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Sample records for relativistic thin disks

  1. Relativistic static thin disks: The counterrotating model

    NASA Astrophysics Data System (ADS)

    González, Guillermo A.; Espitia, Omar A.

    2003-11-01

    A detailed study is presented of the counterrotating model (CRM) for generic finite static axially symmetric thin disks with nonzero radial pressure. A general constraint over the counterrotating tangential velocities, needed to cast the surface energy-momentum tensor of the disk as the superposition of two counterrotating perfect fluids, and expressions for the energy density and pressure of the counterrotating fluids are obtained. We show that, in general, it is not possible to take the two counterrotating fluids as circulating along geodesics nor take the two counterrotating tangential velocities as equal and opposite. A simple family of disks is studied that admits some CRMs with well defined counterrotating tangential velocities and stable against radial perturbations.

  2. General Relativistic Magnetohydrodynamic Simulations of Jet Formation with a Thin Keplerian Disk

    NASA Technical Reports Server (NTRS)

    Mizuno, Yosuke; Nishikawa, Ken-Ichi; Koide, Shinji; Hardee, Philip; Gerald, J. Fishman

    2006-01-01

    We have performed several simulations of black hole systems (non-rotating, black hole spin parameter a = 0.0 and rapidly rotating, a = 0.95) with a geometrically thin Keplerian disk using the newly developed RAISHIN code. The simulation results show the formation of jets driven by the Lorentz force and the gas pressure gradient. The jets have mildly relativistic speed (greater than or equal to 0.4 c). The matter is continuously supplied from the accretion disk and the jet propagates outward until each applicable terminal simulation time (non-rotating: t/tau S = 275 and rotating: t/tau S = 200, tau s equivalent to r(sub s/c). It appears that a rotating black hole creates an additional, faster, and more collimated inner outflow (greater than or equal to 0.5 c) formed and accelerated by the twisted magnetic field resulting from frame-dragging in the black hole ergosphere. This new result indicates that jet kinematic structure depends on black hole rotation.

  3. Relativistic static thin dust disks with an inner edge: An infinite family of new exact solutions

    SciTech Connect

    Gonzalez, Guillermo A.; Gutierrez-Pineres, Antonio C.; Vina-Cervantes, Viviana M.

    2009-06-15

    An infinite family of new exact solutions of the vacuum Einstein equations is presented. The solutions are static and axially symmetric and correspond to an infinite family of thin dust disks with a central inner edge. The metric functions of all the solutions can be explicitly computed, and can be expressed in a simple manner in terms of oblate spheroidal coordinates. The energy density of all the disks of the family is positive everywhere and well behaved, so that the corresponding energy-momentum tensor is in full agreement with all the energy conditions. Moreover, although the total mass of the disks is infinite, the solutions are asymptotically flat and the Riemann tensor is regular everywhere, as it is shown by computing the curvature scalars. Now, besides its importance as a new family of exact solutions of the vacuum Einstein equations, the main importance of this family of solutions is that it can be easily superposed with the Schwarzschild solution in order to describe thin disks surrounding a central black hole. Accordingly, a detailed analysis of this superposition will be presented in a subsequent paper.

  4. Electrovacuum static counterrotating relativistic dust disks

    NASA Astrophysics Data System (ADS)

    García R., Gonzalo; González, Guillermo A.

    2004-06-01

    A detailed study is presented of the counterrotating model (CRM) for generic electrovacuum static axially symmetric relativistic thin disks without radial pressure. We find a general constraint over the counterrotating tangential velocities needed to cast the surface energy-momentum tensor of the disk as the superposition of two counterrotating charged dust fluids. We also find explicit expressions for the energy densities, charge densities and velocities of the counterrotating fluids. We then show that this constraint can be satisfied if we take the two counterrotating streams as circulating along electrogeodesics. However, we show that, in general, it is not possible to take the two counterrotating fluids as circulating along electrogeodesics nor take the two counterrotating tangential velocities as equal and opposite. Four simple families of models of counterrotating charged disks based on Chazy-Curzon-type, Zipoy-Voorhees-type, Bonnor-Sackfield-type, and Kerr-type electrovacuum solutions are considered where we obtain some disks with a CRM well behaved. The models are constructed using the well-known “displace, cut and reflect” method extended to solutions of vacuum Einstein-Maxwell equations.

  5. Observational evidence for thin AGN disks

    NASA Technical Reports Server (NTRS)

    Netzer, Hagai

    1992-01-01

    AGN spectrum and spectral features, polarization, inclination, and X-ray line and continuum reflection features are discussed in a critical way in order to determine the ones that are the least model-dependent. The sign and strength of absorption and emission edges are found to be model-dependent, and relativistic broadening and shifting makes them hard to detect. The presence or absence of the predicted Lyman edge polarization feature may be used as a decisive test for thin, bare AGN disks. Other good model-independent tests are several inclination-related line and continuum correlations in big AGN samples. It is shown that electron temperature near the surface of the disk can greatly exceed the disk equilibrium temperature, which causes deviations from LTE. This effect must be incorporated into realistic disk models.

  6. Stability of general-relativistic accretion disks

    SciTech Connect

    Korobkin, Oleg; Abdikamalov, Ernazar B.; Schnetter, Erik; Stergioulas, Nikolaos; Zink, Burkhard

    2011-02-15

    Self-gravitating relativistic disks around black holes can form as transient structures in a number of astrophysical scenarios such as binary neutron star and black hole-neutron star coalescences, as well as the core collapse of massive stars. We explore the stability of such disks against runaway and nonaxisymmetric instabilities using three-dimensional hydrodynamics simulations in full general relativity using the Thor code. We model the disk matter using the ideal fluid approximation with a {Gamma}-law equation of state with {Gamma}=4/3. We explore three disk models around nonrotating black holes with disk-to-black hole mass ratios of 0.24, 0.17, and 0.11. Because of metric blending in our initial data, all of our initial models contain an initial axisymmetric perturbation which induces radial disk oscillations. Despite these oscillations, our models do not develop the runaway instability during the first several orbital periods. Instead, all of the models develop unstable nonaxisymmetric modes on a dynamical time scale. We observe two distinct types of instabilities: the Papaloizou-Pringle and the so-called intermediate type instabilities. The development of the nonaxisymmetric mode with azimuthal number m=1 is accompanied by an outspiraling motion of the black hole, which significantly amplifies the growth rate of the m=1 mode in some cases. Overall, our simulations show that the properties of the unstable nonaxisymmetric modes in our disk models are qualitatively similar to those in the Newtonian theory.

  7. Stability of general-relativistic accretion disks

    NASA Astrophysics Data System (ADS)

    Korobkin, Oleg; Abdikamalov, Ernazar B.; Schnetter, Erik; Stergioulas, Nikolaos; Zink, Burkhard

    2011-02-01

    Self-gravitating relativistic disks around black holes can form as transient structures in a number of astrophysical scenarios such as binary neutron star and black hole-neutron star coalescences, as well as the core collapse of massive stars. We explore the stability of such disks against runaway and nonaxisymmetric instabilities using three-dimensional hydrodynamics simulations in full general relativity using the Thor code. We model the disk matter using the ideal fluid approximation with a Γ-law equation of state with Γ=4/3. We explore three disk models around nonrotating black holes with disk-to-black hole mass ratios of 0.24, 0.17, and 0.11. Because of metric blending in our initial data, all of our initial models contain an initial axisymmetric perturbation which induces radial disk oscillations. Despite these oscillations, our models do not develop the runaway instability during the first several orbital periods. Instead, all of the models develop unstable nonaxisymmetric modes on a dynamical time scale. We observe two distinct types of instabilities: the Papaloizou-Pringle and the so-called intermediate type instabilities. The development of the nonaxisymmetric mode with azimuthal number m=1 is accompanied by an outspiraling motion of the black hole, which significantly amplifies the growth rate of the m=1 mode in some cases. Overall, our simulations show that the properties of the unstable nonaxisymmetric modes in our disk models are qualitatively similar to those in the Newtonian theory.

  8. Scattering from Thin Dielectric Disks

    NASA Technical Reports Server (NTRS)

    Levine, D. M.; Schneider, A.; Lang, R. H.; Carter, H. G.

    1984-01-01

    A solution was obtained for scattering from thin dielectric disks by approximating the currents induced inside the disk with the currents which would exist inside a dielectric slab of the same thickness, orientation and dielectric properties. This approximation reduces to an electrostatic approximation when the disk thickness, T, is small compared to the wavelength of the incident radiation and the approximation yields a conventional physical optics solution when the dimension, A, characteristic of the geometrical cross section of the disk (e.g., the diameter of a circular disk) is large compared to wavelength. When the ratio A/T is sufficiently large the disk will always be in one or the other of these regimes (T lambda or kA1. Consequently, when A/T is large this solution provides a conventional approximation for the scattered fields which can be applied at all frequencies. As a check on this conclusion, a comparison was made between the theoretical and measured radar cross section of thin dielectric disks. Agreement was found for thin disks with both large and small values of kA.

  9. Exploring Stability of General Relativistic Accretion Disks

    NASA Astrophysics Data System (ADS)

    Korobkin, Oleg; Abdikamalov, Ernazar; Schnetter, Erik; Stergioulas, Nikolaos; Zink, Burkhard

    2011-04-01

    Self-gravitating relativistic disks around black holes can form as transient structures in a number of astrophysical scenarios, involving core collapse of massive stars and mergers of compact ob jects. I will present results on our recent study of the stability of such disks against runaway and non-axisymmetric instabilities, which we explore using three-dimensional hydrodynamics simulations in full general relativity. All of our models develop unstable non-axisymmetric modes on a dynamical timescale. We observe two distinct types of instabilities: the Papaloizou-Pringle and the so-called intermediate type instabilities. The development of the non-axisymmetric mode with azimuthal number m=1 is accompanied by an outspiraling motion of the black hole, which significantly amplifies the growth rate of the m=1 mode in some cases. We will discuss the types, growth rates and pattern speeds of the unstable modes, as well as the detectability of the gravitational waves from such objects.

  10. Conservative GRMHD simulations of moderately thin, tilted accretion disks

    SciTech Connect

    Teixeira, Danilo Morales; Fragile, P. Chris; Zhuravlev, Viacheslav V.; Ivanov, Pavel B.

    2014-12-01

    This paper presents our latest numerical simulations of accretion disks that are misaligned with respect to the rotation axis of a Kerr black hole. In this work, we use a new, fully conservative version of the Cosmos++ general relativistic magnetohydrodynamics (GRMHD) code, coupled with an ad hoc cooling function designed to control the thickness of the disk. Together these allow us to simulate the thinnest tilted accretion disks ever using a GRMHD code. In this way, we are able to probe the regime where the dimensionless stress and scale height of the disk become comparable. We present results for both prograde and retrograde cases. The simulated prograde tilted disk shows no sign of Bardeen-Petterson alignment even in the innermost parts of the disk. The simulated retrograde tilted disk, however, does show modest alignment. The implication of these results is that the parameter space associated with Bardeen-Petterson alignment for prograde disks may be rather small, only including very thin disks. Unlike our previous work, we find no evidence for standing shocks in our simulated tilted disks. We ascribe this to the black hole spin, tilt angle, and disk scale height all being small in these simulations. We also add to the growing body of literature pointing out that the turbulence driven by the magnetorotational instability in global simulations of accretion disks is not isotropic. Finally, we provide a comparison between our moderately thin, untilted reference simulation and other numerical simulations of thin disks in the literature.

  11. Magnetically Torqued Thin Accretion Disks

    NASA Astrophysics Data System (ADS)

    Kluźniak, W.; Rappaport, S.

    2007-12-01

    We compute the properties of a geometrically thin, steady accretion disk surrounding a central rotating, magnetized star. The magnetosphere is assumed to entrain the disk over a wide range of radii. The model is simplified in that we adopt two (alternate) ad hoc, but plausible, expressions for the azimuthal component of the magnetic field as a function of radial distance. We find a solution for the angular velocity profile tending to corotation close to the central star and smoothly matching a Keplerian curve at a radius where the viscous stress vanishes. The value of this ``transition'' radius is nearly the same for both of our adopted B-field models. We then solve analytically for the torques on the central star and for the disk luminosity due to gravity and magnetic torques. When expressed in a dimensionless form, the resulting quantities depend on one parameter alone, the ratio of the transition radius to the corotation radius. For rapid rotators, the accretion disk may be powered mostly by spin-down of the central star. These results are independent of the viscosity prescription in the disk. We also solve for the disk structure for the special case of an optically thick alpha disk. Our results are applicable to a range of astrophysical systems including accreting neutron stars, intermediate polar cataclysmic variables, and T Tauri systems.

  12. Thin Disk Accretion in the Magnetically-Arrested State

    NASA Astrophysics Data System (ADS)

    Avara, Mark J.; McKinney, Jonathan; Reynolds, Christopher S.

    2016-01-01

    Shakura-Sunyaev thin disk theory is fundamental to black hole astrophysics. Though applications of the theory are wide-spread and powerful tools for explaining observations, such as Soltan's argument using quasar power, broadened iron line measurements, continuum fitting, and recently reverberation mapping, a significant large-scale magnetic field causes substantial deviations from standard thin disk behavior. We have used fully 3D general relativistic MHD simulations with cooling to explore the thin (H/R~0.1) magnetically arrested disk (MAD) state and quantify these deviations. This work demonstrates that accumulation of large-scale magnetic flux into the MAD state is possible, and then extends prior numerical studies of thicker disks, allowing us to measure how jet power scales with the disk state, providing a natural explanation of phenomena like jet quenching in the high-soft state of X-ray binaries. We have also simulated thin MAD disks with a misaligned black hole spin axis in order to understand further deviations from thin disk theory that may significantly affect observations.

  13. Spectropolarimetric test of the relativistic disk model for the broad emission lines of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Chen, Kaiyou; Halpern, Jules P.

    1990-01-01

    Previously, it was claimed that the broad emission lines of the radio galaxy Arp 102B can be fitted by the line profile from a simple relativistic Keplerian thin disk. It was argued that the lines originating from the relativistic accretion disk could be polarized due to electron scattering, which is likely to be the dominant opacity in the line-emitting region of Arp 102B. In the present work, the expected polarization properties of these broad emission lines are calculated. The percentage of polarization depends strongly on the inclination angle. For some angles, the red peak of the polarized, double-peaked line profile can be higher than the blue peak. This is in contrast to the total line profile, in which the blue peak is always higher than the red one. Spectropolarimetric observations could, therefore, provide an independent test of the relativistic disk model for the broad emission lines of Arp 102B and other active galactic nuclei.

  14. Self-similar relativistic disks with pressure

    NASA Astrophysics Data System (ADS)

    Lemos, Jose P. S.

    1989-09-01

    Solutions for disks in equilibrium specified by a constant velocity of rotation and constant velocity dispersions are found. The fluid is not perfect because the stress tensor is anisotropic. These disks are self-similar if they are of infinite extent. The solutions are exact when an equal number of particles move in each sense of rotation so that there is no dragging of the inertial frames. For disks rotating with a small velocity a WKB approximation is used to obtain solutions.

  15. ACCELERATION AND COLLIMATION OF RELATIVISTIC MAGNETOHYDRODYNAMIC DISK WINDS

    SciTech Connect

    Porth, Oliver; Fendt, Christian E-mail: fendt@mpia.d

    2010-02-01

    We perform axisymmetric relativistic magnetohydrodynamic simulations to investigate the acceleration and collimation of jets and outflows from disks around compact objects. Newtonian gravity is added to the relativistic treatment in order to establish the physical boundary condition of an underlying accretion disk in centrifugal and pressure equilibrium. The fiducial disk surface (respectively a slow disk wind) is prescribed as boundary condition for the outflow. We apply this technique for the first time in the context of relativistic jets. The strength of this approach is that it allows us to run a parameter study in order to investigate how the accretion disk conditions govern the outflow formation. Substantial effort has been made to implement a current-free, numerical outflow boundary condition in order to avoid artificial collimation present in the standard outflow conditions. Our simulations using the PLUTO code run for 500 inner disk rotations and on a physical grid size of 100 x 200 inner disk radii. The simulations evolve from an initial state in hydrostatic equilibrium and an initially force-free magnetic field configuration. Two options for the initial field geometries are applied-an hourglass-shaped potential magnetic field and a split monopole field. Most of our parameter runs evolve into a steady state solution which can be further analyzed concerning the physical mechanism at work. In general, we obtain collimated beams of mildly relativistic speed with Lorentz factors up to 6 and mass-weighted half-opening angles of 3-7 deg. The split-monopole initial setup usually results in less collimated outflows. The light surface of the outflow magnetosphere tends to align vertically-implying three relativistically distinct regimes in the flow-an inner subrelativistic domain close to the jet axis, a (rather narrow) relativistic jet and a surrounding subrelativistic outflow launched from the outer disk surface-similar to the spine-sheath structure currently

  16. Recording of relativistic particles in thin scintillators

    SciTech Connect

    Tolstukhin, I A.; Somov, Alexander S.; Somov, S. V.; Bolozdynya, A. I.

    2014-11-01

    Results of investigating an assembly of thin scintillators and silicon photomultipliers for registering relativistic particles with the minimum ionization are presented. A high efficiency of registering relativistic particles using an Ej-212 plastic scintillator, BSF-91A wavelength-shifting fiber (Saint-Gobain), and a silicon photomultiplier (Hamamtsu) is shown. The measurement results are used for creating a scintillation hodoscope of the magnetic spectrometer for registering γ quanta in the GlueX experiment.

  17. Relativistic Lines and Reflection from the Inner Accretion Disks Around Neutron Stars

    NASA Astrophysics Data System (ADS)

    Cackett, Edward M.; Miller, Jon M.; Ballantyne, David R.; Barret, Didier; Bhattacharyya, Sudip; Boutelier, Martin; Miller, M. Coleman; Strohmayer, Tod E.; Wijnands, Rudy

    2010-09-01

    A number of neutron star low-mass X-ray binaries (LMXBs) have recently been discovered to show broad, asymmetric Fe K emission lines in their X-ray spectra. These lines are generally thought to be the most prominent part of a reflection spectrum, originating in the inner part of the accretion disk where strong relativistic effects can broaden emission lines. We present a comprehensive, systematic analysis of Suzaku and XMM-Newton spectra of 10 neutron star LMXBs, all of which display broad Fe K emission lines. Of the 10 sources, 4 are Z sources, 4 are atolls, and 2 are accreting millisecond X-ray pulsars (also atolls). The Fe K lines are fit well by a relativistic line model for a Schwarzschild metric, and imply a narrow range of inner disk radii (6-15 GM/c 2) in most cases. This implies that the accretion disk extends close to the neutron star surface over a range of luminosities. Continuum modeling shows that for the majority of observations, a blackbody component (plausibly associated with the boundary layer) dominates the X-ray emission from 8 to 20 keV. Thus it appears likely that this spectral component produces the majority of the ionizing flux that illuminates the accretion disk. Therefore, we also fit the spectra with a blurred reflection model, wherein a blackbody component illuminates the disk. This model fits well in most cases, supporting the idea that the boundary layer illuminates a geometrically thin disk.

  18. RELATIVISTIC LINES AND REFLECTION FROM THE INNER ACCRETION DISKS AROUND NEUTRON STARS

    SciTech Connect

    Cackett, Edward M.; Miller, Jon M.; Ballantyne, David R.; Barret, Didier; Boutelier, Martin; Miller, M. Coleman; Strohmayer, Tod E.

    2010-09-01

    A number of neutron star low-mass X-ray binaries (LMXBs) have recently been discovered to show broad, asymmetric Fe K emission lines in their X-ray spectra. These lines are generally thought to be the most prominent part of a reflection spectrum, originating in the inner part of the accretion disk where strong relativistic effects can broaden emission lines. We present a comprehensive, systematic analysis of Suzaku and XMM-Newton spectra of 10 neutron star LMXBs, all of which display broad Fe K emission lines. Of the 10 sources, 4 are Z sources, 4 are atolls, and 2 are accreting millisecond X-ray pulsars (also atolls). The Fe K lines are fit well by a relativistic line model for a Schwarzschild metric, and imply a narrow range of inner disk radii (6-15 GM/c {sup 2}) in most cases. This implies that the accretion disk extends close to the neutron star surface over a range of luminosities. Continuum modeling shows that for the majority of observations, a blackbody component (plausibly associated with the boundary layer) dominates the X-ray emission from 8 to 20 keV. Thus it appears likely that this spectral component produces the majority of the ionizing flux that illuminates the accretion disk. Therefore, we also fit the spectra with a blurred reflection model, wherein a blackbody component illuminates the disk. This model fits well in most cases, supporting the idea that the boundary layer illuminates a geometrically thin disk.

  19. Thin-disk solid state lasers

    NASA Astrophysics Data System (ADS)

    Giesen, Adolf

    2004-12-01

    The principle ideas of the thin disk laser design will be illustrated and the advantages for operating different laser materials will be explained. The results for cw- and q-switched operation as well as for amplification of short (ns) and ultra-short (ps, fs) pulses demonstrate the potential of the thin disk laser design. The scaling laws for this laser design show that the power limit for cw-operation is far beyond 10 kW for one single disk and the energy limit is higher than 1 J from one disk in pulsed operation. Also the applicability of the thin disk laser concept to optically pumped semiconductor structures will be discussed. When pumping directly into the quantum wells the energy defect between pump- and laser photon can be smaller than 5% thus reducing the waste heat generated inside the semiconductor structure. First results demonstrate the potential of this new concept. Finally, a short overview of the industrial realization of the thin disk laser technology will be given.

  20. ESTIMATION OF RELATIVISTIC ACCRETION DISK PARAMETERS FROM IRON LINE EMISSION

    SciTech Connect

    V. PARIEV; B. BROMLEY; W. MILLER

    2001-03-01

    The observed iron K{alpha} fluorescence lines in Seyfert I galaxies provide strong evidence for an accretion disk near a supermassive black hole as a source of the emission. Here we present an analysis of the geometrical and kinematic properties of the disk based on the extreme frequency shifts of a line profile as determined by measurable flux in both the red and blue wings. The edges of the line are insensitive to the distribution of the X-ray flux over the disk, and hence provide a robust alternative to profile fitting of disk parameters. Our approach yields new, strong bounds on the inclination angle of the disk and the location of the emitting region. We apply our method to interpret observational data from MCG-6-30-15 and find that the commonly assumed inclination 30{degree} for the accretion disk in MCG-6-30-15 is inconsistent with the position of the blue edge of the line at a 3{sigma} level. A thick turbulent disk model or the presence of highly ionized iron may reconcile the bounds on inclination from the line edges with the full line profile fits based on simple, geometrically thin disk models. The bounds on the innermost radius of disk emission indicate that the black hole in MCG-6-30-15 is rotating faster than 30% of theoretical maximum. When applied to data from NGC 4151, our method gives bounds on the inclination angle of the X-ray emitting inner disk of 50 {+-} 10{degree}, consistent with the presence of an ionization cone grazing the disk as proposed by Pedlar et al. (1993). The frequency extrema analysis also provides limits to the innermost disk radius in another Seyfert 1 galaxy, NGC 3516, and is suggestive of a thick disk model.

  1. THICK-DISK EVOLUTION INDUCED BY THE GROWTH OF AN EMBEDDED THIN DISK

    SciTech Connect

    Villalobos, Alvaro; Helmi, Amina; Kazantzidis, Stelios E-mail: ahelmi@astro.rug.n E-mail: villalobos@oats.inaf.i

    2010-07-20

    We perform collisionless N-body simulations to investigate the evolution of the structural and kinematical properties of simulated thick disks induced by the growth of an embedded thin disk. The thick disks used in the present study originate from cosmologically common 5:1 encounters between initially thin primary disk galaxies and infalling satellites. The growing thin disks are modeled as static gravitational potentials and we explore a variety of growing-disk parameters that are likely to influence the response of thick disks. We find that the final thick-disk properties depend strongly on the total mass and radial scale length of the growing thin disk, and much less sensitively on its growth timescale and vertical scale height as well as the initial sense of thick-disk rotation. Overall, the growth of an embedded thin disk can cause a substantial contraction in both the radial and vertical direction, resulting in a significant decrease in the scale lengths and scale heights of thick disks. Kinematically, a growing thin disk can induce a notable increase in the mean rotation and velocity dispersions of thick-disk stars. We conclude that the reformation of a thin disk via gas accretion may play a significant role in setting the structure and kinematics of thick disks, and thus it is an important ingredient in models of thick-disk formation.

  2. Structure of relativistic accretion disk with non-standard model

    NASA Astrophysics Data System (ADS)

    Khesali, A. R.; Salahshoor, K.

    2016-07-01

    The structure of stationary, axisymmetric advection-dominated accretion disk (ADAF) around rotating black hole, using non-standard model, was examined. In this model, the transport efficiency of the angular momentum α was dependent on the magnetic Prandtl number α ∝ Pm^{δ } . The full relativistic shear stress recently obtained by a new manner, was used. By considering black hole spin and Prandtl number instantaneously, the structure of ADAFs was changed in inner and outer region of the disk. It was discovered that the accretion flow was denser and hotter in the inner region, due to the black hole spin, and in the outer region, due to the presence of Prandtl parameter. Inasmuch as the rotation of the black hole affected the transport efficiency of angular momentum in parts of the disk very close to the even horizon, then in these regions, the viscosity depended on the rotation of black hole. Also, it was discovered that the effect of the black hole spin on the structure of the disk was related to the presence of Prandtl parameter.

  3. High energy high brightness thin disk laser

    NASA Astrophysics Data System (ADS)

    Nixon, Matthew D.; Cates, Michael C.

    2012-11-01

    Boeing has been developing solid state lasers for high energy applications since 2004 using Yb:YAG thin disk lasers as pioneered by A. Giesen1 and commercialized by Trumpf Laser GmbH.2 In this paper, we report results of our second generation design and status of a third generation we are currently developing, which will produce 35 kW and a beam quality <2.

  4. A GENERAL RELATIVISTIC MODEL OF ACCRETION DISKS WITH CORONAE SURROUNDING KERR BLACK HOLES

    SciTech Connect

    You Bei; Cao Xinwu; Yuan Yefei E-mail: cxw@shao.ac.cn

    2012-12-20

    We calculate the structure of a standard accretion disk with a corona surrounding a massive Kerr black hole in the general relativistic frame, in which the corona is assumed to be heated by the reconnection of the strongly buoyant magnetic fields generated in the cold accretion disk. The emergent spectra of accretion disk-corona systems are calculated by using the relativistic ray-tracing method. We propose a new method to calculate the emergent Comptonized spectra from the coronae. The spectra of disk-corona systems with a modified {alpha}-magnetic stress show that both the hard X-ray spectral index and the hard X-ray bolometric correction factor L{sub bol}/L{sub X,2-10keV} increase with the dimensionless mass accretion rate, which is qualitatively consistent with the observations of active galactic nuclei. The fraction of the power dissipated in the corona decreases with increasing black hole spin parameter a, which leads to lower electron temperatures of the coronae for rapidly spinning black holes. The X-ray emission from the coronae surrounding rapidly spinning black holes becomes weak and soft. The ratio of the X-ray luminosity to the optical/UV luminosity increases with the viewing angle, while the spectral shape in the X-ray band is insensitive to the viewing angle. We find that the spectral index in the infrared waveband depends on the mass accretion rate and the black hole spin a, which deviates from the f{sub {nu}}{proportional_to}{nu}{sup 1/3} relation expected by the standard thin disk model.

  5. High-energy regenerative thin disk amplifier

    NASA Astrophysics Data System (ADS)

    Chyla, Michal; Smrz, Martin; Mocek, Tomas

    2012-07-01

    Design of a compact regenerative laser amplifier based on two Yb:YAG thin-disks is presented. Energy up to 100 mJ in picoseconds pulses will be delivered with a repetition rate of 1 kHz. System is designed for seeding a kW-class multipass amplifier for industrial and scientific applications. Laser heads are pumped at zero-phonon line (968.825 nm [1]) by stabilized high-power pump diodes operated in pulsed regime. Seed pulses are produced in a fiber oscillator at 1030 nm and CPA technique utilizing transmission gratings for pulse stretching and compression is applied.

  6. High average power scaleable thin-disk laser

    DOEpatents

    Beach, Raymond J.; Honea, Eric C.; Bibeau, Camille; Payne, Stephen A.; Powell, Howard; Krupke, William F.; Sutton, Steven B.

    2002-01-01

    Using a thin disk laser gain element with an undoped cap layer enables the scaling of lasers to extremely high average output power values. Ordinarily, the power scaling of such thin disk lasers is limited by the deleterious effects of amplified spontaneous emission. By using an undoped cap layer diffusion bonded to the thin disk, the onset of amplified spontaneous emission does not occur as readily as if no cap layer is used, and much larger transverse thin disks can be effectively used as laser gain elements. This invention can be used as a high average power laser for material processing applications as well as for weapon and air defense applications.

  7. The spectra of relativistic accretion disks - Application to A0620-00

    NASA Technical Reports Server (NTRS)

    Fu, Albert; Taam, Ronald E.

    1990-01-01

    The X-ray flux emitted from a geometrically thin, relativistic accretion disk in the steady state approximation is investigated in order to place limits on the quiescent state mass flow rate in the soft X-ray transient black hole candidate source A0620-00. Specific attention is focused on the effects associated with gravitational redshifts, Doppler shifts, and on the enhancement of the apparent accretion disk area due to gravitational light bending on the continuum spectrum. It is found that the upper limit to the mass flow rate within the inner regions of the disk, constrained by the lack of soft X-rays in the quiescent state, is about 2.8 x 10 to the -11th solar mass/yr for black hole masses greater than about 5.4 solar mass. The optical data are consistent with these upper limits provided that the inclination angle of the binary system is less than about 65 deg. The upper limits and the lack of a hard X-ray flux, together, suggest that the soft X-ray transient model based upon a mass transfer instability situated in the stellar envelope of the companion is inapplicable to A0620-00.

  8. Stochastic Oscillations of General Relativistic Disks Described by a Fractional Langevin Equation with Fractional Gaussian Noise

    NASA Astrophysics Data System (ADS)

    Zhi-Yun, Wang; Pei-Jie, Chen

    2016-06-01

    A generalized Langevin equation driven by fractional Brownian motion is used to describe the vertical oscillations of general relativistic disks. By means of numerical calculation method, the displacements, velocities and luminosities of oscillating disks are explicitly obtained for different Hurst exponent H. The results show that as H increases, the energies and luminosities of oscillating disk are enhanced, and the spectral slope at high frequencies of the power spectrum density of disk luminosity is also increased. This could explain the observational features related to the Intra Day Variability of the BL Lac objects.

  9. NEUTRINO SPECTRA FROM ACCRETION DISKS: NEUTRINO GENERAL RELATIVISTIC EFFECTS AND THE CONSEQUENCES FOR NUCLEOSYNTHESIS

    SciTech Connect

    Caballero, O. L.; McLaughlin, G. C.; Surman, R. E-mail: olcaball@ncsu.edu E-mail: surmanr@union.edu

    2012-02-01

    Black hole (BH) accretion disks have been proposed as good candidates for a range of interesting nucleosynthesis, including the r-process. The presence of the BH influences the neutrino fluxes and affects the nucleosynthesis resulting from the interaction of the emitted neutrinos and hot outflowing material ejected from the disk. We study the impact of general relativistic effects on the neutrinos emitted from BH accretion disks. We present abundances obtained by considering null geodesics and energy shifts for two different disk models. We find that both the bending of the neutrino trajectories and the energy shifts have important consequences for the nucleosynthetic outcome.

  10. General Relativistic Mini-Disk Dynamics during Black Hole Binary Inspiral

    NASA Astrophysics Data System (ADS)

    Bowen, Dennis

    2016-01-01

    During galaxy mergers, as a result of dynamical friction (stars, gas, etc.) and gravitational slingshot, the supermassive black holes (SMBHs) from each galaxy will become gravitationally bound and eventually merge due to gravitational radiation. It is expected that gas will form a circumbinary accretion disk around the SMBH binary that will persistently feed individual "mini-disks" via dense streams out to their tidal truncation radii. However, these radii are not well known during the late stages of inspiral and merger. We present general relativistic hydrodynamic simulations aimed at resolving this uncertainty and producing templates of unique electromagnetic (EM) signatures for such systems to assist in direct observational detection with currently available observatories. We place particular emphasis on the dynamics of the individual "mini-disks" where violent shocks via disk-disk and disk-stream interactions will likely produce intense EM emission.

  11. Integrability of motion around galactic razor-thin disks

    NASA Astrophysics Data System (ADS)

    Vieira, Ronaldo S. S.; Ramos-Caro, Javier

    2016-06-01

    We consider the three-dimensional bounded motion of a test particle around razor-thin disk configurations, by focusing on the adiabatic invariance of the vertical action associated with disk-crossing orbits. We find that it leads to an approximate third integral of motion predicting envelopes of the form Z(R)∝ [Σ (R)]^{-1/3} , where R is the radial galactocentric coordinate, Z is the z-amplitude (vertical amplitude) of the orbit and Σ represents the surface mass density of the thin disk. This third integral, which was previously formulated for the case of flattened 3D configurations, is tested for a variety of trajectories in different thin-disk models.

  12. Thermal stability of a thin disk with magnetically driven winds

    SciTech Connect

    Li, Shuang-Liang; Begelman, Mitchell C. E-mail: mitch@jila.colorado.edu

    2014-05-01

    The absence of thermal instability in the high/soft state of black hole X-ray binaries, in disagreement with the standard thin disk theory, has been a long-standing riddle for theoretical astronomers. We have tried to resolve this question by studying the thermal stability of a thin disk with magnetically driven winds in the M-dot −Σ plane. It is found that disk winds can greatly decrease the disk temperature and thus help the disk become more stable at a given accretion rate. The critical accretion rate, M-dot {sub crit}, corresponding to the thermal instability threshold, is significantly increased in the presence of disk winds. For α = 0.01 and B {sub φ} = 10B {sub p}, the disk is quite stable even for a very weak initial poloidal magnetic field [β{sub p,0}∼2000,β{sub p}=(P{sub gas}+P{sub rad})/(B{sub p}{sup 2}/8π)]. However, when B {sub φ} = B {sub p} or B {sub φ} = 0.1B {sub p}, a somewhat stronger (but still weak) field (β{sub p,} {sub 0} ∼ 200 or β{sub p,} {sub 0} ∼ 20) is required to make the disk stable. Nevertheless, despite the great increase of M-dot {sub crit}, the luminosity threshold, corresponding to instability, remains almost constant or decreases slowly with increasing M-dot {sub crit} due to decreased gas temperature. The advection and diffusion timescales of the large-scale magnetic field threading the disk are also investigated in this work. We find that the advection timescale can be smaller than the diffusion timescale in a disk with winds, because the disk winds take away most of the gravitational energy released in the disk, resulting in the decrease of the magnetic diffusivity η and the increase of the diffusion timescale.

  13. Hydrodynamic responses of a thin floating disk to regular waves

    NASA Astrophysics Data System (ADS)

    Yiew, L. J.; Bennetts, L. G.; Meylan, M. H.; French, B. J.; Thomas, G. A.

    2016-01-01

    The surge, heave and pitch motions of two solitary, thin, floating disks, extracted from laboratory wave basin experiments are presented. The motions are forced by regular incident waves, for a range of wave amplitudes and frequencies. One disk has a barrier attached to its edge to stop the incident waves from washing across its upper surface. It is shown that the motions of the disk without the barrier are smaller than those of the disk with the barrier. Moreover, it is shown that the amplitudes of the motions, relative to the incident amplitude, decrease with increasing incident wave amplitude for the disk without a barrier and for short incident wavelengths. Two theoretical models of the disk motions are considered. One is based on slope-sliding theory and the other on combined linear potential-flow and thin-plate theories. The models are shown to have almost the same form in the long-wavelength regime. The potential-flow/thin-plate model is shown to capture the experimentally measured disk motions with reasonable accuracy.

  14. Relativistic Iron Emission and Disk Reflection in Galactic Microquasar XTE J1748-288

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Fox, D. W.; DiMatteo, T.; Wijnands, R.; Belloni, T.; Pooley, D.; Kouveliotou, C.; Lewin, W. H. G.

    2001-01-01

    We report evidence for an Fe K-alpha fluorescence line feature and disk reflection in the very high, high-, and low-state X-ray spectra of the Galactic microquasar XTE J1748 - 288 during its 1998 June outburst. Spectral analyses are made on data gathered throughout the outburst by the Rossi X-Ray Timing Explorer Proportional Counter Array. Gaussian line, relativistic disk emission line, and ionized disk reflection models are fitted to the data. In the very high state the line profile appears strongly redshifted, consistent with disk emission from the innermost stable orbits around a maximally rotating Kerr black hole. In the high state the line profile is less redshifted and increasingly prominent. The low-state line profile is very strong (approx. 0.5 keV equivalent width) and centered at 6.7 +/- 0.10 keV; disk line emission model fits indicate that the inner edge of the disk fluctuates between approx. 20R(sub g) and - approx. 100R(sub g) in this state. The disk reflection fraction is traced through the outburst; reflection from an ionized disk is preferred in the very high and high states, and reflection from a relatively neutral disk is preferred in the low state. We discuss the implications of our findings for the binary system dynamics and accretion flow geometry in XTE J1748 - 288.

  15. Relativistic Iron Emission and Disk Reflection in Galactic Microquasar XTE J1748-288

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Fox, D. W.; Matteo, T. DI; Wijnands, R.; Belloni, T.; Pooley, D.; Kouveliotou, C.; Lewin, W. H. G.

    2001-01-01

    We report evidence for an Fe K(alpha) fluorescence line feature and disk reflection in the very high, high-, and low-state X-ray spectra of the Galactic microquasar XTE J1748-288 during its 1998 June outburst. Spectral analyses are made on data gathered throughout the outburst by the Rossi X-Ray Timing Explorer Proportional Counter Array. Gaussian line, relativistic disk emission line, and ionized disk reflection models are fitted to the data. In the very high state the line profile appears strongly redshifted, consistent with disk emission from the innermost stable orbits around a maximally rotating Kerr black hole. In the high state the line profile is less redshifted and increasingly prominent. The low-state line profile is very strong (approx. 0.5 keV equivalent width) and centered at 6.7 +/- 0.10 keV; disk line emission model fits indicate that the inner edge of the disk fluctuates between approx. 20Rg and approx. 100Rg in this state. The disk reflection fraction is traced through the outburst; reflection from an ionized disk is preferred in the very high and high states, and reflection from a relatively neutral disk is preferred in the low state. We discuss the implications of our findings for the binary system dynamics and accretion flow geometry in XTE J1748-288.

  16. Precise curvature measurement of Yb:YAG thin disk

    NASA Astrophysics Data System (ADS)

    Muzik, Jiri; Chyla, Michal; Nagisetty, Siva S.; Miura, Taisuke; Mann, Klaus; Endo, Akira; Mocek, Tomas

    2015-01-01

    We are developing an Yb:YAG thin disk regenerative amplifier operating at 1 kHz repetition rate which should deliver output of 100 W of average power which corresponds to the pulse energy of 100 mJ. In order to achieve such high output energy, large size mode matching on a thin-disk is required to avoid optical damage but on the other hand, larger mode area is more susceptible to the influence of optical phase distortions (OPD's) thus limits achievable pulse energy and beam quality. We developed a compact setup allowing precise measurement of the thin-disk deformations by implementation of a Hartmann-Shack wavefront sensor and a single mode probe laser diode. In comparison to the interferometric measurement methods, our approach brings a number of advantages like simplicity of alignment, compactness and robustness, at the same time keeping the high precision of measurement in a range of few nanometers.

  17. 260-megahertz, megawatt-level thin-disk oscillator.

    PubMed

    Zhang, Jinwei; Brons, Jonathan; Lilienfein, Nikolai; Fedulova, Elena; Pervak, Vladimir; Bauer, Dominik; Sutter, Dirk; Wei, Zhiyi; Apolonski, Alexander; Pronin, Oleg; Krausz, Ferenc

    2015-04-15

    A Kerr-lens mode-locked (KLM) Yb:YAG thin-disk oscillator delivering 215-fs pulses with 75-W average power and 1.4-MW peak power at a repetition rate of 260 MHz is presented. Self-starting KLM is demonstrated at an output power of 68 W. This is the highest repetition rate of any mode-locked thin-disk oscillators so far. Concepts for scaling the repetition rate up to 1 GHz are discussed. PMID:25872033

  18. THE LARGE-SCALE MAGNETIC FIELDS OF THIN ACCRETION DISKS

    SciTech Connect

    Cao Xinwu; Spruit, Hendrik C. E-mail: henk@mpa-garching.mpg.de

    2013-03-10

    Large-scale magnetic field threading an accretion disk is a key ingredient in the jet formation model. The most attractive scenario for the origin of such a large-scale field is the advection of the field by the gas in the accretion disk from the interstellar medium or a companion star. However, it is realized that outward diffusion of the accreted field is fast compared with the inward accretion velocity in a geometrically thin accretion disk if the value of the Prandtl number P{sub m} is around unity. In this work, we revisit this problem considering the angular momentum of the disk to be removed predominantly by the magnetically driven outflows. The radial velocity of the disk is significantly increased due to the presence of the outflows. Using a simplified model for the vertical disk structure, we find that even moderately weak fields can cause sufficient angular momentum loss via a magnetic wind to balance outward diffusion. There are two equilibrium points, one at low field strengths corresponding to a plasma-beta at the midplane of order several hundred, and one for strong accreted fields, {beta} {approx} 1. We surmise that the first is relevant for the accretion of weak, possibly external, fields through the outer parts of the disk, while the latter one could explain the tendency, observed in full three-dimensional numerical simulations, of strong flux bundles at the centers of disk to stay confined in spite of strong magnetororational instability turbulence surrounding them.

  19. Slip effect for thin liquid film on a rotating disk

    NASA Astrophysics Data System (ADS)

    Yanagisawa, Masahiro

    1987-02-01

    A flow for thin liquid films on rotating disks has been theoretically and experimentally studied. Liquid depletion behavior during a spin-coating process is calculated by solving the Navier-Stokes equation, taking into account interface slip between liquid and disk. Excellent agreement is seen between the model prediction and experimental data. According to observed depletion behavior on thin liquid films for various spin-coating parameters, half life falls off at the inverse square of rotational speed, and increases when viscosity increases, although the increasing rate falls off. The interface slip, represented as an external friction coefficient, is thermodynamically explained by the different (Δrc) in critical surface tension (rc) values between the liquid and the disk, which will be proportional to the solubility parameter. An infinite external friction coefficient, representing nonslip flow, may be given, when Δrc is zero. Spin-off experiments for liquids of various rc values, prepared by differing surface treatments, support this consideration.

  20. Nondissipative saturation of the magnetorotational instability in thin disks.

    PubMed

    Liverts, Edward; Shtemler, Yuri; Mond, Michael; Umurhan, Orkan M; Bisikalo, Dmitry V

    2012-11-30

    A new nondissipative mechanism is proposed for the saturation of the axisymmetric magnetorotational (MRI) instability in thin Keplerian disks that are subject to an axial magnetic field. That mechanism relies on the energy transfer from the MRI to stable magnetosonic waves. Such mode interaction is enabled due to the vertical stratification of the disk that results in the discretization of its MRI spectrum, as well as by applying the appropriate boundary conditions. A second order Duffing-like amplitude equation for the initially unstable MRI modes is derived. The solutions of that equation exhibit bursty nonlinear oscillations with a constant amplitude that signifies the saturation level of the MRI. Those results are verified by a direct numerical solution of the full nonlinear reduced set of thin disk magnetohydrodynamics equations. PMID:23368127

  1. Electromagnetic signatures of thin accretion disks in wormhole geometries

    SciTech Connect

    Harko, Tiberiu; Kovacs, Zoltan; Lobo, Francisco S. N.

    2008-10-15

    In this paper, we study the physical properties and characteristics of matter forming thin accretion disks in static and spherically symmetric wormhole spacetimes. In particular, the time averaged energy flux, the disk temperature, and the emission spectra of the accretion disks are obtained for these exotic geometries and are compared with the Schwarzschild solution. It is shown that more energy is emitted from the disk in a wormhole geometry than in the case of the Schwarzschild potential and the conversion efficiency of the accreted mass into radiation is more than a factor of 2 higher for the wormholes than for static black holes. These effects in the disk radiation are confirmed in the radial profiles of temperature corresponding to theses flux distributions, and in the emission spectrum {omega}L({omega}) of the accretion disks. We conclude that specific signatures appear in the electromagnetic spectrum, thus leading to the possibility of distinguishing wormhole geometries by using astrophysical observations of the emission spectra from accretion disks.

  2. DYNAMICAL EVOLUTION OF THIN DISPERSION-DOMINATED PLANETESIMAL DISKS

    SciTech Connect

    Rafikov, Roman R.; Slepian, Zachary S.

    2010-02-15

    We study the dynamics of a vertically thin, dispersion-dominated disk of planetesimals with eccentricities e-tilde and inclinations i-tilde (normalized in Hill units) satisfying e-tilde >> 1, i-tilde <disks. We derive analytical expressions for the planetesimal scattering coefficients and compare them with numerical calculations. We find significant discrepancies in the inclination scattering coefficients obtained by the two approaches and ascribe this difference to the effects not accounted for in the analytical calculation: multiple scattering events (temporary captures, which may be relevant for the production of distant planetary satellites outside the Hill sphere) and distant interaction of planetesimals prior to their close encounter. Our calculations show that the inclination of a thin, dispersion-dominated planetesimal disk grows exponentially on a very short timescale implying that (1) such disks must be very short-lived and (2) planetesimal accretion in this dynamical phase is insignificant. Our results are also applicable to the dynamics of shear-dominated disks switching to the dispersion-dominated regime.

  3. Static thin disks with haloes as sources of conformastatic spacetimes

    NASA Astrophysics Data System (ADS)

    González, Guillermo A.; Pimentel, Oscar M.

    2016-02-01

    Two new families of exact solutions to the Einstein equations for a conformastatic spacetime with axial symmetry are presented which describe thin disks of dust immersed in a spheroidal halo. The solutions are obtained by expressing the metric function in terms of an auxiliary function which satisfies the Laplace equation, a characteristic property of the conformastatic spacetimes. The first family of solutions is obtained from the displacement, cut, and reflection method, which introduces a discontinuity in the first z derivate of the metric tensor across the plane of the disk. The second family of solutions is obtained by using the oblate spheroidal coordinates because they adapt to the shape of the source and introduce naturally a cutting radius for the disk. The energy densities of the disk and the halo are positive everywhere and well behaved, and their energy-momentum tensor agrees with all the energy conditions. Some particular solutions for the energy density of the disk and the halo are presented, and the rotational curves are obtained by solving the geodesic equation for a particle that moves in circular orbits in the plane of the disk.

  4. Binary Black Holes, Accretion Disks and Relativistic Jets: Photocenters of Nearby AGN and Quasars

    NASA Technical Reports Server (NTRS)

    Wehrle, Ann E.; Jones, Dayton L.; Meier, David L.; Piner, B. Glenn; Unwin, Stephen C.

    2004-01-01

    One of the most challenging questions in astronomy today is to understand the origin, structure, and evolution of the central engines in the nuclei of quasars and active galaxies (AGNs). The favoured theory involves the activation of relativistic jets from the fueling of a supermassive black hole through an accretion disk. In some AGN an outer optically thick, dusty torus is seen orbiting the black hole system. This torus is probably related to an inner accretion disk - black hole system that forms the actual powerhouse of the AGN. In radio-loud AGN two oppositely-directed radio jets are ejected perpendicular to the torus/disk system. Although there is a wealth of observational data on AGN, some very basic questions have not been definitively answered. The Space Interferometry Mission (SIM) will address the following three key questions about AGN. 1) Does the most compact optical emission from an AGN come from an accretion disk or from a relativistic jet? 2) Does the separation of the radio core and optical photocenter of the quasars used for the reference frame tie, change on the timescales of their photometric variability, or is the separation stable at the level of a few microarcseconds? 3) Do the cores of galaxies harbor binary supermassive black holes remaining from galaxy mergers? It is not known whether such mergers are common, and whether binaries would persist for a significant time.

  5. Constraints on black hole spins with a general relativistic accretion disk corona model

    NASA Astrophysics Data System (ADS)

    You, Bei; Cao, Xin-Wu; Yuan, Ye-Fei

    2016-04-01

    The peaks in the spectra of the accretion disks surrounding massive black holes in quasars are in the far-UV or soft X-ray band, which are usually not observed. However, in the disk corona model, soft photons from the disk are Comptonized to high energy in the hot corona, and the hard X-ray spectra (luminosity and spectral shape) contain information on the incident spectra from the disk. The values of black hole spin parameter a* are inferred from the spectral fitting, which are spread over a large range, ∼ ‑0.94 to 0.998. We find that the inclination angles and mass accretion rates are well determined by the spectral fitting, but the results are sensitive to the accuracy of black hole mass estimates. No tight constraints on the black hole spins are achieved, if the uncertainties in black hole mass measurements are a factor of four, which are typical for the single-epoch reverberation mapping method. Recently, the accuracy of black hole mass measurement has been significantly improved to 0.2 – 0.4 dex with the velocity resolved reverberation mapping method. The black hole spin can be well constrained if the mass measurement accuracy is ≲ 50%. In the accretion disk corona scenario, a fraction of power dissipated in the disk is transported into the corona, and therefore the accretion disk is thinner than a bare disk for the same mass accretion rate, because the radiation pressure in the disk is reduced. We find that the thin disk approximation, H/R ≲ 0.1, is still valid if 0.3 < ṁ < 0.5, provided half of the dissipated power is radiated in the corona above the disk.

  6. The high-efficiency jets magnetically accelerated from a thin disk in powerful lobe-dominated FRII radio galaxies

    SciTech Connect

    Li, Shuang-Liang

    2014-06-10

    A maximum jet efficiency line R ∼ 25 (R = L {sub jet}/L {sub bol}), found in FRII radio galaxies by Fernandes et al., was extended to cover the full range of jet power by Punsly. Recent general relativistic magnetohydrodynamic simulations of jet formation have mainly focused on the enhancement of jet power. In this work, we suggest that the jet efficiency could be very high even for conventional jet power if the radiative efficiency of disks was much smaller. We adopt the model of a thin disk with magnetically driven winds to investigate the observational high-efficiency jets in FRII radio galaxies. It is found that the structure of a thin disk can be significantly altered by the feedback of winds. The temperature of a disk gradually decreases with increasing magnetic field; the disk density, surface density, and pressure also change enormously. The lower temperature and higher surface density in the inner disk result in the rapid decrease of radiative efficiency. Thus, the jet efficiency is greatly improved even if the jet power is conventional. Our results can explain the observations quite well. The theoretical maximum jet efficiency of R ∼ 1000 suggested by our calculations is large enough to explain all of the high jet efficiency in observations, even considering the episodic activity of jets.

  7. Relativistic Jet Formation from Black Hole Magnetized Accretion Disks: Method, Tests, and Applications of a General RelativisticMagnetohydrodynamic Numerical Code

    NASA Astrophysics Data System (ADS)

    Koide, Shinji; Shibata, Kazunari; Kudoh, Takahiro

    1999-09-01

    Relativistic jets are observed in both active galactic nuclei (AGNs) and ``microquasars'' in our Galaxy. It is believed that these relativistic jets are ejected from the vicinity of black holes. To investigate the formation mechanism of these jets, we have developed a new general relativistic magnetohydrodynamic (GRMHD) code. We report on the basic methods and test calculations to check whether the code reproduces some analytical solutions, such as a standing shock and a Keplerian disk with a steady state infalling corona or with a corona in hydrostatic equilibrium. We then apply the code to the formation of relativistic MHD jets, investigating the dynamics of an accretion disk initially threaded by a uniform poloidal magnetic field in a nonrotating corona (either in a steady state infall or in hydrostatic equilibrium) around a nonrotating black hole. The numerical results show the following: as time goes on, the disk loses angular momentum as a result of magnetic braking and falls into the black hole. The infalling motion of the disk, which is faster than in the nonrelativistic case because of general relativistic effects below 3rS (rS is the Schwarzschild radius), is strongly decelerated around r=2rS by centrifugal force to form a shock inside the disk. The magnetic field is tightly twisted by the differential rotation, and plasma in the shocked region of the disk is accelerated by the JXB force to form bipolar relativistic jets. In addition, and interior to, this magnetically driven jet, we also found a gas-pressure-driven jet ejected from the shocked region by the gas-pressure force. This two-layered jet structure is formed not only in the hydrostatic corona case but also in the steady state falling corona case.

  8. Stationary axially symmetric relativistic thin discs with nonzero radial pressure

    NASA Astrophysics Data System (ADS)

    González, Guillermo A.; Gutiérrez-Piñeres, Antonio C.

    2012-07-01

    A detailed analysis of the surface energy-momentum (SEMT) tensor of stationary axially symmetric relativistic thin discs with nonzero radial pressure is presented. The physical content of the SEMT is analysed and expressions for the velocity vector, energy density, principal stresses and heat flow are obtained. We also present the counter-rotating model interpretation for these discs by considering the SEMT as the superposition of two counter-rotating perfect fluids. We analyse the possibility of counter-rotation along geodesics as well as counter-rotation with equal and opposite tangential velocities, and explicit expressions for the velocities are obtained in both the cases. By assuming a given choice for the counter-rotating velocities, explicit expressions for the energy densities and pressures of the counter-rotating fluids are then obtained. Some simple thin disc models obtained from the Kerr solution are also presented.

  9. General-relativistic magnetohydrodynamics simulations of black hole accretion disks: Dynamics and radiative properties

    NASA Astrophysics Data System (ADS)

    Shiokawa, Hotaka

    The goal of the series of studies in this thesis is to understand the black hole accretion process and predict its observational properties. The highly non-linear process involves a turbulent magnetized plasma in a general relativistic regime, thus making it hard to study analytically. We use numerical simulations, specifically general relativistic magnetohydrodynamics (GRMHD), to construct a realistic dynamical and radiation model of accretion disks. Our simulations are for black holes in low luminous regimes that probably possesses a hot and thick accretion disk. Flows in this regime are called radiatively inefficient accretion flows (RIAF). The most plausible mechanism for transporting angular momentum is turbulence induced by magnetorotational instability (MRI). The RIAF model has been used to model the supermassive black hole at the center of our Milky Way galaxy, Sagittarius A* (Sgr A*). Owing to its proximity, rich observational data of Sgr A* is available to compare with the simulation results. We focus mainly on four topics. First, we analyse numerical convergence of 3D GRMHD global disk simulations. Convergence is one of the essential factors in deciding quantitative outcomes of the simulations. We analyzed dimensionless shell-averaged quantities such as plasma beta, the azimuthal correlation length (angle) of fluid variables, and spectra of the source for four different resolutions. We found that all the variables converged with the highest resolution (384x384x256 in radial, poloidal, and azimuthal directions) except the magnetic field correlation length. It probably requires another factor of 2 in resolution to achieve convergence. Second, we studied the effect of equation of state on dynamics of GRMHD simulation and radiative transfer. Temperature of RIAF gas is high, and all the electrons are relativistic, but not the ions. In addition, the dynamical time scale of the accretion disk is shorter than the collisional time scale of electrons and ions

  10. Electrodeposited Co-Pt thin films for magnetic hard disks

    NASA Astrophysics Data System (ADS)

    Bozzini, B.; De Vita, D.; Sportoletti, A.; Zangari, G.; Cavallotti, P. L.; Terrenzio, E.

    1993-03-01

    ew baths for Co-Pt electrodeposition have been developed and developed and ECD thin films (≤0.3μm) have been prepared and characterized structurally (XRD), morphologically (SEM), chemically (EDS) and magnetically (VSM); their improved corrosion, oxidation and wear resistance have been ascertained. Such alloys appear suitable candidates for magnetic storage systems, from all technological viewpoints. The originally formulated baths contain Co-NH 3-citrate complexes and Pt-p salt (Pt(NH 3) 2(NO 2) 2). Co-Pt thin films of fcc structure are deposited obtaining microcrystallites of definite composition. At Pt ⋍ 30 at% we obtain fcc films with a=0.369 nm, HC=80 kA m, and high squareness; increasing Co and decreasing Pt content in the bath it is possible to reduce the Pt content of the deposit, obtaining fcc structures containing two types of microcrystals with a = 0.3615 nm and a = 0.369 nm deposited simultaneously. NaH 2PO 2 additions to the bath have a stabilizing influence on the fcc structure of a = 0.3615 nm, Pt ⋍ 20 at% and HC as high as 200 kA/m, with hysteresis loops suitable for both longitudinal or perpendicular recording, depending on the thickness. We have prepared 2.5 in. hard disks for magnetic recording with ECD Co-Pt 20 at% with a polished and texturized ACD Ni-P underlayer. Pulse response, 1F & 2F frequency and frequency sweep response behaviour, as well as noise and overwrite characteristics have been measured for both our disks and high-standard sputtered Co-Cr-Ta production disks, showin improved D50 for Co-Pt ECD disks. The signal-to-noise ratio could be improved by pulse electrodeposition and etching post-treatments.

  11. General Relativistic Magnetohydrodynamic Simulations of Jets from Black Hole Accretions Disks: Two-Component Jets Driven by Nonsteady Accretion of Magnetized Disks

    NASA Astrophysics Data System (ADS)

    Koide, Shinji; Shibata, Kazunari; Kudoh, Takahiro

    1998-03-01

    The radio observations have revealed the compelling evidence of the existence of relativistic jets not only from active galactic nuclei but also from ``microquasars'' in our Galaxy. In the cores of these objects, it is believed that a black hole exists and that violent phenomena occur in the black hole magnetosphere, forming the relativistic jets. To simulate the jet formation in the magnetosphere, we have newly developed the general relativistic magnetohydrodynamic code. Using the code, we present a model of these relativistic jets, in which magnetic fields penetrating the accretion disk around a black hole play a fundamental role of inducing nonsteady accretion and ejection of plasmas. According to our simulations, a jet is ejected from a close vicinity to a black hole (inside 3rS, where rS is the Schwarzschild radius) at a maximum speed of ~90% of the light velocity (i.e., a Lorentz factor of ~2). The jet has a two-layered shell structure consisting of a fast gas pressure-driven jet in the inner part and a slow magnetically driven jet in the outer part, both of which are collimated by the global poloidal magnetic field penetrating the disk. The former jet is a result of a strong pressure increase due to shock formation in the disk through fast accretion flow (``advection-dominated disk'') inside 3rS, which has never been seen in the nonrelativistic calculations.

  12. Ultrafast thin disk lasers: sub-100 fs pulse duration and carrier envelope offset detection

    NASA Astrophysics Data System (ADS)

    Saraceno, Clara J.; Pekarek, Selina; Heckl, Oliver H.; Baer, Cyrill R. E.; Schriber, Cinia; Golling, Matthias; Beil, Kolja; Kränkel, Christian; Huber, Günter; Südmeyer, Thomas; Keller, Ursula

    2013-03-01

    We present two milestone results that confirm that thin disk lasers are excellent candidates for driving extreme nonlinear optics experiments. In a first experiment using the broadband mixed sesquioxide gain material Yb:LuScO3, we demonstrate that thin disk lasers can access the sub-100 fs regime. In a second experiment, we detect for the first time the carrier envelope offset (CEO) frequency beat of an Yb:Lu2O3 thin disk laser.

  13. NEAR-INFRARED DETECTION OF A SUPER-THIN DISK IN NGC 891

    SciTech Connect

    Schechtman-Rook, Andrew; Bershady, Matthew A.

    2013-08-10

    We probe the disk structure of the nearby, massive, edge-on spiral galaxy NGC 891 with subarcsecond resolution JHK{sub s}-band images covering {approx} {+-}10 kpc in radius and {+-}5 kpc in height. We measure intrinsic surface brightness (SB) profiles using realistic attenuation corrections constrained from near- and mid-infrared (Spitzer) color maps and three-dimensional Monte Carlo radiative-transfer models. In addition to the well-known thin and thick disks, a super-thin disk with 60-80 pc scale-height-comparable to the star-forming disk of the Milky Way-is visibly evident and required to fit the attenuation-corrected light distribution. Asymmetries in the super-thin disk light profile are indicative of young, hot stars producing regions of excess luminosity and bluer (attenuation-corrected) near-infrared color. To fit the inner regions of NGC 891, these disks must be truncated within {approx}3 kpc, with almost all their luminosity redistributed in a bar-like structure 50% thicker than the thin disk. There appears to be no classical bulge but rather a nuclear continuation of the super-thin disk. The super-thin, thin, thick, and bar components contribute roughly 30%, 42%, 13%, and 15% (respectively) to the total K{sub s}-band luminosity. Disk axial ratios (length/height) decrease from 30 to 3 from super-thin to thick components. Both exponential and sech{sup 2} vertical SB profiles fit the data equally well. We find that the super-thin disk is significantly brighter in the K{sub s}-band than typically assumed in integrated spectral energy distribution models of NGC 891: it appears that in these models the excess flux, likely produced by young stars in the super-thin disk, has been mistakenly attributed to the thin disk.

  14. Thin-disk laser multi-pass amplifier

    NASA Astrophysics Data System (ADS)

    Schuhmann, K.; Ahmed, M. A.; Antognini, A.; Graf, T.; Hänsch, T. W.; Kirch, K.; Kottmann, F.; Pohl, R.; Taqqu, D.; Voss, A.; Weichelt, B.

    2015-02-01

    In the context of the Lamb shift measurement in muonic helium [1,2,3,4] we developed a thin-disk laser composed of a Q-switched oscillator and a multi-pass amplifier delivering pulses of 150 mJ at a pulse duration of 100 ns. Its peculiar requirements are stochastic trigger and short delay time (< 500 ns) between trigger and optical output [5]. The concept of the thin-disk laser allows for energy and power scaling with high efficiency. However the single pass gain is small (about 1.2). Hence a multi-pass scheme with precise mode matching for large beam waists (w = 2 mm) is required. Instead of using the standard 4f design, we have developed a multi-pass amplifier with a beam propagation insensitive to thermal lens effects and misalignments. The beam propagation is equivalent to multiple roundtrips in an optically stable resonator. To support the propagation we used an array of 2 x 8 individually adjustable plane mirrors. Astigmatism has been minimized by a compact mirror placement. Precise alignment of the kinematic array was realized using our own mirror mount design. A small signal gain of 5 for 8 passes at a pump power of 400 W was reached. The laser was running for more than 3 months without the need of realignment. Pointing stability studies is also reported here.

  15. Resonant behavior of stochastic oscillations of general relativistic disks driven by a memory-damped friction

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Yun; Chen, Pei-Jie; Zhang, Liang-Ying

    2015-05-01

    By using a generalized Langevin equation to describe the vertical oscillations of a general relativistic disk subjected to a memory-damped friction and a stochastic force, we derive the power spectrum density (PSD) of accretion disk oscillating luminosity by the method of Laplace transform, and discuss the influence of the system parameters on the resonant behavior in PSD curves. The results show that as the damping strength α and memory time τ of the friction increase, the variation of PSD with spectrum frequency f from monotonous decreasing to occurring maximums, and the phenomenon of a general stochastic resonance (SR) with a single peak and multi-peaks can be found in PSD curves. The radial distance parameter n, the mass M, and spin parameter a* of the black hole determine the inherent frequency of vertical oscillations in the disk, and they have significant influences on the SR phenomena in a system of black hole binaries. Project supported by the National Natural Science Foundation of China (Grant No. 11045004) and the Key Program of the Scientific Research Foundation of the Education Bureau of Hubei Province, China (Grant No. D20132603).

  16. MEASURING THE SPIN OF GRS 1915+105 WITH RELATIVISTIC DISK REFLECTION

    SciTech Connect

    Blum, J. L.; Miller, J. M.; Cackett, E. M.; Fabian, A. C.; Reis, R. C.; Miller, M. C.; Homan, J.; Van der Klis, M.

    2009-11-20

    GRS 1915+105 harbors one of the most massive known stellar black holes in the Galaxy. In 2007 May, we observed GRS 1915+105 for approx117 ks in the low/hard state using Suzaku. We collected and analyzed the data with the Hard X-ray Detector/Positive Intrinsic Negative and X-ray Spectrometer cameras spanning the energy range from 2.3 to 55 keV. Fits to the spectra with simple models reveal strong disk reflection through an Fe K emission line and a Compton backscattering hump. We report constraints on the spin parameter of the black hole in GRS 1915 + 105 using relativistic disk reflection models. The model for the soft X-ray spectrum (i.e., < 10 keV) suggests a-hat=0.56{sup +0.02}{sub -0.02} and excludes zero spin at the 4sigma level of confidence. The model for the full broadband spectrum suggests that the spin may be higher, a-hat=0.98{sup +0.01}{sub =0.01} (1sigma confidence), and again excludes zero spin at the 2sigma level of confidence. We discuss these results in the context of other spin constraints and inner disk studies in GRS 1915 + 105.

  17. Thin-disk models in an integrable Weyl-Dirac theory

    NASA Astrophysics Data System (ADS)

    Vieira, Ronaldo S. S.; Letelier, Patricio S.

    2014-01-01

    We construct a class of static, axially symmetric solutions representing razor-thin disks of matter in the Integrable Weyl-Dirac theory proposed in Israelit (Found Phys 29:1303, 1999). The main differences between these solutions and the corresponding general relativistic one are analyzed, focusing on the behavior of physical observables (rotation curves of test particles, density and pressure profiles). We consider the case in which test particles move along Weyl geodesics. The same rotation curve can be obtained from many different solutions of the Weyl-Dirac theory, although some of these solutions present strong qualitative differences with respect to the usual general relativistic model (such as the appearance of a ring-like density profile). In particular, for typical galactic parameters all rotation curves of the Weyl-Dirac model present Keplerian fall-off. As a consequence, we conclude that a more thorough analysis of the problem requires the determination of the gauge function on galactic scales, as well as restrictions on the test-particle behavior under the action of the additional geometrical fields introduced by this theory.

  18. Abundance Ratios in the Milky Way: The Halo/Thick Disk and Thin Disk Discontinuity

    NASA Astrophysics Data System (ADS)

    Chiappini, C.; Matteucci, F.

    We computed the evolution of different abundance ratios in the MW for two different sets of stellar yields. In one of them stellar rotation is taken into account and we investigate its effects on the chemical evolution model predictions. Moreover, we show that some abundance ratios offer an important tool to investigate the halo-disk discontinuity. For the first time it is shown that the effect of a halt in the star formation between the halo/thick disk and thin disk phases, already suggested from studies based both on Fe/O and Fe/Mg, should also be seen in a C/O versus O/H plot if C is produced mainly by low- and intermediate-mass stars (LIMS). The idea that C originates mainly from LIMS is suggested by the flat behavior of the [C/Fe] ratio as a function of metallicity, from [Fe/H]˜-2.2 to solar and by the fact that very recent C/O measurements for stars in the MW halo and disk seem to show a discontinuity around log(O/H) ˜-3.6. Finally, a more gentle increase of N abundance with metallicity (or time) is predicted when adopting the stellar yields with rotation of Meynet & Maeder (2002 - which do not include hot-bottom burning) than when adopting the yields of van den Höek & Groenewegen (1997), for intermediate mass stars. This fact has some implications for the timescales for the N enrichment and thus for the interpretation of the nature of Damped Lyman Alpha systems (DLAs).

  19. Laser-produced relativistic electron energy and angular distributions in thin foils

    SciTech Connect

    Rastunkov, V.S.; Krainov, V.P.

    2006-02-15

    Energy and angular distributions are obtained for electrons at the rear surface of thin foils irradiated by an oblique relativistic laser pulse. Vacuum heating at the front surface in the summary field of incident and reflected laser waves is considered as a main mechanism of electron heating up to relativistic ponderomotive energies.

  20. Optical model and optimal output coupler for a continuous wave Yb:YAG thin-disk laser with multiple-disk configuration.

    PubMed

    Zhu, Guangzhi; Zhu, Xiao; Zhu, Changhong; Shang, Jianli

    2012-09-10

    This article presents the fundamental principles of operational performance of a continuous wave (cw) thin-disk laser with multiple disks in one resonator. Based on the model of an end-pumped Yb:YAG thin-disk laser with nonuniform temperature distribution, the effect of the multiple disks in one resonator is considered. The analytic expressions are derived to analyze the laser output intensity, laser intensity in the resonator, threshold intensity, and the optical efficiency of a thin-disk laser with multiple disks arranged in series. The dependence of output coupler reflectivity and the number of thin disks on various parameters are investigated, which are useful to determine the optimal output coupler reflectivity of the thin-disk lasers and control the laser intensity in the resonator. PMID:22968282

  1. Nonstationary magnetic microstructures in stellar thin accretion disks.

    PubMed

    Montani, Giovanni; Petitta, Jacopo

    2013-05-01

    We examine the morphology of magnetic structures in thin plasma accretion disks, generalizing a stationary ideal magnetohydrodynamics model for the time-dependent viscoresistive case. Our analysis deals with small-scale perturbations to a central dipolelike magnetic field, which give rise-as in the ideal case-to the periodic modulation of magnetic flux surfaces along the radial direction, corresponding to the formation of a toroidal current channel's sequence. These microstructures suffer an exponential damping in time because of the nonzero resistivity coefficient, allowing us to define a configuration lifetime which mainly depends on the midplane temperature and on the length scale of the structure itself. By means of this lifetime, we show that the microstructures can exist within the inner regions of stellar disks in a defined range of temperatures, precisely for radii of R

  2. Measurements of optically thin electron cyclotron emission from relativistic electrons

    SciTech Connect

    James, R.A.; Silver, E.; Boyd, D.; Ellis, R.F.; Jantz, S.; Lasnier, C.J.; Harvey, R.W.; Lohr, J.; Prater, R.; O'Brien, M.R.

    1987-10-01

    Electron cyclotron emission (ECE) from hot, relativistic electrons has been measured simulataneously at several optically thin frequencies (f/f/sub ce/ = 4.6, 7.0, and 9.6) on the Tandem Mirror Experiment-Upgrade. A method to determine the temporal evolution of the hot electron density, n/sub h/, and temperature T/sub h/ is discussed. Calculations of T/sub h/ agree with the analysis of the high energy x-ray spectra. Heating rates vary between 3 keV/ms and 13 keV/ms and temperatures over 300 keV have been reached by the end of the 50 ms discharge. The ECE analysis provides an order of magnitude improvement in time resolution over the x-ray analysis and shows that fast reductions in the diamagnetic loop signals are predominantly a loss of perpendicular energy stored by the mirror trapped hot electrons. These techniques for determining n/sub h/(t) and T/sub t/(t) will be used on the DIII-D tokamak in order to parameterize the nonthermal electron tail produced during ECH current drive experiments. A vertical view will be utilized and a fast (70 Hz) scanning Michelson interferometer will be used to measure the ECE spectrum between the 2nd and the 15th harmonic. 11 refs., 7 figs.

  3. Multi-kW high brightness Yb:YAG thin disk laser

    NASA Astrophysics Data System (ADS)

    Peng, Y. H.; Lim, Y. X.; Cheng, James; Tan, Y. B.; Lau, Ernest; Lai, K. S.

    2013-03-01

    Simple stable laser resonators with a single Yb:YAG thin disk module have been designed and demonstrated to produce up to 5 kW CW laser output at 1030 nm with M2 factor of 7. Pumped with 940 nm diodes, the optical-to-optical efficiencies were >50 % at full power. Simple I and V-shaped resonators consisting of only two and three optical elements were implemented, including the 16 mm diameter Yb doped thin disk acting as an active mirror. No additional adaptive optics for aberration or mode control was used; instead the results were achieved with laser cavity designs that take into account the changing radius of curvature of the pumped thin disk. The designs ensured the laser always operated well within the stable cavity zone and with an optimised and relatively large fundamental laser mode size on the thin disk. The low optical aberrations and effective thermal management of the thin disk, mounted on a diamond cooled heat sink, together with the above cavity design approach, enabled the realization of such high power and good beam quality thin disk laser in a simple single disk laser oscillator.

  4. On the effects of tidal interaction on thin accretion disks: An analytic study

    NASA Technical Reports Server (NTRS)

    Dgani, R.; Livio, M.; Regev, O.

    1994-01-01

    We calculate tidal effects on two-dimensional thin accretion disks in binary systems. We apply a perturbation expansion to obtain an analytic solution of the tidally induced waves. We obtain spiral waves that are stronger at the inner parts of the disks, in addition to a local disturbance which scales like the strength of the local tidal force. Our results agree with recent calculations of the linear response of the disk to tidal interaction.

  5. The power of relativistic jets is larger than the luminosity of their accretion disks.

    PubMed

    Ghisellini, G; Tavecchio, F; Maraschi, L; Celotti, A; Sbarrato, T

    2014-11-20

    Theoretical models for the production of relativistic jets from active galactic nuclei predict that jet power arises from the spin and mass of the central supermassive black hole, as well as from the magnetic field near the event horizon. The physical mechanism underlying the contribution from the magnetic field is the torque exerted on the rotating black hole by the field amplified by the accreting material. If the squared magnetic field is proportional to the accretion rate, then there will be a correlation between jet power and accretion luminosity. There is evidence for such a correlation, but inadequate knowledge of the accretion luminosity of the limited and inhomogeneous samples used prevented a firm conclusion. Here we report an analysis of archival observations of a sample of blazars (quasars whose jets point towards Earth) that overcomes previous limitations. We find a clear correlation between jet power, as measured through the γ-ray luminosity, and accretion luminosity, as measured by the broad emission lines, with the jet power dominating the disk luminosity, in agreement with numerical simulations. This implies that the magnetic field threading the black hole horizon reaches the maximum value sustainable by the accreting matter. PMID:25409827

  6. Time-resolved deformation measurement of Yb:YAG thin disk using wavefront sensor

    NASA Astrophysics Data System (ADS)

    Chyla, Michal; Nagisetty, Shiva S.; Severova, Patricie; Miura, Taisuke; Mann, Klaus; Endo, Akira; Mocek, Tomas

    2015-03-01

    Even though thin-disk medium mounted on a diamond substrate is generally used for high average power operation, we found that the pulsed pumping of the Yb:YAG thin-disk mounded on a copper-tungsten heatsink could improve both optical-to-optical O-O efficiency and beam quality. We are expecting that the increase of O-O efficiency is caused by the suppression of ASE. However, the mechanism of beam quality improvement is not clear. We developed a precise measurement system of thin-disk deformations based on a Hartmann-Shack wavefront sensor. Investigating thin-disk dynamics under pulsed pumping can help to greatly improve the mode matching and allow obtaining higher output energy.

  7. Near fundamental mode 1.1 kW Yb:YAG thin-disk laser.

    PubMed

    Peng, Yuan Han; Lim, Yu Xian; Cheng, James; Guo, Yipei; Cheah, Yan Ying; Lai, Kin Seng

    2013-05-15

    We report on a Yb:YAG thin-disk laser with 1.1 kW output power and beam quality factor M²<1.4 using a simple stable resonator comprising just a single cavity mirror and a single thin disk, without the use of any aspherical elements or any adaptive optics. An optical-to-optical efficiency of 40% was obtained. The cavity was designed to give good beam quality and low misalignment sensitivity to maintain stable and robust laser operation throughout the changes in the thin-disk curvature. To the best of the authors' knowledge, this is the first time an output power beyond 1 kW has been achieved from a single thin-disk laser in near fundamental mode operation (M²<1.4). PMID:23938919

  8. Zero-phonon-line pumped 100-kHz Yb:YAG thin disk regenerative amplifier

    NASA Astrophysics Data System (ADS)

    Miura, Taisuke; Smrž, Martin; Nagisetty, Siva Sankar; Novák, Ondřej; Chyla, Michal; Severová, Patricie; Endo, Akira; Mocek, Tomáś

    2014-02-01

    We are developing 100-kHz picosecond Yb:YAG thin disk regenerative amplifier with 500-W average power for medical and industrial applications. Especially in case of the next generation of semiconductor lithography, high average power solid-state laser with picosecond pulse duration as pre pulse source is a key element to realize 1-kW EUV lithography source. We compared the output characteristics of CW laser operation pumped at 940-nm and 969-nm, and measured the surface temperature of thin disk. We found that the surface temperature of thin disk pumped at 960-nm was much lower than that pumped at 940-nm. We obtained 83-W output from thin disk regenerative amplifier at the repetition rate of 100-kHz pumped at 969-nm. The measured pulse duration was 1.9-ps.

  9. Thin-disk laser based on an Yb:YAG / YAG composite active element

    NASA Astrophysics Data System (ADS)

    Kuznetsov, I. I.; Mukhin, I. B.; Vadimova, O. L.; Palashov, O. V.

    2015-03-01

    A thin-disk laser module based on an Yb:YAG / YAG composite active element is developed with a small-signal gain of 1.25 and a stored energy of 400 mJ under cw pumping. The gain and thermally induced phase distortions in the module are studied experimentally. Based on this module, a thin-disk laser with an average power of 300 W and a slope efficiency of 42% is designed.

  10. Frequency comb offset dynamics of SESAM modelocked thin disk lasers.

    PubMed

    Emaury, Florian; Diebold, Andreas; Klenner, Alexander; Saraceno, Clara J; Schilt, Stéphane; Südmeyer, Thomas; Keller, Ursula

    2015-08-24

    We present a detailed study of the carrier-envelope offset (CEO) frequency dynamics of SESAM modelocked thin disk lasers (TDLs) pumped by kW-class highly transverse multimode pump diodes with a typical M(2) value of 200-300, and give guidelines for future frequency stabilization of multi-100-W oscillators. We demonstrate CEO frequency detection with > 30 dB signal-to-noise ratio with a resolution bandwidth of 100 kHz from a SESAM modelocked Yb:YAG TDL delivering 140 W average output power with 748-fs pulses at 7-MHz pulse repetition rate. We compare with a low-power CEO frequency stabilized Yb:CALGO TDL delivering 2.1 W with 77-fs pulses at 65 MHz. For both lasers, we perform a complete noise characterization, measure the relevant transfer functions (TFs) and compare them to theoretical models. The measured TFs are used to determine the propagation of the pump noise step-by-step through the system components. From the noise propagation analysis, we identify the relative intensity noise (RIN) of the pump diode as the main contribution to the CEO frequency noise. The resulting noise levels are not excessive and do not prevent CEO frequency stabilization. More importantly, the laser cavity dynamics are shown to play an essential role in the CEO frequency dynamics. The cavity TFs of the two lasers are very different which explains why at this point a tight CEO frequency lock can be obtained with the Yb:CALGO TDL but not with the Yb:YAG TDL. For CEO stabilization laser cavities should exhibit high damping of the relaxation oscillations by nonlinear intra-cavity elements, for example by operating a SESAM in the roll-over regime. Therefore the optimum SESAM operation point is a trade-off between enough damping and avoiding multiple pulsing instabilities. Additional cavity components could be considered for supplementary damping independent of the SESAM operation point. PMID:26368160

  11. On the Stability of Circular Orbits in Galactic Dynamics: Newtonian Thin Disks

    NASA Astrophysics Data System (ADS)

    Vieira, Ronaldo S. S.; Ramos-Caro, Javier

    2015-01-01

    The study of off-equatorial orbits in razor-thin disks is still in its beginnings. Contrary to what was presented in the literature in recent publications, the vertical stability criterion for equatorial circular orbits cannot be based on the vertical epicyclic frequency, because of the discontinuity in the gravitational field on the equatorial plane. We present a rigorous criterion for the vertical stability of circular orbits in systems composed by a razor-thin disk surrounded by a smooth axially symmetric distribution of matter, the latter representing additional structures such as thick disk, bulge and (dark matter) halo. This criterion is satisfied once the mass surface density of the thin disk is positive. Qualitative and quantitative analyses of nearly equatorial orbits are presented. In particular, the analysis of nearly equatorial orbits allows us to construct an approximate analytical third integral of motion in this region of phase-space, which describes the shape of these orbits in the meridional plane.

  12. Modeling of end-pumped Yb:YAG thin-disk lasers with nonuniform temperature distribution.

    PubMed

    Zhu, Guangzhi; Zhu, Xiao; Zhu, Changhong; Shang, Jianli; Wan, Hailin; Guo, Fei; Qi, Lijun

    2012-05-10

    A plane wave model with nonuniform temperature distribution in the thin-disk crystal is developed to describe the dynamic behavior of an end-pumped Yb:YAG thin-disk laser. A set of couple-rate equations and 2D stationary heat-conduction equations are derived. The stable temperature distribution in the disk crystal is calculated using a numerical iterative method. The analytic expression is capable of dealing with more practical laser systems than previous works on this subject as it allows for nonuniform temperature distribution in the disk crystal. Based on these results, we examined laser output intensity as a function of pump intensity, dopant concentration, resonator coupler reflectivity, crystal thickness and temperature of cooling liquid. PMID:22614469

  13. Why the Milky Way's bulge is not only a bar formed from a cold thin disk

    NASA Astrophysics Data System (ADS)

    Di Matteo, P.; Gómez, A.; Haywood, M.; Combes, F.; Lehnert, M. D.; Ness, M.; Snaith, O. N.; Katz, D.; Semelin, B.

    2015-05-01

    By analyzing an N-body simulation of a bulge formed simply via a bar instability mechanism operating on a kinematically cold stellar disk, and by comparing the results of this analysis with the structural and kinematic properties of the main stellar populations of the Milky Way bulge, we conclude that the bulge of our Galaxy is not a pure stellar bar formed from a pre-existing thin stellar disk, as some studies have recently suggested. On the basis of several arguments emphasized in this paper, we propose that the bulge population that, in the Milky Way, is observed to not be part of the peanut structure corresponds to the old Galactic thick disk, thus implying that the Milky Way is a pure thin+thick disk galaxy, with only a possible limited contribution by a classical bulge.

  14. Self-gravitational Force Calculation of Infinitesimally Thin Gaseous Disks on Nested Grids

    NASA Astrophysics Data System (ADS)

    Wang, Hsiang-Hsu; Taam, Ronald E.; Yen, David C. C.

    2016-06-01

    We extend the work of Yen et al. and develop second-order formulae to accommodate a nested grid discretization for the direct self-gravitational force calculation for infinitesimally thin gaseous disks. This approach uses a two-dimensional kernel that is derived for infinitesimally thin disks and is free of artificial boundary conditions. The self-gravitational force calculation is presented in generalized convolution forms for a nested grid configuration. A numerical technique derived from a fast Fourier transform is employed to reduce the computational complexity to be nearly linear. By comparing with analytic potential–density pairs associated with the generalized Maclaurin disks, the extended approach is verified to be of second-order accuracy when using numerical simulations. The proposed method is accurate, computationally fast, and has the potential to be applied to studies of planetary migration and the gaseous morphology of disk galaxies.

  15. Formation of Overheated Regions and Truncated Disks around Black Holes: Three-dimensional General Relativistic Radiation-magnetohydrodynamics Simulations

    NASA Astrophysics Data System (ADS)

    Takahashi, Hiroyuki R.; Ohsuga, Ken; Kawashima, Tomohisa; Sekiguchi, Yuichiro

    2016-07-01

    Using three-dimensional general relativistic radiation-magnetohydrodynamics simulations of accretion flows around stellar mass black holes, we report that the relatively cold disk (≳ {10}7 {{K}}) is truncated near the black hole. Hot and less dense regions, of which the gas temperature is ≳ {10}9 {{K}} and more than 10 times higher than the radiation temperature (overheated regions), appear within the truncation radius. The overheated regions also appear above as well as below the disk, sandwiching the cold disk, leading to the effective Compton upscattering. The truncation radius is ˜ 30{r}{{g}} for \\dot{M}˜ {L}{{Edd}}/{c}2, where {r}{{g}},\\dot{M},{L}{Edd},c are the gravitational radius, mass accretion rate, Eddington luminosity, and light speed, respectively. Our results are consistent with observations of a very high state, whereby the truncated disk is thought to be embedded in the hot rarefied regions. The truncation radius shifts inward to ˜ 10{r}{{g}} with increasing mass accretion rate \\dot{M}˜ 100{L}{{Edd}}/{c}2, which is very close to an innermost stable circular orbit. This model corresponds to the slim disk state observed in ultraluminous X-ray sources. Although the overheated regions shrink if the Compton cooling effectively reduces the gas temperature, the sandwich structure does not disappear at the range of \\dot{M}≲ 100{L}{{Edd}}/{c}2. Our simulations also reveal that the gas temperature in the overheated regions depends on black hole spin, which would be due to efficient energy transport from black hole to disks through the Poynting flux, resulting in gas heating.

  16. Formation of Overheated Regions and Truncated Disks around Black Holes: Three-dimensional General Relativistic Radiation-magnetohydrodynamics Simulations

    NASA Astrophysics Data System (ADS)

    Takahashi, Hiroyuki R.; Ohsuga, Ken; Kawashima, Tomohisa; Sekiguchi, Yuichiro

    2016-07-01

    Using three-dimensional general relativistic radiation-magnetohydrodynamics simulations of accretion flows around stellar mass black holes, we report that the relatively cold disk (≳ {10}7 {{K}}) is truncated near the black hole. Hot and less dense regions, of which the gas temperature is ≳ {10}9 {{K}} and more than 10 times higher than the radiation temperature (overheated regions), appear within the truncation radius. The overheated regions also appear above as well as below the disk, sandwiching the cold disk, leading to the effective Compton upscattering. The truncation radius is ∼ 30{r}{{g}} for \\dot{M}∼ {L}{{Edd}}/{c}2, where {r}{{g}},\\dot{M},{L}{Edd},c are the gravitational radius, mass accretion rate, Eddington luminosity, and light speed, respectively. Our results are consistent with observations of a very high state, whereby the truncated disk is thought to be embedded in the hot rarefied regions. The truncation radius shifts inward to ∼ 10{r}{{g}} with increasing mass accretion rate \\dot{M}∼ 100{L}{{Edd}}/{c}2, which is very close to an innermost stable circular orbit. This model corresponds to the slim disk state observed in ultraluminous X-ray sources. Although the overheated regions shrink if the Compton cooling effectively reduces the gas temperature, the sandwich structure does not disappear at the range of \\dot{M}≲ 100{L}{{Edd}}/{c}2. Our simulations also reveal that the gas temperature in the overheated regions depends on black hole spin, which would be due to efficient energy transport from black hole to disks through the Poynting flux, resulting in gas heating.

  17. Suppression of nonlinear phonon relaxation in Yb:YAG thin disk via zero phonon line pumping.

    PubMed

    Smrž, Martin; Miura, Taisuke; Chyla, Michal; Nagisetty, Siva; Novák, Ondřej; Endo, Akira; Mocek, Tomáš

    2014-08-15

    A quantitative comparison of conventional absorption line (940 nm) pumping and zero phonon line (ZPL) (969 nm) pumping of a Yb:YAG thin disk laser is reported. Characteristics of an output beam profile, surface temperature, and deformation of a thin disk under the different pump wavelengths are evaluated. We found that a nonlinear phonon relaxation (NPR) of the excited state in Yb:YAG, which induces nonlinear temperature rise and large aspheric deformation, did not appear in the case of a ZPL pumped Yb:YAG thin disk. This means that the advantage of ZPL pumping is not only the reduction of quantum defect but also the suppression of NPR. The latter effect is more important for high power lasers. PMID:25121908

  18. Enhanced performance of thin-disk lasers by pumping into the zero-phonon line.

    PubMed

    Weichelt, Birgit; Voss, Andreas; Abdou Ahmed, Marwan; Graf, Thomas

    2012-08-01

    Pumping Yb:YAG or Yb:LuAG into the zero-phonon line at 969 nm instead of using the common pump wavelength of 940 nm reduces the heat generation by 32%. In addition to the 3% increase of the Stokes efficiency, this significantly reduces the diffraction losses caused by the thermally induced phase distortions leading to a remarkable increase of the overall efficiency especially of fundamental-mode thin-disk lasers. Using this pumping scheme in an Yb:LuAG thin-disk laser, we achieved 742 W of nearly diffraction limited (M2≈1.5) output power at an unprecedented high optical efficiency of 58.5%. For multimode operation (M2≈15) the maximum optical efficiency of an Yb:YAG thin-disk laser was increased to 72%. PMID:22859080

  19. Experimental analysis and flow visualization of a thin liquid film on a stationary and rotating disk

    NASA Technical Reports Server (NTRS)

    Thomas, S.; Faghri, A.; Hankey, W.

    1991-01-01

    The mean thickness of a thin liquid film of deionized water with a free surface on a stationary and rotating horizontal disk has been measured with a nonobtrusive capacitance technique. The measurements were taken when the rotational speed ranged from 0-300 rpm and the flow rate varied from 7.0-15.0 lpm. A flow visualization study of the thin film was also performed to determine the characteristics of the waves on the free surface. When the disk was stationary, a circular hydraulic jump was present on the disk. Upstream from the jump, the film thickness was determined by the inertial and frictional forces on the fluid, and the radial spreading of the film. The surface tension at the edge of the disk affected the film thickness downstream from the jump. For the rotating disk, the film thickness was dependent upon the inertial and frictional forces near the center of the disk and the centrifugal forces near the edge of the disk.

  20. Cryogenic Yb:YAG composite-thin-disk for high energy and average power amplifiers.

    PubMed

    Zapata, Luis E; Lin, Hua; Calendron, Anne-Laure; Cankaya, Huseyin; Hemmer, Michael; Reichert, Fabian; Huang, W Ronny; Granados, Eduardo; Hong, Kyung-Han; Kärtner, Franz X

    2015-06-01

    A cryogenic composite-thin-disk amplifier with amplified spontaneous emission (ASE) rejection is implemented that overcomes traditional laser system problems in high-energy pulsed laser drivers of high average power. A small signal gain of 8 dB was compared to a 1.5 dB gain for an uncapped thin-disk without ASE mitigation under identical pumping conditions. A strict image relayed 12-pass architecture using an off-axis vacuum telescope and polarization switching extracted 100 mJ at 250 Hz in high beam quality stretched 700 ps pulses of 0.6-nm bandwidth. PMID:26030570

  1. Radially and azimuthally polarized laser beams by thin-disk laser.

    PubMed

    Aghbolaghi, Reza; Charehjolo, Habib Sahebghoran

    2016-05-01

    The generation of radially and azimuthally polarized beams is theoretically investigated in thin-disk laser configurations by writing Jones matrices for optical elements. Higher modes are omitted by aperture and the mode-selection operation is done by discontinuous phase elements. Two modes, TEM01x and TEM01y, are combined to generate the radially and azimuthally polarized laser beam. The polarization of the output beams is studied by the extended Jones matrices. In addition, the output power of the thin-disk laser is numerically estimated by solving the rate equations in ytterbium-doped materials. PMID:27140363

  2. Experiments on Heat Transfer in a Thin Liquid Film Flowing Over a Rotating Disk

    NASA Technical Reports Server (NTRS)

    Sankaran, Subramanian (Technical Monitor); Ozar, B.; Cetegen, B. M.; Faghri, A.

    2004-01-01

    An experimental study of heat transfer into a thin liquid film on a rotating heated disk is described. Deionized water was introduced at the center of a heated. horizontal disk with a constant film thickness and uniform radial velocity. Radial distribution of the disk surface temperatures was measured using a thermocouple/slip ring arrangement. Experiments were performed for a range of liquid flow rates between 3.01pm and 15.01pm. The angular speed of the disk was varied from 0 rpm to 500 rpm. The local heat transfer coefficient was determined based on the heat flux supplied to the disk and the temperature difference between the measured disk surface temperature and the liquid entrance temperature onto the disk. The local heat transfer coefficient was seen to increase with increasing flow rate as well as increasing angular velocity of the disk. Effect of rotation on heat transfer was largest for the lower liquid flow rates with the effect gradually decreasing with increasing liquid flow rates. Semi-empirical correlations are presented in this study for the local and average Nusselt numbers.

  3. Ion acceleration and plasma jet formation in ultra-thin foils undergoing expansion and relativistic transparency

    NASA Astrophysics Data System (ADS)

    King, M.; Gray, R. J.; Powell, H. W.; MacLellan, D. A.; Gonzalez-Izquierdo, B.; Stockhausen, L. C.; Hicks, G. S.; Dover, N. P.; Rusby, D. R.; Carroll, D. C.; Padda, H.; Torres, R.; Kar, S.; Clarke, R. J.; Musgrave, I. O.; Najmudin, Z.; Borghesi, M.; Neely, D.; McKenna, P.

    2016-09-01

    At sufficiently high laser intensities, the rapid heating to relativistic velocities and resulting decompression of plasma electrons in an ultra-thin target foil can result in the target becoming relativistically transparent to the laser light during the interaction. Ion acceleration in this regime is strongly affected by the transition from an opaque to a relativistically transparent plasma. By spatially resolving the laser-accelerated proton beam at near-normal laser incidence and at an incidence angle of 30°, we identify characteristic features both experimentally and in particle-in-cell simulations which are consistent with the onset of three distinct ion acceleration mechanisms: sheath acceleration; radiation pressure acceleration; and transparency-enhanced acceleration. The latter mechanism occurs late in the interaction and is mediated by the formation of a plasma jet extending into the expanding ion population. The effect of laser incident angle on the plasma jet is explored.

  4. Geometrically thin, hot accretion disks - Topology of the thermal equilibrium curves

    NASA Technical Reports Server (NTRS)

    Kusunose, Masaaki; Mineshige, Shin

    1992-01-01

    All the possible thermal equilibrium states of geometrically thin alpha-disks around stellar-mass black holes are presented. A (vertically) one-zone disk model is employed and it is assumed that a main energy source is viscous heating of protons and that cooling is due to bremsstrahlung and Compton scattering. There exist various branches of the thermal equilibrium solution, depending on whether disks are effectively optically thick or thin, radiation pressure-dominated or gas pressure-dominated, composed of one-temperature plasmas or of two-temperature plasmas, and with high concentration of e(+)e(-) pairs or without pairs. The thermal equilibrium curves at high temperatures (greater than or approximately equal to 10 exp 8 K) are substantially modified by the presence of e(+)e(-) pairs. The thermal stability of these branches are examined.

  5. The flow of a thin liquid film on a stationary and rotating disk. II - Theoretical prediction

    NASA Technical Reports Server (NTRS)

    Rahman, M. M.; Faghri, A.; Hankey, W. L.

    1990-01-01

    The existing theoretical models are improved and a systematic procedure to compute the free surface flow of a thin liquid film is suggested. The solutions for axisymmetric radial flow on a stationary horizontal disk and for the disk rotating around its axis are presented. The theoretical predictions are compared with the experimental data presented in Part I of this report. The analysis shows results for both supercritical and subcritical flows and the flow structure in the vicinity of a hydraulic jump which isolates these two flow types. The detailed flow structure in a hydraulic jump was computed and shown to contain regions of separation including a 'surface roller'. The effects of surface tension are found to be important near the outer edge of the disk where the fluid experiences a free fall. At other locations, the surface tension is negligible. For a rotating disk, the frictional resistance in the angular direction is found to be as important as that in the radial direction.

  6. Ultra-thin overcoats for the head/disk interface tribology

    SciTech Connect

    Bhatia, C.S.

    1997-05-01

    Areal density in magnetic storage is increasing at a blistering pace of 60% annually. Recently IBM announced its mobile product with the industry highest areal density of 2.64 Gb/In{sup 2}. The areal density demonstrations have shown up to 5 Gb/In{sup 2} possible. Reaching higher areal density targets dictate that magnetic spacing between heads and disks be reduced. For the example of a 10 Gb/In{sup 2} areal density goal, the magnetic spacing should be {approx}25 nm. In budgeting this magnetic spacing, it is required that disk and slider air bearing surface overcoats thickness be reduced to 5 nm range. Present choice of carbon overcoat in the magnetic storage hard disk drive industry is sputter deposited, hydrogenated carbon (CH{sub x}) with thickness in the range of 12-15 nm on heads and disks. Novel overcoats such as nitrogenated carbon (CN{sub x}) and cathodic arc carbon films are being developed for future applications. Cathodic arc deposition forms ultra-thin amorphous hard carbon films of high sp{sup 3} content, high hardness, and low coefficient of friction. These properties make it of great interest for head/disk interface application, in particular for contact recording. In many cases, the tribological properties of the head disk interface could be improved by factors up to ten applying cathodic arc overcoats to the slider or disk surface. This paper reviews the results of cathodic arc ultra-thin (2-10 nm) carbon overcoats for head/disk interface tribological applications.

  7. The flow of a thin liquid film on a stationary and rotating disk. I - Experimental analysis and flow visualization

    NASA Technical Reports Server (NTRS)

    Thomas, S.; Faghri, A.; Hankey, W.

    1990-01-01

    The mean thickness of a thin liquid film of deionized water with a free surface on a stationary and rotating horizontal disk has been measured with a nonobtrusive capacitance technique. The measurements were taken when the rotational speed was 0-300 RPM and the flow rate was 7.0-15.0 LPM. A flow visualization study of the thin film was also performed to determine the characteristics of the waves on the free surface. When the disk was stationary, a circular hydraulic jump was present on the disk. Surface waves were found in the supercritical and subcritical regions at all flow rates studied. When the rotational speed of the disk is low, a standing wave at the edge of the disk was present. As the rotational speed increased, the surface waves changed from the wavy-laminar region to a region in which the waves ran nearly radially across the disk on top of a thin substrate of fluid.

  8. Non-linear radial spinwave modes in thin magnetic disks

    SciTech Connect

    Helsen, M. De Clercq, J.; Vansteenkiste, A.; Van Waeyenberge, B.; Weigand, M.

    2015-01-19

    We present an experimental investigation of radial spin-wave modes in magnetic nano-disks with a vortex ground state. The spin-wave amplitude was measured using a frequency-resolved magneto-optical spectrum analyzer, allowing for high-resolution resonance curves to be recorded. It was found that with increasing excitation amplitude up to about 10 mT, the lowest-order mode behaves strongly non-linearly as the mode frequency redshifts and the resonance peak strongly deforms. This behavior was quantitatively reproduced by micromagnetic simulations. Micromagnetic simulations showed that at higher excitation amplitudes, the spinwaves are transformed into a soliton by self-focusing, and collapse onto the vortex core, dispersing the energy in short-wavelength spinwaves. Additionally, this process can lead to switching of the vortex polarization through the injection of a Bloch point.

  9. Non-LTE sodium abundance in galactic thick- and thin-disk red giants

    NASA Astrophysics Data System (ADS)

    Alexeeva, S. A.; Pakhomov, Yu. V.; Mashonkina, L. I.

    2014-07-01

    The non-LTE sodium abundance has been determined from the Na I 6154 and 6161 Å lines for 38 thin-disk stars (15 of them are Ba II stars), 15 thick-disk stars, 13 Hercules-stream stars, and 13 stars that cannot be attributed neither to the thick Galactic disk nor to the thin one. The Na I model atom has been constructed using the most accurate present-day atomic data. For the Na I 6154 and 6161 Å lines, the non-LTEabundance corrections are from -0.06 to -0.24 dex, depending on the stellar parameters. No differences in [Na/Fe] abundance between the thick and thin disks have been detected; the derived ratios are close to the solar ones. The existence of a [Na/Fe] overabundance in the Ba II stars has been confirmed. The Hercules-stream stars exhibit nearly solar [Na/Fe] ratios. The results obtained can be used to test the sodium nucleosynthesis models.

  10. A multi-pass pumping scheme for thin disk lasers with good anti-disturbance ability.

    PubMed

    Huang, Yan; Zhu, Xiao; Zhu, Guangzhi; Shang, Jianli; Wang, Hailin; Qi, Lijun; Zhu, Changhong; Guo, Fei

    2015-02-23

    A multi-pass pumping scheme for thin disk lasers consisting of dual parabolic mirrors with conjugated relationship is presented. The anti-disturbance ability of pumping is analyzed by ray tracing method under different kinds of disturbances. Both theoretical and experiment results show that disturbances in this system won't lead to a misalignment of each pumping spot, but only the position of superposed pumping spot on disk crystal will be changed. Compared with the multi-pass pumping scheme consisting of parabolic mirror and folding prisms, this pumping scheme has a better anti-disturbance ability. PMID:25836497

  11. Regenerative thin-disk amplifier for 300 mJ pulse energy.

    PubMed

    Jung, Robert; Tümmler, Johannes; Will, Ingo

    2016-01-25

    A regenerative amplifier based on thin-disk technology has been upgraded and optimized. Within a CPA laser system chirped 1 ns pulses are amplified to more than 300 mJ pulse energy. In addition to the high pulse energy the amplifier shows a very good energy stability with 0.25% (rms) fluctuation as well as an excellent beam quality of M(2) = 1.04. The regenerative amplifier is equipped with an Yb:YAG thin-disk of 17 mm in diameter pumped with 1.75 kW peak power. It is operated at a repetition rate of 100 Hz. The optical-to-optical efficiency is better than 18%. The laser pulses are compressed to 1.8 ps pulse duration. PMID:26832471

  12. Thermal and laser properties of Yb:LuAG for kW thin disk lasers.

    PubMed

    Beil, Kolja; Fredrich-Thornton, Susanne T; Tellkamp, Friedjof; Peters, Rigo; Kränkel, Christian; Petermann, Klaus; Huber, Günter

    2010-09-27

    Thin disk laser experiments with Yb:LuAG (Yb:Lu(3)Al(5)O(12)) were performed leading to 5 kW of output power and an optical-to-optical efficiency exceeding 60%. Comparative analyses of the laser relevant parameters of Yb:LuAG and Yb:YAG were carried out. While the spectroscopic properties were found to be nearly identical, investigations of the thermal conductivities revealed a 20% higher value for Yb:LuAG at Yb(3+)-doping concentrations of about 10%. Due to the superior thermal conductivity with respect to Yb:YAG, Yb:LuAG offers thus the potential of improved performance in high power thin disk laser applications. PMID:20940967

  13. Modeling and optimization of thin disk structure for high power sub-joule laser

    NASA Astrophysics Data System (ADS)

    Severová, Patricie; Smrz, Martin; Chyla, Michal; Miura, Taisuke; Endo, Akira; Mocek, Tomáš

    2013-05-01

    We analyzed the transient response characteristics of Yb:YAG thin disk in to clarify the experimentally obtained advantages of pulsed pumping in 1-kHz repetition rate reported in ref. 2. We applied commercial 2D FEA software which can calculate transient response of thermal effects. The temperature distributions of thin disk in both the CW power of 125-W and the average power of pulsed 125-W have been calculated. Even the net heat power were same in both CW and pulsed pumping, the temperature distribution was lower in pulsed pumping which can provide higher O-O efficiency and smaller beam distortion. The time evolution of OPD in the pulsed pumping has been analyzed, too.

  14. Noncalculus Treatment of Steady-State Rolling of a Thin Disk on a Horizontal Surface

    NASA Astrophysics Data System (ADS)

    Andersen, W. L.

    2007-10-01

    A coin tossed onto a table often ends up rolling in such a way that the center of mass remains approximately stationary. Although this phenomenon has been studied for many years and is well-documented in the literature, it is perhaps not widely appreciated in the physics education community that the motion can be understood without the use of calculus. In the hopes of providing a pedagogically useful example of physics in everyday life, a solution of the motion of a thin disk rolling in this fashion is reviewed using techniques readily accessible to an algebra-based introductory physics class. In addition, the principal moments of inertia of a thin disk are derived without calculus.

  15. High-power, 1-ps, all-Yb:YAG thin-disk regenerative amplifier.

    PubMed

    Fattahi, Hanieh; Alismail, Ayman; Wang, Haochuan; Brons, Jonathan; Pronin, Oleg; Buberl, Theresa; Vámos, Lénárd; Arisholm, Gunnar; Azzeer, Abdallah M; Krausz, Ferenc

    2016-03-15

    We report a 100 W, 20 mJ, 1-ps, all-Yb:YAG thin-disk regenerative amplifier seeded by a microjoule-level Yb:YAG thin-disk Kerr-lens mode-locked oscillator. The regenerative amplifier is implemented in a chirped pulse amplification system and operates at an ambient temperature in air, delivering ultrastable output pulses at a 5 kHz repetition rate and with a root mean square power noise value of less than 0.5%. Second harmonic generation of the amplifier's output in a 1.5 mm-thick BBO crystal results in more than 70 W at 515 nm, making the system an attractive source for pumping optical parametric chirped pulse amplifiers in the visible and near-infrared spectral ranges. PMID:26977650

  16. Yb:YAG thin-disk chirped pulse amplification laser system for intense terahertz pulse generation.

    PubMed

    Ochi, Yoshihiro; Nagashima, Keisuke; Maruyama, Momoko; Tsubouchi, Masaaki; Yoshida, Fumiko; Kohno, Nanase; Mori, Michiaki; Sugiyama, Akira

    2015-06-01

    We have developed a 1 kHz repetition picosecond laser system dedicated for intense terahertz (THz) pulse generation. The system comprises a chirped pulse amplification laser equipped with a Yb:YAG thin-disk amplifier. At room temperature, the Yb:YAG thin-disk regenerative amplifier provides pulses having energy of over 10 mJ and spectral bandwidth of 1.2 nm. The pulse duration achieved after passage through a diffraction grating pair compressor was 1.3 ps. By employing this picosecond laser as a pump source, THz pulses having a peak frequency of 0.3 THz and 4 µJ of energy were generated by means of optical rectification in an Mg-doped LiNbO3 crystal. PMID:26072862

  17. Thin-disk Raman laser operation of Yb:YVO4/YVO4 around 1120 nm

    NASA Astrophysics Data System (ADS)

    Yang, F. G.; Qiao, L.; Xia, Z. C.

    2015-12-01

    We present diode-pumped Yb:YVO4/YVO4 thin-disk Raman laser operation around 1120 nm. The thin-disk crystals, Yb:YVO4, and the Raman crystal, YVO4, are cut with 250 μm and 20 mm, respectively. In multimode configurations, up to 0.91 W of Raman laser output power and a maximum slope efficiency of 10% are demonstrated corresponding to a pump power of 10 W. A continuous wavelength tuning range of 54 nm from 1096 to 1150 nm with a maximum output power of 320 mW at 1126 nm is confirmed.

  18. Highly efficient 400  W near-fundamental-mode green thin-disk laser.

    PubMed

    Piehler, Stefan; Dietrich, Tom; Rumpel, Martin; Graf, Thomas; Ahmed, Marwan Abdou

    2016-01-01

    We report on the efficient generation of continuous-wave, high-brightness green laser radiation. Green lasers are particularly interesting for reliable and reproducible deep-penetration welding of copper or for pumping Ti:Sa oscillators. By intracavity second-harmonic generation in a thin-disk laser resonator designed for fundamental-mode operation, an output power of up to 403 W is demonstrated at a wavelength of 515 nm with almost diffraction-limited beam quality. The unprecedented optical efficiency of 40.7% of green output power with respect to the pump power of the thin-disk laser is enabled by the intracavity use of a highly efficient grating waveguide mirror, which combines the functions of wavelength stabilization and spectral narrowing, as well as polarization selection in a single element. PMID:26696186

  19. Passively mode-locked Yb3+:Sc2SiO5 thin-disk laser.

    PubMed

    Wentsch, Katrin Sarah; Zheng, Lihe; Xu, Jun; Ahmed, Marwan Abdou; Graf, Thomas

    2012-11-15

    Experimental investigations on a passively mode-locked Yb(3+):Sc(2)SiO(5) (Yb:SSO) thin-disk laser are presented. The mode-locking was performed with a commercially available semiconductor saturable absorber mirror. The laser was operated at a repetition rate of 27 MHz and generated a maximum average output power of 27.8 W with a pulse duration of 298 fs. The spectrum was centered at 1036 nm. The beam was measured to be close to diffraction limited (M(2)<1.1). The promising results confirm the suitability of Yb:SSO for mode-locked thin-disk laser oscillators and indicate that this comparably new material deserves further attention by optimizing the crystal quality (growth and polishing) and doping levels for further power scaling. PMID:23164901

  20. 6.5 kW, Yb:YAG Ceramic Thin Disk Laser

    NASA Astrophysics Data System (ADS)

    Latham, William P.; Lobad, Ahmed; Newell, Tim C.; Stalnaker, Don

    2010-10-01

    The operation of a 1030 nm, single, thin disk laser which produced 6.5 kW of laser output power with 57 percent slope efficiency is reported. The Yb:YAG ceramic gain element is 200 μm thick, bonded to a 1 mm, undoped, ceramic YAG cap. The gain element is pumped by diodes at 940 nm. The maximum incident pump intensity was 5 kW/cm2, which yielded an output intensity of 2.6 kW/cm2 of multimode laser radiation. Rigrod analysis suggests that the laser operates with inhomogeneous gain saturation. This is attributed to the enhanced, spatial-hole-burning effect when the gain element is adjacent to a mirror. The pump threshold and output intensities were independent of pump spot size, which validates area scaling. Observed thermal lensing contributions include thermal-expansion-induced disk flexure, pump-edge-induced temperature profile and a strong thermal imprint of the cooling nozzle due to the direct jet impingement on the high reflection (HR) coated side. Weak absorption of the 1030 nm intracavity intensity in the undoped cap and/or the anti-reflection (AR) coating led to excess heating that limited the extracted power intensity. These results suggest ceramic Yb:YAG can be scaled to higher powers using optimized thin disk elements and improved disk thermal management techniques.

  1. 6.5 kW, Yb:YAG Ceramic Thin Disk Laser

    SciTech Connect

    Latham, William P.; Newell, Tim C.

    2010-10-08

    The operation of a 1030 nm, single, thin disk laser which produced 6.5 kW of laser output power with 57 percent slope efficiency is reported. The Yb:YAG ceramic gain element is 200 {mu}m thick, bonded to a 1 mm, undoped, ceramic YAG cap. The gain element is pumped by diodes at 940 nm. The maximum incident pump intensity was 5 kW/cm{sup 2}, which yielded an output intensity of 2.6 kW/cm{sup 2} of multimode laser radiation. Rigrod analysis suggests that the laser operates with inhomogeneous gain saturation. This is attributed to the enhanced, spatial-hole-burning effect when the gain element is adjacent to a mirror. The pump threshold and output intensities were independent of pump spot size, which validates area scaling. Observed thermal lensing contributions include thermal-expansion-induced disk flexure, pump-edge-induced temperature profile and a strong thermal imprint of the cooling nozzle due to the direct jet impingement on the high reflection (HR) coated side. Weak absorption of the 1030 nm intracavity intensity in the undoped cap and/or the anti-reflection (AR) coating led to excess heating that limited the extracted power intensity. These results suggest ceramic Yb:YAG can be scaled to higher powers using optimized thin disk elements and improved disk thermal management techniques.

  2. Energy scaling of Kerr-lens mode-locked thin-disk oscillators.

    PubMed

    Brons, Jonathan; Pervak, Vladimir; Fedulova, Elena; Bauer, Dominik; Sutter, Dirk; Kalashnikov, Vladimir; Apolonskiy, Alexander; Pronin, Oleg; Krausz, Ferenc

    2014-11-15

    Geometric scaling of a Kerr-lens mode-locked Yb:YAG thin-disk oscillator yields femtosecond pulses with an average output power of 270 W. The scaled system delivers femtosecond (210-330 fs) pulses with a peak power of 38 MW. These values of average and peak power surpass the performance of any previously reported femtosecond laser oscillator operated in atmospheric air. PMID:25490489

  3. High-power radially polarized Yb:YAG thin-disk laser with high efficiency.

    PubMed

    Ahmed, Marwan Abdou; Haefner, Matthias; Vogel, Moritz; Pruss, Christof; Voss, Andreas; Osten, Wolfgang; Graf, Thomas

    2011-03-14

    Radially polarized beams with an output power of 275 W, M2=2.3 and an efficiency of about 52.5% were generated from an Yb:YAG thin-disk laser. An intra-cavity circular resonant waveguide grating was used as a polarization selective mirror inside the laser cavity. We report on the design and the fabrication using a scanning beam interference lithography system and discuss the calculated and measured performances of the presented polarizing grating mirrors. PMID:21445144

  4. Thin-disk laser with Bessel-like output beam: theory and simulations.

    PubMed

    Aghbolaghi, R; Batebi, S; Sabaghzadeh, J

    2013-02-01

    We have numerically shown that a high-power Bessel-Gauss beam can be generated by a solid-state thin-disk laser using an axicon-based resonator. Ytterbium ions doped in the YAG crystal were utilized in this configuration as an active medium. We obtained the output power, intensity, and phase profiles on the output coupler and the active medium. PMID:23385906

  5. Numerical analysis of an end-pumped Yb:YAG thin disk laser with variation of a fractional thermal load.

    PubMed

    Zhu, Guangzhi; Zhu, Xiao; Huang, Yan; Wang, Hailin; Zhu, Changhong

    2014-07-01

    An analytical model is developed to describe the dynamic behavior of an end-pumped Yb:YAG thin disk laser. Within the model, the rate equations, including the nonradiative relaxation process, are calculated taking into account the dependence of the fractional thermal load on the temperature of the thin disk crystal and intracavity laser intensity. The fractional thermal load is analyzed, or can be evaluated clearly, under lasing or nonlasing conditions. The stable temperature and fractional thermal load in a thin disk crystal for different radiative quantum efficiencies are obtained using the numerical iterative method. Furthermore, the dependence of the laser output intensity on variables such as pumping intensity, coupler reflectivity, radiative quantum efficiency, and the temperature of thin disk crystal is discussed. PMID:25090000

  6. The Gaia-ESO Survey: Separating disk chemical substructures with cluster models. Evidence of a separate evolution in the metal-poor thin disk

    NASA Astrophysics Data System (ADS)

    Rojas-Arriagada, A.; Recio-Blanco, A.; de Laverny, P.; Schultheis, M.; Guiglion, G.; Mikolaitis, Š.; Kordopatis, G.; Hill, V.; Gilmore, G.; Randich, S.; Alfaro, E. J.; Bensby, T.; Koposov, S. E.; Costado, M. T.; Franciosini, E.; Hourihane, A.; Jofré, P.; Lardo, C.; Lewis, J.; Lind, K.; Magrini, L.; Monaco, L.; Morbidelli, L.; Sacco, G. G.; Worley, C. C.; Zaggia, S.; Chiappini, C.

    2016-02-01

    Context. Recent spectroscopic surveys have begun to explore the Galactic disk system on the basis of large data samples, with spatial distributions sampling regions well outside the solar neighborhood. In this way, they provide valuable information for testing spatial and temporal variations of disk structure kinematics and chemical evolution. Aims: The main purposes of this study are to demonstrate the usefulness of a rigorous mathematical approach to separate substructures of a stellar sample in the abundance-metallicity plane, and provide new evidence with which to characterize the nature of the metal-poor end of the thin disk sequence. Methods: We used a Gaussian mixture model algorithm to separate in the [Mg/Fe] vs. [Fe/H] plane a clean disk star subsample (essentially at RGC< 10 kpc) from the Gaia-ESO survey (GES) internal data release 2 (iDR2). We aim at decomposing it into data groups highlighting number density and/or slope variations in the abundance-metallicity plane. An independent sample of disk red clump stars from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) was used to cross-check the identified features. Results: We find that the sample is separated into five groups associated with major Galactic components; the metal-rich end of the halo, the thick disk, and three subgroups for the thin disk sequence. This is confirmed with the sample of red clump stars from APOGEE. The three thin disk groups served to explore this sequence in more detail. The two metal-intermediate and metal-rich groups of the thin disk decomposition ([Fe/H] > -0.25 dex) highlight a change in the slope at solar metallicity. This holds true at different radial regions of the Milky Way. The distribution of Galactocentric radial distances of the metal-poor part of the thin disk ([Fe/H] < -0.25 dex) is shifted to larger distances than those of the more metal-rich parts. Moreover, the metal-poor part of the thin disk presents indications of a scale height

  7. First demonstration of passively mode-locked Yb:CaF2 thin-disk laser

    NASA Astrophysics Data System (ADS)

    Dannecker, Benjamin; Délen, Xavier; Wentsch, Katrin S.; Weichelt, Birgit; Hönninger, Clemens; Voss, Andreas; Abdou Ahmed, Marwan; Graf, Thomas

    2015-02-01

    The need for ultra-short (sub-ps) pulsed laser systems with high power and high energy has advanced the mode-locked Ytterbium-doped thin-disk technology in the last decade. Therefore several research groups have made efforts to explore new laser crystals e.g. Yb:SSO, Yb:CAlGO or Yb:Lu2O3 for the generation of sub-500 fs pulses in thin-disk oscillators. Another promising and known candidate for ultra-short pulsed lasers is Yb:CaF2, which has been so far only used in bulk laser architecture. In this work, we present the first demonstration of a mode-locked Yb:CaF2 laser in thin-disk configuration. The resonator cavity was designed for eight passes through the disk per roundtrip at a repetition rate of 35 MHz. A saturable absorber mirror (SESAM) was used to obtain the soliton mode-locking. We achieved close-to transform-limited pulses with a pulse duration of less than 445 fs and an emission spectral width of 2.6 nm at FWHM (i.e. time-bandwidth product of 0.323). At the average output power of 6.6 W this corresponds to a peak-power of 430 kW and pulse energy of 190 nJ. To the best of our knowledge, this is the highest average output power and pulse energy using Yb:CaF2 as gain material reported to date. Taking into account the dispersion, self-phase modulation, pulse energy, output coupling ratio and laser gain, the pulse-duration estimated from the soliton-equation and our numerical calculations of pulse-propagation is in good agreement with the pulse-duration obtained in the experiment. Higher powers and shorter pulse-durations with this material are the subject of our future investigations.

  8. Intra-cavity pumped Yb:YAG thin-disk laser with 1.74% quantum defect.

    PubMed

    Vorholt, Christian; Wittrock, Ulrich

    2015-10-15

    We present, to the best of our knowledge, the first intra-cavity pumped Yb:YAG thin-disk laser. It operates at 1050.7 nm with a quantum defect of just 1.74% due to pumping at 1032.4 nm. Low absorption of the pump light at the pump wavelength of 1032.4 nm is compensated for by placing the disk inside the resonator of another Yb:YAG thin-disk laser which is diode-pumped at 940 nm. The intra-cavity pumped laser has an output power of 10.3 W and a slope efficiency of 8.3%. PMID:26469628

  9. BREAKS IN THIN AND THICK DISKS OF EDGE-ON GALAXIES IMAGED IN THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S{sup 4}G)

    SciTech Connect

    Comeron, Sebastien; Salo, Heikki; Laurikainen, Eija; Laine, Jarkko; Elmegreen, Bruce G.; Athanassoula, E.; Bosma, Albert; Knapen, Johan H.; Gadotti, Dimitri A.; Sheth, Kartik; Munoz-Mateos, Juan Carlos; Kim, Taehyun; Hinz, Joannah L.; Regan, Michael W.; Gil de Paz, Armando; Menendez-Delmestre, Karin; Seibert, Mark; Ho, Luis C.; Mizusawa, Trisha; Holwerda, Benne

    2012-11-10

    Breaks in the radial luminosity profiles of galaxies have until now been mostly studied averaged over disks. Here, we study separately breaks in thin and thick disks in 70 edge-on galaxies using imaging from the Spitzer Survey of Stellar Structure in Galaxies. We built luminosity profiles of the thin and thick disks parallel to midplanes and we found that thin disks often truncate (77%). Thick disks truncate less often (31%), but when they do, their break radius is comparable with that in the thin disk. This suggests either two different truncation mechanisms-one of dynamical origin affecting both disks simultaneously and another one only affecting the thin disk-or a single mechanism that creates a truncation in one disk or in both depending on some galaxy property. Thin disks apparently antitruncate in around 40% of galaxies. However, in many cases, these antitruncations are an artifact caused by the superposition of a thin disk and a thick disk, with the latter having a longer scale length. We estimate the real thin disk antitruncation fraction to be less than 15%. We found that the ratio of the thick and thin stellar disk mass is roughly constant (0.2 < M{sub T} /M{sub t} < 0.7) for circular velocities v{sub c} > 120 km s{sup -1}, but becomes much larger at smaller velocities. We hypothesize that this is due to a combination of a high efficiency of supernova feedback and a slower dynamical evolution in lower-mass galaxies causing stellar thin disks to be younger and less massive than in higher-mass galaxies.

  10. VADER: A flexible, robust, open-source code for simulating viscous thin accretion disks

    NASA Astrophysics Data System (ADS)

    Krumholz, M. R.; Forbes, J. C.

    2015-06-01

    The evolution of thin axisymmetric viscous accretion disks is a classic problem in astrophysics. While models based on this simplified geometry provide only approximations to the true processes of instability-driven mass and angular momentum transport, their simplicity makes them invaluable tools for both semi-analytic modeling and simulations of long-term evolution where two- or three-dimensional calculations are too computationally costly. Despite the utility of these models, the only publicly-available frameworks for simulating them are rather specialized and non-general. Here we describe a highly flexible, general numerical method for simulating viscous thin disks with arbitrary rotation curves, viscosities, boundary conditions, grid spacings, equations of state, and rates of gain or loss of mass (e.g., through winds) and energy (e.g., through radiation). Our method is based on a conservative, finite-volume, second-order accurate discretization of the equations, which we solve using an unconditionally-stable implicit scheme. We implement Anderson acceleration to speed convergence of the scheme, and show that this leads to factor of ∼5 speed gains over non-accelerated methods in realistic problems, though the amount of speedup is highly problem-dependent. We have implemented our method in the new code Viscous Accretion Disk Evolution Resource (VADER), which is freely available for download from

  11. Spatial hole burning in Yb:YAG thin-disk lasers

    NASA Astrophysics Data System (ADS)

    Vorholt, Christian; Wittrock, Ulrich

    2015-09-01

    The spatially varying intensity in a standing wave resonator leads to spatial hole burning in the gain medium of a laser. The spatial hole burning changes the gain of different longitudinal modes and can thus determine the optical spectrum of the laser. We simulate this longitudinal mode competition in standing wave resonators of thin-disk lasers. The resulting optical spectra of the laser are compared to measured optical spectra. We examine two types of resonators: I-resonators and V-resonators with different angles of incidence. In V-resonators, the non-normal incidence of the laser beam on the disk lifts the degeneracy of the polarization. Experiments show that the slight gain advantage for the -polarization does not lead to polarized emission. For both types of resonators, the measured spectra are in good agreement with the simulated ones. The simulations allow to study the influence of spectral intra-cavity losses on the optical spectrum of a thin-disk laser.

  12. Relativistic Outflows from Advection-dominated Accretion Disks around Black Holes

    NASA Astrophysics Data System (ADS)

    Subramanian, P.; Becker, P. A.

    1999-05-01

    Advection dominated accretion flows have been recently proposed as attractive models for explaining low luminosity black hole systems. However, the so-called ADAF models suffer from a serious drawback; namely, the accretion flow has a postive Bernoulli parameter, and is therefore gravitationally unbound. Blandford & Begelman (1999, MNRAS) recently proposed advection-dominated flows that incorporate an outflow that carries away an appreciable amount of mass, energy and angular momentum (ADIOS), thereby alleviating this problem. However, their solutions merely assume the existence of such outflows, and do not elaborate on the mechanisms that could drive them. Subramanian, Becker & Kazanas (1999, ApJ, astro-ph/9805044) have described a mechanism whereby particles are accelerated via collisions with magnetic scattering centers (kinks in the tangled magnetic field) embedded in the accreting plasma and form relativistic outflows. We examine the role of this mechanism in the context of Blandford & Begelman's ADIOS solutions with a view to elucidating the physical processes that drive the outflows, which in turn are a crucial component of the overall solution.

  13. Solar flare X-ray polarimeter utilizing a large area thin beryllium scattering disk

    NASA Technical Reports Server (NTRS)

    Gotthelf, E.; Hamilton, T.; Novick, R.; Chanan, G.; Emslie, A.; Weisskopf, M.

    1989-01-01

    A model of a solar flare X-ray polarimeter utilizing a large-area thin beryllium scattering disk was developed using Monte Carlo techniques for several classes of solar flares. The solar-flare polarimeter consists of a 30-cm-diam Be disk of about 1/3 of a scattering length thickness, which is surrounded by a cylindrical detector composed of six segmented panels of NaI scintillators, each coupled to 15 photomultiplier tubes. The instrument is sensitive to X-rays from 10 to 100 keV. For a class-M-2 solar flare observed for 10 sec from a balloon at an altitude of 150,000 ft, the minimum detectable polarization at the 99 percent statistical confidence level was found to be 1-6 percent over the energy range 20-100 keV.

  14. Forced Turbulence in Relativistic Conformal Fluids

    NASA Astrophysics Data System (ADS)

    Westernacher-Schneider, John Ryan; Green, Stephen; Lehner, Luis; Canon, Kipp; Oz, Yaron

    2015-04-01

    Given the renewed interest arising both from AdS/CFT and astrophysics, we revisit the phenomenon of relativistic turbulence. We build on some recent work which extends known non-relativistic results in turbulence to the case of relativistic (and thus compressible) fluids. In particular, we derive the scaling behaviour of two-point correlation functions in 2+1 dimensions--holographically dual to 3+1 dimensional gravity. Turbulence in 2+1 dimensions also approximates several astrophysical situations, such as thin accretion disks around black holes. We perform numerical simulations of forced steady-state turbulence to verify our derived correlation functions.

  15. The Thickening of the Thin Disk in the Third Galactic Quadrant

    NASA Astrophysics Data System (ADS)

    Carraro, Giovanni; Vázquez, Rubén A.; Costa, Edgardo; Ahumada, Javier A.; Giorgi, Edgar E.

    2015-01-01

    In the third Galactic quadrant (180^\\circ ≤slant l≤slant 270^\\circ ) of the Milky Way, the Galactic thin disk exhibits a significant warp—shown both by gas and young stars—bending down a few kiloparsecs below the formal Galactic plane (b=0^\\circ ). This warp shows its maximum at l˜ 240^\\circ , in the direction of the Canis Major constellation. In a series of papers, we have traced the detailed structure of this region using open star clusters, putting particular emphasis on the spiral structure of the outer disk. We noted a conspicuous accumulation of young star clusters within 2-3 kpc from the Sun and close to b = 0°, which we interpreted as the continuation of the Local (Orion) arm toward the outer disk. While most clusters (and young stars in their background) closely follow the warp of the disk, our decade-old survey of the spiral structure of this region led us to identify three clusters, Haffner 18 (1 and 2) and Haffner 19, which remain very close to b = 0° and lie at distances (4.5, ˜8.0, and 6.4 kpc) where most of the material is already significantly warped. Here, we report on a search for clusters that share the same properties as Haffner 18 and 19, and investigate the possible reasons for such an unexpected occurrence. We present UBVRI photometry of five young clusters, namely NGC 2345, NGC 2374, Trumpler 9, Haffner 20, and Haffner 21, which also lie close to the formal Galactic plane. With the exception of Haffner 20, in the background of these clusters we detected young stars that appear close to b=0^\\circ and are located at distances up to ˜8 kpc from the Sun, thus deviating significantly from the warp. These populations define a structure that distributes over almost the entire third Galactic quadrant. We discuss this structure in the context of a possible thin disk flaring, similar to the Galactic thick disk. Based on observations carried out at Cerro Tololo Inter-American Observatory, under programs CHILE-0008B-017 and CHILE-0010A

  16. The thickening of the thin disk in the third galactic quadrant

    SciTech Connect

    Carraro, Giovanni; Vázquez, Rubén A.; Ahumada, Javier A.; Giorgi, Edgar E. E-mail: rvazquez@fcaglp.unlp.edu.ar E-mail: javier@oac.uncor.edu

    2015-01-01

    In the third Galactic quadrant (180{sup ∘}⩽l⩽270{sup ∘}) of the Milky Way, the Galactic thin disk exhibits a significant warp—shown both by gas and young stars—bending down a few kiloparsecs below the formal Galactic plane (b=0{sup ∘}). This warp shows its maximum at l∼240{sup ∘}, in the direction of the Canis Major constellation. In a series of papers, we have traced the detailed structure of this region using open star clusters, putting particular emphasis on the spiral structure of the outer disk. We noted a conspicuous accumulation of young star clusters within 2–3 kpc from the Sun and close to b = 0°, which we interpreted as the continuation of the Local (Orion) arm toward the outer disk. While most clusters (and young stars in their background) closely follow the warp of the disk, our decade-old survey of the spiral structure of this region led us to identify three clusters, Haffner 18 (1 and 2) and Haffner 19, which remain very close to b = 0° and lie at distances (4.5, ∼8.0, and 6.4 kpc) where most of the material is already significantly warped. Here, we report on a search for clusters that share the same properties as Haffner 18 and 19, and investigate the possible reasons for such an unexpected occurrence. We present UBVRI photometry of five young clusters, namely NGC 2345, NGC 2374, Trumpler 9, Haffner 20, and Haffner 21, which also lie close to the formal Galactic plane. With the exception of Haffner 20, in the background of these clusters we detected young stars that appear close to b=0{sup ∘} and are located at distances up to ∼8 kpc from the Sun, thus deviating significantly from the warp. These populations define a structure that distributes over almost the entire third Galactic quadrant. We discuss this structure in the context of a possible thin disk flaring, similar to the Galactic thick disk.

  17. Synthesis and characterization of boron carbon nitride thin films as protective overcoat for hard disk drives

    NASA Astrophysics Data System (ADS)

    Chen, Yanfeng

    The current goal in the magnetic storage industry is to reach the areal density of 1Tbit/in2 in a few years. This requires the head-media spacing (HMS), which includes media overcoat, lubricant layer, air bearing, and head overcoat, not to exceed 5.0 nm. Trade-off between these layers results in requiring the protective overcoat to be 1.0 nm or less. The protective overcoat must be hard, wear-resistant, continuous, thermally stable, and compatible with the magnetic layer and lubricant. This thesis work is mainly to develop protective overcoat for ultra high density hard disk drives (HDD). Amorphous carbon nitride (a-CNx) thin films were synthesized using pulseDC magnetron sputtering. The influence of substrate bias, substrate tilt, and substrate rotation on film growth and properties was studied. X-ray reflectivity (XRR) was used to measure film density, roughness and thickness. Surface roughness and thickness measurements from XRR are comparable to AFM and surface profiler measurements respectively. a-CNx films have good mechanical properties. Auger electron spectroscopy (AES) and high resolution transmission microscope (HRTEM) were used to obtain the film composition and microstructure. HRTEM cross sectioned experiments showed that CN x film is amorphous. Chemical corrosion experiments display drastic decrease of corrosion spots for thin films synthesized under optimum conditions. In pursuit of new materials for hard disk drive protective overcoat, boron carbide (B4C) and boron carbon nitride (BxC yNz) thin films were synthesized by pulse-DC magnetron sputtering. Effects of target power, target pulse frequency, substrate bias and pulse frequency on surface roughness were studied by AFM. Nitrogen incorporation into B4C films, which gives BxCyNz thin films, has a beneficial effect to decrease the film roughness. Auger electron spectroscopy was used to characterize the film composition. High-resolution cross-sectioned TEM studies showed that both films are amorphous

  18. Improvement of thermal management in the composite Yb:YAG/YAG thin-disk laser

    NASA Astrophysics Data System (ADS)

    Kuznetsov, I. I.; Mukhin, I. B.; Palashov, O. V.

    2016-04-01

    To improve the thermal management in the composite Yb:YAG/YAG thin-disk laser a new design of laser head is developed. Thermal-induced phase distortions, small signal gain and lasing in the upgraded laser head are investigated and compared with previously published results. A substantial decrease of the thermal lens optical power and phase aberrations and increase of the laser slope efficiency are observed. A continuous-wave laser with 440 W average power and 44% slope efficiency is constructed.

  19. Pulsed operation of a high average power Yb:YAG thin-disk multipass amplifier.

    PubMed

    Schulz, M; Riedel, R; Willner, A; Düsterer, S; Prandolini, M J; Feldhaus, J; Faatz, B; Rossbach, J; Drescher, M; Tavella, F

    2012-02-27

    An Yb:YAG thin-disk multipass laser amplifier system was developed operating in a 10 Hz burst operation mode with 800 µs burst duration and 100 kHz intra-burst repetition rate. Methods for the suppression of parasitic amplified spontaneous emission are presented. The average output pulse energy is up to 44.5 mJ and 820 fs compressed pulse duration. The average power of 4.45 kW during the burst is the highest reported for this type of amplifier. PMID:22418308

  20. On the α-element gradients of the Galactic thin disk using Cepheids

    NASA Astrophysics Data System (ADS)

    Genovali, K.; Lemasle, B.; da Silva, R.; Bono, G.; Fabrizio, M.; Bergemann, M.; Buonanno, R.; Ferraro, I.; François, P.; Iannicola, G.; Inno, L.; Laney, C. D.; Kudritzki, R.-P.; Matsunaga, N.; Nonino, M.; Primas, F.; Romaniello, M.; Urbaneja, M. A.; Thévenin, F.

    2015-08-01

    We present new homogeneous measurements of Na, Al, and three α-elements (Mg, Si, Ca) for 75 Galactic Cepheids. The abundances are based on high spectral resolution (R~ 38 000) and high signal-to-noise ratio (S/N ~ 50-300) spectra collected with UVES at ESO VLT. The current measurements were complemented with Cepheid abundances provided by our group (75) or available in the literature, for a total of 439 Galactic Cepheids. Special attention was given to providing a homogeneous abundance scale for these five elements plus iron. In addition, accurate Galactocentric distances (RG) based on near-infrared photometry are also available for all the Cepheids in the sample. They cover a large section of the Galactic thin disk (4.1 ≤RG≤ 18.4 kpc). We found that these five elements display well-defined linear radial gradients and modest standard deviations over the entire range of RG. Moreover, the [element/Fe] abundance ratios are constant across the entire thin disk; only the Ca radial distribution shows marginal evidence of a positive slope. These results indicate that the chemical enrichment history of iron and of the quoted five elements has been quite similar across the four quadrants of the Galactic thin disk. The [element/Fe] ratios are also constant over the entire period range. This empirical evidence indicates that the chemical enrichment of Galactic Cepheids has also been very homogenous within the range in age that they cover (~10-300 Myr). Once again, [Ca/Fe] vs. log P shows a (negative) gradient, since it is underabundant among the youngest Cepheids. Finally, we also find that Cepheid abundances agree quite well with similar abundances for thin and thick disk dwarf stars, and they follow the typical Mg-Al and Na-O correlations. Based on spectra collected with the UVES spectrograph available at the ESO Very Large Telescope (VLT), Cerro Paranal, Chile (ESO Proposals: 081.D-0928(A), PI: S. Pedicelli; 082.D-0901(A), PI: S. Pedicelli; 089.D-0767(C), PI: K

  1. Composite Thin-Disk Laser Scaleable to 100 kW Average Power Output and Beyond

    SciTech Connect

    Zapata, L.; Beach, R.; Payne, S.

    2000-06-01

    By combining newly developed technologies to engineer composite laser components with state of the art diode laser pump delivery technologies, we are in a position to demonstrate high beam quality, continuous wave, laser radiation at scaleable high average powers. The crucial issues of our composite thin disk laser technology were demonstrated during a successful first light effort. The high continuous wave power levels that are now within reach make this system of high interest to future DoD initiatives in solid-state laser technology for the laser weapon arena.

  2. A 12.1-W SESAM mode-locked Yb:YAG thin disk laser

    NASA Astrophysics Data System (ADS)

    Yingnan, Peng; Zhaohua, Wang; Dehua, Li; Jiangfeng, Zhu; Zhiyi, Wei

    2016-05-01

    Pumped by a 940 nm fiber-coupled diode laser, a passively mode-locked Yb:YAG thin disk oscillator was demonstrated with a semiconductor saturable absorber mirror (SESAM). 12.1 W mode-locked pulses were obtained with pulse duration of 698 fs at the repetition rate of 57.43 MHz. Measurement showed that the beam quality was close to the diffraction limit. Project supported by the National Key Basic Research Program of China (Grant No. 2013CB922402), the National Major Instrument Program of China (Grant No. 2012YQ120047), and the National Natural Science Foundation of China (Grant No. 61210017).

  3. On the Global Warping of a Thin Self-gravitating Near-Keplerian Gaseous Disk with Application to the Disk in NGC 4258

    NASA Astrophysics Data System (ADS)

    Papaloizou, John C. B.; Terquem, Caroline; Lin, Doug N. C.

    1998-04-01

    We derive the tilt equation governing the inclination of a thin self-gravitating gaseous disk subject to low-frequency global m = 1 bending perturbations. The disk orbits under the influence of a dominant central mass. However, self-gravity can be important enough that the disk approaches marginal stability to local axisymmetric perturbations (Q ~ 1). The vertical restoring forces due to self-gravity and pressure are evaluated correct to the first order in the aspect ratio H/r. Thus the effects of bending waves are included correct to lowest order in the wave-crossing rate (H/r)Ω, Ω being a characteristic disk rotation frequency. Both free and forced disturbances are considered. The disk response and precession frequency induced by the presence of a binary companion in an orbit with general inclination to the unperturbed disk plane are derived. When the degree of warping and the inclination are small, it is shown that identical results are obtained if, alternatively, perturbation of the disk out of an equilibrium plane coinciding with that of the companion is considered, the time-averaged potential due to the latter being incorporated into the equilibrium potential. The condition for the disk to precess approximately like a rigid body with a small degree of warping is found to be that the density-wave crossing time is significantly shorter than the precession period. We consider the effects of the presence of a viscosity that can be characterized with the standard α parameterization and find that, to the order we work, the precession frequency is unaffected, with any change to the inclination of the slightly warped disk occurring at a slower rate. For α << H/r, effects due to both pressure and self-gravity are important in the response, while for α >> H/r, the response becomes dominated by self-gravity with pressure effects becoming negligible. As an application of these results, we explore the possibility that the recently observed warped disk in the active

  4. Linearly polarized, narrow-linewidth, and tunable Yb:YAG thin-disk laser.

    PubMed

    Rumpel, Martin; Voss, Andreas; Moeller, Michael; Habel, Florian; Moormann, Christian; Schacht, Martin; Graf, Thomas; Ahmed, Marwan Abdou

    2012-10-15

    We report on the design, fabrication, and implementation of grating-waveguide structures (GWS) for intracavity polarization and wavelength selection as well as wavelength tuning. The GWS discussed in this Letter is a combination of a low-index leaky-mode waveguide, a subwavelength diffraction grating, and a highly reflective mirror that was designed to operate in Littrow configuration. Using our device as the end mirror of an Yb:YAG thin-disk laser allowed the extraction of beams that exhibit an extremely narrow laser emission bandwidth of ≈25 pm FWHM and a high degree of linear polarization of 99±0.5%. Moreover, the GWS allows a wavelength tuning range from 1007 to 1053 nm. The high-power suitability and the low loss of the GWS was demonstrated by the intracavity use in an Yb:YAG thin-disk laser with an output power of 325 W in multimode operation (M(2)=6) and with 110 W in fundamental-mode operation (M(2)≈1.2), exhibiting optical efficiencies of 53.2% and 36.2%, respectively. An output power of 1.8 kW, corresponding to a power density of 125 kW/cm(2) on the grating, was achieved in further higher-power experiments. PMID:23073406

  5. ASE and parasitic lasing in thin disk laser with anti-ASE cap.

    PubMed

    Furuse, Hiroaki; Chosrowjan, Haik; Kawanaka, Junji; Miyanaga, Noriaki; Fujita, Masayuki; Izawa, Yasukazu

    2013-06-01

    The amplified spontaneous emission (ASE) and parasitic lasing (PL) effects in thin disk laser with an anti-ASE cap have been investigated in detail by measuring both time-resolved radiated intensity at longer axis of elliptical pump profile (dominant ASE direction) and small signal gain (SSG) in laser amplifier. A cryogenically-cooled total-reflection active-mirror laser consisting of 9.8 at.% doped, 0.6-mm thick Yb:YAG and un-doped YAG trapezoidal ceramics cap was used as a sample. The phased transitions from spontaneous emission (SE) to ASE and from ASE to PL have been unambiguously observed. For several pump beam diameters, the ASE gain parameter g(0)l(ASE) at ASE threshold was about 3, and the SSG coefficient was down to about 65% until PL started. To the best of our knowledge, this is the first quantitative characterization of the ASE/PL effects in the thin disk laser with an anti-ASE cap. PMID:23736565

  6. High-power, picosecond pulse thin-disk lasers in the Hilase project

    NASA Astrophysics Data System (ADS)

    Chyla, Michal; Miura, Taisuke; Smrz, Martin; Severova, Patricie; Novak, Ondrej; Nagisetty, Siva S.; Endo, Akira; Mocek, Tomas

    2013-05-01

    Development of high-power, picosecond laser sources is a desirable venture for both industry and research. Within the Hilase project, we are conducting research on both 500-mJ, 1-kHz and 5-mJ, 100-kHz picosecond laser sources based on the Yb:YAG thin-disk technology. We have developed a prototype thin-disk regenerative amplifier operating up to 10- kHz repetition rate pumped by the 940-nm fiber-coupled laser diodes. We achieved 5-mJ pulse energy at 10-kHz operation and 29.5-mJ at 1-kHz. Afterwards, we developed the high-energy regenerative amplifier operating at fixed repetition rate of 1-kHz and the pulse energy was achieved up to 40-mJ. Simultaneously, we elaborated the highrepetition rate regenerative amplifier operating at 100-kHz with pulse energy of 220-μJ. The amplified pulse was compressed with the efficiency of 88% using chirped volume Bragg grating.

  7. Foreign Object Damage of Two Gas-Turbine Grade Silicon Nitrides in a Thin Disk Configuration

    NASA Technical Reports Server (NTRS)

    Choi, Sung R.; Pereira, J. Michael; Janosik, Lesley A.; Bhatt, Ramakrishna T.

    2003-01-01

    Foreign object damage (FOD) behavior of two commercial gas-turbine grade silicon nitrides, AS800 and SN282, was determined at ambient temperature through post-impact strength testing for thin disks impacted by steel-ball projectiles with a diameter of 1.59 mm in a velocity range from 115 to 440 m/s. AS800 silicon nitride exhibited a greater FOD resistance than SN282, primarily due to its greater value of fracture toughness (K(sub IC)). The critical impact velocity in which the corresponding post-impact strength yielded the lowest value was V(sub c) approx. 440 and 300 m/s for AS800 and SN282, respectively. A unique lower-strength regime was typified for both silicon nitrides depending on impact velocity, attributed to significant radial cracking. The damages generated by projectile impact were typically in the forms of ring, radial, and cone cracks with their severity and combination being dependent on impact velocity. Unlike thick (3 mm) flexure bar specimens used in the previous studies, thin (2 mm) disk target specimens exhibited a unique backside radial cracking occurring on the reverse side just beneath the impact sites at and above impact velocity of 160 and 220 m/s for SN282 and AS800, respectively.

  8. Pulse compression of a high-power thin disk laser using rod-type fiber amplifiers.

    PubMed

    Saraceno, C J; Heckl, O H; Baer, C R E; Südmeyer, T; Keller, U

    2011-01-17

    We report on two pulse compressors for a high-power thin disk laser oscillator using rod-type fiber amplifiers. Both systems are seeded by a standard SESAM modelocked thin disk laser that delivers 16 W of average power at a repetition rate of 10.6 MHz with a pulse energy of 1.5 μJ and a pulse duration of 1 ps. We discuss two results with different fiber parameters with different trade-offs in pulse duration, average power, damage and complexity. The first amplifier setup consists of a Yb-doped fiber amplifier with a 2200 μm2 core area and a length of 55 cm, resulting in a compressed average power of 55 W with 98-fs pulses at a repetition rate of 10.6 MHz. The second system uses a shorter 36-cm fiber with a larger core area of 4500 μm2. In a stretcher-free configuration we obtained 34 W of compressed average power and 65-fs pulses. In both cases peak powers of > 30 MW were demonstrated at several μJ pulse energies. The power scaling limitations due to damage and self-focusing are discussed. PMID:21263681

  9. High brightness continuous wave ceramic Yb:LuAG thin-disk laser.

    PubMed

    Peng, Yuan Han; Cheng, James; Cheah, Yan Ying; Lai, Kin Seng; Lau, Ernest; Ang, Seok Khim

    2015-07-27

    We report on a ceramic Yb:LuAG thin-disk laser in continuous wave operation. The Yb:LuAG ceramic was fabricated using solid-state reactive sintering method. In multi-mode operation in open-air, an output power of 1.74 kW with an optical-to-optical efficiency of 65.0% and slope efficiency of 71.2% was obtained. In near-fundamental mode operation we obtained an output power of 1.29 kW and an average beam quality factor of M2 = 1.44 with an optical-to-optical efficiency of 48.2%. The near-fundamental mode result was realized with a simple evacuated, stable resonator cavity with just the thin-disk gain medium and output coupler. To the best of the authors' knowledge, this is not only the first time more than 1 kW has been demonstrated from a ceramic Yb:LuAG medium, but this is also currently the brightest continuous wave Yb-doped ceramic laser. PMID:26367619

  10. Analytical model of thermal effect and optical path difference in end-pumped Yb:YAG thin disk laser.

    PubMed

    Zhu, Guangzhi; Zhu, Xiao; Wang, Mu; Feng, Yufan; Zhu, Changhong

    2014-10-10

    An analytical model of the thermal effect and optical path difference (OPD) of a thin disk laser is developed with the combination of the analytical method and commercial finite element analysis software. The distributions of temperature, stress, strain, and OPD caused by temperature gradient, axial thermal strain (bulging), thermal strain-induced birefringence, and deformation are obtained. Based on the analytical model, the production mechanisms, features, and influence of OPD in an end-pumped thin disk laser are discussed, which make the causes of spherical and aspherical parts of the OPD more obvious. Furthermore, the OPD including the spherical and aspherical parts of the thin disk crystal is discussed for various pumping intensities. PMID:25322379

  11. Multiwatt diode-pumped Yb:YAG thin disk laser continuously tunable between 1018 and 1053 nm.

    PubMed

    Brauch, U; Giesen, A; Karszewski, M; Stewen, C; Voss, A

    1995-04-01

    A new powerful source of broadly (35-nm) tunable laser radiation in the near-infrared (near 1030 nm) wavelength range is presented. Inserting a birefringent filter into a 10-W diode-pumped Yb:YAG thin disk laser resonator gives several watts of narrow-linewidth (0.07-nm) continuously tunable cw output power. By taking advantage of the power scalability of the thin disk concept, even hundreds of watts of tunable power with near-diffraction-limited beam quality and high efficiency are feasible. Generation and amplification of subpicosecond pulses with high average and peak powers are also promising applications of the Yb:YAG thin disk laser. PMID:19859306

  12. Analytical model of optical field distribution of thin disk laser with thermal-optical aberration gain medium

    NASA Astrophysics Data System (ADS)

    Zhu, Guangzhi; Qiu, Yuli; Wang, Zexiong; Zhu, Xiao; Zhu, Changhong

    2016-08-01

    An analytical model is developed to analyze the optical field distribution of thin disk laser with a thermal-optical aberration gain medium. The fundamental mode field distribution is calculated by using the eigenvector method of the resonator transit matrix for different pumping parameters. The analytical results show that the uniformity of the pumping spot is an important factor that impacts the beam quality of thin disk laser. The uniform pumping spot is beneficial to decrease thermal aberration and Optical Path Difference (OPD) of thin disk crystal, and to improve the beam quality. However, the beam quality still decreases slightly with the increasing of pumping intensity under the uniform pumping condition. The main reason for degradation of beam quality is the aspherical part of OPD which leads to diffraction losses of the resonator and wavefront deformation.

  13. Feasibility study of a conical-toroidal mirror resonator for solar-pumped thin-disk lasers

    NASA Astrophysics Data System (ADS)

    Endo, M.

    2007-04-01

    An optical resonator that is suited to a large-scale, space-based solar-pumped solid-state lasers is proposed, and it is studied by numerical simulations. The resonator consists of a conical-toroidal reflector element on which a doughnut-shaped thin-disk active medium is set, and an output coupler. Unlike the ordinary thin-disk lasers, the optical ray of the proposed resonator passes the medium radially. With this arrangement, the resonator can enjoy the benefits of the thin-disk geometry, i. e., good thermal removability and low index gradient, while getting rid of the disadvantages of them as a solar-pumped laser, low round-trip gain and poor beam quality. The output power, beam quality, thermomechanical properties, and alignment stability of the proposed resonator combined with a Nd/Cr codoped GSGG is discussed.

  14. Feasibility study of a conical-toroidal mirror resonator for solar-pumped thin-disk lasers.

    PubMed

    Endo, M

    2007-04-30

    An optical resonator that is suited to a large-scale, space-based solar-pumped solid-state lasers is proposed, and it is studied by numerical simulations. The resonator consists of a conical-toroidal reflector element on which a doughnut-shaped thin-disk active medium is set, and an output coupler. Unlike the ordinary thin-disk lasers, the optical ray of the proposed resonator passes the medium radially. With this arrangement, the resonator can enjoy the benefits of the thin-disk geometry, i. e., good thermal removability and low index gradient, while getting rid of the disadvantages of them as a solar-pumped laser, low round-trip gain and poor beam quality. The output power, beam quality, thermomechanical properties, and alignment stability of the proposed resonator combined with a Nd/Cr codoped GSGG is discussed. PMID:19532804

  15. Noncontact thermophysical property measurement by levitation of a thin liquid disk.

    PubMed

    Lee, Sungho; Ohsaka, Kenichi; Rednikov, Alexei; Sadhal, Satwindar Singh

    2006-09-01

    The purpose of the current research program is to develop techniques for noncontact measurement of thermophysical properties of highly viscous liquids. The application would be for undercooled liquids that remain liquid even below the freezing point when suspended without a container. The approach being used here consists of carrying out thermocapillary flow and temperature measurements in a horizontally levitated, laser-heated thin glycerin disk. In a levitated state, the disk is flattened by an intense acoustic field. Such a disk has the advantage of a relatively low gravitational potential over the thickness, thus mitigating the buoyancy effects, and helping isolate the thermocapillary-driven flows. For the purpose of predicting the thermal properties from these measurements, it is necessary to develop a theoretical model of the thermal processes. Such a model has been developed, and, on the basis of the observed shape, the thickness is taken to be a minimum at the center with a gentle parabolic profile at both the top and the bottom surfaces. This minimum thickness is much smaller than the radius of disk drop and the ratio of thickness to radius becomes much less than unity. It is heated by laser beam in normal direction to the edge. A general three-dimensional momentum equation is transformed into a two-variable vorticity equation. For the highly viscous liquid, a few millimeters in size, Stokes equations adequately describe the flow. Additional approximations are made by considering average flow properties over the disk thickness in a manner similar to lubrication theory. In the same way, the three-dimensional energy equation is averaged over the disk thickness. With convection boundary condition at the surfaces, we integrate a general three-dimensional energy equation to get an averaged two-dimensional energy equation that has convection terms, conduction terms, and additional source terms corresponding to a Biot number. A finite-difference numerical

  16. High-power Kerr-lens mode-locked thin-disk oscillator in the anomalous and normal dispersion regimes

    NASA Astrophysics Data System (ADS)

    Pronin, Oleg; Brons, Jonathan; Seidel, Marcus; Lücking, Fabian; Grasse, Christian; Boehm, Gerhard; Amann, Marcus C.; Pervak, Vladimir; Apolonski, Alexander; Kalashnikov, Vladimir L.; Krausz, Ferenc

    2013-03-01

    A femtosecond thin-disk Yb:YAG oscillator in both the anomalous and the normal dispersion regime is demonstrated. Both regimes are realized with practically the same resonator configuration. The power scaling potential of the anomalous and normal dispersion regimes is analyzed both theoretically and experimentally. The recipe to obtain Kerr-lens mode-locking (KLM) in the thin-disk configuration is presented here and oscillator characteristics as well as start-up difficulties are described. The oscillator stability in terms of output power, beam pointing and sensitivity to back reflections is measured and corresponds to the level of commercial systems.

  17. In-situ optical phase distortion measurement of Yb:YAG thin disk in high average power regenerative amplifier

    NASA Astrophysics Data System (ADS)

    Miura, Taisuke; Chyla, Michal; Smrž, Martin; Nagisetty, Siva Sankar; Severová, Patricie; Novák, Ondřej; Endo, Akira; Mocek, TomáÅ.¡

    2013-02-01

    We are developing one kilohertz picosecond Yb:YAG thin disk regenerative amplifier with 500-W average power for medical and industrial applications. In case of high energy pulse amplification, a large area mode matching in gain media, which is drastically degenerated by the optical phase distortion, is required to avoid optical damage. We designed in-situ thin disk deformation measurement based on the combination of a precise wavefront sensor and a single mode probe beam. In contrast to a conventional interferometric measurement, this measurement is compact, easy-to-align, and is less affected by mechanical vibrations.

  18. THE HANLE EFFECT AS A DIAGNOSTIC OF MAGNETIC FIELDS IN STELLAR ENVELOPES. V. THIN LINES FROM KEPLERIAN DISKS

    SciTech Connect

    Ignace, R.

    2010-12-10

    This paper focuses on the polarized profiles of resonance scattering lines that form in magnetized disks. Optically thin lines from Keplerian planar disks are considered. Model line profiles are calculated for simple field topologies of axial fields (i.e., vertical to the disk plane) and toroidal fields (i.e., purely azimuthal). A scheme for discerning field strengths and geometries in disks is developed based on Stokes Q - U diagrams for the run of polarization across line profiles that are Doppler-broadened by the disk rotation. A discussion of the Hanle effect for magnetized disks in which the magnetorotational instability (MRI) is operating is also presented. Given that the MRI has a tendency to mix the vector field orientation, it may be difficult to detect the disk fields with the longitudinal Zeeman effect, since the amplitude of the circularly polarized signal scales with the net magnetic flux in the direction of the observer. The Hanle effect does not suffer from this impediment, and so a multi-line analysis could be used to constrain field strengths in disks dominated by the MRI.

  19. CHEMICAL COMPOSITIONS OF THIN-DISK, HIGH-METALLICITY RED HORIZONTAL-BRANCH FIELD STARS

    SciTech Connect

    Afsar, M.; Sneden, C.; For, B.-Q. E-mail: afsar@astro.as.utexas.edu E-mail: biqing@astro.as.utexas.edu

    2012-07-15

    We present a detailed abundance analysis and atmospheric parameters of 76 stars from a survey to identify field Galactic red horizontal-branch (RHB) stars. High-resolution echelle spectra (R {approx_equal} 60,000, S/N {>=} 100) were obtained with the 2.7 m Harlan J. Smith Telescope at McDonald Observatory. The target stars were selected only by color and parallax information. Overall metallicities and relative abundances of proton-capture elements (C, N, O, Li), {alpha}-elements (Ca and Si), and neutron-capture elements (Eu and La) were determined by either equivalent width or synthetic spectrum analyses. We used CN features at the {lambda}{lambda}7995-8040 region in order to determine the {sup 12}C/{sup 13}C ratios of our targets. Investigation of the evolutionary stages, using spectroscopic T{sub eff} and log g values along with derived {sup 12}C/{sup 13}C ratios, revealed the presence of 18 probable RHB stars in our sample. We also derived kinematics of the stars with available distance information. Taking into account both the kinematics and probable evolutionary stages, we conclude that our sample contains 5 thick-disk and 13 thin-disk RHB stars. Up until now, RHB stars have been considered as members of the thick disk, and were expected to have large space velocities and sub-solar metallicities. However, our sample is dominated by low-velocity solar-metallicity RHB stars; their existence cannot be easily explained with standard stellar evolution.

  20. 275 W average output power from a femtosecond thin disk oscillator operated in a vacuum environment.

    PubMed

    Saraceno, Clara J; Emaury, Florian; Heckl, Oliver H; Baer, Cyrill R E; Hoffmann, Martin; Schriber, Cinia; Golling, Matthias; Südmeyer, Thomas; Keller, Ursula

    2012-10-01

    We present an ultrafast thin disk laser that generates an average output power of 275 W, which is higher than any other modelocked laser oscillator. It is based on the gain material Yb:YAG and operates at a pulse duration of 583 fs and a repetition rate of 16.3 MHz resulting in a pulse energy of 16.9 μJ and a peak power of 25.6 MW. A SESAM designed for high damage threshold initiated and stabilized soliton modelocking. We reduced the nonlinearity of the atmosphere inside the cavity by several orders of magnitude by operating the oscillator in a vacuum environment. Thus soliton modelocking was achieved at moderate amounts of self-phase modulation and negative group delay dispersion. Our approach opens a new avenue for power scaling femtosecond oscillators to the kW level. PMID:23188316

  1. Circular grating waveguide structures for intracavity generation of azimuthal polarization in a thin-disk laser.

    PubMed

    Rumpel, Martin; Haefner, Matthias; Schoder, Thomas; Pruss, Christof; Voss, Andreas; Osten, Wolfgang; Ahmed, Marwan Abdou; Graf, Thomas

    2012-05-15

    We report on the generation of beams with azimuthal polarization using resonant grating waveguide structures (GWSs) inside an Yb:YAG thin-disk laser (TDL) oscillator. Two different GWS concepts were used to select the polarization of the emitted beam. The first uses the resonant reflection principle, and the second is based on the leaky-mode approach already reported in our previous work. Up to 93 W and 103 W of output power were extracted from a TDL with an optical efficiency, η(oo), of 36.2% and 40.1% using the first and the second approaches, respectively. In both cases, a pure azimuthal polarization and a beam quality factor, M2, of about 2.2 were measured. The design, fabrication, and different experimental results, as well as the laser performances for both GWSs, are discussed in the present Letter. PMID:22627563

  2. Passive mode locking of thin-disk lasers: effects of spatial hole burning

    NASA Astrophysics Data System (ADS)

    Paschotta, R.; Aus der Au, J.; Spühler, G. J.; Erhard, S.; Giesen, A.; Keller, U.

    We recently demonstrated that passive mode locking of a thin-disk Yb:YAG laser is possible and that this concept leads to sources of femtosecond pulses with very high average power. Here we discuss in detail the effect of spatial hole burning on the mode-locking behavior of such lasers. We have developed an efficient numerical model and arrive at quantitative stability criteria which agree well with experimental data. The main result is that stable soliton mode locking can in general be obtained only in a certain range of pulse durations. We use our model to investigate the influence of various cavity parameters and the situation for different gain media. We also consider several methods to reduce the effect of spatial hole burning in order to expand the range of possible pulse durations.

  3. Passively mode-locked Yb:CaF2 thin-disk laser.

    PubMed

    Dannecker, Benjamin; Délen, Xavier; Wentsch, Katrin S; Weichelt, Birgit; Hönninger, Clemens; Voss, Andreas; Ahmed, Marwan Abdou; Graf, Thomas

    2014-09-22

    We report on the first demonstration of a passively (SESAM) mode-locked Yb:CaF(2) thin-disk laser operating at a repetition rate of 35 MHz with close to diffraction-limited beam quality (M(2) ≈ 1.1) at an average output power of up to 6.6 W. The optical efficiency was 15.3%. Nearly transform limited pulses with a duration of 445 fs and a spectral width of 2.6 nm at full width half maximum (FWHM) were obtained at the maximum output power. This corresponds to a pulse-energy of approximately 0.19 μJ and a peak-power of 0.4 MW. PMID:25321699

  4. High-power 200 fs Kerr-lens mode-locked Yb:YAG thin-disk oscillator.

    PubMed

    Pronin, O; Brons, J; Grasse, C; Pervak, V; Boehm, G; Amann, M-C; Kalashnikov, V L; Apolonski, A; Krausz, F

    2011-12-15

    We demonstrate a power-scalable Kerr-lens mode-locked Yb:YAG thin-disk oscillator. It delivers 200 fs pulses at an average power of 17 W and a repetition rate of 40 MHz. At an increased (180 W) pump power level, the laser produces 270 fs 1.1 μJ pulses at an average power of 45 W (optical-to-optical efficiency of 25%). Semiconductor-saturable-absorber-mirror-assisted Kerr-lens mode locking (KLM) and pure KLM with a hard aperture show similar performance. To our knowledge, these are the shortest pulses achieved from a mode-locked Yb:YAG disk oscillator and this is the first demonstration of a Kerr-lens mode-locked thin-disk laser. PMID:22179870

  5. Experiments on the Flow of a Thin Liquid Film Over a Horizontal Stationary and Rotating Disk Surface

    NASA Technical Reports Server (NTRS)

    Ozar, B.; Cetegen, B. M.; Faghri, A.

    2003-01-01

    Experiments on characterization of thin liquid films flowing over stationary and rotating disk surfaces are described. The thin liquid film was created by introducing deionized water from a flow collar at the center of an aluminum disk with a known initial film thickness and uniform radial velocity. Radial film thickness distribution was measured using a non-intrusive laser light interface reflection technique that enabled the measurement of the instantaneous film thickness over a finite segment of the disk. Experiments were performed for a range of flow rates between 3.01pm and 15.01pm, corresponding to Reynolds numbers based on the liquid inlet gap height and velocity between 238 and 1,188. The angular speed of the disk was varied from 0 rpm to 300 rpm. When the disk was stationary, a circular hydraulic jump was present in the liquid film. The liquid-film thickness in the subcritical region (down-stream of the hydraulic jump) was an order of magnitude greater than that in the supercritical region (upstream of the hydraulic jump) which was of the order of 0.3 mm. As the Reynolds number increased, the hydraulic jump migrated toward the edge of the disk. In the case of rotation, the liquid-film thickness exhibited a maximum on the disk surface. The liquid-film inertia and friction influenced the inner region where the film thickness progressively increased. The outer region where the film thickness decreased was primarily affected by the centrifugal forces. A flow visualization study of the thin film was also performed to determine the characteristics of the waves on the free surface. At high rotational speeds, spiral waves were observed on the liquid film. It was also determined that the angle of the waves which form on the liquid surface was a function of the ratio of local radial to tangential velocity.

  6. No evidence for Bardeen-Petterson alignment in GRMHD simulations and semi-analytic models of moderately thin, prograde, tilted accretion disks

    SciTech Connect

    Zhuravlev, Viacheslav V.; Ivanov, Pavel B.; Teixeira, Danilo Morales

    2014-12-01

    In this paper, we introduce the first results that use data extracted directly from numerical simulations as inputs to the analytic twisted disk model of Zhuravlev and Ivanov. In both numerical and analytic approaches, fully relativistic models of tilted and twisted disks having a moderate effective viscosity around a slowly rotating Kerr black hole are considered. Qualitatively, the analytic model demonstrates the same dynamics as the simulations, although with some quantitative offset. Namely, the general relativistic magnetohydrodynamic simulations typically give smaller variations of tilt and twist across the disk. When the black hole and the disk rotate in the same direction, the simulated tilted disk and analytic model show no sign of Bardeen-Petterson alignment, even in the innermost parts of the disk where the characteristic time for relaxation to a quasi-stationary configuration is of the same order as the computation time. In the opposite case, when the direction of the disk's rotation is opposite to that of the black hole, a partial alignment is observed, in agreement with previous theoretical estimates. Thus, both fully numerical and analytic schemes demonstrate that the Bardeen-Petterson effect may not be possible for the case of prograde rotation provided that disk's effective viscosity is sufficiently small. This may have implications in modeling of different astrophysical phenomena such as disk spectra and jet orientation.

  7. Analysis of Hydrodynamics and Heat Transfer in a Thin Liquid Film Flowing over a Rotating Disk by Integral Method

    NASA Technical Reports Server (NTRS)

    Basu, S.; Cetegen, B. M.

    2005-01-01

    An integral analysis of hydrodynamics and heat transfer in a thin liquid film flowing over a rotating disk surface is presented for both constant temperature and constant heat flux boundary conditions. The model is found to capture the correct trends of the liquid film thickness variation over the disk surface and compare reasonably well with experimental results over the range of Reynolds and Rossby numbers covering both inertia and rotation dominated regimes. Nusselt number variation over the disk surface shows two types of behavior. At low rotation rates, the Nusselt number exhibits a radial decay with Nusselt number magnitudes increasing with higher inlet Reynolds number for both constant wall temperature and heat flux cases. At high rotation rates, the Nusselt number profiles exhibit a peak whose location advances radially outward with increasing film Reynolds number or inertia. The results also compare favorably with the full numerical simulation results from an earlier study as well as with the reported experimental results.

  8. Picosesond pulses in deep ultraviolet produced by a 100 kHz solid-state thin disk laser

    NASA Astrophysics Data System (ADS)

    Turčičová, H.; Novák, O.; Smrž, M.; Miura, T.; Endo, A.; Mocek, T.

    2015-05-01

    We report on the generation of 100 kHz 0.1mJ-level deep ultraviolet pulses based on frequency-quadrupled (257.5 nm) beam of a diode pumped Yb:YAG thin disk laser at the HiLASE Centre. The 100-kHz beamline used for the generation of the harmonic frequencies is operated at an average output power of 100 W level and 2 picosecond duration of pulses. The amplification of the oscillator beam is performed in a regenerative amplifier where the thin disk serves as an active mirror. The CPA technique is used for achieving high average output power of the whole system. The outcoming laser beam at 1030 nm wavelength is frequency-doubled in an LBO crystal and then frequency-quadrupled in BBO crystal, conversion efficiencies being 40% and 19%, resp. The basic characteristics of the harmonics generation in both crystals are given.

  9. Thermal behavior of resonant waveguide-grating mirrors in Yb:YAG thin-disk lasers.

    PubMed

    Rumpel, Martin; Dannecker, Benjamin; Voss, Andreas; Moeller, Michael; Moormann, Christian; Graf, Thomas; Ahmed, Marwan Abdou

    2013-11-15

    We present the experimental investigations of different designs of resonant waveguide-grating (RWG) mirrors, used as intracavity folding mirrors in an Yb:YAG thin-disk laser (TDL). The investigation was focused on the rise of the surface temperature due to the coupling of the incident radiation to a waveguide mode as well as on laser efficiency, polarization, and wavelength selectivity. It was found that the damage threshold and efficiency can be increased significantly with a proper design of the structure in comparison to the simplest design with a single waveguide layer. So far, the presented RWG allow the generation of linear polarization with a narrow spectral linewidth down to 25 pm FWHM in a fundamental mode Yb:YAG TDL. Damage thresholds of 60 kW/cm(2) have been reached where only 63 K of surface temperature increase was observed. This showed that the improved mirrors are suitable for the generation of kW-class narrow linewidth, linearly polarized Yb:YAG TDL. PMID:24322127

  10. High-intracavity-power thin-disk laser for the alignment of molecules.

    PubMed

    Deppe, Bastian; Huber, Günter; Kränkel, Christian; Küpper, Jochen

    2015-11-01

    We propose a novel approach for strong alignment of gas-phase molecules for experiments at arbitrary repetition rates. A high-intracavity-power continuous-wave laser will provide the necessary ac electric field of 10(10)-10(11) W/cm(2). We demonstrate thin-disk lasers based on Yb:YAG and Yb:Lu(2)O(3) in a linear high-finesse resonator providing intracavity power levels in excess of 100 kW at pump power levels on the order of 50 W. The multi-longitudinal-mode operation of this laser avoids spatial-hole burning even in a linear standing-wave resonator. The system will be scaled up as in-vacuum system to allow for the generation of fields of 10(11) W/cm(2). This system will be directly applicable for experiments at modern X-ray light sources, such as synchrotrons or free-electron lasers, which operate at various very high repetition rates. This would allow to record molecular movies through temporally resolved diffractive imaging of fixed-in-space molecules, as well as the spectroscopic investigation of combined X-ray-NIR strong-field effects of atomic and molecular systems. PMID:26561120

  11. THERMAL EQUILIBRIA OF OPTICALLY THIN, MAGNETICALLY SUPPORTED, TWO-TEMPERATURE, BLACK HOLE ACCRETION DISKS

    SciTech Connect

    Oda, H.; Machida, M.; Nakamura, K. E.; Matsumoto, R.

    2010-03-20

    We obtained thermal equilibrium solutions for optically thin, two-temperature black hole accretion disks incorporating magnetic fields. The main objective of this study is to explain the bright/hard state observed during the bright/slow transition of galactic black hole candidates. We assume that the energy transfer from ions to electrons occurs via Coulomb collisions. Bremsstrahlung, synchrotron, and inverse Compton scattering are considered as the radiative cooling processes. In order to complete the set of basic equations, we specify the magnetic flux advection rate instead of beta = p{sub gas}/p{sub mag}. We find magnetically supported (low-beta), thermally stable solutions. In these solutions, the total amount of the heating via the dissipation of turbulent magnetic fields goes into electrons and balances the radiative cooling. The low-beta solutions extend to high mass accretion rates ({approx}>alpha{sup 2}M-dot{sub Edd}) and the electron temperature is moderately cool (T{sub e} {approx} 10{sup 8}-10{sup 9.5} K). High luminosities ({approx}>0.1L{sub Edd}) and moderately high energy cutoffs in the X-ray spectrum ({approx}50-200 keV) observed in the bright/hard state can be explained by the low-beta solutions.

  12. Effects of Yb:KYW thin-disk femtosecond laser ablation on enamel surface roughness

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Sun, Yuchun; Wang, Yong; Lü, Peijun

    2014-07-01

    This study aimed to quantitatively evaluate the surface roughness of enamel following ablation with a Yb:KYW thin-disk femtosecond pulsed laser at different fluences (F), scanning speeds and scanning line spacings. Thirty human extracted teeth were sectioned into crowns and roots along the cementum-enamel junction, and then the crowns were cut longitudinally into sheets about 1.5 mm thick. The samples were randomly divided into ten groups (n=3). Samples of groups 1-8 were irradiated with a femtosecond pulsed laser. These enamel samples were fixed on a stage at focus plane, and a laser beam irradiated onto the samples through a galvanometric scanning system, with which rectangular movement could be achieved. Samples of groups 9 and 10 were prepared with grinding instruments. Following ablation and preparation, the samples were examined for surface roughness with a three-dimensional laser profile measurement microscope. The results showed that scanning speed and scanning line spacing had little influence on the surface roughness of femtosecond pulsed laser-ablated enamel, except when F=4 J/cm2. When a lower fluence was used, the enamel surface roughness was higher, and vice versa. This study showed that various laser fluences, scanning speeds and scanning line spacings can affect and alter enamel surface roughness. Therefore, adequate parameters should be chosen to achieve the proper therapeutic benefits.

  13. Precise measurements of the thermo-optical aberrations of an Yb:YAG thin-disk laser.

    PubMed

    Perchermeier, Julian; Wittrock, Ulrich

    2013-07-15

    We report on interferometric measurements of the thermo-optical aberrations of the laser medium of an Yb:YAG thin-disk laser in pumped and cw lasing conditions at several pump-power levels with a mean repeatability of 5 nm. These measurements build the basis for future intracavity compensation of the aberrations with our deformable mirror in order to improve the fundamental-mode efficiency. PMID:23939068

  14. High-efficiency 1.9 µm Tm3+:LiLuF4 thin-disk laser.

    PubMed

    Stoeppler, Georg; Parisi, Daniela; Tonelli, Mauro; Eichhorn, Marc

    2012-04-01

    We present the first demonstration of a 792 nm diode-pumped Tm3+:LiLuF4 thin-disk laser operation around 1.9 μm. In multimode configuration, up to 21 W of output power and a maximal slope efficiency of 49% with an optical-to-optical efficiency of 40% was demonstrated. A tuning range from 1899 nm to 1927 nm could be achieved by inserting an etalon into the cavity. PMID:22466182

  15. Amplification of picosecond pulses to 100 W by an Yb:YAG thin-disk with CVBG compressor

    NASA Astrophysics Data System (ADS)

    Smrž, Martin; Chyla, Michal; Novák, Ondřej; Miura, Taisuke; Endo, Akira; Mocek, Tomáś

    2015-05-01

    High average power picosecond lasers have become an import tool in many fields of science and industry. We report on progress in development of 100 kHz, 100 W picosecond Yb:YAG thin disk laser amplifier with fundamental spatial mode at the HiLASE laser center. More efficient direct pumping to an upper laser level has been employed in order to suppress thermal loading of the thin disk active medium and to increase system stability. We also carefully analyzed and described all benefits of this so called zero phonon line pumping (ZPL) for fundamental spatial mode cavity design and successfully increased extraction efficiency of the amplifier to > 28 %. A novel approach of high-power picosecond pulse compression using a space saving and easy-to-align chirped-volume Bragg grating (CVBG) with high dispersion and high net efficiency approaching 88 % allowed us to build a robust and highly compact pulse compressor. A 100 kHz train of sub-1-milijoule pulses compressed bellow 2 ps (FWHM) in almost diffraction limited Gaussian beam has been successfully generated from this highly compact (900 x 1200 mm) thin-disk-based Yb:YAG regenerative amplifier.

  16. Kilowatt-level direct-'refractive index matching liquid'-cooled Nd:YLF thin disk laser resonator.

    PubMed

    Ye, Zhibin; Liu, Chong; Tu, Bo; Wang, Ke; Gao, Qingsong; Tang, Chun; Cai, Zhen

    2016-01-25

    A direct-liquid-cooled Nd:YLF thin disk laser resonator is presented, which features the use of refractive index matching liquid (RIML) as coolant. Highly uniform pump intensity distribution with rectangular shape is realized by using metallic planar waveguides. Much attention has been paid on the design of the gain module, including how to achieve excellent cooling ability with multi-channel coolers and how to choose the doping levels of the crystals for realizing well-distributed pump absorption. The flow velocity of the coolant is found to be a key parameter for laser performance and optimized to keep it in laminar flow status for dissipating unwanted heat load. A single channel device is used to measure the convective heat transfer coefficient (CHTC) at different flow velocities. Accordingly, the thermal stress in the disk is analyzed numerically and the maximum permissible thermal load is estimated. Experimentally, with ten pieces of a-cut Nd:YLF thin disks of different doping levels, a linear polarized laser with an average output power of 1120 W is achieved at the pump power of 5202 W, corresponding to an optical-optical efficiency of 21.5%, and a slope efficiency of 30.8%. Furthermore, the wavefront aberration of the gain module is measured to be quite weak, with a peak to valley (PV) value of 4.0 μm when it is pumped at 5202 W, which enables the feasibility of its application in an unstable resonator. To the best of our knowledge, this is the first demonstration of kilowatt-level direct-'refractive index matching liquid'-cooled Nd:YLF thin disk laser resonator. PMID:26832554

  17. Effect of surfactants on the stability of thin liquid film flow on a rotating disk.

    PubMed

    Leneweit, Gero; Roesner, Karl G; Koehler, Reinhard

    2003-04-15

    The effect of surfactants on surface instabilities of thin liquid film flow on a rotating disk was studied at different flow rates Q (0.5

  18. Thin-disk piezoceramic ultrasonic motor. Part I: design and performance evaluation.

    PubMed

    Wen, Fuh Liang; Yen, Chi Yung; Ouyang, Minsun

    2003-08-01

    The purpose of this study is to gain the knowledge and experience in the design of thin-disk piezoceramic-driving ultrasonic actuator dedicated. In this paper, the design and construction of an innovative ultrasonic actuator is developed as a stator, which is a composite structure consisting of piezoceramic (PZT) membrane bonded on a metal sheet. Such a concentric PZT structure possesses the electrical and mechanical coupling characteristics in flexural wave. The driving ability of the actuator comes from the mechanical vibration of extension and shrinkage of a metal sheet due to the converse piezoelectric effect, corresponding to the frequency of a single-phase AC power. By applying the constraints on the specific geometry positions on the metal sheet, the various behaviors of flexural waves have been at the different directions. The rotor is impelled by the actuator with rotational speeds of 600 rpm in maximum using a friction-contact mechanism. Very high actuating and braking abilities are obtained. This simple and inexpensive structure of actuator demonstrates that the mechanical design of actuator and rotor could be done separately and flexibly according to the requirements for various applications. And, its running accuracy and positioning precision are described in Part II.A closed loop servo positioning control i.e. sliding mode control (SMC) is used to compensate automatically for nonlinearly mechanical behaviors such as dry friction, ultrasonic vibrating, slip-stick phenomena. Additionally, SMC scheme has been successfully applied to position tracking to prove the excellent robust performance in noise rejection. PMID:12853080

  19. Strong vortex core pinning and Barkhausen-free magnetization response in thin Permalloy disks induced by implantation of 1 × 10{sup 4} Ga{sup +} ions

    SciTech Connect

    Fani Sani, F. E-mail: mark.freeman@ualberta.ca; Losby, J. E.; Diao, Z.; Parsons, L. C.; Burgess, J. A. J.; Hiebert, W. K.; Freeman, M. R. E-mail: mark.freeman@ualberta.ca; Vick, D.

    2014-05-07

    Artificial vortex core pinning sites are induced in thin Permalloy disks by point exposure to as few as 10 000 ions from a focused Ga{sup +} beam. These pinning sites yield a first-order change in the magnetization response of the disk. A single site can keep the vortex core pinned over an applied field range comparable to the vortex annihilation field of the unaltered disk. Several widely separated sites can work together to keep the core pinned in one place, while the Barkhausen effect is eliminated from the magnetization curve over a range approaching the saturation moment of the disk.

  20. Strong vortex core pinning and Barkhausen-free magnetization response in thin Permalloy disks induced by implantation of 1 × 104 Ga+ ions

    NASA Astrophysics Data System (ADS)

    Fani Sani, F.; Losby, J. E.; Diao, Z.; Parsons, L. C.; Burgess, J. A. J.; Vick, D.; Hiebert, W. K.; Freeman, M. R.

    2014-05-01

    Artificial vortex core pinning sites are induced in thin Permalloy disks by point exposure to as few as 10 000 ions from a focused Ga+ beam. These pinning sites yield a first-order change in the magnetization response of the disk. A single site can keep the vortex core pinned over an applied field range comparable to the vortex annihilation field of the unaltered disk. Several widely separated sites can work together to keep the core pinned in one place, while the Barkhausen effect is eliminated from the magnetization curve over a range approaching the saturation moment of the disk.

  1. Investigation on thermal behavior of resonant waveguide-grating mirrors in an Yb:YAG thin-disk laser

    NASA Astrophysics Data System (ADS)

    Rumpel, Martin; Dannecker, Benjamin; Voss, Andreas; Möller, Michael; Moormann, Christian; Graf, Thomas; Abdou Ahmed, Marwan

    2014-05-01

    We present the experimental investigations of different designs of resonant waveguide-grating mirrors (RWG) which are used as intracavity folding mirror in an Yb:YAG thin-disk laser. The studied mirrors combine structured fused silica substrates, a thin-layer waveguide (Ta2O5), a buffer layer (SiO2) and partial reflectors. The grating period was chosen to be 510 nm to allow resonances at an angle of incidence of ~10° for TE polarization. The waveguide layer has a thickness of 236 nm. It is followed by the buffer layer with a thickness of 580 nm and the subsequent alternating Ta2O5/SiO2 layers. The exact coating sequence depends on the two design approaches which were investigated in this work: either introducing different partial reflectors, i.e. stacks of quarter-wave layers on top of the waveguide while keeping the groove depth of the grating constant, or increasing the grating depth, while keeping an identical partial reflector. The investigation was focused on the rise of the surface temperature due to the coupling of the incident radiation to a waveguide mode, as well as on the laser efficiency, polarization and wavelength selectivity. It is found that, when compared to the simplest RWG design which consists of only a single Ta2O5 waveguide layer, damage threshold as well as laser efficiency can be significantly increased, while the laser performances in terms of polarization- and wavelength selectivity are maintained. So far, the presented RWG allow the generation of linear polarization with a narrow spectral linewidth down to 25 pm FWHM in a fundamental mode Yb:YAG thin-disk laser. Damage thresholds of 60kW/cm2 have been reached where only 63K of surface temperature increase was observed. This shows that the improved mirrors are suitable for the generation of kW-class narrow linewidth, linearly polarized Yb:YAG thin-disk lasers.

  2. Conjugate heat transfer from a heated disk to a thin liquid film formed by a controlled impinging jet

    NASA Technical Reports Server (NTRS)

    Faghri, A.; Thomas, S.; Rahman, M. M.

    1993-01-01

    An experimental and numerical study of the heat transfer from a heated horizontal disk to a thin film of liquid is described. The liquid was delivered to the disk by a collar arrangement such that the film thickness and radial velocity were known at the outer radius of the collar. This method of delivery is termed as a controlled impinging jet. Flow visualization tests were performed and heat transfer data were collected along the radius of the disk for different volumetric flow rates and inlet temperatures in the supercritical and subcritical regions. The heat transfer coefficient was found to increase with flow rate when both supercritical and subcritical regions were present on the heated surface. A numerical simulation of this free surface problem was performed, which included the effects of conjugate heat transfer within the heated disk and the liquid. The numerical predictions agree with the experimental results and show that conjugate heat transfer has a significant effect on the local wail temperature and heat transfer coefficient.

  3. Soft X-Ray Emission Lines from a Relativistic Accretion Disk in MCG -6-30-15 and Mrk 766

    NASA Technical Reports Server (NTRS)

    Branduardi-Raymont, G.; Sako, M.; Kahn, S. M.; Brinkman, A. C.; Kaastra, J. S.; Page, M. J.

    2000-01-01

    XMM-Newton Reflection Grating Spectrometer (RGS) spectra of the Narrow Line Seyfert 1 galaxies MCG -6-30-15 and Mrk 766 are physically and spectroscopically inconsistent with standard models comprising a power-law continuum absorbed by either cold or ionized matter. We propose that the remarkably similar features detected in both objects in the 5 - 35 A band are H-like oxygen, nitrogen, and carbon emission lines, gravitation- ally redshifted and broadened by relativistic effects in the vicinity of a Kerr black hole. We discuss the implications of our interpretation, and demonstrate that the derived parameters can be physically self-consistent.

  4. Numerical simulation of fluid flow and heat transfer in a thin liquid film over a rotating disk

    NASA Technical Reports Server (NTRS)

    Rahman, M. M.; Faghri, A.

    1992-01-01

    The results of a numerical simulation of the flow field and associated heat transfer coefficient are presented for the free surface flow of a thin liquid film adjacent to a horizontal rotating disk. The computation has been performed for different flow rates and rotational velocities using a three-dimensional boundary-fitted coordinate system. Since the geometry of the free surface is unknown and dependent on flow rate, rate of rotation, and other parameters, an interative procedure had to be used to ascertain its location. The computed film height agreed well with existing experimental measurements. The flow was dominated by inertia near the entrance and close to the free surface, and dominated by centrifugal force at larger radii and adjacent to the disk. The rotation enhanced the heat transfer coefficient by a significant amount.

  5. Gross crack initiation and propagation in brittle thin solid and annular disks subjected to impact loading

    SciTech Connect

    Johnson, W.; Bai, Y.L.; Ghosh, S.K.

    1984-04-01

    This paper derives from a study of grinding wheel break-up behavior due to impact. The impact fracture characteristics of circular disks of plaster of Paris with a concentric central hole were studied experimentally for three types of loading: (a) when the disks were suspended freely and loaded intensely at one point on their circumference by an explosive detonator; (b) when the disks were allowed to fall under gravity from a certain height on to a rigid base; and (c) when a disk, resting on a rigid base, was struck by a flat ended rigid body which was dropped on to it from a certain height. Quasi-static flattening tests on the disks were also carried out. The paper describes a theoretical investigation into the stress analysis of disks under impact, classifies the relevant damage sustained by them and attempts to unify the ''gross'' impact fracture patterns which arise in different modes of dynamic loading. The extent of local flattening of the quasi-statically loaded disks before fracture, is also reported. Good correlation between the theory and experimental results is obtained, especially for rings of diameter ratio (D /SUB i/ /D/sub 0/) of around 0.5.

  6. Thin-disk multipass amplifier for ultrashort laser pulses with kilowatt average output power and mJ pulse energies

    NASA Astrophysics Data System (ADS)

    Negel, Jan-Philipp; Voss, Andreas; Abdou Ahmed, Marwan; Bauer, Dominik; Sutter, Dirk; Killi, Alexander; Graf, Thomas

    2014-05-01

    We report on a Yb:YAG thin-disk multipass amplifier for ultrashort laser pulses delivering an average output power of 1.1 kW which to the best of our knowledge is the highest output power reported from such a system so far. A modified commercial TruMicro5050 laser delivers the seed pulses with an average power of 80 W at a wavelength of 1030 nm, a pulse duration of 6.5 ps and a repetition rate of 800 kHz. These pulses are amplified to 1.38 mJ of pulse energy with a duration of 7.3 ps. To achieve this, we developed a scheme in which an array of 40 plane mirrors is used to geometrically fold the seed beam over the pumped thin-disk crystal. Exploiting the incoming linear polarization, an overall number of 40 double-passes through the disk was realized by using the backpath through the amplifier with the orthogonal linear polarization state. Thermal issues on the disk were mitigated by zero-phonon line pumping at a wavelength of 969 nm directly into the upper laser level and by employing a retroreflective mirror pair. The amplifier exhibits an optical efficiency of 44 % and a slope efficiency of 46 %. The beam quality was measured to be better than M2=1.25 at all power levels. As this system can deliver high pulse energies and high average output powers at the same time without the need of a CPA technique, it can be very suitable for high productivity material processing with ultrashort laser pulses.

  7. Accretion disk electrodynamics

    NASA Technical Reports Server (NTRS)

    Coroniti, F. V.

    1985-01-01

    Accretion disk electrodynamic phenomena are separable into two classes: (1) disks and coronas with turbulent magnetic fields; (2) disks and black holes which are connected to a large-scale external magnetic field. Turbulent fields may originate in an alpha-omega dynamo, provide anomalous viscous transport, and sustain an active corona by magnetic buoyancy. The large-scale field can extract energy and angular momentum from the disk and black hole, and be dynamically configured into a collimated relativistic jet.

  8. Neutron-capture elements across the Galactic thin disk using Cepheids

    NASA Astrophysics Data System (ADS)

    da Silva, R.; Lemasle, B.; Bono, G.; Genovali, K.; McWilliam, A.; Cristallo, S.; Bergemann, M.; Buonanno, R.; Fabrizio, M.; Ferraro, I.; François, P.; Iannicola, G.; Inno, L.; Laney, C. D.; Kudritzki, R.-P.; Matsunaga, N.; Nonino, M.; Primas, F.; Przybilla, N.; Romaniello, M.; Thévenin, F.; Urbaneja, M. A.

    2016-02-01

    We present new accurate abundances for five neutron-capture elements (Y, La, Ce, Nd, Eu) in 73 classical Cepheids located across the Galactic thin disk. Individual abundances are based on high spectral resolution (R ~ 38 000) and high signal-to-noise ratio (S/N ~ 50-300) spectra collected with UVES at ESO VLT for the DIONYSOS project. Taking into account similar Cepheid abundances provided by our group (111 stars) and available in the literature, we end up with a sample of 435 Cepheids covering a broad range in iron abundances (-1.6 < [Fe/H] < 0.6). We found, via homogeneous individual distances and abundance scales, well-defined gradients for the above elements. However, the slope of the light s-process element (Y) is at least a factor of two steeper than the slopes of heavy s- (La, Ce, Nd) and r- (Eu) process elements. The s-to-r abundance ratio ([La/Eu]) of Cepheids shows a well-defined anticorrelation with both Eu and Fe. On the other hand, Galactic field stars attain an almost constant value and display a mild enhancement in La only when they approach solar iron abundance. The [Y/Eu] ratio shows slight evidence of a correlation with Eu and, in particular, with iron abundance for field Galactic stars. We also investigated the s-process index ([hs/ls]) and we found a well-defined anticorrelation, as expected, between [La/Y] and iron abundance. Moreover, we found a strong correlation between [La/Y] and [La/Fe] and, in particular, a clear separation between Galactic and Sagittarius red giants. Finally, the comparison between predictions for low-mass asymptotic giant branch stars and the observed[La/Y] ratio indicate a very good agreement over the entire metallicity range covered by Cepheids. However, the observed spread at fixed iron content is larger than predicted by current models. Based on spectra collected with the UVES spectrograph available at the ESO Very Large Telescope (VLT), Cerro Paranal, Chile (ESO Proposals: 081.D-0928(A), PI: S. Pedicelli; 082.D

  9. On the fine structure of the Cepheid metallicity gradient in the Galactic thin disk

    NASA Astrophysics Data System (ADS)

    Genovali, K.; Lemasle, B.; Bono, G.; Romaniello, M.; Fabrizio, M.; Ferraro, I.; Iannicola, G.; Laney, C. D.; Nonino, M.; Bergemann, M.; Buonanno, R.; François, P.; Inno, L.; Kudritzki, R.-P.; Matsunaga, N.; Pedicelli, S.; Primas, F.; Thévenin, F.

    2014-06-01

    We present homogeneous and accurate iron abundances for 42 Galactic Cepheids based on high resolution (R ~ 38 000) high signal-to-noise ratio (S/N ≥ 100) optical spectra collected with UVES at VLT (128 spectra). The above abundances were complemented with high-quality iron abundances provided either by our group (86) or available in the literature. We were careful to derive a common metallicity scale and ended up with a sample of 450 Cepheids. We also estimated accurate individual distances for the entire sample by using homogeneous near-infrared photometry and the reddening free period-Wesenheit relations. The new metallicity gradient is linear over a broad range of Galactocentric distances (RG ~ 5-19 kpc) and agrees quite well with similar estimates available in the literature (-0.060 ± 0.002 dex/kpc). We also uncover evidence that suggests that the residuals of the metallicity gradient are tightly correlated with candidate Cepheid groups (CGs). The candidate CGs have been identified as spatial overdensities of Cepheids located across the thin disk. They account for a significant fraction of the residual fluctuations, and also for the large intrinsic dispersion of the metallicity gradient. We performed a detailed comparison with metallicity gradients based on different tracers: OB stars and open clusters. We found very similar metallicity gradients for ages younger than 3 Gyr, while for older ages we found a shallower slope and an increase in the intrinsic spread. The above findings rely on homogeneous age, metallicity, and distance scales. Finally, by using a large sample of Galactic and Magellanic Cepheids for which accurate iron abundances are available, we found that the dependence of the luminosity amplitude on metallicity is vanishing. Based on spectra collected with the spectrograph UVES available at the ESO Very Large Telescope (VLT), Cerro Paranal, (081.D-0928(A) PI: S. Pedicelli - 082.D-0901(A) PI: S. Pedicelli - 089.D-0767 PI: K. Genovali).Figure 1

  10. Acceleration of relativistic electrons by magnetohydrodynamic turbulence: Implications for non-thermal emission from black hole accretion disks

    SciTech Connect

    Lynn, Jacob W.; Quataert, Eliot; Chandran, Benjamin D. G.; Parrish, Ian J.

    2014-08-10

    We use analytic estimates and numerical simulations of test particles interacting with magnetohydrodynamic (MHD) turbulence to show that subsonic MHD turbulence produces efficient second-order Fermi acceleration of relativistic particles. This acceleration is not well described by standard quasi-linear theory but is a consequence of resonance broadening of wave-particle interactions in MHD turbulence. We provide momentum diffusion coefficients that can be used for astrophysical and heliospheric applications and discuss the implications of our results for accretion flows onto black holes. In particular, we show that particle acceleration by subsonic turbulence in radiatively inefficient accretion flows can produce a non-thermal tail in the electron distribution function that is likely important for modeling and interpreting the emission from low-luminosity systems such as Sgr A* and M87.

  11. Solid dissolution in a thin liquid film on a horizontal rotating disk

    NASA Astrophysics Data System (ADS)

    Peev, G.; Nikolova, A.; Peshev, D.

    2007-02-01

    A model for the rate of dissolution in liquid film on horizontal rotating disk is obtained by the method of Leveque. It as well as models found in the literature are subjected to experimental verification by dissolving disk cast of gypsum in two liquids. Satisfactory agreement with the model predictions is found. The rate with rotation is compared to that in gravitational film. Enhancements up to 2.5 times are established.

  12. Front end for high-repetition rate thin disk-pumped OPCPA beamline at ELI-beamlines

    NASA Astrophysics Data System (ADS)

    Green, Jonathan T.; Novák, Jakub; Antipenkov, Roman; Batysta, František; Zervos, Charalampos; Naylon, Jack A.; Mazanec, TomáÅ.¡; Horáček, Martin; Bakule, Pavel; Rus, Bedřich

    2015-02-01

    The ELI-Beamlines facility, currently under construction in Prague, Czech Republic, will house multiple high power laser systems with varying pulse energies, pulse durations, and repetition rates. Here we present the status of a high repetition rate beamline currently under construction with target parameters of 20 fs pulse duration, 100 mJ pulse energy, and 1 kHz repetition rate. Specifically we present the Yb:YAG thin disk lasers which are intended to pump picosecond OPCPA, synchronization between pump and signal pulses in the OPCPA, and the first stages of OPCPA.

  13. Dual V-type resonators to enhance beam quality of Yb:YAG thin-disk lasers.

    PubMed

    Kazemi, Shahram; Mahdieh, Mohammad Hossein; Aghaie, Mohammad

    2016-04-01

    In this paper, the operating characteristics of a Yb:YAG thin-disk laser using double V-type resonators are reported. The laser maintained stable performance by independently activating either the main or the auxiliary V-type resonator depending on the pumping laser power. Experimental investigations revealed that by reducing the dynamic range in which the main resonator was used for stability and instead employing the auxiliary resonator, the laser beam quality factor M2 could be reduced from 40.2 to 32.3, representing a beam quality enhancement of approximately 20%. PMID:27139657

  14. 60-W average power in 810-fs pulses from a thin-disk Yb:YAG laser.

    PubMed

    Innerhofer, E; Südmeyer, T; Brunner, F; Häring, R; Aschwanden, A; Paschotta, R; Hönninger, C; Kumkar, M; Keller, U

    2003-03-01

    We demonstrate a passively mode-locked diode-pumped thin-disk Yb:YAG laser generating 810-fs pulses at 1030 nm with as much as 60 W of average output power (without using an amplifier). At a pulse repetition rate of 34.3 MHz, the pulse energy is 1.75 microJ and the peak power is as high as 1.9 MW. The beam quality is close to the diffraction limit, with M2 < 1.1. PMID:12659446

  15. The VVV Survey Reveals Classical Cepheids Tracing a Young and Thin Stellar Disk across the Galaxy’s Bulge

    NASA Astrophysics Data System (ADS)

    Dékány, I.; Minniti, D.; Majaess, D.; Zoccali, M.; Hajdu, G.; Alonso-García, J.; Catelan, M.; Gieren, W.; Borissova, J.

    2015-10-01

    Solid insight into the physics of the inner Milky Way is key to understanding our Galaxy’s evolution, but extreme dust obscuration has historically hindered efforts to map the area along the Galactic mid-plane. New comprehensive near-infrared time-series photometry from the VVV Survey has revealed 35 classical Cepheids, tracing a previously unobserved component of the inner Galaxy, namely a ubiquitous inner thin disk of young stars along the Galactic mid-plane, traversing across the bulge. The discovered period (age) spread of these classical Cepheids implies a continuous supply of newly formed stars in the central region of the Galaxy over the last 100 million years.

  16. Thin disk amplifier-based 40 mJ, 1 kHz, picosecond laser at 515 nm.

    PubMed

    Novák, Jakub; Green, Jonathan T; Metzger, Thomas; Mazanec, Tomáš; Himmel, Bedřich; Horáček, Martin; Hubka, Zbyněk; Boge, Robert; Antipenkov, Roman; Batysta, František; Naylon, Jack A; Bakule, Pavel; Rus, Bedřich

    2016-03-21

    We report on a frequency-doubled picosecond Yb:YAG thin disk regenerative amplifier, developed as a pump laser for a kilohertz repetition rate OPCPA. At a repetition rate of 1 kHz, the compressed output of the regenerative amplifier has a pulse duration of 1.2 ps and pulse energy of 90 mJ with energy stability of σ < 0.8% and M2 < 1.2. The pulses are frequency doubled in an LBO crystal yielding 42 mJ at 515 nm. PMID:27136770

  17. 16.2-W average power from a diode-pumped femtosecond Yb:YAG thin disk laser.

    PubMed

    Aus der Au, J; Spühler, G J; Südmeyer, T; Paschotta, R; Hövel, R; Moser, M; Erhard, S; Karszewski, M; Giesen, A; Keller, U

    2000-06-01

    We demonstrate a power-scalable concept for high-power all-solid-state femtosecond lasers, based on passive mode locking of Yb:YAG thin disk lasers with semiconductor saturable-absorber mirrors. We obtained 16.2 W of average output power in pulses with 730-fs duration, 0.47-muJ pulse energy, and 560-kW peak power. This is to our knowledge the highest average power reported for a laser oscillator in the subpicosecond regime. Single-pass frequency doubling through a 5-mm-long lithium triborate crystal (LBO) yields 8-W average output power of 515-nm radiation. PMID:18064208

  18. How Do The Relativistic Effects Effect the Appearance of a Clothed Black Hole?

    NASA Technical Reports Server (NTRS)

    Zhang, Xiaoling; Zhang, S. N.; Feng, Yuxin; Yao, Yangsen

    2002-01-01

    For an accretion disk around a black hole, the strong relativistic effects affect every aspect of the radiation from the disk, including the spectrum, the light-curve, and the image. If the disk is in high inclination angle (nearly edge-on), the image will be greatly distorted; the farther side of the disk will appear to bend toward the observer, photons from the other side of the disk can reach the observer (if they are not blocked by the disk) to form a ghost image. This work differs mainly from previous work by taking into account the temperature distribution of a standard thin disk model and investigating the expected images from different viewing angles and in different energy bands. The edge-blocking effect is also considered. Direct images of black hole systems may be obtained with future X-ray missions like MAXIM pathfinder.

  19. Disk Emission from Magnetohydrodynamic Simulations of Spinning Black Holes

    NASA Astrophysics Data System (ADS)

    Schnittman, Jeremy D.; Krolik, Julian H.; Noble, Scott C.

    2016-03-01

    We present the results of a new series of global, three-dimensional, relativistic magnetohydrodynamic (MHD) simulations of thin accretion disks around spinning black holes. The disks have aspect ratios of H/R˜ 0.05 and spin parameters of a/M=0,0.5,0.9, and 0.99. Using the ray-tracing code Pandurata, we generate broadband thermal spectra and polarization signatures from the MHD simulations. We find that the simulated spectra can be well fit with a simple, universal emissivity profile that better reproduces the behavior of the emission from the inner disk, compared to traditional analyses carried out using a Novikov-Thorne thin disk model. Finally, we show how spectropolarization observations can be used to convincingly break the spin-inclination degeneracy well known to the continuum-fitting method of measuring black hole spin.

  20. Thin-disk laser operation of Pr³⁺,Mg²⁺:SrAl₁₂O₁₉.

    PubMed

    Voss, Andreas; Reichert, Fabian; Metz, Philip Werner; Marzahl, Daniel-Timo; Kränkel, Christian; Huber, Günter; Graf, Thomas

    2014-03-01

    We present first results in applying the thin-disk concept to lasers directly emitting in the visible spectral range. The pump light was provided by 24 InGaN laser diodes emitting 1 W each at 444 nm, which were coupled into a 200 μm fiber. A 300 μm thin Pr3+,Mg2+:SrAl12O19 crystal served as gain medium. In continuous-wave operation an output power of 0.88 W and a slope efficiency of 12% with respect to the absorbed pump power were achieved at an emission wavelength of 643.5 nm. Modulating the pump source at a duty cycle of 10% yielded an instantaneous output power of 1.67 W, corresponding to a slope efficiency of 26%. PMID:24690737

  1. Self-gravitational Force Calculation of Second-order Accuracy for Infinitesimally Thin Gaseous Disks in Polar Coordinates

    NASA Astrophysics Data System (ADS)

    Wang, Hsiang-Hsu; Yen, David C. C.; Taam, Ronald E.

    2015-11-01

    Investigating the evolution of disk galaxies and the dynamics of proto-stellar disks can involve the use of both a hydrodynamical and a Poisson solver. These systems are usually approximated as infinitesimally thin disks using two-dimensional Cartesian or polar coordinates. In Cartesian coordinates, the calculations of the hydrodynamics and self-gravitational forces are relatively straightforward for attaining second-order accuracy. However, in polar coordinates, a second-order calculation of self-gravitational forces is required for matching the second-order accuracy of hydrodynamical schemes. We present a direct algorithm for calculating self-gravitational forces with second-order accuracy without artificial boundary conditions. The Poisson integral in polar coordinates is expressed in a convolution form and the corresponding numerical complexity is nearly linear using a fast Fourier transform. Examples with analytic solutions are used to verify that the truncated error of this algorithm is of second order. The kernel integral around the singularity is applied to modify the particle method. The use of a softening length is avoided and the accuracy of the particle method is significantly improved.

  2. Power Spectrum Density of Stochastic Oscillating Accretion Disk

    NASA Astrophysics Data System (ADS)

    Long, G. B.; Ou, J. W.; Zheng, Y. G.

    2016-06-01

    In this paper, we employ a stochastic oscillating accretion disk model for the power spectral index and variability of BL Lac object S5 0716+714. In the model, we assume that there is a relativistic oscillation of thin accretion disks and it interacts with an external thermal bath through a friction force and a random force. We simulate the light curve and the power spectrum density (PSD) at (i) over-damped, (ii) critically damped and (iii) under-damped cases, respectively. Our results show that the simulated PSD curves depend on the intrinsic property of the accretion disk, and it could be produced in a wide interval ranging from 0.94 to 2.05 by changing the friction coefficient in a stochastic oscillating accretion disk model. We argue that accretion disk stochastic oscillating could be a possible interpretation for observed PSD variability.

  3. Single-layer resonant-waveguide grating for polarization and wavelength selection in Yb:YAG thin-disk lasers.

    PubMed

    Vogel, Moritz M; Rumpel, Martin; Weichelt, Birgit; Voss, Andreas; Haefner, Matthias; Pruss, Christof; Osten, Wolfgang; Ahmed, Marwan Abdou; Graf, Thomas

    2012-02-13

    A single-layer resonant-waveguide grating consisting of a sub-wavelength grating coupler etched into a waveguide is proposed in order to achieve high polarization and high spectral selectivity inside an Yb:YAG thin-disk laser resonator. The designed structure was fabricated with the help of a Lloyd's-mirror interference lithography setup followed by reactive ion beam etching down to the desired grating groove depth. The wavelength and polarization dependent reflectivity is measured and compared to the design results. The behaviour of the device at higher temperatures is also investigated in the present work. The device is introduced as the end mirror of an Yb:YAG thin-disk laser cavity. Output powers of up to 123 W with a spectral bandwidth of about 0.5 nm (FWHM) is demonstrated in a multimode configuration (M2~6). In fundamental-mode operation (TEM00 with M2~1.1) 70 W of power with a spectral bandwidth of about 20 pm have been obtained. Moreover, the degree of linear polarization was measured to be higher than 99% for both multimode and fundamental mode operation. PMID:22418160

  4. Demonstration of a Yb3+-doped Lu3Al5O12 ceramic thin-disk laser.

    PubMed

    Nakao, Hiroaki; Shirakawa, Akira; Ueda, Ken-ichi; Yagi, Hideki; Yanagitani, Takagimi; Weichelt, Birgit; Wentsch, Katrin; Ahmed, Marwan Abdou; Graf, Thomas

    2014-05-15

    Yb:LuAG ceramic is very promising for thin-disk laser and amplifier architectures since it exhibits a higher thermal conductivity at high doping concentrations and a larger emission cross section than Yb:YAG. In this Letter, we present what we believe to be the first demonstration of a thin-disk laser based on Yb:LuAG ceramic. A maximum output power of 101 W with an optical efficiency of 56% and a slope efficiency of 64% was obtained with a multimode laser resonator. Fundamental-mode laser operation with near diffraction limited beam quality (M2≈1.22) was also achieved. The fundamental-mode laser resonator showed the output power of 49 W, an optical efficiency of 31%, and a slope efficiency of 44%. A linearly polarized output beam was demonstrated in multimode operation using an intracavity Brewster window. The depolarization loss was measured to be as low as 0.15% per round trip. PMID:24978228

  5. High-repetition-rate chirped-pulse-amplification thin-disk laser system with joule-level pulse energy.

    PubMed

    Tümmler, J; Jung, R; Stiel, H; Nickles, P V; Sandner, W

    2009-05-01

    We are reporting on the development of a diode-pumped chirped-pulse-amplification (CPA) laser system based on Yb:YAG thin-disk technology with a repetition rate of 100 Hz and output pulse energy in the joule range. The focus lies with the first results of the preamplifier--a regenerative amplifier (RA) and a multipass amplifier (MP). The system consists of a front end including the CPA stretcher followed by an amplifier chain based on Yb:YAG thin-disk amplifiers and the CPA compressor. It is developed in the frame of our x-ray laser (XRL) program and fulfills all requirements for pumping a plasma-based XRL in grazing incidence pumping geometry. Of course it can also be used for other interesting applications. With the RA pulse energies of more than 165 mJ can be realized. At a repetition rate of 100 Hz a stability of 0.8% (1sigma) over a period of more than 45 min has been measured. The optical-to-optical efficiency is 14%. The following MP amplifier can increase the pulse energy to more than 300 mJ. A nearly bandwidth-limited recompression to less than 2 ps could be demonstrated. PMID:19412278

  6. Optimization of beam quality and optical-to-optical efficiency of Yb:YAG thin-disk regenerative amplifier by pulsed pumping.

    PubMed

    Chyla, Michal; Miura, Taisuke; Smrz, Martin; Jelinkova, Helena; Endo, Akira; Mocek, Tomas

    2014-03-15

    We demonstrate an optimization method of beam quality and optical-to-optical (O-O) efficiency by using pulsed pumping. By changing the pulse duration and the peak intensity of pump pulse at the repetition rate of 1 kHz, the beam quality and O-O efficiency of the Yb:YAG thin-disk regenerative amplifier can be improved. We applied this method to the regenerative amplifier under the pumping wavelength of both 940 and 969 nm, and found that the method was effective in both pumping wavelengths. Although a Yb:YAG thin disk soldered on a copper tungsten heat sink, which has poor thermal properties compared with a thin disk mounted on a diamond substrate, was applied as a gain media, we obtained 45 mJ output with 19.3% O-O efficiency and nearly diffraction-limited beam. PMID:24690808

  7. Analytical model of optical path difference in an end-pumped Yb:YAG thin-disk laser with nonuniform pumping light.

    PubMed

    Zhu, Guangzhi; Zhu, Xiao; Dai, Zhongxiong; Wang, Zexiong; Zhu, Changhong

    2015-04-01

    An analytical model of the thermal effect and optical path difference (OPD) of a thin-disk laser is developed by an arbitrary form pumping spot. Based on the analytical model, the distribution of temperature, stress, and strain can be derived using a super-Gaussian form pumping spot. The total OPD caused by temperature gradient, axial thermal strain, thermal strain-induced birefringence, and deformation of the thin-disk crystal is discussed for different super-Gaussian factors and is separated into spherical and aspherical parts. The analytical results show that the aspherical part of the OPD is the main reason leading to the decrease of the laser beam quality and it is closely related to super-Gaussian factors, which are very useful for thin-disk laser design and evaluation. PMID:25967218

  8. General Relativistic Radiative Transfer: Applications to Black-Hole Systems

    NASA Technical Reports Server (NTRS)

    Wu, Kinwah; Fuerst, Steven V.; Mizuno, Yosuke; Nishikawa, Ken-Ichi; Branduardi-Raymont, Graziella; Lee, Khee-Gan

    2007-01-01

    We present general relativistic radiation transfer formulations which include opacity effects due to absorption, emission and scattering explicitly. We consider a moment expansions for the transfer in the presence of scattering. The formulation is applied to calculation emissions from accretion and outflows in black-hole systems. Cases with thin accretion disks and accretion tori are considered. Effects, such as emission anisotropy, non-stationary flows and geometrical self-occultation are investigated. Polarisation transfer in curved space-time is discussed qualitatively.

  9. Experimental characterization of beam quality of a Yb:YAG thin disk laser

    NASA Astrophysics Data System (ADS)

    Kazemi, S.; Mahdieh, M. H.

    2015-02-01

    In this paper we investigate the effects of cooling water temperature and pumping diode laser beam profile on the disk laser beam quality. The results show that both issues are important and can influence the beam quality but at the conditions of our experiment these issues do not affect the beam quality significantly.

  10. Enhanced Oxygen Reduction Activity on Pt/C for Nafion-free, Thin, Uniform Films in Rotating Disk Electrode Studies

    SciTech Connect

    Shinozaki, Kazuma; Pivovar, Bryan S.; Kocha, Shyam S.

    2013-01-01

    Commercially available nanoparticle platinum on high surface area carbon black (Pt/HSC) electrocatalysts were characterized in rotating disk electrode (RDE) setups using varying ink formulations and film drying techniques in an attempt to obtain thin, uniform films and reproducible activity. Electrodes prepared from Nafion-free inks that were dried under an isopropyl alcohol (IPA) atmosphere produced uniform, thin films at low electrocatalyst loadings of ~4.5 mg/cm2 Pt. These Nafion-free/IPA-dried electrodes were found to exhibit oxygen reduction reaction (ORR) activities higher than conventional Nafion-based/Air-dried electrodes by a factor of ~2.8. The magnitude of mass and specific activities were determined to be im ~771 ±56 mA/mgPt and is~812 ±59 mA/cm2Pt respectively and appear to be the highest values reported for RDE measurements on Pt/HSC in 0.1M HClO4 at 20 mV/s and 25°C. Electrochemical diagnostics including ORR I-V profiles, cyclic voltammograms and electrochemical impedance spectroscopy (EIS) studies were conducted to investigate the thin film Pt/HSC electrodes and correlate results to film morphology and electrochemical activity.

  11. Nd:YAG thin-disk laser with large dynamic range unstable resonance

    NASA Astrophysics Data System (ADS)

    Shang, Jianli; Yu, Yi; An, Xiangchao; Gao, Qingsong; Tang, Chun

    2015-02-01

    In this paper, based on the self-reproduction condition of laser wavefront curvature, the influences of disk defocus on laser parameters can be calculated. The laser-pumping overlapping efficiency will decrease by 9%; the magnification will rise to 2.3, and the intra-cavity loss will be high to 30% due to a laser beam size mismatch when each disk has focal length of -100 m in a positive-branch confocal unstable resonator containing four disks with magnification of 1.8. Therefore, the optical conversion efficiency and stability will be reduced significantly. Several methods defocus compensation of are compared, it can be found that inserting variable-focus lens in resonant is useful in large dynamic range. In experiment, the defocus values are measured in different pumping power. A lens group, used for compensate components according to the single pass probe, is carefully designed. Under this compensation, the pulse energy can be maintained in 10 J from 1 Hz to 100 Hz. The output power can be improved 2.33 times compared to non-compensation condition.

  12. Analysis of the Z distribution of young objects in the Galactic thin disk

    NASA Astrophysics Data System (ADS)

    Bobylev, V. V.; Bajkova, A. T.

    2016-01-01

    We have obtained new estimates of the Sun's distance from the symmetry plane Z ⊙ and the vertical disk scale height h using currently available data on stellar OB associations, Wolf-Rayet stars, HII regions, and Cepheids. Based on individual determinations, we have calculated the mean Z ⊙ = -16 ± 2 pc. Based on the model of a self-gravitating isothermal disk for the density distribution, we have found the following vertical disk scale heights: h = 40.2 ± 2.1 pc from OB associations, h = 47.8 ± 3.9 pc from Wolf-Rayet stars, h = 48.4 ± 2.5 pc from HII regions, and h = 66.2 ± 1.6 pc from Cepheids. We have estimated the surface, Σ = 6 kpc-2, and volume, D( Z ⊙) = 50.6 kpc-3, densities from a sample of OB associations. We have found that there could be ˜5000 OB associations in the Galaxy.

  13. Line Emission from Optically Thick RelativisticAccretion Tori

    SciTech Connect

    Fuerst, Steven V.; Wu, Kinwah; /Mullard Space Sci. Lab.

    2007-09-14

    We calculate line emission from relativistic accretion tori around Kerr black holes and investigate how the line profiles depend on the viewing inclination, spin of the central black hole, parameters describing the shape of the tori, and spatial distribution of line emissivity on the torus surface. We also compare the lines with those from thin accretion disks. Our calculations show that lines from tori and lines from thin disks share several common features. In particular, at low and moderate viewing inclination angles they both have asymmetric double-peaked profiles with a tall, sharp blue peak and a shorter red peak which has an extensive red wing. At high viewing inclination angles they both have very broad, asymmetric lines which can be roughly considered as single-peaked. Torus and disk lines may show very different red and blue line wings, but the differences are due to the models for relativistic tori and disks having differing inner boundary radii. Self-eclipse and lensing play some role in shaping the torus lines, but they are effective only at high inclination angles. If inner and outer radii of an accretion torus are the same as those of an accretion disk, their line profiles show substantial differences only when inclination angles are close to 90{sup o}, and those differences are manifested mostly at the central regions of the lines instead of the wings.

  14. Effect of a lateral electric field on an off-center single dopant confined in a thin quantum disk

    NASA Astrophysics Data System (ADS)

    Dujardin, F.; Oukerroum, A.; Feddi, E.; Bosch Bailach, J.; Martínez-Pastor, J.; Zazi, M.

    2012-02-01

    The effect of a lateral electric field on a donor impurity confined in a thin quantum disk is studied theoretically in the framework of mass approximation and using the Ritz variational approach. We show that the binding energy depends on several parameters: the dot size, the position of the donor impurity, the lateral field strength, and its orientation relative to the axis containing the impurity. When the impurity is located at one edge and the electric field is oriented in the opposite direction, the binding energy is considerably reinforced due to the simultaneous additive effects of coulombic potential and electrostatic force. The competition between these effects modifies considerably the probability densities and allows a better comprehension of the binding energy variations. This interesting behavior can contribute to an better understanding of the experimental optical response.

  15. Application of the viscosity-expansion method to a rotating thin fluid disk bound by central gravity

    NASA Astrophysics Data System (ADS)

    Takahashi, Koichi

    2015-07-01

    The 2D rotation of a thin fluid disk with a porous sink around the center is studied within the Navier-Stokes and Euler equations. The viscosity (ν)-expansion method is applied to the viscous fluid bound to the central mass via gravity. The Navier-Stokes equations yield various types of rotation curve, including a flat one, depending on the choice of the pressure function that is not determined within the fluid dynamics. Stationary flow is achieved through the balance of the pressure gradient, gravity, and the centrifugal force. These features of the stationary flow survive in the inviscid limit. The stability of the inviscid flow is examined by the Euler equations for the perturbations. At large distances, the real part of eigenfrequencies (EFs) are dominantly positive and decreasing with distance for flat and rising rotation curves, meaning that the spiral pattern of the perturbations is trailing. One real increasing EF exists for the decaying rotation curve, for which the spiral pattern is leading. Complex frequencies always emerge when the disk has m-fold rotational symmetry with m≥ 2. The shape of the perturbed rotation curve has azimuthal as well as temporal dependences.

  16. High-efficiency wavelength and polarization selective grating-waveguide structures for Yb:YAG thin-disk lasers

    NASA Astrophysics Data System (ADS)

    Rumpel, Martin; Abdou Ahmed, Marwan; Voss, Andreas; Graf, Thomas

    2012-06-01

    We report on Grating Waveguide Structures (GWS) with a high diffraction efficiency used in Littrow configuration to select (and tune) the wavelength of an Yb:YAG thin-disk laser. The structures are composed of a multilayer HR coating, on which an additional low index layer (SiO2) and high index layer (Ta2O5) was deposited. A binary grating with a period of 580 nm is etched on top of the structure with a groove depth of 87 nm for GWS 1 and 72 nm for GWS 2. The simulation results show that the diffraction efficiency in the -1st order can reach a value of 99.99% for TE polarization, whereas it is only about 20% for TM polarization at 1030 nm. The grating was fabricated by standard interference lithography followed by a dry etching process to the desired groove depth. The spectroscopic measurement exhibited a diffraction efficiency of 99.6% for GWS 1 at 1030 nm and 99.7% for GWS 2 at 1048 nm. The devices were placed as end-mirror into the resonator of a Yb:YAG thin-disk laser. An output power of up to 110 W could be obtained from the laser in fundamental-mode operation (M2 ~ 1.2) with GWS 1, corresponding to an optical efficiency of ηoo = 36.2%. In multi-mode operation (M2 ~ 6) a power of 325 W with ηoo = 53.2% could be extracted. The spectral bandwidth of the emitted beam was measured using an Optical Spectrum Analyzer (OSA) to be less than 20 pm in fundamental-mode. We also showed a continuous wavelength tuning range of 46 nm for GWS 1 and of 38 nm for GWS 2. With a commercially available Stokes polarimeter the degree of linear polarization (DOLP) was measured to be higher than 98.6% over the whole power and wavelength tuning range.

  17. Planet signatures and effect of the chemical evolution of the Galactic thin-disk stars

    NASA Astrophysics Data System (ADS)

    Spina, Lorenzo; Meléndez, Jorge; Ramírez, Ivan

    2016-01-01

    Context. Studies based on high-precision abundance determinations revealed that chemical patterns of solar twins are characterised by the correlation between the differential abundances relative to the Sun and the condensation temperatures (Tc) of the elements. It has been suggested that the origin of this relation is related to the chemical evolution of the Galactic disk, but other processes, associated with the presence of planets around stars, might also be involved. Aims: We analyse HIRES spectra of 14 solar twins and the Sun to provide new insights on the mechanisms that can determine the relation between [X/H] and Tc. Methods: Our spectroscopic analysis produced stellar parameters (Teff, log g, [Fe/H], and ξ), ages, masses, and abundances of 22 elements (C, O, Na, Mg, Al, Si, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, and Ba). We used these determinations to place new constraints on the chemical evolution of the Galactic disk and to verify whether this process alone can explain the different [X/H]-Tc slopes observed so far. Results: We confirm that the [X/Fe] ratios of all the species correlate with age. The slopes of these relations allow us to describe the effect that the chemical evolution of the Galactic disk has on the chemical patterns of the solar twins. After subtracting the chemical evolution effect, we find that the unevolved [X/H]-Tc slope values do not depend on the stellar ages anymore. However, the wide diversity among these [X/H]-Tc slopes, covering a range of ± 4 × 10-5 dex K-1, indicates that processes in addition to the chemical evolution may affect the [X/H]-Tc slopes. Conclusions: The wide range of unevolved [X/H]-Tc slope values spanned at all ages by our sample could reflect the wide diversity among exo-planetary systems observed so far and the variety of fates that the matter in circumstellar disks can experience.

  18. Ionization-assisted relativistic electron generation with monoenergetic features from laser thin foil interaction

    SciTech Connect

    Glazyrin, I. V.; Karpeev, A. V.; Kotova, O. G.; Bychenkov, V. Yu.; Fedosejevs, R.; Rozmus, W.

    2012-07-11

    The concept of ionization-induced injection into the laser pulse to produce quasi-monoenergetic bunches of electrons from ultra-thin solid dense targets is analyzed. When the laser pulse propagates through semi-transparent foil the electrons from inner atom shells remain bound during the rise time of the laser pulse and are ionized by the laser intensity near its maximum amplitude, which satisfies the best injection condition for subsequent acceleration. It was found that a bunch of quasimonoenergetic electrons from inner atom shells moves co-directionally with laser pulse and acquire energy {approx}m{sub e}c{sup 2}a{sup 2}/2.

  19. Heating of thin foils with a relativistic-intensity short-pulse laser.

    PubMed

    Audebert, P; Shepherd, R; Fournier, K B; Peyrusse, O; Price, D; Lee, R; Springer, P; Gauthier, J-C; Klein, L

    2002-12-23

    K-shell x-ray spectroscopy of sub-100 nm Al foils irradiated by high contrast, spatially uniform, 150 fs, Ilambda (2)=2 x 10(18) W microm(2)/cm(2), laser pulses is obtained with 500 fs time resolution. Two distinct phases occur: At /=500 fs the resonance transitions dominate. Initial satellites arise from a large area, high density, low temperature (approximately 100 eV) plasma created by fast electrons. Thus, contrary to predictions, a short, high intensity laser incident on a thin foil does not create a uniform, hot dense plasma. PMID:12484827

  20. Finite axisymmetric charged dust disks in conformastatic spacetimes

    NASA Astrophysics Data System (ADS)

    González, Guillermo A.; Gutiérrez-Piñeres, Antonio C.; Ospina, Paolo A.

    2008-09-01

    An infinite family of axisymmetric charged dust disks of finite extension is presented. The disks are obtained by solving the vacuum Einstein-Maxwell equations for conformastatic spacetimes, which are characterized by only one metric function. In order to obtain the solutions, a functional relationship between the metric function and the electric potential is assumed. It is also assumed that the metric function is functionally dependent on another auxiliary function, which is taken as a solution of the Laplace equation. The solutions for the auxiliary function are then taken as given by the infinite family of generalized Kalnajs disks recently obtained by González and Reina [G. A. González and J. I. Reina, Mon. Not. R. Astron. Soc. 371, 1873 (2006).MNRAA40035-871110.1111/j.1365-2966.2006.10819.x], expressed in terms of the oblate spheroidal coordinates and corresponding to a family of well-behaved Newtonian axisymmetric thin disks of finite radius. The obtained relativistic thin disks have a charge density that is equal, except maybe by a sign, to their mass density, in such a way that the electric and gravitational forces are in exact balance. The energy density of the disks is everywhere positive and well behaved, vanishing at the edge. Accordingly, as the disks are made of dust, their energy-momentum tensor agrees with all the energy conditions.

  1. Finite axisymmetric charged dust disks in conformastatic spacetimes

    SciTech Connect

    Gonzalez, Guillermo A.; Gutierrez-Pineres, Antonio C.; Ospina, Paolo A.

    2008-09-15

    An infinite family of axisymmetric charged dust disks of finite extension is presented. The disks are obtained by solving the vacuum Einstein-Maxwell equations for conformastatic spacetimes, which are characterized by only one metric function. In order to obtain the solutions, a functional relationship between the metric function and the electric potential is assumed. It is also assumed that the metric function is functionally dependent on another auxiliary function, which is taken as a solution of the Laplace equation. The solutions for the auxiliary function are then taken as given by the infinite family of generalized Kalnajs disks recently obtained by Gonzalez and Reina [G. A. Gonzalez and J. I. Reina, Mon. Not. R. Astron. Soc. 371, 1873 (2006).], expressed in terms of the oblate spheroidal coordinates and corresponding to a family of well-behaved Newtonian axisymmetric thin disks of finite radius. The obtained relativistic thin disks have a charge density that is equal, except maybe by a sign, to their mass density, in such a way that the electric and gravitational forces are in exact balance. The energy density of the disks is everywhere positive and well behaved, vanishing at the edge. Accordingly, as the disks are made of dust, their energy-momentum tensor agrees with all the energy conditions.

  2. Normal Modes of Black Hole Accretion Disks

    SciTech Connect

    Ortega-Rodriguez, Manuel; Silbergleit, Alexander S.; Wagoner, Robert V.; /Stanford U., Phys. Dept. /KIPAC, Menlo Park

    2006-11-07

    This paper studies the hydrodynamical problem of normal modes of small adiabatic oscillations of relativistic barotropic thin accretion disks around black holes (and compact weakly magnetic neutron stars). Employing WKB techniques, we obtain the eigen frequencies and eigenfunctions of the modes for different values of the mass and angular momentum of the central black hole. We discuss the properties of the various types of modes and examine the role of viscosity, as it appears to render some of the modes unstable to rapid growth.

  3. Evolution of the Milky Way with radial motions of stars and gas. I. The solar neighbourhood and the thin and thick disks

    NASA Astrophysics Data System (ADS)

    Kubryk, M.; Prantzos, N.; Athanassoula, E.

    2015-08-01

    Context. We study the role of radial migration of stars on the chemical evolution of the Milky Way disk. Aims: We are interested in the impact of that process on the local properties of the disk (age-metallicity relation and its dispersion, metallicity distribution, evolution of abundance ratios) and on the morphological properties of the resulting thick and thin disks. Methods: We use a model with several new or up-dated ingredients: atomic and molecular gas phases, star formation that depends on molecular gas, yields from a recent homogeneous grid and observationally inferred SNIa rates. We describe radial migration with parametrised time- and radius-dependent diffusion coefficients, based on the analysis of an N-body+SPH simulation. We also consider parametrised radial gas flows, induced by the action of the Galactic bar. Results: Our model reproduces current values of most of the main global observables of the MW disk and bulge, and also the observed "stacked" evolution of MW-type galaxies. The azimuthally averaged radial velocity of gas inflow is constrained to less than a few tenths of km s-1. Radial migration is constrained by the observed dispersion in the age-metallicity relation. Assuming that the thick disk is the oldest (>9 Gyr) part of the disk, we find that the adopted radial migration scheme can quantitatively reproduce the main local properties of the thin and thick disk: metallicity distributions, "two-branch" behaviour in the O/Fe vs. Fe/H relation and the local surface densities of stars. The thick disk extends up to ~11 kpc and has a scale length of 1.8 kpc, which is considerably shorter than the thin disk, because of the inside-out formation scheme. We also show how, in this framework, current and forthcoming spectroscopic observations can constrain the nucleosynthesis yields of massive stars for the metallicity range of 0.1 Z⊙ to 2-3 Z⊙. Appendices are available in electronic form at http://www.aanda.org

  4. Relativistic electron generation in interactions of a 30 TW laser pulse with a thin foil target.

    PubMed

    Malka, G; Aleonard, M M; Chemin, J F; Claverie, G; Harston, M R; Scheurer, J N; Tikhonchuk, V; Fritzler, S; Malka, V; Balcou, P; Grillon, G; Moustaizis, S; Notebaert, L; Lefebvre, E; Cochet, N

    2002-12-01

    Energy and angular distributions of the fast outgoing electron beam induced by the interaction of a 1 J, 30 fs, 2 x 10(19) W/cm(2), 10 Hz laser with a thin foil target are characterized by electron energy spectroscopy and photonuclear reactions. We have investigated the effect of the target thickness and the intensity contrast ratio level on the electron production. Using a 6-microm polyethylene target, up to 4 x 10(8) electrons with energies between 5 and 60 MeV were produced per laser pulse and converted to gamma rays by bremsstrahlung in a Ta secondary target. The rates of photofission of U as well as photonuclear reactions in Cu, Au, and C samples have been measured. In optimal focusing conditions, about 0.06% of the laser energy has been converted to outgoing electrons with energies above 5 MeV. Such electrons leave the target in the laser direction with an opening angle of 2.5 degrees. PMID:12513407

  5. Relativistic Astrophysics

    NASA Astrophysics Data System (ADS)

    Jones, Bernard J. T.; Markovic, Dragoljub

    1997-06-01

    Preface; Prologue: Conference overview Bernard Carr; Part I. The Universe At Large and Very Large Redshifts: 2. The size and age of the Universe Gustav A. Tammann; 3. Active galaxies at large redshifts Malcolm S. Longair; 4. Observational cosmology with the cosmic microwave background George F. Smoot; 5. Future prospects in measuring the CMB power spectrum Philip M. Lubin; 6. Inflationary cosmology Michael S. Turner; 7. The signature of the Universe Bernard J. T. Jones; 8. Theory of large-scale structure Sergei F. Shandarin; 9. The origin of matter in the universe Lev A. Kofman; 10. New guises for cold-dark matter suspects Edward W. Kolb; Part II. Physics and Astrophysics Of Relativistic Compact Objects: 11. On the unification of gravitational and inertial forces Donald Lynden-Bell; 12. Internal structure of astrophysical black holes Werner Israel; 13. Black hole entropy: external facade and internal reality Valery Frolov; 14. Accretion disks around black holes Marek A. Abramowicz; 15. Black hole X-ray transients J. Craig Wheeler; 16. X-rays and gamma rays from active galactic nuclei Roland Svensson; 17. Gamma-ray bursts: a challenge to relativistic astrophysics Martin Rees; 18. Probing black holes and other exotic objects with gravitational waves Kip Thorne; Epilogue: the past and future of relativistic astrophysics Igor D. Novikov; I. D. Novikov's scientific papers and books.

  6. High-power Kerr-lens mode-locked Yb:YAG thin-disk oscillator in the positive dispersion regime.

    PubMed

    Pronin, O; Brons, J; Grasse, C; Pervak, V; Boehm, G; Amann, M-C; Apolonski, A; Kalashnikov, V L; Krausz, F

    2012-09-01

    We demonstrate a self-starting Kerr-lens mode-locked (KLM) Yb:YAG thin-disk oscillator operating in the regime of positive intracavity group-delay dispersion (GDD). It delivers 1.7 ps pulses at an average power of 17 W and a repetition rate of 40 MHz. Dispersive mirrors compress the pulses to a duration of 190 fs (assuming sech2 shape; Fourier limit: 150 fs) at an average power level of 11 W. To our knowledge, this is the first KLM thin-disk oscillator with positive GDD. Output powers of up to 30 W were achieved with an increased output coupler transmission and intracavity GDD. We demonstrate increase of the pulse energy with increasing positive intracavity GDD, limited by difficulties in initiating mode-locking. PMID:22940943

  7. Self-Oscillated Ultrasonic Stepping Motor with Function of Angular Displacement Self-Correction: Nonaxisymmetric ((2,1))-Mode Thin Disk Motor

    NASA Astrophysics Data System (ADS)

    Chen, Xiaoduo; Aoyagi, Manabu; Kusakabe, Chiharu; Tomikawa, Yoshiro

    1994-05-01

    This paper deals with experimental investigation of a self-oscillated open-loop driving motor using a slitted rotor and a nonaxisymmetric ((2,1)) vibration mode thin annular disk which has four projection teeth on its inner circumference. This motor is suitable for application to watches because it can be constructed in a thin configuration and the slitted rotor enables the self-correction of angular displacement. In the experiment, two types of self-oscillation circuits were investigated for suitable driving. The results were that the self-oscillated driving motor could be achieved by using an operational amplifier and some inverter IC elements. That is, the self-correction function of the angular displacement of a stepping motor was confirmed in the case of the nonaxisymmetric-mode disk motor.

  8. Yb:YAG thin disk laser passively Q-switched by a hydro-thermal grown molybdenum disulfide saturable absorber

    NASA Astrophysics Data System (ADS)

    Zhan, Yi; Wang, Li; Wang, Jie Yu; Li, Hong Wei; Yu, Zhen Huang

    2015-02-01

    We demonstrate a passively Q-switched Yb:YAG thin disk solid-state laser based on nanoflake MoS2 as a saturable absorber. MoS2 is synthesized by a hydro-thermal process. The prepared MoS2 is transferred onto the BK7 glass for ease-of-use in the solid-state laser as a saturable absorber. The average output power could reach up to 250 mW, center wavelength 1030 nm corresponding to a pulse width, a pulse repetition rate, and a per pulse energy of 12 μs, 17 kHz, and 15 μJ, respectively. Our results show that nanoflake MoS2 could be a promising saturable absorber for Q-switching solid-state lasers. The over saturation of the MoS2 saturable absorber at a high pump strength limit in a solid-state laser could be also effective for high power operation.

  9. Moderate high power 1 to 20μs and kHz Ho:YAG thin disk laser pulses for laser lithotripsy

    NASA Astrophysics Data System (ADS)

    Renz, Günther

    2015-02-01

    An acousto-optically or self-oscillation pulsed thin disk Ho:YAG laser system at 2.1 μm with an average power in the 10 W range will be presented for laser lithotripsy. In the case of cw operation the thin disk Ho:YAG is either pumped with InP diode stacks or with a thulium fiber laser which leads to a laser output power of 20 W at an optical-to-optical efficiency of 30%. For the gain switched mode of operation a modulated Tm-fiber laser is used to produce self-oscillation pulses. A favored pulse lengths for uric acid stone ablation is known to be at a few μs pulse duration which can be delivered by the thin disk laser technology. In the state of the art laser lithotripter, stone material is typically ablated with 250 to 750 μs pulses at 5 to 10 Hz and with pulse energies up to a few Joule. The ablation mechanism is performed in this case by vaporization into stone dust and fragmentation. With the thin disk laser technology, 1 to 20 μs-laser pulses with a repetition rate of a few kHz and with pulse energies in the mJ-range are available. The ablation mechanism is in this case due to a local heating of the stone material with a decomposition of the crystalline structure into calcium carbonate powder which can be handled by the human body. As a joint process to this thermal effect, imploding water vapor bubbles between the fiber end and the stone material produce sporadic shock waves which help clear out the stone dust and biological material.

  10. Design of a thin disk amplifier with extraction during pumping for high peak and average power Ti:Sa systems (EDP-TD).

    PubMed

    Chvykov, Vladimir; Nagymihaly, Roland S; Cao, Huabao; Kalashnikov, Mikhail; Osvay, Karoly

    2016-02-22

    Combination of the scheme of extraction during pumping (EDP) and the Thin Disk (TD) technology is presented to overcome the limitations associated with thermal cooling of crystal and transverse amplified spontaneous emission in high average power laser systems based on Ti:Sa amplifiers. The optimized design of high repetition rate 1-10 PW Ti:Sapphire EDP-TD power amplifiers are discussed, including their thermal dynamic behavior. PMID:26907029

  11. Structure of line-emitting accretion disks in active galactic nuclei - Arp 102B

    NASA Technical Reports Server (NTRS)

    Chen, Kaiyou; Halpern, Jules P.

    1989-01-01

    The prime objects of the present self-consistent model of a line-emitting accretion disk able to account for the properties observed in a small class of AGNs are Arp 102B and 3C 390.3, whose double-peaked emission lines have been attributed to a Keplerian disk. Improved calculations of the line profile of a relativistic Keplerian disk, generalized to include a variety of emissivity laws as well as local broadening due to electron scattering or turbulence, are noted to fit Arp 102B; analytic and numerical calculations of the solid angle presented by the outer thin disk to an extended isotropic source of illumination demonstrate that the energy budget requirements for line emission from the disk are also satisfied.

  12. A Roughness Study of Ytterbium-Doped Potassium Yttrium Tungstate (YB: KYW) Thin-Disk Femtosecond Ablated Dentin

    PubMed Central

    Liu, Jing; Chen, Hu; Ge, Wenqi; Wang, Yongbo; Sun, Yuchun; Wang, Yong; Lü, Peijun

    2014-01-01

    Introduction: The aim of this study was to evaluate the morphological changes and quantitatively assess the roughness of dentin after the ablation with a Ytterbium-Doped Potassium Yttrium Tungstate (YB: KYW) thin-disk femtosecond pulsed laser of different fluences, scanning speeds and scanning distances. Method: Twelve extracted human premolars were sectioned into crowns and roots along the cementum-enamel junction, and then the crowns were cut longitudinally into sheets about 1.5 mm thick with a cutting machine. The dentin samples were fixed on a stage at focus plane. The laser beam was irradiated onto the samples through a galvanometric scanning system, so rectangular movement could be achieved. After ablation, the samples were examined with a scanning electron microscope and laser three-dimensional profile measurement microscope for morphology and roughness study.With increasing laser fluence, dentin samples exhibited more melting and resolidification of dentin as well as debris-like structure and occluded parts of dentinal tubules. Results: When at the scanning speed of 2400mm/s and scanning distance of 24μm, the surface roughness of dentin ablated with femtosecond pulsed laser decreased significantly and varied between values of dentin surface roughness grinded with two kinds of diamond burs with different grits. When at the scanning speed of 1200mm/s and scanning distance of 12μm, the surface roughness decreased slightly, and the surface roughness of dentin ablated with femtosecond pulsed laser was almost equal to that grinded with a low grit diamond bur. Conclusion: This study showed that increased laser influence may lead to more collateral damage and lower dentin surface roughness, while scanning speed and scanning distance were also negatively correlated with surface roughness. Adequate parameters should be chosen to achieve therapeutic benefits, and different parameters can result in diverse ablation results. PMID:25606337

  13. VizieR Online Data Catalog: Thin disk BV-GV Hipparcos stars within 333pc (Gontcharov+, 2012)

    NASA Astrophysics Data System (ADS)

    Gontcharov, G. A.

    2016-01-01

    The variations of kinematic parameters with age are considered for a sample of 15402 thin-disk O-F stars with accurate RA, DEC, proper motion, and parallax higher than 3 mas from the Hipparcos catalogue (2007A&A...474..653V) and radial velocities from the PCRV (2006PAZh...32..844G) catalogue. The ages have been calculated from the positions of the stars on the Hertzsprung-Russell diagram relative to the isochrones from the Padova database (http://stev.oapd.inaf.it/cmd) by taking into account the extinction from the previously constructed 3D analytical model (2009AstL...35..780G) and extinction coefficient RV from the 3D map of its variations (2012AstL...38...12G). Smooth, mutually reconciled variations of the velocity dispersions sigma(U), sigma(V), sigma(W), solar motion components Usun, Vsun, Wsun, Ogorodnikov-Milne model parameters, Oort constants, and vertex deviation lxy consistent with all of the extraneous results for which the stellar ages were determined have been found and presented in the table solution.dat. The velocity dispersion variations are well fitted by power laws the deviations from which are explained by the influence of predominantly radial stellar streams: Sirius, Hyades, alpha Cet/Wolf 630, and Hercules. The accuracy of determining the solar motion relative to the local standard of rest is shown to be fundamentally limited due to these variations of stellar kinematics. The deviations of our results from those of Dehnen and Binney (1998MNRAS.294..429D), the Geneva-Copenhagen survey of dwarfs (V/117), and the Besancon model of the Galaxy (2003A&A...409..523R) are explained by the use of PCRV radial velocities with corrected systematic errors. (2 data files).

  14. Herniated disk

    MedlinePlus

    ... the disk. This may place pressure on nearby nerves or the spinal cord. ... Lumbar radiculopathy; Cervical radiculopathy; Herniated intervertebral disk; Prolapsed intervertebral disk; Slipped disk; Ruptured disk; Herniated nucleus pulposus

  15. Relativistic radiative transfer and relativistic plane-parallel flows

    NASA Astrophysics Data System (ADS)

    Fukue, Jun

    2015-04-01

    Relativistic radiative transfer and relativistic plane-parallel flows accelerated from their base like accretion disk winds are numerically examined under the special relativistic treatment. We first solve the relativistic transfer equation iteratively, using a given velocity field, and obtain specific intensities as well as moment quantities. Using the obtained flux, we then solve the hydrodynamical equation, and obtain the new velocity field and the mass-loss rate as an eigen value. We repeat these double-iteration processes until both the intensity and velocity profiles converge. Under this double iteration, we solve the relativistic radiative transfer equation and relativistic flows in the vertical direction, simultaneously. The flows are gradually accelerated, as the optical depth decreases towards the surface. The mass-loss rate dot{J} is roughly expressed in terms of the optical depth τb and terminal speed βs of the flow as dot{J} ˜ 10 τ_b β _s^{-3/4}.

  16. Mode-locked Yb:YAG thin-disk oscillator with 41 µJ pulse energy at 145 W average infrared power and high power frequency conversion.

    PubMed

    Bauer, Dominik; Zawischa, Ivo; Sutter, Dirk H; Killi, Alexander; Dekorsy, Thomas

    2012-04-23

    We demonstrate the generation of 1.1 ps pulses containing more than 41 µJ of energy directly out of an Yb:YAG thin-disk without any additional amplification stages. The laser oscillator operates in ambient atmosphere with a 3.5 MHz repetition rate and 145 W of average output power at a fundamental wavelength of 1030 nm. An average output power of 91.5 W at 515 nm was obtained by frequency doubling with a conversion efficiency exceeding 65%. Third harmonic generation resulted in 34 W at 343 nm at 34% efficiency. PMID:22535061

  17. Numerical and experimental analysis of a thin liquid film on a rotating disk related to development of a spacecraft absorption cooling system

    NASA Technical Reports Server (NTRS)

    Faghri, Amir; Swanson, Theodore D.

    1989-01-01

    The numerical and experimental analysis of a thin liquid film on a rotating and a stationary disk related to the development of an absorber unit for a high capacity spacecraft absorption cooling system, is described. The creation of artificial gravity by the use of a centrifugal field was focused upon in this report. Areas covered include: (1) One-dimensional computation of thin liquid film flows; (2) Experimental measurement of film height and visualization of flow; (3) Two-dimensional computation of the free surface flow of a thin liquid film using a pressure optimization method; (4) Computation of heat transfer in two-dimensional thin film flow; (5) Development of a new computational methodology for the free surface flows using a permeable wall; (6) Analysis of fluid flow and heat transfer in a thin film in the presence and absence of gravity; and (7) Comparison of theoretical prediction and experimental data. The basic phenomena related to fluid flow and heat transfer on rotating systems reported here can also be applied to other areas of space systems.

  18. Observational Signatures of Tilted Black Hole Accretion Disks from Simulations

    NASA Astrophysics Data System (ADS)

    Dexter, Jason; Fragile, P. Chris

    2011-03-01

    Geometrically thick accretion flows may be present in black hole X-ray binaries observed in the low/hard state and in low-luminosity active galactic nuclei. Unlike in geometrically thin disks, the angular momentum axis in these sources is not expected to align with the black hole spin axis. We compute images from three-dimensional general relativistic magnetohydrodynamic simulations of misaligned (tilted) accretion flows using relativistic radiative transfer and compare the estimated locations of the radiation edge with expectations from their aligned (untilted) counterparts. The radiation edge in the tilted simulations is independent of black hole spin for a tilt of 15°, in stark contrast to the results for untilted simulations, which agree with the monotonic dependence on spin expected from thin accretion disk theory. Synthetic emission line profiles from the tilted simulations depend strongly on the observer's azimuth and exhibit unique features such as broad "blue wings." Coupled with precession, the azimuthal variation could generate time fluctuations in observed emission lines, which would be a clear "signature" of a tilted accretion flow. Finally, we evaluate the possibility that the observed low- and high-frequency quasi-periodic oscillations (QPOs) from black hole binaries could be produced by misaligned accretion flows. Although low-frequency QPOs from precessing, tilted disks remains a viable option, we find little evidence for significant power in our light curves in the frequency range of high-frequency QPOs.

  19. Dynamic and quasi-static contact and scratch analysis of micro-nanoscale thin solid films with application to magnetic storage hard disk drives

    NASA Astrophysics Data System (ADS)

    Katta, Raja Ramakanth

    With current demand for decreased size of micro/nanoscale systems, coupled with increased mobility, critical understanding of the ensuing contact or impact related behavior of thin solid films used in these systems is of paramount importance for improved design and reliability. In modern micro/nanodevice technologies significant emphasis has to be placed on the design of thin-films which can provide the required contact and scratch resistance. To aid this endeavor, scientific studies of the contact and scratch processes in these systems, both static and dynamic are needed to provide the tools necessary to help the advancement of these technologies. One such problem is the impact contact or quasi-static contact and scratch of the slider and disk in magnetic storage hard disk drives (HDD). Similar contact problems are encountered during the operation of other micromechanical systems like RF-MEMS switches where surface damage is observed after cyclic contact. One of the most critical elements of multilayer contact analysis is proper determination of the nanomechanical properties of each thin-film on the multilayer system. In the first part of this work the method of determining the mechanical properties using the Oliver and Pharr (O-P) nanoindentation technique is described. For nanometer sized thin-films where the O-P technique gives incorrect results, an improved method is used. Later a dimensional analysis-based method to obtain the mechanical properties from the nanoindentation data is implemented for magnetic storage films. A direct comparison of the properties obtained from conventional O-P nanoindentation technique to this new technique is presented. In the second part of this work, the effect of dynamic contact or impact on multilayer thin films specific to magnetic storage hard disk drives is presented. Since there are no impact models available for multilayer thin films in the literature, a new contact mechanics-based (CM) semi-analytical model of a rigid

  20. Black hole accretion disks in brane gravity via a confining potential

    NASA Astrophysics Data System (ADS)

    Heydari-Fard, Malihe

    2010-12-01

    Accretion disks are among the most luminous and ubiquitous sources in astrophysics and they have drawn a good deal of attention from the observational and theoretical communities. In this paper, we study the process of matter forming thin accretion disks around black hole solutions in the context of the brane-world scenario where our universe is a three-brane embedded in an m-dimensional bulk and localization of matter on the brane is achieved by means of a confining potential. The physical properties of thin accretion disks including the time averaged energy flux, temperature distribution, the emission spectrum as well as the energy conversion efficiency are obtained, and the results are compared with the DMPR, CFM and BMD brane black holes and the standard general relativistic Schwarzschild solution.

  1. Rich Kozai–Lidov Dynamics in an Initially Thin and Eccentric Stellar Disk around a Supermassive Black Hole

    NASA Astrophysics Data System (ADS)

    Haas, Jaroslav; Šubr, Ladislav

    2016-05-01

    There is growing evidence of star formation in the vicinity of supermassive black holes (SMBHs) in galactic nuclei. A viable scenario for this process assumes infall of a massive gas cloud toward the SMBH and subsequent formation of a dense accretion disk, which gives birth to the young stars. Numerical hydrodynamical models indicate that this star formation process is rather fast and precedes full circularization of the accretion flow, i.e., the new stars are born on elliptic orbits. By means of direct numerical N-body modeling, we show in this paper that the nonzero eccentricity of the stellar disks around the SMBH leads to an onset of various types of the Kozai–Lidov oscillations of a non-negligible subset of individual orbits in the disk, showing a remarkable robustness of this classical mechanism. Among others, we demonstrate that under certain circumstances, the presence of an additional spherical cluster (which is generally known to damp Kozai–Lidov oscillations) may trigger such oscillations as a result of affecting the internal flow of the angular momentum through the disk. We conclude that the Kozai–Lidov oscillations are capable of substantially modifying the initial structure of the disk (its thickness and distribution of eccentricities, in particular).

  2. SESAM-modelocked Yb:CaF2 thin-disk-laser generating 285 fs pulses with 1.78 μJ of pulse energy

    NASA Astrophysics Data System (ADS)

    Dannecker, Benjamin; Abdou Ahmed, Marwan; Graf, Thomas

    2016-05-01

    We report on a SESAM-modelocked Yb:CaF2 thin-disk oscillator designed to generate more than 1 μJ of pulse energy at a moderate pulse repetition rate. The goal of our experiment was to explore the potential of Yb:CaF2 in a thin-disk laser (TDL) architecture for high power at pulse durations shorter than 300 fs as compared to other Yb-doped crystals exhibiting broad gain bandwidth. At a repetition rate of 10 MHz the laser produced an average output power of up to 17.8 W (1.78 μJ of pulse energy) with a beam quality factor M 2 below 1.2. The pulse duration was measured to be 285 fs, which results in a peak power of 5.5 MW. To the best of our knowledge, this is the highest pulse energy and peak power demonstrated to date with sub-300 fs pulses generated by SESAM-modelocked oscillators, leading to the conclusion that Yb:CaF2 is a very promising crystal for TDL technology.

  3. Numerical simulation of fluid flow and heat transfer in a thin liquid film over a stationary and rotating disk and comparison with experimental data

    NASA Technical Reports Server (NTRS)

    Faghri, Amir; Swanson, Theodore D.

    1990-01-01

    In the first section, improvements in the theoretical model and computational procedure for the prediction of film height and heat-transfer coefficient of the free surface flow of a radially-spreading thin liquid film adjacent to a flat horizontal surface of finite extent are presented. Flows in the presence and absence of gravity are considered. Theoretical results are compared to available experimental data with good agreement. In the presence of gravity, a hydraulic jump is present, isolating the flow into two regimes: supercritical upstream from the jump and subcritical downstream of it. In this situation, the effects of surface tension are important near the outer edge of the disk where the fluid experiences a free fall. A region of flow separation is present just downstream of the jump. In the absence of gravity, no hydraulic jump or separated flow region is present. The variation of the heat-transfer coefficient for flows in the presence and absence of gravity are also presented. In the second section, the results of a numerical simulation of the flow field and associated heat transfer coefficients are presented for the free surface flow of a thin liquid film adjacent to a horizontal rotating disk. The computation was performed for different flow rates and rotational velocities using a 3-D boundary-fitted coordinate system. Since the geometry of the free surface is unknown and dependent on flow rate, rate of rotation, and other parameters, an iterative procedure had to be used to ascertain its location. The computed film height agreed well with existing experimental measurements. The flow is found to be dominated by inertia near the entrance and close to the free surface and dominated by centrifugal force at larger radii and adjacent to the disk. The rotation enhances the heat transfer coefficient by a significant amount.

  4. THE STRUCTURE AND SPECTRAL FEATURES OF A THIN DISK AND EVAPORATION-FED CORONA IN HIGH-LUMINOSITY ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Liu, J. Y.; Mineshige, S. E-mail: bfliu@nao.cas.cn

    2012-08-01

    We investigate the accretion process in high-luminosity active galactic nuclei (HLAGNs) in the scenario of the disk evaporation model. Based on this model, the thin disk can extend down to the innermost stable circular orbit (ISCO) at accretion rates higher than 0.02 M-dot{sub Edd} while the corona is weak since part of the coronal gas is cooled by strong inverse Compton scattering of the disk photons. This implies that the corona cannot produce as strong X-ray radiation as observed in HLAGNs with large Eddington ratio. In addition to the viscous heating, other heating to the corona is necessary to interpret HLAGN. In this paper, we assume that a part of accretion energy released in the disk is transported into the corona, heating up the electrons, and is thereby radiated away. For the first time, we compute the corona structure with additional heating, fully taking into account the mass supply to the corona, and find that the corona could indeed survive at higher accretion rates and that its radiation power increases. The spectra composed of bremsstrahlung and Compton radiation are also calculated. Our calculations show that the Compton-dominated spectrum becomes harder with the increase of energy fraction (f) liberating in the corona, and the photon index for hard X-ray (2-10 keV) is 2.2 < {Gamma} < 2.7. We discuss possible heating mechanisms for the corona. Combining the energy fraction transported to the corona with the accretion rate by magnetic heating, we find that the hard X-ray spectrum becomes steeper at a larger accretion rate and the bolometric correction factor (L{sub bol}/L{sub 2-10keV}) increases with increasing accretion rate for f < 8/35, which is roughly consistent with the observational results.

  5. A General Relativistic Magnetohydrodynamic Simulation of Jet Formation

    NASA Astrophysics Data System (ADS)

    Nishikawa, K.-I.; Richardson, G.; Koide, S.; Shibata, K.; Kudoh, T.; Hardee, P.; Fishman, G. J.

    2005-05-01

    We have performed a fully three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulation of jet formation from a thin accretion disk around a Schwarzschild black hole with a free-falling corona. The initial simulation results show that a bipolar jet (velocity ~0.3c) is created, as shown by previous two-dimensional axisymmetric simulations with mirror symmetry at the equator. The three-dimensional simulation ran over 100 light crossing time units (τS=rS/c, where rS≡2GM/c2), which is considerably longer than the previous simulations. We show that the jet is initially formed as predicted owing in part to magnetic pressure from the twisting of the initially uniform magnetic field and from gas pressure associated with shock formation in the region around r=3rS. At later times, the accretion disk becomes thick and the jet fades resulting in a wind that is ejected from the surface of the thickened (torus-like) disk. It should be noted that no streaming matter from a donor is included at the outer boundary in the simulation (an isolated black hole not binary black hole). The wind flows outward with a wider angle than the initial jet. The widening of the jet is consistent with the outward-moving torsional Alfvén waves. This evolution of disk-jet coupling suggests that the jet fades with a thickened accretion disk because of the lack of streaming material from an accompanying star.

  6. Edge-facet pumped, multi-aperture, thin-disk laser geometry for very high average power output scaling

    DOEpatents

    Zapata, Luis E.

    2004-12-21

    The average power output of a laser is scaled, to first order, by increasing the transverse dimension of the gain medium while increasing the thickness of an index matched light guide proportionately. Strategic facets cut at the edges of the laminated gain medium provide a method by which the pump light introduced through edges of the composite structure is trapped and passes through the gain medium repeatedly. Spontaneous emission escapes the laser volume via these facets. A multi-faceted disk geometry with grooves cut into the thickness of the gain medium is optimized to passively reject spontaneous emission generated within the laser material, which would otherwise be trapped and amplified within the high index composite disk. Such geometry allows the useful size of the laser aperture to be increased, enabling the average laser output power to be scaled.

  7. Critical condition for the propeller effect in systems with magnetized neutron stars accreting from geometrically thin accretion disks

    NASA Astrophysics Data System (ADS)

    Ertan, Unal

    2016-07-01

    The inner disk radius around a magnetized neutron star in the spin-down phase is usually assumed to be close to the radius at which the viscous and magnetic stresses are balanced. With different assumptions, this radius is estimated to be very close the Alfven radius. Furthermore, it is commonly assumed that the propeller mechanism can expel the matter from the system when this radius is found to be greater than the co-rotation radius. In the present work, we have shown with simple analytical calculations from the first principles that a steady-state propeller mechanism cannot be established at the radius where the viscous and the magnetic torques are balanced. We have found that a steady-state propeller phase can be built up with an inner disk radius that is at least ~10 - 30 times smaller than the Alfven radius depending on the current mass-flow rate of the disk, the field strength and the rotational period of the source. This result also indicates that the critical accretion rate for the accretion-propeller transition is orders of magnitude smaller than the rate found by equating the Alfven and the co-rotation radii. Our results are consistent with the properties of recently discovered transitional millisecond pulsars which show transitions between the rotational powered radio pulsar and the accretion powered X-ray pulsar states.

  8. Passively mode-locked Yb:YAG thin-disk laser with pulse energies exceeding 13 microJ by use of an active multipass geometry.

    PubMed

    Neuhaus, Joerg; Kleinbauer, Jochen; Killi, Alexander; Weiler, Sascha; Sutter, Dirk; Dekorsy, Thomas

    2008-04-01

    We demonstrate the generation of high-energy picosecond pulses directly from a thin-disk laser oscillator by employing a self-imaging active multipass geometry. Stable single-pulse operation has been obtained with an average output power in excess of 50 W, excluding a cw background of 8%, at a repetition rate of 3.8 MHz. Self-starting passive mode locking was accomplished using a semiconductor saturable absorber mirror. The maximum pulse energy was 13.4 microJ at a pulse duration of 1.36 ps with a time-bandwidth product of 0.34. Single-pass external frequency doubling with a conversion efficiency of 60% yielded >28 W of average power at 515 nm. PMID:18382531

  9. Yb:CaGdAlO4 thin-disk laser with 70% slope efficiency and 90 nm wavelength tuning range.

    PubMed

    Beil, Kolja; Deppe, Bastian; Kränkel, Christian

    2013-06-01

    Thin-disk laser experiments with Yb:CaGdAlO(4) (Yb:CALGO) have been performed. A slope efficiency of 70% and an optical-to-optical efficiency of 57% could be achieved with a maximum output power of 30.7 W. These are so far the highest efficiencies obtained with this material. Furthermore, tuning experiments were carried out leading to a tuning range of 90 nm in total and 50 nm with more than 20 W of output power. This is to the best of our knowledge the widest wavelength tuning range of any material demonstrated at this power level. For all experiments the thermal evolution of the crystal surface temperature during laser operation was investigated. PMID:23722805

  10. Investigations on ring-shaped pumping distributions for the generation of beams with radial polarization in an Yb:YAG thin-disk laser.

    PubMed

    Dietrich, Tom; Rumpel, Martin; Graf, Thomas; Ahmed, Marwan Abdou

    2015-10-01

    We present experimental investigations on the generation of radially polarized laser beams excited by a ring-shaped pump intensity distribution in combination with polarizing grating waveguide mirrors in an Yb:YAG thin-disk laser resonator. Hollow optical fiber components were implemented in the pump beam path to transform the commonly used flattop pumping distribution into a ring-shaped distribution. The investigation was focused on finding the optimum mode overlap between the ring-shaped pump spot and the excited first order Laguerre-Gaussian (LG(01)) doughnut mode. The power, efficiency and polarization state of the emitted laser beam as well as the thermal behavior of the disk was compared to that obtained with a standard flattop pumping distribution. A maximum output power of 107 W with a high optical efficiency of 41.2% was achieved by implementing a 300 mm long specially manufactured hollow fiber into the pump beam path. Additionally it was found that at a pump power of 280 W the maximum temperature increase is about 21% below the one observed with standard homogeneous pumping. PMID:26480177

  11. Continuous-wave seeded mid-IR parametric system pumped by the high-average-power picosecond Yb:YAG thin-disk laser

    NASA Astrophysics Data System (ADS)

    Novák, Ondřej; Smrž, Martin; Miura, Taisuke; Turčičová, Hana; Endo, Akira; Mocek, Tomáś

    2015-05-01

    Mid-IR wavelength range offers variety of interesting applications. Down-conversion in the optical parametric devices is promising to generate high average power mid-IR beam due to inherently low thermal load of the nonlinear crystals if a powerful and high quality pump beam is available. We developed 100 kHz pump laser of 100-W level average power. The stretched pulses of Yb-fiber laser oscillator at 1030 nm wavelength are injected into the regenerative amplifier with an Yb:YAG thin-disk. Diode pumping at zero phonon line at wavelength of 969 nm significantly reduces its thermal load and increases conversion efficiency and stability. We obtained the beam with power of 80 W and 2 ps compressed pulsewidth. We are developing a watt level mid-IR picosecond light source pumped by a beam of the thin disk regenerative amplifier. Part of the beam pumps PPLN, which is seeded by a continuous wave laser diode at 1.94 μm to decrease the generation threshold and determine the amplified spectrum. The 3 W pumping gave output of 30 mW, which is by up to two orders higher compared to unseeded operation. The gain of about 107 was achieved in the PPLN in the temporal window of the pump pulse. The spectrum and beam of the generated idler pulses in the mid-IR was measured. We obtained an amplified signal from the second stage with the KTP crystal. We expect watt level mid-IR output for initial 50-W pumping. The generation of longer wavelengths is discussed.

  12. Persistent Patterns in Accretion Disks

    SciTech Connect

    Amin, Mustafa A.; Frolov, Andrei V.; /KIPAC, Menlo Park

    2006-04-03

    We present a set of new characteristic frequencies associated with accretion disks around compact objects. These frequencies arise from persistent rotating patterns in the disk that are finite in radial extent and driven purely by the gravity of the central body. Their existence depends on general relativistic corrections to orbital motion and, if observed, could be used to probe the strong gravity region around a black hole. We also discuss a possible connection to the puzzle of quasi-periodic oscillations.

  13. Design and Characterization of Thin Stainless Steel Burst Disks for Increasing Two-Stage Light Gas Launcher Efficiency

    NASA Technical Reports Server (NTRS)

    Tylka, Jonathan M.; Johnson, Kenneth L.; Henderson, Donald; Rodriguez, Karen

    2012-01-01

    Laser etched 300 series Stainless Steel Burst Disks (SSBD) ranging between 0.178 mm (0.007-in.) and 0.508mm (0.020-in.) thick were designed for use in a 17-caliber two-stage light gas launcher. First, a disk manufacturing method was selected using a combination of wire electrical discharge machining (EDM) to form the blank disks and laser etching to define the pedaling fracture pattern. Second, a replaceable insert was designed to go between the SSDB and the barrel. This insert reduced the stress concentration between the SSBD and the barrel, providing a place for the petals of the SSDB to open, and protecting the rifling on the inside of the barrel. Thereafter, a design of experiments was implemented to test and characterize the burst characteristics of SSBDs. Extensive hydrostatic burst testing of the SSBDs was performed to complete the design of experiments study with one-hundred and seven burst tests. The experiment simultaneously tested the effects of the following: two SSBD material states (full hard, annealed); five SSBD thicknesses 0.178, 0.254, 0.305, 0.381 mm (0.007, 0.010, 0.012, 0.015, 0.020-in.); two grain directions relative); number of times the laser etch pattern was repeated (varies between 5-200 times); two heat sink configurations (with and without heat sink); and, two barrel configurations (with and without insert). These tests resulted in the quantification of the relationship between SSBD thickness, laser etch parameters, and desired burst pressure. Of the factors investigated only thickness and number of laser etches were needed to develop a mathematical relationship predicting hydrostatic burst pressure of disks using the same barrel configuration. The fracture surfaces of two representative SSBD bursts were then investigated with a scanning electron microscope, one burst hydrostatically in a fixture and another dynamically in the launcher. The fracture analysis verified that both burst conditions resulted in a ductile overload failure

  14. The Milky Way disk

    NASA Astrophysics Data System (ADS)

    Carraro, G.

    2015-08-01

    This review summarises the invited presentation I gave on the Milky Way disc. The idea underneath was to touch those topics that can be considered hot nowadays in the Galactic disk research: the reality of the thick disk, the spiral structure of the Milky Way, and the properties of the outer Galactic disk. A lot of work has been done in recent years on these topics, but a coherent and clear picture is still missing. Detailed studies with high quality spectroscopic data seem to support a dual Galactic disk, with a clear separation into a thin and a thick component. Much confusion and very discrepant ideas still exist concerning the spiral structure of the Milky Way. Our location in the disk makes it impossible to observe it, and we can only infer it. This process of inference is still far from being mature, and depends a lot on the selected tracers, the adopted models and their limitations, which in many cases are neither properly accounted for, nor pondered enough. Finally, there are very different opinions on the size (scale length, truncation radius) of the Galactic disk, and on the interpretation of the observed outer disk stellar populations in terms either of external entities (Monoceros, Triangulus-Andromeda, Canis Major), or as manifestations of genuine disk properties (e.g., warp and flare).

  15. Beam delivery and pulse compression to sub-50 fs of a modelocked thin-disk laser in a gas-filled Kagome-type HC-PCF fiber.

    PubMed

    Emaury, Florian; Dutin, Coralie Fourcade; Saraceno, Clara J; Trant, Mathis; Heckl, Oliver H; Wang, Yang Y; Schriber, Cinia; Gerome, Frederic; Südmeyer, Thomas; Benabid, Fetah; Keller, Ursula

    2013-02-25

    We present two experiments confirming that hypocycloid Kagome-type hollow-core photonic crystal fibers (HC-PCFs) are excellent candidates for beam delivery of MW peak powers and pulse compression down to the sub-50 fs regime. We demonstrate temporal pulse compression of a 1030-nm Yb:YAG thin disk laser providing 860 fs, 1.9 µJ pulses at 3.9 MHz. Using a single-pass grating pulse compressor, we obtained a pulse duration of 48 fs (FWHM), a spectral bandwidth of 58 nm, and an average output power of 4.2 W with an overall power efficiency into the final polarized compressed pulse of 56%. The pulse energy was 1.1 µJ. This corresponds to a peak power of more than 10 MW and a compression factor of 18 taking into account the exact temporal pulse profile measured with a SHG FROG. The compressed pulses were close to the transform limit of 44 fs. Moreover, we present transmission of up to 97 µJ pulses at 10.5 ps through 10-cm long fiber, corresponding to more than twice the critical peak power for self-focusing in silica. PMID:23482031

  16. Herniated Disk

    MedlinePlus

    Your backbone, or spine, is made up of 26 bones called vertebrae. In between them are soft disks filled with a jelly-like substance. These disks cushion the vertebrae and keep them in place. As you age, ...

  17. Accretion disks around black holes

    NASA Technical Reports Server (NTRS)

    Abramowicz, M. A.

    1994-01-01

    The physics of accretion flow very close to a black hole is dominated by several general relativistic effects. It cannot be described by the standard Shakura Sunyaev model or by its relativistic version developed by Novikov and Thome. The most important of these effects is a dynamical mass loss from the inner edge of the disk (Roche lobe overflow). The relativistic Roche lobe overflow induces a strong advective cooling, which is sufficient to stabilize local, axially symmetric thermal and viscous modes. It also stabilizes the non-axially-symmetric global modes discovered by Papaloizou and Pringle. The Roche lobe overflow, however, destabilizes sufficiently self-gravitating accretion disks with respect to a catastrophic runaway of mass due to minute changes of the gravitational field induced by the changes in the mass and angular momentum of the central black hole. One of the two acoustic modes may become trapped near the inner edge of the disk. All these effects, absent in the standard model, have dramatic implications for time-dependent behavior of the accretion disks around black holes.

  18. Ringed Accretion Disks: Instabilities

    NASA Astrophysics Data System (ADS)

    Pugliese, D.; Stuchlík, Z.

    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.

  19. A General Relativistic Magnetohydrodynamic Simulation of Jet Formation

    NASA Technical Reports Server (NTRS)

    Nishikawa, K.-I.; Richardson, G.; Koide, S.; Shibata, K.; Kudoh, T.; Hardee, P.; Fishman, G. J.

    2005-01-01

    We have performed a fully three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulation ofjet formation from a thin accretion disk around a Schwarzschild black hole with a free-falling corona. The initial simulation results show that a bipolar jet (velocity approx.0.3c) is created, as shown by previous two-dimensional axi- symmetric simulations with mirror symmetry at the equator. The three-dimensional simulation ran over 100 light crossing time units (T(sub s) = r(sub s)/c, where r(sub s = 2GM/c(sup 2), which is considerably longer than the previous simulations. We show that the jet is initially formed as predicted owing in part to magnetic pressure from the twisting of the initially uniform magnetic field and from gas pressure associated with shock formation in the region around r = 3r(sub s). At later times, the accretion disk becomes thick and the jet fades resulting in a wind that is ejected from the surface ofthe thickened (torus-like) disk. It should be noted that no streaming matter from a donor is included at the outer boundary in the simulation (an isolated black hole not binary black hole). The wind flows outward with a wider angle than the initial jet. The widening of the jet is consistent with the outward-moving torsional Alfven waves. This evolution of disk-jet coupling suggests that the jet fades with a thickened accretion disk because of the iack of streaming materiai from an accompanying star.

  20. Interference in multilayer relativistic mirrors

    NASA Astrophysics Data System (ADS)

    Mirzanejhad, Saeed; Sohbatzadeh, Farshad; Babaei, Javad; Taghipour, Meisam; Mohammadzadeh, Zahra

    2015-10-01

    In this paper, reflection coefficient of a relativistic ultra-thin electron multilayer is calculated using electromagnetic interference procedures. The relativistic electron layers are assumed to be formed by nonlinear plasma wake waves that constitute the electron density cusps. It is shown that the interference between successive relativistic mirrors is restricted by the condition, τ p ≫ ( 2 γ 0 ) 5 / 2 / ω p 0 , where τp is the laser pulse duration. The results showed that tailoring the pulse amplitude, incident wave frequency value, incidence angle, and plasma density leads to increasing reflection coefficient a few orders of magnitudes. This constructive interference condition can be used for increasing conversion efficiency in the reflected energy from relativistic mirrors for the purpose of generating ultra-short coherence pulses in the extreme ultraviolet and x-ray regions. We also performed reflection from relativistic thin electron layers using relativistic 1D3V electromagnetic particle-in-cell (PIC) simulation. It was found that the results of PIC simulation are in agreement with analytical considerations.

  1. Polyanalytic relativistic second Bargmann transforms

    SciTech Connect

    Mouayn, Zouhaïr

    2015-05-15

    We construct coherent states through special superpositions of eigenstates of the relativistic isotonic oscillator. In each superposition, the coefficients are chosen to be L{sup 2}-eigenfunctions of a σ-weight Maass Laplacian on the Poincaré disk, which are associated with the eigenvalue 4m(σ−1−m), m∈Z{sub +}∩[0,(σ−1)/2]. For each nonzero m, the associated coherent states transform constitutes the m-true-polyanalytic extension of a relativistic version of the second Bargmann transform, whose integral kernel is expressed in terms of a special Appel-Kampé de Fériet’s hypergeometric function. The obtained results could be used to extend the known semi-classical analysis of quantum dynamics of the relativistic isotonic oscillator.

  2. Tunable mid-IR parametric conversion system pumped by a high-average-power picosecond Yb:YAG thin-disk laser

    NASA Astrophysics Data System (ADS)

    Novák, Ondřej; Miura, Taisuke; Smrž, Martin; Huynh, Jaroslav; Severová, Patricie; Endo, Akira; Mocek, TomáÅ.¡

    2014-05-01

    The mid-IR wavelength range has gained increased interest due to its applications in gas sensing, medicine, defense, and others. Optical parametric devices play an important role in the generation of radiation in the mid-IR. Low thermal load of nonlinear crystals promises high average power outputs if powerful pump laser is available. We have developed 75-W average power pump laser operating at 100 kHz repetition rate. The pulses of Yb-fiber laser oscillator at 1030-nm wavelength are stretched by a chirped volume Bragg grating from 5 ps to 180 ps and inserted into a cavity of regenerative amplifier with an Yb:YAG thin-disk. The amplified pulses are compressed by a chirped volume Bragg grating with an 88% efficiency. We have proposed a wavelength conversion system generating picosecond pulses tunable between 2 and 3 μm. The seed signal radiation is acquired by the optical parametric generation in the first nonlinear crystal. Signal pulse energy is increased in the subsequent optical parametric amplifiers. Each amplification stage consists of a crystal pair in the walkoff compensating arrangement. The wavelength of the signal beam is tunable between 1.6 and 2.1 μm. The 2.1 - 3 μm tunable source will be the idler beam taken from the last amplification stage. Calculations show the output power of ten watt can be achieved for 100 W pump. The results of preliminary experiments with seeded optical parametric generation and subsequent amplification are presented and discussed.

  3. Gravitomagnetic acceleration from black hole accretion disks

    NASA Astrophysics Data System (ADS)

    Poirier, J.; Mathews, G. J.

    2016-05-01

    We demonstrate how the motion of the neutral masses in an accretion disk orbiting a black hole creates a general-relativistic magnetic-like (gravitomagnetic) field that vertically accelerates neutral particles near an accretion disk upward and then inward toward the axis of the accretion disk. Even though this gravitomagnetic field is not the only mechanism contributing to the production of jets, it presents a novel means to identify one general relativistic effect from a much more complicated problem. In addition, as the accelerated material above or below the accretion disk nears the axis with a nearly vertical direction, a frame-dragging effect twists the trajectories around the axis thus contributing to the collimation of the jet.

  4. GRMHD/RMHD Simulations and Stability of Magnetized Spine-Sheath Relativistic Jets

    NASA Technical Reports Server (NTRS)

    Hardee, Philip; Mizuno, Yosuke; Nishikawa, Ken-Ichi

    2007-01-01

    A new general relativistic magnetohydrodynamics (GRMHD ) code "RAISHIN" used to simulate jet generation by rotating and non-rotating black holes with a geometrically thin Keplarian accretion disk finds that the jet develops a spine-sheath structure in the rotating black hole case. Spine-sheath structure and strong magnetic fields significantly modify the Kelvin-Helmholtz (KH) velocity shear driven instability. The RAISHIN code has been used in its relativistic magnetohydrodynamic (RMHD) configuration to study the effects of strong magnetic fields and weakly relativistic sheath motion, cl2, on the KH instability associated with a relativistic, Y = 2.5, jet spine-sheath interaction. In the simulations sound speeds up to ? c/3 and Alfven wave speeds up to ? 0.56 c are considered. Numerical simulation results are compared to theoretical predictions from a new normal mode analysis of the RMHD equations. Increased stability of a weakly magnetized system resulting from c/2 sheath speeds and stabilization of a strongly magnetized system resulting from d 2 sheath speeds is found.

  5. Optical Disks.

    ERIC Educational Resources Information Center

    Gale, John C.; And Others

    1985-01-01

    This four-article section focuses on information storage capacity of the optical disk covering the information workstation (uses microcomputer, optical disk, compact disc to provide reference information, information content, work product support); use of laser videodisc technology for dissemination of agricultural information; encoding databases…

  6. Relativistic diffusion

    NASA Astrophysics Data System (ADS)

    Haba, Z.

    2009-02-01

    We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution. We discuss drag terms leading to an equilibrium distribution. The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Jüttner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed.

  7. Relativistic diffusion.

    PubMed

    Haba, Z

    2009-02-01

    We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution. We discuss drag terms leading to an equilibrium distribution. The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Jüttner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed. PMID:19391727

  8. Design of a tunable parametric wavelength conversion system between 2 and 3 μm pumped by a high-average-power Yb:YAG thin-disk laser

    NASA Astrophysics Data System (ADS)

    Novák, Ondřej; Miura, Taisuke; Severová, Patricie; Endo, Akira; Mocek, Tomáš

    2013-05-01

    With increasing energy densities of laser pulses the laser induced damage threshold (LIDT) testing becomes an important characterization of optical components. The emission wavelength of several laser materials is in the 2 - 3 μm wavelength-range. We propose a wavelength conversion system generating tunable sub-ns pulses for LIDT measurements in this IR spectral range. The pump beam of the conversion system will be based on the thin-disk laser technology. The Yb-fiber-laser seeded CPA system with high-energy Yb:YAG thin-disk regenerative amplifier will produce uncompressed pulses of 0.5 ns width, 130 mJ energy, at wavelength of 1030 nm with 1 kHz repetition rate giving 130 W of average power. Output of the thin-disk regenerative amplifier will pump an optical parametric generator (OPG) and subsequent optical parametric amplifiers (OPA). The tunable output wavelength of the OPG will be between 1.5 μm - 2.1 μm for the signal beam and between 2.1 μm - 3 μm for the idler beam. The signal will be amplified in the OPAs because the optics and diagnostics is more easily available below 2 μm wavelength. The tunable multi-millijoule source above 2.1 μm will be the idler beam taken from the last amplification stage. High-average output power of 10 W at 1 kHz repetition rate will be unique among 2 - 3 μm tunable systems. Operation of the amplifiers at high-intensities and high-average powers limits the system performance. The thermal load of crystals caused by the partial beam absorption will be studied. Further, the damage threshold of optical components, transmission range of nonlinear crystals, and amplifiers bandwidths will be addressed.

  9. Magnetic disk

    NASA Technical Reports Server (NTRS)

    Mallinson, John C.

    1991-01-01

    Magnetic disk recording was invented in 1953 and has undergone intensive development ever since. As a result of this 38 years of development, the cost per byte and the areal density has halved and doubled, respectively every 2 to 2 1/2 years. Today, the cost per byte is lower than 10(exp -6) dollars per byte and area densities exceed 100 x 10(exp 6) bits per square inch. The recent achievements in magnetic disk recording will first be surveyed briefly. Then the principal areas of current technical development will be outlined. Finally, some comments will be made about the future of magnetic disk recording.

  10. 3-D GRMHD Simulations of Disk-Jet Coupling and Emission

    NASA Astrophysics Data System (ADS)

    Nishikawa, K.-I.; Mizuno, Y.; Fuerst, S.; Wu, K.; Hardee, P.; Richardson, G.; Koide, S.; Shibata, K.; Kudoh, T.; Fishman, G. J.

    2005-11-01

    We have performed a fully three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulation of jet formation from a thin accretion disk around a Schwarzschild black hole with a free-falling corona. The initial simulation results show that a bipolar jet (velocity ~ 0.3c) is created as shown by previous two-dimensional axisymmetric simulations with mirror symmetry at the equator. The 3-D simulation ran over one hundred light-crossing time units (τS = rS/c where rS ≡ 2GM/c2) which is considerably longer than the previous simulations. We show that the jet is initially formed as predicted due in part to magnetic pressure from the twisting the initially uniform magnetic field and from gas pressure associated with shock formation in the region around r = 3rS. At later times, the accretion disk becomes thick and the jet fades resulting in a wind that is ejected from the surface of the thickened (torus-like) disk. It should be noted that no streaming matter from a donor is included at the outer boundary in the simulation (an isolated black hole not binary black hole). The wind flows outwards with a wider angle than the initial jet. The widening of the jet is consistent with the outward moving torsional Alfvén waves (TAWs). This evolution of disk-jet coupling suggests that the jet fades with a thickened accretion disk due to the lack of streaming material from an accompanying star. We have also calculated the free-free emission from a disk/outflow near a rotating black hole using our axisymmetric GRMHD simulation using a covariant radiative transfer formulation. Our calculation shows radiation from a shock, and hence the disk-jet coupling region is observable.