Program OverviewC ModAlcator

− Program Advisory Committee Meeting

February 2, 2005presented by E. S. Marmar

on behalf of the C-Mod Group

C ModAlcator

−Program Overview

• Research Highlights from FY04• Targets and Milestones• C-Mod Fusion Science Priorities• Contributions to high priority ITPA tasks• Initial FY05 run allocations• Comments on 2004 PAC advice• Priorities for major upgrades• Budget and Schedule

C ModAlcator

−Research Highlights 2004

• SOL flows impose a toroidal rotation boundary condition for confined plasma*– Explanation for large flows seen

to drive D/T co-deposition– Explanation for topology

dependence of H-Mode threshold• External control coils used to study

and suppress intrinsic error fields†

– Important scalings for ITER– Allowed first operation to Ip=2.0

MA*LaBombard, APS and EPS invited talks†Wolfe, APS invited talk

C ModAlcator

−Research Highlights 2004 (cont’d)

• ITB control with 2-frequency ICRF – Picture of control mechanisms emerging from fluctuation measurements and non-linear GS2 simulations*

• ICRF fast wave and mode conversion – Fast, Bernstein and IC waves all observed experimentally (PCI); Modeled with TORIC†

– Important code bechmarks– Demonstrated Ip drive– Flow drive not yet definitive • Mode seen with PCI

– k and ν agree with GS2 simulation (TEM drives outward particle transport, balancing pinch)

Wav

enum

ber(

cm-1

)

Time (s)

*Ernst, IAEA†Wukitch, APS invited talk

C ModAlcator

−Research Highlights 2004 (cont’d)

• Improved edge turbulence measurements (300 frame, 250 kHz movies, fast diodes, probes)*– Collaborative turbulence modeling

[Risø†, LLNL (BOUT)‡]• Risø model predicts blob formation

and strong radial propagation, similar to experiment

• Active and ICRF fast-particle driven alfven cascades– Important ITER physics– q-profile diagnostic during ramp-up– Snipes, APS invited talk– Strong modeling collabs with

Gorelenkov, Kramer, Breizman, Zonca

*Grulke, APS invited talk†O.E. Garcia, V. Naulin, A. Nielsen, J.J. Rasmussen‡M. Umansky, T. Rognlien, R. Cohen

C ModAlcator

−Collaborations are Significant in all Aspects of the Program

Recent Ideas Forum: 54/112 Ideas had non-MIT first authors from 11 institutions

Domestic Institutions

Princeton Plasma Physics LabU. Texas FRCU. AlaskaUC-DavisUC-Los AngelesUC-San DiegoCompXDartmouth U.GALLNLLodestarLANLU. MarylandMIT-PSFC TheoryORNLSNLAU. Texas IFSU. Wisconsin

International Institutions

Australian National UniversityBudker Institute, NovosibirskC.E.A. CadaracheC.R.P.P. LausanneCulham LabENEA/FrascatiIGI PaduaIPP GarchingIPP GreifswaldJET/EFDAJT60-U, JFT2-M/JAERIKFA JülichKFKI-RMKI BudapestLHD/NIFSPolitecnico di TorinoRisø National Laboratory. U. Toronto

C ModAlcator

−C-Mod has Prominent Role in

Education

• Typically have ~25-30 graduate students doing their Ph.D. research on C-Mod– Nuclear Engineering, Physics and EECS (MIT)– Collaborators also have students utilizing the facility (U.

Tx, U.C. Davis, U. Wisc., U. Torino)• 2 U. Tx PhD’s completed in 2004 (Alan Lynn, Matt Sampsell)

– Current total is 29• MIT undergraduates participate through UROP program (~5

at any time)• Host National Undergraduate Fusion Fellows during the

summer

1. Operate the facility for 19 weeks (+/- 10%) of single shift research (4 days/week, 8 hours/day). September 2004 — JOULE Milestone: 18 weeks

2. Compare confinement and H-Mode thresholds in single-null, double-null and inner-wall limited discharges. September 2004— JOULE Milestone: September 2004

3. Complete detailed design of advanced ICRF antenna. September 2004— JOULE Milestone: September 2004

4. Install first lower hybrid microwave launcher. September 2004 (1/5/2005)5. Operate to 2 MA plasma current. July 2004 6. Investigate the dependence of scrape-off layer flows on magnetic

topology, and their influence on core rotation. May 2004 7. Test all-digital real-time control system. September 20048. Initial tests of ITER-prototype tungsten brush tiles. September 2004 9. Complete migration to linux computing environment for data acquisition

and analysis. September 2004

FY2004 Program Execution Agreement (PEA) Tasks C ModAlcator

−

C ModAlcator

−2 MA Operation (PEA#5)

• Prior to installation of asymmetric control coils, locked modes prevented operation above 1.6 MA

• Nulling out principal component of error field enabled operation to 2 MA

C ModAlcator

−Targets and Milestones

• FY05 Level 1 JOULE Target– Measure plasma behavior with high-Z

antenna guards and input power greater than 3.5 MW.

• Addresses issues related to first wall choices, and the trade-offs between low-Z and high-Z materials.

• Can affect many important aspects of tokamak operation, including:

– impurity content and radiation losses from the plasma

– hydrogen isotope content in the plasma and retention in the walls

– disruption hardiness of device components.

• All significant when considering choices for next step devices to study burning plasma physics, especially ITER.

2-Strap ICRF Antenna with Mo Guards

C ModAlcator

−Targets and Milestones (cont’d)

• Commissioning the Lower Hybrid Current Drive System (FY05) – First experiments next month

• Disruption mitigation of high absolute pressure plasma (FY05)– High-pressure massive gas-puff

injection• Current profile control with

microwaves (FY05-06)– Far off-axis current drive

• Non-inductive sustainment of plasma current (FY06)– Intermediate goal: 50% non-

inductive Disruption mitigation gas tube(outlet 2 cm from LCFS)

C ModAlcator

−Targets and Milestones (details)

– Commissioning the Lower Hybrid Current Drive System (FY05)

• Theory and past experiments show that microwaves launched as so-called Lower Hybrid waves can be used to drive toroidal plasma currents with high efficiency, and that these currents can be localized radially. Importantly, hollow current profiles can be formed which lead to improved stability, higher plasma pressures, and nearly steady state “Advanced Tokamak operation. To pursue this research on Alcator requires the installation of a microwave transmitter system and an appropriate launcher.

– Disruption mitigation of high pressure plasma (FY05)• Tokamaks are subject to major disruptions, which are sudden, undesirable

terminations of the plasma discharge. Disruptions result in severe thermal loading of internal surfaces, large electromagnetic forces on conducting structures, and uncontrolled high-energy beams of electrons. These damaging effects will be particularly severe in burning-plasma-grade devices such as ITER. A number of methods have been proposed and/or tested to mitigate the consequences of disruptions, including injection of high-pressure gas jets. This technique has been shown to work in relatively low pressure, low energy density plasmas, but it is not at all clear that this method will work in high pressure, high energy density burning-plasma-grade discharges. Alcator C-Mod plasmas have absolute pressures and energy densities that are characteristic of those expected in ITER, and therefore will provide an excellent test bed for the gas jet disruption mitigation experiments

C ModAlcator

−Targets and Milestones (details)

– Current profile control with microwaves (FY05-06)• These experiments are aimed at developing efficient steady-state tokamak

operation by launching microwaves into Alcator C-Mod plasmas. The location of current driven by the “Lower Hybrid” waves we will use depends on their wavelength as measured parallel to the magnetic field. We will vary this wavelength and measure the location and amplitude of the driven current, with the intention of demonstrating an improvement of the plasma confinement through current-profile control. By adding independent plasma heating, the plasma pressure will be raised, and by varying the location of the RF-driven current, we can begin to investigate the stability limit of the plasma, i.e. the maximum pressure the plasma can sustain withoutdeveloping global instabilities.

– Non-inductive sustainment of plasma current (FY06)• In standard tokamak operation, the plasma current is induced by a

transformer coil, which limits the available pulse length. To operate steady-state, a tokamak needs other means, such as RF current drive and self-generated current. The long-term C-Mod objective calls for fully non-inductive sustainment, with 70% of the current self-generated. In the nearer term, as a first step, we intend to demonstrate discharges on Alcator C-Mod with at least 50% of the current driven non-inductively, using the newly installed antenna, which comprises the first phase of the 4.6 GHz microwave system. This will serve to verify the theoretically predicted current-drive efficiency and our ability to control the various plasma parameters needed to optimize it.

C ModAlcator

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Fusion Science (and Technology)C-Mod Priorities (Near Term)

• Evaluation of all-metal machine (OFES Level 1 JOULE target)– Removed all boron-nitride

protection limiters• Replaced with Mo on ICRF, LH

– Cleaned all Mo tiles of boronization residues

– Will make detailed evaluations before and after boronization(PAC 2004 recommendation)

• First operation with Lower Hybrid– System ready to inject power

(March 1)– Establish CD, study localization

and control

LH Launcher Installed

C ModAlcator

−C-Mod Fusion Science Priorities (cont’d)

• Transport– Self-generated flows and momentum

transport (including coupling to edge and SOL and identity expts with DIII-D)

– Edge flows, topology and H-mode threshold– Electron thermal transport and fluctuations– H-mode pedestal width scaling and physics– H-mode pedestal relaxation (including

EDA/QC and small ELM regimes)– ITB access and control mechanisms

(extending to weak and reversed shear regimes via LHCD)

• Plasma Boundary– Turbulence and EDGE/SOL transport– Edge flows and coupling to core rotation– Isotope retention and recycling– Tungsten brush prototypes (Burning Plasma)

W-brush tiles in high heat-flux region of outer divertor

C ModAlcator

−C-Mod Fusion Science Priorities (cont’d)

• Waves– Ion Cyclotron

• Minority 3He heating (50 MHz first, then 80 MHz@8 T)

• Mode conversion current, flow drive

– Lower Hybrid• Coupling physics• Phase studies (current drive,

heating, radial deposition)• Macroscopic Stability

– Disruption mitigation (massive gas puff)

– Locked modes (joint experiments)

– Alfven modes, cascades– NTM β threshold studies (joint

with DIII-D/JET)

TORIC Full-Wave Simulation in excellent agreement with experimental (PCI)

measurements of both density fluctuations and wavenumber

C ModAlcator

−C-Mod Fusion Science Priorities (cont’d)

• Advanced Tokamak Thrust– Current profile control– Internal Transport Barrier

dynamics and control• Both L- and H-mode edges

– Hybrid scenarios– Non-inductive scenarios– Power Handling (up to 8 MW, 1-3

seconds)• Burning Plasma Support Thrust

– First Wall, Materials studies– Integrated H-mode Scenario

Development, Performance enhancement

– Pedestal and Edge Relaxation Studies

– Non-dimensional Scaling Joint Experiments

ITB Control

C ModAlcator

−C-Mod Well Aligned with US Priorities

T1. How does magnetic field structure impact fusion plasma confinement?T2. What limits the maximum pressure that can be achieved in laboratory

plasmas?T3. How can external control and plasma self-organization be used to improve

fusion performance?T4. How does turbulence cause heat, particles, and momentum to escape from

plasmas?T5. How are electromagnetic fields and mass flows generated in plasmas?T6. How do magnetic fields in plasmas reconnect and dissipate their energy?T7. How can high energy density plasmas be assembled and ignited in the

laboratory?T8. How do hydrodynamic instabilities affect implosions to high energy density?T9. How can heavy ion beams be compressed to the high intensities required to

create high energy density matter and fusion conditions?T10. How can a 100-million-degree-C burning plasma be interfaced to its room

temperature surroundings?T11. How do electromagnetic waves interact with plasma?T12. How do high-energy particles interact with plasma?T13. How does the challenging fusion environment affect plasma chamber systems?T14. What are the operating limits for materials in the harsh fusion environment?T15. How can systems be engineered to heat, fuel, pump, and confine steady-

state or repetitively-pulsed burning plasma?

FESAC Priorities Panel Questions (C. Baker presentation at APS, preliminary)

C ModAlcator

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C-Mod Contributes Strongly to 5 of 6 Identified Areas of “Opportunities for Enhanced Progress”

• Top 6 priorities for incremental resources:– Support ITER construction and operation, including

diagnostic R&D.– Predict the formation, structure, and transient

evolution of the H-mode edge pedestal with high confidence.

– Support the TTF initiative with emphasis on extended understanding of electron-scale transport.

– Develop an integrated understanding of plasma self-organization and external control, enabling high-pressure sustained plasmas.

– Understand electron transport and laser-plasma interactions for Fast-Ignition high-energy density plasmas.

– Extend understanding and capability to control and manipulate plasmas with external waves.

C ModAlcator

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C-Mod is addressing High Priority ITPA Research Tasks

• Steady state operation– Hybrid scenarios

• Priority for AT thrust– Develop real time j profile control using heating and CD

actuators; assess predictability, in particular for off-axis CD• Main thrust of LHCD program; also MCCD, FWCD• State of the art modeling tools being developed and applied

(Bonoli, APS invited talk)• Transport Physics

– Address reactor relevant conditions, e.g. electron heating, Te~Ti, impurities, density, edge-core interaction, low momentum input …

• >90% of C-Mod operation is in these regimes– Encourage tests of simulation predictions via comparisons to

measurements of turbulence characteristics, code-code comparisons and comparisons to transport scalings

• Upgraded turbulence diagnostics• Increasingly strong interactions with theory and modeling

– Obtaining physics documentation for transport modeling of ITER hybrid and steady-state demonstration discharges

C ModAlcator

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C-Mod is addressing High Priority ITPA Research Tasks (2)

• MHD– Develop disruption mitigation techniques, particularly by noble gas

injection• Will investigate at absolute plasma pressures comparable to those on

ITER– Study fast particle collective modes in low and reversed shear

configurations: identify key parameters; perform theory data comparisons• Active and passive MHD, PCI, ICRF• Strong theory and modeling effort

– Perform MHD stability analysis of H-mode edge transport barrier under type I and tolerable ELM conditions

• Focusing on small ELM and EDA regimes• Access to type I ELMs in 2004; will pursue further

– Investigate/determine island onset threshold of NTMs … seed island control

• Study at increased β• Sawtooth stabilization (ICRF, LH)

– Construct new disruption DB including conventional and advanced scenarios and heat loads on wall/targets

• Contribute data from all scenarios at high absolute power/energy densities

C ModAlcator

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C-Mod is addressing High Priority ITPA Research Tasks (3)

• Pedestal and Edge– Construct physics-based and empirical scaling of pedestal

parameters• Priority of transport task group; coordinated experiments through

ITPA– Improve predictive capability for ELM size and frequency and

assess accessibility to regimes with small or no ELMs• Emphasis on small ELMs at higher β, and EDA

– Effects of collisionality studied through joint experiments– Improve predictive capability of pedestal structure through profile

modeling• Supplying data to new pedestal profile database

• Confinement Database and Modeling– Evaluate global and local models for plasma confinement by

testing against databases• C-Mod operates with unique dimensional parameters, providing

important constraints

C ModAlcator

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C-Mod is addressing High Priority ITPA Research Tasks (4)

• Divertor and SOL– Understand the effect of disruptions on divertor and first wall structures

• IR and ultra-fast imaging• Disruption mitigation

– Improve understanding of tritium retention and the processes that determine it• Understanding D levels on tiles (including sides) for B and Mo• Understanding removal of H at low tile temperature

♦ Improve understanding of SOL plasma interaction with main chamber♦ Develop improved prescription of SOL perpendicular transport and boundary

conditions for input to modeling♦ Transport studies are a central emphasis addressing both issues

• Diagnostics– Develop new methods to measure steady state magnetic fields accurately in

nuclear environment• Polarimetry is inherently steady-state; no in-principle special difficulty with

nuclear environment– Assess techniques for measurement of dust

• Dust detection system being developed for in-situ measurements during plasma pulses

C ModAlcator

−Initial FY05 Run Allocations

• Funding for 17 weeks of research operation (61 run days + 7 contingency)

• 128 run days required for priority runs (2005 Ideas Forum, plus open Mini-Proposals)

• Note that Science Task Force runs also contribute strongly to AT and BP thrusts

• Fraction of initial allocation for ITER and Burning Plasma support = 1/3

Initial Allocation(days)

Task Force

4Operations/Diags.

8Macro-Stability

6Plasma Boundary

5Lower Hybrid

12ICRF

12Transport

6Burning Plasma Support

8Advanced Tokamak

C ModAlcator

−2004 PAC Recommendations

• Tritium retention is a crucial ITER issue. C-Mod should take advantage of its all-metal uniqueness to address this issue. It should continue planned work and ensure that the impact of boronization on the result is understood– Extensive efforts during current maintenance: tile analysis; remove all BN and

replace with Mo, thorough cleaning of all boronized components– Top-level target for FY05 to understand differences, including effects of

boronization• unique capability to approach ITER divertor plasma conditions … should complete

the installation of the W brush panels for study of short pulse power handling– W brush modules installed, well diagnosed (spectroscopy, IR and visible

imaging)• Proposed massive gas injection for disruption mitigation will have particular impact

on ITER– Hardware installed (orifice within 2 cm of LCFS, 4 µs ultra-fast framing movies)– NIMROD modeling started

• Demonstration of robust ICRF D(3He) minority heating should remain high priority– H-Modes obtained at 8 T, but more development needed– Physics studies first at 50 MHz, direct comparison with D(H) on same shots– When successful, apply to 80 MHz, 8 Tesla for high performance studies

C ModAlcator

−2004 PAC Recommendations (cont’d)

• Locked mode threshold study over wide range of BT will clearly provide essential data not obtainable elsewhere. Studies best carried out in multi-machine comparison expts.– Coordinated comparisons among C-Mod, DIII-D, JET, Compass, already

bearing fruit; more to come in FY05• AT program should be given overall highest priority in the next two years

– Finishing and installing the LH launcher was the number 1 engineering priority during maintenance period

– Now we will get on with commissioning and then physics• Important that MSE is operational on a routine basis at the start of the LHCD

campaign– Substantial effort to understand systematic uncertainties; improved in-

vessel calibration facilities implemented– Long pulse DNB will improve beam into plasma calibrations

• If evaluation of the first LH launcher takes longer than planned, appropriate to delay installation of second launcher– First launcher delayed; will now get operational experience before

finalizing design of second.

C ModAlcator

−2004 PAC Recommendations (cont’d)

• Impact of reduction of 2 MW of ICRF power on physics program should be more carefully evaluated– Preliminary design of new 4-strap ICRF antenna completed in FY04– Have reordered priorities: complete new 4-strap ICRF antenna before adding 4’th

MW of LH. This maintains full ICRF capability when 2’nd LH launcher is installed.• Combination of GPI turbulence studies with wider-field optics upgrade planned for

disruption mitigation jet may allow further insight into edge/SOL plasma flow coupling with core rotation and L-H transition– Optics installed; will be shared between disruption mitigation and turbulence

studies• Program moving into studies of error fields and locked modes, NTMs and TAEs;

beneficial for theory group to identify internal and external resources to address these topics– Strong collaborations with T. Hender (UKAEA), F. Zonca (ENEA), B. Breizman

(UT-IFS), N. Gorelenkov (PPPL), G. Kramer (PPPL)• Installation of new divertor cryopump in early 2005 is expected

– Cryopump was delayed because of extra engineering effort on LH launcher.– Baffles installed for FY05 campaign– Cryopump is now highest engineering priority; installation for FY06 campaign.

C ModAlcator

−Priorities for Major Upgrades (FY05-07)

• Cryopump (install for FY06 campaign) [$520k]– Density control for LHCD/AT

• Polarimeter/Interferometer [$675k]– Current density profiles over entire range of ne operation

• DAC infrastructure upgrades (including Marshall cluster) [$210k]– Replace obsolete CAMAC; Improve modeling capabilities

• Core Thomson upgrade (8 additional channels) [$150k]– Better spatial resolution (especially for ITB discharges)

• Real-time matching upgrade—first transmitter [$90k]– Load-tolerant ICRF coupling

• New 4-strap ICRF antenna [$550k]– Maintain full ICRF capability with addition of second LH launcher

• Second Lower Hybrid Launcher [$720k]– Optimal use of 3MW source; Compound phase launch

• Upgrade outer divertor (advanced material) [$750k]*– Improved power handling for 5 second pulses

• Install 4th MW Lower Hybrid Source Power [$600k]*– Full non-inductive regimes

• Real-time matching – final 3 transmitters [$550k]*• Spare Klystron [$500k]*

*Require incremental funding

C ModAlcator

−Budget Profiles (k$)(no guidance yet for FY06)

25,250(25)

22,222(19)

97

425

2,070

19,630

FY04

28,710(25)

28,710(25)

27,610(25)

5 Year Proposal(run weeks)

22,038(17)

100

415

2,052

19,471

FY05

21,300(12)

22,038(15)

National Project Total(run weeks)

100LANL

415U Texas

2,052PPPL

19,471 MIT

FY06 (decrmt)

FY06 (flat)Institution

C ModAlcator

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Incremental Funds (~10%) Would Significantly Improve Progress

• Facility Operation: 6 additional run weeks [$1100k]– Currently fewer than half of priority runs can be

accommodated • Significantly earlier implementation of key upgrades

– Outer divertor (advanced material) [$375k*2]– 4th MW Lower Hybrid Source Power [$300k*2]

• Increased reliability, increased utilization– Real-time matching – final 3 ICRF transmitters

[$275k*2]– Spare Klystron [$500k]

C ModAlcator

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C-Mod Major Contributor to Fusion Science and Preparations for Burning Plasma

• Unique dimensional regimes• ITER relevant heating and current

drive tools, metal PFCs• Increasingly strong collaborations• Well aligned with Opportunities and

Priorities• Strong, broad contributions to high

priority ITPA research• Exciting prospects in coming 3

years with new tools and diagnostics– LHCD; cryopump– Disruption mitigation– Turbulence measurements– CNPA, Hard X, long-pulse DNB– All digital plasma control system

• Tight coupling to theory and modeling

C-Mod ITER/10

Ip = 1.6MA, BT = 5.3T Ip = 15MA, BT = 5.3T