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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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DOE OSTI2018

Qualification of the U.S. Conductors for ITER TF Magnet System

The U.S. Domestic Agency is one of the six suppliers of the toroidal field (TF) conductor for ITER. To qualify conductors per ITER requirements, we prepared or provided to the Swiss Plasma Center (SPC) eight test articles, sixteen conductors total, that were tested in the SULTAN facility at SPC in the ITER relevant conditions. The strands that were used in these SULTAN samples were fully characterized in the laboratories. In this paper, we report both test results and analysis of the conductors' performance against expected strand performance. The U.S. TF conductors showed a slightly better than average current sharing temperature and a relatively low sensitivity to warm up-cooldown cycles in comparison with other suppliers' conductors. However, the trend in current sharing temperature versus cycles and warm ups did not saturate, which means a continuing slow degradation of the conductor performance if the number of warm up and cooldown cycles will be significantly higher than expected. The ac losses in the U.S. TF conductors are in line with losses in the other TF conductor suppliers.

Martovetsky, Nicolai↗
DOE OSTI2018

Electron mass enhancement and magnetic phase separation near the Mott transition in double-layer ruthenates

Here, we present a detailed investigation of the specific heat of Ca 3 (Ru 1-x M x ) 2 O 7 (M = Ti, Fe, Mn) single crystals. Depending on the dopant and doping level, three distinct regions are present: a quasitwo-dimensional metallic state with antiferromagnetic (AFM) order formed by ferromagnetic bilayers (AFM-b), a Mott insulating state with G-type AFM order (G-AFM), and a localized state with a mixed AFM-b and G-AFM phase. Our specific heat data provide deep insights into the Mott transitions induced by Ti and Mn doping. We observed not only an anomalous large mass enhancement, but also an additional term in the specific heat, i.e., C ∝ T 2 , in the localized region. The C ∝ T 2 term is most likely due to long-wavelength excitations with both FM and AFM components. A decrease in the Debye temperature is observed in the G-type AFM region, indicating lattice softening associated with the Mott transition.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗