Generation of Short X-Ray Pulses Using Crab Cavities at the Advanced Photon Source

There is growing interest within the user community to utilize the pulsed nature of synchrotron radiation from storage ring sources. Conventional third-generation light sources can provide pulses on the order of 100 ps but typically cannot provide pulses of about 1 ps that some users now require to advance their research programs. However, it was recently proposed by A. Zholents et al. to use rf orbit deflection to generate sub-ps x-ray pulses [1]. In this scheme, two crab cavities are used to deliver a longitudinally dependent vertical kick to the beam, thus exciting longitudinally correlated vertical motion of the electrons. This makes it possible to spatially separate the radiation coming from different longitudinal parts of the beam. An optical slit can then be used to slice out a short part of the radiation pulse, or an asymmetrically cut crystal can be used to compress the radiation in time. In this paper we present a feasibility study of this method applied to the Advanced Photon Source (APS). We find that the pulse length can be decreased down to a 1 ps range using superconducting crab cavities.