Non-Accelerator Neutrino Physics and Astrophysics

Participating countries and international organizations:

Belgium, Czech Republic, France, Germany, Italy, Japan, Russia, Slovakia, Switzerland, United Kingdom, USA.

The problem under study and the main purpose of the research:

Search for and investigation of double-neutrino and neutrinoless modes of double beta decay, clarification of the neutrino nature, Majorana or Dirac, and absolute neutrino mass scale and hierarchies. Search for the neutrino magnetic moment and Dark Matter. Use of the neutrino detector for a distant investigation of processes inside the reactor core of the Kalinin Nuclear Power Plant. Search for the signal produced by coherent reactor neutrino scattering. Precision study of the coherent scattering spectrum to search for manifestations of New Physics.  Search for sterile neutrinos. Spectroscopy of nuclei far from stability. Development of new methods for charged and neutral particle detection. Development of methods for the preparation and purification of radionuclide production for the synthesis of radiopharmaceuticals. Application of hyperfine interaction methods to study radiopharmaceuticals and their precursors. Development and application of methods and techniques for the preparation and analysis of low-background materials with ultra low content of radioactive impurities.

Brief annotation and scientific rationale:

The project is aimed at the development of nuclear spectroscopy and radiochemistry methods, including for purposes of astrophysics and neutrino physics.  It involves new particle detection techniques, calibration, background description, uniquely pure materials, etc., and also nuclear medicine isues such as production and purification of radioisotopes, development and synthesis of radiopharmrceuticals, study of influence mechanisms on substance at radionuclides decay locations, etc.

Specific areas are:

1. Novel detectors (semiconductor detectors, liquid and plastic organic scintillators, composite scintillation detection systems, neutron and radon detectors, etc.).

2. “Post-decay” spectroscopy of electrons and other emissions with an emphasis on extremely low energies.

3. Traditional gamma-spectroscopy based on semiconductor detectors (SPDs) with an emphasis on the determination precision for the emission energy and activity of the sources (pointlike and volumetric) to study decay modes and determine cross sections of nuclear reactions.

4. Application of hyperfine interaction (HFI) methods using radioactive tracers, namely the method of perturbed angular correlation (PAC) and the emission mode of Mössbauer spectroscopy for the study of radiopharmaceuticals and their precursors in water-containing systems and other matrices.

5. Development of production and purification methods of radionuclide preparations for the radiopharmaceuticals synthesis, including development of generator routes for their production, physicochemical methods for evaluating properties of radionuclides and radiopharmaceuticals (their precursors) in homogeneous and heterogeneous systems.

6. Development and application of 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) and other analytical and nuclear spectroscopic methods.

Utilization of nuclear spectroscopy and radiochemistry methods in studying neutrino properties, searching for dark matter particles, and researching rare and other physical processes have firmly and deservedly proved effective in numerous experiments on these topics of fundamental physics. Almost the same can be said about their role in nuclear medicine. Thus, the relevance of this topic is undeniable. A key to the scientific novelty of the project is a focus on development the techniques and methods that allow expanding the horizon of the declared target experiments.

Expected results upon completion of the project:

1. New detectors:

– development and application of detectors based on silicon carbide (SiC) for nuclear radiation registration. SiC detectors that have high radiation resistance (10 times higher than silicon) and operability at high temperatures > 400°C are planned to be used for monitoring operation of high-current accelerators and nuclear reactors and for hot plasma diagnostics;

– development and investigation of liquid tellurium-containing scintillators for the search for double neutrinoless β-decay, as well as other types of liquid and plastic scintillators;

– development of composite scintillation registration systems for neutrino experiments;

– development and application of ³He counters for detecting low neutron fluxes (below of 10^-6 n×cm^-2×s), development of a compact sensitive radon detector, development of technology for production of low-radioactive parts using 3D printing.

2.  Experimental study of low-energy electron spectra (0 -50 keV) on the ESA-50 spectrometer and gamma and X-ray radiation spectra on the SCD during radioactive decay to obtain new data on low-excited states of nuclei and post-decay relaxation of atomic systems, search for ways to perform spectrometry of post-decay photons (from the edge of infrared radiation to soft
X-rays) in the energy range 1-200 eV.

3. Development of technique for modelling codes application (Geant4, MCNP and FLUKA) of the HPGe spectrometer characteristics at the LINAC-200 electron accelerator to determine the yields of photonuclear reactions and at other JINR basic facilities, investigation of  decay modes study of a wide range of radionuclides and their content in samples (⁹⁶Zr, ⁴⁰K, ¹³⁸La, etc.) to study rare processes.

4.  Improvement of the methods of perturbed angular correlations (PAC) and Mössbauer spectroscopy (emission mode) using radioactive tracers ¹¹¹In, ¹⁵²Eu, ¹⁵⁴Eu, ¹¹⁹Sb, ^119mSn, ⁵⁷Co, ¹⁶¹Tb, etc., to study of radiopharmaceuticals and their precursors (components) in aqueous systems and other matrices and development of physicochemical methods for evaluation of properties of radionuclides and radiopharmaceuticals in homogeneous and heterogeneous systems.

5. Radiochemistry and nuclear medicine: the study of sorption processes for various solution-sorbent systems as a chemical basis of the purification methods (for low-background materials as well) and preparation of radionuclide generators for production of radiopharmaceuticals;

– development of the method for production of radionuclides and their isolation (including mass separation) from targets irradiated with protons, neutrons and gamma quanta for production of radiopharmaceuticals (¹⁰³Pd, ¹¹⁹Sb, ¹⁶¹Tb, some alpha emitters, etc.);

– development of a wide range of radionuclide generators

(⁴⁴Ti → ⁴⁴Sc, ⁶⁸Ge → ⁶⁸Ga, ⁹⁰Sr→ ⁹⁰Y, ²³⁸U→ ²³⁴Th, ²³⁷Np → ²³³Pa, ²²⁹Th → ²²⁵Ac, ²²⁷Ac→ ²²⁷Th → ²²³Ra, ²⁰²Pb → ²⁰²Tl,
¹⁹⁴Hg → ¹⁹⁴Au, ³²Si → ³²P, etc.) will be continued based on reverse-tandem methods to expand the possibilities of production of medical radionuclides. The possibility of producing 1-2 generators of significant activity for external users will be considered;

– development of radiolabeling methods based on chelators with “slow” kinetics for synthesis of radiopharmaceuticals, study of radium chelation.

6. Development and implementation of sample production methodes (⁸²Se, ⁹⁶Zr, shielding materials, solder, etc.) for astrophysical and neutrino problems at a new ultra-low level of impurity content (from mBq/kg to μmBq/kg of Th and U). The main approaches to solving the above problems are the use of reverse chromatography, low-boiling and other prepared or selected reagents, the use of selected and prepared reactor materials;

– development and implementation of sample analysis methods at an ultra-low sensitivity level (from mBq/kg to μmBq/kg
of Th and U) using ICP-MS, neutron activation analysis (NAA) and other methods, development of methods for precise determination of the chemical and isotopic composition of materials used in astrophysical and neutrino experiments.

Expected results of the project tin the current year:

1.  New detectors:

– results of tests of new SiC detectors for nuclear radiation detection;

– parameters of new liquid tellurium-loaded scintillators developed and created at JINR;

 – R&D results for composite scintillation detection systems for next-generation neutrino experiments; Development of a prototype of a satellite detector for large reactor experiments;

– a new ³He-counter with low internal background, results of the test measurements in Dubna and an underground laboratory;

– technology for production of low-radioactive parts using 3D printing.

2. Establishing ways to perform spectrometry of post-decay photons (from the edge of infrared radiation to soft X rays) in the energy range 1-200 eV.

3. Determination of photonuclear reaction yields, results of precise study of decay modes for a wide range of radionuclides, and their content in samples (⁹⁶Zr, ⁴⁰K, ¹³⁸La, etc.) to study rare processes.

4. Upgrade of perturbed angular correlation spectrometers and commissioning of new setups for Mössbauer spectroscopy (emission mode) using radioactive tracers ¹¹¹In, ¹⁵²Eu, ¹⁵⁴Eu, ¹¹⁹Sb, ^119mSn, ⁵⁷Co, ¹⁶¹Tb.

5. Radiochemistry and nuclear medicine: results of studying sorption processes for various solution-sorbent systems.

6. Development and implementation of methods for obtaining samples (⁹⁶Zr) for astrophysical and neutrino problems at a new ultra-low impurity level;

– begining of implementation of the method for sample analysis at an ultra-low sensitivity level (from mBq/kg to μmBq/kg of Th and U) using ICP-MS.

Brief annotation and scientific rationale:

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

DANSS is an antineutrino spectrometer based on plastic scintillators with a sensitive volume of 1 m³, located at the fourth power unit of the Kalinin NPP. The lifting mechanism makes it possible to move the spectrometer 2 m vertically in the on-line mode, providing a measurement range of 11–13 m from the reactor. The 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 Kalinin nuclear power plant reactor core. 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 searching for rare events is achieved. Registration of the searched events allows the search for New Physics beyond the Standard Model, in addition it can also have a practical usage, for example, in the development of
new-generation detectors for monitoring the operation of a nuclear reactor using the antineutrino flux.

The RICOCHET is a new generation of reactor neutrinos experiments. The RICOCHET detectors are designed to provide the one percent precision measurement of Coherent Elastic Neutrino(n)-Nucleus Scattering (CEνNS) in the sub-100 eV energy region
(i.e. under total coherency condition) to search for New Physics in the electroweak sector. It is planned to be installed until the end of 2023 at the Laue Langevin Institute (ILL) near the research nuclear reactor. The RICOCHET will host two cryogenic detector arrays: the CRYOCUBE (Ge target, based on EDELWEISS developed detector-bolometers) and the Q-ARRAY
(Zn target).

Expected results upon completion of the project:

The main goals of the DANSS experiment are to test with reactor antineutrinos the hypothesis of oscillations into a sterile state and to monitor nuclear reactor operation by measuring the antineutrino flux. 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 increase detection volume, thus the sensitivity to sterile neutrinos will be significantly higher.  The search for oscillations into the light (Δm₁₄² ~ 0.1-10 eV) sterile neutrino is one of the current trends in fundamental neutrino physics. The existence of a sterile neutrino could explain several observed contradictory results, first of all, the reactor and gallium (anti)neutrino anomalies, and at the same time become a revolutionary discovery of New Physics. Reactor experiments on 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 oscillation pattern is not yet smeared. It should be noted that the DANSS spectrometer is the leading one for experiments of this type.

As a result of the project, it is expected to detect for the first time the coherent antineutrino scattering from the reactor and to improve the sensitivity of the neutrino magnetic moment detection to (5-9)×10^-12 m_B after several years of measurements, which will greatly improve the current best limit.

In the RICOCHET experiment the statistical significance of CEνNS detection, after only one reactor cycle, should be between
4.6 and 13.6 σ, depending on the effectiveness of the muon veto. After about 10 reactor cycles, i.e. 3-5 years onsite, the targeted ~1% precision measurement (not including signal systematics) will be obtained, which will lead to orders of magnitude improved sensitivities to various New Physics scenarios compared to the existing experiments. 

Expected results of the project in the current year:

DANSS: Data taking with the current DANSS setup, data analysis. New improved results of oscillation analysis. R&D for DANSS-2. Production, assembly at KNPP and commissioning of DANSS-2.

νGeN: Data taking in the current configuration of the setup. Simultaneous R&D for its upgrade, which will include a new internal veto, upgrade of the lifting platform, and reconfiguration of the muon veto system. New results for the neutrino magnetic moment and coherent scattering.

Ricochet: commission at ILL. Start of the data taking with germanium bolometers. R&D for new detectors. Improved MC model based on 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 EDELWEISS (Expérience pour DEtecter Les WIMPs En Site Souterrain). The first four experiments solve the problems of searching and studying neutrinoless double beta decay. The EDELWEISS experiment aims to search for Dark Matter particles.

Expected results upon completion of the project:

The LEGEND experiment is designed to search for neutrinoless double beta (0νββ) decay of ⁷⁶Ge. In the experiment, germanium detectors fabricated from isotopically enriched material will operate inside a cryogenic fluid shield (liquid argon). The experiment will probe the 0νββ decay of ⁷⁶Ge with a sensitivity of > 10²⁸ years at the 90% confidence level.

The physics programme of the SuperNEMO Demonstrator Module consists of precision measurements of the 2νββ decay mode to constrain nuclear and BSM physics, as well as the best limits on 0νββ, for the isotope ⁸²Se.

The purpose of the MONUMENT is to carrying out experimental measurements of muon capture at several daughter candidates for 0νββ decay nuclei.

The unlimited goal of current R&D and measurements in the EDELWEISS experiment is achievement of sensitivity allowing detection of B-8 solar neutrinos through coherent elastic neutrino-nucleus scattering. The project is in the transformation phase, when the old setup used from 2005 start to be decommissioned with the aim to have a lower-level background setup with a
new-generation cryosystem which will allow timely fulfillmen of the intensive R&D program and Dark Matter search in the regions inaccessible by Ar/Xe experiments.

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

Expected results of the project in the current year:

Adding of newly produced detectors to LEGEND-200 to reach the final ⁷⁶Ge mass of 200 kg. Restart data taking. R&D for LEGEND-1000 hardware components (detector holders, ASICs, lock system, LAr instrumentation, etc.). Start production and acceptance of the new enriched Ge detectors and installation of the LEGEND-1000 facility at the host lab.

Calibration data taking with the SuperNEMO Demonstrator. First data for 0νββ - and 2νββ - ⁸²Se. Completion of the data taking with the SuperNEMO Demonstrator in a configuration without passive protection. Installation of passive shielding of the detector (borated paraffin + borated water + low background iron) and installation of the anti-radon tent.

The MONUMENT programme will include preparation of new experiments at the PSI site. The appropriate R&D at Dubna concerns detectors, targets, calibrations and MC. Measurements of muon capture with titanium 48 and with gas targets of carbon enriched in atomic masses 12 and 13 at PSI; investigation of light nuclei in terms of validation of theoretical models applicable to double beta decay as well as enriched ⁹⁶Mo; data analysis. R&D on application of muon capture in other areas related to physics, such as radiobiology and mesochemistry.

The current EDELWEISS setup will be completely decommissioned at the LSM site. Commissioning of the BINGO setup and integration of new EDELWEISS detectors into the setup as continuation of the synergy between EDELWEISS and CupidMo collaborations. R&D to search for the nature of the heat only events in the bolometers. Simultaneous search for light Dark Matter candidates.

Upgrade of the TGV spectrometer (both detectors and electronics). Measurement of enriched ¹⁰⁶Cd.

 Collaboration