Physical Review Special Topics. Accelerators and Beams (Jun 2009)

Radial focusing and energy compression of a laser-produced proton beam by a synchronous rf field

  • Masahiro Ikegami,
  • Shu Nakamura,
  • Yoshihisa Iwashita,
  • Toshiyuki Shirai,
  • Hikaru Souda,
  • Yujiro Tajima,
  • Mikio Tanabe,
  • Hiromu Tongu,
  • Hiroyuki Itoh,
  • Hiroki Shintaku,
  • Atsushi Yamazaki,
  • Hiroyuki Daido,
  • Akifumi Yogo,
  • Satoshi Orimo,
  • Michiaki Mori,
  • Mamiko Nishiuchi,
  • Koichi Ogura,
  • Akito Sagisaka,
  • Alexander S. Pirozhkov,
  • Hiromitsu Kiriyama,
  • Shyuhei Kanazawa,
  • Shuji Kondo,
  • Yoichi Yamamoto,
  • Takuya Shimomura,
  • Manabu Tanoue,
  • Yoshimoto Nakai,
  • Atsushi Akutsu,
  • Sergei V. Bulanov,
  • Toyoaki Kimura,
  • Yuji Oishi,
  • Koshichi Nemoto,
  • Toshiki Tajima,
  • Akira Noda

DOI
https://doi.org/10.1103/PhysRevSTAB.12.063501
Journal volume & issue
Vol. 12, no. 6
p. 063501

Abstract

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The dynamics of a MeV laser-produced proton beam affected by a radio frequency (rf) electric field has been studied. The proton beam was emitted normal to the rear surface of a thin polyimide target irradiated with an ultrashort pulsed laser with a power density of 4×10^{18} W/cm^{2}. The energy spread was compressed to less than 11% at the full width at half maximum (FWHM) by an rf field. Focusing and defocusing effects of the transverse direction were also observed. These effects were analyzed and reproduced by Monte Carlo simulations. The simulation results show that the transversely focused protons had a broad continuous spectrum, while the peaks in the proton spectrum were defocused. Based on this new information, we propose that elimination of the continuous energy component of laser-produced protons is possible by utilizing a focal length difference between the continuous spectral protons and the protons included in the spectral peak.