Experimental results of a 330 GW impedance-matched Marx generator

Impedance-matched Marx generators (IMGs) are considered next generation pulsed-power drivers because of their long lifetime (> 10,000 shots), repetition rate (> 0.1-Hz), fast rise time (~ 100-ns), and high-energy-delivery efficiency (~ 90%). "TITAN" is a 14-stage IMG designed to deliver 1-TW to a 2-Ω matched load. In this paper, design, simulation, and experimental results for six stages of TITAN including its triggering system, air delivery system, and pulse shaping are presented. To achieve efficiency over 85% and maximize the capability of an IMG, synchronized triggering, reduced pre-fire rate, and pulse shaping ability are crucial. In this paper, novel engineering solutions are introduced, tested, and proven to overcome those challenges. 6-stage TITAN, powered by 102 identical bricks and 102 field-distortion-triggered gas switches, could generate ~ 600-kA and ~ 700-kV across a ~ 0.9-Ω matched load when fully charged to ± 100-kV. In these experiments, 6-stage TITAN is tested up to ± 70-kV charge voltage which delivers a peak power of 330-GW to a 1.2-Ω resistive load.

Kappa distribution from particle correlations in nonequilibrium, steady-state plasmas

Kappa-distributed velocities in plasmas are common in a wide variety of settings, from low-density to high-density plasmas. To date, they have been found mainly in space plasmas, but are recently being considered also in the modeling of laboratory plasmas. Despite being routinely employed, the origin of the kappa distribution remains, to this day, unclear. For instance, deviations from the Maxwell-Boltzmann distribution are sometimes regarded as a signature of the nonadditivity of the thermodynamic entropy, although there are alternative frameworks such as superstatistics where such an assumption is not needed. In this work we recover the kappa distribution for particle velocities from the formalism of nonequilibrium steady-states, assuming only a single requirement on the dependence between the kinetic energy of a test particle and that of its immediate environment. Our results go beyond the standard derivation based on superstatistics, as we do not require any assumption about the existence of temperature or its statistical distribution, instead obtaining them from the requirement on kinetic energies. All of this suggests that this family of distributions may be more common than usually assumed, widening its domain of application in particular to the description of plasmas from fusion experiments. Furthermore, we show that a description of kappa-distributed plasma is simpler in terms of features of the superstatistical inverse temperature distribution rather than the traditional parameters κ and the thermal velocity v_{th}.

Bayesian inference of spectrometric data and validation with numerical simulations of plasma sheath diagnostics of a plasma focus discharge

Plasma Foci are pulsed coaxial discharges with numerous radiation applications and interesting scientific phenomena. Although the physics answered much of the processes involved in these discharges, many related fundamental questions still remains doggedly unresolved. One of the obstacles to deeper knowledge is the scarcity of reliable experimental data. This work presents an elaborate experimental assessment of the electron density in the rundown phase of a 400 J Plasma Focus operating with hydrogen. The rundown of the plasma sheath is basically a hypersonic shock wave between two coaxial electrodes accelerated by the Lorentz force, and it is important to control the pinch formation. The electron density of the passing sheath is measured by means of the Stark broadened hydrogen alpha emission with spatial and temporal resolution. The experimental data is post-processed using Bayesian posterior probability assessment. The results are conflated with the numerical model CShock to construe an educated explanation of the sheath behavior during the rundown. In particular, it is possible to reckon the formation of a toroidal instability reported in previous experiments, and to estimate the plasma sheath temperature (4–20 eV) and velocity (62.5 km/s) at this stage.

Features of Pinch Plasma, Electron, and Ion Beams That Originated in the AECS PF-1 Plasma Focus Device

The measured current traces of alow energy AECS PF-1 plasma focus device are used for studying of the formed plasma, and the produced ion and electron beams. Anadapted version of the Lee model (RADPFV5.15FIB&REB) is applied, taking into account the fitting procedures between the measured and computed current waveforms for each shot. The experiments on AECSPF-1 were performed with three different gases—helium, nitrogen, and argon—for studying the effect of the atomic number on the properties of the generated beams. For numerical experiments using the Lee model, 36 successful shots for each gas were selected. The peak values of the total discharge current Ipeak were 50–55 kA, the pinch currents Ipinchwere34–36 kA, and the final pinch radius reached a minimum value of 0.03 cm for argon. The ion mean energy ranged from 35 keV (for He) to 223 keV (for Ar). The beam energy also had an extreme value of 1.34 J (0.05%E0) for argon. The results presented the highest values of 2.4 × 1014Wm−2 for the power flow density, and adamage factor of around 3.1 × 1010 Wm−2s0.5 for argon. For electron beams, the results also showed that the fluence and flux increased with the higher atomic number and reached a peak of 9.7 × 1022 m−2 and 5.9 × 1030 m−2 s−1 for argon, respectively. The results presented the highest values of 2.2 × 1016Wm−2 for the power flow density (heat flux), and adamage factor of around 3 × 1012 Wm−2s0.5 for argon. The kinetic energy of the relativistic electrons was found to be within the range of 18–23 keV. The results show that the ion and electron beam properties (energy, flux, fluence, ion and electron numbers, current, power flow density, and damage factor) emitted from the plasma focus had wide ranges based on the operational plasma focus parameters. Thus, these results could be used for selection of the suitable plasma focus parameters for desired material processing applications.