https://aurora.auburn.edu/handle/11200/44212 2026-04-18T14:00:50Z 2026-04-18T14:00:50Z https://aurora.auburn.edu/handle/11200/50690 2025-06-04T13:49:46Z

Data for: Comparison of neutral argon R-matrix calculations with experimentally determined apparent cross sections, and the importance of time-dependent metastables in the modeling of low temperature argon plasmas Neutral argon is an important element in a wide range of low temperature plasma applications. Calculations are presented here for the electron-impact excitation cross sections and Maxwellian rate coefficients for neutral argon using the Breit-Pauli R-matrix with PseudoStates (BPRMPS) method. The theoretical cross-section results are compared with experimental apparent cross-section measurements and theoretical data. Spectral modeling using the theoretical data in a collisional-radiative model is performed and compared with observations from the ALEXIS plasma device at Auburn University for wavelengths ranging from 725 nm to 845 nm. The importance is shown of diagnosing the neutral Ar metastable behavior for the plasma before performing any spectral analysis. For the ALEXIS plasma, a time-dependent model, accounting for non-steady-state metastables, produces good agreement with the observed spectral intensities and shows an expected trend with plasma pressure.

https://aurora.auburn.edu/handle/11200/50633 2024-07-01T15:06:02Z

Data for: Multi-delay coherence imaging spectroscopy optimized for ion temperature measurements in the divertor plasma of the Wendelstein 7-X stellarator A new coherence imaging spectroscopy (CIS) diagnostic optimized to measure the C2+ impurity ion temperature Ti spatial distribution in the divertor plasma of the W7-X stellarator is designed, tested, and validated. Using CIS to obtain Ti in the edge of magnetically confined plasmas has historically been challenging because Doppler broadening and Zeeman splitting have comparable effects on the shape of spectral emission lines. To distinguish between these two mechanisms, a novel approach to birefringent crystal design is employed to minimize the diagnostic’s sensitivity to Zeeman splitting. The recently developed pixelated multi-delay CIS approach is also used to obtain four times as much spectral information as traditional CIS approaches. The Ti-optimized CIS diagnostic is validated in a long-pulse W7-X plasma by comparison with a high-resolution spectrometer whose sightlines overlap with the CIS field of view. The CIS and spectrometer Ti profiles have the same shape and agree to within 10% on average and 25% in the worst case. Images of the Ti distribution near the divertor show toroidally elongated bands aligned with the magnetic field, with Ti ranging between 10 and 40 eV. This public data set contains openly documented, machine-readable digital research data corresponding to the figures in the associated article at https://doi.org/10.1063/5.0208586. The data for each figure is stored as a netCDF file. These netCDF files were created using the python package xarray version 2023.12.0. They can be easily read in python using the xarray "open_dataset" function, but are also readable with any software that supports netCDF4.

https://aurora.auburn.edu/handle/11200/50628 2024-01-24T09:30:12Z

Ar/TTIP dust cloud

https://aurora.auburn.edu/handle/11200/50536 2023-06-18T08:30:29Z

Ion acceleration inside foreshock transients Recent observations upstream of Earth's bow shock have revealed that foreshock transients can not only accelerate solar wind ions by reflection at their upstream boundaries but may also accelerate ions inside them. Evidence for the latter comes from comparisons of ion spectra inside and outside the cores, and from evidence of leakage of suprathermal ions from the cores. However, definite evidence for, and the physics of, ion acceleration in the foreshock transients are still open questions. Using case studies of foreshock transients from Time History of Events and Macroscale Interactions during Substorms observations, we reveal an ion acceleration mechanism in foreshock transients that is applicable to ~25% of the transients. The ion energy flux is enhanced between several keV to tens of keV in the cores. We show that these energetic ions are reflected at the earthward moving boundary of foreshock transients, are accelerated through partial gyration along the convection electric field, and can leak out both upstream and downstream of the foreshock transients. Using ions moving self-consistently with a generic 3-D global hybrid simulation of a foreshock transient, we confirm this physical picture of ion acceleration and leakage. These accelerated ions could be further accelerated at the local bow shock and repopulate the foreshock, increasing the efficacy of solar wind-magnetosphere interactions.