Combined Langmuir-magnetic probe measurements of type-I ELMy filaments in the EAST tokamak

Abstract

Detailed investigations on the filamentary structures associated with the type-I edge-localized modes (ELMs) should be helpful for protecting the materials of a plasma-facing wall on a future large device. Related experiments have been carefully conducted in the Experimental Advanced Superconducting Tokamak (EAST) using combined Langmuir-magnetic probes. The experimental results indicate that the radially outward velocity of type-I ELMy filaments can be up to 1.7 km s −1 in the far scrape-off layer (SOL) region. It is remarkable that the electron temperature of these filaments is detected to be ∼50 eV, corresponding to a fraction of 1/6 to the temperature near the pedestal top, while the density 3 10 m 19 3´-() of these filaments could be approximate to the line-averaged density. In addition, associated magnetic fluctuations have been clearly observed at the same time, which show good agreement with the density perturbations. A localized current on the order of ∼100 kA could be estimated within the filaments.

Design and analysis of a PAM launcher at 4.6 GHz for a new LHCD system on EAST

“…As a matter of fact, the δ CD is usually taken as an indicator of the CD efficiency since η CD ∝ 1/N || 2 according to the N.J. Fisch's theory [1]. The calculations suggest that the R C can be less than 1% around the cut-off density of 4.6 GHz wave n e_co ∼ 2.6 × 10 17 m −3 , and the coupling performance with R C ⩽ 6.5% can be kept when the density varies in the range of 0.5n e_co -10n e_co , which is like the plasma edge conditions induced by large Edge Localized Modes pacing [44]. While for the FAM, higher density is required for optimal coupling, namely, n e ⩾ 4n e_co ∼ 1 × 10 18 m −3 , but it has a good coupling (i.e.…”

Design and first result of combined Langmuir-magnetic probe on J-TEXT tokamak

“…On COMPASS [11], a similar probe allows the measurement of electrostatic and magnetic properties of the filaments. The CLMPs are also established on EAST [12,13] and W7-X [14], which accumulate abundant diagnostic data about the electrostatic and magnetic features of type-I ELM and the electromagnetic fluctuation transport. However, the graphite sleeves which are often used as protection may induce eddy current under the alternating magnetic field, thus shielding the magnetic field, especially affecting the measurement of highfrequency magnetic signals.…”