Correlation polarimetry for broadband magnetic fluctuation measurements

Parke, E.; Ding, W. X.; Brower, D. L.

doi:10.1063/1.5038832

Correlation polarimetry for broadband magnetic fluctuation measurements

Journal Article · Fri Sep 21 00:00:00 EDT 2018 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.5038832· OSTI ID:1609214

Parke, E. ^[1]; Ding, W. X. ^[2]; Brower, D. L. ^[2]

Univ. of California, Los Angeles, CA (United States); DOE/OSTI
Univ. of California, Los Angeles, CA (United States)

Correlation techniques have been successfully utilized for plasma diagnostics like electron cyclotron emission to reduce measurement noise. Herein we present the first application of such a technique to Faraday-effect polarimetry measurements on the Madison Symmetric Torus (MST). The MST far infrared (FIR) interferometer-polarimeter diagnostic utilizes 11 vertical chords with a chord separation of 7-8 cm and a heterodyne detection system for fluctuation measurements up to several hundred kHz. The planar-diode mixers viewing each chord represent independent noise sources; modifying the optical setup so that two different mixers view the same chord allows cross correlation between the two independent signals to reduce the noise floor in fluctuation measurements. In this manner, the noise floor in both interferometry and polarimetry measurements in reversed-field pinch discharges has been reduced by a factor of 20-30. The correlation polarimeter provides a sensitive measurement of broadband magnetic fluctuations.

Research Organization:: Univ. of California, Los Angeles, CA (United States); Univ. of Wisconsin, Madison, WI (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)

Grant/Contract Number:: FC02-05ER54814; FG02-01ER54615

OSTI ID:: 1609214

Alternate ID(s):: OSTI ID: 1471801

Journal Information:: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 10 Vol. 89; ISSN 0034-6748

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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