Speaker
Description
Cherenkov Diffraction Radiation (ChDR), generated when a relativistic charged particle travels parallel to and close to a dielectric boundary, has attracted considerable research interest. As a type of polarization radiation, ChDR originates from the time-dependent polarization induced in the medium. Its characteristics are strongly influenced by beam parameters such as beam size, position, trajectory, energy, and bunch length.
Coherent ChDR occurs when the radiation wavelength is comparable to or exceeds the longitudinal bunch size. Under these conditions, the electrons emit radiation almost in phase, resulting in constructive interference and a substantial enhancement of the emitted field. Consequently, the radiation intensity scales with the square of the bunch charge, producing a significant increase in photon output, providing an opportunity to generate intense electromagnetic radiation beams in THz and sub-THz frequency ranges.
When coherent ChDR is emitted by a periodic sequence of bunches, the radiation fields from successive bunches interfere constructively, producing additional amplification at discrete frequencies defined by the accelerating RF frequency. This operating regime, referred to as super-radiant emission [1], enables the generation of highly monochromatic radiation lines [2], whose intensity is determined by the single-bunch length and monochromaticity is defined the beam train length.
In this report, we describe the main properties of super-radiant ChDR in the millimeter-wavelength range, based on experimental studies performed at the MT-25 Microtron in Dubna. We discuss the spatial distribution of the radiation in the pre-wave zone and present an analysis of the polarization properties of super-radiant spectral lines at different frequencies. In addition, we consider the potential application of this phenomenon for longitudinal diagnostics of short charged-particle beams.
We thank FLAP Collaboration for in-kind contribution and discussing the results.
References
[1] A. Gover, et al., Rev. Mod. Phys. 90, 035002 (2018).
[2] P. Karataev, et al., Scientific Reports (2020) 10:20961