Benchmark of collisional-radiative models for ITER beams at Alcator C-Mod tokamak
I. O. Bespamyatnov, W. L. Rowan, K. T. Liao, O. Marchuk, Yuri Ralchenko, R. S.
The beam-based plasma diagnostics on ITER require high accuracy and reliability which accordingly puts challenging requirements on the collisional-radiative (CR) models used for the description of excited states of high energy beam atoms. These states are known to play an essential role in the implementation and interpretation of neutral beam based diagnostics, such as motional Stark effect (MSE), charge-exchange recombination spectroscopy (CXRS), beam-emission spectroscopy (BES), and in the dynamics of beam penetration. Latest analyses demonstrate that the widely used assumption of statistical populations among the beam excited (sub-) states is questionable for high beam energies and high magnetic fields. Here we report an empirical verification of the recently developed non-statistical nkm-resolved CR model (Marchuk O. et al 2010 J. Phys. B. 43 011002) in Alcator C-Mod and the short extrapolation to the relevant parameter range for ITER. The experiment was performed on Alcator C-Mod tokamak, which operates in a unique range of parameters well suited for testing CR models for ITER beams. Beam emission spectra are collected for a selected range of plasma parameters. The line ratios 1/0, 4/3 and / are measured and compared to the n-resolved statistical population model and the new non-statistical nkm-resolved CR model. The measured ratios show clear deviations from the statistical model and a good agreement with the non-statistical results. The measured difference between experimental and nkm-resolved simulations for the most part is within 10% for all three line ratios. The largest deviation here is for the 1/0 ratio that reaches up to 15% for the lowest electron density of 0.6×1020 m-3. In contrast, the difference between experimental and n-resolved (statistical) model is within 10-26% for 50 keV/amu Alcator C-Mod beam and expected to be up to 30% for 100 keV/amu and up to 40% for 500 keV/amu ITER beams. The discussed effect must be taken into the account
, Rowan, W.
, Liao, K.
, Marchuk, O.
, Ralchenko, Y.
and S., R.
Benchmark of collisional-radiative models for ITER beams at Alcator C-Mod tokamak, Plasma Physics and Controlled Fusion, [online], https://doi.org/10.1088/0029-5515/53/12/123010
(Accessed December 3, 2023)