Transition radiation as a source of quasi-monochromatic X-rays

The transition radiation (TR) from ultrarelativistic particles is considere d. It is shown that performing collimation of the TR from the periodic N-fo il stack (parameters of which are selected in a appropriate manner) one obt ains the spectrum of the TR which has a form of a peak position of which om ega(1) depends on the plasma frequency and the thickness of the radiator fo ils. The height and width of the peak depend on the collimation angle theta (c). The height of the peak for given theta(c) is proportional to N. Select ing parameters, one can have the source of X-rays of desired frequency with rather good monochromaticity. Relation with the undulator radiation is dis cussed. (C) 2000 Elsevier Science B.V. All rights reserved.