The geometry of the ICRF-induced wave–SOL interaction. A multi-machine experimental review in view of the ITER operation

As part of ITPA-Integrated Operational Scenario activities, this contribution reviews recent experimental characterizations of radio-frequency (RF)-induced scrape-off layer (SOL) modifications of various tokamaks worldwide and of the LArge Plasma Device at UCLA. The phenomenology, as observed using a large variety of measurement techniques, is consistent with expectations from RF sheath rectification. Emphasis is then put on the complex three-dimensional (3D) spatial patterns of the RF–SOL interaction, in relation to the magnetic topology and the spatial distribution of RF currents over the metallic structures surrounding the RF wave launchers. Dependence on the local plasma parameters in the antenna vicinity is also briefly addressed. The final part discusses implications for future devices.

[1]  V. Bobkov,et al.  Recent progress in modeling ICRF-edge plasma interactions with application to ASDEX Upgrade , 2021, Nuclear Fusion.

[2]  J. Myra.  A tutorial on radio frequency sheath physics for magnetically confined fusion devices , 2021, Journal of Plasma Physics.

[3]  N. Fedorczak,et al.  Perspective of analogy between heat loads and impurity production in L-mode discharges with ICRH in WEST , 2021 .

[4]  J. Ongena,et al.  Ion cyclotron resonance heating fast and slow wave excitation and power deposition in edge plasmas with application to ITER , 2021 .

[5]  N. Fedorczak,et al.  RF wave coupling, plasma heating and characterization of induced plasma-material interactions in WEST L-mode discharges , 2021, Nuclear Fusion.

[6]  Ion cyclotron range of frequency heating for SPARC , 2020, THE 6TH INTERNATIONAL CONFERENCE ON BIOLOGICAL SCIENCE ICBS 2019: “Biodiversity as a Cornerstone for Embracing Future Humanity”.

[7]  W. Zhang,et al.  Improved operating space of the ICRF system in ASDEX upgrade , 2020, THE 6TH INTERNATIONAL CONFERENCE ON BIOLOGICAL SCIENCE ICBS 2019: “Biodiversity as a Cornerstone for Embracing Future Humanity”.

[8]  C. Bourdelle,et al.  First application of Ion Cyclotron resonant frequency waves on WEST plasma scenarios , 2020 .

[9]  N. Fedorczak,et al.  Metallic impurity content behavior during ICRH-heated L-mode discharges in EAST , 2020, Nuclear Fusion.

[10]  B. Van Compernolle,et al.  Measurement and modeling of the radio frequency sheath impedance in a large magnetized plasma , 2020 .

[11]  J. Myra,et al.  Filament-assisted mode conversion in magnetized plasmas , 2020 .

[12]  F. Clairet,et al.  ICRH coupling optimization and impurity behavior in EAST and WEST , 2020, THE 6TH INTERNATIONAL CONFERENCE ON BIOLOGICAL SCIENCE ICBS 2019: “Biodiversity as a Cornerstone for Embracing Future Humanity”.

[13]  F. Durodié,et al.  Traveling wave array for DEMO with proof of principle on WEST , 2019, Fusion Engineering and Design.

[14]  D. Coster,et al.  Scrape-off layer density tailoring with local gas puffing to maximize ICRF power coupling in ITER , 2019, Nuclear Materials and Energy.

[15]  N. Bertelli,et al.  Resolving interactions between ion-cyclotron range of frequencies heating and the scrape-off layer plasma in EAST using divertor probes , 2019, Plasma Physics and Controlled Fusion.

[16]  J. Contributors,et al.  Analysis of metallic impurities during the application of three-ion ICRH scenario at JET-ILW , 2019 .

[17]  Diogo E. Aguiam,et al.  Impact of ICRF on the scrape-off layer and on plasma wall interactions: From present experiments to fusion reactor , 2019, Nuclear Materials and Energy.

[18]  J. Contributors,et al.  2D mappings of ICRF-induced SOL density modifications on JET , 2018 .

[19]  W. Gekelman,et al.  Experimental Observation of Convective Cell Formation due to a Fast Wave Antenna in the Large Plasma Device. , 2017, Physical review letters.

[20]  G. Tynan,et al.  Characterization and Mitigation of ICRF Antenna - Plasma Edge Interaction , 2017 .

[21]  Heng Zhang,et al.  Characterization of the mutual influence of Ion Cyclotron and Lower Hybrid Range of frequencies systems on EAST , 2017 .

[22]  James R. Wilson,et al.  The role of rectified currents in far-field RF sheaths and in SOL losses of HHFW power on NSTX , 2017 .

[23]  L. Colas,et al.  SOL RF physics modelling in Europe, in support of ICRF experiments , 2017 .

[24]  G. Tynan,et al.  Characterization of SOL plasma flows and potentials in ICRF-heated plasmas in Alcator C-mod , 2017, 1703.07538.

[25]  J. Contributors,et al.  Ion cyclotron resonance heating for tungsten control in various JET H-mode scenarios , 2017 .

[26]  P. Bonoli,et al.  ICRF heating schemes for the ITER non-active phase , 2017 .

[27]  J. Contributors,et al.  RF Sheath-Enhanced Plasma Surface Interaction Studies using Beryllium Optical Emission Spectroscopy in JET ITER-Like Wall , 2017 .

[28]  R. Neu,et al.  Reducing ICRF-specific impurity release in ASDEX Upgrade and JET , 2017 .

[29]  M. Reinke.  Experimental pathways to understand and avoid high-Z impurity contamination from ICRF heating in tokamaks , 2016 .

[30]  D. Coster,et al.  Modelling of the ICRF induced E  ×  B convection in the scrape-off-layer of ASDEX Upgrade , 2016 .

[31]  James R. Wilson,et al.  Resonance in fast-wave amplitude in the periphery of cylindrical plasmas and application to edge losses of wave heating power in tokamaks , 2016 .

[32]  R. I. Pinsker,et al.  Maximization of ICRF power by SOL density tailoring with local gas injection , 2016 .

[33]  C. Giroud,et al.  Optimization of ICRH for core impurity control in JET-ILW , 2016 .

[34]  J. Contributors,et al.  Estimates of RF-induced erosion at antenna-connected beryllium plasma-facing components in JET , 2016 .

[35]  Qingxi Yang,et al.  Making ICRF power compatible with a high-Z wall in ASDEX Upgrade , 2016 .

[36]  V. Bobkov,et al.  Progress in controlling ICRF-edge interactions in ASDEX upgrade , 2015 .

[37]  D. V. Eester,et al.  A crude model to study radio frequency induced density modification close to launchers , 2015 .

[38]  R. Dux,et al.  Trends of W behavior in ICRF assisted discharges in ASDEX Upgrade , 2015 .

[39]  J. Contributors,et al.  Impact of localized gas injection on ICRF coupling and SOL parameters in JET-ILW H-mode plasmas , 2015 .

[40]  J. Contributors,et al.  Localized Scrape-Off Layer density modifications by Ion Cyclotron near fields in JET and ASDEX-Upgrade L-mode plasmas , 2015 .

[41]  R. E. Bell,et al.  The contribution of radio-frequency rectification to field-aligned losses of high-harmonic fast wave power to the divertor in the National Spherical Torus eXperiment , 2015 .

[42]  J. Contributors,et al.  Spectroscopic investigation of heavy impurity behaviour during ICRH with the JET ITER-like wall , 2014 .

[43]  Characterization of local heat fluxes around ICRF antennas on JET , 2014 .

[44]  L. Colas,et al.  Radio-frequency sheaths physics: Experimental characterization on Tore Supra and related self-consistent modeling , 2014 .

[45]  V. Rohde,et al.  2-dimensional mapping of ICRF-induced scrape-off layer modifications with a retarding field analyser on ASDEX-Upgrade , 2014 .

[46]  Jean-Marie Noterdaeme,et al.  Influence of gas injection location and magnetic perturbations on ICRF antenna performance in ASDEX Upgrade , 2014 .

[47]  X. Litaudon,et al.  Self-consistent Modeling of Radio-frequency Sheaths: Comparison with Tore Supra Measurements and Predictability for Future Machines , 2014 .

[48]  B. Lipschultz,et al.  ICRF-enhanced plasma potentials in the SOL of Alcator C-Mod , 2014 .

[49]  L. Giannone,et al.  ICRF operation with improved antennas in ASDEX Upgrade with W wall , 2013 .

[50]  G. R. Hanson,et al.  Effects of ICRF power on SOL density profiles and LH coupling during simultaneous LH and ICRF operation on Alcator C-Mod , 2013 .

[51]  L. Colas,et al.  RF-sheath patterns modification via novel Faraday screen and strap voltage imbalance on Tore Supra ion cyclotron antennae , 2013 .

[52]  L. Colas,et al.  Measurement of sheath potential in RF-biased flux tubes using a retarding field analyzer in Tore Supra tokamak , 2013 .

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

[54]  R. Neu,et al.  ICRF specific plasma wall interactions in JET with the ITER-like wall , 2013 .

[55]  Jet Efda Contributors,et al.  RF sheath-enhanced beryllium sources at JET’s ICRH antennas , 2013 .

[56]  J. Contributors,et al.  Characterisation of local ICRF heat loads on the JET ILW , 2013, 1306.6778.

[57]  Jaworski,et al.  Fast-wave power flow along SOL field lines in NSTX and the associated power deposition profile across the SOL in front of the antenna , 2012 .

[58]  F. Liu,et al.  Investigation of lower hybrid wave coupling and the related effects of ion cyclotron range of frequencies in EAST , 2012 .

[59]  J. Terry,et al.  Ion-cyclotron range of frequencies in the scrape-off-layer: fine structure radial electric fields , 2012 .

[60]  X. Litaudon,et al.  Characterization of heat flux generated by ICRH heating with cantilevered bars and a slotted box Faraday screen , 2012 .

[61]  J. Contributors,et al.  Impurity production from the ion cyclotron resonance heating antennas in JET , 2012 .

[62]  B. Lipschultz,et al.  ICRF-induced Radial Electric Fields in the Far Scrape-Off-Layer of Alcator C-Mod , 2012 .

[63]  Hong Wang,et al.  Experimental investigation of the potentials modified by radio frequency sheaths during ion cyclotron range of frequency on EAST , 2012 .

[64]  Z. Vizvary,et al.  Heat loads from ICRF and LH wave absorption in the SOL: characterization on JET and implications for the ITER-Like Wall , 2011 .

[65]  L. Colas,et al.  Attenuation of ICRH‐induced potentials in the SOL of Tore Supra , 2011 .

[66]  R. Felton,et al.  Optimizing ion-cyclotron resonance frequency heating for ITER: dedicated JET experiments , 2011 .

[67]  Z. Vizvary,et al.  Heat loads on JET plasma facing components from ICRF and LH wave absorption in the SOL , 2011 .

[68]  L. Giannone,et al.  ICRF antenna-plasma interactions and its influence on W sputtering in ASDEX upgrade , 2011 .

[69]  G. Agarici,et al.  Heat flux calculation and problem of flaking of boron carbide coatings on the Faraday screen of the ICRH antennas during Tore Supra high power, long pulse operation , 2011 .

[70]  V. Bobkov,et al.  Influence of the phase shift between antennas on W sputtering in ASDEX Upgrade , 2011 .

[71]  L. Giannone,et al.  Assessment of compatibility of ICRF antenna operation with full W wall in ASDEX Upgrade , 2010 .

[72]  J. Contributors,et al.  Recent experiments on alternative dipole phasing with the JET A2 ICRF antennas , 2009 .

[73]  V. Basiuk,et al.  Ion Cyclotron Resonant Heating in Tore Supra , 2009 .

[74]  B. Lipschultz,et al.  ICRF specific impurity sources and plasma sheaths in Alcator C-Mod , 2009 .

[75]  R. Neu,et al.  Plasma-wall interaction and plasma behaviour in the non-boronised all tungsten ASDEX Upgrade , 2009 .

[76]  R. Neu,et al.  Operation of ICRF antennas in a full tungsten environment in ASDEX Upgrade , 2009 .

[77]  B. Pégourié,et al.  Impurity production monitoring during RF experiments in Tore Supra , 2009 .

[78]  J. Contributors,et al.  Effects of ICRF induced density modifications on LH wave coupling at JET , 2009 .

[79]  James R. Wilson,et al.  High harmonic fast wave heating efficiency enhancement and current drive at longer wavelength on the National Spherical Torus Experiment , 2008 .

[80]  Jet Efda Contributors,et al.  Understanding the spatial structure of RF-induced SOL modifications , 2007 .

[81]  V. Basiuk,et al.  RF Coupling and Antenna Heat Load Control for Combined LHCD and ICRH in Tore Supra , 2007 .

[82]  R. Mitteau,et al.  RF heating optimization on Tore Supra using feedback control of infrared measurements , 2007 .

[83]  V. Basiuk,et al.  2-D mapping of ICRF-induced SOL perturbations in Tore Supra tokamak , 2007 .

[84]  B. Lipschultz,et al.  RF-Plasma Edge Interactions and their Impact on ICRF Antenna Performance in Alcator C-Mod , 2007 .

[85]  E. Marmara,et al.  Hydrogen Control in Alcator C-Mod Walls and Plasmas , 2006 .

[86]  R. Guirlet,et al.  Metallic impurity production during high power RF experiments on Tore Supra tokamak , 2005 .

[87]  P. T. Bonoli,et al.  Investigation of performance limiting phenomena in a variable phase ICRF antenna in Alcator C-Mod , 2004 .

[88]  B. Beaumont,et al.  Density Convection near Radiating ICRF Antennas and its Effect on the Coupling of Lower Hybrid Waves , 2003 .

[89]  A. Becoulet,et al.  Hot spot phenomena on Tore Supra ICRF antennas investigated by optical diagnostics , 2003 .

[90]  P. M. Ryan,et al.  Modelling of mixed-phasing antenna–plasma interactions on JET A2 antennas , 2002 .

[91]  L. Colas,et al.  Edge plasma density convection during ion cyclotron resonance heating on Tore Supra , 2002 .

[92]  David R. Smith,et al.  A study of molybdenum influxes and transport in Alcator C-Mod , 2001 .

[93]  D. D'Ippolito,et al.  Radio-frequency sheath mitigation by insulating antenna limiters , 1997 .

[94]  J. Wilgen,et al.  Measurements of edge density profile modifications during IBW on TFTR , 1997 .

[95]  N. Hershkowitz,et al.  RF generated voltage on the Faraday screen of an ICRF antenna and its effect on the Phaedrus-T edge plasma , 1996 .

[96]  N. Hershkowitz,et al.  Edge power deposition reduction in a tokamak by replacing the Faraday screen on an RF antenna with an insulator , 1996 .

[97]  D. D'Ippolito,et al.  Low‐power fast wave antenna loading as a radio‐frequency sheath diagnostic , 1996 .

[98]  A. Lichtenberg,et al.  Principles of Plasma Discharges and Materials Processing , 1994 .

[99]  G. Oost,et al.  The interaction between waves in the ion cyclotron range of frequencies and the plasma boundary , 1993 .

[100]  N. Hershkowitz,et al.  Comparison of the effects of an ICRF antenna with insulating side limiters with and without a Faraday screen on the edge parameters of a tokamak plasma , 1993 .

[101]  J -M Noterdaeme,et al.  The interaction between waves in the ion cyclotron range of frequencies and the plasma boundary , 1993 .