Effects of Mosaicity on Parametric X-Radiation Production

摘要

Previous measurements of parametric x-radiation (PXR) spectra from mosaicgraphite observed yields that greatly exceeded theoretical predictions. At the Bragg scattering condition, the interaction of relativistically charged particles and the atomic planes of a crystal produces scattering of virtual photons. This is known as PXR. The discrepancies between actual yields and theoretical predictions might possibly have been caused by the mosaic spread of the atomic planes of the crystal. Re-analysis of previous data has shown a miscalculation of the effective target thickness used in earlier work. There was also an error in the calculation of the theory that was used for comparison. Correction of the two errors brought the data and theory in closer agreement, but the mosaic spread does change the intensity of the PXR. In this thesis, three samples of thick mosaic carbon graphite crystal with differing mosaic spreads are compared to determine the effect of the mosaicity on PXR yield. By obtaining 'rocking curves' where the target orientation angle is changed with respect to the incident electron beam and observation angle, it was found that the mosaic spread does have an effect on the PXR spectral distribution. This effect is quite significant and can be seen when viewing the 'rocking curves' of the samples. As the mosaicity is increased, the angular distribution was spread out and the coherence condition was relaxed. jg.