On the other side, in the office, Xu Chuan and Peng Hongxi chatted about the problems in controlled nuclear fusion technology.

By the dawn fusion device that had pushed the high-density plasma magnetic confinement run time to forty-five minutes, there was no other trail runner on the path of controlled nuclear fusion.

Neither the domestic EAST nor the foreign Spiral Stone 7X have ever reached this height.

The current dawn fusion pile can be said to be groping its way forward in darkness and chaos.

Chatting about this, Peng Hongxi looked at Xu Chuan and asked, "Speaking of which, the Daybreak device is now running a helium-3 and hydrogen simulation, and it will soon touch the real deuterium-tritium fusion." ”

"In the subsequent deuterium-tritium fusion, how are you going to solve the most difficult problem of tearing the magnetic plane of the current inside the plasma in the tokamak device?"

In the field of controlled nuclear fusion, there are different implementation methods and technologies in different routes.

At present, it is generally accepted that the most promising route is the magnetic confinement route, but this route has several different implementation methods such as tokamak, stellarite, reverse field pinching, cascade magnetic mirror, and spherical ring.

These different methods have different advantages and disadvantages.

For example, the tokamak device has simple technology and low cost; low neoclassical transport; It also has the advantages of strong annular rotation and associated flow shear, as well as weak damping of zonal flow.

But correspondingly, it also has its drawbacks.

For example, it is difficult to generate plasma current, and during operation, the internal current of the plasma will cause problems such as magnetic surface tearing, distortion, and plasma magnetic islands.

In fact, stellarators are the same, with advantages and disadvantages.

Its advantage is that it can operate in a steady-state state for a longer time, and there is no plasma current generation, no magnetic surface tearing, etc.;

But the disadvantages are the high level of neoclassical transmission, the complexity of manufacturing and assembling coils and coil support structures, and so on.

These shortcomings are a necessary obstacle on the road to controlled nuclear fusion, each of which is no less than a world-class problem.

And with the progress of the Daybreak Device, the biggest difficulty of the Tokamak Device will soon be reached.

That is, how to solve the problems of magnetic surface tearing and plasma magnetic island after the real fusion ignition experiment of the deuterium-tritium raw material is opened.

Honestly, he couldn't think of anything too good to fix.

Not to mention him, there is currently no good way to solve the problems of magnetic plane tearing and plasma islanding in tokamak devices.

If it can be solved, the United States will not give up the more mature magnetic constraint to engage in inertial constraint, and the European side will not be more inclined to stellarators.

But maybe the young man in front of him has a unique way of thinking and can create miracles?

Hearing this question, Xu Chuan thought for a moment, and then said: "To be honest, it is quite difficult to comprehensively solve these problems on a certain route. ”

"Problems such as magnetic plane tearing and plasma islanding are among the biggest problems of tokamak and tokamak-like devices."

"To solve this problem, in my personal opinion, we have to start from two aspects."

Hearing this, Peng Hongxi's eyes suddenly showed an interested look, and he asked curiously, "Which two aspects?" ”

Xu Chuan: "Outfield coils and CNC models!" ”

Peng Hongxi quickly asked, "What do you say?" ”

After thinking for a while, Xu Chuan said: "As we all know, problems such as magnetic plane tearing and plasma magnetic islands in the tokamak device mainly come from the way the magnetic field is provided. ”

"In the tokamak, the rotational transformation of the spiral magnetic field is formed by a combination of the toroidal field generated by the outer coil and the polar magnetic field generated by the plasma current."

"This can lead to collisions between the annular and polar magnetic fields, as well as problems such as difficulty balancing, which can cause tearing of the magnetic plane during operation."

"The stellarator has an advantage in this regard, its longitudinal and polar magnetic fields are completely supplied by the outer coil, and the magnetic plane tear does not form inside."

"So theoretically, it can operate without plasma currents, and it can also avoid a lot of instability due to current distribution, which is one of its main advantages."

"I am now considering a follow-up re-transformation of the dawn breaking device, combining the advantages of the stellarator, resetting the outer field coil of the dawnbreaking device, and combining the curved surface advantages of the pebble bed, to try to reduce the magnetic field provided by the polar plasma current, so as to use the external field coil to synchronize control and rotation."

Judging from the experience of Xu Chuan's rebirth, from around 2025, countries have gradually begun to abandon single fusion devices and start to study fusion devices.

For example, the Planck Plasma Institute, Spiral Stone 7X will choose to cooperate with the PPPL laboratory in Princeton, using the PPPL laboratory's magnetic mirror control technology to optimize the neoclassical transmission of the stellarator.

Or the quasi-ring symmetrical stellarizer researched in China is also using tokamak technology to optimize the stellarumer.

It has to be said that after the application of superconducting materials to controlled nuclear fusion technology, the advantages and future of stellarum are actually greater than those of tokamak devices.

The stellarator also has fewer problems to solve than the tokamak.

As for why he still chose to go on the tokamak device, the biggest reason is that the plasma performance of the tokamak device far exceeds that of the stellarator.

That's right, at the moment, even the most advanced Spiral Stone 7X can create a plasma performance that is only an ordinary medium level for a tokamak device.

The tokamak device can easily achieve the plasma temperature of 100 million temperatures, but the stellar simulator has to die if it wants to achieve the temperature of 100 million people.

Anyway, the current stellar simulator can't do it.

The most advanced stellarator at present is the Planck Institute for Plasma Research's 'Spiral Stone 7X'.

Although a record of 50 million degrees and six and a half minutes was previously set, in fact it was only the temperature of the electrons that reached this temperature, and its plasma temperature only reached 20 million degrees.

Although the temperature of 20 million degrees has reached the minimum temperature of deuterium-tritium fusion of more than 14 million degrees, in controlled nuclear fusion, the higher the temperature, the more likely the fusion phenomenon will occur, and the higher the energy that can be provided, which is beyond doubt.

Of course, this is only a simple explanation.

In fact, what really affects the efficiency of fusion is the reaction cross-section, which is the probability of collisions between positively charged nuclei in the plasma.

The factor that affects the probability of collision is the fusion triple product, which is the product of the density of the reaction species, the reaction temperature, and the confinement time.

The greater these three factors, the more likely fusion is possible.

For example, the higher the plasma density, the higher the probability of collisions between plasmas.

For example, the probability of you being trampled during the Spring Festival is much greater than the probability of being trampled on the train you usually take, because there are too many people;

The higher the temperature of the plasma, the higher the activity of the plasma.

After all, the temperature itself reflects the intensity of the particle's motion, and the more active the particle, the higher the probability of collision and fusion.

It's also like the Spring Festival, if everyone sits quietly and waits for the car, it's not easy to be stepped on. The real risk is that when everyone gets up and gets on and off the train, there is a greater probability of stepping on your feet.

Raising the temperature is to make the particles active, and the particles are like crowds, and when they are active, they are easy to collide together.

As for controlling time, then don't talk about it.

And on these three factors, the tokamak has an advantage in the first two, and the stellarum has an advantage in the latter.

This is one of the reasons why Xu Chuan chose to start with a tokamak-like device instead of a stellarroder.

Of course, the advantages of the stellar simulator are still great, and the advantages of controlling the magnetic field are worth learning from the tokamak device.

He plans to take advantage of this and modify Daybreak's outfield coils to optimize problems such as magnetic plane tearing and plasma islanding in the tokamak device.

As for the control model, if the previous problem of resetting the outer field coil of the dawn can be handed over to other researchers to work together, the latter one can probably only be done by himself.

Fortunately, after returning from rebirth, he immediately chose to major in mathematics, which gave him enough mathematical ability to do this.

On the sofa, Peng Hongxi thought for a moment and said, "So you're going to refer to the outfield coil of the stellar to improve Daybreak?" ”

Xu Chuan smiled and nodded, shook his head again, got up and dragged a blackboard out of the corner of the office.

"Yes, but that's the transformation of the outfield coil, as for the mathematical model control, I also have some ideas here, just this year you are old, help take a look?"

Peng Hongxi stood up, walked over and said, "What is not palm-eyed, on the road of controlled nuclear fusion, you have gone much farther than me, and your ability is stronger than that of me, a bad old man." ”

Xu Chuan smiled, took out a white piece of chalk from the chalk box hanging on the edge of the blackboard, and said while writing mathematical formulas on the blackboard:

"In tokamaks, perturbations of bootstrap currents can excite neoclassical tear patterns, and bootstrap currents are proportional to the pressure gradient."

"When a magnetic island is formed, the local pressure gradient within the magnetic island is reduced by a transmission parallel to the flux tube of the magnetic field lines, which results in a decrease in the bootstrap current. So in the tokamak, this negative current disturbance causes the island to grow further. ”

"And from the data of the first ignition operation experiment, I found something interesting, using helium-3 and hydrogen to run the model, in fact, it is not without magnetic surface tearing, but it is much weaker."

"I analyzed the data before and found that the resonance interaction between high-energy ions and the 2/1 tear mode excites the excitation mechanism of the 2/1 fishbone model, and gives a resonance relationship that can explain the energy exchange between the main wave and the high-energy ions in the phase space."

"And the resonance relationship between waves and ions can be mathematically written: nωt+pωp-ω=0"

"If the higher-order correction of the polar drift orbit is considered, the resonance relation is mathematically modified as: ωt+(m+l)ωp-ω=0"

"i.e. co-passingωt+ωp=ω, co-passingωt+2ωp=ω"

"When the ejection angle of the high-energy ion distribution center is Λ0=0.6 and the specific pressure value of the high-energy ion is βh=0.35%, the perturbation distribution function δf near the magnetic moment μ=0.554 in the Pφ-E phase space"

“.”

In the office, Xu Chuan stood in front of the blackboard and wrote some things he had sorted out based on experimental data.

On the side, Peng Hongxi also got up from the sofa and walked over, silently looking at the equations on the blackboard, and listening to Xu Chuan's explanation.

In tokamak installations, problems such as magnetic surface tearing, electromagnetic islanding, plasma islanding, etc., are very troublesome problems in the true ignition of deuterium-tritium.

Even among the various problems encountered in controlled nuclear fusion as a whole, it is one of the most troublesome.

The severity is not weaker than the problems of the first wall material, tritium recovery, neutron radiation, etc.

Because the loss and redistribution of high-energy ions will directly affect the density of high-energy ions in the core, affecting the fusion efficiency.

Secondly, the escape of high-energy ions from the confinement zone and the first wall will also introduce impurities to the plasma, reduce the heating efficiency of high-energy ions, directly affect the performance of plasma in future fusion reactors, and become a stumbling block for steady-state long-pulse operation.

This is a problem that the tokamak has had since it was proposed.

On the one hand, the reason why the stellarator is now starting to be re-favored by various countries is that after the development of superconducting materials has solved the problem of the original magnetron instability of the stellarumer, it is that it does not have the problems of tokamak magnetic plane tearing, plasma magnetic islanding, etc., and is more suitable for control.

But if problems such as magnetic plane tearing and plasma magnetic islanding can be solved, there is no doubt that tokamaks are more suitable for controlled nuclear fusion than stellarators.

Because it has a huge advantage in increasing the temperature of the plasma.

Just, can it be done?

For this question, to be honest, Peng Hongxi does not know.

But on today's blackboard, he sees a glimmer of hope.

Although he is now standing in front of the blackboard, listening to the explanation and looking at the calculations, he can't keep up with the rhythm, and can only roughly understand his thoughts from some words.

But that's sometimes the case with scientific developments, especially in mathematics, and whether an idea is feasible or not, sometimes the intuition at first glance is quite accurate.

From these data, it is feasible to explain the main resonance relationship between high-energy ions and the resonance of the 2/1 tear mode to excite the main resonance relationship of the 2/1 fishbone model by changing the center projectile angle parameter Λ0 in the high-energy ion distribution function to change the types of high-energy ions loaded into the simulation system and their share sizes."

"As for the specific situation, I'm afraid we will need to wait until the Daybreak device realizes the deuterium-tritium fusion experiment, and then collect enough data to confirm."

In front of the blackboard, Xu Chuan threw the chalk head back into the chalk box in his hand and turned his head to look at Peng Hongxi.

The old man didn't answer immediately, he thought for a while, and then said with a glint in his eyes: "From your analysis and data, the tear mode can be coupled with the high-energy ion-driven Alfin mode to produce new physical phenomena, and the large Alfin perturbation can nonlinearly drive the tear mode to reconnect and excite the macroscopic magnetic island. ”

"So, how to stabilize the Alphen perturbation should be your main idea, right?"

Hearing this, Xu Chuan grinned, nodded and praised: "That's right, Peng Lao is still amazing!" See through the core idea at a glance. ”

"If the occurrence of Alphen perturbations can be suppressed to a certain extent, theoretically speaking, the phenomenon of magnetic surface tearing will be much reduced. This may be a solution to the problem of magnetic surface tearing. ”

Hearing Xu Chuan's praise, Peng Hongxi shook his head and said, "What's amazing, old, really old." With such a detailed explanation from you, it would take me a long time to figure it out. ”

"But from what you've said, it might be possible."

After a pause, he continued: "I'm looking forward to it now, with you, maybe I can really see the spark of controlled nuclear fusion light up in my lifetime." ”

PS: It's very Carvin today, so let's start with this chapter.

In addition, I would like to ask you if you are interested in this process of solving the principles of controlled nuclear fusion in detail?

If you're not very interested, I won't write so much later, it's too detailed for me to write, and it's hard for you to understand QAQ, so it's better to skip pretending to be more cool?