A5062010005- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Solar and Space Plasma Dynamics
- Semiconductor materials and devices
- Physics of Superconductivity and Magnetism
- Laser-induced spectroscopy and plasma
- Nuclear Physics and Applications
- Advanced Data Storage Technologies
- Dust and Plasma Wave Phenomena
- Advancements in Semiconductor Devices and Circuit Design
- Atomic and Subatomic Physics Research
- Nuclear reactor physics and engineering
- Geomagnetism and Paleomagnetism Studies
- Electron and X-Ray Spectroscopy Techniques
- Atomic and Molecular Physics
- Non-Destructive Testing Techniques
- Diamond and Carbon-based Materials Research
- Magnetic Field Sensors Techniques
- Aerospace Engineering and Control Systems
- Quantum and electron transport phenomena
General Atomics (United States)
2016-2025
Columbia University
2015-2024
Applied Mathematics (United States)
2023-2024
Culham Science Centre
2015-2024
Culham Centre for Fusion Energy
2015-2024
Max Planck Institute for Plasma Physics
2022
CEA Cadarache
2021
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2021
Oak Ridge Associated Universities
2013-2018
University of California, San Diego
2017-2018
The SPARC tokamak is a critical next step towards commercial fusion energy. designed as high-field ( $B_0 = 12.2$ T), compact $R_0 1.85$ m, $a 0.57$ m), superconducting, D-T with the goal of producing gain $Q>2$ from magnetically confined plasma for first time. Currently under design, will continue path Alcator series tokamaks, utilizing new magnets based on rare earth barium copper oxide high-temperature superconductors to achieve high performance in device. achievable conservative...
Rapid bifurcations in the plasma response to slowly varying $n=2$ magnetic fields are observed as transitions into and out of edge-localized mode (ELM) suppression. The rapid transition ELM suppression is characterized by an increase toroidal rotation a reduction electron pressure gradient at top pedestal that reduces perpendicular flow there near zero. These events occur simultaneously with inner-wall response. observations consistent strong resonant field penetration onset suppression,...
Density pumpout and edge-localized mode (ELM) suppression by applied $n=2$ magnetic fields in low-collisionality DIII-D plasmas are shown to be correlated with the magnitude of plasma response driven on high-field side (HFS) axis but not low-field (LFS) midplane. These distinct responses a direct measurement multimodal response, each structure preferentially excited different spectrum detected LFS or HFS. Ideal resistive magneto-hydrodynamic (MHD) calculations find that is primarily...
Access conditions for full suppression of Edge Localised Modes (ELMs) by Magnetic Perturbations (MP) in low density high confinement mode (H-mode) plasmas are studied the ASDEX Upgrade tokamak. The main empirical requirements ELM our experiments are: 1. poloidal spectrum MP must be aligned best plasma response from weakly stable kink-modes, which amplify perturbation, 2. edge below a critical value, $3.3 \times 10^{19}$~m$^{-3}$. collisionality is range $\nu^*_i = 0.15-0.42$ (ions) and...
Recent EAST/DIII-D joint experiments on the high poloidal beta tokamak regime in DIII-D have demonstrated fully noninductive operation with an internal transport barrier (ITB) at large minor radius, normalized fusion performance increased by ≥30% relative to earlier work (Politzer et al 2005 Nucl. Fusion 45 417). The advancement was enabled improved understanding of 'relaxation oscillations', previously attributed repetitive ITB collapses, and fast ion behavior this regime. It found that...
DIII-D experiments at low density (n_{e}∼10^{19} m^{-3}) have directly measured whistler waves in the 100-200 MHz range excited by multi-MeV runaway electrons. Whistler activity is correlated with intensity (hard x-ray emission level), occurs novel discrete frequency bands, and exhibits nonlinear limit-cycle-like behavior. The frequencies scale magnetic field strength electron as expected from dispersion relation. modes are stabilized increasing field, which consistent wave-particle...
For the first time it is experimentally demonstrated on JET tokamak that a combination of low impurity concentration bulk plasma and large magnetohydrodynamic instabilities able to suppress relativistic electron beams without measurable heat loads onto facing components. Magnetohydrodynamic simulations instability modeling postinstability confirm prompt loss runaways absence regeneration during final current collapse. These surprising findings motivate new approach dissipate runaway...
Diverted discharges at negative triangularity on the DIII-D tokamak sustain normalized confinement and pressure levels typical of standard H-mode scenarios (H98y2 ≃ 1, βN 3) without developing an edge pedestal, despite auxiliary power far exceeding L → H threshold expected from conventional scaling laws. The degradation is substantially weaker than ITER-89P scaling, resulting in a factor that improves with increasing power. absence pedestal beneficial several ways, such as eliminating need...
In a series of high performance diverted discharges on DIII-D, we demonstrate that strong negative triangularity (NT) shaping robustly suppresses all edge-localized mode (ELM) activity over wide range plasma conditions: ⟨n⟩=0.1-1.5×10^{20} m^{-3}, P_{aux}=0-15 MW, and |B_{t}|=1-2.2 T, corresponding to P_{loss}/P_{LH08}∼8. The full dataset is consistent with the theoretical prediction magnetic shear in NT edge inhibits access ELMing H-mode regimes; experimental pressure profiles are found be...
Abstract Strongly-shaped diverted negative triangularity (NT) plasmas in the DIII-D tokamak demonstrate simultaneous access to high normalized density, current, pressure, and confinement. NT are shown exist across an expansive parameter space compatible with fusion power production, revealing surprisingly good core stability properties that compare favorably conventional positive DIII-D. Non-dimensionalizing key parameters, expanded operating spaces featuring edge safety factors below 3,...
Abstract This paper discusses the development of a benign termination scenario for runaway electron (RE) beams on ASDEX Upgrade and TCV. A systematic study revealed that low density ( n e ) companion plasma was required to achieve large MHD instability, which expelled confined REs over wetted area allowed conversion magnetic energy radiation. Control achieved via neutral pressure regulation agnostic material injection method. The recombination found be dependent impurity species, quantity RE...
Abstract Negative triangularity (NT) is a potentially transformative configuration for tokamak-based fusion energy with its high-performance core, edge localized mode (ELM)-free edge, and low-field-side divertors that could readily scale to an integrated reactor solution. Previous NT work on the TCV DIII-D tokamaks motivated installation of graphite-tile armor lower outer wall DIII-D. A dedicated multiple-week experimental campaign was conducted qualify scenario future reactors. During...
Recent results from an ITPA joint experiment to study the onset, growth, and decay of relativistic electrons (REs) indicate that loss mechanisms other than collisional damping may play a dominant role in dynamics RE population, even during quiescent Ip flattop. Understanding physics growth mitigation is motivated by theoretical prediction disruptions full-current (15 MA) ITER discharges could generate up 10 MA REs with 10–20 MeV energies. The MHD group conducting measure detection threshold...
The DIII-D tokamak magnetic diagnostic system [E. J. Strait, Rev. Sci. Instrum. 77, 023502 (2006)] has been upgraded to significantly expand the measurement of plasma response intrinsic and applied non-axisymmetric “3D” fields. placement design 101 additional sensors allow resolution toroidal mode numbers 1 ≤ n 3, poloidal wavelengths smaller than MARS-F, IPEC, VMEC magnetohydrodynamic model predictions. Small 3D perturbations, relative equilibrium field (10−5 < δB/B0 10−4), require...
Abstract The ‘Super H-Mode’ regime is predicted to enable pedestal height and fusion performance substantially higher than standard H-Mode operation. This exists due a bifurcation of the pressure, as function density, that by EPED model occur in strongly shaped plasmas above critical density. Experiments on Alcator C-Mod DIII-D have achieved access Super (and Near H) regime, obtained very high including highest tokamak ( p ped ~ 80 kPa) experiments operating near ITER magnetic field. H...
Realization of a high-current (approaching 1 MA) post-disruption runaway electron (RE) beam in DIII-D yields controlled access to very low edge safety factor (qa) conditions. This enables unique observation and study low-order kink instabilities plasmas where the current is carried entirely by relativistic REs. The conventional external stability boundary (in terms qa internal inductance, ℓi) found accurately predict operational space RE beam, with limited ≈2. Kink appear characteristic...
Edge-localized mode (ELM) suppression by resonant magnetic perturbations (RMPs) generally occurs over very narrow ranges of the plasma current (or safety factor q_{95}) in DIII-D tokamak. However, wide q_{95} ELM are needed for and operational flexibility ITER future reactors. In similar shape plasmas with n=3 RMPs, range is found to increase decreasing electron density. Nonlinear two-fluid MHD simulations reproduce observed windows dependence on density, based conditions field penetration...
Abstract A series of experiments have been executed at JET to assess the efficacy newly installed shattered pellet injection (SPI) system in mitigating effects disruptions. Issues, important for ITER disruption mitigation system, such as thermal load mitigation, avoidance runaway electron (RE) formation, radiation asymmetries during quench electromagnetic control and RE energy dissipation addressed over a large parameter range. The efficiency has examined various SPI strategies. paper...
Full suppression of type-I edge localized modes (ELMs) using n = 4 resonant magnetic perturbations (RMPs) as planned for ITER has been demonstrated the first time (n is toroidal mode number applied RMP). This achieved in EAST plasmas with low input torque and tungsten divertor, target plasma these experiments chosen to be relevant Q 10 operational scenario, thus also addressing significant scenario issues ITER. In lowest neutral beam injection (NBI) around TNBI ∼ 0.44 Nm, which extrapolates...
Instability to high toroidal mode number ($n$) ballooning modes has been proposed as the primary gradient-limiting mechanism for tokamak equilibria with negative triangularity ($\delta$) shaping, preventing access strong H-mode regimes when $\delta\ll0$. To understand how this extrapolates reactor conditions, we model infinite-$n$ stability a function of internal profiles and equilibrium shape using combination CHEASE BALOO codes. While critical $\delta$ required avoiding $2^\mathrm{nd}$...
One of our grand challenges towards fusion energy is the achievement a high-performance plasma core coupled to boundary solution. The high confinement mode (H-mode) provides such due build-up an edge transport barrier leading pedestal. However, it usually features type-I localized modes (ELMs) which pose threat for long-duration operation in future devices as they induce large fluences onto facing components and typically are projected damage first wall. For devices, integration stationary...
Abstract Experiments performed during strongly-shaped high-power diverted negative triangularity (NT) experiments in DIII-D achieved detached divertor conditions and a transient-free edge, showcasing the potential for application of NT to core-edge integrated reactor-like scenario providing first characterization parametric dependencies detachment onset. Detached will be required future devices mitigate heat fluxes. Access dissipative was investigated via an increase upstream density....
Abstract In magnetic fusion devices, error field (EF) sources, spurious perturbations, need to be identified and corrected for safe stable (disruption-free) tokamak operation. Within Work Package Tokamak Exploitation RT04, a series of studies have been carried out test the portability novel non-disruptive method, designed tested in DIII-D (Paz-Soldan et al 2022 Nucl. Fusion 62 126007), perform an assessment model-based EF control strategies towards their applicability ITER. this paper,...