Toward electron temperature profiles in hot-dense plasmas from x-ray spectral ensembles

• Published in: Physics of plasmas 2024-11, Vol.31 (11)
• Main Authors: Kraus, B. F., McPoyle, S. P., Atay, K., Kriz, E., Hollinger, R. C., Benjamin, S. N., Malko, S., Hill, K. W., Gao, Lan, Efthimion, P. C., Wang, Shoujun, King, J., Zahedpour Anaraki, S., Shlyaptsev, V. N., Rocca, J. J.
• Format: Article
• Language: English
• Subjects: Dense plasmas; Electron energy; Embedded systems; High power lasers; Laser beam heating; Lasers; Metal foils; Plasma diagnostics; Repetition; Temperature profiles; X ray spectra; X ray spectrometers
• ISSN: 1070-664X; 1089-7674
• DOI: 10.1063/5.0214771

High repetition rate laser systems enable new strategies for diagnosing plasma behavior with large datasets. Here, we define an ensemble technique that relies on randomized targeting of x-ray tracer micro-stripes. On each shot, a high-intensity laser pulse is focused on a solid target with Ti tracer stripes embedded in an Al foil, randomly targeting a micro-stripe, a portion of a stripe, or a gap between stripes. High-resolution, time-integrated x-ray spectrometers capture line emission from the portion of the micro-stripe that is heated to sufficiently high electron temperatures. Accumulation of many such cases is used to construct ensemble distributions of x-ray line intensities that encompass all relative offsets of the laser focus to the micro-stripe centers. Synthetic intensity distributions are likewise generated using collisional-radiative modeling. Bayesian fitting of modeled to measured intensity distributions establishes the most likely radial temperature profiles, enabling comparison to hydrodynamic models and calling into question the cylindrical symmetry of these micro-stripe-embedded systems. Ensemble techniques have significant potential for high-energy-density plasma diagnostics, especially with the advent of high repetition rate experiments.