INFN Sezione di Ferrara and Dipartimento di Fisica, Università di Ferrara, Via Saragat 1/C, 44122 Ferrara, Italy.
Phys Rev Lett. 2012 Jan 6;108(1):014801. doi: 10.1103/PhysRevLett.108.014801. Epub 2012 Jan 3.
The interaction of a 2 MeV proton beam with an ultrathin unbent Si crystal was studied through simulation and experiment. Crystal thickness along the beam was set at 92 nm, i.e., at half the oscillation wavelength of the protons in the crystal under planar channeling condition. As the nominal beam direction is inclined by less than the critical angle for planar channeling with respect to the crystal planes, under-barrier particles undergo half an oscillation and exit the crystal with the reversal of the transverse momenta; i.e., the protons are "mirrored" by the crystal planes. Over-barrier particles suffer deflection, too, to a direction opposite that of mirroring with a dynamics similar to that of volume reflection in a bent crystal. On the strength of such coherent interactions, charged particle beams can be efficiently steered through an ultrathin unbent crystal by the same physical processes as for thicker bent crystals.
通过模拟和实验研究了 2MeV 质子束与超薄未弯曲硅晶体的相互作用。晶体沿光束的厚度设置为 92nm，即质子在晶体中平面沟道条件下的半振动波长。由于名义光束方向相对于晶体平面的平面沟道临界角倾斜小于，因此，下势垒粒子经历半振动并随着横向动量的反转而离开晶体；即质子被晶体平面“反射”。上势垒粒子也会受到偏转，方向与反射相反，动力学类似于弯曲晶体中的体积反射。基于这种相干相互作用，带电粒子束可以通过超薄未弯曲晶体进行高效导向，其物理过程与更厚的弯曲晶体相同。
