DUOPLASMATRON SOURCE MODIFICATIONS FOR HE-3(+) OPERATION

A duoplasmatron ion source is used to produce 25 mA of He-3(+) with a pulse width of similar to 80 ms at 360 Hz for acceleration to 10.5 MeV . At this energy, He-3 striking water or carbon targets can produce sh ort lived isotopes of C-11, N-13, O-15, and F-18 for medical positron emission tomography (PET). A duoplasmatron ion source was chosen origi nally since it is capable of a sufficient singly charged helium beam w ith an acceptable gas consumption. Stable long-term operation of the s ource required a change in the filament material to molybdenum, and a careful understanding of the oxide filament conditioning, operation an d geometry. Other improvements, particularly in the electronics, were helpful to increasing the reliability. The source has operated for man y months at similar to 2.5% duty factor without significant problems a nd with good stability. We report here the effort that was done to mak e this source understandable and reliable.