In large helical device （LHD）, antenna loadings are different for minority ion cyclotron heating （MICH with 38.47 MHz） and mode-converted ion Bernstein wave heating （MC-IBW with 28.4 MHz）, and it is necessary to...In large helical device （LHD）, antenna loadings are different for minority ion cyclotron heating （MICH with 38.47 MHz） and mode-converted ion Bernstein wave heating （MC-IBW with 28.4 MHz）, and it is necessary to improve antenna loading with low heating efficiency to avoid arching on transmission line. To design a new ion cyclotron range of frequencies （ICRF） antenna in LHD, calculation for a simple antenna model is conducted using three-dimensional electrical magnetic code （high frequency structure simulator, HFSS） for an water loading as an imaginary plasma with low heating efficiency. At resonant frequencies, antenna loading is sensitive to strap width, and resonant frequencies are strongly related to strap height. There is no differences of RF current profile on the strap surface between resonant frequency and non-resonant frequency. The strap should be perpendicularly placed against the magnetic field line, since Faraday-shield angle will lead to a decrease in the effective antenna height.展开更多
Two pairs of high-frequency magnetic probes were installed in the Large Helical Device （LHD）. During the injection of a perpendicular neutral beam, ion cyclotron emissions （ICEs） with the fundamental frequency cor...Two pairs of high-frequency magnetic probes were installed in the Large Helical Device （LHD）. During the injection of a perpendicular neutral beam, ion cyclotron emissions （ICEs） with the fundamental frequency corresponding to the ion cyclotron frequency at the plasma edge were detected, which are the same type of ICE as measured with the former spare ion cyclotron range of frequencies （ICRF） heating antennas. This type of ICE was further investigated with regard to the phase and intensity of signals. Another type of ICE was found in the LHD, and these ICEs were synchronized with bursts of toroidicity induced Alfv^n eigenmodes （TAE） and the rise of intensity of lost ion flux. Therefore the source of these ICEs was thought to be the particles transferred from the core to the outer region of plasma by the TAE bursts. The frequency of ICEs induced by the TAE bursts increases linearly with the magnetic field strength, since the ion cyclotron frequency increases with the magnetic field strength.展开更多
Possibility of the measurement of radiated waves derived from the thermally emitted electron Bernstein wave （EBW） is numerically investigated based on the assumption of the super dense core （SDC） plasma generated ...Possibility of the measurement of radiated waves derived from the thermally emitted electron Bernstein wave （EBW） is numerically investigated based on the assumption of the super dense core （SDC） plasma generated in LHD. EBW that is thermally emitted in the electron cyclotron resonance （ECR） layer may couple with the electromagnetic wave and be emitted to the vacuum via the EBW-extraordinary-ordinary （B-X-O） mode conversion process. We consider the use of one of the transmission lines for electron cyclotron heating （ECH） in LHD as a receiving system of the emission. It is derived that the waves in the fundamental cyclotron frequency range are emitted as the EBW near their upper hybrid resonance （UHR） layer outside the last close flux surface （LCFS）. On the other hand, waves in the second harmonics cyclotron frequency range are emitted in the core region. It means that successful measurement of waves of the second harmonic frequency range emitted from extremely high dense core plasma with setting an aim angle for receiving indicates a possibility of the second harmonic ECH by EBW in the core region with setting the same aim angle and the same polarization for launching.展开更多
Investigation of experimental configuration for the electron Bernstein wave （EBW） heating by using the existing electron cyclotron heating （ECH） antennas on LHD was performed. By using an antenna installed in the ...Investigation of experimental configuration for the electron Bernstein wave （EBW） heating by using the existing electron cyclotron heating （ECH） antennas on LHD was performed. By using an antenna installed in the lower port, direct oblique launching of the extraordinary （X-） mode from the high magnetic field side （HFS） is available. Since the parallel component of the refractive index （NIF） varies during propagation because of the inhomogeneity of the magnetic field, NH can be zero when the launched X-mode crosses the fundamental electron cyclotron resonance （ECR） layer even NⅡ is noonzero initially. In such a condition, if the electron density is above a certain level the obliquely launched X-mode can pass the fundamental ECR layer without being damped out and can be mode-converted to EBW that is absorbed at the Doppler shifted ECR layer. By using an antenna installed in the horizontal port, oblique launching from the lower magnetic field side （LFS） toward the over-dense plasma is available. Excitation of EBW via the mode conversion process of ordinary mode（O）-extraordinary mode（X）-electron Bernstein wave （B） is expected with the O-mode launching toward an appropriate direction. The O-X-B mode conversion rate and the region of power deposition were surveyed by varying the magnetic field strength and the launching direction. The results of the survey suggest that efficient heating in the core region is difficult by using the existing antenna. Rearrangement of the final mirror of the launching antenna may be needed.展开更多
基金supported partially by the JSPS-CAS Core-University program in the field of 'Plasma and Nuclear Fusion'
文摘In large helical device （LHD）, antenna loadings are different for minority ion cyclotron heating （MICH with 38.47 MHz） and mode-converted ion Bernstein wave heating （MC-IBW with 28.4 MHz）, and it is necessary to improve antenna loading with low heating efficiency to avoid arching on transmission line. To design a new ion cyclotron range of frequencies （ICRF） antenna in LHD, calculation for a simple antenna model is conducted using three-dimensional electrical magnetic code （high frequency structure simulator, HFSS） for an water loading as an imaginary plasma with low heating efficiency. At resonant frequencies, antenna loading is sensitive to strap width, and resonant frequencies are strongly related to strap height. There is no differences of RF current profile on the strap surface between resonant frequency and non-resonant frequency. The strap should be perpendicularly placed against the magnetic field line, since Faraday-shield angle will lead to a decrease in the effective antenna height.
基金supported by NIFS budgets NIFS10ULRR003,NIFS11ULRR703,and NIFS11PLRR302
文摘Two pairs of high-frequency magnetic probes were installed in the Large Helical Device （LHD）. During the injection of a perpendicular neutral beam, ion cyclotron emissions （ICEs） with the fundamental frequency corresponding to the ion cyclotron frequency at the plasma edge were detected, which are the same type of ICE as measured with the former spare ion cyclotron range of frequencies （ICRF） heating antennas. This type of ICE was further investigated with regard to the phase and intensity of signals. Another type of ICE was found in the LHD, and these ICEs were synchronized with bursts of toroidicity induced Alfv^n eigenmodes （TAE） and the rise of intensity of lost ion flux. Therefore the source of these ICEs was thought to be the particles transferred from the core to the outer region of plasma by the TAE bursts. The frequency of ICEs induced by the TAE bursts increases linearly with the magnetic field strength, since the ion cyclotron frequency increases with the magnetic field strength.
基金supported in part by the JSPS-CAS Core-University program in the field of 'Plasma and Nuclear Fusion'
文摘Possibility of the measurement of radiated waves derived from the thermally emitted electron Bernstein wave （EBW） is numerically investigated based on the assumption of the super dense core （SDC） plasma generated in LHD. EBW that is thermally emitted in the electron cyclotron resonance （ECR） layer may couple with the electromagnetic wave and be emitted to the vacuum via the EBW-extraordinary-ordinary （B-X-O） mode conversion process. We consider the use of one of the transmission lines for electron cyclotron heating （ECH） in LHD as a receiving system of the emission. It is derived that the waves in the fundamental cyclotron frequency range are emitted as the EBW near their upper hybrid resonance （UHR） layer outside the last close flux surface （LCFS）. On the other hand, waves in the second harmonics cyclotron frequency range are emitted in the core region. It means that successful measurement of waves of the second harmonic frequency range emitted from extremely high dense core plasma with setting an aim angle for receiving indicates a possibility of the second harmonic ECH by EBW in the core region with setting the same aim angle and the same polarization for launching.
基金the budget codes NIFS07ULRR501-3,518,NIFS07KLRR303a grant-in-aid for scientific research of MEXT JAPAN,2008 19740347the JSPS-CAS Core-University program in the field of Plasma and Nuclear Fusion
文摘Investigation of experimental configuration for the electron Bernstein wave （EBW） heating by using the existing electron cyclotron heating （ECH） antennas on LHD was performed. By using an antenna installed in the lower port, direct oblique launching of the extraordinary （X-） mode from the high magnetic field side （HFS） is available. Since the parallel component of the refractive index （NIF） varies during propagation because of the inhomogeneity of the magnetic field, NH can be zero when the launched X-mode crosses the fundamental electron cyclotron resonance （ECR） layer even NⅡ is noonzero initially. In such a condition, if the electron density is above a certain level the obliquely launched X-mode can pass the fundamental ECR layer without being damped out and can be mode-converted to EBW that is absorbed at the Doppler shifted ECR layer. By using an antenna installed in the horizontal port, oblique launching from the lower magnetic field side （LFS） toward the over-dense plasma is available. Excitation of EBW via the mode conversion process of ordinary mode（O）-extraordinary mode（X）-electron Bernstein wave （B） is expected with the O-mode launching toward an appropriate direction. The O-X-B mode conversion rate and the region of power deposition were surveyed by varying the magnetic field strength and the launching direction. The results of the survey suggest that efficient heating in the core region is difficult by using the existing antenna. Rearrangement of the final mirror of the launching antenna may be needed.
