Velocity map imaging spectrometer with an electric-field-matched gas capillary

The design of a velocity map imaging (VMI) spectrometer is presented with a novel gas capillary integrated into the repeller electrode. The capillary is made of semiconductive lead glass, which replicates the electrostatic field of the VMI lenses. Thus, the target gas can be directly supplied to the interaction zone without degrading the VMI resolution. With this design, a high gas density and a large free aperture to focus long wavelength radiation into the VMI spectrometer have been achieved, which facilitates time resolved experiments with intense terahertz (THz)-light fields. The performance of the VMI spectrometer is demonstrated with momentum maps of electrons from multiphoton ionization of xenon and a first extreme ultraviolet-THz-streak experiment