A5050669893- Particle accelerators and beam dynamics
- Magnetic confinement fusion research
- Gyrotron and Vacuum Electronics Research
- Semiconductor materials and devices
- Advanced Data Storage Technologies
- Plasma Diagnostics and Applications
- Electrostatic Discharge in Electronics
- Particle Detector Development and Performance
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Advancements in PLL and VCO Technologies
- Laser-Plasma Interactions and Diagnostics
- Atomic and Molecular Physics
- HVDC Systems and Fault Protection
- Acoustic Wave Resonator Technologies
- Fusion materials and technologies
- Microwave Engineering and Waveguides
- GaN-based semiconductor devices and materials
- Silicon Carbide Semiconductor Technologies
- Superconducting and THz Device Technology
- Particle Accelerators and Free-Electron Lasers
- Electric Motor Design and Analysis
- Dust and Plasma Wave Phenomena
- Semiconductor Lasers and Optical Devices
- Advancements in Semiconductor Devices and Circuit Design
Plasma Technology (United States)
2025
Fusion Academy
2025
General Atomics (United States)
2013-2024
Fusion (United States)
2019
DIII-D National Fusion Facility
2019
University of Wisconsin–Madison
2003-2007
Foundation for Research and Technology Hellas
2001-2002
University of Crete
2001
FORTH Institute of Electronic Structure and Laser
2001
Institute of Physics and Technology
1996
A new frequency-stepped Doppler backscattering (DBS) system has been integrated into a real-time steerable electron cyclotron heating launcher to simultaneously probe local background turbulence (f < 10 MHz) and high-frequency (20–550 density fluctuations in the DIII-D tokamak. The allows for 2D steering (horizontally vertically) over wide angular ranges optimize location wavenumber response. vertical can be optimized during discharge real time. DBS employs programmable frequency...
Energy confinement comparable with tokamak quality is achieved in the Madison Symmetric Torus (MST) reversed field pinch (RFP) at a high beta and low toroidal magnetic field. Magnetic fluctuations normally present RFP are reduced via parallel current drive outer region of plasma. In response, electron temperature nearly triples doubles. The time increases ten-fold (to ∼10 ms), which L- H-mode scaling values for same plasma current, density, heating power, size shape. Runaway evidenced by...
Abstract DIII-D physics research addresses critical challenges for the operation of ITER and next generation fusion energy devices. This is done through a focus on innovations to provide solutions high performance long pulse operation, coupled with fundamental plasma understanding model validation, drive scenario development by integrating core boundary plasmas. Substantial increases in off-axis current efficiency from an innovative top launch system EC power, pressure broadening Alfven...
The electron cyclotron heating (ECH) system on the DIII-D fusion reactor consists of six 110-GHz gyrotrons with 6 MW installed power for pulses limited administratively to 5 s in length. transmission coefficient is better than -1.1 dB four lines, which close theoretical value. A new depressed collector gyrotron was recently and injecting up 720 kW into during 2013 tokamak operations. Three dual waveguide launchers, can steer RF beams ±20° both poloidally toroidally, were used real-time...
Abstract For the first time, experiments on DIII-D tokamak have demonstrated electron cyclotron current drive with more than double conventional efficiency by tailoring wave–particle interactions in velocity space using a novel ‘top launch’ geometry. Steering EC waves to propagate nearly parallel resonance drives efficiently (1) selective damping electrons higher v ||, and (2) longer absorption path compensate for inherently weaker at ||. Experiments fixed-injection top launch system find an...
Abstract The DIII-D tokamak has elucidated crucial physics and developed projectable solutions for ITER fusion power plants in the key areas of core performance, boundary heat particle transport, integrated scenario operation, with closing core-edge integration knowledge gap being overarching mission. New experimental validation high-fidelity, multi-channel, non-linear gyrokinetic turbulent transport models provides strong confidence it will achieve Q ⩾ 10 operation. Experiments identify...
Confinement in the reversed field pinch (RFP) has been shown to increase strongly with current profile control. The MST RFP can operate two regimes: standard regime a naturally occurring density profile, robust reconnection and dynamo activity; improved confinement strong reduction reconnection, transport. New results plasmas include observation of two-fluid Hall effect dynamo, determination that m = 0 edge resonant mode is nonlinearly driven, tearing modes lock wall via eddy currents shell....
Generation and sustainment of the reversed field pinch (RFP) magnetic configuration normally relies on dynamo activity. The externally applied electric tends to drive equilibrium away from relaxed, minimum energy state which is roughly described by a flat normalized parallel current density profile at marginal stability tearing modes. Correlated fluctuations velocity create broadens profile, supplying necessary edge drive. These pervasive are also responsible for destruction flux surfaces,...
The DIII-D electron cyclotron heating (ECH) system consists of six 110-GHz gyrotrons with corrugated coaxial 31.75-mm waveguide transmission lines, and steerable launching mirrors. has been gradually updated, leading to an increased experimental flexibility a high reliability 91% in the past year. Operationally, can generate up total 4.8 MW RF power for pulses 5 seconds. maximum ECH energy injected into is 16.6 MJ. HE1,1 mode content over 85% all coefficient better than -1.1 dB close...
AbstractAbstractThe measurement of the power injected by electron cyclotron heating (ECH) system in DIII-D tokamak is a critical requirement for analysis experiments, tuning gyrotrons maximum and efficiency, tracking long-term operational trends, providing warning problems with system. The ECH at General Atomics consists six 110-GHz, 1-MW-class gyrotrons. radio-frequency (rf) generated each gyrotron determined from calorimetry, using relevant temperature flow measurements cooling circuits...
The DIII-D electron cyclotron heating and current drive (ECH/ECCD) system has been operating with an annual average of 4268 individual gyrotron pulses into the plasma in last four years 3-3.6 MW yearly power availability ten years. This allowed increase number range experiments involving injection 110 117.5 GHz EC tokamak plasma. Some operational limitations encountered for X-mode second harmonic resonance scenario launched overdense plasmas were bypassed alternative use O-mode launch...
The DIII-D ECH complex is being upgraded with three new depressed collector gyrotrons. performance of the existing system has been very good. As more gyrotrons having higher power are added to system, diagnostics gyrotron operation, optimization and qualification components for become important. A FPGA-based control installed, additional capabilities rapid real time variation rf injection angles by Plasma Control System tested infrastructure enhancements completed. Longer term plans continue...
Coupling to the electron Bernstein wave (EBW) via a phased array of waveguides is experimentally investigated in Madison symmetric torus reversed field pinch (RFP). EBWs promise provide localized heating and current drive overdense plasmas such as those RFP, provided technique can be developed efficiently couple power from an externally launched electromagnetic electrostatic EBW. The choice antenna structure polarization are important factors coupling waves with frequencies cyclotron range...
Operational trends for the six-gyrotron electron cyclotron heating system on DIII-D are presented. Losses in transmission lines were measured and values close to theoretical attained one of with existing components. Improved alignment reduction number miter bends will increase power transmitted through waveguide tokamak.
An imminent gyrotron body current fault can now be detected and avoided in less than 10 µs using a high-resolution, real-time, high-voltage reference waveform generator with signal analyzer subroutines. The is restarted full power resumed little over ms.
In the general area of confinement improvement and concept advancement, recent results in Madison Symmetric Torus (MST) reversed-field pinch (RFP) include good both thermal large-orbit ions near doubling total beta to 26% with deuterium pellet injection. Current profile control enables MST reduce stochastic transport achieve tokamak-like confinement. standard RFP operation, substantial MHD tearing mode activity an energy time about 1 ms MST. Application inductive current reduces accompanying...
A new frequency-stepped Doppler backscattering (DBS) system has been integrated with a real-time steerable electron cyclotron heating launcher to probe local background turbulence (f<10 MHz) and high-frequency (20-550 density fluctuations in the DIII-D tokamak. The enables 2D steering (horizontal vertical) over wide angular ranges optimize location wavenumber response, vertical adjustable real time during discharges. DBS utilizes programmable frequency synthesizer dwell time, capable of...
The expansion and upgrading of the electron cyclotron heating current drive (ECH/ECCD) gyrotron complex on DIII-D tokamak are continuing with addition first a series depressed collector tubes in 1 MW class. ultimate goal is 10 system rapid steering rf beams full integration into Plasma Control System using real time EFIT equilibrium calculation to determine ECH/ECCD deposition locations guide requirements for both injected power.