Parametric X-radiation and diffracted transition radiation at REFER electron ring

X-radiation generated by electrons passing through silicon crystal targets of different thicknesses (49.2, 164.4 and 1644.0 mum) and accurately aligne d 10 and 100 layers of 16.4-mum thick monocrystalline silicon foils was mea sured at the 150-MeV REFER electron ring. We observed a clear intensity enh ancement, when compared to the intensity of parametric radiation from singl e crystal targets of equivalent thickness at 14.4 and 28.8 keV, believed to be the diffraction of transition radiation from individual surfaces of the foils off the crystallographic planes. We have used an amorphous molybdenu m foil on the same target holder to normalize the different spectra to the number of electrons. We found that this combination results in a peak at 12 .5 keV and a second harmonic whose amplitudes depend slowly on the tilt ang le. We also found that the measured parametric radiation intensity from the ((1) over bar 3 3) planes is much higher than that of the (0 1 1) plane wh ile theoretically it should be lower. Diffraction of coherent Bremsstrahlun g (CB) from the (0 1 1) planes off the (1 3 3) planes might be the reason f or this increase in intensity. (C) 2001 Elsevier Science B.V. All rights re served.