Modelling of combined ICRF and NBI heating in JET hybrid plasmas

D Gallart ,Philippe Jacquet,M Mantsinen ,J Hobirk ,E Pawelec ,N Krawczyk ,E Joffrin ,M Lennholm ,A Czarnecka ,É Belonohy ,D King ,J P Graves ,M Goniche ,C Hellesen ,J Eriksson ,D Frigione ,E.r Solano ,G Sips ,M Tsalas ,E Lerche ,C Challis ,M Valisa

doi:10.1051/epjconf/201715703015

Abstract

During the 2015-2016 JET campaigns many efforts have been devoted to the exploration of high performance plasma scenarios envisaged for ITER operation. In this paper we model the combined ICRF+NBI heating in selected key hybrid discharges using PION. The antenna frequency was tuned to match the cyclotron frequency of minority hydrogen (H) at the center of the tokamak coinciding with the second harmonic cyclotron resonance of deuterium. The modelling takes into account the synergy between ICRF and NBI heating through the second harmonic cyclotron resonance of deuterium beam ions which allows us to assess its impact on the neutron rate RNT . We evaluate the influence of H concentration which was varied in different discharges in order to test their role in the heating performance. According to our modelling, the ICRF enhancement of RNT increases by decreasing the H concentration which increases the ICRF power absorbed by deuterons. We find that in the recent hybrid discharges this ICRF enhancement was in the range of 10-25%. Finally, we extrapolate the results to D-T and find that the best performing hybrid discharges correspond to an equivalent fusion power of ∼7.0 MW in D-T.

Highlights

During the 2015-2016 JET campaigns many efforts have been devoted to the exploration of high performance plasma scenarios envisaged for ITER operation [1]
The modelling takes into account the synergy between ICRF and NBI heating through the second harmonic cyclotron resonance of deuterium beam ions which allows us to assess its impact on the neutron rate RNT
We find that in the recent hybrid discharges this ICRF enhancement was in the range of 10-25%

Summary

Introduction

During the 2015-2016 JET campaigns many efforts have been devoted to the exploration of high performance plasma scenarios envisaged for ITER operation [1]. The hybrid scenario reached with 33 MW of combined ICRF and NBI power a record neutron rate RNT of 2.9x1016 n/s. We report on simulations aimed at modelling of combined NBI and ICRF heating for high fusion yield in these recent hybrid discharges. We evaluate the performance of H minority heating in the presence of D beam ions using the ICRF modelling code PION [4] coupled to the beam deposition code PENCIL [5]. Our modelling takes into account the synergy between ICRF and NBI heating through the second harmonic cyclotron resonance of deuterium beam ions, which allows us to assess its impact on the fusion performance. We model and extrapolate a record discharge to a 50:50 DT fuel mixture

Resonance position scan for ICRF impurity control

Hydrogen concentration scan

High-performance hybrid discharge

Findings

Conclusions and further steps