Efficient extraction of H- ions from the TRIUMF cyclotron

The TRIUMF cyclotron can produce sufficient cw H- flux for change exchange injection into a 100 μA KAON factory but was designed for extraction by H- stripping. A program at TRIUMF has successfully demonstrated that direct extraction may be achieved by driving a radial resonance with rf electric field and by shielding the deflector septum with a narrow foil. An electrostatic deflector generated a 10 mm wide beam-free region between an extractable H- beam and the circulating beam at the location of a magnetic channel septum. The average beam power was low (450 W) but the peak intensity equivalent to 20 μA cw. An 85% transmission was measured, the remaining 15% being foil stripped into an existing beam line. Further improvements are expected, especially after the operation of an additional accelerating cavity (2x150 kV at 120 kW) presently under construction. The extracted H- ions are accumulated by extended multiturn change exchange injection into a dedicated ring. The results of recent dynamics simulations and equipment studies are presented