Scheme of the experimental setup. Two TDLs are combined and pass the plasma column perpendicular to the axis. The plasma tube can be moved with respect to the laser beams. Data collection system and vacuum equipment are not shown for clarity.
Measurement procedure, recorded is the laser light with and without plasma, plasma light and background. Moreover the calibration signal from the Interferometer with the FSR of 0.3 GHz is shown. Experimental conditions are: 811.5 nm line; p = 80 millibars; z = 2 cm; 68 W input -wave power.
Top: plot of absorbance versus frequency shift for: (a) 772.43 nm line at 0.65 millibars, fitted by a Gaussian function; (b) for 811.53 nm line at 105 millibars, fitted with a Voigt function. By the residue given below, it is clear that a good fit is obtained for 0.65 millibars, while at 105 millibars higher residues are present.
as a function of axial position for different gas pressures. The error bars are decreasing with lower pressure down to 0.65 mbar where the error indication is smaller than the symbol size. For each pressure, the end of the plasma column is indicated by a vertical line.
at the launcher position for different pressures from this experiment (full squares) and measured as described in Ref. 23 by Rayleigh scattering (circles).
Absolute 1s3, 1s4, and 1s5 atom densities for gas pressures of 0.65, 4 and 10 millibars along the plasma column. The ends of the plasma columns are indicated by vertical lines.
The same as in Fig. 6 but for gas pressures of 20, 60, and 105 millibars.
The ratio versus the distance from the launcher, taking the gas temperature into account for the ground state density.
n(1s3) and n(1s4) densities close to the launcher normalized to n(1s5) from the same position as function of pressure (symbol + lines). Indicated are the densities according to Boltzmann equilibrium and (TS) (dashed lines).
Comparison of the n(1s5) with other measurements: TDLS results and data from self-absorption measurements from Ref. 8 as function of the distance to the end of the column (DEC).
Comparison of the ratio at 5 pressures from the experiments (scatter) with a CRM (line) as a function of . Input parameter in the CRM is the experimentally determined, axially constant, 20 .
The measured ratio close to the launcher for different pressures. Comparison is made by means of a full CRM knowing and from Thomson scattering ( is shown). For the normalization with respect to , the gas temperature is taken from the present work.
Summary of transition quantities used in this study.
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