Side-on measurement of hydrodynamics of laser-driven plasmas with high space- and time-resolution x-ray imaging technique

Copyright 2003 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Review of Scientific Instruments, 74(3), 2198-2201, 2003 and may be found at http://dx.doi.org/10.1063/1.153785

FIREX project and effects of self-generated electric and magnetic fields on electron-driven fast ignition.

Fast ignition is a new scheme in laser fusion, in which higher energy gain with a smaller laser pulse energy is expected. A cone target has been introduced for realizing higher coupling efficiency. At ILE, Osaka University, a laser with four beams and a total output of 10 kJ ps−1, laser for fast ignition experiment (LFEX), has been constructed and we have carried out an integrated experiment with one beam of the LFEX. Through experiments it was found that the coupling efficiency is degraded when the laser pre-pulse is not sufficiently small. Namely, the main pulse is absorbed in the long-scale pre-plasma produced by the pre-pulse and the hot electron energy is higher than that for a clean pulse. Furthermore, the distance between the hot electron source and the core plasma is large. Hence, we are exploring how to overcome the pre-pulse effects on the cone target. In this paper it is proposed that a thin foil covers the laser entrance of the cone to mitigate the pre-plasma and a double cone reduces the loss of high-energy electrons from the side wall of the cone. The simulations indicate that a higher coupling efficiency is expected for the double cone target with a thin foil at the laser entrance. Namely, the pre-pulse will be absorbed by the foil and the electromagnetic fields generated on the surface of the inner cone will confine high-energy electrons

Cryogenic deuterium target experiments with the GEKKO XII, green laser system

Copyright 1995 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Plasmas, 2(6), 2495-2503, 1995 and may be found at http://dx.doi.org/10.1063/1.87121

Effect of irradiation uniformity on quasi-isentropic shock compression of solid spheres

Takizawa R., Sakagami H., Nagatomo H., et al. Effect of irradiation uniformity on quasi-isentropic shock compression of solid spheres. High Energy Density Physics 52, 101124 (2024); https://doi.org/10.1016/j.hedp.2024.101124.In inertial confinement fusion using central ignition, the ignition hot spot is generated through self-heating during fuel compression. In contrast, fast ignition creates the hot spot through external heating. This difference allows the fast ignition approach to use a solid sphere as the fusion fuel shape. The implosion of a solid sphere is one form of laser-direct-drive slow implosion. Solid sphere fuel exhibits tolerance to hydrodynamic instability and can be mass-produced relatively easily, offering significant advantages for developing inertial fusion energy. Achieving high fuel peak and areal densities of with a solid sphere requires quasi-isentropic compression, which involves multiple shock waves. Our results show the critical role of uniform laser irradiation in initiating weak shock waves in the early phase, which is essential for forming a uniform and dense fuel core with solid spheres. Furthermore, dynamically adjusting the laser spot diameter could be crucial in optimizing the effectiveness of laser-direct-drive and fast ignition techniques when using solid sphere fuel

Fabrication of high-concentration Cu-doped deuterated targets for fast ignition experiments

In high-energy-density physics, including inertial fusion energy using high-power lasers, doping tracer atoms and deuteration of target materials play an important role in diagnosis. For example, a low-concentration Cu dopant acts as an x-ray source for electron temperature detection while a deuterium dopant acts as a neutron source for fusion reaction detection. However, the simultaneous achievement of Cu doping, a deuterated polymer, mechanical toughness and chemical robustness during the fabrication process is not so simple. In this study, we report the successful fabrication of a Cu-doped deuterated target. The obtained samples were characterized by inductively coupled plasma optical emission spectrometry, differential scanning calorimetry and Fourier transform infrared spectroscopy. Simultaneous measurements of Cu K-shell x-ray emission and beam fusion neutrons were demonstrated using a petawatt laser at Osaka University.Ikeda T., Kaneyasu Y., Hosokawa H., et al. Fabrication of high-concentration Cu-doped deuterated targets for fast ignition experiments. Nuclear Fusion 63, 016010 (2023); https://doi.org/10.1088/1741-4326/aca2ba

Demonstration of a spherical plasma mirror for the counter-propagating kilojoule-class petawatt LFEX laser system

A counter-propagating laser-beam platform using a spherical plasma mirror was developed for the kilojoule-class petawatt LFEX laser. The temporal and spatial overlaps of the incoming and redirected beams were measured with an optical interferometer and an x-ray pinhole camera. The plasma mirror performance was evaluated by measuring fast electrons, ions, and neutrons generated in the counter-propagating laser interaction with a Cu-doped deuterated film on both sides. The reflectivity and peak intensity were estimated as ∼50% and ∼5 × 1018 W/cm2, respectively. The platform could enable studies of counter-streaming charged particles in high-energy-density plasmas for fundamental and inertial confinement fusion research.Kojima S., Abe Y., Miura E., et al. Demonstration of a spherical plasma mirror for the counter-propagating kilojoule-class petawatt LFEX laser system. Optics Express 30, 43491 (2022); https://doi.org/10.1364/oe.475945