Abstract
The high frequency B-dot (HFB) probe diagnostic on the ASDEX Upgrade tokamak has undergone a considerable upgrade during the 2016 opening of the torus. The probe coverage is now greatly expanded toroidally, as well as radially with the addition of probes on the high field side and the removable manipulator head. A new 2-channel fast digitizer now allows to examine and record radio frequency (RF) wave emissions emanating from the plasma in the ion cyclotron range of frequencies (ICRF). Possible studies that can be achieved now include: a study of core ICRF power absorption efficiency; a study of ion cyclotron emissions from the plasma generated by energetic ions; and study of ICRF wave/plasma turbulence interactions in the scrape-off layer region.
Highlights
Radio frequency waves in the ion cyclotron range of frequencies (ICRF) are successfully used to heat magnetized plasmas to fusion relevant temperatures
The strength of the ICRF fast wave amplitude on the high field side is recorded during these modulations (Fig. 2 (f)) to compare with the ICRF power absorption coefficient.To smoothen the effect of edge localized modes (ELMs), which are clearly visible on the time traces of WMHD (Fig. 2 (b)) and VRF (Fig. 2 (f)), we use 5-10 ICRF pulses to obtain a single average ICRF value
Note that the Hminority concentration is ~4-6% in these discharges, suggesting that the reason for the higher VRF and lower ICRF in H-mode discharges with ICRF power at 30.0 MHz is due to a different wavenumber spectrum of the launched ICRF wave
Summary
Radio frequency waves in the ion cyclotron range of frequencies (ICRF) are successfully used to heat magnetized plasmas to fusion relevant temperatures. In order to assist with this task, a number of probes have been installed that directly detect the ICRF waves’ magnetic field components and their properties This set of high frequency B-dot (HFB) probes contains an array of inductors capable of measuring the amplitude, the phase, and the polarization of the ICRF wave [8]. A pair of HFB probes, together with a pair of Langmuir probes, are put together for a new diagnostic head of the ASDEX Upgrade low field side midplane manipulator This additional diagnostic aims to measure the radial profile of the ICRF wave field amplitude in the scrape off layer (SOL), as well as to study the interactions between turbulent SOL plasmas and ICRF wave fields.
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