Cw monoenergetic Cs⁺ ion source by photoionization

Sequential absorption of two photons converts a Cs atomic beam into an ion beam with minimal change in the original thermal energy of the atoms. The random ion energy is measured to be <0.15 eV; consequently this ion beam is one of the "coldest" ion sources to date. Currently, the source brightness is 10 -4 A/cm2 sr eV and appears extendible to ∼5 A/cm 2 sr eV.