STUDY OF CADENCE OPERATING OF XeCl EXCIMER LASER TRIGGERED BY PHOTOIONISATION

This work demonstrates the feasibility of high repetition rate operation of photo triggered excimer lasers. Photo triggering of excimer lasers was put forward in 1982 at Laboratoires de Marcoussis and greatly increases the reliability of the electrical driving circuit : according to this proposal, the laser head is directly connected to the storage line and loaded to its design voltage with a relatively slow rise time pulse. The triggering of a stable discharge is then obtained by rapid initiation of the required electronic density in the interelectrode spacing using photoionisation. The experimental set-up includes a laser head and a gas circulation loop to ensure active medium renewal. A flat nickel anode and a screen cathode form part of the laser head. Its active volume is 30 cm3. A silica encapsulated electrode takes place under the cathode to ensure preionisation. Electrical driving circuit includes two all solid state magnetic switching devices. Using a 2.5 bar gas mixture and for single shot operation the laser delivers a pulse of 40 ns duration with energy up to 50 mj. Best efficiency can reach 2.5 %. For high repetition rate operation up to 400 Hz. 5 W mean power has been obtained