S. F. Paul
A5107500348- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Solar and Space Plasma Dynamics
- Atomic and Subatomic Physics Research
- Nuclear reactor physics and engineering
- Particle Detector Development and Performance
- Laser-induced spectroscopy and plasma
- Magneto-Optical Properties and Applications
- Radiation Detection and Scintillator Technologies
- Dust and Plasma Wave Phenomena
- Atomic and Molecular Physics
- Nuclear Physics and Applications
- Physics of Superconductivity and Magnetism
- Dark Matter and Cosmic Phenomena
- Hydraulic and Pneumatic Systems
- Advanced Optical Sensing Technologies
- Spectroscopy and Laser Applications
- Extremum Seeking Control Systems
- Laser Design and Applications
- CCD and CMOS Imaging Sensors
University of California, Santa Barbara
2024
Fermi National Accelerator Laboratory
2022-2024
University of Chicago
2022-2024
Laboratoire de Physique Nucléaire et de Hautes Énergies
2024
Princeton Plasma Physics Laboratory
2003-2014
Princeton University
1997-2010
University of California, Los Angeles
2006
University of California, Davis
2006
Massachusetts Institute of Technology
1998-2006
University of California, San Diego
2006
Deuterium neutral beams with energies up to 110 keV were injected into TFTR (Tokamak Fusion Test Reactor) plasmas at low magnetic field such that the beam injection velocities comparable Alfv\'en velocity. Excitation of toroidal eigenmodes was observed by Mirnov coils and emission spectroscopy.
High-frequency observations of light emitted from the interactions between plasma ions and injected neutral beam atoms allow measurement moderate-wavelength fluctuations in impurity ion densities. To detect turbulence local density, collisionally excited fluorescence a is measured either separately at several spatial points or with multichannel imaging detector. Similarly, role density using charge exchange recombination transitions by species interest. This technique can access relatively...
Dark matter (DM) particles with sufficiently large cross sections may scatter as they travel through Earth’s bulk. The corresponding changes in the DM flux give rise to a characteristic daily modulation signal detectors sensitive DM-electron interactions. Here, we report results obtained from first underground operation of DAMIC-M prototype detector searching for such MeV-scale mass. A model-independent analysis finds no rate <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"...
Research in NSTX has been conducted to establish spherical torus plasmas be used for high β, auxiliary heated experiments. This device a major radius R0 = 0.86 m and midplane halfwidth of 0.7 m. It operated with toroidal magnetic field B0 ⩽ 0.3 T Ip 1.0 MA. The evolution the plasma equilibrium is analysed between discharges an automated version EFIT code. Limiter, double null lower single diverted configurations have sustained several energy confinement times. stored reached 92 kJ (βt 17.8%)...
Long-wavelength (${\mathit{k}}_{\mathrm{\ensuremath{\perp}}}$${\mathrm{\ensuremath{\rho}}}_{\mathit{i}}$1) density turbulence has been measured with good spatial localization in the core region of a high temperature tokamak plasma auxiliary heating. Density fluctuations n\ifmmode \tilde{}\else \~{}\fi{}/n>0.5% exist for ${\mathit{k}}_{\mathrm{\ensuremath{\perp}}}$2 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ radial and poloidal correlation lengths typically 1--2.5 cm confinement region,...
Experiments in the National Spherical Torus Experiment (NSTX) have shown beneficial effects on performance of divertor plasmas as a result applying lithium coatings graphite and carbon-fiber-composite plasma-facing components. These mostly been applied by pair evaporators mounted at top vacuum vessel which inject collimated streams vapor toward lower divertor. In neutral beam injection (NBI)-heated deuterium H-mode run immediately after application lithium, modifications included decreases...
Steady-state handling of divertor heat flux is a critical issue for ITER and future conventional spherical tokamaks with compact high-power density divertors. A novel ‘snowflake’ (SFD) configuration was theoretically predicted to have significant magnetic geometry benefits mitigation, such as an increased plasma-wetted area higher volume available volumetric power momentum loss processes, compared the standard divertor. Both peak reduction impurity screening been achieved simultaneously core...
Experimental results from NSTX indicate that the snowflake divertor (D. Ryutov, Phys. Plasmas 14, 064502 (2007)) may be a viable solution for outstanding tokamak plasma-material interface issues. Steady-state handling of heat flux and plate erosion remains to critical issues ITER future concept devices based on conventional spherical geometry with high power density divertors. Experiments conducted in 4–6 MW NBI-heated H-mode plasmas demonstrated is compatible high-confinement core plasma...
We report on a recent set of experiments performed in NSTX to explore the effects non-axisymmetric magnetic perturbations stability edge-localized modes (ELMs). The application these 3D fields was found have strong effect ELM stability, including destabilization ELMs H-modes otherwise free large ELMs. Exploiting perturbations, been controllably introduced into lithium-enhanced ELM-free H-modes, causing reduction impurity accumulation while maintaining high confinement. Although show...
The application of nonaxisymmetric magnetic fields is shown to destabilize edge-localized modes (ELMs) during otherwise ELM-free periods discharges in the National Spherical Torus Experiment (NSTX). Profile analysis shows applied increased temperature and pressure gradients, decreasing edge stability. This robust effect was exploited for a new form ELM control: triggering ELMs at will high performance H mode plasmas enabled by lithium conditioning, yielding time-averaged energy confinement...
The Tokamak Fusion Test Reactor (TFTR) (R. J. Hawryluk, to be published in Rev. Mod. Phys.) experiments on high-temperature plasmas, that culminated the study of deuterium–tritium D–T plasmas containing significant populations energetic alpha particles, spanned over two decades from conception completion. During design TFTR, key physics issues were magnetohydrodynamic (MHD) equilibrium and stability, plasma energy transport, impurity effects, reactivity. Energetic particle was given less...
Global magnetohydrodynamic (MHD) stability limits in the National Spherical Torus Experiment (NSTX) have increased significantly recently due to a combination of device and operational improvements. First, more routine H-mode operation with broadened pressure profiles allows access higher normalized β lower internal inductance. Second, correction poloidal field coil induced error-field has largely eliminated locked tearing modes during normal maximum achievable β. As result these...
Previous studies of plasma microturbulence have indicated that the fluctuation power scales with radial wave number, k⊥ , like k⊥−2→k⊥−3.5 for ≥2 cm−1. This implies low k fluctuations may dominate spectrum. Beam emission spectroscopy (BES) has been developed to provide spatially localized measurements density in this region spectrum (k⊥ ≤2 cm−1). A 20-channel system installed on TFTR which images one heating neutral beams (via fiber optics) onto a set photoconductive photodiode detectors....
Coaxial Helicity Injection (CHI) on the National Spherical Torus Experiment (NSTX) has produced 240kA of toroidal current without use central solenoid.Values multiplication ratio (CHI / injector current) up to 10 were obtained, in agreement with predictions.The discharges which lasted for 200ms, limited only by programmed waveform are more than an order magnitude longer duration that any CHI previously a Spheromak or (ST).
Application of Ion Bernstein Wave Heating (IBWH) into the Princeton Beta Experiment-Modification (PBX-M) [Phys. Fluids B 2, 1271 (1990)] tokamak stabilizes sawtooth oscillations and generates peaked density profiles. A transport barrier, spatially correlated with IBWH power deposition profile, is observed in core IBWH-assisted neutral beam injection (NBI) discharges. precursor to fully developed barrier seen soft x-ray data during edge localized mode (ELM) activity. Sustained operation...
The highly indented plasmas of the PBX-M tokamak experiment [Plasma Physics and Controlled Nuclear Fusion Research (IAEA, Vienna, 1989), Vol. 1, p. 97] have reached plasma regimes both high volume-averaged beta (βt), high-beta poloidal (βp), show evidence suppression external surface modes by passive stabilizing system. Values βt up to 4.0 I/aB (% MA/m T) with Ti(0)≊4 keV been obtained. A magnetohydrodynamic analysis βp=2.0 indicates that these are near threshold second stability regime....
A review of TFTR plasma transport studies is presented. Parallel and the confinement suprathermal ions are found to be relatively well described by theory. Cross-field thermal plasma, however, anomalous with momentum diffusivity being comparable ion larger than electron in neutral beam heated discharges. Perturbative experiments have studied nonlinear dependencies coefficients examined role possible nonlocal phenomena. The underlying turbulence has been using microwave scattering, emission...
Transient coaxial helicity injection (CHI) started discharges in the National Spherical Torus Experiment (NSTX) have attained peak currents up to 300 kA and when coupled induction, it has produced 200 additional current over inductive-only operation. CHI NSTX shown be energetically quite efficient, producing a plasma of about 10 A/J capacitor bank energy. In addition, for first time, CHI-produced toroidal that couples induction continues increase with energy supplied by power supply at...
Developing a reactor-compatible divertor has been identified as particularly challenging technology problem for magnetic confinement fusion. Application of lithium (Li) in NSTX resulted improved H-mode confinement, power threshold reduction, and other plasma performance benefits. During the 2010 campaign, application relatively modest amount Li (300 mg prior to discharge) ∼50% reduction heat load on liquid (LLD) attributable enhanced bolometric radiation. These promising results related...
Experiments conducted in high-performance 1.0 and 1.2 MA 6 MW NBI-heated H-mode discharges with a high magnetic flux expansion radiative divertor NSTX demonstrate that significant peak heat reduction access to detachment may be facilitated naturally highly shaped spherical torus (ST) configuration. Improved plasma performance βt = 15–25%, bootstrap current fraction fBS 45–50%, longer pulses an regime smaller ELMs has been achieved the strongly lower single null configuration elongation κ...