An arc chamber assembly for an ion source comprising a housing having a base and at least one pair of side walls extending upwardly from opposite sides of the base to define an arc chamber, the base having a plurality of channels extending to each sidewall; an inlet port connected to the base for delivering a flow of gas into the channels; a bottom liner having at least one pair of notches in each of two opposite side edges thereof and disposed in the housing in spaced parallel relation to the base and opposite the channels for conducting a flow of gas from the inlet port towards the sidewalls, each notch being in communication with a respective channel of the plurality of channels to pass gas upwardly into the arc chamber; and a pair of side liners, each side liner being disposed in the housing in spaced parallel relation to a respective one of the side walls for conducting a flow of gas between the base and the bottom liner, each side liner having at least one pair of slots to horizontally pass gas into the arc chamber.