title: 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(-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.
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Holldack
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Ovsyannikov
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Kuske
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Müller
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Schälicke
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Scheer
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Gorgoi
authors.affiliation: 1] Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany [2] Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, D-14476 Potsdam, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Kühn
authors.affiliation: Institute of Physics of the University of Uppsala, Ångström-laboratoriet, Lägerhyddsvägen 1, 75120 Uppsala, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Leitner
authors.affiliation: Institute of Physics of the University of Uppsala, Ångström-laboratoriet, Lägerhyddsvägen 1, 75120 Uppsala, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Svensson
authors.affiliation: Institute of Physics of the University of Uppsala, Ångström-laboratoriet, Lägerhyddsvägen 1, 75120 Uppsala, Sweden.
authors.forename: N
authors.initials: N
authors.lastname: Mårtensson
authors.affiliation: 1] Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany [2] Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, D-14476 Potsdam, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Föhlisch