Pulses of 500 fs or greater duration and several tens of millijoules at 248 nm are used to trigger discharges in air. We will discuss the influence of beam geometry, the minimum field strength that can be triggered, and the electrical discharge guiding properties. The latest measurements have concentrated on DC discharges in air at up to 200 kV. Thanks to a new technique of background free, single shot interferometry, 2D snapshots of the evolving plasma can be recorded. This will lead to further insight about the dynamics involved in the discharge process. The existing laser system is costly and difficult to use in the field. We will show however that similar performance can be achieved with a solid state laser and frequency conversion by nonlinear optics. Such a compact system can be tuned to cover the wavelength range from 240 nm to 350 nm.
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