Sustained spheromak physics experiment
International Nuclear Information System (INIS)
Hooper, E.B.; Bulmer, R.H.; Cohen, B.I.
2001-01-01
The Sustained Spheromak Physics Experiment, SSPX, will study spheromak physics with particular attention to energy confinement and magnetic fluctuations in a spheromak sustained by electrostatic helicity injection. In order to operate in a low collisionality mode, requiring T e >100 eV, vacuum techniques developed for tokamaks will be applied, and a divertor will be used for the first time in a spheromak. The discharge will operate for pulse lengths of several milliseconds, long compared to the time to establish a steady-state equilibrium but short compared to the L/R time of the flux conserver. The spheromak and helicity injector ('gun') are closely coupled, as shown by an ideal MHD model with force-free injector and edge plasmas. The current from the gun passes along the symmetry axis of the spheromak, and the resulting toroidal magnetic field causes the safety factor, q, to diverge on the separatrix. The q-profile depends on the ratio of the injector current to spheromak current and on the magnetic flux coupling the injector to the spheromak. New diagnostics include magnetic field measurements by a reflectometer operating in combined O- and X-modes and by a transient internal probe (TIP). (author)
Sustained spheromak physics experiment
International Nuclear Information System (INIS)
Hooper, E.B.; Bulmer, R.H.; Cohen, B.I.
1999-01-01
The Sustained Spheromak Physics Experiment, SSPX, will study spheromak physics with particular attention to energy confinement and magnetic fluctuations in a spheromak sustained by electrostatic helicity injection. In order to operate in a low collisionality mode, requiring T e > 100 eV, vacuum techniques developed for tokamaks will be applied, and a divertor will be used for the first time in a spheromak. The discharge will operate for pulse lengths of several milliseconds, long compared to the time to establish a steady-state equilibrium but short compared to the L/R time of the flux conserver. The spheromak and helicity injector ('gun') are closely coupled, as shown by an ideal MHD model with force-free injector and edge plasmas. The current from the gun passes along the symmetry axis of the spheromak, and the resulting toroidal magnetic field causes the safety factor, q, to diverge on the separatrix. The q-profile depends on the ratio of the injector current to spheromak current and on the magnetic flux coupling the injector to the spheromak. New diagnostics include magnetic field measurements by a reflectometer operating in combined O- and X-modes and by a transient internal probe (TIP). (author)
Spheromak type plasma experiment apparatus
International Nuclear Information System (INIS)
Odagiri, Kiyoyuki; Miyauchi, Yasuyuki; Oomura, Hiroshi
1985-01-01
The fusion power reactor which is expected to be the most promising energy has been developed for several plasma confinement systems. Under these circumstances, Spheromak configuration has recently attracted attention because of its simple structure and efficient plasma confinement. This apparatus was ordered by the Engineering Department of University of Tokyo for basic studies of the Spheromak plasma confinement technologies. This forms Spheromak plasma according to the induction discharge system which injects this plasma with magnetic energy generated by a toroidal current in the plasma and discharges the current through the electrical feed through. Toroidal current is induced by the poloidal coil in the vessel. We worked together with the researchers of University of Tokyo to conduct experiments and confirmed the formation and confinement of Spheromak plasma in the initial test. (author)
Energy Technology Data Exchange (ETDEWEB)
Graf, A; Howard, S; Horton, R; Hwang, D; May, M; Beiersdorfer, P; McLean, H; Terry, J
2006-05-15
A novel Doppler spectrometer is currently being used for ion or neutral velocity and temperature measurements on the Alcator C-Mod Tokamak. The spectrometer has an f/No. of {approx}3.1 and is appropriate for visible light (3500-6700 {angstrom}). The full width at half maximum from a line emitting calibration source has been measured to be as small as 0.4 {angstrom}. The ultimate time resolution is line brightness light limited and on the order of ms. A new photon efficient detector is being used for the setup at C-Mod. Time resolution is achieved by moving the camera during a plasma discharge in a perpendicular direction through the dispersion plane of the spectrometer causing a vertical streaking across the camera face. Initial results from C-Mod as well as previous measurements from the Compact Toroid Injection Experiment (CTIX) and the Sustained Spheromak Plasma Experiment (SSPX) are presented.
High aspect ratio spheromak experiments
International Nuclear Information System (INIS)
Robertson, S.; Schmid, P.
1987-05-01
The Reversatron RFP (R/a = 50cm/8cm) has been operated as an ohmically heated spheromak of high aspect ratio. We find that the dynamo can drive the toroidal field upward at rates as high as 10 6 G/sec. Discharges can be initiated and ramped upward from seed fields as low as 50 G. Small toroidal bias fields of either polarity (-0.2 < F < 0.2) do not significantly affect operation. 5 refs., 3 figs
Sustained spheromak experiments in CTX
International Nuclear Information System (INIS)
Jarboe, T.R.; Barnes, C.W.; Henins, I.; Hoida, H.W.; Linford, R.K.; Sherwood, A.R.
1983-01-01
So far, spheromaks can be sustained as long as the source is injecting helicity. When the injection stops the configuration decays. Spheromks have been sustained for more than 1 ms with total lifetimes of more than 2 ms. The physical properties of the sustained spheromak are under investigation in this paper. Preliminary data indicate that (B) approx. = 2 kG, n approx. = 2 x 10 14 -cm -3 and T /sub e/ approx. = 20-30 eV. An helicity decay rate is determined from the ratio of an estimate of the helicity content of the spheromak and the rate of helicity flow from the source. In the coaxial source geometry a constant value of poloidal flux /PHI/ /sub p/ is placed inside the center electrode. By applying a voltage V between the two electrodes toroidal flux is injected (/PHI/ /sub t/ =V) which links the poloidal flux. The rate of helicity injection is then 2V/PHI/ /sub p/ . The helicity content of the spheromak is estimated by measuring the fields at one point and using the model described above to calculate the profiles. The result is that /TAU/ /sub Hel/ approx. = 200 us. This value is about the same as the /TAU/ /sub B/ 2 of a decaying spheromak with similar parameters. These results indicate that helicity injection is possible and that a large fraction (30-100%) of the injected helicity is absorbed
Spheromak Merging Experiments on SSX
Brown, M. R.; Kornack, T. W.; Sollins, P. K.; Luh, W. J.
1997-11-01
Spheromak merging experiments are underway at the Swarthmore Spheromak Experiment (SSX) at Swarthmore College. The spheromaks are formed by identical magnetized plasma guns and equilibrium is established in close fitting 0.5 m diameter copper flux conservers. Partial merging is achieved through openings in the back wall. We observe the formation of a reconnection boundary layer at the interface of the two spheromaks using a linear probe array. The characteristic scale of the flux reversal is about 1 cm (consistent with the diffusion scale δ_diff, the ion Larmor radius ρi and the ion inertial length c/ω_pi). Movies of the formation and evolution of the layer will be presented. Correlations between reconnection events and pulses of soft x-rays and energetic particles will be presented if available. Plans for 2D and 3D imaging of the layer will also be discussed.
Sustained Spheromak Physics Experiment, SSPX
International Nuclear Information System (INIS)
Hooper, E.B.
1997-01-01
The Sustained Spheromak Physics Experiment is proposed for experimental studies of spheromak confinement issues in a controlled way: in steady state relative to the confinement timescale and at low collisionality. Experiments in a flux - conserver will provide data on transport in the presence of resistive modes in shear-stabilized systems and establish operating regimes which pave the way for true steady-state experiments with the equilibrium field supplied by external coils. The proposal is based on analysis of past experiments, including the achievement of T e = 400 eV in a decaying spheromak in CTX. Electrostatic helicity injection from a coaxial ''''gun'''' into a shaped flux conserver will form and sustain the plasma for several milliseconds. The flux conserver minimizes fluxline intersection with the walls and provides MHD stability. Improvements from previous experiments include modem wall conditioning (especially boronization), a divertor for density and impurity control, and a bias magnetic flux for configurational flexibility. The bias flux will provide innovative experimental opportunities, including testing helicity drive on the large-radius plasma boundary. Diagnostics include Thomson scattering for T e measurements and ultra-short pulse reflectrometry to measure density and magnetic field profiles and turbulence. We expect to operate at T e of several hundred eV, allowing improved understanding of energy and current transport due to resistive MHD turbulence during sustained operation. This will provide an exciting advance in spheromak physics and a firm basis for future experiments in the fusion regime
Measurement of magnetic properties of confined compact toroid plasma (spheromak)
International Nuclear Information System (INIS)
Hwang, Fu-Kwun.
1991-01-01
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
Overview of the HIT-SI3 spheromak experiment
Hossack, A. C.; Jarboe, T. R.; Chandra, R. N.; Morgan, K. D.; Sutherland, D. A.; Everson, C. J.; Penna, J. M.; Nelson, B. A.
2017-10-01
The HIT-SI and HIT-SI3 spheromak experiments (a = 23 cm) study efficient, steady-state current drive for magnetic confinement plasmas using a novel method which is ideal for low aspect ratio, toroidal geometries. Sustained spheromaks show coherent, imposed plasma motion and low plasma-generated mode activity, indicating stability. Analysis of surface magnetic fields in HIT-SI indicates large n = 0 and 1 mode amplitudes and little energy in higher modes. Within measurement uncertainties all the n = 1 energy is imposed by the injectors, rather than being plasma-generated. The fluctuating field imposed by the injectors is sufficient to sustain the toroidal current through dynamo action whereas the plasma-generated field is not (Hossack et al., Phys. Plasmas, 2017). Ion Doppler spectroscopy shows coherent, imposed plasma motion inside r 10 cm in HIT-SI and a smaller volume of coherent motion in HIT-SI3. Coherent motion indicates the spheromak is stable and a lack of plasma-generated n = 1 energy indicates the maximum q is maintained below 1 for stability during sustainment. In HIT-SI3, the imposed mode structure is varied to test the plasma response (Hossack et al., Nucl. Fusion, 2017). Imposing n = 2, n = 3, or large, rotating n = 1 perturbations is correlated with transient plasma-generated activity. Work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, under Award Number DE-FG02-96ER54361.
Dynamics of spheromak-like compact toroids in a drift tube
International Nuclear Information System (INIS)
Suzuki, Y.; Kishimoto, Y.; Hayashi, T.
2001-01-01
In order to supply plasma fuel confined in spheromak-like compact toroids (SCTs) to a fusion device, the SCTs must be successfully guided through a drift tube region, in which they might be influenced by the magnetic field leaking from the fusion device. To reveal the SCT dynamics in a drift tube, MHD numerical simulations, where the SCTs are accelerated in a co-axial perfectly conducting cylinder with an external magnetic field, are carried out. In addition, the effect of an extended central electrode is examined by changing the length of the inner conducting cylinder. It is revealed that the SCT penetration depth is shorter than that estimated from the conventional conducting sphere model and that the SCTs are further decelerated by extending the inner conducting cylinder. These results are consistent with the results of the compact toroid injection experiment performed on the TEXT Upgrade tokamak. Finally, the deceleration mechanism of the SCTs is discussed by comparing the simulation result with the proposed theoretical model. (author)
Interaction of a spheromak-like compact toroid with a high beta spherical tokamak plasma
International Nuclear Information System (INIS)
Hwang, D.Q.; McLean, H.S.; Baker, K.L.; Evans, R.W.; Horton, R.D.; Terry, S.D.; Howard, S.; Schmidt, G.L.
2000-01-01
Recent experiments using accelerated spheromak-like compact toroids (SCTs) to fuel tokamak plasmas have quantified the penetration mechanism in the low beta regime; i.e. external magnetic field pressure dominates plasma thermal pressure. However, fusion reactor designs require high beta plasma and, more importantly, the proper plasma pressure profile. Here, the effect of the plasma pressure profile on SCT penetration, specifically, the effect of diamagnetism, is addressed. It is estimated that magnetic field pressure dominates penetration even up to 50% local beta. The combination of the diamagnetic effect on the toroidal magnetic field and the strong poloidal field at the outer major radius of a spherical tokamak will result in a diamagnetic well in the total magnetic field. Therefore, the spherical tokamak is a good candidate to test the potential trapping of an SCT in a high beta diamagnetic well. The diamagnetic effects of a high beta spherical tokamak discharge (low aspect ratio) are computed. To test the penetration of an SCT into such a diamagnetic well, experiments have been conducted of SCT injection into a vacuum field structure which simulates the diamagnetic field effect of a high beta tokamak. The diamagnetic field gradient length is substantially shorter than that of the toroidal field of the tokamak, and the results show that it can still improve the penetration of the SCT. Finally, analytic results have been used to estimate the effect of plasma pressure on penetration, and the effect of plasma pressure was found to be small in comparison with the magnetic field pressure. The penetration condition for a vacuum field only is reported. To study the diamagnetic effect in a high beta plasma, additional experiments need to be carried out on a high beta spherical tokamak. (author)
Magnetic Reconnection Results on the Swarthmore Spheromak Experiment
Kornack, T. W.; Sollins, P. K.; Brown, M. R.
1997-11-01
Linear and 2D arrays of magnetic probes are used to study magnetic reconnection in the Swarthmore Spheromak Experiment (SSX). Opposing coaxial plasma guns form two identical spheromaks into adjacent 0.5 m diameter copper flux conservers. The flux conservers have symmetrical openings that allow the spheromaks to merge in a controlled manner. The stable equilibrium of the spheromaks provides a reservoir of magnetic flux for reconnection experiments. Currently, the magnetic configuration of the spheromaks allows the study of counter-helicity reconnection. Preliminary analysis will be presented and may include 2D B field movies of the reconnection region, measurement of the reconnection rate and comparison to the Sweet-Parker and standard Petschek models.
Spheromak experiment using separate guns for formation and sustainment
International Nuclear Information System (INIS)
Brown, M.R.; Martin, A.
1996-01-01
An experiment is described that incorporates the use of separate magnetized plasma guns for formation and sustainment of a spheromak. It is shown that energy coupling efficiency approaches unity if the gun and spheromak are of comparable size. A large gun should be able to operate at lower current and therefore lower voltage. In addition, it is expected that a gun matched to the size of the spheromak will cause less perturbation to the equilibrium. It is proposed to use a smaller gun for spheromak formation and a large, efficient gun for sustainment. The theoretical basis for the experiment is developed, and the details of the experiment are described. A prediction of the equilibrium magnetic flux surfaces using the EFIT code is presented. 28 refs., 3 figs., 1 tab
Re-examination of spheromak experiments and opportunities
International Nuclear Information System (INIS)
Hooper, B.E.; Hammer, J.H.; Barnes, C.W.; Fernandez, J.C.; Wysocki, F.J.
1996-01-01
The results of spheromak experiments are reexamined in light of the hypothesis that the core energy confinement is considerably better than the global confinement and that it extrapolates favorably with magnetic Reynolds number S. The data in decaying spheromaks are found to be consistent with the hypothesis and with magnetic fluctuations scaling as S -1/2 and determining the electron thermal conductivity. No conclusion is drawn from the data for sustained spheromaks, indicating the importance of a new experiment to determine core energy confinement while helicity is injected. The characteristics of such an experiment are discussed, including the importance of using modern vacuum and wall-conditioning techniques and of minimizing magnetic field errors. 44 refs., 7 figs., 1 tab
Magnetic helicity balance in the Sustained Spheromak Plasma Experiment
International Nuclear Information System (INIS)
Stallard, B.W.; Hooper, E.B.; Woodruff, S.; Bulmer, R.H.; Hill, D.N.; McLean, H.S.; Wood, R.D.
2003-01-01
The magnetic helicity balance between the helicity input injected by a magnetized coaxial gun, the rate-of-change in plasma helicity content, and helicity dissipation in electrode sheaths and Ohmic losses have been examined in the Sustained Spheromak Plasma Experiment (SSPX) [E. B. Hooper, L. D. Pearlstein, and R. H. Bulmer, Nucl. Fusion 39, 863 (1999)]. Helicity is treated as a flux function in the mean-field approximation, allowing separation of helicity drive and losses between closed and open field volumes. For nearly sustained spheromak plasmas with low fluctuations, helicity balance analysis implies a decreasing transport of helicity from the gun input into the spheromak core at higher spheromak electron temperature. Long pulse discharges with continuously increasing helicity and larger fluctuations show higher helicity coupling from the edge to the spheromak core. The magnitude of the sheath voltage drop, inferred from cathode heating and a current threshold dependence of the gun voltage, shows that sheath losses are important and reduce the helicity injection efficiency in SSPX
International Nuclear Information System (INIS)
Jarboe, T.R.
1982-01-01
A major effort is being made in the national program to make the operation of axisymmetric, toroidal confinement systems steady state by the application of expensive rf current drive. Described here is a method by which such a confinement system, the spheromak, can be refluxed indefinitely through the application of dc power. As a step towards dc sustainment we have operated the present CTX source in the slow source mode with a longer power application time (approx. 0.1 ms) and successfully generated long-lived spheromaks. If the erosion of the electrodes can be controlled as well as it is with MPD arcs then dc operation should be very clean. If only a small fraction (approx. 10% for an experiment) of the poloidal flux of the spheromak connects to the source then the dc sustainment can be very efficient. The amount of connecting flux that is necessary for sustainment needs to be determined experimentally
International Nuclear Information System (INIS)
Woodruff, S.; Holbomb, C. T.; Stallard, B. W.; Hill, D. N.; Hooper, E. B.; McLean, H. S.; Wood, R. D.; Bulmer, R.; Cohen, B.; Sovinec, C.; Pearlstein, L. D.
2002-01-01
For the spheromak to be attractive as a reactor concept it would be necessary to sustain the configuration with a low recycling power, reflected in the current amplification factor: A 1 = I tor /I gun , where I tor is the toroidal current and I gun is the gun current. It is understood that A 1 needs to be around 60 for a reactor [1], although the highest obtained so far in the spheromak has been ∼3 [2]. The spheromak is a simply connected toroidal confinement device related to the reversed field pinch in that the q-profile falls at the edge and the first wall is conducting, although the central solenoid is absent. In the spheromak, the paradigm for field generation (and hence current amplification) is the injection of helicity, K = ∫A.BdV = 2ΦΨ where φ and Ψ are linked fluxes. Helicity is additive in the process of electrostatic injection by a coaxial gun [3]: K = 2V gunΨgun , where V gun is the voltage applied between two coaxial electrodes (giving the rate of toroidal flux injection) and Ψ gun is the poloidal vacuum flux connecting them. SSPX [4] is a 1m wide coaxial-gun-driven spheromak with W-coated copper electrodes (FIGURE 1) and a uniquely programmable vacuum field configuration. SSPX was built to assess if confinement can be reasonably preserved during injection, and to address the specific physics of the processes governing helicity injection
Current drive by spheromak injection into a tokamak
International Nuclear Information System (INIS)
Brown, M.R.; Bellan, P.M.
1990-01-01
The authors report the first observation of current drive by spheromak injection into a tokamak due to the process of helicity injection. Current drive is observed in Caltech's ENCORE tokamak (30% increase, ΔI > 1 kA) only when both the tokamak and injected spheromak have the same sign of helicity (where helicity is defined as positive if current flows parallel to magnetic field lines and negative if anti-parallel). The initial increase (decrease) in current is accompanied by a sharp decrease (increase) in loop voltage and the increase in tokamak helicity is consistent with the helicity content of the injected spheromak. In addition, the injection of the spheromak raises the tokamak central density by a factor of six. The introduction of cold spheromak plasma causes sudden cooling of the tokamak discharge from 12 eV to 4 eV which results in a gradual decline in tokamak plasma current by a factor of three. In a second experiment, the authors inject spheromaks into the magnetized toroidal vacuum vessel (with no tokamak plasma). An m = 1 magnetic structure forms in the vessel after the spheromak undergoes a double tilt; once in the cylindrical entrance between gun and tokamak, then again in the tokamak vessel. A horizontal shift of the spheromak equilibrium is observed in the direction opposite that of the static toroidal field. In the absence of net toroidal flux, the structure develops a helical pitch as predicted by theory. Experiments with a number of refractory metal coatings have shown that tungsten and chrome coatings provide some improvement in spheromak parameters. They have also designed and will soon construct a larger, higher current spheromak gun with a new accelerator section for injection experiments on the Phaedrus-T tokamak
International Nuclear Information System (INIS)
Brown, M.R.
2001-01-01
The general goal of the Magnetofluids Laboratory at Swarthmore College is to understand how magnetofluid kinetic energy can be converted to magnetic energy as it is in the core of the earth and sun (the dynamo problem) and to understand how magnetic energy can be rapidly converted back to kinetic energy and heat as it is in solar flares (the magnetic reconnection problem). Magnetic reconnection has been studied using the Swarthmore Spheromak Experiment (SSX) which was designed and built under this Junior Faculty Grant. In SSX we generate and merge two rings of magnetized plasma called spheromaks and study their interaction. The spheromaks have many properties similar to solar flares so this work is directly relevant to basic solar physics. In addition, since the spheromak is a magnetic confinement fusion configuration, issues of formation and stability have direct impact on the fusion program
Spheromak Impedance and Current Amplification
International Nuclear Information System (INIS)
Fowler, T K; Hua, D D; Stallard, B W
2002-01-01
It is shown that high current amplification can be achieved only by injecting helicity on the timescale for reconnection, τ REC , which determines the effective impedance of the spheromak. An approximate equation for current amplification is: dI TOR 2 /dt ∼ I 2 /τ REC - I TOR 2 /τ closed where I is the gun current, I TOR is the spheromak toroidal current and τ CLOSED is the ohmic decay time of the spheromak. Achieving high current amplification, I TOR >> I, requires τ REC CLOSED . For resistive reconnection, this requires reconnection in a cold zone feeding helicity into a hot zone. Here we propose an impedance model based on these ideas in a form that can be implemented in the Corsica-based helicity transport code. The most important feature of the model is the possibility that τ REC actually increases as the spheromak temperature increases, perhaps accounting for the ''voltage sag'' observed in some experiments, and a tendency toward a constant ratio of field to current, B ∝ I, or I TOR ∼ I. Program implications are discussed
International Nuclear Information System (INIS)
Knox, S.O.; Barnes, C.W.; Fernandez, J.C.
1985-01-01
The Los Alamos Spheromak Program consists of two experimental facilities. The confinement physics of sustained and decaying spheromaks are being studied in CTX, which has an extensive array of diagnostics. Experiments are directed towards extending the physics understanding of the spheromak as a magnetic confinement concept. Electrodes for the production of clean sustained spheromaks are developed on the Electrode Facility, which is more flexible in terms of experimental modifications. Improvements to helicity sources and elecrodes which are proven on the Electrode Facility are then considered for incorporation onto CTX
Sutherland, D. A.; Hansen, C. J.; Jarboe, T. R.
2017-10-01
A self-consistent, two-fluid (plasma-neutral) dynamic neutral model has been implemented into the 3-D, Extended-MHD code PSI-Tet. A monatomic, hydrogenic neutral fluid reacts with a plasma fluid through elastic scattering collisions and three inelastic collision reactions: electron-impact ionization, radiative recombination, and resonant charge-exchange. Density, momentum, and energy are evolved for both the plasma and neutral species. The implemented plasma-neutral model in PSI-Tet is being used to simulate decaying spheromak configurations in the HIT-SI experimental geometry, which is being compare to two-photon absorption laser induced fluorescence measurements (TALIF) made on the HIT-SI3 experiment. TALIF is used to measure the absolute density and temperature of monatomic deuterium atoms. Neutral densities on the order of 1015 m-3 and neutral temperatures between 0.6-1.7 eV were measured towards the end of decay of spheromak configurations with initial toroidal currents between 10-12 kA. Validation results between TALIF measurements and PSI-Tet simulations with the implemented dynamic neutral model will be presented. Additionally, preliminary dynamic neutral simulations of the HIT-SI/HIT-SI3 spheromak plasmas sustained with inductive helicity injection will be presented. Lastly, potential benefits of an expansion of the two-fluid model into a multi-fluid model that includes multiple neutral species and tracking of charge states will be discussed.
The University of Maryland spheromak fusion experiment: Final report
International Nuclear Information System (INIS)
Antoniades, J.A.; Chin-Fatt, C.; DeSilva, A.W.; Goldenbaum, G.C.; Hess, R.A.; Shaw, R.S.
1986-01-01
The spheromak is a magnetic plasma confinement configuration that features a simple magnetic structure free of coils that link the plasma torus. It offers the possibility of a simple and efficient confinement system for a fusion plasma. Design of the experimental apparatus occupied the first 15 months of the contract period. At the same time, computer studies of the formation of the spheromak plasma, using a two-dimensional MHD code were performed. After the first 12 months of the contract period, subcontracts were let for major components of the system, particularly for the liquid nitrogen cooled bias magnetic coils, the associated power supplies, and the capacitors for the reversal bank. When the design work was complete, the machining contract for the vacuum vessel was placed. At about this time, work on the operating system for the control computer was begun. The necessary hardware items for the data acquisition computer were decided upon and ordered at the end of the second year. The capacitor bank for the Z-directed current (I/sub z/ bank) was rebuilt from existing parts here, and construction of this bank and of the parts for the reversal bank was accomplished while the outside fabrication of other major parts was in progress. Switching hardware for the two capacitor banks was fabricated in house to reduce costs. As capacitors for the reversal bank were delivered, they were incorporated into the bank modules. A full description of the MS experimental hardware is described in this paper. 2 refs., 9 figs., 1 tab
Simulation of multi-pulse coaxial helicity injection in the Sustained Spheromak Physics Experiment
O'Bryan, J. B.; Romero-Talamás, C. A.; Woodruff, S.
2018-03-01
Nonlinear, numerical computation with the NIMROD code is used to explore magnetic self-organization during multi-pulse coaxial helicity injection in the Sustained Spheromak Physics eXperiment. We describe multiple distinct phases of spheromak evolution, starting from vacuum magnetic fields and the formation of the initial magnetic flux bubble through multiple refluxing pulses and the eventual onset of the column mode instability. Experimental and computational magnetic diagnostics agree on the onset of the column mode instability, which first occurs during the second refluxing pulse of the simulated discharge. Our computations also reproduce the injector voltage traces, despite only specifying the injector current and not explicitly modeling the external capacitor bank circuit. The computations demonstrate that global magnetic evolution is fairly robust to different transport models and, therefore, that a single fluid-temperature model is sufficient for a broader, qualitative assessment of spheromak performance. Although discharges with similar traces of normalized injector current produce similar global spheromak evolution, details of the current distribution during the column mode instability impact the relative degree of poloidal flux amplification and magnetic helicity content.
Sustained spheromak technology
Energy Technology Data Exchange (ETDEWEB)
Platts, D.A.; Sherwood, A.R.; Jarboe, T.R.; Linford, R.K.; Hoida, H.W.; Henins, I.
1984-01-01
The goal of these experiments is to devise a technique for driving a spheromak using dc-powered electrodes. The reduction or elimination of pulsed power components in the spheromak source would result in more attractive reactors, and simpler, cheaper experiments. This is important as experiments get larger and approach reactor size. According to some concepts, the dc spheromak would operate with plasma injection so that it would clean up any impurities produced during its formation. These features make the investigation of dc-powered spheromaks interesting. The questions that need to be answered in this investigation are: (1) can a spheromak be sustained by a dc source; and (2) can a practical source be designed to produce a hot clean plasma. After summarizing the evidence which suggests an answer to question one, the approach being taken to answer question two is discussed.
Sustained spheromak technology
International Nuclear Information System (INIS)
Platts, D.A.; Sherwood, A.R.; Jarboe, T.R.; Linford, R.K.; Hoida, H.W.; Henins, I.
1984-01-01
The goal of these experiments is to devise a technique for driving a spheromak using dc-powered electrodes. The reduction or elimination of pulsed power components in the spheromak source would result in more attractive reactors, and simpler, cheaper experiments. This is important as experiments get larger and approach reactor size. According to some concepts, the dc spheromak would operate with plasma injection so that it would clean up any impurities produced during its formation. These features make the investigation of dc-powered spheromaks interesting. The questions that need to be answered in this investigation are: (1) can a spheromak be sustained by a dc source; and (2) can a practical source be designed to produce a hot clean plasma. After summarizing the evidence which suggests an answer to question one, the approach being taken to answer question two is discussed
Spheromak formation studies in SSPX
International Nuclear Information System (INIS)
Hill, D.N.; Bulmer, R.H.; Cohen, B.L.; Hooper, E.B.; LoDestro, L.L.; Mattor, N.; McLean, H.S.; Moller, J.; Pearlstein, L.D.; Ryutov, D.D.; Stallard, B.W.; Wood, R.D.; Woodruff, S.; Holcomb, C.T.; Jarboe, T.; Sovinec, C.R.; Wang, Z.; Wurden, G.
2000-01-01
We present results from the Sustained Spheromak Physics Experiment (SSPX) at LLNL, which has been built to study energy confinement in spheromak plasmas sustained for up to 2 ms by coaxial DC helicity injection. Peak toroidal currents as high as 600kA have been obtained in the 1m dia. (0.23m minor radius) device using injection currents between 200-400kA; these currents generate edge poloidal fields in the range of 0.2-0.4T. The internal field and current profiles are inferred from edge field measurements using the CORSICA code. Density and impurity control is obtained using baking, glow discharge cleansing, and titanium gettering, after which long plasma decay times (τ (ge) 1.5ms) are observed and impurity radiation losses are reduced from ∼50% to e (0)∼120eV and β e ∼7%. Edge field measurements show the presence of n=1 modes during the formation phase, as has been observed in other spheromaks. This mode dies away during sustainment and decay so that edge fluctuation levels as low as 1% have been measured. These results are compared with numerical simulations using the NIMROD code
Stellarmak a hybrid stellarator: Spheromak
International Nuclear Information System (INIS)
Hartman, C.W.
1980-01-01
This paper discusses hybridization of modified Stellarator-like transform windings (T-windings) with a Spheromak or Field-Reversed-Mirror configuration. This configuration, Stellarmak, retains the important topological advantage of the Spheromak or FRM of having no plasma linking conductors or blankets. The T-windings provide rotational transformation in toroidal angle of the outer poloidal field lines, in effect creating a reversed B/sub Toroidal/ Spheromak or adding average B/sub T/ to the FRM producing higher shear, increased limiting β, and possibly greater stability to kinks and tilt. The presence of field ripple in the toroidal direction may be sufficient to inhibit cancellation of directed ion current by electron drag to allow steady state operation with the toroidal as well as poloidal current maintained by neutral beams
Studies on spheromak plasma production by external-flux-core method, (2)
International Nuclear Information System (INIS)
Arata, Masanori; Katsurai, Makoto
1984-01-01
The spheromak technique, one of magnetic plasma containment techniques, has such arrangement of magnetic fields that the toroidal magnetic field is produced by the poloidal current flowing in plasma, and the poloidal magnetic field is produced by the toroidal current in plasma and the current in external coils. The authors proposed external flux core method as the technique of plasma formation by this spheromak method, in which the toroidal magnetic field is injected by the discharge using electrodes, whereas the poloidal magnetic field is injected by induction discharge without electrode. Its fundamental action was analyzed by computer simulation and confirmed by experiment. In this study, the behavior of the spheromak plasma produced was investigated in detail and summarized. The contents were the measurement of the spheromak configuration produced and the estimation of plasma parameters. The experimental setup, the principle of action, and the experimental results of magnetic field distribution obtained by a magnetic probe, ion current measured by an electrostatic probe, electron temperature by spectroscopic measurement and the behavior of spheromak plasma observed with an image converter camera are reported. (Kako, I.)
Field and current amplification in the SSPX spheromak
International Nuclear Information System (INIS)
Hill, D.N. . hilld@llnl.gov; Bulmer, R.H.; Cohen, B.I.
2003-01-01
Results are presented from experiments relating to magnetic field generation and current amplification in the SSPX spheromak. The SSPX spheromak plasma is driven by DC coaxial helicity injection using a 2MJ capacitor bank. Peak toroidal plasma currents of up to 0.7MA and peak edge poloidal fields of 0.3T are produced; lower current discharges can be sustained up to 3.5msec. When edge magnetic fluctuations are reduced below 1% by driving the plasma near threshold, it is possible to produce plasmas with Te > 150eV, e >∼4% and core χ e ∼30m 2 /s. Helicity balance for these plasmas suggests that sheath dissipation can be significant, pointing to the importance of maximizing the voltage on the coaxial injector. For most operational modes we find a stiff relationship between peak spheromak field and injector current, and little correlation with plasma temperature, which suggests that other processes than ohmic dissipation may limit field amplification. However, slowing spheromak buildup by limiting the initial current pulse increases the ratio of toroidal current to injected current and points to new operating regimes with more favorable current amplification. (author)
Performance and stability limits at near-unity aspect ratio in the Pegasus Toroidal Experiment
International Nuclear Information System (INIS)
Fonck, R.J.
2002-01-01
The Pegasus Toroidal Experiment is a mid-sized extremely-low aspect ratio (A) spherical torus (ST). It has the dual roles of exploring limits of ST behavior as A approaches 1 and studying the physics of ST plasmas in the tokamak-spheromak overlap regime. Major parameters are R 0.25 - 0.45 m, A 1.1 - 1.4, I p ≤ 0.15MA, and B t p =aB t is similar to that observed for NBI-heated START discharges. Achievable plasma current apparently is subject to a 'soft' limit of I p =I t f ≤ 1. Access to higher-current plasmas appears to be restricted by the appearance of large internal MHD activity, including m/n=2/1 and 3/2 modes. Recent experiments have begun to access ideal stability limits, with disruptions observed as q 95 approaches 5, in agreement with numerical predictions. (author)
A spheromak ignition experiment reusing Mirror Fusion Test Facility (MFTF) equipment
International Nuclear Information System (INIS)
Fowler, T.K.
1993-01-01
Based on available experimental results and theory, a scenario is presented to achieve ohmic ignition in a spheromak by slow (∼ 10 sec.) helicity injection using power from the Mirror Fusion Test Facility (MFTF) substation. Some of the other parts needed (vacuum vessel, coils, power supplies, pumps, shielded building space) might also be obtained from MFTF or other salvage, as well as some components needed for intermediate experiments for additional verification of the concept (especially confinement scaling). The proposed ignition experiment would serve as proof-of-principle for the spheromak DT fusion reactor design published by Hagenson and Krakowski, with a nuclear island cost about ten times less than a tokamak of comparable power. Designs at even higher power density and lower cost might be possible using Christofilos' concept of a liquid lithium blanket. Since all structures would be protected from neutrons by the lithium blanket and the tritium inventory can be reduced by continuous removal from the liquid blanket, environmental and safety characteristics appear to be favorable
Advanced spheromak fusion reactor
International Nuclear Information System (INIS)
Fowler, T.K.
1996-01-01
The spheromak has no toroidal magnetic field coils or other structure along its geometric axis, and is thus more attractive than the leading magnetic fusion reactor concept, the tokamak. As a consequence of this and other attributes, the spheromak reactor may be compact and produce a power density sufficiently high to warrant consideration of a liquid 'blanket' that breeds tritium, converts neutron kinetic energy to heat, and protects the reactor vessel from severe neutron damage. However, the physics is more complex, so that considerable research is required to learn how to achieve the reactor potential. Critical physics problems and possible ways of solving them are described. The opportunities and issues associated with a possible liquid wall are considered to direct future research
Amplification of S-1 Spheromak current by an inductive current transformer
International Nuclear Information System (INIS)
Jardin, S.C.; Janos, A.; Yamada, M.
1985-11-01
We attempt to predict the consequences of adding an inductive current transformer (OH Transformer) to the present S-1 Spheromak experiment. Axisymmetric modeling with only classical dissipation shows an increase of toroidal current and a shrinking and hollowing of the current channel, conserving toroidal flux. These unstable profiles will undergo helical reconnection, conserving helicity K = ∫ A-vector x B-vector d tau while increasing the toroidal flux and decreasing the poloidal flux so that the plasma relaxes toward the Taylor state. This flux rearrangement is modeled by a new current viscosity term in the mean-field Ohm's law which conserves helicity and dissipates energy
International Nuclear Information System (INIS)
Hooper, E.B.
1997-01-01
The spheromak is a Magnetic Fusion Energy (MFE) configuration, which is a leading alternative to the tokamak. It has a simple geometry which offers an opportunity to achieve the promise of fusion energy if the physics of confinement, current drive, and pressure holding capability extrapolate favorably to a reactor. Recent changes in the US MFE program, taken in response to budget constraints and programmatic directions from Congress, include a revitalization of an experimental alternative concept effort. Detailed studies of the spheromak were consequently undertaken to examine the major physics issues which need to be resolved to advance it as a fusion plasma, the optimum configuration for an advanced experiment, and its potential as a reactor. As a result of this study, we conclude that it is important to evaluate several physics issues experimentally. Such an experiment might be appropriately be named the Sustained Spheromak Physics Experiment (SSPX). It would address several critical issues, the solution to which will provide the physics basis to enable an advanced experiment. The specific scientific goals of SSPX would be to: * Demonstrate that electron and ion temperatures of a few hundred electron volts can be achieved in a steady-state spheromak plasma sustained by a magnetic dynamo (''helicity injection''). * Relate energy confinement quantitatively to the magnetic turbulence accompanying the dynamo and use this knowledge to optimize performance. * Measure the magnetic field profiles and magnetic turbulence in the plasma and relate these to the science of the magnetic dynamo which drives the current in the plasma. * Examine experimentally the pressure holding capability (''beta limit'') of the spheromak. * Understand the initial phases of the transition of the plasma from an equilibrium supported by a magnetic-flux conserving wall to one supported by external coils
Theoretical issues in Spheromak research
International Nuclear Information System (INIS)
Cohen, R. H.; Hooper, E.B.; LoDestro, L.L.; Mattor, N.; Pearlstein, L.D.; Ryutov, D.D.
1997-01-01
This report summarizes the state of theoretical knowledge of several physics issues important to the spheromak. It was prepared as part of the preparation for the Sustained Spheromak Physics Experiment (SSPX), which addresses these goals: energy confinement and the physics which determines it; the physics of transition from a short-pulsed experiment, in which the equilibrium and stability are determined by a conducting wall (''''flux conserver'''') to one in which the equilibrium is supported by external coils. Physics is examined in this report in four important areas. The status of present theoretical understanding is reviewed, physics which needs to be addressed more fully is identified, and tools which are available or require more development are described. Specifically, the topics include: MHD equilibrium and design, review of MHD stability, spheromak dynamo, and edge plasma in spheromaks
Spheromak tilting and its stability control
International Nuclear Information System (INIS)
Hayashi, T.; Sato, T.
1983-01-01
Spheromak tilting instability was studied. A numerical technique to create a rather arbitrarily-shaped spheromak like the one with a flux hole was investigated. The dynamics governing the tilting instability, namely, the influence of the magnetic index, the toroidal current (q-profile) and the resistivity upon the tilting growth rate, and the roles of magnetc reconnection upon the nonlinear development were studied. The best way to control the tilting instability was invented. The stabilizing effects of the vertical wall, the isolated conducting cylindrical belt, and the horizontal wall were studied. Central pole stabilization was also investigated. The influence of the wall condition, namely, whether the wall acted as a flux conserver in the spheromak creation stage or not is discussed. The present study has shown that the three- dimensional simulation is indeed useful and practical in not only studying the underlying physics but also finding a stabilization technique of spheromaks. (Kato, T.)
Performance and stability limits at near-unity aspect ratio in the pegasus toroidal experiment
International Nuclear Information System (INIS)
Fonck, R.; Diem, S.; Garstka, G.; Kissick, M.; Lewicki, B.; Ostrander, C.; Probert, P.; Reinke, M.; Sontag, A.; Tritz, K.; Unterberg, E.
2003-01-01
The Pegasus Toroidal Experiment is a mid-sized extremely-low aspect ratio (A) spherical torus (ST). It has the dual roles of exploring limits of ST behavior as A approaches 1 and studying the physics of ST plasmas in the tokamak-spheromak overlap regime. Major parameters are R 0.25 - 0.45 m, A 1.1 - 1.4, I p T 20% have been obtained, and the operational space of beta vs I p /aB T is similar to that observed for NBI-heated START discharges. Achievable plasma current is subject to an apparent limit of I p /I tf ∼ 1. Access to higher-current plasmas appears to be restricted by the appearance of large internal MHD activity, including m/n=2/1 and 3/2 modes. Recent experiments have begun to access ideal stability limits, with disruptions observed as q 95 approaches 5, in agreement with numerical predictions for external kink mode onset. (author)
Multi-pulse power injection and spheromak sustainment in SSPX
Stallard, B. W.; Hill, D. N.; Hooper, E. B.; Bulmer, R. H.; McLean, H. S.; Wood, R. D.; Woodruff, S.; Sspx Team
2000-10-01
Lawrence Livermore National Laboratory, Livermore, CA 94550, USA. Spheromak formation (gun injection phase) and sustainment experiments are now routine in SSPX using a multi-bank power system. Gun voltage, impedance, and power coupling show a clear current threshold dependence on gun flux (I_th~=λ_0φ_gun/μ_0), increasing with current above the threshold, and are compared with CTX results. The characteristic gun inductance, L_gun~=0.6 μH, derived from the gun voltage dependence on di/dt, is larger than expected from Corsica modeling of the spheromak equilibrium. It’s value is consistent with the n=1 ‘doughook’ mode structure reported in SPHEX and believed important for helicity injection and toroidal current drive. Results of helicity and power balance calculations of spheromak poloidal field buildup are compared with experiment and used to project sustainment with a future longer pulse power supply. This work was performed under the auspices of US DOE by the University of California Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.
Experiments of spheromak and reversed field configuration in 2m theta pinch
International Nuclear Information System (INIS)
Nogi, Y.; Shimamura, S.; Ogura, H.; Osanai, Y.; Saito, K.; Shiina, S.; Yoshimura, H.
1981-01-01
Since the z-current produces the paramagnetic field near the electrodes, the spheromak formation is more difficult in the straight bias field. In order to help the reconnection at the coil ends, the cusp bias coils are added to both ends of the straight coil. Then the spheromak configuration is formed and the plasma is confined for 5 to 10 μs. On the other hand, the RFC continues for about 30 μs in case of the straight bias field. The confinement time is limited by the rotational instability. Although the start time of the instability is not clear, the elongation of the plasma is detected in 15 to 20 μs after the RFC is formed. The period of the rotation is slightly different every shot. Detailed study of the instability is being pursued
ICRH experiments in a toroidal octupole
International Nuclear Information System (INIS)
Barter, J.D.; Sprott, J.C.
1974-01-01
A 100 kW, 144 μsec pulse of 1.4 MHz rf is used to heat plasmas with densities less than or equal to 3 x 10 12 cm -3 at the ion cyclotron frequency in a toroidal octupole. The rf is coupled to the plasma by a single turn, electrostatically shielded hoop coaxial to the four main hoops and located near the wall. Absorbed power is inferred from plasma loading of the hoop and measured directly with an electrostatic ion energy analyzer and compared to single particle resonance heating theory
Compact toroid formation, compression, and acceleration
International Nuclear Information System (INIS)
Degnan, J.H.; Peterkin, R.E. Jr.; Baca, G.P.; Beason, J.D.; Bell, D.E.; Dearborn, M.E.; Dietz, D.; Douglas, M.R.; Englert, S.E.; Englert, T.J.; Hackett, K.E.; Holmes, J.H.; Hussey, T.W.; Kiuttu, G.F.; Lehr, F.M.; Marklin, G.J.; Mullins, B.W.; Price, D.W.; Roderick, N.F.; Ruden, E.L.; Sovinec, C.R.; Turchi, P.J.; Bird, G.; Coffey, S.K.; Seiler, S.W.; Chen, Y.G.; Gale, D.; Graham, J.D.; Scott, M.; Sommars, W.
1993-01-01
Research on forming, compressing, and accelerating milligram-range compact toroids using a meter diameter, two-stage, puffed gas, magnetic field embedded coaxial plasma gun is described. The compact toroids that are studied are similar to spheromaks, but they are threaded by an inner conductor. This research effort, named MARAUDER (Magnetically Accelerated Ring to Achieve Ultra-high Directed Energy and Radiation), is not a magnetic confinement fusion program like most spheromak efforts. Rather, the ultimate goal of the present program is to compress toroids to high mass density and magnetic field intensity, and to accelerate the toroids to high speed. There are a variety of applications for compressed, accelerated toroids including fast opening switches, x-radiation production, radio frequency (rf) compression, as well as charge-neutral ion beam and inertial confinement fusion studies. Experiments performed to date to form and accelerate toroids have been diagnosed with magnetic probe arrays, laser interferometry, time and space resolved optical spectroscopy, and fast photography. Parts of the experiment have been designed by, and experimental results are interpreted with, the help of two-dimensional (2-D), time-dependent magnetohydrodynamic (MHD) numerical simulations. When not driven by a second discharge, the toroids relax to a Woltjer--Taylor equilibrium state that compares favorably to the results of 2-D equilibrium calculations and to 2-D time-dependent MHD simulations. Current, voltage, and magnetic probe data from toroids that are driven by an acceleration discharge are compared to 2-D MHD and to circuit solver/slug model predictions. Results suggest that compact toroids are formed in 7--15 μsec, and can be accelerated intact with material species the same as injected gas species and entrained mass ≥1/2 the injected mass
ALT-II toroidal belt limiter biasing experiments on TEXTOR
International Nuclear Information System (INIS)
Doerner, R.; Boedo, J.A.; Gray, D.S.
1991-01-01
Edge electric fields have been related to H-mode-like behaviour. The experiments reported here are an attempt to control the SOL profiles by electrostatic biasing of the full toroidal-belt limiter ALT-II. The specific goals are: influencing the edge particle flows, particle removal, power deposition and the global confinement. The ALT-II pump limiter is a full toroidal belt located at 45 o below the outer midplane and consisting of eight graphite covered blades which can be independently biased. Particle scoops located behind the limiter neutralize and direct the incoming plasma into the pumping ducts. (author) 5 refs., 3 figs
Final Report Sustained Spheromak Physics Project FY 1997 - FY 1999
International Nuclear Information System (INIS)
Hooper, E.B.; Hill, D.N.
2000-01-01
This is the final report on the LDRD SI-funded Sustained Spheromak Physics Project for the years FY1997-FY1999, during which the SSPX spheromak was designed, built, and commissioned for operation at LLNL. The specific LDRD project covered in this report concerns the development, installation, and operation of specialized hardware and diagnostics for use on the SSPX facility in order to study energy confinement in a sustained spheromak plasma configuration. The USDOE Office of Fusion Energy Science funded the construction and routine operation of the SSPX facility. The main distinctive feature of the spheromak is that currents in the plasma itself produce the confining toroidal magnetic field, rather than external coils, which necessarily thread the vacuum vessel. There main objective of the Sustained Spheromak Physics Project was to test whether sufficient energy confinement could be maintained in a spheromak plasma sustained by DC helicity injection. Achieving central electron temperatures of several hundred eV would indicate this. In addition, we set out to determine how the energy confinement scales with T c and to relate the confinement time to the level of internal magnetic turbulence. Energy confinement and its scaling are the central technical issues for the spheromak as a fusion reactor concept. Pending the outcome of energy confinement studies now under way, the spheromak could be the basis for an attractive fusion reactor because of its compact size, simply-connected magnetic geometry, and potential for steady-state current drive
Particle confinement and fueling effects on the Maryland spheromak
International Nuclear Information System (INIS)
Filuk, A.B.
1991-01-01
The spheromak plasma confinement concept provides the opportunity to study the evolution of a nearly force-free magnetic field configuration. The plasma currents and magnetic fields are produced self-consistently, making this type of device attractive as a possible fusion reactor. At present, spheromaks are observed to have poorer particle and magnetic confinement than expected from simple theory. The purpose of this study is to examine the role of plasma density in the decay of spheromaks produced in the Maryland Spheromak experiment. Density measurements are made with an interferometer and Langmuir probe, and results are correlated with those of other plasma diagnostics to understand the sources of plasma, the spheromak formation effects on the density, and the magnitude of particle loss during the spheromak decay. A power and particle balance computer model is constructed and applied to the spheromaks studied in order to assess the impact of high density and particle loss rate on the spheromak decay. The observations and model indicate that the decay of the spheromaks is at present dominated by impurity radiation loss. The model also predicts that high density and short particle confinement time play a critical role in the spheromak power balance when the impurity levels are reduced
International Nuclear Information System (INIS)
Jarboe, T.R.
1994-01-01
Spheromak research from 1979 to the present is reviewed including over 160 references. Emphasis is on understanding and interpretation of results. In addition to summarizing results some new interpretations are presented. An introduction and brief history is followed by a discussion of generalized helicity and its time derivative. Formation and sustainment are discussed including five different methods, flux core, θ-pinch z-pinch, coaxial source, conical θ-pinch, and kinked z-pinch. All methods are helicity injections. Steady-state methods and rules for designing spheromak experiments are covered, followed by equilibrium and stability. Methods of stabilizing the tilt and shift modes are discussed as well as their impact on the reactor designs. Current-driven and pressure-driven instabilities as well as relaxation in general are covered. Energy confinement is discussed in terms of helicity decay time and βs limits. The confinement in high and low open-flux geometries are compared and the reactor implications discussed. (author)
Experimental studies of compact toroids
International Nuclear Information System (INIS)
1991-01-01
The Berkeley Compact Toroid Experiment (BCTX) device is a plasma device with a Marshall-gun generated, low aspect ratio toroidal plasma. The device is capable of producing spheromak-type discharges and may, with some modification, produce low-aspect ratio tokamak configurations. A unique aspect of this experimenal devie is its large lower hybrid (LH) heating system, which consists of two 450MHz klystron tubes generating 20 megawatts each into a brambilla-type launching structure. Successful operation with one klystron at virtually full power (18 MW) has been accomplished with 110 μs pulse length. A second klystron is currently installed in its socket and magnet but has not been added to the RF drive system. This report describes current activities and accomplishments and describes the anticipated results of next year's activity
Spheromak Buildup in SSPX using a Modular Capacitor Bank
International Nuclear Information System (INIS)
Wood, R D; McLean, H S; Hill, D N; Hooper, E B; Romero-Talamas, C A
2006-01-01
The Sustained Spheromak Physics Experiment (SSPX) [1] was designed to address both magnetic field generation and confinement. The SSPX produces 1.5-3.5msec, spheromak plasmas with a 0.33m major radius and a minor radius of ∼0.23m. DC coaxial helicity injection is used to build and sustain the spheromak plasma within the flux conserver. Optimal operation is obtained by flattening the profile of λ = μ 0 j/B, consistent with reducing the drive for tearing and other MHD modes, and matching of edge current and bias flux to minimize |(delta)B/B| rms . With these optimizations, spheromak plasmas with central T e >350eV and β e ∼ 5% with toroidal fields of 0.6T [3] have been obtained. If a favorable balance between current drive efficiency and energy confinement can be shown, the spheromak has the potential to yield an attractive magnetic fusion concept [4]. The original SSPX power system consists of two lumped-circuit capacitor banks with fixed circuit parameters. This power system is used to produce an initial fast formation current pulse (10kV, 0.5MJ formation bank), followed by a lower current, 3.5ms flattop sustainment pulse (5kV, 1.5MJ sustainment bank). Experimental results indicate that a variety of injected current pulses, such as a longer sustainment flattop [5], higher and longer fast formation [6], and multiple current pulses [7], might further our understanding of magnetic field generation. Although the formation bank can be split into two independent banks capable of producing other injected current waveforms, the variety of current waveforms produced by this power system is limited. Thus, to extend the operating range of the SSPX, a new pulsed-power system has been designed and partially constructed. In this paper, we discuss the design of the programmable bank and present first results from using the bank to increase the magnetic field in SSPX
Scaling studies of spheromak formation and equilibrium
International Nuclear Information System (INIS)
Geddes, C.G.; Kornack, T.W.; Brown, M.R.
1998-01-01
Formation and equilibrium studies have been performed on the Swarthmore Spheromak Experiment (SSX). Spheromaks are formed with a magnetized coaxial plasma gun and equilibrium is established in both small (d small =0.16 m) and large (d large =3d small =0.50 m) copper flux conservers. Using magnetic probe arrays it has been verified that spheromak formation is governed solely by gun physics (in particular the ratio of gun current to flux, μ 0 I gun /Φ gun ) and is independent of the flux conserver dimensions. It has also been verified that equilibrium is well described by the force free condition ∇xB=λB (λ=constant), particularly early in decay. Departures from the force-free state are due to current profile effects described by a quadratic function λ=λ(ψ). Force-free SSX spheromaks will be merged to study magnetic reconnection in simple magnetofluid structures. copyright 1998 American Institute of Physics
Position indicating split toroid for the RACE experiment
International Nuclear Information System (INIS)
Hurst, B.; Folkman, K.
2007-01-01
Aspects of the recent reactor accelerator coupled experiments (RACE) carried out at University of Texas Nuclear Engineering Teaching Laboratory will be discussed. In particular, a compact instrument that allowed a continuous non-invasive means of determining the relative electron beam position was developed. The operation of the instrument is similar to an inductive current pick up toroid except that the core is sectioned radially, which allows spatial information to be derived from the induced voltages. Results of initial tests, both in beam and with a pulser, will be presented along with plans to optimize future designs
Prospects for spheromak fusion reactors
International Nuclear Information System (INIS)
Fowler, T.K.; Hua, D.D.
1995-01-01
The reactor study of Hagenson and Krakowski demonstrated the attractiveness of the spheromak as a compact fusion reactor, based on physics principles confirmed in CTX experiments in many respects. Most uncertain was the energy confinement time and the role of magnetic turbulence inherent in the concept. In this paper, a one-dimensional model of heat confinement, calibrated by CTX, predicts negligible heat loss by magnetic turbulence at reactor scale
Energy Technology Data Exchange (ETDEWEB)
Podesta, M; Fredrickson, E D; Gorelenkov, N N; LeBlanc, B P; Heidbrink, W W; Crocker, N A; Kubota, S
2010-08-19
The effects of a sheared toroidal rotation on the dynamics of bursting Toroidicity-induced Alfven eigenmodes are investigated in neutral beam heated plasmas on the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40 557 (2000)]. The modes have a global character, extending over most of the minor radius. A toroidal rotation shear layer is measured at the location of maximum drive for the modes. Contrary to results from other devices, no clear evidence of increased damping is found. Instead, experiments with simultaneous neutral beam and radio-frequency auxiliary heating show a strong correlation between the dynamics of the modes and the instability drive. It is argued that kinetic effects involving changes in the mode drive and damping mechanisms other than rotation shear, such as continuum damping, are mostly responsible for the bursting dynamics of the modes.
International Nuclear Information System (INIS)
Podesta, M.; Bell, R.E.; Fredrickson, E.D.; Gorelenkov, N.N.; LeBlanc, B.P.; Heidbrink, W.W.; Crocker, N.A.; Kubota, S.; Yuh, H.
2010-01-01
The effects of a sheared toroidal rotation on the dynamics of bursting Toroidicity-induced Alfven eigenmodes are investigated in neutral beam heated plasmas on the National Spherical Torus Experiment (NSTX) (M. Ono et al., Nucl. Fusion 40 557 (2000)). The modes have a global character, extending over most of the minor radius. A toroidal rotation shear layer is measured at the location of maximum drive for the modes. Contrary to results from other devices, no clear evidence of increased damping is found. Instead, experiments with simultaneous neutral beam and radio-frequency auxiliary heating show a strong correlation between the dynamics of the modes and the instability drive. It is argued that kinetic effects involving changes in the mode drive and damping mechanisms other than rotation shear, such as continuum damping, are mostly responsible for the bursting dynamics of the modes.
Hsu, S C; Bellan, P M
2003-05-30
The magnetohydrodynamic kink instability is observed and identified experimentally as a poloidal flux amplification mechanism for coaxial gun spheromak formation. Plasmas in this experiment fall into three distinct regimes which depend on the peak gun current to magnetic flux ratio, with (I) low values resulting in a straight plasma column with helical magnetic field, (II) intermediate values leading to kinking of the column axis, and (III) high values leading immediately to a detached plasma. Onset of column kinking agrees quantitatively with the Kruskal-Shafranov limit, and the kink acts as a dynamo which converts toroidal to poloidal flux. Regime II clearly leads to both poloidal flux amplification and the development of a spheromak configuration.
International Nuclear Information System (INIS)
Hsu, S.C.; Bellan, P.M.
2003-01-01
The magnetohydrodynamic kink instability is observed and identified experimentally as a poloidal flux amplification mechanism for coaxial gun spheromak formation. Plasmas in this experiment fall into three distinct regimes which depend on the peak gun current to magnetic flux ratio, with (I) low values resulting in a straight plasma column with helical magnetic field, (II) intermediate values leading to kinking of the column axis, and (III) high values leading immediately to a detached plasma. Onset of column kinking agrees quantitatively with the Kruskal-Shafranov limit, and the kink acts as a dynamo which converts toroidal to poloidal flux. Regime II clearly leads to both poloidal flux amplification and the development of a spheromak configuration
The Spheromak path to fusion energy
International Nuclear Information System (INIS)
Hooper, E.B.; Barnes, C.W.; Bellan, P.M.
1998-01-01
The spheromak is a simple and robust magnetofluid configuration with several attractive reactor attributes including compact geometry, no material center post, high engineering β, and sustained steady state operation through helicity injection. Spheromak physics was extensively studied in the US program and abroad (especially Japan) in the 1980' s with work continuing into the 1990s in Japan and the UK. Scientific results included demonstration of self-organization at constant helicity, control of the tilt and shift modes by shaped flux conservers, elucidation of the role of magnetic reconnection in the magnetic dynamo, and sustainment of a spheromak by helicity injection. Several groups attained electron temperatures above 100 eV in decaying plasmas, with CTX reaching 400 eV. This experiment had high magnetic field (>l T on the edge and ∼ 3 T near the symmetry axis) and good confinement. More recently, analysis of CTX found the energy confinement in the plasma core to be consistent with Rechester-Rosenbluth transport in a fluctuating magnetic field, potentially scaling to good confinement at higher electron temperatures. The SPHEX group developed an understanding of the dynamo in sustained spheromaks but in a relatively cold device. These and other physics results provide a foundation for a new ''concept exploration'' experiment to study the physics of a hot, sustained spheromak. If successful, this work leads to a next generation, proof-of-principle program. The new SSPX experiment will address the physics of a large-scale sustained spheromak in a national laboratory (LLNL) setting. The key issue in near term spheromak research will be to explore the possibly deleterious effects of sustainment on confinement. Other important issues include exploring the β scaling of confinement, scaling with Lundquist number S, and determining the need for active current-profile control. Collaborators from universities and other national laboratories are contributing
Field-reversed experiments (FRX) on compact toroids
Energy Technology Data Exchange (ETDEWEB)
Armstrong, W.T.; Linford, R.K.; Lipson, J.; Platts, D.A.; Sherwood, E.G.
1981-11-01
Equilibrium, stability, and confinement properties of compact toroids produced in field-reversed theta-pinch experiments (FRX) are reported. Two experimental facilities, FRX-A and FRX-B, have been used to study highly elongated compact toroid plasmas confined in a purely poloidal field geometry. Spatial scans and fill pressure scaling of the equilibrium plasma parameters are presented. Plasma conditions range from T/sub e/approx.150 eV, T/sub i/approx.800 eV, n/sub m/approx.1 x 10/sup 15/ cm/sup -3/ to T/sub e/approx.100 eV, T/sub i/approx.150 eV, n/sub m/approx.4 x 10/sup 15/ cm/sup -3/. Typical confined plasma dimensions are: major radius Rapprox.4 cm, minor radius aapprox.2 cm, and total length 35--50 cm. The plasma configuration remains in a stable equilibrium for up to 50 ..mu..sec followed by the destructive n = 2 rotational instability. The stable period prior to the onset of the rotational mode is up to one hundred times greater than characteristic Alfven transit times of the plasma. This stable period increases and the mode growth rate decreases with increased a/rho/sub i/ (where rho/sub i/ is the ion gyroradius). Agreement of experimental and theoretical mode frequencies for the instability is observed. Preferential particle loss has been proposed as a likely cause of rotation. The particle inventory at the onset of the instability is consistent with this hypothesis. The particle loss rate is also consistent with the predicted anomalous transport near the separatrix. Contributions to rotational instability from diffusion, end-shorting, equipartition, and compression are also discussed.
Field-reversed experiments (FRX) on compact toroids
International Nuclear Information System (INIS)
Armstrong, W.T.; Linford, R.K.; Lipson, J.; Platts, D.A.; Sherwood, E.G.
1981-01-01
Equilibrium, stability, and confinement properties of compact toroids produced in field-reversed theta-pinch experiments (FRX) are reported. Two experimental facilities, FRX-A and FRX-B, have been used to study highly elongated compact toroid plasmas confined in a purely poloidal field geometry. Spatial scans and fill pressure scaling of the equilibrium plasma parameters are presented. Plasma conditions range from T/sub e/approx.150 eV, T/sub i/approx.800 eV, n/sub m/approx.1 x 10 15 cm -3 to T/sub e/approx.100 eV, T/sub i/approx.150 eV, n/sub m/approx.4 x 10 15 cm -3 . Typical confined plasma dimensions are: major radius Rapprox.4 cm, minor radius aapprox.2 cm, and total length 35--50 cm. The plasma configuration remains in a stable equilibrium for up to 50 μsec followed by the destructive n = 2 rotational instability. The stable period prior to the onset of the rotational mode is up to one hundred times greater than characteristic Alfven transit times of the plasma. This stable period increases and the mode growth rate decreases with increased a/rho/sub i/ (where rho/sub i/ is the ion gyroradius). Agreement of experimental and theoretical mode frequencies for the instability is observed. Preferential particle loss has been proposed as a likely cause of rotation. The particle inventory at the onset of the instability is consistent with this hypothesis. The particle loss rate is also consistent with the predicted anomalous transport near the separatrix. Contributions to rotational instability from diffusion, end-shorting, equipartition, and compression are also discussed
Compact toroids generated by a magnetized coaxial source in the CTX experiment
International Nuclear Information System (INIS)
Sherwood, A.R.; Henins, I.; Hoida, H.W.; Jarboe, T.R.; McKenna, K.F.; Linford, R.K.; Marshall, J.; Platts, D.A.
1981-01-01
Compact toroids containing both toroidal and poloidal magnetic field (Spheromak-type) have been generated in CTX using a magnetized coaxial plasma gun. These CTs tear loose from the gun by magnetic field line reconnection, and they are trapped in flux conservers having various geometries. In a straight cylindrical flux conserver the CTs are observed to be unstable to a gross tilting mode. Stability to the tilting mode has been demonstrated in flux conservers having an oblate trapping region; however, the geometry of the entrance region leading to the trapping volume can also have important effects. Lifetimes of about 150 μs for the CTs are typically observed. Interferometric measurements give a value of about 2 x 10 14 cm -3 for the initial plasma density. The plasma temperature measured at a single spot near the minor magnetic axis decreases to around 10 eV by the time the magnetic reconnection is complete. Spectrographic measurements and pressure probe results are in agreement with this temperature. A snipper coil has been installed to induce the CT to tear loose from the gun sooner. The use of this coil is observed to speed up the magnetic field reconnection process by about a factor of 2
Compact toroids generated by a magnetized coaxial source in the CTX experiment
Energy Technology Data Exchange (ETDEWEB)
Sherwood, A.R.; Henins, I.; Hoida, H.W.; Jarboe, T.R.; McKenna, K.F.; Linford, R.K.; Marshall, J.; Platts, D.A.
1981-01-01
Compact toroids containing both toroidal and poloidal magnetic field (Spheromak-type) have been generated in CTX using a magnetized coaxial plasma gun. These CTs tear loose from the gun by magnetic field line reconnection, and they are trapped in flux conservers having various geometries. In a straight cylindrical flux conserver the CTs are observed to be unstable to a gross tilting mode. Stability to the tilting mode has been demonstrated in flux conservers having an oblate trapping region; however, the geometry of the entrance region leading to the trapping volume can also have important effects. Lifetimes of about 150 ..mu..s for the CTs are typically observed. Interferometric measurements give a value of about 2 x 10/sup 14/ cm/sup -3/ for the initial plasma density. The plasma temperature measured at a single spot near the minor magnetic axis decreases to around 10 eV by the time the magnetic reconnection is complete. Spectrographic measurements and pressure probe results are in agreement with this temperature. A snipper coil has been installed to induce the CT to tear loose from the gun sooner. The use of this coil is observed to speed up the magnetic field reconnection process by about a factor of 2.
International Nuclear Information System (INIS)
Kukushkin, A.B.; Rantsev-Kartinov, V.A.; Terentiev, A.R.
1995-01-01
Experimental results are presented which verify the possibility of the self-generated transformation of the magnetic field in plasma focus discharges to give a closed, spheromak-like magnetic configuration (SLMC). The energy conversion mechanism suggests a possibility of further concentrating the plasma power density by means of natural compressing the SLMC-trapped plasma by the residual magnetic field of the plasma focus discharge
Los Alamos Compact Toroid, fast liner, and High-Density Z-Pinch programs
International Nuclear Information System (INIS)
Linford, R.K.; Hammel, J.E.; Sherwood, H.R.
1982-01-01
The compact Toroid and High Density Z-Pinch are two of the plasma configurations presently being studied at Los Alamos. This paper summarizes these two programs along with the recently terminated Fast Liner Program. Included in this discussion is an analysis of compact Toroid formation techniques showing the tearing and reconnection of the fields that separate the spheromak from the radial fields of the coaxial source, and the final equilibrium state of the elongated FRC in the theta-pinch coil. In addition the typical dimensions of the geometry of the Fast Liner experiments are delineated Z-pinch and electrode assembly is displayed as is a graphic of the temporal behavior of the current required for radial equilibrium. Spheromak is examined in terms of formation, gross stability, and equilibrium and field reversed configuration is discussed in terms of gross stability, equilibrium, and confinement scaling
Power balance and characterization of impurities in the Maryland Spheromak
International Nuclear Information System (INIS)
Cote, C.
1993-01-01
The Maryland Spheromak is a medium size magnetically confined plasma of toroidal shape. Low T e and higher n e than expected contribute to produce a radiation dominated short-lived spheromak configuration. A pyroelectric radiation detector and a VUV spectrometer have been used for space and time-resolved measurements of radiated power and impurity line emission. Results from the bolometry and VUV spectroscopy diagnostics have been combined to give the absolute concentrations of the major impurity species together with the electron temperature. The large amount of oxygen and nitrogen ions in the plasma very early in the discharge is seen to be directly responsible for the abnormally high electron density. The dominant power loss mechanisms are found to be radiation (from impurity line emission) and electron convection to the end walls during the formation phase of the spheromak configuration, and radiation only during the decay phase
Power balance and characterization of impurities in the Maryland Spheromak
Energy Technology Data Exchange (ETDEWEB)
Cote, Claude [Univ. of Maryland, College Park, MD (United States)
1993-01-01
The Maryland Spheromak is a medium size magnetically confined plasma of toroidal shape. Low T_{e} and higher n_{e} than expected contribute to produce a radiation dominated short-lived spheromak configuration. A pyroelectric radiation detector and a VUV spectrometer have been used for space and time-resolved measurements of radiated power and impurity line emission. Results from the bolometry and VUV spectroscopy diagnostics have been combined to give the absolute concentrations of the major impurity species together with the electron temperature. The large amount of oxygen and nitrogen ions in the plasma very early in the discharge is seen to be directly responsible for the abnormally high electron density. The dominant power loss mechanisms are found to be radiation (from impurity line emission) and electron convection to the end walls during the formation phase of the spheromak configuration, and radiation only during the decay phase.
Overview, Progress, and Plans for the Compact Toroidal Hybrid Experiment
Hartwell, G. J.; Allen, N. R.; Ennis, D. A.; Hanson, J. D.; Howell, E. C.; Johnson, C. A.; Knowlton, S. F.; Kring, J. D.; Ma, X.; Maurer, D. A.; Ross, K. G.; Schmitt, J. C.; Traverso, P. J.; Williamson, E. N.
2017-10-01
The Compact Toroidal Hybrid (CTH) is an l = 2 , m = 5 torsatron/tokamak hybrid (R0 = 0.75 m, ap 0.2 m, and | B | disruption studies. The main goals of the CTH experiment are to study disruptive behavior as a function of applied 3D magnetic shaping, and to test and advance the V3FIT reconstruction code and NIMROD modeling of CTH. The disruptive density limit is observed to exceed the Greenwald limit as the vacuum transform is increased with no observed threshold for avoidance. Low-q operations (1.1 routine, with disruptions ceasing if the vacuum transform is raised above 0.07. Sawteeth are observed in CTH and have a similar phenomenology to tokamak sawteeth despite employing a 3D confining field. Application of vacuum transform has been demonstrated to reduce and eliminate the vertical drift of elongated discharges. Internal SXR diagnostics, in conjunction with external magnetics, extend the range of reconstruction accuracy into the plasma core. This work is supported by U.S. Department of Energy Grant No. DE-FG02-00ER54610.
Progress on Thomson scattering in the Pegasus Toroidal Experiment
International Nuclear Information System (INIS)
Schlossberg, D J; Bongard, M W; Fonck, R J; Schoenbeck, N L; Winz, G R
2013-01-01
A novel Thomson scattering system has been implemented on the Pegasus Toroidal Experiment where typical densities of 10 19 m −3 and electron temperatures of 10 to 500 eV are expected. The system leverages technological advances in high-energy pulsed lasers, volume phase holographic (VPH) diffraction gratings, and gated image intensified (ICCD) cameras to provide a relatively low-maintenance, economical, robust diagnostic system. Scattering is induced by a frequency-doubled, Q-switched Nd:YAG laser (2 J at 532 nm, 7 ns FWHM pulse) directed to the plasma over a 7.7 m long beam path, and focused to 80%) and fast-gated ICCDs (gate > 2 ns, Gen III intensifier) with high-throughput (F/1.8), achromatic lensing. A stray light mitigation facility has been implemented, consisting of a multi-aperture optical baffle system and a simple beam dump. Successful stray light reduction has enabled detection of scattered signal, and Rayleigh scattering has been used to provide a relative calibration. Initial temperature measurements have been made and data analysis algorithms are under development
Progress on Thomson scattering in the Pegasus Toroidal Experiment
Schlossberg, D. J.; Bongard, M. W.; Fonck, R. J.; Schoenbeck, N. L.; Winz, G. R.
2013-11-01
A novel Thomson scattering system has been implemented on the Pegasus Toroidal Experiment where typical densities of 1019 m-3 and electron temperatures of 10 to 500 eV are expected. The system leverages technological advances in high-energy pulsed lasers, volume phase holographic (VPH) diffraction gratings, and gated image intensified (ICCD) cameras to provide a relatively low-maintenance, economical, robust diagnostic system. Scattering is induced by a frequency-doubled, Q-switched Nd:YAG laser (2 J at 532 nm, 7 ns FWHM pulse) directed to the plasma over a 7.7 m long beam path, and focused to VPH transmission gratings (eff. > 80%) and fast-gated ICCDs (gate > 2 ns, Gen III intensifier) with high-throughput (F/1.8), achromatic lensing. A stray light mitigation facility has been implemented, consisting of a multi-aperture optical baffle system and a simple beam dump. Successful stray light reduction has enabled detection of scattered signal, and Rayleigh scattering has been used to provide a relative calibration. Initial temperature measurements have been made and data analysis algorithms are under development.
The S-1 Spheromak Control System
International Nuclear Information System (INIS)
Mathe, P.; Mika, R.; Oliaro, G.
1983-01-01
The use of a CAMAC based DEC LSI-11/23 microcomputer to perform all control functions for the S-1 Spheromak is described. The system monitors and controls the three coil systems, Toroidal, Poloidal, and Equilibrium field coils and their associated power sources, the water cooling system, the personnel and machine safety system, the machine and diagnostic timing system and the control room display and operator interface. Future requirements include control of the vacuum system, the gas injection system and interface to the PPPL Data Acquisition System DEC10. The computer is connected to five remotely located CAMAC crates by a fiber-optic serial highway operating at five megahertz. These crates contain interface modules required to control the S-1 experiment. These modules include: D/A and A/D converters, fast transient digitizers, timing modules, temperature sensing modules, CRT alphanumeric display drivers, watchdog timers, and relay and TTL parallel I/O ports. The computer itself resides in crate number0 and consists of an LSI-11/23 with hardware floating post processor, memory management, 256K bytes of memory, four RS-232 serial ports and a 30 megabyte hard disk with a one megabyte floppy disk backup. The majority of software is written in FORTRAN with a few speed critical programs written in PDP-11 MACRO assembly language. The software simulates a sequential state machine which allows easily changeable logic since all logic is represented by standard Boolean Fortran statements. The RSX-11/m operating system allows multiple tasks to be active simultaneously. This provides computing time for operator interactions, editing of critical machine parameters, data analysis and transmission of data to other computers while still maintaining the scan activity which constantly monitors machine parameters
Progress in the SSPX Spheromak
International Nuclear Information System (INIS)
McLean, H S; Woodruff, S; Hill, D N; Bulmer, R H; Cohen, B I; Hooper, E B; Moller, J; Ryutov, D D; Stallard, B W; Wood, R D; Holcomb, C T; Jarboe, T R; Romero-Talamas, C
2003-01-01
The spheromak, with its simply connected geometry, holds promise as a less expensive fusion reactor. It has reasonably good plasma beta and can be formed and sustained in steady state with a magnetized coaxial plasma gun. The Sustained Spheromak Physics Experiment (SSPX) shown in Fig. 1 was constructed to investigate the key issues of magnetic field generation and energy confinement. In addition to the coaxial gun, nine magnetic field coils are utilized to shape the vacuum magnetic flux. This flexibility allows operation in many different regimes producing very different plasma characteristics. Pulse length is extended and magnetic field strength is increased. Improved surface conditioning produces plasmas with low impurity content, and higher electron temperature, T e . Electron heat transport within the separatrix is reduced by a factor of 4. The results strongly suggest the existence of closed flux surfaces even though the plasma is connected to the coaxial source. The CORSICA Grad-Shafranov 2-d equilibrium code with data from edge magnetic probes along with T e and electron density ne from Thomson scattering is used to calculate internal profiles: normalized current γ = μ 0 J/B, safety factor = q, ohmic heating, thermal energy density, and thermal diffusivity = ξ e . Ohmic heating is calculated by assuming spatially constant Spitzer resistivity with Z eff =2.3 estimated by VUV spectroscopy
The Quasi-Toroidal Stellarator: An Innovative Confinement Experiment
International Nuclear Information System (INIS)
Knowlton, S. F.
2001-01-01
To develop a new class of stellarators that exhibit improved confinement compared to conventional stellarators. This approach generally makes use of a designed symmetry of the magnetic field strength along a particular coordinate axis in the toroidal geometry of the stellarator, and is referred to as quasi-symmetry
Experiments on a Toroidal Screw Pinch with Various Field Programming
Energy Technology Data Exchange (ETDEWEB)
Zwicker, H.; Wilhelm, R.; Krause, H. [Max-Planck-Institut Fuer Plasmaphysik, EURATOM-Association, Garching, Munich, Federal Republic of Germany (Germany)
1971-10-15
In the toroidal screw pinch ISAR-IV (large diameter 60 cm, aspect ratio 5, maximum storage, energy 140 kj) attempts were made to get an improved stability of the plasma by different kinds of field programming. The best results were obtained with positive trapped B{sub z}-fields and simultaneous switching of main B{sub z}-field and I{sub z}-current. In this case the dense plasma column (n{sub e} Almost-Equal-To 2-3 x 10{sup 16} , kT Almost-Equal-To 50-100 eV, {beta} Almost-Equal-To 15-20%) is surrounded by a force-free plasma ({beta} = 1%) with weak shear and it behaves stably for, at least, 25 {mu}s. The resulting containment time nr of near 10{sup 12} s cm{sup -3} remains a factor of 2-3 below the upper limit given by the classical diffusion. The following loss of the equilibrium position near the coil axis ({Delta} Almost-Equal-To 1-2 cm) is connected to a strong damping of the axial plasma current which starts near the end of the containment. It may be assumed that the increase of the effective plasma resistance mainly results from a contact of the force-free regions with the tube wall. Attempts were made to improve the containment by suitable programming of a plasma z-current. The results are presented. Experiments with one quartz limiter inside the torus improved the equilibrium but introduced instabilities at the new surface of the dilute plasma. To obtain more information about the outer region, the dilute plasma was produced without a dense core and separated from the tube walls by weak adiabatic compression. Under these Tokamak-like conditions the q-value was varied. In the region of q Almost-Equal-To 1 there appeared instabilities which seem to haver higher m-modes and rather short wavelengths. In a different kind of field programming the field distribution of the ''diffuse pinch'' was realized within an accuracy of 5-10% (kT Almost-Equal-To 100 eV, {beta} Almost-Equal-To 30%). In contrast to the predictions of MHD-theory, stability was observed only for
Engineering status of the superconducting end cap toroid magnets for the ATLAS experiment at LHC
Baynham, D Elwyn; Carr, F S; Courthold, M J D; Cragg, D A; Densham, C J; Evans, D; Holtom, E; Rochford, J; Sole, D; Towndrow, Edwin F; Warner, G P
2000-01-01
The ATLAS experiment at LHC, CERN will utilise a large, superconducting, air-cored toroid magnet system for precision muon measurements. The magnet system will consist of a long barrel and two end-cap toroids. Each end-cap toroid will contain eight racetrack coils mounted as a single cold mass in cryostat vessel of ~10 m diameter. The project has now moved from the design/specification stage into the fabrication phase. This paper presents the engineering status of the cold masses and vacuum vessels that are under fabrication in industry. Final designs of cold mass supports, cryogenic systems and control/protection systems are presented. Planning for toroid integration, test and installation is described. (3 refs).
MHD stability analysis of axisymmetric surface current model tokamaks close to the spheromak regime
International Nuclear Information System (INIS)
Honma, Toshihisa; Kaji, Ikuo; Fukai, Ichiro; Kito, Masafumi.
1984-01-01
In the toroidal coordinates, a stability analysis is presented for very low-aspect-ratio tokamaks with circular cross section which is described by a surface current model (SCM) of axisymmetric equilibria. The energy principle determining the stability of plasma is treated without any expansion of aspect ratio. Numerical results show that, owing to the occurrence of the non-axisymmetric (n=1) unstable modes, there exists no MHD-stable ideal SCM spheromak characterized by zero external toroidal vacuum field. Instead, a stable spheromak-type plasma which comes to the ideal SCM spheromak is provided by the configuration with a very weak external toroidal field. Close to the spheromak regime (1.0 1 aspect ratio< = 1.1), the minimum safety factor and the critical β-values increase mo notonically with aspect ratio decreasing from a large value, and curves of βsub(p) versus β in the marginal stability approach to an ideal SCM spheromak line βsub(p)=β. (author)
Compact toroid fueling of the TdeV tokamak
International Nuclear Information System (INIS)
Martin, F.; Raman, R.; Xiao, C.; Thomas, J.
1993-01-01
Compact toroids have been proposed as a means of centrally fueling tokamak reactors because of the high velocity to which they can be accelerated. These are cold (T e ∼ 10 eV), high density (n e > 10 20 m -3 ) spheromak plasmoids that are accelerated in a magnetized Marshall gun. As a proof of principle experiment, a compact toroid fueler (CTF) has been developed for injection into the TdeV tokamak. The engineering goals of the experiment are to measure and minimize the impurity content of the CT plasma and the neutral gas remaining after CT formation. Also of importance is the effect of CT central fueling on the tokamak density profile and bootstrap current, and the relaxation rate of the density profile providing information on the confinement time of the CT fuel
EMC3-EIRENE modeling of toroidally-localized divertor gas injection experiments on Alcator C-Mod
Energy Technology Data Exchange (ETDEWEB)
Lore, J.D., E-mail: lorejd@ornl.gov [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Reinke, M.L. [York Plasma Institute, Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom); LaBombard, B. [Plasma Science and Fusion Center, MIT, Cambridge, MA 02139 (United States); Lipschultz, B. [York Plasma Institute, Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom); Churchill, R.M. [Plasma Science and Fusion Center, MIT, Cambridge, MA 02139 (United States); Pitts, R.A. [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France); Feng, Y. [Max Planck Institute for Plasma Physics, Greifswald (Germany)
2015-08-15
Experiments on Alcator C-Mod with toroidally and poloidally localized divertor nitrogen injection have been modeled using the three-dimensional edge transport code EMC3-EIRENE to elucidate the mechanisms driving measured toroidal asymmetries. In these experiments five toroidally distributed gas injectors in the private flux region were sequentially activated in separate discharges resulting in clear evidence of toroidal asymmetries in radiated power and nitrogen line emission as well as a ∼50% toroidal modulation in electron pressure at the divertor target. The pressure modulation is qualitatively reproduced by the modeling, with the simulation yielding a toroidal asymmetry in the heat flow to the outer strike point. Toroidal variation in impurity line emission is qualitatively matched in the scrape-off layer above the strike point, however kinetic corrections and cross-field drifts are likely required to quantitatively reproduce impurity behavior in the private flux region and electron temperatures and densities directly in front of the target.
Experiments on toroidal inductively coupled alternating-current gas discharges
International Nuclear Information System (INIS)
Lok, J.
1976-01-01
This report is on an experimental study of a toroidal, inductively coupled a.c. gas discharge sustained at pressures roughly between one tenth of a Torr and some tens of Torrs. After breakdown is obtained at low pressure, additional gas is let in. The energy is inductively coupled into the electrodeless discharge by means of an iron core transformer of which the toroidal plasma column is the secondary winding. The power dissipated in the plasma is between 80 and 260 kW and is delivered by a motor-generator system at a frequency of 8 kHz for times up to 2 seconds. A toroidal magnetic field of 0.5 T maximum can be supplied in a short pulse. Five different gases (hydrogen, deuterium, helium, argon, and nitrogen) are used. The pressure range in which the discharges are sustained is specified, and the dynamic current-voltage characteristics are given for different pressures. Some typical streak pictures with simultaneously obtained recordings of the time behaviour of the discharge current and of the loop voltage are presented for the initial phase - at low pressure - of the discharge. The shape and the position of fully developed discharges at various pressures are discussed on the basis of photographic observations. The temperature of hydrogen plasmas is derived both from the electrical conductivity and from the emission of line radiation. The values of the temperature obtained in these ways differ in magnitude and in time behaviour. A possible explanation of the discrepancy can be obtained in terms of expansion and contraction of electron density and temperature profiles during a period of the discharge current, if it is taken into account that the main part of the light emission always originates from the outer colder regions of the plasma. In a somewhat different pressure regime, this picture is confirmed by microwave measurements
Steady-state operation of spheromaks by inductive techniques
International Nuclear Information System (INIS)
Janos, A.
1984-04-01
A method to maintain a steady-state spheromak configuration inductively using the S-1 Spheromak device is described. The S-1 Spheromak formation apparatus can be utilized to inject magnetic helicity continuously (C.W., not pulsed or D.C.) into the spheromak configuration after equilibrium is achieved in the linked mode of operation. Oscillation of both poloidal- and toroidal-field currents in the flux core (psi-phi Pumping), with proper phasing, injects a net time-averaged helicity into the plasma. Steady-state maintenance relies on flux conversion, which has been earlier identified. Relevant experimental data from the operation of S-1 are described. Helicity flow has been measured and the proposed injection scheme simulated. In a reasonable time practical voltages and frequencies can inject an amount of helicity comparable to that in the initial plasma. Plasma currents can be maintained or increased. This pumping technique is similar to F-THETA Pumping of a Reversed-Field-Pinch but is applied to this inverse-pinch formation
Model predictions for auxiliary heating in spheromaks
International Nuclear Information System (INIS)
Fauler, T.K.; Khua, D.D.
1997-01-01
Calculations are presented of the plasma temperature waited for under auxiliary heating in spheromaks. A model, ensuring good agreement of earlier experiments with joule heating results, is used. The model includes heat losses due to magnetic fluctuations and shows that the plasma temperatures of the kilo-electron-volt order may be achieved in a small device with the radius of 0.3 m only
International Nuclear Information System (INIS)
Moroz, P.E.
1997-03-01
A novel concept for magnetic plasma confinement, Stellarator-Spheromak (SSP), is proposed. Numerical analysis with the classical-stellarator-type outboard stellarator windings demonstrates a number of potential advantages of SSP for controlled nuclear fusion. Among the main ones are: simple and compact magnet coil configuration, absence of material structures (e.g. magnet coils or conducting walls) in the center of the torus, high rotational transform, and a possibility of MHD equilibria with very high β (pressure/magnetic pressure) of the confined plasma
Simulation of Spheromak Evolution and Energy Confinement
International Nuclear Information System (INIS)
Cohen, B; Hooper, E; Cohen, R; Hill, D; McLean, H; Wood, R; Woodruff, S; Sovinec, C; Cone, G
2004-01-01
Simulation results are presented that illustrate the formation and decay of a spheromak plasma driven by a coaxial electrostatic plasma gun, and that model the energy confinement of the plasma. The physics of magnetic reconnection during spheromak formation is also illuminated. The simulations are performed with the three-dimensional, time-dependent, resistive magnetohydrodynamic NIMROD code. The simulation results are compared to data from the SSPX spheromak experiment at the Lawrence Livermore National Laboratory. The simulation results are tracking the experiment with increasing fidelity (e.g., improved agreement with measurements of the magnetic field, fluctuation amplitudes, and electron temperature) as the simulation has been improved in its representations of the geometry of the experiment (plasma gun and flux conserver), the magnetic bias coils, and the detailed time dependence of the current source driving the plasma gun, and uses realistic parameters. The simulations are providing a better understanding of the dominant physics in SSPX, including when the flux surfaces close and the mechanisms limiting the efficiency of electrostatic drive
Simulation of Spheromak Evolution and Energy Confinement
International Nuclear Information System (INIS)
Cohen, B.; Hooper, E.; Cohen, R.; Hill, D.; McLean, H.; Wood, R.; Woodruff, S.
2004-01-01
Simulation results are presented that illustrate the formation and decay of a spheromak plasma driven by a coaxial electrostatic plasma gun, and that model the energy confinement of the plasma. The physics of magnetic reconnection during spheromak formation is also illuminated. The simulations are performed with the three-dimensional, time-dependent, resistive magnetohydrodynamic NIMROD code. The dimensional, simulation results are compared to data from the SSPX spheromak experiment at the Lawrence Livermore National Laboratory. The simulation results are tracking the experiment with increasing fidelity (e.g., improved agreement with measurements of the magnetic field, fluctuation amplitudes, and electron temperature) as the simulation has been improved in its representations of the geometry of the experiment (plasma gun and flux conserver), the magnetic bias coils, and the detailed time dependence of the current source driving the plasma gun, and uses realistic parameters. The simulations are providing a better understanding of the dominant physics in SSPX, including when the flux surfaces close and the mechanisms limiting the efficiency of electrostatic drive
On the jets, kinks, and spheromaks formed by a planar magnetized coaxial gun
International Nuclear Information System (INIS)
Hsu, S.C.; Bellan, P.M.
2005-01-01
Measurements of the various plasma configurations produced by a planar magnetized coaxial gun provide insight into the magnetic topology evolution resulting from magnetic helicity injection. Important features of the experiments are a very simple coaxial gun design so that all observed geometrical complexity is due to the intrinsic physical dynamics rather than the source shape and use of a fast multiple-frame digital camera which provides direct imaging of topologically complex shapes and dynamics. Three key experimental findings were obtained: (1) formation of an axial collimated jet [Hsu and Bellan, Mon. Not. R. Astron. Soc. 334, 257 (2002)] that is consistent with a magnetohydrodynamic description of astrophysical jets (2) identification of the kink instability when this jet satisfies the Kruskal-Shafranov limit, and (3) the nonlinear properties of the kink instability providing a conversion of toroidal to poloidal flux as required for spheromak formation by a coaxial magnetized source [Hsu and Bellan, Phys. Rev. Lett. 90, 215002 (2003)]. An interpretation is proposed for how the n=1 central column instability provides flux amplification during spheromak formation and sustainment, and it is shown that jet collimation can occur within one rotation of the background poloidal field
Compact toroids with Alfvenic flows
International Nuclear Information System (INIS)
Wang Zhehui; Tang, X.Z.
2004-01-01
The Chandrasekhar equilibria form a class of stationary ideal magnetohydrodynamics equilibria stabilized by magnetic-field-aligned Alfvenic flows. Analytic solutions of the Chandrasekhar equilibria are explicitly constructed for both field-reversed configurations and spheromaks. Favorable confinement property of nested closed flux surfaces and the ideal magnetohydrodynamic stability of the compact toroids are of interest for both magnetic trapping of high energy electrons in astrophysics and confinement of high temperature plasmas in laboratory
Spherical tokamak without external toroidal fields
International Nuclear Information System (INIS)
Kaw, P.K.; Avinash, K.; Srinivasan, R.
2001-01-01
A spherical tokamak design without external toroidal field coils is proposed. The tokamak is surrounded by a spheromak shell carrying requisite force free currents to produce the toroidal field in the core. Such equilibria are constructed and it is indicated that these equilibria are likely to have robust ideal and resistive stability. The advantage of this scheme in terms of a reduced ohmic dissipation is pointed out. (author)
Magnetic flux conversion and relaxation toward a minimum-energy state in S-1 spheromak plasmas
International Nuclear Information System (INIS)
Janos, A.
1985-09-01
S-1 Spheromak currents and magnetic fluxes have been measured with Rogowski coils and flux loops external to the plasma. Toroidal plasma currents up to 350 kA and spheromak configuration lifetimes over 1.0 msec have been achieved at moderate power levels. The plasma formation in the S-1 Spheromak device is based on an inductive transfer of poloidal and toroidal magnetic flux from a toroidal ''flux core'' to the plasma. Formation is programmed to guide the configuration into a force-free, minimum-energy Taylor state. Properly detailed programming of the formation process is found not to be essential since plasmas adjust themselves during formation to a final equilibrium near the Taylor state. After formation, if the plasma evolves away from the stable state, then distinct relaxation oscillation events occur which restore the configuration to that stable state. The relaxation process involves reconnection of magnetic field lines, and conversion of poloidal to toroidal magnetic flux (and vice versa) has been observed and documented. The scaling of toroidal plasma current and toroidal magnetic flux in the plasma with externally applied currents is consistent with the establishment of a Taylor state after formation. In addition, the magnetic helicity is proportional to that injected from the flux core, independent of how that helicity is generated
Transport and fluctuations in high temperature spheromak plasmas
International Nuclear Information System (INIS)
McLean, H.S.; Wood, R.D.; Cohen, B.I.; Hooper, E.B.; Hill, D.N.; Moller, J.M.; Romero-Talamas, C.; Woodruff, S.
2006-01-01
Higher electron temperature (T e >350 eV) and reduced electron thermal diffusivity (χ e 2 /s) is achieved in the Sustained Spheromak Physics Experiment (SSPX) by increasing the discharge current=I gun and gun bias flux=ψ gun in a prescribed manner. The internal current and q=safety factor profile derived from equilibrium reconstruction as well as the measured magnetic fluctuation amplitude can be controlled by programming the ratio λ gun =μ 0 I gun /ψ gun . Varying λ gun above and below the minimum energy eigenvalue=λ FC of the flux conserver (∇xB-vector=λ FC B-vector) varies the q profile and produces the m/n=poloidal/toroidal magnetic fluctuation mode spectrum expected from mode-rational surfaces with q=m/n. The highest T e is measured when the gun is driven with λ gun slightly less than λ FC , producing low fluctuation amplitudes ( e as T e increases, differing from Bohm or open field line transport models where χ e increases with T e . Detailed resistive magnetohydrodynamic simulations with the NIMROD code support the analysis of energy confinement in terms of the causal link with the q profile, magnetic fluctuations associated with low-order mode-rational surfaces, and the quality of magnetic surfaces
Reduction of toroidal magnetic field ripple in the advanced material tokamak experiment on JFT-2M
International Nuclear Information System (INIS)
Sato, M.; Miura, Y.; Kimura, H.; Yamamoto, M.; Koike, T.; Nakayama, T.; Hasegawa, M.; Urata, K.
1998-01-01
In order to reduce fast ion losses due to the toroidal field ripple, the reduction of ripple amplitude (δ) by inserting ferritic steel is studied, taking its toroidal mode number into account. The guideline of the design for reduction is wider and thicker ferritic board (FB) is located at further position from VV. The δ depends on the toroidal magnetic field. The value of B r21 /B t in the case of displacement of few cm is about 1 x 10 -5 which is one order smaller than the critical value. The offsetting of FB is not a problem for locked mode. Preliminary experiments with insertion of one or two FB's indicate no adverse effect on global plasma parameters. (author)
Reduction of toroidal magnetic field ripple in the advanced material tokamak experiment on JFT-2M
Energy Technology Data Exchange (ETDEWEB)
Sato, M.; Miura, Y.; Kimura, H.; Yamamoto, M.; Koike, T. [Japan Atomic Energy Research Inst. (Japan); Nakayama, T. [Hitachi Ltd. (Japan); Hasegawa, M. [Mitsubishi Electric Corp. (Japan); Urata, K. [Mitsubishi Heavy Industries Ltd. (Japan)
1998-07-01
In order to reduce fast ion losses due to the toroidal field ripple, the reduction of ripple amplitude ({delta}) by inserting ferritic steel is studied, taking its toroidal mode number into account. The guideline of the design for reduction is wider and thicker ferritic board (FB) is located at further position from VV. The {delta} depends on the toroidal magnetic field. The value of B{sub r21} /B{sub t} in the case of displacement of few cm is about 1 x 10{sup -5} which is one order smaller than the critical value. The offsetting of FB is not a problem for locked mode. Preliminary experiments with insertion of one or two FB's indicate no adverse effect on global plasma parameters. (author)
Formation of a field-reversed configuration by coalescence of spheromaks
International Nuclear Information System (INIS)
Dasgupta, B.; Sato, Tetsuya; Hayashi, Takaya; Watanabe, Kunihiko; Watanabe, Tomohiko
1995-01-01
We present a numerical simulation of the slow formation of FRC by the merging of two spheromaks with opposite toroidal fluxes. A rather important feature of such a method of formation of FRC should be made explicit. A spheromak is basically a Taylor minimum energy state. On the other hand the FRC with its single component poloidal magnetic field and high plasma beta is decidedly far away from a Taylor state. So a numerical simulation of this process, besides demonstrating the feasibility of such FRC formation, is expected to show the traits in the process of transition from a Taylor state to a non-Taylor state. 5 refs., 2 figs., 1 tab
Heat loss by helicity injection in spheromaks
International Nuclear Information System (INIS)
Fowler, T.K.
1994-01-01
A model is presented for spheromak buildup and decay including thermal diffusivity associated with magnetic turbulence during helicity injection. It is shown that heat loss by magnetic turbulence scales more favorably than gyroBohm transport. Thus gyroBohm scaling for the proposed ignition experiment would be the conservative choice, though present experiments may be dominated by magnetic turbulence. Because of a change in boundary conditions when the gun is turned off, the model may account for the observed increase in electron temperature in CTX after turnoff
About the Toroidal Magnetic Field of a Tokamak Burning Plasma Experiment with Superconducting Coils
International Nuclear Information System (INIS)
Mazzucato, E.
2002-01-01
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
International Nuclear Information System (INIS)
Siemon, R.E.
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
Ohmically heated toroidal experiment (OHTE) mobile ignition test reactor facility concept study
International Nuclear Information System (INIS)
Masson, L.S.; Watts, K.D.; Piscitella, R.R.; Sekot, J.P.; Drexler, R.L.
1983-02-01
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
International Nuclear Information System (INIS)
Mazzucato, E.
2000-01-01
The next step in the demonstration of the scientific feasibility of a tokamak fusion reactor is a DT burning plasma experiment for the study and control of self-heated plasmas. In this paper, the authors examine the role of the toroidal magnetic field on the confinement of a tokamak plasma in the ELMy H-mode regime--the operational regime foreseen for ITER
A new diagnostic for spheromaks
International Nuclear Information System (INIS)
Boyd, D.A.
1986-01-01
Electron cyclotron emission from a spheromak plasma may be able to provide information about the confining magnetic field of the system. Emission generated in the extraordinary mode wit hits electric vector perpendicular to the local magnetic field at sufficiently high frequency will propagate out of the plasma while retaining the original orientation if its electric vector. Thus, a measurement of the orientation of the emergent electric vector and the emission frequency will allow one to deduce the orientation and strength of the magnetic field at the radiation source. In this paper, simple models of the Maryland spheromak are used to examine the practicality of such a diagnostic
All plasma spheromak: the plasmak
International Nuclear Information System (INIS)
Koloc, P.; Ogden, J.
1981-01-01
There has been an evolutionary pattern established in magnetic fusion concepts. The flow in ideas follows three directions. By extrapolating this evolutionary movement, we have anticipated the concept called Spheromak and have predicted the omega of this evolution which is called PLASMAK, or Plasma Spheromak. The evolutionary directions are from open systems to closed systems, from zero or low dimensional compression schemes to three dimensional compression, and finally from plasma configurations without any self confining currents to a plasma configuration which is completely self confined except for the mechanical pressure necessary to maintain the verticle field and hoop stress. Nevertheless, the plasma is imprisoned by heavy poloidal coils and a vacuum wall
International Nuclear Information System (INIS)
Barnes, C.W.; Jarboe, T.R.; Marklin, G.J.; Knox, S.O.; Henins, I.
1989-01-01
Electrostatic (dc) helicity injection has previously been shown to successfully sustain the magnetic fields of spheromaks and tokamaks. The magnitude of the injected magnetic helicity balances (within experimental error) the flux lost be resistive decay of the toroidal equilibrium. The problem of optimizing this current drive scheme hence involves maximizing the injected helicity (the voltage-connecting-flux product) while minimizing the current (which multiplied by the voltage represents the energy input and also possible damage to the electrodes). The impedance (voltage-to-current ratio) and energy efficiency of a dc helicity injection experiment are studied on the CTX spheromak. Over several years changes were made in the physical geometry of the coaxial magnetized plasmas source as well as changes in the external electrical circuit. The source could be operated over a wide range of external charging voltage (and hence current), applied axial flux, and source gas flow rate. A database of resulting voltage, helicity injection, efficiency, electron density, and rotation has been created. These experimental results are compared to an ideal magnetohydrodynamic theory of magnetic flux flow. The theory is parameterized by the dimensionless Hall parameter, the ratio of electric to mass current. For a constant Hall parameter the theory explains why the voltage depends quadratically on the current at constant flux. The theory also explains the approximately linear dependence of the impedance-to-current ratio on the current-to-flux ratio of the source. 9 refs., 6 figs
Plasma confinement of Nagoya high-beta toroidal-pinch experiments
International Nuclear Information System (INIS)
Hirano, K.; Kitagawa, S.; Wakatani, M.; Kita, Y.; Yamada, S.; Yamaguchi, S.; Sato, K.; Aizawa, T.; Osanai, Y.; Noda, N.
1977-01-01
Two different types of high-β toroidal pinch experiments, STP [1] and CCT [2,3], have been done to study the confinement of the plasma produced by a theta-pinch. The STP is an axisymmetric toroidal pinch of high-β tokamak type, while the CCT consists of multiply connected periodic toroidal traps. Internal current-carrying copper rings are essential to the CCT. Since both apparatuses use the same fast capacitor bank system, they produce rather similar plasma temperatures and densities. The observed laser scattering temperature and density is about 50 eV and 4x10 15 cm -3 , respectively, when the filling pressure is 5 mtorr. In the STP experiment, strong correlations are found between the βsub(p) value and the amplitude of m=2 mode. It has a minimum around the value of βsub(p) of 0.8. The disruptive instability is observed to expand the pinched plasma column without lowering the plasma temperature. Just before the disruption begins, the q value around the magnetic axis becomes far less than 1 and an increase of the amplitude of m=2 mode is seen. The CCT also shows rapid plasma expansion just before the magnetic field reaches its maximum. Then the trap is filled up with the plasma by this irreversible expansion and stable plasma confinement is achieved. The energy confinement time of the CCT is found to be about 35 μs. (author)
Two novel compact toroidal concepts with Stellarator features
International Nuclear Information System (INIS)
Moroz, P.E.
1997-07-01
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
International Nuclear Information System (INIS)
Woodruff, S.; Hill, D.N.; Stallard, B.W.; Bulmer, R.; Cohen, B.; Holcomb, C.T.; Hooper, E.B.; McLean, H.S.; Moller, J.; Wood, R.D.
2003-01-01
By operating a magnetized coaxial plasma gun continuously with just sufficient current to enable plasma ejection, large gun-voltage spikes (∼1 kV) are produced, giving the highest sustained voltage ∼500 V and highest sustained helicity injection rate observed in the Sustained Spheromak Physics Experiment. The spheromak magnetic field increases monotonically with time, exhibiting the lowest fluctuation levels observed during formation of any spheromak (B-tilde)/B≥2%). The results suggest an important mechanism for field generation by helicity injection, namely, the merging of helicity-carrying filaments
Woodruff, S; Hill, D N; Stallard, B W; Bulmer, R; Cohen, B; Holcomb, C T; Hooper, E B; McLean, H S; Moller, J; Wood, R D
2003-03-07
By operating a magnetized coaxial plasma gun continuously with just sufficient current to enable plasma ejection, large gun-voltage spikes (approximately 1 kV) are produced, giving the highest sustained voltage approximately 500 V and highest sustained helicity injection rate observed in the Sustained Spheromak Physics Experiment. The spheromak magnetic field increases monotonically with time, exhibiting the lowest fluctuation levels observed during formation of any spheromak (B/B>/=2%). The results suggest an important mechanism for field generation by helicity injection, namely, the merging of helicity-carrying filaments.
International Nuclear Information System (INIS)
Noterdaeme, J.M.
1983-05-01
Applying the constraints to the design of a helical axis stellarator we find a limit on the combination of toroidal field, current density and major radius. Another major constraint for this concept is the ability to obtain the plasma physics parameters dictated by similarity considerations. This depends on the heating method used. A minimum scale experiment with 2 periods and no linkage of the toroidal and poloidal coils, would have a major radius of 1.2m, a toroidal field of 3.5T and 2MW of ECRH power (for β = 1% nu 2 = 10)
Hybrid simulation of toroidal Alfvén eigenmode on the National Spherical Torus Experiment
Energy Technology Data Exchange (ETDEWEB)
Liu, D., E-mail: deyongl@uci.edu [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Fu, G. Y.; Podestà, M.; Breslau, J. A.; Fredrickson, E. D. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Crocker, N. A.; Kubota, S. [Department of Physics and Astronomy, University of California, Los Angles, California 90095 (United States)
2015-04-15
Energetic particle modes and Alfvén eigenmodes driven by super-Alfvénic fast ions are routinely observed in neutral beam heated plasmas on the National Spherical Torus eXperiment (NSTX). These modes can significantly impact fast ion transport and thus cause fast ion redistribution or loss. Self-consistent linear simulations of Toroidal Alfvén Eigenmodes (TAEs) in NSTX plasmas have been carried out with the kinetic/magnetohydrodynamic hybrid code M3D-K using experimental plasma parameters and profiles including plasma toroidal rotation. The simulations show that unstable TAEs with n=3,4, or 5 can be excited by the fast ions from neutral beam injection. The simulated mode frequency, mode radial structure, and phase shift are consistent with measurements from a multi-channel microwave reflectometer diagnostic. A sensitivity study on plasma toroidal rotation, safety factor q profile, and initial fast ion distribution is performed. The simulations show that rotation can have a significant destabilizing effect when the rotation is comparable or larger than the experimental level. The mode growth rate is sensitive to q profile and fast ion distribution. Although mode structure and peak position depend somewhat on q profile and plasma rotation, the variation of synthetic reflectometer response is within experimental uncertainty and it is not sensitive enough to see the difference clearly.
Experimental studies of equilibrium in the toroidal Extrap T1 experiment
International Nuclear Information System (INIS)
Drake, J.R.; Hedin, E.R.; Karlsson, P.; Jin Li; Saetherblom, H.E.
1989-03-01
Experimental studies of a toroidal, high-beta plasma discharge with a non-circular cross-section are described. In Extrap T1, four toroidal, current-carrying rings outside the plasma discharge current channel produce a separatrix which bounds the plasma. Plasma currents of up to 40 kA are induced, operating with a toroidal field of up to 0.2 T. The major radius of the device is 0.45 m and the average minor radius of the current channel is about 40 mm. The discharge pulse is approximately 100 μsec long. For the discharges reported here, the peak current density on the discharge axis is about 9 MA/m 2 , which corresponds to an on-axis safety factor q o of about 0.1. The plasma density is in the range n ≅ 0.2 to 1 x 10 21 m -3 , and the electron temperature is in the range T e ≅ 10 to 30 eV. Magnetic flux plots of the experiment have been studied using magnetic probes and current and pressure profiles have been derived from the magnetic data
Summary of US-Japan Exchange 2004 New Directions and Physics for Compact Toroids
Energy Technology Data Exchange (ETDEWEB)
Intrator, T; Nagata, M; Hoffman, A; Guo, H; Steinhauer, L; Ryutov, D; Miller, R; Okada, S
2005-08-15
This exchange workshop was an open meeting coordinated by the P-24 Plasma Physics Group at Los Alamos National Laboratory. We brought together scientists from institutions in the US and Japan who are researching the various and complementary types of Compact Toroids (CT). Many concepts, including both experimental and theoretical investigations, are represented. The range spans Field Reversed Configuration (FRC), spheromak, Reversed Field Pinch (RFP), spherical tokamaks, linear devices dedicated to fundamental physics studies, and hybrid transitions that bridge multiple configurations. The participants represent facilities on which significant experiments are now underway: FRC Injection experiment (FIX), Translation Confinement experiment (TCS), Nihon-University Compact Torus Experiment (NUCTE), HITSI (Helicity Injection experiment, Steady Inductive Helicity Injection (HIT-SIHI)), Field Reversed Configuration experiment-Liner (FRX-L), TS-3/4, Sustained Spheromak Experiment (SSPX), Relaxation Scaling Experiment (RSX), HIST, Caltech Spheromak, or in the design process such as MRX-FRC (PPPL), Pulsed High Density experiment (PHD at UW). Several new directions and results in compact toroid (CT) research have recently emerged, including neutral-beam injection, rotating magnetic fields, flux build up from Ohmic boost coils, electrostatic helicity injection techniques, CT injection into other large devices, and high density configurations for applications to magnetized target fusion and translational compression of CT's. CT experimental programs in both the US and Japan have also shown substantial progress in the control and sustainment of CT's. Both in theory and experiment, there is increased emphasis on 3D dynamics, which is also related to astrophysical and space physics issues. 3D data visualization is now frequently used for experimental data display. There was much discussion of the effects of weak toroidal fields in FRC's and possible implications
A gas puff experiment for partial simulation of compact toroid formation on MARAUDER
International Nuclear Information System (INIS)
Englert, S.E.; Englert, T.J.; Degnan, J.H.; Gahl, J.M.
1994-01-01
Preliminary results will be reported of a single valve gas puff experiment to determine spatial and spectral distribution of a gas during the early ionization stages. This experiment has been developed as a diagnostic test-bed for partial simulation of compact toroid formation on MARAUDER. The manner in which the experimental hardware has been designed allows for a wide range of diagnostic access to evaluate early time evolution of the ionization process. This evaluation will help contribute to a clearer understanding of the initial conditions for the formation stage of the compact toroid in the MARAUDER experiment, where 60 of the same puff valves are used. For the experiment, a small slice of the MARAUDER cylindrical gas injection and expansion region geometry have been re-created but in cartesian coordinates. All of the conditions in the experiment adhere as closely as possible to the MARAUDER experiment. The timing, current rise time, capacitance, resistance and inductance are appropriate to both the simulation of one of the 60 puff valves and current delivery to the load. Both time-resolved images and spectral data have been gathered for visible light emission of the plasma. Processed images reveal characteristics of spatial distribution of the current. Spectral data provide information with respect to electron temperature and density, and entrainment of contaminants
Axisymmetric force-free states and relaxation of a spheroidal spheromak
International Nuclear Information System (INIS)
Throumoulopoulos, G.N.; Pantis, G.
1990-01-01
Axisymmetric force-free equilibrium eigenstates for a prolate as well as an oblate spheroidal Spheromak with arbitrary elongation are obtained. In the framework of the Woltjer-Taylor relaxation theory the relaxed states are also identified. A simple hypothesis for the relaxation process is introduced, which implies that the plasma relaxes from multitoroidal formations to a singly toroidal configuration, in qualitative agreement with experimental results. (author)
Axisymmetric force-free states and relaxation of a spheroidal spheromak
International Nuclear Information System (INIS)
Throumoulopoulos, G.N.; Pantis, G.
1990-01-01
Axisymmetric force-free equilibrium eigenstates for a prolate as well as an oblate spheroidal spheromak with arbitrary elongation are obtained. In the framework of the Woltjer-Taylor relaxation theory the relaxed states are also identified. A simple hypothesis for the relaxation process is introduced which implies that the plasma relaxes from multitoroidal formations to a singly toroidal configuration in qualitative agreement with experimental results. (Author)
CT-TRX1, a triggered-reconnection compact toroid experiment
International Nuclear Information System (INIS)
Hoffman, A.L.
1980-05-01
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
Pressure effect on equilibrium configuration of CTCC-2 spheromak
International Nuclear Information System (INIS)
Nishikawa, M.; Kato, Y.; Satomi, N.; Watanabe, K.
1990-01-01
In CTCC-2 experiment, the initial plasma is produced by a magnetized gun and ejected into a metallic aluminum flux conserver (FC) with thickness of 15 mm. The spheromak is formed in the FC during a life time of 1.5 ms, in which the plasma is isolated from any external feeder. A choking-field-generating coil is equipped on the entrance of the spheroidal FC. The choking field is suppressing some leakage of spheromak field along the entrance duct, which is made of thin stainless steel plate (0.8 mm) for rapid penetration of the choking magnetic field. This resistive part acts as an effective plasma current limiter, which produces stable currentless region (flux hole). The flux hole increases magnetic shear without inserting a central conducting pole along the symmetric axis and is controlled to decrease with the choking field strength. Thus, in CTCC-2 spheromak, a stable oblate spheroidal boundary is rigidly fixed by the metal wall of FC and the entrance hole of FC is effectively closed by choking magnetic field, so that it is suitable to investigate precisely a fine structure of configuration. In spheromak configuration whose aspect ratio is near one, the ratio of the magnetic strength at the inner part to that at the outer part on equi-flux surface (mirror ratio) becomes very large in comparison with that of a large aspect ratio. This extreme configuration with a high mirror ratio may be associated with an anisotropic pressure effect even in collisional state like as our experimental condition. They have investigated the pressure effect on spheromak configuration in more detail. The obtained equilibrium profile is grossly explained by a theoretical profile on assuming low beta limit until now. However, the authors observe a systematic discrepancy between a measured poloidal profile and a theoretical one as mentioned
Toroidal magnetic field system for a 2-MA reversed-field pinch experiment
International Nuclear Information System (INIS)
Melton, J.G.; Linton, T.W.
1983-01-01
The engineering design of the toroidal magnetic field (TF) system for a 2-MA Reversed-Field Pinch experiment (ZT-H) is described. ZT-H is designed with major radius 2.15 meters, minor radius 0.40 meters, and a peak toroidal magnetic field of 0.85 Tesla. The requirement for highly uniform fields, with spatial ripple <0.2% leads to a design with 72 equally spaced circular TF coils, located at minor radius 0.6 meters, carrying a maximum current of 9.0 MA. The coils are driven by a 12-MJ capacitor bank which is allowed to ring in order to aid the reversal of magnetic field. A stress analysis is presented, based upon calculated hoop tension, centering force, and overturning moment, treating these as a combination of static loads and considering that the periodic nature of the loading causes little amplification. The load transfer of forces and moments is considered as a stress distribution resisted by the coils, support structures, wedges, and the structural shell
Reusch, Joshua
2017-10-01
A major goal of the spherical tokamak research program is accessing a state of low internal inductance li, high elongation κ, high toroidal and normalized beta (βt and βN) , and low collisionality without solenoidal current drive. A new local helicity injection (LHI) system in the lower divertor region of the ultra-low aspect ratio Pegasus ST provides non-solenoidally driven plasmas that exhibit most of these characteristics. LHI utilizes compact, edge-localized current sources (Ainj 4 cm2, Iinj 8 kA, Vinj 1.5 kV) for plasma startup and sustainment, and can sustain more than 200 kA of plasma current. Plasma growth via LHI is enhanced by a transition from a regime of high kink-like MHD activity to one of reduced MHD activity at higher frequencies and presumably shorter wavelengths. The strong edge current drive provided by LHI results in a hollow current density profile with low li. The low aspect ratio (R0 / a 1.2) of Pegasus allows ready access to high κ and MHD stable operation at very high normalized plasma currents (IN =Ip /aBT> 15). Thomson scattering measurements indicate Te 100 eV and ne 1 ×19 m-3. The impurity Ti evolution is correlated in time with high frequency magnetic fluctuations, implying substantial reconnection ion heating is driven by the applied helicity injection. Doppler spectroscopy indicates Ti >=Te and that the anomalous ion heating scales consistently with two fluid reconnection theory. Taken together, these features provide access to very high βt plasmas. Equilibrium analyses indicate βt up to 100% and βN 6.5 is achieved. At increasingly low BT, the discharge disrupts at the no-wall ideal stability limit. In these high βt discharges, a minimum |B| well forms over 50% of the plasma volume. This unique magnetic configuration may be of interest for testing predictions of stabilizing drift wave turbulence and/or improving energetic particle confinement. This work supported by US DOE Grants DE-FG02-96ER54375 and DE-SC0006928.
Simulation study of stepwise relaxation in a spheromak plasma
International Nuclear Information System (INIS)
Horiuchi, Ritoku; Uchida, Masaya; Sato, Tetsuya.
1991-10-01
The energy relaxation process of a spheromak plasma in a flux conserver is investigated by means of a three-dimensional magnetohydrodynamic simulation. The resistive decay of an initial force-free profile brings the spheromak plasma to an m = 1/n = 2 ideal kink unstable region. It is found that the energy relaxation takes place in two steps; namely, the relaxation consists of two physically distinguished phases, and there exists an intermediate phase in between, during which the relaxation becomes inactive temporarily. The first relaxation corresponds to the transition from an axially symmetric force-free state to a helically symmetric one with an n = 2 crescent magnetic island structure via the helical kink instability. The n = 2 helical structure is nonlinearly sustained in the intermediate phase. The helical twisting of the flux tube creates a reconnection current in the vicinity of the geometrical axis. The second relaxation is triggered by the rapid growth of the n = 1 mode when the reconnection current exceeds a critical value. The helical twisting relaxes through magnetic reconnection toward an axially symmetric force-free state. It is also found that the poloidal flux reduces during the helical twisting in the first relaxation and the generation of the toroidal flux occurs through the magnetic reconnection process in the second relaxation. (author)
Configuration of gun-generated spheromak in effectively closed metal flux conserver
International Nuclear Information System (INIS)
Kato, Yushi; Nishikawa, Masahiro; Honda, Yoshihide; Satomi, Norio; Watanabe, Kenji
1988-01-01
In the CTCC-II spheromak experiment, the gun-generated plasma is confined in a spheroidal aluminum flux conserver (FC) with a choking coil. This coil produces the additional magnetic field to close perfectly all magnetic surfaces into the FC, i.e. the entrance hole for plasma injection is enable to be closed by magnetic field. Hence the plasma is confined in the effectively closed metal FC. In this experiment the average life time is 1.2 msec, and electron density and temperature are n e = 2 x 10 13 /cc, T e = 30 eV, respectively. The configuration with a flux hole region in which the toroidal magnetic field vanishes around the geometrical axis has been observed in the FC. The radius of the flux hole depends on the condition how the external choking field is applied. The flux hole enhances the magnetic shear near the plasma surfaces and, therefore, has a stabilizing effect even without inserting the central conducting pole. (author)
Full-wave modeling of the O-X mode conversion in the Pegasus toroidal experiment
Energy Technology Data Exchange (ETDEWEB)
Koehn, A. [Institut fuer Plasmaforschung, Universitaet Stuttgart, D-70569 (Germany); Jacquot, J. [IRFM, CEA, F-13108 Saint-Paul-lez-Durance (France); Bongard, M. W.; Hinson, E. T.; Volpe, F. A. [Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Gallian, S. [Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)
2011-08-15
The ordinary-extraordinary (O-X) mode conversion is modeled with the aid of a 2D full-wave code in the Pegasus toroidal experiment as a function of the launch angles. It is shown how the shape of the plasma density profile in front of the antenna can significantly influence the mode conversion efficiency and, thus, the generation of electron Bernstein waves (EBWs). It is therefore desirable to control the density profile in front of the antenna for successful operation of an EBW heating and current drive system. On the other hand, the conversion efficiency is shown to be resilient to vertical displacements of the plasma as large as {+-}10 cm.
International Nuclear Information System (INIS)
Akcay, Cihan; Victor, Brian S.; Jarboe, Thomas R.; Kim, Charlson C.
2013-01-01
We present a comparison study of 3-D pressureless resistive MHD (rMHD) and 3-D presureless two-fluid MHD models of the Helicity Injected Torus with Steady Inductive helicity injection (HIT-SI). HIT-SI is a current drive experiment that uses two geometrically asymmetric helicity injectors to generate and sustain toroidal plasmas. The comparable size of the collisionless ion skin depth d i to the resistive skin depth predicates the importance of the Hall term for HIT-SI. The simulations are run with NIMROD, an initial-value, 3-D extended MHD code. The modeled plasma density and temperature are assumed uniform and constant. The helicity injectors are modeled as oscillating normal magnetic and parallel electric field boundary conditions. The simulations use parameters that closely match those of the experiment. The simulation output is compared to the formation time, plasma current, and internal and surface magnetic fields. Results of the study indicate 2fl-MHD shows quantitative agreement with the experiment while rMHD only captures the qualitative features. The validity of each model is assessed based on how accurately it reproduces the global quantities as well as the temporal and spatial dependence of the measured magnetic fields. 2fl-MHD produces the current amplification (I tor /I inj ) and formation time τ f demonstrated by HIT-SI with similar internal magnetic fields. rMHD underestimates (I tor /I inj ) and exhibits much a longer τ f . Biorthogonal decomposition (BD), a powerful mathematical tool for reducing large data sets, is employed to quantify how well the simulations reproduce the measured surface magnetic fields without resorting to a probe-by-probe comparison. BD shows that 2fl-MHD captures the dominant surface magnetic structures and the temporal behavior of these features better than rMHD
Particle diffusion in a spheromak
International Nuclear Information System (INIS)
Meyerhofer, D.D.; Levinton, F.M.; Yamada, M.
1988-01-01
The local carbon particle diffusion coefficient was measured in the Proto S-1/C spheromak using a test particle injection scheme. When the plasma was not in a force-free Taylor state, and when there were pressure gradients in the plasma, the particle diffusion was five times that predicted by Bohm and was consistent with collisional drift wave diffusion. The diffusion appears to be driven by correlations of the fluctuating electric field and density. During the decay phase of the discharge when the plasma was in the Taylor state, the diffusion coefficient of the carbon was classical. 23 refs., 4 figs
Magnetohydrodynamic stability of spheromak plasma in spheroidal flux conserver
International Nuclear Information System (INIS)
Kaneko, Shobu; Kamitani, Atsushi.
1985-11-01
The MHD equilibrium configurations of spheromak plasmas in a spheroidal flux conserver are determined by use of a pressure distribution whose derivative dp/dψ vanishes on the magnetic axis, and by use of an optimized distribution. Here p is the pressure and ψ is the flux function. These equilibria are shown to be stable for symmetric modes. The stability for localized modes is investigated by the Mercier criterion. The values of the maximum beta ratio β max are evaluated for both pressure distributions and are shown to become about two times larger by optimization. If the condition, q axis max are found to be less than 30 %. The oblate spheroidal flux conserver is shown to be better than the toroidal conserver with a rectangular cross section from the standpoint of stability. (author)
International Nuclear Information System (INIS)
Ikeda, Nagayasu; Tamaru, Ken; Nagata, Akiyoshi.
1979-01-01
Formation of toroidal pre-heat plasma was studied. The pre-heat plasma without residual magnetic field was made by chopping the current for pre-heat, A small toroidal-pinch system was used for the experiment. The magnetic field was measured with a magnetic probe. One turn loop was used for the measurement of the toroidal one-turn electric field. A pair of Rogoski coil was used for the measurement of plasma current. The dependence of residual magnetic field on chopping time was measured. By fast chopping of the primary current in the pre-heating circuit, the poloidal magnetic field was reduced to several percent within 5 microsecond. After chopping, no instability was observed in the principal discharge plasma produced within several microsecond. As the conclusion, it can be said that the control of residual field can be made by current chopping. (Kato, T.)
Development of the STPX Spheromak System
Williams, R. L.; Clark, J.; Weatherford, C. A.
2015-11-01
The progress made in starting up the STPX Spheromak system, which is now installed at the Florida A&M University, is reviewed. Experimental, computational and theoretical activities are underway. The control system for firing the magnetized coaxial plasma gun and for collecting data from the diagnostic probes, based on LabView, is being tested and adapted. Preliminary results of testing the installed magnetic field probes, Langmuir triple probes, cylindrical ion probes, and optical diagnostics will be discussed. Progress in modeling this spheromak using simulation codes, such as NIMROD, will be discussed. Progress in investigating the use of algebraic topology to describe this spheromak will be reported.
Structure of Maryland Spheromak plasmas
International Nuclear Information System (INIS)
Hess, R.; Chinfatt, C.; Cote, C.; DeSilva, A.; Filuk, A.; Goldenbaum, G.; Gauvreau, J.; Hwang, Fukwun
1990-01-01
Recent efforts on the Maryland Spheromak (MS) have concentrated on detailed measurement of magnetic field structures in order to better understand the formation and evolution of the spheromak configuration. These efforts were prompted by results showing a very rapid decay of the magnetic field under certain conditions. It was not known if this loss was a rapid movement of the plasma to the walls of the vacuum vessel, or by some mechanism causing a rapid decay of a more or less stationary field. To investigate the magnetic field structure in more detail, an array of magnetic probes was built that could be moved from shot to shot so as to acquire a complete map of the three magnetic field components in a plane containing the symmetry axis of the machine. Data taken with these probes in a case where the rapid loss of field occurs is given. Further analysis of the data shows that the instability that forms is a combination of tilt and shift. The initial asymmetry of the magnetic field is possibly due to the non-symmetric configuration of the reversal field coils, or the non-symmetric cabling to the I z electrodes. Future work will concentrate on eliminating the initial plasma asymmetry by eliminating any asymmetries in the machine, and on stopping the tilt/shift instability by different configurations for the passive stabilization coils
The Tore Supra toroidal pump limiter: experience feedback of HHF elements series manufacture
Energy Technology Data Exchange (ETDEWEB)
Cordier, J.J.; Bayetti, P.; Chappuis, P.; Durocher, A.; Escourbiac, F.; Grosman, A.; Lipa, M.; Mitteau, R.; Schlosser, J.; Van Houtte, D
2003-07-01
Since 1992, reliable High Heat Flux PFCs based on copper alloy heat sink structures and a CFC armour, have been developed. The final result is an actively cooled high heat flux element that is capable of removing up to 10 MW.m{sup -2} in stationary operating conditions. About 600 of these high performance individual components have then been manufactured and assembled in order to equip a Toroidal Pump Limiter (TPL). The final deliveries was successfully achieved end of 2001. The paper deals with the experience feedback built-up along the four years duration of the TPL components manufacture. We will show where issues were encountered, how solutions were found to achieve the fabrication of components and will highlight what are the main technical lessons to be learned: acceptance criteria, choice of materials, margins of processes. Finally a proposal of an alternative optimised design is presented, fruit of the experience gained from this up to now, unique series manufacture of actively cooled plasma facing HHF components. We believe that such experience will certainly be of use to ITER as well as to Wendelstein 7-X as far as PFC is concerned. (authors)
A 3-MA compact-toroid-plasma-flow-switched plasma focus demonstration experiment on Shiva Star
Energy Technology Data Exchange (ETDEWEB)
Kiuttu, G F; Degnan, J H [Phillips Lab., Kirtland AFB, NM (United States). High Energy Sources Div.; Graham, J D [Maxwell Labs., Albuquerque, NM (United States); and others
1997-12-31
A novel dense plasma focus experiment using the Shiva Star capacitor bank is described. The experiment uses a compact toroid (CT) magnetized plasma flow switch (PFS) to initiate the focus implosion. The CT armature stably and reproducibly translates up to 3 MA from the vacuum feed region through coaxial electrodes to the gas puff central load. The inertia of the 1 mg CT and the work that must be done in compressing the internal magnetic fields during the translation provide a delay in current delivery to the pinch of 5 - 10 {mu}s, which matches the bank quarter cycle time relatively well. Effectiveness of the current delivery was monitored primarily by inductive probes in the PFS region, fast photography of the focus, and x-ray and neutron measurements of the pinch. K shell x-ray yields using neon gas were as high as 1 kJ, and 10{sup 8} neutrons were produced in a deuterium gas focus. (author). 4 figs., 10 refs.
A 3-MA compact-toroid-plasma-flow-switched plasma focus demonstration experiment on Shiva Star
International Nuclear Information System (INIS)
Kiuttu, G.F.; Degnan, J.H.
1996-01-01
A novel dense plasma focus experiment using the Shiva Star capacitor bank is described. The experiment uses a compact toroid (CT) magnetized plasma flow switch (PFS) to initiate the focus implosion. The CT armature stably and reproducibly translates up to 3 MA from the vacuum feed region through coaxial electrodes to the gas puff central load. The inertia of the 1 mg CT and the work that must be done in compressing the internal magnetic fields during the translation provide a delay in current delivery to the pinch of 5 - 10 μs, which matches the bank quarter cycle time relatively well. Effectiveness of the current delivery was monitored primarily by inductive probes in the PFS region, fast photography of the focus, and x-ray and neutron measurements of the pinch. K shell x-ray yields using neon gas were as high as 1 kJ, and 10 8 neutrons were produced in a deuterium gas focus. (author). 4 figs., 10 refs
Energy Technology Data Exchange (ETDEWEB)
Romadanov, I.V.; Ryzhkov, S.V., E-mail: ryzhkov@power.bmstu.ru
2014-12-15
Highlights: • Compact torus formation method with high level of magnetic flux is proposed. • A compact torus is produced in a theta-pinch-coil with pulse mode of operation. • Key feature is a pulse of current in an axial direction. • We report a level of linked magnetic flux is higher than theta-pinch results. - Abstract: The present work reports on compact toroid hydrogen plasma creation by means of a specially designed discharge system and results of magnetic fields introduction. Experiments in the compact toroid challenge (CTC) device at P.N. Lebedev Physical Institute (FIAN) have been conducted since 2005. The CTC device differs from the conventional theta-pinch formation in the use of an axial current for enhanced efficiency. We have used a novel technique to maximize the flux linked to the plasma. The purpose of this method is to increase the energy input into the plasma and the level of trapped magnetic flux using an additional toroidal magnetic field. A study of compact torus formation with axial and toroidal currents was done and a new method is proposed and implemented.
International Nuclear Information System (INIS)
Podesta, M.; Bell, R.E.; Fredrickson, E.D.; Gorelenkov, N.N.; LeBlanc, B.P.; Crocker, N.A.; Kubota, S.; Heidbrink, W.W.; Yuh, H.
2011-01-01
The National Spherical Torus Experiment (NSTX, (Ono et al 2000 Nucl. Fusion 40 557)) routinely operates with neutral beam injection as the primary system for heating and current drive. The resulting fast ion population is super-Alfvenic, with velocities 1 fast /v Alfven < 5. This provides a strong drive for toroidicity-induced Alfven eigenmodes (TAEs). As the discharge evolves, the fast ion population builds up and TAEs exhibit increasing bursts in amplitude and down-chirps in frequency, which eventually lead to a so-called TAE avalanche. Avalanches cause large (∼<30%) fast ion losses over ∼1 ms, as inferred from the neutron rate. The increased fast ion losses correlate with a stronger activity in the TAE band. In addition, it is shown that a n = 1 mode with frequency well below the TAE gap appears in the Fourier spectrum of magnetic fluctuations as a result of non-linear mode coupling between TAEs during avalanche events. The non-linear coupling between modes, which leads to enhanced fast ion transport during avalanches, is investigated.
Overview of recent results and future plans on the Compact Toroidal Hybrid experiment
Maurer, D. A.; Archmiller, M. C.; Cianciosa, M. R.; Ennis, D. A.; Hanson, J. D.; Hartwell, G. J.; Hebert, J. D.; Herfindal, J. L.; Knowlton, S. F.; Ma, X.; Massidda, S.; Pandya, M. D.; Roberds, N. A.; Traverso, P. J.
2015-11-01
Goals of the Compact Toroidal Hybrid (CTH) experiment are to: (1) investigate the dependence of plasma disruptive behavior on the level of applied 3D magnetic shaping, (2) test and advance 3D computational modeling tools in strongly shaped plasmas, and (3) study the implementation of a new island divertor. Progress towards these goals and other developments are summarized. The disruptive density limit is observed to exceed the Greenwald limit as the vacuum transform is increased, but a threshold for disruption avoidance is not observed. Low q operation is routine, with low q disruptions avoided when the vacuum transform is raised to the value of 0.07 or above. Application of vacuum transform has been demonstrated to reduce and eliminate the vertical drift of elongated discharges that would otherwise be vertically unstable. Current efforts at improved equilibrium reconstruction and diagnostic development will beoverviewed. NIMROD is used to model the current ramp phase of CTH and 3D shaped sawtooth behavior. An island divertor design has begun with connection length studies and initial EMC3-Eirene results to model energy deposition on divertor plates located in an edge 1/3 island. This work is supported by U.S. Department of Energy Grant No. DE- FG02-00ER54610.
International Nuclear Information System (INIS)
Podesta, M.; Bell, R.E.; Crocker, N.A.; Fredrickson, E.D.; Gorelenkov, N.N.; Heidbrink, W.W.; Kubota, S.; LeBlanc, B.P.; Yu, H.
2011-01-01
The National Spherical Torus Experiment (NSTX, (M. Ono et al., Nucl. Fusion 40, 557 (2000))) routinely operates with neutral beam injection as the primary system for heating and current drive. The resulting fast ion population is super-Alfvenic, with velocities 1 fast /v Alfven < 5. This provides a strong drive for toroidicity-induced Alfven eigenmodes (TAEs). As the discharge evolves, the fast ion population builds up and TAEs exhibit increasing bursts in amplitude and down-chirps in frequency, which eventually lead to a so-called TAE avalanche. Avalanches cause large (∼<30%) fast ion losses over ∼ 1 ms, as inferred from the neutron rate. The increased fast ion losses correlate with a stronger activity in the TAE band. In addition, it is shown that a n = 1 mode with frequency well below the TAE gap appears in the Fourier spectrum of magnetic fluctuations as a result of non-linear mode coupling between TAEs during avalanche events. The non-linear coupling between modes, which leads to enhanced fast ion transport during avalanches, is investigated.
Energy Technology Data Exchange (ETDEWEB)
Podesta, M; Crocker, N A; Fredrickson, E D; Gorelenkov, N N; Heidbrink, W W; Kubota, S; LeBlanc, B P
2011-04-26
The National Spherical Torus Experiment (NSTX, [M. Ono et al., Nucl. Fusion 40, 557 (2000)]) routinely operates with neutral beam injection as the primary system for heating and current drive. The resulting fast ion population is super-Alfv enic, with velocities 1 < vfast=vAlfven < 5. This provides a strong drive for toroidicity-induced Alfv en eigenmodes (TAEs). As the discharge evolves, the fast ion population builds up and TAEs exhibit increasing bursts in amplitude and down-chirps in frequency, which eventually lead to a so-called TAE avalanche. Avalanches cause large (≤ 30%) fast ion losses over ~ 1 ms, as inferred from the neutron rate. The increased fast ion losses correlate with a stronger activity in the TAE band. In addition, it is shown that a n = 1 mode with frequency well below the TAE gap appears in the Fourier spectrum of magnetic fluctuations as a result of non-linear mode coupling between TAEs during avalanche events. The non-linear coupling between modes, which leads to enhanced fast ion transport during avalanches, is investigated.
Local Helicity Injection Systems for Non-solenoidal Startup in the PEGASUS Toroidal Experiment
Perry, J. M.; Barr, J. L.; Bongard, M. W.; Fonck, R. J.; Hinson, E. T.; Lewicki, B. T.; Redd, A. J.
2013-10-01
Local helicity injection is being developed in the PEGASUS Toroidal Experiment for non-solenoidal startup in spherical tokamaks. The effective loop voltage due to helicity injection scales with the area of the injectors, requiring the development of electron current injectors with areas much larger than the 2 cm2 plasma arc injectors used to date. Solid and gas-effused metallic electrodes were found to be unusable due to reduced injector area utilization from localized cathode spots and narrow operational regimes. An integrated array of 8 compact plasma arc sources is thus being developed for high current startup. It employs two monolithic power systems, for the plasma arc sources and the bias current extraction system. The array effectively eliminates impurity fueling from plasma-material interaction by incorporating a local scraper-limiter and conical-frustum bias electrodes to mitigate the effects of cathode spots. An energy balance model of helicity injection indicates that the resulting 20 cm2 of total injection area should provide sufficient current drive to reach 0.3 MA. At that level, helicity injection drive exceeds that from poloidal induction, which is the relevant operational regime for large-scale spherical tokamaks. Future placement of the injector array near an expanded boundary divertor region will test simultaneous optimization of helicity drive and the Taylor relaxation current limit. Work supported by US DOE Grant DE-FG02-96ER54375.
International Nuclear Information System (INIS)
Kanki, Takashi; Nagata, Masayoshi; Kagei, Yasuhiro
2010-01-01
Kink instability and the subsequent plasma flow during the sustainment of a coaxial gun spheromak are investigated by three-dimensional nonlinear magnetohydrodynamic simulations. Analysis of the parallel current density λ profile in the central open column revealed that the n = 1 mode structure plays an important role in the relaxation and current drive. The toroidal flow (v t ≈ 37 km/s) is driven by magnetic reconnection occurring as a result of the helical kink distortion of the central open column during repetitive plasmoid ejection and merging. (author)
Initial Results of the SSPX Transient Internal Probe System for Measuring Toroidal Field Profiles
Holcomb, C. T.; Jarboe, T. R.; Mattick, A. T.; Hill, D. N.; McLean, H. S.; Wood, R. D.; Cellamare, V.
2000-10-01
Lawrence Livermore National Laboratory, Livermore, CA 94550, USA. The Sustained Spheromak Physics Experiment (SSPX) is using a field profile diagnostic called the Transient Internal Probe (TIP). TIP consists of a verdet-glass bullet that is used to measure the magnetic field by Faraday rotation. This probe is shot through the spheromak by a light gas gun at speeds near 2 km/s. An argon laser is aligned along the path of the probe. The light passes through the probe and is retro-reflected to an ellipsometer that measures the change in polarization angle. The measurement is spatially resolved down to the probes’ 1 cm length to within 15 Gauss. Initial testing results are given. This and future data will be used to determine the field profile for equilibrium reconstruction. TIP can also be used in conjunction with wall probes to map out toroidal mode amplitudes and phases internally. This work was performed under the auspices of US DOE by the University of California Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.
International Nuclear Information System (INIS)
Baker, D.A.; Burkhardt, L.C.; Di Marco, J.N.; Haberstich, A.; Hagenson, R.L.; Howell, R.B.; Karr, H.J.; Schofield, A.E.
1977-01-01
The scaling properties of a toroidal reversed-field Z pinch have been investigated over a limited range by comparing two experiments having conducting walls and discharge-tube minor diameters which differ by a factor of approximately 1.5. Both the confinement time of the plasma column and the electron temperature were found to increase about a factor of two with the increased minor diameter. Both the poloidal field diffusion and the decay of the toroidal reversed field were significantly reduced with the larger tube diameter. These results support the hypothesis that the loss of stability later in the discharge is caused by diffusion-induced deterioration of initially favourable plasma-field profiles to MHD unstable ones. This conclusion has been verified by stability analysis of the magnetic field profiles. Fusion reactor calculations show that small reactors are conceptually possible assuming good containment can be achieved for current densities approximately >20MAm -2 . (author)
Studies of conceptual spheromak fusion reactors
International Nuclear Information System (INIS)
Katsurai, M.; Yamada, M.
1982-01-01
Preliminary design studies are carried out for a spheromak fusion reactor. Simplified circuit theory is applied to obtain the characteristic relations among various parameters of the spheromak configuration for an aspect ratio of A >or approx. 1.6. These relations are used to calculate the parameters for the conceptual designs of three types of fusion reactor: (1) the DT reactor with two-component-type operation, (2) the ignited DT reactor, and (3) the ignited catalysed-type DD reactor. With a total wall loading of approx. 4 MW.m -2 , it is found that edge magnetic fields of only approx. 4 T (DT) and approx. 9 T (Cat. DD) are required for ignited reactors of 1 m plasma (minor) radius with output powers in the gigawatt range. An assessment of various schemes of generation, compression and translation of spheromak plasmas is presented. (author)
Compact toroid theory issues and approaches: a panel report
International Nuclear Information System (INIS)
1985-06-01
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
International Nuclear Information System (INIS)
Bitter, M.; Wong, K.L.; Scott, S.; Hsuan, H.; Grek, B.; Johnson, D.; Tait, G.
1990-01-01
The time history of the central toroidal plasma rotation velocity in Tokamak Fusion Test Reactor (TFTR) experiments [Phys. Rev. Lett. 55, 2587 (1985)] with auxiliary heating by neutral deuterium beam injection and major-radius compression has been measured from the Doppler shift of the emitted Ti XXI Kα line radiation. The experiments were conducted for neutral beam powers in the range 2.1--3.8 MW and line-averaged densities in the range 1.8--3.0x10 19 m -2 . The observed rotation velocity increase during compression is consistent with theoretical estimates
International Nuclear Information System (INIS)
Bell, J.D.; Pare, V.L.
1987-01-01
The data acquisition system assembled to study magnetohydrodynamic (MHD) activity on the Impurity Study Experiment (ISX-B) tokamak at Oak Ridge National Laboratory (ORNL) is being revised for use on the Advanced Toroidal Facility (ATF). The new hardware and software architectures are based on ISX-B experience and will feature different modes of operation for storing various subsets of available data, a user interface that requires less routine activity than the earlier system, and continued support of calibration and testing measurement used on ISX-B. The new hardware organization and software components are described in detail. 2 refs., 5 figs., 1 tab
Expansion of parameter space for Toroidal Alfven Eigenmode experiments in TFTR
International Nuclear Information System (INIS)
Wong, K.L.; Wilson, J.R.; Chang, Z.Y.; Fredrickson, E.; Hammett, G.W.; Bush, C.; Nazikian, R.; Phillips, C.K.; Snipes, J.; Taylor, G.
1993-05-01
Several techniques were used to excite toroidal Alfven Eigenmodes in the Tokamak Fusion Test Reactor (TFTR) at magnetic fields above 10 kG. These involve pellet injection to raise the plasma density, variation of plasma current to change the energetic ion orbit and the q-profile, and ICRF heating to produce energetic hydrogen ions at velocities comparable to 3.5 MeV alpha particles. These experimental results are presented and relevance to fusion reactors are discussed
2009-01-01
three axis fluxgate magnetometer , CMOS sun and star sensors, and a Kalman filter. The work and tasks that have been accomplished on the TOROID... magnetometer . The problem was found to be a missing ferrite bead which connects the 12V power supply to the op-amps which are used to appropriately...establish an overall operational timeline for TOROID. Testing and calibration was performed on the three-axis magnetometer which is primary attitude
Steady-state spheromak reactor studies
International Nuclear Information System (INIS)
Krakowski, R.A.; Hagenson, R.L.
1985-01-01
After summarizing the essential elements of a gun-sustained spheromak, the potential for a steady-state is explored by means of a comprehensive physics/engineering/costing model. A range of cost-optimized reactor design points is presented, and the sensitivity of cost to key physics, engineering, and operational variables is reported
Fluctuations in three Los Alamos experiments
International Nuclear Information System (INIS)
Wright, B.L.
1983-01-01
We review results from three magnetic fusion experiments at Los Alamos: the ZT-40M, a reversed-field toroidal pinch; the CTX, a spheromak produced by a magnetized coaxial source; and the FRX-C, a field-reversed configuration generated by theta-pinch techniques. These experiments share the common feature that a major fraction of the confining magnetic field is associated with currents carried by the plasma. We emphasize here the important role that fluctuations play in the maintenance and evolution of these configurations
Divertor experiments in a toroidal plasma, with E x B drift due to an applied radial electric field
International Nuclear Information System (INIS)
Strait, E.J.
1979-09-01
It is proposed that the E x B drift arising from an externally applied electric field could be used in a tokamak or other toroidal magnetic plasma confinement device to remove plasma and impurities from the region near the wall and reduce the amount of plasma striking the wall. This could either augment or replace a conventional magnetic field divertor. Among the possible advantages of this scheme are easy external control over the rate of removal of plasma, more rapid removal than the naturally occurring rate in a magnetic divertor, and simplification of construction if the magnetic divertor is eliminated. Results of several related experiments performed in the Wisconsin Levitated Octupole are presented
International Nuclear Information System (INIS)
Fields, T.; Guarino, V.; Petereit, E.; Schoessow, P.; Thompson, K.
1996-01-01
This proposal describes an alternative to the reference design for the construction of the toroidal magnet for the detector for the MINOS experiment. This design proposes to construct the steel planes from several steel sheets and laminate them into the required thickness of four centimeters. The 8 meter planes are constructed by cutting all of the steel plates to the same size, which is pie a pie shaped segment of either 30 or 22.5 degrees each. All of the plates in the construction are identical, which is conducive to rapid production and lower cost. The advantages of the proposed laminated construction over the reference design are listed in this paper
Superconducting endcap toroid design report
Energy Technology Data Exchange (ETDEWEB)
Walters, C.R.; Baynham, D.E.; Holtom, E.; Coombs, R.C.
1992-10-01
The Atlas Experiment proposed for the LHC machine will use toroidal magnet systems to achieve high muon momentum resolutions. One of the options under consideration is an air cored superconducting toroidal magnet system consisting of a long barrel toroid with small and cap toroids inserted in it to provide high resolution at high pseudorapidity. The design of the barrel toroid has been studied over the past two years and the design outline is given in a Saclay Report. More recently consideration has been given to an end cap toroid system which is based on air cored superconducting coils. This report presents the basic engineering design of such a system, the proposals for fabrication, assembly and installation, and an outline cost estimate for one end cap is presented in Appendix 1.
Three dimensional simulation study of spheromak injection into magnetized plasmas
International Nuclear Information System (INIS)
Suzuki, Y.; Watanabe, T.H.; Sato, T.; Hayashi, T.
2000-01-01
The three dimensional dynamics of a spheromak-like compact toroid (SCT) plasmoid, which is injected into a magnetized target plasma region, is investigated by using MHD numerical simulations. It is found that the process of SCT penetration into this region is much more complicated than that which has been analysed so far by using a conducting sphere (CS) model. The injected SCT suffers from a tilting instability, which grows with a similar timescale to that of the SCT penetration. The instability is accompanied by magnetic reconnection between the SCT magnetic field and the target magnetic field, which disrupts the magnetic configuration of the SCT. Magnetic reconnection plays a role in supplying the high density plasma, initially confined in the SCT magnetic field, to the target region. The penetration depth of the SCT high density plasma is also examined. It is shown to be shorter than that estimated from the CS model. The SCT high density plasma is decelerated mainly by the Lorentz force of the target magnetic field, which includes not only the magnetic pressure force but also the magnetic tension force. Furthermore, by comparing the SCT plasmoid injection with the bare plasmoid injection, magnetic reconnection is considered to relax the magnetic tension force, i.e. the deceleration of the SCT plasmoid. (author)
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.
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.
International Nuclear Information System (INIS)
Bitter, M.; Scott, S.; Wong, K.L.
1986-07-01
The time history of the central toroidal plasma rotation velocity in Tokamak Fusion Test Reactor (TFTR) experiments with auxiliary heating by neutral deuterium beam injection and major-radius compression has been measured from the Doppler shift of the emitted TiXXI-Kα line radiation. The experiments were conducted for neutral beam powers in the range from 2.1 to 3.8 MW and line-averaged densities in the range from 1.8 to 3.0 x 10 19 m -2 . The observed rotation velocity increase during compression is in agreement with results from modeling calculations which assume classical slowing-down of the injected fast deuterium ions and momentum damping at the rate established in the precompression plasma
Increased particle confinement with the use of external dc bias field in the CTX spheromak
International Nuclear Information System (INIS)
Barnes, C.W.; Hoida, H.W.; Henins, I.; Fernandez, J.C.; Jarboe, T.R.; Marklin, G.J.
1985-01-01
Spheromaks are formed in a mesh flux conserver in the presence of an external dc bias field. The spheromaks remain stable to tilt instabilities with ratios of bias-to-spheromak flux of up to 47 +- 7%. Normally applied bias flux puts the spheromak separatrix inside the metal mesh and improves the particle confinement
Non-Solenoidal Startup Research Directions on the Pegasus Toroidal Experiment
Fonck, R. J.; Bongard, M. W.; Lewicki, B. T.; Reusch, J. A.; Winz, G. R.
2017-10-01
The Pegasus research program has been focused on developing a physical understanding and predictive models for non-solenoidal tokamak plasma startup using Local Helicity Injection (LHI). LHI employs strong localized electron currents injected along magnetic field lines in the plasma edge that relax through magnetic turbulence to form a tokamak-like plasma. Pending approval, the Pegasus program will address a broader, more comprehensive examination of non-solenoidal tokamak startup techniques. New capabilities may include: increasing the toroidal field to 0.6 T to support critical scaling tests to near-NSTX-U field levels; deploying internal plasma diagnostics; installing a coaxial helicity injection (CHI) capability in the upper divertor region; and deploying a modest (200-400 kW) electron cyclotron RF capability. These efforts will address scaling of relevant physics to higher BT, separate and comparative studies of helicity injection techniques, efficiency of handoff to consequent current sustainment techniques, and the use of ECH to synergistically improve the target plasma for consequent bootstrap and neutral beam current drive sustainment. This has an ultimate goal of validating techniques to produce a 1 MA target plasma in NSTX-U and beyond. Work supported by US DOE Grant DE-FG02-96ER54375.
Simulations of Low-q Disruptions in the Compact Toroidal Hybrid Experiment
Howell, E. C.; Hanson, J. D.; Ennis, D. A.; Hartwell, G. J.; Maurer, D. A.
2017-10-01
Resistive MHD simulations of low-q disruptions in the Compact Toroidal Hybrid Device (CTH) are performed using the NIMROD code. CTH is a current-carrying stellarator used to study the effects of 3D shaping on MHD stability. Experimentally, it is observed that the application of 3D vacuum fields allows CTH to operate with edge safety factor less than 2.0. However, these low-q discharges often disrupt after peak current if the applied 3D fields are too weak. Nonlinear simulations are initialized using model VMEC equilibria representative of low-q discharges with weak vacuum transform. Initially a series of symmetry preserving island chains are excited at the q=6/5, 7/5, 8/5, and 9/5 rational surfaces. These island chains act as transport barriers preventing stochastic magnetic fields in the edge from penetrating into the core. As the simulation progresses, predominately m/n=3/2 and 4/3 instabilities are destabilized. As these instabilities grow to large amplitude they destroy the symmetry preserving islands leading to large regions of stochastic fields. A current spike and loss of core thermal confinement occurs when the innermost island chain (6/5) is destroyed. Work Supported by US-DOE Grant #DE-FG02-03ER54692.
Recent results from the Los Alamos CTX spheromak
Energy Technology Data Exchange (ETDEWEB)
Barnes, C.W.; Henins, I.; Hoida, H.W.; Jarboe, T.R.; Knox, S.O.; Linford, R.K.; Platts, D.A.; Sherwood, A.R.
1982-01-01
Continued discharge cleaning, improved vacuum practices, and optimized plasma formation operation have resulted in the Los Alamos CTX spheromak experiment achieving 1 millisecond plasma lifetimes with average temperatures of 20 to 40 eV. Impurity radiation power loss has been reduced significantly and the plasma behavior appears to be dominated by pressure-driven instabilities causing increased particle loss. The major advance in operation has been the use of a constant, uniform background of 5 to 20 mTorr of H/sub 2/ filling the vacuum tank, flux conserver, and plasma source. This fill operation directly reduces the impurities generated in the plasma source, allows operation of the source at parameters resulting in fewer impurities, and provides a neutral source to maintain the density for long lifetimes. In this paper we present data on the improved operation of CTX, and present evidence for its ..beta..-limited operation.
Recent results from the Los Alamos CTX spheromak
International Nuclear Information System (INIS)
Barnes, C.W.; Henins, I.; Hoida, H.W.; Jarboe, T.R.; Knox, S.O.; Linford, R.K.; Platts, D.A.; Sherwood, A.R.
1982-01-01
Continued discharge cleaning, improved vacuum practices, and optimized plasma formation operation have resulted in the Los Alamos CTX spheromak experiment achieving 1 millisecond plasma lifetimes with average temperatures of 20 to 40 eV. Impurity radiation power loss has been reduced significantly and the plasma behavior appears to be dominated by pressure-driven instabilities causing increased particle loss. The major advance in operation has been the use of a constant, uniform background of 5 to 20 mTorr of H 2 filling the vacuum tank, flux conserver, and plasma source. This fill operation directly reduces the impurities generated in the plasma source, allows operation of the source at parameters resulting in fewer impurities, and provides a neutral source to maintain the density for long lifetimes. In this paper we present data on the improved operation of CTX, and present evidence for its β-limited operation
Observation of plasma toroidal-momentum dissipation by neoclassical toroidal viscosity.
Zhu, W; Sabbagh, S A; Bell, R E; Bialek, J M; Bell, M G; LeBlanc, B P; Kaye, S M; Levinton, F M; Menard, J E; Shaing, K C; Sontag, A C; Yuh, H
2006-06-09
Dissipation of plasma toroidal angular momentum is observed in the National Spherical Torus Experiment due to applied nonaxisymmetric magnetic fields and their plasma-induced increase by resonant field amplification and resistive wall mode destabilization. The measured decrease of the plasma toroidal angular momentum profile is compared to calculations of nonresonant drag torque based on the theory of neoclassical toroidal viscosity. Quantitative agreement between experiment and theory is found when the effect of toroidally trapped particles is included.
Critical beta for analytical spheromak equilibria
International Nuclear Information System (INIS)
Freire, E.M.; Clemente, R.A.
1985-01-01
The Mercier criterion is applied to two analytical spheromak equilibria, one with a spherical separatrix and the other with a cylindrical one of variable elongation. The maximum beta, defined as the ratio between the plasma pressure and the magnetic pressure averaged over the plasma volume, for which the criterion is satisfied on every magnetic surface, has been obtained. In the spherical model the critical beta is 0.003, while in the cylindrical case it is a function of the elongation of the separatrix with a maximum of 0.083. (author)
Magnetohydrodynamic equilibrium and stability of spheromak with spheroidal plasma-vacuum interface
International Nuclear Information System (INIS)
Kaneko, Shobu; Kamitani, Atsushi; Takimoto, Akio.
1985-05-01
The analytic solutions to the Grad-Shafranov equation are obtained for a prolate and an oblate spheroidal plasma by using Hill's vortex model. Effects of a toroidal magnetic field Bsub(phi) on the MHD equilibrium configurations are investigated by using these analytic solutions. When Bsub(phi) is larger than that of the force-free configuration, the spheroidal plasmas in a vacuum magnetic field are shown to be unable in the MHD equilibrium. The several physical quantities on the equilibrium configuration are evaluated. The spheromak plasma is proved to be unstable if dp/d psi not equal 0 and d 2 V/d psi 2 >= 0 on the magnetic axis. Here p is the pressure and V(psi) the volume surrounded by a magnetic surface of psi=const. The equilibrium configurations of the spheroidal plasmas by using Hill's vortex model are shown to satisfy the above conditions, i.e., to be unstable. (author)
Magnetohydrodynamic equilibrium and stability of spheromak with spheroidal plasma-vacuum interface
International Nuclear Information System (INIS)
Kaneko, Shobu; Kamitani, Atsushi; Takimoto, Akio
1985-01-01
The analytic solutions to the Grad-Shafranov equation are obtained for a prolate and an oblate spheroidal plasma by using Hill's vortex model. Effects of a toroidal magnetic field Bsub(phi) on the MHD equilibrium configurations are investigated by using these analytic solutions. When Bsub(phi) is stronger than that of the force-free configuration, the spheroidal plasmas in a vacuum magnetic field are shown to be unable in the MHD equilibrium. The several physical quantities on the equilibrium configuration are evaluated. The spheromak plasma is proved to be unstable if dp/d psi not equal 0 and d 2 V/d psi 2 >= 0 on the magnetic axis. Here p is the pressure and V(psi) the volume surrounded by a magnetic surface of psi = const. The equilibrium configurations of the spheroidal plasmas by using Hill's vortex model are shown to satisfy the above conditions, i.e., to be unstable. (author)
Design of a spheromak compressor driven by high explosives
International Nuclear Information System (INIS)
Henins, I.; Fernandez, J.C.; Jarboe, T.R.; Marsh, S.P.; Marklin, G.J.; Mayo, R.M.; Wysocki, F.J.
1990-01-01
High energy density spheromaks can be used to accelerate a thin section of the flux conserver wall to high velocities. The energy density of a spheromak, formed by conventional helicity injection into a flux conserver, can be increased by reducing the flux conserver volume after the spheromak is formed. A method of accomplishing this is by imploding one wall of the flux conserver with high explosives. The authors have embarked on a program to demonstrate that a spheromak can be used as an energy transfer medium, and that a velocity gain over high-explosive driven plate velocities can be achieved. To do this, a plasma gun helicity source that will inject a spheromak with suitable initial energy density and lifetime is needed. Also, an implodable flux conserver that remains intact and clean during the implosion must be developed. The flux conserver problem is probably the more challenging one, because very little experimental work has been done in the past on explosively driven metal plates into a high vacuum, with sizes and travel distances appropriate for their application. There are two necessary practical requirements for an explosive compression of a flux conserver. The first is that the imploding wall does not rupture. The second is that gasses or other debri are not ejected which could penetrate and poison the spheromak plasma, and thus reduce the spheromak lifetime below what is necessary to carry out the spheromak compression and the subsequent acceleration of the flyer plate. The authors have designed and fabricated a plasma gun to be used for injecting the initial spheromak plasma into the collapsible flux conserver
Theory and application of maximum magnetic energy in toroidal plasmas
International Nuclear Information System (INIS)
Chu, T.K.
1992-02-01
The magnetic energy in an inductively driven steady-state toroidal plasma is a maximum for a given rate of dissipation of energy (Poynting flux). A purely resistive steady state of the piecewise force-free configuration, however, cannot exist, as the periodic removal of the excess poloidal flux and pressure, due to heating, ruptures the static equilibrium of the partitioning rational surfaces intermittently. The rupture necessitates a plasma with a negative q'/q (as in reverse field pinches and spheromaks) to have the same α in all its force-free regions and with a positive q'/q (as in tokamaks) to have centrally peaked α's
Computational studies of ohmic heating in the spheromak
International Nuclear Information System (INIS)
Olson, R.E.
1983-01-01
Time-dependent computational simulations using both single-fluid O-D and two-fluid 1 1/2-D models are developed for and utilized in an investigation of the ohmic heating of a spheromak plasma. The plasma density and composition, the applied magnetic field strength, the plasma size, and the plasma current density profile are considered for their effects on the spheromak heating rate and maximum achievable temperature. The feasibility of ohmic ignition of a reactor-size spheromak plasma is also contemplated
Ion temperature measurements in the Maryland Spheromak
International Nuclear Information System (INIS)
Gauvreau, J.L.
1992-01-01
Initial spectroscopic data from MS showed evidence of ion heating as deduced from the line widths of different ion species. Detailed measurements of OIV spectral emission line profiles in space and time revealed that heating takes place at early time, before spheromak formation and is occurring within the current discharge. The measured ion temperature is several times the electron temperature and cannot be explained by classical (Spitzer) resistivity. Classically, ions are expected to have lower temperatures than the electrons and therefore, lower temperatures than observed. High ion temperatures have been observed in different RFP's and Spheromaks but are usually associated with relaxation to the Taylor state and occur in the sustainment phase. During formation, the current delivered to start the discharge is not axisymmetric and as a consequence, X-points appear in the magnetic flux. A two dimensional analysis predicts that magnetic reconnection occurring at an X-point can give rise to high ion heating rates. A simple 0-dimensional calculation showed that within the first 20 μs, a conversion of mass flow kinetic energy into ion temperature could take place due to viscosity
The spheromak as a compact fusion reactor
International Nuclear Information System (INIS)
Hagenson, R.L.; Krakowski, R.A.
1987-03-01
After summarizing the economic and utility-based rationale for compact, higher-power-density fusion reactors, the gun-sustained spheromak concept is explored as one of a number of poloidal-field-dominated confinement configurations that might improve the prospects for economically attractive and operationally simplified fusion power plants. Using a comprehensive physics/engineering/costing model for the spheromak, guided by realistic engineering constraints and physics extrapolation, a range of cost-optimized reactor design points is presented, and the sensitivity of cost to key physics, engineering, and operational variables is reported. The results presented herein provide the basis for conceptual engineering designs of key fusion-power-core (FPC) subsystems and more detailed plasma modeling of this promising, high mass-power-density concept, which stresses single-piece FPC maintenance, steady-state current drive through electrostatic magnetic helicity injection, a simplified co-axial electrode-divertor, and efficient resistive-coal equilibrium-field coils. The optimal FPC size and the cost estimates project a system that competes aggressively with the best offered by alternative energy sources while simplifying considerably the complexity that has generally been associated with most approaches to magnetic fusion energy
The spheromak as a compact fusion reactor
Energy Technology Data Exchange (ETDEWEB)
Hagenson, R.L.; Krakowski, R.A.
1987-03-01
After summarizing the economic and utility-based rationale for compact, higher-power-density fusion reactors, the gun-sustained spheromak concept is explored as one of a number of poloidal-field-dominated confinement configurations that might improve the prospects for economically attractive and operationally simplified fusion power plants. Using a comprehensive physics/engineering/costing model for the spheromak, guided by realistic engineering constraints and physics extrapolation, a range of cost-optimized reactor design points is presented, and the sensitivity of cost to key physics, engineering, and operational variables is reported. The results presented herein provide the basis for conceptual engineering designs of key fusion-power-core (FPC) subsystems and more detailed plasma modeling of this promising, high mass-power-density concept, which stresses single-piece FPC maintenance, steady-state current drive through electrostatic magnetic helicity injection, a simplified co-axial electrode-divertor, and efficient resistive-coal equilibrium-field coils. The optimal FPC size and the cost estimates project a system that competes aggressively with the best offered by alternative energy sources while simplifying considerably the complexity that has generally been associated with most approaches to magnetic fusion energy.
Controlled and spontaneous magnetic field generation in a gun-driven spheromak
International Nuclear Information System (INIS)
Woodruff, S.; Cohen, B.I.; Hooper, E.B.; Mclean, H.S.; Stallard, B.W.; Hill, D.N.; Holcomb, C.T.; Romero-Talamas, C.; Wood, R.D.; Cone, G.; Sovinec, C.R.
2005-01-01
In the Sustained Spheromak Physics Experiment, SSPX [E. B. Hooper, D. Pearlstein, and D. D. Ryutov, Nucl. Fusion 39, 863 (1999)], progress has been made in understanding the mechanisms that generate fields by helicity injection. SSPX injects helicity (linked magnetic flux) from 1 m diameter magnetized coaxial electrodes into a flux-conserving confinement region. Control of magnetic fluctuations (δB/B∼1% on the midplane edge) yields T e profiles peaked at >200 eV. Trends indicate a limiting beta (β e ∼4%-6%), and so we have been motivated to increase T e by operating with stronger magnetic field. Two new operating modes are observed to increase the magnetic field: (A) Operation with constant current and spontaneous gun voltage fluctuations. In this case, the gun is operated continuously at the threshold for ejection of plasma from the gun: stored magnetic energy of the spheromak increases gradually with δB/B∼2% and large voltage fluctuations (δV∼1 kV), giving a 50% increase in current amplification, I tor /I gun . (B) Operation with controlled current pulses. In this case, spheromak magnetic energy increases in a stepwise fashion by pulsing the gun, giving the highest magnetic fields observed for SSPX (∼0.7 T along the geometric axis). By increasing the time between pulses, a quasisteady sustainment is produced (with periodic good confinement), comparing well with resistive magnetohydrodynamic simulations. In each case, the processes that transport the helicity into the spheromak are inductive and exhibit a scaling of field with current that exceeds those previously obtained. We use our newly found scaling to suggest how to achieve higher temperatures with a series of pulses
Controlled and Spontaneous Magnetic Field Generation in a Gun-Driven Spheromak
International Nuclear Information System (INIS)
Woodruff, S; Cohen, B I; Hooper, E B; McLean, H S; Stallard, B W; Hill, D N; Holcomb, C T; Romero-Talamas, C; Wood, R D; Cone, G; Sovinec, C R
2005-04-01
In the Sustained Spheromak Physics Experiment, SSPX, progress has been made in understanding the mechanisms that generate fields by helicity injection. SSPX injects helicity (linked magnetic flux) from 1-m diameter magnetized coaxial electrodes into a flux-conserving confinement region. Control of magnetic fluctuations ((delta)B/B∼1% on the midplane edge) yields T e profiles peaked at > 200eV. Trends indicate a limiting beta (β e ∼ 4-6%), and so we have been motivated to increase T e by operating with stronger magnetic field. Two new operating modes are observed to increase the magnetic field: (A) Operation with constant current and spontaneous gun voltage fluctuations. In this case, the gun is operated continuously at the threshold for ejection of plasma from the gun: stored magnetic energy of the spheromak increases gradually with (delta)B/B ∼2% and large voltage fluctuations ((delta)V ∼ 1kV), giving a 50% increase in current amplification, I tor /I gun . (B) Operation with controlled current pulses. In this case, spheromak magnetic energy increases in a stepwise fashion by pulsing the gun, giving the highest magnetic fields observed for SSPX (∼0.7T along the geometric axis). By increasing the time between pulses, a quasi-steady sustainment is produced (with periodic good confinement), comparing well with resistive MHD simulations. In each case, the processes that transport the helicity into the spheromak are inductive and exhibit a scaling of field with current that exceeds those previously obtained. We use our newly found scaling to suggest how to achieve higher temperatures with a series of pulses
Theory of the evolution of the decaying spheromak
International Nuclear Information System (INIS)
Sgro, A.G.; Marklin, G.; Mirin, A.A.
1986-01-01
The strongly nonlinear dynamics present in decaying Spheromaks has been studied by various computational methods, demonstrating the tendency of the plasma to oscillate about or approach relaxed states and resulting in new insight into the significance of minimum energy states
Effects of passive coils on spheromak gross MHD instabilities
International Nuclear Information System (INIS)
Munson, C.; Janos, A.; Paul, S.; Wysocki, F.; Yamada, M.
1983-01-01
The experimental investigation of the effectiveness of figure-8 coils in stabilizing the n=1 tilting mode of spheromak plasmas in Proto S-1 A/B is extended. In addition, another coil configuration, the saddle coil, is examined
International Nuclear Information System (INIS)
Knoepfel, H.; Mazzitelli, G.
1984-01-01
The article is a rather detailed report on the highlights in the area of the ''Heating in toroidal plasmas'', as derived from the presentations and discussions at the international symposium with the same name, held in Rome, March 1984. The symposium covered both the physics (experiments and theory) and technology of toroidal fusion plasma heating. Both large fusion devices (either already in operation or near completion) requiring auxiliary heating systems at the level of tens of megawatts, as well as physics of their heating processes and their induced side effects (as studied on smaller devices), received attention. Substantial progress was reported on the broad front of auxiliary plasma heating and Ohmic heating. The presentation of the main conclusions of the symposium is divided under the following topics: neutral-beam heating, Alfven wave heating, ion cyclotron heating, lower hybrid heating, RF current drive, electron cyclotron heating, Ohmic heating and special contributions
Investigations into the relationship between spheromak, solar, and astrophysical plasmas
International Nuclear Information System (INIS)
Bellan, P.M.; Hsu, S.C.; Hansen, J.F.; Tokman, M.; Pracko, S.E.; Romero-Talamas, C.A.
2003-01-01
Spheromaks offer the potential for a simple, low cost fusion reactor and involve physics similar to certain solar and astrophysical phenomena. A program to improve understanding of spheromaks by exploiting this relationship is underway using (i) a planar spheromak gun and (ii) a solar prominence simulator. These devices differ in symmetry but both involve spheromak technology whereby high-voltage is applied across electrodes linking a bias magnetic flux created by external coils. The planar spheromak gun consists of a co-planar disk and annulus linked by a poloidal bias field. Application of high voltage across the gap between disk and annulus drives a current along the bias field. If the current to flux ratio exceeds the inverse of the characteristic linear dimension, a spheromak is ejected. A distinct kink forms just below the ejection threshold. The solar simulation gun consists of two adjacent electromagnets which generate a 'horse-shoe' arched bias field. A current is driven along this arched field by a capacitor bank. The current channel first undergoes pinching, then writhes, and finally bulges outwards due to the hoop force. (author)
Zero Quantum Nuclear Magnetic Resonance experiments utilizing a toroid cell and coil
Bebout, William Roach
1989-01-01
Over the past ten to fifteen years the area of Nuclear Magnetic Resonance (NMR) Spectroscopy has seen tremendous growth. For example, in conjunction with multiple quantum NMR, molecular structural mapping of a compound can be easily performed in a two dimensional (2D) experiment. However, only two kinds of detector coils have been typically used in NMR studies. These are the solenoid coil and the Helmholtz coil. The solenoid coil was very popular with the permanent and e...
Directory of Open Access Journals (Sweden)
Saveliev A.N.
2012-09-01
Full Text Available In the paper the possibility of total 3D trapping of electron Bernstein (EB waves in the tokamak equatorial plane in the vicinity of the local density maximum produced by electron pump-out-effect is demonstrated. Thresholds and growth rates of the associated absolute (temporally growing parametric decay instability (PDI leading to anomalous absorption is predicted in the range of less than 100 kW. Its possible role in explanation of ion acceleration observed in ECRH experiments as well as in redistribution of the deposited power is discussed.
Theory of edge plasma in a spheromak
International Nuclear Information System (INIS)
Hooper, E.B.
1998-01-01
Properties of the edge plasma in the SSPX spheromak during the plasma formation and sustainment phases are discussed. For the breakdown and formation phase, the main emphasis is on the analysis of possible plasma contamination by impurities from the electrodes of the plasma gun (helicity injector). The issue of an azimuthally uniform breakdown initiation is also discussed. After the plasma settles down in the main vacuum chamber, one has to sustain the current between the electrodes, in order to continuously inject helicity. We discuss properties of the plasma on the field lines intersecting the electrodes. We conclude that the thermal balance of this plasma is maintained by Joule heating competing with parallel heat losses to the electrodes. The resulting plasma temperature is in the range of 15 - 30 eV. Under the expected operational conditions, the ''current'' velocity of the electrons is only slightly below their thermal velocity. Implications of this observation are briefly discussed
Magnetohydrodynamic equilibrium of axisymmetric systems with toroidal rotation
International Nuclear Information System (INIS)
Mansur, N.L.P.
1986-01-01
A model for studying magnetohydrodynamic equilibrium of axisymetrically confined plasma with toroidal rotation, extended to the Grad. Shafranov equation is presented. The expression used for the scalar pressure is modifiec, and the influence of toroidal magnetic field is included, The equation for general motion of axisymetrically confined plasma, particularizing for rotation movements is described. Two cases are compared: one supposes the entropy as a function of poloidal magnetic flux and other supposes the temperature as a function of flux. The equations for these two cases obtaining a simplified expression by others approximations are established. The proposed model is compared with Shibata model, which uses density as function of flux, and with the ideal spheromak model. A set of cases taking in account experimental data is studied. (M.C.K.) [pt
International Nuclear Information System (INIS)
Smith, B.R.
1995-01-01
This document identifies the candidate materials and manufacturing processes selected for development of the TPX Toroidal Field (TF) Magnet. Supporting rationale and selection criteria are provided for justification and the materials properties database report is included for completeness. Specific properties for each material selection are included in this document
Ohmic heating of a spheromak to 100 eV
Energy Technology Data Exchange (ETDEWEB)
Jarboe, T.R.; Barnes, C.W.; Henins, I.; Hoida, H.W.; Knox, S.O.; Linford, R.K.; Sherwood, A.R.
1984-01-01
The first spheromaks with Thomson-scattering-measured electron temperatures of over 100 eV are described. The spheromak is generated by a magnetized coaxial plasma source in a background gas of 30 mTorr of H/sub 2/, and it is stably confined in an oblate 80 cm diam copper mesh flux conserver. The open mesh design allows rapid impurity transport out of the spheromak. The peak temperature, measured using multipoint Thomson scattering, is observed to rise from approximately 25 eV to over 100 eV in about 0.2 msec due to Ohmic heating from the decaying magnetic fields. Density (approx.5 x 10/sup 13/ cm/sup -3/) and magnetic fields (approximately 2 kG) are measured using interferometry and magnetic probes.
Ohmic heating of a spheromak to 100 eV
International Nuclear Information System (INIS)
Jarboe, T.R.; Barnes, C.W.; Henins, I.; Hoida, H.W.; Knox, S.O.; Linford, R.K.; Sherwood, A.R.
1984-01-01
The first spheromaks with Thomson-scattering-measured electron temperatures of over 100 eV are described. The spheromak is generated by a magnetized coaxial plasma source in a background gas of 30 mTorr of H 2 , and it is stably confined in an oblate 80 cm diam copper mesh flux conserver. The open mesh design allows rapid impurity transport out of the spheromak. The peak temperature, measured using multipoint Thomson scattering, is observed to rise from approximately 25 eV to over 100 eV in about 0.2 msec due to Ohmic heating from the decaying magnetic fields. Density (approx.5 x 10 13 cm -3 ) and magnetic fields (approximately 2 kG) are measured using interferometry and magnetic probes
Resistive stability of the cylindrical spheromak
International Nuclear Information System (INIS)
DeLucia, J.; Jardin, S.C.; Glasser, A.H.
1983-11-01
The growth rates for resistive instabilities in a straight circular cylinder with spheromak profiles are computed by using two complementary methods. The first method employs boundary layer analysis and asymptotic matching, most valid for values of the magnetic Reynolds number S greater than or equal to 10 5 . The second method solved the full linearized resistive MHD equations as an initial value problem, utilizing zone packing around the mode rational surface. Resolution requirements limit this to S less than or equal to 10 7 . The results from these two methods agree to better than 1 in 10 3 in the overlap region 10 7 greater than or equal to S greater than or equal to 10 5 . A scan of parameter space reveals that for parabolic q-profiles, the least unstable configurations have q 0 R/a approx. 0.67. The Hall term in Ohm's Law is easily incorporated into both methods. Recalculating the resistive MHD growth rates in the presence of this term shows that the resistive interchange mode is completely stabilized for a large enough value of the ion cyclotron time
International Nuclear Information System (INIS)
Barbosa, Luis Filipe F.P.W.; Bosco, Edson del.
1994-01-01
This report presents the project and analysis of the circuit for production of the toroidal magnetic field in the Tokamak ETE (Spherical Tokamak Experiment). The ETE is a Tokamak with a small-aspect-ratio parameter to be used for studying the plasma physics for the research on thermonuclear fusion. This machine is being constructed at the Laboratorio Associado de Plasma (LAP) of the Instituto Nacional de Pesquisas Espaciais (INPE) in Sao Jose dos Campos, SP, Brazil. (author). 20 refs., 39 figs., 4 tabs
Progress with energy confinement time in the CTX spheromak
International Nuclear Information System (INIS)
Jarboe, T.R.; Fernandez, J.C.; Wysocki, F.J.; Barnes, C.W.; Henins, I.; Knox, S.O.; Marklin, G.J.
1990-01-01
The 0.67 m radius mesh flux conserver (MFC) in CTX was replaced by a solid flux conserver (SFC), resulting in greatly reduced field errors. Decreased spheromak open flux led to vastly improved decaying discharged, including increased global energy confinement times, τ E (from 20 to 180 μs), and corresponding magnetic energy decay times, τ B 2 (from 0.7 to 2 ms). Improved confinement allowed the observation of the pressure-driven instability (predicted by Mercier) which ejects plasma from the spheromak interior to the wall
Toroidal effects on drift wave turbulence
Energy Technology Data Exchange (ETDEWEB)
LeBrun, M.J.; Tajima, T.; Gray, M.G.; Furnish, G.; Horton, W.
1992-09-23
The universal drift instability and other drift instabilities driven by density and temperature gradients in a toroidal system are investigated in both linear and nonlinear regimes via particle simulation. Runs in toroidal and cylindrical geometry show dramatic differences in plasma behavior, primarily due to the toroidicity-induced coupling of rational surfaces through the poloidal mode number m. In the toroidal system studied, the eigenmodes are seen to possess (i) an elongated, nearly global radial extent (ii) a higher growth rate than in the corresponding cylindrical system, (iii) an eigenfrequency nearly constant with radius, (iv) a global temperature relaxation and enhancement of thermal heat conduction. Most importantly, the measured Xi shows an increase with radius and an absolute value on the order of that observed in experiment. On the basis of our observations, we argue that the increase in Xi with radius observed in experiment is caused by the global nature of heat convection in the presence of toroidicity-induced mode coupling.
Toroidal effects on drift wave turbulence
International Nuclear Information System (INIS)
LeBrun, M.J.; Tajima, T.; Gray, M.G.; Furnish, G.; Horton, W.
1992-01-01
The universal drift instability and other drift instabilities driven by density and temperature gradients in a toroidal system are investigated in both linear and nonlinear regimes via particle simulation. Runs in toroidal and cylindrical geometry show dramatic differences in plasma behavior, primarily due to the toroidicity-induced coupling of rational surfaces through the poloidal mode number m. In the toroidal system studied, the eigenmodes are seen to possess (i) an elongated, nearly global radial extent (ii) a higher growth rate than in the corresponding cylindrical system, (iii) an eigenfrequency nearly constant with radius, (iv) a global temperature relaxation and enhancement of thermal heat conduction. Most importantly, the measured Xi shows an increase with radius and an absolute value on the order of that observed in experiment. On the basis of our observations, we argue that the increase in Xi with radius observed in experiment is caused by the global nature of heat convection in the presence of toroidicity-induced mode coupling
Hsu, S. C.; Bellan, P. M.
2003-01-01
The magnetohydrodynamic kink instability is observed and identified experimentally as a poloidal flux amplification mechanism for coaxial gun spheromak formation. Plasmas in this experiment fall into three distinct regimes which depend on the peak gun current to magnetic flux ratio, with (I) low values resulting in a straight plasma column with helical magnetic field, (II) intermediate values leading to kinking of the column axis, and (III) high values leading immediately to a detached plasma...
International Nuclear Information System (INIS)
Pasqualini, D.; Martin, P.; Koguchi, H.; Yagi, Y.; Hirano, Y.; Sakakita, H.; Spizzo, G.
2006-01-01
The MHD instabilities that sustain the reversed-field pinch (RFP) configuration tend to phase-lock together and also to wall-lock, forming a bulging of the plasma column, called 'locked mode'. This phenomenon is of particular interest, since the locked mode causes a larger plasma resistivity, plasma cooling, and, in some cases, anomalous discharge termination. Up to now, studies of the locked mode have been focused on m=1 modes (being m the poloidal mode number). In this Letter we show that m=0 modes also play a role, based on the cross-check between magnetic spectra and toroidally resolved D α array measurements. (author)
Influence of external toroidal flux on low-aspect-ratio toroidal plasma
International Nuclear Information System (INIS)
Ikuno, S.; Natori, M.; Kamitani, A.
1999-01-01
In the HIST device, the external flux is generated by two kinds of currents: the current I s flowing along the symmetry axis and the bias coil current I D . The influence of the external flux on the MHD equilibrium and stability of the low-aspect-ratio toroidal plasma in the HIST device is investigated numerically. Equilibrium configurations of the low-aspect-ratio toroidal plasma in the HIST device are numerically determined by means of the combination of FDM and BEM. The influence of I s and I D on their stability is also investigated by using the Mercier criterion. The results of computations show that the Mercier limit decreases to zero with increasing I s and with decreasing I D . Moreover, either a further increase in I s or a further decrease in I D raises the Mercier limit considerably. Besides, the equilibrium configuration in the HIST device changes its state from spheromak through ultra-low q to tokamak with increasing I s and with decreasing I D . (author)
International Nuclear Information System (INIS)
Johnson, R.L.
1985-01-01
The Advanced Toroidal Facility (ATF) is a new magnetic confinement plasma device under construction at the Oak Ridge National Laboratory (ORNL) that will lead to improvements in toroidal magnetic fusion reactors. The ATF is a type of stellerator, known as a ''torsatron'' which theoretically has the capability to operate at greater than or equal to8% beta in steady state. The ATF plasma has a major radius of 2.1 m, an average minor radius of 0.3 m, and a field of 2 T for a 2 s duration or 1 T steady state. The ATF device consists of a helical field (HF) coil set, a set of poloidal field (PF) coils, an exterior shell structure to support the coils, and a thin, helically contoured vacuum vessel inside the coils. The ATF replaces the Impurities Studies Experiment (ISX-B) tokamak at ORNL and will use the ISX-B auxiliary systems including 4 MW of electron cyclotron heating. The ATF is scheduled to start operation in late 1986. An overview of the ATF device is presented, including details of the construction process envisioned. 9 refs., 7 figs., 3 tabs
Fisher, Dustin; Zhang, Yue; Wallace, Ben; Gilmore, Mark; Manchester, Ward; Arge, C. Nick
2016-10-01
The Plasma Bubble Expansion Experiment (PBEX) at the University of New Mexico uses a coaxial plasma gun to launch jet and spheromak magnetic plasma configurations into the Helicon-Cathode (HelCat) plasma device. Plasma structures launched from the gun drag frozen-in magnetic flux into the background magnetic field of the chamber providing a rich set of dynamics to study magnetic turbulence, force-free magnetic spheromaks, and shocks. Preliminary modeling is presented using the highly-developed 3-D, MHD, BATS-R-US code developed at the University of Michigan. BATS-R-US employs an adaptive mesh refinement grid that enables the capture and resolution of shock structures and current sheets, and is particularly suited to model the parameter regime under investigation. CCD images and magnetic field data from the experiment suggest the stabilization of an m =1 kink mode trailing a plasma jet launched into a background magnetic field. Results from a linear stability code investigating the effect of shear-flow as a cause of this stabilization from magnetic tension forces on the jet will be presented. Initial analyses of a possible magnetic Rayleigh Taylor instability seen at the interface between launched spheromaks and their entraining background magnetic field will also be presented. Work supported by the Army Research Office Award No. W911NF1510480.
Equilibrium and stability of the Los Alamos spheromak
International Nuclear Information System (INIS)
Marklin, G.
1984-01-01
The open mesh flux conserver (MFC) on the Los Alamos spheromak (CTX) has been equipped with a large number of Rogowski loops measuring the current in the individual segments of the MFC, providing a complete picture of the surface current pattern induced by the equilibrium and oscillations of the confined plasma. An analysis was made of the data from these Rogowski loops
LASL toroidal reversed-field pinch programme
International Nuclear Information System (INIS)
Baker, D.A.; Buchenauer, C.J.; Burkhardt, L.C.
1979-01-01
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)
LASL toroidal reversed-field pinch program
International Nuclear Information System (INIS)
Baker, D.A.; Buchenauer, C.J.; Burkhardt, L.C.
1978-01-01
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 over half of 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 are 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
International Nuclear Information System (INIS)
Herfindal, J. L.; Dawson, J. D.; Ennis, D. A.; Hartwell, G. J.; Loch, S. D.; Maurer, D. A.
2014-01-01
A multi-camera soft x-ray diagnostic has been developed to measure the equilibrium electron temperature profile and temperature fluctuations due to magnetohydrodynamic activity on the Compact Toroidal Hybrid experiment. The diagnostic consists of three separate cameras each employing two 20-channel diode arrays that view the same plasma region through different beryllium filter thicknesses of 1.8 μm and 3.0 μm allowing electron temperature measurements between 50 eV and 200 eV. The Compact Toroidal Hybrid is a five-field period current-carrying stellarator, in which the presence of plasma current strongly modifies the rotational transform and degree of asymmetry of the equilibrium. Details of the soft x-ray emission, effects of plasma asymmetry, and impurity line radiation on the design and measurement of the two-color diagnostic are discussed. Preliminary estimates of the temperature perturbation due to sawtooth oscillations observed in these hybrid discharges are given
Recent results from the HIT-II and HIT-SI helicity injection current drive experiments
International Nuclear Information System (INIS)
Jarboe, T.R.; Hamp, W.T.; Izzo, V.A.; Nelson, B.A.; O'Neill, R.G.; Raman, R.; Redd, A.J.; Sieck, P.E.; Smith, R.J.
2005-01-01
Three important results are reported. 1) CHI startup has produced 100 kA of closed current without using poloidal field (PF) coils or any transformer action. The initial equilibrium is then driven to 240 kA with a 3 V transformer loop voltage, indicating high quality plasma. 2) For the first time CHI alone has produced toroidal currents (350 kA) that far exceed q a I inj , and with I p /I tf as high as 1.2. The key to these new results appears to be having the toroidal field small enough that relaxation will occur. 3) The steady inductive helicity injection spheromak experiment has operated at 5 kHz for 6 ms with current amplitudes up to 11 kA in each injector. The helicity injection rate is nearly constant with the ExB flow always into the plasma and not into the walls. NIMROD simulations of HIT-SI show a buildup of spheromak fields. (author)
International Nuclear Information System (INIS)
Kaneko, Shobu; Tsutsui, Hiroaki; Miyazaki, Takeshi; Taguchi, Masayoshi.
1985-08-01
The magnetohydrodynamic equilibrium states by Hill's vortex model and by the Coulomb-wave-function model are proved to be unstable. New MHD equilibrium configurations are determined by using another model for which dp/dψ = 0 on the magnetic axis. Here p is the pressure and ψ is the flux function. The values of the safety factor on the magnetic axis, q axis , are evaluated for these configurations. The MHD stability of these equilibrium states is investigated by the Mercier criterion. The values of the maximum beta ratio β max are evaluated for this model. The optimized pressure distributions are determined by use of the Mercier criterion and the values of β max are also evaluated for these pressure distributions. The values of β max are shown to be at most 12 %, if the condition q axis < 1 is required. (author)
Energy Technology Data Exchange (ETDEWEB)
Yamada, Masaaki [Princeton Plasma Physics Laboratory, Princeton University Princeton, New Jersey USA (United States)
2016-03-25
This paper briefly reviews a compact toroid reactor concept that addresses critical issues for forming, stabilizing and sustaining a field reversed configuration (FRC) with the use of plasma merging, plasma shaping, conducting shells, neutral beam injection (NBI). In this concept, an FRC plasma is generated by the merging of counter-helicity spheromaks produced by inductive discharges and sustained by the use of neutral beam injection (NBI). Plasma shaping, conducting shells, and the NBI would provide stabilization to global MHD modes. Although a specific FRC reactor design is outside the scope of the present paper, an example of a promising FRC reactor program is summarized based on the previously developed SPIRIT (Self-organized Plasmas by Induction, Reconnection and Injection Techniques) concept in order to connect this concept to the recently achieved the High Performance FRC plasmas obtained by Tri Alpha Energy [Binderbauer et al, Phys. Plasmas 22,056110, (2015)]. This paper includes a brief summary of the previous concept paper by M. Yamada et al, Plasma Fusion Res. 2, 004 (2007) and the recent experimental results from MRX.
Sustained spheromak coaxial gun operation in the presence of an n=1 magnetic distortion
International Nuclear Information System (INIS)
Holcomb, C.T.; Jarboe, T.R.; Hill, D.N.; Woodruff, S.; Wood, R.D.
2006-01-01
The Sustained Spheromak Physics Experiment (SSPX) [E. B. Hooper, L. D. Pearlstein, and R. H. Bulmer, Nucl. Fusion 39, 863 (1999)] uses a magnetized coaxial gun to form and sustain spheromaks by helicity injection. Internal probes give the magnetic profile within the gun. An analysis of these data show that a number of commonly applied assumptions are not completely correct, and some previously unrecognized processes may be at work. Specifically, the fraction of the available vacuum flux spanning the gun that is stretched out of the gun is variable and not usually 100%. The n=1 mode that is present during sustained discharges has its largest value of δB/B within the gun, so that instantaneously B within the gun is not axisymmetric. By applying a rigid-rotor model to account for the mode, the instantaneous field and current structure within the gun are determined. The current density is also highly nonaxisymmetric and the local value of λ≡μ 0 j parallel /B is not constant, although the global value λ g ≡μ 0 I g /ψ g closely matches that expected by axisymmetric models. The current distribution near the gun muzzle suggests a cross-field current exists, and this is explained as a line-tying reaction to plasma rotation
Local drift parameter, j/n/sub e/ and resistivity anomaly measurements in CTX spheromaks
International Nuclear Information System (INIS)
Hoida, H.W.; Barnes, C.W.; Henins, I.; Jarboe, T.R.; Marklin, G.; Buchenauer, C.J.; Knox, S.O.
1985-01-01
In a spheromak, the magnetic fields confining the plasma are generated primarily by internal currents rather than external coils. In order to provide information on the possible existence of current-driven microinstabilities, localized measurements of the ratio of the drift velocity of the electrons generating the internal current to their thermal velocity, V/sub d//V/sub th/ proportional to j/n/sub e/√T/sub e/ (known as the drift or streaming parameter), and j/n/sub e/ (proportional to V/sub d/) are needed. These microinstabilities are in some theories associated with an increase in the resistivity anomaly factor (eta/eta/sub Spitzer/). We present results on local measurements (at the magnetic axis) of the values of V/sub d//V/sub th/ and eta/eta/sub Spitzer/ by combining data from the spatially-resolved diagnostics employed on the CTX spheromak experiment, coupled with current density profile information from equilibrium measurements. The values of V/sub d//V/sub th/ and j/n/sub e/ appear to be correlated with local variations in eta/eta/sub Spitzer/, and can be changed by varying the plasma density. Data sets are presented for three values of n/sub e/
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.
Alfven continuum with toroidicity
International Nuclear Information System (INIS)
Riyopoulos, S.; Mahajan, S.M.
1985-06-01
The symmetry property of the MHD wave propagation operator is utilized to express the toroidal eigenmodes as a superposition of the mutually orthogonal cylindrical modes. Because of the degeneracy among cylindrical modes with the same frequency but resonant surfaces of different helicity the toroidal perturbation produces a zeroth order mixing of the above modes. The toroidal eigenmodes of frequency ω 0 2 have multiple resonant surfaces, with each surface shifted relative to its cylindrical position and carrying a multispectral content. Thus a single helicity toroidal antenna of frequency ω 0 couples strongly to all different helicity resonant surfaces with matching local Alfven frequency. Zeroth order coupling between modes in the continuum and global Alfven modes also results from toroidicity and degeneracy. Our perturbation technique is the MHD counterpart of the quantum mechanical methods and is applicable through the entire range of the MHD spectrum
International Nuclear Information System (INIS)
Ikuta, Kazunari; Miyahara, Akira.
1983-06-01
The concept of the limiter-divertor proposed by Mirnov is extended to a toroidal limiter-divertor (which we call moving toroidal limiter) using the stream of ferromagnetic balls coated with a low Z materials such as plastics, graphite and ceramics. An important advantage of the use of the ferromagnetic materials would be possible soft landing of the balls on a catcher, provided that the temperature of the balls is below Curie point. Moreover, moving toroidal limiter would work as a protector of the first wall not only against the vertical movement of plasma ring but also against the violent inward motion driven by major disruption because the orbit of the ball in the case of moving toroidal limiter distributes over the small major radius side of the toroidal plasma. (author)
Samus Toroid Installation Fixture
Energy Technology Data Exchange (ETDEWEB)
Stredde, H.; /Fermilab
1990-06-27
The SAMUS (Small Angle Muon System) toroids have been designed and fabricated in the USSR and delivered to D0 ready for installation into the D0 detector. These toroids will be installed into the aperture of the EF's (End Toroids). The aperture in the EF's is 72-inch vertically and 66-inch horizontally. The Samus toroid is 70-inch vertically by 64-inch horizontally by 66-inch long and weighs approximately 38 tons. The Samus toroid has a 20-inch by 20-inch aperture in the center and it is through this aperture that the lift fixture must fit. The toroid must be 'threaded' through the EF aperture. Further, the Samus toroid coils are wound about the vertical portion of the aperture and thus limit the area where a lift fixture can make contact and not damage the coils. The fixture is designed to lift along a surface adjacent to the coils, but with clearance to the coil and with contact to the upper steel block of the toroid. The lift and installation will be done with the 50 ton crane at DO. The fixture was tested by lifting the Samus Toroid 2-inch off the floor and holding the weight for 10 minutes. Deflection was as predicted by the design calculations. Enclosed are sketches of the fixture and it relation to both Toroids (Samus and EF), along with hand calculations and an Finite Element Analysis. The PEA work was done by Kay Weber of the Accelerator Engineering Department.
Non-inductively driven tokamak plasmas at near-unity βt in the Pegasus toroidal experiment
Reusch, J. A.; Bodner, G. M.; Bongard, M. W.; Burke, M. G.; Fonck, R. J.; Pachicano, J. L.; Perry, J. M.; Pierren, C.; Rhodes, A. T.; Richner, N. J.; Rodriguez Sanchez, C.; Schlossberg, D. J.; Weberski, J. D.
2018-05-01
A major goal of the spherical tokamak (ST) research program is accessing a state of low internal inductance ℓi, high elongation κ, and high toroidal and normalized beta ( βt and βN) without solenoidal current drive. Local helicity injection (LHI) in the Pegasus ST [Garstka et al., Nucl. Fusion 46, S603 (2006)] provides non-solenoidally driven plasmas that exhibit these characteristics. LHI utilizes compact, edge-localized current sources for plasma startup and sustainment. It results in hollow current density profiles with low ℓi. The low aspect ratio ( R0/a ˜1.2 ) of Pegasus allows access to high κ and high normalized plasma currents ( IN=Ip/a BT>14 ). Magnetic reconnection during LHI provides auxiliary ion heating. Together, these features provide access to very high βt plasmas. Equilibrium analyses indicate that βt up to ˜100% is achieved. These high βt discharges disrupt at the ideal no-wall β limit at βN˜7.
Energy Technology Data Exchange (ETDEWEB)
Wang, Feng; Liu, J. Y. [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Fu, G. Y.; Breslau, J. A. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Tritz, Kevin [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218 (United States)
2013-07-15
Plasmas in spherical and conventional tokamaks, with weakly reversed shear q profile and minimum q above but close to unity, are susceptible to an non-resonant (m,n) = (1,1) internal kink mode. This mode can saturate and persist and can induce a (2,1) seed island for Neoclassical Tearing Mode. [Breslau et al. Nucl. Fusion 51, 063027 (2011)]. The mode can also lead to large energetic particle transport and significant broadening of beam-driven current. Motivated by these important effects, we have carried out extensive nonlinear simulations of the mode with finite toroidal rotation using parameters and profiles of an NTSX plasma with a weakly reversed shear profile. The numerical results show that, at the experimental level, plasma rotation has little effect on either equilibrium or linear stability. However, rotation can significantly influence the nonlinear dynamics of the (1,1) mode and the induced (2,1) magnetic island. The simulation results show that a rotating helical equilibrium is formed and maintained in the nonlinear phase at finite plasma rotation. In contrast, for non-rotating cases, the nonlinear evolution exhibits dynamic oscillations between a quasi-2D state and a helical state. Furthermore, the effects of rotation are found to greatly suppress the (2,1) magnetic island even at a low level.
Unstable universal drift eigenmodes in toroidal plasmas
International Nuclear Information System (INIS)
Cheng, C.Z.; Chen, L.
1979-08-01
The eigenmode equation describing ballooning collisionless drift instabilities is analyzed both analytically and numerically. A new branch of eigenmodes, which corresponds to quasi-bound states due to the finite toroidicity, is shown to be destabilized by electron Landau damping for typical Tokamak parameters. This branch cannot be understood by the strong coupling approximation. However, the slab-like (Pearlstein-Berk type) branch is found to remain stable and experience enhanced shear damping due to finite toroidicity
Relaxation phenomena in the high temperature S-1 spheromak
International Nuclear Information System (INIS)
Ono, Y.; Ellis, R.A. Jr.; Janos, A.C.; Levinton, F.M.; Mayo, R.M.; Motley, R.W.; Ueda, Y.; Yamada, M.
1988-06-01
Operation of the S-1 device in a high current density (j/n/sub e/ ≥ 2 /times/ 10 -14 A/center dot/m) regime has created high electron temperature spheromaks (50eV ≤ T/sub e/ ≤ 130eV). The mechanisms and causes of the periodic relaxation events often observed in these hotter spheromak plasmas were made clear. Also, a relationship between the MHD relaxation cycle and confinement characteristics was revealed for the first time. Resistive loss at the outer edge of the plasma causes a departure from the initial force-free minimum-energy Taylor state to a MHD profile unstable to low-n ideal MHD modes; a relaxation event then returns the configuration to nearly a Taylor state. 11 refs., 5 figs
International Nuclear Information System (INIS)
Nishikawa, M.; Narikawa, T.; Iwamoto, M.; Watanabe, K.
1986-01-01
A study of a conceptual design for a ''cassette'' compact toroid reactor has been performed that emphasizes quick replacement handling. The core plasma, spheromak, is ohmically heated in a merging process between the core plasma and the gun-produced spheromak. The quick handling of replacement accomplished by using a functional material, a shape memory alloy (SMA) joint, which is proposed for release from first-wall high neutron loading in a newly devised mechanical and structural method. The SMA joint can be used for connecting or disconnecting the coupling by simply controlling the SMA temperature without the need for a robot system. Effective heat removal from the first wall and thermal and electromagnetic stress in a fusion core with very high heat flux are discussed from an engineering standpoint
Recent results of the RECE-Christa experiment
International Nuclear Information System (INIS)
Taggart, D.; Parker, M.; Hopman, H.; Jayakumar, R.; Fleischmann, H.H.
1983-01-01
This paper is primarily a description of recent experimental studies in the RECE-Christa device on the dynamics and stability characteristics of mixed-CT configurations which are generated by inducing sizable plasma ring currents in field-reversing E-layers. Other potential CT configurations, in particular the Spheromak-type, have been projected theoretically and also observed experimentally to have a strong tendency towards tilt-instability except under certain circumstances which would tend to exclude potentially very interesting reactor designs. Based on the fact that this instability has never been observed in field-reversing large-orbit electron ring experiments (probably due to coupling through the large-orbit particles between the tilt motion and the internal length parameters of the rings), it has been suggested (4) that this problem may be avoided by adding large-orbit particles carrying some of the ring current to the normal Spheromak configuration. Also, recent theoretical analyses using the angular momentum of the fact particles indicate a stabilizing tendency, although we believe this mechanism is resistively unstable. The present experiments are the first to test this situation, with the results indicating good gross stability even in cases with large plasma currents. In addition we report the generation of highly elongated E-layers and preliminary results of trapping experiments in low toroidal (B/sub theta/) fields
Prospects for toroidal fusion reactors
International Nuclear Information System (INIS)
Sheffield, J.; Galambos, J.D.
1994-01-01
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
Theoretical investigation of field-line quality in a driven spheromak
International Nuclear Information System (INIS)
Cohen, R.H.; Cohen, B.I.; Berk, H.L.
2003-01-01
Theoretical studies aimed at predicting and diagnosing field-line quality in a spheromak are described. These include nonlinear 3-D MHD simulations, stability studies, analyses of confinement in spheromaks dominated by either open (stochastic) field lines or approximate flux surfaces, and a theory of fast electrons as a probe of field-line length. (author)
Tearing-mode stability of a forming Spheromak plasma
International Nuclear Information System (INIS)
Heidbrink, W.W.; Jardin, S.C.; Chance, M.S.
1981-10-01
The results of numerical calculations of Δ' for a class of equilibria typical of those encountered during the early formation stage of the S1 Spheromak are presented. The equilibrium plasma is assumed to be cylindrically symmetric and pressureless. It encloses a current carrying perfect conductor (flux core) and is surrounded by a vacuum with zero longitudinal field. Stability boundaries in the space formed by the equilibrium parameters are mapped. The plasma is tearing mode stable provided B/sub z//B/sub theta/ at the flux core is below a certain critical value which depends on the equilibrium parameters. For typical equilibria, this critical value is 0.65
Properties of spheromaks generated by a magnetized coaxial source
International Nuclear Information System (INIS)
Hoida, H.W.; Henins, I.; Jarboe, T.R.; Linford, R.K.; Lipson, J.; Marshall, J.; Platts, D.A.; Sherwood, A.R.; Tuszewski, M.
1981-01-01
In gun-generated spheromaks impurity contamination plays an important role in determining the energy loss. Metallic impurities can be reduced by an appropriate change of source parameters. The reduction of the level of metal impurities results in a spectrum showing a preponderance of oxygen and carbon lines and OIV radiation is observed to increase indicating a warmer plasma. However, the plasma lifetime is not changed. Discharge cleaning techniques appear to be necessary. It is still possible that electron heat conduction during the reconnection processs will be found to be important once the impurities are reduced
Properties of spheromaks generated by a magnetized coaxial source
Energy Technology Data Exchange (ETDEWEB)
Hoida, H.W.; Henins, I.; Jarboe, T.R.; Linford, R.K.; Lipson, J.; Marshall, J.; Platts, D.A.; Sherwood, A.R.; Tuszewski, M.
1981-01-01
In gun-generated spheromaks impurity contamination plays an important role in determining the energy loss. Metallic impurities can be reduced by an appropriate change of source parameters. The reduction of the level of metal impurities results in a spectrum showing a preponderance of oxygen and carbon lines and OIV radiation is observed to increase indicating a warmer plasma. However, the plasma lifetime is not changed. Discharge cleaning techniques appear to be necessary. It is still possible that electron heat conduction during the reconnection processs will be found to be important once the impurities are reduced.
Local carbon diffusion coefficient measurement in the S-1 spheromak
International Nuclear Information System (INIS)
Mayo, R.M.; Levinton, F.M.; Meyerhofer, D.D.; Chu, T.K.; Paul, S.F.; Yamada, M.
1988-10-01
The local carbon diffusion coefficient was measured in the S - 1 spheromak by detecting the radial spread of injected carbon impurity. The radial impurity density profile is determined by the balance of ionization and diffusion. Using measured local electron temperature T/sub e/ and density n/sub e/, the ionization rate is determined from which the particle diffusion coefficient is inferred. The results found in this work are consistent with Bohm diffusion. The absolute magnitude of D/sub /perpendicular// was determined to be (4/approximately/6) /times/ D/sub Bohm/. 25 refs., 13 figs., 2 tabs
Energy Technology Data Exchange (ETDEWEB)
Gerald, Rex E. II; Sanchez, Jairo; Rathke, Jerome W.
2004-08-10
A video toroid cavity imager for in situ measurement of electrochemical properties of an electrolytic material sample includes a cylindrical toroid cavity resonator containing the sample and employs NMR and video imaging for providing high-resolution spectral and visual information of molecular characteristics of the sample on a real-time basis. A large magnetic field is applied to the sample under controlled temperature and pressure conditions to simultaneously provide NMR spectroscopy and video imaging capabilities for investigating electrochemical transformations of materials or the evolution of long-range molecular aggregation during cooling of hydrocarbon melts. The video toroid cavity imager includes a miniature commercial video camera with an adjustable lens, a modified compression coin cell imager with a fiat circular principal detector element, and a sample mounted on a transparent circular glass disk, and provides NMR information as well as a video image of a sample, such as a polymer film, with micrometer resolution.
Recent progress on the HESS experiment
International Nuclear Information System (INIS)
Mayo, R.M.; Barnes, D.C.; Freeman, B.; Henins, I.; Jarboe, T.R.; Platts, D.
1990-01-01
The new objective of the Los Alamos spheromak program is to assess the use of magnetized plasmas as an energy transfer medium to accelerate material objects to hyper-velocities (approx-gt 20 km/s). In meeting this objective, the authors are committed to the subordinate goals of (1) creating high field, long-lived spheromak discharges, (2) examining the technical feasibility of employing High Explosives (HE) to compress seed spheromaks, and (3) investigate the technical requirements involved in forming spheromaks by Mechanical Helicity Injection (HMI) using HE. This paper describes the recent efforts of the CTR-5, M-4, and M-6 groups at Los Alamos in assessing the feasibility of generating magnetic helicity by mechanical means in the High Explosive Spheromak Source (HESS) experiment
International Nuclear Information System (INIS)
Sherwood, A.R.
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)
Toroidal nuclear fusion device
International Nuclear Information System (INIS)
Ito, Yutaka; Kasahara, Tatsuo; Takizawa, Teruhiro.
1975-01-01
Object: To design a device so as to be formed into a large-size and to arrange ports, through which neutral particles enter, in inclined fashion. Structure: Toroidal coils are wound about vacuum vessels which are divided into plural number. In the outer periphery of the vacuum vessels, ports are disposed inclined in the peripheral direction of the vacuum vessels and communicated with the vacuum vessels, and wall surfaces opposed to the ports of the toroidal coils adjacent at least the inclined sides of the ports are inclined substantially simularly to the port wall surfaces. (Kamimura, M.)
International Nuclear Information System (INIS)
Scheffel, J.
1982-04-01
Ideal MHD-equilibria for the toroidal EXTRAP configuration have been computed with an equilibrium code. The free-boundary prob- lem is solved by using the condition that the current density is proportional to r on a flux surface. It is found that the toroidal Z-pinch, initially induced in the central zero-field region of a transverse octupole field, drifts radially outwards producing an inverse -D shaped cross-section. The plasma current of this high- beta equilibrium may be increased if the plasma is pushed back by altering the external confining magnetic field as demonstrated. (Author)
Eigenvalues of relaxed toroidal plasmas of arbitrary sharp edged cross sections. Vol. 2
Energy Technology Data Exchange (ETDEWEB)
Khalil, Sh M [Plasma Physics and Nuclear Fusion Department, Nuclear Research Center, Atomic Energy Authority, Cairo, (Egypt)
1996-03-01
Relaxed (force-free) toroidal plasmas described by the equations cur 1 B={mu}B, and grad {mu}=O (B is the magnetic field) induces interest in nuclear fusion. Its solution is perceived to describe the gross of the reversed field pinch (RFP), spheromak configuration, current limitation in toroidal plasmas, and others. The parameter {mu} plays an important roll in relaxed states. It cannot exceed the smallest eigenvalue {mu} (min), and that for a toroidal discharge there is a maximum toroidal current which is connected to this value. The values of{mu} were calculated numerically, using the methods of collocation points, for toroids of arbitrary aspect ratio {alpha} ({alpha} = R/a, ratio of major/minor radii of tokamak) and arbitrary curved cross-sections (circle, ellipse, cassini, and D-shaped). The aim of present work is to prove the applicability of the numerical methods for calculating the eigenvalues for toroidal plasmas having sharp edged cross sections and arbitrary aspect ratio. The lowest eigenvalue {mu} (min), satisfy the boundary condition {beta} .n = O (or RB. = O) for which the toroidal flux are calculated. These are the zero field eigenvalues of the equation cur 1 b={mu}B. The poloidal magnetic field lines corresponding to different cross sections are shown by plotting the boundary condition B.n=O. The plots showed good fulfillment of the boundary condition along the whole boundaries of different cross sections. Dependence of eigenvalues {mu}a on aspect ratio {alpha} is also obtained. Several runs of the programme with various wave numbers K showed that {mu}a is very insensitive to the choice of K. 8 figs.
Plasma Discharge in Toroidal System
International Nuclear Information System (INIS)
Usada, Widdi; Suryadi; Purwadi, Agus; Kasiyo
1996-01-01
A toroidal discharge apparatus has been made as an initial research in magnetic confinement system. This system consists of a capacitor, a RF source, an igniter system, a primary coil, a torus, and completed by Rogowski probe as a current detector. In this system, the discharge occurs when the minimum voltage is operated at 5 kV. The experiment result shows that the coupling factor is 0.35, it is proved that there is an equality between estimated and measurement results of the primary inductance i.e 8.5 μH
Pellet injection and toroidal confinement
International Nuclear Information System (INIS)
1989-12-01
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
Stability of force-free spheromak plasma in spheroidal flux conserver
International Nuclear Information System (INIS)
Kaneko, Shobu; Tsutsui, Hiroaki
1988-01-01
The Woltjer-Taylor method is applied to spheromak plasmas in spheroidal flux conservers. As models of the flux conserver, both oblate and prolate spheroidal vessels with a center conductor are used. The plasma is not assumed to be nearly spherical, and the Rayleigh-Ritz method and the finite element method are used to evaluate the eigenvalues. The oblate spheromak is shown to be stable irrespective of the shape of the flux conserver. Though the prolate spheromak is unstable if there is no center conductor, it can be stable if the center conductor is installed. (author)
Stability of spheroidal spheromak plasma by use of force-free approximation
International Nuclear Information System (INIS)
Kaneko, Shobu; Tsutsui, Hiroaki.
1987-09-01
The Woltjer-Taylor method is applied to spheromak plasmas in spheroidal flux conservers. As models of the flux conserver, both oblate and prolate spheroidal vessels with a center conductor are used. The plasma is not assumed to be nearly spherical, and the Rayleigh-Ritz method and the finite element method are used to evaluate the eigenvalues. The oblate spheromak is shown to be stable irrespective of the shape of the flux conserver. Though the prolate spheromak is unstable if there is no center conductor, it can be stable if the center conductor is installed. (author)
2-D skin-current toroidal-MHD-equilibrium code
International Nuclear Information System (INIS)
Feinberg, B.; Niland, R.A.; Coonrod, J.; Levine, M.A.
1982-09-01
A two-dimensional, toroidal, ideal MHD skin-current equilibrium computer code is described. The code is suitable for interactive implementation on a minicomptuer. Some examples of the use of the code for design and interpretation of toroidal cusp experiments are presented
Toroidal drift magnetic pumping
International Nuclear Information System (INIS)
Canobbio, E.
1977-01-01
A set of azimuthal coils which carry properly dephased rf-currents in the KHz frequency range can be used to heat toroidal plasmas by perpendicular Landau damping of subsonic Alfven waves. The heating mechanism and the rf-field structure are discussed in some detail
Energy Technology Data Exchange (ETDEWEB)
Barbosa, Luis Filipe F.P.W.; Bosco, Edson del
1994-12-31
This report presents the project and analysis of the circuit for production of the toroidal magnetic field in the Tokamak ETE (Spherical Tokamak Experiment). The ETE is a Tokamak with a small-aspect-ratio parameter to be used for studying the plasma physics for the research on thermonuclear fusion. This machine is being constructed at the Laboratorio Associado de Plasma (LAP) of the Instituto Nacional de Pesquisas Espaciais (INPE) in Sao Jose dos Campos, SP, Brazil. (author). 20 refs., 39 figs., 4 tabs.
Femtometer toroidal structures in nuclei
International Nuclear Information System (INIS)
Forest, J.L.; Pandharipande, V.R.; Pieper, S.C.; Wiringa, R.B.; Schiavilla, R.; Arriaga, A.
1996-01-01
The two-nucleon density distributions in states with isospin T=0, spin S=1, and projection M S =0 and ±1 are studied in 2 H, 3,4 He, 6,7 Li, and 16 O. The equidensity surfaces for M S =0 distributions are found to be toroidal in shape, while those of M S =±1 have dumbbell shapes at large density. The dumbbell shapes are generated by rotating tori. The toroidal shapes indicate that the tensor correlations have near maximal strength at r 3 He, 4 He, and 6 Li. The toroidal distribution has a maximum-density diameter of ∼1 fm and a half-maximum density thickness of ∼0.9 fm. Many realistic models of nuclear forces predict these values, which are supported by the observed electromagnetic form factors of the deuteron, and also predicted by classical Skyrme effective Lagrangians, related to QCD in the limit of infinite colors. Due to the rather small size of this structure, it could have a revealing relation to certain aspects of QCD. Experiments to probe this structure and its effects in nuclei are suggested. Pair distribution functions in other T,S channels are also discussed; those in T,S=1,1 have anisotropies expected from one-pion-exchange interactions. The tensor correlations in T,S=0,1 states are found to deplete the number of T,S=1,0 pairs in nuclei and cause a reduction in nuclear binding energies via many-body effects. copyright 1996 The American Physical Society
Toroidal mode-conversion in the ICRF
International Nuclear Information System (INIS)
Jaun, A.; Hellsten, T.; Chiu, S.C.
1997-08-01
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
Design of the TPX outboard toroidal limiters
International Nuclear Information System (INIS)
Schaubel, K.M.; Anderson, P.M.; Baxi, C.B.
1995-01-01
The Tokamak Physics Experiment outboard limiter system incorporates the passive stabilizer plates, the ripple armor, the toroidal break and the support structures. These components are designed to withstand substantial steady state heat loads and high mechanical forces caused by plasma disruptions. The design of these components has been developed to deal with the challenging thermal, structural and remote handling requirements
International Nuclear Information System (INIS)
Takizawa, Teruhiro; Shizuoka, Yoshihide.
1982-01-01
Purpose: To reduce the shielding capacity of a current breaker for a current transformer coil and to facilitate the manufacture and the assembly of the current transformer coil. Constitution: A first current transformer coil is provided between a vacuum container for enclosing a plasma and a toroidal magnetic field coil, and a secon current transformer coil is provided outside the toroidal magnetic field coil. The rise of the plasma current is performed by the variation in the current of the coil of the first transformer having high electromagnetic coupling with the plasma current, and the variation in the magnetic flux necessary for maintaining the plasma is performed by the variation in the current of the second transformer coil. In this manner, the current shielding capacity of the first transformer coil can be reduced to decrease the number of coil turns, thereby facilitating the manufacture and assembly. (Seki, T.)
International Nuclear Information System (INIS)
Canobbio, E.
1981-01-01
This paper reports on the 2nd Joint Grenoble-Varenna International Symposium on Heating in Toroidal Plasmas, held at Como, Italy, from the 3-12 September 1980. Important problems in relation to the different existing processes of heating. The plasma were identified and discussed. Among others, the main processes discussed were: a) neutral beam heating, b) ion-(electron)-cyclotron resonance heating, c) hybrid resonance and low frequency heating
BPX toroidal field coil design
International Nuclear Information System (INIS)
Heitzenvoeder, D.J.
1992-01-01
This paper reports on the toroidal field (TF) coil system of the Burning Plasma Experiment (BPX) which consists of (18) beryllium copper magnets arrayed in a wedged configuration with a major radius of 2.6 meters and a field strength capability on axis of 9.0 Tesla. The toroidal array is constructed from six (3)-coil modules to facilitate remote recovery in the event of a magnet failure after nuclear activation precludes hands-on servicing. The magnets are of a modified Bitter plate design with partial cases of type 316-LN stainless steel welded with Inconel 182 weld wire. The coil turn plates are fabricated from CDA C17510 beryllium copper with optimized mechanical, thermal, and electrical characteristics. joints within the turns and between turns are made by welding with C17200 filler wire. Cryogenic cooling is employed to reduce power dissipation and to enhance performance. The magnets are cooled between experimental pulses by pressurized liquid nitrogen flowing through channels in the edges of the coil turns. This arrangement makes possible one full-power pulse per hour. Electrical insulation consists of polyimide-glass sheets bonded in place with vacuum-pressure impregnated epoxy/glass
Tokamak with liquid metal toroidal field coil
International Nuclear Information System (INIS)
Ohkawa, T.; Schaffer, M.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
0-D study of the compression of low temperature spheromaks
International Nuclear Information System (INIS)
Meyerhofer, D.D.; Hulse, R.A.; Zweibel, E.G.
1985-09-01
Compression of low temperature spheromak plasmas has been studied with the aid of a O-D two-fluid computer code. It is found that in a plasma which is radiation dominated, the electron temperature can be increased by up to a factor of seven for a compression of a factor of two, provided the temperature is above some critical value (approx.25eV) and the electron density particle confinement time product n/sub e/tau/sub p/ greater than or equal to 1 x 10 9 s/cm 3 . If the energy balance is dominated by particle confinement losses rather than radiation losses, the effect of compression is to raise the temperature as T/sub e/ approx.C/sup 6/5/, for constant tau/sub p/
Selective decay in a helicity-injected spheromak
International Nuclear Information System (INIS)
MartInez, P L Garcia; Farengo, R
2009-01-01
The non-linear evolution of several unstable equilibria, representative of helicity-injected spheromak configurations inside a cylindrical flux conserver, is studied by means of three dimensional resistive MHD simulations. These equilibria are force-free (∇ x B = λ(ψ)B) but do not correspond to minimum energy states, having linear λ(ψ) profiles with negative slope. Several aspects of this process are studied (magnetic energy relaxation, selective helicity decay, relaxed profiles) for different initial A slopes. The stability threshold predicted by linear theory is recovered. The results show that complete plasma relaxation leading to a uniform A, is achieved only if the initial profile is hollow enough. The evolution for cases just above the stability threshold is more gentle and does not end in a Taylor state. The final state in these cases has a linear λ(ψ) profile, as the initial condition, but with a smaller slope.
Confinement and power balance in the S-1 spheromak
Energy Technology Data Exchange (ETDEWEB)
Levinton, F.M.; Meyerhofer, D.D.; Mayo, R.M.; Janos, A.C.; Ono, Y.; Ueda, Y.; Yamada, M.
1989-07-01
The confinement and scaling features of the S-1 spheromak have been investigated using magnetic, spectroscopic, and Thomson scattering data in conjunction with numerical modeling. Results from the multipoint Thomson scattering diagnostic shows that the central beta remains constant (/beta//sub to/ /approximately/ 5%) as the plasma current density increases from 0.68--2.1 MA/m/sup 2/. The density is observed to increase slowly over this range, while the central electron temperature increases much more rapidly. Analysis of the global plasma parameters shows a decrease in the volume average beta and energy confinement as the total current is increased. The power balance has been modeled numerically with a 0-D non-equilibrium time-dependent coronal model and is consistent with the experimental observations. 20 refs., 12 figs., 2 tabs.
Confinement and power balance in the S-1 spheromak
International Nuclear Information System (INIS)
Levinton, F.M.; Meyerhofer, D.D.; Mayo, R.M.; Janos, A.C.; Ono, Y.; Ueda, Y.; Yamada, M.; Rochester Univ., NY; Los Alamos National Lab., NM; Princeton Univ., NJ
1989-07-01
The confinement and scaling features of the S-1 spheromak have been investigated using magnetic, spectroscopic, and Thomson scattering data in conjunction with numerical modeling. Results from the multipoint Thomson scattering diagnostic shows that the central beta remains constant (β to ∼ 5%) as the plasma current density increases from 0.68--2.1 MA/m 2 . The density is observed to increase slowly over this range, while the central electron temperature increases much more rapidly. Analysis of the global plasma parameters shows a decrease in the volume average beta and energy confinement as the total current is increased. The power balance has been modeled numerically with a 0-D non-equilibrium time-dependent coronal model and is consistent with the experimental observations. 20 refs., 12 figs., 2 tabs
Formation of a compact toroid for enhanced efficiency
Energy Technology Data Exchange (ETDEWEB)
Mozgovoy, A. G. [P.N. Lebedev Physical Institute, Moscow 119991 (Russian Federation); Romadanov, I. V.; Ryzhkov, S. V., E-mail: ryzhkov@power.bmstu.ru [Bauman Moscow State Technical University, Moscow 105005 (Russian Federation)
2014-02-15
We report here our results on the formation of a plasma configuration with the generic name of compact toroid (CT). A method of compact toroid formation to confine, heat and compress a plasma is investigated. Formation of a compact torus using an additional toroidal magnetic field helps to increase the plasma current to a maintainable level of the original magnetic field. We design the Compact Toroid Challenge (CTC) experiment in order to improve the magnetic flux trapping during field reversal in the formation of a compact toroid. The level of the magnetic field immersed in the plasma about 70% of the primary field is achieved. The CTC device and scheme of high level capturing of magnetic flux are presented.
Mechanical Commissioning of the ATLAS Barrel Toroid Magnet
Foussat, A; Dudarev, A; Bajas, H; Védrine, P; Berriaud, C; Sun, Z; Sorbi, M
2008-01-01
ATLAS is a general-purpose detector designed to run at the highest luminosity at the CERN Large Hadron Collider. Its features include the 4 T Barrel Toroid magnet, the largest superconducting magnet (25 m long, 20 m diameter) that provides the magnetic field for the ATLAS muon spectrometer. The coils integrated at CERN, were tested individually at maximum current of 22 kA in 2005. Following the mechanical assembly of the Barrel Toroid in the ATLAS underground cavern, the test of the full Barrel Toroid was performed in October 2006. Further tests are foreseen at the end 2007 when the system will include the two End Cap Toroids (ECT). The paper gives an overview of the good mechanical test results achieved in comparison with model predictions and the experience gained in the mechanical behavior of the ATLAS Toroidal coils is discussed.
Supporting device for Toroidal coils
International Nuclear Information System (INIS)
Araki, Takao.
1985-01-01
Purpose: To reduce the response of a toroidal coil supporting device upon earthquakes and improve the earthquake proofness in a tokamak type thermonuclear device. Constitution: Structural materials having large longitudinal modulus and enduring great stresses, for example, stainless steels are used as the toroidal coil supporting legs and heat insulating structural materials are embedded in a nuclear reactor base mats below the supporting legs. Furthermore, heat insulating concretes are spiked around the heat insulating structural materials to prevent the intrusion of heat to the toroidal coils. The toroidal coils are kept at cryogenic state and superconductive state for the conductors. In this way, the period of proper vibrations of the toroidal coils and the toroidal coil supporting structures can be shortened thereby decreasing the seismic response. Furthermore, since the strength of the supporting legs is increased, the earthquake proofness of the coils can be improved. (Kamimura, M.)
Energy Technology Data Exchange (ETDEWEB)
Podestà, M.; Gorelenkov, N. N.; White, R. B.; Fredrickson, E. D.; Gerhardt, S. P.; Kramer, G. J. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
2013-08-15
A second Neutral Beam (NB) injection line is being installed on the NSTX Upgrade device, resulting in six NB sources with different tangency radii that will be available for heating and current drive. This work explores the properties of instabilities in the frequency range of the Toroidal Alfvén Eigenmode (TAE) for NSTX-U scenarios with various NB injection geometries, from more perpendicular to more tangential, and with increased toroidal magnetic field with respect to previous NSTX scenarios. Predictions are based on analysis through the ideal MHD code NOVA-K. For the scenarios considered in this work, modifications of the Alfvén continuum result in a frequency up-shift and a broadening of the radial mode structure. The latter effect may have consequences for fast ion transport and loss. Preliminary stability considerations indicate that TAEs are potentially unstable with ion Landau damping representing the dominant damping mechanism.
Results of subscale MTF compression experiments
Howard, Stephen; Mossman, A.; Donaldson, M.; Fusion Team, General
2016-10-01
In magnetized target fusion (MTF) a magnetized plasma torus is compressed in a time shorter than its own energy confinement time, thereby heating to fusion conditions. Understanding plasma behavior and scaling laws is needed to advance toward a reactor-scale demonstration. General Fusion is conducting a sequence of subscale experiments of compact toroid (CT) plasmas being compressed by chemically driven implosion of an aluminum liner, providing data on several key questions. CT plasmas are formed by a coaxial Marshall gun, with magnetic fields supported by internal plasma currents and eddy currents in the wall. Configurations that have been compressed so far include decaying and sustained spheromaks and an ST that is formed into a pre-existing toroidal field. Diagnostics measure B, ne, visible and x-ray emission, Ti and Te. Before compression the CT has an energy of 10kJ magnetic, 1 kJ thermal, with Te of 100 - 200 eV, ne 5x1020 m-3. Plasma was stable during a compression factor R0/R >3 on best shots. A reactor scale demonstration would require 10x higher initial B and ne but similar Te. Liner improvements have minimized ripple, tearing and ejection of micro-debris. Plasma facing surfaces have included plasma-sprayed tungsten, bare Cu and Al, and gettering with Ti and Li.
Toroidal rotation studies in KSTAR
Lee, S. G.; Lee, H. H.; Yoo, J. W.; Kim, Y. S.; Ko, W. H.; Terzolo, L.; Bitter, M.; Hill, K.; KSTAR Team
2014-10-01
Investigation of the toroidal rotation is one of the most important topics for the magnetically confined fusion plasma researches since it is essential for the stabilization of resistive wall modes and its shear plays an important role to improve plasma confinement by suppressing turbulent transport. The most advantage of KSTAR tokamak for toroidal rotation studies is that it equips two main diagnostics including the high-resolution X-ray imaging crystal spectrometer (XICS) and charge exchange spectroscopy (CES). Simultaneous core toroidal rotation and ion temperature measurements of different impurity species from the XICS and CES have shown in reasonable agreement with various plasma discharges in KSTAR. It has been observed that the toroidal rotation in KSTAR is faster than that of other tokamak devices with similar machine size and momentum input. This may due to an intrinsically low toroidal field ripple and error field of the KSTAR device. A strong braking of the toroidal rotation by the n = 1 non-resonant magnetic perturbations (NRMPs) also indicates these low toroidal field ripple and error field. Recently, it has been found that n = 2 NRMPs can also damp the toroidal rotation in KSTAR. The detail toroidal rotation studies will be presented. Work supported by the Korea Ministry of Science, ICT and Future Planning under the KSTAR project.
Neoclassical transport in toroidal systems
International Nuclear Information System (INIS)
Wobig, H.
1992-01-01
The neoclassical theory of general toroidal equilibria is reformulated. The toroidal equilibrium of tokamaks and stellarators are described in Hamada coordinates. The relevant geometrical parameters are identified and it is shown how the reduction of Pfirsch-Schluter currents affects neoclassical transport and bootstrap effects. General flux-friction relations between thermodynamic forces and fluxes are derived. In drift-kinetic approximation the neoclassical transport coefficients are Onsager symmetric. Since a toroidal loop voltage is included, the theory is valid for all toroidal systems. (Author)
Current drive by neutral beams, rotating magnetic fields and helicity injection in compact toroids
International Nuclear Information System (INIS)
Farengo, R.
2002-01-01
A Monte-Carlo code is used to study neutral beam current drive in Spheromaks. The exact particle trajectories are followed in the self-consistent equilibria calculated including the beam current. Reducing Z(eff) does not increase the current drive efficiency because the reduction of the stopping cross section is compensated by an increase in the electron canceling current. Significant changes in the safety factor profile can be produced with relatively low beam currents. Minimum dissipation states of a flux core spheromak sustained by helicity injection are presented. Helicity balance is used as a constraint and the resistivity is considered to be non-uniform. Two types of relaxed states are found; one has a central core of open flux surrounded by a toroidal region of closed flux surfaces and the other has the open flux wrapped around the closed flux surfaces. Non-uniform resistivity effects can be very important due to the changes they produce in the safety factor profile. A hybrid, fluid electrons particle ions, code is employed to study ion dynamics in FRCs sustained by rotating magnetic fields. (author)
NCSX Toroidal Field Coil Design
International Nuclear Information System (INIS)
Kalish M; Rushinski J; Myatt L; Brooks A; Dahlgren F; Chrzanowski J; Reiersen W; Freudenberg K.
2005-01-01
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
Toroidal simulation magnet tests
International Nuclear Information System (INIS)
Walstrom, P.L.; Domm, T.C.
1975-01-01
A number of different schemes for testing superconducting coils in a simulated tokamak environment are analyzed for their merits relative to a set of test criteria. Two of the concepts are examined in more detail: the so-called cluster test scheme, which employs two large background field coils, one on either side of the test coil, and the compact torus, a low-aspect ratio toroidal array of a small number of coils in which all of the coils are essentially test coils. Simulation of the pulsed fields of the tokamak is discussed briefly
Trapped ion mode in toroidally rotating plasmas
International Nuclear Information System (INIS)
Artun, M.; Tang, W.M.; Rewoldt, G.
1995-04-01
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 k τ ρ bi much-lt 1, where ρ bi 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
MHD simulation study of compact toroid injection into magnetized plasmas
International Nuclear Information System (INIS)
Suzuki, Yoshio; Kishimoto, Yasuaki
2000-01-01
To understand the fuelling process in a fusion device by a compact toroid (CT) plasmoid injection method, we have carried out MHD numerical simulations where a spheromak-like CT (SCT) is injected into a magnetized target plasma region. So far, we revealed that the penetration depth of the SCT plasma becomes shorter than that estimated from the conducting sphere (CS) model, because in the simulation the Lorentz force of the target magnetic field sequentially decelerates the injected SCT while in the CS model only the magnetic pressure force acts as the deceleration mechanism. In this study, we represent the new theoretical model where the injected SCT is decelerated by both the magnetic pressure force and the magnetic tension force (we call it the non-slipping sphere (NS) model) and investigate in detail the deceleration mechanism of the SCT by comparison with simulation results. As a result, it is found that the decrease of the SCT kinetic energy in the simulation coincides with that in the NS model more than in the CS model. It means that not only the magnetic pressure force but also the magnetic tension force acts as the deceleration mechanism of the SCT. Furthermore, it is revealed that magnetic reconnection between the SCT magnetic field and the target magnetic field plays a role to relax the SCT deceleration. (author)
Advanced Toroidal Facility (ATF)
International Nuclear Information System (INIS)
Thompson, P.B.
1985-01-01
The Advanced Toroidal Facility (ATF) is a new magnetic plasma confinement device, under construction at Oak Ridge National Laboratory (ORNL), which will lead to improvements in toroidal magnetic fusion reactors. ATF is a type of stellarator known as a torsatron which theoretically has the capability at greater than or equal to8% beta in steady state. The ATF plasma has a major radius of 2.1 m, an average minor radius of 0.3 m, and a field of 2 T for a 5-s duration or 1 T steady state. The ATF device consists of a helical field (HF) coil set, a set of poloidal field (PF) coils, an exterior shell structure to support the coils, and a thin helically contoured vacuum vessel inside the coils. The ATF replaces the ISX-B tokamak at ORNL and will use the ISX-B auxiliary systems including 4 MW of neutral injection heating and 0.2 MW of electron cyclotron heating. ATF device is scheduled to start operation in the fall of 1986. An overview of the ATF device is presented including details of the construction process envisioned
Quantum mechanics of toroidal anions
International Nuclear Information System (INIS)
Afanas'ev, G.N.
1990-01-01
We consider a toroidal solenoid with an electric charge attached to it. It turns out that statistical properties of the wave function describing interacting toroidal anions depend on both their relative position and orientation. The influence of the particular gauge choice on the exchange properties of the wave function is studied. 30 refs.; 6 figs
Device for supporting a toroidal coil in a toroidal type nuclear fusion device
International Nuclear Information System (INIS)
Kitazawa, Hakaru; Sato, Hiroshi.
1975-01-01
Object: To easily manufacture a center block having a strength sufficient to withstand an electromagnetic force exerted on the center of toroidal of a toroidal coil and to increase its reliability. Structure: In a device for supporting toroidal coils wherein the electromagnetic force exerted on the center of toroidal of a plurality of toroidal coils arranged in toroidal fashion, the contact surface between the toroidal coil and the center block is arranged parallel to the center axis of toroidal so as to receive the electromagnetic force exerted on the center of toroidal of the toroidal coil as the component of force in a radial direction. (Taniai, N.)
Theoretical aspects of the use of pulsed reflectometry in a spheromak plasma
Energy Technology Data Exchange (ETDEWEB)
Cohen, B. J., LLNL
1998-06-11
Pulsed reflectometry using both ordinary (O) and extraordinary (X) modes has the potential of providing time and space-resolved measurements of the electron density, the magnitude of the magnetic field, and the magnetic shear as a function of radius. Such a diagnostic also yields the current profile from the curl of the magnetic field. This research addresses theoretical issues associated with the use of reflectometry in the SSPX spheromak experiment at the Lawrence Livermore National Laboratory. We have extended a reflectometry simulation model to accommodate O and X-mode mixed polarization and linear mode conversion between the two polarizations. A Wentzel-Kramers-Brillouin-Jeffreys (WKBJ) formula for linear mode conversion agrees reasonably well with direct numerical solutions of the wave equation, and we have reconstructed the magnetic pitch-angle profile by matching the results of the WKBJ formula with the mode conversion data observed in simulations using a least-squares determination of coefficients in trial functions for the profile. The reflectometry data also yield information on fluctuations. Instrumental issues, e.g., the effects of microwave mixers and filters on model reflectometry pulses, have been examined to optimize the performance of the reflectometry diagnostics.
Commissioning Test of ATLAS End-Cap Toroidal Magnets
Dudarev, A; Foussat, A; Benoit, P; Jeckel, M; Olyunin, A; Kopeykin, N; Stepanov, V; Deront, L; Olesen, G; Ponts, X; Ravat, S; Sbrissa, K; Barth, J; Bremer, J; Delruelle, J; Metselaar, J; Pengo, R; Pirotte, O; Buskop, J; Baynham, D E; Carr, F S; Holtom, E
2009-01-01
The system of superconducting toroids in the ATLAS experiment at CERN consists of three magnets. The Barrel Toroid was assembled and successfully tested in 2006. Next, two End-Cap Toroids have been tested on surface at 77 K and installed in the cavern, 100-m underground. The End Cap Toroids are based on Al stabilized Nb-Ti/Cu Rutherford cables, arranged in double pancake coils and conduction cooled at 4.6 K. The nominal current is 20.5 kA at 4.1 T peak field in the windings and the stored energy is 250 MJ per toroid. Prior to final testing of the entire ATLAS Toroidal system, each End Cap Toroid passed a commissioning test up to 21 kA to guarantee a reliable performance in the final assembly. In this paper the test results are described. It includes the stages of test preparation, isolation vacuum pumping and leak testing, cooling down, step-by-step charging to full current, training quenches and quench recovery. By fast discharges the quench detection and protection system was checked to demonstrate a safe e...
Unstable universal drift eigenmodes in toroidal plasmas
International Nuclear Information System (INIS)
Cheng, C.Z.; Chen, L.
1980-01-01
The eigenmode equation describing ballooning collisionless drift instabilities is analyzed both analytically and numerically. A new branch of eigenmodes, which corresponds to quasi-bound states due to toroidal coupling effects such as ion delB drifts, is shown to be destabilized by electron Landau damping for typical tokamak parameters. This branch cannot be understood by the strong coupling approximation. However, the slab-like (Pearlstein--Berk-type) branch is found to remain stable and experience enhanced shear damping
The spheromak as a prototype for ultra-high-field superconducting magnets
International Nuclear Information System (INIS)
Furth, H.P.; Jardin, S.C.
1987-08-01
In view of current progress in the development of superconductor materials, the ultimate high-field limit of superconducting magnets is likely to be set by mechanical stress problems. Maximum field strength should be attainable by means of approximately force-free magnet windings having favorable ''MHD'' stability properties (so that small winding errors will not grow). Since a low-beta finite-flux-hole spheromak configuration qualifies as a suitable prototype, the theoretical and experimental spheromak research effort of the past decade has served to create a substantial technical basis for the design of ultra-high-field superconducting coils. 11 refs
Confinement requirements for OHMIC-compressive ignition of a Spheromak plasma
International Nuclear Information System (INIS)
Olson, R.; Gilligan, J.; Miley, G.
1980-01-01
The Moving Plasmoid Reactor (MPR) is an attractive alternative magnetic fusion scheme in which Spheromak plasmoids are envisioned to be formed, compressed, burned, and expanded as the plasmoids translate through a series of linear reactor modules. Although auxiliary heating of the plasmoids may be possible, the MPR scenario would be especially interesting if ohmic decay and compression along were sufficient to heat the plasmoids to an ignition temperature. In the present work, we will study the transport conditions under which a Spheromak plasmoid could be expected to reach ignition via a combination of ohmic and compression heating
Confinement requirements for ohmic-compressive ignition of a Spheromak plasma
International Nuclear Information System (INIS)
Olson, R.E.; Miley, G.H.
1981-01-01
The Moving Plasmoid Reactor (MPR) is an attractive alternative magnetic fusion scheme in which Spheromak plasmoids are envisioned to be formed, compressed, burned, and expanded as the plasmoids translate through a series of linear reactor modules. Although auxiliary heating of the plasmoids may be possible, the MPR scenario would be especially interesting if ohmic decay and compression alone is sufficient to heat the plasmoids to an ignition temperature. In the present work, we examine the transport conditions under which a Spheromak plasmoid can be expected to reach ignition via a combination of ohmic and compression heating
Confinement time exceeding one second for a toroidal electron plasma.
Marler, J P; Stoneking, M R
2008-04-18
Nearly steady-state electron plasmas are trapped in a toroidal magnetic field for the first time. We report the first results from a new toroidal electron plasma experiment, the Lawrence Non-neutral Torus II, in which electron densities on the order of 10(7) cm(-3) are trapped in a 270-degree toroidal arc (670 G toroidal magnetic field) by application of trapping potentials to segments of a conducting shell. The total charge inferred from measurements of the frequency of the m=1 diocotron mode is observed to decay on a 3 s time scale, a time scale that approaches the predicted limit due to magnetic pumping transport. Three seconds represents approximately equal to 10(5) periods of the lowest frequency plasma mode, indicating that nearly steady-state conditions are achieved.
Toroidal charge exchange recombination spectroscopy on EAST
Energy Technology Data Exchange (ETDEWEB)
Ye, Minyou, E-mail: yemy@ustc.edu.cn [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026 (China); Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Li, Yingying [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Yu, Yi [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026 (China); Shi, Yuejiang [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026 (China); WCI for Fusion Theory, National Fusion Research Institute, 52 Eoeun-Dong, Yusung-Gu, Daejeon 305-333 (Korea, Republic of); Lyu, Bo; Fu, Jia [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); Du, Xuewei; Yin, Xianghui; Zhang, Yi; Wang, Qiuping [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026 (China); Wan, Baonian [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei, Anhui 230031 (China); School of Nuclear Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026 (China)
2015-10-15
A toroidal charge exchange recombination spectroscopy (CXRS) diagnostic, on the basis of a heating neutral beam injector (NBI), is constructed on EAST tokamak. Simulation of Spectra (SOS) code is used to design and evaluate the diagnostic performance. 30 spatial channels work simultaneously in recent experiment, which covers a radial region from 1.55 m to 2.30 m in the cross section. The CXRS has a radial resolution of 1–3.5 cm from core to edge. The acquisition time is typically 10 ms, limited by the poor photon statistics. The diagnostic can observe not only the normal C{sup 5+} emission line at 529.1 nm but also any interested wavelength in the range of 400–700 nm. In this work, a brief overview on the R&D and the instrument performance for the toroidal CXRS diagnostic is described, together with first results.
An important step for the ATLAS toroid magnet
2000-01-01
The ATLAS experiment's prototype toroid coil arrives at CERN from the CEA laboratory in Saclay on 6 October. The world's largest superconducting toroid magnet is under construction for the ATLAS experiment. A nine-metre long fully functional prototype coil was delivered to CERN at the beginning of October and has since been undergoing tests in the West Area. Built mainly by companies in France and Italy under the supervision of engineers from the CEA-Saclay laboratory near Paris and Italy's INFN-LASA, the magnet is a crucial step forward in the construction of the ATLAS superconducting magnet system. Unlike any particle detector that has gone before, the ATLAS detector's magnet system consists of a large toroidal system enclosing a small central solenoid. The barrel part of the toroidal system will use eight toroid coils, each a massive 25 metres in length. These will dwarf the largest toroids in the world when ATLAS was designed, which measure about six metres. So the ATLAS collaboration decided to build a...
Grinding Inside A Toroidal Cavity
Mayer, Walter; Adams, James F.; Burley, Richard K.
1987-01-01
Weld lines ground smooth within about 0.001 in. Grinding tool for smoothing longitudinal weld lines inside toroidal cavity includes curved tunnel jig to guide grinding "mouse" along weld line. Curvature of tunnel jig matched to shape of toroid so grinding ball in mouse follows circular arc of correct radius as mouse is pushed along tunnel. Tool enables precise control of grindout shape, yet easy to use.
Equivelar toroids with few flag-orbits
Collins, José; Montero, Antonio
2018-01-01
An $(n+1)$-toroid is a quotient of a tessellation of the $n$-dimensional Euclidean space with a lattice group. Toroids are generalizations of maps in the torus on higher dimensions and also provide examples of abstract polytopes. Equivelar toroids are those that are induced by regular tessellations. In this paper we present a classification of equivelar $(n+1)$-toroids with at most $n$ flag-orbits; in particular, we discuss a classification of $2$-orbit toroids of arbitrary dimension.
Next generation toroidal devices
International Nuclear Information System (INIS)
Yoshikawa, Shoichi
1998-10-01
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)
Next generation toroidal devices
Energy Technology Data Exchange (ETDEWEB)
Yoshikawa, Shoichi [Princeton Plasma Physics Lab., Princeton Univ., NJ (United States)
1998-10-01
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)
Tunable plasmonic toroidal terahertz metamodulator
Gerislioglu, Burak; Ahmadivand, Arash; Pala, Nezih
2018-04-01
Optical modulators are essential and strategic parts of micro- and nanophotonic circuits to encode electro-optical signals in the optical domain. Here, by using arrays of multipixel toroidal plasmonic terahertz (THz) metamolecules, we developed a functional plasmonic metamodulator with high efficiency and tunability. Technically, the dynamic toroidal dipole induces nonradiating charge-current arrangements leading to have an exquisite role in defining the inherent spectral features of various materials. By categorizing in a different family of multipoles far from the traditional electromagnetic multipoles, the toroidal dipole corresponds to poloidal currents flowing on the surface of a closed-loop torus. Utilizing the sensitivity of the optically driven toroidal momentum to the incident THz beam power and by employing both numerical tools and experimental analysis, we systematically studied the spectral response of the proposed THz plasmonic metadevice. In this Rapid Communication, we uncover a correlation between the existence and the excitation of the toroidal response and the incident beam power. This mechanism is employed to develop THz toroidal metamodulators with a strong potential to be employed for practical advanced and next-generation communication, filtering, and routing applications.
International Nuclear Information System (INIS)
Vlases, G.C.; Pietrzyk, Z.A.
1984-11-01
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
Nonlinear saturation of non-resonant internal instabilities in a straight spheromak
International Nuclear Information System (INIS)
Park, W.; Jardin, S.C.
1982-04-01
An initial value numerical solution of the time dependent nonlinear ideal magnetohydrodynamic equations demonstrates that spheromak equilibria which are linearly unstable to nonresonant helical internal perturbations saturate at low amplitude without developing singularities. These instabilities thus represent the transition from an axisymmetric to a non-axisymmetric equilibrium state, caused by a peaking of the current density
Superconducting magnets for toroidal fusion reactors
International Nuclear Information System (INIS)
Haubenreich, P.N.
1980-01-01
Fusion reactors will soon be employing superconducting magnets to confine plasma in which deuterium and tritium (D-T) are fused to produce usable energy. At present there is one small confinement experiment with superconducting toroidal field (TF) coils: Tokamak 7 (T-7), in the USSR, which operates at 4 T. By 1983, six different 2.5 x 3.5-m D-shaped coils from six manufacturers in four countries will be assembled in a toroidal array in the Large Coil Test Facility (LCTF) at Oak Ridge National Laboratory (ORNL) for testing at fields up to 8 T. Soon afterwards ELMO Bumpy Torus (EBT-P) will begin operation at Oak Ridge with superconducting TF coils. At the same time there will be tokamaks with superconducting TF coils 2 to 3 m in diameter in the USSR and France. Toroidal field strength in these machines will range from 6 to 9 T. NbTi and Nb 3 Sn, bath cooling and forced flow, cryostable and metastable - various designs are being tried in this period when this new application of superconductivity is growing and maturing
Investigation of intrinsic toroidal rotation scaling in KSTAR
Yoo, J. W.; Lee, S. G.; Ko, S. H.; Seol, J.; Lee, H. H.; Kim, J. H.
2017-07-01
The behaviors of an intrinsic toroidal rotation without any external momentum sources are investigated in KSTAR. In these experiments, pure ohmic discharges with a wide range of plasma parameters are carefully selected and analyzed to speculate an unrevealed origin of toroidal rotation excluding any unnecessary heating sources, magnetic perturbations, and strong magneto-hydrodynamic activities. The measured core toroidal rotation in KSTAR is mostly in the counter-current direction and its magnitude strongly depends on the ion temperature divided by plasma current (Ti/IP). Especially the core toroidal rotation in the steady-state is well fitted by Ti/IP scaling with a slope of ˜-23, and the possible explanation of the scaling is compared with various candidates. As a result, the calculated offset rotation could not explain the measured core toroidal rotation since KSTAR has an extremely low intrinsic error field. For the stability conditions for ion and electron turbulences, it is hard to determine a dominant turbulence mode in this study. In addition, the intrinsic toroidal rotation level in ITER is estimated based on the KSTAR scaling since the intrinsic rotation plays an important role in stabilizing resistive wall modes for future reference.
Turbulent and neoclassical toroidal momentum transport in tokamak plasmas
International Nuclear Information System (INIS)
Abiteboul, J.
2012-10-01
The goal of magnetic confinement devices such as tokamaks is to produce energy from nuclear fusion reactions in plasmas at low densities and high temperatures. Experimentally, toroidal flows have been found to significantly improve the energy confinement, and therefore the performance of the machine. As extrinsic momentum sources will be limited in future fusion devices such as ITER, an understanding of the physics of toroidal momentum transport and the generation of intrinsic toroidal rotation in tokamaks would be an important step in order to predict the rotation profile in experiments. Among the mechanisms expected to contribute to the generation of toroidal rotation is the transport of momentum by electrostatic turbulence, which governs heat transport in tokamaks. Due to the low collisionality of the plasma, kinetic modeling is mandatory for the study of tokamak turbulence. In principle, this implies the modeling of a six-dimensional distribution function representing the density of particles in position and velocity phase-space, which can be reduced to five dimensions when considering only frequencies below the particle cyclotron frequency. This approximation, relevant for the study of turbulence in tokamaks, leads to the so-called gyrokinetic model and brings the computational cost of the model within the presently available numerical resources. In this work, we study the transport of toroidal momentum in tokamaks in the framework of the gyrokinetic model. First, we show that this reduced model is indeed capable of accurately modeling momentum transport by deriving a local conservation equation of toroidal momentum, and verifying it numerically with the gyrokinetic code GYSELA. Secondly, we show how electrostatic turbulence can break the axisymmetry and generate toroidal rotation, while a strong link between turbulent heat and momentum transport is identified, as both exhibit the same large-scale avalanche-like events. The dynamics of turbulent transport are
Tearing modes in toroidal geometry
International Nuclear Information System (INIS)
Connor, J.W.; Cowley, S.C.; Hastie, R.J.; Hender, T.C.; Hood, A.; Martin, T.J.
1988-01-01
The separation of the cylindrical tearing mode stability problem into a resistive resonant layer calculation and an external marginal ideal magnetohydrodynamic (MHD) calculation (Δ' calculation) is generalized to axisymmetric toroidal geometry. The general structure of this separation is analyzed and the marginal ideal MHD information (the toroidal generalization of Δ') required to discuss stability is isolated. This can then, in principle, be combined with relevant resonant layer calculations to determine tearing mode growth rates in realistic situations. Two examples are given: the first is an analytic treatment of toroidally coupled (m = 1, n = 1) and (m = 2, n = 1) tearing modes in a large aspect ratio torus; the second, a numerical treatment of the toroidal coupling of three tearing modes through finite pressure effects in a large aspect ratio torus. In addition, the use of a coupling integral approach for determining the stability of coupled tearing modes is discussed. Finally, the possibility of using initial value resistive MHD codes in realistic toroidal geometry to determine the necessary information from the ideal MHD marginal solution is discussed
High current density toroidal pinch discharges with weak toroidal fields
International Nuclear Information System (INIS)
Brunsell, P.; Brzozowski, J.; Drake, J.R.; Hellblom, G.; Kaellne, E.; Mazur, S.; Nordlund, P.
1990-01-01
Toroidal discharges in the ultralow q regime (ULQ) have been studied in the rebuilt Extrap TI device. ULQ discharges are sustained for pulse lengths exceeding 1 ms, which corresponds to more than 10 resistiv shell times. Values for the safety factor at the vacuum vessel wall are between rational values: 1/(n+1) -2 . The magnetic fluctuation level increases during the transition between rational values of q(a). For very low values of q(a), the loop voltage increases and the toroidal field development in the discharge exhibits the characteristic behaviour of the setting-up phase of a field reversed pinch. (author) 1 ref., 2 figs., 1 tab
Toroidal Trivelpiece-Gould modes
International Nuclear Information System (INIS)
Stoessel, F.P.
1979-01-01
Electron plasma waves are treated in quasi-electrostatic approximation in a toroidal cavity of rectangular cross-section in an infinitely strong azimuthal magnetic field. The differential equation for the electrostatic potential, derived from fluid equations, can be separated using cylindrical coordinates. The eigenvalue problem for the radial dependence is solved numerically by a shooting method. Eigenvalues are given for different aspect ratios. Comparison with appropriate modes of the straight geometry shows that the toroidal frequencies generally lie some percent above those for the straight case. Plots of the eigenfunctions demonstrate clearly the influence of toroidicity. The deviation from symmetry (which should appear for straight geometry) depends not only on the aspect ratio but also strongly on the mode numbers. (author)
Toroidal helical quartz forming machine
International Nuclear Information System (INIS)
Hanks, K.W.; Cole, T.R.
1977-01-01
The Scyllac fusion experimental machine used 10 cm diameter smooth bore discharge tubes formed into a simple toroidal shape prior to 1974. At about that time, it was discovered that a discharge tube was required to follow the convoluted shape of the load coil. A machine was designed and built to form a fused quartz tube with a toroidal shape. The machine will accommodate quartz tubes from 5 cm to 20 cm diameter forming it into a 4 m toroidal radius with a 1 to 5 cm helical displacement. The machine will also generate a helical shape on a linear tube. Two sets of tubes with different helical radii and wavelengths have been successfully fabricated. The problems encountered with the design and fabrication of this machine are discussed
MHD equilibrium with toroidal rotation
International Nuclear Information System (INIS)
Li, J.
1987-03-01
The present work attempts to formulate the equilibrium of axisymmetric plasma with purely toroidal flow within ideal MHD theory. In general, the inertial term Rho(v.Del)v caused by plasma flow is so complicated that the equilibrium equation is completely different from the Grad-Shafranov equation. However, in the case of purely toroidal flow the equilibrium equation can be simplified so that it resembles the Grad-Shafranov equation. Generally one arbitrary two-variable functions and two arbitrary single variable functions, instead of only four single-variable functions, are allowed in the new equilibrium equations. Also, the boundary conditions of the rotating (with purely toroidal fluid flow, static - without any fluid flow) equilibrium are the same as those of the static equilibrium. So numerically one can calculate the rotating equilibrium as a static equilibrium. (author)
Compact toroid refueling of reactors
International Nuclear Information System (INIS)
Gouge, M.J.; Hogan, J.T.; Milora, S.L.; Thomas, C.E.
1988-04-01
The feasibility of refueling fusion reactors and devices such as the International Thermonuclear Engineering Reactor (ITER) with high-velocity compact toroids is investigated. For reactors with reasonable limits on recirculating power, it is concluded that the concept is not economically feasible. For typical ITER designs, the compact toroid fueling requires about 15 MW of electrical power, with about 5 MW of thermal power deposited in the plasma. At these power levels, ideal ignition (Q = ∞) is not possible, even for short-pulse burns. The pulsed power requirements for this technology are substantial. 6 ref., 1 figs
Prandtl number of toroidal plasmas
International Nuclear Information System (INIS)
Itoh, K.; Itoh, S.; Fukuyama, A.; Yagi, M.; Azumi, M.
1993-06-01
Theory of the L-mode confinement in toroidal plasmas is developed. The Prandtl number, the ratio between the ion viscosity and the thermal conductivity is obtained for the anomalous transport process which is caused by the self-sustained turbulence in the toroidal plasma. It is found that the Prandtl number is of order unity both for the ballooning mode turbulence in tokamaks and for the interchange mode turbulence in helical system. The influence on the anomalous transport and fluctuation level is evaluated. Hartmann number and magnetic Prandtl number are also discussed. (author)
General Atomic's superconducting toroidal field coil concept
International Nuclear Information System (INIS)
Alcorn, J.; Purcell, J.
1978-01-01
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)
Computer simulations of compact toroid formation and acceleration
International Nuclear Information System (INIS)
Peterkin, R.E. Jr.; Sovinec, C.R.
1990-01-01
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
Toroidal current asymmetry in tokamak disruptions
Strauss, H. R.
2014-10-01
It was discovered on JET that disruptions were accompanied by toroidal asymmetry of the toroidal plasma current I ϕ. It was found that the toroidal current asymmetry was proportional to the vertical current moment asymmetry with positive sign for an upward vertical displacement event (VDE) and negative sign for a downward VDE. It was observed that greater displacement leads to greater measured I ϕ asymmetry. Here, it is shown that this is essentially a kinematic effect produced by a VDE interacting with three dimensional MHD perturbations. The relation of toroidal current asymmetry and vertical current moment is calculated analytically and is verified by numerical simulations. It is shown analytically that the toroidal variation of the toroidal plasma current is accompanied by an equal and opposite variation of the toroidal current flowing in a thin wall surrounding the plasma. These currents are connected by 3D halo current, which is π/2 radians out of phase with the n = 1 toroidal current variations.
Engineering design of the FRX-C experiment
International Nuclear Information System (INIS)
Kewish, R.W. Jr.; Bartsch, R.R.; Siemon, R.E.
1981-01-01
Research on Compact Toroid (CT) configurations has been greatly accelerated in the last few years because of their potential for providing a practical and economical fusion system. Los Alamos research is being concentrated on two types of configurations: (1) magnetized-gun-produced Spheromaks (configurations that contain a mixture of toroidal and poloidal fields); and (2) field-reversed configurations (FRCs) that contain purely poloidal magnetic field. This paper describes the design of FRX-C, a field-reversed theta pinch used to form FRCs
X-ray imaging with toroidal mirror
International Nuclear Information System (INIS)
Aoki, Sadao; Sakayanagi, Yoshimi
1978-01-01
X-ray imaging is made with a single toroidal mirror or two successive toroidal mirrors. Geometrical images at the Gaussian image plane are described by the ray trace. Application of a single toroidal mirror to small-angle scattering is presented. (author)
The Plasmoid Thruster Experiment (PTX)
Eskridge, Richard; Martin, Adam; Koelfgen, Syri; Lee, Mike; Smith, James W.
2003-01-01
A plasmoid is a compact plasma structure with an integral magnetic field. They have been studied extensively in controlled fusion research and are categorized according to the relative strength of the poloidal and toroidal magnetic field (B(phi), and B(tau), respectively). An object with B(phi)/B(tau) >> 1 is classified as a Field Reverse Configuration (FRC); if B(phi) = B(tau), it is called a Spheromak. There are a number of possible advantages to using accelerated plasmoids for in-space propulsion. A thruster based on this concept would operate by repetitively producing plasmoids and ejecting them from the device at high velocity. The plasmoid is formed inside of a single turn conical theta-pinch coil; as this process is inductive, there are no life-limiting electrodes. Similar experiments have yielded plasmoid velocities of at least 50 km/s (l), and calculations indicate that velocities in excess of 100 km/s are possible. A thruster based on this concept would be capable of producing an I(sp) in the range of 5,000 - 10,OOO s, with thrust densities of order 10(exp 5) N/m(exp 2). The current experiment is designed to produce jet powers in the range of 5-10 kW, although the concept should be scalable to higher power. The purpose of this experiment is to determine the feasibility of this plasma propulsion concept. To accomplish this, it will be necessary to determine: a.) specific impulse and thrust, b.) efficiency and mass utilization, c.) which type of plasmoid (FRC-like or Spheromak-like) gives the best performance, and d.) the characteristics required of actual thruster components (i.e., switch and capacitor technology). The plasmoid mass and velocity will be measured with a variety of diagnostics, including internal and external B-dot probes, flux loops, Langmuir probes, high-speed cameras, and an interferometer. Simulations of the plasmoid thruster using MOQUI, a time dependent MHD code, will be carried out concurrently with experimental testing. The PTX
Onsager relaxation of toroidal plasmas
International Nuclear Information System (INIS)
Samain, A.; Nguyen, F.
1997-01-01
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)
Particle simulations in toroidal geometry
International Nuclear Information System (INIS)
Aydemir, A.Y.
1992-09-01
A computational tool to be used in kinetic simulations of toroidal plasmas is being developed. The initial goal of the project is to develop an electrostatic gyrokinetic model for studying transport and stability problems in tokamaks. In this brief report, preliminary results from the early stages of this effort are presented
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.
Hybrid winding concept for toroids
DEFF Research Database (Denmark)
Schneider, Henrik; Andersen, Thomas; Knott, Arnold
2013-01-01
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...
Collapse analysis of toroidal shell
International Nuclear Information System (INIS)
Pomares, R.J.
1990-01-01
This paper describes a study performed to determine the collapse characteristics of a toroidal shell using finite element method (FEM) analysis. The study also included free drop testing of a quarter scale prototype to verify the analytical results. The full sized toroidal shell has a 24-inch toroidal diameter with a 24-inch tubal diameter. The shell material is type 304 strainless steel. The toroidal shell is part of the GE Model 2000 transportation packaging, and acts as an energy absorbing device. The analyses performed were on a full sized and quarter scaled models. The finite element program used in all analyses was the LIBRA code. The analytical procedure used both the elasto-plastic and large displacement options within the code. The loading applied in the analyses corresponded to an impact of an infinite rigid plane oriented normal to the drop direction vector. The application of the loading continued incrementally until the work performed by the deforming structure equalled the kinetic energy developed in the free fall. The comparison of analysis and test results showed a good correlation
Field-Reversed Configuration Formation Scheme Utilizing a Spheromak and Solenoid Induction
International Nuclear Information System (INIS)
Gerhardt, S.P.; Belova, E.V.; Yamada, M.; Ji, H.; Ren, Y.; McGeehan, B.; Inomoto, M.
2008-01-01
A new field-reversed configuration (FRC) formation technique is described, where a spheromak transitions to a FRC with inductive current drive. The transition is accomplished only in argon and krypton plasmas, where low-n kink modes are suppressed; spheromaks with a lighter majority species, such as neon and helium, either display a terminal tilt-mode, or an n=2 kink instability, both resulting in discharge termination. The stability of argon and krypton plasmas through the transition is attributed to the rapid magnetic diffusion of the currents that drive the kink-instability. The decay of helicity during the transition is consistent with that expected from resistivity. This observation indicates a new scheme to form a FRC plasma, provided stability to low-n modes is maintained, as well as a unique situation where the FRC is a preferred state
International Nuclear Information System (INIS)
Meyerhofer, D.D.; Perkins, F.W.
1984-04-01
The kinetic Alfven wave is studied in a cylindrical force-free plasma with self-consistent magnetic fields. This equilibrium represents a reversed field pinch or a spheromak. The stability of the wave is found to depend on the ratio of the electron drift velocity to the Alfven velocity. This ratio varies inversely with the square root of the plasma line density. The critical line density using the Spitzer-Harm electron distribution function is found for reversed field pinches with deuterium plasmas to be approximately 2 x 10 18 m -1 and is 5 x 10 17 m -1 in spheromaks with hydrogen plasmas. The critical line density is in reasonable agreement with experimental data for reversed field pinches
Global magnetic fluctuations in S-1 spheromak plasmas and relaxation toward a minimum-energy state
International Nuclear Information System (INIS)
Janos, A.; Hart, G.W.; Yamada, M.
1986-01-01
Globally coherent modes have been observed during formation in the S-1 Spheromak plasma. These modes play an important role in flux conversion and plasma relaxation toward a minimum-energy state. A significant finding is the temporal progression through the n = 5, 4, 3, 2; m = 1 mode sequence as q rises through rational fractions m/n. Peak amplitudes of the modes relative to the unperturbed field are typically less than 5%, while amplitudes as high as 20% have been observed
Compact toroidal plasmas: Simulations and theory
International Nuclear Information System (INIS)
Harned, D.S.; Hewett, D.W.; Lilliequist, C.G.
1983-01-01
Realistic FRC equilibria are calculated and their stability to the n=1 tilting mode is studied. Excluding kinetic effects, configurations ranging from elliptical to racetrack are unstable. Particle simulations of FRCs show that particle loss on open field lines can cause sufficient plasma rotation to drive the n=2 rotational instability. The allowed frequencies of the shear Alfven wave are calculated for use in heating of spheromaks. An expanded spheromak is introduced and its stability properties are studied. Transport calculations of CTs are described. A power balance model shows that many features of gun-generated CT plasmas can be explained by the dominance of impurity radiation. It is shown how the Taylor relaxation theory, applied to gun-generated CT plasmas, leads to the possibility of steady-state current drive. Lastly, applications of accelerated CTs are considered. (author)
Instantaneous current and field structure of a gun-driven spheromak for two gun polarities
International Nuclear Information System (INIS)
Woodruff, S; Nagata, M
2002-01-01
The instantaneous plasma structure of the SPHEX spheromak is determined here by numerically processing data from insertable Rogowski and magnetic field probes. Data is presented and compared for two modes of gun operation: with the central electrode biased positively and negatively. It is found that while the mean-, or even instantaneous-, field structure would give the impression of a roughly axisymmetric spheromak, the instantaneous current structure does not. Hundred per cent variations in J measured at the magnetic axis can be explained by the rotation of a current filament that has a width equal to half of the radius of the flux-conserving first wall. In positive gun operation, current leaves the filament in the confinement region leading to high wall current there. In negative gun operation, wall current remains low as all injected current returns to the gun through the plasma. The plasma, in either instance, is strongly asymmetric. We discuss evidence for the existence of the current filament in other gun-driven spheromaks and coaxial plasma thrusters
Preparing an ATLAS toroid magnet end-cap for lowering
Claudia Marcelloni
2007-01-01
One of the two 13-m high toroid magnet end-caps for the ATLAS experiment being transported from the construction hall to the experimental area. The end-cap will be lowered into the ATLAS cavern and attached to an end of the detector.
Classification of symmetric toroidal orbifolds
Energy Technology Data Exchange (ETDEWEB)
Fischer, Maximilian; Ratz, Michael; Torrado, Jesus [Technische Univ. Muenchen, Garching (Germany). Physik-Department; Vaudrevange, Patrick K.S. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2012-09-15
We provide a complete classification of six-dimensional symmetric toroidal orbifolds which yield N{>=}1 supersymmetry in 4D for the heterotic string. Our strategy is based on a classification of crystallographic space groups in six dimensions. We find in total 520 inequivalent toroidal orbifolds, 162 of them with Abelian point groups such as Z{sub 3}, Z{sub 4}, Z{sub 6}-I etc. and 358 with non-Abelian point groups such as S{sub 3}, D{sub 4}, A{sub 4} etc. We also briefly explore the properties of some orbifolds with Abelian point groups and N=1, i.e. specify the Hodge numbers and comment on the possible mechanisms (local or non-local) of gauge symmetry breaking.
Hollow nanotubular toroidal polymer microrings.
Lee, Jiyeong; Baek, Kangkyun; Kim, Myungjin; Yun, Gyeongwon; Ko, Young Ho; Lee, Nam-Suk; Hwang, Ilha; Kim, Jeehong; Natarajan, Ramalingam; Park, Chan Gyung; Sung, Wokyung; Kim, Kimoon
2014-02-01
Despite the remarkable progress made in the self-assembly of nano- and microscale architectures with well-defined sizes and shapes, a self-organization-based synthesis of hollow toroids has, so far, proved to be elusive. Here, we report the synthesis of polymer microrings made from rectangular, flat and rigid-core monomers with anisotropically predisposed alkene groups, which are crosslinked with each other by dithiol linkers using thiol-ene photopolymerization. The resulting hollow toroidal structures are shape-persistent and mechanically robust in solution. In addition, their size can be tuned by controlling the initial monomer concentrations, an observation that is supported by a theoretical analysis. These hollow microrings can encapsulate guest molecules in the intratoroidal nanospace, and their peripheries can act as templates for circular arrays of metal nanoparticles.
TFTR toroidal field coil design
International Nuclear Information System (INIS)
Smith, G.E.; Punchard, W.F.B.
1977-01-01
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 18 0 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
Compact toroid formation, compression, and acceleration
International Nuclear Information System (INIS)
Degnan, J.H.; Bell, D.E.; Baca, G.P.; Dearborn, M.E.; Douglas, M.R.; Englert, S.E.; Englert, T.J.; Holmes, J.H.; Hussey, T.W.; Kiuttu, G.F.; Lehr, F.M.; Marklin, G.J.; Mullins, B.W.; Peterkin, R.E.; Price, D.W.; Roderick, N.F.; Ruden, E.L.; Turchi, P.J.; Coffey, S.K.; Seiler, S.W.; Bird, G.
1992-01-01
Research on the formation, compression, and acceleration of milligram Compact Toroids (CTs) will be discussed. This includes experiments with 2-stage coaxial gun discharges and calculations including 2D- MHD. The CTs are formed by 110 μf, 70 KV, 2 MA, 3 μs rise time discharges into 2 mg gas puffs in a 90 cm inner diameter, 7.6 cm gap coaxial gun with approximately 0.15 Tesla of radial-axial initial magnetic field. Reconnection at the neck of the toroidal magnetized plasma bubble extracted from the first stage gun forms the CT. Trapping, relaxation to a minimum energy Taylor state is observed with magnetic probe arrays. Low energy (few hundred KJ, 2 MA) acceleration in straight coaxial geometry, and high energy acceleration using a conical compression stage are discussed. The Phillips Laboratory 1,300 μf, 120 KV, 9.4 MJ SHIVA STAR capacitor bank is used for the acceleration discharge. The charging and triggering of the 36-module bank has been modified to permit use of any multiple of three modules. Highlights of fast photography, current, voltage, magnetic probe array, optical spectroscopy, interferometry, VUV, and higher energy radiation data and 2D-MHD calculations will be presented. Considerably more detail is presented in companion papers
Linear wave propagation in a hot axisymmetric toroidal plasma
International Nuclear Information System (INIS)
Jaun, A.
1995-03-01
Kinetic effects on the propagation of the Alfven wave are studied for the first time in a toroidal plasma relevant for experiments. This requires the resolution of a set of coupled partial differential equations whose coefficients depend locally on the plasma parameters. For this purpose, a numerical wave propagation code called PENN has been developed using either a bilinear or a bicubic Hermite finite element discretization. It solves Maxwell's equations in toroidal geometry, with a dielectric tensor operator that takes into account the linear response of the plasma. Two different models have been implemented and can be used comparatively to describe the same physical case: the first treats the plasma as resistive fluids and gives results which are in good agreement with toroidal fluid codes. The second is a kinetic model and takes into account the finite size of the Larmor radii; it has successfully been tested against a kinetic plasma model in cylindrical geometry. New results have been obtained when studying kinetic effects in toroidal geometry. Two different conversion mechanisms to the kinetic Alfven wave have been described: one occurs at toroidally coupled resonant surfaces and is the kinetic counterpart of the fluid models' resonance absorption. The other has no such correspondence and results directly from the toroidal coupling between the kinetic Alfven wave and the global wavefield. An analysis of a heating scenario suggests that it might be difficult to heat a plasma with Alfven waves up to temperatures that are relevant for a tokamak reactor. Kinetic effects are studied for three types of global Alfven modes (GAE, TAE, BAE) and a new class of kinetic eigenmodes is described which appear inside the fluid gap: it could be related to recent observations in the JET (Joint European Torus) tokamak. (author) 56 figs., 6 tabs., 58 refs
Linear wave propagation in a hot axisymmetric toroidal plasma
Energy Technology Data Exchange (ETDEWEB)
Jaun, A [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP)
1995-03-01
Kinetic effects on the propagation of the Alfven wave are studied for the first time in a toroidal plasma relevant for experiments. This requires the resolution of a set of coupled partial differential equations whose coefficients depend locally on the plasma parameters. For this purpose, a numerical wave propagation code called PENN has been developed using either a bilinear or a bicubic Hermite finite element discretization. It solves Maxwell`s equations in toroidal geometry, with a dielectric tensor operator that takes into account the linear response of the plasma. Two different models have been implemented and can be used comparatively to describe the same physical case: the first treats the plasma as resistive fluids and gives results which are in good agreement with toroidal fluid codes. The second is a kinetic model and takes into account the finite size of the Larmor radii; it has successfully been tested against a kinetic plasma model in cylindrical geometry. New results have been obtained when studying kinetic effects in toroidal geometry. Two different conversion mechanisms to the kinetic Alfven wave have been described: one occurs at toroidally coupled resonant surfaces and is the kinetic counterpart of the fluid models` resonance absorption. The other has no such correspondence and results directly from the toroidal coupling between the kinetic Alfven wave and the global wavefield. An analysis of a heating scenario suggests that it might be difficult to heat a plasma with Alfven waves up to temperatures that are relevant for a tokamak reactor. Kinetic effects are studied for three types of global Alfven modes (GAE, TAE, BAE) and a new class of kinetic eigenmodes is described which appear inside the fluid gap: it could be related to recent observations in the JET (Joint European Torus) tokamak. (author) 56 figs., 6 tabs., 58 refs.
International Nuclear Information System (INIS)
Vlases, G.C.
1989-01-01
During the period from August 1988 to August 1989, the CSS project has made progress in three areas: The Coaxial Slow Source Upgrade CSSU version of the device was operated until January of 1989. In the Fall of 1988 Langmuir probes were installed to measure the end losses, the Thomson scattering system was made more sensitive, and a more detailed scan with internal magnetic probes was performed. Since then, the CSSU-centered work has concentrated on refining the analysis and interpretation of data. The CSS device was rebuilt as CSSP in the period Jan--June 1989, and began operation on July 3, 1989. Simultaneously, a new data acquisition and processing system based on a Vax 3200 workstation and MDS and IDL software was developed. The COAX 2 code was significant improved by the treatment of hydrogen ionization, including the radiative loss terms, and the inclusion of a more consistent transport and impurity radiation package. The improved code was used both to interpret the results of the CSSU experiments, and to predict performance for the CSSP and CSS2 devices. Details of these three areas of progress are given in the following sections
Effects of 3D magnetic perturbations on toroidal plasmas
International Nuclear Information System (INIS)
Callen, J.D.
2011-01-01
Small three-dimensional (3D) magnetic field perturbations have many interesting and possibly useful effects on tokamak and quasi-symmetric stellarator plasmas. Plasma transport equations that include these effects, most notably on diamagnetic-level toroidal plasma flows, have recently been developed. The 3D field perturbations and their plasma effects can be classified according to their toroidal mode number n: low n (say 1-5) resonant (with field line pitch, q = m/n) and non-resonant fields, medium n (∼20, due to toroidal field ripple) and high n (due to microturbulence). Low n non-resonant fields induce a neoclassical toroidal viscosity (NTV) that damps toroidal rotation throughout the plasma towards an offset rotation in the counter-current direction. Recent tokamak experiments have generally confirmed and exploited these predictions by applying external low n non-resonant magnetic perturbations. Medium n toroidal field ripple produces similar effects plus possible ripple-trapping NTV effects and ion direct losses in the edge. A low n (e.g. n = 1) resonant field is mostly shielded by the toroidally rotating plasma at and inside the resonant (rational) surface. If it is large enough it can stop plasma rotation at the rational surface, facilitate magnetic reconnection there and lead to a growing stationary magnetic island (locked mode), which often causes a plasma disruption. Externally applied 3D magnetic perturbations usually have many components. In the plasma their lowest n (e.g. n = 1) externally resonant components can be amplified by kink-type plasma responses, particularly at high β. Low n plasma instabilities (e.g. resistive wall modes, neoclassical tearing modes) cause additional 3D magnetic perturbations in tokamak plasmas. Tearing modes in their nonlinear (Rutherford) regime bifurcate the topology and form magnetic islands. Finally, multiple resonant magnetic perturbations (RMPs) can, if not shielded by plasma rotation effects, cause local magnetic
Heating of toroidal plasmas by neutral injection
International Nuclear Information System (INIS)
Stix, T.H.
1971-08-01
This paper presents a brief review of the physics of ion acceleration, charge exchange and ionization, trajectories for fast ions in toroidal magnetic fields, and fast-ion thermalization. The injection of fast atoms is found to be a highly competitive method both for heating present-day experimental toroidal plasmas and for bringing full-scale toroidal CTR plasmas to low-density ignition. 13 refs., 9 figs
Transport and Dynamics in Toroidal Fusion Systems
Energy Technology Data Exchange (ETDEWEB)
Schnack, Dalton D
2006-05-16
This document reports the successful completion of the OFES Theory Milestone for FY2005, namely, Perform parametric studies to better understand the edge physics regimes of laboratory experiments. Simulate at increased resolution (up to 20 toroidal modes), with density evolution, late into the nonlinear phase and compare results from different types of edge modes. Simulate a single case including a study of heat deposition on nearby material walls. The linear stability properties and nonlinear evolution of Edge Localized Modes (ELMs) in tokamak plasmas are investigated through numerical computation. Data from the DIII-D device at General Atomics (http://fusion.gat.com/diii-d/) is used for the magnetohydrodynamic (MHD) equilibria, but edge parameters are varied to reveal important physical effects. The equilibrium with very low magnetic shear produces an unstable spectrum that is somewhat insensitive to dissipation coefficient values. Here, linear growth rates from the non-ideal NIMROD code (http://nimrodteam.org) agree reasonably well with ideal, i.e. non-dissipative, results from the GATO global linear stability code at low toroidal mode number (n) and with ideal results from the ELITE edge linear stability code at moderate to high toroidal mode number. Linear studies with a more realistic sequence of MHD equilibria (based on DIII-D discharge 86166) produce more significant discrepancies between the ideal and non-ideal calculations. The maximum growth rate for the ideal computations occurs at toroidal mode index n=10, whereas growth rates in the non-ideal computations continue to increase with n unless strong anisotropic thermal conduction is included. Recent modeling advances allow drift effects associated with the Hall electric field and gyroviscosity to be considered. A stabilizing effect can be observed in the preliminary results, but while the distortion in mode structure is readily apparent at n=40, the growth rate is only 13% less than the non-ideal MHD
Magnetic Compression Experiment at General Fusion with Simulation Results
Dunlea, Carl; Khalzov, Ivan; Hirose, Akira; Xiao, Chijin; Fusion Team, General
2017-10-01
The magnetic compression experiment at GF was a repetitive non-destructive test to study plasma physics applicable to Magnetic Target Fusion compression. A spheromak compact torus (CT) is formed with a co-axial gun into a containment region with an hour-glass shaped inner flux conserver, and an insulating outer wall. External coil currents keep the CT off the outer wall (levitation) and then rapidly compress it inwards. The optimal external coil configuration greatly improved both the levitated CT lifetime and the rate of shots with good compressional flux conservation. As confirmed by spectrometer data, the improved levitation field profile reduced plasma impurity levels by suppressing the interaction between plasma and the insulating outer wall during the formation process. We developed an energy and toroidal flux conserving finite element axisymmetric MHD code to study CT formation and compression. The Braginskii MHD equations with anisotropic heat conduction were implemented. To simulate plasma / insulating wall interaction, we couple the vacuum field solution in the insulating region to the full MHD solution in the remainder of the domain. We see good agreement between simulation and experiment results. Partly funded by NSERC and MITACS Accelerate.
ATF [Advanced Toroidal Facility] data management
International Nuclear Information System (INIS)
Kannan, K.L.; Baylor, L.R.
1988-01-01
Data management for the Advanced Toroidal Facility (ATF), a stellarator located at Oak Ridge National Laboratory (ORNL), is provided by DMG, a locally developed, VAX-based software system. DMG is a data storage and retrieval software system that provides the user interface to ATF raw and analyzed data. Data are described in terms of data models and data types and are organized as signals into files, which are internally documented. The system was designed with user accessibility, software maintainability, and extensibility as primary goals. Extensibility features include compatibility with ATF as it moves from pulsed to steady-state operation and capability for use of the DMG system with experiments other than ATF. DMG is implemented as a run-time library of routines available as a shareable image. General-purpose and specialized data acquisition and analysis applications have been developed using the DMG system. This paper describes the DMG system and the interfaces to it. 4 refs., 2 figs
Progress in toroidal confinement and fusion research
International Nuclear Information System (INIS)
Furth, H.P.
1987-10-01
During the past 30 years, the characteristic T/sub i/n tau/sub E/-value of toroidal-confinement experiments has advanced by more than seven orders of magnitude. Part of this advance has been due to an increase of gross machine parameters. Most of this advance has been due to an increase of gross machine parameters. Most of the advance is associated with improvements in the ''quality of plasma confinement.'' The combined evidence of spherator and tokamak research clarifies the role of magnetic-field geometry in determining confinement and points to the importance of shielding out plasma edge effects. A true physical understanding of anomalous transport remains to be achieved. 39 refs., 11 figs., 1 tab
Overview of toroidal momentum transport
International Nuclear Information System (INIS)
Peeters, A.G.; Hornsby, W.A.; Angioni, C.; Hein, T.; Kluy, N.; Strintzi, D.; Tardini, G.; Bortolon, A.; Camenen, Y.; Casson, F.J.; Snodin, A.P.; Szepesi, G.; Duval, B.; Fiederspiel, L.; Idomura, Y.; Mantica, P.; Parra, F.I.; Tala, T.; De Vries, P.; Weiland, J.
2011-01-01
Toroidal momentum transport mechanisms are reviewed and put in a broader perspective. The generation of a finite momentum flux is closely related to the breaking of symmetry (parity) along the field. The symmetry argument allows for the systematic identification of possible transport mechanisms. Those that appear to lowest order in the normalized Larmor radius (the diagonal part, Coriolis pinch, E x B shearing, particle flux, and up-down asymmetric equilibria) are reasonably well understood. At higher order, expected to be of importance in the plasma edge, the theory is still under development.
First ATLAS Barrel Toroid coil casing arrives at CERN
2002-01-01
The first of eight 25-metre long coil casings for the ATLAS experiment's barrel toroid magnet system arrived at CERN on Saturday 2 March by road from Heidelberg. This structure will be part of the largest superconducting toroid magnet ever made. The first coil casing for the toroidal magnets of Atlas arrives at Building 180. This is the start of an enormous three-dimensional jigsaw puzzle. Each of the eight sets of double pancake coils will be housed inside aluminium coil casings, which in turn will be held inside a stainless steel vacuum vessel. A huge construction, the casing that arrived at CERN measures 25 metres in length and 5 metres in width. It weighs 20 tones. And this is just the beginning of the toroid jigsaw: by early April a batch of four double pancake coils, which altogether weighs 65 tones, will arrive from Ansaldo in Italy. The first vacuum vessel will also be arriving from Felguera in Spain this month. It will take about two years for all these 25 m long structures of casings, coils a...
Energy Technology Data Exchange (ETDEWEB)
Melendez L, L.; Chavez A, E.; Colunga S, S.; Valencia A, R.; Lopez C, R.; Gaytan G, E
1992-03-15
In a cylindrical magnetic topology. the confined plasma experiences 'classic' collisional transport phenomena. When bending the cylinder with the purpose of forming a toro, the magnetic field that before was uniform now it has a radial gradient which produces an unbalance in the magnetic pressure that is exercised on the plasma in the transverse section of the toro. This gives place to transport phenomena call 'neo-classicist'. In this work the structure of the toroidal magnetic field produced by toroidal coils of triangular form, to which are added even of coils of compensation with form of half moon is analyzed. With this type of coils it is looked for to minimize the radial gradient of the toroidal magnetic field. The values and characteristics of B (magnetic field) in perpendicular planes to the toro in different angular positions in the toroidal direction, looking for to cover all the cases of importance are exhibited. (Author)
Verification of the Taylor (minimum energy) state in the S-1 Spheromak
International Nuclear Information System (INIS)
Hart, G.W.; Janos, A.; Meyerhofer, D.D.; Yamada, M.
1985-09-01
Experimental measurements of the equilibrium in the S-1 Spheromak by use of magnetic probes inside the plasma show that the final magnetic equilibrium is one which has relaxed close to the Taylor (minimum-energy) state, even though the plasma is far from that state during formation. The comparison is made by calculating the two-dimensional μ profile of the plasma from the probe data, where μ is defined as μ 0 j/sub parallel//B. Measurements using a triple Langmuir probe provide evidence to support the conclusion that the pressure gradients in the relaxed state are confined to the edge region of the plasma
Design of spheromak injector using conical accelerator for large helical device
Energy Technology Data Exchange (ETDEWEB)
Miyazawa, J.; Yamada, H.; Yasui, K.; Kato, S. [National Inst. for Fusion Science, Toki, Gifu (Japan); Fukumoto, N.; Nagata, M.; Uyama, T. [Himeji Inst. of Tech., Hyogo (Japan)
1999-11-01
Optimization of CT injector for LHD has been carried out and conical electrode for adiabatic CT compression is adopted in the design. Point-model of CT acceleration in a co-axial electrode is solved to optimize the electrode geometry and the power supplies. Large acceleration efficiency of 34% is to be obtained with 3.2 m long conical accelerator and 40 kV - 42 kJ power supply. The operation scenario of a CT injector named SPICA mk. I (SPheromak Injector using Conical Accelerator) consisting of 0.8 m conical accelerator is discussed based on this design. (author)
Tilt and shift mode stability in a spheromak with a flux core
Energy Technology Data Exchange (ETDEWEB)
Finn, J.M.; Jardin, S.C.
1984-07-01
The stability of spheromak equilibria with a flux core, or reversal coil, is studied by means of an ideal MHD code. Results depend critically upon whether the flux hole region (the current free area just inside the separatrix) is treated as perfectly conducting plasma or as vacuum. This indicates that the tilt and shift modes persist as resistive instabilities if they are stable in ideal MHD. Specifically, for nonoptimally shaped equilibria, the flux core must nearly touch the current channel if the flux hole is vacuum, whereas the core may be slightly outside the separatrix if the flux hole has conducting plasma. A larger margin exists for optimally shaped equilibria.
Theory and MHD simulation of fuelling process by Compact Toroid (CT) injection
International Nuclear Information System (INIS)
Suzuki, Y.; Hayashi, T.; Kishimoto, Y.
2001-01-01
The fuelling process by a spheromak-like compact toroid (SCT) injection is investigated by using MHD numerical simulations, where the SCT is injected into a magnetized target plasma region corresponding to a fusion device. In our previous study, the theoretical model to determine the penetration depth of the SCT into the target region has been proposed based on the simulation results, in which the SCT is decelerated not only by the magnetic pressure force but also by the magnetic tension force. However, since both ends of the target magnetic field are fixed on the boundary wall in the simulation, the deceleration caused by the magnetic tension force would be overestimated. In this study, the dependence of the boundary condition of the target magnetic field on the SCT penetration process is examined. From these results, the theoretical model we have proposed is improved to include the effect that the wave length of the target magnetic field bent by the SCT penetration expands with the Alfven velocity. In addition, by carrying out the simulation with the torus domain, it is confirmed that the theoretical model is applicable to estimate the penetration depth of the SCT under such conditions. Furthermore, the dependence of the injection position (the side injection and the top/bottom injection) on the penetration process is examined. (author)
Program for development of toroidal superconducting magnets for fusion research, May 1975
International Nuclear Information System (INIS)
Long, H.M.; Lubell, M.S.
1975-11-01
The objective of this program is a tested magnet design which demonstrates the suitability and reliability needed to qualify toroidal superconducting magnets for fusion research devices in a time compatible with the D-T burning experiments time frame. The overall applied development program including tasks, manpower, and cost estimates is detailed here, but for the full toroidal system only the cost and time frame are outlined to show compatibility with the present program. The details of the full toroidal system fall under major device fabrication and will be included in a subsequent document
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…
Fast Dump of the ATLAS Toroids
Dudarev, A; Volpini, Giovanni; Dudarev, Alexey; Kate, Herman Ten
2010-01-01
The toroidal magnet system of the ATLAS Detector at CERN consists of a Barrel Toroid (BT) and two End Cap Toroids (ECT-A and ECT-C). Each toroid is built up from eight racetrack coils wound with an aluminum stabilized NbTi conductor and indirectly cooled by forced flow liquid helium. The three toroids operate in series at 20.5 kA with a total stored energy of 1.5 GJ. In order to verify the reliability and effectiveness of the quench protection system, series of fast dump tests have been performed first of the single toroids and finally of the entire toroidal magnet system. In this paper a model to simulate the fast dump of the ATLAS toroids in single mode operation and in full system configuration is presented. The model is validated through comparison with measured data extracted from the ramp-and-quench runs. The calculated energy dissipation in the various coils is in very good agreement (within 1-2\\%) with the enthalpy changes estimated from the temperature measurements of the different parts of the cold ...
OCLATOR (One Coil Low Aspect Toroidal Reactor)
Energy Technology Data Exchange (ETDEWEB)
Yoshikawa, S.
1980-02-01
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 ..beta.. 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 (One Coil Low Aspect Toroidal Reactor).
Effects of 3D Magnetic Perturbations on Toroidal Plasmas
International Nuclear Information System (INIS)
Callen, J.D.
2010-01-01
Full text: To lowest order tokamaks are two-dimensional (2D) axisymmetric magnetic systems. But small 3D magnetic perturbations (both externally applied and from plasma instabilities) have many interesting and useful effects on tokamak (and quasi-symmetric stellarator) plasmas. Plasma transport equations that include these effects, especially on diamagnetic-level toroidal plasma rotation, have recently been developed. The 3D magnetic perturbations and their plasma effects can be classified according to their toroidal mode number n: low n (1 to 5) resonant (q = m/n in plasma) and non-resonant fields, medium n (due to toroidal field ripple), and high n (due to microturbulence). This paper concentrates on low and medium n perturbations. Low n non-resonant magnetic fields induce a neoclassical toroidal viscosity (NTV) that damps toroidal plasma rotation throughout the plasma toward an offset flow in the counter-I p direction; recent tokamak experiments have confirmed and exploited these predictions by applying external low n non-resonant magnetic perturbations. Medium n perturbations have similar effects plus possible ripple trapping and resultant edge ion losses. A low n resonant magnetic field induces a toroidal plasma torque in the vicinity of the rational surface; when large enough it can stop plasma rotation there and lead to a locked mode, which often causes a plasma disruption. Externally applied 3D magnetic perturbations usually have many components; in the plasma their lowest n components are amplified by plasma responses, particularly at high beta. Low n plasma instabilities (e.g., NTMs, RWMs) cause additional 3D magnetic perturbations in tokamak plasmas; tearing modes can bifurcate the topology and form magnetic islands. Finally, multiple resonant magnetic perturbations (RMPs) can cause local magnetic stochasticity and influence H-mode edge pedestal transport. These various effects of 3D magnetic perturbations can be used to control the toroidal plasma
Development of Toroidal Core Transformers
Energy Technology Data Exchange (ETDEWEB)
de Leon, Francisco [New York Univ. (NYU), Brooklyn, NY (United States). Dept. of Electrical and Computer Engineering
2014-08-01
The original objective of this project was to design, build and test a few prototypes of single-phase 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
Kinetic Modifications to MHD Phenomena in Toroidal Plasmas
International Nuclear Information System (INIS)
Cheng, C.Z.; Gorelenkov, N.N.; Kramer, G.J.; Fredrickson, E.
2004-01-01
Particle kinetic effects involving small spatial and fast temporal scales can strongly affect MHD phenomena and the long time behavior of plasmas. In particular, kinetic effects such as finite ion gyroradii, trapped particle dynamics, and wave-particle resonances have been shown to greatly modify the stability of MHD modes. Here, the kinetic effects of trapped electron dynamics and finite ion gyroradii are shown to have a large stabilizing effect on kinetic ballooning modes in low aspect ratio toroidal plasmas such as NSTX [National Spherical Torus Experiment]. We also present the analysis of Toroidicity-induced Alfven Eigenmodes (TAEs) destabilized by fast neutral-beam injected ions in NSTX experiments and TAE stability in ITER due to alpha-particles and MeV negatively charged neutral beam injected ions
Quasistatic evolution of compact toroids
International Nuclear Information System (INIS)
Sgro, A.G.; Spencer, R.L.; Lilliequist, C.
1981-01-01
Some results are presented of simulations of the post formation evolution of compact toroids. The simulations were performed with a 1-1/2 D transport code. Such a code makes explicit use of the fact that the shapes of the flux surfaces in the plasma change much more slowly than do the profiles of the physical variables across the flux surfaces. Consequently, assuming that the thermodynamic variables are always equilibrated on a flux surface, one may calculate the time evolution of these profiles as a function of a single variable that labels the flux surfaces. Occasionally, during the calculation these profiles are used to invert the equilibrium equation to update the shapes of the flux surfaces. In turn, these shapes imply certain geometric cofficients, such as A = 2 >, which contain the geometric information required by the 1-D equations
Runaway electrons in toroidal discharges
International Nuclear Information System (INIS)
Knoepfel, H.
1979-01-01
Experimental and theoretical studies of runaway electrons in toroidal devices are reviewed here, with particular reference to tokamaks. The complex phenomenology of runaway effects, which have been the subject of research for the past twenty years, is organized within the framework of a number of physical models. The mechanisms and rates for runaway production are discussed first, followed by sections on runaway-driven kinetic relaxation processes and runaway orbit confinement. Next, the equilibrium and stability of runaway-dominated discharges are reviewed. Models for runaway production at early times in the discharge and the scaling of runaway phenomena to larger devices are also discussed. Finally, detection techniques and possible applications of runaways are mentioned. (author)
The control system of the RFX toroidal power supply
International Nuclear Information System (INIS)
Toigo, V.; Piovan, R.; Zanotto, L.; Perna, M.; Coffetti, A.; Freghieri, M.; Povolero, M.
2005-01-01
This paper describes the control system of the toroidal power supply of the RFX experiment and outlines its specific hardware and software structure, which allowed to cope with the numerous requirements of the application with a compact hardware arrangement. The active fault protection strategies, implemented in the control system, are also discussed; finally, a special part of the control, which greatly simplified the long and complex commissioning of the power section of the system, is described
The Electromagnetic Field of Elementary Time-Dependent Toroidal Sources
International Nuclear Information System (INIS)
Afanas'ev, G.N.; Stepanovskij, Yu.P.
1994-01-01
The radiation field of toroidal-like time-dependent current configurations is investigated. Time-dependent charge-current sources are found outside which the electromagnetic strengths disappear but the potentials survive. This can be used to carry out time-dependent Aharonov-Bohm-like experiments and the information transfer. Using the Neumann-Helmholtz parametrization of the current density we present the time-dependent electromagnetic field in a form convenient for applications. 17 refs
International Nuclear Information System (INIS)
Ida, Katsumi
2001-01-01
The structure of the radial electric field and toroidal/poloidal flow is discussed for the high temperature plasma in toroidal systems, tokamak and Heliotron type magnetic configurations. The spontaneous toroidal and poloidal flows are observed in the plasma with improved confinement. The radial electric field is mainly determined by the poloidal flow, because the contribution of toroidal flow to the radial electric field is small. The jump of radial electric field and poloidal flow are commonly observed near the plasma edge in the so-called high confinement mode (H-mode) plasmas in tokamaks and electron root plasma in stellarators including Heliotrons. In general the toroidal flow is driven by the momentum input from neutral beam injected toroidally. There is toroidal flow not driven by neutral beam in the plasma and it will be more significant in the plasma with large electric field. The direction of these spontaneous toroidal flows depends on the symmetry of magnetic field. The spontaneous toroidal flow driven by the ion temperature gradient is in the direction to increase the negative radial electric field in tokamak. The direction of spontaneous toroidal flow in Heliotron plasmas is opposite to that in tokamak plasma because of the helicity of symmetry of the magnetic field configuration. (author)
Unified kinetic theory in toroidal systems
International Nuclear Information System (INIS)
Hitchcock, D.A.; Hazeltine, R.D.
1980-12-01
The kinetic theory of toroidal systems has been characterized by two approaches: neoclassical theory which ignores instabilities and quasilinear theory which ignores collisions. In this paper we construct a kinetic theory for toroidal systems which includes both effects. This yields a pair of evolution equations; one for the spectrum and one for the distribution function. In addition, this theory yields a toroidal generalization of the usual collision operator which is shown to have many similar properties - conservation laws, H theorem - to the usual collision operator
Numerical determination of axisymmetric toroidal magnetohydrodynamic equilibria
International Nuclear Information System (INIS)
Johnson, J.L.; Dalhed, H.E.; Greene, J.M.
1978-07-01
Numerical schemes for the determination of stationary axisymmetric toroidal equilibria appropriate for modeling real experimental devices are given. Iterative schemes are used to solve the elliptic nonlinear partial differential equation for the poloidal flux function psi. The principal emphasis is on solving the free boundary (plasma-vacuum interface) equilibrium problem where external current-carrying toroidal coils support the plasma column, but fixed boundary (e.g., conducting shell) cases are also included. The toroidal current distribution is given by specifying the pressure and either the poloidal current or the safety factor profiles as functions of psi. Examples of the application of the codes to tokamak design at PPPL are given
Rotating bubble and toroidal nuclei and fragmentation
International Nuclear Information System (INIS)
Royer, G.; Haddad, F.; Jouault, B.
1995-01-01
The energy of rotating bubble and toroidal nuclei predicted to be formed in central heavy-ion collisions at intermediate energies is calculated within the generalized rotating liquid drop model. The potential barriers standing in these exotic deformation paths are compared with the three dimensional and plane fragmentation barriers. In the toroidal deformation path of the heaviest systems exists a large potential pocket localised below the plane fragmentation barriers. This might allow the temporary survival of heavy nuclear toroids before the final clusterization induced by the surface and proximity tension. (author)
Toroidal field ripple effects in large tokamaks
International Nuclear Information System (INIS)
Uckan, N.A.; Tsang, K.T.; Callen, J.D.
1975-01-01
In an experimental power reactor, the ripple produced by the finite number of toroidal field coils destroys the ideal axisymmetry of the configuration and is responsible for additional particle trapping, loss regions and plasma transport. The effects of toroidal field ripple on the plasma transport coefficient, the loss of alpha particles and energetic injection ions, and the relaxation of toroidal flows are investigated in a new and systematic way. The relevant results are applied to the ORNL-EPR reference design; the maximum ripple there of about 2.2 percent at the outer edge of the plasma column is found to be tolerable from plasma physics considerations
Calculation of modification to the toroidal magnetic field of the Tokamak Novillo. Part II
International Nuclear Information System (INIS)
Melendez L, L.; Chavez A, E.; Colunga S, S.; Valencia A, R.; Lopez C, R.; Gaytan G, E.
1992-03-01
In a cylindrical magnetic topology. the confined plasma experiences 'classic' collisional transport phenomena. When bending the cylinder with the purpose of forming a toro, the magnetic field that before was uniform now it has a radial gradient which produces an unbalance in the magnetic pressure that is exercised on the plasma in the transverse section of the toro. This gives place to transport phenomena call 'neo-classicist'. In this work the structure of the toroidal magnetic field produced by toroidal coils of triangular form, to which are added even of coils of compensation with form of half moon is analyzed. With this type of coils it is looked for to minimize the radial gradient of the toroidal magnetic field. The values and characteristics of B (magnetic field) in perpendicular planes to the toro in different angular positions in the toroidal direction, looking for to cover all the cases of importance are exhibited. (Author)
Heat characteristic analysis of a conduction cooling toroidal-type SMES magnet
International Nuclear Information System (INIS)
Kim, K.M.; Kim, A.R.; Kim, J.G.; Kim, D.W.; Park, M.; Yu, I.K.; Eom, B.Y.; Sim, K.; Kim, S.H.; Shon, M.H.; Kim, H.J.; Bae, H.J.; Seong, K.C.
2010-01-01
This paper analyzed the heat characteristics of a conduction cooling toroidal-type SMES magnet. The authors designed and manufactured a conduction cooling toroidal-type SMES magnet which consists of 30 double pancake coils. One (a single pancake coil) of a double pancake coil is arranged at an angle of 6 o from each other. The shape of the toroidal-type SMES magnet was designed by a 3D CAD program. The heat invasion was investigated under no-load condition and the thermal characteristic of the toroidal-type SMES magnet was analyzed using the Finite Elements Method program. Both the analyzed and the experiment results are compared and discussed in detail.
A comparison between linear and toroidal Extrap systems
International Nuclear Information System (INIS)
Lehnert, B.
1988-09-01
The Extrap scheme consists of a Z-pinch immersed in an octupole field generated by currents in a set of external conductors. A comparison between linear and toroidal Extrap geometry is made in this paper. As compared to toroidal systems, linear geometry has the advantages of relative simplicity and of a current drive by means of electrodes. Linear devices are convenient for basic studies of Extrap, at moderately high pinch currents and plasma temperatures. Within the parameter ranges of experiments at high pinch currents and plasma temperatures, linear systems have on the other hand some substantial disadvantages, on account of the plasma interaction with the end regions. This results in a limitation of the energy confinement time, and leads in the case of an ohmically heated plasma to excessively high plasma densities and small pinch radii which also complicate the introduction of the external conductors. (author)
Studies on limiter confined toroidal plasma in BETA
International Nuclear Information System (INIS)
Bera, D.; Reddy, C.; Jayakumar, R.; Kaw, P.K.
1984-01-01
Plasma equilibrium and stability in the presence of a toroidal magnetic field and a poloidal limiter is being studied experimentally in the BETA experiment. In a simple toroidal magnetic field, plasma cannot be in equilibrium because of the effect of the magnetic field curvature, which tends to expand the plasma. The electric field, which causes this expansion, is short circuited if a poloidal conducting limiter is placed and this brings about a quasi-equilibrium. In the model the charge separation current flows on the surface of the plasma and closes the path by flowing parallel to the magnetic field away from the limiter and transverse to the field at the limiter. For such an equilibrium, the vertical pressure profile is expected to be uniform, while the radial pressure profile is determined by transport. Such a profile is unstable to Rayleigh-Taylor instabilities, if the magnetic field gradient and the pressure gradient have the same sense
Broadening of the lower hybrid kparallel spectrum by toroidal effects
International Nuclear Information System (INIS)
Barbato, E.; Romanelli, F.
1990-01-01
Toroidal geometry affects the evolution of k parallel (the component of the wave vector parallel to the magnetic field) along the lower hybrid, (LH) wave trajectories. In this paper such variations are investigated both analytically and numerically. The main parameters governing this phenomenon are found and how k parallel upshift can occur within this scheme is elucidated. As a figure of merit a k parallel - upshift factor is defined and discussed in a dimensionless parameter space in which all the LH experiments can be represented. Finally, a discussion of whether and when toroidal effects can fill the gap between the high phase velocity of the injected LH waves and the electron thermal velocity is presented by analyzing different experimental situations
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.
Simulated and experimental compression of a compact toroid
Energy Technology Data Exchange (ETDEWEB)
Johnson, J N; Hwang, D Q; Horton, R D; Evans, R W; Owen, J M
2009-05-06
We present simulation results and experimental data for the compression of a compact toroid by a conducting nozzle without a center electrode. In both simulation and experiment, the flow of the plasma is greatly obstructed by even modest magnetic fields. A simple mechanism for this obstruction is suggested by our simulations. In particular, the configuration of the plasmoid's magnetic field plays a significant role in the success of the experiment. We analyze two types of plasma configurations under compression and demonstrate that the results from the simulations matches those from the experiments, and that the mechanism predicts the different behaviors observed in the two cases.
OCLATOR (One Coil Low Aspect Toroidal Reactor)
International Nuclear Information System (INIS)
Yoshikawa, S.
1980-02-01
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
Steady state compact toroidal plasma production
Turner, William C.
1986-01-01
Apparatus and method for maintaining steady state compact toroidal plasmas. A compact toroidal plasma is formed by a magnetized coaxial plasma gun and held in close proximity to the gun electrodes by applied magnetic fields or magnetic fields produced by image currents in conducting walls. Voltage supply means maintains a constant potential across the electrodes producing an increasing magnetic helicity which drives the plasma away from a minimum energy state. The plasma globally relaxes to a new minimum energy state, conserving helicity according to Taylor's relaxation hypothesis, and injecting net helicity into the core of the compact toroidal plasma. Controlling the voltage so as to inject net helicity at a predetermined rate based on dissipative processes maintains or increases the compact toroidal plasma in a time averaged steady state mode.
Influence of toroidal rotation on tearing modes
Cai, Huishan; Cao, Jintao; Li, Ding
2017-10-01
Tearing modes stability analysis including toroidal rotation is studied. It is found that rotation affects the stability of tearing modes mainly through the interaction with resistive inner region of tearing mode. The coupling of magnetic curvature with centrifugal force and Coriolis force provides a perturbed perpendicular current, and a return parallel current is induced to affect the stability of tearing modes. Toroidal rotation plays a stable role, which depends on the magnitude of Mach number and adiabatic index Γ, and is independent on the direction of toroidal rotation. For Γ >1, the scaling of growth rate is changed for typical Mach number in present tokamaks. For Γ = 1 , the scaling keeps unchanged, and the effect of toroidal rotation is much less significant, compared with that for Γ >1. National Magnetic Confinement Fusion Science Program and National Science Foundation of China under Grants No. 2014GB106004, No. 2013GB111000, No. 11375189, No. 11075161 and No. 11275260, and Youth Innovation Promotion Association CAS.
Bow-shaped toroidal field coils
International Nuclear Information System (INIS)
Bonanos, P.
1981-05-01
Design features of Bow-Shaped Toroidal Field Coils are described and compared with circular and D shaped coils. The results indicate that bow coils can produce higher field strengths, store more energy and be made demountable. The design offers the potential for the production of ultrahigh toroidal fields. Included are representative coil shapes and their engineering properties, a suggested structural design and an analysis of a specific case
Calculations of toroidal EXTRAP equilibria for different toroidal ring current configurations
International Nuclear Information System (INIS)
Drake, J.R.; Scheffel, J.
1985-12-01
EXTRAP is a concept in which a pure Z-pinch is generated along the axis of an octupole field. Experiments in a linear as well as in a sector geometry have demonstrated that the pinch becomes stable against instabilities for many Alfven times. The octupole field in EXTRAP is produced by four, external, current-carrying rings. In the toroidal geometry these rings must be supplemented by additional rings to compensate for the plasma loop force and transformer core leakage flux. Equilibrium studies are carried out for two basically ring designs. The studies are based on numerical equilibrium copmputations using the GOYA code. Sensitivity of the equilibrium to technical imperfections is also analyzed. (author)
Viscous damping of toroidal angular momentum in tokamaks
Energy Technology Data Exchange (ETDEWEB)
Stacey, W. M. [Georgia Tech Fusion Research Center, Atlanta, Georgia 30332 (United States)
2014-09-15
The Braginskii viscous stress tensor formalism was generalized to accommodate non-axisymmetric 3D magnetic fields in general toroidal flux surface geometry in order to provide a representation for the viscous damping of toroidal rotation in tokamaks arising from various “neoclassical toroidal viscosity” mechanisms. In the process, it was verified that the parallel viscosity contribution to damping toroidal angular momentum still vanishes even in the presence of toroidal asymmetries, unless there are 3D radial magnetic fields.
Low-n shear Alfven spectra in axisymmetric toroidal plasmas
International Nuclear Information System (INIS)
Cheng, C.Z.; Chance, M.S.
1985-11-01
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
Celebrating the Barrel Toroid commissioning
Peter Jenni
ATLAS invited Funding Agency representatives and Laboratory Heads directly related to the funding and construction of the Barrel Toroid for a small ceremony on 13th December 2006 at Point 1, in order to mark the successful first full excitation of the BT (see last eNews). On that date, which was during the December CERN Council week, several of the Funding Agency Heads or their representatives could be present, representing CEA France, INFN Italy, BMBF Germany, Spain, Sweden, Switzerland, Russia, JINR Dubna and CERN. Speeches were delivered by the ATLAS spokesperson Peter Jenni thanking the Funding Partners in the name of the Collaboration, by Magnet Project Leader Herman ten Kate tracing the BT construction history, and by the CERN Director-General Robert Aymar congratulating all those who have contributed to the successful project. Herman ten Kate addressing the delegates. The text of the introductory address by Peter Jenni is reproduced here. "It is a great pleasure for me to welcome you all here...
Anomalous transport in toroidal plasmas
International Nuclear Information System (INIS)
Punjabi, A.
1989-12-01
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
Anomalous transport in toroidal plasmas
International Nuclear Information System (INIS)
Punjabi, A.
1991-01-01
We have developed a Monte Carlo method to estimate the transport of different groups of particles for plasmas in toroidal geometries. This method can determine the important transport mechanisms driving the anomalous transport by comparing the numerical results with the experimental data. The important groups of particles whose transport can be estimated by this method include runaway electrons, thermal electrons, both passing and trapped diagnostic beam ions etc. The three basic mechanisms driving the anomalous transport are: spatial variation of magnetic field strength, spatial variation of electrostatic potential within the flux surfaces, and the loss of flux surfaces. The equation of motion are obtained from the drift hamiltonian. The equations of motion are developed in the canonical and in the non-canonical, practical co-ordinates as well. The effects of collisions are represented by appropriate stochastic changes in the constants of motion at each time-step. Here we present the results of application of this method to three cases: superathermal alphas in the rippled field of tokamaks, motion in the magnetic turbulence of takapole II, and transport in the stochastic fields of ZT40. This work is supported by DOE OFE and ORAU HBCU program
Current drive by neutral beams, rotating magnetic fields and helicity injection in compact toroids
International Nuclear Information System (INIS)
Farengo, R.; Arista, N.R.; Lifschitz, A.F.; Clemente, R.A.
2003-01-01
The use of neutral beams (NB) for current drive and heating in spheromaks, the relaxed states of flux core spheromaks (FCS) sustained by helicity injection and the effect of ion dynamics on rotating magnetic field (RMF) current drive in spherical tokamaks (ST) are studied. (author)
Current results from the Los Alamos CTX spheromak
Energy Technology Data Exchange (ETDEWEB)
Barnes, C.W.; Henins, I.; Hoida, H.W.; Jarboe, T.R.; Knox, S.O.; Linford, R.K.; Platts, D.A.; Sherwood, A.R.
1982-01-01
Continued discharge cleaning, improved vacuum practices, and optimized plasma formation operation have resulted in the CTX experiment achieving 1-ms plasma lifetimes with average temperatures of 20 to 40 eV. The major advance in operation has been the use of 5 to 20 mTorr H/sub 2/ gas fill. A multipoint Thomson scattering diagnostic with 12 radial positions yields radial profiles of temperature and densities, an example of which is shown. Local ..beta..'s can be determined from the measured pressure profile, and average values are typically 15 to 20%. In clean, long-lived discharges the density decreases at a more rapid rate than the magnetic field, until it reaches a value around 2 to 4 x 10/sup 13/ cm/sup -3/ where it remains constant. This is in contrast to the colder, radiation-dominated behavior, and is taken as evidence that the plasma ..beta.. is a limit to current operation in CTX.
Effect of the helicity injection rate and the Lundquist number on spheromak sustainment
García-Martínez, Pablo Luis; Lampugnani, Leandro Gabriel; Farengo, Ricardo
2014-12-01
The dynamics of the magnetic relaxation process during the sustainment of spheromak configurations at different helicity injection rates is studied. The three-dimensional activity is recovered using time-dependent resistive magnetohydrodynamic simulations. A cylindrical flux conserver with concentric electrodes is used to model configurations driven by a magnetized coaxial gun. Magnetic helicity is injected by tangential boundary flows. Different regimes of sustainment are identified and characterized in terms of the safety factor profile. The spatial and temporal behavior of fluctuations is described. The dynamo action is shown to be in close agreement with existing experimental data. These results are relevant to the design and operation of helicity injected devices, as well as to basic understanding of the plasma relaxation mechanism in quasi-steady state.
Effect of the helicity injection rate and the Lundquist number on spheromak sustainment
Energy Technology Data Exchange (ETDEWEB)
García-Martínez, Pablo Luis, E-mail: pablogm@cab.cnea.gov.ar [Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and Sede Andina—Universidad Nacional de Río Negro (UNRN), Av. Bustillo 9500, 8400 San Carlos de Bariloche, Río Negro (Argentina); Lampugnani, Leandro Gabriel; Farengo, Ricardo [Instituto Balseiro and Centro Atómico Bariloche (CAB-CNEA), Av. Bustillo 9500, 8400 San Carlos de Bariloche, Río Negro (Argentina)
2014-12-15
The dynamics of the magnetic relaxation process during the sustainment of spheromak configurations at different helicity injection rates is studied. The three-dimensional activity is recovered using time-dependent resistive magnetohydrodynamic simulations. A cylindrical flux conserver with concentric electrodes is used to model configurations driven by a magnetized coaxial gun. Magnetic helicity is injected by tangential boundary flows. Different regimes of sustainment are identified and characterized in terms of the safety factor profile. The spatial and temporal behavior of fluctuations is described. The dynamo action is shown to be in close agreement with existing experimental data. These results are relevant to the design and operation of helicity injected devices, as well as to basic understanding of the plasma relaxation mechanism in quasi-steady state.
Toroidally symmetric/asymmetric effect on the divertor flux due to neon/nitrogen seeding in LHD
Directory of Open Access Journals (Sweden)
H. Tanaka
2017-08-01
Full Text Available Toroidal distributions of divertor particle flux during neon (Ne and nitrogen (N2 seeded discharges were investigated in the Large Helical Device (LHD. By using 14 toroidally distributed divertor probe arrays, which were positioned at radially inner side where the divertor flux concentrates in the inward-shifted magnetic axis configuration, it is found that Ne puffing leads to toroidally quasi-uniform reduction of divertor particle fluxes; whereas toroidally localized reductions were observed with N2 puffing. The toroidally asymmetric reduction pattern with N2 puffing is strongly related to the magnetic field structure around the N2 puffing port. Assuming that nitrogen particles do not recycle, EMC3-EIRENE simulation shows similar reduction pattern with the experiment around the N2 puffing port.
Relaxation and particle diffusion in the Proto S-1/C spheromak
International Nuclear Information System (INIS)
Meyerhofer, D.D.
1987-01-01
The relationship between relaxation and particle diffusion in the Proto S-1C spheromak has been studied. The plasma was formed in a magnetic configuration which was not the minimum-energy Taylor state, and went through a period of relaxation before its magnetic configuration was that of the Taylor state. Early in the relaxation phase, the internal and external magnetic fluctuations were correlated and it was found that, at the time of peak amplitude, they had a radial structure of a tearing mode. After the reconnection of these modes, the plasma continued to evolve towards the Taylor state with only small magnetic fluctuations at the center of plasma. The local particle diffusion coefficient was measured in these Proto S-1C discharges, the technique used was to inject a delta-function source of impurities into the plasma and observe the motion of the impurities relative to the flux surface. It was found that, during the decay phase of the spheromak discharge, when the plasma was in a Taylor state, the carbon diffusion coefficient was explained classically. While the plasma was relaxing towards the Taylor state, the diffusion coefficient was 2 ∼ 4a times larger than classical. At this time, the plasma was not yet force-free. This nonclassical diffusion appears to have been caused by v/sub ExB/ velocities due to correlations between the fluctuating electric field and density. Because the v/sub ExB/ velocity acts on all of the plasma species similarly, the anomalous hydrogen-particle diffusion coefficient should have been as large as that of carbon
Individual Low-Energy Toroidal Dipole State in Mg 24
Nesterenko, V. O.; Repko, A.; Kvasil, J.; Reinhard, P.-G.
2018-05-01
The low-energy dipole excitations in Mg 24 are investigated within the Skyrme quasiparticle random phase approximation for axial nuclei. The calculations with the force SLy6 reveal a remarkable feature: the lowest IπK =1-1 excitation (E =7.92 MeV ) in Mg 24 is a vortical toroidal state (TS) representing a specific vortex-antivortex realization of the well-known spherical Hill's vortex in a strongly deformed axial confinement. This is a striking example of an individual TS which can be much more easily discriminated in experiment than the toroidal dipole resonance embracing many states. The TS acquires the lowest energy due to the huge prolate axial deformation in Mg 24 . The result persists for different Skyrme parametrizations (SLy6, SVbas, SkM*). We analyze spectroscopic properties of the TS and its relation with the cluster structure of Mg 24 . Similar TSs could exist in other highly prolate light nuclei. They could serve as promising tests for various reactions to probe a vortical (toroidal) nuclear flow.
Poloidal and toroidal heat flux distribution in the CCT tokamak
International Nuclear Information System (INIS)
Brown, M.L.; Dhir, V.K.; Taylor, R.J.
1990-01-01
Plasma heat flux to the Faraday shield panels of the UCLA Continuous Current Tokamak (CCT) has been measured calorimetrically in order to identify the dominant parameters affecting the spatial distribution of heat deposition. Three heating methods were investigated: audio frequency discharge cleaning, RF heating, and AC ohmic. Significant poloidal asymmetry is present in the heat flux distribution. On the average, the outer panels received 25-30% greater heat flux than the inner ones, with the ratio of maximum to minimum values attaining a difference of more than a factor of 2. As a diagnostic experiment the current to a selected toroidal field coil was reduced in order to locally deflect the toroidal field lines outward in a ripple-like fashion. Greatly enhanced heat deposition (up to a factor of 4) was observed at this location on the outside Faraday panels. The enhancement was greatest for conditions of low toroidal field and low neutral pressure, leading to low plasma densities, for which Coulomb collisions are the smallest. An exponential model based on a heat flux e-folding length describes the experimentally found localization of thermal energy quite adequately. (orig.)
Stationary shear flows in CGL anisotropic toroidal plasmas
International Nuclear Information System (INIS)
Pastukhov, V.P.; Ilgisonis, V.I.
1996-01-01
Recently a general structure of stationary shear flows in toroidal plasmas was obtained in the frame of ideal isotropic-pressure MHD model. The structure of the stationary plasma flows was shown to be determined by a hidden symmetry of MHD equations inherent in the toroidal systems with nested magnetic surfaces. However, the characteristic frequencies of the stationary plasma motion can considerably exceed the collisional frequencies in real plasma experiments. In this case the CGL collisionless MHD model seems to be more adequate than the simplified isotropic-pressure MHD model to describe the stationary plasma flows. In this paper we have generalized our approach to analyze the stationary plasma flows in the frame of the collisionless CGL model. We have found again that the hidden symmetry inherent in the toroidal topology results in two integral invariants which depend on two independent surface functions. The structure of stationary flows for CGL model is still the same as for isotropic MHD, however, the pressure tensor components satisfy a appreciably modifies the steady state force-balance equation. These results are applied to analyze the generalized equilibrium in axisymmetric (tokamak-like) magnetic confinement systems
Experimental study of high beta toroidal plasmas
International Nuclear Information System (INIS)
Kellman, A.G.
1983-09-01
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%
ZONAL TOROIDAL HARMONIC EXPANSIONS OF EXTERNAL GRAVITATIONAL FIELDS FOR RING-LIKE OBJECTS
Energy Technology Data Exchange (ETDEWEB)
Fukushima, Toshio, E-mail: Toshio.Fukushima@nao.ac.jp [National Astronomical Observatory, Ohsawa, Mitaka, Tokyo 181-8588 (Japan)
2016-08-01
We present an expression of the external gravitational field of a general ring-like object with axial and plane symmetries such as oval toroids or annular disks with an arbitrary density distribution. The main term is the gravitational field of a uniform, infinitely thin ring representing the limit of zero radial width and zero vertical height of the object. The additional term is derived from a zonal toroidal harmonic expansion of a general solution of Laplace’s equation outside the Brillouin toroid of the object. The special functions required are the point value and the first-order derivative of the zonal toroidal harmonics of the first kind, namely, the Legendre function of the first kind of half integer degree and an argument that is not less than unity. We developed a recursive method to compute them from two pairs of seed values explicitly expressed by some complete elliptic integrals. Numerical experiments show that appropriately truncated expansions converge rapidly outside the Brillouin toroid. The truncated expansion can be evaluated so efficiently that, for an oval toroid with an exponentially damping density profile, it is 3000–10,000 times faster than the two-dimensional numerical quadrature. A group of the Fortran 90 programs required in the new method and their sample outputs are available electronically.
International Nuclear Information System (INIS)
Meyerhofer, D.D.; Perkins, F.W.
1984-01-01
The kinetic Alfven wave is studied in a cylindrical force-free plasma with self-consistent magnetic fields. This equilibrium represents a reversed field pinch or a spheromak. The stability of the wave is found to depend on the ratio of the electron drift velocity to the Alfven velocity. This ratio varies inversely with the square root of the plasma line density. The critical line density using the Spitzer--Harm electron distribution function is found for reversed field pinches with deuterium plasmas to be approximately 2 x 10 18 and is 5 x 10 17 m -1 in spheromaks with hydrogen plasmas. The critical line density is in reasonable agreement with experimental data for reversed field pinches
Long-wavelength microinstabilities in toroidal plasmas
International Nuclear Information System (INIS)
Tang, W.W.; Rewoldt, G.
1993-01-01
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
Effects of toroidicity on resistive tearing modes
International Nuclear Information System (INIS)
Izzo, R.; Monticello, D.A.; Manickam, J.; Strauss, H.R.; Grimm, R.; McGuire, K.
1983-03-01
A reduced set of resistive MHD equations is solved numerically in three dimensions to study the stability of tokamak plasmas. Toroidal effects are included self-consistently to leading and next order in inverse aspect ratio, epsilon. The equations satisfy an energy integral. In addition, the momentum equation yields the Grad-Shafranov equation correct to all orders in epsilon. Low beta plasma are studied using several different q-profiles. In all cases, the linear growth rates are reduced by finite toroidicity. Excellent agreement with resistive PEST is obtianed. In some cases, toroidal effects lead to complete stabilization of the mode. Nonlinear results show smaller saturated island widths for finite aspect ratio compared to the cylindrical limit. If the current channel is wide enough so as to produce steep gradients towards the outside of the plasma, both the finite aspect ratio cases and cylindrical cases disrupt
PDX toroidal field coils stress analysis
International Nuclear Information System (INIS)
Nikodem, Z.D.; Smith, R.A.
1975-01-01
A method used in the stress analysis of the PDX toroidal field coil is developed. A multilayer coil design of arbitrary dimensions in the shape of either a circle or an oval is considered. The analytical model of the coil and the supporting coil case with connections to the main support structure is analyzed using the finite element technique. The three dimensional magnetic fields and the non-uniform body forces which are a loading condition on a coil due to toroidal and poloidal fields are calculated. The method of analysis permits rapid and economic evaluations of design changes in coil geometry as well as in coil support structures. Some results pertinent to the design evolution and their comparison are discussed. The results of the detailed stress analysis of the final coil design due to toroidal field, poloidal field and temperature loads are presented
International Nuclear Information System (INIS)
Matthaeus, W.; Brown, M.
2006-01-01
This is the final technical report for a funded program to provide theoretical support to the Swarthmore Spheromak Experiment. We examined mhd relaxation, reconnecton between two spheromaks, particle acceleration by these processes, and collisonless effects, e.g., Hall effect near the reconnection zone,. Throughout the project, applications to space plasma physics and astrophysics were included. Towards the end of the project we were examining a more fully turbulent relaxation associated with unconstrained dynamics in SSX. We employed experimental, spacecraft observations, analytical and numerical methods.
Dynamic processes in field-reversed-configuration compact toroids
International Nuclear Information System (INIS)
Rej, D.J.
1987-01-01
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
Models for large superconducting toroidal magnet systems
International Nuclear Information System (INIS)
Arendt, F.; Brechna, H.; Erb, J.; Komarek, P.; Krauth, H.; Maurer, W.
1976-01-01
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
Guiding Center Equations in Toroidal Equilibria
International Nuclear Information System (INIS)
White, Roscoe; Zakharov, Leonid
2002-01-01
Guiding center equations for particle motion in a general toroidal magnetic equilibrium configuration are derived using magnetic coordinates. Previous derivations made use of Boozer coordinates, in which the poloidal and toroidal angle variables are chosen so that the Jacobian is inversely proportional to the square of the magnetic field. It is shown that the equations for guiding center motion in any equilibrium possessing nested flux surfaces have exactly the same simple form as those derived in this special case. This allows the use of more spatially uniform coordinates instead of the Boozer coordinates, greatly increasing the accuracy of calculations in large beta and strongly shaped equilibria
Current control necessary for toroidal plasma equilibrium
International Nuclear Information System (INIS)
Nagao, S.
1987-01-01
It is shown that a significant amount of dipole current is necessary for the plasma equilibrium of toroidal configurations in general. Through the vector product with the poloidal field, this dipole current force has to balance with the hoop force of plasma pressure itself of the annular shape. The measurement of such a current of dipole type may be interesting for the confirmation of the plasma equilibrium in the toroidal system. Moreover it is certained that there is a new mode of a tokamak operation with such a dipole current component and with smaller vertical field than that based on the classical tokamak theory. (author) [pt
Toroidal Precession as a Geometric Phase
Energy Technology Data Exchange (ETDEWEB)
J.W. Burby and H. Qin
2012-09-26
Toroidal precession is commonly understood as the orbit-averaged toroidal drift of guiding centers in axisymmetric and quasisymmetric configurations. We give a new, more natural description of precession as a geometric phase effect. In particular, we show that the precession angle arises as the holonomy of a guiding center's poloidal trajectory relative to a principal connection. The fact that this description is physically appropriate is borne out with new, manifestly coordinate-independent expressions for the precession angle that apply to all types of orbits in tokamaks and quasisymmetric stellarators alike. We then describe how these expressions may be fruitfully employed in numerical calculations of precession.
Components and system tests on the RFX toroidal power supply
International Nuclear Information System (INIS)
Toigo, V.; Zanotto, L.; Gaio, E.; Perna, M.; Bordignon, P.; Coffetti, A.; Novaro, R.; Bertolotto, P.; Rinaldi, E.; Villa, G.
2005-01-01
The paper deals with the component and system tests performed on the new toroidal power supply system of the RFX experiment. The high technological innovation of the system required a deep experimental characterization and validation campaign; special factory tests were performed on prototypes of single components aimed at verifying the most critical design aspects. Consequently an articulated series of tests were performed, based on a step-by-step approach to achieve the desired coordinate operation of the whole system. The test procedures and the most significant results are described in the paper
Classical impurity ion confinement in a toroidal magnetized fusion plasma.
Kumar, S T A; Den Hartog, D J; Caspary, K J; Magee, R M; Mirnov, V V; Chapman, B E; Craig, D; Fiksel, G; Sarff, J S
2012-03-23
High-resolution measurements of impurity ion dynamics provide first-time evidence of classical ion confinement in a toroidal, magnetically confined plasma. The density profile evolution of fully stripped carbon is measured in MST reversed-field pinch plasmas with reduced magnetic turbulence to assess Coulomb-collisional transport without the neoclassical enhancement from particle drift effects. The impurity density profile evolves to a hollow shape, consistent with the temperature screening mechanism of classical transport. Corroborating methane pellet injection experiments expose the sensitivity of the impurity particle confinement time to the residual magnetic fluctuation amplitude.
Evidence of Inward Toroidal Momentum Convection in the JET Tokamak
DEFF Research Database (Denmark)
Tala, T.; Zastrow, K.-D.; Ferreira, J.
2009-01-01
Experiments have been carried out on the Joint European Torus tokamak to determine the diffusive and convective momentum transport. Torque, injected by neutral beams, was modulated to create a periodic perturbation in the toroidal rotation velocity. Novel transport analysis shows the magnitude...... and profile shape of the momentum diffusivity are similar to those of the ion heat diffusivity. A significant inward momentum pinch, up to 20 m/s, has been found. Both results are consistent with gyrokinetic simulations. This evidence is complemented in plasmas with internal transport barriers....
A model for the neoclassical toroidal viscosity effect on Edge plasma toroidal rotation
Energy Technology Data Exchange (ETDEWEB)
Miron, I.G. [National Institute for Laser, Plasma and Radiation Physics, Euratom-MEdC Association, Bucharest (Romania)
2013-11-15
A semianalytic expression for the edge plasma angular toroidal rotation frequency that includes the neoclassical toroidal viscosity braking influence is obtained. Based on the model presented in a previous paper [I.G. Miron, Contrib. Plasma Phys. 53, 214 (2013)], the less destabilizing error field spectrum is found in order to minimize the nonlinear effect of the NTV on the toroidal rotation of the edge of the plasma. (copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
The effect of sheared toroidal rotation on pressure driven magnetic islands in toroidal plasmas
Energy Technology Data Exchange (ETDEWEB)
Hegna, C. C. [Departments of Engineering Physics and Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)
2016-05-15
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.
Investigation of compact toroid penetration for fuelling spherical tokamak plasmas on CPD
International Nuclear Information System (INIS)
Fukumoto, N.; Hanada, K.; Kawakami, S.
2008-10-01
In previous Compact Toroid (CT) injection experiments on several tokamaks, although CT fuelling had been successfully demonstrated, the CT fuelling process has been not clear yet. We have thus conducted CT injection into simple toroidal or vertical vacuum magnetic fields to investigate quantitatively dynamics of CT plasmoid in the penetration process on a spherical tokamak (ST) device. Understanding the process allows us to address appropriately one of the critical issues for practical application of CT injection on reactor-grade tokamaks. In the experiment, the CT shift amount of about 0.26 m in a vertical magnetic field has been observed by using a fast camera. In addition to toroidal magnetic field, vertical one appears to affect CT trajectory in not conventional tokamak but ST devices operated at rather low toroidal fields. We have also observed CT attacks on the target plate with an IR camera. The IR image has indicated that CT shifts 39 mm at the toroidal field of 261 G. From the calorimetric measurement, an input energy due to CT impact in vacuum without magnetic fields is also estimated to be 530 J, which agrees with the initial CT kinetic energy. (author)
Quench propagation and protection analysis of the ATLAS Toroids
Dudarev, A; Gavrilin, A V; ten Kate, H H J; Baynham, D Elwyn; Courthold, M J D; Lesmond, C
2000-01-01
The ATLAS superconducting magnet system consists of the Barrel Toroid, two End Cap Toroids and the Central Solenoid. However, the Toroids of eight coils each are magnetically separate systems to the Central Solenoid. The Toroids are electrically connected in series and energized by a single power supply. The quench protection system is based on the use of relatively small external dump resistances in combination with quench-heaters activated after a quench event detection to initiate the inte...
New material equations for electromagnetism with toroid polarizations
International Nuclear Information System (INIS)
Dubovik, V.M.; Martsenyuk, M.A.; Saha, B.
1999-09-01
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)
System for calibration of SPEAR transport line toroids
International Nuclear Information System (INIS)
Huang, T.V.; Smith, H.; Crook, K.
1977-01-01
A one nanosecond pulse generator was developed for calibration of the intensity monitors (toroids) in the SPEAR transport lines. The generator, located at the toroid, is simple, low cost and resistant to radiation. The generator and its connection to the standard SLAC toroid calibration system are described
Toroidal groups line bundles, cohomology and quasi-Abelian varieties
Kopfermann, Klaus
2001-01-01
Toroidal groups are the connecting link between torus groups and any complex Lie groups. Many properties of complex Lie groups such as the pseudoconvexity and cohomology are determined by their maximal toroidal subgroups. Quasi-Abelian varieties are meromorphically separable toroidal groups. They are the natural generalisation of the Abelian varieties. Nevertheless, their behavior can be completely different as the wild groups show.
On the stabilization of toroidal pinches by finite larmor radius effects and toroidal magnetic field
International Nuclear Information System (INIS)
Singh, R.; Weiland, J.
1989-01-01
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.)
Anisotropic diffusion in a toroidal geometry
International Nuclear Information System (INIS)
Fischer, Paul F
2005-01-01
As part of the Department of Energy's applications oriented SciDAC project, three model problems have been proposed by the Center for Extended Magnetohydrodynamics Modeling to test the potential of numerical algorithms for challenging magnetohydrodynamics (MHD) problems that are required for future fusion development. The first of these, anisotropic diffusion in a toroidal geometry, is considered in this note
A steady-state axisymmetric toroidal system
International Nuclear Information System (INIS)
Hirano, K.
1984-01-01
Conditions for achieving a steady state in an axisymmetric toroidal system are studied with emphasis on a very-high-beta field-reversed configuration. The analysis is carried out for the electromotive force produced by the Ohkawa current that is induced by neutral-beam injection. It turns out that, since the perpendicular component of the current j-vectorsub(perpendicular) to the magnetic field can be generated automatically by the diamagnetic effect, only the parallel component j-vectorsub(parallel) must be driven by the electromotive force. The drive of j-vectorsub(parallel) generates shear in the field line so that the pure toroidal field on the magnetic axis is rotated towards the plasma boundary and matched to the external field lines. This matching condition determines the necessary amount of injection beam current and power. It is demonstrated that a very-high-beta field-reversed configuration requires only a small amount of current-driving beam power because almost all the toroidal current except that close to the magnetic axis is carried by the diamagnetic current due to high beta. A low-beta tokamak, on the other hand, needs very high current-driving power since most of the toroidal current is composed of j-vectorsub(parallel) which must be driven by the beam. (author)
Escape of magnetic toroids from the Sun
International Nuclear Information System (INIS)
Bieber, John W.; Rust, David M.
1996-01-01
Analysis of heliospheric magnetic fields at 1 AU shows that 10 24 Mx of net toroidal flux escapes from the Sun per solar cycle. This rate is compared with the apparent rate of flux emergence at the solar surface, and it is concluded that escaping toroids will remove at least 20% of the emerging flux, and may remove as much as 100% of emerging flux if multiple eruptions occur on the toroids. The data imply that flux escapes the Sun with an efficiency far exceeding Parker's upper limit estimate of 3%. Toroidal flux escape is almost certainly the source of the observed overwinding of the interplanetary magnetic field spiral. Two mechanisms to facilitate net flux escape are discussed: helicity charging to push open the fields and flux transport with reconnection to close them off. We estimate the Sun will shed ∼2x10 45 Mx 2 of magnetic helicity per solar cycle, leading to a mean helicity density of 100 Mx 2 cm -3 at 1 AU, which agrees well with observations
Toroidal 12 cavity klystron : a novel approach
International Nuclear Information System (INIS)
Hazarika, A.B.R.
2013-01-01
A toroidal 12 cavity klystron is designed to provide with high energy power with the high frequency microwave RF- plasma generated from it. The cavities are positioned in clock hour positions. The theoretical modeling and designing is done to study the novel approach. (author)
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...
Curvature driven instabilities in toroidal plasmas
International Nuclear Information System (INIS)
Andersson, P.
1986-11-01
The electromagnetic ballooning mode, the curvature driven trapped electron mode and the toroidally induced ion temperature gradient mode have been studies. Eigenvalue equations have been derived and solved both numerically and analytically. For electromagnetic ballooning modes the effects of convective damping, finite Larmor radius, higher order curvature terms, and temperature gradients have been investigated. A fully toroidal fluid ion model has been developed. It is shown that a necessary and sufficient condition for an instability below the MHD limit is the presence of an ion temperature gradient. Analytical dispersion relations giving results in good agreement with numerical solutions are also presented. The curvature driven trapped electron modes are found to be unstable for virtually all parameters with growth rates of the order of the diamagnetic drift frequency. Studies have been made, using both a gyrokinetic ion description and the fully toroidal ion model. Both analytical and numerical results are presented and are found to be in good agreement. The toroidally induced ion temperature gradients modes are found to have a behavior similar to that of the curvature driven trapped electron modes and can in the electrostatic limit be described by a simple quadratic dispersion equation. (author)
Discussion of discrete D shape toroidal coil
International Nuclear Information System (INIS)
Kaiho, Katsuyuki; Ohara, Takeshi; Agatsuma, Ko; Onishi, Toshitada
1988-01-01
A novel design for a toroidal coil, called the D shape coil, was reported by J. File. The coil conductors are in pure tension and then subject to no bending moment. This leads to a smaller number of emf supports in a simpler configuration than that with the conventional toroidal coil of circular cross-section. The contours of the D shape are given as solutions of a differential equation. This equation includes the function of the magnetic field distribution in the conductor region which is inversely proportional to the winding radius. It is therefore important to use the exact magnetic field distribution. However the magnetic field distribution becomes complicated when the D shape toroidal coil is comprised of discrete coils and also depends on the D shape configuration. A theory and a computer program for designing the practical pure-tension toroidal coil are developed. Using this computer code, D shape conductors are calculated for various numbers of discrete coils and the results are compared. Electromagnetic forces in the coils are also calculated. It is shown that the hoop stress in the conductors depends only on the total ampere-turns of the coil when the contours of the D shape are similar. (author)
Toroidal vortices in resistive magnetohydrodynamic equilibria
International Nuclear Information System (INIS)
Montgomery, D.; Bates, J.W.; Li, S.
1997-01-01
When a time-independent electric current flows toroidally in a uniform ring of electrically conducting fluid, a Lorentz force results, jxB, where j is the local electric current density, and B is the magnetic field it generates. Because of purely geometric effects, the curl of jxB is nonvanishing, and so jxB cannot be balanced by the gradient of any scalar pressure. Taking the curl of the fluid close-quote s equation of motion shows that the net effect of the jxB force is to generate toroidal vorticity. Allowed steady states necessarily contain toroidal vortices, with flows in the poloidal directions. The flow pattern is a characteristic open-quotes double smoke ringclose quotes configuration. The effect seems quite general, although it is analytically simple only in special limits. One limit described here is that of high viscosity (low Reynolds number), with stress-free wall boundary conditions on the velocity field, although it is apparent that similar mechanical motions will result for no-slip boundaries and higher Reynolds numbers. A rather ubiquitous connection between current-carrying toroids and vortex rings seems to be implied, one that disappears in the open-quotes straight cylinderclose quotes limit. copyright 1997 American Institute of Physics
Neoclassical poloidal and toroidal rotation in tokamaks
International Nuclear Information System (INIS)
Kim, Y.B.; Diamond, P.H.; Groebner, R.J.
1991-01-01
Explicit expressions for the neoclassical poloidal and toroidal rotation speeds of primary ion and impurity species are derived via the Hirshman and Sigmar moment approach. The rotation speeds of the primary ion can be significantly different from those of impurities in various interesting cases. The rapid increase of impurity poloidal rotation in the edge region of H-mode discharges in tokamaks can be explained by a rapid steepening of the primary ion pressure gradient. Depending on ion collisionality, the poloidal rotation speed of the primary ions at the edge can be quite small and the flow direction may be opposite to that of the impurities. This may cast considerable doubts on current L to H bifurcation models based on primary ion poloidal rotation only. Also, the difference between the toroidal rotation velocities of primary ions and impurities is not negligible in various cases. In Ohmic plasmas, the parallel electric field induces a large impurity toroidal rotation close to the magnetic axis, which seems to agree with experimental observations. In the ion banana and plateau regime, there can be non-negligible disparities between primary ion and impurity toroidal rotation velocities due to the ion density and temperature gradients. Detailed analytic expressions for the primary ion and impurity rotation speeds are presented, and the methodology for generalization to the case of several impurity species is also presented for future numerical evaluation
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
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...
Long-wavelength microinstabilities in toroidal plasmas
International Nuclear Information System (INIS)
Tang, W.M.; Rewoldt, G.
1993-01-01
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 Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Nucl. Fusion Res. (International Atomic Energy Agency, Vienna, 1985), Vol. 1, p. 29] 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
Relativistic stars with purely toroidal magnetic fields
International Nuclear Information System (INIS)
Kiuchi, Kenta; Yoshida, Shijun
2008-01-01
We investigate the effects of the purely toroidal magnetic field on the equilibrium structures of the relativistic stars. The basic equations for obtaining equilibrium solutions of relativistic rotating stars containing purely toroidal magnetic fields are derived for the first time. To solve these basic equations numerically, we extend the Cook-Shapiro-Teukolsky scheme for calculating relativistic rotating stars containing no magnetic field to incorporate the effects of the purely toroidal magnetic fields. By using the numerical scheme, we then calculate a large number of the equilibrium configurations for a particular distribution of the magnetic field in order to explore the equilibrium properties. We also construct the equilibrium sequences of the constant baryon mass and/or the constant magnetic flux, which model the evolution of an isolated neutron star as it loses angular momentum via the gravitational waves. Important properties of the equilibrium configurations of the magnetized stars obtained in this study are summarized as follows: (1) For the nonrotating stars, the matter distribution of the stars is prolately distorted due to the toroidal magnetic fields. (2) For the rapidly rotating stars, the shape of the stellar surface becomes oblate because of the centrifugal force. But, the matter distribution deep inside the star is sufficiently prolate for the mean matter distribution of the star to be prolate. (3) The stronger toroidal magnetic fields lead to the mass shedding of the stars at the lower angular velocity. (4) For some equilibrium sequences of the constant baryon mass and magnetic flux, the stars can spin up as they lose angular momentum.
HIFLUX: OBLATE FRCS, DOUBLE HELICES,SPHEROMAKS AND RFPS IN ONE SYSTEM
International Nuclear Information System (INIS)
SCHAFFER, M.J.; BOEDO, J.A.
2003-01-01
OAK-B135 High magnetic flux is required for thermonuclear FRC reactors and, more immediately, to advance the FRC experimental program in general. Oblate FRCs are of special interest because they are predicted to have certain improved MHD stability over elongated FRCs, and oblate FRCs may yield the most compact, magnetically confined fusion reactors. Neither oblate nor high-flux FRCs have been investigated experimentally to date. Our presently proposed technique is to make two high-flux, oppositely-handed plasmas by a pair of large, external, reversed-field pinch (RFP) sources. The plasmas would propagate as two Taylor-relaxed double-helix plasmas, to an oblate main plasma chamber, where they would relax further to a counter-helicity pair of spheromaks, which would finally merge into a single high-flux FRC. A concept for a new experimental facility, HIFLUX, to make and study high-magnetic-flux oblate Field-Reversed Configuration (FRC) plasmas, is described. Similar principles might also enable high flux non-inductive startup of other plasma devices
Development of compact toroids injector for direct plasma controls
Energy Technology Data Exchange (ETDEWEB)
Azuma, K. [Mitsubishi Heavy Industries Ltd., Takasago (Japan); Oda, Y. [Mitsubishi Heavy Industries Ltd., Takasago (Japan); Onozuka, M. [Mitsubishi Heavy Industries Ltd., Takasago (Japan); Uyama, T. [Himeji Inst. of Tech. (Japan); Nagata, M. [Himeji Inst. of Tech. (Japan); Fukumoto, N. [Himeji Inst. of Tech. (Japan)
1995-12-31
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 10{sup 21}m{sup -3}. (orig.).
Development of compact toroids injector for direct plasma controls
International Nuclear Information System (INIS)
Azuma, K.; Oda, Y.; Onozuka, M.; Uyama, T.; Nagata, M.; Fukumoto, N.
1995-01-01
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 10 21 m -3 . (orig.)
Design description of the vacuum vessel for the Advanced Toroidal Facility
International Nuclear Information System (INIS)
Chipley, K.K.; Nelson, B.E.; Vinyard, L.M.; Williamson, D.F.
1983-01-01
The Advanced Toroidal Facility (ATF) will be a stellarator experiment to investigate improvements in toroidal confinement. The vacuum vessel for this facility will provide the appropriate evacuated region for plasma containment within the helical field (HF) coils. The vessel is designed to provide the maximum reasonable volume inside the HF coils and to provide the maximum reasonable access for future diagnostics. The vacuum vessel design is at an early phase and all of the details have not been completed. The heat transfer analysis and stress analysis completed during the conceptual design indicate that the vessel will not change drastically
International Nuclear Information System (INIS)
Brown, Michael R.
2006-01-01
The purpose of the project was to provide theoretical and modeling support to the Swarthmore Spheromak Experiment (SSX). Accordingly, the theoretical effort was tightly integrated into the SSX experimental effort. During the grant period, Michael Brown and his experimental collaborators at Swarthmore, with assistance from W. Matthaeus as appropriate, made substantial progress in understanding the physics SSX plasmas
Equilibrium and stability of a toroidal-sector plasma discharge in an EXTRAP configuration
International Nuclear Information System (INIS)
Drake, J.R.
1982-02-01
Experimental studies of the equilibrium and stability of a sector of a toroidal EXTRAP plasma discharge have been studied. The high β plasma discharge, which had an Alfven transit time about 0.5 μsec, could be positioned in a stable equilibrium for the 300μsec time scale of the experiment. (author)
Are the toroidal shapes of heavy-ion reactions seen in macroscopic drop collisions?
International Nuclear Information System (INIS)
Menchaca R, A.; Borunda, M.; Hidalgo, S.S.; Huidobro, F.; Michaelian, K.; Perez, A.; Rodriguez, V.
1996-01-01
Experiments involving the collisions of water, and mineral oil, drops are reported. The aim is to search for toroidal configurations predicted by, both, macroscopic fluid dynamic and nuclear models. Instead, we find the formation of thin liquid sheets surrounded by a somewhat thicker rim presenting a fingering instability. (Author)
Radial electric field in JET advanced tokamak scenarios with toroidal field ripple
Crombe, K.; Andrew, Y.; Biewer, T. M.; Blanco, E.; de Vries, P. C.; Giroud, C.; Hawkes, N. C.; Meigs, A.; Tala, T.; von Hellermann, M.; Zastrow, K. D.
2009-01-01
A dedicated campaign has been run on JET to study the effect of toroidal field (TF) ripple on plasma performance. Radial electric field measurements from experiments on a series of plasmas with internal transport barriers (ITBs) and different levels of ripple amplitude are presented. They have been
Edge pedestal characteristics in JET and JT-60U tokamaks under variable toroidal field ripple
Urano, H.; Saibene, G.; Oyama, N.; Parail, V.; P. de Vries,; Sartori, R.; Kamada, Y.; Kamiya, K.; Loarte, A.; Lonnroth, J.; Sakamoto, Y.; Salmi, A.; Shinohara, K.; Takenaga, H.; Yoshida, M.
2011-01-01
The effects of toroidal field (TF) ripple on the edge pedestal characteristics were examined in the TF ripple scan experiments at the plasma current I(p) of 1.1 MA in JET and JT-60U. The TF ripple amplitude delta(R) was defined as a value averaged over the existing ripple wells at the separatrix on
Generation of toroidal pre-heat plasma
International Nuclear Information System (INIS)
Ikeda, Nagayasu; Tamaru, Ken; Nagata, Akiyoshi.
1979-01-01
The characteristics of toroidal plasma in the initial stage of electric discharge were investigated. A small toroidal-pinch system was used for the present work. A magnetic probe was used to measure the magnetic field. The time of beginning of discharge was determined by observing the variation of the magnetic field. The initial gas pressure dependence of the induced electric field regions, in which electric discharge can be caused, was studied. It is necessary to increase the initial induced electric field for starting discharge. The delay time of large current discharge was measured, and it was about 2 microsecond. Dependences of the electric fields at the beginning of discharge on the charging voltage of capacitors, on the initial gas pressure, and on the discharge frequency were studied. The formation mechanism of plasma column was analyzed. (Kato, T.)
Form coefficient of helical toroidal solenoids
International Nuclear Information System (INIS)
Amelin, V.Z.; Kunchenko, V.B.
1982-01-01
For toroidal solenoids with continuous spiral coil, winded according to the laws of equiinclined and simple cylindrical spirals with homogeneous, linearly increasing to the coil periphery and ''Bitter'' distribution of current density, the analytical expressions for the dependence between capacity consumed and generated magnetic field, expressions for coefficients of form similar to Fabry coefficient for cylindrical solenoids are obtained and dependence of the form coefficient and relative volume of solenoid conductor on the number of revolutions of screw line per one circumvention over the large torus radius is also investigated. Analytical expressions of form coefficients and graphical material permit to select the optimum geometry as to capacity consumed both for spiral (including ''force-free'') and conventional toroidal solenoids of magnetic systems in thermonulear installations
Reynolds stress of localized toroidal modes
International Nuclear Information System (INIS)
Zhang, Y.Z.; Mahajan, S.M.
1995-02-01
An investigation of the 2D toroidal eigenmode problem reveals the possibility of a new consistent 2D structure, the dissipative BM-II mode. In contrast to the conventional ballooning mode, the new mode is poloidally localized at π/2 (or -π/2), and possesses significant radial asymmetry. The radial asymmetry, in turn, allows the dissipative BM-II to generate considerably larger Reynolds stress as compared to the standard slab drift type modes. It is also shown that a wide class of localized dissipative toroidal modes are likely to be of the dissipative BM-II nature, suggesting that at the tokamak edge, the fluctuation generated Reynolds stress (a possible source of poloidal flow) can be significant
Ballooning instabilities in toroidally linked mirror systems
International Nuclear Information System (INIS)
Hastie, R.J.; Watson, C.J.H.
1977-01-01
This paper examines the stability against ballooning modes of plasma equilibria in toroidally linked mirror configurations consisting of a number of quadrupole minimum-B mirrors linked toroidally. On the basis of the Kruskal-Oberman energy principle, a class of displacements is identified which are potentially unstable, and a necessary criterion for stability is derived. The criterion is obtained from the eigenvalues of an ordinary differential equation, which determines the variation of the displacement along a field line. The coefficients in the equation are determined by the configuration, and by inserting various model configurations, estimates are obtained of the maximum value of β consistent with stability. In cases of interest, quite high β-values are obtained. (author)
Reynolds stress of localized toroidal modes
International Nuclear Information System (INIS)
Zhang, Y.Z.; Mahajan, S.M.
1995-01-01
An investigation of the 2D toroidal eigenmode problem reveals the possibility of a new consistent 2D structure, the dissipative BM-II mode. In contrast to the conventional ballooning mode, the new mode is poloidally localized at π/2 (or -π/2), and possesses significant radial asymmetry. The radial asymmetry, in turn, allows the dissipative BM-II to generate considerably larger Reynolds stress as compared to the standard slab drift type modes. It is also shown that a wide class of localized dissipative toroidal modes are likely to be of the dissipative BM-II nature, suggesting that at the tokamak edge, the fluctuation generated Reynolds stress (a possible source of poloidal flow) can be significant. (author). 15 refs
TORFA - toroidal reactor for fusion applications
International Nuclear Information System (INIS)
Jassby, D.L.
1980-09-01
The near-term goal of the US controlled fusion program should be the development, for practical applications, of an intense, quasi-steady, reliable 14-MeV neutron source with an electrical utilization efficiency at least 10 times larger than the value characterizing beam/solid-target neutron generators. This report outlines a method for implementing that goal, based on tokamak fusion reactors featuring resistive toroidal-field coils designed for ease of demountability
METHODS TO DEVELOP A TOROIDAL SURFACE
Directory of Open Access Journals (Sweden)
DANAILA Ligia
2017-05-01
Full Text Available The paper work presents two practical methods to draw the development of a surface unable to be developed applying classical methods of Descriptive Geometry, the toroidal surface, frequently met in technical practice. The described methods are approximate ones; the development is obtained with the help of points. The accuracy of the methods is given by the number of points used when drawing. As for any other approximate method, when practically manufactured the development may need to be adjusted on site.
Stellarator approach to toroidal plasma confinement
International Nuclear Information System (INIS)
Johnson, J.L.
1981-12-01
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
Protection of toroidal field coils using multiple circuits
International Nuclear Information System (INIS)
Thome, R.J.; Langton, W.G.; Mann, W.R.; Pillsbury, R.D.; Tarrh, J.M.
1983-01-01
The protection of toroidal field (TF) coils using multiple circuits is described. The discharge of a single-circuit TF system is given for purposes of definition. Two-circuit TF systems are analyzed and the results presented analytically and graphically. Induced currents, maximum discharge voltages, and discharge time constants are compared to the single-circuit system. Three-circuit TF systems are analyzed. In addition to induced currents, maximum discharge voltages, and time constants, several different discharge scenarios are included. The impacts of having discharge rates versus final maximum coil temperatures as requirements are examined. The out-of-plane forces which occur in the three-circuit system are analyzed using an approximate model. The analysis of multiplecircuit TF systems is briefly described and results for a Toroidal Fusion Core Experiment (TFCX) scale device are given based on computer analysis. The advantages and disadvantages of using multiple-circuit systems are summarized and discussed. The primary disadvantages of multiple circuits are the increased circuit complexity and potential for out-of-plane forces. These are offset by the substantial reduction in maximum discharge voltages, as well as other design options which become available when using multiple circuits
Cryogenic Characteristics of the ATLAS Barrel Toroid Superconducting Magnet
Pengo, R; Delruelle, N; Pezzetti, M; Pirotte, O; Passardi, Giorgio; Dudarev, A; ten Kate, H
2008-01-01
ATLAS, one of the experiments of the LHC accelerator under commissioning at CERN, is equipped with a large superconducting magnet the Barrel Toroid (BT) that has been tested at nominal current (20500 A). The BT is composed of eight race-track superconducting coils (each one weights about 45 tons) forming the biggest air core toroidal magnet ever built. By means of a large throughput centrifugal pump, a forced flow (about 10 liter/second at 4.5 K) provides the indirect cooling of the coils in parallel. The paper describes the results of the measurements carried out on the complete cryogenic system assembled in the ATLAS cavern situated 100 m below the ground level. The measurements include, among other ones, the static heat loads, i.e., with no or constant current in the magnet, and the dynamic ones, since additional heat losses are produced, during the current ramp-up or slow dump, by eddy currents induced on the coil casing.
Stress analyses of ITER toroidal field coils under fault conditions
International Nuclear Information System (INIS)
Jong, C.T.J.
1990-02-01
The International Thermonuclear Experimental Reactor (ITER) is intended as an experimental thermonuclear tokamak reactor for testing the basic physics, performance and technologies essential to future fusion reactors. The ITER design will be based on extensive new design work, supported by new physical and technological results, and on the great body of experience built up over several years from previous national and international reactor studies. Conversely, the ITER design process should provide the fusion community with valuable insights into what key areas need further development or clarification as we move forward towards practical fusion power. As part of the design process of the ITER toroidal field coils the mechanical behaviour of the magnetic system under fault conditions has to be analysed in more detail. This paper describes the work carried out to create a detailed finite element model of two toroidal field coils as well as some results of linear elastic analyses with fault conditions. The analyses have been performed with the finite element code ANSYS. (author). 5 refs.; 8 figs.; 2 tabs
Shear-Alfven dynamics of toroidally confined plasmas. Part A
International Nuclear Information System (INIS)
Hazeltine, R.D.; Meiss, J.D.
1984-08-01
Recent developments in the stability theory of toroidally confined plasmas are reviewed, with the intention of providing a picture comprehensible to non-specialists. The review considers a class of low-frequency, electromagnetic disturbances that seem especially pertinent to modern high-temperature confinement experiments. It is shown that such disturbances are best unified and understood through consideration of a single, exact fluid moment: the shear-Alfven law. Appropriate versions of this law and its corresponding closure relations are derived - essentially from first principles - and applied in a variety of mostly, but not exclusively, linear contexts. Among the specific topics considered are: flux coordinates (including Hamada coordinates), the Newcomb solubility condition. Shafranov geometry, magnetic island evolution, reduced MHD and its generalizations, drift-kinetic electron response, classical tearing, twisting, and kink instabilities, pressure-modified tearing instability (Δ-critical), collisionless and semi-collisional tearing modes, the ballooning representation in general geometry, ideal ballooning instability, Mercier criterion, near-axis expansions, the second stability region, and resistive and kinetic ballooning modes. The fundamental importance of toroidal topology and curvature is stressed
Impurity control in toroidal devices
International Nuclear Information System (INIS)
1990-01-01
This summary report on the Technical Committee Meeting organized by the IAEA and held in Naka-Gun, Japan, 13-15 February 1989, provides an overview of the results presented. Of the twenty-three papers presented, sixteen were devoted to tokamak experiments. These presented data of plasma behavior in the scrape-off layer and divertor regions, as well as effects of impurities on the core plasma; these are summarized here. Other papers summarized deal with plasma-wall interactions, including wall material behavior. Still others deal with theoretical work on physics modelling in the edge region. Refs, figs and tabs
Alpha heating in toroidal devices
International Nuclear Information System (INIS)
Miley, G.H.
1978-01-01
Ignition (or near-ignition) by alpha heating is a key objective for the achievement of economic fusion reactors. While good confinement of high-energy alphas appears possible in larger reactors, near-term tokamak-type ignition experiments as well as some concepts for small reactors (e.g., the Field-Reversed Mirror or FRM) potentially face marginal situations. Consequently, there is a strong motivation to develop methods to evaluate alpha losses and heating profiles in some detail. Such studies for a TFTR-size tokamak and for a small FRM are described here
Finite toroidal flow generated by unstable tearing mode in a toroidal plasma
Energy Technology Data Exchange (ETDEWEB)
Hao, G. Z., E-mail: haogz@swip.ac.cn; Wang, A. K.; Xu, Y. H.; He, H. D.; Xu, M.; Qu, H. P.; Peng, X. D.; Xu, J. Q.; Qiu, X. M. [Southwestern Institute of Physics, P.O. Box 432, Chengdu 610041 (China); Liu, Y. Q. [Culham Centre for Fusion Energy, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Sun, Y. [Institute of Plasma Physics, Chinese Academic of Sciences, P.O. Box 1126, Hefei 230031 (China); Cui, S. Y. [School of Mathematics and Statistics Science, Ludong University, Yantai 264025 (China)
2014-12-15
The neoclassical toroidal plasma viscosity torque and electromagnetic torque, generated by tearing mode (TM) in a toroidal plasma, are numerically investigated using the MARS-Q code [Liu et al., Phys. Plasmas 20, 042503 (2013)]. It is found that an initially unstable tearing mode can intrinsically drive a toroidal plasma flow resulting in a steady state solution, in the absence of the external momentum input and external magnetic field perturbation. The saturated flow is in the order of 0.5%ω{sub A} at the q=2 rational surface in the considered case, with q and ω{sub A} being the safety factor and the Alfven frequency at the magnetic axis, respectively. The generation of the toroidal flow is robust, being insensitive to the given amplitude of the perturbation at initial state. On the other hand, the flow amplitude increases with increasing the plasma resistivity. Furthermore, the initially unstable tearing mode is fully stabilized by non-linear interaction with the self-generated toroidal flow.
Mirror theory applied to toroidal systems
International Nuclear Information System (INIS)
Cohen, R.H.
1987-01-01
Central features of a mirror plasma are strong departures from Maxwellian distribution functions, ambipolar potentials and densities which vary along a field line, and losses, and the mirror field itself. To examine these features, mirror theorists have developed analytical and numerical techniques to solve the Fokker-Planck equation, evaluate the potentials consistent with the resulting distribution functions, and assess the microstability of these distributions. Various combinations of mirror-plasma fetures are present and important in toroidal plasmas as well, particularly in the edge region and in plasmas with strong r.f. heating. In this paper we survey problems in toroidal plasmas where mirror theory and computational techniques are applicable, and discuss in more detail three specific examples: calculation of the toroidal generalization of the Spitzer-Haerm distribution function (from which trapped-particle effects on current drive can be calculated), evaluation of the nonuniform potential and density set up by pulsed electron-cyclotron heating, and calculation of steady-state distribution functions in the presence of strong r.f. heating and collisions. 37 refs., 3 figs
Mirror theory applied to toroidal systems
International Nuclear Information System (INIS)
Cohen, R.H.
1987-01-01
Central features of a mirror plasma are strong departures from Maxwellian distribution functions, ambipolar potentials and densities which vary along a field line, end losses, and the mirror field itself. To examine these features, mirror theorists have developed analytical and numerical techniques to solve the Fokker-Planck equation, evaluate the potentials consistent with the resulting distribution functions, and assess the microstability of these distributions. Various combinations of mirror-plasma features are present and important in toroidal plasmas as well, particularly in the edge region and in plasmas with strong rf heating. In this paper we survey problems in toroidal plasmas where mirror theory and computational techniques are applicable, and discuss in more detail three specific examples: calculation of the toroidal generalization of the Spitzer-Haerm distribution function (from which trapped-particle effects on current drive can be calculated), evaluation of the nonuniform potential and density set up by pulsed electron-cyclotron heating, and calculation of steady-state distribution functions in the presence of strong rf heating and collisions. 37 refs
Energy Technology Data Exchange (ETDEWEB)
Sutherland, D.A., E-mail: das1990@uw.edu; Jarboe, T.R.; Morgan, K.D.; Pfaff, M.; Lavine, E.S.; Kamikawa, Y.; Hughes, M.; Andrist, P.; Marklin, G.; Nelson, B.A.
2014-04-15
A high-β spheromak reactor concept has been formulated with an estimated overnight capital cost that is competitive with conventional power sources. This reactor concept utilizes recently discovered imposed-dynamo current drive (IDCD) and a molten salt (FLiBe) blanket system for first wall cooling, neutron moderation and tritium breeding. Currently available materials and ITER-developed cryogenic pumping systems were implemented in this concept from the basis of technological feasibility. A tritium breeding ratio (TBR) of greater than 1.1 has been calculated using a Monte Carlo N-Particle (MCNP5) neutron transport simulation. High temperature superconducting tapes (YBCO) were used for the equilibrium coil set, substantially reducing the recirculating power fraction when compared to previous spheromak reactor studies. Using zirconium hydride for neutron shielding, a limiting equilibrium coil lifetime of at least thirty full-power years has been achieved. The primary FLiBe loop was coupled to a supercritical carbon dioxide Brayton cycle due to attractive economics and high thermal efficiencies. With these advancements, an electrical output of 1000 MW from a thermal output of 2486 MW was achieved, yielding an overall plant efficiency of approximately 40%.
Motion of a compact toroid inside a cylindrical flux conserver
Energy Technology Data Exchange (ETDEWEB)
Jarboe, T.R.; Henins, I.; Hoida, H.W.; Linford, R.K.; Marshall, J.; Platts, D.A.; Sherwood, A.R.
1980-10-13
Compact toroids have been generated in a cylindrical resistive flux conserver. They are observed to rotate so that their major axis is perpendicular to the axis of the flux conserver. Subsequently they remain stationary and their magnetic fields decay with a time constant of about 100 ..mu..s. This is the first observation of the predicted tipping mode and its saturation when no external fields are present. The compact toroids contain toroidal fields and are initially prolate in shape.
Motion of a compact toroid inside a cylindrical flux conserver
International Nuclear Information System (INIS)
Jarboe, T.R.; Henins, I.; Hoida, H.W.; Linford, R.K.; Marshall, J.; Platts, D.A.; Sherwood, A.R.
1980-01-01
Compact toroids have been generated in a cylindrical resistive flux conserver. They are observed to rotate so that their major axis is perpendicular to the axis of the flux conserver. Subsequently they remain stationary and their magnetic fields decay with a time constant of about 100 μs. This is the first observation of the predicted tipping mode and its saturation when no external fields are present. The compact toroids contain toroidal fields and are initially prolate in shape
Application of plasma focus device to compression of toroidal plasma
International Nuclear Information System (INIS)
Ikuta, Kazunari
1980-01-01
A new concept of compressing a toroidal plasma using a plasma focus device is considered. Maximum compression ratio of toroidal plasma is determined merely by the initial density ratio of the toroidal plasma to a sheet plasma in a focus device because of the Rayleigh-Taylor instability. An initiation senario of plasma-linear is also proposed with a possible application of this concepts to the creation of a burning plasma in reversed field configurations, i.e., burning plasma vortex. (author)
Structure of DNA toroids and electrostatic attraction of DNA duplexes
International Nuclear Information System (INIS)
Cherstvy, A G
2005-01-01
DNA-DNA electrostatic attraction is considered as the driving force for the formation of DNA toroids in the presence of DNA condensing cations. This attraction comes from the DNA helical charge distribution and favours hexagonal toroidal cross-sections. The latter is in agreement with recent cryo-electron microscopy studies on DNA condensed with cobalt hexammine. We treat the DNA-DNA interactions within the modern theory of electrostatic interaction between helical macromolecules. The size and thickness of the toroids is calculated within a simple model; other models of stability of DNA toroids are discussed and compared
The SSC superconducting air core toroid design development
International Nuclear Information System (INIS)
Fields, T.; Carroll, A.; Chiang, I.H.; Frank, J.S.; Haggerty, J.; Littenberg, L.; Morse, W.; Strand, R.C.; Lau, K.; Weinstein, R.; McNeil, R.; Friedman, J.; Hafen, E.; Haridas, P.; Kendall, H.W.; Osborne, L.; Pless, I.; Rosenson, L.; Pope, B.; Jones, L.W.; Luton, J.N.; Bonanos, P.; Marx, M.; Pusateri, J.A.; Favale, A.; Gottesman, S.; Schneid, E.; Verdier, R.
1990-01-01
Superconducting air core toroids show great promise for use in a muon spectrometer for the SSC. Early studies by SUNY at Stony Brook funded by SSC Laboratory, have established the feasibility of building magnets of the required size. The toroid spectrometer consists of a central toroid with two end cap toroids. The configuration under development provides for muon trajectory measurement outside the magnetic volume. System level studies on support structure, assembly, cryogenic material selection, and power are performed. Resulting selected optimal design and assembly is described. 4 refs., 6 figs
Form factor of some types of toroidal solenoids
International Nuclear Information System (INIS)
Koryavko, V.I.; Litvinenko, Yu.A.
1979-01-01
Obtained were the type of dependence between consumed power and formed field for toroidal helical-wound solenoids and the expression for the form factor analogous to the Fabry coefficient for cylindrical solenoids. Determined were optimum dimensions of the helical winding of ''forceless'' toroidal solenoids satisfying the condition of the formation of maximum field at minimum consumed power. Investigations also covered some types of conventional toroidal solenoids. Presented in the paper diagrams permitted to chose dimensions of the considered toroidal solenoids according to their consumed power and winding material volume
Toroidal plasma enhanced CVD of diamond films
International Nuclear Information System (INIS)
Zvanya, John; Cullen, Christopher; Morris, Thomas; Krchnavek, Robert R.; Holber, William; Basnett, Andrew; Basnett, Robert; Hettinger, Jeffrey
2014-01-01
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 sp 3 peak has a narrow spectral width (FWHM 12 ± 0.5 cm −1 ) and that negligible amounts of the sp 2 band are present, indicating good-quality diamond films
Liquid toroidal drop under uniform electric field
Zabarankin, Michael
2017-06-01
The problem of a stationary liquid toroidal drop freely suspended in another fluid and subjected to an electric field uniform at infinity is addressed analytically. Taylor's discriminating function implies that, when the phases have equal viscosities and are assumed to be slightly conducting (leaky dielectrics), a spherical drop is stationary when Q=(2R2+3R+2)/(7R2), where R and Q are ratios of the phases' electric conductivities and dielectric constants, respectively. This condition holds for any electric capillary number, CaE, that defines the ratio of electric stress to surface tension. Pairam and Fernández-Nieves showed experimentally that, in the absence of external forces (CaE=0), a toroidal drop shrinks towards its centre, and, consequently, the drop can be stationary only for some CaE>0. This work finds Q and CaE such that, under the presence of an electric field and with equal viscosities of the phases, a toroidal drop having major radius ρ and volume 4π/3 is qualitatively stationary-the normal velocity of the drop's interface is minute and the interface coincides visually with a streamline. The found Q and CaE depend on R and ρ, and for large ρ, e.g. ρ≥3, they have simple approximations: Q˜(R2+R+1)/(3R2) and CaE∼3 √{3 π ρ / 2 } (6 ln ρ +2 ln [96 π ]-9 )/ (12 ln ρ +4 ln [96 π ]-17 ) (R+1 ) 2/ (R-1 ) 2.
Review of the Advanced Toroidal Facility program
International Nuclear Information System (INIS)
Lyon, J.F.; Murakami, M.
1987-01-01
This report summarizes the history and design goals of the Advanced Toroidal Facility (ATF). The ATF is nearing completion at ORNL with device completion expected in May 1987 and first useful plasma operation in June/July 1987. ATF is a moderate-aspect-ratio torsatron, the world's largest stellarator facility with R = 2.1 m, α bar = 0.3 m and B = 2 T (5-s pulse) or 1 T (steady-state capability). It has been specifically designed to support the US tokamak program by studying important toroidal confinement issues in a similar magnetic geometry that allows external control of the magnetic configuration properties and their radial profiles: transform, shear, well depth, shaping, axis topology, etc. ATF will operate in a current-free model which allows separation of current-driven and pressure-driven plasma behavior. It also complements the world stellarator program in its magnetic configuration (between Heliotron-E and W VII-AS) and its capabilities (large size, good access, steady state capability, second stability access, etc.). For both roles ATF will require high-power long-pulse heating to carry out its physics goals since the high power NBI pulse is limited to 0.3 s. The ATF program focuses on demonstrating the principles of high-beta, steady-state operation in toroidal geometry through its study of: (1) scaling of beta limits with magnetic configuration properties and the plasma behavior in the second stability regime; (2) transport scaling at low collisionality and the role/control of electric field; (3) control of plasma density and impurities using divertors; (4) plasma heating with NBI, ECH, ICH, and plasma fueling with gas puffing and pellet injection; and (5) optimization of the magnetic configuration
EMPACT: Electrons Muons Partons with Air Core Toroids
International Nuclear Information System (INIS)
Marx, M.D.
1990-01-01
The EMPACT experiment utilizes a broad approach to maximize its discovery potential for new phenomena accessible at the SSC. The high resolution detector has a balances emphasis on, and large acceptance for, electrons, muons, jets, and noninteracting particles, and is capable of utilizing the ultimate luminosity of the SSC. The detector emphasizes excellent calorimetry augmented by TRD tracking, and employs an innovative system of superconducting air core toroids for muon measurements. Significant engineering effort has established the feasibility of a baseline detector concept and has addressed the related issues of support facilities, assembly, and detector integration. The design has been tested against the challenges of predicted phenomena, with the expectation that this will optimize the capacity for observing the unexpected. EMPACT's international collaboration has unprecedented support from major aerospace industries who are providing tools and expertise for project design and integration, which will assure that a detector optimized for performance and cost will be available for the first collisions at the new laboratory
Toroidal electron beam energy storage for controlled fusion
International Nuclear Information System (INIS)
Clark, W.; Korn, P.; Mondelli, A.; Rostoker, N.
1976-01-01
In the presence of an external magnetic field stable equilibria exist for an unneutralized electron beam with ν/γ >1. As a result, it is in principle, possible to store very large quantities of energy in relatively small volumes by confining an unneutralized electron beam in a Tokamak-like device. The energy is stored principally in the electrostatic and self-magnetic fields associated with the beam and is available for rapid heating of pellets for controlled fusion. The large electrostatic potential well in such a device would be sufficient to contain energetic alpha particles, thereby reducing reactor wall bombardment. This approach also avoids plasma loss and wall bombardment by charge exchange neutrals. The conceptual design of an electrostatic Tokamak fusion reactor (ETFR) is discussed. A small toroidal device (the STP machine) has been constructed to test the principles involved. Preliminary experiments on this device have produced electron densities approximately 10% of those required in a reactor
Density Measurement of Compact Toroid with Mach-Zehnder Interferometer
Laufman-Wollitzer, Lauren; Endrizzi, Doug; Brookhart, Matt; Flanagan, Ken; Forest, Cary
2016-10-01
Utilizing a magnetized coaxial plasma gun (MCPG) built by Tri Alpha Energy, a dense compact toroid (CT) is created and injected at high speed into the Wisconsin Plasma Astrophysics Laboratory (WiPAL) vessel. A modified Mach-Zehnder interferometer from the Line-Tied Reconnection Experiment (LTRX) provides an absolute measurement of electron density. The interferometer is located such that the beam intersects the plasma across the diameter of the MCPG drift region before the CT enters the vessel. This placement ensures that the measurement is taken before the CT expand. Results presented will be used to further analyze characteristics of the CT. Funding provided by DoE, NSF, and WISE Summer Research.
Toroidal inhomogeneity of the vertical field in a tokamak apparatus
International Nuclear Information System (INIS)
Sometani, Taro; Takashima, Hidekazu
1977-01-01
An experiment with a model device has been made on the toroidal inhomogeneity of the vertical field in a Tokamak with an iron core. The D.C. vertical field is increased near the yokes of the iron core, while the gross plasma image field (consisting of the components due to the plasma current, the primary current, and its image) is reduced there. These two vertical fields, when superposed, exert force on the plasma as a less inhomogeneous external vertical field. The vertical field can be homogenized satisfactorily by using a compensation winding wound at a proper position on the iron core even if the shielding plates, which are mounted on some Tokamaks, are dispensed with. (auth.)
Characteristics of toroidal energy deposition asymmetries in ASDEX
International Nuclear Information System (INIS)
Evans, T.E.; Neuhauser, J.; Leuterer, F.; Mueller, E.R.
1990-01-01
Large toroidal and poloidal asymmetries with characteristics which are sensitively dependent on q a , the vertical position of the plasma, and the type of additional heating are observed in the energy flow to the ASDEX divertor target plates. The largest asymmetries and total energy depositions are observed during lower hybrid wave injection experiments with approximately 50% of the input energy going to the combined divertor targets and shields. A maximum localized energy density loading of 10 MJ/m 2 is typical under these conditions. Measurements of the asymmetries are consistent with a model in which magnetic islands and ergodicity due to intrinsic magnetic perturbations dominate the energy transpot across the primary magnetic separatrix. The results emphasize the essential role of resonant magnetic perturbations in determining the performance of tokamaks and demonstrate that non-axisymmetric effects caused by small perturbations become increasingly important in determining the transport properties as the injected power is increased. (orig.)
Roles of electric field on toroidal magnetic confinement
International Nuclear Information System (INIS)
Itoh, Kimitaka; Itoh, Sanae; Sanuki, Heiji; Fukuyama, Atsushi.
1992-11-01
Theoretical research on the influence of the electric field on the toroidal magnetic confinement is surveyed. The static electric field is first described. Physics pictures on the generation of the radial electric field and the influence on the confinement are shown. Neoclassical effects as well as the nonclassical processes are discussed. Emphasis is made on the connection with the improved confinement. Convective cell, i.e. the nonuniform potential on the magnetic surface is also discussed. The roles of the fluctuating electric field are then reviewed. The progress in the recent theories on the anomalous transport is addressed. Through these surveys, the impact of the experiments using the heavy ion beam probes on the modern plasma physics is illustrated. (author) 66 refs
Investigations of toroidal wave numbers of the kink instabilities in a toroidal pinch plasma
International Nuclear Information System (INIS)
Hamajima, Takataro; Irisawa, Juichi; Tsukada, Tokuaki; Sugito, Osamu; Maruyama, Hideaki
1979-01-01
The axial toroidal wave numbers of the kink instability of toroidal pinch plasma were measured and investigated with a specially designed coil, and the results were compared with the MHD theory. The schematic figure and the particulars of the experimental apparatus are briefly illustrated in the first part. The method of generating theta-Z pinch plasma, the wave form of the magnetic flux density in Z-direction and the plasma current are also explained. The 360 deg stereoscopic framing photographs were taken with an image converter camera at the intervals of 0.5 μs after the initiation of the main electric discharge in Z-circuit. From these photographs, the growth of the kink instability was observed. The measured magnetic field distribution at t = 2 μs is presented. In the second part, the radial displacement of plasma and toroidal wave number were measured from the above framing photographs. Then the spectra of plasma displacement were analyzed by the Fourier analysis. The measured results of toroidal wave number was analyzed by both the skin current model and the diffuse current model. Many new results obtained from the present study were mainly derived from the observation of the framing photographs, and they are summarized in the final part of this paper. (Aoki, K.)
Toroidal equilibrium of a non-neutral plasma with toroidal current, inertia and pressure
International Nuclear Information System (INIS)
Bhattacharyya, S.N.; Avinash, K.
1992-01-01
Equilibrium of non-neutral clouds in a toroidal vessel with toroidal magnetic field is demonstrated in the presence of a toroidal current, finite mass and finite pressure. With a toroidal current, it is shown that in a large-aspect-ratio conducting torus the equilibrium is governed by competition between forces produced by image charges and image currents. When μ 0 ε 0 E r 2 >B θ 2 (whe re E r and B θ are the self electrostatic and self magnetic fields of the cloud), the confinement is electrostatic and plasma shifts inwards; when μ 0 ε 0 E r 2 θ 2 , the confinement is magnetic and plasma shifts outwards. For μ 0 ε 0 E r 2 = B θ 2 there is no equilibrium. With finite mass or finite pressure, it is shown, in a large-aspect-ratio approximation, that the fluid drift surfaces and equipotential surfaces are displaced with respect to each other. In both cases the fluid drift surfaces are shifted inwards from the equipotential surfaces. (author)
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.
Linear mode conversion in a toroidal plasma
International Nuclear Information System (INIS)
Hellsten, T.
1980-05-01
Linear mode conversion at the perpendicular ion cyclotron resonance has been treated for an axially symmetric toroidal plasma. The mode conversion appears between a fast electromagnetic wave and a slow-quasi electrostatic wave, due to finite electron inertia. The problem reduces to the Orr-Sommerfeld equation where the coefficients determining the reflectron, transmission and conversion are functions of the arc length along a poloidal intersection of the resonance surface. These coefficients can be determined from eigenfunctions of an ordinary differential equation. (author)
Electrical disruption in toroidal plasma of hydrogen
International Nuclear Information System (INIS)
Roberto, M.; Silva, C.A.B.; Goes, L.C.S.; Sudano, J.P.
1991-01-01
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.)
Impurity studies in the advanced toroidal facility
International Nuclear Information System (INIS)
Isler, R.C.; Horton, L.D.; Crume, E.C.; Howe, H.C.; Voronov, G.S.
1989-01-01
Impurities have played an important role in the initial stages of operation of the Advanced Toroidal Facility. Cleanup practices have been adequate enough that plasmas heated by ECH only can be operated in a quasi-steady state; however, neutral beam injected plasmas always collapse to a low temperature. It is not clear whether impurity radiation is actually responsible for initiating the collapse, but at the time the stored energy reaches a maximum, there are indications of poloidal asymmetries in radiation from low ionization stages, such as observed in marfes, which could play a dominant role in the plasma evolution. 3 refs., 5 figs
Convective cells and transport in toroidal plasmas
International Nuclear Information System (INIS)
Hassam, A.B.; Kulsrud, R.M.
1978-12-01
The properties of convective cells and the diffusion resulting from such cells are significantly influenced by an inhomogeneity in the extermal confining magnetic field, such as that in toroidal plasmas. The convective diffusion in the presence of a field inhomogeneity is estimated. For a thermal background, this diffusion is shown to be substantially smaller than classical collisional diffusion. For a model nonthermal background, the diffusion is estimated, for typical parameters, to be at most of the order of collisional diffusion. The model background employed is based on spectra observed in numerical simulations of drift-wave-driven convective cells
Bifurcation theory for toroidal MHD instabilities
International Nuclear Information System (INIS)
Maschke, E.K.; Morros Tosas, J.; Urquijo, G.
1992-01-01
Using a general representation of magneto-hydrodynamics in terms of stream functions and potentials, proposed earlier, a set of reduced MHD equations for the case of toroidal geometry had been derived by an appropriate ordering with respect to the inverse aspect ratio. When all dissipative terms are neglected in this reduced system, it has the same linear stability limits as the full ideal MHD equations, to the order considered. When including resistivity, thermal conductivity and viscosity, we can apply bifurcation theory to investigate nonlinear stationary solution branches related to various instabilities. In particular, we show that a stationary solution of the internal kink type can be found
Modelling of the toroidal asymmetry of poloidal halo currents in conducting structures
International Nuclear Information System (INIS)
Pomphrey, N.; Bialek, J.M.; Part, W.
1998-01-01
During plasma disruptions, substantial toroidal and poloidal eddy currents are generated in the vacuum vessel and other plasma facing conducting structures. Eddy currents that conduct charge through paths which close through the plasma periphery are called halo currents, and these can be of substantial magnitude. Of particular concern for tokamak design and operation is the observed toroidal asymmetry of the halo current distribution: such an asymmetric distribution leads to problematic non-uniform forces on the conducting structures. The premise is adopted that the source of toroidal asymmetry is the plasma deformation resulting from the non-linear external kink instability that develops during the current quench phase of a disruption. A simple model is presented of the kinked plasma that allows an analytic calculation of the dependence of the toroidal peaking factor (TPF) on the ratio of the halo current to the total toroidal plasma current, I h /I p . Expressions for the TPF as a function of I h /I p are derived for m/n=2/1 and m/n=1/1 helical instabilities. The expressions depend on a single parameter, which measures the amplitude of the saturated state of the kink instability. A comparison with disruption data from experiments shows good agreement. Numerical experiments that simulate non-linear external kinks provide guidance on the values expected for the saturated amplitude. It is proposed that a simple plasma halo model is adequate for assessing the engineering impact of asymmetric halo currents, since the force distribution on the conducting structures depends mainly on the 'resistive distribution' of the eddy currents. A brief description is given of an electromagnetics code that calculates the time development of eddy currents in conducting structures, and the code is applied to two halo current disruption scenarios. These are used to emphasize the importance of having an accurate eddy current calculation to correctly estimate the engineering impact of
Structure and damping of toroidal drift waves (and their implications for anomalous transport)
International Nuclear Information System (INIS)
Taylor, J.B.; Connor, J.; Wilson, H.R.
1993-05-01
The conventional theory of high-n toroidal drift waves, based on the ballooning representation, indicates that shear-damping is generally reduced in a torus compared to its plane-slab value. It therefore describes the most unstable class of toroidal drift waves. However, modes of this type occur only i f the diamagnetic frequency ω*(r) has a maximum in r, and they affect only a small fraction, Ο(1/n l/2 ), of the plasma radius around this maximum. Consequently they may produce little anomalous transport. In the present work we show that, within the ballooning description, there is another class of toroidal drift waves with very different properties to the conventional ones. The new modes have greater shear-damping (closer to that in a plane-slab) than the conventional ones and so have a higher instability threshold. However, they occur for any plasma profile and at all radii, and they have larger radial extent. Consequently they may produce much greater anomalous transport than the possibly benign conventional modes. This suggests a picture of anomalous transport in which the plasma profile is determined by marginal stability, but marginal to the new class of modes not to the conventional ones. This might explain why marginally stable profiles calculated for drift waves with plane-slab damping sometimes agree well with the profiles in toroidal experiments. It is also consistent with the fact that experimental profiles may exceed conventional toroidal instability thresholds. The new modes may also be related to the tong radial structures which appear in some plasma simulations and in experiments
Toroidally asymmetric particle transport caused by phase-locking of MHD modes in RFX-mod
International Nuclear Information System (INIS)
Lorenzini, R.; Terranova, D.; Auriemma, F.; Cavazzana, R.; Innocente, P.; Martini, S.; Serianni, G.; Zuin, M.
2007-01-01
The particle and energy transport in reversed field pinch experiments is affected by the locking in phase of the tearing modes, also dubbed dynamo modes, that sustain the magnetic configuration. In standard RFP pulses many m = 1 and m = 0 resonant modes have a relatively large amplitude (a spectrum dubbed MH for multiple helicity). The locking in phase of m = 1 tearing modes produces a helical deformation (locked mode (LM)) of the magnetic surfaces in a region of approximately 40 toroidal degrees. The region of the LM is characterized by a strong plasma-wall interaction and by high losses of energy and particles that account for a significant fraction of the input power and of the total particle outflux. The locking in phase of m = 0 modes modifies the plasma radius, shrinking and enlarging the plasma cross section in two wide toroidal regions of about 100 0 . The purpose of this paper is to investigate to what extent the locking in phase of m = 0 modes introduces toroidal asymmetries in the transport properties of the plasma. This study has been carried out investigating the shape of the density profile in the RFX-mod experiment. The analyses show that the profile exhibits a dependence on the toroidal angle, which is related to the deformation of the plasma column due to the locking in phase of m = 0 modes: the least steep density gradients at the edge are found in the region where the plasma column is shrunk, entailing that in this region the particle transport is enhanced. An analogous asymmetry also characterizes the density and magnetic fluctuations at the edge, which are enhanced in the same toroidal region where the particle transport also is enhanced. This result can be considered the first experimental evidence of an instability localized where the plasma column is shrunk
International Nuclear Information System (INIS)
Narita, Emi; Fukuda, Takeshi; Honda, Mitsuru; Hayashi, Nobuhiko; Urano, Hajime; Ide, Shunsuke
2015-01-01
Tokamak plasmas with an internal transport barrier (ITB) are capable of maintaining improved confinement performance. The ITBs formed in plasmas with the weak magnetic shear and the weak radial electric field shear are often observed to be modest. In these ITB plasmas, it has been found that the electron temperature ITB is steeper when toroidal rotation is in a co-direction with respect to the plasma current than when toroidal rotation is in a counter-direction. To clarify the relationship between the direction of toroidal rotation and heat transport in the ITB region, we examine dominant instabilities using the flux-tube gyrokinetic code GS2. The linear calculations show a difference in the real frequencies; the counter-rotation case has a more trapped electron mode than the co-rotation case. In addition, the nonlinear calculations show that with this difference, the ratio of the electron heat diffusivity χ_e to the ion's χ_i is higher for the counter-rotation case than for the co-rotation case. The difference in χ_e /χ_i agrees with the experiment. We also find that the effect of the difference in the flow shear between the two cases due to the toroidal rotation direction on the linear growth rate is not significant. (author)
Propulsion using the electron spiral toroid
International Nuclear Information System (INIS)
Seward, Clint
1998-01-01
A new propulsion method is proposed which could potentially reduce propellant needed for space travel by three orders of magnitude. It uses the newly patented electron spiral toroid (EST), which stores energy as magnetic field energy. The EST is a hollow toroid of electrons, all spiraling in parallel paths in a thin outer shell. The electrons satisfy the coupling condition, forming an electron matrix. Stability is assured as long as the coupling condition is satisfied. The EST is held in place with a small external electric field; without an external magnetic field. The EST system is contained in a vacuum chamber. The EST can be thought of as an energetic entity, with electrons at 10,000 electron volts. Propulsion would not use combustion, but would heat propellant through elastic collisions with the EST surface and eject them for thrust. Chemical rocket combustion heats propellant to 4000 deg. C; an EST will potentially heat the propellant 29,000 times as much, reducing propellant needs accordingly. The thrust can be turned ON and OFF. The EST can be recharged as needed
Toroidal Simulations of Sawteeth with Diamagnetic Effects
Beidler, Matthew; Cassak, Paul; Jardin, Stephen
2014-10-01
The sawtooth crash in tokamaks limits the core temperature, adversely impacts confinement, and seeds disruptions. Adequate knowledge of the physics governing the sawtooth crash and a predictive capability of its ramifications has been elusive, including an understanding of incomplete reconnection, i.e., why sawteeth often cease prematurely before processing all available magnetic flux. There is an indication that diamagnetic suppression could play an important role in this phenomenon. While computational tools to study toroidal plasmas have existed for some time, extended-MHD physics have only recently been integrated. Interestingly, incomplete reconnection has been observed in simulations when diamagnetic effects are present. In the current study, we employ the three-dimensional, extended-MHD code M3D-C1 to study the sawtooth crash in a toroidal geometry. In particular, we describe how magnetic reconnection at the q = 1 rational surface evolves when self-consistently increasing diamagnetic effects are present. We also explore how the termination of reconnection may lead to core-relaxing ideal-MHD instabilities.
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.
Low-frequency fluctuations in a pure toroidal magnetized plasma
Indian Academy of Sciences (India)
A magnetized, low- plasma in pure toroidal configuration is formed and extensively studied with ion mass as control parameter. Xenon, krypton and argon plasmas are formed at a fixed toroidal magnetic field of 0.024 T, with a peak density of ∼ 1011 cm-3, ∼ 4 × 1010 cm-3 and ∼ 2 × 1010 cm−3 respectively.
Toroidal asymmetries in divertor impurity influxes in NSTX
Directory of Open Access Journals (Sweden)
F. Scotti
2017-08-01
Full Text Available Toroidal asymmetries in divertor carbon and lithium influxes were observed in NSTX, due to toroidal differences in surface composition, tile leading edges, externally-applied three-dimensional (3D fields and toroidally-localized edge plasma modifications due to radio frequency heating. Understanding toroidal asymmetries in impurity influxes is critical for the evaluation of total impurity sources, often inferred from measurements with a limited toroidal coverage. The toroidally-asymmetric lithium deposition induced asymmetries in divertor lithium influxes. Enhanced impurity influxes at the leading edge of divertor tiles were the main cause of carbon toroidal asymmetries and were enhanced during edge localized modes. Externally-applied 3D fields led to strike point splitting and helical lobes observed in divertor impurity emission, but marginal changes to the toroidally-averaged impurity influxes. Power coupled to the scrape-off layer SOL plasma during radio frequency (RF heating of H-mode discharges enhanced impurity influxes along the non-axisymmetric divertor footprint of flux tubes connecting to plasma in front of the RF antenna.
Formation of a compact torus using a toroidal plasma gun
International Nuclear Information System (INIS)
Levine, M.A.; Pincosy, P.A.
1981-01-01
Myers, Levine and Pincosy earlier reported results using a toroidal plasma gun. The device differs from the usual coaxial plasma gun in the use of a strong toroidal bias current for enhanced efficiency, a pair of disk-like accelerating electrodes for reduced viscosity and a fast pulsed toroidal gas valve for more effective use of the injected gas sample. In addition, a technique is used for generating a toroidal current in the plasma ring. The combination offers an opportunity to deliver a plasma with a large amount of energy and to vary the density and relative toroidal and poloidal magnetic field intensities over a range of values. It is the purpose of this paper to report further experimental results, to project the gun's applications to the formation of a compact torus, and to propose a simple modification of the present apparatus as a test
Analysis of MHD equilibria by toroidal multipolar expansions
International Nuclear Information System (INIS)
Alladio, F.; Crisanti, F.
1986-01-01
The use of fully toroidal co-ordinates permits the two-dimensional problem of the axisymmetric plasma toroidal equilibrium to be reduced to the one-dimensional problem of determining a limited number of its toroidal multipolar moments. This has allowed the creation of a fast semi-analytic predictive equilibrium code that can be used in both free and fixed boundary conditions for plasmas with circular or mildly non-circular cross-section. The concept of toroidal multipoles is also particularly suitable for the analysis of experimental data from magnetic probe measurements and clarifies the conditions under which the plasma thermal and electrical self-inductances βsub(p) and lsub(i) can be estimated separately. Finally, the interpretation of the magnetic equilibrium measurements in terms of toroidal multipoles can directly provide the boundary conditions for a fast equilibrium reconstruction code. Examples of the application of such a code to the JET magnetic measurements are reported. (author)
International Nuclear Information System (INIS)
Amemiya, Naoyuki; Takaichi, Kazuaki; Katsurai, Makoto
1989-01-01
The magnetic structure in coaxial-gun-sustained spheromaks has been investigated. The plasma gun has been operated with a small axial/radial bias magnetic flux as compared to the azimuthal magnetic flux produced by the discharge current. Stronger magnetic field is observed in the entrance region (ER) than in the flux conserver (FC). In both ER and FC, the magnetic structure is nearly axisymmetric. The axial magnetic field in ER is amplified up to about sixteen times as large as the bias magnetic field. This amplification is limited by the drastic change in the magnetic structure, which occurs when the discharge current becomes very large. The magnetic structure before the drastic change is interpreted with the Bessel function model. The μ estimation shows that the magnetic structure is mainly determined by the boundary geometry, not by the external magnetic flux and current. (author)
Photoelastic and analytical investigation of stress in toroidal magnetic field coils
International Nuclear Information System (INIS)
Pih, H.; Gray, W.H.
1975-01-01
A series of two-dimensional photoelastic stress analyses on circular and oval toroidal magnetic field coils for fusion reactors were made. The circumferential variation of the coil's magnetic force was simulated by applying different pressures to sixteen segmented regions of the inner surface of the models. Isochromatics and isoclinics were measured at selected points on the loaded model in a transmission polariscope using a microphotometer. Separate principal stresses were obtained using the combination of photoelastic information and isopachic data measured from the solution of Laplace's equation by the electrical analog method. Analysis of the same coil geometries, loadings, and boundary conditions were made using the finite element method. General agreement between theory and experiment was realized. From this investigation several variations of coil geometry and methods of support were evaluated. Based upon this experiment, suggestions for optimum structural design of toroidal field coils are presented
Review of recent experiments on magnetic reconnection in laboratory plasmas
International Nuclear Information System (INIS)
Yamada, M.
1995-02-01
The present paper reviews recent laboratory experiments on magnetic reconnection. Examples will be drawn from electron current sheet experiments, merging spheromaks, and from high temperature tokamak plasmas with the Lundquist numbers exceeding 10 7 . These recent laboratory experiments create an environment which satisfies the criteria for MHD plasma and in which the global boundary conditions can be controlled externally. Experiments with fully three dimensional reconnection are now possible. In the most recent TFTR tokamak discharges, Motional Stark effect (MSE) data have verified the existence of a partial reconnection. In the experiment of spheromak merging, a new plasma acceleration parallel to the neutral line has been indicated. Together with the relationship of these observations to the analysis of magnetic reconnection in space and in solar flares, important physics issues such as global boundary conditions, local plasma parameters, merging angle of the field lines, and the 3-D aspects of the reconnection are discussed
Nonideal magnetohydrodynamic instabilities and toroidal magnetic confinement
International Nuclear Information System (INIS)
Furth, H.P.
1985-05-01
The marked divergence of experimentally observed plasma instability phenomena from the predictions of ideal magnetohydrodynamics led in the early 1960s to the formulations of finite-resistivity stability theory. Beginning in the 1970s, advanced plasma diagnostics have served to establish a detailed correspondence between the predictions of the finite-resistivity theory and experimental plasma behavior - particularly in the case of the resistive kink mode and the tokamak plasma. Nonlinear resistive-kink phenomena have been found to govern the transport of magnetic flux and plasma energy in the reversed-field pinch. The other predicted finite-resistivity instability modes have been more difficult to identify directly and their implications for toroidal magnetic confinement are still unresolved
Design considerations for ITER toroidal field coils
International Nuclear Information System (INIS)
Kalsi, S.S.; Lousteau, D.C.; Miller, J.R.
1987-01-01
The International Thermonuclear Experimental Reactor (ITER) is a new tokamak design project with joint participation from Europe, Japan, the Union of Soviet Socialist Republics (U.S.S.R.), and the United States. This paper describes a magnetic and mechanical design methodology for toroidal field (TF) coils that employs Nb 3 Sn superconductor technology. Coil winding is sized by using conductor concepts developed for the U.S. TIBER concept. Manifold concepts are presented for the complete cooling system. Also included are concepts for the coil structural arrangement. The effects of in-plane and out-of-plane loads are included in the design considerations for the windings and case. Concepts are presented for reacting these loads with a minimum amount of additional structural material. Concepts discussed in this paper could be considered for the ITER TF coils
Magnetohydrodynamic Stability of a Toroidal Plasma's Separatrix
International Nuclear Information System (INIS)
Webster, A. J.; Gimblett, C. G.
2009-01-01
Large tokamaks capable of fusion power production such as ITER, should avoid large edge localized modes (ELMs), thought to be triggered by an ideal magnetohydrodynamic instability due to current at the plasma's separatrix boundary. Unlike analytical work in a cylindrical approximation, numerical work finds the modes are stable. The plasma's separatrix might stabilize modes, but makes analytical and numerical work difficult. We generalize a cylindrical model to toroidal separatrix geometry, finding one parameter Δ ' determines stability. The conformal transformation method is generalized to allow nonzero derivatives of a function on a boundary, and calculation of the equilibrium vacuum field allows Δ ' to be found analytically. As a boundary more closely approximates a separatrix, we find the energy principle indicates instability, but the growth rate asymptotes to zero
Three dimensional transport model for toroidal plasmas
International Nuclear Information System (INIS)
Copenhauer, C.
1980-12-01
A nonlinear MHD model, developed for three-dimensional toroidal geometries (asymmetric) and for high β (β approximately epsilon), is used as a basis for a three-dimensional transport model. Since inertia terms are needed in describing evolving magnetic islands, the model can calculate transport, both in the transient phase before nonlinear saturation of magnetic islands and afterwards on the resistive time scale. In the β approximately epsilon ordering, the plasma does not have sufficient energy to compress the parallel magnetic field, which allows the Alfven wave to be eliminated in the reduced nonlinear equations, and the model then follows the slower time scales. The resulting perpendicular and parallel plasma drift velocities can be identified with those of guiding center theory
Calculation of a toroidal labyrinth shields
International Nuclear Information System (INIS)
Sul'kin, A.G.
1979-01-01
Calculation of protective case with a toroidal labyrinth channel, being one of the main design elements of hose gamma-devices, is presented. The case provides relative isotropic distribution of radiation outside protection limits. The main geometric parameters of the channel are determined: r-radius of the channel hole, rho-bend radius of the channel axis, β-angle of the channel bend. General exposure dose rate of γ-radiation in the detection point at l distance (usually l=100 m during calculations), is also calculated. Differential current dose albedo values have been found for certain combinations of parameters of the labyrinth channel. It is considered for simplification of labyrinth channel calculations, that backward radiation scattering passes, without energy change and isotropically, due to which differential current albedo values of γ-radiation for any incidence angle may be determined from integral albedo current values by the empirie formula
Advanced toroidal facility vaccuum vessel stress analyses
International Nuclear Information System (INIS)
Hammonds, C.J.; Mayhall, J.A.
1987-01-01
The complex geometry of the Advance Toroidal Facility (ATF) vacuum vessel required special analysis techniques in investigating the structural behavior of the design. The response of a large-scale finite element model was found for transportation and operational loading. Several computer codes and systems, including the National Magnetic Fusion Energy Computer Center Cray machines, were implemented in accomplishing these analyses. The work combined complex methods that taxed the limits of both the codes and the computer systems involved. Using MSC/NASTRAN cyclic-symmetry solutions permitted using only 1/12 of the vessel geometry to mathematically analyze the entire vessel. This allowed the greater detail and accuracy demanded by the complex geometry of the vessel. Critical buckling-pressure analyses were performed with the same model. The development, results, and problems encountered in performing these analyses are described. 5 refs., 3 figs
The theory of toroidally confined plasmas
White, Roscoe B
2014-01-01
This graduate level textbook develops the theory of magnetically confined plasma, with the aim of bringing the reader to the level of current research in the field of thermonuclear fusion. It begins with the basic concepts of magnetic field description, plasma equilibria and stability, and goes on to derive the equations for guiding center particle motion in an equilibrium field. Topics include linear and nonlinear ideal and resistive modes and particle transport. It is of use to workers in the field of fusion both for its wide-ranging account of tokamak physics and as a kind of handbook or formulary. This edition has been extended in a number of ways. The material on mode-particle interactions has been reformulated and much new information added, including methodology for Monte Carlo implementation of mode destabilization. These results give explicit means of carrying out mode destabilization analysis, in particular for the dangerous fishbone mode. A new chapter on cyclotron motion in toroidal geometry has ...
Toroidal microinstability studies of high temperature tokamaks
International Nuclear Information System (INIS)
Rewoldt, G.; Tang, W.M.
1989-07-01
Results from comprehensive kinetic microinstability calculations are presented showing the effects of toroidicity on the ion temperature gradient mode and its relationship to the trapped-electron mode in high-temperature tokamak plasmas. The corresponding particle and energy fluxes have also been computed. It is found that, although drift-type microinstabilities persist over a wide range of values of the ion temperature gradient parameter η i ≡ (dlnT i /dr)/(dlnn i /dr), the characteristic features of the dominant mode are those of the η i -type instability when η i > η ic ∼1.2 to 1.4 and of the trapped-electron mode when η i ic . 16 refs., 7 figs
The ground fault detection system for the Tore Supra toroidal pump limiter
International Nuclear Information System (INIS)
Zunino, K.; Cara, P.; Fejoz, P.; Hourtoule, J.; Loarer, T.; Pomaro, N.; Santagiustina, A.; Spuig, P.; Villecroze, F.
2003-01-01
The toroidal pump limiter (TPL) of Tore Supra is electrically insulated from the vacuum-vessel, to allow its polarization at a voltage of up to 1 kV. In order to monitor continuously the integrity of the TPL electrical insulation, an electronic diagnostic system called TPL ground fault detection system (GFDS) has been developed. The paper will report on the design and the operation experience of the GFD system and on the evolution of the TPL grounding
Energy Technology Data Exchange (ETDEWEB)
Frassetto, F.; Poletto, L., E-mail: poletto@dei.unipd.it [National Research Council, Institute of Photonics and Nanotechnologies, via Trasea 7, 35131 Padova (Italy); Trabattoni, A.; Anumula, S.; Sansone, G. [Department of Physics, Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy); Calegari, F. [National Research Council, Institute of Photonics and Nanotechnologies, Piazza L. da Vinci 32, 20133 Milano (Italy); Nisoli, M. [Department of Physics, Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy); National Research Council, Institute of Photonics and Nanotechnologies, Piazza L. da Vinci 32, 20133 Milano (Italy)
2014-10-15
We have developed a novel attosecond beamline designed for attosecond-pump/attosecond probe experiments. Microfocusing of the Extreme-ultraviolet (XUV) radiation is obtained by using a coma-compensated optical configuration based on the use of three toroidal mirrors controlled by a genetic algorithm. Trains of attosecond pulses are generated with a measured peak intensity of about 3 × 10{sup 11} W/cm{sup 2}.
International Nuclear Information System (INIS)
Frassetto, F.; Poletto, L.; Trabattoni, A.; Anumula, S.; Sansone, G.; Calegari, F.; Nisoli, M.
2014-01-01
We have developed a novel attosecond beamline designed for attosecond-pump/attosecond probe experiments. Microfocusing of the Extreme-ultraviolet (XUV) radiation is obtained by using a coma-compensated optical configuration based on the use of three toroidal mirrors controlled by a genetic algorithm. Trains of attosecond pulses are generated with a measured peak intensity of about 3 × 10 11 W/cm 2
Toroidal field magnet and poloidal divertor field coil systems adapted to reactor requirements
International Nuclear Information System (INIS)
Koeppendoerfer, W.
1985-01-01
ASDEX Upgrade is a tokamak experiment with external poloidal field coils, that is now under construction at IPP Garching. It can produce elongated single-null (SN), double-null (DN) and limiter (L) configurations. The SN is the reference configuration with asymmetric load distributions in the poloidal field (PF) system and the toroidal field (TF) magnet. Plasma control and stabilization requires a rigid passive conductor close to the plasma. The design principles of the coils and support structure are described. (orig.)
International Nuclear Information System (INIS)
Koeppendoerfer, W.; Blaumoser, M.; Ennen, K.; Gruber, J.; Gruber, O.; Jandl, O.; Kaufmann, M.; Kollotzek, H.; Kotzlowski, H.; Lackner, E.; Lackner, K.; Larcher, T. von; Noterdaeme, J.M.; Pillsticker, M.; Poehlchen, R.; Preis, H.; Schneider, H.; Seidel, U.; Sombach, B.; Speth, E.; Streibl, B.; Vernickel, H.; Werner, F.; Wesner, F.; Wieczorek, A.
1986-01-01
ASDEX Upgrade is a tokamak experiment with external poloidal field coils that is now under construction at IPP Garching. It can produce elongated single-null (SN), double-null (DN) , and limiter (L) configurations. The SN is the reference configuration with asymmetric load distributions in the poloidal field (PF) system and the toroidal field (TF) magnet. Plasma control and stabilization require a rigid passive conductor close to the plasma. The design principles of the coils and support structure are described. (orig.)
Resonant MHD modes with toroidal coupling
International Nuclear Information System (INIS)
Connor, J.W.; Hastie, R.J.; Taylor, J.B.
1990-07-01
This is part 2 of a study of resonant perturbations, such as resistive tearing and ballooning modes, in a torus. These are described by marginal ideal mhd equations in the regions between resonant surfaces; matching across these surfaces provides the dispersion relation. In part 1 we described how all the necessary information from the ideal mhd calculations could be represented by a so-called E-matrix. We also described the calculation of this E-matrix for tearing modes (even parity in perturbed magnetic field) in a large aspect ratio torus. There the toroidal modes comprise coupled cylinder tearing modes and the E-matrix is a generalization of the familiar Δ' quantity in a cylinder. In the present paper we discuss resistive ballooning, or twisting-modes, which have odd-parity in perturbed magnetic field. We show that, unlike the tearing modes, these odd-parity modes are instrinsically toroidal and are not directly related to the odd-parity modes in a cylinder. This is evident from the analysis of the high-n limit in ballooning-space, where a transition from a stable Δ' to an unstable Δ' occurs for the twisting mode when the ballooning effect exceeds the interchange effect, which can occur even at large aspect ratio (as in a tokamak). Analysis of the high-n limit in coordinate space, rather than ballooning space, clarifies this singular behaviour and indicates how one may define twisting-mode Δ'. It also yields a prescription for treating low-n twisting modes and a method for calculating an E-matrix for resistive ballooning modes in a large aspect ratio tokamak. The elements of this matrix are given in terms of cylindrical tearing mode solutions
Progress on large superconducting toroidal field coils
International Nuclear Information System (INIS)
Haubenreich, P.N.; Luton, J.N.; Thompson, P.B.; Beard, D.S.
1979-01-01
Large superconducting toroidal field coils of competing designs are being produced by six major industrial teams. In the US, teams headed by General Dynamics Convair, General Electric, and Westinghouse are under contract to design and fabricate one coil each to specifications established by the Large Coil Program. A facility for testing 6 coils in a toroidal array at fields to 8 to 12 tesla is under construction at Oak Ridge. Through an international agreement, EURATOM, Japan, and Switzerland will produce one coil each for testing with the US coils. Each test coil will have a 2.5 x 3.5 m D-shape winding bore and is designed to operate at a current of 10 to 18 kA at a peak field of 8T while subjected to pulsed fields of 0.14 T applied in 1.0 s. There are significant differences among the six coil designs: five use NbTi, one Nb 3 Sn; three are cooled by pool boiling helium, three by forced flow; five have welded or bolted stainless steel coil cases, one has aluminum plate structure. All are designed to be cryostable at 8T, with structural margin for extended operation. The three US coil teams are almost or completely finished with detailed design and are now procuring materials and setting up manufacturing equipment. The non-US teams are at various stages of verification testing and design. The GDC and GE coils are scheduled for delivery in the spring of 1981 and the others will be completed a year later. The 11-m diameter vessel at the test facility has been completed and major components of the test stand are being procured. Engineering and procurement to upgrade the helium liquifier-refrigerator system are under way
Investigation of diocotron modes in toroidally trapped electron plasmas using non-destructive method
Lachhvani, Lavkesh; Pahari, Sambaran; Sengupta, Sudip; Yeole, Yogesh G.; Bajpai, Manu; Chattopadhyay, P. K.
2017-10-01
Experiments with trapped electron plasmas in a SMall Aspect Ratio Toroidal device (SMARTEX-C) have demonstrated a flute-like mode represented by oscillations on capacitive (wall) probes. Although analogous to diocotron mode observed in linear electron traps, the mode evolution in toroids can have interesting consequences due to the presence of in-homogeneous magnetic field. In SMARTEX-C, the probe signals are observed to undergo transition from small, near-sinusoidal oscillations to large amplitude, non-linear "double-peaked" oscillations. To interpret the wall probe signal and bring forth the dynamics, an expression for the induced current on the probe for an oscillating charge is derived, utilizing Green's Reciprocation Theorem. Equilibrium position, poloidal velocity of the charge cloud, and charge content of the cloud, required to compute the induced current, are estimated from the experiments. Signal through capacitive probes is thereby computed numerically for possible charge cloud trajectories. In order to correlate with experiments, starting with an intuitive guess of the trajectory, the model is evolved and tweaked to arrive at a signal consistent with experimentally observed probe signals. A possible vortex like dynamics is predicted, hitherto unexplored in toroidal geometries, for a limited set of experimental observations from SMARTEX-C. Though heuristic, a useful interpretation of capacitive probe data in terms of charge cloud dynamics is obtained.
Studies on Plasmoid Merging using Compact Toroid Injectors
Allfrey, Ian; Matsumoto, Tadafumi; Roche, Thomas; Gota, Hiroshi; Edo, Takahiro; Asai, Tomohiko; Sheftman, Daniel; Osin Team; Dima Team
2017-10-01
C-2 and C-2U experiments have used magnetized coaxial plasma guns (MCPG) to inject compact toroids (CTs) for refueling the long-lived advanced beam-driven field-reversed configuration (FRC) plasma. This refueling method will also be used for the C-2W experiment. To minimize momentum transfer from the CT to the FRC two CTs are injected radially, diametrically opposed and coincident in time. To improve understanding of the CT characteristics TAE has a dedicated test bed for the development of CT injectors (CTI), where plasmoid merging experiments are performed. The test bed has two CTIs on axis with both axial and transverse magnetic fields. The 1 kG magnetic fields, intended to approximate the magnetic field strength and injection angle on C-2W, allow studies of cross-field transport and merging. Both CTIs are capable of injecting multiple CTs at up to 1 kHz. The resulting merged CT lives >100 μs with a radius of 25 cm. More detailed results of CT parameters will be presented.
Kinetic energy principle and neoclassical toroidal torque in tokamaks
International Nuclear Information System (INIS)
Park, Jong-Kyu
2011-01-01
It is shown that when tokamaks are perturbed, the kinetic energy principle is closely related to the neoclassical toroidal torque by the action invariance of particles. Especially when tokamaks are perturbed from scalar pressure equilibria, the imaginary part of the potential energy in the kinetic energy principle is equivalent to the toroidal torque by the neoclassical toroidal viscosity. A unified description therefore should be made for both physics. It is also shown in this case that the potential energy operator can be self-adjoint and thus the stability calculation can be simplified by minimizing the potential energy.
Toroidal field effects on the stability of Heliotron E
International Nuclear Information System (INIS)
Carreras, B.A.; Garcia, L.; Lynch, V.E.
1986-02-01
The addition of a small toroidal field to the Heliotron E configuration improves the stability of the n = 1 mode and increases the value of the stability beta critical. Total stabilization of this mode can be achieved with added toroidal fields between 5 and 15% of the total field. In this situation, the plasma can have direct access to the second stability regime. For the Heliotron E configuration, the self-stabilization effect is due to the shear, not to the magnetic well. The toroidal field threshold value for stability depends strongly on the pressure profile and the plasma radius. 21 refs., 15 figs
Poloidal variations in toroidal fusion reactor wall power loadings
International Nuclear Information System (INIS)
Carroll, M.C.; Miley, G.H.
1985-01-01
A geometric formulation is developed by the authors for determining poloidal variations in bremmstrahlung, cyclotron radiation, and neutron wall power loadings in toroidal fusion devices. Assuming toroidal symmetry and utilizing a numerical model which partitions the plasma into small cells, it was generally found that power loadings are highest on the outer surface of the torus, although variations are not as large as some have predicted. Results are presented for various plasma power generation configurations, plasma volume fractions, and toroidal aspect ratios, and include plasma and wall blockage effects
1D equation for toroidal momentum transport in a tokamak
International Nuclear Information System (INIS)
Rozhansky, V A; Senichenkov, I Yu
2010-01-01
A 1D equation for toroidal momentum transport is derived for a given set of turbulent transport coefficients. The averaging is performed taking account of the poloidal variation of the toroidal fluxes and is based on the ambipolar condition of the zero net radial current through the flux surface. It is demonstrated that taking account of the Pfirsch-Schlueter fluxes leads to a torque in the toroidal direction which is proportional to the gradient of the ion temperature. This effect is new and has not been discussed before. The boundary condition at the separatrix, which is based on the results of the 2D simulations of the edge plasma, is formulated.
Deformation energy of a toroidal nucleus and plane fragmentation barriers
International Nuclear Information System (INIS)
Fauchard, C.; Royer, G.
1996-01-01
The path leading to pumpkin-like configurations and toroidal shapes is investigated using a one-parameter shape sequence. The deformation energy is determined within the analytical expressions obtained for the various shape-dependent functions and the generalized rotating liquid drop model taking into account the proximity energy and the temperature. With increasing mass and angular momentum, a potential well appears in the toroidal shape path. For the heaviest systems, the pocket is large and locally favourable with respect to the plane fragmentation barriers which might allow the formation of evanescent toroidal systems which would rapidly decay in several fragments to minimize the surface tension. (orig.)
Performance of a Folded-Strip Toroidally Wound Induction Machine
DEFF Research Database (Denmark)
Jensen, Bogi Bech; Jack, Alan G.; Atkinson, Glynn J.
2011-01-01
This paper presents the measured experimental results from a four-pole toroidally wound induction machine, where the stator is constructed as a pre-wound foldable strip. It shows that if the machine is axially restricted in length, the toroidally wound induction machine can have substantially...... shorter stator end-windings than conventionally wound induction machines, and hence that a toroidally wound induction machine can have lower losses and a higher efficiency. The paper also presents the employed construction method, which emphasizes manufacturability, and highlights the advantages...
Progress in gyrokinetic simulations of toroidal ITG turbulence
International Nuclear Information System (INIS)
Nevins, W.M.; Dimits, A.M.; Cohen, B.I.; Shumaker, D.E.
2001-01-01
The 3-D nonlinear toroidal gyrokinetic simulation code PG3EQ is used to study toroidal ion temperature gradient (ITG) driven turbulence - a key cause of the anomalous transport that limits tokamak plasma performance. Systematic studies of the dependence of ion thermal transport on various parameters and effects are presented, including dependence on E-vectorxB-vector and toroidal velocity shear, sensitivity to the force balance in simulations with radial temperature gradient variation, and the dependences on magnetic shear and ion temperature gradient. (author)
Laser-induced production of large carbon-based toroids
International Nuclear Information System (INIS)
Lyn, M. Elizabeth; He Jibao; Koplitz, Brent
2005-01-01
We report on the production of large carbon-based toroids (CBTs) from fullerenes. The process involves two-step laser irradiation of a mixed fullerene target (76% C 60 , 22% C 70 ). Transmission electron microscopy (TEM) clearly identifies toroidal-shaped structures as well as Q-shaped constructs. The typical diameters of the CBTs are ∼0.2-0.3 μm with tubular diameters of ∼50-100 nm, but toroids as wide as 0.5 μm are observed making them nanostructures on the verge of being microstructures
Toroidal equilibrium and radial profiles from magnetic measurements in Extrap T1
International Nuclear Information System (INIS)
Brunsell, Per; Jin Li; Tennfors, Einar
1991-01-01
The toroidal equilibrium position in the Extrap T1 toroidal Z-pinch is studied by measuring the currents induced in the external octupole field rings. Radial profiles are obtained by an internal magnetic coil array. From the magnetic field, profiles of current density, plasma pressure, safety factor, resistivity and input power density are deduced. A polynomial model is developed to simulate the measured profiles. The classical ion heat conduction losses in Extrap discharges are calculated using this model and compared to the power input. for polynomials matched to magnetic field profiles measured in present experiments, these losses are small. By varying the coefficients of the polynomials, a region is found where the power input can balance the classical heat conduction losses at higher values of Θ and β o . (Author)
Experimental study of toroidicity-induced Alfven eigenmode (TAE) stability at high q(0)
International Nuclear Information System (INIS)
Batha, S.H.; Levinton, F.M.; Spong, D.A.
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 β α (0) required for instability. No TAE activity was observed when the central alpha particle β α 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
Neoclassical viscosities in NCSX and QPS with few toroidal periods and low aspect ratios
International Nuclear Information System (INIS)
Nishimura, S.; Mikkelsen, D.R.; Ku, L.P.; Mynick, H.E.; Zarnstorff, M.C.; Spong, D.A.; Hirshman, S.P.
2008-01-01
Previously reported benchmarking examples for the analytical formulas of neoclassical viscosities were made implicitly assuming applications in a future integrated simulation system for the LHD (Large Helical Device). Therefore the toroidal period numbers assumed there were mainly N=10. In this kind of calculation, however, an implicit (or sometimes explicit) assumption of ι/N<<1 is sometimes included. This assumption is included not only in simplified bounce averaged drift kinetic equations for ripple diffusions, but also in the equation before the averaging for non-bounce-averaged effects determining neoclassical parallel viscosity and the banana-plateau diffusions. To clarify the applicability of the analytical methods even for configurations with extremely low toroidal period numbers (required for low aspect ratios), we show here recent benchmarking examples in NCSX (National Compact Stellarator Experiment) with N=3 and QPS (Quasi-poloidal Stellarator) with N=2. (author)
Conceptual design of a high heat flux toroidal pumped limiter for Tore Supra
International Nuclear Information System (INIS)
Doceul, L.; Schlosser, J.; Chappuis, Ph.; Chatelier, M.; Cocat, J.P.; Deck, C.; Faisse, F.; Grosman, A.; Mitteau, R.; Tonon, G.
1994-01-01
In the frame of the Tore-Supra upgrade, where it is planned to inject up to 25 MW during a time up to 1000 s, a complete toroidal pumped limiter covered of CFC (Carbon Fiber Composite) tiles is being designed. The design is based on the important experience gained from the operation on Tore Supra of actively cooled plasma facing components and pumped limiters. This toroidal limiter covers 7.5 m 2 of the bottom part of the inner vessel and is composed of 576 elementary components. Each element is built from dispersion strengthened copper (DSCu) protected by brazed CFC flat tiles and cooled by pressurised water at 150 deg C. This limiter is designed to sustain 15 MW of convective power. (author) 7 refs.; 5 figs., 3 tabs
Energy Technology Data Exchange (ETDEWEB)
Goumiri, I. R. [Princeton Univ., NJ (United States). Mechanical and Aerospace Dept.; Rowley, C. W. [Princeton Univ., NJ (United States). Mechanical and Aerospace Dept.; Sabbagh, S. A. [Columbia Univ., New York, NY (United States). Dept. of Applied Physics and Applied Mathematics; Gates, D. A. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Gerhardt, S. P. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Boyer, M. D. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Andre, R. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Kolemen, E. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Taira, K. [Florida State Univ, Dept Mech Engn, Tallahassee, FL USA.
2016-02-19
A model-based feedback system is presented to control plasma rotation in a magnetically confined toroidal fusion device, to maintain plasma stability for long-pulse operation. This research uses experimental measurements from the National Spherical Torus Experiment (NSTX) and is aimed at controlling plasma rotation using two different types of actuation: momentum from injected neutral beams and neoclassical toroidal viscosity generated by three-dimensional applied magnetic fields. Based on the data-driven model obtained, a feedback controller is designed, and predictive simulations using the TRANSP plasma transport code show that the controller is able to attain desired plasma rotation profiles given practical constraints on the actuators and the available measurements of rotation.
Electrostatic instabilities and turbulence in a toroidal magnetized plasma
International Nuclear Information System (INIS)
Poli, F. M.
2007-06-01
This Thesis aims at characterizing the linear properties of electrostatic drift instabilities arising in a toroidal plasma and the mechanisms leading to their development into turbulence. The experiments are performed on the TORoidal Plasma EXperiment (TORPEX) at CRPP-EPFL, Lausanne. The first part of the Thesis focuses on the identification of the nature of the instabilities observed in TORPEX, using a set of electrostatic probes, designed and built for this purpose. The global features of fluctuations, analyzed for different values of control parameters such as the magnetic field, the neutral gas pressure and the injected microwave power, are qualitatively similar in different experimental scenarios. The maximum of fluctuations is observed on the low field side, where the pressure gradient and the gradient of the magnetic field are co-linear, indicating that the curvature of the magnetic field lines has an important role in the destabilization of the waves. The power spectrum is dominated by electrostatic fluctuations with frequencies much lower than the ion cyclotron frequency. Taking advantage of the extended diagnostics coverage, the spectral properties of fluctuations are measured over the whole poloidal cross-section. Both drift and interchange instabilities develop and propagate on TORPEX, with the stability of both being affected by the curvature of the magnetic field. It is shown that modes of different nature are driven at separate locations over the plasma cross-section and that the wavenumber and frequency spectra, narrow at the location where the instabilities are generated, broaden during convection, suggesting an increase in the degree of turbulence. The transition from coherent to turbulent spectral features and the role of nonlinear coupling between modes in the development of turbulence are treated in the second part of this work. It is found that nonlinear mode-mode coupling is responsible for the redistribution of spectral energy from the
Structural design of the superconducting toroidal field coils for ITER
International Nuclear Information System (INIS)
Wong, F.M.G.; Sborchia, C.; Thome, R.J.; Malkov, A.; Titus, P.H.
1995-01-01
Structural design issues and features of the superconducting toroidal field (TF) coils for the International Thermonuclear Experimental Reactor (ITER) will be discussed. Selected analyses of the structural and mechanical behavior of the ITER TF coils will also be presented. (orig.)
System and method of operating toroidal magnetic confinement devices
Chance, M.S.; Jardin, S.C.; Stix, T.H.; Grimm, R.C.; Manickam, J.; Okabayashi, M.
1984-08-30
This invention pertains to methods and arrangements for attaining high beta values in plasma confinement devices. More specifically, this invention pertains to methods for accessing the second stability region of operation in toroidal magnetic confinement devices.
Influence of toroidal rotation on resistive tearing modes in tokamaks
International Nuclear Information System (INIS)
Wang, S.; Ma, Z. W.
2015-01-01
Influence of toroidal equilibrium plasma rotation on m/n = 2/1 resistive tearing modes is studied numerically using a 3D toroidal MHD code (CLT). It is found that the toroidal rotation with or without shear can suppress the tearing instability and the Coriolis effect in the toroidal geometry plays a dominant role on the rotation induced stabilization. For a high viscosity plasma (τ R /τ V ≫ 1, where τ R and τ V represent resistive and viscous diffusion time, respectively), the effect of the rotation shear combined with the viscosity appears to be stabilizing. For a low viscosity plasmas (τ R /τ V ≪ 1), the rotation shear shows a destabilizing effect when the rotation is large
Influence of toroidal rotation on resistive tearing modes in tokamaks
Energy Technology Data Exchange (ETDEWEB)
Wang, S.; Ma, Z. W., E-mail: zwma@zju.edu.cn [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China)
2015-12-15
Influence of toroidal equilibrium plasma rotation on m/n = 2/1 resistive tearing modes is studied numerically using a 3D toroidal MHD code (CLT). It is found that the toroidal rotation with or without shear can suppress the tearing instability and the Coriolis effect in the toroidal geometry plays a dominant role on the rotation induced stabilization. For a high viscosity plasma (τ{sub R}/τ{sub V} ≫ 1, where τ{sub R} and τ{sub V} represent resistive and viscous diffusion time, respectively), the effect of the rotation shear combined with the viscosity appears to be stabilizing. For a low viscosity plasmas (τ{sub R}/τ{sub V} ≪ 1), the rotation shear shows a destabilizing effect when the rotation is large.
Effect of toroidicity during lower hybrid mode conversion
International Nuclear Information System (INIS)
Riyopoulos, S.; Mahajan, S.
1985-11-01
The effect of toroidicity during lower hybrid mode conversion is examined by treating the wave propagation in an inhomogeneous medium as an eigenvalue problem for ω 2 (m,n),m,n poloidal and toroidal wave numbers. Since the frequency regime near ω 2 = ω/sub LH/ 2 is an accumulation point for the eigenvalue spectrum, the degenerate perturbation technique must be applied. The toroidal eigenmodes are constructed by a zeroth order superposition of monochromatic solutions with different poloidal dependence m, thus they generically exhibit a wide spectrum in k/sub parallel/ for given fixed ω 2 even for small inverse aspect ratio epsilon. In case that the average is in the neighborhood of k/sub min/, the minimum wave number for accessibility of the mode conversion regime, it is expected that excitation of toroidal modes rather than geometric optics will determine the wave coupling to the plasma
Toroidal and rotating bubble nuclei and the nuclear fragmentation
International Nuclear Information System (INIS)
Royer, G.; Fauchard, C.; Haddad, F.; Jouault, B.
1997-01-01
The energy of rotating bubble and toroidal nuclei predicted to be formed in central heavy ion collisions at intermediate energies is calculated within the generalized rotating liquid drop model. Previously, a one-parameter shape sequence has been defined to describe the path leading to pumpkin-like configurations and toroidal shapes. New analytical expressions for the shape dependent functions have been obtained. The potential barriers standing in these exotic deformation paths are compared with the three-dimensional and plane-fragmentation barriers. Metastable bubble-like minima only appear at very high angular momentum and above the three dimensional fragmentation barriers. In the toroidal deformation path of the heaviest systems exists a large potential pocket localized below the plane-fragmentation barriers. This might allow the temporary survival of heavy nuclear toroids before the final clusterization induced by the surface and proximity tension
Calculation of toroidal fusion reactor blankets by Monte Carlo
International Nuclear Information System (INIS)
Macdonald, J.L.; Cashwell, E.D.; Everett, C.J.
1977-01-01
A brief description of the calculational method is given. The code calculates energy deposition in toroidal geometry, but is a continuous energy Monte Carlo code, treating the reaction cross sections as well as the angular scattering distributions in great detail
Toroidal high-spin isomers in the nucleus 304120
Staszczak, A.; Wong, Cheuk-Yin; Kosior, A.
2017-05-01
Background: Strongly deformed oblate superheavy nuclei form an intriguing region where the toroidal nuclear structures may bifurcate from the oblate spheroidal shape. The bifurcation may be facilitated when the nucleus is endowed with a large angular moment about the symmetry axis with I =Iz . The toroidal high-K isomeric states at their local energy minima can be theoretically predicted using the cranked self-consistent Skyrme-Hartree-Fock method. Purpose: We use the cranked Skyrme-Hartree-Fock method to predict the properties of the toroidal high-spin isomers in the superheavy nucleus 120304184. Method: Our method consists of three steps: First, we use the deformation-constrained Skyrme-Hartree-Fock-Bogoliubov approach to search for the nuclear density distributions with toroidal shapes. Next, using these toroidal distributions as starting configurations, we apply an additional cranking constraint of a large angular momentum I =Iz about the symmetry z axis and search for the energy minima of the system as a function of the deformation. In the last step, if a local energy minimum with I =Iz is found, we perform at this point the cranked symmetry- and deformation-unconstrained Skyrme-Hartree-Fock calculations to locate a stable toroidal high-spin isomeric state in free convergence. Results: We have theoretically located two toroidal high-spin isomeric states of 120304184 with an angular momentum I =Iz=81 ℏ (proton 2p-2h, neutron 4p-4h excitation) and I =Iz=208 ℏ (proton 5p-5h, neutron 8p-8h) at the quadrupole moment deformations Q20=-297.7 b and Q20=-300.8 b with energies 79.2 and 101.6 MeV above the spherical ground state, respectively. The nuclear density distributions of the toroidal high-spin isomers 120304184(Iz=81 ℏ and 208 ℏ ) have the maximum density close to the nuclear matter density, 0.16 fm-3, and a torus major to minor radius aspect ratio R /d =3.25 . Conclusions: We demonstrate that aligned angular momenta of Iz=81 ℏ and 208 ℏ arising from
Polymer- and salt-induced toroids of hexagonal DNA.
Ubbink, J; Odijk, T
1995-01-01
A model is proposed for polymer- and salt-induced toroidal condensates of DNA, based on a recent theory of the undulation enhancement of the electrostatic interaction in the bulk hexagonal phase of semiflexible polyions. In a continuum approximation, the thermodynamic potential of a monomolecular toroid may be split up in bulk, surface, and curvature contributions. With the help of an approximate analytical minimization procedure, the optimal torus dimensions are calculated as a function of t...
Transport in the high temperature core of toroidal confinement systems
International Nuclear Information System (INIS)
Weiland, J.
1994-01-01
Recent theoretical and experimental results on confinement of hot plasmas in toroidal devices, particularly tokamaks, are discussed from general principal points of view and related to predictions from a toroidal drift wave model using a full transport matrix including off diagonal terms. A reactive fluid model corresponding to a two pole approximation of the kinetic response is used. This model has the ability to reproduce both adiabatic and isothermal limits of the perpendicular dynamics. 106 refs, 8 figs, 1 tab
Chaotic magnetic field line in toroidal plasmas
International Nuclear Information System (INIS)
Hatori, Tadatsugu; Abe, Yoshihiko; Urata, Kazuhiro; Irie, Haruyuki.
1989-05-01
This is an introductory review of chaotic magnetic field line in plasmas, together with some new results, with emphasis on the long-time tail and the fractional Brownian motion of the magnetic field line. The chaotic magnetic field line in toroidal plasmas is a typical chaotic phenomena in the Hamiltonian dynamical systems. The onset of stochasticity induced by a major magnetic perturbation is thought to cause a macroscopic rapid phenomena called the current disruption in the tokamak discharges. Numerical simulations on the basis of magnetohydrodynamics reveal in fact the disruptive phenomena. Some dynamical models which include the area-preserving mapping such as the standard mapping, and the two-wave Hamiltonian system can model the stochastic magnetic field. Theoretical results with use of the functional integral representation are given regarding the long-time tail on the basis of the radial twist mapping. It is shown that application of renormalization group technique to chaotic orbit in the two-wave Hamiltonian system proves decay of the velocity autocorrelation function with the power law. Some new numerical results are presented which supports these theoretical results. (author)
''Turbulent Equipartition'' Theory of Toroidal Momentum Pinch
International Nuclear Information System (INIS)
Hahm, T.S.; Diamond, P.H.; Gurcan, O.D.; Rewaldt, G.
2008-01-01
The mode-independent part of magnetic curvature driven turbulent convective (TuroCo) pinch of the angular momentum density (Hahm et al., Phys. Plasmas 14,072302 (2007)) which was originally derived from the gyrokinetic equation, can be interpreted in terms of the turbulent equipartition (TEP) theory. It is shown that the previous results can be obtained from the local conservation of 'magnetically weighted angular momentum density', nm i U # parallel# R/B 2 , and its homogenization due to turbulent flows. It is also demonstrated that the magnetic curvature modification of the parallel acceleration in the nonlinear gyrokinetic equation in the laboratory frame, which was shown to be responsible for the TEP part of the TurCo pinch of angular momentum density in the previous work, is closely related to the Coriolis drift coupling to the perturbed electric field. In addition, the origin of the diffusive flux in the rotating frame is highlighted. Finally, it is illustrated that there should be a difference in scalings between the momentum pinch originated from inherently toroidal effects and that coming from other mechanisms which exist in a simpler geometry.