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Title: Multi-species impurity granule injection and mass deposition projections in NSTX-U discharges Authors

Abstract

By employing a neutral gas shielding (NGS) model to characterize impurity granule injection the pedestal atomic deposition for three different species of granule: lithium, boron, and carbon are determined. Utilizing the duration of ablation events recorded on experiments performed at DIII-D to calibrate the NGS model we are able to quantify the ablation rate and mass deposition location with respect to the plasma density profile. The species specific granule shielding constant is then used to model granule ablation within NSTX-U discharges. Simulations of 300, 500 and 700 micron diameter granules injected at 50 m/sec are presented for NSTX-U L-mode type plasmas as well as H-mode discharges with low natural ELM frequencies. Additionally, ablation calculations of 500 micron granules of each species are presented at velocities ranging from 50 - 150 m/sec. In H-mode type discharges these simulations show that the majority of the injected granule is ablated within or just past the steep gradient region of the discharge. At this radial position, the perturbation to the background plasma generated by the ablating granule can lead to conditions advantageous for the rapid triggering of an ELM crash event.

Authors:
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  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Publication Date:
DOE Contract Number:  
AC02-09CH11466
Product Type:
Dataset
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
Keywords:
Impurity granule injection; Neutral gas shielding; NSTX-U
OSTI Identifier:
1367557
DOI:
10.11578/1367557

Citation Formats

Lunsford, R., Bortolon, A., Roquemore, A.L., Mansfield, D.K., Jaworski, M.A., Kaita, R., Maingi, R., and Nagy, A. Multi-species impurity granule injection and mass deposition projections in NSTX-U discharges Authors. United States: N. p., 2017. Web. doi:10.11578/1367557.
Lunsford, R., Bortolon, A., Roquemore, A.L., Mansfield, D.K., Jaworski, M.A., Kaita, R., Maingi, R., & Nagy, A. Multi-species impurity granule injection and mass deposition projections in NSTX-U discharges Authors. United States. doi:10.11578/1367557.
Lunsford, R., Bortolon, A., Roquemore, A.L., Mansfield, D.K., Jaworski, M.A., Kaita, R., Maingi, R., and Nagy, A. 2017. "Multi-species impurity granule injection and mass deposition projections in NSTX-U discharges Authors". United States. doi:10.11578/1367557. https://www.osti.gov/servlets/purl/1367557. Pub date:Sun Jan 01 00:00:00 EST 2017
@article{osti_1367557,
title = {Multi-species impurity granule injection and mass deposition projections in NSTX-U discharges Authors},
author = {Lunsford, R. and Bortolon, A. and Roquemore, A.L. and Mansfield, D.K. and Jaworski, M.A. and Kaita, R. and Maingi, R. and Nagy, A.},
abstractNote = {By employing a neutral gas shielding (NGS) model to characterize impurity granule injection the pedestal atomic deposition for three different species of granule: lithium, boron, and carbon are determined. Utilizing the duration of ablation events recorded on experiments performed at DIII-D to calibrate the NGS model we are able to quantify the ablation rate and mass deposition location with respect to the plasma density profile. The species specific granule shielding constant is then used to model granule ablation within NSTX-U discharges. Simulations of 300, 500 and 700 micron diameter granules injected at 50 m/sec are presented for NSTX-U L-mode type plasmas as well as H-mode discharges with low natural ELM frequencies. Additionally, ablation calculations of 500 micron granules of each species are presented at velocities ranging from 50 - 150 m/sec. In H-mode type discharges these simulations show that the majority of the injected granule is ablated within or just past the steep gradient region of the discharge. At this radial position, the perturbation to the background plasma generated by the ablating granule can lead to conditions advantageous for the rapid triggering of an ELM crash event.},
doi = {10.11578/1367557},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2017},
month = {1}
}

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