REVIEW OF SCIENTIFIC INSTRUMENTS 85, 11D406 (2014)
High-frequency fluctuation measurements by far-infrared laser Faraday-effect polarimetry-interferometry and forward scattering system on MSTa) W. X. Ding,1,b) L. Lin,1 J. R. Duff,2 and D. L. Brower1 1 2
Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA 90095, USA Department of Physics, University of Wisconsin-Madison, Wisconsin 53706, USA
(Presented 2 June 2014; received 31 May 2014; accepted 29 June 2014; published online 21 July 2014) Magnetic fluctuation-induced transport driven by global tearing modes has been measured by Faraday-effect polarimetry and interferometry (phase measurements) in the MST reversed field pinch. However, the role of small-scale broadband magnetic and density turbulence in transport remains unknown. In order to investigate broadband magnetic turbulence, we plan to upgrade the existing detector system by using planar-diode fundamental waveguide mixers optimized for high sensitivity. Initial tests indicate these mixers have ×10 sensitivity improvement compared to currently employed corner-cube Schottky-diode mixers and ×5 lower noise. Compact mixer design will allow us to resolve the wavenumbers up to k ∼ 1–2 cm−1 for beam width w = 1.5 cm and 15 cm−1 for beam width w = 2 mm. The system can also be used to measure the scattered signal (amplitude measurement) induced by both plasma density and magnetic fluctuations. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4889909] I. INTRODUCTION
A laser-based far-infrared polarimeter-interferometer diagnostic has been employed on the MST reversed-field pinch (RFP) to non-perturbatively measure both density and magnetic fluctuations.1, 2 In addition to these phase measurements, far-forward collective scattering has also been used to extract density perturbation information from the amplitude fluctuations.3 These measurements have focused on global tearing modes in the frequency range
High-frequency fluctuation measurements by far-infrared laser Faraday-effect polarimetry-interferometry and forward scattering system on MSTa) W. X. Ding,1,b) L. Lin,1 J. R. Duff,2 and D. L. Brower1 1 2
Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA 90095, USA Department of Physics, University of Wisconsin-Madison, Wisconsin 53706, USA
(Presented 2 June 2014; received 31 May 2014; accepted 29 June 2014; published online 21 July 2014) Magnetic fluctuation-induced transport driven by global tearing modes has been measured by Faraday-effect polarimetry and interferometry (phase measurements) in the MST reversed field pinch. However, the role of small-scale broadband magnetic and density turbulence in transport remains unknown. In order to investigate broadband magnetic turbulence, we plan to upgrade the existing detector system by using planar-diode fundamental waveguide mixers optimized for high sensitivity. Initial tests indicate these mixers have ×10 sensitivity improvement compared to currently employed corner-cube Schottky-diode mixers and ×5 lower noise. Compact mixer design will allow us to resolve the wavenumbers up to k ∼ 1–2 cm−1 for beam width w = 1.5 cm and 15 cm−1 for beam width w = 2 mm. The system can also be used to measure the scattered signal (amplitude measurement) induced by both plasma density and magnetic fluctuations. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4889909] I. INTRODUCTION
A laser-based far-infrared polarimeter-interferometer diagnostic has been employed on the MST reversed-field pinch (RFP) to non-perturbatively measure both density and magnetic fluctuations.1, 2 In addition to these phase measurements, far-forward collective scattering has also been used to extract density perturbation information from the amplitude fluctuations.3 These measurements have focused on global tearing modes in the frequency range
