High-purity precursor materials are the foundational input for all high-performance inorganic scintillator crystals used in the DoW radiation detection and nuclear forensics missions. Current supply chains for key halides (e.g., LaCl₃, LaBr₃, YCl₃, LiCl, CsCl, CeCl3 etc.) and rare earth oxides (e.g., Gd2O3, CeO2, etc.) are heavily dependent on foreign sources. Several of the materials used for inorganic scintillator crystal growth are included in the U.S. Geological Survey (USGS) 2025 List of Critical Minerals. This need is further reinforced by Executive Order 14415, "Securing America's Defense Supply Chains and Ensuring Domestic Acquisition of Critical Materials" (July 20, 2026), which directs the DoW to prioritize domestic sources for critical materials, restrict routine waivers for adversarial foreign suppliers effective January 1, 2027, and require supply chain mapping and mitigation plans from contractors and subcontractors.
Scaling crystal growth of these scintillators and maintaining consistent performance requires precursor materials with stringent control of purity, stoichiometry, moisture, and trace radioactive contaminants. Poor quality precursor materials often introduce variability that degrades crystal quality, light yield, energy resolution, and PSD figure-of-merit.
Desired materials typically have the following attributes, confirmed by analytical means and demonstrated by crystal growth results:
• High Chemical Purity: At least ≥4N (99.99%) anhydrous metal halides or pre-reacted mixes; sub-ppm levels of contaminants that interfere with the selected scintillator’s performance, such as transition metals (e.g., Fe, Cr, Ni, Cu) and alkali contaminants (e.g., K, Rb).
• Low Moisture / Oxygen Content: < 50 ppm (minimum) for hygroscopic materials.
• Precise Stoichiometry Control (for pre-reacted elpasolites): Precise control of multi-cation ratios to enable growth of phase-pure crystals with minimal secondary phases or compositional gradients
• Radioactive Impurity Control: Minimized 40K, 87Rb, 138La, 176Lu, and U/Th series contaminants to levels supporting low-background detector applications
This topic specifically targets the development of domestic synthesis, purification and quality-assurance processes capable of producing scintillator-grade precursor materials at laboratory, pilot, and eventually production scales. The goal is to reduce or eliminate reliance on foreign sources while enabling the next generation of compact, high-performance, ruggedized detectors for WMD detection and nuclear security applications.
The solution must meet the following minimum specifications:
• Analytical Characterization: Comprehensive analytical characterization confirming chemical purity, low moisture/oxygen content (if applicable) and stochiometric control. Appropriate methods should be used for trace-metal purity or trace moisture measurement.
• Domestic Feedstock Utilization: Primary use of U.S. or allied-nation sourced precursor materials (e.g. carbonates, oxides, chlorides) and any specialized equipment with documented traceability.
• Validation Method: Rapid feasibility screening of material performance, which may include small-scale crystal growth and measurements such as powder radioluminescence or optical transmittance.
• Production Scale: Reliable and reproducible laboratory-scale batches (e.g., 50-100 g) in Phase I; pilot-scale (e.g., 1–5 kg) in Phase II with batch-to-batch consistency. Ultimately, the focus is on material quality and potential for process scale up.
• Open market commercialization: Process development must lead to high-purity precursor materials made commercially available to the broader U.S. industrial base, rather than exclusive licenses, proprietary arrangements, or other restrictions.
Objective specifications (desired but not required for basic consideration):
• Advanced Validation Method: Produced batches must be validated through single crystal growth and complete radiation detection performance benchmarking against commercially available crystals, to include absolute light yield (photons/MeV), energy resolution at 662 keV, and PSD where applicable.
• Production Scale: Demonstration of multi-kilogram batch yields achieving or with a roadmap to achieve cost competitiveness with foreign-sourced material.
• Radiopurity: Identification of means to mitigate or minimize naturally occurring radioactive isotopes that impact detector background.
• Extensibility: Tailoring materials to be directly compatible with transparent ceramic scintillator fabrication processes (e.g. desirable particle size distribution and particle morphology).
This effort shall develop reliable domestic manufacturing processes for high-purity scintillator precursor materials while meeting the performance parameters above. Proposed work must include validation. The developed processes and materials will also be tested and validated in Phase II by delivery to DTRA or a designated partner for independent evaluation.
