Fusion – Ria Lina, Yasmin Andrew and Howard Wilson

Introduction

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Host Introduction

1:53Hello, I'm Brian Cox. I'm Robin Ince and this is the Infinite Mankish Cage. Because today we are in Manchester, which is home, in case you don't know, to some of Brian's favourite childhood bus routes. Those of you who are regular listeners will know, before Brian started getting involved with the stars, he was an avid bus spotter. So what was your favourite? You're coming in from Oldham, you've put on all your kind of Robert Smith make-up, perhaps you're going to Jilly's Rock World.

2:24No, Cloud 9. You're not going to Jilly's Rock World? Cloud 9 and Berlin it was. And it was the 24 bus, by the way, that went from Chatterton to Manchester, Piccadilly bus station. What was it about the 24 that really impressed you? It was the bus that went where I wanted to go from.

Nuclear Fusion

2:39Today we're asking nuclear fusion, when will it be ready? What makes fusion reactors so hard to build when the sun built itself? Fusing only gravity. What are the breakthroughs we're waiting for? To help us understand the challenges, the innovations and the future benefits, we are joined by a fusion scientist with an interest in magnetic confinement, a plasma scientist with an interest in spherical tokamak innovations, and a forensic comedian with an interest in viruses and puns. And they are. My name is Howard Wilson. I'm the Director of Science and Technology at UK Industrial Fusion Solutions, which is the organisation that's leading the delivery of the,

3:15of STEP. STEP is the spherical tokamak for energy production, the UK's first fusion pilot plant here on Earth. I started in fusion in 1988, and about six months later there was the announcement of cold fusion. We were asked to give an example of what we think is a crazy energy source, and I would put cold fusion in that box. I'm Yasmin Andrew, and I'm a Senior Teaching Fellow at Imperial College London. I'm a plasma physicist, and I've been working on magnetic confinement fusion for the last 30 years.

3:47Do you want the unusual energy source? Yeah. Oh, yeah. Yeah, so this is more strange, was this idea of sending a satellite into space while just above Earth, and then making use of the solar wind to drive an electric current, and then beaming that electric current back down to Earth using a laser. I don't know what they've got with that. It's overcomplicated, isn't it? It's very complicated, and the optics aren't up to it, apparently. Is it because when you're looking for finance, if you just say, and lasers, people go, oh, that sounds brilliant, yeah.

4:19They don't hear the rest of them, they just hear lasers, but more plausible than cold fusion. Does that mean I'm winning?

4:28Hi, I'm Ria Lina. I'm a comedian and forensic scientist and virologist, and I don't understand why we're even investigating fusion when we already have the technology of hamster wheels that we could do at a size large enough to put all the children with ADHD in them.

4:47And this is our panel.

4:54Actually, Howard, I need to ask you first, when you said to your friends, I've just joined Steps, in many ways were they then disappointed?

5:02There is a Howard in a boy band, I believe. Yeah, there is. It wasn't me. You're a fantastic conflagration and montage of boy bands with your Steps element, and also you take that element. I thought that was like the 12-step program. And I was waiting for him to come and, like, apologise to all of us. Howard, you mentioned cold fusion there. The first question was to describe what fusion is, but maybe in that context, because many people might not know why cold fusion is your choice as a ridiculous energy source.

What is Fusion

5:32Should we start with what fusion is? Yeah, and then we'll start to realise how ridiculous cold fusion is. So fusion is the process that powers the stars, powers our own star, the sun. You take the light elements, hydrogen, really the light end of the periodic table, or isotopes of hydrogen, heavy forms of hydrogen, and if you push them together close enough, such that the nuclei that sit in the middle of the atom, get those nuclei to touch each other, there is a significant probability that they will fuse to create something heavier, a heavier element, and they release energy at the same time.

6:04And that's the energy that powers the sun. It's actually the process whereby all of you are made, because you start off with the light elements from the Big Bang, and it's through the fusion process that the heavier elements that we're made up from come from. So it's absolutely fundamental in terms of energy, because it's where the sun gets its energy from, and it's fundamental in terms of our being, where our materials come from. So how do you get two nuclei close enough together? That doesn't sound like a hard thing. Well, it is, because they're both positively charged. They don't want to come close together. And so you've got to get enough energy in them

6:35to overcome what we call the Coulomb propulsion, that light charges repel. That takes a lot of energy, and we tend to do it just by heating it to ridiculous temperatures. So the temperature at the centre of the sun is, what, at 10 million degrees centigrade or so. The sun is a fusion reactor, power plant, but it's not a very efficient one. We have to achieve temperatures at 10 times that temperature to get these nuclei to get close enough together. Why do cold fusion think they're going to get these nuclei to come close enough together at room temperature? And there was an argument that by putting them in a particular metal, palladium,

7:08and passing the current through them, that they would come close enough together to fuse. It didn't sound plausible, and it wasn't true. It's because energy from the palladium, again, has such a showbiz air. There's something about you.

Fusion vs Fission

7:22Yasmin, most people, when you think of nuclear power, probably think of nuclear fission. So what's the difference? So fission is the opposite process. So it's what Howard's just described, where you take a very large radioactive nucleus, which is unstable, and then it will break down into smaller particles. And it's the same effect as the binding energy of the nucleus that's released in that decay, and the two smaller particles are released with energy. So it's the exact opposite process. So you're saying that you release energy when you stick hydrogen together to make deuterium or helium,

7:54and you release energy when you split uranium up to make lighter elements. So why? So it's down to mass-energy equivalents. So in the case of fusion, the sum of the starting nuclei is less than the starting mass, and so that difference in mass is released as energy, and it's the same process in fission. So it's the mass-energy equivalents equals mc², which I think is the most famous of physics equations and people will be familiar with. What makes something unstable, then?

8:25Are we talking about, basically, as it increases in size, the stability decreases? So hydrogen is very simple in terms of its structure. And it's very stable. Yes, exactly. So when it becomes very large, then the forces that are required to keep many of the nuclear particles together, the more and more energy is needed to create that nucleus, so it is inherently unstable. So hydrogen or helium that's used for fusion is opposite, which is one of the reasons it's so difficult, because they are stable, and you're almost having to force them to fuse.

8:55One of the other differences between the exact opposites of them is if you look at the fission reaction, as long as you put sufficient fissile, heavy material together, like uranium, so you put enough there and start the fission reaction, it is self-sustaining. If you have more than the critical mass, it will run away unless you do things to it. So in a fusion plant, personally safe, but you, the operator, have to put control rods in to soak up these neutrons to stop the reaction happening. I didn't just say, you said fusion plant. Fission plant, sorry.

9:27Again, this has got your classic music hall routine, fission, fusion, fusion, fission. How do you feel, Ria, about, because, you know, your forensic science, you were fascinated by, viruses you were fascinated by, you know, my mind does get very easily bamboozled by physics, because, you know, the scale that you're dealing on is so kind of fascinating to try and create a picture of it. How do you generally, as you hear these ideas bouncing around? I have so many questions right now. Question number one, if it needs that much heat in order to release energy, you're using energy to create energy,

9:58it feels inefficient. I don't understand why we're heading towards fusion. The amount of heat that we're using to fuse two hydrogen atoms together is still less than what it would release? Yeah, exactly. That's incredible. Yeah, it's a key question. So we have to create conditions such that you put sufficient heat into the plasma that it will start to burn. And this is what we call a burning plasma. So it will be self-sustaining. It will no longer require external heating. And in fact, it will start to produce net heat. Until it runs out of hydrogen atom.

10:30Yeah. And then it'll just be helium plasma. You keep supplying the hydrogen as it's running. You're trying to get the helium out as the... So you're like a drug dealer. Just like, come on, have some more hydrogen. Come on. Yeah. And it just sits there pushing it together. You need to fuel it for as long as you want it to burn. It's essentially the same as the sun, right? The sun is a self-sustaining fusion reaction. But we've all been told that the sun's going to run out at some point. It will. Right. So it isn't. Five billion years. You say that, but it'll come around in no time.

11:05I know there was a very famous story of Patrick Moore where he said that he was giving a lecture and he said that. He said, five billion years, the sun will run out of fuel. It'll swell up. It may engulf the earth. And someone did say, did you say five million or five billion?

11:20I've got, you know, I... And he did say, it doesn't matter.

11:26But it is that thing about time, isn't it? That you go, the first billion years went really slow, but my God, the last four billion just raced past. That's what happens as you get older, don't you? Time means something different. I mean, that was my second question. I mean, if the sun is just constantly creating helium, if it could speak, would it sound like this the whole time, like it ate out of a balloon? See, I wanted you to do that voice. I want you to start with that. You want some more hydrogen? And you go, oh, you want some more helium? I was hoping that was where that was going to go. And then we would go across the whole periodic table. And then I think deuterium probably killed us.

11:57I don't know, but yeah. The first question... Until we get to Americum. Oh my God, aren't we amazing?

12:03We should say, first of all, it's not hydrogen that we use as a fuel. Is it in the reactors that we have now? We could do. You could in principle, but the conditions you need are even more extreme if you use pure hydrogen. So we use two heavy forms of hydrogen. One's called deuterium, which sounds fancy, but actually there's loads of it. It's everywhere. One in every 6,000 hydrogens is in fact deuterium. And if you think about all the water in the world, all the H2O in the world, one in 6,000 of those H's is actually a D. So there's loads of deuterium.

12:35So we're full of deuterium. Absolutely ram full of it, yeah. Yeah, yeah, absolutely ram full of it. What a great insult.

12:42And then the other one we use is tritium. It's not stable and it will decay, but 12 years, it's got a half-life of about 12 years, which means if you have a jar of tritium, go away for 12 years, come back again, half of it's gone, half of it's decayed into something else. So tritium is really rare. There are sources of it, but it does mean we have to manufacture it within the plant and we may come back to that later. But that's the reaction that we use, deuterium and tritium, because although it's still hard, it's not easy to get something to 200 million degrees and hold it here on Earth. We all know that, don't we?

13:14It's not an easy thing to do, but it's the easiest fusion reaction to do. And it gives you helium, as we've been discussing, and it throws out a neutron as well. It's the energy of the neutron that it throws out that we will capture, basically boil water, and drive turbines. So that's the self-sustaining reaction. It's the helium going back in. Yeah. So the helium has one-fifth of the fusion energy. The neutron has four-fifths of the fusion energy. The helium stays inside the deuterium and tritium and gives up its energy to the deuterium and tritium. So once you've got it going, the helium that's produced keeps it going.

13:46Just to double-check, this is all with consent, right? We're not just forcing these atoms together against their will. It is against their will, isn't it? We are forcing them together against their will. And they have a strong will. So, Yasmin, so fusion,

Fusion Challenges

14:01probably most people have heard of it. There's almost a joke, isn't there? It's always 20 years away. But it is often presented as the holy grail of energy production. So I suppose that there are two questions there, which is, why does it always appear to be decades away? And why is it the holy grail? So I think it is a limitless source of energy. And so that's why it's the holy grail. So if it's achieved and it's controlled and it can be hooked up to the grid, it has vast potential for society,

14:32for electricity generation, for many of humanity's problems in terms of inequalities for electricity access. And it doesn't require a lot of fuel. Part of the fuel that we need is very abundant, easily accessible. Personally, I think it's been underfunded for many, many years. It wasn't fashionable. So they had fission. There was no reason to fund fusion research. And so, you know, we've been doing that research for a long time. I think for quite some time, it wasn't very much in the spotlight. It has had decades of funding,

15:03but at a relatively low level, I would say. And so I think when you compare the amount of funding or the efforts that were put into developing fission when that energy source was needed, it's not really comparable. So you can start to see it now. The focus is definitely shifting. I think there is an awareness that fusion is needed. The funding of the research has started to change. And so now it's becoming much more serious. And so now if the efforts are there and we're able to grow the community and we have many strands of fusion research, I think there is hope that it can be developed

15:35and on the grid and in a controlled way. So is that basically that because we're now seeing the implications of climate change, now it's actually becoming a reality? Is that what has finally kind of sped it up in terms of research? I think there's recognition that oil and gas will run out. I'm not sure if it's actually embedded in concerns about climate change. I mean, for me, obviously, that's a huge one. And that's, again, another appeal for fusion. Fossil fuels are not never ending and a replacement is needed.

16:05We need a continuous source of energy that renewables and sustainable energy is very important, but I don't think it's going to fill the gap that fission will until fusion is ready. And when fusion is ready, it looks like it would take the place of, for example, fission, which has its own problems. And that's in about 20 years' time. Is that right? Yeah. Ria, you had a question? No, I was just going to apologise for the lack of funding. I think we've been spending it all this time on vaccine research, but as we all know, that's come to nothing. So I'm really sorry about that.

16:36Have you been taking your paracetamol again?

16:41No, because I'm not pregnant.

16:45So can I add a perspective on this? I think fusion is difficult and fusion is expensive. The research associated with it is expensive. And so there's been a big view that actually fusion will be ready when we need it. And I think a large number of politicians and the general public understand that we do need it for climate change and we do need it for energy security. And that's something that's been particularly important and risen in priority over the last four or five years, for example. And so people now go, yes, we do need it.

17:15And you'll have seen over the last five, six years as people have gone, yes, we need it. You'll see a lot more private investment going in, billions and billions of pounds. And that funding is now starting to accelerate the process. And we are starting to see fusion power plants on the horizon in the next decade or so, at least in a prototype. Sense that demonstrates that it's feasible. How many different technologies are there? Because essentially the point is you have to stick some deuterium and tritium together. So hydrogen, basically. How many different ways are there of doing that?

17:46There are hundreds, but actually they can be categorized as two. One is inertial confinement fusion. One is magnetic confinement fusion. They're both trying to do the same thing. To do fusion, you need a sufficiently high density. You need actually a certain temperature. There's 200 million degrees. And you need to be able to confine your fuel for long enough. You need a good enough system to be able to hold the heat in sufficiently well, a sufficiently insulating system.

18:17And so you have this so-called triple product of density, temperature, and confinement time. In inertial fusion, they take a small pellet of deuterium and tritium, about a millimetre or so in diameter. And they coat it with something, something heavy, typically. And they put it in the size of a big chamber, probably not that much small in this room, actually. And they focus a large number of lasers, like 200 lasers or so, on this poor little pellet, 200 of the world's biggest lasers. And that basically burns off that coating from the deuterium and tritium.

18:48And as it blasts away, it pushes on the deuterium and tritium, compresses it to really high densities, like 1,000 times solid densities, like taking a brick that a building is made out of and just squeezing it down to a Lego brick. So you get really, really high density. You get the temperature as you compress it, but it has really short confinement time because there's nothing holding it there. The only confinement time is associated with the inertia of the fuel, so it's like billions of a second. But that product of density and temperature can, in principle, get you to fusion power. And they demonstrated it once, with one shot a day kind of thing.

19:20They would need to do that 10 times a second in order to deliver fusion power, and much, much more cheaply than they're doing at the moment. So that's inertial fusion. And then magnetic fusion uses the fact that if you heat something to 200 million degrees, it doesn't look like the matter in this room. It looks like something called a plasma. So if you take water, for example, you know the three states of matter that we're familiar with, solid, liquid, gas. Take water, solid state is ice. Heat it, it melts, you get water. Heat that, it vaporizes, you get seam.

19:51Now keep heating it. Your water, your H2O bonds split apart because you're putting so much energy into it. Your H2s split into individual atoms. If you keep heating it, it gets so energetic that the electrons surrounding the nucleus effectively boil off that central nucleus. And you're left with this big ionized gas of positively charged nuclei and negatively charged electrons. The whole thing is still neutral because you haven't made any charge, but now you've got charged particles in there. And that charged particle gas behaves very differently to the gas

20:22that we have in this room. And that's a plasma. Fascinating. I've spent my life doing it. But it's what we have to study in fusion to make fusion happen. Now because the plasma has charged particles, we can hold onto it in magnetic fields. It's lower density, much longer confinement times, and the temperature's the same in both of them. And magnetic confinement is holding that plasma for much longer timescales to create the fusion process. Hi, I'm Dr. Jake Goodman, and I'm the host of Beyond the Script,

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21:25because there are a lot of prescription medications that can help with that. If someone is really opposed to taking medications, there are a few lifestyle modifications that they can do, like avoiding caffeine and spicy foods, trying to stay hydrated, have a regular sleep cycle, get some exercise. Those are all things that could kind of help to limit the symptoms. Hear the full conversation, plus so many fantastic insights into all the stages of life when it comes to women's health. Listen to Beyond the Script, a podcast from CVS Pharmacy, wherever you get your podcasts.

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23:32Yasmin, so your expertise is a plasma physicist initially. So the problems we have building fusion reactors, or the confinement reactors, are essentially associated with controlling that gas, which would seem, as you described it, how it would be quite easy, you just stick it in a magnetic bottle or something, and it just sits there. So Howard's described that really nicely, so how you create the plasma, so you essentially need some way to ionise the gas. And one that people are familiar with would be the neon lights. So you have the different colours

24:03of neon lights, and those are plasmas, essentially they're low-temperature plasmas, and they will have created those by running an electric current through the gas, and that's enough to ionise it. For fusion, we need to heat that plasma up to the very high temperatures needed to actually bring the positive nuclei close together. So then you're going into high-temperature plasmas, and that's where the temperatures that are needed for fusion to happen, you couldn't have such a hot plasma in contact with a wall. So you could put a magnetic field in it,

24:34and then the plasmas, because they're charged particles in the presence of a magnetic field, they start to do really interesting things, and they spiral around the magnetic fields, and it essentially traps them. So that's a great way of moving the plasma away from the walls of whatever you're containing it in. So then you're reducing the problem of melting the walls, the vessel. But you also need to keep the particles in the same place for long enough for fusion to happen. And so if you're constantly leaking particles,

25:06it's just much less likelihood of fusion taking place. So they solve that problem by taking our magnetic fields and basically joining them up at the end, so you have this infinite way around a donut-shaped vessel. So you're reducing those end losses, but because you now have what we call a toroidal geometry, so you have this donut-like geometry, it causes other losses outwards towards the vessel. So again, the confinement is not perfect. And then the really important thing is we have a very high temperature gradient

25:38between the middle of the plasma, where we're trying to get the temperatures high enough for fusion to happen. So if you imagine we've got tens of millions of degrees at the centre of the plasma in this donut, and then the walls of the... On jet, I think, for example, was a big experiment near Oxford. The walls were held at 300 degrees centigrade, so there's a massive temperature gradient between the middle of the plasma and the edge of the plasma. And what's the distance, though, that we're talking about? And that was three metres radius. Three metres. So whenever you have

26:08these huge temperature gradients, I mean, you end up with something called turbulence, and turbulence introduces plasma losses, so again, it influences confinement. Can I recommend you maybe need to watch more Star Trek, because they're always getting breaches in the plasma manifold, and they seem to manage it. No. We'll talk afterwards. We'll have a look. I mean, we should look at Voyager. They got all the way home from the Delta Quadrant, all right?

26:32It's not... It wasn't a spore drive or something. It wasn't... They didn't use it. Oh, oh, I'm in pain. I'm in pain. I'm not familiar with this. Oh, is that something else? I'm not familiar with this. Yeah, no, that was Discovery. That was... Oh, that's Discovery. Oh, Brian, you look like an idiot. I'm not... What was the spore drive, then? The spore drive was... ..was a ship that we don't talk about, that transported along my telial networks and then ended up very far in the future, even though it's all in the future,

27:03but even further in the future, with Spock's sister on it, who now he then never mentioned again because he didn't know he had her when he first started. But there's a lot of show business because each time there's a little moment in this conversation. So we started off with Steps, then we had Palladium, then you bring in Neon, and then I notice when you say Particle Lost, you do Jazz Hands. So I feel that it's the most show-busy physics episode we've done yet, I reckon.

Plasma Turbulence

27:31Howard, getting back to the point. It sounds like at least a simple problem to state, which is we'd like to create a plasma, if that's the kind of fusion we're talking about, and we'd like to confine it, we'd like to hold it long enough, essentially. So why can't we just solve it? We know that fusion works because we see the sun doing it all the time. We know the conditions we have to achieve to make fusion work. What we have been struggling with over the decades is how to achieve those conditions.

28:02And before the fusion process takes over, one has to put in enough energy to spark it up. That churns the plasma up, and that generates this turbulence. Now, the turbulence is a really complex thing. You'll have pictures in your head about turbulence at the bottom of a waterfall, for example, and that's already pretty difficult. If you just look at all the different structures that appear in the bottom of a waterfall, big eddies, small eddies, you can imagine trying to understand that is a very difficult thing. We can understand that, but a plasma turbulence is different again because it has that physics,

28:34so it does have those sorts of churning away, the same as water would have. But in a plasma, remember, the particles are charged, and we are holding on to those charges with a magnetic field. And if those charged particles start jiggling around, as they would with turbulence, your charged particle jiggles around. If you move two charges relative to each other, you create an electric field. So jiggling charged particles around jiggles your electric field. You can also jiggle the magnetic field, and those jiggling electric fields, and those jiggling magnetic fields, feed back on the particles. And they feed back on them in a very special way.

29:06And the best way to think about this is to go to the beach and watch a surfer. And if you watch a surfer, and if the surfer does not paddle, the wave will just go under them, and they'll bob up and down. They're not tapping any of the energy of the wave at all. If a surfer paddles to match their speed with the wave, what we call a resonance, the wave will pick the surfer up and take them into shore, and the surfer is tapping the energy of the wave. Or the particle, as a surfer, is tapping the energy of the wave. Those resonances are happening all the time in plasma physics,

29:36and that interaction between energy in the wave and energy in the particles is happening all the time from all of these different resonances. But to understand those resonances, you not only have to understand where all the particles are, which is what you have to do for water, you also have to understand what their velocities are, which direction they're going in, how fast they're going. And so there's another three dimensions there. It becomes a six-dimensional problem. There isn't a computer in the world that can solve that problem. And so we have a whole bunch of very clever theoretical models which reduce the dimensionality of that

30:07to make them tractable on today's computers. And so we are starting to be able to predict what the turbulence will be and what the consequences of that turbulence are for the heat and particles leaking out through the magnetic field and starting to be able to design our tokamaks, as these machines are called, or stellarators, you might think as well. We can start to understand how best to design those so we can minimise that turbulence. I will make a not-so-bold statement if it wasn't for plasma turbulence. Fusion would have been working decades ago. Up to the point that we are now,

30:37it's been because it's really difficult to simulate. So we're just about managing to do it now. So it's had to be experimental.

30:48So maybe you could talk a bit about JET, which was a world-leading experiment in Oxford. But now, there's a really cool fact about JET, actually. JET reaches these temperatures. We can do 200 million degrees. That is the hottest place in the solar system, in Oxfordshire. So that's a really cool statement. But yeah, so how do you do an experiment in something that's 200 degrees centigrade? How do you see what's inside those plasmas? And we use lasers. You fire the laser in, and the temperature of a gas

31:18is how much your particles are jiggling about. If you heat it up, the particles jiggle around more and more and more. So now if you fire a laser into your plasma, and it hits a jiggling particle, it will scatter off that particle. And so you fire your light in at a very fixed frequency. When you measure it coming out, you find there's a width of frequencies that come out. And that width of frequencies tells you about temperature. But it's far from easy to do the experiments. It's far from easy to do the simulations. We need to do both and combine the two. So JET, you said it's about, what,

31:49three metres? Yes, three metres major radius. And then, so JET stands for the, it started as the Joint European Taurus. And ETA is the international, it originally was called the International Thermonuclear Experimental.

32:05Was it reactor? It was reactor. They used the word reactor. It's not a reactor. It's an experiment. But, and that, I think it's five metres. Six. Six, okay. It's very big. I've seen ETA. So it's a theatre-sized thing. It's a big object. So we have known for a long time that for the magnet technology that was available, that this much larger machine was required to reach the confinement. So the plasma is contained in something called a vacuum vessel. So it's a metal donut-shaped vessel.

32:36And it is usually built in eight different parts. And if they're being built by different people, they have to fit. And the tolerances are very, very small. So even just a few millimetres out on the welding, I think, can cause problems. And they don't perfectly fit because you have to create a very high vacuum in there. There can't be any leaking. Can I go back a step, just going back to turbulence? First of all, you said it's a six-dimensional problem. So what exactly are the six dimensions? You've got the three dimensions that we're living in here. And then the other three dimensions that you have to...

33:07So length, width, depth. Yeah, yeah. Of the confinement or of the particles themselves? Of the plasma. The same as in this room. But then the other one we're still pretty familiar with is just the velocity dimension. So you have to know which ways the particles are going. So there's another three dimensions about where you can move. So you can say, I'm here at any one position, at any one time, and give a spatial dimension about where you are now. So you can give your coordinates in this room. Yeah. But now you might be moving in a certain direction and you could be moving that way, that way, or that way. And that's another three dimensions.

33:38It's just three more pieces of information that we need to know about your position. Not just where you are, it's what direction are you moving in as well. And that's six? That's six. Your three spatial... Is that to anyone else in the room or is that like... Is that like the first three changes? Six numbers per particle. So this is what is determining the turbulence that you're trying to research and resolve. And am I right that you said that the larger the torus, the less problematic the turbulence is? No. So the plasma becomes large enough that the confinement is better.

34:09There's greater likelihood of fusion. You should say, it's not obvious, is it, that if you go... Because people might be thinking, it should be obvious. You go bigger, it's easier. But that was a difficult problem, right? It wasn't... It took a while to realise that, didn't it? Right, so there's been a lot of what we call cross-machine scalings that are looking at the effect of changing the size of the machine. So that is an empirical scaling which has shown that the confinement improves as the plasma size gets bigger. It's purely experimental, that. It's purely experimental. The new technology

34:40that will make a big difference is the high-temperature superconductivity for the coils. So the magnetic fields we can apply to these experiments, it was always limited by the use of copper coils. So with the advent of high-temperature superconducting coils, it's now possible to have much higher magnetic fields on tokamaks. And so that's a route to improving confinement. So that's a fairly recent development. They started work on that in the late 80s, but I think we've only seen

35:10actual application of it really in the last 10 years. You know what I find