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2 Scientific and Technological Value and Interest in a Burning Plasma
Pages 51-70

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From page 51...
... The plasma is said to be burning when alpha particles from the fusion reactions provide the dominant heating of the plasma. All fusion reactors require a burning plasma.
From page 52...
... Such an experiment is the crucial element missing from the world fusion energy science program and a required step in the development of practical fusion energy. Scientific advances in the 1990s significantly improved designs for a burning plasma experiment.
From page 53...
... If it is developed and understood in sufficient detail to provide predictive capability, the scientific knowledge of burning plasmas derived from a tokamak experiment such as ITER will be transferable to other magnetic configurations. The tokamak configuration is closely related to most other leading contenders for fusion energy development, so a wide range of phenomena may be extended from the tokamak to other configurations through theory and computation in the fu ture.
From page 54...
... As important, a burning plasma experiment provides the first opportunity to test many relevant fusion technologies at a reactor scale. SCIENTIFIC IMPORTANCE OF A BURNING PLASMA FOR FUSION ENERGY SCIENCE AND THE DEVELOPMENT OF FUSION ENERGY At each point in the development of fusion science and the implementation of new fusion facilities, new scientific regimes have been explored and important insights have been gained.
From page 55...
... . However, the larger size of a burning plasma experiment is predicted to signifi cantly change the spectrum of unstable Alfvénic fluctuations when they occur, generating turbulence and possibly increasing alpha-particle losses.
From page 56...
... ITER will thus provide a unique opportunity to study these modes in a controlled manner and to provide critical tests of emerging theory. The behavior of an energy-producing fusing plasma will be dominated by the complex nonlinear interactions between plasma heating, stability, and confine ment in a plasma heated by the fusion reactions and can only be studied in an integrated manner for the first time in a burning plasma experiment.
From page 57...
... A burning plasma experiment will test this understanding at larger effective plasma size and in the presence of a substantial alpha-particle population. This study will be espe cially interesting, because strong self-heating by well-confined alpha particles will control the pressure profile evolution, possibly reducing the effectiveness of exist ing external control tools.
From page 58...
... The effective control of heat flow to the chamber walls of the device for sustained operation and control of plasma composition are critical to future fusion concepts and will be tested under more reactor-relevant conditions in the burning plasma experiment than in experiments to date.
From page 59...
... However, a burning plasma experiment and the scientific program that leads to and supports it may make useful contributions to the basic understanding of plasmas. This section explores this possibility by considering the following four fundamental plasma processes, which are not yet fully understood, and their role in the burning plasma experiment: · Magnetic field line reconnection, · Plasma turbulence, · Abrupt plasma behavior, and · Energetic particles in plasmas.
From page 60...
... Gyrokinetic simulation, which was developed to simulate the turbu lence and predict the performance of fusion plasmas, has found a wide range of application to basic plasma physics. The demands of simulating turbulence in the burning plasma experiment will undoubtedly lead to improved computational algorithms that will find subsequent use in other areas of plasma science.
From page 61...
... Second, the burning plasma scientific program will develop tools -- for example, computer codes for analysis -- that will be of use to basic plasma science. Third, it is highly likely that new issues will arise from the studies on the burning plasma experiment.
From page 62...
... 62 BU R N I N GP L A S M A skin depth 2.5 cm (b)
From page 63...
... (a) The measured magnetic field of a shear Alfvén wave launched from a fluctuating current on the order of the skin depth in radius.
From page 64...
... A burning plasma experiment will likely lead to progress in new regimes. There will undoubtedly be unexpected discoveries as well; only a few examples of such connections are mentioned here.
From page 65...
... A burning plasma experiment can offer substantive and important contributions to other fields of science connected to plasma physics, primarily through experi mental access to the fundamental and/or extreme conditions offered by such a state. TECHNOLOGICAL IMPORTANCE FOR FUSION ENERGY SCIENCE AND THE DEVELOPMENT OF FUSION ENERGY The previous sections have considered the scientific importance of a burning plasma experiment.
From page 66...
... While the Canadian supply is expected to be adequate for providing the fuel for the ITER experiment without additional breeding, any fusion reactors beyond ITER must clearly produce and recover more tritium than is burned if fusion energy is to be viable.6 A blanket providing this function is a critical fusion technology; it must be developed on ITER to ensure a tritium fuel supply for future fusion facilities. A burning plasma experiment of the scope of ITER provides the opportunity to evaluate the tritium-breeding ratio and extraction process, the thermome 6Any arrangement to use Canadian tritium would of course have to be negotiated between ITER management and the Canadian government.
From page 67...
... The development of efficient and robust reactor blanket modules is required in order to provide a means of extracting energy from the plasma, to breed the required fuel, and to provide shielding of external subsystems in future reactor concepts. A burning plasma experiment provides the first opportunity to test such blanket concepts.
From page 68...
... The control and recycling of the tritium fuel, while minimizing the tritium inven tory in the plasma chamber, will be required for the routine operation of a burn ing plasma experiment, similar to requirements for the routine operation of future reactors. Magnet Technology The superconducting magnets required for ITER are of unprecedented size and scale, being comparable to those foreseen to be required for a fusion reactor.
From page 69...
... Remote Handling Technology In a fusion reactor, it is critical that the first wall and high-heat-flux compo nents as well as ancillary components such as radio-frequency heating antennas and diagnostics can be remotely repaired, with tolerable downtime for mainte nance. The scientific success of a burning plasma experiment will be critically dependent on the successful use of remote handling tools to minimize lost experi mental time owing to component failure.
From page 70...
... In addi tion, by operating safely, reliably, and within the structural code requirements used by the nuclear industry, a burning plasma experiment can demonstrate the favorable safety characteristics of a fusion reactor.


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