Experimental and theoretical investigation of radiation and dynamics properties in laser-produced carbon plasmas

Investigation of a Collisional Radiative Model for Laser-Produced Plasmas

“…This minimum laser flux can be achieved easily with typical Nd:YAG lasers, with laser pulse energies, pulse widths, and focal spot diameters on the order of 1 J, 10 ns, and 100 µm, respectively. Where spot sizes are on the order of 10s of µm the minimum laser flux is greatly exceeded [6,[8][9][10]. Similarly, with T e = 3 eV and λ = 10.6 µm, a laser flux on the order of 10 7 W/cm 2 is found, which can be exceeded by laser energies, pulse widths, and focal spot diameters on the order of 1 J, 1 µs, and a few mm, respectively.…”

“…Removing ξ Z produces the expected ionization bottlenecks with the NIST χ Z s but removes all features with the CT χ Z s, as shown by the dashed lines in Figure 2a While rate coefficients plots were not shown by Colombant and Tonon, they were examined here, in an effort to interpret the unusual behaviour observed for the ionization bottlenecks. The results from Equations (4), (6), and (8) were plotted for consecutive ion stages. The ground state and up to the sixth ion stage (Sn 5+ ) were chosen, because several changes in the outermost occupied subshell could be observed.…”

“…An example of each of these trends is shown in Figure 3a,b. Equations (4), (6), and (8) indicate that without the ξ Z factor, χ Z is the only other variable for a given temperature (T e ) within the rate coefficient equations and therefore the only influence on the ion stage distributions for a fixed n e . The grouping of ion stages according to the outermost electronic orbital, which are observed when the NIST χ Z s are used with no occupancy factor, makes sense as χ Z most drastically changes between ion stages with different outermost subshells.…”

“…The CR model continues to be used to estimate charge state distributions for the emission spectra of a variety of elements, for example C (Z A = 6), Ge (Z A = 32), and Gd (Z A = 64) [6][7][8]. Typically in these experiments laser pulse lengths are on the order of 10 ns, with wavelengths of 1064 or 532 nm [6][7][8][9][10]. The CR model has seen further use in investigating LPPs through the three-body and radiative recombination rate coefficients [9]; and it has also been extended, for example into a time-dependent version taking into account photoionization [10].…”

“…A list of the terms used to describe the model and parameter configurations used throughout this work, along with a brief description of each. Use of the χ Z values reported by NIST[20] CT χ Z Use of χ Z values calculated from Colombant and Tonon's estimate, Equation(7)[5] No ξ Z Removal of the ξ Z term from Equations (4) and(6) …”