Radial profiles of impurity ions of carbon, neon and iron were measured for high- temperature plasmas in large helical device （LHD） using a space-resolved extreme ultraviolet （EUV） spectrometer in the wavelength r...Radial profiles of impurity ions of carbon, neon and iron were measured for high- temperature plasmas in large helical device （LHD） using a space-resolved extreme ultraviolet （EUV） spectrometer in the wavelength range of 60A to 400 A. The radial positions of the impurity ions obtained are compared with the local ionization energies, El of these impurity ions and the electron temperatures T,z there. The impurity ions with 0.3 keV 〈_ Ei ≤ 1.0 keV are always located in outer region of plasma, i.e., 0.7 ≤ p ≤ 1.0, and those with Ei ≤ 0.3 keV are located in the ergodic layer, i.e., 1.0 ≤ p≤ 1.1, with a sharp peak edge, where p is the normalized radial position. It is newly found that Tez is approximately equal to Ei for the impurity ions with Ei ≤ 0.3 keV, whereas roughly half the value of El for the impurity ions with 0.3 keV≤ Ei ≤ 1.0 keV. It is known that Tez is considerably lower than Ei in the plasma edge and approaches to Ei in the plasma core. Therefore, this result seems to originate from the difference in the transverse transport between the plasma edge at p 〈1.0 and the ergodic layer at p ≥ 1.0. The transverse transport is studied with an impurity transport simulation code. The result revealed that the difference appearing in the impurity radial positions can be qualitatively explained by the different values of diffusion coefficient, e.g., D=0.2 m2/s and 1.0 m2/s, which can be taken as a typical index of the transverse transport.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Radial profiles of impurity ions of carbon, neon and iron were measured for high- temperature plasmas in large helical device （LHD） using a space-resolved extreme ultraviolet （EUV） spectrometer in the wavelength range of 60A to 400 A. The radial positions of the impurity ions obtained are compared with the local ionization energies, El of these impurity ions and the electron temperatures T,z there. The impurity ions with 0.3 keV 〈_ Ei ≤ 1.0 keV are always located in outer region of plasma, i.e., 0.7 ≤ p ≤ 1.0, and those with Ei ≤ 0.3 keV are located in the ergodic layer, i.e., 1.0 ≤ p≤ 1.1, with a sharp peak edge, where p is the normalized radial position. It is newly found that Tez is approximately equal to Ei for the impurity ions with Ei ≤ 0.3 keV, whereas roughly half the value of El for the impurity ions with 0.3 keV≤ Ei ≤ 1.0 keV. It is known that Tez is considerably lower than Ei in the plasma edge and approaches to Ei in the plasma core. Therefore, this result seems to originate from the difference in the transverse transport between the plasma edge at p 〈1.0 and the ergodic layer at p ≥ 1.0. The transverse transport is studied with an impurity transport simulation code. The result revealed that the difference appearing in the impurity radial positions can be qualitatively explained by the different values of diffusion coefficient, e.g., D=0.2 m2/s and 1.0 m2/s, which can be taken as a typical index of the transverse transport.
