Particle-in-cell simulations of plasma accelerators and electron-neutral collisions

Abstract. When considering intense particle or laser beams propagating in dense plasma or gas, ionization plays an important role. Impact ionization and tunnel ionization may create new plasma electrons, altering the physics of wakefield accelerators, causing blue shifts in laser spectra, creating and modifying instabilities, etc. Here we describe the addition of an impact ionization package into the 3-D, object-oriented, fully parallel PIC code OSIRIS. We apply the simulation tool to simulate the parameters of the upcoming E164 Plasma Wakefield Accelerator experiment at the Stanford Linear Accelerator Center (SLAC). We find that impact ionization is dominated by the plasma electrons moving in the wake rather than the 30 GeV drive beam electrons. Impact ionization leads to a significant number of trapped electrons accelerated from rest in the wake.

Section: Modeling the E164 Experimentsmentioning

confidence: 99%

Modeling of Ionization Physics with the PIC Code OSIRIS

Deng¹,

Tsung²,

Lee³

et al. 2002

“…The formation of the plasma has been modeled using the 2.5D (cylindrical symmetric) OOPIC Pro [9]. The geometry used in the model is shown in Fig.…”

Section: Oopic Pro Modelingmentioning

confidence: 99%

The Problem of RF Gradient Limits

Norem

Insepov

Huang

et al. 2010

Abstract. We describe breakdown in rf accelerator cavities in terms of a number of mechanisms. We divide the breakdown process into three stages: 1) we model surface failure using molecular dynamics of fracture caused by electrostatic tensile stress, 2) the ionization and plasma growth is modeled using a particle in cell code, 3) we model surface damage by assuming unipolar arcing. Although unipolar arcs are strictly defined with equipotential boundaries, we find that the cold, dense plasma in contact with the surface produces very small Debye lengths and very high electric fields over a large area, and these high fields produce strong erosion mechanisms, primarily self sputtering, compatible with crater formation. We compare this model with arcs in tokamaks, plasma ablation, electron beam welding, micrometeorite impacts, and other examples.

“…The pulse is launched from the left boundary (constant value of y) of the simulation box and propagates to the right. The description of how laser pulses are launched in OOPIC is given by Bruhwiler et al [10]. OOPIC has a moving window algorithm that enables propagation of the laser pulse over a distance greater than the longitudinal length of the simulation box.…”

Section: Simulation Parametersmentioning

confidence: 99%

“…The object-oriented particle-in-cell (OOPIC) [9,10] code started as a pioneering effort to apply object oriented techniques to plasma simulation codes. OOPIC is a highperformance 2-D PIC code, with support for x-y (slab) and r-z (cylindrical) geometries.…”

Section: The Oopic Particle-in-cell Codementioning

confidence: 99%

Simulations of Laser Propagation and Ionization in l’OASIS Experiments

Dimitrov¹,

Bruhwiler²,

Leemans³

et al. 2002

Abstract. We have conducted particle-in-cell simulations of laser pulse propagation through neutral He, including the effects of tunneling ionization, within the parameter regime of the l'OASIS experiments [1,2] at the Lawrence Berkeley National Lab (LBNL). The simulations show the theoretically predicted [3] blue shifting of the laser frequency at the leading edge of the pulse. The observed blue shifting is in good agreement with the experimental data. These results indicate that such computations can be used to accurately simulate a number of important effects related to tunneling ionization for laser-plasma accelerator concepts, such as steepening due to ionization-induced pump depletion, which can seed and enhance instabilities. Our simulations show self-modulation occurring earlier when tunneling ionization is included then for a pre-ionized plasma.