V.R. Skoy

Investigations of parity violation and interference effects in 235U fission induced by resonance neutrons

Abstract These investigations were performed to test the modern theory and to obtain first estimates of nuclear matrix elements of weak interaction and the main parameters of p -resonances. Combined investigations of the space parity non-conservation effect of 235 U fission fragment emission and the interference effects of the forward-backward and left-right asymmetries were carried out over the range of neutron energies from 0.02 eV to 90 eV. The experimental results are found to be in good agreement with the theory. The first estimates of the nuclear matrix element of the weak interaction for three p -resonances and the main parameters of some low energy p -wave resonances are obtained from a combined theoretical description of all experimental data.

Angular distribution of 4.43-MeV γ-rays produced in inelastic scattering of 14.1-MeV neutrons by 12C nuclei

The work is devoted to measuring the angular distribution of 4.43-MeV γ-rays produced in inelastic scattering of 14.1-MeV neutrons by 12C nuclei. A portable ING-27 neutron generator (designed and fabricated at VNIIA, Moscow) with a built-in 64-pixel silicon α-detector was used as a source of tagged neutrons. The γ-rays of characteristic nuclear radiation from 12C were detected with a spectrometric system that consisted of 22 γ-detectors based on NaI(Tl) crystals arranged around the carbon target. The measured angular distribution of 4.43-MeV γ-rays is analyzed and compared with the results of other published experimental works.

Multilayer passive shielding of scintillation detectors based on BGO, NaI(Tl), and stilbene crystals operating in intense neutron fields with an energy of 14.1 MeV

We discuss the issues related to choosing the optimum type of passive shielding of scintillation detectors based on BGO, NaI(Tl), and stilbene crystals from the direct penetration of neutron radiation with an energy of 14.1 MeV that was emitted isotropically into a solid angle of 4π. A series of experimental measurements of the count-rate suppression factor that may be obtained for the indicated detectors through the use of various shielding filters comprising iron, lead, and borated polyethylene layers with a total thickness not exceeding 50 cm are conducted.

Measurements of epithermal neutron depolarization using a polarized rare earth target

Abstract We described a facility for the production and analysis of the polarization of epithermal neutrons and show its application to the measurement of neutron depolarization in magnetic materials. The polarization of the neutrons is analyzed using the spin dependent transmission of neutrons at energies of compound nuclear resonances in a polarized rare earth target. The technique is applicable to the characterization of magnetic domains in thick samples or materials having large internal magnetizations. We illustrate the use of the technique in measuring the orientational dependence of depolarization in a single crystal of ferromagnetic holmium.

On the KaTRIn project for an experimental study of time-reversal violating effect in polarized neutron propagation through a polarized target

Abstract KaTRIn is the project aimed at building an experimental setup for checking the time-reversal invariance in polarized neutron propagation through a polarized target. A measurement method proposed recently consists in 180° rotation of the neutron polarizer around the target. The method requires only one neutron polarizing device and excludes a number of false effects. The 3He-based neutron polarizer has great advantages for this task. We describe the design of the Rb3He polarizer prototype. The standard NMR technique is used to measure the obtained 3He polarization. The idea of pulse polarized target is discussed.

Neutron spin filter based on optically polarized in a near-zero magnetic field

Abstract A test of polarization of 3 He nuclei via spin-exchange collisions with optically pumped rubidium atoms in an extremely low applied magnetic field was carried out. Permalloy magnetic shields were used to prevent a fast relaxation of 3 He polarization owing to the inhomogeneity of a surrounding magnetic field. The whole installation was placed at the neutron beam line of the IBR-30 facility, and used as a neutron spin filter. Thus, a prototype of new design of neutron polarizer was introduced. We intend to apply this experience for the full-scale KaTRIn facility to test the time reversal violation in neutron-nuclear reactions.

Determination of Moisture Content in Coke with 239 Pu–Be Neutron Source and BGO Scintillation Gamma Detector

A series of experiments has been conducted at the Frank Laboratory of Neutron Physics (FLNP) of the Joint Institute for Nuclear Research (JINR) in order to study the possibility of determining the moisture content of coke using a standard neutron source. The proposed method is based on a measurement of the spectrum of prompt γ rays emitted when samples are irradiated by fast and/or thermal neutrons. The moisture content is determined from the area of the peaks of characteristic γ rays produced in the radiative capture of thermal neutrons by the proton (Eγ = 2.223 MeV) and inelastic scattering of fast neutrons by 16O (Eγ = 6.109 MeV). The 239Pu–Be neutron source (〈E n 〉 ~ 4.5 MeV) with an intensity of ~5 × 106 n/s was used to irradiate the samples under study. A scintillation detector based on a BGO crystal was used to register the characteristic γ radiation from the inelastic fast neutron scattering and slow (thermal) neutron capture. This paper presents the results of humidity measurement in the range of 2–50% [1, 2].

Polarized epithermal neutron studies of magnetic domains

The average size and shape of magnetic domains in a material can be determined from the precession of polarized neutrons traversing the material. Epithermal neutrons (0.5 eV<En<100 eV), which precess more slowly than thermals, effectively probe the internal structure of samples that are thick or have large domains or large internal fields. Such epithermal neutron measurements require a neutron polarizer and analyzer based on cryogenically polarized spin filters. We discuss the measurement at JINR, Dubna, of magnetic domains in a 2.0 cm. diam. crystal of holmium using 1.7 to 59 eV neutrons polarized by a dynamically polarized proton target and analyzed with a statically polarized dysprosium target.

Energy and orientation dependence of neutron depolarization in a large single crystal of ferromagnetic holmium

We report measurements of the depolarization of epithermal neutrons (1.7–59 eV) in magnetic domains of a 2.0-cm-diam cylindrical single crystal of ferromagnetic holmium. The neutrons were polarized by a dynamically polarized proton target and polarization analyzed using a statically polarized rare-earth spin filter. Based on the dependence of the depolarization on neutron energy and crystal orientation, we determined the domains to be laminar, or needlelike, with the long axis slightly deflected from the c crystalline axis and having an average width of 59 μm.

P‐Even Effects in a Direct γ Transition Following Neutron Capture in 113Cd Around Ep=7 eV Resonance

The polarization left‐right asymmetry and angular fore‐aft asymmetry of γ yields were investigated for the direct transition Eγ=9.04 MeV in 114Cd near the p‐wave resonance Ep=7 eV. The experiments were performed at the pulsed reactor IBR‐30 using an LMN‐polarizer of neutrons and NaJ (T1)‐detectors.