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VERSION:2.0
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SUMMARY:Validation of novel hybrid scale ETG simulations in NSTX via compa
 risons of simulated turbulence with a new high-k scattering synthetic diag
 nostic
DTSTART:20180618T103000
DTEND:20180618T113000
DTSTAMP:20260427T215941Z
UID:faa31210d268dc48af24d2c9d740034b8e79a18631d6e6ecfd0ebfe9
CATEGORIES:Conferences - Seminars
DESCRIPTION:Juan Ruiz Ruiz\, Dept. Of Nuclear Science and Engineering\, Ma
 ssachusetts Institute of Technology\, USA\nDespite much research since the
  discovery of ETG (Electron Temperature Gradient) turbulence\, open questi
 ons remain regarding the impact of ETG on the electron thermal transport o
 bserved in spherical tokamak plasmas. A rigorous\, first-of-its-kind\, val
 idation study of ETG turbulence in NSTX H-modes has been performed\, combi
 ning hybrid-scale nonlinear gyrokinetic simulations with a new synthetic d
 iagnostic for high-k scattering. Novel hybrid-scale simulations (GYRO) cap
 ture both ion and electron scale modes\, with minimum kt*rs = 0.3 and maxi
 ma beyond the peak of the linear ETG growth rate. In conditions of low ETG
  drive\, hybrid scale simulations can match the experimental heat flux (Qe
 ) within uncertainty\, but e-scale simulations underpredict Qe. In the str
 ongly driven ETG case\, ion scale modes are shown to be stabilized by ExB 
 shear\, and both hybrid and e-scale simulations underpredict Qe. To quanti
 tatively compare the measured frequency and wavenumber spectra of high-k f
 luctuations\, a new real-space implementation of a synthetic diagnostic fo
 r high-k scattering has been developed. Comparisons with measured turbulen
 ce reveal that when Qe is underpredicted in simulation\, it is still possi
 ble to reproduce the frequency spectral shape (mean frequency and width). 
 But the changes in the fluctuation levels between the two cases and the sh
 ape of the high-k wavenumber spectra disagree with experiment\, suggesting
  for the first time that the measured frequency spectra is not a critical 
 constrain on simulation. The comparison with heat fluxes also indicates th
 at ion scale dynamics\, and possibly cross-scale coupling\, might be neede
 d to account for electron thermal transport in these NSTX H-modes.\n 
LOCATION:PPB 019
STATUS:CONFIRMED
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