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Title: Study of ion-gyroscale fluctuations in low-density L-mode plasmas heated by NBI on KSTAR

Abstract

Broadband density fluctuations with peak frequency ranging from 150 to 400 kHz were measured using a multichannel microwave imaging reflectometer in core region of the low-density L-mode plasmas heated by neutral beam injection on KSTAR. These fluctuations have been studied by comparing the dominant mode scales estimated from the measurement with those predicted from linear gyrokinetic simulation. The measured poloidal wavenumbers are qualitatively comparable to those of the 'fastest growing modes' from simulations, whereas they are larger than those of the 'transport-dominant modes' by about a factor of three. The agreement on wavenumbers between the measurement and linear simulation (for the fastest growing modes) is probably due to sufficiently weak $$E \times B$$ flow shear compared to the maximum linear growth rate. Meanwhile, the transport-dominant modes seem to be related to the fluctuations in lower frequencies (~80–150 kHz) observed in some of the measurement.

Authors:
; ; ; ORCiD logo; ; ; ORCiD logo; ;
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
Sponsoring Org.:
USDOE
Contributing Org.:
The KSTAR Team
OSTI Identifier:
1543946
Resource Type:
Journal Article
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 58; Journal Issue: 4; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
Physics

Citation Formats

Lee, W., Ko, S. H., Leem, J., Yun, G. S., Park, H. K., Wang, W. X., Budny, R. V., Kim, K. W., and Luhmann, N. C. Study of ion-gyroscale fluctuations in low-density L-mode plasmas heated by NBI on KSTAR. United States: N. p., 2018. Web. doi:10.1088/1741-4326/aaac4b.
Lee, W., Ko, S. H., Leem, J., Yun, G. S., Park, H. K., Wang, W. X., Budny, R. V., Kim, K. W., & Luhmann, N. C. Study of ion-gyroscale fluctuations in low-density L-mode plasmas heated by NBI on KSTAR. United States. doi:10.1088/1741-4326/aaac4b.
Lee, W., Ko, S. H., Leem, J., Yun, G. S., Park, H. K., Wang, W. X., Budny, R. V., Kim, K. W., and Luhmann, N. C. Tue . "Study of ion-gyroscale fluctuations in low-density L-mode plasmas heated by NBI on KSTAR". United States. doi:10.1088/1741-4326/aaac4b.
@article{osti_1543946,
title = {Study of ion-gyroscale fluctuations in low-density L-mode plasmas heated by NBI on KSTAR},
author = {Lee, W. and Ko, S. H. and Leem, J. and Yun, G. S. and Park, H. K. and Wang, W. X. and Budny, R. V. and Kim, K. W. and Luhmann, N. C.},
abstractNote = {Broadband density fluctuations with peak frequency ranging from 150 to 400 kHz were measured using a multichannel microwave imaging reflectometer in core region of the low-density L-mode plasmas heated by neutral beam injection on KSTAR. These fluctuations have been studied by comparing the dominant mode scales estimated from the measurement with those predicted from linear gyrokinetic simulation. The measured poloidal wavenumbers are qualitatively comparable to those of the 'fastest growing modes' from simulations, whereas they are larger than those of the 'transport-dominant modes' by about a factor of three. The agreement on wavenumbers between the measurement and linear simulation (for the fastest growing modes) is probably due to sufficiently weak $E \times B$ flow shear compared to the maximum linear growth rate. Meanwhile, the transport-dominant modes seem to be related to the fluctuations in lower frequencies (~80–150 kHz) observed in some of the measurement.},
doi = {10.1088/1741-4326/aaac4b},
journal = {Nuclear Fusion},
issn = {0029-5515},
number = 4,
volume = 58,
place = {United States},
year = {2018},
month = {2}
}