Charge-exchange spectroscopy is a powerful diagnostic tool for determining ion temperatures, densities and rotational velocities in tokamak plasmas. This technique depends on detailed understanding ...of the atomic physics processes that affect the measured apparent velocities with respect to the true ion rotational velocities. These atomic effects are mainly due to energy dependence of the charge-exchange cross-sections, and in the case of poloidal velocities, due to gyro-motion of the ion during the finite lifetime of the excited states. Accurate lifetimes are necessary for correct interpretation of measured poloidal velocities, specially for high density plasma regimes on machines such as ITER, where l-mixing effects must be taken into account. In this work, a full nl-resolved atomic collisional radiative model coupled with a full kinetic calculation that includes the effects of electric and magnetic fields on the ion gyro-motion is presented for the first time. The model directly calculates from atomic physics first principles the excited state lifetimes that are necessary to evaluate the gyro-orbit effects. It is shown that even for low density plasmas where l-mixing effects are unimportant and coronal conditions can be assumed, the nl-resolved model is necessary for an accurate description of the gyro-motion effects to determine poloidal velocities. This solution shows good agreement when compared to three QH-mode shots on DIII-D, which contain a wide range of toroidal velocities and high ion temperatures where greater atomic corrections are needed. The velocities obtained from the model are compared to experimental velocities determined from co- and counter-injection of neutral beams on DIII-D.
The spectra from singly ionized argon Ar II has significant diagnostic capability in the characterization and modelling of both magnetically-confined fusion and astrophysical plasmas. The literature ...has several pre-existing data sets for Ar+ but this paper presents the results from 3 new atomic structure and electron-impact scattering models in order to better constrain the differences in atomic data and how they impact well-known plasma diagnostics. Several independent atomic structure methodologies are employed to calculate the energy levels and transition probabilities for each model. The first approach employs a relativistic Dirac–Coulomb Hamiltonian model, the second approach uses a semi-relativistic Breit–Pauli Hamiltonian with the mass-velocity, Darwin and spin–orbit corrections, and in a third case an ICFT approach. Three atomic structure models provide a foundation for Dirac R-matrix, a semi-relativistic ICFT (Intermediate Coupling Frame Transformation) and a Breit–Pauli R-Matrix with Pseudostates (BPRMPS) calculation. Synthetic spectra utilizing these three data sets are compared against measurements taken at the Compact Toroidal Hybrid (CTH) stellarator, and the total radiative power loss is also benchmarked against previous calculations.
•Present Atomic Structure and Transition probabilities for 3 independent Ar II structure calculations.•Demonstrated convergence between 3 Separate R-Matrix methods (PDARC. BPRMPS and ICFT) for electron-impact excitation.•Resolved deviations in total power loss calculations of CR-Modelling of different collisional calculations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Recombination involving the core excitation of two electrons, which may be termed trielectronic recombination, has been experimentally identified for the first time. Using Cl13+ ions circulating in ...the TSR heavy-ion storage ring, we have observed surprisingly strong low-energy trielectronic recombination resonances, comparable to the dielectronic process. At higher electron-ion collision energies, trielectronic recombination is suppressed due to the autoionization of the triply excited intermediate state into excited final states. The formation of the intermediate state depends sensitively on configuration mixing, making trielectronic recombination a challenge to atomic-structure calculations.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Aims. Merged-beam and plasma recombination rate coefficients for Be-like $\ion{Ne}{vii}$ were extracted from results of a merged-beam type experiment. Methods. The cryring heavy-ion storage ring was ...used to determine merged-beam recombination rate coefficients for Be-like $\mathrm{Ne^{6+}}$. Recombined $\mathrm{Ne^{5+}}$ ions were separated from the stored beam in the first dipole magnet following the electron-ion interaction region. Field-ionization at this dipole magnet prevented detection of recombination into states with the principal quantum number $n>n_{\mathrm{cutoff}}=23$. To account for the field-ionization effects, results obtained with autostructure calculations were used for recombination channels above $n_{\mathrm{cutoff}}$. The merged-beam recombination rate coefficients were then convoluted with Maxwellian electron energy distributions in the $10^{3}{-}3\times10^{6}$ K temperature region, to obtain plasma recombination rate coefficients. Results. Good agreement was found between the experimentally derived rate coefficient spectrum and results of the autostructure calculation. At low energies, several strong dielectronic recombination resonances belonging to the spin-forbidden ${\rm 2s2p}(^{3}\mathrm{P}_{\mathrm{J}})nl$ series dominate the merged-beam spectrum. Recombination through these states dominates at low-temperatures, e.g. at 103 K recombination through these resonances is more than one order of magnitude higher than the radiative recombination rate coefficient. Most data from the literature significantly underestimate the low-temperature plasma rate coefficients below 104 K, with only two calculations showing rate coefficients comparable to our results. Strong contributions from trielectronic recombination were found in the merged-beam spectrum of Be-like Ne, associated with double excitation of the Be-like Ne core, during the attachment of the free electron. Calculated trielectronic recombination resonance positions agree with experimental peaks, however compared to the experiment, the calculation underestimates the strength of trielectronic recombination.
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ColRadPy: A Python collisional radiative solver Johnson, C.A.; Loch, S.D.; Ennis, D.A.
Nuclear materials and energy,
August 2019, 2019-08-00, 2019-08-01, Volume:
20, Issue:
C
Journal Article
Peer reviewed
Open access
•A new python code (ColRadPy) solves collisional radiative & ionization balance equations.•Application of ColRadPy to fusion relevant neutral molybdenum.•Many metastable states are often required to ...accurately model heavy species.•A new method to identify the most important metastable is described.
The properties of emitting ions in a plasma provides both potential for plasma diagnostics and key information required for plasma modeling. Generalized collisional radiative theory provides a powerful tool for the modeling of low and moderately dense plasmas. A new Python program is presented that solves the collisional radiative and ionization balance equations for application to fusion, laboratory, and astrophysical plasmas. It produces generalized coefficients that can be easily imported into existing plasma modeling codes and spectral diagnostics. An overview of the code is presented, along with selected results for applications to high-Z plasma facing components.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Electron-impact Ionization of C+ and C3 Pindzola, M S; Ballance, C P; Loch, S D
Journal of physics. Conference series,
11/2012, Volume:
388, Issue:
6
Journal Article, Conference Proceeding
Peer reviewed
Open access
Non-perturbative close-coupling and perturbative distorted-wave methods are used to calculate electron-impact ionization cross sections for the excited states of C+ and C3+.
A first stage collision database is assembled which contains electron-impact excitation, ionization, and recombination rate coefficients for B, B+, B2+, B3+, and B4+. The first stage database is ...constructed using the R-matrix with pseudostates, time-dependent close-coupling, and perturbative distorted-wave methods. A second stage collision database is then assembled which contains generalized collisional-radiative ionization, recombination, and power loss rate coefficients as a function of both temperature and density. The second stage database is constructed by solution of the collisional-radiative equations in the quasi-static equilibrium approximation using the first stage database. Both collision database stages reside in electronic form at the IAEA Labeled Atomic Data Interface (ALADDIN) database and the Atomic Data Analysis Structure (ADAS) open database.
Recombination through doubly excited states that can be formed only through spin-flip of the excited electrons can give very strong contributions to the recombination rate of Be-like ions. We ...demonstrate this, in this paper, with the electron-ion recombination spectra of Be-like Ne(6+) and Be-like Si(10+), recently measured at the CRYRING storage ring. These resonances have significant effects on the plasma rate coefficients. We show that neglect or imprecise calculation of these resonances is responsible for large spreads observed between various theoretical results from the literature.
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