42 research outputs found
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
Magnetized Fast Isochoric Laser Heating for Efficient Creation of Ultra-High-Energy-Density States
The quest for the inertial confinement fusion (ICF) ignition is a grand
challenge, as exemplified by extraordinary large laser facilities. Fast
isochoric heating of a pre-compressed plasma core with a high-intensity
short-pulse laser is an attractive and alternative approach to create
ultra-high-energy-density states like those found in ICF ignition sparks. This
avoids the ignition quench caused by the hot spark mixing with the surrounding
cold fuel, which is the crucial problem of the currently pursued ignition
scheme. High-intensity lasers efficiently produce relativistic electron beams
(REB). A part of the REB kinetic energy is deposited in the core, and then the
heated region becomes the hot spark to trigger the ignition. However, only a
small portion of the REB collides with the core because of its large
divergence. Here we have demonstrated enhanced laser-to-core energy coupling
with the magnetized fast isochoric heating. The method employs a
kilo-tesla-level magnetic field that is applied to the transport region from
the REB generation point to the core which results in guiding the REB along the
magnetic field lines to the core. 7.7 1.3 % of the maximum coupling was
achieved even with a relatively small radial area density core (
0.1 g/cm). The guided REB transport was clearly visualized in a
pre-compressed core by using Cu- imaging technique. A simplified
model coupled with the comprehensive diagnostics yields 6.2\% of the coupling
that agrees fairly with the measured coupling. This model also reveals that an
ignition-scale areal density core ( 0.4 g/cm) leads to much
higher laser-to-core coupling ( 15%), this is much higher than that achieved
by the current scheme
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
Optical transmittance investigation of 1-keV ion-irradiated sapphire crystals as potential VUV to NIR window materials of fusion reactors
We investigate the optical transmittances of ion-irradiated sapphire crystals as potential vacuum ultraviolet (VUV) to near-infrared (NIR) window materials of fusion reactors. Under potential conditions in fusion reactors, sapphire crystals are irradiated with hydrogen (H), deuterium (D), and helium (He) ions with 1-keV energy and ∼ 1020-m-2 s-1 flux. Ion irradiation decreases the transmittances from 140 to 260 nm but hardly affects the transmittances from 300 to 1500 nm. H-ion and D-ion irradiation causes optical absorptions near 210 and 260 nm associated with an F-center and an F+-center, respectively. These F-type centers are classified as Schottky defects that can be removed through annealing above 1000 K. In contrast, He-ion irradiation does not cause optical absorptions above 200 nm because He-ions cannot be incorporated in the crystal lattice due to the large ionic radius of He-ions. Moreover, the significant decrease in transmittance of the ion-irradiated sapphire crystals from 140 to 180 nm is related to the light scattering on the crystal surface. Similar to diamond polishing, ion irradiation modifies the crystal surface thereby affecting the optical properties especially at shorter wavelengths. Although the transmittances in the VUV wavelengths decrease after ion irradiation, the transmittances can be improved through annealing above 1000 K. With an optical transmittance in the VUV region that can recover through simple annealing and with a high transparency from the ultraviolet (UV) to the NIR region, sapphire crystals can therefore be used as good optical windows inside modern fusion power reactors in terms of light particle loadings of hydrogen isotopes and helium.Iwano K., Yamanoi K., Iwasa Y., et al. Optical transmittance investigation of 1-keV ion-irradiated sapphire crystals as potential VUV to NIR window materials of fusion reactors. AIP Advances 6, 105108 (2016); https://doi.org/10.1063/1.4965927
Hot Electron Spectra in Plain, Cone and Integrated Targets for FIREX-I using Electron Spectrometer
The traditional fast ignition scheme is that a compressed core created by an imploding laser is auxiliary heated and ignited by the hot electrons (produced by a short pulse laser guided through the cone). Here, the most suitable target design for fast ignition can be searched for by comparison of the spectra between varied targets using an electron spectrometer