Monochromatic coherent transition and diffraction radiation from a relativistic electron bunch train

Abstract

Electron beams of most accelerators have a bunched structure and are synchronized with the accelerating RF field. Due to modulation of the electron beam with frequency ν RF one can expect to observe resonances with frequencies ν k=k⋅ ν RF in radiation spectrum generated via any spontaneous emission mechanism (k is an integer and the resonance order). In this paper we present the results of spectral measurements of coherent transition radiation (CTR) generated by an electron bunch train from the Tomsk microtron with ν RF=2.63GHz in the spectral frequency range from 8 to 35 GHz. We also measured the spectrum of coherent diffraction radiation and demonstrated that the observed spectra in both cases consist of monochromatic lines. For spectral measurements the Martin-Puplett interferometer with spectral resolution of 800 MHz (FWMH) was employed. Using a waveguide frequency cut-off we were able to exclude several spectral lines to observe higher resonance orders of up to k =7.

FLAP Collaboration: Tasks and Perspectives. Study of Fundamentals and New Applications of Controllable Generation of Electromagnetic Radiation by Relativistic Electrons Using Functional Materials

“…This regime was observed at the microtron (6.2 MeV) of the Tomsk Polytechnic University (see Fig. 4) [13,14] using coherent transition radiation. A long bunch and low electron energy, however, prevented from reaching THz frequencies.…”

Ultra-monochromatic far-infrared Cherenkov diffraction radiation in a super-radiant regime

“…Accelerator facility. A 6.1 MeV electron microtron was used for the experiment 22,23 . The purpose of this machine is to provide a test bench for experiments related to the interaction of relativistic electrons with matter.…”

“…Assuming a train moving in the vicinity of and parallel to an interface with known dielectric properties as is shown in Fig. 1 , a general expression for radiation intensity is 21 , 22 where N e is the number of particles in a single bunch, ω = 2πc/λ is the photon frequency, f b is the bunch sequence frequency, σ is the rms longitudinal beam size, dW e / dω is the spectrum generated by a single particle (for calculations we used the model derived by Konkov and Shevelev 24 , see “ Methods ”).…”

“…The train form factor, G train , is defined as a superposition of the radiation fields generated by a series of consecutive bunches. Assuming that each bunch out of N b bunches generates the same amplitude, the train form factor is 22 , 23 …”

“…For a Gaussian profile The train form factor, G train , is defined as a superposition of the radiation fields generated by a series of consecutive bunches. Assuming that each bunch out of N b bunches generates the same amplitude, the train form factor is 22,23 As a target we considered a triangular Teflon prism. The radiation generated inside the prism, propagates towards the outer interface, and refracts out towards the observation point (see Fig.…”