Abstract: An ion source for ionizing a source gas includes an arc chamber housing defining an arc chamber to receive the source gas. The arc chamber has a first region and a second region. An electron emitting device is disposed in the arc chamber adjacent the first region and is adapted to emit electrons into the first and the second regions to ionize the source gas. An electron returning device is disposed in the arc chamber adjacent the second region and is adapted to return at least some of the electrons emitted from the electron emitting device into the second region. A gas supply system is adapted to direct the source gas into the first region and into the second region. According to some embodiments, the gas supply system is adapted to provide a greater mass flow rate of the source gas into the first and second regions than is provided into other regions of the arc chamber.