Transport phenomena in radioisotope beam production targets
Bibliographic record
Abstract
This thesis reports on the development of techniques to better investigate elemental transport phenomena in accelerator-based targets for RIB production through the ISOL method. This development has been carried out at TRIUMF, Canada's particle accelerator centre and home to ISAC-TRIUMF, a leading RIB facility where constant development is key to enable cutting-edge experiments performed in user facilities where the radioactive beams are delivered. Elemental diffusion and effusion in ISOL targets are frequently the major bottleneck for delivering RIBs with desired properties; this thesis focuses on developing systems to improve our understanding of their basic release phenomena, as well as enhance target performance. A major component of this thesis comprises the conceptualization, design, testing and irradiation of a spallation-driven two-step target for isotope production. Unlike every target irradiated for the past 25 years at ISAC, where protons induce nuclear reactions by directly impinging on a target material, this prototype produces spallation neutrons which subsequently induce fission in an annular uranium carbide target, and the reaction products are then extracted as a RIB. Besides unlocking new science with radioisotope beams having previously unavailable characteristics, this methodology brings several advantages for studying transport mechanisms at high-temperatures and in mixed particle fields. Such new features and capabilities provide a new parameter space for better understanding transport phenomena in harsh environments. Additionally, this thesis reports on radiotracer experiments performed on table-top systems and using activated materials, to systematically study the high-temperature diffusion and effusion phenomena in exotic materials and complex geometries. First studies were conducted to characterize the release performance of ISOL target samples, so that the most suited material could be irradiated in the ISAC station. Moreover, the first experimental investigations of the effusion phenomenon in ISOL targets are reported, which provide a better understanding of its principles and offers further ground for access to fundamental transport properties in these materials. Such approaches build on previous established work and extend it further to shed more light through systematic investigations. In turn, this will enable new target development activities based on experimental data and dependable models for predicting isotope transport and release.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".