An RF driven H−source has been developed at LBL for use in the Superconducting Super Collider (SSC). To date, an H−current of ∼40 mA can be obtained from a 5.6‐cm‐diameter aperture with the source operated at a pressure of about 12 mTorr and 50 kW of RF power. Attempts have been made to enhance the H−beam current by introducing a small quantity of cesium vapor into the source chamber. It is found that the H−output current can be increased by a factor larger than three if some cesium is applied in the collar around the exit aperture.