A Linear Equation of characteristic time profile of power in subcritical quasi-steady state

Yamane, Yuichi

Journal of Nuclear Science and Technology, 57(8), p.926 - 931, 2020/08

https://doi.org/10.1080/00223131.2020.1736682

An equation of power in subcritical quasi-steady state has been derived based on one-point kinetics equations for the purpose of utilizing it for the development of timely reactivity estimation from complicated time profile of neutron count rate. It linearly relates power, , to a new variable , which is a function of time differential of the power. It has been confirmed by using one-point kinetics code, AGNES, that the calculated points () are perfectly in a line described by the new equation and that points () calculated from transient subcritical experiments by using TRACY made a line with a slope indicated by the new equation.

Progress of neutral beam injection system on JT-60U for long pulse operation

Ikeda, Yoshitaka; NBI Heating Group; NCT Design Team

Journal of the Korean Physical Society, 49, p.S43 - S47, 2006/12

There are two type of NBI systems on JT-60U. One is the positive ion-based NBI (P-NBI) to inject the beam energy of 80-85 kV. The other is the negative ion-based NBI (N-NBI) at the beam energy more than 350 keV. Recently the pulse duration of NBI system was required to extend up to 30 sec so as to study long pulse plasmas. The four P-NBI units, which tangentially inject neutral beam to plasma, were modified to extend the pulse duration up to 30 sec with 2 MW/unit at 85 keV. The seven P-NBI units, each of which perpendicularly injects for 10 sec, were conducted to operate in series for the total pulse duration of 30 sec. The ion source of the N-NBI unit was also modified to reduce the heat load of the grid for 30 sec operation. The pulse duration was extended up to 25 sec, 1 MW at the beam energy of 350keV. In the next step, further pulse extension of NBI up to 100 sec is planned for the modified JT-60U with superconducting coils (so called NCT). This paper reports the recent progress of the NBI system on JT-60U and the design study of the upgraded NBI system for NCT.

N-NBI heating and current drive in JT-60U towards steady-state tokamak

Ikeda, Yoshitaka; Oikawa, Toshihiro; Ide, Shunsuke

Purazuma, Kaku Yugo Gakkai-Shi, 81(10), p.773 - 778, 2005/10

https://doi.org/10.1585/jspf.81.773

In steady-state tokamak fusion reactors, an efficient external current drive and a large fraction of the bootstrap current are required for non-inductive operation at low circulating power. NBI is a powerful and reliable actuator for current drive and heating. A negative ion-based NBI (N-NBI) with a high beam energy more than 350 keV has been installed in the JT-60U tokamak in order to study the NBI current drive and heating in an ITER relevant regime. This paper presents recent progress of N-NBI experiments and its system in JT-60U towards steady-state operation for ITER and tokamak fusion reactors.

Progress in physics basis and its impact on ITER

Shimada, Michiya; Campbell, D.*; Stambaugh, R.*; Polevoi, A. R.*; Mukhovatov, V.*; Asakura, Nobuyuki; Costley, A. E.*; Donn, A. J. H.*; Doyle, E. J.*; Federici, G.*; et al.

Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/11

This paper summarises recent progress in the physics basis and its impact on the expected performance of ITER. Significant progress has been made in many outstanding issues and in the development of hybrid and steady state operation scenarios, leading to increased confidence of achieving ITER's goals. Experiments show that tailoring the current profile can improve confinement over the standard H-mode and allow an increase in beta up to the no-wall limit at safety factors 4. Extrapolation to ITER suggests that at the reduced plasma current of 12MA, high Q 10 and long pulse (1000 s) operation is possible with benign ELMs. Analysis of disruption scenarios has been performed based on guidelines on current quench rates and halo currents, derived from the experimental database. With conservative assumptions, estimated electromagnetic forces on the in-vessel components are below the design target values, confirming the robustness of the ITER design against disruption forces.

Steady-state operation scenarios with a central current hole for JT-60SC

Tamai, Hiroshi; Ishida, Shinichi; Kurita, Genichi; Shirai, Hiroshi; Tsuchiya, Katsuhiko; Sakurai, Shinji; Matsukawa, Makoto; Sakasai, Akira

Fusion Science and Technology, 45(4), p.521 - 528, 2004/06

https://doi.org/10.13182/FST04-A527

The 1.5D time-dependent transport analysis has been carried out to investigate steady state operation scenarios with a central current hole by off-axis current drive schemes consistent with a high bootstrap current fraction for a large superconducting tokamak JT-60SC. A steady state operation scenario with HH=1.4 and =3.7 has been obtained at I=1.5 MA, B=2 T and q=5 where non-inductive currents are developed during the discharge to form a current hole with beam driven currents by tangential off-axis beams in combination with bootstrap currents by additional on-axis perpendicular beams. The bootstrap fraction increases up to nearly 75% of the plasma current and the current hole region is enlarged up to about 30% of the minor radius at 35 s from the discharge initiation. The current hole is confirmed to be sustained afterward for a long duration of 60 s. The stability analysis shows that the beta limit with the conducting wall can be about =4.5, which is substantially above the no wall ideal MHD limit.

A Review of internal transport barrier physics for steady-state operation of tokamaks

Connor, J. W.*; Fukuda, Takeshi*; Garbet, X.*; Gormezano, C.*; Mukhovatov, V.*; Wakatani, Masahiro*; ITB Database Group; ITPA Topical Group on Transport and Internal Barrier Physics*

Nuclear Fusion, 44(4), p.R1 - R49, 2004/04

https://doi.org/10.1088/0029-5515/44/4/R01

This paper first reviews the present state of theoretical and experimental knowledge regarding the formation and characteristics of ITBs in tokamaks. Specifically, the current status of theoretical modeling of ITBs is presented; then, an international ITB database based on experimental information extracted from some nine tokamaks is described and used to draw some general conclusions concerning the necessary conditions for ITBs to appear, comparing these with the theoretical models. The experimental situation regarding the steady-state, or at least quasi-steady-state, operation of tokamaks is reviewed and finally the issues and prospects for achieving such operational modes in ITER are discussed.

Evaluation of susceptibility on crevice corrosion for ITER vacuum vessel

Nakahira, Masataka

JAERI-Tech 2003-083, 79 Pages, 2003/11

JAERI-Tech-2003-083.pdf:10.29MB

The ITER Vacuum Vessel has a double-walled structure and cooling water is filled in between inner and outer shells. It is planned to apply T-welded joints with partial penetration at the connection between outer shell and rib. The length and gap of non-penetrated part are controlled and limited to less than 5mm and 0.5mm respectively. Although it can be considered to be low susceptibility, crevice corrosion can possibly occur, because the water is stagnant in the crevice and impurities will condense. In this report, the corrosion-crevice repassivation potential, E, was experimentally measured under the several density of NaCl solution, and compared to the steady-state corrosion potential in the pertinent environment, to evaluate the susceptibility. Simulated conditions are normal operating condition with water temperature of 150C, baking operation with water temperature of 200C and impurity condense by cyclic wet and dry condition.

Observation of high recycling steady H-mode edge and compatibility with improved core confinement mode on JFT-2M

Kamiya, Kensaku; Kimura, Haruyuki; Ogawa, Hiroaki; Kawashima, Hisato; Tsuzuki, Kazuhiro; Sato, Masayasu; Miura, Yukitoshi; JFT-2M Group

Nuclear Fusion, 43(10), p.1214 - 1219, 2003/10

https://doi.org/10.1088/0029-5515/43/10/024

no abstracts in English

Dynamics of plasma during the formation of a weak negative central magnetic shear configuration using counter neutral beam injection in the JFT-2M tokamak

Kamiya, Kensaku; Kimura, Haruyuki; Ogawa, Hiroaki; Kawashima, Hisato; Tsuzuki, Kazuhiro; Isei, Nobuaki; Sato, Masayasu; Shinohara, Koji

Purazuma, Kaku Yugo Gakkai-Shi, 78(12), p.1361 - 1367, 2002/12

https://doi.org/10.1585/jspf.78.1361

no abstracts in English

Noninductive current drive and steady-state operation in JT-60U

Ushigusa, Kenkichi; Ide, Shunsuke; Oikawa, Toshihiro; Suzuki, Takahiro; Kamada, Yutaka; Fujita, Takaaki; Ikeda, Yoshitaka; Naito, Osamu; Matsuoka, Mamoru*; Kondoh, Takashi; et al.

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.255 - 277, 2002/09

https://doi.org/10.13182/FST02-A228

Studies on non-inductive current drive and development of an integrated steady-state high performance operation in JT-60 are reviewed. Experiments on lower hybrid current drive in JT-60 haven shown a large non-inductive current up to 3.5MA, high current drive efficiency of 3.6x1019m-2A/W. Basic studies on LH waves in JT-60 have contributed to understand current drive physics. Significant progress in neutral beam current drive has been made in JT-60 by testing the performance of negative ion based NBI (N-NBI). The CD efficiency of ~1.5x1019m-2A /W, and N-NB driven current of ~1MA have been demonstrated in N-NBCD. Strongly localized driven current by electron cyclotron current drive was identified with a fundamental O-mode scheme. Efficiency of 0.5x1019m-2A/W and EC driven current of 0.2MA were achieved and suppression of neo-classical tearing mode was demonstrated. Based on these developments, two integrated steady-state operation scenarios were developed in JT-60, which are reversed magnetic shear (R/S) plasmas and high bp ELMy H-mode. In these operation regimes, discharges have been sustained near the steady-state current profile under full non-inductive current drive. High performance plasmas with a high nDotETio and at high normalized density were also produced under fully non-inductive condition in high bp ELMy H-mode and R/S mode.