UV filaments

Thermal effects and shockwave formation due to filaments in air

“…The low-density channel subsides for about 100 µs before being deformed by buoyancy. 9 We present a computational model of the gas-dynamics related to this phenomenon that agrees with the Sedov formula 9,14 for shockwave location (as it moves away from the filament), as well as with experimental data 9 for UV filaments.…”

“…As detailed in previous publications, 8,9 we recorded the evolution of the shock wave created by a filament through shadowgraphy, illuminating the wake of the filament with a pulse at 532 nm delayed with respect to the filamented pulse.…”

“…UV (266 nm) filaments are generated by a home-designed laser system generating pulses of about 170 ps in duration, with energies of up to 300 mJ. 9 Focusing lenses of 50 cm, 1m and 3m focal distance were used to produce the filament. As shown in Figs.…”

“…[1][2][3][4][5][6] More recently, there has been interest in studying the cylindrical shock waves produced by light filaments as a particular heat source. [7][8][9][10] Filaments in air with high-power IR 7,11 and UV pulses 12,13 have been investigated for nearly 3 decades. A filament forms through a balance of self-focusing (Kerr effect) and plasma self-defocusing.…”

“…However, the heat generated through electron-ion recombination produces a cylindrical shock wave behind which a low-density channel is formed. 9 The higher energy of the UV filaments makes it possible to study the shock wave by shadowgraphy. The shock is seen to start supersonic, before transitioning after microseconds to a constant velocity acoustic wave.…”