First demonstration of a fiber optic bolometer on a tokamak plasma (invited)

S. Lee; M. Shafer; M. Reinke; N. Uddin; Q. Sheng; M. Han; D. Donovan; R. O'Neill

doi:10.1063/5.0099546

First demonstration of a fiber optic bolometer on a tokamak plasma (invited)

S. Lee, M. Shafer, M. Reinke, N. Uddin, Q. Sheng, M. Han, D. Donovan, R. O'Neill

Advanced Tokamak Physics

Research output: Contribution to journal › Article › peer-review

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Abstract

A fiber optic bolometer (FOB) was demonstrated observing a fusion plasma for the first time at the DIII-D tokamak. A FOB uses a fiber optics-based interferometric technique that is designed to have a high sensitivity to temperature changes [75 mK/(W/m2) responsivity in high vacuum with 0.38 mK noise level] with a negligible susceptibility to electromagnetic interference (EMI) that can be problematic for resistive bolometers in a tokamak environment. A single-channel test apparatus was installed on DIII-D consisting of a measurement FOB and shielded reference FOB. The single-channel FOB showed a negligible increase in the noise level during typical plasma operations (0.39 mK) compared to the benchtop results (0.38 mK), confirming an insignificant EMI impact to the FOB. Comparisons to DIII-D resistive bolometers showed good agreement with the single-channel FOB, indicating that the FOB is comparable to a resistive bolometer when the impulse calibration is applied. The noise-equivalent power density of the calibrated FOB during a plasma operation was 0.55 W/m2 with an average sampling time of 20 ms. The major potential effect of ionizing radiation on the FOB would be the radiation-induced attenuation, which can be efficiently compensated for by adjusting the probing light power.

Original language	English
Article number	123515
Journal	Review of Scientific Instruments
Volume	93
Issue number	12
DOIs	https://doi.org/10.1063/5.0099546
State	Published - Dec 1 2022

Funding

This work was supported by the US DOE under Grant Nos. DE-AC05-00OR22725 and DE-FC02-04ER54698. The work of M. Reinke was supported by Commonwealth Fusion Systems. The authors would like to thank A. Moser from General Atomics for the instructions on the DIII-D bolometer tomographic reconstruction code. This work was supported by the US DOE under Grant Nos. DE-AC05-00OR22725 and DE-FC02-04ER54698. The work of M. Reinke was supported by Commonwealth Fusion Systems. The authors would like to thank A. Moser from General Atomics for the instructions on the DIII-D bolometer tomographic reconstruction code.

Funders	Funder number
Commonwealth Fusion Systems
General Atomics
U.S. Department of Energy	DE-AC05-00OR22725, DE-FC02-04ER54698

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abstract = "A fiber optic bolometer (FOB) was demonstrated observing a fusion plasma for the first time at the DIII-D tokamak. A FOB uses a fiber optics-based interferometric technique that is designed to have a high sensitivity to temperature changes [75 mK/(W/m2) responsivity in high vacuum with 0.38 mK noise level] with a negligible susceptibility to electromagnetic interference (EMI) that can be problematic for resistive bolometers in a tokamak environment. A single-channel test apparatus was installed on DIII-D consisting of a measurement FOB and shielded reference FOB. The single-channel FOB showed a negligible increase in the noise level during typical plasma operations (0.39 mK) compared to the benchtop results (0.38 mK), confirming an insignificant EMI impact to the FOB. Comparisons to DIII-D resistive bolometers showed good agreement with the single-channel FOB, indicating that the FOB is comparable to a resistive bolometer when the impulse calibration is applied. The noise-equivalent power density of the calibrated FOB during a plasma operation was 0.55 W/m2 with an average sampling time of 20 ms. The major potential effect of ionizing radiation on the FOB would be the radiation-induced attenuation, which can be efficiently compensated for by adjusting the probing light power.",

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First demonstration of a fiber optic bolometer on a tokamak plasma (invited)

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