Reconstruction of plasma edge density profiles from Li I (2s-2p) emission profiles

Abstract

The injection of 10-100 keV Lio diagnostic beams into magnetically confined fusion plasmas causes collisionally induced Lil emission at 670.8 nm, in close relation to the edge plasma electron dcnsity. A numcrical method Cor quantitative reConstruction of the plasma density exclusively from rclaliw Lil 670.8 nm emission profilcs as measured slang the diagnostic beam has been developed, involving all relevant collisional interactions of the Li atoms with plasma constituents. The applicahility of the descrihed algorithm is illustrated by experimental results obtained for the TEXTOR Tokamak edge plasma at KFA Jirlich.

Deconvolution-based correction of alkali beam emission spectroscopy density profile measurements

“…The de-convolution method gives a good estimate of the emissivity on the beam axis from the measured light profile, so that the level of the remaining error due to the observation is in the order of the accuracy of the density profile reconstruction algorithm (in our case the Absolut code [6]). The method allows the use of the one dimensional density calculation methods even for the configurations where the finite width of the beam is not negligible.…”

“…The collisional j → i de-excitation rate coefficients are derived from the corresponding i → j excitation rate coefficients using the principle of detailed balance, while impurity collision rate coefficients are calculated from the proton collisional cross sections using the scaling relations given in [4,15]. The proton impact target electron loss processes are considered instead of treating the ionization and charge exchange channels separately, which is the main difference of the atomic physics kernel from the Absolut [6] inverse problem solver regarding the atomic physics.…”

“…The Absolute code in turn has been critically tested against both Li [6] and Na [5] measurements. In this manner, RENATE is indirectly validated to measurements; the direct validation is under way at the TEXTOR tokamak.…”

“…3c-d, where the corresponding density profiles are plotted together with the differences from the density profile used as input to the light profile calculations (original, dash-dotted line). The density profiles are calculated by the Absolut code [6].…”

“…1 study [6]. All these methods are based on the assumption that the measured light profile is equivalent to the emissivity of the beam.…”