X-ray spectroscopy to study energy transport of a low-Z, reduced mass target irradiated with a high-intensity laser pulse

Heat transport in reduced mass targets irradiated with a high-intensity laser pulse was studied. Kα lines from partially ionized chlorine embedded in the middle of a triple-layered plastic target were measured to evaluate bulk electron temperature in the tracer region inside the target. Two groups of Kα lines, one from Cl+–Cl6+ (hereby called “cold Kα”), and the other from Cl9+ and Cl10+ (“shifted Kα”) are observed from different regions within the target. Two-dimensional collisional particle-in-cell simulations show two distinct heating mechanisms occurring concurrently. These processes, which made the target temperature distribution non-uniform, are responsible for producing the two groups of Kα lines in the experiment. The blue shift of cold Kα lines in the experiment is the signature of higher temperatures achieved by the refluxing heating in smaller mass targets.