A." Mase

H. Negishi

L.N. Vyacheslavov

Y. "Nagayama

National Institute for Fusion Science (NIFS-Repository)

§27. First Result of ECE Imaging on CHS Nagayama, Y., Vyacheslavov, L.N. Negishi, H., Mase, A. (Univ. Tsukuba) The electron cyclotron emission (ECE) has the frequency, which is proportional to the magnetic field, and the intensity, which is proportional to the electron temperature. So, the ECE is useful for the continuous and local measurement of the electron temperature. As the plasma temperature and density are increased significantly thanks to strong heating, the localized magneto-hydro-dynamic (MHO) instabilities (ballooning mode, etc.) become more important, recently. ECE imaging is promised to be a powerful tool to study localized modes. ECE imaging is a measurement of ECE using 2 dimensional detector array. The important issue is the development of a planer detector, since planer detectors can be set 2 dimensionally. In this experiment, a planer detector with pre-amplifier was developed and was applied to the detection of ECE from the CHS plasma. A preliminary result is obtained for the ECE imaging in the CHS. The experimental set up is schematically shown in Fig. 1. The ECE emission from the CHS plasma is imaged on a mixer, which consists of a bow-tie anten~a, a Shottky barrier diode and a pre-amplifier on a GaAs substrate, monolithically. This detector is developed in TERATEC Co. [1] The mixer mixes the ECE and a local microwave, which is generated by a 200 mW, 90 GHz, IMPATT oscillator and is focused using a concave mirror. The intermediate frequency (IF) signal from the mixer is amplified by 96 dB and_ detected by 4 channel radiometer. The experimental result is shown in Fig. 2. In this case, the central magnetic field is 1.75 T, the central electron temperature is 600 e V and the electron density is 2X 1019 m-3. The first peak is-due to ECH. The positive pulse is due to the ECH. The negative trace is a signal. The DC component is 800 m V in the 1 GHz channel and 270 m V in the 3 GHz channel. The signal level is-6 m V in the 1 GHz channel and 3 m V in the 3 GHz channel. Therefore RC filters, which cut DC, are used. Signals are obtained when the 250 magnetic field is between 1.65 T and 1.45 T. This result is preliminary, but is very encouraging to realize the ECE imaging diagnostics. Reference [1] H. Matsuura, et al., Electronics Letters 33 (1997) 1800. 60 em 20 em LO (90GHz) ~< ____ ~> ~.c __ ~> Bow-tie , "", ~... Antenna •'''''''' '" Mixer " .... /_) '-l5(t~-~ __ ""-_... """,""-T - Mirror CHS plasma ~"""'''' ", Amp1 Polyethylene (28dB) lens Band-0.1 Fig. 1 Experimental set-up. > ~ t----1r---,-. > ~ 1--1----1----1-- 20 ms/div (36dB) (32dB) Power Divider Fig. 2 Trace of signals of 1 GHz and 3 G Hz channels. 

First Result of ECE Imaging on CHS

Abstract

Similar works

Full text

Available Versions

National Institute for Fusion Science (NIFS-Repository)