David Grote - Academia.edu (original) (raw)

Papers by David Grote

Applied Sciences, 2020

We considered the topic of explosions from spherical high-explosive (HE) charges. We studied how ... more We considered the topic of explosions from spherical high-explosive (HE) charges. We studied how the turbulent combustion fields scale. On the basis of theories of dimensional analysis by Bridgman and similarity theories of Sedov and Barenblatt, we found that all fields scaled with the explosion length scale r0. This included the blast wave, the mean and root mean squared (RMS) profiles of thermodynamic variables, combustion variables, velocities, vorticity, and turbulent Reynolds stresses. This was a consequence of the formulation of the problem and our numerical method, which both satisfied the similarity conditions of Sedov. We performed numerical simulations of 1 g charges and 1 kg charges; the solutions were identical (within roundoff error) when plotted in scaled variables. We also explored scaling laws related to three-phase pyrotechnic explosions. We show that although the scaling formally broke down, the fireball still essentially scaled with the explosion length scale r0. ...

This dataset contains the inputs, outputs, job submission scripts, and executables used... more This dataset contains the inputs, outputs, job submission scripts, and executables used to create the Figures in "Porting WarpX to GPU-accelerated platforms" by A. Myers et. al, submitted to Parallel Computing as part of the ECP Special Issue on Transitioning to Accelerated nodes. These results were obtained using the October, 2020 release tags of WarpX and AMReX, available on Github here: https://github.com/ECP-WarpX/WarpX and here: https://github.com/AMReX-Codes/amrex The following module files were loaded on Summit: 1) hsi/5.0.2.p5 2) xalt/1.2.0 3) lsf-tools/2.0 4) darshan-runtime/3.1.7 5) DefApps 6) cuda/10.1.243 7) gcc/6.4.0 8) spectrum-mpi/10.3.1.2-20200121 To use nsight-compute for the roofline plots, we also loaded: nsight-compute/2020.1.2 Manifest: BinScan: contains material used to make Figure 1. To generate the figure, use the Jupyter notebook called "bin_size.ipynb". StrongScaling: contains m...

Dependencies AMReX: release <code>21.06</code> PICSAR (<code>development</co... more Dependencies AMReX: release <code>21.06</code> PICSAR (<code>development</code>, incl. QED): <code>c16b642e3dcf860480dd1dd21cefa3874f395773</code> picmistandard: release <code>0.0.14</code> openPMD-api: releases <code>0.12.0-0.13.*</code> List of PRs merged since the last release This list was generated with <pre><code class="lang-sh">git log 21.05.. | grep -A 3 "Author: " | grep -B 1 "\-\-" | sed '/--/d' | sed -e 's/^ /- /' </code></pre> Release 21.06 (#1996) Docs: Ookami (Stony Brook) (#1991) [mini-PR] improve error message in case of wrong type of a reduced diag (#1986) CoarsenIO: Replace Copy with ParallelCopy (#1992) Use Python Indexing in Reduced Diags Headers (#1990) pytables: missing option dependency Docs: Update Summit Perf. Tests (#1994) Minor update to Schwinger documentation (#1995) Added new option <diag>.openpmd_encoding (#1979) repla...

Physics of Plasmas, 2021

It has been demonstrated experimentally that laser plasma accelerators can produce multi-100 MeV ... more It has been demonstrated experimentally that laser plasma accelerators can produce multi-100 MeV electron bunches with a few percent energy spread, and from these electrons multi-MeV quasi-monoenergetic photons have been demonstrated based on Compton up-scattering from a counter-propagating laser. This offers the potential of a high quality, narrow bandwidth, compact, photon source with broad application. The bandwidth of the resulting photons depends directly on the distribution of the electron bunch and is limited in particular by the bunch divergence (i.e., the spread in transverse velocity angle). At the same time, the ability to decelerate electrons after scattering is important to source deployment. We describe a series of plasma structures that expand and then collimate the electron bunch, reducing its divergence and thus reducing the bandwidth of the scattered photons while enabling both high performance scattering and deceleration. These plasma structures are demonstrated in simulations of the accelerator system, showing the potential to reach few-percent photon spread which is important for applications using Nuclear Resonance Fluorescence.

Author(s): Grote, David | Abstract: We present initial results for the self-consistent beam-cloud... more Author(s): Grote, David | Abstract: We present initial results for the self-consistent beam-cloud dynamics simulations for a sample LHC beam, using a newly developed set of modeling capability based on a merge of the three-dimensional parallel Particle-In-Cell accelerator code WARP and the electron cloud code POSINST. Although the storage ring model we use as a test bed to contain the beam is much simpler and shorter than the LHC, its lattice elements are realistically modeled, as is the beam and the electron cloud dynamics. The simulated mechanisms for generation and absorption of the electrons at the walls are based on previously validated models available in POSINST. We will present the details of the models and our most recent results.

In the past, we have studied combustion effects in confined explosions [1] and barometric calorim... more In the past, we have studied combustion effects in confined explosions [1] and barometric calorimeters [2]. We have also studied the evolution of the evolution of turbulence fields in spherical combustion clouds [3]. And we have proposed gasdynamic models of turbulent combustion in TNT explosions [4]. Here we investigate optical emissions from fireballs created by the detonation of spherical highexplosives (HE) charges. The combustion field is modeled by the 3D gasdynamic conservation laws, integrated with a high-order Godonov scheme [4]; Adaptive Mesh Refinement (AMR) is used to capture the turbulent mixing structures on the computational mesh [5]. At each time-step, the flow field (of temperature, density and species) is fed into the 3D LUX code which does ray-tracing to compute the optical emissions of the fireball as a function of time. An example of a simulation of the fireball from a TNT explosion is compared with an experimental photograph in Fig. 1.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2005

Significant experimental and theoretical progress has been made in the US heavy-ion fusion progra... more Significant experimental and theoretical progress has been made in the US heavy-ion fusion program on high-current sources, injectors, transport, final focusing, chambers and targets for high-energy density physics (HEDP) and inertial fusion energy (IFE) driven by induction linac accelerators. One focus of present research is the beam physics associated with quadrupole focusing of intense, space-charge dominated heavy-ion beams, including gas and electron cloud effects at high currents, and the study of long-distance-propagation effects such as emittance growth due to field errors in scaled experiments. A second area of emphasis in present research is the introduction of background plasma to neutralize the space charge of intense heavy-ion beams and assist in focusing the beams to a small spot size. In the near future, research will continue in the above areas, and a new area of emphasis will be to explore the physics of neutralized beam compression and focusing to high intensities required to heat targets to high-energy density conditions as well as for inertial fusion energy.

Journal of Physics: Conference Series, 2016

We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Com... more We have commenced experiments with intense short pulses of ion beams on the Neutralized Drift Compression Experiment (NDCX-II) at Lawrence Berkeley National Laboratory, with 1-mm beam spot size within 2.5 ns full-width at half maximum. The ion kinetic energy is 1.2 MeV. To enable the short pulse duration and mm-scale focal spot radius, the beam is neutralized in a 1.5-meter-long drift compression section following the last accelerator cell. A short-focal-length solenoid focuses the beam in the presence of the volumetric plasma that is near the target. In the accelerator, the line-charge density increases due to the velocity ramp imparted on the beam bunch. The scientific topics to be explored are warm dense matter, the dynamics of radiation damage in materials, and intense beam and beam-plasma physics including select topics of relevance to the development of heavy-ion drivers for inertial fusion energy. Below the transition to melting, the short beam pulses offer an opportunity to study the multi-scale dynamics of radiation-induced damage in materials with pump-probe experiments, and to stabilize novel metastable phases of materials when short-pulse heating is followed by rapid quenching. First experiments used a lithium ion source; a new plasma-based helium ion source shows much greater charge delivered to the target.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2014

The Neutralized Drift Compression Experiment (NDCX-II) is a user facility located at Lawrence Ber... more The Neutralized Drift Compression Experiment (NDCX-II) is a user facility located at Lawrence Berkeley National Laboratory which is uniquely designed for ion-beam-driven high energy density laboratory physics and heavy ion fusion research. Construction was completed in March 2012 and the facility is now in the commissioning phase. A significant amount of engineering was carried out in order to meet the performance parameters required for a wide range of target heating experiments while making the most cost-effective use of high-value hardware available from a decommissioned high current electron induction accelerator. The technical challenges and design of this new ion induction accelerator facility are described.

Intense heavy-ion beams have long been considered a promising driver option for inertial-fusion e... more Intense heavy-ion beams have long been considered a promising driver option for inertial-fusion energy production. This paper briefly compares inertial confinement fusion (ICF) to the more-familiar magnetic-confinement approach and presents some advantages of using beams of heavy ions to drive ICF instead of lasers. Key design choices in heavy-ion fusion (HIF) facilities are discussed, particularly the type of accelerator. We

PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268)

This paper reports progress in the HCX experimental program since the last HIF-VNL Program Adviso... more This paper reports progress in the HCX experimental program since the last HIF-VNL Program Advisory Committee Review (February 14-15 2002). On July 25 2002 the experiment was shut down for about four weeks to move the control room. A principal area of effort has been to obtain and evaluate the first experimental results carried out with a matched and well-aligned K + ion beam transported through 10 electrostatic transport quadrupoles. These are the main results and highlights to date: A1. There is no emittance growth within the sensitivity of the diagnostics, and little beam loss. The beam centroid is aligned to within 0.5 mm and 2 mrad of the central axis of the channel, and the envelope mismatch amplitude is <2 mm. A2. A long-life, alumino-silicate source has replaced a contact-ionization source, eliminating depletioninduced experimental uncertainties. A3. Significant differences between the experimental data and early theoretical calculations of the beam envelope propagating through the electrostatic quadrupoles were encountered. More detailed envelope models and simulations were developed and experimental parameter sensitivities were analyzed. This work has resolved most of the discrepancy and achievable limits on envelope predictability and control are being probed. A4. The experimental current density distribution, J(x,y), and phase-space data are being used to initialize high-resolution simulations to enable realistic modeling and detailed comparisons to experiment.

Proceedings of the 2005 Particle Accelerator Conference

High Energy Density Physics (HEDP) applications require high line charge density ion beams. An ef... more High Energy Density Physics (HEDP) applications require high line charge density ion beams. An efficient method to obtain this type of beams is to extract a long pulse, high current beam from a gun at high energy, and let the beam pass through a decelerating field to compress it. The low energy beam-bunch is loaded into a solenoid and matched to a Brillouin flow. The Brillouin equilibrium is independent of the energy if the relationship between the beam size (a), solenoid magnetic field strength (B) and line charge density is such that (Ba)^2 is proportional to the line charge density. Thus it is possible to accelerate a matched beam at constant line charge density. An experiment, NDCX-1c is being designed to test the feasibility of this type of injectors, where we will extract a 1 microsecond, 100 mA, potassium beam at 160 keV, decelerate it to 55 keV (density ~0.2 μC/m), and load it into a 2.5 T solenoid where it will be accelerated to 100-150 keV (head to tail) at constant line charge density. The head-to-tail velocity tilt can be used to increase bunch compression and to control longitudinal beam expansion. We will present the physics design and numerical simulations of the proposed experiment.

Physical Review Special Topics - Accelerators and Beams, 2005

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2005

Fusion Engineering and Design, 1996

Significant experimental and theoretical progress in the U.S heavy-ion fusion (HIF) program is re... more Significant experimental and theoretical progress in the U.S heavy-ion fusion (HIF) program is reported in modeling and measurements of intense space-charge-dominated heavy ion and electron beams. Measurements of the transport of a well-matched and aligned high current (0.2A) 1.0 MeV potassium ion beam through 10 electric quadrupoles, with a fill factor of 60%, shows no emittance growth within experimental measurement uncertainty, as expected from the simulations. Another experiment shows that passing a beam through an aperture can reduce emittance to near the theoretical limits, and that plasma neutralization of the beam's space-charge can greatly reduce the focal spot radius. Measurements of intense beamlet current density, emittance, charge-state purity, and energy spread from a new, high-brightness, Argon plasma source for HIF experiments are described. New theory and simulations of neutralization of intense beam space charge with plasma in various focusing chamber configurations indicate that near-emittance-limited beam focal spot sizes can be obtained even with beam perveance an order of magnitude higher than in earlier HIF focusing experiments.

Intense ion beams offer an attractive approach to heating dense matter uniformly to extreme condi... more Intense ion beams offer an attractive approach to heating dense matter uniformly to extreme conditions, because their energy deposition is nearly classical and volumetric. Simultaneous transverse and longitudinal beam compression in a neutralizing plasma medium, along with rapid beam acceleration, are being studied as a means of generating such beams for warm dense matter (WDM) and high energy density physics (HEDP) experiments, as well as for inertial fusion. Recent experiments on transverse and longitudinal compression demonstrated significant enhancements in beam intensity. In parallel with the beam compression studies, a new accelerator concept, the Pulse Line Ion Accelerator (PLIA), potentially offers cost-effective high-gradient ion beam acceleration at high line charge density. We describe experimental results on beam neutralization, and neutralized drift compression from a series of experiments. We also describe first the beam dynamics validation experiments exploring the PLIA.

Applied Sciences, 2020

Physics of Plasmas, 2021

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2005

Journal of Physics: Conference Series, 2016

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2014

PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268)

Proceedings of the 2005 Particle Accelerator Conference

Physical Review Special Topics - Accelerators and Beams, 2005

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2005

Fusion Engineering and Design, 1996