Recent Publications

Reaching high fusion gain with grams of spin-polarized fuel

J. F. Parisi

Building on recent ignition-access work of Delgado-Aparicio, Ono, and Menard, we show that even a single-use, gram-scale quantity of spin-polarized fuel (SPF) is useful for increasing fusion power and gain in magnetic confinement fusion machines such as tokamaks and stellarators. While fueling a fusion power plant continuously with SPF requires $\sim$kilograms per day, far beyond present capabilities, a single-use short pulse of SPF allows a fusion plasma to cross into a high-gain regime, and stay there, even after switching back to regular unpolarized fuel. With continuous polarized fueling, polarization also makes high-gain plasmas easier to control: a resonant wave that depolarizes the fuel lowers the reactivity quickly, on a much faster timescale than transport. Grams of polarized fuel can therefore improve plasma performance and open a path to scaling SPF sources and usage, from small first experiments to continuous fueling.

Preliminary experimental tests on the cryogenic pellet injection technology for the DTT machine in collaboration with ORNL

L. Melaragni, S. Migliori, A. Frattolillo, M. Angelucci, L.R. Baylor, G. Calabrò, T.E. Gebhart, A. Iaboni, S.J. Meitner

Hydrogen capacity evaluation of the ZrCo hydrogen isotope storage bed in fusion power plant and verification of its repeated recovery effect

Suneui Lee, Naoko Ashikawa, Daiki Kikuchi, Takumi Chikada, Yuka Shimizu, Yoshinao Matsunaga, Yoshifumi Kume, Colin Baus, Christian Day, Satoshi Konishi

Simplified conductance model for the subdivertor of Wendelstein 7-X based on high-fidelity simulations and comparisons with experimental data

V. Haak, L. Steiniger, C. Day, J. Igitkhanov, F. Litovoli, D. Naujoks, V. Perseo, G. Schlisio, H. Strobel, C. Tantos, et al.

Migration and release mechanism of hydrogen and helium in Li2O: A first-principles study

Li Yang, Brian D Wirth

Understanding the migration and release of hydrogen (H) and helium (He) in neutron irradiated lithium oxide (Li2O) is critical to develop a sustainable tritium fuel cycle for fusion reactors. In this article, we describe results about the formation, migration, and trapping of H and He with and without intrinsic defects in Li2O based on first principles density functional theory (DFT) calculations. The intrinsic defects include single vacancies, single intrinsic interstitials, and Schottky defects (SDs). We observe that the energetically favorable configurations and concentrations of H-related defects depend on their charge characteristics. Our analysis indicates that the migration and release mechanisms of H isotopes vary with temperatures. Below 1000 K, hydrogen diffusion and release depends on H+ and Li vacancies, while above 1000 K, oxygen defects and large defect clusters control H diffusional release. H trapping at intrinsic defects decreases the diffusivity and the resulting release of H. He atoms prefer octahedral interstitial sites, except near -2 charged oxygen mono-vacancies. He atoms do not alter H occupation preference but weaken the H binding to vacancies. The interaction of helium with oxygen vacancies mainly controls the helium release process.

Progress in reactor-core fusion technologies presented at the 30th IAEA Fusion Energy Conference 2025

Jiming Chen, Jianbao Wang, Qixiang Cao, Shen Qu, Zongyu Yang

This paper provides an overview of the recent progress in reactor-core fusion technologies within the vacuum vessel presented at the 30th International Atomic Energy Agency (IAEA) Fusion Energy Conference held in October 2025 in Chengdu, China, including plasma control, neutronics and nuclear data, tritium technologies, design and development of in-vessel components, related materials and intense neutron sources for material irradiation. Plasma control focusing on achievements for ITER and major fusion research devices are covered and the application of digital twin and Artificial Intelligence are highlighted. Research and Development (R&D) results from the International Thermonuclear Experimental Reactor (ITER) and current devices to future Demonstration Fusion Power Plant (DEMO) reactors are summarized, particularly new findings, data validation, design and analysis tool improvement, properties assessment and technical solutions for critical issues.

Engineering Design Frameworks for Commercial Fusion Energy Systems: An Assessment of Technological Architectures, Materials Qualification, and Tritium Fuel Cycle Integration

Alberto Boretti

Design and Commissioning of a Deuterium-Tritium Gas Delivery System for Muon-Catalyzed Fusion in a Diamond Anvil Cell

E. Koukina, C. Fagan, C. R. Shmayda, J. D. Kalow, D. M. Harrington, G. Harris, K. McCormack, M. Mundt, K. Lau, D. Zajac, et al.

Effect of Water Vapor on Hydrogen Permeation Behavior Through Tubular Pd-Ag Alloy Membrane and Permeability Recovery

Kentaro Masuta, Kazunari Katayama, Fumiya Nakamura, Yuki Edao, Youji Someya

Real-Time Hydrogen-Deuterium Fraction Feedback Control on EAST

Li Guo, Juan Huang, Kai Wu, Q. P. Yuan, Kedong Li, Wei Gao, Chengrui Wu, Junjie Huang, Chenyu Pan, Zixin Zhang

The poloidal fuelling location and its effect on the pedestal and H-mode plasma performance in MAST Upgrade

Steven Thomas, Jerry W Hughes, Alex Tookey, Bartosz Lomanowski, Davis Easley, Jack Lovell, Christopher Beckley, James R Harrison, Edward DeWit, Saskia Mordijck, et al.

This paper presents the first results exploiting the high-speed video (HSV) diagnostic on MAST Upgrade to infer neutral deuterium quantities from D α emission. We detail the process for absolute calibration of HSV which now produces 2D line-of-sight-integrated brightness (ph sr -1 m -2 s -1 ) of D α emission in the MAST-U main chamber, showing excellent quantitative agreement with other D α and neutral diagnostics. A typical workflow to combine HSV data with a collisional-radiative model, and electron density, n e , and temperature, T e , measurements to produce 1D radial profiles of neutral density, n 0 , and cold deuterium ionisation source rate, S 0 , is documented. The analysis is applied to a series of double null, neutral beam heated H-mode discharges in MAST-U changing the poloidal fuelling location. It is shown how the low-field side (LFS) pedestal electron density is resilient to, and remains largely unaffected by, the choice of poloidal fuelling location, as does n 0,sep despite differences in neutral pressure measured at the wall. LFS fuelling is seen to increase S 0 , reducing the pedestal electron temperature which decreases edge collisionality, ν*, and allows for core n e to be increased. S 0 is used to constrain inferences of deuterium ion flux, Γ, in a 1D radial transport model. When fuelling from the LFS, Γ becomes increasingly negative at the pedestal top, indicating an inward flux of particles, and is used with the diffusive-convective ansatz showing a negative convective transport coefficient, v, implying an inward particle pinch.

Parametric effects and rate-limiting mechanism analysis of tritium extraction process in permeator against vacuum

Zuocong Liu, Qingjun Zhu, Qiankun Shao, Songlin Liu

Evaluation of Pd/k Medium Preparations for the Thermal Cycling Absorption Process Using Van Deemter Curves

J. R. Hanby, S. Silliman, W. T. Shmayda

Evaluation of Flux- and Depletion-Based Methodologies for Tritium Breeding Ratio Prediction: Limitations of Current 7 Li Nuclear Data Processing

Cihang Lu, Arantxa Cuadra, David Brown, Gustavo Nobre

Extensions to the ITER actuator management architecture for dynamic actuator allocation and pellet system reconfiguration

O. Kudláček, S. Stanek, W. Treutterer, I. Gomez Ortiz, P. Lang, R. Nouailletas, L. Pangione, T. Ravensbergen, M. Reich, J. Schmalz, et al.

Characterizing Permeation of Hydrogen Across Palladium-Silver Membranes

Samuel O. Silliman, Walter T. Shmayda

Observations for a Fusion Tritium Economy

Mohamad Abdallah, Bjorn Cole, Daniel Clark, Jonas Kessing, Felipe Novais, Jonathan Naish, Paul Humrickhouse

System-Level Tritium Transport Modeling for the Outer Fuel Cycle of the SCYLLA Breeding Blanket and Relevance for UNITY-2

Luigi Candido, Luke Taylor-King, Colin Baus, Christian Day, Italo Godoy-Morison, John McGrady, Minoru Jimma, Kyosuke Namba, Jonas Schwenzer, Tim Teichmann, et al.

Effects of Long-Term Tritium Exposure on FKM, FFKM, and Epoxy Resin

Christopher J. Koch, Nasiba Abdurakhmanova, Natalie Wieber, Tim Krentz, Tyler Guin, Dale A. Hitchcock

Self-consistent integrated modeling of the critical processes governing D/T retention in PFMs

Tatyana Sizyuk

Self-consistently integrated models for deuterium plasma interactions with plasma-facing materials (PFMs) have been developed and integrated into the upgraded ITMC-DYN+ simulation package. These models capture critical processes such as bubble and blister growth from nanocavities, blister bursting, defects formation induced by deuterium supersaturation, and changes in deuterium diffusivity resulting from microstructural evolution. Benchmarking against experimental data on deuterium retention and defect evolution in tungsten demonstrates that our integrated approach accurately explains a range of experimental observations for the first time. Key findings include: (a) the dynamics of bubble and blister growth and their impact on trapping site accumulation, (b) the combined effects of cavity growth, bursting, and surrounding dislocation networks, (c) the formation of a deuterium supersaturated surface layer (DSSL), (d) the influence of DSSL on deuterium diffusivity and bulk transport, and (e) differences in deuterium retention between pre-damaged tungsten and tungsten simultaneously irradiated by deuterium and neutrons. This self-consistent analysis reveals synergistic effects of blistering and DSSL formation on deuterium retention and transport in tungsten under varying temperatures and damage rates.