Wang Yifang: Open microscopic channels to understand the material world

Some scientists have predicted that space, time, and matter are illusions of human knowledge. The microscopic world is full of mystery and infinite possibilities, and countless scientists are looking forward to it. However, these studies of understanding matter and exploring the universe are not understood by the public, and they are a group of lonely scientists. Wang Yifang’s neutrino and particle physics research explores the basic laws of the material world. Because it does not produce direct economic benefits, he is often questioned “What’s the use?” He always reluctantly answers “It’s no use.”

“Wang Yifang”, this name is generally known as a “big coffee” in the Chinese scientific community, and is guessed to be one of the Chinese scientists most likely to hit the Nobel Prize. In 2012, he led the team to capture “ghost particles”-the discovery of the third oscillation mode of neutrinos, which made China’s neutrino experimental research from scratch and came to the forefront of the world. As the director of the Institute of High Energy Physics of the Chinese Academy of Sciences and an academician of the Chinese Academy of Sciences, he also walked from behind the scenes to the front of the stage under the witness of major awards and honors at home and abroad-“Top Ten National Science and Technology Workers” and “CCTV Top Ten” “Innovative Person of Science and Technology”, “Influencing China” Science and Technology Person of the Year, won the Zhou Guangzhao Foundation Fundamental Science Award, He Liangheli Fund Science and Technology Progress Award, Panofsky Award for Experimental Particle Physics, “Nikkei Asia Award” Science and Technology Award, and Fundamental Physics Breakthrough Award, National Natural Science First Prize (ranked first), Pontykov Award, Future Science Award… In January this year, he led the completion of “Key Technologies and Applications of 20-inch Microchannel Plate Type Photomultiplier Tubes” The project was awarded the first prize of the 2020 China Industry-University-Research Cooperation Innovation Achievement Award.

Although this research is only a small part of his scientific research, its scientific significance is extraordinary. The means to develop” “the important thing is not the award, but its scientific significance”.

Spanning more than 20 years, I finally got what I wanted

In 2000, in the experiment of energy transfer between carbon monoxide molecules, Chinese scientists observed for the first time that when molecules and molecules collide, they will interfere like light waves. This phenomenon has not only confirmed the theoretical predictions made by foreign scientists more than 10 years ago, but also enriched quantum theory, which has attracted the attention and high praise of international colleagues.

At that time, Wang Yifang from across the ocean was participating in the Palo Verde reactor neutrino experiment at Stanford University. At this time, science and technology have become a revolutionary force determining the future development of the new century, and scientific research in China is also booming. In 2001, he embraced the confidence in the development of high energy physics in China and accepted the invitation of the Institute of High Energy Physics of the Chinese Academy of Sciences (hereinafter referred to as the Institute of High Energy Physics) to return to China to start a new journey.

After he returned to China, he invested in the Beijing spectrometer experiment. Two years later, in 2003, he led the team to start the Daya Bay reactor neutrino experiment project to catch up with the search for the third oscillation mode of neutrino. In 1998 and 2002, two international experimental groups from Japan and Canada used different detection methods to find atmospheric and solar neutrino oscillations respectively. From the very beginning, Wang Yifang firmly believed that studying the oscillation modes of neutrinos would help further reveal the mystery of the origin of the universe. The facts proved his prediction. Therefore, finding the third oscillation mode has become a research hotspot, and many research teams from the United States, France, Japan, South Korea and other countries are intensively exploring this.

At that time, everyone proposed the idea of ​​using a large number of neutrinos produced by China’s Daya Bay nuclear reactor group to find this third type of neutrino oscillation. Because compared with expensive accelerators, nuclear reactors can provide a continuous and abundant number of neutrinos needed for scientific goals, which can greatly save costs. Throughout the process, he has been advocating “to spend every dollar on the blade, make good use of the limited cost, and get the best scientific research results. This is the basic quality of scientific researchers.” In fact, what he wanted to save at the time was the photomultiplier tube (PMT), a vacuum electronic device that could convert weak light signals into electrical signals, which was necessary for experiments. “It is the most basic method in nuclear physics and high energy physics research, and it is also one of the most basic and important devices.” Wang Yifang told reporters.

In the laboratory, the reporter saw a photomultiplier tube that looked exactly like a “round eye bulb”. The outer and inner layers at the bottom were coated with silver and yellow, respectively, with a vacuum in the middle. There were different models and shapes of different sizes. Qian Sen, a distinguished young researcher from the Institute of High Energy Physics, Chinese Academy of Sciences, told reporters: “The photomultiplier tube is a special vacuum glass device that can be used not only for experimental detection, but also for spectral analysis, image acquisition and diagnosis, and environmental monitoring. And many other fields. The photomultiplier tubes used in different fields have different shapes and sizes. For example, when we are doing new coronavirus nucleic acid detection, we use high-sensitivity photomultiplier tubes to capture fluorescence and achieve high-sensitivity detection.” It can be said that photomultiplier tubes The wide range of applications is closely related to people’s daily life. As the “protagonist” in high-energy physics and astroparticle physics experiments, photomultiplier tubes are essential scientific devices.

“Similar experiments in the world require at least a few hundred or a few thousand. I thought at the time that when we do this research in high-energy physics, we can’t just post articles to buy tubes made by others. We have to have the ability. Come and do it.” When Wang Yifang said this sentence, it has been a long time since he initiated the idea of ​​developing photomultiplier tubes by himself. Or more than a dozen, it is not worthwhile to research and develop by yourself. At that time, there was no way when Daya Bay experimented. Time was tight and it was too late.”

After the Daya Bay Neutrino Experimental Group announced the discovery of a new type of neutrino oscillation in March 2012, Wang Yifang and his team won the “Breakthrough Award in Fundamental Physics”, the First Prize of the National Natural Science Award, and many other important domestic and foreign Awards. In 2013, when the Daya Bay Experiment was still in operation, a more advanced and larger-scale project, the Jiangmen Neutrino Experiment (hereinafter referred to as the Jiangmen Experiment), was put into construction. In fact, this idea was brewing much earlier, “Starting in 2008, we started to want to do the Jiangmen experiment, but we didn’t plan to do it right away, so we had time to develop experimental equipment.”

From 2008 to 2015, after nearly 7 years of hard work, Wang Yifang finally led the team to realize the original expectations and completed the prototype development of the photomultiplier tube. Subsequently, in 2016, industrialization was realized; in 2017, mass production began; now, they have begun to expand horizontally, and cooperate with enterprises to develop the next generation of various optoelectronic devices for other aspects.

The successful development of the 20-inch photomultiplier tube sample ended this important device that was produced in the 1980s and had to be imported. This is of extraordinary significance in Wang Yifang’s view. In the research of high energy physics, not only must the research work be done well, but also the research methods must be developed. He explained, “This means, on the one hand, is the ability of researchers to use research methods and tools, and on the other hand, is the ability of enterprises to carry out R&D.” Important support.” The development process of the photomultiplier tube exemplifies this concept well.

challenge 400 million with 20 million

“Major breakthroughs, instruments go first.” From the stars of the universe to elementary particles, human scientific discoveries and technological innovations are increasingly inseparable from “tall” scientific research instruments.

The photomultiplier tube was developed in the 1930s. By the 1960s, China had two factories capable of producing small photomultiplier tubes to meet the needs of national defense and industrial production. But by the 1990s, in the midst of the market economy, they all lost their competitiveness. It should be said that China does not have the ability to develop and produce photomultiplier tubes of more than 5 inches.

Japan’s Hamamatsu Company also started to produce photomultiplier tubes in the 1950s and 1960s, and started almost at the same time as factories in China at that time. In the 1980s, they invented a new 20-inch photomultiplier tube, leading the trend of the entire photomultiplier tube technology, making the Japanese Hamamatsu company the best photomultiplier tube manufacturer in the world. At the same time, its successful development and effective use have also become the core and most critical success factors for the two experiments of Japan’s Kamioka and Super Kamioka. These two experiments won the Nobel Prize in 2002 and 2015 respectively. Under its impetus, 20-inch photomultiplier tubes were developed in Japan.

The same is true for the Jiangmen experiment. To be successful, a core key issue is to use your own photomultiplier tube. In this field of research, many researchers very much hope to develop a new photomultiplier tube, especially to improve its detection efficiency. “If you buy it from Hamamatsu, the index is twice as bad, and it does not meet the experimental standard, and the cost is probably more than twice the price we can bear.” Wang Yifang made up his mind to make a 20-inch photomultiplier tube by himself.

He is notoriously stingy in scientific research funding. Before starting, he worked out an account. He applied for R&D funding of 20 million yuan for the photomultiplier tube. During the on-site review, experts asked him, after spending the money, can he do it well? In fact, he had no idea at the time. He only knew that if he succeeded, he could save about 400 million yuan in scientific research funds.

“At that time, the pressure was quite high, and experts were also asking during the review. I can’t guarantee success for things I’ve never done before. If I fail, I don’t know what to do. But I think it’s worth taking a risk. Risky.” Faced with the same difficulties as the huge “temptation”, Wang Yifang decided to take the team to fight.

In the beginning, they found a research institute and agreed to explore for three years, but the result was not very satisfactory. Later, they found Northern Night Vision Technology Co., Ltd. (hereinafter referred to as Northern Night Vision). The company’s technical capabilities were not particularly strong at the time, but it was very willing to do this. This is especially important in his view, “I think this is very important. It does not lie in how many technologies and scientific researchers you have before, but the core lies in whether you are really determined and willing to do something that no one has done before. “. Starting in 2011, it was another three years. The entire team was working hard, but the results were not satisfactory. After two years of work, we have not yet made a sample tube that meets the standards, and everyone is desperate. For everyone on the team, 2012 and 2013 were particularly tormented. “You feel that the darkness ahead is dark, and you don’t know if there is any hope”. Wang Yifang said that they had a meeting every three months at that time. The first meeting was to look at the progress and results; the second was to look at the main direction of the next step, which problem to solve, and whether to adjust the goal. “Dozens of questions, hundreds of questions, which one should we do first”; and then what is the goal for the next three months. In this way, we persisted, “Everyone overcomes the difficulties and moves forward step by step” until the sample tube that meets the basic requirements is made in 2014, “We see the dawn of hope”.

Counting from the beginning, Wang Yifang led the team after 7 years of hard work, and finally made a brand-new sample tube that met the requirements. But for enterprises, it is just a sample tube, and there is still a way to go for mass production. Can the 20,000 20-inch photomultiplier tubes needed for the Jiangmen experiment be made on schedule? This is also a big test for Northern Night Vision. To be on the safe side, Wang Yifang made a very difficult decision at that time: to buy 15,000 from Northern Night Vision and 5,000 from Hamamatsu, Japan, so as to achieve a balance in all aspects of price, performance, and risk.

“Through such competition, we have obtained the best photomultiplier tube at a very good price. If there is no competition, the final result will probably not be achieved. Our 15,000 photomultiplier tubes have an output value of nearly 300 million yuan, and the final effect is very good. Good. Northern Night Vision has also been continuously developed. It is now providing photomultiplier tubes for other experiments, as well as microchannel plates and photomultiplier tubes for space and nuclear detection applications.”

Basic research drives industrial development

In 2019, Northern Night Vision started to build a large research center dedicated to the research and development of photomultiplier tubes for medical equipment and industrial applications. This company has developed into a high-tech company with independent research and development capabilities from the original enterprise that purely produced micro-channel boards through R&D and production of photomultiplier tubes. “They worked with scientists and learned how to do things that no one had done before. Scientists and engineers are fundamentally different in training, and the combination of the two is one of the most ideal technological development models.”

Wang Yifang is very pleased with this. What he sees is not only the success of the product, but also the final drive to the industry in the process of carrying out basic research. “North Night Vision knows how to do R&D in this process, and their R&D capabilities have been greatly improved. In the process of developing the photomultiplier tube, it has also imperceptibly promoted the improvement of the entire industry and promoted the development of science and technology.”

“When I was at Stanford, I needed to do everything by myself, even the work of soldering the circuit, I needed to do it myself.” After a few years, when Wang Yifang looked back on his experience in the United States. If this experience hadn’t made him understand all aspects of large-scale high-energy physics experiments, many jobs after returning to China would inevitably be detours.

Similarly, if there is no such large scientific research project to lead, the photomultiplier tube will also be difficult to make. “Basic research itself is very important, it can produce results, articles, etc., but another very important function is that it can lead the demand and give researchers the motivation and pressure to do research and development.”

This is the windfall of R&D. “On the one hand, when the product is made, from the perspective of the enterprise, there is demand within the scope of application, which can be sold and profitable; from the perspective of the scientific research unit, the research and development capabilities have been improved, and things that could not be done before are no longer Relying on foreign imports has also saved scientific research funds. On the other hand, it has improved the R&D and mass production capabilities of cooperative enterprises. For enterprises, the overall level has made a qualitative leap.” Wang Yifang said.

China has long raised industry-university-research cooperation to a new level of strategy, linking it with the technological innovation system as an important measure to establish a technological innovation system. In this process, universities and research institutes can approach the market through cooperation with enterprises, deepen their understanding of the industry, and have more targeted R&D goals. To change the past practice of “drawing from the gourd” in the participation of enterprises in innovation, in Wang Yifang’s view, there are many ways to cooperate with industry, university and research. , Let the company get the market to sell, because we don’t know the market demand. What we can do is to put forward the demand, teach the company how to complete the innovation from ‘0 to 1′, and help the company improve its own R&D level.” He said frankly. , “The entire domestic R&D system is still not enough to support such industry-university-research cooperation.”

In addition, “the cooperation between many scientific research institutions and enterprises cannot be successful in the end. In fact, to a large extent, there is a problem with the mechanism of cooperation.” Talking about the experience accumulated in this process, Wang Yifang mentioned that he had formed an “alliance” for this purpose. . The alliance first has a charter, and all members of the participating cooperation group must first approve the charter, otherwise they cannot join. The core of the charter is the “voting system” and the “principle of distribution of benefits”, “everyone vote for large and small matters. The distribution of benefits is based on actual contributions, and all parties are encouraged to work hard and contribute more to the overall project.”

There is almost no financial support at the start-up stage of the project, and it needs to be invested by itself. This condition is almost “harsh”, which Wang Yifang calls “bring your own dry food.” “In the beginning, there must be a stage of’bring your own dry food’. Those who are willing to come and insist on staying must be the ones who can really contribute in the end.” This is the model he has adopted when working on several projects. Many participants said, “When a person puts energy and material resources into it, he must go all out.”

Today, 20-inch photomultiplier tubes have moved from the laboratory to the market. This innovation is not over, but just the beginning. Like many sciences and technologies that originated from basic research, photomultiplier tubes derived from basic physical research are still widely used in industry and life. In Wang Yifang’s view, it is the most ideal detector as a detector. Although semiconductor detectors are also available today, its advantages are irreplaceable. He hopes that in the future, a full range of R&D and production bases for photoelectric detection products can be established in China.

In the eyes of scientists, the importance of basic research is far greater than its practicality. “What we do basic research is to understand the natural world, and we have to say what is useful. This is the so-called contribution. Now this result has helped humans understand the basic structure of the natural world a step further.”

And this time, he can no longer answer questions when facing the media, “At present, it is not clear that neutrinos have any application value.” If the successful development of the photomultiplier tube is likened to a small wave in a big scientific project in Wang Yifang’s scientific career, then he must hope that this wave can be magnificent.

The important thing is not winning, but its scientific significance

In the field of neutrino detection, the Jiangmen neutrino experiment in the future will form a tripartite position with Japan’s “top-level Kamoka” detector and the US’s “deep underground neutrino experiment” facility. “Using reactor neutrino detection technology to study neutrino oscillations and supernova neutrinos, the Jiangmen neutrino experiment will be the best.” Wang Yifang’s confidence comes from a deep academic foundation.

Because of his interest in physics, Wang Yifang applied for the nuclear physics major of the Department of Physics of Nanjing University during the college entrance examination, and it is still an unpopular major so far. In the year of graduation, the Ministry of Education selected talents to study in the L3 experiment led by Nobel Prize winner and physicist Ding Zhaozhong. He luckily passed the exam.

Under the guidance of Ding Zhaozhong, he spent 11 years from graduate to postdoctoral. In 1985, he walked into the European Nuclear Center headquartered in Geneva, Switzerland, which has the world’s largest particle accelerator and is conducting L3 experiments. At that time, Wang Yifang finished his studies at the University of Florence, Italy, while participating in experiments.

With his own efforts, Wang Yifang has set many records in the L3 experimental group: published 3 papers within one year; in 1990, he became the leader of the “new particle search group”, and he was the only leader of all L3 experimental physics analysis groups. In 1991, under the circumstances deemed impossible by the L3 experimental group, the polarization of Tao Lepton was accurately measured…

Later, he bravely challenged and was unwilling to the status quo, said goodbye to his teacher, came to Stanford University to participate in other projects, and then gave up the good environment, returned to China to join the Institute of High Energy Physics, Chinese Academy of Sciences, to participate in and witness the growth and development of China’s particle physics.

At the same time, various honors and awards are coming: In addition to being the first Chinese scientist to receive the “Basic Physics Breakthrough Award”, he is also the first Chinese scientist to receive the Panowski Prize for Experimental Particle Physics from the American Physical Society. He was listed as a national candidate in the “New Century Talent Project”, was selected as a national “Ten Thousand Talents Program”, and was awarded the 2019 Future Science Award…

This journey is glorious and arduous. In the eyes of everyone, he is a “scientific madman” who dares to dare to do something, “No matter when, the mail sent is almost instantly answered.” After many years, this habit has been maintained, and at the same time, there is still the purity of scientific research. Nowadays, his deeds speak louder than words and he is getting closer and closer to his dream, which is to build China into the center of high-energy physics research in the world.

Do not change the original intention, and strive for the future. In 2021, he joined the Institute of High Energy Physics of the Chinese Academy of Sciences (hereinafter referred to as the Institute of High Energy Physics) for the 20th year. The future positioning of the Institute of High Energy and the prospect of China’s high energy physics have all merged with these thousands of thoughts. Hours of interviews.

Source: “China Awards For Science and Technology” magazine

2021.2, total issue 260/February

Reporters: Xiao Dan, Yan Jia

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