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At the heart of TRIUMF is the 500 MeV cyclotron that produces the primary proton beams. A large fraction of the TRIUMF program relies on these beams. These include the ISAC, the Centre for Molecular and Materials Science programs in μSR and β-NMR, and the Proton Treatment Facility. The operation of the main cyclotron has enabled TRIUMF to acquire the expertise to operate the three cyclotrons for MDS Nordion and the TR-13 cyclotron used to produce medical isotopes, and assist companies to exploit commercial opportunities for the sale of cyclotron and other accelerator technologies.
TRIUMF produces negatively charged hydrogen ions (H⁻: 1 proton, 2 electrons) from an ion source. The ions are transported through an evacuated electrostatic beam line containing elements to focus and steer the beam over its 60 m to the cyclotron. The 500 MeV (million electron volts) variable energy cyclotron accelerates these ions with a high frequency alternating electric field and uses a massive six-sector magnet to confine the beam in an outward spiral trajectory. Inserting a very thin graphite extraction foil strips, or removes, the electrons from the H⁻ ion while allowing the proton to pass through. The proton, because it is a positively charged particle, is deflected in the outward direction due to the magnetic field and is directed to a proton beam line.
The accelerating process takes approximately 0.3 ms before the proton achieves three-quarters the speed of light. The success of TRIUMF’s programs depends on the ability to deliver protons from the cyclotron reliably. Typically, the cyclotron, although over 30 years old, averages an uptime of greater than 90% (2000–2007), with the 15-year average just under 90%. Typically the beam is delivered for about 5,000 hours per year with one major (three month) and one minor (one month) maintenance periods. The cyclotron beam properties and capabilities have improved over the years as a result of systems upgrades. The fundamental infrastructure providing the magnetic and electrical fields and the RF resonators as well as the vacuum vessel remain sound and will serve TRIUMF for many more years. In order to maintain and improve the accelerator facilities, TRIUMF has an ongoing refurbishment program that replaces old and obsolete equipment. This strategy has allowed TRIUMF to maintain the availability of the extracted beam steady at more than 90%.
TRIUMF has four independent extraction probes with various sizes of foils to provide protons simultaneously to up to four beam lines. Because of the high energy of the proton beam, these beam lines use magnetic rather than electrostatic focusing and steering elements.
Beam line 1A (BL1A) can deliver 180 to 500 MeV protons to two target systems. The beam power ranges from 50 to 75 kW. The first