@inproceedings{2d8e5adf6de34aadb0dafb56ca9d89b8,
title = "Hydrodynamics and spatio-temporal mapping of oxide formation in laser-produced U plasmas",
abstract = "We combine optical emission spectroscopy with hydrodynamic measurements in laser-produced uranium plasma in air to detect formation of higher uranium oxide states. Generation of uranium oxides reduces the excited atomic uranium population.",
author = "Skrodzki, {P. J.} and M. Burger and I. Jovanovic and Phillips, {M. C.} and Harilal, {S. S.}",
note = "Funding Information: We investigated the plasma expansion in various inert and reactive environments. Figure 1(b) shows representative plasma images recorded in different ambient gases. The plume length along the laser axis as a function of time is shown in Fig. 1(c). Free expansion in low pressure is described by a linear model R ∝ t. For expansion in the presence of an ambient gas, we consider blast and drag models, R ∝ t0.4 and R ∝ (1 − e−βt), respectively. The blast model describes early-time propagation in nitrogen and argon; in both cases, the plume expands with the shockwave. The drag model describes late-time expansion in which collisions between plasma and ambient species cause plume deceleration. The deviation from the blast model at early times and greater plume deceleration in air gives evidence for chemical processes between U from the LPP and oxygen from the environment. In further experiments, we systematically varied the oxygen pressure and found that atomic U persistence decreases monotonically with increasing oxygen partial pressure, while UO persistence peaks at a given concentration (Fig. 2). Simultaneously, in Fig. 2(b), the prominence of the higher U oxide band between 320 and 380 nm which we identified in recent work [5] increases with oxygen concentration. These results imply low oxygen concentrations foster the formation of UO from atomic U, while higher oxygen concentrations deplete both U and UO to form higher U oxides. In summary, our results show that plasma chemistry modifies the hydrodynamics of the plume at later times in its evolution. Moreover, the spatio-temporal mapping technique described in this work is a versatile tool for tacking molecular formation in a transient plasma. Funding & Acknowledgements National Science Foundation Graduate Research Fellowships Program (DGE 1256260); Department of Energy National Nuclear Security Administration, Consortium for Verification Technology (DE-NA0002534); Office of Defense Nuclear Nonproliferation (NA 22); Pacific Northwest National Laboratory (PNNL) is operated for the U.S. DOE by the Battelle Memorial Institute (DE-AC05-76RLO1830); PNNL Radiological Services Department. References 1. S. S. Harilal et al., Appl. Phys. Rev., 5, 021301 (2018). 2. M. S. Finko et al., J. Phys. D 50, 485201 (2017). 3. K. C. Hartig et al., Opt. Express 10, 11477–11490 (2017). 4. S. S. Harilal et al., Opt. Express 16, 20319–20330 (2018). 5. P. J. Skrodzki et al., Opt. Lett. 43, 5118–5121 (2018). Publisher Copyright: {\textcopyright} 2019 The Author(s); CLEO: Science and Innovations, CLEO_SI 2019 ; Conference date: 05-05-2019 Through 10-05-2019",
year = "2019",
doi = "10.1364/CLEO_SI.2019.SW4L.5",
language = "English (US)",
isbn = "9781943580576",
series = "Optics InfoBase Conference Papers",
publisher = "Optica Publishing Group (formerly OSA)",
booktitle = "CLEO",
}