Abstract

The effects of experimental variations in the synchronization, laser power, and plasma density on the final beam parameters of externally injected electrons accelerated in a plasma wave are studied using a hybrid model. This model combines a relativistic fluid description of the plasma wave generated by the laser pulse with particle tracking of the accelerated electrons. For cases in which the effects of beam loading and laser depletion can be neglected, the two parts can be separated, allowing a significant reduction in computational power needed compared to particle in cell codes. Two different approaches to externally injecting electrons into plasma waves are studied: In the first case, the electrons are injected behind a laser pulse with ${a}_{0}=0.32$. In the second case, electrons are injected in front of the laser pulse in three different laser regimes ${a}_{0}=0.32$, ${a}_{0}=0.56$, and ${a}_{0}=1.02$, ranging from linear to nonlinear. For these four cases, the effects of expected experimental variations in synchronization ($\ifmmode\pm\else\textpm\fi{}500\text{ }\text{ }\mathrm{fs}$), laser power ($\ifmmode\pm\else\textpm\fi{}10%$), and plasma density ($\ifmmode\pm\else\textpm\fi{}30%$) are studied. From these simulations, it becomes clear that in some cases, even a small variation in one of these parameters can create a large change in the final energy, energy spread, and trapped charge. For lower laser intensities, the method of injecting behind the laser pulse is the least sensitive to fluctuations while injection in front of the laser pulse becomes less sensitive at higher intensities.

Highlights

  • Laser wakefield acceleration [1] allows the acceleration of electrons in electric fields orders of magnitude larger than those achieved in conventional accelerators

  • One of the major areas of interest is the reproducibility of the beams created in these acceleration experiments. Since these experiments rely on highly nonlinear plasma waves to trap electrons from the plasma and accelerate them, they are sensitive to variations in laser power and plasma density

  • Purpose, we will first look at the effects of timing jitter and variations in the laser energy and plasma density when injecting behind the laser pulse

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Summary

INTRODUCTION

Laser wakefield acceleration [1] allows the acceleration of electrons in electric fields orders of magnitude larger than those achieved in conventional accelerators. One of the major areas of interest is the reproducibility of the beams created in these acceleration experiments. Since these experiments rely on highly nonlinear plasma waves to trap electrons from the plasma (wave breaking) and accelerate them, they are sensitive to variations in laser power and plasma density. In order to evaluate the reproducibility of this scheme, we will use a numerical model to investigate the effect of variations in the laser power and plasma density. Since the use of external injection requires synchronization between the electron source and the laser pulse used to excite the

Framework
Fluid model
Moving fields
Electron bunch parameters
Plasma parameters
Injection approach
Injection behind the laser pulse
Bunch evolution for injection behind the laser pulse
Timing
Laser energy variations
Density
Injection in front of the laser pulse
Bunch evolution for injection before the laser pulse
Effects of timing variations
Effects of laser energy variations
Effects of density variations
CONCLUSIONS
Multibunch characteristics
OUTLOOK
Full Text
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