Physicists would like to work in a much greener way because a particle accelerator consumes energy

It saves many kilowatt hours: the Large Hadron Collider is switched off. Administrator CERN is one of the largest energy consumers in France. The particle accelerator organization uses 1.3 terawatt-hours of electricity annually, roughly a third of Amsterdam’s annual electricity consumption.

CERN is not alone. Virtually all major physics experiments, from particle accelerators to (space) telescopes, consume energy. In recent years, this has received increasing attention from society itself. This is evident, among other things, from scientific publications with quantitative analyzes of CO2footprints of current experiments and of future installations still in the design phase. CO2footprint is the total emission of greenhouse gases, converted to CO2correspondingly, where greenhouse gases that do not contain CO2 is, such as methane, converted into how much CO2 which would have the same contribution to global warming.

Emission telescopes

The authors claim that CO2emissions and the other environmental impact of scientific research as far as possible. “It’s important for scientists to act,” astronomer Annie Hughes said at a press conference on emissions from observatories in late March. “If we as scientists do not respond to our reports and warnings [klimaatwetenschappelijke] colleagues, then it’s like your father telling you not to smoke while he himself lights a cigarette.”

What helps these advocates is the rise in energy prices. This means that low energy consumption also ensures that costs are reduced.

The study by Hughes and her colleagues at the Institute for Research in Astrophysics and Planetology in Toulouse found that all astronomical observatories operating in 2019 combined produced around 20 million tonnes of CO22correspondingly in their lifetime. This can be compared with the annual emissions from e.g. Estonia or Croatia. For this calculation, which appeared in Natural astronomyso the researchers at CO2emissions from the construction and use of telescopes on Earth and space missions – which included the launch.

More accurate estimate

To simplify their estimation, the researchers assumed that CO2emissions from the installations are in proportion to their cost or weight. The more expensive or heavier a telescope, the more CO2emissions were imposed on him. This gives a rough estimate, the researchers acknowledge. They can be wrong by up to 80 percent. For example, they estimate that emissions from the James Webb Space Telescope, launched last year, are between 310,000 and 1.2 million tons of CO.2-corresponding. For a more precise estimate, the researchers would need much more information than is publicly available.

The researchers therefore call on all research institutions and funding bodies to publish a detailed calculation of the total (intended) CO for each project.2footprint, from construction to demolition.

Despite the very rough estimate, the calculation shows, according to the researchers, that the annual CO2emissions from astronomical observatories must be reduced by up to twenty times if they are to meet climate targets.

Unexpected emissions data

A future experiment requiring such extensive CO2calculation has been performed is the Giant Array for Neutrino Detection project (Grand). This experiment will detect cosmic particles with 200,000 antennas from the 1930s.

Three researchers, including two major physicists, calculated the CO2footprint of everything involved: from the construction of the experiment and the software required for the data analysis, to the emissions from the transport of the parts, the journey and the data storage.

They amount to almost 500 tonnes of CO2equivalent per year in the first four years, when the first three hundred antennas are installed. The second phase of more than five years, with ten thousand antennas, is good for more than 1,000 tons of CO22equivalent per year. In the final phase, when the experiment ends, there will be more than 13,400 tons of CO2equivalent per year – it can be compared to the production of a thousand cars, the researchers write.

Physicists are already fantasizing about the next particle accelerator

In all phases, digital technology, such as computers, simulation software, data processing and data storage, was found to be responsible for a large part of the emissions. “We didn’t expect that,” emails physicist Kumiko Kotera of the University of Paris. “We think people are aware of the emissions from travel and the production of the measurement equipment, but forget that large amounts of measurement data that must be processed and stored can also lead to enormous CO2footprint.”

Following the publication of Kotera and her colleagues, a ‘green political plan’ has been drawn up for the Grand. It states, for example, that travel must be kept to a minimum by having local partners carry out as much work as possible on site. Furthermore, the data will be stored in centers with the lowest possible CO2footprint. There will also be a recycling plan for the measuring equipment.

A green higgs factory

The particle accelerator physicists are not sitting still either. They are already fantasizing about another billion-dollar, energy-guzzling particle accelerator. With this, they want to produce Higgs particles – which were discovered in 2012 – on an assembly line in order to study them in detail.

There are several designs on the table for such a Higgs factory. Which one you choose turns out to make a big difference to CO2the machine’s footprint, two particle physicists who examined five designs discovered in October. Two of them, like the LHC, are circular: the FCC at CERN in Geneva and the CEPC. The other three are linear: Japan’s ILC, CERN’s CLIC and the US’s C3.

The particle physicists took a special approach to their comparison. They calculated the energy consumption and CO for each design2footprint per produced Higgs particle. Patrick Janot, particle physicist at CERN explains: “We do this because the ability to do science is directly related to the number of higgs: the more higgs, the better the scientific result.”

The FCC does it better

The circular accelerators come out on top in the energy consumption test because they produce Higgs particles faster than the linear accelerators. The FCC comes out on top with 3 megawatt-hours of electricity per Higgs boson. At the bottom is C3 at 16 megawatt hours – more than five times more than the FCC.


The FCC makes it even better if you include the origin of the power. At CERN, 90 percent of the electricity comes from CO2-free sources, such as nuclear energy. As a result, CO2The FCC’s footprint is only 2 percent of the ILC’s, the least sustainable alternative. It shows that it is best to build your accelerator in a country where CO2emissions from electricity production are low.

If it’s up to Janot, CO2footprint is one of the most important decision criteria when it comes to selecting, designing and optimizing a particle accelerator.

Excessive emissions

“I don’t think the higgs factory designs with the smallest CO2footprint will be built by definition,” says particle physicist Tristan du Pree, from Nikhef and the University of Twente, who is involved in the FCC design. “But those with exorbitant levels of CO2emissions are excluded. In my opinion, CLIC, for example, is a no-go because of the energy consumption.”

“This analysis is a good way to start the conversation about CO2footprint of particle accelerators,” says particle physicist Caterina Vernieri, who is involved in the design of the C3. “But there are several aspects that scientists have not looked at that we need to take into account in order to make a better estimate of CO2footprint.”

The most sustainable scientist is the one who does not do research

For example, Vernieri does not fully agree with the assumption that more Higgs particles are the best way to achieve better scientific results. “In linear accelerators, you can get more information from the Higgs particles you have, even though you’re doing less. That’s not in the calculation.”

Furthermore, it is nowhere mentioned that C3physicists are looking at ways to build a solar park next door, for example, so the machine can run entirely on green power, Vernieri says. “And we are working to automate a lot so that few people need to be present at the trial, which saves emissions from travel.”

Janot and his colleague did not include in their estimate the emissions associated with the travel, construction, data analysis, data storage and simulations of the researchers involved. They defend this choice at the end of the paper, where they show that these emissions are small compared to those from the electricity used to run an accelerator. Janot: “The latter dominates the total CO2footprint and is therefore the most important factor if you want to optimize a machine.”

Cut down on

What these first estimates of CO2footprint of experiments and observatories is that they are complex calculations if you want to perform them accurately. This makes it difficult to properly compare different designs. But it is clear that something must change if physicists and astronomers are to achieve the climate goals.

A relatively simple way to save the climate, which Hughes and her colleagues have recommended, is to slow the rate at which new astronomical observatories are built. And Vernieri calls it essential to start looking at new techniques for particle physics experiments. “Because it is not tenable or sustainable to build ever larger particle accelerators operating at even higher energies.”

The physicists stress that the pursuit of ever less CO2footprints should not paralyze research. After all, the most sustainable scientist is the one who doesn’t do research. DuPree. “I hope that another particle accelerator will be built in the near future.”

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