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

Lunsford, R. ; Bortolon, A. ; Roquemore, A. L. ; Mansfield, D. K. ; Jaworski, M. A. ; Kaita, R. ; Maingi, R. ; Nagy, A.
Issue date: 2017
Rights:
Creative Commons Attribution 4.0 International (CC BY)
Cite as:
Lunsford, R., Bortolon, A., Roquemore, A. L., Mansfield, D. K., Jaworski, M. A., Kaita, R., Maingi, R., & Nagy, A. (2017). Multi-species impurity granule injection and mass deposition projections in NSTX-U discharges [Data set]. Princeton Plasma Physics Laboratory, Princeton University. https://doi.org/10.11578/1367557
@electronic{lunsford_r_2017,
  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.},
  title       = {{Multi-species impurity granule injection
                 and mass deposition projections in NSTX
                -U discharges}},
  publisher   = {{Princeton Plasma Physics Laboratory, Pri
                nceton University}},
  year        = 2017,
  url         = {https://doi.org/10.11578/1367557}
}
Description:

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.

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