Abstract

Takagi's theory is used to calculate the propagation of X-rays in perfect and nearly perfect crystals. In the general case, the equations have to be solved on a computer. The principle of the calculation is given. It has been applied to the case where an incident plane wave is collimated by a slit. The separation of wavefields is observed, each presenting a fine structure shown to be due to the diffraction by the slit. The same calculation is extended to a crystal submitted to a thermal gradient.The propagation and the intensities of wavefields are in good agreement with the predictions of Penning and Polder.