Undulator-type radiation of bunched charged particles in self-wakefield.pdfVIP

UNDULATOR-TYPE RADIATION OF BUNCHED CHARGED PARTICLES IN SELF-WAKEFIELD * Anatoliy Opanasenko** NSC KIPT, Akademicheskaya St. 1, Kharkov, 61108, Ukraine Radiation appearing when relativistic charged particles moves along a periodic structure without external fields is investigated. It is shown that nonsynchronous spatial harmonics of wakefields excited by bunched charged particles can give rise to the particle oscillatory motion that consequently generates the undulator-type radiation (UR). A theory of the undulator-type radiation emitted by ultrarelativistic charged particles in the self-wakefields is given. An analytical expression for the spontaneous UR power of the ultrarelativistic monochromatic charged bunch moving in a weakly corrugated axially-symmetrical waveguide is derived by the perturbation method. The parameter region, a particle number and particle energies at which the spontaneous UR power exceeds the wakefield power is analyzed. 1. As is known, a charged particle bunch moving with a constant velocity along a periodic structure emits the Cherenkov-type radiation (or the diffraction radiation) [1]. The fields of this radiation called wakefields can be expressed as a spatial harmonic series according to the Floquet’s theorem. Action of the synchronous spatial harmonics of the wakefield on the particles results in energy losses associated with the Cherenkov-type radiation. As is well known, the nonsynchronous spatial harmonics do not contribute to an energy change of a beam on the average over the structure period D. However under certain conditions, the nonsynchronous spatial harmonics give rise to the oscillatory motion of the particles with a time period equal to the flight time of the structure period. That, consequently, can provide the generation of the undulator-type radiation. This radiation is the subject of discussion in this article. 2. At the beginning we will consider the radiation of a self-oscillating point c