title: Boosting laser-ion acceleration with multi-picosecond pulses.
abstract: Using one of the world most powerful laser facility, we demonstrate for the first time that high-contrast multi-picosecond pulses are advantageous for proton acceleration. By extending the pulse duration from 1.5 to 6 ps with fixed laser intensity of 1018W cm-2, the maximum proton energy is improved more than twice (from 13 to 33 MeV). At the same time, laser-energy conversion efficiency into the MeV protons is enhanced with an order of magnitude, achieving 5% for protons above 6 MeV with the 6 ps pulse duration. The proton energies observed are discussed using a plasma expansion model newly developed that takes the electron temperature evolution beyond the ponderomotive energy in the over picoseconds interaction into account. The present results are quite encouraging for realizing ion-driven fast ignition and novel ion beamlines.
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.|PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan.
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authors.initials: A
authors.lastname: Yogo
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.|The Graduate School for the Creation of New Photon Industries, Hamamatsu, Shizuoka 431-1202, Japan.
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authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.lastname: Arikawa
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.lastname: Fujioka
authors.affiliation: Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8511, Japan.
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authors.lastname: Johzaki
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.lastname: Sentoku
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
authors.forename: H
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authors.lastname: Nishimura
authors.affiliation: Kansai Photon Science Institute, National Institutes for Quantum and Radiological Science and Technology, Kizugawa 619-0215, Kyoto, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Sagisaka
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.lastname: Kamitsukasa
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.lastname: Kojima
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.lastname: Nagatomo
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.lastname: Nakai
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.lastname: Shiraga
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.lastname: Murakami
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.lastname: Tokita
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.initials: J
authors.lastname: Kawanaka
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Miyanaga
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
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authors.lastname: Yamanoi
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Norimatsu
authors.affiliation: National Institute for Fusion Science, Gifu 509-5292, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Sakagami
authors.affiliation: Kansai Photon Science Institute, National Institutes for Quantum and Radiological Science and Technology, Kizugawa 619-0215, Kyoto, Japan.
authors.forename: S V
authors.initials: SV
authors.lastname: Bulanov
authors.affiliation: Kansai Photon Science Institute, National Institutes for Quantum and Radiological Science and Technology, Kizugawa 619-0215, Kyoto, Japan.
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authors.lastname: Kondo
authors.affiliation: Institute of Laser Engineering, Osaka University, Suita 565-0871, Osaka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Azechi