Exploring Ways to Improve Energy Efficiency in Particle Colliders: A Question Posed by Physicists

Presently, scientists hailing from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have undertaken a comprehensive study to enhance the energy efficiency of a proposed project known as the Cool Copper Collider (C³).

In their quest for greater energy efficiency, the researchers took into account three crucial facets that pertain to the design of any accelerator. They delved into the operational methods of the collider, the initial construction of the collider itself, and even the geographical location where the collider is situated, which, somewhat indirectly, has a substantial influence on the project’s overall carbon emissions.

Caterina Vernieri, an assistant professor at SLAC and one of the co-authors of the new paper published in PRX Energy, emphasized the necessity of considering not just financial expenditures but also the environmental consequences when addressing significant scientific endeavors.

Emilio Nanni, who serves as an assistant professor at SLAC and is another co-author of the paper, shared a similar perspective. He stressed the importance of scientists not only inspiring the public and future generations through their breakthroughs but also by setting an example through their actions. According to Nanni, this entails taking into account both the potential scientific significance and the broader impact on the scientific community. He believes that enhancing the sustainability of facilities can contribute to the realization of both of these objectives.

A multitude of options

C³ represents just one among several proposals for the next-generation accelerator designed to explore the Higgs boson and delve even further into the realm of particle physics. These proposals predominantly adhere to one of two fundamental design categories: linear accelerators, exemplified by C³ and the prospective International Linear Collider, and synchrotrons, or forthcoming circular accelerators, including the Future Circular Collider and the Circular Electron Positron Collider.

Both designs come with their own set of pros and cons. Synchrotrons have the advantage of being able to recirculate particle beams, enabling data collection over multiple loops. However, they face limitations because charged particles like protons and electrons lose energy when their paths are bent into a circular trajectory, resulting in higher power consumption. On the other hand, linear accelerators do not suffer from energy loss issues, which allows them to reach higher energy levels and explore new measurement possibilities. However, they use the particle beam only once, and to achieve higher data rates, they require working with intense beams.

C³ seeks to address the common constraints of linear accelerators, particularly the trade-off between length and energy, through an innovative approach. This includes the implementation of finely-tuned electromagnetic fields introduced at multiple points along the accelerator and the adoption of a state-of-the-art cryogenic cooling system. Furthermore, the project emphasizes the use of interchangeable components and an efficient construction methodology, potentially leading to substantial cost reductions. The ultimate goal is to create a compact and cost-effective collider, measuring as short as approximately five miles, while still capable of exploring the cutting-edge boundaries of particle physics.

Enhancing the sustainability of large-scale physics

Nevertheless, the development and operation of the envisioned C³ collider would demand a substantial allocation of resources. To address an increasingly pressing concern, its proponents have actively considered the environmental impact, particularly in terms of the carbon footprint of large-scale physics projects. Their approach begins with a thorough evaluation of the accelerator’s operational aspects.

In the past, physicists didn’t place a strong emphasis on the energy efficiency of accelerator operations. Nonetheless, the collaborative team from SLAC and Stanford has discovered that even subtle modifications, such as altering the particle beam structure and enhancing the klystron operation responsible for generating the electromagnetic fields driving the beam, can have a significant impact. Collectively, these enhancements have the potential to reduce C³‘s power requirements from approximately 150 megawatts to possibly as low as 77 megawatts, nearly halving the energy consumption. “I would be content with a 50% reduction,” Vernieri expressed.

Conversely, the research team determined that the primary contributor to C³‘s carbon footprint is expected to be its construction phase, particularly as the global trend leans towards adopting more renewable energy sources. The researchers propose that making changes in the choice of construction materials, like alternative forms of concrete, and optimizing the manufacturing and transportation processes can effectively mitigate the project’s contribution to global warming. Additionally, C³‘s relatively compact size, at just eight kilometers in length, results in reduced material requirements and affords greater flexibility in selecting construction sites, potentially streamlining and expediting the construction process.

Additionally, the researchers took into account the prospective location of the C³ project. This choice could influence the balance between fossil-fuel and renewable energy sources that supply power to the collider. It might also involve the construction of a dedicated solar facility, complemented by an energy storage system, to cater to the energy requirements of the accelerator.

How colliders stack up?

Last but not least, the SLAC-Stanford team conducted an assessment of how C³ stacks up against alternative collider proposals for the future. They also examined the relative merits of linear and circular colliders when each is engaged in similar scientific measurements.

Their analysis, combined with sustainability assessments of other accelerators, led the team to the conclusion that construction tends to be the predominant factor influencing a project’s carbon footprint. Furthermore, circular colliders designed to achieve comparable scientific objectives often exhibit higher emissions associated with their construction phase. Similarly, shorter accelerators like C³ and the Compact Linear Collider would typically yield a reduced potential for global warming in comparison to longer counterparts.

Vernieri highlighted the novelty of examining the sustainability of physics projects, underscoring its emerging status as a field of study. She emphasized that it is a crucial area of inquiry, as it prompts a fresh dialogue and raises the question of the environmental impact in the realm of particle physics.

Resources

1. ^NEWSPAPER Collins, N. (2023, November 3). Physicists ask: Can we make a particle collider more energy efficient? Phys.org. [Phys.org]
2. ^JOURNAL Breidenbach, M., Bullard, B., Nanni, E. A., Ntounis, D., & Vernieri, C. (2023). Sustainability strategy for the Cool Copper Collider. PRX Energy, 2(4). [PRX Energy]