In a cleaning process for an ion source chamber, an electrode positioned outside of the ion source chamber includes a suppression plug. When the cleaning gas is introduced intothe source chamber, the suppression plug may engage an extraction aperture of the source chamber to adjust the gas pressure within the chamber to enhance chamber cleaning via. plasma-enhanced chemical reaction. The gas conductance between the source chamber aperture and the suppression plug can be adjusted during the cleaning process to provide optimum cleaning conditions and to exhaust unwanted deposits.