PACS numbers: 41.60 (original) (raw)
Related papers
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2001
We discuss the radiation generated by positrons channeling in a crystalline undulator. The undulator is produced by periodically bending a single crystal with an amplitude much larger than the interplanar spacing. Different approaches for bending the crystal are described and the restrictions on the parameters of the bending are discussed. We also present numeric calculations of the spontaneous emitted radiation and estimate the conditions for stimulated emission. Our investigations show that the proposed mechanism could be an interesting source for high energy photons and is worth to be studied experimentally.
Radiation from relativistic positrons channeled in single crystals
Radiation Effects and Defects in Solids, 1982
... Printed in Great Britain RADIATION FROM RELATIVISTIC POSITRONS CHANNELED IN SINGLE CRYSTALS BISWANATH RATH and ANAND P. PATHAKf School of Physics, University of Hyderabad, Central University PO Hyderabad 500134, India ...
Photon emission by ultra-relativistic positrons in crystalline undulators: the high-energy regime
This paper discusses the undulator radiation emitted by high-energy positrons during planar channeling in periodically bent crystals. We demonstrate that the construction of the undulator for positrons with energies of 10 GeV and above is only possible if one takes into account the radiative energy losses. The frequency of the undulator radiation depends on the energy of the particle. Thus the decrease of the particle's energy during the passage of the crystal should result in the destruction of the undulator radiation regime. However, we demonstrate that it is possible to avoid the destructive influence of the radiative losses on the frequency of the undulator radiation by the appropriate variation of the shape of the crystal channels. We also discuss a method by which, to our mind, it would be possible to prepare the crystal with the desired properties of its channels.
Channeling of ultra-relativistic positrons in bent diamond crystals
Results of numerical simulations of channeling of ultra-relativistic positrons are reported for straight and uniformly bent diamond crystals. The projectile trajectories in a crystal are computed using a newly developed module of the MBN Explorer package which simulates classical trajectories in a crystalline medium by integrating the relativistic equations of motion with account for the interaction between the projectile and the crystal atoms. The Monte Carlo method is employed to sample the incoming positrons and to account for thermal vibrations of the crystal atoms. The channeling parameters and emission spectra of incident positrons with a projectile energy of 855 MeV along C(110) crystallographic planes are calculated for different bending radii of the crystal. Two features of the emission spectrum associated with positron oscillations in a channel and synchrotron radiation are studied as a function of crystal curvature.
Annihilation of relativistic positrons in single crystal with production of one photon
International Journal of Modern Physics A, 2015
The energy and momentum conservation laws prohibit positron–electron single-photon annihilation in vacuum. It is shown that the situation is different in a single crystal with one of the leptons (e.g. positron) moving in the channeling (or in the quasi-channeling) mode. The transverse motion of an oriented or channeled particle may sharply increase the probability of the single-photon annihilation process.
We discuss radiation generated by positrons channeling in a crystalline undulator. The undulator is produced by periodically bending a single crystal with an amplitude much larger than the interplanar spacing. Different approaches for bending the crystal are described and the restrictions on the parameters of the bending are established. We present the results of numeric calculations of the spectral distributions of the spontaneous emitted radiation and estimate the conditions for stimulated emission. Our investigations show that the proposed mechanism provides an efficient source for high energy photons, which is worth to be studied experimentally.
Orientation dependence of relativistic-positron annihilation in single crystals
Physics of Atomic Nuclei, 2016
An effect of the orientation dependence of the cross section for the single-photon annihilation of relativistic positrons with atomic electrons in a crystal is predicted. It is shown that the probability for the single-photon annihilation of a channeled positron in a crystal may be either suppressed in a crystal in relation to a homogeneous medium or, on the contrary, enhanced. The reason is that, depending on their incidence angle, the positrons may be either in the vicinity of ion planes of the crystal, where the electron density is higher, or far away from them, where the electron density is lower.
Gamma radiation production using channeled positron annihilation in crystals
Laser Physics Letters, 2015
The possibility of channeling low-energy relativistic positrons in some ionic crystals with axial symmetry is shown. The annihilation processes of positrons with medium electrons are investigated in detail. The lifetime of a positron in the regime of channeling is estimated; the existence of a long relaxation lifetime has been shown.
Journal of Modern Optics, 2009
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