TRIUMF is a cyclotron facility on the UBC campus in Vancouver. In the summers of 2018 and 2020, I worked as the lead designer and coordinator for the development of an Isotope-Producing Cyclotron target. The target was designed to produce Actinium isotopes that could be used for targeted alpha therapy treatment of late-stage cancer patients.  In this position, I implemented ANSYS-CFX, Ansys-Mechanical and Solidworks FEA to design a manufacturable Thorium and Inconel nuclear target for proton bombardment on TRIUMFs cyclotron beamline. The goal of this project was to develop a design that could be implemented for long-term and scalable Actinium production. The design was optimized from previous iterations to improve the target manufacturability and cooling, and to reduce the radioactive waste and personal dose received during post-processing. 

To optimize the design, I iterated through hundreds of flow solver  simulations on  Ansys-CFX and stress simulations on Ansys-Mechanical to determine the best design for the target that produced minimal thermal stresses and waste. The previous design had a single-sided cooling water flow, which meant a reduced overall target cooling capacity. My design implemented a double-sided contact and improved surface pressure between the cover plates and the thorium target to cause a significant reduction in thermal load.  

The ANSYS model was developed through several rounds of mesh iterations until the element quality aspect ratio and skewness values were all in acceptable ranges, and further mesh refinement iterations did not change the resulting thermal loads. The model was developed using conservative assumptions for thermal contact resistance, ambient pressure and temperature, and material strength properties.

The power loading (shown above) was determined based on a calculation with the Stopping Power of Ions in Matter simulation solver, and the beam profile measurements from the cyclotron physics department. The power loading profile (single gaussian) was generated in Matlab and then imported into the ANSYS CFX model.  The resulting thermal loading stress is shown above. Various beam 2σ values were tested in combination with a range of cyclotron beam currents. The worst-case simulated stress and temperature values were within the acceptable bounds. Throughout the work term, I solved communication challenges by liaising with TRIUMF chemists, while organizing the project’s manufacturing and testing. The design was presented to a review board of machinists, engineers, and physicists for approval for irradiation.

The 2018 target has since been irradiated during several Actinium runs. At the end of my term, I presented my design and won a first-place award at the TRIUMF annual LSPEC Poster Competition. Since completing my term, my work has been published in an Instruments article titled The Design of a Thorium Metal target for Ac-225 Production at TRIUMF.

In the summer of 2020, I returned to TRIUMF to complete the designs of a custom mechanical flow totalizer and an upscaled 2mm Thorium metal target. The goal of the flow totalizer was to verify the accuracy of the flow rate simulations completed for the previous Thorium designs, to ensure that an upscaled target would be safe for irradiation. The flow totalizer (shown below) was manufactured and tested to confirm the potential of the design.

Two variations of the 2mm design were completed, however, the results cannot be shown here, as the manuscript describing the analysis and testing of the target has not yet been published. After further testing, it is expected that one of the thicker 2mm, 2020 targets will replace the thin 0.25mm, 2018 target. The new target could be used for full-scale routine production of Actinium.