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A six-pole Q-band waveguide filter with a notch frequency above the Q-band has been developed for plasma diagnostics. The previous paper [Nishiura et al., J. Instrum. 10, C12014 (2015)] reported that the notch frequency exists within the standard band. In this study, the newly required notch filter extends the function, which prevents a thorny wave from being mixed into an instrument beyond the standard bandwidth of the waveguide. The mode control technique for cavities realizes a deep and sharp filter shape for Q-band notch filters with 56 and 77 GHz notches, respectively. The former filter has an attenuation more than 50 dB at 56.05 GHz and a bandwidth of 1.1 GHz at −3 dB. The latter filter has an attenuation more than 55 dB at 76.95 GHz and a bandwidth of 1.6 GHz at −3 dB. The electron cyclotron emission imaging and the electron cyclotron emission (ECE) diagnostics for the Q-band implemented a pair of the fabricated filters and demonstrated the ECE measurement successfully in the intense stray radiation from a 56 GHz gyrotron. [ABSTRACT FROM AUTHOR]

Microwave to millimeter-wave diagnostic techniques such as interferometry, reflectometry, scattering and radiometry have been powerful tools for diagnosing magnetically confined plasmas. Recent advances in electronic devices and components together with computer technology have enabled the development of advanced diagnostics in microwave to millimeter-wave region. The two-dimensional and three-dimensional profiles of plasma density/temperature and dynamic behaviors of their fluctuations are measured by using the advanced diagnostic systems. The measurements have clarified the physics issues such as stability, wave phenomena and fluctuation-induced transport. We report here on the representative microwave diagnostics and their contribution to plasma confinement physics. [ABSTRACT FROM AUTHOR]

Pulsed radar reflectometry is a suitable reflectometric technique with which to study the effect of strong magnetic shear for the polarization of microwaves in the Large Helical Device. Because pulsed radar reflectometry measures the delay time of the reflected wave, not the phase, X-mode and O-mode polarized waves can be distinguished. At a preliminary stage of X-mode operation it is found that the position of the ergodic edge layer is steady in spite of the increased density in the core region when a neutral beam is injected. If the electron density does not reach the critical cutoff density, the pulsed radar system could be used as a delayometer. The measured delayometer signal is almost in agreement with the numerical calculation under the assumption that polarization of the wave propagated into the plasma is decided at the edge region. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A CO[sub 2] laser polarimeter to measure the Faraday rotation in the large helical device (LHD) was developed and installed on a LHD. A CO[sub 2] laser whose wavelength is 10.6 μm was selected to avoid effects of the refraction. The Faraday rotation angle along toroidally tangential chords is of the order of one degree. The polarimeter utilizes the frequency-shift heterodyne technique with the use of acousto-optic modulators for high resolution. This polarimeter can be operated with a maximum of three channels. The accuracy of the Faraday rotation angle with a time resolution of 16 ms is about 0.01 deg by digital complex demodulation. We succeeded in performing preliminary measurements of the Faraday rotation angle from LHD plasmas and the values were 10%–30% larger than those estimated with the electron density profiles from interferometry. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A CO[sub 2] laser (λ=10.6 μm) imaging interferometer is designed for electron density profile and electron density fluctuation measurements on large helical device (LHD). The purposes of this diagnostic are reliable electron density monitor in high density operation (especially in pellet injection discharge), precise measurement of electron density profiles and observations of density fluctuations. By using a CO[sub 2] laser, refraction effect becomes negligible, and the interferometer promises to be free from fringe jumps at high density. We plan to get 5 mm spatial resolution, (56 ch for each of two 280 mm slab beams, 50 ch for one 250 mm and 16 ch for 80 mm crossed beam), 3×10[sup -3] rad phase resolution and 200 kHz frequency response for the above purpose. And fluctuation will be studied within the wave number range of 7×10[sup -3]<=k<=0.6 mm[sup -1]. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

For high density operation of the large helical device and for a future large plasma machine such as ITER, a powerful 57 μm CH[sub 3]OD laser pumped by a continuous wave 9R(8) CO[sub 2] laser has been developed. The 57 μm (5.2 THz) laser light has been successfully detected by using a GaAs Schottky barrier diode detector with a corner reflector. For optical windows of the plasma vessel and the far-infrared laser crystal quartz etalons have been designed under a concept of a two-wavelength etalon for 119 and 57 μm lights. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Describes the application of a cross-polarization scattering diagnostic method to the GAMMA 10 tandem mirror in order to study electromagnetic plasma waves with frequency less than 10 megahertz. Conversion of the incident ordinary wave to an extraordinary wave in a plasma; Evaluation of frequency spectra and density and magnetic fluctuations of the waves.

Discusses the fabrication of a millimeter-wave two-dimensional imaging array for the diagnosis of plug-cell plasma of the GAMMA 10 tandem mirror. Design of the heterodyne system; Measurement of the time evolution of the axial and radial line-density profiles; Fluctuation spectra of the electron cyclotron emission signals.