X-ray and VUV observations of brightness profiles from Alcator C-Mod plasmas

Abstract

Brightness profiles of x-ray and VUV lines from eight molybdenum charge states between Mo 23+ and Mo 33+ have been measured in Alcator C-Mod plasmas. These spatial profiles agree very well with those predicted by a model which includes ionization, recombination, excitation and transport. Comparison with the profiles of many different charge states provides severe constraints upon the rates used in the model. The charge state density profiles are calculated using measured impurity transport coefficients, measured electron density and temperature profiles and newly calculated ionization and recombination rate coefficients. These new rate coefficients include direct collisional ionization, excitation-autoionization, dielectronic and radiative recombination. Excitation-autoionization is shown to be an important process, since the excellent agreement between the measurements and predictions is obtained only with its inclusion. Fits to newly calculated excitation rate coefficients for the transitions are also presented.

X-ray observations of 2l-nl' transitions and configuration-interaction effects from Kr, Mo, Nb and Zr in near neon-like charge states from tokamak plasmas

“…Shown in Fig.10 have been studied extensively in molybdenum [8,22]. Also shown in Fig.10 is a synthetic spectrum, which is in good agreement with the observations, although there is a ∼ −10 mÅ shift of the calculated wavelength for the magnesiumlike 2p − − 4d − transition at 5436.6 mÅ.…”

“…The identifications of many x-ray lines from neonlike ions allow high resolution experimental data to be used for benchmarking multi-electron atomic structure calculations [17][18][19][20][21][7][8][9]. Collisional radiative modeling of line intensities from neon-, fluorine-, sodium-and magnesiumlike ionization states has demonstrated the importance of excitation-autoionization in overall charge state balance in tokamak plasmas [22]. Rates for this process, in conjunction with the latest dielectronic recombination rates [23], have led to a reassessment of the importance of molybdenum radiation in energy balance [24] in tokamak plasmas.…”

Molybdenum sources and transport in Alcator C-Mod

“…Multiplication of the influx by source area gives the total source flux, Γ Mo . The core Mo content is determined from the brightness of a Mo 33+ line at 3.740 Angstroms and modelling using the core n e and T e profiles [21].…”

A study of molybdenum influxes and transport in Alcator C-Mod

“…Thus one only needs the plasma volume (~1.0 m 3 ) to determine the total core Mo content, N Mo . More details of this method are found elsewhere [29].…”