The development of a beam line using an RFQ and 3-Gap RF accelerators for high energy ion implanter

A high energy beam line system which comprises a radio frequency quadrupole (rfq) and 3-gap radio frequency (rf) accelerators is developed for high energy ion implanter. The rfq bunches and accelerates an ion beam to a fixed energy and the following 3-gap rf accelerators further accelerate or decelerate the ion beam to give continuous energy variation. This beam line scheme relaxes the requirement of an ion source and simplifies an implanter system because the high transmission rate of an ion beam in the rfq raises the utilization of the source beam and also the number of accelerating cavities can be reduced to 2/3 of that of a linac with 2-gap rf accelerators. This results in speed up in automation and improves in current intensity that would not be realizable in a conventional linac scheme. To prove those points, we have designed and constructed two units of the 3-gap rf accelerators, and they have been added to the existing rfq beam line. The output energy of the rfq is 0.92 MeV for B⁺. The 3-gap rf accelerator gives a singly charged ion beam the maximum energy gain of 216 kV at 5 kW of rf power. The for example, of this test stand beam line is from 0.62 to 1.3 MeV. The maximum beam current for B⁺ is approximately 1 mA