Long plasma channels induced by femtosecond laser pulses in air are diagnosed using the sonographic method. By detecting the sound signals along the channels, the length and the electron density of the channels are measured. Refocusing is also observed at different laser energies and different focal lengths. We find that the sonographic method has manifest advantages compared to other techniques.
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机译：Elemental Analysis of Stainless Steel Using Hard X-ray Emission Arising from a High-Density Plasma Produced by an Intense Femtosecond KrF Laser Pulse
