Overview
This research investigates recent advancements in fast and bright scintillators for ultrafast X-ray phase contrast imaging of dynamic materials experiments. The context for this development is the upgraded Advanced Photon Source (APS-U), a fourth-generation synchrotron. The APS-U is designed to facilitate hard X-ray imaging at frame rates reaching at least 13 MHz, which translates to interframe intervals of 77 nanoseconds or less. This operational requirement creates a demand for scintillators possessing a faster response time and a higher light output compared to materials like lutetium yttrium oxyorthosilicate (LYSO).
Research Context
The Advanced Photon Source (APS-U) represents a significant upgrade, offering capabilities for hard X-ray imaging at frame rates of 13 MHz or higher, necessitating scintillator interframe intervals of 77 ns or shorter. Existing scintillators such as LYSO and lutetium oxyorthosilicate (LSO) do not meet the speed requirements for these ultrafast applications. The need is for materials that can deliver both rapid response and high light output for indirect imaging and diffraction combined with ultrafast cameras.
Approach
The study examines commercial lanthanum bromide ($\text{LaBr}_3$) and cerium bromide ($\text{CeBr}_3$) as potential candidates for ultrafast indirect imaging and diffraction. These materials were evaluated for their decay times and light yield per incident X-ray photon. The investigation also involved addressing practical implementation challenges associated with these materials at APS-U, including their hygroscopicity, efficient optical coupling to imaging systems, and achieving high quantum efficiency for converting scintillation light into detectable electronic signals. The primary emission wavelengths of this scintillation light are predominantly below 400 nm. The research includes material characterization, detector integration and packaging, and beamline experiments. Additionally, the study discusses emerging classes of scintillators, specifically perovskites and high-entropy materials, as potential alternatives for future ultrafast X-ray diagnostics.
Findings
- Commercial $\text{LaBr}_3$ and $\text{CeBr}_3$ exhibit decay times approximately a factor of two shorter than those of LYSO and LSO.
- The decay times for $\text{LaBr}_3$ and $\text{CeBr}_3$ are around 40 ns.
- Both $\text{LaBr}_3$ and $\text{CeBr}_3$ maintain a light yield per incident X-ray photon comparable to that of LYSO and LSO.
Why This Matters
The capabilities of the upgraded Advanced Photon Source (APS-U) for hard X-ray imaging at 13 MHz frame rates and 77 ns interframe intervals create a demand for scintillators with improved speed and light output. The identified characteristics of $\text{LaBr}_3$ and $\text{CeBr}_3$ address this specific need, potentially enabling the full utilization of APS-U's ultrafast imaging capabilities for dynamic materials experiments.
Potential Applications
The developed fast and bright scintillators are intended for ultrafast X-ray phase contrast imaging of dynamic materials experiments at the upgraded Advanced Photon Source (APS-U). They are also relevant for indirect imaging and diffraction applications utilizing ultrafast cameras.
Key Limitations Mentioned by Researchers
The implementation of $\text{LaBr}_3$ and $\text{CeBr}_3$ at APS-U faces several challenges. These include material limitations due to their hygroscopicity, the need for efficient optical coupling to imaging systems, and the requirement for high quantum efficiency in converting scintillation light—primarily below 400 nm—into electronic signals.