The Editorial Board of the journal “Bulletin of the Russian Academy of Sciences: Physics” monthly assigns one of the articles of each thematic issue the honorary status of “Editor’s Choice”. We hope that the selected articles will be of interest to a wide range of readers.
Volume 85, issue 4, April 2021
Thematic issue “Physics of Cosmic Rays”
A. N. Turundaevskiy, O. A. Vasiliev, D. E. Karmanov, I. M. Kovalev, I. A. Kudryashov, A. A. Kurganov, A. D. Panov & D. M. Podorozhny, Main Results from the NUCLEON Experiment // Bulletin of the Russian Academy of Sciences: Physics, 2021, Volume 85, Issue 4, P. 353–356.
One of the most urgent problems of cosmic ray (CR) physics now is the determination of the chemical composition of abundant CRs with the highest energy. During the beginning of the work on the NUCLEON observatory, there was a consensus regarding the behavior of the spectra of the main abundant (produced mainly in sources) nuclei up to energies no higher than several TeV. In 2014-2017 the NUCLEON space experiment was carried out. The NUCLEON is a modern high-tech spectrometer that has incorporated the advanced technologies of physical experiment. A characteristic feature of the equipment is the very insignificant consumed flight resources, such as weight, power consumption, dimensions. This is explained by the fact that a new technique for recording the energy of CR particles has been used for the first time in the spectrometer. The authors called this method KLEM (Kinematic Light – Weight Energy Meter) to emphasize its main advantage – a low-mass energy meter, which gives a gain of almost an order of magnitude in the “aperture/mass” parameter in comparison with traditional methods.
Despite the small amount of consumed resources, over 2.5 years of the orbital experiment, a data bank was obtained, including about 20 million events. This number exceeds the total statistics of all direct experiments with similar goals over the past 50 years, which made it possible to obtain spectra of abundant cosmic ray nuclei up to energies of several hundred TeV. For the first time, the integration of ground-based and orbital measurements of the CR energy spectrum took place, which made it possible to directly calibrate the data obtained in ground-based experiments. The difference of the spectrum from the power-law form at 2 – 500 TeV was statistically proved. In the energy range up to 5·1014 eV, the chemical composition of cosmic rays was determined with element-by-element resolution, and a number of features were found in the energy spectra of CR elements. The result obtained is the factual material necessary for constructing and refining models of the Galaxy and its energy balance.
The team of the authors of the article consists of the staff of the Institute of Nuclear Physics of the Moscow State University, who for many years worked on the preparation and conduct of the NUKLON experiment, and then on the processing of the results obtained. The team is one of the leading research groups in the field of cosmic ray astrophysics.