Comparison of the electron density measurements using Thomson scattering and emission spectroscopy for laser induced breakdown in one atmosphere of helium

Abstract

Thomson scattering from laser-induced plasma in atmospheric helium was used to obtain temporally and spatially resolved electron temperature and density profiles. Electron density measurements at 5 μs after breakdown are compared with those derived from the separation of the allowed and forbidden components of the 447.1 nm He I line. Plasma is created using 9 ns, 140 mJ pulses from Nd:YAG laser at 1064 nm. Electron densities of ∼5 × 1016 cm−3 are in good agreement with Thomson scattering measurements, benchmarking this emission line as a useful diagnostic for high density plasmas.