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Minerals on airless bodies exhibit characteristic spectral features such as darkening and reddening. Such space weathering is mainly due to hydrogen-ion irradiation by the solar wind and to micrometeorite impacts. Because of the reactivity of hydrogen, the associated H-implantation into O-bearing minerals can lead to the formation of new chemical bonds and may contribute to formation of water. However, laboratory studies still conflict about production efficiency of water and relevant H-bearing molecules such as OH formed by the H-ion irradiation. The production efficiency of the molecules within minerals may be influenced by short-range structural order of the host minerals. It is thus important to clarify how the implanted H interacts with various irradiation defects produced by H-ion bombardment. Here, we investigated H-ion-irradiated alumina (Al2O3), one of the most basic oxides, using scanning/transmission electron microscopy (S/TEM) and electron energy-loss spectroscopy (EELS). The TEM images revealed dense dislocations, nanoscale voids and nanoscale cracks—instead of amorphization—in the region subject to high energy deposition. Our analyses by STEM–EELS hyperspectral imaging (HSI) isolated a few essential spectral components, suggesting that chemical interactions between the implanted H and the host alumina resulted in local generation of OH species rather than amorphization. We also found a spectral feature which may be explained by H2 gas, presumably remaining in the nanovoids, most of which escaped through fractures formed by the coalescence of the high-pressure H2 nanobubbles. Such fractures/crack surfaces can act as additional reactive sites for the formation of the OH species. The present results strongly imply that H+ irradiation can be a source of water in minerals in various astrophysical conditions. The present methodology can be applied to a wide range of extraterrestrial materials, such as regolith grains, interplanetary-dust particles, and/or presolar grains in primitive meteorites.

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2021-05-18, 資料番号: PA2210017000

We study a strategy to reduce veto-time in the search for neutrino-less double-beta decay (0υββ) with CANDLES-III system. We develop a new likelihood analysis and apply it to our new Run010 data. We show that we can increase the un-vetoed live-time by 11.8%. Thanks to this improvements, We expect to increase a limit on the life-time of 0υββ by a factor of three by analyzing both Run009 and Run010 data.

The core facility of the Wakasa Wan Energy Research Center (WERC) consists of three ion accelerators: a synchrotron, a tandem accelerator and an ion-implanter. Research on the irradiation effects using these accelerators has been performed on space electronics such as solar cells, radiation detectors, image sensors and LSI circuits. In this report, the accelerator facility and ion-irradiation apparatuses at WERC are introduced, focusing on the research on irradiation effects on space electronics. Then, some recent results are summarized.

As the parent bodies of carbonaceous chondrite (CC) meteorites contain valuable information that will help us better understand the formation and evolution of the early solar system, it is vital to search for them. To date, searching for those parent bodies has been conducted by comparing visible to near-infrared reflectance spectra of CCs with those of small bodies. It is known that the reflectance spectra of small bodies and, more widely, airless planetary bodies can be modified via space weathering. However, the effects of irradiated solar wind protons, which account for 95 % of the solar wind, on the spectra of CC-like materials, are still poorly understood. Here we report on the experimental spectral modification of hydrous silicate minerals due to hydrogen irradiation via simulating the implantation of solar wind protons onto parent bodies of CCs. The samples we used for our experiment were serpentine and saponite, which are two major mineral components of CCs. We irradiated the samples with 10 keV H 2 + ions to achieve the estimated saturation level (1.3 to 1.7 × 1018 ions cm−2), and measured their reflectance spectra in the wavelength range from 1.5 to 5 . 0 μ m both before and after irradiation. For serpentine, the sample was irradiated step by step, and the reflectance spectra were measured after each irradiation step. After irradiation, we observed changes in the absorption features at 2 . 77 μ m and 2 . 85 μ m . These changes imply that H2O and Si-OH radicals, respectively, would have been formed by a reaction between the irradiated hydrogen and the hydrous silicate minerals. In this study, spectral modifications due to hydrogen irradiation near 0 . 7 μ m and 2 . 3 μ m were not observed. This indicates that hydrogen irradiation broke the Si-O-Si bonding within the tetrahedra in hydrous silicate mineral structures, but it did not break the metal–OH bonding of the octahedra. In contrast to previous studies, our results imply that solar wind irradiation should also form H2O on anhydrous silicate minerals. This suggests the possibility of H2O formation on the surfaces of planetary bodies located inside of the snow line. The saturation timescale of spectral modification based on our results is estimated to be from 102 to 103 yr at 1 AU. This timescale is much shorter than that of the micrometeorite bombardment (106 to 107 yr), and it is comparable to the exposure age of small bodies. Therefore, we expect that spectral modification for small body surfaces would be mostly saturated.

The hardness and hydrogen content of diamond-like carbon (DLC) films vary depending on the film deposition methods and conditions. Carbon fiber reinforced plastics (CFRP), known as hard-to-machine materials, have been widely used for industrial aircrafts that require structural materials. In this study, the effects of the hardness and hydrogen content in DLC films on the drilling performance of CFRP drills were investigated. Various DLC films, prepared using the T-shaped filtered arc deposition method, were used to coat diamond-coated drills for CFRP processing. The drilling test of the CFRP plates revealed that the occurrence of burrs was suppressed using the drill coated with a hard DLC film containing small amounts of hydrogen, classified as a hydrogenated tetrahedral amorphous carbon (ta-C:H) film. The spherical polishing test of the CFRP plate using DLC-coated balls demonstrated that the DLC films containing hydrogen suppressed the adhesion of the resin material constituting the CFRP. The coating of hard DLC films containing small amounts of hydrogen, such as a ta-C:H film, significantly improved the drilling performance of diamond-coated drills for CFRP processing. The performance improvement of CFRP drills expands the range of CFRP processing conditions.

We have determined the distribution of aluminum in the epidermal cells of mature tea leaves using micro-beam particle-induced X-ray emission. The observed pattern of aluminum distribution in the epidermal cells suggests that aluminum exists in cell walls. Silicon exhibits a distribution that is nearly identical to that of aluminum, suggesting co-localization with aluminum.