It is Suitable Now for China to Build Large Collider

-- Yifang Wang

About the author: Yifang Wang is the director of Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS).

[The original article in Chinese: webpage.]

Today (September 4th) “The Intellectuals” published Prof. Chen-Ning Yang’s article “It’s not suitable now for China to construct the large collider”. As an experimentalist and the current Director of Institute of High Energy Physics, Chinese Academy of Sciences (IHEP, CAS), I cannot agree with him. Prof. Yang is a respected scientist, but I have even more respect for science and rational. I apologize in advance if the following discussion would cause any impoliteness.

The first point of Prof. Yang is that the construction of large colliders is a bottomless money sink. During the construction of the Superconducting Super Collider (SSC) in the US, the prices went so high that this project had to be given up halfway, leading to a waste of 3 billion US dollars. The construction of LHC cost 10 billion US dollars. The large collider of China won’t be cheaper than 20 billion US dollars, and may become a bottomless money sink.

Concerning this point, there are actually three questions: First, why did SSC fail? Secondly, what’s the cost of China’s large collider? Thirdly, is our estimation reliable? Is it another bottomless money sink? Let me discuss them one by one in the following.

(1). Why did SSC fail ? Are all Large colliders bottomless money sinks?

The SSC of the US failed for multiple reasons, including the deficit in the government budget, the competition of funding with the space station project, the political struggle between the Democratic and the Republican party, the competition between Texas and other states for the hosting of the SSC, mismanagement, mistakes in the budget, soaring cost, and not sufficient international cooperation, etc. A detailed analysis and historic documents can be found in the reference [2, 3]. In fact, the budget overrun was definitely not the main reason for its failure. Rather it was quite accidental in special circumstances, mainly due to political reasons.

For the US, the cancellation of the SSC project was a big mistake. Consequently, the high energy physics community of the US lost the chance to find the Higgs boson, lost its foundation and opportunity for further development, and lost its leading position in the international particle physics community. This decision had extremely negative impact to big science projects at the US. It dampened the ambition and courage of an entire generation. The opposition to the SSC in the US at that time shares many common arguments with the criticism of the Chinese large collider project today. In fact, the cancellation of the SSC project didn’t lead to any increase of funding to any disciplines. Of course, the construction of the SSC didn’t lead to any decrease of funding to any other field either. Many people who opposed the SSC came to regret their opposition to the project.

After that, the Europeans built the Large Hadron Collider (LHC) with a great success. Even though there was a small budget overrun, it was not significant, showing that large colliders are not necessarily bottomless money sinks, and could be successful.

The decision making process and political system in China is very different from that of the US, and is actually advantageous for large construction projects. It has less uncertainty. China today has already done a number of things which the US would not or could not do. In the future, more achievements of this kind will happen. The failure of SSC doesn’t means that we are not able to build large colliders in China. Of course, we should learn from the experience of the SSC and be better prepared for the project, including better international cooperation, management and budget estimate.

(2). What’s the cost of this collider?

The large collider we proposed has two phases. The first phase is a Circular Electron Positron Collider (CEPC), which could be constructed during 2022 – 2030. Assuming a tunnel circumference of 100km, the construction cost is roughly 40 billion CNY (not including the cost of land, and the supporting infrastructure such as road, water, internet, power supplies, etc.). If we succeed in the CEPC project and there are hints of physics beyond the SM, and if the novel technology of super conducting materials will have matured so that their cost is reduced to an acceptable level (say, ~ 20 CNY/kA*m), we can start the second phase, the Super Proton Proton Collider (SPPC). The cost of this phase could be controlled to within 100 Billion CNY, and the construction could happen in 2040-2050. As an international project, we expect 30% of the total cost to be covered by international partners. Therefore, the Chinese government needs to invest 30 Billion CNY (3 Billion per year for 10 years) for the first phase and 70 Billion CNY (7 Billion/year) for the second phase (without taking into account inflation). The fact that there is a possible second phase gives this proposed project, CEPC-SPPC, a much longer lifetime. It could stimulate the development of corresponding technologies such as high-Tc superconducting materials. These two phases are highly complementary to each other, in both scientific goals and technology impacts. At this stage, the purpose to discuss SPPC is to make sure that our design, such as tunnel length and cross section, does not limit the option for the future upgrade.

(3). Is this estimate reliable? Would it repeat the failure of SSC?

In the past half a century, many accelerators have been successfully constructed all over the world (LEP, LHC, PEPII, KEKB/SuperKEKB, et. al). There were also some not-so-successful accelerator projects (ISABELLE, SSC, et. al). In this list, all failed projects are proton colliders, with no failed example of electron-positron colliders. The reason is that the proton collider is technologically much more complicated; it’s usually very hard to predict the advancement of the super-conducting technology and it is not easy to properly balance between the cost, technology, and the specification. If the spec is too high, it would result in cost overrun. On the other hand, the choice of low spec would appear to be too conservative.

There had been many successful examples of large construction projects in China. Since its founding 40 years ago, IHEP has carried out many big scientific projects with cost higher than 100 M CNY, including the Beijing Electron Positron Collider (BEPC), the Daya Bay Neutrino experiment, the China Spallation Neutron Sources and the ADS Injector. All these projects have been completed on time, and up to the spec. The actual cost has never exceeded the budget by more than 5%. We have a mature system and deep experience on budget estimate, construction and project management.

In fact, we employed two methods to estimate the cost of CEPC: 1). decomposing the project into a list of equipment, components and sub-systems; 2). making analogies and comparing with similar projects around the world. Both at the sub-system level and for the total cost, these cost estimates are consistent within 20%. In fact, once we finished the Preliminary Conceptual Design Report (Pre-CDR)[1] for the CEPC (the first phase), we generated a list of more than 1000 items, based on which the cost estimate was done, and reviewed by domestic and international experts. If Prof. Yang has any doubt about this cost estimate, another review can be organized.

For the SPPC, we only used the comparison and analogy method, since it is not the main objective now, but only a future possibility. It is meaningless to talk about its construction cost now. We have to wait until the technology is mature enough. How could it become a bottomless money sink?

The second point of Prof. Yang is that, China is still a developing country, and there are still livelihood issues to be solved. A Large collider is not that urgent and should not be considered now.

For any country, especially one with the size of China, it is essential to balance the short-term needs and the long-term plans. The livelihood is certainly an essential issue and it is in fact the main part of the government budget. Meanwhile, we also need to invest in long-term needs, with a reasonable fraction of GDP on basic science, in order to ensure the potential of long term development, and stimulate becoming a leader of the world. A terrible example is the Qing Dynasty. At that time, China had the largest GDP of the world, capable of buying anything from abroad. However, China was not developed in science. Though China bought lots of advanced weapons from abroad, it was still defeated miserably and its livelihood fell all the way down to the bottom of the world.

For centuries, the studies of microscopic structure of matter, from molecules, atoms to nucleus and elementary particles, led the development of science to a large extent. Nowadays, such research takes the form of particle physics, which aims to reveal the fundamental building blocks of matter and their interactions. Particle physics adopted and stimulated the development of technologies such as accelerators, detectors, cryogenics, superconducting materials and cavities, micro wave equipment, vacuum systems, power supplies, precision machinery, automation, computing and networks. Because of its huge impact to science and the boost to the technology development, high energy physics is a very significant and unique field. By constructing the CEPC, China will play a leading role in this important flagship field. In addition, Chinese industries could manufacture related high-technology products and lead the world. Meanwhile, the CEPC will also attract, and train thousands of top scientists and engineers, forming a science and technology center. The CEPC is indeed an urgently priority for China.

In fact, the impression of China to the world is rich and at same time too practical. A big country without contribution to the civilization cannot have big impact and influence in the world. This will in turn affect China’s interests. On the other hand, as a fraction of GDP, the cost of the large collider (CEPC and even SPPC) didn’t exceed that of BEPC, and is lower than that of other constructed and planned facilities (LEP, LHC, SSC and ILC) in the world.

The CEPC provides a unique opportunity for China to assume the leadership in the field of high energy physics in the world. First, the Higgs boson discovered at LHC has a mass that is perfectly suited to allow a circular electron positron collider to be a Higgs factory. Meanwhile, this collider could be upgraded to a proton collider, providing a science program that could last for 50 years. Secondly, we have a time window of roughly 20 years with relatively mild international competition, since Europe, the US and Japan are all occupied by other particle physics projects. Thirdly, with the BEPC, an electron-positron collider, we accumulated sufficient experience and a well-trained team which are just right for CEPC. This window of opportunity will last for only about 10 years. It is hard to predict when would be the next time if we miss it. Meanwhile, China has excellent experiences in large underground projects, and the economy is still in rapid growth. During this restructuring period, there are needs to invest on science. Therefore, CEPC is a well suited project for China now.

The third point of Prof. Yang is that the construction of CEPC will largely squeeze the funding for other disciplines of basic science.

Currently in China, the funding for basic science is roughly 5% of the total R&D spending, while that fraction for developed countries in the world is typically 15%. As a large developing country moving towards a developed one, I think China should gradually increase this ratio to 10% and eventually to 15%. In terms of numbers, there is still a big room for the funding of basic science to increase (roughly 100 B CNY per year). Therefore, construction of the CEPC would not crowd out the funding for other disciplines.

On the other hand, how should we spend the funding from such an increase? It is well known that a significant percentage of our funding is spent on purchasing equipment, especially from abroad. If we suddenly increase the funding uniformly to all disciplines, or toward some disciplines that strongly rely on the international apparatus, it is very likely that such an increase will also boost the GDP of foreign countries. To the contrary, if we invest on the large accelerator for 10 years with a total budget of 30B CNY, more than 90% of the money will be spent in China. Such a spending will stimulate our companies to have technology progresses and more market sharing, train thousands of scientists and engineers that could design and manufacture the needed apparatus, and help the development of other disciplines. In fact, such an investment will not change significantly the balance among different fields. In the long run, it will rebalance the funding distribution to a level comparable to the norm in the world (currently particle physics and nuclear physics are significant low in China relative to the rest of the world). The Chinese government is now calling for proposals to host large international scientific projects. CEPC is an excellent candidate, and not in conflict with other disciplines of basic science.

The fourth point of Prof. Yang is that SUSY particles and Quantum Gravity have not yet been discovered, and it is hopeless for the CEPC to discover such hypothetical particles.

The science goal of CEPC is not what Prof. Yang described. In fact, we described clearly the physics motivation in the “Preliminary Conceptual Design Report of CEPC-SPPC”[1] which I delivered to Prof. Yang in person. In short, the Standard Model (SM) of the particle physics is only an effective theory at low energies. We aim at discovering the fundamental physics principles that underlying the SM. Although there are some experimental evidences for new physics beyond the SM, we still need more data to guide the direction for the future. Currently, most of the problems of the SM are related to the Higgs boson. Therefore, clues of new physics at deeper level shall come from the Higgs boson. CEPC can measure the Higgs boson to an accuracy of 1% level, which is a factor of 10 better than that of the LHC. Such a precision would allow us to determine the properties of the Higgs, and to check its consistency with the prediction of the SM. Meanwhile, CEPC may measure for the first time the self-coupling of the Higgs boson (indirectly) to determine the type of the electroweak phase transition, which is essential for the understanding of the early evolution of the Universe. In short, no matter if LHC discovers new physics or not, CEPC is badly needed and cannot be skipped in the advance of particle physics.

If there is any deviation from the SM observed at the CEPC, for example new coupling and/or new partners of Higgs boson, substructure of the Higgs boson, we could upgrade CEPC to SPPC to directly look for the cause of such deviation, which might be SUSY particles or any other new particles. For experimentalists, we care about theoretical predictions, but we never rely on them. It is too assertive to claim what particles can or cannot be discovered at the future collider. Most people from the international high energy physics community do not think that way either.

The fifth point of Prof. Yang is that major achievement of particle physics in the last 70 years did not offer direct benefit to human life, and it won’t have any in the future.

For 70 years, high energy physics had a lot of achievements. It developed lots of technologies that are closely related to people’s daily life. Without particle physics, there will be no synchrotron light source (coming from electron positron circular collider), free electron laser (coming from electron positron linear collider) and spallation neutron source, which are essential tools for the study of biology, geology, environment, material science, and condensed matter physics. Without particle physics, many medical apparatus such as MRI, PET and radiotherapy would not exist, would not be so advanced, or be invented much later. Many people would have a shorter life span, or their life quality would be severely reduced. Without particle physics, there would be no (or much delayed) touching screen, and therefore no smartphones; there will be no World-Wide-Web (WWW) and we would not be able to surf the web. There would be no e-commerce of course. In fact, WWW has changed profoundly the world and its economical outcome has been much more than all the investment in high energy physics before that.

In terms of the CEPC, how would it affect our daily life? With the 30 Billion CNY investment (3 Billions per year, starting from 2022 for 10 years), we could promote the following technologies in our domestic companies to a world leading position:

a) High Quality Super Conducting Cavity (used in almost all the accelerators)

b) High Efficiency, High power microwave power source(used in radar, broadcasting, communication and accelerators)

c) Large scale cryogenic systems (used in other fundamental researches, rocket engine, medical apparatus)

d) High speed, radiation-hard silicon detectors, electronics and ASICs

In the meantime, we can also lead the world in technologies such as precision machinery, microwave, vacuum, automation, data acquisition and processing, computing and networks. We can train thousands of top-level physicists and engineers, as well as attract thousands top-level scientists and engineers worldwide to form an international center of science. If SPPC is going forward, 7 Billion CNY will be investigated each year starting from 2040, it can promote the application of our technologies of high-Tc superconducting material and superconducting magnets which will be leading the world. The volume of this industry would be much larger than 70 Billion CNY(cost of SPPC). On top of that, there might be unexpected new discoveries and new technologies. The direct application of high energy physics discoveries cannot be predicted now. Indeed there should be no need to ask this question since the importance of the study of the structure of matter and elementary particles cannot be emphasized more. The Chinese may have laughed at the Greeks and the Europeans for their “useless” studies on atoms, gravity, quantum mechanics and the Higgs boson, but there is always a price to pay (which has been paid).

The sixth point of Prof. Yang is that the Institute of High Energy Physics (IHEP) did not have great achievements in the last 30 years. Over 90% of the works for the large collider will be dominated by non-Chinese and the possible Nobel laureates would not be Chinese.

It has been more than 40 years since the establishment of the IHEP. Benefiting from the construction of the Beijing Electron Positron Collider (BEPC), IHEP had been developed significantly with focus on particle physics, astrophysics, multi-discipline research and applications. For particle physics, a major investment to facility at IHEP is the Beijing Electron-Positron Collider (240 M CNY, 1984), its upgrade (640 M CNY, 2004) and the Daya Bay neutrino experiments (170 M CNY, 2007). The total is about 1 Billion CNY. Comparing to other disciplines, for example biology, condensed matter physics and astrophysics as mentioned by Prof. Yang, the funding level of particle physics is not higher (in total or per person). Meanwhile, the output of particle physics, partially measured by national and international awards and honors, is no less than other disciplines. Though such an investment is orders of magnitude lower than that of leading countries, the scientific output is somehow comparable. At least IHEP is one of the four leading particle physics laboratories in the world (CERN, Fermilab, KEK, IHEP).

In the year of 2012, Chinese scientists first independently proposed the CEPC-SPPC project. The international community of particle physics responded strongly to this proposal and gave strong support. We launched the conceptual design afterwards and completed mainly by ourselves, with some international participation, the “Preliminary Conceptual Design Report” (pre CDR)[1] in 2015. Hence we believe that in the future,more than 70% of the works for the large collider will be completed by Chinese, at least the same as the fraction of the Chinese investment. If Prof. Yang still has no confidence, please consult with leaders of major particle physics labs in the world.

In fact, IHEP has over 30 years’ experiences with the electron positron collider. CEPC is proposed after much deliberation. Those who participated the design and construction of BEPC in 80’s agree that it was much more difficult to construct the BEPC in 80’s than to construct the CEPC today. We believe that the younger generation today would do even better and we have the confidence, capacity and courage to accomplish the CEPC by ourselves. On the other hand, we should encourage international participations for this project.

Concerning to the second phase of the hadron collider (SPPC), we admit that we don’t have much experience and need more effort. However, we still have 20 more years, and should be able meet the minimum target of “accomplish works proportional to the funding contribution”. According to our record of progress in the last 30 years, this goal should be achievable.

About the possibility of Nobel Prize to Chinese, I think it is not predictable. It is not the motivation of the investment to basic science by our country, nor that of the individuals who do the research. We ultimately try to understand and reveal fundamental principles of the nature. The Higgs boson is discovered at CERN and its discovery granted the Nobel Prize to Mr. Higgs from the University of Edinburg. We hope that China can host a research institute with the similar scale, scientific output and technology capabilities like CERN. It is not important whether we have our University of Edinburg and Mr. Higgs to win a Nobel Prize.

The seventh point of Prof. Yang is that the future of particle physics lies in the direction of “new concept of acceleration” and “theory of geometry”, not in colliders.

The “new concept of acceleration” (such as plasma acceleration) is indeed promising for the future accelerators. Given enough time, maybe in several decades, such technologies might be applicable to fixed target experiments or other experiments that do not require high quality beams. For high energy colliders, both beam quality and energy efficiency of these novel technologies still have a long way to go. In the meantime, high energy physics should not halt to wait for the maturity of these technologies. And about the “theory of geometry” or “string theory”, they are too far away from being able to be tested by experiments, it is not an issue for us (experimental particle physicists) to consider now.

People always have different opinions about the future direction of particle physics. China does not have Nobel Laureates in physics now, but there are many in the world. Obviously Prof. Yang holds a view different from the majority of them, not only now, but also in the past. Prof. Yang has been pessimistic about particle physics since 1960s, and missed the major discoveries of the Standard Model of particle physics. In 1970s, Prof. Yang opposed the construction of high-energy accelerators in China [4]. Fortunately, Mr. Deng Xiaoping took the suggestions of Prof. T.D. Lee and other prominent scientists. As a result, it became possible to have today’s IHEP, BEPC, Daya Bay, and their great results, as well as large science facilities such as synchrotron light sources and the spallation neutron source serving the science community of the whole country. Facing the future, we should listen more to the young scientists working on the front line of the research, who will make our science flourish and grow into a leading position in the world.



[2] S. Wojcicki, Rev. of Acce. Sci. and Tech. Vol. 1 (2008) 259--302; Vol. 2 (2009) 265--301.

[3] M.Riordan, L. Hoddeson and A. Kolb, Tunnel Vision --- The rise and fall of the Superconducting Super Collider, The University of Chicago Press,2015.

[4] IHEP Annual Report, 1972--1979 (in Chinese).