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The spectral intensity of gamma radiation generated by 855 MeV electrons under the conditions of channeling and volume reflection in silicon and germanium bent crystals was measured at the Mainz Mikrotron MAMI. Both crystals were 15 µm thick and bent along (111) crystal planes. Both crystals were mounted on piezo activated dynamical holder, which allowed us to change the crystal curvature online with neither vacuum braking nor any modification of the setup.
The radiation spectra were recorded for different crystal alignment, namely for channeling, volume reflection, random and “anti volume reflection”, i.e. opposite to the volume reflection direction. Moreover, this experiment was repeated for 4 different crystal curvatures for Si crystal as well as 3 curvatures for Ge. All of the experimental results were reproduced by our simulations using the CRYSTALRAD simulation code.
Radiation under the volume reflection conditions demonstrates lower but comparable radiation intensity w.r.t. the channeling case. At the same time volume reflection possesses considerably higher angular acceptance than channeling. Moreover, the volume reflection angular acceptance as well as the radiation intensity can be balanced by changing of the crystal curvature. The radiation intensity in the Ge bent crystal is roughly twice higher than in the silicon one at the equal conditions.