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

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ON PREVIOUS PAGE Nonlinear simulation of mode conversion of applied radiofrequency waves to shorter-wavelength modes in a tokamak. (From P.T. Bonoli, MIT) 70
tHEME 2: cREatiNG PREdictaBLE, HiGH-PERFoRMaNcE, StEady-StatE PLaSMaS introduction ScopE aNd FocuS This Theme corresponds directly to Theme a of the Priorities, Gaps and opportunities Report 1 , a key resource document for ReneW. its overall goal, as noted in that report, is, “The state of knowledge must be sufficient for the construction, with high confidence, of a device that permits the creation of sustained plasmas that meet simultaneously, all the conditions required for practical production of fusion energy.” This is an exceptionally broad and challenging goal, encompassing a large fraction of the current effort in the Us magnetic Fusion energy sciences program. as described in the preceding chapter on Theme 1, iteR will be an enormously important and necessary step toward obtaining this knowledge base, enabling for the first time the production and study of burning plasmas, in which more energy is produced by fusion than is used to heat them. however, it must be recognized that iteR is not designed to be a prototype for “practical production of fusion energy.” such a demonstration fusion reactor, often referred to as demo, to lead to economic and attractive fusion energy, would need advances in several key areas. two in particular are the foci of Theme 2, as represented by its title: High fusion power density: The needed system size for a given fusion power output is determined by the fusion power density P fus in the burning core. This is the main measure of “high performance.” P fus is directly proportional to the square of the plasma pressure, p 2 ∝ n 2 t i 2 , where n is the density and t i the ion temperature. iteR is designed to achieve near optimal temperatures for fusion cross-sections; hence, the main avenue for improvement is increasing the plasma density. The fusion power is also proportional to b 2 b 4 , where b=2m 0 p/b 2 is the plasma pressure normalized to magnetic pressure, and b is the magnetic field. improvements can thus be realized by increasing b, which is limited by plasma stability and dependent on magnetic configuration, and/ or by increasing magnetic field b. Steady-state: Rather than operating in a pulsed mode, driven inductively by a transformer, a fusion device should be sustained for indefinite durations, with high reliability. For tokamaks, this means current must be provided and sustained by a combination of internally generated “bootstrap” current (driven by gradients in the density and temperature profiles) and externally driven currents (using microwaves or neutral beams). other magnetic configurations, such as stellarators, sustain plasmas without large current, through 3-d (non-axisymmetric) magnetic fields. in order not to use too large a fraction of the electricity produced for plasma sustainment, the amount of required external heating and current drive must be modest. 1 “Priorities, Gaps and Opportunities: Towards A Long-Range Strategic Plan For Magnetic Fusion Energy” Report to FESAC Oct 2007, chaired by M. Greenwald. 71
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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
Page 22 and 23: ReneW Organization: Themes The stru
Page 24 and 25: 22 Table 1. ReNeW Thrusts Address R
Page 26 and 27: ON PREVIOUS PAGE Nonlinear simulati
Page 28 and 29: extended operation phase. The optim
Page 30 and 31: Figure 2. Alpha particles can cause
Page 32 and 33: Figure 3. Spectrogram of the time-v
Page 34 and 35: Do the alpha particles couple to th
Page 36 and 37: • improved understanding of the e
Page 38 and 39: most relevant to iteR. Recent obser
Page 40 and 41: H-mode access: access to the h-mode
Page 42 and 43: although present-day devices have m
Page 44 and 45: estimates indicate that it will be
Page 46 and 47: can enter the plasma core and dimin
Page 48 and 49: ent drive alone cannot account for
Page 50 and 51: Figure 10. Control involves the ele
Page 52 and 53: to operation of iteR. solutions for
Page 54 and 55: • identification and stabilizatio
Page 56 and 57: Disruption prediction accurate pred
Page 58 and 59: Figure 12. The application of non-a
Page 60 and 61: ion losses, a quantitative predicti
Page 62 and 63: due to incompatibility of the measu
Page 64 and 65: agnostic measurements of critical p
Page 66 and 67: quires assessment of when potential
Page 68 and 69: suggesTions for furTher reading 1.
Page 70 and 71: miTigaTing TransienT eVenTs in a se
Page 74 and 75: increasing power density and pulse
Page 76 and 77: of recent accomplishments that have
Page 78 and 79: ity limits have been maintained. in
Page 80 and 81: highly risky in such an environment
Page 82 and 83: proximity-coil-based magnetics is ~
Page 84 and 85: will dominate the external sources
Page 86 and 87: The barrier gradient is generally l
Page 88 and 89: interaction with plasma boundary an
Page 90 and 91: itER-at aRiES-i aRiES-at b n (%) 3.
Page 92 and 93: and morphology, are needed. new mea
Page 94 and 95: field and temperature fluctuations
Page 96 and 97: large-scale process control problem
Page 98 and 99: tics. integrated control methods fo
Page 100 and 101: ing and design include computationa
Page 102 and 103: dated in the corresponding structur
Page 104 and 105: These requirements are applicable t
Page 106 and 107: • assess computationally, on test
Page 108 and 109: Research Requirements for Electron
Page 110 and 111: the launcher design is partly “tr
Page 112 and 113: tunities and goals for a few of the
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
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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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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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