• A. Yogo
  JAEA, Ibaraki-ken

We report the demonstrated irradiation effect of laser-accelerated protons on human cancer cells. In-vitro (living) A549 cells are irradiated with a proton beam having a single bunch duration of 20 ns and a beam flux of ~10¹⁴cm⁻²s⁻¹*. The dynamics differ by seven orders of magnitude to the case of a typical Ion Beam Therapy (IBT) operation with a synchrotron: 0.4 s in bunch duration and ~10⁷cm⁻²s⁻¹ in beam flux. We have measured the yield of DNA double-strand break with phosphorylated histone H2AX immunostaining method and estimated Relative Biological Effectiveness (RBE) of the laser-accelerated protons.

* A. Yogo et al., Appl. Phys. Lett. 94, 181502 (2009).

• M. Nishiuchi, P.R. Bolton, T. Hori, K. Kondo, A.S. Pirozhkov, A. Sagisaka, H. Sakaki, A. Yogo
  JAEA, Ibaraki-ken
• Y. Iseki, T. Yoshiyuki
  Toshiba, Tokyo
• S. Kanazawa, H. Kiriyama, M. Mori, K. Ogura, S. Orimo
  JAEA/Kansai, Kyoto
• A. Noda, H. Souda, H. Tongu
  Kyoto ICR, Uji, Kyoto
• T. Shirai
  NIRS, Chiba-shi

The interaction between the high intensity laser and the solid target produces a strong electrostatic proton acceleration field (1 TV/m) with extraordinary small size, contributing to downsizing of the particle accelerator. The proton beam exhibits significant features. having very small source size(~10 um), short pulse duration (~ps) and very low transverse emittance. However it is a diverging beam (half angle of ~10 deg) with wide energy spread of ~100 %. Because of these peculiar characteristics the proton beam attracts many fields for applications including medical applications. To preserve these peculiar characteristics, which are not possessed by those beams from the conventional accelerators, towards the irradiation points, we need to establish a peculiar beam transport line. As the first step, here we report the demonstration of the proto-type laser-driven proton medical accelerator beam line in which we combine the laser-driven proton source with the beam transport technique already established in the conventional accelerator for the purpose of comparison between the data and the particle transport simulation code, PARMILA*.

*Harunori Takeda, 2005, Parmila LANL (LA-UR-98-4478).

• H. Sakaki, P.R. Bolton, T. Hori, K. Kondo, M. Nishiuchi, F. Saito, H. Takahashi, M. Ueno, A. Yogo
  JAEA, Ibaraki-ken
• H. Iwase
  KEK, Ibaraki
• K. Niita
  RIST, Ibaraki

The concept of a compact ion particle accelerator has become attractive in view of recent progress in laser-driven hadrons acceleration. The Photo Medical Research Centre (PMRC) of JAEA was established to address the challenge of laser-driven ion accelerator development for hadrons therapeutic. In the development of the instrument, it is necessary to do the bench-mark of the amount of the different types of radiation by the simulation code for shielding. The Monte Carlo Particle and Heavy Ion Transport code (PHITS) was used for bench-mark the dose on laser-shot radiations of short duration. The code predicts reasonably well the observed total dose as measured with a glass dosimeter in the laser-driven radiations.

• A. Sagisaka, P.R. Bolton, S.V. Bulanov, H. Daido, T. Esirkepov, T. Hori, S. Kanazawa, H. Kiriyama, K. Kondo, S. Kondo, M. Mori, Y. Nakai, M. Nishiuchi, K. Ogura, H. Okada, S. Orimo, A.S. Pirozhkov, H. Sakaki, F. Sasao, H. Sasao, T. Shimomura, A. Sugiyama, H. Sugiyama, M. Tampo, M. Tanoue, D. Wakai, A. Yogo
  JAEA, Kyoto
• I.W. Choi, J. Lee
  APRI-GIST, Gwangju
• H. Nagatomo
  ILE Osaka, Suita
• K. Nemoto, Y. Oishi
  Central Research Institute of Electric Power Industry, Yokosuka-shi, Kanagawa

High-intensity laser and thin-foil interactions produce high-energy particles, hard x-ray, high-order harmonics, and terahertz radiation. A proton beam driven by a high-intensity laser has received attention as a compact ion source for medical applications. We have performed the high intensity laser-matter interaction experiments using a thin-foil target irradiated by Ti:sapphire laser (J-KAREN) at JAEA. In this laser system, the pulse duration is 40 fs (FWHM). The laser beam is focused by an off-axis parabolic mirror at the target. The estimated peak intensity is ~5x10¹⁹ W/cm². We have developed on-line real time monitors such as a time-of-flight proton spectrometer which is placed behind the target and interferometer for electron density profile measurement of preformed plasma. We observed the maximum proton energy of ~7 MeV.

• T. Nakamura, S.V. Bulanov, H. Daido, T. Esirkepov, A. Faenov, Y. Fukuda, Y. Hayashi, T.K. Kameshima, M. Kando, T. Pikuz, A.S. Pirozhkov, M. Tampo, A. Yogo
  JAEA/Kansai, Kyoto

Intense laser pulse is utilized to generate compact sources of electrons, ions, x-rays, neutrons. Recently, high energy negative ions are also observed in experiments using cluster or gas target*. To explain the acceleration of negative ions from laser-generated plasmas, we proposed Coulomb implosion mechanism**. When clusters or underdense plasmas are irradiated by an intense laser pulse, positive ions are accelerated inside the clusters or in the self-focusing channel by the Coulomb explosion. This could lead to the acceleration of negative ions towards target center. The maximum energy of negative ions is typically several times lower than that of positive ions. A theoretical description and corresponding Particle-in-Cell simulations of Coulomb implosion mechanism are presented. We show the evidence of the negative ion acceleration observed in our experiments using high intensity laser pulse and the cluster-gas targets.

* S.Ter-Avetisyan et al., J. Phys. B 37 (2004) 3633.
** T.Nakamura et al., Phys. Plasmas 16 (2009) 113106.