Radiation from asymmetric laser-induced plasmas collected by a lens or optical fiber

A method of calculating radiation spectra of an asymmetric (ellipsoidal) laser-induced plasma plume is developed for two cases, when the radiation is collected by a lens and by an optical fiber. The lens receives the radiation coming from the entire plasma plume, while the view sight of an optical fiber is restricted to an acceptance cone so that only the radiation coming with an incident angle smaller than the cone angle is collected. The method incorporates the solution of the radiative transfer equation along the line of sight. An optimal number of lines is found to achieve the numerical convergence with a relative error <1%. Several practical simulations are carried out that include different placements and orientations of the lens and optic fiber. The effect of a motion of the center of the mass of the plasma plume on the radiation spectra is also investigated.