Electron temperature and soft x-ray intensity scaling in laser heavy element plasma interaction

Hiromu Kawasaki,Yuta Shimada,Takeshi Higashiguchi,Takeo Ejima,Weihua Jiang,Masaharu Nishikino,Gerry O’Sullivan,Shinichi Namba,Atsushi Sunahara

doi:10.1063/5.0009946

Abstract

We achieved a relative optically thin state in laser-produced heavy element plasmas at determined electron temperatures, which has been predicted by power balance and collisional-radiative models. We also mapped the power-loss processes in sub-nanosecond and nanosecond laser-produced high-Z plasmas. The electron temperature evaluation was in good agreement with the power balance model and was supported by the spectral analysis. The output flux in the soft x-ray region was stronger at a higher critical density.

Highlights

√ scaling is typically given by Te ∝ ILλ2L, where IL and λL are the laser intensity and the laser wavelength, respectively.18 As an example, the electron temperature, Te, has been shown to depend on the laser intensity as IL0.57 for a 2-ns, KrF laser-produced plasma.19 The laser intensity dependence of the electron temperature, is weaker due to the radiative energy loss flow for high-Z elements than for low-Z elements
We focus on the evaluation of electron temperature as a function of various laser parameters with dominant energy loss mapping in high-Z laser-produced plasmas
As the laser pulse propagates in the plasma, laser absorption is induced near the surface of the target, and the hot, dense plasma expands into the vacuum

Summary

Introduction

√ scaling is typically given by Te ∝ ILλ2L, where IL and λL are the laser intensity and the laser wavelength, respectively.18 As an example, the electron temperature, Te, has been shown to depend on the laser intensity as IL0.57 for a 2-ns, KrF laser-produced plasma.19 The laser intensity dependence of the electron temperature, is weaker due to the radiative energy loss flow for high-Z elements than for low-Z elements. It is important to understand the energy flow, related to radiation transportation, by highly charged ions (HCIs) in heavy element (high-Z) plasmas.14 In addition, it is important to optimize electron temperature, related to laser intensity (laser power density), for efficient shorter wavelength light sources.

Results

Conclusion