We already have a sun, so why do we need to research "artificial sun"?

Review expert: Gan Qiang, lecturer at Beijing Institute of Technology, PhD in Applied Chemistry

The "artificial sun" broke the record again, the domestically-made large passenger aircraft C919 achieved commercial operation, Xinjiang's saline-alkali land had a bumper harvest of seafood, the medical heavy ion accelerator was put into clinical application, the first domestically-made large cruise ship "Aida Magic City" successfully completed its sea trial, and the world's deepest underground laboratory was waiting for a "visit" from dark matter... In 2023, my country's science and technology continued to make new breakthroughs, bringing new possibilities and opportunities to human life and development.

On the occasion of the 74th anniversary of the founding of the People's Republic of China, Digital Beijing Science Center has brought you a special column "Great Power Science and Technology Style", allowing us to review the scientific and technological achievements made this year under the leadership of the Party.

On August 25, 2023, the Southwest Institute of Physics under China National Nuclear Corporation announced that the new generation of "artificial sun" "China Tokamak No. 3" (HL-2M) has achieved high confinement mode operation under a plasma current of 1 million amperes for the first time. It is based on the nuclear fusion reaction inside the sun and can release huge energy after the reaction.

CAD drawing of China's Circulation 3 Source: Wikipedia

This breakthrough is a reflection of the comprehensive capabilities of the nuclear fusion device and an important milestone in my country's nuclear fusion energy development process. Earlier in November 2022, the Institute of Nuclear and Astronomy announced that the HL-2M plasma current exceeded 1 million amperes for the first time. What is the significance of the "high confinement mode operation" achieved this time?

1

What is the research significance and operating principle of the “artificial sun”?

The "artificial sun" is actually a large-scale thermonuclear fusion reactor, and its core technology is nuclear fusion technology. Nuclear fusion is a process that fuses light elements (such as hydrogen) into heavy elements (such as helium) under high temperature and high pressure conditions, releasing huge amounts of energy through fusion reactions . This form of energy release through artificial fusion reactions is very similar to the nuclear fusion reactions that occur in the star sun, so it is called an "artificial sun."

Deuterium-tritium nuclear fusion reaction produces helium and neutrons Source: Wikipedia

The conditions for achieving nuclear fusion are very demanding. In the sun, the nuclear fusion process occurs at extremely high temperatures (millions of degrees Celsius) and extremely high pressures, both of which are indispensable. Scientists use strong magnetic fields and plasma to simulate these conditions on Earth.

Plasma is a high-temperature gas state, usually composed of hydrogen isotopes (such as deuterium and tritium). It is an ionized gaseous substance composed of positive and negative ions produced when some atoms and atomic groups are ionized and their electrons are deprived. Scientists use magnetic fields to control the movement of charged plasma to prevent it from contacting the container shell, which would cause serious consequences such as damage to the device.

To get the plasma to the required high temperatures, scientists use various heating systems, such as lasers, microwaves or radio frequency heaters . When the plasma reaches a high enough temperature and pressure, nuclear fusion reactions begin to occur. This process fuses hydrogen isotope nuclei into heavier elements, usually deuterium-tritium reactions, producing helium and neutrons and releasing huge amounts of energy.
Once nuclear fusion occurs, the energy released needs to be captured and utilized. This energy is converted into electrical energy through heat exchange equipment around the reaction chamber.

Although a commercial controlled nuclear fusion power plant has not yet been built, international cooperation projects, such as the International Thermonuclear Experimental Reactor (ITER), are actively promoting the realization of this goal.

2

Research progress of "artificial sun"

The "International Thermonuclear Experimental Reactor (ITER) Project" is the official name of the "artificial sun". It is one of the world's largest and most far-reaching international scientific research cooperation projects. The ITER device is a superconducting magnetic confinement fusion device, also known as a "tokamak", which can be used for large-scale nuclear fusion reactions. China officially joined the ITER project negotiations in January 2003. In May 2006, the Chinese ITER negotiation joint team signed a cooperation agreement with six parties including the European Union and India. In 2006, it independently designed and developed the world's first all-superconducting magnetic confinement fusion device, which passed the national acceptance in 2007.

my country's decision to participate in the ITER project is not only to improve the country's basic physics research level, but also to consider long-term energy needs and environmental conditions, to ensure the ability to develop efficient and clean future energy and ensure the sustainable development of Chinese society.

Small model of ITER's tokamak device Source: Wikipedia

On July 28, 2020, the major project launch ceremony of the International Thermonuclear Experimental Reactor (ITER) was held at its headquarters in France.

On December 28, 2020, South Korea's superconducting tokamak advanced research set a new world record. The superconducting magnetic confinement fusion device successfully maintained a high temperature state of plasma at over 100 million degrees Celsius for 20 seconds.

At 3:02 a.m. on May 28 this year, after 40 years of hard work by Chinese researchers, the "China Hullus-3" fully superconducting magnetic confinement fusion device achieved 101 seconds of plasma operation at an extremely high temperature of 120 million degrees Celsius . Even after the temperature was raised to a terrifying 160 million degrees Celsius, the fusion device was still able to operate at high temperature for 20 seconds. This is a major scientific and technological progress made by China in the field of controlled nuclear fusion, and an important step in the field of global scientific research and engineering.

3

Future opportunities and challenges

The controlled nuclear fusion technology used in the "artificial sun" is a major challenge in the field of basic physics. The research and application of nuclear fusion is a huge and complex scientific and engineering challenge. Thousands of scientists and engineers around the world have worked together day and night to explore the secrets and spent decades exploring the core technology of controlled nuclear fusion, which also consumed huge material and human resources. However, there are still some spaces and difficulties that need to be made up for in today's controlled nuclear fusion.

① Huge demand and loss of electricity

To control the high-temperature plasma in the "artificial sun", a huge magnetic field is needed. Taking the International Thermonuclear Reactor (IETR) as an example, its magnetic field is as high as 130,000 gauss. To maintain this intensity of magnetic field, a huge current needs to be passed through the conductor. Due to the existence of resistance, the conductor heats up very seriously, which will cause huge power loss. Most of the current superconducting materials require a high-pressure and low-temperature environment, which makes an "artificial sun" appear "ice and fire", which is difficult to achieve.

Suspended superconducting material Source: Wikipedia

② Balance of energy input and output

In controlled nuclear fusion, it is necessary to ensure that the energy input is greater than or equal to the output to maintain the nuclear fusion process, which is also known as the "Lawson criterion." This requires engineers to collect and convert the energy generated while investing a lot of energy to heat the plasma.

③Material tolerance

Currently, the high-energy neutrons produced by plasma can damage the shell and other materials. Therefore, materials scientists still need to develop new materials to improve their irradiation tolerance so that the reactor can operate stably for a long time.

④Control plasma

Plasma is a highly unstable state, and the temperature and pressure inside it are not uniformly distributed in space, which makes plasma very unstable. Scientists are studying more stable ways to achieve precise control to prevent it from drifting, twisting or magnetic field instability.

⑤ Large-scale funds

To conduct controlled nuclear fusion research, it is necessary to build huge laboratories, such as the International Thermonuclear Experimental Reactor (ITER), which requires huge funds and international cooperation. These constructions are designed to accommodate complex equipment and large-scale experiments to simulate nuclear fusion reactions.

Fusion energy has many advantages, such as unlimited raw materials, zero environmental pollution, and no high-level radioactive nuclear waste. Therefore, it is considered one of the main prospects for human energy in the future. Researching "artificial sun" is a key step taken by mankind in the process of searching for new energy.

Despite these difficulties and challenges, scientists are constantly improving technology and equipment, taking solid steps toward the goal of achieving controlled nuclear fusion. We are expected to make more breakthroughs in the near future, providing more options for solving energy problems and mitigating climate change.