Invited Paper-An H- Meson Facility

With the continuing evolution of the various types of meson factories the relative merits of the H- spiral ridge eyclotron appear to be improving. The development and design of such an accelerator has been led by UCLA. Recently three universities in British Columbia have combined personnel for a design study intended to lead to an H- meson facility called TRIUMF - Tri University Meson Facility). Among the various meson factories the H- facility is the only one which combines the following advantages: (1) large duty factor; (2) variable energy; (3) ease of beam extraction; (4) use of simultaneous beams; (5) high beam quality. Until recently it faced two problems: (a) uncertainty about field dissociation of negative ions; (b) lack of polarized ion sourees. Recent UCLA measurements of field dissociation and the advent of polarized H- ion sources and axial injection into cyclotrons remove these problems. The field dissociation measurements agree with Hiskes´ calculations and enable the use of higher fields than previously proposed for H- facilities. The TRIUMF project concerns a machine whose beam characteristics (maximum energy 500 MeV; maximum beam radius 271 inches; beam current 20-100 ¿A) were selected for optimum use in nuelear structure experiments, for low cost and for operating simplieity.