Comparison of BES measurements of ion-scale turbulence with direct gyro-kinetic simulations of MAST L-mode plasmas
Observations of ion-scale (kyρi 1) density turbulence of relative amplitude 0.2% are available on the Mega Amp Spherical Tokamak (MAST) using a 2D (8 radial × 4 poloidal channel) imaging beam emission spectroscopy diagnostic. Spatial and temporal characteristics of this turbulence, i.e., amplitudes,...
| Main Authors: | , , , , , , , , , |
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| Format: | Journal article |
| Language: | English |
| Published: |
2014
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| _version_ | 1826292037362647040 |
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| author | Field, A Dunai, D Ghim, Y Hill, P McMillan, B Roach, C Saarelma, S Schekochihin, A Zoletnik, S Team, MAST |
| author_facet | Field, A Dunai, D Ghim, Y Hill, P McMillan, B Roach, C Saarelma, S Schekochihin, A Zoletnik, S Team, MAST |
| author_sort | Field, A |
| collection | OXFORD |
| description | Observations of ion-scale (kyρi 1) density turbulence of relative amplitude 0.2% are available on the Mega Amp Spherical Tokamak (MAST) using a 2D (8 radial × 4 poloidal channel) imaging beam emission spectroscopy diagnostic. Spatial and temporal characteristics of this turbulence, i.e., amplitudes, correlation times, radial and perpendicular correlation lengths and apparent phase velocities of the density contours, are determined by means of correlation analysis. For a low-density, L-mode discharge with strong equilibrium flow shear exhibiting an internal transport barrier in the ion channel, the observed turbulence characteristics are compared with synthetic density turbulence data generated from global, non-linear, gyro-kinetic simulations using the particle-in-cell code NEMORB. This validation exercise highlights the need to include increasingly sophisticated physics, e.g., kinetic treatment of trapped electrons, equilibrium flow shear and collisions, to reproduce most of the characteristics of the observed turbulence. Even so, significant discrepancies remain: an underprediction by the simulations of the turbulence amplitude and heat flux at plasma periphery and the finding that the correlation times of the numerically simulated turbulence are typically two orders of magnitude longer than those measured in MAST. Comparison of these correlation times with various linear timescales suggests that, while the measured turbulence is strong and may be 'critically balanced', the simulated turbulence is weak. © 2014 IOP Publishing Ltd. |
| first_indexed | 2024-03-07T03:08:31Z |
| format | Journal article |
| id | oxford-uuid:b364a74c-db90-4406-bb5b-7389524ac77a |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T03:08:31Z |
| publishDate | 2014 |
| record_format | dspace |
| spelling | oxford-uuid:b364a74c-db90-4406-bb5b-7389524ac77a2022-03-27T04:18:46ZComparison of BES measurements of ion-scale turbulence with direct gyro-kinetic simulations of MAST L-mode plasmasJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:b364a74c-db90-4406-bb5b-7389524ac77aEnglishSymplectic Elements at Oxford2014Field, ADunai, DGhim, YHill, PMcMillan, BRoach, CSaarelma, SSchekochihin, AZoletnik, STeam, MASTObservations of ion-scale (kyρi 1) density turbulence of relative amplitude 0.2% are available on the Mega Amp Spherical Tokamak (MAST) using a 2D (8 radial × 4 poloidal channel) imaging beam emission spectroscopy diagnostic. Spatial and temporal characteristics of this turbulence, i.e., amplitudes, correlation times, radial and perpendicular correlation lengths and apparent phase velocities of the density contours, are determined by means of correlation analysis. For a low-density, L-mode discharge with strong equilibrium flow shear exhibiting an internal transport barrier in the ion channel, the observed turbulence characteristics are compared with synthetic density turbulence data generated from global, non-linear, gyro-kinetic simulations using the particle-in-cell code NEMORB. This validation exercise highlights the need to include increasingly sophisticated physics, e.g., kinetic treatment of trapped electrons, equilibrium flow shear and collisions, to reproduce most of the characteristics of the observed turbulence. Even so, significant discrepancies remain: an underprediction by the simulations of the turbulence amplitude and heat flux at plasma periphery and the finding that the correlation times of the numerically simulated turbulence are typically two orders of magnitude longer than those measured in MAST. Comparison of these correlation times with various linear timescales suggests that, while the measured turbulence is strong and may be 'critically balanced', the simulated turbulence is weak. © 2014 IOP Publishing Ltd. |
| spellingShingle | Field, A Dunai, D Ghim, Y Hill, P McMillan, B Roach, C Saarelma, S Schekochihin, A Zoletnik, S Team, MAST Comparison of BES measurements of ion-scale turbulence with direct gyro-kinetic simulations of MAST L-mode plasmas |
| title | Comparison of BES measurements of ion-scale turbulence with direct gyro-kinetic simulations of MAST L-mode plasmas |
| title_full | Comparison of BES measurements of ion-scale turbulence with direct gyro-kinetic simulations of MAST L-mode plasmas |
| title_fullStr | Comparison of BES measurements of ion-scale turbulence with direct gyro-kinetic simulations of MAST L-mode plasmas |
| title_full_unstemmed | Comparison of BES measurements of ion-scale turbulence with direct gyro-kinetic simulations of MAST L-mode plasmas |
| title_short | Comparison of BES measurements of ion-scale turbulence with direct gyro-kinetic simulations of MAST L-mode plasmas |
| title_sort | comparison of bes measurements of ion scale turbulence with direct gyro kinetic simulations of mast l mode plasmas |
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