ITER-like current ramps in JET with ILW: experiments, modelling and consequences for ITER

Since the ITER-like wall in JET (JET-ILW) came into operation, dedicated ITER-like plasma current (Ip) ramp-up (RU) and ramp-down (RD) experiments have been performed and matched to similar discharges with the carbon wall (JET-C). The experiments show that access to H-mode early in the Ip RU phase and maintaining H-mode in the Ip RD as long as possible are instrumental to achieve low internal plasma inductance (li) and to minimize flux consumption. In JET-ILW, at a given current rise rate similar variations in li (0.7–0.9) are obtained as in JET-C. In most discharges no strong W accumulation is observed. However, in some low density cases during the early phase of the Ip strong core radiation due to W influx led to hollow electron temperature (Te) profiles. In JET-ILW Zeff is significantly lower than in JET-C. W significantly disturbs the discharge evolution when the W concentration approaches 10−4; this threshold is confirmed by predictive transport modelling using the CRONOS code. Ip RD experiments in JET-ILW confirm the result of JET-C that sustained H-mode and elongation reduction are both instrumental in controlling li.

[1]  W. Kerner,et al.  Plasma confinement in JET H?mode plasmas with H, D, DT and T isotopes , 1999 .

[2]  T. Aniel,et al.  Validation of a new mixed Bohm/gyro-Bohm model for electron and ion heat transport against the ITER, Tore Supra and START database discharges , 1998 .

[3]  J. Contributors,et al.  Tungsten transport in JET H-mode plasmas in hybrid scenario, experimental observations and modelling , 2014 .

[4]  D. J. Campbell,et al.  Chapter 1: Overview and summary , 1999 .

[5]  Impact of W on Scenario Simulations for ITER , 2015 .

[6]  Massimiliano Mattei,et al.  Experimental studies of ITER demonstration discharges , 2009 .

[7]  Jet Efda Contributors,et al.  Observations on the W-transport in the core plasma of JET and ASDEX Upgrade , 2013 .

[8]  R. H. Bulmer,et al.  Sustained Spheromak Physics Experiment (SSPX): design and physics results , 2012 .

[9]  R. Neu,et al.  Tungsten divertor erosion in all metal devices: Lessons from the ITER like wall of JET , 2013 .

[10]  R. Neu,et al.  Calculation and experimental test of the cooling factor of tungsten , 2010 .

[11]  Douglass E. Post,et al.  Steady-state radiative cooling rates for low-density, high-temperature plasmas , 1977 .

[12]  J. Lister,et al.  Achieving and sustaining advanced scenarios in ITER modelled by CRONOS and DINA-CH , 2013 .

[13]  E. Joffrin,et al.  The CRONOS suite of codes for integrated tokamak modelling , 2010 .

[14]  Luca Zaccarian,et al.  First experimental results with the Current Limit Avoidance System at the JET tokamak , 2013 .

[15]  Jet Efda Contributors,et al.  The effect of a metal wall on confinement in JET and ASDEX Upgrade , 2013 .

[16]  R. Felton,et al.  Fuel retention studies with the ITER-Like Wall in JET , 2013 .

[17]  Massimiliano Mattei,et al.  Current ramps in tokamaks: from present experiments to ITER scenarios , 2011 .

[18]  T. Luce,et al.  Validation of the thermal transport model used for ITER startup scenario predictions with DIII-D experimental data , 2010 .

[19]  Tomonori Takizuka,et al.  Power requirement for accessing the H-mode in ITER , 2008 .

[20]  F. G. Rimini,et al.  Shape Control with the eXtreme Shape Controller During Plasma Current Ramp-Up and Ramp-Down at the JET Tokamak , 2014 .

[21]  Jet Efda Contributors,et al.  First scenario development with the JET new ITER-like wall , 2013 .

[22]  E. Joffrin,et al.  Characterisation of plasma breakdown at JET with a carbon and ITER-like wall , 2013 .

[23]  Julien Fuchs,et al.  Impurity behaviour in the ASDEX Upgrade divertor tokamak with large area tungsten walls , 2002 .

[24]  Jet Efda Contributors,et al.  L–H power threshold studies in JET with Be/W and C wall , 2013 .

[25]  M. Rosenbluth,et al.  Model for the sawtooth period and amplitude , 1996 .