Overview of High-Field Divertor Tokamak
Results from Alcator C-Mod*Earl Marmar
on behalf of the Alcator C-Mod TeamMIT Plasma Science and Fusion Center and CollaboratingInstitutions*Supported by the U.S. Dept of Energy, Fusion Energy Sciences

OV/2-5, 26th IAEA Fusion Energy Conference,Kyoto, Japan, October 17, 2016

Compact, High B Tokamak Physics
Very Productive 2015-2016 Experimental Campaigns• Core and Pedestal Transport– ELM-less enhanced confinement regimes (EDA-H, I-mode)– Multi-scale gyrokinetic simulations• ICRF: 3-ion mode conversion heating• SOL and Divertor– feedback controlled detachment– Divertor Test Tokamak• Compact, high magnetic field approach– Leverage high field, HTS superconductor technology– ARC Pilot Plant• Completion of C-Mod operations in FY2016– Plasma pressure record– Plans
E. Marmar, FEC 2016 OV/2-5

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At High Field, C-Mod Naturally Accesses
Enhanced Confinement with no ELMS
• EDA H-mode– Peeling-Ballooning stablepedestal, avoids damaging
ELM heat pulses• Edge regulation throughcontinuous (quasicoherent) modes• E and imp comparable toELMy H-mode

E. Marmar, IAEA FEC 2016 OV/2-5

High Performance 5.4T EDA H-mode

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At High Field, C-Mod Naturally Accesses
Enhanced Confinement with no ELMS
• I-mode*– H-mode energy confinement,
L-mode density pedestal, lowparticle/impurity confinement– Edge regulation throughcontinuous (weakly-coherent)modes/broadened by GAMs
– Best access with ion B drift
away from active X-point– Highly attractive for fusionenergyHigh Performance 8T I-mode: H98~1*A. Hubbard EX/3-1
E. Marmar, IAEA FEC 2016 OV/2-5

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At High Field, C-Mod Naturally Accesses
Enhanced Confinement with no ELMS
• I-mode*– H-mode energy confinement,L-mode density pedestal, lowparticle/impurity confinement– Stationary densities, which arereadily controlled– Edge regulation throughcontinuous (weakly-coherent)modes/broadened by GAMs
– Highly attractive for fusionenergyHigh Performance 8T I-mode: H98~1*A. Hubbard EX/3-1
E. Marmar, IAEA FEC 2016 OV/2-55

8 T I-modes confirm & extend thepromising trends with BT• P(L-I)/ne~ BT0.25− Weak BT thresholddependence (agreeswith ASDEX-Uresults)• Power range at 8 Teven larger than at~5.5 T•No 8 T discharges had
I-H transitions, up tomaximum ICRF power(Ptot/S = 0.63 MW/m2)*A. Hubbard EX/3-1
E. Marmar, IAEA FEC 2016 OV/2-56

• Gyrokinetic
simulations
incorporating only ionscale turbulenceshows shortfall inelectron channel heat
flux (esp. in reactorrelevant equilibrated
e-i regimes)• State-of the art
multiscale simulations,
including ion- andelectron-scales
simultaneously, show
important interactions
E. Marmar, IAEA FEC 2016 OV/2-5y/sMulti-Scale Gyrokinetic Simulations Help
Resolve Long-Standing Transport Puzzle*

x/s*N.T. Howard et al., Phys. Plasma 23(2016)056109
C. Holland TH/6-1
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Multi-Scale Gyrokinetic Simulations Help
Resolve Long-Standing Transport Puzzle*

MW/m2

Ion and Electron Heat Fluxes:
Ion-scale simulation in red
Multiscale simulation in blue

MW/m2

• State-of the art
multiscale
simulations, includingion- and electronscales
simultaneously, show
importantinteractions– Resolves Qe
discrepancy

a/LTia/LTi

Particularly relevant for coupled ion-electronregimes (as on C-Mod and in reactors)*N.T. Howard et al., Phys. Plasma 23(2016)056109
E. Marmar, IAEA FEC 2016 OV/2-58

Experimental Demonstration of Novel 3-ion (HD-3He) ICRF Scenario• On C-Mod (in collaboration
with JET colleagues): firstexperimental verification of
3-ion species heatingscenario*– Heating efficiency(W/PICRF) significantly
greater than for 3Heminority• 24 kJ/MW versus 14kJ/MW

B=7.8T*Kazakov NF 032001 (2015)
E. Marmar, IAEA FEC 2016 OV/2-5

J. Wright EX/P3-59

Experimental Demonstration of Novel 3-ion (HD-3He) ICRF Scenario
Frequency (MHz)

1.5
1.4
1.3
1.2
1.16

Te0 (keV)• Destabilization of core TAEmodes (Tornado modes)
indicates production of ~ MeV
3He ion populations –proxy forfusion alphas• Could be applied during
non-nuclear phase on ITER
• Could also be used for D-T
majority plasmas*• 3rd ion candidates: 7Li, 9Be
or 11B

Tornado modes measured with
Phase Contrast Imaging

543*Kazakov NF 032001 (2015)
E. Marmar, IAEA FEC 2016 OV/2-5

0.94 0.95 0.96 0.97
Time (s)J. Wright EX/P3-510

Divertor Power Handling and Sustainment
Challenges• (Multiple) Facilities needed to solve dual(related) challenges of power handlingand sustainment• Current devices (especially C-Mod) andITER design at limits of power handlingfor divertor– Challenge in reactors increases bynearly an order of magnitude*• Sustainment in reactor regimes (highdensity, equilibrated ions/electrons, lowor no rotation drive) not yet developed**• Divertor Test Tokamak with Advanced RFsustainment should be designed and built

ADX Concept for a Divertor TestTokamak***G. Wallace, EX/7-1; P. Bonoli TH/5-1

E. Marmar, IAEA FEC 2016 OV/2-5*B. LaBombard, et al.,Nuclear Fusion 55(2015)053020

11Divertor Power Handling and Sustainment
Challenges• (Multiple) Facilities needed to solve dual High-Field Side very favorable for
RF Launchers**(related) challenges of power handlingand sustainment• Current devices (especially C-Mod) andITER design at limits of power handlingfor divertor– Challenge in reactors increases bynearly an order of magnitude*• Sustainment in reactor regimes (highdensity, equilibrated ions/electrons, lowor no rotation drive) not yet
LHCD Launcher
ICRF Antennadeveloped**• Divertor Test Tokamak with Advanced
Improves: RF coupling,RF sustainment should be designed andCD, impurity screening
built**G. Wallace, EX/7-1;P. Bonoli TH/5-1 Reduces: erosion, neutronloading
E. Marmar, IAEA FEC 2016 OV/2-5

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High B HTS Superconductors: New Technology
Opens Pathway to High Field Reactors••••

Leverage High Temperature (HighField) Superconductors
Device about the size of JET, but at10 Tesla– Projects to 500 MW fusion power,~200 MW net power– Takes advantage of the many
designs for high B copper burning
plasma concepts (BPX, FIRE,Ignitor, etc.)– C-Mod data base gives increased
confidence in performance
HTS could also accommodate jointed
coils, allowing for modular
construction, removable internal
components
R&D needed to develop coils at scale,joints
E. Marmar, IAEA FEC 2016 OV/2-5

ARC Pilot Reactor Concept**Sorbom, et al., Fus. Eng. Des. 100(2015)378;
D. Whyte TIP/P7-6

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September 30, 2016: Attained New Tokamak World
Record for Volume Average Pressure (2.05 atm)

• Lawson:
Require highabsolute(P*E) forfusion power• Surpassed 2005 (C-Mod) record by 15%• 3 different approaches were pursued– Each produced high performance
E. Marmar, IAEA FEC 2016 OV/2-5

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September 30, 2016: Attained New Tokamak World
Record for Volume Average Pressure (2.05 atm)

E. Marmar, IAEA FEC 2016 OV/2-5

EDA H-Mode1160930033• Maintained above <P>=1.7
atm for 10 energy
confinement times• Utilized nitrogen seeding tokeep molybdenum
source/core radiated powerlow• B=5.7 T, q95=3.2, N=1.5,n/ngreenwald=0.56– Safely away from all
operational and stabilitylimits

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Histogram of Maximum <Pressure>from the Entire C-Mod Database

E. Marmar, IAEA FEC 2016 OV/2-516

Plans• Much analysis of data remains to be done
• Experimental team will concentrate moreheavily on collaborations at other facilities(including DIII-D, NSTX-U, ASDEX-U, JET,WEST, W7-X, EAST, KSTAR, etc.)• Propose to help lead national design ofDivertor Test Tokamak• Develop HTS High-Field Superconductors forfusion

E. Marmar, IAEA FEC 2016 OV/2-517

Summary• ELM-suppressed confinement modes look increasingly promising forreactor operation– Particularly I-mode at high magnetic field• Important progress on low z-seeding, with feedback to ameliorate
divertor power handling challenge• High field side in near double-null– impurity shielding confirmed– significant advantages for RF launchers and heating/current-drive
effectiveness• State-of-the art multi-scale gyrokinetic simulations reveal importantrole of coupling between ion and electron scale turbulence in Qe• New absolute tokamak pressure record: <P>=2.05 atmosphere• High-field, High Temperature Superconductors open new path tocompact, high B pilot plant/reactors
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C-Mod Related Presentations at 2016 IAEA FEC
Wednesday Morning:••••••••

M. Porkolab: Studies of Turbulence and Transport in the Alcator C-Mod and DIII-D Tokamaks with Phase Contrast Imaging andGyrokinetic Modelling, EX/P3-1
J.E. Rice: Effects of the q Profile on Toroidal Rotation in Alcator C-Mod LHCD Plasmas, EX/P3-2
M. Reinke: Investigations of Radial High-Z Transport Mechanisms in ICRF-Heated Alcator C-Mod H-Mode Plasmas, EX/P3-3
J.C. Wright: Experimental Results from Three-Ion Species Heating Scenario on Alcator C-Mod, EX/P3-5
B. LaBombard: Plasma Profiles and Impurity Screening Behaviour of the High-Field Side Scrape-Off Layer in Near-Double-Null
Configurations: Prospect for Mitigating Plasma-Material Interactions on RF Actuators and First-Wall Components, EX/P3-6
D. Brunner: Divertor and Core Plasma Performance Optimization Enabled by Direct Feedback Control of Surface Heat Flux onAlcator C-Mod’s High-Z Vertical Target Plate Divertor, EX/P3-7
R. Granetz: Developing Disruption Warning Algorithms Using Large Databases on Alcator C-Mod and EAST Tokamaks, EX/P3-8
D. Shirakid: Disruption Mitigation in the Presence of Pre-Existing MHD Instabilities, EX/P3-20

Wednesday Afternoon:•••

A. Hubbard: Advances in Physics and Performance of the I-Mode Regime over an Expanded Operating Space on Alcator C-Mod,
EX/3-1
T. Jenkins: High-Performance Computational Modelling of Plasma-Surface Interactions and RF Antennas, TH/P4-34
L. Delgado-Aparicio: Locked-Mode Avoidance and Recovery without External Momentum Input Using ICRH, EX/P4-39

Thursday Afternoon•C. Myers: A Multimachine Analysis of Nonaxisymmetric and Rotating Halo Currents, EX/P6-46

Friday Morning:••••

G. Wallace: Influence of the Scrape-Off Layer on RF Actuator Performance, EX/7-1
C. Holland: Demonstrating the Multiscale Nature of Electron Transport through Experimentally Validated Simulations, TH/6-1
D. Whyte: Smaller & Sooner: Exploiting High Magnetic Fields from New Superconductors for a More Attractive Fusion Energy
Development Path, FIP/P7-6
B.J. Ding: Recent Experimental and Modelling Advances in the Understanding of Lower Hybrid Current Drive in ITER-RelevantRegimes,
EX/P7-5
E. Marmar,
IAEA FEC 2016 OV/2-5

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The C-Mod Team (2014-2016)
MIT: S. Abraham, S. Agabian, A. Alexandridis, E. Anderson, C. Arlington, D. Arsenault, S. Baek, R. Ballinger, W. Beck, L.

Berkowitz, A. Binus, P. Bonoli, J. Bosco, L. Bromberg, D. Brunner, W. Burke, W. Byford, N Cao, C. Cauley, V. Censabella, J.
Chicarello, M. Chilenski, W Cochran, J. Coco, K. Cote, A. Creely, E. Dames, E. Davis, G. Dekow, P. Diamond, J. Doody, E.
Edlund, P. Ennever, D. Ernst, I Faust, C. Fiore, E. Fitzgerald, W. Forbes, T. Fredian, M. Fulton, C. Gao, T. Golfinopoulos, R.
Granetz, M. Greenwald, W. Han, Z. Hartwig, H. Hoffmann, N. Howard, A. Hubbard, J. Hughes, I. Hutchinson, J. Irby, M.
Iverson, D. Johnson, A. Kanojia, C. Kasten, W. Keating, L. Kesler, M. Khoury, P. Koert, M. Kralj, F. Kreisel, A. Kuang, D. Kwak,B. LaBombard, A. Latham, J. Lee, P. Lienard, Y. Lin, B. Linehan, G. MacKay, E. Marmar, W. McCarthy, K. Montes, N. Mucic, R.
Mumgaard, R. Murrray, D. Muttart, J. Nickerson, R. Parker, W. Parkin, M. Partha, J. Penna, A. Pfeiffer, S. Pierson, M. Porkolab,J. Rice, P. Rodriguez-Fernandez, R. Rosati, J. Ruiz-Ruiz, B. Savage, H. Savelli, C. Schaefer, M. Schmidtmayr, F. Sciortino, S.
Shiraiwa, J. Sierchio, M. Silveira, B. Sorbom, J. Stillerman, L. Sugiyama, C. Sung, D. Terry, J. Terry, A. Tinguely, T. Toland, E.
Tolman, D. Vestal, R. Vieira, J. Walk, G. Wallace, B. Wang, R. Watterson, A. White, D. Whyte, T. Wilks, D. Winklehner, S.
Wolfe, K. Woller, G. Wright, J. Wright, S. Wukitch, L. Zhou

Domestic Collaborators: A. Bader, S. Ballinger, H. Barnard, L. Berry, A. Bhattacharjee, M. Bitter, R.

Boivin, M. Brookman, J. Canik, M. Churchill, L. Delgado-Aparicio, A. Diallo, D. D’Ippolito, F. Ebrahimi, D. Garnier, M. Garrett, R.
Goldston, W. Guttenfelder, R. Harvey, D. Hatch, K. Hill, C. Holland, R. Hong, W. Horton, J. Hosea, S. Houshmandyar, C. Kessel,M. Kotschenreuther, A. Kritz, S-H. Ku, C. Kung, C. Lau, K. Liao, Z. Liu, J. Lore, J. Maddox, S. Mahajan, D. Mikkelsen, S.
Mordijck, C. Myers, J. Myra, R. Ochoukov, T. Osborne, N. Pablant, D. Pace, A. Pankin, C. Paz-Soldan, R. Perkins, P. Phillips, R.
Pinsker, M. Podesta, Y. Podpaly, F. Poli, M. Pueschel, M. Reinke, B. Rogers, T. Rognlien, W. Rowan, D. Russell, S. Scott, P.
Snyder, B. Stratton, G. Tynan, M. Umansky, Weigang Wan, Weixing Wang, K. Widmann, J.R. Wilson, X.Q. Xu, S. Zweben

International Collaborators: J. Allcock, C. Arnas, I. Bandyopadhyay, M. Barnes, L. Boettger, X.

Bonin, F. Casson, M. Cerretti, I. Cziegler, W. Dekeyser, G. DeTemmerman, P. DeVries, B. Ding, M. Dunne, B. Duval, C. Fenzi, O.
Garcia, C. Giroud, T. Goerler, O. Grulke, F. Halpern, J. Harrison, D. Hartmann, W. Helou, J. Hillairet, Y. Kazakov, V. Kazantzidis,J-H. Kim, R. Kube, M. Lehnen, B. Lipschultz, S. Lisgo, A. Loarte, Y. Ma, R. McDermott, D. Moulton, S. Murakami, I. Nunes, G.
Olynyk, J. Ongena, F. Parra-Diaz, Y. Peysson, S. Pitcher, R. Pitts, A. Powell, I. Pusztai, P. Ricci, F. Ryter, T. Shinya, G. Sips, Y.
Takase, T. Tala, C. Theiler, N. Tsujii, D. Van Eester, S. Vartanian, C. Yang, X-J. Zhang, Y-P. Zhao

E. Marmar, IAEA FEC 2016 OV/2-520