Plasma characteristics of long-pulse discharges heated by neutral beam injection in the large helical device

Y. Takeiri, Y. Nakamura, N. Noda, M. Osakabe, K. Kawahata, Y. Oka, O. Kaneko, K. Tsumori, M. Sato, T. Mutoh, T. Shimozuma, M. Goto, K. Ida, S. Inagaki, S. Kado, S. Masuzaki, S. Morita, Y. Nagayama, K. Narihara, B. J. PetersonS. Sakakibara, K. Sato, M. Shoji, K. Tanaka, P. C. De Vries, S. Sudo, N. Ohyabu, O. Motojima

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

Long-pulse neutral beam injection heating has been achieved in the large helical device (LHD). Two different confinement states are observed for different averaged densities in the long-pulse plasmas. A quasi-steady-state plasma was sustained for 21 s with an injection power of 0.6 MW, where the central plasma temperature was around 1 keV with a line-averaged electron density of 0.3×1019 m-3. The discharge duration can be so extended as to keep the plasma properties in the short-pulse discharge. The energy confinement time is nearly the same as that of the short-pulse discharge, which is 1.3 times as long as the international stellarator scaling ISS95. At higher densities, a relaxation oscillation phenomenon, observed as if the plasma would breathe, lasted for 20 s with a period of 1-2 s. The phenomenon is characterized with profile expansion and contraction of the electron temperature. The density oscillation is out of phase with the temperature oscillation and is related to the density clamping phenomenon. The observed plasma properties are shown in detail for the `breathing' oscillation phenomenon. Possible mechanisms for the breathing oscillation are also discussed, with a view of the screening effect near the last closed magnetic surface and the power balance between the heating and the radiation powers. The long-pulse heating results indicate unique characteristics of the LHD where no special feedback stabilization is required due to absence of disruption and no need for current drive.

Original languageEnglish
Pages (from-to)147-159
Number of pages13
JournalPlasma Physics and Controlled Fusion
Volume42
Issue number2
DOIs
Publication statusPublished - Feb 1 2000
Externally publishedYes

Fingerprint

beam injection
neutral beams
Plasmas
oscillations
pulses
breathing
Heating
pulse heating
heating
quasi-steady states
stellarators
plasma temperature
Electron temperature
contraction
screening
stabilization
Carrier concentration
electron energy
injection
Screening

All Science Journal Classification (ASJC) codes

  • Nuclear Energy and Engineering
  • Condensed Matter Physics

Cite this

Plasma characteristics of long-pulse discharges heated by neutral beam injection in the large helical device. / Takeiri, Y.; Nakamura, Y.; Noda, N.; Osakabe, M.; Kawahata, K.; Oka, Y.; Kaneko, O.; Tsumori, K.; Sato, M.; Mutoh, T.; Shimozuma, T.; Goto, M.; Ida, K.; Inagaki, S.; Kado, S.; Masuzaki, S.; Morita, S.; Nagayama, Y.; Narihara, K.; Peterson, B. J.; Sakakibara, S.; Sato, K.; Shoji, M.; Tanaka, K.; De Vries, P. C.; Sudo, S.; Ohyabu, N.; Motojima, O.

In: Plasma Physics and Controlled Fusion, Vol. 42, No. 2, 01.02.2000, p. 147-159.

Research output: Contribution to journalArticle

Takeiri, Y, Nakamura, Y, Noda, N, Osakabe, M, Kawahata, K, Oka, Y, Kaneko, O, Tsumori, K, Sato, M, Mutoh, T, Shimozuma, T, Goto, M, Ida, K, Inagaki, S, Kado, S, Masuzaki, S, Morita, S, Nagayama, Y, Narihara, K, Peterson, BJ, Sakakibara, S, Sato, K, Shoji, M, Tanaka, K, De Vries, PC, Sudo, S, Ohyabu, N & Motojima, O 2000, 'Plasma characteristics of long-pulse discharges heated by neutral beam injection in the large helical device', Plasma Physics and Controlled Fusion, vol. 42, no. 2, pp. 147-159. https://doi.org/10.1088/0741-3335/42/2/307
Takeiri, Y. ; Nakamura, Y. ; Noda, N. ; Osakabe, M. ; Kawahata, K. ; Oka, Y. ; Kaneko, O. ; Tsumori, K. ; Sato, M. ; Mutoh, T. ; Shimozuma, T. ; Goto, M. ; Ida, K. ; Inagaki, S. ; Kado, S. ; Masuzaki, S. ; Morita, S. ; Nagayama, Y. ; Narihara, K. ; Peterson, B. J. ; Sakakibara, S. ; Sato, K. ; Shoji, M. ; Tanaka, K. ; De Vries, P. C. ; Sudo, S. ; Ohyabu, N. ; Motojima, O. / Plasma characteristics of long-pulse discharges heated by neutral beam injection in the large helical device. In: Plasma Physics and Controlled Fusion. 2000 ; Vol. 42, No. 2. pp. 147-159.
@article{6fee2a334bc84cd5bb0219a9c0ae566f,
title = "Plasma characteristics of long-pulse discharges heated by neutral beam injection in the large helical device",
abstract = "Long-pulse neutral beam injection heating has been achieved in the large helical device (LHD). Two different confinement states are observed for different averaged densities in the long-pulse plasmas. A quasi-steady-state plasma was sustained for 21 s with an injection power of 0.6 MW, where the central plasma temperature was around 1 keV with a line-averaged electron density of 0.3×1019 m-3. The discharge duration can be so extended as to keep the plasma properties in the short-pulse discharge. The energy confinement time is nearly the same as that of the short-pulse discharge, which is 1.3 times as long as the international stellarator scaling ISS95. At higher densities, a relaxation oscillation phenomenon, observed as if the plasma would breathe, lasted for 20 s with a period of 1-2 s. The phenomenon is characterized with profile expansion and contraction of the electron temperature. The density oscillation is out of phase with the temperature oscillation and is related to the density clamping phenomenon. The observed plasma properties are shown in detail for the `breathing' oscillation phenomenon. Possible mechanisms for the breathing oscillation are also discussed, with a view of the screening effect near the last closed magnetic surface and the power balance between the heating and the radiation powers. The long-pulse heating results indicate unique characteristics of the LHD where no special feedback stabilization is required due to absence of disruption and no need for current drive.",
author = "Y. Takeiri and Y. Nakamura and N. Noda and M. Osakabe and K. Kawahata and Y. Oka and O. Kaneko and K. Tsumori and M. Sato and T. Mutoh and T. Shimozuma and M. Goto and K. Ida and S. Inagaki and S. Kado and S. Masuzaki and S. Morita and Y. Nagayama and K. Narihara and Peterson, {B. J.} and S. Sakakibara and K. Sato and M. Shoji and K. Tanaka and {De Vries}, {P. C.} and S. Sudo and N. Ohyabu and O. Motojima",
year = "2000",
month = "2",
day = "1",
doi = "10.1088/0741-3335/42/2/307",
language = "English",
volume = "42",
pages = "147--159",
journal = "Plasma Physics and Controlled Fusion",
issn = "0741-3335",
publisher = "IOP Publishing Ltd.",
number = "2",

}

TY - JOUR

T1 - Plasma characteristics of long-pulse discharges heated by neutral beam injection in the large helical device

AU - Takeiri, Y.

AU - Nakamura, Y.

AU - Noda, N.

AU - Osakabe, M.

AU - Kawahata, K.

AU - Oka, Y.

AU - Kaneko, O.

AU - Tsumori, K.

AU - Sato, M.

AU - Mutoh, T.

AU - Shimozuma, T.

AU - Goto, M.

AU - Ida, K.

AU - Inagaki, S.

AU - Kado, S.

AU - Masuzaki, S.

AU - Morita, S.

AU - Nagayama, Y.

AU - Narihara, K.

AU - Peterson, B. J.

AU - Sakakibara, S.

AU - Sato, K.

AU - Shoji, M.

AU - Tanaka, K.

AU - De Vries, P. C.

AU - Sudo, S.

AU - Ohyabu, N.

AU - Motojima, O.

PY - 2000/2/1

Y1 - 2000/2/1

N2 - Long-pulse neutral beam injection heating has been achieved in the large helical device (LHD). Two different confinement states are observed for different averaged densities in the long-pulse plasmas. A quasi-steady-state plasma was sustained for 21 s with an injection power of 0.6 MW, where the central plasma temperature was around 1 keV with a line-averaged electron density of 0.3×1019 m-3. The discharge duration can be so extended as to keep the plasma properties in the short-pulse discharge. The energy confinement time is nearly the same as that of the short-pulse discharge, which is 1.3 times as long as the international stellarator scaling ISS95. At higher densities, a relaxation oscillation phenomenon, observed as if the plasma would breathe, lasted for 20 s with a period of 1-2 s. The phenomenon is characterized with profile expansion and contraction of the electron temperature. The density oscillation is out of phase with the temperature oscillation and is related to the density clamping phenomenon. The observed plasma properties are shown in detail for the `breathing' oscillation phenomenon. Possible mechanisms for the breathing oscillation are also discussed, with a view of the screening effect near the last closed magnetic surface and the power balance between the heating and the radiation powers. The long-pulse heating results indicate unique characteristics of the LHD where no special feedback stabilization is required due to absence of disruption and no need for current drive.

AB - Long-pulse neutral beam injection heating has been achieved in the large helical device (LHD). Two different confinement states are observed for different averaged densities in the long-pulse plasmas. A quasi-steady-state plasma was sustained for 21 s with an injection power of 0.6 MW, where the central plasma temperature was around 1 keV with a line-averaged electron density of 0.3×1019 m-3. The discharge duration can be so extended as to keep the plasma properties in the short-pulse discharge. The energy confinement time is nearly the same as that of the short-pulse discharge, which is 1.3 times as long as the international stellarator scaling ISS95. At higher densities, a relaxation oscillation phenomenon, observed as if the plasma would breathe, lasted for 20 s with a period of 1-2 s. The phenomenon is characterized with profile expansion and contraction of the electron temperature. The density oscillation is out of phase with the temperature oscillation and is related to the density clamping phenomenon. The observed plasma properties are shown in detail for the `breathing' oscillation phenomenon. Possible mechanisms for the breathing oscillation are also discussed, with a view of the screening effect near the last closed magnetic surface and the power balance between the heating and the radiation powers. The long-pulse heating results indicate unique characteristics of the LHD where no special feedback stabilization is required due to absence of disruption and no need for current drive.

UR - http://www.scopus.com/inward/record.url?scp=0033895065&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0033895065&partnerID=8YFLogxK

U2 - 10.1088/0741-3335/42/2/307

DO - 10.1088/0741-3335/42/2/307

M3 - Article

AN - SCOPUS:0033895065

VL - 42

SP - 147

EP - 159

JO - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

SN - 0741-3335

IS - 2

ER -