TY - JOUR
T1 - Core tungsten transport in WEST long pulse L-mode plasmas
JF - Nuclear Fusion
Y1 - 2020
A1 - Yang, X.
A1 - Manas, P.
A1 - Bourdelle, C.
A1 - Artaud, J. F.
A1 - Sabot, R.
A1 - Camenen, Y.
A1 - Citrin, J.
A1 - Clairet, F.
A1 - Desgrange, C.
A1 - Devynck, P.
A1 - Dittmar, T.
A1 - Ekedahl, A.
A1 - Fedorczak, N.
A1 - Gil, L.
A1 - Loarer, T.
A1 - Lotte, P.
A1 - Meyer, O.
A1 - Morales, J.
A1 - Peret, M.
A1 - Peysson, Y.
A1 - Stephens, C. D.
A1 - Urbanczyk, G.
A1 - Vezinet, D..
A1 - Zhang, L.
A1 - Gong, X.
AB - Tungsten transport is investigated in WEST long pulse L-mode plasmas operated with the strike point on the actively cooled upper tungsten divertor. The pulses are mostly heated by lower hybrid waves. It is experimentally found that tungsten does not centrally accumulate throughout these similar to 30 s reproducible discharges despite large normalised electron density gradients R/L-ne. To explain these observations, turbulent and neoclassical transport of electrons and tungsten ions are computed with GKW Peeters A.G. et al (2009 Computer Phys. Commnun. 180 2650) and NEO Belli E. and Candy J. (2008 Plasma Phys. Control. Fusion 50 095010), Belli E. and Candy J. (2012 Plasma Phys. Control. Fusion 54 015015) respectively. Additionally, interpretative integrated modelling simulations are also performed to keep data coherency despite the lack of measurements of some quantities such as the Ti profiles. Modelled R/Lne are found consistent with interferometry inversions and the tungsten peaking factor R/L-nW remains comparable to R/L-ne due to dominant turbulent diffusivities inside r/a = 0.3-0.8. In the central region r/a < 0.3 neoclassical W transport dominates but the convective velocities are several order of magnitudes lower compared to plasmas with toroidal rotation velocities induced by a neutral beam injection (NBI) torque. Finally, nitrogen is seeded in these pulses leading to an enhanced energy content which is consistent with stabilised ion temperature gradient modes from dilution.
PB - IOP Publishing
VL - 60
IS - 8
U1 - FP
U2 - IMT
U5 - 01c2c12463f6cb1eb28bf607a3bd6131
ER -
TY - JOUR
T1 - Application of Gaussian process regression to plasma turbulent transport model validation via integrated modelling
JF - Nuclear Fusion
Y1 - 2019
A1 - Ho, A.
A1 - Citrin, J.
A1 - Auriemma, F.
A1 - Bourdelle, C.
A1 - Casson, F. J.
A1 - Kim, H. T.
A1 - Manas, P.
A1 - Szepesi, G.
A1 - Weisen, H.
A1 - JET Contributors
AB - This paper outlines an approach towards improved rigour in tokamak turbulence transport model validation within integrated modelling. Gaussian process regression (GPR) techniques were applied for profile fitting during the preparation of integrated modelling simulations allowing for rigourous sensitivity tests of prescribed initial and boundary conditions as both fit and derivative uncertainties are provided. This was demonstrated by a JETTO integrated modelling simulation of the JET ITER-like-wall H-mode baseline discharge #92436 with the QuaLiKiz quasilinear turbulent transport model, which is the subject of extrapolation towards a deuterium–tritium plasma. The simulation simultaneously evaluates the time evolution of heat, particle, and momentum fluxes over ~10 confinement times, with a simulation boundary condition at rho tor=0.85. Routine inclusion of momentum transport prediction in multi-channel flux-driven transport modelling is not standard and is facilitated here by recent developments within the QuaLiKiz model. Excellent agreement was achieved between the fitted and simulated profiles for n e , T e , T i , and omega tor within 2x, but the simulation underpredicts the mid-radius T i and overpredicts the core n e and T e profiles for this discharge. Despite this, it was shown that this approach is capable of deriving reasonable inputs, including derivative quantities, to tokamak models from experimental data. Furthermore, multiple figures-of-merit were defined to quantitatively assess the agreement of integrated modelling predictions to experimental data within the GPR profile fitting framework.

VL - 59
IS - 5
U1 - FP

U2 - IMT

U5 - 9b651392bcad55886e0c0848df55a9f0
ER -