The Heart of the Machine
On the campus of the University of British Columbia sits the world's largest cyclotron, the centerpiece of TRIUMF, Canada's national particle accelerator centre. The name stands for Tri-University Meson Facility, a nod to its 1968 founding by three universities: UBC, Simon Fraser University, and the University of Victoria. Today, the consortium includes 21 universities across the country.
The main cyclotron is a massive particle accelerator dominated by a 4,000-tonne magnet that measures 18 meters (59 feet) in diameter. This six-sector magnet guides negatively charged hydrogen ions (H⁻), a proton with two electrons, on an expanding spiral path. An electric field oscillating 23 million times per second gives the particles a "kick" of energy with every turn. In just 326 microseconds, the ions complete 1,500 orbits and reach their maximum speed of 224,000 kilometers per second, or 75% the speed of light.
To extract a beam for experiments, the accelerated H⁻ ions are passed through an incredibly thin carbon foil. This foil strips the two electrons from each ion, leaving a positively charged proton. The main magnetic field, which was containing the negative ions, now bends the positive protons in the opposite direction, sending them out of the cyclotron and down one of four beamlines. This method allows four separate beams of different energies and intensities to be extracted simultaneously for a wide range of experiments.
From Stardust to Medicine
The proton beams generated by the cyclotron are used for a research program including materials science, nuclear medicine, and fundamental physics. By smashing the proton beam into specially designed targets, scientists can produce rare, short-lived isotopes. These exotic particles allow researchers to study the processes of nucleosynthesis that occur inside stars and learn more about the origins of the elements.
TRIUMF is also a major producer of medical isotopes used for diagnostic imaging and therapy. The facility has developed technology for producing technetium-99m (Tc-99m), the most commonly used medical radioisotope in the world, which is used in tens of millions of diagnostic scans every year. The lab also produces isotopes for PET (Positron Emission Tomography) scans, such as fluorine-18 and carbon-11.
One of the beamlines was dedicated to a unique form of cancer treatment. From 1995 to 2017, the Proton Therapy facility, operated in partnership with BC Cancer, used a 70 MeV proton beam to treat ocular melanoma, a rare cancer of the eye. The precision of the proton beam allowed doctors to deliver a high dose of radiation directly to the tumor while minimizing damage to the optic nerve and other surrounding tissues, preserving vision in many cases.