The invention relates to a collimator electrode, comprising an electrode body (81) that is provided with a central electrode aperture (82), wherein the electrode body defines an electrode height between two opposite main surfaces, and wherein the electrode body accommodates a cooling conduit (105) inside the electrode body for transferring a cooling liquid (102). The electrode body preferably has a disk shape or an oblate ring shape.The invention further relates to a collimator electrode stack for use in a charged particle beam generator, comprising a first collimator electrode and a second collimator electrode that are each provided with a cooling conduit (105) for transferring the cooling liquid (102), and a connecting conduit (110) for a liquid connection between the cooling conduits of the first and second collimator electrodes.