Two-dimensional structure of density fluctuations is examined during the current jump phase, indicating a change from the open magnetic fields to the closed ones. During the smooth current ramp-up phase the two-dimensional contour of the LiI intensity shows vertically alignment, consistent with the magnetic surfaces. At the inflection point in Ip ramp-up the LiI intensity contour becomes flat in the observation regime and then suddenly a steep gradient and higher intensity regime are formed in the vertical direction. This higher intensity corresponds to a burst of LiI waveform. According to these changes in the contour, it is found that, within ±1 ms around the burst of LiI, a low frequency coherent wave with a long wavelength rapidly grows. The relations with other signals (magnetic flux and microwave stray power) are discussed with respect to the topological change in the magnetic configuration and mode conversion of the incident electromagnetic waves.
The differential-phase reflectometry has been developed to measure the density profile, concerning electron Bernstein Wave (EBW) heating and current drive in the QUEST. The Phased Array Antenna (PAA) system was proposed for the reflectometry to improve the ratio of signal to noise. The PAA was confirmed to be effective, as a launching antenna to receive the larger reflected-wave signal.
We report the measurement of force-detected electron spin resonance (FDESR) at 154 GHz using a gyrotron. The high output power allows the use of a strong transverse magnetic field larger than 10 À4 T, which is sufficient to cause ESR saturation. We obtained the FDESR signal with a high spin sensitivity on the order of 10 12 spins/G at 280 K. Our system has promising applications in high-frequency ESR studies of low-spin concentration samples, such as metalloprotein solutions.
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