Launched in March 2024, the iSAS project
(Innovate for Sustainable Accelerating Systems) aims to demonstrate new technologies that drastically reduce the environmental impact of particle accelerators.
By coordinating efforts on the European scale and pooling resources, scientists seek to achieve rapid gains by acting on three key levers: cryogenic systems, radiofrequency power, and beam energy recovery. This project is coordinated by CNRS-IN2P3 at IJCLab (Achille Stocchi) with a scientific leader at the University of Brussels VUB (Jorgen D'Hondt).
Cross-section view of the cryomodule from the PERLE project.
Around 40,000—that is the number of particle accelerators currently in operation worldwide, in both research and industry. These machines, notoriously energy-hungry, could in the near future collectively consume around 1% of the total annual electricity demand of a country like Germany.
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In this context, and given the climate challenges, when working on particle accelerators, we must address their electricity consumption," explains Maud Baylac of LPSC, external relations coordinator for the project
. It is now more urgent than ever to bring together all those developing more sustainable and energy-efficient systems, to coordinate these efforts and harmonize them. That's the goal of the iSAS project."
For this, the project has a budget of 5 million euros provided by Europe, distributed among eight European partners who are experts in the field, including CERN, IN2P3 with IJCLab and LPSC, and CEA, among others.
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We are not starting from scratch," says Guillaume Olry from IJCLab, leader of a working group. "
For decades now, numerous initiatives have sprung up in laboratories to optimize certain subsystems. However, up until now, different groups addressed individual issues specific to their own machines without necessarily coordinating their research activities. The iSAS project aims to unite scientists across Europe by offering them a privileged framework to share their unique expertise in this area through dedicated working groups, in order to take this topic to the next level."
The project team at IJCLab
The iSAS project efforts concentrate on the cryomodule, which is the basic building block for particle acceleration. In the cryomodule, superconducting radiofrequency (RF) cavities accelerate particles through a highly intense, alternating high-frequency electric field, established by injecting radiofrequency power. A cryogenic system is necessary to cool and maintain the cavities at 2 kelvins (about -271°C or -456°F) to ensure their superconducting properties. The iSAS project seeks to optimize both the efficiency of RF power injection and minimize thermal losses.
iSAS concretely aims to drive the development of innovative subsystems, whose integration into a "cryomodule of the future" could drastically reduce the electricity consumption of accelerators around the globe. The project focuses first on extremely precise and fast regulation of the frequency of the electric field, using an innovative system that significantly reduces the power consumption in the cavities.
In parallel, the goal is to improve power injection into the cavities by optimizing power couplers and developing "HOM" couplers to better extract parasitic higher-order RF modes that can increase cryogenic consumption. “
Limiting cryogenic losses within the cryomodule is an absolute priority for our project. It's essential to understand that a single watt transmitted to parts cooled at 2 kelvins results in 800 actual watts of power drawn from the grid! It's obvious that with such a factor, every watt saved counts,” emphasizes Guillaume Olry.
Regarding cryogenics, one major challenge is to construct cavities that operate at higher temperatures to reduce the electrical consumption needed to cool the liquid helium that bathes the RF cavities. "
One of the goals of iSAS is to achieve RF cavity operation at 4 kelvins (around -269°C or -452°F), compared to the current 2 kelvins,” explains Guillaume Olry
. To achieve this, the key is to apply thin film coatings on the walls of the RF cavities. The technical challenges in producing and exploiting these coatings remain, due to the complex shape of the cavities".
But that's not all: the iSAS project also aims to implement a technology to recover beam energy by decelerating it in the same RF cavities used for acceleration: this energy, thus returned to the RF cavities, can be used to accelerate the next beam, significantly reducing the system's overall power consumption.
Such a device could be applied to machines with particle beams that are minimally altered after interaction, such as particle colliders or light sources. It requires the development of a specially adapted cryomodule, which the international PERLE project, currently under construction at IJCLab (Orsay), aims to achieve. PERLE is an ERL demonstrator targeting a high-power, multi-turn beam regime.
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We are not the first to explore these technologies. Our goal here is to push the boundaries of the state of the art in beam energy recovery, to validate this technology for their future high-power projects" (several MW), notes Walid Kaabi, head of the accelerator division at IJCLab.
Optimizing all of these technologies over the next four years within the framework of iSAS should lead to the design of more energy-efficient prototypes, whose features could influence both the upgrades of existing accelerators and the construction of future ones.
For Maud Baylac, the project's purpose is crystal clear: "
With iSAS, we are working to reduce the environmental impact of accelerators. We are bringing together communities to achieve concrete objectives and contribute to designing the accelerators of the future in line with the ecological transition."