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Title: Fast ignition realization experiment with high-contrast kilo-joule peta-watt LFEX laser and strong external magnetic field

Abstract

A petawatt laser for fast ignition experiments (LFEX) laser system [N. Miyanaga et al., J. Phys. IV France 133, 81 (2006)], which is currently capable of delivering 2 kJ in a 1.5 ps pulse using 4 laser beams, has been constructed beside the GEKKO-XII laser facility for demonstrating efficient fast heating of a dense plasma up to the ignition temperature under the auspices of the Fast Ignition Realization EXperiment (FIREX) project [H. Azechi et al., Nucl. Fusion 49, 104024 (2009)]. In the FIREX experiment, a cone is attached to a spherical target containing a fuel to prevent a corona plasma from entering the path of the intense heating LFEX laser beams. The LFEX laser beams are focused at the tip of the cone to generate a relativistic electron beam (REB), which heats a dense fuel core generated by compression of a spherical deuterized plastic target induced by the GEKKO-XII laser beams. Recent studies indicate that the current heating efficiency is only 0.4%, and three requirements to achieve higher efficiency of the fast ignition (FI) scheme with the current GEKKO and LFEX systems have been identified: (i) reduction of the high energy tail of the REB; (ii) formation of a fuel coremore » with high areal density using a limited number (twelve) of GEKKO-XII laser beams as well as a limited energy (4 kJ of 0.53-μm light in a 1.3 ns pulse); (iii) guiding and focusing of the REB to the fuel core. Laser–plasma interactions in a long-scale plasma generate electrons that are too energetic to efficiently heat the fuel core. Three actions were taken to meet the first requirement. First, the intensity contrast of the foot pulses to the main pulses of the LFEX was improved to >10{sup 9}. Second, a 5.5-mm-long cone was introduced to reduce pre-heating of the inner cone wall caused by illumination of the unconverted 1.053-μm light of implosion beam (GEKKO-XII). Third, the outside of the cone wall was coated with a 40-μm plastic layer to protect it from the pressure caused by imploding plasma. Following the above improvements, conversion of 13% of the LFEX laser energy to a low energy portion of the REB, whose slope temperature is 0.7 MeV, which is close to the ponderomotive scaling value, was achieved. To meet the second requirement, the compression of a solid spherical ball with a diameter of 200-μm to form a dense core with an areal density of ∼0.07 g/cm{sup 2} was induced by a laser-driven spherically converging shock wave. Converging shock compression is more hydrodynamically stable compared to shell implosion, while a hot spot cannot be generated with a solid ball target. Solid ball compression is preferable also for compressing an external magnetic field to collimate the REB to the fuel core, due to the relatively small magnetic Reynolds number of the shock compressed region. To meet the third requirement, we have generated a strong kilo-tesla magnetic field using a laser-driven capacitor-coil target. The strength and time history of the magnetic field were characterized with proton deflectometry and a B-dot probe. Guidance of the REB using a 0.6-kT field in a planar geometry has been demonstrated at the LULI 2000 laser facility. In a realistic FI scenario, a magnetic mirror is formed between the REB generation point and the fuel core. The effects of the strong magnetic field on not only REB transport but also plasma compression were studied using numerical simulations. According to the transport calculations, the heating efficiency can be improved from 0.4% to 4% by the GEKKO and LFEX laser system by meeting the three requirements described above. This efficiency is scalable to 10% of the heating efficiency by increasing the areal density of the fuel core.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;  [1] more »; « less
  1. Institute of Laser Engineering, Osaka University, 2-6 Yamada-Oka, Suita, Osaka 565-0871 Japan (Japan)
Publication Date:
OSTI Identifier:
22600247
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 23; Journal Issue: 5; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CAPACITORS; COMPARATIVE EVALUATIONS; COMPRESSION; COMPUTERIZED SIMULATION; DENSITY; ELECTRON BEAMS; ELECTRONS; HEATING; IMPLOSIONS; LASERS; MAGNETIC FIELDS; MAGNETIC MIRRORS; MAGNETIC REYNOLDS NUMBER; MEV RANGE 01-10; PETAWATT POWER RANGE; PLASMA; RELATIVISTIC RANGE; SHOCK WAVES; SPHERICAL CONFIGURATION; THERMONUCLEAR IGNITION

Citation Formats

Fujioka, Shinsuke, Arikawa, Yasunobu, Kojima, Sadaoki, Nagatomo, Hideo, Lee, Seung Ho, Morace, Alessio, Vaisseau, Xavier, Sakata, Shohei, Abe, Yuki, Matsuo, Kazuki, Farley Law, King Fai, Tosaki, Shota, Yogo, Akifumi, Shigemori, Keisuke, Hironaka, Yoichiro, Fujimoto, Yasushi, Yamanoi, Kohei, Norimatsu, Takayoshi, Tokita, Shigeki, Nakata, Yoshiki, and others, and. Fast ignition realization experiment with high-contrast kilo-joule peta-watt LFEX laser and strong external magnetic field. United States: N. p., 2016. Web. doi:10.1063/1.4948278.
Fujioka, Shinsuke, Arikawa, Yasunobu, Kojima, Sadaoki, Nagatomo, Hideo, Lee, Seung Ho, Morace, Alessio, Vaisseau, Xavier, Sakata, Shohei, Abe, Yuki, Matsuo, Kazuki, Farley Law, King Fai, Tosaki, Shota, Yogo, Akifumi, Shigemori, Keisuke, Hironaka, Yoichiro, Fujimoto, Yasushi, Yamanoi, Kohei, Norimatsu, Takayoshi, Tokita, Shigeki, Nakata, Yoshiki, & others, and. Fast ignition realization experiment with high-contrast kilo-joule peta-watt LFEX laser and strong external magnetic field. United States. https://doi.org/10.1063/1.4948278
Fujioka, Shinsuke, Arikawa, Yasunobu, Kojima, Sadaoki, Nagatomo, Hideo, Lee, Seung Ho, Morace, Alessio, Vaisseau, Xavier, Sakata, Shohei, Abe, Yuki, Matsuo, Kazuki, Farley Law, King Fai, Tosaki, Shota, Yogo, Akifumi, Shigemori, Keisuke, Hironaka, Yoichiro, Fujimoto, Yasushi, Yamanoi, Kohei, Norimatsu, Takayoshi, Tokita, Shigeki, Nakata, Yoshiki, and others, and. Sun . "Fast ignition realization experiment with high-contrast kilo-joule peta-watt LFEX laser and strong external magnetic field". United States. https://doi.org/10.1063/1.4948278.
@article{osti_22600247,
title = {Fast ignition realization experiment with high-contrast kilo-joule peta-watt LFEX laser and strong external magnetic field},
author = {Fujioka, Shinsuke and Arikawa, Yasunobu and Kojima, Sadaoki and Nagatomo, Hideo and Lee, Seung Ho and Morace, Alessio and Vaisseau, Xavier and Sakata, Shohei and Abe, Yuki and Matsuo, Kazuki and Farley Law, King Fai and Tosaki, Shota and Yogo, Akifumi and Shigemori, Keisuke and Hironaka, Yoichiro and Fujimoto, Yasushi and Yamanoi, Kohei and Norimatsu, Takayoshi and Tokita, Shigeki and Nakata, Yoshiki and others, and},
abstractNote = {A petawatt laser for fast ignition experiments (LFEX) laser system [N. Miyanaga et al., J. Phys. IV France 133, 81 (2006)], which is currently capable of delivering 2 kJ in a 1.5 ps pulse using 4 laser beams, has been constructed beside the GEKKO-XII laser facility for demonstrating efficient fast heating of a dense plasma up to the ignition temperature under the auspices of the Fast Ignition Realization EXperiment (FIREX) project [H. Azechi et al., Nucl. Fusion 49, 104024 (2009)]. In the FIREX experiment, a cone is attached to a spherical target containing a fuel to prevent a corona plasma from entering the path of the intense heating LFEX laser beams. The LFEX laser beams are focused at the tip of the cone to generate a relativistic electron beam (REB), which heats a dense fuel core generated by compression of a spherical deuterized plastic target induced by the GEKKO-XII laser beams. Recent studies indicate that the current heating efficiency is only 0.4%, and three requirements to achieve higher efficiency of the fast ignition (FI) scheme with the current GEKKO and LFEX systems have been identified: (i) reduction of the high energy tail of the REB; (ii) formation of a fuel core with high areal density using a limited number (twelve) of GEKKO-XII laser beams as well as a limited energy (4 kJ of 0.53-μm light in a 1.3 ns pulse); (iii) guiding and focusing of the REB to the fuel core. Laser–plasma interactions in a long-scale plasma generate electrons that are too energetic to efficiently heat the fuel core. Three actions were taken to meet the first requirement. First, the intensity contrast of the foot pulses to the main pulses of the LFEX was improved to >10{sup 9}. Second, a 5.5-mm-long cone was introduced to reduce pre-heating of the inner cone wall caused by illumination of the unconverted 1.053-μm light of implosion beam (GEKKO-XII). Third, the outside of the cone wall was coated with a 40-μm plastic layer to protect it from the pressure caused by imploding plasma. Following the above improvements, conversion of 13% of the LFEX laser energy to a low energy portion of the REB, whose slope temperature is 0.7 MeV, which is close to the ponderomotive scaling value, was achieved. To meet the second requirement, the compression of a solid spherical ball with a diameter of 200-μm to form a dense core with an areal density of ∼0.07 g/cm{sup 2} was induced by a laser-driven spherically converging shock wave. Converging shock compression is more hydrodynamically stable compared to shell implosion, while a hot spot cannot be generated with a solid ball target. Solid ball compression is preferable also for compressing an external magnetic field to collimate the REB to the fuel core, due to the relatively small magnetic Reynolds number of the shock compressed region. To meet the third requirement, we have generated a strong kilo-tesla magnetic field using a laser-driven capacitor-coil target. The strength and time history of the magnetic field were characterized with proton deflectometry and a B-dot probe. Guidance of the REB using a 0.6-kT field in a planar geometry has been demonstrated at the LULI 2000 laser facility. In a realistic FI scenario, a magnetic mirror is formed between the REB generation point and the fuel core. The effects of the strong magnetic field on not only REB transport but also plasma compression were studied using numerical simulations. According to the transport calculations, the heating efficiency can be improved from 0.4% to 4% by the GEKKO and LFEX laser system by meeting the three requirements described above. This efficiency is scalable to 10% of the heating efficiency by increasing the areal density of the fuel core.},
doi = {10.1063/1.4948278},
url = {https://www.osti.gov/biblio/22600247}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 5,
volume = 23,
place = {United States},
year = {2016},
month = {5}
}