title: Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy.
abstract: We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ∼10(6) photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >10(7) laser pulses, we also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments.
authors.affiliation: National Institute of Standards and Technology , Boulder, Colorado 80305, USA.
authors.forename: L
authors.initials: L
authors.lastname: Miaja-Avila
authors.affiliation: National Institute of Standards and Technology , Boulder, Colorado 80305, USA.
authors.forename: G C
authors.initials: GC
authors.lastname: O'Neil
authors.affiliation: Department of Chemical Physics, Lund University , Lund, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Uhlig
authors.affiliation: National Institute of Standards and Technology , Boulder, Colorado 80305, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: Cromer
authors.affiliation: National Institute of Standards and Technology , Boulder, Colorado 80305, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Dowell
authors.affiliation: JILA, University of Colorado , Boulder, Colorado 80309, USA.
authors.forename: R
authors.initials: R
authors.lastname: Jimenez
authors.affiliation: Los Alamos National Laboratory , Los Alamos, New Mexico 87545, USA.
authors.forename: A S
authors.initials: AS
authors.lastname: Hoover
authors.affiliation: National Institute of Standards and Technology , Boulder, Colorado 80305, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: Silverman
authors.affiliation: National Institute of Standards and Technology , Boulder, Colorado 80305, USA.
authors.forename: J N
authors.initials: JN
authors.lastname: Ullom