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.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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.
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
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.
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
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)
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.
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.
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
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
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)
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
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
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
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.
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
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)
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
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
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.
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
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
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
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
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
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
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
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)
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
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
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
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.
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
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
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
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
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
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
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
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
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
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
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
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)
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
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)
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
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.
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
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
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
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
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
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...
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
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
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
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
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
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
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
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
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
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
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
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
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
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)
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
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
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
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
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)
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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$.
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.
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
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
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
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
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.)
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
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
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
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
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
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
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
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
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
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
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)
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
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
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)
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)
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.
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
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
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
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
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
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
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
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
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
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
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
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.