Lasing from the domain of collision of ionisation waves produced due to electric field concentration at electrodes with a small radius of curvature

The characteristics of UV lasing in nitrogen and of diffusive discharge produced without an additional ionisation source were experimentally investigated in a nonuniform electric field formed by electrodes with different profiles. High-voltage nanosecond pulses were applied to the blade- and cylinder-shaped electrodes. It was determined that the gap breakdown at elevated pressure was caused by diffusive jets which propagate from the electrodes with a small radius of curvature. The electric field increased in the intersection of counter-propagating jets, with the effect that the threshold of lasing in the C³Π_u — B³Π_g (λ = 337.1 nm) molecular nitrogen band was attained for low average electric fields (below 60 V cm^-1 Torr^-1) and at pressures of 760 Torr and above. With lowering the pressure from 760 to 20 Torr, the voltage of gap breakdown in the nonuniform electric field was observed to increase for a voltage pulse rise time of ~300 ps and to decrease for a pulse rise time of ~2 ns.