Showing papers on "Rotation published in 2009"

Magnetic rotary system for input devices

Abstract: Embodiments of the present invention include a roller for an input device, where the roller's absolute angular position is measured by a magnetic encoder. A magnet is attached to the roller, possibly inside the roller so as to make the embodiment more compact. In one embodiment, the magnetization is simple and low cost. Further, tight tolerances are not required, and such a system is easy to manufacture. In one embodiment, the sensor is covered by any non-ferromagnetic material, to protect it from foreign particles, and to reduce ESD. In one embodiment, the wheel consumes much less power than conventional wheels in input devices. In one embodiment, the tilting of the wheel is measured using the same sensor that is used for measuring the rotation of the wheel. In one embodiment, a ratcheting feel provided to the user when rotating the wheel is synchronized with the rotation signal.

Gigahertz Dynamics of a Strongly Driven Single Quantum Spin

Abstract: Two-level systems are at the core of numerous real-world technologies such as magnetic resonance imaging and atomic clocks. Coherent control of the state is achieved with an oscillating field that drives dynamics at a rate determined by its amplitude. As the strength of the field is increased, a different regime emerges where linear scaling of the manipulation rate breaks down and complex dynamics are expected. By calibrating the spin rotation with an adiabatic passage, we have measured the room-temperature "strong-driving" dynamics of a single nitrogen vacancy center in diamond. With an adiabatic passage to calibrate the spin rotation, we observed dynamics on sub-nanosecond time scales. Contrary to conventional thinking, this breakdown of the rotating wave approximation provides opportunities for time-optimal quantum control of a single spin.

Stellar Rotation in M35: Mass-Period Relations, Spin-Down Rates, and Gyrochronology

Abstract: We present the results of a five month photometric time-series survey for stellar rotation over a 40' × 40' field centered on the 150 Myr open cluster M35. We report rotation periods for 441 stars within this field and determine their cluster membership and binarity based on a decade-long radial velocity survey, proper-motion measurements, and multiband photometric observations. We find that 310 of the stars with measured rotation periods are late-type members of M35. The distribution of rotation periods for cluster members span more than 2 orders of magnitude from ~0.1 to 15 days, not constrained by the sampling frequency and the timespan of the survey. With an age between the zero-age main sequence and the Hyades, and with ~6 times more rotation periods than measured in the Pleiades, M35 permit detailed studies of early rotational evolution of late-type stars. Nearly 80% of the 310 rotators lie on two distinct sequences in the color-period plane, and define clear relations between stellar rotation period and color (mass). The M35 color-period diagram enables us to determine timescales for the transition between the two rotational states, of ~60 Myr and ~140 Myr for G and K dwarfs, respectively. These timescales are inversely related to the mass of the convective envelope, and offer constraints on the rates of internal and external angular momentum transport and of the evolution of stellar dynamos. A comparison to the Hyades, confirm the Skumanich spin-down dependence for G dwarfs on one rotational state, but suggest that K dwarfs spin down more slowly. The locations of the rotational sequences in the M35 color-period diagram support the use of rotational isochrones to determine ages for coeval stellar populations. We use such gyrochronology to determine gyro-ages for M35 from 134 Myr to 161 Myr. We use the M35 data to evaluate new color dependences for the rotational isochrones.

The Effect of Stellar Rotation on Colour-Magnitude Diagrams: On the apparent presence of multiple populations in intermediate age stellar clusters

Abstract: A significant number of intermediate age clusters (1-2 Gyr) in the Magellanic Clouds appear to have multiple stellar populations within them, derived from bi-modal or extended main sequence turn offs. If this is interpreted as an age spread, the multiple populations are separated by a few hundred Myr, which would call into question the long held notion that clusters are simple stellar populations. Here we show that stellar rotation in stars with masses between 1.2-1.7 Msun can mimic the effect of a double or multiple population, whereas in actuality only a single population exists. The two main causes of the spread near the turn-off are the effects of stellar rotation on the structure of the star and the inclination angle of the star relative to the observer. Both effects change the observed effective temperature, hence colour, and flux of the star. In order to match observations, the required rotation rates are 20-50% of the critical rotation, which are consistent with observed rotation rates of similar mass stars in the Galaxy. We provide scaling relations which can be applied to non-rotating isochrones in order to mimic the effects of rotation. Finally, we note that rotation is unlikely to be the cause of the multiple stellar populations observed in old globular clusters, as low mass stars (<1 Msun) are not expected to be rapid rotators.

Physics of non-diffusive turbulent transport of momentum and the origins of spontaneous rotation in tokamaks

Abstract: Recent results in the theory of turbulent momentum transport and the origins of intrinsic rotation are summarized. Special attention is focused on aspects of momentum transport critical to intrinsic rotation, namely the residual stress and the edge toroidal flow velocity pinch. Novel results include a systematic decomposition of the physical processes which drive intrinsic rotation, a calculation of the critical external torque necessary to hold the plasma stationary against the intrinsic residual stress, a simple model of net velocity scaling which recovers the salient features of the experimental trends and the elucidation of the impact of the particle flux on the net toroidal velocity pinch. Specific suggestions for future experiments are offered.

Experimental study of the ion critical-gradient length and stiffness level and the impact of rotation in the JET tokamak.

Abstract: Experiments were carried out in the JET tokamak to determine the critical ion temperature inverse gradient length (R/L-Ti = R vertical bar del T-i vertical bar/T-i) for the onset of ion temperature gradient modes and the stiffness of Ti profiles with respect to deviations from the critical value. Threshold and stiffness have been compared with linear and nonlinear predictions of the gyrokinetic code GS2. Plasmas with higher values of toroidal rotation show a significant increase in R/L-Ti, which is found to be mainly due to a decrease of the stiffness level. This finding has implications on the extrapolation to future machines of present day results on the role of rotation on confinement.

Propagation dynamics of optical vortices due to Gouy phase

Abstract: We study the propagation of off-axis vortices in a paraxial beam formed by two collinear Laguerre-Gauss beams. We show that the vortices move about the beam axis as the light propagates resulting in a rotation of the beam's transverse profile. This rotation is explained by the Gouy phase acquired by the component beams. Experimental measurements of the angular position of the vortices are in good agreement with a two-mode theory.

Rotation and outflow motions in the very low-mass class 0 protostellar system hh 211 at subarcsecond resolution

Abstract: HH 211 is a nearby young protostellar system with a highly collimated jet. We have mapped it in 352 GHz continuum, SiO (J = 8 – 7), and HCO+ (J = 4 – 3) emission at up to ~02 resolution with the Submillimeter Array (SMA). The continuum source is now resolved into two sources, SMM1 and SMM2, with a separation of ~ 84 AU. SMM1 is seen at the center of the jet, probably tracing a (inner) dusty disk around the protostar driving the jet. SMM2 is seen to the southwest of SMM1 and may trace an envelope-disk around a small binary companion. A flattened envelope-disk is seen in HCO+ around SMM1 with a radius of ~ 80 AU perpendicular to the jet axis. Its velocity structure is consistent with a rotation motion and can be fitted with a Keplerian law that yields a mass of ~50 ± 15 M Jup (a mass of a brown dwarf) for the protostar. Thus, the protostar could be the lowest mass source known to have a collimated jet and a rotating flattened envelope-disk. A small-scale (~200 AU) low-speed (~2 km s–1) outflow is seen in HCO+ around the jet axis extending from the envelope-disk. It seems to rotate in the same direction as the envelope-disk and may carry away part of the angular momentum from the envelope-disk. The jet is seen in SiO close to ~100 AU from SMM1. It is seen with a "C-shaped" bending. It has a transverse width of 40 AU and a velocity of ~ 170 ± 60 km s–1. A possible velocity gradient is seen consistently across its innermost pair of knots, ~0.5 km s–1 at ~10 AU, consistent with the sense of rotation of the envelope-disk. If this gradient is an upper limit of the true rotational gradient of the jet, then the jet carries away a very small amount of angular momentum of 5 AU km s–1 and thus must be launched from the very inner edge of the disk near the corotation radius.

Optical position measuring device

Abstract: An optical position-measuring device includes a light source, a measuring reflector movable in space, a detection unit and a light-beam deflection unit that can align at least one beam of rays, emitted by the light source, in the direction of the measuring reflector. The light-beam deflection unit includes a cardan system having two cardan frames. A first cardan frame is adjustable by motor about a first axis of rotation, and a second cardan frame within the first cardan frame is adjustable by motor about a second axis of rotation oriented in a direction perpendicular to the first axis of rotation. The two axes of rotation intersect in a fixed reference point, at which a reference reflector is disposed. A plurality of mirrors are disposed rigidly on the cardan frames, so that the beam of rays can be pivoted about the fixed reference point via the mirrors during alignment.

Tri-axis Angular Rate Sensor

Abstract: Angular rate sensor for detecting rotation about first, second and third mutually perpendicular input axes having a plurality of generally planar proof masses coupled together for linear drive-mode oscillation along multi-directional drive axes in a plane formed by the first and second input axes. The masses are mounted on a generally planar sense frame for linear movements relative to the sense frame in drive-mode and for rotation together with the sense frame in sense modes. The sense frame is mounted for rotation with the masses in sense modes about the first, second, and third input axes independent of each other, in response to Coriolis forces produced by rotation of the masses about the first, second, and third input axes respectively. And capacitance sensors responsive to the rotational movements of the masses and the sense frame in sense modes are employed for monitoring rate of rotation.

Step-by-step rotation of a molecule-gear mounted on an atomic-scale axis.

Abstract: Designing and building molecular machines at the nanometre scale is a conceptual and synthetic challenge. Rotation of a single molecule has been observed but controlling the direction of the rotation has so far proved difficult. The step-by-step rotation of a molecular gear mounted on an atomic-scale axis is now controlled by a scanning tunnelling microscope. Gears are microfabricated down to diameters of a few micrometres. Natural macromolecular motors, of tens of nanometres in diameter, also show gear effects1. At a smaller scale, the random rotation of a single-molecule rotor encaged in a molecular stator has been observed2, demonstrating that a single molecule can be rotated with the tip of a scanning tunnelling microscope3,4 (STM). A self-assembled rack-and-pinion molecular machine where the STM tip apex is the rotation axis of the pinion was also tested5. Here, we present the mechanics of an intentionally constructed molecule-gear on a Au(111) surface, mounting and centring one hexa-t-butyl-pyrimidopentaphenylbenzene molecule on one atom axis. The combination of molecular design, molecular manipulation and surface atomic structure selection leads to the construction of a fundamental component of a planar single-molecule mechanical machine. The rotation of our molecule-gear is step-by-step and totally under control, demonstrating nine stable stations in both directions.

Numerical simulations of a rotating red giant star. i. three-dimensional models of turbulent convection and associated mean flows

Abstract: With the development of one-dimensional stellar evolution codes including rotation and the increasing number of observational data for stars of various evolutionary stages, it becomes more and more possible to follow the evolution of the rotation profile and angular momentum distribution in stars. In this context, understanding the interplay between rotation and convection in the very extended envelopes of giant stars is very important considering that all low- and intermediate-mass stars become red giants after the central hydrogen burning phase. In this paper, we analyze the interplay between rotation and convection in the envelope of red giant stars using three-dimensional numerical experiments. We make use of the Anelastic Spherical Harmonics code to simulate the inner 50% of the envelope of a low-mass star on the red giant branch. We discuss the organization and dynamics of convection, and put a special emphasis on the distribution of angular momentum in such a rotating extended envelope. To do so, we explore two directions of the parameter space, namely, the bulk rotation rate and the Reynolds number with a series of four simulations. We find that turbulent convection in red giant stars is dynamically rich, and that it is particularly sensitive to the rotation rate of the star. Reynolds stresses and meridional circulation establish various differential rotation profiles (either cylindrical or shellular) depending on the convective Rossby number of the simulations, but they all agree that the radial shear is large. Temperature fluctuations are found to be large and in the slowly rotating cases, a dominant ? = 1 temperature dipole influences the convective motions. Both baroclinic effects and turbulent advection are strong in all cases and mostly oppose one another.

The main-sequence rotation-colour relation in the Coma Berenices open cluster

Abstract: We present the results of a photometric survey of rotation rates in the Coma Berenices (Melotte 111) open cluster, using data obtained as part of the SuperWASP exoplanetary transit-search programme. The goal of the Coma survey was to measure precise rotation periods for main-sequence F, G and K dwarfs in this intermediate-age (similar to 600 Myr) cluster, and to determine the extent to which magnetic braking has caused the stellar spin periods to converge. We find a tight, almost linear relationship between rotation period and J - K colour with an rms scatter of only 2 per cent. The relation is similar to that seen among F, G and K stars in the Hyades. Such strong convergence can only be explained if angular momentum is not at present being transferred from a reservoir in the deep stellar interiors to the surface layers. We conclude that the coupling time-scale for angular momentum transport from a rapidly spinning radiative core to the outer convective zone must be substantially shorter than the cluster age, and that from the age of Coma onwards stars rotate effectively as solid bodies. The existence of a tight relationship between stellar mass and rotation period at a given age supports the use of stellar rotation period as an age indicator in F, G and K stars of Hyades age and older. We demonstrate that individual stellar ages can be determined within the Coma population with an internal precision of the order of 9 per cent (rms), using a standard magnetic braking law in which rotation period increases with the square root of stellar age. We find that a slight modification to the magnetic-braking power law, P proportional to t0.56, yields rotational and asteroseismological ages in good agreement for the Sun and other stars of solar age for which p-mode studies and photometric rotation periods have been published.

Direct Numerical Simulation of Turbulent Flow and Heat Transfer in a Square Duct Rotating along Its Spanwise Direction

Abstract: Turbulent flow and heat transfer in a square duct rotating along its spanwise direction is investigated by direct numerical simulation.The spatial terms in the governing equations are discretized by second-order central difference scheme and the time terms are discretized by the Adams-Bashforth scheme.The influence of rotation on the streamwise velocity,crosswise velocity and the mean temperature is analyzed.The results show that the mean velocity and the mean turbulent kinetic energy decreases with the increase of rotation number when the centrifugal buoyancy force is neglected.The mean turbulent kinetic energy of Roτ=1.5 decreases by 15 percent compared with that of Roτ=0.If the effect of the centrifugal buoyancy force is taken into account,for the radially outwards flow,the mean velocity and turbulent kinetic energy increase with rotation number compared with those without the effect of centrifugal force,and the results are converse for the flow radially inwards.It is found that the mean turbulent kinetic energy increases by 17 percent for the radially outwards flow at Roτ=1.5 compared with that of Grτ,L=0,but it decreases by 43 percent for the flow radially inwards.

Influence of the centrifugal force and parallel dynamics on the toroidal momentum transport due to small scale turbulence in a tokamak

Abstract: The paper derives the gyro-kinetic equation in the comoving frame of a toroidally rotating plasma, including both the Coriolis drift effect [A. G. Peeters et al., Phys. Rev. Lett. 98, 265003 (2007)] as well as the centrifugal force. The relation with the laboratory frame is discussed. A low field side gyro-fluid model is derived from the gyro-kinetic equation and applied to the description of parallel momentum transport. The model includes the effects of the Coriolis and centrifugal force as well as the parallel dynamics. The latter physics effect allows for a consistent description of both the Coriolis drift effect as well as the ExB shear effect [R. R. Dominguez and G. M. Staebler, Phys. Fluids B 5, 3876 (1993)] on the momentum transport. Strong plasma rotation as well as parallel dynamics reduce the Coriolis (inward) pinch of momentum and can lead to a sign reversal generating an outward pinch velocity. Also, the ExB shear effect is, in a similar manner, reduced by the parallel dynamics and stronger rotation.

Mobile device with an inclinometer

Abstract: A method is disclosed that includes detecting a change in an inclination at a panel of an electronic device. The panel has a display surface. The method also includes detecting a rotation of the panel from a first orientation to a second orientation. The method also includes automatically redrawing an image displayed at the display surface responsive to the rotation when the change in the inclination of the panel does not exceed a threshold during the rotation.

Angular Momentum Transport In Solar-Type Stars: Testing the Timescale For Core-Envelope Coupling

Abstract: We critically examine the constraints on internal angular momentum transport which can be inferred from the spin down of open cluster stars. The rotation distribution inferred from rotation velocities and periods are consistent for larger and more recent samples, but smaller samples of rotation periods appear biased relative to vsini studies. We therefore focus on whether the rotation period distributions observed in star forming regions can be evolved into the observed ones in the Pleiades, NGC2516, M34, M35, M37, and M50 with plausible assumptions about star-disk coupling and angular momentum loss from magnetized solar-like winds. Solid body models are consistent with the data for low mass fully convective stars but highly inconsistent for higher mass stars where the surface convection zone can decouple for angular momentum purposes from the radiative interior. The Tayler-Spruit magnetic angular momentum transport mechanism, commonly employed in models of high mass stars, predicts solid-body rotation on extremely short timescales and is therefore unlikely to operate in solar-type pre-MS and MS stars at the predicted rate. Models with core-envelope decoupling can explain the spin down of 1.0 and 0.8 solar mass slow rotators with characteristic coupling timescales of 55+-25 Myr and 175+-25 Myr respectively. The upper envelope of the rotation distribution is more strongly coupled than the lower envelope of the rotation distribution, in accord with theoretical predictions that the angular momentum transport timescale should be shorter for more rapidly rotating stars. Constraints imposed by the solar rotation curve are also discussed (Abridged)

Pulsation modes in rapidly rotating stellar models based on the self-consistent field method

Abstract: Context. New observational means such as the space missions CoRoT and Kepler and ground-based networks are and will be collecting stellar pulsation data with unprecedented accuracy. A significant fraction of the stars in which pulsations are observed are rotating rapidly.Aims. Our aim is to characterise pulsation modes in rapidly rotating stellar models so as to be able to interpret asteroseismic data from such stars.Methods. A new pulsation code is applied to stellar models based on the self-consistent field (SCF) method.Results. Pulsation modes in SCF models follow a similar behaviour to those in uniformly rotating polytropic models, provided that the rotation profile is not too differential. Pulsation modes fall into different categories, the three main ones being island, chaotic, and whispering gallery modes, which are rotating counterparts to modes with low, medium, and high values, respectively. The frequencies of the island modes follow an asymptotic pattern quite similar to what was found for polytropic models. Extending this asymptotic formula to higher azimuthal orders reveals more subtle behaviour as a function of m and provides a first estimate of the average advection of pulsation modes by rotation. Further calculations based on a variational principle confirm this estimate and provide rotation kernels that could be used in inversion methods. When the rotation profile becomes highly differential, it becomes more and more difficult to find island and whispering gallery modes at low azimuthal orders. At high azimuthal orders, whispering gallery modes, and in some cases island modes, reappear.Conclusions. The asymptotic formula found for frequencies of island modes can potentially serve as the basis of a mode identification scheme in rapidly rotating stars when the rotation profile is not too differential.

Use of Pitch and Heave Motion Cues in a Pitch Control Task

Abstract: During pitch rotation of the aircraft, a pilot, seated in front of the aircraft center of gravity, is subjected to rotational pitch and vertical heave motion. The heave motion is a combination of the vertical motion of the aircraft center of gravity and the heave motion as a result of the pitch rotation. In a pitch tracking task, all of these cues could potentially have a positive effect on performance and control behavior, as they are all related to the aircraft pitch attitude. To improve the tuning of flight simulator motion filters, a better understanding of how these motion components are used by the pilot is required. First, the optimal use of the different motion components was evaluated using an optimal control analysis. Next, an aircraft pitch attitude control experiment was performed in the SIMONA Research Simulator, investigating the effects of pitch rotation, pitch heave, and center of gravity heave on pilot control behavior. Pilot performance significantly improved with pitch motion, with an increased crossover frequency for the disturbance open loop. The increase in performance was a result of an increased visual gain and a reduction in visual lead, allowed for by the addition of pitch motion. Pitch heave motion showed similar but smaller effects. The center of gravity heave motion, although taking up most of the simulator motion space, was found to have no significant effects on performance and control behavior.

Rotation-angle-detecting apparatus, rotating machine, and rotation-angle-detecting method

Abstract: An apparatus for detecting a rotation angle using a magnet rotor comprising a magnet having 2N poles, wherein N is a natural number, and a sensor device for detecting the direction of a magnetic flux from the magnet rotor, at least one of two output voltages obtained in radial and rotational directions by the sensor device being multiplied by a correction coefficient, and the rotation angle being calculated from the two corrected output voltages to increase the detection accuracy of the rotation angle.

Effect of neutral gas motion on the rotation of dust clusters in an axial magnetic field

Abstract: Experiments are carried out to investigate the rotation of dust clusters in a radio-frequency plasma sheath with a vertical magnetic field. Our observations are in disagreement with the standard model, in which it was assumed that the neutral gas is at rest and that a steady rotation is attained when the ion-drag force is balanced by neutral friction. Here, we re-examine this basic assumption by carefully designed experiments. Our results suggest that the neutral gas is set into rotation by E×B induced ion flow through ion-neutral collisions and that the dust particles are advected by this flow. A hydrodynamic model is proposed to describe the rotation of the neutral gas and it can explain our observations.

Handheld or vehicle-mounted platform stabilization system

Abstract: A hand-held or vehicle-mounted stabilization system including a platform supported by two or more rotatably-coupled gimbal frames each having a pivot assembly disposed at its rotation axis to couple an actuator to a rotation sensor having a rotation-sensitive sensor axis that is preferably fixedly disposed with respect to the rotation axis, and a controller for accepting the sensor signals and for producing each motor signal needed to dispose the platform in a predetermined angular position with respect to each rotation axis independent of changes in mount orientation. An alternative embodiment includes a controller for accepting an external slew signal sequence and for producing the motor signals needed to move the platform along a predetermined sequence of positions represented by the slew signal sequence.

Motion capture apparatus and method

Abstract: Provided are an apparatus and a method of effectively creating real-time movements of a three dimensional virtual character by use of a small number of sensors. More specifically, the motion capture method, which maps movements of a human body into a skeleton model to generate movements of a three-dimensional (3D) virtual character, includes measuring a distance between a portion of a human body to which a measurement sensor is positioned and a reference position and rotation angles of the portion, and estimating relative rotation angles and position coordinates of each portion of the human body by use of the measured distance and rotation angles.

The Interaction Between Earth's Rotation and Geophysical Processes

Abstract: 1.Motions of the Earth 2.Pole's motion and irregularities in the Earth's rotation rate 3.Estimation theory of the effect of atmospheric processes on the Earth's spin 4.Tides and rotation of the Earth 5.Seasonal distribution of the air masses and the Earth's spin 6.Angular momentum of atmospheric winds 7.Nature of the zonal circulation of the atmosphere 8.Interannual oscillations of the Earth-ocean-atmosphere system 9.Mechanical action of the atmosphere on the Earth's rotation 10.Decadal fluctuations in geophysical processes Appendices List of Abbreviations Bibliography

Derotation of the cosmic microwave background polarization: Full-sky formalism

Abstract: Mechanisms have been proposed that might rotate the linear polarization of the cosmic microwave background (CMB) as it propagates from the surface of last scatter. In the simplest scenario, the rotation will be uniform across the sky, but the rotation angle may also vary across the sky. We develop in detail the complete set of full-sky quadratic estimators for the rotation of the CMB polarization that can be constructed from the CMB temperature and polarization. We derive the variance with which these estimators can be measured and show that these variances reduce to the simpler flat-sky expressions in the appropriate limit. We evaluate the variances numerically. While the flat-sky formalism may be suitable if the rotation angle arises as a realization of a random field, the full-sky formalism will be required to search for rotations that vary slowly across the sky as well as for models in which the angular power spectrum for the rotation angle peaks at large angles.

Dependence of the L- to H-mode power threshold on toroidal rotation and the link to edge turbulence dynamics

Abstract: The injected power required to induce a transition from L-mode to H-mode plasmas is found to depend strongly on the injected neutral beam torque and consequent plasma toroidal rotation. Edge turbulence and flows, measured near the outboard midplane of the plasma (0.85 < r/a < 1.0) on DIII-D with the high-sensitivity 2D beam emission spectroscopy (BES) system, likewise vary with rotation and suggest a causative connection. The L–H power threshold in plasmas with the ion ∇B drift directed away from the X-point decreases from 4–6 MW with co-current beam injection, to 2–3 MW near zero net injected torque and to <2 MW with counter-injection in the discharges examined. Plasmas with the ion ∇B drift directed towards the X-point exhibit a qualitatively similar though less pronounced power threshold dependence on rotation. 2D edge turbulence measurements with BES show an increasing poloidal flow shear as the L–H transition is approached in all conditions. As toroidal rotation is varied from co-current to balanced in L-mode plasmas, the edge turbulence changes from a uni-modal character to a bi-modal structure, with the appearance of a low-frequency (f = 10–50 kHz) mode propagating in the electron diamagnetic direction, similar to what is observed as the ion ∇B drift is directed towards the X-point in co-rotating plasmas. At low rotation, the poloidal turbulence flow near the edge reverses prior to the L–H transition, generating a significant poloidal flow shear that exceeds the measured turbulence decorrelation rate. This increased poloidal turbulence velocity shear appears to facilitate the L–H transition. No such reversal is observed in high rotation plasmas. The high-frequency poloidal turbulence velocity spectrum exhibits a transition from a geodesic acoustic mode zonal flow to a higher-power, lower frequency zero-mean-frequency zonal flow as rotation varies from co-current to balanced during a torque scan at constant injected neutral beam power, perhaps also facilitating the L–H transition. This reduced power threshold at lower toroidal rotation may benefit inherently low-rotation plasmas such as ITER.

Apparatus and method for providing an output signal indicative of a speed of rotation and a direction of rotation of a ferromagnetic object

Abstract: An apparatus and a method provide an output signal indicative of a speed of rotation and a direction of rotation of a ferromagnetic object capable of rotating. A variety of signal formats of the output signal are described.