International Nuclear Information System (INIS)
Two older projects associated with very high energy density plasmas, specifically the High Density Field Reversed Configuration and the Liner Plasma Compression Experiment, have been completed. Attention has been turned to compact toroid experiments of more conventional density, and three experiments have been initiated. These include the Coaxial Slow Source Experiment, the Variable Length FRC Experiment, and Variable Angle CthetaP Experiment. In each case, the project was begun in order to provide basic plasma physics information on specific unresolved issues of progammatic importance to the national CT Program
Liu, Wei; Li, Hui
2009-01-01
We present results from three-dimensional ideal magnetohydrodynamic simulations of low $\\beta$ compact toroid (CT) injection into a hot strongly magnetized plasma, with the aim of providing insight into CT fueling of a tokamak with parameters relevant for ITER (International Thermonuclear Experimental Reactor). A regime is identified in terms of CT injection speed and CT-to-background magnetic field ratio that appears promising for precise core fueling. Shock-dominated regimes, which are probably unfavorable for tokamak fueling, are also identified. The CT penetration depth is proportional to the CT injection speed and density. The entire CT evolution can be divided into three stages: (1) initial penetration, (2) compression in the direction of propagation, and reconnection with the background magnetic field, and (3) coming to rest and spreading in the direction perpendicular to injection. Tilting of the CT is not observed due to the fast transit time of the CT across the background plasma.
Energy Technology Data Exchange (ETDEWEB)
Liu, Wei [Los Alamos National Laboratory; Hsu, Scott [Los Alamos National Laboratory; Li, Hui [Los Alamos National Laboratory
2009-01-01
We present results from three-dimensional ideal magnetohydrodynamic simulations of low {beta} compact toroid (CT) injection into a hot strongly magnetized plasma, with the aim of providing insight into CT fueling of a tokamak with parameters relevant for ITER (International Thermonuclear Experimental Reactor). A regime is identified in terms of CT injection speed and CT-to-background magnetic field ratio that appears promising for precise core fueling. Shock-dominated regimes, which are probably unfavorable for tokamak fueling, are also identified. The CT penetration depth is proportional to the CT injection speed and density. The entire CT evolution can be divided into three stages: (1) initial penetration, (2) compression in the direction of propagation and reconnection, and (3) coming to rest and spreading in the direction perpendicular to injection. Tilting of the CT is not observed due to the fast transit time of the CT across the background plasma.
Compact toroid formation experiments
International Nuclear Information System (INIS)
We present the design and experimental performance of a compact toroid (CT) formation experiment. The device has co-axial electrode diameters of 0.9 m (inner) and 1.25 m (outer), and an electrode length of ∼ 1.2 m, including an expansion/drift section. The CT is formed by a 0.1--0.2 Tesla initial radial magnetic field embedded co-axial puff gas discharge. The gas puff is injected with an array of 60 pulsed solenoid driven fast valves. The formation discharge is driven by a 108 microfarad, 40 to 100 KV, 86 to 540 kilojoule 2 to 5 megamp capacitor discharge with ∼ 20 nanohenry initial total discharge inductance. The hardware includes transmission line connections for a Shiva Star (1300 microfarad, up to 120 KV, 0.4 megajoule) capacitor bank driven acceleration discharge. Experimental measurements include current, voltage; azimuthal, radial and axial magnetic field at numerous location; fast photography, optical spectroscopy; microwave, CO2 laser, and He-Ne laser interferometry. Auxiliary experiments include Penning ionization gauge, pressure probe, and breakdown gas trigger diagnostics of gas injection, and Hall probe measurements of magnetic field injection
International Nuclear Information System (INIS)
This report describes work performed at the University of Washington Aerospace and Energetics Research Program involving the ''compact toroid'' approach to magenetic confinement of plasmas. The five experiments comprising the effort are: The coaxial slow source experiment; the CSS project; the variable length experiment; the merging spheromak experiment; and the variable angle conical theta pinch experiment
Compact toroid fueling for ITER
International Nuclear Information System (INIS)
Experimental and theoretical work indicates that deep fueling of ITER may be possible by Compact Toroid (CT) injection. CT velocities sufficient for center fueling of a reactor have been demonstrated in the RACE device. CT injections into the TdeV tokamak have achieved central penetration at 1.4 T, and have increased the particle inventory by more than 30% without disruption. Tests on the MARAUDER device have achieved CT mass-densities suitable for injection into 5 T tokamaks. Techniques for producing multiple-shot CT's with passive electric switching are being tested on CTIX. The advantages of deep fueling by CT injection include profile peaking to reach ignition, profile control, low tritium inventory and others. In this paper, the CT experimental results are summarized, a conceptual design of a CT fueler for ITER is presented, and the implications on ITER operation and fuel cycle are discussed. 16 refs., 2 figs., 1 tab
Computational modelling of compact toroidal plasmas
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Preliminary simulations of the formation of compact toroids are presented. This work is in support of current experiments in which compact toroids - a minimum magnetic energy configuration with linked toroidal and poloidal flux - are being formed, accelerated and compressed. Simulations were performed using MACH2, a 2D magnetohydrodynamic code with a newly implemented Van Lear transport scheme. Simulations also include a detailed modelling of the initial poloidal flux distribution produced by the external solenoidal coils, which is through to significantly effect the toroid's formation
Computer simulations of compact toroid formation and acceleration
International Nuclear Information System (INIS)
Experiments to form, accelerate, and focus compact toroid plasmas will be performed on the 9.4 MJ SHIVA STAR fast capacitor bank at the Air Force Weapons Laboratory during the 1990. The MARAUDER (magnetically accelerated rings to achieve ultrahigh directed energy and radiation) program is a research effort to accelerate magnetized plasma rings with the masses between 0.1 and 1.0 mg to velocities above 10 8 cm/sec and energies above 1 MJ. Research on these high-velocity compact toroids may lead to development of very fast opening switches, high-power microwave sources, and an alternative path to inertial confinement fusion. Design of a compact toroid accelerator experiment on the SHIVA STAR capacitor bank is underway, and computer simulations with the 2 1/2-dimensional magnetohydrodynamics code, MACH2, have been performed to guide this endeavor. The compact toroids are produced in a magnetized coaxial plasma gun, and the acceleration will occur in a configuration similar to a coaxial railgun. Detailed calculations of formation and equilibration of a low beta magnetic force-free configuration (curl B = kB) have been performed with MACH2. In this paper, the authors discuss computer simulations of the focusing and acceleration of the toroid
Optical spectroscopic analysis of compact toroids
International Nuclear Information System (INIS)
Time- and space-resolved plasma emission spectra from the Weapons Laboratory compact toroid (MARAUDER) experiment have been recorded using an optical multichannel analyzer (OMA). The OMA is optically coupled to the emitting plasmas using fiber optic cables. Results are presented in terms of the composition and purity of plasma species and ionization states for compact toroids formed of hydrogen and argon. The authors use relative line strengths with a collisional radiative equilibrium (CRE) model to estimate the plasma temperature and density. Electron density has also been determined from line profile analysis of the Hβ line in hydrogen
Development of compact toroids injector for direct plasma controls
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The application of the compact toroids injector for direct plasma controls has been investigated. The compact toroids injection can fuel particles directly into the core of the plasma and modify the plasma profiles at the desired locations. The acceleration tests of the compact toroids have been conducted at Himeji Institute of Technology. The tests showed that the hydrogen compact toroid was accelerated up to 80km/s and the plasma density of the compact toroid was compressed to 1.2 x 1021m-3. (orig.)
Proposal to produce large compact toroids
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Relatively large, hot compact toroids might be produced in the annular space between two concentric one-turn coils. With currents in the two coils flowing in the same direction, the magnetic fields on each side of the plasma are in opposite directions. As the fields are raised, the plasma ring is heated and compressed radially towards the center of the annular space. By the addition of two sets of auxiliary coils, the plasma ring can be ejected out one end of the two-coil system into a long axial magnetic field
Sawtooth Instability in the Compact Toroidal Hybrid
Herfindal, J. L.; Maurer, D. A.; Hartwell, G. J.; Ennis, D. A.; Knowlton, S. F.
2015-11-01
Sawtooth instabilities have been observed in the Compact Toroidal Hybrid (CTH), a current-carrying stellarator/tokamak hybrid device. The sawtooth instability is driven by ohmic heating of the core plasma until the safety factor drops below unity resulting in the growth of an m = 1 kink-tearing mode. Experiments varying the vacuum rotational transform from 0.02 to 0.13 are being conducted to study sawtooth property dependance on vacuum flux surface structure. The frequency of the sawtooth oscillations increase from 2 kHz to 2.8 kHz solely due the decrease in rise time of the oscillation, the crash time is unchanged. CTH has three two-color SXR cameras, a three-channel 1mm interferometer, and a new bolometer system capable of detecting the signatures of sawtooth instabilities. The new bolometer system consists of two cameras, each containing a pair of diode arrays viewing the plasma directly or through a beryllium filter. Electron temperature measurements are found with the two-color SXR cameras through a ratio of the SXR intensities. Impurity radiation can drastically affect the electron temperature measurement, therefore new filters consisting of aluminum and carbon were selected to avoid problematic line radiation while maximizing the signal for a 100 eV plasma. This work is supported by U.S. Department of Energy Grant No. DE-FG02-00ER54610.
Compact toroid injection into C-2U
Roche, Thomas; Gota, H.; Garate, E.; Asai, T.; Matsumoto, T.; Sekiguchi, J.; Putvinski, S.; Allfrey, I.; Beall, M.; Cordero, M.; Granstedt, E.; Kinley, J.; Morehouse, M.; Sheftman, D.; Valentine, T.; Waggoner, W.; the TAE Team
2015-11-01
Sustainment of an advanced neutral beam-driven FRC for a period in excess of 5 ms is the primary goal of the C-2U machine at Tri Alpha Energy. In addition, a criteria for long-term global sustainment of any magnetically confined fusion reactor is particle refueling. To this end, a magnetized coaxial plasma-gun has been developed. Compact toroids (CT) are to be injected perpendicular to the axial magnetic field of C-2U. To simulate this environment, an experimental test-stand has been constructed. A transverse magnetic field of B ~ 1 kG is established (comparable to the C-2U axial field) and CTs are fired across it. As a minimal requirement, the CT must have energy density greater than that of the magnetic field it is to penetrate, i.e., 1/2 ρv2 >=B2 / 2μ0 . This criteria is easily met and indeed the CTs traverse the test-stand field. A preliminary experiment on C-2U shows the CT also capable of penetrating into FRC plasmas and refueling is observed resulting in a 20 - 30% increase in total particle number per single-pulsed CT injection. Results from test-stand and C-2U experiments will be presented.
Compact-Toroid development: status and technical needs
International Nuclear Information System (INIS)
This document contains the description, goals, status, plans, and strategy for the technical development of a class of magnetic confinement configurations collectively identified as Compact Toroids. This component of the magnetic fusion development program has been characterized by its potential for physical compactness and range of output power
Compact toroid theory issues and approaches: a panel report
International Nuclear Information System (INIS)
In the six years since the initiation of the compact toroid program by the Office of Fusion Energy, remarkable scientific advances have occurred on both field-reversed configurations (FRC) and spheromaks. This progress has been stimulated by a diverse experimental program with facilities at six laboratories, and by a small but nevertheless broad theoretical research effort encompassing more than a dozen institutions. The close coupling between theoretical and experimental programs has contributed immeasurably to this progress. This document offers guidance for future compact toroid theory by identifying and discussing the key physics issues. In most cases promising approaches to these issues are offered
Investigation of compact toroid physics. Annual report, period ending September 30, 1980
Energy Technology Data Exchange (ETDEWEB)
Vlases, G C; Pietrzyk, Z A
1980-01-01
In the past year the major emphases have been on: (a) initiation of a small high density compact toroid experiment of the FRC configuration, characterized by no toroidal field and high ..beta..; (b) construction and testing of an imploding shell device for plasma heating; and (c) two-dimensional modeling of CT-FRC plasmas for our own use, as well as for interpretation and predictions for experiments at LASL and MSNW. In addition, we have nearly completed our work on material end plugging of dense linear open field plasma columns.
Experimental study of high beta toroidal plasmas
International Nuclear Information System (INIS)
Experiments on the Wisconsin Levitated Toroidal Octupole have produced a wide range of stable high β plasmas with β significantly above single fluid MHD theory predictions. A stable β approx. 8% plasma, twice the fluid limit, is obtained with 5 rho/sub i/ approx. L/sub n/ and tau/sub β/ approx. = 6000 tau/sub Alfven/ = 600 μsec. The enhanced stability is explained with a kinetic treatment that includes the effect of finite ion gyroradius which couples the ballooning mode to an ion drift wave. In a more collisional, large gyroradius (2 rho/sub i/ approx. L/sub n/) regime, a stable β approx. 35% plasma is obtained with a decay time of 1000 Alfven times. Measurement of the equilibrium magnetic field in this regime indicates that the diamagnetic current density is five times smaller than predicted by ideal MHD, probably due to ion gyroviscosity. Particle transport is anomalous and ranges from agreement with the classical diffusion rate at the highest beta, lowest field plasma (B/sub P/ = 200 G), to thirteen times the classical rate in a β=11%, high field plasma (B/sub P/ = 860 G) where the level of enhancement increase with magnetic field. Fluctuations in density, electrostatic potential, and magnetic field have been studied in plasmas with β from 0.1% to 40%
Theoretical studies of non inductive current drive in compact toroids
Farengo, R; Lifschitz, AF; Caputi, KI; Arista, NR; Clemente, RA
2002-01-01
Three non inductive current drive methods that can be applied to compact toroids axe studied. The use of neutral beams to drive current in field reversed configurations and spheromaks is studied using a Monte Carlo code that includes a complete ionization package and follows the exact particle orbit
Computational simulation of compact toroidal plasma formation
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The following computational efforts are part of the MARAUDER (magnetically accelerated rings to achieve ultra-high directed energy and radiation) research program at the High Energy Plasma Division of the Weapons Laboratory. The program is investigating plasma toroids with magnetic fields similar to those of tokamaks. These fields confine the plasma between a pair of cylindrical conductors. The objective of the research is to first form such toroids and then compress and accelerate them. A 500 kJ capacitor bank will be used for the formation, and the 9 MJ Shiva Star will be used for acceleration. The first set of experiments and current computational work consider only the formation process. The computer program used for these simulations is MACH2. It is a two-dimensional MHD code and was originally developed by Mission Research Corporation under a Weapons Laboratory contract to support z-pinch research. MACH2 is an Arbitrary Lagrangian-Eulerian code with an adaptive mesh capability. Its diffusion routines use a multigrid technique to accelerate convergence. Recently, a second-order advection scheme has been added
International Nuclear Information System (INIS)
Progress over the past year has enabled us to complete the comprehensive experimental investigation of the equilibrium and stability of the linear heliac and the linear l = 1 stellarator configration. In the case of the heliac work, we discoverd axisymmetric hot plasma near the axial conductor (''hardcore'') in amounts which are comparable to the helically symmetric hot plasma centered on the magnetic axis. From this result came the motivation for an extended investigation which concentrates on the details of high-beta heliac formation. Important first results of the formation study have been obtained. In the case of the stellarator work, we have observed the flute-like m = 1 instability foe a specific set of experimental parameters and, for a different set, we have observed the mode stabilized by the combined effects of a finite ion Larmor radius and a nearby conducting wall. The single-discharge CV ion-temperature diagnostic system has been debugged and has yielded a heliac temperature measurement of (90 +- 10)eV. The plasma density diagnostic system based on cross-tube interferometry has been modified from its previous design for use with the somewhat wrinkly helical discharge tube
Effect of toroidal magnetic field and plasma rotation on compact toriequilibria
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The effect of toroidal magnetic field and plasma rotation on compact tori equilibrium configurations is studied. It is found that the equilibrium configurations exist in any toroidal fields. The field dependences of toroidal parameters are analyzed. The effect of opening of the toroidal separatrix and the influence of the toroidal magnetic field, toroidal rotation, the pressure profile type behind the separatrix on it is studied as well. 13 refs.; 11 figs.; 2 tabs
Compact toroid development. Resource needs for field reversed configurations
International Nuclear Information System (INIS)
This document contains the goals and technical approach for the five years 1985 to 1990 for the investigation of the properties of a magnetic configuration for plasma confinement identified as the field reversed configuration (FRC). The included material represents the third phase of FRC program planning. The first was reported in DOE/ER-0160: Compact Toroid Development, Status and Technical Needs, February 1983. The second was reported in DOE/ER-0197: Compact Toroid Development, Activity Plans for Field Reversed Configurations, June 1984. This planning identifies the facilities and resources needed to achieve the goals set forth in the first two phases. The information in this document is based on technical recommendations provided by the FRC community
Interferometry on the Weapons Laboratory's compact toroid experiment
International Nuclear Information System (INIS)
Interferometric measurements of line averaged free electron density are being taken as part of the compact toroid experiment at the Weapons Laboratory's High Energy Plasma Division. A double pass optical interferometer using either a CO2 far-infrared laser or a He-Ne laser and a separate single pass millimeter wave interferometer is used. With this wide range of wavelengths, a very wide range of density measurements were made of the various states of the experiment
Two novel compact toroidal concepts with Stellarator features
International Nuclear Information System (INIS)
Two novel compact toroidal concepts are presented. One is the Stellarator-Spheromak (SSP) and another is the Extreme-Low-Aspect-Ratio Stellarator (ELARS). An SSP device represents a hybrid between a spherical stellarator (SS) and a spheromak. This configuration retains the main advantages of spheromaks ans has a potential for improving the spheromak concept regarding its main problems. The MHD equilibrium in an SSP with very high β of the confined plasma is demonstrated. Another concept, ELARS, represents an extreme limit of the SS approach, and considers devices with stellarator features and aspect ratios A ∼ 1. We have succeeded in finding ELARS configurations with extremely compact, modular, and simple design compatible with significant rotational transform, large plasma volume, and good particle transport characteristics
Compact toroid development: activity plan for field reversed configurations
International Nuclear Information System (INIS)
This document contains the description, goals, status, plans, and approach for the investigation of the properties of a magnetic configuration for plasma confinement identified as the field reversed configuration (FRC). This component of the magnetic fusion development program has been characterized by its potential for physical compactness and a flexible range of output power. The included material represents the second phase of FRC program planning. The first was completed in February 1983, and was reported in DOE/ER-0160; Compact Toroid Development. This planning builds on that previous report and concentrates on the detailed plans for the next several years of the current DOE sponsored program. It has been deliberately restricted to the experimental and theoretical efforts possible within the present scale of effort. A third phase of this planning exercise will examine the subsequent effort and resources needed to achieve near term (1987 to 1990) FRC technical objectives
Dynamic processes in field-reversed-configuration compact toroids
International Nuclear Information System (INIS)
In this lecture, the dynamic processes involved in field-reversed configuration (FRC) formation, translation, and compression will be reviewed. Though the FRC is related to the field-reversed mirror concept, the formation method used in most experiments is a variant of the field-reversed Θ-pinch. Formation of the FRC eqilibrium occurs rapidly, usually in less than 20 μs. The formation sequence consists of several coupled processes: preionization; radial implosion and compression; magnetic field line closure; axial contraction; equilibrium formation. Recent experiments and theory have led to a significantly improved understanding of these processes; however, the experimental method still relies on a somewhat empirical approach which involves the optimization of initial preionization plasma parameters and symmetry. New improvements in FRC formation methods include the use of lower voltages which extrapolate better to larger devices. The axial translation of compact toroid plasmas offers an attractive engineering convenience in a fusion reactor. FRC translation has been demonstrated in several experiments worldwide, and these plasmas are found to be robust, moving at speeds up to the Alfven velocity over distances of up to 16 m, with no degradation in the confinement. Compact toroids are ideal for magnetic compression. Translated FRCs have been compressed and heated by imploding liners. Upcoming experiments will rely on external flux compression to heat a translater FRC at 1-GW power levels. 39 refs
International Nuclear Information System (INIS)
Potential commercial fusion power systems must be acceptable from a safety and environmental standpoint. They must also promise to be competitive with other sources of energy (i.e., fossil, fission, etc.) when considered from the standpoint of the cost of electricity (COE) and the unit direst cost (UDC) in ($/kWe). These costs are affected by a host of factors including recirculating power, plant availability, construction time, capital cost etc., and are, thus, influenced by technological complexity. In a attempt to meet these requirements, the emphasis of fusion research in the United States has been moving toward smaller, lower-cost systems. There is increased interest in higher beta tokamaks and stellarators, and in compact alternate concepts such as the Reversed Field Pinch (RFP) and the Compact Toroids (CTs) which are, in part, the subject of this paper
Magnetic probe measurements of compact toroid formation experiments
International Nuclear Information System (INIS)
Magnetic loop probes with areas ranging from 0.2 to 0.9 cm2 were used to observe azimuthal, radial, and axial magnetic fields versus time at 28 locations in Compact Toroid formation discharges. The probes were enclosed in 6 mm outer diameter, 4 mm inner diameter glass tubes which were inserted through the 90 cm diameter inner (electrically hot) electrode. Probe signals were sent to an array of Tektronix 7903 oscilloscopes via fiber optic links. Typical field values ranged from 0.1 to 2 Tesla. Typical discharge currents were -3 microsecond rise time. Probe calibrations, experimental field distribution histories, and comparison with 2D-MHD predictions are discussed. Such comparisons show good agreement
International Nuclear Information System (INIS)
This report summarizes work done on the high-beta Q machine (HBQM), which is a 3-meter long, low-compression theta pinch with a 22-cm diameter segmented compression coil with a minimum axial peridicity length of 10 cm. The main activities are low-density field-reversed cell formation and radiofrequency fast-wave heating experiment on a zero-bias plasma column. In addition we report further engineering improvements on the HBQM and on the digital data acquisition system
International Nuclear Information System (INIS)
This article reports on the acceleration dynamics of a compact toroid plasma configuration in a background hydrogen gas. The acceleration dynamics are investigated experimentally using magnetic probes and chordal interferometry. These measurements are then compared to two-dimensional simulations that show good agreement with experiments. The experimental measurements indicate that the velocity and field strength initially increase as a function of accelerator voltage, however, at higher voltages the compact toroid velocity ceases to increase with increased accelerator voltage. In our investigation, we examine the 'blowby' effect along with additional processes such as mass accumulation and charge exchange as potential mechanisms contributing to the stagnation of the compact toroid's velocity. (author)
Control of Compact-Toroid Characteristics by External Copper Shell
Matsumoto, T.; Sekiguchi, J.; Asai, T.; Gota, H.; Roche, T.; Allfrey, I.; Cordero, M.; Garate, E.; Kinley, J.; Valentine, T.; Waggoner, W.; the TAE Team
2015-11-01
A collaborative research project by Tri Alpha Energy and Nihon University has been conducted for several years, which led to the development of a new compact toroid (CT) injector for efficient FRC particle refueling in the C-2U experiment. The CT is formed by a magnetized coaxial plasma gun (MCPG), consisting of coaxial cylindrical electrodes. In CT formation via MCPG, the magnetic helicity content of the generated CT is one of the critical parameters. A bias coil is inserted into the inner electrode to generate a poloidal flux. The resultant bias magnetic field is spread out of MCPG with time due to its low-frequency bias current. To obtain a more effectively distributed bias magnetic field as well as to improve the voltage breakdown between electrodes, the MCPG incorporates a novel ~ 1 mm thick copper shell mounted outside of the outer electrode. This allows for reliable and controlled operation and more robust CT generation. A detailed discussion of the copper shell and experimental test results will be presented.
Development of Compact Toroid Injector for C-2 FRCs
Matsumoto, Tadafumi; Sekiguchi, Junichi; Asai, Tomohiko; Gota, Hiroshi; Garate, Eusebio; Allfrey, Ian; Valentine, Travis; Smith, Brett; Morehouse, Mark; TAE Team
2014-10-01
Collaborative research project with Tri Alpha Energy has been started and we have developed a new compact toroid (CT) injector for the C-2 device, mainly for fueling field-reversed configurations (FRCs). The CT is formed by a magnetized coaxial plasma-gun (MCPG), which consists of coaxial cylinder electrodes; a spheromak-like plasma is generated by discharge and pushed out from the gun by Lorentz force. The inner diameter of outer electrode is 83.1 mm and the outer diameter of inner electrode is 54.0 mm. The surface of the inner electrode is coated with tungsten in order to reduce impurities coming out from the electrode. The bias coil is mounted inside of the inner electrode. We have recently conducted test experiments and achieved a supersonic CT translation speed of up to ~100 km/s. Other typical plasma parameters are as follows: electron density ~ 5 × 1021 m-3, electron temperature ~ 40 eV, and the number of particles ~0.5-1.0 × 1019. The CT injector is now planned to be installed on C-2 and the first CT injection experiment will be conducted in the near future. The detailed MCPG design as well as the test experimental results will be presented.
Spectroscopic Measurements of Non-Hydrogenic Compact Toroids on CTIX
Hwang, D. Q.; Buchenauer, D.; Horton, R. D.; Evans, R. W.; Klauser, R.; Whaley, J. A.; Mills, B. E.
2015-11-01
The CTIX device is currently being used to investigate the production of compact-toroid plasmas consisting primarily of high-Z ions, using ionization and accretion of high-Z neutrals in the acceleration region. The axial density profile of the high-Z ions will be determined by transverse spectroscopic measurements, which are able to identify particular ion species. Ion velocity can then be deduced from axial time of flight. In addition, high-resolution spectroscopy will be used to directly measure high-Z ion velocity via Doppler shifts. These results are important in determining the degree of slip of high-Z ion velocity relative to CT magnetic field. Scaling of this slippage can be measured as a function of ion species, magnetic field strength, and gas injection location, and compared with a test-particle simulation. The results are relevant to determining the ability of the CT to penetrate a magnetic field, either for the purposes of shock formation study, or for applications to runaway electron suppression in large tokamak experiments. Beneficial effects, in terms of discharge reproducibility and surface durability, for a new tungsten-coated inner electrode will also be presented, along with a design for improved diagnostic access through the outer electrode. This work was supported by USDOE grant # DE-FG02-03ER54732 at UC Davis, and USDOE contract DE-AC04-94AL85000 at Sandia National Laboratories.
International Nuclear Information System (INIS)
This document contains papers contributed by the participants of the Third Symposium on Physics and Technology of Compact Toroids in the Magnetic Fusion Energy Program. Subjects include reactor aspects of compact toroids, energetic particle rings, spheromak configurations (a mixture of toroidal and poloidal fields), and field-reversed configurations
Energy Technology Data Exchange (ETDEWEB)
Siemon, R.E. (comp.)
1981-03-01
This document contains papers contributed by the participants of the Third Symposium on Physics and Technology of Compact Toroids in the Magnetic Fusion Energy Program. Subjects include reactor aspects of compact toroids, energetic particle rings, spheromak configurations (a mixture of toroidal and poloidal fields), and field-reversed configurations (FRC's that contain purely poloidal field).
Design and construction progress of the compact toroidal hybrid
International Nuclear Information System (INIS)
The Compact Toroidal Hybrid (CTH) is a stellarator/tokamak hybrid device currently under construction at Auburn University. The primary goal of CTH is to investigate both ideal and resistive current-driven instabilities in low aspect ratio (Ap=4) stellarator plasmas. Current-driven MHD instabilities in stellarator plasmas are generally of interest because the bootstrap and Pfirsch-Schlueter currents could potentially destabilize external kink modes in high β stellarators. Of particular interest is the susceptibility of current-driven stellarator discharges to major disruptions, and the extent to which the helical stellarator field can passively stabilize them. Previous studies on W7-A and JIPPT-II have shown that the stellarator field can extend the stable regime of tokamak operation and suppress disruptions, yet current-driven disruptions can still be obtained in stellarator plasmas with a relatively small fraction of the rotational transform derived from the plasma current. The issue of MHD stability of current-carrying stellarator plasmas is important within the US stellarator program since two low aspect ratio stellarators under consideration, NCSX and QPS , will have significant levels of bootstrap current. In CTH, the susceptibility and severity of current-driven stellarator plasmas to disruptions will be experimentally examined with ohmic currents applied to RF-generated stellarator plasmas. Both peaked and hollow bootstrap-like current profiles will be generated in CTH and comparisons will be made with 3-D stability theory. 1-D and some supporting 3-D stability studies show that CTH can be made to operate at the predicted stability boundary of ideal kink and vertical instabilities. Disruptions from resistive tearing modes can be expected, as observed in the previous current-driven stellarator experiments. Copyright (2002) Australian National University- Research School of Physical Sciences and Engineering
International Nuclear Information System (INIS)
Results of an experimental investigation of compact toroid formation, dynamics, and plasma loss in a 50-cm-long field reversed theta pinch are presented. A combination of radio frequency incipient ionization coupled with fast ringing theta discharges was used to trap a uniform 0.92 kG magnetic bias field in a deuterium gas over a 20 to 200 mtorr fill pressure range in a 9-cm diameter discharge tube. A reversed 4.54 kJ crowbarred discharge with a rise time of 3.4 μs was used to form compact toroids exhibiting lifetimes up to 60 μs. A diamagnetic loop, magnetic loop, magnetic probes, pressure probes, spectroscopy, photodiodes, and photography were used as diagnostics to investigate preionization, bias field generation, and trapping, stable lifetime characteristics, and eventual compact toroid destruction. Separatrix radius electron temperature, and electron density as a function of time and pressure are calculated from experimental data. Symmetry and rotational stability are illustrated over the lifetime of the compact toroids. Results indicate that like the Russian experiments but unlike the results at Los Alamos, compact toroids formed in the Penn State machine were limited in life by the decay characteristics of the applied magnetic field and not by the n = 2 rotational instability
Physics progress towards compact tokamak reactors with normal conducting toroidal field coils
International Nuclear Information System (INIS)
Very low aspect ratio (R0/a ∼ 1.2) tokamaks utilizing a demountable, normal conducting center leg to carry the toroidal field current are estimated to lead to compact (R0 + a ∼ 5.4 m) and economically competitive fusion power plants, given certain key plasma properties. Calculations are carried out to determine if these properties can be obtained for such low R0/a, using tokamak physics models recently improved by data from START. High toroidal field utilization (Ip/Itfc ∼ 1-2) and strong plasma ''shaping'' S (≡ Ipqψ/ABt0 ∼ 100-200 MA·m-1·T-1) can be obtained using only two pairs of outboard poloidal field coils. The fraction of the scrap-off layer (SOL) connected to the inboard side of such plasmas diminishes as R0/a is reduced, while the remainder is diverted. Order-unity toroidal average betas (t> ≡ 2μo/B2t0 ∼ 0.5-1) which are ballooning stable are obtained having a second-regime core of low magnetic shear and high q0 (5 ≥ q0 ≥ 3), and a first-regime periphery of high magnetic shear and high edge qψ (22 ≥ qψ 11). Large self-driven currents (Iself/Ip ≤ 0.7), well aligned with a hollow plasma current in these equilibria, are calculated for an element of β1 ≤ 0.9. For marginal MHD stability of the outboard SOL, it is shown that the minimum pressure e-folding length λp scales approximately according to (niTi/R)(Lc/B)2, ni and Ti being the edge ion density and temperature, respectively, and Lc being the connected field line length. A large outboard SOL pressure e-folding thickness can therefore exist for low R0 and Bt0 configurations of very low R0/a (λp ∼ ΔSOL/3 ∼ 10 cm in the case of reactors). This reduces the divertor heat flux expected in compact fusion systems of high power density. Progress in these topics will help ensure that very low R0/a tokamaks are effective vehicles for fusion power as well as blanket testing. (author). 26 refs, 5 figs, 4 tabs
Use of field-reversed compact plasma toroids for tokamak plasma make-up
International Nuclear Information System (INIS)
Main requirements to the parameters of compact plasma toroids, injection of which into tokamak plasma can be used for fuel make-up, are considered. The numeric modelling results attest that minimum disturbances of tokamak magnetic configuration can be expected when the injection direction is close to torus tangent line. In addition, an experimental device SAPFIR used for studying the formation of toroids of high value at plasma accelerators is described briefly. 7 refs.; 3 figs
Effects of compact torus injection on toroidal flow in the STOR-M tokamak
International Nuclear Information System (INIS)
In compact torus injection (CTI) experiments on the STOR-M tokamak, an ion Doppler spectrometer is installed to observe the effects of CTI on toroidal plasma flows. The intrinsic toroidal flow in ohmic discharges without CTI is sheared with counter plasma current flow in the core region and co-current direction at the periphery. With tangential CTI along the co-current direction, the flow velocity in the core region decreases by more than 5 km s−1, while in the periphery the flow velocity increases by 3–4 km s−1. These data indicate that the observed flow change is due to the injection of toroidal momentum. Density increase and high soft x-ray emission after CTI are observed during the changes in the toroidal flow. (paper)
Fuelling effect of tangential compact toroid injection in STOR-M Tokamak
International Nuclear Information System (INIS)
Compact torus injection (CTI) is the only known candidate for directly fuelling the core of a tokamak fusion reactor. Compact torus (CT) injection into the STOR-M tokamak has induced improved confinement accompanied by an increase in the electron density, reduction in Hα emission, and suppression of the saw-tooth oscillations. The measured change in the toroidal flow velocity following tangential CTI has demonstrated momentum injection into the STOR-M plasma. (author)
Los Alamos compact toroid, fast-liner, and high-density Z-pinch programs
Energy Technology Data Exchange (ETDEWEB)
Linford, R.K.; Sherwood, A.R.; Hammel, J.E.
1981-03-01
The Compact Toroid (CT) and High Density Z-Pinch (HDZP) are two of the plasma configurations presently being studied at Los Alamos. The purpose of these two programs, plus the recently terminated (May 1979) Fast Liner (FL) program, is summarized in this section along with a brief description of the experimental facilities. The remaining sections summarize the recent results and the experimental status.
Toroidal High-β Experiments in Compact Axisymmetric Configurations
International Nuclear Information System (INIS)
The confinement of plasmas heated by fast-rising (B/B ≈ 1 JJS) and confined by slowly decaying (|B/B| > 1 ms) magnetic fields is studied in axisymmetric toroidal configurations. Small aspect ratios R/a (R = major radius, a = characteristic minor dimension) are chosen to reach relatively high current densities and to confine plasmas of higher S below the Kruskal-Shafranov (K.S.) limit. In a first experiment (Helical Hard-core Thetapinch), plasmas with temperatures T ≈ 20 eV, densities n > 1016 cm-3 and strongly elliptical (typically b/a = 3) cross-sections are produced at the end of the fast compression. By adjusting the voltages and currents of the hard-core and the theta coil, and the, time-delay between switching the banks, R can be varied and the net plasma momentum in r direction can be made ≈ 0 at the end of the dynamic phase. Slower variations of R, resulting from the diffusion of the toroidal field into the plasma (β decreases to 15% in a few μs) and from the contraction of the plasma cross-section in the z-direction occur later. They can be controlled by programming the hard-core current. Theoretical results on the equilibrium plasma configuration agree with the result of magnetic-probe and optical measurements which further indicate some triangular deformation of the plasma cross-section. Outside the plasma, a vacuum magnetic field configuration is observed. The angle of rotational transform ℓ was varied by changing R and the ellipticity; the plasma appears hydromagnetically stable when q = 2 π/ℓ > 2.5. The observed confinement time (≈ 30 μs) agrees then with the decay time of the toroidal plasma current and can be explained by the relatively low plasma temperature. A second experiment is being built to study the high-fi stability limit in a torus with circular cross-section and larger dimensions (R = 25 cm, rw = 10 cm). The toroidal magnetic field (≤ 10 kG) and the discharge current rise simultaneously in 1.6 us. It will be attempted to
Investigation of compact toroid physics. Annual report, period ending September 30, 1980
International Nuclear Information System (INIS)
In the past year the major emphases have been on: (a) initiation of a small high density compact toroid experiment of the FRC configuration, characterized by no toroidal field and high β; (b) construction and testing of an imploding shell device for plasma heating; and (c) two-dimensional modeling of CT-FRC plasmas for our own use, as well as for interpretation and predictions for experiments at LASL and MSNW. In addition, we have nearly completed our work on material end plugging of dense linear open field plasma columns
Finite beta and compressibility effects on stability of resistive modes in toroidal geometry
Energy Technology Data Exchange (ETDEWEB)
Leboeuf, J.-N.G. [Oak Ridge National Lab., TN (United States); Kurita, Gen-ichi
1998-03-01
Linear resistive stability results obtained from the toroidal magnetohydrodynamic codes FAR developed at the Oak Ridge National Laboratory in United States of America and AEOLUS developed at the Japan Atomic Energy Research Institute are compared for carefully constructed benchmark profiles and parameters. These are unstable to a tearing mode with toroidal mode number n=1. The eigenvalues and eigenfunctions calculated with both codes are in close agreement and show that the effect of compressibility is weak for these modes. The effect of finite plasma beta is considered, and the eigenvalues calculated by the FAR and AEOLUS codes also show good agreement. It is shown that the finite beta has a stabilizing effect on the toroidal tearing mode, but that the compressibility also has little effect on finite beta tearing modes. (author)
Stability of toroidally compact Kaluza-Klein theories
Energy Technology Data Exchange (ETDEWEB)
Blau, S.K.; Guendelman, E.I.; Taormina, A.; Wijewardhana, L.C.R.
1984-08-23
The authors study the stability at the one loop level, of finite temperature Kaluza-Klein theories coupled to matter fields. They restrict their attention to space-times containing compact manifolds which are toruses and Klein bottles. If the cosmological constant is chosen so that the effective potential vanishes at its minimum, and if twisted bosons or untwisted fermions are introduced into the theory, then these space-times are stable below a critical temperature of the order of the particle masses. The authors also discuss some subtleties that arise when Fermi fields are defined on non-simply connected manifolds.
On the stability of toroidally compact Kaluza-Klein theories
Blau, S. K.; Guendelman, E. I.; Taormina, A.; Wijewardhana, L. C. R.
1984-08-01
We study the stability ar the one loop level, of finite temperature Kaluza-Klein theories coupled to matter fields. We restrict our attention to space-times containing compact manifolds which are toruses and Klein bottles. If the cosmological constant is chosen so that the effective potential vanishes at its minimum, and if twisted bosons or untwisted fermions are introduced into the theory, then these space-times are stable below a critical temperature of the order of the particle masses. We also discuss some subtleties that arises when Fermi fields are defined on non-simply connected manifolds.
Stability of toroidally compact Kaluza-Klein theories
Energy Technology Data Exchange (ETDEWEB)
Blau, S.K.; Guendelman, E.I.; Wijewardhana, L.C.R. (Massachusetts Inst. of Tech., Cambridge (USA). Lab. for Nuclear Science; Massachusetts Inst. of Tech., Cambridge (USA). Dept. of Physics); Taormina, A. (Mons Univ. (Belgium). Faculte des Sciences)
1984-08-23
We study the stability at the one loop level, of finite temperature Kaluza-Klein theories coupled to matter fields. We restrict our attention to space-times containing compact manifolds which are toruses and Klein bottles. If the cosmological constant is chosen so that the effective potential vanishes at its minimum, and if twisted bosons or untwisted fermions are introduced into the theory, then these space-times are stable below a critical temperature of the order of the particle masses. We also discuss some subtleties that arise when Fermi fields are defined on non-simply connected manifolds.
On some corrections to beta spectra measured by toroidal inron-free beta spectrometer
International Nuclear Information System (INIS)
In the investigations of the features of neutron-deficient isotopes to study low-intensity branches of positron decay ST-2 the iron-free beta spectrometer with toroidal magnetic field (light intensity approximately 20%, resolution ability approximately 1%) is used. The influence of the factors distorting β-spectra in case of the ST-2 spectrometer has been studied. In using the sources without the carriers the source thickness at Esub(β) > 100 keV doesn't distort the spectrum. The investigation of the dependence of 22Na positron counting at different energies on theckness of the substrate made it possible to determine the paremeters of backscattering. It was shown that the backgroud of the spectrometer in positron measuring regime at energies Esub(β) > 100 keV didn't depend on the energy. The measurements at the energies higher than maximum positron energy give directly the background value. According to experimental distribution of the lines of conversion electrons the analytical kind of response function of the spectrometer has been obtained. Spectral distribution of monochromatic electrons consists of the peak, described by Gauss distribution, and exponential ''tail'' in the direction of small energies. The investigations showed that with the help of the ST-2 beta spectrometer the decay positron btanches with the intensity up to 0.01% per decay may be determined with the accuracy 2-3 keV. There is principal possibility to study form factors of β-spectra
Demountable Toroidal Field Magnets for Use in a Compact Modular Fusion Reactor
Mangiarotti, F. J.; Goh, J.; Takayasu, M.; Bromberg, L.; Minervini, J. V.; Whyte, D.
2014-05-01
A concept of demountable toroidal field magnets for a compact fusion reactor is discussed. The magnets generate a magnetic field of 9.2 T on axis, in a 3.3 m major radius tokamak. Subcooled YBCO conductors have a critical current density adequate to provide this large magnetic field, while operating at 20 K reduces thermodynamic cooling cost of the resistive electrical joints. Demountable magnets allow for vertical replacement and maintenance of internal components, potentially reducing cost and time of maintenance when compared to traditional sector maintenance. Preliminary measurements of contact resistance of a demountable YBCO electrical joint between are presented.
On particle transport in toroidal plasmas at low beta values
International Nuclear Information System (INIS)
The plasma-neutral gas balance is considered for the boundary layer of a magnetically confined plasma being near the density (Murakami) limit. It is found that, due to the high rate of charge separation by the guiding centre drifts in an inhomogeneous toroidal magnetic field, Pfirsch-Schlueter particle diffusion can prevail, even in presence of magnetic disturbances which perturb the magnetic surfaces and strongly enhance the electron heat conductivity. In the boundary layer the Nernst and Ware effects become negligible in a first approximation. The characteristic plasma pressure and density gradients in this layer are independent of the plasma diffusion rate, whereas the ratio between the average plasma density and the neutral density at a surrounding wall (limiter) depends on the same rate. The deduced plasma density and pressure gradients and the plasma-neutral density ratio are of the same order as those obtained from tokamak experients. Finally, the heat losses from plasma-neutral gas interaction can in some cases become comparable to the ohmic heating power, thereby affecting the energy containment time. (Author)
Observations of toroidal and poloidal rotation in the high beta tokamak Torus II
International Nuclear Information System (INIS)
The macroscopic rotation of plasma in a toroidal containment device is an important feature of the equilibrium. Toroidal and poloidal rotation in the high beta tokamak Torus II is measured experimentally by examining the Doppler shift of the 4685.75 A He II line emitted from the plasma. The toroidal flow at an average velocity of 1.6 x 106 cm/sec, a small fraction of the ion thermal speed, moves in the same direction as the toroidal plasma current. The poloidal flow follows the ion diamagnetic current direction, also at an average speed of 1.6 x 106 cm/sec. In view of certain ordering parameters, the toroidal flow is compared with predictions from neoclassical theory in the collosional, Pfirsch-Schluter regime. The poloidal motion, however results from an E x B drift in a positive radial electric field, approaching a stable ambipolar state. This radial electric field is determined from theory by using the measured poloidal velocity. Mechanisms for the time evolution of rotation are also examined. It appears that the circulation damping is governed by a global decay of the temperature and density gradients which, in turn, may be functions of radiative cooling, loss of equilibrium due to external field decay, or the emergence of a growing instability, occasionally observed in CO2 interferometry measurements
Summary of US-Japan Exchange 2004 New Directions and Physics for Compact Toroids
Energy Technology Data Exchange (ETDEWEB)
Intrator, T; Nagata, M; Hoffman, A; Guo, H; Steinhauer, L; Ryutov, D; Miller, R; Okada, S
2005-08-15
This exchange workshop was an open meeting coordinated by the P-24 Plasma Physics Group at Los Alamos National Laboratory. We brought together scientists from institutions in the US and Japan who are researching the various and complementary types of Compact Toroids (CT). Many concepts, including both experimental and theoretical investigations, are represented. The range spans Field Reversed Configuration (FRC), spheromak, Reversed Field Pinch (RFP), spherical tokamaks, linear devices dedicated to fundamental physics studies, and hybrid transitions that bridge multiple configurations. The participants represent facilities on which significant experiments are now underway: FRC Injection experiment (FIX), Translation Confinement experiment (TCS), Nihon-University Compact Torus Experiment (NUCTE), HITSI (Helicity Injection experiment, Steady Inductive Helicity Injection (HIT-SIHI)), Field Reversed Configuration experiment-Liner (FRX-L), TS-3/4, Sustained Spheromak Experiment (SSPX), Relaxation Scaling Experiment (RSX), HIST, Caltech Spheromak, or in the design process such as MRX-FRC (PPPL), Pulsed High Density experiment (PHD at UW). Several new directions and results in compact toroid (CT) research have recently emerged, including neutral-beam injection, rotating magnetic fields, flux build up from Ohmic boost coils, electrostatic helicity injection techniques, CT injection into other large devices, and high density configurations for applications to magnetized target fusion and translational compression of CT's. CT experimental programs in both the US and Japan have also shown substantial progress in the control and sustainment of CT's. Both in theory and experiment, there is increased emphasis on 3D dynamics, which is also related to astrophysical and space physics issues. 3D data visualization is now frequently used for experimental data display. There was much discussion of the effects of weak toroidal fields in FRC's and possible implications
CT-TRX1, a triggered-reconnection compact toroid experiment
International Nuclear Information System (INIS)
A new compact toroid experiment, CT-TRX1, based on the field reversed theta pinch is under construction. The unique feature of this experiment is the incorporation of several quasi-steady and pulsed magnets to carefully control the reconnection process. The motivation for this emphasis is to duplicate and extend the results reported by Kurtmullaev, et al., where delayed reconnection produced efficient axial shock heating and resulted in large diameter compact toroids which exhibited complete MHD stability for the 100 μsec decay time of their pulsed magnets. CT-TRX1 incorporates moderate E/sub theta/ radial shock heating, along with the triggered reconnection capability, to investigate the full range of conditions between the USSR experiments and the radial shock heated experiments at LASL, where m = 2 rotational instabilities occur. An additional feature of CT-TRX1 is the incorporation of a compound magnet which will provide long magnetic field decay times. The requirements for both high field quasi-steady outer magnets, and several high voltage, individually triggered pulsed inner magnets, present unique engineering design problems which are discussed
Global kink and ballooning modes in high-beta systems and stability of toroidal drift modes
International Nuclear Information System (INIS)
A numerical code (HBT) has been developed which solves for the equilibrium, global stability and high-n stability of plasmas with arbitrary cross-section. Various plasmas are analysed for their stability to these modes in the high-beta limit. Screw-pinch equilibria are stable to high-n ballooning modes up to betas of 18%. The eigenmode equation for drift waves is analysed numerically. The toroidal branch is shown to be destabilized by the non-adiabatic response of trapped and circulating particles. (author)
Divertor detachment, He exhaust and compact toroid injection on TdeV
International Nuclear Information System (INIS)
Progressive detachment with increasing density is shown to proceed with a marked reduction of the ion flux to the divertor plates, a pressure gradient between a ionization front and the plate, and strong cross-field transport in the divertor. The divertor He exhaust is not affected by detachment although the He enrichment remains low but constant. A moderate density of n-bare ∼ 5 x 1019 m-3 seems to be sufficient both for efficient peak power load reduction at the plate and good He exhaust through the divertor. Simulations indicate possible divertor geometry improvements which will soon be verified experimentally in the new TdeV-96 divertor upgrade. Finally, central fuelling with compact toroid injection is reported with no detrimental effects on the plasma. (author). 16 refs, 8 figs
Elastic-plastic analysis of the toroidal field coil inner leg of the compact ignition tokamak
International Nuclear Information System (INIS)
Elastic-plastic analyses were made for the inner leg of the Compact Ignition Tokamak toroidal field (TF) coil, which is made of copper-Inconel composite material. From the result of the elastic-plastic analysis, the effective Young's moduli of the inner leg were determined by the analytical equations. These Young's moduli are useful for the three-dimensional, elastic, overall TF coil analysis. Comparison among the results of the baseline design (R = 1.324 m), the bucked pressless design, the 1.527-m major radius design, and the 1.6-m major radius design was also made, based on the elastic-plastic TF coil inner leg analyses
International Nuclear Information System (INIS)
The use of deuterium-tritium fuel in the Compact Ignition Tokamak will require applying remote handling technology for ex-vessel maintenance and replacement of machine components. Highly activated and contaminated components of the fusion devices auxiliary systems, such as diagnostics and RF heating, must be replaced using remotely operated maintenance equipment in the test cell. In-vessel remote maintenance included replacement of divertor and first wall hardware, faraday shields, and for an in-vessel inspection system. Provision for remote replacement of a vacuum vessel sector, toroidal field coil or poloidal field ring coil was not included in the project baseline. As a result of recent coil failures experienced at a number of facilities, the CIT project decided to reconsider the question of remote recovery from a coil failure and, in January of 1990, initiated a coil replacement study. This study focused on the technical requirements and impact on fusion machine design associated with remote recovery from any coil failure
Development of Multi-pulse Compact Toroid Injector System for C-2U
Allfrey, I.; Garate, E.; Morehouse, M.; Roche, T.; Gota, H.; Valentine, T.; Waggoner, W.; Putvinski, S.; Cordero, M.; Asai, T.; Matsumoto, T.; Sekiguchi, J.; the TAE Team
2015-11-01
The C-2U experiment aims at sustaining a dynamically formed field reversed configuration (FRC) for 5 + ms via injection of 10 +MW of neutral beams. One of the systems currently used to refuel the C-2U plasma is a single pulse compact toroid injector (CTI). The CTI is a magnetized co-axial plasma gun, which generates a spheromak-like plasma that is injected into the core of the advanced beam-driven FRC of C-2U. In order to refuel the recent long-lived plasmas in C-2U, a multi-pulse CTI system, whose modular design allows for expandable burst numbers, is being designed. Details of the pulsed power systems used to energize the single pulse and the upgraded multi-pulse CTI will be discussed. Results of injector performance carried out on a dedicated test stand as well as some refueling data on C-2U will also be presented.
Two and three dimensional imaging of compact toroid plasmas using fast photography
International Nuclear Information System (INIS)
As is discussed in a companion paper, Degnan el al, fast photography is used as a visual diagnostic tool for high energy plasma research at the Phillips Laboratory. Both, two dimensional and three dimensional images, are gathered by using nanosecond and microsecond range fast photography techniques. A set of microchannel plate cameras and a fast framing camera are used to record images of a compact toroid plasma during formation and acceleration stages. These images are subsequently digitized and enhanced to bring out detailed information of interest. This spatial information is combined with other diagnostic results as well as theoretical models in order to build a more complete picture of the fundamental physics associated with high-energy plasmas
High-beta equilibria in tokamaks with pressure anisotropy and toroidal flow
Layden, B.; Hole, M. J.; Ridden-Harper, R.
2015-12-01
We extend previous analytical calculations of 2D high-β equilibria in order-unity aspect ratio tokamaks with toroidal flow to include pressure anisotropy, assuming guiding-center theory for a bi-Maxwellian plasma and the ideal MHD Ohm's law. Equilibrium solutions are obtained in the core region (which fills most of the plasma volume) and the boundary layer. We find that pressure anisotropy with p∥>p⊥ ( p∥Ωmin ) were previously found to suppress the field-free region (diamagnetic hole) that exists in static isotropic high-β equilibria. We find that all equilibrium solutions with pressure anisotropy suppress the diamagnetic hole. For the static case with a volume-averaged toroidal beta of 70%, plasmas with max (p∥/p⊥)>α1=1.07 have equilibrium solutions. We find that α1 decreases with increasing toroidal flow speed, and above the flow threshold Ωmin we find α1=1 , so that all p∥>p⊥ plasmas have equilibrium solutions. On the other hand, for p∥p⊥ , while the converse is true for p∥
Approximate model for toroidal force balance in the high-beta stellarator
International Nuclear Information System (INIS)
A simple model for estimating the body force acting on a diffuse plasma confined in a three-dimensional, high-beta stellarator geometry is given. The equilibrium is treated by an asymptotic expansion about a straight theta pinch with diffuse, circular cross section. The expansion parameter delta is the strength of the applied helical fields. This expansion leads to an inconsistent set of equations for the equilibrium in second order. Nevertheless, by averaging the equilibrium equations over the volume of the confined plasma, a unique condition for toroidal equilibrium is obtained. When the results are compared with the predictions of previous equilibrium theory, which is based on the sharp-boundary model, a large deviation is found. This correction is especially large for l = 0,1 systems at high beta and must be accounted for in any confinement experiment
Active Stability Control of a High-Beta Self-Organized Compact Torus
International Nuclear Information System (INIS)
Full text: A magnetized coaxial plasma gun (MCPG) has been proposed as an effective device for control of a high-beta self-organized compact torus of field-reversed configuration (FRC). The initial results demonstrate that the application of an MCPG suppresses the most prominent FRC instability of the centrifugally-driven interchange mode with toroidal mode number n = 2. This observation was made on the Nihon University Compact Torus Experiment (NUCTE), a flexible theta-pinch-based FRC facility. In the series of experiments, a MCPG generates a spheromak-like plasmoid which can then travel axially to merge with a pre-existing FRC. Since the MCPG is mounted on-axis and generates a significant helicity, it provides the FRC-relevant version of coaxial helicity injection (CHI) that has been applied in both spheromaks and spherical tokamaks. When CHI is applied, the onset of elliptical deformation of FRC cross-section is delayed until 45 - 50 μs from FRC formation compared to the onset time of 25 μs in the case without CHI. Besides delaying instability, MCPG application reduces the toroidal rotation frequency from 67 kHz to 41 kHz. Moreover, the flux decay time is extended from 57 to 67 μs. These changes have been made despite the quite modest flux content of the plasmoid: ∼0.05 mWb of poloidal and 0.01 mWb of toroidal flux, compared with the 0.4 mWb of poloidal flux in the pre-formed FRC. The observed global stabilization and confinement improvements suggest that the MCPG can actively control the rotational instability. This global instability can also be suppressed by externally applied static multipole fields. However, it has been known that nonaxisymmetric multipole fields have adverse effects on confinement. This indicates an advantage of MCPG in that it shows both improved confinement and stability. The conventional technique does not slow the toroidal rotation down. Therefore, MCPG introduces a different stabilization mechanism that may be the same as that
Magnetized plasma flow injection into tokamak and high-beta compact torus plasmas
Matsunaga, Hiroyuki; Komoriya, Yuuki; Tazawa, Hiroyasu; Asai, Tomohiko; Takahashi, Tsutomu; Steinhauer, Loren; Itagaki, Hirotomo; Onchi, Takumi; Hirose, Akira
2010-11-01
As an application of a magnetized coaxial plasma gun (MCPG), magnetic helicity injection via injection of a highly elongated compact torus (magnetized plasma flow: MPF) has been conducted on both tokamak and field-reversed configuration (FRC) plasmas. The injected plasmoid has significant amounts of helicity and particle contents and has been proposed as a fueling and a current drive method for various torus systems. In the FRC, MPF is expected to generate partially spherical tokamak like FRC equilibrium by injecting a significant amount of magnetic helicity. As a circumstantial evidence of the modified equilibrium, suppressed rotational instability with toroidal mode number n = 2. MPF injection experiments have also been applied to the STOR-M tokamak as a start-up and current drive method. Differences in the responses of targets especially relation with beta value and the self-organization feature will be studied.
Traverso, P. J.; Maurer, D. A.; Ennis, D. A.; Hartwell, G. J.; Goforth, M. M.; Loch, S. D.; Pearce, A. J.; Cianciosa, M. R.
2014-10-01
A Thomson scattering system using standard commercially available components has been designed for the non-axisymmetric plasmas of the Compact Toroidal Hybrid (CTH). The initial system takes a single point measurement and will be used to assess options for an upgrade to a multi-point system providing electron temperature and density profiles. This single point measurement will reduce the uncertainty in the reconstructed peak pressure by an order of magnitude for both ohmically driven, current-carrying plasmas and future gyrotron-heated stellarator plasmas. A principle design goal is to minimize stray laser light, geometrically on the machine side and spectrally on the collection side, to allow measurements of both full and half Thomson scattered spectral profiles. The beam, generated by a frequency doubled Continuum 2 J Nd:YaG laser, is passed vertically through an entrance Brewster window and an aperturing baffle system to minimize stray light. Light collection, spectral processing, and signal detection are accomplished with an f / # ~ 1 aspheric lens, a Holospec f/1.8 spectrometer, and an Andor iStar DH740-18U-C3 image intensified camera. The estimated number of scattered photons per channel will be of the order of 5 ×103 with a signal to noise ratio of S / N = 19 This work is supported by U.S. Department of Energy Grant No. DE-FG02-00ER54610.
First Results from a Coherence Imaging Diagnostic for the Compact Toroidal Hybrid
Ennis, D. A.; Hartwell, G. J.; Johnson, C. A.; Maurer, D. A.; Allen, S. L.
2015-11-01
An optical coherence imaging diagnostic is being commissioned for time-resolved measurements (~ 10 ms) of ion emissivity, velocity, and temperature in the Compact Toroidal Hybrid (CTH) experiment. The Coherence Imaging (CI) technique measures the spectral coherence of an emission line with an imaging interferometer of fixed delay. CI has a number of advantages when compared to dispersive Doppler spectroscopy, including higher throughput and the capability to provide 2D spectral images, making it advantageous for investigating the non-axisymmetric geometry of CTH plasmas. A spectral survey of the visible and ultraviolet emission for a range of CTH discharges has identified helium and carbon impurity lines that will be utilized for CI measurements in CTH. First CI measurements of He II (468.6 nm) emission from CTH plasmas will be presented along with interferograms from a calibration light source and details of the instrument design. Results from this diagnostic will aid in characterizing the equilibrium ion parameters in both the edge and core of CTH plasmas for planned island divertor and MHD mode-locking experiments. Work supported by USDoE grant DE-FG02-00ER54610.
International Nuclear Information System (INIS)
Initial results are reported on the formation of compact toroidal plasmas in an oblate shaped metallic flux conserver. A schematic of the experimental apparatus is shown. The plasma injector is a coaxial plasma gun with solenoid coils wound on the inner and outer electrodes. The electrode length is 100 cm, the diameter of the inner (outer) electrode is 19.3 cm (32.4 cm). Deuterium gas is puffed into the region between electrodes by eight pulsed valves located on the outer electrode 50 cm from the end of the gun. The gun injects into a cylindrically symmetrical copper shell (wall thickness = 1.6 mm) which acts as a flux conserver for the time scale of experiments reported here. The copper shell consists of a transition cylinder 30 cm long, 34 cm in diameter, a cylindrical oblate pill box 40 cm long, 75 cm in diameter and a downstream cylinder 30 cm long, 30 cm in diameter. The gap between the gun and transition cylinder is 6 cm. An axial array of coils outside the vacuum chamber can be used to establish an initial uniform bias field
Design and performance of FRX-C/T: A compact toroid translation experiment
International Nuclear Information System (INIS)
The FRX-C/T experiment is a combination of the FRX-C Θ-pinch, which forms field-reversed configuration (FRC) compact toroids, with a dc solenoid section, where the FRC (typical plasma parameters of n = 1-3 x 10/sup 15/ cm/sup -3/, T/sub e/+T/sub i/ = 0.2-0.7 keV, tau/sub E/ ≅ 100 μs) is translated and trapped in an axial dc guide field B/sub o/. The experiment combines pulsed, high-voltage technology for the Θ-pinch formation region with a dc energized magnet set for the translation section. Five stainless steel tank modules form the translation vacuum chamber. A B/sub o/ field of ≤ 8kG is generated by the thirty-nine water-cooled pancake magnets of the dc magnet set that is mounted concentric with the vacuum vessel. A dc magnetic mirror (ratio ≤ 5) is at the end of the translation region. The dc magnets are powered by a computer controlled and monitored 0.3 kV, 2.5 MW dc power supply. A computer monitored 78 channel digital thermal switch system and 128 channel analog thermistor system ensure that the coils do not overheat
Thomson scattering diagnostic system design for the Compact Toroidal Hybrid experiment.
Traverso, P J; Maurer, D A; Ennis, D A; Hartwell, G J; Goforth, M M; Loch, S D; Pearce, A J; Cianciosa, M R
2014-11-01
A new Thomson scattering system using standard commercially available components has been designed for the non-axisymmetric plasmas of the Compact Toroidal Hybrid (CTH). The beam, generated by a frequency doubled Continuum PL DLS 2 J Nd:YAG laser, is passed vertically through an entrance Brewster window and an aperturing baffle system to minimize the stray laser light that could enter the collection optics. The beam line has been designed with an 8 m propagation distance to the mid-plane of the CTH device with the beam diameter kept less than 3 mm inside the plasma volume. The beam exits the vacuum system through another Brewster window and enters a beam dump, again to minimize the stray light in the vacuum chamber. Light collection, spectral processing, and signal detection are accomplished with an f/#∼ 1 aspheric lens, a commercially available Holospec f/1.8 spectrometer, and an Andor iStar DH740-18U-C3 image intensified camera. Spectral rejection of stray laser light, if needed, can be performed with the use of an optional interference filter at the spectrometer input. The system has been developed for initial single point measurements of plasmas with core electron temperatures of approximately 20-300 eV and densities of 5 × 10(18) to 5 × 10(19) m(-3) dependent upon operational scenario. PMID:25430265
Knowlton, S. F.; Hartwell, G. J.; Maurer, D. A.; Marushchenko, N. B.; Turkin, Y.; Bigelow, T.
2015-11-01
Plasmas in the Compact Toroidal Hybrid (CTH), a five field period, l = 2 torsatron (B0 = 0 . 5 T R0 = 0 . 75 m, ap ~ 0 . 2 m) will be heated by second harmonic X-mode electron cyclotron heating with power provided by a 28 GHz gyrotron capable of producing up to 200 kW. Ray-tracing calculations that will guide the selection of the launching position, antenna focal length, and beam-steering characteristics are performed with the TRAVIS code. Non-axisymmetric vacuum and current-carrying CTH equilibria for the ray tracing are modeled with the V3FIT code. The calculated absorption is highest for vertically propagating rays that traverse the region where a saddle of resonant field strength exists. However, the absorption for top-launched waves is more sensitive to variations in the magnetic equilibria than for a radial side launch where the magnetic field profile is tokamak-like. This work is supported by U.S. Department of Energy Grant No. DE-FG02-00ER54610.
International Nuclear Information System (INIS)
The purpose of the Workshop was to identify the most important physics issues that need to be addressed in the near term in order to assure the optimal design and timely interpretation of Compact Toroid (CT) experiments. The Panel was also asked to assess the levels of effort required to obtain priority information on appropriate time scales compatible with DOE plans to design a CT proof-of-principle experiment. The fiscal year cost anticipated for the effort recommended by the Workshop Panel (excluding costs for computing) is estimated to be approximately $5.7M. CT theory is currently funded at a level of approximately $2.0M per year
International Nuclear Information System (INIS)
The Seventh Symposium on Compact Toroid (CT) Research was held in Santa Fe, New Mexico, on May 21-23, 1985. As has been the case for the last few CT symposia, CT research progress was reported in a combination of invited talks and poster sessions. The following record of these presentations in the form of four page papers is in keeping with the format followed in previous years. We have continued the practice of dividing the papers into three subject categories - spheromak, FRC (Field Reversed Configuration), and other (mostly particle rings)
Energy Technology Data Exchange (ETDEWEB)
Sherwood, A.R. (comp.)
1986-09-01
The Seventh Symposium on Compact Toroid (CT) Research was held in Santa Fe, New Mexico, on May 21-23, 1985. As has been the case for the last few CT symposia, CT research progress was reported in a combination of invited talks and poster sessions. The following record of these presentations in the form of four page papers is in keeping with the format followed in previous years. We have continued the practice of dividing the papers into three subject categories - spheromak, FRC (Field Reversed Configuration), and other (mostly particle rings).
Increase in compact toroid mass by accelerator-region ionization of high-Z noble gas on CTIX
Horton, Robert D.; Hwang, David Q.; Liu, Fei; Hong, Sean; Klauser, Ruth; Evans, Russell W.; Buchenauer, Dean A.
2012-10-01
A promising technique for runaway electron (RE) mitigation in large-tokamak disruptions is the injection of compact toroid (CT) plasmas of high atomic number. With sufficient kinetic energy density, high-Z CTs can reach the tokamak magnetic axis where RE effects are strongest. At CT velocities of 100 km/s or more, penetration to the axis occurs on a sub-millisecond time scale. In addition to reducing avalanche RE production by collisions, high-Z CTs can cool RE by bremsstrahung effects. From theoretical calculations, using Xe ions, bremsstrahlung cooling exceeds the effect of collisions at RE energy above about 10 MeV, a value expected to be well exceeded in large tokamaks. Past experiments on the CTIX compact-toroid injector have demonstrated increased CT mass using snowplow accretion of puffed noble gas by an initial hydrogenic CT. These experiments will be continued using a higher ratio of accreted high-Z plasma to H plasma, to maximize CT kinetic energy density. Results will be compared with a 1D model using external circuit effects, coaxial railgun kinetics, and ionization. The model will be used to predict performance of CT injectors of greater energy, suitable for RE suppression on mid-sized tokamaks.
International Nuclear Information System (INIS)
The Fusion Engineering Design Center (FEDC) is part of a national design team that is developing the conceptual design of the Compact Ignition Tokamak (CIT). To achieve a compact device with the minimum major radius, a vertical preload system is being developed to react the vertical separating force normally carried by the inboard leg of the toroidal field (TF) coils. The preload system is in the form of a hydraulic press. Challenges in the design include the development of hydraulic and structural systems for very large force requirements, which could interface with the CIT machine, while allowing maximum access to the top, bottom, and radial periphery of the machine. Maximum access is necessary for maintenance, diagnostics, instrumentation, and control systems. Materials used in the design must function in the nuclear environment and in the presence of high magnetic fields. The structural system developed is an arrangement in which the CIT device is installed in the jaws of the press. Large built-up beams above and below the CIT span the machine and deliver the vertical force to the center cylinder formed by the inboard legs of the TF coils. During the conceptual design study, the vertical force requirement has ranged between 25,000 and 52,000 t. The access requirement on top and bottom limits the width of the spanning beams. Nonmagnetic steel materials are also required because of operation in the high magnetic fields. In the hydraulic system design for the press, several options are being explored. These range from small-diameter jacks operating at very high pressure [228 MPa (33 ksi)] to large-diameter jacks operating at pressures up to 69 MPa (10 ksi). Configurations with various locations for the hydraulic cylinders have also been explored. The nuclear environment and maintenance requirements are factors that affect cylinder location. This paper presents the configuration development of the hydraulic press used to vertically preload the CIT device
Matsumoto, T; Sekiguchi, J; Asai, T; Gota, H; Garate, E; Allfrey, I; Valentine, T; Morehouse, M; Roche, T; Kinley, J; Aefsky, S; Cordero, M; Waggoner, W; Binderbauer, M; Tajima, T
2016-05-01
A compact toroid (CT) injector was developed for the C-2 device, primarily for refueling of field-reversed configurations. The CTs are formed by a magnetized coaxial plasma gun (MCPG), which consists of coaxial cylindrical electrodes and a bias coil for creating a magnetic field. First, a plasma ring is generated by a discharge between the electrodes and is accelerated by Lorenz self-force. Then, the plasma ring is captured by an interlinkage flux (poloidal flux). Finally, the fully formed CT is ejected from the MCPG. The MCPG described herein has two gas injection ports that are arranged tangentially on the outer electrode. A tungsten-coated inner electrode has a head which can be replaced with a longer one to extend the length of the acceleration region for the CT. The developed MCPG has achieved supersonic CT velocities of ∼100 km/s. Plasma parameters for electron density, electron temperature, and the number of particles are ∼5 × 10(21) m(-3), ∼40 eV, and 0.5-1.0 × 10(19), respectively. PMID:27250428
On the development of a compact toroid injector at the University of Illinois at Urbana-Champaign
Christenson, Michael; Jung, Soonwook; Stemmley, Steven; Sang, Xia; Kalathiparambil, Kishor; Ruzic, David
2015-11-01
The ThermoElectric-driven Liquid-metal plasma-facing Structures (TELS) device is a gas-puff driven, theta pinched, transient plasma source used to simulate extreme events incident on materials in the edge and divertor regions of a tokamak plasma. Previous work has shown that in its current form, TELS can bombard a target with a peak energy of 0.08 MJ m-2 over a 0.15 ms pulse, leading to a total heat flux of 0.5 GW m-2. While these values are sufficient to mimic Type 1 ELMs in smaller devices, the plasma energy of TELS must be improved by a factor of greater than two to adequately simulate larger-scale Type 1 ELMs. It is for this reason that modifications to the existing TELS device have been proposed in the form of developing a compact toroid (CT) injector since the new self-contained structure allows for higher densities and energies delivered onto a target. The new setup will use a bias field, generating a peak magnetic field greater than 0.1 T and a peak magnetic flux greater than 2 mWb, surrounding the existing plasma gun arrangement to create the CT and the existing theta pinch to compress and translate the plasmoid. Preliminary results and analyses are presented and discussed in relationship to interactions with both solid and liquid metal targets. Supported by DOE Grant DE-SC0008587.
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TRX-1 is a new 20 cm diameter, 1-m long field reversed theta pinch with a magnetic field swing of 10 kG in 3 μsec. It employs z discharge preionization and octopole barrier fields to maximize flux trapping on first half cycle operation. Cusp coils are used at the theta pinch ends to delay reconnection and fast mirror coils are used to trigger reconnection at a time designed to maximize axial heating efficiency and toroid lifetime. These controls are designed to study toroid formation methods which are claimed to be especially efficient by Russian experimenters. Studies have been conducted on flux trapping efficiency, triggered reconnection, and equilibrium and lifetime
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This report discusses the following topics: Nonaxisymmetric radio- frequency heating in an l = 1 stellarator and in a linear plasma column; measurement of induced current in a hardcore theta pinch; externally driven tilt mode study on an FRC; elimination of induced plasma current in a hardcore theta pinch; and simulated toroidicity studies
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This paper presents direct experimental observations of potential profiles of a toroidal helical plasma in the Compact Helical System, using a 200 keV heavy ion beam probe. Electron cyclotron heated plasmas show a positive potential profile in a low density regime (n-bare = 3x1012 cm-3), while neutral beam injection heated plasmas (n-bare = 8x1012 cm-3) exhibit a negative potential profile. A loss cone structure evaluated from the observed potential is discussed to understand the behavior of high energy particle in a toroidal helical plasma. (author)
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This paper discusses induced axial current studies in a hardcore Theta-Pinch; nonaxisymmetric RF heating of a high-Beta plasma column; formation of Axisymmetric hardcore theta pinches with notched hardcore current; and externally driven till made experiments on the high-beta Q machine field reversed configuration
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The US-Japan Workshop on Field-Reversed Configurations with Steady-State High-Temperature Fusion Plasma and the 11th US-Japan Workshop on Compact Toroids were held at Los Alamos National Laboratory, Los Alamos, New Mexico on November 7--9, 1989. These proceedings contain the papers presented at the workshops as submitted by the authors. These papers have been indexed separately
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Design criteria for the Compact Ignition Tokamak, Toroidal-Field (TF) Coil, Turn-to-Turn Insulation System require an insulation sheet and bonding system that will survive cryogenic cycling in a radiation environment and maintain structural integrity during exposure to the significant compressive and shear loads associated with each operating cycle. For thermosetting resin systems, a complex interactive dependency exists between optimum peak value, in-service property performance capabilities of candidate generic materials; key handling and processing parameters required to achieve their optimum in-service property performance as an insulation system; and suitability of their handling and processing parameters as a function of design configuration and assembly methodology. This dependency is assessed in a weighted study matrix in which two principal programmatic approaches for the development of the TF Coil Subassembly Insulation System have been identified. From this matrix study, two viable approaches to the fabrication of the insulation sheet were identified: use of a press-formed sheet bonded in place with epoxy for mechanical bonding and tolerance take-up and formation of the insulation sheet by placement of dry cloth and subsequent vacuum pressure impregnation. Laboratory testing was conducted to screen a number of combinations of resins and hardeners on a generic basis. These combinations were chosen for their performance in similar applications. Specimens were tested to screen viscosity, thermal-shock tolerance, and cryogenic tolerance. Cryogenic shock and cryogenic temperature proved to be extremely lethal to many combinations of resin, hardener, and cure. Two combinations survived: a heavily flexibilized bisphenol A resin with a flexibilized amine hardener and a bisphenol A resin with cycloaliphatic amine hardener. 7 refs., 12 figs., 6 tabs
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Gorelenkov, N.N. [Princeton Plasma Physics Laboratory, Princeton University (United States)], E-mail: ngorelen@pppl.gov; Berk, H.L. [IFS, Austin, Texas (United States); Fredrickson, E. [Princeton Plasma Physics Laboratory, Princeton University (United States); Sharapov, S.E. [Euroatom/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire (United States)
2007-10-08
New global MHD eigenmode solutions arising in gaps in the low frequency Alfven-acoustic continuum below the geodesic acoustic mode (GAM) frequency have been found numerically and have been used to explain relatively low frequency experimental signals seen in NSTX and JET tokamaks. These global eigenmodes, referred to here as Beta-induced Alfven-Acoustic Eigenmodes (BAAE), exist in the low magnetic safety factor region near the extrema of the Alfven-acoustic continuum. In accordance to the linear dispersion relations, the frequency of these modes shifts as the safety factor, q, decreases. We show that BAAEs can be responsible for observations in JET plasmas at relatively low beta <2% as well as in NSTX plasmas at relatively high-beta >20%. In contrast to the mostly electrostatic character of GAMs the new global modes also contain an electromagnetic (magnetic field line bending) component due to the Alfven coupling, leading to wave phase velocities along the field line that are large compared to the sonic speed. Qualitative agreement between theoretical predictions and observations are found.
Energy Technology Data Exchange (ETDEWEB)
Gorelenkov, N. N.; Berk, H. L.; Fredrickson, E.; Sharapov, S. E.
2007-07-02
New global MHD eigenmode solutions arising in gaps in the low frequency Alfvén -acoustic continuum below the geodesic acoustic mode (GAM) frequency have been found numerically and have been used to explain relatively low frequency experimental signals seen in NSTX and JET tokamaks. These global eigenmodes, referred to here as Beta-induced Alfvén-Acoustic Eigenmodes (BAAE), exist in the low magnetic safety factor region near the extrema of the Alfvén-acoustic continuum. In accordance to the linear dispersion relations, the frequency of these modes shifts as the safety factor, q, decreases. We show that BAAEs can be responsible for observations in JET plasmas at relatively low beta < 2% as well as in NSTX plasmas at relatively high beta > 20%. In contrast to the mostly electrostatic character of GAMs the new global modes also contain an electromagnetic (magnetic field line bending) component due to the Alfvén coupling, leading to wave phase velocities along the field line that are large compared to the sonic speed. Qualitative agreement between theoretical predictions and observations are found.
Comparison of the physics performance of D-He3 fusion in high- and low-beta toroidal devices
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This paper reports on the use of D-He3 in future fusion reactors which is one of the most promising alternative to D-T fueled fusion devices. One of the difficulties with these alternatives is related to the higher requirements for confinement quality. As examples for possible high (>0.7) and low (3, there are enormous uncertainties due to the small physics data base. On the other hand, the lower beta of the Tokamak makes it less well suited to D-He3 operation but its advanced stage of development is a clear advantage. Three variations of the Tokamak concept, for D-T and D-He3, are under investigation in the US Advanced Reactor Innovation and Evaluation Study ARIES; the High Field Tokamak (HFT), the second stability version (SST) and the Spherical Torus (ST)
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Potential control and flow generation have been studied on the Proto-RT device that is equipped with an internal ring coil producing a stationary magnetic field. Biasing the surface of the internal coil, the radial electric field is controlled. Supersonic flow has been generated when the plasma is negatively biased. The present experiment is limited in a low-density (∼ 1014 m-3) regime, and hence, only electrostatic effects dominate the structure and stability. Higher density plasma will be produced in a new device Mini-RT that has a super-conducting levitated internal ring. When the flow velocity becomes comparable to the Alfven speed, the hydrodynamic pressure can produce a new type of high-beta (diamagnetic) equilibrium, so-called 'double Beltrami (DB) state'. Recent theory predicts 'self-organization' of a DB state that may have Lyapunov stability. This regime is the target of the new device Mini-RT that is equipped with a super-conducting levitated internal coil system. (author)
Fernandez-Nieves, Alberto
We will discuss how nematic liquid crystals organize inside toroidal droplets. When the director is parallel to the bounding surface, we find spontaneous reflection symmetry breaking, which we attribute to the role played by saddle-splay contributions to the Frank free energy. When the director is perpendicular to the bounding surface, we find that the structure is reminiscent of the escape radial configuration seen in cylinders, but with a central doubly-twisted organization, which we attribute to the geometry of the torus. We will end by presenting recent experiments with active nematics on the toroidal surface. In this case, topology and activity both affect the structure and dynamics of the material.
Advances in compact torus research
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A compact torus is a low aspect ratio, axisymmetric, closed magnetic field line configuration with no vessel wall or magnetic field coils linking the hole in the plasma toroid. This concept offers reactor advantages such as simplicity, high β, and the possibility of translation. Several methods have been used to generate compact toroids, including plasma guns, high energy particle rings, and field-reversed theta pinches. This document summarizes the results of recent work on compact toroids, presented at the first IAEA Technical Committee Meeting on Compact Torus Research held in Sydney, Australia from 4 to 7 March 1985
The upgraded Pegasus Toroidal Experiment
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The Pegasus Toroidal Experiment was developed to explore the physics limits of plasma operation as the aspect ratio (A) approaches unity. Initial experiments on the device found that access to high normalized current and toroidal beta was limited by the presence of large-scale tearing modes. Major upgrades have been conducted of the facility to provide the control tools necessary to mitigate these resistive modes. The upgrades include new programmable power supplies, new poloidal field coils and increased, time-variable toroidal field. First ohmic operations with the upgraded system demonstrated position and current ramp-rate control, as well as improvement in ohmic flux consumption from 2.9 MA Wb-1 to 4.2 MA Wb-1. The upgraded experiment will be used to address three areas of physics interest. First, the kink and ballooning stability boundaries at low A and high normalized current will be investigated. Second, clean, high-current plasma sources will be studied as a helicity injection tool. Experiments with two such sources have produced toroidal currents three times greater than predicted by geometric field line following. Finally, the use of electron Bernstein waves to heat and drive current locally will be studied at the 1 MW level; initial modelling indicates that these experiments are feasible at a frequency of 2.45 GHz
Raybould, T. A.; Fedotov, V. A.; Papasimakis, N.; Kuprov, I.; Youngs, I. J.; Chen, W. T.; Tsai, D. P.; Zheludev, N. I.
2016-07-01
We demonstrate that the induced toroidal dipole, represented by currents flowing on the surface of a torus, makes a distinct and indispensable contribution to circular dichroism. We show that toroidal circular dichroism supplements the well-known mechanism involving electric dipole and magnetic dipole transitions. We illustrate this with rigorous analysis of the experimentally measured polarization-sensitive transmission spectra of an artificial metamaterial, constructed from elements of toroidal symmetry. We argue that toroidal circular dichroism will be found in large biomolecules with elements of toroidal symmetry and should be taken into account in the interpretation of circular dichroism spectra of organics.
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Results are given for work during this period on each of the following areas: (1) spheromak production using conical theta pinch guns; (2) detection of CT fluctuation spectra via CO2 forward scattering; (3) high density field reversal experiment; (4) plasma compression experiment; (5) material end plugging experiment; and (6) design of computerized data acquisition systems
Next generation toroidal devices
International Nuclear Information System (INIS)
A general survey of the possible approach for the next generation toroidal devices was made. Either surprisingly or obviously (depending on one's view), the technical constraints along with the scientific considerations lead to a fairly limited set of systems for the most favorable approach for the next generation devices. Specifically if the magnetic field strength of 5 T or above is to be created by superconducting coils, it imposes minimum in the aspect ratio for the tokamak which is slightly higher than contemplated now for ITER design. The similar technical constraints make the minimum linear size of a stellarator large. Scientifically, it is indicated that a tokamak of 1.5 times in the linear dimension should be able to produce economically, especially if a hybrid reactor is allowed. For the next stellarator, it is strongly suggested that some kind of helical axis is necessary both for the (almost) absolute confinement of high energy particles and high stability and equilibrium beta limits. The author still favors a heliac most. Although it may not have been clearly stated in the main text, the stability afforded by the shearless layer may be exploited fully in a stellarator. (author)
Induced toroid structures and toroid polarizabilities
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The frequency-dependent toroid dipole polarizability γ(ω) of a (nonrelativistic, spinless) hydrogen-like atom in its ground state is calculated analytically in terms of two Gauss hypergeometric functions. The static result reads simply γ(ω=0)=(23/60)α2Z-4a05 (α - fine structure constant, Z - nucleus charge number, a0 - Bohr radius). Comparing the present evaluations for H-like atoms with previous ones for pions, one sees that the role of the induced toroid moments (as against that of the usual electric ones) increases considerably when passing from atomic to particle physics
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The possibility of using, for the ALICE forward muon spectrometer, a superconducting toroidal magnet has been considered in place of the SC dipole. The study has been restricted to the acceptance calculations and to the tracking simulations of the toroidal magnet but without technical investigations. The estimated performances are found maladjusted to the physics requirements of the heavy ion runs. (author)
Hedberg V
On the 15th of June 2001 the EB approved a new conceptual design for the toroid shield. In the old design, shown in the left part of the figure above, the moderator part of the shielding (JTV) was situated both in the warm and cold areas of the forward toroid. It consisted both of rings of polyethylene and hundreds of blocks of polyethylene (or an epoxy resin) inside the toroid vacuum vessel. In the new design, shown to the right in the figure above, only the rings remain inside the toroid. To compensate for the loss of moderator in the toroid, the copper plug (JTT) has been reduced in radius so that a layer of borated polyethylene can be placed around it (see figure below). The new design gives significant cost-savings and is easier to produce in the tight time schedule of the forward toroid. Since the amount of copper is reduced the weight that has to be carried by the toroid is also reduced. Outgassing into the toroid vacuum was a potential problem in the old design and this is now avoided. The main ...
2002-01-01
Because of its exceptional size, it was not feasible to assemble and test the Barrel Toroid - made of eight coils - as an integrated toroid on the surface, prior to its final installation underground in LHC interaction point 1. It was therefore decided to test these eight coils individually in a dedicated test facility.
Quasisymmetric toroidal plasmas with large mean flows
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Geometric condition for quasisymmetric toroidal plasmas with large mean flows on the order of the ion thermal speed are investigated. Equilibrium momentum balance equations including the inertia term due to the large flow velocity are used to show that, for rotating quasisymmetic plasmas with no local currents crossing flux surfaces, all components of the metric tensor should be independent of the toroidal angle in the Boozer coordinates, and consequently these systems need to be rigorously axisymmetric. Unless the local radial currents vanish, the Boozer coordinates do not exist and the toroidal flow velocity cannot take any value other than a very limited class of eigenvalues corresponding to very rapid rotation especially for low beta plasmas. (author)
Invisibility cloaks for toroids.
You, Yu; Kattawar, George W; Yang, Ping
2009-04-13
The material properties of toroidal invisibility cloaks are derived based on the coordinate transformation method. The permittivity and permeability tensors for toroidal cloaks are substantially different from those for spherical cloaks, but quite similar to those for 2D cylindrical cloaks because a singularity is involved at the inner boundary in both the cases. The cloaking effect is confirmed by the electric field distribution in the vicinity of toroidal cloaks simulated from the generalized discrete-dipole approximation (DDA) method. This study extends the concept of electromagnetic cloaking of arbitrarily-shaped objects to a complex geometry. PMID:19365485
NCSX Toroidal Field Coil Design
Energy Technology Data Exchange (ETDEWEB)
Kalish, M.; Rushinski, J.; Myatt, L.; Brooks, A.; Dahlgren, F.; Chrzanowski, J.; Reiersen, W.; Freudenberg, K.
2005-10-07
The National Compact Stellarator Experiment (NCSX) is an experimental device whose design and construction is underway at the Department of Energy's Princeton Plasma Physics Laboratory (PPPL). The primary coil systems for the NCSX device consist of the twisted plasma-shaping Modular Coils, the Poloidal Field Coils, and the Toroidal Field (TF) Coils. The TF Coils are D-shaped coils wound from hollow copper conductor, and vacuum impregnated with a glass-epoxy resin system. There are 18 identical, equally spaced TF coils providing 1/R field at the plasma. They operate within a cryostat, and are cooled by LN2, nominally, to 80K. Wedge shaped castings are assembled to the inboard face of these coils, so that inward radial loads are reacted via the nesting of each of the coils against their adjacent partners. This paper outlines the TF Coil design methodology, reviews the analysis results, and summarizes how the design and analysis support the design requirements.
Drift waves in general toroidal geometry
International Nuclear Information System (INIS)
A model, based on gyro-kinetic ions and fluid electrons, to study drift waves in low-beta [beta = (kinetic pressure)/(magnetic pressure)] stellarator plasmas is presented. The model equations are written in straight-field-line coordinates and are valid for arbitrary, fully three-dimensional configurations with closed, nested magnetic surfaces. An implicit method, coupled with a subcycling technique for the electrons, is used to solve the time-dependent, along-the-field-line equations. Numerical calculations are carried out for a 3-field-period toroidal heliac. The geometrical effects that enter the model equations are calculated and displayed in physical space using advanced visualization techniques
Approximations to toroidal harmonics
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Toroidal harmonics P/sub n-1/2/1(cosh μ) and Q/sub n-1/2/1(cosh μ) are useful in solutions to Maxwell's equations in toroidal coordinates. In order to speed their computation, a set of approximations has been developed that is valid over the range 0 -10. The simple method used to determine the approximations is described. Relative error curves are also presented, obtained by comparing approximations to the more accurate values computed by direct summation of the hypergeometric series
Drift in toroidal configurations
Evangelidis, E. A.
1990-12-01
This paper considers possible mechanisms involved in amplifying the drift velocity of plasma particles, under conditions of toroidal geometry. It is shown that particles constrained to move on an axisymmetric circular spheroidal surface, develop a sinusoidal motion with a characteristic frequency which depends on the energy of the particles, the value of the isoflux surface, and the value of the general momentum. It is also shown that the incorporation of the effects of toroidal geometry in the Lorentz equation produces a nonambipolar charge-dependent particle flux amplified by a factor 2(q/epsilon) squared.
Design of the national compact stellarator experiment (NCSX)
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Nelson, B.E. E-mail: nelsonbe@ornl.gov; Berry, L.A.; Brooks, A.B.; Cole, M.J.; Chrzanowski, J.C.; Fan, H.-M.; Fogarty, P.J.; Goranson, P.L.; Heitzenroeder, P.J.; Hirshman, S.P.; Jones, G.H.; Lyon, J.F.; Neilson, G.H.; Reiersen, W.T.; Strickler, D.J.; Williamson, D.E
2003-09-01
The National Compact Stellarator Experiment (NCSX) [http://www.pppl.gov/ncsx/Meetings/CDR/CDRFinal/EngineeringOverview{sub R}2.pdf] is being designed as a proof of principal test of a quasi-axisymmetric compact stellarator. This concept combines the high beta and good confinement features of an advanced tokamak with the low current, disruption-free characteristics of a stellarator. NCSX has a three-field-period plasma configuration with an average major radius of 1.4 m, an average minor radius of 0.33 m and a toroidal magnetic field on axis of up to 2 T. The stellarator core is a complex assembly of four coil systems that surround the highly shaped plasma and vacuum vessel. Heating is provided by up to four, 1.5 MW neutral beam injectors and provision is made to add 6 MW of ICRH. The experiment will be built at the Princeton Plasma Physics Laboratory, with first plasma expected in 2007.
Recent advances in the stability theory of toroidal plasmas
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Many of the most persistent instabilities of a magnetically confined plasma have short wavelength perpendicular to the magnetic field but long wavelength parallel to it. Such instabilities are difficult to treat in a toroidal system because the simple eikonal representation of short wavelength oscillations. X(r) = Y(r) esup(iS(r)/γ) with γ << 1 proves to be incompatible with the other requirements of toroidal periodicity and long parallel wavelength (which would require BETA.ΔS = O). A new method of representing perturbations in a torus will be outlined. By using this, the two-dimensional stability problem posed by an axisymmetric toroidal equilibrium can be reduced to that of solving a one-dimensional eigenvalue equation. This technique essentially completes the linear stability theory of magnetohydrodynamic modes in a toroidal plasma, and is also applicable to the investigation of micro-instabilities that are described by the Vlasov-Maxwell equations. (author)
Physics aspects of the compact ignition tokamak
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The Compact Ignition Tokamak (CIT) is a proposed modest-size ignition experiment designed to study the physics of alpha particle heating. The basic concept is to achieve ignition in a modest-size minimum cost experiment by using a high plasma density to achieve nτE ≅ 2 x 1020 s/m3 required for ignition. The high density requires a high toroidal field (10 T). The high toroidal field allows a large plasma current (10 MA) which provides a high level of ohmic heating, improves the energy confinement, and allows a relatively high beta (≅ 6%). The present CIT design also has a high degree of elongation (κ ≅ 1.8) to aid in producing the large plasma current. A double null poloidal divertor and pellet injection are part of the design to provide impurity and particle control, improve the confinement, and provide flexibility for improving the plasma profiles. Auxiliary heating is expected to be necessary to achieve ignition, and 10-20 MW of ICRF is to be provided. (orig.)
Elongated toroid fusion device
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A device for achieving ignition of a plasma with ohmic heating is described comprising: means for defining a toroidal plasma chamber,a and confining gas therein, and means including electrically conductive coils for generating plasma within the chamber and for confining and shaping such plasma substantially into and filling a predetermined single region of the chamber without an axisymmetric internal separatix and ohmically heating the confined plasma to ignition. The predetermined region is toroidal with a major axis defining an axial direction parallel thereto and a transaxial direction perpendicular to the axis and having an axial cross section with an elongation, k, greater than 4, where k is the ratio of the maximum axial dimension of the cross section to the maximum transaxial dimension of the cross section
Tokamak with liquid metal toroidal field coil
Ohkawa, Tihiro; Schaffer, Michael J.
1981-01-01
Tokamak apparatus includes a pressure vessel for defining a reservoir and confining liquid therein. A toroidal liner disposed within the pressure vessel defines a toroidal space within the liner. Liquid metal fills the reservoir outside said liner. Electric current is passed through the liquid metal over a conductive path linking the toroidal space to produce a toroidal magnetic field within the toroidal space about the major axis thereof. Toroidal plasma is developed within the toroidal space about the major axis thereof.
International Nuclear Information System (INIS)
This paper discusses experiments on linear high beta helical axis stellarators. Experiments considered are: formation of linear high beta heliac plasma configurations; Alfven wave heating in a straight tube and in a linear high beat stellarator; shifted hardcore heliac studies; a system for measuring the timing of high-current switches in a pulsed high voltage fusion experiment; HBQM general refurbishment; and proposed experiment on excitation of the m = 1 tilt mode in field-reversed configurations
Resistive instabilities in toroidal confinement
International Nuclear Information System (INIS)
Low-m tearing modes constitute the dominant instability problem in present-day tokamaks. In this paper, the stability criteria for representative current profiles with q(0) values in the vicinity of unity are reviewed; sawtooth reconnection to q(0) values just at, or slightly exceeding, unity is generally destabilizing to the m = 2, n = 2 and m = 3, n = 2 modes and limits the range of stable profile shapes. Major disruptions can be produced by the simultaneous growth of m = 2, n = 1 and m = 3, n = 2 magnetic islands, leading to destabilization of higher-order modes and to the overlapping of several island chains. Internal disruptions---or sawteeth---arise in a variety of forms other than that produced by the classically reconnecting m = 1 mode. In some case, the q(r) value is apparently close to unity over a large central part of the plasma; in other cases, the q(0) value remains substantially below unity throughout a sawtooth cycle. Toroidal effects are sufficient to stabilize the resistive m = 1 mode in the latter case. Feedback stabilization of m ≥ 2 modes by rf heating or current drive, applied locally at the magnetic islands, appears feasible; feedback by island current drive is much more efficient, in terms of the radio-frequency power required, than feedback by island heating. Feedback stabilization of the m = 1 resistive mode---although yielding particularly beneficial effects for resistive-tearing and high-beta stability by allowing q(0) values substantially below unity---is more problematical, unless the m = 1 ideal MHD mode can be given sufficient positive stability. This appears possible, however, either by strong triangular shaping of the central flux surfaces or by appropriate tailoring of the current profile in the vicinity of the q = 1 surface
International Nuclear Information System (INIS)
The limitations of ohmic heating in achieving the thermonuclear ignition of a low-β toroidal plasma can be overcome by using several heating methods. Such methods are: fast neutral beam injection (possibly combined with an adiabatic compression or any other means) and HF heating, the most interesting schemes being based on plasma resonances. The basic physical phenomena in each method are briefly explained and results obtained are given. A new heating scheme using an outer frequency of a few kHz is described, that makes it possible to locate the exciting coils outside the vacuum vessel (some of these coils can be that producing the vertical magnetic field for the plasma equilibrium)
Toroidal Multipole Confinement Experiment
International Nuclear Information System (INIS)
Confinement of plasma is studied in the General Atomic toroidal octopole machine. The magnetic field is produced by four current carrying rings supported inside a contoured conductor. The rings are energized by a transformer core linking the machine. The major radius of the machine is 63.5 cm with an aspect ratio of 5. The magnetic field on the minor axis is zero and increases to 3500 G at the wall between the rings. After crowbarring, the field decays in 6 msec to its half value. The MHD stability calculation has been carried out and the stability is assured up to the plasma pressure of 1016 eV cm-3. Hydrogen plasmas from either a coaxial gun or a pinch gun with ion energies of 50 to 200 eV and with densities of 1014 cm-3 are successfully injected through a port located at the outer conductor wall. After the injection, plasma spreads azimuthally, filling the machine. Electric probes, magnetic probes, and calorimetric probes have been used extensively. Optical spectrometers and particle detectors are also used. The initial plasma density of 1013 cm-'3 decays with a time constant of 700 μsec. The electron temperature decays more quickly in about 100 μsec. No electric or magnetic fluctuations have been observed on any of the probes. Since no provision is made to avoid the plasma loss to the ring supports which penetrate the plasma region, the decay of ion temperature may be attributed to the support loss. (author)
PEGASUS Toroidal Experimental Facility*
Lewicki, B.; Pegasus Group
1998-11-01
P EGASUS began operations in June 98 and will study the characteristics of Extremely Low-Aspect Ratio Tokamak (ELART) plasmas. The 2.0m diameter, thin-walled (6.35 mm) vacuum vessel is a continuous stainless steel shell with generous port access. Initial pump down base pressure was 5 × 10-8 torr. The high stress ohmic solenoid is powered by a 15 kV, 4.5 MJ capacitor bank and will be impedance-matched through a 10:1 step-down transformer to extend the pulse length. Operating at peak fields of 13 - 20 T, the solenoid can achieve a flux swing of up to 190mV-s over 60 ms. The toroidal field of 0.1 T on axis is powered by a 3 MVA AC/DC converter capable of 3.5 kA at 600 VDC. The equilibrium and shaping field magnets are powered by 2.2 F of commutated capacitor banks plus a 0.5 MVA programmable switching supply. Modest waveform control is available to compensate for the resistive vacuum vessel and aid in plasma shaping for elongated and diverted plasmas. Operational diagnostics include internal magnetic pickup loops, high resolution and fast framing cameras, and impurity monitoring systems. * *Supported by U.S. DoE grant No. DE-FG02-96ER54375
Compact torus experiments and theory
International Nuclear Information System (INIS)
Two types of compact toroids have been studied: spheromaks and field-reversed configurations (FRC). Spheromaks, which contain both toroidal and poloidal fields, have been formed with a magnetized coaxial injector and trapped in both prolate and oblate flux conservers. As expected from theory, the prolate configuration always tilts, but the oblate configuration can be made stable even in the presence of a guide field. Observations include 150μs lifetimes, approx. 1014 cm-3, and a decrease of field fluctuations by a factor of 100 at the time of complete reconnection. Theoretical studies of the FRC (no toroidal field) have been compared with the results of two field-reversed theta-pinches, FRX-A and FRX-B
Bootstrap transition to high beta equilibrium in helical system
International Nuclear Information System (INIS)
It is shown theoretically and computationally that helical magnetic field, produced by continuous winding helical coils and without the toroidal coil, can sustain MHD stable high beta plasma. Pressure driven toroidal current (bootstrap current) cancels the external magnetic field and reduces the MHD potential energy, depending on the plasma beta values. Ramp-up of heating power input induces bootstrap transition to higher beta plasmas with flat-top pressure profiles. Helical pitch parameter dependence of MHD stability is analyzed. (author)
Heavy ion toroidal collective accelerator
International Nuclear Information System (INIS)
Experiments on HIPAC at Maxwell Laboratories have shown that almost all of the confined electrons are trapped and do not go around the torus. A toroidal electric field produces a negligible toroidal electron current. An ion accelerator where electrons are magnetically contained and their space charge contains ions is considered. A toroidal electric field of suitable magnitude can be applied so that it accelerates all of the ions but does not accelerate most of the electrons. This is possible if the magnetic moment of electrons μsub(e) > μsub(i)/Z, where μsub(i) is the ion magnetic moment and Z is the charge of the ion. Ions would be contained by the electron space-charge electric field E, for energies up to ZeER/2 approximately 100 GeV where Z = 60, E = 107 V/cm and the major radius of the torus is R = 3.3 metres. (author)
RF breakdown by toroidal helicons
Indian Academy of Sciences (India)
S K P Tripathi; D Bora; M Mishra
2001-04-01
Bounded whistlers are well-known for their efﬁcient plasma production capabilities in thin cylindrical tubes. In this paper we shall present their radio frequency (RF) breakdown and discharge sustaining capabilities in toroidal systems. Pulsed RF power in the electronmagnetohydrodynamic (EMHD) frequency regime is fed to the neutral background medium. After the breakdown stage, discharge is sustained by toroidal bounded whistlers. In these pulsed experiments the behaviour of the time evolution of the discharge could be studied in four distinct phases of RF breakdown, steady state attainment, decay and afterglow. In the steady state average electron density of ≈ 1012 per cc and average electron temperature of ≈ 20 eV are obtained at 10-3 mbar of argon ﬁlling pressure. Experimental results on toroidal mode structure, background effects and time evolution of the electron distribution function will be presented and their implications in understanding the breakdown mechanism are discussed.
Hybrid winding concept for toroids
DEFF Research Database (Denmark)
Schneider, Henrik; Andersen, Thomas; Knott, Arnold;
2013-01-01
This paper proposes a hybrid winding concept for toroids using the traces in a printed circuit board to make connection to bended copper foil cutouts. In a final product a number of strips with a certain thickness would be held by a former and the whole assembly could be placed by pick and...... placement machinery. This opens up the possibility for both an automated manufacturing process and an automated production process of toroidal magnetics such as power inductors, filtering inductors, air core inductors, transformers etc. Both the proposed hybrid and the common wire wound winding...
The complex and unique ATLAS Toroid family
2002-01-01
Big parts for the toroid magnets that will be used in the ATLAS experiment have been continuously arriving at CERN since March. These structures will create the largest superconducting toroid magnet ever.
Plasma transport in a Compact Ignition Tokamak
International Nuclear Information System (INIS)
Nominal predicted plasma conditions in a Compact Ignition Tokamak (CIT) are illustrated by transport simulations using experimentally calibrated plasma transport models. The range of uncertainty in these predictions is explored by using various models that have given almost equally good fits to experimental data. Using a transport model that best fits the data, thermonuclear ignition occurs in a CIT design with a major radius of 1.32 m, plasma half-width of 0.43 mn, elongation of 2.0, and toroidal field and plasma current ramped in 6 s from 1.7 to 10.4 T and 0.7 to 10 MA, respectively. Ignition is facilitated by 20 MW of heating deposited off the magnetic axis near the /sup 3/He minority cyclotron resonance layer. Under these conditions, sawtooth oscillations are small and have little impact on ignition. Tritium inventory is minimized by preconditioning most discharges with deuterium. Tritium is injected, in large frozen pellets, only after minority resonance preheating. Variations of the transport model, impurity influx, heating profile, and pellet ablation rates have a large effect on ignition and on the maximum beta that can be achieved
Intrinsic rotation of toroidally confined magnetohydrodynamics
Morales, Jorge; Bos, Wouter; Schneider, Kai; Montgomery, David
2012-01-01
The spatiotemporal self-organization of viscoresistive magnetohydrodynamics (MHD) in a toroidal geometry is studied. Curl-free toroidal magnetic and electric fields are imposed. It is observed in our simulations that a flow is generated, which evolves from dominantly poloidal to toroidal when the Lundquist numbers are increased. It is shown that this toroidal organization of the flow is consistent with the tendency of the velocity field to align with the magnetic field. Up-down asymmetry of t...
Technology of toroidal plasma devices
International Nuclear Information System (INIS)
After research into many different magnetic confinement systems, there is now general agreement that the most favorable ones for future fusion reactors are all based on toroidal geometry, as distinct from having open ends like mirror machines. For this reason plasma physics research, even when not aimed directly at the fusion problems, has in recent years increasingly concentrated on toroidal systems. One reason is that by using their good confinement properties the experimenter has available a range of high temperature plasma parameters in quasisteady (or even steady) state conditions not otherwise available on Earth. Despite the wide variety of both geometrical possibilities and sizes, ranging from table-top experiments with plasmas a few centimetres across to near reactor scale ones like JET with plasmas several metres across, toroidal systems have many common features, both in their physical principles and of experimental design: the purpose of this paper is to highlight those common features, using some specific examples for illustration, and emphasizing some of the more practical aspects. It will also try to point out important differences between two of the main classes of toroidal systems
ATLAS superconducting toroids and solenoid
ten Kate, H H J
2005-01-01
The ATLAS particle detector in the Large Hadron Collider at CERN features a hybrid system of four superconducting magnets: a Central Solenoid surrounded by 2 End-cap Toroids and a Barrel Toroid. The magnet system dimensions are 20 m in diameter and 26 m in length. With its 1.55 GJ stored energy in air, it actually is the largest superconducting magnet in the world. The construction of the magnets has started in 1998 and will end in 2006 with the completion of the installation underground. Currently, in October 2004, practically all magnet parts are manufactured and delivered to CERN for final integration. The first two out of 8 full size 25*5 m/sup 2/ size coils for the Barrel Toroid have been completed and tested while the other 6 are near to completion as well. The production of the so- called End-Cap Toroids is progressing well. The Central Solenoid is complete and ready for installation. The installation underground of the entire system including its services has commenced. In the paper the main features ...
Lowering the first ATLAS toroid
Maximilien Brice
2004-01-01
The ATLAS detector on the LHC at CERN will consist of eight toroid magnets, the first of which was lowered into the cavern in these images on 26 October 2004. The coils are supported on platforms where they will be attached to form a giant torus. The platforms will hold about 300 tonnes of ATLAS' muon chambers and will envelop the inner detectors.
Toroidal solutions in Horava Gravity
Ghodsi, Ahmad
2009-01-01
Recently a new four-dimensional non relativistic renormalizable theory of gravity was proposed by Horava. This gravity reduces to Einstein gravity at large distances. In this paper by using the new action for gravity we present different toroidal solutions to the equations of motion. Our solutions describe the near horizon geometry with slow rotating parameter.
Onsager relaxation of toroidal plasmas
International Nuclear Information System (INIS)
The slow relaxation of isolated toroidal plasmas towards their thermodynamical equilibrium is studied in an Onsager framework based on the entropy metric. The basic tool is a variational principle, equivalent to the kinetic equation, involving the profiles of density, temperature, electric potential, electric current. New minimization procedures are proposed to obtain entropy and entropy production rate functionals. (author)
Extremely high Q-factor toroidal metamaterials
Basharin, Alexey A; Volsky, Nikita; Kafesaki, Maria; Economou, Eleftherios N; Ustinov, Alexey V
2016-01-01
We demonstrate that, owing to the unique topology of the toroidal dipolar mode, its electric/magnetic field can be spatially confined within subwavelength, externally accessible regions of the metamolecules, which makes the toroidal planar metamaterials a viable platform for high Q-factor resonators due to interfering toroidal and other dipolar modes in metamolecules.
ATLAS End Cap toroid in upstanding position
2005-01-01
End Cap toroid The ATLAS End Cap toroid weights 240-ton and is 12-m diameter high. The parts of this vacuum vessel had to be integrated and tested so that End Cap Toroid has no leaks. After that it could be cooled down to 80 K.
Measurement of magnetic properties of confined compact toroid plasma (spheromak)
International Nuclear Information System (INIS)
The theoretical aspect of the spheromak is described in this paper. The MS machine hardware will be explored along with the formation scheme and diagnostic systems. The magnetic pickup probes, their calibration procedures and the data analysis methods will be discussed. Observations from the probe measurements and magnetic properties of the MS spheromak are considered. The axisymmetric Grad-Shafranov equilibrium code calculations are presented and compared with the measurements. Magnetic helicity and its correlation with the experimental observations is described
Intrinsic rotation of toroidally confined magnetohydrodynamics.
Morales, Jorge A; Bos, Wouter J T; Schneider, Kai; Montgomery, David C
2012-10-26
The spatiotemporal self-organization of viscoresistive magnetohydrodynamics in a toroidal geometry is studied. Curl-free toroidal magnetic and electric fields are imposed. It is observed in our simulations that a flow is generated, which evolves from dominantly poloidal to toroidal when the Lundquist numbers are increased. It is shown that this toroidal organization of the flow is consistent with the tendency of the velocity field to align with the magnetic field. Up-down asymmetry of the geometry causes the generation of a nonzero toroidal angular momentum. PMID:23215195
International Nuclear Information System (INIS)
A transition of a core localized type toroidal Alfven eigenmode with n 1 toroidal mode number to two n = 1 global Alfven eignemodes was observed in NBI-heated plasmas in the Compact Helical System (CHS) heliotron/torsatron. This transition phenomenon is interpreted based on the temporal evolution of the rotational transform near the plasma center caused by the increased in the beam-driven current. (author)
International Nuclear Information System (INIS)
The lectures of a Varenna Summer School about the theme Instabilities and Confinement in toroidal Plasmas are given. The topics included are: high-beta toroidal pinches, non-MHD instabilities and anomalous transport, analogy between turbulent transfer in velocity space and plasma collisioned transport in real space, the magnetohydrodynamic approach of plasma confinement in closed magnetic configurations, properties of isodynamical equilibrium configurations and their generalization, transport theory for toroidal plasmas, plasma physics, low-β toroidal machines, the neoclassical theory of transit time magnetic pumping, radio frequency heating of toroidal plasmas, plasma heating at lower hybrid frequency, RF-plasma heating with L-structures, numerical simulation, dynamical stabilization of low frequency waves in inhomogeneous plasmas, dynamic and feedback stabilization of plasmas and problems with nuclear fusion reactors
Design and Simulation of Toroidal Twister Model
Institute of Scientific and Technical Information of China (English)
TIAN Huifang; LIN Xizhen; ZENG Qinqin
2006-01-01
Toroidal composite vessel winded with fiber is a new kind of structural pressure vessels, which not only has high structure efficiency of compound materials pressure vessel, good security and so on, but also has special shape and the property of utilizing toroidal space, and the prospect of the application of toroidal composite vessel winded with fiber is extremely broad. By introducing parameters establishment of toroidal vessel and elaborating the principle of filament winding for toroidal vessel, the design model of filament winding machine for toroidal vessel has been introduced, and the design model has been dynamically simulated by the software of ADAMS, which will give more referrence for the design of real toroidal vessel twister.
Czech Academy of Sciences Publication Activity Database
Skálová, Tereza; Dohnálek, Jan; Spiwok, V.; Lipovová, P.; Vondráčková, Eva; Petroková, Hana; Dušková, Jarmila; Strnad, Hynek; Králová, B.; Hašek, Jindřich
2005-01-01
Roč. 353, č. 2 (2005), s. 282-294. ISSN 0022-2836 R&D Projects: GA ČR(CZ) GA204/02/0843; GA AV ČR(CZ) KJB500500512 Institutional research plan: CEZ:AV0Z40500505 Keywords : glycosyl hydrolase * .beta.-galactosidase * cold -active Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.229, year: 2005
Alpha particle destabilization of the toroidicity-induced Alfven eigenmodes
International Nuclear Information System (INIS)
The high frequency, low mode number toroidicity-induced Alfven eigenmodes (TAE) are shown to be driven unstable by the circulating and/or trapped α-particles through the wave-particle resonances. Satisfying the resonance condition requires that the α-particle birth speed vα ≥ vA/2|m-nq|, where vA is the Alfven speed, m is the poloidal model number, and n is the toroidal mode number. To destabilize the TAE modes, the inverse Landau damping associated with the α-particle pressure gradient free energy must overcome the velocity space Landau damping due to both the α-particles and the core electrons and ions. The growth rate was studied analytically with a perturbative formula derived from the quadratic dispersion relation, and numerically with the aid of the NOVA-K code. Stability criteria in terms of the α-particle beta βα, α-particle pressure gradient parameter (ω*/ωA) (ω* is the α-particle diamagnetic drift frequency), and (vα/vA) parameters will be presented for TFTR, CIT, and ITER tokamaks. The volume averaged α-particle beta threshold for TAE instability also depends sensitively on the core electron and ion temperature. Typically the volume averaged α-particle beta threshold is in the order of 10-4. Typical growth rates of the n=1 TAE mode can be in the order of 10-2ωA, where ωA=vA/qR. Other types of global Alfven waves are stable in D-T tokamaks due to toroidal coupling effects
TFTR toroidal field coil design
International Nuclear Information System (INIS)
The design of the Tokamak Fusion Test Reactor (TFTR) Toroidal Field (TF) magnetic coils is described. The TF coil is a 44-turn, spiral-wound, two-pancake, water-cooled configuration which, at a coil current of 73.3 kiloamperes, produces a 5.2-Tesla field at a major radius of 2.48 meters. The magnetic coils are installed in titanium cases, which transmit the loads generated in the coils to the adjacent supporting structure. The TFTR utilizes 20 of these coils, positioned radially at 180 intervals, to provide the required toroidal field. Because it is very highly loaded and subject to tight volume constraints within the machine, the coil presents unique design problems. The TF coil requirements are summarized, the coil configuration is described, and the problems highlighted which have been encountered thus far in the coil design effort, together with the development tests which have been undertaken to verify the design
Classification of symmetric toroidal orbifolds
Energy Technology Data Exchange (ETDEWEB)
Fischer, Maximilian; Ratz, Michael; Torrado, Jesus [Technische Univ. Muenchen, Garching (Germany). Physik-Department; Vaudrevange, Patrick K.S. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2012-09-15
We provide a complete classification of six-dimensional symmetric toroidal orbifolds which yield N{>=}1 supersymmetry in 4D for the heterotic string. Our strategy is based on a classification of crystallographic space groups in six dimensions. We find in total 520 inequivalent toroidal orbifolds, 162 of them with Abelian point groups such as Z{sub 3}, Z{sub 4}, Z{sub 6}-I etc. and 358 with non-Abelian point groups such as S{sub 3}, D{sub 4}, A{sub 4} etc. We also briefly explore the properties of some orbifolds with Abelian point groups and N=1, i.e. specify the Hodge numbers and comment on the possible mechanisms (local or non-local) of gauge symmetry breaking.
Hollow nanotubular toroidal polymer microrings
Lee, Jiyeong; Baek, Kangkyun; Kim, Myungjin; Yun, Gyeongwon; Ko, Young Ho; Lee, Nam-Suk; Hwang, Ilha; Kim, Jeehong; Natarajan, Ramalingam; Park, Chan Gyung; Sung, Wokyung; Kim, Kimoon
2014-02-01
Despite the remarkable progress made in the self-assembly of nano- and microscale architectures with well-defined sizes and shapes, a self-organization-based synthesis of hollow toroids has, so far, proved to be elusive. Here, we report the synthesis of polymer microrings made from rectangular, flat and rigid-core monomers with anisotropically predisposed alkene groups, which are crosslinked with each other by dithiol linkers using thiol-ene photopolymerization. The resulting hollow toroidal structures are shape-persistent and mechanically robust in solution. In addition, their size can be tuned by controlling the initial monomer concentrations, an observation that is supported by a theoretical analysis. These hollow microrings can encapsulate guest molecules in the intratoroidal nanospace, and their peripheries can act as templates for circular arrays of metal nanoparticles.
Prospects for toroidal fusion reactors
International Nuclear Information System (INIS)
Work on the International Thermonuclear Experimental Reactor (ITER) tokamak has refined understanding of the realities of a deuterium-tritium (D-T) burning magnetic fusion reactor. An ITER-like tokamak reactor using ITER costs and performance would lead to a cost of electricity (COE) of about 130 mills/kWh. Advanced tokamak physics to be tested in the Toroidal Physics Experiment (TPX), coupled with moderate components in engineering, technology, and unit costs, should lead to a COE comparable with best existing fission systems around 60 mills/kWh. However, a larger unit size, ∼2000 MW(e), is favored for the fusion system. Alternative toroidal configurations to the conventional tokamak, such as the stellarator, reversed-field pinch, and field-reversed configuration, offer some potential advantage, but are less well developed, and have their own challenges
Magnetic Properties of 3D Printed Toroids
Bollig, Lindsey; Otto, Austin; Hilpisch, Peter; Mowry, Greg; Nelson-Cheeseman, Brittany; Renewable Energy; Alternatives Lab (REAL) Team
Transformers are ubiquitous in electronics today. Although toroidal geometries perform most efficiently, transformers are traditionally made with rectangular cross-sections due to the lower manufacturing costs. Additive manufacturing techniques (3D printing) can easily achieve toroidal geometries by building up a part through a series of 2D layers. To get strong magnetic properties in a 3D printed transformer, a composite filament is used containing Fe dispersed in a polymer matrix. How the resulting 3D printed toroid responds to a magnetic field depends on two structural factors of the printed 2D layers: fill factor (planar density) and fill pattern. In this work, we investigate how the fill factor and fill pattern affect the magnetic properties of 3D printed toroids. The magnetic properties of the printed toroids are measured by a custom circuit that produces a hysteresis loop for each toroid. Toroids with various fill factors and fill patterns are compared to determine how these two factors can affect the magnetic field the toroid can produce. These 3D printed toroids can be used for numerous applications in order to increase the efficiency of transformers by making it possible for manufacturers to make a toroidal geometry.
A paramagnetic nearly isodynamic compact magnetic confinement system
International Nuclear Information System (INIS)
A coreless compact magnetic confinement system that consists of sets of helical windings and vertical magnetic field coils is investigated. The helical coils produce a small toroidal translation of the magnetic field lines and seed paramagnetism. The force-free component of the toroidal current strongly enhances the paramagnetism such that isodynamic conditions near the plasma centre can be approached. At β 5%, the configuration is stable to local MHD modes. Global MHD modes limit the toroidal current 2πJ to about 60kA for peaked J. Bootstrap-like hollow current profiles generate quasiaxisymmetric systems that require a close fitting conducting shell to satisfy external kink stability. (author)
Toroidal Super-Heavy Nuclei in Skyrme-Hartree-Fock Approach
Staszczak, Andrzej; Wong, Cheuk-Yin
2008-01-01
Within the self-consistent constraint Skyrme-Hartree-Fock+BCS model (SHF+BCS), we found equilibrium toroidal nuclear density distributions in the region of super-heavy elements. For nuclei with a sufficient oblate deformation ($Q_{20}\\leq$ -200 b), it becomes energetically favourable to change the genus of nuclear surface from 0 to 1, i.e., to switch the shape from a biconcave disc to a torus. The energy of the toroidal (genus=1) SHF+BCS solution relative to the compact (genus=0) ground state...
Directory of Open Access Journals (Sweden)
Charles Swartz
2009-12-01
Full Text Available We give a characterization in terms of the transpose operator for a continuous linear operator between locally convex spaces to map bounded sets into relatively weakly compact [relatively compact, precompact] sets. Our results give a known characterization for compact operators between Banach spaces.
Beam Transport in Toroidal Magnetic Field
Joshi, N; Meusel, O; Ratzinger, U
2016-01-01
The concept of a storage ring with toroidal magnetic field was presented in the two previous EPAC conferences. Here we report the first results of experiments performed with beam transport in toroidal magnetic fields and details of the injection system. The beam transport experiments were carried out with 30 degree toroidal segments with an axial magnetic field of 0.6T. The multi turn injection system relies on a transverse injection coil together with an electric kicker system.
Trapped particle dynamics in toroidally rotating plasmas
International Nuclear Information System (INIS)
A detailed single particle orbit analysis is toroidally rotating plasma yields new analytical formulas for the second adiabatic invariant, the bounce frequency, and the precession frequency up to the first order correction in ρpi(poloidal ion gyroradium)/Lv(scale length of rotation velocity), for toroidal flow values of the order of ion thermal velocity. Toroidal plasma rotation effects on the trapped ion instabilities in tokamaks are investigated in the context of local theory. Toroidal plasma rotation increases both the fraction of trapped particles and their precession drift velocity. Consequently, the growth rate of trapped ion instability increases in both dissipative and collisionless regimes
Effect of toroidal plasma flow and flow shear on global MHD modes
International Nuclear Information System (INIS)
The effect of a subsonic toroidal flow on the linear magnetohydrodynamic stability of a tokamak plasma surrounded by an external resistive wall is studied. A complex non-self-adjoint eigenvalue problem for the stability of general kink and tearing modes is formulated, solved numerically, and applied to high β tokamaks. Results indicate that toroidal plasma flow, in conjunction with dissipation in the plasma, can open a window of stability for the position of the external wall. In this window, stable plasma beta values can significantly exceed those predicted by the Troyon scaling law with no wall. Computations utilizing experimental data indicate good agreement with observations
Pellet injection and toroidal confinement
International Nuclear Information System (INIS)
The proceedings of a technical committee meeting on pellet injection and toroidal confinement, held in Gut Ising, Federal Republic of Germany, 24-26 October, 1988, are given in this report. Most of the major fusion experiments are using pellet injectors; these were reported at this meeting. Studies of confinement, which is favorably affected, impurity transport, radiative energy losses, and affects on the ion temperature gradient instability were given. Studies of pellet ablation and effects on plasma profiles were presented. Finally, several papers described present and proposed injection guns. Refs, figs and tabs
Regimes of pulsed formation of a compact plasma configuration with a high energy input
Energy Technology Data Exchange (ETDEWEB)
Romadanov, I. V.; Ryzhkov, S. V., E-mail: svryzhkov@bmstu.ru [Bauman Moscow State Technical University (Russian Federation)
2015-10-15
Results of experiments on the formation of a compact toroidal magnetic configuration at the Compact Toroid Challenge setup are presented. The experiments were primarily aimed at studying particular formation stages. Two series of experiments, with and without an auxiliary capacitor bank, were conducted. The magnetic field was measured, its time evolution and spatial distribution over the chamber volume were determined, and its influence on the formation regimes was investigated.
Toroidal Theory of MHD Instabilities
International Nuclear Information System (INIS)
We continue with the adventures of the Alfven wave and its two magnetosonic companions as they travel in the curved space of magnetic surfaces and field lines (Sec. 2), find themselves trapped in singularities of an unprecedented richness (Sec. 3), decide to get themselves better maps of the landscape to do the required twisting while some of their youthful energy is leaking away (Sec. 4), cause trouble at the edge of a powerful empire (Sec. 5), and finally see the light in a distant future (Sec. 6). Needed on the trip are the evolution equations of both ideal and resistive MHD 'derived' in reference [1], the solutions to the toroidal equilibrium equations discussed in reference [2], the general background on spectral theory of inhomogeneous plasmas presented in reference [3], which is extended in the two directions of toroidal geometry and resistivity in this lecture [4]. This leads to such intricate dynamics that numerical techniques are virtually the only way to proceed. This aspect is further elaborated in reference [5] on numerical techniques
Toroidal Alfven wave stability in ignited tokamaks
Energy Technology Data Exchange (ETDEWEB)
Cheng, C.Z.; Fu, G.Y.; Van Dam, J.W.
1989-01-01
The effects of fusion-product alpha particles on the stability of global-type shear Alfven waves in an ignited tokamak plasma are investigated in toroidal geometry. Finite toroidicity can lead to stabilization of the global Alfven eigenmodes, but it induces a new global shear Alfven eigenmodes, which is strongly destabilized via transit resonance with alpha particles. 8 refs., 2 figs.
Electrostatics of a Family of Conducting Toroids
Lekner, John
2009-01-01
An exact solution is found for the electrostatic potential of a family of conducting charged toroids. The toroids are characterized by two lengths "a" and "b", with "a" greater than or equal to "2b". They are closed, with no hole in the "doughnut". The results are obtained by considering the potential of two equal charges, displaced from the…
Cutoff frequency of toroidal plasma waveguide
International Nuclear Information System (INIS)
The cutoff frequencies of E and H-modes of empty and plasma filled toroidal waveguides are evaluated. The effects of space curvature and plasma density on cutoff frequencies for both modes are investigated. Using a suitable variable change, a scalar wave equation in the direction of propagation was obtained. The study indicates that the curvature in the direction of wave propagation in toroidal waveguide has an analogous effect as a straight waveguide filled with anisotropic media. The Rayleigh-Schrodinger perturbation method was employed to solve for cutoff frequencies in the first order of approximation. In the limit of small space curvature, the toroidal waveguide cutoff frequencies for both E and H-modes approach those of TM and TE modes of empty cylindrical waveguide with a radius equal to toroidal waveguide minor radius. The analysis shows that the curvature in the direction of propagation in toroidal waveguides leads to the removal of the degeneracy between E and H-modes
Asymmetric Magnon Excitation by Spontaneous Toroidal Ordering
Hayami, Satoru; Kusunose, Hiroaki; Motome, Yukitoshi
2016-05-01
The effects of spontaneous toroidal ordering on magnetic excitation are theoretically investigated for a localized spin model that includes a staggered Dzyaloshinsky-Moriya interaction and anisotropic exchange interactions, which arise from the antisymmetric spin-orbit coupling and the multiorbital correlation effect. We show that the model exhibits a Néel-type antiferromagnetic order, which simultaneously accompanies a ferroic toroidal order. We find that the occurrence of toroidal order modulates the magnon dispersion in an asymmetric way with respect to the wave number: a toroidal dipole order on the zigzag chain leads to a band-bottom shift, while a toroidal octupole order on the honeycomb lattice gives rise to a valley splitting. These asymmetric magnon excitations could be a source of unusual magnetic responses, such as nonreciprocal magnon transport. A variety of modulations are discussed while changing the lattice and magnetic symmetries. The implications regarding candidate materials for asymmetric magnon excitations are presented.
Toroidal Vortices in Resistive Magnetohydrodynamic Equilibria
Montgomery, D C; Li, S; Montgomery, David; Bates, Jason W.; Li, Shuojun
1996-01-01
Resistive steady states in toroidal magnetohydrodynamics (MHD), where Ohm's law must be taken into account, differ considerably from ideal ones. Only for special (and probably unphysical) resistivity profiles can the Lorentz force, in the static force-balance equation, be expressed as the gradient of a scalar and thus cancel the gradient of a scalar pressure. In general, the Lorentz force has a curl directed so as to generate toroidal vorticity. Here, we calculate, for a collisional, highly viscous magnetofluid, the flows that are required for an axisymmetric toroidal steady state, assuming uniform scalar resistivity and viscosity. The flows originate from paired toroidal vortices (in what might be called a ``double smoke ring'' configuration), and are thought likely to be ubiquitous in the interior of toroidally driven magnetofluids of this type. The existence of such vortices is conjectured to characterize magnetofluids beyond the high-viscosity limit in which they are readily calculable.
Development of Toroidal Core Transformers
Energy Technology Data Exchange (ETDEWEB)
Leon, Francisco
2014-05-31
The original objective of this project was to design, build and test a few prototypes of singlephase dry-type distribution transformers of 25 kVA, 2.4 kV primary to 120 V transformers using cores made of a continuous steel strip shaped like a doughnut (toroid). At different points during the development of the project, the scope was enhanced to include the more practical case of a 25 kVA transformer for a 13.8 kV primary system voltage. Later, the scope was further expanded to design and build a 50 kVA unit to transformer voltage from 7.62 kV to 2x120 V. This is a common transformer used by Con Edison of New York and they are willing to test it in the field. The project officially started in September 2009 and ended in May 2014. The progress was reported periodically to DOE in eighteen quarterly reports. A Continuation Application was submitted to DOE in June 2010. In May 2011 we have requested a non-cost extension of the project. In December 2011, the Statement of Project Objectives (SOPO) was updated to reflect the real conditions and situation of the project as of 2011. A second Continuation Application was made and funding was approved in 2013 by DOE and the end date was extended to May 2014.The technical challenges that were overcome in this project include: the development of the technology to pass the impulse tests, derive a model for the thermal performance, produce a sound mechanical design, and estimate the inrush current. However, the greatest challenge that we faced during the development of the project was the complications of procuring the necessary parts and materials to build the transformers. The actual manufacturing process is relatively fast, but getting all parts together is a very lengthy process. The main products of this project are two prototypes of toroidal distribution transformers of 7.62 kV (to be used in a 13.8 kV system) to 2x120 V secondary (standard utilization voltage); one is rated at 25 kVA and the other at 50 kVA. The 25 k
Tokamak with mechanical compression of toroidal magnetic field
Ohkawa, Tihiro
1981-01-01
A tokamak apparatus includes a pressure vessel for defining a reservoir and confining liquid therein. A collapsible toroidal liner disposed within the pressure vessel defines a toroidal space within the liner. Liquid metal fills the reservoir outside said liner. A toroidal magnetic field is developed within the toroidal space about the major axis thereof. A toroidal plasma is developed within the toroidal space about the major axis thereof. Pressure is applied to the liquid metal to collapse the liner and reduce the volume of the toroidal space, thereby increasing the toroidal magnetic flux density therein.
ATF [Advanced Toroidal Facility]-2 studies
International Nuclear Information System (INIS)
Design studies for a low-aspect-ratio, large next-generation stellarator, ATF-II, with high-current-density, high-field, stable NbTi/Cu helical windings are described. The design parameters are an average plasma radius of 0.52 m, a major radius of 2 m, and a field on axis of 4-5 T, with 10 to 15 MW of heating power. Such a device would be comparable in scope to other next-generation stellarators but would have roughly the same aspect ratio as the tokamaks without, however, the need for current drive to sustain steady-state operation. A number of low-aspect-ratio physics issues need to be addressed in the design of ATF-II, primarily compromises between high-beta capability and good confinement properties. A six-field-period Compact Torsatron is chosen as a reference design for ATF-II, and its main features and performance predictions are discussed. An integrated (beta capability and confinement) optimization approach and optimization of superconducting windings are also discussed. 36 refs., 13 figs., 2 tabs
Performance and stability of near-unity aspect ratio plasmas in the Pegasus Toroidal Experiment
International Nuclear Information System (INIS)
The Pegasus Toroidal Experiment [R. Fonck et al., Bull. Am. Phys. Soc. 41, 1400 (1996)] is a spherical torus designed to study the limits of plasma behavior as the aspect ratio A approaches unity. Access to near-unity A is achieved through the use of a novel high-stress reinforced solenoid magnet. High toroidal beta βt is obtained in ohmically-heated plasmas by operation at low field with densities up to the Greenwald limit. Values of βt up to 20% and normalized beta up to 5 have been obtained. The ratio of plasma current to toroidal field rod current, known as the toroidal field utilization, reaches values as large as 1 but appears to approach a 'soft' boundary at that level related to both ohmic flux limitations and the onset of resistive magnetohydrodynamic (MHD) activity. The m/n=2/1 and 3/2 modes are most frequently observed, in agreement with the inferred safety factor profiles. Experiments are beginning to access the external kink stability boundary at edge safety factor q95=5, which is significantly higher than that observed in conventional tokamaks. Calculations using the DCON code [A. H. Glasser and M. S. Chance, Bull. Am. Phys. Soc. 42, 1848 (1997)] confirm instability to the ideal kink
Average beta measurement in EXTRAP T1
International Nuclear Information System (INIS)
Beginning with the ideal MHD pressure balance equation, an expression for the average poloidal beta, ΒΘ, is derived. A method for unobtrusively measuring the quantities used to evaluate ΒΘ in Extrap T1 is described. The results if a series of measurements yielding ΒΘ as a function of externally applied toroidal field are presented. (author)
Ohmically heated toroidal experiment (OHTE) mobile ignition test reactor facility concept study
International Nuclear Information System (INIS)
This report presents the results of a study to evaluate the use of an existing nuclear test complex at the Idaho National Engineering Laboratory (INEL) for the assembly, testing, and remote maintenance of the ohmically heated toroidal experiment (OHTE) compact reactor. The portable reactor concept is described and its application to OHTE testing and maintenance requirements is developed. Pertinent INEL facilities are described and several test system configurations that apply to these facilities are developed and evaluated
The toroid moment of Majorana neutrino
International Nuclear Information System (INIS)
The total set of electromagnetic characteristics of Majorana neutrinos is considered. It is shown that in the static limit (mi=mf=mν) the Majorana neutrinos possess only one electromagnetic characteristic, the toroidal dipole moment (anapole). We have calculated the diagonal toroidal moment (form factor) of the Majorana neutrino in the one-loop approximation of the Standard Model by the dispersion method. All external particles are on the mass shells and there are no problems with the physical interpretation of the final result. Different applications of the toroidal moment of Majorana neutrino are also discussed. 12 refs., 2 figs., 1 tab
Experimental study of toroidicity-induced Alfven eigenmode (TAE) stability at high q(0)
Energy Technology Data Exchange (ETDEWEB)
Batha, S.H.; Levinton, F.M. [Fusion Physics and Technology, Torrance, CA (United States); Spong, D.A. [Oak Ridge National Lab., TN (United States)] [and others
1995-07-01
Experiments to destabilize the Toroidicity-induced Alfven Eigenmode (TAE) by energetic alpha particles were performed on the Tokamak Fusion Test Reactor using deuterium and tritium fuel. To decrease the alpha particle pressure instability threshold, discharges with an elevated value of q(0) > 1.5 were used. By raising q(0), the radial location of the low toroidal-mode-number TAE gaps moves toward the magnetic axis and into alignment with the region of maximum alpha pressure gradient, thereby (in theory) lowering the value of {beta}{sub {alpha}}(0) required for instability. No TAE activity was observed when the central alpha particle {beta}{sub {alpha}} reached 0.08% in a discharge with fusion power of 2.4 MW. Calculations show that the fusion power is within a factor of 1.5 to 3 of the instability threshold.
Sliding joint concept for toroidal field coils of a tokamak
International Nuclear Information System (INIS)
A low-cost, compact, copper-coil ignition tokamak is the focus of design studies in FY85. For a minimum-cost machine, the toroidal field (TF) coils must be as compact as practical. On the other hand, smaller TF coils inhibit the assembly and maintenance of the components entrapped by the TF coils, such as the plasma vacuum vessel, limiter, poloidal field coils, etc. If the compact TF coil has at least two demountable electrical joints, removal of the outer part of the TF coil would permit servicing of the entrapped components. The vertical straight leg of a TF coil has the smallest cross-sectional area, but it experiences the largest tensile and compressive forces. The tensile load on the vertical leg can be eliminated if the demountable joints can slide. A possible sliding joint design concept is described in this paper. This sliding joint transfers only current. No forces are transferred from the outer curved leg to the straight leg of the TF coils. The outer curved leg can be separated at the sliding joint to gain access to the components inside the TF coil bore
Kinetic extensions of magnetohydrodynamic models for axisymmetric toroidal plasmas
International Nuclear Information System (INIS)
A nonvariational kinetic-MHD stability code (NOVA-K) has been developed to integrate a set of non-Hermitian integro-differential eigenmode equations due to energetic particles for axisymmetric toroidal plasmas in a general flux coordinate system with an arbitrary Jacobian. The NOVA-K code employs the Galerkin method involving Fourier expansions in the generalized poloidal angle θ and generalized toroidal angle /zeta/ directions, and cubic-B spline finite elements in the radial /Psi/ direction. Extensive comparisons with the existing variational ideal MHD codes show that the ideal MHD version of the NOVA-K code converges faster and gives more accurate results. The NOVA-K code is employed to study the effects of energetic particles on MHD-type modes: the stabilization of ideal MHD internal kink modes and the excitation of ''fishbone'' internal kink modes; and the alpha particle destabilization of toroidicity-induced Alfven eigenmodes (TAE) via transit resonances. Analytical theories are also presented to help explain the NOVA-K results. For energetic trapped particles generated by neutral beam injection (NBI) or ion cyclotron resonant heating (ICRH), a stability window for the n = 1 internal kink mode in the hot particle beta space exists even in the absence of the core ion finite Larmor radius effect. On the other hand, the trapped alpha particles are found to have negligible effects on the stability of the n = 1 internal kink mode, but the circulating alpha particles can strongly destabilize TAE modes via inverse Landau damping associated with the spatial gradient of the alpha particle pressure. 60 refs., 24 figs., 1 tab
Pareto optimal design of sectored toroidal superconducting magnet for SMES
Energy Technology Data Exchange (ETDEWEB)
Bhunia, Uttam, E-mail: ubhunia@vecc.gov.in; Saha, Subimal; Chakrabarti, Alok
2014-10-15
Highlights: • The optimization approach minimizes both the magnet size and necessary cable length of a sectored toroidal SMES unit. • Design approach is suitable for low temperature superconducting cable suitable for medium size SMES unit. • It investigates coil parameters with respect to practical engineering aspects. - Abstract: A novel multi-objective optimization design approach for sectored toroidal superconducting magnetic energy storage coil has been developed considering the practical engineering constraints. The objectives include the minimization of necessary superconductor length and torus overall size or volume, which determines a significant part of cost towards realization of SMES. The best trade-off between the necessary conductor length for winding and magnet overall size is achieved in the Pareto-optimal solutions, the compact magnet size leads to increase in required superconducting cable length or vice versa The final choice among Pareto optimal configurations can be done in relation to other issues such as AC loss during transient operation, stray magnetic field at outside the coil assembly, and available discharge period, which is not considered in the optimization process. The proposed design approach is adapted for a 4.5 MJ/1 MW SMES system using low temperature niobium–titanium based Rutherford type cable. Furthermore, the validity of the representative Pareto solutions is confirmed by finite-element analysis (FEA) with a reasonably acceptable accuracy.
Stability analysis of toroidicity-induced Alfven eigenmodes in TFTR DT experiments
International Nuclear Information System (INIS)
The toroidicity-induced Alfvin eigenmodes (TAE) with radially extended structure are found to be stable in the Tokamak Fusion Test Reactor Deuterium-Tritium plasmas. A core localized TAE mode is shown to exist near the center of the plasma at small magnetic shear and finite plasma beta, which can be destabilized by energetic alpha particles on TFTR. With additional instability drive from fast minority ions powered by ICRH, both the global and the core localized TAE modes can be readily destabilized
Tokamak with in situ magnetohydrodynamic generation of toroidal magnetic field
Schaffer, Michael J.
1986-01-01
A tokamak apparatus includes an electrically conductive metal pressure vessel for defining a chamber and confining liquid therein. A liner disposed within said chamber defines a toroidal space within the liner and confines gas therein. The metal vessel provides an electrically conductive path linking the toroidal space. Liquid metal is forced outwardly through the chamber outside of the toroidal space to generate electric current in the conductive path and thereby generate a toroidal magnetic field within the toroidal space. Toroidal plasma is developed within the toroidal space about the major axis thereof.
Toroidal Horizons in Binary Black Hole Mergers
Bohn, Andy; Teukolsky, Saul A
2016-01-01
We find the first binary black hole event horizon with a toroidal topology. It had been predicted that generically the event horizons of merging black holes should briefly have a toroidal topology, but such a phase has never been seen prior to this work. In all previous binary black hole simulations, in the coordinate slicing used to evolve the black holes, the topology of the event horizon transitions directly from two spheres during the inspiral to a single sphere as the black holes merge. We present a coordinate transformation to a foliation of spacelike hypersurfaces that "cut a hole" through the event horizon surface, resulting in a toroidal event horizon. A torus could potentially provide a mechanism for violating topological censorship. However, these toroidal event horizons satisfy topological censorship by construction, because we can always trivially apply the inverse coordinate transformation to remove the topological feature.
OCLATOR (One Coil Low Aspect Toroidal Reactor)
International Nuclear Information System (INIS)
A new approach to construct a tokamak-type reactor(s) is presented. Basically the return conductors of toroidal field coils are eliminated and the toroidal field coil is replaced by one single large coil, around which there will be placed several tokamaks or other toroidal devices. The elimination of return conductors should, in addition to other advantages, improve the accessibility and maintainability of the tokamaks and offer a possible alternative to the search for special materials to withstand large neutron wall loading, as the frequency of changeover would be increased due to minimum downtime. It also makes it possible to have a low aspect ratio tokamak which should improve the β limit, so that a low toroidal magnetic field strength might be acceptable, meaning that the NbTi superconducting wire could be used. This system is named OCLATOR
LASL toroidal reversed-field pinch programme
International Nuclear Information System (INIS)
The determination of the absolute energy loss due to radiation from impurities in the LASL toroidal reversed-field pinch experiment ZT-S is reported. The measurements show that over half the energy loss is accounted for by this mechanism. Thomson-scattering electron density measurements indicate only a gradual increase in temperature as the filling pressure is reduced, indicating an increased energy loss at lower pressures. Cylindrical and toroidal simulations of the experiment indicate either that a highly radiative pinch boundary or anomalous transport is needed to match the experimental results. New effects on the equilibrium due to plasma flows induced by the toroidal geometry are predicted by the toroidal simulations. The preliminary results on the low-temperature discharge cleaning of the ZT-S torus are reported. A description of the upgrade of the ZT-S experiment and the objectives, construction and theoretical predictions for the new ZT-40 experiment are given. (author)
Development of manufacturing technologies for ITER toroidal field coil conductors
International Nuclear Information System (INIS)
The Japan Atomic Energy Agency (JAEA) is responsible for procuring 25% of the ITER toroidal field (TF) coil conductors as the Japanese Domestic Agency (JADA) for the ITER project. The TF conductor is a circular shaped, cable-in-conduit conductor, composed of a cable and a stainless-steel conduit (jacket). The outer diameter and maximum length of the TF conductor are 43.7 mm and 760 m, respectively. JAEA has constructed a new conductor manufacturing facility. Prior to starting the conductor manufacturing, JAEA manufactured a 760 m-long Cu dummy conductor as a conductor manufacturing process qualification, such as processes of welding, cable insertion, compaction and spooling. All manufacturing processes have been qualified and JAEA has started to fabricate superconducting conductors for the TF coils. (author)
PIV-Analysis of collapsing toroidal droplets
Pairam, Ekapop; Berger, Eric; Fernandez-Nieves, Alberto; Georgia Tech Team
2012-11-01
Toroidal droplets are unstable and always undergo a transformation into spherical droplets driven by surface tension. They either break ala Rayleigh-Plateau if the torus is thin or grow fatter to become a single spherical droplet if the torus is fat. We analyze the velocity field inside and outside the toroidal droplet as it transforms into spherical droplets using the particle image velocimetry (PIV) method and compare with recent theoretical calculations for this process. NSF CAREER.
Time-Dependent of Accretion Flow with Toroidal Magnetic Field
Khesali, Alireza
2008-01-01
In the present study time evolution of quasi-spherical polytropic accretion flow with toroidal magnetic field was investigated. The study especially focused the astrophysically important case in which the adiabatic exponent $\\gamma=5/3$. In this scenario, it was assumed that the angular momentum transport is due to viscous turbulence and used $\\alpha$-prescription for kinematic coefficient of viscosity. The equations of accretion flow are solved in a simplified one-dimensional model that neglects the latitudinal dependence of the flow. In order to solve the integrated equations which govern the dynamical behavior of the accretion flow, self-similar solution was used. The solution provides some insight into the dynamics of quasi-spherical accretion flow and avoids many of the strictures of the steady self-similar solution. The effect of the toroidal magnetic field is considered with additional variable $\\beta[=p_{mag}/p_{gas}]$, where $p_{mag}$ and $p_{gas}$ are the magnetic and gas pressure, respectively. The...
Celebrating the Barrel Toroid commissioning
Peter Jenni
ATLAS invited Funding Agency representatives and Laboratory Heads directly related to the funding and construction of the Barrel Toroid for a small ceremony on 13th December 2006 at Point 1, in order to mark the successful first full excitation of the BT (see last eNews). On that date, which was during the December CERN Council week, several of the Funding Agency Heads or their representatives could be present, representing CEA France, INFN Italy, BMBF Germany, Spain, Sweden, Switzerland, Russia, JINR Dubna and CERN. Speeches were delivered by the ATLAS spokesperson Peter Jenni thanking the Funding Partners in the name of the Collaboration, by Magnet Project Leader Herman ten Kate tracing the BT construction history, and by the CERN Director-General Robert Aymar congratulating all those who have contributed to the successful project. Herman ten Kate addressing the delegates. The text of the introductory address by Peter Jenni is reproduced here. "It is a great pleasure for me to welcome you all here...
Anomalous transport in toroidal plasmas
International Nuclear Information System (INIS)
When the magnetic moment of particle is conserved, there are three mechanisms which cause anomalous transport. These are: variation of magnetic field strength in flux surface, variation of electrostatic potential in flux surface, and destruction of flux surface. The anomalous transport of different groups of particles resulting from each of these mechanisms is different. This fact can be exploited to determine the cause of transport operative in an experimental situation. This approach can give far more information on the transport than the standard confinement time measurements. To implement this approach, we have developed Monte Carlo codes for toroidal geometries. The equations of motion are developed in a set of non-canonical, practical Boozer co-ordinates by means of Jacobian transformations of the particle drift Hamiltonian equations of motion. Effects of collisions are included by appropriate stochastic changes in the constants of motion. Effects of the loop voltage on particle motions are also included. We plan to apply our method to study two problems: the problem of the hot electron tail observed in edge region of ZT-40, and the energy confinement time in TOKAPOLE II. For the ZT-40 problem three situations will be considered: a single mode in the core, a stochastic region that covers half the minor radius, a stochastic region that covers the entire plasma. A turbulent spectrum of perturbations based on the experimental data of TOKAPOLE II will be developed. This will be used to simulate electron transport resulting from ideal instabilities and resistive instabilities in TOKAPOLE II
Deconfinement in Yang-Mills Theory through Toroidal Compactification
Energy Technology Data Exchange (ETDEWEB)
Simic, Dusan; Unsal, Mithat; /Stanford U., Phys. Dept. /SLAC
2011-08-12
We introduce field theory techniques through which the deconfinement transition of four-dimensional Yang-Mills theory can be moved to a semi-classical domain where it becomes calculable using two-dimensional field theory. We achieve this through a double-trace deformation of toroidally compactified Yang-Mills theory on R{sup 2} x S{sub L}{sup 1} x S{sub {beta}}{sup 1}. At large N, fixed-L, and arbitrary {beta}, the thermodynamics of the deformed theory is equivalent to that of ordinary Yang-Mills theory at leading order in the large N expansion. At fixed-N, small L and a range of {beta}, the deformed theory maps to a two-dimensional theory with electric and magnetic (order and disorder) perturbations, analogs of which appear in planar spin-systems and statistical physics. We show that in this regime the deconfinement transition is driven by the competition between electric and magnetic perturbations in this two-dimensional theory. This appears to support the scenario proposed by Liao and Shuryak regarding the magnetic component of the quark-gluon plasma at RHIC.
Low-n shear Alfven spectra in axisymmetric toroidal plasmas
International Nuclear Information System (INIS)
In toroidal plasmas, the toroidal magnetic field is nonuniform over a magnetic surface and causes coupling of different poloidal harmonics. It is shown both analytically and numerically that the toroidicity not only breaks up the shear Alfven continuous spectrum, but also creates new, discrete, toroidicity-induced shear Alfven eigenmodes with frequencies inside the continuum gaps. Potential applications of the low-n toroidicity-induced shear Alfven eigenmodes on plasma heating and instabilities are addressed. 17 refs., 4 figs
MHD-Vlasov simulation of the toroidal Alfven eigenmode
International Nuclear Information System (INIS)
A new simulation method has been developed to investigate the excitation and saturation processes of toroidal Alfven eigenmodes (TAE modes). The background plasma is described by a full-MHD fluid model, while the kinetic evolution of energetic alpha particles is followed by the drift kinetic equation. The magnetic fluctuation of n = 2 mode develops and saturates at the level of 1.8x10-3 of the equilibrium field when the initial beta of alpha particles is 2% at the magnetic axis. After saturation, the TAE mode amplitude shows an oscillatory behavior with a frequency corresponding to the bounce frequency of the alpha particles trapped by the TEA mode. The decrease of the power transfer rate from the alpha particles to the TAE mode, which is due to the trapped particle effect of a finite-amplitude wave, causes the saturation. From the linear growth rate the saturation level can be estimated. (author)
Plasma engineering assessments of compact ignition experiments
International Nuclear Information System (INIS)
Confinement, startup sequences, and fast-alpha particle effects are assessed for a class of compact tokamak ignition experiments having high toroidal magnetic fields (8 to 12 T) and high toroidal currents (7 to 10 MA). The uncertainties in confinement scaling are spanned through examples of performance with an optimistic model based on ohmically heated plasmas and a pessimistic model that includes confinement degradation by both auxiliary and alpha heating. The roles of neoclassical resistivity enhancement and sawtooth behavior are also evaluated. Copper toroidal field coils place restrictions on pulse lengths due to resistive heating, so a simultaneous rampup of the toroidal field and plasma current is proposed as a means of compressing the startup phase and lengthening the burn phase. If the ignition window is small, fast-alpha particle physics is restricted to the high-density regime where a short slowing-down time leads to low fast-particle density and pressure contributions. Under more optimistic confinement, a larger ignition margin broadens the range of alpha particle physics that can be addressed. These issues are illustrated through examples of transport simulations for a set of machine parameters called BRAND-X, which typify the designs under study
... South Asian (Indian, Pakistani, etc.), Southeast Asian and Chinese descent. 1 Beta Thalassemia ßß Normal beta globin ... then there is a 25% chance with each pregnancy that their child will inherit two abnormal beta ...
Long-wavelength microinstabilities in toroidal plasmas
International Nuclear Information System (INIS)
Realistic kinetic toroidal eigenmode calculations have been carried out to support a proper assessment of the influence of long-wavelength microturbulence on transport in tokamak plasmas. In order to efficiently evaluate large-scale kinetic behavior extending over many rational surfaces, significant improvements have been made to a toroidal finite element code used to analyze the fully two-dimensional (r,θ) mode structures of trapped-ion and toroidal ion temperature gradient (ITG) instabilities. It is found that even at very long wavelengths, these eigenmodes exhibit a strong ballooning character with the associated radial structure relatively insensitive to ion Landau damping at the rational surfaces. In contrast to the long-accepted picture that the radial extent of trapped-ion instabilities is characterized by the ion-gyroradius-scale associated with strong localization between adjacent rational surfaces, present results demonstrate that under realistic conditions, the actual scale is governed by the large-scale variations in the equilibrium gradients. Applications to recent measurements of fluctuation properties in TFTR L-mode plasmas indicate that the theoretical trends appear consistent with spectral characteristics as well as rough heuristic estimates of the transport level. Benchmarking calculations in support of the development of a three-dimensional toroidal gyrokinetic code indicate reasonable agreement with respect to both the properties of the eigenfunctions and the magnitude of the eigenvalues during the linear phase of the simulations of toroidal ITG instabilities
ORNL Levitated Toroidal Multipole Program
International Nuclear Information System (INIS)
We are studying confinement of gun-injected and microwave-produced plasmas in a levitated toroidal quadrupole in which internal hoop supports are not present to limit plasma confinement. Electromagnetic levitation is made possible by reducing the 60 Hz skin depth in the copper walls with liquid nitrogen cooling. The cooling also increases the magnetic field lifetime so that an e-folding time of 17 ms was measured after crowbarring. Computations indicate that in a properly designed, larger device, an e-folding time of 100 ms can be reached. Washer-gun hydrogen plasmas and Bostick-type lithium gun plasmas were injected into the levitated quadrupole with typical parameters: B ≥ 3 kG, Te ≈ 3 eV, ni ≈ 109 cm-3, and 1 i i ≈ 1010 cm-3, Te ≈ 30 eV, and τ/τBohm ≈ 30. Density fluctuations (Δn/n) in the region of good field curvature were less than 0.05 and in the region of bad curvature 0.10-0.25. With the removal of the magnetic well (by removing the inner hoop), τ/τBohm and ni each dropped a factor of 4 and Δn/n became greater than 0.25. Recent experiments using 200 W at λ = 3 cm have produced plasmas with higher densities (n > 1011 cm-3 assuming Te ≈ 100 eV), higher temperatures (Te ≈ 100 eV) and longer lifetimes (τ ≈ 80 μs ≈ 40 τBohm) than in the λ = 12 cm experiments. Detailed probe measurements of density and temperature are consistent with models for plasma behaviour based on computed magnetic field plots. Probe data show clear evidence of the changes in heating zones during the variation of the sinusoidal magnetic field and a large obstacle intercepting all flux lines effectively prevents the formation of the plasma. We are also studying a levitated helical hexapole, whose advantages over the quadrupole are a better ratio of connection length to radius of bad curvature and more confinement volume. (author)
Superconducting toroid design for the ATLAS experiment at LHC
International Nuclear Information System (INIS)
The ATLAS Experiment proposed for LHC will use toroidal magnet systems to achieve high muon momentum resolution. The proposal is based on an air-cored superconducting toroid magnet system consisting of a long barrel toroid with a pair of end cap toroids to provide high resolution at large rapidity. Each end cap toroid will have an outer diameter of approximately 11m and an axis length of 5m and will provide field integrals in the range 4-8Tm over the rapidity span η = 1.5--2.8. This paper presents the magnetic, mechanical and cryogenic design of the end cap toroid magnet systems
Tokamak with liquid metal for inducing toroidal electrical field
Ohkawa, Tihiro
1981-01-01
A tokamak apparatus includes a vessel for defining a reservoir and confining liquid therein. A toroidal liner disposed within said vessel defines a toroidal space within the liner confines gas therein. Liquid metal fills the reservoir outside the liner. A magnetic field is established in the liquid metal to develop magnetic flux linking the toroidal space. The gas is ionized. The liquid metal and the toroidal space are moved relative to one another transversely of the space to generate electric current in the ionized gas in the toroidal space about its major axis and thereby heat plasma developed in the toroidal space.
Bazeia, D; Menezes, R
2015-01-01
We study the presence of lumplike solutions in models described by a single real scalar field with standard kinematics in two-dimensional spacetime. The results show several distinct models that support the presence of bell-shaped, lumplike structures which may live in a compact space.
About the Toroidal Magnetic Field of a Tokamak Burning Plasma Experiment with Superconducting Coils
International Nuclear Information System (INIS)
In tokamaks, the strong dependence on the toroidal magnetic field of both plasma pressure and energy confinement is what makes possible the construction of small and relatively inexpensive burning plasma experiments using high-field resistive coils. On the other hand, the toroidal magnetic field of tokamaks using superconducting coils is limited by the critical field of superconductivity. In this article, we examine the relative merit of raising the magnetic field of a tokamak plasma by increasing its aspect ratio at a constant value of the peak field in the toroidal magnet. Taking ITER-FEAT as an example, we find that it is possible to reach thermonuclear ignition using an aspect ratio of approximately 4.5 and a toroidal magnetic field of 7.3 T. Under these conditions, fusion power density and neutron wall loading are the same as in ITER [International Thermonuclear Experimental Reactor], but the normalized plasma beta is substantially smaller. Furthermore, such a tokamak would be able to reach an energy gain of approximately 15 even with the deterioration in plasma confinement that is known to occur near the density limit where ITER is forced to operate
A Classification Scheme For Toroidal Molecules
Berger, J; Berger, Jorge; Avron, Joseph E.
1995-01-01
We construct a class of periodic tilings of the plane, which corresponds to toroidal arrangements of trivalent atoms, with pentagonal, hexagonal and heptagonal rings. Each tiling is characterized by a set of four integers and determines a toroidal molecule. The tiling rules are motivated by geometric considerations and the tiling patterns are rich enough to describe a wide class of toroidal carbon molecules, with a broad range of shapes and numbers of atoms. The molecular dimensions are simply related to the integers that determine the tiling. The configurational energy and the delocalisation energy of several molecules obtained in this way were computed for Tersoff and H\\"uckel models. The results indicate that many of these molecules are not strained, and may be expected to be stable. We studied the influence of size on the H\\"{u}ckel spectrum: it bears both similarities and differences as compared with the case of tubules.
Toroidal high temperature superconducting coils for ISTTOK
Energy Technology Data Exchange (ETDEWEB)
Fernandes, H., E-mail: hf@ipfn.ist.utl.pt [Associacao Euratom/IST, Instituto de Plasmas e Fusao Nuclear, Laboratorio Associado, Instituto Superior Tecnico, 1049-001 Lisboa (Portugal); Goemoery, F. [Institute of Electrical Engineering, Slovak Academy of Sciences, Dubravska cesta 9, 84104 Bratislava (Slovakia); Corte, A. della; Celentano, G. [ENEA C.R. Frascati, Via E. Fermi 45, 00044 Frascati (Italy); Souc, J. [Institute of Electrical Engineering, Slovak Academy of Sciences, Dubravska cesta 9, 84104 Bratislava (Slovakia); Silva, C.; Carvalho, I.; Gomes, R. [Associacao Euratom/IST, Instituto de Plasmas e Fusao Nuclear, Laboratorio Associado, Instituto Superior Tecnico, 1049-001 Lisboa (Portugal); Di Zenobio, A.; Messina, G. [ENEA C.R. Frascati, Via E. Fermi 45, 00044 Frascati (Italy)
2011-10-15
High temperature superconductors (HTS) are very attractive to be used in fusion devices mainly due to lower operations costs. The HTS technology has reached a point where the construction of toroidal field coils for a tokamak is possible. The feasibility of a tokamak operating with HTS is extremely relevant and ISTTOK is the ideal candidate for a meaningful test due to its small size (and consequently lower cost) and the possibility to operate in a steady-state inductive regime. In this paper, a conceptual study of the ISTTOK upgrade to a superconducting device is presented, along with the relevant boundary conditions to achieve a permanent toroidal field with HTS. It is shown that the actual state of the art in HTS allows the design of a toroidal field coil capable of generating the appropriate field on plasma axis while respecting the structural specification of the machine.
Toroidal high temperature superconducting coils for ISTTOK
International Nuclear Information System (INIS)
High temperature superconductors (HTS) are very attractive to be used in fusion devices mainly due to lower operations costs. The HTS technology has reached a point where the construction of toroidal field coils for a tokamak is possible. The feasibility of a tokamak operating with HTS is extremely relevant and ISTTOK is the ideal candidate for a meaningful test due to its small size (and consequently lower cost) and the possibility to operate in a steady-state inductive regime. In this paper, a conceptual study of the ISTTOK upgrade to a superconducting device is presented, along with the relevant boundary conditions to achieve a permanent toroidal field with HTS. It is shown that the actual state of the art in HTS allows the design of a toroidal field coil capable of generating the appropriate field on plasma axis while respecting the structural specification of the machine.
Toroidal mode-conversion in the ICRF
International Nuclear Information System (INIS)
Mode-conversion is studied in the ion-cyclotron range of frequencies (ICRF) taking into account the toroidal geometry relevant for tokamaks. The global wavefields obtained using the gyrokinetic toroidal PENN code illustrate how the fast wave propagates to the neighborhood of the ion-ion hybrid resonance, where it is converted to a slow wave which deposits the wave energy through resonant interactions with the particles. The power deposition profiles obtained are dramatically different from the toroidal resonance absorption, showing that Budden's model is not a good approximation in the torus. Radially and poloidally localized wavefield structures characteristic of slow wave eigenmodes are predicted and could in experiments be driven to large amplitudes so as to interact efficiently with fast particles. (author) 5 figs., 1 tab., 48 refs
Toroidal mode conversion in the ICRF
International Nuclear Information System (INIS)
Mode conversion is studied in the ion cyclotron range of frequencies (ICRF), taking into account the toroidal geometry relevant for tokamaks. The global wavefields obtained using the gyrokinetic toroidal PENN code illustrate how the fast wave propagates to the neighbourhood of the ion-ion hybrid resonance, where it is converted to a slow wave that deposits the wave energy through resonant Landau and cyclotron interactions with the particles. The power deposition profiles obtained are dramatically different from the toroidal resonance absorption, showing that Budden's fluid model is not a good approximation in the torus. Radially and poloidally localized wavefield structures characteristic of slow wave eigenmodes are predicted, which could be used in experiments to form transport barriers and to interact with fast particles. (author)
Models for large superconducting toroidal magnet systems
International Nuclear Information System (INIS)
Prior to the design of large GJ toroidal magnet systems it is appropriate to procure small scale models, which can simulate their pertinent properties and allow to investigate their relevant phenomena. The important feature of the model is to show under which circumstances the system performance can be extrapolated to large magnets. Based on parameters such as the maximum magnetic field and the current density, the maximum tolerable magneto-mechanical stresses, a simple method of designing model magnets is presented. It is shown how pertinent design parameters are changed when the toroidal dimensions are altered. In addition some conductor cost estimations are given based on reactor power output and wall loading
Toroidal Horizons in Binary Black Hole Mergers
Bohn, Andy; Kidder, Lawrence E.; Teukolsky, Saul A.
2016-01-01
We find the first binary black hole event horizon with a toroidal topology. It had been predicted that generically the event horizons of merging black holes should briefly have a toroidal topology, but such a phase has never been seen prior to this work. In all previous binary black hole simulations, in the coordinate slicing used to evolve the black holes, the topology of the event horizon transitions directly from two spheres during the inspiral to a single sphere as the black holes merge. ...
Toroidal Precession as a Geometric Phase
Energy Technology Data Exchange (ETDEWEB)
J.W. Burby and H. Qin
2012-09-26
Toroidal precession is commonly understood as the orbit-averaged toroidal drift of guiding centers in axisymmetric and quasisymmetric configurations. We give a new, more natural description of precession as a geometric phase effect. In particular, we show that the precession angle arises as the holonomy of a guiding center's poloidal trajectory relative to a principal connection. The fact that this description is physically appropriate is borne out with new, manifestly coordinate-independent expressions for the precession angle that apply to all types of orbits in tokamaks and quasisymmetric stellarators alike. We then describe how these expressions may be fruitfully employed in numerical calculations of precession.
Some properties of toroidal isodynamic magnetostatic equilibria
Energy Technology Data Exchange (ETDEWEB)
Aly, J.-J. [AIM, Unite Mixte de Recherche CEA, CNRS, Universite Paris VII, UMR no 7158, Centre d' Etudes de Saclay, F-91191 Gif sur Yvette Cedex (France)
2011-09-15
We establish some general properties of a 3D isodynamic magnetostatic equilibrium admitting a family of nested toroidal flux surfaces. In particular, we use the virial theorem to prove a simple relation between the total pressure (magnetic + thermal) and the magnetic pressure on each flux surface, and we derive some useful consequences of the latter. We also show the constancy on each rational surface of two integrals along magnetic lines. As a simple application of our results, we show the nonexistence of an equilibrium with vanishing toroidal current, and of an equilibrium with closed lines.
Anomalous transport equations in toroidal plasmas
International Nuclear Information System (INIS)
Reduced transport equations for a toroidal plasma with fluctuations are derived. These equations include the effects of both anomalous and standard neoclassical transport, and allow clarification of the structure of convective fluxes caused by electrostatic and magnetic fluctuations. Special attention is paid to the combined effects of fluctuations and toroidicity on the transport. The formulation retains the effects of a magnetic field inhomogeneity on the anomalous transport. It is shown that phase space diffusion caused by the gradient in the equilibrium magnetic field appears as a pinch flux in the real space
The effect of sheared toroidal rotation on pressure driven magnetic islands in toroidal plasmas
Hegna, C. C.
2016-05-01
The impact of sheared toroidal rotation on the evolution of pressure driven magnetic islands in tokamak plasmas is investigated using a resistive magnetohydrodynamics model augmented by a neoclassical Ohm's law. Particular attention is paid to the asymptotic matching data as the Mercier indices are altered in the presence of sheared flow. Analysis of the nonlinear island Grad-Shafranov equation shows that sheared flows tend to amplify the stabilizing pressure/curvature contribution to pressure driven islands in toroidal tokamaks relative to the island bootstrap current contribution. As such, sheared toroidal rotation tends to reduce saturated magnetic island widths.
Non-compact Torsion Free Ball Quotients
Kasparian, Azniv
2012-01-01
The present note specifies the Kodaira-Enriques classification type of a non-compact torsion free ball quotient ${\\mathbb B} / \\Gamma$. It turns out that ${\\mathbb B} / \\Gamma$ can be birational to a non-simple abelian surface, to an elliptic fibration of Kodaira dimension 1 with base of genus $\\leq 1$ or to a minimal surface of general type. The argument makes use of the embedding of the fundamental group $\\pi_1(T_i)$ of a smooth elliptic irreducible component $T_i$ of the toroidal compactifying divisor $T= ({\\mathbb B} / \\Gamma)' \\setminus ({\\mathbb B} / \\Gamma)$ in the fundamental group $\\pi_1 (X')$ of the toroidal compactification $X'= ({\\mathbb B} / \\Gamma)$. The note elaborates also on various consequences of the Kobayashi non-hyperbolicity of $X'$ and the Kobayashi hyperbolicity of $ {\\mathbb B} / \\Gamma$.
Energy Technology Data Exchange (ETDEWEB)
Bluemich, Bernhard; Haber-Pohlmeier, Sabina; Zia, Wasif [RWTH Aachen Univ. (Germany). Inst. fuer Technische und Makromolekulare Chemie (ITMC)
2014-06-01
Nuclear Magnetic Resonance (NMR) spectroscopy is the most popular method for chemists to analyze molecular structures, while Magnetic Resonance Imaging (MRI) is a non-invasive diagnostic tool for medical doctors that provides high-contrast images of biological tissue. In both applications, the sample (or patient) is positioned inside a large, superconducting magnet to magnetize the atomic nuclei. Interrogating radio-frequency pulses result in frequency spectra that provide the chemist with molecular information, the medical doctor with anatomic images, and materials scientist with NMR relaxation parameters. Recent advances in magnet technology have led to a variety of small permanent magnets to allow compact and low-cost instruments. The goal of this book is to provide an introduction to the practical use of compact NMR at a level nearly as basic as the operation of a smart phone.
International Nuclear Information System (INIS)
Nuclear Magnetic Resonance (NMR) spectroscopy is the most popular method for chemists to analyze molecular structures, while Magnetic Resonance Imaging (MRI) is a non-invasive diagnostic tool for medical doctors that provides high-contrast images of biological tissue. In both applications, the sample (or patient) is positioned inside a large, superconducting magnet to magnetize the atomic nuclei. Interrogating radio-frequency pulses result in frequency spectra that provide the chemist with molecular information, the medical doctor with anatomic images, and materials scientist with NMR relaxation parameters. Recent advances in magnet technology have led to a variety of small permanent magnets to allow compact and low-cost instruments. The goal of this book is to provide an introduction to the practical use of compact NMR at a level nearly as basic as the operation of a smart phone.
New material equations for electromagnetism with toroid polarizations
International Nuclear Information System (INIS)
With regard to the toroid contributions, a modified system of equations of electrodynamics moving continuous media has been obtained. Alternative formalisms to introduce the toroid moment contributions in the equations of electromagnetism has been worked out. The two four-potential formalism has been developed. Lorentz transformation laws for the toroid polarizations has been given. Covariant form of equations of electrodynamics of continuous media with toroid polarizations has been written. (author)
Matter in the form of toroidal electromagnetic vortices
Hagen, Wilhelm F.
2015-09-01
The creation of charged elementary particles from neutral photons is explained as a conversion process of electromagnetic (EM) energy from linear to circular motion at the speed of light into two localized, toroidal shaped vortices of trapped EM energy that resist change of motion, perceptible as particles with inertia and hence mass. The photon can be represented as a superposition of left and right circular polarized transverse electric fields of opposite polarity originating from a common zero potential axis, the optical axis of the photon. If these components are separated by interaction with a strong field (nucleon) they would curl up into two electromagnetic vortices (EMV) due to longitudinal magnetic field components forming toroids. These vortices are perceptible as opposite charged elementary particles e+/- . These spinning toroids generate extended oscillating fields that interact with stationary field oscillations. The velocity-dependent frequency differences cause beat signals equivalent to matter waves, leading to interference. The extended fields entangled with every particle explain wave particle duality issues. Spin and magnetic moment are the natural outcome of these gyrating particles. As the energy and hence mass of the electron increases with acceleration so does its size shrink proportional to its reduced wavelength. The artificial weak and strong nuclear forces can be easily explained as different manifestations of the intermediate EM forces. The unstable neutron consists of a proton surrounded by a contracted and captured electron. The associated radial EM forces represent the weak nuclear force. The deuteron consists of two axially separated protons held together by a centrally captured electron. The axial EM forces represent the strong nuclear force, providing stability for "neutrons" only within nucleons. The same principles were applied to determine the geometries of force-balanced nuclei. The alpha-particle emerges as a very compact
Trapped ion mode in toroidally rotating plasmas
International Nuclear Information System (INIS)
The influence of radially sheared toroidal flows on the Trapped Ion Mode (TIM) is investigated using a two-dimensional eigenmode code. These radially extended toroidal microinstabilities could significantly influence the interpretation of confinement scaling trends and associated fluctuation properties observed in recent tokamak experiments. In the present analysis, the electrostatic drift kinetic equation is obtained from the general nonlinear gyrokinetic equation in rotating plasmas. In the long perpendicular wavelength limit kτρbi much-lt 1, where ρbi is the average trapped-ion banana width, the resulting eigenmode equation becomes a coupled system of second order differential equations nmo for the poloidal harmonics. These equations are solved using finite element methods. Numerical results from the analysis of low and medium toroidal mode number instabilities are presented using representative TFTR L-mode input parameters. To illustrate the effects of mode coupling, a case is presented where the poloidal mode coupling is suppressed. The influence of toroidal rotation on a TFTR L-mode shot is also analyzed by including a beam species with considerable larger temperature. A discussion of the numerical results is presented
ATLAS Barrel Toroid magnet reached nominal field
2006-01-01
Â OnÂ 9 November the barrel toroid magnet reached its nominal field of 4 teslas, with an electrical current of 21 000 amperes (21 kA) passing through the eight superconducting coils as shown on this graph
Celebration for the ATLAS Barrel Toroid magnet
2007-01-01
Representatives from Funding Agencies and Barrel Toroid Magnet Laboratories during the ceremony. From left to right: Jean Zinn-Justin (Head of DAPNIA/CEA/Saclay), CERN Director-General Robert Aymar, and Roberto Petronzio (President INFN).Allan Clark (DPNC University Geneva) and Enrique Fernandez (IFAE Barcelona) were among the guests visiting the ATLAS cavern. The barrel toroid is visible in the background. A celebration took place at Point 1 on 13 December to toast the recent powering-up of the ATLAS barrel toroid magnet to full field (Bulletin No. 47-48/06). About 70 guests were invited to attend, mainly composed of representatives from funding partners and key members of the laboratory management teams of the barrel toroid magnet, representing CEA France, INFN Italy, BMBF Germany, Spain, Sweden, Switzerland, Russia, JINR Dubna and CERN. An introductory speech by ATLAS spokesperson Peter Jenni the scene for evening. This was followed by the ATLAS magnet system project leader Herman Ten Kate's account of the...
ATLAS: Full power for the toroid magnet
2006-01-01
The 9th of November was a memorable day for ATLAS. Just before midnight, the gigantic Barrel toroid magnet reached its nominal field of 4 teslas in the coil windings, with an electrical current of 21000 amperes (21 kA) passing through the eight superconducting coils (as seen on the graph). This achievement was obtained after several weeks of commissioning. The ATLAS Barrel Toroid was first cooled down for about six weeks in July-August to -269Â°C (4.8 K) and then powered up step-by-step in successive test sessions to 21 kA. This is 0.5 kA above the current required to produce the nominal magnetic field. Afterwards, the current was safely switched off and the stored magnetic energy of 1.1 gigajoules was dissipated in the cold mass, raising its temperature to a safe -218Â°C (55 K). 'We can now say that the ATLAS Barrel Toroid is ready for physics,' said Herman ten Kate, project leader for the ATLAS magnet system. The ATLAS barrel toroid magnet is the result of a close collaboration between the magnet la...
Reduced Magnetohydrodynamic Equations in Toroidal Geometry
Institute of Scientific and Technical Information of China (English)
REN Shen-Ming; YU Guo-Yang
2001-01-01
By applying a new assumption of density, I.e. R2 p = const, the continuity equation is satisfied to the order ofe2`+with e being the inverse aspect ratio. In the case of large aspect ratio, a set of reduced magnetohydrodynamicequations in toroidal geometry are obtained. The new assumption about the density is supported by experimentalobservation to some extent.
Chiral Anomaly in Toroidal Carbon Nanotubes
Sasaki, K.
2001-01-01
It is pointed out that the chiral anomaly in 1+1 dimensions should be observed in toroidal carbon nanotubes on a planar geometry with varying magnetic field. We show that the chiral anomaly is closely connected with the persistent current in a one-dimensional metallic ring.
Toroidal groups line bundles, cohomology and quasi-Abelian varieties
Kopfermann, Klaus
2001-01-01
Toroidal groups are the connecting link between torus groups and any complex Lie groups. Many properties of complex Lie groups such as the pseudoconvexity and cohomology are determined by their maximal toroidal subgroups. Quasi-Abelian varieties are meromorphically separable toroidal groups. They are the natural generalisation of the Abelian varieties. Nevertheless, their behavior can be completely different as the wild groups show.
On the stabilization of toroidal pinches by finite larmor radius effects and toroidal magnetic field
International Nuclear Information System (INIS)
The radial eigenvalue problem for internal modes in a large aspect ratio toriodal pinch has been solved. A particularly stable regime for a weak but nonzero toroidal magnetic field has been found. (31 refs.)
International Nuclear Information System (INIS)
It has been observed that 'runaway oscillations' in the toroidal current of the magnetized resistive toroidal plasma may cause continuous tearing activity, resulting in 'spiky' net toroidal current and modulation of toroidal and poloidal magnetic fields of the plasma with a definite phase relationship, depending upon the magnitude of vertical magnetic field. The present experimental results on current decay and recovery are explained from the point of view of helicity conservation. (author)
Dynamical model for the toroidal sporadic meteors
Energy Technology Data Exchange (ETDEWEB)
Pokorný, Petr; Vokrouhlický, David [Institute of Astronomy, Charles University, V Holešovičkách 2, CZ-18000 Prague 8 (Czech Republic); Nesvorný, David [Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Suite 300, Boulder, CO 80302 (United States); Campbell-Brown, Margaret; Brown, Peter, E-mail: petr.pokorny@volny.cz, E-mail: vokrouhl@cesnet.cz, E-mail: davidn@boulder.swri.edu, E-mail: margaret.campbell@uwo.ca, E-mail: pbrown@uwo.ca [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada)
2014-07-01
More than a decade of radar operations by the Canadian Meteor Orbit Radar have allowed both young and moderately old streams to be distinguished from the dispersed sporadic background component. The latter has been categorized according to broad radiant regions visible to Earth-based observers into three broad classes: the helion and anti-helion source, the north and south apex sources, and the north and south toroidal sources (and a related arc structure). The first two are populated mainly by dust released from Jupiter-family comets and new comets. Proper modeling of the toroidal sources has not to date been accomplished. Here, we develop a steady-state model for the toroidal source of the sporadic meteoroid complex, compare our model with the available radar measurements, and investigate a contribution of dust particles from our model to the whole population of sporadic meteoroids. We find that the long-term stable part of the toroidal particles is mainly fed by dust released by Halley type (long period) comets (HTCs). Our synthetic model reproduces most of the observed features of the toroidal particles, including the most troublesome low-eccentricity component, which is due to a combination of two effects: particles' ability to decouple from Jupiter and circularize by the Poynting-Robertson effect, and large collision probability for orbits similar to that of the Earth. Our calibrated model also allows us to estimate the total mass of the HTC-released dust in space and check the flux necessary to maintain the cloud in a steady state.
The Segmented Bifilar Contrawound Toroidal Helical Antenna.
Vanvoorhies, Kurt Louis
The segmented bifilar contrawound toroidal helical antenna, a.k.a. QuadContra antenna creates a toroidal magnetic current whose radiated electromagnetic fields emulate those of an electric dipole located normal to the plane of the toroidal helix. This antenna is a magnetic dual of the constant current electric loop antenna. Its principal advantages of reduced size and low profile result from both its circular geometry and from the velocity factor of its slow wave contrawound helical structure. This antenna is constructed by winding two conductors in contrawound relation to each other on a toroidal form, dividing the winding into an even number of segments, and reversing the pitch sense of each conductor from one segment to another. Feed ports are located on the conductors at the segment boundaries, and are connected in alternate phase to a central signal terminal via balanced and tuned transmission line elements. At resonance, each winding segment supports a quarter-wave sinusoidal current distribution. Toroidal electric current components are canceled, and poloidal current components are enhanced in the resulting anti-symmetric mode current distribution. This study measured and simulated the velocity factor, input impedance, bandwidth and simulated the radiation gain and pattern for a variety of linear and toroidal structures. The velocity factor, modeled as a power function of the ratio of axial winding length to wire length, was two to three times slower for the anti-symmetric mode contrawound helix than for a comparable monofilar helix. The radiation characteristics of the antenna were simulated using the OSU ESP4 Moment Method based program, after making extensive improvements to accommodate a wide variety of antenna configurations and to automatically find resonant frequencies. The simulated QuadContra antenna radiates with vertically polarization in a dipole-like pattern having a gain about 2 dB less than the dipole. The gain falls off dramatically for
Muon dynamics in a toroidal sector magnet
International Nuclear Information System (INIS)
The present scenario for the cooling channel in a high brightness muon collider calls for a quasi-continuous solenoidal focusing channel. The beam line consists of a periodic array of hydrogen absorbers immersed in a solenoid with alternating focusing field and rf linacs at the zero field points. Solenoids and toroidal sectors have a natural place in muon collider design given the large emittance of the beam and consequently, the large transverse momentum of the initial pion beam or the decay muon beam. Bent solenoids as shown were studied for use at the front end of the machine, as part of the capture channel and more recently as part of a diagnostic setup to measure the position and momentum of muons. The authors present a Hamiltonian formulation of muon dynamics in toroidal sector solenoids (bent solenoid)
Anomalous transport theory for toroidal helical plasmas
International Nuclear Information System (INIS)
Anomalous transport coefficients in toroidal helical plasmas are studied, based on the innovative theoretical method. The self-sustained turbulence is analyzed by balancing the nonlinear growth due to the current diffusivity with the nonlinear damping by the ion viscosity and thermal conductivity. Interchange and ballooning mode turbulence is investigated, and the geometrical dependence of the anomalous transport coefficient is clarified. Variation of transport owing to the geometrical difference in toroidal helical plasmas is illustrated. The mechanism for confinement improvement is searched for. To verify the nonlinear destabilization and the self-sustained state, the nonlinear simulation of the interchange mode turbulence is performed in a sheared slab. It is demonstrated that the nonlinear enhancement of the growth rate occurs when the fluctuation amplitude exceeds the critical level. In the saturation stage, the fluctuation level becomes higher associated with the enhanced nonlinear growth. (author)
Diffusiophoresis of a charged toroidal polyelectrolyte.
Tseng, Shiojenn; Hsu, Yen-Rei; Hsu, Jyh-Ping
2016-06-01
Considering recent application of concentration driven motion of charged nanoparticles in sensing technology, we model the diffusiophoresis of an isolated toroidal polyelectrolyte (PE) for the first time. Choosing an aqueous KCl solution for illustration, its behavior under various conditions is simulated by varying the double layer thickness, the size of toroid, and its softness and fixed charge density. We show that the behavior of the present PE can be different both quantitatively and qualitatively from that of the corresponding spherical PE. This arises from the competition of the hydrodynamic force and the electric force acting on a PE. The geometry and the nature of a PE can also influence appreciably its behavior, yielding complicated and interesting results. PMID:26970033
Antimicrobial Peptides in Toroidal and Cylindrical Pores
Mihajlovic, Maja; Lazaridis, Themis
2010-01-01
Antimicrobial peptides (AMPs) are small, usually cationic peptides, which permeabilize biological membranes. Their mechanism of action is still not well understood. Here we investigate the preference of alamethicin and melittin for pores of different shapes, using molecular dynamics (MD) simulations of the peptides in pre-formed toroidal and cylindrical pores. When an alamethicin hexamer is initially embedded in a cylindrical pore, at the end of the simulation the pore remains cylindrical or ...
Kinetic Damping of Toroidal Alfven Eigenmodes
Energy Technology Data Exchange (ETDEWEB)
G.Y. Fu; H.L. Berk; A. Pletzer
2005-05-03
The damping of Toroidal Alfven Eigenmodes in JET plasmas is investigated by using a reduced kinetic model. Typically no significant damping is found to occur near the center of the plasma due to mode conversion to kinetic Alfven waves. In contrast, continuum damping from resonance near the plasma edge may be significant, and when it is, it gives rise to damping rates that are compatible with the experimental observations.
Toroidal geometry subroutines for MORSE-CG
International Nuclear Information System (INIS)
The equations, coding, and procedures that are required to include a torus in the Combinatorial Geometry subroutines of the MORSE-CG code are described. The derivation and solutions of the quartic equation that describes a torus along with additional subroutines and the modifications to existing subroutines required to carry out the transport of neutrons and gamma rays in toroidal geometry are presented. The input requirements and a sample problem are included
Stellarator approach to toroidal plasma confinement
International Nuclear Information System (INIS)
An overview is presented of the development and current status of the stellarator approach to controlled thermonuclear confinement. Recent experimental, theoretical, and systems developments have made this concept a viable option for the evolution of the toroidal confinement program. Some experimental study of specific problems associated with departure from two-dimensional symmetry must be undertaken before the full advantages and opportunities of steady-state, net-current-free operation can be realized
Aspects of Tokamak toroidal magnet protection
Energy Technology Data Exchange (ETDEWEB)
Green, R.W.; Kazimi, M.S.
1979-07-01
Simple but conservative geometric models are used to estimate the potential for damage to a Tokamak reactor inner wall and blanket due to a toroidal magnet field collapse. The only potential hazard found to exist is due to the MHD pressure rise in a lithium blanket. A survey is made of proposed protection methods for superconducting toroidal magnets. It is found that the two general classifications of protection methods are thermal and electrical. Computer programs were developed which allow the toroidal magnet set to be modeled as a set of circular filaments. A simple thermal model of the conductor was used which allows heat transfer to the magnet structure and which includes the effect of temperature dependent properties. To be effective in large magnets an electrical protection system should remove at least 50% of the stored energy in the protection circuit assuming that all of the superconductor in the circuit quenches when the circuit is activated. A protection system design procedure based on this criterion was developed.
First qualification of ITER Toroidal Field Coil conductor jacketing
Energy Technology Data Exchange (ETDEWEB)
Hamada, Kazuya, E-mail: hamada.kazuya@jaea.go.jp [Japan Atomic Energy Agency (Japan); Takahashi, Yoshikazu; Isono, Takaaki; Nunoya, Yoshihiko; Matsui, Kunihiro; Kawano, Katsumi; Oshikiri, Masayuki; Tsutsumi, Fumiaki; Koizumi, Norikiyo; Nakajima, Hideo; Okuno, Kiyoshi [Japan Atomic Energy Agency (Japan); Matsuda, Hidemitsu; Yano, Yoshitaka [Nippon Steel Engineering Co. Ltd (Japan); Devred, Arnauld; Bessette, Denis [ITER Organization (France)
2011-10-15
The Japan Atomic Energy Agency (JAEA) has the responsibility to procure 25% of the ITER Toroidal Field Coil conductors as the Japanese Domestic Agency (JADA) in the ITER project. The TF conductor is a circular shaped, cable-in-conduit conductor, composed of a cable and a stainless steel conduit (jacket). The outer diameter and maximum length of the TF conductor are 43.7 mm and 760 m, respectively. JAEA started to produce strand, cables and jacket sections and to construct a conductor manufacturing (jacketing) facility in 2008. Following preparation in December 2009 of the jacketing facility, the dummy cable, the jacket sections and fabrication procedures, such as welding, cable insertion, compaction and spooling, JAEA manufactured a 760 m long Cu dummy conductor for process qualification. Into the 760 m long Cu dummy conductor jacketing, JAEA successfully inserted the cable with a maximum force of 32 kN. The outer diameter of the cross section of the spooled conductor was 43.7 {+-} 0.15 mm, which complies with the ITER target requirement of 43.7 {+-} 0.3 mm. Following qualification of all manufacturing processes, JAEA has started to fabricate superconducting conductors for the TF coils.
First qualification of ITER Toroidal Field Coil conductor jacketing
International Nuclear Information System (INIS)
The Japan Atomic Energy Agency (JAEA) has the responsibility to procure 25% of the ITER Toroidal Field Coil conductors as the Japanese Domestic Agency (JADA) in the ITER project. The TF conductor is a circular shaped, cable-in-conduit conductor, composed of a cable and a stainless steel conduit (jacket). The outer diameter and maximum length of the TF conductor are 43.7 mm and 760 m, respectively. JAEA started to produce strand, cables and jacket sections and to construct a conductor manufacturing (jacketing) facility in 2008. Following preparation in December 2009 of the jacketing facility, the dummy cable, the jacket sections and fabrication procedures, such as welding, cable insertion, compaction and spooling, JAEA manufactured a 760 m long Cu dummy conductor for process qualification. Into the 760 m long Cu dummy conductor jacketing, JAEA successfully inserted the cable with a maximum force of 32 kN. The outer diameter of the cross section of the spooled conductor was 43.7 ± 0.15 mm, which complies with the ITER target requirement of 43.7 ± 0.3 mm. Following qualification of all manufacturing processes, JAEA has started to fabricate superconducting conductors for the TF coils.
Pareto optimal design of sectored toroidal superconducting magnet for SMES
Bhunia, Uttam; Saha, Subimal; Chakrabarti, Alok
2014-10-01
A novel multi-objective optimization design approach for sectored toroidal superconducting magnetic energy storage coil has been developed considering the practical engineering constraints. The objectives include the minimization of necessary superconductor length and torus overall size or volume, which determines a significant part of cost towards realization of SMES. The best trade-off between the necessary conductor length for winding and magnet overall size is achieved in the Pareto-optimal solutions, the compact magnet size leads to increase in required superconducting cable length or vice versa The final choice among Pareto optimal configurations can be done in relation to other issues such as AC loss during transient operation, stray magnetic field at outside the coil assembly, and available discharge period, which is not considered in the optimization process. The proposed design approach is adapted for a 4.5 MJ/1 MW SMES system using low temperature niobium-titanium based Rutherford type cable. Furthermore, the validity of the representative Pareto solutions is confirmed by finite-element analysis (FEA) with a reasonably acceptable accuracy.
Toroidal rotation and halo current produced by disruptions
Strauss, Henry; Sugiyama, Linda; Paccagnella, Roberto; Breslau, Joshua; Jardin, Stephen
2013-10-01
In several experiments including JET, it was observed that disruptions were accompanied by toroidal rotation. There is a concern that there may be a resonance between rotating toroidal perturbations and the resonant frequencies of the ITER vacuum vessel, causing enhanced damage. MHD simulations with M3D demonstrate that disruptions produce toroidal rotation. The toroidal velocity can produce several rotations of the sideways force during a disruption. Edge localized modes (ELMs) also produce poloidal and toroidal rotation. A theory of rotation produced by MHD activity will be presented. In the case of ELMs, the theory gives toroidal rotation Alfven Mach number, Mϕ ~10-2βN . This is consistent with a scaling for intrinsic toroidal rotation in H mode tokamaks. It was also discovered on JET that disruptions were accompanied by toroidal variation of the plasma current Iϕ. From ∇ . j = 0 , the toroidal current variation ΔIϕ is proportional to the 3D halo current, ∮Jn Rdl , where Jn is the normal current density at the wall. The 3D halo current is calculated analytically and computationally. A bound on ΔIϕ /Iϕ is found, proportional to the halo current fraction and toroidal peaking factor. Supported by USDOE and ITER.
Design status of the NET toroidal coils
International Nuclear Information System (INIS)
The Toroidal Field Coil System consists of 16 superconducting coil windings, their coil casings and the intercoil structure. All of these components are located inside a common cryostat vessel and will therefore be at a temperature of about 4.50 degK during operation of the machine. The 16 coils are arranged in a toroidal configuration in order to provide a magnetic field for the confinement of the ring shaped plasma. The inner legs of the D-shaped coils form a vault which is subjected to the centering forces that are caused by the toroidal field itself. The interaction between the poloidal field and the toroidal currents creates Lorentz Forces which are perpendicular to the TF coil plane. Intercoil structure and vault have to resist these forces. The huge size of the coils in combination with the fact that an A15 conductor material has to be used require techniques that are somewhat beyond the present state of the art. Therefore, a conductor and magnet development program has been launched. The development studies carried out by Associated Laboratories in cooperation with NET Team have resulted in several flow cooled composite conductors. Futheron, full size conductor samples were manufactured and two subsize conductors were manufactured and wound into two 12 T model coils. Proposals for the manufacture of the coil winding, the power supply and quench protection system, the cooling system and the instrumentation have been worked out in the course of these studies. To ensure the feasibility of the cois two study contracts have been placed with industry. This report will stress the most difficult aspects of the coil manufacture, the assembly of the winding in its steel casing and the assembly of the 16 coils with the intercoil structure to a toroidal configuration. The results of the thermomechanical and electromagnetic analysis (e.g. eddy currents in coils case, stress, a.c. losses) - will be reported and their impact on the design of the TF system will be
Compact tokamak reactors. Part 1 (analytic results)
International Nuclear Information System (INIS)
We discuss the possible use of tokamaks for thermonuclear power plants, in particular tokamaks with low aspect ratio and copper toroidal field coils. Three approaches are presented. First we review and summarize the existing literature. Second, using simple analytic estimates, the size of the smallest tokamak to produce an ignited plasma is derived. This steady state energy balance analysis is then extended to determine the smallest tokamak power plant, by including the power required to drive the toroidal field, and considering two extremes of plasma current drive efficiency. The analytic results will be augmented by a numerical calculation which permits arbitrary plasma current drive efficiency; the results of which will be presented in Part II. Third, a scaling from any given reference reactor design to a copper toroidal field coil device is discussed. Throughout the paper the importance of various restrictions is emphasized, in particular plasma current drive efficiency, plasma confinement, plasma safety factor, plasma elongation, plasma beta, neutron wall loading, blanket availability and recirculating electric power. We conclude that the latest published reactor studies, which show little advantage in using low aspect ratio unless remarkably high efficiency plasma current drive and low safety factor are combined, can be reproduced with the analytic model
An overview on research developments of toroidal continuously variable transmissions
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
As environmental protection agencies enact new regulations for automotive fuel economy and emission, the toroidal continuously variable transmissions (CVTs) keep on contribute to the advent of system technologies for better fuel consumption of automobiles with internal combustion engines (ICE). Toroidal CVTs use infinitely adjustable drive ratios instead of stepped gears to achieve optimal performance. Toroidal CVTs are one of the earliest patents to the automotive world but their torque capacities and reliability have limitations in the past. New developments and implementations in the control strategies, and several key technologies have led to development of more robust toroidal CVTs, which enables more extensive automotive application of toroidal CTVs. This paper concerns with the current development, upcoming and progress set in the context of the past development and the traditional problems associated with toroidal CVTs.
Macroscopic electromagnetic response of metamaterials with toroidal resonances
Savinov, V; Zheludev, N I
2013-01-01
Toroidal dipole, first described by Ia. B. Zeldovich [Sov. Phys. JETP 33, 1184 (1957)], is a distinct electromagnetic excitation that differs both from the electric and the magnetic dipoles. It has a number of intriguing properties: static toroidal nuclear dipole is responsible for parity violation in atomic spectra; interactions between static toroidal dipole and oscillating magnetic dipole are claimed to violate Newton's Third Law while non-stationary charge-current configurations involving toroidal multipoles have been predicted to produce vector potential in the absence of electromagnetic fields. Existence of the toroidal response in metamaterials was recently demonstrated and is now a growing field of research. However, no direct analytical link has yet been established between the transmission and reflection of macroscopic electromagnetic media and toroidal dipole excitations. To address this essential gap in electromagnetic theory we have developed an analytical approach linking microscopic and macrosc...
Compact ignition tokamak physics and engineering basis
International Nuclear Information System (INIS)
The Compact Ignition Tokamak (CIT) is a high-field, compact tokamak design whose objective is the study of physics issues associated with burning plasmas. The toroidal and poloidal field coils employ a copper-steel laminate, manufactured by explosive-bonding techniques, to support the forces generated by the design fields: 10 T toroidal field at the plasma center; 21 T in the OH solenoid. A combination of internal and external PF coils provides control of the equilibrium and the ability to sweep the magnetic separatrix across the divertor plates during a pulse. At temperatures and βα levels characteristic of ITER designs, the fusion power in CIT approaches 800 MW and can be the limiting factor in the pulse length. Ignition requires that the confinement time exceed present L-mode scalings by about a factor of two, which is anticipated to occur as a result of the operational flexibility incorporated into the design. Conventional operating limits given by 20 e and qψ ≤ 3.2 have been chosen and, in the case of MHD limits, have been justified by ideal stability analysis. The power required for CIT ignition ranges from 10 MW to 40 MW or more, depending on confinement assumptions, and either ICRF or ECRF heating, or both, will be used. (author). 17 refs, 6 figs, 1 tab
Macroscopic electromagnetic response of metamaterials with toroidal resonances
Savinov, V.; Fedotov, V. A.; Zheludev, N. I.
2013-01-01
Toroidal dipole, first described by Ia. B. Zeldovich [Sov. Phys. JETP 33, 1184 (1957)], is a distinct electromagnetic excitation that differs both from the electric and the magnetic dipoles. It has a number of intriguing properties: static toroidal nuclear dipole is responsible for parity violation in atomic spectra; interactions between static toroidal dipole and oscillating magnetic dipole are claimed to violate Newton's Third Law while non-stationary charge-current configurations involving...
Modular Coil Design Developments for the National Compact Stellarator Experiment (NCSX)
Energy Technology Data Exchange (ETDEWEB)
Williamson, David E [ORNL; Brooks, A. [Princeton Plasma Physics Laboratory (PPPL); Brown, T. [Princeton Plasma Physics Laboratory (PPPL); Chrzanowski, J. [Princeton Plasma Physics Laboratory (PPPL); Cole, Michael J [ORNL; Fan, H-M. [Princeton Plasma Physics Laboratory (PPPL); Freudenberg, Kevin D [ORNL; Fogarty, Paul J [ORNL; Hargrove, Tom [ORNL; Heitzenroeder, P. [Princeton Plasma Physics Laboratory (PPPL); Lovett, G. [MK Technologies, Knoxville, TN; Miller, P. [MK Technologies, Knoxville, TN; Myatt, R. [Myatt Consulting, Norfolk, MA; Nelson, Brad E [ORNL; Reiersen, W. [Princeton Plasma Physics Laboratory (PPPL); Strickler, Dennis J [ORNL
2005-01-01
The National Compact Stellarator Experiment (NCSX) is a quasi-axisymmetric facility that combines the high beta and good confinement features of an advanced tokamak with the low current, disruption-free characteristics of a stellarator. The experiment is based on a three field-period plasma configuration with an average major radius of 1.4 m, a minor radius of 0.3m, and a toroidal magnetic field on axis of up to 2 T. The modular coils are set in a complex assembly of four coil systems that surround the highly shaped plasma. There are six each of three coil types in the assembly for a total of 18 modular coils. The coils are constructed by winding copper cable onto a cast stainless steel winding form that has been machined to high accuracy, so that the current center of the winding pack is within 1.5 mm of its theoretical position. The modular coils operate at a temperature of 80K and are subjected to rapid heating and stress during a pulse. At this time, the project has completed construction of several prototype components which validate the fabrication and inspection processes that are planned for the production coils. In addition, some advanced techniques for error-field compensation and assembly simulation using computer-aided design (CAD) have been developed.
Modular coil design developments for the National Compact Stellarator Experiment (NCSX)
Energy Technology Data Exchange (ETDEWEB)
Williamson, D. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6169 (United States)]. E-mail: williamsonde@ornl.gov; Brooks, A. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, NJ 08502 (United States); Brown, T. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, NJ 08502 (United States); Chrzanowski, J. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, NJ 08502 (United States); Cole, M. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6169 (United States); Fan, H.-M. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, NJ 08502 (United States); Freudenberg, K. [BWXT Y-12, P.O. Box 2009, Oak Ridge, TN 37831-8073 (United States); Fogarty, P. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6169 (United States); Hargrove, T. [Hargrove Engineering, 118 Colonial Dr, Scottsboro, AL 35768 (United States); Heitzenroeder, P. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, NJ 08502 (United States); Lovett, G. [MK Technologies, P.O. Box 30197, Knoxville, TN 37930 (United States); Miller, P. [MK Technologies, P.O. Box 30197, Knoxville, TN 37930 (United States); Myatt, R. [Myatt Consulting, Norfolk, MA 02056 (United States); Nelson, B. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6169 (United States); Reiersen, W. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, NJ 08502 (United States); Strickler, D. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6169 (United States)
2005-11-15
The National Compact Stellarator Experiment (NCSX) is a quasi-axisymmetric facility that combines the high beta and good confinement features of an advanced tokamak with the low current, disruption-free characteristics of a stellarator. The experiment is based on a three field-period plasma configuration with an average major radius of 1.4 m, a minor radius of 0.3 m, and a toroidal magnetic field on axis of up to 2 T. The modular coils are one set in a complex assembly of four coil systems that surround the highly shaped plasma. There are six, each of three coil types in the assembly for a total of 18 modular coils. The coils are constructed by winding copper cable onto a cast stainless steel winding form that has been machined to high accuracy, so that the current center of the winding pack is within {+-}1.5 mm of its theoretical position. The modular coils operate at a temperature of 80 K and are subjected to rapid heating and stress during a pulse. At this time, the project has completed construction of several prototype components which validate the fabrication and inspection processes that are planned for the production coils. In addition, some advanced techniques for error-field compensation and assembly simulation using computer-aided design (CAD) have been developed.
International Nuclear Information System (INIS)
Weyl's Gauge Principle of 1929 has been used to establish Weyl's Quantum Principle (WQP) that requires that the Weyl scale factor should be unity. It has been shown that the WQP requires the following: quantum mechanics must be used to determine system states; the electrostatic potential must be non-singular and quantified; interactions between particles with different electric charges (i.e. electron and proton) do not obey Newton's Third Law at sub-nuclear separations, and nuclear particles may be much different than expected using the standard model. The above WQP requirements lead to a potential fusion reactor wherein deuterium nuclei are preferentially fused into helium nuclei. Because the deuterium nuclei are preferentially fused into helium nuclei at temperatures and energies lower than specified by the standard model there is no harmful radiation as a byproduct of this fusion process. Therefore, a reactor using this reaction does not need any shielding to contain such radiation. The energy released from each reaction and the absence of shielding makes the deuterium-plus-deuterium-to-helium (DDH) reactor very compact when compared to other reactors, both fission and fusion types. Moreover, the potential energy output per reactor weight and the absence of harmful radiation makes the DDH reactor an ideal candidate for space power. The logic is summarized by which the WQP requires the above conditions that make the prediction of DDH possible. The details of the DDH reaction will be presented along with the specifics of why the DDH reactor may be made to cause two deuterium nuclei to preferentially fuse to a helium nucleus. The presentation will also indicate the calculations needed to predict the reactor temperature as a function of fuel loading, reactor size, and desired output and will include the progress achieved to date
Toroidal plasma enhanced CVD of diamond films
International Nuclear Information System (INIS)
An inductively coupled toroidal plasma source is used as an alternative to microwave plasmas for chemical vapor deposition of diamond films. The source, operating at a frequency of 400 kHz, synthesizes diamond films from a mixture of argon, methane, and hydrogen. The toroidal design has been adapted to create a highly efficient environment for diamond film deposition: high gas temperature and a short distance from the sample to the plasma core. Using a toroidal plasma geometry operating in the medium frequency band allows for efficient (≈90%) coupling of AC line power to the plasma and a scalable path to high-power and large-area operation. In test runs, the source generates a high flux of atomic hydrogen over a large area, which is favorable for diamond film growth. Using a deposition temperature of 900–1050 °C and a source to sample distance of 0.1–2.0 cm, diamond films are deposited onto silicon substrates. The results showed that the deposition rate of the diamond films could be controlled using the sample temperature and source to sample spacing. The results also show the films exhibit good-quality polycrystalline diamond as verified by Raman spectroscopy, x-ray diffraction, and scanning electron microscopy. The scanning electron microscopy and x-ray diffraction results show that the samples exhibit diamond (111) and diamond (022) crystallites. The Raman results show that the sp3 peak has a narrow spectral width (FWHM 12 ± 0.5 cm−1) and that negligible amounts of the sp2 band are present, indicating good-quality diamond films
Edge ambipolar potential in toroidal fusion plasmas
Energy Technology Data Exchange (ETDEWEB)
Spizzo, G., E-mail: gianluca.spizzo@igi.cnr.it; Vianello, N.; Agostini, M.; Puiatti, M. E.; Scarin, P.; Spolaore, M.; Terranova, D. [Consorzio RFX, Euratom-ENEA Association and Istituto Gas Ionizzati del CNR, Corso Stati Uniti, 4 35127 Padova (Italy); White, R. B. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543 (United States); Abdullaev, S. S.; Schmitz, O. [Institut für Energieforschung-Plasmaphysik, Association EURATOM-FZJ, Jülich (Germany); Cavazzana, R. [Consorzio RFX, Euratom-ENEA Association, Corso Stati Uniti, 4 35127 Padova (Italy); Ciaccio, G. [Dipartimento di Fisica, Università degli studi di Padova, Padova (Italy)
2014-05-15
A series of issues with toroidally confined fusion plasmas are related to the generation of 3D flow patterns by means of edge magnetic islands, embedded in a chaotic field and interacting with the wall. These issues include the Greenwald limit in Tokamaks and reversed-field pinches, the collisionality window for ELM mitigation with the resonant magnetic perturbations (RMPs) in Tokamaks, and edge islands interacting with the bootstrap current in stellarators. Measurements of the 2D map of the edge electric field E{sup r}(r=a,θ,ϕ) in the RFX reversed-field pinch show that E{sup r} has the same helicity of the magnetic islands generated by a m/n perturbation: in fact, defining the helical angle u=mθ−nϕ+ωt, maps show a sinusoidal dependence as a function of u, E{sup r}=E{sup ~r}sin u. The associated E × B flow displays a huge convective cell with v(a)≠0 which, in RFX and near the Greenwald limit, determines a stagnation point for density and a reversal of the sign of E{sup r}. From a theoretical point of view, the question is how a perturbed toroidal flux of symmetry m/n gives rise to an ambipolar potential Φ=Φ{sup ~}sin u. On the basis of a model developed with the guiding center code ORBIT and applied to RFX and the TEXTOR tokamak, we will show that the presence of an m/n perturbation in any kind of device breaks the toroidal symmetry with a drift proportional to the gyroradius ρ, thus larger for ions (ρ{sub i} ≫ ρ{sub e}). Immediately, an ambipolar potential arises to balance the drifts, with the same symmetry as the original perturbation.
Electrical disruption in toroidal plasma of hydrogen
International Nuclear Information System (INIS)
The initial phase of ionization of a toroidal plasma produced in hydrogen was investigated using zero-dimensional model. The model describes the temporal evolution of plasma by spatial medium of particle density and temperature, on whole plasma volume. The energy and particle (electrons and ions) balance equations are considered. The electron loss is due to ambipolar diffusion in the presence of magnetic field. The electron energy loss involves ionization, Coulomb interaction and diffusion. The ohmic heating converter gives the initial voltage necessary to disruption. (M.C.K.)
Plasma current resonance in asymmetric toroidal systems
Energy Technology Data Exchange (ETDEWEB)
Hazeltine, R. D. [Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712 (United States); Catto, Peter J. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, 167 Albany Street, Cambridge, Massachusetts 02139 (United States)
2015-09-15
The well-known singularity in the magnetic differential equation for plasma current in an asymmetric toroidal confinement system is resolved by including in the pressure tensor corrections stemming from finite Larmor radius. The result provides an estimate of the amplitude of spikes in the parallel current that occur on rational magnetic surfaces. Resolution of the singularity is shown to depend on both the ambipolarity condition—the requirement of zero surface-averaged radial current—and the form of the magnetic differential equation near the rational surface.
General Atomic's superconducting toroidal field coil concept
International Nuclear Information System (INIS)
General Atomic's concept for a superconducting toroidal field coil is presented. The concept is generic for large tokamak devices, while a specific design is indicated for a 3.8 meter (major radius) ignition/burn machine. The concept utilizes bath cooled NbTi conductor to generate a peak field of 10 tesla at 4.2 K. The design is simple and straightforward, requires a minimum of developmental effort, and draws extensively upon the perspective of past experience in the design and construction of large superconducting magnets for high energy physics. Thus, the primary emphasis is upon economy, reliability, and expeditious construction scheduling. (author)
Electric disruption in a hydrogen toroidal plasma
International Nuclear Information System (INIS)
By using a zero-dimensional model the ionizing initial phase of a toroidal plasma produced in hydrogen was investigated. The model consists on describing the plasma time evolution through the density and particle temperature space averaged on the plasma volume. The involved equations are energy and particles balance equations (electrons and ions). The electron loss is due to ambipolar diffusion in the presence of magnetic field. The electron energy loss is due to ionizing, processes of Coulomb interaction and diffusion. The ohmic heating transformer gives a initial voltage necessary to the breaking
Toroidal membrane vesicles in spherical confinement
Bouzar, Lila; Müller, Martin Michael
2015-01-01
We investigate the morphology of a toroidal fluid membrane vesicle confined inside a spherical container. The equilibrium shapes are assembled in a geometrical phase diagram as a function of scaled area and reduced volume of the membrane. For small area the vesicle can adopt its free form. When increasing the area, the membrane cannot avoid contact and touches the confining sphere along a circular contact line, which extends to a zone of contact for higher area. The elastic energies of the equilibrium shapes are compared to those of their confined counterparts of spherical topology to predict under which conditions a topology change is favored energetically.
Toroidal membrane vesicles in spherical confinement.
Bouzar, Lila; Menas, Ferhat; Müller, Martin Michael
2015-09-01
We investigate the morphology of a toroidal fluid membrane vesicle confined inside a spherical container. The equilibrium shapes are assembled in a geometrical phase diagram as a function of scaled area and reduced volume of the membrane. For small area the vesicle can adopt its free form. When increasing the area, the membrane cannot avoid contact and touches the confining sphere along a circular contact line, which extends to a zone of contact for higher area. The elastic energies of the equilibrium shapes are compared to those of their confined counterparts of spherical topology to predict under which conditions a topology change is favored energetically. PMID:26465512
3D Printing the ATLAS' barrel toroid
Goncalves, Tiago Barreiro
2016-01-01
The present report summarizes my work as part of the Summer Student Programme 2016 in the CERN IR-ECO-TSP department (International Relations – Education, Communication & Outreach – Teacher and Student Programmes). Particularly, I worked closely with the S’Cool LAB team on a science education project. This project included the 3D designing, 3D printing, and assembling of a model of the ATLAS’ barrel toroid. A detailed description of the project' development is presented and a short manual on how to use 3D printing software and hardware is attached.
Pulsar Wind Nebulae with Thick Toroidal Structure
Chevalier, Roger A.; Reynolds, Stephen P.
2011-01-01
We investigate a class of pulsar wind nebulae that show synchrotron emission from a thick toroidal structure. The best studied such object is the small radio and X-ray nebula around the Vela pulsar, which can be interpreted as the result of interaction of a mildly supersonic inward flow with the recent pulsar wind. Such a flow near the center of a supernova remnant can be produced in a transient phase when the reverse shock reaches the center of the remnant. Other nebulae with a thick toroida...
Burn control resulting from toroidal field ripple
International Nuclear Information System (INIS)
The enhanced transport due to toroidal magnetic field ripple is proposed as a means of averting thermal runaway in a tokamak reactor in the post-ignition stage. A theoretical analysis applied to a typical reactor design reveals that peak-to-average edge ripple of the order of 2% is sufficient to terminate the thermal excursion at reasonable values of β without significantly increasing the difficulty of reaching ignition. These analytic predictions, which are shown to agree well with radial transport code results, suggest that a properly specified ripple is one way of achieving a controlled burn in tokamak reactors. (author)
Continuum damping of ideal toroidal Alfven eigenmodes
International Nuclear Information System (INIS)
A perturbation theory based on the two dimensional (2D) ballooning transform is systematically developed for ideal toroidal Alfven eigenmodes (TAEs). A formula, similar to the Fermi golden rule for decaying systems in quantum mechanics, is derived for the continuum damping rate of the TAE; the decay (damping) rate is expressed explicitly in terms of the coupling of the TAE to the continuum spectrum. Numerical results are compared with previous calculations. It is found that in some narrow intervals of the parameter mε the damping rate varies very rapidly. These regions correspond precisely to the root missing intervals of the numerical solution by Rosenbluth et al
3D blob dynamics in toroidal geometry
DEFF Research Database (Denmark)
Nielsen, Anders Henry; Reiser, Dirk
DIESEL code is an extension of the ESEL code [1]. It solves a simple interchange model in full 3D tokamak geometry, where the toroidal direction is divided into a number of drift planes. On each drift plane the equations are solved in a domain corresponding to the full 2D cross section of the tokamak and...... communicate parallel with the nearest drift planes using parameterized velocities, the ion sound speed, Cs for the density equation and the Alfvén speed VA for the vorticity equation. Results show that a decrease of Alfvénic interaction of electric potential and current density leads to the expected radial...
Spherical torus, compact fusion at low field
International Nuclear Information System (INIS)
A spherical torus is obtained by retaining only the indispensable components on the inboard side of a tokamak plasma, such as a cooled, normal conductor that carries current to produce a toroidal magnetic field. The resulting device features an exceptionally small aspect ratio (ranging from below 2 to about 1.3), a naturally elongated D-shaped plasma cross section, and ramp-up of the plasma current primarily by noninductive means. As a result of the favorable dependence of the tokamak plasma behavior to decreasing aspect ratio, a spherical torus is projected to have small size, high beta, and modest field. Assumption Mirnov confinement scaling, an ignition spherical torus at a field of 2 T features a major radius of 1.5 m, a minor radius of 1.0 m, a plasma current of 14 MA, comparable toroidal and poloidal field coil currents, an average beta of 24%, and a fusion power of 50 MW. At 2 T, a Q = 1 spherical torus will have a major radius of 0.8 m, a minor radius of 0.5 m, and a fusion power of a few megawatts
Aspects of Tokamak toroidal magnet protection
International Nuclear Information System (INIS)
Simple but conservative geometric models are used to estimate the potential for damage to a Tokamak reactor inner wall and blanket due to a toroidal magnet field collapse. The ofly potential hazard found to exist is due to the MHD pressure rise in a lithium blanket. A survey is made of proposed protection methods for superconducting torgidal magnets. It is found that the two general classificatigls of protectign methods are thermal and electrical. Computer programs were developed which aldow the toroidal magnet set to be modeled as a set of circular filaments. A simple thermal model of the conductor was used which allows heat transfer to the magnet structure and which includes the effect of temperature dependent properties. To be effective in large magnets an electrical protection system should remove at least 50% of the stored energy in the protection circuit assuming that all of the superconductor in the circuit quenches when the circuit is activated. A protection system design procedure based on this criterion was developed
Microwave produced plasma in a Toroidal Device
Singh, A. K.; Edwards, W. F.; Held, E. D.
2010-11-01
A currentless toroidal plasma device exhibits a large range of interesting basic plasma physics phenomena. Such a device is not in equilibrium in a strict magneto hydrodynamic sense. There are many sources of free energy in the form of gradients in plasma density, temperature, the background magnetic field and the curvature of the magnetic field. These free energy sources excite waves and instabilities which have been the focus of studies in several devices in last two decades. A full understanding of these simple plasmas is far from complete. At Utah State University we have recently designed and installed a microwave plasma generation system on a small tokamak borrowed from the University of Saskatchewan, Saskatoon, Canada. Microwaves are generated at 2.45 GHz in a pulsed dc mode using a magnetron from a commercial kitchen microwave oven. The device is equipped with horizontal and vertical magnetic fields and a transformer to impose a toroidal electric field for current drive. Plasmas can be obtained over a wide range of pressure with and without magnetic fields. We present some preliminary measurements of plasma density and potential profiles. Measurements of plasma temperature at different operating conditions are also presented.
Propulsion using the electron spiral toroid
International Nuclear Information System (INIS)
A new propulsion method is proposed which could potentially reduce propellant needed for space travel by three orders of magnitude. It uses the newly patented electron spiral toroid (EST), which stores energy as magnetic field energy. The EST is a hollow toroid of electrons, all spiraling in parallel paths in a thin outer shell. The electrons satisfy the coupling condition, forming an electron matrix. Stability is assured as long as the coupling condition is satisfied. The EST is held in place with a small external electric field; without an external magnetic field. The EST system is contained in a vacuum chamber. The EST can be thought of as an energetic entity, with electrons at 10,000 electron volts. Propulsion would not use combustion, but would heat propellant through elastic collisions with the EST surface and eject them for thrust. Chemical rocket combustion heats propellant to 4000 deg. C; an EST will potentially heat the propellant 29,000 times as much, reducing propellant needs accordingly. The thrust can be turned ON and OFF. The EST can be recharged as needed
Design description of the Advanced Toroidal Facility
International Nuclear Information System (INIS)
The Advanced Toroidal Facility (ATF) is a large torsatron being designed at Oak Ridge National Laboratory (ORNL) to replace the Impurity Study Experiment (ISX-B) tokamak. ATF will have a major radius of 2.1 m and an average plasma minor radius of 0.3 m. Major components of the device include the coil sets, structure, and vacuum vessel. The coil sets are designed for broad operating envelopes, including the capability to drive up to 100 kA of plasma current, to produce helical axis configurations, and to operate continuously at one-half the baseline currents. The ATF structure consists of a 40-mm-thick stainless steel toroidal shell encasing the helical coil set. The shell is constructed from 24 identical upper and lower segments, with 12 pairs of intermediate panels to provide access to the helical field (HF) coil joints. The lower portion of the shell also serves as an assembly fixture for the HF coil set. The vacuum vessel is a highly contoured 6-mm-thick stainless steel shell closely fitting the bore and sidewalls of the HF coil winding to provide maximum volume for the plasma. Forty-eight large ports allow good access for diagnostics and neutral beam injection
Transport and Dynamics in Toroidal Fusion Systems
Energy Technology Data Exchange (ETDEWEB)
Schnack, Dalton D
2006-05-16
This document reports the successful completion of the OFES Theory Milestone for FY2005, namely, Perform parametric studies to better understand the edge physics regimes of laboratory experiments. Simulate at increased resolution (up to 20 toroidal modes), with density evolution, late into the nonlinear phase and compare results from different types of edge modes. Simulate a single case including a study of heat deposition on nearby material walls. The linear stability properties and nonlinear evolution of Edge Localized Modes (ELMs) in tokamak plasmas are investigated through numerical computation. Data from the DIII-D device at General Atomics (http://fusion.gat.com/diii-d/) is used for the magnetohydrodynamic (MHD) equilibria, but edge parameters are varied to reveal important physical effects. The equilibrium with very low magnetic shear produces an unstable spectrum that is somewhat insensitive to dissipation coefficient values. Here, linear growth rates from the non-ideal NIMROD code (http://nimrodteam.org) agree reasonably well with ideal, i.e. non-dissipative, results from the GATO global linear stability code at low toroidal mode number (n) and with ideal results from the ELITE edge linear stability code at moderate to high toroidal mode number. Linear studies with a more realistic sequence of MHD equilibria (based on DIII-D discharge 86166) produce more significant discrepancies between the ideal and non-ideal calculations. The maximum growth rate for the ideal computations occurs at toroidal mode index n=10, whereas growth rates in the non-ideal computations continue to increase with n unless strong anisotropic thermal conduction is included. Recent modeling advances allow drift effects associated with the Hall electric field and gyroviscosity to be considered. A stabilizing effect can be observed in the preliminary results, but while the distortion in mode structure is readily apparent at n=40, the growth rate is only 13% less than the non-ideal MHD
Performance of a Folded-Strip Toroidally Wound Induction Machine
DEFF Research Database (Denmark)
Jensen, Bogi Bech; Jack, Alan G.; Atkinson, Glynn J.; Mecrow, Barrie C.
2011-01-01
This paper presents the measured experimental results from a four-pole toroidally wound induction machine, where the stator is constructed as a pre-wound foldable strip. It shows that if the machine is axially restricted in length, the toroidally wound induction machine can have substantially sho...
Optimization of the ARIES-CS compact stellarator reactor parameters
International Nuclear Information System (INIS)
optimum reactor size are the minimum distance between coils, neutron and radiative power flux to the wall, and the beta limit. A reactor systems/optimization code is used to optimize the reactor parameters for minimum cost of electricity subject to a large number of physics, engineering, materials, and reactor component constraints. Different transport models, reactor component models, and costing algorithms are used to test sensitivities to different models and assumptions. A 1-D power balance code is used to study the path to ignition and the effect of different plasma and confinement assumptions including density and temperature profiles, impurity density levels and peaking near the outside, confinement scaling, beta limits, alpha particle losses, etc. for each plasma and coil configuration. Variations on two different magnetic configurations were analyzed in detail: a three-field-period (M = 3) NCSX-based plasma with coils modified to allow a larger plasma-coil spacing, and an M = 2 plasma with coils that are closer to the plasma on the outboard side with less toroidal excursion. The reactors have major radii R in the 7-9 m range with an improved blanket and shield concept and an advanced superconducting coil approach. The results show that compact stellarator reactors should be cost competitive with tokamak reactors. (author)
International Nuclear Information System (INIS)
Experimental devices to study the physics of high-beta (β>∼4%), low aspect ratio (A<∼4.5) stellarator plasmas require coils that will produce plasmas satisfying a set of physics goals, provide experimental flexibility, and be practical to construct. In the course of designing a flexible coil set for the National Compact Stellarator Experiment, we have made several innovations that may be useful in future stellarator design efforts. These include: the use of Singular Value Decomposition methods for obtaining families of smooth current potentials on distant coil winding surfaces from which low current density solutions may be identified; the use of a Control Matrix Method for identifying which few of the many detailed elements of the stellarator boundary must be targeted if a coil set is to provide fields to control the essential physics of the plasma; the use of Genetic Algorithms for choosing an optimal set of discrete coils from a continuum of potential contours; the evaluation of alternate coil topologies for balancing the tradeoff between physics objective and engineering constraints; the development of a new coil optimization code for designing modular coils, and the identification of a 'natural' basis for describing current sheet distributions. (author)
Plasmonic Toroidal Dipolar Response under Radially Polarized Excitation
Bao, Yanjun; Zhu, Xing; Fang, Zheyu
2015-01-01
Plasmonic toroidal resonance has attracted growing interests because of its low loss electromagnetic properties and potential high sensitive nanophotonic applications. However, the realization in a metamaterial requires three-dimensional complicated structural design so far. In this paper, we design a simple metal-dielectric-metal (MIM) sandwich nanostructure, which exhibits a strong toroidal dipolar resonance under radially polarized excitation. The toroidal dipole moment as the dominant contribution for the scattering is demonstrated by the mirror-image method and further analyzed by Lagrangian hybridization model. The proposed toroidal configuration also shows a highly tolerant for misalignment between the structure center and the incident light focus. Our study proves the way for the toroidal plasmonic application with the cylindrical vector beams. PMID:26114966
Toroidal gyrofluid equations for simulations of tokamak turbulence
International Nuclear Information System (INIS)
A set of nonlinear gyrofluid equations for simulations of tokamak turbulence are derived by taking moments of the nonlinear toroidal gyrokinetic equation. The moment hierarchy is closed with approximations that model the kinetic effects of parallel Landau damping, toroidal drift resonances, and finite Larmor radius effects. These equations generalize the work of Dorland and Hammett [Phys. Fluids B 5, 812 (1993)] to toroidal geometry by including essential toroidal effects. The closures for phase mixing from toroidal rB and curvature drifts take the basic form presented in Waltz, et al. [Phys. Fluids B 4, 3138 (1992)], but here a more rigorous procedure is used, including an extension to higher moments, which provides significantly improved accuracy. In addition, trapped ion effects and collisions are incorporated. This reduced set of nonlinear equations accurately models most of the physics considered important for ion dynamics in core tokamak turbulence and is simple enough to be used in high resolution direct numerical simulations
Quench propagation and protection analysis of the ATLAS Toroids
Dudarev, A; ten Kate, H H J; Baynham, D Elwyn; Courthold, M J D; Lesmond, C
2000-01-01
The ATLAS superconducting magnet system consists of the Barrel Toroid, two End Cap Toroids and the Central Solenoid. However, the Toroids of eight coils each are magnetically separate systems to the Central Solenoid. The Toroids are electrically connected in series and energized by a single power supply. The quench protection system is based on the use of relatively small external dump resistances in combination with quench-heaters activated after a quench event detection to initiate the internal dump of stored energy in all the coils. A rather strong quench-back effect due to eddy-currents in the coil casings at the transport current decay is beneficial for the quench protection efficiency in the event of heater failures. The quench behaviour of the ATLAS Toroids was computer simulated for normal operation of the quench protection system and its complete non-operation (failure) mode. (3 refs).
Scintillator based beta batteries
Rensing, Noa M.; Tiernan, Timothy C.; Shirwadkar, Urmila; O'Dougherty, Patrick; Freed, Sara; Hawrami, Rastgo; Squillante, Michael R.
2013-05-01
Some long-term, remote applications do not have access to conventional harvestable energy in the form of solar radiation (or other ambient light), wind, environmental vibration, or wave motion. Radiation Monitoring Devices, Inc. (RMD) is carrying out research to address the most challenging applications that need power for many months or years and which have undependable or no access to environmental energy. Radioisotopes are an attractive candidate for this energy source, as they can offer a very high energy density combined with a long lifetime. Both large scale nuclear power plants and radiothermal generators are based on converting nuclear energy to heat, but do not scale well to small sizes. Furthermore, thermo-mechanical power plants depend on moving parts, and RTG's suffer from low efficiency. To address the need for compact nuclear power devices, RMD is developing a novel beta battery, in which the beta emissions from a radioisotope are converted to visible light in a scintillator and then the visible light is converted to electrical power in a photodiode. By incorporating 90Sr into the scintillator SrI2 and coupling the material to a wavelength-matched solar cell, we will create a scalable, compact power source capable of supplying milliwatts to several watts of power over a period of up to 30 years. We will present the latest results of radiation damage studies and materials processing development efforts, and discuss how these factors interact to set the operating life and energy density of the device.
Inductive Eigenmodes of a resistive toroidal surface in vacuum
International Nuclear Information System (INIS)
In this paper it has been studied the Electro-Magnetic (EM) Eigenmodes, sufficiently slow as to legitimate the pre-Maxwell approximation of Maxwell's system (or inductive Eigenmodes), of a given smooth, toroidal-unknotted, electrically resistive surface Τ with given smooth (surface) resistivity 0 degree 3. Within the above limitations (to be made more precise), the geometry of Τ is arbitrary. With the eigenvalue associated with the generic Eigenmode being defined as the opposite of its logarithmic time-derivative, one expects that the resulting spectrum be discrete and strictly positive. It shall be interested into the degenerate case where Τ be cut (i.e. electrically broken) along one or more of its irreducible cycles. This case will be analyzed autonomously, rather than as a limit (for ρdegree → ∞ along the cuts) of the regular case. Without cuts, the Eigenproblem under consideration is nothing but the two-dimensional (2-dim) generalization of the classical case of a smooth, unknotted, electrically conductive, simple coil in infinite vacuum. Its analysis hinges on the classical potential theory, and turns out to be a special application of the linear, integrodifferential (elliptic) equation theory on a compact, multiply connected, 2-dim manifold. The attention and approach will be confined to strong (or classical) solutions, both in Τ and C Τ = R3 / Τ. This study is divided in two parts: a General Part (Sects 1 divided 4) is devoted to the case of generic Τ and ρdegree (within the convenient smoothness requirements), whereas a Special Part (Sects 5 divided 7) deals with the (more or less formal) discussion of a couple of particular cases (Τ ≡ a canonical torus), both of which with uniform ρdegree. Some propaedeutical/supplementary information is provided in a number of Appendices
Perturbing macroscopic magnetohydrodynamic stability for toroidal plasmas
Comer, Kathryn J.
We have introduced a new perturbative technique to rapidly explore the dependence of long wavelength ideal magnetohydrodynamic (MHD) instabilities on equilibrium profiles, shaping properties, and wall parameters. Traditionally, these relations are studied with numerical parameter scans using computationally intensive stability codes. Our perturbative technique first finds the equilibrium and stability using traditional methods. Subsequent small changes in the original equilibrium parameters change the stability. We quickly find the new stability with an expansion of the energy principle, rather than with another run of the stability codes. We first semi-analytically apply the technique to the screw pinch after eliminating compressional Alfven wave effects. The screw pinch results validate the approach, but also indicate that allowable perturbations to equilibria with certain features may be restricted. Next, we extend the approach to toroidal geometry using experimental equilibria and a simple constructed equilibrium, with the ideal MHD stability code GATO. Stability properties are successfully predicted from perturbed toroidal equilibria when only the vacuum beyond the plasma is perturbed (through wall parameter variations), rather than the plasma itself. Small plasma equilibrium perturbations to both experimental and simple equilibria result in very large errors to the predicted stability, and valid results are found only over a narrow range of most perturbations. Despite the large errors produced when changing plasma parameters, the wall perturbations revealed two useful applications of this technique. Because the calculations are non-iterative matrix multiplications, the convergence issues that can disrupt a full MHD stability code are absent. Marginal stability, therefore, is much easier to find with the perturbative technique. Also, the perturbed results can be input as the initial guess for the eigenvalue for a full stability code, and improve subsequent
Toroidicity and shape dependence of peeling mode growth rates in axisymmetric toroidal plasmas
International Nuclear Information System (INIS)
The growth rate of the peeling mode instability with large toroidal mode number is calculated for general axisymmetric toroidal plasmas, including tokamaks and the spherical torus (ST) equilibia by using formalism presented by Connor et al. Analytic equilibia with non-zero edge current density and quasi-uniform current profiles are assumed. It is found that in sharp D-shape tokamak plasma, the derivative of the safety factor with respect to the poloidal flux becomes very large, making the perturbed poloidal motion very large, in turn making a significant reduction of the growth rate of the peeling mode, similar to the X-point effect in diverted plasma. The large aspect ratio effect is also studied, which reduces the growth rate further. (physics of gases, plasmas, and electric discharges)
Goumiri, Imene; Rowley, Clarence; Sabbagh, Steven; Gates, David; Gerhardt, Stefan
2014-10-01
A model-based system to control plasma rotation in a magnetically confined toroidal fusion device is developed to maintain plasma stability for long pulse operation. This research uses experimental measurements from the National Spherical Torus Experiment (NSTX) and is aimed to control plasma rotation by using momentum from injected neutral beams and viscosity generated by three-dimensional applied magnetic fields as actuators. Based on the data driven model obtained, a feedback controller is designed to theoretically sustain the toroidal momentum of the plasma in a stable fashion and to achieve desired plasma rotation profiles. On going work includes extending this method to NSTX Upgrade which has more complete radial coverage of the neutral beams momentum sources which enable simultaneous control of plasma stored energy (Beta control).
Ferromagnetic and resistive wall effects on beta limit in a tokamak
International Nuclear Information System (INIS)
Ferromagnetic and resistive wall effect on beta limit in a tokamak is investigated. It is shown that the beta limit is reduced to 90% of that without ferromagnetic effect for high aspect ratio tokamak, if the ferromagnetic wall of relative permeability of 2 is used. The effect of toroidal plasma flow is also investigated, and the flow velocity of 0.03vta, vta is toroidal Alfven velocity, is sufficient for the resistive wall to have stability effect of ideal wall. Both the resistive wall and ideal kink modes are destabilized by the ferromagnetic wall effects. (author)
Helicity of a toroidal vortex with swirl
Bannikova, E. Yu.; Kontorovich, V. M.; Poslavsky, S. A.
2016-04-01
Based on the solutions of the Bragg-Hawthorne equation, we discuss the helicity of a thin toroidal vortex in the presence of swirl, orbital motion along the torus directrix. The relation between the helicity and circulations along the small and large linked circumferences (the torus directrix and generatrix) is shown to depend on the azimuthal velocity distribution in the core of the swirling ring vortex. In the case of nonuniform swirl, this relation differs from the well-known Moffat relation, viz., twice the product of such circulations multiplied by the number of linkages. The results can find applications in investigating the vortices in planetary atmospheres and the motions in the vicinity of active galactic nuclei.
Helicity of the toroidal vortex with swirl
Bannikova, Elena Yu; Poslavsky, Sergey A
2016-01-01
On the basis of solutions of the Bragg-Hawthorne equations we discuss the helicity of thin toroidal vortices with the swirl - the orbital motion along the torus diretrix. It is shown that relationship of the helicity with circulations along the small and large linked circles - directrix and generatrix of the torus - depends on distribution of the azimuthal velocity in the core of the swirling vortex ring. In the case of non-homogeneous swirl this relationship differs from the well-known Moffat relationship - the doubled product of such circulations multiplied by the number of links. The results can be applied to vortices in planetary atmospheres and to vortex movements in the vicinity of active galactic nuclei.
Nonideal magnetohydrodynamic instabilities and toroidal magnetic confinement
International Nuclear Information System (INIS)
The marked divergence of experimentally observed plasma instability phenomena from the predictions of ideal magnetohydrodynamics led in the early 1960s to the formulations of finite-resistivity stability theory. Beginning in the 1970s, advanced plasma diagnostics have served to establish a detailed correspondence between the predictions of the finite-resistivity theory and experimental plasma behavior - particularly in the case of the resistive kink mode and the tokamak plasma. Nonlinear resistive-kink phenomena have been found to govern the transport of magnetic flux and plasma energy in the reversed-field pinch. The other predicted finite-resistivity instability modes have been more difficult to identify directly and their implications for toroidal magnetic confinement are still unresolved
Toroidal microinstability studies of high temperature tokamaks
Energy Technology Data Exchange (ETDEWEB)
Rewoldt, G.; Tang, W.M.
1989-07-01
Results from comprehensive kinetic microinstability calculations are presented showing the effects of toroidicity on the ion temperature gradient mode and its relationship to the trapped-electron mode in high-temperature tokamak plasmas. The corresponding particle and energy fluxes have also been computed. It is found that, although drift-type microinstabilities persist over a wide range of values of the ion temperature gradient parameter /eta//sub i/ /equivalent to/ (dlnT/sub i//dr)/(dlnn/sub i//dr), the characteristic features of the dominant mode are those of the /eta//sub i/-type instability when /eta//sub i/ > /eta//sub ic/ /approximately/1.2 to 1.4 and of the trapped-electron mode when /eta//sub i/ < /eta//sub ic/. 16 refs., 7 figs.
ATF [Advanced Toroidal Facility] data management
International Nuclear Information System (INIS)
Data management for the Advanced Toroidal Facility (ATF), a stellarator located at Oak Ridge National Laboratory (ORNL), is provided by DMG, a locally developed, VAX-based software system. DMG is a data storage and retrieval software system that provides the user interface to ATF raw and analyzed data. Data are described in terms of data models and data types and are organized as signals into files, which are internally documented. The system was designed with user accessibility, software maintainability, and extensibility as primary goals. Extensibility features include compatibility with ATF as it moves from pulsed to steady-state operation and capability for use of the DMG system with experiments other than ATF. DMG is implemented as a run-time library of routines available as a shareable image. General-purpose and specialized data acquisition and analysis applications have been developed using the DMG system. This paper describes the DMG system and the interfaces to it. 4 refs., 2 figs
The theory of toroidally confined plasmas
White, Roscoe B
2014-01-01
This graduate level textbook develops the theory of magnetically confined plasma, with the aim of bringing the reader to the level of current research in the field of thermonuclear fusion. It begins with the basic concepts of magnetic field description, plasma equilibria and stability, and goes on to derive the equations for guiding center particle motion in an equilibrium field. Topics include linear and nonlinear ideal and resistive modes and particle transport. It is of use to workers in the field of fusion both for its wide-ranging account of tokamak physics and as a kind of handbook or formulary. This edition has been extended in a number of ways. The material on mode-particle interactions has been reformulated and much new information added, including methodology for Monte Carlo implementation of mode destabilization. These results give explicit means of carrying out mode destabilization analysis, in particular for the dangerous fishbone mode. A new chapter on cyclotron motion in toroidal geometry has ...
Advanced toroidal facility vaccuum vessel stress analyses
International Nuclear Information System (INIS)
The complex geometry of the Advance Toroidal Facility (ATF) vacuum vessel required special analysis techniques in investigating the structural behavior of the design. The response of a large-scale finite element model was found for transportation and operational loading. Several computer codes and systems, including the National Magnetic Fusion Energy Computer Center Cray machines, were implemented in accomplishing these analyses. The work combined complex methods that taxed the limits of both the codes and the computer systems involved. Using MSC/NASTRAN cyclic-symmetry solutions permitted using only 1/12 of the vessel geometry to mathematically analyze the entire vessel. This allowed the greater detail and accuracy demanded by the complex geometry of the vessel. Critical buckling-pressure analyses were performed with the same model. The development, results, and problems encountered in performing these analyses are described. 5 refs., 3 figs
Nonideal magnetohydrodynamic instabilities and toroidal magnetic confinement
Energy Technology Data Exchange (ETDEWEB)
Furth, H.P.
1985-05-01
The marked divergence of experimentally observed plasma instability phenomena from the predictions of ideal magnetohydrodynamics led in the early 1960s to the formulations of finite-resistivity stability theory. Beginning in the 1970s, advanced plasma diagnostics have served to establish a detailed correspondence between the predictions of the finite-resistivity theory and experimental plasma behavior - particularly in the case of the resistive kink mode and the tokamak plasma. Nonlinear resistive-kink phenomena have been found to govern the transport of magnetic flux and plasma energy in the reversed-field pinch. The other predicted finite-resistivity instability modes have been more difficult to identify directly and their implications for toroidal magnetic confinement are still unresolved.
Fluid interaction with spinning toroidal tanks
Fester, D. A.; Anderson, J. E.
1977-01-01
An experimental study was conducted to evaluate propellant behavior in spinning torroidal tanks that could be used in a retropropulsion system of an advanced outer-planet Pioneer orbiter. Information on propellant slosh and settling and on ullage orientation and stability was obtained. The effects of axial acceleration, spin rate, spin-rate change, and spacecraft wobble, both singly and in combination, were evaluated using a one-eighth scale transparent tank in one-g and low-g environments. Liquid loadings ranged from 5% to 96% full. The impact of a surface tension acquisition device was assessed by comparison with bare-tank results. The testing simulated the behavior of the fluorine/hydrazine and nitrogen textroxide/monomethylhydrazine propellants. Results are presented that indicate that no major fluid behavior problems would be encountered with any of the four propellants in the toroidal tanks of a spin-stabilized orbiter spacecraft.
Plasma Density Distribution Profile in Toroidal Discharge
International Nuclear Information System (INIS)
Tokamak is an electrode less toroidal plasma discharge system whichcontains and heats the plasma by using magnetic field and heating system suchas RF and neutral beams respectively. Using the system, tokamak is expectedto be a most advanced facility in fusion reactor concept. The importantparameters in tokamak are plasma current, plasma discharge voltage,temperature and density, plasma density profile and confinement time.However, the facility belonged to this center (P3TM) is very simple thatmeans a toroidal discharge without confinement magnetic filed and anadditional heating. The preceding result showed that it had been obtainedsome important parameters such as plasma current, discharge current, plasmavoltage and induced poloidal magnetic field. While plasma temperature andplasma density and its profile have not been observed. The one of somediagnostics to be used to determine this parameter is a Langmuir probe.Langmuir probe is an oldest diagnostic tool, simple and quite easy to bemade. The most advantage by using this probe is its ability to measure thecurrent locally. In this experiment, the home made Langmuir probe is atungsten wire with 0.8 mm in diameter enveloped by glass tube and inserted intorus tube. The torus is operated at 1 mbar argon gas pressure and 7.5 kVoperating voltage. The power source is a 330006 Maxwell type capacitor with15 micro farad, and charging system is a 825-100 Hipotronics model which canhold 20 kV of voltage and deliver 100 mA of current. The experiment resultshowed that the relative radial density profile has an exponential relationwith the approaching function is nrel ∝ e-0.54r, r isradial position. (author)
Petascale Parallelization of the Gyrokinetic Toroidal Code
Energy Technology Data Exchange (ETDEWEB)
Ethier, Stephane; Adams, Mark; Carter, Jonathan; Oliker, Leonid
2010-05-01
The Gyrokinetic Toroidal Code (GTC) is a global, three-dimensional particle-in-cell application developed to study microturbulence in tokamak fusion devices. The global capability of GTC is unique, allowing researchers to systematically analyze important dynamics such as turbulence spreading. In this work we examine a new radial domain decomposition approach to allow scalability onto the latest generation of petascale systems. Extensive performance evaluation is conducted on three high performance computing systems: the IBM BG/P, the Cray XT4, and an Intel Xeon Cluster. Overall results show that the radial decomposition approach dramatically increases scalability, while reducing the memory footprint - allowing for fusion device simulations at an unprecedented scale. After a decade where high-end computing (HEC) was dominated by the rapid pace of improvements to processor frequencies, the performance of next-generation supercomputers is increasingly differentiated by varying interconnect designs and levels of integration. Understanding the tradeoffs of these system designs is a key step towards making effective petascale computing a reality. In this work, we examine a new parallelization scheme for the Gyrokinetic Toroidal Code (GTC) [?] micro-turbulence fusion application. Extensive scalability results and analysis are presented on three HEC systems: the IBM BlueGene/P (BG/P) at Argonne National Laboratory, the Cray XT4 at Lawrence Berkeley National Laboratory, and an Intel Xeon cluster at Lawrence Livermore National Laboratory. Overall results indicate that the new radial decomposition approach successfully attains unprecedented scalability to 131,072 BG/P cores by overcoming the memory limitations of the previous approach. The new version is well suited to utilize emerging petascale resources to access new regimes of physical phenomena.
Compact Stellarator Path to DEMO
Lyon, J. F.
2007-11-01
Issues for a DEMO reactor are sustaining an ignited/high-Q plasma in steady state, avoiding disruptions and large variations in power flux to the wall, adequate confinement of thermal plasma and alpha-particles, control of a burning plasma, particle and power handling, etc. Compact stellarators have key advantages -- steady-state high-plasma-density operation without external current drive or disruptions, stability without a close conducting wall or active feedback systems, and low recirculating power -- in addition to moderate plasma aspect ratio, good confinement, and high-beta potential. The ARIES-CS study established that compact stellarators can be competitive with tokamaks as reactors. Many of the issues for a compact stellarator DEMO can be answered using results from large tokamaks, ITER D-T experiments and fusion materials, technology and component development programs, in addition to stellarators in operation, under construction or in development. However, a large next-generation stellarator will be needed to address some physics issues: size scaling and confinement at higher parameters, burning plasma issues, and operation with a strongly radiative divertor. Technology issues include simpler coils, structure, and divertor fabrication, and better cost information.
Review of compact, alternate concepts for magnetic confinement fusion
International Nuclear Information System (INIS)
This report documents a study of compact alternate magnetic confinement fusion experiments and conceptual reactor designs. The purpose of this study is to identify those devices with a potential to burn tritium in the near future. The bulk of the report is made up of a review of the following compact alternates: compact toroids, high power density tokamaks, linear magnetic systems, compact mirrors, reversed field pinches and some miscellaneous concepts. Bumpy toruses and stellarators were initially reviewed but were not pursued since no compact variations were found. Several of the concepts show promise of either burning tritium or evolving into tritium burning devices by the early 1990's: RIGGATRON, Ignitor, OHTE, Frascati Tokamak upgrade, several driven (low or negative net power) mirror experiments and several Reversed Field Pinch experiments that may begin operation around 1990. Of the above only the Frascati Tokamak Upgrade has had funds allocated. Also identified in this report are groups who may have tritium burning experiments in the mid to late 1990's. There is a discussion of the differences between the reviewed devices and the mainline tokamak experiments. This discussion forms the basis of recommendations for R and D aimed at the compact alternates and the applicability of the present CFFTP program to the needs of the compact alternates. These recommendations will be presented in a subsequent report
Kinetic effect of toroidal rotation on the geodesic acoustic mode
Energy Technology Data Exchange (ETDEWEB)
Guo, W., E-mail: wfguo@ipp.ac.cn; Ye, L.; Zhou, D.; Xiao, X. [Institute of Plasma Physics, Chinese Academy of Science, Hefei, Anhui 230031 (China); Wang, S. [Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)
2015-01-15
Kinetic effects of the toroidal rotation on the geodesic acoustic mode are theoretically investigated. It is found that when the toroidal rotation increases, the damping rate increases in the weak rotation regime due to the rotation enhancement of wave-particle interaction, and it decreases in the strong rotation regime due to the reduction of the number of resonant particles. Theoretical results are consistent with the behaviors of the geodesic acoustic mode recently observed in DIII-D and ASDEX-Upgrade. The kinetic damping effect of the rotation on the geodesic acoustic mode may shed light on the regulation of turbulence through the controlling the toroidal rotation.
Toroidal dipole resonances in the relativistic random phase approximation
Vretenar, D; Ring, P
2002-01-01
The isoscalar toroidal dipole strength distributions in spherical nuclei are calculated in the framework of a fully consistent relativistic random phase approximation, based on effective mean-field Lagrangians with nonlinear meson self-interaction terms. It is suggested that the recently observed "low-lying component of the isoscalar dipole mode" might in fact correspond to the toroidal giant dipole resonance. Although predicted by several theoretical models, the existence of toroidal resonances has not yet been confirmed in experiment. In the present analysis the vortex dynamics of these states is displayed by the corresponding velocity fields.
Laser-induced production of large carbon-based toroids
International Nuclear Information System (INIS)
We report on the production of large carbon-based toroids (CBTs) from fullerenes. The process involves two-step laser irradiation of a mixed fullerene target (76% C60, 22% C70). Transmission electron microscopy (TEM) clearly identifies toroidal-shaped structures as well as Q-shaped constructs. The typical diameters of the CBTs are ∼0.2-0.3 μm with tubular diameters of ∼50-100 nm, but toroids as wide as 0.5 μm are observed making them nanostructures on the verge of being microstructures
Toroidal Spiral Strings in Higher-dimensional Spacetime
Igata, Takahisa
2010-01-01
We report on our progress in research of separability of the Nambu-Goto equation for test strings with a symmetric configuration in a shape of toroidal spiral in a five-dimensional Kerr-AdS black hole. In particular, for a Hopf loop string which is a special class of the toroidal spirals, we show the complete separation of variables occurs in two cases, Kerr background and Kerr-AdS background with equal angular momenta. We also obtain the dynamical solution for the Hopf loop around a black hole and for the general toroidal spiral in Minkowski background.
Magnetic divertor design for the compact reversed-field pinch reactor
International Nuclear Information System (INIS)
A recently completed design of a pumped-limiter-based Compact Reversed-Field Pinch Reactor is used to estimate for the first time the impact of magnetic divertors. A range of divertor options for the low-toroidal-field RFP is examined, and a design selection is made constrained by consideration of field ripple (magnetic island), blanket displacement, recirculating power, cost, heat flux, and access. Design choices based on diversion of minority (toroidal) field lead to a preference for (poloidally) symmetric or bundle divertor geometries
Physics aspects of the Compact Ignition Tokamak
International Nuclear Information System (INIS)
The Compact Ignition Tokamak (CIT) is a proposed modest-size ignition experiment designed to study the physics of alpha-particle heating. The basic concept is to achieve ignition in a modest-size minimum cost experiment by using a high plasma density to achieve the condition of ntau/sub E/ ∼ 2 x 1020 sec m-3 required for ignition. The high density requires a high toroidal field (10 T). The high toroidal field allows a large plasma current (10 MA) which improves the energy confinement, and provides a high level of ohmic heating. The present CIT design also has a gigh degree of elongation (k ∼ 1.8) to aid in producing the large plasma current. A double null poloidal divertor and a pellet injector are part of the design to provide impurity and particle control, improve the confinement, and provide flexibility for impurity and particle control, improve the confinement, and provide flexibility for improving the plasma profiles. Since auxiliary heating is expected to be necessary to achieve ignition, 10 to 20 MW of Ion Cyclotron Radio Frequency (ICRF) is to be provided
System studies of compact ignition tokamaks
Energy Technology Data Exchange (ETDEWEB)
Galambos, J.D.; Blackfield, D.T.; Peng, Y.K.M.; Reid, R.L.; Strickler, D.J.; Selcow, E.
1987-08-01
The new Tokamak Systems Code, used to investigate Compact Ignition Tokamaks (CITs), can simultaneously vary many parameters, satisfy many constraints, and minimize or maximize a figure of merit. It is useful in comparing different CIT design configurations over wide regions of parameter space and determining a desired design point for more detailed physics and engineering analysis, as well as for performing sensitivity studies for physics or engineering issues. Operational windows in major radius (R) and toroidal field (B) space for fixed ignition margin are calculated for the Ignifed and Inconel candidate CITs. The minimum R bounds are predominantly physics limited, and the maximum R portions of the windows are engineering limited. For a modified Kaye-Goldston plasma-energy-confinement scaling, the minimum size is 1.15 m for the Ignifed device and 1.25 m for the Inconel device. With the Ignition Technical Oversight Committee (ITOC) physics guidance of B/sup 2/a/q and I/sub p/ >10 MA, the Ignifed and Base-line Inconel devices have a minimum size of 1.2 and 1.25 m and a toroidal field of 11 and 10.4 T, respectively. Sensitivity studies show Ignifed to be more sensitive to coil temperature changes than the Inconel device, whereas the Inconel device is more sensitive to stress perturbations.
Physics aspects of the Compact Ignition Tokamak
Energy Technology Data Exchange (ETDEWEB)
Post, D.; Bateman, G.; Houlberg, W.; Bromberg, L.; Cohn, D.; Colestock, P.; Hughes, M.; Ignat, D.; Izzo, R.; Jardin, S.
1986-11-01
The Compact Ignition Tokamak (CIT) is a proposed modest-size ignition experiment designed to study the physics of alpha-particle heating. The basic concept is to achieve ignition in a modest-size minimum cost experiment by using a high plasma density to achieve the condition of ntau/sub E/ approx. 2 x 10/sup 20/ sec m/sup -3/ required for ignition. The high density requires a high toroidal field (10 T). The high toroidal field allows a large plasma current (10 MA) which improves the energy confinement, and provides a high level of ohmic heating. The present CIT design also has a gigh degree of elongation (k approx. 1.8) to aid in producing the large plasma current. A double null poloidal divertor and a pellet injector are part of the design to provide impurity and particle control, improve the confinement, and provide flexibility for impurity and particle control, improve the confinement, and provide flexibility for improving the plasma profiles. Since auxiliary heating is expected to be necessary to achieve ignition, 10 to 20 MW of Ion Cyclotron Radio Frequency (ICRF) is to be provided.
System studies of compact ignition tokamaks
International Nuclear Information System (INIS)
The new Tokamak Systems Code, used to investigate Compact Ignition Tokamaks (CITs), can simultaneously vary many parameters, satisfy many constraints, and minimize or maximize a figure of merit. It is useful in comparing different CIT design configurations over wide regions of parameter space and determining a desired design point for more detailed physics and engineering analysis, as well as for performing sensitivity studies for physics or engineering issues. Operational windows in major radius (R) and toroidal field (B) space for fixed ignition margin are calculated for the Ignifed and Inconel candidate CITs. The minimum R bounds are predominantly physics limited, and the maximum R portions of the windows are engineering limited. For a modified Kaye-Goldston plasma-energy-confinement scaling, the minimum size is 1.15 m for the Ignifed device and 1.25 m for the Inconel device. With the Ignition Technical Oversight Committee (ITOC) physics guidance of B2a/q and I/sub p/ >10 MA, the Ignifed and Base-line Inconel devices have a minimum size of 1.2 and 1.25 m and a toroidal field of 11 and 10.4 T, respectively. Sensitivity studies show Ignifed to be more sensitive to coil temperature changes than the Inconel device, whereas the Inconel device is more sensitive to stress perturbations
Nicodeme, Pierre
1991-01-01
We show how it is possible to split Compact Tries described as bit-lists in a segmented and ﬂexible structure of B-tree type, keeping the compactness advantages of the Compact Tries and recovering all the important properties of B-trees.
Beta-limiting Instabilities and Global Mode Stabilization in NSTX
Sabbagh, Steven
2001-10-01
Low aspect ratio and high edge q theoretically alter the plasma stability and mode structure compared to standard tokamak configurations. Below the no-wall limit, stability calculations with PEST, GATO, and DCON show the perturbed radial field is maximized near the center column and DCON and VALEN calculations show that mode stability is not greatly improved by a nearby conducting wall due to the short poloidal wavelength in this region. In contrast, as beta reaches and exceeds the no-wall limit, the mode becomes strongly ballooning with long poloidal wavelength at large major radius and is highly wall stabilized. In this way, wall stabilization is more effective at higher beta in low aspect ratio geometry. Research on the stability of spherical torus plasmas at and above the no-wall beta limit is being addressed on NSTX, which has produced low aspect ratio plasmas, R/a = 1.27 at plasma current up to 1.4 MA with high energy confinement (TauE/TauE-ITER89P = 2). Toroidal and normalized beta have reached 22%, and 4.3, respectively in q = 7 plasmas. The beta limit is observed to increase with increasing plasma internal inductance, li, and the stability factor betaN/li has reached 5.8, limited by sudden beta collapses at low li that was achieved by use of high-harmonic fast wave heating (HHFW). DCON stability analysis of equilibria reconstructed with EFIT using external magnetics show that the plasmas are below or at the no-wall beta limit for the n = 1 mode, which has characteristics of a current-driven kink. With more peaked current profiles (li greater than 0.7), core MHD instabilities are observed which saturate or slowly degrade beta. Sawteeth with large inversion radii can also cause substantial beta collapses, although current profile modification using HHFW, altered plasma growth, and increased toroidal field have each been successful in mitigating this effect.
The effect of toroidal field on the rotating magnetic field current drive in rotamak plasmas
Institute of Scientific and Technical Information of China (English)
Zhong Fang-Chuan; Huang Tian-Sen; Petrov Yuri
2007-01-01
A rotamak is one kind of compact spherically shaped magnetic-confinement device. In a rotamak the plasma current is driven by means of rotating magnetic field (RMF). The driven current can reverse the original equilibrium field and generate a field-reversed-configuration. In a conventional rotamak, a toroidal field (TF) is not necessary for the RMF to drive plasma current, but it was found that the present of an additional TF can influence the RMF current drive. In this paper the effect of TF on the RMF current drive in a rotamak are investigated in some detail.The experimental results show that addition of TF increases the RMF driven current greatly and enhances the RMF penetration dramatically. Without TF, the RMF can only penetrate into plasma in the edge region. When a TF is added, the RMF can reach almost the whole plasma region. This is an optimal strength of toroidal magnetic field for getting maximum plasma current when Bv and radio frequency generator power are fixed. Besides driving current,the RMF generates high harmonic fields in rotamak plasma. The effect of TF on the harmonic field spectra are also reported.
Influence of toroidal rotation on resistive tearing modes in tokamaks
International Nuclear Information System (INIS)
Influence of toroidal equilibrium plasma rotation on m/n = 2/1 resistive tearing modes is studied numerically using a 3D toroidal MHD code (CLT). It is found that the toroidal rotation with or without shear can suppress the tearing instability and the Coriolis effect in the toroidal geometry plays a dominant role on the rotation induced stabilization. For a high viscosity plasma (τR/τV ≫ 1, where τR and τV represent resistive and viscous diffusion time, respectively), the effect of the rotation shear combined with the viscosity appears to be stabilizing. For a low viscosity plasmas (τR/τV ≪ 1), the rotation shear shows a destabilizing effect when the rotation is large
Influence of toroidal rotation on resistive tearing modes in tokamaks
Wang, S.; Ma, Z. W.
2015-12-01
Influence of toroidal equilibrium plasma rotation on m/n = 2/1 resistive tearing modes is studied numerically using a 3D toroidal MHD code (CLT). It is found that the toroidal rotation with or without shear can suppress the tearing instability and the Coriolis effect in the toroidal geometry plays a dominant role on the rotation induced stabilization. For a high viscosity plasma (τR/τV ≫ 1, where τR and τV represent resistive and viscous diffusion time, respectively), the effect of the rotation shear combined with the viscosity appears to be stabilizing. For a low viscosity plasmas (τR/τV ≪ 1), the rotation shear shows a destabilizing effect when the rotation is large.
Influence of toroidal rotation on resistive tearing modes in tokamaks
Energy Technology Data Exchange (ETDEWEB)
Wang, S.; Ma, Z. W., E-mail: zwma@zju.edu.cn [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China)
2015-12-15
Influence of toroidal equilibrium plasma rotation on m/n = 2/1 resistive tearing modes is studied numerically using a 3D toroidal MHD code (CLT). It is found that the toroidal rotation with or without shear can suppress the tearing instability and the Coriolis effect in the toroidal geometry plays a dominant role on the rotation induced stabilization. For a high viscosity plasma (τ{sub R}/τ{sub V} ≫ 1, where τ{sub R} and τ{sub V} represent resistive and viscous diffusion time, respectively), the effect of the rotation shear combined with the viscosity appears to be stabilizing. For a low viscosity plasmas (τ{sub R}/τ{sub V} ≪ 1), the rotation shear shows a destabilizing effect when the rotation is large.
Effect of toroidicity during lower hybrid mode conversion
International Nuclear Information System (INIS)
The effect of toroidicity during lower hybrid mode conversion is examined by treating the wave propagation in an inhomogeneous medium as an eigenvalue problem for ω2(m,n),m,n poloidal and toroidal wave numbers. Since the frequency regime near ω2 = ω/sub LH/2 is an accumulation point for the eigenvalue spectrum, the degenerate perturbation technique must be applied. The toroidal eigenmodes are constructed by a zeroth order superposition of monochromatic solutions with different poloidal dependence m, thus they generically exhibit a wide spectrum in k/sub parallel/ for given fixed ω2 even for small inverse aspect ratio epsilon. In case that the average is in the neighborhood of k/sub min/, the minimum wave number for accessibility of the mode conversion regime, it is expected that excitation of toroidal modes rather than geometric optics will determine the wave coupling to the plasma
Inductive Eigenmodes of a resistive toroidal surface in vacuum
Energy Technology Data Exchange (ETDEWEB)
Lo Surdo, C. [ENEA, Centro Ricerche Frascati, Rome (Italy). Dipt. Innovazione
1999-07-01
In this paper it has been studied the Electro-Magnetic (EM) Eigenmodes, sufficiently slow as to legitimate the pre-Maxwell approximation of Maxwell's system (or inductive Eigenmodes), of a given smooth, toroidal-un knotted, electrically resistive surface {tau} with given smooth (surface) resistivity 0 < {rho}{sub d}egree < {infinity}, and lying in the (empty) R{sup 3}. Within the above limitations (to be made more precise), the geometry of {tau} is arbitrary. With the eigenvalue associated with the generic Eigenmode being defined as the opposite of its logarithmic time-derivative, one expects that the resulting spectrum be discrete and strictly positive. It shall be interested into the degenerate case where {tau} be cut (i.e. electrically broken) along one or more of its irreducible cycles. This case will be analyzed autonomously, rather than as a limit (for {rho}{sub d}egree {yields} {infinity} along the cuts) of the regular case. Without cuts, the Eigenproblem under consideration is nothing but the two-dimensional (2-dim) generalization of the classical case of a smooth, unknotted, electrically conductive, simple coil in infinite vacuum. Its analysis hinges on the classical potential theory, and turns out to be a special application of the linear, integrodifferential (elliptic) equation theory on a compact, multiply connected, 2-dim manifold. The attention and approach will be confined to strong (or classical) solutions, both in {tau} and C {tau} = R{sup 3} / {tau}. This study is divided in two parts: a General Part (Sects 1 divided 4) is devoted to the case of generic {tau} and {rho}{sub d}egree (within the convenient smoothness requirements), whereas a Special Part (Sects 5 divided 7) deals with the (more or less formal) discussion of a couple of particular cases ({tau} {identical_to} a canonical torus), both of which with uniform {rho}{sub d}egree. Some propaedeutical/supplementary information is provided in a number of Appendices. [Italian] Il presente
CPS Transformation of Beta-Redexes
DEFF Research Database (Denmark)
Danvy, Olivier; Nielsen, Lasse
2005-01-01
The extra compaction of the most compacting CPS transformation in existence, which is due to Sabry and Felleisen, is generally attributed to (1) making continuations occur first in CPS terms and (2) classifying more redexes as administrative. We show that this extra compaction is actually...... independent of the relative positions of values and continuations and furthermore that it is solely due to a context-sensitive transformation of beta-redexes. We stage the more compact CPS transformation into a first-order uncurrying phase and a context-insensitive CPS transformation. We also define a context......-insensitive CPS transformation that provides the extra compaction. This CPS transformation operates in one pass and is dependently typed....
CPS Transformation of Beta-Redexes
DEFF Research Database (Denmark)
Danvy, Olivier; Nielsen, Lasse R.
The extra compaction of the most compacting CPS transformation in existence, which is due to Sabry and Felleisen, is generally attributed to (1) making continuations occur first in CPS terms and (2) classifying more redexes as administrative. We show that this extra compaction is actually...... independent of the relative positions of values and continuations and furthermore that it is solely due to a context-sensitive transformation of beta-redexes. We stage the more compact CPS transformation into a first-order uncurrying phase and a context-insensitive CPS transformation. We also define a context......-insensitive CPS transformation that provides the extra compaction. This CPS transformation operates in one pass and is dependently typed....
Turbulent and neoclassical toroidal momentum transport in tokamak plasmas
International Nuclear Information System (INIS)
The goal of magnetic confinement devices such as tokamaks is to produce energy from nuclear fusion reactions in plasmas at low densities and high temperatures. Experimentally, toroidal flows have been found to significantly improve the energy confinement, and therefore the performance of the machine. As extrinsic momentum sources will be limited in future fusion devices such as ITER, an understanding of the physics of toroidal momentum transport and the generation of intrinsic toroidal rotation in tokamaks would be an important step in order to predict the rotation profile in experiments. Among the mechanisms expected to contribute to the generation of toroidal rotation is the transport of momentum by electrostatic turbulence, which governs heat transport in tokamaks. Due to the low collisionality of the plasma, kinetic modeling is mandatory for the study of tokamak turbulence. In principle, this implies the modeling of a six-dimensional distribution function representing the density of particles in position and velocity phase-space, which can be reduced to five dimensions when considering only frequencies below the particle cyclotron frequency. This approximation, relevant for the study of turbulence in tokamaks, leads to the so-called gyrokinetic model and brings the computational cost of the model within the presently available numerical resources. In this work, we study the transport of toroidal momentum in tokamaks in the framework of the gyrokinetic model. First, we show that this reduced model is indeed capable of accurately modeling momentum transport by deriving a local conservation equation of toroidal momentum, and verifying it numerically with the gyrokinetic code GYSELA. Secondly, we show how electrostatic turbulence can break the axisymmetry and generate toroidal rotation, while a strong link between turbulent heat and momentum transport is identified, as both exhibit the same large-scale avalanche-like events. The dynamics of turbulent transport are
Low-aspect-ratio toroidal equilibria of electron clouds
International Nuclear Information System (INIS)
Toroidal electron clouds with a low aspect ratio (as small as 1.3) and lasting for thousands of poloidal rotation periods have been formed in the laboratory. Characteristic toroidal effects like a large inward shift of the minor axis of equipotential contours, elliptical and triangular deformations, etc., have been observed experimentally for the first time. The results of new analytic and numerical investigations of low-aspect-ratio electron cloud equilibria, which reproduce many of the observed features, are also presented
Effective toroidal curvature and error field on NBT
International Nuclear Information System (INIS)
The effective toroidal curvature and the poloidal drift velocity for transit electrons with v sub(parallel)/v = 1 are measured for NBT-I device by use of an electron beam probing. The axis of the drift surfaces shifts inward by 12 cm due to the toroidal effect. The error field averaged along the torus is found to be spatially varying and is 1.1 x 10-3 at the minor axis. (author)
Numerical solution of quasilinear kinetic diffusion equations in toroidal plasmas
Höök, Lars Josef
2013-01-01
One of the main challenges for the realization of a working fusion power plant is an increased detailed understanding of kinetic phenomena in toroidal plasmas. The tokamak is a toroidal, magnetically confined plasma device and is currently the main line towards a power plant. The spatial and temporal scales in a tokamak plasma are extreme and the only tractable path for quantitative studies is to rely on computer simulations. Present day simulation codes can resolve only some of these scales....
Advances in the simulation of toroidal gyro Landau fluid model turbulence
International Nuclear Information System (INIS)
The gyro-Landau fluid (GLF) model equations for toroidal geometry have been recently applied to the study ion temperature gradient (ITG) mode turbulence using the 3D nonlinear ballooning mode representation (BMR). The present paper extends this work by treating some unresolved issues conceming ITG turbulence with adiabatic electrons. Although eddies are highly elongated in the radial direction long time radial correlation lengths are short and comparable to poloidal lengths. Although transport at vanishing shear is not particularly large, transport at reverse global shear, is significantly less. Electrostatic transport at moderate shear is not much effected by inclusion of local shear and average favorable curvature. Transport is suppressed when critical ExB rotational shear is comparable to the maximum linear growth rate with only a weak dependence on magnetic shear. Self consistent turbulent transport of toroidal momentum can result in a transport bifurcation at suffciently large r/(Rq). However the main thrust of the new formulation in the paper deals with advances in the development of finite beta GLF models with trapped electron and BMR numerical methods for treating the fast parallel field motion of the untrapped electrons
Toroidal fusion reactor design based on the reversed-field pinch
Energy Technology Data Exchange (ETDEWEB)
Hagenson, R.L.
1978-07-01
The toroidal reversed-field pinch (RFP) achieves gross equilibrium and stability with a combination of high shear and wall stabilization, rather than the imposition of tokamak-like q-constraints. Consequently, confinement is provided primarily by poloidal magnetic fields, poloidal betas as large as approximately 0.58 are obtainable, the high ohmic-heating (toroidal) current densities promise a sole means of heating a D-T plasma to ignition, and the plasma aspect ratio is not limited by stability/equilibrium constraints. A reactor-like plasma model has been developed in order to quantify and to assess the general features of a power system based upon RFP confinement. An ''operating point'' has been generated on the basis of this plasma model and a relatively detailed engineering energy balance. These results are used to generate a conceptual engineering model of the reversed-field pinch reactor (RFPR) which includes a general description of a 750 MWe power plant and the preliminary consideration of vacuum/fueling, first wall, blanket, magnet coils, iron core, and the energy storage/transfer system.
Fluctuations and symmetry breaking during regeneration of Hydra vulgaris tissue toroids
Krahe, Michael; Lin, Kao-Nung; Fischer, Julia; Fütterer, Claus
2012-01-01
While much is known in single cell mechanics, the mechanics of regeneration of naturally grown tissues and cell assemblies is largely unexplored. We found a symmetry breaking scenario accompanied by shape fluctuations in dissected regenerating Hydra vulgaris tissue tori. A subsequent folding and merging process leads finally to a regenerating spheroid. These phenomena are related to the dynamics of fluorescent beta- and trans-cellular alpha-actin structures. By embedding the tissues in a hydro-gel the fluctuations could be studied over a longer period of time. The power spectrum of the torus-fluctuations shows a non-trivial energy distribution dynamics depending on the gel stiffness. During the transition, many higher modes where found but in the end the 2nd mode wins in most cases. The toroid builds up an uniform alpha-actin ring along the inner edge of the torus. We found this ring in the inner cellular layer to be responsible for the force generation destabilizing the toroid shape. This actin structure is ...
Efficient magnetic fields for supporting toroidal plasmas
Landreman, Matt; Boozer, Allen H.
2016-03-01
The magnetic field that supports tokamak and stellarator plasmas must be produced by coils well separated from the plasma. However, the larger the separation, the more difficult it is to produce a given magnetic field in the plasma region, so plasma configurations should be chosen that can be supported as efficiently as possible by distant coils. The efficiency of an externally generated magnetic field is a measure of the field's shaping component magnitude at the plasma compared to the magnitude near the coils; the efficiency of a plasma equilibrium can be measured using the efficiency of the required external shaping field. Counterintuitively, plasma shapes with low curvature and spectral width may have low efficiency, whereas plasma shapes with sharp edges may have high efficiency. Two precise measures of magnetic field efficiency, which correctly identify such differences in difficulty, will be examined. These measures, which can be expressed as matrices, relate the externally produced normal magnetic field on the plasma surface to the either the normal field or current on a distant control surface. A singular value decomposition (SVD) of either matrix yields an efficiency ordered basis for the magnetic field distributions. Calculations are carried out for both tokamak and stellarator cases. For axisymmetric surfaces with circular cross-section, the SVD is calculated analytically, and the range of poloidal and toroidal mode numbers that can be controlled to a given desired level is determined. If formulated properly, these efficiency measures are independent of the coordinates used to parameterize the surfaces.
Toroidal nanotraps for cold polar molecules
Salhi, Marouane; Passian, Ali; Siopsis, George
2015-09-01
Electronic excitations in metallic nanoparticles in the optical regime that have been of great importance in surface-enhanced spectroscopy and emerging applications of molecular plasmonics, due to control and confinement of electromagnetic energy, may also be of potential to control the motion of nanoparticles and molecules. Here, we propose a concept for trapping polarizable particles and molecules using toroidal metallic nanoparticles. Specifically, gold nanorings are investigated for their scattering properties and field distribution to computationally show that the response of these optically resonant particles to incident photons permit the formation of a nanoscale trap when proper aspect ratio, photon wavelength, and polarization are considered. However, interestingly the resonant plasmonic response of the nanoring is shown to be detrimental to the trap formation. The results are in good agreement with analytic calculations in the quasistatic limit within the first-order perturbation of the scalar electric potential. The possibility of extending the single nanoring trapping properties to two-dimensional arrays of nanorings is suggested by obtaining the field distribution of nanoring dimers and trimers.
Ballooning mode spectrum in general toroidal systems
Energy Technology Data Exchange (ETDEWEB)
Dewar, R.L.; Glasser, A.H.
1982-04-01
A WKB formalism for constructing normal modes of short-wavelength ideal hydromagnetic, pressure-driven instabilities (ballooning modes) in general toroidal magnetic containment devices with sheared magnetic fields is developed. No incompressibility approximation is made. A dispersion relation is obtained from the eigenvalues of a fourth order system of ordinary differential equations to be solved by integrating along a line of force. Higher order calculations are performed to find the amplitude equation and the phase change at a caustic. These conform to typical WKB results. In axisymmetric systems, the ray equations are integrable, and semiclassical quantization leads to a growth rate spectrum consisting of an infinity of discrete eigenvalues, bounded above by an accumulation point. However, each eigenvalue is infinitely degenerate. In the nonaxisymmetric case, the rays are unbounded in a four dimensional phase space, and semiclassical quantization breaks down, leading to broadening of the discrete eigenvalues and accumulation point of the axisymmetric case into continuum bands. Analysis of a model problem indicates that the broadening of the discrete eigenvalues is numerically very small, the dominant effect being broadening of the accumulation point.
Tearing Mode Stability of Evolving Toroidal Equilibria
Pletzer, A.; McCune, D.; Manickam, J.; Jardin, S. C.
2000-10-01
There are a number of toroidal equilibrium (such as JSOLVER, ESC, EFIT, and VMEC) and transport codes (such as TRANSP, BALDUR, and TSC) in our community that utilize differing equilibrium representations. There are also many heating and current drive (LSC and TORRAY), and stability (PEST1-3, GATO, NOVA, MARS, DCON, M3D) codes that require this equilibrium information. In an effort to provide seamless compatibility between the codes that produce and need these equilibria, we have developed two Fortran 90 modules, MEQ and XPLASMA, that serve as common interfaces between these two classes of codes. XPLASMA provides a common equilibrium representation for the heating and current drive applications while MEQ provides common equilibrium and associated metric information needed by MHD stability codes. We illustrate the utility of this approach by presenting results of PEST-3 tearing stability calculations of an NSTX discharge performed on profiles provided by the TRANSP code. Using the MEQ module, the TRANSP equilibrium data are stored in a Fortran 90 derived type and passed to PEST3 as a subroutine argument. All calculations are performed on the fly, as the profiles evolve.
Pseudo-Anosov flows in toroidal manifolds
Barbot, Thierry
2010-01-01
We first prove rigidity results for pseudo-Anosov flows in prototypes of toroidal 3-manifolds: we show that a pseudo-Anosov in a Seifert fibered manifold is up to finite covers topologically conjugate to a geodesic flow. We also show that a pseudo-Anosov flow in a solv manifold is topologically conjugate to a suspension Anosov flow. Then we analyse immersed and embedded incompressible tori in optimal position with respect to a pseudo-Anosov flow. We also study the interaction of a pseudo-Anosov flow with possible Seifert fibered pieces in the torus decomposition: if the fiber is associated to a periodic orbit of the flow, we produce a standard form for the flow in the piece using Birkhoff annuli. Finally we introduce several new classes of examples, some of which are generalized pseudo-Anosov flows which have one prong singularities. The examples show that the results above in Seifert fibered and solvable manifolds do not apply to one prong pseudo-Anosov flows. In addition we also construct a large new class ...
''Turbulent Equipartition'' Theory of Toroidal Momentum Pinch
International Nuclear Information System (INIS)
The mode-independent part of magnetic curvature driven turbulent convective (TuroCo) pinch of the angular momentum density (Hahm et al., Phys. Plasmas 14,072302 (2007)) which was originally derived from the gyrokinetic equation, can be interpreted in terms of the turbulent equipartition (TEP) theory. It is shown that the previous results can be obtained from the local conservation of 'magnetically weighted angular momentum density', nmi U#parallel# R/B2, and its homogenization due to turbulent flows. It is also demonstrated that the magnetic curvature modification of the parallel acceleration in the nonlinear gyrokinetic equation in the laboratory frame, which was shown to be responsible for the TEP part of the TurCo pinch of angular momentum density in the previous work, is closely related to the Coriolis drift coupling to the perturbed electric field. In addition, the origin of the diffusive flux in the rotating frame is highlighted. Finally, it is illustrated that there should be a difference in scalings between the momentum pinch originated from inherently toroidal effects and that coming from other mechanisms which exist in a simpler geometry.
Turbulent Equipartition Theory of Toroidal Momentum Pinch
Energy Technology Data Exchange (ETDEWEB)
T.S. Hahm, P.H. Diamond, O.D. Gurcan, and G. Rewaldt
2008-01-31
The mode-independet part of magnetic curvature driven turbulent convective (TuroCo) pinch of the angular momentum density [Hahm et al., Phys. Plasmas 14,072302 (2007)] which was originally derived from the gyrokinetic equation, can be interpreted in terms of the turbulent equipartition (TEP) theory. It is shown that the previous results can be obtained from the local conservation of "magnetically weighted angular momentum density," nmi U|| R/B2, and its homogenization due to turbulent flows. It is also demonstrated that the magnetic curvature modification of the parallel acceleration in the nonlinear gyrokinetic equation in the laboratory frame, which was shown to be responsible for the TEP part of the TurCo pinch of angular momentum density in the previous work, is closely related to the Coriolis drift coupling to the perturbed electric field. In addition, the origin of the diffusive flux in the rotating frame is highlighted. Finally, it is illustratd that there should be a difference in scalings between the momentum pinch originated from inherently toroidal effects and that coming from other mechanisms which exist in a simpler geometry.
An important step for the ATLAS toroid magnet
2000-01-01
The ATLAS experiment's prototype toroid coil arrives at CERN from the CEA laboratory in Saclay on 6 October. The world's largest superconducting toroid magnet is under construction for the ATLAS experiment. A nine-metre long fully functional prototype coil was delivered to CERN at the beginning of October and has since been undergoing tests in the West Area. Built mainly by companies in France and Italy under the supervision of engineers from the CEA-Saclay laboratory near Paris and Italy's INFN-LASA, the magnet is a crucial step forward in the construction of the ATLAS superconducting magnet system. Unlike any particle detector that has gone before, the ATLAS detector's magnet system consists of a large toroidal system enclosing a small central solenoid. The barrel part of the toroidal system will use eight toroid coils, each a massive 25 metres in length. These will dwarf the largest toroids in the world when ATLAS was designed, which measure about six metres. So the ATLAS collaboration decided to build a...
International Nuclear Information System (INIS)
In this Letter, the influence of the ''Coriolis drift'' on small scale instabilities in toroidal plasmas is shown to generate a toroidal momentum pinch velocity. Such a pinch results because the Coriolis drift generates a coupling between the density and temperature perturbations on the one hand and the perturbed parallel flow velocity on the other. A simple fluid model is used to highlight the physics mechanism and gyro-kinetic calculations are performed to accurately assess the magnitude of the pinch. The derived pinch velocity leads to a radial gradient of the toroidal velocity profile even in the absence of a torque on the plasma and is predicted to generate a peaking of the toroidal velocity profile similar to the peaking of the density profile. Finally, the pinch also affects the interpretation of current experiments
Steady-state resistive toroidal-field coils for tokamak reactors
International Nuclear Information System (INIS)
If spatially-averaged values of the beta ratio can reach 5 to 10% in tokamaks, as now seems likely, resistive toroidal-field coils may be advantageous for use in reactors intended for fusion-neutron applications. The present investigation has parameterized the design of steady-state water-cooled copper coils of rectangular cross section in order to maximize figures of merit such as the ratio of fusion neutron wall loading to coil power dissipation. Four design variations distinguished by different ohmic-heating coil configurations have been examined. For a wall loading of 0.5 MW/m2, minimum TF-coil lifetime costs (including capital and electricity costs) are found to occur with coil masses in the range 2400 to 4400 tons, giving 200 to 250 MW of resistive dissipation, which is comparable with the total power drain of the other reactor subsystems
Okamura, Hajime; OUCHI, Masahiro
2003-01-01
Self-compacting concrete was first developed in 1988 to achieve durable concrete structures. Since then, various investigations have been carried out and this type of concrete has been used in practical structures in Japan, mainly by large construction companies. Investigations for establishing a rational mix-design method and self-compactability testing methods have been carried out from the viewpoint of making self-compacting concrete a standard concrete.
Salvetti, M.; Coppi, B.
2015-11-01
Recently there has been an increased awareness of the fact that the line of research based on compact high field machines is the most promising to approach ignition conditions in DT burning plasmas and has acquired new perspectives for its applications. Then the technological solutions that have made these machines possible have become subject to new attention and, in some cases, to rediscovery. The Alcator Program and, followed by Ignitor Program, has led to invent the coupled air-core former poloidal field system that has made compact machine possible and has been adopted on all advanced toroidal machines that came after Alcator. A recently rediscovered solution aimed at reducing the mechanical stresses in the inner legs of the toroidal magnet coils is the ``Upper and Lower Bracing Rings'' system that has had a key role in the design of the Ignitor machine and its evolution. Another solution to minimize the machine dimensions while maintaining high toroidal fields, in order to achieve high plasma current densities, is that of ``bucking and wedging'' of the toroidal magnet by coupling it mechanically to the central solenoid. Sponsored in part by the U.S. DoE.
Physics models in the toroidal transport code PROCTR
Energy Technology Data Exchange (ETDEWEB)
Howe, H.C.
1990-08-01
The physics models that are contained in the toroidal transport code PROCTR are described in detail. Time- and space-dependent models are included for the plasma hydrogenic-ion, helium, and impurity densities, the electron and ion temperatures, the toroidal rotation velocity, and the toroidal current profile. Time- and depth-dependent models for the trapped and mobile hydrogenic particle concentrations in the wall and a time-dependent point model for the number of particles in the limiter are also included. Time-dependent models for neutral particle transport, neutral beam deposition and thermalization, fusion heating, impurity radiation, pellet injection, and the radial electric potential are included and recalculated periodically as the time-dependent models evolve. The plasma solution is obtained either in simple flux coordinates, where the radial shift of each elliptical, toroidal flux surface is included to maintain an approximate pressure equilibrium, or in general three-dimensional torsatron coordinates represented by series of helical harmonics. The detailed coupling of the plasma, scrape-off layer, limiter, and wall models through the neutral transport model makes PROCTR especially suited for modeling of recycling and particle control in toroidal plasmas. The model may also be used in a steady-state profile analysis mode for studying energy and particle balances starting with measured plasma profiles.
Physics models in the toroidal transport code PROCTR
International Nuclear Information System (INIS)
The physics models that are contained in the toroidal transport code PROCTR are described in detail. Time- and space-dependent models are included for the plasma hydrogenic-ion, helium, and impurity densities, the electron and ion temperatures, the toroidal rotation velocity, and the toroidal current profile. Time- and depth-dependent models for the trapped and mobile hydrogenic particle concentrations in the wall and a time-dependent point model for the number of particles in the limiter are also included. Time-dependent models for neutral particle transport, neutral beam deposition and thermalization, fusion heating, impurity radiation, pellet injection, and the radial electric potential are included and recalculated periodically as the time-dependent models evolve. The plasma solution is obtained either in simple flux coordinates, where the radial shift of each elliptical, toroidal flux surface is included to maintain an approximate pressure equilibrium, or in general three-dimensional torsatron coordinates represented by series of helical harmonics. The detailed coupling of the plasma, scrape-off layer, limiter, and wall models through the neutral transport model makes PROCTR especially suited for modeling of recycling and particle control in toroidal plasmas. The model may also be used in a steady-state profile analysis mode for studying energy and particle balances starting with measured plasma profiles
Active toroidal field ripple reduction system in FAST
International Nuclear Information System (INIS)
The fusion advanced studies torus (FAST) has been proposed as a flexible and cost effective machine that is able to support the development of ITER and DEMO operating scenarios exploiting some innovative technology solutions and to investigate the physics of high-performance plasmas in a dimensionless parameter range close to ITER. The FAST magnet consists of 18 coils, spaced by 20o in the toroidal angle, each made up of 14 copper plates, suitably arranged in order to realise 3 turns in the radial direction, with 89.2 kA per coil (in the H-mode plasma scenario 6.5 MA at 7.5 T). The finite number and toroidal extension of the toroidal field coils (TFCs) cause a periodic variation of the toroidal field from its nominal value called toroidal field ripple (TFR). An active ripple reduction system has been comprehensively investigated, by using proper 3D finite elements models, to provide an efficient and flexible system able to minimize the TFR in the region of interest. An optimization study of position and size of the coils required to reduce to an acceptable level for the operations the maximum ripple on the plasma (well below 0.3%), feeding them with currents sustainable during the whole scenario (∼1/10 of the current flowing in TFCs), is presented in this paper.
Toroidal linear force-free magnetic fields with axial symmetry
Vandas, M.; Romashets, E.
2016-01-01
Aims: Interplanetary magnetic flux ropes are often described as linear force-free fields. To account for their curvature, toroidal configurations must be used. The aim is to find an analytic description of a linear force-free magnetic field of the toroidal geometry in which the cross section of flux ropes can be controlled. Methods: The solution is found as a superposition of fields given by linear force-free cylinders tangential to a generating toroid. The cylindrical field is expressed in a series of terms that are not all cylindrically symmetric. Results: We found the general form of a toroidal linear force-free magnetic field. The field is azimuthally symmetric with respect to the torus axis. It depends on a set of coefficients that enables controlling the flux rope shape (cross section) to some extent. By varying the coefficients, flux ropes with circular and elliptic cross sections were constructed. Numerical comparison suggests that the simple analytic formula for calculating the helicity in toroidal flux ropes of the circular cross section can be used for flux ropes with elliptic cross sections if the minor radius in the formula is set to the geometric mean of the semi-axes of the elliptic cross section.
Optical toroidal dipolar response by an asymmetric double-bar metamaterial
Dong, Zheng-Gao; Rho, Junsuk; Li, Jia-Qi; Lu, Changgui; Yin, Xiaobo; Zhang, X; 10.1063/1.4757613
2012-01-01
We demonstrate that the toroidal dipolar response can be realized in the optical regime by designing a feasible nanostructured metamaterial, comprising asymmetric double-bar magnetic resonators assembled into a toroid-like configuration. It is confirmed numerically that an optical toroidal dipolar moment dominates over other moments. This response is characterized by a strong confinement of an E-field component at the toroid center, oriented perpendicular to the H-vortex plane. The resonance-enhanced optical toroidal response can provide an experimental avenue for various interesting optical phenomena associated with the elusive toroidal moment.
Uniaxial backfill block compaction
International Nuclear Information System (INIS)
The main parts of the project were: to make a literature survey of the previous uniaxial compaction experiments; do uniaxial compaction tests in laboratory scale; and do industrial scale production tests. Object of the project was to sort out the different factors affecting the quality assurance chain of the backfill block uniaxial production and solve a material sticking to mould problem which appeared during manufacturing the blocks of bentonite and cruched rock mixture. The effect of mineralogical and chemical composition on the long term functionality of the backfill was excluded from the project. However, the used smectite-rich clays have been tested for mineralogical consistency. These tests were done in B and Tech OY according their SOPs. The objective of the Laboratory scale tests was to find right material- and compaction parameters for the industrial scale tests. Direct comparison between the laboratory scale tests and industrial scale tests is not possible because the mould geometry and compaction speed has a big influence for the compaction process. For this reason the selected material parameters were also affected by the previous compaction experiments. The industrial scale tests were done in summer of 2010 in southern Sweden. Blocks were done with uniaxial compaction. A 40 tons of the mixture of bentonite and crushed rock blocks and almost 50 tons of Friedland-clay blocks were compacted. (orig.)
Dynamics of the Disruption Halo Current Toroidal Asymmetry in NSTX
Energy Technology Data Exchange (ETDEWEB)
S.P. Gerhardt
2012-09-27
This paper describes the dynamics of disruption halo current non-axisymmetries in the lower divertor of the National Spherical Torus Experiment [M. Ono, et al. Nuclear Fusion 40, 557 (2000)]. While. The halo currents typically have a strongly asymmetric structure where they enter the divertor floor, and this asymmetry has been observed to complete up to 7 toroidal revolutions over the duration of the halo current pulse. However, the rotation speed and toroidal extend of the asymmetry can vary significantly during the pulse. The rotation speed, halo current pulse duration, and total number of revolutions tend to be smaller in cases with large halo currents. The halo current pattern is observed to become toroidally symmetric at the end of the halo current pulse. It is proposed that this symmeterization is due to the loss of most or all of the closed field line geometry in the final phase of the vertical displacement event.
Toroidal drift waves with an equilibrium velocity field
International Nuclear Information System (INIS)
The author investigated the effect of a radially sheared poloidal velocity field on the toroidal drift wave which is well known to escape magnetic shear damping through toroidal coupling between different poloidal harmonics centered on individual rational surfaces. He endeavored to model the velocity profile according to that observed at the plasma edge during H-mode shots. The resultant wave formed by the interference of different poloidal harmonics now sees an antiwell created by the H-mode type velocity profile in the radial direction (in contrast to a well formed by the diamagnetic frequency in the absence of velocity fields). The wave, therefore, convects energy outward and hence undergoes damping. Outgoing wave boundary condition then introduces a negative imaginary contribution to the global eigenvalue -- once again confirming the stabilizing role of H-mode type velocity profiles. On the other hand, L-mode type velocity profiles have destabilizing action on toroidal drift waves
Axion Haloscopes with Toroidal Geometry at CAPP/IBS
Ko, B R
2016-01-01
The present state of the art axion haloscope employs a cylindrical resonant cavity in a solenoidal field. We, the Center for Axion and Precision Physics Research (CAPP) of the Institute for Basic Science (IBS) in Korea, are also pursuing halo axion discovery using this cylindrical geometry. However, the presence of end caps of cavities increases challenges as we explore higher frequency regions for the axion at above 2 GHz. To overcome these challenges we exploit a toroidal design of cavity and magnetic field. A toroidal geometry offers several advantages, two of which are a larger volume for a given space and greatly reduced fringe fields which interfere with our preamps, in particular the planned quantum-based devices. We introduce the concept of toroidal axion haloscopes and present ongoing research activities and plans at CAPP/IBS.
Reduction of toroidal ripple by using high Tc superconductors
International Nuclear Information System (INIS)
In this paper we present a new method to reduce the toroidal ripple with use of high Tc superconductors. High Tc superconductors can behave as ferromagnetic or diamagnetic materials depending on their magnetic hysteresis. If they are appropriately arranged and magnetized between the toroidal field coils, they possibly decrease the toroidal field ripple. Here, the preliminary design of ITER is taken as an example, and the effect of the high Tc superconductors on the ripple is evaluated. The magnetic induction due to the superconductors is calculated by the current vector potential method based on the critical state model. Several arrangements of the high Tc superconductors were quantitatively examined in order to reduce the ripple. The results obtained by the calculation show that the maximum ripple value can be reduced to be the required value. (orig.)
Vlasov tokamak equilibria with shearad toroidal flow and anisotropic pressure
Throumoulopoulos, George; Kuiroukidis, Apostolos; Tasso, Henri
2015-11-01
By choosing appropriate deformed Maxwellian ion and electron distribution functions depending on the two particle constants of motion, i.e. the energy and toroidal angular momentum, we reduce the Vlasov axisymmetric equilibrium problem for quasineutral plasmas to a transcendental Grad-Shafranov-like equation. This equation is then solved numerically under the Dirichlet boundary condition for an analytically prescribed boundary possessing a lower X-point to construct tokamak equilibria with toroidal sheared ion flow and anisotropic pressure. Depending on the deformation of the distribution functions these steady states can have toroidal current densities either peaked on the magnetic axis or hollow. These two kinds of equilibria may be regarded as a bifurcation in connection with symmetry properties of the distribution functions on the magnetic axis. This work has received funding from (a) the National Programme for the Controlled Thermonuclear Fusion, Hellenic Republic, (b) Euratom research and training programme 2014-2018 under grant agreement No 633053.
Vlasov tokamak equilibria with shearad toroidal flow and anisotropic pressure
Kuiroukidis, Ap; Tasso, H
2015-01-01
By choosing appropriate deformed Maxwellian ion and electron distribution functions depending on the two particle constants of motion, i.e. the energy and toroidal angular momentum, we reduce the Vlasov axisymmetric equilibrium problem for quasineutral plasmas to a transcendental Grad-Shafranov-like equation. This equation is then solved numerically under the Dirichlet boundary condition for an analytically prescribed boundary possessing a lower X-point to construct tokamak equilibria with toroidal sheared ion flow and anisotropic pressure. Depending on the deformation of the distribution functions these steady states can have toroidal current densities either peaked on the magnetic axis or hollow. These two kinds of equilibria may be regarded as a bifurcation in connection with symmetry properties of the distribution functions on the magnetic axis.
Bi-2223 HTS winding in toroidal configuration for SMES coil
Energy Technology Data Exchange (ETDEWEB)
Kondratowicz-Kucewicz, B; Kozak, S; Kozak, J; Wojtasiewicz, G; Majka, M [Electrotechnical Institute in Warsaw (Poland); Janowski, T, E-mail: t.janowski@pollub.p [Lublin University of Technology (Poland)
2010-06-01
Energy can be stored in the magnetic field of a coil. Superconducting Magnetic Energy Storage (SMES) is very promising as a power storage system for load levelling or power stabilizer. However, the strong electromagnetic force caused by high magnetic field and large coil current is a problem in SMES systems. A toroidal configuration would have a much less extensive external magnetic field and electromagnetic forces in winding. The paper describes the design of HTS winding for SMES coil in modular toroid configuration consist of seven Bi-2223 double-pancakes as well as numerical analysis of SMES magnet model using FLUX 3D package. As the results of analysis the paper presents the optimal coil configuration and the parameters such as radius of toroidal magnet, energy stored in magnet and magnetic field distribution.
Vlasov tokamak equilibria with sheared toroidal flow and anisotropic pressure
Energy Technology Data Exchange (ETDEWEB)
Kuiroukidis, Ap, E-mail: kouirouki@astro.auth.gr [Technological Education Institute of Serres, 62124 Serres (Greece); Throumoulopoulos, G. N., E-mail: gthroum@uoi.gr [Department of Physics, University of Ioannina, GR 451 10 Ioannina (Greece); Tasso, H., E-mail: het@ipp.mpg.de [Max-Planck-Institut für Plasmaphysik, D-85748 Garching (Germany)
2015-08-15
By choosing appropriate deformed Maxwellian ion and electron distribution functions depending on the two particle constants of motion, i.e., the energy and toroidal angular momentum, we reduce the Vlasov axisymmetric equilibrium problem for quasineutral plasmas to a transcendental Grad-Shafranov-like equation. This equation is then solved numerically under the Dirichlet boundary condition for an analytically prescribed boundary possessing a lower X-point to construct tokamak equilibria with toroidal sheared ion flow and anisotropic pressure. Depending on the deformation of the distribution functions, these steady states can have toroidal current densities either peaked on the magnetic axis or hollow. These two kinds of equilibria may be regarded as a bifurcation in connection with symmetry properties of the distribution functions on the magnetic axis.
Linear wave propagation in a hot axisymmetric toroidal plasma
International Nuclear Information System (INIS)
Kinetic effects on the propagation of the Alfven wave are studied for the first time in a toroidal plasma relevant for experiments. This requires the resolution of a set of coupled partial differential equations whose coefficients depend locally on the plasma parameters. For this purpose, a numerical wave propagation code called PENN has been developed using either a bilinear or a bicubic Hermite finite element discretization. It solves Maxwell's equations in toroidal geometry, with a dielectric tensor operator that takes into account the linear response of the plasma. Two different models have been implemented and can be used comparatively to describe the same physical case: the first treats the plasma as resistive fluids and gives results which are in good agreement with toroidal fluid codes. The second is a kinetic model and takes into account the finite size of the Larmor radii; it has successfully been tested against a kinetic plasma model in cylindrical geometry. New results have been obtained when studying kinetic effects in toroidal geometry. Two different conversion mechanisms to the kinetic Alfven wave have been described: one occurs at toroidally coupled resonant surfaces and is the kinetic counterpart of the fluid models' resonance absorption. The other has no such correspondence and results directly from the toroidal coupling between the kinetic Alfven wave and the global wavefield. An analysis of a heating scenario suggests that it might be difficult to heat a plasma with Alfven waves up to temperatures that are relevant for a tokamak reactor. Kinetic effects are studied for three types of global Alfven modes (GAE, TAE, BAE) and a new class of kinetic eigenmodes is described which appear inside the fluid gap: it could be related to recent observations in the JET (Joint European Torus) tokamak. (author) 56 figs., 6 tabs., 58 refs
On rotation of multi-species plasmas in toroidal systems
International Nuclear Information System (INIS)
This paper describes the poloidal and toroidal spin-up of an isothermal plasma in toroidal equilibria. The mechanism is the Stringer spin-up mechanism which will be generalized to an arbitrary toroidal equilibrium using the Hamada coordinate system. Viscous damping or magnetic pumping balances the accelerating forces and determines the threshold of spin-up. The accelerating forces arise from the Coriolis forces which couple the radial flow to the poloidal flow velocity. The theory presented here is a continuation of a previous paper and applies to a multi-species plasma with impurities. In the two-fluid model - or including impurities - in a multi-fluid model, the flux-friction relations derived on every magnetic surface are the basic equations for computing the poloidal and toroidal flow velocities of the particle species. Futhermore, the effect of turbulent forces on the mean flow is analysed. The Reynolds stresses resulting from anisotropic turbulence provide a force in the tangential direction and thus contribute to the poloidal and toroidal spin-up. Furthermore, turbulence increases the Stringer spin-up mechanism and introduces enhanced plasma losses. The final result is a set of differential equations describing the poloidal and toroidal flow on every magnetic surface. The formalism is valid in every regime of collisionality; however, to obtain specific results, appropriate appoximations must be found for every regime. This will be outlined for the collisional regime where the viscous forces are given by Braginskii's equations. The relation between plasma rotation and the zonal circulation in planetary atmospheres will be discussed. (Author)
Active trajectory control for a heavy ion beam probe on the compact helical system
International Nuclear Information System (INIS)
A 200 keV heavy ion beam probe (HIBP) on the Compact Helical System torsatron/heliotron uses a newly proposed method in order to control complicated beam trajectories in non-axisymmetrical devices. As a result, the HIBP has successfully measured potential profiles of the toroidal helical plasma. The article will describe the results of the potential profile measurements, together with the HIBP hardware system and procedures to realize the method. (author)
Toroidal vortices as a solution to the dust migration problem
Loren-Aguilar, Pablo
2015-01-01
In an earlier letter, we reported that dust settling in protoplanetary discs may lead to a dynamical dust-gas instability that produces global toroidal vortices. In this letter, we investigate the evolution of a dusty protoplanetary disc with two different dust species (1 mm and 50 cm dust grains), under the presence of the instability. We show how toroidal vortices, triggered by the interaction of mm grains with the gas, stop the radial migration of metre-sized dust, potentially offering a natural and efficient solution to the dust migration problem.
Experiments with a fully toroidal Extrap Z-pinch
International Nuclear Information System (INIS)
In the Extrap plasma confinement scheme, a Z-pinch is produced along the null of an octupole field generated by currents in external conductors. In the paper, studies of the discharge startup process in a fully toroidal configuration are described. Startup involves first breaking down a toroidal discharge and then driving up the current in order to reach the pinch parameter regime. Current densities of 2x106 A·m-2 have been achieved. The estimated plasma density is 6x1020m-3, and the temperature is about 4 eV. These parameters correspond to pinch conditions. (author)
Low frequency wave propagation in hot toroidal plasma
International Nuclear Information System (INIS)
The equation for low frequency wave propagation in full toroidal geometry with arbitrary cross section is derived. It is mainly shown that, when including self consistently the various absorption terms from Vlasov equation in the dielectric tensor, the global wave structure is described by a fourth order system, which even reduces to a second order Helmoltz type equation when neglecting toroidal corrections. Close to the singular ion ion conversion layer, the structure of the wave is strongly affected. Finite Larmor radius conversion effects there compete with simple absorption mechanisms via Landau or cyclotron Landau damping making the FLR effects not likely to dominate nor even occur
Toroidal equilibrium of plasma with concentrated relativistic electron beam
International Nuclear Information System (INIS)
A simplified model has been given for toroidal equilibrium of a tokamak-type plasma with high-current concentrated electron beam. The plasma has a thermal pressure, and the electron beam has effective inertial pressure. Strong deformations of tokamak equilibria have been simulated by numerical calculations. Toroidal equilibria with relatively large vertical field are obtained when we consider high-energy intense electron beam. The beam orbit, which is shifted outward from the magnetic axis of the plasma, is closed by the sum of the externally applied relatively large vertical field and the poloidal magnetic field of the plasma. (author)
Development and verification of printed circuit board toroidal transformer model
DEFF Research Database (Denmark)
Pejtersen, Jens; Mønster, Jakob Døllner; Knott, Arnold
2013-01-01
comparing calculated parameters with 3D finite element simulations and experimental measurement results. The developed transformer model shows good agreement with the simulated and measured results. The model can be used to predict the parameters of printed circuit board toroidal transformer configurations......An analytical model of an air core printed circuit board embedded toroidal transformer configuration is presented. The transformer has been developed for galvanic isolation of very high frequency switch-mode dc-dc power converter applications. The theoretical model is developed and verified by...
Development and verification of printed circuit board toroidal transformer model
DEFF Research Database (Denmark)
Pejtersen, Jens; Mønster, Jakob Døllner; Knott, Arnold
comparing calculated parameters with 3D finite element simulations and experimental measurement results. The developed transformer model shows good agreement with the simulated and measured results. The model can be used to predict the parameters of printed circuit board toroidal transformer configurations......An analytical model of an air core printed circuit board embedded toroidal transformer configuration is presented. The transformer has been developed for galvanic isolation of very high frequency switch-mode dc-dc power converter applications. The theoretical model is developed and verified by...
Comparative study between toroidal coordinates and the magnetic dipole field
Chávez-Alarcón, Esteban
2012-01-01
There is a similar behaviour between the toroidal coordinates and the dipole magnetic field produced by a circular loop. In this work we evaluate up to what extent the former can be used as a representation of the latter. While the tori in the toroidal coordinates have circular cross sections, those of the circular loop magnetic field are nearly elliptical ovoids, but they are very similar for large aspect ratios.The centres of the latter displace from the axis faster than the former. By making a comparison between tori of similar aspect ratios, we find quantitative criteria to evaluate the accuracy of the approximation.
Self-interference of a toroidal Bose–Einstein condensate
International Nuclear Information System (INIS)
We demonstrate the self-interference of a single Bose–Einstein condensate on a non-simply connected geometry, focussing on a toroidally trapped ring-shaped condensate. First, we show how the opposite parts of the ring can interfere using the Wigner function representation. Then, using analytical expressions for the time-evolution of a freely expanding ring-shaped condensate with and without a persistent current, we show that the self-interference of the ring-shaped condensate is possible only in the absence of the persistent current. We conclude by proposing an experimental protocol for the creation of ring dark solitons using the toroidal self-interference
Ion temperature gradient modes in toroidal helical systems
International Nuclear Information System (INIS)
Linear properties of ion temperature gradient (ITG) modes in helical systems are studied. The real frequency, growth rate, and eigenfunction are obtained for both stable and unstable cases by solving a kinetic integral equation with proper analytic continuation performed in the complex frequency plane. Based on the model magnetic configuration for toroidal helical systems like the Large Helical Device (LHD), dependences of the ITG mode properties on various plasma equilibrium parameters are investigated. Particularly, relative effects of ∇B-curvature drifts driven by the toroidicity and by the helical ripples are examined in order to compare the ITG modes in helical systems with those in tokamaks. (author)
Toroidal Spiral Strings in Higher-dimensional Spacetime
Igata, Takahisa; Ishihara, Hideki
2010-01-01
We report on our progress in research of separability of the Nambu-Goto equation for test strings with a symmetric configuration in a shape of toroidal spiral in a five-dimensional Kerr-AdS black hole. In particular, for a Hopf loop string which is a special class of the toroidal spirals, we show the complete separation of variables occurs in two cases, Kerr background and Kerr-AdS background with equal angular momenta. We also obtain the dynamical solution for the Hopf loop around a black ho...
Reevaluation of the Braginskii viscous force for toroidal plasma
Johnson, Robert W
2009-01-01
The model by Braginskii for the viscous stress tensor is used to determine the shear and gyroviscous forces acting within a toroidally confined plasma. Comparison is made to previous evaluations which contain an inconsistent treatment of the radial derivative and neglect the effect of the pitch angle. A radial gyroviscous force is found to survive the limit of constant density and rigid toroidal rotation of the flux surface, and a radial shear viscous force may develop for sufficient vertical asymmetry to the ion velocity profile.
Induction Motor with Switchable Number of Poles and Toroidal Winding
Directory of Open Access Journals (Sweden)
MUNTEANU, A.
2011-05-01
Full Text Available This paper presents a study of an induction motor provided with toroidal stator winding. The ring-type coils offer a higher versatility in obtaining a different number of pole pairs by means of delta/star and series/parallel connections respectively. As consequence, the developed torque can vary within large limits and the motor can be utilized for applications that require, for example, high load torque values for a short time. The study involves experimental tests and FEM simulation for an induction machine with three configurations of pole pairs. The conclusions attest the superiority of the toroidal winding for certain applications such as electric vehicles or lifting machines.
UWMAK-I: a Wisconsin toroidal fusion reactor design. Volume I
International Nuclear Information System (INIS)
The design details of a low-β, D-T fusion reactor based on the Tokamak confinement concept is described. Included in the report are technological problems that have been assessed or uncovered, whether or not detailed solutions are presented. The thermal power output of the plant is 5000 MW. The basic structural material is 316 stainless steel and the heat transfer medium is lithium. Materials compatibility limits the maximum temperature to 5000C implying an electrical output of approximately 1500 MW/sub e/ is to be expected. The plasma is characterized by an average toroidal beta of 0.052 and an average poloidal beta of 1.08. The nominal plasma radius is 5 meters and the torus radius is 13 meters, giving an aspect ratio of 2.6. The ion and electron temperatures are 11.1 keV and 11 keV, respectively, and the average ion density is 0.8 x 1014 (D+T) ions/cm3. The mean particle confinement time is 14.2 seconds and the fractional burnup is 7.2 percent, and the burn time is 5400 seconds
International Nuclear Information System (INIS)
The effects of a sheared toroidal rotation on the dynamics of bursting Toroidicity-induced Alfven eigenmodes are investigated in neutral beam heated plasmas on the National Spherical Torus Experiment (NSTX) (M. Ono et al., Nucl. Fusion 40 557 (2000)). The modes have a global character, extending over most of the minor radius. A toroidal rotation shear layer is measured at the location of maximum drive for the modes. Contrary to results from other devices, no clear evidence of increased damping is found. Instead, experiments with simultaneous neutral beam and radio-frequency auxiliary heating show a strong correlation between the dynamics of the modes and the instability drive. It is argued that kinetic effects involving changes in the mode drive and damping mechanisms other than rotation shear, such as continuum damping, are mostly responsible for the bursting dynamics of the modes.
Energy Technology Data Exchange (ETDEWEB)
Podesta, M; Fredrickson, E D; Gorelenkov, N N; LeBlanc, B P; Heidbrink, W W; Crocker, N A; Kubota, S
2010-08-19
The effects of a sheared toroidal rotation on the dynamics of bursting Toroidicity-induced Alfven eigenmodes are investigated in neutral beam heated plasmas on the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40 557 (2000)]. The modes have a global character, extending over most of the minor radius. A toroidal rotation shear layer is measured at the location of maximum drive for the modes. Contrary to results from other devices, no clear evidence of increased damping is found. Instead, experiments with simultaneous neutral beam and radio-frequency auxiliary heating show a strong correlation between the dynamics of the modes and the instability drive. It is argued that kinetic effects involving changes in the mode drive and damping mechanisms other than rotation shear, such as continuum damping, are mostly responsible for the bursting dynamics of the modes.
The sensitivity of barley, field beans and sugar beet to soil compaction
Brereton, Jeremy Charles
1986-01-01
The sensitivity of spring barley (Hordeum vulgare, cv. Carnival), field beans (Vicia faba, ev. Maris Bead) and sugar beet (Beta vulgaris,cv. Monoire) to topsoil compaction induced by tractor wheelings, post sowing, on a coarse gravelly loam of the Arrow series was investigated in 1983 and 1984. The study revealed that in both years topsoil compaction increased the dry bulk density, vane shear strength and cone resistance of the soil. Although compaction reduced only the plant population o...
Finding regions of interest on toroidal meshes
Energy Technology Data Exchange (ETDEWEB)
Wu Kesheng; Sinha, Rishi R; Shoshani, Arie [Lawrence Berkeley National Laboratory, Berkeley, CA (United States); Jones, Chad; Ma, Kwan-Liu [University of California, Davis, CA (United States); Ethier, Stephane [Princeton Plasma Physics Laboratory, Princeton, NJ (United States); Klasky, Scott [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Winslett, Marianne, E-mail: kwu@lbl.gov [University of Illinois, Urbana-Champaign, IL (United States)
2011-01-15
Fusion promises to provide clean and safe energy, and a considerable amount of research effort is under way to turn this aspiration into a reality. This work focuses on a building block for analyzing data produced from the simulation of microturbulence in magnetic confinement fusion devices: the task of efficiently extracting regions of interest. Like many other simulations where a large number of data are produced, the careful study of 'interesting' parts of the data is critical to gain understanding. In this paper, we present an efficient approach for finding these regions of interest. Our approach takes full advantage of the underlying mesh structure in magnetic coordinates to produce a compact representation of the mesh points inside the regions and an efficient connected component labeling algorithm for constructing regions from points. This approach scales linearly with the surface area of the regions of interest instead of the volume as shown with both computational complexity analysis and experimental measurements. Furthermore, this new approach is hundreds of times faster than a recently published method based on Cartesian coordinates.
Finding Regions of Interest on Toroidal Meshes
International Nuclear Information System (INIS)
Fusion promises to provide clean and safe energy, and a considerable amount of research effort is underway to turn this aspiration intoreality. This work focuses on a building block for analyzing data produced from the simulation of microturbulence in magnetic confinement fusion devices: the task of efficiently extracting regions of interest. Like many other simulations where a large amount of data are produced, the careful study of 'interesting' parts of the data is critical to gain understanding. In this paper, we present an efficient approach for finding these regions of interest. Our approach takes full advantage of the underlying mesh structure in magnetic coordinates to produce a compact representation of the mesh points inside the regions and an efficient connected component labeling algorithm for constructing regions from points. This approach scales linearly with the surface area of the regions of interest instead of the volume as shown with both computational complexity analysis and experimental measurements. Furthermore, this new approach is 100s of times faster than a recently published method based on Cartesian coordinates.
Finding regions of interest on toroidal meshes
International Nuclear Information System (INIS)
Fusion promises to provide clean and safe energy, and a considerable amount of research effort is under way to turn this aspiration into a reality. This work focuses on a building block for analyzing data produced from the simulation of microturbulence in magnetic confinement fusion devices: the task of efficiently extracting regions of interest. Like many other simulations where a large number of data are produced, the careful study of 'interesting' parts of the data is critical to gain understanding. In this paper, we present an efficient approach for finding these regions of interest. Our approach takes full advantage of the underlying mesh structure in magnetic coordinates to produce a compact representation of the mesh points inside the regions and an efficient connected component labeling algorithm for constructing regions from points. This approach scales linearly with the surface area of the regions of interest instead of the volume as shown with both computational complexity analysis and experimental measurements. Furthermore, this new approach is hundreds of times faster than a recently published method based on Cartesian coordinates.
Energy Technology Data Exchange (ETDEWEB)
Hartmann, Betti [School of Engineering and Science, Jacobs University, Postfach 750 561, D-28725 Bremen (Germany); Kleihaus, Burkhard; Kunz, Jutta [Institut fuer Physik, Universitaet Oldenburg, Postfach 2503, D-26111 Oldenburg (Germany); Schaffer, Isabell, E-mail: i.schaffer@jacobs-university.de [School of Engineering and Science, Jacobs University, Postfach 750 561, D-28725 Bremen (Germany)
2012-07-24
We consider compact boson stars that arise for a V-shaped scalar field potential. They represent a one parameter family of solutions of the scaled Einstein-Gordon equations. We analyze the physical properties of these solutions and determine their domain of existence. Along their physically relevant branch emerging from the compact Q-ball solution, their mass increases with increasing radius. Employing arguments from catastrophe theory we argue that this branch is stable, until the maximal value of the mass is reached. There the mass and size are on the order of magnitude of the Schwarzschild limit, and thus the spiraling respectively oscillating behaviour, well known for compact stars, sets in.
Current profile reconstruction using X-ray imaging on the PEGASUS toroidal experiment
Tritz, Kevin Lee
Internal plasma profiles, specifically the current profile, are necessary to accurately characterize the plasma equilibrium and perform detailed stability analyses of magnetically confined toroidal plasmas. External magnetic measurements alone are not sufficient to properly constrain the current profile for an equilibrium reconstruction. This work confirms the insensitivity of the profiles to external magnetics and demonstrates the successful incorporation of tangential X-ray imaging into a modified equilibrium code for current profile reconstruction in highly shaped, low aspect-ratio plasmas. An equilibrium reconstruction code was developed that used two dimensional X-ray images to constrain a flexible spline parameterization of the plasma profiles. Image constraint modeling was performed with this code, demonstrating that the profiles were well constrained, with less than 10% deviation of the reconstructed central safety factor, if the image measurement noise was held below 2% for emissivity constraints, and below 1% for intensity constraints. Two tangential soft X-ray pinhole camera imaging systems, a transmissive and reflective phosphor design, were built and operated on the PEGASUS toroidal experiment. Intensity image contours from these systems were used to constrain equilibrium reconstructions of the plasma discharge. The shapes and values of the q profiles determined by these reconstructions correspond well with the presence of coherent MHD activity observed in the plasmas. A comparison of the X-ray intensity-constrained equilibria with the external-magnetics-only reconstructions showed good agreement between most gross plasma parameters, but large variation between the reconstructed profiles. A next generation X-ray imaging system was designed to provide higher sensitivity, a more compact form factor, and multiple time point capability. The increased sensitivity will allow the variance of the experimental reconstructed profiles to achieve the level
The Superconducting Toroid for the New International AXion Observatory (IAXO)
Shilon, I; Silva, H; Wagner, U; Kate, H H J ten
2013-01-01
IAXO, the new International AXion Observatory, will feature the most ambitious detector for solar axions to date. Axions are hypothetical particles which were postulated to solve one of the puzzles arising in the standard model of particle physics, namely the strong CP (Charge conjugation and Parity) problem. This detector aims at achieving a sensitivity to the coupling between axions and photons of one order of magnitude beyond the limits of the current detector, the CERN Axion Solar Telescope (CAST). The IAXO detector relies on a high-magnetic field distributed over a very large volume to convert solar axions to detectable X-ray photons. Inspired by the ATLAS barrel and end-cap toroids, a large superconducting toroid is being designed. The toroid comprises eight, one meter wide and twenty one meters long racetrack coils. The assembled toroid is sized 5.2 m in diameter and 25 m in length and its mass is about 250 tons. The useful field in the bores is 2.5 T while the peak magnetic field in the windings is 5....
Theory of the M = 1 Kink Mode in Toroidal Plasma
de Blank, H. J.; Schep, T. J.
1991-01-01
The energy principle of ideal magnetohydrodynamics (MHD) is used to study the ideal MHD stability of the m = 1 internal kink mode in a toroidal plasma. The equilibrium configurations that are considered allow for a broad region where the safety factor q is close to unity. This region may extend to t
A toroidal inductor integrated in a standard CMOS process
DEFF Research Database (Denmark)
Vandi, Luca; Andreani, Pietro; Temporiti, Enrico;
2007-01-01
This paper presents a toroidal inductor integrated in a standard 0.13 um CMOS process. Finite-elements preliminary simulations are provided to prove the validity of the concept. In order to extract fundamental parameters by means of direct calculations, two different and well-known approaches...
First studies of plasma confined in a toroidal heliac
International Nuclear Information System (INIS)
The first experimental results obtained on plasma confined in a toroidal heliac are reported. A simple method of generating highly ionized, weakly collisional plasma is described. It is found that the geometry of the plasma in general and the measured pressure profiles in particular conform closely with the calculated helical axis magnetic surfaces. Preliminary indications of plasma confinement are favourable
Plasma Heating and Losses in Toroidal Multipole Fields
International Nuclear Information System (INIS)
The heating and loss of plasmas have been studied in three pulsed, toroidal multipole devices: a large levitated octupole, a small supported octupole and a very small supported quadrupole. Plasmas are produced by gun injection and heated by electron and ion cyclotron resonance heating and ohmic heating. Electron cyclotron heating rates have been measured over a wide range of parameters, and the results are in quantitative agreement with stochastic heating theory. Electron cyclotron resonance heating produces ions with energies larger than predicted by theory. With the addition of a toroidal field, ohmic heating gives densities as high as 1013cm-3 in the toroidal quadrupole and 1012cm-3 in the small octupole. Plasma losses for n=5 x 109cm-3 plasmas are inferred from Langmuir probe and Fabry-Perot interferometer measurements, and measured with special striped collectors on the wall and rings. The loss to a levitated ring is measured using a modulated light beam telemeter. The confinement is better than Bohm but considerably worse than classical. Low frequency convective cells which are fixed in space are observed. These cells around the ring are diminished when a weak toroidal field is added, and loss collectors show a vastly reduced flux to the rings. Analysis of the spatial density profile shows features of B-independent diffusion. The confinement is sensitive to some kinds of dc field errors, but surprisingly insensitive to perturbations of the ac confining field
ATLAS-Lowering the first Barrel Toroid coil
CERN Audiovisual Unit
2004-01-01
Cranes lowered the first of ATLAS's eight Barrel Toroid coils into the cavern. The part is 25 metres long and the cranes had to hold the 100 tonne coil at a sharp angle while it passed through the 18-metre diameter vertical shaft into the cavern. Then they laid the magnet to a horisontal robust platform. Images from Camera 1
ATLAS-Lowering the first Barrel Toroid coil
CERN Audiovisual Unit
2004-01-01
Cranes lowered the first of ATLAS's eight Barrel Toroid coils into the cavern. The part is 25 meters long and the cranes had to hold the 100 tonne coil at a sharp angle while it passed through the 18-meter diameter vertical shaft into the cavern. Then they laid the magnet to a horizontal robust platform. Images from Camera 2
Construction and initial operation of the Advanced Toroidal Facility
International Nuclear Information System (INIS)
The Advanced Toroidal Facility (ATF) torsatron was designed on a physics basis for access to the second stability regime and on an engineering basis for independent fabrication of high-accuracy components. The actual construction, assembly, and initial operation of ATF are compared with the characteristics expected during the design of ATF. 31 refs., 19 figs., 2 tabs
Plasma Processes : Minimum dissipative relaxed states in toroidal plasmas
Indian Academy of Sciences (India)
R Bhattacharyya; M S Janaki; B Dasgupta
2000-11-01
Relaxation of toroidal discharges is described by the principle of minimum energy dissipation together with the constraint of conserved global helicity. The resulting Euler-Lagrange equation is solved in toroidal coordinates for an axisymmetric torus by expressing the solutions in terms of Chandrasekhar-Kendall (C-K) eigenfunctions analytically continued in the complex domain. The C-K eigenfunctions are obtained as hypergeometric functions that are solutions of scalar Helmholtz equation in toroidal coordinates in the large aspect-ratio approximation. Equilibria are constructed by assuming the current to vanish at the edge of plasma. For the = 0; = 0 ( and are the poloidal and toroidal mode numbers respectively) relaxed states, the magnetic ﬁeld, current, (safety factor) and pressure proﬁles are calculated for a given value of aspect-ratio of the torus and for different values of the eigenvalue 0. The new feature of the present model is that solutions allow for both tokamak as well as RFP-like behaviour with increase in the values of 0, which is related directly to volt-sec in the experiment.
First ATLAS Barrel Toroid coil casing arrives at CERN
2002-01-01
The first of eight 25-metre long coil casings for the ATLAS experiment's barrel toroid magnet system arrived at CERN on Saturday 2 March by road from Heidelberg. This structure will be part of the largest superconducting toroid magnet ever made. The first coil casing for the toroidal magnets of Atlas arrives at Building 180. This is the start of an enormous three-dimensional jigsaw puzzle. Each of the eight sets of double pancake coils will be housed inside aluminium coil casings, which in turn will be held inside a stainless steel vacuum vessel. A huge construction, the casing that arrived at CERN measures 25 metres in length and 5 metres in width. It weighs 20 tones. And this is just the beginning of the toroid jigsaw: by early April a batch of four double pancake coils, which altogether weighs 65 tones, will arrive from Ansaldo in Italy. The first vacuum vessel will also be arriving from Felguera in Spain this month. It will take about two years for all these 25 m long structures of casings, coils a...
An Overview of Plasma Confinement in Toroidal Systems
Dini, Fatemeh; Baghdadi, Reza; Amrollahi, Reza; Khorasani, Sina
2009-01-01
This overview presents a tutorial introduction to the theory of magnetic plasma confinement in toroidal confinement systems with particular emphasis on axisymmetric equilibrium geometries, and tokamaks. The discussion covers three important aspects of plasma physics: Equilibrium, Stability, and Transport. The section on equilibrium will go through an introduction to ideal magnetohydrodynamics, curvilinear system of coordinates, flux coordinates, extensions to axisymmetric equilibrium, Grad-Sh...
Stationary magnetohydrodynamic equilibrium of toroidal plasma in rotation
International Nuclear Information System (INIS)
The stationary equations of classical magnetohydrodynamics are utilized to study the toroidal motion of a thermonuclear magnetically - confined plasma with toroidal symmetry (Tokamak). In the present work, we considered a purely toroidal stationary rotation and te problem is reduced to studing a second order partial differencial equation of eliptic type Maschke-Perrin. Assuming that the temperature remains constant on the magnetic surfaces, an analitic solution, valid for low Mach numbers (M ≤ 0 .4), was obtained for the above-mentioned equation by means of a technique developed by Pantuso Sudano. From the solution found, we traced graphs for the quantities which described the equilibrium state of the plasma, namely: mass density, pressure, temperature, electric current density and toroidal magnetic field. Finally we compare this analitical model with others works which utilized differents analitical models and numerical simulations. We conclude that the solutions obtained are in good agreement with the previos results. In addition, however, our model contains the results of Sudano-Goes with the additional advantage of employing much simple analitical expressions. (author)
Evidence of Inward Toroidal Momentum Convection in the JET Tokamak
DEFF Research Database (Denmark)
Tala, T.; Zastrow, K.-D.; Ferreira, J.;
2009-01-01
Experiments have been carried out on the Joint European Torus tokamak to determine the diffusive and convective momentum transport. Torque, injected by neutral beams, was modulated to create a periodic perturbation in the toroidal rotation velocity. Novel transport analysis shows the magnitude an...
Barrel Toroid fully charged to nominal field, and it works!
Herman ten Kate
After a few weeks of testing up to intermediate currents, finally, on Thursday evening November 9, the current in the Barrel Toroid was pushed up to its nominal value of 20500 A and even 500 A beyond this value to prove that we have some margin. It went surprisingly well. Of course, the 8 coils forming the toroid were already tested individually at the surface but still, some surprise may have come from those parts added to the toroid in the cavern for the first time like the 8 cryoring sections linking the coils as well as the valve box at the bottom in sector 13 regulating the helium flow or the current lead cryostat on the top in sector 5. No training quenches, nothing to worry about, and the test was concluded with a fast dump triggered at 00:40 in the very early morning of November 10. (left) The toroid current during the evening and night of November 9. (right) The test crew oscillated between fear and hope while looking at the control panels as the current approached 21kA. Big relief was in the...
Stability of toroidal magnetic fields in stellar interiors
Ibañez-Mejia, Juan C
2015-01-01
We present 3D MHD simulations of purely toroidal and mixed poloidal-toroidal magnetic field configurations to study the behavior of the Tayler instability. For the first time the simultaneous action of rotation and magnetic diffusion are taken into account and the effects of a poloidal field on the dynamic evolution of unstable toroidal magnetic fields is included. In the absence of diffusion, fast rotation (rotation rate compared to Alfv\\'en frequency) is able to suppress the instability when the rotation and magnetic axes are aligned and when the radial field strength gradient p 1.5, rapid rotation does not suppress the instability but instead introduces a damping factor to the growth rate in agreement with the analytic predictions. For the mixed poloidal-toroidal fields we find an unstable axisymmetric mode, not predicted analytically, right at the stability threshold for the non-axisymmetric modes; it has been argued that an axisymmetric mode is necessary for the closure of the Tayler-Spruit dynamo loop.
The Quasi-Toroidal Stellarator: An Innovative Confinement Experiment
International Nuclear Information System (INIS)
To develop a new class of stellarators that exhibit improved confinement compared to conventional stellarators. This approach generally makes use of a designed symmetry of the magnetic field strength along a particular coordinate axis in the toroidal geometry of the stellarator, and is referred to as quasi-symmetry
Toroidal and poloidal momentum transport studies in JET
DEFF Research Database (Denmark)
Tala, T.; Andrew, Y.; Crombe, K.;
2007-01-01
This paper reports on the recent studies of toroidal and poloidal momentum transport in JET. The ratio of the global energy confinement time to the momentum confinement is found to be close to tau(E)/tau(phi) = 1 except for the low density or low collisionality discharges where the ratio is tau(E...
Toroidal solenoids in the electromagnetic field and Aharonov-Casher effect
International Nuclear Information System (INIS)
The current toroidal configurations are found which generate gauge nonequivalent vector potentials and correspond to the same quantum scattering of charged particles. The equations for the motion of toroidal moment in the magnetic field are obtained. It is proved the existence of Aharonov-Casher effect for the toroidal solenoids. The relating experiments are proposed. 19 refs.; 7 figs
Homogeneous Construction of the Toroidal Lie Algebra of Type A1
Institute of Scientific and Technical Information of China (English)
Haifeng Lian; Cui Chen; Qinzhu Wen
2007-01-01
In this paper,we consider an analogue of the level two homogeneous construc-tion of the affine Kac-Moody algebra A1(1) by vertex operators.We construct modules for the toroidal Lie algebra and the extended toroidal Lie algebra of type A1.We also prove that the module is completely reducible for the extended toroidal Lie algebra.
Results of the variable toroidal field ripple experiments in JET
International Nuclear Information System (INIS)
The main goal of ITER is to produce plasmas with high fusion gain (QDT > 10), where a large fraction of the plasma heating is supplied by the α-particles from fusion reactions. To first order, this requires both thermal and fast ion confinement to be at least as good as predictions. In all tokamak devices, the finite number and toroidal extension of the toroidal field (TF) coils causes a periodic variation of the toroidal field from its nominal value, called toroidal field ripple δBT = (Bmax - Bmin)/Bav. It is well known that ripple in the toroidal field adversely affects fast ion confinement, and in the case of ITER, this has been accounted for by including in the design Ferritic Insets (FI) compensation, reducing δBT from approx 1.2% to approx 0.5%, to reduce first wall power loads. In these conditions, the main α-particle loss mechanism in ITER will be ripple banana orbit diffusion, and that the magnitude of these losses is expected to be in the 1% region, therefore negligible in terms of alpha-particle confinement. Experimental results from JT60-U and H-mode dimensionless H-mode experiments in JET and JT-60U have indicated that ripple may also affect the H-mode confinement, pedestal height, ELM size and plasma rotation. Although the physics mechanisms at the root of the reduced energy confinement with δBT was not identified unambiguously, the implication of a reduction of energy confinement on projected ITER performance due to ripple stimulated a series of experiments at JET. The experiments were carried out in the ELMy H-mode regime with q95 = 3, and investigated the effect of δBT on the pedestal and core properties of the plasma. Plasma density pump out and reduction of the global energy confinement was found for δBT around 0.5, in some experimental conditions. Ripple was also found to affect the size and frequency of ELMs. Plasma toroidal rotation was also strongly affected by ripple: the toroidal velocity is reduced for increased ripple and becomes
Roller compaction of theophylline
Hadzovic, Ervina
2008-01-01
1. Summary Direct compaction requires a very good flowability and compressibility of the materials. Those parameters become even more critical if the formulation contains large amount of active substance. To overcome these problems, several alternatives have been used. Roller compaction is a very attractive technology in the pharmaceutical industry. It is a fast and efficient way of producing granules, especially suitable for moisture sensitive materials. The intention of this work was to ...
Microfabrication of toroidal inductors integrated with nanolaminated ferromagnetic metallic cores
International Nuclear Information System (INIS)
We report microfabricated toroidal inductors with nanolaminated ferromagnetic metallic cores for chip-scale, high-power switching converters. The fabrication process of the toroidal inductor is based on individual manufacturing of partial windings (i.e. bottom and vertical conductors) and nanolaminated magnetic core, and integrating them by means of a drop-in approach. The nanolaminated ferromagnetic metallic cores presented in this paper consist of many multilayers of electrodeposited CoNiFe films, each layer with sub-micron thickness, with a total core thickness exceeding tens of microns. The beneficial magnetic properties (i.e. high saturation flux density and low coercivity) of CoNiFe alloys are well suited for chip-scale inductors as they achieve both large energy storage capacity as well as minimized volumetric core losses at high operating frequencies due to their nanolaminated structure. A drop-in integration approach, introduced to combine the microfabricated toroidal inductor windings with the magnetic cores, allows ease of integration. An advantage of this hybrid approach over monolithic fabrication in this application is the potential use of a wide variety of core materials, both microfabricated and bulk-fabricated, and which may or may not ultimately be CMOS-compatible. Exploiting this drop-in approach, 30-turn- and 50-turn-toroidal inductors integrated with nanolaminated CoNiFe cores, having 10 mm outer diameter and 1 mm thickness, have been successfully developed. Both types of inductors exhibit inductances higher than 1 µH at frequencies up to tens of MHz, showing ten times the inductance of an air core device with the same nominal geometry. The peak quality factor of the 30-turn-toroidal inductor reaches 18 at 1 MHz. (paper)
Dynamical conservation of invariants by toroidal trajectories of guiding centres
International Nuclear Information System (INIS)
The classical problem of calculating toroidal trajectories is treated here by comparing the results of two different methods in a given magnetic configuration, a standard divergence-free magnetic field model. The present work consists of adapting the analytical criteria of MERCIER et al. for classical toroidal trajectories, and to examine numerically the dynamical conservation of the toroidal invariant. The first method is based on the evolution equations for the guiding centres. These equations are then solved numerically (code TRATORIA) and the trajectories are drawn for different initial conditions. We use a modified standard model for the magnetic field, which insures a manifestly divergence-free field. Moreover we take into account the contribution of the poloidal field to the total strength of the magnetic field. These corrections contribute to the analytical expression of the conserved toroidal momentum. The latter is verified to be conserved by the present numerical simulation with a precision generally of the order of 10-14. The second method is based on the analytical treatment of the invariants to yield a semi-analytical (semi graphical) determination of the intersection point of a given trajectory with the equatorial plane. Both methods allows one to recover well-known toroidal trajectories with passing and trapped particles (bananas). The present analysis brings a clear description of some other, less well-known types of trajectories, namely the stagnation orbits, the smallest D-shape banana, some small circulating de-flated bananas, some huge classical bananas (potatoes), and the largest puffed bananas which exhibit only local mirroring, along with several kind of escaping or open trajectories which are of importance for fast ion losses and target damages in the machines
BETA-S, Multi-Group Beta-Ray Spectra
International Nuclear Information System (INIS)
1 - Description of program or function: BETA-S calculates beta-decay source terms and energy spectra in multigroup format for time-dependent radionuclide inventories of actinides, fission products, and activation products. Multigroup spectra may be calculated in any arbitrary energy-group structure. The code also calculates the total beta energy release rate from the sum of the average beta-ray energies as determined from the spectral distributions. BETA-S also provides users with an option to determine principal beta-decaying radionuclides contributing to each energy group. The CCC-545/SCALE 4.3 (or SCALE4.2) code system must be installed on the computer before installing BETA-S, which requires the SCALE subroutine library and nuclide-inventory generation from the ORIGEN-S code. 2 - Methods:Well-established models for beta-energy distributions are used to explicitly represent allowed, and 1., 2. - and 3. -forbidden transition types. Forbidden non-unique transitions are assumed to have a spectral shape of allowed transitions. The multigroup energy spectra are calculated by numerically integrating the energy distribution functions using an adaptive Simpson's Rule algorithm. Nuclide inventories are obtained from a binary interface produced by the ORIGEN-S code. BETA-S calculates the spectra for all isotopes on the binary interface that have associated beta-decay transition data in the ENSDF-95 library, developed for the BETA-S code. This library was generated from ENSDF data and contains 715 materials, representing approximately 8500 individual beta transition branches. 3 - Restrictions on the complexity of the problem: The algorithms do not treat positron decay transitions or internal conversion electrons. The neglect of positron transitions in inconsequential for most applications involving aggregate fission products, since most of the decay modes are via electrons. The neglect of internal conversion electrons may impact on the accuracy of the spectrum in the low
Spectroscopic study of turbulent heating in the high beta tokamak - Torus II
International Nuclear Information System (INIS)
Visible spectroscopy, involving line profile and line intensity measurements, was used to study the turbulent heating of the rectangular cross-section high-beta tokamak Torus II. The spectroscopy was done in the visible wave-length region using a six channel polychrometer having 0.2 A resolution, which is capable of radial scans of the plasma. The plasma, obtained by ionizing helium, is heated by poloidal skin currents, induced by a rapid (tau/sub R/ approx. = 1.7 μsec) change of the toroidal magnetic field either parallel or anti-parallel to the initial toroidal bias magnetic field, which converts a cold toroidal Z-pinch plasma into a hot tokamak plasma
International Nuclear Information System (INIS)
Full text: The Pegasus experiment is an ultralow aspect ratio spherical tokamak. The research program on this experiment is developing non-solenoidal startup and growth techniques for tokamaks, and exploring plasma stability at near-unity aspect ratio. Helicity injection from localized current sources in the plasma periphery have produced total tokamak plasma current up to 0.17 MA with less than 4kA injected. These results are consistent with a simple theory invoking helicity balance and Taylor relaxation constraints. Startup discharges created with helicity injection and poloidal field induction produce reasonable target plasmas for further current drive. For example, they readily couple to ohmic induction after helicity injection. Increasing the nonsolenoidal startup current to 0.3 MA will test theory to the point where parallel conduction losses may dominate the helicity loss rate. This regime must be addressed for extrapolation to larger fusion-scale experiments. Nonsolenoidal plasma growth following startup may be pursued via Higher Harmonic Fast Wave heating and/or Electron Bernstein Wave heating and current drive. The ability to strongly modify the plasma current profile through helicity injection and/or detailed field programming is opening a path to the unique high normalized current, high-beta regime at near-unity aspect ratio. Earlier experiments indicated a soft limit wherein the total plasma current was limited to approximately the total toroidal field rod current. Current profile manipulation mitigates the large-scale internal tearing modes that previously limited the plasma current. This opens access to the high beta regime where the plasma current can substantially exceed the toroidal field current. Finally, operation at near-unity aspect ratio provides easy access to regimes of high peeling and ballooning mode drive in the plasma edge region. Electromagnetic filamentary structures are observed in the Pegasus edge region and they display
Carrasco, Pablo D
2011-01-01
According to the work of Dennis Sullivan, there exists a smooth flow on the 5-sphere all of whose orbits are periodic although there is no uniform bound on their periods. The question addressed in this article is whether such an example can occur in the partially hyperbolic context. That is, does there exist a partially hyperbolic diffeomorphism of a compact manifold such that all the leaves of its center foliation are compact although there is no uniform bound for their volumes. We will show that the previous question has negative answer under very natural hypothesis as one-dimensional center foliation, transitivity or in the volume preserving case. Moreover we study the dynamical properties of partially hyperbolic maps preserving a compact center foliation. We prove in particular that if the number of center leaves with non-trivial holonomy is finite then the map is plaque expansive.
Low-frequency fluctuations in a pure toroidal magnetized plasma
Indian Academy of Sciences (India)
P K Sharma; R Singh; D Bora
2009-12-01
A magnetized, low- plasma in pure toroidal configuration is formed and extensively studied with ion mass as control parameter. Xenon, krypton and argon plasmas are formed at a fixed toroidal magnetic field of 0.024 T, with a peak density of ∼ 1011 cm-3, ∼ 4 × 1010 cm-3 and ∼ 2 × 1010 cm−3 respectively. The experimental investigation of time-averaged plasma parameter reveals that their profiles remain insensitive to ion mass and suggests that saturated slab equilibrium is obtained. Low-frequency (LF) coherent fluctuations ( < ci) are observed and identified as flute modes. Here ci represents ion cyclotron frequency. Our results indicate that these modes get reduced with ion mass. The frequency of the fluctuating mode decreases with increase in the ion mass. Further, an attempt has been made to discuss the theory of flute modes to understand the relevance of some of our experimental observations.
Quasars a supermassive rotating toroidal black hole interpretation
Spivey, R J
2000-01-01
A supermassive rotating toroidal black hole (TBH) is proposed as the fundamental structure of quasars and other jet-producing active galactic nuclei. Rotating protogalaxies gather matter from the central gaseous region leading to the birth of massive toroidal stars whose internal nuclear reactions proceed very rapidly. Once the nuclear fuel is spent, gravitational collapse produces a slender ring-shaped TBH remnant. These events are typically the first supernovae of the host galaxies. Given time the TBH mass increases through continued accretion by several orders of magnitude, the event horizon swells whilst the central aperture shrinks. The difference in angular velocities between the accreting matter and the TBH induces a magnetic field that is strongest in the region of the central aperture and innermost ergoregion. Due to the presence of negative energy states when such a gravitational vortex is immersed in an electromagnetic field, circumstances are near ideal for energy extraction via non-thermal radiat...
Stabilization of ballooning modes with sheared toroidal rotation
International Nuclear Information System (INIS)
A new code demonstrates the stabilization of MHD ballooning modes by sheared toroidal rotation. A shifted-circle model is used to elucidate the physics, and numerically reconstructed equilibria are used to analyze DIII-D discharges. In the ballooning representation, the modes shift periodically along the field line to the next point of unfavorable curvature. The shift frequency (dΩ/dq, where Ω is the angular toroidal velocity and q is the safety factor) is proportional to the rotation shear and inversely proportional to the magnetic shear. Stability improves with increasing shift frequency and, in the shifted circle model, direct stable access to the second stability regime occurs when this frequency is a fraction of the Alfven frequency, ωA = VA/qR. Shear stabilization is also demonstrated for an equilibrium reconstruction of a DIII-D VH-mode. (author). 9 refs, 3 figs
Cooling of Neutron Stars with Strong Toroidal Magnetic Fields
Page, D; Küker, M; Page, Dany; Geppert, Ulrich; Kueker, Manfred
2007-01-01
We present models of temperature distribution in the crust of a neutron star in the presence of a strong toroidal component superposed to the poloidal component of the magnetic field. The presence of such a toroidal field hinders heat flow toward the surface in a large part of the crust. As a result, the neutron star surface presents two warm regions surrounded by extended cold regions and has a thermal luminosity much lower than in the case the magnetic field is purely poloidal. We apply these models to calculate the thermal evolution of such neutron stars and show that the lowered photon luminosity naturally extends their life-time as detectable thermal X-ray sources.
Experimental investigation of transitional flow in a toroidal pipe
Kühnen, J; Hof, B; Kuhlmann, H
2015-01-01
The flow instability and further transition to turbulence in a toroidal pipe (torus) with curvature (tube-to-coiling diameter) 0.049 is investigated experimentally. The flow inside the toroidal pipe is driven by a steel sphere fitted to the inner pipe diameter. The sphere is moved with constant azimuthal velocity from outside the torus by a moving magnet. The experiment is designed to investigate curved pipe flow by optical measurement techniques. Using stereoscopic particle image velocimetry, laser Doppler velocimetry and pressure drop measurements, the flow is measured for Reynolds numbers ranging from 1000 to 15000. Time- and space-resolved velocity fields are obtained and analysed. The steady axisymmetric basic flow is strongly influenced by centrifugal effects. On an increase of the Reynolds number we find a sequence of bifurcations. For Re=4075 a supercritical bifurcation to an oscillatory flow is found in which waves travel in the streamwise direction with a phase velocity slightly faster than the mean...
Control and monitoring of the Tore Supra toroidal superconducting coils
International Nuclear Information System (INIS)
Light nuclei controlled fusion reactions are seen as a possible way to produce nuclear energy. For this reason, the interest in hot plasma researches in tokamaks has increased. The Tore Supra main characteristic is related to the superconducting magnet coils. They allow a suitable energy balance, however, they require an accurate and preventive fault detection. The Tore Supra machine and the different methods to detect a transition (from superconducting to normal mode) in the toroidal coils are described. The voltage of the coils, the pressure of the helium superfluid at 1.8 K and the electric current in the circuit parallel resistances, are measured. A computer aided control system allows the toroidal field monitoring (current in the coils, fault detection). The superconducting magnet configuration chosen for Tore Supra seems to be suitable for future large Tokamak devices
ATLAS barrel toroid integration and test area in building 180
Maximilien Brice
2003-01-01
The ATLAS barrel toroid system consists of eight coils, each of axial length 25.3 m, assembled radially and symmetrically around the beam axis. The coils are of a flat racetrack type with two 'double-pancake' windings made of 20.5 kA aluminium-stabilized niobium-titanium superconductor. The barrel toroid is being assembled in building 180 on the Meyrin site. In the first phase of assembly, the coils are packed into their aluminium-alloy casing. These photos show the double-pancake coils from ANSALDO and the coil casings from ALSTOM. In the foreground is the tooling from COSMI used to turn over the coil casings during this first phase. In the right background is the yellow lifting gantry manufactured at JINR-Dubna, Russia which will transport the coil casings to a heating table for prestressing. Two test benches with magnetic mirror are also visible.
Toroidal Field Ripple reduction studies for ITER and FAST
International Nuclear Information System (INIS)
Two different approaches to control the Toroidal Field Ripple (TFR) amplitude in ITER and FAST devices are presented in this paper. The approach currently adopted to reduce the TFR in ITER is based on the installation of ferromagnetic inserts between the vacuum vessel shells. The same approach has been analyzed in the design of the Fusion Advanced Studies Torus (FAST) proposal. Details of the system's layout are given. A new approach based on the insertion of active coils between the outer legs of the Toroidal Field Coils (TFCs) and the plasma, has been extensively investigated for these two machines. This active system would allow reducing the TFR to values even smaller than with the ferromagnetic inserts. The case of a localized disturb like that introduced by a Test Blanket Module (TBM) for ITER is presented where only well localized active coils can produce a significant ripple reduction.
On the radiation of electric, magnetic and toroidal dipoles
International Nuclear Information System (INIS)
We consider the radiation of electric, magnetic and toroidal dipoles uniformly moving in unbounded medium (this corresponds to the Tamm-Frank problem). The densities of these dipoles are obtained from the corresponding charge-current densities in an infinitesimal limit. The behaviour of radiation intensities in the neighbourhood of the Cherenkov threshold β = 1/n is investigated. The frequency and velocity regions are defined where radiation intensities are maximal. The comparison with previous attempts is given. We consider also the radiation of electric, magnetic and toroidal dipoles uniformly moving in medium, in a finite space interval (this corresponds to the Tamm problem). The properties of radiation arising from the precession of a magnetic dipole are studied
Neoclassical electron and ion transport in toroidally rotating plasmas
Energy Technology Data Exchange (ETDEWEB)
Sugama, H.; Horton, W.
1997-01-01
Neoclassical transport processes of electrons and ions are investigated in detail for toroidally rotating axisymmetric plasmas with large flow velocities on the order of the ion thermal speed. The Onsager relations for the flow-dependent neoclassical transport coefficients are derived from the symmetry properties of the drift kinetic equation with the self-adjoint collision operator. The complete neoclassical transport matrix with the Onsager symmetry is obtained for the rotating plasma consisting of electrons and single-species ions in the Pfirsch-Schlueter and banana regimes. It is found that the inward banana fluxes of particles and toroidal momentum are driven by the parallel electric field, which are phenomena coupled through the Onsager symmetric off-diagonal coefficients to the parallel currents caused by the pressure gradient and by the flow shear, respectively. (author)
Modelling of density limit phenomena in toroidal helical plasmas
Energy Technology Data Exchange (ETDEWEB)
Itoh, K. [National Inst. for Fusion Science, Toki, Gifu (Japan); Itoh, S.-I. [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics; Giannone, L. [Max Planck Institut fuer Plasmaphysik, EURATOM-IPP Association, Garching (Germany)
2000-03-01
The physics of density limit phenomena in toroidal helical plasmas based on an analytic point model of toroidal plasmas is discussed. The combined mechanism of the transport and radiation loss of energy is analyzed, and the achievable density is derived. A scaling law of the density limit is discussed. The dependence of the critical density on the heating power, magnetic field, plasma size and safety factor in the case of L-mode energy confinement is explained. The dynamic evolution of the plasma energy and radiation loss is discussed. Assuming a simple model of density evolution, of a sudden loss of density if the temperature becomes lower than critical value, then a limit cycle oscillation is shown to occur. A condition that divides the limit cycle oscillation and the complete radiation collapse is discussed. This model seems to explain the density limit oscillation that has been observed on the W7-AS stellarator. (author)
A comparison between linear and toroidal Extrap systems
International Nuclear Information System (INIS)
The Extrap scheme consists of a Z-pinch immersed in an octupole field generated by currents in a set of external conductors. A comparison between linear and toroidal Extrap geometry is made in this paper. As compared to toroidal systems, linear geometry has the advantages of relative simplicity and of a current drive by means of electrodes. Linear devices are convenient for basic studies of Extrap, at moderately high pinch currents and plasma temperatures. Within the parameter ranges of experiments at high pinch currents and plasma temperatures, linear systems have on the other hand some substantial disadvantages, on account of the plasma interaction with the end regions. This results in a limitation of the energy confinement time, and leads in the case of an ohmically heated plasma to excessively high plasma densities and small pinch radii which also complicate the introduction of the external conductors. (author)
An Overview of Plasma Confinement in Toroidal Systems
Dini, Fatemeh; Amrollahi, Reza; Khorasani, Sina
2009-01-01
This overview presents a tutorial introduction to the theory of magnetic plasma confinement in toroidal confinement systems with particular emphasis on axisymmetric equilibrium geometries, and tokamaks. The discussion covers three important aspects of plasma physics: Equilibrium, Stability, and Transport. The section on equilibrium will go through an introduction to ideal magnetohydrodynamics, curvilinear system of coordinates, flux coordinates, extensions to axisymmetric equilibrium, Grad-Shafranov Equation (GSE), Green's function formalism, as well as analytical and numerical solutions to GSE. The section on stability will address topics including Lyapunov Stability in nonlinear systems, energy principle, modal analysis, and simplifications for axisymmetric machines. The final section will consider transport in toroidal systems. We present the flux-surface-averaged system of equations describing classical and non-classical transport phenomena. Applications to the small-sized high-aspect-ratio Damavand tokam...
Initial value problem of the toroidal ion temperature gradient mode
International Nuclear Information System (INIS)
The initial value problem of the toroidal ion temperature gradient mode is studied based on the Laplace transform of the ion gyrokinetic equation and the electron Boltzmann relation with the charge neutrality condition. Due to the toroidal magnetic drift, the Laplace-transformed density and potential perturbations have a branch cut as well as poles on the complex-frequency plane. The inverse Laplace transform shows that the temporal evolution of the density and potential perturbations consists of the normal modes and the continuum mode, which correspond to contributions from the poles and the branch cut, respectively. The normal modes have exponential time dependence with the eigenfrequencies determined by the dispersion relation while the continuum mode shows power-law decay oscillation. For the stable case, the long-time asymptotic behavior of the potential and density perturbations is dominated by the continuum mode which decays slower than the normal modes. (author)
Mechanical tests of the ITER toroidal field model coil
International Nuclear Information System (INIS)
The ITER toroidal field model coil (TFMC) was designed to allow an overall mechanical test representative of the ITER toroidal field (TF) coils. The paper details the mechanical tests performed, compares them to model predictions and discusses the experience gained in the understanding of the mechanical behaviour of the ITER TF coils. The good agreement found between prediction given by a finite element model and mechanical measurements performed during the tests demonstrates that coil mechanical behaviour is well understood. The reproducibility of the evolution of stresses and coil deformation during testing including cycling tests showed that no measurable degradation of the mechanical properties of the coil occurred. This test contributed to the qualification of the design and manufacturing procedures of the ITER TF coils
Toroidal AC transformer for beam intensity measurements in CSR
International Nuclear Information System (INIS)
The intensity of a pulsed beam of charged particles in the Cooling Storage Ring Project of Heavy Ion Research Facility in Lanzhou (HIRFL-CSR) will be measured with a toroidal current transformer. By comparing and analyzing the properties of kinds of magnetic cores, a strip wound toroidal core is adopted, which is made of a high-permeability alloy and can measure a pulsed beam with frequency range of 0.2 to 2 MHz. The permeability of Fe-based nanocrystalline alloy varying with frequency is measured and the noises in the circuit are analyzed. By adding a low-noise operational amplifier into the circuit, the current down to 1 μA can be detected
Counterformal contacts of full toroidal continuously variable transmission
Institute of Scientific and Technical Information of China (English)
ATTIA Nabil Abdulla; QIN Da-tong
2005-01-01
The point and the line contacts of a toroidal continuously variable transmission (CVT) are studied. The contact shapes between the roller and input and output disks are formulated by using the classical Hertz contact theory. Based on the formulated equations, different system factors affecting the maximum Hertz stress in the elliptical and strip contacts of the full toroidal CVT are explored, which include the properties of the contacting material (Young's modulus), operating condition (pushing load) and geometrical parameters (aspect cavity ratio, aspect roller ratio). The comparative results reveal the relations between the maximum Hertz stress and the speed ratio in the form of graphs. These graphs give useful information for designer to know the maximum Hertz stress during operation in such systems.
Nonlinear particle simulation of ion cyclotron waves in toroidal geometry
Energy Technology Data Exchange (ETDEWEB)
Kuley, A., E-mail: akuley@uci.edu; Lin, Z. [Department of Physics and Astronomy, University of California Irvine, CA-92697 (United States); Bao, J. [Fusion Simulation Center, Peking University, Beijing (China); Department of Physics and Astronomy, University of California Irvine, CA-92697 (United States); Wei, X. S.; Xiao, Y. [Institute of Fusion Theory and Simulation, Zhejiang University, Hangzhou (China)
2015-12-10
Global particle simulation model has been developed in this work to provide a first-principles tool for studying the nonlinear interactions of radio frequency (RF) waves with plasmas in tokamak. In this model, ions are considered as fully kinetic particles using the Vlasov equation and electrons are treated as guiding centers using the drift kinetic equation with realistic electron-to-ion mass ratio. Boris push scheme for the ion motion has been developed in the toroidal geometry using magnetic coordinates and successfully verified for the ion cyclotron and ion Bernstein waves in global gyrokinetic toroidal code (GTC). The nonlinear simulation capability is applied to study the parametric decay instability of a pump wave into an ion Bernstein wave side band and a low frequency ion cyclotron quasi mode.
Stability analysis of electromagnetic interchange modes in toroidal geometry
International Nuclear Information System (INIS)
An investigation is presented of how the stability of collisionless electromagnetic interchange modes depends on εn (the ratio of the magnetic drift frequency to the diamagnetic drift frequency), the ion temperature gradient and the electron temperature gradient. A linear two fluid model in toroidal geometry is used. The eigenvalue problem is solved analytically and then the complex frequency is solved numerically from the dispersion relation. Comparison is made with Merciers criterion, in the magnetohydrodynamic limit. The most important observed effects are : 1. When εn increases Merciers criterion becomes increasingly incorrect. The toroidal system becomes more stable than Merciers criterion predicts. εn is large in regions where we have flat density profiles, Ln >> LB (the characteristic scale length of density and magnetic field inhomogeneities). 2. Finite ηi (Ln / LTi) may cause instability below the critical pressure gradient in the Mercier criterion
A novel electron density reconstruction method for asymmetrical toroidal plasmas
International Nuclear Information System (INIS)
A novel reconstruction method is developed for acquiring the electron density profile from multi-channel interferometric measurements of strongly asymmetrical toroidal plasmas. It is based on a regularization technique, and a generalized cross-validation function is used to optimize the regularization parameter with the aid of singular value decomposition. The feasibility of method could be testified by simulated measurements based on a magnetic configuration of the flexible helical-axis heliotron device, Heliotron J, which has an asymmetrical poloidal cross section. And the successful reconstruction makes possible to construct a multi-channel Far-infrared laser interferometry on this device. The advantages of this method are demonstrated by comparison with a conventional method. The factors which may affect the accuracy of the results are investigated, and an error analysis is carried out. Based on the obtained results, the proposed method is highly promising for accurately reconstructing the electron density in the asymmetrical toroidal plasma
The toroidal field coil design for ARIES-ST
International Nuclear Information System (INIS)
An evolutionary process was used to develop the toroidal field (TF) coil design for the ARIES-ST (Spherical Tokamak). Design considerations included fabricability, assembly, maintenance, energy efficiency, and structural robustness. The design addresses a number of the concerns (complexity) and criticisms (high cost, high recirculating power) of fusion. It does this by: (1) Applying advanced, but available laser forming and spray casting techniques for manufacturing the TF coil system; (2) Adopting a simple single toroidal field coil system to make assembly and maintenance much easier, the single turn design avoids the necessity of using the insulation as a structural component of the TF coils, and hence is much more robust than multi-turn designs; and (3) Using a high conductivity copper alloy and modest current densities to keep the recirculating power modest
Magnetohydrodynamic equilibrium of axisymmetric systems with toroidal rotation
International Nuclear Information System (INIS)
A model for studying magnetohydrodynamic equilibrium of axisymetrically confined plasma with toroidal rotation, extended to the Grad. Shafranov equation is presented. The expression used for the scalar pressure is modifiec, and the influence of toroidal magnetic field is included, The equation for general motion of axisymetrically confined plasma, particularizing for rotation movements is described. Two cases are compared: one supposes the entropy as a function of poloidal magnetic flux and other supposes the temperature as a function of flux. The equations for these two cases obtaining a simplified expression by others approximations are established. The proposed model is compared with Shibata model, which uses density as function of flux, and with the ideal spheromak model. A set of cases taking in account experimental data is studied. (M.C.K.)
Superconducting toroidal magnets for fusion feasibility experiments and power reactors
International Nuclear Information System (INIS)
It has been recognized that large superconducting magnets will have to be developed in order to obtain power economically from a thermonuclear reactor. In the present paper, compelling reasons are offered to illustrate how vital they are even for the sizes envisioned for hydrogen feasibility and D-T burning experiments. Detailed discussion is given on the type of magnets used for the plasma confinement in a tokamak-type machine. Illustrations are given to show that their development is within the present technological progress of superconductivity. The methods used to estimate the cost of such a toroidal system are provided along with how the cost varies with changes in magnet aspect ratio, major radius (proportional to Rsup(1.95) and stored energy (proportional to Esub(S)sup(0.65)). The latter quantity is presented as a valid figure of merit for quickly estimating the cost of any large superconducting toroidal system. (author)
18–22 cm VLBA Observational Evidence for Toroidal B-Field Components in Six AGN Jets
Directory of Open Access Journals (Sweden)
Juliana Cristina Motter
2016-08-01
Full Text Available The formation of relativistic jets in Active Galactic Nuclei (AGN is related to accretion onto their central supermassive black holes, and magnetic (B fields are believed to play a central role in launching, collimating, and accelerating the jet streams from very compact regions out to kiloparsec scales. We present results of Faraday rotation studies based on Very Long Baseline Array (VLBA data obtained at 18–22 cm for six well known AGN (OJ 287, 3C 279, PKS 1510-089, 3C 345, BL Lac, and 3C 454.3, which probe projected distances out to tens of parsecs from the observed cores. We have identified statistically significant, monotonic, transverse Faraday rotation gradients across the jets of all but one of these sources, indicating the presence of toroidal B fields, which may be one component of helical B fields associated with these AGN jets.
Toroidal nano-traps for cold polar molecules
Salhi, Marouane; Passian, Ali; Siopsis, George
2015-01-01
Electronic excitations in metallic nanoparticles in the optical regime that have been of great importance in surface enhanced spectroscopy and emerging applications of molecular plasmonics, due to control and confinement of electromagnetic energy, may also be of potential to control the motion of nanoparticles and molecules. Here, we propose a concept for trapping polarizable particles and molecules using toroidal metallic nanoparticles. Specifically, gold nanorings are investigated for their...
Path Integral Quantization for a Toroidal Phase Space
Bodmann, Bernhard G.; Klauder, John R.
1999-01-01
A Wiener-regularized path integral is presented as an alternative way to formulate Berezin-Toeplitz quantization on a toroidal phase space. Essential to the result is that this quantization prescription for the torus can be constructed as an induced representation from anti-Wick quantization on its covering space, the plane. When this construction is expressed in the form of a Wiener-regularized path integral, symmetrization prescriptions for the propagator emerge similar to earlier path-inte...
Toroidal field coil system for STARFIRE, a preliminary assessment
International Nuclear Information System (INIS)
An important element of STARFIRE is the 12-coil superconducting toroidal field coil system which is required to generate 5.6 tesla at the 7.0 m plasma axis, with a peak-to-peak field ripple of 1% (maximum). Internal spatial requirements dictate a clear bore about 15 1/2 m high x 10 m wide, resulting in a total stored energy of 67 GJ
Operating tokamaks with steady-state toroidal current
International Nuclear Information System (INIS)
Continuous operation of a tokamak requires, among other things, a means of continuously providing the toroidal current. Various methods have been proposed to provide this current including methods which utilize radio-frequency waves in any of several frequency regimes. Here we elaborate on the prospects of incorporating these current-drive techniques in tokamak reactors, concentrating on the theoretical minimization of the power requirements
An approach to cylindrical approximation of toroidal geometry
International Nuclear Information System (INIS)
Neutron transport processes in Tokamak fusion devices are described with same mathematical equipment as that used in fission reactor calculations. The aim of this paper is to show some of these methods in toroidal geometry problem. A new approach to cylindrical approximation is described. All calculations are performed by ANISN one-dimensional Sn code. To validate the present method, comparison have been done with Monte Carlo results, as well as with calculations done on previous geometry approximation (author)
Stability of a stiffened toroidal sector under uniform external pressure
International Nuclear Information System (INIS)
This paper present the results of a stability analysis on a sector of the FTU (Frascati Tokamak Upgrade) toroidal vacuum vessel. FTU is an experimental machine, now under construction, mainly devoted to the study of the effects of lower hybrid radiofrequency heating on plasmas in reactor relevant conditions. Its vacuum chamber is a stainless steel structure completely welded with a major radius of 0.935 m and a minor radius of 0.335 m consisting of 12 toroidal thin sector joined together by thick ribs. This structure is loaded by comprensive electromagnetic forces both in toroidal and in radial direction that can create instability conditions. One of the major problems in its design is to determine the points where this phenomenon is likely to occur in order to avoid dangerous buckling situations. Theoretical analysis of the stability behaviour of one of these sector has been conducted by means of the ABAQUAS finite element code. The critical load has been determined by a classical algorithm and by the modified Riks methods. Both methods have given similar results in an elastic analysis. Furthermore the second one has been applied also using an elastoplastic model of the material to determine the critical load and the post buckling behaviour of the structure. Experimental tests have been conducted on a full scale model of the toroidal sector. The model has been placed in a large tank filled with water where the pressure has been gradually increased up to the collapse of the structure. The theoretical and experimental results have been compared and a good agreement has been found between them
Self-Sustained Magnetic Braiding in Toroidal Plasmas
Itoh, K; Fukuyama, A.; Itoh, S.-I.; Yagi, M.; Azumi, M.
1994-01-01
Theory for the magnetic braiding in toroidal plasmas, which is caused by microscopic pressure-gradient-driven turbulence, is developed. When the pressure gradient exceeds a threshold, the self-sustaining of the magnetic braiding and enhanced anomalous transport occur. The balance between the nonlinear destabilization and nonlinear stabilization, which determines the stationary turbulence, is solved analytically for the case of interchange mode. The enhanced thermal conductivity and magneti...
Vacuum magnetic fields in the toroidal Extrap device
International Nuclear Information System (INIS)
A model of the ring system of the Extrap T1 device is developed. The model is used for calculating the distribution of poloidal flux and the vacuum magnetic field in the device. Numerical data from the model are compared with measurements. Effects of the vacuum vessel resistivity are discussed qualitatively. Measured profiles of the toroidal and the vertical bias magnetic field in the device are presented. Time constants of the vacuum vessel and the ring structure are estimated. (authors)
From toroidal to rod-like condensates of semiflexible polymers
Hoang, Trinh Xuan; Giacometti, Achille; Podgornik, Rudolf; Nguyen, Nhung T. T.; Banavar, Jayanth R.; Maritan, Amos
2014-01-01
The competition between toroidal and rod-like conformations as possible ground states for DNA condensation is studied as a function of the stiffness, the length of the DNA and the form of the long-range interactions between neighboring molecules, using analytical theory supported by Monte Carlo simulations. Both conformations considered are characterized by a local nematic order with hexagonal packing symmetry of neighboring DNA molecules, but differ in global configuration of the chain and t...
Toroidal plasma reactor with low external magnetic field
International Nuclear Information System (INIS)
A toroidal pinch configuration with safety factor q < 0.5 decreasing from the center to periphery without field reversal is proposed. This is capable of containing high pressure plasma with only small toroidal external magnetic field. Sufficient conditions for magnetohydrodynamic stability are fulfilled in this configuration. The stability is studied by constructing the Lyapunov functional and investigating its extrema both analytically and numerically. Comparison of the Lyapunov stability conditions with the conventional linear theory is carried out. Stable configurations are found with average β near 15%, with magnetic field associated mainly with plasma current. The β value calculated with the external magnetic field can be over 100%. Fast charged particles produced by fusion reactions are asymmetrically confined by the poloidal magnetic field (and due to the lack of strong toroidal field). They thus generate a current in the noncentral part of plasma to reinforce the poloidal field. This current drive can sustain the monotonic decrease of q with radius. 20 refs., 9 figs
Sustainment of spheromak plasma by driving the toroidal current
International Nuclear Information System (INIS)
Spheromak plasma productions by means of quasi-static method on the basis of z-discharge and theta-discharge have been investigated using the machine named TS-3. This machine consists of a SUS vacuum vessel with an inner diameter of 76 cm and an axial length of 95 cm, two internal poloidal coils enclosed with SUS thin cases with a major diameter of 43 cm and an axial separation of 39 cm, and two sets of eight pairs of electrodes around each poloidal coil. Up to 0.2 T vertical magnetic field can be applied using an external DC mirror type magnet. Either one or two isolated spheromak(s) can be generated by the selection of sets of electrodes in proper manner. An optional current transformer with an outer cylinder diameter of 9 cm installed along the major symmetric axis of the vessel enables us to perform toroidal current driving of spheromak plasma. Spheromak plasmas produced in He has of about 10 mTorr have a decay time of about 30 micro sec. with the center conductor when it has no current for the toroidal current driving. However, when a flux change of 30 to 60 Wb/s is given to the center coil during 100 micro sec after the initiation of the spheromak configuration, the sustainment of the configuration is observed by the measurement of both poloidal and toroidal field spatial profile
Neoclassical offset toroidal velocity and auxiliary ion heating in tokamaks
Lazzaro, E.
2016-05-01
In conditions of ideal axisymmetry, for a magnetized plasma in a generic bounded domain, necessarily toroidal, the uniform absorption of external energy (e.g., RF or any isotropic auxiliary heating) cannot give rise to net forces or torques. Experimental evidence on contemporary tokamaks shows that the near central absorption of RF heating power (ICH and ECH) and current drive in presence of MHD activity drives a bulk plasma rotation in the co- I p direction, opposite to the initial one. Also the appearance of classical or neoclassical tearing modes provides a nonlinear magnetic braking that tends to clamp the rotation profile at the q-rational surfaces. The physical origin of the torque associated with P RF absorption could be due the effects of asymmetry in the equilibrium configuration or in power deposition, but here we point out also an effect of the response of the so-called neoclassical offset velocity to the power dependent heat flow increment. The neoclassical toroidal viscosity due to internal magnetic kink or tearing modes tends to relax the plasma rotation to this asymptotic speed, which in absence of auxiliary heating is of the order of the ion diamagnetic velocity. It can be shown by kinetic and fluid calculations, that the absorption of auxiliary power by ions modifies this offset proportionally to the injected power thereby forcing the plasma rotation in a direction opposite to the initial, to large values. The problem is discussed in the frame of the theoretical models of neoclassical toroidal viscosity.
3D toroidal physics: Testing the boundaries of symmetry breakinga)
Spong, Donald A.
2015-05-01
Toroidal symmetry is an important concept for plasma confinement; it allows the existence of nested flux surface MHD equilibria and conserved invariants for particle motion. However, perfect symmetry is unachievable in realistic toroidal plasma devices. For example, tokamaks have toroidal ripple due to discrete field coils, optimized stellarators do not achieve exact quasi-symmetry, the plasma itself continually seeks lower energy states through helical 3D deformations, and reactors will likely have non-uniform distributions of ferritic steel near the plasma. Also, some level of designed-in 3D magnetic field structure is now anticipated for most concepts in order to provide the plasma control needed for a stable, steady-state fusion reactor. Such planned 3D field structures can take many forms, ranging from tokamaks with weak 3D edge localized mode suppression fields to stellarators with more dominant 3D field structures. This motivates the development of physics models that are applicable across the full range of 3D devices. Ultimately, the questions of how much symmetry breaking can be tolerated and how to optimize its design must be addressed for all fusion concepts. A closely coupled program of simulation, experimental validation, and design optimization is required to determine what forms and amplitudes of 3D shaping and symmetry breaking will be compatible with the requirements of future fusion reactors.
Reduction of toroidal ripple by using high Tc conductors
International Nuclear Information System (INIS)
The loss of alpha particles in a rippled toroidal field is one of the most critical issues for the design of tokamak reactors, because it has direct impacts on the design of toroidal field (TF) coils and the first wall. In the preliminary design of the ITER, the alpha particle ripple loss and the additional first wall heat load due to such loss has been assessed. From these assessments the maximum ripples (Bmax - Bmin)/(Bmax + Bmin), at the plasma edge is required to be decreased to 1 - 1.5%. There are several possible ways to decrease the ripple value without changing the TF coil shape. One of them is to use ferromagnetic balls in the vacuum vessel under the outer TF coil legs. Preliminary estimations show that in this way the ripple can be decreased by a factor of 2. In this paper, a new method to reduce the toroidal ripple using high Tc superconductors is presented. High Tc superconductor have the advantage of working above the boiling temperature of liquid nitrogen and they have other properties that make their practical applications. For example, they behave as a ferromagnetic or diamagnetic material depending on their magnetization. Therefore, if superconductors are appropriately arranged and magnetized, they decrease the maximum ripple at the plasma edge to the required value
Modeling and analysis of silicon-embedded MEMS toroidal inductors
Araghchini, M.; Lang, J. H.
2013-12-01
This paper presents the modeling and analysis of three-dimensional silicon-embedded toroidal inductors designed for power converter applications. Special attention is given to modeling phenomena associated with the presence of silicon, namely an increase in loss and parasitic capacitance. Silicon-embedded inductors can be fabricated with silicon inside the donut-shaped toroidal core and inside the donut hole, as well as with silicon above, below and outside the inductor. It is argued here that, with the exception of the losses in the core at high doping densities, the losses in the silicon can be tolerated in many power applications, making fully-integrated silicon-embedded air-core inductors viable for power applications. An equivalent circuit model is presented for such inductors which captures the stored magnetic energy, the parasitic electric energy stored between the windings and the silicon, the loss in the toroidal windings, and the electrically- and magnetically-driven losses inside the silicon. The model developed here is verified against experimental data, and the comparison shows a good match over the frequency range of interest to power electronics applications.
Measurement of toroidal and poloidal plasma rotation in TCA
International Nuclear Information System (INIS)
With optimal observation geometry we have measured both the toroidal and poloidal rotation velocities in the edge and in the bulk of the TCA plasma. Regular calibration and correction for variations in the spectrometer temperature permitted a measurement with an error of ∼0.5 km/s which is an order of magnitude smaller than the range of measured velocities. In general, changes in the velocities are observed to be stronger and faster in the plasma edge than in the plasma bulk. With increasing density, the toroidal velocity is observed to change sign and follow the plasma density, while the poloidal velocity increases. These two effects lead to an increase in the absolute value of the radial electric field. With very strong gas puffing, the toroidal velocity is observed to again reverse and tend to zero, an effect which is stronger as the gradient of the density ramp is increased. Comparison between gas puffing and high power AWH does not show a significant difference in the radial electric field that could be responsible for the large associated density rise, which still remains unexplained. (author) 4 figs., 2 refs
Axisymmetric toroidal equilibrium with flow and anisotropic pressure
International Nuclear Information System (INIS)
Axisymmetric toroidal plasma equilibria with mass flows and anisotropic pressure are investigated. The equilibrium system is derived for a general functional form of the pressures, which includes both fluid models, such as the magnetohydrodynamic (MHD) and the double-adiabatic models, and Grad's guiding centre model. This allows for detailed comparisons between the models and clarifies how the 'first hyperbolic region', occurring in the fluid theory when the poloidal flow is of the order of the poloidal sound speed, can be eliminated in guiding centre theory. In the case of a pure toroidal rotation, macroscopic equations of state are derived from the guiding centre model, characterized by a parallel temperature that is constant on each magnetic surface and a perpendicular temperature that varies with the magnetic field. The outward centrifugal shifts of the magnetic axis and of the mass density profile, due to toroidal rotation, are increased by anisotropy. The guiding centre model shows that poloidal flow produces an inward shift of the density profile, in contrast with the MHD result. (author) 1 fig., 1 tab., 17 refs
Point-to-point focusing equation for double toroidal analyzer
International Nuclear Information System (INIS)
Highlights: • We deduce a general and simple equation for the point-to-point focusing in the radial plane of double toroidal analyzer (DTA). • Graphically solve the equation to get the geometrical configuration of DTA for a given situation. • The obtained geometry is in good agreement with the trajectory simulation by SIMION program, which indicates that the equation is quite useful in analytically design of DTA. - Abstract: Toroidal analyzer (TA) has high detection efficiency due to the parallel measurement of the energies and the angles of charged particles in wide range. Compared to a normal TA, double toroidal analyzer (DTA) has the advantages of flat focal plane and normal incidence angles of particles onto the detector surface. However, no analytical formula is available to describe the point-to-point focusing in its radial plane. In the present work, a simple equation for the point-to-point focusing is obtained. The calculated deflection angles using this equation are in good agreement with the trajectory simulations. This indicates the equation could be quite useful for the future analytical design of DTA
3D toroidal physics: Testing the boundaries of symmetry breaking
Energy Technology Data Exchange (ETDEWEB)
Spong, Donald A., E-mail: spongda@ornl.gov [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6169 (United States)
2015-05-15
Toroidal symmetry is an important concept for plasma confinement; it allows the existence of nested flux surface MHD equilibria and conserved invariants for particle motion. However, perfect symmetry is unachievable in realistic toroidal plasma devices. For example, tokamaks have toroidal ripple due to discrete field coils, optimized stellarators do not achieve exact quasi-symmetry, the plasma itself continually seeks lower energy states through helical 3D deformations, and reactors will likely have non-uniform distributions of ferritic steel near the plasma. Also, some level of designed-in 3D magnetic field structure is now anticipated for most concepts in order to provide the plasma control needed for a stable, steady-state fusion reactor. Such planned 3D field structures can take many forms, ranging from tokamaks with weak 3D edge localized mode suppression fields to stellarators with more dominant 3D field structures. This motivates the development of physics models that are applicable across the full range of 3D devices. Ultimately, the questions of how much symmetry breaking can be tolerated and how to optimize its design must be addressed for all fusion concepts. A closely coupled program of simulation, experimental validation, and design optimization is required to determine what forms and amplitudes of 3D shaping and symmetry breaking will be compatible with the requirements of future fusion reactors.
Toroidal Continuously Variable Transmission Systems: Terminology and Present Studies
Directory of Open Access Journals (Sweden)
Ahmet YILDIZ
2014-04-01
Full Text Available The use of continuously variable transmission systems in many different areas such as aerospace, robotics, machinery and automotive industries as an alternative to conventional speed changers with constant ratio becomes widely.Especially in the automotive industry, these systems have been used increasingly, since they enable that internal combustion engines in vehicles run at optimal speeds, and consequently provide considerable fuel savings and therefore lower emission values and also they provide powerful acceleration and quiet working. CVT systems have several constructive variants such as belted, chained, balled, toroidal etc. In this paper, toroidal CVT systems based on elastohydrodynamic principles are concerned with, and fundamental works of last two decades in this field are reviewed. However, the relevant terminology and dynamics along with the control of these systems are briefly treated for better understanding of the literature mentioned. Attention is drawn to the lack of some significant issues in present research works, and potential future works are pointed out. This paper, to the authors’ knowledge, will be the first review on toroidal CVT systems in Turkish literature
Expansions of non-symmetric toroidal magnetohydrodynamic equilibria
Weitzner, Harold
2016-06-01
Expansions of non-symmetric toroidal ideal magnetohydrodynamic equilibria with nested flux surfaces are carried out for two cases. The first expansion is in a topological torus in three dimensions, in which physical quantities are periodic of period 2 π in y and z. Data is given on the flux surface x = 0. Despite the possibility of magnetic resonances the power series expansion can be carried to all orders in a parameter which measures the flux between x = 0 and the surface in question. Resonances are resolved by appropriate addition resonant fields, as by Weitzner, [Phys. Plasmas 21, 022515 (2014)]. The second expansion is about a circular magnetic axis in a true torus. It is also assumed that the cross section of a flux surface at constant toroidal angle is approximately circular. The expansion is in an analogous flux coordinate, and despite potential resonance singularities, may be carried to all orders. Non-analytic behavior occurs near the magnetic axis. Physical quantities have a finite number of derivatives there. The results, even though no convergence proofs are given, support the possibility of smooth, well-behaved non-symmetric toroidal equilibria.
Overview of the Lockheed Martin Compact Fusion Reactor (CFR) Program
McGuire, Thomas
2015-11-01
The Lockheed Martin Compact Fusion Reactor (CFR) Program endeavors to quickly develop a compact fusion power plant with favorable commercial economics and military utility. An overview of the concept and its diamagnetic, high beta magnetically encapsulated linear ring cusp confinement scheme will be given. The analytical model of the major loss mechanisms and predicted performance will be discussed, along with the major physics challenges. Key features of an operational CFR reactor will be highlighted. The proposed developmental path following the current experimental efforts will be presented. ©2015 Lockheed Martin Corporation. All Rights Reserved.
Magnetic Bunch Compression for a Compact Compton Source
Energy Technology Data Exchange (ETDEWEB)
Gamage, B. [ODU; Satogata, Todd J. [JLAB
2013-12-01
A compact electron accelerator suitable for Compton source applications is in design at the Center for Accelerator Science at Old Dominion University and Jefferson Lab. Here we discuss two options for transverse magnetic bunch compression and final focus, each involving a 4-dipole chicane with M_{56} tunable over a range of 1.5-2.0m with independent tuning of final focus to interaction point $\\beta$*=5mm. One design has no net bending, while the other has net bending of 90 degrees and is suitable for compact corner placement.
Local Helicity Injection Systems for Non-solenoidal Startup in the PEGASUS Toroidal Experiment
Perry, J. M.; Barr, J. L.; Bongard, M. W.; Fonck, R. J.; Hinson, E. T.; Lewicki, B. T.; Redd, A. J.
2013-10-01
Local helicity injection is being developed in the PEGASUS Toroidal Experiment for non-solenoidal startup in spherical tokamaks. The effective loop voltage due to helicity injection scales with the area of the injectors, requiring the development of electron current injectors with areas much larger than the 2 cm2 plasma arc injectors used to date. Solid and gas-effused metallic electrodes were found to be unusable due to reduced injector area utilization from localized cathode spots and narrow operational regimes. An integrated array of 8 compact plasma arc sources is thus being developed for high current startup. It employs two monolithic power systems, for the plasma arc sources and the bias current extraction system. The array effectively eliminates impurity fueling from plasma-material interaction by incorporating a local scraper-limiter and conical-frustum bias electrodes to mitigate the effects of cathode spots. An energy balance model of helicity injection indicates that the resulting 20 cm2 of total injection area should provide sufficient current drive to reach 0.3 MA. At that level, helicity injection drive exceeds that from poloidal induction, which is the relevant operational regime for large-scale spherical tokamaks. Future placement of the injector array near an expanded boundary divertor region will test simultaneous optimization of helicity drive and the Taylor relaxation current limit. Work supported by US DOE Grant DE-FG02-96ER54375.
International Nuclear Information System (INIS)
Compact, high-power-density approaches to fusion power are proposed to improve economic viability through the use of less-advanced technology in systems of considerably reduced scale. The rationale for and the means by which these systems can be achieved are discussed, as are unique technological problems
Limestone compaction: an enigma
Shinn, Eugene A.; Halley, Robert B.; Hudson, J. Harold; Lidz, Barbara H.
1977-01-01
Compression of an undisturbed carbonate sediment core under a pressure of 556 kg/cm2 produced a “rock” with sedimentary structures similar to typical ancient fine-grained limestones. Surprisingly, shells, foraminifera, and other fossils were not noticeably crushed, which indicates that absence of crushed fossils in ancient limestones can no longer be considered evidence that limestones do not compact.
Suyama, T
2005-01-01
We discuss condensations of closed string tachyons localized in compact spaces. Time evolution of an on-shell condensation is naturally related to the worldsheet RG flow. Some explicit tachyonic compactifications of Type II string theory is considered, and some of them are shown to decay into supersymmetric theories known as the little string theories.
Fusion potential for spherical and compact tokamaks
Energy Technology Data Exchange (ETDEWEB)
Sandzelius, Mikael
2003-02-01
The tokamak is the most successful fusion experiment today. Despite this, the conventional tokamak has a long way to go before being realized into an economically viable power plant. In this master thesis work, two alternative tokamak configurations to the conventional tokamak has been studied, both of which could be realized to a lower cost. The fusion potential of the spherical and the compact tokamak have been examined with a comparison of the conventional tokamak in mind. The difficulties arising in the two configurations have been treated from a physical point of view concerning the fusion plasma and from a technological standpoint evolving around design, materials and engineering. Both advantages and drawbacks of either configuration have been treated relative to the conventional tokamak. The spherical tokamak shows promising plasma characteristics, notably a high {beta}-value but have troubles with high heat loads and marginal tritium breeding. The compact tokamak operates at a high plasma density and a high magnetic field enabling it to be built considerably smaller than any other tokamak. The most notable down-side being high heat loads and neutron transport problems. With the help of theoretical reactor studies, extrapolating from where we stand today, it is conceivable that the spherical tokamak is closer of being realized of the two. But, as this study shows, the compact tokamak power plant concept offers the most appealing prospect.
Performance and stability limits at near-unity aspect ratio in the pegasus toroidal experiment
International Nuclear Information System (INIS)
The Pegasus Toroidal Experiment is a mid-sized extremely-low aspect ratio (A) spherical torus (ST). It has the dual roles of exploring limits of ST behavior as A approaches 1 and studying the physics of ST plasmas in the tokamak-spheromak overlap regime. Major parameters are R 0.25 - 0.45 m, A 1.1 - 1.4, Ip T 20% have been obtained, and the operational space of beta vs Ip/aBT is similar to that observed for NBI-heated START discharges. Achievable plasma current is subject to an apparent limit of Ip/Itf ∼ 1. Access to higher-current plasmas appears to be restricted by the appearance of large internal MHD activity, including m/n=2/1 and 3/2 modes. Recent experiments have begun to access ideal stability limits, with disruptions observed as q95 approaches 5, in agreement with numerical predictions for external kink mode onset. (author)
Safety and deterministic failure analyses in high-beta D-D tokamak reactors
International Nuclear Information System (INIS)
Safety and deterministic failure analyses were performed to compare major component failure characteristics for different high-beta D-D tokamak reactors. The primary focus was on evaluating damage to the reactor facility. The analyses also considered potential hazards to the general public and operational personnel. Parametric designs of high-beta D-D tokamak reactors were developed, using WILDCAT as the reference. The size, and toroidal field strength were reduced, and the fusion power increased in an independent manner. These changes were expected to improve the economics of D-D tokamaks. Issues examined using these designs were radiation induced failurs, radiation safety, first wall failure from plasma disruptions, and toroidal field magnet coil failure
Toroidal modeling of interaction between resistive wall mode and plasma flow
Liu, Yueqiang
2013-01-01
The non-linear interplay between the resistive wall mode (RWM) and the toroidal plasma flow is numerically investigated in a full toroidal geometry, by simultaneously solving the initial value problems for the n=1 RWM and the n=0 toroidal force balance equation. Here n is the toroidal mode number. The neoclassical toroidal viscous torque is identified as the major momentum sink that brakes the toroidal plasma flow during the non-linear evolution of the RWM. This holds for a mode that is initially either unstable or stable. For an initially stable RWM, the braking of the flow, and hence the eventual growth of the mode, depends critically on the initial perturbation amplitude.
Toroidal cell and battery. [storage battery for high amp-hour load applications
Nagle, W. J. (Inventor)
1981-01-01
A toroidal storage battery designed to handle relatively high amp-hour loads is described. The cell includes a wound core disposed within a pair of toroidal channel shaped electrodes spaced apart by nylon insulator. The shape of the case electrodes of this toroidal cell allows a first planar doughnut shaped surface and the inner cylindrical case wall to be used as a first electrode and a second planar doughnut shaped surface and the outer cylindrical case wall to be used as a second electrode. Connectors may be used to stack two or more toroidal cells together by connecting substantially the entire surface area of the first electrode of a first cell to substantially the entire surface area of the second electrode of a second cell. The central cavity of each toroidal cell may be used as a conduit for pumping a fluid through the toroidal cell to thereby cool the cell.
Kinetic resonance damping rate of the toroidal ion temperature gradient mode
International Nuclear Information System (INIS)
The linear damping rates of the toroidal ion temperature gradient (ηi) mode due to the toroidal resonance are calculated in the local kinetic limit. The well-known Landau contour method is generalized to treat the analytic continuation problem of the guiding center dispersion function in the toroidal resonance system where the resonance occurs from both the magnetic ΔB-curvature drift and the parallel ion transit drift. A detailed numerical analysis is presented for the dependence of the damping rate of the toroidal ηi mode on various parameters such as var-epsilon n, κy, and the trapped electron fraction. In addition, a consideration is presented on the decay problem of the ballistic response by the phase mixing in the toroidal system, which is directly related to the present damping problem of the wave normal modes by the toroidal resonance
Axisymmetric magnetic fields in stars: relative strengths of poloidal and toroidal components
Braithwaite, J.
2008-01-01
In this third paper in a series on stable magnetic equilibria in stars, I look at the stability of axisymmetric field configurations and in particular at the relative strengths of the toroidal and poloidal components. Both toroidal and poloidal fields are unstable on their own, and stability is achieved by adding the two together in some ratio. I use Tayler's (1973) stability conditions for toroidal fields and other analytic tools to predict the range of stable ratios and then check these pre...
PARTICLE-HOLE NATURE OF THE LIGHT HIGH-SPIN TOROIDAL ISOMERS
Energy Technology Data Exchange (ETDEWEB)
Staszczak, A. [Maria Curie-Sklodowska University, Poland; Wong, Cheuk-Yin [ORNL
2015-01-01
Nuclei under non-collective rotation with a large angular momentum above some threshold can assume a toroidal shape. In our previous work, we showed by using cranked Skyrme Hartree Fock approach that even even, N = Z, high-K, toroidal isomeric states may have general occurrences for light nuclei with 28 < A < 52. We present here some additional results and systematics on the particle-hole nature of these high-spin toroidal isomers.
The vector potential of a circular cylindrical antenna in terms of a toroidal harmonic expansion
Selvaggi, Jerry; Salon, Sheppard; Chari, M. V. K.
2008-08-01
A toroidal harmonic expansion is developed which is used to represent the vector potential due to a circular cylindrical antenna with a rectangular cross section at any arbitrary point in space. The singular part of the antenna kernel is represented by an associated toroidal harmonic expansion and the analytic part of the kernel is represented by a binomial expansion. A simple example is given to illustrate the application of the toroidal expansion.
Toroidal Spiral Nambu-Goto Strings around Higher-Dimensional Black Holes
Igata, Takahisa
2009-01-01
We present solutions of the Nambu-Goto equation for test strings in a shape of toroidal spiral in five-dimensional spacetimes. In particular, we show that stationary toroidal spirals exist around the five-dimensional Myers-Perry black holes. We also show the existence of innermost stationary toroidal spirals around the five-dimensional black holes like geodesic particles orbiting around four-dimensional black holes.
The United Nations Global Compact
DEFF Research Database (Denmark)
Rasche, Andreas; Waddock, Sandra; McIntosh, Malcolm
2013-01-01
This article reviews the interdisciplinary literature on the UN Global Compact. The review identifies three research perspectives, which scholars have used to study the UN Global Compact so far: a historical perspective discussing the Global Compact in the context of UN-business relations, an ope...
Energy Technology Data Exchange (ETDEWEB)
Placidi, M.; Jung, J. -Y.; Ratti, A.; Sun, C.
2014-07-25
This paper describes beam distribution schemes adopting a novel implementation based on low amplitude vertical deflections combined with horizontal ones generated by Lambertson-type septum magnets. This scheme offers substantial compactness in the longitudinal layouts of the beam lines and increased flexibility for beam delivery of multiple beam lines on a shot-to-shot basis. Fast kickers (FK) or transverse electric field RF Deflectors (RFD) provide the low amplitude deflections. Initially proposed at the Stanford Linear Accelerator Center (SLAC) as tools for beam diagnostics and more recently adopted for multiline beam pattern schemes, RFDs offer repetition capabilities and a likely better amplitude reproducibility when compared to FKs, which, in turn, offer more modest financial involvements both in construction and operation. Both solutions represent an ideal approach for the design of compact beam distribution systems resulting in space and cost savings while preserving flexibility and beam quality.
CERN. Geneva
2015-01-01
Fusion research is currently to a large extent focused on tokamak (ITER) and inertial confinement (NIF) research. In addition to these large international or national efforts there are private companies performing fusion research using much smaller devices than ITER or NIF. The attempt to achieve fusion energy production through relatively small and compact devices compared to tokamaks decreases the costs and building time of the reactors and this has allowed some private companies to enter the field, like EMC2, General Fusion, Helion Energy, Lawrenceville Plasma Physics and Lockheed Martin. Some of these companies are trying to demonstrate net energy production within the next few years. If they are successful their next step is to attempt to commercialize their technology. In this presentation an overview of compact fusion reactor concepts is given.
International Nuclear Information System (INIS)
Low-aspect-ratio torsatron configurations could lead to compact stellarator reactors with R0 = 8--11m, roughly one-half to one-third the size of more conventional stellarator reactor designs. Minimum-size torsatron reactors are found using various assumptions. Their size is relatively insensitive to the choice of the conductor parameters and depends mostly on geometrical constraints. The smallest size is obtained by eliminating the tritium breeding blanket under the helical winding on the inboard side and by reducing the radial depth of the superconducting coil. Engineering design issues and reactor performance are examined for three examples to illustrate the feasibility of this approach for compact reactors and for a medium-size (R0 ≅ 4 m,/bar a/ /approx lt/ 1 m) copper-coil ignition experiment. 26 refs., 11 figs., 7 tabs
Landsman, N.P.
1999-01-01
Quantum groupoids are a joint generalization of groupoids and quantum groups. We propose a definition of a compact quantum groupoid that is based on the theory of C*-algebras and Hilbert bimodules. The essential point is that whenever one has a tensor product over the complex numbers in the theory of quantum groups, one now uses a certain tensor product over the base algebra of the quantum groupoid.
Compactly Generated Domain Theory
Battenfeld, Ingo; Schröder, Matthias; Simpson, Alexander
2006-01-01
We propose compactly generated monotone convergence spaces as a well-behaved topological generalisation of directed-complete partial orders (dcpos). The category of such spaces enjoys the usual properties of categories of 'predomains' in denotational semantics. Moreover, such properties are retained if one restricts to spaces with a countable pseudobase in the sense of E. Michael, a fact that permits connections to be made with computability theory, realizability semantics and recent work on ...
Compact Torsatron configurations
International Nuclear Information System (INIS)
Low-aspect-ratio stellarator configurations can be realized by using torsatron winding. Plasmas with aspect ratios in the range of 3.5 to 5 can be confined by these Compact Torsatron configurations. Stable operation at high Β should be possible in these devices, if a vertical field coil system is adequately designed to avoid breaking of the magnetic surfaces at finite Β. 17 refs., 21 figs., 1 tab
International Nuclear Information System (INIS)
The Energy Report compact 2015 from the Ministry of the Environment, Climate Protection and the Energy Sector and the State Office for Statistics Baden-Wuerttemberg provides an overview on the energy sector developments in Baden-Wuerttemberg in 2013. It contains numerous information on the energy consumption in Baden-Wuerttemberg, the energy productivity, the share of renewable energy sources, power generation and the energy-related CO2 emissions.
Current drive, heating and fueling by compact torus injection
International Nuclear Information System (INIS)
The possibility of injecting small compact-torus (CT) plasma rings into magnetic fusion devices is considered. This discussion concentrates on a proposed new method for efficient current drive in Tokamaks and other toroidal devices in which the magnetic flux in the CT acts to excite the current. In addition to this aspect, CTs may be selectively loaded with matter or energetic particles, or may be accelerated to high kinetic energy (0.1 to 1 MeV/ion) to provide fuel or auxiliary heating for low-density fusion devices including tandem mirrors. The potential exists for high-Q (approx. 100) Tokamak operation as well as penetration to distances well beyond those available by neutral beams or fuel particles
Observation of non diffusive term of toroidal momentum transport in the JFT-2M tokamak
International Nuclear Information System (INIS)
Toroidal rotation velocity profiles are measured with multi-chord charge-exchange spectroscopy for the discharge that the neutral beams are interchanged from parallel (co) to anti-parallel (counter) to the direction of the plasma current. Transport analysis of toroidal momentum in the transient phase suggests the existence of non-diffusive term in the toroidal momentum transport. This non-diffusive term appears as spontaneous source of the toroidal momentum in the direction of anti-parallel to the plasma current. (author)
The comparative analysis of the different mechanisms of toroidal rotation in tokamaks
Energy Technology Data Exchange (ETDEWEB)
Sabot, R. [Association Euratom-CEA, Centre d`Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Parail, V. [Kurchatov Institute, Moscow (Russian Federation)
1994-07-01
The toroidal plasma rotation appears as one the possible mechanism for suppression of plasma turbulence. Several mechanisms are believed to contribute to the toroidal plasma rotation. The results of numerical simulation of the toroidal rotation on JET are presented, where are taken into consideration the following effects: the neoclassical viscosity due to banana and ripple trapped particles, the anomalous viscosity due to plasma turbulence, the momentum input by NBI (neutron beam injection) and ion momentum loss near the separatrix due to prompt ion losses. The NBI appeared to be the principal source of toroidal plasma rotation. 6 refs., 2 figs.
International Nuclear Information System (INIS)
Pressure driven MHD instabilities in Heliotron E were studied by shifting the vacuum magnetic axis position outward (Δv > 0) or inward (Δv v ≤ 0 cm. It is believed that the pressure profile was unintentionally adjusted to improve stability; however, this improvement was not clear for β(0) > or approx. (2-3)%. A new type of ideal low-n stability code was developed which relies on an averaging procedure in the toroidal direction of a three-dimensional finite beta MHD equilibrium. This approach seems to include realistic finite beta configuration in the stability calculation better than the usual stellarator expansion method. For the Heliotron E the difference between the two results is fairly small. (author). 9 refs, 5 figs
Fernandez, Pablo
2003-01-01
We prove that in a world without leverage cost the relationship between the levered beta ( L) and the unlevered beta ( u) is the No-costs-of-leverage formula: L = u + ( u - d) D (1 - T) / E. We also analyze 6 alternative valuation theories proposed in the literature to estimate the relationship between the levered beta and the unlevered beta (Harris and Pringle (1985), Modigliani and Miller (1963), Damodaran (1994), Myers (1974), Miles and Ezzell (1980), and practitioners) and prove that all ...
Edge magnetohydrodynamic instability studies in the Pegasus Toroidal Experiment
Bongard, Michael W.
Peeling modes, an instability mechanism underlying deleterious Edge Localized Mode (ELM) activity in fusion-grade plasmas, are observed at the plasma edge in the PEGASUS Toroidal Experiment under conditions of high edge current density (Jedge(˜ 0.1 MA/m2) and low magnetic field (B ˜0.1 T) present at near-unity aspect ratio. Their macroscopic properties are measured using external Mirnov coil arrays, Langmuir probes, and high-speed visible imaging. The modest edge parameters and short pulse lengths of PEGASUS discharges permit direct measurement of the internal magnetic field structure with an insertable array of Hall-effect sensors, providing the current profile and its dynamical evolution on ELM-relevant timescales. Peeling modes generate coherent, edge-localized electromagnetic activity with low toroidal mode numbers n ≤ 3 and high poloidal mode numbers, in agreement with theoretical expectations of a low- n external kink structure. Coherent MHD fluctuation amplitudes are found to be strongly dependent on the experimentally measured J edge/B peeling instability drive, consistent with theory. An equilibrium reconstruction obtained during peeling activity with its current profile constrained by internal Hall measurements is used to test the predictions of analytic peeling stability theory and the ideal MHD stability model. Both approaches are in agreement with experiment, with the latter finding instability to an external kink. Peeling modes nonlinearly generate ELM-like, field-aligned filamentary structures. They detach from the edge and transiently accelerate radially outward, followed by propagation with constant velocity. Time-resolved Jedge measurements demonstrate that the filaments are formed from an initial current-hole perturbation and carry net toroidal currents If ˜ 100--200 A, less than 0.2% of the plasma current. Their constant-velocity radial motions are in qualitative agreement with rates given by electromagnetic blob transport theory.
Observation of Central Toroidal Rotation Induced by ICRF on EAST
Pan, Xiayun; Wang, Fudi; Zhang, Xinjun; Lyu, Bo; Chen, Jun; Li, Yingying; Fu, Jia; Shi, Yuejiang; Yu, Yi; Ye, Minyou; Wan, Baonian
2016-02-01
Core plasma rotation of both L-mode and H-mode discharges with ion cyclotron range of frequency (ICRF) minority heating (MH) scheme was measured with a tangential X-ray imaging crystal spectrometer on EAST (Experimental Advanced Superconducting Tokamak). Co-current central impurity toroidal rotation change was observed in ICRF-heated L- and H-mode plasmas. Rotation increment as high as 30 km/s was generated at ∼1.7 MW ICRF power. Scaling results showed similar trend as the Rice scaling but with significant scattering, especially in L-mode plasmas. We varied the plasma current, toroidal field and magnetic configuration individually to study their effect on L-mode plasma rotation, while keeping the other major plasma parameters and heating unchanged during the scanning. It was found that larger plasma current could induce plasma rotation more efficiently. A scan of the toroidal magnetic field indicated that the largest rotation was obtained for on-axis ICRF heating. A comparison between lower-single-null (LSN) and double-null (DN) configurations showed that LSN discharges rendered a larger rotation change for the same power input and plasma parameters. supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2013GB112004 and 2015GB103002), National Natural Science Foundation of China (Nos. 11175208, 11305212, 11375235, 11405212 and 11261140328), the Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology (2014FXCX003) and Brain Korea 21 Program for Leading Universities & Students (BK21 PLUS)
DEFF Research Database (Denmark)
Frazzini, Andrea; Heje Pedersen, Lasse
.S. equities, 20 international equity markets, Treasury bonds, corporate bonds, and futures; (2) A betting-against-beta (BAB) factor, which is long leveraged low beta assets and short high-beta assets, produces significant positive risk-adjusted returns; (3) When funding constraints tighten, the return of the...
DEFF Research Database (Denmark)
Christoffersen, Peter; Jacobs, Kris; Vainberg, Gregory
Few issues are more important for finance practice than the computation of market betas. Existing approaches compute market betas using historical data. While these approaches differ in terms of statistical sophistication and the modeling of the time-variation in the betas, they are all backward-...
Fabrication of toroidal composite pressure vessels. Final report
International Nuclear Information System (INIS)
A method for fabricating composite pressure vessels having toroidal geometry was evaluated. Eight units were fabricated using fibrous graphite material wrapped over a thin-walled aluminum liner. The material was wrapped using a machine designed for wrapping, the graphite material was impregnated with an epoxy resin that was subsequently thermally cured. The units were fabricated using various winding patterns. They were hydrostatically tested to determine their performance. The method of fabrication was demonstrated. However, the improvement in performance to weight ratio over that obtainable by an all metal vessel probably does not justify the extra cost of fabrication
Nonlinear hybrid simulation of toroidicity-induced alfven eigenmode
International Nuclear Information System (INIS)
Gyrokinetic/Magnetohydrodynamics hybrid simulations have been carried out using MH3D-K code to study the nonlinear saturation of the toroidicity-induced Alfven eigenmode driven by energetic particles in a tokamak plasma. It is shown that the wave particle trapping is the nonlinear saturation mechanism for the parameters considered. The corresponding density profile flattening of hot particles is observed. The saturation amplitude is proportional to the square of linear growth rate. In addition to TAE modes, a new n = 1, m = 0 global Alfven eigenmode is shown to be excited by the energetic particles
Free-boundary toroidal Alfvén eigenmodes
Chen, Eugene Y.; Berk, H. L.; Breizman, B.; Zheng, L. J.
2011-05-01
A numerical study is presented for the n = 1 free-boundary toroidal Alfvén eigenmodes (TAE) in tokamaks, which shows that there is considerable sensitivity of n = 1 modes to the position of the conducting wall. An additional branch of the TAE is shown to emerge from the upper continuum as the ratio of conducting wall radius to plasma radius increases. Such phenomena arise in plasma equilibria with both circular and shaped cross sections, where the shaped profile studied here is similar to that found in Alcator C-Mod.
Results of the ITER toroidal field model coil project
International Nuclear Information System (INIS)
In the scope of the ITER EDA one of the seven largest projects was devoted to the development, manufacture and testing of a Toroidal Field Model Coil (TFMC). The industry consortium AGAN manufactured the TFMC based on on a conceptual design developed by the ITER EDA EU Home Team. The TFMC was completed and assembled in the test facility TOSKA of the Forschungszentrum Karlsruhe in the first half of 2001. The first testing phase started in June 2001 and lasted till October 2001. The first results have shown that the main goals of the project have been achieved
Electromagnetic formulation of global gyrokinetic particle simulation in toroidal geometry
International Nuclear Information System (INIS)
The fluid-kinetic hybrid electron model for global electromagnetic gyrokinetic particle simulations has been formulated in toroidal geometry using magnetic coordinates, providing the capabilities to describe low frequency processes in electromagnetic turbulence with electron dynamics. In the limit of long wavelength and no parallel electric field our equations reduce to the ideal magnetohydrodynamic equations. The formulation has been generalized to include equilibrium flows. The equations for zonal components of electrostatic and vector potentials have been derived, demonstrating the electron screening of the zonal vector potential.
Ceramic toroidal vacuum chamber for the ZT-40 experiment
International Nuclear Information System (INIS)
The design and fabrication of the large ceramic vacuum vessel now in use in the ZT-40 experiment are discussed. The torus has a major diameter of 228 cm, a minor diameter of 40 cm, and it is made of 99.5% pure alumina. The design includes a number of sapphire viewing windows as well as ceramic diagnostic and pump ports. Presented are several design features unique in toroidal chamber fabrication using segmented ceramics. The electrical and thermal insulation applied to this vessel is discussed as well as the handling technique used to accomplish final installation in the experiment
Comments on structural types of toroidal carbon nanotubes
Chuang, Chern; Jin, Bih-Yaw
2012-01-01
We clarify the relationships between the eight structural types of toroidal carbon nanotubes (TCNTs), which can be identified as the eight corners of a cube of structural transformation. The four families with Dnh symmetry can be related by rim rotations, and the same is true for those with Dnd symmetries. These two sets are then connected by horizontal shiftings, thereby completing the cube. Moreover, we further point out that there are five more highly symmetric Dnh structural types that can be derived from performing the generalized Stone-Wales transformatoin on certain TCNTs with Dnh structural types.
Hydraulic jumps in inhomogeneous strongly coupled toroidal dust flows
Piel, Alexander; Wilms, Jochen
2016-07-01
The inhomogeneous flow of strongly coupled dust particles in a toroidal particle trap with harmonic radial confinement is analyzed in the incompressible fluid limit. It is shown that the flow can spontaneously generate shock-like events, which are similar to the hydraulic jump in open channel flows. A definition of the Froude number for this model is given and the critical speed is recovered as the group velocity of surface waves. This hydraulic model is compared with molecular-dynamics simulations, which show that a sudden bifurcation of the flow lines and a localized temperature peak appear just at the point where the critical condition for the hydraulic jump is located.
Experimental observation of crystalline particle flows in toroidal dust clouds
Energy Technology Data Exchange (ETDEWEB)
Wilms, Jochen, E-mail: wilms@physik.uni-kiel.de; Piel, Alexander [IEAP, Christian-Albrechts-Universität, D-24098 Kiel (Germany); Reichstein, Torben [IEAP, Christian-Albrechts-Universität, D-24098 Kiel (Germany); DME, Kiel University of Applied Sciences, Grenzstr. 3, D-24147 Kiel (Germany)
2015-06-15
The dust flow in a toroidal dust trap is studied experimentally. The flow is driven by the Hall component of the ion drag force in a magnetized plasma. Dust density waves are found in a torus with a large minor radius a, which allows for several wavelength, 2a>5λ, in the (mostly) radial direction of the ion flow. Beyond an intermediate state with radial sloshing oscillations, a crystalline dust flow with suppressed wave activity could be realized for 2a<2λ. The particles arrange themselves in distinct layers with hexagonal-like local order. Smooth transitions between states with different numbers of layers are found in the inhomogeneous flow.
Stationary motion of a self gravitating toroidal incompressible liquid layer
Fusco, Giorgio; Oliva, Waldyr M
2012-01-01
We consider an incompressible fluid contained in a toroidal stratum which is only subjected to Newtonian self-attraction. Under the assumption of infinitesimal tickness of the stratum we show the existence of stationary motions during which the stratum is approximatly a round torus (with radii r, R and R>>r) that rotates around its axis and at the same time rolls on itself. Therefore each particle of the stratum describes an helix-like trajectory around the circumference of radius R that connects the centers of the cross sections of the torus.
Acquisition system for the diagnostics data from a toroidal machine
International Nuclear Information System (INIS)
The data acquisition system 'ARIANE' has been conceived by the SIG (Service d'Ionique Generale), for physical measurements on the toroidal machines PETULA and WEGA, which were designed to study the H.F. heating of pulsed plasmas. These systems are constitued of electronic modules which permit them to be adapted to different kinds of measurements, either by analogue channels or by pulse counting. The programmation of these systems, are achieved, either by multiswitches accessible manually on front panels, or by a computer which performs the numerical computations
System design of toroidal field power supply of CDD tokamak
Energy Technology Data Exchange (ETDEWEB)
Liu, Zheng Zhi
1996-12-01
This report deals with system design of Toroidal Field Power Supply of CDD tokamak (CDD-TFPS). The general design philosophy and design variations are introduced. After the outline of CDD-TFPS, the short-circuit calculation, the evaluation of converter parameters, the compatibility of converter and line are carried out. the specifications of major components, semi-conductor devices and accessories are given. High attention is paid to protection system. The design of sub-control and grounding system are described too. Some more general material for power supply design are attached in appendices for reference. (author). 30 tabs., 21 figs.
Meshing analysis of toroidal drive by computer algebra system
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Presents the meshing analysis based on the Computer Algebra System to make it easier to deduce complex formulas while the expression of more complicated surface equations are visualized, by which, the contact line, mesh ing bordlines and undercut bordlines of toroidal drive are deduced, and the results obtained are consistent with the re sults discussed in literature[1] , and concludes that the absolute value of the induced normal curvature is usually smaller (less than 0.12, for example), and it increases as parameters ψ2, V and R increase, decreases as parameter r in creases, and hardly varies with W2, and the variation with a, i21 is not definite.
Self-sustained magnetic braiding in toroidal plasmas
International Nuclear Information System (INIS)
Theory for the magnetic braiding in toroidal plasmas, which is caused by microscopic pressure-gradient-driven turbulence, is developed. When the pressure gradient exceeds a threshold, the self-sustaining of the magnetic braiding and enhanced anomalous transport occur. The balance between the nonlinear destabilization and nonlinear stabilization, which determines the stationary turbulence, is solved analytically for the case of interchange mode. The enhanced thermal conductivity and magnetic perturbation amplitude as well as the threshold pressure gradient are obtained. Cusp-type catastrophe is predicted, allowing the abrupt burst of magnetic perturbations. (author)
Toroidal and poloidal momentum transport studies in tokamaks
DEFF Research Database (Denmark)
Tala, T.; Crombé, K.; Vries, P.C. de; Ferreira, J.; Mantica, P.; Peeters, A.G.; Andrew, Y.; Budny, R.; Corrigan, G.; Eriksson, A.; Garbet, X.; Giroud, C.; Hua, M.-D.; Nordman, H.; Naulin, Volker; Nave, M.F.F.; Parail, V.; Rantamäki, K.; Scott, B.D.; Strand, P.; Tardini, G.; Thyagaraja, A.; Weiland, J.; Zastrow, K.-D.
The present status of understanding of toroidal and poloidal momentum transport in tokamaks is presented in this paper. Similar energy confinement and momentum confinement times, i.e. τE/τφ ≈ 1 have been reported on several tokamaks. It is more important though, to study the local transport both in...... the core and edge plasma separately as, for example, in the core plasma, a large scatter in the ratio of the local effective momentum diffusivity to the ion heat diffusivity χφeff/χi,eff among different tokamaks can be found. For example, the value of effective Prandtl number is typically around χφeff...
Magnetic and drift surfaces in toroidal-plasma equilibria
International Nuclear Information System (INIS)
A method was developed for following magnetic field lines and guiding center orbits of isolated charged particles in toroidal plasma configurations with no spatial symmetries. The heart of the method lies in a divergence-free approximation to a numerical equilibrium magnetic field B that has been computed over a grid of points by the computer code of Betancourt and Garabedian. Considerations from the KAM theory for Hamiltonian systems and the results of our studies lead us to believe that the solenoidal property of B, del . B = 0 must be preserved to be able to follow trajectories in the torus adequately
Symbolic derivation of bicycle kinematics with toroidal wheels
Directory of Open Access Journals (Sweden)
Wang Everett X.
2015-01-01
Full Text Available Bicycle kinematics with toroidal wheels is presented in this paper. Using symbolic mathematic tool Maple, we obtain two holonomic and four nonholonomic constraint equations due to front and rear wheels of a bicycle. We show that the two holonomic constraints cannot be expressed in quartic form for bicycle rear body pitch angle unless the minor (crown radius of the torus are the same for both the front and rear wheels. In addition, we show that all the constraints can be written in differential form, from which a constraint matrix is constructed, according to standard procedure for developing dynamics in robotics.
Toroidal Imploding Detonation Wave Initiator for Pulse Detonation Engines
Jackson, S. I.; Shepherd, J. E.
2007-01-01
Imploding toroidal detonation waves were used to initiate detonations in propane–air and ethylene–air mixtures inside of a tube. The imploding wave was generated by an initiator consisting of an array of channels filled with acetylene–oxygen gas and ignited with a single spark. The initiator was designed as a low-drag initiator tube for use with pulse detonation engines. To detonate hydrocarbon–air mixtures, the initiator was overfilled so that some acetylene oxygen spilled into the tube. The...
Application of toroidal multipoles to facilitate tokamak reactor studies
International Nuclear Information System (INIS)
A method of calculating the vacuum magnetic flux for plasma equilibrium over a range of aspect ratio A and major radius R is presented. Toroidal multipoles are used to fit the vacuum flux for a set of reference equilibria and the fitted moments are then used to parametrize the flux over the design space in A and R. An example is given in which the equilibrium flux for a D-shaped tokamak plasma is predicted and compared with the actual equilibrium code vacuum flux
Observation of finite-. beta. MHD phenomena in tokamaks
Energy Technology Data Exchange (ETDEWEB)
McGuire, K.M.
1984-09-01
Stable high-beta plasmas are required for the tokamak to attain an economical fusion reactor. Recently, intense neutral beam heating experiments in tokamaks have shown new effects on plasma stability and confinement associated with high beta plasmas. The observed spectrum of MHD fluctuations at high beta is clearly dominated by the n = 1 mode when the q = 1 surface is in the plasma. The m/n = 1/1 mode drives other n = 1 modes through toroidal coupling and n > 1 modes through nonlinear coupling. On PDX, with near perpendicular injection, a resonant interaction between the n = 1 internal kink and the trapped fast ions results in loss of beam particles and heating power. Key parameters in the theory are the value of q/sub 0/ and the injection angle. High frequency broadband magnetic fluctuations have been observed on ISX-B and D-III and a correlation with the deterioration of plasma confinement was reported. During enhanced confinement (H-mode) discharges in divertor plasmas, two new edge instabilities were observed, both localized radially near the separatrix. By assembling results from the different tokamak experiments, it is found that the simple theoretical ideal MHD beta limit has not been exceeded. Whether this represents an ultimate tokamak limit or if beta optimized configurations (Dee- or bean-shaped plasmas) can exceed this limit and perhaps enter a second regime of stability remains to be clarified.
Liu, Yueqiang; Ryan, D.; Kirk, A.; Li, Li; Suttrop, W.; Dunne, M.; Fischer, R.; Fuchs, J. C.; Kurzan, B.; Piovesan, P.; Willensdorfer, M.; the ASDEX Upgrade Team; the EUROfusion MST1 Team
2016-05-01
The plasma response to the vacuum resonant magnetic perturbation (RMP) fields, produced by the ELM control coils in ASDEX Upgrade experiments, is computationally modelled using the MARS-F/K codes (Liu et al 2000 Phys. Plasmas 7 3681, Liu et al 2008 Phys. Plasmas 15 112503). A systematic investigation is carried out, considering various plasma and coil configurations as in the ELM control experiments. The low q plasmas, with {{q}95}∼ 3.8 (q 95 is the safety factor q value at 95% of the equilibrium poloidal flux), responding to low n (n is the toroidal mode number) field perturbations from each single row of the ELM coils, generates a core kink amplification effect. Combining two rows, with different toroidal phasing, thus leads to either cancellation or reinforcement of the core kink response, which in turn determines the poloidal location of the peak plasma surface displacement. The core kink response is typically weak for the n = 4 coil configuration at low q, and for the n = 2 configuration but only at high q ({{q}95}∼ 5.5 ). A phase shift of around 60 degrees for low q plasmas, and around 90 degrees for high q plasmas, is found in the coil phasing, between the plasma response field and the vacuum RMP field, that maximizes the edge resonant field component. This leads to an optimal coil phasing of about 100 (‑100) degrees for low (high) q plasmas, that maximizes both the edge resonant field component and the plasma surface displacement near the X-point of the separatrix. This optimal phasing closely corresponds to the best ELM mitigation observed in experiments. A strong parallel sound wave damping moderately reduces the core kink response but has minor effect on the edge peeling response. For low q plasmas, modelling shows that both the resonant electromagnetic torque and the neoclassical toroidal viscous (NTV) torque (due to the presence of 3D magnetic field perturbations) contribute to the toroidal flow damping, in particular near the
Predictive Simulations of ITER Including Neutral Beam Driven Toroidal Rotation
Energy Technology Data Exchange (ETDEWEB)
Halpern, Federico D.; Kritz, Arnold H.; Bateman, Glenn; Pankin, Alexei Y.; Budny, Robert V.; McCune, Douglas C.
2008-06-16
Predictive simulations of ITER [R. Aymar et al., Plasma Phys. Control. Fusion 44, 519 2002] discharges are carried out for the 15 MA high confinement mode (H-mode) scenario using PTRANSP, the predictive version of the TRANSP code. The thermal and toroidal momentum transport equations are evolved using turbulent and neoclassical transport models. A predictive model is used to compute the temperature and width of the H-mode pedestal. The ITER simulations are carried out for neutral beam injection (NBI) heated plasmas, for ion cyclotron resonant frequency (ICRF) heated plasmas, and for plasmas heated with a mix of NBI and ICRF. It is shown that neutral beam injection drives toroidal rotation that improves the confinement and fusion power production in ITER. The scaling of fusion power with respect to the input power and to the pedestal temperature is studied. It is observed that, in simulations carried out using the momentum transport diffusivity computed using the GLF23 model [R.Waltz et al., Phys. Plasmas 4, 2482 (1997)], the fusion power increases with increasing injected beam power and central rotation frequency. It is found that the ITER target fusion power of 500 MW is produced with 20 MW of NBI power when the pedesta temperature is 3.5 keV. 2008 American Institute of Physics. [DOI: 10.1063/1.2931037
Kinetic and electromagnetic transport processes in toroidal devices
International Nuclear Information System (INIS)
A brief review of transport processes in toroidal devices is presented. Particular attention is given to radial transport of power by the Poynting's vector and kinetic electron flow. This work is primarily focused on the Reversed Field Pinch (RFP) which holds the added complexity of a dynamo process that sustains poloidal current in the edge region, where the toroidal field is reversed. The experimental observation of superthermal unidirectional electrons in the plasma edge of ZT-40M and HBTX1C is noted, and the rapid, nonclassical ion heating in RFPs is taken account of. Radial transport parallel to fluctuating magnetic field lines is deemed a likely candidate for both electromagnetic and kinetic energy transport. Two models are discussed and compared. It is concluded that electromagnetic transport using a local Ohm's law best describes nonclassical ion heating, and the transport of kinetic energy by long mean free path electrons best represents the half-Maxwellian of electrons observed in the edge of several RFPs. A nonlocal Ohm's law is essential for the kinetic electron model. 18 refs
Coupling of Applied Non-axisymmetric Fields to Toroidal Torque
Logan, N. C.; Park, J.-K.; Menard, J. E.; Strait, E. J.; Paz-Soldan, C.; Lanctot, M. J.
2014-10-01
Recent advances in the modeling of neoclassical toroidal viscosity (NTV) have enabled realistic predictions of the coupling between applied non-axisymmetric fields and the resultant toroidal torque in the DIII-D tokamak. The strong dependence of the NTV on the amplified plasma kink response reduces the control of the non-resonant torque to a single mode model, in which the torque optimization is equivalent to an optimization of the net non-axisymmetric field's overlap with the spatial structure of the dominant mode. This single mode model has enabled efficient feed-forward correction of the n = 1 and n = 2 intrinsic error fields and n = 1-3 proxy error fields in NTV dominated scenarios. In addition, rotation drive toward a neoclassical offset using multiple coil sets has been optimized in accordance with the single mode model. Similar linear optimization techniques could be used to design future coil sets for rotation control, while inclusion of multimodal effects will be necessary for rotation profile control. Work supported by the US Department of Energy under DE-AC02-09CH11466 and DE-FC02-04ER54698.
Last End Cap Toroid installation : The Pharaonic enterprise
Arnaud Foussat
After the successful and impressive transport feat from Building 191 to Point 1 was carried out by the Friderici crew on 28th June, the second and last Toroid End Cap, ECT-C, was transferred into the surface building, SX1, on 2nd July. The ECT-C was installed in the ATLAS cavern on the C-side on 12th July. As the person responsible for the project, in my opinion, one of the crucial points of this project was to design all the tooling and installation sequences taking into account the building infrastructure dimensional constraints. View of the ECT installation tooling and preparation for the ECT-C descent into the ATLAS 80m-shaft by the ATLAS magnet group and DBS teams. The movement of the 240-ton magnet and 12-m diameter toroid end-cap was achieved in collaboration with SCALES, a subcontractor company, using a hydraulic gantry able to lower the ECT inside the shaft by 5m below the floor level . This allowed the DBS team to attach the end-cap with the 2 x 140 tons overhead crane and lower it onto the c...
Theoretical Analysis of the Electron Spiral Toroid Concept
Cambier, Jean-Luc; Micheletti, David A.; Bushnell, Dennis M. (Technical Monitor)
2000-01-01
This report describes the analysis of the Electron Spiral Toroid (EST) concept being promoted by Electron Power Systems Inc. (EPS). The EST is described as a toroidal plasma structure composed Of ion and electron shells. It is claimed that the EST requires little or no external confinement, despite the extraordinarily large energy densities resulting from the self-generating magnetic fields. The present analysis is based upon documentation made available by EPS, a previous description of the model by the Massachusetts Institute of Technology (MIT), and direct discussions with EPS and MIT. It is found that claims of absolute stability and large energy storage capacities of the EST concept have not been substantiated. Notably, it can be demonstrated that the ion fluid is fundamentally unstable. Although various scenarios for ion confinement were subsequently suggested by EPS and MIT, none were found to be plausible. Although the experimental data does not prove the existence of EST configurations, there is undeniable experimental evidence that some type of plasma structures whose characteristics remain to be determined are observed. However, more realistic theoretical models must first be developed to explain their existence and properties before applications of interest to NASA can he assessed and developed.
Testing of the Toroidal Field model Coil (TFMC)
International Nuclear Information System (INIS)
The paper shortly describes the Toroidal Field Model Coil (TFMC) design, fabrication choices and issues with respect to technological and management aspects. The experience gained during the assembly and disassembly of the TFMC for phase 1 testing, as well as the assembly with the LCT coil for phase 2 testing will be reported. During phase 1 the TFMC was energised at 80 kA and was fast discharged several times without changes in the coil performances. The first test campaign has demonstrated the feasibility and operability of the ITER Toroidal Field coils including the joints. An in depth analysis of the test results will be presented in the paper. The goal for phase 2 testing is to determine the actual margins which have been achieved in the design and manufacture of the TFMC in selected areas. For this purpose, the TFMC will be operated beyond the design conditions in terms of current, temperature and parameters related to coil protection (discharge time constant, quench detection time). This second phase has started in September 2002 and will last about four months, therefore the test results can be used to optimise the ITER design, in particular on the conductors and insulation system. (author)
Shear-Alfven dynamics of toroidally confined plasmas. Part A
International Nuclear Information System (INIS)
Recent developments in the stability theory of toroidally confined plasmas are reviewed, with the intention of providing a picture comprehensible to non-specialists. The review considers a class of low-frequency, electromagnetic disturbances that seem especially pertinent to modern high-temperature confinement experiments. It is shown that such disturbances are best unified and understood through consideration of a single, exact fluid moment: the shear-Alfven law. Appropriate versions of this law and its corresponding closure relations are derived - essentially from first principles - and applied in a variety of mostly, but not exclusively, linear contexts. Among the specific topics considered are: flux coordinates (including Hamada coordinates), the Newcomb solubility condition. Shafranov geometry, magnetic island evolution, reduced MHD and its generalizations, drift-kinetic electron response, classical tearing, twisting, and kink instabilities, pressure-modified tearing instability (Δ-critical), collisionless and semi-collisional tearing modes, the ballooning representation in general geometry, ideal ballooning instability, Mercier criterion, near-axis expansions, the second stability region, and resistive and kinetic ballooning modes. The fundamental importance of toroidal topology and curvature is stressed
From toroidal to rod-like condensates of semiflexible polymers.
Hoang, Trinh Xuan; Giacometti, Achille; Podgornik, Rudolf; Nguyen, Nhung T T; Banavar, Jayanth R; Maritan, Amos
2014-02-14
The competition between toroidal and rod-like conformations as possible ground states for DNA condensation is studied as a function of the stiffness, the length of the DNA, and the form of the long-range interactions between neighboring molecules, using analytical theory supported by Monte Carlo simulations. Both conformations considered are characterized by a local nematic order with hexagonal packing symmetry of neighboring DNA molecules, but differ in global configuration of the chain and the distribution of its curvature as it wraps around to form a condensate. The long-range interactions driving the DNA condensation are assumed to be of the form pertaining to the attractive depletion potential as well as the attractive counterion induced soft potential. In the stiffness-length plane we find a transition between rod-like to toroid condensate for increasing stiffness at a fixed chain length L. Strikingly, the transition line is found to have a L(1/3) dependence irrespective of the details of the long-range interactions between neighboring molecules. When realistic DNA parameters are used, our description reproduces rather well some of the experimental features observed in DNA condensates. PMID:24527935
Protection of toroidal field coils using multiple circuits
International Nuclear Information System (INIS)
The protection of toroidal field (TF) coils using multiple circuits is described. The discharge of a single-circuit TF system is given for purposes of definition. Two-circuit TF systems are analyzed and the results presented analytically and graphically. Induced currents, maximum discharge voltages, and discharge time constants are compared to the single-circuit system. Three-circuit TF systems are analyzed. In addition to induced currents, maximum discharge voltages, and time constants, several different discharge scenarios are included. The impacts of having discharge rates versus final maximum coil temperatures as requirements are examined. The out-of-plane forces which occur in the three-circuit system are analyzed using an approximate model. The analysis of multiplecircuit TF systems is briefly described and results for a Toroidal Fusion Core Experiment (TFCX) scale device are given based on computer analysis. The advantages and disadvantages of using multiple-circuit systems are summarized and discussed. The primary disadvantages of multiple circuits are the increased circuit complexity and potential for out-of-plane forces. These are offset by the substantial reduction in maximum discharge voltages, as well as other design options which become available when using multiple circuits
ITER-hard Toroidal Field coil structural analysis
International Nuclear Information System (INIS)
The High Aspect Ratio Design (HARD) for the International Thermonuclear Experimental Reactor (ITER) has Toroidal Field (TF) coils that are farther out from the center of the Toroidal ring and more elongated than the previous design (CDA). These coils should see higher forces than in CDA and were designed accordingly. The objective of this work, conducted at LLNL and the MIT Plasma Fusion Center, was to determine whether stress levels in the ITER-HARD design are acceptable. A global finite element model, representing one of the coils, was modeled at MIT to obtain stresses and displacements both during operation of the TF coils alone, and during the End of Burn phase with TF and PF (Poloidal Field) coils operating. At LLNL, a detail model of the TF coil straight leg near the equator was used to obtain stresses and displacements during TF operation only. Further detailed analysis of the winding pack of this model was done to estimate stress concentrations in the conduit and insulation
Design study of toroidal traction CVT for electric vehicles
Raynard, A. E.; Kraus, J.; Bell, D. D.
1980-01-01
The development, evaluation, and optimization of a preliminary design concept for a continuously variable transmission (CVT) to couple the high-speed output shaft of an energy storage flywheel to the drive train of an electric vehicle is discussed. An existing computer simulation program was modified and used to compare the performance of five CVT design configurations. Based on this analysis, a dual-cavity full-toroidal drive with regenerative gearing is selected for the CVT design configuration. Three areas are identified that will require some technological development: the ratio control system, the traction fluid properities, and evaluation of the traction contact performance. Finally, the suitability of the selected CVT design concept for alternate electric and hybrid vehicle applications and alternate vehicle sizes and maximum output torques is determined. In all cases the toroidal traction drive design concept is applicable to the vehicle system. The regenerative gearing could be eliminated in the electric powered vehicle because of the reduced ratio range requirements. In other cases the CVT with regenerative gearing would meet the design requirements after appropriate adjustments in size and reduction gearing ratio.
Incorporation of toroidal boundary conditions into program POISSON
International Nuclear Information System (INIS)
A technique is developed for introduction of a boundary condition applicable to relaxation computations for magnetic problems with axial symmetry and with no sources (currents, or magnetized material) external to the boundary. The procedure as described in this note is restricted to cases in which the (toroidal) boundary will surround completely the region of physical interest but will not encompass the axis of rotational symmetry. The technique accordingly provides the opportunity of economically excluding from the relaxation process regions of no direct concern in the immediate neighborhood of the symmetry axis and hence can have useful application to annular magnetic devices with axial symmetry. The procedure adopted makes use internally of the characteristic form of the vector-potential function, in a source-free region, when expressed in toroidal coordinates. The relevant properties of associated Legendre functions of half-integral degree are summarized in this connection and their introduction into the program POISSON is outlined. Results of some test cases are included, to illustrate the application of this technique for configurations with median-plane symmetry. 8 refs., 9 figs
Cryogenic Characteristics of the ATLAS Barrel Toroid Superconducting Magnet
Pengo, R; Delruelle, N; Pezzetti, M; Pirotte, O; Passardi, Giorgio; Dudarev, A; ten Kate, H
2008-01-01
ATLAS, one of the experiments of the LHC accelerator under commissioning at CERN, is equipped with a large superconducting magnet the Barrel Toroid (BT) that has been tested at nominal current (20500 A). The BT is composed of eight race-track superconducting coils (each one weights about 45 tons) forming the biggest air core toroidal magnet ever built. By means of a large throughput centrifugal pump, a forced flow (about 10 liter/second at 4.5 K) provides the indirect cooling of the coils in parallel. The paper describes the results of the measurements carried out on the complete cryogenic system assembled in the ATLAS cavern situated 100 m below the ground level. The measurements include, among other ones, the static heat loads, i.e., with no or constant current in the magnet, and the dynamic ones, since additional heat losses are produced, during the current ramp-up or slow dump, by eddy currents induced on the coil casing.
Compact synchrotron radiation source
International Nuclear Information System (INIS)
A compact 800 MeV synchrotron radiation source is discussed. The storage ring has a circumference of 30.3 m, two 90 degree and four 45 degree bending magnet sections, two long straight sections and four short straight sections. The radius of the bending magnet is 2.224m. The critical wave length is 24A. The injector is a 15 Mev Microtron Electrons are accelerated from 15 Mev to 800 Mev by ramping the field of the ring. The expected stored current will be around 100 ma
Atacama Compact Array Antennas
Saito, Masao; Inatani, Junji; Nakanishi, Kouichiro; Naoi, Takahiro; Yamada, Masumi; Saito, Hiro; Ikenoue, Bungo; Kato, Yoshihiro; Morita, Kou-ichiro; Mizuno, Norikazu; Iguchi, Satoru
2011-01-01
We report major performance test results of the Atacama Compact Array (ACA) 7-m and 12-m antennas of ALMA (Atacama Large Millimeter/submillimeter Array). The four major performances of the ACA antennas are all-sky pointing (to be not more than 2.0 arcsec), offset pointing (to be < 0.6 arcsec) surface accuracy (< 25(20) micrometer for 12(7)m-antenna), stability of path-length (15 micrometer over 3 min), and high servo capability (6 degrees/s for Azimuth and 3 degrees/s for Elevation). The high...
Bazeia, D; Marques, M A; Menezes, R; da Rocha, R
2016-01-01
In this work we deal with non-topological solutions of the Q-ball type in two space-time dimensions, in models described by a single complex scalar field that engenders global symmetry. The main novelty is the presence of stable Q-balls solutions that live in a compact interval of the real line and appear from a family of models controlled by two distinct parameters. We find analytical solutions and study their charge and energy, and show how to control the parameters to make the Q-balls classically and quantum mechanically stable.
Preliminary Study of Ideal Operational MHD Beta Limit in HL-2A Tokamak Plasmas
Shen, Yong; Dong, Jiaqi; He, Hongda; D. Turnbull, A.
2009-04-01
Magnetohydrodynamic (MHD) n = 1 kink mode with n the toroidal mode number is studied and the operational beta limit, constrained by the mode, is calculated for the equilibrium of HL-2A by using the GATO code. Approximately the same beta limit is obtained for configurations with a value of the axial safety factor q0 both larger and less than 1. Without the stabilization of the conducting wall, the beta limit is found to be 0.821% corresponding to a normalized beta value of βcN = 2.56 for a typical HL-2A discharge with a plasma current Ip = 0.245 MA, and the scaling of βcN ~constant is confirmed.
Preliminary Study of Ideal Operational MHD Beta Limit in HL-2A Tokamak Plasmas
Institute of Scientific and Technical Information of China (English)
SHEN Yong; DONG Jiaqi; HE Hongda; A. D. TURNBULL
2009-01-01
Magnetohydrodynamic (MHD) n=1 kink mode with n the toroidal mode number is studied and the operational beta limit, constrained by the mode, is calculated for the equilibrium of HL-2A by using the GATO code. Approximately the same beta limit is obtained for configurations with a value of the axial safety factor q0 both larger and less than 1. Without the stabilization of the conducting wall, the beta limit is found to be 0.821% corresponding to a normalized beta value of βcN=2.56 for a typical HL-2A discharge with a plasma current Ip=0.245 MA, and the scaling of βcN～constant is confirmed.
Energy Technology Data Exchange (ETDEWEB)
Melendez L, L.; Chavez A, E.; Colunga S, S.; Valencia A, R.; Lopez C, R.; Gaytan G, E
1992-03-15
In a cylindrical magnetic topology. the confined plasma experiences 'classic' collisional transport phenomena. When bending the cylinder with the purpose of forming a toro, the magnetic field that before was uniform now it has a radial gradient which produces an unbalance in the magnetic pressure that is exercised on the plasma in the transverse section of the toro. This gives place to transport phenomena call 'neo-classicist'. In this work the structure of the toroidal magnetic field produced by toroidal coils of triangular form, to which are added even of coils of compensation with form of half moon is analyzed. With this type of coils it is looked for to minimize the radial gradient of the toroidal magnetic field. The values and characteristics of B (magnetic field) in perpendicular planes to the toro in different angular positions in the toroidal direction, looking for to cover all the cases of importance are exhibited. (Author)
Bootstrap current in toroidal systems in the presence of a nonuniform radial electric field
International Nuclear Information System (INIS)
The sheared toroidal rotation driven by non-uniform radial electric field can essentially affect on a bootstrap current profile near the edge E-shear layer in the toroidal systems. The high Eγ and pressure gradients would generate the strong peaking off-axis bootstrap current and naturally sustain the hollow current density profile. (author)