X1-Experiment : Parametric X-radiation (PXR)



   Smith Purcell



The angular distribution and energy width of PXR from a silicon single crystal has been studied at a beam energy of 855 MeV. The measurements of the angular distributions and photon fluxes are in accord with the Feranchuk-Ivashin theory of PXR production [3]. An intrinsic energy width of less than 3 eV has been measured for the (111) reflex with a critical absorption technique at the K-absorption edge of titanium at 4.96 keV [4].

The energy width is limited by geometrical line broadening effects which can be optimized to reach the ultimate limit given by the finite length of the wave train. Experimental and Theoretical studies of the line shape have been performed in backward direction in which geometrical line broading effects could be kept to a minimum. A silicon single crystal served as monochromator. Line shapes have been measured for the (111) up to the (555) reflection showing that the natural linewidth th the order of a few meV is significantly broaded due to small angle scattering of the electrons in crystal [10].
PXR Production Mechanism

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