Burning Plasma Bringing a Star to Earth (2004) / Chapter Skim
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3 Readiness for Undertaking a Burning Plasma Experiment
3 Readiness for Undertaking a Burning Plasma Experiment
Pages 71-87
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From page 71... ...
In analyzing the readiness issues, the ITER design is used as a prototypical example of the burning plasma experiments under consideration; relevant differences for other designs are noted. A successful burning plasma experiment will provide the opportunity to address most, if not all, of the scientific and technical issues discussed in Chapter 2.
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From page 72... ...
Plasma control techniques. It is the committee's judgment that each of these six scientific areas must be sufficiently understood before a burning plasma experiment can be positioned for success.
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From page 73... ...
NOTE: Symbols on plot are defined as follows: ITER -- International Thermonuclear Experimental Reactor; ASDEX -- Axially Symmetric Divertor Experiment; AUG -- ASDEX Upgrade Project; CMOD -- Alcator C-Mod Tokamak Fusion Research Project; D3D -- DIII-D National Fusion Facility; JET -- Joint European Torus; JT-60U -- flagship tokamak of Japanese magnetic-confinement program; PBXM -- Princeton Beta Experiment Modification; and PDX -- Poloidal Divertor Experiment. Courtesy of J
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From page 74... ...
in which the remaining nondimensional parameters are held fixed at the values expected in the burning plasma experiment. While this analysis has not been done for the current ITER design, the resulting projection of the confinement time with *
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From page 75... ...
Such modeling contributes to an understanding of whether the consequence of violating a particular operational boundary will be a degradation in performance or a catastrophic loss of confinement followed by a disruption of the plasma current. Within this stable operating regime, there is another instability, called the neoclassical tearing mode, that can degrade plasma performance.
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From page 76... ...
Park, Princeton Plasma Physics Laboratory.
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From page 77... ...
Recent experiments have shown that disruptions can be avoided by operating below established stability limits. If excursions beyond these safe operating limits should occur, new techniques, such as the injection of argon gas, may be used to quench the plasma and avoid damage due to runaway electrons and reduce erosion due to high heat fluxes (see Figure 3.5)
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From page 78... ...
While there is such confidence, further research and development are needed to develop plasma operating regimes that present less stringent heat loads to plasma-facing components. Maintenance of Plasma Purity The introduction of impurities into the plasma, either as helium from fusion reactions or from sputtered first-wall materials, can significantly degrade plasma performance.
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From page 79... ...
RE A D I N E S S F O RU N D E R T A K I N G AB U R N I N GP L A S M AE XP E R I M E N T 79 FIGURE 3.5 The controlled termination of a DIII-D tokamak discharge by injection of a noble gas. This technique holds great promise as a means of mitigating damage that might otherwise occur during an abnormal event in ITER.
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From page 80... ...
Characterization Techniques The scientific evaluation of a burning plasma experiment requires the reliable measurement of key quantities with good spatial and temporal resolution in a high-neutron environment. Important factors include adequate diagnostic access and the remote maintenance of measurement instruments.
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From page 81... ...
All of these scientific developments positively impact the potential for developing an attractive fusion concept, as well as increasing our fundamental understanding of the plasma state of matter. This type of progress in fusion science and fusion technology has led to confidence that the global fusion community is scientifically ready to take the burning plasma step.
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From page 82... ...
The design of a burning plasma device must include adequate shielding for the mag netic field coils; thus, research is continuing to improve the radiation resistance of electrical insulators to permit increased mission life. This effort will be particularly important for insulators in copper-coil designs in order to optimize the number of full-power discharges.9 Further research and development are needed for diag nostics, including those sited in high-neutron-flux areas and those requiring trans parent optical materials.
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From page 83... ...
FIGURE 3.7 ITER central solenoid model coil that achieved 13 T Courtesy of ITER.
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From page 84... ...
84 B U R N I N GP L A S M A FIGURE 3.8 Prototype of a divertor plasma-facing component (PFC)
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From page 85... ...
Tritium Inventory Control Safety analyses have found that all of the proposed burning plasma devices meet fusion safety standards, and none of the devices requires an evacuation plan beyond the site boundary. There are proven techniques11 for separating hydrogen isotopes, cleaning up tritium gas, and delivering deuterium and tritium to the plasma.
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From page 86... ...
SOURCE: J Jacquinot, in "Recent Developments Towards Steady State Physics and Technology of Tokamaks in Cadarache," Proceedings of the 19th International Atomic Energy Agency Fusion Energy Conference, Lyon, France, October 2002; forthcoming in Nuclear Fusion, Winter 2003.
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From page 87... ...
It is clear that ongoing research can be expected to adequately address technical issues requiring continued attention, but no issues remain that would undermine the fusion community's assertion that it is technically ready to undertake a burning plasma experiment. It is worth noting that many of the confidence-building steps mentioned here were accomplished by researchers outside the United States at fusion research facilities in Europe, Japan, and the Russian Federation, with U.S.
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