China's largest single superconducting magnet was successfully developed

At 5 pm on September 19, the scene of the major reconstruction project of the Electronic Collider of the Institute of High Energy Physics of the Chinese Academy of Sciences was a joyous scene. A celebration of a simple and warm atmosphere was held here. After three years of hard work, the Beijing Spectrometer III (BESIII) superconducting magnet developed by Chinese scientists and engineers and technicians was successfully excited.

“BESIII superconducting magnet is one of the key components of Beijing spectrometer. It is necessary to have a strong magnetic field to achieve electron collision. The way to get strong magnetic field is to increase the number of coils of electromagnet coil and increase the current of electromagnet. Multi-wound coils can cause difficulties such as excessive magnet volume and high temperature. Superconducting magnets use the phenomenon that the conductor has zero resistance under certain temperature conditions, and a strong current is added to the magnet to obtain a strong magnetic field. Wang Yufang, deputy director of the Institute of Physics, said, "We use liquid nitrogen and liquid helium to cool the system to achieve superconductivity at around 270 °C. This morning, the superconducting magnet was successfully excited at 8:00. The test results show that the superconducting magnet is excited to 10,000. Gauss is 20,000 times of the earth's magnetic field, the current reaches 3,368 amps, and the maximum energy storage reaches 10 million joules. The various indicators meet the design requirements. Its successful development marks a great advancement in China's superconducting technology. An important milestone in the construction of the major reconstruction project of the collision aircraft. At present, only the European and American countries in Japan can carry out such large-scale detector single superconducting magnets.

"We use a single superconducting magnet. Compared with other combined superconducting magnets, the single superconducting magnet has a large diameter, a high magnetic field strength, and a uniform magnetic field strength, which is the magnetic field expected by the Beijing spectrometer. Conditions." Because of continuous day and night, plus a small half cup of celebration champagne, the head of the high-energy Beijing spectrometer superconducting magnet system Zhu Zi'an from the bottom of the eye to the neck is a little red.

The superconducting magnet developed by High Energy Physics has a diameter of 3.4 meters and a length of 4 meters. Zhu Zi'an said that when winding superconducting coils, the requirements for pre-stressing and internal cleanliness of superconducting wires are very high. Twelve engineers and technicians were divided into two groups. They were drilled into the magnet for 24 hours, brushed with low temperature glue, and dried for 3 months. Because of the special low-temperature epoxy glue, the low-temperature adhesive has strong penetration. Although the technician wears rubber protective gloves, many people take off their hands on the hands. Later, they use ventilation during construction. This problem was solved by measures such as sweat removal, double protection of rubber and cotton gloves.

The current lead is a transition piece that energizes the superconducting magnet and is one of the key components of the superconducting magnet. Due to problems with current leads imported from the United States, the progress of the BESIII superconducting magnet system has been greatly affected. In order to ensure the progress of the project, the superconducting magnet group decided to carry out the research and made the current lead. After consulting the experts of low temperature and superconducting magnets at home and abroad, after fully discussing and calculating, they designed a new current lead and in the valve box. The design of the cooling chamber has been added and a detailed test plan has been developed. The superconducting magnet group carefully organizes the materials, design, processing, assembly, etc., and overtime work has completed the test of the current lead. The test results prove that the self-developed current lead has superior comprehensive performance and can ensure the stability and reliability of the superconducting magnet. . "Because the development of such a large superconducting magnet involves many technical details, it has not been done before in China. During the development process, we hired two retired foreign superconducting experts, and also received enthusiastic help from experts from the United States, Japan and Germany. The BESIII superconducting magnet is the largest superconducting magnet in China developed by the Institute of High Energy Physics. This shows that we have the power to make achievements in superconducting magnet technology. The application of superconducting magnets in national economy and population health care Widely, but China is almost entirely dependent on imports. After the high-energy physics of the Chinese Academy of Sciences has all such a foundation, the next step is to transform the results. At present, it has begun to develop superconducting magnets for medical magnetic resonance imaging and to remove trace magnetic impurities in coal and other substances. Superconducting iron remover. We will strive to make a difference in civilian superconducting magnets." Zhu Zi'an said.