Near-field imaging of optical diffraction radiation generated by a 7-GeV electron beam

Abstract

We report the first unambiguous demonstration of near-field imaging of optical diffraction radiation (ODR). The source of the ODR was an aluminum metal reflective surface with a 7-GeV electron beam passing nearby its single edge. Because of the high Lorentz factor involved, appreciable ODR is emitted at visible wavelengths even for impact parameters of 1 to 2 mm, so standard imaging techniques were employed. The experimental results are compared to a simple near-field model. We show that the ODR signals are sensitive to both beam size and position. Applications to multi-GeV beams in transport lines in the major synchrotron radiation facilities, x-ray free-electron lasers, energy recovering linacs, and the International Linear Collider are possible.

Imaging of optical diffraction radiation in pre-wave zone and spatial resolution of non-invasive beam size diagnostics

“…As follows from the given results (see the calculations [6] also), an ODR monitor allows the beam size to be determined only in the x-direction, which coincides with the target edge. In the perpendicular direction, even when the slit target is used, the measurements are complicated and the transverse size restoration (relative to the slit) is connected with the usage of a chosen model that limits the accuracy of the restoration procedure [10].…”

“…Here, as mentioned above, the calculated results for y = Àh are given (just along the edge target image). The other parameters (c = 13,700, k = 800 nm, H = 100 lm) have been chosen as identical to those in [6]. As follows from the figure, increasing the size of r x leads to the noticeable ''smoothing" of the dip in the x-component of the ODR intensity.…”

“…In recent work [6] a beam size along a single-edge of a ODR target was measured. The authors observed imaging of the ODR source induced by the electron beam with an 0168-583X/$ -see front matter Ó 2008 Elsevier B.V. All rights reserved.…”

Nonintercepting diagnostics for transverse beam parameters: From rings to ERLs

“…The downstream Cherenkov detector is used as a localized loss monitor to evaluate if beam halo particles are hitting the metal blade. Our initial results have been described elsewhere [9,10], but we show the reference OTR image of the 7-GeV electron beam in Fig. 7a.…”

Initial Imaging of 7-GeV Electron Beams with OTR/ODR Techniques at the APS

“…However, in the straight transport lines an alternate method to measure beam size is needed. Optical diffraction radiation (ODR) is under investigation [1][2][3][4][5][6] to monitor beam size and beam trajectory in the booster synchrotron-to-storage ring (BTS) beamline during top-up operations. We have performed our initial measurements with an Al blade/mirror that served as an optical transition radiation (OTR) monitor when fully inserted into the beam and as an ODR monitor when the beam passed near the edge.…”