IamA (I built a fusion reactor in my bedroom) AMA!

This is legal?

To my knowledge, yes.

How dangerous is it to have such a reactor in a home?

While it it running, living things should not be within 35 feet as x-ray radiation is quite high but drops off as the square of the distance (assuming isotropic emission from a spherical source). I have a Geiger counter and was not able to detect a rise in radiation at 35 feet away. The power supply is remotely operated.

Would the x-rays near the device harm electronics?

X-rays can be detected on digital cameras. They appear as white dots. Here is an example: https://postimg.org/image/h453pcklj/

When you told your parents that you're building a fusion reactor in your bedroom, just how much didn't they believe you it's not dangerous? Did they know what it is? It's sounds terribly dangerous for the layman.

My mom almost called the police and the fire department... twice. My dad is a firefighter. Every time I want to do another test, my mom leaves the house. She is now more supportive but still fears for my safety like most mothers would.

I have one question. Why?

Mostly for the learning experience. I learned so much by doing this project. Plasma physics, high vacuum systems, high voltage, electrical engineering, mechanical engineering, nuclear physics, etc. I hope to use our reactor for future research that might benefit the fusion effort. Also, I have made so many connections. I am on a first name basis with several top professors and an extremely successful entrepreneur.

No doubt about it, you're going to do well for yourself. You've already accomplished more academically in your 19 years than most people will in a full lifetime.

Edit: Whoops, forgot to ask a question. Have you made a decision about where you'll go to college, exactly what you'll be studying, and what you'd like to do long-term?

Spending 3+ hours a day on a project during junior and senior year did not help my grades. My counselor told me that I wouldn't get into the top colleges because of this reason. I believed her and didn't apply to my dream colleges. I regret that decision but am hopeful for the future. I will be attending UC Santa Cruz next fall to begin a degree in electrical engineering (they don't offer nuclear engineering). I have already made great connections with the physics chair and electrical engineering chair.

After submitting my college applications, I began making more connections. When I apply to other colleges as a junior, I will be getting likely 5+ recommendations from various chairs and professors at MIT, UC Berkeley, and UC Santa Cruz.

Edit: I can't spel

Given your connections, why on earth couldn't you go to MIT or Berkeley?

Apparently professors have little direct influence over admissions as it is a separate department from academics. Recommendation letters will certainly help my chances next time I apply.

Hello, I am a fusion scientist and graduate of the MIT-PSFC. I don't think you should be distraught at all about winding up at UC-Santa Cruz. It is a fine school. Most programs have very little if any plasma physics at the undergrad level, and graduate programs don't really expect a strong background in it. (My background was in Mechanical Engineering, so EE is already a step up!). However it is extremely important to have strong fundamentals in physics and math, and UCSC should be able to get you those.

In the near term, I would strongly recommend applying to the SULI program for the summer after your Sophomore or Junior year. If you do get a recommendation from Dennis Whyte or someone of that caliber, you will probably be a shoo-in. I did the precursor program back in 2003 and that's what got me started in the field.

Thank you so much for responding and offering your advice. I will definitely look into the SULI program that you recommended. I have been in correspondence with Dr. Whyte and Dr. Short who runs undergraduate nuclear engineering at MIT.

I'm sorry what?
The EU has a whole team of scientists working on fusion, but you and your brother built a reactor in your house?
I'm deeply interested in seeing fusion energy take off, does this approach produce an appreciable amount of power for the amount of work required to get it working?

ITER is attempting breakeven fusion (output energy > input energy). We are nowhere near breakeven fusion. Our reactor is very inefficient largely due to the fact that the cathode is constantly bombarded with ions, which then lose energy and lack the required kinetic energy to fuse.

While it's certainly more complicated than using a piece of metal as cathode, did you consider using an electrical arc instead? It's conductive, yet it cannot be destroyed by high energy particles.

Arc discharges occur at a much higher pressure than glow discharges. This means that in order to excite the particles in an arc discharge to fusion conditions, much more energy must be used. I am operating the plasma at around several millionths of an atmosphere at several hundred million degrees Kelvin. This means that the particles can gain energy while not immediately losing that energy due to collisions. The power supply I use is about 400 watts. To get an arc discharge to fusion conditions might require hundreds of kilowatts.

An alternative is to generate a glow discharge and then confine it using a magnetic field. This reduces wall and possibly cathode collisions. Solving this problem might be the answer to fusion as a viable energy source. Plasma instability is also a huge problem.

• What is the cost of the device you created?
• What are the risks involved in creating and running the reactor, and how do you manage them?
• Do you have a rough guess as to how many such small reactors exist?
• What do the ladies say when they enter your bedroom?

The reactor cost about 6k in total. A major part of the project was just figuring out how to acquire such a sum of money. I raised most of that from a part-time job as a 3D designer. Also, we asked many friends and family for help.

Ionizing radiation and high voltages are the greatest risks. Our reactor produces dangerous amounts of x-ray radiation when running. I have a Geiger counter that can detect these x-rays. We opertate the reactor from a distance of 35 feet. Due to the fact that the source is spherical, radiation intensity decreases as the square of the distance. There are no detectable x-rays at the operating distance. The high voltage power supply is controlled remotely.

We are the 16th and 17th high school students in the world to have completed this project. I think there are about 50 amateur scientists who have built such devices.

A photographer from the high school paper came to our house to take some pictures. She wasn't quite sure what to say.

What are you going to build next?

I have already built 3 Tesla coils (one plays music), a wood burning CO2 laser turret, a 1,000 amp transformer, and a fusion reactor. My room looks like the set of a poorly directed sci-fi film. I guess I could work on an induction smelter. Those things are pretty cool.

How does one detect fast neutrons?

Neutron bubble dosimeter. It is basically a tube full of gel suspending small drops of a special liquid. If a fast neutron strikes one of these droplets, the drop vaporizes and turns into a visible bubble. It still amazes me that a single neutron has enough energy to make its presence known to my naked eye. See the 4th link I posted in the description for an image of the detector holding bubbles.

Wow. Since it was published more than 10 years ago, fusor.net just reached the most users online ever!

Most users ever online was 358 on Mon Jul 18, 2016 3:41 pm

So the fittings and flanges around the fusion chamber, are those all stainless steel? What kind of torque spec is needed on the flange bolts to insure vacuum won't fail? Any special types of gaskets? Sorry, just really interested in how the whole chamber and vacuum all works together.

Excellent work on this, you guys have a bright future ahead of you!

Thanks! All flanges are SS. We used both copper and Viton (Fluorocarbon elastomer) gaskets. We used a torque wrench set at 15 foot pounds. The chamber can hold a vacuum of six trillionths of an atmosphere (the deepest vacuum we achieved).

0.06 micropascal, unless I missed a zero? What vacuum pumps are you using?

Diffusion pump is Varian VHS-4. It is very powerful.

Dang. A rebuilt and refurbished one cost $2000. Was this the costliest item for the build?

I bought most parts used off eBay. The diffusion pump cost me $450. The main chamber cost $2000. That was the most expensive part as it was made on order.

Did you win the Science Fair? If not, what was the first place submission?

I completed the project just several months ago. Too late to enter it in a youth science fair. There are several fusion reactors made by others that have won 1st place (Taylor Wilson).

What's the operating cost of your reactor? Put another way, what input power does your reactor need for fusion?

Power supply: 400 Watts, Diffusion pump: 1400 Watts, Mechanical pump: 745 Watts

Whats the worst thing that can go wrong if you somehow messed up? Explosion?

Implosion. At its lowest pressure, the chamber reaches about six trillionths of an atmosphere. While every part is rated for that pressure, an unlucky tap on the viewport might lead to some problems.

Also, the diffusion pump gets to around 220 degrees Celsius on its base.

The plasma inside the reactor reaches temperatures of several hundred million degrees Kelvin. While not particularly dangerous, having particles of such high energy can cause problems for the vacuum system.

Did you have any close calls or near misses during the process of building, testing and operating?

It's an amazing project, and the write-up you posted explained it in a really easy-to-grasp way.

I'm a Redditor, but I found the AMA because it was also linked over on HN btw, which might be worth a browse afterwards. (Unless you're lsllc on HN!)

Thanks for letting me know about HN. We actually had to rebuild the entire chamber three times due to leaks and insulation adjustments. The power supply broke twice and I contacted the engineer who designed it. We are now great friends. Due to the varying and unstable resistive load that is a plasma, maintaining fusion level voltages proved nearly impossible. We had to set up a series of ballast resistors and operate the fusor in a very complicated way. Needless to say there were countless failures and mistakes made, luckily not dangerous ones.

Would you say that your process was driven more by trial and error or did you follow a fairly specific set of instructions? Is there anything in your fusor that is significantly different from the previous 60-ish people to have built one?

There is not a clear set of instructions. Most of the process was trial and error. There was a lot of error. Our project is not that different from the others except for the fact that we wanted ours to be aesthetically pleasing, not just functional.

Did you put this on your college application?

I said that I was building a fusion reactor, but it was not yet completed at that time (January 15 this year).

Build diagrams or any other resources for people looking to attempt a similar project?

I wrote an article about the process of IEC fusion. Here it is for anyone interested. Reddit has a 10,000 character limit per post, so I had to put this in two posts.

Nuclear fusion is the process of two lighter atoms combining to form a heavier atom. In this process, large amounts of energy are released in accordance with Einstein’s famous equation: E = mc^2. Unlike nuclear fission, fusion requires a large quantity of energy to initiate. The sun uses its gravity to fuse atoms together in its core, but on Earth we lack the technology required to recreate such extreme conditions. Instead, scientists must find other ways to initiate nuclear fusion. For amateur scientists, the easiest is a method called inertial electrostatic confinement or IEC for short. IEC fusion reactors use strong electric fields to heat atoms to fusion conditions. Temperatures in these reactors usually exceed several hundred million degrees Kelvin, which makes the reactor core the hottest place in our known universe according to scientists’ current understanding. You may have some questions such as “how is that possible?” or “is that even safe?” or “can this be done in my bedroom?” Don’t worry, all of these questions will soon be answered.

A standard IEC fusion reactor consists of two vacuum pumps, a mechanical vacuum pump and an oil diffusion pump, a gate valve, a main chamber, an inner conductor also called the grid, a power supply, a pressure gauge, and a lecture bottle of deuterium gas with a regulator and needle valve. First, the mechanical vacuum pump is turned on, which evacuates the entire system to a pressure of about one 100 thousandth of an atmosphere. For reference, one atmosphere is the air pressure at sea level. Then the oil diffusion pump is turned on, which takes almost all of the remaining air out of the vacuum system. Interestingly, diffusion pumps have no moving parts. They remove air by shooting scalding streams of oil at the air molecules. The oil then falls to the base of the diffusion pump where the mechanical pump can easily remove the trapped air from the system. After the diffusion pump is finished pumping down the chamber, the pressure is equivalent to around six trillionths of an atmosphere.

Then deuterium gas is leaked into the chamber until the pressure rises to about six millionths of an atmosphere. This ensures that the contents of the chamber is only deuterium. Now you may be wondering why deuterium gas is so important. Deuterium is the special name for hydrogen atoms that have one extra neutron in their nucleus. This makes deuterium atoms less stable than regular hydrogen atoms, which means that deuterium atoms can fuse with less energy. Maintaining a constant deuterium pressure is difficult, as both the deuterium leak rate into the chamber and the rate of gas flow out of the chamber must be the same. The needle valve controls the flow of deuterium into the chamber and the gate valve is able to throttle the diffusion pump, limiting its ability to remove gas from the system. After the main vacuum chamber contains a constant pressure of deuterium gas, the power supply can be turned on.

When the power supply is active, the grid becomes charged to a very high negative electric potential. The charged grid generates a strong electric field. This electric field is so strong, it is able to knock electrons off some of the deuterium atoms. The now free electrons go on to knock more electrons off other deuterium atoms. This process is called ionization and results in the generation of a deuterium plasma. Plasma is the fourth state of matter that consists of ions, charged particles such as atomic nuclei and electrons. A deuterium plasma is basically a mess of positively charged deuterium nuclei, also called deuterons, and free electrons. The positively charged deuterons are attracted to the negatively charged grid. The specific geometry of the grid causes the generated electric field to have weak spots. This can cause beams of plasma to shoot out from the grid’s interior. The deuterons accelerate to very high velocities following a Maxwell-Boltzmann velocity distribution. This means that only some of the deuterons have enough energy to undergo fusion. The grid is bombarded with deuterons, which causes it to glow white hot as the kinetic energy of the particles is transferred into heat energy. Some of the deuterons do not collide with the grid and have a small chance to fuse with each other.

However, there is something that is not adding up. If two deuterons are both positively charged, don’t they repel each other? The answer is yes. The coulomb repulsion force between them is actually so powerful, they would require an infinite amount of energy to meet. So then why does the sun shine? The answer lies in the strong nuclear force and quantum tunneling.

The specifics of strong force interactions between subatomic particles can get a little confusing, so here is a brief explanation of why the strong force is so important. Consider a helium atom. Its nucleus is composed of two protons and two neutrons. As I mentioned before, positively charged particles repel each other. The two protons in the helium nucleus want to get as far away from each other as possible, but for some reason they are attracted. This can be explained by the strong force. The strong force is incredibly powerful, but its range is very limited. For two protons to experience an attraction due to the strong force, they must be within just several protons' width of each other. However, once they are within that range, it becomes nearly impossible to split them apart. The distance at which the attractive strong force overpowers the repulsive Coulomb force is called the coulomb barrier. In order to overcome that energy barrier, two positively charged particles must approach each other with very high kinetic energies. If they are not moving fast enough, they will simply be repelled without experiencing any attraction due to the strong force.

In order to solidify this concept, consider a marble on a frictionless track. The track has two very steep hills and a valley between them. Your goal is to find a way to get the marble trapped in the valley. The only tool you have to do this is a spring launcher that can launch the marble at a specified speed. However, after several attempts you will realize that this task is impossible. If you give the marble enough energy so that it can go over the first hill, it will also have enough energy to continue along the path and then go over the second hill. The marble will have to lose energy while in the valley in order to become trapped. You can probably guess that I am not really talking about marbles. Think of the marble as a speeding deuteron and the bottom of the valley as deuteron that is fixed in place. The hills represent both the repulsive Coulomb force and the attractive strong force. As one deuteron approaches the other, the Coulomb force increases just like the slope of the hill. The peak of the hill represents the coulomb barrier. If a deuteron has enough energy to overcome the coulomb barrier, it accelerates towards the other deuteron due to strong force interactions. This is represented by the valley between the two hills. However, just like in the marble example, a deuteron that enters the attractive realm of the strong force can actually escape and pass the coulomb barrier on the other side. This means that in order to accomplish fusion, the deuterons have to perform a nearly perfect collision.

Now you may think that this solves the deuteron fusion problem, but for our specific case involving an IEC fusion reactor built in my bedroom, it does not. The kinetic energies of the deuterons are simply not high enough to breach the coulomb barrier. Now you may be wondering why I went through that long explanation of the coulomb barrier if it is not even the mechanism that allows fusion to occur. Well, we’ll get back to that in a moment, but right now I need to explain quantum tunneling.

I will start out by saying that quantum tunneling counters our classical physics based intuition. Subatomic particles such as electrons and atomic nuclei don’t have a defined position until they are observed. These particles’ probabilistic nature can be described by wave functions. The probability of a particle being observed at a specific location is dependent on the wave function of that particle. For example, let’s allow the wave function of the speeding deuteron in our previous example to be interpreted as a probability cloud. In this example, the probability cloud is essentially a mass of points, where each point represents a possible location of the deuteron after it has been observed. The points are denser near the center of this cloud as there is a high probability of finding the particle near that location. Going back to our marble on a track example, let’s apply the phenomenon of quantum tunneling.

Let’s say that the spring launcher gave the marble just enough energy to reach three quarters of the height of the first hill. At the three quarter mark, the marble changes direction and rolls back down the hill as is does not have enough energy to reach the peak. This is consistent with classical physics and does not account for quantum tunneling. However, if quantum tunneling is considered, this seemingly simple test can yield a different and surprising result. Let’s freeze the moment that the marble reaches the maximum height on the hill. If we replace the marble with a probability cloud, you will notice that there are points in the cloud that exist on the other side of the hill. This means that there is a chance that the marble may be found inside the valley if observed. When the marble tunnels through the barrier it does not gain or lose energy, so it cannot escape the valley as it lacks the required energy. The marble then oscillates between the two hills. It is important to point out that if the marble was given more initial energy and was able to climb higher on the hill, its probability cloud would have more of its points in the valley, which means that its probability of tunneling would be higher. But, marbles do not tunnel through barriers. I am really discussing the behavior of two deuterons. The marble tunneling through the hill is an analogy of a deuteron tunneling though the coulomb barrier. When a deuteron tunnels past the coulomb barrier, it becomes trapped by the energy well created by the attractive strong force. The two deuterons then oscillate around each other until one of them releases energy and they fuse together.

Consider two deuterons that are about to fuse. In order for the fusion to occur, energy must be released. In deuterium-deuterium fusion, there are two possible results that can occur. Either a neutron is ejected leaving a helium-3 atom, or a proton is ejected leaving a tritium atom. This ejection of mass allows one of the oscillating particles to lose energy, which leads to the synthesis of new atoms and the generation of energy.

IEC fusion is just one of the many methods that may lead to a fusion-powered future. One of the largest ongoing fusion projects, ITER, is located in France and has gained international support. ITER is a tokamak fusion reactor that uses strong magnetic fields to confine a fusion plasma in a torus-shaped vessel. ITER is being designed to produce around 500 megawatts of output power while only needing 50 megawatts to operate. While ITER will not provide continuous power to the surrounding area when it is turned on in the late 2020s, the project hopes to demonstrate that nuclear fusion is a viable source of energy and provide a platform for continued research and development of fusion systems. Once fusion power is realized, human society's increasing demand for energy may be satisfied. Fusion power produces no dangerous waste and does not pose environmental threats to surrounding areas. Fusion is the energy of the future and has the capacity to push humanity to new breakthroughs in science and technology leading to prosperity in a society without suffering. I am optimistic that this future may be realized, but it will take a global initiative to become a reality.

Where did you get the deuterium? Isn't is very costly and rare? Also how did you parents let you build a fusion reactor at home?

I got the deuterium from a fellow fusioneer.

My parents were very concerned, but I did my research and presented the facts that disproved many of their speculations.

Does this release high levels of ozone in your house when it is running?

There is only deuterium in the reactor so no ozone is produced. The products of deuterium-deuterium fusion are tritium and helium 3. In a 20 minute run, I calculated that about 139,000,000 atoms were produced, which is not much.

so how long till your powering your house with it?

The reactor is incredibly inefficient. You would be lucky to get one trillionth of your input energy back. However, it can be used as a platform for research, which is one of the reasons I decided to build it.

Curious what the major inefficiencies are

Mostly ions colliding with the inner conductor and then losing energy. I had to use tungsten in order to prevent the cathode from melting.

How much did this cost?

The reactor cost about 6k in total. A major part of the project was just figuring out how to acquire such a sum of money. I raised most of that from a part-time job as a 3D designer. Also, we asked many friends and family for help.

Really impressive, man! One question, did you get any help regarding the research bit? like from professors or that kinda stuff

The professors were very helpful to verify the results, but our research was mostly independent. The fusor.net community was very helpful.

One more question, if you could answer please. What's the coolest thing you've witnessed during this whole experience? I bet it was magical when those bubbles appeared inside the liquid!

The coolest thing was getting this image. It may not look like much, but the chances of getting that picture were incredibly low. That is the moment that a plasma initiated in the reactor. I'm not sure how long it lasts but it is likely less than a hundredth of a second.

What do you plan to use the fusion reactor for?

The reactor is essentially a small fast neutron generator. This can be used to activate certain metals. More importantly, the reactor can be used as a platform for experimentation.

Are there any agencies you've had to deal with (NRC, etc) and if so, how have they reacted to civilian fusion engineering?

I haven't had to deal with the NRC, but I'm thinking that might not be good. I have unsuccessfully attempted to get deuterium from some local gas supply companies. In one instance, I approached the counter and asked if I could get a bottle of deuterium. Without hesitation, the employee said that they didn't have deuterium. I had previously checked their catalog and they definitely have deuterium. I managed to get my deuterium another way...

I managed to get my deuterium another way...

Careful man, the Lybians will find you.

He is 19, I'd be surprised if he catches this reference without help.

help plz

Don't you fear that it could cause a meltdown?

Fusion reactors can't melt down. You are thinking about fission.

Have you ever tasted Deuterium? If so how does it taste to you?

It is chemically identical to hydrogen (protium), so that is what it would taste like. Odorless, colorless, and tasteless.

How much math do you need for this? At about what level math can you do now?

I just finished taking AP Calculus AB. I know some people my age taking math classes three years ahead of that. Operating the reactor is more of an art form than a science. I understand the theory better than the math.

This is a massive achievement in terms of building and experimenting (and vaccum tech if I might guess). Is there anything you would have liked in terms of software or theoretical model support that would have helped you?

I would love to be able to model the electric field due to three perpendicular charged rings with the same center position. That would help me understand how the ions travel in the reactor.

Can i see some kind of proof ? Any papers ???

Here is a lab report I wrote. Check the description for some links to fusor.net pages.