Showing papers by "Princeton Plasma Physics Laboratory published in 1994"
TL;DR: In this paper, the utility of extracting CY particle power and then diverting this power to fast fuel ions, is investigated, and it is shown that fusion reactors with power density about twice what otherwise might be obtained can be contemplated, so long as a substantial amount of the 01 particle power can be diverted.
Abstract: The utility of extracting CY particle power, and then diverting this power to fast fuel ions, is investigated. As power is diverted to fast ions and then to ions, a number of effects come into play, as the relative amounts of pressure taken up by electrons, fuel ions and fast CY particles shift. In addition, if the CY particle power is diverted to fast fuel ions, there is an enhanced fusion reactivity because of the non-thermal component of the ion distribution. Some useful expressions for describing these effects are derived, and it is shown that fusion reactors with power density about twice what otherwise might be obtained can be contemplated, so long as a substantial amount of the 01 particle power can be diverted. Interestingly, in this mode of operation, once the electron heat is sufficiently confined, further improvement in confinement is actually not desirable. A similar improvement in fusion power density can be obtained for advanced fuel mixtures such as D-3He, where the power of both the energetic CY particles and the energetic protons might be diverted advantageously.
82 citations
TL;DR: An approach to obtaining efficient single pass mode conversion at high parallel wavenumber from the fast magnetosonic wave to the slow ion Bernstein wave, in a two ion species tokamak plasma, is described and can be adapted to off-axis current drive for current profile control.
Abstract: An approach to obtaining efficient single pass mode conversion at high parallel wavenumber from the fast magnetosonic wave to the slow ion Bernstein wave, in a two ion species tokamak plasma, is described. The intent is to produce localized electron heating or current drive via the mode converted slow wave. In particular, this technique can be adapted to off-axis current drive for current profile control. Modelling for the case of deuterium-tritium plasmas in TFTR is presented.
71 citations
TL;DR: It has been found that the [omega][sup *]-stabilization criterion of the two-fluid collisionless [ital m]=1 reconnection mode agrees very well with the presence or absence of sawteeth in TFTR and no beta limits to the sawtooth stabilization have been observed.
Abstract: Measurements from the Tokamak Fusion Test Reactor (TFTR) of the q profile using motional Stark effect polarimetry and the pressure profiles have allowed detailed comparison of both supershots and L-mode discharges to theoretical models describing the stability of sawteeth. In TFTR supershots sawteeth are usually absent, whereas in L-mode discharges they are generally present, and in both cases q(0) is less than 1. It has been found that the ${\mathrm{\ensuremath{\omega}}}^{\mathrm{*}}$-stabilization criterion of the two-fluid collisionless m=1 reconnection mode agrees very well with the presence or absence of sawteeth in TFTR and no beta limits to the sawtooth stabilization have been observed.
69 citations
TL;DR: The gyrokinetic and gyrofluid models show the most promise for large scale simulations of tokamak microturbulence as discussed by the authors, and detailed comparisons of these two complementary approaches are discussed.
Abstract: The gyrokinetic and gyrofluid models show the most promise for large scale simulations of tokamak microturbulence. This paper discusses detailed comparisons of these two complementary approaches. Past comparisons with linear theory have been fairly good, therefore the emphasis here is on nonlinear comparisons. Simulations include simple two‐dimensional slab test cases, turbulent three‐dimensional slab cases, and toroidal cases, each modeling the nonlinear evolution of the ion temperature gradient instability. There is good agreement in both turbulent and coherent nonlinear slab comparisons in terms of the ion heat flux, both in magnitude and scaling with magnetic shear. However, the nonlinear saturation level for ‖Φ‖ in the slab comparisons shows differences of approximately 40%. Preliminary toroidal comparisons show agreement within 50%, in terms of ion heat flux and saturation level.
52 citations
TL;DR: Measurements and calculations of the resonance between the Ly-[alpha] line of magnesium and the 2[ital s][r arrow]3[ital p] transition in neonlike germanium are presented and show a good resonance between magnesium and germium.
Abstract: Measurements and calculations of the resonance between the Ly-\ensuremath{\alpha} line of magnesium and the 2s\ensuremath{\rightarrow}3p transition in neonlike germanium are presented This resonance is of possible use as part of a resonantly photo-pumped x-ray laser scheme recently proposed which would lase on several 2p\ensuremath{\rightarrow}2s transitions between 64 and 89 \AA{} in neonlike germanium Measurements of the resonance are made by three different approaches: one using the electron beam ion trap, the second using laser-produced plasma, and the third on a tokamak These results are compared with calculations and other measurements Certain discrepancies are observed with previous measurements which may be due to the partial overlap between oxygenlike and neonlike lines in germanium The results do show a good resonance between magnesium and germanium, with the germanium line between the two Ly-\ensuremath{\alpha} components of magnesium but nearer to the short-wavelength component
21 citations
TL;DR: In this article, a kinetic-MHD field-aligned eigenmode stability analysis of low frequency ballooning-mirror instabilities has been performed for anisotropic pressure plasmas in the magnetosphere.
Abstract: A kinetic-MHD field-aligned eigenmode stability analysis of low frequency ballooning-mirror instabilities has been performed for anisotropic pressure plasmas in the magnetosphere. The ballooning mode is mainly a transverse wave driven unstable by pressure gradient in the bad curvature region. The mirror mode with a dominant compressional magnetic field perturbation is excited when the product of plasma beta and pressure anisotropy (P⊥/P|| > 1) is large. In the limit that the wave frequency is smaller than the energetic trapped particle magnetic drift frequency, which is usually much smaller than the energetic trapped particle bounce frequency, the energetic trapped particles experience the bounce-averaged wave structure due to their rapid bounce motion. For modes with north-south symmetric field-aligned structure of parallel perturbed magnetic field the energetic trapped particle kinetic pressure response is finite and cancels with their fluid pressure response so that the symmetric mode is stable. Physically the energetic trapped particles precess very rapidly across the B field, and their motion becomes very rigid with respect to low frequency symmetric MHD perturbations. For antisymmetric modes the energetic trapped particle kinetic pressure response from the northern hemisphere cancels with that from the southern hemisphere in a bounce period, and the instability β threshold of the antisymmetric mode is determined by the energetic particle fluid free energy. Pressure anisotropy with P⊥/P|| > 1 reduces the β|| threshold. The antisymmetric mode changes from a ballooning mode with dominant transverse magnetic field components at P⊥/P|| = 1 to a hybrid ballooning-mirror type mode with comparable transverse and compressional magnetic field components near the equator as P⊥/P|| increases. With large equatorial plasma beta (β|| ≥ Ο(1)) and pressure anisotropy (P⊥/P|| > 1) the field-aligned wave structure of antisymmetric ballooning-mirror mode resembles the multisatellite observations of a long lasting compressional Pc 5 wave event during November 14-15, 1979 (Takahashi et al., 1987). From the AMPTE/ CCE particle and magnetic field data observed during Pc 4-5 wave events we compute the ballooning-mirror instability parameters and perform a correlation study with the theoretical instability threshold. We find that compressional Pc 5 waves approximately satisfy the ballooning-mirror instability condition, and transverse Pc 4-5 waves are probably related to resonant ballooning instabilities with small pressure anisotropy.
20 citations
TL;DR: The ITER-EDA(93) design has been analyzed to evaluate the physics basis for: (i) size and design trade-off issues, (ii) confinement capability, (iii) power levels, and (iv) burn control as discussed by the authors.
Abstract: The ITER-EDA(93) design has been analyzed to evaluate the physics basis for: (i) size and design trade-off issues, (ii) confinement capability, (iii) power levels, and (iv) burn control.
10 citations
TL;DR: The final hardware modifications for tritium operation have been completed for the Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324] as mentioned in this paper.
Abstract: The final hardware modifications for tritium operation have been completed for the Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324 (1992)]. These activities include preparation of the tritium gas handling system, installation of additional neutron shielding, conversion of the toroidal field coil cooling system from water to a FluorinertTM system, modification of the vacuum system to handle tritium, preparation, and testing of the neutral beam system for tritium operation and a final deuterium–deuterium (D–D) run to simulate expected deuterium–tritium (D–T) operation. Testing of the tritium system with low concentration tritium has successfully begun. Simulation of trace and high power D–T experiments using D–D have been performed. The physics objectives of D–T operation are production of ≊10 MW of fusion power, evaluation of confinement, and heating in deuterium–tritium plasmas, evaluation of α‐particle heating of electrons, and collective effects driven by alpha particles and testing of diag...
8 citations
TL;DR: In this paper, a specified-profile, global analysis code has been developed to evaluate the performance of fusion reactor designs, and two measures of performance are available for this purpose: the ignition margin or the confinement level required to achieve a prescribed ignition margin.
7 citations
TL;DR: The Tokamak Physics Experiment (TPX) as discussed by the authors was proposed to extend the recent advances in these areas, achieved in pulsed tokamaks, to the steady-state regime.
Abstract: Improvements in the confinement, stability limits, current-drive efficiency and divertor performance, combined with steady-state operation, can lead to a more economical tokamak fusion reactor than one based on the present physics data base. The Tokamak Physics Experiment (TPX) is planned to extend the recent advances in these areas, achieved in pulsed tokamaks, to the steady-state regime. In so doing, it will develop a data base needed for the design of an economically attractive tokamak reactor.
6 citations
TL;DR: In this paper, an extensive effort was undertaken to optimize the distribution of heating of the bumper limiter tiles during the past three Tokamak Fusion Test Reactor (TFTR) vacuum vessel machine openings.
Abstract: During the past three Tokamak Fusion Test Reactor (TFTR) vacuum vessel machine openings, an extensive effort was undertaken to optimize the distribution of heating of the bumper limiter tiles. The ...
TL;DR: In this paper, the fusion power density was optimized at constant-β for non-thermal distributions that are self-consistently maintained by channeling of energy from charged fusion products.
Abstract: If the energy of charged fusion products can be diverted directly to fuel ions, non-Maxwellian fuel ion distributions and temperature differences between species will result. To determine the importance of these nonthermal effects, the fusion power density is optimized at constant-β for nonthermal distributions that are self-consistently maintained by channeling of energy from charged fusion products. For D-T and D-3He reactors, with 75% of charged fusion product power diverted to fuel ions, temperature differences between electrons and ions increase the reactivity by 40–70%, while non-Maxwellian fuel ion distributions and temperature differences between ionic species increase the reactivity by an additional 3–15%.
TL;DR: In this article, the TFTR D-T experimental plan was used to simulate the radiation fields of future fusion reactors, and the results confirmed that the efficiency of the basic radiation shielding was sufficient to allow the FD-D experimental plan, and provide empirical guidance for simulating the radiation field of future nuclear fusion reactors.
Abstract: Extensive neutron and gamma radiation contour, shielding efficiency, and spectral measurements were performed during high power TFTR D-D operations at the tokamak Test Cell inner walls, ceiling, roof, and outer walls, in nearby control rooms, work areas, and personnel pathways, outdoors along the site fence at 125 m, and out to the nearest property lines at 180 m. The results confirmed that the efficiency of the basic radiation shielding was sufficient to allow the TFTR D-T experimental plan, and provide empirical guidance for simulating the radiation fields of future fusion reactors.
TL;DR: In this article, the authors calculate numerical solutions for the alpha energy transfer and study a range of conditions that are favorable for wave amplification from alpha energy, and they find that it is possible for fusion alpha particles to transfer a large fraction of their energy to the lower hybrid wave.
Abstract: The interaction between a lower hybrid wave and a fusion alpha particle displaces the alpha particle simultaneously in space and energy. This results in coupled diffusion. Diffusion of alphas down the density gradient could lead to their transferring energy to the wave. This could, in turn, put energy into current drive. An initial analytic study was done by Fisch and Rax (1992). Here the authors calculate numerical solutions for the alpha energy transfer and study a range of conditions that are favourable for wave amplification from alpha energy. They find that it is possible for fusion alpha particles to transfer a large fraction of their energy to the lower hybrid wave. The numerical calculation shows that the net energy transfer is not sensitive to the value of the diffusion coefficient over a wide range of practical values. An extension of this idea, the use of a lossy boundary to enhance the energy transfer, is investigated. This technique is shown to offer a large potential benefit.
TL;DR: In this article, it was shown that the Dirac-Wigner sense of Lorentz invariance is not in full compliance with the Einstein-Minkowski reguirements of the world space Mach principle of all physical laws.
Abstract: It is shown that some sections of the invariance (or symmetry) principles such as the space reversal symmetry (or parity P) and time reversal symmetry T (of elementary particle and condensed matter physics, etc.) are not really truly Lorentz covariant. Indeed, I find that the Dirac-Wigner sense of Lorentz invariance is not in full compliance with the Einstein-Minkowski reguirements of the Lorentz covariance of all physical laws (i.e., the world space Mach principle).
TL;DR: In this article, the authors present data of experiments on the resonant photopumping of Mo vii by Mo xii as a method of generating a coherent vacuum UV source near 600 A.
Abstract: We present data of experiments on the resonant photopumping of Mo vii by Mo xii as a method of generating a coherent vacuum UV source near 600 A. The experiment is based on a scheme in which the 4p6–4p56s transition in Mo vii is resonantly photopumped by the 4p 2P3/2–5s2S1/2 transition in Mo xii. Results of the laser-produced plasma experiments show the successful enhancement of the population of the Mo vii 4p56s upper lasing level when Mo vii is pumped by an adjacent Mo xii plasma. No enhancement was seen in a control experiment in which the Mo vii plasma was irradiated by a Zr x plasma. Finally, estimates of the relative population densities between the 5s and the 6p levels are given to show that the experimental conditions are close to those needed to produce a population inversion.
TL;DR: In this paper, the authors illustrate the designs of radiation shielding for the TFTR DT diagnostics using the ACX and TVTS systems as specific examples, and the main emphasis here is on the radiation transport analyses carried out in support of the designs.
Abstract: The authors illustrate the designs of radiation shielding for the TFTR DT diagnostics using the ACX and TVTS systems as specific examples. The main emphasis here is on the radiation transport analyses carried out in support of the designs. Initial results from the DT operation indicate that the diagnostics have been functioning as anticipated and the shielding designs are satisfactory. The experience accumulated in the shielding design for the TFTR DT diagnostics should be useful and applicable to future devices, such as TPX and ITER, where many similar diagnostic systems are expected to be used.
TL;DR: An overview of the various issues and a summary of various design analyses that have been performed thus far to quantify the issues and to guide the design toward near-optimal engineering solutions to the problems are presented in this paper.
Abstract: The Tokamak Physics Experiment (TPX) device, which is under conceptual design in the US, presents several neutronics and shielding issues that are challenging from the design analysis viewpoint. This paper presents an overview of the various issues and a summary of the various design analyses that have been performed thus far to quantify the issues and to guide the design toward near-optimal engineering solutions to the problems. Some planned activities are also discussed.