Observation of bright monochromatic x rays generated by relativistic electrons passing through a multilayer mirror

We have observed the emission of 15 keV x rays produced by 500 MeV electron s passing through a x-ray multilayer mirror. The mirror consisted of 300 pa irs of W and B4C layers with layer spacing of 12.36 Angstrom and supported by a 100 mu m Si substrate. The x rays were emitted at the Bragg angle thet a(gamma) = 33.15 mrad with respect to the mirror surface and at the angle t heta(D) = 66.3 mrad with respect to the electron-beam direction. The spatia l distribution and the spectral angular dependence of the x rays were measu red and shown to be larger than the parametric x rays emitted from the Si s ubstrate. The value of the differential photon efficiency was estimated to be about 0.22 photons/electron/str. (C) 2000 American Institute of Physics. [S0003-6951(00)02724-8].