Electron cyclotron emission based q-profile measurement and concept for equilibrium reconstruction

Abstract

Measuring the plasma equilibrium is essential for real time plasma control and for the investigation of an abundance of physics questions. However, many existing kinetic equilibria reconstruction techniques rely heavily on integrated magnetic measurements and neutronsensitive diagnostics, which will be difficult to design and operate in ITER and DEMO. Here we present and test a conceptual design for a non-magnetic equilibrium reconstruction method using data from a radial electron cyclotron emission diagnostic and an image of the plasma boundary -diagnostics which can be robustly designed in high-neutron environments. This technique is based on the measurement of a discrete q-profile and the symmetry mapping of the electron temperature profile, both of which can be acquired with ECE.

Experimental evidence of electron-cyclotron current drive-based neoclassical tearing mode suppression threshold reduction during mode locking on DIII-D

“…Both islands are large enough to flatten the local temperature gradient, as seen in figure 5. While the n = 1 mode exists outside of the available electron cyclotron emission (ECE) diagnostic coverage for these discharges, the n = 2 mode is well covered by ECE and can be detected with standard techniques [29]. The frequency of the n = 2 mode is measured to be exactly twice the frequency of the n = 1 mode throughout the discharge (ω 3,2 = 2ω 2,1 ), suggesting that the large modes present here are subject to strong phase locking [30].…”