$10,000 Budget

[Kuba Anglin]

Hello,

To put it simply, I have $10,000 to construct a neutron producing fusion reactor. While this will be my first fusor, I have a couple years of previous experience with high voltage apparatuses and other related devices. I am well aware of the safety precautions required around high voltage and radioactive devices. I have read all the FAQs relating to the development and operation of a fusion reactor. The purpose of the fusor will be to use it as a platform for experimentation. I am thinking of buying a custom-made, 12" diameter, steel, spherical vacuum chamber for around $5,000-$6,000 from Lesker. I have made several designs with Lesker's chamber builder, but have not decided on anything yet. The chamber will need 12 ports. 6 of the ports will be surrounding the chamber in a symmetrical cubic formation and will be used for experimentation. 2 will be used for view-ports/neutron detection, 1 for the vacuum pump system, 1 for a pressure gauge, 1 for the deuterium inlet, and the last for the HV feed. I am planning on buying most of the vacuum components from Lesker. The mechanical pump will be from eBay, but I am still deciding on whether to get a diffusion pump or a turbomolecular pump to achieve the ultimate vacuum. I would like to get a Glassman or Spellman -40 to -50KV, 20 to 30mA PSU, but have not seen any on eBay for the past several months (I check on a daily basis). I will be buying the deuterium gas from Sigma-Aldrich. The grid will be made of tungsten wire, welded with my spot welder.

The reason I am posting here is because I would like advice. As stated in one of the FAQs, $10,000 should be able to cover the expenses of a research-grade fusion reactor. I am apprehensive about purchasing any parts yet, as I would hate to waste any money or possibly bottleneck the fusor. I am asking any experienced or knowledgeable fusioneers: How would you build a $10,000 fusion reactor? Any responses would be greatly appreciated. I realize that I may be breaking a couple of forum rules by posting this, so if there is a problem, please notify me.

Thank you,
Kuba Anglin

[Scott Moroch]

Kuba,

You are one lucky guy if you have 10,000 dollars for a fusor!! Although I have not yet finished my neutron producing fusor, I do have experience with regards to the finances. Personally, if I had 10,000 dollars I would not spend 5-6k on a chamber. The chamber is a very important part, and it will certainly be high end if it is made by lesker, however, keep in mind that you have many other components to buy. I know other members of the forum have been able to make a spherical chamber for much less than 5,000. Also, lesker tends to be on the expensive side when it comes to vacuum components. You may be able to find the same vacuum components for cheaper elsewhere. Also, if I had 10,000 I would not plan my fusor to use every last dime. From experience I have learned that you will buy equipment that may not work perfectly, or a part that is close to what you need but not exactly what you need. I would always save a little extra money in case this happens.

Keep in mind that the other systems will add up very quickly and you want to make sure you have the money to cover the expenses. Personally, if I had 10,000 I would want to make sure my fusor at all of the bells and whistles and probably would not spend 6k on just one component.

Hope this helps!
Scott Moroch

[Kuba Anglin]

Unfortunately, I do not think I have another option regarding the chamber as I will need 12 ports. It may cost more for me to manufacture the chamber myself. Using hemispheres will not be an option as I need ports on the "equator" of the chamber. Here is a rendered model I made of the proposed chamber. The budget can be exceeded (within reason) if necessary.

[Rich Feldman]

I wonder if the fabrication incurs extra trouble and expense when no ports are big enough to admit a welder's hand?
I bet the pros use automatic tube welding machines when they can.

chanber1.jpg (30.04 KiB) Viewed 8162 times

Neither of my own hands can fit through a 3 inch round hole.
Well maybe in a life-or-death emergency, and with plenty of lube.

[Richard Hull]

Scott and Rich have it right of course. You will come to regret not using hemispheres. ....And to blowing 5K plus on a chamber. I purchased 100% of my current chamber parts for under $300... but did 100% of the work on it myself. Based on your wanting a top grade "research" fusor I would say that $20,000 might not be enough.

If I had 10 kilobucks starting out, I would buy a brand new Welch forepump of 5CFM or greater capacity and the best used diff pump around. Then, I would buy a neutron detector, 3He only! Next, a good supply of at least 50kv 30ma capability and only then worry about the fusor chamber, itself, making do with what I had left over.

Richard Hull

[John Futter]

Kuba
Not understanding how vacuum chambers are welded together is evident in your renders.
To stop virtual leaks all joints should be welded on the inside to eliminate the virtual leak problem. Outside welds only prove it was welded together by someone you should not use for serious vacuum work.
Now its time to work out how one would weld all the ports in your render with a perfect view of the weld during welding.
Two halves makes it easy a full sphere makes it impossible.

[Kuba Anglin]

Thanks for all the information. I really appreciate it. The renders are not of great quality as I made them in about fifteen minutes with the sole purpose of showing where the ports would be located. I understand that the welds must be on the interior. I guess my plan for the 6 symmetrical cube-formation experiment ports will have to be modified if I build the chamber from hemispheres. I will begin planning a double hemisphere type chamber and attempt to give it all 12 ports with correct configurations. I have never seen any 12" diameter hemisphere-constructed vacuum chambers on this forum. Maybe because they are too big? Is there a downside to making the chamber this big other than increased pump-down time?

On a random note, I recently finished my second Tesla coil with my twin brother. I still need to tune it slightly. Video Here: https://www.youtube.com/watch?v=718hnoMDuEQ

[Nick Peskosky]

Kuba,

It would probably cut your expenses to 'double' up on some of your CF ports. You can pump, admit gas, and measure vacuum all from the same flange (due to molecular flow) with the use of a 4-way CF cross as I did with my reactor. Also, you mention utilizing a port for neutron detection but there really is no need for this as the neutrons will freely permeate through the SS with only minor attenuation/scattering. You'll want to minimize your viewport size (2.75" CFF is an ideal size) especially above -30kV because the shielding required to block the x-rays streaming through the glass (and SS) will be quite substantial. If you want a separate port for gas admittance you need not use CF as a male VCR nipple will be more than adequate. Amplifying what others have said, I'd recommend spending the money on a quality neutron metrology setup (He-3 highly recommended) and finding a suitably sized HVPS. Vacuum fabrication costs, especially on spherical chambers, scales almost exponentially with increased diameter because of material costs. You'll want to keep in mind that the larger bolts, Cu gaskets, and blind flanges also add substantial assembly cost for anything usually larger than 6-8" CFF.

[Tom McCarthy]

Hi Kuba,

While $10,000 is a huge amount for a Fusor, you're still going to need to send plenty of nicely-worded emails and do a good bit of scrounging to get all your equipment. I raised €10,000 myself for my Fusor (not finished yet) and while I have about 3k left, I wouldn't have been able to afford all my equipment without all the discounts and free parts given to me. I got a professionally made chamber for about €1.75k (Not paying for work time or polishing, materials only!) and that's been a fantastic investment. However, before you go spending big, do out a list of all the parts you'll need and leave about €1,000 in spares, because you're going to go over what you think you will. I have a rough budget for my Fusor done out here - http://tommccarthyprojects.com/pricing-and-good-news/ - It's only a guideline and in hindsight it wasn't all that accurate, but for me it made pricing things and sorting out how much I'd spend on things a lot easier. Most everybody else will tell you that even with the big bucks, you're going to need to spend time finding good deals and scrounging out for bits and pieces. Richard's FAQ (here: viewtopic.php?f=24&t=3247) pretty much outlines what you're dealing with now.

All the best,
Tom

[Dan Tibbets]

Just a reminder that two half spheres do not need to be arranged so that the join represents the equator with one reference port- the feed through port(?) being at a pole. The join could be at 30 degrees, 45 degrees inclination or any inclination that would accommodate the positioning of other ports. The simplest solution might be to merely move the feed through to any non polar port that might accommodate it. Other ports would have to accommodate the viewing angles you desire. Also, the grid probably does not need to be orientated exactly parallel to the feed through, especially in a spherical chamber. You may be able to bend/ tilt it to one side.

An example of a non equatorial join of two half spheres is here- the third picture/illustration:

http://iec.neep.wisc.edu/

Dan Tibbets

[Werner Engel]

Hi Kuba!

When I started planning my fusor, I also wanted to buy a perfect sphere as my first investment. Excellent equipment was also around 6000€ without electro polishing on the inside. I asked at Pfeiffer, Lesker, VACOM and several others delivering to local uni-institutes.
Soon I found out that there are a lot of other challenges which have to be solved before. It took me many weeks to decide if my parts should be made out of aluminum, steel (which steel), or to select the right pressure gauge and mass flow controller. Or the simple decision between ISO-KF and CF and metric or inch based parts.
So I started with the roughing pump, using a glass based construction for the first plasma tests. Then the turbo-pump followed. Now I’m switching to a double-cross (DN100) – which is quite cheap. The HVPS will be the next major thing which is just in production. Isolating 45 kV will be one of the next not so easy tasks.

My hint: Start with the easy parts and select them in a way, that you can reuse most of them later (as base for an ion gun or something else).
It's not about buying stuff, but about learning how to handle the componentens and the different new technologies. Example: Nobody can show you how fast you can vent your Turbo - you have to try. Doing it too fast, might cost you 4k€

Good luck!
Werner

Attached you see one of the first tests (mixed He + air)at 50 kV but only a few µA just to see how isolation works and to get used to HV, radiation and shielding.