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Journal Articles

Welding technology on sector assembly of the JT-60SA vacuum vessel

Shibama, Yusuke; Okano, Fuminori; Yagyu, Junichi; Kaminaga, Atsushi; Miyo, Yasuhiko; Hayakawa, Atsuro*; Sagawa, Keiich*; Mochida, Tsutomu*; Morimoto, Tamotsu*; Hamada, Takashi*; et al.

Fusion Engineering and Design, 98-99, p.1614 - 1619, 2015/10

 Times Cited Count:3 Percentile:32.14(Nuclear Science & Technology)

The JT-60SA vacuum vessel (150 tons) is a double wall torus structure and the maximum major radius of 5.0 m and height of 6.6 m. The manufacturing design concept is that the vessel is split in the 10 toroidal sectors manufactured at factory, and assembled on-site; seven of the 40-degree sectors, two of the 30-degree beside final one, and the final of the 20-degree. The final sector is assembled with the VV thermal shield and toroidal field magnets into the 340-degree as prepared in one sector. Sectors are temporally fitted on-site and adjusted one over the other before the assembly. After measurement of the dimensions and the reference, these sectors are transferred onto the cryostat base. First, three 80-degree sectors are manufactured with mating each 40-degree sector by direct joint welding. The rest sectors including the final sector are jointed with splice plates. Welding manipulator and its guide rails are used for these welding. In this paper, the detail of the VV sectors assembly including the final sector is explained. Welding technologies to joint the two of 40-degree sectors are reported with the present manufacturing status and the welding trial on the vertical stub with the partial mock-up of the final sector are discussed with the assembly process.

Journal Articles

Dismantlement of large fusion experimental device JT-60U

Ikeda, Yoshitaka; Okano, Fuminori; Sakasai, Akira; Hanada, Masaya; Akino, Noboru; Ichige, Hisashi; Kaminaga, Atsushi; Kiyono, Kimihiro; Kubo, Hirotaka; Kobayashi, Kazuhiro; et al.

Nihon Genshiryoku Gakkai Wabun Rombunshi, 13(4), p.167 - 178, 2014/12

The JT-60U torus was disassembled so as to newly install the superconducting tokamak JT-60SA torus. The JT-60U used the deuterium for 18 years, so the disassembly project of the JT-60U was the first disassembly experience of a fusion device with radioactivation in Japan. All disassembly components were stored with recording the data such as dose rate, weight and kind of material, so as to apply the clearance level regulation in future. The lessons learned from the disassembly project indicated that the cutting technologies and storage management of disassembly components were the key factors to conduct the disassembly project in an efficient way. After completing the disassembly project, efforts have been made to analyze the data for characterizing disassembly activities, so as to contribute the estimation of manpower needs and the radioactivation of the disassembly components on other fusion devices.

Journal Articles

Safe disassembly and storage of radioactive components of JT-60U torus

Ikeda, Yoshitaka; Okano, Fuminori; Hanada, Masaya; Sakasai, Akira; Kubo, Hirotaka; Akino, Noboru; Chiba, Shinichi; Ichige, Hisashi; Kaminaga, Atsushi; Kiyono, Kimihiro; et al.

Fusion Engineering and Design, 89(9-10), p.2018 - 2023, 2014/10

 Times Cited Count:2 Percentile:19.81(Nuclear Science & Technology)

Disassembly of the JT-60U torus was started in 2009 after 18-years D$$_{2}$$ operations, and was completed in October 2012. The JT-60U torus was featured by the complicated and welded structure against the strong electromagnetic force, and by the radioactivation due to D-D reactions. Since this work is the first experience of disassembling a large radioactive fusion device in Japan, careful disassembly activities have been made. About 13,000 components cut into pieces with measuring the dose rates were removed from the torus hall and stored safely in storage facilities by using a total wokers of 41,000 person-days during 3 years. The total weight of the disassembly components reached up to 5,400 tons. Most of the disassembly components will be treated as non-radioactive ones after the clearance verification under the Japanese regulation in future. The assembly of JT-60SA has started in January 2013 after this disassembly of JT-60U torus.

JAEA Reports

Storage management of disassembled and radioactive components of JT-60 tokamak device; Storage of radioactive components by containers

Nishiyama, Tomokazu; Miyo, Yasuhiko; Okano, Fuminori; Sasajima, Tadayuki; Ichige, Hisashi; Kaminaga, Atsushi; Miya, Naoyuki; Sukegawa, Atsuhiko; Ikeda, Yoshitaka; Sakasai, Akira

JAEA-Technology 2014-006, 30 Pages, 2014/03

JAEA-Technology-2014-006.pdf:4.87MB

JT-60 tokamak device and the peripheral equipment were disassembled so as to be upgraded to the superconducting tokamak JT-60SA. The disassembled components were stored into storage and airtight containers at the radioactive control area. The total weight and the total number of those components are about 1,100 tons and about 11,500 except for large components. Radiation measurements and records of the radioactive components were required one by one under the law of Act on Prevention of Radiation Disease Due to Radioisotopes, etc. for the control of transport and storage from the radioactive control area to the other area. The storage management of the radioactive components was implemented by establishing the work procedure and the component management system by barcode tags. The radioactive components as many as 11,500 were surely and effectively stored under the law. The report gives the outline of the storage of JT-60 radioactive components by the storage containers.

JAEA Reports

Disassembly of JT-60 tokamak device and ancillary facilities for JT-60 tokamak

Okano, Fuminori; Ichige, Hisashi; Miyo, Yasuhiko; Kaminaga, Atsushi; Sasajima, Tadayuki; Nishiyama, Tomokazu; Yagyu, Junichi; Ishige, Yoichi; Suzuki, Hiroaki; Komuro, Kenichi; et al.

JAEA-Technology 2014-003, 125 Pages, 2014/03

JAEA-Technology-2014-003.pdf:13.32MB

The disassembly of JT-60 tokamak device and its peripheral equipments, where the total weight was about 5400 tons, started in 2009 and accomplished in October 2012. This disassembly was required process for JT-60SA project, which is the Satellite Tokamak project under Japan-EU international corroboration to modify the JT-60 to the superconducting tokamak. This work was the first experience of disassembling a large radioactive fusion device based on Radiation Hazard Prevention Act in Japan. The cutting was one of the main problems in this disassembly, such as to cut the wielded parts together with toroidal field coils, and to cut the vacuum vessel into two. After solving these problems, the disassembly completed without disaster and accident. This report presents the outline of the JT-60 disassembly, especially tokamak device and ancillary facilities for tokamak device.

JAEA Reports

Assembly work and transport of JT-60SA cryostat base

Okano, Fuminori; Masaki, Kei; Yagyu, Junichi; Shibama, Yusuke; Sakasai, Akira; Miyo, Yasuhiko; Kaminaga, Atsushi; Nishiyama, Tomokazu; Suzuki, Sadaaki; Nakamura, Shigetoshi; et al.

JAEA-Technology 2013-032, 32 Pages, 2013/11

JAEA-Technology-2013-032.pdf:8.86MB

Japan Atomic Energy Agency started to construct a fully superconducting tokamak experiment device, JT-60SA, to support the ITER since January, 2013 at the Fusion Research and Development Directorate in Naka, Japan. The JT-60SA will be constructed with enhancing the previous JT-60 infrastructures, in the JT-60 torus hall, where the ex-JT-60 machine was disassembled. The JT-60SA Cryostat Base, for base of the entire tokamak structure, were assembly as first step of this construction. The Cryostat Base (CB, 250 tons) is consists of 7 main made of stainless steel, 12m diameter and 3m height. It was built in the Spain and transported to the Naka site with the seven major parts split, via Hitachi port. The assembly work of these steps, preliminary measurements, sole plate adjustments of its height and flatness, and assembly of the CB. Introduces the concrete result of assembly work and transport of JT-60SA cryostat base.

JAEA Reports

Disassembly of JT-60 tokamak device

Okano, Fuminori; Ikeda, Yoshitaka; Sakasai, Akira; Hanada, Masaya; Ichige, Hisashi; Miyo, Yasuhiko; Kaminaga, Atsushi; Sasajima, Tadayuki; Nishiyama, Tomokazu; Yagyu, Junichi; et al.

JAEA-Technology 2013-031, 42 Pages, 2013/11

JAEA-Technology-2013-031.pdf:18.1MB

The disassembly of JT-60 tokamak device and its peripheral equipments, where the total weight was about 6200 tons, started in 2009 and accomplished in October 2012. This disassembly was required process for JT-60SA project, which is the Satellite Tokamak project under Japan-EU international corroboration to modify the JT-60 to the superconducting tokamak. This work was the first experience of disassembling a large radioactive fusion device based on Radiation Hazard Prevention Act in Japan. The cutting was one of the main problems in this disassembly, such as to cut the wielded parts together with toroidal field coils, and to cut the vacuum vessel into two. After solving these problems, the disassembly completed without disaster and accident. This report presents the outline of the JT-60 disassembly, especially tokamak device.

Journal Articles

Design study of JT-60SA vacuum pumping system

Kaminaga, Atsushi; Matsunaga, Go; Masaki, Kei; Sakasai, Akira

Heisei-24-Nendo Kyoto Daigaku Sogo Gijutsu Kenkyukai Hokokusho (CD-ROM), 4 Pages, 2013/03

no abstracts in English

Journal Articles

Flexible heat resistant neutron shielding resin

Sukegawa, Atsuhiko; Anayama, Yoshimasa*; Okuno, Koichi*; Sakurai, Shinji; Kaminaga, Atsushi

Journal of Nuclear Materials, 417(1-3), p.850 - 853, 2011/10

 Times Cited Count:20 Percentile:85.03(Materials Science, Multidisciplinary)

A flexible heat resistant neutron shielding material has been developed, which consists of polymer resin with 1 weight % boron. The neutron shielding performance of the developed resin, examined by the $$^{252}$$Cf neutron source is almost the same as that of the polyethylene. The outgas of H$$_{2}$$, H$$_{2}$$O, CO and CO$$_{2}$$ from the resin have been measured at 250 $$^{circ}$$C environment. The resin will be applied around the port of the vacuum vessel as an additional shielding material and prevented the effects on the neutron streaming of the superconducting tokamak device such as JT-60SA.

Journal Articles

Development of flexible neutron-shielding resin as an additional shielding material

Sukegawa, Atsuhiko; Anayama, Yoshimasa*; Onishi, Seiki; Sakurai, Shinji; Kaminaga, Atsushi; Okuno, Koichi*

Journal of Nuclear Science and Technology, 48(4), p.585 - 590, 2011/04

Soft-type neutron shielding resin has been developed by improving an existing hard-type neutron shielding material by the epoxy-based resin as the additional shielding material. A flexible heat resistant neutron shielding material has been developed, which consists of newly polymer-based resin with boron. The neutron shielding performance of the developed flexible heat resistant resin by the $$^{252}$$Cf neutron source is almost the same as that of the polyethylene. The outgas of H, H$$_{2}$$, NH$$_{4}$$, H$$_{2}$$O, CO, O$$_{2}$$, C$$_{4}$$H$$_{10}$$ and CO$$_{2}$$ from the developed resin have been measured at high temperature environment (250$$^{circ}$$C) by thermal desorption spectroscopy methods. The soft-type resin and the newly developed heat resistant resin will be applied to prevent the effects of the neutron streaming and to control the movement of vibrated pipe as the seal material around the plumbing in the future fast reactor and the innovative fission reactor.

Journal Articles

Fuelling characteristics of supersonic molecular beam injection in JT-60U

Takenaga, Hidenobu; Miyo, Yasuhiko; Bucalossi, J.*; Marty, V.*; Urano, Hajime; Asakura, Nobuyuki; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; Kaminaga, Atsushi

Nuclear Fusion, 50(11), p.115003_1 - 115003_10, 2010/11

 Times Cited Count:17 Percentile:59.53(Physics, Fluids & Plasmas)

The supersonic molecular beam injection (SMBI) was successfully operated in JT-60U. Frequent density jumps were clearly observed in the main plasma against the SMBI pulses with the background gas pressure ($$P$$$$_{rm BK}$$) of 2-6 bar. Fuelling efficiency exhibited weak dependence on $$P$$$$_{rm BK}$$ and the injection direction (high- and low-field-side injections). The amount of the fuelling necessary for achieving the same density level is much smaller for the SMBI than for the gas-puffing. It is comparable for the SMBI and the pellet injection even with shallower penetration of the SMBI as discussed below. The SMBI ionization area was estimated based on emission measured using the fast TV camera with a time resolution of 0.167 ms. The estimations indicated similar penetration position for $$P$$$$_{rm BK}$$ = 6 and 2 bar, although the ionization area was larger for 6 bar. This result supports the weak $$P$$$$_{rm BK}$$ dependence of the fuelling efficiency. The front of the ionization area moved between first and second frames of the fast TV camera and it reached just inside the separatrix in the second frame. The ionization area was significantly expanded from the expected SMB size and the expansion was also enhanced between two frames. These relatively slow changes between two frames suggest that interaction between SMB and plasma significantly influences the fuelling characteristics.

Journal Articles

The Characteristics of the internal transport barrier under reactor relevant conditions in JT-60U weak shear plasmas

Takenaga, Hidenobu; Oyama, Naoyuki; Urano, Hajime; Sakamoto, Yoshiteru; Asakura, Nobuyuki; Kamiya, Kensaku; Miyo, Yasuhiko; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; et al.

Nuclear Fusion, 49(7), p.075012_1 - 075012_11, 2009/07

 Times Cited Count:9 Percentile:36.96(Physics, Fluids & Plasmas)

Characteristics of internal transport barrier (ITB) have been investigated under reactor relevant condition with edge fuelling and electron heating in JT-60U weak shear plasmas. High confinement was sustained at high density with edge fuelling by shallow pellet injection or supersonic molecular beam injection (SMBI). The ion temperature (T$$_{i}$$) in the central region inside the ITB decreased due to cold pulse propagation even with edge fuelling. By optimizing the injection frequency and the penetration depth, the decreased central T$$_{i}$$ was recovered and good ITB was sustained with enhanced pedestal pressure. The T$$_{i}$$-ITB also degraded significantly with electron cyclotron heating (ECH), when stiffness feature was strong in the electron temperature (T$$_{e}$$) profile. The ion thermal diffusivity in the ITB region increased with the electron thermal diffusivity, indicating existence of clear relation between ion and electron thermal transport. On the other hand, T$$_{i}$$-ITB unchanged or even grew, when stiffness feature was weak in the T$$_{e}$$ profile. Density fluctuation level at ITB seemed to be unchanged during ECH, however, correlation length became longer in the T$$_{i}$$-ITB degradation case and shorter in the T$$_{i}$$-ITB unchanging case.

Journal Articles

Analysis of residual gas by high-resolution mass spectrometry during helium glow discharge cleaning in JT-60U

Hayashi, Takao; Kaminaga, Atsushi; Arai, Takashi; Sato, Masayasu

Fusion Engineering and Design, 84(2-6), p.908 - 910, 2009/06

 Times Cited Count:3 Percentile:26.15(Nuclear Science & Technology)

The residual gas analysis has been conducted by high-resolution mass spectrometry which can discriminate between D$$_{2}$$ and He gas species during helium glow discharge cleaning (He-GDC) in JT-60U in order to investigate the effect of He-GDC. The residual gas analyzer was able to distinguish between D$$_{2}$$ and He peaks during He-GDC. Since the He-GDC started, the partial pressure of D$$_{2}$$ gas increases with time and reached its highest pressure (3.8 $$times$$ 10$$^{-4}$$ Pa), which is about ten times larger than that before the He-GDC (3.5 $$times$$ 10$$^{-5}$$ Pa). The total amount of D$$_{2}$$, which was released during the He-GDC (7 hours), was evaluated as 4 Pa m$$^{3}$$. The pressure of D$$_{2}$$ (5.7 $$times$$ 10$$^{-6}$$ Pa) about 7 hours after the He-GDC (7 hours) is significantly lower than before the He-GDC, which indicates the He-GDC is effective to remove the deuterium from plasma facing components.

Journal Articles

RF heated wall conditioning discharges in JT-60U

Itami, Kiyoshi; Asakura, Nobuyuki; Tamai, Hiroshi; Moriyama, Shinichi; Kaminaga, Atsushi

Journal of Nuclear Materials, 390-391, p.983 - 987, 2009/06

 Times Cited Count:15 Percentile:72.74(Materials Science, Multidisciplinary)

In series of experiments in 2000 and 2008, ECRF (Electron Cyclotron Range of Frequency) wall conditioning discharges were extensively studied in JT-60U with toroidal magnetic field of $$B$$$$_{rm T}$$ = 3.6 T and ECRF heating power of PECH $$le$$ 2.5 MW. Homogeneous He (helium) conditioning discharges were reproducibly obtained by applying the horizontal field as large as 0.2% of $$B$$$$_{rm T}$$. It was found that the horizontal field is effective to extend He plasma toward high field side from the fundamental ECH resonant surfaces. The ECRF wall conditioning discharge with PECH = 2.5 MW and pulse length of $$t$$$$_{rm pulse}$$ = 1.5 s was applied to the plasma disruption with the stored energy of W = 3.3 MJ. And the successful recovery of the current ramp-up with 0.5 V/m of ohmic electric field was obtained.

Journal Articles

Conceptual design of JT-60SA cryostat

Shibama, Yusuke; Sakurai, Shinji; Masaki, Kei; Sukegawa, Atsuhiko; Kaminaga, Atsushi; Sakasai, Akira; Matsukawa, Makoto

Fusion Engineering and Design, 83(10-12), p.1605 - 1609, 2008/12

 Times Cited Count:5 Percentile:37.69(Nuclear Science & Technology)

The conceptual design of JT-60SA cryostat is summarized. JT-60SA is designed to be a fully superconducting device and assumed deuterium operation, therefore a cryostat is introduced to secure three functions, which are thermal insulation for entire superconducting magnets, bio-shielding, and gravity support for the entire tokamak device. The cryostat is required to cover up the tokamak devices, which are 15 m of total height and 7 m of radius, and to support the total devices weight of 2550 tons. The cryostat consists of vessel body, gravity support and auxiliary facilities, such as 80 K thermal shield and exhaust system. Each of them is outlined with JT-60SA design conditions, and the operational condition of auxiliary system is clarified, especially, capacity of the exhaust system, which is related to the 80 K thermal shield design.

Journal Articles

Characteristics of internal transport barrier under reactor relevant condition in JT-60U weak shear plasmas

Takenaga, Hidenobu; Oyama, Naoyuki; Urano, Hajime; Sakamoto, Yoshiteru; Kamiya, Kensaku; Miyo, Yasuhiko; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; Kaminaga, Atsushi; et al.

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

Characteristics of internal transport barrier (ITB) have been investigated under reactor relevant condition with edge fuelling and electron heating in JT-60U weak shear plasmas. High confinement was sustained at high density with edge fuelling by shallow pellet injection or supersonic molecular beam injection (SMBI). The ion temperature ($$T_{i}$$) in the central region decreased even with edge fuelling. The $${it T}_{i}$$ decrease with edge fuelling was larger inside the ITB than that outside the ITB, which can be described by cold pulse propagation using the ion thermal diffusivity ($$chi_{i}$$) estimated from power balance analysis in the SMBI case. By optimizing the injection frequency and the penetration depth, the decreased $$T_{i}$$ was recovered and good ITB was sustained with enhanced pedestal pressure. The $$T_{i}$$-ITB also degraded significantly when stiffness feature was strong in the electron temperature ($$T_{e}$$) profile against electron cyclotron heating (ECH). The value of $$chi_{i}$$ in the ITB region increased with the electron thermal diffusivity ($${it chi}_{e}$$), indicating existence of clear relation between ion and electron thermal transport. On the other hand, $$T_{i}$$-ITB unchanged or even grew, when stiffness feature was weak in the $$T_{e}$$ profile. Density fluctuation level seemed to be unchanged during ECH, however, correlation length became longer in the $${it T}_{i}$$-ITB degradation case and shorter in the $$T_{i}$$-ITB unchanging case.

Journal Articles

Tokamak machine monitoring and control system for JT-60

Miyo, Yasuhiko; Yagyu, Junichi; Nishiyama, Tomokazu; Honda, Masao; Ichige, Hisashi; Kaminaga, Atsushi; Sasajima, Tadayuki; Arai, Takashi; Sakasai, Akira

Fusion Engineering and Design, 83(2-3), p.337 - 340, 2008/04

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Development of 300$$^{circ}$$C heat resistant boron-loaded resin for neutron shielding

Morioka, Atsuhiko; Sakurai, Shinji; Okuno, Koichi*; Sato, Satoshi; Verzirov, Y. M.; Kaminaga, Atsushi; Nishitani, Takeo; Tamai, Hiroshi; Shibama, Yusuke; Yoshida, Shigeru*; et al.

Journal of Nuclear Materials, 367-370(2), p.1085 - 1089, 2007/08

 Times Cited Count:22 Percentile:82.92(Materials Science, Multidisciplinary)

A 300$$^{circ}$$C heat-resistant neutron shielding material is newly developed, which consists of phenol-based resin with 6 weight-% boron. The neutron shielding performance of the developed resin, examined by the $$^{252}$$Cf neutron source, is almost the same as that of the polyethylene. The neutron shielding characteristic was also estimated by 3D Monte Carlo Code MCNP-4C2 using the continuous energy cross section data sets based on the JENDL-3.2. The calculation result agrees well with the experimental result. To understand the kinds of the outgas from the developed resin in the high temperature region, the mass spectrum of the outgas was measured until $$sim$$300$$^{circ}$$C by Thermal Desorption Specroscopy (TDS). The observed mass number was 2, 17, 18, 28, 32, and 44. The number corresponds to hydrogen (H$$_{2}$$), ammonia (NH$$_{3}$$), water (H$$_{2}$$O), carbon monoxide (CO), oxygen (O$$_{2}$$), carbon dioxide (CO$$_{2}$$), respectively. The main outgas component from the resin at 100$$sim$$150$$^{circ}$$C was NH $$_{3}$$ and H$$_{2}$$O. The outgas of NH$$_{3}$$ and H$$_{2}$$O from the resin have been measured, however, the neutron shielding performance of the resin after 200$$^{circ}$$C baking was almost the same as that before baking. The quantitative analysis of the outgas from the resin in the high temperature region was done by the Temperature Programmed Desorption (TPD) / Gas Chromatography and Mass spectrometry (GC/MS). The 13 kinds of organic gases have been observed by the amount of $$mu$$g/g at 300$$^{circ}$$C. The neutron shielding performance of the developed resin at 300$$^{circ}$$C was simulated by the 3D analysis. The resonance cross section of the nucleus is broad at the high temperature region by the Doppler effect. The calculation results using 327$$^{circ}$$C library and 20$$^{circ}$$C library are almost same.

Journal Articles

Pulsed supersonic gas injection installation for JT-60

Miyo, Yasuhiko; Nishiyama, Tomokazu; Takenaga, Hidenobu; Kaminaga, Atsushi; Sasajima, Tadayuki; Masaki, Kei

Heisei-18-Nendo Nagoya Daigaku Sogo Gijutsu Kenkyukai Sochi Gijutsu Kenkyukai Hokokushu, p.124 - 127, 2007/03

no abstracts in English

Journal Articles

Characterization of JT-60U exhaust gas during experimental operation

Isobe, Kanetsugu; Nakamura, Hirofumi; Kaminaga, Atsushi; Tsuzuki, Kazuhiro; Higashijima, Satoru; Nishi, Masataka; Kobayashi, Yasunori*; Konishi, Satoshi*

Fusion Engineering and Design, 81(1-7), p.827 - 832, 2006/02

 Times Cited Count:11 Percentile:63.08(Nuclear Science & Technology)

Exhaust gas from JT-60U during experimental operation has been measured with Gas Chromatography (GC), and the gas exhaust characteristic from JT-60U on plasma discharge conditions has been investigated during the JT-60U experimental campaign in 2003-2004. During experimental operation of JT-60U, hydrogen isotope concentration strongly depended on the type of discharges such as high performance, long pulse and so on. On the other hand, impurity species, such as helium, hydrocarbon and carbon oxide, were detected during plasma discharges occasionally. During the experimental operation, plasma disruption remarkably tended to produce high concentration impurities. Glow discharge and Taylor discharge for wall conditioning also produced impurities. In the case of normal plasma, impurity was detected and high performance plasma, such as high $$beta$$ plasma, tended to produce high concentration impurities. This result indicated that impurities concentration might be higher in the case of normal plasma in ITER, because of its high performance.

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