Helium-3 Fusor Thread

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Jackson Oswalt
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Helium-3 Fusor Thread

Post by Jackson Oswalt »

Hello!

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.

Thanks!
-JO
Last edited by Jackson Oswalt on Wed Mar 21, 2018 8:11 am, edited 1 time in total.
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Re: Helium-3 Fusor Thread

Post 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.
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Re: Helium-3 Fusor Thread

Post 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.

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Re: Helium-3 Fusor Thread

Post 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.
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Re: Helium-3 Fusor Thread

Post 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
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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Re: Helium-3 Fusor Thread

Post by Robert Dwyer »

Jackson,

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.
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Re: Helium-3 Fusor Thread

Post 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.
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Re: Helium-3 Fusor Thread

Post 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.
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Re: Helium-3 Fusor Thread

Post 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.

-Matthew
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Re: Helium-3 Fusor Thread

Post 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.

Thanks!
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Re: Helium-3 Fusor Thread

Post by Michael Bretti »

Jackson,

Some very important things to note about these extra high voltages. Once you start getting up into the +100KV range, things get much, much more challenging to deal with. Working with a fusor at 50kv or lower is very different from 100kv, and don't assume that once you have worked with one level the other level will be the same. At these voltages, electricity can act quite bizarrely and counter-intuitively. Surface tracking for one becomes a major issue. High voltage at these levels will no longer necessarily take the shortest path between two points, and can track very long distances along a surface. Another major issue is corona losses. At these voltages, you will have significant corona discharge spraying from any metal surface that is not smooth or has a very large, even diameter. Any sharp edges drastically increases field enhancement effects, making these voltages even more difficult to deal with. Also, depending on the amount of corona losses you have, your load will suffer from fluctuations and instabilities. Large corona losses will also load down your power supply.

The injector of our facility's electron linac is biased anywhere from -125kv to -150kv. The whole gun and all of the controls, monitoring, pulsing, and drivers also float at this voltage on an isolated deck on top of a large isolation transformer. The entire deck, along with the injector has to be contained in a specially designed corona shield, which has very large diameter corners and smooth surfaces. The whole thing sits inside a large metal shack with several dehumidifiers and a temperature control unit to control ambient temperature and humidity. Even at the long distances, between the corona shield and overall enclosure, depending on the humidity, it can still arc occasionally. Especially on very humid days, in our second test injector, we can observe very large corona losses and instabilities at the higher end over 125kv. Also, current at these levels have a major impact, especially on corona losses, surface tracking, and arcing. We run our injector at probably less than a mA normally, but with humidity it can draw several mA from the supply. Turning up the current even just a couple of mA can introduce very large corona losses, and with it, system instabilities and arcing. Running a power supply for this type of fusor not only at +100kv voltages, but currents in the tens of mA range is incredibly difficult, and dangerous to control.

From the x-ray standpoint, our entire test bunker has several layers of almost 2 feet thick of special iron-weighted concrete blocks, stacked to prevent direct line-of-sight between seams of adjacent bricks to minimize radiation leakage (the actual linac injector, not the test stand, is inside a massively shielded room with many feet of shielding, but this is mainly for the neutron shielding.) Everything is controlled remotely from outside of the controller. It is not a small setup, and is much more complex than running a typical fusor on a workbench. At these voltage levels, you will be looking at a similar setup for the fusor.

If your insulator is only rated for 25kv, you may get away with running it at 50kv, as you have without issue. Over 100kv, this will not be the case. At these voltages, if the insulator is not long enough, the arc can very easily track along the surface (the reason why these insulators have wavy structures is to increase the surface distance between two points to reduce surface tracking possibility as opposed to a straight insulator.) At voltages and current you will be looking at, it is also very difficult to insulate, and can punch through even seemingly thick insulation with ease, especially if there are any gaps or defects. Even applying insulation yourself over a connector or between two points requires very special step gradations with various insulators and thicknesses to deal with and manage field potential distributions and gradients. The arc can snake in between cracks, seams, and joints. Something known as the "triple junction effect" also becomes an issue, where localized geometric field enhancement occurs when insulators of two different permittivities (such as air and ceramic) meet at an electrode, which can initiate discharges that can propagate along a surface. Add high currents to this and it becomes a very formidable challenge.

You also have to consider your vacuum system at this point too - all of the points above are only for the outside of the system, we haven't even gotten to issues actually in the system. Pressure and breakdown voltage are related - look up the Paschen curve. Under certain conditions, an arc can travel extremely far at even very low voltages. You also have to consider all inside surfaces that they are flawlessly smooth, especially your grid - any tiny sharp edge not perfectly ground down and smooth will cause immediate issues. You also have to deal with the effects of water vapor and surface contamination in your system - to run a fusor like this at these levels, proper conditioning is an absolute must. It takes us many, many hours of conditioning at high voltages before we can even turn on our electron beam - if it is not conditioned well enough at ultra-high vacuum levels, it will arc over internally when the beam is on.

For your idea on lining the inside with ceramic, this may not actually prevent arcing as you expect. Charged particles bombarding insulator surfaces in vacuum systems will build up a charge on the insulator, and can easily cause it to arc and flash over. This is very observable in systems such as high power RF windows as well as insulating structures in beam systems. RF windows actually have to be coated with a special metal layer to prevent charge buildup and secondary field emissions which in turn cause breakdown across the ceramic. In fact, one of the major issues for DC accelerators with a stacked ring-insulator topology, is that the beam cannot be allowed to "see" the insulators. If it does, charge will build up, causing arc over. Therefore, special shaped rings are placed internally to guard over the insulators to prevent charge from directly depositing on them. It's also a phenomenon in sputtering systems: one of the reasons why you cannot sputter insulators with DC is that charge will build up on the insulator surface from ion bombardment from the plasma. RF is needed to prevent this and sputter these materials correctly. Just adding ceramic insulators will not necessarily prevent arcing in your system, and depends how and where they are set up. If all of the walls are lined, it may also cause issues with actually running the fusor itself, and could lead to unforeseen instabilities.

Again, a fusor, or any high voltage system, is very different at tens of kv vs. over 100kv, and there are many things to consider, both inside and outside the system. It will become a much more serious engineering effort and require a lot more planning, research, and money. It is do-able, but you are entering the realm outside of what can be done on a desk at home.
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Re: Helium-3 Fusor Thread

Post by Richard Hull »

As I noted, 3He-D fusion is more or less impossible in amateur hands for far more reasons than enumerated here. Money is the big stopper of big dreams. The thoughts and ideas cost nothing. The verve to see it through would require someone with the time and energy to spare....Very, very rare.

The less machining, high voltage and materials skills one possesses, means more and more big money would have to be poured into the effort. The general meaning here is that you would have to bring to bear expensive outside talent, billed by the hour.

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
Michael Bretti
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Re: Helium-3 Fusor Thread

Post by Michael Bretti »

As Richard Hull said, thoughts and ideas cost nothing. Continue to explore and research! Even if there is something you may not actually be able to build or run yourself, you will gain invaluable knowledge nonetheless, which could help you in other pursuits. There are so many fields and applications that have overlapping fundamental principles that you could very well use to solve other problems in areas that you can tackle. D-He3 fusion is not impossible, but from a technical and financial standpoint it is beyond what most amateurs and home experimenters have access to themselves, and requires much more planning than a standard fusor. It starts entering the realm of better equipped and funded research labs. But you can still glean a lot of valuable information still studying these systems, and having the drive and motivation to further explore and push forward on these ideas and pursuits is an admirable trait and will drive you towards a bright future.

Collect papers on anything and everything even remotely related to these topics, immerse yourself in the field, and build up a library of knowledge and reference material. Over the years I have collected and read over a thousand technical, academic, and industry papers on everything I can find on high voltage, plasma, pulsed power, etc, and have been building up a large amount of supplemental resources - binders, notebooks, and textbooks full of data and reference material. Even though most of the technology is not stuff I can build myself (mainly from a financial standpoint), it has been beyond valuable in my own pursuits in engineering. Especially now that you have started these pursuits so early, you have a very large head start, especially if these are fields you want to continue exploring as a career/hobby.

Since you already have a verified, working neutron producing fusor, why not work on further optimizing your output and experimenting with your system? You have run the fusor to produce neutrons, but have you done more to push your system? Have you hit the meganeutron mark? What about 2 million n/s? What about 5? Have you tried different grid topologies? Ion beam injection? Pulsed operation? Activation? What about an automated pumpdown and control system with a full user interface and data logging? There are still a ton of things to explore now, and having a working system is the very beginning of the pursuit! That is where the real fun begins!
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Re: Helium-3 Fusor Thread

Post by Frank Sanns »

Early on there was much discussion about Helium-3 and Phil Fostini actually did some fusion runs. He has several posts on it. Here is one in the Images Section.


viewtopic.php?f=18&t=7695


Also, as previously stated. U of Wisc Madison has some papers on using it as a fuel. Graphs and neutron output vs voltage and pressure are out there. They were also the subject of discussion on here back around 2005-7. Maybe.
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Re: Helium-3 Fusor Thread

Post by Michael Bretti »

While it is very cool to see different color poissors in a fusor (the blue glow of an argon one would be awesome to see), the issue is mainly running proper voltage and currents for the reaction to occur and verifying He3-D fusion, with proper safety measures. The pictures in the referenced post from Phil Fostini do not show anything more than a fusor running on different gases. Reading the archived posts, I do not see any data verifying the reaction, unless I am missing it. Anyone can inject any gas into a fusor, including He3. However, just running a fusor with He3 in it does not show He3-D fusion, nor does more than produce different color plasmas. Since the reaction produces no neutrons itself, the fact that neutrons are measured only shows D-D fusion occurring. In order to verify He3-D, more advanced activation or detection is required.

The paper from University of Madison-Wisconsin verifies this reaction with activation of Mo-94 to Tc-94m. This requires very high voltage at reasonable currents, and enough proton flux for activation. Someone could get away with it at lower inputs, but the time required for activation will go up considerably. It is do-able, but such power supplies, shielding, and activation is considerably greater of a challenge than most people have access to on the average hobbyist budget (not to mention the cost of He3 to begin with.) AlI things considered, for someone who has experience at these voltage levels and shielded systems I don't believe this would be difficult to run or be an insurmountable technical feat, it mainly comes down to cost - power supply, gas, shielding, supporting infrastructure, and a means of verifying the reaction, the easiest of which would probably be activation.
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Re: Helium-3 Fusor Thread

Post by Michael Bretti »

Here are a couple of more papers I have on the subject regarding He3 beam-injected fusor systems:

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