1056 seconds! China's "artificial sun" EAST sets a new record for the longest discharge

On the evening of December 30, 2021, the world record for the longest time high-temperature plasma operation of the Tokamak device was broken again!

China's "artificial sun" EAST successfully achieved 1056 seconds of long-pulse high-parameter plasma operation, breaking its own record of the longest discharge of 411 seconds (the original record was set on June 27, 2012), and the operating time exceeded four digits for the first time!

Image source: China Science Expo

How did the new record come about? What does it mean? Members of the EAST research team tell you.

Part 1

First, let me introduce the record-breaking player——EAST

"Artificial sun" is a popular term for "nuclear fusion reaction device". It is called artificial sun because its reaction principle is the same as that of the sun. The purpose of studying artificial sun is to solve the energy crisis facing mankind.

In a nutshell, controlled nuclear fusion is to imitate the principle of the sun's energy generation, with the goal of generating a steady stream of clean energy at extremely high efficiency. Based on the current theoretical basis, there are several ways to achieve controlled nuclear fusion, and tokamak is one of them. The fully superconducting tokamak nuclear fusion experimental device in Hefei, referred to as EAST, is one of the most important nuclear fusion research experimental platforms in the world.

No way, no way, there is no one who doesn’t know what EAST is?

Part 2

1000+ seconds of discharge, exciting moment

At 21:55 on December 30, EAST started the 106915th discharge experiment. The goal of this discharge was to obtain an ultra-long pulse high-temperature plasma of more than 1000 seconds. The preset discharge length was 1057 seconds, which would be a new world record if successful. With the end of the 60-second countdown, the plasma was successfully established, and the low-noise current drive and electron cyclotron were subsequently put into stable operation.

Live discharge in the EAST control hall

(Image source: provided by the author)

After that, there was a long wait. For nearly 18 minutes, everyone stared at the main control screen, looking forward to the birth of a new record. Some colleagues even took out their mobile phones to record this exciting moment. At 22:14, the plasma landed smoothly, and the duration on the screen finally stopped at 1056.66 seconds. The longest discharge record of 1000+ seconds ultra-long pulse high-temperature plasma was born, and warm applause rang out all around.

1056 seconds ultra-long pulse discharge

(Image source: provided by the author)

Part 3

1000+ seconds breakthrough for the first time, challenging three major scientific problems

This experiment is the first time that EAST has broken the 1,000-second mark. In order to successfully obtain 1,000-second ultra-long pulse high-temperature plasma, there are many scientific problems to be faced, the most prominent of which are: completely non-inductive current drive, recycling and impurity control, heat and particle discharge, etc.

First, the operation of ultra-long pulse plasma depends on radio frequency wave current drive. EAST is mainly based on radio frequency wave heating. It is the only device in the world that has the same heating method as the International Thermonuclear Experimental Reactor (ITER) and is most capable of achieving long pulse high-performance operation on the particle balance time scale. The 1056-second long pulse plasma was obtained this time, and EAST's low-clutter current drive and electron cyclotron drive both achieved full follow-up, providing important guarantees.

EAST is one of the most advanced nuclear fusion experimental devices in the world.

(Image source: provided by the author)

Secondly, the problem of impurity control is also very critical. As the operation time scale increases, the interaction between the plasma and the wall will lead to a large explosion of impurities. In this experiment, the EAST team suppressed impurities through lithium injection to ensure the realization of long pulses.

In addition, the extension of time will also lead to a large amount of heat and particle accumulation, which need to be effectively discharged. EAST's advanced divertor design successfully solves this problem.

The upgraded inner vacuum chamber of EAST

(Plasma runs here)

Part 4

1000+ seconds behind the scenes, collaborative operations

As a large-scale scientific project, EAST is a systematic project. Behind the breakthrough of 1000-second ultra-long pulse high-temperature plasma is the coordinated operation of multiple systems.

Among them, it is worth mentioning the solution to the problem of magnetic measurement signal drift. Accurate magnetic measurement is the basis of plasma balance control. Any small measurement error may be amplified after 1000 seconds of accumulation until it affects the control of the plasma. At the beginning of this round of experiments, the EAST team's plasma control group, electromagnetic measurement group, experimental operation group, etc. carried out relevant tests and optimization work on the problem of magnetic measurement signal drift. After much exploration and improvement, the working group developed a fitting weight model to achieve accurate deduction of signal drift and ensure the accuracy of plasma control over a long time scale.

Optimization of EAST magnet measurement system

Part.5

1000+ seconds is the goal and the starting point

EAST is the world's first fully superconducting tokamak experimental device with a non-circular cross-section, independently designed and built by my country. It has three major scientific goals: 1 trillion ampere plasma current, 100 million degree high-temperature plasma, and 1000 seconds of operation time.

EAST device

The EAST device, built in 2006, operated a plasma current of 1 megaampere in 2010, obtained a high-temperature plasma of 100 million degrees for the first time in 2018, and successfully achieved repeatable plasma operation at 120 million degrees Celsius for 101 seconds and 160 million degrees Celsius for 20 seconds in May 2021 (How did China's "artificial sun" set another world record?

https://mp.weixin.qq.com/s/9bXJcquNPFcQ5lJTiMYFrw), and achieve operation time of more than 1000 seconds by the end of 2021. The three major scientific goals have been independently completed.

On November 28, 2010, EAST ran a plasma current of 1 mA (34128)

On July 11, 2018, EAST obtained a plasma with an electron temperature greater than 100 million degrees Celsius for the first time (78841)

At the morning meeting on December 31, researcher Gong Xianzu, the general manager of the EAST experiment operation, concluded that "achievements belong to the past. 1000 seconds is a stage goal and a new starting point." The joy of success has not yet faded, and all members of the EAST team have invested in new experiments and continue to work hard for the next experimental goal.

So far, EAST has discharged more than 100,000 times. Along the way, each record is like a deep footprint, recording every step of my country's journey to develop and utilize fusion energy. There is only one destination on this road, which is to "light the first lamp of fusion energy in China." We believe that the end will always be reached.

Produced by: Science Popularization China

Produced by: Wang Teng

Unit: Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences

Producer: Computer Network Information Center, Chinese Academy of Sciences

(The images with source indicated in this article have been authorized)

The article only represents the author's views and does not represent the position of China Science Expo

This article was first published in China Science Expo (kepubolan)

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