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

doi:10.1063/1.5039418

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

Full Record
Other Related Research

Abstract

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.

Authors:

Kubota, S. ^[1]; Majeski, R. ^[2];

^[2];

^[2]; Kozub, T. ^[2]; Lantsov, R. ^[1]; Merino, E. ^[2]; Nguyen, X. V. ^[1]; Peebles, W. A. ^[1]; Rhodes, T. L. ^[1]

Univ. of California, Los Angeles, CA (United States)
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Publication Date:: 2018-09-14

Research Org.:: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

Sponsoring Org.:: USDOE

OSTI Identifier:: 1484244

Alternate Identifier(s):: OSTI ID: 1470793

Grant/Contract Number:: AC02-09CH11466; FG02-99ER54527

Resource Type:: Accepted Manuscript

Journal Name:: Review of Scientific Instruments

Additional Journal Information:: Journal Volume: 89; Journal Issue: 10; Journal ID: ISSN 0034-6748

Publisher:: American Institute of Physics (AIP)

Country of Publication:: United States

Language:: English

Subject:: 47 OTHER INSTRUMENTATION

Citation Formats


                    Kubota, S., Majeski, R., Boyle, D. P., Kaita, R., Kozub, T., Lantsov, R., Merino, E., Nguyen, X. V., Peebles, W. A., and Rhodes, T. L. Millimeter-wave interferometry and far-forward scattering for density fluctuation measurements on LTX-β.  United States: N. p., 2018. 
        Web.  doi:10.1063/1.5039418.

Copy to clipboard


                    Kubota, S., Majeski, R., Boyle, D. P., Kaita, R., Kozub, T., Lantsov, R., Merino, E., Nguyen, X. V., Peebles, W. A., & Rhodes, T. L. Millimeter-wave interferometry and far-forward scattering for density fluctuation measurements on LTX-β.  United States.  doi:10.1063/1.5039418.

Copy to clipboard


                    Kubota, S., Majeski, R., Boyle, D. P., Kaita, R., Kozub, T., Lantsov, R., Merino, E., Nguyen, X. V., Peebles, W. A., and Rhodes, T. L. Fri .  
        "Millimeter-wave interferometry and far-forward scattering for density fluctuation measurements on LTX-β".  United States.  doi:10.1063/1.5039418.  https://www.osti.gov/servlets/purl/1484244.

Copy to clipboard


                    
@article{osti_1484244,

  title        = {Millimeter-wave interferometry and far-forward scattering for density fluctuation measurements on LTX-β},

  author       = {Kubota, S. and Majeski, R. and Boyle, D. P. and Kaita, R. and Kozub, T. and Lantsov, R. and Merino, E. and Nguyen, X. V. and Peebles, W. A. and Rhodes, T. L.},

  abstractNote = {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.},

  doi          = {10.1063/1.5039418},

  journal      = {Review of Scientific Instruments},

  number       = 10,

  volume       = 89,

  place        = {United States},

  year         = {2018},

  month        = {9}

}

Copy to clipboard

Journal Article:

Free Publicly Available Full Text

Accepted Manuscript (Publisher)

Accepted Manuscript (DOE)

Publisher's Version of Record

DOI: 10.1063/1.5039418

Other availability

Search WorldCat to find libraries that may hold this journal

Save / Share:

Export Metadata

Save to My Library

Similar Records in DOE PAGES and OSTI.GOV collections:

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

Journal Article Kubota, S. ; Majeski, R. ; Boyle, D. P. ; ... - Review of Scientific Instruments
DOI: 10.1063/1.5039418
High-frequency fluctuation measurements by far-infrared laser Faraday-effect polarimetry-interferometry and forward scattering system on MST

Journal Article Ding, W. X., E-mail: wding@ucla.edu ; Lin, L. ; Brower, D. L. ; ... - Review of Scientific Instruments

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{sup −1}more »« less
DOI: 10.1063/1.4889909
The charge exchange recombination spectroscopy diagnostic on the upgraded Lithium Tokamak eXperiment (LTX- β )

Journal Article Elliott, D. B. ; Biewer, T. M. ; Boyle, D. P. ; ... - Review of Scientific Instruments

The Lithium Tokamak eXperiment has undergone an upgrade to LTX- β, a major part of which is the addition of neutral beam injection (NBI). NBI has allowed for a new charge exchange recombination spectroscopy (CHERS) system to be installed in order to measure impurity concentrations, ion temperature, and toroidal velocity. Previously on LTX measuring these parameters relied on passive spectroscopy and inversion techniques and had large uncertainty. The CHERS system has 52 total views, split into four groups of 13, half facing toward the beam and half symmetrically facing away from the beam, so the background non-beam related emission canmore »« less
DOI: 10.1063/1.5039368

Full Text Available
Density fluctuation measurements by far-forward collective scattering in the MST reversed-field pinch

Journal Article Ding, W. X. ; Lin, L. ; Brower, D. L. ; ... - Review of Scientific Instruments

The multichannel polarimeter-interferometer system on the MST reversed-field pinch can be utilized to measure far-forward collective scattering from electron density fluctuations. The collective scattering system has 11 viewing chords with {approx}8 cm spacing. The source is a 432 {mu}m (694 GHz) far infrared laser and the scattered power is measured using a heterodyne detection scheme. Collective scattering provides a line-integrated measurement of fluctuations within the divergence of the probe beam covering wavenumber range: k{sub Up-Tack} < 1.3 cm{sup -1}, corresponding k{sub Up-Tack }{rho}{sub s} < 1.3 ({rho}{sub s} is the ion-sound Larmor radius), the region of primary interest for turbulentmore »« less
DOI: 10.1063/1.4728098
Electron density and gas density measurements in a millimeter-wave discharge

Journal Article Schaub, S. C. ; Hummelt, J. S. ; Guss, W. C. ; ... - Physics of Plasmas

Here, electron density and neutral gas density have been measured in a non-equilibrium air breakdown plasma using optical emission spectroscopy and two-dimensional laser interferometry, respectively. A plasma was created with a focused high frequency microwave beam in air. Experiments were run with 110 GHz and 124.5 GHz microwaves at powers up to 1.2 MW. Microwave pulses were 3 μs long at 110 GHz and 2.2 μs long at 124.5 GHz. Electron density was measured over a pressure range of 25 to 700 Torr as the input microwave power was varied. Electron density was found to be close to the criticalmore »« less
Cited by 3
DOI: 10.1063/1.4959171

Full Text Available

Similar Records