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Details of the background, that is, “unwanted signals accumulated by the data acquisition system of neutron instruments,” observed by the cold-neutron chopper spectrometer AMATERAS installed at the Materials and Life Science Experimental Facility at J-PARC are reported. In the design phase of AMATERAS, we carefully considered the achievement of high signal-to-noise ratio, and possible countermeasures were implemented. Actually, recent scientific outputs from AMATERAS indicates that the spectrometer is one of excellent neutron instruments with low background. In spite of that, in nine years of AMATERAS operation, we have encountered unwanted signals due to various reasons, including γ rays emitted at materials on or near the beam line including the sample itself, scattered neutrons from the beam line devices, air scattering, electronic noise in data acquisition system, cosmic rays, T0 burst, and other unknown sources. In this report, we discuss the background observed by AMATERAS, especially in the conditions of without samples, comprehensively. The possible sources of these signals and the countermeasures considered against the above sources are discussed, which may be helpful to those who are engaged in other existing or planned neutron-scattering instruments.

Seven time-of-flight quasielastic/inelastic neutron scattering instruments are installed on six beamlines in the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC). Four of these instruments are chopper-type direct-geometry spectrometers, one is a near-backscattering indirect-geometry spectrometer, and the other two are spin-echo-type spectrometers. This paper reviews the characteristic features, recent scientific outcomes, and progress in development of MLF spectrometers.

Magnets are important for studying magnetism and are commonly used as sample environment devices of neutron scattering instruments. However, the use of magnets was prevented at the time-of-flight direct-geometry neutron spectrometer 4SEASONS in Materials and Life Science Experimental Facility (MLF) at J-PARC, because the instrument is surrounded by iron components, and it is equipped with a piece of equipment operated with magnetic bearings. In the present work, we investigate the influence of stray magnetic fields from a superconducting magnet which is shared among neutron scattering instruments in MLF. Based on the investigation, we modified 4SEASONS such that it can be used with the magnet. Finally, we successfully performed the first inelastic neutron scattering experiments with applied magnetic fields using this sample environment.

We have conducted inelastic neutron scattering measurements to investigate the crystal-electric-field (CEF) levels associated with Pr3+ 4 f 2 -electron configuration in the PrTr2X20 (Tr: transition metal, X: Al and Zn). Hybridization between conduction electrons and 4 f electrons has been deduced from the spectral widths, which is a key factor for understanding the anomalous low-temperature transport properties and the ordering phase transitions in the PrTr2X20. We also discuss structural-transition effects on local symmetries of the Pr-ion sites.

J-PARC, Japan Proton Accelerator Research Complex provides short pulse proton beam at a repetition rate 25Hz and the maximum power is expected to be 1MW. Materials and Life Science Experimental Facility (MLF) has 23 neutron beam ports and 21 instruments have already been operated or under construction/commissioning. There are 6 inelastic/quasi-elastic neutron scattering spectrometers and the complementary use of these spectrometers will open new insight for life science.This article is part of a Special Issue entitled “Science for Life” Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo.

Hydration water is essential for a protein to perform its biological function properly. In this study, the dynamics of hydration water around F-actin and myosin subfragment-1 (S1), which are the partner proteins playing a major role in various cellular functions related to cell motility including muscle contraction, was characterized by incoherent quasielastic neutron scattering (QENS). The QENS measurements on the D2O- and H2O-solution samples of F-actin and S1 provided the spectra of hydration water, from which the translational diffusion coefficient (DT), the residence time (τT), and the rotational correlation time (τR) were evaluated. The DT value of the hydration water of S1 was found to be much smaller than that of the hydration water of F-actin while the τT values were similar between S1 and F-actin. On the other hand, the τR values of the hydration water of S1 was found to be larger than that of the hydration water of F-actin. It was also found that the DT and τR values of the hydration water of F-actin are similar to those of bulk water. These results suggest a significant difference in mobility of the hydration water between S1 and F-actin: S1 has the typical hydration water, the mobility of which is reduced compared with that of bulk water, while F-actin has the unique hydration water, the mobility of which is close to that of bulk water rather than the typical hydration water around proteins., Highlights • Hydration water dynamics of F-actin and myosin S1 was studied by neutron scattering. • Both translational and rotational motions are higher for F-actin hydration water. • Mobility of F-actin hydration water is close to that of bulk water. • High mobility of F-actin hydration water would promote the actomyosin interaction.

In ErNi 2 B 2 C a microscopic and stable coexistence of ferromagnetism and superconductivity has been confirmed. In order to explore a possibility of the spontaneous vortex state, we performed small angle neutron scattering experiments. The results show that, in a field cooled process, an effective field evaluated by the vortex distance (scattering pattern) shows a clear increase as the system enters the weak ferromagnetic phase. This provides a direct evidence that an internal magnetic field mediated by the weak ferromagnetic order creates new vortices and affects the flux line lattice structure.

Inelastic neutron scattering experiments were performed on single crystals of NaxCoO2 ( x ∼ 0.3 ) . The results reveal that an inelastic scattering signal appears at Δ E ∼ 5.5 meV and q ∼ (0 1 0) in the orthorhombic notation. Intensity of the signal decreases with increasing temperature, and disappears above 100 K. The origin of this signal is of magnetic. However, we also found the signal is absent in samples from a different batch at the same T and Q conditions. This indicates that the signal is very sensitive to condition in sample preparation. It might be attributed to Na ion ordering (disordering).