Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
Phys Rev Lett. 2010 Aug 6;105(6):065003. doi: 10.1103/PhysRevLett.105.065003. Epub 2010 Aug 5.
It is found that stable proton acceleration from a thin foil irradiated by a linearly polarized ultraintense laser can be realized for appropriate foil thickness and laser intensity. A dual-peaked electrostatic field, originating from the oscillating and nonoscillating components of the laser ponderomotive force, is formed around the foil surfaces. This field combines radiation-pressure acceleration and target normal sheath acceleration to produce a single quasimonoenergetic ion bunch. A criterion for this mechanism to be operative is obtained and verified by two-dimensional particle-in-cell simulation. At a laser intensity of ∼5.5×10(22) W/cm(2), quasimonoenergetic GeV proton bunches are obtained with ∼100 MeV energy spread, less than 4° spatial divergence, and ∼50% energy conversion efficiency from the laser.
研究发现，当激光强度和薄箔厚度适当时，可以实现由线偏振超强激光辐照薄箔的稳定质子加速。在薄箔表面周围形成双峰值静电场，源自激光 ponderomotive 力的振荡和非振荡分量。该场结合辐射压力加速和靶法线鞘层加速，产生单准单能离子束。得到了该机制起作用的判据，并通过二维粒子模拟进行了验证。在激光强度约为 5.5×10(22) W/cm(2)时，从激光获得具有约 100 MeV 能散度、小于 4°空间发散度和约 50%能量转换效率的准单能 GeV 质子束。
