ELEMENTARY PARTICLE PHYSICS

Introduction

Due to the AWAKE project at CERN there is a great interest in proton driven wakefield generation, as they are considered to be a promising way of accelerating electrons to the TeV scale. This is investigated using carefully planned Particle-In-Cell (PIC) simulations at the cutting edge of high performance computing technology. At the same time the ELI-NP project is gaining momentum. ELI-NP promises to become an ultra-high field laser facility where novel high-field experiments can be carried out. Also in this project the interaction of short and ultra-intense laser pulses with ultra-thin foils and nano targets in cooperation with J. Schreiber and L. Veisz at the Max Planck Institute of Quantum Optics is studied. The resulting generation of fast particles in the MeV up to GeV range as well as strong electro-magnetic radiation can be employed in fundamental science and medical applications.

In both cases a detailed understanding of the expected physics, backed up by in-silico experiments, is needed and can strongly increase the return on the investment. Further results in laser driven proton acceleration can potentially help to cut costs in the order of €100M for cancer therapy centers by a factor of ten

Results and Methods.

The Plasma-Simulation-Code (PSC) is a general purpose framework to solve the extended Maxwell-Vlasov-Boltzmann system of equations via the PIC approach [1]. Recent extensions comprise the self-field effects of radiation and electron-positron pair production in strong fields. The original FORTRAN version evolved to a modern modularized C simulation framework supporting bindings to FORTRAN as well as C/CUDA and features selectable field and particle pushers. The PIC approach is well-known for its good scaling capability via configuration space parallelization. A Hilbert-Peano space filling curve is used for efficient, dynamic and adaptive load and memory balancing allowing for complex and dynamic geometries.

AWAKE

In the AWAKE project the interaction of a 450 GeV proton beam of the SPS pre-accelerator at CERN with a 10 m long plasma is studied (Fig. 1). The required resolution is on the µm scale and therefore 735 billion grid cells are necessary (Fig. 3). Moving window technology allows for reducing the active memory footprint and the costs to about 3% of the total simulation, but it still takes several weeks on a large fraction of SuperMUC. A minimum of 10 full output steps produce around 300 TB. The researchers were able to demonstrate via a full 3D kinetic simulation that a maximum acceleration field of 700 MV is generated (Fig. 2), in accordance with 2D cylindrically symmetric codes [3], and therefore showing that PIC represents the physics correctly while opening research possibilities to important effects like beam filamentation.