Using a Tokamak to Study Atomic Physics: Brightness Ratios of Transitions Within the n=2 Levels of Be I-like Ions (C III to Cr XXI)

Abstract

Although the primary motivation for constructing devices which produce magnetically confined high-temperature plasmas is controlled thermonuclear fusion, these devices can also be used to study the physics of highly ionized atoms. This paper reviews an example of such a study in which the n=2 to n=2 transition lines in the Be I isoelectronic sequence were measured with photometrically calibrated extreme ultraviolet instrumentation. The brightness ratios of the 2s2p ³P-2p^{2 3}P (R) and the 2s^{2 1}S₀-2s2p ³P₁(R*) lines to the resonance 2s^{2 1}S₀-2s2p ¹P₁line were determined and compared with theoretical predictions. At low nuclear charge, Z, the experimental values agree with those computed by the R-matrix method which includes the effect of resonances. At higher Z, the data agrees very well with calculations based on the distorted wave approximation. In addition to confirming the theoretical methods, this agreement lends confidence to the use of line ratios for diagnostic studies of high-temperature plasmas.