Canfranc is a name that evokes several things at once. From the landscape of the Aragonese Pyrenees to the majesty of its international train station. Also, the intrigues that this municipality lived during the Second World War, being a land of spies. And, since the end of the 20th century, the town of Alto Aragon has also been associated with the scientific avant-garde thanks to its subway laboratory, an international reference center located in the Somport tunnel, which links Spain and France, under 800 meters of the rock that forms the Tobazo mountain. This natural shield allows scientists to work in isolation from cosmic rays and to study particles as special as neutrinos, which can help to understand the origins of matter, to approach dark matter or to understand how living organisms develop in an environment without radiation.
To give an example of its weight, suffice it to say that its permanent staff consists of about thirty people, but its facilities host more than 250 researchers from 51 centers and eleven different nationalities. And, of course, it develops cutting-edge experiments that place this laboratory in a privileged position. “”It is certainly unique in Spain and is the second most important in Europe. It is a jewel to have a facility like this, which attracts scientists and engineers from all over the world,” explains the director of the Canfranc Underground Laboratory (LSC), Carlos Peña Garay.
It was in 1985 when this center was launched, at the initiative of scientists from the University of Zaragoza. The location between the current road tunnel and the old railway tunnel, abandoned since the 1970s, was chosen by the Nuclear Physics research group of the Aragonese Campus to set up what is now this laboratory. Since then, it has been enlarged and renovated and is currently the second largest of its kind in Europe.
An umbrella against cosmic rays
In addition, the LSC is considered an ITCS, i.e. a Singular Technical Scientific Facility, like the Mare Nostrum supercomputer in Barcelona or the Gran Telescopio de Canarias. A consortium formed by the Ministry of Economy and Competitiveness, the Government of Aragon and the University of Zaragoza currently manages the center.
In it, up to twenty experiments in physics, biology, geology and other branches of science are carried out in an exceptional environment. “When scientists and engineers build very sensitive detectors, on the surface what they are going to measure is mainly cosmic rays,” says the director. “To be able to use these detectors and discover new phenomena or characterize them in high sensitivity, you have to protect them, and that’s what we do by putting ground in between,” he continues. “In a way, we put a kind of sunglasses or umbrella on them to eliminate that cosmic noise,” he says.
An umbrella of 800 meters of rock that allows, for example, to carry out the NEXT experiment, currently the most important at the LSC. It is focused on demonstrating that neutrinos “have a very special property,” says Peña, “they are both matter and antimatter”.
“By demonstrating that they are matter and antimatter we could explain and understand how the universe, in the first fraction of a second, was able to form a little more matter, which is us, and not our alter ego, which is antimatter,” adds the scientist.
To do this, NEXT uses xenon 136, a “very special” gas, since its nucleus “has a very rare and special disintegration, it emits two electrons at the same time”. In this emission, in addition, there are “two particles that we know less about and that are like ghosts,” says the head of the center. That is: neutrinos.
After dark matter
The ANAIS project, led by University of Zaragoza researcher Marisa Sarsa, is the center’s other flagship. “In this case, it is looking for a component of matter that is very different from the one we are part of,” says Peña. This is dark matter, which accounts for no less than 84% of the matter in the universe. “We know it exists because we notice it through gravity, but we can’t see it,” he says.
This project uses sodium iodide crystals and aims to try to verify or refute an Italian experiment, DAMA/LIBRA, “which observed a signal compatible with the existence of dark matter,” stresses the director. “Anais is competing with two other experiments in the world – one in South Korea and one in the United States – and, in fact, it is the one with the lead, so we are very proud,” he stresses.
The LSC goes beyond these two flagship investigations and is configured as “a hotel of experiments with a lot of services,” Peña exemplifies. Thus, the center is pioneering the development of areas “such as studying what happens to life when you are in the absence of muons -a charged particle similar to the electron, but with a mass 200 times higher- and cosmic radiation”.
Canfranc, with the Hyper-KamioKande
Speaking of biology, and asked what the future of the laboratory should be, its director reflects: “One of the most interesting things you learn in biology is that the future, in general, is extinction”. And he adds: “Everything, as a human creation, will eventually become extinct, it will cease to make sense; we will only exist as long as we make sense, that is, we have that utility, which is to serve a scientific community that has inventions and where it is essential or necessary to have a resource like this one”.
A future that, among other actions, involves being the coordinating center for the Spanish contribution to the construction of the Hyper-KamioKande, a gigantic Japanese experiment that seeks to deepen our knowledge of neutrinos and their properties.
This project consists of a giant ultrapure water tank 68 meters in diameter and another 71 meters high that will be installed in Japan, in a space similar to that of the LSC. “In that darkness we will be able to see neutrinos coming from stars and, by looking at those neutrinos, we will be able to know what is happening inside them,” says Peña.
Well, the Canfranc laboratory will coordinate the actions in which Spain will participate, which represents “3% of the total budget” and 10% of the budget dedicated to the construction of the detector. “There is a lot of industrial work, 75% of the budget is for our industry to build components that we will then send to Japan,” he concludes.