Efficient production of MeV proton beam from a Polyimide target driven by an intense femto-second laser

Nishiuchi, Mamiko; Daido, Hiroyuki; Yogo, Akifumi; Orimo, Satoshi; Ogura, Koichi; Ma, J.-L.; Sagisaka, Akito; Mori, Michiaki; Pirozhkov, A. S.; Kiriyama, Hiromitsu; Bulanov, S. V.; Esirkepov, T. Z.; Nagatomo, Hideo*; Nagai, Keiji*; Oishi, Yuji*; Nemoto, Koshichi*; Choi, I. W.*; Kim, C. M.*; Jeong, T. M.*; Hafz, N.*; Yu, T. J.*; Sung, J. H.*; Noh, Y.-C.*; Ko, D.-K.*; Lee, J.*; Azuma, Hirozumi*

The efficient proton beam whose maximum energy of up to 4 MeV was produced by the 50TW short pulse intensity Ti:Sap laser irradiated on the polyimide target [(CHON)n] with the thicknesses of 7.5m, 12.5m, 25m, which is transparent to the 800 nm laser. The laser parameters are energy of 1.7J, pulse width of 35fs and the intensity of 310 Wcm. The contrast of the ASE component is 410. The conversion efficiency from laser energy into the proton kinetic energy is up to 3%. This conversion efficiency is comparable or even higher than the results obtained with the same level laser ( J energy) interacts with the nano-meter level ultra thin target. In this paper we discuss on the comparison between our results and other experimental results obtained in other facilities.