The characteristics of neutron scintillation detectors built on monolithic and heterogeneous scintillators containing 6Li were studied. The detectors were tested on a thermal neutron beam and on a stand with a source of γ-quanta 60Co. To process the signals received from the detector with a monolithic scintillator, three different γ-radiation discrimination algorithms were used: registration of pulses at a constant threshold and selection according to the pulse shape using two digital signal separation methods: charge integration and pulse duration measurement. For a homogeneous scintillator, pulse shape selection methods work approximately the same when separating thermal neutrons and γ-quanta and are significantly inferior to the method of registration at a constant threshold. In this case, the quality of the n/γ separation is worse than the result obtained with a heterogeneous scintillator when recording at a constant threshold. The purpose of the work is to compare the results of using digital methods for discrimination of gamma-quanta with the results obtained using heterogeneous scintillators.

Samples of composite scintillators consisting of NE 912 lithium glass fragments located in an organic matrix have been developed and manufactured. Samples were made in sizes of ∅40 × 2 mm with 25, 30, and 35% lithium glass concentration. Epoxy and acrylic resins, as well as a silicone compound, were used as a neutral matrix. Samples were tested as part of a scintillation detector on a thermal neutron beam and with source of γ-quanta 60 Co. The efficiency of thermal neutrons' registration and γ-sensitivity compared to a homogeneous glass scintillator was determined. The results obtained confirmed the possibility of reducing the sensitivity of the detector to γ-quanta by two orders of magnitude due to a slight (50%) decrease in the efficiency of neutron detection.

— A Monte Carlo model of the thermal-neutron scintillation detector based on NE 912 lithium glass has been created and verified. The simulation was validated by comparing its result to experimental data from a prototype detector exposed to thermal-neutron and γ-ray beams. The light yield in the scintillator for a captured thermal neutron, the quenching factor, and the decay times of the scintillator were determined. The accuracy in reproducing the pulse shapes obtained in the experiment is sufficient to allow analysis of experimental data and estimation of the efficiency of n /γ discrimination techniques. Based on the simulation, it is possible to develop detector models with a low γ-ray sensitivity using heterogeneous composite scintillators with various geometries.

The results of modeling and optimization of a composite scintillator for recording thermal neutrons are presented. The interaction of thermal neutrons and γ-quanta with composites consisting of fragments of a glass scintillator containing 6Li was observed. The aim of the research was to determine the structure of a composite with high sensitivity to thermal neutrons and to provide effective suppression of signals from γ‑quanta. During the simulation, the optimal structural parameters of the composite were determined, such as the size of the fragments and the concentration of glass. According to the presented simulation results, optimized composites under thermal neutron irradiation can provide a neutron detection efficiency of at least 50% with a sensitivity to γ-quanta at the level η < 10–6.

We performed a search for the decay $K_L^0 \rightarrow 3\gamma$ with the E391a detector at KEK. In the data accumulated in 2005, no event was observed in the signal region. Based on the assumption of $K_L^0 \rightarrow 3\gamma$ proceeding via parity-violation, we obtained the single event sensitivity to be $(3.23\pm0.14)\times10^{-8}$, and set an upper limit on the branching ratio to be $7.4\times10^{-8}$ at the 90% confidence level. This is a factor of 3.2 improvement compared to the previous results. The results of $K_L^0 \rightarrow 3\gamma$ proceeding via parity-conservation were also presented in this paper.

The rare decay K L 0 → π 0 ν ṽ branching ratio measurement is one of the clearest Standard Model test. Calculations based on the SM predict Br( K L 0 → π 0 ν ṽ ) ≈ 2.8 × 10 −11 , but the most accurate experimental value Br( K L 0 → π 0 ν ṽ ) < 6.7 × 10 −8 (90

The rare decay K L 0 → π0ν\(\tilde v\) branching ratio measurement is one of the clearest Standard Model test. Calculations based on the SM predict Br(K L 0 → π0ν\(\tilde v\)) ≈ 2.8 × 10−11, but the most accurate experimental value Br(K L 0 → π0ν\(\tilde v\)) < 6.7 × 10−8 (90% C.L.). We present design of a new experimental setup KLOD (U-70 accelerator, IHEP, Protvino) for K L 0 → π0ν\(\tilde v\) branching ratio measurement. Sensitivity of the KLOD experiment will be enough for registration of 2.4 events K L 0 → π0ν\(\tilde v\) for every 10 days of the data taking (according to SM predictions).

A 100-channel scintillation multichannel detector of thermal neutrons has been designed and manufactured for modernizing the D7a neutron diffractometer on the IVV-2M reactor. The detector is built in accordance with the modular approach and allows arrangement of sensitive surfaces of channels on a cylindrical surface of arbitrary radius. The sensitive volume of a channel is a multilayer composition of stripes of an ND scintillation screen and wavelength-shifting fibers. The dimensions of the entrance aperture of the channel’s sensitive volume are 3 × 120 mm. The average detection efficiency in channels for neutrons of wavelength λ = 1.53 Å is 70%. The gamma sensitivity of the detector channels is no higher than 1 × 10 −7 . The maximum counting rate of an individual channel is ≥ 1 × 10 5 neutrons/s. Each module of the detector is an independent device and contains ten channels for neutron detection, signal-processing electronics, a high-voltage supply system, and computer-interfacing electronics. A CAN interface is used to acquire data from the modules, set the registration parameters, and control the modules.

A frozen-spin- polarized deuteron target cooled by the 3He/4He dilution refrigerator is described. Fully deuterated 1,2-propanediol was used as a target material. Deuteron vector polarization about 40% was obtained for the target in the shape of a cylinder of 2-cm diameter and 6-cm length. The target is intended for a study of 3N interactions at the polarized neutron beam generated by the Van de Graaff accelerator at the Charles University in Prague.

New accurate data on the neutron-proton spin-dependent total cross section difference Δ σ L ( np ) at the neutron beam kinetic energies 1.4, 1.7, 1.9 and 2.0 GeV are presented. A number of physical and methodical results on investigation of an elastic np→pn charge exchange process over a few GeV region are also presented. Measurements were carried out at the Synchrophasotron and Nuclotron of the Veksler and Baldin Laboratory of High Energies of the Joint Institute for Nuclear Research.