Showing papers by "Princeton Plasma Physics Laboratory published in 1986"
TL;DR: In this paper, a combination of analytic and computer solutions of the electron heat diffusion equation is used to clarify previous work and to develop new methods for determining χe in the plasma.
Abstract: The time-scales for sawtooth repetition and heat pulse propagation are much longer (tens of milliseconds) in the large tokamak TFTR than in previous, smaller tokamaks. This extended time-scale, coupled with more detailed diagnostics, has led us to revisit the analysis of heat pulse propagation as a method to determine the electron heat diffusivity χe in the plasma. A combination of analytic and computer solutions of the electron heat diffusion equation is used to clarify previous work and to develop new methods for determining χe. Direct comparison of the predicted heat pulses with soft-X-ray and ECE data indicates that the space-time evolution is diffusive. However, the χe determined from heat pulse propagation usually exceeds that determined from background plasma power balance considerations by a factor ranging from two to ten. Some hypotheses for resolving this discrepancy are discussed.
100 citations
TL;DR: In this article, a generic reactor model is used to examine the economic viability of electricity generation by magnetic fusion using a simple model using components that are representative of those used in previous re...
Abstract: A generic reactor model is used to examine the economic viability of electricity generation by magnetic fusion. The simple model uses components that are representative of those used in previous re...
78 citations
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TL;DR: In this article, the Bohm criterion (ion drift velocity out of the plasma must equal the ion acoustic speed) was derived from both the plasma and the sheath equations separately.
Abstract: Outline: Section 2 simply describes, without attempt at explanation, what happens electrically when a plasma is in contact with a solid surface. The practical implications of the interaction are briefly described. Section 3 provides a physical explanation of why these effects occur and deduces initial estimates of the plasma-solid voltage difference and the spatial extent of this voltage drop. Section 4 deduces the Bohm Criterion (ion drift velocity out of the plasma must equal the ion acoustic speed) using ion fluid models. The Criterion is obtained from both the plasma and the sheath equations separately. Section 5 deduces simple formulae for the particle and energy flux which is transmitted by a sheath, both for electrically floating and biased objects. Section 6 gives a brief indication of how the sheath particle and energy transmission characteristics influence the modeling of the edge plasma in magnetically confined plasma devices, while Section 7 gives a similar brief introduction to their use in the interpretation of plasma probe data.
74 citations
TL;DR: In this paper, it was shown that the possibility of achieving polarized spin in a fusion plasma cannot be ruled out and that the physics of such plasmas is well worth pursuing both for its intrinsic interest and for its benefit to fusion.
Abstract: If the nuclear spins in a fusion reactor are oriented, or polarized, in an appropriate manner, then the nuclear reactions are modified in such a way as to enhance the performance of the reactor. The methods by which the spins can be polarized and the various difficulties connected with these methods are discussed. The processes by which the polarization can be lost owing to various physical processes in a confined plasma are assessed. The different polarization modes of the plasma ions are applicable to the different nuclear reactions, D–T, D–3He and D–D. The benefits for reactor performance of these modes are discussed. It is concluded that on the basis of current knowledge, the possibility of achieving polarized spin in a fusion plasma cannot be ruled out and that the physics of such plasmas is well worth pursuing both for its intrinsic interest and for its benefit to fusion. Further, detailed calculations of the modification of the D–T nuclear reaction produced by spin polarization are given, as well as calculations of the depolarization rates for physical processes in a confined plasma. Finally, a kinetic description of a polarized plasma is outlined which generalizes the normal kinetic description of a plasma.
60 citations
TL;DR: In this paper, measured wavelengths of a number of highly ionized atoms are reported, including the 3s23p-3s3p2 and 3s 23p−3s23d transitions in the aluminum isoelectronic sequence of Zn xviii, Ge xx, Se xxii, Zr xxviii and Mo xxx, and Ag xxxv.
Abstract: Measured wavelengths of a number of highly ionized atoms are reported. These include the 3s23p–3s3p2 and 3s23p–3s23d transitions in the aluminum isoelectronic sequence of Zn xviii, Ge xx, Se xxii, Zr xxviii, Mo xxx, and Ag xxxv; several transitions in the n = 2 shell of Zn xxii, Zn xxiii, and Zn xxiv; and the resonance and intercombination lines of Ag xxxvi–Ag xxxvii and of Ge xxix–Ge xxx.
37 citations
TL;DR: The potential for achieving x-ray lasing action in Kr-like ions pumped by a KrF excimer laser is most favorable at high Z as mentioned in this paper, where the energy-level structure of ions in the Kr isoelectronic sequence show singly and multiply excited states that provide suitable strong radiative transitions in the region of 10 nm.
Abstract: We consider some possible mechanisms for producing gain in the 10-nm spectral region. They involve the creation of a population inversion in a confined plasma column by selective excitation of multiply charged ions through absorption of many (>10) ultraviolet photons. Calculations of the energy-level structure of ions in the Kr isoelectronic sequence show singly and multiply excited states that provide suitable strong radiative transitions in the region of 10 nm. The potential for achieving x-ray lasing action in Kr-like ions pumped by a KrF excimer laser is most favorable at high Z.
24 citations
TL;DR: In this article, the selfconsistent theory of RF current drive in an axisymmetric torus is used to compute the MHD equilibrium generated by the fast (magnetosonic) wave current driver.
Abstract: One key to achieving high beta in a tokamak may be the proper control of the plasma pressure and current density profiles. In principle, if steady-state RF current drive is used, the current density may be tailored by a careful selection of the wave frequency and the power spectrum. This study uses the selfconsistent theory of RF current drive in an axisymmetric torus to compute the MHD equilibrium generated by the fast (magnetosonic) wave current driver. This is accomplished by iterations in a calculation of the MHD equilibrium for a given diamagnetism function, F(ψ) = RBt, and a ray-tracing calculation which determines F(ψ). The various wave and plasma characteristics which determine the equilibrium are examined, and it appears possible to create a large diversity of equilibria.
21 citations
TL;DR: In this paper, an analytical and two-dimensional computational solution for the plasma parameters near a toroidally symmetric limiter is illustrated for the projected parameters of a tokamak fusion core experiment (TFCX).
Abstract: Analytic and two-dimensional computational solution for the plasma parameters near a toroidally symmetric limiter are illustrated for the projected parameters of a tokamak fusion core experiment (TFCX). The temperature near the limiter plate is below 20 eV, except when the density 10 cm inside the limiter contact is 8 x 10/sup 13/ cm-/sup 3/ or less and the thermal diffusivity in the edge region is 2 x 10/sup 4/ cm/sup 2//S or less. Extrapolation of recent experimental data suggests that neither of these conditions is likely to be met near ignition in TFCX, so as a low plasma temperature near the limiter should be considered a likely possibility.
19 citations
01 Jan 1986
TL;DR: In this article, the recycling of neutral atoms and molecules formed as plasma ions strike device walls at the plasma edge is studied, and it is shown that this fraction will decrease in future machines with larger discharge times.
Abstract: Particle confinement times in present day controlled fusion devices are typically less than a tenth of the discharges’ duration, and this fraction will decrease in future machines with larger discharge times. Thus it is important to study the mechanism of the recycling of neutral atoms and molecules formed as plasma ions strike device walls at the plasma edge.
19 citations
TL;DR: In this paper, the wavenumber selection in nonlinear spatially periodic states of driven systems is systematically investigated using analytic and numerical techniques on equations modeling convection and different selection mechanisms yield different results, arguing against the existence of a general minimizing principle.
18 citations
TL;DR: In this article, a fast-fission blanket around a fusion plasma exploits high neutron multiplication for superior breeding and high energy multiplication to generate significant net electrical power, and a major improvement over previous fast fission blanket concepts is the use of mobile fuel, namely a pebble-bed configuration with helium cooling.
Abstract: A fast-fission blanket around a fusion plasma exploits high neutron multiplication for superior breeding and high-energy multiplication to generate significant net electrical power. A major improvement over previous fast-fission blanket concepts is the use of mobile fuel, namely a pebble-bed configuration with helium cooling. Upon loss of coolant, the mobile fuel can be gravity-dumped to a separately cooled dump tank before excessive temperatures are reached. The pebble bed is also compatible with rapid fuel exchange and a low-cost reprocessing method. With the ignited tokamak plasma producing 620 MW of fusion power, the net electric power is 1600 MWe and the annual fissile production exceeds 3 tonnes.
TL;DR: In this paper, measurements of the fusion reaction rate in the Tokamak Fusion Test Reactor (TFTR) covering a wide range of plasma conditions and injected neutral-beam powers up to 6.3 MW were reported.
Abstract: We report measurements of the fusion reaction rate in the Tokamak Fusion Test Reactor (TFTR) covering a wide range of plasma conditions and injected neutral-beam powers up to 6.3 MW. The fusion neutron production rate in beam-injected plasmas decreases slightly with increasing plasma density ne, even though the energy confinement parameter neτE generally increases with density. The measurements indicate and Fokker-Planck simulations show that with increasing density the source of fusion neutrons evolves from mainly beam-beam and beam-target reactions at very low ne to a combination of beam-target and thermonuclear reactions at high ne. At a given plasma current, the reduction in neutron source strength at higher ne is due to both a decrease in electron temperature and in beam-beam reaction rate. The Fokker-Planck simulations also show that at low ne, plasma rotation can appreciably reduce the beam-target reaction rate for experiments with coinjection only. The variation of neutron source strength with plasma and beam parameters is as expected for beam-dominated regimes. However, the Fokker-Planck simulations systematically overestimate the measured source strength by a factor of 2–3; the source of this discrepancy has not yet been identified.
TL;DR: The Tokamak Fusion Test Reactor (TFTR) at Princeton University has been designed 1) to reach power break-even, Q approx. = 1 (Q = fusion power/heating power), in neutral-beam-injected, two-energy-component D-T plasmas, where the density confinement time requirement is less stringent than that for maxwellian, one-energy component Plasmas as mentioned in this paper.
Abstract: The Tokamak Fusion Test Reactor (TFTR) at Princeton University has been designed 1) to reach power break-even, Q approx. = 1 (Q = fusion power/heating power), in neutral-beam-injected, two-energy-component D-T plasmas, where the density confinement time requirement is less stringent than that for maxwellian, one-energy-component plasmas, and 2) to provide the physics understanding of reactor-like plasmas required for the development of tokamak reactors. TFTR has now been in operation for more than two years. Nearly 15,000 individual high power plasma discharges have been produced. Deuterium plasmas with ohmic heating currents up to 2.5 MA, deuterium neutral beam injection (NBI) with beam powers up to 6.3 MW (28 MW projected for 1986) and 80 KeV energy (120 KeV projected), deuterium pellet injection and adiabatic deuterium plasma compression have been investigated. The neutron source strength of a fusion plasma is a direct indicator of the fusion power generated. However, its measurement is complicated for a number of reasons. 1) The neutron source is extended and time varying. 2) It is surrounded by large, fixed scatterers near both source and detectors. 3) The dynamic range of interest in present experiments covers some ten orders of magnitude. In Section II the authors discuss brieflymore » the plasma, its properties, the detectors, their useful ranges and limitations and their calibration. Section II contains some of the neutron measurement results obtained so far.« less
TL;DR: In this paper, a variety of RF experiments are conducted on PLT in order to explore RF techniques which could improve Tokamak performance parameters, such as ion Bernstein wave (IBW) heating, lower hybrid MHD stabilization and electron heating, down-shifted electron cyclotron heating, and fast wave current drive.
Abstract: A variety of RF experiments are being conducted on PLT in order to explore RF techniques which could improve Tokamak performance parameters. Of special importance are the studies of ion Bernstein wave (IBW) heating, lower hybrid MHD stabilization and electron heating, down-shifted electron cyclotron heating, and fast wave current drive. Ion Bernstein wave heating results at modest power indicate that the particle confinement time could be enhanced relative to that for fast wave heating in the ion cyclotron range of frequencies (ICRF) and neutral beam heating. At these power levels a conclusive determination of energy confinement scaling with power cannot yet be given. Central sawtooth and m=1 MHD stabilization is being obtained with centrally peaked lower hybrid (LH) current drive and the central electron temperature is peaking to values ( approximately 5 keV) well outside the bounds of 'profile consistency'. In this case the electron energy confinement is apparently increased relative to the ohmic value.
TL;DR: In this paper, a theory is developed for explaining the generation of neutral-beam-driven ion cyclotron instability (ion Bernstein mode) and the results are compared with the experimental data.
Abstract: Results obtained from experiments in PDX with neutral beam injection show the emission of several harmonics of a frequency centred in the ion cyclotron frequency range. The structure of the magnetic signals registered is suggestive of an electromagnetic ion cyclotron type instability. A theory is developed for explaining the generation of neutral-beam-driven ion cyclotron instability (ion Bernstein mode) and the results are compared with the experimental data. An increase in beam density towards the outside of the plasma is possible if the beam ion population in that region increases owing to either counter-injection orbits or 'fishbone' effects. A calculation is made of the threshold density necessary to drive such an instability in a plasma with anisotropic beam ion distribution, and the effects due to the curvature drift of hot ions are included. The quasi-linear evolution of the beam is studied in order to understand possible beam isotropization and spreading in velocity space.
TL;DR: In this paper, the S-1 device utilizes a flux core to form a spheromak inductively, and the spheroms can be sustained by oscillating the currents in the poloidal and toroidal field coils within the flux core.
Abstract: Inductive formation and sustainment of spheromaks are examined. The S-1 device utilizes a flux core to form a spheromak inductively. Plasmas are observed to relax during formation toward a minimum energy state, independent of initial conditions. Inductive sustainment of spheromaks is considered possible by utilizing this relaxation process. One method uses a poloidal flux transformer along the major axis, similar to the ohmic heating transformer in a tokamak. Alternatively, spheromaks can be established with the outermost poloidal field lines linked around the flux core to provide coupling between the plasma and external circuits. The spheromak configuration then can be sustained by oscillating the currents in the poloidal and toroidal field coils within the flux core. These proposed current drive schemes are investigated using the concept of magnetic helicity injection.
TL;DR: In this article, the magnetic pick-up loops (Mirnov coils) located on the inner wall of the tokamak fusion test reactor (TFTR) vacuum vessel have been used to study magnetic fluctuations in the plasma.
Abstract: Magnetic pick‐up loops (Mirnov coils) located on the inner wall of the tokamak fusion test reactor (TFTR) vacuum vessel have been used to study magnetic fluctuations in the plasma. To study the high‐frequency magnetic turbulence associated with beam injection, the signal from one coil is passed through a comb filter, which gives a measure of the frequency spectrum throughout the shot. To look for tearing modes, the signals from a poloidal array of 15 coils are summed in an analog system to give the amplitudes of the m=2, 3, and 4 coherent modes throughout the shot. Additionally, 20 coil signals are digitized individually at a rate of 100 kHz for 80 ms and at 10 kHz for 800 ms. These data may also be analyzed off line to get both the toroidal and poloidal mode numbers as well as the frequency spectrum for a limited portion of the discharge.
TL;DR: This poster presents a probabilistic procedure to constrain the number and type of particles that can be inserted into the response of the immune cells of the central nervous system.
Abstract: Note: Part 2A Reference CRPP-ARTICLE-1986-029View record in Web of Science Record created on 2008-04-16, modified on 2017-05-12
TL;DR: The Compact Ignition Tokamak (CIT) as discussed by the authors is a tokamak with a high filed (10 T), high current (10 MA), poloidal divertor, and liquid-nitrogen-cooled coils.
Abstract: The goal of the Compact Ignition Tokamak (CIT)d program is to provide a cost-effective route to the production of a burning deuterium-tritium plasma, so that alpha-particle effects may be studied. A key issue to be studied in the CIT is whether alpha power behaves like other power sources in affecting tokamak plasma confinement. The program is managed by the Princeton Physics Laboratory and includes broad community involvement. Guidelines for the preliminary design effort have been provided by the Ignition Technical Oversight Committee in discussion with the tokamak community. The reference design is a tokamak with a high filed (10 T), high current (10 MA), poloidal divertor, and liquid-nitrogen-cooled coils. It is a small, high-power-density device of the type proposed by Bruno Coppi (MIT). It has a major radius of 1.23 m, a minor radius of 0.43 m, and plasma elipticity of 1.8. This paper reviews the aims of the program and the basis for the physics guidelines. The role of the CIT in the longer-term tokamak program is briefly discussed. 23 refs., 9 figs., 1 tab.
TL;DR: In this article, a review of experimental spheromak research is presented, together with prospects of near-future experiments and some reactor considerations, in the several experiments based on different schemes.
Abstract: A review of experimental spheromak research is presented, together with prospects of near-future experiments and some reactor considerations. In the several experiments based on different schemes, ...
TL;DR: The mechanical aspects of tandem mirror and tokamak concepts for the tritium production mission are compared and a proposed breeding blanket configuration for each type of reactor is presented in detail, along with a design outline of the complete fusion reactor system.
Abstract: The mechanical aspects of tandem mirror and tokamak concepts for the tritium production mission are compared and a proposed breeding blanket configuration for each type of reactor is presented in detail, along with a design outline of the complete fusion reactor system. In both cases, the reactor design is developed sufficiently to permit preliminary cost estimates of all components. A qualitative comparison is drawn between both concepts from the view of mechanical design and serviceability, and suggestions are made for technology proof tests on unique mechanical features. Detailed cost breakdowns indicate less than 10% difference in the overall costs of the two reactors.
TL;DR: In this article, a super high field mode of tokamak operation that uses either near or near ohmic heating to ignition is discussed, where the auxiliary power is less than the heating power.
Abstract: The authors discuss a super high field mode of tokamak operation that uses ohmic heating or near ohmic heating to ignition. The super high field mode of operation uses very high values of BETA/sup 2/..cap alpha.., where BETA is the magnetic field and a is the minor radius (BETA/sup 2/..cap alpha.. > 100 T/sup 2/m). We analyze copper magnet devices with major radii from 1.7 to 3.0 meters. Minimizing or eliminating the need for auxiliary heating has the potential advantages of reducing uncertainty in extrapolating the energy confinement time of current tokamak devices, and reducing engineering problems associated with large auxiliary heating requirements. It may be possible to heat relatively short pulse, inertially cooled tokamaks to ignition with ohmic power alone. However, there may be advantages in using a very small amount of auxiliary power (less than the ohmic heating power) to boost the ohmic heating and provide a faster start-up, expecially in relatively compact devices.
01 Jan 1986
TL;DR: In this paper, the authors examined the effects of reflective coatings on the microspheres using the diffusion approximation and showed that the volume of the laser can be reduced by at least an order of magnitude by coating the micropellets.
Abstract: An aerosol core reactor concept can overcome efficiency and/or chemical activity problems of other fuel-reactant interface concepts. In the design of a laser using nuclear energy for a “photon-intermediate” pumping scheme, several features of the aerosol core reactor are attractive. First, the “photon-intermediate” pumping concept coupled with photon concentration methods and the aerosol fuel can provide the high power densities required to drive high energy/power lasers efficiently (about 25 to 100 kW/cc). Second, the intermediate photons should have a relatively large mean free path in the aerosol fuel which will allow the concept to scale more favorably. Finally, the aerosol core reactor concept can use materials which should allow the system to operate at high temperatures. The design of an aerosol core reactor is complex, as demonstrated by a conceptual study previously published by the authors. In the earlier work, the individual micropellets, which make up the aerosol, were assumed to be black absorbers. Despite this assumption, it was estimated that an integrated reactor/laser would have a volume of 46 m3 per MJ of laser energy (MJ = 1 MegaJoule). One of the most attractive features of the aerosol core concept, placing a reflective coating on the micropellets, was not explored as a means of increasing the photon mean free path. This study does examine the effects of reflective coatings on the microspheres using the diffusion approximation. It appears that the volume of the laser can be reduced by at least an order of magnitude by coating the micropellets.
TL;DR: In this paper, a mathematical model of a single-arm x-ray pulse-height analyzer (PHA) system is developed, and a maximum likelihood technique is applied to calculate the peak electron temperature and enhancement factor of the plasma.
Abstract: A mathematical model of a single‐arm x‐ray pulse‐height analyzer (PHA) system is developed. Given an assumption on the electron temperature and density profiles, a maximum likelihood technique is applied to calculate the peak electron temperature and enhancement factor of the plasma. This method is currently being used in the analysis of x‐ray data from the tokamak fusion test reactor (TFTR); sample results are presented.
TL;DR: In this paper, the authors evaluated the plasma performance with sawtoothing for two tokamak reactor experiments, the proposed Tokamak Fusion Core Experiment (TFCX) and the joint European Torus (JET).
Abstract: The plasma performance with sawtoothing is assessed for two tokamak reactor experiments, the proposed Tokamak Fusion Core Experiment (TFCX) and the joint European Torus (JET). TFCX is ignitable with sawtoothing and impurities assuming neo-Alcator plus Gorbunov-Mirnov-Strelkov scalings for plasma confinement. JET is also ignitable at optimistically high currents (greater than or equal to7 MA).
TL;DR: In this paper, an expansion method was developed for long-wavelength heliac and stellarator equilibrium, where time-dependent equations of motion were solved numerically to give equilibria which can include magnetic islands and stochastic field regions.
Abstract: An expansion method is developed for long-wavelength heliac and stellarator equilibrium. Time-dependent equations of motion are solved numerically to give equilibria which can include magnetic islands and stochastic field regions. Analytic low-beta equilibria are found which are in good agreement with computations.
01 Jan 1986
TL;DR: The Tokamak Fusion Test Reactor (TFTR) was designed to explore plasma confinement and heating at reactor-like parameters as discussed by the authors, and considerable progress has been made in this endeavor.
Abstract: The Tokamak Fusion Test Reactor (TFTR) was designed to explore plasma confinement and heating at reactor-like parameters. Since the first plasma in December 1982, considerable progress has been made in this endeavor. During the run period ending April 13, 1985, operation of both the toroidal field and plasma current at full design parameters was achieved. The plasma parameters achieved are summarized in Table 1.
TL;DR: In this article, the Thomson scattering profiles of neutral-beam-heated ISX-B plasmas are analyzed in terms of the modification of the plasma equilibrium arising from toroidal rotation or other enhancements of the toroidal component of the stored energy density.
Abstract: In some neutral-beam-heated ISX-B plasmas, the Thomson scattering profiles show that of constant temperature and surfaces of constant density do not coincide. This discrepancy is analysed in terms of the modification of the plasma equilibrium arising from toroidal rotation or other enhancements of the toroidal component of the stored energy density.
TL;DR: In this article, the minimum annual demand for fissile fuel of a system of naval reactors and the required capacity of a fusion neutron source that could supply the fuel by breeding in a thorium-containing blanket were estimated.
Abstract: This note estimates the minimum annual demand for fissile fuel of a system of naval reactors and the required capacity of a fusion neutron source that could supply the fuel by breeding in a thorium-containing blanket.
TL;DR: In this paper, a generic magnetic fusion reactor study carried out at ORNL was presented, which concluded that both the physics and economics would be achievable with present magnetic configurations with present configurations.
Abstract: Comments are made pertaining to a generic magnetic fusion reactor study carried out at ORNL. A second study was made of the required reactor characteristics for attractive fusion reactors. The study concluded that both the physics and economics would be achievable with present magnetic configurations.