Abstract
Over many years collective ion acceleration has been considered, but only recently, some exciting experimental results of collective acceleration based on intense laser driven ion acceleration have been obtained. Currently, the highest proton energy driven by an ultra-intense lasers is >50MeV with high efficiency of >5% as well as very low transverse emittance of 0.004 mm•mrad. The paper reviews the recent achievement of such ion generation studies. First, the mechanisms of the ion generation are described including the plasma sheath model which describes energetic proton generation driven by sub-ps high energy lasers. A pre-pulse plays a significant role especially for the fs laser driven ion generation. The under-dense plasma model described here is one of the mechanisms, which utilize pre-pulses. The quasi-mono-energetic ion beam obtained theoretically and computationally is reviewed. Then the experimental results on the ion generation driven by sub-ps large energy lasers as well as fs lasers are reviewed. Although lower maximum proton energy and efficiency compared with those driven by sub-ps lasers at present, the results given by the fs lasers are precisely described because the fs lasers may be closer to real applications. Finally the present project on the ultra small ion accelerator development for cancer therapy and related topics are reviewed.
