Measurement of preheating due to radiation and nonlocal electron heat transport in laser-irradiated targets

Abstract

This paper reports an experimental study on preheating of laser-irradiated targets. We performed temperature measurements at the rear surface of laser-irradiated targets under conditions of two different laser wavelengths ͑0.35 or 0.53 m͒ and several intensities ͑2 ϫ 10 13 -1ϫ 10 14 W / cm 2 ͒ in order to verify an effect of radiation and nonlocal electron heat transport. The preheating temperature was evaluated by observing self-emission, reflectivity, and expansion velocity at the rear surface of planar polyimide foils. The experimental results show that the x-ray radiation is dominant for preheating for 0.35-m laser irradiation, but contribution of nonlocal electron heat transport is not negligible for 0.53-m laser irradiation conditions.

Measurements of Preformed Plasma Generation and Its Suppression Inside a Cone in a Cone-in-Shell Target for Fast Ignition

“…In typical VISAR measurements, velocity data at a reflecting surface are extracted along with associated fringe shifts. However, in this measurement, the fringe rapidly vanished when the cone tip surface was heated beyond the ionizing temper- ature, which was observed in previous experiments [12]. Ultimately, as per the VISAR, an estimate of preformed plasma generation levels was rendered with the intensity of reflected light at the central portion of the cone tip.…”

Effect of preheating on the nonlinear evolution of the ablative Rayleigh-Taylor instability

“…[2,3], and the preheated region in front of the temperature gradient of the heat-wave front is often spatially extended. The heat transport process involved in the region is rather complex and several models have been introduced [2, 3,13,14].…”

“…Generation of higher harmonics in the region of interest and their interactions shall be investigated. An unstable initial (the fundamental) single mode perturbation with wave number k 1 = 2π/λ 1 can excite harmonic modes with wave numbers k n = nk 1 , where n = 2, 3, ... [2,3,14]. The total surface displacement of the interface can thus be expressed as ξ(y, t) = n ξ n (y, t) cos(k n y).…”

Study of the Performance of a Streaked Optical Pyrometer System for Temperature Measurement of Shocked Materials

“…for Temperature Measurement of Shocked Materials * ZHANG Chen ( ) 1 , LIU Hao ( ) 2 , WANG Zhebin ( ) 2 , JIANG Xiaohua ( ) 2 , ZHANG Huige ( ) 2 , LIU Yonggang ( ) 2 , LI Zhichao ( ) 2 , LI Sanwei ( ) 2 , YANG Dong ( ) 2 , DING Yongkun ( ) 2 , ZHAO Bin ( ) 1 , HU Guangyue ( ) 1 , ZHENG Jian ( ) 1 1 Introduction…”

“…In order to achieve an extreme pressure, intense laser pulses or radiation fluxes are irradiated onto a sample to launch a strong shock. Usually, people are just interested in the density and pressure of the shocked material that can be inferred from the shock speed and the shocked fluid velocity in combination with the conservation laws of hydrodynamics, and pay a lot of attention to the Hugoniot relation [1,2] . In recent years, the temperature of a sample before and after shock has attracted more and more attention because the sample could be preheated with hard X-rays or hot electrons and its state can remarkably vary before being shocked.…”