Density Profile and Fluctuation Measurements by Microwave Reflectometry on EAST

Abstract

A microwave reflectometry system operating in the V-band frequency with extraordinary mode polarization has been developed on the EAST tokamak. The reflectometry system, using a voltage-controlled oscillator (VCO) source driven by an arbitrary waveform generator with high temporal resolution, can operate for the density profile measurement. The result of the bench test shows that the output frequency of the VCO has a linear dependence on time. The dispersion of reflectometry system is determined and reported in this paper. The evolution of a pedestal density profile during the L-H transition is observed by the reflectometry in H-mode discharges on EAST tokamak. A frequency synthesizer is used to replace the VCO as microwave source for density fluctuation measurements. The level of density fluctuation in the pedestal shows an abrupt decrease when the plasma enters into H-mode. A coherent mode with a frequency of about 100 kHz is observed and the mode frequency decreases gradually as the pedestal evolves.

Experimental investigation on divertor tungsten sputtering with neon seeding in ELMy H-mode plasma in EAST tokamak

“…[24] Figure 7 displays two density profiles measured by the microwave reflectometry before and during the ELM supersession. [25] The density gradient in the pedestal is softened during ELM suppression compared with that before, which could be attributed to the enhanced pedestal transport. These results indicate that ELMs can be suppressed due to the changed pedestal transport by impurities.…”

Study of power width scaling in scrape-off layer with 2D electrostatic turbulence code based on EAST L-mode discharges

“…The electron density was measured by reflectometry (Refl). [27][28][29] The electron temperature was measured by a Michelson interferometer (MI), 30 a heterodyne radiometer system (HRS), 31 and Thomson scattering (TS). 32 The ion temperature was measured by charge exchange recombination spectroscopy (CXRS).…”

Stabilizing effect of enhanced resistivity on peeling-ballooning instabilities on EAST

“…In this work, we carried out the linear stability analysis of equilibrium 1 with relatively lower Z eff ~ 2.8 at about 1880 ms, which is operated with line-averaged density <n e > ~ 3.510 19 Figure 2 shows the electron density, electron temperature, total plasma pressure and current density profiles of the two equilibria. The edge electron density profiles are measured by microwave reflectometer system [34] which is located at low-field side midplane. The electron temperature profiles are obtained from Thomson Scattering system [35,36].…”