Ferran Boix Pamies

Topic

Radiation Damage in Materials for High-Power Accelerator Applications

Department of Physics and Astronomy

Date & location

• Tuesday, August 4, 2026
• 9:00 A.M.
• Virtual Defence

Examining Committee

Supervisory Committee

• Dr. Alexander Gottberg, Department of Physics and Astronomy, University of Victoria (Co-Supervisor)
• Dr. Tobias Junginger, Department of Physics and Astronomy, UVic (Co-Supervisor)
• Dr. Lori Walters, Advanced Reactor Materials & Chemistry Branch, Canadian Nuclear Laboratories (Outside Member)

External Examiner

• Dr. Yong Dai, Laboratory for Nuclear Materials, Paul Scherrer Institut, Switzerland

Chair of Oral Examination

• Dr. Stan Dosso, School of Earth and Ocean Sciences, UVic

Abstract

High-power accelerator facilities rely on beam-intercepting components that operate under intense fluxes of energetic particles, where radiation damage often becomes a primary factor limiting component lifetime. In these environments, irradiation produces atomic displacements and significant transmutation, leading to microstructural evolution and degradation of material properties. Understanding these effects is therefore essential for the reliable design and operation of present and future accelerator facilities.

This thesis investigates radiation damage in materials for high-power accelerator applications through a combination of theoretical analysis, development of experimental capability, and postirradiation characterization. Particular attention is given to accelerator-specific features of primary damage, including high-energy displacement cascades and transmutation-assisted defect evolution. Because predictive models remain subject to substantial uncertainty, experimental studies are required to establish reliable links between irradiation conditions, microstructure, and mechanical performance. In practice, however, such data are scarce because accelerator irradiations are difficult to access, beam time is limited, representative exposures often require long operating periods, and the resulting materials are challenging to handle and characterize because of induced radioactivity.

To address this limitation, this thesis combines two complementary experimental approaches at TRIUMF. First, a secondary irradiation capability was developed at the ISAC facility to enable controlled materials studies in parallel with accelerator operation. Second, service-exposed components were recovered and analyzed to obtain direct information from materials irradiated under real operating conditions. The secondary irradiation setup was extensively characterized, including estimates of damage, transmutation, and irradiation temperature, providing the basis for reliable experimentation.

The thesis presents microstructural and mechanical results for several accelerator-relevant materials, spanning both exploratory candidate materials and alloys already used in service. The equiatomic CrMnFeCoNi alloy is examined as a multicomponent system of interest for nuclear applications and is compared with cold-worked 316L stainless steel, showing broadly similar mechanical evolution under high-energy proton irradiation while also exhibiting earlier helium bubble formation. In aluminum alloys irradiated using the secondary irradiation setup, the observed softening is assessed against radiation-enhanced diffusion as a possible contributing mechanism, but the results indicate that irradiation temperature excursions are the more likely dominant cause. The analysis of service-exposed aluminum beam-window material further quantifies the helium bubble microstructure, revealing features including a bimodal size distribution consistent with accelerator environments with high helium production. Together, these results inform both the assessment of emerging material classes and the extension of service lifetimes in accelerator components already in use.

Overall, this work establishes a practical framework for secondary irradiation studies in a high-power accelerator environment and provides new experimental insight into radiation damage in materials for accelerator applications.