Research Needs for Magnetic Fusion Energy Sciences - US Burning ...

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• develop and validate theoretical and numerical models of edge transport and turbulence in the st, including new codes with gyrofluid and gyrokinetic models. to help validate the models, develop and implement new diagnostic measurements to elucidate the edge electron and ion distribution functions, edge flows, and edge neutral density. Links to other thrusts: Theme 3, plasma-material interface (Thrusts 9-12) b. Develop and understand liquid metal plasma facing components. liquid metal plasma facing components (PFcs) may advance the st by: 1) significantly reducing anomalous electron transport, 2) allowing operation at high wall fusion power loading, 3) providing density control, 4) permitting density and pressure profile control at high beta (via the fueling profile), 5) providing edge and core stability enhancements, 6) controlling high-z impurities (if utilizing liquid lithium), and other issues common to conventional tokamaks. high recycling liquid metal PFcs such as gallium may be better suited than lithium to high-power density divertor designs. however, the technology requirements for liquid metal PFc development are largely independent of the choice of liquid metal. The near-term deployment of liquid lithium PFcs will inform the development of high recycling liquid metal PFcs as well. actions: • implement and evaluate full liquid lithium wall in an st, with full core neutral beam fueling to assess if high ohmic energy confinement can be extended to core-fueled, auxillary-heated sts. • implement and investigate a full liquid lithium divertor in an st with full core fueling to assess whether a full lithium wall is required, or if partial walls or a divertor alone are sufficient. • diagnose edge plasma effects and plasma-material interactions with liquid lithium walls. Use this data to validate models for the plasma edge, and core-edge coupling, over a range of global recycling coefficients. Understand the effect of low recycling on the edge and core plasma sufficiently well to project the results to larger, hotter devices. • implement and evaluate a full flowing liquid metal wall and divertor in an st, with pulse length comparable to the flow time for liquid metal from inlet to outlet, over the liquid metal “former” or guide wall, jet path, etc. evaluate plasma magnetohydrodynamic (mhd) effects on liquid metal flows, stability, and influx to the core plasma, to determine whether liquid metal walls can be implemented, and whether liquid metals can control recycling, in a fusion nuclear device. Links to other thrusts: Theme 3, plasma-material interface — liquid metal test stand work, MHD simulations (Thrusts 10, 11) 3. Utilize upgraded facilities to increase plasma temperature and magnetic field to understand St confinement and stability at fusion-relevant parameters. 362
Recent nstX and mast results indicate that the parametric dependencies of energy confinement in the st differ from conventional tokamak scaling, creating the possibility of better than expected confinement at low-a. in particular, the energy confinement improves faster with increasing magnetic field and decreasing plasma collisionality in the st than at high-a. The differences appear related to strong flow-shear suppression of turbulent ion transport in the st to near neoclassical (collisional) levels, together with increased electron thermal transport. since neoclassical ion transport and some of the instabilities thought to drive rapid electron transport, such as micro-tearing modes, have a strong collisionality and field dependence, it is important to understand how this transport scales to higher field and lower collisionality. The latter strongly affects the large trapped particle population in sts and is the dimensionless variable of largest extrapolation from present to future sts. Furthermore, with its relatively low viscosity and high flow rates, the low ion transport regime accessible in the st offers a unique test of our understanding of ion transport in toroidal plasmas. in addition, a large gap exists between experimental observations and our understanding of energetic particle (eP) effects on plasma heating, current drive and transport. importantly, the energetic particle populations of present sts have ratios of fast ion velocity to alfvén velocity similar to those of the alpha populations in tokamak reactors. Thus, st eP research is highly relevant for burning plasmas and iteR. actions in the area of thermal transport: • determine confinement trends in the st over an extended range of collisionality, current, field, power input, aspect ratio, and wall recycling conditions. studies would begin in planned upgraded sts (near-term) and could require new st experiments with engineering parameters several times those of present devices for confident extrapolation to next-step devices. • Understand the causes for anomalous electron transport utilizing advanced diagnostics for high and low wavelength, electrostatic and magnetic turbulence in the planned upgraded sts, including diagnosis of electron temperature gradient streamers and microtearing instabilities. • measure the ion and electron velocity distribution function in the st to supplement power-balance transport assessments. • develop a predictive understanding of anomalous transport in the st utilizing numerical codes (including synthetic diagnostics) and transport control tools to optimize the performance of future reactors — in particular, optimizing the aspect ratio. actions in the area of energetic particle transport and their interaction with the background plasma: • develop numerical and theoretical models for energetic particle transport in the presence of multiple instabilities arising from the large normalized gyroradius, r*, of fast ions in the st. This key parameter will differ from present-day sts by a factor of 2 in a component test facility (ctF) and 4 in burning plasma sts, challenging predictive models. experiments at intermediate r* (e.g., ctF) are required to extrapolate to burning plasma demo-class sts. 363
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Research Needs for Magnetic Fusion
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Research Needs for Magnetic Fusion
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ExEcutivE SuMMaRy nuclear fusion
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Magnetic confinement magnetic confi
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The thrusts span a wide range of si
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eactor, most heat comes from fusion
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thrust 18: achieve high-performance
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confinement is measured by the so-c
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PART I: ISSUES AND RESEARCH REQUIRE
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ReneW Organization: Themes The stru
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22 Table 1. ReNeW Thrusts Address R
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ON PREVIOUS PAGE Nonlinear simulati
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extended operation phase. The optim
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Figure 2. Alpha particles can cause
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Figure 3. Spectrogram of the time-v
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Do the alpha particles couple to th
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• improved understanding of the e
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most relevant to iteR. Recent obser
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H-mode access: access to the h-mode
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although present-day devices have m
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estimates indicate that it will be
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can enter the plasma core and dimin
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ent drive alone cannot account for
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Figure 10. Control involves the ele
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to operation of iteR. solutions for
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• identification and stabilizatio
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Disruption prediction accurate pred
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Figure 12. The application of non-a
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ion losses, a quantitative predicti
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due to incompatibility of the measu
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agnostic measurements of critical p
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quires assessment of when potential
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suggesTions for furTher reading 1.
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miTigaTing TransienT eVenTs in a se
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ON PREVIOUS PAGE Nonlinear simulati
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increasing power density and pulse
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of recent accomplishments that have
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ity limits have been maintained. in
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highly risky in such an environment
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proximity-coil-based magnetics is ~
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will dominate the external sources
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The barrier gradient is generally l
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interaction with plasma boundary an
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itER-at aRiES-i aRiES-at b n (%) 3.
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and morphology, are needed. new mea
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field and temperature fluctuations
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large-scale process control problem
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tics. integrated control methods fo
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ing and design include computationa
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dated in the corresponding structur
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These requirements are applicable t
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• assess computationally, on test
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Research Requirements for Electron
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the launcher design is partly “tr
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tunities and goals for a few of the
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front layers of the field magnets c
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R&D Strategy a number of critical t
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formance burning plasmas are covere
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CreaTing prediCTaBle, high-performa
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magneTs JosePh mineRvini, massachus
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ON PREVIOUS PAGE Design of the ITER
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to stabilize deleterious plasma mod
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longer than the (solid) thermal equ
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Promising new ideas have been devel
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to handle 10 mW/m 2 , and elms with
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• liquid surface PFc operation in
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integrated effort that includes fun
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Taming The plasma-maTerial inTerfaC
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138
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ON PREVIOUS PAGE Design of an ITER
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trons in the breeding blanket. Thes
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Safety and Environment • developm
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plasma and gas to the scrape-off la
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gaps: need to select and test the t
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• neutron and other radiation tra
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emphasis on modeling and expertise
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gap: Current understanding of stren
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Research needs critical research ne
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• Proposing integrated safety des
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• techniques and instruments to a
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Qualifying DEMO Components Possible
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• developing the design of an eff
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harnessing fusion power Theme memBe
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168
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ON PREVIOUS PAGE Reconstruction of
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Figure 1. Configuration space for t
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of 40%.) localized instabilities (t
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• Reduction of spheromak magnetic
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ment, but also micro- and macro-ins
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esearch requirements • evaluate t
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the banana regime, low turbulent tr
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in stellarator discharges with ohmi
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• investigate how demountable coi
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tion using a central solenoid is al
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functions, edge flows, and edge neu
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Development of predictive capabilit
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Edge localized modes (ELMs): edge l
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theory predictions for alfvén inst
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coils, to permit replacement of the
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stand the relative roles of long-to
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Table 1. 202
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primarily electrostatic, in the cas
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to be important in present experime
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PLaSMa bOunDaRy intERaCtiOnS The ex
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calized field errors that can cause
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needed Theory, Computation, Modelin
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Scientific Issues and research requ
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esearch requirements new facilities
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small, concept exploration experime
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tRanSPORt: DEtERMinE unDERLying tRa
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esearch requirements analysis of ne
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nEEDED FaCiLitiES nEEDED tHEORy, CO
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connections Between Research Requir
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opTimizing The magneTiC ConfiguraTi
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230
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Proposed actions: • Prioritize bu
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3) as planning matures for the rese
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that have high impact, that benefit
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could have an impact on the identif
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The Us fusion program is well posit
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Mitigation of disruptions in the ev
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elevant plasmas for very long pulse
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and stability, and mitigation requi
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• control alpha heating feedback
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heavy ion beam probes (already in u
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alpha particles (ash removal). mode
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• determine minimum heating power
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Research should focus on developing
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estal structure need to be coupled
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• sufficient heating with little
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Proposed actions: Short-term: begin
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Demonstrate active control of the p
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Demonstrate burn control and contro
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Develop the means for and demonstra
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Medium-term: Test and optimize full
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276
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• Recruit, train and support dedi
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With this information in hand, phys
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to carry out the validation program
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and new devices could be designed w
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• high-field sc magnets for stead
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Element 2 — High current conducto
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Element 7 — integration of conduc
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many other scientific fields are be
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• based on these assessments, pro
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systems include neutral beams, ion
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The Us d-t facility, studied in 1b,
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300
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• design and implement innovation
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the controlling instabilities and s
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cross-field transport in the pedest
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The modeling of near-surface plasma
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Page 314 and 315: • build large-size test stands wh
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Page 326 and 327: The elements of a thrust to develop
Page 328 and 329: The plasma facing components in a d
Page 330 and 331: to demonstrate that steady and tran
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Page 336 and 337: introduction harnessing fusion powe
Page 338 and 339: each Thrust 13 element includes the
Page 340 and 341: Figure 3. System concept for perfor
Page 342 and 343: equirements. Understanding the fuel
Page 344 and 345: • Use a combination of existing a
Page 346 and 347: chemical interactions between the s
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Page 350 and 351: Use a combination of existing and n
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Page 354 and 355: evaluate, through advanced design a
Page 356 and 357: at the time when the demo design is
Page 358 and 359: 3. Computational analysis managemen
Page 360 and 361: Materials and Components: Fuel Cycl
Page 362 and 363: • employ energetic particle beams
Page 366 and 367: • develop new diagnostics for int
Page 368 and 369: • increase sustained noninductive
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Page 372 and 373: Proposed actions: 1. conduct two qu
Page 374 and 375: The key areas in which new knowledg
Page 376 and 377: • exploration of high-temperature
Page 378 and 379: • availability of high-power radi
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Page 382 and 383: • study FRc stability at small io
Page 384 and 385: techniques for integrated data anal
Page 386 and 387: 4. based on the outcome of actions
Page 388 and 389: 2. With information from action 1,
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Page 392 and 393: aCROnyMS anD abbREViatiOnS (continu
Page 398 and 399: aPPENdix c: tHEME WoRKSHoPS tHEME W
Page 400 and 401: 14. d.l. humphreys, Active Realtime
Page 402 and 403: tHEME 2: CREating PREDiCtabLE HigH-
Page 404 and 405: 43. t.W. Petrie, White Paper: Some
Page 406 and 407: tHEME 3: taMing tHE PLaSMa MatERiaL
Page 408 and 409: 37. e.J. strait, J.c. Wesley, m.J.
Page 410 and 411: 20. s.a. maloy and e. Pitcher, Fusi
Page 412 and 413: tHEME 5: OPtiMizing tHE MagnEtiC CO
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39. P.W. terry, a. boozer, J.s. sar
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don coRRell, lawrence livermore nat
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GeoRGe mckee, University of Wiscons
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tony tayloR, General atomics RichaR
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