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

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integrated effort that includes fundamental improvements in modeling coupled with experimental validation of the models on both dedicated test stands and confinement devices. other challenges concern the antenna straps, Faraday shield or front grill of launchers and additional nearby structure and surfaces. Radiofrequency breakdown/arcing is one of the main power limiting issues with operating the antenna in a plasma environment and is poorly understood. The anticipated large outer gap on demo (and iteR) and the resulting impact on loading will likely push operating voltages to at least as high as the iteR design limit of 45 kv. The interaction of the antenna surfaces with the plasma (including elms) and the role of the resulting particles and local gas load on breakdown and loading are issues that need improved understanding. The antenna structure and Faraday shield will likely be constructed from layered or coated materials. launcher materials require good conductivity and high heat resistance. The behavior of these structures in a nuclear environment and the survivability in long-term operations is a concern. The exposed antenna or launcher surfaces must be resistive to high heat (1-10 mW/m 2 ) and neutron fluxes with acceptable levels of impurity production. launcher windows and antenna insulators must retain their function in high-radiation environments. also, issues that result from operating at ~600 °c, as required by demo, need to be addressed. For remotely maintained d-t experiments, the performance criteria for radiofrequency antennas and launchers become more demanding, as replacement or repair becomes complicated. shadowing components may be required in some cases where extensive particle deposition can impede function. in present-day ech launchers, a final mirror is used to direct the microwave power toroidally and poloidally to achieve optimal coupling to the plasma. The final mirror must have a highly reflecting surface to reduce the heat load on the mirror itself. The obvious concern is that this surface will not last for many years when exposed to the burning plasma. inTernal Coils Can the severity of off-normal events be lessened or eliminated by using 3-D internal coil systems? Can insulating and conductive materials be developed with specific materials, coatings, and heat sinks suitable for internal coil components for the fusion environment, resulting in components that are robust and tolerant of plasma conditions? There are fundamental gaps in our understanding of internal control coils in future confinement devices as fusion research proceeds toward demo. Reliable and predictable cancellation of error fields, suppression of resistive wall modes, RmPs, and elms, and control of vertical stability cannot be achieved unless these gaps are closed. integration of fully 3-d mhd codes with realistic control coil geometry is needed to understand how the coils affect the plasma and how the different coil sets interact with each other. Three-dimensional fields could have an impact on the sol and possibly the divertor, and could result in toroidally asymmetric heat and particle loads on the PFcs. This could be beneficial by spreading the heat flux, or deleterious, by increasing the peak heat flux. The impact of these effects has not been considered for iteR or demo. to address these 134
gaps, we propose an integrated effort that includes fundamental improvement in modeling coupled with experimental validation of the models on confinement devices. basic research needs to be performed on the development of insulators and conductors that can perform in the high heat and neutron environment of a d-t demo. studies need to be performed on appropriate methods for extracting the heat from the coils generated by resistive losses and nuclear heating. Research thrusts The following table summarizes the research thrusts that will address the research requirements described above and bridge the knowledge gap on the path to demo. Requirement Research Thrust to address Requirement diagnostic investments for edge characterization 1 and 9 dedicated experimental time for edge characterization 1, 5, 9, and 10 improved models and code components for edge region 9 and 10 innovative divertor concepts and testing 9 and 11 transient impact on plasma facing components 2, 6, and 10 innovative design of solid surface PFcs 10 and 11 testing necessary to validate codes, improved physics models, and new designs 10 and 11 liquid surface development 11 improved diagnostic parts in edge 1, 2, 9, 10, and 11 antenna and launcher development 10 internal coils 2 and 5 integrated demonstration of taming plasma materials interactions 12 135
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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
Page 86 and 87: The barrier gradient is generally l
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Page 100 and 101: ing and design include computationa
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Page 104 and 105: These requirements are applicable t
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Page 108 and 109: Research Requirements for Electron
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Page 114 and 115: front layers of the field magnets c
Page 116 and 117: R&D Strategy a number of critical t
Page 118 and 119: formance burning plasmas are covere
Page 120 and 121: CreaTing prediCTaBle, high-performa
Page 122 and 123: magneTs JosePh mineRvini, massachus
Page 124 and 125: ON PREVIOUS PAGE Design of the ITER
Page 126 and 127: to stabilize deleterious plasma mod
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Page 130 and 131: Promising new ideas have been devel
Page 132 and 133: to handle 10 mW/m 2 , and elms with
Page 134 and 135: • liquid surface PFc operation in
Page 138 and 139: Taming The plasma-maTerial inTerfaC
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Page 142 and 143: ON PREVIOUS PAGE Design of an ITER
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Page 146 and 147: Safety and Environment • developm
Page 148 and 149: plasma and gas to the scrape-off la
Page 150 and 151: gaps: need to select and test the t
Page 152 and 153: • neutron and other radiation tra
Page 154 and 155: emphasis on modeling and expertise
Page 156 and 157: gap: Current understanding of stren
Page 158 and 159: Research needs critical research ne
Page 160 and 161: • Proposing integrated safety des
Page 162 and 163: • techniques and instruments to a
Page 164 and 165: Qualifying DEMO Components Possible
Page 166 and 167: • developing the design of an eff
Page 168 and 169: harnessing fusion power Theme memBe
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Page 172 and 173: ON PREVIOUS PAGE Reconstruction of
Page 174 and 175: Figure 1. Configuration space for t
Page 176 and 177: of 40%.) localized instabilities (t
Page 178 and 179: • Reduction of spheromak magnetic
Page 180 and 181: ment, but also micro- and macro-ins
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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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234
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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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310
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• build large-size test stands wh
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trol of the energy, impact angle, a
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ties that take advantage of simple
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ased materials development with adv
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introduction Thrust 11 addresses th
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technology is now evolving to inclu
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The elements of a thrust to develop
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The plasma facing components in a d
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to demonstrate that steady and tran
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mum of nuclear activation and prese
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332
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introduction harnessing fusion powe
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each Thrust 13 element includes the
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Figure 3. System concept for perfor
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equirements. Understanding the fuel
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• Use a combination of existing a
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chemical interactions between the s
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dose fusion-relevant environment wi
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Use a combination of existing and n
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350
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evaluate, through advanced design a
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at the time when the demo design is
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3. Computational analysis managemen
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Materials and Components: Fuel Cycl
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• employ energetic particle beams
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• develop and validate theoretica
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• develop new diagnostics for int
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• increase sustained noninductive
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368
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Proposed actions: 1. conduct two qu
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The key areas in which new knowledg
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• exploration of high-temperature
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• availability of high-power radi
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378
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• study FRc stability at small io
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techniques for integrated data anal
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4. based on the outcome of actions
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2. With information from action 1,
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388
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aCROnyMS anD abbREViatiOnS (continu
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aPPENdix c: tHEME WoRKSHoPS tHEME W
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14. d.l. humphreys, Active Realtime
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tHEME 2: CREating PREDiCtabLE HigH-
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43. t.W. Petrie, White Paper: Some
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tHEME 3: taMing tHE PLaSMa MatERiaL
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37. e.J. strait, J.c. Wesley, m.J.
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20. s.a. maloy and e. Pitcher, Fusi
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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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