The time evolution of the resistances and inductances of the discharges in a pulsed gas laser through its current waveforms

Abstract

In the present work, the time-dependent resistances and inductances of the electric discharges in a pulsed gas laser are revealed through the current waveforms of the circuit. This can be achieved combining step-by-step the experimental current waveforms with the current differential equations of the system. Thus, digitizing the signal, the derivative is calculated through a computer. For a certain time instant, substituting the values of the current and its derivative into the integrodifferential equations describing the performance of the circuit loops, we form relationships which connect the values of the resistance and inductance for this particular time instant. Combining relationships originating from very close adjacent time instants, the values of the resistances and inductances can be found. Scanning the entire time region of the discharges, the time dependence of the resistances and inductances of the discharges are revealed. Their behavior shows an abrupt drop for the resistances and a sharp peak for the inductances, both during the formation phase. After that, the above characteristic quantities fluctuate slowly around constant values. The sharp drop of the resistances was expected, bearing in mind that the number of the charges increases dramatically through the electron avalanche multiplication during the first few nanoseconds, causing the abrupt reduction of the resistances. On the other hand, the sharp peak of the inductances was unexpected. A plausible explanation for this phenomenon is that the plasma undergoes a temporary constriction which is due to the predominant attractive magnetic forces during the formation phase of the discharge.