WorldWideScience

Sample records for cdx-u spheromak

  1. Liquid Lithium Experiments in CDX-U

    International Nuclear Information System (INIS)

    The initial results of experiments involving the use of liquid lithium as a plasma facing component in the Current Drive Experiment-Upgrade (CDX-U) are reported. Studies of the interaction of a steady-state plasma with liquid lithium in the Plasma Interaction with Surface and Components Experimental Simulator (PISCES-B) are also summarized. In CDX-U a solid or liquid lithium covered rail limiter was introduced as the primary limiting surface for spherical torus discharges. Deuterium recycling was observed to be reduced, but so far not eliminated, for glow discharge-cleaned lithium surfaces. Some lithium influx was observed during tokamak operation. The PISCES-B results indicate that the rates of plasma erosion of lithium can exceed predictions by an order of magnitude at elevated temperatures. Plans to extend the CDX-U experiments to large area liquid lithium toroidal belt limiters are also described

  2. Investigations of Low and Moderate Harmonic Fast Wave Physics on CDX-U

    International Nuclear Information System (INIS)

    Third harmonic hydrogen cyclotron fast wave heating studies are planned in the near term on CDX-U to investigate the potential for bulk ion heating. In preparation for these studies, the available radio-frequency power in CDX-U has been increased to 0.5 MW. The operating frequency of the CDX-U radio-frequency transmitter was lowered to operate in the range of 8-10 MHz, providing access to the ion harmonic range 2* ∼ 4* in hydrogen. A similar regime is accessible for the 30 MHz radio-frequency system on the National Spherical Torus Experiment (NSTX), at 0.6 Tesla in hydrogen. Preliminary computational studies over the plasma regimes of interest for NSTX and CDX-U indicate the possibility of strong localized absorption on bulk ion species

  3. High frequency fast wave results from the CDX-U spherical torus

    International Nuclear Information System (INIS)

    The Current Drive Experiment-Upgrade (CDX-U) is the first spherical torus (ST) to investigate radio frequency (RF) heating and current drive. To address the concern that large magnetic field line pitch at the outboard midplane of ST's could inhibit successful coupling to the high harmonic fast wave (HHFW), a rotatable, two strap antenna was installed on CDX-U. Parasitic loading and impurity generation were discovered to be weak and nearly independent of antenna phasing and angle over a wide range, and fast wave electron heating has been observed. Plasma densities up to about 1012cm-3 were obtained with noninductive startup solely with HHFW. New ST diagnostics under development on CDX-U include a multilayer mirror (MLM) detector to measure ultrasoft X-rays, a twelve spatial point Thomson scattering (TS) system, and an Electron Bernstein Wave (EBW) system for both electron heating and electron temperature measurements. Preliminary experiments with a boron low velocity edge micropellet injector have also been performed, and further studies of its effectiveness for impurity control will be conducted with a variety of spectroscopic and imaging diagnostics on CDX-U. (author)

  4. Mode-converted electron Bernstein wave emission research on CDX-U and NSTX

    International Nuclear Information System (INIS)

    Electron Bernstein waves (EBWs) may enable electron temperature profile measurements and local electron heating and current drive in high β overdense (ωpe/ωce>>1) plasmas. Significant results are presented from the measurement of X-mode radiation, converted from EBWs observed normal to the magnetic field on the mid-plane of overdense plasmas in CDX-U and NSTX. A radially scannable, in-vessel, quad-ridged antenna and Langmuir probe array on CDX-U studied EBW to X-mode conversion. A local limiter optimized the conversion efficiency by modifying the density scale length at the mode conversion layer. The fundamental EBW conversion efficiency increased, by an order of magnitude, to ∼100% when the local limiter and antenna were inserted near the conversion layer. This technique can be extended to large, high temperature devices. Another significant observation was that the EBW emission source was localized near the electron cyclotron resonance. As a result, mode-converted EBW radiometry has measured radial transport in CDX-U. In addition, a threefold increase in conversion efficiency was observed at the L to H transition in NSTX. Measured conversion efficiency agreed well with theoretical predictions. EBW ray tracing and bounce-averaged Fokker-Planck codes are being used to model EBW heating and current drive scenarios for NSTX equilibria with β up to 40%. So far, results show that it is possible to drive localized currents on the high field side of the magnetic axis in NSTX at β ∼ 12% with current drive efficiency which compares favorably with ECCD. (authors)

  5. CDX-U Operation with a Large Area Liquid Lithium Limiter

    International Nuclear Information System (INIS)

    The Current Drive experiment-Upgrade (CDX-U) at the Princeton Plasma Physics Laboratory has begun experiments with a fully toroidal liquid lithium limiter. CDX-U is a compact [R = 34 cm, a = 22 cm, B(subscript)toroidal = 2 kG, I(subscript)P = 100 kA, T(subscript)e(0) ∼ 100 eV, n(subscript)e(0) ∼ 5 x 1019 m-3] short-pulse (<25 msec) spherical torus with extensive diagnostics. The limiter, which consists of a shallow circular stainless steel tray of radius 34 cm and width 10 cm, can be filled with lithium to a depth of a few millimeters, and forms the lower limiting surface for the discharge. Heating elements beneath the tray are used to liquefy the lithium prior to the experiment. Surface coatings are evident on part of the lithium. Despite the surface coatings, tokamak discharges operated in contact with the lithium-filled tray show evidence of reduced impurities and recycling. The reduction in recycling is largest when the lithium is liquefied by heating to 250 degrees Celsius

  6. Results from the CDX-U lithium wall and NSTX lithium pellet experiments

    International Nuclear Information System (INIS)

    Full text: CDX-U has been operated with the vacuum vessel wall and limiter surfaces nearly completely coated with lithium, with dramatic improvements to plasma performance. Discharges achieved global energy confinement times of up to 5-6 ms, exceeding previous CDX-U results by 5x, and ITER98P(y1) scaling by 2-3x. Lithium wall coatings were applied by electron beam-induced evaporation of a lithium-filled limiter and vapor deposition from a resistively heated lithium-filled oven, up to 1000 Angstrom thick, between discharges. The e-beam experiments also produced up to 60 MW/m2 power density in a 0.3 cm2 spot. Total beam power was modest (1.6 kW), but duration was up to 300 seconds. Convective transport of heat away from the beam spot was so effective that the entire lithium inventory (140 g), rather than just the area under the beam spot, was heated to evaporation (400-500 deg C). There was no observable hot spot within the beam footprint to the limit of resolution (10 deg C) of an infrared-red camera, which imaged the surface of the lithium during beam heating. These results are promising for the future implementation of lithium plasma-facing components in reactor scale devices. Lithium coating of carbon PFCs has been initiated also on NSTX, to control the density rise during long-duration H-modes, and to optimize density profiles for non-inductive current sustainment. Lithium pellets were injected into ohmically heated helium plasmas to deposit lithium on plasma contact areas. In the first experiment, pellets were injected into repeated ohmic helium discharges to deposit about 30 mg of lithium on the Center Stack Limiter. A following deuterium reference discharge with NBI exhibited a reduction in the volume-average density by a factor of about four and a peaked density profile. In a similar subsequent experiment, diverted, Lower Single-Null helium discharges about 25 mg of lithium was deposited on the lower divertor. The density exhibited a factor of about two

  7. Results from the CDX-U lithium wall and NSTX lithium pellet experiments

    International Nuclear Information System (INIS)

    CDX-U has been operated with the vacuum vessel wall and limiter surfaces nearly completely coated with lithium, with dramatic improvements to plasma performance. Discharges achieved global energy confinement times of up to 5-6 ms, exceeding previous CDX-U results by 5x, and ITER98P(y1) scaling by 2-3. Lithium wall coatings up to A thick were applied between discharges by electron-beam-induced evaporation of a lithium-filled limiter and vapor deposition from a resistively heated oven. The e-beam power was modest (1.6 kW) but it produced up to 60 MW/m2 power density in a 0.3 cm2 spot; the duration was up to 300 s. Convective transport of heat away from the beam spot was so effective that the entire lithium inventory (140 g) was heated to evaporation (400-500 deg. C) and there was no observable hot spot on the lithium surface within the beam footprint. These results are promising for use of lithium plasma-facing components in reactor scale devices. Lithium coating has been applied to NSTX carbon plasma-facing surfaces, to control the density rise during long-duration H-modes for non-inductive current sustainment. First, lithium pellets were injected into sequences of Ohmically heated helium plasmas in both center stack limiter (CSL) and lower single-null divertor (LSND) configurations to deposit a total of 25-30 mg of lithium on the respective plasma contact areas. In both cases, the first subsequent L mode, deuterium discharge with NBI showed a reduction in the volume-average density by a factor ∼3 compared to lithium discharges before the lithium coating. Recently, a lithium evaporator was installed aimed toward the graphite tiles of the lower center stack and divertor. Twelve depositions, ranging from about 10 mg to 5 g of lithium, were performed. The effects on LSND L-mode, double-null divertor (DND) H-mode, and DND reversed-shear plasmas were variable but, immediately after coating, there were decreases in the density and significant increases in the electron

  8. Results from the CDX-U Lithium Wall and NSTX Lithium Pallet Injection and Evaporation Experiments

    International Nuclear Information System (INIS)

    CDX-U has been operated with the vacuum vessel wall and limiter surfaces nearly completely coated with lithium, producing dramatic improvements to plasma performance. Discharges achieved global energy confinement times up to 6 ms, exceeding previous CDX-U results by a factor of 5, and ITER98P(y,1) scaling by 2-3. Lithium wall coatings up to 1000 (angstrom) thick were applied between discharges by electron-beam-induced evaporation of a lithium-filled limiter and vapor deposition from a resistively heated oven. The e-beam power was modest (1.6 kW) but it produced up to 60 MW/m2 power density in a 0.3 cm2 spot; the duration was up to 300 s. Convective transport of heat away from the beam spot was so effective that the entire lithium inventory (140 g) was heated to evaporation (400-500 C) and there was no observable hot spot on the lithium surface within the beam footprint. These results are promising for use of lithium plasma-facing components in reactor scale devices. Lithium coating has also been applied to NSTX carbon plasma-facing surfaces, to control the density rise during long-duration H-modes for non-inductive current sustainment. First, lithium pellets were injected into sequences of Ohmically heated helium plasmas in both center stack limiter (CSL) and lower single-null divertor (LSND) configurations to deposit a total of 25-30 mg of lithium on the respective plasma contact areas. In both cases, the first subsequent L mode, deuterium discharge with NBI showed a reduction in the volume-average density by a factor ∼3 compared to similar discharges before the lithium coating. Recently, a lithium evaporator was installed aimed toward the graphite tiles of the lower center stack and divertor. Twelve depositions, ranging from about 10 mg to 5 g of lithium, were performed. The effects on LSND L-mode, double-null divertor (DND) H-mode, and DND reversed-shear plasmas were variable but, immediately after coating, there were decreases in the density and significant

  9. Spherical torus plasma interactions with large-area liquid lithium surfaces in CDX-U

    International Nuclear Information System (INIS)

    The current drive experiment-upgrade (CDX-U) device at the Princeton Plasma Physics Laboratory (PPPL) is a spherical torus (ST) dedicated to the exploration of liquid lithium as a potential solution to reactor first-wall problems such as heat load and erosion, neutron damage and activation, and tritium inventory and breeding. Initial lithium limiter experiments were conducted with a toroidally-local liquid lithium rail limiter (L3) from the University of California at San Diego (UCSD). Spectroscopic measurements showed a clear reduction of impurities in plasmas with the L3, compared to discharges with a boron carbide limiter. The evidence for a reduction in recycling was less apparent, however. This may be attributable to the relatively small area in contact with the plasma, and the presence of high-recycling surfaces elsewhere in the vacuum chamber. This conclusion was tested in subsequent experiments with a fully toroidal lithium limiter that was installed above the floor of the vacuum vessel. The new limiter covered over ten times the area of the L3 facing the plasma. Experiments with the toroidal lithium limiter have recently begun. This paper describes the conditioning required to prepare the lithium surface for plasma operations, and effect of the toroidal liquid lithium limiter on discharge performance

  10. Stabilized Spheromak Fusion Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Fowler, T

    2007-04-03

    The U.S. fusion energy program is focused on research with the potential for studying plasmas at thermonuclear temperatures, currently epitomized by the tokamak-based International Thermonuclear Experimental Reactor (ITER) but also continuing exploratory work on other plasma confinement concepts. Among the latter is the spheromak pursued on the SSPX facility at LLNL. Experiments in SSPX using electrostatic current drive by coaxial guns have now demonstrated stable spheromaks with good heat confinement, if the plasma is maintained near a Taylor state, but the anticipated high current amplification by gun injection has not yet been achieved. In future experiments and reactors, creating and maintaining a stable spheromak configuration at high magnetic field strength may require auxiliary current drive using neutral beams or RF power. Here we show that neutral beam current drive soon to be explored on SSPX could yield a compact spheromak reactor with current drive efficiency comparable to that of steady state tokamaks. Thus, while more will be learned about electrostatic current drive in coming months, results already achieved in SSPX could point to a productive parallel development path pursuing auxiliary current drive, consistent with plans to install neutral beams on SSPX in the near future. Among possible outcomes, spheromak research could also yield pulsed fusion reactors at lower capital cost than any fusion concept yet proposed.

  11. Spheromak injection into a tokamak

    OpenAIRE

    Brown, M R; Bellan, P. M.

    1990-01-01

    Recent results from the Caltech spheromak injection experiment [to appear in Phys. Rev. Lett.] are reported. First, current drive by spheromak injection into the ENCORE tokamak as a result of the process of magnetic helicity injection is observed. An initial 30% increase in plasma current is observed followed by a drop by a factor of 3 because of sudden plasma cooling. Second, spheromak injection results in an increase of tokamak central density by a factor of 6. The high-current/high-density...

  12. Theoretical issues in Spheromak research

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, R. H.; Hooper, E. B.; LoDestro, L. L.; Mattor, N.; Pearlstein, L. D.; Ryutov, D. D.

    1997-04-01

    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.

  13. Theoretical issues in Spheromak research

    International Nuclear Information System (INIS)

    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

  14. Spheromak heating with Alfven waves

    International Nuclear Information System (INIS)

    The temperature of present spheromak plasmas will need to be raised in order to test the feasibility of the confinement concept. In addition, a spatially-selective rf heating pulse can be used to study transport. As the ohmic heating power within a spheromak can be quite large (6-MW), low frequencies where large amounts of power are available are preferred. For the Los Alamos spheromak experiment CTX, we propose to add heating energy via a shear Alfven wave resonance. This resonance can be made to occur upon a particular flux surface, thus depositing most of the energy locally. A 2-dimensional equilibrium code (toroidally symmetric) is used to establish flux surfaces and magnetic field values for the desired configuration, either with or without plasma pressure

  15. Comparison of Spheromaks and FRCs

    International Nuclear Information System (INIS)

    Within the past year there have been dramatic advances in both the Spheromak and FRC branches of the Compact Toroid (CT) research program. The long-troublesome n=2 rotational instability has been controlled in FRC experiments at Osaka University and MSNW, while improved impurity control techniques have lead to the extension of spheromak configurational lifetimes to the 1 ms range at LANL and Osaka. It thus seems appropriate, on the occasion of this 5th CT Symposium, to compare the two approaches with respect to present status and potential for extrapolation to reactors and critical research needs

  16. Sustained Spheromak Physics Experiment, SSPX

    International Nuclear Information System (INIS)

    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 Te = 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 Te measurements and ultra-short pulse reflectrometry to measure density and magnetic field profiles and turbulence. We expect to operate at Te 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

  17. Sustained Spheromak Physics Experiment, SSPX

    Energy Technology Data Exchange (ETDEWEB)

    Hooper, E.B.

    1997-05-15

    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{sub 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{sub e} measurements and ultra-short pulse reflectrometry to measure density and magnetic field profiles and turbulence. We expect to operate at T{sub 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.

  18. Spheromak formation studies in SSPX

    International Nuclear Information System (INIS)

    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≥1.5ms) are observed and impurity radiation losses are reduced from ∼50% to e(0)∼120eV and ∼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. (author)

  19. Development of the STPX Spheromak System

    Science.gov (United States)

    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.

  20. A Development Path for the Stabilized Spheromak

    Energy Technology Data Exchange (ETDEWEB)

    Fowler, T K

    2007-07-13

    In Refs. [1] - [3], I suggest a concerted computational effort to study profile control of spheromaks, in anticipation that it is timely to incorporate the q < 1 regime of RFP's and spheromaks into an integrated advanced toroidal confinement program, together with improvements in tokamaks and stellarators now being pursued. For profile control of spheromaks by neutral beam injection, with care to avoid super-Alfvenic beam instability the main issue is excitation of tearing modes that can be studied using the NIMROD code already calibrated to MST and SSPX. In this note, I show that profile control on spheromaks could be demonstrated in a device the size of SSPX, leading ultimately to a very compact ignition facility, and possibly modular fusion reactors with a shorter development path.

  1. Advances in spheromak understanding and parameters

    International Nuclear Information System (INIS)

    A spheromak is a toroidally-shaped magnetized plasma configuration in which no material links the torus so that the topology of the spheromak boundary is spherical. The magnetic fields in the plasma are generated by the internal plasma currents. In the period of ten years since the properties of a nearly force-free spheromak configuration were described using single-fluid MHD theory, remarkable theoretical and experimental advances have been made. This paper highlights some of that work. Spheromak not only have been successfully produced in the laboratory using a variety of methods, but also translated, compressed and stably sustained for many resistive-decay times. Spheromak formation, equilibrium and stability to current-driven modes have been successfully modeled by single-fluid MHD coupled with the concepts of magnetic helicity and relaxation toward the minimum-energy force-free state. There is evidence, however, that the relaxation mechanism which drives parallel plasma currents is due to effects beyond the scope of single-fluid resistive MHD. The confinement properties of clean spheromaks have been measured, and shown to be excellent, provided the fraction of open magnetic flux at the edge is decreased sufficiently. It has been shown theoretically how plasma left-angle β right-angle vol limits of ∼10% can be obtained by properly shaping either the conducting wall geometry or the spheromak current profile. In addition to studies directly relating to fusion, the use of spheromaks for other goals is briefly described, including tokamak refueling, radiation production, magnetically-insulted inertially confined fusion, demonstration of helicity injection by mechanical means, and energy storage/transfer to accelerate fast metallic projectiles

  2. Internal tilting mode stability of non-sperical spheromak

    International Nuclear Information System (INIS)

    Fixed boundary tilting mode stability is analyzed for spheromak with arbitrarily shaped cross section. A prolate spheromak can be stabilized against tilting mode by adding a conducting shell of triangular or trapesoidal half-cross section

  3. Reconnection in Spheromak formation and sustainment

    International Nuclear Information System (INIS)

    The Spheromak is a magnetic confinement device that is being explored in both the US and Japanese fusion programs. It is a member of the Compact Torus family of magnetic structures characterized by a set of closed, nested toroidal flux surfaces but without any coils, transformer cores, etc. protruding through the hole in the torus. The Speromak is closely elated to the Reversed Field Pinch (RFP) in that most of the magnetic field is produced by plasma currents flowing along the magnetic field lines (a near force free field) rather than by external coils. The Spheromak has magnetic field components of comparable strength in both the toroidal (azimuthal) and poloidal (in the plane perpendicular to the azimuthal unit vector) directions. The large internal magnetic energy in the Spheromak makes it rich in magnetohydrodynamic phenomena and reconnection, in particular, plays an important role in the formation, resistive decay and instability processes

  4. Progress on SPHEX, the spheromak at Manchester

    International Nuclear Information System (INIS)

    The Sphex spheromak, was designed to minimize field errors in the flux conserver, with the intention of minimizing the amount of flux penetrating the wall and hence minimizing helicity loss. Here details are presented of magnetic field measurements on Sphex, both in the flux conserver and the entrance region, and of their relationship with parameters of the Marshall gun. Sphex is producing magnetic field configurations which are close to an ideal spheromak and show considerable flux amplification. The magnitude of the spheromak field is essentially controlled by the solenoid flux rather than the gun current, provided the latter is high enough to eject plasma into the flux conserver. However, there is clearly current flowing to the wall, probably caused by processes other than flux diffusion

  5. EUV spectroscopy on the SSPX spheromak

    Energy Technology Data Exchange (ETDEWEB)

    Clementson, J T; Beiersdorfer, P; Gu, M F; McLean, H S; Wood, R D

    2008-03-17

    EUV plasma spectroscopy is one the diagnostics implemented at the Sustained Spheromak Physics Experiment (SSPX) at the Lawrence Livermore National Laboratory. A grating spectrometer covering the spectral region of 25-450 {angstrom} with a resolution of 0.4 {angstrom} was used as an impurity diagnostic to monitor the plasmas and to carry out atomic physics research. Several low-Z impurities have been found in the spheromak, notably B, C, N, and O. Of the heavier elements, Ti, Cu, and W were found in the plasmas. As a relatively dense and low-temperature laboratory plasma device, SSPX served as an excellent radiation source for investigation of atomic spectra in a regime not readily attained in other devices. We have injected atomic titanium and tungsten hexacarbonyl into the spheromak under different operating conditions. We also report on electron temperature and electron density measurements based on the K{alpha} lines from B IV at 60 {angstrom}.

  6. MHD stable high beta spheromak equilibrium

    International Nuclear Information System (INIS)

    Recent observations of a pressure driven mode in CTX indicate that its performance is being limited by the low beta stability requirements typical of conventional spheromak designs. Improved designs with higher beat limits therefore have the potential to dramatically increase the temperature and lifetime of CTX and other spheromak experiments. This paper describes the results of an optimization study examining radically different geometries, but all with minimum energy current profiles which can easily be created experimentally and should be automatically stable to all ideal and resistive current drive modes. 2 refs., 3 figs

  7. The Spheromak path to fusion energy

    Energy Technology Data Exchange (ETDEWEB)

    Hooper, E.B., Barnes, C.W., Bellan, P.M., [and others

    1998-04-01

    The spheromak is a simple and robust magnetofluid configuration with several attractive reactor attributes including compact geometry, no material center post, high engineering {beta}, 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 {approximately} 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 {beta} 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

  8. Particle confinement and fueling effects on the Maryland spheromak

    International Nuclear Information System (INIS)

    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

  9. Steady-state spheromak reactor studies

    International Nuclear Information System (INIS)

    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

  10. NIMROD Resistive Magnetohydrodynamic Simulations of Spheromak Physics

    Energy Technology Data Exchange (ETDEWEB)

    Hooper, E B; Cohen, B I; McLean, H S; Wood, R D; Romero-Talamas, C A; Sovinec, C R

    2007-12-11

    The physics of spheromak plasmas is addressed by time-dependent, three-dimensional, resistive magneto-hydrodynamic simulations with the NIMROD code. Included in some detail are the formation of a spheromak driven electrostatically by a coaxial plasma gun with a flux-conserver geometry and power systems that accurately model the Sustained Spheromak Physics Experiment (SSPX) (R. D. Wood, et al., Nucl. Fusion 45, 1582 (2005)). The controlled decay of the spheromak plasma over several milliseconds is also modeled as the programmable current and voltage relax, resulting in simulations of entire experimental pulses. Reconnection phenomena and the effects of current profile evolution on the growth of symmetry-breaking toroidal modes are diagnosed; these in turn affect the quality of magnetic surfaces and the energy confinement. The sensitivity of the simulation results address variations in both physical and numerical parameters, including spatial resolution. There are significant points of agreement between the simulations and the observed experimental behavior, e.g., in the evolution of the magnetics and the sensitivity of the energy confinement to the presence of symmetry-breaking magnetic fluctuations.

  11. MHD equilibrium and stability of the spheromak

    Energy Technology Data Exchange (ETDEWEB)

    Okabayashi, M.; Todd, A.M.M.

    1979-08-01

    The MHD stability of spheromak type equilibria from the classical spheromak configuration to the diffuse pinch limit are analyzed numerically. It is found that oblate configurations of ellipticity 0.5 have the optimum stability properties with regard to internal MHD modes and can be stabilized up to an engineering ..beta.. of 15% (defined with respect to the applied external field strength for equilibrium). Stability to global modes requires that a conducting shell surround the plasma. The location of the shell is dependent on geometry and the current profile, but realistic configurations that are stable to all ideal MHD modes have been found with the shell located at approx. 1.2 minor radii.

  12. 3D MHD Simulations of Spheromak Compression

    Science.gov (United States)

    Stuber, James E.; Woodruff, Simon; O'Bryan, John; Romero-Talamas, Carlos A.; Darpa Spheromak Team

    2015-11-01

    The adiabatic compression of compact tori could lead to a compact and hence low cost fusion energy system. The critical scientific issues in spheromak compression relate both to confinement properties and to the stability of the configuration undergoing compression. We present results from the NIMROD code modified with the addition of magnetic field coils that allow us to examine the role of rotation on the stability and confinement of the spheromak (extending prior work for the FRC). We present results from a scan in initial rotation, from 0 to 100km/s. We show that strong rotational shear (10km/s over 1cm) occurs. We compare the simulation results with analytic scaling relations for adiabatic compression. Work performed under DARPA grant N66001-14-1-4044.

  13. Simulation of Spheromak Evolution and Energy Confinement

    International Nuclear Information System (INIS)

    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

  14. Increased particle confinement with the use of external dc bias field in the CTX spheromak

    International Nuclear Information System (INIS)

    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

  15. Current drive by spheromak injection into a tokamak

    OpenAIRE

    Brown, M. R.; Bellan, P. M.

    1990-01-01

    We report the first observation of current drive by injection of a spheromak plasma into a tokamak (Caltech ENCORE small reasearch tokamak) due to the process of helicity injection. After an abrupt 30% increase, the tokamak current decays by a factor of 3 due to plasma cooling caused by the merging of the relatively cold spheromak with the tokamak. The tokamak density profile peaks sharply due to the injected spheromak plasma (n¯3 increases by a factor of 6) then becomes hollow, suggestive of...

  16. Computational studies of ohmic heating in the spheromak

    International Nuclear Information System (INIS)

    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

  17. The spheromak as a compact fusion reactor

    International Nuclear Information System (INIS)

    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

  18. Design Point for a Spheromak Compression Experiment

    Science.gov (United States)

    Woodruff, Simon; Romero-Talamas, Carlos A.; O'Bryan, John; Stuber, James; Darpa Spheromak Team

    2015-11-01

    Two principal issues for the spheromak concept remain to be addressed experimentally: formation efficiency and confinement scaling. We are therefore developing a design point for a spheromak experiment that will be heated by adiabatic compression, utilizing the CORSICA and NIMROD codes as well as analytic modeling with target parameters R_initial =0.3m, R_final =0.1m, T_initial =0.2keV, T_final =1.8keV, n_initial =1019m-3 and n_final = 1021m-3, with radial convergence of C =3. This low convergence differentiates the concept from MTF with C =10 or more, since the plasma will be held in equilibrium throughout compression. We present results from CORSICA showing the placement of coils and passive structure to ensure stability during compression, and design of the capacitor bank needed to both form the target plasma and compress it. We specify target parameters for the compression in terms of plasma beta, formation efficiency and energy confinement. Work performed under DARPA grant N66001-14-1-4044.

  19. Ion temperature measurements in the Maryland Spheromak

    Energy Technology Data Exchange (ETDEWEB)

    Gauvreau, J.L.

    1992-12-31

    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 {mu}s, a conversion of mass flow kinetic energy into ion temperature could take place due to viscosity.

  20. Ion temperature measurements in the Maryland Spheromak

    International Nuclear Information System (INIS)

    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

  1. Spheromak Energy Transport Studies via Neutral Beam Injection

    Energy Technology Data Exchange (ETDEWEB)

    McLean, H S; Hill, D N; Wood, R D; Jayakumar, J; Pearlstein, L D

    2008-02-11

    Results from the SSPX spheromak experiment provide strong motivation to add neutral beam injection (NBI) heating. Such auxiliary heating would significantly advance the capability to study the physics of energy transport and pressure limits for the spheromak. This LDRD project develops the physics basis for using NBI to heat spheromak plasmas in SSPX. The work encompasses three activities: (1) numerical simulation to make quantitative predictions of the effect of adding beams to SSPX, (2) using the SSPX spheromak and theory/modeling to develop potential target plasmas suitable for future application of neutral beam heating, and (3) developing diagnostics to provide the measurements needed for transport calculations. These activities are reported in several publications.

  2. Measurement of magnetic properties of confined compact toroid plasma (spheromak)

    International Nuclear Information System (INIS)

    The theoretical aspect of the spheromak is described in this paper. The MS machine hardware will be explored along with the formation scheme and diagnostic systems. The magnetic pickup probes, their calibration procedures and the data analysis methods will be discussed. Observations from the probe measurements and magnetic properties of the MS spheromak are considered. The axisymmetric Grad-Shafranov equilibrium code calculations are presented and compared with the measurements. Magnetic helicity and its correlation with the experimental observations is described

  3. Sustainment of spheromak plasma by driving the toroidal current

    International Nuclear Information System (INIS)

    Spheromak plasma productions by means of quasi-static method on the basis of z-discharge and theta-discharge have been investigated using the machine named TS-3. This machine consists of a SUS vacuum vessel with an inner diameter of 76 cm and an axial length of 95 cm, two internal poloidal coils enclosed with SUS thin cases with a major diameter of 43 cm and an axial separation of 39 cm, and two sets of eight pairs of electrodes around each poloidal coil. Up to 0.2 T vertical magnetic field can be applied using an external DC mirror type magnet. Either one or two isolated spheromak(s) can be generated by the selection of sets of electrodes in proper manner. An optional current transformer with an outer cylinder diameter of 9 cm installed along the major symmetric axis of the vessel enables us to perform toroidal current driving of spheromak plasma. Spheromak plasmas produced in He has of about 10 mTorr have a decay time of about 30 micro sec. with the center conductor when it has no current for the toroidal current driving. However, when a flux change of 30 to 60 Wb/s is given to the center coil during 100 micro sec after the initiation of the spheromak configuration, the sustainment of the configuration is observed by the measurement of both poloidal and toroidal field spatial profile

  4. Investigations into the relationship between spheromak, solar, and astrophysical plasmas

    International Nuclear Information System (INIS)

    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)

  5. Minimum energy states in spheromaks with external driving

    International Nuclear Information System (INIS)

    Relaxation theory, which postulates that a magnetised plasma minimises its magnetic energy whilst conserving magnetic helicity, has been applied to explain field configurations in Reverse Field Pinches and spheromaks. The related state is described by ∇XB = μB (1) where μ j.B/B2 (2) is spatially constant. For spheromaks with some flux embedded in external conductors, relaxed states are possible for all values of μ, with resonance as μ approaches the first eigenvalue μ1. In a gun-injected spheromak such as CTX or SPHEX, current is electrostatically driven on open flux which connects the electrodes, and this external driving causes departures from simple relaxed states. This process of helicity injection sustains the spheromak against resistive decay. Fields are approximately force-free, described by (1) with μ varying across the field. Measurements confirm that μ is higher on the driven flux and lower near the magnetic axis during sustainment although the profile can be quite complex. Spheromak equilibria with non-constant-μ have been modeled, but assumptions such as linear dependence of μ on flux, must be made: a model is required to predict the μ profile for given driving and dissipation. Diffusive models with helicity transport proportional to ∇μ give monotonic μ profiles. A new approach, retaining the fundamental assumptions of relaxation theory and yet predicting non-constant μ profiles, is outlined here. (author) 9 refs., 1 fig

  6. Power balance and characterization of impurities in the Maryland Spheromak

    Energy Technology Data Exchange (ETDEWEB)

    Cote, C.

    1993-12-31

    The Maryland Spheromak is a medium size magnetically confined plasma of toroidal shape. Low T{sub e} and higher n{sub 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.

  7. Status of fabrication of the S-1 Spheromak device

    International Nuclear Information System (INIS)

    The S-1 Spheromak is nearing completion and the first plasma operation is scheduled for March, 1983. The design started in 1980. A budget adjustment forced postponement of completion from December 1982 to August 1983. The quasistatic inductive transfer of flux has been tested in prototype devices at the Princeton University Plasma Physics Laboratory. This method of producing a spheromak employs poloidal (PF) and toroidal (TF) windings in a flux core first to produce a plasma surrounding the flux core that subsequently forms a spheromak by a reconnection process. The equilibrium is maintained by a steady field (EF) supplied by a coil system that is mounted on the vacuum vessel. The state of construction of the principal elements of the S-1 device are described

  8. Power balance and characterization of impurities in the Maryland Spheromak

    International Nuclear Information System (INIS)

    The Maryland Spheromak is a medium size magnetically confined plasma of toroidal shape. Low Te and higher ne 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

  9. Energy confinement and magnetic field generation in the SSPX spheromak

    Energy Technology Data Exchange (ETDEWEB)

    Hudson, B; McLean, H S; Wood, R D; Hooper, E B; Hill, D N; Jayakumar, J; Moller, J; Romero-Talamas, C; Casper, T A; LoDestro, L L; Pearlstein, L D; Johnson, III, J A; Mezonlin, E

    2008-02-11

    The Sustained Spheromak Physics Experiment (SSPX) [E.B. Hooper, et. al., Nuclear Fusion, Vol. 39, No. 7] explores the physics of efficient magnetic field buildup and energy confinement, both essential parts of advancing the spheromak concept. Extending the spheromak formation phase increases the efficiency of magnetic field generation with the maximum edge magnetic field for a given injector current (B/I) from 0.65 T/MA previously to 0.9 T/MA. We have achieved the highest electron temperatures (T{sub e}) recorded for a spheromak with T{sub e} > 500 eV, toroidal magnetic field {approx}1 T and toroidal current ({approx}1 MA) [R.D. Wood, D.N. Hill, H.S. McLean, E.B. Hooper, B.F. Hudson, J.M. Moller, 'Improved magnetic field generation efficiency and higher temperature spheromak plasmas', submitted to Physical Review Letters]. Extending the sustainment phase to > 8 ms extends the period of low magnetic fluctuations (< 1 %) by 50%. The NIMROD 3-D resistive MHD code [C.R. Sovinec, T.A. Gianakon, E.D. Held, S.E. Kruger and D.D. Schnack, The NIMROD Team, Phys. Plasmas 10, 1727 (2003)] reproduces the observed flux amplification {Psi}{sub pol}/{Psi}{sub gun}. Successive gun pulses are demonstrated to maintain the magnetic field in a quasi-steady state against resistive decay. Initial measurements of neutral particle flux in multi-pulse operation show charge-exchange power loss < 1% of gun input power and dominantly collisional majority ion heating. The evolution of electron temperature shows a distinct and robust feature of spheromak formation: a hollow-to-peaked T{sub e}(r) associated with q {approx} 1/2.

  10. Confinement studies in high temperature spheromak plasmas

    International Nuclear Information System (INIS)

    Full text: Recent results from the SSPX spheromak experiment demonstrate the potential for obtaining good energy confinement (Te > 350 eV and radial electron thermal diffusivity comparable to tokamak L-mode values) in a self-organized toroidal plasma. In this paper we discuss energy confinement and transport in ohmically-heated SSPX discharges and compare data against several transport models applicable to self-organized systems maintained by DC helicity injection. A strong decrease in thermal conductivity with temperature is observed and at the highest temperatures, transport is well below that expected from the Rechester-Rosenbluth model. Recent improvements to performance (raising Te from 200 eV) result from increasing both gun flux and current to increase the magnetic field while keeping a relatively flat current profile to minimize magnetic fluctuations. In the near term, a new capacitor bank is expected to produce higher magnetic fields and longer pulses, allowing operation with temperatures as high as 0.5 keV. At temperatures above 300 eV, it becomes possible to use modest (1.8 MW) amounts of neutral beam injection (NBI) auxiliary heating to significantly change the power balance in the core plasma, making it an effective tool for improving transport analysis. We are now developing detailed designs for adding NBI to SSPX and have developed a new module for the CORSICA transport code to compute the correct fast-ion orbits in SSPX. This module, coupled to a deposition code (NFREYA), is used to calculate the particle, current and power deposition from Neutral Beam injection. Initial CORSICA results show that a substantial fraction of the injected bean, of order 70%, is confined as fast ions, which is sufficient to raise the electron temperature and total plasma pressure in the core by a factor of two. (author)

  11. Field and current amplification in the SSPX spheromak

    International Nuclear Information System (INIS)

    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 χe∼30m2/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)

  12. Spheromak reactor with poloidal flux-amplifying transformer

    Science.gov (United States)

    Furth, Harold P.; Janos, Alan C.; Uyama, Tadao; Yamada, Masaaki

    1987-01-01

    An inductive transformer in the form of a solenoidal coils aligned along the major axis of a flux core induces poloidal flux along the flux core's axis. The current in the solenoidal coil is then reversed resulting in a poloidal flux swing and the conversion of a portion of the poloidal flux to a toroidal flux in generating a spheromak plasma wherein equilibrium approaches a force-free, minimum Taylor state during plasma formation, independent of the initial conditions or details of the formation. The spheromak plasma is sustained with the Taylor state maintained by oscillating the currents in the poloidal and toroidal field coils within the plasma-forming flux core. The poloidal flux transformer may be used either as an amplifier stage in a moving plasma reactor scenario for initial production of a spheromak plasma or as a method for sustaining a stationary plasma and further heating it. The solenoidal coil embodiment of the poloidal flux transformer can alternately be used in combination with a center conductive cylinder aligned along the length and outside of the solenoidal coil. This poloidal flux-amplifying inductive transformer approach allows for a relaxation of demanding current carrying requirements on the spheromak reactor's flux core, reduces plasma contamination arising from high voltage electrode discharge, and improves the efficiency of poloidal flux injection.

  13. Steady-state operation of spheromaks by inductive techniques

    International Nuclear Information System (INIS)

    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

  14. Motion and equilibrium of a spheromak in a toroidal flux conserver

    OpenAIRE

    Brown, M R; Cutrer, D. M.; Bellan, P. M.

    1991-01-01

    A number of experiments have been performed on spheromaks injected into the empty vacuum vessel of the Caltech ENCORE tokamak (i.e., without tokamak plasma) [Phys. Rev. Lett. 64, 2144 (1990); Phys. Fluids B 2, 1306 (1990)]. Magnetic probe arrays (in a number of configurations) have been used to make single shot, unaveraged, in situ measurements of the spheromak equilibrium. These measurements are important because (i) they reveal for the first time the equilibrium structure of spheromaks in a...

  15. Characterization of a spheromak plasma gun: The effect of refractory electrode coatings

    OpenAIRE

    Brown, M R; Bailey, A. D.; Bellan, P. M.

    1991-01-01

    In order to investigate the proposition that high-Z impurities are responsible for the anomalously short lifetime of the Caltech spheromak, the center electrode of the spheromak plasma gun has been coated with a variety of metals (bare steel, copper, nickel, chromium, rhodium, and tungsten). Visible light (230–890 nm) emitted directly from the plasma in the gun breech was monitored for each of the coated electrodes. Plasma density and temperature and spheromak lifetime were compared for each ...

  16. Numerical simulation of slow spheromak formation: Flux control by formation speed

    Energy Technology Data Exchange (ETDEWEB)

    Sato, T.; Todd, A.M.M.; Okuda, H.

    1983-03-01

    Two-dimensional magnetohydrodynamic simulations of the Princeton S-1 Spheromak have been carried out for several formation speeds. It is found that the spheromak size and shape, and hence the confined poloidal and toroidal fluxes, are largely dependent upon the formation speed, provided this is moderately slow. Specifically, the total toroidal and poloidal fluxes in a spheromak increase as the formation speed is reduced. The role of externally driven reconnection as a cause for this dependence is discussed.

  17. Slow formation and sustainment of spheromaks by a coaxial magnetized plasma source

    Energy Technology Data Exchange (ETDEWEB)

    Jarboe, T.R.; Henins, I.; Sherwood, A.R.; Barnes, C.W.; Hoida, H.W.

    1983-07-04

    Two steps have been taken towards determining if the flux absorption and relaxation properties of a spheromak will allow dc-powered electrodes to form and sustain a steady-state spheromak. Without changing the physical properties of the spheromak, the formation time was increased from an Alfven time to a tearing time, reducing the coaxial source power from approx.10 GW to approx.500 MW. With use of approx.50 MW, spheromaks were formed and then sustained at constant density and field for 1 ms, much longer than a magnetic energy decay time.

  18. Taylor relaxation and lambda decay of unbounded, freely expanding spheromaks

    OpenAIRE

    Yee, J; Bellan, P. M.

    2000-01-01

    A magnetized coaxial gun is discharged into a much larger vacuum chamber and the subsequent evolution of the plasma is observed using high speed cameras and a magnetic probe array. Photographic results indicate four distinct regimes of operation, labeled I–IV, each possessing qualitatively different dynamics, with the parameter lambdagun = µ0Igun/Phibias determining the operative regime. Plasmas produced in Regime II are identified as detached spheromak configurations. Images depict a donut-l...

  19. Neutral Beam Current Drive in Spheromak plasma and plasma stability

    Science.gov (United States)

    Pearlstein, L. D.; Jayakumar, R. J.; Hudson, B.; Hill, D. N.; Lodestro, L. L.; McLean, H. S.; Fowler, T. K.; Casper, T. A.

    2007-11-01

    A key question for the Sustained Spheromak Physics Experiment (SSPX) is understanding how spheromaks can be sustained by other current drive tools such as neutral beam current drive. Another question is whether the present relationship between current and maximum spheromak magnetic field (plasma beta) is related to Alcator-like ohmic confinement limit or is a stability limit. Using the code CORSICA, the fraction of neutral beam current drive that can be achieved has been calculated for different injection angles with a fixed equilibrium. It is seen that relaxing the equilibrium with this drive simply drives the core safety factor to low values. Other equilibria where the NBI may give aligned current drive are being explored. Free-boundary equilibria calculations are underway to see what hyper-resistivity model gives the observed sustained SSPX performance and include that in the NBI calculations. Work performed under the auspices of the US DOE by University of California Lawrence Livermore National Laboratory under contract W-7405-ENG-48.

  20. Improved operation and modeling of the SSPX Spheromak

    International Nuclear Information System (INIS)

    Progress in understanding both magnetic field generation and confinement is enabling the production of high magnetic field spheromaks with plasma core electron temperatures (Te) >200eV in the Sustained Spheromak Physics Experiment (SSPX). The highest measured Te occurs when the edge magnetic fluctuation amplitude is lowest. Improvements over previous results were produced with higher formation bank current, longer discharges, and better matching of edge current and bias flux to minimize magnetic fluctuations. New experiments show for the first time that the field energy of the spheromak can be increased in a step-wise manner using repetitive current pulses. These multi-pulse discharges produce the strongest magnetic fields yet in SSPX (0.7 T at the geometric axis), and an important scaling of magnetic field with current has been exceeded. 3D resistive MHD simulations with NIMROD for conditions similar to SSPX single and double pulse discharges with increasingly realistic representations of the gun geometry, magnetic bias coils, and current-drive pulse histories, and with Braginski temperature-dependent resistivity and anisotropic thermal conductivities are tracking the reconstructions of the magnetic configuration, and the temperature and magnetic fluctuation histories with increasing fidelity. (author)

  1. Multi-pulse power injection and spheromak sustainment in SSPX

    Science.gov (United States)

    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.

  2. Spheromak formation and sustainment studies at the sustained spheromak physics experiment using high-speed imaging and magnetic diagnostics

    OpenAIRE

    Romero-Talamás, C. A.; Holcomb, C; Bellan, P. M.; Hill, D. N.

    2006-01-01

    A high-speed imaging system with shutter speeds as fast as 2 ns and double frame capability has been used to directly image the formation and evolution of the sustained spheromak physics experiment (SSPX) [E. B. Hooper et al., Nucl. Fusion 39, 863 (1999)]. Reproducible plasma features have been identified with this diagnostic and divided into three groups, according to the stage in the discharge at which they occur: (i) breakdown and ejection, (ii) sustainment, and (iii) decay. During the fi...

  3. Ultrashort-pulse reflectometer performance on Sustained Spheromak Physics Experiment

    International Nuclear Information System (INIS)

    Time-resolved density profiles on the Sustained Spheromak Physics Experiment device are now generated automatically from data collected by an ultrashort-pulse reflectometry (USPR) diagnostic comprised of 24 frequency channels spanning 34-75 GHz. Upgrades in USPR timing electronics and reconstruction software, coupled with new low noise amplifiers and reduced bandwidth filters, have significantly decreased amplitude and timing jitter enabling simultaneous density profile and multilayer density fluctuation operation. Hardware and software components of the upgraded USPR system are described, and sample profile and fluctuation data are presented. A new system layout is proposed to increase the USPR dynamic range by 8-10 dB

  4. Progress in spheromaks for power amplification and transfer to hypervelocity projectiles

    International Nuclear Information System (INIS)

    The goal of the spheromak program at Los Alamos is to develop a new scheme to accelerate material objects to hypervelocities (velocities above a few kilometers per second). This capability would provide a valuable tool to other research programs, such as weapons lethality tests, studies of the properties of materials at extremely high pressures, and magnetically-insulated impact fusion. In the authors' scheme, the magnetized spheromak plasma, confined by a metallic wall, would act as an energy storage and transfer medium. As high explosives (HE) compress part of the metallic wall against the spheromak magnetic field, the spheromak stores energy. Once the spheromak reaches a critical dimension, the MHD equilibrium is expected to switch (much faster than the compression time) to a new configuration, which is the minimum-energy state of the new geometry. This witching action would result in the spheromak magnetic field imparting a sudden, strong pressure to a small section of the wall, which would then break away as an accelerated projectile. The scheme, including the basis for the spheromak switching effect, are described

  5. New mode of operating a magnetized coaxial plasma gun for injecting magnetic helicity into a spheromak.

    Science.gov (United States)

    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

    2003-03-01

    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. PMID:12689228

  6. New mode of operating a magnetized coaxial plasma gun for injecting magnetic helicity into a spheromak

    International Nuclear Information System (INIS)

    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

  7. Simulation study of stepwise relaxation in a spheromak plasma

    International Nuclear Information System (INIS)

    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)

  8. The University of Maryland spheromak fusion experiment: Final report

    International Nuclear Information System (INIS)

    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

  9. Stability and confinement of spheromaks and field-reversed configurations

    International Nuclear Information System (INIS)

    The formation, confinement and stability of two types of compact toroids, spheromaks and field reversed configurations (FRC), are reviewed. Spheromaks, which contain both toroidal and poloidal magnetic fields, have been formed with magnetized coaxial plasma guns, by a combination of Z- and theta-pinch techniques and by an electrodeless slow induction technique, and trapped in both prolate and oblate flux conservers. As predicted by theory, the prolate configuration is unstable to the tilt mode, but the oblate configuration with a conducting wall is stable. Configuration lifetimes of up to 0.8 ms are observed. The FRC is a high-beta, highly prolate compact toroid formed with field-reversed theta-pinch techniques and having purely poloidal magnetic field. Theory predicts unstable fluting and internal tilting modes, but they are not observed experimentally. Configurations with high densities approx. 1015 cm-3 and with lifetimes of 50 to 120 μs are terminated by an n=2 rotational mode of instability

  10. The Physics of a Spheromak with Applied Vertical Field

    Science.gov (United States)

    Woodruff, S.; Hill, D. N.; Hooper, E. B.; Holcomb, C. T.; Stallard, B. W.; Wood, R. D.; Bulmer, R. H.; Cohen, B. I.; Lodestro, L.; Pearlstein, L. D.; Sspx Team

    2000-10-01

    Lawrence Livermore National Laboratory, Livermore, California, USA. The physics basis of the initial flux configurations producible by the newly installed bias coils in SSPX is elucidated, and the anticipated results are explored. Broadly, the new configurations should increase the helicity injection rate, reduce the proportion of the spheromak flux that intersects the material boundary (‘field errors’) and increase particle confinement time. The effect of the applied field on equilibrium (CORSICA in SSPX geometry[1]) and stability (DCON[2]) will be discussed. Also, the effects on the dominant modes will be explored through 3D resistive MHD simulation (NIMROD[3]). Finally, a means for sustaining the spheromak in the absence of the n=1 mode, thought to be necessary for current drive, will be examined. [1] Hooper et al Nuc. Fusion v39, no.7, pp863-871 1999 [2] Glasser LANL report LA-UR-95-528 1995 [3] Glasser et al Plas. Phys. Cont. Fus. 41, A747 1999. Work performed under the auspices of US DOE by the University of California Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.

  11. Magnetic field diffusion and flux loss within a spheromak

    International Nuclear Information System (INIS)

    This paper considers the magnetic confinement of a plasma within a prototype controlled fusion experiment, the spheromak. This device has a containment vessel that is topologically spherical, offering considerable engineering advantages compared with conventional toroidal systems. The authors' aim has been to evaluate possible designs for the flux conserver and gun magnetic field coils, taking account of flux penetration into the walls caused by finite resisitivity. The copper walls cannot remain perfect magnetic flux surfaces for the duration of the experiment, and we calculate the magnetic field penetration into the walls for a range of designs. This study is in response to recent results showing that wall conditions and flux loss are a vital element of the system's performance, with a substantial increase in global resistance arising if field becomes embedded in the walls creating a dead space that is not driven by the gun current. The authors develop a model bearing general application to magnetic field interaction with resistive walls in complex geometries, with particular reference to the UMIST spheromak experiment SPHEX

  12. Fundamental Magnetofluid Physics Studies on the Swarthmore Spheromak Experiment: Reconnection and Sustainment

    International Nuclear Information System (INIS)

    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

  13. 0-D study of the compression of low temperature spheromaks

    International Nuclear Information System (INIS)

    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 109s/cm3. 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/

  14. Transport and fluctuations in high temperature spheromak plasmas

    Science.gov (United States)

    McLean, Harry

    2005-10-01

    A systematic analysis is presented of thermal transport in a driven spheromak that extends well into the collisionless regime and spans a wide range of magnetic fluctuation levels. The relationship between internal fluctuations and energy/helicity transport is of fundamental interest to many self-organized configurations in laboratory and space plasmas and the subject of ongoing multi-institutional collaborations. With the recent achievement on the SSPX spheromak[1] of electron temperature Te˜350eV in the core, and good confinement (core electron thermal diffusivity χe200eV), we are now comparing heat transport in the experiment with a variety of models including classical, Bohm, and stochastic[2]/diffusive[3]/open[4] field lines. Using Thomson scattering to measure Te, ne profiles and the CORSICA equilibrium code to calculate internal current profiles from magnetic probe fits, we find that χe decreases as Te increases, a scaling behavior more classical-like than Bohm or open field line models would indicate. Lower Te and higher χe is observed in the transition region between the core and the separatrix where NIMROD 3d resistive MHD calculations[5] show the possible existence of chaotic field lines. We will also discuss plans including multi-pulse Thomson scattering and neutral beam heating. [1] E.B. Hooper, et al., Nucl. Fusion 39, 863 (1999). [2] A.B. Rechester and M.N. Rosenbluth, Phys. Rev. Lett. 40, 38 (1978). [3] J.D. Callen, Phys. Rev. Lett. 94, 055002 (2005). [4] R.W. Moses, et al., Phys. Plasmas 8, 4839 (2001). [5] B.I. Cohen, et al., Phys. Plasmas 12, 056106 (2005). This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

  15. Magnetohydrodynamic simulation on co- and counter-helicity merging of spheromaks and driven magnetic reconnection

    International Nuclear Information System (INIS)

    A magnetohydrodynamic relaxation process of spheromak merging is studied by means of an axisymmetric numerical simulation. As a result of counter-helicity merging, a field-reversed configuration is obtained in the final state, while a larger spheromak is formed after co-helicity merging. In the counter-helicity case, a clear pressure profile of which iso-surfaces coincide with flux surfaces is generated by thermal transport of a poloidal flow induced by driven reconnection. It is also found that a sharp pressure gradient formed in the vicinity of a reconnection point causes a bouncing motion of spheromaks. According to the bounce motion, the reconnection rate changes repeatedly. As shown by the Tokyo University Spherical Torus No. 3 (TS-3) experiments [M. Yamada, et al., Phys. Rev. Lett. 65, 721 (1990)], furthermore, strong acceleration of a toroidal flow and reversal of a toroidal field in the counter-helicity merging were observed. copyright 1997 American Institute of Physics

  16. Magnetohydrodynamic simulation on Co- and counter-helicity merging of spheromaks and driven magnetic reconnection

    International Nuclear Information System (INIS)

    A magnetohydrodynamic relaxation process of spheromak merging is studied by means of an axi-symmetric numerical simulation. As a result of counter-helicity merging, a field-reversed configuration is obtained in the final state, while a larger spheromak is formed after co-helicity merging. In the counter-helicity case, a clear pressure profile of which iso-surfaces coincide with flux surfaces is generated by thermal transport of a poloidal flow that is induced by driven reconnection. It is also found that a sharp pressure gradient formed at the edge of a current sheet causes a bouncing motion of spheromaks. According to the bounce motion, the reconnection rate changes repeatedly. As is shown by the TS-3 experiments, furthermore, strong acceleration of a toroidal flow and reversal of a toroidal field are observed in the counter-helicity merging. (author)

  17. Energy balance for sustained spheromak plasmas in SSPX

    Science.gov (United States)

    Hill, D. N.; Auerbach, D.; Bulmer, R.; McLean, H.; Wood, R.; Woodruff, S.

    2001-10-01

    Formation of self-organized spheromak plasmas requires, at a minimum, that the input power exceed the loss power in order to increase magnetic field strength. Other factors, such as injector geometry or low-order MHD modes, are also thought to affect the formation process. In SSPX we measure both the input power at the coaxial source, and the loss power to the flux conserver (radiation and plasma conduction) to obtain the global power balance which we can relate to the field buildup. The radiation loss is determined by wide field-of-view bolometers, both time-integrated and time-resolved. Radiation losses are dominated by low-Z impurities and are typically less than 20energy input for clean discharges. We use edge magnetic probe measurements as input to the CORSICA code to determine the total stored magnetic energy and ohmic heating power, which then allows us to compute the energy confinement time from density and temperature profiles obtained by Thomson scattering. 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.

  18. Simple Model of the (alpha)(omega) Dynamo: Self-Excited Spheromaks

    Energy Technology Data Exchange (ETDEWEB)

    Fowler, T K

    2010-01-26

    The astrophysical {alpha}{omega} dynamo converting angular momentum to magnetic energy can be interpreted as a self-excited Faraday dynamo together with magnetic relaxation coupling the dynamo poloidal field to the toroidal field produced by dynamo currents. Since both toroidal and poloidal fields are involved, the system can be modeled as helicity creation and transport, in a spheromak plasma configuration in quasi-equilibrium on the time scale of changes in magnetic energy. Neutral beams or plasma gun injection across field lines could create self-excited spheromaks in the laboratory.

  19. Relaxed, minimum dissipation states, for a flux core spheromak sustained by helicity injection

    NARCIS (Netherlands)

    Farengo, R; Caputi, KI

    2002-01-01

    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 formed by the flux that links the electrodes

  20. Studies of Helicity Injection in a Spheromak Formed by a Large Area Planar Coaxial Gun

    Science.gov (United States)

    Hsu, Scott; Bellan, Paul; Pracko, Steven

    2000-10-01

    A new planar coaxial gun has been constructed in order to study the process of helicity injection during spheromak formation. Improvements in helicity injection, a key method for poloidal field sustainment in spheromaks, would increase the attractiveness of the spheromak configuration as a fusion energy scheme. The goal of this research is to create simple, well-defined experiments allowing the details of helicity injection to be resolved and better understood. The design of the new gun, which was motivated by insights gained from ongoing solar prominence experiments [Bellan and Hansen, Phys. Plasmas 5, 1991 (1998)], involves large planar electrodes with a low field solenoid, in contrast to smaller cylindrical guns with high field solenoids commonly in existence. More efficient spheromak formation and better ``λ-matching'' should be possible in the new setup. The formation and dynamical evolution of twisted flux tubes will be studied using a variety of optical and probe diagnostics, including (1) visible light photography using a pair of fast, gated intensified CCD cameras, (2) local magnetic field measurements using an array of small pickup coils, (3) density and electron temperature measurements using a triple Langmuir probe, and (4) measurements of local ion distribution functions using laser-induced fluorescence. Details of the new gun design and initial experimental results will be presented.

  1. Numerical investigation and optimization of multi-pulse CHI spheromak performance

    Science.gov (United States)

    O'Bryan, J. B.; Romero-Talamas, C. A.; Woodruff, S.

    2015-11-01

    Nonlinear extended-MHD computation with the NIMROD code is used to explore spheromak formation and sustainment with multi-pulse coaxial helicity injection (CHI). The goal of this research is to optimize spheromak performance in order to find candidate modes of operation for future experimental studies. We are modeling multiple specific shots from the Sustained Spheromak Physics eXperiment (SSPX) to both diagnose the parameters that affect efficiency--in particular, how the injector current and bias flux affect plasma confinement and magnetic helicity content relative to injected power--and to validate the numerical model. Preliminary results show quantitative agreement between several synthetic and experimental diagnostic measurements. The results also find--in addition to changing the magnetic topology and being the mechanism for poloidal flux amplification [E.B. Hooper et al. PPCF 2012]--the non-axisymmetric column mode decreases the decay rate of magnetic helicity relative to the injected current. Operational regimes will eventually be extended beyond those achieved in SSPX. We are also exploring the effect of the flux conserver and injector geometries on spheromak performance. This work is supported by DARPA under grant no. N66001-14-1-4044.

  2. Investigation of spheromak configuration generated by inductive methods in the S-1 device

    International Nuclear Information System (INIS)

    This paper summarizes the characteristics of the spheromak plasmas obtained during the past five-year operation period of S-1 experiments. The S-1 Spheromak device, which began operation in 1983, generates a compact toroid in which the self-generated toroidal field in the plasma is comparable to the poloidal field. The S-1 experiment is unique in that spheromak plasmas are formed by inductive transfer of magnetic flux from a toroidal-shaped ''flux core,'' and plasma stability is maintained by shaping of the externally applied equilibrium field and using loose-fitting passive conductors. The most important objective for the S-1 experiment is to investigate the confinement feature of the spheromak configuration. With a rather extensive diagnostic system for this size device, the transport characteristics of the S-1 spheromak have been measured for plasmas with 10 /approx lt/ T/sub e/ ≤ 130 eV and 2 /approx lt/ n/sub e/ /approx lt/ 15 /times/ 1013 cm/sup /minus/3/. The scaling of electron temperature T/sub e/ and density n/sub e/ with plasma current density has been obtained in a wide operation regime. The most important finding is that the peak electron pressure scales as n/sub eo/T/sub eo/ /proportional to/ j/sub o/2 (j/sub o/ = peak toroidal current density) with T/sub eo/ /proportinal to/ j/sub o/2 and n/sub eo/ ≅ constant. These scaling results, which are similar to those obtained in the reversed-field pinch device, suggest that β = constant. Energy and particle confinement times are determined. 44 refs., 35 figs

  3. Coupling of helicity and power for spheromak buildup and sustainment in SSPX

    Science.gov (United States)

    Stallard, B. W.; Woodruff, S.; Fowler, T. K.; Hill, D. N.; Hooper, E. B.; Bulmer, R. H.; McLean, H. S.

    2001-10-01

    Coaxial gun-injected power provides buildup and sustainment in SSPX. Current flowing along the open field lines in the spheromak edge dissipates power in electrode sheaths, the resistive edge, and coupling to plasma turbulence. In this paper we compare both power and helicity balance models to calculate plasma buildup. Because both power and helicity are rapidly dissipated in the sheaths and edge resistance, the power and helicity input providing for buildup is modeled from the observed increase in gun impedance above a current threshold. Measurements of the gun voltage and current provide information on the gun impedance. From Thomson scattering measurements of the electron temperature and the CORSICA mhd equilibrium, estimates can be made for the edge dissipation and ηJ^2 resistive losses within the spheromak core. 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.

  4. A numerical study of MHD equilibrium and stability of the spheromak

    International Nuclear Information System (INIS)

    The MHD-stability of spheromak-type equilibria from the classical spheromak configuration to the diffuse-pinch limit is analysed numerically. It is found that oblate configurations of ellipticity 0.5 have optimum stability properties with regard to internal MHD-modes and can be stabilized up to an engineering β of 15% (defined with respect to the applied external field strength for equilibrium). Stability to global modes requires that a conducting shell surround the plasma. The location of the shell is dependent on geometry and current profile, but realistic configurations that are stable to all ideal MHD-modes have been found with the shell located at about 1.2 of the minor radius. (author)

  5. Slow formation of field-reversed configuration by use of two merging spheromaks

    Energy Technology Data Exchange (ETDEWEB)

    Ono, Yasushi [Univ. of Tokyo (Japan)

    1995-04-01

    A novel slow formation method of field-reversed configuration (FRC) has been developed by magnetic reconnection of two force-free spheromaks with opposite toroidal magnetic field. The merging process cancels their opposite magnetic helicities, realizing a non-Taylor relaxation from the force-free state to the high-{beta} FRC state with zero helicity. A significant increase in the ion temperature has been documented up to 180 eV during this fully anti-parallel reconnection. The dissipated toroidal magnetic energy of the merging toroids is transformed mostly to the ion thermal energy, revealing a unique relaxation mechanism to the high-beta equilibrium. The merging toroids are found to relax either to an FRC or to a new spheromak, depending on whether their total helicity is larger or smaller than a critical value. 10 refs., 5 figs.

  6. Controlled and spontaneous magnetic field generation in a gun-driven spheromak

    OpenAIRE

    WOODRUFF, S; Cohen, B. I.; Hooper, E.B.; McLean, H. S.; Stallard, B. W.; Hill, D. N.; Holcomb, C. T.; Romero-Talamás, 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 (delta B/B similar to 1% on the midplane edge) yields T-e profiles peaked at > 200 eV. Trends indic...

  7. Controlled and spontaneous magnetic field generation in a gun-driven spheromak

    International Nuclear Information System (INIS)

    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 Te profiles peaked at >200 eV. Trends indicate a limiting beta (βe∼4%-6%), and so we have been motivated to increase Te 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, Itor/Igun. (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

  8. Controlled and Spontaneous Magnetic Field Generation in a Gun-Driven Spheromak

    International Nuclear Information System (INIS)

    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 Te profiles peaked at > 200eV. Trends indicate a limiting beta (βe ∼ 4-6%), and so we have been motivated to increase Te 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, Itor/Igun. (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

  9. Large-amplitude electron density and Hα fluctuations in the sustained spheromak physics experiment

    International Nuclear Information System (INIS)

    New types of toroidally rotating fluctuations (toroidal mode numbers n=1 and n=2) of line-integrated electron density and Hα emission, with frequencies ranging from 10 to 100 kHz, are observed in the sustained spheromak physics experiment (SSPX). The rotating directions of these fluctuations are the same as the direction determined by ExB, while the E and B directions are determined by the gun voltage and gun magnetic flux polarities, respectively. These results take advantage of one distinctive signature of spheromaks, i.e. it is possible to observe toroidal MHD activity during decay and sustainment at any toroidal angle. A theoretical constraint on line-integrated measurement is proposed and is found to be consistent with experimental observations. Fluctuation analysis in the time and frequency domains indicates that the observed density and Hα fluctuations correlate with magnetic modes. Observation of Hα fluctuations correlating with magnetic fluctuations indicates that, at least in some cases, MHD n=1 modes are due to the so-called 'dough-hook' current paths that connect the coaxial gun to the flux conserver, rather than internal kink instabilities. These results also show that electron density and Hα emission diagnostics complement other tools for spheromak mode study. (author)

  10. Magnetic flux conversion and relaxation toward a minimum-energy state in S-1 spheromak plasmas

    Energy Technology Data Exchange (ETDEWEB)

    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.

  11. Magnetic flux conversion and relaxation toward a minimum-energy state in S-1 spheromak plasmas

    International Nuclear Information System (INIS)

    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

  12. Final Report - Effect of Magnetic Configuration on Spheromak Performances, FY2000 - FY2001, Tracking No.00-SI-008

    Energy Technology Data Exchange (ETDEWEB)

    Hill, D N; Hooper, E B; McLean, H S; Stallard, B W; Woodruff, S; Wood, R D

    2002-02-06

    This is the final report on LDRD SI-funded research to determine the Effect of Magnetic Field Configurations on Spheromak Performance for the years FY2000-FY2001, during which a new set of bias magnetic field coils was used to change the vacuum magnetic field configuration of the SSPX spheromak at LLNL. The USDOE Office of Fusion Energy Science funded the routine operation of the SSPX facility during FY00 and FY01. A photo of the SSPX facility as it appeared in mid-FY01, appears in this report. The main distinctive feature of the spheromak is that currents in the plasma itself produce the confining toroidal magnetic field, rather than a complex set of external coils. The Sustained Spheromak Physics Experiment (SSPX) device was designed and built study how well the spheromak can contain plasma energy while dynamo processes in the plasma maintain the confining magnetic fields. The spheromak potentially offers advantages over other fusion reactor concepts because it is compact, has no field coils linking the vacuum vessel, and can be operated in a steady state with voltage applied to external electrodes. It is predicted that the ability of the SSPX to contain the plasma thermal energy will increase with increasing plasma electron temperature; that is, the hotter it is, the better it will work. Our near-term goal for the SSPX facility is to determine which of several magnetic field configurations works best to produce hot, well-confined spheromak plasmas. We also want to verify the predicted inverse relation between plasma temperature and heat loss, and to use these results to design an even higher-temperature follow-on experiment that will push closer to fusion conditions. New features of the SSPX spheromak include a large-radius coaxial plasma injector to improve efficiency, a conformal flux conserver to minimize open field lines around the plasma, a divertor to aid in cold-particle exhaust, and the programmable-bias magnetic field coils to vary the magnetic geometry

  13. Amplification of S-1 Spheromak current by an inductive current transformer

    International Nuclear Information System (INIS)

    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

  14. Magnetohydrodynamic simulation of kink instability and plasma flow during sustainment of a coaxial gun spheromak

    International Nuclear Information System (INIS)

    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 (vt ≈ 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)

  15. 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)

  16. Experimental investigation of line-tying effects on the spheromak tilt mode

    Energy Technology Data Exchange (ETDEWEB)

    Wysocki, F.J.

    1986-02-01

    A variety of passive stabilization techniques compatible with S-1 inductive spheromak formation has been evaluated for effectiveness against the MHD tilting instability. A line-tying stabilization effect has been previously identified theoretically. In the present work, the effects have been experimentally identified and investigated. The perturbed current patterns within passive stabilizing structures have been measured, and line-tying currents have been identified. The simple ring model of tilting has been expanded to include line-tying, and has provided estimates for growth rates which agree well with the measured values. 51 refs., 18 figs., 1 tab.

  17. Energy Efficiency Analysis of the Discharge Circuit of Caltech Spheromak Experiment

    OpenAIRE

    Kumar, Deepak; Moser, Auna L.; Bellan, Paul M.

    2010-01-01

    The Caltech spheromak experiment uses a size A ignitron in switching a 59-μF capacitor bank (charged up to 8 kV) across an inductive plasma load. Typical power levels in the discharge circuit are ~200 MW for a duration of ~10 μs. This paper describes the setup of the circuit and the measurements of various impedances in the circuit. The combined impedance of the size A ignitron and the cables was found to be significantly larger than the plasma impedance. This causes the ...

  18. On the jets, kinks, and spheromaks formed by a planar magnetized coaxial gun

    International Nuclear Information System (INIS)

    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

  19. Sustained spheromak coaxial gun operation in the presence of an n=1 magnetic distortion

    International Nuclear Information System (INIS)

    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≡μ0jparallel/B is not constant, although the global value λg≡μ0Ig/ψg 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

  20. 3D Canonical Momentum Measurements During the Merging of Two Counter-Helicity Spheromaks

    Science.gov (United States)

    You, Setthivoine; Balandin, Alexander; Tanabe, Hiroshi; Ono, Yasushi

    2009-11-01

    A pair of counter-helicity spheromaks can merge in two possible ways to form a single final compact toroid depending on their toroidal magnetic field direction. Magnetohydrodynamically, no difference should be expected but experimentally, a positive/negative merging or negative/positive merging will generate final compact toroids with different lifetimes and sizes. A pair of multichannel spectroscopic diagnostics have been installed on the TS-4 experiment with view chords designed for measuring 3D ion velocities and temperature. One set retrieves toroidal velocities and temperature from conventional Abel inversion. The second, novel arrangement retrieves poloidal velocities from 3D vector tomography reconstruction and temperature from scalar tomography. With in situ magnetic probe arrays, the ion canonical momentum is thus determined in the complete volume. The ion temperature at the reconnection plane is also evaluated [1]. Both sets of measurements are followed over several repeatable shots during the spheromak merging to also track the evolution of ion self-helicity.[0pt][1] Tanabe, You, Balandin, Ono, poster this meeting.

  1. Effect of the helicity injection rate and the Lundquist number on spheromak sustainment

    Science.gov (United States)

    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.

  2. 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.

  3. On the jets, kinks, and spheromaks formed by a planar magnetized coaxial gun

    CERN Document Server

    Hsu, S C

    2004-01-01

    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, P...

  4. Experimental identification of the kink instability as a poloidal flux amplification mechanism for coaxial gun spheromak formation.

    Science.gov (United States)

    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. PMID:12786562

  5. Experimental identification of the kink instability as a poloidal flux amplification mechanism for coaxial gun spheromak formation

    International Nuclear Information System (INIS)

    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

  6. Experimental Identification of the Kink Instability as a Poloidal Flux Amplification Mechanism for Coaxial Gun Spheromak Formation

    CERN Document Server

    Hsu, S C

    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.

  7. Experimental Identification of the Kink Instability as a Poloidal Flux Amplification Mechanism for Coaxial Gun Spheromak Formation

    OpenAIRE

    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...

  8. Measurements of spheromak formation and field buildup at SSPX using a double magnetic probe array

    Science.gov (United States)

    Romero-Talamas, C. A.; Ohia, O. O.; Jayakumar, R.

    2007-11-01

    A specially designed magnetic probe consisting of two linear arrays that measure Bx, By, and Bz, is being used to investigate magnetic evolution during spheromak formation, and during multiple gun current pulses on top of a baseline current at SSPX. The measurements reveal that at the start of each pulse there is a time lag in the magnetic response of the closed flux region, while the open flux (intercepting the gun electrodes) responds immediately. This is interpreted as the time to build enough helicity on the open flux, before reconnecting and adding flux to the closed surfaces. Magnetic reconstructions after pulsed buildup using CORSICA show good agreement with the data. A code that simulates the magnetic field from current-carrying flux ropes is used to reproduce the field measured during flux buildup. The code includes an optimization routine that finds the rope shape that best fits the data in order to estimate helicity in the open flux. Work performed under the auspices of the US DOE by University of California Lawrence Livermore National Laboratory under contract W-7405-ENG-48.

  9. Formation and sustainment of field reversed configuration (FRC) plasmas by spheromak merging and neutral beam injection

    Science.gov (United States)

    Yamada, Masaaki

    2016-03-01

    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.

  10. Measurements of Plasma Jets and Collimated Flux Tubes that are the Precursors of Spheromak Self-organization

    OpenAIRE

    Bellan, P. M.; You, S.; Yun, G. S.

    2007-01-01

    A magnetized planar coaxial plasma gun is used to study the physics of spheromak formation. Eight magnetic flux tubes spanning from the cathode to the anode electrode are first filled with plasma by a rapid MHD pumping mechanism which ingests plasma from nozzles at the wall. The ingested plasma convects toroidal flux and the pile-up of this flux in the flux tube causes the flux tube to become collimated. The eight collimated flux tubes first have the shape of spider legs, but then merge to fo...

  11. The impedance of energy efficiency of a coaxial magnetized plasma source used for spheromak formation and sustainment

    International Nuclear Information System (INIS)

    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

  12. Magnetic structure in the entrance region of spheromaks sustained by a magnetized coaxial plasma gun under long pulse operation

    International Nuclear Information System (INIS)

    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)

  13. Extreme ultraviolet spectroscopy and modeling of Cu on the SSPX Spheromak and laser plasma 'Sparky'

    Energy Technology Data Exchange (ETDEWEB)

    Weller, M. E.; Safronova, A. S.; Kantsyrev, V. L.; Safronova, U. I.; Petkov, E. E.; Wilcox, P. G.; Osborne, G. C. [University of Nevada, Reno, Nevada 89557 (United States); Clementson, J.; Beiersdorfer, P. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

    2012-10-15

    Impurities play a critical role in magnetic fusion research. In large quantities, impurities can cool and dilute plasma creating problems for achieving ignition and burn; however in smaller amounts the impurities could provide valuable information about several plasma parameters through the use of spectroscopy. Many impurity ions radiate within the extreme ultraviolet (EUV) range. Here, we report on spectra from the silver flat field spectrometer, which was implemented at the Sustained Spheromak Physics experiment (SSPX) to monitor ion impurity emissions. The chamber within the SSPX was made of Cu, which makes M-shell Cu a prominent impurity signature. The Spect3D spectral analysis code was utilized to identify spectral features in the range of 115-315 A and to more fully understand the plasma conditions. A second set of experiments was carried out on the compact laser-plasma x-ray/EUV facility 'Sparky' at UNR, with Cu flat targets used. The EUV spectra were recorded between 40-300 A and compared with results from SSPX.

  14. Maryland magnetic fusion research progam, MS spheromak

    International Nuclear Information System (INIS)

    In this report, we will summarize briefly the work done on the MS experimental device from April 1988 to the beginning of the present contract period in November 1989, and then discuss in more detail the work accomplished in the contract period, such as, impurity control, MHD equilibrium, temperature measurements, and microwave preionization

  15. Safety assessment for the S-1 Spheromak

    International Nuclear Information System (INIS)

    The S-1 machine is part of the Magnetic Fusion Program. The goal of the Magnetic Fusion Program is to develop and demonstrate the practical application of fusion. S-1 is an experimental device which will provide an essential link in the research effort aiming at the realization of fusion power

  16. Diagnosing the Magnetic Structure of the Sustained Spheromak Experiment

    Science.gov (United States)

    Cummings, Hillary; Romero Talamas, Carlos

    2005-10-01

    Unlike in traditional fusion devices, SSPX plasmas are confined by a magnetic field that is predominately generated by the plasma itself. The process by which plasma creates and changes the magnetic field is complicated and therefore makes it difficult to know its exact structure everywhere in the plasma at any point in time. This poster describes three different methods of studying the magnetic structure of the experiment; using edge probes in conjunction with Corsica- an equilibrium fitting code, imaging the plasma with a high-speed intensified CCD camera, and inserting an array of magnetic probes internal to the plasma. The research was performed under appointment to the Fusion Energy Sciences Fellowship Program and supported by US DOE. This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

  17. Magnetohydrodynamic equilibrium and stability of spheromak plasma in flux conserver

    International Nuclear Information System (INIS)

    The Green-function method is applied to the Grad-Shafranov equation for the plasma in a flux conserver with a rectangular cross section. The linear and the nonlinear MHD equilibrium configurations for various strengths of the toroidal magnetic field B are determined by this method. The average beta value and the safety factor are also evaluated. When B is increased from zero, decreases and vanishes at a force-free configuration. The safety factor takes a maximum value on the magnetic axis. A sufficient condition for stability to symmetric perturbations is derived by use of Edenstrasser's condition. This sufficient condition holds for the flux conserver of any shape. As an example, the region, in which this sufficient condition is fulfilled, is shown graphically for the flux conserver with rectangular cross section. (author)

  18. Linear MHD Stability Analysis of the SSPX Spheromak

    Science.gov (United States)

    Jayakumar, R.; Cohen, B. I.; Hooper, E. B.; Lodestro, L. L.; McLean, H. S.; Pearlstein, L. D.; Wood, R.; Turnbull, A. D.; Sovinec, C.

    2007-11-01

    Good correlation between the toroidal mode numbers of measured magnetic fluctuations in high temperature SSPX plasmas and presence of low-order rational surfaces in the reconstructed q profiles, suggests that the quality of magnetic surfaces in SSPX is sufficiently good for applying standard linear MHD stability analyses. Previously we have reported on benchmarking the code NIMROD against GATO, with good agreement in growth rates for ideal-MHD internal kinks and an external kinks with no current on open field lines (for equilibria imported from the code Corsica). Recent stability analyses also show that presence of low order rational surfaces causes internal modes to become unstable. We will report on the progress in applying these tools for assessing beta limits in SSPX, using NIMROD analyses including current on open field lines and for comparison with experiments.

  19. On the jets, kinks, and spheromaks formed by a planar magnetized coaxial gun

    OpenAIRE

    Hsu, S. C.; Bellan, P. M.

    2004-01-01

    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 dy...

  20. Performance projections for the Lithium Tokamak eXperiment (LTX)

    International Nuclear Information System (INIS)

    Use of a large-area liquid lithium limiter in the CDX-U tokamak produced the largest enhancements in ohmic tokamak confinement ever observed. Numerical simulations of CDX-U low recycling discharges have now been performed with the ASTRA code, utilizing a model with neoclassical ion transport and boundary conditions suitable to a nonrecycling wall, with fueling via edge gas puffing. This transport model has successfully reproduced the experimental values of the energy confinement (5-6 msec), loop voltage (2, during electron beam evaporation experiments on CDX-U. Similar results were obtained with solid surface overlaying a liquid lithium-filled target, although the solid surface was in this case composed of oxides of lithium. Here we reproduce the latter experiments, using a thin walled (0.125 mm) lithium-filled container, e-beam heated from the side. Results with various target geometries will be presented. (author)

  1. Performance Projections For The Lithium Tokamak Experiment (LTX)

    Energy Technology Data Exchange (ETDEWEB)

    Majeski, R.; Berzak, L.; Gray, T.; Kaita, R.; Kozub, T.; Levinton, F.; Lundberg, D. P.; Manickam, J.; Pereverzev, G. V.; Snieckus, K.; Soukhanovskii, V.; Spaleta, J.; Stotler, D.; Strickler, T.; Timberlake, J.; Yoo, J.; Zakharov, L.

    2009-06-17

    Use of a large-area liquid lithium limiter in the CDX-U tokamak produced the largest relative increase (an enhancement factor of 5-10) in Ohmic tokamak confinement ever observed. The confinement results from CDX-U do not agree with existing scaling laws, and cannot easily be projected to the new lithium tokamak experiment (LTX). Numerical simulations of CDX-U low recycling discharges have now been performed with the ASTRA-ESC code with a special reference transport model suitable for a diffusion-based confinement regime, incorporating boundary conditions for nonrecycling walls, with fuelling via edge gas puffing. This model has been successful at reproducing the experimental values of the energy confinement (4-6 ms), loop voltage (<0.5 V), and density for a typical CDX-U lithium discharge. The same transport model has also been used to project the performance of the LTX, in Ohmic operation, or with modest neutral beam injection (NBI). NBI in LTX, with a low recycling wall of liquid lithium, is predicted to result in core electron and ion temperatures of 1-2 keV, and energy confinement times in excess of 50 ms. Finally, the unique design features of LTX are summarized.

  2. Control of the Helicity Content of a Gun-Generated Spheromak by Incorporating a Conducting Shell into a Magnetized Coaxial Plasma Gun

    Science.gov (United States)

    Matsumoto, Tadafumi; Sekiguchi, Jun'ichi; Asai, Tomohiko

    In the formation of magnetized plasmoid by a magnetized coaxial plasma gun (MCPG), the magnetic helicity content of the generated plasmoid is one of the critical parameters. Typically, the bias coil to generate a poloidal flux is mounted either on the outer electrode or inside the inner electrode. However, most of the flux generated in the conventional method spreads even radially outside of the formation region. Thus, only a fraction of the total magnetic flux is actually exploited for helicity generation in the plasmoid. In the proposed system, the plasma gun incorporates a copper shell mounted on the outer electrode. By changing the rise time of the discharge bias coil current and the geometrical structure of the shell, the magnetic field structure and its time evolution can be controlled. The effect of the copper shell has been numerically simulated for the actual gun structure, and experimentally confirmed. This may increase the magnetic helicity content results, through increased poloidal magnetic field.

  3. Validation of single-fluid and two-fluid magnetohydrodynamic models of the helicity injected torus spheromak experiment with the NIMROD code

    International Nuclear Information System (INIS)

    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 di 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 (Itor/Iinj) and formation time τf demonstrated by HIT-SI with similar internal magnetic fields. rMHD underestimates (Itor/Iinj) and exhibits much a longer τf. 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

  4. Chemical response of lithiated graphite with deuterium irradiation

    OpenAIRE

    Taylor, C N; B. Heim; Allain, Jean Paul

    2011-01-01

    Lithium wall conditioning has been found to enhance plasma performance for graphite walled fusion devices such as TFTR, CDX-U, T-11M, TJ-II and NSTX. Among observed plasma enhancements is a reduction in edge density and reduced deuterium recycling. The mechanism by which lithiated graphite retains deuterium is largely unknown. Under controlled laboratory conditions, X-ray photoelectron spectroscopy (XPS) is used to observe the chemical changes that occur on ATJ graphite after lithium depositi...

  5. Deuterium ion-surface interactions of liquid-lithium thin films on micro-porous molybdenum substrates

    OpenAIRE

    Heim, Bryan; Taylor, C. N.; Zigon, D. M.; O., S; Allain, Jean Paul

    2011-01-01

    Lithium has been utilized to enhance the plasma performance for a variety of fusion devices such as TFTR, CDX-U and NSTX. Lithium in both the solid and liquid states has been studied extensively for its role in hydrogen retention and reduction in sputtering yield. A liquid lithium diverter (LLD) was recently installed in the National Spherical Torus Experiment (NSTX) fusion reactor to investigate lithium applications for plasma-facing surfaces (PFS). Representative samples of LLD material wer...

  6. Final Technical Report - ''Determining How Magnetic Helicity Injection Really Works''

    International Nuclear Information System (INIS)

    This research program involved direct observation of the complicated plasma dynamics underlying spheromak formation. Spheromaks are self-organizing magnetically dominated plasma configurations which potentially offer a simple, low-cost means for confining the plasma in a controlled thermonuclear fusion reactor. The spheromak source used in these studies was a coaxial co-planar magnetized plasma gun which was specifically designed to have the simplest relevant geometry. The simplicity of the geometry facilitated understanding of the basic physics and minimized confusion that would otherwise have resulted from complexities due to the experimental geometry. The coaxial plasma gun was mounted on one end of a large vacuum tank that had excellent optical access so the spheromak formation process could be tracked in detail using ultra-high speed cameras. The main accomplishments of this research program were (1) obtaining experimental data characterizing the detailed physics underlying spheromak formation and the development of new theoretical models motivated by these observations, (2) determining the relationship between spheromak physics and astrophysical jets, (3) developing a new high-speed camera diagnostic for the SSPX spheromak at the Lawrence Livermore National Lab, and (4) training graduate students and postdoctoral fellows

  7. Final Techical Report - "Determining How Magnetic Helicity Injection Really Works"

    Energy Technology Data Exchange (ETDEWEB)

    Paul M. Bellan

    2005-02-15

    This research program involved direct observation of the complicated plasma dynamics underlying spheromak formation. Spheromaks are self-organizing magnetically dominated plasma configurations which potentially offer a simple, low-cost means for confining the plasma in a controlled thermonuclear fusion reactor. The spheromak source used in these studies was a coaxial co-planar magnetized plasma gun which was specifically designed to have the simplest relevant geometry. The simplicity of the geometry facilitated understanding of the basic physics and minimized confusion that would otherwise have resulted from complexities due to the experimental geometry. The coaxial plasma gun was mounted on one end of a large vacuum tank that had excellent optical access so the spheromak formation process could be tracked in detail using ultra-high speed cameras. The main accomplishments of this research program were (1) obtaining experimental data characterizing the detailed physics underlying spheromak formation and the development of new theoretical models motivated by these observations, (2) determining the relationship between spheromak physics and astrophysical jets, (3) developing a new high-speed camera diagnostic for the SSPX spheromak at the Lawrence Livermore National Lab, and (4) training graduate students and postdoctoral fellows.

  8. Application of a magnetized coaxial plasma gun for formation of a high-beta field-reversed configuration

    International Nuclear Information System (INIS)

    We have tested a field-reversed configuration (FRC) formation with a spheromak injection for the first time. In this method, initial pre-ionized plasma is injected as a magnetized spheromak-like plasmoid into the discharge chamber prior to main field reversal. The FRC plasma with an electron density of 1.3 x 1021 m-3, a separatrix radius of 0.04 m and a plasma length of 0.8 m was produced successfully in initial background plasma of about 1.6 x 1019 m-3 by spheromak injection. The density is about one third of the conventional formed by the z-ionized method

  9. Surface Treatment of a Lithium Limiter for Spherical Torus Plasma Experiments

    International Nuclear Information System (INIS)

    The concept of a flowing lithium first wall for a fusion reactor may lead to a significant advance in reactor design, since it could virtually eliminate the concerns with power density and erosion, tritium retention, and cooling associated with solid walls. As part of investigations to determine the feasibility of this approach, plasma interaction questions in a toroidal plasma geometry are being addressed in the Current Drive eXperiment-Upgrade (CDX-U) spherical torus (ST). The first experiments involved a toroidally local lithium limiter (L3). Measurements of pumpout rates indicated that deuterium pumping was greater for the L3 compared to conventional boron carbide limiters. The difference in the pumpout rates between the two limiter types decreased with plasma exposure, but argon glow discharge cleaning was able to restore the pumping effectiveness of the L3. At no point, however, was the extremely low recycling regime reported in previous lithium experiments achieved. This may be due to the much larger lithium surfaces that were exposed to the plasma in the earlier work. The possibility will be studied in the next set of CDX-U experiments, which are to be conducted with a large area, fully toroidal lithium limiter

  10. Internal Magnetic Field Measurements for Equilibrium Reconstruction and Fluctuation Analysis in SSPX

    Science.gov (United States)

    Holcomb, Chris; Hill, David; Woodruff, Simon; Wood, Reg; McLean, Harry; Jarboe, Tom; Kim, Hyundae

    2002-11-01

    To achieve efficient spheromak field build-up, a better understanding of how current is transferred from injector to core is needed. This requires knowledge of the current profile and the spatial extent of magnetic fluctuations in both the injector and confinement regions of the plasma. We present internal probe measurements of magnetic field in the Sustained Spheromak Physics Experiment (SSPX). Three internal probes map the field profile in the coaxial helicity injector electrode gap, and one probe is used in the main body of the spheromak. These data are used to better constrain the 2D equilibrium as calculated by the code CORSICA. The resulting current profiles are presented, as well as the measured fluctuation profiles. Fluctuations in the injector and in the spheromak are compared to address field build-up models. 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.

  11. Two novel compact toroidal concepts with Stellarator features

    International Nuclear Information System (INIS)

    Two novel compact toroidal concepts are presented. One is the Stellarator-Spheromak (SSP) and another is the Extreme-Low-Aspect-Ratio Stellarator (ELARS). An SSP device represents a hybrid between a spherical stellarator (SS) and a spheromak. This configuration retains the main advantages of spheromaks ans has a potential for improving the spheromak concept regarding its main problems. The MHD equilibrium in an SSP with very high β of the confined plasma is demonstrated. Another concept, ELARS, represents an extreme limit of the SS approach, and considers devices with stellarator features and aspect ratios A ∼ 1. We have succeeded in finding ELARS configurations with extremely compact, modular, and simple design compatible with significant rotational transform, large plasma volume, and good particle transport characteristics

  12. Increasing the magnetic helicity content of a plasma by pulsing a magnetized source.

    Science.gov (United States)

    Woodruff, S; Stallard, B W; McLean, H S; Hooper, E B; Bulmer, R; Cohen, B I; Hill, D N; Holcomb, C T; Moller, J; Wood, R D

    2004-11-12

    By operating a magnetized coaxial gun in a pulsed mode it is possible to produce large voltage pulses of duration approximately 500 mus while reaching a few kV, giving a discrete input of helicity into a spheromak. In the sustained spheromak physics experiment (SSPX), it is observed that pulsing serves to nearly double the stored magnetic energy and double the temperature. We discuss these results by comparison with 3D MHD simulations of the same phenomenon. PMID:15600933

  13. Progress towards high-performance, steady-state spherical torus.

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.G (Korea Basic Science Institute, Taejon, Republic of Korea); Kugel, W. (Princeton University, NJ); Efthimion, P. C. (Princeton University, NJ); Kissick, M. W. (University of Wisconsin, WI); Bourdelle, C. (CEA Cadarache, France); Kim, J.H (Korea Advanced Institute of Science and Technology, Taejon, Republic of Korea); Gray, T. (Princeton University, NJ); Garstka, G. D. (University of Wisconsin, WI); Fonck, R. J. (University of Wisconsin, WI); Doerner, R. (University of California, San Diego, CA); Diem, S.J. (University of Wisconsin, WI); Pacella, D. (ENEA, Frascati, Italy); Nishino, N. (Hiroshima University, Hiroshima, Japan); Ferron, J. R. (General Atomics, San Diego, CA); Skinner, C. H. (Princeton University, NJ); Stutman, D. (Johns Hopkins University, Baltimore, MD); Soukhanovskii, V. (Princeton University, NJ); Choe, W. (Korea Advanced Institute of Science and Technology, Taejon, Republic of Korea); Chrzanowski, J. (Princeton University, NJ); Mau, T.K. (University of California, San Diego, CA); Bell, Michael G. (Princeton University, NJ); Raman, R. (University of Washington, Seattle, WA); Peng, Y-K. M. (Oak Ridge National Laboratory, Oak Ridge, TN); Ono, M. (Princeton University, NJ); Park, W. (Princeton University, NJ); Hoffman, D. (Princeton University, NJ); Maqueda, R. (Los Alamos National Laboratory, Los Alamos, NM); Kaye, S. M. (Princeton University, NJ); Kaita, R. (Princeton University, NJ); Jarboe, T.R. (University of Washington, Seattle, WA); Hill, K.W. (Princeton University, NJ); Heidbrink, W. (University of California, Irvine, CA); Spaleta, J. (Princeton University, NJ); Sontag, A.C (University of Wisconsin, WI); Seraydarian, R. (University of California, San Diego, CA); Schooff, R.J. (University of Wisconsin, WI); Sabbagh, S.A. (Columbia University, New York, NY); Menard, J. (Princeton University, NJ); Mazzucato, E. (Princeton University, NJ); Lee, K. (University of California, Davis, CA); LeBlanc, B. (Princeton University, NJ); Probert, P. H. (University of Wisconsin, WI); Blanchard, W. (Princeton University, NJ); Wampler, William R.; Swain, D. W. (Oak Ridge National Laboratory, Oak Ridge, TN); Ryan, P.M. (Oak Ridge National Laboratory, Oak Ridge, TN); Rosenberg, A. (Princeton University, NJ); Ramakrishnan, S. (Princeton University, NJ); Phillips, C.K. (Princeton University, NJ); Park, H.K. (Princeton University, NJ); Roquemore, A. L. (Princeton University, NJ); Paoletti, F. (Columbia University, New York, NY); Medley, S. S. (Princeton University, NJ); Fredrickson, E. D. (Princeton University, NJ); Kessel, C. E. (Princeton University, NJ); Stevenson, T. (Princeton University, NJ); Darrow, D. S. (Princeton University, NJ); Majeski, R. (Princeton University, NJ); Bitter, M. (Princeton University, NJ); Neumeyer, C. (Princeton University, NJ); Nelson, B.A. (University of Washington, Seattle, WA); Paul, S. F. (Princeton University, NJ); Manickam, J. (Princeton University, NJ); Ostrander, C. N. (University of Wisconsin, WI); Mueller, D. (Princeton University, NJ); Lewicki, B.T (University of Wisconsin, WI); Luckhardt, S. (University of California, San Diego, CA); Johnson, D.W. (Princeton University, NJ); Grisham, L.R. (Princeton University, NJ); Kubota, Shigeru (University of California, Los Angeles, CA); Gates, D.A. (Princeton University, NJ); Bush, C. (Oak Ridge National Laboratory, Oak Ridge, TN); Synakowski, E.J. (Princeton University, NJ); Schaffer, M. (General Atomics, San Diego, CA); Boedo, J. (University of California, San Diego, CA); Maingi, R. (Oak Ridge National Laboratory, Oak Ridge, TN); Redi, M. (Princeton University, NJ); Pinsker, R. (General Atomics, San Diego, CA); Bigelow, T. (Oak Ridge National Laboratory, Oak Ridge, TN); Bell, R. E. (Princeton University, NJ)

    2004-06-01

    Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta ({beta}), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values {beta}{sub T} of up to 35% with a near unity central {beta}{sub T} have been obtained. NSTX will be exploring advanced regimes where {beta}{sub T} up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction ({approx}60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fast wave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX

  14. Progress Towards High Performance, Steady-state Spherical Torus

    Energy Technology Data Exchange (ETDEWEB)

    M. Ono; M.G. Bell; R.E. Bell; T. Bigelow; M. Bitter; W. Blanchard; J. Boedo; C. Bourdelle; C. Bush; W. Choe; J. Chrzanowski; D.S. Darrow; S.J. Diem; R. Doerner; P.C. Efthimion; J.R. Ferron; R.J. Fonck; E.D. Fredrickson; G.D. Garstka; D.A. Gates; T. Gray; L.R. Grisham; W. Heidbrink; K.W. Hill; D. Hoffman; T.R. Jarboe; D.W. Johnson; R. Kaita; S.M. Kaye; C. Kessel; J.H. Kim; M.W. Kissick; S. Kubota; H.W. Kugel; B.P. LeBlanc; K. Lee; S.G. Lee; B.T. Lewicki; S. Luckhardt; R. Maingi; R. Majeski; J. Manickam; R. Maqueda; T.K. Mau; E. Mazzucato; S.S. Medley; J. Menard; D. Mueller; B.A. Nelson; C. Neumeyer; N. Nishino; C.N. Ostrander; D. Pacella; F. Paoletti; H.K. Park; W. Park; S.F. Paul; Y.-K. M. Peng; C.K. Phillips; R. Pinsker; P.H. Probert; S. Ramakrishnan; R. Raman; M. Redi; A.L. Roquemore; A. Rosenberg; P.M. Ryan; S.A. Sabbagh; M. Schaffer; R.J. Schooff; R. Seraydarian; C.H. Skinner; A.C. Sontag; V. Soukhanovskii; J. Spaleta; T. Stevenson; D. Stutman; D.W. Swain; E. Synakowski; Y. Takase; X. Tang; G. Taylor; J. Timberlake; K.L. Tritz; E.A. Unterberg; A. Von Halle; J. Wilgen; M. Williams; J.R. Wilson; X. Xu; S.J. Zweben; R. Akers; R.E. Barry; P. Beiersdorfer; J.M. Bialek; B. Blagojevic; P.T. Bonoli; M.D. Carter; W. Davis; B. Deng; L. Dudek; J. Egedal; R. Ellis; M. Finkenthal; J. Foley; E. Fredd; A. Glasser; T. Gibney; M. Gilmore; R.J. Goldston; R.E. Hatcher; R.J. Hawryluk; W. Houlberg; R. Harvey; S.C. Jardin; J.C. Hosea; H. Ji; M. Kalish; J. Lowrance; L.L. Lao; F.M. Levinton; N.C. Luhmann; R. Marsala; D. Mastravito; M.M. Menon; O. Mitarai; M. Nagata; G. Oliaro; R. Parsells; T. Peebles; B. Peneflor; D. Piglowski; G.D. Porter; A.K. Ram; M. Rensink; G. Rewoldt; P. Roney; K. Shaing; S. Shiraiwa; P. Sichta; D. Stotler; B.C. Stratton; R. Vero; W.R. Wampler; G.A. Wurden

    2003-10-02

    Research on the Spherical Torus (or Spherical Tokamak) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect-ratio devices, such as the conventional tokamak. The Spherical Tours (ST) experiments are being conducted in various U.S. research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium-size ST research facilities: Pegasus at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the U.S., an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high-performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta (B), noninductive sustainment, ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values bT of up to 35% with the near unity central betaT have been obtained. NSTX will be exploring advanced regimes where bT up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for noninductive sustainment in NSTX is the high beta-poloidal regime, where discharges with a high noninductive fraction ({approx}60% bootstrap current + neutral-beam-injected current drive) were sustained over the resistive skin time. Research on radio-frequency-based heating and current drive utilizing HHFW (High Harmonic Fast Wave) and EBW (Electron Bernstein Wave) is also pursued on NSTX, Pegasus, and CDX-U. For noninductive start-up, the Coaxial Helicity Injection (CHI), developed in HIT/HIT-II, has been

  15. Progress towards high-performance, steady-state spherical torus

    Energy Technology Data Exchange (ETDEWEB)

    Ono, M.; Bell, M. G.; Bell, R. E.; Bigelow, T.; Bitter, M.; Blanchard, W.; Boedo, J.; Bourdelle, C.; Bush, C.; Choe, W.; Chrzanowski, J.; Darrow, D. S.; Diem, S. J.; Doerner, R.; Efthimion, P. C.; Ferron, J. R.; Fonck, R. J.; Fredrickson, E. D.; Garstka, G. D.; Gates, D A; Gray, T.; Grisham, L. R.; Heidbrink, W.; Hill, K. W.; Hoffman, D.; Jarboe, T. R.; Johnson, D. W.; Kaita, R.; Kaye, S. M.; Kessel, C.; Kim, J. H.; Kissick, M. W.; Kubota, S.; Kugel, H. W.; LeBlanc, B. P.; Lee, K.; Lee, S. G.; Lewicki, B. T.; Luckhardt, S.; Maingi, R.; Majeski, R.; Manickam, J.; Maqueda, R.; Mau, T. K.; Mazzucato, E.; Medley, S. S.; Menard, J.; Mueller, D.; Nelson, B. A.; Neumeyer, C.; Nishino, N.; Ostrander, C. N.; Pacella, D.; Paoletti, F.; Park, H. K.; Park, W.; Paul, S. F.; Peng, Y-K M.; Phillips, C. K.; Pinsker, R.; Probert, P. H.; Ramakrishnan, S.; Raman, R.; Redi, M.; Roquemore, A. L.; Rosenberg, A.; Ryan, P. M.; Sabbagh, S. A.; Schaffer, M.; Schooff, R. J.; Seraydarian, R.; Skinner, C. H.; Sontag, A. C.; Soukhanovskii, V.; Spaleta, J.; Stevenson, T.; Stutman, D.; Swain, D. W.; Synakowski, E.; Takase, Y.; Tang, X.; Taylor, G.; Timberlake, J.; Tritz, K. L.; Unterberg, E. A.; Halle, A. Von.; Wilgen, J.; Williams, M.; Wilson, J. R.; Xu, X.; Zweben, S. J.; Akers, R.; Barry, R. E.; Beiersdorfer, P.; Bialek, J. M.; Blagojevic, B.; Bonoli, P. T.; Carter, M. D.; Davis, W.; Deng, B.; Dudek, L.; Egedal, J.; Ellis, R.; Finkenthal, M.; Foley, J.; Fredd, E.; Glasser, A.; Gibney, T.; Gilmore, M.; Goldston, R. J.; Hatcher, R. E.; Hawryluk, R. J.; Houlberg, W.; Harvey, R.; Jardin, S. C.; Hosea, J. C.; Ji, H.; Kalish, M.; Lowrance, J.; Lao, L. L.; Levinton, F. M.; Luhmann, N. C.; Marsala, R.; Mastravito, D.; Menon, M. M.; Mitarai, O.; Nagata, M.; Oliaro, G.; Parsells, R.; Peebles, T.; Peneflor, B.; Piglowski, D.; Porter, G. D.; Ram, A. K.; Rensink, M.; Rewoldt, G.; Robinson, J.; Roney, P.; Shaing, K.; Shiraiwa, S.; Sichta, P.; Stotler, D.; Stratton, B. C.; Vero, R.; Wampler, W. R.; Wurden, G. A.

    2003-12-01

    Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta (β), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values βT of up to 35% with a near unity central βT have been obtained. NSTX will be exploring advanced regimes where βT up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction (~ 60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fast wave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX to

  16. Progress Towards High-Performance, Steady-State Spherical Torus

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence Livermore National Laboratory

    2004-01-04

    Research on the spherical torus (or spherical tokamak) (ST) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect ratio devices, such as the conventional tokamak. The ST experiments are being conducted in various US research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium sized ST research facilities: PEGASUS at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta ({beta}), non-inductive sustainment, Ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values {beta}{sub T} of up to 35% with a near unity central {beta}{sub T} have been obtained. NSTX will be exploring advanced regimes where {beta}{sub T} up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for non-inductive sustainment in NSTX is the high beta poloidal regime, where discharges with a high non-inductive fraction ({approx}60% bootstrap current+NBI current drive) were sustained over the resistive skin time. Research on radio-frequency (RF) based heating and current drive utilizing high harmonic fastwave and electron Bernstein wave is also pursued on NSTX, PEGASUS, and CDX-U. For non-inductive start-up, the coaxial helicity injection, developed in HIT/HIT-II, has been adopted on NSTX

  17. Progress Towards High Performance, Steady-state Spherical Torus

    International Nuclear Information System (INIS)

    Research on the Spherical Torus (or Spherical Tokamak) is being pursued to explore the scientific benefits of modifying the field line structure from that in more moderate aspect-ratio devices, such as the conventional tokamak. The Spherical Tours (ST) experiments are being conducted in various U.S. research facilities including the MA-class National Spherical Torus Experiment (NSTX) at Princeton, and three medium-size ST research facilities: Pegasus at University of Wisconsin, HIT-II at University of Washington, and CDX-U at Princeton. In the context of the fusion energy development path being formulated in the U.S., an ST-based Component Test Facility (CTF) and, ultimately a Demo device, are being discussed. For these, it is essential to develop high-performance, steady-state operational scenarios. The relevant scientific issues are energy confinement, MHD stability at high beta (B), noninductive sustainment, ohmic-solenoid-free start-up, and power and particle handling. In the confinement area, the NSTX experiments have shown that the confinement can be up to 50% better than the ITER-98-pby2 H-mode scaling, consistent with the requirements for an ST-based CTF and Demo. In NSTX, CTF-relevant average toroidal beta values bT of up to 35% with the near unity central betaT have been obtained. NSTX will be exploring advanced regimes where bT up to 40% can be sustained through active stabilization of resistive wall modes. To date, the most successful technique for noninductive sustainment in NSTX is the high beta-poloidal regime, where discharges with a high noninductive fraction (∼60% bootstrap current + neutral-beam-injected current drive) were sustained over the resistive skin time. Research on radio-frequency-based heating and current drive utilizing HHFW (High Harmonic Fast Wave) and EBW (Electron Bernstein Wave) is also pursued on NSTX, Pegasus, and CDX-U. For noninductive start-up, the Coaxial Helicity Injection (CHI), developed in HIT/HIT-II, has been adopted

  18. Plasma transport control and self-sustaining fusion reactor

    International Nuclear Information System (INIS)

    The possibility of a high performance/low cost fusion reactor concept which can simultaneously satisfy (1) high beta, (2) high bootstrap fraction (self-sustaining), and (3) high confinement is discussed. In CDX-U, a tokamak configuration was created and sustained solely by internally generated bootstrap currents, in which a seed current is created through a non-classical current diffusion process. Recent theoretical studies of MHD stability limits in spherical torus .g., the National Spherical Torus Experiment (NSTX) reduced a promising regime with stable beta of 45% and bootstrap current fraction of ≥99%. Since the bootstrap current is generated by the pressure gradient, to satisfy the needed current profile for MHD stable high beta regimes, it is essential to develop a means to control the pressure profile. It is suggested that the most efficient approach for pressure profile control is through a creation of transport barriers (localized regions of low plasma transport) in the plasma. As a tool for creating the core transport barrier, poloidal-sheared-flow generation by ion Bernstein waves (IBW) near the wave absorption region appears to be promising. In PBX-M, application of IBW power produced a high-quality internal transport barrier where the ion energy and particle transport became neoclassical in the barrier region. The observation is consistent with the IBW-induced-poloidal-sheared-flow model. An experiment is planned on TFTR to demonstrate this concept with D-T reactor-grade plasmas. For edge transport control, a method based on electron ripple injection (ERI), driven by electron cyclotron heating (ECH), is being developed on CDX-U. It is estimated that both the IBW and ERI methods can create a transport barrier in reactor-grade plasmas (e.g., ITER) with a relatively small amount of power (∼10 MW much-lt Pfusion)

  19. Reduction of plasma density in the Helicity Injected Torus with Steady Inductance experiment by using a helicon pre-ionization source

    International Nuclear Information System (INIS)

    A helicon based pre-ionization source has been developed and installed on the Helicity Injected Torus with Steady Inductance (HIT-SI) spheromak. The source initiates plasma breakdown by injecting impurity-free, unmagnetized plasma into the HIT-SI confinement volume. Typical helium spheromaks have electron density reduced from (2–3) × 1019 m−3 to 1 × 1019 m−3. Deuterium spheromak formation is possible with density as low as 2 × 1018 m−3. The source also enables HIT-SI to be operated with only one helicity injector at injector frequencies above 14.5 kHz. A theory explaining the physical mechanism driving the reduction of breakdown density is presented

  20. Ion kinetic effect on bifurcated relaxation to a field-reversed configuration in TS-4 CT experiment

    International Nuclear Information System (INIS)

    Ion kinetic effect on the bifurcated relaxation of merging spheromaks to a field-reversed configuration (FRC) was studied experimentally using varied S* which is the ratio of the minor radius to the ion skin depth from 1 to 7. The two merging spheromaks were observed to relax to an FRC or a new spheromak depending on whether the initial poloidal eigen value was smaller or larger than a threshold value. The threshold initial poloidal eigen value for the relaxation to an FRC increased with decreasing S* value. Decrease in S* promoted the relaxation to an FRC, annihilating the magnetic helicity, in sharp contrast with the conventional Taylor relaxation. Suppression of the low-n mode by the rotation shear of the toroidal modes is the most probable reason why the low-S* condition promotes the relaxation into an FRC. (author)

  1. Proceedings of the third symposium on the physics and technology of compact toroids in the magnetic fusion energy program

    International Nuclear Information System (INIS)

    This document contains papers contributed by the participants of the Third Symposium on Physics and Technology of Compact Toroids in the Magnetic Fusion Energy Program. Subjects include reactor aspects of compact toroids, energetic particle rings, spheromak configurations (a mixture of toroidal and poloidal fields), and field-reversed configurations

  2. Parallel-beam correlation technique for measuring density fluctuations in plasmas with strong magnetic shear

    International Nuclear Information System (INIS)

    A laser diagnostic scheme is described which facilitates localization of density fluctuations along the line of sight. The method exploits both the generally observed anisotropy of density fluctuations in low-beta plasmas, as well as the twisting of the magnetic field which occurs across the minor diameter of reversed-field pinches, spheromaks, etc. Both interferometric and schlieren variations are discussed

  3. Theoretical plasma physics: Progress report, January 1, 1987-December 31, 1987

    International Nuclear Information System (INIS)

    During the past year, research has been carried out on current drive in tokamaks and in spheromaks, fast integration techniques for magnetic field lines, alpha particle diagnostics that use CO2 laser scattering, and plasma turbulence. This paper discusses this research

  4. Princeton Plasma Physics Laboratory annual report, October 1, 1983-September 30, 1984

    International Nuclear Information System (INIS)

    Progress made during this reporting period is reported for each of the following areas: (1) principal parameters achieved in experimental devices, (2) TFTR, (3) PLT, (4) PBX, (5) S-1 Spheromak, (6) advanced concepts Torus-1, (7) x-ray laser studies, (8) theory, (9) tokamak modeling, (10) reactor studies, (11) spin-polarized fusion program, (12) tokamak fusion core experiment, and (13) engineering

  5. Princeton Plasma Physics Laboratory annual report, October 1, 1984-September 30, 1985

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, C.A. (ed.)

    1985-01-01

    Summaries of research progress during this period are given for the following areas: (1) TFTR, (2) PLT, (3) PBX, (4) S-1 Spheromak, (5) Advanced Concepts Torus-1, (6) x-ray laser studies, (7) theory, (8) tokamak modeling, (9) spin-polarization, and (10) ignition studies. (MOW)

  6. Annual report, October 1, 1979-September 30, 1980

    Energy Technology Data Exchange (ETDEWEB)

    1981-05-01

    This annual report covers research progress on each of the following areas: (1) PLT device, (2) PDX, (3) spheromak, (4) smaller devices, (5) theory, (6) TFTR, (7) applied physics, (8) TFTR blanket module experiments, (9) advanced toroidal facility, (10) advanced projects design and analysis, (11) engineering, and (12) fabrication, operations and maintenance. (MOW)

  7. Annual report, October 1, 1979-September 30, 1980

    International Nuclear Information System (INIS)

    This annual report covers research progress on each of the following areas: (1) PLT device, (2) PDX, (3) spheromak, (4) smaller devices, (5) theory, (6) TFTR, (7) applied physics, (8) TFTR blanket module experiments, (9) advanced toroidal facility, (10) advanced projects design and analysis, (11) engineering, and (12) fabrication, operations and maintenance

  8. Princeton Plasma Physics Laboratory annual report, October 1, 1984-September 30, 1985

    International Nuclear Information System (INIS)

    Summaries of research progress during this period are given for the following areas: (1) TFTR, (2) PLT, (3) PBX, (4) S-1 Spheromak, (5) Advanced Concepts Torus-1, (6) x-ray laser studies, (7) theory, (8) tokamak modeling, (9) spin-polarization, and (10) ignition studies

  9. Theoretical studies of non inductive current drive in compact toroids

    NARCIS (Netherlands)

    Farengo, R; Lifschitz, AF; Caputi, KI; Arista, NR; Clemente, RA

    2002-01-01

    Three non inductive current drive methods that can be applied to compact toroids axe studied. The use of neutral beams to drive current in field reversed configurations and spheromaks is studied using a Monte Carlo code that includes a complete ionization package and follows the exact particle orbit

  10. Confinement and heating of high beta plasmas with emphasis on compact toroids: Final progress report period ending February 15, 1987

    International Nuclear Information System (INIS)

    This report describes work performed at the University of Washington Aerospace and Energetics Research Program involving the ''compact toroid'' approach to magenetic confinement of plasmas. The five experiments comprising the effort are: The coaxial slow source experiment; the CSS project; the variable length experiment; the merging spheromak experiment; and the variable angle conical theta pinch experiment

  11. Confinement and heating of high-beta plasmas with emphasis on compact toroids. Task I. Annual report for period ending May 31, 1982

    International Nuclear Information System (INIS)

    Results are given for work during this period on each of the following areas: (1) spheromak production using conical theta pinch guns; (2) detection of CT fluctuation spectra via CO2 forward scattering; (3) high density field reversal experiment; (4) plasma compression experiment; (5) material end plugging experiment; and (6) design of computerized data acquisition systems

  12. Princeton Plasma Physics Laboratory: Annual report, October 1, 1986--September 30, 1987

    International Nuclear Information System (INIS)

    This report contains papers on the following topics: Principle Parameters Achieved in Experimental Devices (FY87); Tokamak Fusion Test Reactor; Princeton Beta Experiment-Modification; S-1 Spheromak; Current-Drive Experiment; X-Ray Laser Studies; Theoretical Division; Tokamak Modeling; Compact Ignition Tokamak; Engineering Department; Project Planning and Safety Office; Quality Assurance and Reliability; Administrative Operations; and PPPL Patent Invention Disclosures (FY87)

  13. International Atomic Energy Agency Technical Committee Meeting, Innovative approaches to fusion energy, Pleasanton, CA, October 20-23, 1997

    International Nuclear Information System (INIS)

    The Purpose of this Meeting is to provide a forum for discussion of approaches to fusion other than conventional tokamaks and stellarators, such as: (1) quasi-steady-state systems (mirrors, RFP's, spheromaks, FRC'S, spherical tori,...); (2) short-pulsed systems (liners, Z-pinch variants, plasma foci, novel ICF, ...); and (3) fusion technology innovations

  14. Princeton Plasma Physics Laboratory: Annual report, October 1, 1986--September 30, 1987

    Energy Technology Data Exchange (ETDEWEB)

    1987-01-01

    This report contains papers on the following topics: Principle Parameters Achieved in Experimental Devices (FY87); Tokamak Fusion Test Reactor; Princeton Beta Experiment-Modification; S-1 Spheromak; Current-Drive Experiment; X-Ray Laser Studies; Theoretical Division; Tokamak Modeling; Compact Ignition Tokamak; Engineering Department; Project Planning and Safety Office; Quality Assurance and Reliability; Administrative Operations; and PPPL Patent Invention Disclosures (FY87).

  15. Proceedings of the third symposium on the physics and technology of compact toroids in the magnetic fusion energy program

    Energy Technology Data Exchange (ETDEWEB)

    Siemon, R.E. (comp.)

    1981-03-01

    This document contains papers contributed by the participants of the Third Symposium on Physics and Technology of Compact Toroids in the Magnetic Fusion Energy Program. Subjects include reactor aspects of compact toroids, energetic particle rings, spheromak configurations (a mixture of toroidal and poloidal fields), and field-reversed configurations (FRC's that contain purely poloidal field).

  16. Final Technical Report for NSF/DOE partnership grant ER54905; 2006-2009

    International Nuclear Information System (INIS)

    The nonlinear physics of electron magnetohydrodynamics (EMHD) in plasmas. Time-varying wave magnetic field exceeding the background magnetic field produces highly nonlinear whistler mode since the wave dispersion depends on the total magnetic field. There exists no theory for such whistler modes. The present experimental work is the first one to explore this regime of nonlinear whistlers. A field-reversed configuration has been found which has the same vortex topology as an MHD spheromak, termed a whistler spheromak. Whistler mirrors have compressed and twisted field lines propagating in the whistler mode. Their helicity properties have been studied. Whistler spheromaks and mirrors have different propagation and damping characteristics. Wave collisions have been studied. Head-on collisions of two whistler spheromaks form a stationary field-reversed configuration (FRC) without helicity. When whistler spheromaks are excited the toroidal current flows mainly in the toroidal null line. It is only carried by electrons since ion currents and displacement currents are negligible. A change in the poloidal (axial) magnetic field induces a toroidal electric field which drives the current. Magnetic energy is dissipated and converted into electron kinetic energy. This process is called magnetic reconnection in 2D geometries, which are simplifications for theoretical convenience but rarely occur in nature. A crucial aspect of reconnection is its rate, determined by the electron collisionality. Regular Coulomb collisions can rarely account for the observed reconnection rates. In the present experiments we have also observed fast reconnection and explained it by electron transit time damping in the finite-size null layer. Electrons move faster than a whistler spheromak, hence transit through the toroidal null line where they are freely accelerated. The transit time is essentially the collision time but no particle collisions are required. Strong electron heating and visible light

  17. Transient transport experiments in the current-drive experiment upgrade spherical torus

    International Nuclear Information System (INIS)

    Electron transport has been measured in the Current-Drive Experiment Upgrade (CDX-U) (T. Jones, Ph.D. thesis, Princeton University, 1995) using two separate perturbative techniques. Sawteeth at the q=1 radius (r/a∼0.15) induced outward-propagating heat pulses, providing time-of-flight information leading to a determination of χe as a function of radius. Gas modulation at the plasma edge introduced inward-propagating cold pulses, providing a complementary time-of-flight based χe profile measurement. This work represents the first localized measurement of χe in a spherical torus. Core (r/ae values from the sawtooth study are 1-2 m2/s, and from the gas modulation study are 1-6 m2/s, increasing by an order of magnitude or more outside of the core region. Furthermore, the χe profile exhibits a sharp transition near r/a=1/3. Spectral and profile analyses of the soft x-rays, scanning interferometer, and edge probe data show no evidence of a significant magnetic island causing the high χe region. Comparisons are performed to several theoretical models, with measured χe≅5-10x neoclassical estimates in the core

  18. High-harmonic ion cyclotron heating and current drive in ultra-small aspect ratio tokamaks

    International Nuclear Information System (INIS)

    Ultra-small aspect ratio tokamaks present a totally new plasma environment for heating and current drive experiments and involve a number of physics issues that have not previously been explored. These devices operate at low magnetic field and relatively high density so that the effective dielectric constant of the plasma to high harmonic fast waves (HHFW), is quite high, and perpendicular wavelength of fast waves is very short. λ ∼ 2.0 cm compared with λ - 10-20 cm. This makes possible strong electron absorption at high harmonics of the ion cyclotron frequency, Ωi, and at fairly high phase velocity in relation to electron thermal velocity. If the antenna system can control the parallel wave spectrum, this offers the promise of high efficiency off-axis current drive and the possibility for current drive radial profile control. Antenna phasing is ineffective for profile control in conventional tokamaks because of central absorption. There are also challenges for antenna design in this regime because of the high dielectric constant and the large angle of the magnetic field with respect to the equatorial plane (∼45 degrees), which varies greatly during current ramp. Preliminary experiments in this HHFW regime are being carried out in CDX-U

  19. Deuterium ion-surface interactions of liquid-lithium thin films on micro-porous molybdenum substrates

    International Nuclear Information System (INIS)

    Lithium has been utilized to enhance the plasma performance for a variety of fusion devices such as TFTR, CDX-U and NSTX. Lithium in both the solid and liquid states has been studied extensively for its role in hydrogen retention and reduction in sputtering yield. A liquid lithium diverter (LLD) was recently installed in the National Spherical Torus Experiment (NSTX) fusion reactor to investigate lithium applications for plasma-facing surfaces (PFS). Representative samples of LLD material were exposed to lithium depositing and simulated plasma conditions offline at Purdue University to study changes in surface chemical functionalities of Mo, O, Li and D. X-ray photoelectron spectroscopy (XPS) conducted on samples revealed two distinct peak functionalities of lithiated porous molybdenum exposed to deuterium irradiation. The two-peak chemical functionality noticed in porous molybdenum deviates from similar studies conducted on lithiated graphite; such deviation in data is correlated to the complex surface morphology of the porous surface and the correct 'wetting' of lithium on the sample surface. The proper lithium 'wetting' on the sample surface is essential for maximum deuterium retention and corresponding LLD pumping of deuterium.

  20. Study of electron ripple injection concept for radial electric field control in a tokamak

    International Nuclear Information System (INIS)

    A theoretical study has been performed to examine the possibility of generating a radial electric field at the periphery of a tokamak plasma. A localized magnetic well can be produced by a ripple coil system and electron cyclotron resonance heating (ECRH) is used to increase the ripple trapped fraction of the electrons. The magnetic field ripple is arranged in such a way that the ripple trapped electrons then drift vertically, due to nabla B, towards the plasma centre. A semi-analytic kinetic analysis has been performed to estimate the ECRH-induced temperature anisotropy of the electrons, which is directly related to the ripple trapping fraction; and a numerical Monte Carlo guiding centre simulation has been performed to study the generation of the radial electric field by the nabla B injection of the ripple trapped electrons and the E x B detrapping of them. The present study suggests that about 23 kW of ECRH power in the CDX-U device and 10 MW in ITER may be able to create a large enough radial electric field for the H mode transition. (author). 25 refs, 22 figs

  1. MHD simulations for investigating interaction processes between a CME and ambient solar wind

    Science.gov (United States)

    An, Junmo; Magara, Tetsuya

    2016-05-01

    The interaction between coronal mass ejections (CMEs) and ambient solar winds is one of the important issues of space weather because it affects the trajectory of a flying CME, which determines whether the CME hits the Earth and produces geomagnetic disturbances or not. In this study, two-step 3D magnetohydrodynamic (MHD) simulations including a spheromak-type CME and an ambient solar wind are performed to investigate their interaction processes such as deflection and rotation of a CME. We perform the 1st-step MHD simulation using averaged surface magnetic field data to construct a steady state with an ambient solar wind. A spheromak-type CME is then injected through the solar surface, and subsequent evolution is reproduced by performing the 2nd-step MHD simulation. We discuss key parameters that characterize interaction processes between a CME and ambient solar wind.

  2. Review of recent experiments on magnetic reconnection in laboratory plasmas

    International Nuclear Information System (INIS)

    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 107. 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

  3. Demonstration of steady inductive helicity injection

    International Nuclear Information System (INIS)

    Initial results demonstrating the concept of constant inductive helicity injection are presented. Constant helicity injection is achieved using two oscillating inductive helicity injectors, with the goal of producing a bow tie spheromak. Each injector is a 1800 segment of a reverse field pinch and they are driven 900 out of phase. Approximately 5 MW of power is injected during the 6 ms pulse, and the input power has been maintained at a fairly constant value by directly fuelling the injectors with neutral gas. Motivation for the experiment is given, including beta-limit calculations for the bow tie spheromak. Fuelling the injectors with neutral gas during the discharge is shown to produce injector parameters that are more constant in time. A series of discharges with increasing power input shows a promising increase in toroidal current. Unique construction techniques of the experiment are also described

  4. Compact torus experiments and theory

    International Nuclear Information System (INIS)

    Two types of compact toroids have been studied: spheromaks and field-reversed configurations (FRC). Spheromaks, which contain both toroidal and poloidal fields, have been formed with a magnetized coaxial injector and trapped in both prolate and oblate flux conservers. As expected from theory, the prolate configuration always tilts, but the oblate configuration can be made stable even in the presence of a guide field. Observations include 150μs lifetimes, approx. 1014 cm-3, and a decrease of field fluctuations by a factor of 100 at the time of complete reconnection. Theoretical studies of the FRC (no toroidal field) have been compared with the results of two field-reversed theta-pinches, FRX-A and FRX-B

  5. Tilt stability of rotating current rings with passive conductors

    International Nuclear Information System (INIS)

    We study the combined effects of rotation and resistive passive conductors on the stability of a rigid current in an external magnetic field. We present numerical and approximate analytical solutions to the equations of motion, which show that the ring is always tilt unstable on the resistive decay timescale of the conductors, although rotation and eddy currents may stabilize it over short times. Possible applications of our model include spheromaks which rotate or which are encircled by energetic particle rings

  6. Spherical Tori. Report on the joint meeting of the IAEA technical committee meeting on spherical tori and the fourth international workshop on spherical tori held at the University of Tokyo, Tokyo, Japan 26-28 October 1998

    International Nuclear Information System (INIS)

    Spherical tori (ST), represented mainly by the spherical tokamak, are of growing importance for fusion research, and several new devices are planned or under construction around the world. The purpose of the Joint Meeting was to provide a forum for discussion of approaches to fusion energy based on ST. Other toroidal configurations, such as low aspect ratio helical systems and spheromaks, were also included in the scope of this meeting

  7. Experimental Results from Initial Operation of Plasma Injector 1

    Science.gov (United States)

    Howard, Stephen

    2010-11-01

    General Fusion has begun operation of its first full-scale plasma injector, designed to accelerate high density spheromak plasmas into the compression chamber of a proposed MTF reactor. The geometry of Plasma Injector 1 (PI-1) is that of a two stage coaxial Marshal gun with a conical converging accelerator electrodes, similar in shape to the MARAUDER device, while pulsed power is applied in the same configuration as the RACE device. PI-1 is 5 meters in length and 1.9 m in diameter at the expansion region where a high aspect ratio (4.4) spheromak is formed with a minimum lambda of 9 m-1. The acceleration/compression stage is 4 m long and tapers to a final outer diameter of 40 cm. PI-1 is now operating at 1 MJ of total capacitor power, which will be doubled again before it reaches its design parameters. Diagnostics include 3 interferometer chords, 21 magnetic probes (2 axis poloidal/toroidal), 13 fast photodiode chords, as well as one Thomson scattering chord, a visible light survey spectrometer, and a Langmuir triple probe. Electrode voltage and current are also monitored. So far spheromaks of poloidal flux exceeding 100 mWb have been formed in the expansion region, and spheromaks of 40-50 mWb have been formed and accelerated out the end of the accelerator into a flux conserving target chamber. Expansion region densities are typically ˜5 x10^14cm-3, while conditions in the target chamber have reached ne˜10^16cm-3, and lifetimes of 300 μs.

  8. Princeton Plasma Physics Laboratory:

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, C.A. (ed.)

    1986-01-01

    This paper discusses progress on experiments at the Princeton Plasma Physics Laboratory. The projects and areas discussed are: Principal Parameters Achieved in Experimental Devices, Tokamak Fusion Test Reactor, Princeton Large Torus, Princeton Beta Experiment, S-1 Spheromak, Current-Drive Experiment, X-ray Laser Studies, Theoretical Division, Tokamak Modeling, Spacecraft Glow Experiment, Compact Ignition Tokamak, Engineering Department, Project Planning and Safety Office, Quality Assurance and Reliability, and Administrative Operations.

  9. Princeton Plasma Physics Laboratory annual report, October 1, 1983-September 30, 1984

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, C.A. (ed.)

    1984-01-01

    Progress made during this reporting period is reported for each of the following areas: (1) principal parameters achieved in experimental devices, (2) TFTR, (3) PLT, (4) PBX, (5) S-1 Spheromak, (6) advanced concepts Torus-1, (7) x-ray laser studies, (8) theory, (9) tokamak modeling, (10) reactor studies, (11) spin-polarized fusion program, (12) tokamak fusion core experiment, and (13) engineering. (MOW)

  10. Annual report covering the period October 1, 1980 to September 30, 1981

    International Nuclear Information System (INIS)

    Research during this period is described for each of the following areas: (1) Princeton Large Torus, (2) Poloidal Divertor Experiment, (3) Spheromak, (4) smaller devices, (5) x-ray laser studies, (6) theory, (7) TFTR, (8) applied physics, (9) design studies for new devices, (10) advanced projects design and analysis, (11) engineering, (12) fabrication, operations, and maintenance (13) Projects Office, (14) Computer Division, (15) Administration, and (16) Graduate Education

  11. Princeton Plasma Physics Laboratory:

    International Nuclear Information System (INIS)

    This paper discusses progress on experiments at the Princeton Plasma Physics Laboratory. The projects and areas discussed are: Principal Parameters Achieved in Experimental Devices, Tokamak Fusion Test Reactor, Princeton Large Torus, Princeton Beta Experiment, S-1 Spheromak, Current-Drive Experiment, X-ray Laser Studies, Theoretical Division, Tokamak Modeling, Spacecraft Glow Experiment, Compact Ignition Tokamak, Engineering Department, Project Planning and Safety Office, Quality Assurance and Reliability, and Administrative Operations

  12. Tilt stability of rotating current rings with passive conductors

    Energy Technology Data Exchange (ETDEWEB)

    Zweibel, E.G.; Pomphrey, N.

    1984-12-01

    We study the combined effects of rotation and resistive passive conductors on the stability of a rigid current in an external magnetic field. We present numerical and approximate analytical solutions to the equations of motion, which show that the ring is always tilt unstable on the resistive decay timescale of the conductors, although rotation and eddy currents may stabilize it over short times. Possible applications of our model include spheromaks which rotate or which are encircled by energetic particle rings.

  13. EMAPS: An Efficient Multiscale Approach to Plasma Systems with Non-MHD Scale Effects

    Energy Technology Data Exchange (ETDEWEB)

    Omelchenko, Yuri A [SciberQuest, Inc; Karimabadi, Homa [SciberQuest, Inc

    2014-10-14

    Using Discrete-Event Simulation (DES) as a novel paradigm for time integration of large-scale physics-driven systems, we have achieved significant breakthroughs in simulations of multi-dimensional magnetized plasmas where ion kinetic and finite Larmor radius (FLR) and Hall effects play a crucial role. For these purposes we apply a unique asynchronous simulation tool: a parallel, electromagnetic Particle-in-Cell (PIC) code, HYPERS (Hybrid Particle Event-Resolved Simulator), which treats plasma electrons as a charge neutralizing fluid and solves a self-consistent set of non-radiative Maxwell, electron fluid equations and ion particle equations on a structured computational grid. HYPERS enables adaptive local time steps for particles, fluid elements and electromagnetic fields. This ensures robustness (stability) and efficiency (speed) of highly dynamic and nonlinear simulations of compact plasma systems such spheromaks, FRCs, ion beams and edge plasmas. HYPERS is a unique asynchronous code that has been designed to serve as a test bed for developing multi-physics applications not only for laboratory plasma devices but generally across a number of plasma physics fields, including astrophysics, space physics and electronic devices. We have made significant improvements to the HYPERS core: (1) implemented a new asynchronous magnetic field integration scheme that preserves local divB=0 to within round-off errors; (2) Improved staggered-grid discretizations of electric and magnetic fields. These modifications have significantly enhanced the accuracy and robustness of 3D simulations. We have conducted first-ever end-to-end 3D simulations of merging spheromak plasmas. The preliminary results show: (1) tilt-driven relaxation of a freely expanding spheromak to an m=1 Taylor helix configuration and (2) possibility of formation of a tilt-stable field-reversed configuration via merging and magnetic reconnection of two double-sided spheromaks with opposite helicities.

  14. [Fusion energy research

    International Nuclear Information System (INIS)

    This report discusses the following topics: principal parameters achieved in experimental devices (FY88); tokamak fusion test reactor; Princeton beta Experiment-Modification; S-1 Spheromak; current drive experiment; x-ray laser studies; spacecraft glow experiment; plasma deposition and etching of thin films; theoretical plasma; tokamak modeling; compact ignition tokamak; international thermonuclear experimental reactor; Engineering Department; Project Planning and Safety Office; quality assurance and reliability; and technology transfer

  15. (Fusion energy research)

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, C.A. (ed.)

    1988-01-01

    This report discusses the following topics: principal parameters achieved in experimental devices (FY88); tokamak fusion test reactor; Princeton beta Experiment-Modification; S-1 Spheromak; current drive experiment; x-ray laser studies; spacecraft glow experiment; plasma deposition and etching of thin films; theoretical plasma; tokamak modeling; compact ignition tokamak; international thermonuclear experimental reactor; Engineering Department; Project Planning and Safety Office; quality assurance and reliability; and technology transfer.

  16. A laboratory plasma experiment for studying magnetic dynamics of accretion discs and jets

    OpenAIRE

    Hsu, S. C.; Bellan, P. M.

    2002-01-01

    This work describes a laboratory plasma experiment and initial results which should give insight into the magnetic dynamics of accretion discs and jets. A high-speed multiple-frame CCD camera reveals images of the formation and helical instability of a collimated plasma, similar to MHD models of disc jets, and also plasma detachment associated with spheromak formation, which may have relevance to disc winds and flares. The plasmas are produced by a planar magnetized coaxial gun. The resulting...

  17. New Revelation of Lightning Ball Observation and Proposal for a Nuclear Reactor Fusion Experiment

    OpenAIRE

    Tar, Domokos

    2009-01-01

    In this paper, the author brings further details regarding his Lightning Ball observation that were not mentioned in the first one (Ref.1-2). Additionally, he goes more into detail as the three forces that are necessary to allow the residual crescent form the hydrodynamic vortex ring to shrink into a sphere.Further topics are the similarities and analogies between the Lightning Ball formation's theory and the presently undertaken Tokamak-Stellarator-Spheromak fusion reactor experiments. A new...

  18. Possibilities for magnetic control of fission plasma propulsion

    International Nuclear Information System (INIS)

    Magnetic fusion energy research suggests the use of some magnetoplasma configurations to address certain critical issues in the gas-core fission approach to nuclear-thermal propulsion. The general framework of such an investigation that was outlined in a previous paper is directed here at the spheromak configuration in greater detail. In some unoptimized examples, the authors explore the compatibility of gas-core fission reactor criticality conditions with the dynamo action needed to non-inductively sustain the spheromak. The Lundquist number S is identified as a figure of merit, and is estimated by modeling to be as large as 100 in near-critical uranium (233U) plasmas of several-meter dimensions diluted with lithium (7Li) when the spheromak power consumption is treated as a constraint; whereas S as small as 200 is observed to be still able to preserve MHD dynamo activity in 3D resistive MHD simulations. Further optimization studies are required to ascertain whether these two values can be made to coincide

  19. A Study of Plasma Dynamics in HIT-SI using Ion Doppler Spectroscopy

    Science.gov (United States)

    Hossack, Aaron Clark

    The HIT-SI device is a unique experiment which uses inductive helicity injectors to form and sustain a spheromak plasma. The n = 1 symmetry of the injectors enables stable spheromak sustainment by imposed-dynamo current drive (IDCD). The experiment is diagnosed with spectroscopy, interferometry, imaging, and internal and surface magnetic probes. Two methods of density reduction and control are presented. A helicon preionization source enables plasma breakdown and operations at densities an order of magnitude lower than previously possible. The system is critical for all operations at injector frequencies greater than 14.5 kHz and single-injector operations. Additionally, a high-speed piezoelectric gas injection valve was developed to enable dynamic injector fueling adjustable on a timescale of ~0.5 ms. The focus of this work is on results from an ion Doppler spectrometer (IDS) which was upgraded to multi-chord capability. Two coherent, linear fiber optic cables with small, wide-angle lenses simultaneously collect light from 30 - 40 chords. Additionally, biorthogonal decomposition is used as a novel filtering method for raw data. Impurity radiation measurements of high power plasmas show no toroidal flow associated with toroidal current and temperature evolution which rises during toroidal current ramp-up and falls during current sustainment. Coherent velocity fluctuations show rigid, oscillatory motion of the spheromak plasma driven by the helicity injectors. The coherent motion combined with a lack of magnetic instabilities indicates that the spheromak is stable. Comparisons with NIMROD and PSI-TET simulations show similar chord-averaged velocity oscillations but fail to show the observed coherent, rigid motion of the spheromak. Additionally, strong flows and reconnection events in simulations which are not observed in the experiment indicate that agreement may improve with higher viscosity. The measured C III temperatures lie between the two codes' estimates

  20. ARIES-ST STUDIES REPORT FOR THE PERIOD JANUARY 1, 1998 THROUGH DECEMBER 31, 1998

    International Nuclear Information System (INIS)

    During 1998, the General Atomics (GA) ARIES-Spherical Torus (ST) team examined several critical issues related to the physics performance of the ARIES-ST design, and a number of suggestions were made concerning possible improvements in performance. These included specification of a reference plasma equilibrium, optimization about the reference equilibrium to achieve higher beta limits, examination of three possible schemes for plasma initiation, development of a detailed scenario for ramp-up of the plasma current and pressure to its full, final operating values, an assessment of the requirement for electron confinement, and several suggestions for divertor heat flux reduction. The reference equilibrium was generated using the TOQ code, with the specification of a 100%, self-consistent bootstrap current. The equilibrium has β = 51%, 10% below the stability limit (a margin specified by the ARIES-ST study). In addition, a series of intermediate equilibria were defined, corresponding to the ramp-up scenario discussed. A study of the influence of shaping on ARIES-ST performance indicates that significant improvement in both kink and ballooning stability can be obtained by modest changes in the squareness of the plasma. In test equilibria the ballooning beta limit is increased from 58% to 67%. Also the maximum allowable plasma-wall separation for kink stability can be increased by 30%. Three schemes were examined for noninductive plasma initiation. These are helicity injection (HICD), electron cyclotron heating (ECH)-assisted startup, and inductive startup using only the external equilibrium coils. HICD startup experiments have been done on the HIT and CDX devices. ECH-assisted startup has been demonstrated on CDX-U and DIII-D. External coil initiation is based on calculations for a proposed DIII-D experiment. In all cases, plasma initiation and preparation of an approximately 0.3 MA plasma for ARIES-ST appears entirely feasible

  1. Liquid Metal Walls, Lithium, And Low Recycling Boundary Conditions In Tokamaks

    Science.gov (United States)

    Majeski, R.

    2010-05-01

    At present, the only solid material believed to be a viable option for plasma-facing components (PFCs) in a fusion reactor is tungsten. Operated at the lower temperatures typical of present-day fusion experiments, tungsten is known to suffer from surface degradation during long-term exposure to helium-containing plasmas, leading to reduced thermal conduction to the bulk, and enhanced erosion. Existing alloys are also quite brittle at temperatures under 700°C. However, at a sufficiently high operating temperature (700 - 1000 °C), tungsten is self-annealing and it is expected that surface damage will be reduced to the point where tungsten PFCs will have an acceptable lifetime in a reactor environment. The existence of only one potentially viable option for solid PFCs, though, constitutes one of the most significant restrictions on design space for DEMO and follow-on fusion reactors. In contrast, there are several candidates for liquid metal-based PFCs, including gallium, tin, lithium, and tin-lithium eutectics. We will discuss options for liquid metal walls in tokamaks, looking at both high and low recycling materials. We will then focus in particular on one of the candidate liquids, lithium. Lithium is known to have a high chemical affinity for hydrogen, and has been shown in test stands and fusion experiments to produce a low recycling surface, especially when liquid. Because it is also low-Z and is usable in a tokamak over a reasonable temperature range (200 - 400 °C), it has been now been used as a PFC in several confinement experiments (TFTR, T11-M, CDX-U, NSTX, FTU, and TJ-II), with favorable results. The consequences of substituting low recycling walls for the traditional high recycling variety on tokamak equilibria are very extensive. We will discuss some of the expected modifications, briefly reviewing experimental results, and comparing the results to expectations.

  2. Liquid Metal Walls, Lithium, And Low Recycling Boundary Conditions In Tokamaks

    International Nuclear Information System (INIS)

    At present, the only solid material believed to be a viable option for plasma-facing components (PFCs) in a fusion reactor is tungsten. Operated at the lower temperatures typical of present-day fusion experiments, tungsten is known to suffer from surface degradation during long-term exposure to helium-containing plasmas, leading to reduced thermal conduction to the bulk, and enhanced erosion. Existing alloys are also quite brittle at temperatures under 700 deg. C. However, at a sufficiently high operating temperature (700 - 1000 deg. C), tungsten is self-annealing and it is expected that surface damage will be reduced to the point where tungsten PFCs will have an acceptable lifetime in a reactor environment.The existence of only one potentially viable option for solid PFCs, though, constitutes one of the most significant restrictions on design space for DEMO and follow-on fusion reactors. In contrast, there are several candidates for liquid metal-based PFCs, including gallium, tin, lithium, and tin-lithium eutectics. We will discuss options for liquid metal walls in tokamaks, looking at both high and low recycling materials. We will then focus in particular on one of the candidate liquids, lithium.Lithium is known to have a high chemical affinity for hydrogen, and has been shown in test stands and fusion experiments to produce a low recycling surface, especially when liquid. Because it is also low-Z and is usable in a tokamak over a reasonable temperature range (200 - 400 deg. C), it has been now been used as a PFC in several confinement experiments (TFTR, T11-M, CDX-U, NSTX, FTU, and TJ-II), with favorable results. The consequences of substituting low recycling walls for the traditional high recycling variety on tokamak equilibria are very extensive. We will discuss some of the expected modifications, briefly reviewing experimental results, and comparing the results to expectations.

  3. Liquid Metal Walls, Lithium, And Low Recycling Boundary Conditions In Tokamaks

    International Nuclear Information System (INIS)

    At present, the only solid material believed to be a viable option for plasma-facing components (PFCs) in a fusion reactor is tungsten. Operated at the lower temperatures typical of present-day fusion experiments, tungsten is known to suffer from surface degradation during long-term exposure to helium-containing plasmas, leading to reduced thermal conduction to the bulk, and enhanced erosion. Existing alloys are also quite brittle at temperatures under 700 C. However, at a sufficiently high operating temperature (700-1000 C), tungsten is selfannealing and it is expected that surface damage will be reduced to the point where tungsten PFCs will have an acceptable lifetime in a reactor environment. The existence of only one potentially viable option for solid PFCs, though, constitutes one of the most significant restrictions on design space for DEMO and follow-on fusion reactors. In contrast, there are several candidates for liquid metal-based PFCs, including gallium, tin, lithium, and tin-lithium eutectics. We will discuss options for liquid metal walls in tokamaks, looking at both high and low recycling materials. We will then focus in particular on one of the candidate liquids, lithium. Lithium is known to have a high chemical affinity for hydrogen, and has been shown in test stands and fusion experiments to produce a low recycling surface, especially when liquid. Because it is also low-Z and is usable in a tokamak over a reasonable temperature range (200-400 C), it has been now been used as a PFC in several confinement experiments (TFTR, T11- M, CDX-U, NSTX, FTU, and TJ-II), with favorable results. The consequences of substituting low recycling walls for the traditional high recycling variety on tokamak equilibria are very extensive. We will discuss some of the expected modifications, briefly reviewing experimental results, and comparing the results to expectations.

  4. Liquid Metal Walls, Lithium, And Low Recycling Boundary Conditions In Tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    R. Majeski

    2010-01-15

    At present, the only solid material believed to be a viable option for plasma-facing components (PFCs) in a fusion reactor is tungsten. Operated at the lower temperatures typical of present-day fusion experiments, tungsten is known to suffer from surface degradation during long-term exposure to helium-containing plasmas, leading to reduced thermal conduction to the bulk, and enhanced erosion. Existing alloys are also quite brittle at temperatures under 700oC. However, at a sufficiently high operating temperature (700 - 1000 oC), tungsten is selfannealing and it is expected that surface damage will be reduced to the point where tungsten PFCs will have an acceptable lifetime in a reactor environment. The existence of only one potentially viable option for solid PFCs, though, constitutes one of the most significant restrictions on design space for DEMO and follow-on fusion reactors. In contrast, there are several candidates for liquid metal-based PFCs, including gallium, tin, lithium, and tin-lithium eutectics. We will discuss options for liquid metal walls in tokamaks, looking at both high and low recycling materials. We will then focus in particular on one of the candidate liquids, lithium. Lithium is known to have a high chemical affinity for hydrogen, and has been shown in test stands1 and fusion experiments2,3 to produce a low recycling surface, especially when liquid. Because it is also low-Z and is usable in a tokamak over a reasonable temperature range (200 - 400 oC), it has been now been used as a PFC in several confinement experiments (TFTR, T11- M, CDX-U, NSTX, FTU, and TJ-II), with favorable results. The consequences of substituting low recycling walls for the traditional high recycling variety on tokamak equilibria are very extensive. We will discuss some of the expected modifications, briefly reviewing experimental results, and comparing the results to expectations.

  5. 13. TOPICAL CONFERENCE ON HIGH TEMPERATURE PLASMA DIAGNOSTICS SCIENTIFIC PROGRAM

    International Nuclear Information System (INIS)

    Electron cyclotron emission (ECE) has been employed as a standard electron temperature profile diagnostic on many tokamaks and stellarators, but most magnetically confined plasma devices cannot take advantage of standard ECE diagnostics to measure temperature. They are either overdense, operating at high density relative to the magnetic field (e.g. ωpe >> (Omega)ce in a spherical torus) or they have insufficient density and temperature to reach the blackbody condition (τ > 2). Electron Bernstein waves (EBWs) are electrostatic waves which can propagate in overdense plasmas and have a high optical thickness at the electron cyclotron resonance layers, as a result of their large Ki. This talk reports on measurements of EBW emission on the CDX-U spherical torus, where B0 ∼ 2 kG, e> ∼ 1013 cm-3 and Te ∼ 10 - 200 eV. Results will be presented for both direct detection of EBWs and for mode-converted EBW emission. The EBW emission was absolutely calibrated and compared to the electron temperature profile measured by a multi-point Thomson scattering diagnostic. Depending on the plasma conditions, the mode-converted EBW radiation temperature was found to be ≤ Te and the emission source was determined to be radially localized at the electron cyclotron resonance layer. A Langmuir triple probe was employed to measure changes in edge density profile in the vicinity of the upper hybrid resonance where the mode conversion of the EBWs is expected to occur. Changes in the mode conversion efficiency may explain the observation of mode-converted EBW radiation temperatures below Te. Initial results suggest EBW emission and EBW heating are viable concepts for plasmas where ωpe >> (Omega)ce

  6. 13th TOPICAL CONFERENCE ON HIGH TEMPERATURE PLASMA DIAGNOSTICS SCIENTIFIC PROGRAM

    Energy Technology Data Exchange (ETDEWEB)

    C. BARNES

    2000-07-01

    Electron cyclotron emission (ECE) has been employed as a standard electron temperature profile diagnostic on many tokamaks and stellarators, but most magnetically confined plasma devices cannot take advantage of standard ECE diagnostics to measure temperature. They are either overdense, operating at high density relative to the magnetic field (e.g. {omega}{sub pe} >> {Omega}{sub ce} in a spherical torus) or they have insufficient density and temperature to reach the blackbody condition ({tau} > 2). Electron Bernstein waves (EBWs) are electrostatic waves which can propagate in overdense plasmas and have a high optical thickness at the electron cyclotron resonance layers, as a result of their large K{sub i}. This talk reports on measurements of EBW emission on the CDX-U spherical torus, where B{sub 0} {approx} 2 kG, {approx} 10{sup 13} cm{sup -3} and T{sub e} {approx} 10 - 200 eV. Results will be presented for both direct detection of EBWs and for mode-converted EBW emission. The EBW emission was absolutely calibrated and compared to the electron temperature profile measured by a multi-point Thomson scattering diagnostic. Depending on the plasma conditions, the mode-converted EBW radiation temperature was found to be {le} T{sub e} and the emission source was determined to be radially localized at the electron cyclotron resonance layer. A Langmuir triple probe was employed to measure changes in edge density profile in the vicinity of the upper hybrid resonance where the mode conversion of the EBWs is expected to occur. Changes in the mode conversion efficiency may explain the observation of mode-converted EBW radiation temperatures below T{sub e}. Initial results suggest EBW emission and EBW heating are viable concepts for plasmas where {omega}{sub pe} >> {Omega}{sub ce}.

  7. Extreme ultra-violet movie camera for imaging microsecond time scale magnetic reconnection

    International Nuclear Information System (INIS)

    An ultra-fast extreme ultra-violet (EUV) movie camera has been developed for imaging magnetic reconnection in the Caltech spheromak/astrophysical jet experiment. The camera consists of a broadband Mo:Si multilayer mirror, a fast decaying YAG:Ce scintillator, a visible light block, and a high-speed visible light CCD camera. The camera can capture EUV images as fast as 3.3 × 106 frames per second with 0.5 cm spatial resolution. The spectral range is from 20 eV to 60 eV. EUV images reveal strong, transient, highly localized bursts of EUV radiation when magnetic reconnection occurs

  8. Alternate fusion concepts

    International Nuclear Information System (INIS)

    This review summarizes the status of alternate fusion concepts and plans for their future. The concepts selected for review are those employing electromagnetic confinement for which there have been reasonable predictions of net energy gain from pure fusion and which have shown significant recent development or are the subjects of ongoing international activity. They include advanced tokamaks, stellarators, the spherical torus, reversed-field pinch and dense z-field pinch devices, field reversed configuration, and spheromaks. In addition, an overall view of the status of each concept with respect to achieving ignition and to reactor designs is presented

  9. Extreme ultra-violet movie camera for imaging microsecond time scale magnetic reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Chai, Kil-Byoung; Bellan, Paul M. [Applied Physics, Caltech, 1200 E. California Boulevard, Pasadena, California 91125 (United States)

    2013-12-15

    An ultra-fast extreme ultra-violet (EUV) movie camera has been developed for imaging magnetic reconnection in the Caltech spheromak/astrophysical jet experiment. The camera consists of a broadband Mo:Si multilayer mirror, a fast decaying YAG:Ce scintillator, a visible light block, and a high-speed visible light CCD camera. The camera can capture EUV images as fast as 3.3 × 10{sup 6} frames per second with 0.5 cm spatial resolution. The spectral range is from 20 eV to 60 eV. EUV images reveal strong, transient, highly localized bursts of EUV radiation when magnetic reconnection occurs.

  10. Whither fusion research?

    International Nuclear Information System (INIS)

    The author maintains that the magnetic fusion program is ready for a dramatic change of course. The author's criteria for a desirable fusion power reactor are: it must produce power at a competitive price; it must work with high reliability and maintenance must be easy, fast and low cost, and that the fusion reactor must be safe and not damage the environment. The author's feelings are based on years of observation of the utility industry in general and commercial nuclear power development in particular. The author's views on the undesirability of tokamaks are discussed. Two concepts discussed as alternatives are the Reversed Field Pinch (RFP) and the spheromak

  11. Magnetic vortex growth in the transition layer of a mildly relativistic plasma shock

    International Nuclear Information System (INIS)

    A two-dimensional particle simulation models the collision of two electron-ion plasma clouds along a quasiparallel magnetic field. The collision speed is 0.9c and the density ratio, 10. A current sheet forms at the front of the dense cloud, in which the electrons and the magnetic field reach energy equipartition with the ions. A structure composed of a solenoidal and a toroidal magnetic field grows in this sheet. It resembles the cross-section of the torus of a spheromak, which may provide the coherent magnetic fields in gamma-ray burst jets needed for their prompt emissions.

  12. Observation of the growth of a magnetic vortex in the transition layer of a mildly relativistic oblique plasma shock

    CERN Document Server

    Murphy, G C; Drury, L O'C

    2010-01-01

    A 2D particle simulation models the collision of two electron-ion plasma clouds along a quasi-parallel magnetic field. The collision speed is 0.9c and the density ratio 10. A current sheet forms at the front of the dense cloud, in which the electrons and the magnetic field reach energy equipartition with the ions. A structure composed of a solenoidal and a toroidal magnetic field grows in this sheet. It resembles that in the cross-section of the torus of a force-free spheromak, which may provide the coherent magnetic fields in gamma-ray burst (GRB) jets needed for their prompt emissions.

  13. Compact toroid theory issues and approaches: a panel report

    International Nuclear Information System (INIS)

    In the six years since the initiation of the compact toroid program by the Office of Fusion Energy, remarkable scientific advances have occurred on both field-reversed configurations (FRC) and spheromaks. This progress has been stimulated by a diverse experimental program with facilities at six laboratories, and by a small but nevertheless broad theoretical research effort encompassing more than a dozen institutions. The close coupling between theoretical and experimental programs has contributed immeasurably to this progress. This document offers guidance for future compact toroid theory by identifying and discussing the key physics issues. In most cases promising approaches to these issues are offered

  14. Proceedings of the seventh symposium on the physics and technology of compact toroids in the Magnetic Fusion Energy Program

    International Nuclear Information System (INIS)

    The Seventh Symposium on Compact Toroid (CT) Research was held in Santa Fe, New Mexico, on May 21-23, 1985. As has been the case for the last few CT symposia, CT research progress was reported in a combination of invited talks and poster sessions. The following record of these presentations in the form of four page papers is in keeping with the format followed in previous years. We have continued the practice of dividing the papers into three subject categories - spheromak, FRC (Field Reversed Configuration), and other (mostly particle rings)

  15. Environmental monitoring report for calendar year 1984

    International Nuclear Information System (INIS)

    The results of the environmental monitoring program for CY84 for the Princeton Plasma Physics Laboratory (PPPL) are presented and discussed. The Princeton Large Torus (PLT), Princeton Beta Experiment (PBX), and PPPL's largest tokamak, the Tokamak Fusion Test Reactor (TFTR) had a complete year of run time. In addition, the S-1 Spheromak was in operation and the RF Test Facility came on-line. The phased approach of TFTR environmental monitoring continued with the addition of neutron monitors. During CY84 there were no adverse effects to the environment resulting from any operational program at PPPL, and the Laboratory was in compliance with all applicable Federal, State, and local environmental regulations

  16. Large density amplification measured on jets ejected from a magnetized plasma gun

    OpenAIRE

    Yun, Gunsu S.; You, Setthivoine; Bellan, Paul M.

    2007-01-01

    Observation of a large density amplification in the collimating plasma jet ejected from a coplanar coaxial plasma gun is reported. The jet velocity is ~30 km s^-1 and the electron density increases from ~10^20 to 10^(22–23) m^-3. In previous spheromak experiments, electron density of the order 10^(19–21) m^-3 had been measured in the flux conserver region, but no density measurement had been reported for the source gun region. The coplanar geometry of our electrodes permits direct observation...

  17. A Laboratory Plasma Experiment for Studying Magnetic Dynamics of Accretion Discs and Jets

    CERN Document Server

    Hsu, S C

    2002-01-01

    This work describes a laboratory plasma experiment and initial results which should give insight into the magnetic dynamics of accretion discs and jets. A high-speed multiple-frame CCD camera reveals images of the formation and helical instability of a collimated plasma, similar to MHD models of disc jets, and also plasma detachment associated with spheromak formation, which may have relevance to disc winds and flares. The plasmas are produced by a planar magnetized coaxial gun. The resulting magnetic topology is dependent on the details of magnetic helicity injection, namely the force-free state eigenvalue alpha_gun imposed by the coaxial gun.

  18. Proceedings of the seventh symposium on the physics and technology of compact toroids in the Magnetic Fusion Energy Program

    Energy Technology Data Exchange (ETDEWEB)

    Sherwood, A.R. (comp.)

    1986-09-01

    The Seventh Symposium on Compact Toroid (CT) Research was held in Santa Fe, New Mexico, on May 21-23, 1985. As has been the case for the last few CT symposia, CT research progress was reported in a combination of invited talks and poster sessions. The following record of these presentations in the form of four page papers is in keeping with the format followed in previous years. We have continued the practice of dividing the papers into three subject categories - spheromak, FRC (Field Reversed Configuration), and other (mostly particle rings).

  19. Three-dimensional magnetic reconnection through a moving magnetic null

    Directory of Open Access Journals (Sweden)

    V. S. Lukin

    2011-11-01

    Full Text Available A computational study of three-dimensional magnetic reconnection between two flux ropes through a moving reconnection site is presented. The configuration is considered in the context of two interacting spheromaks constrained by a perfectly conducting cylindrical boundary and oriented to form a single magnetic field null at its center. The initial magnetic field configuration is embedded into a uniform thermal plasma and is unstable to tilting. As the spheromaks tilt, their magnetic fields begin to reconnect at the null, subsequently displacing both the null and the reconnection site. The motion of the reconnection region and the magnetic null are shown to be correlated, with stronger correlation and faster reconnection observed in plasmas with lower thermal to magnetic pressure ratio. It is also shown that ion inertial effects allow for yet faster reconnection, but do not qualitatively change the dynamics of the process. Implications of the coupling between moving magnetic nulls and reconnection sites, as well as of possible mechanisms for fast reconnection through a moving reconnection region, are discussed. The simulations are conducted using both single-fluid and Hall MHD plasma models within the HiFi multi-fluid modeling framework.

  20. Future Directions for the SSPX Experiment

    Science.gov (United States)

    Hill, David

    2002-11-01

    The research program for the SSPX spheromak is focused on understanding the physics of magnetic field generation by coaxial helicity injection and determining what processes govern the energy transport. Over the next three years, we plan to make several major modifications to the SSPX spheromak in order to improve the injection efficiency and allow testing of several models describing the coaxial injection process. The modifications include an extended large-radius injector, addition of a second, small-radius injector at the opposite end of the flux conserver, and a modular programmable power supply (capacitor bank) to provide flexible control of the injection rate with improved impedance matching to the coaxial injector. Recent diagnostic improvements, including higher power for the Thomson scattering laser and probes at the throat of the coaxial injector, will provide data to compare with numerical simulations such as the NIMROD 3d resistive MHD code and the CORSICA 2d code. 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

  1. Application of Coaxial Ion Gun for Film Generation and Ion Implantation

    Science.gov (United States)

    Takatsu, Mikio; Asai, Tomohiko; Kurumi, Satoshi; Suzuki, Kaoru; Hirose, Hideharu; Masutani, Shigeyuki

    A magnetized coaxial plasma gun (MCPG) is here utilized for deposition on high-melting-point metals. MCPGs have hitherto been studied mostly in the context of nuclear fusion research, for particle and magnetic helicity injection and spheromak formation. During spheromak formation, the electrode materials are ionized and mixed into the plasmoid. In this study, this ablation process by gun-current sputtering is enhanced for metallic thin-film generation. In the proposed system geometry, only ionized materials are electromagnetically accelerated by the self-Lorentz force, with ionized operating gas as a magnetized thermal plasmoid, contributing to the thin-film deposition. This reduces the impurity and non-uniformity of the deposited thin-film. Furthermore, as the ions are accelerated in a parallel direction to the injection axis, vertical implantation of the ions into the substrate surface is achieved. To test a potential application of the developed system, experiments were conducted involving the formation of a buffer layer on hard ceramics, for use in dental materials.

  2. Flux amplification and sustainment of ST plasmas by multi-pulsed coaxial helicity injection on HIST

    Science.gov (United States)

    Higashi, T.; Ishihara, M.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

    2010-11-01

    The Helicity Injected Spherical Torus (HIST) device has been developed towards high-current start up and sustainment by Multi-pulsed Coaxial Helicity Injection (M-CHI) method. Multiple pulses operation of the coaxial plasma gun can build the magnetic field of STs and spheromak plasmas in a stepwise manner. So far, successive gun pulses on SSPX at LLNL were demonstrated to maintain the magnetic field of spheromak in a quasi-steady state against resistive decay [1]. The resistive 3D-MHD numerical simulation [2] for STs reproduced the current amplification by the M-CHI method and confirmed that stochastic magnetic field was reduced during the decay phase. By double pulsed operation on HIST, the plasma current was effectively amplified against the resistive decay. The life time increases up to 10 ms which is longer than that in the single CHI case (4 ms). The edge poloidal fields last between 0.5 ms and 6 ms like a repetitive manner. During the second driven phase, the toroidal ion flow is driven in the same direction as the plasma current as well as in the initial driven phase. At the meeting, we will discuss a current amplification mechanism based on the merging process with the plasmoid injected secondly from the gun. [1] B. Hudson et al., Phys. Plasmas Vol.15, 056112 (2008). [2] Y. Kagei et al., J. Plasma Fusion Res. Vol.79, 217 (2003).

  3. Effects of the current boundary conditions at the plasma-gun gap on density in SSPX

    Science.gov (United States)

    Kolesnikov, Roman; Lodestro, L. L.; Meyer, W. H.

    2012-10-01

    The Sustained Spheromak Physics Experiment (SSPX) was a toroidal magnetic-confinement device without toroidal magnetic-field coils or a central transformer but which generated core-plasma currents by dynamo processes driven by coaxial plasma-gun injection into a flux-conserving vessel. Record electron temperatures in a spheromak (Te˜500eV) were achieved, and final results of the SSPX program were reported in [1]. Plasma density, which depended strongly on wall conditions, was an important parameter in SSPX. It was observed that density rises with Igun and that confinement improved as the density was lowered. Shortly after the last experiments, a new feature was added to the Corsica code's solver used to reconstruct SSPX equilibria. Motivated by n=0 fields observed in NIMROD simulations of SSPX, an insulating boundary condition was implemented at the plasma-gun gap. Using this option we will perform new reconstructions of SSPX equilibria and look for correlations between the location of the separatrix (which moves up the gun wall and onto the insulating gap as Igun increases) and plasma density and magnetic-flux amplification [2].[4pt] [1] H. S. McLean, APS, DPP, Dallas, TX, 2008.[0pt] [2] E. B. Hooper et al., Nucl. Fusion 47, 1064 (2007).

  4. An Imposed Dynamo Current Drive Experiment: Demonstration of Confinement

    Science.gov (United States)

    Jarboe, Thomas; Hansen, Chris; Hossack, Aaron; Marklin, George; Morgan, Kyle; Nelson, Brian; Sutherland, Derek; Victor, Brian

    2014-10-01

    An experiment for studying and developing the efficient sustainment of a spheromak with sufficient confinement (current-drive power heats the plasma to its stability β-limit) and in the keV temperature range is discussed. A high- β spheromak sustained by imposed dynamo current drive (IDCD) is justified because: previous transient experiments showed sufficient confinement in the keV range with no external toroidal field coil; recent results on HIT-SI show sustainment with sufficient confinement at low temperature; the potential of IDCD of solving other fusion issues; a very attractive reactor concept; and the general need for efficient current drive in magnetic fusion. The design of a 0.55 m minor radius machine with the required density control, wall loading, and neutral shielding for a 2 s pulse is presented. Peak temperatures of 1 keV and toroidal currents of 1.35 MA and 16% wall-normalized plasma beta are envisioned. The experiment is large enough to address the key issues yet small enough for rapid modification and for extended MHD modeling of startup and code validation.

  5. A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. IV. Unusual Magnetic Cloud and Overall Scenario

    CERN Document Server

    Grechnev, V V; Chertok, I M; Belov, A V; Filippov, B P; Slemzin, V A; Jackson, B V

    2014-01-01

    The geomagnetic superstorm of 20 November 2003 with Dst = -422 nT, one of the most intense in history, is not well understood. The superstorm was caused by a moderate solar eruptive event on 18 November, comprehensively studied in our preceding Papers I-III. The analysis has shown a number of unusual and extremely complex features, which presumably led to the formation of an isolated right-handed magnetic-field configuration. Here we analyze the interplanetary disturbance responsible for the 20 November superstorm, compare some of its properties with the extreme 28-29 October event, and reveal a compact size of the magnetic cloud (MC) and its disconnection from the Sun. Most likely, the MC had a spheromak configuration and expanded in a narrow angle of < 14 degree. A very strong magnetic field in the MC up to 56 nT was due to the unusually weak expansion of the disconnected spheromak in an enhanced-density environment constituted by the tails of the preceding ICMEs. Additional circumstances favoring the su...

  6. 3D Ion Temperature Reconstruction

    Science.gov (United States)

    Tanabe, Hiroshi; You, Setthivoine; Balandin, Alexander; Inomoto, Michiaki; Ono, Yasushi

    2009-11-01

    The TS-4 experiment at the University of Tokyo collides two spheromaks to form a single high-beta compact toroid. Magnetic reconnection during the merging process heats and accelerates the plasma in toroidal and poloidal directions. The reconnection region has a complex 3D topology determined by the pitch of the spheromak magnetic fields at the merging plane. A pair of multichord passive spectroscopic diagnostics have been established to measure the ion temperature and velocity in the reconnection volume. One setup measures spectral lines across a poloidal plane, retrieving velocity and temperature from Abel inversion. The other, novel setup records spectral lines across another section of the plasma and reconstructs velocity and temperature from 3D vector and 2D scalar tomography techniques. The magnetic field linking both measurement planes is determined from in situ magnetic probe arrays. The ion temperature is then estimated within the volume between the two measurement planes and at the reconnection region. The measurement is followed over several repeatable discharges to follow the heating and acceleration process during the merging reconnection.

  7. Overview of the HIT-SI3 Experiment and Ion Doppler Spectroscopy Results from HIT-SI

    Science.gov (United States)

    Hossack, A. C.; Morgan, K. D.; Hansen, C. J.; Everson, C. J.; Sutherland, D. A.; Summers, A. W.; Chandra, R. N.; Nguyen, N. H.; Nelson, B. A.; Jarboe, T. R.; Elliott, D. B.; Victor, B. S.

    2015-11-01

    HIT-SI3 is a one-meter diameter spheromak current drive experiment. The plasma is formed and sustained by three inductive helicity injectors. The loop voltage and magnetic flux in each injector are oscillated in phase. The three injectors can be phased 120 or 60 degrees apart giving constant helicity injection. Operating frequencies include 14.5 kHz, 47.5 kHz, and higher. Toroidal current 3 times greater than the quadrature sum of injector currents has been achieved. Results are presented from a new, internal magnetic probe which spans the entire major radius of the flux conserver. Initial results will also be presented from the multi-point Thomson scattering diagnostic, ion Doppler spectrometer (IDS), and laser-induced fluorescence neutral density diagnostic. IDS results from the previous experiment, HIT-SI, are also presented. The spheromak plasma exhibits coherent motion driven by the injector currents and higher injector driving frequencies yielded higher betas than low frequency. Measurements are also compared with NIMROD and PSI-TET simulations and show qualitative agreement with temperature and velocity profiles. Work supported by USDoE.

  8. 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

  9. Stability and α-particle confinement in the Sphellamak reactor concept

    International Nuclear Information System (INIS)

    The Sphellamak is a coreless hybrid system with Tokamak, Stellarator and Spheromak features.The absence of a central conductor permits the realisation of a compact toroidal system, as internal shielding becomes un- necessary. With a peaked toroidal current profile, a sequence of reactor-sized Sphellamak equilibria is computed numerically in which the current in the helical coils Ihc is varied while the toroidal plasma current Ip = -30 MA and the volume average β = 7.3% remain fixed. Ideal global external kink modes are weakly unstable but indicate stability for Ihc > 138 MA. The local ideal magnetohydrodynamic stability criteria are satisfied in the range 42 MA hc < 122 MA. The peaked toroidal current generates local maximal of the modulus of the magnetic field strength in the central region of the plasma, which has very favourable implications for energetic and thermal particle confinement. This is confirmed through the computation of a very small α-particle guiding centre orbit loss fraction. (author)

  10. The evolution of the plasmoidal structure in the pinched column in plasma focus discharge

    Science.gov (United States)

    Kubes, P.; Paduch, M.; Cikhardt, J.; Klir, D.; Kravarik, J.; Rezac, K.; Cikhardtova, B.; Kortanek, J.; Zielinska, E.

    2016-04-01

    In this paper, a description is provided of the evolution of the dense spherical-like structures—plasmoids—formed in the pinched column of the dense plasma focus at the current of 1 MA at the final phase of implosion of the deuterium plasma sheath and at the phase of evolution of instabilities both at the time of HXR and neutron production. At the stratification of the plasma column, the plasma injected to the dense structures from the axially neighboring regions forms small turbulences which increase first the toroidal structures, and finally generates a non-chaotic current plasmoidal structure with central maximal density. This spontaneous evolution supports the hypothesis of the spheromak-like model of the plasmoid and its sub-millimeter analogy, high-energy spot. These spots, also called nodules formed in the filamentary structure of the current can be a source of the energy capable of accelerating the fast charged particles.

  11. CTR plasma engineering studies. Annual progress report, 1 November 1982-30 October 1983

    International Nuclear Information System (INIS)

    During FY 1983, much effort was devoted to work in support of alternate confinement concepts, especially those involving field reversal. This work includes: (1) study of possible steady-state operation of the Reversed Field Pinch (RFP) via driven dynamo action, (2) the development of particle and energy confinement scaling for the RFP and the Field Reversed Theta Pinch (FRTP), and (3) analysis of start-up (heating and plasma build) for the spheromak and Field Reversed Mirror (FRM). In addition, a block of projects were concerned with fusion product heating and the possible effects of fusion product-driven instability. These include: (1) effects of alpha-driven microinstabilities on heating in tokamaks, (2) exploratory studies of loss-cone-driven fusion product instabilities in tandem mirrors, and (3) fusion product transport, including effects of large angle scattering in reversed field devices such as the FRM

  12. Physical interpretations of permutation entropy scaling analyses of turbulent space and laboratory fluids

    Science.gov (United States)

    Rock, Ariel; Parks, Holden; Schaffner, David; Brown, Michael

    2015-11-01

    Statistical properties of various turbulent laboratory and natural (magneto)fluids are investigated using both complexity measures of ordinal pattern distribution and temporal increments. The systems analyzed are solar wind | B | time series from the Cluster satellites, streamwise velocity time series from the Johns Hopkins University Corsin Wind Tunnel, and | Ḃ | time series from the Swarthmore Spheromak Experiment (SSX) MHD wind tunnel. Plasma in the SSX wind tunnel has parameters B ~ . 2 T, n >=1021 m-3, and Ti >= 20 eV. By comparing the permutation entropy and Jensen-Shannon complexity with the behavior of the structure functions derived from the intermittency analysis, the connections between the complexity measures and dissipation mechanisms can be determined. The Corsin Wind Tunnel velocity data is used to compare the statistical signatures of dissipation in conventional hydrofluids with that seen in magnetofluids. Work supported by DOE OFES and NSF CMSO.

  13. Progress In Magnetized Target Fusion Driven by Plasma Liners

    Science.gov (United States)

    Thio, Francis Y. C.; Kirkpatrick, Ronald C.; Knapp, Charles E.; Cassibry, Jason; Eskridge, Richard; Lee, Michael; Smith, James; Martin, Adam; Wu, S. T.; Schmidt, George; Rodgers, Stephen L. (Technical Monitor)

    2001-01-01

    Magnetized target fusion (MTF) attempts to combine the favorable attributes of magnetic confinement fusion (MCF) for energy confinement with the attributes of inertial confinement fusion (ICF) for efficient compression heating and wall-free containment of the fusing plasma. It uses a material liner to compress and contain a magnetized plasma. For practical applications, standoff drivers to deliver the imploding momentum flux to the target plasma remotely are required. Spherically converging plasma jets have been proposed as standoff drivers for this purpose. The concept involves the dynamic formation of a spherical plasma liner by the merging of plasma jets, and the use of the liner so formed to compress a spheromak or a field reversed configuration (FRC).

  14. Laboratory Experiments on Propagating Plasma Bubbles into Vacuum, Vacuum Magnetic Field, and Background Plasmas

    Science.gov (United States)

    Lynn, Alan G.; Zhang, Yue; Gilmore, Mark; Hsu, Scott

    2014-10-01

    We discuss the dynamics of plasma ``bubbles'' as they propagate through a variety of background media. These bubbles are formed by a pulsed coaxial gun with an externally applied magnetic field. Bubble parameters are typically ne ~1020 m-3, Te ~ 5 - 10 eV, and Ti ~ 10 - 15 eV. The structure of the bubbles can range from unmagnetized jet-like structures to spheromak-like structures with complex magnetic flux surfaces. Some of the background media the bubbles interact with are vacuum, vacuum with magnetic field, and other magnetized plasmas. These bubbles exhibit different qualitative behavior depending on coaxial gun parameters such as gas species, gun current, and gun bias magnetic field. Their behavior also depends on the parameters of the background they propagate through. Multi-frame fast camera imaging and magnetic probe data are used to characterize the bubble evolution under various conditions.

  15. Preliminary scoping studies for nozzle-based coaxial plasma thrusters

    International Nuclear Information System (INIS)

    The ideal steady-state properties of nozzle-based coaxial plasma guns are modelled by means of a magnetic Bernoulli equation. Formulas for thrust, power usage, mass flow rate, and specific impulse using hydrogen are thereby obtained, and are used to approximately assess the mission performance capabilities of such thrusters. Parameters in the range of experience of the Los Alamos spheromak group are addressed within the context of orbit raising, slow (cargo) missions to mars, and fast missions to mars. The various internal atomic and plasma effects on hydrogen plasma thruster performance are approximately estimated or bounded. It is concluded that such devices may be relevant to mission performance at reasonable power levels

  16. CTR plasma engineering studies. Annual progress report, 1 December 1984-30 November 1985

    International Nuclear Information System (INIS)

    Work under this project is focused on plasma engineering developments in support of fusion reactor studies. The work described in this annual progress report covers a variety of topics ranging from plasma transport modelling for compact tori to radiation heating of the first wall in a fusion device. Sections 2 and 3 decribe computer codes developed for use with field-reversed configurations such as spheromaks and field-reversed mirrors. Section 4 presents an evaluation of the feasibility of heating a RFP-type reactor to ignition with ohmic current input alone. Sections 5 and 6 describe new work that has been initiated on optimal control theory for fusion reactors. Sections 7 to 9 discuss recent results on alpha-particle transport, instabilities, and diagnostics. In the final section, methods for analysis of the poloidal variation in the thermal wall loading of a tokamak reactor are discussed and some typical results are presented

  17. Performance and stability limits at near-unity aspect ratio in the Pegasus Toroidal Experiment

    International Nuclear Information System (INIS)

    The Pegasus Toroidal Experiment is a mid-sized extremely-low aspect ratio (A) spherical torus (ST). It has the dual roles of exploring limits of ST behavior as A approaches 1 and studying the physics of ST plasmas in the tokamak-spheromak overlap regime. Major parameters are R 0.25 - 0.45 m, A 1.1 - 1.4, Ip ≤ 0.15MA, and Btp=aBt is similar to that observed for NBI-heated START discharges. Achievable plasma current apparently is subject to a 'soft' limit of Ip=Itf ≤ 1. Access to higher-current plasmas appears to be restricted by the appearance of large internal MHD activity, including m/n=2/1 and 3/2 modes. Recent experiments have begun to access ideal stability limits, with disruptions observed as q95 approaches 5, in agreement with numerical predictions. (author)

  18. Development of Synthetic Diagnostics for use in Validation

    Science.gov (United States)

    Lemmon, Danielle; Woodruff, Simon; Romero-Talamas, Carlos A.; O'Bryan, John; Darpa Spheromak Team

    2015-11-01

    Synthetic diagnostics are reproductions of experimental measurements obtained from simulation data, taking the same spatial averages (point, line, plane or volume) as in the experiment. This reduction of data facilitates meaningful direct quantitative comparisons which then allows for validation of simulation results. We demonstrate the development with data sets produced by highly spatially and temporally resolved NIMROD simulations with reference to the spheromak concept under development at UMBC. We present here results from a set of synthetic diagnostics that are scripted in Octave. Quantities such as magnetic field, temperature, and density are visually represented by color-coded graphs and movies to demonstrate how these quantities change over time. We discuss errors that enter into the computation of the quantities. Work performed under DARPA grant N66001-14-1-4044.

  19. The benefits of ITER for the portfolio of fusion configurations

    Energy Technology Data Exchange (ETDEWEB)

    Goldston, R.J. [Princeton Plasma Physics Lab., NJ (United States)

    2002-10-01

    Recent plasma science challenges are 1) what limits the pressure in plasmas? (macroscopic stability), 2) how do hot particles and plasma waves interact in the non-linear regime? (wave-particle interactions), 3) what causes plasma transport? (microscopic turbulence and transport) and 4) how can high-temperature plasma and material surface co-exist? (plasma-material interactions). This fusion plasma science is addressed using a 'Portfolio' of configurations, like Stellarator, Tokamak, Spherical Torus, Reversed Field Pinch, Spheromak, and Field Reversed Configuration. Namely, the scientific results from one configuration benefit progress in others. Recent example of this effort can be found in NCSX, NSTX and RFP. ITER will provide very significant benefits to the development of the full fusion portfolio; macroscopic stability, wave-particle interactions, microturbulence and transport, plasma-material interactions, and technical demonstration of an integrated fusion system. (author)

  20. The benefits of ITER for the portfolio of fusion configurations

    International Nuclear Information System (INIS)

    Recent plasma science challenges are 1) what limits the pressure in plasmas? (macroscopic stability), 2) how do hot particles and plasma waves interact in the non-linear regime? (wave-particle interactions), 3) what causes plasma transport? (microscopic turbulence and transport) and 4) how can high-temperature plasma and material surface co-exist? (plasma-material interactions). This fusion plasma science is addressed using a 'Portfolio' of configurations, like Stellarator, Tokamak, Spherical Torus, Reversed Field Pinch, Spheromak, and Field Reversed Configuration. Namely, the scientific results from one configuration benefit progress in others. Recent example of this effort can be found in NCSX, NSTX and RFP. ITER will provide very significant benefits to the development of the full fusion portfolio; macroscopic stability, wave-particle interactions, microturbulence and transport, plasma-material interactions, and technical demonstration of an integrated fusion system. (author)

  1. Environmental monitoring report for calendar year 1984

    Energy Technology Data Exchange (ETDEWEB)

    Stencel, J.R.

    1985-05-01

    The results of the environmental monitoring program for CY84 for the Princeton Plasma Physics Laboratory (PPPL) are presented and discussed. The Princeton Large Torus (PLT), Princeton Beta Experiment (PBX), and PPPL's largest tokamak, the Tokamak Fusion Test Reactor (TFTR) had a complete year of run time. In addition, the S-1 Spheromak was in operation and the RF Test Facility came on-line. The phased approach of TFTR environmental monitoring continued with the addition of neutron monitors. During CY84 there were no adverse effects to the environment resulting from any operational program at PPPL, and the Laboratory was in compliance with all applicable Federal, State, and local environmental regulations.

  2. Environmental monitoring report for calendar year 1985

    Energy Technology Data Exchange (ETDEWEB)

    Stencel, J.R.

    1986-05-01

    The results of the environmental monitoring program for CY85 for the Princeton Plasma Physics Laboratory (PPPL) are presented and discussed. All of the tokamak machines, the Princeton Large Torus (PLT), Princeton Beta Experiment (PBX), and the Tokamak Fusion Test Reactor (TFTR), has a full year of run time. In addition, the S-1 Spheromak and the RF Test Facility were in operation. The phased approach to TFTR environmental monitoring continued with the establishment of locations for off-site monitoring. An environmental committee established in December 1984 reviewed items of environmental importance. During CY85 no adverse effects to the environmental resulted from any operational program activities at PPPL, and the Laboratory was in compliance with all applicable Federal, State, and local environmental regulations.

  3. SYMTRAN - A Time-dependent Symmetric Tandem Mirror Transport Code

    International Nuclear Information System (INIS)

    A time-dependent version of the steady-state radial transport model in symmetric tandem mirrors in Ref. [1] has been coded up and first tests performed. Our code, named SYMTRAN, is an adaptation of the earlier SPHERE code for spheromaks, now modified for tandem mirror physics. Motivated by Post's new concept of kinetic stabilization of symmetric mirrors, it is an extension of the earlier TAMRAC rate-equation code omitting radial transport [2], which successfully accounted for experimental results in TMX. The SYMTRAN code differs from the earlier tandem mirror radial transport code TMT in that our code is focused on axisymmetric tandem mirrors and classical diffusion, whereas TMT emphasized non-ambipolar transport in TMX and MFTF-B due to yin-yang plugs and non-symmetric transitions between the plugs and axisymmetric center cell. Both codes exhibit interesting but different non-linear behavior

  4. Environmental monitoring report for Calendar Year 1986

    International Nuclear Information System (INIS)

    The results of the 1986 environmental monitoring program for the Princeton Plasma Physics Laboratory (PPPL) are presented and discussed. Two of three large tokamak machines, the Princeton Large Torus (PLT) and the Tokamak Fusion Test Reactor (TFTR) were in operation during the year. The Princeton Beta Experiment (PBX) was shut down in December 1985 to undergo major modifications, and will recommence operations in 1987. PLT was shut down in December 1986. In addition, the S-1 Spheromak and the Radio-Frequency Test Facility (RFTF) were operated on a limited basis in 1986. The Environmental Committee became a standing committee of the Executive Safety Board (ESB) and continued to review items of environmental importance. During CY86 no adverse effects to the environment or public resulted from any operational program activities at PPPL, and the Laboratory was in compliance with all applicable federal, state, and local environmental regulations

  5. Magnetic reconnection and self-organized plasma systems

    International Nuclear Information System (INIS)

    In this paper the recent results from the Magnetic Reconnection Experiment (MRX) at PPPL are discussed along with their relationship to observations from solar flares, the magnetosphere, and current carrying pinch discharges such as tokamaks, reversed field pinches, spheromaks and field reversed configurations. It is found that the reconnection speed decreases as the angle of merging field lines decreases, consistent with the well-established observation in the dayside magnetosphere. This observation can also provide a qualitative interpretation of a generally observed trend in pinch plasmas, namely that magnetic field diffuses (or reconnects) faster when magnetic shear is larger. A recently conceived research project, SPIRIT (Self-organized Plasma with Induction, Reconnection, and Injection Techniques), will also be discussed. (author)

  6. Development of Multi-pulse Compact Toroid Injector System for C-2U

    Science.gov (United States)

    Allfrey, I.; Garate, E.; Morehouse, M.; Roche, T.; Gota, H.; Valentine, T.; Waggoner, W.; Putvinski, S.; Cordero, M.; Asai, T.; Matsumoto, T.; Sekiguchi, J.; the TAE Team

    2015-11-01

    The C-2U experiment aims at sustaining a dynamically formed field reversed configuration (FRC) for 5 + ms via injection of 10 +MW of neutral beams. One of the systems currently used to refuel the C-2U plasma is a single pulse compact toroid injector (CTI). The CTI is a magnetized co-axial plasma gun, which generates a spheromak-like plasma that is injected into the core of the advanced beam-driven FRC of C-2U. In order to refuel the recent long-lived plasmas in C-2U, a multi-pulse CTI system, whose modular design allows for expandable burst numbers, is being designed. Details of the pulsed power systems used to energize the single pulse and the upgraded multi-pulse CTI will be discussed. Results of injector performance carried out on a dedicated test stand as well as some refueling data on C-2U will also be presented.

  7. Magnetic structure of Coronal Mass Ejections

    CERN Document Server

    Lyutikov, Maxim

    2012-01-01

    We present several models of the magnetic structure of solar coronal mass ejections (CMEs). First, we model CMEs as expanding force-free magnetic structures. While keeping the internal magnetic field structure of the stationary solutions, expansion leads to complicated internal velocities and rotation, while the field structures remain force-free. Second, expansion of a CME can drive resistive dissipation within the CME changing the ionization states of different ions. We fit in situ measurements of ion charge states to the resistive spheromak solutions. Finally, we consider magnetic field structures of fully confined stable magnetic clouds containing both toroidal and poloidal magnetic fields and having no surface current sheets. Expansion of such clouds may lead to sudden onset of reconnection events.

  8. Magnetohydrodynamic equilibrium of axisymmetric systems with toroidal rotation

    International Nuclear Information System (INIS)

    A model for studying magnetohydrodynamic equilibrium of axisymetrically confined plasma with toroidal rotation, extended to the Grad. Shafranov equation is presented. The expression used for the scalar pressure is modifiec, and the influence of toroidal magnetic field is included, The equation for general motion of axisymetrically confined plasma, particularizing for rotation movements is described. Two cases are compared: one supposes the entropy as a function of poloidal magnetic flux and other supposes the temperature as a function of flux. The equations for these two cases obtaining a simplified expression by others approximations are established. The proposed model is compared with Shibata model, which uses density as function of flux, and with the ideal spheromak model. A set of cases taking in account experimental data is studied. (M.C.K.)

  9. Temporal and Spatial Turbulent Spectra of MHD Plasma and an Observation of Variance Anisotropy

    CERN Document Server

    Schaffner, D A; Lukin, V S

    2014-01-01

    The nature of MHD turbulence is analyzed through both temporal and spatial magnetic fluctuation spectra. A magnetically turbulent plasma is produced in the MHD wind-tunnel configuration of the Swarthmore Spheromak Experiment (SSX). The power of magnetic fluctuations is projected into directions perpendicular and parallel to a local mean field; the ratio of these quantities shows the presence of variance anisotropy which varies as a function of frequency. Comparison amongst magnetic, velocity, and density spectra are also made, demonstrating that the energy of the turbulence observed is primarily seeded by magnetic fields created during plasma production. Direct spatial spectra are constructed using multi-channel diagnostics and are used to compare to frequency spectra converted to spatial scales using the Taylor Hypothesis. Evidence for the observation of dissipation due to ion inertial length scale physics is also discussed as well as the role laboratory experiment can play in understanding turbulence typica...

  10. Permutation Entropy and Statistical Complexity Analysis of Turbulence in Laboratory Plasmas and the Solar Wind

    CERN Document Server

    Weck, Peter J; Brown, Michael R; Wicks, Robert T

    2014-01-01

    The Bandt-Pompe permutation entropy and the Jensen-Shannon statistical complexity are used to analyze fluctuating time series of three different plasmas: the magnetohydrodynamic (MHD) turbulence in the plasma wind tunnel of the Swarthmore Spheromak Experiment (SSX), drift-wave turbulence of ion saturation current fluctuations in the edge of the Large Plasma Device (LAPD) and fully-developed turbulent magnetic fluctuations of the solar wind taken from the WIND spacecraft. The entropy and complexity values are presented as coordinates on the CH plane for comparison among the different plasma environments and other fluctuation models. The solar wind is found to have the highest permutation entropy and lowest statistical complexity of the three data sets analyzed. Both laboratory data sets have larger values of statistical complexity, suggesting these systems have fewer degrees of freedom in their fluctuations, with SSX magnetic fluctuations having slightly less complexity than the LAPD edge fluctuations. The CH ...

  11. Environmental monitoring report for calendar year 1985

    International Nuclear Information System (INIS)

    The results of the environmental monitoring program for CY85 for the Princeton Plasma Physics Laboratory (PPPL) are presented and discussed. All of the tokamak machines, the Princeton Large Torus (PLT), Princeton Beta Experiment (PBX), and the Tokamak Fusion Test Reactor (TFTR), has a full year of run time. In addition, the S-1 Spheromak and the RF Test Facility were in operation. The phased approach to TFTR environmental monitoring continued with the establishment of locations for off-site monitoring. An environmental committee established in December 1984 reviewed items of environmental importance. During CY85 no adverse effects to the environmental resulted from any operational program activities at PPPL, and the Laboratory was in compliance with all applicable Federal, State, and local environmental regulations

  12. Experimental investigation on tilt stabilizing effect of external toroidal field in low aspect ratio tokamak

    International Nuclear Information System (INIS)

    This paper describes experimental investigations on the equilibrium and global stability of low aspect ratio tokamaks with different aspect ratios ranging from 1.1 to 1.9. The Z-θ pinch spheromak formation technique is used to produce low aspect ratio tokamaks in an external toroidal field generated by the center conductor. Using this operation, the plasma stability has been investigated in the transition regime from tokamaks to spheromaks. It has been found that there exists a lower critical value of the center conductor current to surpress the global plasma instability of the n=1 tilt and/or shift modes. The ratio of this critical current to plasma current is experimentally measured for the first time as a function of the aspect ratio. Glass-tube cylindrical limiters with different radii are installed along the symmetric center axis of the Spherical Torus-3 device [Y. Ono et al., Phys. Fluids B 5, 3691 (1993)]. As the aspect ratio is decreased from 1.9 to 1.1, it is observed that the critical ratio of the center conductor current to plasma current decreases from 1.2 to 0.2. The safety factor q at the plasma edge corresponding to this critical current is roughly 1.5 to 3.0. Similar experiments are also carried out with a thin metal cover surrounding the surface of the glass tube limiter. The thin metal cover permits the decrease in the critical current and the corresponding edge q value of q∼1. These experimental results of the critical current ratio are found to be comparable to that predicted from theoretical models where the restoring force against the tilt motion is considered to be generated by the interaction of the external toroidal field with the n=1 induced surface currents in the tilt motion. copyright 1997 American Institute of Physics

  13. Progress in the Plasma Science and Innovation Center

    International Nuclear Information System (INIS)

    Full text: Highlights of recent progress in the Plasma Science and Innovation (PSI) Center include adding reacting neutrals in the MHD model, providing capability for CAD description to grid generation to MHD simulation, incorporating energetic particles in extended MHD modeling, simulating 3D physics with Hall MHD, such as rotating magnetic field (RMF) current drive and inductive asymmetric current drive. The PSI Center is a collaborative effort to refine existing computational tools with the goal of improving computational predictability. The Center collaborates with experimental research groups to test the codes and to support the experiments. The Center refines primarily NIMROD and HiFi to have sufficient physics, boundary conditions, and geometry to be calibrated with experiments to achieve predictive capabilities. This paper describes some of the recent code advances, applications to experimental devices, and comparison to experimental data. The HIT-SI bow tie spheromak uses geometrically asymmetric injectors to inject helicity. From experimental data and Hall-MHD NIMROD simulations, the spheromak is formed and sustained by a combination of reconnection and quiescent dynamo drive. The HiFi code uses a 3D finite element spatial discretization that uses a multi-block grid, imported from a CAD description from the experimental design. The grid quality is determined using an a priori error estimator that identifies regions that need improved grid resolution. The TCSU field reversed configuration (FRC) investigates RMF current drive to generate and sustain an FRC. Three-dimensional Hall-MHD NIMROD simulations using experimental parameters show the generation of an FRC with toroidal magnetic field and size that compare well with experimental results. A reacting plasma model, which has a singly ionized plasma and a dynamic, neutral gas, that undergo ionization, recombination, and charge exchange reactions, has been implemented in HiFi and used to simulate the ELF

  14. Active Stability Control of a High-Beta Self-Organized Compact Torus

    International Nuclear Information System (INIS)

    Full text: A magnetized coaxial plasma gun (MCPG) has been proposed as an effective device for control of a high-beta self-organized compact torus of field-reversed configuration (FRC). The initial results demonstrate that the application of an MCPG suppresses the most prominent FRC instability of the centrifugally-driven interchange mode with toroidal mode number n = 2. This observation was made on the Nihon University Compact Torus Experiment (NUCTE), a flexible theta-pinch-based FRC facility. In the series of experiments, a MCPG generates a spheromak-like plasmoid which can then travel axially to merge with a pre-existing FRC. Since the MCPG is mounted on-axis and generates a significant helicity, it provides the FRC-relevant version of coaxial helicity injection (CHI) that has been applied in both spheromaks and spherical tokamaks. When CHI is applied, the onset of elliptical deformation of FRC cross-section is delayed until 45 - 50 μs from FRC formation compared to the onset time of 25 μs in the case without CHI. Besides delaying instability, MCPG application reduces the toroidal rotation frequency from 67 kHz to 41 kHz. Moreover, the flux decay time is extended from 57 to 67 μs. These changes have been made despite the quite modest flux content of the plasmoid: ∼0.05 mWb of poloidal and 0.01 mWb of toroidal flux, compared with the 0.4 mWb of poloidal flux in the pre-formed FRC. The observed global stabilization and confinement improvements suggest that the MCPG can actively control the rotational instability. This global instability can also be suppressed by externally applied static multipole fields. However, it has been known that nonaxisymmetric multipole fields have adverse effects on confinement. This indicates an advantage of MCPG in that it shows both improved confinement and stability. The conventional technique does not slow the toroidal rotation down. Therefore, MCPG introduces a different stabilization mechanism that may be the same as that

  15. Stability and {alpha}-particle confinement in the Sphellamak reactor concept

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, W. Anthony; Fischer, Olivier [Ecole Polytechnique Federale de Lausanne, Centre de Recherches en Physique des Plasmas (CRPP), CH-1015 Lausanne (Switzerland)

    2000-10-01

    The Sphellamak is a coreless hybrid system with Tokamak, Stellarator and Spheromak features.The absence of a central conductor permits the realisation of a compact toroidal system, as internal shielding becomes un- necessary. With a peaked toroidal current profile, a sequence of reactor-sized Sphellamak equilibria is computed numerically in which the current in the helical coils I{sub hc} is varied while the toroidal plasma current I{sub p} = -30 MA and the volume average {beta} = 7.3% remain fixed. Ideal global external kink modes are weakly unstable but indicate stability for I{sub hc} > 138 MA. The local ideal magnetohydrodynamic stability criteria are satisfied in the range 42 MA < I{sub hc} < 122 MA. The peaked toroidal current generates local maximal of the modulus of the magnetic field strength in the central region of the plasma, which has very favourable implications for energetic and thermal particle confinement. This is confirmed through the computation of a very small {alpha}-particle guiding centre orbit loss fraction. (author) [French] Le Sphellamak est un systeme hybride sans noyau central compose par des elements de Tokamak, de Stellerateur et de Spheromak. L'absence de colonne centrale permet la realisation d 'un systeme toroidal compact puisque le manteau de protection interne ne devient plus necessaire. Avec un profil de courant pique, une sequence d 'equilibres Sphellamak de dimension reacteur est calculee numeriquement en variant le courant des bobines helicoidales I{sub hc} tout en fixant le courant toroidal du plasma I{sub p} = -30 MA ainsi que la moyenne volumique {beta} = 7.3%. Les modes globaux externes du type kink sont faiblement instables mais suffisent a garantir la stabilite pour I{sub hc} > 138 MA. Les criteres de stabilite magnetohydrodynamique ideale locale sont realises pour des courants de 42 MA < I{sub hc} < 122 MA. Le courant toroidal pique pro- duit localement des valeurs maximales pour le module du champs

  16. Exploring reconnection, current sheets, and dissipation in a laboratory MHD turbulence experiment

    Science.gov (United States)

    Schaffner, D. A.

    2015-12-01

    The Swarthmore Spheromak Experiment (SSX) can serve as a testbed for studying MHD turbulence in a controllable laboratory setting, and in particular, explore the phenomena of reconnection, current sheets and dissipation in MHD turbulence. Plasma with turbulently fluctuating magnetic and velocity fields can be generated using a plasma gun source and launched into a flux-conserving cylindrical tunnel. No background magnetic field is applied so internal fields are allowed to evolve dynamically. Point measurements of magnetic and velocity fluctuations yield broadband power-law spectra with a steepening breakpoint indicative of the onset of a dissipation scale. The frequency range at which this steepening occurs can be correlated to the ion inertial scale of the plasma, a length which is characteristic of the size of current sheets in MHD plasmas and suggests a connection to dissipation. Observation of non-Gaussian intermittent jumps in magnetic field magnitude and angle along with measurements of ion temperature bursts suggests the presence of current sheets embedded within the turbulent plasma, and possibly even active reconnection sites. Additionally, structure function analysis coupled with appeals to fractal scaling models support the hypothesis that current sheets are associated with dissipation in this system.

  17. Ball plasma dynamics for FBX BURNER reactor

    International Nuclear Information System (INIS)

    The authors have been conducting fundamental experiments on the moving plasma balls in the major axis direction. This has a fundamental importance for the quasi-steady fusion reactor scheme FBX BURNER. This configuration is the descendants of Spheromak type nuclear fusion scheme but with long toroidal field coils. The main issues have been focused onto the dynamic stability of the moving plasma balls. The second issue is the collision between two successive plasma balls as shown. This shows a basic result from an optical measurement. The comparison with magnetic measurements shows peculiar but interesting features of the system. The dimension of the plasma injector is 2 m in length as a whole. It is in a coaxial configuration. The external electrode is 150 mm in inner diameter and the inner electrode is 50 mm in diameter. This is attached to a 1 m insulation reservoir with same inner diameter. An axial magnetic field up to 0.1 Tesla is applied on the discharge with a current of up to 10 kA in few ms. The authors show their experimental and numerical simulation results on these problems

  18. An ion Doppler spectrometer instrument for ion temperature and flow measurements on SSPX

    International Nuclear Information System (INIS)

    A high-resolution ion Doppler spectrometer (IDS) has been installed on the sustained spheromak plasma experiment to measure ion temperatures and plasma flow. The system is composed of a 1 m focal length Czerny-Turner spectrometer with a diffraction grating line density of 2400 lines/mm, which allows for first order spectra between 300 and 600 nm. A 16-channel photomultiplier tube detection assembly combined with output coupling optics provides a spectral resolution of 0.0126 nm/channel. We calculate in some detail the mapping of curved slit images onto the linear detector array elements. This is important in determining the wavelength resolution and setting the optimum vertical extent of the slit. Also, because of the small wavelength window of the IDS, a miniature fiber-optic survey spectrometer sensitive to a wavelength range 200-1100 nm and having a resolution of 0.2 nm is used to obtain a time-integrated spectrum for each shot to verify specific impurity line radiation. Several measurements validate the systems operation. Doppler broadening of C III 464.72 nm line in the plasma shows time-resolved ion temperatures up to 250 eV for hydrogen discharges, which is consistent with neutral particle energy analyzer measurements. Flow measurements show a sub-Alfvenic plasma flow ranging from 5 to 45 km/s for helium discharges.

  19. CTR plasma engineering studies. Annual progress report, 1 November 1981-30 October 1982

    International Nuclear Information System (INIS)

    During FY 82, much effort was devoted to work in support of alternate confinement concepts, especially those involving field reversal. This work includes: (1) development of particle and energy confinement scaling for the Reversed Field Pinch (RFP) and the Field Reversed Theta Pinch (FRTP), and (2) analysis of start-up (heating and plasma build) for the spheromak and Field Reversed Mirror (FRM). In addition, a block of projects were concerned with fusion product effects, including heating and ash build-up. These include, (1) a study of possible use of radial electric fields to control ash build-up in tokamaks, (2) effects of alpha-driven microinstabilities on heating in tokamaks, and (3) fusion product transport, including effects of large angle scattering on orbits, in EBT and FRM devices. In a related study, the possibility of hot-ion mode operation (assuming strong transfer of fusion product energy to ions, e.g. via microinstabilities) was done with emphasis on calculation of ion-electron equilibration rates

  20. Modeling electron heat transport during magnetic field buildup in SSPX

    International Nuclear Information System (INIS)

    A model for spheromak magnetic field buildup and electron thermal transport, including a thermal diffusivity associated with magnetic turbulence during helicity injection is applied to a SSPX equilibrium, with a maximum final magnetic field of 1.3 T. Magnetic field-buildup times of 1.0 X 10-3, 5.0 X 10-4 and 1.0 X 10-4 s were used in the model to examine their effects on electron thermal transport. It is found that at transport run time of 4 x 10-3 s, the fastest buildup-time results in the highest final temperature profile, with a core temperature of 0.93 kev while requiring the lowest input energy at 140 KJ. The results show that within the model the most rapid buildup rate generates the highest electron temperature at the fastest rate and at the lowest consumption of energy. However, the peak power requirements are large (> 600 MW for the fastest buildup case examined)

  1. Predictive Modeling of Tokamak Configurations*

    Science.gov (United States)

    Casper, T. A.; Lodestro, L. L.; Pearlstein, L. D.; Bulmer, R. H.; Jong, R. A.; Kaiser, T. B.; Moller, J. M.

    2001-10-01

    The Corsica code provides comprehensive toroidal plasma simulation and design capabilities with current applications [1] to tokamak, reversed field pinch (RFP) and spheromak configurations. It calculates fixed and free boundary equilibria coupled to Ohm's law, sources, transport models and MHD stability modules. We are exploring operations scenarios for both the DIII-D and KSTAR tokamaks. We will present simulations of the effects of electron cyclotron heating (ECH) and current drive (ECCD) relevant to the Quiescent Double Barrier (QDB) regime on DIII-D exploring long pulse operation issues. KSTAR simulations using ECH/ECCD in negative central shear configurations explore evolution to steady state while shape evolution studies during current ramp up using a hyper-resistivity model investigate startup scenarios and limitations. Studies of high bootstrap fraction operation stimulated by recent ECH/ECCD experiments on DIIID will also be presented. [1] Pearlstein, L.D., et al, Predictive Modeling of Axisymmetric Toroidal Configurations, 28th EPS Conference on Controlled Fusion and Plasma Physics, Madeira, Portugal, June 18-22, 2001. * Work performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

  2. Simulations of broadband short-pulse reflectometry for diagnosing plasma density and magnetic-field profiles

    International Nuclear Information System (INIS)

    Numerical simulations of the use of ultra-short-pulse reflectometry to diagnose plasma density and magnetic-field profiles are presented. Numerical solutions of Maxwell's equations are used to model the propagation of ordinary modes into a plasma from whose reflected signals' time-of-flight (group delay) as a function of frequency is deduced the electron density profile. Similar methods are used to simulate the propagation and reflection of extraordinary waves, from which is deduced the magnetic-field profile if the electron density is already known (the cutoff relation for the extraordinary mode depends jointly on the electron density and the magnetic field). The simulation results presented here demonstrate that the determination of plasma density and magnetic-field profiles from ultra-short-pulse reflectometry is relatively robust. In order to use more realistic plasma and magnetic-field configurations in the reflectometry simulations as well as to be able to simulate, assess, and tune the performance of the diagnostic in the experimental configurations of interest, O-mode and X-mode reflectometry simulation packages have been merged into the CORSICA comprehensive plasma modelling framework. Examples of CORSICA reflectometry simulations of the DIII-D tokamak and the SSPX spheromak being built at the Lawrence Livermore National Laboratory are presented. (author)

  3. Fast magnetic and electric dynamos in flat Klein bottle plasma flows

    CERN Document Server

    de Andrade, L C Garcia

    2009-01-01

    Recently Shukurov et al [Phys Rev \\textbf{E} (2008)] presented a numerical solution of a Moebius strip dynamo flow, to investigate its use in modelling dynamo flows in Perm torus of liquid sodium dynamo experiments. Here, by analogy one presents an electric dynamo on a twisted torus or Klein bottle topology. An exact solution in the form of flat Klein bottle dynamo flow is obtained. It is shown that even in the absence of magnetic dynamos initial electric fields can be amplified in distinct points of the Klein bottle. In this case diffusion is taken as ${\\eta}\\approx{5.0{\\times}10^{-3}{\\Omega}-m}$ the electric potential is obtained. The difference of electric fields at the beginning of plasma flow profile is ${\\Delta}E_{Dyn}\\approx{468\\frac{V}{m}}$, which is stronger than the electric dynamo field obtained in the magnetic axis of spheromaks, which is of the order of $E_{Dyn}\\approx{200\\frac{V}{m}}$. The potential of the dynamo at the surface of the Earth computed by Boozer [Phys Fluids \\textbf{B} (1993)] of $...

  4. Flow and dynamo measurements during the coaxial helicity injection on HIST

    Science.gov (United States)

    Ando, K.; Higashi, T.; Nakatsuka, M.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

    2009-11-01

    The current drive by Coaxial Helicity Injection (CHI-CD) was performed on HIST in a wide range of configurations from high-q ST to low-q ST and spheromak generated by the utilization of the toroidal field. It is a key issue to investigate the dynamo mechanism required to maintain each configuration. To identify the detail mechanisms, it is needed to manifest a role of plasma flows in the CHI-CD. For this purpose, we have measured the ion flow and the dynamo electric field using an ion Doppler spectrometer (IDS) system, a Mach probe and a dynamo probe. The new dynamo probe consists of 3-axis Mach probes and magnetic pick-up coils. The flow measurements have shown that the intermittent generation of the flow is correlated to the fluctuation seen on the electron density and current signals during the driven phase. At this time, the toroidal direction of the ion flow in the central open flux column is opposite to that of the toroidal current there, i.e. the same direction as electrons. After the plasma enters to the resistive decay phase, the toroidal flow tends to reverse to the same direction as the toroidal current. The results are consistent with the model of the repetitive plasmoid ejection and coalescence proposed for CHI-CD. The plasma jet emanating from the gun source and magnetic field generations through reconnection during the driven phase is well reflected in the 3D MHD simulation.

  5. Development of a polarization resolved spectroscopic diagnostic for measurements of the magnetic field in the Caltech coaxial magnetized plasma jet experiment

    Science.gov (United States)

    Shikama, Taiichi; Bellan, Paul M.

    2011-11-01

    Measurements of the magnetic field strength in current-carrying magnetically confined plasmas are necessary for understanding the underlying physics governing the dynamical behavior. Such a measurement would be particularly useful in the Caltech coaxial magnetized plasma gun, an experiment used for fundamental studies relevant to spheromak formation, astrophysical jet formation/propagation, solar coronal physics, and the general behavior of twisted magnetic flux tubes that intercept a boundary. In order to measure the field strength in the Caltech experiment, a non-perturbing spectroscopic method is being implemented to observe the Zeeman splitting in the emission spectra. The method is based on polarization-resolving spectroscopy of the Zeeman-split σ components, a technique previously used in both solar and laboratory plasmas. We have designed and constructed an optical system that can simultaneously detect left- and right-circularly polarized emission with both high throughput and small extinction ratio. The system will be used on the 489.5 nm NII line, chosen because of its simple Zeeman structure and minimal Stark broadening.

  6. Formation and Acceleration Physics on Plasma Injector 1

    Science.gov (United States)

    Howard, Stephen

    2012-10-01

    Plasma Injector 1 (PI-1) is a two stage coaxial Marshal gun with conical accelerator electrodes, similar in shape to the MARAUDER device, with power input of the same topology as the RACE device. The goal of PI-1 research is to produce a self-confined compact toroid with high-flux (200 mWb), high-density (3x10^16 cm-3) and moderate initial temperature (100 eV) to be used as the target plasma in a MTF reactor. PI-1 is 5 meters long and 1.9 m in diameter at the expansion region where a high aspect ratio (4.4) spheromak is formed with a minimum lambda of 9 m-1. The acceleration stage is 4 m long and tapers to an outer diameter of 40 cm. The capacitor banks store 0.5 MJ for formation and 1.13 MJ for acceleration. Power is delivered via 62 independently controlled switch modules. Several geometries for formation bias field, inner electrodes and target chamber have been tested, and trends in accelerator efficiency and target lifetime have been observed. Thomson scattering and ion Doppler spectroscopy show significant heating (>100 eV) as the CT is compressed in the conical accelerator. B-dot probes show magnetic field structure consistent with Grad-Shafranov models and MHD simulations, and CT axial length depends strongly on the lambda profile.

  7. Development of Compact Toroid Injector for C-2 FRCs

    Science.gov (United States)

    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.

  8. Annual report, October 1, 1981-September 30, 1982

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, C.A. (ed.)

    1984-01-01

    The construction of the Tokamak Fusion Test Reactor (TFTR) has been proceeding in a highly satisfactory manner, giving confidence that the project schedule will be met. The vacuum vessel and toroidal-field coil systems are now in place, and the entire mechanical assembly process is about to be completed. Experimental operation of TFTR will begin with ohmic-heating studies in early CY83, and will proceed to intensive neutral-beam heating in CY84. Radio-frequency experiments on the Princeton Large Torus (PLT) have used a new 3-MW ion cyclotron heating source to demonstrate second-harmonic heating of hydrogen ions up to temperatures of 3 keV. Lower hybrid current drive has sustained plasma currents as large as 400 kA in quasi-steady state. The 7-MW neutral-beam-heating capability of the Poloidal Divertor Experiment (PDX) was utilized to investigate finite-beta stability limits. Beta values above 3% were achieved at safety factor values as low as 1.7. A physical mechanism for beta-limitation was discovered and documented: the energetic-ion-driven, fishbone mode of MHD instability. Construction of the S-1 spheromak is progressing on schedule, with preliminary experimental operation planned for early CY83.

  9. Demonstration of Multipulsed Current Drive Scenario using Coaxial Helicity Injection in the HIST Spherical Torus Plasmas

    International Nuclear Information System (INIS)

    Full text: The Helicity Injected Spherical Torus (HIST) device has been developed towards high-current start up and sustainment by Mutipulsed Coaxial Helicity Injection (M-CHI) method. Multiple pulses operation of the coaxial plasma gun can build the magnetic field of spherical torus (ST) and spheromak plasmas in a stepwise manner. Successive double gun pulses have been demonstrated to amplify the magnetic field and the plasma current against resistive decay. The resistive 3D-MHD numerical simulation has reproduced the current amplification by the M-CHI method and confirmed that stochastic magnetic field is reduced so that closed flux surfaces are created during the current drive. These experimental and computational results from STs have provided, for the first time, availability of a quasi-steady-state 'refluxing' mode in which the magnetic field is allowed to decay partially before being rebuilt. Our goal is to achieve simultaneously the good energy confinement and the current sustainment by the M-CHI method. (author)

  10. CTR plasma engineering studies. Annual progress report, 1 October 1980-30 September 1981

    International Nuclear Information System (INIS)

    During FY 81 much of the effort has been directed at the development of new models and codes involving the following three areas: (1) a 1 1/2-D code for startup and burn studies of high-β systems such as the spheromak and reversed field pinch (RFP); (2) a 1-D code for analysis of field reversed theta pinch (FR theta P) systems including scale up of present experiments and pilot reactor concepts; and (3) a dynamic burn code for analysis of pulsed systems such as the moving plasmoid reactor (MPR), including provisions for detailed treatment of high-energy particle slowing. Also refinement and extension of the continued work were performed on electric field control of impurity transport, 1-D radial hybrid start-up code for field-reversed mirror systems, nuclear elastic scattering and anomalous slowing effects on fusion product transport along with RFP start-up. Major findings and computer packages developed and tested with the corresponding systems are of vital information that can be used and compared for plasma behavior in the near-term systems

  11. Equilibrium and Stability Calculations in HIT-SI

    Science.gov (United States)

    Hansen, Chris; Marklin, George; Jarboe, Thomas

    2012-10-01

    The PSI-TET equilibrium code solves for solutions to the Ideal MHD equilibrium equation μ0j = λB in arbitrary 3D geometry. A mimetic discretization on a tetrahedral mesh is employed, with up to 3rd order spatial representation. Geometric and polynomial multigrid along with a hybrid MPI/OpenMP parallelism model is used to provide solver scalability. Lambda is allowed to vary across flux surfaces but must be constant in stochastic regions. A scalar flux surface variable is computed by solving an artificial diffusion problem with a large ratio of parallel to perpendicular thermal conductivity. A fixed lambda profile, specified as a function of this flux surface variable, is defined. Equilibria in HIT-SI have been computed for the homogenous (spheromak) and inhomogeneous (injector) fields separately. Combined equilibria of interest with injector driving have also been computed for various lambda profiles. A linearized Ideal MHD module has been developed to evaluate the stability properties of computed equilbria. Equilibrium states and stability analysis will be presented for a range of lambda profiles. Results will also be presented comparing linear to high order Mimetic representations and Mimetic to standard nodal finite element representations. Work supported by DOE.

  12. Maryland magnetic fusion research program: MS speromak

    International Nuclear Information System (INIS)

    The main theme of our present experimentation on MS is to prolong the spheromak lifetime. This research has been concerned with such topics as passive MHD stabilization coils, impurity control and increased energy storage. At the present time the longest lived plasmas appear to be line tied to the liner or reversal coils. The natural consequence of having net flux outside the separatrix and a resistive plasma is that the plasma shrinks in time. At some point in time the plasma is far enough from the liner, or stabilization coils, that it becomes unstable. If we increase the bias field so as to move the separatrix further inside the liner, the plasma becomes unstable earlier as the separatrix moves to a smaller radius in a shorter time than if it starts out outside the liner. We have tried to circumvent this behavior with various configurations of passive conductors used as stabilizing elements. In this paper, we detail some of the machine modifications that have been tried in attempts to produce a stable, long-lived plasma

  13. Fifty Years of Magnetic Fusion Research (1958–2008: Brief Historical Overview and Discussion of Future Trends

    Directory of Open Access Journals (Sweden)

    Laila A. El-Guebaly

    2010-06-01

    Full Text Available Fifty years ago, the secrecy surrounding magnetically controlled thermonuclear fusion had been lifted allowing researchers to freely share technical results and discuss the challenges of harnessing fusion power. There were only four magnetic confinement fusion concepts pursued internationally: tokamak, stellarator, pinch, and mirror. Since the early 1970s, numerous fusion designs have been developed for the four original and three new approaches: spherical torus, field-reversed configuration, and spheromak. At present, the tokamak is regarded worldwide as the most viable candidate to demonstrate fusion energy generation. Numerous power plant studies (>50, extensive R&D programs, more than 100 operating experiments, and an impressive international collaboration led to the current wealth of fusion information and understanding. As a result, fusion promises to be a major part of the energy mix in the 21st century. The fusion roadmaps developed to date take different approaches, depending on the anticipated power plant concept and the degree of extrapolation beyond ITER. Several Demos with differing approaches will be built in the US, EU, Japan, China, Russia, Korea, India, and other countries to cover the wide range of near-term and advanced fusion systems.

  14. Performance and stability limits at near-unity aspect ratio in the pegasus toroidal experiment

    International Nuclear Information System (INIS)

    The Pegasus Toroidal Experiment is a mid-sized extremely-low aspect ratio (A) spherical torus (ST). It has the dual roles of exploring limits of ST behavior as A approaches 1 and studying the physics of ST plasmas in the tokamak-spheromak overlap regime. Major parameters are R 0.25 - 0.45 m, A 1.1 - 1.4, Ip T 20% have been obtained, and the operational space of beta vs Ip/aBT is similar to that observed for NBI-heated START discharges. Achievable plasma current is subject to an apparent limit of Ip/Itf ∼ 1. Access to higher-current plasmas appears to be restricted by the appearance of large internal MHD activity, including m/n=2/1 and 3/2 modes. Recent experiments have begun to access ideal stability limits, with disruptions observed as q95 approaches 5, in agreement with numerical predictions for external kink mode onset. (author)

  15. Spontaneous and artificial generation of sheared flow in oblate FRCs in TS-3 and 4 FRC experiments

    International Nuclear Information System (INIS)

    Spontaneous formation of toroidal flow was measured for the first time in oblate FRCs produced in TS-3 and 4 experiments. The toroidal ion flow (Vi∼10km/sec) was found to peak around the magnetic axis, indicating formation of high flow shear inside the separatrix. The toroidal flow was observed to deform the magnetic field lines of the FRC, producing bipolar toroidal field profile. In high-s FRC (averaged number of ion gyro-radius 's'=4.5) with slow flow, its n=1 mode kept growing, causing collapse of the whole configuration. However, in low-s FRC (s=3) with fast flow, the rotating n=2 mode (saturated) became dominant after n=1 mode saturation. The spontaneous formation of flow shear possibly transformed the n=1 mode into the n=2 mode, suggesting a new sheared flow stabilization of n=1 mode. The flow shear was also generated artificially using the 'sling shot' effect of the counter helicity reconnection. The n=1 and 2 mode amplitudes were reduced down to 1/5-1/10 due to the generated flow shear. A new method for continuous sheared-flow generation was proposed for stabilization and heating of FRC by use of intermittent merging of spheromaks with opposing Bt. (author)

  16. Spontaneous and artificial generation of shear flow in oblate FRCs in TS-3 and 4 FRC experiments

    International Nuclear Information System (INIS)

    Spontaneous formation of toroidal flow shear was identified for the first time in oblate FRCs of TS-3 and 4 experiments. Their velocities around 10 km/sec were found to peak around the magnetic axes. In high-s FRC (averaged number of ion gyro-radius 's' ∼4.5) with low velocity, its n=1 mode kept growing, causing collapse of the whole configuration. However, in low-s FRC (s∼3) with fast flow, the rotating n=2 mode became dominant after n=1 mode saturation. The spontaneous formation of flow shear possibly transformed the n=1 mode into the n=2 rotational mode, suggesting a new flow-shear stabilization of n=1 mode. The forced generation of flow shear was also demonstrated using the 'sling shot' effect of the counterhelicity reconnection. The n=1 and 2 mode amplitudes were reduced by factor 5-10 due to the shear-flow. A new continuous generation of shear flow is being demonstrated for the stabilization and heating of FRC by use of multiple (more than two) merging of spheromaks with opposing Bt. (author)

  17. Spontaneous and artificial generation of sheared-flow in oblate FRCs in TS-3 and 4 FRC Experiments

    International Nuclear Information System (INIS)

    Spontaneous formation of toroidal flow was measured for the first time in oblate field-reversed configurations (FRCs) produced in TS-3 and TS-4 experiments. The toroidal ion flow (Vi ∼ 10 km s-1) was found to peak around the magnetic axis, indicating that the FRC had a peaked ion current in sharp contrast to its hollow electric current. The peaked ion flow also indicated the formation of high flow shear inside the separatrix. The toroidal flow was observed to deform the magnetic field lines of the FRC, producing bipolar toroidal field profile. In high-s FRC (averaged number of ion gyro-radii in the separatrix: 's' = 4.5) with slow flow, its n = 1 mode kept growing, causing collapse of the whole configuration. However, in low-s FRC (s = 3) with fast flow, the rotating n = 2 mode (saturated) became dominant after n = 1 mode saturation. The spontaneous formation of flow-shear possibly transformed the n = 1 mode into the n = 2 mode, suggesting a new sheared-flow stabilization of the n = 1 mode. The flow-shear was also generated artificially using the 'sling shot' effect of the counterhelicity reconnection. The n = 1 and 2 mode amplitudes were reduced to (1/5)-(1/10) due to the generated flow-shear. A new method for continuous sheared-flow generation was proposed for stabilization and heating of FRC by the use of intermittent merging of spheromaks with opposing toroidal field. (author)

  18. A mimetic spectral element solver for the Grad-Shafranov equation

    Science.gov (United States)

    Palha, A.; Koren, B.; Felici, F.

    2016-07-01

    In this work we present a robust and accurate arbitrary order solver for the fixed-boundary plasma equilibria in toroidally axisymmetric geometries. To achieve this we apply the mimetic spectral element formulation presented in [56] to the solution of the Grad-Shafranov equation. This approach combines a finite volume discretization with the mixed finite element method. In this way the discrete differential operators (∇, ∇×, ∇ṡ) can be represented exactly and metric and all approximation errors are present in the constitutive relations. The result of this formulation is an arbitrary order method even on highly curved meshes. Additionally, the integral of the toroidal current Jϕ is exactly equal to the boundary integral of the poloidal field over the plasma boundary. This property can play an important role in the coupling between equilibrium and transport solvers. The proposed solver is tested on a varied set of plasma cross sections (smooth and with an X-point) and also for a wide range of pressure and toroidal magnetic flux profiles. Equilibria accurate up to machine precision are obtained. Optimal algebraic convergence rates of order p + 1 and geometric convergence rates are shown for Soloviev solutions (including high Shafranov shifts), field-reversed configuration (FRC) solutions and spheromak analytical solutions. The robustness of the method is demonstrated for non-linear test cases, in particular on an equilibrium solution with a pressure pedestal.

  19. Comparative study of the electron density profiles in the compact torus plasma merging experiments

    International Nuclear Information System (INIS)

    Following two previous papers on the comparative studies of the electron density distributions for a single compact torus (CT) and a spherical tokamak (ST), and for the a single ST and a merged ST, a comparative study on the dynamics of the electron density profile and after the CT and ST plasma merging process was performed. The sharpness of the peak in the electron density profile around the mid-plane just after the merging of CT with a low safety factor (q value) such as RFP or spheromak is found to be related to the speed of the magnetic axis during the plasma merging process. It is also found that the electron density gradient near the plasma edge in a high q ST is larger than that of a low q CT. High q ST is found to be provided with the magnetic structure which is able to sustain a large thermal pressure by a strong j x B force. Despite these differences in the electron density profile between CT and ST during merging, the confinement characteristics evaluated from the number of electrons confined within the magnetic separatrix after the completion of the merging is almost similar between in the merging CT and in the merging ST. For all configurations, the electron density profiles after the completion of the merging are analogous to those of the corresponding single configuration produced without the merging process. (author)

  20. Interaction of the neutral deuterium flux with a field-reversed configuration

    International Nuclear Information System (INIS)

    Recycling effects arising from the penetration of cold neutrals into a hot plasma has been known to contribute to confinement properties of tokamaks, mirrors, RFPs, and spheromaks. To data, however, ionization and charge exchange processes associated with the possible influx of neutrals have been neglected in FRC transport models, or their effects have been found negligible for experiments with short lifetimes (< 20 μs). These processes are also neglected when ascertaining the experimental particle confinement time tau/sub N/. As experimental FRC lifetimes have recently been extended to record values (greater than or equal to 300 μs), these effects on transport may no longer be negligible. Furthermore, these losses can be enhanced when FRCs translate at axial speeds much greater than the thermal speeds of the neutrals. The purpose of this analysis is to examine the interaction of neutral deuterium with an FRC. The relevant atomic and molecular processes are reviewed. A simple, steady-state, multi-species 1-D (radial) neutral transport model is described and applied to FRC plasma parameters observed earlier. Estimates of the power loss due to these neutrals are made for both stationary and translating plasmas

  1. Investigation on the relation between edge radial electric field asymmetries in RFX-mod and density limit

    Energy Technology Data Exchange (ETDEWEB)

    Spizzo, Gianluca; Scarin, Paolo; Agostini, Matteo; Alfier, Alberto; Auriemma, Fulvio; Bonfiglio, Daniele; Cappello, Susanna; Fassina, Alessandro; Franz, Paolo; Piron, Lidia; Piovesan, Paolo; Puiatti, Maria Ester; Valisa, Marco; Vianello, Nicola, E-mail: gianluca.spizzo@igi.cnr.i, E-mail: paolo.scarin@igi.cnr.i [Consorzio RFX, Euratom-ENEA Association, Padova (Italy)

    2010-09-15

    In all major confinement devices (tokamaks, stellarators, spheromaks and reversed-field pinches-RFPs), a density limit has been found. Results summarized in a recent work by Puiatti et al (2009 Nucl. Fusion 49 045012) show that in the RFP high density does not cause a disruption, but a sequence of increasingly critical phenomena. First, at intermediate density there is the disappearance of the high-confinement quasisingle helicity/single helical axis regimes. Then, at densities close to the Greenwald limit, toroidally and radially localized density accumulation and radiation condensation are observed, together with a fast resistive decay of the plasma current, which constitutes the real operative limit of the device. In this paper we discuss the effect of the magnetic ripple on test particle motion, showing that the accumulation of electrons in the X-points of the edge m = 0 islands is responsible for a modulation of the radial electric field E{sub r} which is at the core of the density limit mechanism. These results can be also relevant for the explanation of X-point multifaceted asymmetric radiation from the edge formation, observed in L-mode density limit discharges of JET.

  2. A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. III. Catastrophe of the Eruptive Filament in a Magnetic Null Point and Formation of an Opposite-Handedness CME

    CERN Document Server

    Uralov, A M; Rudenko, G V; Myshyakov, I I; Chertok, I M; Filippov, B P; Slemzin, V A

    2014-01-01

    Our analysis in Papers I and II (Grechnev et al., 2014, Solar Phys. 289, 289 and 1279) of the 18 November 2003 solar event responsible for the 20 November geomagnetic superstorm has revealed a complex chain of eruptions. In particular, the eruptive filament encountered a topological discontinuity located near the solar disk center at a height of about 100 Mm, bifurcated, and transformed into a large cloud, which did not leave the Sun. Concurrently, an additional CME presumably erupted close to the bifurcation region. The conjectures about the responsibility of this compact CME for the superstorm and its disconnection from the Sun are confirmed in Paper IV (Grechnev et al., Solar Phys., submitted), which concludes about its probable spheromak-like structure. The present paper confirms the presence of a magnetic null point near the bifurcation region and addresses the origin of the magnetic helicity of the interplanetary magnetic clouds and their connection to the Sun. We find that the orientation of a magnetic...

  3. Ultrashort pulse reflectometry for electron density profile measurements on SSPX

    International Nuclear Information System (INIS)

    A broadband ultrashort pulse reflectometry (USPR) diagnostic has been developed for measuring electron density profiles of the sustained spheromak physics experiment (SSPX) device. In USPR, an extremely short pulse or chirped wave form is propagated which contains a broad range of frequency components spanning the desired plasma density profile (or a significant fraction thereof). Upon reflection, each frequency component in the incident waveform reflects from a different spatial location (density layer) in the plasma, thus spreading out the reflected wave packet in time. By simultaneously collecting double-pass time delay data at many distinct frequencies, the time delay data may then be inverted to generate plasma density profiles using a single source and a single set of measurements. On SSPX, wideband mixers are utilized to up- and downconvert 6--18 GHz chirp signals to millimeter-wave frequencies (33--158 GHz) to form a 48 channel O-mode reflectometer system. In this article we describe details of the new USPR system installed on the SSPX device and provide preliminary time-of-flight results

  4. Annual report, October 1, 1981-September 30, 1982

    International Nuclear Information System (INIS)

    The construction of the Tokamak Fusion Test Reactor (TFTR) has been proceeding in a highly satisfactory manner, giving confidence that the project schedule will be met. The vacuum vessel and toroidal-field coil systems are now in place, and the entire mechanical assembly process is about to be completed. Experimental operation of TFTR will begin with ohmic-heating studies in early CY83, and will proceed to intensive neutral-beam heating in CY84. Radio-frequency experiments on the Princeton Large Torus (PLT) have used a new 3-MW ion cyclotron heating source to demonstrate second-harmonic heating of hydrogen ions up to temperatures of 3 keV. Lower hybrid current drive has sustained plasma currents as large as 400 kA in quasi-steady state. The 7-MW neutral-beam-heating capability of the Poloidal Divertor Experiment (PDX) was utilized to investigate finite-beta stability limits. Beta values above 3% were achieved at safety factor values as low as 1.7. A physical mechanism for beta-limitation was discovered and documented: the energetic-ion-driven, fishbone mode of MHD instability. Construction of the S-1 spheromak is progressing on schedule, with preliminary experimental operation planned for early CY83

  5. Temporal and spatial turbulent spectra of MHD plasma and an observation of variance anisotropy

    International Nuclear Information System (INIS)

    The nature of magnetohydrodynamic (MHD) turbulence is analyzed through both temporal and spatial magnetic fluctuation spectra. A magnetically turbulent plasma is produced in the MHD wind tunnel configuration of the Swarthmore Spheromak Experiment. The power of magnetic fluctuations is projected into directions perpendicular and parallel to a local mean field; the ratio of these quantities shows the presence of variance anisotropy which varies as a function of frequency. Comparisons among magnetic, velocity, and density spectra are also made, demonstrating that the energy of the turbulence observed is primarily seeded by magnetic fields created during plasma production. Direct spatial spectra are constructed using multi-channel diagnostics and are used to compare to frequency spectra converted to spatial scales using the Taylor hypothesis. Evidence for the observation of dissipation due to ion inertial length scale physics is also discussed, as well as the role laboratory experiments can play in understanding turbulence typically studied in space settings such as the solar wind. Finally, all turbulence results are shown to compare fairly well to a Hall-MHD simulation of the experiment.

  6. Advanced fusion concepts project summaries, FY 1988

    International Nuclear Information System (INIS)

    This report summarizes all the projects supported by the Advanced Fusion Concepts Branch of the Applied Plasma Physics Division of the Office of Fusion Energy, US Department of Energy. Each project summary was written by the respective principal investigator using the format: title, principal investigators, funding levels, purpose, approach, progress, plans, milestones, graduate students, graduates, other professional staff, and recent publications. This report is organized into three sections: Section one contains five summaries describing work in the reversed-field pinch program being performed by a diversified group of contractors, these include a national laboratory, a private company, and several universities. Section two contains eight summaries of work from the compact toroid area which encompasses field-reversed configurations, spheromaks, and heating and formation experiments. Section three contains summaries from two other programs, a density Z-pinch experiment and high-beta Q machine experiment. The intent of this collection of project summaries is to help the contractors of the Advanced Fusion Concepts Branch understand their relationship with the rest of the branch's activities. It is also meant to provide background to those outside the program by showing the range of activities of interest of the Advanced Fusion Concepts Branch

  7. Study of plasma equilibrium in toroidal fusion devices using mesh-free numerical calculation method

    Science.gov (United States)

    Rasouli, C.; Abbasi Davani, F.; Rokrok, B.

    2016-08-01

    Plasma confinement using external magnetic field is one of the successful ways leading to the controlled nuclear fusion. Development and validation of the solution process for plasma equilibrium in the experimental toroidal fusion devices is the main subject of this work. Solution of the nonlinear 2D stationary problem as posed by the Grad-Shafranov equation gives quantitative information about plasma equilibrium inside the vacuum chamber of hot fusion devices. This study suggests solving plasma equilibrium equation which is essential in toroidal nuclear fusion devices, using a mesh-free method in a condition that the plasma boundary is unknown. The Grad-Shafranov equation has been solved numerically by the point interpolation collocation mesh-free method. Important features of this approach include truly mesh free, simple mathematical relationships between points and acceptable precision in comparison with the parametric results. The calculation process has been done by using the regular and irregular nodal distribution and support domains with different points. The relative error between numerical and analytical solution is discussed for several test examples such as small size Damavand tokamak, ITER-like equilibrium, NSTX-like equilibrium, and typical Spheromak.

  8. Models of large-scale magnetic fields in stellar interiors. Application to solar and ap stars

    International Nuclear Information System (INIS)

    Stellar astrophysics needs today new models of large-scale magnetic fields, which are observed through spectropolarimetry at the surface of Ap/Bp stars, and thought to be an explanation for the uniform rotation of the solar radiation zone, deduced from helio seismic inversions. During my PhD, I focused on describing the possible magnetic equilibria in stellar interiors. The found configurations are mixed poloidal-toroidal, and minimize the energy for a given helicity, in analogy with Taylor states encountered in spheromaks. Taking into account the self-gravity leads us to the 'non force-free' equilibria family, that will thus influence the stellar structure. I derived all the physical quantities associated with the magnetic field; then I evaluated the perturbations they induce on gravity, thermodynamic quantities as well as energetic ones, for a solar model and an Ap star. 3D MHD simulations allowed me to show that these equilibria form a first stable states family, the generalization of such states remaining an open question. It has been shown that a large-scale magnetic field confined in the solar radiation zone can induce an oblateness comparable to a high core rotation law. I also studied the secular interaction between the magnetic field, the differential rotation and the meridional circulation in the aim of implementing their effects in a next generation stellar evolution code. The influence of the magnetism on convection has also been studied. Finally, hydrodynamic processes responsible for the mixing have been compared with diffusion and a change of convection's efficiency in the case of a CoRoT star target. (author)

  9. Calculation of Boozer magnetic coordinates for multiple plasma regions (with either closed or open flux surfaces) connected by magnetic separatrices

    International Nuclear Information System (INIS)

    Magnetic coordinates (ψT=radial label of flux surfaces, θ=poloidal, and φ=toroidal angle) are introduced in toroidal magnetoplasma equilibria in order to straighten the field lines [described by: θ-ι(ψT)φ=constant on any flux surface, ι/(ψT) being the rotational transform]. The simplest method for analyzing the ideal magnetohydrodynamic (MHD) stability expands the perturbed plasma displacement ξ-vector in magnetic coordinates and solves the normal mode equation through one-dimensional (1D) radial finite elements. This paper extends the calculation of (Boozer) magnetic coordinates to simply connected equilibria that embed a magnetic separatrix, with regular X-points (B-vector≠0), and reach the symmetry axis, with singular magnetic X-points (B-vector=0). These configurations include multiple plasma regions, whose outermost one (surrounding plasma) is not composed by toroidal surfaces closed around a single magnetic axis. Two examples are chosen: (i) flux-core-spheromak (FCS) configurations, where the surrounding plasma is a screw pinch, with open flux surfaces; (ii) Chandrasekhar-Kendall-Furth (CKF) configurations, where it is a toroidal shell, carved by multiple toroidal plasma regions. This paper shows that a proper ordering of the radial coordinate ψT, the requirement of continuity for θ and φ and an ι matching condition (between neighboring mesh points on opposite sides of the connecting separatrix) resolve the ambiguities in the definition of magnetic coordinates in both CKF and FCS cases. However, a few metric coefficients diverge at the separatrices; therefore, often numerical MHD stability codes do not use magnetic coordinates there, but adopt local two-dimensional (2D) finite elements. This paper instead investigates all the divergences, in order to allow for the asymptotic analysis of ξ-vector near the separatrices, with the purpose of maintaining the magnetic coordinate method and the 1D radial finite elements in the ideal MHD stability

  10. Engineering overview of the National Spherical Tokamak Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Chrzanowski, J.H.; Fan, H.M.; Heitzenroeder, P.J.; Ono, M.; Robinson, J. [Princeton Plasma Physics Lab., NJ (United States)

    1995-12-31

    The National Spherical Tokamak Experiment (NSTX) is an ultra low aspect ratio device designed for a plasma current of 1 MA. It features auxiliary heating and current drive and a close-fitting conducting shell to maximize plasma pressure. NSTX is designed for a 5 sec. experimental pulse to demonstrate quasi-steady state non-inductively driven advanced tokamak operation. The device will be sited in the former Princeton Large Torus (PLT) test cell and will utilize the PLT radiation shielding, base structure, and cell utilities. NSTX will utilize the S-1 Spheromak vacuum vessel, poloidal field coils, and capacitor banks (for helicity injection). The poloidal Beta Experiment-Modified (PBX-M) power supplies will be shared to power the PF and TF coil systems. Existing RF hardware and infrastructure will be used for heating systems. TFTR data acquisition and diagnostics resources are planned to be used. In total, NSTX will utilize site credits with a value of {approximately}$50 M, reducing base construction cost of the device to $18.6 M. Twelve water-cooled copper demountable toroidal field (TF) coils provide the 5.4 kg (pulsed) and 3.5 kg (long pulse > 5 sec) toroidal field at the plasma center. Poloidal fields are generated by windings contained in the center column and four pairs water-cooled copper coils supported directly on the vacuum vessel. One of the most critical components of the device is the center stack, which consists of the inner legs of the TF coils overwrapped with ohmic heating and poloidal field windings. The ohmic heating coil windings are designed to optimize the V-s and together with the PF coils, produce a flux swing of 1 V-s.

  11. Princeton Plasma Physics Laboratory annual report, October 1, 1982-September 30, 1983

    International Nuclear Information System (INIS)

    The Tokamak Fusion Test Reactor (TFTR) achieved first plasma at 3:05 a.m. on December 24, 1982. During the course of the year, the plasma current was raised to a maximum of 1 MA, and extensive confinement studies were carried out with ohmic-heated plasmas. The most important finding was that tokamak energy confinement time increases as the cube of the plasma size. The Princeton Large Torus (PLT) carried out a number of high-powered plasma-heating experiments in the ion cyclotron frequency range, and also demonstrated for the first time that a 100-kA tokamak discharge can be built up by means of rf-waves in the lower hybrid range, without any need for inductive current drive by the conventional tokamak transformer system. The Poloidal Divertor Experiment (PDX) demonstrated that substantial improvements in plasma confinement during intense neutral-beam heating can be obtained by means of either a magnetic divertor or a mechanical scoop limiter. The S-1 spheromak experiment has come into operation, with first plasma in January 1983, and machine completion in August. The soft X-ray laser development experiment continues to make strong progress towards the demonstration of laser amplification. Thus far, a single-pass gain of 3.5 has been achieved, using the 182 A line of CVI. Theoretical MHD-stability studies have shed new light on the nature of the energetic-ion-driven ''fishbone instability,'' and the utilization of the bean-shaping technique to reach higher beta values in the tokamak

  12. Eigenvalues of relaxed toroidal plasmas of arbitrary sharp edged cross sections. Vol. 2

    International Nuclear Information System (INIS)

    Relaxed (force-free) toroidal plasmas described by the equations cur 1 B=μB, and grad μ=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 μ plays an important roll in relaxed states. It cannot exceed the smallest eigenvalue μ (min), and that for a toroidal discharge there is a maximum toroidal current which is connected to this value. The values ofμ were calculated numerically, using the methods of collocation points, for toroids of arbitrary aspect ratio α (α = 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 μ (min), satisfy the boundary condition β .n = O (or RB. = O) for which the toroidal flux are calculated. These are the zero field eigenvalues of the equation cur 1 b=μB. 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 μa on aspect ratio α is also obtained. Several runs of the programme with various wave numbers K showed that μa is very insensitive to the choice of K. 8 figs

  13. Kinetic stabilization of field-reversed configurations

    International Nuclear Information System (INIS)

    The tilt instability in field-reversed configurations (FRC's) may be roughly divided into two categories, depending on the nature of the unstable eigenfunction. The internal tilt instability, which could also be called an n = 1 ballooning mode, is defined here to be an instability in which the displacement of the flux surfaces is confined to the closed region of magnetic field and the separatrix remains fixed in time. Since, for a fixed separatrix, the only destabilizing term in deltaW is proportional to the pressure gradient times the parallel curvature of the magnetic field, the internal tilt could be considered a ''pressure'' driven mode. The external tilt is defined here to be an instability in which the entire closed field line FRC rotates rigidly about some axis perpendicular to the symmetry axis of the FRC. The external tilt results from magnetic interactions involving the toroidal plasma current. In spheromaks (at zero beta) the tilt instability is due to these same interactions, so in this sense the external mode might be considered ''current'' driven. However, since in FRC's the toroidal current comes solely from having finite plasma pressure, the distinction between pressure and current driven instabilities in FRC's is not meaningful (there is no parallel current). For oblate FRC's the eigenfunction of the external tilt is a rigid rotation of the closed field line FRC. For FRC's that are only moderately prolate the distinction between internal and external tilt modes is not clear, and the eigenfunction of the tilt mode may be a combination of internal and external displacements of the flux surfaces

  14. Princeton Plasma Physics Laboratory annual report, October 1, 1982-September 30, 1983

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, C.A. (ed.)

    1983-01-01

    The Tokamak Fusion Test Reactor (TFTR) achieved first plasma at 3:05 a.m. on December 24, 1982. During the course of the year, the plasma current was raised to a maximum of 1 MA, and extensive confinement studies were carried out with ohmic-heated plasmas. The most important finding was that tokamak energy confinement time increases as the cube of the plasma size. The Princeton Large Torus (PLT) carried out a number of high-powered plasma-heating experiments in the ion cyclotron frequency range, and also demonstrated for the first time that a 100-kA tokamak discharge can be built up by means of rf-waves in the lower hybrid range, without any need for inductive current drive by the conventional tokamak transformer system. The Poloidal Divertor Experiment (PDX) demonstrated that substantial improvements in plasma confinement during intense neutral-beam heating can be obtained by means of either a magnetic divertor or a mechanical scoop limiter. The S-1 spheromak experiment has come into operation, with first plasma in January 1983, and machine completion in August. The soft X-ray laser development experiment continues to make strong progress towards the demonstration of laser amplification. Thus far, a single-pass gain of 3.5 has been achieved, using the 182 A line of CVI. Theoretical MHD-stability studies have shed new light on the nature of the energetic-ion-driven ''fishbone instability,'' and the utilization of the bean-shaping technique to reach higher beta values in the tokamak.

  15. Improved stability and confinement in a novel high-β spherical-torus-like field-reversed configuration

    International Nuclear Information System (INIS)

    A novel spherical-torus- (ST-) like field-reversed configuration (FRC), with an extremely high-β (over 85%), has been produced in the translation, confinement, and sustainment (TCS) experiment by highly super Alfvenic translation of a spheromak-like plasmoid [H.Y. Guo, A.L. Hoffman, K.E. Miller et. al, Phys. Rev. Lett. 92, 245001 (2004)]. Such a compact FRC-ST carries predominantly a diamagnetic current with the toroidal field magnitude much smaller than that of the poloidal field. However, when combined with the high elongation and small aspect ratio, it results in a safety factor exceeding unity over much of the configuration with a significant magnetic shear near the edge. Relaxation has been demonstrated, for the first time, in such a high-β plasma state, i.e., clearly not a Taylor state. Modeling using the newly developed nearby-fluids theory [L.C. Steinhauer, and H.Y. Guo, 'Nearby-fluids equilibria - II: zonal flows in a high-β, self-organized plasma experiment', Phys. Plasmas 13 (2006); in press] shows that a broad core of the FRC-ST resembles a two-fluid minimum energy state. This FRC-ST state exhibits significantly reduced transport with up to four times improvement in confinement [H.Y. Guo, A.L. Hoffman, L.C. Steinhauer et al., Phys. Rev. Lett. 95, 175001 (2005)] over the scaling of conventional θ-pinch formed FRCs. It also exhibits remarkable stability to global low-n modes such as the normally lifetime terminating n=2 centrifugally driven interchange modes present in θ-pinch FRCs. This is explained, for the first time, by a simple stability model, accounting for the magnetic shear of the unique FRC-ST configuration. Comparisons will also be made with the calculations from a 3D two-fluid NIMROD code. (author)

  16. KTM Tokamak is prototype of X XI century reactor. Future International laboratory of thermonuclear materials testing and power engineering

    International Nuclear Information System (INIS)

    In 29-31 May of 2000 the presentation of the joint Kazakhstan-Russian draft of Kazakhstan material-testing tokamak (KTM) was carried out. KTM tokamak is implementing by decision of the President and Government of Republic of Kazakhstan for supporting of the Kazakhstan participation in development of draft within framework of ITER fusion reactor construction. Scientific head of the project is Russian academician - Velikhov V. and Russian Research Center 'Kurchatovskij Institute' , General designers - Scientific Research Institute for Electrophysical Equipment after D. V. Efremov (Russian Federation) and Kazakh Research Inst. for Energy Industry (KazNIIEhnergoprom). Scientific part of the project is working out in National Nuclear Center of Republic of Kazakhstan and Scientific Research Institute of Experimental and Theoretical Physics. KTM tokamak is experimental fusion device for materials testing study, as well as for designing of methods for protection of the reactor first wall, in-chamber elements and divertor planes, high frequency heat of antennas in energetic load regimes close to both the ITER and the future fusion energy reactors. KTM by it design presents spheric tokamak, which successfully combining advantages of the spheromaks (compactness) and the tokamaks (high plasma density). Now in the world there are similar operating spheric tokamaks: NSTX (USA), MAST (Great Britain), GLOBUS-M (Russian Federation). Principal peculiarity of KTM tokamak is existence of moving divertor device, which with help of manipulator allows to changing of examining samples without high vacuum disruption. Values of the thermal loads and fluences in the KTM are equal or higher than loads in operating tokamaks and correspond with ITER reactor loads. KTM tokamak will be the only mega-ampere device in the world with the aspect ratio A=2

  17. The End of the Turbulent Cascade?: Exploring possible signatures of MHD turbulent dissipation beyond spectra in a magnetically-dynamic laboratory plasma

    Science.gov (United States)

    Schaffner, David

    2015-11-01

    A typical signature of dissipation in conventional fluid turbulence is the steepening power spectrum of velocity fluctuations, signaling the transition from the inertial range to the dissipation range where scales become small enough for fluid viscosity effects to be dominant and convert flow energy into thermal energy. In MHD fluids, resistivity can play an analogous role to viscosity for magnetic field fluctuations, where collisional scales determine the onset of dissipation. However, turbulent plasmas can exhibit other mechanisms for converting magnetic energy into thermal energy such as through the generation of current sheets and magnetic reconnection or through coupling to kinetic scale fluctuations such as Kinetic Alfven waves or Whistler waves. In collisionless plasmas such as the solar wind, only these alternative dissipation mechanisms are likely active. Recent experiments with MHD turbulence generated in the wind-tunnel configuration of the Swarthmore Spheromak Experiment (SSX) provide an environment in which various potential non-resistive signatures of magnetic turbulent energy dissipation can be studied. SSX plasma is magnetically dynamic with no background field. Previous work has demonstrated that a steepening in the magnetic fluctuation spectrum is observed which can be roughly interpreted as a transition from inertial range to a dissipation range magnetic turbulence. The frequency range at which this steepening occurs can be correlated to the ion inertial scale of the plasma, a length which is characteristic of the size of current sheets in MHD plasmas. Detailed intermittency and structure function analysis presented here coupled with appeals to fractal scaling models support the hypothesis that the observed turbulence is being affected by a global dissipation mechanism such as the generation of current sheets. Information theory based analysis techniques using permutation entropy and statistical complexity are also applied to seek dissipation

  18. Ideal MHD stability calculations in presence of magnetic separatrices

    International Nuclear Information System (INIS)

    The use of magnetic coordinates, in which field lines are straight, defines the simplest approach to the numerical study of the ideal MHD stability of magnetoplasma equilibria: it allows the use of 1-dimensional radial finite elements, while adopting a Fourier decomposition in the poloidal angle. However the magnetic coordinates become singular in presence of magnetic separatrices. This difficulty becomes particularly relevant in the stability analysis of a simply connected axisymmetric plasmas (Flux-Core-Spheromak or Chandrasekhar-Kendall-Furth configurations), which embed a magnetic separatrix with regular X-points (B different from 0) and are bounded by an edge magnetic separatrix that includes a part of the symmetry axis (R=0) and is limited by two singular X-points (B=0). The approach taken in the present paper is that of maintaining the 1-dimensional radial finite elements, while using an asymptotic analysis of the perturbed plasma displacement near the separatrices. The permissible asymptotic limits for the perturbed displacement are derived: they have simple analytical expressions in Boozer magnetic coordinates. An intensified numerical radial mesh following Boozer magnetic coordinates is set up near the magnetic separatrices; it requires: a logarithmic fit to the rotational transform near the embedded magnetic separatrix; a minimum distance between the radial mesh and both separatrices; finally an extended spectrum of poloidal mode numbers in the Boozer angle. The numerical results are compared with the permissible asymptotic limits for the perturbed displacement. The radial displacement variable (radial contra-variant component of the perturbed displacement) is found to be always near to its most unstable asymptotic limit, while the full range of permissible asymptotic behaviours can be obtained for the bi-normal and parallel displacement variables (which are combinations of the poloidal and toroidal contra-variant components of the perturbed displacement

  19. Exploiting laboratory and heliophysics plasma synergies

    Energy Technology Data Exchange (ETDEWEB)

    Dahlburg, J.; Amatucci, W.; Chen, J.; Chua, D.; Dahlburg, R.; Doschek, G.; Howard, R.; Huba, J.; Ko, Y.-K.; Krall, J.; Laming, J. M.; Linton, M.; Lukin, V; Murphy, R.; Rakowski, C.; Socker, D.; Tylka, A.; Vourlidas, A.; Warren, H.; Wood, B. [Naval Research Laboratory, Washington, DC 20375 (United States); Brown, M. [Swarthmore College, Swarthmore, PA 19081 (United States); Chan, V. [General Atomics, San Diego, CA 92186 (United States); Cothran, Ch. [Global Defense Technology and Systems, Inc., Crofton, MD 21114 (United States); Egedal, J. [Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Forest, C. [University of Wisconsin, Madison, WI 53706 (United States); Lin, R. [University of California, Berkeley, CA 94720 (United States)

    2010-07-01

    direct experimental observation of reconnection dynamics; and the Swarthmore Spheromak Experiment, which provides well-diagnosed data on three-dimensional (3D) null-point magnetic reconnection that is also applicable to solar active regions embedded in pre-existing coronal fields. New computer capabilities highlighted include: HYPERION, a fully compressible 3D magnetohydrodynamics (MHD) code with radiation transport and thermal conduction; ORBIT-RF, a 4D Monte-Carlo code for the study of wave interactions with fast ions embedded in background MHD plasmas; the 3D implicit multi-fluid MHD spectral element code, HiFi; and, the 3D Hall MHD code VooDoo. Research synergies for these new tools are primarily in the areas of magnetic reconnection, plasma charged particle acceleration, plasma wave propagation and turbulence in a diverging magnetic field, plasma atomic processes, and magnetic dynamo behavior. (author)

  20. Development of a Neutral Particle Flow Fueling System by using a Compact Torus Plasma Injector for LHD

    International Nuclear Information System (INIS)

    Full text: The Compact toroid (CT) fueler of SPICA (SPheromak Injector using Conical Accelerator) for LHD has been developed at NIFS. Recently, in order to apply CT injection technique to more effective fueling, production and injection of super-high speed neutral particle flow (NPF) have been studied. The NPF injection has a performance advantage over supersonic gas jet and can play a specific role beyond neutral beam injection (NBI). We have then proposed a fueling system of CT-based NPF injection. The system may allow us to make various plasma controls. The SPICA injector had two-stage coaxial electrodes for CT formation and acceleration. However, for practical setup of SPICA on LHD, the system should be simple and reliable for easy operation and maintenance. We thus attempted single-stage operation by connecting only the acceleration bank unit to both electrodes. By using the simple SPICA injector, we launched the study on production of super-high speed NPF in the following scenario; SPICA accelerates a CT plasmoid and injects it into a long drift tube as a neutralizer cell filled with hydrogen gas, then super-high speed NPF is produced through charge-exchange (CX) reaction between CT plasma and neutral gas. In the first phase of the experiment, we have investigated the performance of the simple SPICA. CT speed was obtained to be ∼ 100 km/s and CT density was up to 1 x 1022 m-3. Although the speed is rather low, the density is remarkably high. If the CT plasmoid is completely neutralized, the particle inventory of NPF is estimated to be 2 x 1020 from the FWHM of an electron density signal. This can provide a density increment of 7 x 1018 m-3 in an LHD plasma. The penetration depth of NPF is estimated roughly at 6 mm, which is several hundredths of that of NBI. The input power is, however, calculated to be 32 MW since the NPF is injected at a short pulse of about 100x10-6 s. The injector corresponds to a NBI at 100 eV and 320 kA. It would be almost impossible

  1. Exploiting laboratory and heliophysics plasma synergies

    International Nuclear Information System (INIS)

    direct experimental observation of reconnection dynamics; and the Swarthmore Spheromak Experiment, which provides well-diagnosed data on three-dimensional (3D) null-point magnetic reconnection that is also applicable to solar active regions embedded in pre-existing coronal fields. New computer capabilities highlighted include: HYPERION, a fully compressible 3D magnetohydrodynamics (MHD) code with radiation transport and thermal conduction; ORBIT-RF, a 4D Monte-Carlo code for the study of wave interactions with fast ions embedded in background MHD plasmas; the 3D implicit multi-fluid MHD spectral element code, HiFi; and, the 3D Hall MHD code VooDoo. Research synergies for these new tools are primarily in the areas of magnetic reconnection, plasma charged particle acceleration, plasma wave propagation and turbulence in a diverging magnetic field, plasma atomic processes, and magnetic dynamo behavior. (author)

  2. Research using small tokamaks

    International Nuclear Information System (INIS)

    discharges, production and self-organization of a turbulent plasma column in a spheromak (''SK-CG-1''), and (iv) a planned large-aspect ratio, high-beta tokamak (HBT-EP) experiment. Refs, figs and tabs

  3. Theoretical Study of Radiation from a Broad Range of Impurity Ions for Magnetic Fusion Diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Safronova, Alla [Univ. of Nevada, Reno, NV (United States)

    2014-03-14

    Spectroscopy of radiation emitted by impurities plays an important role in the study of magnetically confined fusion plasmas. The measurements of these impurities are crucial for the control of the general machine conditions, for the monitoring of the impurity levels, and for the detection of various possible fault conditions. Low-Z impurities, typically present in concentrations of 1%, are lithium, beryllium, boron, carbon, and oxygen. Some of the common medium-Z impurities are metals such as iron, nickel, and copper, and high-Z impurities, such as tungsten, are present in smaller concentrations of 0.1% or less. Despite the relatively small concentration numbers, the aforementioned impurities might make a substantial contribution to radiated power, and also influence both plasma conditions and instruments. A detailed theoretical study of line radiation from impurities that covers a very broad spectral range from less than 1 Å to more than 1000 Å has been accomplished and the results were applied to the LLNL Electron Beam Ion Trap (EBIT) and the Sustained Spheromak Physics Experiment (SSPX) and to the National Spherical Torus Experiment (NSTX) at Princeton. Though low- and medium-Z impurities were also studied, the main emphasis was made on the comprehensive theoretical study of radiation from tungsten using different state-of-the-art atomic structure codes such as Relativistic Many-Body Perturbation Theory (RMBPT). The important component of this research was a comparison of the results from the RMBPT code with other codes such as the Multiconfigurational Hartree–Fock developed by Cowan (COWAN code) and the Multiconfiguration Relativistic Hebrew University Lawrence Atomic Code (HULLAC code), and estimation of accuracy of calculations. We also have studied dielectronic recombination, an important recombination process for fusion plasma, for variety of highly and low charged tungsten ions using COWAN and HULLAC codes. Accurate DR rate coefficients are needed for

  4. Exploiting Laboratory and Heliophysics Plasma Synergies

    Directory of Open Access Journals (Sweden)

    Jill Dahlburg

    2010-05-01

    provides direct experimental observation of reconnection dynamics; and the Swarthmore Spheromak Experiment, which provides well-diagnosed data on three-dimensional (3D null-point magnetic reconnection that is also applicable to solar active regions embedded in pre-existing coronal fields. New computer capabilities highlighted include: HYPERION, a fully compressible 3D magnetohydrodynamics (MHD code with radiation transport and thermal conduction; ORBIT-RF, a 4D Monte-Carlo code for the study of wave interactions with fast ions embedded in background MHD plasmas; the 3D implicit multi-fluid MHD spectral element code, HiFi; and, the 3D Hall MHD code VooDoo. Research synergies for these new tools are primarily in the areas of magnetic reconnection, plasma charged particle acceleration, plasma wave propagation and turbulence in a diverging magnetic field, plasma atomic processes, and magnetic dynamo behavior.

  5. Final Technical Report for NSF/DOE partnership grant 1004284/ER54905/SC0004660; 2011- 2013

    Energy Technology Data Exchange (ETDEWEB)

    Stenzel, Reiner [University of California, Los Angeles, CA (United States); Urrutia, Manuel [University of California, Los Angeles, CA (United States)

    2014-10-15

    Research has been performed on two topics: (1) Nonlinear time-dependent phenomena in the regime of electron magnetohydrodynamics (EMHD). (2) Plasma structures forming ”bubbles”. The latter are regions of localized density depletions or enhancements separated from the ambient plasma by sheaths or double layers. Three-dimensional magnetic null points can also be considered as ”magnetic bubbles”. Nonlinear EMHD fields are generated by pulsed magnetic loops. The magnetic field varies in time faster than an ion cyclotron period, hence interacts only with electrons. Space charge electric fields are created when magnetic forces try to separate electrons from ions. Electric and magnetic forces nearly balance to keep the plasma quasi neutral. This leads to rotational electron motions, i.e. Hall currents and associated magnetic perturbations. When the time scale falls between the ion and electron cyclotron period the magnetic perturbation is convected in the whistler mode. When the time-varying magnetic field exceeds the background magnetic field the whistler mode becomes highly nonlinear since its properties depend on the total magnetic field. When the time-varying magnetic field creates magnetic null points or null lines EMHD breaks down. Electrons can be accelerated in null lines which dissipated magnetic energy like in magnetic reconnection. Energized electrons with anisotropic distributions create secondary whistler instabilities. These effects have been observed in field topologies resembling spheromaks and field-reversed configurations (FRCs). The whistler mode propagation near magnetic nulls is not trivial when the field gradients and wavelength are comparable. Ray tracing is inappropriate when the WKB approximation breaks down. Experiments have been started to map wave propagation on curved field lines with null points. Initial results show that whistlers in highly nonuniform fields have highly oblique phase velocities but the energy flow remains dominantly

  6. Self-organization in magnetic flux ropes

    Science.gov (United States)

    Lukin, Vyacheslav S.

    2014-06-01

    This cross-disciplinary special issue on 'Self-organization in magnetic flux ropes' follows in the footsteps of another collection of manuscripts dedicated to the subject of magnetic flux ropes, a volume on 'Physics of magnetic flux ropes' published in the American Geophysical Union's Geophysical Monograph Series in 1990 [1]. Twenty-four years later, this special issue, composed of invited original contributions highlighting ongoing research on the physics of magnetic flux ropes in astrophysical, space and laboratory plasmas, can be considered an update on our state of understanding of this fundamental constituent of any magnetized plasma. Furthermore, by inviting contributions from research groups focused on the study of the origins and properties of magnetic flux ropes in a variety of different environments, we have attempted to underline both the diversity of and the commonalities among magnetic flux ropes throughout the solar system and, indeed, the universe. So, what is a magnetic flux rope? The answer will undoubtedly depend on whom you ask. A flux rope can be as narrow as a few Larmor radii and as wide as the Sun (see, e.g., the contributions by Heli Hietala et al and by Angelous Vourlidas). As described below by Ward Manchester IV et al , they can stretch from the Sun to the Earth in the form of interplanetary coronal mass ejections. Or, as in the Swarthmore Spheromak Experiment described by David Schaffner et al , they can fit into a meter-long laboratory device tended by college students. They can be helical and line-tied (see, e.g., Walter Gekelman et al or J Sears et al ), or toroidal and periodic (see, e.g., John O'Bryan et al or Philippa Browning et al ). They can form in the low plasma beta environment of the solar corona (Tibor Török et al ), the order unity beta plasmas of the solar wind (Stefan Eriksson et al ) and the plasma pressure dominated stellar convection zones (Nicholas Nelson and Mark Miesch). In this special issue, Setthivoine You