Laboratory of Physics of the exotic nuclei

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Laboratory of Physics of the exotic nuclei


Introduction
Laboratory of Physics of the exotic nuclei (LPEN) was established in 2003 by evolving from the laboratory IRIS (Investigation of Radioactive Isotopes on the Synchrocyclotron), based since 1975 at the on-line mass separator setup with the accelerator PNPI. At the end of 2013 LPEN was reorganized by separating the groups of proton therapy and radiochemistry, and the introduction in its structure a group of young physicists- researchers and graduate students.
  • The main milestone of research by the staff LPEN in the laboratory IRIS was an involvement in the launch of this first installation in the country and the specific rationale for its scientific program (E. Berlovich, E. Ignatenko and Yu. Novikov. Proc. Leysin Conference, CERN, 1973). The program of the study of nuclides far from the valley of beta-stability with the suggestion of investigation some new physical phenomena that are specific to nuclear physics and astrophysics was developed. A significant part of this program was implemented at PNPI and was developed in foreign centers. The main results obtained by the staff LPEN are listed below in the following paragraphs.

    • New effects of delayed emission of particles tritium and 3He. were predicted. Delayed nucleus of tritium were subsequently experimentally detected in the work of group at CERN. The predicted phenomenon of delayed fission by E.Ye. Berlovich and Yu.N. Novikov was experimentally discovered at JINR (Dubna) and has continued in research at PNPI and CERN. This phenomenon plays an extremely important role in the nuclear cosmochronology (the determination of the age of the Universe). The group IRIS measured probability of this process in heavy neutron-rich nuclides (Fr, Ra) and showed that it does not affect the determination of the age of the Universe by a pair of U/Th, contrary to the hypothesis put forward in the literature leading to the revision of several cosmological postulates.

    • It was shown that superheavy nuclides of the Periodic system of elements can be formed in the astrophysical process of rapid neutron capture (r-process) occurring in the explosion of stars and responsible for the formation of elements in nature. Despite numerous attempts, Superheavy nuclides has not been found yet in nature.

    • Another astrophysical process of rapid proton capture in stellar environments (rp-process) responsible for the generation of energy in stars was investigated in the first joint experiments with the participation of Russian scientists on a setup ISOLDE at CERN, dedicated spectroscopic studies of 73Rb and neighboring nuclides. The experiments have shown that the rp-process must not be interrupted in this nuclide area. The similar result, but in the area of nuclides Sn-Te, was obtained in the joint experiments at the University of Jyvaskyla (Finland). Coordinator of the both experiments was Yu. N. Novikov (LPEN).

    • Fifteen new isotopes of various elements were discovered at the setup IRIS. This was facilitated by the cooperation with the department of nuclear spectroscopy JINR (Dubna), provided the original node of the "target-ion source" for the mass separator IRIS, allowed very productively to perform numerous joint experiments. These works, with the participation of the members of both groups, were awarded two of the JINR prizes for the best works and awards of the PNPI. A doctoral and three PhD's theses were defended in PNPI according to the results of the work.

    • Successful implementation of measurement technique for the end-point energies of the positron spectra with the hyperpure germanium detector allowed to determine masses of the nuclides in the area of rare earth elements and identify for the first time the boundary of proton stability of the nuclei (so called proton drip-line).

    • Since the mid-1990s LPEN participated in the international consortium on mass measurements of relativistic nuclei at the storage ring at the German national centre GSI (Darmstadt). As a result of the pioneering measurements by the method of Schottky mass spectrometry of cooled ions and the method of detection of ions in an isochronous mode of the storage ring hundreds of nuclides in the region of large mass numbers were measured, that led to a number of interesting physical findings. The work was awarded IUPAP (international Union of Pure and Applied Physics). This activity continued in the 2000s by developing of the ILIMA project for the future FAIR facility (Darmstadt). Yu.N. Novikov was the coordinator of this international project until 2006.

    • The search for unknown alpha emitters in the field of superheavy nuclides required for recovering the mass landscape generated a great interest in the first decade of the 2000s. Initiated by scientists of LPEN this program was implemented with their participation in three setups: in the University of Jyvaskyla (Finland), Japanese center JAERI (Tokai) and GSI (Germany).

    • From 2011 to 2014 LPEN participated in the pan-European project LAGUNA-LBNO within the framework of the program FP-7 devoted to the projects of giant neutrino detectors for future studies of neutrino oscillations. LPEN was responsible for research in the field of low energy neutrinos. The result was a proposal to study neutrino oscillations within the dimensions of the detector, called the neutrino oscillometry, which is possible with the use of artificial neutrino sources produced at the high-flux reactors, such as the PIK, and the detection of neutrinos with 100-meter detector of liquid scintillator LENA.

  • Employees of LPEN (before the reorganization in 2013) participated in applied research:

    • Group of proton therapy, based on the PNPI synchrocyclotron, performed spot irradiation of patients with proton beam of the PNPI-synchrocyclotron.

    • Together with the Radium Institute and the Institute of Macromolecular Compounds with the coordinating role LPEN an international project has been performed under the auspices of the ISTC, dedicated to the creation of carbon matrixes for storage and transmutation of the products of spent nuclear fuel of reactors.
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