Separating the Penning and Analyzing Fields in the Isis H-Ion Source

The development of H-ion sources with performances exceeding those achieved today is a key requirement for the next generation of high power proton accelerators. The ion source development program at ISIS is now well established. To allow different ion source designs to be fully tested, the ability to vary the Penning field is required. Until now the Penning field has been generated by the same magnetic circuit that creates the analyzing field, giving no practical way of altering the Penning field alone. This paper describes the infrastructure changes required to allow the Penning field to be independently varied. The effect the Penning field has on beam current, emittance and discharge stability are discussed.