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Title: Millimeter-wave interferometry and far-forward scattering for density fluctuation measurements on LTX-β

Journal Article · · Review of Scientific Instruments
DOI: https://doi.org/10.1063/1.5039418 · OSTI ID:1484244

The λ ≈ 1 mm (f = 288 GHz) interferometer for the Lithium Tokamak Experiment-β (LTX-β) will use a chirped-frequency source and a centerstack-mounted retro-reflector mirror to provide electron line density measurements along a single radial chord at the midplane. The interferometer is unique in the use of a single source (narrow-band chirped-frequency interferometry) and a single beam splitter for separating and recombining the probe and reference beams. The current work provides a documentation of the interferometry hardware and evaluates the capabilities of the system as a far-forward collective scattering diagnostic. As such, the current optical setup is estimated to have a detection range of 0.4 ≲ k ≲ 1.7 cm–1, while an improved layout will extend the upper k limit to ~3 cm–1. Measurements with the diagnostic on LTX are presented, showing interferometry results and scattered signal data. Furthermore, these diagnostics are expected to provide routine measurements on LTX-β for high frequency coherent density oscillations (e.g., Alfvénic modes during neutral beam injection) as well as for broadband turbulence.

Research Organization:
Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
AC02-09CH11466; FG02-99ER54527
OSTI ID:
1484244
Alternate ID(s):
OSTI ID: 1470793
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

References (18)

Performance projections for the lithium tokamak experiment (LTX) journal April 2009
Design and operation of a low cost, reliable millimeter-wave interferometer journal January 1999
Observation of Flat Electron Temperature Profiles in the Lithium Tokamak Experiment journal July 2017
Assessment of microwave power flow for reflectometry measurements in tokamak plasmas journal January 2008
Density fluctuation measurements by far-forward collective scattering in the MST reversed-field pinch journal October 2012
Multichannel interferometer system for the helically symmetric experiment journal January 2001
Compatibility of lithium plasma-facing surfaces with high edge temperatures in the Lithium Tokamak Experiment journal May 2017
Study of density fluctuations in plasmas by small-angle CO2 laser scattering journal January 1980
A frequency-modulated continuous-wave reflectometer for the Lithium Tokamak Experiment journal May 2017
Beam tracing in inhomogeneous anisotropic plasmas journal October 1998
Applications of the Fraunhofer-diffraction method for plasma-wave measurements journal October 1983
Far-forward collective scattering measurements of density fluctuations in the helically symmetric experiment stellarator journal October 2010
Fourier optics approach to far forward scattering and related refractive index phenomena in laboratory plasmas journal July 1982
Diffraction of a Gaussian beam at an aperture journal January 1990
Far-forward collective scattering measurements by FIR polarimeter-interferometer on J-TEXT tokamak journal August 2016
Far infrared laser polarimetry and far forward scattering diagnostics for the C-2 field reversed configuration plasmas journal November 2014
Characterization of a Dual-Mode Horn for Submillimeter Wavelengths (Short Papers) journal August 1984
Exploration of spherical torus physics in the NSTX device journal March 2000