Proton probing of magnetic fields in exploding wire experiments

Summary form only given. Determination of B-field structures in pulsed power driven exploding wire experiments is vital to recover detailed information about the evolution, driving mechanisms of ablation, and subsequent instability development, but is complicated by the presence of large volumes of hot, dense plasma. Optical and electrical probe diagnostics typically fail early in the experiment. We present progress on a new project, which examines the use of proton deflectometry to measure magnetic fields in pulsed power plasmas. Experimental work is carried out at the Nevada Terawatt Facility (NTF) using both 10 J, 0.3 ps Leopard laser and the 1.6 MA Zebra pulsed power driver. Leopard provided focused intensities of ~5×10¹⁹ W cm^-2, and generated up to 8 MeV protons from thin metallic targets with good reproducibility and low divergence, even when placed within the ZEBRA chamber. Interpretation of experimental results can only be achieved by performing many iterations of simulation, which may then be compared to actual data. Quantitative data from experiments detailing the conditions of the plasma, such as density and temperature, unique to each experimental setup, is used to constrain the simulation of wire plasmas performed using the 3D resistive MHD code, GORGON. Protons are then injected and tracked through the plasma using the 3D PIC (Particle-In-Cell) Large Scale Plasma code in order to produce possible proton image plane data. All computational work is carried out using a new 304-processor cluster, PLEIADES, installed at the San Diego Super Computer Center at UCSD. The first simulations of protons through single wire plasmas in pulsed power experiments, along with comparison to recent experimental results will be presented.