Modeling the extraction of bound rubber from silica-filled styrene-butadiene rubber with toluene

Tamura, Yukiko*; Arakawa, Masato*; Takenaka, Mikihito*; Nakanishi, Yohei*; Fujinami, So*; Shibata, Motoki*; Yamamoto, Katsuhiro*; Miyata, Noboru*; Yamada, Masako*; Seto, Hideki*; et al.

Polymer, 333, p.128662_1 - 128662_8, 2025/08

https://doi.org/10.1016/j.polymer.2025.128662

Operation status of the J-PARC high-intensity RF-driven negative hydrogen ion source in 2023/2024

Shinto, Katsuhiro; Okoshi, Kiyonori; Shibata, Takanori*; Nammo, Kesao*; Kawai, Isao*; Ikegami, Kiyoshi*; Ueno, Akira

Proceedings of 21st Annual Meeting of Particle Accelerator Society of Japan (Internet), p.525 - 528, 2024/10

https://www.pasj.jp/web_publish/pasj2024/proceedings/PDF/WEP0/WEP096.pdf

A decade has elapsed since the radio frequency (RF)-driven negative hydrogen (H) ion source initiated operation at J-PARC. In the 2023/2024 campaign, a single RF-driven H ion source has generated H beams with a beam current of 60 mA, which enabled the J-PARC linac to inject them into the 3 GeV rapid cycling synchrotron (RCS) with a beam current of 50 mA. The continuous operation time of the ion source reached exceeding 4,900 hours in this campaign, which signifies a notable enhancement in operational longevity in comparison to the preceding longest campaign in 2022/2023, which spanned 4,412 hours. This paper provides the operational status of the RF-driven H ion source during this campaign and the current status of the J-PARC-made antenna, which is currently under development.

Neutron reflectivity study on the adsorption layer of polyethylene grown on Si substrate

Shimokita, Keisuke*; Yamamoto, Katsuhiro*; Miyata, Noboru*; Shibata, Motoki*; Nakanishi, Yohei*; Arakawa, Masato*; Takenaka, Mikihito*; Kida, Takumitsu*; Tokumitsu, Katsuhisa*; Tanaka, Ryo*; et al.

Langmuir, 40(30), p.15758 - 15766, 2024/07

https://doi.org/10.1021/acs.langmuir.4c01584

Simple 3D PIC analysis for beam phase space oscillation in RF driven negative hydrogen ion source

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

https://doi.org/10.1088/1742-6596/2743/1/012007

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.

Factors influencing the fluctuation amplitude of the H ion beam extracted from an RF wave excited ion source plasma

Wada, Motoi*; Shibata, Takanori*; Shinto, Katsuhiro

Journal of Physics; Conference Series, 2743, p.012031_1 - 012031_5, 2024/05

https://doi.org/10.1088/1742-6596/2743/1/012031

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.

Discoloration of RF antenna coil surface after long-term operation of J-PARC ion source

Shibata, Takanori*; Shinto, Katsuhiro; Nammo, Kesao*; Okoshi, Kiyonori; Ikegami, Kiyoshi*; Oguri, Hidetomo; Ishida, Masaki*; Wada, Motoi*

Journal of Instrumentation (Internet), 19(1), p.C01009_1 - C01009_8, 2024/01

https://doi.org/10.1088/1748-0221/19/01/C01009

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.

Design of a matching circuit for a high-intensity negative hydrogen ion source driving with 324 MHz RF power source

Shinto, Katsuhiro; Shibata, Takanori*; Wada, Motoi*

Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.392 - 395, 2023/11

https://www.pasj.jp/web_publish/pasj2023/proceedings/PDF/TUP3/TUP38.pdf

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.

Influence of plutonium content in dissolver solutions derived from irradiated fast reactor fuels on plutonium stripping in multistage countercurrent liquid-liquid extraction with acid split flowsheet

Nakahara, Masaumi; Shibata, Atsuhiro

Journal of Nuclear Science and Technology, 60(7), p.849 - 858, 2023/07

https://doi.org/10.1080/00223131.2022.2162137

To develop the acid split method which has highly nuclear proliferation resistance, influence of Pu content in dissolver solutions derived from irradiated fast reactor fuel on the Pu stripping was investigated in experiments and a calculation. The Pu content in the U/Pu and U products increased with increasing the Pu content in the dissolver solution. Moreover, the calculated results indicate that the Pu leakage into the U product is suppressed with the Pu stripping solution only at low temperature.

Neutron reflectivity study on the nanostructure of PMMA chains near substrate interfaces based on contrast variation accompanied with small molecule sorption

Shimokita, Keisuke*; Yamamoto, Katsuhiro*; Miyata, Noboru*; Nakanishi, Yohei*; Shibata, Motoki*; Takenaka, Mikihito*; Yamada, Norifumi*; Seto, Hideki*; Aoki, Hiroyuki; Miyazaki, Tsukasa*

Soft Matter, 19(11), p.2082 - 2089, 2023/03

https://doi.org/10.1039/D2SM01482C

Outgassing characteristics from the J-PARC-made internal antenna for a high-intensity radio-frequency H ion source

Shinto, Katsuhiro; Shibata, Takanori*; Okoshi, Kiyonori; Nammo, Kesao*; Ikegami, Kiyoshi*; Oguri, Hidetomo

Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.675 - 679, 2023/01

In J-PARC, we have been conducting the test of a J-PARC-made internal antenna in order to establish the production method and understand the beam characteristics of the antenna. At this time, we investigated the outgas characteristics during the production of a high-density plasma by using the J-PARC-made antenna. It is confirmed that no remarkable impurities are emitted from the antenna by a residual gas analysis using a quadrupole mass analyzer installed downstream the ion source and a spectroscopic analysis of the plasma in the ion source. It is found that the emittances of the H beam extracted from the J-PARC radio-frequency H ion source by using the antenna was similar as those in case by using SNS antenna.