Active lamp pulse driver circuit

A circuit for optically pumping a laser medium comprising:

• a partially evacuated flashlamp tube exhibiting a negative resistance characteristic with a longitudinal bore containing an ionizable gas between an anode oppositely positioned at one end of said tube from a cathode electrode;
• a storage capacitor coupled to discharge directly through said anode;
• an ignition voltage source coupled to a third electrode of said flashlamp, for applying a voltage spike to said third electrode with sufficient magnitude to create an arc of partial ionization of gas within said bore;
• a direct current power supply directly coupled to said anode and continuously providing energy to said anode for maintaining said arc of partial ionization of said gas while cyclically charging said storage capacitor to a potential of sufficient magnitude to fill said bore with a plasma of said gas;
• a transistor with an emitter, connected in a common emitter configuration with the collector operatively coupled to said cathode electrode;
• bias means coupled to the base of said transistor to hold a junction between said emitter and collector in a reverse bias condition;
• a multivibrator cyclically generating a reference voltage pulse of predetermined duration;
• an operational amplifier coupled between said transistor and said multivibrator and being receptive to the reference voltage pulse to provide a drive signal to said base of sufficient magnitude to forwardly bias said junction between said base and said collector during reception of said reference voltage pulse;
• a reference potential source having a lower voltage than the potential of said power supply;
• and
• an impedance coupled between said emitter and said reference potential, having a tap coupled to said operational amplifier thereby providing said operational amplifier with a sense signal proportional in magnitude to the amplitude of electrical current through said emitter.

A circuit for generating optical energy, comprising:

• a partially evacuated tube with a bore containing an ionizable gas between an anode electrode disposed apart from a cathode electrode, exhibiting a negative resistance characteristic during a first operational condition occurring in response to application of a voltage to said anode electrode with sufficient magnitude for maintaining a minor electrical current through an arc of partial ionization of said gas, a change from said first condition to a second operational condition occurring upon an increase in said minor current to a major current with sufficient magnitude for causing a plasma of said gas to fill said bore, and a change from said second condition to said first condition occurring in response to a decrease in said major current to the level of said minor current;
• energy storage means exhibiting a single and capacitive reactive impedance component for supplying said major electrical current to said electrodes during said second operational condition;
• energy supply means for applying said voltage directly and continuously to said anode electrode and providing energy during said first operational condition directly to said energy storage means;
• circuit switching means for providing a variable internal impedance for discharge of said energy storage means through said tube during said second operational condition;
• amplification means for periodically shifting said tube between said first and second operational conditions by varying said internal impedance of said circuit switching means between a non-conducting mode and a linearly responsive conducting mode;
• and
• sensing means responsive to the amplitude of said electrical currents, providing a first signal to said amplification means whereby said internal impedance is varied by said operational means linearly in dependence upon amplitude of said electrical currents.