Penetration depths of injected/sputtered tungsten in the plasma edge layer of TEXTOR

Abstract

To quantify tungsten (W) sputtering measurements by spectroscopy , two experiments have been carried out in the tokamak TEXTOR. The erosion of a W limiter in the plasma edge was studied spectrocopically under different plasma conditions. Conversion of the photon fluxes of neutral W lines was performed [1] with the aid of inverse photon efficiencies, measured in situ in a second experiment with WF 6 injection to realise a controllable W source. Penetration depths, particle velocities and line ratios of W I were determined and compared between the two sources of W. The velocities of injected and sputtered W differ by a factor of 3 as the analysis of the penetration depth shows, while the line ratios for different W I lines are comparable. A comparison of the e-folding length with the model code GKU was performed which reveals a deviation of at least a factor of 6. Inverse photon efficiencies at T e = 40 eV were determined to be about 44 for W I (400.88 nm) and about 63 for W I (429.46 nm).