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The TRIUMF accelerator routinely delivers up to 120 Â¿A of 500 MeV protons. For tests, 150 Â¿A have been extracted in a cw mode, 225 Â¿A equivalent in a 10% dutycycle pulsed mode. Longitudinal space-charge effects are observed at these higher currents. A lead target, used as a beam dump and thermal neutron source, is being upgraded to allow extracted currents up to 375 Â¿A cw. The reliability and performance of the cyclotron has significantly increased as the result of several recent developments. Improvements to the main magnet power supply (18,000 A) have resulted in a magnetic field stability better than Â±0.8 ppm for periods of 2 h. The effect on beam phase, instability and separated turn operation is presented. A Lamb-shift polarized H- source provides up to 300 nA extracted. An ECR proton source has been tested as a replacement for the duoplasmatron on the polarized source. A gain in current of order 5 is expected. To satisfy the long-term needs, work has begun on developing an intense optically pumped, polarized source with the aim of increasing the current by a factor of 100.
Date of Publication: Aug. 1983