A gas distributor is easily removable and replaceable in an ion source. The ion source has a removable anode assembly, including the gas distributor, that is separable and from a base assembly to allow for ease of servicing consumable components of the anode assembly. The gas distributor may be mounted to a thermal control plate in the anode assembly with several set screws. The gas distributor may be disk-shaped with counterbores in a surface to recess the heads of the set screws. Alternately, the gas distributor may be clamped or held in place by other structures or components of the ion source.