Title: A novel Doppler backscattering (DBS) system to simultaneously measure radio frequency plasma fluctuations and low frequency turbulence

Abstract

A novel quadrature Doppler Backscattering (DBS) system has been developed and optimized for the E-band (60–90 GHz) frequency range using either O-mode or X-mode polarization in DIII-D plasmas. In general, DBS measures the amplitude of density fluctuations and their velocity in the lab frame. The system can simultaneously monitor both low-frequency turbulence (f < 10 MHz) and radiofrequency plasma density fluctuations over a selectable frequency range (20–500 MHz). Detection of high-frequency fluctuations has been demonstrated for low harmonics of the ion cyclotron frequency (e.g., 2fci ∼ 23 MHz) and externally driven high-frequency helicon waves (f = 476 MHz) using an adjustable frequency down conversion system. Importantly, this extends the application of DBS to a high-frequency spectral domain while maintaining important turbulence and flow measurement capabilities. This unique system has low phase noise, good temporal resolution (sub-millisecond), and excellent wavenumber coverage (kθ ∼ 1–20 cm−1 and kr ≲ 30 cm−1). As a demonstration, localized internal DIII-D plasma measurements are presented from turbulence (f ≤ 5 MHz), Alfvenic waves (f ∼ 6.5 MHz), ion cyclotron waves (f ≥ 20 MHz), as well as fluctuations around 476 MHz driven by an external high-power 476 MHz helicon wave antenna. In the future, helicon measurements will be used to validate GENRAY and AORSA modeling tools for predictionmore » of helicon wave propagation, absorption, and current drive location for the newly installed helicon current drive system on DIII-D.« less

Authors:

Chowdhury, Satyajit  ^[1];

• Search DOE PAGES for author "Chowdhury, Satyajit"
• Search DOE PAGES for ORCID "0000-0001-8435-6693"

Crocker, Neal A.  ^[1];

• Search DOE PAGES for author "Crocker, Neal A."
• Search DOE PAGES for ORCID "0000-0003-2379-5814"

Peebles, W. A.  ^[1];

• Search DOE PAGES for author "Peebles, W. A."
• Search DOE PAGES for ORCID "0000-0002-4210-6749"

Rhodes, Terry L.  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-8311-4892"

Zeng, Lei  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-5856-3912"

Lantsov, R. ^[1]; Van Compernolle, B. ^[2]; Brookman, Michael  ^[3];

• Search DOE PAGES for author "Brookman, Michael"
• Search DOE PAGES for ORCID "0000-0002-5838-1630"

Pinsker, Robert I.  ^[2];

• Search DOE PAGES for author "Pinsker, Robert I."
• Search DOE PAGES for ORCID "0000-0003-2683-9480"

Lau, Cornwall  ^[4]

• Search DOE PAGES for author "Lau, Cornwall"
• Search DOE PAGES for ORCID "0000-0002-8576-5867"

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+ Show Author Affiliations

1. Univ. of California, Los Angeles, CA (United States)
2. General Atomics, San Diego, CA (United States)
3. General Atomics, San Diego, CA (United States); Commonwealth Fusion Systems, Devens, MA (United States)
4. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Publication Date:

Wed Jul 26 00:00:00 EDT 2023

Research Org.:

Univ. of California, Los Angeles, CA (United States); General Atomics, San Diego, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Fusion Energy Sciences (FES); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)

OSTI Identifier:

1993278

Alternate Identifier(s):

OSTI ID: 1993078

Grant/Contract Number:  

SC0020649; FC02-04ER54698; SC0020337

Resource Type:

Accepted Manuscript

Journal Name:

Review of Scientific Instruments

Additional Journal Information:

Journal Volume: 94; Journal Issue: 7; Journal ID: ISSN 0034-6748

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Doppler backscattering; Microwave; Turbulence; RF waves