AVS 57th International Symposium & Exhibition | |
Plasma Science and Technology | Thursday Sessions |
Session PS-ThP |
Session: | Plasma Science and Technology Poster Session |
Presenter: | R. Machorro, Universidad Nacional Autonoma de Mexico |
Authors: | N. Abundiz, UNAM-CICESE, Mexico C. Velez, UABC, Mexico E. Luna, Universidad Nacional Autónoma de México S. Zazueta, Universidad Nacional Autónoma de México R. Machorro, Universidad Nacional Autonoma de Mexico |
Correspondent: | Click to Email |
Plasmas generated by pulsed laser have a brief existence and their properties are far from uniform. Optical spectroscopy provides information about the spatial and temporal evolution of transient species produced by the laser-matter interaction, such as excited atoms, ions or molecules. This knowledge is essential to understand the ablation phenomenon, and develop better models.
In this work, we use a Nd-YAG laser with 3J energy, 1064nm wavelength, and 7 ns duration pulsed beam, focused with a 20cm focal length biconvex lens into ambient air. Fluence of the order of 3*E+6 J/m2 creates an electric field of 3*E+9 V/m, enough to ionize the air atoms, creating a plasma.
A camera lens forms the plume image into the image plane, where an optical fiber array with 12∗12 fibers is placed. The array is re-arranged to form a one-dimensional column with 144 fibers, which becomes the entrance slit of the spectrograph. A gated image intensified CCD captures the output plane of the spectrograph. An electronic device produces a precise time delay between laser pulse and image capture. From this data is possible to get density and temperature maps of the species, and its discrete time evolution. Moving the camera lens and fiber array along the optical axis, we make a confocal scanning of the plasma.
In the high density regime, the plasma is dominated by collisions, and intensity ratios of lines from the same ion will depend exclusively on the temperature in the manner prescribed by the Boltzmann distribution. We present reconstruction of spectral images of the plasma, as a function of time and axial displacement.
Partial support from the CONACyT project 60351 and DGAPA-UNAM project IN100910 is acknowledged, student NA thanks Conacyt for her scholarship.