Participating countries and international organizations:
Azerbaijan, Belgium, Bulgaria, Czech Republic, France, Germany, Italy, Japan, Kazakhstan, Russia, Slovakia, Switzerland, United Kingdom, USA, Uzbekistan.

The problem under study and the main purpose of the research:
Search for neutrinoless and two-neutrino modes of double beta decay and their investigation, revelation of the neutrino nature, Majorana or Dirac, determination of the absolute neutrino mass scale and hierarchy, search for the magnetic moment of electron neutrinos, search for possible manifestations of dark matter. Investigations of nuclear reactor in-core processes at the Kalinin Nuclear Power Plant. Search for signals from coherent reactor antineutrino scattering and their investigation. Precision study of the coherent scattering spectrum to search for manifestations of New Physics. Search for sterile neutrinos. Spectroscopy of nuclei far from the line of beta stability. Study of interactions between intermediate-energy pions and helium nuclei. Development of new methods for detection of charged and neutral particles. Development of methods for producing and purifying radionuclide preparations for synthesis of radiopharmaceuticals. Application of hyperfine interaction methods to studying radiopharmaceuticals and their precursors. Development and application of methods and techniques to manufacture and analyze low-background materials with an ultra-low content of radioactive impurities.

Projects: 

Brief annotation and scientific rationale:
The project is aimed at developing methods of nuclear spectroscopy and radiochemistry for the use in nuclear medicine, astrophysics and neutrino physics. The project involves novel techniques for particle detection, calibration of experimental facilities, determination of background and also the design of uniquely pure materials, etc., as well as development of methods for nuclear medicine – such as production and purification of radioisotopes, development and synthesis of radiopharmaceuticals, study of mechanisms affecting the tissues at radionuclide decay locations, etc.

Specific area:
- novel detectors (semiconductor detectors, liquid and plastic organic scintillators, composite scintillation detection systems, neutron and radon detectors, etc.).

- post-decay spectroscopy of electrons and other emissions, with the focus on extremely low energies.

- standard gamma-spectroscopy based on semiconductor particle detectors (SPDs), with the focus on precision measurements of emission energy and source activity (of both point-like and volume sources) in order to study decay modes and to determine cross sections of nuclear reactions.

- methods of hyperfine interactions using radioactive tracers, namely the Method of Perturbed Angular Correlations (PAC) and Emission Mössbauer Spectroscopy to study radiopharmaceuticals and their precursors in aqueous systems and other matrices.

- methods for production and purification of radionuclide preparations to synthesize radiopharmaceuticals, including their production with generators, physicochemical methods for evaluating properties of radionuclides and radiopharmaceuticals (their precursors) in homogeneous and heterogeneous systems.

- methods and techniques for production and analysis of low-background materials with a uniquely low content of radioactive impurities, in particular, using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), as well as other analytical techniques and those of nuclear spectroscopy.

Methods of nuclear spectroscopy and radiochemistry for studying neutrino properties, searching for dark matter particles and investigating rare physical processes have long and deservedly proved effective in numerous experiments in fundamental physics and nuclear medicine. The relevance of this topic is certain. The focus on the development of methods and techniques expanding the horizon of the experiments being performed at DLNP JINR guarantees the scientific novelty of the project.

Expected results upon completion of the project:
New detectors:
- detectors based on silicon carbide (SiC) will be designed and then applied to the detection of nuclear radiation; SiC detectors with a high radiation hardness and good operability at high temperatures (> 400°C) are intended to be used for monitoring the operation of high-current accelerators, nuclear reactors, as well as for diagnostics of hot plasma;

- liquid tellurium-loaded scintillators are expected to be designed and applied to search for the neutrinoless double β-decay, as well as other types of liquid and plastic scintillators;

- composite scintillation detection systems will be developed for neutrino experiments;

- ³He counters will be developed and applied to the detection of low neutron fluxes (of below 10^-6 n×cm^-2×s); a compact sensitive radon detector will be designed, as well as the technology to produce low-level radioactive components using 3D printing.

It is planned to experimentally study the spectra of low-energy electrons (0–50 keV) with the ESA-50 spectrometer and the spectra of gamma and X-ray radiation with SPDs during radioactive decay in order to obtain new data on low excited states of nuclei and post-decay relaxation of atomic systems, as well as to search for ways to perform the spectrometry of post-decay photons (from the edge of infrared radiation up to soft X-rays) in the energy range of 1–200 eV.

The method for using the codes (Geant4, MCNP and FLUKA) to simulate parameters of HPGe spectrometers both at the LINAC-200 Electron Accelerator intended to determine yields of photonuclear reactions, and also at other basic facilities of JINR will be developed; decay modes of a wide range of radionuclides will be studied, and their content in samples (⁹⁶Zr, ⁴⁰K, ¹³⁸La, etc.) will be determined in order to investigate rare processes.

It is expected that the methods of Perturbed Angular Correlations (PAC) and Emission Mössbauer Spectroscopy using radioactive tracers ¹¹¹In, ¹⁵²Eu, ¹⁵⁴Eu, ¹¹⁹Sb, ^119mSn, ⁵⁷Co, ¹⁶¹Tb, etc., will be mastered in order to study radiopharmaceuticals and their precursors (components) in aqueous systems and other matrices; physicochemical methods to evaluate properties of radionuclides and radiopharmaceuticals in homogeneous and heterogeneous systems will be improved. 

Radiochemistry and nuclear medicine:
- sorption processes in various solution-sorbent systems as a chemical basis of methods for purification of radiopharmaceuticals (also of low-background materials) are planned to be studied, and radionuclide generators for production of radiopharmaceuticals to be designed;

- methods for production of radionuclides and their separation (including mass separation) from targets irradiated with protons, neutrons and gammas for production of radiopharmaceuticals (¹⁰³Pd, ¹¹⁹Sb, ¹⁶¹Tb, some alpha emitters, etc.) will be developed;

- on the basis of reverse-tandem schemes, the development of a wide range of radionuclide generators will be continued in order to expand the possibilities of producing medical radionuclides; the possibility of producing 1–2 generators of significant activity for external users will be considered;

- methods for radiolabelling based on chelators with "slow" kinetics for synthesis of radiopharmaceuticals will be developed; radium chelation will be investigated.

Methods for producing samples (⁸²Se, ⁹⁶Zr, shielding materials, solder, etc.) with a new ultra-low content of impurities (from mBq/kg to μmBq/kg of Th and U) to solve problems in astrophysics and neutrino physics will be developed and employed; reverse chromatography will be used, low-boiling and other reagents, prepared or selected, will be utilized, as well as reactor materials, selected and prepared;

- it is planned that the methods for the analysis of samples at an ultra-low level of sensitivity (mBq/kg – μmBq/kg of Th and U) using ICP-MS, the neutron activation analysis (NAA) and other techniques will be developed and employed; that the methods for precise determination of the chemical and isotopic composition of materials used in astrophysical and neutrino experiments will be designed.

Expected results of the project this year:
New detectors:
- characteristics of the detectors based on ultra-high purity silicon carbide (SiC) will be determined for spectroscopy of nuclear radiation;

- techniques for manufacturing plastic scintillators applicable to the separation of n/γ-radiation by the pulse shape will be tested;

- results of designing of composite scintillation detection systems for next-generation neutrino experiments will be obtained; a prototype auxiliary detector for large reactor experiments will be developed;

- a novel ³He counter with a low internal background will be tested;

- technology for manufacturing components of low-level radioactive plastics using 3D printing will be developed.

Schemes of post-decay photon spectrometers (from the edge of infrared radiation up to soft X-rays) in the energy range of 1–200 eV will be proposed.

Experimental data on the low-energy electron spectra from the decay of radioisotopes of ⁵⁶Co, ⁵⁷Co, ⁸³Rb, ¹⁵⁵Eu with the ESA-50 beta spectrometer are planned to be obtained in order to test the available computer codes for evaluating dose components of Auger and conversion electrons in radiation hygiene and radionuclide therapy.

Photonuclear reaction yields will be determined; decay modes of a wide range of radionuclides, their content in samples will be specified to study rare processes.

PAC spectrometers will be upgraded; new Emission Mössbauer Spectrometers will be launched (radioactive tracers ¹¹¹In, ¹⁵²Eu, ¹⁵⁴Eu, ¹¹⁹Sb, ^119mSn, ⁵⁷Co, ¹⁶¹Tb, etc., will be used in studies).

Radiochemistry and nuclear medicine: the results of studying sorption processes of various solution-sorbent systems, as well as novel schemes of radionuclide separation are expected.

Methods for obtaining samples (⁹⁶Zr) with a new ultra-low content of impurities to solve problems in astrophysics and neutrino physics will be developed and utilized.

It is planned to calibrate the mass spectrometer (ICP-MS) with standard samples; methods for sample analysis at an ultra-low level of sensitivity to Th and U will be acquired.

Brief annotation and scientific rationale:
The project combines the experiments DANSS, Ricochet and νGeN focused on the study of antineutrino fluxes from nuclear reactors at distances of less than 20 m. The experiments are united by a common area of research, by scientific problems overlapping and coinciding in many respects and by the ways to solve them. In addition, these studies are united by the common JINR staff and infrastructure resources.

DANSS is an experiment using an antineutrino spectrometer based on plastic scintillators, with a sensitive volume of 1 m³, located at Power Unit 4 at the Kalinin NPP. The lifting mechanism makes it possible to move the spectrometer 2 m vertically in the online mode, providing the range of measurements at the distance of 11–13 m from the reactor. A high degree of detector segmentation and the use of combined active and passive shielding ensure background suppression down to several percent relative to ~5000 IBD events recorded per day.

The νGeN experiment is aimed at studying the fundamental properties of neutrinos, in particular, searching for the neutrino magnetic moment (NMM), coherent elastic neutrino scattering (CEvNS) and other rare processes. The νGeN spectrometer is located under the reactor core of Power Unit 3 at the Kalinin NPP. Neutrino scatterings are detected with a special low-threshold, low-background germanium detector. With systems of active and passive shielding from background radiation, a low level of background in the region of the search for rare events is achieved. The detection of events of interest ensures the search for New Physics beyond the Standard Model, in addition, it can also be applied practically, for example, in the development of new-generation detectors for monitoring the operation of a nuclear reactor using the antineutrino flux.

Ricochet is a new-generation reactor neutrino experiment aimed at the one-percent-precision measurement of coherent elastic neutrino-nucleus scattering (CEνNS) in the sub-100-eV recoil nucleus energy region, which could reveal New Physics in the electroweak sector. It is planned to install the facility near the research nuclear reactor at the Laue-Langevin Institute (ILL) until the end of 2024. Ricochet will host two cryogenic detector arrays: CRYOCUBE (Ge bolometers based on those developed by the EDELWEISS experiment) and Q-ARRAY (superconducting Zn).

Expected results upon completion of the project:
The main goals of the DANSS experiment are to test the hypothesis of oscillations of reactor antineutrinos into a sterile state and to precisely monitor the operation of the nuclear reactor by measuring the antineutrino flux for a long time. In few years, it is planned to make a new upgraded setup DANSS-2. The aims of the upgrade are to improve energy resolution and to increase the detection volume, thus, the sensitivity to sterile neutrinos will be significantly higher. The search for oscillations into the light sterile neutrino (Δm₁₄² ~ 0.1–10 eV) is one of the current trends in fundamental neutrino physics. The existence of a sterile neutrino could explain several contradictory observations, first of all, the reactor and gallium (anti)neutrino anomalies, and at the same time become a revolutionary discovery of New Physics. Reactor experiments with a short baseline (<30 m) have several competitive advantages in this area of research: a giant antineutrino flux from the most intense available artificial sources of (anti)neutrinos on Earth and a small distance from the radiation source where the hypothesized oscillation pattern is not smeared yet. It should be noted that the DANSS spectrometer is the leader among the facilities of this type.

It is expected that the νGeN project will detect coherent scattering of reactor antineutrinos for the first time and increase the sensitivity to the neutrino magnetic moment to ~1×10^-11 m_B during several years of measurements to come, which will greatly improve the present-day best limit.

In the Ricochet experiment, according to the elaborated and experimentally proven background model, the statistical significance of the CEνNS detection after only one reactor cycle will be between 7.5 and 13.6 σ, depending on the effectiveness of the muon veto. The targeted ~1%-precision measurement is expected to be reached after about ten reactor cycles (3–5 years onsite). It will increase the probability of discovering New Physics by an order of magnitude compared to that of the ongoing experiments.

Expected results of the project this year:
DANSS: data taking and processing at the DANSS setup will be continued; new results of studies of oscillations of neutrinos into a sterile state are expected; R&D of DANSS-2 is planned, as well as the DANSS-2 manufacture and assembly at the Kalinin NPP.

νGeN: Data taking in the current setup configuration and a simultaneous upgrade of the setup are planned, including a new internal veto, replacement of passive shielding, modernization of the data taking system; it is expected that new results considering the neutrino magnetic moment and CEvNS will be obtained; the backgrounds, including a neutron one, will be measured and analyzed.

Ricochet: new results at the setup at ILL are expected; the upgrade of the detectors will proceed; an improved Monte Carlo model is planned to be developed on the basis of the experimental data.

Brief annotation and scientific rationale:
The project consists of five main experiments: LEGEND (The Large Enriched Germanium Experiment for Neutrinoless double beta Decay), TGV (Telescope Germanium Vertical), SuperNEMO (Neutrino Ettore Majorana Observatory), MONUMENT (Muon Ordinary capture for the NUclear Matrix elemENTs) and Zr-BNO. The experiments solve the problems of searching for and studying the neutrinoless double beta decay.

Expected results upon completion of the project:
The LEGEND experiment is designed to search for the neutrinoless double beta decay (0νββ) of ⁷⁶Ge. In LEGEND, bare detectors of isotopically enriched ⁷⁶Ge immersed in liquid argon are used. The ultimate goal of the project is to reach the sensitivity to the 0νββ decay of ⁷⁶Ge > 10²⁸ years (90% C.L.).

The physics programme of the SuperNEMO Demonstrator Module contains precision measurements of the 2νββ decay mode. The programme is aimed at reaching the best limits on 0νββ for the isotope ⁸²Se.

The purpose of the MONUMENT experiment is to measure the muon capture by several daughter nuclei, the candidates for the 0νββ decay.

The Zr-BNO experiment is aimed at the search for the double beta decay of ⁹⁶Zr into exited states of ⁹⁶Mo and at the search for the beta decay of ⁹⁶Zr into ⁹⁶Nb.

The TGV spectrometer will be used for further investigations of the ECEC decay of ¹⁰⁶Cd and ¹³⁰Ba. According to estimations and theoretical predictions considering these rare processes, we hope to detect these decays in the direct experiment for the first time.

Expected results of the project this year:
The first results of the large-scale LEGEND experiment searching for the 0νββ decay are expected; R&D of hardware components of LEGEND-1000 are planned (detector holders, ASICs, detector immersion system, argon veto, etc.); the start of manufacture of new Ge-enriched detectors and their testing; the start of the assembly of the LEGEND-1000 facility at the host underground lab.

Taking of calibration data with the spectrometer SuperNEMO Demonstrator; taking of data on 0νββ and 2νββ decays in the ⁸²Se nucleus.

The MONUMENT activities will proceed; a series of new experiments at the PSI site will be prepared (including R&D at JINR – purchase of detectors and targets, calibrations and simulations) and performed; data taking and processing of accumulated data; it is intended to measure the muon capture with a solid ⁴⁸Ti target and gas targets of carbon enriched in atomic masses 12 and 13 (investigation of light nuclei in terms of validation of theoretical models applicable to double beta decay), as well as with enriched ⁹⁶Mo; R&D on application of muon capture in other physics-related areas, such as radiobiology and mesonic chemistry.

The upgrade of the TGV spectrometer (both detectors and electronics); measurements of enriched ¹⁰⁶Cd with the TGV setup.

Zr-BNO: the results of measurements of the enriched sample of ⁹⁶Zr at the low-background facilities at JINR and BNO. 

Brief annotation and scientific rationale:
This project is part of the programme “Study of coherent elastic neutrino scattering off atoms, nuclei and electrons and measurements of electromagnetic neutrino characteristics with the intense antineutrino tritium source” (SATURNE project: SArov TritiUm neutRiNo Experiment) funded by the Federal Budget of RF and Rosatom. In this project, DLNP JINR is involved in developing low-temperature detection systems, namely in manufacturing prototype low-temperature helium and silicon detectors based on the ³Не/⁴Не dilution cryostat and also in studying different ways of generation and detection of elementary excitation pulses in superfluid helium.

Expected results of the activity upon completion:
Data on different ways of generation and detection of elementary excitation pulses in superfluid helium.

Expected results of the activity in the current year:
Development and commissioning of the cryogenic system based on the dry ³Не/⁴Не dilution cryostat.