High time resolved electron temperature measurements by using the multi-pass Thomson scattering system in GAMMA 10/PDX

High time resolved electron temperature measurements are useful for fluctuation study. A multi-pass Thomson scattering (MPTS) system is proposed for the improvement of both increasing the TS signal intensity and time resolution. The MPTS system in GAMMA 10/PDX has been constructed for enhancing the Thomson scattered signals for the improvement of measurement accuracy. The MPTS system has a polarization-based configuration with an image relaying system. We optimized the image relaying optics for improving the multi-pass laser confinement and obtaining the stable MPTS signals over ten passing TS signals. The integrated MPTS signals increased about five times larger than that in the single pass system. Finally, time dependent electron temperatures were obtained in MHz sampling

Development of a Multi-Channel Horn Mixer Array for Microwave Imaging Plasma Diagnostics

Microwave to millimeter-wave diagnostics techniques, such as interferometry, reflectometry, scattering, and radiometry, have been powerful tools for diagnosing magnetically confined plasmas. The resultant measurements have clarified several physics issues, including instability, wave phenomena, and fluctuation-induced transport. Electron cyclotron emission imaging has been an important tool in the investigation of temperature fluctuations, while reflectometry has been employed to measure plasma density profiles and their fluctuations. We have developed a horn-antenna mixer array (HMA), a 50 - 110 GHz 1D antenna array, which can be easily stacked as a 2D array. This article describes an upgrade to the horn mixer array that combines well-characterized mixers, waveguide-to-microstrip line transitions, intermediate frequency amplifiers, and internal local oscillator modules using a monolithic microwave integrated circuit technology to improve system performance. We also report on the use of a multi-channel HMA system

Spatiotemporal Structure of Hα Emission from the Detached Plasma in GAMMA 10/PDX

High-speed camera measurement was performed for analyses of detached plasma fluctuation in the GAMMA 10/PDX tandem mirror device. Significant spectral peaks at frequencies of 1.5 and 3 kHz were observed to have several local maxima along the vertical, near the entrance of the V-shaped target. Wavelet analysis indicated that 1.5- and 3-kHz fluctuations became non-simultaneously strong. Their phase relationships demonstrated inversion-symmetric and symmetric features with respect to the midplane. Such spectral patterns were interpreted as the line-integral of odd- and even-mode structures. It is suspected that the vertical edge part was due to radially elongated structures with an azimuthal phase shift