New capabilities for modeling intense beams in heavy ion fusion drivers

FO26.4 NEW CAPABILITIES FOR MODELING INTENSE BEAMS IN HEAVY ION FUSION DRIVERS A. Friedman, 1,2∗ J. J. Barnard, 1,2 F. M. Bieniosek, 1,3 C. M. Celata, 1,3 R. H. Cohen, 1,2 R. C. Davidson, 1,4 D. P. Grote, 1,2 I. Haber, 5 E. Henestroza, 1,3 E. P. Lee, 1,3 S. M. Lund, 1,2 H. Qin, 1,4 W. M. Sharp, 1,2 E. Startsev, 1,4 and J-L. Vay 1,3 Heavy Ion Fusion Virtual National Laboratory Lawrence Livermore National Laboratory, Livermore CA USA Lawrence Berkeley National Laboratory, Berkeley CA USA Princeton Plasma Physics Laboratory, Princeton NJ USA University of Maryland, College Park MD USA pretation of experiments, and facilitate the design of future facilities. This paper describes progress toward this goal, emphasizing beam modeling for the driver accelerator. Significant advances have been made in modeling the intense beams of heavy-ion beam-driven Inertial Fusion Energy (Heavy Ion Fusion). In this paper, a roadmap for a validated, predictive driver simulation capability, build- ing on improved codes and experimental diagnostics, is presented, as are examples of progress. The Mesh Re- finement and Particle-in-Cell methods were integrated in the WARP code; this capability supported an injector ex- periment that determined the achievable current rise time, in good agreement with calculations. In a complemen- tary effort, a new injector approach based on the merging of ∼100 small beamlets was simulated, its basic feasibil- ity established, and an experimental test designed. Time- dependent 3D simulations of the High Current Experiment (HCX) were performed, yielding voltage waveforms for an upcoming study of bunch-end control. Studies of collective beam modes which must be taken into account in driver designs were carried out. The value of using experimental data to tomographically “synthesize” a 4D beam particle distribution and so initialize a simulation was established; this work motivated further development of new diagnos- tics which yield 3D projections of the beam phase space. Other developments, including improved modeling of ion beam focusing and transport through the fusion chamber environment and onto the target, and of stray electrons and their effects on ion beams, are briefly noted. I. INTRODUCTION A key goal of the Heavy Ion Fusion (HIF) program is a well benchmarked, integrated source-to-target simulation capability that can be used to support the design and inter- ∗ af@llnl.gov; Figure 1: A depiction of the strategy being pursued for con- sistent, detailed end-to-end beam simulation. The Heavy Ion Fusion beam research program [1, 2, 3] employs a suite of simulation codes; see Fig. 1 for a roadmap. For studies of beams in the driver accelerator, drift-compression line, and final-focusing optical system, the principal tool is a particle-in-cell (PIC) code known as WARP [4] (named for the “warped” coordinates it uses for a bent beam line). In the fusion chamber, the principal tool is the hybrid implicit electromagnetic PIC code LSP [5] (“Large Scale Plasmas”). BEST [6] (“Beam Equilibrium, Stability, and Transport”), a nonlinear perturbative particle code with minimal statistical “noise,” is the principal tool for studies of plasma modes on the beams. Hermes and Circe are moment-based models in WARP which are use- ful for rapid iterative design. The Semi-Lagrangian Vlasov L-645 LLNL, P.O. Box 808, Livermore CA 94550 USA