This award will support basic research with three-dimensions simulations including full-scale modeling of ongoing or planned experiments with the primary tool being three-dimensional particle-in-cell (PIC) simulations. The simulations provide a test bed for theoretical ideas and, once validated, a method to guide experiments. High-fidelity full-scale modeling will provide a means to extrapolate parameters into regimes that will not be accessible to experiments for years to come. The research group will exploit an unmatched array of PIC codes and data analysis tools, a detailed understanding of the key PWFA experiments, and close connections to experimental programs within the US and abroad. In particular, the research will investigate the following 1. Explore the physics necessary to make a compact LWFA or PWFA stage. 2. Explore the physics necessary to make a linear collider based on wakefield stages a reality. 3. Carry out full-scale 3D PIC simulations of beam and laser-plasma experiments, e.g., at UCLA, SLAC, the L'OASIS lab at LBL, the Hercules laser at Michigan, the Texas Petatwatt laser, and RAL (England). 4. Continue to develop the PIC infrastructure including reduced PIC algorithms. 5. Continue to develop predictive theory and scaling laws.
The High Energy Density Science (HEDS) area of intense laser and beam-matter interactions has an impact on plasma-based acceleration and radiation sources, and even on the fast ignitor fusion concept. Compact particle accelerators might eventually have an impact on particle physics, material science, structural biology, medicine, fusion research, and transmutation of nuclear waste. The students and post-doctoral researchers trained under this grant will be part of the twenty-first century work force in computational science and engineering as well as experts in HEDS. UCLA codes and algorithms are being used by other groups throughout the world. This grant supported a female graduate student. An effort is underway to share this group's parallel simulation codes with Florida A&M, a historically black university.
This project has led to fundamental discoveries regarding how intense lasers and particle beams interact with both low and high density plasmas. This subject is an integral part of what is referred to as high energy density physics. These new results and discoveries may someday lead to the development of compact accelerators that could be the basis for a future TeV class linear collider, for a future compact light source, and for future proton beams that could be used in medical therapy. The primary research tool was mutli-dimensional including three-dimensional particle-in-cell simulations. In plasma based acceleration a plasma wave wake moving near the speed of light is excited by either the radiation pressure of an intense laser or the space charge electric field of an intense particle beam. These wakes have electric fields more than three orders of magnitude larger than in existing accelerators. The wavelength of these structures is also much smaller than in existing accelerators. This makes injecting beams of particles into the structures challenging. We developed the first threshold calculation for injecting particles into the wake through ionization by the elecric field of a laser (or particle beam). We then used this threshold and the understanding that results from it study existing experimental results, to develop new injection methods that might someday lead to the highest brightness electron beams to date, and to develop future experiments. We have also made progress on understanding how to make the process of generating the wake and extracting energy from it as efficient as possible. We have also developed a new explantion for how laser energy is absorbed and then converted into energetic electrons when an intense laser impinges on a very dense. This explanation predictes very different behavior for linearly or circularly polarized lasers which is seen in simulations and experiments. Understanding these interactions weill be useful in developing new ideas for generating mono energetic protons at energies exceeding 100 MeV We have also showed the usefulness simulating intense laser or particle beam plasma interactions in a Lorentz boosted frame. We used this technique to study how near term lasers could generate 10 GeV electron beams. We have also improved on this technique by analyzing a numerical instability that results when a plasm drifts at relativistic energies. And we have developed a new code that uses FFTs and not finite difference operators to solve the equations which updates the forces (electric and magnetic filed). This new algorithm essentiall eliminates the instability. We have also greatly improved another simulation technique for intense laser and beam plasma interactions. In this technique the laser/particle beam is assumed to not change much that makes wh
