YouSaid · the spoken record

David Kirtley

lines on the record: 180
first: 2025-11-17
most recent: 2025-11-17
sittings or episodes: 1
sources: podcast

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“But it's really important. And the good analogy here is a top Literally atop a spinning top. And so you have a top spinning on your desk. You know that it'll spin for a little while and then it will fall over. It is unstable. However, if you spin it fast enough, if you take a top and you spin it fast enough, put enough angular momentum, enough angular inertia into that system, it'll stay upright. Even though it wants to just fall over, even though it's unstable. And we do the same thing in an FRC. It's if you can drive it fast enough, if you can add enough kinetic energy and inertia to the particles, it will stay stable. However, you can do another really key thing. We are not limited now to having a very skinny top. We can actually make it much bigger. So the good analogy here is if you have a coin and you know you're spending that coin, if you spend it faster and faster, it'll stay spinning longer. However, eventually it'll slow down and fall over. But if you had a roll of duct tape,”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“We don't have that access. We don't have any mechanical things inside these fusion systems. There are 100 million degrees. You can't put any mechanical things inside them. And so we have nothing to hold on to it. And so it's unstable. So when you learn about the FRC, that's the first thing you learn. And it took us a number of years to learn about a parameter of how to make them stable. And that's pretty fundamental, but most people who've heard of an FRC haven't understood this really key fact. And so we have a parameter we call S star over E. And we're getting really into the physics weeds here.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“And so, the good way to think about this is a tokame and accelerator are stable because those plasmas that are going around in the donut, there's a force on that donut. But that plasma donut is very well held by all those magnetic fields, by all those magnetic coils. If it tried to move, it would be confined by that magnetic coil. But in an FRC is unconfined. So the plasma is confined, but the whole topology can do something what is called tilt is that this whole plasma donut, because it's under pressure, can just turn over. The way I think about this is think about the emotor is a good example. An armature in the center of your motor, you have a spinning armature. You have this spinning magnet on the inside, and it is held by the main axis of the magnet. It can't go anywhere.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Density and temperature of the fusion fuel. And that's really critical. All plasmas have all fusion plasmas have some beta, some number. The FRC has one of the highest betas, beta equal one. However, what you also learn in school when you learn about beta the first time is you learn that high beta plasmas are typically unstable.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Doughnut to compress it, the plasma particles on the inside push back. And what's really interesting is you have an equation for magnetic pressure, which is b squared over 2 mu naught. The magnetic field squared is the external magnetic pressure. Any magnetic field anywhere generates this pressure. But the plasma particles themselves also have a pressure. This is the ideal gas law. And we use the definition in KT, density Boltzmann constant and temperature for pressure. And in high beta, they're the same. B squared over 2 mu naught is NKT. So for known magnetic field, I know what the density and the temperature of the plasma is. And just to circle back to it, when we talked about fusion, we talked about it had to be hot enough and it had to be dense enough. And that's in and that's T. Now I have a very clear equation between magnetic field.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Plasma beta is the ratio of the magnetic pressure to the particle pressure. And so what that fundamentally means is I talked about how you have a magnetic field. And in that magnetic field, plasma is trapped on that magnetic field. But it's not very well trapped. It can escape. It can leave either down the ends. It can freely travel, or it can also travel across the magnetic field. And so we have a term called plasma beta, which gives us an understanding of how well trapped that plasma is. So as you apply a magnetic pressure, a magnetic field to this plasma, it pushes back and does it push back a little or does it push back a lot. And for a field reverse configuration in one of our plasmas, beta is very close to one. In fact, usually by definition, one at any point in the system, which means that every time I apply a magnetic force on this”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“This electromagnetic force induces an electrical current on the armature, on the shaft. And this is getting into the details, but into the armature of an electrical motor, that actually is what spins. And so the outside of a motor doesn't spin. You have flow electrical current through it. And the inside does spin. That electromagnetic force is what is spinning that armature. In our case, we're inducing an electrical force in that electromagnet, and that's putting electrical current just like in the armature into that plasma. And we can use that force to do interesting things. So that electromagnetic force can compress the fusion plasma. It can expand the fusion plasma. But here's the problem. It's unstable. And so this is something you learn very early in your graduate work as a student infusion is you learn about plasmas that are called high beta plasmas.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Magnetic field, and that magnetic field has pressure. And this is the other thing that's really interesting. So we talked about how this theta pench compresses a magnetic field. It applies a pressure on the outside. But the plasma itself has a pressure on the inside. And it has both a particle pressure, literally the particle's bouncing think about hot gas in a balloon. The particles expanding, the ideal gas law expanding and contracting inside a balloon, but they also have a magnetic pressure. They have the electromagnetism is pushing back. And so I like to think about this as the motor in a Tesla. In your electric car, you have a motor, electric motor. And what that motor has is a series of windings. Those windings, you flow electrical current. In this case from a battery, hit the gas. Electricity flows from the battery into the motor, into those windings, and it generates an electromagnetic force, a Lorentz force is what it's technically called.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“And there's the hard part because I just described a solar flare And yes, we've seen the pictures of them, but we've also watched them and they appear, they fly away from the sun and then they go away. And that's not what we want infusion, right? We want to be able to control this. And so that's the hard part of the job. And so that's what we've spent the last number of years learning how to do ourselves and others on these pulsed closed field FRC systems. Let's first talk about how to make them. And then we'll talk about how to make them stable because they're two different things and we spend a lot of time on both. So we talked about time scales. You have to reverse the field. You have to change the electrical current in a millionth of a second. And so how do you do that? So I've described this system as you have a series of magnets. You have a magnetic field on the outside. And then on the inside of this, you have this doughnut, this FRC that has its own electrical current. And we didn't talk about this yet, but it's generated.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“You look at the sun, we see solar flares. And in a solar flare, we've all seen the pictures of the photosphere, of the sun, and this large arc of plasma coming out. That plasma has current, electrical current flowing in it. And then we see this solar flare rip off of the sun. And that solar flare then can flow throughout and continue into the solar system. And for a little while anyway, it makes something called a plasmoid. That plasmoid is in fact electrical current flowing in the plasma generate a magnetic field and holding it for longer than it would otherwise. And so we've observed these for hundred years. And we've known about these plasmoids for a long time. And there's researchers that have tried intentionally to make them. But fundamentally, that's what we do every day is make one of these self-organized closed field plasmas.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“And that's the key. And so, in your tokamak and your donut, and in your funky donut, your stellarator, you make the magnets and you trap your plasma in it. In an FRC, you make the plasma, which makes the magnets. And it traps itself. And the craziest part of this, in my mind, is that we actually see this in nature all the time”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Current is flowing in this transformer, if you want to think about it primary and secondary. And here's the craziest part of it. Electrical current, how did I describe a magnet? An electromagnet is a loop that has electrical current flowing in it that generates a magnetic field. And for a theta pinch, and for a mirror and for a tokamak, in that magnetic field, the plasma gets trapped. In an FRC, this electrical current is the plasma. And that plasma then generates its own magnetic field. And it's then trapped on its own magnetic field.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“In this condition, you have a conductor, an electrical conductor, where current can flow, and you have an electrical current flowing on the outside, electrical current flows on the inside. And in that case, I've described two pieces of metal. Now let's go one step further, and that inner conductor is not a piece of metal anymore. It's one of these high temperature gases, this plasma, this charged particles. So now you have current electrical current flowing in the plasma. This is really, really interesting. We talked about these charges moving back and forth. Well, moving electrical charges is current. So in every plasma condition, we've talked about the tokamak, the theta pinch, the stellarator, there's electrical current flowing in the plasma. But in the field reverse configuration, you have a lot of electrical current flowing in the plasma, massive amounts of it. And that's the key. So you have this center core where electrical”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“So, what I like to do is use an analogy here of once you've made it. It's actually somewhat straightforward to understand. Getting to it is tricky and how they discovered it the first time is absolutely amazing. But once you've made it, it's a lot more straightforward to understand. So in a magnetic coil, when you have a round electrical coil, you have electrical current flowing in that coil. And if you have a conductor, if you have a metal inside that coil, and this is called Linz's law, in one of the Maxwell equations, is that as you have electrons and you have current flowing in that coil and equal and opposite electrical current is induced in a piece of metal nearby. This is the same thing that happens in a transformer where you have a primary on a transformer and you have electricity flowing it and you have a secondary where electricity flows exactly the opposite direction. We use this every day in our lives.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“This is hard, and it's only we can only do it now because of semiconductor switching, because we can move things, we can switch things like the transistor in every CPU and a computer switches at a gigahertz. That means in a nanosecond. It's switching in a billionth of a second. And so now, which we didn't in the 1950s when these theta pinches were invented, but now we have the semiconductors to be able to do that.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“You have to reverse the electrical current faster than a million degree, which is a very hot gas particle, can move. And so that means we have to do it on the order of a millionth of a second. To do it in a millionth of a second And so, in practice.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Reconnects internally. And so now, what you're left with is an outside magnetic field, an electrical coil, and inside the plasma where now it was before it was moving along, it's now moving internally.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“The direction of the magnetic field. And this is what we call field reversal. And this is really the key that you start with the plasma going in one direction and then very rapidly you change the direction. You change the direction and reverse the direction of that field. And something really interesting happens, which is the plasma, this fusion fuel, these charged particles, which are trapped on the magnetic field lines that are moving back and forth, you change the direction. What that means is that you're trying to take that electrical current and that magnetic field and reverts its direction, flip it, but it can't flip fast enough that the plasma is sitting there and you can't move the particles. And so what's really interesting is what happens is that because the particles can't move, but you've now flipped the direction of the magnetic field, you've inverted it, something really, really unique happens, which is that the plasma itself”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Is happening here. This is an accidental discovery in plasma physics that something new is happening. And what we discovered is we now call the field reverse configuration. There's numerous programs of FRC, field reverse configuration programs both at national labs. There's actually a number of private companies now people building field reverse configurations. And they have some really unique properties. But fundamentally, talking about the main difference, I describe the solenoid with magnetic fields throughout the center of that volume and plasma trapped going back and forth. But some other things can happen, which is really interesting. And what they discovered early is if they have field going in one direction, so the plasma, the electrical current is going around the loop, and the plasma is going back and forth along this magnetic field line inside that solenoid, inside that theta pench. But then they change.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“And so they, those pioneers, went in a different direction. And they started down the laser inertial path of saying like, okay, well, we can't do these electromagnetic pinches, but we now have, this new thing has invented the laser, which turns on in a nanoseconds. It's vast. It's interesting. Let's go down that path. And it's not, you have to fast forward a couple of decades to researchers found with some of these theta pinches when they're operated in a very specific way something else happened, something new happened, and that these plasmas where before they squeezed them very hard and just like squeezing a tube of toothpaste, they squirted out the ends. Now it didn't squirt out the ends. It actually pushed back. It stayed confined. It stayed trapped inside that linear topology, even though the ends were open, the plasma didn't leave. And so there was a large amount of programs of like, what?”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Theta pinch topology. Can you just squeeze the plasma down fast enough, hard enough? This was 1958, the transistor was sitting in the laboratory, and they were commuting, they were turning on millions of amps of electrical current. And they were doing it. We haven't talked about the timescales, but they were doing it in millionths of a second, microseconds, megahertz speeds. And this was in 1958. No transistor, no CPUs, and no electrical switches, none of the things that I take for granted every day. And so they were able to show at that time the highest performing fusion systems. They got to temperatures. They didn't get to 100 million degrees, not quite then, but they got to 50 million degrees. They were outperforming everything else in fusion, but they reached a technical limit where they just could not build it anymore.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Get closer and closer and closer together so you increase the density. And now fusion starts to really happen. But they ended up hitting a technological limit. So, this is the part that I look back and I look at the pioneers that in 1958 there were some pioneering work done, and this was in California, what later became Livermore Labs. There was also some work done at”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Imagine hot gas in a balloon tries to get out the ends. You could not hold it tight enough at the ends to keep those particles in. And in fact, the problem is the hottest ones were the ones that would escape. And so you do a good job of heating it and they'd all leave out the ends. So then the next iteration has said, okay, well, why don't we just not try to hold on to it very long? Why don't we squeeze it? And so rather than just holding it constantly, let's now crush it. So we built this solenoid. We pinched the ends and then we crushed it. And what I mean by crushing it is not actually like crushing any magnets or changing the topology or moving any parts, but just rapidly increasing the magnetic field. And so going from a magnetic field that's just holding it to now taking all those particles, if you imagine they were in a streaming around together and then rapidly increasing the magnetic field so that those particles”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“And that became, that evolved into the Stellarator and the Tokamak, different ways of taking those solenoids and wrapping them around so that the plasmas go around and around in that magnetic field and those charged particles are held long enough that fusion happens. But there's a different way to do it. And so the theta pinch was what was born in the 1950s of take this magnetic field and, oh, they're trying to escape. Great. Let's not let them escape. Let's close the bottle. Let's close the ends. And so we make the magnetic field much stronger at the ends. This one was called the mirror. And so the idea was that the particles would bounce in between. And that worked and they got hotter and hotter and hotter. But guess what? As you kind of would imagine, as this mirror topology, this linear topology, the pressure increased inside the particle pressure, the particles tried to push back on the magnetic field. They were trying to escape now. They're getting hotter and hotter. And just as you imagine.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Solenoid. Here's the challenge. Those particles, as they're sitting in that magnetic field in this nice magnet, escape. They leave out the ends because there's nothing holding the men. Great. So that makes sense. And so that doesn't work, okay? So then the next approach is say, well, one branch of fusion said, okay, well, to solve that, why don't we take this solenoid and bend it around? Let's just make it a big donut. So as they're escaping, they go around and around in a circle. Great, that's a great approach. And so one branch of fusion went down that direction.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“So, to understand that, we can actually go back in history a little bit and think about the evolution of some of these approaches to fusion. And so from our perspective, we look at the technology that we use as built on physics experiments that were very successful in the 1950s. And in those systems, the earliest pioneers of fusion said, I know, we understand the physics, we have to take these gases, heat them to 100 million degrees, and then confine them, push them together so that fusion happens. And so what is the best way to do that? So some of the earliest programs we call them theta pinch. And what those programs were were a linear topology because we knew how to build these magnets. It's called a solenoid, where you take a series of electric coils, you run electrical current through them that generates a magnetic field. Great. So you have a magnetic field. Now you add your fusion particles. Okay. So you've added fusion particles to this.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“And so that's what happens when you put particles in a magnetic field and you try to hold on to it. The challenge is that's really hard to hold on to them long enough. These particles are moving around. They're moving at very high velocity millions of miles per hour. They're colliding with each other and they're getting knocked off and getting knocked away. So we've talked about inertial fusion where you try to confine a fusion plasma by crushing it as fast as possible. And magnetic fusion where you just simply have a magnetic field and your goal is to hold on to it for as long as possible. But there's another way to do fusion. And in some ways it's one of the earliest approaches for fusion that was successful. As scientists and engineers maybe were not too creative with the terminology, we call the technique that Helion uses magneto inertial fusion because it does a little bit of both.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“The Tokamak and the accelerator are both magnetic systems. Their goal is to generate this magnetic field and hold on to the fusion fuel long enough. Like I mentioned, these charged particles are trapped on the magnetic field. In fact, they're oscillating. We call that a gyro orbit as the radius that they oscillate around this magnetic field. And we've been talking about atomic physics where everything is at this nanoscale. Gyro orbits are not. Gyro orbits for these fusion particles are measured in inches. And so they're on a scale that we can see and measure and understand really intuitively. And in a magnetic system, your goal is to simply trap as many of these particles as you can for long enough and heat them so they're hot enough so that they bang into each other. They collide enough that you're doing fusion. And you're doing enough fusion to overcome as fast as you're losing those particles.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“In infusion, the physics we're using is actually quite old, that the fundamental electromagnetic physics is 1800s physics. The fundamental atomic physics is early 1900s. And so the fundamental physics of how these work is very well understood. Putting them all together into a power plant, that's hard. And so you can do the math. You can do the math every introductory grad student does the math on a stellarator and say, this is all I need to do. I just need to make a magnetic coil in this very complicated shape. And then fusion will happen. However, doing that in practice is actually quite challenging.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“The charged particles, the northern lights, is a charged particle trapped in the Earth's magnetic field going around the Earth's magnetic field. And in the same way in fusion, we do the same thing here on Earth, but in a smaller direction where we trap these particles on magnetic fields. And they can go around and stay a trap to that magnetic field line.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“That magnetic coil has some really special properties. And we take advantage of those properties to do fusion. And some of those properties are not intuitive. So here's one of my favorites. When you have an electromagnetic field, you have this coil with electricity going around it and you have a magnetic field inside of it. And then you have a test particle, a charged particle, an electron or an ion, which is if you imagine to generate this, I have a coil with electrons moving around it. But if I put one in the middle of it, in this magnetic field, some really interesting things happen, that electron or that ion, that charged particles, what's called magnetized. And what magnetized means is that it's trapped on that field line. In fact, even really more interesting is that it oscillates around that field line. And so the way I think about this is if you think about the Earth's magnetosphere again and you think about”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Currents is a little bit different. And what we do is that we have a loop of wire. And the simplest way to think about it is literally around loop. And in that loop, you have electrons. You have an electrical current that's running. And when electrical current, this is some of Maxwell's equations that we discovered in the 1800s, that when you have an electrical current in a wire, it generates a magnetic field inside that wire. And so when you look at fusion systems, you always have these big magnetic coils with large amounts of current. We don't run a little bit of current. In our systems, we have hundreds of mega amps of current. If you think about at your house, you have your breaker box with 200 amps or maybe a 400 amp breaker box and rerun 100 million amps of electrical current. So massive amounts of electrical current to be able to do this. So that magnetic field that's generated inside”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“In a magnetic system, your goal is not to push together those particles as fast as possible. Your goal is to hold on to them for as long as possible. And to do that, we use magnetic fields. So let's take a step back. What is a magnetic field? In an electromagnet, there's a variety of ways to make a magnetic field. One of the most famous I think everyone is familiar with is Earth itself. Earth has what we call the magnetosphere, which is the magnetic protection that's generated actually by the core of the Earth. But we have a magnetic field around the Earth. And that magnetic field protects us from particles coming from the galaxy, galactic cosmic rays, and solar particles that would come to Earth. That magnetic field, when you run a compass, you see the magnetic field from the Earth. So we know it's happening. It's all over. But how we generate it with electricity.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Favorite, and so we'll talk about those graduate student infusion, the stellarator is the first thing you learn about. Because there's a mathematical solution for a stellarator that solves perfectly. And you can write it out and you can solve it and analytically it's very simple. Building one is very hard. And so it's taken humanity a number of decades to be able to build stellarators. And we can do it now with the Wendellstein 7X that came online in the last few years being the premier stellar in the world.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Actually, it has quite a different profile, which is an interesting thing to talk about. But in public funding and federal funding in the United States, there's two mainline programs called inertial fusion and magnetic fusion. And in inertial fusion, what you're trying to do is bring together and push together by a variety of means, physical means, those particles, you push them together. The most common is called laser inertial fusion. Our colleagues at the National Ignition Facility did this really well and made world records in the last few years for being able to demonstrate you can do this and do it at scale, where you take very high power lasers and pulse them together to combine them to diffusion for a pulse for a very short period of time, nanoseconds, billions of a second. The other extreme, and you mentioned tokamax and stellarators, stellarators are actually my”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“So there are a number of ways to do fusion. And fundamentally, in all fusion approaches, you're trying to do the same fundamental physical process, which is take these lightweight isotopes, heat them up so that they can move at high velocity over 100 million degrees, bring enough of them together. We call it density, enough of them together in a certain volume so that you have reactions happening at a higher rate and keep them together long enough that they are able to collide into each other and do fusion and release energy. That's the fundamental core. Now, how you do that, how you bring those particles together, how you hold them together long enough, there's a wide range of technologies that as humans, we've been exploring since the 1950s. And I think about several main categories. If you look at the fusion funding out there, government funding in the world, private funding.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“And work with the state agencies to license these fusion particle accelerators. We were, as far as we know, the first licensed fusion system ever as a particle accelerator for those first systems. First license we had was in 2020. We then have gone on and now licensed several of our fusion systems that we've built that do fusion, both the shielding as well as some of the fuel processes.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“We've even been building fusion systems that do fusion a long time. And at some level, they got powerful enough doing enough fusion. We started building these shields and shielding them like a particle accelerator. And I went to the regulatory bodies that regulate part 30. This is in Washington state. It's the Department of Health. And so I went to the Department of Health and said, here's an application for a fusion generator shielding permit as a particle accelerator. And the very first question I got asked was, great, where do the patients go? Because the standard form had a patient as a hospital, the patient dose for the particle accelerator, and then the shielding. And we talked all about the shielding and the operators, which is very similar for a helion system. We said, no, no patients at all. No one's inside this thing. Our goal is to generate electricity one day. This was a lot of years ago. And we are able to go through.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Year called the Advance Act, which is really powerful because it says for the very first time how the US government, leading the way on this, which I'm really proud of, will regulate fusion. And this gets into a little bit of the details, but the way the nuclear regulatory commission regulates nuclear things in the United States is in these different sets of statutes. And nuclear reactors are regulated under something what's called Part 50. And there's a lot of variety of the regulatory language around that, but most of it is to handle special nuclear materials, uranium and plutonium. But fusion is not. Fusion is regulated under something called part 30. And part 30 is how hospitals are regulated. Story related to that.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“So the fusion reaction itself is still fundamentally an atomic reaction. And so during this reaction, you do create ionizing radiation. You create x-rays, you create neutrons, and you create all these charged particles. The charged particles themselves for fusion reaction are all contained in the fusion system. And the X-ray is similar to think about a dentist's office, although a lot more than that, but that type of same X-ray and X-ray energy is absorbed by the fusion system. But the thing we do care about is those neutrons. And so we do have in a fusion system activation during its operation, neutrons are made and leave. And so we have to shield these fusion systems during their operation. And so this is very similar. In fact, this is a lot of the work we did with the Nuclear Regulatory Commission over the last number of years, that there was a landmark agreement that happened for the NRC that then was codified into law last.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“One second of fuel at any time in the system, and having a tank of deuterium, which we have around all the time, can't do fusion by itself. It needs that complex system.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Is that if something really catastrophic happened for whatever reason, you have all that fuel that's not in the system. And fusion is so hard to make happen, you hit it with a meteor, you do anything in that nature, and fusion doesn't happen. That hydrogen, that heavy water, that deuterium just goes back into the environment safely and cleanly without issue. And so that's the fundamental safety mechanism of fusion. And you can compare that with other types of power plants, oil or coal power plant. You might have a large pile of coal that then catches fire and burns. And it's not catastrophic, but you have a large coal fire for a long time releasing toxic fumes that you may have to deal with. And in nuclear power and efficient power plant, you may have several years of fuel sitting in the core. And in that case, if something bad happened, you have all that potential energy for things to happen. But in fusion, you have literally...”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“And so the analysis we did is assume you have a fusion power plant that's operating. And then at any one time, a meteor strikes it. The whole thing is vaporized. What is the impact of that? So this is worse than you could ever imagine an actual physical scenario, but let's start there. And the answer is you don't need to evacuate the populace nearby the fusion power plant. One of the keys, I think, that I come to when I think about this is the fuel in that in a fusion generator, you are continuously feeding in this hydrogen, these deuterium fuels. And at any one time in a helion fusion system, and most fusion systems, you have one second of fuel in that system. And so what that means is if you stop turning fuel into that system, fusion just stops. But what it also means”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Yes, fusion power is fundamentally safe. The physics and the reactions of the fusion system itself means you don't have runaways. And so we've talked about some of the human factors around power plants and power systems, industrial scale systems. And that's something that we build into the design of these from today. We look at how these systems might fail. And in fact, some of the analysis we do is we did this analysis for the nuclear regulatory commission over the last few years looking at how do you regulate fusion power as we're building the first fusion power plant. We need to make sure we're regulated safely. And so we spent a lot of time doing the technical case and the political case in the United States of how to regulate fusion.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“I certainly do that. The fuel is in seawater all over Earth. Everybody has deuterium. Everybody has it. And so you can't have a monopoly on the fuel and no one can control the fuel and no one can turn off the fuel. No one can cut a pipeline. Like that just cannot happen with fusion. And so if we can deploy those plants and we can deploy them quickly, then it It decouples the ability of anyone or any few countries to control energy.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“Question I would want to ask is what would you do if we could deliver for you low cost, clean, industrial scale tens or hundreds of megawatts of fusion power that's low cost, clean baseload and doesn't have the geopolitical consequences of uranium and plutonium, of fissile material. Would you do there? How would that change your view of the next 30 years?”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“That having a lot more centrifuges happening all over the world would lead to more weapons, at least the possibility of it. And so they are pushing us as fast as possible. Go build fusion generators and get them deployed everywhere. Not just in the United States, but all over the world so that we're building fusion power and that's meeting humanity's needs, not this other thing. And so I was really pleasantly surprised. We've written a number of papers and worked with those communities on this of what does it mean? How is fusion power safe and can't be used for nuclear weapons?”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“World, because we know the challenges the geopolitical challenges that happen. And we went to those proliferation experts, and we were worried they would have the sort of the same historical question of like, well, the word nuclear is in fusion, so therefore it must be related. And in fact, the total opposite happened. What they told us is, please, please go develop fusion power plants absolutely as fast as possible. The world needs this. and the proliferation experts were telling us that otherwise people would start enriching uranium throughout the world and we'd be building enriched uranium power plants because we need the electricity that's clean and baseload but in those processes they'll be making fuel that could be one day used for atomic weapons for nuclear weapons and they were worried that that”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“And if you take away that fizz out material, that nuclear fission reaction, the fusion reaction doesn't happen at all. In fact, there's been researchers that have over the decades tried to make an all-fusion bomb and been very unsuccessful at it. The physics and the engineering don't support it. They can ever happen with our understanding today. The topic we're talking about is more broadly called proliferation. And this is the creation of nuclear weapons in the world and the distribution of those weapons. And something we know as physicists and engineers is that fusion can't be used to make nuclear weapons. We know that. But that is not sort of widely known. And part of what we win out to do is work with the proliferation experts in the world, the people who work to prevent nuclear weapons from being made, being created, being shared throughout the world.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source
“It will not just create a reaction, but it will create a supercritical reaction that will then continue and grow and release a tremendous amount of energy all at once. And that is a bomb. That is a bad situation. And that is what we want to avoid. A lot of the key is recognizing that even though there are things called fusion bombs, the H-bomb, the hydrogen bomb, the hydrogen bomb has uranium in it. It's still a fission bomb. And so how this fundamentally works is that you have a fission reaction, a primary. And that creates radiation that induces a fusion reaction with a small amount of fusion fuel that then boosts that uranium reaction again. And so most of the energy, in fact, 90% of the energy in an H-bomb is all still from the uranium reactions themselves.”
2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source