155: Chapter 155 Fully Superconducting Tokamak Nuclear Fusion Experimental Device

Leaving the main control hall, Academician Yang and Engineer Yang led Chen Youhua through several heavy protective doors and into an even larger experimental hall with an extremely high ceiling.

The air here carried a unique, faint scent—a mixture of metal, insulating materials, and cryogenic coolant—and the temperature seemed slightly lower than outside.

The first thing that caught Chen Youhua's eye was an incredibly massive, ring-shaped device.

It was not a single, monolithic piece, but rather a layered assembly of countless giant silver-white metal modules, superconducting cables, copper pipes, steel support frames, and various high-precision diagnostic instruments labeled with English abbreviations.

This was the main body of the Experimental Advanced Superconducting Tokamak.

It stood silently in the center of the hall, its volume filling one's entire field of vision. The intricate, complex intersection of mechanical and electronic equipment made it impossible for any man who saw it to look away.

"Come, Youhua, this way. We'll follow the visitor's path."

Academician Yang Zhenyu acted as a guide, his tone carrying the familiarity and pride of someone introducing their own child.

"First, look at the core: that ring-shaped vacuum chamber wrapped in layers."

He pointed toward the massive ring structure at the very center of the device.

"Its inner wall is made of a special stainless steel alloy, requiring extremely high internal precision. Plasma is created within this doughnut-shaped device and is simultaneously confined inside it."

"To achieve an ultra-high vacuum environment, we have a very complex vacuum pumping system."

Chen Youhua looked up and noticed that the exterior of the vacuum chamber was connected to countless ports and windows of various sizes.

Academician Yang explained, following his gaze.

"Most of these ports are reserved for diagnostic and measurement equipment."

"To monitor the state of the plasma in real-time, we need many types of sensors: laser interferometers to measure temperature, microwave reflectometers for density and distribution, high-speed cameras to observe plasma behavior, and various spectrometers to measure impurity spectra... Behind every diagnostic tool is a dedicated research team."

As they walked slowly forward, Academician Yang pointed to the massive circular coils surrounding the vacuum chamber.

"These are one of the cores of the device: the Superconducting Toroidal Field Coils."

"They are made of niobium-titanium or niobium-tin superconducting materials and are immersed in a cryogenic environment created by liquid helium, close to absolute zero. Only then can they generate a powerful, stable toroidal magnetic field without resistance, which is the key to confining the high-temperature plasma."

"Maintaining such a low temperature must be a massive engineering challenge, right?"

Chen Youhua asked, seeing the complex cryogenic transport pipes and insulation systems connected to the coils.

"It's enormous!"

Academician Yang confirmed.

"The cryogenic system itself is an incredibly complex piece of engineering."

"Any tiny heat leak could cause the superconductor to quench, and that instantaneous release of energy is very dangerous."

"That's why these support and insulation structures are designed with such meticulous care."

Next, Academician Yang pointed to another set of coils wrapped around the outside of the toroidal field coils.

"These are the Poloidal Field Coils."

"They are responsible for generating and controlling the shape and position of the plasma, preventing it from touching the walls of the vacuum chamber."

"Their current needs very fast and precise feedback control based on the state of the plasma."

Engineer Yang added a detail from the side.

"The power supply system controlling these coils is extremely powerful, requiring millisecond-level response times. It puts quite a strain on the power grid."

They walked to another side of the device, where some ports connected to thick pipes were visible.

"These are the inlets for the heating system," Academician Yang introduced.

"To heat the plasma to over a hundred million degrees, we need a massive energy input."

"We mainly use two methods. One is Neutral Beam Injection, which injects high-energy neutral atom beams into the plasma to heat it through collisions."

"The other is Ion Cyclotron Resonance Heating and Electron Cyclotron Resonance Heating, which use microwave energy at specific frequencies to heat it."

Chen Youhua noticed an area at the bottom of the device where the structure looked particularly heavy and the materials seemed different.

"Is that the Divertor region?" he guessed based on the materials he had read before.

"Exactly! Good eye!" Academician Yang praised.

"The Divertor is a key component for handling exhaust gases and removing heat."

"Impurities and helium ash in the high-temperature plasma are guided by specific magnetic field configurations to the Divertor target plates."

"The materials there must withstand extremely high heat loads and particle bombardment. Currently, we've tested carbon fiber composites, tungsten-copper alloys, and so on, but the challenges remain immense."

Throughout the tour, technicians and researchers in work uniforms passed by them from time to time, all greeting Academician Yang respectfully and casting curious, admiring glances at Chen Youhua.

Academician Yang would occasionally stop one or two of them to ask about the commissioning progress of a certain component or the status of some data, demonstrating his deep understanding of every detail of this massive device.

The entire tour lasted nearly an hour.

Finally, they walked up a set of stairs to a relatively high observation platform, from where they could overlook the entire east device.

From this perspective, one could better appreciate the complexity of its structure and the grandeur of its scale.

Academician Yang looked out over the railing and began to systematically summarize the entire nuclear fusion operation process.

"Youhua, look. This entire device exists solely to achieve and maintain a controlled nuclear fusion reaction."

"Roughly speaking, the entire process can be divided into several steps."

He held up his fingers, counting them off one by one:

"Step one: first, pump that ring-shaped vacuum chamber to an ultra-high vacuum to avoid any impurities. Then, inject a tiny amount of hydrogen isotope fuel—usually deuterium gas."

"Step two: ignition and confinement. Start the superconducting magnet system to generate a powerful confining magnetic field."

"First, use the primary coil to induce a plasma current, which also generates heat. Then, use Neutral Beam Injection and radio-frequency wave heating to ionize the fuel gas into plasma and continue heating it to over a hundred million degrees Celsius."

"At this point, the magnetic field is responsible for confinement, keeping the entire nuclear fusion reaction process in the center of the vacuum chamber so it doesn't touch any of the walls."

"Then comes maintenance and burn. We need to precisely control various parameters."

"Magnetic field configuration, plasma current, density, temperature, heating power, and so on—striving to keep the plasma in a stable, high-performance state for a sufficiently long time."

"In this phase, the deuterium nuclei have enough opportunity to collide with each other, undergo a fusion reaction, and release energy and neutrons."

"The final step: handling the energy and products."

"The high-energy neutrons produced by fusion carry most of the energy and penetrate the magnetic field. They are absorbed by the Blanket structure surrounding the vacuum chamber. Theoretically, in the future, materials in the Blanket will absorb the neutron energy, convert it into heat, and then generate electricity through a traditional heat exchange system."

"As for the helium ash produced by fusion, if too much accumulates, it will cool the plasma. So, the Divertor system is needed to effectively exhaust these waste gases."

"Of course," Academician Yang sighed.

"It sounds like just a few steps, but every single one is filled with countless scientific and engineering difficulties."

"Plasma itself is very hard to tame. All sorts of instabilities, impurities, energy losses... if any link in the chain fails, the experiment could fail."

Chen Youhua listened in silence, his gaze slowly sweeping across the massive device below, which embodied the blood, sweat, and wisdom of countless people.

It was quite a while before he spoke.

"It's very systematic and truly awe-inspiring."

"From the macroscopic theoretical framework to the engineering design of every specific component, material selection, control algorithms, and then to daily maintenance and commissioning—the span between these is even more massive than I imagined."

"My mathematical models work on a highly simplified and idealized level, whereas your work involves dealing with a real physical world full of uncertainties and extreme constraints."

He paused and pointed toward the Divertor and the heating system.

"Particularly the behavior of materials under extreme conditions and the real-time balance control of energy injection and exhaust—these might be even more decisive bottlenecks than the plasma physics theory itself."

"My previous calculations might have pursued a certain mathematical optimum, but it seems I must consider these engineering implementation limits and response times more deeply."

"For the day after tomorrow's experiment, I will pay special attention to the real-time data on Divertor heat load, plasma boundary stability, and heating system feedback efficiency."

Academician Yang slapped the railing hard in agreement.

"Exactly! Theory pursues beauty and the ultimate, while engineering focuses on reliability and feasibility."

"With you here for the experiment the day after tomorrow, I feel much more confident!"

The tour ended, and the group left the grand experimental hall.

Returning to the surface, the afternoon sunlight spilled in through the tall windows.

Academician Yang checked the time and said to Chen Youhua.

"Youhua, this afternoon the various groups will compile the commissioning data from the last few days. There might be some detailed issues I'll have to trouble you to look over with us."

"Tonight, I'll have the cafeteria prepare a few local specialty dishes. We can chat while we eat, how about it?"

"Alright, I'll follow your arrangements," Chen Youhua nodded in agreement.

Part of his mind had already flown to the data that was about to be sent over, and to that critical experiment the day after tomorrow.

Through this massive nuclear fusion device, Chen Youhua could gain a deeper understanding and learn how to apply his mathematical abilities to these complex engineering instruments in the real world.