Schematic of setup for Thomson scatter. The baffle arms are fitted with Brewster angle windows to reduce stray light scatter, a double grating spectrometer with a gated ICCD camera is used.
Sample spectrum taken at a delay of and from the target surface. The fit curve shows a moderate of 1.3 in the collective scatter regime. Also shown is the fitting to the Raman satellites which were subtracted in the fitting of the Thomson scatter.
Evolution of the electron density and temperature with time delay, for the plasma probed at (a) , (b) , (c) , and (d) from the target.
(a) Evolution of normalized electron density (filled squares) compared to normalized Rayleigh scattering intensity (filled circles), which is proportional to the number density of atoms in the plasma plume from the target surface. The dashed line is a fit to ; the solid line is a fit to , where . (b) Plot of interpolated electron densities taken at each of the four spatial positions assuming three different expansion velocities (note that all three cases share the data point at ). The solid line is a fit to .
(a) Lateral profile of the electron density and temperature at from the target surface and after heating. The solid and dashed lines correspond to Gaussian and parabolic fits to the temperature profile. (b) Electron density normalized to the Rayleigh scatter with both Gaussian (solid line) and parabolic (dashed line) fits to the Rayleigh profile.
Normalized lateral profile of the Rayleigh scatter at from the target surface and after heating. The solid and dashed lines correspond to double Gaussian and double parabolic fits.
Comparison of experimental and simulated electron density at (a) and (b) from the target surface. The isothermal solution is the solid line and the isentropic model is represented by the dashed line. The models assume a fixed ionization degree of 1.7 and an ablated vapor mass of .
High resolution emission spectrum from a Mg plume, delay from the target surface. The gate time for the ICCD was for all the emission spectra. The spectrum is an accumulation of 25 shots. The peak at is fitted with a Voigt function.
Electron density evolution with time for plasma from the target surface, determined by calculating the Stark width of the emission line of at , compared to results from Thomson scatter. The agreement is not perfect with an apparently slower fall with time for the Stark data.
Emission spectrum recorded with lower dispersion spectrometer (a) principal lines and (b) zoomed spectrum to show weaker lines.
Boltzmann plots of line ratios for Mg emission at from target for (a) delay and (b) delay.
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