Two-Dimensional Modeling of the Capillary Plasma With the Kinetic Ablation Model
A steady 2-D magnetohydrodynamic model of a capillary discharge is presented. Special attention is paid to the ablation/deposition process at the capillary wall, and the results show distinct 2-D features.
A Flexible Waveform Conditioning Strategy of an Air-Core Pulsed Alternator
As a new type of pulsed power supply, an air-core pulsed alternator concentrates all the functions of energy storage, energy conversion, and power conditioning in one machine. It is also easy to condition the output voltage and current waveforms. These advantages make it a promising compact power supply system for the electrothermal-chemical gun (ETCG). However, the use of multiphase air-core pulsed alternators as the power supply of ETCGs may give rise to problems such as generating high voltage trigger pulse and providing proper voltage and current waveforms. According to the special requirements of ETCGs, a novel circuit topology and a flexible waveform conditioning strategy of an air-core pulsed alternator were proposed. In the initial stage of the discharge process, the two-phase armature windings are connected in series to generate a high voltage pulse to ignite the capillary. The series mode does not need a high-voltage capacitor and its charger to ignite the capillary, which makes the whole system more compact. After the capillary is ignited, the two-phase armature windings are connected in parallel. Adding conditioning inductors and controlling the trigger angles can make the voltage and current waveforms more flexible. The mathematical model of the two-phase air-core pulsed alternator was established to obtain the basic relationship of the variables. Based on the mathematical model and the circuit topology, the performances of the ETCG powered by the alternator using the flexible waveform conditioning strategy were analyzed. The results indicate that with the new strategy of the air-core pulsed alternator it is feasible to provide more flexibility in pulse conditioning than with the conventional strategy.
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.