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Helium-3 Fusor Thread

Posted: Wed Mar 21, 2018 12:04 am
by Jackson Oswalt

Instead of making several scattered posts on the subject, I figured it would be better to make a single thread that I can regularly update with updates and results. In addition, if someone in the future wants to attempt D + He3 fusion, they will have easy access to information on the subject. As a 13 year old, my physics knowledge is very limited, so please correct me if I make a mistake.
Disclaimer: If you have not achieved D+D fusion, I wouldn't spend too much time on this post.

#1. High Energy Protons (Gamma rays)

For those who aren't aware, the D+He3 reaction is as follows:

D +He3 -> He4 (3.6 MeV) + p (14.7 MeV)

The difference between this and the D+D reaction is that no neutron is produced, meaning a neutron detector will be of use. Funny enough, the two people who have previously attempted this reaction have expected to detect neutrons. Instead of a neutron, a high energy proton, or gamma ray, will be produced. At 14.7 MeV, these are far more dangerous than the neutrons a conventional Fusor would produce. Fortunately, some of this energy is kinetic energy, but that doesn't change the fact that these are very dangerous, cancer causing particles. So, here are a few questions:

1. What precautions should be taken in shielding against these protons?

2. What detector is best suited (and easily obtainable) for detecting the protons produced in the D+He3 reaction?

#2. Higher High Voltage

Along with requiring a different means of detecting fusion, the D+He3 reaction also requires higher voltage. Instead of requiring at least 30kv for the D+D reaction, about 80kv is required for the D+He3 reaction. Since I've got a smaller Fusor (5-way cross) I'm planning to use alumina tubing in order to separate the grid from the SS walls of the chamber. I only have one question on this topic:

Is using alumina tubing in order to boost the voltage capacity of my fusor needed?

#3. Gas Delivery System

Since two gases are used in the reaction, the system required to deliver the gas to the chamber is more complex. Without the right mix of Deuterium and Helium-3, the reaction will most likely not occur or at the very least not be as efficient. So, the easiest way to control the gas flow is with two Mass Flow Controllers. New, MFC's can be extraordinarily expensive ($1000+), but thanks to eBay, I managed to pick up two 10sccm MFC's for $160. The tricky part is that these MFC's are for N2, not Deuterium or Helium-3. So, a conversion factor must be used. If you'd like to see more on this topic, visit the second page of this post: viewtopic.php?f=46&t=12169&start=10. Here are some questions:

1. How exactly is this conversion factor used? Is it a proportion that, for example, would make 10sccm of nitrogen however many sccm of helium-3 or deuterium?

2. Is a regulator still required or does a MFC replace that as well? (I have no experience with MFC's at this point)

#4. Acquiring Helium-3

In case you're not aware, Helium-3 is exorbitantly expensive. Just to give you an idea, 10L of deuterium from Signa-Aldrich is around $200. For 10L of Helium-3, also from Sigma-Alrich, you will be paying $30,000. This was a punch in a gut when I received the quote. So, I've had to take it down to 1Liter, which, as you may expect, is $3,000. Spending three grand is obviously not an option at this point and I'm having a hard time convincing my school to donate $3,000 to my cause. If anyone has a small amount of Helium-3 they'd be willing to sell for a lesser price please PM me. However, I doubt anyone does. Here is my question:

What is the smallest amount of Helium-3 that would still be enough to last quite a while? 1L? 1/2L? 1/4L?

That's all for now. I'll post a reply to this thread as soon as I've got any updates on my D+He3 fusion endeavor.


Re: Helium-3 Fusor Thread

Posted: Wed Mar 21, 2018 3:42 am
by Ben_Minnix
I have not achieved fusion yet, though I have read into great detail on it. Wikipedia says that if you bombard conventional Li6 with neutrons, He3 is produced. Perhaps you could find a way to mount a few small pieces of Li6 in your fusor in a place that they won't melt. Lithium has a very low melting point in atmospheric pressure not sure what it is in deep vacuum. That way, the fusor will produce a very small amount of helium 3 in situ. Keep in mind that I am new to this kind of stuff so there is likely a few things that I am overlooking.

Re: Helium-3 Fusor Thread

Posted: Wed Mar 21, 2018 4:05 am
by Richard Hull
Jason here is the hard part. I fear you nor anyone else here will even do detectable 3He-d fusion.

80Kv is a start on this fusion as it peaks at over 200kv applied. I do realize this is the potential where the D-D and D-3He cross sections are equal.
The 3He gas is out of the reach of any pocket book and will remain so for the foreseeable future.
I do not believe 14mev protons will exit the shell of a fusor device as these are charged particles and will indeed wind up as mostly bremsstrahlung x-and gamma rays exiting the shell. I do not think you will realize the super potent gammas you want, but a broad spectrum of same. You will certainly not get the protons external to the fusor. However, a very thin beryllium window at one arm of the cross might allow a tiny fraction of what protons are produced to exit.

Over all, this is a big looser in amateur hands. While not hyper-hopeless as is P-B11 fusion, it is just merely hopeless.

The shielding you will need will be for the 80+KEV x-radiation from the power supply and, if successful, super heavy shielding for the super hot gamma. You will need no shielding for the protons as they will not leave the fusor, but create a hail of nasty bremsstrahlung as they try to claw their way through the chamber shell.

Finally, the idea that neutrons in a common fusor bombarding Li6 will make enough 3He to enter into a D-3He reaction in the chamber is absolute fantasy as we have run the math on this some years ago. Some here posited that the tritium ash produced in a D-D fusor would make enough T to make the much more intense T-D reaction start. The math said It would not impact the rate one iota. You gotta' run the math.

Richard Hull

Re: Helium-3 Fusor Thread

Posted: Wed Mar 21, 2018 12:10 pm
by Jackson Oswalt
Well, I'm up for the challenge. Even if I don't achieve the D+He3 reaction, I'll still have gained invaluable knowledge and experience with things like Mass flow controllers and proton detectors.

Re: Helium-3 Fusor Thread

Posted: Wed Mar 21, 2018 3:21 pm
by Richard Hull
The best proton detector might be a gamma spec placed outside, but near the chamber. If you get a large gamma signature over your applied voltage, you can be sure it is protons burning themselves out in the shell. However, you need to watch out for neutrons as there would be a whole lot of D-D fusion taking place as well. Any gammas or odd neutrons in the scintillator due to D-D would have to be factored out. Tricky, but doable with a good BGO type scintillation xtal.

Richard Hull

Re: Helium-3 Fusor Thread

Posted: Thu Mar 22, 2018 3:31 am
by Robert Dwyer

This sounds like a fun project. The acquisition of He3 would seem to be the hardest, along with obtaining a kilowatt-level power supply to run your fusor and 80kv or higher. You may be able to get lucky and find a university or old radiology lab that may have spare power supplies used in old x-ray machines or accelerators.

As Richard pointed out, at these voltages x-rays become a real issue. Lead bricks, of course, are an easy solution, and so are concrete blocks. Space for such a setup is also needed, and so is capital (unless of course the university or radiology lab also has spare shielding they are willing to let you borrow). Also make sure you have a good ion chamber handy so you can get accurate ratings of your dose, and are able to find any leaks in your shielding if you construct such a device capable of these voltages.

Another issue that must be mentioned, if you are serious about constructing the device and have the necessary equipment to begin experimenting and testing your device, is legality. Assuming you aren't running the bare minimum and are running over 100kv, there is a real health hazard from a radiation safety standpoint. This might be enough to raise an eyebrow from the local governments or (if you aren't in an agreement state) the NRC. Normally fusor builders don't run above 60kv (which can be blocked by lead sheets with ease) and the neutron yields are easily shielded with distance. The radiation yields are small enough that most regulatory bodies do not care about standard fusors. An He3 device, even when not fusing, may produce enough x-rays for someone to want it classified as an "x-ray machine" and you may have to deal with all the humbug that goes with that.

It would be a fun project, and learning experience, to construct such a device. Doing so amateurely though, would be a long and frustrating process that may not yield the results you expect, if any at all.

It is more practical that such a device be built at as a project, or alongside with, a university or similar institution, as they have the space, funding, and technical know-how to make such projects happen.

I believe a while back I read a paper on D+He3 fusion at The University of Wisconsin-Madison. I will see if I can the paper or other article on the subject and link it. It may contain some useful contacts for you to inquire into.

Re: Helium-3 Fusor Thread

Posted: Thu Mar 22, 2018 7:37 pm
by ian_krase
I wonder goes D-He3 Beam On Target machine would work. He3 in the target, and swamped in excessive D, one might get away with a very small amount of adsorbed He3.

Still a very difficult undertaking.

Re: Helium-3 Fusor Thread

Posted: Thu Mar 22, 2018 8:55 pm
by Michael Bretti
This link was posted in the forums quite a number of years ago, but is relevant to this discussion. A presentation from the University of Wisconson-Madison on fusion with D-He3 in a fusor system, looking at yields from embedded ions in the grid:

I think D-He3 would certainly be viable with a beam on target system as well, given proper target loading and power input parameters. It also appears from the above PDF that they were able to verify the D-He3 reaction by activation of Mo-94 to detect the signatures of Tc-94m with an NaI scintillation detector. Of course at full tilt the system was running at 3.3KW of input power (110kv, 30mA), which presents a real challenge to any amatuer efforts. Not to mention the plethora of safety issues of shielding as described by others above.

Re: Helium-3 Fusor Thread

Posted: Fri Mar 23, 2018 12:19 am
by MatthewL
On your question regarding the use of alumina tubing to increase the voltage capacity of the fusor, are you referring to an HV feedthrough, or do you mean to use the tubing as a lining for the chamber walls (with a gap for gas flow)? If you mean the latter method, do you have plans for the feedthrough? I haven't seen any feedthroughs rated for 200kv, only 70kv, and they are still very expensive. You would probably have to make one.
Also, I was wondering if an He3 detector tube would work as a less expensive source for the gas. As far as I know it is pure He3, and the ones I have seen for sale are around 4 atmospheres. Am I correct the gas is pure, or is it only a small amount of He3 mixed with another gas? It would, of course, be tough to ruin a good tube, so it would have to be done when the whole system has been built.
Good luck in your endeavors.


Re: Helium-3 Fusor Thread

Posted: Fri Mar 23, 2018 12:53 am
by Jackson Oswalt
I plan to line the chamber walls with alumina tubing. My feed through already has extra alumina tubing on it since it's only rated for 25kv. Considering I run it at voltages up to 50kv, it can handle much higher voltage than what it's rated for. I'm sure manufacturers have to drastically decrease the voltage they say it can handle in order to avoid the danger of an underperforming feed through. As for using a He3 tube, I wondered that as well. However, I doubt the He-3 is pure or in large amounts considering the prices the tubes run for.