The Momentatron is a device developed to measure the intrinsic transverse momentum distribution of an electron beam emitted from a photocathode material.  

The cathode sample is mounted in an electrically isolated holder and floated at 10kV.  Electrons are emitted from a small laser-illuminated spot from a UV monochromator on the cathode sample and accelerated through a grounded mesh grid.  They then then impact a microchannel plate electron multiplier coupled to a phosphor screen  The resulting image is read out using a 16-bit high resolution CCD detector.