Polymer photonic crystals prepared by triblock copolymerization-induced microphase separation

Isozaki, Yuka*; Higashiharaguchi, Seiya*; Kaneko, Naoya*; Yamazaki, Shun*; Taniguchi, Tatsuo*; Karatsu, Takashi*; Ueda, Yuki; Motokawa, Ryuhei

Chemistry Letters, 51(6), p.625 - 628, 2022/06

https://doi.org/10.1246/cl.220089

Photonic crystals fabricated by block copolymerization-induced microphase separation

Motokawa, Ryuhei; Taniguchi, Tatsuo*; Kumada, Takayuki; Iida, You*; Aoyagi, Shota*; Sasaki, Yusuke*; Kori, Michinari*; Kishikawa, Keiki*

Macromolecules, 49(16), p.6041 - 6049, 2016/08

https://doi.org/10.1021/acs.macromol.6b01190

Progress in development and design of the neutral beam injector for JT-60SA

Hanada, Masaya; Kojima, Atsushi; Tanaka, Yutaka; Inoue, Takashi; Watanabe, Kazuhiro; Taniguchi, Masaki; Kashiwagi, Mieko; Tobari, Hiroyuki; Umeda, Naotaka; Akino, Noboru; et al.

Fusion Engineering and Design, 86(6-8), p.835 - 838, 2011/10

https://doi.org/10.1016/j.fusengdes.2011.04.068

Neutral beam (NB) injectors for JT-60 Super Advanced (JT-60SA) have been designed and developed. Twelve positive-ion-based and one negative-ion-based NB injectors are allocated to inject 30 MW D beams in total for 100 s. Each of the positive-ion-based NB injector is designed to inject 1.7 MW for 100s at 85 keV. A part of the power supplies and magnetic shield utilized on JT-60U are upgraded and reused on JT-60SA. To realize the negative-ion-based NB injector for JT-60SA where the injection of 500 keV, 10 MW D beams for 100s is required, R&Ds of the negative ion source have been carried out. High-energy negative ion beams of 490-500 keV have been successfully produced at a beam current of 1-2.8 A through 20% of the total ion extraction area, by improving voltage holding capability of the ion source. This is the first demonstration of a high-current negative ion acceleration of 1 A to 500 keV. The design of the power supplies and the beamline is also in progress. The procurement of the acceleration power supply starts in 2010.

Achievement of 500 keV negative ion beam acceleration on JT-60U negative-ion-based neutral beam injector

Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.

Nuclear Fusion, 51(8), p.083049_1 - 083049_8, 2011/08

https://doi.org/10.1088/0029-5515/51/8/083049

Hydrogen negative ion beams of 490 keV, 3 A and 510 keV, 1 A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 2 m for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60SA and ITER.

Improvement of voltage holding capability in the 500 keV negative ion source for JT-60SA

Tanaka, Yutaka; Hanada, Masaya; Kojima, Atsushi; Akino, Noboru; Shimizu, Tatsuo; Oshima, Katsumi; Inoue, Takashi; Watanabe, Kazuhiro; Taniguchi, Masaki; Kashiwagi, Mieko; et al.

Review of Scientific Instruments, 81(2), p.02A719_1 - 02A719_3, 2010/02

https://doi.org/10.1063/1.3279399

The JT-60U negative ion source is required to produce 44 A of 500 keV D ion beams for the JT-60SA. So far, acceleration voltage of 450 kV was achieved without beam acceleration and 416 kV with beam acceleration. These are lower than the rated voltage for JT-60SA due to vacuum breakdowns. To examine the cause of vacuum breakdown, the complicated structure of the accelerator was modeled for the calculation of electric field inside the accelerator. At the corners of the grid support flanges, the electric fields are locally concentrated to be 5.2-5.5 kV/mm. This is higher than other parts of the accelerator where the averaged field is around 3 kV/mm. To reduce the concentrated electric field, the support structures were modified to extend the gap lengths between grids. By repeating the high-voltage application of 3 s pulses, the applied voltage was increased. After 15 hours of conditioning, the accelerator sustained its rated value of 500 kV without beam acceleration.

Radiocaesium dynamics in forested watersheds in Fukushima Prefecture

Taniguchi, Keisuke*; Takeuchi, Yukio*; Fujita, Kazuki*; Dohi, Terumi; Hayashi, Seiji*; Kuramoto, Takayuki*; Nomura, Naoki*; Aono, Tatsuo*

no journal, , 

In Fukushima Prefecture, although decontamination has been completed except for difficult-to-return areas, most of the forest has not been decontaminated yet. From the forest, radiocaesium may enter rivers and affect downstream areas. A survey was conducted in three forested watersheds of the Nanokazawa, Saruta, Nuno rivers located in Fukushima Prefecture to understand the amount and characteristics of radiocaesium flowing out. In each watershed, suspended solids (SS) were collected by a suspended sand sampler, water was collected every few months, and the water level and flow rate were measured. After freeze-drying the SS sample, the concentration of suspended Cs-137 was measured by a germanium semiconductor detector. The water sample was filtered through a membrane filter with a pore size of 0.45 m, then the dissolved Cs-137 was collected by the solid-phase extraction disk method or AMP coprecipitation method, and the dissolved Cs-137 concentration was measured by a germanium semiconductor detector. The ranges of dissolved Cs-137 concentration in FY2019 were 69-190 mBq/L in the Saruta River, 9.7-16 mBq/L in the Nanokazawa river, and ND-3.2 mBq/L in the Nuno River. In the poster, we will also present the results of SS measurements and flow observations.