Gridded Ionization Chambers for Time Resolved X-Ray Absorption Spectroscopy

Common parallel plate ionization chambers are bandwidth limited by the ion drift velocity. Therefore they can severely decrease the effective energy resolution of time resolved EXAFS or XANES spectra. We therefore developed gridded ionization chambers which suppress the ionic component of the ionization current, which results in a substantial improvement of its bandwidth of typically two orders of magnitude. The rise time of these chambers is measured to be less than 5.5 mu s. We have investigated the step response of parallel plate and gridded ionization chambers and discuss their influence on QEXAFS spectra.