"The ion source used for hydrogen and deuterium ions in the variable energy cyclotron at the University of Rochester is of the hooded arc type. For the past year it has been operating with a new feature which has greatly improved its performance. The new feature is a magnetic mirror built into the upper end of the arc hood by a simple insertion of a steel bearing ball 1/8" in diameter. The magnetic field gradient near the ball provides a magnetic mirror action on electrons moving up the arc channel toward the ball, reflecting may of them."