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Journal Articles

Behavior of light elements in iron-silicate-water-sulfur system during early Earth's evolution

Iizuka, Riko*; Goto, Hirotada*; Shito, Chikara*; Fukuyama, Ko*; Mori, Yuichiro*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; Kagi, Hiroyuki*

Scientific Reports (Internet), 11(1), p.12632_1 - 12632_10, 2021/06

 Times Cited Count:0 Percentile:0.01(Multidisciplinary Sciences)

The Earth's core consist of Fe-Ni alloy with some light elements (H, C, O, Si, S etc.). Hydrogen (H) is the most abundant element in the universe and one of the promising candidates. In this study, we have investigated the effects of sulfur(S) on hydrogenation of iron-hydrous silicate system containing saturated water in the ideal composition of the primitive Earth. We observed a series of phase transitions of Fe, dehydration of the hydrous mineral, and formation of olivine and enstatite with increasing temperature. The FeS formed as the coexisting phase of Fe under high-pressure and temperature condition, but its unit cell volume did not increase, suggesting that FeS is hardly hydrogenated. Recovered samples exhibited that H and S can be incorporated into solid Fe, which lowers the melting temperature as Fe(H$$_{x}$$)-FeS system. No detection of other light elements (C, O, Si) in solid Fe suggests that they dissolve into molten iron hydride and/or FeS in the later process of Earth's core-mantle differentiation.

Journal Articles

Incorporation of U, Pb and rare earth elements in calcite through crystallisation from amorphous calcium carbonate; Simple preparation of reference materials for microanalysis

Miyajima, Yusuke*; Saito, Ayaka*; Kagi, Hiroyuki*; Yokoyama, Tatsunori; Takahashi, Yoshio*; Hirata, Takafumi*

Geostandards and Geoanalytical Research, 45(1), p.189 - 205, 2021/03

 Times Cited Count:0 Percentile:0.01(Geochemistry & Geophysics)

Uncertainty for elemental and isotopic analyses of calcite by LA-ICP-MS is largely controlled by the homogeneity of the reference materials (RMs) used for normalization and validation. In order to produce calcite RMs with homogeneous elemental and isotopic compositions, we incorporated elements including U, Pb, and rare earth elements into calcite through heat- and pressure-induced crystallization from amorphous calcium carbonate that was precipitated from element-doped reagent solution. X-ray absorption spectra showed that U was present as U(VI) in the synthesized calcite, probably with a different local structure from that of aqueous uranyl ions. The uptake rate of U by our calcite was higher in comparison to synthetic calcite of previous studies. Variations of element mass fractions in the calcite were better than 12% 2RSD, mostly within 7%. The $$^{207}$$Pb/$$^{206}$$Pb ratio in the calcite showed $$<$$1% variations, while the $$^{238}$$U/$$^{206}$$Pb ratio showed 3-24% variations depending on element mass fractions. Using the synthetic calcite as primary RMs, we could date a natural calcite RM, WC-1, with analytical uncertainty as low as $$<$$3%. The method presented can be useful to produce calcite with controlled and homogeneous element mass fractions, and is a promising alternative to natural calcite RMs for U-Pb geochronology.

Journal Articles

Experimental evidence for the existence of a second partially-ordered phase of ice VI

Yamane, Ryo*; Komatsu, Kazuki*; Gochi, Jun*; Uwatoko, Yoshiya*; Machida, Shinichi*; Hattori, Takanori; Ito, Hayate*; Kagi, Hiroyuki*

Nature Communications (Internet), 12, p.1129_1 - 1129_6, 2021/02

 Times Cited Count:4 Percentile:89.3(Multidisciplinary Sciences)

Ice exhibits extraordinary structural variety in its polymorphic structures. The existence of a new form of diversity in ice polymorphism has recently been debated in both experimental and theoretical studies, questioning whether hydrogen-disordered ice can transform into multiple hydrogen-ordered phases, contrary to the known one-to-one correspondence between disordered ice and its ordered phase. Here we report a new high-pressure phase, ice XIX, which is a second hydrogen-ordered phase of ice VI. This is the first discovery to demonstrate that disordered ice undergoes different manners of hydrogen ordering. Such multiplicity can appear in all disordered ice, and it widely provides a new research approach to deepen our knowledge, for example of the crucial issues of ice: the centrosymmetry of hydrogen-ordered configurations and potentially induced (anti-)ferroelectricity. Ultimately, this research opens up the possibility of completing the phase diagram of ice.

Journal Articles

Neutron diffraction study of hydrogen site occupancy in Fe$$_{0.95}$$Si$$_{0.05}$$ at 14.7 GPa and 800 K

Mori, Yuichiro*; Kagi, Hiroyuki*; Kakizawa, Sho*; Komatsu, Kazuki*; Shito, Chikara*; Iizuka, Riko*; Aoki, Katsutoshi*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; et al.

Journal of Mineralogical and Petrological Sciences, 116(6), p.309 - 313, 2021/00

The Earth's core is believed to contain some light elements because it is 10% less dense than pure Fe under the corresponding pressure and temperature conditions. Hydrogen, a promising candidate among light elements, has phase relations and physical properties that have been investigated mainly for the Fe-H system. This study specifically examined an Fe-Si-H system using in-situ neutron diffraction experiments to investigate the site occupancy of deuterium of hcp-Fez$$_{0.95}$$Si$$_{0.05}$$ hydride at 14.7 GPa and 800 K. Results of Rietveld refinement indicate hcp-Fe$$_{0.95}$$Si$$_{0.05}$$ hydride as having deuterium (D) occupancy of 0.24(2) exclusively at the interstitial octahedral site in the hcp lattice. The effect on the site occupancy of D by addition of 2.6 wt% Si into Fe (Fe$$_{0.95}$$Si$$_{0.05}$$) was negligible compared to results obtained from an earlier study of an Fe-D system (Machida et al., 2019).

Journal Articles

Anomalous hydrogen dynamics of the ice VII-VIII transition revealed by high-pressure neutron diffraction

Komatsu, Kazuki*; Klotz, S.*; Machida, Shinichi*; Sano, Asami; Hattori, Takanori; Kagi, Hiroyuki*

Proceedings of the National Academy of Sciences of the United States of America, 117(12), p.6356 - 6361, 2020/03

 Times Cited Count:3 Percentile:42.88(Multidisciplinary Sciences)

Above 2 GPa the phase diagram of water simplifies considerably and exhibits only two solid phases up to 60 GPa, ice VII and ice VIII. The two phases are related to each other by hydrogen ordering, with the oxygen sub-lattice being essentially the same. Here we present neutron diffraction data to 15 GPa which reveal that the rate of hydrogen-ordering at the ice VII-VIII transition decreases strongly with pressure to reach time scales of minutes at 10 GPa. Surprisingly, the ordering process becomes more rapid again upon further compression. We show that such an unusual change in transition rate can be explained by a slowing-down of the rotational dynamics of water molecules with a simultaneous increase of translational motion of hydrogen under pressure, as previously suspected. The observed crossover in the hydrogen dynamics in ice is likely the origin of various hitherto unexplained anomalies of ice VII in the 10-15 GPa range reported by Raman spectroscopy, X-ray diffraction, and proton conductivity.

Journal Articles

Ice I$$_{rm c}$$ without stacking disorder by evacuating hydrogen from hydrogen hydrate

Komatsu, Kazuki*; Machida, Shinichi*; Noritake, Fumiya*; Hattori, Takanori; Sano, Asami; Yamane, Ryo*; Yamashita, Keishiro*; Kagi, Hiroyuki*

Nature Communications (Internet), 11(1), p.464_1 - 464_5, 2020/02

 Times Cited Count:14 Percentile:88.53(Multidisciplinary Sciences)

Water freezes below 0$$^{circ}$$C at ambient pressure ordinarily to ice I$$_{rm h}$$, with hexagonal stacking sequence. Under certain conditions, ice with a cubic stacking sequence can also be formed, but ideal ice I$$_{rm c}$$ without stacking-disorder has never been formed until recently. Here we demonstrate a route to obtain ice I$$_{rm c}$$ without stacking-disorder by degassing hydrogen from the high-pressure form of hydrogen hydrate, C$$_{2}$$, which has a host framework isostructural with ice I$$_{rm c}$$. The stacking-disorder free ice I$$_{rm c}$$ is formed from C$$_{2}$$ via an intermediate amorphous or nano-crystalline form under decompression, unlike the direct transformations occurring in ice XVI from neon hydrate, or ice XVII from hydrogen hydrate. The obtained ice I$$_{rm c}$$ shows remarkable thermal stability, until the phase transition to ice I$$_{rm h}$$ at 250 K, originating from the lack of dislocations. This discovery of ideal ice I$$_{rm c}$$ will promote understanding of the role of stacking-disorder on the physical properties of ice as a counter end-member of ice I$$_{rm h}$$.

Journal Articles

Crystal structure of a high-pressure phase of magnesium chloride hexahydrate determined by ${it in-situ}$ X-ray and neutron diffraction methods

Yamashita, Keishiro*; Komatsu, Kazuki*; Hattori, Takanori; Machida, Shinichi*; Kagi, Hiroyuki*

Acta Crystallographica Section C; Structural Chemistry (Internet), 75(12), p.1605 - 1612, 2019/12

 Times Cited Count:1 Percentile:21.27(Chemistry, Multidisciplinary)

A crystal structure of a high-pressure phase of magnesium chloride hexahydrate (MgCl$$_{2}$$ $$cdot$$ 6H$$_{2}$$O-II) and its deuterated counterpart (MgCl$$_{2}$$ $$cdot$$ 6D$$_{2}$$O-II) have been identified for the first time by in-situ single-crystal X-ray and powder neutron diffraction. The crystal structure was analyzed by the Rietveld method for the neutron diffraction pattern based on the initial structure determined by single-crystal X-ray diffraction. This high-pressure phase has a similar framework to that in the known ambient-pressure phase, but exhibits some structural changes with symmetry reduction caused by a subtle modification in the hydrogen-bond network around the Mg(H$$_{2}$$O)$$_{6}$$ octahedra. These structural features reflect the strain in the high-pressure phases of MgCl$$_{2}$$ hydrates.

Journal Articles

Impact of stellar superflares on planetary habitability

Yamashiki, Yosuke*; Maehara, Hiroyuki*; Airapetian, V.*; Notsu, Yuta*; Sato, Tatsuhiko; Notsu, Shota*; Kuroki, Ryusuke*; Murashima, Keiya*; Sato, Hiroaki*; Namekata, Kosuke*; et al.

Astrophysical Journal, 881(2), p.114_1 - 114_24, 2019/08

 Times Cited Count:14 Percentile:80.03(Astronomy & Astrophysics)

The impact of Stellar flares on extrasolar planetary systems has been discussed and argued, especially whether there is a potential impact on their life systems. Here, we propose a comprehensive evaluation system for stellar flares, focusing on Stellar Proton Events (SPE) on selected extrasolar planets with hypothetical atmospheres and oceans. This is done by cross-linking KIC flare-observed and flare-estimated stars by their start pots that are directly linked with the Monte Carlo simulation system PHITS through the exoplanetary database system ExoKyoto. The estimated dose at ground level for each planetary surface did not exceed the critical dose for complex animals.

Journal Articles

Diffusion and sorption behavior of HTO, Cs, I and U in mortar

Akagi, Yosuke*; Kato, Hiroyasu*; Tachi, Yukio; Sakamoto, Hiroyuki*

Progress in Nuclear Science and Technology (Internet), 5, p.233 - 236, 2018/11

A large amount of radioactive contaminated concrete will be generated from the decommissioning in the Fukushima Dai-ichi Nuclear Power Plant (NPP). For developing the plans of decommissioning and waste management including decontamination and disposal, it is important to estimate radionuclides inventory and concentration distribution in the concrete materials. In this study, effective diffusivities (De) and distribution coefficients (Kd) of HTO, Cs, I and U in OPC mortar were measured by through-diffusion and batch sorption experiments. De values derived were in the sequence of HTO, I, Cs, U, implying that cation exclusion effects may be important mechanisms in OPC mortar. Kd values derived by batch tests were higher by more than one order of magnitude than the diffusion-derived Kd values, indicating that crushing of samples had a strong influence on sorption. Diffusion and sorption mechanisms in OPC mortar were evaluated to predict the penetration behavior of these radionuclides.

Journal Articles

Direct observation of symmetrization of hydrogen bond in $$delta$$-AlOOH under mantle conditions using neutron diffraction

Sano, Asami; Hattori, Takanori; Komatsu, Kazuki*; Kagi, Hiroyuki*; Nagai, Takaya*; Molaison, J. J.*; Dos Santos, A. M.*; Tulk, C. A.*

Scientific Reports (Internet), 8(1), p.15520_1 - 15520_9, 2018/10

 Times Cited Count:22 Percentile:89.54(Multidisciplinary Sciences)

The pressure response of hydrogen bond in aluminous hydroxide $$delta$$-AlOOH, which is an important candidate for water carrier to the deep Earth in a subducting slab, was investigated using neutron diffraction under high pressure. The symmetrization of hydrogen bond in which hydrogen locates at the center between two oxygen atoms was observed directly for the first time. The present result indicates that the changes of mineral properties such as increase in bulk modulus and sound velocities, which were previously found, were induced by the symmetrization and disorder state that was also found at just below the symmetrization pressure. Even the symmetrization is a small change in the hydrogen location but it is playing an important role in determining the physical properties of minerals.

Journal Articles

Pressure-induced stacking disorder in boehmite

Ishii, Yusuke*; Komatsu, Kazuki*; Nakano, Satoshi*; Machida, Shinichi*; Hattori, Takanori; Sano, Asami; Kagi, Hiroyuki*

Physical Chemistry Chemical Physics, 20(24), p.16650 - 16656, 2018/06

 Times Cited Count:3 Percentile:21.86(Chemistry, Physical)

The structure of an aluminum layered hydroxide, boehmite ($$gamma$$-AlOOH), as a function of pressure was studied by using ${it in situ}$ synchrotron X-ray and neutron diffraction. Peak broadening and subsequent splitting, which are only found for hkl (h $$neq$$ 0) peaks in the X-ray diffraction patterns above 25 GPa, are explained by stacking disorder accompanied with a continuously increasing displacement of the AlO$$_{6}$$ octahedral layer along a-axis. This finding could be the first experimental result for the pressure-induced stacking disorder driven by the continuous layer displacement. The magnitude of the layer displacement was estimated from the X-ray scattering profile calculation based on the stacking disordered structure model. Hydrogen bond geometries of boehmite, obtained by structure refinements on the observed neutron diffraction patterns for deuterated sample up to 10 GPa, show linearly approaching O-D covalent and D$$cdots$$O hydrogen bond distances and they could merge below 26 GPa. The pressure-induced stacking disorder would make the electrostatic potential of hydrogen bonds asymmetric, yielding less chance for the proton-tunnelling.

Journal Articles

High-pressure-high-temperature study of benzene; Refined crystal structure and new phase diagram up to 8 GPa and 923 K

Chanyshev, A. D.*; Litasov, K. D.*; Rashchenko, S.*; Sano, Asami; Kagi, Hiroyuki*; Hattori, Takanori; Shatskiy, A. F.*; Dymshits, A. M.*; Sharygin, I. S.*; Higo, Yuji*

Crystal Growth & Design, 18(5), p.3016 - 3026, 2018/05

 Times Cited Count:14 Percentile:88.87(Chemistry, Multidisciplinary)

The high-temperature structural properties of solid benzene were studied at 1.5-8.2 GPa up to melting or decomposition using multi-anvil apparatus and in situ neutron and X-ray diffraction. The crystal structure of deuterated benzene phase II (P2$$_{1}$$/c unit cell) was refined at 3.6-8.2 GPa and 473-873 K. Our data show a minor temperature effect on the change in the unit cell parameters of deuterated benzene at 7.8-8.2 GPa. At 3.6-4.0 GPa, we observed the deviation of deuterium atoms from the benzene ring plane and minor zigzag deformation of the benzene ring, enhancing with the temperature increase caused by the displacement of benzene molecules and decrease of van der Waals bond length between the $$pi$$-conjuncted carbon skeleton and the deuterium atom of adjacent molecule. Deformation of benzene molecule at 723-773 K and 3.9-4.0 GPa could be related to the benzene oligomerization at the same conditions. In the pressure range of 1.5-8.2 GPa, benzene decomposition was defined between 773-923 K. Melting was identified at 2.2 GPa and 573 K. Quenched products analyzed by Raman spectroscopy consist of carbonaceous material. The defined benzene phase diagram appears to be consistent with those of naphthalene, pyrene, and coronene at 1.5-8 GPa.

Journal Articles

Decontamination of radioactive concrete waste and reuse of aggregate using pulsed power technology

Sakamoto, Hiroyuki*; Akagi, Yosuke*; Yamada, Kazuo*; Tachi, Yukio; Fukuda, Daisuke*; Ishimatsu, Koichi*; Matsuda, Mikiya*; Saito, Nozomi*; Uemura, Jitsuya*; Namihira, Takao*; et al.

Nihon Genshiryoku Gakkai Wabun Rombunshi, 17(2), p.57 - 66, 2018/05

Concrete debris contaminated with radioactive cesium and other nuclides have been generated from the accident in the Fukushima Dai-ichi Nuclear Power Plant and there will be generated due to the decommissioning of nuclear power plants in the future. Although conventional decontamination techniques are effective for flat concrete surfaces such as floors and walls, it is not clear what techniques to apply for decontaminating radioactive concrete debris. In this study, focusing on a pulsed power discharge technique, fundamental experimental works were carried out. Decontamination of concrete by applying the aggregate recycling technique using the pulsed power discharge technique was evaluated by measuring radioactivity of aggregate and sludge separated from the contaminated concrete. The results suggest that the separation into aggregate and sludge of the contaminated concrete debris could achieve decontamination and volume reduction of the radioactive concrete debris.

Journal Articles

Operation status of the J-PARC RF-driven H$$^{-}$$ ion source

Oguri, Hidetomo; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Asano, Hiroyuki; Shibata, Takanori*; Nammo, Kesao*; Ueno, Akira; Shinto, Katsuhiro

AIP Conference Proceedings 1869, p.030053_1 - 030053_7, 2017/08

 Times Cited Count:5 Percentile:94.13

A cesiated RF-driven negative hydrogen ion source was started to operate in September, 2014 in response to the need for upgrading J-PARC's linac beam current. The ion source mainly comprises a stainless-steel plasma chamber, a beam extractor, and a large vacuum chamber with two turbo molecular pumps of 1500 L/s for differential pumping. The ion source has been successfully providing the required beam current to the accelerator without any significant issues other than a single-incident antenna failure occurred in October, 2014. Continuous operation for approximately 1,000 h was achieved with a beam current and duty factor of 45 mA and 1.25 % (0.5 msec and 25 Hz), respectively. In this paper, we will present the some operation parameters and the beam stability through the long-term user operation.

Journal Articles

High density plasma calculation of J-PARC RF negative ion source

Shibata, Takanori*; Asano, Hiroyuki; Ikegami, Kiyoshi*; Naito, Fujio*; Nammo, Kesao*; Oguri, Hidetomo; Okoshi, Kiyonori; Shinto, Katsuhiro; Takagi, Akira*; Ueno, Akira

AIP Conference Proceedings 1869, p.030017_1 - 030017_11, 2017/08

 Times Cited Count:4 Percentile:91.4

From September 2014, operation of Cs-seeded, multi-cusp, Radio Frequency (RF), hydrogen negative ion source (J-PARC source) has been started. The operation for 1,000 hours of J-PARC source has been achieved with H$$^{-}$$ beam current 45 mA and duty factor of 1.25 % (0.5 msec and 25 Hz). In the present study, mechanisms of hydrogen plasma ramp-up and H$$^{-}$$ production/transport processes in the steady state (which lasts for few 100 us) are investigated by numerical modeling for RF plasma. In the simulation, charged particle (e, H$$^{+}$$, H$$_2^{+}$$, and Cs$$^{+}$$) transport, time variations of inductive and capacitive electromagnetic field, collision processes between charged and neutral (H, H$$_{2}$$) particles are solved simultaneously. The model is applied to KEK parallel computation System-A with 32 nodes and 256 GB memory in order to solve high density RF plasma up to around 10$$^{18}$$ m$$^{-3}$$ with adequate statisticity. In the presentation, time variations of plasma density distributions and average energy are shown with electromagnetic field variations.

Journal Articles

Bulk moduli and equations of state of ice VII and ice VIII

Klotz, S.*; Komatsu, Kazuki*; Kagi, Hiroyuki*; Kunc, K.*; Sano, Asami; Machida, Shinichi*; Hattori, Takanori

Physical Review B, 95(17), p.174111_1 - 174111_7, 2017/05

AA2017-0082.pdf:0.79MB

 Times Cited Count:21 Percentile:79.87(Materials Science, Multidisciplinary)

The compression behaviour of deuterated ice VII and VIII was investigated by high pressure neutron scattering in the pressure range 2-13.7 GPa between 93 K and 300 K. We establish equations-of-state which contain accurate values for the bulk moduli B$${}_{0}$$, their pressure derivatives B'$${}_{0}$$, as well as the ambient pressure volumina V$${}_{0}$$. These equations-of-state hold over a large part of the stability domain of ice VII, by comparison with available X-ray data, and to at least $${approx}$$ 13 GPa for ice VIII. They are indistinguishable at low pressures, but beyond $${approx}$$ 7 GPa and at low temperatures ice VIII appears to become stiffer than expected. This might be related to an anomalous phonon hardening observed previously in ice VIII in this $$P/T$$ range [D.D. Klug et al., Physical Review B, 70, 144113 (2004)].

Journal Articles

LEBT commissioning of the J-PARC LINAC

Shibata, Takanori*; Ikegami, Kiyoshi*; Liu, Y.*; Maruta, Tomofumi*; Naito, Fujio*; Takagi, Akira*; Asano, Hiroyuki; Kondo, Yasuhiro; Miura, Akihiko; Oguri, Hidetomo; et al.

Proceedings of 28th International Linear Accelerator Conference (LINAC 2016) (Internet), p.251 - 253, 2017/05

After upgrade of J-PARC Linac in 2014, Low Energy Beam Transport (LEBT) beam commissioning of the J-PARC LINAC has been made for improving H$$^{-}$$ beam intensity extracted from Linac. Currents of two solenoid coils and steering magnets in LEBT are optimized with extraction and acceleration voltages for static acceleration in ion source (IS) which decides on an initial emittance diagram of H$$^{-}$$ beam. As a result of LEBT and IS parameter optimization, beam transmission rate of RFQ has been reached up to 96% in 50 mA H$$^{-}$$ current operation. Moreover, PIC-MC (Particle-In-Cell Monte-Carlo) simulation models developed for H$$^{-}$$ transport in LEBT. Comparison between experimental and numerical results are presented to clarify beam physics from IS exit to RFQ entrance.

Journal Articles

A 3 MeV linac for development of accelerator components at J-PARC

Kondo, Yasuhiro; Asano, Hiroyuki*; Chishiro, Etsuji; Hirano, Koichiro; Ishiyama, Tatsuya; Ito, Takashi; Kawane, Yusuke; Kikuzawa, Nobuhiro; Meigo, Shinichiro; Miura, Akihiko; et al.

Proceedings of 28th International Linear Accelerator Conference (LINAC 2016) (Internet), p.298 - 300, 2017/05

We have constructed a linac for development of various accelerator components at J-PARC. The ion source is same as the J-PARC linac's, and the RFQ is a used one in the J-PARC linac. The beam energy is 3 MeV and nominal beam current is 30 mA. The accelerator has been already commissioned, and the first development program, laser-charge-exchange experiment for the transmutation experimental facility, has been started. In this paper, present status of this 3-MeV linac is presented.

Journal Articles

Behavior of intermolecular interactions in $$alpha$$-glycine under high pressure

Shinozaki, Ayako*; Komatsu, Kazuki*; Kagi, Hiroyuki*; Fujimoto, Chikako*; Machida, Shinichi*; Sano, Asami; Hattori, Takanori

Journal of Chemical Physics, 148(4), p.044507_1 - 044507_8, 2017/01

 Times Cited Count:8 Percentile:57.04(Chemistry, Physical)

Pressure-response on the crystal structure of deuterated $$alpha$$-glycine was investigated at room temperature, using powder and single-crystal X-ray diffraction, and powder neutron diffraction measurements under high pressure. No phase change was observed up to 8.7 GPa, although anisotropy of the lattice compressibility was found. Neutron diffraction measurements indicated the distance of the intermolecular D$$cdots$$O bond along with the $$c$$-axis increase with compression up to 6.4 GPa. The distance of another D$$cdots$$O bond along with the $$a$$-axis decreased with increasing pressure, and became the shortest intermolecular hydrogen bond above 3 GPa. In contrast, the lengths of the bifurcated N-D$$cdots$$O and C-D$$cdots$$O hydrogen bonds, which are formed between the layers of the $$alpha$$-glycine molecules along the $$b$$-axis, decreased significantly with increasing pressure. The decrease of the intermolecular distances resulted in the largest compressibility of the $$b$$-axis, compared to the other two axes. Hirshfeld analysis suggested that the reduction of the void region size, rather than shrinkage of the strong N-D$$cdots$$O hydrogen bonds, occurred with compression.

Journal Articles

Status of the J-PARC RF ion source

Okoshi, Kiyonori; Ikegami, Kiyoshi*; Takagi, Akira*; Asano, Hiroyuki; Ueno, Akira; Shibata, Takanori*; Nammo, Kesao*; Shinto, Katsuhiro; Oguri, Hidetomo

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.940 - 943, 2016/11

In 2014 October, operation of cesium-seeded Radio Frequency (RF)-driven negative hydrogen ion (H$$^{-}$$) source was started in J-PARC LINAC. Due to the skillful RF antenna screening and the proper pre-conditioning process, long term unscheduled beam stop due to the antenna failure did not occur for more than 1 year. The continuous operation of 1,350 hours with a peak beam current of 45 mA was achieved in the recent beam run. Moreover, the fluctuation of beam current in a low energy beam transport (LEBT) is kept within $$pm$$2% of target value by application of three feedback systems. An ion source test-stand was assembled to investigate the ion source beam characteristic, for example, the emittance at the position of the RFQ entrance. In the presentation, we will report the recent status of the ion source operation and some experimental results obtained at the ion source test-stand.

153 (Records 1-20 displayed on this page)