TY - JOUR A1 - Merk, Sven A1 - Demidov, Alexandr A1 - Shelby, D. A1 - Gornushkin, Igor B. A1 - Panne, Ulrich A1 - Smith, B.W. A1 - Omenetto, N. T1 - Diagnostic of laser-induced plasma using Abel inversion and radiation modeling JF - Applied spectroscopy N2 - A method based on matching synthetic and experimental emissivity spectra was applied to spatially resolved measurements of a laser-induced plasma ignited in argon at atmospheric pressure. The experimental emissivity spectra were obtained by Abel inversion of intensity spectra measured from a thin plasma slice perpendicular to the plasma axis. The synthetic spectra were iteratively calculated from an equilibrium model of plasma radiation that included free free, free–bound, and bound–bound transitions. From both the experimental and synthetic emissivity spectra, spatial and temporal distributions of plasma temperature and number densities of plasma species (atoms, ions, and electrons) were obtained and compared. For the best-fit synthetic spectra, the temperature and number densities were read directly from the model; for experimental spectra, these parameters were obtained by traditional Boltzmann plot and Stark broadening methods. In both cases, the same spectroscopic data were used. Two approaches revealed a close agreement in electron number densities, but differences in plasma excitation temperatures and atom number densities. The trueness of the two methods was tested by the direct Abel transform that reconstructed the original intensity spectra for comparing them to the measured spectra. The comparison yielded a 9 and 13% difference between the reconstructed and experimental spectra for the numerical and traditional methods, respectively. It was thus demonstrated that the spectral fit method is capable of providing more accurate plasma diagnostics than the Boltzmann plot and Stark broadening methods. KW - Abel inversion KW - Laser-induced plasma KW - LIBS KW - Plasma spectrum analysis PY - 2013 DO - https://doi.org/10.1366/12-06929 SN - 0003-7028 SN - 1943-3530 VL - 67 IS - 8 SP - 851 EP - 859 PB - Society for Applied Spectroscopy CY - Frederick, Md. AN - OPUS4-30433 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gornushkin, Igor B. A1 - Smith, B.W. A1 - Panne, Ulrich A1 - Omenetto, N. T1 - Laser-induced breakdown spectroscopy combined with spatial heterodyne spectroscopy JF - Applied spectroscopy N2 - A spatial heterodyne spectrometer (SHS) is tested for the first time in combination with laser-induced breakdown spectroscopy (LIBS). The spectrometer is a modified version of the Michelson interferometer in which mirrors are replaced by diffraction gratings. The SHS contains no moving parts and the gratings are fixed at equal distances from the beam splitter. The main advantage is high throughput, about 200 times higher than that of dispersive spectrometers used in LIBS. This makes LIBS-SHS a promising technique for low-light standoff applications. The output signal of the SHS is an interferogram that is Fourier-transformed to retrieve the original plasma spectrum. In this proof-of-principle study, we investigate the potential of LIBS-SHS for material classification and quantitative analysis. Brass standards with broadly varying concentrations of Cu and Zn were tested. Classification via principal component analysis (PCA) shows distinct groupings of materials according to their origin. The quantification via partial least squares regression (PLS) shows good precision (relative standard deviation , 10%) and accuracy (within 6 5% of nominal concentrations). It is possible that LIBS-SHS can be developed into a portable, inexpensive, rugged instrument for field applications. KW - Spatial heterodyne spectroscopy KW - Laser-induced breakdown spectroscopy KW - Fourier transform spectroscopy KW - LIBS KW - Laser-induced plasma KW - Interferometry PY - 2014 DO - https://doi.org/10.1366/14-07544 SN - 0003-7028 SN - 1943-3530 VL - 68 IS - 9 SP - 1076 EP - 1084 PB - Society for Applied Spectroscopy CY - Frederick, Md. AN - OPUS4-32163 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -