A Rotatable Cold Cathode Penning ion Source

A rotatable cold cathode Penning ion source has been designed and is now operating in the Oak Ridge Isochronous Cyclotron (ORIC). Previous sources for positive heavy ions have been severely limited in life-time by cathode sputtering and buildup of sputtered cathode material. The new ion source extends the cathode lifetime by a factor of ~ 6. The source cathodes are discs of tantalum, 7/8 in. in diameter and 3/8 in. thick. Upon completion of an ion source "burn" at one position on the circular edge of the cathode discs, each disc is rotated to an unused position for the next "burn." Provision exists for continuous rotation of the cathodes. The plasma collimating holes, where the sputtered cathode tantalum is deposited, also are on discs with six possible positions. The new source has resulted in increased accelerated beam currents and greater stability for heavy ions. The source has also been used to produce light ion beams (H, D, α) over a wide range of intensities.