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4. Fusion Plasma Confinement and Heating
4. Fusion Plasma Confinement and Heating
Pages 144-242
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From page 144... ...
fuel reserves of near-zero cost, fusion power is perceived to offer many advantages over alternatives, such as solar power or the breeder reactor. Environmentally, fusion has the potential to provide a much safer system than the breeder reactor, with respect both to the safety of the plant itself and to all aspects of its fuel cycle: fissionable materials are not involved; fusion's "ashes" are inert; and radioactivity associated with plant operation can be minimized and made to be short lived.
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From page 145... ...
By the late-19SOs, it became clear that more basic research would be required before any practical, large-scale fusion device would be possible. Theoretical efforts directed toward the fundamental understanding of plasma confinement and heating received high priority, and these efforts were reinforced by many experiments directed more toward the development of plasma physics than toward the immediate objective of fusion power.
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From page 146... ...
Plasma confinement and heating are not the only issues to be resolved before a practical fusion reactor can be built. However, for the first time in the history of fusion research, there seems now to be a substantial and reliable experimental basis for the detailed description of the fundamental scientific requirements of such a reactor-at least in the case of the magnetic-confinement approaches.
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From page 147... ...
FIGURE 4.1 (a) The cross section cr for various fusion reactions as a function of the relative energy of the colliding ions.
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From page 148... ...
For example, thermalized breakeven in a plasma with an average ion temperature of 10 keV requires that the confinement parameter exceed 6 x 10~3 particles per cubic centimeter seconds. Approaches to fusion that utilize magnetic confinement divide into two main classes: (i)
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From page 149... ...
Approaches to fusion that utilize inertial confinement seek to compress a deuterium-tritium pellet to a density of about 1025 particles per cubic centimeter and to maintain a thermonuclear "burn" at fusion temperatures for about 10-9 S before the pellet disassembles. In the case of the lower-density magnetic approaches, where the plasma can be penetrated by beams of energetic particles, a significant improvement in the confinement requirement-by almost a factor of 10-can be realized by using reacting beams of very high energy to heat the plasma.
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From page 150... ...
The principal approaches to fusion magnetic confinement utilizing either toroidal or mirror magnetic fields and inertial confinement are illustrated in Figure 4.3. Magnetic Confinement The most successful approach to the confinement of plasma at fusion temperatures makes use of the fact that charged particles tend to gyrate in tight spirals along the lines of force in a magnetic field.
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From page 151... ...
Charged particles gyrate in tight spirals about closed magnetic field lines, passing time and time again around the doughnut-shaped containment vessel.
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From page 152... ...
The ratio of the two pressures is ,B = 8rnTlB2 reactor economics by better utilization of the magnetic energy, which can result either in reduced requirements on field strength or in a more compact reactor configuration; in the latter case, however, the higher fusion power density can represent a formidable engineering problem. The various magnetic bottles that are possible candidates for confining a fusion plasma divide into two main classes: toroidal (doughnutshaped)
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From page 153... ...
Although the stability and transport of magnetically confined plasmas tend to be quite sensitive to the shape of the magnetic bottle, the various techniques that have been developed for heating a confined plasma tend to be applicable in a wide variety of magnetic configurations. A number of confined plasmas notably tokamaks are subject to one intrinsic type of heating, which arises from the resistive dissipation of the plasma currents that are needed to maintain plasma equilibrium.
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From page 154... ...
that will be required to heat a plasma to fusion conditions can be estimated by noting that a deuterium-tritium plasma with a pressure of 6 atmospheres produces a fusion power density of about 5 MW/m3, corresponding to an alpha-particle heating power density of about 1 MW/m3. An auxiliary-heating power density of about half this value is found to be needed to heat an initially cold plasma to temperatures at which self-heating by fusion reactions becomes important.
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From page 155... ...
Inertial-confinement fusion diners from magnetic fusion in that plasma confinement is provided by the inertia of the exploding pellet, not by a magnetic bottle. A key parameter in inertial fusion, equivalent to the confinement (Lawson)
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From page 156... ...
Pellets have been compressed to a hundred times solid density, fusion temperatures have been reached, and remarkable advances have been made in driver technology. However, much further progress needs to be made to satisfy simultaneously all the requirements for the practical realization of fusion power.
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From page 158... ...
FT Italy 0.8 19 100 1.0 1 C,RF TFR-600 France 1.0 20 60 0.6 1 C,RF ASDEX FRG 1.6 40 28 0.5 10 PD,PW,C,B T-10 USSR 1.5 37 30 0.5 1 C,RF JFT-2M Japan 1.3 45 15 0.5 1 B,NB,RF TEXTOR FRG 1.7 50 26 0.5 3 PW JIPP T-II Japan 0.9 25 20 0.3 0.3 TS,RF,F DITE UK 1.2 28 27 0.3 0.5 BD,F,NB,PW T-7 USSR 1.2 31 24 0.2 1 SC,CD JFT-2 Japan 0.9 16 20 0.3 0.3 B,NB,RF a Listed in descending magnitude of plasma current, with U.S. devices listed first.
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From page 159... ...
Substantial supporting work is undertaken in universities such as the University of Texas at Austin; Columbia University; New York University; the University of California, Los Angeles; and the University of Wisconsin. TABLE 4.2 Representative Stellaratorsa Major Minor Field Pulse Radius Radiusb Strength Rotational Length Program Device Location (m)
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From page 160... ...
160 o ~ or US o ED ED ~ ~=' ~o~ =' ~i '=i~ o o C ~_ X 1 C~ 1 · 1 J ·_ ~ _, ~ ~1 ~, o 1 a' =, CL.
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From page 161... ...
OPTIMIZATION OF EXPERIMENTAL PERFORMANCE · The development of powerful auxiliary heating, coupled with improved techniques for plasma control, has been the key to the realization of reactorlike plasma parameters. Demonstrations of the efficacy of magnetic diverters for impurity control, and of steady-state transformer-free current drive, have further improved the prospects of the tokamak as a viable reactor candidate.
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From page 162... ...
The best plasma parameters achieved have been as follows: central ion temperature of up to 7 keV; central electron temperature of up to 4 keV (both in PLT) ; confinement parameter of up to 8 x 10~3 particles per cubic centimeter seconds (Alcator C)
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From page 163... ...
CONFINEMENT · Toroidal systems have the potential for very favorable plasma confinement, if classical-like processes prevail. In tokamaks, anomalous processes of electron loss arise that, while not thoroughly understood from a fundamental viewpoint, are found to obey empirical laws that scale favorably with increasing plasma size.
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From page 164... ...
For particles moving parallel to the field, the projected orbit on a minor cross section of the plasma is a circle displaced slightly from a surface of constant pressure. Particles with greater perpendicular motion may be reflected from regions of higher magnetic-field strength.
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From page 165... ...
and high plasma current density, it was possible to vary the plasma density over a wide range. It was found that the electron thermal diffusivity (the rate at which energy residing in the electron component diffuses to the vessel walls)
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From page 166... ...
This degradation may be a direct result of differences in heating techniques, or it may be due to increases in plasma beta. The scaling of energy confinement is also quite different: confinement is found to be relatively insensitive to plasma density but increases with the strength of the poloidal magnetic field and with the square of the plasma minor or major radius.
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From page 167... ...
This mode is frequently seen as a variation of the x-ray emission from the plasma center; it limits the central density and temperature but is otherwise relatively harmless. If the current profile is not properly controlled, higher-order tearing modes can arise, which can interact with each other to give a sudden loss of plasma confinement, called a disruption.
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From page 168... ...
In particular, these codes have provided definitive results on theoretical beta limits and, coupled with better diagnosed experiments, have given a detailed picture of the disruption phenomenon. Current Frontiers of Research · A new generation of tokamak facilities is coming into operation worldwide, with the capability of producing reactorlike confinement parameters and reactor-grade hydrogen and (deuteriumtritium)
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From page 169... ...
The goals of this phase of the program are the following: To study confinement at low collisionality and high beta in hydrogen and D-T reactor-grade plasmas, To study plasma behavior for longer pulse lengths, To develop advanced toroidal confinement concepts that can lead to more attractive reactor configurations. It is expected that this phase will provide the technical foundation for the next step in the tokamak program, namely a device that will operate with an ignited D-T plasma during a long-pulse equilibrium to provide for the study of a plasma heated by fusion alpha-particles.
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From page 170... ...
Even at low efficiency, current drive may still make an important contribution. For example, it may be used to start and raise the plasma current, thereby freeing the transformer for use only in current maintenance.
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From page 171... ...
Simultaneously, the program will be developing concepts for improved performance of toroidally confined plasmas in a wide range of areas: High beta operation with good confinement Current drive: assisted start-up, plasma profile control, steady-state operation; -Steady-state stellarator operation; Disruption-free operation; and Simplified particle and impurity control. Each of these improvements will depend on further advances in theoretical analysis, in computer modeling, and in the diagnosis and analysis of experimental data.
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From page 172... ...
Fusion plasmas can be magnetically confined in an open-ended tube by strengthening the magnetic field at the ends of the tube to form magnetic mirrors. Open-ended systems possess some important advantages for fusion purposes.
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From page 173... ...
This angle-dependent nature of the particle losses leads inevitably to trapped-particle distributions having empty loss cones, i.e., departing from the isotropic distribution in velocity angle that characterizes an ordinary gas, with the consequent negative implications for the stability of mirror-confined plasmas discussed below in the section on Current Frontiers of Research. Mirror systems of the type described have confinement times that are low, bounded by the time required for an ion to be deflected through 90°.
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From page 174... ...
However, despite the encouragement from such an achievement, it was recognized that the single-cell mirror machine would have confinement too poor to satisfy the requirements for economic fusion power, i.e., too large a fraction of the fusion energy yield would have to be fed back to keep the system going. The challenge thus became to enhance the confinement in a mirror system to the point of engineering and economic practicality for a fusion power plant.
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From page 175... ...
description of particle transport processes within the magnetic fields of tandem mirrors. Turning to technological advances, mirror research has been responsible for some major contributions, including energetic neutral beams, high-field superconducting magnets of complex shape, and the development and application of microwave sources for plasma heating.
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From page 176... ...
This need stems, of course, from the ultimate goal of fusion research-to achieve net fusion power by the most direct and economical means possible. Central to the issue of achieving a net fusion power yield from any magnetic-confinement system is an understanding of the rate at which heat is lost from the confinement zone.
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From page 177... ...
All the tandem-mirror devices operating or under construction are shown in Table 4.3. The values cited for the confinement parameter (product of plasma density and confinement time)
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From page 178... ...
The thermal-barrier end cell develops the plugging potential necessary for confining the central cell plasma with an end-cell density below that in the central cell, thereby reducing both the end-cell maintenance power and the required magnetic field. The central cell of a tandem mirror is essentially a large-volume mirror confinement cell with a moderately large mirror ratio (strength of mirror field divided by the strength of the central field)
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From page 179... ...
FIGURE 4.9 Variation of the confinement parameter no with ion energy Ei for single-cell mirrors and the central cell of tandem mirrors, showing a strong improvement with increasing ion energy and a sharp increase due to electrostatic plugging. Here n is the plasma density, ~ the confinement time in the single cell or central cell, R the mirror ratio, and me the electrostatic plugging potential.
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From page 180... ...
While the original tandem mirror idea worked well to enhance mirror confinement times, from a future economic standpoint it had several drawbacks that prompted a search for improvements. The density of the plug plasmas had to be substantially larger than that of the central plasma, in order to establish the required potential "hill" confining the central cell ions.
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From page 181... ...
MACROSTABILITY: EQUILIBRIUM AND BETA LIMITS · With careful attention to design of the end-cell magnetic fields, the open system's high-beta capability can be realized in a tandem mirror, with calculated beta limits in the range of 35-50 percent. The requirement for a pressure equilibrium between the plasma and its confining field that is stable against gross plasma motion (magnetohydrodynamic instability)
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From page 182... ...
the plasma pressure gradients themselves, abetted by effects associated with the curvature of the magnetic field lines and by centrifugal effects if the plasma is rotating. The field-line curvature enters in a fundamental way: regions where the field is convex toward the plasma are locally stabilizing; those concave are destabilizing.
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From page 183... ...
If the underlying theoretical models are validated in upcoming experiments, an important physics aspect of the design of tandem-mirror fusion power plants will be secure. RADIAL CONFINEMENT: PARTICLE TRANSPORT AND RADIAL POTENTIAL CONTROL · Control of cross-field particle transport in tandem-mirror systems involves taking into account the symmetry of the magnetic fields and the effects of radial electric fields.
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From page 184... ...
Prospects for Future Advances in Mirror Confinement · In the growing quest for the most practical avenues to fusion power, the inherent flexibility of the mirror approach may lead to advantageous systems that are new or simpler. One of the attractive features of mirror-based approaches to fusion power is the versatility and flexibility with respect to their design.
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From page 185... ...
Increased understanding of basic mirror principles should advance the mirror approach to magnetic confinement. The goal is a simple and effective fusion reactor.
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From page 186... ...
1 11 ~4061 ~ me, W/~ ~242 ''J N DAM ENTAL CORE PLASMA HEATING (~.0 T) FIGURE 4.11 A single canted mirror sector of a bumpy torus, showing field lines (dashed lines)
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From page 187... ...
The stability of the ring depends on dynamic decoupling from the core plasma, and sets a limit on the core-plasma beta, which has not yet been tested experimentally. Experiments in the Elmo linear mirror, and thereafter in the EBT-1 toroidal device, established that stable hot electron ring plasmas could be generated steady state and that the rings could stabilize a warm, moderately dense core plasma (plasma density of 10~2 particles per cubic centimeter and electron temperatures of 100-400 eV)
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From page 188... ...
This beta limit cannot be tested on the present generation of EBT devices. Current Frontiers of Research · The emphasis in current EBT research is on increasing the core plasma density and temperature, so as to test the beta limit, and on understanding and optimizing the confinement of the core plasma.
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From page 189... ...
for the toroidal core plasma. From theory have come a number of ideas for improved containment of particle orbits, such as advanced coil designs, reversing the ambipolar potential, reconfiguring the standard bumpy torus into bumpy straight sections with high-field corners, and hybrid combinations of an EBT with rotational transform.
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From page 190... ...
~ - - RADIUS it- M ET AL WA LL FIGURE 4.12 Magnetic fields in the reversed-field pinch. The plasma current is induced by the transformer primary windings, whereas the toroidal magnetic field is produced initially by the toroidal field windings.
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From page 191... ...
tokamak is that in a tokamak the dominant confining field is the toroidal field, produced by an external magnet winding, whereas in an RFP it is the poloidal field produced by the plasma current that is responsible for plasma confinement. To maintain stability in a tokamak, the poloidal field, and hence the plasma current, must be kept small compared with the toroidal confining field.
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From page 192... ...
As ~ is increased (by increasing the plasma current, for instance) F must decrease, and when ~ reaches 1.2, the toroidal field at the wall must vanish.
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From page 193... ...
Another major step forward has been the confirmation that RFP configurations can be formed over comparatively long times. Until the induced plasma current becomes large enough to cause the pitch of the helical magnetic field lines near the wall to reverse, the plasma is potentially unstable.
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From page 194... ...
frequencies. Theory predicts that the plasma will rectify the oscillations and maintain a net toroidal plasma current.
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From page 195... ...
With these machines, temperatures in the kiloelectron-volt range should be attained, with an electron density of approximately 10~4 particles per cubic centimeter and an energy confinement time in the 10-ms range. COMPACT TOROIDS Introduction · Compact toroids are a class of toroidal plasma configurations that might lead to a smaller, less expensive reactor core.
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From page 196... ...
The FRC has an elongated prolate shape, whereas stable spheromaks are ablate. values of temperature and magnetic field, while preserving the high beta and stability, CTs will offer important advantages for the fusion power core of a reactor.
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From page 197... ...
was achieved with electron rings in 1972, but reactor studies have indicated that neither electron nor ion particle rings are likely to produce econorr,ically attractive reactors. However, some work on particle rings continues, because a merger of such rings with spheromaks or FRCs has the potential of aiding stability, heating, and sustainment of CTs.
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From page 198... ...
Improvements in diagnostics, impurity control, and other experimental techniques developed in the fusion community have also contributed strongly to the recent successes. One measure of the rapid progress that has been made is shown by the improvement in plasma lifetime plotted in Figure 4.15.
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From page 199... ...
Reactors based on this slower technique could use standard rotating machinery to power the spheromak source. The breakthrough in sustainment was achieved on the CTX device when magnetic fields and plasma density were held constant for 1 ms, a time long compared with the natural decay time of the configuration, by applying continuous electrical currents from the electrodes of the plasma source.
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From page 200... ...
200 sit ~ .C ~ E sin 3 O ._ ·~= ~ Ct C,0 Ce _% ._ I_ ·V)
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From page 201... ...
The best FRC confinement parameters have been produced on FRX-C, which has achieved values of the confinement parameter of about 4 x 10~i particles per cubic centimeter seconds. Plasma parameters consistent with this value are given in Table 4.6.
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From page 202... ...
If the boundaries are made properly, will the energy confinement time increase sufficiently with size and field to meet-the requirements of a practical reactor? Much of the near-term research will be focused on this question.
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From page 203... ...
If these are successful, the confinement parameter for spheromaks should exceed 10~ particles per cubic centimeter seconds. Similarly, the FRX-C and TRX-2 experiments at Los Alamos and at Spectra Technology (formerly Mathematical Sciences Northwest)
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From page 204... ...
. In tandem mirrors, steady-state high-frequency microwaves at the multimegawatt level will be used to create potential wells or thermal barriers (see section on Magnetic Mirror Systems)
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From page 205... ...
On a slower time scale, the resonant particles transfer the energy gained from the wave to the rest of the particles by collisions. Since the energy confinement time in a reactor-grade plasma (a few seconds)
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From page 206... ...
Heating at the fundamental or harmonics of the electron gyrofrequency is called electron cyclotron resonance heating (ECRH) and that at the fundamental or harmonics of the ion gyrofrequency is called ion cyclotron resonance heating (ICRH)
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From page 207... ...
While the fundamental theory of wave propagation and absorption was developed in the 1950s and 1960s, many of the applications to wave propagation in the magnetic-field geometries of tokamaks, tandem mirrors, and bumpy tori are being developed only now. Furthermore, theories of wave heating associated with toroidal geometry, absorption of the magnetosonic wave in a two-ion-species plasma, propagation and scattering of the lower-hybrid wave by density fiuctuations in a tokamak, propagation and absorption of electron cyclotron waves in a hot dense plasma, and absorption of electron cyclotron waves in a weakly relativistic plasma were developed only recently.
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From page 208... ...
208 ~ _ ho ~ ~ _ ~ e,.c ~ ~ a.
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From page 209... ...
This has been a consequence of a better understanding of the physics of rf heating, improvements in the technology that allowed injection of rf power at the megawatt level, and experimental devices with better particle and energy confinement times. Thus, while in the mid-1970s rf powers injected in any given device were limited to the 0.1-0.2 MW level, and consequently the temperature rise was limited to less than 200 eV, in recent experiments temperature rises in excess of a kiloelectron volt have been produced on injection of about a megawatt of power, at all frequencies of interest.
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From page 210... ...
At present, important ECRH and ICRH experiments are being carried out on the TMX-U tandem mirror at the Lawrence Livermore National Laboratory: ECRH is being used to aid in the formation of the thermal barrier, and ICRH is being tested for heating (and start-up) of the central-cell plasma.
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From page 211... ...
These experiments are aimed at clarifying the physics issues of wave propagation and absorption, and (in the case of tokamaks) at investigating energy and particle confinement times, and impurity injection, under conditions when the rf power significantly exceeds the intrinsic heating power because of the plasma current.
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From page 212... ...
Current drive refers to a process of interest mainly in tokamaksfor maintaining a current in a plasma by means other than transformerinduced electric fields. One of the most important areas of progress in the entire field of tokamak research has been the theoretical prediction and experimental demonstration of the feasibility of driving steadystate currents by radio-frequency waves.
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From page 213... ...
Although this efficiency varies from wave to wave, it is generally found that, in a reactor, 10 percent or more of the fusion power produced would be needed to generate the rf power required to maintain the toroidal current. Specifically, at least 50 MW of rf power would be required to maintain about 5 MA of steady-state toroidal current.
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From page 214... ...
In PLT at Princeton and Alcator C at MIT, the plasma current has been sustained for a second or longer without any applied voltage. The experimental verification of theoretical predictions of lowerhybrid current drive has been one of the most exciting and productive developments in recent tokamak research.
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From page 215... ...
should scale inversely with plasma density n and major radius R and should improve with increasing energy of the current-carrying electrons. To show that this relationship is verified, we plot the quantity nIRlP versus electron temperature Te from a number of different experiments.
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From page 216... ...
The present lower-hybrid waves should, however, be satisfactory for the quasi-steady-state mode of current-drive operation. PROSPECTS FOR FUTURE ADVANCES · Lower-hybrid current drive will be tested at reactorlike plasma parameters in large tokamaks.
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From page 217... ...
Accordingly, the physics of the neutral-beam injection process itself can be said to be well understood. However, it has been found that, as the injected beam power exceeds a few megawatts (a few times larger than the heating power due to the plasma current)
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From page 219... ...
PROSPECTS FOR FUTURE ADVANCES . Next-generation neutral-beam systems for tokamak and mirror applications will have higher beam energy and greatly increased pulse length.
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From page 220... ...
The capability for fueling the plasma center may be unique to neutral beams, and is particularly important for mirror reactors. Table 4.11 presents projections of requirements for neutral-beam systems in fusion reactors.
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From page 221... ...
(s) Pulsed tokamak Heating to ignition 400 30-50 10-50 Pulsed tokamak Pulsed current 400 '30 100 drive Steady-state Continuous 1000- 50 Continuous tokamak current drive Tandem mirrors Central cell 20050b Continuous heating and fueling Tandem mirrors End plug potential 50010 Continuous Stellarator Heating to ignition 40050 10-50 a Tandem-mirror requirements assume 50 MW of ECH power for the thermal barrier.
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From page 223... ...
Inertial fusion works by focusing an intense beam of laser light or particles onto the outer layers of a spherical shell encapsulating fusion fuel, as illustrated in Figure 4.20. The fuel is then compressed by pressures of tens to hundreds of millions of atmospheres generated by the rocketlike blowoff of the surface material.
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From page 224... ...
Inertial-confinement fusion research in the United States is conducted mainly at the Lawrence Livermore National Laboratory, Livermore, California, and at the Los Alamo s National Laboratory, Los Alamos, New Mexico. Smaller programs are under way at the Naval Research Laboratory, Washington, D.C.; at KMS Fusion Inc., Ann Arbor, Michigan; at the University of Rochester, Rochester, New York; and at Sandia National Laboratories, Albuquerque, New Mexico.
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From page 225... ...
TABLE 4.12 Major Inertial-Confinement Fusion Facilities .
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From page 226... ...
in conventional high-energy accelerators. Accelerators needed to supply such beams for inertial fusion would be expensive but would have many properties desirable for inertial-fusion reactors; they could provide highly efficient, repeatedly pulsable, and focusable beams.
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From page 227... ...
Instrumentation to measure the properties of the beam-target interaction has evolved at a remarkable pace in the last decade. Typically, quite extreme ranges of plasma conditions are encountered in a single inertial-confinement experiment: the density ranges downward from 1000 times solid density to near vacuum; the temperature ranges in some cases from 1 eV to beyond 1Os eV; the electromagnetic radiation emitted extends from the infrared region into the gamma-ray region; and various ion and electron populations may be present with energies extending from electron volts to millions of electron volts.
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From page 228... ...
The critical densities are about 102~ and 10~9 particles per cubic centimeter, for the neodymiumglass laser and CO2 laser, respectively. Some experiments have also been carried out using crystals to double, triple, and quadruple the frequency of a neodymium-glass laser, and the critical densities are then correspondingly higher.
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From page 229... ...
The waves, in turn, can heat the plasma particles or scatter the incident light. Heating of the plasma by excited plasma waves is often undesirable, since suprathermal electrons can be generated.
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From page 230... ...
In addition to instabilities driven directly by the laser light, many other important processes can occur in laser-irradiated targets. For example, ion turbulence and self-generated magnetic fields can be created in the interaction process.
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From page 231... ...
Short-wavelength laser light improves heat transport efficiency but may lead to greater nonuniformities in the implosion. In the direct-illumination approach to inertial-confinement fusion, the laser-heated electrons are dominant in transporting energy to an ablation surface, as shown in Figure 4.21.
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From page 232... ...
is comparable with the final shell velocity. Shorter-wavelength lasers improve the hydrodynamic efficiency because the energy is absorbed at higher plasma density and closer to the ablation surface.
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From page 233... ...
Ablatively driven pellets have compressed D-T fuel to nearly a hundred times solid density, albeit with low temperature (about 400 eV)
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From page 234... ...
Hydrodynamic Rayleigh-Taylor instability can occur whenever a lighter fluid accelerates a heavy fluid. Inertial fusion analogs of the Rayleigh-Taylor instability occur when the low-density ablating plasma accelerates the dense shell, or later in the implosion when the dense shell decelerates on compressing the lighter fuel.
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From page 235... ...
The new machines coming on line in the next few years will allow significant tests of key inertial-confinement fusion principles. For example, it is anticipated that the NOVA laser will be able to compress D-T fuel to about one thousand times liquid density, with fuel temperatures in the central hot spot in the 1-2 keV range.
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From page 236... ...
However, fusion processes offer a wide range of other possible applications, from production of fuel for light-water fission reactors to direct production of electricity using advanced fusion fuels. If achievable, advanced-fuel fusion reactors would produce almost no neutrons, thus reducing reactor activation by orders of magnitude, and would eliminate the need for tritium production.
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From page 237... ...
Also, since the x rays and fast neutrons produced by a fusion plasma can pass through the walls of a reactor vessel and heat a blanket to almost any desired temperature, such reactors could find uses in high-temperature processing and in high-efficiency heat engines. Some attention has been given to the direct recovery of the energy of electrically charged fusion reaction products, but the possible applications of such fusion reactors have not yet been explored in any depth.
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From page 238... ...
In addition, the utility industry through the Electric Power Research Institute funds some fusion studies and small-scale developmental activities.) Fusion approaches based on magnetic confinement are funded through the Department of Energy's Office of Energy Research, Office of Fusion Energy; inertial confinement is funded primarily through the Division of Military Applications, Office of Inertial Fusion, with some funding from the Office of Energy Research for the heavy-ion-beam approach.
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From page 239... ...
Dollars O L:~ 71 72 73 74 75 76 77 78 79 80 81 82 83 84 FISCAL YEAR ~ b ~ Inertial Conf i nement - 81 Actua I Current Do I I a rs ~ Constant (1984) Dollars 72 73 74 75 76 77 78 79 80 8 1 82 83 84 F I SCAL YEAR FIGURE 4.23 Federal appropriations for fusion research in actual and constant (1984)
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From page 240... ...
However, if the United States' pre-eminent position in the worldwide fusion program is to be maintained into the 1990s in the face of aggressive Japanese and European competition, the pace of newdevice authorization that characterized the early 1970s must be restored soon. The science of plasma confinement and heating has reached a stage of development that fully justifies the recent recommendations of the Magnetic Fusion Advisory Committee-an advisory committee to the Director of Energy Research, U.S.
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From page 241... ...
Continued research on alternate fusion concepts is essential to advance basic understanding of plasma confinement and to foster the development of approaches that show significant promise of improved reactor configurations. Intensive research must continue on the theoretical and computational descriptions of magnetically confined plasmas and on supporting experiments in basic plasma physics.
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From page 242... ...
These fuel densities are within a factor of 10 of the compression needed for a high-gain target. On the basis of these findings, we recommend the following nearterm emphasis and strategy for inertial-confinement fusion research: · Use present driver facilities to determine the physics and scaling of energy transport and fluid and plasma instabilities to regimes characteristic of high-gain targets.
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