量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum Science and Technology.
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Motivated by the development of next-generation heavy ion sources, we have investigated the
ionization and acceleration dynamics of an ultra intense laser-driven high-Z silver target, experimentally,
numerically and analytically. Using a novel ion measurement technique allowing us to
uniquely identify silver ions, we experimentally demonstrate generation of highly charged silver ions
(Z=45+2
????2) with energies of >20 MeV/nucleon (>2.2 GeV) from sub-micron silver targets driven
by a laser with intensity 51021 W/cm2, with increasing ion energy and charge state for decreasing
target thickness. We show that although target pre-expansion by the unavoidable rising edge of
state-of-the-art high power lasers can limit proton energies, it is advantageous for heavy ion acceleration.
Two-dimensional particle-in-cell simulations show that the Joule heating in the target
bulk results in a high temperature (10 keV) solid density plasma, leading to the generation of high
particle number highly charged ions (Z=40+2
????2 , &10 MeV/nucleon) via electron collisional ionization,
which are extracted and accelerated with a small divergence by an extreme sheath eld at
the target rear. However, with reduced target thickness this favorable acceleration is degraded due
to the target deformation via laser hole boring, which accompanies higher energy ions with higher
charge states but in an uncontrollable manner. Our elucidation of the fundamental processes of
high intensity laser driven ionization and ion acceleration provides a path for improving the control
and parameters of laser driven heavy ion sources, a key component for next-generation heavy ion
accelerators.
Dynamics of Laser-driven Heavy Ion Acceleration Claried by Ion Charge States
