Ablative Capillary Discharge Research Articles

The effect of external pressure on the plasma parameters in ablative capillary discharges

The effect of external pressure on the plasma parameters (pressure, density, velocity, temperature, kinetic energy) in an ablative capillary discharge is studied for electrothermal and electrothermal-chemical launchers. A comparison between the plasma parameters in such a situation and those obtained when the pressure outside the capillary is negligibly small was performed. The theoretically predicted results for the electrical characteristics of the discharge were compared to the corresponding experimentally obtained values, and were found to be in good agreement.

An experimental investigation of ablative capillary discharges as possible sources for amplified spontaneous emission in the XUV

A fast-rise-time capillary discharge was designed and investigated as a possible source of amplified spontaneous emission in the extreme ultraviolet spectral range. The capillaries were made of or with radii in the range 0.25 - 1 mm and lengths from 1 - 5 cm. Discharge currents of up to 15 kA and current rise-times down to 20 ns could be achieved. Spatially resolved spectra could be recorded with a time resolution of 5 ns. During the cooling phase an increase in the intensity of the H-like Li III 729 Å line could be found, accompanied by a decrease in spatial divergence. By a length variation of 3 - 5 cm of capillaries with 0.5 mm radius an indication of the gain of the Li-like O VI 520 Å line could be obtained.

A proof of the need for consistent treatment in modelling of capillary ablative discharges

In the framework of a one-dimensional model for plasma flow in ablative capillary discharges, we use a consistent method for obtaining the appropriate boundary conditions, and a new method for describing the radiative energy flux from the plasma to the wall. Good agreement is reached between the calculated and the measured values for the temporal behaviour of the plasma's main parameters. The agreement is particularly satisfying for the plasma conductance (resistance), the voltage across the capillary, the total input energy, the maximum input power and the plasma pressure. This gives us confidence that the model also predicts correct values for the remaining plasma parameters that are difficult to measure accurately, such as the plasma density, the temperature and the velocity (inside the capillary as well as at its exit). The knowledge of these parameters is crucial in order to use the ablative capillary as an efficient plasma source for different applications.

A numerical study of the evolution of plasma parameters in an ablative capillary discharge for a two-pulse form of the input energy

A study of spatial and temporal dependences of plasma-relevant parameters has been done in the frame of a general quasi-one-dimensional model for ablative capillary discharges and for a specific time-dependence of the input energy. Particular attention was given to the effect of the so-called 'second boost of input energy' that leads to a substantial increase of some of the main plasma parameters such as exit velocity (26%), mass flux (177%) and energy flux (exit power) (285%). Calculations and experiments are in good agreement. The reliabilities of the model and numerical approach are supported by energy conservation condition fulfilment and the critical value of the exit Mach number.

A theoretical investigation of steady state critical plasma flows in ablative, capillary, high pressure discharges

A new method for the consistent study of stationary, critical flows in ablative capillary discharges is presented. This method enables one to determine the correct values of the plasma characteristics (mass density, flow velocity and temperature) at both closed (z = 0, say) and open (z = l ends of the capillary; a subsequent integration of the basic model equations used provides correct solutions at all axial distances along the capillary. The method is independent of the complexity of the model equations used and holds for any kind of critical (fluid) flow, in the presence of various types of external energy inflow. For demonstration, we here considered the familiar, relatively simpler, non-ideal hydrodynamic equations obtained by averaging two-dimensional equations over the capillary cross-section; these quasi one-dimensional equations describe (correctly) the essential 2D features of the ablative capillary discharge, namely, the radial outward radiative transfer of energy and the radial inward ablative mass flow.