Coherent X radiation from periodic materials

来自周期性物质的各种类型的相干x辐射已经被发现；参数x射线（PXR），通道辐射，共振跃迁辐射，并在前苏联等地进行了研究。目前的研究项目已经成功地积累了系统的数据，这些数据可以使我们通过在两种辐射现象可以同时发生的条件下进行测量，以更一致的方式理解迄今为止分别描述的辐射现象。在实验结果中，有以下几点需要强调。首次成功地观测到了PXR的二维角分布。结果表明，在分布的中心点没有我们的非相干模型所期望的倾斜，但绝对强度明显高于任何理论计算。在电子能量为450和200mev时，通道效应很小。当我们增加放置在电子束中的单晶箔的数量时，观察到x射线强度的迅速增加。特别地，用倾斜的多层箔在布拉格角探测到的X射线呈二次增长。这里发现的最后一种现象可能用于研制强单色x射线源。x射线强度的进一步增加是预期的特殊安排，其中电子穿过晶体多箔多次。

Various types of coherent x radiations from periaodic materials have benn known ; Parametric X-ray (PXR) , Channeling radiation, Resonant Transition Radiation, and have been studied in the former Soviet Union and other places. The present reasearch project have succeeded in accumulating systematic data which may enable us to understand the heretofore separately described radaiation phenomena in a more consistent way by making measurements under the conditions where two radiation phenomena can take place at the same time. Among the experimental consequences, the following points are to be underlined.1. The two dimentional angular distribution of PXR was successfully observed for the first time. The results indicated that there is no dip at the central point of the distribution which is expected by our Incoherent Model but that the absolute intensity is appreciably higher than any theoretical calculation.2. The effect of channeling is small at the electron energies 450 and 200MeV.3. A rapid increase of x-ray intensity was observed when we increase the number of monocrystalline foils placed in an electron beam. In particular, a quadratic increase was observed for the X rays detected at the Bragg angle by using inclined multi foils.The last phenomena found here may possibly used for developing an intense monochromaticd x-ray source. Further increase of X-ray intensity is expected for a special arrangement in which the electrons traversescrystalline multifoils many times.