EARTH

Dubna collider finds ‘heart’ to reveal secrets of the universe

Dubna collider finds heart to reveal secrets of the universe

Employees of the Joint Institute for Nuclear Research (JINR) have completed the installation of a magnetic crystalline system in Dubna, which is the “heart” of the NICA collider. The 70-tonne device arrived in Russia from Italy in November 2020, but due to the pandemic and restrictive measures against coronaviruses, installation has been repeatedly postponed. We explain why this is an important scientific event and why the NICA collider was needed in the first place.

Particle physics in practice :
The adventures of the Italian equipment in Russia are interesting in their own right. It took an international team of specialists five years to design and develop the magnetocrystalline system. Because of its size and scientific value, the super-important part of the NICA collider was carefully transported from Italy exclusively by water: the cargo followed the route from Genoa to St Petersburg and then along the Neva, Ladoga, Onegas and Beloe lakes, through the Rybinsk reservoir and on along the Volga to the port of Dubna. You can see how it all happened here:

The difficulty in transporting it was that the main part of the magnet, a vacuum cylindrical steel cryostat with a diameter of over 5 metres and a superconducting solenoid inside, is an extremely complex and delicate device. Superconductivity in the solenoid occurs at very low temperatures, so a winding of niobium-titanium wire is cooled with liquid helium to a temperature of 40-80 K. For safety, the cryostat had to be placed in a large metal sarcophagus and fitted with shock absorbers to ensure that the magnet, assembled by Italian engineers to a design by Russian designers from Neva-Magnit, would arrive safely at the site.

A crane and two 680 hp tractors were used to unload the scientific cargo weighing 120 tonnes in the harbour. The sarcophagus with the magnet was transported to the MPD experimental facility by a special train and with great care. They even had to cut off power to half the city’s science city: power cables and other city utilities were temporarily removed along the way, disrupting the journey.

Assembly of the first parts for the magnet began a year ago, in July 2020, at a dedicated site for the MPD detector. Within a few weeks, the magnet supports – 13 fairway plates – were installed and the MPD magnet’s two support rings were mounted with high precision. It took eight months to fully assemble the equipment. Had it not been for the corona virus and the associated constraints, things would have gone faster. But the NICA collider is a major international project involving more than 40 institutes worldwide and more than 500 scientists from five continents. It took a long time for the Italian side to get to Russia to install the equipment because of the pandemic ravaging both countries: borders were closed and science was on pause.

According to the creators of the collider, the solenoid coil with a diameter of 5.6 m and a length of 8 m not only creates a uniform magnetic field in a large volume, but also acts as a mechanical structure for the other parts of the device. In other words, the MPD detector cannot be built without this solenoid, and of course it is impossible to start the collider.

What will happen in the accelerator when it finally starts? Two particle beams will fly towards each other and collide in this magnet, where particle collision detectors will be installed. Each detector will target a different region of energy and be responsible for a different area of physics. Scientists will decode this data and tell the world what happens when particles collide, replicating at the microscopic level the first moments after the Big Bang. This knowledge is expected to take particle physics and astronomy to a new level.

Unlike its more powerful counterpart, the Large Hadron Collider at CERN, the NICA Collider is designed to produce the heaviest possible plasma – just like at the beginning of our universe.

Stirring the filling 14 billion years ago :
It is commonly said that “mincemeat cannot be turned over backwards”. But JINR scientists are about to do just that – rewind time 14 billion years to see the first microsecond of the world’s birth. Physicists have already studied well and extensively how the universe expanded from the very first second, but they still can’t understand what came before and whether it existed at all. The NICA Collider is meant to be a kind of scientific “time machine” that will take us back to the beginning of the universe and help us answer what they call “science’s damnedest questions”.

One of them sounds paradoxical: why is there anything other than pure light in our universe at all? In theory, physicists know that every division is symmetrical. There is always left and right, plus and minus, past and future, and according to scientists’ calculations, every particle that is born inevitably gives rise to a symmetrical antiparticle. But where is it? How do you catch it? What does it represent? Scientists are waiting for answers from the NICA collider.

“Once upon a time, the universe was filled with particles and antiparticles in almost equal proportions,” explains Alexei Semikhatov, Science Channel broadcaster, doctor of physics and head of the Laboratory of the Theory of Fundamental Interactions at the Lebedev Physical Institute of the Russian Academy of Sciences. “There were 1 billion antiparticles and 1 particle per 1 billion antiparticles. Only one extra particle per billion! Over time, each particle found its antiparticle, they pro-annihilated, i.e. turned into radiation and disappeared. And all we see now, all that the world is filled with, is just this one-billionth remnant. But where it came from is a mystery. Thankfully, it came from somewhere! If that initial disturbance between particles and antiparticles hadn’t existed, there would be no you and me, because there would be nothing to create a world out of.” In scientific terms, this problem is called the “baryonic asymmetry of the universe”.

In NICA’s collider, heavy metal ions would collide with each other at carefully selected energies, not to smash into pieces but to “stick together” for a moment. Scientists speculate that this is how the very super-dense quark-gluon plasma that is thought to have made up our universe during the first microsecond of creation could be produced. If quark-gluon plasma exhibited asymmetry in the Big Bang, something similar will happen in the small plasma explosion in the collider – just what physicists are hoping for.

Once NISA is up and running, we will also find out what happens inside neutron stars. Quark-gluon matter in them may be produced by the enormous gravity. The matter there simply crushes itself: first negatively charged electrons are squeezed into positively charged protons, and neutrons are formed as neutral particles. If gravity is sufficient, neutrons can also fail and be crushed in cold, dense quark-gluon plasma. Until now, it has been impossible to create this unique state of matter on Earth. The density in the deep layers of a neutron star is at least 20 billion tonnes per 1 cm³. That’s like compressing Lake Baikal into a teaspoon. Scientists dare not even estimate the density of quark-gluon matter in well-known, concrete units.

“The NICA accelerator is set to reproduce what happens at high energy densities, which may have existed in the early stages of the formation of the universe, – told the channel “Science” Dmitry Kazakov, head of the laboratory of theoretical physics, doctor of physical sciences, corresponding member of the RAS. “We want to see what happens when there is very high matter density. We are interested in high densities of nuclear matter – more than in ordinary nuclei. Such matter in ordinary nature is almost unknown to us, we don’t encounter it. It can be found in neutron stars. But neutron stars are not everyday objects either.

The NICA collider dates from the 1950s :
The NICA collider managed to become the international flagship project for studying quark gluon plasma because the energies to which the particles are accelerated in Dubna were previously almost unsuitable for such a task.

As early as 65 years ago, Soviet physicists developed a particle accelerator, the synchrophasotron. Since 1957, it has made it possible to accelerate protons to energies that had never been reached before – 10 GeV. This amazing device was not removed; technically it provides stability to the building, which will drive the second and third speed rings of the NICA “gearbox” – the booster and the nucleonotron. The historic structure weighs 36,000 tonnes. If it is dismantled, the stability of the structure will be disrupted and the paths of all the systems and installations operating here will float. In addition, JINR scientists consider the synchrophasor to be a scientific monument to humanity that must not be destroyed.

“In a way, it was fortunate that the historically existing synchrophasotron gave just such energy to accelerated protons or nuclei that, if pushed into the collider rings, according to the existing models gave maximum density,” Dr Yury Kudenko, head of the High Energy Physics Laboratory at JINR, told the Science channel. “It turned out so well that what was here in Dubna, if we build the rings that are now being completed, gives maximum density.”

Adults love numbers. And here are some to compare. The energies achieved in 2018 by the most powerful accelerator of our time, the Large Hadron Collider, are 700 times higher than the Soviet synchrophasor photon (10 GeV). The NICA accelerator doesn’t need that much to produce an ultra-dense quark-gluon plasma. That’s enough for each proton in the heavy ions that will fly around the accelerator ring to reach an energy of 11 GeV, which is slightly more than it was at the synchrophasotron.

The average man might exclaim: “So what, science! A slight improvement on an iron that’s over 60 years old!” But in fact, the solutions applied to the accelerator and detectors in the NICA collider are state-of-the-art in experimental scientific technology. Provided, of course, that everything works as scientists imagine and that the elementary particles obey them.

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