N. S. Konovalova

Prospects of the Study of Geological Structures by Muon Radiography Based on Emulsion Track Detectors

For the first time in Russia, researchers of the Lebedev Physical Institute and Skobeltsyn Institute of Nuclear Physics perform test experiments for studying the internal structure of large natural and industrial objects by the muon radiography method using the emulsion technique. The used technique is based on the high penetrability of cosmic muons and implies the detection of the attenuation of their flux passed through the object under study using nuclear photoemulsions with a uniquely high spatial resolution. The results of the first test experiment are presented, which confirm the promising application of the method when using emulsion track detectors and their subsequent hi-tech automated processing.

Search for superheavy elements in galactic cosmic rays

The charge distribution of approximately 6000 nuclei with charge numbers above 55 in galactic cosmic rays has been obtained in the OLIMPIYA project. Three superheavy nuclei with the charge numbers in the range 105 < Z < 130 have been detected. The regression analysis has provided a more accurate estimate of the charge number of one of these nuclei (119−6+10 with a probability of 95%). Such nuclei should form stability islands. Their detection in nature confirms theoretical predictions and justifies efforts for their synthesis under terrestrial conditions. The model calculations performed in this work possibly can explain the results of some experiments on the investigation of the charge composition of cosmic rays in which particles with charge numbers in the range 94 < Z < 100 were detected (they cannot enter into the composition of primary cosmic radiation because their lifetime is very short). The calculations indicate that events with Z > 92 are due to the fragmentation of heavier nuclei from the stability island, rather than to methodical inaccuracies or fault of instruments. Several such events have been revealed. Thus, the track method makes it possible to obtain the results very important for understanding of the physical picture of the world. The results obtained within the OLIMPIYA project show that the study of tracks of galactic cosmic rays in olivine crystals from meteorites opens new capabilities for the investigation of fluxes and spectra in cosmic rays in the region of heavy and superheavy nuclei.

Detecting galactic cosmic ray transuranium nuclei in olivine crystals from meteorites

Results from the experimental search for and identification of tracks from the superheavy and transuranium nuclei of galactic cosmic rays in pallacite olivine crystals, conducted as part of project OLIMPIA [1], are presented. To date, 170 crystals from Marjalahti and Eagle Station pallacites have been processed and 6800 tracks corresponding to nuclei with charges Z > 55 have been found; 45 of these are from nuclei with charges of 88 < Z < 92 and three super-long ones were produced by nuclei with Z > 105. The charge of one of these nuclei is estimated in the first approximation as Z = 119(+10,−6). Our data confirm the hypothesis of islands of stability for natural trans-Fermi nuclei.

Calibration measurements of the characteristics of tracks from superheavy nuclei in olivine crystals from meteorites

To identify the charge of detected cosmic ray nuclei, it is necessary that the dynamic and geometric parameters of tracks (the etching rate of a nuclear track, as well as the length and the diameter of the track channel) be determined with a high accuracy. Results of the experimental investigations of tracks produced in olivine crystals from the Marjalahti pallasite by accelerated Xe and U nuclei are presented. These investigations were performed as part of the Olimpiya project. It is shown that the etching rate and the fully etched track length are independent of the track orientation relative to the crystallographic symmetry axes of each olivine crystal under investigation.

Using muon radiography to study the structure of massive objects

The Lebedev Physical Institute of the Russian Academy of Sciences and the Skobeltsyn Institute of Nuclear Physics of Moscow State University conduct experiments using nuclear photoemulsion to study the internal structure of large objects via muon radiography. Analysis of an experiment in a mine in Obninsk belonging to the Geophysical Service of the Russian Academy of Sciences is of particular interest. Calculated and experimental data are presented.

Charge spectrum of superheavy nuclei of galactic cosmic rays obtained in the OLIMPIA experiment

In this paper, we present the last results of the OLIMPIA experiment on the search for and study of traces of heavy and superheavy element nuclei of galactic cosmic rays in olivine crystals from meteorites. The charge spectrum of cosmic rays in the region of heavy nuclei is obtained, three superheavy nuclei of natural origin with charges in the range 105 < Z < 130 and lifetimes longer than 3000 years, being a part of the so-called “stability island”, are identified.

Technique for determining the charge of cosmic ray nuclei by tracks in olivine crystals from meteorites

A technique for identifying the charge of cosmic ray nuclei, based on measurements of the length and average etch rate of tracks chemically etched in olivine crystals from the Marjalahti pallasite is described.

Search for the “stability island” of superheavy nuclei using natural track detectors

The method of using natural track detectors, i.e., meteorite olivine crystals, is developed and improved applied to the problem of searching for superheavy nuclei in nature, in galactic cosmic rays (GCR). The new technique implements the sequence of etching, grinding, and track identification operations using the automated PAVICOM facility. The data on the track length and etching rate in combination with the results of calibration on heavy nucleus accelerators allowed the development of a technique for determining the GCR nucleus charge with an accuracy of ±2. On this basis, a significant set of experimental data on superheavy nuclei of natural origin was obtained (21743GCRheavy nucleiwithZ >20, including three nucleiwith a charge of 119−6+10). The minimum lifetime Tmin of the last-mentioned is within 50 years< Tmin < 100 years, which exceeds the lifetime of transfermium nuclei synthesized on accelerators by many orders of magnitude. The long-lived superheavy nuclei detected in the GCR spectrum can belong to the “stability island”.

Charge distribution of superheavy elements in galactic cosmic rays on base of investigations in olivine crystals from meteorites

An original method of studying chemically etched tracks of heavy nuclei in olivine from pallasite meteorites was used to obtain a charge distribution of approximately 9000 nuclei with charges above 55 in galactic cosmic rays. Three superheavy nuclei with the charges in the range of 105<Z<130 were detected. Regression analysis enabled to amend the charge of one of these nuclei up to the value 119−6+10 with the probability of 95%. Such nuclei have to form islands of stability of superheavy elements; their occurrence in nature supports the validity of theoretical predictions and justifies efforts for their synthesis under the Earth conditions.

Simulation of Passage of Gallactic Cosmic Ray Nuclei in Meteorite-Pallasite Substance

The results are presented of model calculation of the interaction and yield of galactic-cosmic-ray superheavy-element nuclear fragmentation products from the 50 < Z < 92 range of their charges as they pass through a certain meteorite-pallasite substance thickness.