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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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21 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

First lower hybrid current drive experiments on the WEST tokamak

The first lower hybrid current drive experiments in the full tungsten WEST tokamak are reported. Good wave coupling is found at rather low plasma current (q 95 ~4.3) and medium density (n e ~3×10 19 m -3 ). Reflection coefficient is in agreement with the expectation from the linear theory of coupling. With low reflection coefficients, 5MW was coupled for 2 seconds. High central electron temperature, up to 5keV, is achieved at ne = 3-4×10 19 m -3 . Flat and even hollow profiles of tungsten density are derived from the bolometry diagnostic. The stored thermal energy follows the H96-P scaling law with very slight degradation with density. The current drive efficiency has been assessed in low loop voltage (V L ~0.15V) discharges. Low plasma current operation and rather high effective charge (Z eff ~3) lead to modest current drive efficiency (η = 0.5-0.65 × 10 19 A.W -1 m -2 ). Long pulse operation (~30s) with high LHCD power (P LH =2.7MW) is achieved with stationary parameters, in particular electron and impurity densities, with the upper water-cooled tungsten divertor.

Goniche, M.↗
DOE OSTI2025

Fiber-optic bolometers with high-temperature tolerance and reduced time constants for fusion plasma diagnostics

Fiber-optic bolometers (FOBs) designed for plasma radiation measurement in magnetically confined fusion environments have been previously developed and tested at the DIII-D tokamak. These FOBs utilize a silicon Fabry–Perot interferometer at the fiber tip for temperature measurement and a gold disk as a radiation absorber. This paper presents recent advancements in the development of FOBs with reduced cooling time constants and enhanced temperature tolerance. We also demonstrate high-temperature operation and report findings from irradiation tests. By incorporating a copper sensor holder as a thermal sink and integrating two closely packed sensor heads into a compact design, the cooling time constants were reduced to ∼100 ms in vacuum, while minimizing uncertainties caused by temperature gradients. The FOBs were subjected to heating at 400 °C for five hours, with no observed degradation in noise performance post-heating. High-temperature operation tests were conducted at ∼220 °C using a 404 nm square-wave modulated laser to simulate the plasma radiation. In addition, four FOBs constructed from copper-coated pure-silica fibers were fabricated and underwent irradiation testing, enduring a total γ-radiation dose of 15.2 MGy and a neutron fluence of 1.6 × 10 18 n/cm 2 . As a result, the FOBs maintained their physical integrity and the optical signal shows high visibility throughout the test.

42 ENGINEERING↗
DOE OSTI2025

Fiber-optic bolometer with low detection limit fabricated using thermal release tape and precise laser heating

Fiber-optic bolometers (FOBs) based on a fiber-tipped silicon Fabry–Perot (FP) interferometric temperature sensor and a gold disk absorber have been shown to be an attractive alternative to conventional resistive bolometers for plasma radiation measurement in fusion devices. Either a high-finesse FP or a low-finesse FP can be used, each with trade-offs between noise performance and fabrication complexity. In this paper, we present an FOB design that overcomes these limitations by combining a low-finesse long silicon FP cavity with a large gold disk absorber to achieve enhanced sensitivity and noise performance without increasing the fabrication complexity and the time constant. We also demonstrated a fabrication method for the sensor head facilitated by thermal release tape and precise laser heating. Our FOB demonstrates a temperature resolution of 0.08 mK, a cooling time constant of 230 ms, and a noise equivalent power density of 0.015 W m −2 . This represents an eightfold improvement over previous high-finesse FOBs and 26-fold improvement over previous low-finesse FOBs with similar demodulation bandwidths and similar cooling time constants.

Fabry–Perot interferometer↗