A5088056725- Parallel Computing and Optimization Techniques
- Magnetic confinement fusion research
- Distributed and Parallel Computing Systems
- Advanced Data Storage Technologies
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Laser-Plasma Interactions and Diagnostics
- Ionosphere and magnetosphere dynamics
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Advanced Fiber Laser Technologies
- Stellar, planetary, and galactic studies
- Advanced Frequency and Time Standards
- Simulation Techniques and Applications
- Solar and Space Plasma Dynamics
- Atomic and Subatomic Physics Research
- Spectroscopy and Laser Applications
- Particle Accelerators and Free-Electron Lasers
- Particle accelerators and beam dynamics
- Computational Physics and Python Applications
- Astrophysics and Star Formation Studies
- Superconducting Materials and Applications
- Electromagnetic Launch and Propulsion Technology
- Astro and Planetary Science
- Plasma Diagnostics and Applications
Advanced Micro Devices (United States)
2023-2025
Woodwell Climate Research Center
2022
Harvard University
2022
Lawrence Berkeley National Laboratory
2020-2021
National Energy Research Scientific Computing Center
2021
Barcelona Supercomputing Center
2021
Universitat Politècnica de Catalunya
2021
University of Pittsburgh
2021
Center for Astrophysics Harvard & Smithsonian
2017-2019
Oberlin College
2012-2017
The accretion flow around the Galactic Centre black hole Sagittarius A* (Sgr A*) is expected to have an electron temperature that distinct from ion temperature, due weak Coulomb coupling in low-density plasma. We present four two-temperature general relativistic radiative magnetohydrodynamic (GRRMHD) simulations of Sgr performed with code KORAL. These use different heating prescriptions, motivated by models underlying plasma microphysics. compare Landau-damped turbulent cascade model used a...
Abstract Hot collisionless accretion flows, such as the one in Sgr A* at our Galactic center, provide a unique setting for investigation of magnetic reconnection. Here protons are nonrelativistic, while electrons can be ultrarelativistic. By means 2D particle-in-cell simulations, we investigate electron and proton heating outflows transrelativistic reconnection (i.e., <?CDATA ${\sigma }_{w}\sim 0.1\mbox{--}1$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">...
WarpX is a general purpose electromagnetic particle-in-cell code that was originally designed to run on many-core CPU architectures. We describe the strategy, based AMReX library, followed allow use GPU-accelerated nodes OLCF’s Summit supercomputer, strategy we believe will extend upcoming machines Frontier and Aurora. summarize challenges encountered, lessons learned, give current performance results series of relevant benchmark problems.
The fully electromagnetic particle-in-cell code WarpX is being developed by a team of the U.S. DOE Exascale Computing Project (with additional non-U.S. collaborators on part code) to enable modeling chains tens hundreds plasma accelerator stages exascale supercomputers, for future collider designs. combining latest algorithmic advances (e.g., Lorentz boosted frame and pseudo-spectral Maxwell solvers) with mesh refinement runs computer processing unit graphical (GPU) architectures. In this...
During relativistic magnetic reconnection, antiparallel fields undergo a rapid change in topology, releasing large amount of energy the form non-thermal particle acceleration. This work explores application mesh refinement to 2D reconnection simulations efficiently model inherent disparity length-scales. We have systematically investigated effects and determined necessary modifications algorithm required mitigate non-physical artifacts at coarse–fine interface. used ultrahigh-order...
The plasma in low-luminosity accretion flows, such as the one around black hole at center of M87 or Sgr A* our Galactic Center, is expected to be collisioness and two-temperature, with protons hotter than electrons. Here, particle heating controlled by magnetic reconnection transrelativistic regime $\sigma_{w}\sim 0.1$-$1$, where magnetization $\sigma_{w}$ ratio energy density enthalpy density. By means large-scale 2D particle-in-cell simulations, we explore for a fiducial $\sigma_w=0.1$ how...
Abstract Particle energization in shear flows is invoked to explain nonthermal emission from the boundaries of relativistic astrophysical jets. Yet physics particle injection, i.e., mechanism that allows thermal particles participate shear-driven acceleration, remains unknown. With particle-in-cell simulations, we study development Kelvin–Helmholtz (KH) instabilities seeded by velocity between a magnetically dominated electron–positron jet and weakly magnetized electron–ion ambient plasma....
We study the linear stability of a planar interface separating two fluids in relative motion, focusing on symmetric configuration where have same properties (density, temperature, magnetic field strength, and direction). consider most general case with arbitrary sound speed $c_{\rm s}$, Alfv\'en $v_{\rm A}$, orientation. For instability associated fast mode, we find that lower bound unstable shear velocities is set by requirement projection velocity onto fluid-frame wavevector larger than...
Abstract We study the linear stability of a planar interface separating two fluids in relative motion, focusing on conditions appropriate for boundaries relativistic jets. The jet is magnetically dominated, whereas ambient wind gas-pressure-dominated. derive most general form dispersion relation and provide an analytical approximation its solution sound speed much smaller than Alfvén v A , as realistic systems. properties are chiefly determined by angle ψ between wavevector magnetic field....
Abstract Relativistic magnetic reconnection is a nonideal plasma process that source of nonthermal particle acceleration in many high-energy astrophysical systems. Particle-in-cell (PIC) methods are commonly used for simulating from first principles. While much progress has been made understanding the physics reconnection, especially 2D, adoption advanced algorithms and numerical techniques efficiently modeling such systems limited. With GPU-accelerated PIC code WarpX, we explore accuracy...
We present an experimental and theoretical investigation of two-photon direct frequency-comb spectroscopy performed through velocity-selective excitation. In particular, we explore the effect repetition rate on $5{S}_{1/2}\ensuremath{\rightarrow}5{D}_{3/2,5/2}$ transitions excited in a rubidium atomic vapor cell. The occur via stepwise excitation $5{P}_{1/2,3/2}$ states by use output optical frequency comb. Experiments were with two different combs, one $\ensuremath{\approx}925$ MHz...
Scientific machine learning (SciML) promises to have a transformational impact on scientific exploration, by combining state-of-the-art AI methods with the latest generation of supercomputers. However, efficiently leverage ML techniques high-performance computing (HPC) systems, it is critical understand performance characteristics underlying algorithms modern computational systems. In this work, we present new methodology for developing detailed understanding benchmarks. To demonstrate our...
Abstract The Particle-In-Cell code WarpX is being developed by a team of the U.S. DOE Exascale Computing Project to enable modeling chains tens plasma accelerators on exascale supercomputers, for future collider designs. combining latest algorithmic advances (e.g., boosted frame, pseudo-spectral Maxwell solvers) with mesh refinement and runs CPU GPU architectures. An example application up three successive muti-GeV stages presented. implementation architectures also reported.
We present an experimental determination of the $4 \: S_{1/2} \rightarrow 6\: S_{1/2}$ transition frequency in atomic potassium, $^{39}$K, using direct comb spectroscopy. The output a stabilized optical was used to excite thermal vapor. repetition rate scanned and transitions were excited step-wise two-photon excitation. center gravity for found be $\nu_\textrm{cog} = 822\, 951\, 698.09(13)$ MHz measured hyperfine $A$ coefficient $6\: state $21.93(11)$ MHz. measurements are agreement with...
During relativistic magnetic reconnection, antiparallel fields undergo a rapid change in topology, releasing large amount of energy the form non-thermal particle acceleration. This work explores application mesh refinement to 2D reconnection simulations efficiently model ineherent disparity length-scales. We have systematically investigated effects and determined necessary modifications algorithm required mitigate non-physical artifacts at coarse-fine interface. used ultrahigh-order...
Maintaining computational load balance is important to the performant behavior of codes which operate under a distributed computing model. This especially true for GPU architectures, can suffer from memory oversubscription if improperly balanced. We present enhancements traditional balancing approaches and explicitly target exploring resulting performance. A key component our introduction several GPU-amenable strategies assessing compute work. These are implemented benchmarked find most...
Relativistic magnetic reconnection is a non-ideal plasma process that source of non-thermal particle acceleration in many high-energy astrophysical systems. Particle-in-cell (PIC) methods are commonly used for simulating from first principles. While much progress has been made understanding the physics reconnection, especially 2D, adoption advanced algorithms and numerical techniques efficiently modeling such systems limited. With GPU-accelerated PIC code WarpX, we explore accuracy potential...