Radiation model of a xenon flash lamp in a laser amplifier pump cavity

Yongzhong Wu,Jianqiang Zhu,Zhixiang Zhang,Yangshuai Li

doi:10.1017/hpl.2015.34

Abstract

Understanding the radiation model of a flash lamp is essential for the reflector design of a laser amplifier. Reflector design often involves several simplifying assumptions, like a point or Lambertian source; either of these assumptions may lead to significant errors in the output distribution. In practice, source non-idealities usually result in sacrificing the amplifier’s gain coefficient. We propose a novel test technique for attaining the xenon flash lamp absolute spectral intensity at various angles of view, and then accurately predict radiation distributions and generate the reflector shape. It is shown that due to the absorption of emitted radiation by the lamp itself, the behavior of the radiation model at various wavelengths is different. Numerical results of xenon plasma absorption coefficient were compared with the measured data. A reasonable agreement was obtained for the absorption coefficient parameters. Thus, this work provides a useful analytical tool for the engineering design of laser amplifier reflectors using xenon flash lamps as pumps.

Highlights

To attain ignition conditions, a laser driver for inertial confinement fusion (ICF) should have output energy of the order of megajoules at the appropriate wavelength over a pulselength of a few nanoseconds[1,2,3,4]
Following Trenholme–Emmett[12], we discovered that the radiation model was a uniform cylinder of hot plasma that filled or nearly filled the lamp bore, and the output spectral distribution of the flash lamp operating in the quasi-stationary regime was based on a large quantity of Downloaded from https://www.cambridge.org/core
According to Equation (7) and Figure 2(e), the observed decrease of radiation efficiency with increasing flash lamp current density is caused by a flash lamp opacity mechanism in which some of the light absorbed by the xenon plasma is not reradiated in the pump region

Summary

Introduction

A laser driver for inertial confinement fusion (ICF) should have output energy of the order of megajoules at the appropriate wavelength over a pulselength of a few nanoseconds[1,2,3,4]. We assume that xenon plasma absorption coefficients change with current density, lamp diameter, and xenon pressure. According to Equation (7) and Figure 2(e), the observed decrease of radiation efficiency with increasing flash lamp current density is caused by a flash lamp opacity mechanism in which some of the light absorbed by the xenon plasma is not reradiated in the pump region.

Results

Conclusion