Investigation of the Structure of X–ray Interference Patterns Formed in Two–crystal Systems

The research divells upon the structures of the displacement fringes recorded from two–block crystalline systems with a non–diffracting zone, depending on both the thickness of the blocks and the width of the non–diffracting zone. The interference wave field of the X–ray narrow–gap double–block interferometer is theoretically investigated and the intensity distribution in the pattern obtained from it is determined. It is proved that the period of displacement fringes is directly proportional to the sum of block thickness. The relation between the period of the displacement fringes and the width of the non–diffracting zone has been revealed. It is shown that when the blocks are close enough to each other and their total thickness satisfies the condition, then the interference pattern of the displacement lines is observed, and with increasing width of the non–diffracting zone the period of the displacement fringes decreases. It is experimentally proved that at the minimum value of the total thickness or the maximum value of the width of the non–diffracting zone, for a given experiment, the periods of the mixing fringes become impossible to register: the period is very small, the resolution of the interference system is insufficient.