New 100 Hz repetition rate soft x-ray laser plasma source for ultrafast XANES applications

摘要

We present here a laser based time resolved ultrafast XANES beam line operating with the 100 Hz ALLS facility laser system (100 mJ and 35 fs at 800 nm wavelength). This system is based on a broadband soft x-ray plasma source, produced with a tantalum solid target, and a grazing flat field incidence grating designed to work in the 1-5 nm range. This femtosecond x-ray absorption spectroscopy experimental set up is used to study ultrafast phase transition in vanadium dioxide (VO_2). In this model system we are probing the electronic dynamics occurring during semiconductor to metal phase transition following excitation by a femtosecond laser pulse.