A new electromagnetic probe array diagnostic for analyzing electrostatic and magnetic fluctuations in EAST plasmas

Abstract

A novel electro-magnetic probe array (EMPA) diagnostic which consists of a magnetic probe array and an electrostatic probe array has been developed on EAST recently. The EMPA is fixed near the first wall at horizontal port P. The magnetic probe array of the EMPA consists of 24 same magnetic probes, and each of them can measure toroidal, poloidal and radial magnetic fluctuations simultaneously which provides additional toroidal magnetic fluctuation measurements comparing with the regular magnetic probes on EAST. With higher sampling rate of 2 MHz, the EMPA magnetic probes can provide higher frequency magnetic fluctuation measurements. The magnetic probe array of the EMPA is arranged by 2 parallel layers of magnetic probes with radial distance of 63 mm. And each layer of the magnetic probes is arranged in 4 poloidal rows and 3 toroidal columns. The compact arrangement of the EMPA magnetic probe array largely improve the toroidal mode number measurement ability from -8≤n≤8 to -112≤n≤112, and also improve the high poloidal wave number measurement ability of magnetic fluctuations comparing with the regular high frequency magnetic probes on EAST. The electrostatic probe array of the EMPA consists of 2 sets of four-tip probes and a single-tip probe array with 3 poloidal rows and 4 toroidal columns. It complements the electrostatic parameter measurements behind the main limiter and near the first wall in EAST. The engineering details of the EMPA diagnostic including the mechanical system, electrical system, acquisition and control system, and effective area calibration are presented. The preliminary applications of the EMPA in L-mode and H-mode discharges on EAST have demonstrated that the EMPA works well for providing the information of the magnetic and electrostatic fluctuations and can contribute to deeper physical analysis in future EAST experiments.

Diagnosing ratio of electron density to collision frequency of plasma surrounding scaled model in a shock tube using low-frequency alternating magnetic field phase shift

“…As long as n e /v e is obtained, the phase characteristics of the LF alternating magnetic field passing through the plasma can be calculated by using an equivalent circuit. Conversely, n e /v e can be diagnosed by using the LF phase characteristic formula (18). In this work, the cylindrical shock-tube plasma is taken for example and analyzed by using the cylindrical enveloping plasma model.…”

“…The electrostatic probe method [15][16][17][18] is straightforward and portable and has a time resolution better than 1 µs and a measurement dynamic range spanning nearly three orders of magnitude. The electron density and electron temperature can be calculated through measuring the voltammetry characteristic curve by using probes, and the collision frequency can be obtained from an empirical formula.…”

Line identification of extreme ultraviolet spectra from aluminum ions in EAST Tokamak plasmas

“…However, in these spectra, we still found some unrecognized lines that did not come from the impurity elements that have been identified. During the 2021-2022 EAST experimental campaigns, a novel electromagnetic probe array (EMPA) diagnostic has been adopted [17][18][19]. One fundamental measurement unit of this EMPA is the carefully designed 3D magnetic probe, which can measure the magnetic fluctuations in poloidal, radial, and toroidal directions simultaneously.…”