Abstract
We report on the observation of incoherent Cherenkov radiation emitted by a 5.3GeV 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 0.8mm). 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 2cm long radiator and for an impact parameter of 1mm. This will find applications in accelerators as noninvasive beam diagnostics for both leptons and hadrons.
Highlights
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
In this Letter, we refer to Cherenkov diffraction radiation (CDR) as the radiation emitted through the Cherenkov effect by particles traveling at a distance h from the surface of a dielectric, called the impact parameter
The light produced at the beginning and the end of the dielectric will change according to the distance between the particle and the surface of the material. We studied if this reduction in light intensity could come from vignetting effects due to the limited angular aperture of the optical system, but the diffusivity of the sandblasted surface is so large that we expect the light to be scattered up to a very broad angle, such that vignetting effects can be discarded
Summary
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). A light yield of 0.8 × 10−3 photon per particle per turn has been measured at a wavelength of 600 Æ 10 nm in a 2 cm long radiator and for an impact parameter of 1 mm.
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