The Proton Displacement Damage Effect Simulation Test Facility (PREF) is constructed by the Institute of Modern Physics, Chinese Academy of Sciences. It can provide high-quality proton beams with continuously and precisely adjustable energy in the range of 10-60 MeV, high beam current, high duty cycle, and large scanning area. It is currently the only dedicated facility for displacement damage effect simulation tests in China. Developed based on the needs of major basic frontier research, this facility will fill the gap in China's space radiation effect test capabilities and become an important experimental platform supporting the development of China's space science, space technology, and domestic aerospace components. Meanwhile, the completion and beam extraction of this facility will also lay a solid foundation for the further promotion of China's applied accelerators. Based on the accumulated technology and experience in designing and constructing ion accelerators over generations, the accelerator team of the Institute of Modern Physics has, for the first time, adopted new technologies such as ultra-high vacuum chambers with titanium alloy ceramic ring linings and full-energy-storage non-resonant high-power power supplies in ultra-small proton synchrotrons. They have developed fast-rising full-waveform dynamic magnetic field compensation and real-time measurement technology for the synchronization of the entire system, realizing the digital simulation of the entire accelerator process and precise control of the beam. At the same time, the team has strictly controlled process specifications and procedures through BIM modeling of the entire engineering system, significantly improving project quality and laying a good foundation for the efficient operation of the facility. Traveling all the way west from Lanzhou, Gansu Province, across 2,000 kilometers, a reporter from *Science and Technology Daily* arrived at the Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences (hereinafter referred to as "Xinjiang Institute of Physics and Chemistry"). Here, lies the world's first Proton Displacement Damage Effect Simulation Test Facility (PREF) — a 60MeV (megaelectron volt) proton accelerator. In the invisible realm, hundreds of millions of charged protons are racing at a speed of a fraction of the speed of light. They gather together, forming a mighty beam. What can such tiny protons do? "For a long time, China has lacked a key facility capable of comprehensively evaluating the on-orbit radiation damage risks of devices, which has brought serious hidden dangers to spacecraft and payloads," Ruan Shuang, an associate researcher at the Accelerator General Office of the Institute of Modern Physics, Chinese Academy of Sciences (hereinafter referred to as "Institute of Modern Physics"), told the reporter. PREF will provide important support for research on the space displacement damage effects of devices and test evaluation methods. As the national team for scientific and technological innovation, in November 2018, the Chinese Academy of Sciences took on the heavy responsibility: with the Xinjiang Institute of Physics and Chemistry taking the lead and the Institute of Modern Physics in Lanzhou, Gansu Province in charge of the design, they jointly built PREF for carrying out ground simulation tests. A "Scarf" A seemingly ordinary small building located on Kexue 2nd Street in the New Urban District of Urumqi has no special features, except for the words "Commissioning Successful" on the red banner in front of the building, which makes it stand out. The reporter followed Ruan Shuang into the building, took the elevator down, and arrived at the accelerator hall, where the hardware equipment of PREF was in sight. The term "bird's-eye view" is not applicable to PREF. The facility is built underground, covering an area of about two mu (a Chinese unit of area, approximately 1,333 square meters), making it impossible to see its full view. However, when the reporter walked into its "core" and saw the array of various instruments, he was still deeply shocked. The entire accelerator consists of a proton source, a linear injector, a synchrotron, and two terminals. From the schematic diagram, it looks like a knotted scarf — the synchrotron is the "scarf ring", and the proton source and terminals are the two ends fluttering in the wind. Entering through the protective door, the first things that catch the eye are blue, yellow, and silver blocks. They are important working units of PREF: magnets and cavities. "The blue dipole magnets are used to make protons turn, the yellow quadrupole magnets are to constrain protons to move in the pipeline, and that silver magnetic alloy radio frequency cavity is to accelerate protons," Ruan Shuang told the reporter. These large components are connected in sequence to form a ring, i.e., the synchrotron. It looks small, and its circumference is indeed only 18 meters, making it the smallest in China. "Miniaturization is a prominent advantage of PREF," Shen Guodong, deputy director of the Accelerator General Office, said proudly. "Because it is small, its power consumption is low, making it more convenient for popularization and application." Ruan Shuang pointed to the blue block and gestured: "If you look closely, there are coils underneath. When a strong current is passed through them, the beam can be made to circle along the synchrotron." Every time the beam circles once, it passes through the radio frequency magnetic alloy loaded cavity once, and its speed increases a little. After millions of circles, it can reach a maximum speed of about 0.35 times the speed of light, and then be slowly extracted to the terminal for proton irradiation experiments. On this "scarf", there are also some silver cylinders dotted, which are titanium sublimation pumps. Titanium sublimation pumps use a chemically active titanium film on the surface to pump out gas, so as to obtain and maintain an ultra-high vacuum. "When 2.5MeV low-energy protons are injected, a high vacuum environment must be provided," Shen Guodong said. "Otherwise, the beam will disappear quickly." Two Unique Skills "Power supply and vacuum technology are the two unique skills of PREF," Ruan Shuang introduced to the reporter while showing around. A fast magnetic field change rate must rely on a fast-cycling power supply, but traditional power supplies, when working in a fast-cycling state, will cause serious impacts on the power grid. To solve this problem, the Institute of Modern Physics proposed a new technology of full-energy-storage non-resonant high-power power supply. This technology can recover the energy in the magnet load to the power supply for the next pulse use, which not only reduces costs and increases efficiency but also saves energy and reduces emissions. The fast-cycling vacuum chamber is another challenge for PREF. There are two solutions: one is thin-walled stiffening, and the other is all-ceramic vacuum chamber. "The former involves welding a circle of stiffeners on the outside of a 0.3mm thick stainless steel vacuum chamber, which works well, but it requires a special type of steel, and there are no manufacturers in China producing it. The latter, on the other hand, lacks the technology for making large-sized integral ceramic vacuum chambers, and air leakage will occur with existing technologies," Shen Guodong said. How to solve this problem? In early 2019, Yang Jiancheng, director of the Accelerator Center of the Institute of Modern Physics and chief engineer of the High-Intensity Heavy Ion Accelerator Facility (HIAF), led the team to "take the plunge". At the technical research seminar, team members "opened their minds" — since stiffeners can be added to the outside of the vacuum chamber, why can't they be added to the inside? It should be particularly strong, just like the arch in a city gate. After three years of effort, the team innovatively proposed a ceramic-lined vacuum chamber scheme. After three technical iterations and upgrades, they finally produced a titanium alloy-lined ultra-high vacuum chamber. This scheme was praised by Fritz Caspers, a senior technical expert from CERN (European Organization for Nuclear Research). He suggested naming the vacuum chamber "China Dragon". When the reporter said "I really want to see its true appearance", Ruan Shuang laughed: "The vacuum chamber is embedded in the magnet, and the titanium alloy lining skeleton is inside the vacuum chamber, so it can't be seen." Three Wishes Leaving the accelerator hall and returning to the ground, the reporter came to the central control room. Here, there are remote control equipment such as power supplies, radio frequency power sources, beam diagnosis and vacuum systems, as well as real-time monitoring systems for water cooling and ventilation, control networks, radiation protection, etc., all operating in an orderly manner. In the central control room, the reporter met Yao Liping, an assistant researcher at the Accelerator General Office. She and Ruan Shuang had come to Xinjiang from Lanzhou and had been working here for more than half a year. "Only by practicing the 'basic skills' well and fighting a 'coordinated battle' can we do things beautifully. I often think of what Director Yang said," Yao Liping said. Yang Jiancheng, who was directing from Lanzhou, did not deny this: "I have high requirements, speak directly, and am very strict with them. They have gotten used to it." The strictness stems from a profound lesson. "When we commissioned the facility in Wuwei, Gansu Province for the first time, we made many low-level mistakes," Yang Jiancheng said, adding that one of the mistakes took him a full six months to find out. Since then, to ensure the smooth launch of the equipment, each test link has to be repeated many times. Under Yang Jiancheng's strict requirements, the accelerator team is bold but careful and good at fighting tough battles. In March 2023, the process equipment was delivered and installed; on August 9, the test was completed, and preparations were made for commissioning and beam extraction. Based on past experience, Yang Jiancheng and the team were prepared to "work hard for 3 months". Unexpectedly, good news came on the same day: PREF was completed and achieved beam extraction. It not only successfully realized the efficient and uniform extraction of protons but also met the device irradiation requirements, which can provide an advanced experimental platform for China's space radiation effect research. When receiving the good news call, the plane that Yang Jiancheng had taken from Lanzhou to Urumqi had just landed. "I originally planned to give the team another boost, but I didn't expect them to give me such a big surprise!" At that moment, Yang Jiancheng, who had been on tenterhooks for years, finally got a moment of relaxation. He joked with the team members: "Can I go back now?" After hanging up the phone, Yang Jiancheng's nose felt sour: "The project is for aerospace use, and I have never slackened off over the years." Striving and innovating endlessly, Yang Jiancheng plans to conduct in-depth planning for PREF in combination with technologies such as artificial intelligence. He has three wishes: to enable non-professionals to operate PREF; to make it a standardized module that users can directly purchase; and to combine new principles, new technologies, and new materials to make it even smaller and accelerate the pace of its promotion and application. "I believe that in another 10 years, the research level of our proton accelerators will definitely stand at the international forefront and benefit all mankind!" Looking forward to the future, Yang Jiancheng's words are firm and powerful. Source: *Guangming Daily*, *Science and Technology Daily*