What Is Fusion and How Do You Get It to Work?

you one of the things you can do with plasma is trying to make energy let's look at the closest operating fusion nuclear fusion reactor to us right now the Sun the Sun takes hydrogen and it eventually converts it to helium now the reaction that the Sun is doing is a very difficult one in fact this first step most people would say is just plain impossible you're actually taking a proton and turning it into a neutron it's not supposed to happen it's an extremely slow reaction but you know what the Sun has a lot of time and has an enormous mass and it has enormous gravity confining this plasma together in fact those are the things you need to be able to get a fusion reaction to work you need density and the density of the Sun is 100 times that of water you think oh it's like a flame I can put my hand through a flame right right you can put your hand through the Sun right if you see some science fiction show and it shows some how they're able to get a ship to go through a star but man it crashes on the earth opposite Suns ten times denser and not getting through the Sun it also the signs density needs to be hot and the Sun is 15 million degrees bringing that steel melts it may be 2500 degrees that's really really really super hot the other thing you need is confinement the Sun does that by gravity we can't do that here on earth the size of the earth is oh I don't like the size of my finger tip right here compared to the size of the Sun so this kind of gravity confinement system you're going to cut a tear down on earth what we want to do on earth to make Fusion let's first use a much simpler reaction deuterium a isotope of hydrogen which has one proton the yellow and one Neutron the blue with another isotope of hydrogen called tritium still has one proton and two neutrons this is the easiest fusion reaction to take place notice there are a couple disadvantages of it tritium does not naturally occur it's radioactive has a half-life of 12 years however we can make tritium fairly easily out of lithium an element which we have a very large supply on the planet so if I take tritium and deuterium and I get it hot enough that 15 million degrees that the Sun was you think wow that's really really super hot well we can do better than that on earth the temperature doesn't seem to be as big of a problem we can get to a hundred million degrees we get up to those temperatures fusion takes place and it turns into helium and a neutron this side the helium and the neutron have less mass because of the way the helium is bound compared to the deuterium and tritium helium is a much more stable nuclei we have rearranged nuclear bonds into a more stable state and in this process you give off energy how was that energy manifested well the deuterium and tritium over here have to move fairly fast to combine after all they're both positively charged they have to overcome that to be able to to combine they're moving but man over here the helium and the neutron they're moving a thousand times faster that's where the heat comes from the energy of the products the speed of the products is much higher than the speed of the reactants energy is released this reaction is good because it's easy it's not the best reaction because of two things first we do have to use a radioactive fuel not tremendously dangerous not long half-life but something that means the technology to do it has to be very good can't let any of that tritium get out tritium turns to treated water we're mostly water it's not good biologically and this pesky Neutron neutrons are what make things radioactive so the vessel itself you do the fusion reaction in will become radioactive the half-lives are not enormous it can be eventually buried as probably even low-level waste but it can't be repaired by people for many years because it will be too radioactive so if you make a fusion reactor and something needs maintenance or being broken it'll have to be done robotically not impossible after all the inside of fission reactors has this same issue and they work very well the nice thing about fusion though is there is a future here are some other reactions the first one is the same one we were just talking about through cherrymon tritium but you could just use two deuterium's now this is better because you don't start with a radioactive fuel and half the time you don't end up with neutrons the other half you do so while this reaction is better in several ways it still has some of the disadvantages also unfortunately this reaction is much harder to do it takes a higher temperature there is a fusion reaction sort of the holy grail of fusion reactions where you can take boron and a proton and all you get out is helium no radioactive fuel no neutrons to make your device radioactive unfortunately it also takes extremely high temperatures and while there is an optimistic timeline of sort of when maybe we will do these it's certainly not probably the timeline of when you'll see power plants based on this and perhaps even this third reaction here is beyond our technology but as long as we're learning about fusion there are alternatives potential alternatives that can give us a exhaustible supply of energy in a simpler technology in the respect that it isn't radioactive let's talk a minute about how to actually make them take place remember we need density temperature confinement time the good thing about plasmas is that you can use a magnetic field to move them around take a look at this demo there's a current going from one electrode to the other and that current is actually the plasma if you remember some basic physics you put your thumb in the direction of the current your fingers curl in the direction of the magnetic field a moving current gives you a magnetic field and since the plasma is a moving current you can see if I put a magnet up to this I can actually bend the plasma around I can confine the plasma not using a solid material because it would melt but I can confine it using a magnetic field let's take a look at how this might work you see if I just have a cylinder and I've got electrons and ions running around on it they gonna be which way they want but if I put a magnetic field as shown here along the axis the charged particles will actually spiral around the magnetic field and this is great because now I can keep them confined it and keep them away from the walls which they might otherwise melt take this shape and you say wow this is fantastic except for the ends all this plasma is still hitting the ends so why not take those ends and put them together into a doughnut wonderful now we have no end and you can do that by putting these blue coils around toroidal field coils and that makes this magnetic field and all the particles follow it sort of as soon as a magnetic field line starts to turn into this circle it causes the particles to drift either up to the top what are the bottom and if they do that all of a sudden were hitting the walls again we can't hit the walls so we need to do one more thing we need to give the plasma a twist we can do that in a couple ways a stellarator does it by having a actual magnetic coil that's twisted a tokamak does it by having the current pass through the plasma and create that twist and you can see that what you end up with is another magnetic field going around this way so your resultant field is this twisted magnetic field in a doughnut and that shape is a minimum energy State what do you mean minimum energy State it's like a ball rolling downhill the ball will settle in the bottom of the hill all by itself so does this minimum energy state really exist yes look right here here's a picture of a solar flare and notice how the solar flare twists around and if we imagine it connecting back inside the Sun makes the doughnut shape nature knows that this is a minimum energy state and fortunately people figured it out as well if you put the plasma in state it will be confined so all we have to do is figure out how to make this on earth the device I'm standing in front of is the hybrid Illinois device for research and application it is a fusion confinement device and you can see the large blue coils are the toroidal field coils an enormous current goes through there producing a magnetic field which holds the plasma together the thing is that because it's curved just having these coils isn't good enough you have to have a twist this is a hybrid device because it's both a stellarator and a tokamak and that is caused because it has more coils that are hard to see it has a helical winding you can kind of get the idea of it by looking at these cooling lines you see how they go in a in a helical direction it wraps as an angle around the machine inside this first layer are two more coils that wrap in a helix around the device this is how we can make that twist and keep the plasma confined a tokamak is a Russian acronym for toroidal confinement magnetic and a tokamak makes the twist in a different way in the very center of this device is a five-ton leg of iron and it's connected to these each individual post is one ton of solid iron and that makes a transformer the red coils at the very bottom can get a pulsed current that go through them and when it does just like the can crusher it creates a current in the plasma itself the plasma is the wire and that wire is going to get hot and it's going to exert magnetic pressure and as a tokamak that produces the twists and heats the plasma so this device can be run as a stellarator in steady state or as a tokamak for a brief moment but getting to much higher and hotter temperatures this device came from Germany we were fortunate enough to be able to get it here at Illinois because they built the world's largest elevator a billion-dollar device that would take much more than even just this building size to hold on this device not only will we learn more about various aspects of fusion energy but we will also use it for many different types of applications we have a star and we invite the world to put something in it and to learn what we can about a confined plasmas interactions with the materials a fusion device needs confinement and we get that from the magnetic fields but we also have to get the plasma hot enough this plasma in this device is not going to make much fusion and that's fine it's a research tool it needs to be much bigger to be able to do that but still we need to be able to get energy into the plasma and just like the RF plasma chamber with the coils in it we can do something very similar here pumping microwave energy or radiofrequency energy which will heat up the plasma this whole process takes a lot of energy the Transformers you see behind me actually allow us to use 2 million watts and that's not just for a brief period of time that's steady-state this device for its energy input is 2 megawatts it's like having 20,000 100 watt light bulbs all on at the same time putting power into the device I think it's something around 3 or 4 percent of all of the electrical energy on campus when this is running in addition getting it here was quite a chore because I the total weight of all of these components remember the stuff is solid iron is 70 tons it arrived in the fall of 2014 and as we're filming this is in the middle of 2015 the hope is by the end of the year we're gonna have plasmas in this device and use it not just for research but for education even today having students work on the machine in its assembly phases is a fantastic learning experience hydrogen glows pink and to give yourself some framework here you're going into the bustle and here you're coming out around the side you're looking in the edge of a doughnut if I drew the view imagine I've got this shape going around right here's the center line and this would be the other cross-section of it on the other side but we're just looking this way our eye sees the inner side here right and we're looking through like that here you see the plasma but it doesn't necessarily look like it's somehow held together I see pink everywhere well let's put a certain filter on this a filter that doesn't look at the hydrogen because after all we really have hydrogen everywhere it's just much denser in the middle but something that gets rid of all the hydrogen light and just looks at the impurities the impurities that would be trapped and not able to get into this magnetic bottle I press the button here this shows the actual magnetic bottle just think it's an awesome picture once again you're looking through the edge of a doughnut it shirts back around that way and here it comes outside and why do you see this bright halo around the edge think about it if I had a frosted glazed doughnut and I was looking at it my eye right like this if I look right through the edge I'll see a lot of frosting glazing that's this part on the outside if I look right through here I'm going to see all the frosting on the inside where the doughnut hole came out and that's what you see right in here this is a wonderful picture of this magnetic paddle held within the physical walls of the device you might say well wait professor ruzek you said you have magnetic confinement why do you need a physical bottle at all well we have to keep out the air remember this is made of hydrogen and it's not very much hydrogen basically it's a vacuum vessel you pump all the gas out and then you put just a little bit of hydrogen in you turn it into a plasma you can fine it and the very last thing you need to do is you need to heat it up and you got a variety of tools you could just pass a current through it like a toaster you could compress it by upping the magnetic fields you could use radio frequency or other electromagnetic waves to try to actually make resonances with the plasma that's going around and heat it that way or you could actually throw in neutral atoms that are moving at a very high velocity and once they get into the plasma they become ionized and our by the magnetic field this gives you density temperature and confinement time and as long as I have these three things and their product is high enough temperature has to be at least 100 million degrees density and confinement as long as these two multiplied together I could have short confinement and higher density or less density and higher confinement if I get that I can make sustained fusion reactions which will give us net energy which could of course someday produce electricity that's what you need to know about fusion [Music] you

Channel: Illinois EnergyProf

Views: 182,092

Keywords:

Id: cDoQ-sKNKxs

Length: 20min 28sec (1228 seconds)

Published: Tue May 14 2019

Reddit Comments

[u/NigelLeisure]

I love this YouTube channel.

[u/ElmarM]

Good series. Things I would like to see added: Alternative confinement concepts such a FRCs (which are lately making great progress) or a Sheared Flow Stabilized Z- Pinch (maybe also how it is different from a regular Z- Pinch)? Those are good candidates for relatively compact power plants (when compared to toroids like Tokamaks and Stellerators) . The former is very high Beta, the latter can be super compact. For FRCs I like the work Helion Energy and PPPL have been doing. Those two are unfortunately often overlooked. Also missing was Helium3 boosted Deuterium - Deuterium- Fusion, which is interesting, because it does not need an external source of He3 (He3 being a product of D+D along Tritium, which eventually decays into more He3). I think it is a great intermediate step towards PB11 fusion.

[u/hhgomp]

I started getting flooded by this guy's stuff last week. What does the algorithm see in this?