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.