Alcator C Mod. Integrated Scenarios ITER H-mode Baseline. Presented by: Stephen M. Wolfe

Transcription

1 Integrated Scenarios ITER H-mode Baseline Presented by: Stephen M Wolfe C-Mod PAC Meeting MIT Plasma Science & Fusion Center Cambridge, MA Mar 2-4, 2011

2 Definitions and Scope By Integrated Scenarios, we mean research aimed at reaching attractive operating points, generally cutting across multiple science topics and often involving interaction and compatibility issues between different plasma processes or regions The ITER Q = 10 DT H-mode baseline scenario features Positive shear, q 0 < 1 q 95 3, β N = 18, H H 1, f NI 025, n/n G 085 Edge transport barrier B T = 53T,I p = 15MA, n e m 3 Research effort also supports aspects of the ITER Pre-nuclear Commissioning Phase Operation in H and/or He majority Reduced parameters ( 1 2 B T, I p ) Alternate RF Scenarios Issues of H-mode access, character C-Mod PAC Meeting Mar 2-4, 2011 smw 1

3 Research Focus and Orientation Compared to the Topical Science areas, the H-mode Integrated Scenarios Research Program is more focussed on support of ITER construction and operations planning Respond to requirements identified by IO Strong IO participation in program planning IO staff involvement in design, execution, analysis of experiments Participate in identification, definition, and execution of Joint Experiments and High Priority research activities of ITPA Proactively identify and address issues relevant to ITER planning and operation Address C-Mod issues of integration and scenario development impacting our ability to carry out ITER-related research C-Mod PAC Meeting Mar 2-4, 2011 smw 2

4 Addressing ITER H-mode Scenario issues in C-Mod requires integration Issues, Challenges are similar for C-Mod and ITER Divertor and wall materials and conditioning High heat flux requirement Compatibility with low core radiation, Z eff Hydrogen isotope retention and recovery ICRF Heating Challenging RF power density Compatibility with H-mode edge, high n e operation, ELMs Compatibility with wall conditioning requirements Control of pedestal parameters, edge relaxation Variation of edge parameters (ν,β) Particle and impurity control ELM control C-Mod PAC Meeting Mar 2-4, 2011 smw 3

5 C-Mod H-mode Scenarios Research Topics Demonstration and validation of ITER reference scenarios Ramp-up/Ramp-down phases Flattop ITER demo discharges Benchmarking of Simulation Models H-mode access and performance requirements Power handling, particle control, and impurity seeding Scenarios for ITER Pre-nuclear phase Reduced field, current H, He majority operation IC Heating Scenarios Development and validation of Plasma Control strategies Plasma Material Interactions (addressed in Boundary section presentations) ELM and Pedestal Physics (see presentations on Transport and Pedestal Physics) C-Mod PAC Meeting Mar 2-4, 2011 smw 4

6 ITER has determined that early diverting and large Validation of will ITER bore plasmas be reference its baselinestartup startup scenarioc Kessel ITER is planning to divert at ~ 15 s in a 100 s Ip Proposed rampupramp to 15 MA flattop in 80 sec scales to C-Mod 135MA in 035 to 06 sec In order on to simulate (depending htei) ITER-like discharges in C-Mod, the time has been reduced to ms out Fulldivert bore plasma with x-point formation at 14 of a 500 ms Ip rampup maximum current needed to avoid overheating Cleaner early plasma ITER limiters conditions compared ITER startup scenariotorequires low 07 < li < 1 previous year for vertical stability; needs to conserve V-sec to increase burn time 2008 Progress in experiments Perform density variations in rampup? Examine effect on V-sec consumption, li, etc? Ohmic, ICRH, LHCD ramp-ups with similar 2009 target n e 05 00? Addresses Time, spac 2010 Recommendation Examine LH injection in rampup ITER must conserve volt-seconds in Ip and control the current profile C-Mod confirms V-s saving with ICRF heating in rampup o h m ic IC R F C-Mod indicates no c li with ICRF heating, in TSC simulations C -Mo d? Validate ITER simulations which showed LH has strongest impact in V-s and li of IC/EC/LH Benchmarking models used for ITER simulations IT E R C-Mod PAC Meeting Mar 2-4, 2011 smw 5

7 Effect of density variation in ITER-like Ohmic ramp-up experiments C Kessel Density range 065 < n e < m 3 (008 < n/n G < 02) Low density is required for significant V-sec saving Increased Z eff at low, intermediate density compensates increased T e Delayed sawtooth onset, reduced l i for lowest density case Uniform response of temperature profile at beginning of flattop C-Mod PAC Meeting Mar 2-4, 2011 smw 6

8 Initial results with LH injection in current ramp show savings of V-sec At Low density ( n e m 3 ) 400kW LH saves V-sec, relative to OH (or IC) l i reduced by 10% Surface voltage drops promptly at LH turn-on P rad and Z eff are elevated relative to ohmic Effect reduced at higher n e Hard X-rays observed at all densities Higher LH power may be beneficial Possible relation to density limit effect (see LH presentation) C-Mod PAC Meeting Mar 2-4, 2011 smw 7

9 Comparison of semi-empirical energy transport models in C-Mod ramp-up simulations C Kessel Theory-based models (eg GLF23) have difficulty modeling L-mode, higher q95, rampup phase Compare semi-empirical models Coppi-Tang, Bohm-gyroBohm, Current Diffusive Ballooning Model (CDBM) BgB did reasonably well with Ohmic, but predicted too high li with ICRF CT (with Cq = 35, Xmult = 275) reasonable in ICRF, too low li in ohmic CDBM reasonable in ohmic, too high li and too peaked Te with ICRF Coppi-Tang with original settings based on TFTR ohmic discharges had overly peaked Te profiles and high li None of these models appear to sufficiently capture details of C-Mod ramp-up experiments C-Mod PAC Meeting Mar 2-4, 2011 smw 8

10 ITER-like plasma rampdown experiments C-Mod rampdown experiments address issues, indicate that the density tracks Ip in ICRF constraints on ITER rampdown heated H-modes Examined 3 rampdown rates These results have already been used in ITER simulations Start rampdown with EDA Start rampdown with H-mode EDA H-mode Inject ICRF power at varying Inject ICRF power at levels, sustaining H-modes varying levels late into ramp Sustaining H-modes thru rampdown phase current ( constant Density tracks n/ng) in ICRF heated H-mode Requires ICRF power Highly reproducible Tped also drops smoothly with e trajectories for li and n current H-mode avoids OH overcurrent so long as H-mode avoids IpCS (OH1) is fast rampdown over-current forenough sufficiently fast ramp, at the expense of increasing li These results have already been used in ITER simulations C-Mod PAC Meeting Mar 2-4, 2011 smw 9

11 Scenario demonstrations: Full discharge sequence Demonstration of ITER-like equilibrium, p, T e /T i, power density Control of operating point Benchmark transport, stability modeling Evaluate impurity, particle control Evaluate disruptivity, stability issues Exploration of variations about reference scenario Continue Validation of robust ramp-down, shut-down sequence Compatibility of core and boundary Interaction with plasma-facing materials, including heat-flux and particle control, impurity seeding Demonstration of reliable, benign fault-handling and mitigation techniques C-Mod PAC Meeting Mar 2-4, 2011 smw 10

12 ITER Scenario Demonstration: IOS-11 ITPA Joint Experiment IOS 11 ITER baseline at q=3, β N = 18,n e = 085n G (D, H, He) Some flexibility allowed in parameters Issues for C-Mod include ICRF at high density, stationary H-mode at q < 35, acheivable β N with available power Lower field option relieves some constraints Relevant to pre-nuclear phase studies Experiments at half-field (27 T) ( ) Field overlap with other participating tokamaks, eg JET, provides gyro-size scaling opportunity Full-field C-Mod experiments at modest n/n G ( ) Extension of demo experiments at higher and lower density in next campaigns Target condition for seeding experiment IOS-12, Ramp-down validation IOS-22 C-Mod PAC Meeting Mar 2-4, 2011 smw 11

13 Half field demonstration of access to ITER-like (IOS-11) parameters in EDA discharges C Kessel Targeting q 95 3, β N > 17, κ 18,n/n G 85,H 98 1 B = 27 T, use 2nd harmonic H-minority ICRF heating scenario, f 80 MHz I p = 650kA operation (compares to 75MA in ITER at 27T (half-field)) q 95 = 3 32 β N < 19 H 98 = κ 175 Some high β N discharges exhibit n=2,3 low frequency MHD (NTM?) or small ELM activity, in addition to typical EDA QC mode signature C-Mod PAC Meeting Mar 2-4, 2011 smw 12

14 Near-term directions for C-Mod scenario validation work Continue development of half-field ITER-like discharge Develop and exploit full field (54 T) ITER-like discharge supporting ITPA Joint Experiments Extend Ramp-up experiments with LHCD H-mode access and sustainment during current ramps (up and down) Continue evaluation and benchmarking of transport models to improve projections to ITER C-Mod PAC Meeting Mar 2-4, 2011 smw 13

15 H-mode access: Power Requirements for high confinement H-modes Motivation: ITER Q DT = 10 H-mode Scenario requires H 98 1 with P net /P th (P th = 049n 072 e B 08 S 094 ) q div < 10MW m 2 P rad /P loss 08 P o div /P loss < 02 Experimental goals: Examine pedestal and confinement characteristics as function of margin above threshold power Evaluate margin above P th required to reach H 1 in stationary conditions Role of core/edge radiation on power requirement H 98 1 achievable for sufficient P net = P loss P rad core Low P o div achievable with low Z seeding Impurity Seeding Power [MW] [MW] A Loarte(IO),JHughes, MReinke Overview of Alc P ICRH and impurity species/a H 98 Power to outer divertor P in P RAD,CORE 02 N Time [sec] Ar Ne 52 nd APS Division of Plasma Physi C-Mod PAC Meeting Mar 2-4, 2011 smw 14 L

16 Power requirements for high confinement H-modes (cont) Plasma confinement directly correlated with pe Universal correlation (Seeded & Unseeded H-m Higher H 98 for low Z seeding associated with hi High confinement (H 98y2 1) achieved for high P net Seeding allows variation of P loss, P rad,total H98 Confinement directly correlated with T ped consistent with picture based on core profile stiffness P net /P th is good ordering parameter (roughly equivalent to net power / particle ) Impurity seeding allows scanning both P T e,95 (ev) in and P rad in controlled fashion same P net with different P in and P rad,core ( P rad,total /P loss ) Pedestal cooling at low P net more pronounced with Ar than Ne or N 2, as expected from radiation profiles Low Z Impurity seeding results in higher performance H-modes reduces incidence of high Z impurity injections and also reduces ICRF trips H 98,P net /P th in ITER target range obtained with low Z seeding N 2 Ne Ar unseeded Power Flow & Confinement : Seeded H-modes High confinement achieved for high P net and no overfuelling of SOL H98 52 nd APS Division ITER of Plasma Physics Meeting, Chicago, Illinois N 2 Ne Ar unseeded P net / P th 52 nd APS Division of Plasma Physics Meeting, Chicago, Illinois, USA C-Mod PAC Meeting Mar 2-4, 2011 smw 15 Page 10

17 Low divertor heat flux with low-z seeding meets ITER spec Partially detached divertor conditions achieved with Ne and P net NP th 2 seeding (or high and enough H 98 1 T ped ) required to maintain H 98 ~ 1 ITER If P net Peak P th q reduced high P rad,div by over, low aqfactor div (& divertor 5 detachment) can be achieved with H 98 from = 1 unseeded by low Z case seeding in C-Mod ITER ITER QExceeds DT = 10 ITER requirements (H 98 = P net /P th ~ 1 & P o-div /P loss < 02) have been achieved Outer divertor by impurity temperature seeding in H-modes optimization of impurity reduced mix (Ar from vs 1000 Ne, N C to ) may be required C for highest P rad /Z eff in ITER with P net >2MW H 98,P o div in ITER target range ITER obtained with low-z seeding Summary and Conclusions 12 ITER H98 N 2 Ne Ar unseeded H ITER-98(y,2) unseeded Ne seeded N 2 seeded Ar seeded P net / P th P o-divertor / P loss C-Mod PAC Meeting Mar 2-4, 2011 smw 16

18 Control of divertor power balance using radiation seeding (IOS-12) C-Mod experiments feature ITER-like divertor power density, geometry, neutral opacity, Extensive pedestal and divertor diagnostics Build on seeding results from H-mode access experiment ( ) Optimization of Seeding, Radiative divertor control ( ) Extend toward more ITER-like core plasma (lower q 95, ) Evaluate at higher density, investigate effect of high edge n e Localization of impurity puff to minimize core contamination, maximize divertor protection Dynamic comparison of recycling (Ne) and non-recycling (N 2 ) seed Develop feedback control for optimized divertor protection, core performance ( ) Apply to ITER-like conditions Discharges with high n e,edge follo large P net /P loss New experiments New divertor : gas feed 5 Optimisation to achieve highest P th requirements (core Z eff ) M Determine mechanisms of confin Reinke PSI Experiments are needed to opt loaction NINJA capillaries C-Mod PAC Meeting Mar 2-4, 2011 smw 17 Com requ loca U D m Dev Feed X T

19 ITER Pre-Nuclear Phase (first 2-3 years) No deuterium operation majority H (or He), minority He 3 Heating, CD sources under commissioning P tot < 73MW (NBI, EC, IC) 40 < f ICRF < 55MHz, P ICRF 20MW f ECRF = 170GHz, P ECRF 20MW B T between half and full field CFC divertor (decision on transition to W tbd) Issues: Access to H-mode ECRH launchers designed to optimise use of EC heating of plasmas off-axis) influence o C Mod access and performance needs to be asse ρ ICRH < 015 ρ ECRH < 05 ρ ECRH < 09 H 0 NB shinethrough (armour, 4MW/m 2 ) ne = 085 ngw q 95 = 3 Ability to validate ELM mitigation technique Alternate RF scenarios I p (MA) ITER Heating availability in H and He plasmas in H in 4 He EC IC H minority in He IC 3 He minority in H and He B T (T) EC n e (10 20 m 3 ) I p (MA) C-mod Ideas Forum ITER Heati ρ ICRH < ρ ECRH < ρ ECRH < ne D 0 NB shinethrou (armour, 4MW/m q 95 C-Mod PAC Meeting Mar 2-4, 2011 smw 18

20 Access to ELMy H-mode in helium majority plasmas C-Mod experiment comparing He to D majority plasma in same configuration as used for EPED-1 validation study run on previous day Operation with majority He (some residual D) Robust access to ELMy discharges at similar power levels as in D Pedestal parameters also comparable to deuterium H 98 1 obtained with T ped e 800eV Results obtained over range of density, current, power for comparison with comparables in D, model validation Results favorable for prospects of accessing ELMy H-mode in ITER pre-nuclear phase (with sufficient power) 0 Ip (MA) nebar(1e20/m3) ICRF power (MW) HeII monitor Electron betap(95) (%) H ITER98y C-Mod PAC Meeting Mar 2-4, 2011 smw 19

21 Near-term C-Mod Activities in support of pre-nuclear phase Investigate L-H and H-L threshold Species dependence of transition and confinement He (and H?) majority Evaluate dependence on X-point height, equilibrium details (Pedestal/Transport Group) Evaluate dependence on heating profile (relevant to fixed frequency EC) (Pedestal/Transport Group) Characterize He majority H-modes in ITER-like configurations Assess relevant ICRF scenarios He 3 minority in H majority plasmas (ICRF Group) Consider H majority scenarios C-Mod PAC Meeting Mar 2-4, 2011 smw 20

22 Development of plasma operational control methods C-Mod & ITER PF sets have similar arrangement and (multi-parameter) functionality Large vessel and structure currents, especially during startup, ramp-down MIMO shape control with few actuators, minimal null space, operation near current, voltage, stress limits RF-based actuators for heating, non-inductive current drive Negligible central particle, momentum sources C-Mod PAC Meeting Mar 2-4, 2011 smw 21

23 ITER Requires Large Gaps for Tr Development and testing of plasma control Modeling of an H-mode to L-mode Transition algorithms Testing of plasma control strategies in relevant scenarios Effects of sensor noise, transient events Effects of currents in passive structures on control and reconstructions Benchmarking of simulation codes ITER Requires Large Gaps for Transient Control Development and testing of machine protection algorithms Identification of and Modeling response of toan sensor, H-mode actuator to L-mode Radial inward Transition displacement at Q=10 can with be 10cm 15 MA contact faults Duration of inner wall contact depends on the central Response to proximity to actuator limits Peak engineering heat loads of ~40MW/m 2 Be tile adaptive transfer to safe shutdown sequence or PCS must maintain large enough gaps or trigger the di real-time pulse rescheduling Need experiments & modeling to demonstrate & extra Real-time identification of proximity to plasma J A Snipes, 2011 C-Mod Ideas Forum, MIT instability boundaries Radial inward displacement can be 10cm contact with the inner wall Duration of inner wall contact depends on the central solenoid saturation state C-Mod PAC Meeting Mar Peak 2-4, engineering 2011 heat loads of ~40MW/m 2 Be tiles would melt in ~ 03 smws! 22

24 Development and testing of plasma control algorithms: Safe Shutdown Sequence Example: Runaway electron discharges sometimes encountered when running low density Current carried by fast (MeV) electron tail Large hard X-ray flux can damage sensitive electronics Runaway beam can damage internal components, blamed for some melt damage on guard limiters Generally undesirable condition I p (MA) n e (10 20 m -3 ) Hard X-rays (AU) Runaway Sensing Standard Soft rampdown Jump-ahead routine implements soft landing Senses Hard X-ray levels above threshold during pre-set interval Jumps into ramp-down sequence by advancing synchronous time counter In routine use during Experimental Campaign No false positives 31 Successful discharge terminations I p Program (MA) 05 Jump-to time 00 Xjump Gate t (sec) C-Mod PAC Meeting Mar 2-4, 2011 smw 23

25 Burn Control simulation experiments with ICRH 1 Study evolution and stationary states of plasma with power dependent on plasma parameters (IOS-63: Control of experimentally simulated burning state) Use ICRF minority heating to mimic centrally peaked fast ion heating Control (part of) P ICRF n 2 f(t ) or R DD to simulate burn Apply feedback to try to maintain constant burn power against perturbations such as ELMs, sawteeth, MHD, density excursions, etc Experiments in suggested by P Politzer (GA) C-Mod PAC Meeting Mar 2-4, 2011 smw 24

26 C-Mod H-mode Scenarios Research Program Program elements paced by ITER priorities C-Mod facility capabilities Actuators, Diagnostics, Control system, Internals (since last PAC meeting): Approximately 95 run days so far (including FY10-11) Scenario demonstrations: Ramp-up, ramp-down; half-field scenarios H-mode access: Power requirements for high confinement Extension of impurity seeding studies Pre-nuclear phase: ELM characteristics in He majority plasmas Testing of pedestal model (see Pedestal presentation) : New rotated 4-strap ICRF antenna, Improved seeding capability, Optimization of radiative H-modes ITER demos (IOS-11) at full field Extend impurity seeding (IOS-12) studies, develop feedback control of divertor radiation Evaluation of transient control requirements H-mode access and characteristics during current ramps Current rampup scenarios with LHCD : Second New 4-strap ICRF antenna and automatic matching system, Additional LH launcher, DPCS enhancements Burn control studies Continue impurity seeding and power handling studies Development and testing of advanced plasma control/fault sensing algorithms C-Mod PAC Meeting Mar 2-4, 2011 smw 25

27 C-Mod Research on Integrated Scenarios for ITER H-mode Baseline H-mode baseline research program addresses cross-cutting physics and technology issues Exploits ITER-relevant C-Mod parameters and tools Addresses High-priority ITER Research Needs Strongly coupled to ITPA tasks, Joint Experiments Many additional ITER-related experiments in Topical Science Groups and Alternate Scenarios C-Mod PAC Meeting Mar 2-4, 2011 smw 26