Ultimately, the U of T Linac proved to be a footnote in the local history of particle physics. Much subsequent research has taken place as part of collaborative international projects at sites such as CERN in Switzerland, as well as the Fermi and Argonne National Laboratories in the United States.
Such participation began as high-energy particle physics gained momentum at the University of Toronto during the 1960s. For instance, in 1963, the University of Toronto helped to analyze data from the hydrogen bubble chamber at the newly installed 12.5 BeV proton accelerator at the Argonne National Laboratory at Lemont, Illinois.
Only a few artifacts survive to document this history of international collaboration. Three are shown here.
Prototype Light Guide of a Calorimeter for the Superconducting Super Collider (c. 1990)
An early prototype instrument designed for a massive American accelerator that was never completed.
This is a small-scale prototype of a liquid scintillator calorimeter designed in the early 1990s by the University of Toronto High Energy Physics Group for the Superconducting Super Collider (SSC) project. The SSC was planned for a site near Waxahachie, Texas. A liquid scintillator calorimeter is a particle detector that is used to characterize particles by measuring their energy. A liquid scintillator medium (in this case, an oil with sulfur dissolved in it) emits light when absorbing the energy of a charged particle. This light is converted into an electrical signal using a photomultiplier.
One disadvantage of this arrangement is that the scintillator medium gradually discolours with radiation exposure. This design placed the scintillator liquid in tubes so that it could be replaced periodically. This prototype was built to determine whether a signal could be obtained from a photomultiplier tube. This experiment was successful, and a larger prototype was constructed. However, the Superconducting Super Collider project was cancelled mid-construction in 1993.
Prototype Superconducting Radio Frequency Cavity (c. 2012)
Such cavities are essential to several recent high-energy physics experiments.
This RF cavity is a testing unit that was used around 2010 as part of developmental work towards the planned International Linear Collider (ILC). Made of niobium due to its low-temperature superconducting properties, such cavities are arranged in modular banks and immersed in liquid helium. High-energy electrical fields generated within the cavities accelerate a particle beam as it passes through the aperture of each chamber.
Development of the SRF chamber has taken place across many international laboratories. The U of T High Energy Physics Group, led by Professor Robert S. Orr, has developed widely used diagnostic tools to assist in the production of such chambers. Whether or not the ILC is built, such chambers are already in use in several recent accelerators, including the Canadian TRIUMF e-linac accelerator used for rare isotope production.
Prototype Strip Silicon Detector for Large Hadron Collider Upgrade (c. 2014)
This test piece is a tiny component of a complex sensor upgrade to the LHC.
This is an early prototype of a sensor component of the ATLAS detector upgrade that planned for vfor a major upgrade to the CERN LHC. It is part of a sensor arrangement designed to track particles released by high-energy collisions. The ATLAS development involves many international collaborators performing highly coordinated and scheduled tasks.
Upgrades to the LHC are based, in part, on the lifespans of sensor components subject to intense radiation from the particle beam. This prototype sensor is one example; All of its electronics are radiation hardened to maximize the 14-year lifespan of the sensor. The U of T High Energy Physics Group used this prototype as part of efforts to quantify the effects of radiation damage on sensor readings over time.
As of August 2025, the ATLAS ITk is scheduled for commissioning at the beginning of the first run of the high-luminosity upgrade in June of 2030.