Experiments and simulations of magnetically driven implosions in high repetition rate dense plasma focus

Summary form only given. Results on coordinated experiments and MHD simulations on magnetically driven dense plasma focus implosions are presented. The aim of this effort is to use a repetitively fired dense plasma focus (DPF) to gather data from 100´s to 1000´s of shots, so as to better refine numerical codes. The emphasis of this research effort is on current diffusion and heat transport in magnetically driven implosions. The experimental results will feed the first fully 3D simulations of DPF devices, adding new capabilities to the GORGON code.Experiments are run at DPF-3, a Mather-type PF based at Alameda Applied Sciences Corporation (AASC). This DPF consist of a four-capacitor bank arrangement switched with a rail gap system. Its peak operational current is 480 kA with a maximum stored energy of 5.8 kJ when charged to 20kV, with typical experiments run at 300 kA. The capability of running experiments at 0.33 Hz is key in this project. This high repetition rate is supported by fast digitizers that allow gathering of data on each shot. A typical day´s run might gather data from 1000 shots. The relatively large data sets in turn enable a significant statistically analysis, hence a refinement of the GORGON. Simultaneous diagnostics used to characterize the plasma include interferometry, collimated light emission collected by fiber-optic-photodiode arrays and a B-dot matrix array. The experiments are carried out with different gases, such as Ar, Ne, and He; pressures of ~1-20 Torr are used, depending on the drive current parameter. This allows control over mass sheath and pinch time, amongst other properties. Simulations are run at the Pulsed Power Plasmas Group Cluster, a 96-core HP blade server cluster using 3Ghz processors with 4GB RAM per node, based at UC San Diego. Preliminary results show a plasma sheath velocity of ~6x104 m/s and thickness of ~4 mm in the axial phase. These are in agreement with the snow-plough model of PFs. Electron densities on the ord- r of 1018 cm-3 and magnetic field measurements in the radial compression phase of 10´s of Tesla are anticipated.