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Pedestal fluctuation measurements with charge exchange imaging at the DIII-D tokamak
- Source :
- The Review of scientific instruments. 93(11)
- Publication Year :
- 2022
-
Abstract
- A new high radial resolution 2D multichannel Charge eXchange Imaging (CXI) diagnostic is under development for deployment at DIII-D. The diagnostic system will measure low-to-intermediate radial wavenumber carbon density fluctuations by observing the n = 8 − 7 ( λ = 529.06 nm) C-VI emission line, resulting from charge exchange collisions between heating neutral beam atoms and the intrinsic carbon ion density. The new CXI diagnostic will provide measurements with Δ R ∼ 0.4 cm to access higher k r instabilities ( k r < 8 cm−1) predicted to arise in the steep-gradient region of the H-mode pedestal. The CXI system will feature 60 fiber bundles in a 12 × 5 arrangement, with each bundle consisting of four 1 mm fibers. A custom optical system has been designed to filter and image incoming signals onto an 8 × 8 avalanche photodiode array. Additionally, a novel electronics suite has been designed and commissioned to amplify and digitize the relatively low-intensity carbon signal at a 2 MHz bandwidth. Forward modeling results of the active C-VI emission suggest sufficient signal to noise ratios to resolve turbulent fluctuations. Prototype measurements demonstrate the ability to perform high frequency pedestal measurements.
- Subjects :
- Instrumentation
Subjects
Details
- ISSN :
- 10897623
- Volume :
- 93
- Issue :
- 11
- Database :
- OpenAIRE
- Journal :
- The Review of scientific instruments
- Accession number :
- edsair.doi.dedup.....98c1e258b455cb427fb995277c5811d2