Doppler-free, laser saturated absorption profile of 414 nm helium line for plasma density measurements

The role of photon self-absorption on the H (n = 2) density determination by means of VUV emission spectroscopy and TDLAS in low pressure plasmas

“…This procedure revealed a possible underestimation of the measured value of n H (n=2) by roughly 15 % under the standard conditions of the setup. This is connected to a value of the saturation parameter (after [21,22]) of S 0 = 0.33. To obtain a higher signal-to-noise ratio, the laser power is not, however, reduced and the underestimation is assigned by an additional error bar.…”