Toroidal Axis Research Articles

Morpho-kinematic and photoionization models of the multipolar structures in planetary nebula NGC 6572

ABSTRACT We have studied planetary nebula (PN) NGC 6572 through 3D morpho-kinematic and photoionization modelling. The 3D morphology is reconstructed from the Hubble Space Telescope images in different narrow-band filters and position–velocity spectra. The PN has a multipolar morphology consisting of highly collimated outflows. The nebular image shows signatures of multiple lobes within a spiral-ring-like structure. The multipolar structure is modelled with two bipolar shells (axes ratios ∼5.5:1 and ∼3:1), having closed and open lobes, respectively. A toroidal structure (radius:height ∼ 1:3) surrounds the shells at the waist. The toroidal axis aligns with the major axes of the bipolar shells. Our study reveals the nebula to have a history of collimated polar outflow perpendicular to a higher density equatorial wind with the outflow seemingly having episodes of changing direction of ejection. We construct a photoionization model of NGC 6572 using the optical spectra obtained at the 2 m Himalayan Chandra Telescope. For the photoionization model, we configure the input shell geometry in the form of a highly bipolar nebular shell with reference to the 3D morphology. Our photoionization model satisfactorily reproduces the observables. We estimate nebular elemental abundances, and important characteristic parameters of the central star (e.g. effective temperature, luminosity, gravity, mass, etc.) and the nebula (e.g. hydrogen density profiles, radii, etc.). We compare the resolved H β, [O iii], and [N ii] profiles obtained using the 4.2 m William Herschel Telescope with that from the photoionization model and find a good characteristic match.

The upgraded TOMAS device: A toroidal plasma facility for wall conditioning, plasma production, and plasma-surface interaction studies.

The Toroidal Magnetized System device has been significantly upgraded to enable development of various wall conditioning techniques, including methods based on ion and electron cyclotron (IC/EC) range of frequency plasmas, and to complement plasma-wall interaction research in tokamaks and stellarators. The toroidal magnetic field generated by 16 coils can reach its maximum of 125 mT on the toroidal axis. The EC system is operated at 2.45GHz with up to 6 kW forward power. The IC system can couple up to 6 kW in the frequency range of 10 MHz-50MHz. The direct current glow discharge system is based on a graphite anode with a maximum voltage of 1.5 kV and a current of 6A. A load-lock system with a vertical manipulator allows exposure of material samples. A number of diagnostics have been installed: single- and triple-pin Langmuir probes for radial plasma profiles, a time-of-flight neutral particle analyzer capable of detecting neutrals in the energy range of 10 eV-1000eV, and a quadrupole mass spectrometer and video systems for plasma imaging. The majority of systems and diagnostics are controlled by the Siemens SIMATIC S7 system, which also provides safety interlocks.

Adaptive method of 5-axis milling of sculptured surfaces elements with a curved line contour

In this paper, an attempt to develop a new adaptive method of controlling the axis orientation of a toroidal milling cutter (leading angle α) depending on the radius of curvature (radius ρ1 in the feed direction, i.e. on a curved contour) of the treated surface profile in a 5-axis milling process was made. An application of this method required the development, based on the results of simulation and experimental tests (own tests), of a special procedure for selection of the lead angle α of the milling cutter depending on the continuously changing radius of curvature ρ1 in the direction of the milling cutter. This procedure was implemented in a commercial CAM system, thus modifying the classical strategy of controlling the movement of the tool into an adaptive strategy. The proposed method after entering the criterion of the permissible value of the deviation of shape Δk and limiting the permissible parameter Ra of the surface roughness, allows adapting the lead angle α of the toroidal axis to the current value of the radius of curvature ρ1 of the processed composite surface profile. By conducting experimental research on the example of the blade machining of the turbine blade, it was shown that the concept of a new method of controlling the axis of the toroidal milling axis allows the parameters of the lead angle and radius of curvature (α, ρ1) to increase the accuracy of the 5-axis surface treatment of complex elements with contours curvilinear by about 25 %.

Modification of neutron emission spectrum by Alfvén eigenmodes in a deuterium–tritium plasma

The neutron emission spectrum can be modified from Gaussian due to excited Alfvén eigenmodes (AEs). We evaluate the neutron emission spectrum when the fuel-ion velocity distribution functions are distorted by AEs, assuming an ITER-like deuterium–tritium tokamak plasma. When shear AEs are excited by energetic particles in a plasma, the non-Maxwellian tails are created in the fuel-ion distribution functions in directions that are parallel and antiparallel to the magnetic field lines. Due to formation of these tails, the non-Gaussian components are formed in the neutron emission spectrum in the same and opposite directions of the toroidal axis. The anisotropic, non-Gaussian neutron emission spectrum can be used for experimental verification and diagnostics of the non-Maxwellian tails in the fuel-ion velocity distribution functions formed by AEs.

Numerical study of the MHD flow around a bounded heating cylinder: Heat transfer and pressure drops

This work studies numerically the flow around an electrically insulated heating cylinder, bounded by walls of non-uniform electrical conductivity and subjected to a transversal magnetic field, with non-null components in the toroidal and poloidal directions. The configuration is representative of a typical breeding blanket segment in tokamak fusion reactors: to minimize magnetohydrodynamic (MHD) pressure drops, the liquid metal can be employed just as tritium breeder, whereas a non-conductive secondary fluid is used as coolant. The coolant is carried in the breeding zone by pipes that, being transversal to the stream-wise direction, affect the flow features and heat transfer. The flow is investigated by simulations performed in a 3D domain for Reynolds number 20 and 40, 0≤M≤50 for the Hartmann number and 0°≤α≤32° for the magnetic field inclination on the toroidal axis. The transition to the MHD regime causes the suppression of the cylinder wake and the disappearance of the steady vortex structures. Electromagnetic coupling balances the flow rates between the top and bottom sub-channels, individuated by the cylinder. The flow pattern modifications affect the heat transfer, which is found to increase with both M and α in the considered range, albeit for the latter in a non-monotonic trend. The pressure drop in the channel exhibits a similar behaviour. Moreover, it is dominated by the fully developed component due to the 2D currents, whereas the cylinder pressure drop contribution decreases steadily with the intensity of the applied magnetic field. The simulations were performed with ANSYS CFX-15.

Cutting layer and cutting forces in a 5-axis milling of sculptured surfaces using the toroidal cutter

The purpose of this article was to evaluate the significance of the influence of five- axis orientation parameters of a toroidal cutter axis and the geometrical parameters of the machined sculptured surface on the intersection of the cut layer in a 5-axis machining. An impact assessment was performed by simulating concave-convex and convex-concave surfaces using a discrete method of direct transformation in a CAD environment. It was shown that only the radius of curvature of the surface in the feed direction and the angle of the tool axis affected the change in the intersection of the cutting layer. Subsequently, experimental tests were conducted that aimed at determining the mathematical models of the influence of these important parameters on the components of the cutting force. The object of the experimental studies was a convex and concave surface of a turbine blade of Inconel 718 alloy. The R300-016B20L-08L Sandvik Coromant toroid cutter was used for the tests. Based on the results of the study it was found that the lead angle in the machining of the convex surface and concave turbine blade should be continuously varied with the change of radius of curvature in the direction of the machined surface profile

Wpływ parametrów kinematycznych i geometrycznych na przekrój warstwy skrawanej w pięcioosiowej obróbce powierzchni złożonych

Results of simulation studies made using the direct CAD method are presented. The significance of the influence of the toroidal cutter axis orientation parameters and curvature radius of the sculptured surface on the cut layer in a 5-axis milling of the convex-concave and concave-convex surfaces, was assessed.

Five-axis milling of sculptured surfaces of the turbine blade

PurposeThe purpose of this paper is to determine the influence of a toroidal cutter axis orientation and a variable radius of curvature of the machined contour of sculptured surface on the five-axes milling process. Simulation and experimental research performed in this work are aimed to determine the relationship between the parameters of five-axes milling process and the shape and dimensional accuracy of curved outline of Inconel 718 alloy workpiece.Design/methodology/approachA subject of research are sculptured surfaces of the turbine blade. Simulation research was performed using the method of direct mapping tools in the CAD environment. The machining research was carried out with the use of multi-axis machining center DMU 100 monoBLOCK DMG, equipped with rotating dynamometer to measure the components of the cutting force. To control the shape and dimensional accuracy, the coordinate measuring machine ZEISS ACCURA II was used.FindingsIn this paper, the effect of the toroidal cutter axis orientation and the variable radius of curvature of the machined contour on the parameters of five-axes milling process and the accuracy of the sculptured surfaces was determined.Practical implicationsFive-axes milling with the use of a toroidal cutter is found in the aviation industry, where sculptured surfaces of the turbine blades are machined. The results of the research allow more precise planning of five-axes milling and increase of the turbine blades accuracy.Originality/valueThis paper significantly complements the current state of knowledge in the field of five-axes milling of turbine blades in terms of their accuracy.

Structural, magnetic characterization (dependencies of coercivity and loss with the frequency) of magnetic cores based in Finemet

We report changes of coercivity, induced magnetic anisotropy, magneto-optical domain structure and frequency dependencies of coercivity and energy loss (up to 10MHz) associated with the structural modifications produced by thermal treatments under applied magnetic field (field annealing) in toroidal wound cores of Fe73.5Cu1Nb3Si15.5B7 amorphous alloy. The thermal treatment (535°C, 1h) leads to the typical nanocrystalline structure of α-Fe(Si) nanograins (60–65% relative volume, 10–20nm average grain size embedded in a residual amorphous matrix, while the magnetic field with the possibility to be applied in two directions to the toroidal core axis, that is in transverse (which is equivalent to the transverse direction of the ribbon) or longitudinal (equivalent to the longitudinal direction of the ribbon), develops a macroscopic uniaxial magnetic anisotropy in the transverse (around 245J/m3) or longitudinal (around 85J/m3) direction of the ribbon, respectively. It is remarkable the quasi-unhysteretic character of the cores with these two kinds of field annealing as comparing with that of the as-quenched one. Magneto-optical study by Kerr-effect of the ribbons provides useful information on the domain structure of the surface in agreement with the direction and intensity of the induced magnetic anisotropy. This induced uniaxial magnetic anisotropy plays a very important role on the Hc(f) and EL(f) curves, (f: frequency), being drastic the presence and direction of the induced magnetic anisotropy. In addition, these frequency dependencies show a significant change at the frequency around 100Hz.

A-b Anisotropy of the Intra-Unit-Cell Magnetic Order in YBa_{2}Cu_{3}O_{6.6}.

Within the complex phase diagram of the hole-doped cuprates, seizing the nature of the mysterious pseudogap phase is essential for unraveling the microscopic origin of high-temperature superconductivity. Below the pseudogap temperature T^{⋆}, evidence for intra-unit-cell orders breaking the fourfold rotation symmetry have been provided by neutron diffraction and scanning tunneling spectroscopy. Using polarized neutron diffraction on a detwinned YBa_{2}Cu_{3}O_{6.6} sample, we here report a distinct a-b anisotropy of the intra-unit-cell magnetic structure factor below T^{⋆}, highlighting that intra-unit-cell order in this material breaks the mirror symmetry of the CuO_{2} bilayers. This is likely to originate from a crisscrossed arrangement of loop currents within the CuO_{2} bilayer, resulting in a bilayer mean toroidal axis along the b direction.

Measurement and tricubic interpolation of the magnetic field for the OLYMPUS experiment

The OLYMPUS experiment used a 0.3T toroidal magnetic spectrometer to measure the momenta of outgoing charged particles. In order to accurately determine particle trajectories, knowledge of the magnetic field was needed throughout the spectrometer volume. For that purpose, the magnetic field was measured at over 36,000 positions using a three-dimensional Hall probe actuated by a system of translation tables. We used these field data to fit a numerical magnetic field model, which could be employed to calculate the magnetic field at any point in the spectrometer volume. Calculations with this model were computationally intensive; for analysis applications where speed was crucial, we pre-computed the magnetic field and its derivatives on an evenly spaced grid so that the field could be interpolated between grid points. We developed a spline-based interpolation scheme suitable for SIMD implementations, with a memory layout chosen to minimize space and optimize the cache behavior to quickly calculate field values. This scheme requires only one-eighth of the memory needed to store necessary coefficients compared with a previous scheme (Lekien and Marsden, 2005 [1]). This method was accurate for the vast majority of the spectrometer volume, though special fits and representations were needed to improve the accuracy close to the magnet coils and along the toroidal axis.

Wpływ orientacji osi freza toroidalnego na składowe siły skrawania w pięcioosiowej obróbce łopatki turbiny ze stopu INCONEL 718

Wpływ orientacji osi freza toroidalnego na składowe siły skrawania w pięcioosiowej obróbce łopatki turbiny ze stopu INCONEL 718

GLOBAL TRENDS OF CME DEFLECTIONS BASED ON CME AND SOLAR PARAMETERS

Accurate space weather forecasting requires knowledge of the trajectory of coronal mass ejections (CMEs), including any deflections close to the Sun or through interplanetary space. Kay et al. 2013 introduced ForeCAT, a model of CME deflection resulting from the background solar magnetic field. For a magnetic field solution corresponding to Carrington Rotation (CR) 2029 (declining phase, April-May 2005), the majority of the CMEs deflected to the Heliospheric Current Sheet (HCS), the minimum in magnetic pressure on global scales. Most of the deflection occurred below 4 Rs. Here we extend ForeCAT to include a three dimensional description of the deflecting CME. We attempt to answer the following questions: a) Do all CMEs deflect to the magnetic minimum? and b) Does most deflection occur within the first few solar radii (~4 Rs)? Results for solar minimum and declining phase CMEs show that not every CME deflects to the magnetic minimum and that the deflection is typically determined below 2 Rs. Slow, wide, low mass CMEs in declining phase solar backgrounds with strong magnetic field and magnetic gradients exhibit the largest deflections. Local gradients related to active regions tend to cause the largest deviations from the deflection predicted by global magnetic gradients, but variations can also be seen for CMEs in the quiet sun regions of the declining phase CR. We show the torques due to differential forces along the CME can cause rotation about the CME's toroidal axis.

Potash in a salt mushroom at Hormoz Island, Hormoz Strait, Iran

Increasing volumes of potash are currently being discovered in a cluster of diapirs of Hormoz (formerly Hormuz) salt near Bandar Abbas, Iran. Most of the potash beds studied so far occur in complex recumbent folds in a salt mountain that would be difficult to exploit safely. However, Holocene marine erosion removed any salt mountains from a sub-group of near-shore Zagros diapirs and exposed their deeper structural levels. Even though these diapirs are still active, their potash deposits are likely more tractable to safe exploitation than in a salt mountain — as we make clear here for Hormoz Island. Geochemical surveys on Hormoz Island reveal two separate potash anomalies that are valuable pseudo-stratigraphic markers. Integrating field measurements of the attitudes of bedding with lineaments on air photos suggests that Hormoz Island consists of a mature bell- or plume-shaped mushroom diapir with potash beds wound around a toroidal axis of rotation near current exposure levels. 2D numerical models simulate the salt mushroom on Hormoz Island and its internal circulation. They also suggest that the diapir has a wide overhand above a narrow stem in this gas-rich region. We use the mushroom diapir model to outline a regional exploration strategy that has the potential of influencing the world potash market thereafter.

Surface waves on a semitoroidal water ring

We study the dynamics of surface waves on a semitoroidal ring of water that is excited by vertical vibration. We create this specific fluid volume by patterning a glass plate with a hydrophobic coating, which confines the fluid to a precise geometric region. To excite the system, the supporting plate is vibrated up and down, thus accelerating and decelerating the fluid ring along its toroidal axis. When the driving acceleration is sufficiently high, the surface develops a standing wave, and at yet larger accelerations, a traveling wave emerges. We also explore frequency dependencies and other geometric shapes of confinement.

The CLAS drift chamber system

Experimental Hall B at Jefferson Laboratory houses the CEBAF Large Acceptance Spectrometer, the magnetic field of which is produced by a superconducting toroid. The six coils of this toroid divide the detector azimuthally into six sectors, each of which contains three large multi-layer drift chambers for tracking charged particles produced from a fixed target on the toroidal axis. Within the 18 drift chambers are a total of 35,148 individually instrumented hexagonal drift cells. The novel geometry of these chambers provides for good tracking resolution and efficiency, along with large acceptance. The design and construction challenges posed by these large-scale detectors are described, and detailed results are presented from in-beam measurements.

A toroidal boundary-value problem in resistive magnetohydrodynamics

Under a standard set of assumptions, the magnetic flux function for a static, resistive magnetofluid is determined in axisymmetric toroidal geometry for two different scalar-conductivity profiles; in one case the conductivity is spatially uniform, and in the other it is proportional to the square of the distance from the toroidal axis. Exact analytic expressions are found in both cases for a magnetofluid that is surrounded by a perfectly conducting toroidal shell with a circular cross section.

MLM polychromator monitoring soft-x-ray spectral line emissions of C, O, and Fe used in transport studies of the Phaedrus-T tokamak plasma during ohmic, rf-heated, and H-mode discharges

The MLM (multilayer mirror) polychromator has two modes of operation. In the first mode, it simultaneously monitors the Ly α and β emissions of H-like O at 19.0 and 16.0 Å, respectively, the Ly α emission of C at 33.7 Å, and the singlet and triplet transitions of He-like C at 40.5 Å. In the second mode, it simultaneously monitors the Ly α and β emissions of H-like C at 33.7 and 28.5 Å, respectively, as well as the 15.6 and 93.9 Å emissions of F-like Fe. The MLM polychromator has a wavelength resolution that varies from 0.3 Å at 16.0 Å to 2 Å at 40.5 Å and 7 Å at 93.9 Å. It was mounted on the midplane of the Phaedrus-T tokamak with its line of sight along the major radius. On a shot by shot basis, the MLM polychromator, with a temporal resolution of 1 ms and a spatial resolution of 1 cm, scanned the plasma in the z direction ±15 cm from the toroidal magnetic axis. Vertical asymmetries in the soft x-ray spectral line brightness profiles were measured and found to depend on the direction of BT. The brightness profiles were inverted and modeled with a poloidally asymmetric Gaussian emissivity profile. The measured results were compared with the predicted emissivity profiles to determine the transport of carbon.

Three-dimensional waves in excitable reaction-diffusion systems

The eikonal equation [5] for excitable media is generalised to three dimensional systems. The main result of the investigation is the demonstration of the existence of toroidal and twisted toroidal scroll waves in the limit of large values of the major radius of the torus. The existence of a helical wave near the z-axis follows from the eidonal equation but its connection with the twisted toroidal scroll remains to be demonstrated. The eikonal equation also predicts a non-uniform rate of rotation of the cross-sectional spiral wave near the toroidal axis. The notion of geometrical stability is introduced for the case of an expanding sphere; in particular it is shown that a discussion of stability of solutions of the eikonal equation must take into account the possible shift in the origin of the coordinate systems with respect to which patterns are defined.

An algorithm for the calculation of three-dimensional ICRF fields in tokamak geometry

A computational scheme is developed which permits tractable calculation of three-dimensional full-wave solutions to the Vlasov-Maxwell equations under typical ion cyclotron range of frequencies (ICRF) experimental conditions. The method is unique in that power deposition to the plasma is determined via the anti-Hermitian part of a truncated warm plasma dielectric operator, rather than as the result of an assumed phenomenological collision frequency. The resulting computer code allows arbitrary variation of density, temperature, magnetic field and minority concentration in the poloidal plane by performing a convolution of poloidal modes to produce a coupled system of differential equations in the radial variable. By assuming no inhomogeneity along the toroidal axis, an inverse transform over k‖ is performed, yielding the global three-dimensional fast wave field solutions. The application of the code to TFTR-like plasmas shows a mild resonance structure in antenna loading related to the changing number of wavelengths between the antenna and the resonance layer.