Spectroscopic diagnostics on JET (invited)

Abstract

The present spectroscopic diagnostics on Joint European Torus (JET) consist of bolometry, fiber- and close-coupled visible spectroscopy (200–700 nm), as well as survey (10–170 nm) and spatial scan VUV spectroscopy (10–250 nm). Visible bremsstrahlung is used routinely for Zeff measurements. Hydrogen and impurity influxes from walls, limiters, and rf antennas are derived from visible spectral lines. Visible charge-exchange spectroscopy, utilizing part of the JET heating beams, yields ion temperatures, rotation velocities, and impurity concentrations in the plasma. VUV spectroscopy is employed for measuring the impurity content in the bulk plasma using an impurity transport code. Spatial scan spectrometers allow verification of the transport models by means of recorded emission shells. A 20-m-high resolution crystal spectrometer yields ion temperatures and rotation velocities from the He- and H-like resonance lines, as well as other plasma parameters. A pulse-height analysis system covers the energy range of metal and Cl-K lines and can be used for electron temperature measurements. In the near future XUV (0.7–35 nm) and double-crystal spectrometers (0.1–2 nm), one of them providing a spatial scan, will be available, enabling studies of H- and He-like light impurities, as well as Ne-, He-, and H-like metals. Bolometry, visible spectroscopy, and two crystal instruments will be the only diagnostics left during the JET active phase. By then, models and methods must have been established for assessing the behavior of the important impurities C, O (,Be), and Ni with these diagnostics.