Parametric X-ray radiation along relativistic electron velocity in asymmetric Laue geometry
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Parametric XRay Radiation along Relativistic Electron Velocity in Asymmetric Laue Geometry S. V. Blazhevicha and A. V. Noskovb, * a
Belgorod State University, Belgorod, 308015 Russia Belgorod University of Consumers’ Cooperation, Belgorod, 308023 Russia *email: [email protected]
b
Received May 14, 2009
Abstract—An analysis is presented of the parametric Xray radiation emitted by a relativistic electron at a small angle to its velocity as it passes through a singlecrystal plate in asymmetric Laue geometry (including symmetric geometry as a particular case). Expressions describing the spectralangular distributions of para metric Xray radiation, transition radiation, and their interference are obtained. The effect of asymmetry on the spectralangular distributions is examined. PACS numbers: 41.60.m, 41.75.Ht, 42.25.Fx DOI: 10.1134/S1063776109120012
1. INTRODUCTION When a fast charged particle passes through a per fect crystal, the virtual photons associated with its Coulomb field are scattered from a set of parallel atomic planes of the crystal, giving rise to parametric Xray radiation (PXR) [1–3]. For a relativistic parti cle, the PXR theory predicts emission not only in the Bragg direction, but also along the particle velocity (forward parametric Xray radiation, FPXR) [4–6]. The latter phenomenon is due to the contribution of dynamical diffraction effects to PXR. Experimental studies of FPXR were attempted in [7–11], but the first observation of FPXR was reported relatively recently in [10], where the contribution of transition radiation to the Xray background near the Bragg fre quency was suppressed by destructive interference between the transition radiation waves generated at the entrance and exit surfaces of the crystal plate. How ever, the presentation in [10] did not include any anal ysis of the narrow peak appearing in the transition radiation spectrum near the Bragg frequency because of dynamical effects [12], which could well be inter preted as an FPXR peak in an experimental study. In the experiment reported in [11], Xray radiation from relativistic electrons passing through a thick single crystal target was detected under FPXR generation conditions, but the desired reflex was barely observable against the background emission from electrons inter acting with parts of the experimental setup. Thus, the oretical characterization of FPXR and finding optimal conditions for observation of this dynamical effect remain challenging tasks. A detailed theoretical description of the dynamical phenomenon of FPXR and the accompanying back
ground of transition radiation in symmetric geometry was given in [13–15]. A theoretical description of PXR and transition radiation (TR) in asymmetric geometry was given in [16–18], and FPXR in Bragg geometry was analyzed in [19]. Those studies demonstrated a strong dependence of the spectralangular distribu tions associated with these radiation mechanisms on reflection asymmetry and revealed effects due to asymmetry. In this paper, we ana
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