How to fly to Mars in a month? To do this, you need to give the spacecraft a good boost. Alas, the best fuel available to man - nuclear gives a specific impulse of 3000 seconds, and the flight stretches for many months. Isn't there something more energetic at hand? Theoretically there is: thermonuclear fusion; it provides an impulse of hundreds of thousands of seconds, and the use of antimatter will provide an impulse of millions of seconds.
Antimatter nuclei are built of antinucleons and the outer shell consists of positrons. Due to the invariance of the strong interaction with respect to charge conjugation (C-invariance), antinuclei have a mass and energy spectrum the same as those of nuclei consisting of the corresponding nucleons, and the atoms of antimatter and matter must have identical structure and chemical properties, with one single HO, the collision of an object, consisting of matter, with an object of antimatter leads to the annihilation of particles and antiparticles included in their composition.
The annihilation of slow electrons and positrons leads to the formation of gamma quanta, and the annihilation of slow nucleons and antinucleons leads to the formation of several pi-mesons. As a result of subsequent decays of mesons, hard gamma radiation with an energy of gamma quanta of more than 70 MeV is formed.
Antielectrons (positrons) were predicted by P. Dirac and after that experimentally discovered in “showers” by P. Anderson, who did not even know about Dirac's prediction at that time. This discovery was awarded the Nobel Prize in Physics in 1936. Antiproton was discovered in 1955 at the Bevatron in Berkeley, which was also awarded the Nobel Prize. In 1960, an antineutron was discovered there. With the commissioning of the Serpukhov accelerator, our physicists also managed to get ahead in some ways - in 1969 antihelium nuclei were discovered there. But the atoms of antimatter could not be obtained. And to be frank, during the entire existence of accelerators, antiparticles have received insignificant quantities - all antiprotons synthesized at CERN in a year will be enough to operate one light bulb for several seconds.
The first message about the synthesis of nine atoms of antimatter - antihydrogen within the framework of the ATRAP project (CERN) appeared in 1995. Having existed for about 40 ns, these single atoms died, releasing the prescribed amount of radiation (which was recorded). The goals were clear and justified the efforts, the tasks were determined, and in 1997, near Geneva, thanks to international financial assistance, CERN began construction of a desselerator (let's not translate it with the dissonant equivalent of “inhibitor”), which allowed to slow down (“cool”) antiprotons back in ten million times over the 1995 installation. This device, called the Antiproton Moderator (AD), entered service in February 2002.
The setup, after the antiprotons leave the slowing down ring, consists of four main parts: a trap for trapping antiprotons, a positron storage ring, a mixing trap, and an antihydrogen detector. The antiproton flux is first decelerated by microwave radiation, then cooled as a result of heat exchange with a flux of low-energy electrons, after which it falls into a trap - a mixer, where it is at a temperature of 15 K. The positron storage device successively slows down, captures and accumulates positrons from a radioactive source; about half of them fall into a mixing trap, where they are additionally cooled by synchrotron radiation. All this is necessary to significantly increase the probability of the formation of antihydrogen atoms.
At the Antiproton Moderator, a tough competition between two groups of scientists, participants in the ATHENA experiments (39 scientists from different countries of the world) and ATRAP, began.
In Nature 2002, vol. 419, p. 439, ibid p. 456), published on October 3, 2002, the ATHENA experiment claimed that they had succeeded in producing 50,000 antimatter atoms - antihydrogen. The presence of antimatter atoms was recorded at the time of their annihilation, which was evidenced by the intersection at one point of the traces of two hard quanta formed during electron-positron annihilation, and traces of pions resulting from the annihilation of an antiproton and a proton. The first "portrait" of antimatter (photo at the beginning) was obtained - a computer image synthesized from such points. Since only those atoms that "slipped" out of the trap were annihilated (and there were only 130 of them reliably counted), the declared 50,000 antihydrogen atoms only create an invisible background of the "portrait".
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The problem is that antihydrogen annihilation was recorded against a general, stronger background of positron and antiproton annihilation. This, naturally, caused a healthy skepticism among colleagues from the adjacent competing project ATRAP. They, in turn, having synthesized antihydrogen at the same facility, were able to register antihydrogen atoms with the help of complex magnetic traps without any background signal. The antihydrogen atoms formed in the experiment became electrically neutral and, unlike positrons and antiprotons, could freely leave the region where charged particles were confined. It was there, without a background, that they were registered.
It is estimated that approximately 170,000 antihydrogen atoms were formed in the trap, as the researchers reported in an article published in Physical Review Letters.
And this is already a success. Now the received amount of antihydrogen may well be enough to study its properties. For antihydrogen atoms, for example, it is proposed to measure the frequency of the 1s-2s electronic transition (from the ground state to the first excited state) by high-resolution laser spectroscopy methods. (The frequency of this transition in hydrogen is known with an accuracy of 1.8 · 10–14 - it is not for nothing that the hydrogen maser is considered a frequency standard.) According to the theory, they should be the same as in ordinary hydrogen. If, for example, the absorption spectrum turns out to be different, then you will have to make adjustments to the fundamental foundations of modern physics.
But interest in antimatter - antimatter is by no means purely theoretical. An antimatter engine can work, for example, as follows. First, two clouds of several trillion antiprotons are created, which are kept from touching matter by an electromagnetic trap. Then a 42-nanogram particle of fuel is injected between them. It is a uranium-238 capsule containing a mixture of deuterium and helium-3, or deuterium and tritium.
Antiprotons instantly annihilate with uranium nuclei and cause them to decay into fragments. These fragments, together with the resulting gamma quanta, heat up the inside of the capsule so much that a thermonuclear reaction begins there. Its products, which have tremendous energy, are accelerated even more by the magnetic field and escaped through the engine nozzle, providing the spacecraft with unheard of thrust.
As for the flight to Mars in one month, American physicists recommend using another technology for it - nuclear fission catalyzed by antiprotons. Then the entire flight will require 140 nanograms of antiprotons, not counting radioactive fuel.
New measurements carried out at the Stanford Research Center (California), where a linear particle accelerator is installed, have allowed scientists to make progress in answering the question of why matter prevails over antimatter in the universe.
The results of the experiment confirm the earlier assumptions about the development of an imbalance of these opposite entities. However, scientists say that the studies carried out have posed more questions than answers: experiments with an accelerator cannot provide a complete explanation of why there is so much matter in space - billions of galaxies filled with stars and planets.
Scientists working with the accelerator measured a parameter known as the sine of two beta (0.74 plus or minus 0.07). This indicator reflects the degree of asymmetry between matter and antimatter.
As a result of the Big Bang, the same amount of matter and antimatter should have been formed, which then annihilated and left nothing but energy. However, the universe we are observing is indisputable evidence of the victory of matter over antimatter.
To understand how this could happen, physicists looked at an effect called charge equality violation. To observe this effect, scientists studied B-mesons and anti-B-mesons, particles with a very short life span - trillionths of a second.
The differences in the behavior of these absolutely opposite particles show the differences between matter and antimatter and partly explain why one prevails over the other. The millions of B-mesons and anti-B-mesons required for the experiment were formed as a result of collisions in the accelerator of the beams of electrons and positrons. The first results, obtained back in 2001, clearly show a violation of the equality of charges for B-mesons.
"This was an important discovery, but a lot of data still needs to be collected to validate the sine of two beta as a fundamental constant in quantum physics," said Stewart Smith of Princeton University. "The new results were announced after three years of intensive research and analysis of 88 million events."
The new measurements are consistent with the so-called "standard model", which describes elementary particles and their interactions. The confirmed degree of violation of the equality of charges by itself is not sufficient to explain the imbalance of matter and antimatter in the universe.
“Apparently, in addition to the inequality of charges, something else happened, which caused the predominance of matter turned into stars, planets and living organisms,” commented Hassan Jawahery, a staff member of the University of Maryland. “In the future, we may be able to understand these hidden processes and answer the question of what brought the universe to its present state and this will be the most exciting discovery."