Orbit stability and feedback control in synchrotron radiation rings

International Nuclear Information System (INIS)

Yu, L.H.

1989-01-01

Stability of the electron orbit is essential for the utilization of a low emittance storage ring as a high brightness radiation source. We discuss the development of the measurement and feedback control of the closed orbit, with emphasis on the activities as the National Synchrotron Light Source of BNL. We discuss the performance of the beam position detectors in use and under development: the PUE rf detector, split ion chamber detector, photo-emission detector, solid state detector, and the graphite detector. Depending on the specific experiments, different beamlines require different tolerances on the orbit motion. Corresponding to these different requirements, we discuss two approaches to closed orbit feedback: the global and local feedback systems. Then we describe a new scheme for the real time global feedback by implementing a feedback system based upon a harmonic analysis of both the orbit movements and the correction magnetic fields. 14 refs., 6 figs., 2 tabs

More White Supremacy? "The Lord of the Rings" as Pro-American Imperialism

Science.gov (United States)

Knaus, Christopher

2005-01-01

"The Lord of the Rings" continues Hollywood's recurrent theme of good triumphing over evil. The viewer is supposed to identify with the heroes, whiteness, and goodness, which of course triumphs over evil and blackness. Although the cast is made up almost entirely of White people, people also do not question this narrative of White supremacy. To…

The Thermal Expansion of Ring Particles and the Secular Orbital Evolution of Rings Around Planets and Asteroids

Science.gov (United States)

Rubincam, David P.

2013-01-01

The thermal expansion and contraction of ring particles orbiting a planet or asteroid can cause secular orbit evolution. This effect, called here the thermal expansion effect, depends on ring particles entering and exiting the shadow of the body they orbit. A particle cools off in the shadow and heats up again in the sunshine, suffering thermal contraction and expansion. The changing cross-section it presents to solar radiation pressure plus time lags due to thermal inertia lead to a net along-track force. The effect causes outward drift for rocky particles. For the equatorial orbits considered here, the thermal expansion effect is larger than Poynting-Robertson drag in the inner solar system for particles in the size range approx. 0.001 - 0.02 m. This leads to a net increase in the semimajor axis from the two opposing effects at rates ranging from approx. 0.1 R per million years for Mars to approx. 1 R per million years for Mercury, for distances approx. 2R from the body, where R is the body's radius. Asteroid 243 Ida has approx. 10 R per million years, while a hypothetical Near-Earth Asteroid (NEA) can have faster rates of approx. 0.5 R per thousand years, due chiefly to its small radius compared to the planets. The thermal expansion effect weakens greatly at Jupiter and is overwhelmed by Poynting-Robertson for icy particles orbiting Saturn. Meteoroids in eccentric orbits about the Sun also suffer the thermal expansion effect, but with only approx. 0.0003e2 AU change in semimajor axis over a million years for a 2 m meteoroid orbiting between Mercury and Earth.

Neural network technique for orbit correction in accelerators/storage rings

International Nuclear Information System (INIS)

Bozoki, E.; Friedman, A.

1995-01-01

The authors are exploring the use of Neural Networks, using the SNNS simulator, for orbit control in accelerators (primarily circular accelerators) and storage rings. The orbit of the beam in those machines are measured by orbit monitors (input nodes) and controlled by orbit corrector magnets (output nodes). The physical behavior of an accelerator is changing slowly in time. Thus, an adoptive algorithm is necessary. The goal is to have a trained net which will predict the exact corrector strengths which will minimize a measured orbit. The relationship between open-quotes kickclose quotes from the correctors and open-quotes responseclose quotes from the monitors is in general non-linear and may slowly change during long-term operation of the machine. In the study, several network architectures are examined as well as various training methods for each architecture

Spin motion at and near orbital resonance in storage rings with Siberian snakes I. At orbital resonance

International Nuclear Information System (INIS)

Barber, D.P.; Vogt, M.

2006-12-01

Here, and in a sequel, we invoke the invariant spin field to provide an in-depth study of spin motion at and near low order orbital resonances in a simple model for the effects of vertical betatron motion in a storage ring with Siberian Snakes. This leads to a clear understanding, within the model, of the behaviour of the beam polarization at and near so-called snake resonances in proton storage rings. (orig.)

Quantum ring with the Rashba spin-orbit interaction in the regime of strong light-matter coupling

Science.gov (United States)

Kozin, V. K.; Iorsh, I. V.; Kibis, O. V.; Shelykh, I. A.

2018-04-01

We developed the theory of electronic properties of semiconductor quantum rings with the Rashba spin-orbit interaction irradiated by an off-resonant high-frequency electromagnetic field (dressing field). Within the Floquet theory of periodically driven quantum systems, it is demonstrated that the dressing field drastically modifies all electronic characteristics of the rings, including spin-orbit coupling, effective electron mass, and optical response. In particular, the present effect paves the way to controlling the spin polarization of electrons with light in prospective ring-shaped spintronic devices.

Energy transfer, orbital angular momentum, and discrete current in a double-ring fiber array

International Nuclear Information System (INIS)

Alexeyev, C. N.; Volyar, A. V.; Yavorsky, M. A.

2011-01-01

We study energy transfer and orbital angular momentum of supermodes in a double-ring array of evanescently coupled monomode optical fibers. The structure of supermodes and the spectra of their propagation constants are obtained. The geometrical parameters of the array, at which the energy is mostly confined within the layers, are determined. The developed method for finding the supermodes of concentric arrays is generalized for the case of multiring arrays. The orbital angular momentum carried by a supermode of a double-ring array is calculated. The discrete lattice current is introduced. It is shown that the sum of discrete currents over the array is a conserved quantity. The connection of the total discrete current with orbital angular momentum of discrete optical vortices is made.

Energy transfer, orbital angular momentum, and discrete current in a double-ring fiber array

Energy Technology Data Exchange (ETDEWEB)

Alexeyev, C. N.; Volyar, A. V. [Taurida National V.I. Vernadsky University, Vernadsky Prospekt, 4, Simferopol, 95007, Crimea (Ukraine); Yavorsky, M. A. [Taurida National V.I. Vernadsky University, Vernadsky Prospekt, 4, Simferopol, 95007, Crimea (Ukraine); Universite Bordeaux and CNRS, LOMA, UMR 5798, FR-33400 Talence (France)

2011-12-15

We study energy transfer and orbital angular momentum of supermodes in a double-ring array of evanescently coupled monomode optical fibers. The structure of supermodes and the spectra of their propagation constants are obtained. The geometrical parameters of the array, at which the energy is mostly confined within the layers, are determined. The developed method for finding the supermodes of concentric arrays is generalized for the case of multiring arrays. The orbital angular momentum carried by a supermode of a double-ring array is calculated. The discrete lattice current is introduced. It is shown that the sum of discrete currents over the array is a conserved quantity. The connection of the total discrete current with orbital angular momentum of discrete optical vortices is made.

Reconstructing Northeastern United States temperatures using Atlantic white cedar tree rings

Science.gov (United States)

Pearl, Jessie K.; Anchukaitis, Kevin J.; Pederson, Neil; Donnelly, Jeffrey P.

2017-11-01

Our knowledge of climate variability in the densely populated Northeastern United States is limited to instrumental data of the last century. Most regional paleoclimate proxies reflect a mix of climate responses, which makes reconstructing historical climate a challenge. Here we analyze tree-ring chronologies from Atlantic white cedar (Chamaecyparis thyoides) as a potential regional paleotemperature proxy. We evaluate our tree-ring network for spatiotemporal climate signal strength and reconstruction skill across New England. Atlantic white cedar sites in the northern section of the species’ range exhibit positive significant annual growth relationships with local and regional temperatures. Chronologies constructed from northern sites yield skillful reconstructions of temperature that reproduce centennial, multidecadal, and interannual variability in the instrumental record, providing a novel paleotemperature record for New England.

Global DC closed orbit correction experiments on the NSLS X-ray ring and SPEAR

International Nuclear Information System (INIS)

Chung, Y.; Decker, G.; Evans, K. Jr.; Safranek, J.; So, I.; Tang, Y.; Corbett, W.J.; Hettel, R.

1993-01-01

The global closed orbit correction experiments conducted on the NSLS X-ray ring and the SPEAR using the technique of singular value decomposition (SVD) are presented. The beam response matrix, defined as beam motion at beam position monitor (BPM) locations per unit kick by corrector magnets, was measured and then analyzed using SVD. The BPMs and correctors are reconfigured into open-quotes transformedclose quotes BPMs (t-BPMs) and open-quotes transformedclose quotes correctors (t-correctors), with each T-BPM coupled to at most one t-corrector and vice versa for orbit correction. The decoupled t-BPMs are used to estimate the limit on orbit correction, while the decoupled t-correctors are used to optimize the corrector strengths. As a result the vertical r.m.s. orbit error at the BPM locations was reduced from 208 μm to 61 μm about an arbitrary reference orbit in the NSLS X-ray ring. In SPEAR, the vertical closed orbit was brought to the BPM centers at the selected BPM locations with an r.m.s. error of 215 μm reduced from the initial 780 μm

Model-independent and fast determination of optical functions in storage rings via multiturn and closed-orbit data

Directory of Open Access Journals (Sweden)

Bernard Riemann

2011-06-01

Full Text Available Multiturn (or turn-by-turn data acquisition has proven to be a new source of direct measurements for Twiss parameters in storage rings. On the other hand, closed-orbit measurements are a long-known tool for analyzing closed-orbit perturbations with conventional beam position monitor (BPM systems and are necessarily available at every storage ring. This paper aims at combining the advantages of multiturn measurements and closed-orbit data. We show that only two multiturn BPMs and four correctors in one localized drift space in the storage ring (diagnostic drift are sufficient for model-independent and absolute measuring of β and φ functions at all BPMs, including the conventional ones, instead of requiring all BPMs being equipped with multiturn electronics.

Model-independent and fast determination of optical functions in storage rings via multiturn and closed-orbit data

Science.gov (United States)

Riemann, Bernard; Grete, Patrick; Weis, Thomas

2011-06-01

Multiturn (or turn-by-turn) data acquisition has proven to be a new source of direct measurements for Twiss parameters in storage rings. On the other hand, closed-orbit measurements are a long-known tool for analyzing closed-orbit perturbations with conventional beam position monitor (BPM) systems and are necessarily available at every storage ring. This paper aims at combining the advantages of multiturn measurements and closed-orbit data. We show that only two multiturn BPMs and four correctors in one localized drift space in the storage ring (diagnostic drift) are sufficient for model-independent and absolute measuring of β and φ functions at all BPMs, including the conventional ones, instead of requiring all BPMs being equipped with multiturn electronics.

Orbital and spin dynamics of intraband electrons in quantum rings driven by twisted light.

Science.gov (United States)

Quinteiro, G F; Tamborenea, P I; Berakdar, J

2011-12-19

We theoretically investigate the effect that twisted light has on the orbital and spin dynamics of electrons in quantum rings possessing sizable Rashba spin-orbit interaction. The system Hamiltonian for such a strongly inhomogeneous light field exhibits terms which induce both spin-conserving and spin-flip processes. We analyze the dynamics in terms of the perturbation introduced by a weak light field on the Rasha electronic states, and describe the effects that the orbital angular momentum as well as the inhomogeneous character of the beam have on the orbital and the spin dynamics.

Depolarization of the electron spin in storage rings by nonlinear spin-orbit coupling

International Nuclear Information System (INIS)

Kewisch, J.

1985-10-01

Electrons and positrons which circulate in the storage ring are polarized at the emission of synchrotron radiation by the so called Sokolov-Ternov effect. This polarization is on the one hand of large interest for the study of the weak interaction, on the other hand it can be used for the accurate measurement of the beam energy and by this of the mass of elementary particles. The transverse and longitudinal particle vibrations simultaneously excited by the synchrotron radiation however can effect that this polarization is destroyed. This effect is called spin-orbit coupling. For the calculation of the spin-orbit coupling the computer program SITROS was written. This program is a tracking program: The motion of some sample particles and their spin vectors are calculated for some thousand circulations. From this the mean depolarization and by extrapolation the degree of polarization of the equilibrium state is determined. Contrarily to the known program SLIM which is based on perturbational calculations in SITROS the nonlinear forces in the storage ring can be regarded. By this the calculation of depolarizing higher order resonances is made possible. In this thesis the equations of motion for the orbital and spin motion of the electrons are derived which form the base for the program SITROS. The functions of the program and the approximations necessary for the saving of calculational time are explained. The comparison of the SITROS results with the measurement results obtained at the PETRA storage ring shows that the SITROS program is a useful means for the planning and calculation of storage rings with polarized electron beams. (orig.) [de

Persistent current in triangle silicene rings with spin–orbit interaction

Energy Technology Data Exchange (ETDEWEB)

Xu, Ning, E-mail: nxu@ycit.cn [Department of Physics, Yancheng Institute of Technology, Yancheng 224051 (China); Zhang, Haiyang; Wu, Xiuqiang; Bai, Yujie [Department of Physics, Yancheng Institute of Technology, Yancheng 224051 (China); Ding, Jianwen, E-mail: jwding@xtu.edu.cn [Department of Physics, Xiangtan University, Xiangtan 411105 (China)

2017-06-28

The energy spectrum and magnetic response of triangle silicene rings (TSRs) are investigated within the tight-binding model. It is shown that the flux-dependent energy spectrum is divided into bands, with three levels per band, owing to the three-fold rotational symmetry structure of TSRs. The zigzag TSRs are metallic, exhibiting either diamagnetic or paramagnetic response depending on the size of inner ring radius. Armchair TSRs are semiconducting, exhibiting diamagnetic response. Taking into account the intrinsic spin–orbit interaction, the magnetic-field-driven spin-up electrons flow anticlockwise around the TSRs and the spin-down electrons flow clockwise around the TSRs. Additionally, paramagnetism–diamagnetism or diamagnetism–paramagnetism transitions are observed with the increase of exchange field. The results may be very helpful for the design and application of TSR-based nanodevices. - Highlights: • The zigzag TSRs are metallic. • Armchair TSRs which exhibit diamagnetic response are semiconducting. • The spin-up electrons flow anticlockwise and spin-down electrons flow clockwise around the rings.

Characteristics of persistent spin current components in a quasi-periodic Fibonacci ring with spin–orbit interactions: Prediction of spin–orbit coupling and on-site energy

International Nuclear Information System (INIS)

Patra, Moumita; Maiti, Santanu K.

2016-01-01

In the present work we investigate the behavior of all three components of persistent spin current in a quasi-periodic Fibonacci ring subjected to Rashba and Dresselhaus spin–orbit interactions. Analogous to persistent charge current in a conducting ring where electrons gain a Berry phase in presence of magnetic flux, spin Berry phase is associated during the motion of electrons in presence of a spin–orbit field which is responsible for the generation of spin current. The interplay between two spin–orbit fields along with quasi-periodic Fibonacci sequence on persistent spin current is described elaborately, and from our analysis, we can estimate the strength of any one of two spin–orbit couplings together with on-site energy, provided the other is known. - Highlights: • Determination of Rashba and Dresselhaus spin–orbit fields is discussed. • Characteristics of all three components of spin current are explored. • Possibility of estimating on-site energy is given. • Results can be generalized to any lattice models.

Characteristics of persistent spin current components in a quasi-periodic Fibonacci ring with spin–orbit interactions: Prediction of spin–orbit coupling and on-site energy

Energy Technology Data Exchange (ETDEWEB)

Patra, Moumita; Maiti, Santanu K., E-mail: santanu.maiti@isical.ac.in

2016-12-15

In the present work we investigate the behavior of all three components of persistent spin current in a quasi-periodic Fibonacci ring subjected to Rashba and Dresselhaus spin–orbit interactions. Analogous to persistent charge current in a conducting ring where electrons gain a Berry phase in presence of magnetic flux, spin Berry phase is associated during the motion of electrons in presence of a spin–orbit field which is responsible for the generation of spin current. The interplay between two spin–orbit fields along with quasi-periodic Fibonacci sequence on persistent spin current is described elaborately, and from our analysis, we can estimate the strength of any one of two spin–orbit couplings together with on-site energy, provided the other is known. - Highlights: • Determination of Rashba and Dresselhaus spin–orbit fields is discussed. • Characteristics of all three components of spin current are explored. • Possibility of estimating on-site energy is given. • Results can be generalized to any lattice models.

Use of eigenvectors in understanding and correcting storage ring orbits

International Nuclear Information System (INIS)

Friedman, A.; Bozoki, E.

1994-01-01

The response matrix A is defined by the equation X=AΘ, where Θ is the kick vector and X is the resulting orbit vector. Since A is not necessarily a symmetric or even a square matrix we symmetrize it by using A T A. Then we find the eigenvalues and eigenvectors of this A T A matrix. The physical interpretation of the eigenvectors for circular machines is discussed. The task of the orbit correction is to find the kick vector Θ for a given measured orbit vector X. We are presenting a method, in which the kick vector is expressed as linear combination of the eigenvectors. An additional advantage of this method is that it yields the smallest possible kick vector to correct the orbit. We will illustrate the application of the method to the NSLS X-ray and UV storage rings and the resulting measurements. It will be evident, that the accuracy of this method allows the combination of the global orbit correction and local optimization of the orbit for beam lines and insertion devices. The eigenvector decomposition can also be used for optimizing kick vectors, taking advantage of the fact that eigenvectors with corresponding small eigenvalue generate negligible orbit changes. Thus, one can reduce a kick vector calculated by any other correction method and still stay within the tolerance for orbit correction. The use of eigenvectors in accurately measuring the response matrix and the use of the eigenvalue decomposition orbit correction algorithm in digital feedback is discussed. (orig.)

Unconventional low-field magnetic response of a diffusive ring with spin–orbit coupling

International Nuclear Information System (INIS)

Patra, Moumita; Maiti, Santanu K.

2017-01-01

We report an unconventional behavior of electron transport in the limit of zero magnetic flux in a one-dimensional disordered ring, be it completely random or any correlated one, subjected to Rashba spin–orbit (SO) coupling. It exhibits much higher circulating current compared to a fully perfect ring for a wide range of SO coupling yielding larger electrical conductivity which is clearly verified from our Drude weight analysis. - Highlights: • Unconventional behavior of electron transport in a 1D disordered ring is reported. • Interplay between Rashba So interaction and disorder is discussed. • Disordered ring provides much higher current compared to a perfect one. • Results are independent with disorderness, be it correlated or random. • MI transition and selective switching effects are discussed.

Unconventional low-field magnetic response of a diffusive ring with spin–orbit coupling

Energy Technology Data Exchange (ETDEWEB)

Patra, Moumita; Maiti, Santanu K., E-mail: santanu.maiti@isical.ac.in

2017-01-30

We report an unconventional behavior of electron transport in the limit of zero magnetic flux in a one-dimensional disordered ring, be it completely random or any correlated one, subjected to Rashba spin–orbit (SO) coupling. It exhibits much higher circulating current compared to a fully perfect ring for a wide range of SO coupling yielding larger electrical conductivity which is clearly verified from our Drude weight analysis. - Highlights: • Unconventional behavior of electron transport in a 1D disordered ring is reported. • Interplay between Rashba So interaction and disorder is discussed. • Disordered ring provides much higher current compared to a perfect one. • Results are independent with disorderness, be it correlated or random. • MI transition and selective switching effects are discussed.

Stochastic orbital migration of small bodies in Saturn's rings

Science.gov (United States)

Rein, H.; Papaloizou, J. C. B.

2010-12-01

Many small moonlets that create propeller structures have been found in Saturn's rings by the Cassini spacecraft. We study the dynamical evolution of such 20-50 m sized bodies, which are embedded in Saturn's rings. We estimate the importance of various interaction processes with the ring particles on the moonlet's eccentricity and semi-major axis analytically. For low ring surface densities, the main effects on the evolution of the eccentricity and the semi-major axis are found to be caused by collisions and the gravitational interaction with particles in the vicinity of the moonlet. For high surface densities, the gravitational interaction with self-gravity wakes becomes important. We also perform realistic three-dimensional, collisional N-body simulations with up to a quarter of a million particles. A new set of pseudo shear periodic boundary conditions is used, which reduces the computational costs by an order of magnitude compared to previous studies. Our analytic estimates are confirmed to within a factor of two. On short timescales the evolution is always dominated by stochastic effects caused by collisions and gravitational interaction with self-gravitating ring particles. These result in a random walk of the moonlet's semi-major axis. The eccentricity of the moonlet quickly reaches an equilibrium value owing to collisional damping. The average change in semi-major axis of the moonlet after 100 orbital periods is 10-100m. This translates to an offset in the azimuthal direction of several hundred kilometres. We expect that such a shift is easily observable. Two movies are only available in electronic form at http://www.aanda.org

Digital closed orbit feedback system for the Advanced Photon Source storage ring

International Nuclear Information System (INIS)

Chung, Y.; Barr, D.; Decker, G.; Galayda, J.; Lenkszus, F.; Lumpkin, A.; Votaw, A.J.

1995-01-01

Closed orbit feedback for the Advanced Photon Source (APS) storage ring employs unified global an local feedback systems for stabilization of particle and photon beams based on digital signal processing (DSP). Hardware and software aspects of the system will be described. In particular, we will discuss global and local orbit feedback algorithms, PID (proportional, integral, and derivative) control algorithm. application of digital signal processing to compensate for vacuum chamber eddy current effects, resolution of the interaction between global and local systems through decoupling, self-correction of the local bump closure error, user interface through the APS control system, and system performance in the frequency and time domains. The system hardware, including the DSPS, is distributed in 20 VNE crates around the ring, and the entire feedback system runs synchronously at 4-kHz sampling frequency in order to achieve a correction bandwidth exceeding 100 Hz. The required data sharing between the global and local feedback systems is facilitated via the use of fiber-optically-networked reflective memories

1393 Ring Bus at JPL: Description and Status

Science.gov (United States)

Wysocky, Terry R.

2007-01-01

Completed Ring Bus IC V&V Phase - Ring Bus Test Plan Completed for SIM Project - Applicable to Other Projects Implemented a Avionics Bus Based upon the IEEE 1393 Standard - Excellent Starting Point for a General Purpose High-Speed Spacecraft Bus - Designed to Meet SIM Requirements for - Real-time deterministic, distributed systems. - Control system requirements - Fault detection and recovery Other JPL Projects Considering Implementation F'light Software Ring Bus Driver Module Began in 2006, Continues Participating in Standard Revision. Search for Earth-like planets orbiting nearby stars and measure the masses and orbits of the planets it finds. Survey 2000 nearby stars for planetary systems to learn whether our Solar System is unusual, or typical. Make a new catalog of star position 100 times more accurate than current measurements. Learn how our galaxy formed and will evolve by studying the dynamics of its stars. Critically test models of exactly how stars shine, including exotic objects like black holes, neutron stars and white dwarfs.

IDIOPATHIC MULTIFOCAL CHOROIDITIS PRESENTING WITH A TRANSIENT PERIPAPILLARY WHITE RING.

Science.gov (United States)

Gattoussi, Sarra; Ghadiali, Quraish; Dolz-Marco, Rosa; Freund, K Bailey

2017-11-22

We describe with multimodal imaging the presentation and follow-up for a patient with idiopathic multifocal choroiditis and a transient peripapillary white ring. Case report. A 39-year-old Asian woman was initially seen for an evaluation of lattice degeneration in 2015. Her medical history included Graves disease and psoriasis. Best-corrected visual acuity was 20/25 in her right eye and 20/25 in her left eye. Ultra-widefield fundus autofluorescence imaging showed a curvilinear hyperautofluorescent line in her right eye. One year later, the patient returned complaining of floaters in her right eye for 1 month. Her visual acuity was unchanged. Funduscopic examination showed new inflammatory yellowish lesions in the right eye corresponding to hyperreflective sub-retinal pigment epithelium lesions on structural spectral domain optical coherence tomography. Fluorescein angiography showed corresponding late staining of these active lesions. Late-phase indocyanine green angiography showed multiple nummular hypocyanescent dots. Ultra-widefield fundus autofluorescence showed large areas of hyperautofluorescence. The patient was started on a 60-mg oral prednisone taper and demonstrated subsequent regression of the inflammatory lesions. Ten months later, the patient returned emergently with complaints of floaters in both eyes for 2 days and a new temporal scotoma in her left eye. Funduscopic examination demonstrated a white ring around the optic nerve of the left eye corresponding to a hyperautofluorescent lesion. Ultra-widefield fundus autofluorescence showed new areas of hyperautofluorescence in both eyes. Structural spectral domain optical coherence tomography showed new sub-retinal pigment epithelium inflammatory lesions and a disruption of the ellipsoid zone in both eyes. The patient was again treated with a 60-mg oral prednisone taper and demonstrated subsequent restoration of the ellipsoid zone. To our knowledge, this is the first report of a transient annular white

A digital feedback system for transverse orbit stabilization in the NSLS rings

International Nuclear Information System (INIS)

Friedman, A.; Bozoki, E.

1993-01-01

We are reporting on the design and preliminary results of a prototype digital feedback system for the storage rings at the NSLS. the system will use a nolinear eigenvector decomposition algorithm. It will have a wide dynamic range and will be able to correct noise in the orbit over a bandwidth in excess of 60 Hz. A Motorola-162 CPU board is used to sample the PUE's at a minimum rate of 200 Hz and an HP-742rt board is used to read the sampled signals and to generate a correction signal for the orbit correctors

Conductance of a quantum ring with spin-orbit interaction in the presence of an impurity

International Nuclear Information System (INIS)

Kovalev, V. M.; Chaplik, A. V.

2006-01-01

The conductance of a quantum ring has been calculated on the basis of the tunneling Hamiltonian in the quasiballistic regime of the motion of electrons with allowance for the spin-orbit interaction. The effect of the scattering of electrons by a single short-range interacting impurity in the quantum ring on the tunneling electron current is analyzed. Two types of impurities, spinless and paramagnetic, are considered. The conductance symmetry is discussed for various electron-spin orientations with respect to change in the sign of the magnetic flux through the quantum ring

White-light laser cooling of ions in a storage ring

International Nuclear Information System (INIS)

Calabrese, R.; Guidi, V.; Lenisa, P.; Grimm, R.; Miesner, H.J.; Mariotti, E.; Siena Univ.; Moi, L.; Siena Univ.

1996-01-01

We propose the use of a white laser for laser cooling of ions in a storage ring. The use of a broad-band laser provides a radiation pressure force with wide velocity capture range and high magnitude, which is promising to improve the performance of both longitudinal and indirect transverse cooling. This wide-range force could also be suitable for direct transverse cooling of low-density beams. (orig.)

THE HABITABILITY AND DETECTION OF EARTH-LIKE PLANETS ORBITING COOL WHITE DWARFS

Energy Technology Data Exchange (ETDEWEB)

Fossati, L.; Haswell, C. A.; Patel, M. R.; Busuttil, R. [Department of Physical Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Bagnulo, S. [Armagh Observatory, College Hill, Armagh BT61 9DG (United Kingdom); Kowalski, P. M. [GFZ German Research Centre for Geosciences, Telegrafenberg, D-14473 Potsdam (Germany); Shulyak, D. V. [Institute of Astrophysics, Georg-August-University, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany); Sterzik, M. F., E-mail: l.fossati@open.ac.uk, E-mail: C.A.Haswell@open.ac.uk, E-mail: M.R.Patel@open.ac.uk, E-mail: r.busuttil@open.ac.uk, E-mail: sba@arm.ac.uk, E-mail: kowalski@gfz-potsdam.de, E-mail: denis.shulyak@gmail.com, E-mail: msterzik@eso.org [European Southern Observatory, Casilla 19001, Santiago 19 (Chile)

2012-09-20

Since there are several ways planets can survive the giant phase of the host star, we examine the habitability and detection of planets orbiting white dwarfs. As a white dwarf cools from 6000 K to 4000 K, a planet orbiting at 0.01 AU would remain in the continuous habitable zone (CHZ) for {approx}8 Gyr. We show that photosynthetic processes can be sustained on such planets. The DNA-weighted UV radiation dose for an Earth-like planet in the CHZ is less than the maxima encountered on Earth, and hence non-magnetic white dwarfs are compatible with the persistence of complex life. Polarization due to a terrestrial planet in the CHZ of a cool white dwarf (CWD) is 10{sup 2} (10{sup 4}) times larger than it would be in the habitable zone of a typical M-dwarf (Sun-like star). Polarimetry is thus a viable way to detect close-in rocky planets around white dwarfs. Multi-band polarimetry would also allow us to reveal the presence of a planet atmosphere, providing a first characterization. Planets in the CHZ of a 0.6 M{sub Sun} white dwarf will be distorted by Roche geometry, and a Kepler-11d analog would overfill its Roche lobe. With current facilities a super-Earth-sized atmosphereless planet is detectable with polarimetry around the brightest known CWD. Planned future facilities render smaller planets detectable, in particular by increasing the instrumental sensitivity in the blue.

THE HABITABILITY AND DETECTION OF EARTH-LIKE PLANETS ORBITING COOL WHITE DWARFS

International Nuclear Information System (INIS)

Fossati, L.; Haswell, C. A.; Patel, M. R.; Busuttil, R.; Bagnulo, S.; Kowalski, P. M.; Shulyak, D. V.; Sterzik, M. F.

2012-01-01

Since there are several ways planets can survive the giant phase of the host star, we examine the habitability and detection of planets orbiting white dwarfs. As a white dwarf cools from 6000 K to 4000 K, a planet orbiting at 0.01 AU would remain in the continuous habitable zone (CHZ) for ∼8 Gyr. We show that photosynthetic processes can be sustained on such planets. The DNA-weighted UV radiation dose for an Earth-like planet in the CHZ is less than the maxima encountered on Earth, and hence non-magnetic white dwarfs are compatible with the persistence of complex life. Polarization due to a terrestrial planet in the CHZ of a cool white dwarf (CWD) is 10 2 (10 4 ) times larger than it would be in the habitable zone of a typical M-dwarf (Sun-like star). Polarimetry is thus a viable way to detect close-in rocky planets around white dwarfs. Multi-band polarimetry would also allow us to reveal the presence of a planet atmosphere, providing a first characterization. Planets in the CHZ of a 0.6 M ☉ white dwarf will be distorted by Roche geometry, and a Kepler-11d analog would overfill its Roche lobe. With current facilities a super-Earth-sized atmosphereless planet is detectable with polarimetry around the brightest known CWD. Planned future facilities render smaller planets detectable, in particular by increasing the instrumental sensitivity in the blue.

Exact solutions of the Schrodinger equation for an electron in the circular quantum ring taking into account spin-orbit interactions

International Nuclear Information System (INIS)

Kudryashov, V.V.; Baran, A.V.

2012-01-01

The exact solutions of the Schrodinger equation are obtained for an electron in two-dimensional circular semiconductor quantum ring in the presence of the Rashba and Dresselhaus spin-orbit interactions of equal strength. Confinement is simulated by a realistic potential well of finite depth. The dependence of energy levels on the strength of spin-orbit interaction, the relative ring width, and the depth of a potential well is presented. (authors)

Periventricular heterotopia and white matter abnormalities in a girl with mosaic ring chromosome 6.

Science.gov (United States)

Nishigaki, Satsuki; Hamazaki, Takashi; Saito, Mika; Yamamoto, Toshiyuki; Seto, Toshiyuki; Shintaku, Haruo

2015-01-01

Ring chromosome 6 is a rare chromosome abnormality that arises typically de novo. The phenotypes can be highly variable, ranging from almost normal to severe malformations and neurological defects. We report a case of a 3-year-old girl with mosaic ring chromosome 6 who presented with being small for gestational age and intellectual disability, and whose brain MRI later revealed periventricular heterotopia and white matter abnormalities. Mosaicism was identified in peripheral blood cells examined by standard G-bands, mos 46,XX,r(6)(p25q27)[67]/45,XX,-6[25]/46,XX,dic r(6:6)(p25q27:p25q27)[6]/47,XX,r(6)(p25q27) × 2[2]. Using array-comparative genomic hybridization, we identified terminal deletion of 6q27 (1.5 Mb) and no deletion on 6p. To our knowledge, this is the first report of periventricular heterotopia and white matter abnormalities manifested in a patient with ring chromosome 6. These central nervous system malformations are further discussed in relation to molecular genetics.

Digital closed orbit feedback system for the advanced photon source storage ring

International Nuclear Information System (INIS)

Chung, Y.; Barr, D.; Decker, G.

1995-01-01

The Advanced Photon Source (APS) is a dedicated third-generation synchrotron light source with a nominal energy of 7 GeV and a circumference of 1104 m. The closed orbit feedback system for the APS storage ring employs unified global and local feedback systems for stabilization of particle and photon beams based on digital signal processing (DSP). Hardware and software aspects of the system will be described in this paper. In particular, we will discuss global and local orbit feedback algorithms, PID (proportional, integral, and derivative) control algorithm, application of digital signal processing to compensate for vacuum chamber eddy current effects, resolution of the interaction between global and local systems through decoupling, self-correction of the local bump closure error, user interface through the APS control system, and system performance in the frequency and time domains. The system hardware including the DSPs is distributed in 20 VME crates around the ring, and the entire feedback system runs synchronously at 4-kHz sampling frequency in order to achieve a correction bandwidth exceeding 100 Hz. The required data sharing between the global and local feedback systems is facilitated via the use of fiber-optically-networked reflective memories

A multiple-orbit time-of-flight mass spectrometer based on a low energy electrostatic storage ring

Science.gov (United States)

Sullivan, M. R.; Spanjers, T. L.; Thorn, P. A.; Reddish, T. J.; Hammond, P.

2012-11-01

The results are presented for an electrostatic storage ring, consisting of two hemispherical deflector analyzers (HDA) connected by two separate sets of cylindrical lenses, used as a time-of-flight mass spectrometer. Based on the results of charged particle simulations and formal matrix model, the Ion Storage Ring is capable of operating with multiple stable orbits, for both single and multiply charged ions simultaneously.

Binary Star Orbits. V. The Nearby White Dwarf/Red Dwarf Pair 40 Eri BC

Science.gov (United States)

Mason, Brian D.; Hartkopf, William I.; Miles, Korie N.

2017-11-01

A new relative orbit solution with new dynamical masses is determined for the nearby white dwarf-red dwarf pair 40 Eri BC. The period is 230.09 ± 0.68 years. It is predicted to close slowly over the next half-century, getting as close as 1.″32 in early 2066. We determine masses of 0.575 ± 0.018 {{ M }}⊙ for the white dwarf and 0.2041 ± 0.0064 {{ M }}⊙ for the red dwarf companion. The inconsistency of the masses determined by gravitational redshift and dynamical techniques, due to a premature orbit calculation, no longer exists.

High Astrometric Precision in the Calculation of the Coordinates of Orbiters in the GEO Ring

Science.gov (United States)

Lacruz, E.; Abad, C.; Downes, J. J.; Hernández-Pérez, F.; Casanova, D.; Tresaco, E.

2018-04-01

We present an astrometric method for the calculation of the positions of orbiters in the GEO ring with a high precision, through a rigorous astrometric treatment of observations with a 1-m class telescope, which are part of the CIDA survey of the GEO ring. We compute the distortion pattern to correct for the systematic errors introduced by the optics and electronics of the telescope, resulting in absolute mean errors of 0.16″ and 0.12″ in right ascension and declination, respectively. These correspond to ≍25 m at the mean distance of the GEO ring, and are thus good quality results.

A general harmonic spin matching formalism for the suppression of depolarisation caused by closed orbit distortion in electron storage rings

International Nuclear Information System (INIS)

Barber, D.P.; Mais, H.; Ripken, G.; Rossmanith, R.

1985-03-01

We present a general formalism for correcting perturbations to the equilibrium sspin axis in electron storage rings due to the orbit errors so that depolarizing effects due to machine misalignments can be controlled. The method proposed is suitable for rings containing e.g. solenoids, skew quadrupoles and vertical bends and since it is based on a SLIM-like representation of the orbital and spin motion it can be conveniently realized as a straight forward extension to that program. (orig.)

Effects and Correction of Closed Orbit Magnet Errors in the SNS Ring

Energy Technology Data Exchange (ETDEWEB)

Bunch, S.C.; Holmes, J.

2004-01-01

We consider the effect and correction of three types of orbit errors in SNS: quadrupole displacement errors, dipole displacement errors, and dipole field errors. Using the ORBIT beam dynamics code, we focus on orbit deflection of a standard pencil beam and on beam losses in a high intensity injection simulation. We study the correction of these orbit errors using the proposed system of 88 (44 horizontal and 44 vertical) ring beam position monitors (BPMs) and 52 (24 horizontal and 28 vertical) dipole corrector magnets. Correction is carried out numerically by adjusting the kick strengths of the dipole corrector magnets to minimize the sum of the squares of the BPM signals for the pencil beam. In addition to using the exact BPM signals as input to the correction algorithm, we also consider the effect of random BPM signal errors. For all three types of error and for perturbations of individual magnets, the correction algorithm always chooses the three-bump method to localize the orbit displacement to the region between the magnet and its adjacent correctors. The values of the BPM signals resulting from specified settings of the dipole corrector kick strengths can be used to set up the orbit response matrix, which can then be applied to the correction in the limit that the signals from the separate errors add linearly. When high intensity calculations are carried out to study beam losses, it is seen that the SNS orbit correction system, even with BPM uncertainties, is sufficient to correct losses to less than 10-4 in nearly all cases, even those for which uncorrected losses constitute a large portion of the beam.

TRANSIT MODEL OF PLANETS WITH MOON AND RING SYSTEMS

International Nuclear Information System (INIS)

Tusnski, Luis Ricardo M.; Valio, Adriana

2011-01-01

Since the discovery of the first exoplanets, those most adequate for life to begin and evolve have been sought. Due to observational bias, however, most of the discovered planets so far are gas giants, precluding their habitability. However, if these hot Jupiters are located in the habitable zones of their host stars, and if rocky moons orbit them, then these moons may be habitable. In this work, we present a model for planetary transit simulation considering the presence of moons and planetary rings around a planet. The moon's orbit is considered to be circular and coplanar with the planetary orbit. The other physical and orbital parameters of the star, planet, moon, and rings can be adjusted in each simulation. It is possible to simulate as many successive transits as desired. Since the presence of spots on the surface of the star may produce a signal similar to that of the presence of a moon, our model also allows for the inclusion of starspots. The result of the simulation is a light curve with a planetary transit. White noise may also be added to the light curves to produce curves similar to those obtained by the CoRoT and Kepler space telescopes. The goal is to determine the criteria for detectability of moons and/or ring systems using photometry. The results show that it is possible to detect moons with radii as little as 1.3 R ⊕ with CoRoT and 0.3 R ⊕ with Kepler.

Use of regularization method in the determination of ring parameters and orbit correction

International Nuclear Information System (INIS)

Tang, Y.N.; Krinsky, S.

1993-01-01

We discuss applying the regularization method of Tikhonov to the solution of inverse problems arising in accelerator operations. This approach has been successfully used for orbit correction on the NSLS storage rings, and is presently being applied to the determination of betatron functions and phases from the measured response matrix. The inverse problem of differential equation often leads to a set of integral equations of the first kind which are ill-conditioned. The regularization method is used to combat the ill-posedness

EXOSAT observations of V471 Tauri - a 9.25 minute white dwarf pulsation and orbital phase dependent X-ray dips

International Nuclear Information System (INIS)

Jensen, K.A.; Swank, J.H.; Petre, P.; Guinan, E.F.; Sion, E.M.; Navy, E. O. Hulburt Center for Space Research, Washington, DC; Villanova Univ., PA)

1986-01-01

New results obtained from a 28 hr continuous observation of V471 Tauri with the EXOSAT satellite are reported. The detection of soft X-ray fluxes from both the white dwarf and the K dwarf, the discovery of a 9.25 minute pulsation from the white dwarf, and the discovery of orbital phase-related soft X-ray dips are discussed. The dips may be correlated with the triangular Lagrangian points of the binary orbit. The X-ray flux from the white dwarf is consistent with thermal models for a white dwarf photosphere with T(eff) of about 35,000 K, log g = 8.0-8.5, and log N(H) = 18.65 + or - 0.2. 25 references

A 12 MINUTE ORBITAL PERIOD DETACHED WHITE DWARF ECLIPSING BINARY

International Nuclear Information System (INIS)

Brown, Warren R.; Kilic, Mukremin; Kenyon, Scott J.; Hermes, J. J.; Winget, D. E.; Prieto, Carlos Allende

2011-01-01

We have discovered a detached pair of white dwarfs (WDs) with a 12.75 minute orbital period and a 1315 km s -1 radial velocity amplitude. We measure the full orbital parameters of the system using its light curve, which shows ellipsoidal variations, Doppler boosting, and primary and secondary eclipses. The primary is a 0.25 M sun tidally distorted helium WD, only the second tidally distorted WD known. The unseen secondary is a 0.55 M sun carbon-oxygen WD. The two WDs will come into contact in 0.9 Myr due to loss of energy and angular momentum via gravitational wave radiation. Upon contact the systems may merge (yielding a rapidly spinning massive WD), form a stable interacting binary, or possibly explode as an underluminous Type Ia supernova. The system currently has a gravitational wave strain of 10 -22 , about 10,000 times larger than the Hulse-Taylor pulsar; this system would be detected by the proposed Laser Interferometer Space Antenna gravitational wave mission in the first week of operation. This system's rapid change in orbital period will provide a fundamental test of general relativity.

Cassini Operational Sun Sensor Risk Management During Proximal Orbit Saturn Ring Plane Crossings

Science.gov (United States)

Bates, David M.

2016-01-01

NASA's Cassini Spacecraft, launched on October 15th, 1997 which arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. As the first spacecraft to achieve orbit at Saturn, Cassini has collected science data throughout its four-year prime mission (2004–08), and has since been approved for a first and second extended mission through 2017. As part of the final extended missions, Cassini will begin an aggressive and exciting campaign of high inclination, low altitude flybys within the inner most rings of Saturn, skimming Saturn’s outer atmosphere, until the spacecraft is finally disposed of via planned impact with the planet. This final campaign, known as the proximal orbits, requires a strategy for managing the Sun Sensor Assembly (SSA) health, the details of which are presented in this paper.

Influence of the Rashba and Dresselhaus spin-orbit interactions on the electron states in circular quantum rings

International Nuclear Information System (INIS)

Kudryashov, V.V.; Baran, A.V.

2015-01-01

Within the framework of perturbation theory the energy levels and wave functions are found for an electron in two-dimensional semiconductor circular quantum rings in the presence of the Rashba and Dresselhaus spin-orbit interactions with a realistic axially symmetric confining square well potential of finite depth. (authors)

Simultaneous effects of hydrostatic pressure and spin–orbit coupling on linear and nonlinear intraband optical absorption coefficients in a GaAs quantum ring

International Nuclear Information System (INIS)

Mughnetsyan, V.N.; Manaselyan, A.Kh.; Barseghyan, M.G.; Kirakosyan, A.A.

2013-01-01

In this paper the simultaneous effect of hydrostatic pressure and Rashba spin–orbit interaction on intraband linear and nonlinear light absorption has been investigated in cylindrical quantum ring. The one electron energy spectrum has been found using the effective mass approximation and diagonalization procedure. We have found that the Rashba interaction can lead both to the blue- or to the red-shift of the absorption spectrum depending on the transitions character, while the only red-shift is observed due to the hydrostatic pressure. - Highlights: ► The effects of hydrostatic pressure and spin–orbit coupling are investigated for quantum ring. ► The non-linear absorption coefficient is calculated. ► The hydrostatic pressure leads to the decrease in the absorption coefficient. ► Spin–orbit coupling weakens some transitions and strengthens others.

A canonical eight-dimensional formalism for linear and non-linear classical spin-orbit motion in storage rings

International Nuclear Information System (INIS)

Barber, D.P.; Heinemann, K.; Ripken, G.

1991-05-01

In the following report we begin to reformulate work by Derbenev on the behaviour of coupled quantized spin-orbit motion. To this end we present a classical symplectic treatment of linear and non-linear spin-orbit motion for storage rings using a fully coupled eight-dimensional formalism which generalizes earlier investigations of coupled synchro-betatron oscillations by introducing two additional canonical spin variables which behave, in a small-angle limit, like those already used in linearised spin theory. Thus in addition to the usual x-z-s couplings, both the spin to orbit and orbit to spin coupling are described canonically. Since the spin Hamiltonian can be expanded in a Taylor series in canonical variables, the formalism is convenient for use in 8-dimensional symplectic tracking calculations with the help, for example, of Lie algebra or differential algebra for the study of chaotic spin motion, for construction of spin normal forms and for the study of the effect of Stern-Gerlach forces. (orig.)

Software package for modeling spin-orbit motion in storage rings

Science.gov (United States)

Zyuzin, D. V.

2015-12-01

A software package providing a graphical user interface for computer experiments on the motion of charged particle beams in accelerators, as well as analysis of obtained data, is presented. The software package was tested in the framework of the international project on electric dipole moment measurement JEDI (Jülich Electric Dipole moment Investigations). The specific features of particle spin motion imply the requirement to use a cyclic accelerator (storage ring) consisting of electrostatic elements, which makes it possible to preserve horizontal polarization for a long time. Computer experiments study the dynamics of 106-109 particles in a beam during 109 turns in an accelerator (about 1012-1015 integration steps for the equations of motion). For designing an optimal accelerator structure, a large number of computer experiments on polarized beam dynamics are required. The numerical core of the package is COSY Infinity, a program for modeling spin-orbit dynamics.

White spots on Smoke rings by Bruce Nauman: a case study on contemporary art conservation using microanalytical techniques.

Science.gov (United States)

Mafalda, Ana Cardeira; da Câmara, Rodrigo Bettencourt; Strzelec, Patrick; Schiavon, Nick; Mirão, José; Candeias, António; Carvalho, Maria Luísa; Manso, Marta

2015-02-01

The artwork "Smoke Rings: Two Concentric Tunnels, Non-Communicating" by Bruce Nauman represents a case study of corrosion of a black patina-coated Al-alloy contemporary artwork. The main concern over this artwork was the widespread presence of white spots on its surface. Alloy substrate, patina, and white spots were characterized by means of energy-dispersive X-ray fluorescence and scanning electron microscopy with energy-dispersive spectroscopy. Alloy substrate was identified as an aluminum alloy 6,000 series Al-Si-Mg. Patina's identified composition confirmed the documentation provided by the atelier. Concerning the white spots, zircon particles were found on patina surface as external elements.

Emission of orbital-angular-momentum-entangled photon pairs in a nonlinear ring fiber utilizing spontaneous parametric down-conversion

Czech Academy of Sciences Publication Activity Database

Javůrek, D.; Svozilík, J.; Peřina ml., Jan

2014-01-01

Roč. 90, č. 4 (2014), "043844-1"-"043844-12" ISSN 1050-2947 R&D Projects: GA ČR GAP205/12/0382 Institutional support: RVO:68378271 Keywords : photon pairs * orbital-angular-momentum-entangled * nonlinear ring fiber * spontaneous parametric down-conversion Subject RIV: BH - Optics , Masers, Lasers Impact factor: 2.808, year: 2014

RAPID ORBITAL DECAY IN THE 12.75-MINUTE BINARY WHITE DWARF J0651+2844

Energy Technology Data Exchange (ETDEWEB)

Hermes, J. J.; Winget, D. E. [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Kilic, Mukremin; Gianninas, A.; Kenyon, Scott J. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks Street, Norman, OK 73019 (United States); Brown, Warren R. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Allende Prieto, Carlos; Cabrera-Lavers, Antonio [Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain); Mukadam, Anjum S., E-mail: jjhermes@astro.as.utexas.edu [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States)

2012-10-01

We report the detection of orbital decay in the 12.75-minute, detached binary white dwarf (WD) SDSS J065133.338+284423.37 (hereafter J0651). Our photometric observations over a 13 month baseline constrain the orbital period to 765.206543(55) s and indicate that the orbit is decreasing at a rate of (- 9.8 {+-} 2.8) Multiplication-Sign 10{sup -12} s s{sup -1} (or -0.31 {+-} 0.09 ms yr{sup -1}). We revise the system parameters based on our new photometric and spectroscopic observations: J0651 contains two WDs with M{sub 1} = 0.26 {+-} 0.04 M{sub Sun} and M{sub 2} = 0.50 {+-} 0.04 M{sub Sun }. General relativity predicts orbital decay due to gravitational wave radiation of (- 8.2 {+-} 1.7) Multiplication-Sign 10{sup -12} s s{sup -1} (or -0.26 {+-} 0.05 ms yr{sup -1}). Our observed rate of orbital decay is consistent with this expectation. J0651 is currently the second-loudest gravitational wave source known in the milli-Hertz range and the loudest non-interacting binary, which makes it an excellent verification source for future missions aimed at directly detecting gravitational waves. Our work establishes the feasibility of monitoring this system's orbital period decay at optical wavelengths.

Influence of the Rashba and Dresselhaus spin-orbit interactions of equal strength on the electron states in the circular quantum ring in the presence of a magnetic field

International Nuclear Information System (INIS)

Kudryashov, V.V.; Baran, A.V.

2012-01-01

The solutions of the Schrodinger equation are obtained for an electron in the two-dimensional circular semiconductor quantum ring in the presence of both an external magnetic and the Rashba and Dresselhaus spin-orbit interactions of equal strength . Confinement is simulated by a realistic potential well of finite depth. The dependence of energy levels on the magnetic field, the strength of spin-orbit interaction, and the relative ring width is presented. (authors)

Software package for modeling spin–orbit motion in storage rings

Energy Technology Data Exchange (ETDEWEB)

Zyuzin, D. V., E-mail: d.zyuzin@fz-juelich.de [St. Petersburg State University (Russian Federation)

2015-12-15

A software package providing a graphical user interface for computer experiments on the motion of charged particle beams in accelerators, as well as analysis of obtained data, is presented. The software package was tested in the framework of the international project on electric dipole moment measurement JEDI (Jülich Electric Dipole moment Investigations). The specific features of particle spin motion imply the requirement to use a cyclic accelerator (storage ring) consisting of electrostatic elements, which makes it possible to preserve horizontal polarization for a long time. Computer experiments study the dynamics of 10{sup 6}–10{sup 9} particles in a beam during 10{sup 9} turns in an accelerator (about 10{sup 12}–10{sup 15} integration steps for the equations of motion). For designing an optimal accelerator structure, a large number of computer experiments on polarized beam dynamics are required. The numerical core of the package is COSY Infinity, a program for modeling spin–orbit dynamics.

Heliotropic dust rings for Earth climate engineering

Science.gov (United States)

Bewick, R.; Lücking, C.; Colombo, C.; Sanchez, J. P.; McInnes, C. R.

2013-04-01

This paper examines the concept of a Sun-pointing elliptical Earth ring comprised of dust grains to offset global warming. A new family of non-Keplerian periodic orbits, under the effects of solar radiation pressure and the Earth's J2 oblateness perturbation, is used to increase the lifetime of the passive cloud of particles and, thus, increase the efficiency of this geoengineering strategy. An analytical model is used to predict the orbit evolution of the dust ring due to solar-radiation pressure and the J2 effect. The attenuation of the solar radiation can then be calculated from the ring model. In comparison to circular orbits, eccentric orbits yield a more stable environment for small grain sizes and therefore achieve higher efficiencies when the orbit decay of the material is considered. Moreover, the novel orbital dynamics experienced by high area-to-mass ratio objects, influenced by solar radiation pressure and the J2 effect, ensure the ring will maintain a permanent heliotropic shape, with dust spending the largest portion of time on the Sun facing side of the orbit. It is envisaged that small dust grains can be released from a circular generator orbit with an initial impulse to enter an eccentric orbit with Sun-facing apogee. Finally, a lowest estimate of 1 × 1012 kg of material is computed as the total mass required to offset the effects of global warming.

Flux qubits on semiconducting quantum ring

International Nuclear Information System (INIS)

Szopa, M; Zipper, E

2010-01-01

The ability to control the quantum state of a single electrons in a quantum ring made of a semiconductor is at the heart of recent developments towards a scalable quantum computer. A peculiar dispersion relation of quantum rings allows to steer the ground state properties by the magnetic flux and offers spin and orbital degrees of freedom for quantum manipulations. We show that such ring can be effectively reduced to the two-state system forming a qubit on orbital or spin degrees of freedom.

RAPID ORBITAL DECAY IN THE 12.75-MINUTE BINARY WHITE DWARF J0651+2844

International Nuclear Information System (INIS)

Hermes, J. J.; Winget, D. E.; Kilic, Mukremin; Gianninas, A.; Kenyon, Scott J.; Brown, Warren R.; Allende Prieto, Carlos; Cabrera-Lavers, Antonio; Mukadam, Anjum S.

2012-01-01

We report the detection of orbital decay in the 12.75-minute, detached binary white dwarf (WD) SDSS J065133.338+284423.37 (hereafter J0651). Our photometric observations over a 13 month baseline constrain the orbital period to 765.206543(55) s and indicate that the orbit is decreasing at a rate of (– 9.8 ± 2.8) × 10 –12 s s –1 (or –0.31 ± 0.09 ms yr –1 ). We revise the system parameters based on our new photometric and spectroscopic observations: J0651 contains two WDs with M 1 = 0.26 ± 0.04 M ☉ and M 2 = 0.50 ± 0.04 M ☉ . General relativity predicts orbital decay due to gravitational wave radiation of (– 8.2 ± 1.7) × 10 –12 s s –1 (or –0.26 ± 0.05 ms yr –1 ). Our observed rate of orbital decay is consistent with this expectation. J0651 is currently the second-loudest gravitational wave source known in the milli-Hertz range and the loudest non-interacting binary, which makes it an excellent verification source for future missions aimed at directly detecting gravitational waves. Our work establishes the feasibility of monitoring this system's orbital period decay at optical wavelengths.

Storage ring development at the National Synchrotron Light Source

International Nuclear Information System (INIS)

Krinsky, S.; Bittner, J.; Fauchet, A.M.; Johnson, E.D.; Keane, J.; Murphy, J.; Nawrocky, R.J.; Rogers, J.; Singh, O.V.; Yu, L.H.

1991-09-01

This report contains papers on the following topics: Transverse Beam Profile Monitor; Bunch Length Measurements in the VUV Storage Ring; Photoelectric Effect Photon Beam Position Monitors; RF Receivers for Processing Electron Beam Pick-up Electrode Signals; Real-Time Global Orbit Feedback Systems; Local Orbit Feedback; Active Interlock System for High Power Insertion Devices in the X-ray Ring; Bunch Lengthening Cavity for the VUV Ring; SXLS Storage Ring Design

Effects of Rashba spin–orbit coupling and a magnetic field on a polygonal quantum ring

International Nuclear Information System (INIS)

Tang, Han-Zhao; Zhai, Li-Xue; Shen, Man; Liu, Jian-Jun

2014-01-01

Using standard quantum network method, we analytically investigate the effect of Rashba spin–orbit coupling (RSOC) and a magnetic field on the spin transport properties of a polygonal quantum ring. Using Landauer–Büttiker formula, we have found that the polarization direction and phase of transmitted electrons can be controlled by both the magnetic field and RSOC. A device to generate a spin-polarized conductance in a polygon with an arbitrary number of sides is discussed. This device would permit precise control of spin and selectively provide spin filtering for either spin up or spin down simply by interchanging the source and drain. - Highlights: • Spin conductance of polygon with RSOC and magnetic field is calculated analytically. • We show how the RSOC and a magnetic field control the phase of electron in polygon. • The AB oscillation and shape-dependent conductance are studied in a polygonal ring. • Our model can provide spin filtering simply by interchanging the source and drain

Spin-polarization and spin-flip in a triple-quantum-dot ring by using tunable lateral bias voltage and Rashba spin-orbit interaction

Energy Technology Data Exchange (ETDEWEB)

Molavi, Mohamad, E-mail: Mo_molavi@yahoo.com [Faculty of Physics, Kharazmi University, Tehran (Iran, Islamic Republic of); Faizabadi, Edris, E-mail: Edris@iust.ac.ir [School of Physics, Iran University of Science and Technology, 16846 Tehran (Iran, Islamic Republic of)

2017-04-15

By using the Green's function formalism, we investigate the effects of single particle energy levels of a quantum dot on the spin-dependent transmission properties through a triple-quantum-dot ring structure. In this structure, one of the quantum dots has been regarded to be non-magnetic and the Rashba spin-orbit interaction is imposed locally on this dot while the two others can be magnetic. The on-site energy of dots, manipulates the interference of the electron spinors that are transmitted to output leads. Our results show that the effects of magnetic dots on spin-dependent transmission properties are the same as the difference of on-site energies of the various dots, which is applicable by a controllable lateral bias voltage externally. Besides, by tuning the parameters such as Rashba spin-orbit interaction, and on-site energy of dots and magnetic flux inside the ring, the structure can be indicated the spin-flip effect and behave as a full spin polarizer or splitter. - Highlights: • The effects of magnetic dots on spin-dependent transmission properties are the same as the difference of on-site energies of the various dots. • In the situation that the QDs have non-zero on-site energies, the system can demonstrate the full spin-polarization. • By tuning the Rashba spin-orbit strength and magnetic flux encountered by the ring the system operates as a Stern-Gerlach apparatus.

ORBITAL EVOLUTION OF COMPACT WHITE DWARF BINARIES

Energy Technology Data Exchange (ETDEWEB)

Kaplan, David L. [Physics Department, University of Wisconsin-Milwaukee, Milwaukee, WI 53211 (United States); Bildsten, Lars [Kavli Institute for Theoretical Physics and Department of Physics, Kohn Hall, University of California, Santa Barbara, CA 93106 (United States); Steinfadt, Justin D. R., E-mail: kaplan@uwm.edu, E-mail: bildsten@kitp.ucsb.edu, E-mail: jdrsteinfadt@gmail.com [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106 (United States)

2012-10-10

The newfound prevalence of extremely low mass (ELM, M{sub He} < 0.2 M{sub Sun }) helium white dwarfs (WDs) in tight binaries with more massive WDs has raised our interest in understanding the nature of their mass transfer. Possessing small (M{sub env} {approx} 10{sup -3} M{sub Sun }) but thick hydrogen envelopes, these objects have larger radii than cold WDs and so initiate mass transfer of H-rich material at orbital periods of 6-10 minutes. Building on the original work of D'Antona et al., we confirm the 10{sup 6} yr period of continued inspiral with mass transfer of H-rich matter and highlight the fact that the inspiraling direct-impact double WD binary HM Cancri likely has an ELM WD donor. The ELM WDs have less of a radius expansion under mass loss, thus enabling a larger range of donor masses that can stably transfer matter and become a He mass transferring AM CVn binary. Even once in the long-lived AM CVn mass transferring stage, these He WDs have larger radii due to their higher entropy from the prolonged H-burning stage.

Perturbation of a slowly rotating black hole by a stationary axisymmetric ring of matter. II. Penrose processes, circular orbits, and differential mass formulae

International Nuclear Information System (INIS)

Will, C.M.

1975-01-01

We present a detailed description of the phenomenon of energy extraction (''Penrose'') from a slowly rotating black hole perturbed by a stationary axisymmetric ring of matter, and show that the gravitational interaction between the ring and the particles used in the Penrose process must be taken into account. For the case of a black-hole-ring configuration of ''minimum enregy'' we show that a Penrose process can extract further energy, but that by measns of their gravitational forces, the particles used in the process cause the radius of the ring to change, releasing precisely sufficient gravitational potential energy to make up for that extracted. By analyzing the properties of circular test-particle orbits in black-hole-ring spacetimes, we show quantitatively how this change in radius is produced. A ''differential mass formula'' relating the total masses of neighboring black-hole-ring configurations is also derived

Population differentiation in tree-ring growth response of white fir (Abies concolor) to climate: Implications for predicting forest responses to climate change

Energy Technology Data Exchange (ETDEWEB)

Jensen, Deborah Bowne [Univ. of California, Berkeley, CA (United States)

1993-01-01

Forest succession models and correlative models have predicted 200--650 kilometer shifts in the geographic range of temperate forests and forest species as one response to global climate change. Few studies have investigated whether population differences may effect the response of forest species to climate change. This study examines differences in tree-ring growth, and in the phenotypic plasticity of tree-ring growth in 16-year old white fir, Abies concolor, from ten populations grown in four common gardens in the Sierra Nevada of California. For each population, tree-ring growth was modelled as a function of precipitation and degree-day sums. Tree-ring growth under three scenarios of doubled CO₂ climates was estimated.

Determination of the orientation of the white dwarf's magnetic axis from X-ray orbital light curves

International Nuclear Information System (INIS)

Andronov, I.L.

1986-01-01

The directional pattern of soft X-ray radiation produced in a ''polar cap'' on the white dwarf's surface is calculated taking into account the absorption in the axially symmetrical accretion column, homogeneous along its height. An algorithm for the determination of orientation of the magnetic axis of a compact star from orbital curves of soft X-ray flux, is suggested. The values of the orbital inclination i (51 deg <=i<64 deg) and the angle between the rotational and magnetic axes σ (30 deg <=σ<=34 deg) were calculated for the polar AM Herculis for different values of model parameters

The Dynamical History of Chariklo and Its Rings

Energy Technology Data Exchange (ETDEWEB)

Wood, Jeremy [Hazard Community and Technical College, Community College Drive, Hazard, KY 41701 (United States); Horner, Jonti; Marsden, Stephen C. [Computational Engineering and Science Research Centre, University of Southern Queensland, West Street, Toowoomba, QLD 4350 (Australia); Hinse, Tobias C., E-mail: jeremy.wood@kctcs.edu [Korea Astronomy and Space Science Institute, 776 Daedukdae-ro, Yuseong-gu, Daejeon 305-348 (Korea, Republic of)

2017-06-01

Chariklo is the only small solar system body confirmed to have rings. Given the instability of its orbit, the presence of rings is surprising, and their origin remains poorly understood. In this work, we study the dynamical history of the Chariklo system by integrating almost 36,000 Chariklo clones backward in time for 1 Gyr under the influence of the Sun and the four giant planets. By recording all close encounters between the clones and planets, we investigate the likelihood that Chariklo’s rings could have survived since its capture to the Centaur population. Our results reveal that Chariklo’s orbit occupies a region of stable chaos, resulting in its orbit being marginally more stable than those of the other Centaurs. Despite this, we find that it was most likely captured to the Centaur population within the last 20 Myr, and that its orbital evolution has been continually punctuated by regular close encounters with the giant planets. The great majority (>99%) of those encounters within 1 Hill radius of the planet have only a small effect on the rings. We conclude that close encounters with giant planets have not had a significant effect on the ring structure. Encounters within the Roche limit of the giant planets are rare, making ring creation through tidal disruption unlikely.

PyORBIT: A Python Shell For ORBIT

Energy Technology Data Exchange (ETDEWEB)

Jean-Francois Ostiguy; Jeffrey Holmes

2003-07-01

ORBIT is code developed at SNS to simulate beam dynamics in accumulation rings and synchrotrons. The code is structured as a collection of external C++ modules for SuperCode, a high level interpreter shell developed at LLNL in the early 1990s. SuperCode is no longer actively supported and there has for some time been interest in replacing it by a modern scripting language, while preserving the feel of the original ORBIT program. In this paper, we describe a new version of ORBIT where the role of SuperCode is assumed by Python, a free, well-documented and widely supported object-oriented scripting language. We also compare PyORBIT to ORBIT from the standpoint of features, performance and future expandability.

PyORBIT: A Python Shell For ORBIT

International Nuclear Information System (INIS)

Jean-Francois Ostiguy; Jeffrey Holmes

2003-01-01

ORBIT is code developed at SNS to simulate beam dynamics in accumulation rings and synchrotrons. The code is structured as a collection of external C++ modules for SuperCode, a high level interpreter shell developed at LLNL in the early 1990s. SuperCode is no longer actively supported and there has for some time been interest in replacing it by a modern scripting language, while preserving the feel of the original ORBIT program. In this paper, we describe a new version of ORBIT where the role of SuperCode is assumed by Python, a free, well-documented and widely supported object-oriented scripting language. We also compare PyORBIT to ORBIT from the standpoint of features, performance and future expandability

Manipulating femtosecond spin-orbit torques with laser pulse sequences to control magnetic memory states and ringing

Science.gov (United States)

Lingos, P. C.; Wang, J.; Perakis, I. E.

2015-05-01

Femtosecond (fs) coherent control of collective order parameters is important for nonequilibrium phase dynamics in correlated materials. Here, we propose such control of ferromagnetic order based on using nonadiabatic optical manipulation of electron-hole (e -h ) photoexcitations to create fs carrier-spin pulses with controllable direction and time profile. These spin pulses are generated due to the time-reversal symmetry breaking arising from nonperturbative spin-orbit and magnetic exchange couplings of coherent photocarriers. By tuning the nonthermal populations of exchange-split, spin-orbit-coupled semiconductor band states, we can excite fs spin-orbit torques that control complex magnetization pathways between multiple magnetic memory states. We calculate the laser-induced fs magnetic anisotropy in the time domain by using density matrix equations of motion rather than the quasiequilibrium free energy. By comparing to pump-probe experiments, we identify a "sudden" out-of-plane magnetization canting displaying fs magnetic hysteresis, which agrees with switchings measured by the static Hall magnetoresistivity. This fs transverse spin-canting switches direction with magnetic state and laser frequency, which distinguishes it from the longitudinal nonlinear optical and demagnetization effects. We propose that sequences of clockwise or counterclockwise fs spin-orbit torques, photoexcited by shaping two-color laser-pulse sequences analogous to multidimensional nuclear magnetic resonance (NMR) spectroscopy, can be used to timely suppress or enhance magnetic ringing and switching rotation in magnetic memories.

Possible origin of Saturn's newly discovered outer ring

International Nuclear Information System (INIS)

Moehlmann, D.

1986-01-01

Within a planetogonic model the self-gravitationally caused formation of pre-planetary and pre-satellite rings from an earlier thin disk is reported. The theoretically derived orbital radii of these rings are compared with the orbital levels in the planetary system and the satellite systems of Jupiter, Saturn and Uranus. From this comparison it is concluded that at the radial position of Saturn's newly discovered outer ring an early pre-satellite ring of more or less evolved satellites could have existed. These satellites should have been disturbed in their evolution by the gravitation of the neighbouring massive satellite Titan. The comparison also may indicate similarities between the asteroidal belt and the newly discovered outer ring of Saturn

Exoplanet recycling in massive white-dwarf debris discs

Science.gov (United States)

van Lieshout, R.; Kral, Q.; Charnoz, S.; Wyatt, M. C.; Shannon, A.

2018-05-01

Several tens of white dwarfs are known to host circumstellar discs of dusty debris, thought to arise from the tidal disruption of rocky bodies originating in the star's remnant planetary system. This paper investigates the evolution of such discs if they are very massive, as may be the case if their progenitor was a terrestrial planet, moon, or dwarf planet. Assuming the discs are physically thin and flat, like Saturn's rings, their evolution is governed by Poynting-Robertson drag or viscous spreading, where the disc's effective viscosity is due to self-gravity wakes. For discs with masses ≳ 1026 g, located in the outer parts of the tidal disruption zone, viscous spreading dominates the evolution, and mass is transported both in- and outwards. When outwards-spreading material flows beyond the Roche limit, it coagulates into new (minor) planets in a process analogous to the ongoing formation of moonlets at the outer edge of Saturn's rings. The newly formed bodies migrate outwards by exchanging angular momentum with the disc and coalesce into larger objects through mutual collisions. Eventually, the disc's Roche-limit overflow recycles tens of percent of the original disc mass; most ends up in a single large body near 2:1 mean-motion resonance with the disc's outer edge. Hence, the recycling of a tidally disrupted super-Earth, for example, could yield an Earth-mass planet on a ˜10-h orbit, located in the habitable zone for 2-to-10-Gyr-old white dwarfs. The recycling process also creates a population of smaller bodies just outside the Roche limit, which may explain the minor planets recently postulated to orbit WD 1145+017.

Neural networks and orbit control in accelerators

International Nuclear Information System (INIS)

Bozoki, E.; Friedman, A.

1994-01-01

An overview of the architecture, workings and training of Neural Networks is given. We stress the aspects which are important for the use of Neural Networks for orbit control in accelerators and storage rings, especially its ability to cope with the nonlinear behavior of the orbit response to 'kicks' and the slow drift in the orbit response during long-term operation. Results obtained for the two NSLS storage rings with several network architectures and various training methods for each architecture are given

Spin-polarization and spin-dependent logic gates in a double quantum ring based on Rashba spin-orbit effect: Non-equilibrium Green's function approach

International Nuclear Information System (INIS)

Eslami, Leila; Esmaeilzadeh, Mahdi

2014-01-01

Spin-dependent electron transport in an open double quantum ring, when each ring is made up of four quantum dots and threaded by a magnetic flux, is studied. Two independent and tunable gate voltages are applied to induce Rashba spin-orbit effect in the quantum rings. Using non-equilibrium Green's function formalism, we study the effects of electron-electron interaction on spin-dependent electron transport and show that although the electron-electron interaction induces an energy gap, it has no considerable effect when the bias voltage is sufficiently high. We also show that the double quantum ring can operate as a spin-filter for both spin up and spin down electrons. The spin-polarization of transmitted electrons can be tuned from −1 (pure spin-down current) to +1 (pure spin-up current) by changing the magnetic flux and/or the gates voltage. Also, the double quantum ring can act as AND and NOR gates when the system parameters such as Rashba coefficient are properly adjusted

Nonadiabatic generation of spin currents in a quantum ring with Rashba and Dresselhaus spin-orbit interactions

International Nuclear Information System (INIS)

Niţa, Marian; Ostahie, Bogdan; Marinescu, D C; Manolescu, Andrei; Gudmundsson, Vidar

2012-01-01

When subjected to a linearly polarized terahertz pulse, a mesoscopic ring endowed with spin-orbit interaction (SOI) of the Rashba-Dresselhaus type exhibits non-uniform azimuthal charge and spin distributions. Both types of SOI couplings are considered linear in the electron momentum. Our results are obtained within a formalism based on the equation of motion satisfied by the density operator which is solved numerically for different values of the angle φ, the angle determining the polarization direction of the laser pulse. Solutions thus obtained are later employed in determining the time-dependent charge and spin currents, whose values are calculated in the stationary limit. Both these currents exhibit an oscillatory behavior complicated in the case of the spin current by a beating pattern. We explain this occurrence on account of the two spin-orbit interactions which force the electron spin to oscillate between the two spin quantization axes corresponding to Rashba and Dresselhaus interactions. The oscillation frequencies are explained using the single particle spectrum.

Rings of Molecular Line Emission in the Disk Orbiting the Young, Close Binary V4046 Sgr

Science.gov (United States)

Dickson-Vandervelde, Dorothy; Kastner, Joel H.; Qi, C.; Forveille, Thierry; Hily-Blant, Pierre; Oberg, Karin; Wilner, David; Andrews, Sean; Gorti, Uma; Rapson, Valerie; Sacco, Germano; Principe, David

2018-01-01

We present analysis of a suite of subarcsecond ALMA Band 6 (1.1 - 1.4 mm) molecular line images of the circumbinary, protoplanetary disk orbiting V4046 Sgr. The ~20 Myr-old V4046 Sgr system, which lies a mere ~73 pc from Earth, consists of a close (separation ~10 Rsun) pair of roughly solar-mass stars that are orbited by a gas-rich crcumbinary disk extending to ~350 AU in radius. The ALMA images reveal that the molecules CO and HCN and their isotopologues display centrally peaked surface brightness morphologies, whereas the cyanide group molecules (HC3N, CH3CN), deuterated molecules (DCN, DCO+), hydrocarbons (as traced by C2H), and potential CO ice line tracers (N2H+, and H2CO) appear as a sequence of sharp and diffuse rings of increasing radii. The characteristic sizes of these molecular emission rings, which range from ~25 to >100 AU in radius, are evident in radial emission-line surface brightness profiles extracted from the deprojected disk images. We find that emission from 13CO emission transitions from optically thin to thick within ~50 AU, whereas C18O emission remains optically thin within this radius. We summarize the insight into the physical and chemical processes within this evolved protoplanetary disk that can be obtained from comparisons of the various emission-line morphologies with each other and with that of the continuum (large-grain) emission on size scales of tens of AU.This research is supported by NASA Exoplanets program grant NNX16AB43G to RIT

Planetary period oscillations in Saturn's magnetosphere: New results from the F-ring and proximal orbits

Science.gov (United States)

Provan, G.; Cowley, S. W. H.; Bunce, E. J.; Hunt, G. J.; Dougherty, M. K.

2017-12-01

We investigate planetary period oscillations (PPOs) in Saturn's magnetosphere using Cassini magnetic field data during the high cadence ( 7 days) F-ring and proximal orbits. Previous results have shown that there are two PPO systems, one in each hemisphere. Both PPO periods show seasonal dependence, and since mid-2014 the Northern PPO period has been 10.8 h and the Southern PPO period 10.7 h. The beat period of the two oscillations is 45 days. Previous results demonstrated that in the Northern (Southern) polar region only pure Northern (Southern) oscillations can be observed, whilst in the equatorial region both oscillations are present and constructively and destructively interfere over the beat-cycle of the two oscillations. The PPOs are believed to be driven by twin-cell convection patterns in the polar ionosphere/thermosphere regions, with two systems of field-aligned currents transmitting the PPO flows to the magnetospheric plasma.The F-ring and proximal orbits uniquely observe the PPOs over 6 orbits during each PPO beat cycle. This high-cadence data demonstrates that over a beat cycle both the periods and amplitudes of the PPO observed within the each polar region are modulated by the PPO system from the opposite hemisphere. When the two oscillations are in phase (anti-phase) the `drag' of one system on the other acts to decrease (increase) the amplitude of the oscillations and the two PPO periods diverge (converge). We present a theoretical model showing that this coupling is due to the PPO flows from one hemisphere not just being communicated to the magnetosphere as previously assumed, but also to the opposite hemisphere. The result is inter-hemispheric coupling of the PPO flow systems within the ionosphere/thermosphere system, so that the northern PPO system drives a northern twin-cell convection pattern in the southern hemisphere, and vice versa, thus leading to the observed polar modulations of the PPOs.We will also present PPO phase models determined

Cassini at Saturn Proximal Orbits - Attitude Control Challenges

Science.gov (United States)

Burk, Thomas A.

2013-01-01

The Cassini mission at Saturn will come to an end in the spring and summer of 2017 with a series of 22 orbits that will dip inside the rings of Saturn. These are called proximal orbits and will conclude with spacecraft disposal into the atmosphere of the ringed world on September 15, 2017. These unique orbits that cross the ring plane only a few thousand kilometers above the cloud tops of the planet present new attitude control challenges for the Cassini operations team. Crossing the ring plane so close to the inner edge of the rings means that the Cassini orientation during the crossing will be tailored to protect the sensitive electronics bus of the spacecraft. This orientation will put the sun sensors at some extra risk so this paper discusses how the team prepares for dust hazards. Periapsis is so close to the planet that spacecraft controllability with RCS thrusters needs to be evaluated because of the predicted atmospheric torque near closest approach to Saturn. Radiation during the ring plane crossings will likely trigger single event transients in some attitude control sensors. This paper discusses how the attitude control team deals with radiation hazards. The angular size and unique geometry of the rings and Saturn near periapsis means that star identification will be interrupted and this paper discusses how the safe mode attitude is selected to best deal with these large bright bodies during the proximal orbits.

Guide to the Main Ring DO overpass

International Nuclear Information System (INIS)

Turkot, F.

1985-01-01

The DO overpass is a modification of the beam orbit in Main Ring in order to better accommodate a Tevatron collider detector at DO. The orbit is moved up approx. 51 inches over most of the long straight section at DO, thus making the Main Ring the world's first non-planar proton synchrotron. A similar overpass, but with four times the displacement, is planned for the CDF detector at the BO straight section. The nominal separation between the beam orbit in the Main Ring and the orbit in the Tevatron is 25.5 inches. Early in the design study of a detector that would utilize the Tevatron is a anti pp collider, it was apparent that a larger separation at the detector was highly desirable. In 1981, Tom Collins proposed a specific lattice geometry in the Main Ring for achieving larger separation, called ''the screw beam''. His proposal has served as the basis for the design of both the BO and DO overpasses. The main purpose of this report is to describe in some detail the implementation of the DO overpass. Topics to be covered include: (a) geometry of the overpass orbit, (b) the new hardware in the tunnel, (c) the power supply system, (d) the control facility, (e) accelerator beam dynamics ramifications, and (f) commissioning experience. A secondary purpose is to provide a fairly complete ''bibliography'' to the sources of information on the overpass. 17 refs., 17 figs

Orbiting compressor for residential air-conditioners

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyun Jin; Kim, Woo Young; Ahn, Jong Min [Department of Mechanical Engineering, University of Incheon, 12-1 Songdo-dong, Yeonsu-gu, Incheon 406-840 (Korea)

2010-01-15

A new type of compressor, called an orbiting compressor, is introduced in this paper. The orbiting compressor is characterized by an orbiting piston, and the piston or orbiter consists of a circular base plate and a ring type vane protruding vertically from the base plate. The orbiter is made to orbit in an annular space formed between two concentric circular walls via an Oldham-ring mechanism, producing two sealed gas pockets on both sides of the vane wrap with a 180 phase difference. This operating mechanism leads to alternating compression and discharge processes, which results in low torque variation. The orbiting compressor has been designed for an R410A residential air conditioner with a cooling capacity of 10.0 kW. The performance of the orbiting compressor model has been analytically investigated, where the volumetric, adiabatic and mechanical efficiencies were calculated to be 94.8%, 90.4% and 93.4%, respectively for the ARI condition. The EER was estimated to be about 10.86 with a motor efficiency of 89%. (author)

Ionic ring current during magnetic disturbances according to observations at a geostationary orbit

International Nuclear Information System (INIS)

Vlasova, N.A.; Kovtyuk, A.S.; Panasyuk, M.I.

1987-01-01

Experimental data on the measurements of H + and group (C, N, O) ion fluxes with different charges obtained using the ''Gorizont'' geostationary satellite (1985 - 07A) during three moderate magnetic disturbances with the amplitudes of D st -variations of several tens nT, have been analyzed. It is shown that during magnetic storms with clearly pronounced main phases a powerful injection of H + and (N, O) 2+ ion fluxes in the absence of noticeable increases in multicharge (C, N, O) ion fluxes with the energies of tens keV/e takes place. The resuts testify in favour of ionospheric plasma as the main source of ring current particles in the energy range. Indications that the filling of geostationary orbit with solar origin ions takes place at the recovery phase of a storm in nighttime hours are obtained

THE RINGS OF CHARIKLO UNDER CLOSE ENCOUNTERS WITH THE GIANT PLANETS

Energy Technology Data Exchange (ETDEWEB)

Araujo, R. A. N.; Sfair, R.; Winter, O. C., E-mail: ran.araujo@gmail.com, E-mail: rsfair@feg.unesp.br, E-mail: ocwinter@gmail.com [UNESP - Univ. Estadual Paulista, Grupo de Dinâmica Orbital e Planetologia, CEP 12516-410, Guaratingueta, SP (Brazil)

2016-06-20

The Centaur population is composed of minor bodies wandering between the giant planets that frequently perform close gravitational encounters with these planets, leading to a chaotic orbital evolution. Recently, the discovery of two well-defined narrow rings was announced around the Centaur 10199 Chariklo. The rings are assumed to be in the equatorial plane of Chariklo and to have circular orbits. The existence of a well-defined system of rings around a body in such a perturbed orbital region poses an interesting new problem. Are the rings of Chariklo stable when perturbed by close gravitational encounters with the giant planets? Our approach to address this question consisted of forward and backward numerical simulations of 729 clones of Chariklo, with similar initial orbits, for a period of 100 Myr. We found, on average, that each clone experiences during its lifetime more than 150 close encounters with the giant planets within one Hill radius of the planet in question. We identified some extreme close encounters that were able to significantly disrupt or disturb the rings of Chariklo. About 3% of the clones lose their rings and about 4% of the clones have their rings significantly disturbed. Therefore, our results show that in most cases (more than 90%), the close encounters with the giant planets do not affect the stability of the rings in Chariklo-like systems. Thus, if there is an efficient mechanism that creates the rings, then these structures may be common among these kinds of Centaurs.

Diamagnetic response in zigzag hexagonal silicene rings

International Nuclear Information System (INIS)

Xu, Ning; Chen, Qiao; Tian, Hongyu; Ding, Jianwen; Liu, Junfeng

2016-01-01

Highlights: • Hexagonal silicene rings possess unusually large diamagnetic moments. • The magnetic-field-driven spin-up electrons flow anticlockwise and spin-down electrons flow clockwise along the rings. • The large diamagnetic moment is the result of competition of spin-up and spin-down electrons. - Abstract: Hexagonal silicene rings with unusually large diamagnetic moments have been found in a theoretical study of the electronic and magnetic properties. In the presence of effective spin–orbit coupling, the magnetic-field-driven spin-up electrons flow anticlockwise exhibiting colossal diamagnetic moments, while the spin-down electrons flow clockwise exhibiting colossal paramagnetic moments along the rings. The large diamagnetic moment is thus the result of competition of spin-up and spin-down electrons, which can be modulated by spin–orbit coupling strength and exchange field.

Diamagnetic response in zigzag hexagonal silicene rings

Energy Technology Data Exchange (ETDEWEB)

Xu, Ning, E-mail: nxu@ycit.cn [Department of Physics, Yancheng Institute of Technology, Yancheng 224051 (China); Chen, Qiao [Department of Physics, Hunan Institute of Engineering, Xiangtan 411104 (China); Tian, Hongyu [Department of Physics, Yancheng Institute of Technology, Yancheng 224051 (China); Ding, Jianwen [Department of Physics, Xiangtan University, Xiangtan 411105 (China); Liu, Junfeng, E-mail: liu.jf@sustc.edu.cn [Department of Physics, South University of Science and Technology of China, Shenzhen 518055 (China)

2016-09-16

Highlights: • Hexagonal silicene rings possess unusually large diamagnetic moments. • The magnetic-field-driven spin-up electrons flow anticlockwise and spin-down electrons flow clockwise along the rings. • The large diamagnetic moment is the result of competition of spin-up and spin-down electrons. - Abstract: Hexagonal silicene rings with unusually large diamagnetic moments have been found in a theoretical study of the electronic and magnetic properties. In the presence of effective spin–orbit coupling, the magnetic-field-driven spin-up electrons flow anticlockwise exhibiting colossal diamagnetic moments, while the spin-down electrons flow clockwise exhibiting colossal paramagnetic moments along the rings. The large diamagnetic moment is thus the result of competition of spin-up and spin-down electrons, which can be modulated by spin–orbit coupling strength and exchange field.

Induced spin-accumulation and spin-polarization in a quantum-dot ring by using magnetic quantum dots and Rashba spin-orbit effect

International Nuclear Information System (INIS)

Eslami, L.; Faizabadi, E.

2014-01-01

The effect of magnetic contacts on spin-dependent electron transport and spin-accumulation in a quantum ring, which is threaded by a magnetic flux, is studied. The quantum ring is made up of four quantum dots, where two of them possess magnetic structure and other ones are subjected to the Rashba spin-orbit coupling. The magnetic quantum dots, referred to as magnetic quantum contacts, are connected to two external leads. Two different configurations of magnetic moments of the quantum contacts are considered; the parallel and the anti-parallel ones. When the magnetic moments are parallel, the degeneracy between the transmission coefficients of spin-up and spin-down electrons is lifted and the system can be adjusted to operate as a spin-filter. In addition, the accumulation of spin-up and spin-down electrons in non-magnetic quantum dots are different in the case of parallel magnetic moments. When the intra-dot Coulomb interaction is taken into account, we find that the electron interactions participate in separation between the accumulations of electrons with different spin directions in non-magnetic quantum dots. Furthermore, the spin-accumulation in non-magnetic quantum dots can be tuned in the both parallel and anti-parallel magnetic moments by adjusting the Rashba spin-orbit strength and the magnetic flux. Thus, the quantum ring with magnetic quantum contacts could be utilized to create tunable local magnetic moments which can be used in designing optimized nanodevices.

Perfect tuning of spin-polarization in a ring-shaped multiple-quantum-dot nanostructure in the presence of Rashba spin–orbit coupling

Energy Technology Data Exchange (ETDEWEB)

Eslami, L., E-mail: Leslami@iust.ac.ir; Chaghari, Z.; Faizabadi, E.

2013-09-02

Spin-dependent electronic transport through an open multiple-quantum-dot ring threaded by a magnetic flux is theoretically investigated by using the single particle Green's function method. By introducing local Rashba spin–orbit interaction on an individual quantum dot and local magnetic moments on two of other quantum dots, we calculate the spin-polarization in the output lead. We find the spin-polarization can be tuned by manipulating magnetic moments, adjusting magnetic flux and setting the Rashba spin–orbit strength. It is also shown the system can operate as an efficient spin-inverter when the structure is adjusted properly. The analysis can be utilized in designing optimized nanodevices.

Paleoclimate Signals and Temperature Reconstructions for the Northeastern United States using Atlantic White Cedar Tree-Rings

Science.gov (United States)

Pearl, J. K.; Anchukaitis, K. J.; Pederson, N.; Donnelly, J. P.

2016-12-01

High-resolution paleoclimate records of the Common Era are essential for improving detection and attribution of internal and forced climate system responses. The densely populated northeastern United States is at risk from impending climate shifts as well as sea level rise. Here we present a new network of annually resolved proxy data from Atlantic white cedar trees throughout the northeastern United States. Ring width variability reflects winter through summer temperatures at inland sites north of New Jersey. Climate signals embedded in the full network are evaluated for their potential to provide reconstructions of both temperature and drought variability. We demonstrate skillful climate reconstructions for the last several centuries and the potential to use subfossil samples to extend these records over the Common Era. Our tree-ring network provides the long-term context at multidecadal and centennial time scales for the large-scale ocean-atmospheric processes that influence the climate of the region.

EVOLUTION OF A RING AROUND THE PLUTO–CHARON BINARY

Energy Technology Data Exchange (ETDEWEB)

Bromley, Benjamin C. [Department of Physics and Astronomy, University of Utah, 115 S 1400 E, Rm 201, Salt Lake City, UT 84112 (United States); Kenyon, Scott J., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA 02138 (United States)

2015-08-10

We consider the formation of satellites around the Pluto–Charon binary. An early collision between the two partners likely produced the binary and a narrow ring of debris, out of which arose the moons Styx, Nix, Kerberos, and Hydra. How the satellites emerged from the compact ring is uncertain. Here we show that a particle ring spreads from physical collisions and collective gravitational scattering, similar to migration. Around a binary, these processes take place in the reference frames of “most circular” orbits, akin to circular ones in a Keplerian potential. Ring particles damp to these orbits and avoid destructive collisions. Damping and diffusion also help particles survive dynamical instabilities driven by resonances with the binary. In some situations, particles become trapped near resonances that sweep outward with the tidal evolution of the Pluto–Charon binary. With simple models and numerical experiments, we show how the Pluto–Charon impact ring may have expanded into a broad disk, out of which grew the circumbinary moons. In some scenarios, the ring can spread well beyond the orbit of Hydra, the most distant moon, to form a handful of smaller satellites. If these small moons exist, New Horizons will find them.

MIGRATION OF SMALL MOONS IN SATURN's RINGS

Energy Technology Data Exchange (ETDEWEB)

Bromley, Benjamin C. [Department of Physics and Astronomy, University of Utah, 115 S 1400 E, Rm 201, Salt Lake City, UT 84112 (United States); Kenyon, Scott J., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)

2013-02-20

The motions of small moons through Saturn's rings provide excellent tests of radial migration models. In theory, torque exchange between these moons and ring particles leads to radial drift. We predict that moons with Hill radii r {sub H} {approx} 2-24 km should migrate through the A ring in 1000 yr. In this size range, moons orbiting in an empty gap or in a full ring eventually migrate at the same rate. Smaller moons or moonlets-such as the propellers-are trapped by diffusion of disk material into corotating orbits, creating inertial drag. Larger moons-such as Pan or Atlas-do not migrate because of their own inertia. Fast migration of 2-24 km moons should eliminate intermediate-size bodies from the A ring and may be responsible for the observed large-radius cutoff of r {sub H} {approx} 1-2 km in the size distribution of the A ring's propeller moonlets. Although the presence of Daphnis (r {sub H} Almost-Equal-To 5 km) inside the Keeler gap challenges this scenario, numerical simulations demonstrate that orbital resonances and stirring by distant, larger moons (e.g., Mimas) may be important factors. For Daphnis, stirring by distant moons seems the most promising mechanism to halt fast migration. Alternatively, Daphnis may be a recent addition to the ring that is settling into a low inclination orbit in {approx}10{sup 3} yr prior to a phase of rapid migration. We provide predictions of observational constraints required to discriminate among possible scenarios for Daphnis.

INJECTION EFFICIENCY IN COMPTON RING NESTOR

Directory of Open Access Journals (Sweden)

P. I. Gladkikh

2017-12-01

Full Text Available NESTOR is the hard X-ray source that is under commissioning at NSC KIPT. NESTOR based on the Compton scattering of laser photons on relativistic electrons. The structure of the facility can be represented as the following components: a linear accelerator, a transport channel, a storage ring, and a laser-optical system. Electrons are stored in the storage ring for energy of 40-200 MeV. Inevitable alignment errors of magnetic elements are strongly effect on the beam dynamics in the storage ring. These errors lead to a shift of the equilibrium orbit relative to the ideal one. Significant shift of the equilibrium orbit could lead to loss of the beam on physical apertures. Transverse sizes of electron and laser beams are only few tens of microns at the interaction point. The shift of electron beam at the interaction point could greatly complicate the operation adjustment of storage ring without sufficient beam position diagnostic system. This article presents the simulation results of the efficiency of electron beam accumulation in the NESTOR storage ring. Also, this article is devoted to electron beam dynamics due to alignment errors of magnetic element in the ring.

Adaptive frozen orbital treatment for the fragment molecular orbital method combined with density-functional tight-binding

Science.gov (United States)

Nishimoto, Yoshio; Fedorov, Dmitri G.

2018-02-01

The exactly analytic gradient is derived and implemented for the fragment molecular orbital (FMO) method combined with density-functional tight-binding (DFTB) using adaptive frozen orbitals. The response contributions which arise from freezing detached molecular orbitals on the border between fragments are computed by solving Z-vector equations. The accuracy of the energy, its gradient, and optimized structures is verified on a set of representative inorganic materials and polypeptides. FMO-DFTB is applied to optimize the structure of a silicon nano-wire, and the results are compared to those of density functional theory and experiment. FMO accelerates the DFTB calculation of a boron nitride nano-ring with 7872 atoms by a factor of 406. Molecular dynamics simulations using FMO-DFTB applied to a 10.7 μm chain of boron nitride nano-rings, consisting of about 1.2 × 106 atoms, reveal the rippling and twisting of nano-rings at room temperature.

Stable carbon isotopes and drought signal in the tree-rings of northern white-cedar trees from boreal central Canada. (Invited)

Science.gov (United States)

Tardif, J. C.; Au, R.

2010-12-01

Despite the demonstrated value of tree-ring δ13C analysis, there have been a limited number of dendroisotopic δ13C studies conducted throughout the North American boreal forest. Dendroisotopic series are generally short and few tree species/habitats have been investigated. We present recent work conducted in the boreal forest of Manitoba, central Canada. Old northern white-cedar (Thuja occidentalis L.) trees were sampled at their northwestern limit of distribution. The objectives of the study were 1) to determine the major climatic factors associated with each of the ring-width and δ13C chronology and 2) to provide a multi-century inference of drought events based on tree-ring δ13C and ring width analyses. We also compared the δ13C chronology developed from Thuja occidentalis trees to that of white spruce (Picea glauca Moench) and jack pine (Pinus banksiana Lamb.) trees developed in northern Manitoba. Fifteen T. occidentalis trees were selected for δ13C analysis and holocellulose was isolated from each tree-ring through standard chemical extraction techniques. The annually resolved δ13C chronology spanned from 1650 to 2006 A.D. and incorporated dead and living T. occidentalis trees selected from two sites. Hydric organic conditions on horizontal topography punctuated by scattered wet depressions prevailed at both sites. A ring-width chronology was also developed from both dead and living T. occidentalis trees from the region. All chronology development followed standardization of each of the δ13C series using a 60-year cubic spline function with a 50% frequency response. Results indicated that ring width was more often associated with climate conditions prevailing in the year prior to ring formation compared to the δ13C values. During the year of ring-formation, ring width was associated with spring and early summer conditions whereas, δ13C was more indicative of overall summer conditions. Conditions conducive to moisture stress were however important for

Self-assembly of concentric quantum double rings.

Science.gov (United States)

Mano, Takaaki; Kuroda, Takashi; Sanguinetti, Stefano; Ochiai, Tetsuyuki; Tateno, Takahiro; Kim, Jongsu; Noda, Takeshi; Kawabe, Mitsuo; Sakoda, Kazuaki; Kido, Giyuu; Koguchi, Nobuyuki

2005-03-01

We demonstrate the self-assembled formation of concentric quantum double rings with high uniformity and excellent rotational symmetry using the droplet epitaxy technique. Varying the growth process conditions can control each ring's size. Photoluminescence spectra emitted from an individual quantum ring complex show peculiar quantized levels that are specified by the carriers' orbital trajectories.

Present status of beam position stabilization at photon factory storage ring

International Nuclear Information System (INIS)

Nakamura, Norio

1990-01-01

Stabilization of photon beam position became a major issue in the operation of the storage rings dedicated as synchrotron radiation source. At the Photon Factory storage ring (PF ring), the orbit movement appeared remarkably when the low-emittance operation started. This orbit movement became a serious problem to synchrotron radiation users because the photon beam to drift with a large amplitude. The horizontal and vertical orbit feedback systems were constructed and developed in order to suppress the orbit movement globally. As a result, the horizontal and vertical orbit movements were reduced by a factor of five and ten, respectively. In addition, another type of feedback system using a local bump was constructed. In the test operation, this system could remove the fast photon beam motion as well as the slow photon beam drift for a beamline. (author)

On Orbit Immuno-Based, Label-Free, White Blood Cell Counting System with MicroElectroMechanical Sensor (MEMS) Technology (OILWBCS-MEMS), Phase II

Data.gov (United States)

National Aeronautics and Space Administration — Aurora Flight Sciences Corporation and partner, Draper Laboratory, propose to develop an on-orbit immuno-based label-free white blood cell counting system using MEMS...

On Orbit Immuno-Based, Label-Free, White Blood Cell Counting System with MicroElectroMechanical Sensor (MEMS) Technology (OILWBCS-MEMS), Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Aurora Flight Sciences Corporation and our partner, Draper Laboratory, propose to develop an on orbit immuno-based, label-free, white blood cell counting system for...

Ringing of White Storks Ciconia ciconia in NE Slovenia during the 1984–2013 period

Directory of Open Access Journals (Sweden)

Bračko Franc

2016-12-01

Full Text Available In a period of 30 years (1984-2013, 1,535 White Stork pulli were ringed on nest and 1,226 nests examined in NE Slovenia. The ringing was implemented in the regions of Dravsko polje, Slovenske gorice and Pomurje. In each season, from 9 to 85 nests were examined, the great majority of them built on overhead powerline pylons. On average, 51.16 pulli or 16.66% were ringed and 40.86 or 18.91% nests visited compared to the census of fledged pulli and inventoried nests in 1999 in NE Slovenia. A total of 71 finds or 4.6% were registered and 37 rings or 52% finds read. There were 26 (36.62% local recoveries, while in foreign countries 34 (47.88% recoveries of Slovenian-ringed storks were made. Two of our recoveries were registered abroad prior to 1984. There were 11 (15.49% foreign recoveries. Local recoveries (n = 26 indicate breeding relationship (mixing between the eastern and southern Slovenian breeding populations. The longest distance of breeding was 115 km in a beeline, the shortest 62 km (n = 4. Other 12 local recoveries at 1 to 38 km from the place of hatching concerns the native NE breeding area. Young sexually mature storks search for new breeding sites only in their fourth year of age. No ringed stork returned to the native nest as a young breeder. The oldest was 14 years old. Some of them breed in the wider area of the Pannonian Plain outside Slovenia, e.g. 3 in Austria, 2 in Serbia and 1 in Croatia. One of them bred in Slovakia 463 km away. In view of the presented recoveries it has been ascertained that the storks from NE Slovenia migrate across the Pannonian Plain, the Balkans and Asia Minor, down to the South African Republic of 8,923 km in a beeline (4 recoveries, using the eastern migration route. The western migration route was not ascertained. The majority of recoveries originated from the autumn migration period, with only one recovery known from the spring migration period. No less than 23 ringed storks, particularly young ones

The injection system of the stretcher ring ELSA

International Nuclear Information System (INIS)

Dreist, A.

1989-07-01

For the stretcher ring ELSA in the framwork of this thesis an injection system has been concipated and constructed which should allow all projected operational modes of this stretcher ring, the stretcher, the post-acceleration, and the accumulation mode. The proof could be performed that the realized concept allows all these operational modes. Furthermore it could be shown that the injection shifted from the equilibrium orbit has no disadvantageous effects on a uniform extraction and by this on a high touching ratio. In fact it is even possible to apply the decay of the coherent betatron oscillations around the equilibrium orbit, caused by injection of the incident beam shifted from the equilibrium orbit, to diagnosis purposes: By reproduction of this damping process in a simulation model statements on nonlinearities present in the ring and by this statements on the actual phase-space structure are possible. It has so been shown that the concept presented in this thesis and realized for this thesis represents a suited injection system for the stretcher ring ELSA. (orig.) [de

Local orbit feedback

International Nuclear Information System (INIS)

Anon.

1991-01-01

Critically aligned experiments are sensitive to small changes in the electron beam orbit. At the NSLS storage rings, the electron beam and photon beam motions have been monitored over the past several years. In the survey conducted in 1986 by the NSLS Users Executive Committee, experimenters requested the vertical beam position variation and the vertical angle variation, within a given fill, remain within 10 μm and 10 μr, respectively. This requires improvement in the beam stability by about one order of magnitude. At the NSLS and SSRL storage rings, the beam that is originally centered on the position monitor by a dc orbit correction is observed to have two kinds of motion: a dc drift over a storage period of several hours and a beam bounce about its nominal position. These motions are a result of the equilibrium orbit not being held perfectly stable due to time-varying errors introduced into the magnetic guide field by power supplies, mechanical vibration of the magnets, cooling water temperature variations, etc. The approach to orbit stabilization includes (1) identifying and suppressing as many noise sources on the machine as possible, (2) correcting the beam position globally (see Section 6) by controlling a number of correctors around the circumference of the machine, and (3) correcting the beam position and angle at a given source location by position feedback using local detectors and local orbit bumps. The third approach, called Local Orbit Feedback will be discussed in this section

Fano and Dicke effects in a double Rashba-ring system

International Nuclear Information System (INIS)

Apel, V M; Orellana, P A; Pacheco, M

2008-01-01

The electronic transport in a system of two quantum rings side-coupled to a quantum wire is studied via a single-band tunneling tight-binding Hamiltonian. We derived analytical expressions for the conductance and spin polarization when the rings are threaded by magnetic fluxes with Rashba spin-orbit interaction. We show that by using the Fano and Dicke effects this system can be used as an efficient spin filter even for small spin-orbit interaction and small values of magnetic fluxes. We compare the spin-dependent polarization of this design and the polarization obtained with one ring side-coupled to a quantum ring. As a main result, we find better spin polarization capabilities as compared to the one-ring design

AN N-BODY INTEGRATOR FOR GRAVITATING PLANETARY RINGS, AND THE OUTER EDGE OF SATURN'S B RING

International Nuclear Information System (INIS)

Hahn, Joseph M.; Spitale, Joseph N.

2013-01-01

A new symplectic N-body integrator is introduced, one designed to calculate the global 360° evolution of a self-gravitating planetary ring that is in orbit about an oblate planet. This freely available code is called epi i nt, and it is distinct from other such codes in its use of streamlines to calculate the effects of ring self-gravity. The great advantage of this approach is that the perturbing forces arise from smooth wires of ring matter rather than discreet particles, so there is very little gravitational scattering and so only a modest number of particles are needed to simulate, say, the scalloped edge of a resonantly confined ring or the propagation of spiral density waves. The code is applied to the outer edge of Saturn's B ring, and a comparison of Cassini measurements of the ring's forced response to simulations of Mimas's resonant perturbations reveals that the B ring's surface density at its outer edge is σ 0 = 195 ± 60 g cm –2 , which, if the same everywhere across the ring, would mean that the B ring's mass is about 90% of Mimas's mass. Cassini observations show that the B ring-edge has several free normal modes, which are long-lived disturbances of the ring-edge that are not driven by any known satellite resonances. Although the mechanism that excites or sustains these normal modes is unknown, we can plant such a disturbance at a simulated ring's edge and find that these modes persist without any damping for more than ∼10 5 orbits or ∼100 yr despite the simulated ring's viscosity ν s = 100 cm 2 s –1 . These simulations also indicate that impulsive disturbances at a ring can excite long-lived normal modes, which suggests that an impact in the recent past by perhaps a cloud of cometary debris might have excited these disturbances, which are quite common to many of Saturn's sharp-edged rings

Frontal intradiploic epidomoid cyst with orbital and out cerebral extension

International Nuclear Information System (INIS)

Fernandez Latorre, F.; Revert Ventura, A.; Diaz Ramon, C.; Arana, E.; Esteban Masanet, J.M.; Tortosa Giner, A.

1995-01-01

We studied six patients with exophthalmos and inferior displacement of the eyeball produced by orbital extension of a frontal intradiploic epidermoid cyst. All the patients were studied by conventional radiography five with CT and three with MR. Plain x-ray disclosed a single, well-defined lytic lesion with sclerosis margin, located in the outer supraorbital region of the frontal bone in all cases. CT revealed the intradiploic site of the lesion, its expansive nature, the state of the bone tables and demonstrated the existence of an intra orbital mass. MR showed a lesion with a greater signal intensity than LCR, similar to the white matter in T1-weighted sequences in two cases and hyperintense in a third. The lesions were hyperintense in T2-weighted sequences. The preoperative presumed diagnosis was established by means of plain radiography on the basis of site and the sclerosis ring surrounding the lesion. CT disclosed the bone structures and confirmed the existence of an intra orbital mass containing soft portions. The basic contribution of MR was in the assessment of the intracranial extension and in ruling out cerebral involvement.(Author)

Quantum rings in magnetic fields and spin current generation.

Science.gov (United States)

Cini, Michele; Bellucci, Stefano

2014-04-09

We propose three different mechanisms for pumping spin-polarized currents in a ballistic circuit using a time-dependent magnetic field acting on an asymmetrically connected quantum ring at half filling. The first mechanism works thanks to a rotating magnetic field and produces an alternating current with a partial spin polarization. The second mechanism works by rotating the ring in a constant field; like the former case, it produces an alternating charge current, but the spin current is dc. Both methods do not require a spin-orbit interaction to achieve the polarized current, but the rotating ring could be used to measure the spin-orbit interaction in the ring using characteristic oscillations. On the other hand, the last mechanism that we propose depends on the spin-orbit interaction in an essential way, and requires a time-dependent magnetic field in the plane of the ring. This arrangement can be designed to pump a purely spin current. The absence of a charge current is demonstrated analytically. Moreover, a simple formula for the current is derived and compared with the numerical results.

An Orbit And Dispersion Correction Scheme for the PEP II

International Nuclear Information System (INIS)

Cai, Y.; Donald, M.; Shoaee, H.; White, G.; Yasukawa, L.A.

2011-01-01

To achieve optimum luminosity in a storage ring it is vital to control the residual vertical dispersion. In the original PEP storage ring, a scheme to control the residual dispersion function was implemented using the ring orbit as the controlling element. The 'best' orbit not necessarily giving the lowest vertical dispersion. A similar scheme has been implemented in both the on-line control code and in the simulation code LEGO. The method involves finding the response matrices (sensitivity of orbit/dispersion at each Beam-Position-Monitor (BPM) to each orbit corrector) and solving in a least squares sense for minimum orbit, dispersion function or both. The optimum solution is usually a subset of the full least squares solution. A scheme of simultaneously correcting the orbits and dispersion has been implemented in the simulation code and on-line control system for PEP-II. The scheme is based on the eigenvector decomposition method. An important ingredient of the scheme is to choose the optimum eigenvectors that minimize the orbit, dispersion and corrector strength. Simulations indicate this to be a very effective way to control the vertical residual dispersion.

Periodic seasonal variation of magnets level of the STB ring

International Nuclear Information System (INIS)

Takahashi, Shigenobu

2003-01-01

The Stretcher-Booster (STB) ring, a 1.2 GeV electron synchrotron, was completed in December, 1997 at the Laboratory of Nuclear Sciences (LNS), Tohoku University. The total weight more than 400 tons were placed near the STB ring, such as concrete blocks for radiation shielding and a spectrometer magnet for nuclear physics experiments after the completion of the STB ring. Re-surveying of magnets alignment was started after 2000. Very recently a new building of an experimental hall was constructed close to the building of the STB ring for use of high energy γ-ray from the electron beam. The building will give rise the changes of magnet levels due to its seasonal distortion. The measurements of the magnet level after construction are continued as well as an expected change of the closed orbit distortion (COD) in the STB ring. The serious influence of the variation of the magnet level may be a change of the beam orbit of extracted beam in the stretcher operation. Difference of the orbit distortion reaches more than 5 mm. Correlation between the COD and the seasonal change of the magnet position is not clear at the moment. However, the machine operation and the beam diagnostics are getting better recently. Continuous surveying of the magnet level will be a useful data for a feed forward correction of the beam orbit. Future subjects and prospects are discussed on surveying. (Y. Tanaka)

Magnetization of two coupled rings

International Nuclear Information System (INIS)

Avishai, Y; Luck, J M

2009-01-01

We investigate the persistent currents and magnetization of a mesoscopic system consisting of two clean metallic rings sharing a single contact point in a magnetic field. Many novel features with respect to the single-ring geometry are underlined, including the explicit dependence of wavefunctions on the Aharonov-Bohm fluxes, the complex pattern of two-fold and three-fold degeneracies, the key role of length and flux commensurability, and in the case of commensurate ring lengths the occurrence of idle levels which do not carry any current. Spin-orbit interactions, induced by the electric fields of charged wires threading the rings, give rise to a peculiar version of the Aharonov-Casher effect where, unlike for a single ring, spin is not conserved. Remarkably enough, this can only be realized when the Aharonov-Bohm fluxes in both rings are neither integer nor half-integer multiples of the flux quantum

First demonstration of 'white-light' laser cooling of a stored ion beam

International Nuclear Information System (INIS)

Atutov, S.N.; Biancalana, V.; Calabrese, R.; Clauser, T.; Grimm, R.; Guidi, V.; Lamanna, G.; Lauer, I.; Lenisa, P.; Luger, V.; Mariotti, E.; Moi, L.; Schramm, U.; Stagno, V.; Stoessel, M.; Tecchio, L.; Variale, V.

1998-01-01

'White-light' cooling of an ion beam confined in a storage ring has been demonstrated at Test Storage Ring in Heidelberg. Measurements aimed at comparing 'white-light' with single-mode laser cooling show that 'white-light' cooling gives lower temperatures at higher ion densities both in a coasting and in a bunched beam

Single-pass BPM system of the Photon Factory storage ring.

Science.gov (United States)

Honda, T; Katoh, M; Mitsuhashi, T; Ueda, A; Tadano, M; Kobayashi, Y

1998-05-01

At the 2.5 GeV ring of the Photon Factory, a single-pass beam-position monitor (BPM) system is being prepared for the storage ring and the beam transport line. In the storage ring, the injected beam position during the first several turns can be measured with a single injection pulse. The BPM system has an adequate performance, useful for the commissioning of the new low-emittance lattice. Several stripline BPMs are being installed in the beam transport line. The continuous monitoring of the orbit in the beam transport line will be useful for the stabilization of the injection energy as well as the injection beam orbit.

Detectability of planetary rings around super-earths by direct infrared imaging

International Nuclear Information System (INIS)

Morel, Carine

2013-01-01

Super-Earths, of which more than 80 have already been discovered, draw a lot of attention. With masses between those of the Earth and Neptune, they are ideal targets for searching for bio-signatures. All the gas giants of the solar system have a ring system, and even the Earth is suspected to have had rings in the past; their presence around super-Earths is thus expected and could give information on the formation process of these planets. The characterization of Super-Earths and their environment has thus become an important goal of modern astronomy. They are still difficult to study because of their small size, but the potential presence of planetary rings can make them easier to observe by the transit method and by direct imaging. This PhD evaluates the possibilities of detecting and characterizing rings around super-Earths by direct infrared imaging with the ELT-METIS instrument. To do this, a model to simulate the thermal emission of a super-Earth and its rings is developed. It is then used to study the influence of physical parameters and orientation of the rings and of planetary orbit on their detectability. The results show that ELT-METIS will be able to detect rings similar to the B and C rings of Saturn, extended within the Roche limit. The super-Earths surrounded by rings will be observable in middle orbit, between about 0.4 and 1 AU, around hot stars within 20 pc of the Sun. It is also shown that the photometric monitoring along the orbit of a super-Earth surrounded by rings should help constrain some of their physical characteristics. (author) [fr

Diamond Light Source Booster fast orbit feedback system

International Nuclear Information System (INIS)

Gayadeen, S.; Duncan, S.R.; Christou, C.; Heron, M.T.; Rowland, J.

2012-01-01

The Fast Orbit Feedback system that has been installed on the Diamond Light Source Storage ring has been replicated on the Booster synchrotron in order to provide a test bed for the development of the Storage Ring controller design. To realise this the Booster is operated in DC mode. The electron beam is regulated in two planes using the Fast Orbit Feedback system, which takes the beam position from 22 beam position monitors for each plane, and calculates offsets to 44 corrector power supplies at a sample rate of 10 kHz. This paper describes the design and realization of the controller for the Booster Fast Orbit Feedback, presents results from the implementation and considers future development

PS Booster Orbit Correction

CERN Document Server

Chanel, M; Rumolo, G; Tomás, R; CERN. Geneva. AB Department

2008-01-01

At the end of the 2007 run, orbit measurements were carried out in the 4 rings of the PS Booster (PSB) for different working points and beam energies. The aim of these measurements was to provide the necessary input data for a PSB realignment campaign during the 2007/2008 shutdown. Currently, only very few corrector magnets can be operated reliably in the PSB; therefore the orbit correction has to be achieved by displacing (horizontally and vertically) and/or tilting some of the defocusing quadrupoles (QDs). In this report we first describe the orbit measurements, followed by a detailed explanation of the orbit correction strategy. Results and conclusions are presented in the last section.

Non-Linear Dynamics of Saturn's Rings

Science.gov (United States)

Esposito, L. W.

2016-12-01

Non-linear processes can explain why Saturn's rings are so active and dynamic. Ring systems differ from simple linear systems in two significant ways: 1. They are systems of granular material: where particle-to-particle collisions dominate; thus a kinetic, not a fluid description needed. Stresses are strikingly inhomogeneous and fluctuations are large compared to equilibrium. 2. They are strongly forced by resonances: which drive a non-linear response, that push the system across thresholds that lead to persistent states. Some of this non-linearity is captured in a simple Predator-Prey Model: Periodic forcing from the moon causes streamline crowding; This damps the relative velocity. About a quarter phase later, the aggregates stir the system to higher relative velocity and the limit cycle repeats each orbit, with relative velocity ranging from nearly zero to a multiple of the orbit average. Summary of Halo Results: A predator-prey model for ring dynamics produces transient structures like `straw' that can explain the halo morphology and spectroscopy: Cyclic velocity changes cause perturbed regions to reach higher collision speeds at some orbital phases, which preferentially removes small regolith particles; surrounding particles diffuse back too slowly to erase the effect: this gives the halo morphology; this requires energetic collisions (v ≈ 10m/sec, with throw distances about 200km, implying objects of scale R ≈ 20km).Transform to Duffing Eqn : With the coordinate transformation, z = M2/3, the Predator-Prey equations can be combined to form a single second-order differential equation with harmonic resonance forcing.Ring dynamics and history implications: Moon-triggered clumping explains both small and large particles at resonances. We calculate the stationary size distribution using a cell-to-cell mapping procedure that converts the phase-plane trajectories to a Markov chain. Approximating it as an asymmetric random walk with reflecting boundaries

Systematic Search for Rings around Kepler Planet Candidates: Constraints on Ring Size and Occurrence Rate

Science.gov (United States)

Aizawa, Masataka; Masuda, Kento; Kawahara, Hajime; Suto, Yasushi

2018-05-01

We perform a systematic search for rings around 168 Kepler planet candidates with sufficient signal-to-noise ratios that are selected from all of the short-cadence data. We fit ringed and ringless models to their light curves and compare the fitting results to search for the signatures of planetary rings. First, we identify 29 tentative systems, for which the ringed models exhibit statistically significant improvement over the ringless models. The light curves of those systems are individually examined, but we are not able to identify any candidate that indicates evidence for rings. In turn, we find several mechanisms of false positives that would produce ringlike signals, and the null detection enables us to place upper limits on the size of the rings. Furthermore, assuming the tidal alignment between axes of the planetary rings and orbits, we conclude that the occurrence rate of rings larger than twice the planetary radius is less than 15%. Even though the majority of our targets are short-period planets, our null detection provides statistical and quantitative constraints on largely uncertain theoretical models of the origin, formation, and evolution of planetary rings.

Gear Tooth Root Stresses of a Very Heavily Loaded Gear Pair-Case Study: Orbiter Body Flap Actuator Pinion and Ring Gear

Science.gov (United States)

Krantz, Timothy L.; Handschuh, Robert F.

2015-01-01

The space shuttle orbiter's body flap actuator gearing was assessed as a case study of the stresses for very heavily loaded external-internal gear pairs (meshing pinion and ring gear). For many applications, using the high point of single tooth contact (HPSTC) to locate the position of the tooth force is adequate for assessing the maximum tooth root stress condition. But for aerospace gearing such an approach may be inadequate for assessing the stress condition while also simultaneously minimizing mass. In this work specialized contact analyses and finite element methods were used to study gear tooth stresses of body flap actuator gears. The analytical solutions considered the elastic deformations as an inherent part of the solutions. The ratio for the maximum tooth stresses using the HPSTC approach solutions relative to the contact analysis and finite element solutions were 1.40 for the ring gear and 1.28 for the pinion gear.

Rotating Wigner molecules and spin-related behaviors in quantum rings

International Nuclear Information System (INIS)

Yang Ning; Zhu Jialin; Dai Zhensheng

2008-01-01

The trial wavefunctions for few-electron quantum rings are presented to describe the spin-dependent rotating Wigner molecule states. The wavefunctions are constructed from the single-particle orbits which contain two variational parameters to describe the shape and size dependence of electron localization in the ring-like confinement. They can explicitly show the size dependence of single-particle orbital occupation to give an understanding of the spin rules of ground states without magnetic fields. They can also correctly describe the spin and angular momentum transitions in magnetic fields. By examining the von Neumann entropy, it is demonstrated that the wavefunctions can illustrate the entanglement between electrons in quantum rings, including the AB oscillations as well as the spin and size dependence of the entropy. Such trial wavefunctions will be useful in investigating spin-related quantum behaviors of a few electrons in quantum rings

White light coronagraph in OSO-7

International Nuclear Information System (INIS)

Koomen, M.J.; Detwiler, C.R.; Brueckner, G.E.; Cooper, H.W.; Tousey, R.

1975-01-01

A small, externally occulted Lyot-type coronagraph, designated for use in the seventh unmanned Orbiting Solar Observatory (OSO-7), is described. Optical configuration, suppression of stray light, SEC vidicon detector, and data system are discussed, as well as integration of the instrument into the spacecraft and operation in orbit. Orbital operation produced daily images of the white light corona, from 2.8 to 10 solar radii, at least once per day for 2 3/4 yr. The first records of white light coronal transient events were obtained, and the corona was shown to be constantly changing

Planetary ring systems properties, structures, and evolution

CERN Document Server

Murray, Carl D

2018-01-01

Planetary rings are among the most intriguing structures of our solar system and have fascinated generations of astronomers. Collating emerging knowledge in the field, this volume reviews our current understanding of ring systems with reference to the rings of Saturn, Uranus, Neptune, and more. Written by leading experts, the history of ring research and the basics of ring–particle orbits is followed by a review of the known planetary ring systems. All aspects of ring system science are described in detail, including specific dynamical processes, types of structures, thermal properties and their origins, and investigations using computer simulations and laboratory experiments. The concluding chapters discuss the prospects of future missions to planetary rings, the ways in which ring science informs and is informed by the study of other astrophysical disks, and a perspective on the field's future. Researchers of all levels will benefit from this thorough and engaging presentation.

Rashba diamond in an Aharonov-Casher ring

KAUST Repository

Wang, Xuhui

2011-10-07

Spin interference due to Rashba spin-orbit interaction(SOI) in a ballistic two-dimensional electron gas ring conductor submitted to a bias voltage is investigated theoretically. We calculate the scattering matrices and differential conductance with lead-ring junction coupling as an adjustable parameter. Due to the interference of electronic waves traversing the ring, the differential conductance modulated by both bias voltage and SOI exhibits a diamond-shaped pattern, thus termed as Rashba diamond. This feature offers a supplementary degree of freedom to manipulate phase interference.

Rashba diamond in an Aharonov-Casher ring

KAUST Repository

Wang, Xuhui; Manchon, Aurelien

2011-01-01

Spin interference due to Rashba spin-orbit interaction(SOI) in a ballistic two-dimensional electron gas ring conductor submitted to a bias voltage is investigated theoretically. We calculate the scattering matrices and differential conductance with lead-ring junction coupling as an adjustable parameter. Due to the interference of electronic waves traversing the ring, the differential conductance modulated by both bias voltage and SOI exhibits a diamond-shaped pattern, thus termed as Rashba diamond. This feature offers a supplementary degree of freedom to manipulate phase interference.

Illuminating massive black holes with white dwarfs: orbital dynamics and high-energy transients from tidal interactions

International Nuclear Information System (INIS)

MacLeod, Morgan; Goldstein, Jacqueline; Ramirez-Ruiz, Enrico; Guillochon, James; Samsing, Johan

2014-01-01

White dwarfs (WDs) can be tidally disrupted only by massive black holes (MBHs) with masses less than ∼10 5 M ☉ . These tidal interactions feed material to the MBH well above its Eddington limit, with the potential to launch a relativistic jet. The corresponding beamed emission is a promising indication of an otherwise quiescent MBH of relatively low mass. We show that the mass transfer history, and thus the light curve, is quite different when the disruptive orbit is parabolic, eccentric, or circular. The mass lost each orbit exponentiates in the eccentric-orbit case, leading to the destruction of the WD after several tens of orbits. We examine the stellar dynamics of clusters surrounding MBHs to show that single-passage WD disruptions are substantially more common than repeating encounters. The 10 49 erg s –1 peak luminosity of these events makes them visible to cosmological distances. They may be detectible at rates of as many as tens per year by instruments like Swift. In fact, WD-disruption transients significantly outshine their main-sequence star counterparts and are the tidal interaction most likely to be detected arising from MBHs with masses less than 10 5 M ☉ . The detection or nondetection of such WD-disruption transients by Swift is, therefore, a powerful tool to constrain the lower end of the MBH mass function. The emerging ultralong gamma-ray burst class of events all have peak luminosities and durations reminiscent of WD disruptions, offering a hint that WD-disruption transients may already be present in existing data sets.

Observations of the effect of varying Hoop stress on fatigue failure and the formation of white etching areas in hydrogen infused 100Cr6 steel rings

DEFF Research Database (Denmark)

Janakiraman, Shravan; West, Ole; Klit, Peder

2015-01-01

White etching cracks (WECs) in wind turbine gearbox bearings have been studied previously. Rolling contact fatigue (RCF) tests are conducted on 100Cr6 bearing steel rings, in this study, to generate WECs like those found in wind turbine bearings. This research studies the effect of two different...

IGR J14257-6117, a magnetic accreting white dwarf with a very strong strong X-ray orbital modulation

Science.gov (United States)

Bernardini, F.; de Martino, D.; Mukai, K.; Falanga, M.

2018-04-01

IGR J14257-6117 is an unclassified source in the hard X-ray catalogues. Optical follow-ups suggest it could be a Cataclysmic Variable of the magnetic type. We present the first high S/N X-ray observation performed by XMM-Newton at 0.3-10 keV, complemented with 10-80 keV coverage by Swift/BAT, aimed at revealing the source nature. We detected for the first time a fast periodic variability at 509.5 s and a longer periodic variability at 4.05 h, ascribed to the white dwarf (WD) spin and binary orbital periods, respectively. These unambiguously identify IGR J14257-6117 as a magnetic CV of the Intermediate Polar (IP) type. The energy resolved light curves at both periods reveal amplitudes decreasing with increasing energy, with the orbital modulation reaching ˜100% in the softest band. The energy spectrum shows optically thin thermal emission with an excess at the iron complex, absorbed by two dense media (NH ˜ 1022 - 23 cm-2), partially covering the X-ray source. These are likely localised in the magnetically confined accretion flow above the WD surface and at the disc rim, producing the energy dependent spin and orbital variabilities, respectively. IGR J14257-6117, joins the group of strongest orbitally modulated IPs now counting four systems. Drawing similarities with low-mass X-ray binaries displaying orbital dips, these IPs should be seen at large orbital inclinations allowing azimuthally extended absorbing material fixed in the binary frame to intercept the line of sight. For IGR J14257-6117, we estimate (50o ≲ i ≲ 70o). Whether also the mass accretion rate plays a role in the large orbital modulations in IPs cannot be established with the present data.

Performance of the SRRC storage ring and wiggler commissioning

International Nuclear Information System (INIS)

Kuo, C.C.; Hsu, K.T.; Luo, G.H.

1995-01-01

A 1.3 GeV synchrotron radiation storage ring at SRRC has been operated for more than a year since October 1993. Starting from April 1994, the machine has been open to the user community. In February 1995, the authors installed a wiggler magnet of 1.8 tesla 25-pole in the ring and successfully commissioned. The machine was scheduled for the users' runs from the middle of April this year. The authors describe the performance of the machine without wiggler magnet system and then report the wiggler effects on the beam dynamics of the storage ring, e.g., tune shift, beta-beating, orbit change, nonlinear dynamics effect, etc. Some measurements are compared with the model prediction and agreement between them was fairly good. Possible actions to minimize wiggler effects have been taken, such as orbit correction as a function wiggler gap change. The machine improvement projects, such as longitudinal and transverse damping systems as well as orbit stability feedback system are under construction and will be in use soon

Absorption coefficient and refractive index changes of a quantum ring in the presence of spin-orbit couplings: Temperature and Zeeman effects

Science.gov (United States)

Zamani, A.; Azargoshasb, T.; Niknam, E.

2017-10-01

Effects of applied magnetic field, temperature and dimensions on the optical absorption coefficients (AC) and refractive index (RI) changes of a GaAs quantum ring are investigated in the presence of both Rashba and Dresselhaus spin-orbit interactions (SOI). To this end, the finite difference method (FDM) is used in order to numerically calculate the energy eigenvalues and eigenstates of the system while the compact density matrix approach is hired to calculate the optical properties. It is shown that application of magnetic field, temperature as well as the geometrical size in the presence of spin-orbit interactions, alter the electronic structure and consequently influence the linear and third-order nonlinear optical absorption coefficients as well as the refractive index changes of the system. Results show an obvious blue shift in optical curves with enhancing external magnetic field and temperature while the increment of dimensions result in red shift.

A ring system detected around the Centaur (10199) Chariklo.

Science.gov (United States)

Braga-Ribas, F; Sicardy, B; Ortiz, J L; Snodgrass, C; Roques, F; Vieira-Martins, R; Camargo, J I B; Assafin, M; Duffard, R; Jehin, E; Pollock, J; Leiva, R; Emilio, M; Machado, D I; Colazo, C; Lellouch, E; Skottfelt, J; Gillon, M; Ligier, N; Maquet, L; Benedetti-Rossi, G; Ramos Gomes, A; Kervella, P; Monteiro, H; Sfair, R; El Moutamid, M; Tancredi, G; Spagnotto, J; Maury, A; Morales, N; Gil-Hutton, R; Roland, S; Ceretta, A; Gu, S-h; Wang, X-b; Harpsøe, K; Rabus, M; Manfroid, J; Opitom, C; Vanzi, L; Mehret, L; Lorenzini, L; Schneiter, E M; Melia, R; Lecacheux, J; Colas, F; Vachier, F; Widemann, T; Almenares, L; Sandness, R G; Char, F; Perez, V; Lemos, P; Martinez, N; Jørgensen, U G; Dominik, M; Roig, F; Reichart, D E; LaCluyze, A P; Haislip, J B; Ivarsen, K M; Moore, J P; Frank, N R; Lambas, D G

2014-04-03

Hitherto, rings have been found exclusively around the four giant planets in the Solar System. Rings are natural laboratories in which to study dynamical processes analogous to those that take place during the formation of planetary systems and galaxies. Their presence also tells us about the origin and evolution of the body they encircle. Here we report observations of a multichord stellar occultation that revealed the presence of a ring system around (10199) Chariklo, which is a Centaur--that is, one of a class of small objects orbiting primarily between Jupiter and Neptune--with an equivalent radius of 124 ±  9 kilometres (ref. 2). There are two dense rings, with respective widths of about 7 and 3 kilometres, optical depths of 0.4 and 0.06, and orbital radii of 391 and 405 kilometres. The present orientation of the ring is consistent with an edge-on geometry in 2008, which provides a simple explanation for the dimming of the Chariklo system between 1997 and 2008, and for the gradual disappearance of ice and other absorption features in its spectrum over the same period. This implies that the rings are partly composed of water ice. They may be the remnants of a debris disk, possibly confined by embedded, kilometre-sized satellites.

ENERGY DISSIPATION THROUGH QUASI-STATIC TIDES IN WHITE DWARF BINARIES

International Nuclear Information System (INIS)

Willems, B.; Deloye, C. J.; Kalogera, V.

2010-01-01

We present a formalism to study tidal interactions in white dwarf binaries in the limiting case of quasi-static tides, in which the tidal forcing frequencies are small, compared to the inverse of the white dwarf's dynamical timescale. The formalism is valid for arbitrary orbital eccentricities and therefore applicable to white dwarf binaries in the Galactic disk as well as globular clusters. In the quasi-static limit, the total perturbation of the gravitational potential shows a phase shift with respect to the position of the companion, the magnitude of which is determined primarily by the efficiency of energy dissipation through convective damping. We determine rates of secular evolution of the orbital elements and white dwarf rotational angular velocity for a 0.3 M sun helium white dwarf in binaries with orbital frequencies in the Laser Interferometer Space Antenna (LISA) gravitational wave frequency band and companion masses ranging from 0.3 M sun to 10 5 M sun . The resulting tidal evolution timescales for the orbital semimajor axis are longer than a Hubble time, so that convective damping of quasi-static tides need not be considered in the construction of gravitational wave templates of white dwarf binaries in the LISA band. Spin-up of the white dwarf, on the other hand, can occur on timescales of less than 10 Myr, provided that the white dwarf is initially rotating with a frequency much smaller than the orbital frequency. For semi-detached white dwarf binaries spin-up can occur on timescales of less than 1 Myr. Nevertheless, the timescales remain longer than the orbital inspiral timescales due to gravitational radiation, so that the degree of asynchronism in these binaries increases. As a consequence, tidal forcing eventually occurs at forcing frequencies beyond the quasi-static tide approximation. For the shortest period binaries, energy dissipation is therefore expected to take place through dynamic tides and resonantly excited g-modes.

NANOGRAIN DENSITY OUTSIDE SATURN’S A RING

Energy Technology Data Exchange (ETDEWEB)

Johnson, Robert E. [Engineering Physics, University of Virginia, Charlottesville, VA 22902 (United States); Tseng, Wei-Ling [National Taiwan Normal University, No. 88, Sec. 4, Tingzhou Road, Wenshan District, Taipei 11677, Taiwan (China); Elrod, M. K. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Persoon, A. M., E-mail: rej@virginia.edu, E-mail: wltseng@ntnu.edu.tw, E-mail: meredith.k.elrod@nasa.gov, E-mail: ann-persoon@uiowa.edu [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States)

2017-01-01

The observed disparity between the radial dependence of the ion and electron densities measured by the Cassini plasma (CAPS) and radio (RPWS) science instruments are used to show that the region between the outer edge of Saturn’s main rings and its tenuous G ring is permeated with small charged grains (nanograins). These grains emanate from the edge of the A ring and from the tenuous F and G rings. This is a region of Saturn’s magnetosphere that is relatively unexplored, but will be a focus of Cassini ’s F ring orbits prior to the end of mission in 2017 September. Confirmation of the grain densities predicted here will enhance our ability to describe the formation and destruction of material in this important region of Saturn’s magnetosphere.

The "g-2" Muon Storage Ring

CERN Multimedia

CERN PhotoLab

1974-01-01

The "g-2" muon storage ring, shortly before completion in June 1974. Bursts of pions (from a target, hit by a proton beam from the 26 GeV PS) are injected and polarized muons from their decay are captured on a stable orbit. When the muons decay too, their precession in the magnetic field of the storage ring causes a modulation of the decay-electron counting rate, from which the muon's anomalous magnetic moment can be determined. In 1977, the "g-2" magnets were modified to build ICE (Initial Cooling Experiment), a proton and antiproton storage ring for testing stochastic and electron cooling. Later on, the magnets had a 3rd life, when the ion storage ring CELSIUS was built from them in Uppsala. For later use as ICE, see 7711282, 7802099, 7809081,7908242.

Orbit Correction for the Newly Developed Polarization-Switching Undulator

Science.gov (United States)

Obina, Takashi; Honda, Tohru; Shioya, Tatsuro; Kobayashi, Yukinori; Tsuchiya, Kimichika; Yamamoto, Shigeru

2007-01-01

A new scheme of undulator magnet arrangements has been proposed and developed as a polarization-switching radiation source, and its test-stand was installed in the 2.5-GeV Photon Factory storage ring (PF ring) in order to investigate the effects on the beam orbit. The closed orbit distortion (COD) over 200 μm was produced in a vertical direction when we switched the polarization of the radiation from the test-stand. In a horizontal direction, the COD was less than 50μm. The results agreed well with the predictions from the magnetic-field measurement on the bench. In order to suppress the CODs and realize a stable operation of the ring with the polarization-switching, we developed an orbit correction system which consists of an encoder to detect motion of magnets, a pair of beam position monitors (BPMs), signal processing parts, and a pair of steering magnets. We succeeded in suppressing the CODs to the level below 3μm using the system even when we switch the polarization at a maximum frequency of 0.8 Hz.

The Jovian rings as observed from Jupiter.

Science.gov (United States)

Malinnikova Bang, A.; Joergensen, J. L.; Joergensen, P. S.; Denver, T.; Connerney, J. E. P.; Bolton, S. J.; Levin, S.

2017-12-01

Juno entered a highly eliptic orbit around Jupiter on the 4. July 2016. Since then, it has completed 8 perijove passages. The Magnetometer experiment consists of two measurement platforms mounted 10m and 12m from the spacecraft spin axis, on one of three large solar panels. Each magnetometer platform is equipped with two star trackers to provide accurate attitude information to the vector magnetometers. The star trackers are pointed 13deg from the (anti) spin vector, and clocked 180deg to avoid simultaneous blinding effects from bright Jupiter only 6000km away, during perijove. This brings Juno well inside the innermost known satellite, Metis. The star trackers pointing close to, and above the Jovian horizon for most of each rotation of Juno, has an excellent view of the Jovian ring systems with a beta-angle close to 180deg. We report on the ring imaging performed during the first 8 orbits, discuss the structure, optical depth and moon sheparding of the inner rings as measured so far.

RINGED ACCRETION DISKS: INSTABILITIES

Energy Technology Data Exchange (ETDEWEB)

Pugliese, D.; Stuchlík, Z., E-mail: d.pugliese.physics@gmail.com, E-mail: zdenek.stuchlik@physics.cz [Institute of Physics and Research Centre of Theoretical Physics and Astrophysics, Faculty of Philosophy and Science, Silesian University in Opava, Bezručovo náměstí 13, CZ-74601 Opava (Czech Republic)

2016-04-01

We analyze the possibility that several instability points may be formed, due to the Paczyński mechanism of violation of mechanical equilibrium, in the orbiting matter around a supermassive Kerr black hole. We consider a recently proposed model of a ringed accretion disk, made up by several tori (rings) that can be corotating or counter-rotating relative to the Kerr attractor due to the history of the accretion process. Each torus is governed by the general relativistic hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. We prove that the number of the instability points is generally limited and depends on the dimensionless spin of the rotating attractor.

Global orbit feedback utilizing analog and digital technologies

International Nuclear Information System (INIS)

Singh, O.; Tang, Y.; Ramamoorthy, S.; Krinsky, S.; Yu, L.H.

1997-01-01

At the NSLS, an analog global orbit feedback system is used in regular operations, and a digital global orbit feedback system is available in machine physics studies on the X-Ray Ring. Here, the authors discuss the relative merits of utilizing analog and digital technology in orbit feedback. Results of experiments are reported characterizing the performance of the analog and digital systems when operated individually or together. They give their thoughts on plans for future development of the orbit feedback systems at the NSLS

Specific heat in diluted magnetic semiconductor quantum ring

Science.gov (United States)

Babanlı, A. M.; Ibragimov, B. G.

2017-11-01

In the present paper, we have calculated the specific heat and magnetization of a quantum ring of a diluted magnetic semiconductor (DMS) material in the presence of magnetic field. We take into account the effect of Rashba spin-orbital interaction, the exchange interaction and the Zeeman term on the specific heat. We have calculated the energy spectrum of the electrons in diluted magnetic semiconductor quantum ring. Moreover we have calculated the specific heat dependency on the magnetic field and Mn concentration at finite temperature of a diluted magnetic semiconductor quantum ring.

FIRST BEAM TESTS OF THE APS MBA UPGRADE ORBIT FEEDBACK CONTROLLER

Energy Technology Data Exchange (ETDEWEB)

Sereno, N. S.; Arnold, N.; Brill, A.; Bui, H.; Carwardine, J.; Decker, G.; Deriy, B.; Emery, L.; Farnsworth, R.; Fors, T.; Keane, R.; Lenkszus, F.; Lill, R.; Paskvan, D.; Pietryla, A.; Shang, H.; Shoaf, S.; Veseli, S.; Wang, J.; Xu, S.; Yang, B.X.

2017-03-25

The new orbit feedback system required for the APS multi-bend acromat (MBA) ring must meet challenging beam stability requirements. The AC stability requirement is to correct rms beam motion to 10 % the rms beam size at the insertion device source points from 0.01 to 1000 Hz. The vertical plane represents the biggest challenge for AC stability which is required to be 400 nm rms for a 4 micron vertical beam size. In addition long term drift over a period of 7 days is required to be 1 micron or less at insertion de- vice BPMs and 2 microns for arc bpms. We present test re- sults of theMBA prototype orbit feedback controller (FBC) in the APS storage ring. In this test, four insertion device BPMs were configured to send data to the FBC for process- ing into four fast corrector setpoints. The configuration of four bpms and four fast correctors creates a 4-bump and the configuration of fast correctors is similar to what will be implemented in the MBA ring. We report on performance benefits of increasing the sampling rate by a factor of 15 to 22.6 kHz over the existing APS orbit feedback system, lim- itations due to existing storage ring hardware and extrapo- lation to theMBA orbit feedback design. FBC architecture, signal flow and processing design will also be discussed.

Rings Research in the Next Decade

Science.gov (United States)

Burns, J. A.; Tiscareno, M. S.

2009-12-01

The study of planetary ring systems forms a key component of planetary science for several reasons: 1) The evolution and current states of planets and their satellites are affected in many ways by rings, while 2) conversely, properties of planets and moons and other solar system populations are revealed by their effects on rings; 3) highly structured and apparently delicate ring systems may be bellwethers, constraining various theories of the origin and evolution of their entire planetary system; and finally, 4) planetary rings provide an easily observable analogue to other astrophysical disk systems, enabling real “ground truth” results applicable to disks much more remote in space and/or time, including proto-planetary disks, circum-stellar disks, and even galaxies. Significant advances have been made in rings science in the past decade. The highest-priority rings research recommendations of the last Planetary Science Decadal Survey were to operate and extend the Cassini orbiter mission at Saturn; this has been done with tremendous success, accounting for much of the progress made on key science questions, as we will describe. Important progress in understanding the rings of Saturn and other planets has also come from Earth-based observational and theoretical work, again as prioritized by the last Decadal Survey. However, much important work remains to be done. At Saturn, the Cassini Solstice Mission must be brought to a successful completion. Priority should also be placed on sending spacecraft to Neptune and/or Uranus, now unvisited for more than 20 years. At Jupiter and Pluto, opportunities afforded by visiting spacecraft capable of studying rings should be exploited. On Earth, the need for continued research and analysis remains strong, including in-depth analysis of rings data already obtained, numerical and theoretical modeling work, laboratory analysis of materials and processes analogous to those found in the outer solar system, and continued Earth

Evaluation of the global orbit correction algorithm for the APS real-time orbit feedback system

International Nuclear Information System (INIS)

Carwardine, J.; Evans, K. Jr.

1997-01-01

The APS real-time orbit feedback system uses 38 correctors per plane and has available up to 320 rf beam position monitors. Orbit correction is implemented using multiple digital signal processors. Singular value decomposition is used to generate a correction matrix from a linear response matrix model of the storage ring lattice. This paper evaluates the performance of the APS system in terms of its ability to correct localized and distributed sources of orbit motion. The impact of regulator gain and bandwidth, choice of beam position monitors, and corrector dynamics are discussed. The weighted least-squares algorithm is reviewed in the context of local feedback

THE LINK BETWEEN PLANETARY SYSTEMS, DUSTY WHITE DWARFS, AND METAL-POLLUTED WHITE DWARFS

International Nuclear Information System (INIS)

Debes, John H.; Walsh, Kevin J.; Stark, Christopher

2012-01-01

It has long been suspected that metal-polluted white dwarfs (types DAZ, DBZ, and DZ) and white dwarfs with dusty disks possess planetary systems, but a specific physical mechanism by which planetesimals are perturbed close to a white dwarf has not yet been fully posited. In this paper, we demonstrate that mass loss from a central star during post-main-sequence evolution can sweep planetesimals into interior mean motion resonances with a single giant planet. These planetesimals are slowly removed through chaotic excursions of eccentricity that in time create radial orbits capable of tidally disrupting the planetesimal. Numerical N-body simulations of the solar system show that a sufficient number of planetesimals are perturbed to explain white dwarfs with both dust and metal pollution, provided other white dwarfs have more massive relic asteroid belts. Our scenario requires only one Jupiter-sized planet and a sufficient number of asteroids near its 2:1 interior mean motion resonance. Finally, we show that once a planetesimal is perturbed into a tidal crossing orbit, it will become disrupted after the first pass of the white dwarf, where a highly eccentric stream of debris forms the main reservoir for dust-producing collisions. These simulations, in concert with observations of white dwarfs, place interesting limits on the frequency of planetary systems around main-sequence stars, the frequency of planetesimal belts, and the probability that dust may obscure future terrestrial planet finding missions.

Correction of vertical dispersion and betatron coupling for the CLIC damping ring

CERN Document Server

Korostelev, M S

2006-01-01

The sensitivity of the CLIC damping ring to various kinds of alignment errors has been studied. Without any correction, fairly small vertical misalignments of the quadrupoles and, in particular, the sextupoles, introduce unacceptable distortions of the closed orbit as well as intolerable spurious vertical dispersion and coupling due to the strong focusing optics of the damping ring. A sophisticated beam-based correction scheme has been developed to bring the design target emittances and the dynamic aperture back to the ideal value. The correction using dipolar correctors and several skew quadrupole correctors allows a minimization of the closed-orbit distortion, the cross-talk between vertical and horizontal closed orbits, the residual vertical dispersion and the betatron coupling.

Ethinyl Estradiol and Etonogestrel Vaginal Ring

Science.gov (United States)

... or infection of the vagina white or yellow vaginal discharge vaginal bleeding or spotting when it is not time ... Follow your doctor's directions for examining your breasts; report any lumps ... and ethinyl estradiol vaginal ring.Do not let anyone else use your ...

Ground Movement in SSRL Ring

International Nuclear Information System (INIS)

Sunikumar, Nikita

2011-01-01

Users of the Stanford Synchrotron Radiation Lightsource (SSRL) are being affected by diurnal motion of the synchrotron's storage ring, which undergoes structural changes due to outdoor temperature fluctuations. In order to minimize the effects of diurnal temperature fluctuations, especially on the vertical motion of the ring floor, scientists at SSRL tried three approaches: painting the storage ring white, covering the asphalt in the middle of the ring with highly reflective Mylar and installing Mylar on a portion of the ring roof and walls. Vertical motion in the storage ring is measured by a Hydrostatic Leveling System (HLS), which calculates the relative height of water in a pipe that extends around the ring. The 24-hr amplitude of the floor motion was determined using spectral analysis of HLS data, and the ratio of this amplitude before and after each experiment was used to quantitatively determine the efficacy of each approach. The results of this analysis showed that the Mylar did not have any significant effect on floor motion, although the whitewash project did yield a reduction in overall HLS variation of 15 percent. However, further analysis showed that the reduction can largely be attributed to a few local changes rather than an overall reduction in floor motion around the ring. Future work will consist of identifying and selectively insulating these local regions in order to find the driving force behind diurnal floor motion in the storage ring.

Beam-beam diagnostics from closed-orbit distortion

International Nuclear Information System (INIS)

Furman, M.; Chin, Y.H.; Eden, J.; Kozanecki, W.; Tennyson, J.; Ziemann, V.

1992-07-01

We study the applicability of beam-beam deflection techniques as a tuning tool for asymmetric B factories, focusing on PEP-II as an example. Assuming that the closed orbits of the two beams are separated vertically at the interaction point by a local orbit bump that is nominally closed, we calculate the residual beam orbit distortions due to the beam-beam interaction. Difference orbit measurements, performed at points conveniently distant from the interaction point (IP), provide distinct signatures that can be used to maintain the beams in collision and perform detailed optical diagnostics at the IP. A proposal to test this method experimentally at the TRISTAN ring is briefly discussed

Growth of planetisimals in a gaseous ring

International Nuclear Information System (INIS)

Hourigan, K.

1981-01-01

The aggregation of planetesimals in a gaseous ring leads to the development of a dominant body amongst the planetesimal population. The presence of the gas in the form of a differentially rotating ring serves to constrain the orbits of the planetesimals and grains to within a thin toroidal region through the action of gas drag. This situation allows for the efficient aggregation of bodies and, as a result of the low resultant relative velocites, the minimization of collisional fragmentation effects

ACCELERATORS: Beam based alignment of the SSRF storage ring

Science.gov (United States)

Zhang, Man-Zhou; Li, Hao-Hu; Jiang, Bo-Cheng; Liu, Gui-Min; Li, De-Ming

2009-04-01

There are 140 beam position monitors (BPMs) in the Shanghai Synchrotron Radiation Facility (SSRF) storage ring used for measuring the closed orbit. As the BPM pickup electrodes are assembled directly on the vacuum chamber, it is important to calibrate the electrical center offset of the BPM to an adjacent quadrupole magnetic center. A beam based alignment (BBA) method which varies individual quadrupole magnet strength and observes its effects on the orbit is used to measure the BPM offsets in both the horizontal and vertical planes. It is a completely automated technique with various data processing methods. There are several parameters such as the strength change of the correctors and the quadrupoles which should be chosen carefully in real measurement. After several rounds of BBA measurement and closed orbit correction, these offsets are set to an accuracy better than 10 μm. In this paper we present the method of beam based calibration of BPMs, the experimental results of the SSRF storage ring, and the error analysis.

TRANSVERSE PHASE SPACE PAINTING FOR SNS ACCUMULATOR RING INJECTION.

Energy Technology Data Exchange (ETDEWEB)

BEEBE-WANG,J.; LEE,Y.Y.; RAPARIA,D.; WEI,J.

1999-03-29

The result of investigation and comparison of a series of transverse phase space painting schemes for the injection of SNS accumulator ring [1] is reported. In this computer simulation study, the focus is on the creation of closed orbit bumps that give desired distributions at the target. Space charge effects such as tune shift, emittance growth and beam losses are considered. The results of pseudo end-to-end simulations from the injection to the target through the accumulator ring and Ring to Target Beam Transfer (RTBT) system [2] are presented and discussed.

Persistent currents in an ensemble of isolated mesoscopic rings

International Nuclear Information System (INIS)

Altland, A.; Iida, S.; Mueller-Groelling, A.; Weidenmueller, H.A.

1992-01-01

In this work, the authors calculate the persistent current induced at zero temperature by an external, constant, and homogeneous magnetic field in an ensemble of isolated mesoscopic rings. In each ring, the electrons are assumed to move independently under the influence of a Gaussian white noise random impurity potential. They account for the magnetic field only in terms of the flux threading each ring, without considering the field present in the body of the ring. Particular attention is paid to the constraint of integer particle number on each ring. The authors evaluate the persistent current non-perturbatively, using a generating functional involving Grassmann integration. The magnetic flux threading each ring breaks the orthogonal symmetry of the formalism; forcing us to calculate explicitly the orthogonal-unitary crossover. 24 refs., 1 fig

Spin transitions in semiconductor quantum rings

International Nuclear Information System (INIS)

Baxevanis, Benjamin; Pfannkuche, Daniela

2010-01-01

We adopt the path integral Monte Carlo method to accurately resolve the total spin of the ground state of electrons confined in a quantum ring with different geometries. Using this method, an evaluation of the ground state of three electrons in a ring shows a spin transition to the fully polarized state by increasing the radius and thereby enhancing the Coulomb interaction. The total spin of the ground state is determined by the mutual interplay of confinement and electron-electron interaction. An analysis of the four-electron ring demonstrates that in this case no spin transitions take place. Furthermore, the effect of geometric distortion of the ring on its ground state has been investigated. Elliptically deforming the ring breaks the symmetry of the system and leads to the removal of orbital degeneracy. For strong distortion the splitting between hybridized states is sufficient to overcome the exchange-energy saving associated with a higher spin state. We have found that this effect removes the polarization of three electrons. Even in a four-electron ring the ground state is forced by the distortion to be unpolarized and thus suppressing the Hund's rule ground state.

Dragging of inertial frames in the composed black-hole-ring system

International Nuclear Information System (INIS)

Hod, Shahar

2015-01-01

A well-established phenomenon in general relativity is the dragging of inertial frames by a spinning object. In particular, due to the dragging of inertial frames by a ring orbiting a central black hole, the angular velocity Ω H BH-ring of the black-hole horizon in the composed black-hole-ring system is no longer related to the black-hole angular momentum J H by the simple Kerr-like (vacuum) relation Ω H Kerr (J H ) = J H /2M 2 R H (here M and R H are the mass and horizon-radius of the black hole, respectively). Will has performed a perturbative treatment of the composed black-hole-ring system in the regime of slowly rotating black holes and found the explicit relation Ω H BH-ring (J H = 0, J R , R) = 2J R /R 3 for the angular velocity of a central black hole with zero angular momentum, where J R and R are respectively the angular momentum of the orbiting ring and its proper circumferential radius. Analyzing a sequence of black-hole-ring configurations with adiabatically varying (decreasing) circumferential radii, we show that the expression found by Will for Ω H BH-ring (J H = 0, J R , R) implies a smooth transition of the central black-hole angular velocity from its asymptotic near-horizon value Ω H BH-ring (J H = 0, J R , R → R H + ) → 2J R /R H 3 (that is, just before the assimilation of the ring by the central black hole), to its final Kerr (vacuum) value Ω H Kerr (J H new )= J H new /2M new2 R H new [that is, after the adiabatic assimilation of the ring by the central black hole. Here J H new = J R , M new , and R H new are the new parameters of the resulting Kerr (vacuum) black hole after it assimilated the orbiting ring]. We use this important observation in order to generalize the result of Will to the regime of black-hole-ring configurations in which the central black holes possess non-zero angular momenta. In particular, it is shown that the continuity argument (namely, the characteristic smooth evolution of the black-hole angular velocity

A hybrid numerical method for orbit correction

International Nuclear Information System (INIS)

White, G.; Himel, T.; Shoaee, H.

1997-09-01

The authors describe a simple hybrid numerical method for beam orbit correction in particle accelerators. The method overcomes both degeneracy in the linear system being solved and respects boundaries on the solution. It uses the Singular Value Decomposition (SVD) to find and remove the null-space in the system, followed by a bounded Linear Least Squares analysis of the remaining recast problem. It was developed for correcting orbit and dispersion in the B-factory rings

Establishment of a tolerance budget for the advanced photon source storage ring

International Nuclear Information System (INIS)

Bizek, H.; Crosbie, E.; Lessner, E.; Teng, L.

1993-01-01

The limitations on the dynamic aperture of the Advanced Photon Source storage ring due to magnet misalignments and fabrication errors are presented. The reduction of the dynamic aperture is analyzed first for each error considered individually, and then for combined error multipole fields in dipole, quadrupole, and sextupole magnets, excluding and including magnet misalignments. Since misalignments of the strong quadrupoles in the ring induce large orbit distortions, the effects on the dynamic aperture are investigated before and after orbit correction. Effects of off-momentum particles and the tune dependence with momentum are also presented. This extensive analysis leads to the establishment of a tolerance budget. With all the errors set at the tolerance level, and with the orbit distortions corrected, the dynamic aperture reduction is no greater than 50% of that of the ideal machine

Establishment of a tolerance budget for the Advanced Photon Source storage ring

International Nuclear Information System (INIS)

Bizek, H.; Crosbie, E.; Lessner, E.; Teng, L.

1993-01-01

The limitations on the dynamic aperture of the Advanced Photon Source storage ring due to magnet misalignments and fabrication errors are presented. The reduction of the dynamic aperture is analyzed first for each error considered individually, and then for combined error multipole fields in dipole, quadrupole, and sextupole magnets, excluding and including magnet misalignments. Since misalignments of the strong quadrupoles in the ring induce large orbit distortions, the effects on the dynamic aperture are investigated before and after orbit correction. Effects of off-momentum particles and the tune dependence with momentum are also presented. This extensive analysis leads to the establishment of a tolerance budget. With all the errors set at the tolerance level and with the orbit distortions corrected, the dynamic aperture reduction is no greater than 50% of that of the ideal machine

Indirect evidences for a gas/dust torus along the Phobos orbit

International Nuclear Information System (INIS)

Dubinin, E.M.; Lundin, R.; Pissarenko, N.F.; Barabash, S.V.; Zakharov, A.V.; Koskinen, H.; Schwingenshuh, K.; Yeroshenko, Ye.G.

1990-01-01

Observations from the PHOBOS-2 space-craft of plasma and magnetic field effects in the solar wind near Mars suggest that a neutral gas (dust?)torus/ring resides along the orbit of the Martian satellite Phobos. Magnetic cavities (strong decreases of the magnetic field strength) coincident with strong plasma density increases (up to a factor of ten) are observed during the first elliptic transition orbits when the spacecraft approached the Phobos orbits. The characteristic transverse dimension of the structures along the spacecraft orbit is in the range 100-1,000 km. Torus effects also have characteristics similar to the formation of a bow shock with increases of plasma density and ion temperature, and a characteristic deflection of the ion flow. This suggests a rather strong interaction between the solar wind plasma and plasma near Phobos orbit. The interaction appears quite similar to that of the solar wind with a comet. The outgassing of matter from Phobos (and Deimos) is also suggested by plasma observations in the wake/tail of the Martian satellites. Altogether, the authors observations imply that a neutral gas cloud - possibly also associated with a faint dust ring - exists along the Phobos orbit

Gravitoelectrodynamics in Saturn's F ring: encounters with Prometheus and Pandora

International Nuclear Information System (INIS)

Matthews, Lorin Swint; Hyde, Truell W

2003-01-01

The dynamics of Saturn's F ring have been a matter of curiosity ever since Voyagers 1 and 2 sent back pictures of the ring's unusual features. Some of these images showed three distinct ringlets with the outer two displaying a kinked and braided appearance. Many models have been proposed to explain the braiding seen in these images; most of these invoke perturbations caused by the shepherding moons or kilometre-sized moonlets embedded in the ring and are purely gravitational in nature. These models also assume that the plasma densities and charges on the grains are small enough that electromagnetic forces can be ignored. However, Saturn's magnetic field exerts a significant perturbative force on even weakly charged micron- and submicron-sized grains causing the grains to travel in epicyclic orbits about a guiding centre. This study examines the effect of Saturn's magnetic field on the dynamics of micron-sized grains along with gravitational interactions between the F ring's shepherding moons, Prometheus and Pandora. Due to the differences in charge-to-mass ratios of the various sized grains, a phase difference between different size populations is observed in the wavy orbits imposed by passage of the shepherding moons

Closed orbit distortion and the beam-beam interaction

Energy Technology Data Exchange (ETDEWEB)

Furman, M.; Chin, Y.H.; Eden, J. [Lawrence Berkeley Lab., CA (United States); Kozanecki, W. [CEA Centre d`Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France)]|[Stanford Linear Accelerator Center, Menlo Park, CA (United States); Tennyson, J.; Ziemann, V. [Stanford Linear Accelerator Center, Menlo Park, CA (United States)

1992-06-01

We study the applicability of beam-beam deflection techniques as a tuning tool for the SLAC/LBL/LLNL B factory, PEP-II. Assuming that the closed orbits of the two beams are separated vertically at the interaction point by a local orbit bump that is nominally closed, we calculate the residual beam orbit distortions due to the beam-beam interaction. Difference orbit measurements, performed at points conveniently distant from the IP, provide distinct coordinate- or frequency-space signatures that can be used to maintain the beams in collision and perform detailed optical diagnostics at the IP. A proposal to test this method experimentally at the TRISTAN ring is briefly discussed.

Closed orbit distortion and the beam-beam interaction

International Nuclear Information System (INIS)

Furman, M.; Chin, Y.H.; Eden, J.; Kozanecki, W.; Tennyson, J.; Ziemann, V.

1992-01-01

We study the applicability of beam-beam deflection techniques as a tuning tool for the SLAC/LBL/LLNL B factory, PEP-II. Assuming that the closed orbits of the two beams are separated vertically at the interaction point by a local orbit bump that is nominally closed, we calculate the residual beam orbit distortions due to the beam-beam interaction. Difference orbit measurements, performed at points conveniently distant from the IP, provide distinct coordinate- or frequency-space signatures that can be used to maintain the beams in collision and perform detailed optical diagnostics at the IP. A proposal to test this method experimentally at the TRISTAN ring is briefly discussed

Stochastic behaviour of particle orbits in field reversed geometries

International Nuclear Information System (INIS)

Finn, J.M.

1979-01-01

Studies of stochastic or ergodic behaviour of beam particle orbits in axisymmetric systems with field reversal produced by ion rings or by neutral injection are presented. In the former case a large class of orbits is ergodic, whereas in the latter most are integrable. Effects of ergodic behaviour on particle confinement, equilibrium, magnetic compression, and stability are discussed. The modification, due to ergodic orbits of the stability criterion for low frequency (ω << ωsub(ci)) resonant instabilities is presented. (author)

Two Electron States in a Quantum Ring on a Sphere

International Nuclear Information System (INIS)

Kazaryan, Eduard M.; Shahnazaryan, Vanik A.; Sarkisyan, Hayk A.

2014-01-01

Two electron states in a quantum ring on a spherical surface are discussed. The problem is discussed within the frameworks of Russell–Saunders coupling scheme, that is, the spin–orbit coupling is neglected. Treating Coulomb interaction as a perturbation, the energy correction for different states is calculated. The dependence of the Coulomb interaction energy on external polar boundary angle of quantum ring is obtained. In analogue with the helium atom the concept of states exchange time is introduced, and its dependence on geometrical parameters of the ring is shown. (author)

A Saturn Ring Observer Mission Using Multi-Mission Radioisotope Power Systems

International Nuclear Information System (INIS)

Abelson, Robert D.; Spilker, Thomas R.; Shirley, James H.

2006-01-01

Saturn remains one of the most fascinating planets within the solar system. To better understand the complex ring structure of this planet, a conceptual Saturn Ring Observer (SRO) mission is presented that would spend one year in close proximity to Saturn's A and B rings, and perform detailed observations and measurements of the ring particles and electric and magnetic fields. The primary objective of the mission would be to understand ring dynamics, including the microphysics of individual particles and small scale (meters to a few kilometers) phenomena such as particle agglomeration behavior. This would be accomplished by multispectral imaging of the rings at multiple key locations within the A and B rings, and by ring-particle imaging at an unprecedented resolution of 0.5 cm/pixel. The SRO spacecraft would use a Venus-Earth-Earth-Jupiter Gravity Assist (VEEJGA) and be aerocaptured into Saturn orbit using an advanced aeroshell design to minimize propellant mass. Once in orbit, the SRO would stand off from the ring plane 1 to 1.4 km using chemical thrusters to provide short propulsive maneuvers four times per revolution, effectively causing the SRO vehicle to 'hop' above the ring plane. The conceptual SRO spacecraft would be enabled by the use of a new generation of multi-mission Radioisotope Power Systems (RPSs) currently being developed by NASA and DOE. These RPSs include the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) and Stirling Radioisotope Generator (SRG). The RPSs would generate all necessary electrical power (≥330 We at beginning of life) during the 10-year cruise and 1-year science mission (∼11 years total). The RPS heat would be used to maintain the vehicle's operating and survival temperatures, minimizing the need for electrical heaters. Such a mission could potentially launch in the 2015-2020 timeframe, with operations at Saturn commencing in approximately 2030

Ion production and trapping in electron rings

International Nuclear Information System (INIS)

Gluckstern, R.C.; Ruggiero, A.G.

1979-08-01

The electron beam in the VUV and X-ray rings of NSLS will ionize residual gas by collisions. Positive ions will be produced with low velocity, and will be attracted by the electron beam to the beam axis. If they are trapped in stable (transverse) orbits, they may accumulate, thereby increasing the ν/sub x,z/ of the individual electrons. Since the accumulated ions are unlikely to be of uniform density, a spread in ν/sub x,z/ will also occur. Should these effects be serious, it may be necessary to introduce clearing electrodes, although this may increase Z/n in the rings, thereby adding to longitudinal instability problems. The seriousness of the above effect for the VUV and X-ray rings is estimated

FORMATION OF CENTAURS’ RINGS THROUGH THEIR PARTIAL TIDAL DISRUPTION DURING PLANETARY ENCOUNTERS

Energy Technology Data Exchange (ETDEWEB)

Hyodo, Ryuki; Charnoz, Sébastien [Institut de Physique du Globe, F-75005 Paris, France (France); Genda, Hidenori [Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8550 (Japan); Ohtsuki, Keiji [Department of Planetology, Kobe University, Kobe 657-8501 (Japan)

2016-09-01

Centaurs are minor planets orbiting between Jupiter and Neptune that have or had crossing orbits with one or more giant planets. Recent observations and reinterpretation of previous observations have revealed the existence of ring systems around 10199 Chariklo and 2060 Chiron. However, the origin of the ring systems around such a minor planet is still an open question. Here, we propose that the tidal disruption of a differentiated object that experiences a close encounter with a giant planet could naturally form diverse ring–satellite systems around the Centaurs. During the close encounter, the icy mantle of the passing object is preferentially ripped off by the planet's tidal force and the debris is distributed mostly within the Roche limit of the largest remnant body. Assuming the existence of a 20−50 wt% silicate core below the icy mantle, a disk of particles is formed when the objects pass within 0.4–0.8 of the planet's Roche limit with the relative velocity at infinity 3−6 km s{sup −1} and 8 hr initial spin period of the body. The resultant ring mass is 0.1%–10% of the central object's mass. Such particle disks are expected to spread radially, and materials spreading beyond the Roche limit would accrete into satellites. Our numerical results suggest that ring formation would be a natural outcome of such extreme close encounters, and Centaurs can naturally have such ring systems because they cross the orbits of the giant planets.

FORMATION OF CENTAURS’ RINGS THROUGH THEIR PARTIAL TIDAL DISRUPTION DURING PLANETARY ENCOUNTERS

International Nuclear Information System (INIS)

Hyodo, Ryuki; Charnoz, Sébastien; Genda, Hidenori; Ohtsuki, Keiji

2016-01-01

Centaurs are minor planets orbiting between Jupiter and Neptune that have or had crossing orbits with one or more giant planets. Recent observations and reinterpretation of previous observations have revealed the existence of ring systems around 10199 Chariklo and 2060 Chiron. However, the origin of the ring systems around such a minor planet is still an open question. Here, we propose that the tidal disruption of a differentiated object that experiences a close encounter with a giant planet could naturally form diverse ring–satellite systems around the Centaurs. During the close encounter, the icy mantle of the passing object is preferentially ripped off by the planet's tidal force and the debris is distributed mostly within the Roche limit of the largest remnant body. Assuming the existence of a 20−50 wt% silicate core below the icy mantle, a disk of particles is formed when the objects pass within 0.4–0.8 of the planet's Roche limit with the relative velocity at infinity 3−6 km s"−"1 and 8 hr initial spin period of the body. The resultant ring mass is 0.1%–10% of the central object's mass. Such particle disks are expected to spread radially, and materials spreading beyond the Roche limit would accrete into satellites. Our numerical results suggest that ring formation would be a natural outcome of such extreme close encounters, and Centaurs can naturally have such ring systems because they cross the orbits of the giant planets.

Whirling orbits around twirling black holes from conformal symmetry

Energy Technology Data Exchange (ETDEWEB)

Hadar, Shahar [Department of Applied Mathematics and Theoretical Physics, University of Cambridge,Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Porfyriadis, Achilleas P. [Department of Physics, UCSB,Santa Barbara, CA 93106 (United States)

2017-03-03

Dynamics in the throat of rapidly rotating Kerr black holes is governed by an emergent near-horizon conformal symmetry. The throat contains unstable circular orbits at radii extending from the ISCO down to the light ring. We show that they are related by conformal transformations to physical plunges and osculating trajectories. These orbits have angular momentum arbitrarily higher than that of ISCO. Using the conformal symmetry we compute analytically the radiation produced by the physical orbits. We also present a simple formula for the full self-force on such trajectories in terms of the self-force on circular orbits.

Evaluation of the synchrotron close orbit

International Nuclear Information System (INIS)

Bashmakov, Yu.A.; Karpov, V.A.

1991-01-01

The knowledge of the closed orbit position is an essential condition for the effective work of any accelerator. Therefore questions of calculations, measurements and controls have great importance. For example, during injection of particles into a synchrotron, the amplitudes of their betatron oscillations may become commensurable with the working region of the synchrotron. This makes one pay attention at the problem of formation of the optimum orbit with use of correcting optical elements. In addition, it is often necessary to calculate such an orbit at the end of the acceleration cycle when particles are deposited at internal targets or removed from the synchrotron. In this paper, the computation of the close orbit is reduced to a determination at an arbitrarily chosen azimuth of the eigenvector of the total transfer matrix of the synchrotron ring and to tracing with this vector desired orbit. The eigenvector is found as a result of an iteration

Ringed Accretion Disks: Evolution of Double Toroidal Configurations

Energy Technology Data Exchange (ETDEWEB)

Pugliese, D.; Stuchlík, Z., E-mail: daniela.pugliese@fpf.slu.cz, E-mail: zdenek.stuchlik@physics.cz [Institute of Physics and Research Centre of Theoretical Physics and Astrophysics, Faculty of Philosophy and Science, Silesian University in Opava, Bezručovo náměstí 13, CZ-74601 Opava (Czech Republic)

2017-04-01

We investigate ringed accretion disks composed of two tori (rings) orbiting on the equatorial plane of a central supermassive Kerr black hole. We discuss the emergence of the instability phases of each ring of the macro-configuration (ringed disk) according to the Paczynski violation of mechanical equilibrium. In the full general relativistic treatment, we consider the effects of the geometry of the Kerr spacetimes relevant to the characterization of the evolution of these configurations. The discussion of ring stability in different spacetimes enables us to identify particular classes of central Kerr attractors depending on their dimensionless spin. As a result of this analysis, we set constraints on the evolutionary schemes of the ringed disks relative to the torus morphology and on their rotation relative to the central black hole and to each other. The dynamics of the unstable phases of this system is significant for the high-energy phenomena related to accretion onto supermassive black holes in active galactic nuclei and the extremely energetic phenomena in quasars, which could be observed in their X-ray emission.

A simulation study of the global orbit feedback system for Pohang light source

International Nuclear Information System (INIS)

Kim, Kukhee; Shim, Kyuyeol; Cho, Moohyun; Namkung, Won; Ko, In Soo; Choi, Jinhyuk

2000-01-01

This paper describes the simulation of the global orbit feedback system using the singular value decomposition (SVD) method, the error minimization method, and the neural network method. Instead of facing unacceptable correction result raised occasionally in the SVD method, we choose the error minimization method for the global orbit feedback. This method provides minimum orbit errors while avoiding unacceptable corrections, and keeps the orbit within the dynamic aperture of the storage ring. We simulate the Pohang Light Source (PLS) storage ring using the Methodical Accelerator Design (MAD) code that generates the orbit distortions for the error minimization method and the learning data set for neural network method. In order to compare the effectiveness of the neural network method with others, a neural network is trained by the learning algorithm using the learning data set. The global response matrix with a minimum error and the trained neural network are used to the global orbit feedback system. The simulation shows that a selection of beam position monitors (BPMs) is very sensitive in the reduction of rms orbit distortions, and the random choice gives better results than any other cases. (author)

SXLS storage ring design

International Nuclear Information System (INIS)

Anon.

1991-01-01

X-ray lithography has emerged as a strong candidate to meet the demands of ever finer linewidths on integrated circuits, particularly for linewidths less than .25 microns. Proximity printing X-ray lithography makes use of soft X-rays to shadow print an image of a mask onto a semiconductor wafer to produce integrated circuits. To generate the required X-rays in sufficient quantities to make commercial production viable, electron storage rings have been proposed as the soft X-ray sources. Existing storage rings have been used to do the initial development work and the success of these efforts has led the lithographers to request that new rings be constructed that are dedicated to X-ray lithography. As a result of a series of workshops held at BNL [10.3] which were attended by both semiconductor and accelerator scientists, the following set of zeroth order specifications' on the light and electron beam of a storage ring for X-ray lithography were developed: critical wavelength of light: λ c = 6 to 10 angstroms, white light power: P = 0.25 to 2.5 watts/mrad, horizontal collection angle per port: θ = 10 to 50 mrad, electron beam sizes: σ x ∼ σ y y ' < 1 mrad

Emergence of unstable itinerant orbits in a recurrent neural network model

International Nuclear Information System (INIS)

Suemitsu, Yoshikazu; Nara, Shigetoshi

2005-01-01

A recurrent neural network model with time delay is investigated by numerical methods. The model functions as both conventional associative memory and also enables us to embed a new kind of memory attractor that cannot be realized in models without time delay, for example chain-ring attractors. This is attributed to the fact that the time delay extends the available state space dimension. The difference between the basin structures of chain-ring attractors and of isolated cycle attractors is investigated with respect to the two attractor pattern sets, random memory patterns and designed memory patterns with intended structures. Compared to isolated attractors with random memory patterns, the basins of chain-ring attractors are reduced considerably. Computer experiments confirm that the basin volume of each embedded chain-ring attractor shrinks and the emergence of unstable itinerant orbits in the outer state space of the memory attractor basins is discovered. The instability of such itinerant orbits is investigated. Results show that a 1-bit difference in initial conditions does not exceed 10% of a total dimension within 100 updating steps

White dwarfs in cataclysmic variables

International Nuclear Information System (INIS)

Sion, E.M.

1987-01-01

The physical properties and evolutionary state of the underlying white dwarfs in CVs are explored. Observations of 25 white dwarfs with effective temperature upper limits of 9000-75,000 K are discussed. Correlations between effective temperature, orbital period, accretion rate, and CV type with respect to the CV period gap are considered. Quasi-static and hydrodynamic evolutionary models are used to explain the surface temperature/luminosity distribution ratios. 42 references

Nonlinear dynamics aspects of modern storage rings

International Nuclear Information System (INIS)

Helleman, R.H.G.; Kheifets, S.A.

1986-01-01

It is argued that the nonlinearity of storage rings becomes an essential problem as the design parameters of each new machine are pushed further and further. Yet the familiar methods of classical mechanics do not allow determination of single particle orbits over reasonable lengths of time. It is also argued that the single particle dynamics of a storage ring is possibly one of the cleanest and simplest nonlinear dynamical systems available with very few degrees of freedom. Hence, reasons are found for accelerator physicists to be interested in nonlinear dynamics and for researchers in nonlinear dynamics to be interested in modern storage rings. The more familiar methods of treating nonlinear systems routinely used in acclerator theory are discussed, pointing out some of their limitations and pitfalls. 39 refs., 1 fig

Saturn Rings Origin: Quantum Trapping of Superconducting Iced Particles and Meissner Effect Lead to the Stable Rings System

Science.gov (United States)

Viktorovich Tchernyi, Vladimir

2018-06-01

Saturn Rings Origin: Quantum Trapping of Superconducting Iced Particles and Meissner Effect Lead to the Stable Rings System Vladimir V. Tchernyi (Cherny), Andrew Yu. Pospelov Modern Science Institute, SAIBR, Moscow, Russia. E-mail: chernyv@bk.ruAbstractIt is demonstrated how superconducting iced particles of the protoplanetary cloud of Saturn are coming to magnetic equator plane and create the stable enough rings disk. There are two steps. First, after appearance of the Saturn magnetic field due to Meissner phenomenon all particles orbits are moving to the magnetic equator plane. Finally they become distributed as rings and gaps like iron particles around magnet on laboratory table. And they are separated from each other by the magnetic field expelled from them. It takes up to few tens of thousands years with ten meters rings disk thickness. Second, due to their quantum trapping all particles become to be trapped within magnetic well at the magnetic equator plane due to Abrikosov vortex for superconductor. It works even when particles have small fraction of superconductor. During the rings evolution some contribution to the disk also could come from the collision-generated debris of the current moon and from the geysers like it happened due to magnetic coupling of Saturn and Enceladus. The rings are relict of the early days of the magnetic field of Saturn system.

Spin-dependent heat and thermoelectric currents in a Rashba ring coupled to a photon cavity

Science.gov (United States)

Abdullah, Nzar Rauf; Tang, Chi-Shung; Manolescu, Andrei; Gudmundsson, Vidar

2018-01-01

Spin-dependent heat and thermoelectric currents in a quantum ring with Rashba spin-orbit interaction placed in a photon cavity are theoretically calculated. The quantum ring is coupled to two external leads with different temperatures. In a resonant regime, with the ring structure in resonance with the photon field, the heat and the thermoelectric currents can be controlled by the Rashba spin-orbit interaction. The heat current is suppressed in the presence of the photon field due to contribution of the two-electron and photon replica states to the transport while the thermoelectric current is not sensitive to changes in parameters of the photon field. Our study opens a possibility to use the proposed interferometric device as a tunable heat current generator in the cavity photon field.

Electronic structure and Landé g-factor of a quantum ring in the presence of spin-orbit coupling: Temperature and Zeeman effect

Science.gov (United States)

Zamani, A.; Setareh, F.; Azargoshasb, T.; Niknam, E.

2017-10-01

A wide variety of semiconductor nanostructures have been fabricated experimentally and both theoretical and experimental investigations of their features imply the great role they have in new generation technological devices. However, mathematical modeling provide a powerful means due to definitive goal of predicting the features and understanding of such structures behavior under different circumstances. Therefore, effective Hamiltonian for an electron in a quantum ring with axial symmetry in the presence of both Rashba and Dresselhaus spin-orbit interactions (SOI) is derived. Here we report our study of the electronic structure and electron g-factor in the presence of spin-orbit (SO) couplings under the influence of external magnetic field at finite temperature. This investigation shows that, when Rashba and Dresselhaus couplings are simultaneously present, the degeneracy is removed and energy levels split into two branches. Furthermore, with enhancing the applied magnetic field, separation of former degenerate levels increases and also avoided crossings (anti-crossing) in the energy spectra is detected. It is also discussed how the energy levels of the system can be adjusted with variation of temperature as well as the magnetic field and geometrical sizes.

Long-term stability of orbits in storage rings

International Nuclear Information System (INIS)

Warnock, R.L.; Ruth, R.D.

1990-06-01

We describe a numerical method to establish long-term bounds on nonlinear Hamiltonian motion. By bounding the change in a nearly constant action variable, uniformly in initial condition, one can predict stability for N turns by tracking many orbits for a member of turns of N 0 much less than N. In a first application to a model sextupole lattice in a region of strong nonlinearity, we predict stability of betatron motion in two degrees of freedom for 10 8 turns. 5 refs., 3 figs

Dragging of inertial frames in the composed black-hole-ring system

Energy Technology Data Exchange (ETDEWEB)

Hod, Shahar [The Ruppin Academic Center, Emeq Hefer (Israel); The Hadassah Institute, Jerusalem (Israel)

2015-11-15

A well-established phenomenon in general relativity is the dragging of inertial frames by a spinning object. In particular, due to the dragging of inertial frames by a ring orbiting a central black hole, the angular velocity Ω{sub H}{sup BH-ring} of the black-hole horizon in the composed black-hole-ring system is no longer related to the black-hole angular momentum J{sub H} by the simple Kerr-like (vacuum) relation Ω{sub H}{sup Kerr}(J{sub H}) = J{sub H}/2M{sup 2}R{sub H} (here M and R{sub H} are the mass and horizon-radius of the black hole, respectively). Will has performed a perturbative treatment of the composed black-hole-ring system in the regime of slowly rotating black holes and found the explicit relation Ω{sub H}{sup BH-ring}(J{sub H} = 0, J{sub R}, R) = 2J{sub R}/R{sup 3} for the angular velocity of a central black hole with zero angular momentum, where J{sub R} and R are respectively the angular momentum of the orbiting ring and its proper circumferential radius. Analyzing a sequence of black-hole-ring configurations with adiabatically varying (decreasing) circumferential radii, we show that the expression found by Will for Ω{sub H}{sup BH-ring}(J{sub H} = 0, J{sub R}, R) implies a smooth transition of the central black-hole angular velocity from its asymptotic near-horizon value Ω{sub H}{sup BH-ring}(J{sub H} = 0, J{sub R}, R → R{sub H}{sup +}) → 2J{sub R}/R{sub H}{sup 3} (that is, just before the assimilation of the ring by the central black hole), to its final Kerr (vacuum) value Ω{sub H}{sup Kerr}(J{sub H}{sup new})= J{sub H}{sup new}/2M{sup new2}R{sub H}{sup new} [that is, after the adiabatic assimilation of the ring by the central black hole. Here J{sub H}{sup new} = J{sub R}, M{sup new}, and R{sub H}{sup new} are the new parameters of the resulting Kerr (vacuum) black hole after it assimilated the orbiting ring]. We use this important observation in order to generalize the result of Will to the regime of black-hole-ring configurations

Dragging of inertial frames in the composed black-hole–ring system

Energy Technology Data Exchange (ETDEWEB)

Hod, Shahar, E-mail: shaharhod@gmail.com [The Ruppin Academic Center, 40250, Emeq Hefer (Israel); The Hadassah Institute, 91010, Jerusalem (Israel)

2015-11-19

A well-established phenomenon in general relativity is the dragging of inertial frames by a spinning object. In particular, due to the dragging of inertial frames by a ring orbiting a central black hole, the angular velocity Ω{sub H}{sup BH-ring} of the black-hole horizon in the composed black-hole–ring system is no longer related to the black-hole angular momentum J{sub H} by the simple Kerr-like (vacuum) relation Ω{sub H}{sup Kerr}(J{sub H})=J{sub H}/2M{sup 2}R{sub H} (here M and R{sub H} are the mass and horizon-radius of the black hole, respectively). Will has performed a perturbative treatment of the composed black-hole–ring system in the regime of slowly rotating black holes and found the explicit relation Ω{sub H}{sup BH-ring}(J{sub H}=0,J{sub R},R)=2J{sub R}/R{sup 3} for the angular velocity of a central black hole with zero angular momentum, where J{sub R} and R are respectively the angular momentum of the orbiting ring and its proper circumferential radius. Analyzing a sequence of black-hole–ring configurations with adiabatically varying (decreasing) circumferential radii, we show that the expression found by Will for Ω{sub H}{sup BH-ring}(J{sub H}=0,J{sub R},R) implies a smooth transition of the central black-hole angular velocity from its asymptotic near-horizon value Ω{sub H}{sup BH-ring}(J{sub H}=0,J{sub R},R→R{sub H}{sup +})→2J{sub R}/R{sub H}{sup 3} (that is, just before the assimilation of the ring by the central black hole), to its final Kerr (vacuum) value Ω{sub H}{sup Kerr}(J{sub H}{sup new})=J{sub H}{sup new}/2M{sup new2}R{sub H}{sup new} [that is, after the adiabatic assimilation of the ring by the central black hole. Here J{sub H}{sup new}=J{sub R}, M{sup new}, and R{sub H}{sup new} are the new parameters of the resulting Kerr (vacuum) black hole after it assimilated the orbiting ring]. We use this important observation in order to generalize the result of Will to the regime of black-hole–ring configurations in which the

Slow Orbit Feedback at the ALS Using Matlab

International Nuclear Information System (INIS)

Portmann, G.

1999-01-01

The third generation Advanced Light Source (ALS) produces extremely bright and finely focused photon beams using undulatory, wigglers, and bend magnets. In order to position the photon beams accurately, a slow global orbit feedback system has been developed. The dominant causes of orbit motion at the ALS are temperature variation and insertion device motion. This type of motion can be removed using slow global orbit feedback with a data rate of a few Hertz. The remaining orbit motion in the ALS is only 1-3 micron rms. Slow orbit feedback does not require high computational throughput. At the ALS, the global orbit feedback algorithm, based on the singular valued decomposition method, is coded in MATLAB and runs on a control room workstation. Using the MATLAB environment to develop, test, and run the storage ring control algorithms has proven to be a fast and efficient way to operate the ALS

CESAR, 2 MeV electron storage ring; construction period; general view.

CERN Multimedia

Service Photo; CERN PhotoLab

1962-01-01

A general view of the 2-MeV electron storage-ring model during the last stages of assembly. The injection line for the electrons enters at the bottom of the picture (under the ladder) and meets the ring at the back, to the right. Near there, Joseph Karouanton (S.G.T.E, Paris) (inside the ring), and Marcel Bernasconi (AR Division) are seen testing for leaks in the vacuum system. In white coats are Mervin Barnes (left) and Boony Bruggerman (AR Division), considering the reading shown by one of the vacuum gauges.

Link calibrations for the TDRSS orbiting VLBI experiment

International Nuclear Information System (INIS)

Edwards, C.D.

1987-01-01

The first successful interferometric observations of extragalactic radio sources using an orbiting antenna as one of the observing stations were achieved in July and August 1986 using the TDRSS. The technical obstacles to maintaining phase coherence between the orbiting antenna and the ground stations are reviewed, with an emphasis on the effects of spacecraft motion. An analysis of the interferometric delay and phase reveals the signature of errors in the spacecraft ephemeris. Various calibration schemes are discussed, including the use of a ground beacon at White Sands to calibrate the communications link between White Sands and the TDRSE satellite. Using all available calibrations, coherence of 84 percent was achieved for 700-sec integrations

Persistent organic pollutants in ringed seals from the Russian Arctic.

Science.gov (United States)

Savinov, Vladimir; Muir, Derek C G; Svetochev, Vladislav; Svetocheva, Olga; Belikov, Stanislav; Boltunov, Andrey; Alekseeva, Ludmila; Reiersen, Lars-Otto; Savinova, Tatiana

2011-06-15

Organochlorine compounds total DDT (ΣDDT), total HCH isomers (ΣHCH), toxaphenes (sum of Parlar 26, 50, 62), mirex, endrin, methoxychlor, total chlorinated benzenes (ΣCBz), total chlordane compounds (ΣCHL), polychlorinated biphenyls (total of 56 congeners; ΣPCBs), polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), and polybrominated diphenyl ethers (sum of 7 tri- to hepta congeners; ΣPBDEs) were analysed in the blubber of adult ringed seals from the four areas of the Russian Arctic (White Sea, Barents Sea, Kara Sea and Chukchi Sea) collected in 2001-2005. Ringed seals from the south-western part of the Kara Sea (Dikson Island - Yenisei estuary) were the most contaminated with ΣDDTs, ΣPCBs, ΣCHL, and mirex as compared with those found in the other three areas of Russian Arctic, while the highest mean concentrations of ΣHCHs and PCDD/Fs were found in the blubber of ringed seals from the Chukchi Sea and the White Sea, respectively. Among all organochlorine compounds measured in ringed seals from the European part of the Russian Arctic, concentrations of ΣDDT and ΣPCBs only were higher as compared with the other Arctic regions. Levels of all other organochlorine compounds were similar or lower than in seals from Svalbard, Alaska, the Canadian Arctic and Greenland. ΣPBDEs were found in all ringed seal samples analysed. There were no significant differences between ΣPBDE concentrations found in the blubber of ringed seals from the three studied areas of the European part of the Russian Arctic, while PBDE contamination level in ringed seals from the Chukchi Sea was 30-50 times lower. ΣPBDE levels in the blubber of seals from the European part of the Russian Arctic are slightly higher than in ringed seals from the Canadian Arctic, Alaska, and western Greenland but lower compared to ringed seals from Svalbard and eastern Greenland. Copyright © 2011 Elsevier B.V. All rights reserved.

Survey and alignment of photon factory storage ring at KEK

International Nuclear Information System (INIS)

Araki, A.; Honjo, I.; Katoh, M.; Kamiya, Y.; Kihara, M.

1987-01-01

The heights of the magnets for both the ring and the beam transport line (BT-line) have been periodically measured at the Photon Factory. The accumulated data showed that the ring was considerably declined due to the construction of the large experimental hall and the tunnel of the TRISTAN project, and that the BT-line also sank several centimeters at some locations. These displacements of the magnets produce a significantly large closed orbit distortion and the vertical dispersion

An observation of the earth tides in the SPring-8 storage ring

International Nuclear Information System (INIS)

Date, S.; Kumagai, N.

1998-01-01

The SPring-8 storage ring is under the operation dedicated to synchrotron light users since October, 1997. The stability of the electron beam orbit during a long term of the operation is one of the main subjects to be achieved. Data on the beam orbit taken for this purpose show very clear signature of an effect of the earth tide. (author)

The Rings of Saturn

Science.gov (United States)

Cuzzi, J. N.; Filacchione, G.; Marouf, E. A.

2018-03-01

One could become an expert on Saturn's iconic rings pretty easily in the early 1970s, as very little was known about them beyond the distinction between the A, B, and C rings, and the Cassini Division or "gap" between rings A and B (Alexander, 1962; Bobrov, 1970). Water ice was discovered spectroscopically on the ring particle surfaces, and radar and microwave emission observations proved that the particles must be centimeters to meters in size, consisting primarily, not just superficially, of water ice (Pollack, 1975). While a 2:1 orbital resonance with Mimas had long been suspected of having something to do with the Cassini Division, computers of the time were unable to model the subtle dynamical effects that we now know to dominate ring structure. This innocent state of affairs was exploded by the Voyager 1 and 2 encounters in 1980 and 1981. Spectacular images revealed filigree structure and odd regional color variations, and exquisitely detailed radial profiles of fluctuating particle abundance were obtained from the first stellar and radio occultations, having resolution almost at the scale of single particles. Voyager-era understanding was reviewed by Cuzzi et al. (1984) and Esposito et al. (1984). While the Voyager data kept ring scientists busy for decades, planning which led to the monumentally successful NASA-ESA-ASI Cassini mission, which arrived in 2004, had been under way even before Voyager got to Saturn. A review of pre-Cassini knowledge of Saturn's Rings can be found in Orton et al. (2009). This chapter will build on recent topical and process-specific reviews that treat the gamut of ring phenomena and its underlying physics in considerable detail (Colwell et al., 2009; Cuzzi et al., 2009; Horányi et al., 2009; Schmidt et al., 2009; Esposito, 2010; Tiscareno, 2013b; Esposito, 2014). We will follow and extend the general organization of Cuzzi et al. (2010), the most recent general discussion of Saturn's rings. For brevity and the benefit of the

Dynamics of satellites, asteroids, and rings

International Nuclear Information System (INIS)

Dermott, S.F.

1987-01-01

Work is reported on: (1) the shapes and the internal structures of satellites; (2) the tidal heating of Miranda; (3) the dynamics of arc-like rings; and (4) the structure of the zodiacal cloud that was revealed by the Infrared Astronomy Satellite. Significant progress was made in determining the shape and internal structure of Mimas and in understanding the dynamical evolution of Miranda's orbit

Update on orbital reconstruction.

Science.gov (United States)

Chen, Chien-Tzung; Chen, Yu-Ray

2010-08-01

Orbital trauma is common and frequently complicated by ocular injuries. The recent literature on orbital fracture is analyzed with emphasis on epidemiological data assessment, surgical timing, method of approach and reconstruction materials. Computed tomographic (CT) scan has become a routine evaluation tool for orbital trauma, and mobile CT can be applied intraoperatively if necessary. Concomitant serious ocular injury should be carefully evaluated preoperatively. Patients presenting with nonresolving oculocardiac reflex, 'white-eyed' blowout fracture, or diplopia with a positive forced duction test and CT evidence of orbital tissue entrapment require early surgical repair. Otherwise, enophthalmos can be corrected by late surgery with a similar outcome to early surgery. The use of an endoscope-assisted approach for orbital reconstruction continues to grow, offering an alternative method. Advances in alloplastic materials have improved surgical outcome and shortened operating time. In this review of modern orbital reconstruction, several controversial issues such as surgical indication, surgical timing, method of approach and choice of reconstruction material are discussed. Preoperative fine-cut CT image and thorough ophthalmologic examination are key elements to determine surgical indications. The choice of surgical approach and reconstruction materials much depends on the surgeon's experience and the reconstruction area. Prefabricated alloplastic implants together with image software and stereolithographic models are significant advances that help to more accurately reconstruct the traumatized orbit. The recent evolution of orbit reconstruction improves functional and aesthetic results and minimizes surgical complications.

Infrared Spectroscopy Beamline Based on a Tabletop Storage Ring

OpenAIRE

Haque, Md. Monirul; Moon, Ahsa; Yamada, Hironari

2012-01-01

An optical beamline dedicated to the infrared (IR) spectroscopy has been constructed at MIRRORCLE, a tabletop storage ring. The beamline has been designed for the use of infrared synchrotron radiation (IRSR) emitted from a bending magnet of 156 mm bending radius with the acceptance angle of 355(H) × 138(V) mrad to obtain high flux. The IR emission is forced by an exactly circular optics, named photon storage ring (PhSR), placed around the electron orbit and is collected by a “magic mirror” as...

STS-93 M.S. Michel Tognini in white room

Science.gov (United States)

1999-01-01

STS-93 Mission Specialist Michel Tognini of France is checked out by white room closeout crew members before entering the orbiter Columbia. Tognini is with the Centre National d'Etudes Spatiales (CNES). The white room is an environmental chamber at the end of the orbiter access arm that provides entry to the orbiter crew compartment. STS-93 is a five-day mission primarily to release the Chandra X-ray Observatory, which will allow scientists from around the world to study some of the most distant, powerful and dynamic objects in the universe. After Space Shuttle Columbia's July 20 and 22 launch attempts were scrubbed, the launch was again rescheduled for Friday, July 23, at 12:24 a.m. EDT. The target landing date is July 27 at 11:20 p.m. EDT.

The Age of Saturn's Rings Constrained by the Meteoroid Flux Into the System

Science.gov (United States)

Kempf, S.; Altobelli, N.; Srama, R.; Cuzzi, J. N.; Estrada, P. R.

2017-12-01

The origin of Saturn's ring is still not known. There is an ongoing argument whether Saturn's ring are rather young or have been formed shortly after Saturn together with its satellites. The water-ice rings contain about 5% rocky material resulting from continuous meteoroid bombardment of the ring material with interplanetary micrometeoroids. Knowledge of the incoming mass flux would allow to estimate the ring's exposure time. Model calculations suggest exposure times of 108 years implying a late ring formation. This scenario is problematic because the tidal disruption of a Mimas-sized moon or of a comet within the planet's Roche zone would lead to a much larger rock content as observed today. Here we report on the measurement of the meteoroid mass flux into the Saturnian system obtained by the charge-sensitive entrance grid system (QP) of the Cosmic Dust Analyser (CDA) on the Cassini spacecraft. Interplanetary dust particles (IDPs) entering Saturn's sphere of gravitational influence are identified through the measurements of their speed vectors. We analyzed the full CDA data set acquired after Cassini's arrival at Saturn in 2004, identified the impact speed vectors of 128 extrinsic micrometeoroids ≥ 2 μm, and determined their orbital elements. On the basis of these measurements we determined the mass flux into the Saturnian system. Our preliminary findings are in support of an old ring. The knowledge of the meteoroids orbital elements allows us for the first time to characterize the meteoroid environment in the outer solar system based on direct measurements.

Correlation of photon beam motion with vacuum chamber cooling on the NSLS x-ray ring

International Nuclear Information System (INIS)

Johnson, E.D.; Fauchet, A.M.; Zhang, Xiaohao.

1991-01-01

The NSLS X-ray ring exhibits a direct correlation between photon beam motion, and distortion of the ring vacuum chamber induced by fluctuations in the cooling system. We have made long term measurements of photon beam vertical position, accelerator vacuum chamber motion, process water temperatures, and angular motions of the magnets around one superperiod of the NSLS x-ray ring. Short term transients in water temperature cause deflection of the ring vacuum chamber which have in turn been shown to induce very small angular rotations of the magnets, on the order of 10 micro-radians. A larger and more difficult to correct effect is the drift in beam position over the course of a fill. This problem has been shown to be related to the thermal gradients that develop across the vacuum chamber which, as a consequence of the configuration of the chamber cooling, depend upon stored current. Orbit simulations based upon the measured rotations are in agreement with the observed beam motions, and reveal that certain patterns of correlated motions of the magnets can produce much larger errors than random motion or concerted motion of all the magnets. During the course of these measurements global orbit feedback was installed, and found to significantly reduce the orbit errors which could not be corrected at their source

Difference between ²JC2H3 and ²JC3H2 spin-spin couplings in heterocyclic five- and six-membered rings as a probe for studying σ-ring currents: a quantum chemical analysis.

Science.gov (United States)

Contreras, Rubén H; dos Santos, Francisco P; Ducati, Lucas C; Tormena, Cláudio F

2010-12-01

Adequate analyses of canonical molecular orbitals (CMOs) can provide rather detailed information on the importance of different σ-Fermi contact (FC) coupling pathways (FC term transmitted through the σ-skeleton). Knowledge of the spatial distribution of CMOs is obtained by expanding them in terms of natural bond orbitals (NBOs). Their relative importance for transmitting the σ-FC contribution to a given spin-spin coupling constants (SSCCs) is estimated by resorting to the expression of the FC term given by the polarisation propagator formalism. In this way, it is possible to classify the effects affecting such couplings in two different ways: delocalisation interactions taking place in the neighbourhood of the coupling nuclei and 'round the ring' effects. The latter, associated with σ-ring currents, are observed to yield significant differences between the FC terms of (2)J(C2H3) and (2)J(C3H2) SSCCs which, consequently, are taken as probes to gauge the differences in σ-ring currents for the five-membered rings (furan, thiophene, selenophene and pyrrol) and also for the six-membered rings (benzene, pyridine, protonated pyridine and N-oxide pyridine) used in the present study. Copyright © 2010 John Wiley & Sons, Ltd.

Tuning of few-electron states and optical absorption anisotropy in GaAs quantum rings.

Science.gov (United States)

Wu, Zhenhua; Li, Jian; Li, Jun; Yin, Huaxiang; Liu, Yu

2017-11-15

The electronic and optical properties of a GaAs quantum ring (QR) with few electrons in the presence of the Rashba spin-orbit interaction (RSOI) and the Dresselhaus spin-orbit interaction (DSOI) have been investigated theoretically. The configuration interaction (CI) method is employed to calculate the eigenvalues and eigenstates of the multiple-electron QR accurately. Our numerical results demonstrate that the symmetry breaking induced by the RSOI and DSOI leads to an anisotropic distribution of multi-electron states. The Coulomb interaction offers additional modulation of the electron distribution and thus the optical absorption indices in the quantum rings. By tuning the magnetic/electric fields and/or electron numbers in a quantum ring, one can change its optical properties significantly. Our theory provides a new way to control the multi-electron states and optical properties of a QR by hybrid modulations or by electrical means only.

Development of digital shade guides for color assessment using a digital camera with ring flashes.

Science.gov (United States)

Tung, Oi-Hong; Lai, Yu-Lin; Ho, Yi-Ching; Chou, I-Chiang; Lee, Shyh-Yuan

2011-02-01

Digital photographs taken with cameras and ring flashes are commonly used for dental documentation. We hypothesized that different illuminants and camera's white balance setups shall influence color rendering of digital images and affect the effectiveness of color matching using digital images. Fifteen ceramic disks of different shades were fabricated and photographed with a digital camera in both automatic white balance (AWB) and custom white balance (CWB) under either light-emitting diode (LED) or electronic ring flash. The Commission Internationale d'Éclairage L*a*b* parameters of the captured images were derived from Photoshop software and served as digital shade guides. We found significantly high correlation coefficients (r² > 0.96) between the respective spectrophotometer standards and those shade guides generated in CWB setups. Moreover, the accuracy of color matching of another set of ceramic disks using digital shade guides, which was verified by ten operators, improved from 67% in AWB to 93% in CWB under LED illuminants. Probably, because of the inconsistent performance of the flashlight and specular reflection, the digital images captured under electronic ring flash in both white balance setups revealed less reliable and relative low-matching ability. In conclusion, the reliability of color matching with digital images is much influenced by the illuminants and camera's white balance setups, while digital shade guides derived under LED illuminants with CWB demonstrate applicable potential in the fields of color assessments.

A FODO racetrack ring for nuSTORM: design and optimization

Energy Technology Data Exchange (ETDEWEB)

Liu, A.; Bross, A.; Neuffer, D.

2017-07-01

The goal of nuSTORM is to provide well-defined neutrino beams for precise measurements of neutrino cross-sections and oscillations. The nuSTORM decay ring is a compact racetrack storage ring with a circumference of ~ 480 m that incorporates large aperture (60 cm diameter) magnets. There are many challenges in the design. In order to incorporate the Orbit Combination section (OCS), used for injecting the pion beam into the ring, a dispersion suppressor is needed adjacent to the OCS . Concurrently, in order to maximize the number of useful muon decays, strong bending dipoles are needed in the arcs to minimize the arc length. These dipoles create strong chromatic effects, which need to be corrected by nonlinear sextupole elements in the ring. In this paper, a FODO racetrack ring design and its optimization using sextupolar fields via both a Genetic Algorithm (GA) and a Simulated Annealing (SA) algorithm will be discussed.

Galaxies and Saturn's rings: Gravitational analogues of nonneutral plasmas

International Nuclear Information System (INIS)

Mark, J.W.K.

1985-01-01

Orbit and collective dynamics in disk galaxies and in Saturn's rings are gravitational analogues of those occurring in nonneutral plasmas. The interesting problems for such ''gravitational plasmas'' are analogous to single-disk studies of transverse dynamics in particle beams. Of particular interest are various orbit-resonances with spiral density and bending waves in these disks which are analogous to electrostatic waves in nonneutral beam plasmas. The background physics, terminology and results of astrophysical investigations in these fields are surveyed in this paper. 53 refs., 19 figs., 1 tab

White dwarf planets

Directory of Open Access Journals (Sweden)

Bonsor Amy

2013-04-01

Full Text Available The recognition that planets may survive the late stages of stellar evolution, and the prospects for finding them around White Dwarfs, are growing. We discuss two aspects governing planetary survival through stellar evolution to the White Dwarf stage. First we discuss the case of a single planet, and its survival under the effects of stellar mass loss, radius expansion, and tidal orbital decay as the star evolves along the Asymptotic Giant Branch. We show that, for stars initially of 1 − 5 M⊙, any planets within about 1 − 5 AU will be engulfed, this distance depending on the stellar and planet masses and the planet's eccentricity. Planets engulfed by the star's envelope are unlikely to survive. Hence, planets surviving the Asymptotic Giant Branch phase will probably be found beyond ∼ 2 AU for a 1  M⊙ progenitor and ∼ 10 AU for a 5 M⊙ progenitor. We then discuss the evolution of two-planet systems around evolving stars. As stars lose mass, planet–planet interactions become stronger, and many systems stable on the Main Sequence become destabilised following evolution of the primary. The outcome of such instabilities is typically the ejection of one planet, with the survivor being left on an eccentric orbit. These eccentric planets could in turn be responsible for feeding planetesimals into the neighbourhood of White Dwarfs, causing observed pollution and circumstellar discs.

Ionic ring current during magnetic disturbances according to observations at geostationary orbit

International Nuclear Information System (INIS)

Vlasova, N.A.; Kovtyukh, A.S.; Panasyuk, M.I.; Sosnovets, Eh.N.; Grafodanskij, O.S.; Islyaev, Sh.N.; Kozlov, A.G.

1988-01-01

Experimental data on variations of H + , (N,O) 2+ and (C,N,O) 4+ flows acquired at communication geostationary satellite GORIZONT (1985-07A) during and after weak magnetic disturbances (with amplitudes of D st -variations which are less than a few tens of nT) are analyzed. Dynamics of ion relative content is investigated. Change of ring current ionic composition within ∼ 50-120 keV/c energy range characterized by the increase of relative content of heavy ions of both solar and ionospheric origin was observed after two weak geomagnetic disturbances on 19-20.02 and 07.03.1985. Examples of disturbances where H + ions and (N,O) 2+ ionospheric ions are the main components of the injected ring current are presented along with the disturbances of such type

Present status of the ion ring compressor approach to fusion

International Nuclear Information System (INIS)

Fleischmann, H.H.

1975-01-01

A short review is given of the present research status with regard to the Ion Ring Compressor. A consideration of the reactor characteristics of this fusion scheme indicates the potential for a number of technologically and economically interesting features, in particular with respect to the high-confinement characteristics expected for such minimum-B configurations. Experimental results from the RECE-program at Cornell indicate generally good gross stability of strong electron rings, including purely collisional decay, stability against field perturbations and others. Most-recent experiments have extended the ring lifetime to more than 2 x 10 5 electron orbits. Strong electron rings have been shifted over an axial distance of up to 30 cm. Experiments with magnetic-field insulated diodes indicate ion pulses of up to 300 nsec, and field insulation of up to 800 nsec when metallic electrodes are used

An electron undulating ring for VLSI lithography

International Nuclear Information System (INIS)

Tomimasu, T.; Mikado, T.; Noguchi, T.; Sugiyama, S.; Yamazaki, T.

1985-01-01

The development of the ETL storage ring ''TERAS'' as an undulating ring has been continued to achieve a wide area exposure of synchrotron radiation (SR) in VLSI lithography. Stable vertical and horizontal undulating motions of stored beams are demonstrated around a horizontal design orbit of TERAS, using two small steering magnets of which one is used for vertical undulating and another for horizontal one. Each steering magnet is inserted into one of the periodic configulation of guide field elements. As one of useful applications of undulaing electron beams, a vertically wide exposure of SR has been demonstrated in the SR lithography. The maximum vertical deviation from the design orbit nCcurs near the steering magnet. The maximum vertical tilt angle of the undulating beam near the nodes is about + or - 2mrad for a steering magnetic field of 50 gauss. Another proposal is for hith-intensity, uniform and wide exposure of SR from a wiggler installed in TERAS, using vertical and horizontal undulating motions of stored beams. A 1.4 m long permanent magnet wiggler has been installed for this purpose in this April

Radio Pumping of Ionospheric Plasma with Orbital Angular Momentum

International Nuclear Information System (INIS)

Leyser, T. B.; Norin, L.; McCarrick, M.; Pedersen, T. R.; Gustavsson, B.

2009-01-01

Experimental results are presented of pumping ionospheric plasma with a radio wave carrying orbital angular momentum (OAM), using the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. Optical emissions from the pumped plasma turbulence exhibit the characteristic ring-shaped morphology when the pump beam carries OAM. Features of stimulated electromagnetic emissions (SEE) that are attributed to cascading Langmuir turbulence are well developed for a regular beam but are significantly weaker for a ring-shaped OAM beam in which case upper hybrid turbulence dominates the SEE

Dispersion and betatron function correction in the Advanced Photon Source storage ring using singular value decomposition

International Nuclear Information System (INIS)

Emery, L.

1999-01-01

Magnet errors and off-center orbits through sextuples perturb the dispersion and beta functions in a storage ring (SR), which affects machine performance. In a large ring such as the Advanced Photon Source (APS), the magnet errors are difficult to determine with beam-based methods. Also the non-zero orbit through sextuples result from user requests for steering at light source points. For expediency, a singular value decomposition (SVD) matrix method analogous to orbit correction was adopted to make global corrections to these functions using strengths of several quadrupoles as correcting elements. The direct response matrix is calculated from the model of the perfect lattice. The inverse is calculated by SVD with a selected number of singular vectors. Resulting improvement in the lattice functions and machine performance will be presented

Orbit monitoring in the SLC

International Nuclear Information System (INIS)

Sanchez-Chopitea, L.; Emma, P.; Van Olst, D.

1991-05-01

Beam orbits in the SLC are monitored in real time and the data is stored for future trend and correlation analysis. A background process acquires Beam Position Monitor (BPM) and Toroid data on a periodic basis and saves the general quantities such as orbit RMS and beam intensity in addition to the individual readings. Some of this data is archived by the SLC History Buffer facility and the rest is saved in files for later analysis. This has permitted the tracing of interaction point instabilities to specific devices as far away as the damping rings. In addition, the data is displayed for the operators both in summary and in full form. The different displays can be configured from the control consoles. 2 refs., 5 figs

Spin tune dependence on closed orbit in RHIC

International Nuclear Information System (INIS)

Ptitsyn, V.; Bai, M.; Roser, T.

2010-01-01

Polarized proton beams are accelerated in RHIC to 250 GeV energy with the help of Siberian Snakes. The pair of Siberian Snakes in each RHIC ring holds the design spin tune at 1/2 to avoid polarization loss during acceleration. However, in the presence of closed orbit errors, the actual spin tune can be shifted away from the exact 1/2 value. It leads to a corresponding shift of locations of higher-order ('snake') resonances and limits the available betatron tune space. The largest closed orbit effect on the spin tune comes from the horizontal orbit angle between the two snakes. During RHIC Run in 2009 dedicated measurements with polarized proton beams were taken to verify the dependence of the spin tune on the local orbits at the Snakes. The experimental results are presented along with the comparison with analytical predictions.

Design studies for the electron storage ring EUTERPE

Energy Technology Data Exchange (ETDEWEB)

Boling, Xi

1995-05-18

The 400 MeV electron storage ring EUTERPE is under construction at Eindhoven University of Technology. The ring is to be used as an experimental tool for accelerator physics studies and synchroton radiation applications. The main task of the current research work is the electron optical design of the ring. Lattice design is a basis for machine design as a whole. Design aspects regarding the basic lattice, based on single particle dynamics, include determination of the equilibrium beam size and bunch length, design of achromatic bending sections, selection of tune values, correction of chromaticity, and minimization of the natural emittance in the ring. The basic lattice designed for the EUTERPE ring has a high flexibility so that different electron optical modes can be realized easily. In low energy storage rings with a high beam current, collective effects can cause a significant change in the bunch length, the transverse emittance and the beam lifetime. In order to ensure a good optical performance for the ring, the choice of suitable parameters concerning the vacuum and RF system are essential as far as collective effects are concerned. An estimation of the collective effects in the ring is given. The injector for EUTERPE is a 75 MeV racetrack microtron which is injected from a 10 MeV linac. In order to get sufficient beam current in the ring, a special procedure of continuous injection with an adjustable locally shifted closed orbit has been presented. Details of the injection procedure and numerical simulations are given. (orig./HSI).

Design studies for the electron storage ring EUTERPE

International Nuclear Information System (INIS)

Xi Boling.

1995-01-01

The 400 MeV electron storage ring EUTERPE is under construction at Eindhoven University of Technology. The ring is to be used as an experimental tool for accelerator physics studies and synchroton radiation applications. The main task of the current research work is the electron optical design of the ring. Lattice design is a basis for machine design as a whole. Design aspects regarding the basic lattice, based on single particle dynamics, include determination of the equilibrium beam size and bunch length, design of achromatic bending sections, selection of tune values, correction of chromaticity, and minimization of the natural emittance in the ring. The basic lattice designed for the EUTERPE ring has a high flexibility so that different electron optical modes can be realized easily. In low energy storage rings with a high beam current, collective effects can cause a significant change in the bunch length, the transverse emittance and the beam lifetime. In order to ensure a good optical performance for the ring, the choice of suitable parameters concerning the vacuum and RF system are essential as far as collective effects are concerned. An estimation of the collective effects in the ring is given. The injector for EUTERPE is a 75 MeV racetrack microtron which is injected from a 10 MeV linac. In order to get sufficient beam current in the ring, a special procedure of continuous injection with an adjustable locally shifted closed orbit has been presented. Details of the injection procedure and numerical simulations are given. (orig./HSI)

Second and third harmonic generations of a quantum ring with Rashba and Dresselhaus spin-orbit couplings: Temperature and Zeeman effects

Science.gov (United States)

Zamani, Ali; Azargoshasb, Tahereh; Niknam, Elahe

2017-10-01

In current article, the Zeeman effect is considered in the presence of simultaneous Rashba and Dresselhaus spin-orbit interactions (SOI) and under such circumstances the second and third harmonic generations (SHG and THG) of a GaAs quantum ring are investigated at finite temperature. The effective Hamiltonian is derived in cylindrical coordinate while the angular part is eliminated because of axial symmetry and the energy eigenvalues and eigenvectors of two lowest levels are obtained numerically. Eventually, the optical properties of such system are studied hiring compact density matrix approach. The results show that, an increase in the magnetic field, leads to blue shift in resonant peaks of both SHG and THG. Furthermore, by reducing the temperature, all the resonant peaks of both SHG and THG experience a red shift. Finally, the effect of the structure dimension is studied and results illustrate that variation of size leads to both red and blue shifts in resonant peaks.

Hubble again views Saturn's Rings Edge-on

Science.gov (United States)

1995-01-01

Saturn's magnificent ring system is seen tilted edge-on -- for the second time this year -- in this NASA Hubble Space Telescope picture taken on August 10, 1995, when the planet was 895 million miles (1,440 million kilometers) away. Hubble snapped the image as Earth sped back across Saturn's ring plane to the sunlit side of the rings. Last May 22, Earth dipped below the ring plane, giving observers a brief look at the backlit side of the rings. Ring-plane crossing events occur approximately every 15 years. Earthbound observers won't have as good a view until the year 2038. Several of Saturn's icy moons are visible as tiny starlike objects in or near the ring plane. They are from left to right, Enceladus, Tethys, Dione and Mimas. 'The Hubble data shows numerous faint satellites close to the bright rings, but it will take a couple of months to precisely identify them,' according to Steve Larson (University of Arizona). During the May ring plane crossing, Hubble detected two, and possibly four, new moons orbiting Saturn. These new observations also provide a better view of the faint E ring, 'to help determine the size of particles and whether they will pose a collision hazard to the Cassini spacecraft,' said Larson. The picture was taken with Hubble's Wide Field Planetary Camera 2 in wide field mode. This image is a composite view, where a long exposure of the faint rings has been combined with a shorter exposure of Saturn's disk to bring out more detail. When viewed edge-on, the rings are so dim they almost disappear because they are very thin -- probably less than a mile thick.The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

Saturn's F Ring Core: Calm in the Midst of Chaos

Science.gov (United States)

Cuzzi, J. N.; Whizin, A. D.; Hogan, R. C.; Dobrovolskis, A. R.; Dones, L.; Showalter. M. R.; Colwell, J. E.; Scargle, J. D.

2013-01-01

The long-term stability of the narrow F Ring core has been hard to understand. Instead of acting as "shepherds", Prometheus and Pandora together stir the vast preponderance of the region into a chaotic state, consistent with the orbits of newly discovered objects like S/2004S6. We show how a comb of very narrow radial locations of high stability in semimajor axis is embedded within this otherwise chaotic region. The stability of these semimajor axes relies fundamentally on the unusual combination of rapid apse precession and long synodic period which characterizes the region. This situation allows stable "antiresonances" to fall on or very close to traditional Lindblad resonances which, under more common circumstances, are destabilizing. We present numerical integrations of tens of thousands of test particles over tens of thousands of Prometheus orbits that map out the effect. The stable antiresonance zones are most stable in a subset of the region where Prometheus first-order resonances are least cluttered by Pandora resonances. This region of optimum stability is paradoxically closer to Prometheus than a location more representative of "torque balance", helping explain a longstanding paradox. One stable zone corresponds closely to the currently observed semimajor axis of the F Ring core. While the model helps explain the stability of the narrow F Ring core, it does not explain why the F Ring material all shares a common apse longitude; we speculate that collisional damping at the preferred semimajor axis (not included in the current simulations) may provide that final step. Essentially, we find that the F Ring core is not confined by a combination of Prometheus and Pandora, but a combination of Prometheus and precession.

Optical control of spin-dependent thermal transport in a quantum ring

Science.gov (United States)

Abdullah, Nzar Rauf

2018-05-01

We report on calculation of spin-dependent thermal transport through a quantum ring with the Rashba spin-orbit interaction. The quantum ring is connected to two electron reservoirs with different temperatures. Tuning the Rashba coupling constant, degenerate energy states are formed leading to a suppression of the heat and thermoelectric currents. In addition, the quantum ring is coupled to a photon cavity with a single photon mode and linearly polarized photon field. In a resonance regime, when the photon energy is approximately equal to the energy spacing between two lowest degenerate states of the ring, the polarized photon field can significantly control the heat and thermoelectric currents in the system. The roles of the number of photon initially in the cavity, and electron-photon coupling strength on spin-dependent heat and thermoelectric currents are presented.

The Unruh effect and quantum fluctuations of electrons in storage rings

International Nuclear Information System (INIS)

Bell, J.S.; Leinaas, J.M.

1987-01-01

The quantum fluctuation of electron orbits in ideal storage rings is a sort of Fulling-Unruh effect (heating by acceleration in vacuum). To spell this out, the effect is analyzed in an appropriate comoving, and so accelerating and rotating, co-ordinate system. The depolarization of the electrons is a related effect, but is greatly complicated by spin-orbit coupling. This analysis confirms the standard result for the polarization, except in the neighbourhood of a narrow resonance. (orig.)

The Unruh effect and quantum fluctuations of electrons in storage rings

International Nuclear Information System (INIS)

Bell, J.S.; Leinaas, J.M.

1995-01-01

The quantum fluctuation of electron orbits in ideal storage rings is a sort of Fulling-Unruh effect (heating by acceleration in vacuum). To spell this out, the effect is analyzed in an appropriate comoving, and so accelerating and rotating, co-ordinate system. The depolarization of the electrons is a related effect, but is greatly complicated by spin-orbit coupling. This analysis confirms the standard result for the polarization, except in the neighbourhood of a narrow resonance. (author)

The New Horizons and Hubble Space Telescope search for rings, dust, and debris in the Pluto-Charon system

Science.gov (United States)

Lauer, Tod R.; Throop, Henry B.; Showalter, Mark R.; Weaver, Harold A.; Stern, S. Alan; Spencer, John R.; Buie, Marc W.; Hamilton, Douglas P.; Porter, Simon B.; Verbiscer, Anne J.; Young, Leslie A.; Olkin, Cathy B.; Ennico, Kimberly; New Horizons Science Team

2018-02-01

We conducted an extensive search for dust or debris rings in the Pluto-Charon system before, during, and after the New Horizons encounter in July 2015. Methodologies included attempting to detect features by back-scattered light during the approach to Pluto (phase angle α ∼ 15°), in situ detection of impacting particles, a search for stellar occultations near the time of closest approach, and by forward-scattered light imaging during departure (α ∼ 165°). An extensive search using the Hubble Space Telescope (HST) prior to the encounter also contributed to the final ring limits. No rings, debris, or dust features were observed, but our new detection limits provide a substantially improved picture of the environment throughout the Pluto-Charon system. Searches for rings in back-scattered light covered the range 35,000-250,000 km from the system barycenter, a zone that starts interior to the orbit of Styx, the innermost minor satellite, and extends out to four times the orbital radius of Hydra, the outermost known satellite. We obtained our firmest limits using data from the New Horizons LORRI camera in the inner half of this region. Our limits on the normal I/F of an unseen ring depends on the radial scale of the rings: 2 ×10-8 (3σ) for 1500 km wide rings, 1 ×10-8 for 6000 km rings, and 7 ×10-9 for 12,000 km rings. Beyond ∼ 100, 000 km from Pluto, HST observations limit normal I/F to ∼ 8 ×10-8 . Searches for dust features from forward-scattered light extended from the surface of Pluto to the Pluto-Charon Hill sphere (rHill = 6.4 ×106 km). No evidence for rings or dust clouds was detected to normal I/F limits of ∼ 8.9 ×10-7 on ∼ 104 km scales. Four stellar occulation observations also probed the space interior to Hydra, but again no dust or debris was detected. The Student Dust Counter detected one particle impact 3.6 × 106 km from Pluto, but this is consistent with the interplanetary space environment established during the cruise of New

Origin of very-short orbital-period binary systems

International Nuclear Information System (INIS)

Miyaji, S.

1983-01-01

Recent observations of four close binaries have established that there is a group of very-short orbital-period (VSOP) binaries whose orbital periods are less than 60 minutes. The VSOP binaries consist of both X-ray close binaries and cataclysmic variables. Their orbital periods are too short to have a main-sequence companion. However, four binaries, none of which belongs to any globular cluster, are too abundant to be explained by the capturing mechanism of a white dwarf. Therefore it seemed to be worthwhile to present an evolutionary scenario from an original binary system which can be applied for all VSOP binaries. (Auth.)

The AD and ELENA orbit, trajectory and intensity measurement systems

Science.gov (United States)

Marco-Hernández, R.; Alves, D.; Angoletta, M. E.; Marqversen, O.; Molendijk, J.; Oponowicz, E.; Ruffieux, R.; Sánchez-Quesada, J.; SØby, L.

2017-07-01

This paper describes the new Antiproton Decelerator (AD) orbit measurement system and the Extra Low ENergy Antiproton ring (ELENA) orbit, trajectory and intensity measurement system. The AD machine at European Organization for Nuclear Research (CERN) is presently being used to decelerate antiprotons from 3.57 GeV/c to 100 MeV/c for matter vs anti-matter comparative studies. The ELENA machine, presently under commissioning, has been designed to provide an extra deceleration stage down to 13.7 MeV/c. The AD orbit system is based on 32 horizontal and 27 vertical electrostatic Beam Position Monitor (BPM) fitted with existing low noise front-end amplifiers while the ELENA system consists of 24 \\gls{BPM}s equipped with new low-noise head amplifiers. In both systems the front-end amplifiers generate a difference (delta) and a sum (sigma) signal which are sent to the digital acquisition system, placed tens of meters away from the AD or ELENA rings, where they are digitized and further processed. The beam position is calculated by dividing the difference signal by the sum signal either using directly the raw digitized data for measuring the turn-by-turn trajectory in the ELENA system or after down-mixing the signals to baseband for the orbit measurement in both machines. The digitized sigma signal will be used in the ELENA system to calculate the bunched beam intensity and the Schottky parameters with coasting beam after passing through different signal processing chain. The digital acquisition arrangement for both systems is based on the same hardware, also used in the ELENA Low Level Radio Frequency (LLRF) system, which follows the VME Switched Serial (VXS) enhancement of the Versa Module Eurocard 64x extension (VME64x) standard and includes VITA 57 standard Field Programmable Gate Array Mezzanine Card (FMC). The digital acquisition Field Programmable Gate Array (FPGA) and Digital Signal Processor (DSP) firmware shares many common functionalities with the LLRF system but

Conceptual design of a linac-stretcher ring to obtain a 2-gev continuous electron beam

International Nuclear Information System (INIS)

Cho, Y.; Holt, R.J.; Jackson, H.E.; Khoe, T.K.; Mavrogenes, G.S.

1981-01-01

In order to obtain a high duty factor, >100 /mu/A 2-Gev electron beam, a linac-stretcher ring system was designed. The system is an attractive option because it draws heavily on the existing accelerator technology. The linac-stretcher ring consists of a 2-Gev SLAC-type pulsed linac which injects into a storage ring. In between linac pulses, the stored electron beam is to extract resonantly. This design differs from those discussed recently in several important respects. The storage ring includes an rf system whose purpose is to control the beam orbit and rate of extraction from the ring. With an rf system in the ring, the injection scheme consists of a few turns of synchronous transfers of beam between the linac and storage ring. 4 refs

Conditioning of BPM pickup signals for operations of the Duke storage ring with a wide range of single-bunch current

Science.gov (United States)

Xu, Wei; Li, Jing-Yi; Huang, Sen-Lin; Z. Wu, W.; Hao, H.; P., Wang; K. Wu, Y.

2014-10-01

The Duke storage ring is a dedicated driver for the storage ring based oscillator free-electron lasers (FELs), and the High Intensity Gamma-ray Source (HIGS). It is operated with a beam current ranging from about 1 mA to 100 mA per bunch for various operations and accelerator physics studies. High performance operations of the FEL and γ-ray source require a stable electron beam orbit, which has been realized by the global orbit feedback system. As a critical part of the orbit feedback system, the electron beam position monitors (BPMs) are required to be able to precisely measure the electron beam orbit in a wide range of the single-bunch current. However, the high peak voltage of the BPM pickups associated with high single-bunch current degrades the performance of the BPM electronics, and can potentially damage the BPM electronics. A signal conditioning method using low pass filters is developed to reduce the peak voltage to protect the BPM electronics, and to make the BPMs capable of working with a wide range of single-bunch current. Simulations and electron beam based tests are performed. The results show that the Duke storage ring BPM system is capable of providing precise orbit measurements to ensure highly stable FEL and HIGS operations.

Environmental studies using earth orbital photography

Energy Technology Data Exchange (ETDEWEB)

Wobber, F J

1969-01-01

Orbital remote sensing, and particularly orbital photography, can provide immediately useful data for scientists familiar with applying aerial photographic techniques to environmental problems. Despite the expansion of analytical techniques in the earth sciences, the environmental data base has remained relatively static compared with increased information needs because of the difficulty of effective worldwide surveys and the high cost of timely data collection. Color, color infrared and black and white space photographs obtained incident to the Gemini and Apollo programs provide unique synoptic tools for analyzing modern environments and processes, and data that cannot be duplicated by aerial photographic mosaics. Principal advantages of orbital surveys include repetitious worldwide coverage promising environmental synthesis within the full spectrum of seasonal contrasts, and synoptic observations on a scale generally impossible from aircraft. The general categories of environmental data that can be extracted from orbital photography are summarized. 26 references, 37 figures, 3 tables.

Spin-polarized currents in a two-terminal double quantum ring driven by magnetic fields and Rashba spin-orbit interaction

Science.gov (United States)

Dehghan, E.; Khoshnoud, D. Sanavi; Naeimi, A. S.

2018-06-01

Aim of this study is to investigate spin transportation in double quantum ring (DQR). We developed an array of DQR to measure the transmission coefficient and analyze the spin transportation through this system in the presence of Rashba spin-orbit interaction (RSOI) and magnetic flux estimated using S-matrix method. In this article, we compute the spin transport and spin-current characteristics numerically as functions of electron energy, angles between the leads, coupling constant of the leads, RSOI, and magnetic flux. Our results suggest that, for typical values of the magnetic flux (ϕ /ϕ0) and Rashba constant (αR), such system can demonstrates many spintronic properties. It is possible to design a new geometry of DQR by incoming electrons polarization in a way to optimize the system to work as a spin-filtering and spin-inverting nano-device with very high efficiency. The results prove that the spin current will strongly modulate with an increase in the magnetic flux and Rashba constant. Moreover it is shown that, when the lead coupling is weak, the perfect spin-inverter does not occur.

Control of the spin geometric phase in semiconductor quantum rings.

Science.gov (United States)

Nagasawa, Fumiya; Frustaglia, Diego; Saarikoski, Henri; Richter, Klaus; Nitta, Junsaku

2013-01-01

Since the formulation of the geometric phase by Berry, its relevance has been demonstrated in a large variety of physical systems. However, a geometric phase of the most fundamental spin-1/2 system, the electron spin, has not been observed directly and controlled independently from dynamical phases. Here we report experimental evidence on the manipulation of an electron spin through a purely geometric effect in an InGaAs-based quantum ring with Rashba spin-orbit coupling. By applying an in-plane magnetic field, a phase shift of the Aharonov-Casher interference pattern towards the small spin-orbit-coupling regions is observed. A perturbation theory for a one-dimensional Rashba ring under small in-plane fields reveals that the phase shift originates exclusively from the modulation of a pure geometric-phase component of the electron spin beyond the adiabatic limit, independently from dynamical phases. The phase shift is well reproduced by implementing two independent approaches, that is, perturbation theory and non-perturbative transport simulations.

Longitudinal and spin Hall conductance of a one-dimensional Aharonov-Bohm ring

International Nuclear Information System (INIS)

Moca, Catalin Pascu; Marinescu, D C

2006-01-01

The longitudinal and spin Hall conductances of an electron gas with Rashba-Dresselhaus spin-orbit interaction, confined to a quasi-one-dimensional Aharonov-Bohm ring, are studied as functions of disorder and magnetic flux. The system is mapped onto a one-dimensional virtual lattice and is described, in a tight binding approximation, by a Hamiltonian that depends parametrically on the nearest neighbour hopping integral t, the Rashba spin-orbit coupling V R , the Dresselhaus spin-orbit coupling V D and an Anderson-like, on-site disorder energy strength W. Numerical results are obtained within a spin dependent Landauer-Buettiker formalism

Spin relaxation in semiconductor quantum rings and dots--a comparative study.

Science.gov (United States)

Zipper, Elżbieta; Kurpas, Marcin; Sadowski, Janusz; Maśka, Maciej M

2011-03-23

We calculate spin relaxation times due to spin-orbit-mediated electron-phonon interactions for experimentally accessible semiconductor quantum ring and dot architectures. We elucidate the differences between the two systems due to different confinement. The estimated relaxation times (at B = 1 T) are in the range between a few milliseconds to a few seconds. This high stability of spin in a quantum ring allows us to test it as a spin qubit. A brief discussion of quantum state manipulations with such a qubit is presented.

First turn beam correction for the Advanced Photon Source storage ring

International Nuclear Information System (INIS)

Qian, Y.; Crosbie, E.; Teng, L.

1991-01-01

A procedure was developed for precise realignment of the quadrupoles in a synchrotron radiation storage ring which can substantially ease the required precision of the initial survey. The procedure consists of first using the injected beam to obtain a closed orbit which is centered on the beam position monitors by the correction dipoles. The strengths of the correction dipoles then give the required fine-adjustment of the quadrupole positions. In this paper the authors discuss only the algorithm for obtaining the closed orbit

Radius constraints from high-speed photometry of 20 low-mass white dwarf binaries

International Nuclear Information System (INIS)

Hermes, J. J.; Brown, Warren R.; Kilic, Mukremin; Gianninas, A.; Chote, Paul; Sullivan, D. J.; Winget, D. E.; Bell, Keaton J.; Falcon, R. E.; Winget, K. I.; Harrold, Samuel T.; Montgomery, M. H.; Mason, Paul A.

2014-01-01

We carry out high-speed photometry on 20 of the shortest-period, detached white dwarf binaries known and discover systems with eclipses, ellipsoidal variations (due to tidal deformations of the visible white dwarf), and Doppler beaming. All of the binaries contain low-mass white dwarfs with orbital periods of less than four hr. Our observations identify the first eight tidally distorted white dwarfs, four of which are reported for the first time here. We use these observations to place empirical constraints on the mass-radius relationship for extremely low-mass (≤0.30 M ☉ ) white dwarfs. We also detect Doppler beaming in several of these binaries, which confirms their high-amplitude radial-velocity variability. All of these systems are strong sources of gravitational radiation, and long-term monitoring of those that display ellipsoidal variations can be used to detect spin-up of the tidal bulge due to orbital decay.

Radius constraints from high-speed photometry of 20 low-mass white dwarf binaries

Energy Technology Data Exchange (ETDEWEB)

Hermes, J. J. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Brown, Warren R. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Kilic, Mukremin; Gianninas, A. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks Street, Norman, OK 73019 (United States); Chote, Paul; Sullivan, D. J. [School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140 (New Zealand); Winget, D. E.; Bell, Keaton J.; Falcon, R. E.; Winget, K. I.; Harrold, Samuel T.; Montgomery, M. H. [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Mason, Paul A., E-mail: j.j.hermes@warwick.ac.uk [Department of Physics, University of Texas at El Paso, El Paso, TX 79968 (United States)

2014-09-01

We carry out high-speed photometry on 20 of the shortest-period, detached white dwarf binaries known and discover systems with eclipses, ellipsoidal variations (due to tidal deformations of the visible white dwarf), and Doppler beaming. All of the binaries contain low-mass white dwarfs with orbital periods of less than four hr. Our observations identify the first eight tidally distorted white dwarfs, four of which are reported for the first time here. We use these observations to place empirical constraints on the mass-radius relationship for extremely low-mass (≤0.30 M {sub ☉}) white dwarfs. We also detect Doppler beaming in several of these binaries, which confirms their high-amplitude radial-velocity variability. All of these systems are strong sources of gravitational radiation, and long-term monitoring of those that display ellipsoidal variations can be used to detect spin-up of the tidal bulge due to orbital decay.

Molecular-orbital and structural descriptors in theoretical investigation of electroreduction of nitrodiazoles

Directory of Open Access Journals (Sweden)

BRANKO KOLARIC

2005-07-01

Full Text Available It is shown how a simple theoretical approach can be used for the investigation of electro-organic reactions.Mononitroimidazoles and mononitropyrazoles were studied by the semiempirical MNDO-PM3 molecular orbital method. The electrochemical reduction potentials of diazoles have been correlated with the energy of the lowest unoccupied molecular orbital (LUMO. It was found that an admirable correlation could be obtained by the introduction of simple structural descriptors as a correction to the energy of the LUMO. The interaction of a molecule with its surrounding depends on electrostatic potential and on steric hindrance. Most of these steric effects are taken into account using two parameters having a very limited set of integer values. The first (b is the position of a ring substituent regarding ring nitrogens, which accounts for the different orientations of dipole moments and for the different shape of the electrostatic potential. The second (structural parameter (t is the type of the ring, which accounts mostly for different modes of electrode approach, and for different charge polarization patterns in two diazole rings. The extended correlation with ELUMO, b and t, is very good, having a regression coefficient r = 0.991. The intrinsic importance of b and t is exemplified by their high statistical weight.

MIGRATION OF A MOONLET IN A RING OF SOLID PARTICLES: THEORY AND APPLICATION TO SATURN'S PROPELLERS

International Nuclear Information System (INIS)

Crida, Aurelien; Papaloizou, John C. B.; Rein, Hanno; Charnoz, Sebastien; Salmon, Julien

2010-01-01

Hundred-meter-sized objects have been identified by the Cassini spacecraft in Saturn's A ring through the so-called propeller features they create in the ring. These moonlets should migrate due to their gravitational interaction with the ring; in fact, some orbital variations have been detected. The standard theory of type I migration of planets in protoplanetary disks cannot be applied to the ring system as it is pressureless. Thus, we compute the differential torque felt by a moonlet embedded in a two-dimensional disk of solid particles, with a flat surface density profile, both analytically and numerically. We find that the corresponding migration rate is too small to explain the observed variations of the propeller's orbit in Saturn's A ring. However, local density fluctuations (due to gravity wakes in the marginally gravitationally stable A ring) may exert a stochastic torque on a moonlet. Our simulations show that this torque can be large enough to account for the observations depending on the parameters of the rings. We find that on timescales of several years the migration of propellers is likely to be dominated by stochastic effects (while the former, non-stochastic migration dominates after ∼10 4 -10 5 years). In that case, the migration rates provided by observations so far suggest that the surface density of the A ring should be on the order of 700 kg m -2 . The age of the propellers should not exceed 1-100 million years depending on the dominant migration regime.

Conceptual design of a linac-stretcher ring to obtain a 2-GeV continuous electron beam

International Nuclear Information System (INIS)

Cho, Y.; Holt, R.J.; Jackson, H.E.; Khoe, T.K.; Mavrogenes, G.S.

1981-01-01

In order to obtain a high duty factor, > 100 μA 2-GeV electron beam, we have designed a linac-stretcher ring system. The system is an attractive option because it draws heavily on the existing accelerator technology. The linac-stretcher ring consists of a 2-GeV SLAC-type pulsed linac which injects into a storage ring. In between linac pulses, the stored electron beam is to extract resonantly. This design differs from those discussed recently in several important respects. The storage ring includes an RF system whose purpose is to control the beam orbit and rate of extraction from the ring. With an RF system in the ring, the injection scheme consists of a few turns of synchronous transfers of beam between the linac and storage ring

Spin separation driven by quantum interference in ballistic rings

International Nuclear Information System (INIS)

Bellucci, S; Onorato, P

2008-01-01

We propose an all-electrical nanoscopic structure where a pure spin current is induced in the transverse probes attached to a quantum-coherent ballistic quasi-one-dimensional ring when conventional unpolarized charge current is injected through its longitudinal leads. The study is essentially based on the spin-orbit coupling (SOC) arising from the laterally confining electric field (β-SOC). This sets the basic difference with other works employing mesoscopic rings with the conventional Rashba SO term (α-SOC). The β-SOC ring generates oscillations of the predicted spin Hall current due to spin-sensitive quantum-interference effects caused by the difference in phase acquired by opposite spins states traveling clockwise and counterclockwise. We focus on single-channel transport and solve analytically the spin polarization of the current. We relate the presence of a polarized spin current with the peaks in the longitudinal conductance.

A model of ATL ground motion for storage rings

International Nuclear Information System (INIS)

Wolski, Andrzej; Walker, Nicholas J.

2003-01-01

Low emittance electron storage rings, such as those used in third generation light sources or linear collider damping rings, rely for their performance on highly stable alignment of the lattice components. Even if all vibration and environmental noise sources could be suppressed, diffusive ground motion will lead to orbit drift and emittance growth. Understanding such motion is important for predicting the performance of a planned accelerator and designing a correction system. A description (known as the ATL model) of ground motion over relatively long time scales has been developed and has become the standard for studies of the long straight beamlines in linear colliders. Here, we show how the model may be developed to include beamlines of any geometry. We apply the model to the NLC and TESLA damping rings, to compare their relative stability under different conditions

STS-93 M.S. Stephen Hawley in the White Room

Science.gov (United States)

1999-01-01

STS-93 Mission Specialist Stephen A. Hawley (Ph.D.) is checked out by white room closeout crew members before entering the orbiter Columbia. In the background is Mission Specialist Michel Tognini of France, waiting to enter Columbia. The white room is an environmental chamber at the end of the orbiter access arm that provides entry to the orbiter crew compartment. STS-93 is a five-day mission primarily to release the Chandra X-ray Observatory, which will allow scientists from around the world to study some of the most distant, powerful and dynamic objects in the universe. After Space Shuttle Columbia's July 20 and 22 launch attempts were scrubbed, the launch was again rescheduled for Friday, July 23, at 12:24 a.m. EDT. The target landing date is July 27 at 11:20 p.m. EDT.

Quantitative MR imaging of intra-orbital structures: Tissue-specific measurements and age dependency compared to extra-orbital structures using multispectral quantitative MR imaging.

Science.gov (United States)

Watanabe, Memi; Buch, Karen; Fujita, Akifumi; Jara, Hernán; Qureshi, Muhammad Mustafa; Sakai, Osamu

2017-08-01

The orbit can be affected by unique pathologic conditions and often requires MRI evaluation. The purpose of this study was to investigate the age-related changes in multiple intra-orbital structures using quantitative MRI (qMRI). Thirty-eight subjects (20 males, 18 females; ages 0.5-87 years) underwent MRI with a mixed turbo spin echo sequence. T1 and T2 measurements were obtained within ROI in 6 intra-orbital structures (medial and lateral rectus muscles, medial and lateral retrobulbar fat, lacrimal gland, and optic nerve), and compared with those of corresponding extra-orbital structures (masseter muscle, subcutaneous cheek fat, buccal fat, parotid gland, and frontal white matter). Statistical analyses were performed using Pearson's correlation coefficients. T1 and T2 values of the extra-ocular muscles increased with age, with higher T1 and T2 values compared to the masseter muscles. Retrobulbar fat showed significant age-associated increases in T1 values in the lateral side and in T2 values in both sides. T1 and T2 values in the lacrimal gland increased with age, while the parotid gland showed an age-associated increase in T2 values and decrease in T1 values. Optic nerves demonstrated age-related changes, similar to that of frontal white matter; rapid decreases with age in T1 and T2 times in early stages of life, and slight increases in T1 and T2 times later in life. Intra-orbital structures demonstrated specific qMRI measurements and aging patterns, which were different from extra-orbital structures. Location-specific age-related changes of intra-orbital structures should be considered in the qMRI assessment of the orbital pathology.

Multipole error analysis using local 3-bump orbit data in Fermilab Recycler

International Nuclear Information System (INIS)

Yang, M.J.; Xiao, M.

2005-01-01

The magnetic harmonic errors of the Fermilab Recycler ring were examined using circulating beam data taken with closed local orbit bumps. Data was first parsed into harmonic orbits of first, second, and third order. Each of which was analyzed for sources of magnetic errors of corresponding order. This study was made possible only with the incredible resolution of a new BPM system that was commissioned after June of 2003

Vertical orbit excursion fixed field alternating gradient accelerators

Directory of Open Access Journals (Sweden)

Stephen Brooks

2013-08-01

Full Text Available Fixed field alternating gradient (FFAG accelerators with vertical orbit excursion (VFFAGs provide a promising alternative design for rings with fixed-field superconducting magnets. They have a vertical magnetic field component that increases with height in the vertical aperture, yielding a skew quadrupole focusing structure. Scaling-type VFFAGs are found with fixed tunes and no intrinsic limitation on momentum range. This paper presents the first multiparticle tracking of such machines. Proton driver rings to accelerate the 800 MeV beam from the ISIS synchrotron are presented, in terms of both magnet field geometry and longitudinal behavior during acceleration with space charge. The 12 GeV ring produces an output power of at least 2.18 MW. Possible applications of VFFAGs to waste transmutation, hadron therapy, and energy-recovery electron accelerators are also discussed.

Polarized beams in high energy storage rings

Energy Technology Data Exchange (ETDEWEB)

Montague, B W [European Organization for Nuclear Research, Geneva (Switzerland)

1984-11-01

In recent years there has been a considerable advance in understanding the spin motion of particles in storage rings and accelerators. The survey presented here outlines the early historical development in this field, describes the basic ideas governing the kinetics of polarized particles in electromagnetic fields and shows how these have evolved into the current description of polarized beam behaviour. Orbital motion of particles influences their spin precession, and depolarization of a beam can result from excitation of spin resonances by orbit errors and oscillations. Electrons and positrons are additionally influenced by the quantized character of synchrotron radiation, which not only provides a polarizing mechanism but also enhances depolarizing effects. Progress in the theoretical formulation of these phenomena has clarified the details of the physical processes and suggested improved methods of compensating spin resonances. Full use of polarized beams for high-energy physics with storage rings requires spin rotators to produce longitudinal polarization in the interaction regions. Variants of these schemes, dubbed Siberian snakes, provide a curious precession topology which can substantially reduce depolarization in the high-energy range. Efficient polarimetry is an essential requirement for implementing polarized beams, whose utility for physics can be enhanced by various methods of spin manipulation.

Expected first-order effects of a notional equatorial ring on Earth's night sky: a geometric consideration

Science.gov (United States)

Hancock, L. O.

2013-12-01

G. Jones (1856) was first to suggest that the Earth might have its own ring, noting that an Earth ring in the ecliptic plane would account for the latitude dependence of the zodiacal light. Jones's proposal was not accepted: it is difficult to see why the ecliptic would accumulate mass within the Earth-Moon system. Very recently, however, this objection has been mitigated by the discovery of Saturn's Phoebe ring: evidently, the plane of a planetary moon's orbit has now been observed as the site of mass accumulation. An adjustment of just a few degrees from ecliptic to the plane of the lunar orbit gives Jones's proposal the boost of an existing Solar System analogue, mysterious though the analogue is. J. O'Keefe (1980) was first to suggest that an Earth ring system could drive climate: a ring in the equatorial plane, waxing and waning in optical depth, could drive the alternation of Ice Age and interglacial climates. This driver would account for the observation that the Ice Age climate was mainly a difference in winter only. Could Earth have a ring system with one or both elements? Even if light and unstable, it would be important to assess, as it could drive climate change. Dust assessments have not discovered a ring system, but they do not cover low orbits well, nor rule out very small particles stringently. Yet tiny particles can be optically important. There are many difficulties with this hypothesis: Why have ground-based observers never identified an equatorial ring, which after all should be the brightest element of a ring system? Why should a ring system be made of very small particles only? The material must be constantly falling to Earth - where is it? Finally, can we believe in the level of lunar geological activity needed to sustain an Earth ring system? This presentation addresses only one issue: Could ground-based observers have seen but misidentified an equatorial ring? To support consideration of that question, herewith a simple geometric exercise

Design, installation, and commissioning of the D0 overpass at the Fermilab main ring

International Nuclear Information System (INIS)

Gerig, R.; May, M.; Moore, C.; Ohnuma, S.; Pruss, S.; Turkot, F.

1985-06-01

In order to accommodate large detectors for anti pp studies at the Tevatron, the Main Ring has been modified to be non-planar. A 700 foot-long portion of the ring has been reworked to create an overpass which displaces the beam orbit upwards by 51 inches at the D0 long straight section. The overpass region follows the ''screw'' geometry proposed by T. Collins. A set of four vertically bending dipoles were inserted into the Main Ring lattice; they are powered on a separate bus and operate at twice the current and field level of a standard bend. To make space for these vertical bends, at each vertical bend point two of the four standard dipoles in a half-cell are removed and the other two are powered at twice the current and field level of the rest of the ring. The vertical bends also have a set of trim coils powered by a separate supply so that any difference in the horizontal and vertical bending strengths can be compensated. The D0 overpass was commissioned with beam in November-December 1984. The principal effect on beam dynamics - predicted and observed - is the introduction of momentum dispersion in the vertical dimension of peak value 1.9m. To preserve closed orbit quality during acceleration, the vertical bends must track the rest of the ring with a precision of better than 0.1%. The Main Ring-Tevatron complex has now been running the fixed-target program for four months; the impact of the D0 overpass on accelerator performance has been minimal

Operational Status of PF-Ring and PF-AR after the Earthquake

International Nuclear Information System (INIS)

Honda, T; Asaoka, S; Haga, K; Harada, K; Honda, Y; Izawa, M; Kamiya, Y; Kobayashi, Y; Miyajima, T; Miyauchi, H; Nagahashi, S; Nakamura, N; Nogami, T; Obina, T; Ozaki, T; Sagehashi, H; Sakai, H; Sakanaka, S; Sasaki, H; Sato, Y

2013-01-01

In 2011, two SR sources of KEK, PF-ring and PF-AR, needed to change the operation schedule because of the unprecedented earthquake on March 11. Though the injector linac and the storage rings suffered a serious damage, temporary recovery was accomplished quickly and the trial operation started in May. The regular user operation could be resumed in October 2011. In the restoration work after the earthquake, some old vacuum components were removed from PF-ring. This work fortunately brought an effect of settling the quadrupole-mode longitudinal instability. For the top-up injection of PF-ring, the pulsed sextupole magnet has been used instead of the conventional kicker magnets since 2011. The hybrid-fill mode in place of the single-bunch mode has become available. Recently, the 10-Hz orbit switching for the tandem circularly polarized undulators has been developed for the user operation.

Planning and Prototyping for a Storage Ring Measurement of the Proton Electric Dipole Moment

Energy Technology Data Exchange (ETDEWEB)

Talman, Richard [Cornell Univ., Ithaca, NY (United States)

2015-07-01

Electron and proton EDM's can be measured in "frozen spin" (with the beam polarization always parallel to the orbit, for example) storage rings. For electrons the "magic" kinetic energy at which the beam can be frozen is 14.5 MeV. For protons the magic kinetic energy is 230 MeV. The currently measured upper limit for the electron EDM is much smaller than the proton EDM upper limit, which is very poorly known. Nevertheless, because the storage ring will be an order of magnitude cheaper, a sensible plan is to first build an all-electric electron storage ring as a prototype. Such an electron ring was successfully built at Brookhaven, in 1954, as a prototype for their AGS ring. This leaves little uncertainty concerning the cost and performance of such a ring. (This is documentedin one of the Physical Review papers mentioned above.)

Studies Performed in Preparation for the Spallation Neutron Source Accumulator Ring Commissioning

CERN Document Server

Cousineau, Sarah M; Henderson, Stuart; Holmes, Jeffrey Alan; Plum, Michael

2005-01-01

The Spallation Neutron Source accumulator ring will compress 1.5?1014, 1 GeV protons from a 1 ms bunch train to a single 695 ns proton bunch for use in neutron spallation. Due to the high beam power, unprecedented control of beam loss will be required in order to control radiation and allow for hands-on maintenance in most areas of the ring. A number of detailed investigations have been performed to understand the primary sources of beam loss and to predict and mitigate problems associated with radiation hot spots in the ring. The ORBIT particle tracking code is used to perform realistic simulations of the beam accumulation in the ring, including detailed modeling of the injection system, transport through the measured magnet fields including higher order multipoles, and beam loss and collimation. In this paper we present the results of a number of studies performed in preparation for the 2006 commissioning of the accumulator ring.

Model calibration and beam control systems for storage rings

International Nuclear Information System (INIS)

Corbett, W.J.; Lee, M.J.; Ziemann, V.

1993-04-01

Electron beam storage rings and linear accelerators are rapidly gaining worldwide popularity as scientific devices for the production of high-brightness synchrotron radiation. Today, everybody agrees that there is a premium on calibrating the storage ring model and determining errors in the machine as soon as possible after the beam is injected. In addition, the accurate optics model enables machine operators to predictably adjust key performance parameters, and allows reliable identification of new errors that occur during operation of the machine. Since the need for model calibration and beam control systems is common to all storage rings, software packages should be made that are portable between different machines. In this paper, we report on work directed toward achieving in-situ calibration of the optics model, detection of alignment errors, and orbit control techniques, with an emphasis on developing a portable system incorporating these tools

Active interlock system for high power insertion devices in the x-ray ring

International Nuclear Information System (INIS)

Anon.

1991-01-01

In modern synchrotron radiation rings photon beams generated by high power insertion devices (IDs) may be sufficiently intense to cause severe thermal damage to the machine vacuum chamber if mis-steered. Thus when operating a storage ring with the IDs, great care must be exercised to prevent mis-steering of the electron beam orbit. At present, the X-ray ring operates with three IDs, namely two hybrid wigglers (HBW) at X-21 and X-25,a nd a 5-Tesla superconducting wiggler at X-17. All wigglers are located in low-beta straight sections. In the straight sections. In the straight sections, beam orbit may be deflected by as much as ±8 mrad without scraping the chamber wall. For various reasons it was not possible to design the X-ray ring vacuum chamber to be safe under all possible operating conditions, however, the chamber is safe for i < 7 mA, all horizontal beam deflection angles and for vertical angles < ± 2.5 mrad. To protect the machine vacuum chamber from damage due to mis-steered beams, and interlock system has been developed and installed. This system utilizes active beam position detectors which continuously monitor beam motion in each of the ID straight sections and logic circuitry which interrupts the RF and dumps the stored beam in the case of a fault

Plutonium in tree rings from France and Japan

International Nuclear Information System (INIS)

Garrec, J.-P.; Suzuki, T.; Mahara, Y.; Santry, D.C.; Miyahara, S.; Sugahara, M.; Zheng, J.; Kudo, A.

1995-01-01

Plutonium, along with other radionuclide concentrations, was measured in evergreen tree rings from two different locations. This was used as an information source for the past two centuries. Tree rings are a product of annual layers and thus chronological information is clearly visible. Three trees were harvested in 1988-1990: a French white fir (137 years old) and a spruce tree (177 years old) from the France-Germany border near Nancy, France and a sugi (78 years old) from Nagasaki, Japan. The highest 239 + 240 Pu concentration of 30.0 mBq/kg of dry wood was obtained from the tree rings from Nagasaki, located at the centre of the local fallout of the Pu A-bomb detonated in 1945. This concentration peak was, however, observed in tree rings of 1965-67. The concentration was only 2.9 mBq/kg for the tree rings of 1944-46. The contribution of the local fallout on the surface soils from the A-bomb was 181 mBq/cm 2 at the harvested area of the tree, while the contribution of global fallout by many weapons testing was 5.9 mBq/cm 2 (or 3.3% total fallout in the region). The reason for the over 20 year time lag of 239 + 240 Pu uptake by the tree rings is unknown because many factors influence the routes of Pu into the tree rings. Also the chemical form of Pu in surface soils may have been changed by the surrounding environment. The highest concentration in the tree rings from France was 9.4 mBq/kg which is about 31% of Nagasaki 239 + 240 Pu concentration. (author)

Unstable low-mass planetary systems as drivers of white dwarf pollution

Science.gov (United States)

Mustill, Alexander J.; Villaver, Eva; Veras, Dimitri; Gänsicke, Boris T.; Bonsor, Amy

2018-05-01

At least 25 {per cent} of white dwarfs show atmospheric pollution by metals, sometimes accompanied by detectable circumstellar dust/gas discs or (in the case of WD 1145+017) transiting disintegrating asteroids. Delivery of planetesimals to the white dwarf by orbiting planets is a leading candidate to explain these phenomena. Here, we study systems of planets and planetesimals undergoing planet-planet scattering triggered by the star's post-main-sequence mass loss, and test whether this can maintain high rates of delivery over the several Gyr that they are observed. We find that low-mass planets (Earth to Neptune mass) are efficient deliverers of material and can maintain the delivery for Gyr. Unstable low-mass planetary systems reproduce the observed delayed onset of significant accretion, as well as the slow decay in accretion rates at late times. Higher-mass planets are less efficient, and the delivery only lasts a relatively brief time before the planetesimal populations are cleared. The orbital inclinations of bodies as they cross the white dwarf's Roche limit are roughly isotropic, implying that significant collisional interactions of asteroids, debris streams and discs can be expected. If planet-planet scattering is indeed responsible for the pollution of white dwarfs, many such objects, and their main-sequence progenitors, can be expected to host (currently undetectable) super-Earth planets on orbits of several au and beyond.

Ring Current He Ion Control by Bounce Resonant ULF Waves

Science.gov (United States)

Kim, Hyomin; Gerrard, Andrew J.; Lanzerotti, Louis J.; Soto-Chavez, Rualdo; Cohen, Ross J.; Manweiler, Jerry W.

2017-12-01

Ring current energy He ion (˜65 keV to ˜520 keV) differential flux data from the Radiation Belt Storm Probe Ion Composition Experiment (RBSPICE) instrument aboard the Van Allan Probes spacecraft show considerable variability during quiet solar wind and geomagnetic time periods. Such variability is apparent from orbit to orbit (˜9 h) of the spacecraft and is observed to be ˜50-100% of the nominal flux. Using data from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument, also aboard the Van Allen Probes spacecraft, we identify that a dominant source of this variability is from ULF waveforms with periods of tens of seconds. These periods correspond to the bounce resonant timescales of the ring current He ions being measured by RBSPICE. A statistical survey using the particle and field data for one full spacecraft precession period (approximately 2 years) shows that the wave and He ion flux variations are generally anticorrelated, suggesting the bounce resonant pitch angle scattering process as a major component in the scattering of He ions.

Comparison of ring-focus image profile with predictions for the AXAF VETA-I test

Science.gov (United States)

Zissa, David E.

1993-01-01

The X-ray test of the largest pair of nearly cylindrical mirrors for the Advanced X-ray Astrophysics Facility (AXAF) was completed in October 1991 at Marshall Space Flight Center. The test assembly was named the Verification Engineering Test Article I (VETA-I). The ring-focus portion of the test measured the imaging quality of azimuthal sections of VETA-I. This gives information about the core of the on-orbit image. The finite source distance, VETA-I mirror spacing, and VETA-I structural deformation caused the core of the image to be spread over a diameter of nearly 4 arc seconds at the VETA-I overall focus. The results of a preliminary analysis of the ring-focus data and the implications for the on-orbit image of the telescope are discussed. An upper limit for the on-orbit encircled-energy fraction at 1 arc second diameter was determined to be 0.82 at 0.277 keV X-ray energy. This assumes that the bottoms of the mirrors in the VETA-I arrangement are representative of the mirror surfaces and that the on-orbit system would be aligned using a combination of preliminary measurements and predictions for the mirror surface shapes.

WD1145+017 (Abstract)

Science.gov (United States)

Motta, M.

2017-12-01

(Abstract only) WD1145 is a 17th magnitude white dwarf star 570 light years away in Virgo that was discovered to have a disintegrating planetoid in close orbit by Andrew Vanderburg, a graduate student at Harvard CfA, while data mining the elucidate the nature of its rather bizarre transit light curves. I obtained multiple observations of WD1145 over the course of a year, and found a series of complex transit light curves that could only be interpreted as a ring complex or torus in close orbit around WD1145. Combined with data from other amateur astronomers, professional observations, and satellite data, it became clear that WD1145 has a small planetoid in close orbit at the Roche limit and is breaking apart, forming a ring of debris material that is then raining down on the white dwarf. The surface of the star is "polluted" by heavy metals, determined by spectroscopic data. Given that in the intense gravitational field of a white dwarf any heavy metals could not for long last on the surface, this confirms that we are tracking in real time the destruction of a small planet by its host star.

Electric currents induced by twisted light in Quantum Rings.

Science.gov (United States)

Quinteiro, G F; Berakdar, J

2009-10-26

We theoretically investigate the generation of electric currents in quantum rings resulting from the optical excitation with twisted light. Our model describes the kinetics of electrons in a two-band model of a semiconductor-based mesoscopic quantum ring coupled to light having orbital angular momentum (twisted light). We find the analytical solution, which exhibits a "circular" photon-drag effect and an induced magnetization, suggesting that this system is the circular analog of that of a bulk semiconductor excited by plane waves. For realistic values of the electric field and material parameters, the computed electric current can be as large as microA; from an applied perspective, this opens new possibilities to the optical control of the magnetization in semiconductors.

EX-111 thermal emission from hot white dwarfs: the suggested He abundance-temperature correlation. EX-112: the unique emission line white dwarf star GD 356. Semiannnual status report, 1 December 1985-1 June 1986

International Nuclear Information System (INIS)

Shipman, H.L.

1986-08-01

Progress in the EXOSAT data analysis program is reported. EXOSAT observations for four white dwarfs (WD1031-115, WD0004+330, WD1615-154, and WD0109-264) were obtained. Counting rates were unexpectedly low, indicating that these objects have a substantial amount of x-ray absorbing matter in their photosheres. In addition, soft x-ray pulsations characterized by a 9.25 minute cycle were discovered in the DA white dwarf V471 Tauri. A residual x-ray flux from the K dwarf companion can be seen during the white dwarf eclipse at orbital phase 0.0. Pronounced dips in the soft x-ray light curve occur at orbital phases 0.15, 0.18, and 0.85. The dips may be correlated with the triangular Lagrangian points of the binary orbit. Smaller dips at phases near the eclipse may be associated with cool loops in the K star corona. Data for the white dwarf H1504+65 was also analyzed. This object is particularly unusual in that its photoshere is devoid of hydrogen and helium. Finally, existing data on the white dwarf Sirius B were analyzed to see what constraints from other data can be placed on the properties of this star. Interrelationships between radius, rotational velocity, and effective temperature were derived

Analytical solutions for the invariant spin field for model storage rings

International Nuclear Information System (INIS)

Mane, S.R.

2002-01-01

We present nonperturbative analytical expressions for the invariant spin field for several storage ring models. In particular, we solve the important models of a ring with one Snake and a single resonance driving term, and a ring with two Snakes and a single resonance driving term. We also treat several other models, all of which contain Siberian Snakes. Our solutions contain some novel features, e.g. in some cases the polarization does not point along the direction of the closed-orbit spin quantization axis. We also include vertical resonance driving terms, and consider the contributions of sextupoles and higher order multipoles to the resonance driving terms, and argue that these can play a significant role in some circumstances. We offer some brief remarks on the so-called Snake resonances. We relate our results to observations of higher-order depolarizing spin resonances for polarized proton beams in a real ring, and offer some suggestions as to how our ideas might be verified

Performance of high-resolution position-sensitive detectors developed for storage-ring decay experiments

International Nuclear Information System (INIS)

Yamaguchi, T.; Suzaki, F.; Izumikawa, T.; Miyazawa, S.; Morimoto, K.; Suzuki, T.; Tokanai, F.; Furuki, H.; Ichihashi, N.; Ichikawa, C.; Kitagawa, A.; Kuboki, T.; Momota, S.; Nagae, D.; Nagashima, M.; Nakamura, Y.; Nishikiori, R.; Niwa, T.; Ohtsubo, T.; Ozawa, A.

2013-01-01

Highlights: • Position-sensitive detectors were developed for storage-ring decay spectroscopy. • Fiber scintillation and silicon strip detectors were tested with heavy ion beams. • A new fiber scintillation detector showed an excellent position resolution. • Position and energy detection by silicon strip detectors enable full identification. -- Abstract: As next generation spectroscopic tools, heavy-ion cooler storage rings will be a unique application of highly charged RI beam experiments. Decay spectroscopy of highly charged rare isotopes provides us important information relevant to the stellar conditions, such as for the s- and r-process nucleosynthesis. In-ring decay products of highly charged RI will be momentum-analyzed and reach a position-sensitive detector set-up located outside of the storage orbit. To realize such in-ring decay experiments, we have developed and tested two types of high-resolution position-sensitive detectors: silicon strips and scintillating fibers. The beam test experiments resulted in excellent position resolutions for both detectors, which will be available for future storage-ring experiments

Lattice modeling and calibration with turn-by-turn orbit data

Directory of Open Access Journals (Sweden)

Xiaobiao Huang

2010-11-01

Full Text Available A new method that explores turn-by-turn beam position monitor (BPM data to calibrate lattice models of accelerators is proposed. The turn-by-turn phase space coordinates at one location of the ring are first established using data from two BPMs separated by a simple section with a known transfer matrix, such as a drift space. The phase space coordinates are then tracked with the model to predict positions at other BPMs, which can be compared to measurements. The model is adjusted to minimize the difference between the measured and predicted orbit data. BPM gains and rolls are included as fitting variables. This technique can be applied to either the entire or a section of the ring. We have tested the method experimentally on a part of the SPEAR3 ring.

Lattice modeling and calibration with turn-by-turn orbit data

Science.gov (United States)

Huang, Xiaobiao; Sebek, Jim; Martin, Don

2010-11-01

A new method that explores turn-by-turn beam position monitor (BPM) data to calibrate lattice models of accelerators is proposed. The turn-by-turn phase space coordinates at one location of the ring are first established using data from two BPMs separated by a simple section with a known transfer matrix, such as a drift space. The phase space coordinates are then tracked with the model to predict positions at other BPMs, which can be compared to measurements. The model is adjusted to minimize the difference between the measured and predicted orbit data. BPM gains and rolls are included as fitting variables. This technique can be applied to either the entire or a section of the ring. We have tested the method experimentally on a part of the SPEAR3 ring.

James Webb Space Telescope Observations of Stellar Occultations by Solar System Bodies and Rings

Science.gov (United States)

Santos-Sanz, P.; French, R. G.; Pinilla-Alonso, N.; Stansberry, J.; Lin, Z-Y.; Zhang, Z-W.; Vilenius, E.; Mueller, Th.; Ortiz, J. L.; Braga-Ribas, F.;

Uranium mobility across annual growth rings in three deciduous tree species.

Science.gov (United States)

McHugh, Kelly C; Widom, Elisabeth; Spitz, Henry B; Wiles, Gregory C; Glover, Sam E

2018-02-01

Black walnut (Juglans nigra), slippery elm (Ulmus rubra), and white ash (Fraxinus americana) trees were evaluated as potential archives of past uranium (U) contamination. Like other metals, U mobility in annual growth rings of trees is dependent on the tree species. Uranium concentrations and isotopic compositions (masses 234, 235, 236, and 238) were analyzed by thermal ionization mass spectrometry to test the efficacy of using tree rings to retroactively monitor U pollution from the FFMPC, a U purification facility operating from 1951 to 1989. This study found non-natural U (depleted U and detectable 236 U) in growth rings of all three tree species that pre-dated the start of operations at FFMPC and compositional trends that did not correspond with known contamination events. Therefore, the annual growth rings of these tree species cannot be used to reliably monitor the chronology of U contamination. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis, X-ray Structure, Optical, and Electrochemical Properties of a White-Light-Emitting Molecule

Directory of Open Access Journals (Sweden)

Jiun-Wei Hu

2016-01-01

Full Text Available A new white-light-emitting molecule (1 was synthesized and characterized by NMR spectroscopy, high resolution mass spectrometry, and single-crystal X-ray diffraction. Compound 1 crystallizes in the orthorhombic space group Pnma, with a = 12.6814(6, b = 7.0824(4, c = 17.4628(9 Å, α = 90°, β = 90°, γ = 90°. In the crystal, molecules are linked by weak intermolecular C-H···O hydrogen bonds, forming an infinite chain along [100], generating a C(10 motif. Compound 1 possesses an intramolecular six-membered-ring hydrogen bond, from which excited-state intramolecular proton transfer (ESIPT takes place from the phenolic proton to the carbonyl oxygen, resulting in a tautomer that is in equilibrium with the normal species, exhibiting a dual emission that covers almost all of the visible spectrum and consequently generates white light. It exhibits one irreversible one-electron oxidation and two irreversible one-electron reductions in dichloromethane at modest potentials. Furthermore, the geometric structures, frontier molecular orbitals (MOs, and the potential energy curves (PECs for 1 in the ground and the first singlet excited state were fully rationalized by density functional theory (DFT and time-dependent DFT calculations. The results demonstrate that the forward and backward ESIPT may happen on a similar timescale, enabling the excited-state equilibrium to be established.

Design of low energy ring(s)

CERN Document Server

Lachaize, Antoine

During the last two years, several upgrades of the initial baseline scenario were studied with the aim of increasing the average intensity of ion beams in the accelerator chain of the Beta Beam complex. This is the reason why the Rapid Cycling Synchrotron (RCS) specifications were reconsidered many times [1], [2], [3].General considerations on the optical design were presented at the Beta Beam Task Meetings held at CERN and at Saclay in 2005 [4]. More detailed beam optics studies were performed during the next months. Lattices, RF system parameters, multi-turn injection scheme, fast extraction, closed orbit correction and chromaticity correction systems were proposed for different versions of the RCS [5], [6], [7].Finally, the RCS specifications have stabilized in November 2006 after the fourth Beta Beam Task Meeting when it was decided to fix the maximum magnetic rigidity of ion beams to 14.47 T.m (3.5 GeV equivalent proton energy) and to adopt a ring physical radius of 40 m in order to facilitate injectio...

THE HYADES CLUSTER: IDENTIFICATION OF A PLANETARY SYSTEM AND ESCAPING WHITE DWARFS

International Nuclear Information System (INIS)

Zuckerman, B.; Xu, S.; Klein, B.; Jura, M.

2013-01-01

Recently, some hot DA-type white dwarfs have been proposed to plausibly be escaping members of the Hyades. We used hydrogen Balmer lines to measure the radial velocities of seven such stars and confirm that three, and perhaps two others, are/were indeed cluster members and one is not. The other candidate Hyad is strongly magnetic and its membership status remains uncertain. The photospheres of at least one quarter of field white dwarf stars are ''polluted'' by elements heavier than helium that have been accreted. These stars are orbited by extended planetary systems that contain both debris belts and major planets. We surveyed the seven classical single Hyades white dwarfs and the newly identified (escaping) Hyades white dwarfs and found calcium in the photosphere of LP 475-242 of type DBA (now DBAZ), thus implying the presence of an orbiting planetary system. The spectrum of white dwarf GD 31, which may be, but probably is not, an escaping member of the Hyades, displays calcium absorption lines; these originate either from the interstellar medium or, less likely, from a gaseous circumstellar disk. If GD 31 was once a Hyades member, then it would be the first identified white dwarf Hyad with a cooling age >340 Myr.

Compact high-efficiency vortex beam emitter based on a silicon photonics micro-ring

DEFF Research Database (Denmark)

Li, Shimao; Ding, Yunhong; Guan, Xiaowei

2018-01-01

Photonic integrated devices that emit vortex beam carrying orbital angular momentum are becoming key components for multiple applications. Here we propose and demonstrate a high-efficiency vortex beam emitter based on a silicon micro-ring resonator integrated with a metal mirror. Such a compact...

Weather, logging, and tree growth associated with fir engraver attack scars in white fir

Science.gov (United States)

George T. Ferrell

1973-01-01

The boles of 32 recently killed, and 41 living, white fir were examined for embedded fir engraver (Scolytus ventralis) attack scars. Of 287 scars found in annual rings for the years 1934-69, only 2 to 3 percent represented reproductively successful attacks. Trends in scar abundance were directly correlated with trends in white fir killed by ...

Beam position monitor system for storage rings

International Nuclear Information System (INIS)

Nakamura, M.; Hinkson, J.A.

1985-05-01

Beam position monitors (BPM) for synchrotron light storage rings usually consist of beam pickup electrodes, coaxial relays and a narrowband receiver. While accurate, these systems are slow and of limited use in the commissioning of an accelerator. A beam position monitor is described which is intended to be a principal diagnostic during debug and routine running of a storage ring. It is capable of measuring the position of a single bunch on the first or nth orbit to an accuracy of a few percent. Stored beam position is more accurately measured with averaging techniques. Beam position changes can be studied in a bandwidth from DC to a few MHz. The beam monitor electronics consist of a separate amplification, detection, and sampling channel for each beam pickup electrode. Fast switches in each channel permit selection of the nth turn for measurement (single bunch mode). A calibration pulse is injected into each channel after beam measurement to permit gain offsets to be measured and removed from the final data. While initially more costly than the usual beam position monitor system, this sytem will pay for itself in reduced storage ring debug and trouble shooting time. 5 refs., 5 figs

Vertical dispersion produced by random closed orbit distortions and sextupoles

International Nuclear Information System (INIS)

Suzuki, Toshio.

1977-01-01

Vertical dispersion appears even in a machine designed with plane symmetry because of vertical closed orbit distortions, linear coupling and coupling due to sextupoles. This gives rise to several undesirable effects in an electron-positron storage ring such as PEP. Vertical dispersion at the interaction point will increase beam height and reduce luminosity. Vertical dispersion around the ring will modify vertical emittance and partition numbers for synchrotron radiation damping. It will also induce betatron-synchrotron resonance and affect chromaticity correction. Vertical dispersion due to random closed orbit distortions and sextupoles has been studied by Piwinski, and he has indicated that correction of chromaticity and chromatic change of β-function is important. However, he has assumed one error element and evaluated the dispersion at the position of the element. We generalize his argument to a more realistic case and derive more precise criteria for the correction of vertical dispersion. Horizontal dispersion due to perturbations is also studied. Vertical dispersion due to linear coupling is neglected in this note, since it has been studied by other authors. 7 refs

Discovery Of B Ring Propellers In Cassini UVIS, And ISS

Science.gov (United States)

Sremcevic, Miodrag; Stewart, G. R.; Albers, N.; Esposito, L. W.

2012-10-01

We present evidence for the existence of propellers in Saturn's B ring by combining data from Cassini Ultraviolet Imaging Spectrograph (UVIS) and Imaging Science Subsystem (ISS) experiments. We identify two propeller populations: (1) tens of degrees wide propellers in the dense B ring core, and (2) smaller, more A ring like, propellers populating the inner B ring. The prototype of the first population is an object observed at 18 different epochs between 2005 and 2010. The ubiquitous propeller "S" shape is seen both in UVIS occultations as an optical depth depletion and in ISS as a 40 degrees wide bright stripe in unlit geometries and dark in lit geometries. Combining the available Cassini data we infer that the object is a partial gap embedded in the high optical depth region of the B ring. The gap moves at orbital speed consistent with its radial location. From the radial separation of the propeller wings we estimate that the embedded body, which causes the propeller structure, is about 1.5km in size located at a=112,921km. The UVIS occultations indicate an asymmetric propeller "S" shape. Since the object is located at an edge between high and relatively low optical depth, this asymmetry is most likely a consequence of the strong surface mass density gradient. We estimate that there are possibly dozen up to 100 other propeller objects in Saturn's B ring. The location of the discovered body, at an edge of a dense ringlet within the B ring, suggests a novel mechanism for the up to now illusive B ring irregular large-scale structure of alternating high and low optical depth ringlets. We propose that this B ring irregular structure may have its cause in the presence of many embedded bodies that shepherd the individual B ring ringlets.

SEEING THROUGH THE RING: NEAR-INFRARED PHOTOMETRY OF V582 MON (KH 15D)

Energy Technology Data Exchange (ETDEWEB)

Arulanantham, Nicole A.; Herbst, William [Astronomy Department, Wesleyan University, Middletown, CT 06459 (United States); Cody, Ann Marie [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Stauffer, John R.; Rebull, Luisa M. [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); Agol, Eric; Windemuth, Diana [Department of Astronomy, University of Washington, Seattle, WA 98195-1580 (United States); Marengo, Massimo [Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Winn, Joshua N. [Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Hamilton, Catrina M. [Physics and Astronomy Department, Dickinson College, Carlisle, PA 17013 (United States); Mundt, Reinhard [Max Planck Institute for Astronomy, D-69117 Heidelberg (Germany); Johns-Krull, Christopher M. [Department of Physics and Astronomy, Rice University, Houston, TX 77005 (United States); Gutermuth, Robert A. [Department of Astronomy, University of Massachusetts, Amherst, MA 01002 (United States)

2016-04-15

We examine the light and color evolution of the T Tauri binary KH 15D through photometry obtained at wavelengths between 0.55 and 8.0 μm. The data were collected with A Novel Dual Imaging CAMera (ANDICAM) on the 1.3 m SMARTS telescope at Cerro-Tololo Inter-American Observatory and with InfraRed Array Camera on the Spitzer Space Telescope. We show that the system’s circumbinary ring, which acts as a screen that covers and uncovers different portions of the binary orbit as the ring precesses, has reached an orientation where the brighter component (star B) fully or nearly fully emerges during each orbital cycle. The fainter component (star A) remains fully occulted by the screen at all phases. The leading and trailing edges of the screen move across the sky at the same rate of ∼15 m s{sup −1}, consistent with expectation for a ring with a radius and width of ∼4 au and a precession period of ∼6500 years. Light and color variations continue to indicate that the screen is sharp edged and opaque at VRIJH wavelengths. However, we find an increasing transparency of the ring edge at 2.2, 3.6, and 4.5 μm. Reddening seen at the beginning of the eclipse that occurred during the CSI 2264 campaign particularly suggests selective extinction by a population of large dust grains. Meanwhile, the gradual bluing observed while star B is setting is indicative of forward scattering effects at the edge of the ring. The spectral energy distribution of the system at its bright phase shows no evidence of infrared excess emission that can be attributed to radiation from the ring or other dust component out to 8 μm.

Effect of an elliptical orbit on SPECT resolution and image uniformity

International Nuclear Information System (INIS)

Gottschalk, S.; Salem, D.

1982-01-01

This paper studies the impact of elliptical motion on SPECT resolution and detector flood correction as implemented in a Technicare Omega 500. Bringing the detector closer to the object improves detector resolution in each view, which results in improved resolution in the reconstructed image. In the Omega 500 the elliptical orbit is realized by a succession of translational and rotational motions of the detector head. This introduces motion of the detector center relative to the object center. Statistical fluctuations in the flood correction matrix due to the finite acquisition time result in ring artifacts for the circular orbit. The relative center motion of an elliptical orbit results in an averaging of the flood correction noise and a significant reduction in artifacts. These two aspects of SPECT spatial resolution and flood correction response improvement in elliptical orbit have been analyzed through computer simulations for point sources and a uniform activity 20 x 30 cm ellipse. Results compared a 35 cm diameter circular orbit to a 35 x 25 cm elliptical orbit

AGS - The ISR computer program for synchrotron design, orbit analysis and insertion matching

International Nuclear Information System (INIS)

Keil, E.; Marti, Y.; Montague, B.W.; Sudboe, A.

1975-01-01

This is a detailed guide to the use of the current version of a FORTRAN program for carrying out computations required in the design or modification of alternating-gradient synchrotrons and storage rings. The program, which runs on the CDC 7600 computer at CERN, computes linear transformation functions, and modifications of parameters to achieve specified properties; it tracks sets of particle trajectories, finds closed orbits when elements of the structure are displaced, computes the equilibrium orbit, designs closed-orbit bumps, tracks betatron functions through the structure, and matches insertions in the structure to specified betatron and dispersion functions. The report supersedes CERN 69-5 (AGS - The ISR computer system for synchrotron design and orbit analysis, by E. Keil and P. Strolin). (Author)

Photochemistry in Saturn’s Ring-Shadowed Atmosphere: Modulation of Hydrocarbons and Aerosols

Science.gov (United States)

Edgington, Scott G.; Atreya, Sushil K.; Wilson, Eric H.; Baines, Kevin H.; West, Robert A.; Bjoraker, Gordon L.; Fletcher, Leigh N.; Momary, Tom

2015-11-01

Cassini has been orbiting Saturn for over eleven years now. During this epoch, the ring shadow has moved from covering much of the northern hemisphere (the solar inclination was 24 degrees) to covering a large swath south of the equator and it continues to move southward. At Saturn Orbit Insertion in 2004, the projection of the A-ring onto Saturn reached as far as 40N along the central meridian (52N at the terminator). At its maximum extent, the ring shadow can reach as far as 48N/S (58N/S at the terminator). The net effect is that the intensity of both ultraviolet and visible sunlight penetrating through the rings to any particular latitude will vary depending on both Saturn’s axis relative to the Sun and the optical thickness of each ring system. In essence, the rings act like semi-transparent venetian blinds.Our previous work, examined the variation of the solar flux as a function of solar inclination, i.e. for each 7.25-year season at Saturn. Here, we report on the impact of the oscillating ring shadow on the photolysis and production rates of hydrocarbons (acetylene, ethane, propane, and benzene) and phosphine in Saturn’s stratosphere and upper troposphere. The impact of these production and loss rates on the abundance of long-lived photochemical products leading to haze formation are explored. Similarly, we assess their impact on phosphine abundance, a disequilibrium species whose presence in the upper troposphere can be used as a tracer of convective processes in the deeper atmosphere.We will also present our ongoing analysis of Cassini’s datasets that provide an estimate of the evolving haze content of the northern hemisphere and we will begin to assess the implications for dynamical mixing. In particular, we will examine how the now famous hexagonal jet stream acts like a barrier to transport, isolating Saturn’s north polar region from outside transport of photochemically-generated molecules and haze.The research described in this paper was carried

Progress in measurement and understanding of beam polarization in electron positron storage rings

International Nuclear Information System (INIS)

Barber, D.P.; Bremer, H.D.; Kewisch, J.; Lewin, H.C.; Limberg, T.; Mais, H.; Ripken, G.; Rossmanith, R.; Schmidt, R.

1983-07-01

A report is presented on the status of attempts to obtain and measure spin polarization in electron-positron storage rings. Experimental results are presented and their relationship to predictions of calculations discussed. Examples of methods for decoupling orbital and spin motion and thus improving polarization are discussed. (orig.)

Electromagnetic pulse-driven spin-dependent currents in semiconductor quantum rings.

Science.gov (United States)

Zhu, Zhen-Gang; Berakdar, Jamal

2009-04-08

We investigate the non-equilibrium charge and spin-dependent currents in a quantum ring with a Rashba spin-orbit interaction (SOI) driven by two asymmetric picosecond electromagnetic pulses. The equilibrium persistent charge and persistent spin-dependent currents are investigated as well. It is shown that the dynamical charge and the dynamical spin-dependent currents vary smoothly with a static external magnetic flux and the SOI provides a SU(2) effective flux that changes the phases of the dynamic charge and the dynamic spin-dependent currents. The period of the oscillation of the total charge current with the delay time between the pulses is larger in a quantum ring with a larger radius. The parameters of the pulse fields control to a certain extent the total charge and the total spin-dependent currents. The calculations are applicable to nanometre rings fabricated in heterojunctions of III-V and II-VI semiconductors containing several hundreds of electrons.

Storage ring to investigate cold unidimensional atomic collisions

International Nuclear Information System (INIS)

Marcassa, L. G.; Caires, A. R. L.; Nascimento, V. A.; Dulieu, O.; Weiner, J.; Bagnato, V. S.

2005-01-01

In this paper we employ a circulating ring of trapped atoms, that we have named the atomotron, to study cold collisions. The atomotron is obtained from a conventional magneto-optical trap when the two pairs of normally retroreflecting Gaussian laser beams in the x-y plane are slightly offset. Circulating stable atomic orbits then form a racetrack geometry in this plane. The circulating atom flux behaves similarly to an atomic beam with an average tangential velocity much greater than the transverse components, and is therefore suitable for one-dimensional atomic collision studies. Using the atomotron, we have investigated the polarization dependence of ultracold photoassociation collisions between Rb atoms circulating in the racetrack. The ability to investigate collisions in ultracold circulating atomic rings reveals alignment and orientation properties that are averaged away in ordinary three-dimensional magneto-optical trap collision processes

Characterizing Longitude-Dependent Orbital Debris Congestion in the Geosynchronous Orbit Regime

Science.gov (United States)

Anderson, Paul V.

The geosynchronous orbit (GEO) is a unique commodity of the satellite industry that is becoming increasingly contaminated with orbital debris, but is heavily populated with high-value assets from the civil, commercial, and defense sectors. The GEO arena is home to hundreds of communications, data transmission, and intelligence satellites collectively insured for an estimated 18.3 billion USD. As the lack of natural cleansing mechanisms at the GEO altitude renders the lifetimes of GEO debris essentially infinite, conjunction and risk assessment must be performed to safeguard operational assets from debris collisions. In this thesis, longitude-dependent debris congestion is characterized by predicting the number of near-miss events per day for every longitude slot at GEO, using custom debris propagation tools and a torus intersection metric. Near-miss events with the present-day debris population are assigned risk levels based on GEO-relative position and speed, and this risk information is used to prioritize the population for debris removal target selection. Long-term projections of debris growth under nominal launch traffic, mitigation practices, and fragmentation events are also discussed, and latitudinal synchronization of the GEO debris population is explained via node variations arising from luni-solar gravity. In addition to characterizing localized debris congestion in the GEO ring, this thesis further investigates the conjunction risk to operational satellites or debris removal systems applying low-thrust propulsion to raise orbit altitude at end-of-life to a super-synchronous disposal orbit. Conjunction risks as a function of thrust level, miss distance, longitude, and semi-major axis are evaluated, and a guidance method for evading conjuncting debris with continuous thrust by means of a thrust heading change via single-shooting is developed.

Saturn's Magnetic Field from the Cassini Grand Finale orbits

Science.gov (United States)

Dougherty, M. K.; Cao, H.; Khurana, K. K.; Hunt, G. J.; Provan, G.; Kellock, S.; Burton, M. E.; Burk, T. A.

2017-12-01

The fundamental aims of the Cassini magnetometer investigation during the Cassini Grand Finale orbits were determination of Saturn's internal planetary magnetic field and the rotation rate of the deep interior. The unique geometry of the orbits provided an unprecedented opportunity to measure the intrinsic magnetic field at close distances never before encountered. The surprising close alignment of Saturn's magnetic axis with its spin axis, known about since the days of Pioneer 11, has been a focus of the team's analysis since Cassini Saturn Orbit Insertion. However, the varying northern and southern magnetospheric planetary period oscillations, which fill the magnetosphere, has been a factor in masking the field signals from the interior. Here we describe an overview of the magnetometer results from the Grand Finale orbits, including confirmation of the extreme axisymmetric nature of the planetary magnetic field, implications for knowledge of the rotation rate and the behaviour of external magnetic fields (arising from the ring current, field aligned currents both at high and low latitudes and the modulating effect of the planetary period oscillations).

S.C. correction coils and magnets for the HERA proton ring

International Nuclear Information System (INIS)

Daum, C.; Geerinck, J.; Schmueser, P.

1986-05-01

The quadrupole and sextupole correction coils of the HERA proton ring are mounted on the cold beam pipe inside the main dipole magnets. Superferric dipole magnets for orbit correction are located adjacent to the main quadrupole magnets in a common cryostat which also contains the beam monitor. The design, manufacture and performance of both types of correction elements are described. (orig.)

Natural occupation numbers in two-electron quantum rings.

Science.gov (United States)

Tognetti, Vincent; Loos, Pierre-François

2016-02-07

Natural orbitals (NOs) are central constituents for evaluating correlation energies through efficient approximations. Here, we report the closed-form expression of the NOs of two-electron quantum rings, which are prototypical finite-extension systems and new starting points for the development of exchange-correlation functionals in density functional theory. We also show that the natural occupation numbers for these two-electron paradigms are in general non-vanishing and follow the same power law decay as atomic and molecular two-electron systems.

Natural occupation numbers in two-electron quantum rings

Energy Technology Data Exchange (ETDEWEB)

Tognetti, Vincent, E-mail: vincent.tognetti@univ-rouen.fr [Normandy Univ., COBRA UMR 6014 & FR 3038, Université de Rouen, INSA Rouen, CNRS, 1 rue Tesniére, 76821 Mont Saint Aignan, Cedex (France); Loos, Pierre-François [Research School of Chemistry, Australian National University, Canberra ACT 2601 (Australia)

2016-02-07

Natural orbitals (NOs) are central constituents for evaluating correlation energies through efficient approximations. Here, we report the closed-form expression of the NOs of two-electron quantum rings, which are prototypical finite-extension systems and new starting points for the development of exchange-correlation functionals in density functional theory. We also show that the natural occupation numbers for these two-electron paradigms are in general non-vanishing and follow the same power law decay as atomic and molecular two-electron systems.

WD1145+017

Science.gov (United States)

Motta, Mario

2017-06-01

WD1145 is a 17th magnitude white dwarf star 570 light years away in Virgo, that was discovered to have a disintegrating planetoid in close orbit by Andrew Vanderburg a graduate student at Harvard CFA, while data mining the Kepler 2 mission. He contacted me to obtain transit data to elucidate the nature of its rather bizarre transit light curves. I obtained multiple observations of WD1145 over the course of a year, and found a series of complex transit light curves that could only be interpreted as a ring complex or torus in close orbit around WD1145. Combined with data from other amateur astronomers, professional observations, and satellite data it became clear that WD1145 has a small planetoid in close orbit at the Roche limit and is breaking apart forming a ring of debris material that is then raining down on the white dwarf. The surface of the star is "polluted" by heavy metals by spectroscopic data. Given that in the intense gravitational field of a white dwarf any heavy metals could not for long last on the surface, this confirms that we are tracking in real time the destruction of a small planet by its host star.

Non-Linear Dynamics of Saturn’s Rings

Science.gov (United States)

Esposito, Larry W.

2015-11-01

Non-linear processes can explain why Saturn’s rings are so active and dynamic. Ring systems differ from simple linear systems in two significant ways: 1. They are systems of granular material: where particle-to-particle collisions dominate; thus a kinetic, not a fluid description needed. We find that stresses are strikingly inhomogeneous and fluctuations are large compared to equilibrium. 2. They are strongly forced by resonances: which drive a non-linear response, pushing the system across thresholds that lead to persistent states.Some of this non-linearity is captured in a simple Predator-Prey Model: Periodic forcing from the moon causes streamline crowding; This damps the relative velocity, and allows aggregates to grow. About a quarter phase later, the aggregates stir the system to higher relative velocity and the limit cycle repeats each orbit.Summary of Halo Results: A predator-prey model for ring dynamics produces transient structures like ‘straw’ that can explain the halo structure and spectroscopy: This requires energetic collisions (v ≈ 10m/sec, with throw distances about 200km, implying objects of scale R ≈ 20km).Transform to Duffing Eqn : With the coordinate transformation, z = M2/3, the Predator-Prey equations can be combined to form a single second-order differential equation with harmonic resonance forcing.Ring dynamics and history implications: Moon-triggered clumping at perturbed regions in Saturn’s rings creates both high velocity dispersion and large aggregates at these distances, explaining both small and large particles observed there. We calculate the stationary size distribution using a cell-to-cell mapping procedure that converts the phase-plane trajectories to a Markov chain. Approximating the Markov chain as an asymmetric random walk with reflecting boundaries allows us to determine the power law index from results of numerical simulations in the tidal environment surrounding Saturn. Aggregates can explain many dynamic aspects

Coupling correction using closed orbit measurements

International Nuclear Information System (INIS)

Safranek, J.; Krinsky, S.

1994-01-01

The authors describe a coupling correction scheme they have developed and used to successfully reduce the vertical emittance of the NSLS X-Ray ring by a factor of 6 to below 2 A. This gives a vertical to horizontal emittance ratio of less than 0.2%. They find the strengths of 17 skew quadrupoles to simultaneously minimize the vertical dispersion and the coupling. As a measure of coupling they utilize the shift in vertical closed orbit resulting from a change in strength of a horizontal steering magnet. Experimental measurements confirm the reduced emittance

Double Rashba Quantum Dots Ring as a Spin Filter

Directory of Open Access Journals (Sweden)

Chi Feng

2008-01-01

Full Text Available AbstractWe theoretically propose a double quantum dots (QDs ring to filter the electron spin that works due to the Rashba spin–orbit interaction (RSOI existing inside the QDs, the spin-dependent inter-dot tunneling coupling and the magnetic flux penetrating through the ring. By varying the RSOI-induced phase factor, the magnetic flux and the strength of the spin-dependent inter-dot tunneling coupling, which arises from a constant magnetic field applied on the tunneling junction between the QDs, a 100% spin-polarized conductance can be obtained. We show that both the spin orientations and the magnitude of it can be controlled by adjusting the above-mentioned parameters. The spin filtering effect is robust even in the presence of strong intra-dot Coulomb interactions and arbitrary dot-lead coupling configurations.

Toward Detection of Exoplanetary Rings via Transit Photometry: Methodology and a Possible Candidate

Energy Technology Data Exchange (ETDEWEB)

Aizawa, Masataka; Masuda, Kento; Suto, Yasushi [Department of Physics, The University of Tokyo, Tokyo, 113-0033 (Japan); Uehara, Sho [Department of Physics, Tokyo Metropolitan University, Tokyo 192-4397 (Japan); Kawahara, Hajime, E-mail: aizawa@utap.phys.s.u-tokyo.ac.jp [Department of Earth and Planetary Science, The University of Tokyo, Tokyo 113-0033 (Japan)

2017-04-01

The detection of a planetary ring of exoplanets remains one of the most attractive, but challenging, goals in the field of exoplanetary science. We present a methodology that implements a systematic search for exoplanetary rings via transit photometry of long-period planets. This methodology relies on a precise integration scheme that we develop to compute a transit light curve of a ringed planet. We apply the methodology to 89 long-period planet candidates from the Kepler data so as to estimate, and/or set upper limits on, the parameters of possible rings. While the majority of our samples do not have sufficient signal-to-noise ratios (S/Ns) to place meaningful constraints on ring parameters, we find that six systems with higher S/Ns are inconsistent with the presence of a ring larger than 1.5 times the planetary radius, assuming a grazing orbit and a tilted ring. Furthermore, we identify five preliminary candidate systems whose light curves exhibit ring-like features. After removing four false positives due to the contamination from nearby stars, we identify KIC 10403228 as a reasonable candidate for a ringed planet. A systematic parameter fit of its light curve with a ringed planet model indicates two possible solutions corresponding to a Saturn-like planet with a tilted ring. There also remain two other possible scenarios accounting for the data; a circumstellar disk and a hierarchical triple. Due to large uncertain factors, we cannot choose one specific model among the three.

Ring Theory

CERN Document Server

Jara, Pascual; Torrecillas, Blas

1988-01-01

The papers in this proceedings volume are selected research papers in different areas of ring theory, including graded rings, differential operator rings, K-theory of noetherian rings, torsion theory, regular rings, cohomology of algebras, local cohomology of noncommutative rings. The book will be important for mathematicians active in research in ring theory.

Measurement of a beam equilibrium orbit in the NAP-M storage ring

International Nuclear Information System (INIS)

Zagorodnikov, E.I.; Kalinin, A.S.; Medvedko, A.S.

1976-01-01

The equipment for measurement of the beam equilibrium orbit position in the NAP-M accumulator is described. The measurements are taken by the electrostatic transducers. The signals are delivered from the transducer electrodes to the source followers. At the output of the followers the signals are subtracted by the transformer with a volumetric coil. The total signal is picked off the common load of the followers. The further processing of the total and differential signals is performed with the 1st beam frequency harmonic and consists in rating of the differential signal for the beam current with subsequent synchronous detection. For discrimination of the 1st harmonic, a frequency converter employing field transistors has been designed. The problem of the increasing the accuracy of coincidence of the transmitter electric and geometric centers is discussed. The measuring system operates at the number of the particles on the orbit amounting to (1-2)x10 9 and the beam revesal frequency band within 0.36 - 2.5 MHz. The system has the beam displacement resolution of about 1 mm

Observation of helium flow induced beam orbit oscillations at RHIC

International Nuclear Information System (INIS)

Montag, C.; Bonati, R.; Brennan, J.M.; Butler, J.; Cameron, P.; Ganetis, G.; He, P.; Hirzel, W.; Jia, L.X.; Koello, P.; Louie, W.; McIntyre, G.; Nicoletti, A.; Rank, J.; Roser, T.; Satogata, T.; Schmalzle, J.; Sidi-Yekhlef, A.; Sondericker, J.; Tallerico, T.

2006-01-01

Horizontal beam orbit jitter at frequencies around 10 Hz has been observed at RHIC for several years. The distinct frequencies of this jitter have been found at superconducting low-beta quadrupole triplet magnets around the ring, where they coincide with mechanical vibration modes of the cold masses. Recently, we have identified liquid helium flow as the driving force of these oscillations

Mapping the Thermal Inertia of Saturn’s Rings with Cassini CIRS

Science.gov (United States)

Brooks, Shawn M.; Spilker, L. J.; PIlorz, S. H.; Showalter, M. R.

2013-10-01

We use data from Cassini's Composite Infrared Spectrometer to map out the thermal response of Saturn's ring particles passing through Saturn's shadow and to determine variations in ring thermal inertia. CIRS records far infrared radiation in three separate detectors, each of which covers a distinct wavelength range. In this work, we analyze rings spectra recorded at focal plane 1 (FP1), as its wavelength response (16.7-1000 microns) is well suited to detecting direct thermal emission from Saturn's rings. The thermal budget of the rings is typically dominated by solar radiation. When ring particles enter Saturn’s shadow this source of energy is abruptly cut off with a consequential drop in ring temperature. Likewise, temperatures rebound when particles exit the shadow. To characterize these heating and cooling events, FP1 was repeatedly scanned across the main rings. Each scan was offset from either the ingress or egress shadow boundary by an amount corresponding to a fraction of a Keplerian orbit. By resampling these scans onto a common radial grid, we can map out the rings’ response to the abrupt changes in insolation at shadow ingress and egress. Periods near equinox represent a unique situation. During this time the Sun's disk crosses the ring plane and its rays strike the rings at zero incidence. Solar heating is virtually absent, and thermal radiation from Saturn and sunlight reflected by Saturn dominate the thermal environment. While ring temperature variations at equinox are much more subtle, they represent temperature contrasts that vary at the unique timescale corresponding to variations in Saturn contributions to the rings’ thermal budget. By analyzing CIRS data at a variety of locations and epochs, we will map out thermal inertia across the rings and attempt to tease out structural information about the particles which comprise Saturn’s rings. This presentation will report upon our progress towards these ends. This research was carried out at the

Survey of Digital Feedback Systems in High Current Storage Rings

International Nuclear Information System (INIS)

Teytelman, Dmitry

2003-01-01

In the last decade demand for brightness in synchrotron light sources and luminosity in circular colliders led to construction of multiple high current storage rings. Many of these new machines require feedback systems to achieve design stored beam currents. In the same time frame the rapid advances in the technology of digital signal processing allowed the implementation of these complex feedback systems. In this paper I concentrate on three applications of feedback to storage rings: orbit control in light sources, coupled-bunch instability control, and low-level RF control. Each of these applications is challenging in areas of processing bandwidth, algorithm complexity, and control of time-varying beam and system dynamics. I will review existing implementations as well as comment on promising future directions

Quantum nano ring composed of quantum dots as a source of pure persistent spin or charge current

International Nuclear Information System (INIS)

Eslami, L.; Faizabadi, E.; Ahmadi, S.

2016-01-01

Spin-dependent persistent current in a quantum ring constituted by two normal and one magnetic quantum dots, in the presence of Rashba spin–orbit interaction is studied by using Green function technique. It is shown that the presence of the magnetic quantum dot breaks the degeneracy of the density of states of electrons with different spin states. Besides, the Rashba spin–orbit interaction along with the magnetic quantum dot develops tunable persistent spin and charge currents. Moreover, the persistent charge current induces a fully adjustable magnetic flux whose direction and magnitude can be tuned by altering the strength of the Rashba spin–orbit interaction. - Highlights: • An array of normal and magnetic quantum dots with Rashba effect is studied. • Spin-dependent persistent current and DOS are studied using Green function method. • The magnetic quantum dot breaks degeneracy of DOS of up and down spin electrons. • The persistent spin and charge currents are tuned by adjusting the Rashba constant. • The persistent charge current induces tunable magnetic field at the center of ring.

Noise destroys the coexistence of periodic orbits of a piecewise linear map

International Nuclear Information System (INIS)

Wang Can-Jun; Yang Ke-Li; Qu Shi-Xian

2013-01-01

The effects of Gaussian white noise and Gaussian colored noise on the periodic orbits of period-5 (P-5) and period-6 (P-6) in their coexisting domain of a piecewise linear map are investigated numerically. The probability densities of some orbits are calculated. When the noise intensity is D = 0.0001, only the orbits of P-5 exist, and the coexisting phenomenon is destroyed. On the other hand, the self-correlation time τ of the colored noise also affects the coexisting phenomenon. When τ c c , only the orbits of P-5 appear, and the stability of the orbits of P-5 is enhanced. However, when τ > τ' c (τ c and τ c ' are critical values), only the orbits of P-6 exist, and the stability of the P-6 orbits is enhanced greatly. When τ c , the orbits of P-5 and P-6 coexist, but the stability of the P-5 orbits is enhanced and that of P-6 is weakened with τ increasing

Achievement of ultralow emittance coupling in the Australian Synchrotron storage ring

Directory of Open Access Journals (Sweden)

R. Dowd

2011-01-01

Full Text Available Investigations into producing an electron beam with ultralow vertical emittance have been conducted using the Australian Synchrotron 3 GeV storage ring. A method of tuning the emittance coupling (ϵ_{y}/ϵ_{x} has been developed using a machine model calibrated through the linear optics from closed orbits method. Direct measurements of the beam emittance have not been possible due to diagnostic limitations, however two independent indirect measurements both indicate a vertical emittance of 1.2–1.3 pm rad (ϵ_{y}/ϵ_{x}=0.01%. Other indirect measurements support the validity of these results. This result is the smallest vertical emittance currently achieved in a storage ring.

Report of the eRHIC Ring-Ring Working Group

Energy Technology Data Exchange (ETDEWEB)

Aschenauer, E. C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Berg, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Blaskiewicz, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Brennan, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Fedotov, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Fischer, W. [Brookhaven National Lab. (BNL), Upton, NY (United States); Litvinenko, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Montag, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Palmer, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Parker, B. [Brookhaven National Lab. (BNL), Upton, NY (United States); Peggs, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Ptitsyn, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Ranjbar, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tepikian, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Trbojevic, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Willeke, F. [Brookhaven National Lab. (BNL), Upton, NY (United States)

2015-10-13

This report evaluates the ring-ring option for eRHIC as a lower risk alternative to the linac-ring option. The reduced risk goes along with a reduced initial luminosity performance. However, a luminosity upgrade path is kept open. This upgrade path consists of two branches, with the ultimate upgrade being either a ring-ring or a linac-ring scheme. The linac-ring upgrade could be almost identical to the proposed linac-ring scheme, which is based on an ERL in the RHIC tunnel. This linac-ring version has been studied in great detail over the past ten years, and its significant risks are known. On the other hand, no detailed work on an ultimate performance ring-ring scenario has been performed yet, other than the development of a consistent parameter set. Pursuing the ring-ring upgrade path introduces high risks and requires significant design work that is beyond the scope of this report.

LONG-TERM EVOLUTION OF DOUBLE WHITE DWARF BINARIES ACCRETING THROUGH DIRECT IMPACT

International Nuclear Information System (INIS)

Kremer, Kyle; Kalogera, Vassiliki; Sepinsky, Jeremy

2015-01-01

We calculate the long-term evolution of angular momentum in double white dwarf binaries undergoing direct impact accretion over a broad range of parameter space. We allow the rotation rate of both components to vary and account for the exchange of angular momentum between the spins of the white dwarfs and the orbit, while conserving the total angular momentum. We include gravitational, tidal, and mass transfer effects in the orbital evolution, and allow the Roche radius of the donor star to vary with both the stellar mass and the rotation rate. We examine the long-term stability of these systems, focusing in particular on those systems that may be progenitors of AM CVn or SNe Ia. We find that our analysis yields an increase in the predicted number of stable systems compared to that in previous studies. Additionally, we find that by properly accounting for the effects of asynchronism between the donor and the orbit on the Roche-lobe size, we eliminate oscillations in the orbital parameters, which were found in previous studies. Removing these oscillations can reduce the peak mass transfer rate in some systems, keeping them from entering an unstable mass transfer phase

INMS measures an influx of molecules from Saturn's rings

Science.gov (United States)

Perry, M. E.

2017-12-01

In 1984, Connerney and Waite proposed water influx from Saturn's rings to explain the low electron densities measured during Pioneer and Voyager radio occultation experiments. Charge exchange with this minor species depleted the H+ ions and provided a faster path to electron recombination. With ice the primary constituent of the rings, water was the most likely in-falling molecule. During the Grand Finale orbits, Cassini's Ion and Neutral Mass Spectrometer (INMS) detected and quantified an influx from the rings. Unexpectedly, the primary influx molecules are CH4 and a heavier carbon-bearing species. Water was detected, but quantities were factors of ten lower than these other species. Distribution in both altitude and latitude are consistent with a ring influx. The concentration of the minor species in Saturn's atmosphere shows that they enter Saturn's atmosphere from the top. Both molecules have their highest concentrations at the highest altitudes, with concentrations >0.4% at 3,500 km altitude and only 0.02% at 2,700 km. Molecules from the rings deorbit to Saturn's atmosphere at altitudes near 4,000 km, consistent with the INMS measurements. The latitudinal dependence of the minor species indicates that their source is near the equatorial plane. At high altitudes, the minor species were observed primarily at zero latitude, where the 28u species was six times more concentrated than at 5° latitude. At lower altitudes, the peaking ratio was 1, indicating that the species had diffused and was fully mixed into Saturn's H2 atmosphere. The lighter molecule, CH4, diffuses more rapidly than the 28u species. INMS also detected both of these species during the earlier F-ring passes, finding that the neutrals were centered at the ring plane and extended 3,000 km (half width, half max) north and south.

A dusty road connecting Saturn and its rings - preliminary results from Cassini Cosmic Dust Analyser during the Grand Finale Mission

Science.gov (United States)

Hsu, S.; Burton, M. E.; Horanyi, M.; Kempf, S.; Khawaja, N.; Moragas-Klostermeyer, G.; Postberg, F.; Schirdenwahn, D.; Seiss, M.; Schmidt, J.; Spahn, F.; Srama, R.

2017-12-01

The Cosmic Dust Analyzer observations during the Cassini Grand Finale Orbits were designed for the in situ characterization of Saturn's ring composition and to study their interaction with the host planet. It is found that the gap between the inner most D ring and Saturn is almost free of larger, micron-sized dust grains but rich in nanodust particles (radius smaller than 100 nm) that only become detectable by CDA because of the high spacecraft speed of 30 km/s through this region. Regarding the grain composition, while the majority of CDA mass spectra recorded during this phase are too faint to be individually calibrated, two types of mass spectra have been identified - water ice and silicates. These two types of grains were detected at different locations with respect to the ring plane, indicating that there are compositional differences across the rings. As for the dynamics, the observations confirm the transport of charged nanodust from the main rings along magnetic field lines to the planet, as previously proposed. The agreement between the simulated density profile and the observation strongly suggests nanodust as a pathway of ring-planet interaction associated with both exogenous (e.g., impactor ejecta) and endogenous (ionospheric plasma charging) processes. CDA measurements do not indicate significant temporal variation during the the Grand Finale orbits. The measured flux corresponds to a mass transport of < 0.1 kg/sec from the main rings to Saturn in the form of nanodust, with most of the deposition occurring near the equator.

Habitable planets around white and brown dwarfs: the perils of a cooling primary.

Science.gov (United States)

Barnes, Rory; Heller, René

2013-03-01

White and brown dwarfs are astrophysical objects that are bright enough to support an insolation habitable zone (IHZ). Unlike hydrogen-burning stars, they cool and become less luminous with time; hence their IHZ moves in with time. The inner edge of the IHZ is defined as the orbital radius at which a planet may enter a moist or runaway greenhouse, phenomena that can remove a planet's surface water forever. Thus, as the IHZ moves in, planets that enter it may no longer have any water and are still uninhabitable. Additionally, the close proximity of the IHZ to the primary leads to concern that tidal heating may also be strong enough to trigger a runaway greenhouse, even for orbital eccentricities as small as 10(-6). Water loss occurs due to photolyzation by UV photons in the planetary stratosphere, followed by hydrogen escape. Young white dwarfs emit a large amount of these photons, as their surface temperatures are over 10(4) K. The situation is less clear for brown dwarfs, as observational data do not constrain their early activity and UV emission very well. Nonetheless, both types of planets are at risk of never achieving habitable conditions, but planets orbiting white dwarfs may be less likely to sustain life than those orbiting brown dwarfs. We consider the future habitability of the planet candidates KOI 55.01 and 55.02 in these terms and find they are unlikely to become habitable.

Spin-orbit coupling and applied magnetic field effects on electromagnetically induced transparency of a quantum ring at finite temperature

Science.gov (United States)

Zamani, A.; Setareh, F.; Azargoshasb, T.; Niknam, E.

2018-03-01

A wide variety of semiconductor nanostructures have been fabricated and studied experimentally and alongside theoretical investigations show the great role they have in new generation opto-electronic devices. However, mathematical modeling provide important information due to their definitive goal of predicting features and understanding of such structures' behavior under different circumstances. Hence, in the current work, the effects of applied magnetic field, temperature and dimensions of the structure on the electromagnetically induced transparency (EIT) of a GaAs quantum ring are studied while both Rashba and Dresselhaus spin-orbit interactions (SOI) are taken into account. The Schrödinger equation is solved in cylindrical coordinate with axial symmetry and in order to study the EIT, the imaginary (absorption) and real (refractive index) parts of susceptibility as well as the group velocity of the probe light pulse are investigated. The absorption and refractive index plots show that, for a specific frequency of probe field the absorption vanishes and refractive index becomes unity (known as EIT) while around such frequency the group index is positive (sub-luminal probe propagation) and for higher and lower frequencies it alters to negative (super-luminal probe propagation). The numerical results reveal that the EIT frequency, transparency window and sub(super)-luminal frequency intervals shift as we change applied magnetic field, temperature and also the structure dimensions.

Photon-induced tunability of the thermospin current in a Rashba ring

Science.gov (United States)

Abdullah, Nzar Rauf; Arnold, Thorsten; Tang, Chi-Shung; Manolescu, Andrei; Gudmundsson, Vidar

2018-04-01

The goal of this work is to show how the thermospin polarization current in a quantum ring changes in the presence of Rashba spin-orbit coupling and a quantized single photon mode of a cavity the ring is placed in. Employing the reduced density operator and a general master equation formalism, we find that both the Rashba interaction and the photon field can significantly modulate the spin polarization and the thermospin polarization current. Tuning the Rashba coupling constant, degenerate energy levels are formed corresponding to the Aharonov-Casher destructive phase interference in the quantum ring system. Our analysis indicates that the maximum spin polarization can be observed at the points of degenerate energy levels due to spin accumulation in the system without the photon field. The thermospin current is thus suppressed. In the presence of the cavity, the photon field leads to an additional kinetic momentum of the electron. As a result the spin polarization can be enhanced by the photon field.

High Precision Optical Observations of Space Debris in the Geo Ring from Venezuela

Science.gov (United States)

Lacruz, E.; Abad, C.; Downes, J. J.; Casanova, D.; Tresaco, E.

2018-01-01

We present preliminary results to demonstrate that our method for detection and location of Space Debris (SD) in the geostationary Earth orbit (GEO) ring, based on observations at the OAN of Venezuela is of high astrometric precision. A detailed explanation of the method, its validation and first results is available in (Lacruz et al. 2017).

Beam separation for p-anti p collisions in a single ring in the multibunch mode

International Nuclear Information System (INIS)

Berley, D.; Garren, A.A.; Month, M.

1978-01-01

A discussion is given of proton-antiproton colliding beam operation in storage rings. Some means of separating the beams at points where no experiment is being performed seems to be an important feature for a p-anti p colliding beam ring. By exciting a betatron oscillation in some appropriate, localized region, one could create a specific collision point while at the same time cause the p and anti p beams to oscillate in opposition so that their orbits meet at only a small number of points, roughly given by twice the tune, 2ν

Localized persistent spin currents in defect-free quasiperiodic rings with Aharonov–Casher effect

International Nuclear Information System (INIS)

Qiu, R.Z.; Chen, C.H.; Cheng, Y.H.; Hsueh, W.J.

2015-01-01

We propose strongly localized persistent spin current in one-dimensional defect-free quasiperiodic Thue–Morse rings with Aharonov–Casher effect. The results show that the characteristics of these localized persistent currents depend not only on the radius filling factor, but also on the strength of the spin–orbit interaction. The maximum persistent spin currents in systems always appear in the ring near the middle position of the system array whether or not the Thue–Morse rings array is symmetrical. The magnitude of the persistent currents is proportional to the sharpness of the resonance peak, which is dependent on the bandwidth of the allowed band in the band structure. The maximum persistent spin currents also increase exponentially as the generation order of the system increases. - Highlights: • Strongly localized persistent spin current in quasiperiodic AC rings is proposed. • Localized persistent spin currents are much larger than those produced by traditional mesoscopic rings. • Characteristics of the localized persistent currents depend on the radius filling factor and SOI strength. • The maximum persistent current increases exponentially with the system order. • The magnitude of the persistent currents is related to the sharpness of the resonance

Photochemistry in Saturn's Ring-Shadowed Atmosphere: Modulation of Hydrocarbons and Observations of Dust Content

Science.gov (United States)

Edgington, S. G.; Atreya, S. K.; Wilson, E. H.; Baines, K. H.; West, R. A.; Bjoraker, G. L.; Fletcher, L. N.; Momary, T.

2016-12-01

Cassini has been orbiting Saturn for over twelve years now. During this epoch, the ring shadow has moved from covering much of the northern hemisphere with solar inclination of 24 degrees to covering a large swath south of the equator and it continues to move southward. At Saturn Orbit Insertion in 2004, the projection of the A-ring onto Saturn reached as far as 40N along the central meridian (52N at the terminator). At its maximum extent, the ring shadow can reach as far as 48N/S (58N/S at the terminator). The net effect is that the intensity of both ultraviolet and visible sunlight penetrating through the rings to any particular latitude will vary depending on both Saturn's axis relative to the Sun and the optical thickness of each ring system. In essence, the rings act like semi-transparent venetian blinds.Previous work examined the variation of the solar flux as a function of solar inclination, i.e. for each 7.25-year season at Saturn. Here, we report on the impact of the oscillating ring shadow on the photolysis and production rates of hydrocarbons (acetylene, ethane, propane, and benzene) and phosphine in Saturn's stratosphere and upper troposphere. The impact of these production and loss rates on the abundance of long-lived photochemical products leading to haze formation are explored. We assess their impact on phosphine abundance, a disequilibrium species whose presence in the upper troposphere can be used as a tracer of convective processes in the deeper atmosphere.We will also present our ongoing analysis of Cassini's CIRS, UVIS, and VIMS datasets that provide an estimate of the evolving haze content of the northern hemisphere and we will begin to assess the implications for dynamical mixing. In particular, we will examine how the now famous hexagonal jet stream acts like a barrier to transport, isolating Saturn's north polar region from outside transport of photochemically-generated molecules and haze.The research described in this paper was carried out

ASSOCIATIVE RINGS SOLVED AS LIE RINGS

Directory of Open Access Journals (Sweden)

M. B. Smirnov

2011-01-01

Full Text Available The paper has proved that an associative ring which is solvable of a n- class as a Lie ring has a nilpotent ideal of the nilpotent class not more than 3×10n–2  and a corresponding quotient ring satisfies an identity [[x1, x2, [x3, x4

Low energy plasma observations at synchronous orbit

International Nuclear Information System (INIS)

Reasoner, D.L.; Lennartsson, W.

1977-08-01

The University of California at San Diego Auroral Particles Experiment on the ATS-6 Satellite in synchronous orbit has detected a low-energy plasma population which is separate and distinct from both the ring current and plasma sheet populations. These observations suggest that this plasma is the outer zone of the plasmasphere. During magnetically active periods, this low energy plasma is often observed flowing sunward. In the dusk sector, enhanced plasma flow is often observed for 1-2 hours prior to the onset of a substorm-associated particle injection. (author)

Optimization of magnet sorting in a storage ring using genetic algorithms

International Nuclear Information System (INIS)

Chen Jia; Wang Lin; Li Weimin; Gao Weiwei

2013-01-01

In this paper, the genetic algorithms are applied to the optimization problem of magnet sorting in an electron storage ring, according to which the objectives are set so that the closed orbit distortion and beta beating can be minimized and the dynamic aperture maximized. The sorting of dipole, quadrupole and sextupole magnets is optimized while the optimization results show the power of the application of genetic algorithms in magnet sorting. (authors)

Noncircular features in Saturn's rings IV: Absolute radius scale and Saturn's pole direction

Science.gov (United States)

French, Richard G.; McGhee-French, Colleen A.; Lonergan, Katherine; Sepersky, Talia; Jacobson, Robert A.; Nicholson, Philip D.; Hedman, Mathew M.; Marouf, Essam A.; Colwell, Joshua E.

2017-07-01

We present a comprehensive solution for the geometry of Saturn's ring system, based on orbital fits to an extensive set of occultation observations of 122 individual ring edges and gaps. We begin with a restricted set of very high quality Cassini VIMS, UVIS, and RSS measurements for quasi-circular features in the C and B rings and the Cassini Division, and then successively add suitably weighted additional Cassini and historical occultation measurements (from Voyager, HST and the widely-observed 28 Sgr occultation of 3 Jul 1989) for additional non-circular features, to derive an absolute radius scale applicable across the entire classical ring system. As part of our adopted solution, we determine first-order corrections to the spacecraft trajectories used to determine the geometry of individual occultation chords. We adopt a simple linear model for Saturn's precession, and our favored solution yields a precession rate on the sky n^˙P = 0.207 ± 0 .006‧‧yr-1 , equivalent to an angular rate of polar motion ΩP = 0.451 ± 0 .014‧‧yr-1 . The 3% formal uncertainty in the fitted precession rate is approaching the point where it can provide a useful constraint on models of Saturn's interior, although realistic errors are likely to be larger, given the linear approximation of the precession model and possible unmodeled systematic errors in the spacecraft ephemerides. Our results are largely consistent with independent estimates of the precession rate based on historical RPX times (Nicholson et al., 1999 AAS/Division for Planetary Sciences Meeting Abstracts #31 31, 44.01) and from theoretical expectations that account for Titan's 700-yr precession period (Vienne and Duriez 1992, Astronomy and Astrophysics 257, 331-352). The fitted precession rate based on Cassini data only is somewhat lower, which may be an indication of unmodeled shorter term contributions to Saturn's polar motion from other satellites, or perhaps the result of inconsistencies in the assumed

THE CORE COMPOSITION OF A WHITE DWARF IN A CLOSE DOUBLE-DEGENERATE SYSTEM

International Nuclear Information System (INIS)

Vennes, S.; Kawka, A.

2012-01-01

We report the identification of the double-degenerate system NLTT 16249 that comprises a normal, hydrogen-rich (DA) white dwarf and a peculiar, carbon-polluted white dwarf (DQ) showing photospheric traces of nitrogen. We disentangled the observed spectra and constrained the properties of both stellar components. In the evolutionary scenario commonly applied to the sequence of DQ white dwarfs, both carbon and nitrogen would be dredged up from the core. The C/N abundance ratio (≈50) in the atmosphere of this unique DQ white dwarf suggests the presence of unprocessed material ( 14 N) in the core or in the envelope. Helium burning in the DQ progenitor may have terminated early on the red giant branch after a mass-ejection event leaving unprocessed material in the core, although current mass estimates do not favor the presence of a low-mass helium core. Alternatively, some nitrogen in the envelope may have survived an abridged helium-core burning phase prior to climbing the asymptotic giant branch. Based on available data, we estimate a relatively short orbital period (P ∼< 13 hr) and ongoing spectroscopic observations will help determine precise orbital parameters.

Habitable Planets Around White and Brown Dwarfs: The Perils of a Cooling Primary

Science.gov (United States)

Heller, René

2013-01-01

Abstract White and brown dwarfs are astrophysical objects that are bright enough to support an insolation habitable zone (IHZ). Unlike hydrogen-burning stars, they cool and become less luminous with time; hence their IHZ moves in with time. The inner edge of the IHZ is defined as the orbital radius at which a planet may enter a moist or runaway greenhouse, phenomena that can remove a planet's surface water forever. Thus, as the IHZ moves in, planets that enter it may no longer have any water and are still uninhabitable. Additionally, the close proximity of the IHZ to the primary leads to concern that tidal heating may also be strong enough to trigger a runaway greenhouse, even for orbital eccentricities as small as 10−6. Water loss occurs due to photolyzation by UV photons in the planetary stratosphere, followed by hydrogen escape. Young white dwarfs emit a large amount of these photons, as their surface temperatures are over 104 K. The situation is less clear for brown dwarfs, as observational data do not constrain their early activity and UV emission very well. Nonetheless, both types of planets are at risk of never achieving habitable conditions, but planets orbiting white dwarfs may be less likely to sustain life than those orbiting brown dwarfs. We consider the future habitability of the planet candidates KOI 55.01 and 55.02 in these terms and find they are unlikely to become habitable. Key Words: Extrasolar terrestrial planets—Habitability—Habitable zone—Tides—Exoplanets. Astrobiology 13, 279–291. PMID:23537137

Structured LDPC Codes over Integer Residue Rings

Directory of Open Access Journals (Sweden)

Mo Elisa

2008-01-01

Full Text Available Abstract This paper presents a new class of low-density parity-check (LDPC codes over represented by regular, structured Tanner graphs. These graphs are constructed using Latin squares defined over a multiplicative group of a Galois ring, rather than a finite field. Our approach yields codes for a wide range of code rates and more importantly, codes whose minimum pseudocodeword weights equal their minimum Hamming distances. Simulation studies show that these structured codes, when transmitted using matched signal sets over an additive-white-Gaussian-noise channel, can outperform their random counterparts of similar length and rate.

An electrostatic storage ring for low kinetic energy electron collisions

Energy Technology Data Exchange (ETDEWEB)

Reddish, T J; Tessier, D R; Sullivan, M R; Thorn, P A [Department of Physics, University of Windsor, Windsor, N9B 3P4 (Canada); Hammond, P; Alderman, A J [School of Physics, CAMSP, University of Western Australia, Perth WA 6009 (Australia); Read, F H [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom)

2009-11-01

The criteria are presented for stable multiple orbits of charged particles in a race-track shaped storage ring and applied to an electrostatic system consisting of two hemispherical deflector analyzers (HDA) connected by two separate sets of cylindrical lenses. The results of charged particle simulations and the formal matrix theory, including aberrations in the energy-dispersive electrostatic 'prisms', are in good agreement with the observed experimental operating conditions for this Electron Recycling Spectrometer (ERS).

Equatorial circular orbits in the Kerr-de Sitter spacetimes

International Nuclear Information System (INIS)

Stuchlik, Zdenek; Slany, Petr

2004-01-01

Equatorial motion of test particles in Kerr-de Sitter spacetimes is considered. Circular orbits are determined, their properties are discussed for both black-hole and naked-singularity spacetimes, and their relevance for thin accretion disks is established. The circular orbits constitute two families that coalesce at the so-called static radius. The orientation of the motion along the circular orbits is, in accordance with case of asymptotically flat Kerr spacetimes, defined by relating the motion to the locally nonrotating frames. The minus-family orbits are all counterrotating, while the plus-family orbits are usually corotating relative to these frames. However, the plus-family orbits become counterrotating in the vicinity of the static radius in all Kerr-de Sitter spacetimes, and they become counterrotating in the vicinity of the ring singularity in Kerr-de Sitter naked-singularity spacetimes with a low enough rotational parameter. In such spacetimes, the efficiency of the conversion of the rest energy into heat energy in the geometrically thin plus-family accretion disks can reach extremely high values exceeding the efficiency of the annihilation process. The transformation of a Kerr-de Sitter naked singularity into an extreme black hole due to accretion in the thin disks is briefly discussed for both the plus-family and minus-family disks. It is shown that such a conversion leads to an abrupt instability of the innermost parts of the plus-family accretion disks that can have strong observational consequences

Mapping Ring Particle Cooling across Saturn's Rings with Cassini CIRS

Science.gov (United States)

Brooks, Shawn M.; Spilker, L. J.; Edgington, S. G.; Pilorz, S. H.; Deau, E.

2010-10-01

Previous studies have shown that the rings' thermal inertia, a measure of their response to changes in the thermal environment, varies from ring to ring. Thermal inertia can provide insight into the physical structure of Saturn's ring particles and their regoliths. Low thermal inertia and quick temperature responses are suggestive of ring particles that have more porous or fluffy regoliths or that are riddled with cracks. Solid, coherent particles can be expected to have higher thermal inertias (Ferrari et al. 2005). Cassini's Composite Infrared Spectrometer has recorded millions of spectra of Saturn's rings since its arrival at Saturn in 2004 (personal communication, M. Segura). CIRS records far infrared radiation between 10 and 600 cm-1 (16.7 and 1000 µm) at focal plane 1 (FP1), which has a field of view of 3.9 mrad. Thermal emission from Saturn's rings peaks in this wavelength range. FP1 spectra can be used to infer ring temperatures. By tracking how ring temperatures vary, we can determine the thermal inertia of the rings. In this work we focus on CIRS observations of the shadowed portion of Saturn's rings. The thermal budget of the rings is dominated by the solar radiation absorbed by its constituent particles. When ring particles enter Saturn's shadow this source of energy is abruptly cut off. As a result, ring particles cool as they traverse Saturn's shadow. From these shadow observations we can create cooling curves at specific locations across the rings. We will show that the rings' cooling curves and thus their thermal inertia vary not only from ring to ring, but by location within the individual rings. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2010 California Institute of Technology. Government sponsorship acknowledged.

CIRS High-Resolution Thermal Scans and the Structure of Saturn's B Ring

Science.gov (United States)

Brooks, S. M.; Spilker, L. J.; Showalter, M.; Pilorz, S.; Edgington, S. G.

2017-12-01

The flyby of Titan on November 29, 2016, sent the Cassini spacecraft on a trajectory that would take it within 10,000 kilometers of Saturn's F ring multiple times before a subsequent Titan encounter on April 22, 2017, would send it on ballistic trajectory carrying it between Saturn's cloud tops and the planet's D ring for several flybys. This geometry has proven beneficial for high-resolution studies of the rings, not just because of Cassini's proximity to the rings, but also because of the spacecraft's high elevation angle above the rings, which reduces the foreshortening that tends to degrade resolution in the ring plane. We will report on several observations of Saturn's main rings at the high spatial resolutions enabled by the end-of-mission geometry, particulary the B ring, with the Composite Infrared Spectrometer onboard Cassini during the F-ring and proximal orbits. CIRS' three infrared detectors cover a combined spectral range of 10 to 1400 cm-1 (1 mm down to 7 microns). We focus on data from Focal Plane 1, which covers the 10 to 600 cm-1 range (1 mm to 16 microns). The apodized spectral resolution of the instrument can be varied from 15 cm-1 to 0.5 cm-1 (Flasar et al. 2004). FP1's wavelength range makes it well-suited to sensing thermal emission from objects at temperatures typical of Saturn's rings. Correlating ring optical depth with temperatures retrieved from scans of the face of the rings exposed to direct solar illumination (the lit face) and the opposite (unlit) face suggests differences in ring structure or particle transport between the lit and unlit sides of the rings in different regions of the B ring. Lit side temperatures in the core of the B ring range between 82 and 87 K; temperatures on the unlit side of the core vary from 66 K up to 74 K. Ferrari and Reffet (2013) and Pilorz et al. (2015) published thorough analyses of the thermal throughput across this optically thick ring. We will discuss these recent CIRS rings observations and their

DFT Study of the Structure, Reactivity, Natural Bond Orbital and Hyperpolarizability of Thiazole Azo Dyes

Directory of Open Access Journals (Sweden)

Osman I. Osman

2017-02-01

Full Text Available The structure, reactivity, natural bond orbital (NBO, linear and nonlinear optical (NLO properties of three thiazole azo dyes (A, B and C were monitored by applying B3LYP, CAM-B3LYP and ωB97XD functionals with 6-311++G** and aug-cc-pvdz basis sets. The geometrical parameters,dipolemoments,HOMO-LUMO(highest occupied molecular orbital,lowest unoccupied molecular orbital energy gaps, absorption wavelengths and total hyperpolarizabilities were investigated in carbon tetrachloride (CCl4 chloroform (CHCl3, dichloromethane (CH2Cl2 and dimethlysulphoxide (DMSO. The donor methoxyphenyl group deviates from planarity with the thiazole azo moiety by ca. 38◦; while the acceptor dicyanovinyl, indandione and dicyanovinylindanone groups diverge by ca. 6◦. The HOMOs for the three dyes are identical. They spread over the methoxyphenyl donor moiety, the thiazole and benzene rings as π-bonding orbitals. The LUMOs are shaped up by the nature of the acceptor moieties. The LUMOs of the A, B and C dyes extend over the indandione, malononitrile and dicyanovinylindanone acceptor moieties, respectively, as π-antibonding orbitals. The HOMO-LUMO splittings showed that Dye C is much more reactive than dyes A and B. Compared to dyes A and B, Dye C yielded a longer maximum absorption wavelength because of the stabilization of its LUMOs relative to those of the other two. The three dyes show solvatochromism accompanied by significant increases in hyperpolarizability. The enhancement of the total hyperpolarizability of C compared to those of A and B is due to the cumulative action of the long π-conjugation of the indanone ring and the stronger electron-withdrawing ability of the dicyanovinyl moiety that form the dicyanovinylindanone acceptor group. These findings are facilitated by a natural bond orbital (NBO technique. The very high total hyperpolarizabilities of the three dyes define their potent nonlinear optical (NLO behaviour.

Performance and upgrades of the NSLS storage rings and photon sources

International Nuclear Information System (INIS)

1991-01-01

The usefulness of synchrotron radiation sources is not only determined by current, energy and magnetic field but also orbit stability and lifetime. The status and developments at NSLS in storage ring performance are discussed. Efforts at NSLS to look toward the future in source development are presented. In particular, small gap undulator development and studies toward development of UV Free Electron Laser at the Accelerator Test Facility are described. 5 refs., 2 figs., 1 tab

High Resolution BPM Upgrade for the ATF Damping Ring at KEK

International Nuclear Information System (INIS)

Eddy, N.; Briegel, C.; Fellenz, B.; Gianfelice-Wendt, E.; Prieto, P.; Rechenmacher, R.; Semenov, A.; Voy, D.; Wendt, M.; Zhang, D.; Terunuma, N.

2011-01-01

A beam position monitor (BPM) upgrade at the KEK Accelerator Test Facility (ATF) damping ring has been accomplished, carried out by a KEK/FNAL/SLAC collaboration under the umbrella of the global ILC R and D effort. The upgrade consists of a high resolution, high reproducibility read-out system, based on analog and digital down-conversion techniques, digital signal processing, and also implements a new automatic gain error correction schema. The technical concept and realization as well as results of beam studies are presented. The next generation of linear colliders require ultra-low vertical emittance of <2 pm-rad. The damping ring at the KEK Accelerator Test Facility (ATF) is designed to demonstrate this mission critical goal. A high resolution beam position monitor (BPM) system for the damping ring is one of the key tools for realizing this goal. The BPM system needs to provide two distnict measurements. First, a very high resolution (∼100-200nm) closed-orbit measurement which is averaged over many turns and realized with narrowband filter techniques - 'narrowband mode'. This is needed to monitor and steer the beam along an optimum orbit and to facilitate beam-based alignment to minimize non-linear field effects. Second, is the ability to make turn by turn (TBT) measurements to support optics studies and corrections necessary to achieve the design performance. As the TBT measurement necessitates a wider bandwidth, it is often referred to as 'wideband mode'. The BPM upgrade was initiated as a KEK/SLAC/FNAL collaboration in the frame of the Global Design Initiative of the International Linear Collider. The project was realized and completed using Japan-US funds with Fermilab as the core partner.

Observations of ions of ionospheric origin in the storm-time ring current

International Nuclear Information System (INIS)

Johnson, R.G.; Sharp, R.D.; Shelley, E.G.

1977-01-01

O + , He + , and H + ions in the energy range 0.5 to 16 keV have been observed in the storm-time ring current with an energetic ion mass spectrometer aboard the polar-orbiting S3-3 satellite. During the main phases of the 29 December 1976, 6 April 1977, and 19 April 1977 magnetic storms, the O + number density within the instrument energy range in the inner ring current (L=2.8--4.0) was larger than the H + density in the altitude range from about 5000--7000 km. At two days after the main phase of the 29 December 1976 storm, O + was still the dominant ion at MLT=14.5 hours in the L=2.6--3.4 range at altitudes near 6000 km

An Ionosphere/Magnetosphere Coupling Current System Located in the Gap Between Saturn and its Rings

Science.gov (United States)

Khurana, K. K.; Dougherty, M. K.; Cao, H.; Hunt, G. J.; Provan, G.

2017-12-01

The Grand Finale Orbits of the Cassini spacecraft traversed through Saturn's D ring and brought the spacecraft to within 3000 km of Saturn's cloud tops. The closest approaches (CA) were near the equatorial plane of Saturn and were distributed narrowly around the local noon. The difference field (observations - internal field - magnetospheric ring current field) obtained from the Grand Finale orbits show persistent residual fields centered around the CA which diminish at higher latitudes on field lines that connect to the ring. Modeling of this perturbation in terms of internal harmonics shows that the perturbation is not of internal origin but is produced by external currents that couple the ionosphere to the magnetosphere. The sense of the current system suggests that the southern feet of the field lines in the ionosphere lead their northern footprints. We show that the observed field perturbations are consistent with a meridional Pedersen current whose strength is 1 MA/radian, i.e. comparable in strength to the Planetary-period-oscillation related current systems observed in the auroral zone. We show that the implied Lorentz force in the ionosphere extracts momentum from the faster moving southern ionosphere and passes it on to the northern ionosphere. We discuss several ideas for generating this current system. In particular, we highlight a mechanism that involves shears in the neutral winds in the thermospheric region to generate the observed magnetic field.

TIDAL NOVAE IN COMPACT BINARY WHITE DWARFS

International Nuclear Information System (INIS)

Fuller, Jim; Lai Dong

2012-01-01

Compact binary white dwarfs (WDs) undergoing orbital decay due to gravitational radiation can experience significant tidal heating prior to merger. In these WDs, the dominant tidal effect involves the excitation of outgoing gravity waves in the inner stellar envelope and the dissipation of these waves in the outer envelope. As the binary orbit decays, the WDs are synchronized from outside in (with the envelope synchronized first, followed by the core). We examine the deposition of tidal heat in the envelope of a carbon-oxygen WD and study how such tidal heating affects the structure and evolution of the WD. We show that significant tidal heating can occur in the star's degenerate hydrogen layer. This layer heats up faster than it cools, triggering runaway nuclear fusion. Such 'tidal novae' may occur in all WD binaries containing a CO WD, at orbital periods between 5 minutes and 20 minutes, and precede the final merger by 10 5 -10 6 years.

WHITE DWARF/M DWARF BINARIES AS SINGLE DEGENERATE PROGENITORS OF TYPE Ia SUPERNOVAE

International Nuclear Information System (INIS)

Wheeler, J. Craig

2012-01-01

Limits on the companions of white dwarfs in the single-degenerate scenario for the origin of Type Ia supernovae (SNe Ia) have gotten increasingly tight, yet igniting a nearly Chandrasekhar mass C/O white dwarf from a condition of near hydrostatic equilibrium provides compelling agreement with observed spectral evolution. The only type of non-degenerate stars that survive the tight limits, M V ∼> 8.4 on the SN Ia in SNR 0509-67.5 and M V ∼> 9.5 in the remnant of SN 1572, are M dwarfs. While M dwarfs are observed in cataclysmic variables, they have special properties that have not been considered in most work on the progenitors of SNe Ia: they have small but finite magnetic fields and they flare frequently. These properties are explored in the context of SN Ia progenitors. White dwarf/M dwarf pairs may be sufficiently plentiful to provide, in principle, an adequate rate of explosions even with slow orbital evolution due to magnetic braking or gravitational radiation. Even modest magnetic fields on the white dwarf and M dwarf will yield adequate torques to lock the two stars together, resulting in a slowly rotating white dwarf, with the magnetic poles pointing at one another in the orbital plane. The mass loss will be channeled by a 'magnetic bottle' connecting the two stars, landing on a concentrated polar area on the white dwarf. This enhances the effective rate of accretion compared to spherical accretion. Luminosity from accretion and hydrogen burning on the surface of the white dwarf may induce self-excited mass transfer. The combined effects of self-excited mass loss, polar accretion, and magnetic inhibition of mixing of accretion layers give possible means to beat the 'nova limit' and grow the white dwarf to the Chandrasekhar mass even at rather moderate mass accretion rates.

The dipole corrector magnets for the RHIC fast global orbit feedback system

International Nuclear Information System (INIS)

Thieberger, P.; Arnold, L.; Folz, C.; Hulsart, R.; Jain, A.; Karl, R.; Mahler, G.; Meng, W.; Mernick, K.; Michnoff, R.; Minty, M.; Montag, C.; Ptitsyn, V.; Ritter, J.; Smart, L.; Tuozzolo, J.; White, J.

2011-01-01

The recently completed RHIC fast global orbit feedback system uses 24 small 'window-frame' horizontal dipole correctors. Space limitations dictated a very compact design. The magnetic design and modelling of these laminated yoke magnets is described as well as the mechanical implementation, coil winding, vacuum impregnation, etc. Test procedures to determine the field quality and frequency response are described. The results of these measurements are presented and discussed. A small fringe field from each magnet, overlapping the opposite RHIC ring, is compensated by a correction winding placed on the opposite ring's magnet and connected in series with the main winding of the first one. Results from measurements of this compensation scheme are shown and discussed.

Characterizing Accreting Double White Dwarf Binaries with the Laser Interferometer Space Antenna and Gaia

Science.gov (United States)

Breivik, Katelyn; Kremer, Kyle; Bueno, Michael; Larson, Shane L.; Coughlin, Scott; Kalogera, Vassiliki

2018-02-01

We demonstrate a method to fully characterize mass-transferring double white dwarf (DWD) systems with a helium-rich (He) white dwarf (WD) donor based on the mass–radius (M–R) relationship for He WDs. Using a simulated Galactic population of DWDs, we show that donor and accretor masses can be inferred for up to ∼60 systems observed by both Laser Interferometer Space Antenna (LISA) and Gaia. Half of these systems will have mass constraints {{Δ }} {M}{{D}} ≲ 0.2 {M}ȯ and {{Δ }} {M}{{A}} ≲ 2.3 {M}ȯ . We also show how the orbital frequency evolution due to astrophysical processes and gravitational radiation can be decoupled from the total orbital frequency evolution for up to ∼50 of these systems.

Electron spin polarization in high-energy storage rings

International Nuclear Information System (INIS)

Mane, S.R.

1987-01-01

In a high energy storage ring, a single photon emission has relatively little effect on the orbital motion, but it can produce a relatively large change in the electron spin state. Hence the unperturbed orbital motion can be satisfactorily described using classical mechanics, but the spin must be treated quantum mechanically. The electron motion is therefore treated semi-classically in this thesis. It is explained how to diagonalize the unperturbed Hamiltonian to the leading order in Planck's constant. The effects of perturbations are then included, and the relevant time-scales and ensemble averages are elucidated. The Derbenev-Kondratenko formula for the equilibrium degree of polarization is rederived. Mathematical details of the rederivation are given. Since the original authors used a different formalism, a proof is offered of the equivalence between their method and the one used in this thesis. An algorithm is also presented to evaluate the equilibrium polarization. It has a number of new features, which enable the polarization to be calculated to a higher degree of approximation than has hitherto been possible. This facilitates the calculation of so-called spin resonances, which are points at which the polarization almost vanishes. A computer program has been written to implement the above algorithm, in the approximation of linear orbital dynamics, and sample results are presented

Analysis of closed orbit deviations for a first direct deuteron electric dipole moment measurement at the cooler synchrotron COSY

Science.gov (United States)

Schmidt, V.; Lehrach, A.

2017-07-01

The Jülich Electric Dipole moment Investigations (JEDI) collaboration in Julich is preparing a direct EDM measurement of protons and deuterons first at the storage ring COSY (COoler SYnchrotron) and later at a dedicated storage ring. Ensuring a precise measurement, various beam and spin manipulating effects have to be considered and investigated. A distortion of the closed orbit is one of the major sources for systematic uncertainties. Therefore misalignments of magnets and residual power supply oscillations are simulated using the MAD-X code in order to analyse their effect on the orbit. The underlying model for all simulations includes the dipoles, quadrupoles and sextupoles at COSY as well as the corrector magnets and BPMs (Beam Position Monitors). Since most sextupoles are only used during beam extraction, the sextupole strengths are set to zero resulting in a linear machine. The optics is adjusted in a way that the dispersion is zero in the straight sections. The closed orbit studies are performed for deuterons with a momentum of 970 MeV/c.

KOI 1224: A FOURTH BLOATED HOT WHITE DWARF COMPANION FOUND WITH KEPLER

International Nuclear Information System (INIS)

Breton, R. P.; Van Kerkwijk, M. H.; Rappaport, S. A.; Carter, J. A.

2012-01-01

We present an analysis and interpretation of the Kepler binary system KOI 1224. This is the fourth binary found with Kepler that consists of a thermally bloated, hot white dwarf in a close orbit with a more or less normal star of spectral class A or F. As we show, KOI 1224 contains a white dwarf with T eff = 14, 700 ± 1000 K, mass = 0.22 ± 0.02 M ☉ , and radius = 0.103 ± 0.002 R ☉ , and an F-star companion of mass 1.59 ± 0.06 M ☉ that is somewhat beyond its terminal-age main sequence. The orbital period is quite short at 2.69802 days. The ingredients that are used in the analysis are the Kepler binary light curve, including the detection of the Doppler boosting effect; the NUV and FUV fluxes from the GALEX images of this object; an estimate of the spectral type of the F-star companion; and evolutionary models of the companion designed to match its effective temperature and mean density. The light curve is modeled with a new code named Icarus which we describe in detail. Its features include the full treatment of orbital phase-resolved spectroscopy, Doppler boosting, irradiation effects, and transits/eclipses, which are particularly suited to irradiated eclipsing binaries. We interpret the KOI 1224 system in terms of its likely evolutionary history. We infer that this type of system, containing a bloated hot white dwarf, is the direct descendant of an Algol-type binary. In spite of this basic understanding of the origin of KOI 1224, we discuss a number of problems associated with producing a system with an orbital period this short.

A radio-pulsing white dwarf binary star.

Science.gov (United States)

Marsh, T R; Gänsicke, B T; Hümmerich, S; Hambsch, F-J; Bernhard, K; Lloyd, C; Breedt, E; Stanway, E R; Steeghs, D T; Parsons, S G; Toloza, O; Schreiber, M R; Jonker, P G; van Roestel, J; Kupfer, T; Pala, A F; Dhillon, V S; Hardy, L K; Littlefair, S P; Aungwerojwit, A; Arjyotha, S; Koester, D; Bochinski, J J; Haswell, C A; Frank, P; Wheatley, P J

2016-09-15

White dwarfs are compact stars, similar in size to Earth but approximately 200,000 times more massive. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies. Here we report the discovery of a white dwarf/cool star binary that emits from X-ray to radio wavelengths. The star, AR Scorpii (henceforth AR Sco), was classified in the early 1970s as a δ-Scuti star, a common variety of periodic variable star. Our observations reveal instead a 3.56-hour period close binary, pulsing in brightness on a period of 1.97 minutes. The pulses are so intense that AR Sco's optical flux can increase by a factor of four within 30 seconds, and they are also detectable at radio frequencies. They reflect the spin of a magnetic white dwarf, which we find to be slowing down on a 10 7 -year timescale. The spin-down power is an order of magnitude larger than that seen in electromagnetic radiation, which, together with an absence of obvious signs of accretion, suggests that AR Sco is primarily spin-powered. Although the pulsations are driven by the white dwarf's spin, they mainly originate from the cool star. AR Sco's broadband spectrum is characteristic of synchrotron radiation, requiring relativistic electrons. These must either originate from near the white dwarf or be generated in situ at the M star through direct interaction with the white dwarf's magnetosphere.

Status and biology of ringed seals (Phoca hispida in Svalbard

Directory of Open Access Journals (Sweden)

Christian Lydersen

1998-06-01

water prior to weaning. They are capable of diving for up to 12min and dive to the bottom of the study areas (max. 89 m. Nursing females spend more than 80% of their time in the water. Maximum recorded dive duration for mothers was 21.2 min. In order to produce a weaned pup, the net energy expenditure for a ringed seal mother is 1,073 MJ. This energy value corresponds to the consumption of 185 kg of polar cod or 282 kg of P. libellula. The annual gross energy consumption for adult males and females is calculated to be 5,600 MJ and 7,300 MJ, respectively. The main predators of ringed seals in Svalbard are polar bears (Ursus maritimus and Arctic foxes (Alopex lagopus. In addition, both glaucous gulls (Larus hyperboreus and walruses (Odobenus rosmarus are documented as predators of ringed seals in this area. Heavy predation pressure is probably the main factor explaining why pups of this species start diving at such a young age, why they have access to so many breathing holes (8.7 on average and why they keep their white coat long after its thermoregulatory properties have vanished. Pollution levels in ringed seals from Svalbard are, generally speaking, similar to levels in other areas of the Arctic.

Double Degenerates among DA white dwarfs

International Nuclear Information System (INIS)

Bragaglia, A.; Greggio, L.; Renzini, A.; D'odorico, S.

1990-01-01

The results of a spectroscopic survey of catalog white dwarfs in search of radial velocity variations indicative of a binary motion are reported. In a sample of 54 DA white dwarfs, one Double Degenerate (DD) system with a period of 1.15 days (the shortest period DD system yet discovered) is found. Two other excellent and two good DD candidates, and two white dwarf + red dwarf pairs were also found. If all the candidates should be confirmed, this would indicate a frequency of about 13 percent of interacting binaries in an unbiased sample of evolved stars, with a DD frequency of about 10 percent. These results suggest fairly large values for the common-envelope parameter alpha, implying that a source of energy other than orbital may be required to eject the envelope during common-envelope events. Finally, in combination with previous evidence our result implies that DDs with WD components of the DA variety are unlikely to be the precursors of Type I supernovae, but DDs with non-DA components remain very attractive candidates. 20 refs

Structured LDPC Codes over Integer Residue Rings

Directory of Open Access Journals (Sweden)

Marc A. Armand

2008-07-01

Full Text Available This paper presents a new class of low-density parity-check (LDPC codes over ℤ2a represented by regular, structured Tanner graphs. These graphs are constructed using Latin squares defined over a multiplicative group of a Galois ring, rather than a finite field. Our approach yields codes for a wide range of code rates and more importantly, codes whose minimum pseudocodeword weights equal their minimum Hamming distances. Simulation studies show that these structured codes, when transmitted using matched signal sets over an additive-white-Gaussian-noise channel, can outperform their random counterparts of similar length and rate.

Correction of the closed orbit and vertical dispersion and the tuning and field correction system in ISABELLE

International Nuclear Information System (INIS)

Parzen, G.

1979-01-01

Each ring in ISABELLE will have 10 separately powered systematic field correction coils to make required corrections which are the same in corresponding magnets around the ring. These corrections include changing the ν-value, shaping the working line in ν-space, correction of field errors due to iron saturation effects, the conductor arrangements, the construction of the coil ends, diamagnetic effects in the superconductor and to rate-dependent induced currents. The twelve insertion quadrupoles in the insertion surrounding each crossing point will each have a quadrupole trim coil. The closed orbit will be controlled by a system of 84 horizontal dipole coils and 90 vertical dipole coils in each ring, each coil being separately powered. This system of dipole coils will also be used to correct the vertical dispersion at the crossing points. Two families of skew quadrupoles per ring will be provided for correction of the coupling between the horizontal and vertical motions. Although there will be 258 separately powered correction coils in each ring

Freeform TIR collimators for the removal of angular color variation in white LED spotlights

NARCIS (Netherlands)

Prins, C.R.; Schneider, C.; IJzerman, W.L.; Tukker, T.W.; Thije Boonkkamp, ten J.H.M.; Winston, R.; Gordon, J.

2013-01-01

Angular color variation in white, phosphor-converted LEDs causes undesirable yellow rings in the beams of spotlights. We developed an inverse method to design TIR collimators that remove the angular color variation for point light sources and significantly reduce color variation for extended light

Precision analog signal processor for beam position measurements in electron storage rings

International Nuclear Information System (INIS)

Hinkson, J.A.; Unser, K.B.

1995-05-01

Beam position monitors (BPM) in electron and positron storage rings have evolved from simple systems composed of beam pickups, coaxial cables, multiplexing relays, and a single receiver (usually a analyzer) into very complex and costly systems of multiple receivers and processors. The older may have taken minutes to measure the circulating beam closed orbit. Today instrumentation designers are required to provide high-speed measurements of the beam orbit, often at the ring revolution frequency. In addition the instruments must have very high accuracy and resolution. A BPM has been developed for the Advanced Light Source (ALS) in Berkeley which features high resolution and relatively low cost. The instrument has a single purpose; to measure position of a stable stored beam. Because the pickup signals are multiplexed into a single receiver, and due to its narrow bandwidth, the receiver is not intended for single-turn studies. The receiver delivers normalized measurements of X and Y position entirely by analog means at nominally 1 V/mm. No computers are involved. No software is required. Bergoz, a French company specializing in precision beam instrumentation, integrated the ALS design m their new BPM analog signal processor module. Performance comparisons were made on the ALS. In this paper we report on the architecture and performance of the ALS prototype BPM

Characterizing exo-ring systems around fast-rotating stars using the Rossiter-McLaughlin effect

Science.gov (United States)

de Mooij, Ernst J. W.; Watson, Christopher A.; Kenworthy, Matthew A.

2017-12-01

Planetary rings produce a distinct shape distortion in transit light curves. However, to accurately model such light curves the observations need to cover the entire transit, especially ingress and egress, as well as an out-of-transit baseline. Such observations can be challenging for long period planets, where the transits may last for over a day. Planetary rings will also impact the shape of absorption lines in the stellar spectrum, as the planet and rings cover different parts of the rotating star (the Rossiter-McLaughlin effect). These line-profile distortions depend on the size, structure, opacity, obliquity and sky-projected angle of the ring system. For slow-rotating stars, this mainly impacts the amplitude of the induced velocity shift; however, for fast-rotating stars the large velocity gradient across the star allows the line distortion to be resolved, enabling direct determination of the ring parameters. We demonstrate that by modelling these distortions we can recover ring system parameters (sky-projected angle, obliquity and size) using only a small part of the transit. Substructure in the rings, e.g. gaps, can be recovered if the width of the features (δW) relative to the size of the star is similar to the intrinsic velocity resolution (set by the width of the local stellar profile, γ) relative to the stellar rotation velocity (v sini, i.e. δW/R* ≳ vsini/γ). This opens up a new way to study the ring systems around planets with long orbital periods, where observations of the full transit, covering the ingress and egress, are not always feasible.

Years of annual ring formation of trees and elements of minute amount

International Nuclear Information System (INIS)

Katayama, Yukio

1988-01-01

The structure of the trunks of trees is briefly explained, and the effect of environmental factors such as light, rain, soil, temperature and so on and the effect of environmental pollution are conceivable. The examples of the research on the quantitative determination of the elements of minute amount contained in the annual rings of trees and their use as the living things for environmental pollution index are shown, and the problems are considered. The concentration of manganese contained in annual rings may be used as environmental pollution index. It was pointed out that cadmium accumulated in annual rings had a strong correlation with the decrease of annual ring width. K-40 once taken in annual rings moved radially in connection with physical and physiological actions. The authors have examined the distribution of the elements of minute amount in the trunks, using Japanese cedar, white fir and oak as the specimens. For the quantitative analysis of the elements of minute amount, thermal neutron radioactivation analysis was used, which can analyze many elements simultaneously by nondestructive method. The elements of minute amount in the trunks of Japanese cedar, the difference of the distribution according to the kinds of trees, and the movement of elements within trunks are reported. The application of PIXE method to this analysis is considered. (Kako, I.)

Black rings

International Nuclear Information System (INIS)

Emparan, Roberto; Reall, Harvey S

2006-01-01

A black ring is a five-dimensional black hole with an event horizon of topology S 1 x S 2 . We provide an introduction to the description of black rings in general relativity and string theory. Novel aspects of the presentation include a new approach to constructing black ring coordinates and a critical review of black ring microscopics. (topical review)

Titan Orbiter Aerorover Mission with Enceladus Science (TOAMES)

Science.gov (United States)

Sittler, E.; Cooper, J.; Mahaffy, P.; Fairbrother, D.; de Pater, I.; Schulze-Makuch, D.; Pitman, J.

2007-08-01

same time made us aware of how little we understand about these bodies. For example, the source, and/or recycling mechanism, of methane in Titan's atmosphere is still puzzling. Indeed, river beds (mostly dry) and lakes have been spotted, and occasional clouds have been seen, but the physics to explain the observations is still mostly lacking, since our "image" of Titan is still sketchy and quite incomplete. Enceladus, only 500 km in extent, is even more puzzling, with its fiery plumes of vapor, dust and ice emanating from its south polar region, "feeding" Saturn's E ring. Long term variability of magnetospheric plasma, neutral gas, E-ring ice grain density, radio emissions, and corotation of Saturn's planetary magnetic field in response to Enceladus plume activity are of great interest for Saturn system science. Both Titan and Enceladus are bodies of considerable astrobiological interest in view of high organic abundances at Titan and potential subsurface liquid water at Enceladus. We propose to develop a new mission to Titan and Enceladus, the Titan Orbiter Aerorover Mission with Enceladus Science (TOAMES), to address these questions using novel new technologies. TOAMES is a multi-faceted mission that starts with orbit insertion around Saturn using aerobraking with Titan's extended atmosphere. We then have an orbital tour around Saturn (for 1-2 years) and close encounters with Enceladus, before it goes into orbit around Titan (via aerocapture). During the early reconnaissance phase around Titan, perhaps 6 months long, the orbiter will use altimetry, radio science and remote sensing instruments to measure Titan's global topography, subsurface structure and atmospheric winds. This information will be used to determine where and when to release the Aerorover, so that it can navigate safely around Titan and identify prime sites for surface sampling and analysis. In situ instruments will sample the upper atmosphere which may provide the seed population for the complex

Variations in Ring Particle Cooling across Saturn's Rings with Cassini CIRS

Science.gov (United States)

Brooks, S. M.; Spilker, L. J.; Pilorz, S.; Edgington, S. G.; Déau, E.; Altobelli, N.

2010-12-01

Cassini's Composite Infrared Spectrometer has recorded over two million of spectra of Saturn's rings in the far infrared since arriving at Saturn in 2004. CIRS records far infrared radiation between 10 and 600 cm-1 ( 16.7 and 1000 μ {m} ) at focal plane 1 (FP1), which has a field of view of 3.9 mrad. Thermal emission from Saturn’s rings peaks in this wavelength range. Ring temperatures can be inferred from FP1 data. By tracking how ring temperatures vary, we can determine the thermal inertia of the rings. Previous studies have shown that the rings' thermal inertia, a measure of their response to changes in the thermal environment, varies from ring to ring. Thermal inertia can provide insight into the physical structure of Saturn's ring particles and their regoliths. Low thermal inertia and rapidly changing temperatures are suggestive of ring particles that have more porous or fluffy regoliths or that are riddled with cracks. Solid particles can be expected to have higher thermal inertias. Ferrari et al. (2005) fit thermal inertia values of 5218 {Jm)-2 {K}-1 {s}-1/2 to their B ring data and 6412 {Jm)-2 {K}-1 {s}-1/2 to their C ring data. In this work we focus on CIRS observations of the shadowed portion of Saturn's rings. The rings’ thermal budget is dominated by its absorption of solar radiation. As a result, ring particles abruptly cool as they traverse Saturn's shadow. From these shadow observations we can create cooling curves at specific locations across the rings. We will show that the rings' cooling curves and thus their thermal inertia vary not only from ring to ring, but by location within the individual rings. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2010 California Institute of Technology. Government sponsorship acknowledged.

NASA logo painted on orbiter Endeavour

Science.gov (United States)

1998-01-01

A KSC worker paints the NASA logo on the port wing of the orbiter Endeavour, which is scheduled to launch in December for STS-88. The paint is a special pigment that takes 18 hours to dry; the whole process takes approximately two weeks to complete. The NASA logo, termed 'meatball,' was originally designed in the late 1950s. It symbolized NASA's role in aeronautics and space in the early years of the agency. The original design included a white border surrounding it. The border was dropped for the Apollo 7 mission in October 1968, replaced with royal blue to match the background of the emblem. In 1972 the logo was replaced by a simple and contemporary design -- the 'worm' -- which was retired from use last year. NASA reverted to its original logo in celebration of the agency's 40th anniversary in October, and the 'golden age' of America's space program. All the orbiters will bear the new logo.

Alternative loop rings

CERN Document Server

Goodaire, EG; Polcino Milies, C

1996-01-01

For the past ten years, alternative loop rings have intrigued mathematicians from a wide cross-section of modern algebra. As a consequence, the theory of alternative loop rings has grown tremendously. One of the main developments is the complete characterization of loops which have an alternative but not associative, loop ring. Furthermore, there is a very close relationship between the algebraic structures of loop rings and of group rings over 2-groups. Another major topic of research is the study of the unit loop of the integral loop ring. Here the interaction between loop rings and group ri

Primitivity and weak distributivity in near rings and matrix near rings

International Nuclear Information System (INIS)

Abbasi, S.J.

1993-08-01

This paper shows the structure of matrix near ring constructed over a weakly distributive and primative near ring. It is proved that a weakly distributive primitive near ring is a ring and the matrix near rings constructed over it is also a bag. (author). 14 refs

Newborn exoplanet eyed for moons and rings

Science.gov (United States)

Clery, Daniel

2018-01-01

Astronomers are staring at a nearby star in hopes of seeing a giant baby of a planet—perhaps accompanied by dust clouds, rings, or newborn moons—pass across its face. Last week, the newest and tiniest telescope joined the vigil, when the French-built PicSat rode into orbit on an Indian rocket. It will be able to continuously monitor the star, β Pictoris, until chances of seeing the once-in-20-year transit event diminish in a few months' time. Astronomers are fascinated by β Pictoris, a bright star just 63 light-years away, because it is a natural laboratory for how solar systems form given its age of only 24 million years—an infant in stellar terms.

Pseudo-single-bunch mode for a 100 MHz storage ring serving soft X-ray timing experiments

Science.gov (United States)

Olsson, T.; Leemann, S. C.; Georgiev, G.; Paraskaki, G.

2018-06-01

At many storage rings for synchrotron light production there is demand for serving both high-flux and timing users simultaneously. Today this is most commonly achieved by operating inhomogeneous fill patterns, but this is not preferable for rings that employ passive harmonic cavities to damp instabilities and increase Touschek lifetime. For these rings, inhomogeneous fill patterns could severely reduce the effect of the harmonic cavities. It is therefore of interest to develop methods to serve high-flux and timing users simultaneously without requiring gaps in the fill pattern. One such method is pseudo-single-bunch (PSB), where one bunch in the bunch train is kicked onto another orbit by a fast stripline kicker. The light emitted from the kicked bunch can then be separated by an aperture in the beamline. Due to recent developments in fast kicker design, PSB operation in multibunch mode is within reach for rings that operate with a 100 MHz RF system, such as the MAX IV and Solaris storage rings. This paper describes machine requirements and resulting performance for such a mode at the MAX IV 1.5 GeV storage ring. A solution for serving all beamlines is discussed as well as the consequences of beamline design and operation in the soft X-ray energy range.

Solar system history as recorded in the Saturnian ring structure

International Nuclear Information System (INIS)

Alfven, H.

1983-04-01

The paper is based on Holbergs analysis of the Voyager photographs in both reflected and transparent light, combined with occulation data of stars seen through the rings. Besides rapidly varying phenomena (spokes, braided ring, etc.), which according to Mendis are due to gravito-electromagnetic effects, the ring consists of a bulk structure, a fine structure, and also a hyperfine structure, showing more than 10000 ringlets. The large number of ringlets can be explained by the Baxter-Thompson negative diffusion. This gives the ringlets a stability which makes it possible to interprete them as fossils, which originated at cosmogonic times. It is shown that the bulk structure can be explained by the combined cosmogonic shadows of the satellites Mimas, Janus (co-orbiting satellites) and the Shepherd satellites. This structure originated at the transition from the plasma phase to the planetesimal phase (which probably took place 4-5 times 10 9 years ago). Further, Holberg has discovered that the shadows are not simple void regions but exhibit a certain characteristic signature. This is not yet understood theoretically. Parts of the fine structure are explained by Holberg as resonances with the satellites. Parts are here interpreted as cosmogonic shadow effects. However, there are a number of ringlets which can neither be explained by cosmogonic nor by resonance effects. The most important conclusion is that an analysis of the ring data is liekly to lead to a reconstruction of the plasma-planetesimal transition with an accuracy of a few percent. (author)

Pruning The ELM Survey: Characterizing Candidate Low-mass White Dwarfs through Photometric Variability

Energy Technology Data Exchange (ETDEWEB)

Bell, Keaton J.; Winget, D. E.; Montgomery, M. H.; Castanheira, B. G.; Vanderbosch, Z.; Winget, K. I. [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Gianninas, A.; Kilic, Mukremin [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States); Hermes, J. J. [Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599 (United States); Brown, Warren R., E-mail: keatonb@astro.as.utexas.edu [Smithsonian Astrophysical Observatory, Cambridge, MA 02138 (United States)

2017-02-01

We assess the photometric variability of nine stars with spectroscopic T {sub eff} and log g values from the ELM Survey that locates them near the empirical extremely low-mass (ELM) white dwarf instability strip. We discover three new pulsating stars: SDSS J135512.34+195645.4, SDSS J173521.69+213440.6, and SDSS J213907.42+222708.9. However, these are among the few ELM Survey objects that do not show radial velocity (RV) variations that confirm the binary nature expected of helium-core white dwarfs. The dominant 4.31 hr pulsation in SDSS J135512.34+195645.4 far exceeds the theoretical cut-off for surface reflection in a white dwarf, and this target is likely a high-amplitude δ Scuti pulsator with an overestimated surface gravity. We estimate the probability to be less than 0.0008 that the lack of measured RV variations in four of eight other pulsating candidate ELM white dwarfs could be due to low orbital inclination. Two other targets exhibit variability as photometric binaries. Partial coverage of the 19.342 hr orbit of WD J030818.19+514011.5 reveals deep eclipses that imply a primary radius >0.4 R {sub ⊙}—too large to be consistent with an ELM white dwarf. The only object for which our time series photometry adds support to ELM white dwarf classification is SDSS J105435.78−212155.9, which has consistent signatures of Doppler beaming and ellipsoidal variations. We conclude that the ELM Survey contains multiple false positives from another stellar population at T {sub eff}≲9000 K, possibly related to the sdA stars recently reported from SDSS spectra.

Interaction of ring dark solitons with ring impurities in Bose-Einstein condensates

International Nuclear Information System (INIS)

Xue Jukui

2005-01-01

The interaction of ring dark solitons/vortexes with the ring-shaped repulsive and attractive impurities in two-dimensional Bose-Einstein condensates is investigated numerically. Very rich interaction phenomena are obtained, i.e., not only the interaction between the ring soliton and the impurity, but also the interaction between vortexes and the impurity. The interaction characters, i.e., snaking of ring soliton, quasitrapping or reflection of ring soliton and vortexes by the impurity, strongly depend on initial ring soliton velocity, impurity strength, initial position of ring soliton and impurity. The numerical results also reveal that ring dark solitons/vortexes can be trapped and dragged by an adiabatically moving attractive ring impurity

Features of the mass transfer in magnetic cataclysmic variables with fast-rotating white dwarfs

Directory of Open Access Journals (Sweden)

Isakova Polina

2014-01-01

Full Text Available The flow structure in magnetic cataclysmic variables was investigated taking into account the effects of strong magnetic field and fast rotation of the white dwarf. We modeled the AE Aqr system as a unique object that has the rotation period of the white dwarf is about 1000 times shorter than the orbital period of the binary system. Observations show that in spite of fast rotation of the white dwarf some part of the stream from the inner Lagrange point comes into the Roche lobe region. We analyzed possible mechanisms preventing material to outflow from the system.

Storage Rings

International Nuclear Information System (INIS)

Fischer, W.

2010-01-01

Storage rings are circular machines that store particle beams at a constant energy. Beams are stored in rings without acceleration for a number of reasons (Tab. 1). Storage rings are used in high-energy, nuclear, atomic, and molecular physics, as well as for experiments in chemistry, material and life sciences. Parameters for storage rings such as particle species, energy, beam intensity, beam size, and store time vary widely depending on the application. The beam must be injected into a storage ring but may not be extracted (Fig. 1). Accelerator rings such as synchrotrons are used as storage rings before and after acceleration. Particles stored in rings include electrons and positrons; muons; protons and anti-protons; neutrons; light and heavy, positive and negative, atomic ions of various charge states; molecular and cluster ions, and neutral polar molecules. Spin polarized beams of electrons, positrons, and protons were stored. The kinetic energy of the stored particles ranges from 10 -6 eV to 3.5 x 10 12 eV (LHC, 7 x 10 12 eV planned), the number of stored particles from one (ESR) to 1015 (ISR). To store beam in rings requires bending (dipoles) and transverse focusing (quadrupoles). Higher order multipoles are used to correct chromatic aberrations, to suppress instabilities, and to compensate for nonlinear field errors of dipoles and quadrupoles. Magnetic multipole functions can be combined in magnets. Beams are stored bunched with radio frequency systems, and unbunched. The magnetic lattice and radio frequency system are designed to ensure the stability of transverse and longitudinal motion. New technologies allow for better storage rings. With strong focusing the beam pipe dimensions became much smaller than previously possible. For a given circumference superconducting magnets make higher energies possible, and superconducting radio frequency systems allow for efficient replenishment of synchrotron radiation losses of large current electron or positron beams

Note on beam--beam tune shift in single ring multi bunch mode

International Nuclear Information System (INIS)

Month, M.

1978-01-01

If many identical counter-rotating bunches of protons and antiprotons are stored in a single ring, they will have identical orbits. The question is: Is this total tune shift relevant to the problem of beam stability. The answer is: not in general. The nonlinear force is described by its ''strength'', Δν/sub I/, for each bunch interaction individually. It is not at all clear that the sum of the individual Δν/sub I/ is the significant quantity

Commissioning of the APS real-time orbit feedback system

International Nuclear Information System (INIS)

Carwardine, J.; Decker, G.; Evans, K. Jr.; Hillman, A.; Lenkszus, F.; Merl, R.; Pietryla, A.

1997-01-01

A unified global and local closed-orbit feedback system has been implemented at the Advanced Photon Source in order to stabilize both particle and photon beams. Beam stability requirements in the band up to 50 Hz are 17 microm in the horizontal plane and 4.4 microm vertically. Orbit feedback algorithms are implemented digitally using multiple digital signal processors, with computing power distributed in 20 VME crates around the storage ring. Each crate communicates with all others via a fast reflective memory network. The system has access to 320 rf beam position monitors together with x-ray beam position monitors in both insertion device and bending magnet beamlines. Up to 317 corrector magnets are available to the system. The global system reduces horizontal rms beam motion at the x-ray source points by more than a factor of two in the frequency band from 10 mHz to 50 Hz

Identifying Lattice, Orbit, And BPM Errors in PEP-II

International Nuclear Information System (INIS)

Decker, F.-J.; SLAC

2005-01-01

The PEP-II B-Factory is delivering peak luminosities of up to 9.2 · 10 33 1/cm 2 · l/s. This is very impressive especially considering our poor understanding of the lattice, absolute orbit and beam position monitor system (BPM). A few simple MATLAB programs were written to get lattice information, like betatron functions in a coupled machine (four all together) and the two dispersions, from the current machine and compare it the design. Big orbit deviations in the Low Energy Ring (LER) could be explained not by bad BPMs (only 3), but by many strong correctors (one corrector to fix four BPMs on average). Additionally these programs helped to uncover a sign error in the third order correction of the BPM system. Further analysis of the current information of the BPMs (sum of all buttons) indicates that there might be still more problematic BPMs

Closed orbit feedback with digital signal processing

International Nuclear Information System (INIS)

Chung, Y.; Kirchman, J.; Lenkszus, F.

1994-01-01

The closed orbit feedback experiment conducted on the SPEAR using the singular value decomposition (SVD) technique and digital signal processing (DSP) is presented. The beam response matrix, defined as beam motion at beam position monitor (BPM) locations per unit kick by corrector magnets, was measured and then analyzed using SVD. Ten BPMs, sixteen correctors, and the eight largest SVD eigenvalues were used for closed orbit correction. The maximum sampling frequency for the closed loop feedback was measured at 37 Hz. Using the proportional and integral (PI) control algorithm with the gains Kp = 3 and K I = 0.05 and the open-loop bandwidth corresponding to 1% of the sampling frequency, a correction bandwidth (-3 dB) of approximately 0.8 Hz was achieved. Time domain measurements showed that the response time of the closed loop feedback system for 1/e decay was approximately 0.25 second. This result implies ∼ 100 Hz correction bandwidth for the planned beam position feedback system for the Advanced Photon Source storage ring with the projected 4-kHz sampling frequency

On the Number of Comets Around White Dwarf Stars: Orbit Survival During the Late Stages of Stellar Evolution

Energy Technology Data Exchange (ETDEWEB)

Parriott, J. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Alcock, C. [Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States)

1998-07-01

The accretion of comets onto DA white dwarfs can produce observable metal absorption lines. We show here that comet systems around the progenitor main-sequence star are vulnerable to being lost during asymptotic giant branch mass loss, if the mass loss is sufficiently asymmetric to impart modest linear momentum to the white dwarf. This may have bearing on the frequency of observation of heavy elements in white dwarf stars and on inferences regarding the frequency of comet systems, if the imparted linear velocities of white dwarfs can be estimated. {copyright} {ital {copyright} 1998.} {ital The American Astronomical Society}

Development of closed orbit diagnostics towards EDM measurements at COSY in Juelich

Energy Technology Data Exchange (ETDEWEB)

Hinder, Fabian [Forschungszentrum Juelich, Institut fuer Kernphysik IV (Germany); RWTH Aachen University, III. Physikalisches Institut B (Germany); Collaboration: JEDI-Collaboration

2016-07-01

Electric Dipole Moments (EDMs) violate parity and time reversal symmetries. Assuming the CPT-theorem, this leads to CP violation, which is needed to explain the matter over antimatter dominance in the Universe. Thus, a non-zero EDM is a hint to new physics beyond the Standard Model. The JEDI collaboration (Juelich Electric Dipole moment Investigations) has started investigations of a direct EDM measurement of protons and deuterons at a storage ring. To measure a tiny EDM signal with high precision, systematic effects have to be controlled to the same level. One major source of systematic uncertainties is a distortion of the closed orbit. To control and measure this effect, the orbit measurement system, including the readout electronics, the orbit correction system and the beam position monitor pick-ups are improved. All the mentioned developments are ongoing at the Cooler Synchrotron (COSY) at Juelich. The achievements in the mentioned fields are presented at the conference.

Rings in drugs.

Science.gov (United States)

Taylor, Richard D; MacCoss, Malcolm; Lawson, Alastair D G

2014-07-24

We have analyzed the rings, ring systems, and frameworks in drugs listed in the FDA Orange Book to understand the frequency, timelines, molecular property space, and the application of these rings in different therapeutic areas and target classes. This analysis shows that there are only 351 ring systems and 1197 frameworks in drugs that came onto the market before 2013. Furthermore, on average six new ring systems enter drug space each year and approximately 28% of new drugs contain a new ring system. Moreover, it is very unusual for a drug to contain more than one new ring system and the majority of the most frequently used ring systems (83%) were first used in drugs developed prior to 1983. These observations give insight into the chemical novelty of drugs and potentially efficient ways to assess compound libraries and develop compounds from hit identification to lead optimization and beyond.

On the need for a partial revision in the orbital assignments of cyclopropane (C3H6)

International Nuclear Information System (INIS)

Brunger, M.J.; Weigold, E.

1993-09-01

An electron momentum spectroscopy investigation was carried out into the orbital assignment for the two bands in the 15-18 eV binding energy range of the photoelectron spectrum of the saturated, 3-member ring hydrocarbon, cyclopropane (C 3 H 6 ). The present experimental momentum distributions for these states provide compelling evidence that the earlier hypothesis of Schweig and Thiel is correct. That is, the orbital assignments of these two bands are in fact opposite to the sequence of the respective ab initio eigenvalues. 11 refs., 2 figs

A unique method of retaining orbital prosthesis with attachment systems - a clinical report.

Science.gov (United States)

Guttal, Satyabodh S; Akash, N R; Prithviraj, D R; Lekha, K

2014-06-01

Diminution of the orbital contents post-surgical removal of a malignant tumor can have a severe psychological impact on the patient in terms of function and esthetics. Therefore, esthetic remedy should be planned subsequently, since tumor obliteration precedes cosmetic concern. A convenient option for successful rehabilitation in such patients is a simple, user-friendly, removable orbital prosthesis. Retention of the prosthesis is one of the key factors for the successful rehabilitation. Spectacle frame, conformers, adhesives, osseointegrated implants, magnets or buttons have been used to impart retention to the prosthesis. The use of semi precision attachments in maxillofacial prostheses is limited to the osseointegrated prostheses. This case report describes a conventional spectacle frame technique, to retain the silicone orbital prosthesis using two different types of stud attachments viz., dalla bona and O-ring attachment systems. Copyright © 2013 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Commissioning results of the APS storage ring rf beam position monitors

International Nuclear Information System (INIS)

Kahana, E.; Chung, Y.

1996-01-01

The commissioning of the 360 rf beam position monitors (BPMs) in the Advanced Photon Source (APS) storage ring (SR) is nearing completion. After using the single-turn capability of the BPM electronics in the early ring commissioning phase, resolution measurements versus current and bandwidth were successfully performed. In the standard Sr vacuum chamber geometry, the resolution was measured with beam as 0.16 micromA/√(Hz). For the insertion device vacuum chamber geometry, the resolution was measured to be 0.1 micromA/√(Hz). Since the photon beam stability requirement for the users is only 4.5 microns rms in the vertical direction, investigations of rf BPM offset versus current and bunch pattern have also been initiated. Both single bunch and multibunch beam patterns with varying intensity were used to determine offset stability for both the global and the local orbit feedback applications

Simulation of 4-turn algorithms for reconstructing lattice optic functions from orbit measurements

International Nuclear Information System (INIS)

Koscielniak, S.; Iliev, A.

1994-06-01

We describe algorithms for reconstructing tune, closed-orbit, beta-function and phase advance from four individual turns of beam orbit acquisition data, under the assumption of coherent, almost linear and uncoupled betatron oscillations. To estimate the beta-function at, and phase advance between, position monitors, we require at least one anchor location consisting of two monitors separated by a drift. The algorithms were submitted to a Monte Carlo analysis to find the likely measurement accuracy of the optics functions in the KAON Factory Booster ring racetrack lattice, assuming beam position monitors with surveying and reading errors, and assuming an imperfect lattice with gradient and surveying errors. Some of the results of this study are reported. (author)

Simulation of a transverse feedback system for the SSRF storage ring

International Nuclear Information System (INIS)

Jiang Bocheng; Chinese Academy of Sciences, Beijing; Liu Guimin; Zhao Zhentang

2007-01-01

Resistive wall instability is a serious problem in many light sources. An active transverse feedback system (TFS) is required to operate the machine in a good condition when beam current is high. In order to investigate beam dynamics with TFS turned on, we developed a TFS simulation program. The feedback effectiveness for the Shanghai Synchrotron Radiation Facility (SSRF) storage ring is simulated under various conditions such as closed orbit distortion included, beam position monitor reading errors added, and finite-duration impulse-response filter strategy changed. (authors)

Orbital motion of the secondary in three AM Her systems: evidence for low-mass white dwarfs

Energy Technology Data Exchange (ETDEWEB)

Mukai, K; Charles, P A

1987-05-01

In an earlier paper the spectroscopic detection was reported of the secondaries in the three AM Her type systems, CW1103+254, PG1550+191 and E2003+225. In this paper, high-resolution spectrophotometry of these stars is presented in the wavelength region lambda lambda 7550-8850. In all three cases, the radial velocity variation of the second star has been detected using the Na I doublet at lambda lambda 8183-94. Combined with values for each system's inclination estimated from polarimetry, constraints on the white dwarf masses are derived. The average of our best estimates for the white dwarf masses in these systems and AM Her itself is approx.0.6 solar masses, essentially coincident with the masses of isolated white dwarfs.

Electron Cloud Simulations of a Proton Storage Ring Using Cold Proton Bunches

International Nuclear Information System (INIS)

Sato, Y.; Holmes, Jeffrey A.; Lee, S.Y.; Macek, R.

2008-01-01

Using the ORBIT code we study the sensitivity of electron cloud properties with respect to different proton beam profiles, the secondary electron yield (SEY) parameter, and the proton loss rate. Our model uses a cold proton bunch to generate primary electrons and electromagnetic field for electron cloud dynamics. We study the dependence of the prompt and swept electron signals vs the bunch charge and the recovery of electron clouds after sweeping on the beam loss rate and the SEY. The simulation results are compared with the experimental data measured at the proton storage ring at the Los Alamos National Laboratory. Our simulations indicate that the fractional proton loss rate in the field-free straight section may be an exponential function of proton beam charge and may also be lower than the averaged fractional proton loss rate over the whole ring.

Precision analog signal processor for beam position measurements in electron storage rings

International Nuclear Information System (INIS)

Hinkson, J.A.; Unser, K.B.

1995-01-01

Beam position monitors (BPM) in electron and positron storage rings have evolved from simple systems composed of beam pickups, coaxial cables, multiplexing relays, and a single receiver (usually a analyzer) into very complex and costly systems of multiple receivers and processors. The older may have taken minutes to measure the circulating beam closed orbit. Today instrumentation designers are required to provide high-speed measurements of the beam orbit, often at the ring revolution frequency. In addition the instruments must have very high accuracy and resolution. A BPM has been developed for the Advanced Light Source (ALS) in Berkeley which features high resolution and relatively low cost. The instrument has a single purpose; to measure position of a stable stored beam. Because the pickup signals are multiplexed into a single receiver, and due to its narrow bandwidth, the receiver is not intended for single-turn studies. The receiver delivers normalized measurements of X and Y posit ion entirely by analog means at nominally 1 V/mm. No computers are involved. No software is required. Bergoz, a French company specializing in precision beam instrumentation, integrated the ALS design m their new BPM analog signal processor module. Performance comparisons were made on the ALS. In this paper we report on the architecture and performance of the ALS prototype BPM

Analysis of possibilities for a spin flip in high energy electron ring HERA

International Nuclear Information System (INIS)

Stres, S.; Pestotnik, R.

2007-01-01

In a high energy electron ring the spins of electrons become spontaneously polarized via the emission of spin-flip synchrotron radiation. By employing a radio frequency (RF) radial dipole field kicker, particle spin directions can be rotated slowly over many turns. A model which couples three dimensional spin motion and longitudinal particle motion was constructed to describe non-equilibrium spin dynamics in high energy electron storage rings. The effects of a stochastic synchrotron radiation on the orbital motion in the accelerator synchrotron plane and its influence on the spin motion are studied. The main contributions to the spin motion, the synchrotron oscillations and the stochastic synchrotron radiation, have different influence on the spin polarization reversal in different regions of the parameter space. The results indicate that polarization reversal might be obtained in high energy electron storage rings with a significant noise even with relatively small strengths of a perturbing magnetic field. The only experimental datum avaliable agrees with the model prediction, however further experimental data would be necessary to validate the model

[right] - DUST RING AROUND STAR OFFERS NEW CLUES INTO PLANET FORMATION

Science.gov (United States)

2002-01-01

A NASA Hubble Space Telescope false-color near infrared image of a novel type of structure seen in space - a dust ring around a star. Superficially resembling Saturn's rings -- but on a vastly larger scale -- the 'hula-hoop' around the star called HR 4796A offers new clues into the possible presence of young planets. The near-infrared light reflecting off the dust ring is about 1,000 times fainter than the illuminating central star. Astronomers used a coronagraphic camera on Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS), specifically designed to enable observations of very faint and low surface brightness objects in the close proximity to bright stars. Even with the coronagraph, the glare from HR 4796A overwhelms the much-fainter ring at distances less than about 4 billion miles (inside the blacked-out circle, centered on the star). Hubble's crisp view was able to resolve the ring, seen at lower resolution at longer wavelengths, in ground-based thermal infrared images, as a disk with some degree of central clearing. The ring has an angular radius of 1.05 arc seconds, equivalent to the apparent size of a dime seen more than 4 miles away. Unlike the extensive disks of dust seen around other young stars, the HR 4796A dust ring, 6.5 billion miles from the star, is tightly confined within a relatively narrow zone less than 17 Astronomical Units wide. An Astronomical Unit is the distance from the Earth to the Sun). For comparison, the ring width is approximately equal to the distance separating the orbits of Mars and Uranus in our own Solar System. All dust rings, whether around stars or planets, can only stay intact by some mechanism confining the dust, likely the gravitational tug of unseen planets. The image was taken on March 15, 1998, centered at a near infrared wavelength of 1.1 microns. The false-color corresponds to the ring's brightness (yellow is bright, purple is faint). The ring, which is undoubtedly circular, appears elliptical since

Genesis of magnetic fields in isolated white dwarfs

Science.gov (United States)

Briggs, Gordon P.; Ferrario, Lilia; Tout, Christopher A.; Wickramasinghe, Dayal T.

2018-05-01

A dynamo mechanism driven by differential rotation when stars merge has been proposed to explain the presence of strong fields in certain classes of magnetic stars. In the case of the high field magnetic white dwarfs (HFMWDs), the site of the differential rotation has been variously thought to be the common envelope, the hot outer regions of a merged degenerate core or an accretion disc formed by a tidally disrupted companion that is subsequently accreted by a degenerate core. We have shown previously that the observed incidence of magnetism and the mass distribution in HFMWDs are consistent with the hypothesis that they are the result of merging binaries during common envelope evolution. Here we calculate the magnetic field strengths generated by common envelope interactions for synthetic populations using a simple prescription for the generation of fields and find that the observed magnetic field distribution is also consistent with the stellar merging hypothesis. We use the Kolmogorov-Smirnov test to study the correlation between the calculated and the observed field strengths and find that it is consistent for low envelope ejection efficiency. We also suggest that field generation by the plunging of a giant gaseous planet on to a white dwarf may explain why magnetism among cool white dwarfs (including DZ white dwarfs) is higher than among hot white dwarfs. In this picture a super-Jupiter residing in the outer regions of the white dwarf's planetary system is perturbed into a highly eccentric orbit by a close stellar encounter and is later accreted by the white dwarf.

The not-so-extreme white dwarf of the CV GD 552

International Nuclear Information System (INIS)

Unda-Sanzana, E; Hinojosa-Goni; Marsh, T R; Gaensicke, B T; Maxted, P F L; Morales-Rueda, L; Dhillon, V S; Thoroughgood, T D; Watson, C A; Tremou, E

2009-01-01

GD 552 is a cataclysmic binary which was previously believed to be composed of an M-star and a white dwarf, the latter having an extreme mass of 1.4 solar masses. In a recent paper we showed that this is not compatible with new observational evidence and presented an alternative model in which the white dwarf has a typical mass and the companion is a brown dwarf, making the system a likely member of the elusive group of CVs which have already evolved through minimum orbital period. Here we present additional spectroscopical evidence supporting this conclusion by means of skew mapping.

Field-reversing electron and ion rings for the confinement and heating of plasmas. Annual progress report, September 1, 1980-August 31, 1981

International Nuclear Information System (INIS)

Fleischmann, H.H.

1981-09-01

Our experimental work on the RECE-Christa device during the present period concentrated on obtaining conditions for first measurements of plasma confinement and on the generation of mixed-CT configurations. The most important results in these areas included the generation of rings with plasma currents significantly larger than originally hoped for, and - on the other hand - a failure to propagate rings efficiently in background gas densities below 1 mTorr. In addition, a digital data management system has been acquired and the respective software is being completed. Finally, theoretical work was performed on calculating banana drift orbits in Spheromak-type configurations and on developing a semi-analytic model for the equilibrium of ion rings which could be used for estimating the ring behavior during the slow-down of the ions

The cryogenic storage ring CSR

Science.gov (United States)

von Hahn, R.; Becker, A.; Berg, F.; Blaum, K.; Breitenfeldt, C.; Fadil, H.; Fellenberger, F.; Froese, M.; George, S.; Göck, J.; Grieser, M.; Grussie, F.; Guerin, E. A.; Heber, O.; Herwig, P.; Karthein, J.; Krantz, C.; Kreckel, H.; Lange, M.; Laux, F.; Lohmann, S.; Menk, S.; Meyer, C.; Mishra, P. M.; Novotný, O.; O'Connor, A. P.; Orlov, D. A.; Rappaport, M. L.; Repnow, R.; Saurabh, S.; Schippers, S.; Schröter, C. D.; Schwalm, D.; Schweikhard, L.; Sieber, T.; Shornikov, A.; Spruck, K.; Sunil Kumar, S.; Ullrich, J.; Urbain, X.; Vogel, S.; Wilhelm, P.; Wolf, A.; Zajfman, D.

2016-06-01

An electrostatic cryogenic storage ring, CSR, for beams of anions and cations with up to 300 keV kinetic energy per unit charge has been designed, constructed, and put into operation. With a circumference of 35 m, the ion-beam vacuum chambers and all beam optics are in a cryostat and cooled by a closed-cycle liquid helium system. At temperatures as low as (5.5 ± 1) K inside the ring, storage time constants of several minutes up to almost an hour were observed for atomic and molecular, anion and cation beams at an energy of 60 keV. The ion-beam intensity, energy-dependent closed-orbit shifts (dispersion), and the focusing properties of the machine were studied by a system of capacitive pickups. The Schottky-noise spectrum of the stored ions revealed a broadening of the momentum distribution on a time scale of 1000 s. Photodetachment of stored anions was used in the beam lifetime measurements. The detachment rate by anion collisions with residual-gas molecules was found to be extremely low. A residual-gas density below 140 cm-3 is derived, equivalent to a room-temperature pressure below 10-14 mbar. Fast atomic, molecular, and cluster ion beams stored for long periods of time in a cryogenic environment will allow experiments on collision- and radiation-induced fragmentation processes of ions in known internal quantum states with merged and crossed photon and particle beams.

The cryogenic storage ring CSR.

Science.gov (United States)

von Hahn, R; Becker, A; Berg, F; Blaum, K; Breitenfeldt, C; Fadil, H; Fellenberger, F; Froese, M; George, S; Göck, J; Grieser, M; Grussie, F; Guerin, E A; Heber, O; Herwig, P; Karthein, J; Krantz, C; Kreckel, H; Lange, M; Laux, F; Lohmann, S; Menk, S; Meyer, C; Mishra, P M; Novotný, O; O'Connor, A P; Orlov, D A; Rappaport, M L; Repnow, R; Saurabh, S; Schippers, S; Schröter, C D; Schwalm, D; Schweikhard, L; Sieber, T; Shornikov, A; Spruck, K; Sunil Kumar, S; Ullrich, J; Urbain, X; Vogel, S; Wilhelm, P; Wolf, A; Zajfman, D

2016-06-01

An electrostatic cryogenic storage ring, CSR, for beams of anions and cations with up to 300 keV kinetic energy per unit charge has been designed, constructed, and put into operation. With a circumference of 35 m, the ion-beam vacuum chambers and all beam optics are in a cryostat and cooled by a closed-cycle liquid helium system. At temperatures as low as (5.5 ± 1) K inside the ring, storage time constants of several minutes up to almost an hour were observed for atomic and molecular, anion and cation beams at an energy of 60 keV. The ion-beam intensity, energy-dependent closed-orbit shifts (dispersion), and the focusing properties of the machine were studied by a system of capacitive pickups. The Schottky-noise spectrum of the stored ions revealed a broadening of the momentum distribution on a time scale of 1000 s. Photodetachment of stored anions was used in the beam lifetime measurements. The detachment rate by anion collisions with residual-gas molecules was found to be extremely low. A residual-gas density below 140 cm(-3) is derived, equivalent to a room-temperature pressure below 10(-14) mbar. Fast atomic, molecular, and cluster ion beams stored for long periods of time in a cryogenic environment will allow experiments on collision- and radiation-induced fragmentation processes of ions in known internal quantum states with merged and crossed photon and particle beams.

The cryogenic storage ring CSR

Energy Technology Data Exchange (ETDEWEB)

Hahn, R. von; Becker, A.; Berg, F.; Blaum, K.; Fadil, H.; Fellenberger, F.; Froese, M.; George, S.; Göck, J.; Grieser, M.; Grussie, F.; Guerin, E. A.; Herwig, P.; Karthein, J.; Krantz, C.; Kreckel, H.; Lange, M.; Laux, F.; Lohmann, S.; Menk, S. [Max-Planck-Institut für Kernphysik, 69117 Heidelberg (Germany); and others

2016-06-15

An electrostatic cryogenic storage ring, CSR, for beams of anions and cations with up to 300 keV kinetic energy per unit charge has been designed, constructed, and put into operation. With a circumference of 35 m, the ion-beam vacuum chambers and all beam optics are in a cryostat and cooled by a closed-cycle liquid helium system. At temperatures as low as (5.5 ± 1) K inside the ring, storage time constants of several minutes up to almost an hour were observed for atomic and molecular, anion and cation beams at an energy of 60 keV. The ion-beam intensity, energy-dependent closed-orbit shifts (dispersion), and the focusing properties of the machine were studied by a system of capacitive pickups. The Schottky-noise spectrum of the stored ions revealed a broadening of the momentum distribution on a time scale of 1000 s. Photodetachment of stored anions was used in the beam lifetime measurements. The detachment rate by anion collisions with residual-gas molecules was found to be extremely low. A residual-gas density below 140 cm{sup −3} is derived, equivalent to a room-temperature pressure below 10{sup −14} mbar. Fast atomic, molecular, and cluster ion beams stored for long periods of time in a cryogenic environment will allow experiments on collision- and radiation-induced fragmentation processes of ions in known internal quantum states with merged and crossed photon and particle beams.

Vertical dispersion generated by correlated closed orbit deviations

International Nuclear Information System (INIS)

Kewisch, J.; Limberg, T.; Rossbach, J.; Willeke, F.

1986-02-01

Vertical displacement of quadrupole magnets is one of the main causes of a vertical dispersion in a flat storage ring and thus a major contributor to the height of an electron beam. Computer simulations of the beam height in the HERA electron ring give a value of the ratio ε z /ε x of more than 10 percent. This large value occurs even for an rms value of the quadrupole vertical displacements Δz as small as 0.01 mm. Such a vertical emittance is much larger than one expects on the base of a theoretical estimate and it is clearly necessary to investigate the origin of the disagreements especially since the beam height has such an important influence on the machine performance. The key to the understanding of this discrepancy lies in the correlations of the closed orbit deviations at different position of the machine. This is investigated in the next section and in the section which follows we derive the expression for the rms value of dispersion and the vertical emittance. Finally the theoretical results are compared with computer simulations. (orig.)

Colliding or co-rotating ion beams in storage rings for EDM search

International Nuclear Information System (INIS)

Koop, I A

2015-01-01

A new approach to search for and measure the electric dipole moment (EDM) of the proton, deuteron and some other light nuclei is presented. The idea of the method is to store two ion beams, circulating with different velocities, in a storage ring with crossed electric and magnetic guiding fields. One beam is polarized and its EDM is measured using the so-called ‘frozen spin’ method. The second beam, which is unpolarized, is used as a co-magnetometer, sensitive to the radial component of the ring’s magnetic field. The particle’s magnetic dipole moment (MDM) couples to the radial magnetic field and mimics the EDM signal. Measuring the relative vertical orbit separation of the two beams, caused by the presence of the radial magnetic field, one can control the unwanted MDM spin precession. Examples of the parameters for EDM storage rings for protons and other species of ions are presented. The use of crossed electric and magnetic fields helps to reduce the size of the ring by a factor of 10–20. We show that the bending radius of such an EDM storage ring could be about 2–3 m. Finally, a new method of increasing the spin coherence time, the so-called ‘spin wheel’, is proposed and its applicability to the EDM search is discussed. (paper)

Rapid Evolution of the Gaseous Exoplanetary Debris Around the White Dwarf Star HE 1349--2305

OpenAIRE

Dennihy, E.; Clemens, J. C.; Dunlap, B. H.; Fanale, S. M.; Fuchs, J. T.; Hermes, J. J.

2018-01-01

Observations of heavy metal pollution in white dwarf stars indicate that metal-rich planetesimals are frequently scattered into star-grazing orbits, tidally disrupted, and accreted onto the white dwarf surface, offering direct insight into the dynamical evolution of post-main-sequence exoplanetary systems. Emission lines from the gaseous debris in the accretion disks of some of these systems show variations on timescales of decades, and have been interpreted as the general relativistic preces...

Cassini-Huygens Nears Saturn Orbit Insertion

Science.gov (United States)

Showstack, Randy

2004-06-01

After nearly 7 years and a 3.5-billion-km, circuitous journey from Earth, the $3-billion Cassini-Huygens mission to Saturn and Titan-an international effort by NASA, the European Space Agency, and the Italian Space Agency-now is just days away from its critical Saturn orbit insertion. Scheduled for 30 June, this will begin the 4-years part of the mission to study the Saturnian system. At a 3 June briefing at NASA headquarters in Washington, D.C., Robert Mitchell, the Cassini program manager with the Jet Propulsion Laboratory in Pasadena, California, said that scientists involved with the program are feeling excited, relieved, and also a bit anxious as the Cassini-Huygens spacecraft draws near to the ringed planet and its system.

MagAO IMAGING OF LONG-PERIOD OBJECTS (MILO). II. A PUZZLING WHITE DWARF AROUND THE SUN-LIKE STAR HD 11112

International Nuclear Information System (INIS)

Rodigas, Timothy J.; Arriagada, Pamela; Faherty, Jacqueline K.; Weinberger, Alycia; Butler, R. Paul; Bergeron, P.; Simon, Amélie; Anglada-Escudé, Guillem; Mamajek, Eric E.; Males, Jared R.; Morzinski, Katie; Close, Laird M.; Hinz, Philip M.; Bailey, Jeremy; Tinney, C. G.; Wittenmyer, Rob; Carter, Brad; Jenkins, James S.; Jones, Hugh; O’Toole, Simon

2016-01-01

HD 11112 is an old, Sun-like star that has a long-term radial velocity (RV) trend indicative of a massive companion on a wide orbit. Here we present direct images of the source responsible for the trend using the Magellan Adaptive Optics system. We detect the object (HD 11112B) at a separation of 2.″2 (100 au) at multiple wavelengths spanning 0.6–4 μ m and show that it is most likely a gravitationally bound cool white dwarf. Modeling its spectral energy distribution suggests that its mass is 0.9–1.1 M ⊙ , which corresponds to very high eccentricity, near edge-on orbits from a Markov chain Monte Carlo analysis of the RV and imaging data together. The total age of the white dwarf is >2 σ , which is discrepant with that of the primary star under most assumptions. The problem can be resolved if the white dwarf progenitor was initially a double white dwarf binary that then merged into the observed high-mass white dwarf. HD 11112B is a unique and intriguing benchmark object that can be used to calibrate atmospheric and evolutionary models of cool white dwarfs and should thus continue to be monitored by RV and direct imaging over the coming years.

MagAO IMAGING OF LONG-PERIOD OBJECTS (MILO). II. A PUZZLING WHITE DWARF AROUND THE SUN-LIKE STAR HD 11112

Energy Technology Data Exchange (ETDEWEB)

Rodigas, Timothy J.; Arriagada, Pamela; Faherty, Jacqueline K.; Weinberger, Alycia; Butler, R. Paul [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015 (United States); Bergeron, P.; Simon, Amélie [Département de Physique, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, Québec H3C 3J7 (Canada); Anglada-Escudé, Guillem [School of Physics and Astronomy, Queen Mary, University of London, 327 Mile End Road, London (United Kingdom); Mamajek, Eric E. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627-0171 (United States); Males, Jared R.; Morzinski, Katie; Close, Laird M.; Hinz, Philip M. [Steward Observatory, The University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States); Bailey, Jeremy; Tinney, C. G.; Wittenmyer, Rob [Exoplanetary Science at UNSW, School of Physics, UNSW Australia, Sydney, NSW 2052 (Australia); Carter, Brad [Computational Engineering and Science Research Centre, University of Southern Queensland, Springfield, QLD 4300 (Australia); Jenkins, James S. [Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Las Condes, Santiago (Chile); Jones, Hugh [Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield, Herts AL10 9AB (United Kingdom); O’Toole, Simon, E-mail: trodigas@carnegiescience.edu [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670 (Australia); and others

2016-11-10

HD 11112 is an old, Sun-like star that has a long-term radial velocity (RV) trend indicative of a massive companion on a wide orbit. Here we present direct images of the source responsible for the trend using the Magellan Adaptive Optics system. We detect the object (HD 11112B) at a separation of 2.″2 (100 au) at multiple wavelengths spanning 0.6–4 μ m and show that it is most likely a gravitationally bound cool white dwarf. Modeling its spectral energy distribution suggests that its mass is 0.9–1.1 M {sub ⊙}, which corresponds to very high eccentricity, near edge-on orbits from a Markov chain Monte Carlo analysis of the RV and imaging data together. The total age of the white dwarf is >2 σ , which is discrepant with that of the primary star under most assumptions. The problem can be resolved if the white dwarf progenitor was initially a double white dwarf binary that then merged into the observed high-mass white dwarf. HD 11112B is a unique and intriguing benchmark object that can be used to calibrate atmospheric and evolutionary models of cool white dwarfs and should thus continue to be monitored by RV and direct imaging over the coming years.

Token Ring Project

Directory of Open Access Journals (Sweden)

Adela Ionescu

2007-01-01

Full Text Available Ring topology is a simple configuration used to connect processes that communicate among themselves. A number of network standards such as token ring, token bus, and FDDI are based on the ring connectivity. This article will develop an implementation of a ring of processes that communicate among themselves via pipe links. The processes are nodes in the ring. Each process reads from its standard input and writes in its standard output. N-1 process redirects the its standard output to a standard input of the process through a pipe. When the ring-structure is designed, the project can be extended to simulate networks or to implement algorithms for mutual exclusion

Fundamentals of the orbit and response for TianQin

Science.gov (United States)

Hu, Xin-Chun; Li, Xiao-Hong; Wang, Yan; Feng, Wen-Fan; Zhou, Ming-Yue; Hu, Yi-Ming; Hu, Shou-Cun; Mei, Jian-Wei; Shao, Cheng-Gang

2018-05-01

TianQin is a space-based laser interferometric gravitational wave detector aimed at detecting gravitational waves at low frequencies (0.1 mHz–1 Hz). It is formed by three identical drag-free spacecrafts in an equilateral triangular constellation orbiting around the Earth. The distance between each pair of spacecrafts is approximately 1.7 × 105 ~km . The spacecrafts are interconnected by infrared laser beams forming up to three Michelson-type interferometers. The detailed mission design and the study of science objectives for the TianQin project depend crucially on the orbit and the response of the detector. In this paper, we provide the analytic expressions for the coordinates of the orbit for each spacecraft in the heliocentric-ecliptic coordinate system to the leading orders. This enables a sufficiently accurate study of science objectives and data analysis, and serves as a first step to further orbit design and optimization. We calculate the response of a single Michelson detector to plane gravitational waves in arbitrary waveform which is valid in the full range of the sensitive frequencies. It is then used to generate the more realistic sensitivity curve of TianQin. We apply this model on a reference white-dwarf binary as a proof of principle.

Semi-algebraic function rings and reflectors of partially ordered rings

CERN Document Server

Schwartz, Niels

1999-01-01

The book lays algebraic foundations for real geometry through a systematic investigation of partially ordered rings of semi-algebraic functions. Real spectra serve as primary geometric objects, the maps between them are determined by rings of functions associated with the spectra. The many different possible choices for these rings of functions are studied via reflections of partially ordered rings. Readers should feel comfortable using basic algebraic and categorical concepts. As motivational background some familiarity with real geometry will be helpful. The book aims at researchers and graduate students with an interest in real algebra and geometry, ordered algebraic structures, topology and rings of continuous functions.

The critical binary star separation for a planetary system origin of white dwarf pollution

Science.gov (United States)

Veras, Dimitri; Xu, Siyi; Rebassa-Mansergas, Alberto

2018-01-01

The atmospheres of between one quarter and one half of observed single white dwarfs in the Milky Way contain heavy element pollution from planetary debris. The pollution observed in white dwarfs in binary star systems is, however, less clear, because companion star winds can generate a stream of matter which is accreted by the white dwarf. Here, we (i) discuss the necessity or lack thereof of a major planet in order to pollute a white dwarf with orbiting minor planets in both single and binary systems, and (ii) determine the critical binary separation beyond which the accretion source is from a planetary system. We hence obtain user-friendly functions relating this distance to the masses and radii of both stars, the companion wind, and the accretion rate on to the white dwarf, for a wide variety of published accretion prescriptions. We find that for the majority of white dwarfs in known binaries, if pollution is detected, then that pollution should originate from planetary material.

Nitrile/Buna N Material Failure Assessment for an O-Ring used on the Gaseous Hydrogen Flow Control Valve (FCV) of the Space Shuttle Main Engine

Science.gov (United States)

Wingard, Doug

2006-01-01

After the rollout of Space Shuttle Discovery in April 2005 in preparation for return-to-flight, there was a failure of the Orbiter (OV-103) helium signature leak test in the gaseous hydrogen (GH2) system. Leakage was attributed to the Flow Control Valve (FCV) in Main Engine 3. The FCV determined to be the source of the leak for OV-103 is designated as LV-58. The nitrile/Buna N rubber O-ring seal was removed from LV-58, and failure analysis indicated radial cracks providing leak paths in one quadrant. Cracks were eventually found in 6 of 9 FCV O-rings among the three Shuttle Orbiters, though none were as severe as those for LV-58, OV-103. Testing by EM10 at MSFC on all 9 FCV O- rings included: laser dimensional, Shore A hardness and properties from a dynamic mechanical analyzer (DMA) and an Instron tensile machine. The following test data was obtained on the cracked quadrant of the LV-58, OV-103 O-ring: (1) the estimated compression set was only 9.5%, compared to none for the rest of the O-ring; (2) Shore A hardness for the O.D. was higher by almost 4 durometer points than for the rest of the O-ring; and (3) DMA data showed that the storage/elastic modulus E was almost 25% lower than for the rest of the O-ring. Of the 8 FCV O-rings tested on an Instron, 4 yielded tensile strengths that were below the MIL spec requirement of 1350 psi-a likely influence of rubber cracking. Comparisons were made between values of modulus determined by DNA (elastic) and Instron (Young s). Each nitrile/Buna N O-ring used in the FCV conforms to the MIL-P-25732C specification. A number of such O-rings taken from shelf storage at MSFC and Kennedy Space Center (KSC) were used to generate a reference curve of DMA glass transition temperature (Tg) vs. shelf storage time ranging from 8 to 26 years. A similar reference curve of TGA onset temperature (of rubber weight loss) vs. shelf storage time was also generated. The DMA and TGA data for the used FCV O-rings were compared to the reference

CERN PS Optical Properties Measured with Turn-By-Turn Orbit Data

CERN Document Server

Bach, T; Giovannozzi, M; Hernalsteens, C; Lachaize, A; Sterbini, G; Tom´as, R; Wasef, R

2013-01-01

The performance of the CERN Proton Synchrotron (PS) has been constantly increasing over the years both in terms of beam parameters (intensity and brightness) and beam manipulations (transverse and longitudinal splitting). This implies a very good knowledge of the linear and non-linear model of the ring. In this paper we report on a detailed campaign of beam measurements based on turn-by-turn orbit data aimed at measuring the optics in several conditions as well as the resonance driving terms.

The terminal Eocene event - Formation of a ring system around the earth

Science.gov (United States)

Okeefe, J. A.

1980-01-01

It is suggested that the formation of a ring system about the earth by particles and debris related to the North American strewn tektite field is responsible for the terminal Eocene event of 34 million years ago, in which severe climatic changes accompanied by widespread biological extinctions occurred. Botanical data is cited which implies a 20-C decrease in winter temperature with no change in summer temperature, and evidence of the correlation of the North American tektite fall, which is estimated to have a total mass of 10 to the 9th to 10 to the 10th tons, with the disappearance of five of the most abundant species of radiolaria is presented. The possible connection between the tektites and climatic change is argued to result from the screening of sunlight by an equatorial ring of trapped particles of extraterrestrial origin in geocentric orbit which would cut off sunlight only in the winter months. Such a ring, located at a distance of between 1.5 and 2.5 earth radii (the Roche limit) is estimated to have a lifetime of a few million years.

Rotating ring-ring electrode theory and experiment

NARCIS (Netherlands)

Kuiken, H.K.; Bakkers, E.P.A.M.; Ligthart, H.; Kellyb, J.J.

2000-01-01

A model is presented for the rotating ring-ring electrode. Although the electrode is defined by four characteristic lengths, it is shown that the collection efficiency depends on only two dimensionless parameters. A simple relationship between these and the corresponding parameters for the rotating

Emittance measurements in low energy ion storage rings

Science.gov (United States)

Hunt, J. R.; Carli, C.; Resta-López, J.; Welsch, C. P.

2018-07-01

The development of the next generation of ultra-low energy antiproton and ion facilities requires precise information about the beam emittance to guarantee optimum performance. In the Extra-Low ENergy Antiproton storage ring (ELENA) the transverse emittances will be measured by scraping. However, this diagnostic measurement faces several challenges: non-zero dispersion, non-Gaussian beam distributions due to effects of the electron cooler and various systematic errors such as closed orbit offsets and inaccurate rms momentum spread estimation. In addition, diffusion processes, such as intra-beam scattering might lead to emittance overestimates. Here, we present algorithms to efficiently address the emittance reconstruction in presence of the above effects, and present simulation results for the case of ELENA.

Proto-jet configurations in RADs orbiting a Kerr SMBH: symmetries and limiting surfaces

Science.gov (United States)

Pugliese, D.; Stuchlík, Z.

2018-05-01

Ringed accretion disks (RADs) are agglomerations of perfect-fluid tori orbiting around a single central attractor that could arise during complex matter inflows in active galactic nuclei. We focus our analysis to axi-symmetric accretion tori orbiting in the equatorial plane of a supermassive Kerr black hole; equilibrium configurations, possible instabilities, and evolutionary sequences of RADs were discussed in our previous works. In the present work we discuss special instabilities related to open equipotential surfaces governing the material funnels emerging at various regions of the RADs, being located between two or more individual toroidal configurations of the agglomerate. These open structures could be associated to proto-jets. Boundary limiting surfaces are highlighted, connecting the emergency of the jet-like instabilities with the black hole dimensionless spin. These instabilities are observationally significant for active galactic nuclei, being related to outflows of matter in jets emerging from more than one torus of RADs orbiting around supermassive black holes.

Electronic States and Persistent Currents in Nanowire Quantum Ring

Science.gov (United States)

Kokurin, I. A.

2018-04-01

The new model of a quantum ring (QR) defined inside a nanowire (NW) is proposed. The one-particle Hamiltonian for electron in [111]-oriented NW QR is constructed taking into account both Rashba and Dresselhaus spin-orbit coupling (SOC). The energy levels as a function of magnetic field are found using the exact numerical diagonalization. The persistent currents (both charge and spin) are calculated. The specificity of SOC and arising anticrossings in energy spectrum lead to unusual features in persistent current behavior. The variation of magnetic field or carrier concentration by means of gate can lead to pure spin persistent current with the charge current being zero.

Topological ring currents in the "empty" ring of benzo-annelated perylenes.

Science.gov (United States)

Dickens, Timothy K; Mallion, Roger B

2011-01-27

Cyclic conjugation in benzo-annelated perylenes is examined by means of the topological π-electron ring currents calculated for each of their constituent rings, in a study that is an exact analogy of a recent investigation by Gutman et al. based on energy-effect values for the corresponding rings in each of these structures. "Classical" approaches, such as Kekulé structures, Clar "sextet" formulas, and circuits of conjugation, predict that the central ring in perylene is "empty" and thus contributes negligibly to cyclic conjugation. However, conclusions from the present calculations of topological ring currents agree remarkably with those arising from the earlier study involving energy-effect values in that, contrary to what would be predicted from the classical approaches, rings annelated in an angular fashion relative to the central ring of these perylene structures materially increase the extent of that ring's involvement in cyclic conjugation. It is suggested that such close quantitative agreement between the predictions of these two superficially very different indices (energy effect and topological ring current) might be due to the fact that, ultimately, both depend, albeit in ostensibly quite different ways, only on an adjacency matrix that contains information about the carbon-carbon connectivity of the conjugated system in question.

Kayser-Fleischer Rings

Science.gov (United States)

... Support Contacts Lab Tracker/Copper Calculator Stories Programs & Research ... About Everything you need to know about Wilson Disease Kayser-Fleischer Rings Definition Kayser-Fleischer Ring: Clinical sign. Brownish-yellow ring visible around the corneo- ...

Planetary Rings

Science.gov (United States)

Nicholson, P. D.

2001-11-01

A revolution in the studies in planetary rings studies occurred in the period 1977--1981, with the serendipitous discovery of the narrow, dark rings of Uranus, the first Voyager images of the tenuous jovian ring system, and the many spectacular images returned during the twin Voyager flybys of Saturn. In subsequent years, ground-based stellar occultations, HST observations, and the Voyager flybys of Uranus (1986) and Neptune (1989), as well as a handful of Galileo images, provided much additional information. Along with the completely unsuspected wealth of detail these observations revealed came an unwelcome problem: are the rings ancient or are we privileged to live at a special time in history? The answer to this still-vexing question may lie in the complex gravitational interactions recent studies have revealed between the rings and their retinues of attendant satellites. Among the four known ring systems, we see elegant examples of Lindblad and corotation resonances (first invoked in the context of galactic disks), electromagnetic resonances, spiral density waves and bending waves, narrow ringlets which exhibit internal modes due to collective instabilities, sharp-edged gaps maintained via tidal torques from embedded moonlets, and tenuous dust belts created by meteoroid impact onto parent bodies. Perhaps most puzzling is Saturn's multi-stranded, clumpy F ring, which continues to defy a simple explanation 20 years after it was first glimpsed in grainy images taken by Pioneer 11. Voyager and HST images reveal a complex, probably chaotic, dynamical interaction between unseen parent bodies within this ring and its two shepherd satellites, Pandora and Prometheus. The work described here reflects contributions by Joe Burns, Jeff Cuzzi, Luke Dones, Dick French, Peter Goldreich, Colleen McGhee, Carolyn Porco, Mark Showalter, and Bruno Sicardy, as well as those of the author. This research has been supported by NASA's Planetary Geology and Geophysics program and the

Preparation for electron ring - plasma ring merging experiments in RECE-MERGE

International Nuclear Information System (INIS)

Taggart, D.; Sekiguchi, A.; Fleischmann, H.H.

1986-01-01

The formation of a mixed-CT using relativistic electron rings and gun-produced plasma rings by MERGE-ing them axially is simulated. This process is similar to the axial stacking of relativistic electron rings in RECE-Christa. The results of their first plasm production experiment are reported here. After study of the gun-produced plasma's properties is completed, the gun will be mounted at the downstream end of the vacuum tank and the source of relativistic electron rings will be at the upstream end. The two rings, formed at opposite ends of the tank, will be translated axially and merged

An IFU-view of Planetary Nebulae: Exploring NGC 6720 (Ring Nebula) with KCWI

Science.gov (United States)

Hoadley, Keri; Matuszewski, Matt; Hamden, Erika; Martin, Christopher; Neill, Don; Kyne, Gillian

2018-01-01

Studying the interaction between the ejected stellar material and interstellar clouds is important for understanding how stellar deaths influences the pollution of matter that will later form other stars. Planetary nebulae provide ideal laboratories to study such interactions. I will present on a case study of one close-by planetary nebula, the Ring Nebula (M 57, NGC 6720), to infer the abundances, temperatures, structures, and dynamics of important atomic and ionic species in two distinct regions of the nebula using a newly-commissioned integral field spectrograph (IFS) on Keck: the Keck Cosmic Web Imager (KCWI). The advantage of an IFS over traditional filter-imaging techniques is the ability to simultaneously observe the spectrum of any given pixel in the imaging area, which provides crucial information about the dynamics of the observed region. This technique is powerful for diffuse or extended astrophysical objects, and I will demonstrate the different imaging and spectral modes of KCWI used to observe the Ring Nebula.KCWI observations of the Ring Nebula focused mainly on the innermost region of the nebula, with a little coverage of the Inner Ring. We also observed the length of the Ring in one set of observations, for which we will estimate the elemental abundances, temperatures, and dynamics of the region. KCWI observations also capture an inner arc and blob that have distinctly difference characteristics than the Ring itself and may be a direct observation of either the planetary nebula ramming into an interstellar cloud projected onto the sightline or a dense interstellar cloud being illuminated by the stellar continuum from the hot central white dwarf.

On the Existence of Regular and Irregular Outer Moons Orbiting the Pluto–Charon System

Energy Technology Data Exchange (ETDEWEB)

Michaely, Erez; Perets, Hagai B.; Grishin, Evgeni [Physics Department, Technion—Israel Institute of Technology, Haifa 3200004 (Israel)

2017-02-10

The dwarf planet Pluto is known to host an extended system of five co-planar satellites. Previous studies have explored the formation and evolution of the system in isolation, neglecting perturbative effects by the Sun. Here we show that secular evolution due to the Sun can strongly affect the evolution of outer satellites and rings in the system, if such exist. Although precession due to extended gravitational potential from the inner Pluto–Charon binary quench such secular evolution up to a {sub crit} ∼ 0.0035 au (∼0.09 R {sub Hill} the Hill radius; including all of the currently known satellites), outer orbits can be significantly altered. In particular, we find that co-planar rings and satellites should not exist beyond a {sub crit}; rather, satellites and dust particles in these regions secularly evolve on timescales ranging between 10{sup 4} and 10{sup 6} years, and quasi-periodically change their inclinations and eccentricities through secular evolution (Lidov–Kozai oscillations). Such oscillations can lead to high inclinations and eccentricities, constraining the range where such satellites (and dust particles) can exist without crossing the orbits of the inner satellites or crossing the outer Hill stability range. Outer satellites, if such exist are therefore likely to be irregular satellites, with orbits limited to be non-circular and/or highly inclined. Current observations, including the recent data from the New-Horizons mission explored only inner regions (<0.0012 au) and excluded the existence of additional satellites; however, the irregular satellites discussed here should reside farther, in the yet uncharted regions around Pluto.

On the Existence of Regular and Irregular Outer Moons Orbiting the Pluto–Charon System

International Nuclear Information System (INIS)

Michaely, Erez; Perets, Hagai B.; Grishin, Evgeni

2017-01-01

The dwarf planet Pluto is known to host an extended system of five co-planar satellites. Previous studies have explored the formation and evolution of the system in isolation, neglecting perturbative effects by the Sun. Here we show that secular evolution due to the Sun can strongly affect the evolution of outer satellites and rings in the system, if such exist. Although precession due to extended gravitational potential from the inner Pluto–Charon binary quench such secular evolution up to a crit ∼ 0.0035 au (∼0.09 R Hill the Hill radius; including all of the currently known satellites), outer orbits can be significantly altered. In particular, we find that co-planar rings and satellites should not exist beyond a crit ; rather, satellites and dust particles in these regions secularly evolve on timescales ranging between 10 4 and 10 6 years, and quasi-periodically change their inclinations and eccentricities through secular evolution (Lidov–Kozai oscillations). Such oscillations can lead to high inclinations and eccentricities, constraining the range where such satellites (and dust particles) can exist without crossing the orbits of the inner satellites or crossing the outer Hill stability range. Outer satellites, if such exist are therefore likely to be irregular satellites, with orbits limited to be non-circular and/or highly inclined. Current observations, including the recent data from the New-Horizons mission explored only inner regions (<0.0012 au) and excluded the existence of additional satellites; however, the irregular satellites discussed here should reside farther, in the yet uncharted regions around Pluto.

Gamma radiation physical-chemical effects on vitamin C contents in white and red guavas

International Nuclear Information System (INIS)

Amaro, Jose Daniel V.; Mansur Netto, Elias

1995-01-01

Guava (Psidium guajava L.) is valuable tropical fruit because its high C vitamin content. Red an white are the most common species of guava found in tropical areas. The ionizing radiation is normally used as a ripen ring retardant for longer storage periods. This work studies gamma radiation effects on the C vitamin concentration in white and red guava. Samples of juices were irradiated using a source of Cobalt-60, with doses of 1,0 2,5 and 5,0 kGy and storing periods of 0,15 and 30 days. The white guava juice showed a 49% loss in the C vitamin concentration with 5 kGy radiation dose, while the red guava juice showed 33% under the same condition. This shows that the juice of white guava is more sensitive to gamma radiations than the red guava. This results suggests a protection mechanism by colour pigments we believe is associated to the aromatic structures in the red specie. (author). 4 refs., 2 tabs

New beam-position monitor system for upgraded Photon Factory storage ring.

Science.gov (United States)

Haga, K; Honda, T; Tadano, M; Obina, T; Kasuga, T

1998-05-01

Accompanying the brilliance-upgrading project at the Photon Factory storage ring, the beam-position monitor (BPM) system has been renovated. The new system was designed to enable precise and fast measurements to correct the closed-orbit distortion (COD), as well as to feed back the orbit position during user runs. There are 42 BPMs newly installed, amounting to a total of 65 BPMs. All of the BPMs are calibrated on the test bench using a coaxially strung metallic wire. The measured electrical offsets are typically 200 micro m in both directions, which is 1/2-1/3 of those of the old-type BPMs. In the signal-processing system, PIN diode switches are employed in order to improve reliability. In the fastest mode, this system is capable of measuring COD within about 10 ms; this fast acquisition will allow fast suppression of the beam movement for frequencies up to 50 Hz using a global feedback system.

TRANSIT SURVEYS FOR EARTHS IN THE HABITABLE ZONES OF WHITE DWARFS

International Nuclear Information System (INIS)

Agol, Eric

2011-01-01

To date the search for habitable Earth-like planets has primarily focused on nuclear burning stars. I propose that this search should be expanded to cool white dwarf stars that have expended their nuclear fuel. I define the continuously habitable zone of white dwarfs and show that it extends from ∼0.005 to 0.02 AU for white dwarfs with masses from 0.4 to 0.9 M sun , temperatures less than ∼10 4 K, and habitable durations of at least 3 Gyr. As they are similar in size to Earth, white dwarfs may be deeply eclipsed by terrestrial planets that orbit edge-on, which can easily be detected with ground-based telescopes. If planets can migrate inward or reform near white dwarfs, I show that a global robotic telescope network could carry out a transit survey of nearby white dwarfs placing interesting constraints on the presence of habitable Earths. If planets were detected, I show that the survey would favor detection of planets similar to Earth: similar size, temperature, and rotation period, and host star temperatures similar to the Sun. The Large Synoptic Survey Telescope could place even tighter constraints on the frequency of habitable Earths around white dwarfs. The confirmation and characterization of these planets might be carried out with large ground and space telescopes.

WHITE DWARF-RED DWARF SYSTEMS RESOLVED WITH THE HUBBLE SPACE TELESCOPE. II. FULL SNAPSHOT SURVEY RESULTS

International Nuclear Information System (INIS)

Farihi, J.; Hoard, D. W.; Wachter, S.

2010-01-01

Results are presented for a Hubble Space Telescope Advanced Camera for Surveys high-resolution imaging campaign of 90 white dwarfs with known or suspected low-mass stellar and substellar companions. Of the 72 targets that remain candidate and confirmed white dwarfs with near-infrared excess, 43 are spatially resolved into two or more components, and a total of 12 systems are potentially triples. For 68 systems where a comparison is possible, 50% have significant photometric distance mismatches between their white dwarf and M dwarf components, suggesting that white dwarf parameters derived spectroscopically are often biased due to the cool companion. Interestingly, 9 of the 30 binaries known to have emission lines are found to be visual pairs and hence widely separated, indicating an intrinsically active cool star and not irradiation from the white dwarf. There is a possible, slight deficit of earlier spectral types (bluer colors) among the spatially unresolved companions, exactly the opposite of expectations if significant mass is transferred to the companion during the common envelope phase. Using the best available distance estimates, the low-mass companions to white dwarfs exhibit a bimodal distribution in projected separation. This result supports the hypothesis that during the giant phases of the white dwarf progenitor, any unevolved companions either migrate inward to short periods of hours to days, or outward to periods of hundreds to thousands of years. No intermediate projected separations of a few to several AU are found among these pairs. However, a few double M dwarfs (within triples) are spatially resolved in this range, empirically demonstrating that such separations were readily detectable among the binaries with white dwarfs. A straightforward and testable prediction emerges: all spatially unresolved, low-mass stellar and substellar companions to white dwarfs should be in short-period orbits. This result has implications for substellar companion and

Ring faults and ring dikes around the Orientale basin on the Moon.

Science.gov (United States)

Andrews-Hanna, Jeffrey C; Head, James W; Johnson, Brandon; Keane, James T; Kiefer, Walter S; McGovern, Patrick J; Neumann, Gregory A; Wieczorek, Mark A; Zuber, Maria T

2018-08-01

The Orientale basin is the youngest and best-preserved multiring impact basin on the Moon, having experienced only modest modification by subsequent impacts and volcanism. Orientale is often treated as the type example of a multiring basin, with three prominent rings outside of the inner depression: the Inner Rook Montes, the Outer Rook Montes, and the Cordillera. Here we use gravity data from NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission to reveal the subsurface structure of Orientale and its ring system. Gradients of the gravity data reveal a continuous ring dike intruded into the Outer Rook along the plane of the fault associated with the ring scarp. The volume of this ring dike is ~18 times greater than the volume of all extrusive mare deposits associated with the basin. The gravity gradient signature of the Cordillera ring indicates an offset along the fault across a shallow density interface, interpreted to be the base of the low-density ejecta blanket. Both gravity gradients and crustal thickness models indicate that the edge of the central cavity is shifted inward relative to the equivalent Inner Rook ring at the surface. Models of the deep basin structure show inflections along the crust-mantle interface at both the Outer Rook and Cordillera rings, indicating that the basin ring faults extend from the surface to at least the base of the crust. Fault dips range from 13-22° for the Cordillera fault in the northeastern quadrant, to 90° for the Outer Rook in the northwestern quadrant. The fault dips for both outer rings are lowest in the northeast, possibly due to the effects of either the direction of projectile motion or regional gradients in pre-impact crustal thickness. Similar ring dikes and ring faults are observed around the majority of lunar basins.

The Northern arc of Eridani’s Debris Ring as seen by ALMA

OpenAIRE

Booth, Mark; Dent, William R. F.; Jordán, Andrés; Lestrade, Jean-François; Hales, Antonio S.; Wyatt, Mark C.; Casassus, Simon; Ertel, Steve; Greaves, Jane; Kennedy, Grant M.; Matrà, Luca; Augereau, Jean-Charles; Villard, Eric

2017-01-01

We present the first Atacama Large Millimeter/submillimeter Array (ALMA) observations of the closest known extrasolar debris disc. This disc orbits the star ε Eri, a K-type star just 3.2 pc away. Due to the proximity of the star, the entire disc cannot fit within the ALMA field of view. Therefore, the observations have been centred 18" North of the star, providing us with a clear detection of the Northern arc of the ring, at a wavelength of 1.3 mm. The observed disc emission is found to be na...

Groups, rings, modules

CERN Document Server

Auslander, Maurice

2014-01-01

This classic monograph is geared toward advanced undergraduates and graduate students. The treatment presupposes some familiarity with sets, groups, rings, and vector spaces. The four-part approach begins with examinations of sets and maps, monoids and groups, categories, and rings. The second part explores unique factorization domains, general module theory, semisimple rings and modules, and Artinian rings. Part three's topics include localization and tensor products, principal ideal domains, and applications of fundamental theorem. The fourth and final part covers algebraic field extensions

Saturn's Rings Edge-on

Science.gov (United States)

1995-01-01

In one of nature's most dramatic examples of 'now-you see-them, now-you-don't', NASA's Hubble Space Telescope captured Saturn on May 22, 1995 as the planet's magnificent ring system turned edge-on. This ring-plane crossing occurs approximately every 15 years when the Earth passes through Saturn's ring plane.For comparison, the top picture was taken by Hubble on December 1, 1994 and shows the rings in a more familiar configuration for Earth observers.The bottom picture was taken shortly before the ring plane crossing. The rings do not disappear completely because the edge of the rings reflects sunlight. The dark band across the middle of Saturn is the shadow of the rings cast on the planet (the Sun is almost 3 degrees above the ring plane.) The bright stripe directly above the ring shadow is caused by sunlight reflected off the rings onto Saturn's atmosphere. Two of Saturn's icy moons are visible as tiny starlike objects in or near the ring plane. They are, from left to right, Tethys (slightly above the ring plane) and Dione.This observation will be used to determine the time of ring-plane crossing and the thickness of the main rings and to search for as yet undiscovered satellites. Knowledge of the exact time of ring-plane crossing will lead to an improved determination of the rate at which Saturn 'wobbles' about its axis (polar precession).Both pictures were taken with Hubble's Wide Field Planetary Camera 2. The top image was taken in visible light. Saturn's disk appears different in the bottom image because a narrowband filter (which only lets through light that is not absorbed by methane gas in Saturn's atmosphere) was used to reduce the bright glare of the planet. Though Saturn is approximately 900 million miles away, Hubble can see details as small as 450 miles across.The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.This image and other images and

The Rotating Ring-Ring Electrode. Theory and Experiment

NARCIS (Netherlands)

Kuiken, H.K.; Bakkers, E.P.A.M.; Ligthart, H.; Kelly, J.J.

2000-01-01

A model is presented for the rotating ring-ring electrode. Although the electrode is defined by four characteristic lengths, it is shown that the collection efficiency depends on only two dimensionless parameters. A simple relationship between these and the corresponding parameters for the rotating

From Data to Equations: Inferring the Laws governing Saturn's Ring Temperature

Science.gov (United States)

Altobelli, N.; Lopez-Paz, D.; Spilker, L.; Pilorz, S.

2011-10-01

Six years after Saturn Orbit Insertion (SOI), the Composite Infrared Spectrometer (CIRS) on-board the Cassini Spacecraft has been performing a thermal mapping of Saturn's main rings, by measuring the thermal radiance in the far-infrared ( [10-600] cm-1 ) for different viewing geometries. So far, more than 2.5 millions individual spectra have been recorded, from Saturn's northern winter solstice till Saturn's northern spring. We present a first attempt of treating the data set globally by applying numerical data mining techniques inherited from the field of artificial intelligence, such as neural networks and genetic programing.

Wear Analysis of Top Piston Ring to Reduce Top Ring Reversal Bore Wear

Directory of Open Access Journals (Sweden)

P. Ilanthirayan

2017-12-01

Full Text Available The piston rings are the most important part in engine which controls the lubricating oil consumption and blowby of the gases. The lubricating film of oil is provided to seal of gases towards crankcase and also to give smooth friction free translatory motion between rings and liner. Of the three rings present top ring is more crucial as it does the main work of restricting gases downwards the crankcase. Boundary lubrication is present at the Top dead centre (TDC and Bottom dead centre (BDC of the liner surface. In addition to this, top ring is exposed to high temperature gases which makes the oil present near the top ring to get evaporated and decreasing its viscosity, making metal-metal contact most of the time. Due to this at TDC, excess wear happens on the liner which is termed as Top ring reversal bore wear. The wear rate depends upon many parameters such as lubrication condition, viscosity index, contact type, normal forces acting on ring, geometry of ring face, surface roughness, material property. The present work explores the wear depth for different geometries of barrel ring using Finite Element model with the help of Archard wear law and the same is validated through experimentation. The study reveals that Asymmetric barrel rings have less contact pressure which in turn reduces the wear at Top dead centre.

PREFACE: Special section on vortex rings Special section on vortex rings

Science.gov (United States)

Fukumoto, Yasuhide

2009-10-01

This special section of Fluid Dynamics Research includes five articles on vortex rings in both classical and quantum fluids. The leading scientists of the field describe the trends in and the state-of-the-art development of experiments, theories and numerical simulations of vortex rings. The year 2008 was the 150th anniversary of 'vortex motion' since Hermann von Helmholtz opened up this field. In 1858, Helmholtz published a paper in Crelle's Journal which put forward the concept of 'vorticity' and made the first analysis of vortex motion. Fluid mechanics before that was limited to irrotational motion. In the absence of vorticity, the motion of an incompressible homogeneous fluid is virtually equivalent to a rigid-body motion in the sense that the fluid motion is determined once the boundary configuration is specified. Helmholtz proved, among other things, that, without viscosity, a vortex line is frozen into the fluid. This Helmholtz's law immediately implies the preservation of knots and links of vortex lines and its implication is enormous. One of the major trends of fluid mechanics since the latter half of the 20th century is to clarify the topological meaning of Helmholtz's law and to exploit it to develop theoretical and numerical methods to find the solutions of the Euler equations and to develop experimental techniques to gain an insight into fluid motion. Vortex rings are prominent coherent structures in a variety of fluid motions from the microscopic scale, through human and mesoscale to astrophysical scales, and have attracted people's interest. The late professor Philip G Saffman (1981) emphasized the significance of studies on vortex rings. One particular motion exemplifies the whole range of problems of vortex motion and is also a commonly known phenomenon, namely the vortex ring or smoke ring. Vortex rings are easily produced by dropping drops of one liquid into another, or by puffing fluid out of a hole, or by exhaling smoke if one has the skill

Cassini Attitude and Articulation Control Subsystem Fault Protection Challenges During Saturn Proximal Orbits

Science.gov (United States)

Bates, David M.

2015-01-01

NASA's Cassini Spacecraft, launched on October 15th, 1997 arrived at Saturn on June 30th, 2004, is the largest and most ambitious interplanetary spacecraft in history. As the first spacecraft to achieve orbit at Saturn, Cassini has collected science data throughout its four-year prime mission (2004-08), and has since been approved for a first and second extended mission through 2017. As part of the final extended mission, Cassini will begin an aggressive and exciting campaign of high inclination low altitude flybys within the inner most rings of Saturn, skimming Saturn's outer atmosphere, until the spacecraft is finally disposed of via planned impact with the planet. This final campaign, known as the proximal orbits, presents unique fault protection related challenges, the details of which are discussed in this paper.

Vortex rings

CERN Document Server

Akhmetov, D G

2009-01-01

This text on vortex rings covers their theoretical foundation, systematic investigations, and practical applications such as the extinction of fires at gushing oil wells. It pays special attention to the formation and motion of turbulent vortex rings.

FUZZY RINGS AND ITS PROPERTIES

Directory of Open Access Journals (Sweden)

Karyati Karyati

2017-01-01

  One of algebraic structure that involves a binary operation is a group that is defined  an un empty set (classical with an associative binary operation, it has identity elements and each element has an inverse. In the structure of the group known as the term subgroup, normal subgroup, subgroup and factor group homomorphism and its properties. Classical algebraic structure is developed to algebraic structure fuzzy by the researchers as an example semi group fuzzy and fuzzy group after fuzzy sets is introduced by L. A. Zadeh at 1965. It is inspired of writing about semi group fuzzy and group of fuzzy, a research on the algebraic structure of the ring is held with reviewing ring fuzzy, ideal ring fuzzy, homomorphism ring fuzzy and quotient ring fuzzy with its properties. The results of this study are obtained fuzzy properties of the ring, ring ideal properties fuzzy, properties of fuzzy ring homomorphism and properties of fuzzy quotient ring by utilizing a subset of a subset level  and strong level  as well as image and pre-image homomorphism fuzzy ring.   Keywords: fuzzy ring, subset level, homomorphism fuzzy ring, fuzzy quotient ring

Skylab ultraviolet stellar spectra - A new white dwarf, HD 149499 B

Science.gov (United States)

Parsons, S. B.; Wray, J. D.; Benedict, G. F.; Henize, K. G.; Laget, M.

1976-01-01

The letter reports the discovery of a cool star with excess brightness in the vacuum ultraviolet on an objective-prism photograph obtained during the second Skylab mission. This star, HD 149499, is of type K0 V and has a companion with an apparent magnitude of about 11.8; the relatively flat UV spectrum observed at the position of HD 149499 is characteristic of a 10th or 11th magnitude unreddened O- or early B-type star. It is shown that the excess VUV brightness is due to the companion, HD 149499B, which probably lies in the region of the H-R diagram occupied by the hot white dwarfs. Inspection of white dwarf lists indicates that this star is the sixth or seventh brightest white dwarf known. A maximum orbital motion of 0.025 arcsec/yr is estimated along with a period of just under 500 yr.

Polarization Insensitivity in Double-Split Ring and Triple-Split Ring Terahertz Resonators

International Nuclear Information System (INIS)

Wu Qian-Nan; Lan Feng; Tang Xiao-Pin; Yang Zi-Qiang

2015-01-01

A modified double-split ring resonator and a modified triple-split ring resonator, which offer polarization-insensitive performance, are investigated, designed and fabricated. By displacing the two gaps of the conventional double-split ring resonator away from the center, the second resonant frequency for the 0° polarized wave and the resonant frequency for the 90° polarized wave become increasingly close to each other until they are finally identical. Theoretical and experimental results show that the modified double-split ring resonator and the modified triple-split ring resonator are insensitive to different polarized waves and show strong resonant frequency dips near 433 and 444 GHz, respectively. The results of this work suggest new opportunities for the investigation and design of polarization-dependent terahertz devices based on split ring resonators. (paper)

Universal Borromean Binding in Spin-Orbit-Coupled Ultracold Fermi Gases

Directory of Open Access Journals (Sweden)

Xiaoling Cui

2014-08-01

Full Text Available Borromean rings and Borromean binding, a class of intriguing phenomena as three objects are linked (bound together while any two of them are unlinked (unbound, widely exist in nature and have been found in systems of biology, chemistry, and physics. Previous studies have suggested that the occurrence of such a binding in physical systems typically relies on the microscopic details of pairwise interaction potentials at short range and is, therefore, nonuniversal. Here, we report a new type of Borromean binding in ultracold Fermi gases with Rashba spin-orbit coupling, which is universal against short-range interaction details, with its binding energy only dependent on the s-wave scattering length and the spin-orbit-coupling strength. We show that the occurrence of this universal Borromean binding is facilitated by the symmetry of the single-particle dispersion under spin-orbit coupling and is, therefore, symmetry selective rather than interaction selective. The state is robust over a wide range of mass ratios between composing fermions, which are accessible by Li-Li, K-K, and K-Li mixtures in cold-atom experiments. Our results reveal the importance of single- particle spectral symmetry in few-body physics and shed light on the emergence of new quantum phases in a many-body system with exotic few-body correlations.

Theoretical and experimental studies of the orbit expansion effect

International Nuclear Information System (INIS)

Glazov, A.A.; Denisov, Yu.N.; Dmitrievskij, V.P.

1985-01-01

Calculation and experiment results of investigations on the orbit expansion effect in the periodic magnetic structures are considered. Experiments, conducted with the use of ring cyclotron electron model, have shown, that the orbit expansion effect leads to the beam cross section radial size increase. This phenomenon was eliminated through the introduction of correction coils, which provide for the required low harmonic phase and value change in the whole acceleration area. Energy spread leads to the spreading of beam in the expansion area. Numeric calculations show, that for the electron model used the relative energy spread must be less than 10 -3 . The conclusion is drawn, that the only real possibility to obtain an accelerated beam with such an energy spread is to perform the ''flat-top'' regime. Equipment for cyclotron electron model RF supply is developed and produced to realise this regime. Particle dinamics calculation in the ''flat-top'' regime and the first experiments have shown, that acceleration asymmetry leads to the rapid coherent oscillation swing in the centre up to the amplitude of 6-7 sm

THREE-DIMENSIONAL ATMOSPHERIC CIRCULATION OF HOT JUPITERS ON HIGHLY ECCENTRIC ORBITS

International Nuclear Information System (INIS)

Kataria, T.; Showman, A. P.; Lewis, N. K.; Fortney, J. J.; Marley, M. S.; Freedman, R. S.

2013-01-01

Of the over 800 exoplanets detected to date, over half are on non-circular orbits, with eccentricities as high as 0.93. Such orbits lead to time-variable stellar heating, which has major implications for the planet's atmospheric dynamical regime. However, little is known about the fundamental dynamical regime of such planetary atmospheres, and how it may influence the observations of these planets. Therefore, we present a systematic study of hot Jupiters on highly eccentric orbits using the SPARC/MITgcm, a model which couples a three-dimensional general circulation model (the MITgcm) with a plane-parallel, two-stream, non-gray radiative transfer model. In our study, we vary the eccentricity and orbit-average stellar flux over a wide range. We demonstrate that the eccentric hot Jupiter regime is qualitatively similar to that of planets on circular orbits; the planets possess a superrotating equatorial jet and exhibit large day-night temperature variations. As in Showman and Polvani, we show that the day-night heating variations induce momentum fluxes equatorward to maintain the superrotating jet throughout its orbit. We find that as the eccentricity and/or stellar flux is increased (corresponding to shorter orbital periods), the superrotating jet strengthens and narrows, due to a smaller Rossby deformation radius. For a select number of model integrations, we generate full-orbit light curves and find that the timing of transit and secondary eclipse viewed from Earth with respect to periapse and apoapse can greatly affect what we see in infrared (IR) light curves; the peak in IR flux can lead or lag secondary eclipse depending on the geometry. For those planets that have large temperature differences from dayside to nightside and rapid rotation rates, we find that the light curves can exhibit 'ringing' as the planet's hottest region rotates in and out of view from Earth. These results can be used to explain future observations of eccentric transiting exoplanets.

Measurement of Systematic Error Effects for a Sensitive Storage Ring EDM Polarimeter

Science.gov (United States)

Imig, Astrid; Stephenson, Edward

2009-10-01

The Storage Ring EDM Collaboration was using the Cooler Synchrotron (COSY) and the EDDA detector at the Forschungszentrum J"ulich to explore systematic errors in very sensitive storage-ring polarization measurements. Polarized deuterons of 235 MeV were used. The analyzer target was a block of 17 mm thick carbon placed close to the beam so that white noise applied to upstream electrostatic plates increases the vertical phase space of the beam, allowing deuterons to strike the front face of the block. For a detector acceptance that covers laboratory angles larger than 9 ^o, the efficiency for particles to scatter into the polarimeter detectors was about 0.1% (all directions) and the vector analyzing power was about 0.2. Measurements were made of the sensitivity of the polarization measurement to beam position and angle. Both vector and tensor asymmetries were measured using beams with both vector and tensor polarization. Effects were seen that depend upon both the beam geometry and the data rate in the detectors.

The binary white dwarf LHS 3236

Energy Technology Data Exchange (ETDEWEB)

Harris, Hugh C.; Dahn, Conard C.; Canzian, Blaise; Guetter, Harry H.; Levine, Stephen E.; Luginbuhl, Christian B.; Monet, Alice K. B.; Stone, Ronald C.; Subasavage, John P.; Tilleman, Trudy; Walker, Richard L. [US Naval Observatory, 10391 West Naval Observatory Road, Flagstaff, AZ 86001-8521 (United States); Dupuy, Trent J.; Liu, Michael C. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Hartkopf, William I. [US Naval Observatory, 3450 Massachusetts Avenue, N.W., Washington, DC 20392-5420 (United States); Ireland, Michael J. [Department of Physics and Astronomy, Macquarie University, New South Wales, NSW 2109 (Australia); Leggett, S. K., E-mail: hch@nofs.navy.mil [Gemini Observatory, 670 N. Aohoku Place, Hilo, HI 96720 (United States)

2013-12-10

The white dwarf LHS 3236 (WD1639+153) is shown to be a double-degenerate binary, with each component having a high mass. Astrometry at the U.S. Naval Observatory gives a parallax and distance of 30.86 ± 0.25 pc and a tangential velocity of 98 km s{sup –1}, and reveals binary orbital motion. The orbital parameters are determined from astrometry of the photocenter over more than three orbits of the 4.0 yr period. High-resolution imaging at the Keck Observatory resolves the pair with a separation of 31 and 124 mas at two epochs. Optical and near-IR photometry give a set of possible binary components. Consistency of all data indicates that the binary is a pair of DA stars with temperatures near 8000 and 7400 K and with masses of 0.93 and 0.91 M {sub ☉}; also possible is a DA primary and a helium DC secondary with temperatures near 8800 and 6000 K and with masses of 0.98 and 0.69 M {sub ☉}. In either case, the cooling ages of the stars are ∼3 Gyr and the total ages are <4 Gyr. The combined mass of the binary (1.66-1.84 M {sub ☉}) is well above the Chandrasekhar limit; however, the timescale for coalescence is long.

Proposal for the generation of photon pairs with nonzero orbital angular momentum in a ring fiber

Czech Academy of Sciences Publication Activity Database

Javůrek, D.; Svozilík, J.; Peřina ml., Jan

2014-01-01

Roč. 22, č. 19 (2014), s. 23743-23748 ISSN 1094-4087 R&D Projects: GA ČR GAP205/12/0382 Institutional support: RVO:68378271 Keywords : photon pairs * orbital-angular-momentum states * spontaneous parametric down-conversion Subject RIV: BH - Optics , Masers, Lasers Impact factor: 3.488, year: 2014

RINGED ACCRETION DISKS: EQUILIBRIUM CONFIGURATIONS

Energy Technology Data Exchange (ETDEWEB)

Pugliese, D.; Stuchlík, Z., E-mail: d.pugliese.physics@gmail.com, E-mail: zdenek.stuchlik@physics.cz [Institute of Physics and Research Centre of Theoretical Physics and Astrophysics, Faculty of Philosophy and Science, Silesian University in Opava, Bezručovo náměstí 13, CZ-74601 Opava (Czech Republic)

2015-12-15

We investigate a model of a ringed accretion disk, made up by several rings rotating around a supermassive Kerr black hole attractor. Each toroid of the ringed disk is governed by the general relativity hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. Properties of the tori can then be determined by an appropriately defined effective potential reflecting the background Kerr geometry and the centrifugal effects. The ringed disks could be created in various regimes during the evolution of matter configurations around supermassive black holes. Therefore, both corotating and counterrotating rings have to be considered as being a constituent of the ringed disk. We provide constraints on the model parameters for the existence and stability of various ringed configurations and discuss occurrence of accretion onto the Kerr black hole and possible launching of jets from the ringed disk. We demonstrate that various ringed disks can be characterized by a maximum number of rings. We present also a perturbation analysis based on evolution of the oscillating components of the ringed disk. The dynamics of the unstable phases of the ringed disk evolution seems to be promising in relation to high-energy phenomena demonstrated in active galactic nuclei.

Stirling engine piston ring

Science.gov (United States)

Howarth, Roy B.

1983-01-01

A piston ring design for a Stirling engine wherein the contact pressure between the piston and the cylinder is maintained at a uniform level, independent of engine conditions through a balancing of the pressure exerted upon the ring's surface and thereby allowing the contact pressure on the ring to be predetermined through the use of a preloaded expander ring.

Physics of quantum rings

International Nuclear Information System (INIS)

Fomin, Vladimir M.

2014-01-01

Presents the new class of materials of quantum rings. Provides an elemental basis for low-cost high-performance devices promising for electronics, optoelectronics, spintronics and quantum information processing. Explains the physical properties of quantum rings to cover a gap in scientific literature. Presents the application of most advanced nanoengineering and nanocharacterization techniques. This book deals with a new class of materials, quantum rings. Innovative recent advances in experimental and theoretical physics of quantum rings are based on the most advanced state-of-the-art fabrication and characterization techniques as well as theoretical methods. The experimental efforts allow to obtain a new class of semiconductor quantum rings formed by capping self-organized quantum dots grown by molecular beam epitaxy. Novel optical and magnetic properties of quantum rings are associated with non-trivial topologies at the nanoscale. An adequate characterization of quantum rings is possible on the basis of modern characterization methods of nanostructures, such as Scanning Tunneling Microscopy. A high level of complexity is demonstrated to be needed for a dedicated theoretical model to adequately represent the specific features of quantum rings. The findings presented in this book contribute to develop low-cost high-performance electronic, spintronic, optoelectronic and information processing devices based on quantum rings.

How does the blue-ringed octopus (Hapalochlaena lunulata) flash its blue rings?

Science.gov (United States)

Mäthger, Lydia M; Bell, George R R; Kuzirian, Alan M; Allen, Justine J; Hanlon, Roger T

2012-11-01

The blue-ringed octopus (Hapalochlaena lunulata), one of the world's most venomous animals, has long captivated and endangered a large audience: children playing at the beach, divers turning over rocks, and biologists researching neurotoxins. These small animals spend much of their time in hiding, showing effective camouflage patterns. When disturbed, the octopus will flash around 60 iridescent blue rings and, when strongly harassed, bite and deliver a neurotoxin that can kill a human. Here, we describe the flashing mechanism and optical properties of these rings. The rings contain physiologically inert multilayer reflectors, arranged to reflect blue-green light in a broad viewing direction. Dark pigmented chromatophores are found beneath and around each ring to enhance contrast. No chromatophores are above the ring; this is unusual for cephalopods, which typically use chromatophores to cover or spectrally modify iridescence. The fast flashes are achieved using muscles under direct neural control. The ring is hidden by contraction of muscles above the iridophores; relaxation of these muscles and contraction of muscles outside the ring expose the iridescence. This mechanism of producing iridescent signals has not previously been reported in cephalopods and we suggest that it is an exceptionally effective way to create a fast and conspicuous warning display.

α-Skew π-McCoy Rings

Directory of Open Access Journals (Sweden)

Areej M. Abduldaim

2013-01-01

Full Text Available As a generalization of α-skew McCoy rings, we introduce the concept of α-skew π-McCoy rings, and we study the relationships with another two new generalizations, α-skew π1-McCoy rings and α-skew π2-McCoy rings, observing the relations with α-skew McCoy rings, π-McCoy rings, α-skew Armendariz rings, π-regular rings, and other kinds of rings. Also, we investigate conditions such that α-skew π1-McCoy rings imply α-skew π-McCoy rings and α-skew π2-McCoy rings. We show that in the case where R is a nonreduced ring, if R is 2-primal, then R is an α-skew π-McCoy ring. And, let R be a weak (α,δ-compatible ring; if R is an α-skew π1-McCoy ring, then R is α-skew π2-McCoy.

VUV optical ring resonator for Duke storage ring free electron laser

Energy Technology Data Exchange (ETDEWEB)

Park, S.H.; Litvinenko, V.N.; Madey, J.M.J. [Duke Univ., Durham, NC (United States)] [and others

1995-12-31

The conceptual design of the multifaceted-mirror ring resonator for Duke storage ring VUV FEL is presented. The expected performance of the OK-4 FEL with ring resonator is described. We discuss in this paper our plans to study reflectivity of VUV mirrors and their resistivity to soft X-ray spontaneous radiation from OK-4 undulator.

Comparative analysis of long-time variations of multicomponent ion ring current according to data of geostationary Gorizont satellite

International Nuclear Information System (INIS)

Kovtyukh, A.S.; Panasyuk, M.I.; Vlasova, N.A.; Sosnovets, Eh.N.

1990-01-01

Long-time variations of the fluxes of the H + , [N,O] 2+ and [C,N,O] 6 6 + ions with energy E/Q∼60-120 keV/e measured by the GORIZONT (1985-07A) satellite in the geostationary orbit at noon time are analyzed. The results are dsicussed and are compared with current models of the formation of the Earth's ion ring current

Interaction Region Design for a Ring-Ring LHeC

CERN Document Server

Thompson, L N S; Bernard, N R; Fitterer, M; Holzer, B; Klein, M; Kostka, P

2011-01-01

tively low energy and moderately high intensity provides high luminosity TeV-scale e-p collisions at one of the LHC interaction points, running simultaneously with existing experiments. Two designs are studied; an electron ring situated in the LHC tunnel, and an electron linac. The focus of this paper is on the ring design. Designing an e-p machine presents interesting accelerator physics and design challenges, particularly when considering the interaction region. These include coupled optics, beam separation and unconventional mini-beta focusing schemes. Designs are constrained by an array of interdependent factors, including beam-beam interaction, detector dimensions and acceptance, luminosity and synchrotron radiation. Methods of addressing these complex issues are discussed. The current designs for the LHeC Ring-Ring interaction region and long straight section are presented and discussed, in the context of the project goals and design challenges encountered. Future developments and work are also discusse...

Ab Initio Calculations of 31P NMR Chemical Shielding Anisotropy Tensors in Phosphates: Variations Due to Ring Formation

Directory of Open Access Journals (Sweden)

Todd M. Alam

2002-08-01

Full Text Available Abstract: Ring formation in phosphate systems is expected to influence both the magnitude and orientation of the phosphorus (31P nuclear magnetic resonance (NMR chemical shielding anisotropy (CSA tensor. Ab initio calculations of the 31P CSA tensor in both cyclic and acyclic phosphate clusters were performed as a function of the number of phosphate tetrahedral in the system. The calculation of the 31P CSA tensors employed the GAUSSIAN 98 implementation of the gauge-including atomic orbital (GIAO method at the Hartree-Fock (HF level. It is shown that both the 31P CSA tensor anisotropy, and the isotropic chemical shielding can be used for the identification of cyclic phosphates. The differences between the 31P CSA tensor in acyclic and cyclic phosphate systems become less pronounced with increasing number of phosphate groups within the ring. The orientation of the principal components for the 31P CSA tensor shows some variation due to cyclization, most notably with the smaller, highly strained ring systems.

Uniquely Strongly Clean Group Rings

Institute of Scientific and Technical Information of China (English)

WANG XIU-LAN

2012-01-01

A ring R is called clean if every element is the sum of an idempotent and a unit,and R is called uniquely strongly clean (USC for short) if every element is uniquely the sum of an idempotent and a unit that commute.In this article,some conditions on a ring R and a group G such that RG is clean are given.It is also shown that if G is a locally finite group,then the group ring RG is USC if and only if R is USC,and G is a 2-group.The left uniquely exchange group ring,as a middle ring of the uniquely clean ring and the USC ring,does not possess this property,and so does the uniquely exchange group ring.

WD0837+185: THE FORMATION AND EVOLUTION OF AN EXTREME MASS-RATIO WHITE-DWARF-BROWN-DWARF BINARY IN PRAESEPE

International Nuclear Information System (INIS)

Casewell, S. L.; Burleigh, M. R.; Wynn, G. A.; Alexander, R. D.; Lawrie, K. A.; Jameson, R. F.; Napiwotzki, R.; Dobbie, P. D.; Hodgkin, S. T.

2012-01-01

There is a striking and unexplained dearth of brown dwarf companions in close orbits ( ☉ (B9). The high mass of the white dwarf means the substellar companion must have been engulfed by the B star's envelope while it was on the late asymptotic giant branch (AGB). Hence, the initial separation of the system was ∼2 AU, with common envelope evolution reducing the separation to its current value. The initial and final orbital separations allow us to constrain the combination of the common envelope efficiency (α) and binding energy parameters (λ) for the AGB star to αλ ∼ 3. We examine the various formation scenarios and conclude that the substellar object was most likely captured by the white dwarf progenitor early in the life of the cluster, rather than forming in situ.

Mean Orbital Elements for Geosynchronous Orbit - II - Orbital inclination, longitude of ascending node, mean longitude

Directory of Open Access Journals (Sweden)

Kyu-Hong Choi

1990-06-01

Full Text Available The osculating orbital elements include the mean, secular, long period, and short period terms. The iterative algorithm used for conversion of osculating orbital elements to mean orbital elements is described. The mean orbital elements of Wc, Ws, and L are obtained.

Influence of ring growth rate on damage development in hot ring rolling

NARCIS (Netherlands)

Wang, C.; Geijselaers, H. J.M.; Omerspahic, E.; Recina, V.; van den Boogaard, A. H.

2015-01-01

As an incremental forming process of bulk metal, ring rolling provides a cost effective process route to manufacture seamless rings. In the production of hot rolled rings, defects such as porosity can sometimes be found in high alloyed steel, manufactured from ingots having macro-segregation. For

Orbit Determination for the Lunar Reconnaissance Orbiter Using an Extended Kalman Filter

Science.gov (United States)

Slojkowski, Steven; Lowe, Jonathan; Woodburn, James

2015-01-01

Since launch, the FDF has performed daily OD for LRO using the Goddard Trajectory Determination System (GTDS). GTDS is a batch least-squares (BLS) estimator. The tracking data arc for OD is 36 hours. Current operational OD uses 200 x 200 lunar gravity, solid lunar tides, solar radiation pressure (SRP) using a spherical spacecraft area model, and point mass gravity for the Earth, Sun, and Jupiter. LRO tracking data consists of range and range-rate measurements from: Universal Space Network (USN) stations in Sweden, Germany, Australia, and Hawaii. A NASA antenna at White Sands, New Mexico (WS1S). NASA Deep Space Network (DSN) stations. DSN data was sparse and not included in this study. Tracking is predominantly (50) from WS1S. The OD accuracy requirements are: Definitive ephemeris accuracy of 500 meters total position root-mean-squared (RMS) and18 meters radial RMS. Predicted orbit accuracy less than 800 meters root sum squared (RSS) over an 84-hour prediction span.

Ring rotational speed trend analysis by FEM approach in a Ring Rolling process

Science.gov (United States)

Allegri, G.; Giorleo, L.; Ceretti, E.

2018-05-01

Ring Rolling is an advanced local incremental forming technology to fabricate directly precise seamless ring-shape parts with various dimensions and materials. In this process two different deformations occur in order to reduce the width and the height of a preform hollow ring; as results a diameter expansion is obtained. In order to guarantee a uniform deformation, the preform is forced toward the Driver Roll whose aim is to transmit the rotation to the ring. The ring rotational speed selection is fundamental because the higher is the speed the higher will be the axial symmetry of the deformation process. However, it is important to underline that the rotational speed will affect not only the final ring geometry but also the loads and energy needed to produce it. Despite this importance in industrial environment, usually, a constant value for the Driver Roll angular velocity is set so to result in a decreasing trend law for the ring rotational speed. The main risk due to this approach is not fulfilling the axial symmetric constrain (due to the diameter expansion) and to generate a high localized ring section deformation. In order to improve the knowledge about this topic in the present paper three different ring rotational speed trends (constant, linearly increasing and linearly decreasing) were investigated by FEM approach. Results were compared in terms of geometrical and dimensional analysis, loads and energies required.

Mechanical improvement of metal reinforcement rings for a finite ring-shaped superconducting bulk

Science.gov (United States)

Huang, Chen-Guang; Zhou, You-He

2018-03-01

As a key technique, reinforcement of type-II superconducting bulks with metal rings can efficiently improve their mechanical properties to enhance the maximum trapped field. In this paper, we study the magnetostrictive and fracture behaviors of a finite superconducting ring bulk reinforced by three typical reinforcing structures composed of metal rings during the magnetizing process by means of the minimization of magnetic energy and the finite element method. After a field-dependent critical current density is adopted, the magnetostriction, pinning-induced stress, and crack tip stress intensity factor are calculated considering the demagnetization effects. The results show that the mechanical properties of the ring bulk are strongly dependent on the reinforcing structure and the material and geometrical parameters of the metal rings. Introducing the metal ring can significantly reduce the hoop stress, and the reduction effect by internal reinforcement is much improved relative to external reinforcement. By comparison, bilateral reinforcement seems to be the best candidate structure. Only when the metal rings have particular Young's modulus and radial thickness will they contribute to improve the mechanical properties the most. In addition, if an edge crack is pre-existing in the ring bulk, the presence of metal rings can effectively avoid crack propagation since it reduces the crack tip stress intensity factor by nearly one order of magnitude.

Ring correlations in random networks.

Science.gov (United States)

Sadjadi, Mahdi; Thorpe, M F

2016-12-01

We examine the correlations between rings in random network glasses in two dimensions as a function of their separation. Initially, we use the topological separation (measured by the number of intervening rings), but this leads to pseudo-long-range correlations due to a lack of topological charge neutrality in the shells surrounding a central ring. This effect is associated with the noncircular nature of the shells. It is, therefore, necessary to use the geometrical distance between ring centers. Hence we find a generalization of the Aboav-Weaire law out to larger distances, with the correlations between rings decaying away when two rings are more than about three rings apart.

"Ring rain" on Saturn's ionosphere: densities and temperatures from 2011 observations and re-detection in 2013 observations

Science.gov (United States)

O'Donoghue, J.; Moore, L.; Melin, H.; Connerney, J. E. P.; Oliversen, R. J.