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Takahara, Shogo; Iimoto, Takeshi*; Igarashi, Takayuki*; Kawabata, Masako*
Journal of Radiation Protection and Research, 50(1), p.1 - 9, 2025/03
The Health Physics Society of Japan established a working group to obtain insights and findings from articles related to the 1F accident, published in the Japanese Journal of Health Physics. This study describes the review results of 47 articles classified into the field without risk communication, environmental measurement and monitoring, radiation dose measurement and assessment, radiation medicine, and radioactive waste. The reviewed articles contain various insights and issues depending on the authors' standpoints and relevant social interests. As a result, the 1F accident relevant articles offer various discussion points depending on the authors' awareness of the issues, which give an opportunity to make reconsiderations on what kind of academic system health physics or radiation protection should be on the basis of the experiences from the 1F accident. Note that this is an English translation of an article published in Japanese Journal of Health Physics.
Takahara, Shogo; Iimoto, Takeshi*; Igarashi, Takayuki*; Kawabata, Masako*
Hoken Butsuri (Internet), 58(2), p.50 - 58, 2023/08
The Health Physics Society of Japan established a working group to obtain the insights and findings from the articles, which are related to the Fukushima Daiichi Nuclear Power Station (1F) accident, published in the Japanese Journal of Health Physics. This paper describes the results of the review on 47 articles, which are classified into the field without risk communication, environmental measurement and monitoring, radiation dose measurement and assessment, radiation medicine and radioactive waste. In the reviewed articles, there are various insights and issues depending on the standpoint of the authors and social interests in the timing those published. It is important to face these insights and issues to consider prudently "what is health physics or radiation protection?" for the future development of the Health Physics society.
Nagai, Yasuki; Hashimoto, Kazuyuki; Hatsukawa, Yuichi; Saeki, Hideya; Motoishi, Shoji; Sonoda, Nozomi; Kawabata, Masako; Harada, Hideo; Kin, Tadahiro*; Tsukada, Kazuaki; et al.
Journal of the Physical Society of Japan, 82(6), p.064201_1 - 064201_7, 2013/06
Times Cited Count：47 Percentile：84.90(Physics, Multidisciplinary)Kobayashi, Takayuki; Isayama, Akihiko; Fasel, D.*; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; et al.
Journal of Plasma and Fusion Research SERIES, Vol.9, p.363 - 368, 2010/08
Improvements are required for expanding the pulse length of the JT-60 ECRF system (5s) for JT-60SA (100s). Newly developed power supplies will be fabricated and installed by EU. The conditioning operation of an improved gyrotron equipping a newly designed mode convertor has been started. The mode convertor will reduce heat flux on the internal components and therefore expected to enable long pulse operation at 1 MW. Pre-programmed and/or feedback control of the heater current and anode voltage, which was successfully demonstrated in JT-60U, will be key techniques because the beam current decreases during a shot. The evacuated transmission lines have a capability of 1 MW per line. Since maintenance of the components in the vacuum vessel is difficult, a linear motion antenna concept was proposed to reduce risks of water leakage and fault of the driving mechanism in the vacuum vessel. The detailed design and the low power test of a mock-up antenna have been started.
Kobayashi, Takayuki; Terakado, Masayuki; Sato, Fumiaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Hiranai, Shinichi; Igarashi, Koichi; et al.
Plasma and Fusion Research (Internet), 4, p.037_1 - 037_10, 2009/08
Electron cyclotron (EC) heating and current drive (CD) are key tools to control fusion plasma especially for effective electron heating and for suppression of neoclassical tearing mode (NTM). Recently, developments of a high power gyrotron and a power modulation technique have been successfully achieved on JT-60U ECRF system in order to enhance the system performance. Stable gyrotron oscillation with oscillation power of 1.5 MW for 1 s was demonstrated in 2007, for the first time. Then temperature rise of cavity and collector has been investigated. It has been shown that the longer pulse operation with 1.5 MW by an improved 110 GHz gyrotron is possible. In addition, modulated ECCD in synchronized with NTM rotation has been performed with the oscillation power of 0.8 MW and the frequency around 5 kHz. The synchronizing system has worked very well and it has played an essential role in NTM suppression experiments on JT-60U.
Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Terakado, Masayuki; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Hiranai, Shinichi; et al.
Nuclear Fusion, 49(8), p.085001_1 - 085001_7, 2009/07
Times Cited Count：21 Percentile：58.89(Physics, Fluids & Plasmas)In the gyrotron development in JT-60U ECRF system, output power of 1.5 MW for 1 s has been achieved at 110 GHz. It is the world highest power oscillation 
1 s. In addition to the carefully designed cavity and collector in view of thermal stress, an RF shield for the adjustment bellows, and a low-dielectric-loss DC break enabled this achievement. Power modulation technique by anode voltage control was improved to obtain high modulation frequency and 5 kHz has been achieved for NTM stabilizing experiments. Long pulse demonstration of 0.4 MW, 30 s injection to the plasma has been achieved with real time control of anode/cathode-heater. It has been confirmed that the temperature of cooled components were saturated and no evidence of damage were found. An innovative antenna having wide range of beam steering capability with linearly-moving-mirror concept has been designed for long pulse. Beam profile and mechanical strength analyses shows the feasibility of the antenna.
Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Igarashi, Koichi; Sato, Fumiaki; Wada, Kenji; et al.
JAEA-Technology 2008-065, 98 Pages, 2008/10
JAEA-Technology-2008-065.pdf:38.83MB
Construction of the JT-60SA (super advanced) is planned as an upgrade of JT-60U as the satellite tokamak in ITER broader approach and as the national centralized tokamak facility program in Japan. The present JT-60U will be disassembled and the JT-60SA will be constructed at the same location in the JT-60 tours hall. The disassembly work will be planned in the period from 2009 to 2011. In this report, disassembly of the radio frequency heating system of JT-60U in the amplifier rooms and heating power supply building is studied on (1) object for disassembly, (2) work plan, (3) estimation of materials amount, (4) procedure.
Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Terakado, Masayuki; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Hiranai, Shinichi; et al.
Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10
In the gyrotron development in JT-60U ECRF system, output power of 1.5 MW for 1 s has been achieved at 110 GHz. It is the world highest power oscillation 1 s. In addition to the carefully designed cavity and collector in view of thermal stress, an RF shield for the adjustment bellows, and a low-dielectric-loss DC break enabled this achievement. Power modulation technique by anode voltage control was improved to obtain high modulation frequency and 5 kHz has been achieved for NTM stabilizing experiments. Long pulse demonstration of 0.4 MW, 30 s injection to the plasma has been achieved with real time control of anode/cathode-heater. It has been confirmed that the temperature of cooled components were saturated and no evidence of damage were found. An innovative antenna having wide range of beam steering capability with linearly-moving-mirror concept has been designed for long pulse. Beam profile and mechanical strength analyses shows the feasibility of the antenna.
Isayama, Akihiko; Kobayashi, Takayuki; Moriyama, Shinichi; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Terakado, Masayuki; Hiranai, Shinichi; et al.
no journal, ,
no abstracts in English
Moriyama, Shinichi; Kobayashi, Takayuki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Igarashi, Koichi; et al.
no journal, ,
no abstracts in English
Moriyama, Shinichi; Kobayashi, Takayuki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Igarashi, Koichi; et al.
no journal, ,
The electron cycrotron range of frequency (ECRF) system (3 MW
5 s at 110 GHz with 4 gyrotrons) will be upgraded to the system having 9 gyrotrons (7 MW 
100 s at 110 GHz and 140 GHz) for JT-60SA (super advanced). For the reference antenna design having rotary mirrors, an effective and reliable method of mirror cooling without water is under consideration. As an alternative antenna design, a new concept with a mirror driven in the linear motion which eliminates the flexible tube for coolant supply is under development. The design study featuring beam profile calculation showed feasibility of the antenna in the 0.48 m 0.48 m port. On the gyrotron development, 1.5 MW, 1s has been achieved using Si
N
insulator instead of Al
O. Improvement of the mode converter is in progress and the test aiming at 1 MW, 100 s oscillation will be started in March.
Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; et al.
no journal, ,
Full specification of 4 MW for 5s was achieved by simultaneous operation of 4 gyrotrons, and 3 MW was injected to the JT-60U plasma by the completion of experiments in August 2008. In the inspection of the antenna after the operation, there were no large damages but the color of the mirror surfaces were slightly changed and some evidences of arcing were found. In the statistical analysis of operation, the rate of successful shots to the plasma was higher than 85% in the last 3 years. Development of long-pulse gyrotron with improved mode converter is on going and the conditioning was started in the end of 2008 aiming at 1 MW, 100s for JT-60SA. It was confirmed that the diffraction loss was remarkably decreased and the pulse length reached 1 MW 17s so far. A new operation technique of active anode voltage control was developed to obtain high efficiency, and the pulse length for 1.5 MW oscillation was extended from 1s to 4s.
Kobayashi, Takayuki; Moriyama, Shinichi; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; Igarashi, Koichi; et al.
no journal, ,
In JT-60SA, 7 MW of electron cyclotron heating and current drive will be performed with four units of 110 GHz and five units of 140 GHz electron cyclotron range of frequency (ECRF) systems. Transmission lines will be connected into four upper outer ports where quasi-optical antennas will be installed. Two types of antenna systems are being considered. One is a conventional type rotation antenna and the other is a new concept antenna which can control incident angle by a linearly driven mirror. Those antennas are now being evaluated from the view points of cooling structure, the range of incident angle and beam width. In addition, 1.5 MW for 1 s oscillation was carried out by one gyrotron of JT-60U ECRF system. Moreover, the present 110 GHz gyrotron will be improved which aims at the development of JT-60SA gyrotron. In this presentation, current status of design study for JT-60SA ECRF system and the latest results of the JT-60U ECRF system will be presented.
Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; et al.
no journal, ,
no abstracts in English
Moriyama, Shinichi; Kobayashi, Takayuki; Isayama, Akihiko; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Sawahata, Masayuki; Suzuki, Sadaaki; Terakado, Masayuki; Hiranai, Shinichi; et al.
no journal, ,
The electron cyclotron range of frequency (ECRF) system (3 MW 5s at 110 GHz with 4 gyrotrons) of JT-60U will be upgrade to the system having 9 gyrotrons (7 MW 100s) for JT-60SA (super advanced). As heat removal from the mirrors is essential for a long pulse antenna, a new concept with a mirror driven in the linear motion which eliminates the flexible tube for coolant supply is under development. The design study featuring beam profile calculation showed feasibility of the antenna in the 0.48 m 0.48 m port. The low power rf test with simple mockup antenna has just been begun. Aging of the gyrotron with improved mode converter was started in the end of 2008, aiming at 1 MW, 100s oscillation. Because the current capacity of the present high voltage power supply is not enough to realize 100s oscillation, LHRF power supply having twice larger current capacity is connected to the gyrotron in March 2009. The gyrotron aging will be started soon again.
Kobayashi, Takayuki; Isayama, Akihiko; Sawahata, Masayuki; Terakado, Masayuki; Shimono, Mitsugu; Igarashi, Koichi; Hinata, Jun; Kajiwara, Ken; Kasugai, Atsushi; Sakamoto, Keishi; et al.
no journal, ,
High power gyrotron operation at an output power of 1.5 MW was carried out using the JT-60 gyrotron. Pulse length had been limited to 100 ms at an output power of well exceeding 1 MW. An oscillation at 1.5 MW with a pulse length of 1 s was demonstrated, for the first time, in 2007 by the JT-60 gyrotron. We evaluated the heat load on each component of the gyrotron and it was shown that the gyrotron could be operated at 1.5 MW with the pulse length of up to 3 s from the view point of the heat load. In 2009, we tried the operation at the output power of 1.5 MW aiming at the demonstration of the pulse length of 3 s or longer. An operation technique, by which an anode voltage was changed only at the beginning of the pulse, was developed and it resulted in obtaining relatively higher oscillation efficiency. The oscillation at 1.5 MW for 4 s was demonstrated for the first time.
Isayama, Akihiko; Kobayashi, Takayuki; Moriyama, Shinichi; Sawahata, Masayuki; Suzuki, Sadaaki; Yokokura, Kenji; Shimono, Mitsugu; Hasegawa, Koichi; Terakado, Masayuki; Hiranai, Shinichi; et al.
no journal, ,
no abstracts in English
Terakado, Masayuki; Kobayashi, Takayuki; Sato, Fumiaki; Sawahata, Masayuki; Suzuki, Sadaaki; Shimono, Mitsugu; Hiranai, Shinichi; Igarashi, Koichi; Suzuki, Takashi; Wada, Kenji; et al.
no journal, ,
no abstracts in English
Terakado, Masayuki; Shimono, Mitsugu; Sawahata, Masayuki; Igarashi, Koichi; Sato, Fumiaki; Wada, Kenji; Kobayashi, Takayuki; Moriyama, Shinichi; Fujii, Tsuneyuki
no journal, ,
no abstracts in English
Kobayashi, Takayuki; Isayama, Akihiko; Terakado, Masayuki; Sato, Fumiaki; Sawahata, Masayuki; Suzuki, Sadaaki; Hiranai, Shinichi; Igarashi, Koichi; Wada, Kenji; Shimono, Mitsugu; et al.
no journal, ,
It is recognized that stabilization of neoclassical tearing mode (NTM) instabilities using power modulated electron cyclotron current drive (ECCD) is effective. Although a modulation frequency of around 5 kHz was required to NTM suppression experiments in JT-60U, the achieved frequency had been limited to 3 kHz due to the slow response time of the high voltage circuit and over-current during charging/discharging. In this study, the anode voltage divider of the system was improved and the capacitance and resistance in the high voltage circuit was optimized resulting in the modulation frequency of over 5 kHz. The robust modulated operation region was also studied with suppressing undesired mode. Moreover, the real-time synchronizing system was developed to control the phase and duty ratio of the modulated ECCD synchronizing with the NTM frequency which varies during ECCD with plasma rotation, and modulated ECCD experiments with NTM suppression was carried out in JT-60U.
