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publications

FARSIGHT

A Forward Adaptively Refined and Regularized Semi-Lagrangian Integral GPU- and Hierarchical Tree-code-accelerated method for the Vlasov-Poisson system.

Recommended citation: (in preparation) R.T. Sandberg, A.G.R. Thomas, and R. Krasny. "FARSIGHT: A Forward Adaptively Refined and Regularized Semi-Lagrangian Integral GPU- and Hierarchical Tree-code-accelerated method for the Vlasov-Poisson system."

Photon Acceleration from Optical to XUV

Published in unknown, 2023

Frequency upshift of a laser pulse in wake of relativistic electron beam.

Recommended citation: R.T. Sandberg, and A.G.R. Thomas. "Photon Acceleration from Optical to XUV."

talks

Numerical finite particle effects and wave breaking limits

Published: October 24, 2019

Seminal works of Dawson, Akhiezer and Polovin, and Coffey provide theoretical cold, relativistic, and warm wave breaking limits, respectively. There is renewed interest in understanding wave breaking limits to either achieve or avoid them, depending on the injection and acceleration mechanism. Numerical simulations are often used to investigate breaking limits. When particle methods are used, they commonly employ finite numerical particle size or, equivalently, a smoothed Green’s function for the electric interaction. In this work we present studies of finite numerical particle effects on wave breaking limits. We discuss phase mixing times and breaking limits in relativistic and non relativistic cases when using finite sized numerical particles in simulation. We compare PIC models with the Dawson sheet model and other particle methods, using a 1d grid-free particle method employing a smoothed kernel.

FARRSIGHT: A Forward Adaptively Refined and Regularized Semi-Lagrangian Integral Green’s function Hierarchical Tree-code accelerated method for the Vlasov-Poisson system

Published: November 12, 2020

In this talk we present a new forward semi-Lagrangian particle method for the Vlasov-Poisson (VP) system. Recent methods for solving the VP system include deformable particles and high-order and/or discontinuous-Galerkin Eulerian methods. In contrast to these, we do not use any operator splitting and obtain the electric field by summing regularized pairwise particle interactions using a hierarchical treecode. We use remeshing and adaptive mesh refinement to maintain an efficient representation of phase space. We benchmark on several standard test cases including Landau damping and the two-stream instability.

FARRSIGHT: A Forward Adaptively Refined and Regularized Semi-Lagrangian Integral GPU- and Hierarchical Treecode-Accelerated Method for the Vlasov-Poisson System

Published: March 05, 2021

In this talk we present a new forward semi-Lagrangian particle method for the Vlasov-Poisson (VP) system. Recently developed methods for the VP system include deformable particles and high-order or discontinuous-Galerkin Eulerian methods. In contrast to these, we do not use any operator splitting and obtain the electric field by summing regularized pairwise particle interactions using a GPU-accelerated tree-code. We remesh and use adaptive mesh refinement to maintain an efficient representation of phase space. We benchmark on several standard test cases including Landau damping and the two-stream instability. We also compare the multi-threaded and single-GPU performance of the method.

Phase matched plasma wakefield photon acceleration

Published: November 09, 2021

We present Phase Matched Plasma Wakefield Photon Acceleration (PMPA), a scheme for dephasingless photon acceleration in a particle-beam-driven wake.
Electromagnetic radiation seeing a decreasing plasma gradient shifts up in frequency.
In PMPA, a laser pulse is situated in the wake of a relativistic electron bunch so that it sees a decreasing density gradient.
Using a tapered density profile to keep witness laser pulse at the phase in the wake where the density is decreasing, simulations suggest that the frequency of the witness pulse can be shifted up by a factor of 5-10.

Ryan Sandberg