Diffraction radiation diagnostics for moderate to high energy charged particle beams

Diffraction radiation (DR) is produced when a charged particle passes throu gh an aperture or near a discontinuity in the media in which it is travelin g. DR is closely related to transition radiation (TR), which is produced wh en a charged particle traverses the boundary between media with different d ielectric constants. In contrast to TR, which is now extensively used for b eam diagnostic purposes, the potential of DR as a non-interceptive, multi-p arameter beam diagnostic remains largely undeveloped. For diagnostic measur ements it is useful to observe backward reflected DR from a circular apertu re or slit inclined with respect to the beam velocity. However, up to now, well-founded equations for the spectral-angular intensities of backward DR from such apertures have not been available. We present a new derivation of the spectral-angular intensity of backward DR produced from an inclined sl it for two orientations of the slit axis, i.e., perpendicular and parallel to the plane of incidence. Our mathematical approach is generally applicabl e to any geometry and simpler than the Wiener Hopf method previously used t o calculate DR from single edges. Our results for the slit are applied to t he measurement of orthogonal beam size and divergence components. We discus s the problem of separating the simultaneous effects of these beam paramete rs on the angular distribution of DR and provide solutions to this difficul ty. These include use of the horizontal and vertical polarization component s of the radiation from a single slit and interferences from two inclined s lits. Examples of DR diagnostics for a 500 MeV beam are presented and the c urrent limitations of the technique are discussed. (C) 2001 Elsevier Scienc e B.V. All rights reserved.