A doubly preionised ArF laser

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Abstract
A doubly preionised ArF excimer laser is described using a pulse forming network (PFN) with an LC-inversion circuit totally enclosed inside the laser volume. The high potential difference across the capacitors uniformly preionises the laser gas and arcing is prevented by carefully shaping the metal surfaces inside the laser. By applying normal preionisation techniques the main discharge runs in a stable mode. The output energy of the laser from a volume of 65 cm3 was 50 mJ at a charging voltage of 25 kV and the performance of the laser with the pre-ionisation technique is compared with the performance of two other excimer lasers without the use of this technique. A circuit model indicates that good preionisation results in better impedance matching between the PFN and the laser plasma.