Impurities in tokamaks

Abstract

Impurities continue to be a concern for future fusion devices, and ongoing efforts are made to study their generation, confinement, and control. Techniques for analysis of concentrations, power losses, and confinement of impurities are surveyed, and experimental examples illustrating typical observations in tokamak plasmas are presented. The use of impurities for diagnosing plasma properties is outlined briefly.

Vacuum Ultraviolet Spectroscopy at TEXTOR

“…[3][4][5] The most fundamental experimental access to identify impurity species is the measurement of their characteristic line radiation by spectroscopy. 6,7 Under the plasma conditions typical for magnetic fusion experiments, the strongest spectral lines of most of the relevant impurity ions are located in the vacuum ultraviolet~VUV! wavelength range~10 to 200 nm!, which can dominate the total radiation power losses of the plasma.…”

Observations of centrally peaked impurity profiles following pellet injection in the Alcator-C tokamak

“…Thus the measured values are of the order of the neoclassical predictions. Typically most tokamaks 4 , including Alcator for non-pellet discharges 5 , have reported that impurity diffusivities are one to two orders of magnitude larger than the neoclassical prediction.…”

“…The transport of impurities, and the ensuing implications for current profiles and sawtooth dynamics, are crucial issues for tokamak physics'- 4 and future reactor designs.…”

High efficiency extreme ultraviolet overview spectrometer: Construction and laboratory testing

“…The monitoring of plasma impurities in magnetically confined fusion plasmas is frequently performed using broadband spectrometers in the vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) wavelength range [1][2][3][4][5] . However, over the past decades only a limited number of spectrometer concepts have been developed and applied for the diagnostics of magnetic fusion plasmas.…”