Single bunch X-ray pulses on demand from a multi-bunch synchrotron radiation source

Abstract

Synchrotron radiation facilities routinely operate in a multi-bunch regime, but applications relying on time-of-flight schemes require single bunch operation. Here we show that pulse picking by resonant excitation in a storage ring creates in addition to the multi-bunch operation a distinct and separable single bunch soft X-ray source. It has variable polarization, a photon flux of up to 10 7 -10 9 ph s À 1 /0.1%BW at purity values of 10 4 -10 2 and a repetition rate of 1.25 MHz. The quasi-resonant excitation of incoherent betatron oscillations of electrons allows horizontal pulse separation at variable (also circular) polarization accessible for both, regular 30 ps pulses and ultrashort pulses of 2-3 ps duration. Combined with a new generation of angularly resolving electron spectrometers this creates unique opportunities for time-resolved photoemission studies as confirmed by time-of-flight spectra. Our pulse picking scheme is particularly suited for surface physics at diffraction-limited light sources promising ultimate spectral resolution.

Preparing the MAX IV storage rings for timing-based experiments

“…Pulse picking by resonant excitation (PPRE) [12] and pseudo single bunch (PSB) [13] are two methods that have been developed to enable storage rings to serve both high-intensity experiments and timing-based experiments simultaneously. In PPRE the emittance of one bunch in the train is increased by excitation and an aperture in the beamline ensures that only light from the excited bunch is accepted.…”

Electron spectroscopy using ultra brilliant synchrotron X-ray sources

“…Another possibility is to modify the path or the extension of the hybrid electron bunch in the storage ring. In this way it is possible to arrange a beamline in such a way that the X-rays from this bunch can be separated from the X-rays from the main bunch train [18,19]. A detector gating technique has also been developed where it possible to block the electrons originating from the general bunch from reaching the detector [20].…”

FEMTOSPEX Molecules and Surfaces: Electron spectroscopy setup for time-resolved laser-pump/ X-ray-probe experiments at BESSY II

“…We are currently exploring in in-house projects the possibility to use the PPRE bunch available during normal user operation (Holldack et al, 2014) for time-resolved studies with a temporal resolution of about 60ps as well as using a HHG source for femtosecond time-resolved experiments. The chamber is equipped with a VG Scienta ArTOF (Ovsyannikov et al, 2013) using a lens with an acceptance angle of 60 degrees.…”