Diagnostics
(1) Microwave Camera for fast visualization of MHD instabilities
The ECEI system installed at the KSTAR tokamak has been developed by the Fusion Plasma Center at POSTECH led by prof. Hyeon Park (fusion.postech.ac.kr).
The ECEI diagnostic is a culmination of decades-long innovations in microwave technologies led by prof. Luhmann, Jr. at UC Davis and visionary efforts for imaging diagnostics by prof. Hyeon Park.
The KSTAR ECEI system is the world-best imaging diagnostic tool and has been successful in visualizing the very details of the dynamics of important MHD instabilities in tokamaks. See the details in the Research/MHD section.
Figure 1. Schematic view of ECEI system installed on KSTAR. The system consists of large aperture optics and detector arrays.
(2) Plasma wave diagnostics
Outside the KSTAR tokamak, the system for measurement of RF wave has been installed with two types of antennas (Spiral/Bowtie), a filter-bank spectrometer, and fast digitizers (Up to 10GSa/s) as its main components.
Figure 2. RF antennas are installed outside tokamak vessel. Digitizers for RF system are located inside a Faraday cage (below the deck) to block external noises.
Figure 3. RF emissions at and during pedestal collapse (KSTAR shot: 21118: B0 = 1.82 T, Ip = 500 kA). Vertical gray dash-dot line indicates the start of the collapse. Both broadband and narrow-band intense whistler-frequency waves are observed during the pedestal collapse as indicted by the two dashed white lines.
Recent study focuses on the interaction between edge localized mode filament and plasma waves such as ion cyclotron emission (ICE). Motivated by theoretical work by P. M. Bellan, RF diagnostic system provides a unique opportunity to study the role of Alfven and whistler waves in the magnetic reconnection process.
(3) Hard X-ray diagnostics
The system for detection of high-energy waves (over 10 keV) is installed on the KSTAR, which is expected to provide evidence on the role of energetic electrons during plasma instabilities such as sawtooth crash.