We developed and installed an electron cyclotron emission radiometer for taking measurements of Korea Superconducting Tokamak Advanced Research (KSTAR) plasma. In order to precisely measure the absolute value of electron temperatures, a calibration measurement of the whole radiometer system was performed, which confirmed that the radiometer has an acceptably linear output signal for changes in input temperature. It was also found that the output power level predicted by a theoretical calculation agrees with that obtained by the calibration measurement. We also showed that the system displays acceptable noise-temperature performance around 0.23 eV.
Microwave reflectometric measurement is applied to diagnose vital signal of a human. The reflectometer signal is processed by a quadrature phase detector in order to obtain both phase and amplitude components of the signal. The phase component is analyzed by using fast-Fourier transform and wavelet transform to evaluate the frequency spectrum of the heartbeat and respiration. Various applications of the microwave measurement are discussed.
1 October 2004 in Review of Scientific Instruments
In this article we perform a numerical study of microwave imaging reflectometry (MIR) and compare it with conventional reflectometry system. As an approximation to the reflections by real plasma fluctuations, a corrugated wheel is used. As far as general performance is concerned, our simulations confirm the results by Munsat et al. [Plasma Phys. Controlled Fusion 45, 469 (2003)] that the MIR system reproduces shape of corrugation far from the wheel while conventional systems fail to do so. We addressed the effects of asymmetry and defocusing of the wheel-reflectometer system as well as spectral sensitivity of the imaging reflectometer. For a particular geometry we estimated the deterioration of the MIR performance due to misalignments and existence of broadband fluctuations.
1 January 2001 in Review of Scientific Instruments
A numerical simulation of cross-polarization scattering (CPS) was performed by using frequency dependent finite difference time domain method. In the CPS process, an incident ordinary (extraordinary) wave is converted to an extraordinary (ordinary) wave by magnetic fluctuations in a plasma. It is confirmed in the simulation that an incident wave propagates in an anisotropic dispersive media properly. The relation between scattered electric field and magnetic fluctuations is also obtained.
1 January 2001 in Review of Scientific Instruments
In the GAMMA10 tandem mirror, a strong ion cyclotron range of frequency heating is performed. As a result of the heating, the Alfvén ion cyclotron (AIC) modes are spontaneously excited due to the strong temperature anisotropy. The AIC modes in the GAMMA10 are excited as the axial eigenmodes and detected at the whole of the device. In the recent experiments, the clear standing wave structure is observed with the magnetic probe measurements. Characteristics of the AIC modes and the measurement of the axial profile are presented.
An analytical model of fluctuation reflectometry is developed, which is capable of handling the plasma profiles of arbitrary shape and curvature. The experimental profiles are piece-wise approximated by the functions, which allow for the integration of the full-wave O-mode equation. The model is applied to the reflectometry of the JT-60U tokamak plasma to provide a preliminary estimation of the fluctuation amplitude and spectral width.