U.S. Department of EnergyOffice of Scientific and Technical Information
Dynamics of filaments during the edge-localized mode crash on NSTX
Abstract
Edge localized modes (ELMs) are routinely observed in H-mode plasma regimes of the National Spherical Torus Experiment (NSTX). Due to the explosive nature of the instability, only diagnostics with high temporal and spatial resolution could provide a detailed insight into the dynamics associated with the ELMs. Gas-puff imaging (GPI) at NSTX provides 2D measurements of the magnetic field aligned fluctuations (e.g. ELM filaments) in the scrape-off layer and the at the plasma edge with 2.5 us temporal and 10 mm optical resolution.A novel analysis technique was developed to estimate the frame-by-frame velocities and the spatial parameters of the dominant structures associated with the ELMs. The analysis was applied to single ELM events to characterize the ELM crash dynamics, and then extended to a database of 169 ELM events.Statistical analysis was performed in order to find the characterizing dynamics of the ELM crash. The results show that on average an ELM crash consists of a filament with a circular cross-section which is propelled outwards with a characterizing peak radial velocity of ~3.3 km/s. The radial velocity was found to be linearly dependent on the distance of the filament from the separatrix, which has never been seen before. The ELM filament ismore »
- Authors:
-
- Princeton University (PPPL)
- Publication Date:
- DOE Contract Number:
- AC02-09CH11466
- Research Org.:
- Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC)
- Subject:
- ELMs; GPI; NSTX; correlation; dynamics
- OSTI Identifier:
- 1814943
- DOI:
- https://doi.org/10.11578/1814943
Citation Formats
Lampert, Mate, Diallo, Ahmed, Myra, James R, and Zweben, Stewart J. Dynamics of filaments during the edge-localized mode crash on NSTX. United States: N. p., 2021.
Web. doi:10.11578/1814943.
Lampert, Mate, Diallo, Ahmed, Myra, James R, & Zweben, Stewart J. Dynamics of filaments during the edge-localized mode crash on NSTX. United States. doi:https://doi.org/10.11578/1814943
Lampert, Mate, Diallo, Ahmed, Myra, James R, and Zweben, Stewart J. 2021.
"Dynamics of filaments during the edge-localized mode crash on NSTX". United States. doi:https://doi.org/10.11578/1814943. https://www.osti.gov/servlets/purl/1814943. Pub date:Wed Jan 20 04:00:00 UTC 2021
@article{osti_1814943,
title = {Dynamics of filaments during the edge-localized mode crash on NSTX},
author = {Lampert, Mate and Diallo, Ahmed and Myra, James R and Zweben, Stewart J},
abstractNote = {Edge localized modes (ELMs) are routinely observed in H-mode plasma regimes of the National Spherical Torus Experiment (NSTX). Due to the explosive nature of the instability, only diagnostics with high temporal and spatial resolution could provide a detailed insight into the dynamics associated with the ELMs. Gas-puff imaging (GPI) at NSTX provides 2D measurements of the magnetic field aligned fluctuations (e.g. ELM filaments) in the scrape-off layer and the at the plasma edge with 2.5 us temporal and 10 mm optical resolution.A novel analysis technique was developed to estimate the frame-by-frame velocities and the spatial parameters of the dominant structures associated with the ELMs. The analysis was applied to single ELM events to characterize the ELM crash dynamics, and then extended to a database of 169 ELM events.Statistical analysis was performed in order to find the characterizing dynamics of the ELM crash. The results show that on average an ELM crash consists of a filament with a circular cross-section which is propelled outwards with a characterizing peak radial velocity of ~3.3 km/s. The radial velocity was found to be linearly dependent on the distance of the filament from the separatrix, which has never been seen before. The ELM filament is characterized by propagation in the ion-diamagnetic direction poloidally with a peak velocity of 11.4 km/s. The ELM crash lasts for approximately 100us until the radial propulsion settles back to the pre-ELM level. The experimental findings were compared with analytical theory. Two possible mechanisms were identified for explaining the observations: the curvature interchange model and the current-filament interaction model.},
doi = {10.11578/1814943},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jan 20 04:00:00 UTC 2021},
month = {Wed Jan 20 04:00:00 UTC 2021}
}