A plasma processing apparatus and method are disclosed which improve the repeatability of various plasma processes. The actual implanted dose is a function of implant conditions, as well as various other parameters. This method used knowledge of current implant conditions, as well as information about historical data to improve repeatability. In one embodiment, a plasma is created, a first sensing system is used to monitor a composition of the plasma and a second sensing system is used to monitor a total number of ions implanted. Information about plasma composition and dose per pulse is used to control one or more operating parameters in the plasma chamber. In another embodiment, this information is combined with historical data to control one or more operating parameters in the plasma chamber. In another embodiment, the thickness of material on the walls is measured, and used to modify one or more operating parameters.