Impedance monitor to protect the thyratron in metal vapor lasers

It is found that the appearance of high reverse-voltage spikes on the thyratron anode in the discharge of metal vapor lasers due to high laser impedances can easily be monitored by a dc current meter in series with the bypass inductor of the discharge circuit. Experiments are demonstrated using a copper vapor laser. Results show that the proposed impedance monitor is effective, reliable, and economical. The meter deflection corresponding to acceptable, well-behaved thyratron operation can be obtained easily by the residual ionization-control method using a clean laser tube. By keeping the deflection within a specified limit, the lifetime of thyratron can greatly be extended.