Direct Observation of Incoherent Cherenkov Diffraction Radiation in the Visible Range

Abstract

We report on the observation of incoherent Cherenkov radiation emitted by a 5.3 GeV positron beam circulating in the Cornell electron-positron storage ring as the beam passes in the close vicinity of the surface of a fused silica radiator (i.e., at a distance larger than 0.8 mm). The shape of the radiator was designed in order to send the Cherenkov photons towards the detector, consisting of a compact optical system equipped with an intensified camera. The optical system allows both the measurements of 2D images and angular distribution including polarization study. The corresponding light intensity has been measured as a function of the distance between the beam and the surface of the radiator and has shown a good agreement with theoretical predictions. For highly relativistic particles, a large amount of incoherent radiation is produced in a wide spectral range. A light yield of 0.8×10^{-3} photon per particle per turn has been measured at a wavelength of 600±10 nm in a 2 cm long radiator and for an impact parameter of 1 mm. This will find applications in accelerators as noninvasive beam diagnostics for both leptons and hadrons.

Radiation of a charge moving along the boundary of dielectric prism

“…In the far-field (Fraunhofer) area, the field can be calculated using formulas (5). One can show that for the case of the prism these formulas can be written in the following form:…”

“…The radiation of charged particles in the presence of dielectric objects with a complicated form is of essential interest for applications in accelerator and beam physics [1][2][3][4][5]. As an example, one can point out a new method of noninvasive bunch diagnostics where Cherenkov radiation (frequently also referred to as Cherenkov-diffraction radiation) outside a dielectric object should be registered [2,5]. As a rule, the complex geometry of the object does not allow obtaining the rigorous solution of the problem.…”

“…This object is actively used not only in optics but also in accelerator and beam physics. For instance, such a target is offered to be applied in the new noninvasive method of bunch diagnostics [2,5]. Note that earlier we have studied the charge radiation in the presence of such an object [7] but only in the region of ray-optics applicability.…”

Noninvasive bunch length measurements exploiting Cherenkov diffraction radiation

“…The emission of Cherenkov radiation by charged particles travelling through matter was discovered in 1934 [1,2] and, due to its fascinating properties (i.e., the emission of a large number of photons in a narrow and well-defined solid angle), has found numerous applications in many fields including astrophysics [3], and particle detection and identification [4,5]. Recently, a first experimental study was performed to demonstrate the potential of noninvasive beam diagnostic techniques based on the detection of incoherent Cherenkov diffraction radiation (ChDR) [6]. The latter refers to the emission of Cherenkov radiation by charged particles traveling not inside, but in the vicinity of a dielectric material.…”

Beam-based sub-THz source at the CERN linac electron accelerator for research facility

“…This is the goal for the next future. Meanwhile, different kind of sources have been explored based on different mechanisms of radiation, as coherent transition radiation (CTR), coherent diffraction radiation (CDR) and coherent Cherenkov-diffraction radiation (CChDR) [29][30][31]. The experimental comparison among different mechanisms in terms of peak power and energy per pulse has been made, showing that CChDR is more promising than the other mechanisms.…”