Publications associated with Plasma Theory

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

Physical Review A American Physical Society 101 (2020) 53431

LMR Hobbs, D Burridge, MP Hill, DJ Hoarty, CRD Brown, R Charles, G Cooper, SF James, LA Wilson, W Babbage, PW Hatfield, P Beiersdorfer, J Nilsen, H Scott, S Rose

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. 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 ± 16 18% 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.

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