Direct fast heating efficiency of a counter-imploded core plasma employing a laser for fast ignition experiments (LFEX)

Abstract Fast heating efficiency when a pre-imploded core is directly heated with an ultraintense laser (heating laser) was investigated. ‘Direct heating’ means that a heating laser hits a pre-imploded core without applying either a laser guiding cone or an external field. The efficiency, η , is def...

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Bibliographic Details
Published in:Nuclear fusion 2022-09, Vol.62 (9), p.96013
Main Authors: Kitagawa, Yoneyoshi, Mori, Yoshitaka, Ishii, Katsuhiro, Hanayama, Ryohei, Okihara, Shinichiro, Arikawa, Yasunobu, Abe, Yuki, Miura, Eisuke, Ozaki, Tetsuo, Komeda, Osamu, Suto, Hiroyuki, Umetani, Yusuke, Sunahra, Atsushi, Johzaki, Tomoyuki, Sakagami, Hitoshi, Iwamoto, Akifumi, Sentoku, Yasuhiko, Nakajima, Nozomi, Sakata, Shohei, Matsuo, Kazuki, Mirfayzi, Reza S., Kawanaka, Junji, Fujiokua, Shinsuke, Tsubakimoto, Koji, Shigemori, Keisuke, Yamanoi, Kohei, Yogo, Akifumi, Nakao, Ayami, Asano, Masatada, Shiraga, Hiroyuki, Motohiro, Tomoyoshi, Hioki, Tatsumi, Azuma, Hirozumi
Format: Article
Language:English
Subjects:
counter implosion
direct heating
fast ignition
heating efficiency
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Summary:Abstract Fast heating efficiency when a pre-imploded core is directly heated with an ultraintense laser (heating laser) was investigated. ‘Direct heating’ means that a heating laser hits a pre-imploded core without applying either a laser guiding cone or an external field. The efficiency, η , is defined as the increase in the internal core energy divided by the energy of the heating laser. Six beams (output of 1.6 kJ) from the GEKKO XII (GXII) green laser system at the Institute of Laser Engineering (ILE), Osaka University were applied to implode a spherical deuterated polystyrene (CD) shell target to form a dense core. The DD-reacted protons and the core x-ray emissions showed a core density of 2.8 ± 0.7 g cm −3 , or 2.6 times the solid density. Furthermore, DD-reacted thermal neutrons were utilized to estimate the core temperature between 600 and 750 eV. Thereafter, the core was directly heated by a laser for fast-ignition experiments (LFEX, an extremely energetic ultrashort pulse laser) at ILE with its axis lying along or perpendicular to the GXII bundle axis, respectively. The former and latter laser configurations were termed ‘axial’ and ‘transverse modes’, respectively. The η was estimated from three independent methods: (1) the core x-ray emission, (2) the thermal neutron yield, and (3) the runaway hot electron spectra. For the axial mode, 0.8% < η < 2.1% at low power (low LFEX energy) and 0.4% < η < 2.5% at high power (high LFEX energy). For the transverse mode, 2.6% < η < 7% at low power and 1.5% < η < 7.7% at high power. Their efficiencies were compared with that in the uniform implosion mode using 12 GXII beams, 6% < η < 12%, which appeared near to the η for the transverse mode, except that the error bar is very large.
ISSN:0029-5515
1741-4326
DOI:10.1088/1741-4326/ac7966