Optimization of the optical system for electron cyclotron emission imaging diagnostics on the HL-2A tokamak

Abstract

The optical system of the electron cyclotron emission imaging diagnostics on the HL-2A tokamak has been optimized in both the narrow zoom pattern and the wide zoom pattern. The two main features of the improved optical system are (1) larger coverage of the measurement region in the plasma and (2) a flatter imaging surface. The new optics has good focal characteristics over the whole plasma cross section. The curvature of the field of the image surface (ΔR between the core channel and the edge channel) is within 5.3 cm in the narrow zoom pattern and 6.7 cm in the wide zoom pattern after optimization, whereas the values with the present optics were 23 cm in the narrow zoom pattern and 15 cm in the wide zoom pattern. The optics will be fabricated, tested and installed on the HL-2A tokamak before the next experimental campaign.

Progress of microwave diagnostics development on the HL-2A tokamak

“…It is very useful to observe the temperature fluctuations at different locations. The optical system has been optimized to match the curvature of the field [13]. This system has been installed and successfully operated on the HL-2A tokamak, and 2D structures of the MHD activities, such as double e-fishbones, tearing mode, sawtooth crash and Alfven eigenmodes, have been clearly observed [9,28,29].…”

“…With the characteristic of local measurement, good accessibility, and without external perturbation to plasmas, more and more attentions have been paid to microwave diagnostics by scientists, and some new techniques have been developed and applied to the hardware development, signal processing and data interpretation in recent twenty years. So far, significant progresses have been made, especially on ECEI, microwave imaging reflectometry (MIR), multi-channel DBS reflectometer and high temporal resolution frequency modulation (FM) reflectometers [12][13][14][15][16][17][18][19].…”

The general optics structure of millimeter-wave imaging diagnostic on TOKAMAK

“…In the previous millimeter-wave imaging diagnostic systems on tokamaks [4,7,9,10], only the focus and zoom features have been implemented, but not pay much attention on the following four functions which are also important in optics design, including: field curvature adjustment function, incident angle function, decoupling function and combination function.…”

“…In the recent years, millimeter-wave imaging diagnostic systems have significantly improved because of rapid developments of related technologies. Advanced millimeter-wave imaging diagnostic systems, including the Electron Cyclotron Emission Imaging (ECEI) [1] and Microwave Imaging Reflectometry (MIR) [2] have been used to study electron temperature and density distributions and fluctuations in tokamak plasma physics [3][4][5][6][7][8][9][10]. Both MHD instability with a large-scale structure and micro-turbulence with small-scale structure have been observed by these intelligent diagnostic tools, including: sawtooth crash [11], TEM turbulence [12], Alfven eigenmodes [6], Board band EHO, and Coherent Edge Mode.…”

Optics design for Electron Cyclotron Emission Imaging system on J-TEXT

“…The electron cyclotron emission imaging (ECEI) diagnostic systems have been widely installed on numerous tokamaks including TEXT-U [1], RTP [2], TEXTOR [3], HT-7 [4], DIII-D [5], ASDEX-U [6], EAST [7], HL-2A [8], and KSTAR [9]. The ECEI system has been proven to be a powerful tool for measuring two-dimensional electron temperature and mgnetohydrodynamics (MHD) instabilities.…”