Centre de Recherches en Physique des Plasmas EPFL, Association Euratom-Fédération Suisse, Lausanne, Switzerland S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of recent and current research on the TCV tokamak for the TCV team* S. Coda *including collaborating institutions: S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012

Overview of research in TCV 2 TCV parameters and capabilities Scientific mission of the TCV program TCV science  ELM control by ECRH and by plasma shaping  Physics of the snowflake divertor  New insights into energy confinement  Pulse optimization by r/t control and r/t simulations  Integrated MHD instability control Summary and outlook Outline

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 3 TCV R = 0.88 m, a = 0.25 m I p < 1 MA, B T < 1.54 T  < 2.8, -0.6 <  < MW ECRH power, 7 steerable launchers ×4 ×2

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 4 Study plasma and fusion science for ITER and next step  flexibility and proven ability to test new theories quickly Develop and test techniques for reactor operation  strong emphasis on real-time control, particularly with event triggers TCV mission

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 5 Outline TCV parameters and capabilities Scientific mission of the TCV program TCV science  ELM control by ECRH and by plasma shaping  Physics of the snowflake divertor  New insights into energy confinement  Pulse optimization by r/t control and r/t simulations  Integrated MHD instability control Summary and outlook

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 6 Local ECRH in pedestal influences ELMs J.X. Rossel et al, NF 52, (2012) X2 Resonances X3  =0.97  =0.93  =0.85 As power deposition moves towards plasma boundary, ELMs become smaller and more frequent (good!)… …even though less power is absorbed  simple scaling of type-I ELMs (frequency increases with power) is incomplete: power deposition location must play a role too

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 7 ELM detected  power cut for a set time  power restored to trigger next ELM ELM period still governed by energy input (longer cut  less energy  longer period), but r/t control regularizes it Pacing: r/t ECRH steadies ELM period standard deviation of period cw heating pacing

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 8 ECRH triggers individual ELMs independently of preceding ones For a given trigger sequence, the resulting ELM sequence is highly reproducible see also B.P. Duval et al, EX/1-2 (poster session P2, now)

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 9 Shaping influences ELMs: smaller, more frequent at negative triangularity A. Pochelon et al, to be published in Plasma and Fusion Research (2012)

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 10 Outline TCV parameters and capabilities Scientific mission of the TCV program TCV science  ELM control by ECRH and by plasma shaping  Physics of the snowflake divertor  New insights into energy confinement  Pulse optimization by r/t control and r/t simulations  Integrated MHD instability control Summary and outlook

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 11 The snowflake divertor: an advanced configuration proven to lessen wall loads  = (distance between X-points)  (minor radius) Merging of 2 X-points   B  =0  4 strike points Benefits: doubling of strike points + flux expansion On TCV, average ELM energy release reduced too

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 12 Lower strike point activated for  <1.2 in H-mode, for  <0.6 in L-mode Infrared data Extra snowflake strike points are activated well before X-points coalesce see also W.A.J. Vijvers et al, EX/P5-22 (Thursday morning)see D. Ryutov et al, TH/P4-18 (Wednesday afternoon)  =1.6  =0.4  =1.2 t-t ELM (ms)  =0.8 Data qualitatively consistent with prediction of convection-dominated flux for  p > 1 Langmuir probe ion saturation current during ELM cycle Lower strike point activated for  <1.2

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 13 TCV parameters and capabilities Scientific mission of the TCV program TCV science  ELM control by ECRH and by plasma shaping  Physics of the snowflake divertor  New insights into energy confinement  Pulse optimization by r/t control and r/t simulations  Integrated MHD instability control Summary and outlook Outline

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 14 L-mode confinement degradation: is it due to power deposition profile? Vary ECRH deposition width from peaked to Ohmic-like P ECRH P OH P 

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 15 L-mode confinement degradation is not due to power deposition profile all profile widths: standard L-mode scaling further degradation with off-axis heating

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 16 L-mode confinement is degraded further as power is deposited outside q=1 see also N. Kirneva et al, EX/P3-05 (Wednesday morning) N. Kirneva et al, PPCF 54, (2012)  eE /  L-mode q=1

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 17 TCV parameters and capabilities Scientific mission of the TCV program TCV science  ELM control by ECRH and by plasma shaping  Physics of the snowflake divertor  New insights into energy confinement  Pulse optimization by r/t control and r/t simulations  Integrated MHD instability control Summary and outlook Outline

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 18 Adding live simulation to measurements: a new paradigm for r/t control Use physics knowledge when measurements are inadequate (e.g. for q profile, bootstrap current) State observer methodology incorporates new observers and new models seamlessly 1 ms simulation cycle, ≪ current diffusion time see also F. Felici et al, EX/P3-12 (Wednesday morning) F. Felici et al, NF 51, (2011) Pilot TCV SIMULINK implementation: RAPTOR Control of T e0 (measured) and l i (simulated)

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 19 Reactor economics: current profile control by Ohmic transformer in ramp-up lessens power demands later Current profile best manipulated at low current (short skin time, less power needed) Successful nonlinear control of l i on TCV General formalism for optimization of tokamak pulse trajectories developed in parallel using offline version of RAPTOR F. Felici et al, PPCF 54, (2012) see also J.A. Romero et al, EX/P4-35 (Wednesday afternoon) J.A. Romero et al, NF 52, (2012)

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 20 TCV parameters and capabilities Scientific mission of the TCV program TCV science  ELM control by ECRH and by plasma shaping  Physics of the snowflake divertor  New insights into energy confinement  Pulse optimization by r/t control and r/t modeling  Integrated MHD instability control Summary and outlook Outline

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 21 Sawtooth pacing by ECRH: complete control of individual crash times Pacing also achieved through destabilization (ECRH inside q=1) or locking to modulation frequency M. Lauret et al, NF 52, (2012) Crash occurs when stabilizing q=1 power is removed T.P. Goodman et al, PRL 106, (2012)

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 22 Long sawteeth cause large seed islands  control them by pacing Preëmptive ECRH only at known sawtooth crash time: economical way to reduce seed island size High-power ECRH stabilizes NTM directly if needed Failsafe NTM prevention: sawtooth pacing + preëmptive low-power ECRH on island + backup power for NTM stabilization F. Felici et al, NF 52, (2012) see also B.P. Duval et al, EX/1-2 (poster session P2, now) 200 kW not enough for prevention 320 kW: NTM-free shot

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 23 ELM mitigation by local ECRH in pedestal and by shaping Studies of edge physics at snowflake strike points for varying X-point separation Basic investigation of L-mode confinement Demonstration of expanded r/t control scheme including live simulation Pulse optimization by Ohmic transformer control Deployment of integrated MHD (sawtooth + NTM) control Summary

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 24 Outlook: major upgrades and research opportunities TCV science is built on unique versatility in shaping and heating Versatility to be strengthened and operational domain to be expanded by MW-level NBI heating and additional X3 ECRH The TCV program is flexible and  can quickly test new ideas  welcomes worldwide collaborators willing to work on TCV

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 25 TCVTCV  EX/1-2: B.P. Duval, “Real time control on TCV”, P2 poster session, Tue pm  EX/P3-05: N. Kirneva, “Confinement with ECRH”, Wed am  EX/P3-12: F. Felici, “Real-time model-based control”, Wed am  EX/P4-32: E. Lazzaro, “Triggerless onset and effect of rotation on NTMs”, Wed pm  EX/P4-35: J.A. Romero, “Current profile control using the Ohmic heating coil”, Wed pm  EX/P5-22: W.A.J. Vijvers, “Snowflake divertor in L- and H-mode”, Thu am  EX/P6-08: T.P. Goodman, “ECRH absorption measurement for real-time polarization optimization and studies of quasilinear effects”, Thu pm Fusion technologyFusion technology  ITR/2-5: P. Bruzzone, “Test results of ITER conductors in the SULTAN facility”, Wed pm  FTP/4-5Ra: J. Fikar, “Optimization of nanostructured ferritic steel fabrication”, Fri am  FTP/P7-11: M. Battabyal, “Development of W based materials for fusion reactors”, Fri am DIII-DDIII-D  EX/P4-09: H. Reimerdes, “Rotation braking from test blanket module in ITER”, Wed pm Basic plasma physicsBasic plasma physics  EX/P6-28: A. Fasoli, “Turbulence and fast ions in magnetized toroidal plasmas”, Thu pm TheoryTheory  TH/P4-14: P. Ricci, “Global validated simulation of edge plasma turbulence”, Wed pm  TH/7-1: W. Cooper, “Bifurcated helical core equilibrium states in tokamaks”, Fri am CRPP contributions

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 26 ELM frequency and size successfully r/t controlled by ECRH simply by varying the duration of the power cut based on a measurement of the ELM frequency see also B.P. Duval et al, EX/1-2 (poster session P2, now)

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 27

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 28 Inverted quasi-bolometric tomography, at ELM crash Extra snowflake strike points are activated well before X-points coalesce  =1.2  =0.4  =0.8

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 29

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 30 Measuring poloidal rotation: a new, more sensitive, indirect method Incompressible flows: v ,HFS – v ,LFS ≈ 4qv  4q ≫ 1  toroidal speed asymmetry amplifies measurement of poloidal speed A. Bortolon et al, submitted to NF (2012)

S. Coda, 24 th IAEA Fusion Energy Conference, OV/4-4, San Diego, 9 October 2012 Overview of research in TCV 31 Poloidal rotation is neoclassical in TCV