Ultrafast-laser investigations of radiation damage in nuclear materials
Abstract/Contents
- Abstract
- Ionizing radiation—in the form of fission fragments, gamma rays, and alpha particles—is a major source of damage in nuclear materials. Energy from sources of ionizing radiation is deposited primarily into the electronic subsystem of a material over timescales shorter than that required for electron-phonon coupling. This induces highly non-equilibrium conditions that causes damage on femtosecond-to-nanosecond timescales. These short timescales have, thus far, made the direct observation of ionizing radiation damage impossible. Furthermore, the non-equilibrium conditions intrinsic to the damage process are difficult to model. This dissertation reports on the use of ultrafast lasers to better understand the process of ionizing radiation damage in nuclear materials. Studies of nuclear materials subjected to static high-pressure conditions were also conducted in order to better understand the interplay between induced defects and material properties and behavior. Structural phase transformations driven by ultrafast laser irradiation in ZrO2 and Gd2O3 were compared to previous results from swift heavy ion irradiation. Identical phase transformations were induced by the two irradiation techniques. This observation served as an experimental proof-of-concept for the use of ultrafast lasers to investigate ionizing radiation damage. The separation of thermal- and pressure-affected zones in ultrafast laser-irradiated materials provided the basis for understanding the phase transformation mechanism in Ln2O3 (Ln = Er-Lu). Although all investigated Ln2O3 compositions underwent the same transformation, their transformation mechanisms were found to differ. The transformation was pressure-driven for Ln = Tm--Lu, consistent with the material's phase behavior under equilibrium conditions. However, the transformation was thermally driven for Ln = Er, revealing that the non-equilibrium conditions of ionizing radiation can lead to unexpected transformation pathways. The use of ultrafast lasers also allowed time-resolved experiments to be performed, permitting the process of ionizing radiation damage to be observed in real-time. Investigations into the response of UO2 revealed a long-lived GHz-scale mode, which had not been observed under equilibrium conditions. This mode was attributed to the production of a photogenerated species. This species was found to originate in the dynamical magnetic structure of UO2. Investigation of the pressure-dependent mode behavior revealed coupling to the electronic structure of UO2. This non-equilibrium mode provides the basis for understanding the anomalously high resistance of UO2 to ionizing radiation damage.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2018; ©2018 |
| Publication date | 2018; 2018 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Rittman, Dylan Ray |
|---|---|
| Degree supervisor | Ewing, Rodney C |
| Degree supervisor | Mao, Wendy (Wendy Li-wen) |
| Thesis advisor | Ewing, Rodney C |
| Thesis advisor | Mao, Wendy (Wendy Li-wen) |
| Thesis advisor | Gleason, Arianna, 1980- |
| Degree committee member | Gleason, Arianna, 1980- |
| Associated with | Stanford University, Department of Geological Sciences. |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Dylan Ray Rittman. |
|---|---|
| Note | Submitted to the Department of Geological Sciences. |
| Thesis | Thesis Ph.D. Stanford University 2018. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2018 by Dylan Ray Rittman
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
Also listed in
Loading usage metrics...