Speaker
Yu. F. Baranov
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.1102.pdf
On the mechanism of the plasma fuelling in JET experiment with external gas puff.
Yu.F.Baranov1, A.Salmi2, T.Tala2, G.Corrigan1, D.Harting1, F.J.Casson1, F.Koechl1,
E.Militello Asp1, V.Parail1and JET Contributors*
1
CCFE, Culham Science Centre, Abingdon, OX14 3DB, UK
2
VTT, P.O. Box 1000, FI-02044 VTT, Espoo, Finland
Scenario development for ITER requires an understanding of the mechanism of the
plasma fuelling with external particle source. Experiments on plasma fuelling with modulated
gas puff have been done on JET [1] to clarify details of the particle penetration into the
plasma core. The modulation caused a periodic variation of the plasma parameters in the
scrape off layer (SOL), divertor and the plasma core, which have been measured by
numerous JET diagnostics. An evolution of the plasma parameters has been modelled with
the JINTRAC code [2]. The modelling results have been compared with the experimental
data.
The plasma fuelling in the experiment was provided by a constant source from the
NBI system, and modulated gas puff from the top of the plasma chamber [1]. The level of the
puff was relatively small, and it did not change the global plasma confinement significantly.
The experiments have been done in D and H plasmas. Qualitatively, the observations were
similar in both gases. The density variation caused by the modulated gas puff were observed
propagating from the plasma periphery to the core. The modulation footprint was seen in the
plasma SOL and divertor.
The integrated suite of core and SOL/divertor transport codes JINTRAC [2] has been
used to self-consistently model the plasma evolution during modulated gas puff. The suite
couples JETTO/SANCO, a 1.5D core transport solver that includes impurities, with
EDGE2D/EIRENE, a 2D SOL/edge multi-fluid solver that includes plasma interactions with
the JET Be wall and W divertor.
Transport properties in the core were assumed to be governed by a combination of the
neoclassical and Bohm/gyro-Bohm model with anomalous particle pinch. The boundary
conditions were deduced from EDGE2D calculations. The accuracy of the predictive
modelling of the plasma temperature and density was tested against free parameters used in
the model. Good agreement between measured and modelled plasma parameters in the core,
SOL and divertor has been found, including density evolution, saturation ion current and ion
flux in the divertor. The modelling revealed the relationship between the variation of the gas
puff rate, plasma density in SOL/core and the neutral particle flux through the separatrix. The
modelling results showed that the modulated core plasma fuelling is defined by the boundary
conditions on the separatix rather than by the neutral particle flux from the gas puff through
the separatrix. This conclusion is valid for both H and D gases and it does not depend on the
choice of the model describing the transport, provided that the evolution of the plasma
parameters is consistent with experimental observation.
[1] A.Salmi et al., “Investigation of gas fuelling characteristics in JET experiments”, EPS 2017
[2] M.Romanelli et al., “JINTRAC: A System of Codes for Integrated Simulation of Tokamak
Scenarios”, Plasma and Fusion Research, 9, 3403023 (2014)
*See the author list of “X. Litaudon et al 2017 Nucl. Fusion 57 102001″
