Production of positron beams with energies Ee+⩾0.2 GeV by 4.5 GeV electrons in amorphous and crystalline converters

Channeling of Positrons Through Periodically Bent Crystals: On the Feasibility of Crystalline Undulator and Gamma-Laser

“…It is important to note that the position of sharp undulator radiation peaks, their narrow widths, and the radiated intensity are, practically, insensitive to the choice of the approximation used to describe the interplanar potential. In addition, provided the first two conditions from (17) are fulfilled, these peaks are well separated (in the photon energy scale) from the peaks of the channeling radiation. Therefore, if one is only interested in the spectral distribution of the undulator radiation, one may disregard the channeling oscillations and to assume that the projectile moves along the centerline of the bent channel [1,2].…”

“…These are exactly the values for which we predicted the strong undulator effect. However, in these papers, where the authors mention all the conditions (17) and stress their importance, there is no proper reference to our works. Instead, our paper [2], labeled as Ref.…”

“…Hence, the reader can deduce that λ = v/f = 4.65 × 10 −2 cm, if taking the value v = 4.65 × 10 5 cm/s for the sound velocity in Si [104]. The values of ε, a and λ, together with the maximal gradient of the interplanar field (qU ′ max ) Si = 6.9 Gev/cm [61], allows one to calculate C = 2.65 × 10 −2 (see (17)), and, consequently, to estimate the dechanneling length L d (C) = 6.47 × 10 −2 cm. As a result, we find that the number of the undulator periods in the suggested system is N = 1.4, which is not at all N ≫ 1 as it is implied by the authors (this is explicitly accented by them in the remark in the line just below their equation (2) on page 62).…”

“…Below we present the results of numerical calculations of the parameters of the undulator (the first harmonic energy and the number of periods) and of the volume density n of the bunch particles needed to achieve G(ω) = 1. The calculations were performed for relativistic positrons, muons, protons and heavy ions and took into account all the conditions summarized in (17). The results presented correspond to the cases of the lowest values of n needed to ensure G(ω) = 1 and which, simultaneously, produce the largest available values of N.…”

Computer simulation of coherent interaction of charged particles and photons with crystalline solids at high energies

“…The similar simplified Monte Carlo simulation model was employed in [13,14]. The simulation procedure has been improved by taking into account the peculiarities of the emission angles of photons and electrons in case of coherent effects (see Eq.…”