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

Kubota, S.; Majeski, R.; Boyle, D. P.; Kaita, R.; Kozub, T.; Lantsov, R.; Merino, E.; Nguyen, X. V.; Peebles, W. A.; Rhodes, T. L.

doi:10.1063/1.5039418

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

Journal Article · 13 September 2018 · Review of Scientific Instruments

DOI: https://doi.org/10.1063/1.5039418 · OSTI ID:1484244

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)

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.

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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

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