MHD stability of the Large Helical Device (LHD) plasmas produced with intenseneutral beam injection is experimentally studied. When the steep pressure gradient near the edge isproduced through L-H transition or linear...MHD stability of the Large Helical Device (LHD) plasmas produced with intenseneutral beam injection is experimentally studied. When the steep pressure gradient near the edge isproduced through L-H transition or linear density ramp experiment, interchange-like MHD modes whoserational surface is located very close to the last closed flux surface are strongly excited in acertain discharge condition and affect the plasma transport appreciably. In NBI-heated plasmasproduced at low toroidal field, various Alfven eigenmodes are often excited. Bursting toroidalAlfven egenmodes excited by the presence of energetic ions induce appreciable amount of energeticion loss, but also trigger the formation of internal and edge transport barriers.展开更多
Experimental progress of lower hybrid current drive （LHCD） and ion Bernstein wave （IBW） heating was achieved significantly in HT-7. Long pulse plasmas, up to 400 s, were obtained by LHCD. High power lower hybrid w...Experimental progress of lower hybrid current drive （LHCD） and ion Bernstein wave （IBW） heating was achieved significantly in HT-7. Long pulse plasmas, up to 400 s, were obtained by LHCD. High power lower hybrid wave （LHW）, with PLHW of 800 kW at 2.45 GHz, was launched and the current drive efficiency was studied for different wave powers. Electron temperature and Zeff were measured in LHCD discharges. Heating experiment and recent results of high power ion Bernstein wave, with PIBW of 600 kW at 27 MHz, were summarized.展开更多
The particle diffusion coefficient and the convection velocity were studied based on the density modulation using D2 gas puffing on the HT-7 tokamak. The density was measured by a five-channel FIR interferometer. The ...The particle diffusion coefficient and the convection velocity were studied based on the density modulation using D2 gas puffing on the HT-7 tokamak. The density was measured by a five-channel FIR interferometer. The density modulation amplitude was 10% of the central chord averaged background density and the modulation frequency was 10 Hz in the experiments. The particle diffusion coefficient （D） and the convection velocity （V） were obtained for different background plasmas with the central chord averaged density 〈ne〉 = 1.5×10^19m^-3 and 3.0×10^19 m^-3 respectively. It was observed that the influence of density modulation on the main plasma parameters was very weak. This technology is expected to be useful for the analysis of LHW and IBW heated plasmas on HT-7 tokamak in the near future.展开更多
Recent progress in the physics and engineering design study for themodification programme of JT-60 is presented. In order to achieve a steady state high-βplasmaoperation, which is the dominant issue of this programme...Recent progress in the physics and engineering design study for themodification programme of JT-60 is presented. In order to achieve a steady state high-βplasmaoperation, which is the dominant issue of this programme, physics design for the MHD control and thestability analysis is investigated. Engineering design and the R & D for the superconducting coils,irradiation shield are performed well towards the mission of programme.展开更多
Beam-ion losses induced by fast-ion-driven toroidal Alfven eigenmodes （TAE） were measured with a scintillator-based lost fast-ion probe （SLIP） in the large helical device （LHD）. The SLIP gave simultaneously the ...Beam-ion losses induced by fast-ion-driven toroidal Alfven eigenmodes （TAE） were measured with a scintillator-based lost fast-ion probe （SLIP） in the large helical device （LHD）. The SLIP gave simultaneously the energy E and the pitch angle X=arccos（v///v） distribution of the lost fast ions. The loss fluxes were investigated for three typical magnetic configurations of Rax-vac=3.60 m, 3.75 m. and 3.90 m, where Rax-vac is the magnetic axis position of the vacuum field. Dominant losses induced by TAEs in these three configurations were observed in the E/X regions of 50-190 keV/40°, 40-170 keV/25°, and 30-190 keV/30°, respectively. Lost-ion fluxes induced by TAEs depend clearly on the amplitude of TAE magnetic fluctuations, Rax-vac and the toroidal field strength Bt. The increment of the loss fluxes has the dependence of （bTAE/Bt）s. The power s increases from s = 1 to 3 with the increase of the magnetic axis position in finite beta plasmas.展开更多
Coherent magnetic fluctuations in an acoustic range of frequency have been regularly observed in low-density（n_e〈0.2×10^（19）m^（-3））plasmas with strong second harmonic electron cyclotron resonance heating（...Coherent magnetic fluctuations in an acoustic range of frequency have been regularly observed in low-density（n_e〈0.2×10^（19）m^（-3））plasmas with strong second harmonic electron cyclotron resonance heating（ECRH）on the Large Helical Device.Hard X-ray measurements indicated that energetic electrons are generated in these ECRH discharges.The magnetic fluctuations are suppressed in higher density discharges where energetic electrons are not present.The ECRH power modulation experiment indicated that the observed magnetohydrodynamic（MHD）mode has an acoustic nature rather than an Alfvenic nature.展开更多
基金The project supported by the Core-University Program between Japan and China on Plasmas and Nuclear Fusion, and a Grant-in-Aid for Scientific Research from Japan Society for the Promotion of Science
文摘MHD stability of the Large Helical Device (LHD) plasmas produced with intenseneutral beam injection is experimentally studied. When the steep pressure gradient near the edge isproduced through L-H transition or linear density ramp experiment, interchange-like MHD modes whoserational surface is located very close to the last closed flux surface are strongly excited in acertain discharge condition and affect the plasma transport appreciably. In NBI-heated plasmasproduced at low toroidal field, various Alfven eigenmodes are often excited. Bursting toroidalAlfven egenmodes excited by the presence of energetic ions induce appreciable amount of energeticion loss, but also trigger the formation of internal and edge transport barriers.
基金supported in part by the JSPS-CAS Core-University Program in the field of Plasma and Nuclear Fusion,National Natural Science Foundation of China (No.10721505)
文摘Experimental progress of lower hybrid current drive （LHCD） and ion Bernstein wave （IBW） heating was achieved significantly in HT-7. Long pulse plasmas, up to 400 s, were obtained by LHCD. High power lower hybrid wave （LHW）, with PLHW of 800 kW at 2.45 GHz, was launched and the current drive efficiency was studied for different wave powers. Electron temperature and Zeff were measured in LHCD discharges. Heating experiment and recent results of high power ion Bernstein wave, with PIBW of 600 kW at 27 MHz, were summarized.
基金supported partly by Japanese Society of Promotion of Science and Chinese Academy of Sciences Core-University Program on Plasma and Nuclear Fusion in 2004
文摘The particle diffusion coefficient and the convection velocity were studied based on the density modulation using D2 gas puffing on the HT-7 tokamak. The density was measured by a five-channel FIR interferometer. The density modulation amplitude was 10% of the central chord averaged background density and the modulation frequency was 10 Hz in the experiments. The particle diffusion coefficient （D） and the convection velocity （V） were obtained for different background plasmas with the central chord averaged density 〈ne〉 = 1.5×10^19m^-3 and 3.0×10^19 m^-3 respectively. It was observed that the influence of density modulation on the main plasma parameters was very weak. This technology is expected to be useful for the analysis of LHW and IBW heated plasmas on HT-7 tokamak in the near future.
文摘Recent progress in the physics and engineering design study for themodification programme of JT-60 is presented. In order to achieve a steady state high-βplasmaoperation, which is the dominant issue of this programme, physics design for the MHD control and thestability analysis is investigated. Engineering design and the R & D for the superconducting coils,irradiation shield are performed well towards the mission of programme.
基金supported in part by the Grant-in-Aid for Scientific Research from MEXT (No. 16082209)from JSPS (Nos. 21360457, 21340175,and 22-7912)+1 种基金the LHD project budget (NIFS09ULHH508)partially supported by the JSPS-CAS Core-University program in thefield of‘Plasma and Nuclear Fusion’
文摘Beam-ion losses induced by fast-ion-driven toroidal Alfven eigenmodes （TAE） were measured with a scintillator-based lost fast-ion probe （SLIP） in the large helical device （LHD）. The SLIP gave simultaneously the energy E and the pitch angle X=arccos（v///v） distribution of the lost fast ions. The loss fluxes were investigated for three typical magnetic configurations of Rax-vac=3.60 m, 3.75 m. and 3.90 m, where Rax-vac is the magnetic axis position of the vacuum field. Dominant losses induced by TAEs in these three configurations were observed in the E/X regions of 50-190 keV/40°, 40-170 keV/25°, and 30-190 keV/30°, respectively. Lost-ion fluxes induced by TAEs depend clearly on the amplitude of TAE magnetic fluctuations, Rax-vac and the toroidal field strength Bt. The increment of the loss fluxes has the dependence of （bTAE/Bt）s. The power s increases from s = 1 to 3 with the increase of the magnetic axis position in finite beta plasmas.
基金supported by the Grant-in-Aid for Encouragement of Scientists from the Japan Society for the Promotion of Science(No.20656150)supported by the JSPS-NRF-NSFC A3 Foresight Program in the field of Plasma Physics(NSFC:No.11261140328 and NRF:No.2012K2A2A6000443)
文摘Coherent magnetic fluctuations in an acoustic range of frequency have been regularly observed in low-density（n_e〈0.2×10^（19）m^（-3））plasmas with strong second harmonic electron cyclotron resonance heating（ECRH）on the Large Helical Device.Hard X-ray measurements indicated that energetic electrons are generated in these ECRH discharges.The magnetic fluctuations are suppressed in higher density discharges where energetic electrons are not present.The ECRH power modulation experiment indicated that the observed magnetohydrodynamic（MHD）mode has an acoustic nature rather than an Alfvenic nature.
