick and the job progressed, although my welds did need some grinding.

The rack will house the vacuum system as well as the HV power supply at the bottom, and the top section will be a Faraday cage, so I will fit mesh over all the openings, with the front panels being on hinges so they can be opened, they will also have interlock switches to deactivate the HV if a door is opened.

Casters on each leg makes it easy to work on the project.
frame construct.jpg
Finished Frame
More to follow, and happy new year to all.

Re: FICS II Planning and construction

Posted: Sat Jan 02, 2016 5:11 pm
by Dennis P Brown
Good that you are both starting and now have an interesting project - I really enjoy watching such projects grow. Starting from scratch will really be a good project for all of us to watch as you address construction issues and design systems. I guess the hardest part is when a component becomes difficult that at first appeared to be easy ...had a few of those but worse is when something already working then becomes the problem - had a few of those, too (lol.) Look forward to your progress and posts. Best of luck and regardless of your final results, the quest will be a lot of fun to watch!

Re: FICS II Planning and construction

Posted: Wed Jan 13, 2016 10:03 pm
by Steven Sesselmann
FICS- - 1 (1).jpg
FICS Fusion Cage Stage
FICS- - 3 (1).jpg
FICS Fusion High Voltage Interlock
FICS- - 2 (1).jpg
FICS Fusion Fore Pump and PSU
FICS- - 4 (1).jpg
FICS Fusion PTFE HV stand offs
Making some progress on the project here, and it's starting to look like something...

The Faraday cage has now been fitted into the frame, with all panels fixed except for the two doors at the front, these are hinged and close with magnetic latches. I have fitted micro switches on the doors which loop through the Glassman HV interlock system.

The dual stage rotary fore pump and my 16 liter vacuum tank (some might think this is superfluous) has been fitted, and I am in the process of aligning the Varian V200 turbo pump. I finally managed to get a manual for the Varian V200 online and discovered to my surprise the two bolt holes I thought were for attaching the pump were the water cooling inlet and outlets, so now I need to rig up a cooling system as well. Varian recommend that the pump not run for more than 10 minutes without cooling. This would explain the issues I had last time, where the pump would randomly stop after 20-30 minutes running.

In the last picture you can see that I have started machining the PTFE high voltage stand offs which will hold a floating table, on which the gas handling system will live. The red line on the aluminium plate is a rough outline of where the table will be.

I am back at work now so progress might be a little slower going forward..


Re: FICS II Planning and construction

Posted: Sat Jan 16, 2016 7:41 am
by Steven Sesselmann
FICS- - 1 (2).jpg
Varian V200 turbo pump fitted
Aligned the turbo pump and welded a bracket to attach it to the frame. I made up some stainless steel straps that clamp the heavy gate valve to the frame. Seems like a reasonable solution as it now feels quite solid and vibration free. Parts for the ISO100 flange with 50 mm duct and KF25 fittings which will extend up into the cage arrived last week, and is now with the welder for assembly.

I can hardly wait to get it to the vacuum stage, it's always nice when you get the chamber to a stage where you can pull a vacuum and leave it under vacuum, because then after a few days of pumping you get a feel for the leak rate.