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Title: Superdense core mode in the Large Helical Device with an internal diffusion barrier

Abstract

In reduced recycling discharges using a local island divertor in the Large Helical Device [O. Motojima, H. Yamada, A. Komori et al., Phys. Plasmas 6, 1843 (1999)], a stable high-density plasma develops in the core region when a series of pellets is injected. A core region with {approx}5x10{sup 20} m{sup -3} and temperature of 0.85 keV is maintained by an internal diffusion barrier (IDB). The density gradient at the IDB (r/a{approx}0.6) is very high, and the particle confinement time in the core region is {approx}0.4 s. Because of the increase in the central pressure, a large Shafranov shift up to {approx}0.3 m is observed. The critical ingredients for IDB formation are a strongly pumped divertor to reduce edge recycling, and multiple pellet injection to ensure efficient central fueling. No serious magnetohydrodynamics activity and impurity accumulation have been observed so far in this improved discharge.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;  [1]
  1. National Institute for Fusion Science, Toki 509-5292 (Japan) (and others)
Publication Date:
OSTI Identifier:
20975051
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 5; Other Information: DOI: 10.1063/1.2718530; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BOUNDARY LAYERS; CONFINEMENT TIME; DIFFUSION BARRIERS; DIVERTORS; ELECTRON TEMPERATURE; ION TEMPERATURE; KEV RANGE; LHD DEVICE; MAGNETIC ISLANDS; MAGNETOHYDRODYNAMICS; PELLET INJECTION; PLASMA; PLASMA CONFINEMENT; PLASMA DENSITY; PLASMA IMPURITIES; STELLARATORS

Citation Formats

Morisaki, T., Ohyabu, N., Masuzaki, S., Kobayashi, M., Sakamoto, R., Miyazawa, J., Funaba, H., Ida, K., Ikeda, K., Kaneko, O., Morita, S., Mutoh, S., Nagaoka, K., Nagayama, Y., Nakajima, N., Narihara, K., Oka, Y., Osakabe, M., Peterson, B. J., and Sakakibara, S. Superdense core mode in the Large Helical Device with an internal diffusion barrier. United States: N. p., 2007. Web. doi:10.1063/1.2718530.
Morisaki, T., Ohyabu, N., Masuzaki, S., Kobayashi, M., Sakamoto, R., Miyazawa, J., Funaba, H., Ida, K., Ikeda, K., Kaneko, O., Morita, S., Mutoh, S., Nagaoka, K., Nagayama, Y., Nakajima, N., Narihara, K., Oka, Y., Osakabe, M., Peterson, B. J., & Sakakibara, S. Superdense core mode in the Large Helical Device with an internal diffusion barrier. United States. doi:10.1063/1.2718530.
Morisaki, T., Ohyabu, N., Masuzaki, S., Kobayashi, M., Sakamoto, R., Miyazawa, J., Funaba, H., Ida, K., Ikeda, K., Kaneko, O., Morita, S., Mutoh, S., Nagaoka, K., Nagayama, Y., Nakajima, N., Narihara, K., Oka, Y., Osakabe, M., Peterson, B. J., and Sakakibara, S. Tue . "Superdense core mode in the Large Helical Device with an internal diffusion barrier". United States. doi:10.1063/1.2718530.
@article{osti_20975051,
title = {Superdense core mode in the Large Helical Device with an internal diffusion barrier},
author = {Morisaki, T. and Ohyabu, N. and Masuzaki, S. and Kobayashi, M. and Sakamoto, R. and Miyazawa, J. and Funaba, H. and Ida, K. and Ikeda, K. and Kaneko, O. and Morita, S. and Mutoh, S. and Nagaoka, K. and Nagayama, Y. and Nakajima, N. and Narihara, K. and Oka, Y. and Osakabe, M. and Peterson, B. J. and Sakakibara, S.},
abstractNote = {In reduced recycling discharges using a local island divertor in the Large Helical Device [O. Motojima, H. Yamada, A. Komori et al., Phys. Plasmas 6, 1843 (1999)], a stable high-density plasma develops in the core region when a series of pellets is injected. A core region with {approx}5x10{sup 20} m{sup -3} and temperature of 0.85 keV is maintained by an internal diffusion barrier (IDB). The density gradient at the IDB (r/a{approx}0.6) is very high, and the particle confinement time in the core region is {approx}0.4 s. Because of the increase in the central pressure, a large Shafranov shift up to {approx}0.3 m is observed. The critical ingredients for IDB formation are a strongly pumped divertor to reduce edge recycling, and multiple pellet injection to ensure efficient central fueling. No serious magnetohydrodynamics activity and impurity accumulation have been observed so far in this improved discharge.},
doi = {10.1063/1.2718530},
journal = {Physics of Plasmas},
number = 5,
volume = 14,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}