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We describe the application of a novel, fast optical imaging camera, TimepixCam, to molecular photoionization experiments using the velocity map imaging technique at a free-electron laser.

TimepixCam is a 256×256 pixel CMOS camera that is able to detect and time-stamp ion hits with 20 ns timing resolution, thus making it possible to record ion momentum images for all fragment ions simultaneously and avoiding the need to gate the detector on a single fragment.

This allows recording significantly more data within a given amount of beamtime and is particularly useful for pump-probe experiments, where drifts, e.g., in the timing and pulse energy of the free-electron laser, severely limit the comparability of pump-probe scans for different fragments that are taken consecutively.

In principle, it should also allow applying ion-ion covariance or coincidence techniques to determine angular correlations between fragments.

Papers