Results 1 - 10 of 1742
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[en] The features of quasicharacteristic radiation based on direct radiative transitions between the above-barrier energy levels corresponding to the dynamic diffraction of electrons and the levels of channeled electron motion in crystals are considered. The structure and features of such radiative transitions are studied using diffraction in the Laue and Bragg geometry. The main advantages of these transitions in relation to channeling are associated with a high probability of excitation of the diffraction state, low scattering and deceleration of moving particles, long duration of the orientational (i.e., not chaotic, related to certain planes) motion regime, and large corresponding matrix element of the dipole momentum of the radiative transition. It is shown that the radiation based on these transitions can display a large integral and spectral intensity and can be implemented at a lower particle energy than the traditionally considered quasicharacteristic radiation between channeling levels.
[en] The angular distributions of fast charged particles passing through oriented crystals are calculated. It is shown that the distribution in the phase space may be restored from the angular distribution with a large degree of accuracy. It is shown that the effect of radiation beam self-focusing can occur in q number of cases
[en] The origin of electron channelling patterns (ECPs) is briefly described. A method for generating selected area channelling patterns (SACPs) in a SEM is discussed. A detailed setting-up procedure for obtaining SACPs (down to about 5 um across) on a production SEM, the Cambridge Stereoscan 250 Mk 3, is given. The types of information that can be obtained from SACPs are also discussed
[en] Experiments have been performed at the Mainz Microtron MAMI to explore the radiation emission from a 4-period epitaxially grown strained layer Si1-χGeχ undulator with a period length λu= 9.9 μm. Electron energies of 270 and 855 MeV have been chosen. In comparison with a flat silicon reference crystal, a broad excess yield around photon energies of 0.069 and 0.637 MeV, respectively, has been observed for channeling at the undulating (110) planes. The results are discussed within the framework of the classical undulator theory. (Author)
[en] The spontaneous radiation of electrons in planar and axial channeling has been investigated theoretically in crystals with a superlattice under resonance conditions when the energy difference of two levels of the transverse motion in the averaged potential of the channel is approximately equal to a multiple of 2πhc/l, where l is the period of the superlattice along the channel axis. It is shown that the total energy levels of the electrons are split under the action of the spatially periodic perturbation. This changes the spectral and angular characteristics of the radiation substantially. In particular, resonance splitting of individual bands of the quasicharacteristic radiation is predicted. The magnitude of this splitting is estimated. It is established that there is no observable splitting in the channeling of positrons