[Table of Contents]

Plasma and Fusion Research

Volume 2, 040 (2007)

Regular Articles

Relative Frequency Calibration for Fast Frequency Sweep Microwave Reflectometry
Akira EJIRI, Yoshiyuki SHIMADA, Takuma YAMADA1), Takuya OOSAKO, Yuichi TAKASE and Hiroshi KASAHARA2)
Graduate School of Frontier Sciences, The University of Tokyo
1)
Research Institute for Applied Mechanics, Kyushu University
2)
National Institute for Fusion Science
(Received 18 May 2007 / Accepted 6 July 2007 / Published 28 August 2007)

Abstract

A frequency-modulated reflectometer with a frequency band of 26.5 to 40 GHz has been constructed and installed in the TST-2 spherical tokamak to measure fast density profile evolution. In order to calibrate the instantaneous frequency for various frequency sweep rates, a waveform matching method has been proposed and applied to the reflectometer. This method compares the interference patterns (i.e., waveforms) of a fixed target reflection, which do not depend on the sweep rate, and obtains the instantaneous frequency by fitting the target waveform time to the time for a reference sweep waveform. This allows evaluation of output frequency stability. The overall frequency error, including reproducibility, is around 0.1 GHz. Sweep rates up to 20 μs were used to measure the density profile evolution during rf heating.

Keywords

microwave reflectometry, density profile measurement, frequency modulation, frequency sweep, plasma diagnostic

DOI: 10.1585/pfr.2.040

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This paper may be cited as follows:

Akira EJIRI, Yoshiyuki SHIMADA, Takuma YAMADA, Takuya OOSAKO, Yuichi TAKASE and Hiroshi KASAHARA, Plasma Fusion Res. 2, 040 (2007).