薄晶体中相对论电子对辐射角分布和偏振的多次散射效应
Multiple scattering effect on angular distribution and polarization of radiation by relativistic electrons in a thin crystal
摘要：
超相对论电子在非晶物质中的多次散射导致了辐射谱的软部被抑制（Landau-Pomeranchuk-Migdal效应），并从本质上改变了发射光子的角分布。晶体中相对论电子的相干辐射也会发生类似的效应，本文给出了相对论电子以小角度穿过薄晶体（与相干长度相比）时辐射的角分布和偏振的理论研究结果。采用考虑相干和非相干散射效应的二元碰撞模型，模拟了电子在晶体中的运动轨迹。辐射和偏振的角分布被计算为每个电子的辐射之和，结果表明，存在着非平凡的发射光子的角分布和它们的偏振，它们与原子行对电子的相干散射（“甜甜圈散射”效应）和辐射抑制（类似于非晶物质中的Landau-Pomeranchuk-Migdal效应）的叠加有关。它还表明，在所考虑的情况下，辐射的圆偏振是恒零。
英文摘要：
The multiple scattering of ultra relativistic electrons in an amorphous matter leads to the suppression of the soft part of radiation spectrum (the Landau-Pomeranchuk-Migdal effect), and also can change essentially the angular distribution of the emitted photons. A similar effect must take place in a crystal for the coherent radiation of relativistic electron. The results of the theoretical investigation of angular distributions and polarization of radiation by a relativistic electron passing through a thin (in comparison with a coherence length) crystal at a small angle to the crystal axis are presented. The electron trajectories in crystal were simulated using the binary collision model which takes into account both coherent and incoherent effects at scattering. The angular distribution of radiation and polarization were calculated as a sum of radiation from each electron. It is shown that there are nontrivial angular distributions of the emitted photons and their polarization that are connected to the superposition of the coherent scattering of electrons by atomic rows ("doughnut scattering" effect) and the suppression of radiation (similar to the Landau-Pomeranchuk-Migdal effect in an amorphous matter). It is also shown that circular polarization of radiation in the considered case is identically zero.
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