Test measurements with a perfect crystal neutron interferometer

Two widely separated coherent neutron beams from dynamical diffraction in a perfect Si-crystal are used for neutron interferometric measurements. Al and Bi samples cause phase shifts within the individual beams which result in a marked intensity oscillation of the interfering beams behind theE-shaped interferometer crystal. With this interferometer interesting features of various physical quantities can be investigated in a new way, e.g. refracting index, scattering amplitudes, magnetic domain structures, density inhomogeneities, and coherence properties of the neutron beams.     

Basic to industrial research on neutron platform in Japan

The co-location of reactor- and accelerator-based neutron sources offers a great opportunity for complementary use of steady and pulsed neutron beams in a wide variety of neutron science and technology areas ranging from basic research to industrial applications. In Japan, such a balance of two kinds of neutron sources has a long tradition and now we are entering into a new era with the commissioning of the world’s most intense pulsed neutron beams at JSNS/J-PARC plus the existing JRR-3 reactor both co-located within 1 km of each other in Tokai. The joint operation of these neutron facilities in close proximity under a program called ‘neutron platform’, will allow neutron beam access not only to professional users, familiar with both pulsed and steady state techniques but also to first-time academics and industrial researchers to neutron scattering.      

Control of the parameters of a beam of thermal neutrons

The reflection of thermal neutron beams from a quartz single crystal was investigated in the Laue geometry under the external influences. The controllability of a neutron beam in space and time is analyzed and its parameters are estimated (relative maximum intensity, the angular and energy distribution of obtained beams etc.).     

On the Possibility of Observing the Effect of Anomalous Neutron Transmission in Predominantly Resonance Absorption by Perfect Crystals of InSb

Dynamic neutron diffraction on perfect InSb crystals is analyzed theoretically both under conditions of predominantly potential scattering and under conditions of predominantly resonant scattering. Attention is given primarily to the effect of anomalous neutron transmission. A project of an experiment aimed at studying this effect in predominantly resonant neutron scattering via a simultaneous detection of reflected and transmitted beams and secondary gamma rays is proposed. It is shown that such an experiment may be performed in beams from high-flow reactors.

     

Neutrons against cancer

The review is devoted to the analysis and generalization of the research carried out during recent years in industrially advanced countries on the use of fast, epithermal, and thermal neutrons for therapy of malignant tumors. Basic facilities for neutron production used for cancer treatment are presented. Optimal parameters of therapeutic beams are described. Techniques using neutrons of different energy regions are discussed. Results and medical treatment efficiency are given. Comparison of the current state of neutron therapy of tumors and alternative treatments with beams of protons and carbon ions has been conducted. Main attention is given to the possibility of the practical use of accumulated experience of application of neutron beams for cancer therapy.     

基于加速器的多终端硼中子俘获治疗装置的束流整形组件设计

硼中子俘获治疗(Boron Neutron Capture Therapy,BNCT)是一种新型的精准放射治疗方法,束流整形组件(Beam Shaping Assembly,BSA)作为硼中子俘获治疗装置的重要组成部分,对于产生适用于BNCT的中子束至关重要.通过BSA可以将快中子慢化到适当的能量范围,并且减少其他不需...     

Nested neutron microfocusing optics on SNAP

The high source intensity of the Spallation Neutron Source (SNS), together with efficient detectors and large detector solid angles, now makes possible neutron experiments with much smaller sample volumes than previously were practical. Nested Kirkpatrick–Baez supermirror optics provide a promising and efficient way to further decrease the useable neutron sample size by focusing polychromatic neutrons into microbeams. Because the optics are nondispersive, they are ideal for spallation sources and for polychromatic and wide bandpass experiments on reactor sources. Theoretical calculations indicate that nested mirrors can preserve source brilliance at the sample for small beams and for modest divergences that are appropriate for diffraction experiments. Although the flux intercepted by a sample can be similar with standard beam-guided approaches, the signal-to-background is much improved with small beams on small samples. Here we describe the design, calibration and performance of a nested neutron mirror pair for the Spallation Neutrons At Pressure (SNAP) beamline at the SNS. High-pressure neutron diffraction is but one example of a large class of neutron experiments that will benefit from spatially-resolved microdiffraction.     

Generation of neutrons at the relaxation of fast deuterons in deuterium matter

We analyze the fusion process involving two deuterium nuclei in the case of deceleration of a fast deuteron with an energy of approximately 100 keV located in a deuterium target. We calculate the probability ω _fus(ε) of generating a neutron by a fast deuteron with an initial kinetic energy ε during its deceleration. The mean free path of fast deuterons with respect to their relaxation is found for various deuterium targets. The data are analyzed for neutron generation in deuterium cluster beams under laser irradiation. The method of neutron generation in the collision of two deuterium cluster beams is suggested. The text was submitted by the author in English.     

Hypernuclear Spectroscopy with Stable Heavy Ion Beams and Rare-isotope Beams:HypHI Project at GSI and FAIR

The international HypHI collaboration proposes to perform hypernuclear spectroscopy with stable heavy ion beams and rare isotope beams at GSI and FAIR in order to study neutron and proton rich hypernuclei and to measure directly hypernuclear magnetic moments for the first time.The project is divided into four phases.In the first Phase 0 experiment,the feasibility of precise hypernuclear spectroscopy with heavy ion beams will be demonstrated by observing π~- decay channels of ~e_ΛH,~4_ΛH and ~5_ΛHe with ~6Li projectiles at 2 AGeV impinging on a ~(12)C target.In the later Phases 1 through 3,studies of proton and neutron rich hypernuclei,direct measurements of hypernuclear magnetic moments and the spectroscopy of hypernuclei toward the nucleon drip-lines are planned.     

放射性束装置给核结构研究带来的新机遇

利用放射性束装置所提供的高强度和高分辨率的短寿命核束流可达到核中质比的极端值 ,新的现象 ,如中子晕、质子晕、中子皮、质子皮、壳的减弱或消失 ,以及在滴线附近对力的重要性和核物质中质子 -中子对的新超导相的可能存在等不断涌现 .对这些现象进行研究和理解 ,然后回到实验上较易达到的稳定区核去检验人们的理解 ,会对进一步研究核结构、核合成、核天文和自然界基本对称性提供新的机遇 .By making use of the facility for radioactive beams which would be able to supply intense high resolution beams of short lived (radioactive) nuclei, the neutron proton ratio can be extended to extreme values, where some new phenomena such as neutron halo, proton halo, neutron skin, proton skin, growing evidence of the fragility or disappearance of shell structure far from stability, the importance of pairing correlation near drip line, and the possible existence of new superconducting phases of...     

Bonse-Hart angular profiles realized for multiply Bragg reflected neutrons

We have produced a monochromatic neutron beam with the sharpest angular profile to date. Multiple Bragg reflections from optimally designed channel-cut silicon single crystals have produced neutron beams with theoretical Darwin angular profiles. This experiment constitutes the first realization of the proposal made by Bonse and Hart 35 years ago and opens up avenues for ultrasmall angle neutron scattering studies down to wave vector transfers of 10(-5) A(-1).     

In the wonderland of ultra-parallel neutron beams

Bragg reflections from single crystals yield angular widths of a few arcsec for thermal neutron beams. The Bonse-Hart proposal to attain a sharp, nearly rectangular profile by Bragg reflecting neutrons multiply from a channel-cut single crystal, was realized in its totality three and a half decades later by achieving the corresponding Darwin reflection curves for 5.23 Å neutrons. This facilitated SUSANS (Super USANS) measurements in the Q ～ 10^?5 Å^?1 range. The polarized neutron option was introduced into the SUSANS set-up by separating the up- and down-spin neutron beams by ～10 arcsec with a magnetic (air) prism. The neutron angular width has recently been reduced further by an order of magnitude to ～0.6 arcsec by diffracting 5.3 Å neutrons from a judiciously optimized Bragg prism. This constitutes the most parallel monochromatic neutron beam produced to date. I present the first SUSANS spectra probing the Q ～ 10^?6 Å^?1 domain, recorded with this beam.     

Acquired polarization ink·I PNC experiments

Parity non-conserving neutron transmission asymmetries have been calculated for unpolarized beams on polarized targets. As the neutron beam propagates through a polarized target, some components are preferentially absorbed. This acquired polarization complicates the interpretation of transmission measurements. We extend the analysis of Postma et al. to include parity mixing in the neutron resonances and emphasize the importance of the nuclear resonance spectroscopy. The relative importance of the acquired polarization contribution is determined by the spectroscopic parameters.     

Use of rotating ion-collectors for the preparation of isotopically pure targets

The rotating ion collectors of E.M. isotope separators offer interesting possibilities to produce thin. very extended and uniform mono-isotopic layers deposited on thin A1 backings. Such targets are needed for high resolution electron spectroscopy studies following neutron eapture reactions induced by high flux neutron beams.     

The neutron interferometer as a macroscopic quantum device

Neutron interferometry is a unique tool for investigations in the field of particle-wave dualism because massive elementary particles behave like waves within the interferometer. The invention of perfect crystal neutron interferometers providing widely separated coherent beams stimulated a great variety of experiments with matter waves in the field of basic quantum mechanics. The phase of the spatial and spinor wave function become a measurable quantity and can be influenced individually. High degrees of coherence and high order interferences have been observed by this technique. The 4π-symmetry of a spinor wave function and the mutual modulation of nuclear and magnetic phase shifts have been measured in the past. Recent experiments dealt with polarized neutron beams, which are handled to realize the spin-superposition of two oppositionally polarized subbeams resulting in a final polarization perpendicular to both initial beam polarizations. The different actions on the coherent beams of static (DC) and dynamic (HF) flippers have been visualized.     

Magnetic layered structure for the production of polarized neutron microbeams

A neutron waveguide is a three-layer structure in which a guiding layer with low optical potential is placed between two cladding layers with high optical potential. Under proper operation conditions, the neutron density is resonantly enhanced inside the guiding layer. In our experimental scheme, the neutron beam enters through the surface of the top layer at glancing angle and goes out from the edge of the guiding layer, with an angular distribution corresponding to Fraunhofer diffraction from a narrow slit. The incident neutron beam is relatively wide (0.1 mm) and highly collimated (0.01°). The outgoing sub-micron beam is extremely narrow at the outlet (0.1 μm) and more divergent (0.1°). So far only the production of unpolarized sub-micron neutron beams has been reported. Here we present first experiments on polarized sub-micron neutron beams. For these studies a polarized incident beam was used and two types of magnetic waveguides were investigated: a polarizing magnetic waveguide Fe(20 nm)/Cu(140 nm)/Fe(50 nm)//glass and a non-polarizing magnetic waveguide Py(10 nm)/Al(140 nm)/Py(50 nm)//glass (Py is permalloy). The waveguide samples were characterized by polarized neutron reflectometry.     

Investigation of neutron emission in the interaction of relativistic protons and deuterons with lead targets

Measurements of neutron double-differential cross sections and yields in time-of-flight experiments with various lead targets and beams of protons and deuterons with an energy of about 2 GeV are discussed. Space and energy distribution of neutrons in an extended lead target is studied by threshold detectors in the proton energy range of 1–3.7 GeV. The average multiplicity of neutrons, neutron energy, and neutron multiplication in lead as functions of target dimension, type, and energy of the beam particle are analyzed.     

Stationary setup for identifying explosives using the tagged neutron method

The results of using a stationary setup for detecting and identifying explosives using the tagged neutron method (or associated particle imaging (API) method) have been presented. The source of 14.1-MeV tagged neutron beams is an ING-27 portable neutron generator made by VNIIA (Moscow). It contains an embedded 64-pixel silicon α detector with double-sided strip readout developed by the Joint Institute for Nuclear Research (JINR). The setup was tested for the identification of more than 30 explosives.