First demonstration of a fiber optic bolometer on a tokamak plasma (invited).
- Resource Type
- Article
- Authors
- Lee, S.; Shafer, M.; Reinke, M.; Uddin, N.; Sheng, Q.; Han, M.; Donovan, D.; O'Neill, R.
- Source
- Review of Scientific Instruments. 12/1/2022, Vol. 93 Issue 12, p1-9. 9p.
- Subject
- *BOLOMETERS
*TOKAMAKS
*IONIZING radiation
*ELECTROMAGNETIC interference
*POWER density
- Language
- ISSN
- 0034-6748
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. [ABSTRACT FROM AUTHOR]