title: Design and characterization of a prototype divertor viewing infrared video bolometer for NSTX-U.
abstract: The InfraRed Video Bolometer (IRVB) is a powerful tool to measure radiated power in magnetically confined plasmas due to its ability to obtain 2D images of plasma emission using a technique that is compatible with the fusion nuclear environment. A prototype IRVB has been developed and installed on NSTX-U to view the lower divertor. The IRVB is a pinhole camera which images radiation from the plasma onto a 2.5 μm thick, 9 × 7 cm2Pt foil and monitors the resulting spatio-temporal temperature evolution using an IR camera. The power flux incident on the foil is calculated by solving the 2D+time heat diffusion equation, using the foil's calibrated thermal properties. An optimized, high frame rate IRVB, is quantitatively compared to results from a resistive bolometer on the bench using a modulated 405 nm laser beam with variable power density and square wave modulation from 0.2 Hz to 250 Hz. The design of the NSTX-U system and benchtop characterization are presented where signal-to-noise ratios are assessed using three different IR cameras: FLIR A655sc, FLIR A6751sc, and SBF-161. The sensitivity of the IRVB equipped with the SBF-161 camera is found to be high enough to measure radiation features in the NSTX-U lower divertor as estimated using SOLPS modeling. The optimized IRVB has a frame rate up to 50 Hz, high enough to distinguish radiation during edge-localized-modes (ELMs) from that between ELMs.
authors.affiliation: Dutch Institute for Fundamental Energy Research, 5612 AJ Eindhoven, The Netherlands.
authors.forename: G G
authors.initials: GG
authors.lastname: van Eden
authors.affiliation: Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Reinke
authors.affiliation: National Institute for Fusion Science, Toki 509-5292, Japan.
authors.forename: B J
authors.initials: BJ
authors.lastname: Peterson
authors.affiliation: Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: T K
authors.initials: TK
authors.lastname: Gray
authors.affiliation: Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543, USA.
authors.forename: L F
authors.initials: LF
authors.lastname: Delgado-Aparicio
authors.affiliation: Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543, USA.
authors.forename: M A
authors.initials: MA
authors.lastname: Jaworski
authors.affiliation: Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors.forename: J
authors.initials: J
authors.lastname: Lore
authors.affiliation: National Institute for Fusion Science, Toki 509-5292, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Mukai
authors.affiliation: National Institutes for Quantum and Radiological Science and Technology, Naka 311-0193, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Sano
authors.affiliation: Institute for Plasma Research, Bhat Village, Gandhinagar, 382428 Gujarat, India.
authors.forename: S N
authors.initials: SN
authors.lastname: Pandya
authors.affiliation: Dutch Institute for Fundamental Energy Research, 5612 AJ Eindhoven, The Netherlands.
authors.forename: T W
authors.initials: TW
authors.lastname: Morgan