M Barbaglia

Research on pinch plasma focus devices of hundred of kilojoules to tens of joules

At present the Plasma Physics and Plasma Technology Group of the Comision Chilena de Energia Nuclear (CCHEN) has the experimental facilities in order to study fast dense transient discharges in a wide range of energy and current, namely: I) energy from hundred of kilojoules to tens of joules, II) current from megaamperes to tens of kiloamperes. Also several diagnostics have been implemented. An overview of the work being carried out on dense pinch plasma focus discharges at the Comision Chilena de Energia Nuclear is presented. The plasma energy density and scaling laws for the neutron yield are discussed. Possible applications of the radiation emitted are also discussed.

Experimental study of the hard x-ray emissions in a plasma focus of hundreds of Joules

An experimental study on hard x-ray production in a small plasma focus device operating in a few hundreds of Joule range is presented. A threshold in the voltage drop on the pinch was observed for x-ray emission. A comparison with Dreicer theory for electrons runaway in plasmas yields significant agreement. The study was performed at a constant pressure (1.8 mbar) of deuterium with three different anode lengths.

A simple plasma diagnostic based on processing the electrical signals from coaxial discharges

A technique for the determination of the inductance evolution in coaxial discharges based on measurements of the voltage between the electrodes and of the discharge current time derivative is presented and discussed. The technique is applied to measurements performed in a 5.7 kJ plasma focus device operating with deuterium filling in the 1–6 mbar range (which is the neutron yield range) and the obtained results are in good agreement with the expected evolution of a current sheet within the electrodes system.

A lumped parameter model of free expanding Plasma Focus

In this paper, a model of Plasma Focus without surrounding cathode containing the radial expansion of the current sheath is presented. This configuration has been increasingly used in recent miniature devices. The model, based on the snowplow approximation, was applied to calculate the voltage along the pinch in a small 300 J device, showing good agreement with the experiments. The results can be useful in the design of x-rays applications of Plasma-Focus devices.

Effect of the external outer electrode in plasma-focus discharges

The pinching efficiency of a plasma focus operating with an open cathode was studied by reconstructing the temporal evolution of the inductance of the plasma-electrodes system. It was found that the performance as a neuron generator is substantially reduced compared with the same device configured with a surrounding cage-like cathode. In particular, no pinching occurred in 30 shots performed at 1, 2 and 3?mbar without outer electrode.

Time-Varying Inductance of the Plasma Sheet in the PF1000 Plasma-Focus Device

The time-varying inductance of the plasma-electrode system in the large plasma focus (PF) device PF1000 is experimentally determined from voltage and current-time derivative signals. The signals were acquired in several shots performed at the same conditions (2.4 mbar of D2, 24 kV). Using these results, the temporal evolution of the voltage drop on the pinch column is also assessed. The maximum values of these voltage drops exceed 100 kV in all the shots.

Temporal shock wave analysis produced by copper exploding wires in air at atmospheric pressure

In this work, experimental results concerning the temporal evolution of the shock wave radii generated by an exploding copper wire of fixed length are presented. The variables of the experience were the diameter dimension—from 50 to 500 μm—and the initial capacitor voltage—from 5 to 25 kV. The diagnostic device was a streak shadow image system synchronized with the experiment. The result is a parametric collection of data showing the shock wave position across the time depicting the different stages of the experience.

Electrical behavior of exploding copper wire in ambient air

This work experimentally investigates the electrical behavior of an exploding wire when the initial energy of the system varies from 28 to 709 J. This experiment uses 50-μm-diameter, 33-mm-long copper wires. The wire is surrounded by air at normal atmospheric pressure and temperature. The experiment monitored the current derivative, voltage between wire ends, total visible radiation emitted, and the shadow image of the wire to study how the electrical parameters vary as a function of initial energy. The results indicate a change in the initial discharge mechanism.This work experimentally investigates the electrical behavior of an exploding wire when the initial energy of the system varies from 28 to 709 J. This experiment uses 50-μm-diameter, 33-mm-long copper wires. The wire is surrounded by air at normal atmospheric pressure and temperature. The experiment monitored the current derivative, voltage between wire ends, total visible radiation emitted, and the shadow image of the wire to study how the electrical parameters vary as a function of initial energy. The results indicate a change in the initial discharge mechanism.

A model of hard X-rays emission from free expanding Plasma-Focus discharges

A planar-piston model of the hard x-ray production in Plasma-Focus devices is presented. The model applies Von Karman approximations to represent the inner structure of the pinch. The hard x-ray emission is calculated assuming Bremsstrahlung from the collision on the anode base of an electron current running away from the pinch. The model was applied to analyse the experimental data of a small Plasma Focus without surrounding cathode, founding good agreement.

Multiple pinching in the miniature plasma focus nanoPLADEMA

This work presents evidence of multiple pinching deduced from electrical diagnoses taken during discharges on the Plasma-Focus nanoPLADEMA, of extremely low energy. The dimensions of the anode are 2mm OD and 0.5mm length, the insulator is an alumina tube 4 mm OD and 2.3 mm length. The cathode is open, so the current sheet expands radially free.