@article{oai:repo.qst.go.jp:00079116,
 author = {Dover, NicholasPeter and Nishiuchi, Mamiko and Sakaki, Hironao and Kondo, Kotaro and A. Alkhimova, M. and Ya. Faenov, A. and Hata, M. and Iwata, N. and Kiriyama, Hiromitsu and Kevin Koga, James and Miyahara, Takumi and A. Pikuz, T. and Pirozhkov, Alexander and Sagisaka, Akito and Sentoku, Y. and Watanabe, Y. and Kando, Masaki and Kondo, Kiminori and Dover, NicholasPeter and Mamiko, Nishiuchi and Hironao, Sakaki and Kotaro, Kondo and Hiromitsu, Kiriyama and Kevin Koga, James and Miyahara, Takumi and Pirozhkov, Alexander and Akito, Sagisaka and Masaki, Kando and Kiminori, Kondo},
 journal = {Physical Review Letters},
 month = {Mar},
 note = {Acceleration of particles from the interaction of ultra-intense laser pulses up to $5\times10^{21}$ Wcm$^{-2}$ with thin foils is investigated experimentally.  The electron beam parameters varied with decreasing spot size, not just laser intensity, resulting in reduced temperatures and divergence.  In particular, the temperature saturated due to insufficient acceleration length in the tightly focused spot.  These dependencies affected the sheath-accelerated protons, which showed poorer spot-size scaling than widely used scaling laws.  It is therefore shown that maximizing laser intensity by using very small focii has reducing returns for some applications.},
 title = {Effect of small focus on electron heating and proton acceleration in ultra-relativistic laser-solid interactions},
 volume = {124},
 year = {2020}
}