Characterization of ELM Pacing via Vertical Jogs on DIII-D
Abstract
Edge localized mode (ELM) pacing via vertical plasma oscillations or jogging has been successfully demonstrated on DIII-D. Rapid vertical movement of the plasma toward the X-point has been shown to effectively trigger ELMs. By vertically oscillating the plasma at a rate of 10 Hz, the ELM frequency increased from ∼5~Hz, the natural ELM frequency in similar DIII-D discharges, to 10~Hz. Downward jogs have been observed to trigger multiple ELMs in one cycle. ELMs triggered at higher than natural frequencies lead to smaller decreases in stored energy, from ~10\% to as little as below 1\%. As a consequence, the peak heat flux to the divertor has been observed to be reduced by a factor of ∼2. In addition, a reduction in the carbon impurity concentration has been observed. During downward jogs in the lower single null (LSN) configuration, the X-point movement is slower and smaller than the top of the plasma. As a result, a reduction in the plasma cross section and hence volume has been observed. To understand the mechanism of ELM triggering by jogging, a toy model of the edge toroidal current has been built and tested with DIII-D experiment data. The experimental data and model suggest that when the plasma moves down towards the X-point, a net positive toroidal current is locally induced in the edge region. ELITE stability analysis suggests that this current pushes the plasma state across the peeling side of the peeling-ballooning stability boundary into the unstable region triggering ELMs.
Related
- Robust Control of ECH Deposition Profiles on DIII-D
- Assessing the effect of error field penetration during plasma current ramp-up in the DIII-D tokamak
- Overview of Enhanced D-alpha and Quasi Continuous Exhaust H-modes at DIII-D
- Perfectly vertical polarization-splitting grating coupler array for space–polarization multiplexed optical interfaces
- Deblocking a confined experiment: Comprehensive scaled model tests of a Vertical-Axis Cross-Flow Tidal Turbine
BibTeX
@misc{yasoda2026characterization,
title = {{Characterization of ELM Pacing via Vertical Jogs on DIII-D}},
author = {Kei Yasoda and Dario Panici and Andrew Oak Nelson and Florian M. Laggner and Sangkyeun Kim and Egemen Kolemen},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2605.00165},
eprint = {2605.00165},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.00165},
}
RIS
TY - UNPB
TI - Characterization of ELM Pacing via Vertical Jogs on DIII-D
AU - Kei Yasoda
AU - Dario Panici
AU - Andrew Oak Nelson
AU - Florian M. Laggner
AU - Sangkyeun Kim
AU - Egemen Kolemen
PY - 2026
DA - 2026/08/28
PB - arXiv
DO - 10.48550/arxiv.2605.00165
UR - https://arxiv.org/abs/2605.00165
AB - Edge localized mode (ELM) pacing via vertical plasma oscillations or jogging has been successfully demonstrated on DIII-D. Rapid vertical movement of the plasma toward the X-point has been shown to effectively trigger ELMs. By vertically oscillating the plasma at a rate of 10 Hz, the ELM frequency increased from ∼5~Hz, the natural ELM frequency in similar DIII-D discharges, to 10~Hz. Downward jogs have been observed to trigger multiple ELMs in one cycle. ELMs triggered at higher than natural frequencies lead to smaller decreases in stored energy, from ~10\% to as little as below 1\%. As a consequence, the peak heat flux to the divertor has been observed to be reduced by a factor of ∼2. In addition, a reduction in the carbon impurity concentration has been observed. During downward jogs in the lower single null (LSN) configuration, the X-point movement is slower and smaller than the top of the plasma. As a result, a reduction in the plasma cross section and hence volume has been observed. To understand the mechanism of ELM triggering by jogging, a toy model of the edge toroidal current has been built and tested with DIII-D experiment data. The experimental data and model suggest that when the plasma moves down towards the X-point, a net positive toroidal current is locally induced in the edge region. ELITE stability analysis suggests that this current pushes the plasma state across the peeling side of the peeling-ballooning stability boundary into the unstable region triggering ELMs.
ER -