Calculations and analysis of cross sections required for argon charge exchange recombination spectroscopy

Abstract

A large set of calculations has been carried out providing a basis for diagnostics of fusion plasmas through emission resulting from radiative de-excitation following charge transfer between hydrogen and highly charged argon ions, so-called argon charge exchange recombination spectroscopy. These results have been obtained using the classical trajectory Monte Carlo (CTMC) method to treat charge transfer to states with principal quantum numbers up to 30 or more. Nine collision energies between 13.3333 and 250 keV/u pertinent to neutral beam injection have been considered for Ar q+ (q = 15-18) colliding with atomic hydrogen in both the ground and metastable states. Atomic orbital close coupling calculations have also been undertaken in order to provide a fully quantum mechanical test of the CTMC results for Ar 18+ + H(1s) collisions. The results of the calculations are discussed here and the full set of data is made available through a web posting.

Atomic-orbital close-coupling calculations for collisions involving fusion relevant highly charged impurity ions using very large basis sets

“…In fig.1, we compare n-resolved cross sections of Ar 18+ + H(1s) from our AOCC calculations to classical trajectory Monte Carlo (CTMC) calculations from Schultz et al [9]. We used a basis including basis states for complete n-shells on the Argon center for 5 ≤ n ≤ 15, leading to 660 bound Laguerre type states.…”

“…We used a basis including basis states for complete n-shells on the Argon center for 5 ≤ n ≤ 15, leading to 660 bound Laguerre type states. On the hydrogen center ) and CTMC ( ) [9] of n-resolved charge exchange cross sections for Ar 18+ + H(1s) collisions. The left plot shows total CX cross sections as well as cross sections for capture into subshells 5 ≤ n ≤ 9 where the agreement is excellent.…”

Jovian Auroral Ion Precipitation: X‐Ray Production From Oxygen and Sulfur Precipitation

“…In general, energy levels reached by excitation of the projectile ion will be predominantly to lower levels than those from charge transfer. Charge transfer proceeds to states with principal quantum number n peaked at q (Grozdanov & Janev, ; Olson, ), with a distribution below and above this, falling off at high quantum number as 1/n (Oppenheimer, ; Schultz et al, ). In contrast, excitation proceeds dominantly to the next highest n level and rapidly falls off for higher n. (Note: Another consideration is forbidden excitation transitions for each charge state; however, that requires a much more in‐depth study of the situation beyond the scope of the research presented here.)…”

Atomic data for beam-stimulated plasma spectroscopy in fusion plasmas

“…The partial CX cross sections σ nl signi¿cantly vary for different calculations, and experimental cross sections for such H-like impurities are still very rare. Indeed, the nl-resolved cross sections differ by an order of magnitude and the total CX cross section deviates by a factor of two among different calculations [7,8,9]. In addition to this, CR models are to be extended to high n without assumption of statistical redistribution for Δn = 0.…”

“…The details of calculations could be found in [10,13]. The nl-resolved CX cross-sections were taken from [7,8]. Figure 2 shows the calculated effective rate coef¿cients for H-like argon [10,11,12,13].…”