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DOE OSTI2024

Elucidating non-radiative decay in near-infrared lumiphores: Leveraging new design principles to develop a telecom band organic dye laser

Organic near-infrared (NIR) lumiphores have been targeted for biological and technological applications; however, these dyes exhibit exponentially decreasing quantum yields with decreasing energy gaps. The accepted model of this phenomenon invokes C–H stretching modes as the dominant route of non-radiative energy dissipation. Reducing the number of these modes is a popular strategy for the design of bright NIR lumiphores, but quantitative experimental validation of this strategy is lacking. Here, we evaluate the role of C–H modes in non-radiative relaxation through isotopic labeling of a NIR-emitting complex. Measurements comparing relaxation between protonated and perdeuterated complexes indicate that C–H modes do not contribute significantly to non-radiative relaxation. We instead propose that skeletal modes may play a larger role and suggest that minimizing scaffold size is a promising route for bright NIR lumiphores. In conclusion, we demonstrate the promise of such strategies through the development of the reddest organic-based laser dye yet reported.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2026

Optical diagnostic design for measuring the radiation front with a mid-leg pumped divertor on DIII-D

The design of an optical diagnostic system to localize the radiation front in a mid-leg pumped divertor configuration on DIII-D is presented. Divertor detachment is a key mechanism for handling power exhaust in tokamaks, and mid-leg pumping offers a promising approach to radiatively dissipate power while maintaining acceptable core performance. To predict the location of the radiation front and design a spectroscopic diagnostic to measure its position, a database of SOLPS-ITER simulations across a range of input powers and gas puffing rates representative of DIII-D operation was employed. These simulations provide self-consistent plasma backgrounds for a Cherab-Raysect synthetic diagnostic framework, which incorporates detailed tokamak geometry and physically accurate ray-tracing. Synthetic simulations of optical sightlines and viewing cone geometry were used to calculate line-integrated emission from the plasma, particularly of the C III 465 nm line, to serve as a proxy for the T e ≈ 7 − 10 eV temperature region associated with the onset and evolution of divertor detachment. Neutral deuterium emission is also evaluated for comparison. The synthetic diagnostic is used to assess the performance of existing DIII-D optical systems, including filterscopes and the Multichord Divertor Spectrometer, and to optimize line-of-sight placement within mechanical and installation constraints. The results provide quantitative guidance for diagnostic implementation on DIII-D and demonstrate the advantage of integrated synthetic diagnostics for divertor design studies and future advanced divertor concepts.

Cherab↗

DOE OSTI2021

Organs at Risk Considerations for Thoracic Stereotactic Body Radiation Therapy: What Is Safe for Lung Parenchyma?

Stereotactic body radiation therapy (SBRT) has become the standard of care for inoperable early-stage non-small cell lung cancer and is often used for recurrent lung cancer and pulmonary metastases. Radiation-induced lung toxicity (RILT), including radiation pneumonitis and pulmonary fibrosis, is a major concern for which it is important to understand dosimetric and clinical predictors.