engleski

Nitrogen Laser Beam Interaction with Copper Surface

The ultraviolet and visible spectra of plasmas produced by N2-laser radiation focused onto a copper target in air and in vacuum have been recorded photographically. The nitrogen laser beam ( wavelength 337 nm) had a maximum energy density of 1.1 J/cm2, the pulse duration was 6 ns, and the repetition rate 0.2 Hz. The measured electron temperature was 15000 K(+- 30%) in air and 13000 K (+- 50%) in vacuum and the electron densities were 6.5 x (10 exp 17) /cm3 (+-60%) and 3.0 x (10 exp 17)/cm3 (+- 60%), respectively. The irradiated surface in air and in vacuum was studied employing a metallographic microscope. In vacuum, the droplets were created and expulsed at the crater edges. Their formation is explained by the hydrodynamical model. They were formed in a time interval which is about two times shorter than the duration of the laser pulse. In air, droplets were also formed. The weight loss from the Cu-crater in vacuum was about 0.3x (10 exp -4) micromole/pulse, in air it was about three times less.

Laser-induced plasma; N2-laser radiation; short pulses; copper surface

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