Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Shibata, Takanori*; Shinto, Katsuhiro; Nakano, Haruhisa*; Hoshino, Kazuo*; Miyamoto, Kenji*; Okoshi, Kiyonori; Nammo, Kesao*; Ikegami, Kiyoshi*; Kawai, Isao*; Oguri, Hidetomo; et al.
Journal of Physics; Conference Series, 2743, p.012007_1 - 012007_5, 2024/05
Oscillation of the negative hydrogen ion (H
) beam phase space in Radio Frequency (RF) ion source is investigated by a simple 3D Particle-In-Cell (PIC) model which takes into account the transport processes of electron, proton and H in the extraction region. The calculation domain is in vicinity of the single beam aperture in J-PARC ion source configuration. In order to understand relation between the plasma density oscillation and the extracted H beam characteristics, the input electron and proton fluxes from the driver region are varied parametrically with the 1st and the 2nd harmonics of the J-PARC RF frequency (2 or 4 MHz). The numerical results give an idea to the main physical processes between the oscillations of the plasma parameters and the extracted H ion trajectories in the different RF phases. Countermeasures to reduce the oscillation mechanisms are also discussed in the presentation.
ion beam extracted from an RF wave excited ion source plasmaWada, Motoi*; Shibata, Takanori*; Shinto, Katsuhiro
Journal of Physics; Conference Series, 2743, p.012031_1 - 012031_5, 2024/05
An internal antenna type RF driven negative hydrogen (H) ion source supplies beams to the J-PARC accelerator facility. The H ion beam current exhibits high stability, while it fluctuates with less than 5% amplitude of the DC current when a Faraday cup measures the current extracted from the source mounted on a test stand. Two frequencies are identified as the main oscillation components, 2 MHz and 4 MHz which are the driving RF frequency and the second harmonics, respectively. The amplitude levels of these components appear larger as parts of the beam directing specific angles passing through a slit are detected. A possible reason for observing a small amplitude oscillation in the total beam intensity is the averaged phase-shift of the local beam depending upon the position of the H ion production and the succeeding trajectory reaching the Faraday cup. To confirm if the phase-shift is the main reason for diminishing the oscillation amplitude for the total beam, the phase-shift between the 2 MHz and 4 MHz components were measured for beams passing through a 0.1 mm slit coupled to a Faraday cup having a 0.1 mm entrance slit. The result indicated the phase-shift changed substantially depending upon the position, but no simple model can explain the measured spatial distribution of the phase-shift. Further attempts will be made to clarify the beam dynamics relevant to the H ion beam transport including the measurements of the beam current phase-shift with respect to the RF antenna current, and the time evolution of Balmer-
light emission.
Wada, Motoi*; Shibata, Takanori*; Shinto, Katsuhiro
Journal of Instrumentation (Internet), 19(2), p.C02019_1 - C02019_7, 2024/02
A negative hydrogen (H) ion source with the plasma excited by 2 MHz radio frequency (RF) power serves as the beam source for the Japan Proton Accelerator Research Complex (J-PARC). We have been studying the H ion beam intensity modulation at the frequency of plasma excitation RF power since we have found the beam carried the fluctuation at 2 MHz after the RFQ linac. Higher frequency components were found present in the peripheral region of the plasma, and the highspeed emittance measurement system developed to clarify the change of the beam in phase space revealed the existence of diverging halo component oscillating at 2 MHz. The fluctuation amplitude at the beam center was less than about 20%, while there was observed the component oscillating at 4 MHz. The 4 MHz component seems related to the production of high energy electrons by the RF antenna as the intensity of the RF induction electric field takes the maximum twice in each cycle. On the other hand, the direction of RF magnetic field and the direction of electron flow change at 2 MHz frequency. Thus, H ion formation mechanisms in the ion source can be estimated through precisely characterizing the extracted H ion beam. The H ion beam fluctuation can be observed in the H ion current measured with a Faraday cup. Before introducing Cs, the measured beam current showed the fluctuation at 4 MHz frequency when the axial magnetic field correction (AMFC) coil was turned off. The main fluctuation frequency changed to 2 MHz as the voltage to excite the coil to induce AMFC was increased. Injection of Cs into the ion source increased the H ion current, while the 4 MHz component nearly disappeared for both cases of AMFC on and AMFC off. Possible mechanisms responsible for diminishing 4 MHz fluctuation component by Cs injections are discussed.
Shibata, Takanori*; Shinto, Katsuhiro; Nammo, Kesao*; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Oguri, Hidetomo; Ishida, Masaki*; Wada, Motoi*
Journal of Instrumentation (Internet), 19, p.C01009_1 - C01009_8, 2024/01
From Nov. 2020 to Apr. 2021, the continuous ion source operation for 3,651 hours (5 months) was achieved. As the lifetime of the RF ion source is mainly limited by failure on the enamel coating of the RF antenna, detailed evaluation of the antenna surface is required to ensure feasibility of the further extension of the operation time. In the present study, surface discoloration on the RF antenna coil observed after the 5 months operation is investigated by application of digital microscope and SEM/EDS analyses. The material mapping and the line spectrum obtained by the EDS analysis show that depositions of the sputtered source chamber wall materials and the injected cesium on to the enamel coating are the most possible candidate for the discoloration. The dimension measurements of the RF antenna thickness before and after the long-term operation support the idea that the discoloration is due to the deposited materials and hence insulation of the RF antenna coil by enamel coating is maintained. The emittance measurement after the operation also shows that the RF plasma and the beam formations are not affected by the deposition on the antenna.
Shinto, Katsuhiro; Shibata, Takanori*; Wada, Motoi*
Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.392 - 395, 2023/11
Negative hydrogen (H) ion sources which are used at high-intensity proton accelerator facilities such as J-PARC or neutral beam injection system for plasma heating in the fusion devices such as ITER produce plasmas by using RF sources driving with the frequency of 1-2 MHz. We have shown that the H beams extracted from the RF-driven H ion source with the frequency of several MHz have some fluctuations with the frequency of the fundamental and second harmonics. The reason is that the high plasma density is produced in the ion source with the low driving frequency. Therefore, we propose the driving RF frequency same as the RF sources with that of 324 MHz in the J-PARC linac, which is much higher than the ion plasma frequency, is used for producing the plasma to suppress the H beam fluctuations. As a first step, we performed a design of a matching circuit for the higher frequency driven H ion source. We present the background for decision of a new RF amplifier with much higher frequency and the design results.
Cs activity concentration in the aquatic insect 
(Tricoptera: Stenopsychidae) in the Ota River, Fukushima, JapanIshii, Yumiko*; Miura, Hikaru*; Jo, J.*; Tsuji, Hideki*; Saito, Rie; Koarai, Kazuma; Hagiwara, Hiroki; Urushidate, Tadayuki*; Nishikiori, Tatsuhiro*; Wada, Toshihiro*; et al.
PLOS ONE (Internet), 17(5), p.e0268629_1 - e0268629_17, 2022/05
Times Cited Count：3 Percentile：38.08(Multidisciplinary Sciences)We investigated the variability in Cs activity concentration in individual aquatic insects in detritivorous caddisfly () and carnivorous dobsonfly (
) larvae from the Ota River, Fukushima. Caddisfly larvae showed sporadically higher radioactivity, whereas no such outliers were observed in dobsonfly larvae. Autoradiography and scanning electron microscopy analyses confirmed that these caddisfly larvae samples contained radiocesium-bearing microparticles (CsMPs), which are insoluble Cs-bearing silicate glass particles. CsMPs were also found in potential food sources of caddisfly larvae, such as periphyton and drifting particulate organic matter, indicating that larvae may ingest CsMPs along with food particles of similar size. Although CsMPs distribution and uptake by organisms in freshwater ecosystems is relatively unknown, our study demonstrates that CsMPs can be taken up by aquatic insects.
beam extracted from an RF-driven high-intensity H ion sourceShinto, Katsuhiro; Shibata, Takanori*; Wada, Motoi*
Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.230 - 233, 2021/10
In most proton accelerator facilities such as J-PARC, SNS, CERN, a H ion source equipped with a 2-MHz rf driver for plasma generation produces H beams. We have reported H beam characteristics extracted from the J-PARC rf-driven high-intensity H ion source. We have been developing an emittance measurement apparatus equipped with a highly time-resolved data acquisition system in order to observe fluctuation of the beam emittance in association with the frequency of the rf driver. By using this apparatus, we found that the beam emittance is fluctuated with the frequency with the rf driver and higher harmonics. We will show some obtained results of the emittance fluctuation.
Shibata, Takanori*; Shinto, Katsuhiro; Wada, Motoi*; Oguri, Hidetomo; Ikegami, Kiyoshi*; Okoshi, Kiyonori; Nammo, Kesao*
AIP Conference Proceedings 2373, p.050002_1 - 050002_9, 2021/08
Oscillation of emittance and Twiss parameters in the negative ion beam from the J-PARC 2-MHz RF ion source is measured by applications of a double-slit emittance monitor located at the RFQ (Radio Frequency Quadrupole) entrance. The emittance monitor is equipped with a newly-developed 60 MS/s data acquisition system, so that beam current oscillation in a few MHz can be observed with enough time resolution. From the measurement, it is shown that the beam phase space consists of (1) a DC component in the beam core, (2) a 2-MHz oscillating component which takes place both in the beam core and the halo and (3) a doubled RF frequency (4 MHz) oscillation which slightly exists in the beam halo. The major component is the 2-MHz component, which resultantly decides the beam emittance oscillation frequency. A typical value of the beam emittance in the present experiment is 0.34 
mm-mrad, while the amplitude of the 2 MHz oscillation is around 0.04 mm-mrad. The results indicate that the high-frequency oscillation component occupying about ten-percent of the beam from the RF source travels a few meters passing through a magnetic lens focusing system.
ion sourceWada, Motoi*; Shinto, Katsuhiro; Shibata, Takanori*; Sasao, Mamiko*
Review of Scientific Instruments, 91(1), p.013330_1 - 013330_5, 2020/01
Times Cited Count：4 Percentile：27.22(Instruments & Instrumentation)The ions are extracted from an ion source through a plasma sheath where a low frequency electromagnetic induction drives transport of charged particles including the target ions. High frequency alternating current commonly excites plasmas in sources for negative hydrogen (H) ions at a frequency in the MHz range. A high-speed beam current monitor system coupled to a narrow entrance slit enabled the investigation of the special distribution of the AC component intensity of the H ion beam extracted from an ion source driven by a 2 MHz radio frequency (RF) power. The distribution showed a smaller oscillation of the beam at the center.
ion sourceShinto, Katsuhiro; Shibata, Takanori*; Miura, Akihiko; Miyao, Tomoaki*; Wada, Motoi*
AIP Conference Proceedings 2011, p.080016_1 - 080016_3, 2018/09
Times Cited Count：6 Percentile：93.67(Physics, Applied)Kobata, Masaaki; Okane, Tetsuo; Nakajima, Kunihisa; Suzuki, Eriko; Owada, Kenji; Kobayashi, Keisuke*; Yamagami, Hiroshi; Osaka, Masahiko
Journal of Nuclear Materials, 498, p.387 - 394, 2018/01
Times Cited Count：18 Percentile：87.53(Materials Science, Multidisciplinary)In this study, for the understandings of Cesium (Cs) adsorption behavior on structure materials in severe accidents at a light water nuclear reactor, the chemical state of Cs and its distribution on the surface of SUS304 stainless steel (SS) with different Si concentration were investigated by hard X-ray photoelectron spectroscopy (HAXPES) and scanning electron microscope / energy dispersive X-ray spectroscopy (SEM/EDX). As a result, it was found that Cs is selectively adsorbed at the site where Si distributes with high concentration. CsFeSiO
is a dominant Cs products in the case of low Si content, mainly formed, while Cs
SiO
and CsSiO
are formed in addition to CsFeSiO in the case of high Si content. The chemical forms of the Cs compounds produced in the adsorption process on the SS surface has a close correlation with the concentration and chemical states of Si originally included in SS.
ion source upon the extracted beamShinto, Katsuhiro; Shibata, Takanori*; Wada, Motoi*
Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.648 - 650, 2017/12
In J-PARC, peak H current of several tens mA is extracted from an ion source driven by a solid-state rf amplifier with the frequency of 2 MHz for production of a cesiated hydrogen plasma. In case of the rf-driven ion source for producing the high-intensity H current, the plasma density in the source chamber is so high that the ion sheath around the beam extraction area can follow the rf oscillation. The H beam current fluctuation as large as approximately 1 mA was observed at the average beam current of 44 mA measured by a Faraday cup installed downstream of the ion source. The beam exhibited some fluctuation to the transverse motion as well. To further clarify this high frequency oscillation of the beam extraction sheath, we propose a measurement system using a time-resolved and highly sensitive emittance monitor in order to observe the real-time beam fluctuation in the phase space.
Unno, Masayoshi*; Sugishima, Masakazu*; Wada, Kei*; Hagiwara, Yoshinori*; Kusaka, Katsuhiro*; Tamada, Taro; Fukuyama, Keiichi*
Nihon Kessho Gakkai-Shi, 57(5), p.297 - 303, 2015/10
Bilin compounds are fundamentally important for oxygenic photosynthetic organisms, because they are utilized as pigments for photosynthesis (phycobilins) and photoreceptors (phytochromobilin). Phycocyanobilin (PCB), a phycobilin, comprises the chromophore of algal phytochromes and the core phycobiliprotein antennae of cyanobacteria and red algae. PCB is biosynthesized by a member of the ferredoxin-dependent bilin reductase family, phycocyanobilin:ferredoxin oxidoreductase (PcyA). In the present study, we determined the neutron crystal structure of PcyA in complex with its substrate biliverdin (BV). This neutron structure revealed the protonation state of BV and the surrounding residues. We found that two forms of BV, neutral BV and protonated BVH
, were coupled with the two conformation/protonation states of the essential residue Asp105. Further, His88 and His74 near BV were singly protonated and were connected with an intervening hydronium ion. Neutron analysis also revealed how X-ray irradiation of the PcyA-BV crystal altered the structure of the PcyA-BV complex.
Nakajima, Kyo*; Teramoto, Takahiro*; Akagi, Hiroshi; Fujikawa, Takashi*; Majima, Takuya*; Minemoto, Shinichiro*; Ogawa, Kanade*; Sakai, Hirofumi*; Togashi, Tadashi*; Tono, Kensuke*; et al.
Scientific Reports (Internet), 5, p.14065_1 - 14065_11, 2015/09
Times Cited Count：38 Percentile：83.79(Multidisciplinary Sciences)We report on the measurement of deep inner-shell 2p X-ray photoelectron diffraction (XPD) patterns from laser-aligned I molecules using X-ray free-electron laser (XFEL) pulses. The XPD patterns of the I molecules, aligned parallel to the polarization vector of the XFEL, were well matched with our theoretical calculations. Further, we propose a criterion for applying our molecular-structure-determination methodology to the experimental XPD data. In turn, we have demonstrated that this approach is a significant step toward the time-resolved imaging of molecular structures.
Unno, Masayoshi*; Ishikawa, Kumiko*; Kusaka, Katsuhiro*; Tamada, Taro; Hagiwara, Yoshinori*; Sugishima, Masakazu*; Wada, Kei*; Yamada, Taro*; Tomoyori, Katsuaki; Hosoya, Takaaki*; et al.
Journal of the American Chemical Society, 137(16), p.5452 - 5460, 2015/04
Times Cited Count：28 Percentile：63.97(Chemistry, Multidisciplinary)Phycocyanobilin, a light-harvesting and photoreceptor pigment in higher plants, algae, and cyanobacteria, is synthesized from biliverdin IX (BV) by phycocyanobilin:ferredoxin oxidoreductase (PcyA) via two steps of two-proton-coupled two-electron reduction. We determined the neutron structure of PcyA from cyanobacteria complexed with BV, revealing the exact location of the hydrogen atoms involved in catalysis. Notably, approximately half of the BV bound to PcyA was BVH, a state in which all four pyrrole nitrogen atoms were protonated. The protonation states of BV complemented the protonation of adjacent Asp105. The "axial "water molecule that interacts with the neutral pyrrole nitrogen of the A-ring was identified. His88 N
was protonated to form a hydrogen bond with the lactam O atom of the BV A-ring. His88 and His74 were linked by hydrogen bonds via H
O. These results imply that Asp105, His88, and the axial water molecule contribute to proton transfer during PcyA catalysis.
Shinto, Katsuhiro; Wada, Motoi*; Nishida, Tomoaki*; Demura, Yasuhiro*; Sasaki, Daichi*; Tsumori, Katsuyoshi*; Nishiura, Masaki*; Kaneko, Osamu*; Kisaki, Masashi*; Sasao, Mamiko*
AIP Conference Proceedings 1390, p.675 - 683, 2011/09
Times Cited Count：0 Percentile：0.19(Physics, Atomic, Molecular & Chemical)Shinto, Katsuhiro; Wada, Motoi*; Kaneko, Osamu*; Tsumori, Katsuyoshi*; Nishiura, Masaki*; Sasao, Mamiko*; Kisaki, Masashi*
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.999 - 1001, 2010/05
We propose a negative ion beam probe system as a new scheme to diagnose beam profile of high power positive ion beams. Two RF linacs of IFMIF have to drive the neutron source by providing continuous-wave (CW) positive deuterium ion beams with the intensity of 125 mA each at the beam energy of 40 MeV. During the CW beam operations, the extreme intensity of the beam and the severe radiation levels make the beam diagnostics with conventional techniques in the transport lines terribly difficult. A beam of negative ions liable to lose the additional electron at the occasion of impact with a high energy particle can work as a probe to measure the positive ion beam profile. On possible configuration to achieve high intensity beam profile measurement is to inject a negative ion probe beam into the target beam perpendicularly, and measure the attenuation of the negative ion beam by beam-beam interaction at each position. We have started an experimental study for the proof-of-principle of the new beam profile monitoring system. The paper presents the status quo of this beam profile monitor system development and the prospects to apply the system to the IFMIF beam line controls.
Miyazawa, Yutaka*; Sakashita, Tetsuya; Funayama, Tomoo; Hamada, Nobuyuki*; Negishi, Hiroshi*; Kobayashi, Akie*; Kaneyasu, Tomoko*; Oba, Atsushi*; Morohashi, Keita*; Kakizaki, Takehiko*; et al.
Journal of Radiation Research, 49(4), p.373 - 379, 2008/07
Times Cited Count：29 Percentile：64.75(Biology)We examined the role of root cap and elongation zone cells in root hydrotropism using heavy-ion and laser microbeam. Heavy-ion microbeam irradiation of the elongation zone, but not that of the columella cells, significantly and temporary suppressed the development of hydrotropic curvature. However, laser ablation confirmed that columella cells are indispensable for hydrotropism. Systemic heavy-ion broad-beam irradiation suppressed 
expression of 
gene, but not 
gene. Our results indicate that both the root cap and elongation zone have indispensable and functionally distinct roles in root hydrotropism, and that gene expression might be required for hydrotropism in the elongation zone, but not in columella cells.
using heavy-ion microbeamMiyazawa, Yutaka*; Sakashita, Tetsuya; Negishi, Hiroshi*; Kobayashi, Akie*; Kaneyasu, Tomoko*; Oba, Atsushi*; Morohashi, Keita*; Kakizaki, Takehiko*; Funayama, Tomoo; Hamada, Nobuyuki*; et al.
JAEA-Review 2007-060, JAEA Takasaki Annual Report 2006, P. 116, 2008/03
We examined the role of root cap and elongation zone cells in root hydrotropism of using heavy ion and laser microbeam. Heavy ion microbeam irradiation of the elongation zone, but not that of the columella cells, significantly and temporarily suppressed the development of hydrotropic curvature. However, laser ablation confirmed that columella cells are indispensable for hydrotropism. Systemic heavy ion broad beam irradiation suppressed de novo expression of INDOLE ACETIC ACID 5 gene. Our results indicate that both the root cap and elongation zone have indispensable and functionally distinct roles in root hydrotropism, and that de novo gene expression might be required for hydrotropism in the elongation zone, but not in columella cells.
Ru
O thin filmsTerai, Kota*; Yoshii, Kenji; Takeda, Yukiharu; Fujimori, Shinichi; Saito, Yuji; Owada, Kenji; Inami, Toshiya; Okane, Tetsuo; Arita, Masashi*; Shimada, Kenya*; et al.
Physical Review B, 77(11), p.115128_1 - 115128_6, 2008/03
Times Cited Count：16 Percentile：56.47(Materials Science, Multidisciplinary)