Chapter 764: Need a Credible Demonstration Reactor Design

Just as Xu Qingzhou immersed himself in improving the liquid metal partial filter design, on August 27, the Max Planck Institute for Plasma Physics in Germany released stunning news.

The W7-X stellarator successfully maintained its Lawson criterion threshold for 360 seconds.

This meant the W7-X stellarator surpassed America’s NIF and became the most promising device for commercial fusion energy.

For fusion research, achieving commercialization requires meeting two independent metrics: the Q-value and the Lawson criterion.

Xu Qingzhou’s team’s current approach is to first meet the Lawson criterion, proving self-sustaining fusion, then break through the Q-value to achieve net energy gain.

The W7-X stellarator did the opposite: last October, its Q-value reached 15 with an operational duration of 30 minutes.

If its Q-value is already at 15—far exceeding the tokamak demonstration reactor standard—why hasn’t a reactor been built yet?

This is because the W7-X’s plasma density has not met the requirement.

The Lawson criterion demands a density of at least 10^20 particles per cubic meter, but stellarators, constrained by their magnetic field structure, typically maintain lower densities to preserve plasma stability.

In simple terms, it’s like a rocket engine reaching ignition temperature with a combustion chamber large enough to sustain thrust for 30 minutes, but the fuel injection concentration is too low—thrust never crosses the threshold, rendering it useless for actual launch.

Now, it has met the Lawson criterion and maintained it for six minutes.

That means, besides sustaining thrust for 30 minutes, the engine can now propel the rocket to fly at high altitude for six minutes.

Although it will still crash after six minutes, the fact that it can now lift off at all represents a qualitative leap.

Next, as long as they continue extending the duration of both the Lawson criterion and the Q-value, building a demonstration reactor is merely a matter of time—putting them a full step ahead of America.

“Expected.”

Xu Qingzhou was not surprised by Klinge’s team’s achievement.

In timing, Germany acquired the superconducting thin films and upgraded its superconducting magnets nearly a year faster than America; even half a year now can create a significant gap.

“Stellarator commercialization seems considerably faster than tokamaks.”

“No wonder Klinge said in his email not to be too shocked.”

Xu Qingzhou leaned back in his chair, gazed out the window with half-closed eyes, and smiled faintly, “From every perspective, this is unprecedented progress—but Qiankun No.1 isn’t far behind.”

“If everything goes smoothly, we’ll begin the next experiment by mid-October.”

He had full confidence in the device he designed.

Setting aside distractions, Xu Qingzhou turned his attention to the conventional tokamak design data.

Academician Ren Nan's magnetohydrodynamic (MHD) diversion technology validation proceeded smoothly; now TBR ≥ 1.03, just 0.6 away from solving the tritium self-sufficiency challenge.

The divertor modification is showing promise; he planned to focus on the two key issues of spherical tokamaks: insufficient toroidal field strength and low neutral beam injection efficiency.

While completing the net energy gain experiment, they must also produce a credible demonstration reactor design.

At 5 p.m., Xu Qingzhou returned to the lab.

“There’s still a 0.2% gap from the estimate. Run a few more experiments to find where the problem lies.”

In the lab, Xu Qingzhou told the team lead, Hu Jingxuan.

Hu Jingxuan’s team was responsible for magnetohydrodynamic vortex impurity capture to further raise the upper limit of first-wall thermal load capacity.

“Got it.”

Hu Jingxuan replied crisply.

Xu Qingzhou took the data to Senior Ren Xiaoling; for this period, Ren Xiaoling had been staying at the lab, while he handled data analysis and tokamak demonstration reactor design.

Hu Jingxuan told her three team members: “Alright, everyone go eat first. Meet back at 6:30 to discuss how to enhance the MHD shielding as Professor Xu suggested.”

“Alright.”

They packed up, prepared to go eat, and began chatting.