Wall conditioning in fusion devices with superconducting coils

Wall conditioning is essential in tokamak and stellarator research to achieve plasma performance and reproducibility. This paper presents an overview of recent conditioning results, both from experiments in present devices and modelling, in view of devices with superconducting coils, with focus on W7-X, JT-60SA and ITER. In these devices, the coils stay energised throughout an experimental day or week which demands for new conditioning techniques that work in presence of the nominal field, in addition to the proven conditioning methods such as baking, glow discharge conditioning (GDC) and low-Z wall coating through GDC-plasma, which do not work under such condition. The discussed techniques are RF conditioning without plasma current, both in the ion cyclotron and electron cyclotron range of frequencies, and diverted conditioning plasmas with nested magnetic flux surfaces. Similarities and differences between tokamaks and stellarators are highlighted. Finally a conditional tritium recovery strategy for ITER is proposed based on Ion Cyclotron Wall Conditioning and L-mode plasma results from JET, equipped with an ITER-like wall (beryllium main chamber wall and tungsten divertor).

[1]  H. Grote,et al.  Wall conditioning at the Wendelstein 7-X stellarator operating with a graphite divertor , 2020, Physica Scripta.

[2]  K. Heinola,et al.  Effect of composition and surface characteristics on fuel retention in beryllium-containing co-deposited layers , 2020, Physica Scripta.

[3]  C. P. Dhard,et al.  Impurity sources and fluxes in W7-X: from the plasma-facing components to the edge layer , 2020, Physica Scripta.

[4]  J. Vega,et al.  Advances in the physics studies for the JT-60SA tokamak exploitation and research plan , 2019, Plasma Physics and Controlled Fusion.

[5]  S. Wiesen,et al.  First divertor physics studies in Wendelstein 7-X , 2019, Nuclear Fusion.

[6]  C. Gil,et al.  Ramping up RF power and increasing pulse length in the full tungsten environment of WEST , 2019 .

[7]  R. Cavazzana,et al.  Designing high efficiency glow discharge cleaning systems , 2019, Nuclear Materials and Energy.

[8]  R. Neu,et al.  Real-time wall conditioning by controlled injection of boron and boron nitride powder in full tungsten wall ASDEX Upgrade , 2019, Nuclear Materials and Energy.

[9]  S. Brezinsek,et al.  A SCENARIO OF PULSED ECRH WALL CONDITIONING IN HYDROGEN FOR THE WENDELSTEIN 7-X HELIAS , 2019, Problems of Atomic Science and Technology.

[10]  Sandeep Kumar Pathak,et al.  Determination of isotope ratio in the divertor of JET-ILW by high-resolution Hα spectroscopy: H–D experiment and implications for D–T experiment , 2019, Nuclear Fusion.

[11]  P. Barabaschi,et al.  Progress of the JT-60SA project , 2013, Nuclear Fusion.

[12]  P. Barabaschi,et al.  Progress of the JT-60SA project , 2019 .

[13]  R. Neu,et al.  Real-time wall conditioning through B powder injection in fusion devices , 2019 .

[14]  R. Burhenn,et al.  Reduction of intrinsic impurities by wall boronization in Wendelstein 7-X as observed by VUV spectroscopy , 2019 .

[15]  H. Grote,et al.  Wall conditioning strategy at the Wendelstein 7-X stellarator operating with graphite divertor , 2019 .

[16]  R. König,et al.  Wall conditioning throughout the first carbon divertor campaign on Wendelstein 7-X , 2018, Nuclear Materials and Energy.

[17]  S. Brezinsek,et al.  Wall conditioning by ECRH discharges and He-GDC in the limiter phase of Wendelstein 7-X , 2018 .

[18]  R. König,et al.  Strategy and Optimisation of Wall Conditioning at the Wendelstein 7-X Stellarator , 2018 .

[19]  S. Coda,et al.  Development of helium electron cyclotron wall conditioning on TCV , 2018 .

[20]  R. Wolf,et al.  Development of an ICRH antenna system at W7-X for plasma heating and wall conditioning , 2017 .

[21]  V. Bobkov,et al.  A PIC-MCC code RFdinity1d for simulation of discharge initiation by ICRF antenna , 2017 .

[22]  G. Gantenbein,et al.  Advanced electron cyclotron heating and current drive experiments on the stellarator Wendelstein 7-X , 2017 .

[23]  R. Neu,et al.  Surface modification of He pre-exposed tungsten samples by He plasma impact in the divertor manipulator of ASDEX Upgrade , 2017 .

[24]  A. Isayama,et al.  Efficiency improvement by application of horizontal magnetic fields for second- and fundamental harmonic EC wall conditioning in JT-60U , 2017 .

[25]  K. Heinola,et al.  Efficiency of thermal outgassing for tritium retention measurement and removal in ITER , 2017 .

[26]  J. Contributors,et al.  Overview of fuel inventory in JET with the ITER-like wall , 2017 .

[27]  P. Barabaschi,et al.  Recent progress of the JT-60SA project , 2017 .

[28]  V. Rohde,et al.  Optimization of the ASDEX Upgrade glow discharge , 2017 .

[29]  V. Bobkov,et al.  Plasma-wall interaction studies in the full-W ASDEX upgrade during helium plasma discharges , 2017 .

[30]  F. Louche,et al.  Discharge initiation by ICRF antenna in IShTAR , 2017 .

[31]  Alfredo Pironti,et al.  Physics and operation oriented activities in preparation of the JT-60SA tokamak exploitation , 2017 .

[32]  T. Wauters,et al.  Monte Carlo simulation of ICRF discharge initiation in ITER , 2015 .

[33]  J. Contributors,et al.  Wall conditioning for ITER: Current experimental and modeling activities , 2015 .

[34]  J. Contributors,et al.  Isotope Exchange by Ion Cyclotron Wall Conditioning on JET , 2015 .

[35]  J. Contributors,et al.  Fuel retention in JET ITER-like wall from post-mortem analysis , 2015 .

[36]  J. Contributors,et al.  Beryllium migration in JET ITER-like wall plasmas , 2015 .

[37]  Á. Cappa,et al.  Second harmonic ECRH breakdown experiments in the TJ-II stellarator , 2015 .

[38]  Jet Efda Contributors,et al.  Plasma isotopic changeover experiments in JET under carbon and ITER-like wall conditions , 2015 .

[39]  S. Brezinsek,et al.  Plasma-surface interaction in the Be/W environment: Conclusions drawn from the JET-ILW for ITER , 2015 .

[40]  R. Pitts,et al.  Modelling of tokamak glow discharge cleaning I: physical principles , 2015 .

[41]  R. A. Pitts,et al.  Modelling of tokamak glow discharge cleaning II: comparison with experiment and application to ITER , 2015 .

[42]  J. Contributors,et al.  Material migration patterns and overview of first surface analysis of the JET ITER-like wall , 2014 .

[43]  V. Bobkov,et al.  Monte Carlo simulation of initial breakdown phase for magnetised toroidal ICRF discharges , 2014 .

[44]  M. Preynas,et al.  Ion and electron cyclotron wall conditioning in stellarator and tokamak magnetic field configuration on WEGA , 2014 .

[45]  E. Joffrin,et al.  ICRF Discharge Production for Ion Cyclotron Wall Conditioning on JET , 2014 .

[46]  M. Vervier,et al.  Monte Carlo simulation of ICRF discharge initiation at ω , 2014 .

[47]  M. Otte,et al.  Study of Plasma Start-up Initiated by Second Harmonic Electron Cyclotron Resonance Heating on WEGA Experiment , 2014 .

[48]  V. Philipps,et al.  Self-consistent application of ion cyclotron wall conditioning for co-deposited layer removal and recovery of tokamak operation on TEXTOR , 2013 .

[49]  H.-S. Bosch,et al.  Towards assembly completion and preparation of experimental campaigns of Wendelstein 7-X in the perspective of a path to a stellarator fusion power plant , 2013 .

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

[51]  F. C. Schüller,et al.  Simulation of ITER full-field ICWC scenario in JET: RF physics aspects , 2012 .

[52]  J..  Wall Conditioning in Fusion Devices and its Influence on Plasma Performance , 2012 .

[53]  O. Marchuk,et al.  0D model of magnetized hydrogen–helium wall conditioning plasmas , 2011 .

[54]  M. N. A. Beurskens,et al.  JET ITER-like wall—overview and experimental programme , 2011 .

[55]  B. Pégourié,et al.  Isotope exchange experiments on TEXTOR and TORE SUPRA using Ion Cyclotron Wall Conditioning and Glow Discharge Conditioning , 2011 .

[56]  W. Fundamenski,et al.  Modelling of beryllium erosion–redeposition on ITER first wall panels , 2011 .

[57]  F. C. Schüller,et al.  Recent results on Ion Cyclotron Wall Conditioning in mid and large size tokamaks , 2011 .

[58]  T. Lunt,et al.  ECRH-assisted plasma start-up with toroidally inclined launch: multi-machine comparison and perspectives for ITER , 2011 .

[59]  P. Barabaschi,et al.  Status and prospect of the JT-60SA project , 2010 .

[60]  D. A. Humphreys,et al.  Understanding and predicting the dynamics of tokamak discharges during startup and rampdown , 2009 .

[61]  Daniela Farina,et al.  A Quasi-Optical Beam-Tracing Code for Electron Cyclotron Absorption and Current Drive: GRAY , 2007 .

[62]  R. Neu,et al.  Wall conditioning in ASDEX Upgrade , 2007 .

[63]  B. Beaumont,et al.  ICRF PLASMAS FOR FUSION REACTOR APPLICATIONS , 2007 .

[64]  Eric Gauthier,et al.  Review of radio frequency conditioning discharges with magnetic fields in superconducting fusion reactors , 2005 .

[65]  W. Jacob,et al.  Stability of plasma-deposited amorphous hydrogenated boron films , 1997 .

[66]  C. Gil,et al.  Wall conditioning technique development in Tore Supra with permanent magnetic field by ICRF wave injection , 1997 .

[67]  G. Oost,et al.  ICRF wall conditioning at TEXTOR-94 in the presence of a 2.25 T magnetic field , 1997 .

[68]  J. Winter,et al.  REVIEW ARTICLE: Wall conditioning in fusion devices and its influence on plasma performance , 1996 .

[69]  N. Noda,et al.  Characteristics of Cleaning and Carbonizing Plasmas in TEXTOR , 1987 .