Efficient Capture in an Accumulator Ring of 20,000 Turns of Beam Injected from TRIUMF

For the TRIUMF KAON Factory a 450 MeV Accumulator ring is required to match the cw 100 μA beam from the isochronous cyclotron to the first acceleration stage, a 50 Hz 3 GeV Booster Synchrotron. H- ions would be charge exchange injected into the Accumulator through a 250 μ g cm-2 carbon foil. Approximately 2 A of protons would be accumulated over the 20 ms Booster period and transferred to the Booster in one turn. The first protons injected circulate for about 2×104 turns before extraction. If a substantial fraction of the circulating protons traverse the foil each turn, both the lifetime of the foil and the amount of beam lost would be unacceptable. The proposed acceptances of the Accumulator are 100 π μm horizontally, 30 π μm vertically and 7.6×10-2 eV-s longitudinally. These are much larger than the TRIUMF emittances of 2 πmmmrad in each transverse plane and 10-3 eV-s longitudinally. It is shown that with simultaneous stacking in the transverse and longitudinal acceptances it is possible to reduce the number of foil traversals per proton to an acceptable number ~ 100.