Plasma Science Advancing Knowledge in the National Interest (2007) / Chapter Skim
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1 Overview
Pages 5-37
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The vast regions between galaxies in galaxy clusters are filled with hot magnetized plasmas. Stars are dense plasmas heated by fusion reactions.
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The bright lines are the illumination of some of the complicated magnetic field lines by plasma emission. Courtesy of Transition Region and Coronal Explorer (TRACE)
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Detailed analyses are contained in five chapters representing the subfields: low-temperature plasma science and engineering; high-energy-density (HED) plasma science; magnetic fusion plasma science; space and astrophysical plasmas; and basic plasma science.
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While these examples by no means constitute a comprehensive survey, they give a flavor of the breadth and depth of the field. The fourth section discusses the growth in predictive capability and the emergence of new plasma regimes, two scientific themes that pervade recent advances.
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Each one of us touches or is touched by plasma-enabled technologies every day. Products from microelectronics, large-area displays, lighting, packaging, and solar cells to jet engine turbine blades and biocompatible human implants either directly use or are manufactured with, and in many cases would not exist without, plasmas.
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From page 10... ...
The study of HED plasma physics has been greatly enhanced by the remarkable progress in producing such plasmas (and copious amounts of x rays) by passing large currents through arrays of wires in Sandia National Laboratories' Z machine.
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Of course, there are at least as many plasma researchers who are not members of the APS. For more information about the demographics of the plasma science and engineering community, especially the fusion community, please see Fusion Energy Sciences Advisory Committee, Fusion in the Era of Burning Plasma Studies: Workforce Planning for 2004-2014, DOE/SC-0086, Washington, D.C.: U.S.
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Space plasma physics knowledge gained in the last few years through our continuous activities in space is teaching us much about the environment in which our planet functions and the important plasma processes that affect our life on the ground. Biotechnology and Health Care Dental patients might be surprised to know that their dentist is using a tiny plasma to treat their teeth.
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From page 13... ...
. • Sterilization. The goal fig plasma sterilization is to destroy undesirable of 1.1.1 a, b biological activity with absolute confidence.
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The 200 most frequently cited papers over the past decade from each of six major journals were reviewed and the proportion of foreign-based lead authors was tabulated. The results were as follows: Nuclear Fusion, 68 percent foreign; Plasma Physics and Controlled Fusion, 78 percent foreign; Physics Review E (selecting the plasma-related articles by keyword)
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From page 15... ...
Accelerating Particles with Plasma Wake Fields When an electron bunch moves at nearly the speed of light through a plasma, the electrostatic repulsion of the bunch on the stationary plasma electrons pushes them aside, punching a hole in the plasma electron density. The unbalanced positive charge in the hole attracts the plasma electrons back into the hole, setting up
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From page 16... ...
The chief advantage of plasma wake field accelerators is the enormous accelerating force on the electrons -- currently greater than 50 GV/m, or a thousand times the force in a conventional accelerator. From the very beginning of research in plasma accelerators, high-resolution multidimensional computer simulations have helped identify and resolve the sci entific issues.
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Can the present success be scaled to much longer plasmas, taking the particles to much higher energies? Fusion Burning Plasmas in a Magnetic Bottle The pursuit of a nearly limitless, zero-carbon-emitting energy source through the process of nuclear fusion has been an inspiration to many plasma researchers (Box 1.3)
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From page 18... ...
The helium nucleus produced in the fusion reaction is also contained by the magnetic field, and each one deposits its 3.5 MeV of energy in the plasma. Plasmas begin to burn when the self-heating from fusion alpha particles provides most of the heat necessary to keep the plasma hot.
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It is clear that the next critical step in the development of fusion power is a burning plasma experiment. ITER is that step.
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It is projected to generate about 500 MW of fusion power. These projections are based on conservative regimes where plasma behavior is well understood.
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The scientific advances that ITER will enable will considerably improve our ability to predict the behavior of burning plasmas in all kinds of configurations. But to become economical, fusion power will require developments beyond ITER -- perhaps refinements in the magnetic configuration will be needed and certainly it will be necessary to develop the engineering and technology of the first generation of fusion reactors.
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From page 22... ...
In the solar corona, the random braiding of field lines proceeds until narrow dissipative regions are formed and reconnection releases the magnetic energy stored in the tangled field. Early estimates of the rate and effectiveness of reconnection suggested that the Sun's field should be considerably more tangled than is observed.
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Field lines reconnect in the narrower electron-decoupling region. Reconnected field lines exit the narrow region dragging plasma outflows (Figure 1.9b)
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Such progress would enhance predictive capability in a huge number of plasma applications, from fusion to astrophysics. Fusion Ignition in an Exploding Pellet In 2009, the 1.8-MJ NIF laser system will begin full-power operation at Law rence Livermore National Laboratory in California.
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Plasma Physics and Black Holes Black holes are among the most remarkable predictions of theoretical physics. So much mass is compressed into such a small volume that nothing, not even light, can escape.
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Massive stars that have exhausted their nuclear fuel collapse to form black holes with masses about 10 times that of our Sun -- there are perhaps 10 million such black holes in a galaxy like our own. There is now compelling evidence that nearly every galaxy contains, in addition to these roughly solar-mass objects, a much more massive black hole at its center -- these range in mass from a million to a billion solar masses.
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Further progress on understanding general relativistic plasma physics (i.e., plasma physics in curved space-time) is essential both for interpreting observations of black holes in nature and for achieving the long-sought goal of using such observations to test general relativity's predictions for the strong gravity around black holes.
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Such mag netic fields provide the necessary viscous angular momentum transport in most accretion disks and also help generate powerful outflows such as those seen in Figure 1.13. Much remains to be understood about plasma physics in the vicinity of black holes.
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In the next decade, more new regimes are expected. For example, ITER will begin studying magnetically confined plasmas heated by alpha particles produced in fusion reactions -- the burning plasma regime.
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It is still not clear how nature accelerates particles so effectively or what can be learned from this behavior in the laboratory. • Turbulence and transport in plasmas. Magnetic fusion plasmas, accretion discs around black holes, Earth's magnetosphere, laser-heated plasmas, and many industrial plasmas are permeated with turbulence that transports heat, particles, and momentum.
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From page 31... ...
It is poised to make significant breakthroughs in the next decade that will transform the field. For example, the international magnetic fusion experiment -- ITER -- is expected to confine burning plasma for the first time, a critical step on the road to commercial fusion.
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However, the emergence of new research directions necessitates a concomitant evolution in the structure and portfolio of programs at the federal agencies that support plasma science. The committee has identified four significant research challenges that the federal plasma science portfolio as currently organized is not equipped to exploit optimally: • Fundamental low-temperature plasma science. The many emerging appli cations of low-temperature plasma science are challenging and even out stripping fundamental understanding.
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From page 33... ...
The discoveries that intermediate-scale facilities would foster are unlikely to happen within the current paradigm of federal support for plasma science. • Crosscutting research. Federal stewardship of plasma research is disaggre gated and dispersed across four main agencies -- the Department of Energy, the National Science Foundation, the Department of Defense, and the National Aeronautics and Space Administration -- and within those, across many offices (e.g., magnetic fusion is primarily supported through DOE's Office of Science, and inertial confinement fusion is primarily supported through DOE's NNSA)
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From page 34... ...
However, while such an approach might stimulate some crosscutting research, it would not, in itself, create research initiatives in fundamental low-temperature plasma science and discovery-driven, HED plasma science. An interagency task force cannot facilitate the development of intermediate-scale facilities for the emerging science if those facilities are all within one large agency.
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Principal Recommendation: To fully realize the opportunities in plasma research, a unified approach is required. Therefore, the Department of En ergy's Office of Science should reorient its research programs to incorporate magnetic and inertial fusion energy sciences; basic plasma science; non mission-driven, high-energy-density plasma science; and low-temperature plasma science and engineering.
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HED programs in plasma accelerators would remain in the DOE Office of High Energy Physics. Inertial confinement fusion research enabling the stockpile stewardship mission of DOE's NNSA would remain there.
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the science of magnetic fusion and the science of inertial fusion. Indeed, the Office of Science will steward plasma science long after the current large facilities have come and gone.
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