X-ray-line coincidence photopumping in a potassium-chlorine mixed plasma

• Published in: Physical review. A 2020-05, Vol.101 (5), Article 053431
• Main Authors: Hobbs, L. M. R., Burridge, D., Hill, M. P., Hoarty, D. J., Brown, C. R. D., Charles, R., Cooper, G., James, S. F., Wilson, L. A., Babbage, W., Hatfield, P. W., Beiersdorfer, P., Nilsen, J., Scott, H., Rose, S. J.
• Format: Article
• Language: English
• Subjects: ATOMIC AND MOLECULAR PHYSICS; Atomic spectra; dark matter; x-ray astronomy; x-ray generation in plasmas
• ISSN: 2469-9926; 2469-9934
• DOI: 10.1103/PhysRevA.101.053431

Exploiting the multiple long pulse capability and suite of x-ray diagnostics of the Orion laser, we have set out to explore line coincidence photopuming—the enhancement in population of an atomic level brought on by resonant absorption of x rays from a different emitting ion. Unlike previous work, the two ions are in the same plasma and so the experiment is an x-ray analog of the well-known Bowen resonance fluorescence mechanism that operates in astrophysical situations in the optical region. Herein, our measurements have shown enhanced fluorescence in a chlorine plasma, attributable to line coincident photopumping from co-mixed potassium ions. To detect this relatively low signal-to-noise phenomenon, the data from multiple shots are combined, and the statistical method of bootstrapping is used to assign a confidence value to the measured enhancement, resulting in an estimate of the enhancement of 39±1816% compared to the null case, where no pumping occurs. The experimental results have been compared to coupled radiation-transport and radiation hydrodynamics simulations using the CRETIN code together with the NYM radiation hydrodynamics model and agreement has been found, with the simulations also predicting modest enhancement.