TY - JOUR KW - Model KW - Target KW - Measurements KW - Measurement KW - USA KW - Surface KW - Emission KW - Pulse KW - Velocity KW - Experimental KW - Algorithm KW - Interferometry KW - Material KW - Ablation KW - Laser KW - Laser ablation KW - Laser ablation KW - Breakdown KW - Time-resolved KW - Time KW - Ca KW - E KW - Form KW - Plasma KW - Solids KW - Number KW - Pulses KW - Vapor KW - C KW - Metals KW - Ionization KW - Electron number densities KW - Plasmas KW - Picosecond KW - Picosecond laser KW - Picosecond laser ablation KW - Density KW - Pulsed laser KW - Pulsed laser KW - Targets KW - Electron KW - Electron number density KW - Number density KW - Order KW - Ha KW - Metal KW - Dynamics KW - Results KW - Expansion KW - Plume KW - Atmosphere KW - Physics KW - Air KW - Air breakdown KW - Electron emission KW - Electron-emission KW - Forms KW - Heat transfer KW - Laser plasma KW - Laser plasmas KW - Pulsed laser ablation (PLA) KW - Pulsed laser ablation (PLA) KW - Theoretical-model KW - Vapor plume AU - Samuel S Mao AU - Xianglei Mao AU - Ralph Greif AU - Richard E Russo AB -

Picosecond time-resolved images of plasma initiation were recorded during pulsed-laser ablation of metal targets in an air atmosphere. An early-stage plasma was observed to form before the release of a material vapor plume. Close to the target surface, interferometry measurements indicate that the early-stage plasma has an electron number density on the order of 1020 cm-3. The longitudinal expansion of the ionization front for this plasma has a velocity 109 cm/s, during the laser pulse. In contrast, a material-vapor plume forms approximately 200 ps after the laser pulse, and it moves away from the target at 106 cm/s. The experimental observations of the early-stage plasma were simulated by using a theoretical model based on a two-fluids description of laser plasmas. The results indicate that the initiation of the plasma is due to air breakdown assisted by electron emission from the target.

AD -

Univ Calif Berkeley, Lawrence Berkeley Lab, Berkeley, CA 94720 USA

BT - Applied Physics Letters C2 - LBNL-46390 DA - 10/2000 DO - 10.1063/1.1318239 IS - 16 LA - eng LB - Laser N2 -

Picosecond time-resolved images of plasma initiation were recorded during pulsed-laser ablation of metal targets in an air atmosphere. An early-stage plasma was observed to form before the release of a material vapor plume. Close to the target surface, interferometry measurements indicate that the early-stage plasma has an electron number density on the order of 1020 cm-3. The longitudinal expansion of the ionization front for this plasma has a velocity 109 cm/s, during the laser pulse. In contrast, a material-vapor plume forms approximately 200 ps after the laser pulse, and it moves away from the target at 106 cm/s. The experimental observations of the early-stage plasma were simulated by using a theoretical model based on a two-fluids description of laser plasmas. The results indicate that the initiation of the plasma is due to air breakdown assisted by electron emission from the target.

PY - 2000 SP - 2464 EP - 2466 T2 - Applied Physics Letters TI - Initiation of an early-stage plasma during picosecond laser ablation of solids VL - 77 ER -