The purpose of the present study is to establish a new convenient detection method for γ-ray irradiation history. To measure very weak thermal emission spectra of γ-irradiated seashells, a new multichannel Fourier-transform chemiluminescence spectrometer, an interferometer of which is composed of a Savart plate, a quartz lens, and two linear polarizers, was used. When irradiated mussel shells were cleaned by water, crushed by a freezing crusher, and heated at 473 K, spatial interferogram was obtained from signals on each CCD pixel, which was converted to thermal emission spectra by Fourier transformation. The observed spectra were modeled with one Gaussian curve by least-squares fitting, showing a peak position at about 641 nm. We found that the spectral intensity depends on the dose of γ-ray irradiation and the history of 0.1 kGy irradiation is detectable. In addition, the emission spectrum of a sample washed by only water was found to be similar to that washed by 5％ NaOCl solution, meaning that the washing by the solution is not required. The method proposed in the present study is expected to develop as a new convenient method to know the γ-ray irradiation history of seashells.
For the first time, LIGO gravitational wave telescopes have observed gravitational waves (GWs) from a coalescence of a binary black hole on September 14th in 2015. This confirmed not only a major prediction of Albert Einstein’s general theory of relativity in 1915, but also the existence of black holes and their binary systems in the Universe. The other GW signal on December 26th in 2015 was also confirmed later. Such multi-detection of GWs convinced us the beginning of a new era of gravitational wave astronomy. These GWs detections also justified general relativity in the regime of the extremely strong gravity field for the first time. However, the way to reach these historical GW detections was so hard that it took almost a half century to measure a 10−22 part of kilo-meters length of a laser interferometer GW detectors. In this article, I will explain the gravity and GWs in the regime of general relativity, their expected sources, a history of GW detectors development, the battle with noises in an interferometric GW detectors, results of GW detection by LIGO and future plans to detect GWs for the wider frequency ranges.
Since the discovery of the atmospheric neutrino oscillation in 1998, various properties of neutrino, a very light and elusive particle, have been revealed. In this article, the recent progress of researches to study properties of neutrino is reported focusing on the Super-Kamiokande and the other experiments. Also, the remaining problem and the relation to solve the matter dominant universe is briefly discussed.
Studying the dynamical properties of structurally isotropic materials such as glass, liquid, and polycrystalline powder samples, the inelastic neutron scattering measurement by chopper spectrometer in pulsed neutron source shows the whelming strength compared with that by triple axis spectrometer in research reactor. When a new material exhibiting the unusual physical properties is discovered, it might be difficult to grow the single crystal and only possible to obtain the powder form in the early stage of research. The strong neutron beam of J-PARC can provide opportunity promptly for the dynamical study of newly-discovered materials. The chopper spectrometers in J-PARC have the potential to create innovative research outcomes.
AMATERAS is a cold-neutron disk-chopper spectrometer installed at Materials and Life science Facility (MLF) in J-PARC. The spectrometer is designed to realize both high-resolution and high-intensity with high flexibility in inelastic and quasielastic neutron scattering experiment by devoting state-of-art techniques and devices. One of the prominent future of AMATERAS is a pulse-shaping technique. The spectrometer has a pulse-shaping chopper in addition to a monochromating chopper which conventional chopper spectrometers have. By combination of two choppers, AMATERAS produces a sharp neutron pulse with high-peak-intensity from a board source pulse of a coupled moderator at MLF, and it is used for high-resolution and high-intensity experiments at this spectrometer. These choppers are newly developed high-speed disk-choppers, which maximum revolution rate is 350 Hz. Also, AMATERAS equips a large volume (59 m3) vacuumed scattering chamber, a detector bank of large area (covering solid angle: 0.67π Sr), a super mirror beam transport (vertically focused and horizontally curved) and B4C contained mortar shielding, all of which contribute to high precision measurements on AMATERAS. On AMATERAS, experiments have been carried out in broad range of research fields, such as investigations in magnetic and structural excitations, diffusive motions of atoms and molecules in liquid, glass and amorphous, slow dynamic in polymers and biomaterials and etc.