Mission: Antimatter transport

The craziest scientific challenges

To drill kilometers underground, to reach the poles, to set foot on the moon… The whole history of mankind is interspersed with these craziest challenges. And it’s not going to stop! Science and life continues the series about the most incredible scientific missions. This month we met physicists who are planning to transport antimatter!

It is the most expensive substance in the world and potentially the most dangerous: producing 1 kg of antimatter would cost 60 billion euros, and one gram would be enough to power several Ariane-5 takeoffs! But it is also the most fragile, the slightest contact with ordinary matter makes it instantly annihilate and disappear in a sheaf of pure energy. This is an exciting substance, scientists for the first time in history will try to solve the incredible task … to transport it! Two experiments at CERN have been given the green light to capture antiparticles, store them, and then move them on trucks several hundred meters. The particles in question will be antiprotons from the Antimatter Factory. “the only place in the world producing antiprotons slow enough to be handled and stored” assures François Boutin, who oversees two experiments on behalf of CERN: on the one hand, the one called Base-Step, a portable version of Base (an experiment with baryon and antibaryon symmetry), on the other, Puma (antiproton annihilation of unstable matter). .

High-voltage transport at CERN

© ANTOINE DAGAN

ANTIMATTER: ANTIPROTONS WERE STORED AT -269°C…

The antiprotons will be produced by the CERN particle accelerator and then slowed down by Helena, a 30.4m circumference hexagonal moderator commissioned in 2018, at the end of which they will run aground in a particle bottle: the “Penning trap”. “Due to its high magnetic stability, this is the best antiparticle storage device we know of.” , says Stefan Ulmer, founder and director of the Base collaboration. This must be filled with an extremely high vacuum equivalent to what exists in interstellar space! “The only technology that can achieve such an extreme vacuum is cryogenics. explains François Boutin. Thanks to liquid helium, the device will be submerged in water at a temperature of -269°C.”

All this helps to store antimatter. Now it remains only to transfer. Because if the trap itself is only a few tens of centimeters long, it must necessarily remain in the center of an impressive superconducting magnet that generates a magnetic field, to which are added a cooling system and batteries that provide electrical autonomy. Therefore, it is necessary to move the entire device. The Base-Step trap will contain several thousand antiprotons with a total weight of about 1 ton and will be transported by van. Meanwhile, the Puma collaboration aims to capture up to a billion antiprotons. “It’s more of a technical challenge, explains Francois Boutin, because at these densities we are no longer dealing with particles that evolve independently of each other, but to a true antiproton plasma, whose collective dynamics are much more difficult to control.” In this case, the device will weigh 10 tons and will need to be towed by a heavy vehicle.

>> Read: Antimatter: on the trail of antistars?

THEN THE ANTIPROTONS SLOWED UP TO 4000 KM/S!

Day D “The created antiprotons will be sent to the Antiproton Deselerator, a symbolic device at CERN, the source of everything we have learned about antimatter in twenty years” , according to Alexander Obertelli, spokesman for Puma. The antiprotons will exit it slowed down to 32,000 km/s, then rush to Helena, where they will be slowed down to 4,000 km/s, ready to be absorbed by the cryogenic trap at the end of the line. Once it is filled with valuable cargo, operators will have to manually detach it from Elena in order to attach it to an overhead crane that will take it to a truck at the entrance to the building. “This step is delicate: improper manipulation can lead to the annihilation of antiprotons, anticipates Roberto Rinaldesi, who will oversee the transport. In the case of Puma, they will generate a small burst of gamma radiation, potentially harmful to living organisms. So take every possible precaution! Mobile cranes will deliver two experiments to special vehicles in about twenty minutes, where they will be loaded and connected to a generator. The vehicles will then start moving.

The big unknown will be the vibration of the truck. “Perhaps they indirectly heat the plasma, perhaps to such an extent that the antiparticles on the walls of the trap annihilate, afraid of Alexander Obertelli. But the vibration transfers between the macroscopic system of the vehicle on the road and the microscopic structure of the trap are too complex to calculate.” Therefore, to avoid the slightest risk, the driver must move at a speed of only a few kilometers per hour. François Boutin, he wants to be sure. “There should be no oscillatory relationship between the excitation of the truck and the excitation of the plasma. In any case, we planned to repeat transport with electrons, a few days earlier”. After several hours of travel, the car finally reaches its destination, the Isolde (an online isotope separator), where the process will have to be repeated… in reverse. “We will have one month to conduct our experiments. Indeed, this is the estimated lifetime of our plasma of one billion antiprotons,” says Alexander Obertelli. “From our side, since we will only have a few thousand antiparticles, their lifetime will be at least 40 years.”says Stefan Ulmer.

Mission 1: Uncover the secrets of antimatter

To understand why the universe is filled with matter and not antimatter, Base-Step tracks the smallest differences that can exist between protons and antiprotons.

Mission: Antimatter transport

Mission 2: investigate the structure of the nuclei of radioactive atoms

Puma will use antiprotons to bombard very neutron-rich nuclei to see how they fit together. Objective: To better understand neutron stars.

Mission: Antimatter transport

>> Read also: CERN: Opening of Odderon by TOTEM and DØ joint efforts

ASYMMETRY FOR THE BENEFITS OF MATTER?

Therefore, nothing should be left to chance. Each step must be carefully prepared… but to what end? Why undertake such a mission? Base, one of CERN’s most famous and oldest collaborations, has spent ten years tracking down the smallest differences that could exist between protons and antiprotons. “According to the standard particle model, there are none, explains Stefan Ulmer. The antiproton is supposed to have exactly the same characteristics as its counterpart, except that its electrical charge is negative rather than positive.” Yes, but the standard model of cosmology predicts that matter and antimatter should have formed in equal amounts during the Big Bang. Therefore, they should have annihilated and left only the Universe filled with energy. This is clearly not the case, since our Universe is filled with matter: gas, stars, planets…

The main goal, then, is to check whether there is an asymmetry between protons and antiprotons, which would initially introduce a billionth of more matter into the Universe. Last January, the researchers published the results of their latest research into the charge-to-mass ratio of antiprotons. It is identical to that of protons with an accuracy of … 0.000 000 000 3%. “Our experiment has become so sensitive that we can no longer ignore the fluctuations in the magnetic field created by the machines installed at the Antimatter Factory.” , explains Stefan Ulmer. That is why they are planning to move their experiment to another laboratory, to a quieter place in terms of the magnetic field, a place that they have yet to determine.

Puma’s problem is radically different. “We want to use antiprotons as tools to study the structure of the nuclei of radioactive atoms, explains Alexander Obertelli. This will be a historic first!” Physicists plan to bombard very neutron-rich nuclei with antiprotons to study how they fit together in space. These studies could greatly improve our understanding of the neutron stars in the Milky Way. But there is a problem: these neutron nuclei are unstable, they decay in a fraction of a second. Therefore, it is impossible to keep them. For their experiments, the members of the Puma have no choice but to deliver the antiprotons to the source where the radioactive nuclei are forged, in this case Iseult.

Since the two experiments are almost ready, the transport should take place during 2023. In this way, the two teams will assess the technical and economic feasibility of transporting antimatter, as the idea is that it will be “democratized” in the future. “Today, researchers who want to manipulate antiprotons have to go to CERN, notes Alexander Obertelli.

The goal is to deliver them to universities or laboratories around the world and thus advance science in this area.” According to Stefan Ulmer, the democratization of antimatter transport will depend on the discovery of asymmetry with matter. “If the team discovers this, then not only will they receive a Nobel Prize, but everyone on the planet will rush to acquire a sample of the antiproton and study it from all angles!” On the other hand, transport will need to be made more economical first. At the moment, Base-Step estimates the displacement of several thousand antiprotons at 2 million euros … And then it will have to be miniaturized. Who knows, maybe one day, like the first elementary computers that took up an entire room, it will be possible to reduce the size of antimatter traps to the size of a simple electric battery. The battery, filled with the best fuel in the universe, is ideal for future interstellar travel…

Mission: Antimatter transport

We planned to rehearse the electron transport a few days before. FRANCOIS BOUTIN, CERN engineer, technical coordinator of the Antimatter Factory and Puma

>> See also: Antimatter and matter will behave the same under the influence of gravity

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