High repetition rate laser produced soft x-ray source for ultrafast x-ray absorption near edge structure measurements

Abstract

Recent progress in high intensity ultrafast laser systems provides the opportunity to produce laser plasma x-ray sources exhibiting broad spectrum and high average x-ray flux that are well adapted to x-ray absorption measurements. In this paper, the development of a laser based x-ray absorption near edge structure (XANES) beamline exhibiting high repetition rate by using the Advanced Laser Light Source (ALLS) facility 100 Hz laser system (100 mJ, 35 fs at 800 nm) is presented. This system is based on a broadband tantalum solid target soft x-ray source and a grazing incidence grating spectrometer in the 1-5 nm wavelength range. To demonstrate the high potential of this laser based XANES technique in condensed matter physics, material science, or biology, measurements realized with several samples are presented: VO2 vanadium L edge, Si3N4 nitrogen K edge, and BPDA/PPD polyimide carbon K edge. The characteristics of this laser based beamline are discussed in terms of brightness, signal to noise ratio, and compared to conventional synchrotron broadband x-ray sources which allow achieving similar measurements. Apart from the very compact size and the relative low cost, the main advantages of such a laser based soft x-ray source are the picosecond pulse duration and the perfect synchronization between this x-ray probe and a laser pulse excitation which open the way to the realization of time resolved x-ray absorption measurements with picosecond range time resolution to study the dynamics of ultrafast processes and phase transition.

High average power, highly brilliant laser-produced plasma source for soft X-ray spectroscopy

“…Therefore, new source schemes have emerged in the last couple of decades such as high harmonics generation 6,7 and emission from dense plasmas. [8][9][10] High harmonic generation produces ultra-short coherent radiation with sub fs pulse duration and photon energies up to 2 keV. 11 However, the average photon flux of these sources in the water window is rather low 6 and in the 1 keV region with a flux of 10 5 ph/s in 0.1% bandwidth 11 still far from a level suitable for fluorescence applications.…”

“…Both discharge-plasmas 12,13 as well as laser-produced plasmas (LPPs) 8,10,14,15 are already a) Present address: ELI-DC AISBL, 23 Rue Montoyer, 1000 Brussels, Belgium. used in various generation schemes.…”

Double conical crystal x-ray spectrometer for high resolution ultrafast x-ray absorption near-edge spectroscopy of Al K edge

“…11 This XAFS technique has already been developed by different groups which had designed various kinds of spectrometers adapted to a specific energy range dependent on the studied system. [12][13][14][15] Several experiments have been recently performed taking advantage of this technique for the study of different dynamical processes: laser-shock compression of materials, 16 chemical reactions, 17 and solid-liquidplasma phase transitions, [18][19][20] to cite only a few. In each case, the characteristics required for the spectrometer are fixed by the energy range of interest and the parameters of the laser facility, as for example the repetition rate.…”

More power to X‐rays: New developments in X‐ray spectroscopy

“…Other low repetition rate X-ray sources using ultrafast lasers to interact with the target material have been developed. Fourmaux et al reported recently on a new source working at a 100-Hz repetition rate with 30-fs duration and 100 mJ/pulse energy [50]. The emitted picosecond X-rays are in the soft X-ray region (100 to 1000 eV).…”