Update on Light-Ion Calculations

During the time span of the CRP, calculations were (1) initiated extending previous work regarding elastic and transport cross sections relevant to light-species impurity-ion transport modeling, (2) completed for total and state-selective charge transfer (C5+, N6+, O6+, O7+ + H; C5+, C6+, O7+, O8+ + He; and C6+ + H, H2) for diagnostics such as charge exchange recombination spectroscopy, and (3) completed for excitation of atomic hydrogen by ion impact (H+, He2+, Be4+, C6+) for diagnostics including beam emission spectroscopy and motional Stark effect spectroscopy. The first calculations undertaken were to continue work begun more than a decade ago providing plasma modelers with elastic total and differential cross sections, and related transport cross sections, used to model transport of hydrogen ions, atoms, and molecules as well as other species including intrinsic and extrinsic impurities. This body of work was reviewed in the course of reporting recent new calculations in a recent paper (P.S. Krstic and D.R. Schultz, Physics of Plasmas, 16, 053503 (2009)). After initial calculations for H+ + O were completed, work was discontinued in light of other priorities. Charge transfer data for diagnostics provide important knowledge about the state of the plasma from the edge to the core and are therefore of significant interest to continually evaluate and improve. Further motivation for such calculations comes from recent and ongoing benchmark measurements of the total charge transfer cross section being made at Oak Ridge National Laboratory by C.C. Havener and collaborators. We have undertaken calculations using a variety of theoretical approaches, each applicable within a range of impact energies, that have led to the creation of a database of recommended state-selective and total cross sections composed of results from the various methods (MOCC, AOCC, CTMC, results from the literature) within their overlapping ranges of applicability. Results for all systems enumerated in item (2) above are complete and the following papers reporting them have been published so far: Y. Wu et al., ''Theoretical investigation of charge transfer between N6+ and atomic hydrogen,'' Phys. Rev. A 84, 022711 (2011); Y. Wu et al., ''Theoretical investigation of total and state-dependent charge exchange in O6+ collisions with atomic hydrogen,'' J. Phys. B 45, 235201 (2012); and J.L. Nolte et al., ''Final-state resolved charge exchange in C5+ collisions with H,''J. Phys. B 45, 245202 (2012); with the rest in preparation. Other important diagnostics depending on a large database of atomic physics are those based on the motional Stark effect and beam emission spectroscopy. In collaboration with Y. Ralchenko and O. Marchuk, we have computed the cross sections and density matrix elements for a large number of impact energies to follow their variation as input to a collisional-radiative model for protons, injected or fusion alphas, Be4+, and C6+ exciting atomic hydrogen. Results have been published for proton-impact (O. Marchuk et al., ''Non-statistical population distributions for hydrogen beams in fusion plasmas,'' Plasma Phys. Control. Fusion 54, 095011 (2012)) showing, for example, the importance of consideration of non-statistical populations in interpreting these diagnostics. Work to complete the collisional-radiative models and perform simulations of relevant plasmas (such as those for ITER) is underway for the higher charged ions. (author)