Coherent X-ray radiation generated by a relativistic electron in an artificial periodic structure
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Coherent Xray Radiation Generated by a Relativistic Electron in an Artificial Periodic Structure S. V. Blazhevicha, I. V. Kolosovab, and A. V. Noskovb a
b
Belgorod State University, Belgorod, 308015 Russia Belgorod University of Consumer Cooperatives, Belgorod, 308023 Russia email: [email protected] Received January 26, 2011
Abstract—A theory of coherent Xray radiation from a relativistic electron crossing an artificial periodic lay ered structure in the Laue scattering geometry is constructed. The expressions describing the spectralangular radiation parameters are obtained. It is shown that the radiation yield in such a medium may substantially exceed the radiation yield in a crystal under analogous conditions. DOI: 10.1134/S1063776112020021
1. INTRODUCTION The emission of radiation from a relativistic parti cle in a periodic layered structure has been tradition ally considered in the Bragg scattering geometry for the case when reflecting layers are parallel to the input surface (i.e., for the case of symmetric reflection). Radiation in a periodic layered structure was usually considered as resonant transition radiation [1, 2]. In [3], radiation from a multilayer periodic structure was represented as the sum of diffracted transition radia tion (DTR) and parametric Xray radiation (PXR). In the above publications, radiation from a relativistic particle in a multilayer medium was considered in the Bragg scattering geometry for the particular case of symmetric reflection of the particle field relative to the target surface (for diffracting layers parallel to the tar get surface). In [3], radiation was analyzed analo gously to coherent radiation induced by a relativistic electron in a crystalline medium [4–7]. Here, we develop a dynamic theory of coherent radiation in an artificial periodic structure in the Laue scattering geometry for an arbitrary asymmetry of reflection of the electron field relative to the target sur face (i.e., for an arbitrary angle between the reflecting structure and the target surface). An important feature of the geometry considered here is that in contrast to the traditional Bragg scattering geometry [1–3], emit ted photons move forward and intersect the target. The possibility of changing the photon yield of coherent radiation in a crystal due to dynamic effects in radia tion (in particular, asymmetry in the field reflection relative to the target surface) has been demonstrated earlier [8–10]. The influence of the reflection asym metry on the radiation yield in a crystal is confirmed by the results of experiments in [11]. In [10], coherent Xray radiation in a direction close to that of the veloc ity of a relativistic electron crossing the crystal was
considered as the sum of the contributions of forward parametric Xray radiation (FPXRs) and transition radiation (TR) (Fig. 1).
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FPXR + TR ωV µ 2 k V
g
PXR + DTR µ kg
θ
ωV 2 + g V
θ'
δ θB
ψ0 ψg
L
n
Fig. 1. Geometry of emission: θ and θ' are angles of inci dence of radiation, θ
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