Laser triggered high voltage air gap investigation at intermediary pressures

Nd:YAG laser triggered centimetric air gap in a homogeneous electric field and for pressures ranged between 0.5 and 5 bar is studied. The laser intensity threshold dependance is investigated and the influence of optically enhanced collisional processes is pointed out. The initial electron density threshold necessary to initiate the gap breakdown is evaluated. Breakdown transient voltage and current are measured and the formative time lag dependance on reduced field and laser intensity is analyzed.