Build A Fusion Reactor

Step 7 Fire It Up (and cross your fingers)

Time to turn it on (don't forget to cover any viewports/cameras with lead! Also x-rays can pour out of ceramic feedthroughs so point them away from people. It is a good idea to be monitoring for x-rays where any people are present). The basic procedure is:

-Turn on the roughing pump and wait for sufficient backing pressure, turn on the diffusion or turbo pump and wait for it to fully warm up or achieve running speed
-Throttle the chamber back (with the valve between the diffusion/turbo pump and the chamber)
-Ever so slightly open the needle valve to the deuterium tank
-Turn up the high voltage until either plasma establishes on the camera, or you've reached 40kv and nothing has happened (don't forget, you only get one chance in your life to screw up with voltages of this degree)
-If nothing has happened, keep admitting more gas and the pressure should keep going up. Plasma should form around 40kv at about 10-15 microns of deuterium.

If all goes well, you should see on your camera the image below, and you should be detecting neutrons at this point.

Operation is quite a balancing act, since the voltage is controlled by both the power supply, but also by Paschen's Curve and Ohm's Law relating to the pressure in the chamber. Great patience is required to "Get the hang of it", but after doing so it becomes quite simple to run. Operation can be aided by an ion-gun which will not be discussed in this article.

Comments

[pwnag3]

Would Hydrogen obtained via electrolysis work in this?

[christensent]

Only if you do it on heavy water thus getting deuterium instead of hydrogen.

[Nuclear_Ninja]

Nice Project I would like to give it a try myself. What inspired you to build this?
Can you give me an estimated cost to build what you did?
Also do you have to TIG weld the parts or can another type of welding work?
One last question what type of shielding other than the lead did you use?

[christensent]

I was just looking for a science project online, found it, and it sparked my interest. I spent about $6000 on it, but it could be done for less with better planning. Yes, the parts need to be TIG welded. Other forms of welding are not completely vacuum tight. I used only lead. While it is possible to shield neutrons, it is extremely expensive and bulky, and isn't really necessary for the neutron levels produced by this device.

[Nuclear_Ninja]

on what scale are you talking like what counts were you getting off the neutron detector?
and thank you for the information

[christensent]

At peak run a typical home built reactor will make one to two million neutrons per second. This may sound like a lot, but it is very few from a biological hazard. You could stand a few feet from it for days with effectively no risk.

[Nuclear_Ninja]

Ok what are you currently using your neutrons for or are you just running it for the sake of running it? and if you dont mind me asking are you in college if so what degree are you working on

[christensent]

I was pretty much running it for the sake of building it, tweaking it, and having fun with it... It is possible for it to be used as a useful neutron source for experimentation, however I lacked sufficient equipment to do that stuff. I no longer run it since I am not at home. I built this in high school, and am now at college at MIT studying electrical engineering and physics.

[Nuclear_Ninja]

ok and congrats on the MIT thing I an studying nuclear engineering at nc state. hints at my intrest in a reactor. thank you for all the information. If I end up building one of my own I will post pics.
Once again thank you for the info

[crash landing]

any chance your next project could be a table top model of the hadron collider? I started on mine but my wife wanted her washing machine back so the project is on hold for the moment.

[munkey906]

oooo yes... table top hadron collider, that would be sweet!

[A good name]

My particle physics are a bit hazy, isn't it currently impossible to run a fusion reactor without incinerating everything within a two mile radius?

[wberry]

no you can do it, they did it over about a 30 year period, but they never could get it to sustain the reaction on its own, and you can fuse nuclei at room temperature, the controversy is simply how its done, nobody in the US patent office will listen, and so they proclaim it bs when its legit

[kaitheninja]

Yep, Is where too atoms fuse, i think its hydrogen, and produce energy, its only been done once by man, and that was for like 0.000000001 of a second!

[wberry]

nope, they got it to work with the bombs, they just cant find a practical way to get it to fuse and become self sustaiend

[A good name]

I can tell you one thing, it doesn't work with bombs. It occurs in bombs as a byproduct, but the energy is produced via fission.

[squiggy2]

actually the fusion mentioned for bombs is the "H-Bomb". It uses nuclear fission so compress deuterium and tritium enough to fuse into helium, which in turn releases enough energy to split more uranium or plutonium, and repeats.

and as for fusion plants, actually it's been done a number of times.
The leading design so far is the tokamak type generator.
The record for the longest fusion reaction so far is 0.5 seconds, and produced 1997 produced 10mW of power (65% of the input).
United States, China, the European Union (EU), India, Japan, the Russian Federation, and South Korea. are currently building a new reactor which hopes to sustain a fusion reaction for several minutes.

This January, scientists in Italy produced a "cold fusion" nickel-hydrogen fusion reaction, which could turn out to be a very promising step forward

[Lefrançois]

What is the usefulness?

[christensent]

It is a neutron source which can be used in neutron activation experiments

[echaa]

When you built it, did you intend for it to be anything other than a neutron source? Would it be possible to get power out of it, and to get more power output than input?

[elih]

It is not yet possible to get more power out of a fusion reactor than it takes to run it. That would be a Nobel Prize discovery haha.

[vincent7520]

If I build one and press the switch,will be the Master of the World ?… or is it not worth the pain ?…

[Whales]

Is there a way you can record a video about this? not like a replacment for this, just of this thing working and a few other things. Just so i know for sures your not trying to get me on a terrorist watchlist

[christensent]

Not sure what it has to do with YOU getting on a terrorist watchlist, but here are two videos:

http://www.youtube.com/watch?v=XN8OCYwZ_7w
http://www.youtube.com/watch?v=AFE6AukCB8I

[burpreynolds]

Who are you?

[christensent]

A college freshman... I'm not about to post my biography on here

[thalass]

You're an absolute champion, that's who you are. Now i just need a Mr Fusion to power my electric car...

[Cobalt59]

Obviously you've seen back to the future.

[mario59]

Hi christensent ! ! !
but... what a *BAD* LAST SHOT you did for such demanding homebuilt project!
You did lots of detailed photos... but the last one, which should be the "cake's cherry atop" if the really worst one ! ! !
If I could make ask you, could you post (one o even more) better shots of the running chamber? Mayb also the neutron counter running, would be nice to see!
Anyway CONGRATULATIONS ! ! !

[christensent]

The reason is at high power levels, all I put on the viewport is a cheap webcam because my nice cameras could be damaged by x-rays (dead pixels formed, etc).

A demonstration of my neutron counting system can be seen here: http://www.youtube.com/watch?v=XN8OCYwZ_7w

[MKD]

What an interesting project. What is the practical end of this? Is this more of a back yard science experiment or does it have an application? Forgive my ignorance on this topic; I presume that this project is fundamental for other more elaborate constructions.

[christensent]

It is practical for doing neutron activations of elements, and for getting into prestigious colleges. That's about it, unless you have hopes of "figuring it out" and solving the fusion puzzle and saving the energy crisis.

[aqwiz]

Now how am I gonna top THAT for the epilog Challenge, Gee Thanks :P

[wesley93]

alright i really dont have the recources nor the desire to conduct a project this large so could someone tell me, is this forreal or just a bunch of bs?

[christensent]

It's for real, if my own answering of this question is sufficiently legitimate for you.

[gfwhell]

As soon as the plasma is established ,I would expect to see the primary current jump up, would that not be an indicator of a healthy plasma?
Could this process be obtained usinfg a couple of Magnetrons?

GFWHELL

[christensent]

Yes, with no plasma there is very little if not zero current in the single digit uA range. When the plasma fires, all of a sudden it jumps up into the mA range. I usually try to operate in the 10-15mA range.

Magnetrons can be used as an auxiliary ion source, however you still need the high voltage to accelerate them to the fusion cross section.

[UKtheBUNNY]

Does anyone know if a refrigeration compressor would create a strong enough vacuum?

[eggmcmffn]

A 'refrigeration compressor' will pull down low 10^-2 to 10^-3 Torr, for just making a plasma its okay, but for a plasma 'experiment' you want to evacuate enough neutrals as not to interfere with your reactions. So 10^-6Torr would be a good place to start. Turbo-pumps (turbine pumps) are fairly inexpensive but some controllers are prone to suffer around electrical noise and the turbine cannot handle high pressure surges. Cryo-pumps on the other hand, require a compressor and work by cryogenically freezing neutral particles to a sub-strait. Those are more robust but costlier.

[christensent]

A refrigeration compressor would not be appropriate, a refrigeration vacuum pump (used by people servicing refrigeration systems) could work but are not preferable over a belt drive vacuum pump.