MLM polychromator monitoring soft-x-ray spectral line emissions of C, O, and Fe used in transport studies of the Phaedrus-T tokamak plasma during ohmic, rf-heated, and H-mode discharges

Abstract

The MLM (multilayer mirror) polychromator has two modes of operation. In the first mode, it simultaneously monitors the Ly α and β emissions of H-like O at 19.0 and 16.0 Å, respectively, the Ly α emission of C at 33.7 Å, and the singlet and triplet transitions of He-like C at 40.5 Å. In the second mode, it simultaneously monitors the Ly α and β emissions of H-like C at 33.7 and 28.5 Å, respectively, as well as the 15.6 and 93.9 Å emissions of F-like Fe. The MLM polychromator has a wavelength resolution that varies from 0.3 Å at 16.0 Å to 2 Å at 40.5 Å and 7 Å at 93.9 Å. It was mounted on the midplane of the Phaedrus-T tokamak with its line of sight along the major radius. On a shot by shot basis, the MLM polychromator, with a temporal resolution of 1 ms and a spatial resolution of 1 cm, scanned the plasma in the z direction ±15 cm from the toroidal magnetic axis. Vertical asymmetries in the soft x-ray spectral line brightness profiles were measured and found to depend on the direction of BT. The brightness profiles were inverted and modeled with a poloidally asymmetric Gaussian emissivity profile. The measured results were compared with the predicted emissivity profiles to determine the transport of carbon.