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

Abstract

The development of nonintercepting (NI) diagnostics for beam size continues to be of interest in the accelerator community. In the three rings of the Advanced Photon Source (APS) facility, we use optical and x-ray synchrotron radiation generated as the electron beam transits the dipole magnetic fields as an NI mechanism to image the beam during top-up operations. However, in the straight transport lines an alternate beam-size measurement method is needed. Optical diffraction radiation (ODR) is under investigation to monitor 7-GeV beam size and trajectory in the booster synchrotron-tostorage ring (BTS) beamline during top-up operations. We have performed our initial measurements with an Aluminum 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.

FAST Low-Energy Beamline Studies: Toward High-Peak 5D Brightness Beams for FAST-GREENS

“…The electron beam bunch length was also measured after the compressor using a streak camera setup at X121. This measurement used an OTR screen and used the synchroscan streak camera method established in numerous studies (e.g., in [19]) to characterize the pulse length. Note that the beam conditions were different (no CC2 and different laser pulse on the cathode for these measurements) so a direct comparison cannot be performed.…”

“…Still, considering the parameters fitted from the current experimental setup, these measurements yielded comparable results to the GPT simulations, after factoring in a resolution term due to the height of the collimating slit which sets the spot vertical limit in focus mode for the static spread function before the deflecting voltage is on. There is also a chromatic dispersion term to consider and better results could also be obtained by using a bandpass filter to minimize dispersion effects in the transport as discussed in [19]. See Figure 3 for details.…”

Coherent Optical Transition Radiation Imaging for Laser-Driven Plasma Accelerator Electron-Beam Diagnostics

“…The modeling of the OTR point spread function (PSF) [8][9][10][11][12] used in beam-size imaging and the OTR angular distribution [6,7,13] have been described previously. We will report the results of our modeling in the next section.…”

“…Optical transition radiation is emitted at the boundary of two media when relativistic charged particles induce currents in the media [4][5][6][7]. Both forward and backward OTR are generated as schematically shown in Fig.…”

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.…”