Combination Doppler backscattering/cross-polarization scattering diagnostic for the C-2W field-reversed configuration

Schmitz, L.; Deng, B. H.; Thompson, M. C.; Gota, H.; Lau, Calvin; Fulton, Daniel; Zhang, Lin; Tajima, T.; Binderbauer, Michl; Team, Tae

doi:10.1063/1.5038914

Cited by 4 publications

(3 citation statements)

References 19 publications

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“…Consequently, broad operating range and functionality for each diagnostic system is essential on C-2W. As shown in figure 3, plasma performance and parameters at different zones/areas are investigated and provided by a comprehensive suite of diagnostics that includes magnetic sensors [28], Langmuir probes [29], far-infrared interferometry/polarimetry [30], Thomson scattering [31], VUV/visible/IR spectroscopy, bolometry, reflectometry [32], energy analyzers [33], neutral particle analyzers, fusion product detectors, secondary electron emission detectors [34], and multiple fast imaging cameras [35]. In addition, extensive ongoing work focuses on advanced methods of measuring separatrix shape and plasma current profile that will facilitate equilibrium reconstruction and active control of FRCs [36].…”

Section: Plasma Diagnostic Suitementioning

confidence: 99%

Formation of hot, stable, long-lived field-reversed configuration plasmas on the C-2W device

Gota¹,

Binderbauer²,

Tajima³

et al. 2019

Nucl. Fusion

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TAE Technologies' research is devoted to producing high temperature, stable, long-lived field-reversed configuration (FRC) plasmas by neutral-beam injection (NBI) and edge biasing/control. The newly constructed C-2W experimental device (also called "Norman") is the world's largest compact-toroid (CT) device, which has several key upgrades from the preceding C-2U device such as higher input power and longer pulse duration of the NBI system as well as installation of inner divertors with upgraded electrode biasing systems. Initial C-2W experiments have successfully demonstrated a robust FRC formation as well as its translation into the confinement vessel through the newly installed inner divertor with adequate guide magnetic field. They also produced dramatically improved initial FRC parameters with higher plasma temperatures (Te up to 300 eV; total electron and ion temperature >1.5 keV) and more trapped flux (up to ~15 mWb, based on rigid-rotor model) inside the FRC immediately after the merger of collided two CTs in the confinement section. As for effective edge biasing/control on FRC stabilization, a number of edge biasing schemes have been tried via open-fieldlines, in which concentric electrodes located in both inner and outer divertors as well as end-on plasma guns are electrically biased independently. As a result of effective outer-divertor electrode biasing alone, FRC plasma diamagnetism duration has reached up to ~9 ms which is equivalent to C-2U plasma duration. Magnetic field flaring/expansion in both inner and outer divertors plays an important role in creating a thermal insulation on open-field-lines to reduce a loss rate of electrons, which leads to improvement of the edge as well as core FRC confinement properties.

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Section: Plasma Diagnostic Suitementioning

confidence: 99%

Formation of hot, stable, long-lived field-reversed configuration plasmas on the C-2W device

Gota¹,

Binderbauer²,

Tajima³

et al. 2019

Nucl. Fusion

Self Cite

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“…The diagnostics deployed on C-2W are required to provide data for a very wide range of plasma parameters to follow the discharge evolution from a seed FRC to a much hotter and higher energy state. Plasma performance and various other parameters are discerned using this comprehensive suite of diagnostics that includes: a variety of magnetic probes [29]; several iterations of bolometers; multiple interferometers including a far-infrared (FIR) interferometer/polarimeter [30], millimeter-wave interferometer [31], dispersion interferometer [32], and micrometer-wave interferometer [33]; core and jet region Thomson scattering systems [34,35]; spectroscopy of many varieties including impurity-and main-ion chargeexchange recombination spectroscopy (ChERS) [36,37], a combination doppler backscattering/cross-polarization scattering reflectometer [38], fast-ion D α spectrometer [39],…”

Section: Plasma Diagnostic Suitementioning

confidence: 99%

“…A four-channel Doppler backscattering (DBS) system is used in C-2W to investigate radial profiles and properties of turbulent density fluctuations [38]. Due to the ability to control the incidence angle of the combined launched microwave beam (of width ΔW 3 cm), the toroidal density fluctuation wavenumber spectrum ñ(k θ ) can be acquired from the amplitude of the backscattered signal.…”

Section: Density Fluctuationmentioning

confidence: 99%

Overview of C-2W: high temperature, steady-state beam-driven field-reversed configuration plasmas

Gota¹,

Binderbauer²,

Tajima³

et al. 2021

Nucl. Fusion

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TAE Technologies, Inc. (TAE) is pursuing an alternative approach to magnetically confined fusion, which relies on field-reversed configuration (FRC) plasmas composed of mostly energetic and well-confined particles by means of a state-of-the-art tunable energy neutral-beam (NB) injector system. TAE’s current experimental device, C-2W (also called ‘Norman’), is the world’s largest compact-toroid device and has made significant progress in FRC performance, producing record breaking, high temperature (electron temperature, T e > 500 eV; total electron and ion temperature, T tot > 3 keV) advanced beam-driven FRC plasmas, dominated by injected fast particles and sustained in steady-state for up to 30 ms, which is limited by NB pulse duration. C-2W produces significantly better FRC performance than the preceding C-2U experiment, in part due to Google’s machine-learning framework for experimental optimization, which has contributed to the discovery of a new operational regime where novel settings for the formation section and the confinement region yield consistently reproducible, hot, and stable plasmas. An active plasma control system has been developed and utilized in C-2W to produce consistent FRC performance as well as for reliable machine operations using magnets, electrodes, gas injection, and tunable NBs. The active control system has demonstrated stabilization of FRC axial instability. Overall FRC performance is well correlated with NBs and edge-biasing system, where higher total plasma energy is obtained by increasing both NB injection power and applied-voltage on biasing electrodes. C-2W divertors have demonstrated a good electron heat confinement on open-field-lines using strong magnetic mirror fields as well as expanding the magnetic field in the divertors (expansion ratio > 30); the energy lost per electron ion pair, η e ∼ 6–8, is achieved, which is close to the ideal theoretical minimum.

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Integrated diagnostic and data analysis system of the C-2W advanced beam-driven field-reversed configuration plasma experiment

Thompson

Schindler

Mendoza

et al. 2018

Review of Scientific Instruments

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The new C-2W experiment (also called Norman) at TAE Technologies, Inc. studies the evolution of field-reversed configuration (FRC) plasmas sustained by neutral beam injection. Data on the FRC plasma performance are provided by a comprehensive suite of diagnostics that includes over 700 magnetic sensors, four interferometer systems, multi-chord far-infrared polarimetry, two Thomson scattering systems, ten types of spectroscopic measurements, multiple fast imaging cameras with selectable atomic line filters, bolometry, reflectometry, neutral particle analyzers, and fusion product detectors. Most of these diagnostic systems are newly built using experience and data from the preceding C-2U experiment to guide the design process. A variety of commercial and custom acquisition electronics collect over 4000 raw signals from the C-2W diagnostics. These data are processed into physics results using a large-scale database of diagnostics metadata and analysis software, both built using open-source software tools.

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Combination Doppler backscattering/cross-polarization scattering diagnostic for the C-2W field-reversed configuration

Cited by 4 publications

References 19 publications

Formation of hot, stable, long-lived field-reversed configuration plasmas on the C-2W device

Formation of hot, stable, long-lived field-reversed configuration plasmas on the C-2W device

Overview of C-2W: high temperature, steady-state beam-driven field-reversed configuration plasmas

Integrated diagnostic and data analysis system of the C-2W advanced beam-driven field-reversed configuration plasma experiment

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