LBNL, Berkeley, California
LLNL, Livermore, California
It was shown recently that it may be computationally advantageous to perform computer simulations in a Lorentz boosted frame for a certain class of particle acceleration devices or problems such as: free electron laser, laser-plasma accelerator, and particle beams interacting with electron clouds*. However, even if the computer model relies on a covariant set of equations, it was pointed out that algorithmic difficulties related to discretization errors may have to be overcome in order to take full advantage of the potential speedup**. Further complications arise from the need to transform input and output data between the laboratory frame and the frame of calculation, but can be overcome at low additional computational cost***. We will present the theory behind the speed-up of numerical simulation in a boosted frame, our latest developments of numerical methods, and examples of application to the modeling of the above-cited problems and others if applicable.
LBNL, Berkeley, California
Tech-X, Boulder, Colorado
Laser plasma generated wakefields sustain accelerating gradient a thousand times higher than conventional accelerators, allowing acceleration of electron beams to high energy over short distances. Recently, experiments have demonstrated the production of high quality electron bunches at 1GeV within only a few centimeters. We present simulations, with the VORPAL framework, of the next generation of experiments, likely to use externally injected beams and accelerate them in a meter long 10 GeV laser plasma accelerator stage, which will operate in the quasi-linear regime where the acceleration of electrons and positrons is nearly symmetric. We will show that by using scaling of the physical parameters it is possible to perform fully consistent particle-in-cell simulations at a reasonable cost. These simulations are used to design efficient stages. In particular, we will show that we can use higher order laser modes to tailor the focusing forces, which play an important role in determining the beam quality. This makes it possible to increase the matched electron beam radius and hence the total charge in the bunch while preserving the low bunch emittance required for applications.