LAUSR

The influence of the laser wavelength on nanosecond laser-produced Al plasma in a transverse magnetic field is studied and presented. A Q-switch Nd:YAG pulsed laser (FWHM: 6 ns) is used to ablate an aluminum sample at 50 mJ at the fundamental, second, and fourth harmonics of 1064 nm, 532 nm, and 266 nm, respectively. A permanent magnetic trap is used with a nearly uniform magnetic field of 0.8 T to confine plasma expansion, reduce both fast and slow components of plasma velocity, and increase signal intensity. Fast photography is performed using an Intensified Charged Coupled Device camera to study the plume hydrodynamics as it evolves through the induced magnetic field. Optical Emission Spectroscopy is used to determine the effect of the laser wavelength on key ionic and neutral emission lines, as well as to study the enhancement and reduction of certain emission lines in the presence of a magnetic field. Fast photography results confirm that the laser wavelength has a significant effect on plume hydrodynamics, especially as it evolves through the magnetic field. The magnetic field confines both fast and slow components of the plasma as early as ∼45 ns after laser impact for all laser wavelengths used, as well as reducing the velocity of the plasma by about 5×. It is shown that the 266 nm laser wavelength under the magnetic field enhanced both ionic and neutral lines by up to 11×, while 532 nm laser plasma only showed enhancements in ionic lines with reduction in neutral. A laser wavelength of 1064 nm showed a slight enhancement of ionic lines with a significant reduction in neutral lines under the same conditions.