A comparative benchmarking of optical Thomson scattering and various X-ray emission spectroscopies in nanosecond laser-produced plasmas

Abstract

X-ray emission spectroscopy (XES) and optical Thomson scattering (OTS) are two of the most indispensable diagnostics for characterization of plasma parameters such as Te and ne in intense laser-produced plasmas (LPPs), but both can also provide weighted-average values owing to the line-of-sight, space, and time-integrated effects of optical/X-ray diagnostic techniques, which has not been thoroughly investigated. In this work, for the first time, the consistency and discrepancy between Te from XES and OTS are examined using intense lasers with a large focal spot to irradiate the smaller tip of a cylindrically symmetric titanium wire. Experimental results reveal that Te profiles derived from the two methods are approximately consistent in the earlier period of 1 ns, but exhibit different trends with increasing time. In addition, the impacts of the three integration effects on the interpretation of Te are assessed through an analysis of three types of XES methods, namely, time- and space-resolved, time-resolved but space-integrated, and time-integrated but space-resolved. Our findings indicate that the line-of-sight integration effect causes uncertainties of less than 5% in the electron temperature of corona LPPs, time-integrated XES can replace time-resolved measurements with an uncertainty of 10% for 1–2 ns laser duration, and space-integrated XES reflects the high-temperature region within 200 μm in front of the target surface, ∼10% lower than the maximum. These insights establish a foundation for the applications of experimental data in LPPs, particularly in the fields of laser-driven inertial confinement fusion and high-energy-density physics.