GA–A22950 The DIII–D Five-Year Program Plan 1999 – 2003 by PROJECT STAFF AUGUST 1998 GENERAL ATOMICS GA–A22950 THE DIII–D FIVE-YEAR PROGRAM PLAN 1999–2003 by PROJECT STAFF ABRIDGED VERSION This is an abridged version of the DIII–D Five-Year Technical Proposal. Not included are sections which include resumes, past publications and GA management structure. Work prepared under Contract Nos. DE-AC03-89ER51114, W-31-109-ENG-38, W-7405-ENG-36, W-7405-ENG-48, DE-AC05-96OR22464, DE-AC02-76CH03073, DE-AC04-94AL85000, and Grant Nos. DE-FG02-89ER53297, DE-FG02-86ER53223, DE-FG03-89ER51116, DE-FG03-86ER53266, DE-FG03-86ER53225, DE-FG03-95ER54294, DE-FG05-96ER64373, and DE-FG03-97ER54415 for the U.S. Department of Energy GA PROJECT 3466 AUGUST 1998 DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. TABLE OF CONTENTS 1.0 THE DIII–D FIVE-YEAR PROGRAM SUMMARY .................................................................................... 1-1 1.0.1. The DIII–D National Program Overview and Mission ............................................................ 1-1 1.0.2. The Proposed DIII–D Five-Year Program Plan...................................................................... 1-2 1.0.3. Leadership ............................................................................................................................ 1-3 1.1. Tokamak Research Using the DIII–D National Facility ..................................................................... 1-5 1.1.1. Science Research ................................................................................................................ 1-9 1.1.2. DIII–D Facility Operations ..................................................................................................... 1-14 1.2. Upgrade DIII–D Components and Systems to Achieve Program Objectives ................................... 1-19 1.2.1. ECH Upgrade ........................................................................................................................ 1-20 1.2.2. Divertor Upgrade ................................................................................................................... 1-21 1.2.3. Magnet Pulse Length Upgrade.............................................................................................. 1-22 1.2.4. Upgrade Contingency Options ............................................................................................. 1-23 2. TECHNICAL DISCUSSION: THE DIII–D FIVE-YEAR PROGRAM PLAN ............................................. 2.1-1 2.1. The DIII–D Five-Year Program Plan ................................................................................................. 2.1-1 2.1.1. The DIII–D Mission ............................................................................................................... 2.1-1 2.1.2. The DIII–D Program ............................................................................................................. 2.1-3 2.1.3. National Leadership .............................................................................................................. 2.1-8 2.1.4. Benefits of DIII–D Research ................................................................................................. 2.1-8 2.1.5. The DIII–D National Team .................................................................................................... 2.1-10 2.2. The DIII–D Advanced Tokamak Program ......................................................................................... 2.2-1 2.2.1. The Plan ............................................................................................................................... 2.2-1 2.2.2. What is an Advanced Tokamak? .......................................................................................... 2.2-6 2.2.3. The Science, the Tools, and the Integration ......................................................................... 2.2-6 2.3. Fusion Energy Science in DIII–D ...................................................................................................... 2.3-1 2.3.1. Confinement Science and Transport Barrier Control ............................................................ 2.3-2 2.3.2. Stability Science ................................................................................................................... 2.3-20 2.3.3. Boundary Science ................................................................................................................ 2.3-35 2.3.4. Physics of Current Drive and Heating .................................................................................. 2.3-62 2.4. Pathways to the Future...................................................................................................................... 2.4-1 2.4.1. The Path to ITER................................................................................................................... 2.4-1 2.4.2. The Path to an Optimized Superconducting Tokamak Power System .................................. 2.4-7 2.4.3. The Path to a Compact Ignition Experiment ......................................................................... 2.4-13 2.4.4. The Path to the Spherical Tokamak Pilot Plant .................................................................... 2.4-15 2.4.5. Research Implications for DIII–D from a Look at Future Tokamak Possibilities ................... 2.4-18 General Atomics Report GA-A22950 iii 2.5. The DIII–D National Fusion Facility — Status and Upgrades............................................................ 2.5-1 2.5.1. Electron Cyclotron Heating and Current Drive Systems Upgrade ........................................ 2.5-14 2.5.2. Divertor System Upgrades ................................................................................................... 2.5-16 2.5.3. Magnet Pulse Length Upgrade (Baseline) ............................................................................ 2.5-21 2.5.4. Improvements to the DIII–D Tokamak (Completed as Part of Tokamak Research) ............. 2.5-23 2.5.5. Diagnostic Systems (Tokamak Research)............................................................................. 2.5-28 2.5.6. Control, Data Acquisition and Analysis Systems (Tokamak Research) ................................ 2.5-39 2.5.7. Fast Wave ICRF Systems (Option) ...................................................................................... 2.5-45 2.5.8. Neutral Beam Heating Systems ........................................................................................... 2.5-47 2.5.9. Other Upgrade Options ........................................................................................................ 2.5-50 2.6. The DIII–D National Fusion Program ................................................................................................ 2.6-1 2.6.1. National Leadership Role ..................................................................................................... 2.6-2 2.6.2. Collaborations and Outreach ................................................................................................ 2.6-3 2.6.3. The DIII–D National Team .................................................................................................... 2.6-20 2.6.4. DIII–D National Program Governance .................................................................................. 2.6-34 3. OTHER PERTINENT INFORMATION ...................................................................................................... 3-1 3.1. Development Process of the DIII–D Five-Year National Program Plan ............................................ 3-1 3.2. History and Accomplishments of the DIII–D Program........................................................................ 3-5 3.2.1. Origin of the Program ............................................................................................................ 3-5 3.2.2. Accomplishments of the 1993 Five-Year DIII–D Plan and Context for the 1998 Five-Year Plan ......... 3-6 3.2.3. DIII–D Scientific Progress and Accomplishments ................................................................. 3-12 3.2.4. DIII–D Operations and Facility Improvements....................................................................... 3-17 3.2.5. Transition to a National Program .......................................................................................... 3-20 LIST OF FIGURES 1-1. The DIII–D program plan progresses from short pulse AT physics, through optimization, to 10 s operation ............ 1-3 1-2. DIII–D Advanced Tokamak research plan will integrate the upgraded heating and divertor to optimize performance ... 1-5 1-3. Implementation of the proposed DIII–D research requires the plasma control tools defined in the facility upgrades ... 1-7 1-4. Pursuit of the key research thrusts requires the diagnostic upgrades included in the DIII–D Plan ............................ 1-7 1-5. Recent technical developments of 110 GHz gyrotrons and a high-power diamond window (upper right) motivate an accelerated ECH program .................................................................................................................................. 1-19 1-6. We plan to implement a high triangularity pumped divertor in stages ................................................................. 1-20 1-7. The DIII–D upgrade plan includes contingency options to adapt to evolving scientific outcomes .......................... 1-20 2.1-1. DIII–D Program linkages provide intellectual inputs, research inputs and staff opportunities ............................ 2.1-3 2.1-2. The DIII–D research plan culminates in integrated, Advanced Tokamak operating scenarios ........................... 2.1-5 2.1-3. DIII–D program schedule .................................................................................................................................... 2.1-7 2.2-1. The 1999–2003 research plan advances facility capability in step with advancing confinement, stability, boundary and current drive science ............................................................................................................................................. 2.2-4 2.2-2. ECH barrier control is illustrated by a three-case comparison ............................................................................ 2.2-20 2.3-1. E×B shear suppression enables transport barrier control.................................................................................... 2.3-4 2.3-2. An opposing NB will enable transport barrier control through manipulation of E×B shear ................................. 2.3-7 2.3-3. DIII–D E×B shear regulation occasionally results in modest electron transport reductions................................. 2.3-9 2.3-4. Energy confinement enhancement factor increases with pedestal pressure in ITER ......................................... 2.3-15 2.3-5. Stability limits for the n=1 ideal kink mode .......................................................................................................... 2.3-24 2.3-6. Wall stabilization is predicted to allow ideal n=1 kink stability.............................................................................. 2.3-25 2.3-7. Simulations with good experimental foundation indicate additional particle pumping will maintain higher q(0) ... 2.3-29 2.3-8. Better bootstrap alignment could increase li while preserving NCS ................................................................... 2.3-31 2.3-9. Strong emissivity peaks at low temperatures is the key to a radiative divertor ................................................... 2.3-36 2.3-10. The standard model predicts radiated heat flux limits for the divertor ................................................................. 2.3-36 2.3-11. Radiation evenly distributed from the X–point region is in stark contrast to standard divertor model predictions . 2.3-38 2.3-12. Te measurements do not support model predictions of significant electron conduction ..................................... 2.3-39 2.3-13. Divertor measurements and modeling show < 2 eV Td, permitting volume recombination to compete with ionization ........................................................................................................................................................................... 2.3-40 2.3-14. Volume recombination remains small until the momentum is reduced via ion-neutral interactions .................... 2.3-41 2.3-15. Carbon radiation dominates partially detached divertor operation induced by deuterium puffing ....................... 2.3-42 2.3-16. Either impurities or better neutral baffling are needed to achieve the AT scenario .............................................. 2.3-44 2.3-17. Slanted RDP structures should aid in obtaining impurity enrichment in the divertor............................................ 2.3-45 2.3-18. Pellet fueling with divertor pumping shows the Greenwald limit is not an obstacle ............................................ 2.3-52 2.3-19. Scientific progress: DIII–D fusion performance has doubled every 2 years ....................................................... 2.3-53 2.3-20. A large pressure decrease in ELMing H–mode discharges is rewarded with an increase in confinement quality .. 2.3-54 2.3-21. Models predict the RDP baffles will reduce core ionization by an order of magnitude ........................................ 2.3-55 2.3-22. A 26 MW energy loss per Type I ELM is predicted for ITER ................................................................................ 2.3-57 2.3-23. Localized noninductive current drive can yield improved confinement and stability ........................................... 2.3-64 2.3-24. The allowable power range of DIII–D AT scenarios can be estimated from simple relationships ....................... 2.3-66 2.3-25. Optimum ramp-up begins at ßp close to the equilibrium limit .............................................................................. 2.3-70 2.3-26. One–dimensional simulations show bootstrap overdrive can generate 1 MA in 2 s ........................................... 2.3-72 2.4-1. DIII–D research connects to four possible tokamak program directions ............................................................. 2.4-2 2.4-2. The major radius of superconducting tokamaks is constrained by wall loading at low aspect ratio and by stress at high aspect ratio .................................................................................................................................................................... 2.4-8 2.4-3. High aspect ratio superconducting tokamaks have relatively low fusion power .................................................. 2.4-8 2.4-4. DIII–D research projects to a spherical tokamak power system ......................................................................... 2.4-16 2.5-1. The DIII–D tokamak facility spans a half city block ............................................................................................. 2.5-2 2.5-2. The heart of the facility is the DIII–D tokamak with its many support systems, utilities and diagnostics ................. 2.5-3 2.5-3. DIII–D capabilities allow a wide range of research and technology issues to be addressed .............................. 2.5-5 2.5-4. The entire DIII–D first wall is graphite ................................................................................................................. 2.5-5 2.5-5. The upper divertor cryopump is optimized to pump highly triangular double-null divertor discharges .................... 2.5-6 2.5-6. An extensive array of computer systems operates the tokamak and collects and analyzes the data ..................... 2.5-7 2.5-7. Quarterly boundary radiation levels show the site is maintained well below the 40 mrem operating limit ............ 2.5-9 2.5-8. Proposed facility development incorporates ideas from GA, collaborators and the February, 1998 workshop ... 2.5-10 2.5-9. The carbon first wall and divertor targets protect the vacuum vessel and limit high-Z impurities ....................... 2.5-16 2.5-10. The planned completion of the Radiative Divertor installation includes the lower baffle and the private flux baffles 2.5-17 2.5-11. Divertor and first wall surface options will be tested on DIII–D ........................................................................... 2.5-19 2.5-12. The toroidal field coil is capable of 10 s and longer pulse operation with the completion of the proposed upgrade 2.5-21 2.5-13. Additional coils would give an improved match to the outer vacuum vessel wall mode structure ...................... 2.5-24 2.5-14. The new MSE system features a tangential and radial view of a single beam line ............................................. 2.5-32 2.5-15. New interferometer concept overcomes the difficulty with measurement of the first order term ......................... 2.5-36 2.5-16. Several possible beamline rotation options would allow counter-injection .......................................................... 2.5-48 2.5-17. The LANL RACE compact toroidal injector is of the size needed for DIII–D ....................................................... 2.5-51 2.5-18. Operation of DIII–D at 3.4 T requires upgrades .................................................................................................. 2.5-52 2.6-1. The DIII–D program advances fusion energy science and improves the tokamak concept ............................... 2.6-2 2.6-2. DIII–D collaborates with the world’s premier tokamak facilities .......................................................................... 2.6-4 2.6-3. The DIII–D tokamak is capable of producing plasma shapes of other tokamaks ............................................... 2.6-14 2.6-4. The DIII–D program is implemented through a line management organization which includes collaborators and four GA research divisions ................................................................................................................................................... 2.6-35 3-1. Scientific progress: DIII–D fusion performance has doubled every two years ................................................... 3-12 LIST OF TABLES 1-1. DIII–D program collaborators insure coordination of national and international tokamak optimization .................. 1-4 2.1-1. Advanced tokamak program — objectives, challenges, and targets .................................................................. 2.1-6 2.1-2. DIII–D program collaborators .............................................................................................................................. 2.1-11 2.2-1. Program logic defines tools and approaches ...................................................................................................... 2.2-5 2.2-2. Parameters of DIII–D scenarios .......................................................................................................................... 2.2-18 2.3-1. Results of dimensionless parameter scaling experiments in DIII–D for various regimes .................................... 2.3-11 2.3-2. Tools for L–H transition physics studies .............................................................................................................. 2.3-14 2.3-3. Elements of divertor physics ............................................................................................................................... 2.3-36 2.3-4. Enrichment of neon and argon is presented for four cases of induced deuterium flow ...................................... 2.3-43 2.4-1. ρ* scaling from ITER to various tokamaks .......................................................................................................... 2.4-3 2.4-2. From ITER to DIII–D and Alcator C–Mod varying ν* and ρ* ............................................................................... 2.4-5 2.4-3. DIII–D contributions to ITER ................................................................................................................................ 2.4-6 2.4-4. ρ* scaling from an optimized superconducting power plant to DIII–D ................................................................ 2.4-10 2.4-5. DIII–D contributions to the superconducting tokamak path ................................................................................. 2.4-12 2.4-6. ρ* scaling from DIII–D to a compact ignition experiment..................................................................................... 2.4-14 2.4-7. DIII–D contributions to the compact ignition path ................................................................................................ 2.4-15 2.4-8. β scaling from an ST pilot plant to DIII–D ........................................................................................................... 2.4-19 2.4-9. DIII–D contributions to the ST path ..................................................................................................................... 2.4-20 2.4-10. DIII–D contributions to future tokamak paths ...................................................................................................... 2.4-21 2.5-1. Power to plasma of auxiliary heating systems .................................................................................................... 2.5-6 2.5-2. Power capability of heating systems after proposed upgrades are complete .................................................... 2.5-11 2.5-3. Summary of the five areas of research into nonaxisymmetric magnetic phenomena and how they would be addressed by the proposed external and internal coil systems .................................................................................................... 2.5-23 2.5-4. Diagnostic systems installed on DIII–D ............................................................................................................... 2.5-29 2.5-5. Upper divertor diagnostic additions ..................................................................................................................... 2.5-30 2.5-6. Lower divertor diagnostic modifications .............................................................................................................. 2.5-31 2.6-1. DIII–D program collaborators .............................................................................................................................. 2.6-1 2.6-2. Recent SBIR collaborations with the GA Fusion Group ...................................................................................... 2.6-9 2.6-3. DIII–D 1997 experiments emphasized urgent ITER physics R&D ...................................................................... 2.6-16 2.6-4. General Atomics provides ITER support in addition to DIII–D program support ................................................. 2.6-17 2.6-5. Past and present graduate and post-doctoral students at DIII–D ....................................................................... 2.6-19 2.6-6. DIII–D collaborations related to stability and disruption physics ......................................................................... 2.6-21 2.6-7. DIII–D collaborations related to transport and fluctuations ................................................................................. 2.6-22 2.6-8. Recent collaborations related to DIII–D work in the wave/particle topical area .................................................. 2.6-23 2.6-9. DIII–D collaborations related to divertor and boundary physics .......................................................................... 2.6-24 2.6-10. Programmatic responsibilities of major DIII–D U.S. collaborators ...................................................................... 2.6-25 2.6-11. Programmatic roles of DIII–D university collaborators (1997) ............................................................................. 2.6-25 2.6-12. Programmatic roles of other collaborations ......................................................................................................... 2.6-26 3-1. Changes in five-year plan since July 1997 .......................................................................................................... 3-1 3-2. Comparison of 1993 upgrade plan with actual upgrades implemented .............................................................. 3-7 3-3. An assessment of progress on the 1993 advanced tokamak research goals ..................................................... 3-8 3-4. An assessment of resolution of 1993 divertor research program functions/needs issues .................. 3-10 3-5. An assessment of accomplishments of 1993 divertor program goals and guidelines ......................... 3-10 3-6. Integrated advanced tokamak parameter goals and achievements .................................................... 3-11 3-7. Comparison of 1993 plan and actual GA funding levels and operations weeks ................................. 3-17 3-8. Facility improvements planned and implemented in FY94–98 ............................................................ 3-18 3-9. An assessment of the 1993 five-year DIII–D new diagnostic plan and accomplishments .................. 3-19 3-10. New diagnostics implemented on DIII–D that were not anticipated in the 1993 five-year plan ........... 3-20 1. THE DIII–D FIVE-YEAR PROGRAM SUMMARY 1.0.1. THE DIII–D NATIONAL PROGRAM OVERVIEW AND MISSION The strategy for the recently restructured U.S. Fusion Energy Sciences Program focuses on innovation and scientific discovery to strengthen the program’s ties to other fields of science, to position the United States to continue playing a meaningful role in the world fusion energy effort within available resources, and to preserve the basis for a future expanded U.S. Fusion Energy Program. The DIII–D Research Program is a cornerstone element in this national fusion program strategy (see 2.1). The problem addressed by this proposal is the optimization of the tokamak. Within this context, the DIII–D Program mission is: To establish the scientific basis for the optimization of the tokamak approach to fusion energy production. The DIII–D Program is an Advanced Tokamak (AT) Program using and advancing fusion energy science to provide the basis for future fusion initiatives. Tokamak optimization has been a basic organizing thrust of the DIII–D Research Program for several years. In implementing the new DIII–D research plan, we will pursue AT science and integrated performance optimization as the most promising direction for determining the tokamak’s highest potential. The DIII–D Program mission seeks to develop and exploit fusion science (confinement, stability, power and particle control, and current drive) to advance fusion energy. DIII–D will produce demonstrated, scalable plasma performance; backed up by a firm, comprehensive theoretical model; and achieved in a configuration that has the potential to be attractive as a power plant concept. Thus, the proposed research will contribute significantly to the three legs of the U.S. Fusion Program: fusion energy science, concept innovation, and burning plasmas. In support of the DIII–D overall mission, the specific goals of DIII–D AT research in the period 1999–2003 are: ● To attain the theoretically predicted minimum in the cross-field transport of heat and energy; ● To extend the operation of DIII–D to the theoretically predicted limits of plasma stability; ● To seek a plasma that exhibits full recombination in the divertor before it reaches a material surface, thus achieving the simple description of magnetic confinement as using magnetic fields to prevent hot plasma from touching a material surface; ● To develop methods of plasma current generation (initiation, ramp-up, sustainment, and profile control) to provide future devices the basis for full steady-state transformerless operation; and ● To integrate the above objectives in single steady-state operational scenarios to demonstrate the possibility of simultaneous optimization of the tokamak in the four major areas of fusion science. The DIII–D National Program consists of a tokamak facility with its operating staff and a national collaborative research team that utilizes the facility to carry out research to support the goals of the U.S. Fusion Energy Sciences Program. DIII–D is the world’s most flexible tokamak and the largest magnetic fusion device in the U.S. program. Its ability to control a variety of complex plasma shapes and its diagnostic instrument set are the best in the world. It has reliable heating and current drive systems, pumped divertor systems, and a digital plasma control system capable of achieving the plasma control essential to the tokamak optimization mission. The DIII–D open data system architecture enhances the effectiveness of the large collaborative national team. The DIII–D Program has strong linkages (Section 2.6) to foreign and domestic experiments (the U.S. Theory Program) enabling technology development programs, the general science community, and the designers of future fusion initiatives such as International Thermonuclear Experimental Reactor (ITER). Links to universities and laboratories provide broad intellectual input to the DIII–D Program and provide paths for flow of research results between other groups and the DIII–D Program. 1.0.2. THE PROPOSED DIII–D FIVE-YEAR PROGRAM PLAN An outline of the proposed research plan is presented in Fig. 1–1. Two major in-vessel installations divide the upcoming five-year time frame into three major experimental periods. The research emphasis progresses from short pulse AT physics to extended pulse and more optimized AT physics, and then to sustained 10 second AT physics. During the fall of 1999, we expect to complete the private flux baffle and pump in the upper divertor of the DIII–D vessel. In year 2000, we expect to complete installation of a set of external asymmetric magnetohydrodynamic (MHD) feedback coils. During the fall of 2001, we expect to complete installation of the lower divertor upgrade. By adding 110 GHz microwave gyrotrons, the ECH power will reach 6 MW in the fall of 2000 and 10 MW by 2003. These installations naturally separate the experimental program into three parts: ● The first period will continue the present research program into 1999. We expect to obtain deeper understanding of transport, obtain results on the improvement of stability limits using wall stabilization, elucidate the mechanisms which lead to edge instabilities that limit high confinement regimes and reduce the maximum beta, exploit the microwave heating and current drive, increase understanding of the physics of parallel heat transport in the scrapeoff layer and divertor, and further explore plasma shape optimization. ● The period 1999–2001 will be an intensive AT experimental period devoted to exploring the open-versus-closed divertor question and to developing pressure and current profile control and fueling techniques for sustained, quasi-stationary operation. Further experiments to implement theoretically predicted optimized profiles will also be undertaken. ● The third intensive experimental period, from the end of 2002 through 2003, will be devoted to using the systems installed in 2001 to develop integrated, near steady-state (10 s), optimized AT scenarios. There will be a particularly intensive effort to control the current profile and the pressure profile using rf systems using the full double-null divertor. 1.0.3. LEADERSHIP A key responsibility of the DIII–D Program, for the period 1999–2003, is to provide national program leadership in optimization of the tokamak approach to fusion energy. We propose to accomplish this mission with the diverse capabilities of the DIII–D National Team consisting of about 120 operating staff and 100 research scientists drawn from 8 U.S. National Laboratories, 19 foreign laboratories, 17 universities, and 5 industrial partnerships (see Table 1–1 and Section 2.6). As the contractor for the DIII–D National Fusion Facility, GA will provide leadership for the DIII–D Program of toroidal fusion research. GA is responsible for optimizing the pace for the research program for the most scientific and cost-effective output, and for safe and environmentally sound operation in accordance with applicable DOE, federal, state, and local government rules and regulations. Fig. 1–1. The DIII–D program plan progresses from short pulse Advanced Tokamak physics, through optimization, to 10 s operation. The baseline plan is to operate 18 weeks per year for each of the next five years. The electron cyclotron heating capacity will increase to 6 MW by 2001 and 10 MW by 2003 and installation of the upper and lower radiative divertors are scheduled for 1999 and 2001. TABLE 1–1: DIII–D PROGRAM COLLABORATORS INSURE COORDINATION OF NATIONAL AND INTERNATIONAL TOKAMAK OPTIMIZATION - National Laboratories: ANL, INEL, LANL, LLNL*, ORNL*, PNL, PPPL*, SNL* - Universities: Cal Tech, Columbia U., Hampton U., Johns Hopkins U., Lehigh, MIT, Moscow State U., Palomar College, RPI, U. Maryland, U. Texas, U. Washington, U. Wisconsin, UCB, UCI, UCLA*, UCSD* - Industry Collaborators: CompX, CPI (Varian), GA*, Gycom, Orincon - International Laboratories: ASIPP (China), Cadarache (France), CCFM (Canada), Culham (England), FOM (Netherlands), Frascati (Italy), Ioffe (Russia), IPP (Germany), JAERI (Japan), JET (EC), KAIST (Korea), Keldysh Inst. (Russia), KFA (Germany), Kurchatov (Russia), Lausanne (Switzerland), NIFS (Japan), Troitsk (Russia), SWIP (China), Tsukuba U. (Japan) [*DIII–D Executive Committee Membership.] 1.1. TOKAMAK RESEARCH USING THE DIII–D NATIONAL FACILITY (SOW AND WBS TASK 1) The technical approach which we will use to pursue the DIII–D Program mission and goals can usefully be described in different cross-cutting ways. At the highest level, we see the Program as two main lines, core plasma and boundary plasma physics, both of which work toward an eventual integration demonstrated by sustaining a 5% beta plasma for 10 seconds. Figure 1–2 gives some of our numerical targets for tokamak optimization and indicates some of the areas of integrated research between core and boundary physics. The second way we view the program is as an integrated AT Program (see Section 2.2). The AT Program approach to optimizing the tokamak is expressed in lines of action or research thrusts. Our ability to pursue these research thrusts motivates the plasma control tools and diagnostics the program needs. Finally, the broadest view of the DIII–D Program is by the science topical areas (confinement, stability, power and particle control, and steady state). We present the program in those WBS categories. RESEARCH THRUSTS The four principal DIII–D research thrusts are: 1. Controlling interior plasma profiles and wall stabilization for higher stability and confinement. 2. Controlling the plasma edge for sustained AT performance and better confinement. 3. Developing the basis of steady-state operation. 4. Developing advanced divertor operating modes. Detailed descriptions: 1. Controlling the Interior Current and Pressure Profiles: Controlling current density profile J(r) via ECCD (off-axis) and FWCD (on-axis) to sustain negative central shear (NCS) and high li profiles. Sheared E×B flow suppresses turbulence; tools include off-axis ECH, divertor pumping, and wall stabilization using nonaxisymmetric coils (C-coil and segmented coils). 2. Controlling the Plasma Edge for Sustained AT Performance and Better Confinement: Regulating edge gradients, neutral influx, and ELMs via the Radiative Divertor Project (RDP), pellet fueling, radiating mantle (RI-mode), and edge ergodization. 3. Developing the Basis of Steady-State Operation: Noninductive current drive (NBCD, ECCD, FWCD), bootstrap current overdrive, disruption avoidance/mitigation (neural networks, cryogenic liquid jet injection), and density control. 4. Developing Advanced Divertor Operating Modes: Convective parallel heat transport, divertor enrichment, detached divertor operation, and full volume recombination. 1.1.1. SCIENCE RESEARCH (WBS SUBTASK 1.1) Organized into four key topical areas: 1.1.1.1. Confinement (WBS 1.1.1): Transport of particles, angular momentum, and heat; E×B velocity shear stabilization; reducing electron thermal transport; dimensionless parameter scaling; L–H transition physics; RI–mode. 1.1.1.2. Stability (WBS 1.1.2): Ideal and non-ideal MHD stability; wall stabilization (RWM); profile and shape optimization; neoclassical tearing modes (NTM); disruption avoidance and mitigation. 1.1.1.3. Power and Particle Control (WBS 1.1.3): Divertor physics; fully recombining plasmas; double-null divertor operation; impurity enrichment; pellet fueling; density limits. 1.1.1.4. Steady State (WBS 1.1.4): Noninductive current initiation, ramp-up, and profile control using ECCD, FWCD, and bootstrap overdrive (fbs > 100%). 1.1.1.5. Applications Programming (WBS 1.1.5): Data warehousing, distributed analysis, open data architecture. 1.1.1.6. New Diagnostics (WBS 1.1.6): Central Thomson scattering, electron transport diagnostics, 3-D equilibrium reconstructions, high-density current profile measurements. 1.1.1.7. Physics Support and Leadership (WBS 1.1.7): Supporting collaborations, research planning, and scientific dissemination. 1.1.2. DIII–D FACILITY OPERATIONS (WBS SUBTASK 1.2) Subtasks include Tokamak Systems, Neutral Beams, ECH Heating, ICRF Heating, Diagnostics, Data Systems, and Operations Support. Baseline research operation is planned for 18 weeks per year (single shift), with an option for 18 shift-and-a-half weeks. 1.2. UPGRADE DIII–D COMPONENTS AND SYSTEMS TO ACHIEVE PROGRAM OBJECTIVES (WBS AND SOW TASK 2) Key baseline upgrades include: 1.2.1. ECH Upgrade (WBS 2.1): Increase 110 GHz ECH power from 2 MW to 6 MW by 2000, and to 10 MW by 2003 with 1 MW 10 s pulse gyrotrons featuring diamond windows. 1.2.2. Divertor Upgrade (WBS 2.2): Implementation of the double-null Radiative Divertor Project (RDP) with cryopumping and baffling (Phase 1B in 1999, full RDP in 2001). 1.2.3. Magnet Pulse Length Upgrade (WBS 2.3): Extend full-field pulse length from 5 s to 10 s for 2 MA discharges. 1.2.4. Upgrade Contingency Options: ICRF upgrade (8 MW / combline antennas), counter neutral beam injection, liquid jet disruption mitigation, internal MHD coils, tungsten/B4C divertor walls. 2. TECHNICAL DISCUSSION: THE DIII–D FIVE-YEAR PROGRAM PLAN 2.1.1. THE DIII–D MISSION Mission goal: To establish the scientific basis for the optimization of the tokamak approach to fusion energy production. Optimization means demonstrating performance at theoretically predicted limits and sustaining a 5% beta plasma for 10 s under integrated, near steady-state conditions. 2.1.2. THE DIII–D PROGRAM Combines a world-class flexible facility with an integrated national collaborative team. Supports the six national fusion energy objectives, primarily understanding/optimization of toroidal plasmas and improved integrated predictive modeling. TABLE 2.1–1: ADVANCED TOKAMAK PROGRAM — OBJECTIVES, CHALLENGES, AND TARGETS - Confinement: Neoclassical confinement through transport barrier control | Understanding turbulence; long pulse | H -> 4 (>5 s) - Stability: Long-pulse, high beta_N AT operation | Profile control; neoclassical islands; wall stabilization | beta_N -> 6 (>5 s) - Divertor: Fully recombining divertor plasma | Compatibility with low-collisionality AT plasmas | Recombination -> 100%, Enrichment -> 8, Peak heat flux reduction -> 5 - Steady State: Fully transformerless operation | Profile control; long pulse; startup | f_bs -> 100% 2.2. THE DIII–D ADVANCED TOKAMAK (AT) PROGRAM Focuses on active external intervention and control to improve confinement, stability, divertor heat dispersal, and current drive. TABLE 2.2–1: PROGRAM LOGIC DEFINES TOOLS AND APPROACHES - Wall Stabilization -> Smart shell feedback, counter beamline rotation. - Interior J Profile Control -> ECCD (>6 MW), combline antennas for MCCD, on-axis FWCD. - Pressure Profile Control -> Density pumping, counter NBI, off-axis ECH. - Edge Stability & Neutrals -> Baffled RDP, pellet fueling, radiating mantle, edge ergodization. - Steady-State & Transformerless -> Bootstrap overdrive, outer PF coil startup, 10 s magnet upgrade. - Divertor Physics -> RDP baffles, convective parallel heat transport, impurity enrichment. TABLE 2.2–2: PARAMETERS OF DIII–D SCENARIOS (Simulations with ONETWO code) Key parameters for Cases 1–5: - Beta (%): 5.0 to 11.5% - Normalized beta (beta_N): 3.8 to 6.2 - Plasma current (Ip): 1.6 to 2.2 MA - Bootstrap current (I_bootstrap): 1.07 to 2.1 MA - Heating power: 12 to 20 MW (NBI, ECH, FWCD) - H89P confinement enhancement factor: 3.4 to 4.95 2.3.1. CONFINEMENT SCIENCE AND TRANSPORT BARRIER CONTROL Highlights the physics of E×B velocity shear stabilization of turbulence across edge (H-mode, VH-mode) and core (NCS) transport barriers. Key governing radial force balance equation: E_r = (Z_i * n_i * e)^(-1) * grad(P_i) - v_phi,i * B_theta + v_theta,i * B_phi Turbulence is suppressed when the shearing rate omega_E×B exceeds the turbulence decorrelation rate Delta_omega_D. Subsections discuss: - Anomalous Electron Transport: Investigating whether high k (eta_e) or magnetic turbulence drives electron heat transport. - Tests of Turbulent Transport Models: Critical gradient experiments using ECH heat pulses. - Dimensionless Parameter Scaling: Testing rho*, beta, and nu* scalings (Table 2.3–1). - Fuel and Impurity Transport: Helium ash exhaust and neoclassical impurity transport. - L–H Transition and Pedestal Physics: Investigating edge Reynolds stress and pedestal scaling. 2.3.2. STABILITY SCIENCE Addresses MHD stability limits, targeting beta_N ~ 6 and H ~ 4 for compact reactors. Subsections cover: - Shape and Profile Optimization: Synergy of strong shaping (triangularity, elongation) and broad pressure profiles (Fig. 2.3–5). - Wall Stabilization of Resistive Wall Modes (RWM): Rotation stabilization and active feedback control ('smart shell' and 'fake rotating wall'). - Nonideal Instabilities: Stabilization of neoclassical tearing modes (NTMs) at rational surfaces (3/2, 2/1) using localized ECCD. - Disruption Avoidance and Mitigation: Real-time neural network detection, fast shutdown via cryogenic liquid helium jet injection and killer pellets. - Steady-State Issues: Alignment of bootstrap current profiles (Fig. 2.3–8) with total current density profiles. 2.3.3. BOUNDARY SCIENCE Covers divertor physics, core-edge boundary coupling, and plasma-material interactions. Governing equations for parallel heat transport and radiation limits: d(q_||)/d(l_||) = n_e^2 * f_I * L(T_e) q_|| = - kappa_0 * T_e^(5/2) * (d T_e / d l_||) Key areas: - Advanced Divertor Physics: Convective parallel heat flow, 2-D flow patterns, divertor impurity enrichment (Table 2.3–4), and volume recombination (<2 eV). - Core Boundary & Density Limits: Neutral baffling with the RDP, high-field-side (HFS) pellet fueling, exceeding Greenwald density limits (Fig. 2.3–18). - Materials & DiMES: Net erosion and redeposition of carbon, tungsten, and advanced low-Z coatings. 2.3.4. PHYSICS OF CURRENT DRIVE AND HEATING Addresses noninductive current generation, profile control, and heating physics. Key topics: - Profile Maintenance: Off-axis ECCD, on-axis FWCD, and MCCD to sustain weak or negative central magnetic shear. - Transformerless Startup & Current Ramp-Up: Outer PF coil startup, helicity injection current drive (HICD), and bootstrap current overdrive (f_bs > 100%, Fig. 2.3–26). - Heating & Damping Physics: Strong electron heating (T_e ~ T_i), fast ion absorption of fast waves, and rotational shear manipulation. - RF Stabilization: Suppressing sawteeth, NTMs, and ELMs with localized ECCD and FW power. 2.4. PATHWAYS TO THE FUTURE Connects DIII–D research along dimensionless parameter scaling paths to four potential future tokamak initiatives: 1. ITER: Scaling ELMing H-mode along rho* paths; divertor detachment and density limit physics (Tables 2.4–1, 2.4–2, 2.4–3). 2. Optimized Superconducting Power Plants (ARIES–RS): Wall-stabilized high beta_N, high bootstrap fraction, and low-density radiating divertors (Tables 2.4–4, 2.4–5). 3. Compact Copper Ignition Experiments (CIT/BPX/IGNITOR): GyroBohm scaling to high-field compact devices (Tables 2.4–6, 2.4–7). 4. Spherical Tokamak (ST) Pilot Plant: Beta-scaling to low-aspect-ratio, high-beta (beta_T ~ 50%) transformerless systems (Tables 2.4–8, 2.4–9, 2.4–10). 2.5. THE DIII–D NATIONAL FUSION FACILITY — STATUS AND UPGRADES Details facility parameters, existing infrastructure, and proposed hardware upgrades: - Auxiliary Systems: Neutral beams (20 MW), ICRF (6 MW), ECH (2–3 MW). - ECH Upgrades: Expansion to 6 MW (2000) and 10 MW (2003) using 110 GHz gyrotrons with diamond windows. - Divertor Upgrades: Radiative Divertor Program (RDP) upper inner pump/baffle (1999) and lower divertor modification (2001). - Pulse Length Extension: 10 s pulse operation at full 2.2 T toroidal field and 2 MA. - Nonaxisymmetric Coils: External and internal active coils for RWM stabilization, rotation drive, and edge ergodization. - Diagnostic & Computer Upgrades: Central Thomson scattering, MSE Er upgrades, 3D equilibrium reconstruction, 100 Mb/s network upgrade, and open data architecture. 2.6. THE DIII–D NATIONAL FUSION PROGRAM Describes the national team structure, collaborations, governance, and educational outreach: - Collaborative Team: ~120 technical staff and ~100 research scientists across 9 U.S. labs, 16 universities, 5 industrial partners, and 19 foreign institutions. - Governance: DIII–D Executive Committee (DEC), Research Planning Committee (RPC), and Program Advisory Committee (DAC). - Outreach: Small Business Innovation Research (SBIR), graduate/postdoctoral training, undergraduate fellowships, and San Diego science education outreach. 3. OTHER PERTINENT INFORMATION 3.1. DEVELOPMENT PROCESS OF THE DIII–D FIVE-YEAR NATIONAL PROGRAM PLAN Chronicles plan formulation from the February 1997 brainstorming session, July 1997 National Workshop revisions (Table 3–1), and the February 1998 DIII–D Advisory Committee review. 3.2. HISTORY AND ACCOMPLISHMENTS OF THE DIII–D PROGRAM Reviews thirty years of fusion achievements from Doublet I, II, IIA, and Doublet III to DIII–D. Details how the fusion triple product n*tau*T has doubled every two years (Fig. 3–1), assesses progress against 1993 five-year goals (Tables 3–2 to 3–10), and highlights the successful transition into a premier national collaborative user facility.