# Modeling laser wakefield accelerators in a Lorentz boosted frame

## Abstract

Modeling of laser-plasma wakefield accelerators in an optimal frame of reference is shown to produce orders of magnitude speed-up of calculations from first principles. Obtaining these speedups requires mitigation of a high-frequency instability that otherwise limits effectiveness in addition to solutions for handling data input and output in a relativistically boosted frame of reference. The observed high-frequency instability is mitigated using methods including an electromagnetic solver with tunable coefficients, its extension to accomodate Perfectly Matched Layers and Friedman's damping algorithms, as well as an efficient large bandwidth digital filter. It is shown that choosing the frame of the wake as the frame of reference allows for higher levels of filtering and damping than is possible in other frames for the same accuracy. Detailed testing also revealed serendipitously the existence of a singular time step at which the instability level is minimized, independently of numerical dispersion, thus indicating that the observed instability may not be due primarily to Numerical Cerenkov as has been conjectured. The techniques developed for Cerenkov mitigation prove nonetheless to be very efficient at controlling the instability. Using these techniques, agreement at the percentage level is demonstrated between simulations using different frames of reference, with speedups reaching twomore »

- Authors:

- Publication Date:

- Research Org.:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

- Sponsoring Org.:
- Accelerator& Fusion Research Division

- OSTI Identifier:
- 985930

- Report Number(s):
- LBNL-3746E

Journal ID: ISSN 0021-9991; JCTPAH; TRN: US1006273

- DOE Contract Number:
- DE-AC02-05CH11231

- Resource Type:
- Journal Article

- Journal Name:
- Journal of Computational Physics

- Additional Journal Information:
- Journal Name: Journal of Computational Physics; Journal ID: ISSN 0021-9991

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCURACY; ALGORITHMS; DAMPING; DIGITAL FILTERS; INSTABILITY; LASERS; MITIGATION; PLASMA GUNS; SIMULATION; TESTING; WAKEFIELD ACCELERATORS

### Citation Formats

```
Vay, J -L, Geddes, C G.R., Cormier-Michel, E, and Grotec, D P.
```*Modeling laser wakefield accelerators in a Lorentz boosted frame*. United States: N. p., 2010.
Web. doi:10.1063/1.3520322.

```
Vay, J -L, Geddes, C G.R., Cormier-Michel, E, & Grotec, D P.
```*Modeling laser wakefield accelerators in a Lorentz boosted frame*. United States. doi:10.1063/1.3520322.

```
Vay, J -L, Geddes, C G.R., Cormier-Michel, E, and Grotec, D P. Tue .
"Modeling laser wakefield accelerators in a Lorentz boosted frame". United States. doi:10.1063/1.3520322. https://www.osti.gov/servlets/purl/985930.
```

```
@article{osti_985930,
```

title = {Modeling laser wakefield accelerators in a Lorentz boosted frame},

author = {Vay, J -L and Geddes, C G.R. and Cormier-Michel, E and Grotec, D P},

abstractNote = {Modeling of laser-plasma wakefield accelerators in an optimal frame of reference is shown to produce orders of magnitude speed-up of calculations from first principles. Obtaining these speedups requires mitigation of a high-frequency instability that otherwise limits effectiveness in addition to solutions for handling data input and output in a relativistically boosted frame of reference. The observed high-frequency instability is mitigated using methods including an electromagnetic solver with tunable coefficients, its extension to accomodate Perfectly Matched Layers and Friedman's damping algorithms, as well as an efficient large bandwidth digital filter. It is shown that choosing the frame of the wake as the frame of reference allows for higher levels of filtering and damping than is possible in other frames for the same accuracy. Detailed testing also revealed serendipitously the existence of a singular time step at which the instability level is minimized, independently of numerical dispersion, thus indicating that the observed instability may not be due primarily to Numerical Cerenkov as has been conjectured. The techniques developed for Cerenkov mitigation prove nonetheless to be very efficient at controlling the instability. Using these techniques, agreement at the percentage level is demonstrated between simulations using different frames of reference, with speedups reaching two orders of magnitude for a 0.1 GeV class stages. The method then allows direct and efficient full-scale modeling of deeply depleted laser-plasma stages of 10 GeV-1 TeV for the first time, verifying the scaling of plasma accelerators to very high energies. Over 4, 5 and 6 orders of magnitude speedup is achieved for the modeling of 10 GeV, 100 GeV and 1 TeV class stages, respectively.},

doi = {10.1063/1.3520322},

journal = {Journal of Computational Physics},

issn = {0021-9991},

number = ,

volume = ,

place = {United States},

year = {2010},

month = {6}

}