#353 – 丹尼斯·怀特：核聚变与能源的未来

你无法超越这个规律。

Like you can't beat that.

所以无论你做什么，如果你在思考——我为什么要关心这个？

So whatever you do, if you're thinking about, and why do I care about this?

因为质量就像是燃料，对吧？

Well, because mass is like the fuel, right?

这意味着收集燃料所需的资源，将其聚集在一起，处理它，以及它可能对环境造成的影响。

So this means gathering the resources that it takes to gather a fuel, to hold it together, to deal with it, the environmental impact it would have.

核聚变每次反应释放的能量总是能达到传统能源的2000万倍。

And fusion will always have 20,000,000 times the amount of energy released per reaction that you could have those.

正因如此，我们认为它是最环保的终极能源。

So this is why, you know, we consider it the ultimate environmentally friendly energy source is because of that.

那么广义上，是否可以将质量视为能量的一种储存形式？

So is it correct to think of mass broadly as a kind of storage of energy?

是的。

Yes.

你提到它很环保。

You mentioned it's environmentally friendly.

核聚变是一种能源。

So nuclear fusion is a source of energy.

它廉价、清洁、安全，燃料获取便捷且供应近乎无限，不产生温室气体，据称放射性废料也极少。

It's cheap, clean, safe, so easy access to fuel and virtually unlimited supply, no production of greenhouse gases, little radioactive waste produced allegedly.

嗯。

Mhmm.

能否详细说说为什么它廉价、清洁又安全？

Can can you sort of elaborate why it's cheap, clean, and safe?

我从最简单的'廉价'开始解释。

I'll start with the easiest one, cheap.

目前它还不廉价，因为尚未实现商业化规模生产。

It is not cheap yet because it hasn't been made at a commercial scale.

欢乐时光总觉短暂。

Rime flies when you're having fun.

是的。

Yes.

对，对。

Yeah, yeah.

但是，不是

But yes, not

还。

yet.

我们会

We'll

谈论

talk about

实际上，我们会回头讨论这个问题，因为用更经济或更技术准确的术语来说，经济性目前确实是聚变面临的主要挑战。

Actually, we'll come back to that because this is cheaper or a more technically correct term that it's economically is really the primary challenge, actually, of fusion at this point.

但我想我们可以回头再谈。

But I think we can get back to that.

你刚才说的其他几点是什么？

So what were the other ones you said?

非常便宜，实际上当我们说便宜时，我们考虑的是渐近意义上的。

So so cheap, we're we're actually, when we're talking about cheap, we're thinking like asymptotically.

就像，如果你展望几百年后，那某种程度上是因为可利用的资源有多么丰富。

Like, if you take it forward several hundred years, that's sort of because of how much availability there is of resources to use.

燃料的。

Of the fuel.

是啊。

Yeah.

关于燃料的。

Of the fuel.

我们应该把这两者分开。

We should separate those two.

燃料会...所有的燃料都已经很便宜了。

The fuel will all the fuel is already cheap.

基本上是免费的。

It's basically free.

对吧？

Right?

你说的'基本上是免费'是什么意思？

What do mean by basically free?

如果我们用聚变燃料源来供能，假设我们周围只有聚变发电厂，那么每人每年的燃料成本大概只有0.1美元。

So if we were to be using fusion fuel sources to power your and it's like that's all we had was fusion power plants around, and we were doing it the fuel cost per person are something like $0.10 a year.

这是免费的。

It's free.

好吧。

Okay.

这就是为什么在某种程度上，我觉得人们很难理解聚变——因为他们看到这个就会说'哦，如果燃料免费，那能源就是免费的'。

This is why it's hard to, in some ways I think, it's hard to understand fusion because people see this and go, oh, if the fuel is free, this means the energy source is free.

因为我们习惯了这样的能源——我们投入资源钻井获取天然气或石油，或者砍柴，或者制造煤炭、寻找煤炭这类事情。

Because we're used to energy sources like this, so we spend resources and drill to get gas or oil, or we chop wood, or we make coal, we find coal, or these things.

核聚变，这就是核聚变的本质。

Fusion, this is what makes fusion.

而且，它不像风能和太阳能那样是间歇性的可再生能源。

And it's also, it's not an intermittent renewable energy source like wind and solar.

这使得它难以理解。

This makes it hard to understand.

那么，如果你说燃料是免费的，为什么能源不是免费的呢？

So if you're saying the fuel is free, why isn't the energy source free?

这是因为必须应用必要的技术来重现实际上存在于恒星中心的条件。

And it's because of the necessary technologies which must be applied to basically recreate the conditions which are in stars, in the center of stars, in fact.

宇宙中只有一个自然地方会发生核聚变能，那就是恒星的内部。

So there's only one natural place in the universe that fusion energy occurs that's in the center of stars.

因此，根据重现这些条件所需技术的规模和复杂性，这将带来一定的成本。

So that's going to bring a price to it depending on the size and complexity of the technology that's needed to recreate those things.

我们会详细讨论的。

We'll talk about the details of Yeah.

我们会搞清楚的。

We'll get it.

技术以及哪些部分现在可能昂贵，哪些部分可能在两百年后仍然昂贵。

Technologies and which parts might be expensive today and which parts might be expensive in two hundred years.

没错。

Exactly.

它将带来一场革命，我对此深信不疑。

It will have a revolution, I'm I'm certain of it.

那么关于清洁能源。

So about clean.

清洁能源的核心在于，它本质上将氢转化为氢的较重形态——我们地球上最常用的形式，并进一步转化为氦及其他产物，但主要残留物是氦。

So clean is, at its heart, what it does is converts it basically converts hydrogen into its heavier forms of hydrogen, the most predominant one that we use on Earth, and converts it into helium and some other products, but primarily helium is the product that's left behind.

氦气，安全惰性气体，你知道的。

So helium, safe inert gas, you know.

事实上，这正是太阳正在进行的活动——最终会因产生过多氦气而自我熄灭。

In fact, that's actually what our sun is doing, is eventually going to extinguish itself because it'll just make so much helium that it doesn't do that.

从这个意义上说，它是清洁的，因为燃料燃烧本身不会直接排放碳或污染物。

So in that sense, clean because there's no emissions of carbon or pollutants that come directly from the combustion of the fuel itself.

而且安全。

And safe.

安全，没错。

Safe, yeah.

我们讨论的是极高的温度。

We're talking about very high temperatures.

是的。

Yeah.

对。

Yeah.

这也是反直觉的地方。

So this is also the counterintuitive thing.

我之前提到的温度约5000万度，实际上我们真正瞄准的是接近1亿度的温度。

So I told you temperatures which are like 50,000,000 degrees or It actually tends to be more like about 100,000,000 degrees is really what we aim for.

那么100,000,000度的高温怎么可能是安全的呢？

So how can 100,000,000 degrees be safe?

它之所以安全，是因为这个温度远超地球上任何物质的温度——要知道地球环境大约只有300开尔文，也就是几十摄氏度。

And it's safe because this is so much hotter than anything on Earth, where everything on Earth is at around 300 Kelvin, you know, it's around a few tens of degrees Celsius.

这意味着要让介质达到如此高温，必须将其与地球环境完全隔离。

And what this means is that in order to get a medium to those temperatures, you have to completely isolate it from anything to do with terrestrial environment.

基本上它不能与地球上任何物质接触。

It can have no contact, like with anything on earth, basically.

这就是我刚才描述的技术原理。

So this means what we this is the technology that I just described.

本质上，这项技术是将燃料与地球环境完全隔离，使其完全感知不到处于地球环境。

Fundamentally, what it does is it takes this fuel and it isolates it from any terrestrial conditions so that it has no idea it's on Earth.

它不会接触任何处于室温的物体。

It's not touching any object that's at room temperature.

包括

Including the

安全壳建筑的墙壁。

walls of the containment building.

包括安全壳建筑或容器的墙壁，甚至是空气等任何物质。

Including the walls of the containment building or containment device, or even air or anything like this.

正是这个特性确保了安全性，其实还有另一个层面的原因。

So it's that part that makes it safe, and there's actually another aspect to it.

但这个基本原理已经让它如此安全。

But that fundamental part makes it so safe.

核聚变的主流方法同样要求极高的温度，但在我们观察的发电装置中，任何时刻的粒子数量都极其稀少。

And the mainline approach to fusion is also that it's very hot, but there's very, very few particles at any time in the thing that we view the power plant.

实际上更准确的说法是：单位体积内的粒子数量非常少。

Actually, the more correct way to do it is you say there's very few particles per unit volume.

比如在一立方厘米或一立方米这样的空间里。

So in a cubic centimeter, in a cubic meter, something like that.

所以我们可以这样做。

So we can do this.

虽然我们通常不会意识到空气由原子构成，但它确实存在密度——当我挥手时，能感受到空气拂过面颊的阻力。

So right now, although we don't think of air really as there's atoms floating around us, there's a density, because if I wave my hand, I can feel the air pushing against my face.

这意味着我们处于某种流体或气体的包围中。

That means we're in a fluid, or a gas, which is around us.

这种介质每立方米含有特定数量的原子。

That has a particular number of atoms per cubic meter.

对吧？

Right?

实际数值大约是10的25次方。

So this actually turns out to be 10 to the twenty fifth.

也就是1后面跟着25个零，每立方米的原子数。

So this is one with 25 zeros behind it per cubic meter.

我们可以这样估算一立方米的大小，比如这张桌子的整体体积。

So we can figure out what a cubic meter is about like this, the volume of this table, like the whole volume of this table.

非常好。

Very good.

就像核聚变，这样的技术有几种。

So like fusion, there's a few of those.

主流核聚变技术，比如我们在MIT研究的这种，单位体积内的粒子数会比那种少十万倍。

So fusion, like the mainstream one of fusion, like what we're working on at MIT, will have 100,000 times less particles per unit volume than that.

这非常有趣，因为它虽然温度极高，达到一亿度，但物质却极其稀薄。

So this is very interesting because it's extraordinarily hot, 100,000,000 degrees, but it's very tenuous.

从工程和安全角度来看，关键在于单位体积内储存的能量多少。

And what matters from the engineering and safety point of view is the amount of energy which is stored per unit volume.

因为这决定了可能发生的情景，也是你最需要担心的。

Because this tells you about the scenarios, and that's what you worry about.

当这类能量突然释放时，后果会怎样，对吧？

Because when those kinds of energies are released suddenly, it's like what would be the consequences, right?

所以这种技术的后果基本可以忽略不计。

So the consequences of this are essentially zero.

因为其蕴含的能量还不如烧开水的能量多。

Because that's less energy content than boiling water.

是因为密度低吗？

Because of the low density?

因为

Because of

密度低。

the low density.

水的密度大约是这种物质的一亿到十亿倍。

So if you take water is at about 100,000,000 to a billion times more dense than this.

所以尽管温度低得多，它实际上仍含有更多能量。

So even though it's at much lower temperature, it's actually still, it has more energy content.

因此，你看，我解释这一点的方式之一是：想象一个为马萨诸塞州剑桥市供电的发电厂——虽然你不会直接这样做，但如果你这样操作，实际上会熄灭聚变反应，因为它会立即变得太冷。

So for this reason, you know, one of the ways that I explain this is that if you imagine a power plant that's like powering Cambridge, Massachusetts, like if you were to, which you wouldn't do this directly, but if you went like this on it, it actually extinguishes the fusion because it gets too cold immediately.

对。

Yeah.

这就是另一个原因。

So that's the other one.

另一部分是它不会失控，因为其工作原理是保持高温而非链式反应。

And the other part is that it does not because it works by staying hot rather than a chain reaction, it can't run out of control.

这是它的另一个特点。

That's the other part of it.

顺便说，这正是它与裂变的最大区别。

So by the way, this is what very much distinguishes it from fission.

这不是一个会失控的过程，因为它在热力学上是稳定的。

It's not a process that can run away from you because it's basically thermally stable.

这里说的'热力学稳定'是什么意思？

What does thermally stable mean here?

这意味着你需要让它在最佳温度下运行，一旦偏离该温度，反应活性就会降低。

That means is that you want to run it at the optimization in temperature such that if it deviates away from that temperature, the reactivity gets lower.

这是因为维持反应活性本身就很困难。

And the reason for this is because it's hard to keep the reactivity going.

基本上，就像要维持一团难以持续的火焰。

Like, it's a very hard fire to keep going, basically.

哦，所以它不会从你身边跑掉？

Oh, so it doesn't it doesn't run away from you?

它跑不掉的

It can't run away

那么控制它保持这种状态有多难呢？

from So how difficult is the control there to keep it at that?

这因概念而异，但总体来说，做到这点相当容易。

It varies from concept to concept, but in general, it's fairly easy to do that.

最简单的是，它物理上无法逃离你，因为另一个原因是任何时候可用的聚变燃料量都非常非常少。

And the easiest thing, it can't physically run away from you because the other part of it is that at any given time, there's a very, very small amount of fuel available to fuse anyway.

这意味着它本质上始终受限于此。

So this means that that's always intrinsically limited to this.

所以即使设备功耗上升，它也会立即自行耗尽。

So even if the power consumption of the device goes up, it just kind of burns itself out immediately.

是的。

Yeah.

那么你是——稍微岔开话题——麻省理工学院等离子体科学与聚变中心的主任。

So you are the just to take a tan another tangent on a tangent, you're the director of MIT's plasma science and fusion center.

我们可以聊聊中心历史中一些有趣的部分，包括麻省理工更广泛的历史，乃至科学工程史和人类文明史，同时也关联到安全方面。

We'll talk about maybe you can mention some interesting aspects of the history of the center in the broader history of MIT and maybe broader history of science and engineering and the history of human civilization, but also just the link on the safety aspect.

对。

Yeah.

你知道，你们设计的那些惊人反应堆，要如何预防某些问题呢？

You know, how how do you prevent, you know, some some of the amazing reactors that you're designing?

你们如何防止在这个过程中毁灭整个人类文明？

How do you prevent from destroying all of human civilization in the process?

安全协议是什么？

What what's the safety protocols?

核聚变之所以有趣，是因为它无法直接武器化。我的意思是，你必须付出极大努力才能创造出能从聚变中获取能量增益的条件。

Fusion is interesting because it's not really directly weaponizable because what I mean by that is that you have you have to work very hard to make these conditions in which you can get energy gain from from fusion.

这意味着当我们设计这些应用于能源领域的装置时，由于它们会产生大量能量且内部存在高温部件，其工业危险等级与化工厂等设施非常相似。

And this means that when we design these devices with respect to application in the energy field, is that they, you know, because they're producing large amounts of power and they will have hot things inside of them, this means that they have like a level of industrial hazard, which is very similar to what you would have like in a chemical processing plant or anything like that.

实际上任何类型的能源工厂也都存在这些风险。

And any kind of energy plant actually has these as well too.

但最核心的基础技术因其释放的能量特性，无法被直接用于邪恶目的。

But the underlying, underneath it, core technology can't be directly used in a nefarious way because of the power that's being emitted.

基本上如果你试图这么做，通常它就会直接停止运作。

It just basically if you try to do those things, typically it just stops working.

所以安全顾虑主要来自常规问题，比如设备故障、熔化这类与聚变本身无关的情况。

So the safety concerns have to do with just regular things that, like equipment malfunctioning, melting of equipment, like all this kind of stuff that has nothing to do with fusion necessarily.

我们通常更担心的是设备可行性，毕竟最终我们建造的是相当复杂的装置来实现这些要求，因此会极力避免损坏这些组件。

I mean, usually what we worry about is the viability, because in the end, we build pretty complex objects to realize these requirements, and so what we try really hard to do is like not damage those components.

但这些都属于聚变装置内部问题，不像你说的会毁灭人类文明，因为聚变过程本身就对能量释放存在固有限制。

But those are things which are internal to the fusion device, and this is not something that you would consider about like it would, as you say, destroy human civilization because that release of energy is just inherently limited because of the fusion process.

这并不是说风险为零——你问到了另一个特性——但它确实是安全的。

So it doesn't say that there's zero, so you asked about the other feature, but that it's safe.

这个过程本身具有本质安全性，但由于技术复杂，仍需考虑相关安全因素。

So it is, the process itself is intrinsically safe, but because it's a complex technology, you still have to take into consideration aspects of the safety.

它能瞬间产生电离辐射，所以必须小心处理，这意味着需要对其进行屏蔽。

So it produces ionizing radiation instantaneously, so you have to take care of this, which means that you shield it.

想象一下牙科X光或癌症治疗等情况，我们总是需要屏蔽这些辐射。

Think of like your dental x rays or treatments for cancer and things like this, we always shield ourselves from this.

这样我们既能获得有益效果，又能将其有害影响降到最低。

So we get the beneficial effects, but we minimize the harmful effects of those.

所以这其中还涉及到所有这些方面的问题。

So there there there are all those aspects of it as well too.

是的。

Yeah.

我们稍后会回到麻省理工学院的等离子体科学与聚变中心，但现在让我们继续探讨人类文明毁灭的话题，这引出了核裂变的主题。

So we'll return to MIT's plasma science and fusion center, but let us linger on the destruction of human civilization, which brings us to the topic of nuclear fission.

那是什么？

What is that?

这就是核武器和当前核电站内部发生的反应过程。

So the the process that is inside nuclear weapons and current nuclear power plants.

它基于相同的物理原理，但实际上是相反的，从名称就能看出来。

So it relies on the same underlying physical principle, but it's exactly the opposite, which actually the names imply.

聚变意味着将物质结合，裂变则是将物质分裂。

Fusion means bringing things together, fission means splitting things apart.

因此裂变需要最重而非最轻、最不稳定而非最稳定的元素。

So fission requires the heaviest instead of the lightest, and the most unstable versus the most stable elements.

所以这通常是铀或钚，主要是铀。

So this tends to be uranium or plutonium, primarily uranium.

以铀为例。

So take uranium.

铀235是最重的不稳定元素之一。

So uranium-two 35 is one the heaviest unstable elements.

其裂变过程是由不带电的中子等亚原子粒子靠近触发，这种接近足以引发本就处于不稳定边缘的原子核内部失稳，从而使其分裂。

And what happens is that is fission is triggered by the fact that one of these subatomic particles, the neutron, which has no electric charge, basically gets in proximity enough to this triggers an instability effectively inside of this, what is teetering on the border of instability, and basically splits it apart.

这就是裂变，核裂变。

And that's the fission, right, the fissioning.

当裂变发生时，产物大致分裂为两部分，但实际上过程更为复杂。

And so when that happens, because the products that are it roughly splits in two, but it's not even that, it's actually more complicated.

它会分裂成一系列较轻的元素和原子核。

It splits into this whole array of lighter elements and nuclei.

当这种情况发生时，剩余的静止质量会比原来的少。

And when that happens, there's less rest mass left than the original one.

所以实际上是一样的，这再次是强核力的重新排列，但这就是能量的来源。

So it's actually the same, so it's again, it's rearrangement of the strong nuclear force that's happening, but that's the source of the energy.

最后，这是我们常展示给大家的著名图表，基本上它显示了周期表中所有存在的元素，构成万物的基础。记得你问了个好问题。

And so in the end, so this is a famous graph that we show everybody, is basically it turns out every element that exists in the periodic table, all the things that make up everything, a Remember, you asked a good question.

就像这样，我们是否应该认为质量等同于储存的能量？

It was like, so should we think of mass as being the same as stored energy?

是的。

Yes.

所以你可以绘制一个图表，基本上展示所有稳定元素中储存的相对能量，这些元素构成了世界，乃至宇宙。

So you can make a plot that basically shows the relative amount of stored energy in all of the elements that are stable and make up basically the world, okay, in the universe.

结果发现，铁元素具有最高的稳定性或储存能力。

And it turns out that this one has a maximum amount of stability or storage at iron.

所以它大致位于元素周期表的中间位置，因为范围大约是这样。

So it's kind of in the middle of the periodic table because this goes from, it's roughly that.

这意味着如果你取比铁更重的元素，比如铀（其质量是铁的两倍多），并设法神奇地将其分裂成更轻的组成部分，由于它会移动到更稳定的能量状态，从而释放出动能。

And so what that means is that if you take something heavier than iron, like uranium, which is more than twice as heavy than that, and you split apart, somehow just magically, you can just split apart its constituents and you get something that's lighter, because it moves to a more stable energy state, it releases kinetic energy.

这就是我们利用的能量。

That's the energy that we use.

动能指的是物体的运动能量，因此实际上是一种可以加以利用的能量。

Kinetic energy meaning the movement of things, so it's actually an energy you can do something with.

而核聚变则位于另一端，因为它也是向铁元素靠拢，但必须通过聚变来实现。

And fusion sits on the other side of that because it's also moving towards iron, but it has to do it through fusion together.

这导致了一些深刻的差异。

So this leads to some pretty profound differences.

正如我所说，它们在基础物理或科学上有相近之处，但实际上是相反的。

As I said, they have some underlying physics or science proximity to each other, but they're literally the opposite.

那么为什么核聚变会这样呢？

So fusion why is this?

这实际上涉及到其实际应用——核裂变可以在室温下发生。

It actually goes into practical implications of it, which is that fission could happen at room temperature.

这是因为中子不带电荷，因此实际上是室温下的中子触发了反应。

It's because this neutron has no electric charge and therefore it's literally room temperature neutrons that actually trigger the reaction.

这意味着为了弄清楚其运作机制（它通过链式反应工作），你可以在室温下实现这一点。

So this means in order to establish what's going on with it, and it works by chain reaction, is that you can do this at room temperature.

所以恩里科·费米是在大学校园里完成这项工作的，芝加哥大学的校园。

So Enrico Fermi did this like on a university campus, University of Chicago campus.

第一次持续的链式反应是在一个壁球场的下方完成的，使用了大量石墨块。

The first sustained chain reaction was done underneath a squash court with big blocks of graphite.

请别误会，这仍然是一项了不起的人类成就，对吧？

It was still, don't get me wrong, an incredible human achievement, right?

但你看，然后想想核聚变，我得建造某种装置，要达到1亿度的高温。

But that's, you know, and then you think about fusion, I have to build a contraption of some kind that's going to get to 100,000,000 degrees.

好吧，哇，这差别可太大了。

Okay, wow, that's a big difference.

另一个是关于链式反应的，即核裂变的工作原理是，当裂变发生时，实际上会产生自由中子。

The other one is about the chain reaction, that namely fission works by the fact that when that fission occurs, it actually produces free neutrons.

自由中子，特别是当它们被减速到室温时，如果附近有其他铀或裂变材料，就能触发其他裂变反应。

Free neutrons, particularly if they get slowed down to room temperature, can trigger other fission reactions if there's other uranium nearby or fissile materials.

这意味着能量释放的方式是，你需要非常谨慎地设置条件，使得平均每次反应恰好释放足够的中子并减速，从而实际引发另一次反应，且仅有一次。

So this means that the way that it releases energy is that you set this up in a very careful way such that every, on average, every reaction that happens exactly releases enough neutrons and slows down that they actually make another reaction, exactly one.

这意味着由于每次反应释放固定能量，这样操作后，随着时间的推移，系统会呈现稳定的功率输出。

And what this means is that because each reaction releases a fixed amount of energy, you do this, and then in time, this looks like just a constant power output.

这就是我们的核裂变发电站的工作原理。

So that's how our fission power plan works.

因此他们对链式反应的控制极其困难，也极其重要

And so their control of the chain reactions is extremely difficult and extremely important for

这非常重要。

It's very important.

当你刻意设计它时，就会产生不止一个‘嗯’。

And when you intentionally design it, that it it creates more than one Mhmm.

每次初始反应的裂变反应，随后呈指数级增长。

Fission reaction per per starting reaction, then it exponentiates away.

但核武器的本质正是如此。

But which is which is what a nuclear weapon is.

对。

Yeah.

那么原子武器是如何工作的？

So how does an atomic weapon work?

氢弹又是如何运作的？

How does a hydrogen bomb work?

帮朋友问的。

Asking for a friend.

对。

Yeah.

没错。

Yeah.

本质上，你所做的就是快速聚集足够多的能在室温中子下发生裂变的材料。

So at its heart, what it what you do is you very quickly put together enough of these materials that can undergo fission with room temperature neutrons.

你以足够快的速度将它们聚集，使得这一过程能在数学意义上极速增长。

And you put them together fast enough that what happens is that this process can essentially grow mathematically, like very fast.

因此会释放出巨大能量。

And so this releases large amounts of energy.

这就是它运作的根本原因。

So that's the underlying reason that it works.

你听说过聚变武器，这很有趣，但它与聚变能源不同，实际上你是在利用聚变反应，但这只是增加了武器的能量输出，本质上它仍然是一种裂变武器。

So you've heard of a fusion weapon, so this is interesting, but it's dislike fusion energy in the sense that what happens is that you're using fusion reactions, but it simply increases the gain, actually, of the weapon rather than, it's not a pure, at its heart, it's still a fission weapon.

你只是将聚变反应作为一种中间催化剂，从而从中获取更多能量。

You're just using fusion reactions as a sort of intermediate catalyst to basically to get even more energy out of it.

但它并不能直接应用于能源领域。

But it's not directly applicable to be used in in energy source.

从哲学角度退一步想，人类竟能运用物理和工程学创造出如此强大的武器，这难道不让你感到恐惧吗？

Does it terrify you just to, again, step back at the philosophical that humans have been able to use physics and engineering to create such powerful weapons?

我不会用'恐惧'这个词。

I wouldn't say terrify.

我认为，这正是人类进步的体现。

I mean, we should be this is the progress of humanity.

每次我们获得新的能力，就像你说的'宇宙改变之日'。

Every time that we've gotten access, you talk the day the universe changed.

当我们获得新型能源时，世界确实发生了根本性改变。

Those really changed when we got access to new kinds of energy sources.

但每次获得新能力，通常都意味着你能获取更强大的能量，对吧？

But every time you get access and typically what this meant was you get access to more intense energy, right?

事实正是如此。

And that's what that was.

从燃烧木材到使用煤炭，再到使用汽油和石油，最终到利用这种能量，这种能力的跃迁既提升了能量强度，也放大了使用后果。

And so the ability to move from burning wood to using coal to using gasoline and petroleum, and then finally to use this, is that both the potency and the consequences are elevated around those things.

正如你所说，核聚变改变世界的方式，我认为除非我们深入思考，否则无法预见我们能创造出的一些东西。

It's just like you said, the the way that fusion, nuclear fusion, would change the world, I don't think, unless we think really deeply, we'll be able to anticipate some of the things we can create.

未来将会有许多令人惊叹的事物。

There's going going to be a lot of amazing stuff.

是啊。

Yeah.

但那些令人惊叹的事物会催生更多神奇的东西，不幸的是——或者说取决于你怎么看——更强大的武器。

But then that amazing stuff is gonna enable more amazing stuff and more, unfortunately, or depending how you see on it, more powerful weapons.

嗯，确实。

Well yeah.

但你看，关键就在这里。

But see, that's the thing.

核聚变通过以下方式打破了这一趋势。

Fusion breaks that trend in the following way.

首先，核聚变不依赖链式反应。

So one of them so fusion doesn't work on a chain reaction.

不存在链式反应。

There's no chain reaction.

完全没有。

Zero.

这意味着它物理上不可能在你面前呈指数级爆发。

So this means it cannot physically exponentiate away on you.

因为它的工作原理——其实这就是为什么恒星如此稳定，顺便说一句，我们早就知道这一点。

Because it works, and actually this is why star By the way, we know this already, it's why stars are so stable.

为何大多数恒星和太阳如此稳定。

Why most stars and suns are so stable.

这是因为它们通过自身的温度和加热进行调节。

It's because they are regulated through their own temperature and their heating.

因为实际情况并非存在某种概率使其指数级衰减，而是聚变释放的能量基本上维持着高温。

Because what's happening is not that there's some probability of this exponentiating away, it's that the energy that's being released by fusion basically is keeping the fire hot.

当涉及到热力学等原理时，这些现象往往有其原因，例如像烤箱这样的系统很容易保持恒温。

And these tend to be, and when it comes down to thermodynamics and things like this, there's a reason, for example, it's pretty easy to keep a constant temperature, like in an oven and things like this.

聚变中也是同样的道理。

It's the same thing in fusion.

因此我认为聚变的一个特点是，虽然理论上比裂变具有更高的能量密度，但实际上不会导致失控和能量快速释放的后果，因为物理系统本身就不倾向于那样做。

So this is actually one of the features that I would argue fusion breaks the trend of this is that has more energy intensity than fission on paper, but it actually does not have the consequences of control and sort of rapid release of the energy because it's actually it it the physical system just doesn't want to do that.

是啊。

Yeah.

我们得另寻他处寻找第三次世界大战的武器了。

We're gonna have to look elsewhere for the weapons with which we fight World War three.

有道理。

Fair enough.

那么你提到或没提到的等离子体是什么？

So what is plasma that you may or may have not mentioned?

你提到了离子和电子。

You mentioned ions and electrons.

但没提等离子体。

Did not mention plasma.

那么什么是等离子体？

So what is plasma?

等离子体在核聚变中起什么作用？

What is the role of plasma in nuclear fusion?

等离子体是物质的一种相态或状态。

So plasma is a phase of matter or state of matter.

遗憾的是，我们的学校不教这个，我不确定为什么，但所有孩子都学过物质的三态。

So unfortunately, our schools don't it's like, I'm not sure why this is the case, but all children learn the three phases of matter.

对吧？

Right?

这意味着什么？

So what does this mean?

我们以水为例。

So we'll take water as an example.

如果温度低，水会结冰，处于固态。

So if it's cold, it's ice, it's in a solid phase.

然后当你加热时，通常是温度决定相态，虽然不只是温度。

And then if you heat it up, it's the temperature that typically sets the phase, although it's not only temperature.

你加热后它会变成液体，显然物理性质会改变，因为你可以倒出来等等，对吧？

So you heat it up and you go to a liquid, and obviously it changes its physical properties because you can pour it and so forth, right?

如果再继续加热，它就会变成气体。

And then if you heat this up enough, it turns into a gas.

气体的行为不同，因为密度会发生非常突然的变化，实际上就是这样发生的。

And a gas behaves differently because there's a very sudden change in the density, actually that's what's happening.

所以当你在常压下将其转化为蒸汽时，其密度相比液态会发生约一万倍的变化。

So it changes by about a factor of 10,000 in density from the liquid phase into when you make it into steam at atmospheric pressure.

一切都很好。

All very good.

只是问题在于他们忘记了，比如，如果你持续升高温度会发生什么。

Except the problem is they forgot, like, what happens if you just keep elevating the temperature.

你不想给孩子们启发。

You don't want to give kids ideas.

他们会开始做实验，会开始加热东西

They're going to start experimenting, they're going start It's heating up the good

反正都会开始这么做。

to start doing it anyway.

结果发现一旦超过约五千到一万摄氏度，就会进入物质的新相态。

So you it turns out that once you get above, it's approximately five or 10,000 degrees Celsius, then you hit a new phase of matter.

事实上，这个物质相态适用于所有高于该温度的情况。

And actually, that's the phase of matter that is for all, pretty much all the temperatures that are above that as well too.

这意味着什么？

And so what does that mean?

实际上它发生了相变。

So it actually changes phase.

这是一种不同的物质状态。

So it's a different state of matter.

之所以会变成不同的物质状态，是因为温度高到足以使构成物质的原子——回到费曼的理论，万物都是由这些独立的原子构成的——发生改变。

And the reason that it becomes a different state of matter is that it's hot enough that what happens is that the atoms that make up go back to Feynman, Everything's made up of these individual things, these atoms.

但原子本身实际上是由原子核构成的，原子核包含带正电的粒子和中子，以及非常非常轻的电子，其质量远小于原子核，且环绕在我们周围。

But atoms can actually themselves be, which are made of nuclei, which contain the positive particles and the neutrons, and then the electrons, which are very, very light, very much less mass than the nucleus, and that surround us.

这就是构成原子的基本成分。

This is what makes up an atom.

等离子体就是当你剥离足够多电子使其脱离离子束缚时形成的状态。

So a plasma is what happens when you start pulling away enough of those electrons so that they're free from the ions.

组成我们身体和周围水分子的所有原子中，电子都处于紧密结合状态，本质上它们极其稳定。

So all the atoms that make us up in this water and all that, the electrons are in tightly bound states and basically they're extremely stable.

当温度达到约5000到10000度时，电子就开始被剥离。

Once you're at about 5,000 or 10,000 degrees, you start pulling off the electrons.

这意味着现在存在的介质中，其组成粒子大多带有净电荷。

And what this means is that now the medium that is there, its constituent particles mostly have net charge on them.

那么这为什么重要呢？

So why does that matter?

因为现在这意味着粒子可以通过它们的电荷相互作用。

It's because now this means that the particles can interact through their electric charge.

在某种程度上，当它们在原子内部时也是如此。

In some sense they were when it was in the atom as well, too.

但现在它们是自由粒子，这意味着它们开始从根本上改变行为。

But now that they're free particles, this means that they start, it fundamentally changes the behavior.

它不像气体那样表现，也不像固体或液体，它的行为像等离子体。

It doesn't behave like a gas, it doesn't behave like a solid or a liquid, it behaves like a plasma.

那么为什么我们对此避而不谈会令人失望呢？

So why is it disappointing that we don't speak about this?

这是因为宇宙中99%的物质都处于等离子态。

It's because 99% of the universe is in the plasma state.

它们被称为恒星。

It's called stars.

事实上，我们的太阳也是如此，太阳中心显然是等离子体，而太阳表面温度约5500摄氏度，同样因为足够高温而呈现等离子态。

And in fact, our own sun, at the center of the sun is clearly a plasma, but actually the surface of the sun, which is around 5,500 Celsius, is also a plasma because it's hot enough that it's hot enough.

实际上，你看到的那些太阳表面的壮观景象，比如卫星拍摄到的巨大光臂和太阳耀斑，都是等离子体。

In fact, things that you see, sometimes you see these pictures from the surface of the sun, amazing, like satellite photographs of those big arms of things and of light coming off of the surface of the sun and solar flares, those are plasmas.

这种受迫物质状态与气体有哪些有趣的不同之处？

What are some interesting ways that this forced state of matter is different than gas?

我们先来了解气体的工作原理。

Let's go to how a gas works.

这要归功于费曼的洞见，他指出这是最重要的概念。

So the reason a gas and it goes back to Feitman's brilliance in saying that this is the most important concept.

固体、液体和气体之所以表现出不同相态，本质上是原子间相互作用方式发生了变化。

The reason actually solid, liquid, and gas phases work is because the nature of the interaction between the atoms changes.

以气体为例，你可以想象这个房间里的分子虽然看不见，但它们四处飞散，并会以一定频率相互碰撞。

And so in a gas, you can think of this as being this room and the things, although you can't see them, is that the molecules are flying around, but then with some frequency they basically bounce into each other.

当它们相互碰撞时，就会交换动量和能量。

And when they bounce into each other, they exchange momentum and energy around on this.

事实证明，正是这些碰撞的概率、距离和散射方式决定了气体的行为特性。

And so it turns out that the probability and the distances and the scattering of those of what they do, it's those interactions that set about how a gas behaves.

你这么说是什么意思？

So what do you mean by this?

举个例子，如果我设想某种测试粒子，比如向空气中喷洒某种特定颜色的物质，实际上在液体中也能做到，观察它是如何逐渐远离你扩散的。

So for example, if I take an imaginary test particle of some kind, like I spray something into the air that's got a particular color, in fact you can do it in liquids as well too, like how it gradually will disperse away from you.

这从根本上是由粒子相互碰撞的方式决定的。

This is fundamentally set because of the way that those particles are bouncing into

每个这些粒子的概率

each The probabilities of those The particle

它们的运动速率、移动距离等等。

rate that they go at and the distance that they go at and so forth.

这是爱因斯坦等人在布朗运动初期就研究明白的，这类现象都是如此。

So this was figured out by Einstein and others at the beginning of the Brownian motion, all these kinds of things.

这些理论在上世纪初就已确立，当时确实像一场伟大的启示。

These were set up at the beginning of the last century, and it was really like this great revelation.

哇，原来这就是物质如此表现的原因。

Wow, this is why matter behaves the way that it does.

就像，哇哦。

Like, wow.

确实如此，而且在液体和固体中，真正关键的是你与最近邻的相互作用方式。

It's really like, and also in liquids and in solids, what really matters is how you're interacting with your nearest neighbor.

所以想象一下，气体粒子基本上是在四处游荡。

So you think about that one, the gas particles are basically going around.

除非它们真正相互碰撞，否则其实不会交换信息。

Until they actually hit into each other, though, they don't really exchange information.

在液体中也是如此。

And it's the same in a liquid.

你们彼此相邻，但可以四处移动。

You're kind of beside each other, but you can kind of move around.

而在固体中，你就像被固定在邻居旁边一样动弹不得。

And in a solid, you're literally like stuck beside your neighbor.

你不能像在移动那样自由活动。

You can't move like you're moving.

等离子体的奇特之处在于它并非如此运作。

Plasmas are weird in the sense that it's not like that.

这是因为粒子带有电荷，意味着它们无需紧密接触就能相互排斥。

And it's because the particles have electric charge, this means that they can push against each other without actually being in close proximity to each other.

这个说法并非绝对正确——如果采用Gelli理论会更专业些——但本质上这意味着可以产生远距离作用或信息交换。

That's not an infinitely true statement, if you go with Gelli, it's a little bit more technical, but basically this means that you can start having action or exchange of information at a distance.

事实上这就是等离子体的定义：这些现象有个专业术语叫库仑碰撞，即带电粒子间通过这种力相互作用，等离子体的定义就是其集体行为由这种远距离碰撞主导的介质。

And that's in fact the definition of a plasma, that it says these have a technical name, it's called a Coulomb collision, it just means that it's dictated by this force which is being pushed between charged particles, is that the definition of a plasma is a medium in which the collective behavior is dominated by these collisions at a distance.

可以想象这会导致一些奇特现象，我简单说明下。

So you can imagine then this starts to give you some strange behaviors, which I quickly talk about.

最反直觉的现象之一是：等离子体温度越高，碰撞反而越不频繁。

One of the most counterintuitive ones is as plasmas get more hot, as they get higher in temperature, then the collisions happen less frequently.

比如呢？

Like what?

这完全说不通啊。

That doesn't make any sense.

按说粒子运动越快，碰撞应该更频繁才对。

When particles go faster, you think they would collide more often.

但由于粒子是通过它们的电场相互作用的，当它们运动得更快时，实际上在彼此的场中停留的时间更短，因此从能量和动量交换的角度来看，它们之间的相互作用反而减少了。

But because the particles are interacting through their electric field, when they're going faster, they actually spend less time in the influential field of each other, and so they talk to each other less in an energy and momentum exchange point of view.

有意思。

Interesting.

这是等离子体反直觉特性之一。

Which is one of the count one of the counterintuitive aspects of plasmas.

这可能与核聚变非常相关。

Which is probably very relevant for nuclear fusion.

是的。

Yes.

正是如此。

Exactly.

那么我来试着总结一下核聚变反应堆应该做什么。

So if I can try to summarize what a nuclear fusion reactor is supposed to do.

所以你有，比如说，几种元素。

So you have, what, a couple of elements.

通常是什么元素？

What are usually the elements?

通常是氘和氚，它们是氢的重同位素。

Usually, deuterium and tritium, which are the heavy forms of hydrogen.

氢。

Hydrogen.

你有了这些元素后，就开始加热它们。

You have those, and you start heating it.

然后当你开始加热它时，我忘了你说的温度，

And then as you start heating it, I forgot the temperature you said,

但大约是1000亿度。

but About a 100,000,000,000.

对。

Yeah.

不对。

No.

首先首先，它会变成哦，

First first, it becomes Oh,

首先，它会变成等离子体。

first, it becomes plasma.

所以它最初是气体，然后在大约1万度时转变为等离子体。

So it's it's a gas, and then it turns into a plasma at about 10,000 degrees.

然后你就有了一堆电子和离子四处飞散，接着你继续加热这东西。

And then so you have a bunch of electrons and ions flying around, and then you keep heating the thing.

我猜随着你加热这东西，离子之间的碰撞会越来越稀少。

And I guess as you heat the thing, the ions hit each other rarer and rarer.

是的。

Yes.

所以，哦天啊，这可不好玩。

So, oh, man, that's not fun.

所以你必须持续加热它，直到它们碰撞的概率变得足够高。

So you have to keep heating it such that you you have to keep hitting it until the probability of them colliding becomes reasonably high.

而且，除此之外，还要防止它们撞击墙壁，准确来说。

And So it turns also on top of that, and sorry to interrupt, you have to prevent them from hitting the walls Exactly.

反应堆的墙壁，准确来说。

Of the reactor Exactly.

不知怎么做到的。

Somehow.

你刚才问到聚变反应的要求定义。

So you asked about the the the definitions of the requirements for fusion.

最著名、或者说最直观的一个指标就是温度。

So the most famous one, or in some sense the most intuitive one, is the temperature.

因为你可以制造出许多根本不发生聚变的等离子体。

And the reason for that is that you can make many, many kinds of plasmas that have zero fusion going on in them.

平均而言，你可以制造约1万度的等离子体——顺便说，欢迎来我们PSFC实验室参观，我可以演示用肉眼可见的等离子体，温度约1万度，你可以把手放在旁边，完全没有任何聚变反应发生。

And the reason for this is that the average, you can make a plasma at around 10,000, in fact if you come, by the way, you're welcome to come to our laboratory at the PSFC, I can show you a demonstration of a plasma that you can see with your eyes and it's at about 10,000 degrees and you can put your hand up beside it and all this, and it's like and nothing there's zero fusion going on.

抱歉打断一下。

So you have sorry.

那个等离子体的温度是多少？

What was the temperature of the plasma?

大约1万度。

About 10,000 degrees.

你能把手伸进去？

You can stick your hand in?

呃，不能直接伸进去，外面有玻璃管隔着。

Well, you can't stick your hand into it, but there's a glass tube.

你基本上可以用肉眼看到这个。

You can basically see this with your bare eye.

是的。

Yeah.

你可以把手放在玻璃管上，因为它是...

And you can put your hand on the glass tube because it's What's

什么颜色？

the color?

是紫色吗？

Is it purple?

是紫色的。

It's it's purple.

对。

Yeah.

没错。

Yeah.

蓝色和紫色。

Blue and purple.

是蓝色的

It's blue

和紫色。

and purple.

它确实挺漂亮的。

It is it is kind of beautiful.

是的。

Yeah.

等离子体有时在美感上确实相当惊人。

Plasmas are actually quite astonishing sometimes in their beauty.

顺便说一句，实际上闪电是最神奇的等离子体形态之一，它是地球上一种瞬时存在的等离子体形态，但由于周围环境处于室温，它会立即消失。

Actually, one of the most amazing forms of plasma is lightning, by the way, which is an instantaneous form of plasma that exists on Earth, but immediately goes away because everything else around it is at room temperature.

那真是

That's

太迷人了。

fascinating.

没错。

Yeah.

所以这里面有不同的要求。

So there's different requirements in this.

所以制造等离子体大概需要这样。

So making a plasma takes about this.

但在1万度，甚至100万度下，核聚变反应发生的概率几乎为零。

But at 10,000 degrees, even at a million degrees, there's almost no probability of the fusion reactions occurring.

这是因为虽然带电粒子可以相互碰撞，但如果你回溯到最初，记得我说过，这些带电粒子必须接近到原子核大小的距离才能触发强核力作用。

And this is because while the charged particles can hit into each other, if you go back to the very beginning of this, remember I said, oh, these charged particles have to get to within distances which are like this size of a nucleus because of the strong nuclear force.

不幸的是，当粒子靠得越近，电荷产生的库仑斥力会以距离平方反比的规律增强。

Well, unfortunately, as the particles get closer, the repulsion that comes from the charge, the Coulomb force, increases like the inverse distance squared.

哦，糟糕。

Oh, no.

所以当它们越靠近时，彼此间的排斥力就越强。

So as they get closer, they're pushing harder and harder apart.

然后情况会变得稍微奇异些，不过你可能会喜欢。

So then it gets a little bit more exotic, which maybe you'll like, though.

但事实证明，在卢瑟福发现原子核后的时代初期，人们就已经理解了这一点。

But it turns out that people understood this at the beginning of the age after Rutherford discovered the nucleus.

当时人们反应是‘哦，好吧’。

Was like, oh, yeah.

就像在问‘这要怎么运作？’

Was like, how is this going to work?

对吧？

Right?

因为你怎么能让任何东西进入这么小的距离？

Because how do you get anything within these distances?

这需要极其巨大的能量。

It's like, inquire extraordinary energy.

而它确实如此。

And it does.

事实上，当你观察那些能量时，会发现它们非常高。

And in fact, when you look at those energies, they're very, very high.

但事实证明量子物理学能解决这个问题，因为粒子不仅仅是粒子，它们也是波。

But it turns out quantum physics comes to the rescue because the particles aren't actually just particles, they're also waves.

这就是量子力学的关键——你可以同时把它们视为波和粒子。

This is the point of quantum, You can treat them both as waves and as particles.

事实证明，当它们彼此足够接近时，粒子会通过一种称为量子隧穿的效应穿越这个能量势垒，这本质上只是波动性的体现，使其具有有限的概率实现这一点。

And it turns out if they get in close enough proximity to each other, then the particle pops through basically this energy barrier through an effect called quantum tunneling, which is really just the transposition of the fact that it's a wave so that it has a finite probability of this.

顺便问一下，你在谈论这个时，是否觉得难以形成概念？

By the way, you talk about like, do you have a hard time conceptualizing this?

这就是其中之一。

This is one of them.

量子隧穿是其中之一

Quantum tunnel is one of

。

them.

这就像把乒乓球扔向一张纸，然后每100个球中就有几个神奇地出现在纸的另一侧，似乎没有破坏纸张。

This is like throwing a ping pong ball at a piece of paper, and then every 100 of them just magically show up on the other side of the paper without seemingly breaking the paper.

我是说，用个物理比喻来解释。

I mean, to use a physical analogy.

而这种现象对核聚变功能的实现至关重要。

And that that phenomena is important is critical for the function of nuclear fusion.

是的。

Yes.

适用于所有类型的聚变。

For all kinds of fusion.

所以这也是恒星能够运行的原因。

So this is the reason why stars can work as well too.

实际上，如果没有这种效应，恒星需要变得极其炽热才可能点燃——甚至不清楚它们是否真的能点燃。

Like, Stars would have to be much, much hotter actually to be able to in fact, it's not clear that they would actually ignite, in fact, without this effect.

所以我们谈到这一点。

So we get to that.

这就是为什么还有另一个要求。

So this is why there's another requirement.

不是说你必须制造等离子体，而是为了让反应有显著的聚变概率，你还必须将其加热到非常高的温度。

Not so you must make a plasma, but you also must get it very hot in order for the reactions to have a significant probability to actually fuse.

而且实际上在较低温度下，它也会几乎降至零。

And it actually falls effectively almost to zero for lower temperatures as well too.

所以有个很好的方程式，是的。

So there's nice equation Yes.

这能达到五千万度，或者说，是的。

That gets you to 50,000,000 degrees, or like Yeah.

或者像你说的，实际上是一亿度。

Or that you said, practically speaking, a 100,000,000.

所以这是个非常简单的方程式。

So it's a really simple equation.

基本上，这几乎就是理想气体定律。

It's the ideal gas law, basically, almost.

最终，你有一定数量的这些处于等离子态的聚变粒子，它们处于等离子态，有一定数量的粒子。

So in the end, you've got a certain number of these fusion particles in the plasma state, they're in the plasma state, there's a certain number of particles.

如果约束是完美的，如果你输入一定量的能量，那么基本上最终会达到一个温度，并且温度会升得很高。

And if the confinement is perfect, if you put in a certain content of energy, then basically eventually come up in a temperature and they go up to high temperature.

顺便说一下，这实际上需要极其微小的能量。

This turns out to be, by the way, extraordinarily small amounts of energy.

然后你说，什么？

And you go, what?

就像我要把某样东西加热到1亿度，那将需要我见过的最大的火焰燃烧器。

It's like I'm getting something to like 100,000,000 degrees that's going to take the biggest flame burner that I've ever seen.

不。

No.

这样做的原因是它回到了这个的能量含量上。

And the reason for this is it goes back to the energy content of this.

所以是的，你必须让它达到高平均能量，但粒子非常非常少。

So yeah, you have to get it to high average energy, but there's very, very few particles.

这是低密度的。

This is low density.

怎么做到

How do get

让反应堆里的密度变低？

it to be low density in a reactor?

所以主要的方法是，再次说明，并非所有类型的聚变都完全如此，但在我们主要研究的磁约束聚变中，这一切都发生在高真空中。

So the way that you do this is primarily, again, this is not exactly true in all kinds of fusion, but in the primary one that we work on magnetic fusion, this is all happening in a hard vacuum.

就像是在外太空发生的一样。

So it's like it's happening in outer space.

所以基本上，你已经除去了所有其他粒子，只留下这些特殊的...所以你几乎没有它们

So basically, you've gotten rid of all the other particles except for these specialized So you've few had them

一次一个

one at

一段时间。

a time.

不。

No.

实际上，比那还要简单。

Actually, it's even easier than that.

你连接一个气阀，基本上就是往里面漏气。

You connect a gas valve, and you basically leak gas into it.

以可控的方式。

In a controlled fashion.

是的。

Yeah.

对。

Yeah.

哇。

Wow.

这太美了。

This is beautiful.

这是个气瓶。

It's a gas cylinder.

你怎么防止它撞到墙壁？

How do you get it from hitting the walls?

没错。

Yeah.

那么你现在已经谈到了其他必要条件。

So now you've touched on the other necessary requirements.

所以事实证明，不仅需要温度，还必须进行约束。

So it turns out it's not just temperature that's required, you must also confine it.

那么‘约束它’是什么意思呢？

So what does this mean, confine it?

而约束方式有两种，

And there's two types of confinement,

正如你提到的。

as you mentioned.

你提到了磁约束。

You mentioned the magnetic one.

磁约束，还有一种叫惯性约束。

Magnetic one, and there's one called inertial as well too.

但基本原理其实与你具体采用什么技术来约束它无关。

But the general principle actually has nothing to do with, in particular, with what the technology is that you use to confine it.

因为这归根结底取决于高温和热容量的要求。

It's because this goes back to the fact that the requirement in this is high temperature and thermal content.

这就像生火一样。

So it's like building a fire.

这意味着当你向其中释放能量或加热时，如果热量瞬间泄漏，就永远无法升温。

And what this means is that when you release the energy into this or apply heat to this, if it just instantly leaks out, it can never get hot.

你应该很熟悉这个道理，就像你试图加热某个东西，却让热量快速散失一样。

So you're familiar with this, it's like you've got something that you're trying to apply heat to, but you're just throwing the heat away very quickly.

顺便说一下，这就是我们给房屋做隔热之类措施的原因。

This is why we insulate homes, by the way, and things like this.

你不希望进入这个房间的热量立刻流失，否则你将消耗无限的热量来试图保持室内温度。

You don't want the heat that's coming into this room to just immediately leave because you'll just start consuming infinite amounts of heat to try to keep it hot.

所以最终，这是其中一个必要条件，它实际上有个名称，我们称之为能量约束时间。

So in the end, this is one of the requirements, and it actually has a name we call the energy confinement time.

这意味着如果你向燃料中释放一定量的能量，你需要观察并计时，看看这些能量需要多长时间才能从系统中流失。

So this means if you release a certain amount of energy into this fuel, of how long, you sit there and you look at your watch, how long does it take for this energy to leave the system?

你可以想象在这个房间里，加热器正在向空气中注入能量，如果你打开窗户等上一天，所有的热量都会散失到室外。

So you could imagine that in this room, that these heaters are putting energy into the air in this room, and you waited for a day, but all the heat have gone to outside if I open up the windows.

哦，这就是能量约束时间。

Oh, that's energy confinement time.

好的，所以这和那个是同一个概念。

Okay, so it's the same concept as that.

所以这个很重要。

So this is an important one.

因此所有聚变都必须有约束。

So all fusion must have confinement.

这背后还有一个更玄妙的原因，人们常常将温度和能量混为一谈。

There's another more esoteric reason for this, which is that people often confuse temperature and energy.

我这么说是什么意思呢？

So what do I mean by that?

这里的温度是字面意义上的，意味着在这个系统中，所有粒子——每一个粒子都具有高动能，实际上处于完全松弛状态，即熵已达到最大化。

So this is literally a temperature, which means that it is a system in which all the particles, every particle, has high kinetic energy and is actually in a fully relaxed state, namely that entropy has been maximized.

我认为这稍微有些技术性，但基本上意味着这是一个热力系统。

I think it's a little bit more technical, but this means that basically it is a thermal system.

就像这个房间里的空气，就像水，就是这里的水。

So it's like the air in this room, it's like the water, it's the water in this.

这些都有温度，意味着存在能量分布，因为粒子碰撞频繁以至于...这与高能粒子不同，比如我们在CERN等粒子加速器中看到的那种。

These all have temperatures, which means that there's a distribution of those energies because the particles have collided so much that it's a So this is distinguished from having high energy particles, like what we have in particle accelerators like CERN and so forth.

那些是高动能，但不是温度，所以实际上不算作约束。

Those are high kinetic energy, but it's not a temperature, so it actually doesn't count as confinement.

所以我们梳理所有这些条件，需要有温度，另一个要求也不意外，就是燃料密度必须足够高。

So we go through all of those, you have temperature, and then the other requirement, not too surprising, is actually that there has to be enough density of the fuel.

足够，但不要

Enough, but not

过高。

too much.

对，足够但不要过高。

Enough, but not too much, yes.

最终这种方式有个专业名称，叫劳森判据，是1956或1957年英国科学家提出的。

And so in the end, the way that it, there's a fancy name for it, it's called the Lawson Criterion because it was formulated by scientists in The United Kingdom about 1956 or 1957.

这本质上是对'无论采用何种约束方法，都需要满足这些条件'的认识。

And this was essentially the realization of, oh, this is what it's going to take, regardless of the confinement method.

本质上就是功率平衡的问题。

Is the basic, what it is actually power balance.

简单说就是：聚变反应本身产生的热量输入与热量流失速度之间的平衡。

It just says, oh, there's a certain amount of heat coming in, which is coming from the fusion reaction itself, because the fusion reaction heats the fuel, versus how fast you would lose it.

这基本上可以归纳为这三个参数，它们相当简单。

And it basically is summarized by those three parameters, which are fairly simple.

所以温度，我们说1亿度的原因在于，对于氘氚聚变这类反应，密度与约束时间乘积的最小值大约出现在1亿度。

So temperature, and then the reason we say 100,000,000 degrees is because almost for this kind of fusion, deuterium tritium fusion, the minimum in the density and the confinement time product is at about 100,000,000.

因此你几乎总是围绕这个最小值来设计装置。

So you almost always design your device around that minimum.

然后你努力实现足够好的约束，并尝试获得足够的密度。

And then you try to get it contained well enough, and you try to get enough density.

这个温度听起来很疯狂对吧？

So that temperature thing sounds crazy, right?

这实际上是我们已经在实验室里实现过的。

That's what we've actually achieved in the laboratory.

比如我们MIT的实验在最佳配置运行时，就达到了1亿度。

Like our experiment here at MIT when it ran its optimum configuration, it was at 100,000,000 degrees.

但当时密度与约束时间的乘积实际上不足，虽然我们实现了聚变反应，但还没达到净能量增益的状态。

But it wasn't actually the product of the density and the confinement time wasn't sufficient that we were at a place that we were getting high net energy gain, but it was making fusion reactions.

这就是你需要经历的流程。

So this is the sequence that you go through.

先制造等离子体，然后加热到足够温度，当温度足够高时，聚变反应会剧烈到超过热量向外流失的速度，最终它就会像恒星一样自持。

Make a plasma, then you get it hot enough, and when you get it hot enough, the fusion reactions start happening so rapidly that it's overcoming the rate at which it's leaking heat to the outside world, and at some point it just becomes like a star.

就像太阳——我们的太阳和其他恒星都没有外接电源。

Like a sun and our own sun and a star doesn't have anything plugged into it.

它们仅通过自身的聚变反应就能保持高温。

It's just keeping itself hot through its own fusion reactions.

最终，那与聚变发电厂的外观非常接近。

In the end, that's really close to what a fusion power plant would look like.

它是什么

What does it

看起来像什么？

visually look like?

它看起来像，就像你说的，像紫色等离子体吗？

Does it look like, like you said, like purple plasma?

是的。

Yeah.

实际上，它对肉眼是不可见的，因为它温度极高，发出的光频率超出了我们的感知范围。

Actually, it's invisible to the eye because it's so hot that it's basically emitting light in frequencies that we can't detect.

它是看不见的。

It's invisible.

事实上，可见光能轻易穿透它。以我们的特定装置为例，最终形成的是一种环形真空容器，用于隔绝空气。

In fact, light goes through it, visible light goes through it so easy that if you were to look at it, what you would see in our own particular configuration, what we make is in the end is a donut shaped, it's a vacuum vessel to keep the air out of it.