451 ISSN 0021-3640, JETP Letters, 2018, Vol. 107, No. 8, pp. 451–454. © Pleiades Publishing, Inc., 2018. Original Russian Text © A.G. Afonin, E.V. Barnov, G.I. Britvich, A.P. Bugorskii, A.A. Durum, M.Yu. Kostin, I.S. Lobanov, A.V. Lutchev, Yu.E. Sandomirskii, V.I. Pitalev, I.V. Poluektov, S.F. Reshetnikov, Yu.A. Chesnokov, P.N. Chirkov, A.A. Yanovich, 2018, published in Pis’ma v Zhurnal Eksperimental’noi i Teoreticheskoi Fiziki, 2018, Vol. 107, No. 8, pp. 477–480. Emission of Photons at the Interaction of a High-Energy Electron Beam with a Sequence of Bent Single Crystals A. G. Afonin a , E. V. Barnov a , G. I. Britvich a , A. P. Bugorskii a , A. A. Durum a , M. Yu. Kostin a , I. S. Lobanov a , A. V. Lutchev a , Yu. E. Sandomirskii a , V. I. Pitalev a , I. V. Poluektov a , S. F. Reshetnikov a , Yu. A. Chesnokov a, *, P. N. Chirkov a , and A. A. Yanovich a a Institute for High Energy Physics, National Research Center Kurchatov Institute, Protvino, Moscow region, 142281 Russia *e-mail: chesnokov@ihep.ru Received February 6, 2018 A radiation source based on the emission of electrons and positrons moving in a short bent crystal has been recently discovered. The emission of particles is due to oscillations of their trajectories near the point of reflections, where trajectories approach a tangent to bent atomic planes. In the experiment performed with the secondary electron beam of the U70 accelerator, it has been shown that the emission intensity can be increased by using a sequence of oriented bent crystals. Passing through six 2.5-mm-long silicon crystals, 7-GeV electrons lose on average 2.0 GeV on emission. This value is several times larger than that in an amor- phous medium. Thus, an intense source of radiation has been demonstrated with prospects of application at accelerators. DOI: 10.1134/S0021364018080076 A new source of photons based on the motion of electrons and positrons in a slightly bent crystal was predicted in [1]. Undergoing bulk reflection, particles intersect bent crystallographic planes. As a result, their transverse velocity aperiodically oscillates and a new type of intense coherent radiation appears. Because of a large Lorentz factor γ of light leptons, this radiation is more intense than that from other parti- cles. Figure 1а illustrates the process of bulk reflection of an ultrarelativistic particle in a system of bent crys- tallographic planes. Near the point of contact, the transverse velocity of the particle approaches zero and the particle is reflected (undergoes coherent scatter- ing). In addition, moving in this region, the particle intersects a number of crystallographic planes at small angles; as a result, its velocity oscillates aperiodically with a significant amplitude (Fig. 1b). Such a motion of electrons and positrons undergoing bulk reflection is accompanied by the emission of intense gamma radiation. The first experiment [2] at the U70 acceler- ator and subsequent experiments at CERN Super Pro- OPTICS AND LASER PHYSICS Fig. 1. (а) Motion of a particle in a crystal at volume reflection. (b) Time dependence of the transverse velocity of the particle; the time corresponds to the entry of the particle into the crystal. v (a) (b) = 0 t