Some Considerations in the Design of a High Power, Pulsed N_2 Laser

Abstract

Pulsed, megawatt laser power levels at 3371 A from nitrogen gas require the formation of a high density plasma of high electron temperature in the first few nanoseconds of gaseous breakdown. This has been obtained from a laser tube powered by a pulse forming network in the form of a low impedance, parallel plate transmission line. Another low impedance, parallel plate transmission line, charged to 30 kV is used to pulse charge the pulse forming line by means of a synchronized, multiple spark gap switch. The pulse forming transmission line terminates in a continuous high voltage electrode which runs parallel to the axis of the tube, i.e., in the direction of the light beam. The finite, nonzero time required for the gas in the laser tube to break down, permits (a) pulse charging this line to voltages many times larger than the dc breakdown voltage of the nitrogen in the laser tube, and (b) the placement of the switch in the circuit where its impedance does not limit the rate of rise of current during the laser excitation process. Furthermore, it is shown that decreasing the impedance of the pulse forming line increases the laser output power, when the current in the laser circuit is not limited by circuit inductance.