M. Iwase

Kindai University

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H. Idei

Kyushu University

S. Kubo

Hokkaido University

ΚO

Κ. Ohkubo

University of Fukui

S. Okamura

National Institute for Fusion Science

T. Watari

National Institute for Fusion Science

K. Ida

National Institute for Fusion Science

K. Narihara

National Institute for Fusion Science

R. Kumazawa

The University of Tokyo

Y. Kusama

Toyo University

A. Ejiri

The University of Tokyo

Cooperative Institutions

National Institute for Fusion Science

National Institutes of Natural Sciences

The Graduate University for Advanced Studies, SOKENDAI

Nagoya University

The University of Tokyo

Kyoto University

Kyushu University

Japan Atomic Energy Agency

Advanced Science Research Center

Princeton Plasma Physics Laboratory

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Papers

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High power local ECH in CHS

AIP conference proceedings (1996)

S. Kubo H. Idei M. Iwase Κ. Ohkubo T. Minami

Electron cyclotron heating (ECH) experiments with 200 kW and 400 kW gyrotrons at the frequency of 53.2 GHz have been performed in Compact Helical System (CHS). Microwave power from both gyrotrons is transmitted with quasi‐optical transmission line and highly focused on the mid‐plane of CHS. The main purpose of these experiments is to understand the heating and energy transport mechanisms in CHS at the low collisional regime. The combination of the magnetic field, focal position and polarization enables the investigation of the on/off axis local heating effect with fundamental and second harmonic ECH.

Gyrotron

Harmonic

Harmonic Analysis

10.1063/1.49570

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Citations (0)

Statistical Estimation of Electron Power Deposition Profile by Power Balance Analysis

Annual report of National Institute for Fusion Science/Annual report (2014)

M. Iwase S. Kubo H. Idei Κ. Ohkubo

Power Balance

Deposition

Power analysis

Statistical Analysis

Source

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Citations (0)

Characteristics of Alfvén eigenmodes, burst modes and chirping modes in the Alfvén frequency range driven by negative ion based neutral beam injection in JT-60U

Nuclear Fusion (1999)

Y. Kusama G. Krämer H. Kimura M. Saigusa T. Ozeki

The excitation and stabilization of Alfvén eigenmodes and their impact on energetic ion confinement were investigated with negative ion based neutral beam injection at 330-360 keV into weak or reversed magnetic shear plasmas on JT-60U. Toroidicity induced Alfvén eigenmodes (TAEs) were observed in weak shear plasmas with ⟨βh⟩ ⩾ 0.1% and 0.4 ⩽ vb||/vA ⩽ 1. The stability of TAEs is consistent with predictions by the NOVA-K code. New burst modes and chirping modes were observed in the higher β regime of ⟨βh⟩ ⩾ 0.2%. The effect of TAEs, burst modes and chirping modes on fast ion confinement has been found to be small so far. It was found that a strongly reversed shear plasma with internal transport barrier suppresses AEs.

Chirp

Neutral Beam Injection

10.1088/0029-5515/39/11y/324

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Citations (78)

Antenna and transmission system for high power electron cyclotron heating in a compact helical system

Fusion Engineering and Design (1995)

S. Kubo Κ. Ohkubo H. Idei Masahiko Sato Y. Takita

Gyrotron

Power transmission

Gaussian beam

Microwave transmission

Transmission system

10.1016/0920-3796(94)00197-f

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Citations (23)

Effects of low particle fuelling and electron heating on the internal transport barrier in ICRF heated reversed magnetic shear plasmas of JT-60U

Plasma Physics and Controlled Fusion (1999)

M. Iwase Y. Koide K. Tobita S. Moriyama H. Takenaga

Plasmas with an internal transport barrier (ITB) were heated with a second-harmonic ion cyclotron range of frequency (ICRF) minority heating during the reversed magnetic shear (RS) experiments in JT-60U. In order to control the central particle fuelling, the input power of the neutral beam injection (NBI) heating during ICRF heating was scanned shot-by-shot. The electron temperature gradient around the ITB increased with the total input power. Steeper gradients were obtained with additional ICRF heating by avoiding collapses induced by the steep pressure gradient. The difference of the time derivative at the ICRF injection timing indicated a fast ion loss of about 40% during the RS operation. The density gradient was increased with the central fuelling by the NBI heating and the shoulder position of the slope at the ITB moved outward with the particle fuelling. The particle confinement time at the ITB increased with the central particle fuelling while the particle confinement time of the low-fuelling discharges were similar to that of the normal shear L-mode discharge.

Particle (ecology)

10.1088/0741-3335/41/9/310

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Citations (3)

RF heating experiments in CHS and RF development for LHD

AIP conference proceedings (1997)

T. Watari R. Kumazawa Kazuo Nishimura T. Mutoh T. Seki

A compact helical system has been used to examine the key ideas for ICR heating in the large helical device, which is in its final construction phase. Two types of antennas used in the initial stage of heating. The temporal evolution of plasma parameters, their dependence on the magnetic field, and the confinement time are obtained in the heating experiments.

Large Helical Device

Dielectric Heating

Heating system

Induction Heating

Plasma confinement

Electromagnetic heating

10.1063/1.53392

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Citations (1)

Band Rejection Filter for Measurement of Electron Cyclotron Emission during Electron Cyclotron Heating

Research Report NIFS-Series (1996)

M. Iwase Κ. Ohkubo S. Kubo H. Idei

j :~~~i= j:·········~~~~ ~f~~5~~~A=R9X Abstract For the measurement of electron cyclotron emission from the high temperature plasma, a band re- jection filter in the range of 40 - 60 GHZ is designed to reject the 53.2 GHZ signal with large amplitude from the gyrotron for the purpose of plasma electron heating. The filter developed with ten sets of three quarters-wavelength coupled by TE111 mode of tunable resonant cavity has rejection of 50 dB and 3 dB bandwidth of 500 MHz. The modified model of Tschebysheff type for the prediction of rejection is pro- posed. It is confirmed that the measured rejection as a function of frequency agrees well with the ex- perimental results for small coupling hole, and also clarified that the rejection ratio increases for the large coupling hole.

Gyrotron

Electron temperature

Source

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Citations (1)

ECH Experiment with 106GHz Gyrotron

Annual report of National Institute for Fusion Science/Annual report (2014)

S. Kubo H. Idei Tsutomu Minami K. A. Tanaka M. Iwase

Gyrotron

Source

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ICRF heating of plasmas with internal transport barrier during reversed magnetic shear experiments in JT-60U

AIP conference proceedings (1999)

M. Iwase Y. Koide K. Tobita S. Moriyama H. Takenaga

Ion cyclotron range of frequency, ICRF, waves were injected into plasmas with an internal transport barrier, ITB, during reversed magnetic shear, RS, operations in JT-60U to study the electron heating and the low central fueling effects to plasmas with ITB. Steep gradients at the ITB in the electron temperature, Te, and in the ion temperature, Ti, profiles were sustained during ICRF heating. However, the density gradient was degraded during ICRF heating with low NBI power which corresponds to a low central particle fueling. We have found that the energy confinement time in the ICRF heated RS plasmas was increased compared to normal shear discharges, whereas the particle confinement time was the same as in normal shear discharges.

Electron temperature

10.1063/1.59740

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Citations (0)

Statistical Estimation of Power Deposition Profile in Electron Cyclotron Heated Plasmas

Japanese Journal of Applied Physics (1998)

M. Iwase S. Kubo H. Idei Κ. Ohkubo Takashi Minami

The power deposition profile by modulated fundamental electron cyclotron heating is deduced with the confidence interval derived from the statistical treatment of experimental data. The second harmonic electron cyclotron emission is used for the measurement of electron temperature that is necessary in this analysis. It is shown that the resultant deposition profile is consistent with the prediction resulting from the ray tracing calculation, including the multireflection effect at the vessel wall. The local adiabatic time scale for the thermal diffusion is derived and the propriety of the time scale in the power balance analysis is confirmed. The statistical confidence interval implies a broad profile of the power absorption. The obtained results show the necessity of using the statistical approach for analysis of the experimental data.

Deposition

Electron temperature

Power Balance

Tracing

10.1143/jjap.37.678

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Citations (4)