Katsuya Hirota

Development of a neutron detector based on a position-sensitive photomultiplier

A neutron scintillation detector based on a position-sensitive photomultiplier has been developed for neutron spin echo and small angle neutron scattering measurements. This photomultiplier has good spatial resolution, less than 1 mm2. The detection efficiency of gamma ray background is very low for using a thin ZnS/6LiF scintillator. The effective area of this detector is around 60 cm2.

A focusing-geometry small-angle neutron scattering instrument with a magnetic neutron lens

We have constructed a focusing-geometry small-angle neutron scattering (FSANS) instrument, SANS-J-II, with two kinds of neutron focusing device: a series of compound refractive lenses made of MgF2 and a magnetic neutron lens based on an extended Halbach-type sextupole magnet. In this study, we investigated the performance of the FSANS instrument with the magnetic neutron lens. The intensity distribution of a direct neutron beam focused on the detector plane by the magnetic neutron lens had a ratio of the peak height to the background level of \sim\!6\times 10^4 for a polarized neutron beam with a polarization degree of \sim \!0.99. It is found that a minimum value of the measurable q range [where q is the modulus of the scattering vector and is defined as q = (4\pi/\lambda)\sin(\theta/2), where \theta is the scattering angle and \lambda is the neutron wavelength], q_{\rm min}, of 6.5 \times 10^{-4} A−1 can be achieved by the FSANS instrument with the magnetic neutron lens using neutrons with \lambda = 6.6 A and \Delta \lambda/\lambda = 0.13 for the full width at half maximum.

Practical Applications of Permanent Magnet Multipoles

Permanent magnets are superior to electromagnets in generating strong multipole magnetic fields. Their fields are sometimes stronger than those that can be generated by superconducting magnets with the same bore radius, when the number of poles are higher. Three fabricated multipoles including a quadrupole magnet for the ILC (International Linear Collider) final focus doublet, a quadrupole magnets as a spin filter for cold neutrons, and a sextupole magnet for neutron beam focusing are described.

Development of high spatial resolution cold/ultra- cold neutron detector using fine-grained nuclear emulsion

We have been developing neutron detectors with spatial resolution of submicron to several tens of nanometers using fine-grained nuclear emulsion with nuclides with large neutron absorption cross sections such as 6Li and 10B. Those detectors were demonstrated their ability to detect cold and ultra-cold neutrons.

Measurement Of Neutron Scattering With Noble Gas To Search For A Short-range Unknown Force

We are searching for an unknown force that could couple to mass using neutron scattering from a noble gas. The neutron is a chargeless massive particle with a long lifetime, which consequently is suitable for the precision measurement of a small interaction with a range of the order of 1 nm by measurements of the momentum transfer distribution. We measured neutron scattering at the low-divergence beam branch on the BL05 NOP beamline in the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC). We measured 105 scattering events and report our most recent analysis.

Research toward the development of compact neutron interference imaging instrument with gratings

The neutron interference imaging experiment with two absorption gratings has been done. We develop new way to fabricate absorption gratings for neutron with the pitch of 150 μ m, 180 μ m, and 200 μ m. Compact imaging detector system is developed, whose weight is 2kg. Small break in an acrylic plate, the welded place of Nb plate were observed, it reveals that the neutron interference imaging method can become new method of a nondestructive inspection for reinforced plastics and composite material such as CFRP and so on.

High Flux X‐ray Beam Intensity Monitor Based upon Rare Gas Scintillation

We have developed a new X‐ray beam intensity monitor based upon rare gas scintillation in order to solve (i) the non‐ion‐saturation problem occurring ionization chambers when irradiated with high flux X‐ray beams and (ii) the slow time response of ionization chambers. When argon gas is used, it has been confirmed that the scintillation output was proportional to an X‐ray intensity up to 1015 xph/sec, and responded to an X‐ray beam with a time resolution better than 50 nsec. The rare gas scintillation X‐ray beam monitor developed is compatible to ionization chamber in terms of its readout electronics and the physical size, so that it can easily substitute existing ionization chambers when needed.

A 128-channel microstrip Germanium detector for Compton scattering experiments at the SPring-8 facility

A 128-channel microstrip Germanium detector system has been developed to efficiently detect Compton-scattered X-rays and to effectively reject the background X-rays associated in the Compton spectrometer of the high-energy inelastic scattering beamline at the SPring-8 facility. In order to handle the large number of the readout channels, four 32-parallel-input front-end hybrid boards have been adopted as charge-sensitive pre-amplifiers and discriminators, which are currently controlled by a Windows-based PC data-acquisition system.

Search for deviations from the inverse square law of gravity at nm range using a pulsed neutron beam

We describe an experimental search for deviations from the inverse-square law of gravity at the nanometer length scale using neutron scattering from noble gases on a pulsed slow neutron beam line. By measuring the neutron momentum transfer (q) dependence of the differential cross section for xenon and helium and comparing to their well-known analytical forms, we place an upper bound on the strength of a new interaction as a function of interaction length λ which improves upon previous results in the region λ<0.1  nm, and remains competitive in the larger-λ region. A pseudoexperimental simulation is developed for this experiment and its role in the data analysis is described. We conclude with plans for improving sensitivity in the larger-λ region.

Measurements of neutronic characteristics of rectangular and cylindrical coupled hydrogen moderators

ABSTRACT Extensive simulation calculations were performed in the design studies of the coupled hydrogen moderator for the pulsed spallation neutron source of the Japan Proton Accelerator Research Facility (J-PARC). It was indicated that a para-hydrogen moderator had an intensity-enhanced region at the fringe part, and that pulse shapes emitted from a cylindrical para-hydrogen moderator gave higher pulse-peak intensities with narrower pulse widths than those from a rectangular one without penalizing the time-integrated intensities. To validate the peculiar distribution and advantages in pulse shapes experimentally, some measurements were performed at the neutron source of the Hokkaido University electron linear accelerator facility. It was observed that the neutron intensity was enhanced at edges of the para-hydrogen moderators, whereas it decreased at the same part of the ortho-rich-hydrogen moderator, where the dimension of those moderators was 50 mm in thickness and 120 mm in width and height. The spatial distribution and pulse shapes were also measured for a cylindrical coupled para-hydrogen moderator that has the same dimensions as for the coupled moderator employed for J-PARC. The measured results from the cylindrical moderator were consistent with the results obtained in the design studies for the moderator for J-PARC.