WorldWideScience

Sample records for brillouin scattering instability

  1. Thomson-scattering study of the subharmonic decay of ion-acoustic waves driven by the Brillouin instability

    International Nuclear Information System (INIS)

    Bandulet, H.C.; Labaune, C.; Lewis, K.; Depierreux, S.

    2004-01-01

    Thomson scattering (TS) has been used to investigate the two-ion decay instability of ion acoustic waves generated by stimulated Brillouin scattering in an underdense CH plasma. Two complementary TS diagnostics, spectrally and spatially resolved, demonstrate the occurrence of the subharmonic decay of the primary ion acoustic wave into two secondary waves. The study of the laser intensity dependence shows that the secondary ion acoustic waves are correlated with the SBS reflectivity saturation, at a level of a few percent

  2. Brillouin scattering at high pressures

    International Nuclear Information System (INIS)

    Grimsditch, M.; Polian, A.

    1988-02-01

    Technical advances which have made Brillouin scattering a useful tool in high pressure diamond anvil cell (DAC) studies, viz. multipassing and tandem operation of Fabry-Perot interferometers, are reviewed. Experimental aspects, such as allowed scattering geometries, are outlined and the data analysis required to transform Brillouin spectra into sound velocities and elastic constants is presented. Experimental results on H 2 , N 2 , Ar, and He are presented, and the close relationship between the Brillouin scattering results and equations of state is highlighted

  3. Shear Brillouin light scattering microscope.

    Science.gov (United States)

    Kim, Moonseok; Besner, Sebastien; Ramier, Antoine; Kwok, Sheldon J J; An, Jeesoo; Scarcelli, Giuliano; Yun, Seok Hyun

    2016-01-11

    Brillouin spectroscopy has been used to characterize shear acoustic phonons in materials. However, conventional instruments had slow acquisition times over 10 min per 1 mW of input optical power, and they required two objective lenses to form a 90° scattering geometry necessary for polarization coupling by shear phonons. Here, we demonstrate a confocal Brillouin microscope capable of detecting both shear and longitudinal phonons with improved speeds and with a single objective lens. Brillouin scattering spectra were measured from polycarbonate, fused quartz, and borosilicate in 1-10 s at an optical power level of 10 mW. The elastic constants, phonon mean free path and the ratio of the Pockels coefficients were determined at microscopic resolution.

  4. Stimulated Brillouin scattering experiments

    International Nuclear Information System (INIS)

    Slater, D.C.; Berger, R.L.; Busch, G.; Kinzer, C.M.; Mayer, F.J.; Powers, L.V.; Tanner, D.J.

    1981-01-01

    This report describes two experiments in which SBS would be expected to play an important role. In the first experiment, we find a clear signature of the Brillouin backscatter of a short (100 psec) pulse from a long (approx. 50 μm) gradient length gas target plasma. The second experiment used much longer (approx. 1 nsec) pulses on spherical glass shell targets. These experiments were done with both narrow ( 30A) bandwidth laser light. Using one-dimensional, spherically symmetric fluid simulations, we have attempted to model many of the laser-plasma interaction processes which combine to determine the amount of absorbed energy in the long-pulse experiments. These simulations indicate that modest laser bandwidths are successful in reducing the level of SBS at the irradiances ( 15 W/cm 2 ) used in these experiments

  5. Transient effects on stimulated Brillouin scattering

    International Nuclear Information System (INIS)

    Faris, G.W.; Dyer, M.J.; Hickman, A.P.

    1992-01-01

    We present a detailed comparison of theory and experiment for transient stimulated Brillouin scattering for a pump pulse with Gaussian temporal profile. A new approach for measuring Brillouin linewidths is demonstrated, and an unexplained asymmetry is observed

  6. Neutron Brillouin scattering in dense fluids

    Energy Technology Data Exchange (ETDEWEB)

    Verkerk, P. [Technische Univ. Delft (Netherlands); FINGO Collaboration

    1997-04-01

    Thermal neutron scattering is a typical microscopic probe for investigating dynamics and structure in condensed matter. In contrast, light (Brillouin) scattering with its three orders of magnitude larger wavelength is a typical macroscopic probe. In a series of experiments using the improved small-angle facility of IN5 a significant step forward is made towards reducing the gap between the two. For the first time the transition from the conventional single line in the neutron spectrum scattered by a fluid to the Rayleigh-Brillouin triplet known from light-scattering experiments is clearly and unambiguously observed in the raw neutron data without applying any corrections. Results of these experiments are presented. (author).

  7. Brillouin Instability in Fiber Lasers Doped By Power | Bouras ...

    African Journals Online (AJOL)

    The effect of Brillouin back scattering is theoretically analysed by two-coupled modes laser model. We consider the Fabry-Perot fiber laser cavity. The rich and complex dynamic behaviours are observed. In particular the quasi periodic dynamic is identified and studied. Keywords: Stimulated Brillouin Scattering; high power ...

  8. Stimulated Brillouin scattering of electromagnetic Alfven waves in a plasma

    International Nuclear Information System (INIS)

    Sharma, R.R.; Sharma, R.C.; Sharma, O.P.

    1981-01-01

    The phenomenon of stimulated Brillouin scattering of electromagnetic Alfven waves in a plasma is investigated by employing fluid model approach. The low frequency nonlinearity of ion acoustic wave arises through the ponderomotive force on ions and high frequency nonlinearity arises through the equation of continuity. For a typical isothermal plasma (Tsub(e)/Tsub(i)approx.=10), Alfven wave frequency ω 0 approx.=10 6 rad. sec -1 , the threshold for this instability in a uniform plasma is approx.= milliwatt cm -2 . Above the threshold, the growth rate for forward and back scatterings are approx.=10 -3 rad.sec -1 and approx.=10 -4 rad.sec. -1 , respectively. (author)

  9. Limitation of brillouin scatter in plasmas

    International Nuclear Information System (INIS)

    Kruer, W.L.; Valeo, E.J.; Estabrook, K.G.

    1975-01-01

    A simple model is proposed for the limitation of Brillouin backscatter often observed experimentally. This limitation is a natural consequence of the limited mass and heat capacity of the underdense plasma. In this model a reflection front moves through the underdense plasma supersonically. For plasmas prepared by a prepulse, the reflectivity could then be time-dependent in agreement with some recent experimental measurements. (U.S.)

  10. Electron Gyro-Harmonic Effects on Ionospheric Stimulated Brillouin Scatter

    Science.gov (United States)

    2014-08-21

    SECURITY CLASSIFICATION OF: Stimulated Brillouin scattering (SBS) and resonant phenomena are well known in the context of laser fusion, fiber optics ... fiber optics , and piezoelectric semiconductor plasmas, as well as in various biological applications. Due to recent advances, active space experiments... fiber optics , and piezoelectric semiconductor plasmas, as well as in various biological applications. Due to recent advances, active space

  11. High-speed stimulated Brillouin scattering spectroscopy at 780 nm

    Directory of Open Access Journals (Sweden)

    Itay Remer

    2016-09-01

    Full Text Available We demonstrate a high-speed stimulated Brillouin scattering (SBS spectroscopy system that is able to acquire stimulated Brillouin gain point-spectra in water samples and Intralipid tissue phantoms over 2 GHz within 10 ms and 100 ms, respectively, showing a 10-100 fold increase in acquisition rates over current frequency-domain SBS spectrometers. This improvement was accomplished by integrating an ultra-narrowband hot rubidium-85 vapor notch filter in a simplified frequency-domain SBS spectrometer comprising nearly counter-propagating continuous-wave pump-probe light at 780 nm and conventional single-modulation lock-in detection. The optical notch filter significantly suppressed stray pump light, enabling detection of stimulated Brillouin gain spectra with substantially improved acquisition times at adequate signal-to-noise ratios (∼25 dB in water samples and ∼15 dB in tissue phantoms. These results represent an important step towards the use of SBS spectroscopy for high-speed measurements of Brillouin gain resonances in scattering and non-scattering samples.

  12. Nonlinear Fluid Simulation Study of Stimulated Raman and Brillouin Scatterings in Shock Ignition

    Science.gov (United States)

    Ren, Chuang; Hao, Liang; Yan, Rui; Li, Jun; Liu, Wenda

    2017-10-01

    We developed a new nonlinear fluid laser-plasma-instability code FLAME using a multi-fluid plasma model combined with full electromagnetic wave equations. The completed one-dimensional (1D) version of FLAME was used to study laser-plasma instabilities in shock ignition. The simulations results showed that absolute Stimulated Raman Scattering (SRS) modes growing near the quarter-critical surface were saturated by Langmuir-wave Decay Instabilities (LDI) and pump depletion. The ion-acoustic waves from LDI acted as seeds of Stimulated Brillouin Scattering (SBS), which displayed a bursting pattern and caused strong pump depletion. Re-scattering of SRS was also observed in a high temperature case. These results largely agreed with corresponding Particle-in-Cell simulations. Work funded by DOE (DE-SC0012316), NSF (PHY-1314734), NSFC (11642020, 11621202), and Science Challenge Project (No. JCKY2016212A505).

  13. Extreme temperature sensing using brillouin scattering in optical fibers

    CERN Document Server

    Fellay, Alexandre

    Stimulated Brillouin scattering in silica-based optical fibers may be considered from two different and complementary standpoints. For a physicist, this interaction of light and pressure wave in a material, or equivalently in quantum theory terms between photons and phonons, gives some glimpses of the atomic structure of the solid and of its vibration modes. For an applied engineer, the same phenomenon may be put to good use as a sensing mechanism for distributed measurements, thanks to the dependence of the scattered light on external parameters such as the temperature, the pressure or the strain applied to the fiber. As far as temperature measurements are concerned, Brillouin-based distributed sensors have progressively gained wide recognition as efficient systems, even if their rather high cost still restricts the number of their applications. Yet they are generally used in a relatively narrow temperature range around the usual ambient temperature; in this domain, the frequency of the scattered light incre...

  14. Momentum transfer in a Brillouin surface scattering

    International Nuclear Information System (INIS)

    Khater, A.F.

    1980-01-01

    The theory of acoustic excitation scattering in the surface of Brilloiun of opaque materials, is related to the question of momentum transfexed from radiation fields to the material when the incident eight is scattered in a measurable spectrum. (A.C.A.S.) [pt

  15. SBS [stimulated Brillouin scattering] pulse distortion in multimode optical fibers

    International Nuclear Information System (INIS)

    Smith, J.R.; Hawkins, R.J.; Laumann, C.W.; Hatch, J.

    1989-01-01

    We have observed sever temporal-pulse-shape distortion due to stimulated Brillouin scattering (SBS) in multimode optical fibers used to diagnose 351 m laser pulses on the Nova laser system. Our measurements can be fit by a basic model of SBS and provide a clear indication of the intensity and temporal regimes where significant SBS-induced temporal-pulse-shape distortion can be avoided. 15 refs., 3 figs., 1 tab

  16. Linear approximation of Rayleigh-Brillouin scattering spectra.

    Science.gov (United States)

    Binietoglou, Ioannis; Giampouras, Paris; Belegante, Livio

    2016-09-20

    Rayleigh-Brillouin scattering is the basis of many remote sensing techniques, including high spectral resolution lidar measurements of aerosols and wind. Rayleigh-Brillouin spectra can be accurately estimated using physics-based models like the so-called Tenti's S6 and Pan's S7 models. Unfortunately, these are computationally expensive and can be the bottleneck for real-time lidar processing and iterative parameter estimation problems. This short article describes a very efficient linear approximation of the Rayleigh-Brillouin spectra based on Principal Component Analysis (PCA). Using PCA, the outputs of the above models can be approximated with very high accuracy using a single matrix multiplication. The described method can be applied to the output of any detailed scattering model, thus it can be used for a wide range of problems, e.g., for scattering from different gases (Air, N2, O2,…) and for different ranges of temperature and pressure. The precision of the approximation can be adapted to the requirements of the studied problem, and can easily exceed the actual accuracy of the reference models.

  17. Stimulated Brillouin scattering materials, experimental design and applications: A review

    Science.gov (United States)

    Bai, Zhenxu; Yuan, Hang; Liu, Zhaohong; Xu, Pengbai; Gao, Qilin; Williams, Robert J.; Kitzler, Ondrej; Mildren, Richard P.; Wang, Yulei; Lu, Zhiwei

    2018-01-01

    Stimulated Brillouin scattering (SBS), as one type of third-order nonlinear optics effect, is extensively exploited and rapidly developed in the field of lasers and optoelectronics. A large number of theoretical and experimental studies on SBS have been carried out in the past decades. Especially, the exploration of new SBS materials and new types of SBS modulation methods have been engaged simultaneously, as the properties of different materials have great influence on the SBS performance such as generation threshold, Brillouin amplification efficiency, frequency shift, breakdown threshold, etc. This article provides a comprehensive review of the characteristics of different types of SBS materials, SBS applications, experimental design methods, as well as the parameter optimization method, which is expected to provide reference and guidance to SBS related experiments.

  18. Stimulated Brillouin scattering in long-scale-length laser plasmas

    International Nuclear Information System (INIS)

    Chirokikh, A.; Seka, W.; Simon, A.; Craxton, R.S.; Tikhonchuk, V.T.

    1998-01-01

    Brillouin scattering from a preformed, inhomogeneous, expanding plasma has been investigated. Backscattered light near the incident laser wavelength (λ=1054 nm) from CH planar targets has been spectrally and temporally resolved. By varying the time delay of the interaction beam, the scattering was studied for different plasma conditions. The backscattered light is predominantly blue-shifted and appears before the peak of the laser pulse. The experimental time-integrated reflectivity of backscattered light is in the range of 1%endash 10% and decreases with the plasma density. The time-resolved spectra and total reflectivity were calculated using a theory of convective stimulated Brillouin scattering (SBS) in a flowing inhomogeneous plasma combined with a statistical hot spot model for the interaction beam. The plasma parameters for these calculations were provided by simulations using a two-dimensional hydrodynamic code. The calculated SBS spectra are similar to the experimental observations. The time-integrated reflectivities agree well with the experimental results for the higher peak density interactions, but are below the observations by orders of magnitude for the lowest peak density cases. copyright 1998 American Institute of Physics

  19. Stimulated brillouin scattering of electromagnetic waves in a dusty plasma

    International Nuclear Information System (INIS)

    Salimullah, M.; Sen, A.

    1991-08-01

    The stimulated Brilluoin scattering of electromagnetic waves in a homogeneous, unmagnetized and collisionless dusty plasma has been investigated theoretically. The Vlasov equation has been solved perturbatively to find the nonlinear response of the plasma particles. The presence of the dust particles introduces a background inhomogeneous electric field which significantly influences the dispersive properties of the plasma. At the ion acoustic branch we find the usual scattering slightly modified by the charged dust grains. However, at the frequency lower than the ion acoustic branch we find a new mode of the plasma arising from the oscillations of the ions in the static structure of the dust distribution. This low frequency branch causes enhanced stimulated Brillouin scattering of electromagnetic waves in a dusty plasma. (author). 15 refs

  20. Spontaneous Rayleigh-Brillouin scattering spectral analysis based on Wiener filter

    Science.gov (United States)

    Shang, Jingcheng; Wu, Tao; Yang, Chuanyin; Yu, Huan; He, Xingdao

    2017-10-01

    In this paper, a spontaneous Rayleigh-Brillouin scattering spectrometer is developed to measure the gaseous spontaneous Rayleigh-Brillouin scattering (SRBS) profiles over the pressure range 1 to 6 atm for a wavelength of 532nm at the constant room temperature of 296K and 900 scattering angle. The measured Rayleigh-Brillouin scattering spectra are deconvolved using Wiener filtering to remove the effect of the Airy transmission function of the Fabry-Pérot scanning interferometer and get high resolution Rayleigh-Brillouin scattering spectra. The root-mean-square error is less than 2% and χ 2 is less than 15 over the pressure range 1 to 6 atm. The comparison between theoretical spectra (Tenti S6 model) and deconvolved Rayleigh-Brillouin scattering spectra is made. Some factors that effected the deconvolution of accuracy are analyzed and discussed.

  1. Brillouin light scattering from surface acoustic waves in a subwavelength-diameter optical fibre.

    Science.gov (United States)

    Beugnot, Jean-Charles; Lebrun, Sylvie; Pauliat, Gilles; Maillotte, Hervé; Laude, Vincent; Sylvestre, Thibaut

    2014-10-24

    Brillouin scattering in optical fibres is a fundamental interaction between light and sound with important implications ranging from optical sensors to slow and fast light. In usual optical fibres, light both excites and feels shear and longitudinal bulk elastic waves, giving rise to forward-guided acoustic wave Brillouin scattering and backward-stimulated Brillouin scattering. In a subwavelength-diameter optical fibre, the situation changes dramatically, as we here report with the first experimental observation of Brillouin light scattering from surface acoustic waves. These Rayleigh-type surface waves travel the wire surface at a specific velocity of 3,400 m s(-1) and backscatter the light with a Doppler shift of about 6 GHz. As these acoustic resonances are sensitive to surface defects or features, surface acoustic wave Brillouin scattering opens new opportunities for various sensing applications, but also in other domains such as microwave photonics and nonlinear plasmonics.

  2. Brillouin Scattering Spectrum Analysis Based on Auto-Regressive Spectral Estimation

    Science.gov (United States)

    Huang, Mengyun; Li, Wei; Liu, Zhangyun; Cheng, Linghao; Guan, Bai-Ou

    2018-03-01

    Auto-regressive (AR) spectral estimation technology is proposed to analyze the Brillouin scattering spectrum in Brillouin optical time-domain refelectometry. It shows that AR based method can reliably estimate the Brillouin frequency shift with an accuracy much better than fast Fourier transform (FFT) based methods provided the data length is not too short. It enables about 3 times improvement over FFT at a moderate spatial resolution.

  3. Brillouin light scattering spectroscopy for tissue engineering application

    Science.gov (United States)

    Akilbekova, Dana; Yakupov, Talgat; Ogay, Vyacheslav; Umbayev, Bauyrzhan; Yakovlev, Vladislav V.; Utegulov, Zhandos N.

    2018-02-01

    Biomechanical properties of mammalian bones, such as strength, toughness and plasticity, are essential for understanding how microscopic scale mechanical features can link to macroscale bones' strength and fracture resistance. We employ Brillouin light scattering (BLS) micro-spectroscopy for local assessment of elastic properties of bones under compression and the efficacy of the tissue engineering approach based on heparin-conjugated fibrin (HCF) hydrogels, bone morphogenic proteins (BMPs) and osteogenic stem cells in the regeneration of the bone tissues. BLS is noninvasive and label-free imaging modality for probing mechanical properties of hard tissues that can give information on structure-function properties of normal and pathological tissues. Results showed that HCF gels containing combination of all factors had the best effect with complete defect regeneration at week 9 and that the bones with fully consolidated fractures have higher values of elastic moduli compared to the bones with defects.

  4. BRILLOUIN INSTABILITY IN FIBER LASERS DOPED BY POWER ...

    African Journals Online (AJOL)

    afin de décrire l'évolution temporelle du milieu amplificateur. On ne tient pas compte des ordres supérieurs des composantes Stokes. Le gain de la diffusion Brillouin n'est plus considéré comme instantané [1]. Les ondes sont décrites en termes d'amplitudes des champs optiques et acoustique et des conditions aux limites.

  5. Multi-wavelength Praseodymium fiber laser using stimulated Brillouin scattering

    Science.gov (United States)

    Ahmad, H.; Aidit, S. N.; Tiu, Z. C.

    2018-02-01

    A multi-wavelength Brillouin Praseodymium fiber laser (MWBPFL) operating at 1300 nm region is demonstrated based on the hybrid scheme by utilizing Brillouin gain medium and Praseodymium-doped fluoride fiber as linear gain medium. A 15 μm air gap is incorporated into the cavity to allow the switching of Brillouin frequency spacing from double to single spacing. Under the Brillouin pump of 8 dBm and the 1020 nm pump power of 567.2 mW, 36 Stokes lines with a wavelength spacing of 0.16 nm and 24 Stokes lines with a wavelength spacing of 0.08 nm are achieved. The wavelength tunability of 8 nm is realized for both MWBPFLs by shifting the Brillouin pump wavelength. The MWBPFLs exhibit an excellent stability in the number of generated Stokes and power level over one-hour period.

  6. Anti-Stokes scattering and Stokes scattering of stimulated Brillouin scattering cascade in high-intensity laser-plasma interaction

    Science.gov (United States)

    Feng, Q. S.; Liu, Z. J.; Zheng, C. Y.; Xiao, C. Z.; Wang, Q.; Zhang, H. C.; Cao, L. H.; He, X. T.

    2017-07-01

    Anti-Stokes scattering and Stokes scattering in stimulated Brillouin scattering (SBS) cascades have been researched using the Vlasov-Maxwell simulation. In high-intensity laser-plasma interactions, stimulated anti-Stokes Brillouin scattering (SABS) will occur after second stage SBS rescattering. The mechanism of SABS has been put forward to explain this phenomenon. In the early phase of SBS evolution, only first stage SBS appears and total SBS reflectivity comes from first stage SBS. However, when high-stage SBS and SABS occur, SBS reflectivity will display burst behavior and the total reflectivity comes from the SBS cascade and SABS superimposition. The SABS will compete with the SBS rescattering to determine the total SBS reflectivity. Thus, SBS rescattering including SABS is an important saturation mechanism of SBS and should be taken into account in high-intensity laser-plasma interaction.

  7. Wide-range temperature dependences of Brillouin scattering properties in polymer optical fiber

    Science.gov (United States)

    Minakawa, Kazunari; Hayashi, Neisei; Shinohara, Yuri; Tahara, Masaki; Hosoda, Hideki; Mizuno, Yosuke; Nakamura, Kentaro

    2014-04-01

    We investigate the temperature dependences of the Brillouin scattering properties in a perfluorinated graded-index (PFGI-) polymer optical fiber (POF) in a wide temperature range from -160 to 125 °C. The temperature dependences of the Brillouin frequency shift, linewidth, and Stokes power are almost linear at lower temperature down to -160 °C while they show nonlinear dependences at higher temperature. These behaviors appear to originate from the partial glass transition of the polymer material.

  8. Brillouin scattering, piezobirefringence, and dispersion of photoelastic coefficients of CdS and ZnO

    DEFF Research Database (Denmark)

    Berkowicz, R.; Skettrup, Torben

    1975-01-01

    We have measured the dispersion of the Brillouin scattering from acoustoelectrical domains in CdS and ZnO. These spectra are compared with the birefringence spectra obtained by applying uniaxial stress. The resonant cancellation of the Brillouin scattering occurs at the spectral position of the i......We have measured the dispersion of the Brillouin scattering from acoustoelectrical domains in CdS and ZnO. These spectra are compared with the birefringence spectra obtained by applying uniaxial stress. The resonant cancellation of the Brillouin scattering occurs at the spectral position...... of the isotropic point of the stress-induced birefringence. From these spectra it is concluded that the Brillouin scattering in CdS and ZnO is determined by elasto-optic effects alone. The spectra of some of the photoelastic coefficients have been determined. A model dielectric constant is derived where both....... It is found that the exchange interaction between the excitons may change the values of the photoelastic coefficients in ZnO about 10%....

  9. Spontaneous Rayleigh-Brillouin scattering of ultraviolet light in nitrogen, dry and moist air

    NARCIS (Netherlands)

    Witschas, B.; Vieitez, M.O.; van Duijn, E.-J.; Reitebuch, O.; Van de Water, W.; Ubachs, W.M.G.

    2010-01-01

    Atmospheric lidar techniques for the measurement of wind, temperature, and optical properties of aerosols rely on the exact knowledge of the spectral line shape of the scattered laser light on molecules. We report on spontaneous Rayleigh-Brillouin scattering measurements in the ultraviolet at a

  10. High-pressure Brillouin scattering in a simple molecular system

    CERN Document Server

    Shimizu, H

    2002-01-01

    Recent developments in high-pressure in situ Brillouin spectroscopy of a simple molecular system are reviewed by demonstrating experimental and analytical methods for the study of acoustic velocities in any direction, adiabatic elastic constants, and elastic anisotropy. Detailed applications to solid argon (Ar) are presented, at pressures up to 70 GPa in a diamond anvil cell, using recently developed approaches that combine the method of in situ Brillouin spectroscopy, for a single crystal of Ar up to 4 GPa, and the envelope method applied to both longitudinal acoustic and transverse acoustic modes, for recrystallized Ar between 4 and 70 GPa.

  11. Stimulated Brillouin scattering of the beat wave of two lasers in a plasma

    International Nuclear Information System (INIS)

    Panwar, Anuraj; Sharma, A. K.

    2009-01-01

    Stimulated Brillouin scattering of two collinear lasers in a plasma is investigated. Lasers exert a longitudinal ponderomotive force on electrons, imparting them oscillatory axial velocity at the beat frequency. This velocity acts as a driver for parametric excitation of an ion acoustic wave (ω,k-vector) and a noncollinear sideband electromagnetic wave (ω ' ,k-vector ' ). The driver velocity v-vector 0- couples to the sideband wave to exert a ponderomotive force at (ω,k-vector) on the electrons, driving the ion acoustic wave. The density perturbation of ion acoustic wave beats with v-vector 0- to produce a nonlinear current at (ω ' ,k-vector ' ), driving the sideband. In the case of finite spot size Gaussian laser beams, the beat wave has a Gaussian profile and excites an ion acoustic wave (ω,k-vector) and a backscattered TM mode (ω ' ,k-vector z ' ). The growth rate scales as the product of amplitudes of the lasers and maximizes at optimum values of scattering angles. The parametric instability of difference frequency driver is stronger than the sum frequency driver.

  12. Observation of acoustically induced modulation instability in a Brillouin photonic crystal fiber laser.

    Science.gov (United States)

    Stiller, Birgit; Sylvestre, Thibaut

    2013-05-01

    We report the experimental observation of self-induced modulation instability (MI) in a Brillouin fiber laser made with a solid-core photonic crystal fiber (PCF) with strong anomalous dispersion. We identify this MI as the result of parametric amplification of optical sidebands generated by guided acoustic modes within the core of the PCF. It is further shown that MI leads to passive harmonic mode locking and to the generation of a picosecond pulse train at a repetition rate of 1.15 GHz which matches the acoustic frequency of the fundamental acoustic mode of the PCF.

  13. Observation of depolarized guided acoustic-wave Brillouin scattering in partially uncoated optical fibers

    Science.gov (United States)

    Hayashi, Neisei; Set, Sze Yun; Yamashita, Shinji

    2018-02-01

    We observed the depolarized guided acoustic-wave Brillouin scattering (GAWBS) spectrum in a highly nonlinear fiber with a partially side-stripped polymer coat. The linewidth of the GAWBS spectral line at 941 MHz was measured to be 6.4 MHz, which was 0.9 times that of a coated fiber.

  14. Effects of hydrodynamics on Stimulated Brillouin Scattering in multiple plasma interaction

    International Nuclear Information System (INIS)

    Yahia, V.; Depierreux, S.; Goyon, C.; Loisel, G.; Borisenko, N. G.; Masson-Laborde, P. E.; Orekhov, A.; Rienecker, T.; Rosmej, O.; Labaune, C.

    2013-01-01

    In this paper, an experiment carried out on LULI2000 facility is presented. It was designed to investigate how two successive plasmas interact through hydrodynamic coupling and electromagnetic radiations. Contributions of both effects have been successfully identified and the effects of hydrodynamic coupling on Stimulated Brillouin Scattering has been observed. (authors)

  15. Temperature retrieval from Rayleigh-Brillouin scattering profiles measured in air

    NARCIS (Netherlands)

    Witschas, B.; Ubachs, W.M.G.

    2014-01-01

    In order to investigate the performance of two different algorithms for retrieving temperature from Rayleigh-Brillouin (RB) line shapes, RB scattering measurements have been performed in air at a wavelength of 403 nm, for a temperature range from 257 K to 330 K, and atmospherically relevant

  16. Rayleigh-Brillouin scattering profiles of air at different temperatures and pressures

    NARCIS (Netherlands)

    Gu, Z.; Witschas, B.; van der Water, W.; Ubachs, W.M.G.

    2013-01-01

    Rayleigh-Brillouin (RB) scattering profiles for air have been recorded for the temperature range from 255 to 340 K and the pressure range from 640 to 3300 mbar, covering the conditions relevant for the Earth's atmosphere and for planned atmospheric light detection and ranging (LIDAR) missions. The

  17. Suppression of Stimulated Brillouin Scattering in Optical Fibers Using a Linearly Chirped Diode Laser

    Science.gov (United States)

    2012-07-02

    output,” Proc. SPIE 7914, 79140B, 79140B-8 (2011). 9. C. G. Carlson, R. B. Ross, J. M. Schafer, J. B. Spring, and B. G. Ward, “Full vectorial analysis...Stimulated Brillouin scattering (SBS) is a major factor limiting the output power of a fiber laser. In a lossless, passive fiber, SBS occurs when the product

  18. Anti-Stokes scattering and Stokes scattering of stimulated Brillouin scattering cascade in high-intensity laser-plasmas interaction

    Science.gov (United States)

    Feng, Qingsong; Zheng, Chunyang; Liu, Zhanjun; Xiao, Chengzhuo; Wang, Qing; Cao, Lihua; He, Xiantu

    2017-10-01

    The anti-Stokes scattering and Stokes scattering in stimulated Brillouin scattering (SBS) cascade have been researched by the Vlasov-Maxwell simulation. In the high-intensity laser-plasmas interaction, the stimulated anti-Stokes Brillouin scattering (SABS) will occur after the second stage SBS rescattering. The mechanism of SABS has been put forward to explain this phenomenon. In the early time of SBS evolution, only the first stage SBS appears, and the total SBS reflectivity comes from the first stage SBS. However, when the high-stage SBS and SABS occur, the SBS reflectivity will appear a burst behavior, and the total reflectivity comes from the SBS cascade and SABS superimposition. The SABS will compete with the SBS rescattering to determine the total SBS reflectivity. Thus, the SBS rescattering including the SABS is an important saturation mechanism of SBS, and should be taken into account in the high-intensity laser-plasmas interaction. This research was supported by the National Natural Science Foundation of China (Grant Nos. 11375032, 11575035, 11475030 and 11435011), National Basic Research Program of China (Grant No. 2013CB834101) and Science Challenge Project, No. TZ2016005.

  19. Guided acoustic and optical waves in silicon-on-insulator for Brillouin scattering and optomechanics

    Directory of Open Access Journals (Sweden)

    Christopher J. Sarabalis

    2016-10-01

    Full Text Available We numerically study silicon waveguides on silica showing that it is possible to simultaneously guide optical and acoustic waves in the technologically important silicon on insulator (SOI material system. Thin waveguides, or fins, exhibit geometrically softened mechanical modes at gigahertz frequencies with phase velocities below the Rayleigh velocity in glass, eliminating acoustic radiation losses. We propose slot waveguides on glass with telecom optical frequencies and strong radiation pressure forces resulting in Brillouin gains on the order of 500 and 50 000 W−1m−1 for backward and forward Brillouin scattering, respectively.

  20. Guided acoustic and optical waves in silicon-on-insulator for Brillouin scattering and optomechanics

    Science.gov (United States)

    Sarabalis, Christopher J.; Hill, Jeff T.; Safavi-Naeini, Amir H.

    2016-10-01

    We numerically study silicon waveguides on silica showing that it is possible to simultaneously guide optical and acoustic waves in the technologically important silicon on insulator (SOI) material system. Thin waveguides, or fins, exhibit geometrically softened mechanical modes at gigahertz frequencies with phase velocities below the Rayleigh velocity in glass, eliminating acoustic radiation losses. We propose slot waveguides on glass with telecom optical frequencies and strong radiation pressure forces resulting in Brillouin gains on the order of 500 and 50 000 W-1m-1 for backward and forward Brillouin scattering, respectively.

  1. Brillouin-scattering measurements of the acoustic absorption coefficient in liquid CS2

    Science.gov (United States)

    Coakley, R. W.; Detenbeck, R. W.

    1975-01-01

    High-resolution Brillouin spectra were recorded for light scattered at small angles from liquid CS2. The use of a single-mode He-Ne laser, locked in frequency to a Fabry-Perot interferometer, permitted measurements of line widths of the order of 10 MHz for frequencies in the range 300-1000 MHz. These measurements extend previous Brillouin line-width measurements at higher frequencies into the region where relaxation effects are dominant and connect the optical measurements with lower-frequency acoustical data.

  2. Theoretical analysis and experiment performance of slow-light based on stimulated Brillouin scattering (SBS)

    International Nuclear Information System (INIS)

    Zhou Hongyan; Zhong Kun; Zhang Ru; Lang Peilin

    2011-01-01

    Slow light technology will play a key role in future all-optical communication. The slow-light technology based on stimulated Brillouin scattering has become a research highlight because of its additional advantages, such as compatibility of the devices with existing telecommunication systems, room-temperature operation, and tunable at arbitrary wavelengths. According to the propagation of a cw pulse through a Brillouin fiber amplifier, whose frequency is near the Stokes resonance, via three-wave coupling equations, both pump depletion and fiber losses taken into consideration, the principle of how slow-light effect based on stimulated Brillouin scattering produced and the mathematical expression of time delay are strictly deduced. A delay of 8 ns is obtained when the input Stokes pulse is 200ns and the SBS (stimulated Brillouin scattering) gain G is ∼18 in our designed experiment of SBS slow-light system. Then the extent of transformation from pump waves to Stokes waves is measured using MATLAB numerical simulation according to the experiment dates, based on the relation between output pump light power and input pump light power and also the relation between output Stokes light power and input pump light power. And the relation between the input light power and propagation distance is discussed as well. Finally the relation between slow light pulse delay and SBS gain is also obtained.

  3. Influence of core diameter and length of polymer optical fiber on Brillouin scattering properties

    Science.gov (United States)

    Mizuno, Yosuke; Ishigure, Takaaki; Nakamura, Kentaro

    2012-02-01

    Brillouin scattering in perfluorinated graded-index polymer optical fibers (PFGI-POFs) is potentially useful in developing high-accuracy distributed temperature sensors with reduced strain sensitivity. In this study, we investigate, both experimentally and theoretically, the influence of the fiber core diameter and length on the Brillouin gain spectra (BGS) in PFGI-POFs. First, we show that smaller core diameter drastically enhances the Stokes power using PFGI-POFs with 62.5-μm and 120-μm core diameters, and discuss the Brillouin threshold power. Then, we demonstrate that the PFGI-POF length has little influence on the BGS when the length is longer than 50 m. We also predict that, at 1.55-μm wavelength, it is difficult to reduce the Brillouin threshold power of PFGI-POFs below that of long silica single-mode fibers even if their core diameter is sufficiently reduced to satisfy the single-mode condition. Finally, making use of the enhanced Stokes signal, we confirm the Brillouin linewidth narrowing effect.

  4. An ultrawide tunable range single passband microwave photonic filter based on stimulated Brillouin scattering.

    Science.gov (United States)

    Xiao, Yongchuan; Guo, Jing; Wu, Kui; Qu, Pengfei; Qi, Huajuan; Liu, Caixia; Ruan, Shengping; Chen, Weiyou; Dong, Wei

    2013-02-11

    A single passband microwave photonic filter with ultrawide tunable range based on stimulated Brillouin scattering is theoretically analyzed. Combining the gain and loss spectrums, tuning range with 44GHz is obtained without crosstalk by introducing two pumps. Adding more pumps, Tuning range multiplying with the multiplication factor equaling to the total quantity of pump can be achieved, which has potential application in microwave and millimeter wave wireless communication systems.

  5. Rayleigh-Brillouin scattering in SF6 in the kinetic regime

    NARCIS (Netherlands)

    Wang, Yuanqing; Yu, Yin; Liang, Kun; Marques, Wilson; van de Water, Willem; Ubachs, Wim

    2017-01-01

    Rayleigh-Brillouin spectral profiles are measured with a laser-based scatterometry setup for a 90° scattering angle at a high signal-to-noise ratio (r.m.s. noise below 0.15% w.r.t. peak intensity) in sulfur-hexafluoride gas for pressures in the range 0.2–5 bar and for a wavelength of λ=403.0 nm. The

  6. Stimulated Brillouin scattering of an electromagnetic wave in weakly ...

    Indian Academy of Sciences (India)

    The importance of the laser–plasma interaction becomes an active field of research in the laser-fusion experiments, charged particle acceleration experiments, X-ray generation, propagation of EM waves in ionosphere etc. and the stimulated Bril- louin scattering (SBS) plays an important role in laser–plasma interaction as it.

  7. Rayleigh-Brillouin scattering in NH4Cl under hydrostatic pressure

    International Nuclear Information System (INIS)

    Hikita, Tomoyuki; Kitabatake, Makoto; Ikeda, Takuro

    1981-01-01

    Rayleigh-Brillouin scattering in NH 4 Cl has been studied under hydrostatic pressure. Brillouin shifts of the longitudinal phonons propagating along the and directions and of the transverse phonons propagating along the direction are measured as a function of temperature at four fixed pressures up to 2.3 kbar. All components increase almost linearly with decreasing temperature in the disordered phase and show incremental increases similar to the temperature dependence of the long range order parameter in the ordered phase. It was found that the longitudinal modes exhibit large despersion effect even at high pressures. On the other hand, the transverse mode appears to give no dispersion effect. The intensity of the Rayleigh component in the VV polarization condition increases as the temperature approaches the transition point, while that in the VH polarization does not show such anomalous increase. (author)

  8. A fully computerized multi-pass Fabry-Perot interferometer for Rayleigh-Brillouin scattering experiments

    International Nuclear Information System (INIS)

    Bohidar, H.; Berland, T.; Boger, F.; Joessang, T.; Feder, J.

    1987-01-01

    The development of a Multipass Fabry-Perot interforometer assembly for use in Rayleigh-Brillouin scattering experiments is reported. The optical alignment and the scattered signal data acquisition have been completely computerized. Digital scanning and alignment strategies of the Fabry-Perot resonator have been incorporated, which makes this instrument quite unique in this respect. The high contrast (∼10 10 ) and finesse (∼50) offered by this instrument makes it possible to detect Brillouin peaks from samples that have a small Brillouin scattering cross-section. As part of this system a compatible and precision sample chamber has been constructed, which has been designed to operate in the pressure and temperature ranges of 1-1000B and 20-150 o C, respectively. The cell has been constructed to be small and compact, but it still has a large heat capacity (∼250J/K) which ensures easy and stable temperature control of the liquid sample volume which has a size of 40 mm 3 . The achievable temperature stability is +-1mK and +-2mK for operating temperatures below and above 100 o C, respectively. The pressure stability is in the range of +-0.05B of the set pressure for pressures below 100B and it is +-0.05% for higher pressures up to 1000B. Both pressure and temperature are remotely monitored and controlled by a ND/100 computer. Special care has been taken in designing the optics of the pressure cell to ensure that both the primary and secondary reflections from the entrance window, as well as the main beam, go out of the scattering region in order to achieve higher signal-to-noise ratio in actual experiments

  9. Rayleigh-Brillouin scattering to determine one-dimensional temperature and number density profiles of a gas flow field

    Science.gov (United States)

    Lock, James A.; Seasholtz, Richard G.; John, W. T.

    1992-01-01

    Rayleigh-Brillouin spectra for heated nitrogen gas were measured by imaging the output of a Fabry-Perot interferometer onto a CCD array. The spectra were compared with the theoretical 6-moment model of Rayleigh-Brillouin scattering convolved with the Fabry-Perot instrument function. Estimates of the temperature and a dimensionless parameter proportional to the number density of the gas as functions of position in the laser beam were calculated by least-squares deviation fits between theory and experiment.

  10. The Measurement of Tropospheric Temperature Profiles using Rayleigh-Brillouin Scattering : Results from Laboratory and Atmospheric Studies

    NARCIS (Netherlands)

    Witschas, Benjamin; Reitebuch, Oliver; Lemmerz, Christian; Kableka, Pau Gomez; Kondratyev, Sergey; Gu, Z.; Ubachs, Wim

    2016-01-01

    In this letter, we suggest a new method for measuring tropospheric temperature profiles using Rayleigh-Brillouin (RB) scattering. We report on laboratory RB scattering measurements in air, demonstrating that temperature can be retrieved from RB spectra with an absolute accuracy of better than 2 K.

  11. Stimulated Brillouin scattering in dispersion-decreasing fiber with ultrahigh-speed femtosecond soliton pulse compression.

    Science.gov (United States)

    Hirooka, Toshihiko; Ono, Shinpei; Hagiuda, Ken-ichi; Nakazawa, Masataka

    2005-02-15

    We report that stimulated Brillouin scattering (SBS) in a dispersion-decreasing fiber (DDF) is particularly disadvantageous with ultrahigh-speed femtosecond soliton compression that exceeds 40 GHz. It is important to note that the increase in the longitudinal mode power of a soliton is proportional to the square of the repetition rate. The SBS threshold is determined by the dispersion-decreasing rate of the DDF, rather than its fiber loss. We suppressed the SBS by applying 30-MHz frequency modulation to a mode-locked fiber laser and successfully obtained a stable 40-GHz, 100-fs pulse train.

  12. Observation of spin-wave dispersion in Nd-Fe-B magnets using neutron Brillouin scattering

    International Nuclear Information System (INIS)

    Ono, K.; Inami, N.; Saito, K.; Takeichi, Y.; Kawana, D.; Yokoo, T.; Itoh, S.; Yano, M.; Shoji, T.; Manabe, A.; Kato, A.; Kaneko, Y.

    2014-01-01

    The low-energy spin-wave dispersion in polycrystalline Nd-Fe-B magnets was observed using neutron Brillouin scattering (NBS). Low-energy spin-wave excitations for the lowest acoustic spin-wave mode were clearly observed. From the spin-wave dispersion, we were able to determine the spin-wave stiffness constant D sw (100.0 ± 4.9 meV.Å 2 ) and the exchange stiffness constant A (6.6 ± 0.3 pJ/m)

  13. Elastic properties of boron carbide films via surface acoustic waves measured by Brillouin light scattering

    Energy Technology Data Exchange (ETDEWEB)

    Salas, E.; Jimenez-Villacorta, F.; Jimenez Rioboo, R.J.; Prieto, C. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid (Spain); Sanchez-Marcos, J. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid (Spain); Departamento de Quimica-Fisica Aplicada, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Munoz-Martin, A.; Prieto, J.E.; Joco, V. [Centro de Microanalisis de Materiales, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2013-03-15

    Surface acoustic wave (SAW) velocity has been determined by high resolution Brillouin light scattering to study the mechano-elastic properties of boron carbide films prepared by radio frequency (RF) sputtering. The comparison of experimentally observed elastic behaviour with simulations made by considering film composition obtained from elastic recoil detection analysis-time of flight (ERDA-ToF) spectroscopy allows establishing that elastic properties are determined by that of crystalline boron carbide with a lessening of the SAW velocity values due to surface oxidation. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Distributed Strain Measurement along a Concrete Beam via Stimulated Brillouin Scattering in Optical Fibers

    Directory of Open Access Journals (Sweden)

    Romeo Bernini

    2011-01-01

    Full Text Available The structural strain measurement of tension and compression in a 4 m long concrete beam was demonstrated with a distributed fiber-optic sensor portable system based on Brillouin scattering. Strain measurements provided by the fiber-optic sensor permitted to detect the formation of a crack in the beam resulting from the external applied load. The sensor system is valuable for structural monitoring applications, enabling the long-term performance and health of structures to be efficiently monitored.

  15. Angular characteristics of the stimulated-Brillouin-scattering spectrum from a laser plasma with strong acoustic-wave damping

    International Nuclear Information System (INIS)

    Saikia, P.

    1981-01-01

    The spectrum of stimulated Brillouin scattering from an inhomogeneous moving laser plasma is analyzed. The damping of acoustic waves and scattered electromagnetic waves is taken into account. Spectra are derived for various scattering angles and for various radii of the laser beam. For all observation angles the center of the spectral line is at an unshifted frequency. As the observation angle increases, the width of the red wing in the spectrum increases. The intensity of the scattered light is very anisotropic

  16. Brillouin Spectroscopy Data Base for Biological Threats

    National Research Council Canada - National Science Library

    Rubel, Glenn

    2003-01-01

    .... Brillouin scattering from DNA, ovalbumen, the Bacillus spores globigii and thuringiensis were measured to determine the feasibility of biological material discrimination using Brillouin scattering...

  17. An experimental investigation of stimulated Brillouin scattering in laser-produced plasmas relevant to inertial confinement fusion

    Energy Technology Data Exchange (ETDEWEB)

    Bradley, Keith Stanley [Univ. of California, Davis, CA (United States)

    1993-02-11

    Despite the apparent simplicity of controlled fusion, there are many phenomena which have prevented its achievement. One phenomenon is laser-plasma instabilities. An investigation of one such instability, stimulated Brillouin scattering (SBS), is reported here. SBS is a parametric process whereby an electromagnetic wave (the parent wave) decays into another electromagnetic wave and an ion acoustic wave (the daughter waves). SBS impedes controlled fusion since it can scatter much or all of the incident laser light, resulting in poor drive symmetry and inefficient laser-plasma coupling. It is widely believed that SBS becomes convectively unstable--that is, it grows as it traverses the plasma. Though it has yet to be definitively tested, convective theory is often invoked to explain experimental observations, even when one or more of the theory`s assumptions are violated. In contrast, the experiments reported here not only obeyed the assumptions of the theory, but were also conducted in plasmas with peak densities well below quarter-critical density. This prevented other competing or coexisting phenomena from occurring, thereby providing clearly interpretable results. These are the first SBS experiments that were designed to be both a clear test of linear convective theory and pertinent to controlled fusion research. A crucial part of this series of experiments was the development of a new instrument, the Multiple Angle Time Resolving Spectrometer (MATRS). MATRS has the unique capability of both spectrally and temporally resolving absolute levels of scattered light at many angles simultaneously, and is the first of its kind used in laser-plasma experiments. A detailed comparison of the theoretical predictions and the experimental observations is made.

  18. Direct ion heating in overdense plasmas through the Brillouin instability driven by relativistic whistler waves

    Science.gov (United States)

    Sano, Takayoshi; Hata, Masayasu; Iwata, Natsumi; Mima, Kunioki; Sentoku, Yasuhiko

    2017-10-01

    Strong magnetic fields over kilo-Tesla have been available in the laboratory by the use of ultra-intense lasers. It would be interesting to apply those strong fields to other laser experiments such as the inertial confinement fusion and laboratory astrophysics. The characteristics of laser-plasma interactions could be modified significantly by the presence of such strong magnetic fields. We investigate electromagnetic wave propagation in overdense plasmas along the magnetic field for a right-hand circularly polarized wave by PIC simulations. Since the whistler mode has no cutoff density, it can penetrate into overdense plasmas and interact directly with charged particles there. When the external field strength is near a critical value defined by that the cyclotron frequency is equal to the laser one, it is reported that electrons are accelerated efficiently by the cyclotron resonance. However, if the field strength is far beyond the critical value, the cyclotron resonance is inefficient, while the ions gain a large amount of energy directly from the laser light owning to the Brillouin scattering. As the result, only ions are heated up selectively. We will discuss about the application of this ion heating in dense plasmas. This work was supported by JSPS KAKENHI Grant Number JP15K21767.

  19. Elastic constants and dimensions of imprinted polymeric nanolines determined from Brillouin light scattering

    International Nuclear Information System (INIS)

    Johnson, W L; Kim, S A; Geiss, R; Flannery, C M; Soles, C L; Wang, C; Stafford, C M; Wu, W-L; Torres, J M; Vogt, B D; Heyliger, P R

    2010-01-01

    Elastic constants and cross-sectional dimensions of imprinted nanolines of poly(methyl methacrylate) (PMMA) on silicon substrates are determined nondestructively from finite-element inversion analysis of dispersion curves of hypersonic acoustic modes of these nanolines measured with Brillouin light scattering. The results for the cross-sectional dimensions, under the simplifying assumption of vertical sides and a semicircular top, are found to be consistent with dimensions determined from critical-dimension small-angle x-ray scattering measurements. The elastic constants C 11 and C 44 are found to be, respectively, 11.6% and 3.1% lower than their corresponding values for bulk PMMA. This result is consistent with the dimensional dependence of the quasi-static Young's modulus determined from buckling measurements on PMMA films with lower molecular weights. This study provides the first evidence of size-dependent effects on hypersonic elastic properties of polymers.

  20. Neutron Brillouin scattering experiments with pulsed neutrons on high resolution chopper spectrometer HRC

    International Nuclear Information System (INIS)

    Itoh, S; Yokoo, T; Endoh, Y; Kawana, D; Kaneko, Y; Tokura, Y; Fujita, M; Yoshida, K; Saito, K; Inami, N; Takeichi, Y; Ono, K

    2014-01-01

    We improved the High Resolution Chopper Spectrometer (HRC), which is installed at MLF in J-PARC, in order to perform neutron Brillouin scattering (NBS) experiments, and successfully demonstrated a feasibility of this method. Gapless spin-wave excitations were observed in La 0.8 Sr 0.2 MnO 3 , which were in good agreement with previous results using single crystals, on the other hand, a large energy gap in the ferromagnetic spin waves was found in SrRuO 3 . Spin-wave peaks in a permanent magnet Nd 2 Fe 14 B were on the dispersion curve determined previously using a single crystal. Excitations, so-called fast sound, in liquid D 2 O were in a good agreement with previous inelastic neutron scattering experiments and the dispersion curve were extended to the lower Q region.

  1. Rayleigh-Brillouin light scattering spectroscopy of nitrous oxide (N2O)

    Science.gov (United States)

    Wang, Y.; Liang, K.; van de Water, W.; Marques, W.; Ubachs, W.

    2018-02-01

    High signal-to-noise and high-resolution light scattering spectra are measured for nitrous oxide (N2O) gas at an incident wavelength of 403.00 nm, at 90° scattering, at room temperature and at gas pressures in the range 0.5 - 4 bar. The resulting Rayleigh-Brillouin light scattering spectra are compared to a number of models describing in an approximate manner the collisional dynamics and energy transfer in this gaseous medium of this polyatomic molecular species. The Tenti-S6 model, based on macroscopic gas transport coefficients, reproduces the scattering profiles in the entire pressure range at less than 2% deviation at a similar level as does the alternative kinetic Grad's 6-moment model, which is based on the internal collisional relaxation as a decisive parameter. A hydrodynamic model fails to reproduce experimental spectra for the low pressures of 0.5-1 bar, but yields very good agreement ( viscosity of ηb ∼(6 ± 2) ×10-5 Pa · s. A 'rough-sphere' model, previously shown to be effective to describe light scattering in SF6 gas, is not found to be suitable, likely in view of the non-sphericity and asymmetry of the N-N-O structured linear polyatomic molecule.

  2. Bandwidth-tunable narrowband rectangular optical filter based on stimulated Brillouin scattering in optical fiber.

    Science.gov (United States)

    Wei, Wei; Yi, Lilin; Jaouën, Yves; Hu, Weisheng

    2014-09-22

    We propose a rectangular optical filter based on stimulated Brillouin scattering (SBS) in optical fiber with bandwidth tuning from 50 MHz to 4 GHz at less than 15-MHz resolution. The rectangular shape of the filter is precisely achieved utilizing digital feedback control of the comb-like pump spectral lines. The passband ripple is suppressed to ~1 dB by mitigating the nonlinearity influences of the comb-like pump lines generated in electrical and optical components and fibers. Moreover a fiber with a single Brillouin peak is employed to further reduce the in-band ripple and the out-of-band SBS gain at the same time. Finally, we analyze the noise performance of the filter at different bandwidth cases and demonstrate the system performance of the proposed filter with 2.1-GHz bandwidth and 19-dB gain by amplifying a 2-GHz orthogonal frequency-division-multiplexing (OFDM) signal with quadrature-phase-shift-keying (QPSK) and 16-quadrature-amplitude-modulation (16-QAM) on each subscriber.

  3. Acoustic Anomalies and Fast Relaxation Dynamics of Amorphous Progesterone as Revealed by Brillouin Light Scattering

    Directory of Open Access Journals (Sweden)

    Tae Hyun Kim

    2017-12-01

    Full Text Available The amorphous state of pharmaceuticals has attracted much attention due to its high bioavailability and other advantages. The stability of the amorphous state in relation with the local molecular mobility is important from both fundamental and practical points of view. The acoustic properties of amorphous progesterone, one of the representative steroid hormones, were investigated by using a Brillouin inelastic light scattering technique. The Brillouin spectrum of the longitudinal acoustic mode exhibited distinct changes at the glass transition and the cold-crystallization temperatures. The acoustic dispersions of the longitudinal sound velocity and the acoustic absorption coefficient were attributed to the fast and possibly the secondary relaxation processes in the glassy and supercooled liquid states, while the structural relaxation process was considered as the dominant origin for the significant acoustic damping observed even in the liquid phase. The persisting acoustic dispersion in the liquid state was attributed to the single-molecule nature of the progesterone which does not exhibit hydrogen bonds in the condensed states.

  4. Suppression of Brillouin scattering in fibre-optical parametric amplifier by applying temperature control and phase modulation

    DEFF Research Database (Denmark)

    Lorenzen, Michael Rodas; Noordegraaf, Danny; Nielsen, Carsten Vandel

    2009-01-01

    An increased gain in a fibre-optical parametric amplifier through suppression of stimulated Brillouin scattering is demonstrated by applying a temperature distribution along the fibre for a fixed phase modulation of the pump. The temperature distribution slightly impacts the gain spectrum....

  5. Angle-resolved spin wave band diagrams of square antidot lattices studied by Brillouin light scattering

    Energy Technology Data Exchange (ETDEWEB)

    Gubbiotti, G.; Tacchi, S. [Istituto Officina dei Materiali del Consiglio Nazionale delle Ricerche (IOM-CNR), Sede di Perugia, c/o Dipartimento di Fisica e Geologia, Via A. Pascoli, I-06123 Perugia (Italy); Montoncello, F.; Giovannini, L. [Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, Via G. Saragat 1, I-44122 Ferrara (Italy); Madami, M.; Carlotti, G. [Dipartimento di Fisica e Geologia, Università di Perugia, Via A. Pascoli, I-06123 Perugia (Italy); Ding, J.; Adeyeye, A. O. [Information Storage Materials Laboratory, Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore)

    2015-06-29

    The Brillouin light scattering technique has been exploited to study the angle-resolved spin wave band diagrams of squared Permalloy antidot lattice. Frequency dispersion of spin waves has been measured for a set of fixed wave vector magnitudes, while varying the wave vector in-plane orientation with respect to the applied magnetic field. The magnonic band gap between the two most dispersive modes exhibits a minimum value at an angular position, which exclusively depends on the product between the selected wave vector magnitude and the lattice constant of the array. The experimental data are in very good agreement with predictions obtained by dynamical matrix method calculations. The presented results are relevant for magnonic devices where the antidot lattice, acting as a diffraction grating, is exploited to achieve multidirectional spin wave emission.

  6. Temperature dependence of Brillouin light scattering spectra of acoustic phonons in silicon

    International Nuclear Information System (INIS)

    Olsson, Kevin S.; Klimovich, Nikita; An, Kyongmo; Sullivan, Sean; Weathers, Annie; Shi, Li; Li, Xiaoqin

    2015-01-01

    Electrons, optical phonons, and acoustic phonons are often driven out of local equilibrium in electronic devices or during laser-material interaction processes. The need for a better understanding of such non-equilibrium transport processes has motivated the development of Raman spectroscopy as a local temperature sensor of optical phonons and intermediate frequency acoustic phonons, whereas Brillouin light scattering (BLS) has recently been explored as a temperature sensor of low-frequency acoustic phonons. Here, we report the measured BLS spectra of silicon at different temperatures. The origins of the observed temperature dependence of the BLS peak position, linewidth, and intensity are examined in order to evaluate their potential use as temperature sensors for acoustic phonons

  7. Stimulated Brillouin scattering continuous wave phase conjugation in step-index fiber optics.

    Science.gov (United States)

    Massey, Steven M; Spring, Justin B; Russell, Timothy H

    2008-07-21

    Continuous wave (CW) stimulated Brillouin scattering (SBS) phase conjugation in step-index optical fibers was studied experimentally and modeled as a function of fiber length. A phase conjugate fidelity over 80% was measured from SBS in a 40 m fiber using a pinhole technique. Fidelity decreases with fiber length, and a fiber with a numerical aperture (NA) of 0.06 was found to generate good phase conjugation fidelity over longer lengths than a fiber with 0.13 NA. Modeling and experiment support previous work showing the maximum interaction length which yields a high fidelity phase conjugate beam is inversely proportional to the fiber NA(2), but find that fidelity remains high over much longer fiber lengths than previous models calculated. Conditions for SBS beam cleanup in step-index fibers are discussed.

  8. Brillouin scattering: its application to the study of damage and amorphization

    International Nuclear Information System (INIS)

    Grimsditch, M.; Bhadra, R.; Gray, K.; Kampwirth, R.T.; Okamoto, P.; Pearson, J.; Rehn, L.

    1988-02-01

    A brief review of Brillouin scattering is made emphasizing its advantages and disadvantages over conventional ultrasonic techniques. One of its advantages is that the elastic properties of very thin films (∼ 1μ) can be investigated. The authors have used this technique to study changes in shear elastic constants of materials irradiated with high energy ions. These particles only penetrate ∼ 1μ into the material but produce very high defect concentrations which, in certain cases, can lead to amorphization. In Nb 3 Ir and Zr 3 Al very large changes are observed before the onset of amorphization, while in Si the changes occur concomitantly with amorphization. The significance of the hardening observed in Zr 3 Al when it becomes amorphous will be discussed

  9. The broad Brillouin doublet and CP of KTaO3, second sound vs. Two-phonon difference scattering

    International Nuclear Information System (INIS)

    Farhi, E.; Tagantsev, A.K.; Hehlen, B.; Courtens, E.; Boatner, L.A.

    1999-01-01

    Complete text of publication follows. Low-T Brillouin spectra of the incipient ferroelectric KTaO 3 exhibit a broad central peak (CP) (1), and some additional broad Brillouin doublet (BD) (2), that can both relate to phonon-density fluctuations (3). Starting from extensive new high resolution neutron scattering measurements in pure crystals, low lying phonon sheets were modelled in the central part of Brillouin zone. Such a parameterisation was then used in order to analyse those up-mentioned unusual features in teens of two-phonon mechanisms (4). Numerical evaluations show that transverse acoustic (TA) phonons whose normal damping is faster than the BD frequency (Γ DB > ω DB ) may produce hydrodynamic second sound (propagation of heat). Moreover, two-phonon difference scattering from low damping thermal TA phonons ((Γ DB DB ) can contribute to the spectra with either a sharp or a broader BD, depending on the phonon group velocity and phonon-sheet anisotropy. The position of the doublet is consistent with both mechanisms, but comparing the computed anisotropies with experimental Brillouin and neutron scattering data, one favours the second process. (author)

  10. Geophysical Remote Sensing Using the HF Pumped Stimulated Brillouin Scatter (SBS) Emission Lines Produced by HAARP

    Science.gov (United States)

    Bernhardt, P. A.; Selcher, C. A.

    2009-12-01

    An ordinary or extraordinary mode electromagnetic wave can decay into a low frequency electrostatic wave and a scattered electromagnetic wave by a process called stimulated Brillouin scatter (SBS). The low frequency wave can be either an ion acoustic wave (IA) or an electrostatic ion cyclotron (EIC) wave. The first detection ion acoustic waves by this process during ionospheric modification with high power radio waves was reported by Norin et al. (2009) using the HAARP transmitter in Alaska. The first detection of the electrostatic ion cyclotron waves is reported here using HAARP during the March 2009 campaign. Subsequent experiments have provided additional verification of the SBS process and quantitative interpretation of the scattered wave frequency offsets to yield measurements of the electron temperatures in the heated ionosphere by Bernhardt et al. (2009). Using the SBS technique to generate ion acoustic waves, electron temperatures between 3000 and 4000 K were measured over the HAARP facility. The matching conditions for decay of the high frequency pump wave show that in addition to the production of an ion-acoustic wave, an electrostatic ion cyclotron wave can produced by the generalized SBS processes only if the pump waves makes a large angle with the magnetic field. When the EIC mode is produced, it is seen as a narrow of stimulated electromagnetic emissions at the ion cyclotron frequency. Occasionally, multiple lines are seen and analyzed to yield the relative abundance of oxygen, and molecular ions in the lower ionosphere. This ion mass spectrometer interpretation of the SBS data is new to the field of ionosphere remote sensing. In addition, based on the matching condition theory, the first profiles of the scattered wave amplitude are produced using the stimulated Brillouin scatter (SBS) matching conditions. These profiles are consistent with maximum ionospheric interactions at the upper-hybrid resonance height and at a region just below the plasma

  11. Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT

    Directory of Open Access Journals (Sweden)

    H. Y. Fu

    2015-08-01

    Full Text Available Observations of secondary radiation, stimulated electromagnetic emission (SEE, produced during ionospheric modification experiments using ground-based, high-power, high-frequency (HF radio waves are considered. The High Frequency Active Auroral Research Program (HAARP facility is capable of generating narrowband SEE in the form of stimulated Brillouin scatter (SBS and stimulated ion Bernstein scatter (SIBS in the SEE spectrum. Such narrowband SEE spectral lines have not been reported using the European Incoherent Scatter (EISCAT heater facility before. This work reports the first EISCAT results of narrowband SEE spectra and compares them to SEE previously observed at HAARP during electron gyro-harmonic heating. An analysis of experimental SEE data shows observations of emission lines within 100 Hz of the pump frequency, interpreted as SBS, during the 2012 July EISCAT campaign. Experimental results indicate that SBS strengthens as the pump frequency approaches the third electron gyro-harmonic. Also, for different heater antenna beam angles, the CUTLASS radar backscatter induced by HF radio pumping is suppressed near electron gyro-harmonics, whereas electron temperature enhancement weakens as measured by EISCAT/UHF radar. The main features of these new narrowband EISCAT observations are generally consistent with previous SBS measurements at HAARP.

  12. Brillouin Light Scattering from Magnetic Excitations in Superparamagnetic and Ferromagnetic Co-Al-O Granular Films

    Science.gov (United States)

    Yoshihara, Akira; Maeda, Toshiteru; Kawamura, Satoshi; Nakamura, Shintaro; Nojima, Tsutomu; Takeda, Yoshihiko; Ohnuma, Shigehiro

    2018-04-01

    A systematic study of Brillouin light scattering (BLS) from superparamagnetic (SPM) and ferromagnetic (FM) Co-Al-O granular films was performed under magnetic fields of up to 4.6 kOe in the standard backscattering geometry at room temperature. The SPM and FM boundary, defined as the Co composition at which the exchange field vanishes, was found to be located at xC(Co) = 59.3 ± 1.3 at. %. From FM films we observed a pair of bulk spin-wave peaks on both the positive- and negative-frequency sides and a surface localized Damon-Eshbach peak only on the positive-frequency side under the present scattering conditions. From SPM films, a pair of broader but propagative excitation peaks with asymmetric intensity were observed on both frequency sides in a spectrum. We performed a numerical analysis of the BLS spectrum by employing the theory developed by Camley and Mills (CM) while retaining dipole and exchange couplings for FM films and only dipole coupling for SPM films. The CM theory successfully reproduced the observed spectrum for both SPM and FM films. The SPM spectrum exhibits a singlet-doublet peak structure similarly to an FM SW spectrum. The SPM peak stems from the dipole-coupled larger-amplitude precession motion of the granule magnetic moment around the external-field-induced magnetization.

  13. Rayleigh-Brillouin scattering in SF6 in the kinetic regime

    Science.gov (United States)

    Wang, Yuanqing; Yu, Yin; Liang, Kun; Marques, Wilson; van de Water, Willem; Ubachs, Wim

    2017-02-01

    Rayleigh-Brillouin spectral profiles are measured with a laser-based scatterometry setup for a 90° scattering angle at a high signal-to-noise ratio (r.m.s. noise below 0.15% w.r.t. peak intensity) in sulfur-hexafluoride gas for pressures in the range 0.2-5 bar and for a wavelength of λ = 403.0 nm. The high quality data are compared to a number of light scattering models in order to address the effects of rotational and vibrational relaxation. While the vibrational relaxation rate is so slow that vibration degrees of freedom remain frozen, rotations relax on time scales comparable to those of the density fluctuations. Therefore, the heat capacity, the thermal conductivity and the bulk viscosity are all frequency-dependent transport coefficients. This is relevant for the Tenti model that depends on the values chosen for these transport coefficients. This is not the case for the other two models considered: a kinetic model based on rough-sphere interactions, and a model based on fluctuating hydrodynamics. The deviations with the experiment are similar between the three different models, except for the hydrodynamic model at pressures p≲ 2bar . As all models are in line with the ideal gas law, we hypothesize the presence of real gas effects in the measured spectra.

  14. Large On-Chip Amplification in Silicon via Forward Stimulated Brillouin Scattering.

    Energy Technology Data Exchange (ETDEWEB)

    Kittlaus, Eric [Yale Univ., New Haven, CT (United States); Shin, Heedeuk [Yale Univ., New Haven, CT (United States); Rakich, Peter [Yale Univ., New Haven, CT (United States)

    2015-10-15

    Strong Brillouin coupling has only recently been realized in silicon using a new class of op- tomechanical waveguides that yield both optical and phononic con nement. Despite these major advances, appreciable Brillouin ampli cation has yet to be observed in silicon. Using new membrane- suspended silicon waveguide we report large Brillouin ampli cation for the rst time, reaching levels greater than 5 dB for modest pump powers, and demonstrate a record low (5 mW) threshold for net ampli cation. This work represents a crucial advance necessary to realize high-performance Brillouin lasers and ampli ers in silicon.

  15. Analytical study of nonlinear phase shift through stimulated Brillouin scattering in single mode fiber with the pump power recycling technique

    International Nuclear Information System (INIS)

    Al-Asadi, H A; Mahdi, M A; Bakar, A A A; Adikan, F R Mahamd

    2011-01-01

    We present a theoretical study of nonlinear phase shift through stimulated Brillouin scattering in single mode optical fiber. Analytical expressions describing the nonlinear phase shift for the pump and Stokes waves in the pump power recycling technique have been derived. The dependence of the nonlinear phase shift on the optical fiber length, the reflectivity of the optical mirror and the frequency detuning coefficient have been analyzed for different input pump power values. We found that with the recycling pump technique, the nonlinear phase shift due to stimulated Brillouin scattering reduced to less than 0.1 rad for 5 km optical fiber length and 0.65 reflectivity of the optical mirror, respectively, at an input pump power equal to 30 mW

  16. Micro-focused Brillouin light scattering: imaging spin waves at the nanoscale

    Directory of Open Access Journals (Sweden)

    Thomas eSebastian

    2015-06-01

    Full Text Available Spin waves constitute an important part of research in the field of magnetization dynamics. Spin waves are the elementary excitations of the spin system in a magnetically ordered material state and magnons are their quasi particles. In the following article, we will discuss the optical method of Brillouin light scattering (BLS spectroscopy which is a now a well established tool for the characterization of spin waves. BLS is the inelastic scattering of light from spin waves and confers several benefits: the ability to map the spin wave intensity distribution with spatial resolution and high sensitivity as well as the potential to simultaneously measure the frequency and the wave vector and, therefore, the dispersion properties.For several decades, the field of spin waves gained huge interest by the scientific community due to its relevance regarding fundamental issues of spindynamics in the field of solid states physics. The ongoing research in recent years has put emphasis on the high potential of spin waves regarding information technology. In the emerging field of textit{magnonics}, several concepts for a spin-wave based logic have been proposed and realized. Opposed to charge-based schemes in conventional electronics and spintronics, magnons are charge-free currents of angular momentum, and, therefore, less subject to scattering processes that lead to heating and dissipation. This fact is highlighted by the possibility to utilize spin waves as information carriers in electrically insulating materials. These developments have propelled the quest for ways and mechanisms to guide and manipulate spin-wave transport. In particular, a lot of effort is put into the miniaturization of spin-wave waveguides and the excitation of spin waves in structures with sub-micrometer dimensions.For the further development of potential spin-wave-based devices, the ability to directly observe spin-wave propagation with spatial resolution is crucial. As an optical

  17. Does Brillouin light scattering probe the primary glass transition process at temperatures well above glass transition?

    Science.gov (United States)

    Voudouris, P; Gomopoulos, N; Le Grand, A; Hadjichristidis, N; Floudas, G; Ediger, M D; Fytas, G

    2010-02-21

    The primary alpha-relaxation time (tau(alpha)) for molecular and polymeric glass formers probed by dielectric spectroscopy and two light scattering techniques (depolarized light scattering and photon correlation spectroscopy) relates to the decay of the torsional autocorrelation function computed by molecular dynamics simulation. It is well known that Brillouin light scattering spectroscopy (BLS) operating in gigahertz frequencies probes a fast (10-100 ps) relaxation of the longitudinal modulus M*. The characteristic relaxation time, irrespective of the fitting procedure, is faster than the alpha-relaxation which obeys the non-Arrhenius Vogel-Fulcher-Tammann equation. Albeit, this has been noticed, it remains a puzzling finding in glass forming systems. The available knowledge is based only on temperature dependent BLS experiments performed, however, at a single wave vector (frequency). Using a new BLS spectrometer, we studied the phonon dispersion at gigahertz frequencies in molecular [o-terphenyl (OTP)] and polymeric [polyisoprene (PI) and polypropylene (PP)] glass formers. We found that the hypersonic dispersion does relate to the glass transition dynamics but the disparity between the BLS-relaxation times and tau(alpha) is system dependent. In PI and PP, the former is more than one order of magnitude faster than tau(alpha), whereas the two relaxation times become comparable in the case of OTP. The difference between the two relaxation times appears to relate to the "breadth" of the relaxation time distribution function. In OTP the alpha-relaxation process assumes a virtually single exponential decay at high temperatures well above the glass transition temperature, in clear contrast with the case of the amorphous bulk polymers.

  18. A Brillouin scattering study of the effect of chemical passivation on the elastic properties of porous silicon

    Science.gov (United States)

    Fan, H. J.; Kuok, M. H.; Ng, S. C.; Boukherroub, R.; Lockwood, D. J.

    2002-07-01

    Brillouin scattering has been performed to probe acoustic waves in porous silicon films that have been chemically modified with either 1-decene, decyl aldehyde, undecylenic acid, or ethyl undecylenate. The shift in the frequencies of acoustic modes in the passivated porous silicon samples, relative to those in freshly prepared porous silicon, is different for different chemical modifiers. The magnitude of the frequency shift is qualitatively correlated with the change, caused by the passivation, in the average densities and elastic constants of the samples.

  19. Multifunctional microwave photonic signal processor based on dual-parallel Mach-Zehnder modulator and stimulated Brillouin scattering

    Science.gov (United States)

    Shi, Zhan; Wang, Ling; Yang, Cheng Wu; Li, Ming; Zhu, Ning Hua; Li, Wei

    2017-09-01

    We report a multifunctional microwave photonic signal processor based on dual-parallel Mach-Zehnder modulator and stimulated Brillouin scattering. The signal processor acts as a microwave photonic filter (MPF) and microwave photonic phase shifter (MPS) simultaneously. The MPF and MPS can be tuned separately. Experimental results demonstrate that the central frequency of the bandpass MPF is tunable from 3 to 18 GHz while the MPS in the passband of the MPF is continuously adjustable over 360 deg.

  20. High temperature surface Brillouin scattering study of mechanical properties of boron-doped epitaxial polysilicon

    Directory of Open Access Journals (Sweden)

    B. A. Mathe

    2017-02-01

    Full Text Available A study of the mechanical properties of a boron-doped epitaxial polysilicon layer deposited on a Si (100 substrate specimen has been carried out by surface Brillouin scattering at high temperatures. This type of specimen is widely used in micro-electro-mechanical systems (MEMS. By accumulating spectra with the Rayleigh mode and the Lamb continuum the isotropic elastic constants C44 and C11 were obtained, from which the values of the bulk, shear and Young’s moduli and Poisson’s ratio for the layer were determined over a range of temperatures from 20 °C to 110 °C. By contrast, an examination of the literature on polycrystalline silicon shows that other methods each provide a limited range of the above properties and thus additional experiments and techniques were needed. The SBS method is applicable to other polycrystalline materials such as silicon carbide, silicon nitride, silicon germanium and amorphous diamond that have also been used for MEMS applications.

  1. Stimulated Brillouin scattering in highly birefringent multimode tapered chalcogenide photonic crystal fiber for distributed optical sensors (Retraction Notice)

    Science.gov (United States)

    Baili, Amira; Cherif, Rim; Zghal, Mourad

    2016-09-01

    This paper, originally published on September 15, 2016, was retracted from the SPIE Digital Library on October 5, 2016, due to a high degree of similarity between specific portions of the text of the paper to the following publications: J. Tchahame, J. Beugnot, A. Kudlinski, and T. Sylvestre, "Multimode Brillouin spectrum in a long tapered birefringent photonic crystal fiber," Opt. Lett. 40, 4281-4284 (2015). doi: 10.1364/OL.40.004281 W. W. Ke, X. J. Wang and X. Tang, "Stimulated Brillouin Scattering Model in Multi-Mode Fiber Lasers," in IEEE Journal of Selected Topics in Quantum Electronics, vol. 20, no. 5, pp. 305-314, Sept.-Oct. 2014. doi: 10.1109/JSTQE.2014.2303256.

  2. Brillouin scattering measurements of the temperature dependence of sound velocity and acoustic absorption in simple alcohols

    Science.gov (United States)

    Stevens, J. R.; Coakley, R. W.

    2011-07-01

    A scanning Fabry-Perot interferometer was used to measure Brillouin spectra of methanol, isopropanol and a 95% ethanol-water mixture for temperatures ranging between 285 K and 320 K. The Brillouin frequency shifts and linewidths were used to calculate the velocities and absorption coefficients of hypersonic acoustic waves in these liquids. The temperature dependence of sound speed and acoustic attenuation was determined. For all three materials, both sound velocity and absorption coefficient decreased with temperature.

  3. Dimensionality reduction and dynamical filtering: Stimulated Brillouin scattering in optical fibers.

    Science.gov (United States)

    Setra, Rafael G; Arroyo-Almanza, Diana A; Ni, Zetian; Murphy, Thomas E; Roy, Rajarshi

    2015-08-01

    Stimulated Brillouin scattering (SBS) is a noise-driven nonlinear interaction between acoustical and optical waves. In optical fibers, SBS can be observed at relatively low optical powers and can severely limit signal transmission. Although SBS is initiated by high dimensional noise, it also exhibits many of the hallmarks of a complex nonlinear dynamical system. We report here a comprehensive experimental and numerical study of the fluctuations in the reflected Stokes wave produced by SBS in optical fibers. Using time series analysis, we demonstrate a reduction of dimensionality and dynamical filtering of the Stokes wave. We begin with a careful comparison of the measured average transmitted and reflected intensities from below the SBS threshold to saturation of the transmitted power. Initially the power spectra and correlation functions of the time series of the reflected wave fluctuations at the SBS threshold and above are measured and simulated. Much greater dynamical insight is provided when we study the scaling behavior of the intensity fluctuations using Hurst exponents and detrended fluctuation analysis for time scales extending over six orders of magnitude. At the highest input powers, we notice the emergence of three distinct dynamical scaling regimes: persistent, Brownian, and antipersistent. Next, we explore the Hilbert phase fluctuations of the intensity time series and amplitude-phase coupling. Finally, time-delay embedding techniques reveal a gradual reduction in dimensionality of the spatiotemporal dynamics as the laser input is increased toward saturation of the transmitted power. Through all of these techniques, we find a transition from noisier to smoother dynamics with increasing input power. We find excellent agreement between our experimental measurements and simulations.

  4. Dimensionality reduction and dynamical filtering: Stimulated Brillouin scattering in optical fibers

    Science.gov (United States)

    Setra, Rafael G.; Arroyo-Almanza, Diana A.; Ni, Zetian; Murphy, Thomas E.; Roy, Rajarshi

    2015-08-01

    Stimulated Brillouin scattering (SBS) is a noise-driven nonlinear interaction between acoustical and optical waves. In optical fibers, SBS can be observed at relatively low optical powers and can severely limit signal transmission. Although SBS is initiated by high dimensional noise, it also exhibits many of the hallmarks of a complex nonlinear dynamical system. We report here a comprehensive experimental and numerical study of the fluctuations in the reflected Stokes wave produced by SBS in optical fibers. Using time series analysis, we demonstrate a reduction of dimensionality and dynamical filtering of the Stokes wave. We begin with a careful comparison of the measured average transmitted and reflected intensities from below the SBS threshold to saturation of the transmitted power. Initially the power spectra and correlation functions of the time series of the reflected wave fluctuations at the SBS threshold and above are measured and simulated. Much greater dynamical insight is provided when we study the scaling behavior of the intensity fluctuations using Hurst exponents and detrended fluctuation analysis for time scales extending over six orders of magnitude. At the highest input powers, we notice the emergence of three distinct dynamical scaling regimes: persistent, Brownian, and antipersistent. Next, we explore the Hilbert phase fluctuations of the intensity time series and amplitude-phase coupling. Finally, time-delay embedding techniques reveal a gradual reduction in dimensionality of the spatiotemporal dynamics as the laser input is increased toward saturation of the transmitted power. Through all of these techniques, we find a transition from noisier to smoother dynamics with increasing input power. We find excellent agreement between our experimental measurements and simulations.

  5. Influence of KF substitution on the ferroelectric phase transition of lead titanate single crystals studied by Brillouin light scattering

    Directory of Open Access Journals (Sweden)

    Seonhyeop Shin

    2015-06-01

    Full Text Available The elastic properties of KF-substituted perovskite lead titanate (PbTiO3 were investigated by dielectric measurements and Brillouin light scattering. The ferroelectric phase transition occurred at substantially lower temperature due to KF substitution, which was attributed to the modification of the covalency in Pb–O and Ti–O bonds. The longitudinal acoustic (LA mode of KF-substituted PbTiO3 showed a frequency softening in the paraelectric phase, which was accompanied by increasing acoustic damping. This indicated that polarization fluctuations responsible for the acoustic anomalies were enhanced by KF substitution.

  6. Martensitic phase transition in Cu–14%Al–4%Ni shape memory alloys studied by Brillouin light scattering

    International Nuclear Information System (INIS)

    Graczykowski, B; Mielcarek, S; Mroz, B; Breczewski, T; No, M L; San-Juan, J

    2013-01-01

    The paper presents the influence of the martensitic phase transition on hypersonic thermally excited surface acoustic waves propagating in Cu–14%Al–4%Ni (wt%) shape memory alloy. Non-destructive and non-contact testing using Brillouin light scattering spectroscopy permitted determination of the elastic constants of austenite versus temperature. Experimental results obtained for martensite were interpreted using the proposed model of the cubic to orthorhombic martensitic phase transition based on the Landau model of a first-order phase transition. Additionally we adopted the approximation of the domain structure of martensite by a polycrystalline sample using the Voigt–Reuss–Hill procedure of averaging the elastic constants. (paper)

  7. Coherent Forward Stimulated-Brillouin Scattering of a Spatially Incoherent Laser Beam in a Plasma and Its Effect on Beam Spray

    International Nuclear Information System (INIS)

    Grech, M.; Riazuelo, G.; Pesme, D.; Weber, S.; Tikhonchuk, V. T.

    2009-01-01

    A statistical model for forward stimulated-Brillouin scattering is developed for a spatially incoherent, monochromatic, laser beam propagating in a plasma. The threshold above which the laser beam spatial incoherence cannot prevent the coherent growth of forward stimulated-Brillouin scattering is computed. It is found to be well below the threshold for self-focusing. Three-dimensional simulations confirm its existence and reveal the onset of beam spray above it. From these results, we propose a new figure of merit for the control of propagation through a plasma of a spatially incoherent laser beam

  8. Transition from hydrodynamic to fast sound in a He-Ne mixture a neutron Brillouin scattering experiment

    CERN Document Server

    Bafile, U; Barocchi, F; Sampoli, M

    2002-01-01

    The presence of a fast-sound mode in the microscopic dynamics of the rare-gas mixture He-Ne, predicted by theoretical studies and molecular-dynamics simulations, was demonstrated by an inelastic neutron scattering experiment. In order to study the transition between the fast and the normal acoustic modes in the hydrodynamic regime, k values lower by about one order of magnitude than in the usual experiments have to be probed. We describe here the results of the first neutron Brillouin scattering experiment performed with this purpose on the same system already investigated at larger k. The results of both experiments, together with those of a new molecular-dynamics simulation, provide a complete and consistent description, still missing so far, of the onset of fast-sound propagation in a binary mixture. (orig.)

  9. Water dynamics in a lithium chloride aqueous solution probed by Brillouin neutron and x-ray scattering.

    Science.gov (United States)

    Mamontov, E; De Francesco, A; Formisano, F; Laloni, A; Sani, L; Leu, B M; Said, A H; Kolesnikov, A I

    2012-02-15

    We studied the collective excitations in an aqueous solution of lithium chloride over the temperature range of 270-205 K using neutron and x-ray Brillouin scattering. Both neutron and x-ray experiments revealed the presence of low- and high-frequency excitations, similar to the low- and high-frequency excitations in pure water. These two excitations were detectable through the entire temperature range of the experiment, at all probed values of the scattering momentum transfer (0.2 Å(-1) temperature range was investigated using elastic intensity neutron and x-ray scans. Clear evidence of the crossover in the dynamics of the water molecules in the solution was observed in the single-particle relaxational dynamics on the µeV (nanosecond) time scale, but not in the collective dynamics on the meV (picosecond) time scale.

  10. 40-gHz, 100-fs stimulated-Brillouin-scattering-free pulse generation by combining a mode-locked laser diode and a dispersion-decreasing fiber.

    Science.gov (United States)

    Hagiuda, Ken-ichi; Hirooka, Toshihiko; Nakazawa, Masataka; Arahira, Shin; Ogawa, Yoh

    2005-03-15

    A 40-GHz, 100-fs pulse train was successfully generated by soliton compression of a mode-locked laser diode (MLLD) pulse with a dispersion-decreasing fiber. The MLLD had a longitudinal mode linewidth as broad as 60 MHz, which made it possible to suppress stimulated Brillouin scattering and achieve stable, ultrahigh-speed pulse compression without applying external frequency modulation.

  11. Brillouin scattering study of surface acoustic waves in crystalline GaP

    Science.gov (United States)

    Zuk, J.; Kiefte, H.; Clouter, M. J.

    1992-10-01

    Surface acoustic modes in GaP crystals have been observed and identified using the technique of high-contrast Brillouin spectroscopy. Surface acoustic wave velocities were determined for (100) GaP in different directions of wave propagation. The values of the velocities are: 3250 m/s in the [010] direction and 3467 m/s in the [011] direction on the (100) GaP surface. These results are discussed and compared with theoretical calculations and with similar measurements in GaAs and Si.

  12. Elastic properties of aspirin in its crystalline and glassy phases studied by micro-Brillouin scattering

    Science.gov (United States)

    Ko, Jae-Hyeon; Lee, Kwang-Sei; Ike, Yuji; Kojima, Seiji

    2008-11-01

    The acoustic waves propagating along the direction perpendicular to the (1 0 0) cleavage plane of aspirin crystal were investigated using micro-Brillouin spectroscopy from which C11, C55 and C66 were obtained. The temperature dependence of the longitudinal acoustic waves could be explained by normal anharmonic lattice models, while the transverse acoustic waves showed an abnormal increase in the hypersonic attenuation at low temperatures indicating their coupling to local remnant dynamics. The sound velocity as well as the attenuation of the longitudinal acoustic waves of glassy aspirin showed a substantial change at ˜235 K confirming a transition from glassy to supercooled liquid state in vitreous aspirin.

  13. Size-dependent magnetization dynamics in individual Ni80Fe20 disk using micro-focused Brillouin Light Scattering spectroscopy

    Directory of Open Access Journals (Sweden)

    G. Shimon

    2015-09-01

    Full Text Available A direct and systematic investigation of the magnetization dynamics in individual circular Ni80Fe20 disk of diameter (D in the range from 300 nm to 1 μm measured using micro-focused Brillouin Light Scattering (μ-BLS spectroscopy is presented. At high field, when the disks are in a single domain state, the resonance frequency of the uniform center mode is observed to reduce with reducing disk’s diameter. For D = 300 nm, additional edge and end-domains resonant modes are observed due to size effects. At low field, when the disks are in a vortex state, a systematic increase of resonant frequency of magnetostatic modes in a vortex state with the square root of the disks’ aspect ratio (thickness divided by radius is observed. Such dependence diminishes for disks with larger aspect ratio due to an increasing exchange energy contribution. Micromagnetic simulations are in excellent agreement with the experiments.

  14. OPTICAL DATA PROCESSING: Realization of associative memory with the aid of a nonlinear selective stimulated-Brillouin-scattering mirror

    Science.gov (United States)

    Matveyev, A. Z.; Pasmanik, G. A.

    1993-05-01

    An associative memory using only optical elements has been realized experimentally. The key element of the arrangement is a stimulated-Brillouin-scattering (SBS) selector consisting of a short SBS medium at the focus of a lens. The qualitative advantage of the selector over an SBS mirror is demonstrated experimentally. The response time of the arrangement is ~ 10-8 s and is determined by the duration of the SBS. Estimates show that the SBS selector is capable in practice of distinguishing a signal against background noise when the initial distortion level of the object beam is 10-3. Reliable operation of the SBS selector has been demonstrated for radiative and energy loads reaching 2 GW/cm2 and 2 J, respectively.

  15. Optical Generation of 80 GHz Downstream Data in Radio over Fiber System Based on Stimulated Brillouin Scattering

    Directory of Open Access Journals (Sweden)

    Husaini M.M.H

    2017-01-01

    Full Text Available In this work, we proposed Stimulated Brillouin Scattering (SBS in an optical generation of millimeter waves (mm-waves for radio over fiber (RoF system with the transmission of 2.5 Gbps data rate. SBS method is achieved by imposing continuous wave (CW laser in a single mode optical fiber (SMF via Mach-Zehnder Modulator (MZM with Erbium-Doped Fiber Amplifier (EDFA and two pump lasers. Mm-waves signal of 80 GHz was generated from a 40 GHz radio frequency (RF synthesizer. Simulation result and the analysis comparison of effective light power are investigated with different SMF loop length from 20 km until 120 km. The performance of SBS system is analysed and the generated of millimeter waves signal can be transmit with length up to 120 km based on eye pattern and Bit Error Rate (BER curve.

  16. Single-crystal elasticity of diaspore, AlOOH, to 12 GPa by Brillouin scattering

    Science.gov (United States)

    Jiang, Fuming; Majzlan, Juraj; Speziale, Sergio; He, Duanwei; Duffy, Thomas S.

    2008-11-01

    The high-pressure elasticity of diaspore (AlOOH) has been determined by Brillouin spectroscopy to 12 GPa in diamond anvil cells. Experiments were carried out using a 16:3:1 methanol-ethanol-water mixture as pressure medium, and ruby as pressure standard. Acoustic velocities were measured in three roughly orthogonal planes at ambient and eight elevated pressures. The nine individual elastic stiffness constants of the orthorhombic crystal were obtained by fitting the velocity data to Christoffel's equation. Aggregate elastic moduli and pressure derivatives were calculated from the Cijs by fits to Eulerian finite strain equations, yielding: K=152(1) GPa, G0 = 117.2(5) GPa, (/∂P)T=3.7(1),   (=1.5(1) for the Voigt-Reuss-Hill average. All individual Cijs increase with pressure but C23 and C55 exhibit anomalously low pressure derivatives. From calculated linear compressibilities, the a-axis is the most compressible. The b-axis becomes the least compressible axis at high pressures. Over the examined pressure range, the azimuthal P-wave anisotropy decreased from 22% to 16%, while the azimuthal S-wave anisotropy increased from 15% to 21%. Both volume and axial compression curves calculated using our Brillouin results are in good agreement with the results from static compression studies. High-pressure sound velocities in diaspore exceed those of other hydrous minerals as well as many anhydrous phases relevant to Earth's upper mantle.

  17. Phasing of Stokes radiation under shock excitation of stimulated Brillouin scattering

    Energy Technology Data Exchange (ETDEWEB)

    Gordeev, A A; Efimkov, V F; Zubarev, I G; Mikhailov, S I [P N Lebedev Physical Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2011-11-30

    Interaction of counterpropagating waves in Brillouin-active media has been analysed by numerical computation. The dynamics of the development of acoustic waves is described using a secondorder equation. It is shown that in the case of counterpropagating waves with sufficiently steep leading pulse edges ({tau}{sub f} {<=} 3T{sub 2}, where T{sub 2} is the acoustic phonon lifetime), SBS begins from the level of acoustic waves induced by shock excitation in the bulk of the active medium rather than from the spontaneous noise level. This mechanism determines the phase of the output Stokes wave, which is generated in the backward direction to the wave with the highest input intensity, irrespective of the ratio of counterpropagating-wave frequencies.

  18. Elastic Constants of Brucite (Mg(OH)2) and Diaspore (AlO(OH)) to 12 GPa by Brillouin Scattering

    Science.gov (United States)

    Jiang, F.; Speziale, S.; Majzlan, J.; Duffy, T. S.

    2005-12-01

    Hydroxides such as brucite, Mg(OH)2, and diaspore, AlO(OH), serve as analogs for the more complex hydrogen-bearing minerals found in subduction zones. The single-crystal elastic constants of these two minerals were determined by Brillouin scattering up to 12 GPa in a diamond anvil cell. A 16:3:1 methanol-ethanol-water and 4:1 methanol-ethanol mixture were used as pressure media and ruby as pressure calibrant. Two platelets of brucite and three platelets of diaspore were measured at room pressure and over nine elevated pressures. Brillouin spectra were recorded in 37 directions with a 5-degree step for each plane. All individual elastic stiffness constants were retrieved by fitting the velocity data to the Christoffel's equation. The individual elastic constants, aggregate bulk and shear moduli, were then fitted to the finite Eulerian stain equations to obtain their pressure derivatives. For brucite, aggregate moduli and their pressure derivatives are KT0=35.9(9) GPa, GO=31.3(2) GPa, (∂ Kt/∂ P)T0=8.9(3), (∂ G/∂ P)O=4.33(4) for the Reuss bound. Diaspore aggregate moduli and their pressure derivatives are KT0=147.0(7) GPa, GO=114.8(5) GPa, (∂ Ks/∂ P)T0=4.1(1), (∂ G/∂ P)O=1.6(1). For diaspore, both individual and aggregate elastic moduli define nearly linear modulus pressure trend within the measured pressure range. For Brucite, there are clear deviations from linear modulus - pressure trends. In comparison with diaspore, brucite exhibits strong anisotropy. The ratio of the linear compressibility of brucite along the c and a axes decreased from 4.7 to 1.3 over the examined pressure range. The shear anisotropy (C66/C44) decreased from 2.6 at ambient condition to 1.3 with increase of pressure to 12 GPa. Compression curves constructed from our Brillouin data for both brucite and diaspore are in good agreement with previous x-ray diffraction data.

  19. Stimulated Brillouin scattering phase-locking using a transient acoustic standing wave excited through an optical interference field

    International Nuclear Information System (INIS)

    Ondrej Slezak; Milan Kalal; Hon Jin Kong

    2010-01-01

    Complete text of publication follows. Analytical description of an experimentally verified scheme leading to a phase-locked stimulated Brillouin scattering (SBS), used in a laser beam combination systems, is presented. The essential condition for the phase-locking effect for SBS is the fixation of the starting position and time of the acoustic Brillouin wave. It is shown that the starting position fixation of this acoustic wave may have its origin in a transient acoustic standing wave initiated by an arising optical interference field produced by the back-seeding concave mirror. This interference field leads to a stationary density modulation of the medium. However, the way to the formation of this density modulation leads via the acoustic standing wave. An appropriate solution, in the form of the standing wave, was obtained from solving the acoustic wave-equation using the electrostriction as a driving force. As a consequence of the damping term included in this equation the acoustic standing wave becomes gradually attenuated and contrary to the undamped solution published earlier, thus constitutes a truly transient phenomenon. Using a mathematical formalism similar to that which is used for the SBS description in the case of a random phase, the coupled equations describing the phase-locked SBS were derived. Contrary to the case without the back-seeding mirror, where the wave chosen from the thermal noise background subsequently plays the role of a trigger of the stimulated process, in this case it is replaced by the transient standing wave produced as a consequence of the presence of an optical interference field arisen in the focal region of the back-seeding concave mirror.

  20. Monitoring the distributed impact wave on a concrete slab due to the traffic based on polarization dependence on stimulated Brillouin scattering

    International Nuclear Information System (INIS)

    Bao Xiaoyi; Zhang Chunshu; Li Wenhai; Eisa, M; El-Gamal, S; Benmokrane, B

    2008-01-01

    For the first time to our knowledge, distributed impact waves due to the highway traffic on concrete slabs reinforced with FRP bars are monitored in real time using stimulated Brillouin scattering. The impact wave is caused by the traffic passing on the highway pavement at high speed (>100 km h −1 ), which induced pressure on the concrete slabs, and in turn created a local birefringence change, leading to variation of the local state of polarization change (SOP). The pump and probe waves of the stimulated Brillouin scattering 'see' the SOP change and react with a decrease of the Brillouin gain or loss signal, when the pump and probe waves have the same input polarization state. The frequency difference between the pump and probe waves are locked at the static-strain-related Brillouin frequency. Optical fiber was embedded throughout the concrete pavement continuously reinforced with FRP bars in Highway 40 East, Montréal, Quebec to detect impact waves caused by cars and trucks passing on these pavements at a sampling rate of 10 kHz. A spatial resolution of 2 m was used over a sensing length of 300 m

  1. High resolution Brillouin scattering studies of β-Gd2(MoO4)3; the bulk and surface phase transitions

    International Nuclear Information System (INIS)

    Mielcarek, S; Trzaskowska, A; Mroz, B; Andrews, T

    2005-01-01

    We present here results of Brillouin scattering from bulk and surface phonons propagating in a well known ferroelectric-ferroelastic crystal β-Gd 2 (MoO 4 ) 3 , in the temperature range covering the phase transition. Temperature dependences of the velocity of Rayleigh surface acoustic waves, propagating in a few planes of this crystal, have been calculated. The surface phonon velocities determined experimentally have been found to show a different character of temperature dependences, especially in the phase transition range

  2. Pump spectral linewidth influence on stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) and self-termination behavior of SRS in liquids

    Energy Technology Data Exchange (ETDEWEB)

    He, Guang S.; Kuzmin, Andrey; Prasad, Paras N. [The Institute for Lasers, Photonics and Biophotonics, State University of New York, Buffalo, NY (United States)

    2016-12-15

    The threshold, temporal behavior, and conversion efficiency of stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SBS) in three liquids (benzene, hexane, and dimethyl sulfoxide) and two crystals (calcite and barium nitrate) have been investigated under three largely different spectral linewidth conditions. Pumped with 532-nm and nanosecond duration laser pulses of ≤ 0.01 cm{sup -1} linewidth, only SBS can be generated in all tested liquids with a high nonlinear reflectivity. However when the pump spectral linewidth is ∝0.07 cm{sup -1} or ∝0.8 cm{sup -1}, both SBS and SRS can be observed in benzene while only SRS can be generated in dimethyl sulfoxide; in all these cases SRS is the dominant contribution to the stimulated scattering but the efficiency values are drastically decreased due to the self-termination behavior of SRS in liquids, which arises from the thermal self-defocusing of both pump beam and SRS beam owing to Stokes-shift related opto-heating effect. In contrast, for SRS process in the two crystals, the thermal self-defocusing influence is negligible benefitting from their much greater thermal conductivity, and a higher conversion efficiency of SRS generation can be retained under all three pump conditions. (copyright 2016 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Elastic Characterization of Transparent and Opaque Films, Multilayers and Acoustic Resonators by Surface Brillouin Scattering: A Review

    Directory of Open Access Journals (Sweden)

    Giovanni Carlotti

    2018-01-01

    Full Text Available There is currently a renewed interest in the development of experimental methods to achieve the elastic characterization of thin films, multilayers and acoustic resonators operating in the GHz range of frequencies. The potentialities of surface Brillouin light scattering (surf-BLS for this aim are reviewed in this paper, addressing the various situations that may occur for the different types of structures. In particular, the experimental methodology and the amount of information that can be obtained depending on the transparency or opacity of the film material, as well as on the ratio between the film thickness and the light wavelength, are discussed. A generalization to the case of multilayered samples is also provided, together with an outlook on the capability of the recently developed micro-focused scanning version of the surf-BLS technique, which opens new opportunities for the imaging of the spatial profile of the acoustic field in acoustic resonators and in artificially patterned metamaterials, such as phononic crystals.

  4. pF3D Simulations of Large Outer-Beam Brillouin Scattering from NIF Rugby Hohlraums

    Science.gov (United States)

    Langer, Steven; Strozzi, David; Chapman, Thomas; Amendt, Peter

    2015-11-01

    We assess the cause of large outer-beam stimulated Brillouin scattering (SBS) in a NIF shot with a rugby-shaped hohlraum, which has less wall surface loss and thus higher x-ray drive than a cylindrical hohlraum of the same radius. This shot differed from a prior rugby shot with low SBS in three ways: outer beam pointing, split-pointing of the four beams within each outer-beam quadruplet, and a small amount of neon added to the hohlraum helium fill gas. We use pF3D, a massively-parallel, paraxial-envelope laser plasma interaction code, with plasma profiles from the radiation-hydrodynamics code Lasnex. We determine which change between the two shots increased the SBS by adding them one at a time to the simulations. We compare the simulations to experimental data for total SBS power, its spatial distribution at the lens, and the SBS spectrum. For each shot, we use profiles from Lasnex simulations with and without a model for mix at the hohlraum wall-gas interface. Work performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344. Release number LLNL-ABS-674893.

  5. Discrete modes of a ferromagnetic stripe dipolarly coupled to a ferromagnetic film: a Brillouin light scattering study

    International Nuclear Information System (INIS)

    Gubbiotti, G; Tacchi, S; Carlotti, G; Ono, T; Roussigne, Y; Tiberkevich, V S; Slavin, A N

    2007-01-01

    Spin wave excitations in a magnetic structure consisting of a series of long permalloy stripes of a rectangular cross section magnetized along the stripe length and situated above a continuous permalloy film are studied both experimentally and theoretically. Stripes and continuous film are coupled by dipole-dipole interaction across 10 nm thick Cu spacers. Experimental measurements made using the Brillouin light scattering technique (with the light wavevector oriented along the stripe width) provide evidence for one dispersive spin wave mode associated with the continuous film and several discrete non-dispersive modes resonating within the finite width of the stripes. To interpret the experimental spectra, an analytic theory based on the spin wave formalism for finite-width magnetic stripes has been developed, achieving a good qualitative and partly quantitative description of the experimentally observed spin wave spectrum of the system. In particular, it is explained why the presence of a continuous magnetic film near the magnetic stripe leads to a substantial decrease of the frequencies of the discrete dipolar spin wave modes localized within the stripes. A more quantitative description of the measured frequencies and of the spatial profiles of the spin wave eigenmodes has been obtained by numerical calculations performed using a finite element method

  6. Localized spin-wave modes in a triangular magnetic element studied by micro-focused Brillouin light scattering

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, S.; Kwon, J.-H. [School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005 (Korea, Republic of); Grünberg, P. [Grünberg Center for Magnetic Nanomaterials, Gwangju Institute of Science and Technology (GIST), Gwangju 61005 (Korea, Republic of); Cho, B.K., E-mail: chobk@gist.ac.kr [School of Materials Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005 (Korea, Republic of)

    2017-09-01

    Highlights: • Direct evidence of localized mode in a triangular nano-magnet using μ-BLS. • Localized regions are identified by the internal field distribution. • The spatially resolved measurement was performed to obtain 2-D intensity map. • Spin modes in same positions can be distinguish comparing with simulated spectrum. • Localized modes were identified by comparing with the simulated spatial profiles. - Abstract: Localized spin-wave modes, which were thermally excited at a specific position in a triangular magnetic element, were investigated using micro-focused Brillouin light scattering in two saturated states, the buckle and Y-states, with an applied magnetic field of 0.24 T parallel and perpendicular to the basal edge, respectively. The measured frequency spectrum at a specific beam spot position, rather than an integrated spectrum, was analyzed by comparing it with the simulation data at a precisely selected position within the beam spot area. The analyzed results were used to plot a two-dimensional intensity map and simulation spatial profile to verify the validity of the analysis. From the analysis process, two localized spin-wave modes in a triangular magnetic element were successfully identified near the apex region in the buckle state and near the basal edge region in the Y-state.

  7. High-input dynamic range and selectivity stimulated Brillouin scattering-based microwave photonic filter utilizing a dual-stage scheme.

    Science.gov (United States)

    Zhang, Ke; Zhong, Yibo; Ke, Changjian; Liu, Deming

    2017-09-01

    A high-input dynamic range and selectivity stimulated Brillouin scattering (SBS)-based microwave photonic filter (MPF) is proposed and experimentally demonstrated. By utilizing a pump-splitting dual-stage scheme to mitigate the gain saturation, an input dynamic range of >40  dB and a selectivity of >49  dB are achieved simultaneously for the first time, to the best of our knowledge. The bandwidth is reconfigurable from 50 MHz to 200 MHz by tailoring the Brillouin pump precisely. During the bandwidth turning, the passband ripple is maintained <1.3  dB, and the 20-dB shape factor is 1.2 for the 200-MHz case. The superior performance makes the proposed SBS-MPF one of the best candidates for microwave photonics applications.

  8. Interfacial Dzyaloshinskii-Moriya interaction sign in Ir/Co2FeAl systems investigated by Brillouin light scattering

    Science.gov (United States)

    Belmeguenai, M.; Gabor, M. S.; Roussigné, Y.; Petrisor, T.; Mos, R. B.; Stashkevich, A.; Chérif, S. M.; Tiusan, C.

    2018-02-01

    C o2FeAl (CFA) ultrathin films, of various thicknesses (0.9 nm ≤tCFA≤1.8 nm ), have been grown by sputtering on Si substrates, using Ir as a buffer layer. The magnetic properties of these structures have been studied by vibrating sample magnetometry (VSM), miscrostrip ferromagnetic resonance (MS-FMR), and Brillouin light scattering (BLS) in the Damon-Eshbach geometry. VSM characterizations show that films are mostly in-plane magnetized and the saturating field perpendicular to the film plane increases with decreasing CFA thickness suggesting the existence of a perpendicular interface anisotropy. The presence of a magnetic dead layer of 0.44 nm has been detected by VSM. The MS-FMR with the magnetic field applied perpendicularly to the film plane has been used to determine the gyromagnetic factor. The BLS measurements reveal a pronounced nonreciprocal spin wave propagation, due to the interfacial Dzyaloshinskii-Moriya interaction (DMI) induced by the Ir interface with CFA, which increases with decreasing CFA thickness. The DMI sign has been found to be the same (negative) as that of Pt/Co, in contrast to the ab initio calculation on Ir/Co, where it is found to be positive. The thickness dependence of the effective DMI constant shows the existence of two regimes similarly to that of the perpendicular anisotropy constant. The surface DMI constant Ds was estimated to be -0.37 pJ /m for the thickest samples, where a linear thickness dependence of the effective DMI constant has been observed.

  9. Solar Wind Electron Scattering by Kinetic Instabilities and Whistler Turbulence

    Science.gov (United States)

    Gary, S. P.

    2015-12-01

    The expansion of the solar wind away from the Sun drives electron velocity distributions away from the thermal Maxwellian form, yielding distributions near 1 AU which typically can be characterized as consisting of three anisotropic components: a more dense, relatively cool core, a relatively tenuous , relatively warm halo and a similarly tenuous, warm strahl. Each of these nonthermal components are potential sources of kinetic plasma instabilities; the enhanced waves from each instability can scatter the electrons, acting to reduce the various anisotropies and making their overall velocity distribution more nearly (but not completely) thermal. In contrast, simulations are demonstrating that the forward decay of whistler turbulence can lead to the development of a T||> T_perp electron anisotropy. This presentation will review linear theories of electron-driven kinetic instabilities (following the presentation by Daniel Verscharen at the 2015 SHINE Workshop), and will further consider the modification of electron velocity distributions as obtained from particle-in-cell simulations of such instabilities as well as from the decay of whistler turbulence.

  10. Modeling of stimulated Brillouin scattering near the critical-density surface in the plasmas of direct-drive inertial confinement fusion targets

    International Nuclear Information System (INIS)

    Maximov, A.V.; Myatt, J.; Seka, W.; Short, R.W.; Craxton, R.S.

    2004-01-01

    OAK-B135 The nonlinear propagation of laser beams, smoothed by spatial and temporal bandwidth, near the critical density surface of direct-drive inertial confinement fusion (ICF) targets has been modeled. The interplay between filamentation and forward and backward stimulated Brillouin scattering (SBS) is described in the presence of light reflected from the critical density surface and high absorption of light near the critical density. The spectrum of backscattered light develops a red shift due to SBS, which can be seeded by the reflection of light from the critical surface. The intensity of backscattered light decreases moderately as the bandwidth of smoothing by spectral dispersion (SSD) is increased

  11. Analysis of beam plasma instability effects on incoherent scatter spectra

    Directory of Open Access Journals (Sweden)

    M. A. Diaz

    2010-12-01

    Full Text Available Naturally Enhanced Ion Acoustic Lines (NEIALs detected with Incoherent Scatter Radars (ISRs can be produced by a Langmuir decay mechanism, triggered by a bump on tail instability. A recent model of the beam-plasma instability suggests that weak-warm beams, such those associated with NEIAL events, might produce Langmuir harmonics which could be detected by a properly configured ISR. The analysis performed in this work shows that such a beam-driven wave may be simultaneously detected with NEIALs within the baseband signal of a single ISR. The analysis shows that simultaneous detection of NEIALs and the first Langmuir harmonic is more likely than simultaneous detection of NEIALs and enhanced plasma line. This detection not only would help to discriminate between current NEIAL models, but could also aid in the parameter estimation of soft precipitating electrons.

  12. Temporal evolution of stimulated Brillouin backscatter

    International Nuclear Information System (INIS)

    Hinkel, D.E.; Williams, E.A.; Berger, R.L.

    1994-01-01

    A qualitative understanding of the time dependence of stimulated Brillouin scattering (SBS) provides estimates of the amount of temporal growth that occurs in current inertial confinement fusion and short laser pulse interaction experiments when the growth is limited by the length of the experiment or by motion of the ''hot spots'' of the laser intensity pattern induced by beam smoothing. In the weak coupling limit, the instantaneous growth rate depends upon the plasma initial conditions early in time, is proportional to t -1/2 later in time, and asymptotically approaches the absolute growth rate (in the absence of damping). When the instability is strongly coupled, the growth rate depends upon the plasma initial conditions early in time but is proportional to t -1/3 later in time. When the growth rate drops to a value comparable to that of the ion acoustic frequency, the instability becomes effectively weakly coupled. The effects of damping are also discussed

  13. ITER Plasma at Electron Cyclotron Frequency Domain: Tokamak Core Plasma Diagnostics Based on the Synergy of Stimulated Raman and Brillouin Scatterings

    Science.gov (United States)

    Stefan, V. Alexander

    2012-10-01

    A novel plasma diagnostic method is proposed based on the synergy of stimulated Raman and Brillouin scatterings. A nonlinear plasma mode is excited in a 4-wave coupling,footnotetextV. Alexander STEFAN, Nonlinear Electromagnetic Radiation Plasma Interactions, (S-U-Press, 2008). leading to the appearance of suprathermal electrons and accelerated ions at the plasma edgefootnotetextV. Alexander Stefan, Abstract: D1.00018 : ITER Plasma at Electron Cyclotron Frequency Domain: Stimulated Raman Scattering off Gould-Trivelpiece Modes and Generation of Suprathermal Electrons and Energetic Ions; Bulletin of the American Physical Society APS April Meeting 2011 Volume 56, Number 4. with the parameters directly dependent on the plasma parameters in the core of tokamak. Accordingly, plasma diagnostic in the core region, (ion temperature), can be performed by the diagnostics of suprathermal electrons and accelerated ions at the edge plasma.

  14. Brillouin scattering, DSC, dielectric and X-ray diffraction studies of phase transitions in antiferroelectric PbHfO{sub 3}:Sn

    Energy Technology Data Exchange (ETDEWEB)

    Mączka, Mirosław, E-mail: m.maczka@int.pan.wroc.pl [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław 2 (Poland); Kim, Tae Hyun [Institute of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Gągor, Anna [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław 2 (Poland); Jankowska-Sumara, Irena [Institute of Physics, Pedagogical University, ul. Podchorążych 2, 30-084 Kraków (Poland); Majchrowski, Andrzej [Institute of Applied Physics, Military University of Technology, 2 Kaliskiego Str., 00-908 Warszawa (Poland); Kojima, Seiji [Institute of Materials Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan)

    2015-02-15

    Highlights: • Phase transition mechanisms were studied in antiferroelectric PbHf{sub 0.975}Sn{sub 0.025}O{sub 3.} • Acoustic phonons showed anomalies at 472 and 426 K due to phase transitions. • Brillouin data showed evidence for presence of polar clusters in paraelectric phase. • An order-disorder mechanism of the PE to AFE2 transition was proved. - Abstract: Specific heat, dielectric, powder X-ray diffraction and Brillouin scattering studies of phase transitions in antiferroelectric PbHf{sub 0.975}Sn{sub 0.025}O{sub 3} crystal were performed. The specific heat data revealed clear anomalies at T{sub 1} = 473.5 and T{sub 2} = 426.3 K on cooling, which could be attributed to onset of first order phase transitions from the paraelectric (PE) phase to an intermediate antiferroelectric phase (AFE2) and the AFE2 phase to another antiferroelectric phase (AFE1), respectively. The estimated entropy changes at T{sub 1} and T{sub 2} pointed to mainly an order-disorder and displacive character of these transitions, respectively. X-ray diffraction data showed a complex superstructure of the intermediate phase with a = 11.895(6) Å, b = 11.936(4) Å, c = 8.223(3) Å at 453 K. Brillouin studies revealed pronounced softening of longitudinal acoustic (LA) mode in the PE phase associated with its broadening. The broadening and softening exhibited maximum values at T{sub 1}. Additional acoustic anomalies, that is, abrupt frequency shifts for LA and transverse acoustic (TA) modes were also observed at T{sub 2}. Brillouin scattering data also showed presence of a broad central peak (CP) that exhibited highest intensity at T{sub 1}. The observed temperature dependences of acoustic modes and CP indicate order-disorder character of the FE to AFE2 phase transition and importance of polar precursor clusters in the PE phase. The obtained data also suggest that the intermediate antiferroelectric phases in Sn{sup 4+} doped PbHfO{sub 3} and PbZrO{sub 3} may have very similar structures

  15. Advances of a Brillouin Scattering Lidar System for the Detection of Temperature Profiles in the Ocean: Laboratory Measurements and Field Test

    Science.gov (United States)

    Walther, T.; Rupp, D.; Friman, S.; Trees, C.; Fournier, G.

    2016-02-01

    Recently we have demonstrated the feasibility of remotely measuring temperature profiles in water under a laboratory environment employing our real-time Brillouin Scattering LIDAR (BSL) system. The working principle is based on the frequency and time resolved detection of the backscattered spontaneous Brillouin signal of a short light pulse fired into the ocean. The light source consists of a frequency-doubled fiber-amplified External Cavity Diode Laser (ECDL) providing high-energy, Fourier transform-limited laser pulses in the green spectral range. The Brillouin shift is detected with high accuracy (low uncertainty) by employing an edge filter based on an Excited State Faraday Anomalous Dispersion Optical Filter (ESFADOF). Time-resolution allows for the depth resolution and the frequency resolved shift is proportional to the speed of sound. Thus, the temperature profile can be extracted from the measurements. In our laboratory setup we were able to resolve water temperatures with a mean accuracy of up to 0.07 oC and a spatial resolution of 1 m depending on the amount of averaging. In order to prepare the system for a first field test under realistic conditions on the coast of the Mediterranean at CMRE in La Spezia, almost all of the components have been upgraded. This first test is planned for November 2015. We will present the above mentioned measurements, details about the upgrades and report on our experiences during this maritime field test.Ultimately, the plan is to operate the system from a mobile platform, e.g., a helicopter or vessel, in order to precisely determine the temperature of the surface mixed layer of the ocean with high spatial resolution.

  16. Unusual features of long-range density fluctuations in glass-forming organic liquids: A Rayleigh and Rayleigh-Brillouin light scattering study

    International Nuclear Information System (INIS)

    Patkowski, A.; Fischer, E. W.; Steffen, W.; Glaser, H.; Baumann, M.; Ruths, T.; Meier, G.

    2001-01-01

    A new feature of glass-forming liquids, i.e., long-range density fluctuations of the order of 100 nm, has been extensively characterized by means of static light scattering, photon correlation spectroscopy and Rayleigh-Brillouin spectroscopy in orthoterphenyl (OTP) and 1,1-di(4 # prime#-methoxy-5 # prime#methyl-phenyl)-cyclohexane (BMMPC). These long-range density fluctuations result in the following unusual features observed in a light scattering experiment, which are not described by the existing theories: (i) strong q-dependent isotropic excess Rayleigh intensity, (ii) additional slow component in the polarized photon correlation function, and (iii) high Landau-Placzek ratio. These unusual features are equilibrium properties of the glass-forming liquids and depend only on temperature, provided that the sample has been equilibrated long enough. The temperature-dependent equilibration times were measured for BMMPC and are about 11 orders of magnitude longer than the α process. It was found that the glass-forming liquid OTP may occur in two states: with and without long-range density fluctuations ('clusters'). We have characterized the two states by static and dynamic light scattering in the temperature range from T g to T g +200 K. The relaxation times of the α process as well as the parameters of the Brillouin line are identical in both OTP with and without clusters. The α process (density fluctuations) in OTP was characterized by measuring either the polarized (VV) or depolarized (VH) correlation function, which are practically identical and q-independent. This feature, which is commonly observed in glass-forming liquids, is not fully explained by the existing theories

  17. A Brillouin scattering study of La0.77Ca0.23MnO3 across the metal-insulator transition

    International Nuclear Information System (INIS)

    Seikh, Md Motin; Narayana, Chandrabhas; Sudheendra, L; Sood, A K; Rao, C N R

    2004-01-01

    Temperature-dependent Brillouin scattering studies have been carried out on La 0.77 Ca 0.23 MnO 3 across the paramagnetic insulator-ferromagnetic metal (I-M) transition (T C ∼ 230 K). The spectra show modes corresponding to a surface Rayleigh wave (SRW) and a high velocity pseudo-surface wave (HVPSAW) along with bulk acoustic waves (B1 and B2). The Brillouin shifts associated with the SRW and HVPSAW increase, whereas the B1 and B2 frequencies decrease, below T C . The temperature dependence of the SRW and HVPSAW modes is related to the increase in the elastic constant C 11 across the I-M transition. The decrease in frequency across the I-M transition of the bulk modes is understood to be due to enhanced self-energy corrections as a result of increased magnon-phonon interaction across the I-M transition. Correspondingly, these modes show a large increase in the full width at half maximum (FWHM) as the temperature decreases. We also observe a central peak whose width is maximum at T C

  18. Surface Brillouin scattering measurement of the elastic constants of single crystal InAs{sub 0.91}Sb{sub 0.09}

    Energy Technology Data Exchange (ETDEWEB)

    Kotane, L M; Comins, J D; Every, A G [Materials Physics Research Institute, School of Physics, University of the Witwatersrand, Johannesburg, Wits 2050 (South Africa); Botha, J R, E-mail: Lesias.Kotane@wits.ac.z [Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth (South Africa)

    2011-01-01

    Surface Brillouin scattering of light has been used to measure the angular dependence of the Rayleigh surface acoustic wave (SAW), pseudo surface acoustic wave (PSAW) and longitudinal lateral wave (LLW) speeds in a (100)-oriented single crystal of the ternary semiconductor alloy InAs{sub 0.91}Sb{sub 0.09}. The wave speed measurements have been used to determine the room temperature values of the elastic constants C{sub 11}, C{sub 12} and C{sub 44} of the alloy. A simple and robust fitting procedure has been implemented for recovering the elastic constants, in which the merit function is constructed from explicit secular functions that determine the surface and lateral wave speeds in the [001] and [011] crystallographic directions. In the fitting, relatively larger weighting factors have been assigned to the SAW and PSAW data because of the greater precision with which the surface modes can be measured as compared with the lateral wave.

  19. Surface Brillouin scattering measurement of the elastic constants of single crystal InAs0.91Sb0.09

    International Nuclear Information System (INIS)

    Kotane, L M; Comins, J D; Every, A G; Botha, J R

    2011-01-01

    Surface Brillouin scattering of light has been used to measure the angular dependence of the Rayleigh surface acoustic wave (SAW), pseudo surface acoustic wave (PSAW) and longitudinal lateral wave (LLW) speeds in a (100)-oriented single crystal of the ternary semiconductor alloy InAs 0.91 Sb 0.09 . The wave speed measurements have been used to determine the room temperature values of the elastic constants C 11 , C 12 and C 44 of the alloy. A simple and robust fitting procedure has been implemented for recovering the elastic constants, in which the merit function is constructed from explicit secular functions that determine the surface and lateral wave speeds in the [001] and [011] crystallographic directions. In the fitting, relatively larger weighting factors have been assigned to the SAW and PSAW data because of the greater precision with which the surface modes can be measured as compared with the lateral wave.

  20. THE EFFECT OF TWO-MAGNON SCATTERING ON PARALLEL-PUMP INSTABILITY THRESHOLDS.

    Science.gov (United States)

    Following a general description of the important properties and symmetries of the parallel-pump coupling and of two- magnon scattering, several...theoretical approaches to the problem of the effect of two- magnon scattering on the parallel-pump instability threshold are explored. A successful approach

  1. Micro-focused Brillouin light scattering study of the magnetization dynamics driven by Spin Hall effect in a transversely magnetized NiFe nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Madami, M., E-mail: marco.madami@fisica.unipg.it; Carlotti, G. [Dipartimento di Fisica e Geologia, Università di Perugia, Perugia (Italy); Gubbiotti, G.; Tacchi, S. [Istituto Officina dei Materiali del CNR (CNR-IOM), Unità di Perugia, c/o Dipartimento di Fisica e Geologia, Università di Perugia, Perugia (Italy); Moriyama, T.; Tanaka, K.; Ono, T. [Institute for Chemical Research, Kyoto University, Kyoto (Japan); Siracusano, G.; Finocchio, G. [Department of Electronic Engineering, Industrial Chemistry and Engineering, University of Messina, Messina (Italy); Carpentieri, M. [Department of Electrical and Information Engineering, Politecnico of Bari, Bari (Italy)

    2015-05-07

    We employed micro-focused Brillouin light scattering to study the amplification of the thermal spin wave eigenmodes by means of a pure spin current, generated by the spin-Hall effect, in a transversely magnetized Pt(4 nm)/NiFe(4 nm)/SiO{sub 2}(5 nm) layered nanowire with lateral dimensions 500 × 2750 nm{sup 2}. The frequency and the cross section of both the center (fundamental) and the edge spin wave modes have been measured as a function of the intensity of the injected dc electric current. The frequency of both modes exhibits a clear redshift while their cross section is greatly enhanced on increasing the intensity of the injected dc. A threshold-like behavior is observed for a value of the injected dc of 2.8 mA. Interestingly, an additional mode, localized in the central part of the nanowire, appears at higher frequency on increasing the intensity of the injected dc above the threshold value. Micromagnetic simulations were used to quantitatively reproduce the experimental results and to investigate the complex non-linear dynamics induced by the spin-Hall effect, including the modification of the spatial profile of the spin wave modes and the appearance of the extra mode above the threshold.

  2. Development of low-temperature and high-pressure Brillouin scattering spectroscopy and its application to the solid I form of hydrogen sulphide

    CERN Document Server

    Murase, S; Sasaki, S; Kume, T; Shimizu, H

    2002-01-01

    A new experimental system has been developed for low-temperature and high-pressure Brillouin scattering measurements. The new system allows us to investigate the elastic properties of samples in a diamond anvil cell (DAC) down to liquid N sub 2 temperature (approx 80 K). In contrast to the case in our conventional technique, the optics in the system can be rotated for measuring the direction dependence of acoustic velocities of the samples in the DAC fixed in the cryostat. The new experimental technique was applied to the solid I form of hydrogen sulphide (H sub 2 S). As a result, three ratios of elastic constants to density were successfully determined at P = 3.70 GPa, T = 240 K: C sub 1 sub 1 /rho = 16.4, C sub 1 sub 2 /rho = 12.4, C sub 4 sub 4 /rho = 7.57 x 10 sup 6 m sup 2 s sup - sup 2. These values are almost the same as those obtained at room temperature.

  3. Dependence of Interfacial Dzyaloshinskii-Moriya Interaction on Layer Thicknesses in Ta /Co -Fe -B /TaOx Heterostructures from Brillouin Light Scattering

    Science.gov (United States)

    Chaurasiya, Avinash Kumar; Choudhury, Samiran; Sinha, Jaivardhan; Barman, Anjan

    2018-01-01

    The interfacial Dzyaloshinskii-Moriya interaction (IDMI) has recently drawn extensive research interest due to its fundamental role in stabilizing chiral spin textures in ultrathin ferromagnets, which are suitable candidates for future magnetic-memory devices. Here, we explore the ferromagnetic and heavy-metal layer-thickness dependence of IDMI in technologically important Ta /Co20Fe60B20/TaOx heterostructures by measuring nonreciprocity in spin-wave frequency using the Brillouin light-scattering technique. The observed value of the IDMI constant agrees with that obtained from a separate measurement of in-plane angular dependence of frequency nonreciprocity, which is also in good agreement with the theory predicted by Cortes-Ortuno and Landeros. Linear scaling behavior of IDMI with the inverse of Co-Fe-B thicknesses suggests that IDMI originates primarily from the interface in these heterostructures, whereas we observe a weak dependence of Ta thickness on the strength of IDMI. Importantly, the observed value of the IDMI constant is reasonably large by a factor of 3 compared to annealed Ta /Co -Fe -B /MgO heterostructures. We propose that the observation of large IDMI is likely due to the absence of boron diffusion towards the Ta /Co -Fe -B interface as the heterostructures are as deposited. Our detailed investigation opens up a route to designing thin-film heterostructures with the tailored IDMI constant for controlling Skyrmion-based magnetic-memory devices.

  4. Dynamics of a self-Q-switched fiber laser with a Rayleigh-stimulated Brillouin scattering ring mirror

    Science.gov (United States)

    Fotiadi, Andrei A.; Mégret, Patrice; Blondel, Michel

    2004-05-01

    Backward light scattering can cause passive Q switching in fiber lasers. We propose a self-consistent description of the laser dynamics. Our model quantitatively reproduces the temporal structure of pulsation and is also attractive for analysis of laser stability and statistics. The validity of the model is directly verified in an experiment.

  5. Ionospheric modification and parametric instabilities

    International Nuclear Information System (INIS)

    Fejer, J.A.

    1979-01-01

    Thresholds and linear growth rates for stimulated Brillouin and Raman scattering and for the parametric decay instability are derived by using arguments of energy transfer. For this purpose an expression for the ponderomotive force is derived. Conditions under which the partial pressure force due to differential dissipation exceeds the ponderomotive force are also discussed. Stimulated Brillouin and Raman scattering are weakly excited by existing incoherent backscatter radars. The parametric decay instability is strongly excited in ionospheric heating experiments. Saturation theories of the parametric decay instability are therefore described. After a brief discussion of the purely growing instability the effect of using several pumps is discussed as well as the effects of inhomogenicity. Turning to detailed theories of ionospheric heating, artificial spread F is discussed in terms of a purely growing instability where the nonlinearity is due to dissipation. Field-aligned short-scale striations are explained in terms of dissipation of the parametrically excited Langmuir waves (plasma oscillations): they might be further amplified by an explosive instability (except the magnetic equator). Broadband absorption is probably responsible for the 'overshoot' effect: the initially observed level of parametrically excited Langmuir waves is much higher than the steady state level

  6. Conjugation and transformation of the wave front by stimulated Brillouin scattering of vortex Laguerre - Gaussian laser modes

    International Nuclear Information System (INIS)

    Kopalkin, A V; Bogachev, V A; Dolgopolov, Yu V; Kochemasov, G G; Kulikov, S M; Maslov, N V; Starikov, F A; Sukharev, Stanislav A; Feoktistov, V V; Bagdasarov, V Kh; Denisov, N N; Malyutin, A A

    2011-01-01

    We study experimentally stimulated Brilluoin scattering (SBS) of vortex laser beams, namely, the LG 1 1 and LG 0 1 Laguerre -Gaussian modes. The wave front transformation is experimentally demonstrated in the case of SBS of the LG 1 1 laser mode, directly focused into the SBS cell, when the fundamental Gaussian mode LG 0 0 rather than the conjugate mode is selected from the Stokes beam. It is shown that optical vortices become phase conjugate by destroying the laser mode structure in the SBS cell. Phase conjugation (PC) of the LG 0 1 and LG 1 1 modes is obtained in the SBS mirror using a regular aberrator (microlens raster) in the system of laser beam focusing into the SBS cell.

  7. Observation of narrowband intrinsic spectra of Brillouin dynamic gratings.

    Science.gov (United States)

    Song, Kwang Yong; Yoon, Hyuk Jin

    2010-09-01

    We experimentally demonstrate that the reflection spectrum of a Brillouin dynamic grating in a polarization-maintaining fiber can be much narrower than the intrinsic linewidth of the stimulated Brillouin scattering, matching well with the theory of a fiber Bragg grating in terms of the linewidth and the reflectivity. A 3 dB bandwidth as narrow as 10.5 MHz is observed with the Brillouin dynamic grating generated in a 9 m uniform fiber.

  8. Development of High Spectral Resolution Technique for Registration Quasielastic Light Scattering Spectra Including Rayleigh and Brillouin Scattering as a Diagnostic Tool in Materials Characterization

    National Research Council Canada - National Science Library

    Bairamov, Bakhysh

    2004-01-01

    ...: As detailed in an on-line proposal the contractor will: 1) develop and build an optical device, fitted to a Fabry-Perot interferometer, to perform high-resolution quasieleastic light scattering spectroscopy; 2...

  9. Stimulated Brillouin processes in crystals and glasses

    International Nuclear Information System (INIS)

    Faris, G.W.; Hickman, A.P.

    1992-02-01

    The basic physics and material properties needed to describe and predict the Brillouin gain for a variety of materials have been investigated. Lawrence Livermore National Laboratory (LLNL) has identified transverse stimulated Brillouin scattering (SBS) as an important limiting mechanism in high power laser fusion systems. At sufficiently high laser intensities, SBS drives acoustic vibrations that can damage optical components. SRI has performed measurements and developed the corresponding theory for stimulated Brillouin gain spectroscopy in anisotropic crystals. Absolute Brillouin steady-state gain coefficients, linewidths, and frequency shifts have been determined at 532 nm for a number of optical materials of interest to LLNL. This knowledge can be used to select optical materials and devise suppression schemes that will allow much higher laser fluences to be used in laser fusion

  10. Measurement of the stimulated thermal Rayleigh scattering instability

    International Nuclear Information System (INIS)

    Karr, T.J.; Rushford, M.C.; Murray, J.R.; Morris, J.R.

    1989-04-01

    Growth of perturbations due to stimulated thermal Rayleigh scattering was observed on a laser beam propagating in a 1 meter cell of CC14. Initial sinusoidal irradiance perturbations were seeded onto the laser leam, and their amplification in the cell was recorded by a near field camera. The perturbation growth rate is in agreement with analytical predictions of linearized propagation theory

  11. Stimulated ion Compton scattering instability of whistlers in plasmas

    International Nuclear Information System (INIS)

    Shukla, P. K.; Shukla, Nitin; Stenflo, L.

    2006-01-01

    The nonlinear interactions between magnetic field-aligned broadband whistler wave packets (hereafter referred to as whistlerons) and ion quasimodes in magnetized plasmas are considered. By treating the whistlerons as quasiparticles, their nonlinear propagation in a slowly varying medium supported by ion quasimode density perturbations is studied. A nonlinear dispersion relation within the framework of the wave-kinetic (for the whistlerons) and Vlasov (for the ion quasimodes) descriptions is derived. The dispersion relation admits a kinetic modulational instability. The growth rate of the latter is presented. The present result can improve our understanding of the nonlinear propagation of incoherent whistlers, which have been frequently observed in the Earth's magnetosphere as well as in laboratory plasmas

  12. Dynamic stimulated Brillouin scattering analysis

    DEFF Research Database (Denmark)

    Djupsöbacka, A.; Jacobsen, Gunnar; Tromborg, Bjarne

    2000-01-01

    We present a new simple analysis - including the effect of spontaneous emission - of the (dynamic) influence of SBS on the detected receiver eye diagram. It applies in principle for general types of modulation formats such as the digital formats of ASK, FSK, and PSK. The analysis is formulated fo...

  13. Instability Versus Equilibrium Propagation of Laser Beam in Plasma

    OpenAIRE

    Lushnikov, Pavel M.; Rose, Harvey A.

    2003-01-01

    We obtain, for the first time, an analytic theory of the forward stimulated Brillouin scattering instability of a spatially and temporally incoherent laser beam, that controls the transition between statistical equilibrium and non-equilibrium (unstable) self-focusing regimes of beam propagation. The stability boundary may be used as a comprehensive guide for inertial confinement fusion designs. Well into the stable regime, an analytic expression for the angular diffusion coefficient is obtain...

  14. Brillouin, Prof. Leon

    Indian Academy of Sciences (India)

    Home; Fellowship. Fellow Profile. Elected: 1939 Honorary. Brillouin, Prof. Leon. Date of birth: 7 August 1889. Date of death: 4 October 1969 ... Posted on 21 December 2017. ASTROPHYSICS: An Observational View of the Universe. Math Art and Design: MAD about Math, Math Education and Outreach. Math and Finance ...

  15. Saturation of backward stimulated scattering of laser in kinetic regime: Wavefront bowing, trapped particle modulational instability, and trapped particle self-focusing of plasma waves

    International Nuclear Information System (INIS)

    Yin, L.; Albright, B. J.; Bowers, K. J.; Daughton, W.; Rose, H. A.

    2008-01-01

    Backward stimulated Raman and Brillouin scattering (SRS and SBS) of laser are examined in the kinetic regime using particle-in-cell simulations. The SRS reflectivity measured as a function of the laser intensity in a single hot spot from two-dimensional (2D) simulations shows a sharp onset at a threshold laser intensity and a saturated level at higher intensities, as obtained previously in Trident experiments [D. S. Montgomery et al., Phys. Plasmas 9, 2311 (2002)]. In these simulations, wavefront bowing of electron plasma waves (ion acoustic waves) due to the trapped particle nonlinear frequency shift, which increases with laser intensity, is observed in the SRS (SBS) regime for the first time. Self-focusing from trapped particle modulational instability (TPMI) [H. A. Rose, Phys. Plasmas 12, 12318 (2005)] is shown to occur in both two- and three-dimensional SRS simulations. The key physics underlying nonlinear saturation of SRS is identified as a combination of wavefront bowing, TPMI, and self-focusing of electron plasma waves. The wavefront bowing marks the beginning of SRS saturation and self-focusing alone is sufficient to terminate the SRS reflectivity, both effects resulting from cancellation of the source term for SRS and from greatly increased dissipation rate of the electron plasm waves. Ion acoustic wave bowing also contributes to the SBS saturation. Velocity diffusion by transverse modes and rapid loss of hot electrons in regions of small transverse extent formed from self-focusing lead to dissipation of the wave energy and an increase in the Landau damping rate in spite of strong electron trapping that reduces Landau damping initially. The ranges of wavelength and growth rate associated with transverse breakup of the electron-plasma wave are also examined in 2D speckle simulations as well as in 2D periodic systems from Bernstein-Greene-Kruskal equilibrium and are compared with theory predictions

  16. Nonlinear behavior of stimulated scatter in large underdense plasmas

    International Nuclear Information System (INIS)

    Kruer, W.L.; Estabrook, K.G.

    1979-01-01

    Several nonlinear effects which limit Brillouin and Raman scatter of intense light in large underdense plasmas are examined. After briefly considering ion trapping and harmonic generation, we focus on the self-consistent ion heating which occurs as an integral part of the Brillouin scattering process. In the long-term nonlinear state, the ion wave amplitude is determined by damping on the heated ion tail which self-consistently forms. A simple model of the scatter is presented and compared with particle simulations. A similar model is also applied to Raman scatter and compared with simulations. Our calculations emphasize that modest tails on the electron distribution function can significantly limit instabilities involving electron plasma waves

  17. Sound velocities and hypersonic dampings of Pb[(Mg1/3Nb2/3)0.45Ti0.55]O3 single crystals studied by Brillouin light scattering.

    Science.gov (United States)

    Ko, Jae-Hyeon; Kim, Tae Hyun; Kojima, Seiji; Bokov, Alexei A; Ye, Zuo-Guang

    2010-12-08

    A Brillouin spectroscopic investigation was carried out on PMN-55%PT single crystals, which are known to have no chemically ordered regions and undergo a well-defined structural phase transition at T(C) ∼ 521 K. The longitudinal and transverse sound velocities probed on a right-angle scattering geometry exhibited a remarkable softening and increasing hypersonic damping on approaching T(C) from T(B) ∼ 610 K that was characterized by the deviation of the dielectric permittivity from the high-temperature Curie-Weiss behavior. The acoustic anomalies of the longitudinal acoustic mode at the backward scattering were more substantial than those observed at the right-angle scattering, which could be understood in the framework of normal acoustic dispersion considering the difference in the acoustic frequency. The softening of the transverse sound velocity was more significant than that of the longitudinal one upon cooling toward T(C), suggesting that this acoustic anomaly may be related to the local rhombohedral transformation, occurring in polar nano-regions (PNRs). The observed acoustic behaviors combined with the central peak dynamics clearly indicated the existence of dynamic polar nano-regions in PMN-55%PT where there are no chemically ordered regions, and seem to suggest that the order parameter fluctuations due to two kinds of coupling contribute to the acoustic anomalies in the temperature range of T(C) ∼ T(B): electrostrictive coupling between the acoustic waves and the dynamic PNRs, and linear coupling between the acoustic waves and the precursor polar clusters, i.e., the ordering unit responsible for the order-disorder-type slowing down behavior probed by the central peak.

  18. TURBISCAN MA 2000: multiple light scattering measurement for concentrated emulsion and suspension instability analysis.

    Science.gov (United States)

    Mengual, O; Meunier, G; Cayré, I; Puech, K; Snabre, P

    1999-09-13

    Emulsion or suspension destabilisation often results from coalescence or particle aggregation (flocculation) leading to particle migration (creaming or sedimentation). Creaming and sedimentation are often considered as reversible, while coalescence and flocculation spell disaster for the formulator. Thus, it is of prime importance to detect coalescence or cluster formation at an early stage to shorten the ageing tests and to improve the formulations. This work mainly concerns the independent and anisotropic scattering of light from an emulsion or suspension in a cylindrical glass measurement cell, in relation with the optical analyser TURBISCAN MA 2000. The propagation of light through a concentrated dispersion can be used to characterise the system physico-chemical stability. Indeed, photons undergo many scattering events in an optically thick dispersion before escaping the medium and entering a receiver aperture. Multiple scattering thus contributes significantly to the transmitted and backscattered flux measured by TURBISCAN MA 2000. We present statistical models and numerical simulations for the radiative transfer in a suspension (plane or cylindrical measurement cells) only involving the photon mean path length, the asymmetry factor and the geometry of the light receivers. We further have developed an imaging method with high grey level resolution for the visualisation and the analysis of the surface flux in the backscattered spot light. We compare the results from physical models and numerical simulations with the experiments performed with the imaging method and the optical analyser TURBISCAN MA 2000 for latex beads suspensions (variable size and particle volume fraction). We then present a few examples of concentrated emulsion and suspension instability analysis with TURBISCAN 2000. It is shown that the instrument is able to characterise particle or aggregate size variation and particle/aggregate migration and to detect these phenomena much more earlier

  19. Self-pulsation threshold of Raman amplified Brillouin fiber cavities

    DEFF Research Database (Denmark)

    Ott, Johan Raunkjær; Pedersen, Martin Erland Vestergaard; Rottwitt, Karsten

    2009-01-01

    An implicit equation for the oscillation threshold of stimulated Brillouin scattering from Raman amplified signals in fibers with external feedback is derived under the assumption of no depletion. This is compared to numerical investigations of Raman amplification schemes showing good agreement...

  20. Stimulated Brillouin Cavity Optomechanics in Liquid Droplets

    Science.gov (United States)

    Giorgini, A.; Avino, S.; Malara, P.; De Natale, P.; Yannai, M.; Carmon, T.; Gagliardi, G.

    2018-02-01

    Liquid droplets are ubiquitous in nature wherein surface tension shapes them into perfect spheres with atomic-scale smooth surfaces. Here, we use stable droplets that cohost equatorial acoustical and optical resonances phase matched to enable the exchange of energy and momentum between sound and light. Relying on free-space laser excitation of multiple whispering-gallery modes, we harness a triple-resonant forward Brillouin scattering to stimulate optomechanical surface waves. Nonlinear amplification of droplet vibrations in the 60-70 MHz range is realized with spectral narrowing beyond the limit of material loss, thereby activating the droplet as hypersound-laser emitter.

  1. Brillouin suppression in a fiber optical parametric amplifier by combining temperature distribution and phase modulation

    DEFF Research Database (Denmark)

    Lorenzen, Michael Rodas; Noordegraaf, Danny; Nielsen, Carsten Vandel

    2008-01-01

    We demonstrate an increased gain in optical parametric amplier through suppression of stimulated Brillouin scattering by applying a temperature distribution along the fiber resulting in a reduction of the required phase modulation.......We demonstrate an increased gain in optical parametric amplier through suppression of stimulated Brillouin scattering by applying a temperature distribution along the fiber resulting in a reduction of the required phase modulation....

  2. Anomalous inelastic neutron scattering from calcite

    International Nuclear Information System (INIS)

    Dove, M.T.; Harris, M.J.; Winkler, B.; Hagen, M.E.; Keele Univ.; Powell, B.M.; Steigenberger, U.

    1992-01-01

    Inelastic neutron scattering measurements on calcite (CaCO 3 ) in its low temperature phase have revealed the existence of an unusual column of inelastic scattering at the wavevector corresponding to the F point of the high temperature Brillouin zone. At the same wavevector there is also a transverse acoustic soft mode and the column of scattering ranges in energy from zero up to the soft mode. The intensity of the anomalous scattering increases rapidly with temperature, and is consistent with an Arrhenius relation of the form exp(-T * /T), where T * = 1035 K. We speculate that this scattering arises from thermal fluctuations of the calcite structure into a different ordered structure, which is related to an ordering instability at the F point. Evidence for this possibility has also been obtained from lattice energy calculations. (author)

  3. Brillouin spectroscopy as a new method of screening for increased CSF total protein during bacterial meningitis.

    Science.gov (United States)

    Steelman, Zachary; Meng, Zhaokai; Traverso, Andrew J; Yakovlev, Vladislav V

    2015-05-01

    Bacterial meningitis is a disease of pronounced clinical significance, especially in the developing world. Immediate treatment with antibiotics is essential, and no single test can provide a conclusive diagnosis. It is well established that elevated total protein in cerebrospinal fluid (CSF) is associated with bacterial meningitis. Brillouin spectroscopy is a widely used optical technique for noninvasive determination of the elastic moduli of materials. We found that elevated protein levels in CSF alter the fluid elasticity sufficiently to be measurable by Brillouin spectroscopy, with model healthy and diseased fluids distinguishable to marked significance (P = 0.014), which increases with sample concentration by dialysis. Typical raw output of a 2-stage VIPA Brillouin spectrometer: inelastically scattered Brillouin peaks (arrows) and elastically scattered incident radiation (center cross). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Two-stream instability for a scattered beam propagating in a collisional plasma

    International Nuclear Information System (INIS)

    Newberger, B.S.; Thode, L.E.

    1979-01-01

    Significant progress was made in the understanding of the collisional stabilization of the high-frequency two-stream instability in a relativistic electron beam through a rigorous Vlasov treatment. Substantially different scaling with parameters are obtained in comparison with previous, essentially phenomenological, models and we have gained insight into the mechanism of the stabilization process. Further investigation of the 2-D case remains to be done. The issue of stabilization of the two-stream instability in finite geometry is as yet unexplored as is that of nonlinear saturation, by trapping, of the instability in the presence of momentum spread on the beam and collisions on the plasma electrons. These are important in the application of relativistic electron beams to the heating of dense plasmas and possibly in the interpretation of neutral gas propagation experiments. Extension of our research into these areas will necessarily rely on the investigations outlined above

  5. Mechanical characterisation of hydrogels using Brillouin microscopy, ultrasound and unconfined compression tests (Conference Presentation)

    Science.gov (United States)

    Wu, Pei-Jung; Kabakova, Irina V.; Song, ChengZe; Paterson, Carl; Overby, Darryl R.; Török, Peter

    2017-02-01

    Mechanical characterisation of biomaterials provides the basis for investigating disease-related changes in the biomechanical properties of living tissues and cells. Brillouin microscopy offers a non-invasive and label-free method to measure material properties. Briefly, Brillouin scattering involves energy exchange between photons and acoustic phonons, resulting in an optical frequency shift of the scattered light. This shift is proportional to the speed of sound in the material, and consequently to the longitudinal elastic modulus (M). However, it is unclear how Brillouin measurements, which characterize the mechanical response at GHz frequencies, relate to mechanical properties measured at much lower frequencies ( 1 Hz) relevant to physiological conditions. Furthermore, as most biomaterials are hydrated, it remains unclear how the relative incompressibility of water influences the acoustic wave speed so as to affect Brillouin measurements of hydrated biomaterials. In this study, we aim to establish the relationship between Brillouin frequency shift, acoustic wave speed and quasi-static elastic modulus of hydrogels of varying stiffness. Hydrogels are homogeneous and isotropic materials that mimic the poroelastic nature of biological tissues. Each measurement probes the mechanics of hydrogels in a significantly different frequency range: GHz for Brillouin imaging, MHz for ultrasound and Hz for unconfined compression tests. The acoustic wave speed falls into range from 1490 to 1533 m/s in both MHz (ultrasound) and GHz (Brillouin) frequency ranges. The quasi-static modulus correlates positively with Brillouin frequency shift, increasing from 6 to 54 kPa. All the results indicate the measurements obtained by Brillouin microscopy are capable of representing the material properties of hydrogels in quasi-static condition.

  6. Pilot study on rugged fiber optic brillouin sensors for large-strain measurements to ensure the safety of transportation structures.

    Science.gov (United States)

    2012-07-01

    Brillouin-scattering Optical Time Domain Reflectometry (BOTDR) is a viable technology for simultaneous, distributed : strain and temperature measurements for miles-long transportation structures. It is a promising tool to ensure the smooth : operatio...

  7. The influence of current neutralization and multiple Coulomb scattering on the spatial dynamics of resistive sausage instability of a relativistic electron beam propagating in ohmic plasma

    Science.gov (United States)

    Kolesnikov, E. K.; Manuilov, A. S.; Petrov, V. S.; Klyushnikov, G. N.; Chernov, S. V.

    2017-06-01

    The influence of the current neutralization process, the phase mixing of the trajectories of electrons and multiple Coulomb scattering of electrons beam on the atoms of the background medium on the spatial increment of the growth of sausage instability of a relativistic electron beam propagating in ohmic plasma channel has been considered. It has been shown that the amplification of the current neutralization leads to a significant increase in this instability, and phase mixing and the process of multiple scattering of electrons beam on the atoms of the background medium are the stabilizing factor.

  8. High-resolution stimulated Brillouin gain spectroscopy in glasses and crystals

    International Nuclear Information System (INIS)

    Faris, G.W.; Jusinski, L.E.; Hickman, A.P.

    1993-01-01

    Theory and measurements are presented for stimulated Brillouin gain spectroscopy in anisotropic media. The coupling between arbitrary pump and Stokes waves and the corresponding acoustic wave is formulated in terms of the elastic displacement vector and the photoelastic tensor. A propagation equation that fully includes transient effects is obtained for the Stokes wave. In the limit of small-signal gains this propagation equation can be solved analytically, yielding expressions that relate experimentally accessible quantities to material properties. Absolute Brillouin steady-state gain coefficients, linewidths, and frequency shifts are thereby determined in a number of optical materials at 532 nm. The Brillouin gain coefficient for fused silica is measured by three techniques, providing the reference for absolute gain measurements. Quantitative agreement is found between theory and experiment for transient effects on stimulated Brillouin scattering

  9. Scattering V-type asteroids during the giant planet instability: a step for Jupiter, a leap for basalt

    Science.gov (United States)

    Brasil, P. I. O.; Roig, F.; Nesvorný, D.; Carruba, V.

    2017-06-01

    V-type asteroids are a taxonomic class whose surface is associated with a basaltic composition. The only known source of V-type asteroids in the Main Asteroid Belt is (4) Vesta, which is located in the inner part of the Main Belt. However, many V-type asteroids cannot be dynamically linked to Vesta, in particular, those asteroids located in the middle and outer parts of the Main Belt. Previous works have failed to find mechanisms to transport V-type asteroids from the inner to the middle and outer belts. In this work, we propose a dynamical mechanism that could have acted on primordial asteroid families. We consider a model of the giant planet migration known as the jumping Jupiter model with five planets. Our study is focused on the period of 10 Myr that encompasses the instability phase of the giant planets. We show that, for different hypothetical Vesta-like paleo-families in the inner belt, the perturbations caused by the ice giant that is scattered into the asteroid belt before being ejected from the Solar system are able to scatter V-type asteroids to the middle and outer belts. Based on the orbital distribution of V-type candidates identified from the Sloan Digital Sky Survey and the VISTA Survey colours, we show that this mechanism is efficient enough provided that the hypothetical paleo-family originated from a 100 to 500 km crater excavated on the surface of (4) Vesta. This mechanism is able to explain the currently observed V-type asteroids in the middle and outer belts, with the exception of (1459) Magnya.

  10. Parametric instabilities study in a shock ignition relevant regime

    Science.gov (United States)

    Cecchetti, C. A.; Giulietti, A.; Koester, P.; Labate, L.; Levato, T.; Gizzi, L. A.; Antonelli, L.; Patria, A.; Batani, D.; Kozlová, M.; Margarone, D.; Nejdl, J.; Rus, B.; Sawicka, M.; Lafon, M.; Ribeyre, X.; Schurtz, G.

    2011-06-01

    Inertial Confinement Fusion with Shock Ignition relies on a very strong shock created by a laser pulse at an intensity of the order of 1016W/cm2. In this context, an experimental campaign at the Prague Asterix Laser System (PALS) has been carried out within the frame of the HiPER project. Two beams have been used, the first to create an extended preformed plasma (scale length of the order of hundreds of micrometers) on a planar target, the second to generate a strong shock wave. Different diagnostics were used to study both the shock breakout at the rear surface of the target and the laserplasma coupling and parametric instabilities. This paper is focused on back-scattering analysis to measure the backreflected energy and to characterize parametric instabilities such as stimulated Brillouin and Raman scattering. Our experimental data show that parametric instabilities do not play a strong role in the laser plasma coupling. Moreover, preliminary analysis of the back reflected light from the interaction region shows that less than 5% of the total incident laser energy was back-reflected, with only a small fraction of that light was originating from parametric instabilities.

  11. KrF laser amplifier with phase-conjugate Brillouin retroreflectors.

    Science.gov (United States)

    Gower, M C

    1982-09-01

    We have demonstrated the use of phase-conjugate stimulated Brillouin scattering mirrors to produce high-quality, short-pulse KrF laser beams from angular multiplexed and regenerative amplifiers. The mirror was also shown to isolate systems optically from amplifier spontaneous emission. Automatic alignment of targets using this mirror as a retroreflector was also demonstrated.

  12. Strongly coupled stimulated Brillouin amplification in pump-ionizing plasma

    Science.gov (United States)

    Peng, H.; Wu, Z. H.; Zuo, Y. L.; Zhou, K. N.; Wang, X. D.; Li, Q.; Zhu, H. Y.; Su, J. Q.

    2018-02-01

    Laser amplification based on strongly coupled stimulated Brillouin scattering in plasma is investigated. The pump and seed are at the same wavelength of 800 nm and the same duration of 3.5 ps, but with a different intensity. The plasma is produced by the front part of the pump via tunnel ionization from hydrogen. The hydrogen is fully ionized to eliminate small-scale density fluctuations in the plasma, so the transmission level of the seed is enhanced to 22%, and a relative amplification factor of 6 is obtained.

  13. Relaxation dynamics of lead-free (Na{sub 1/2}Bi{sub 1/2})TiO{sub 3}–BaTiO{sub 3} single crystals studied by Brillouin scattering

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Byoung Wan [Department of Physics, Hallym University, Chuncheon, Gangwondo 24252 (Korea, Republic of); Ko, Jae-Hyeon, E-mail: hwangko@hallym.ac.kr [Department of Physics, Hallym University, Chuncheon, Gangwondo 24252 (Korea, Republic of); Li, Xiaobing; Luo, Haosu [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2016-10-01

    The acoustic properties of 0.95(Na{sub 1/2}Bi{sub 1/2})TiO{sub 3}–0.05BaTiO{sub 3} (NBT–0.05BT) single crystals were investigated in a hypersonic frequency range and compared to those of archetypal relaxor Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3} (PMN). Temperature dependences of the Brillouin frequency shift of the longitudinal acoustic (LA) mode, as well as its half width, of NBT–5%BT and PMN exhibited diffuse and broad anomalies over a wide temperature range, which were related to the softening of the sound velocity and substantial increase in the hypersonic damping toward the dielectric maximum temperature. These broad acoustic anomalies of unpoled NBT–0.05BT suggest the existence of noncentrosymmetric polar nanoregions in the paraelectric phase which do not evolve into a long-range ferroelectric order. The calculated relaxation times of NBT–0.05BT exhibited much longer values compared to those of PMN, which suggests that the size of polar nanoregions of NBT–0.05BT is larger than that of PMN.

  14. Slope instability mapping around L'Aquila (Abruzzo, Italy) with Persistent Scatterers Interferometry from ERS, ENVISAT and RADARSAT datasets

    Science.gov (United States)

    Righini, Gaia; Del Conte, Sara; Cigna, Francesca; Casagli, Nicola

    2010-05-01

    In the last decade Persistent Scatterers Interferometry (PSI) was used in natural hazards investigations with significant results and it is considered a helpful tool in ground deformations detection and mapping (Berardino et. al., 2003; Colesanti et al., 2003; Colesanti & Wasowski, 2006; Hilley et al., 2004). In this work results of PSI processing were interpreted after the main seismic shock that affected the Abruzzo region (Central Italy) on 6th of April 2009, in order to carry out a slope instability mapping according to the requirement of National Department of Civil Protection and in the framework of the Landslides thematic services of the EU FP7 project ‘SAFER' (Services and Applications For Emergency Response - Grant Agreement n° 218802). The area of interest was chosen in almost 460 km2 around L'Aquila according the highest probability of reactivations of landslides which depends on the local geological conditions, on the epicenter location and on other seismic parameters (Keefer, 1984). The radar images datasets were collected in order to provide estimates of the mean yearly velocity referred to two distinct time intervals: historic ERS (1992-2000) and recent ENVISAT (2002-2009), RADARSAT (2003-2009); the ERS and RADARSAT images were processed by Tele-Rilevamento Europa (TRE) using PS-InSAR(TM) technique, while the ENVISAT images were processed by e-GEOS using PSP-DIFSAR technique. A pre-existing landslide inventory map was updated through the integration of conventional photo interpretation and the radar-interpretation chain, as defined by Farina et al. (2008) and reported in literature (Farina et al. 2006, Meisina et al. 2007, Pancioli et al., 2008; Righini et al., 2008, Casagli et al., 2008, Herrera et al., 2009). The data were analyzed and interpreted in Geographic Information System (GIS) environment. Main updates of the pre-existing landslides are focusing on the identification of new landslides, modification of boundaries through the spatial

  15. SCATTER

    International Nuclear Information System (INIS)

    Broome, J.

    1965-11-01

    The programme SCATTER is a KDF9 programme in the Egtran dialect of Fortran to generate normalized angular distributions for elastically scattered neutrons from data input as the coefficients of a Legendre polynomial series, or from differential cross-section data. Also, differential cross-section data may be analysed to produce Legendre polynomial coefficients. Output on cards punched in the format of the U.K. A. E. A. Nuclear Data Library is optional. (author)

  16. BRILLOUIN INSTABILITY IN FIBER LASERS DOPED BY POWER ...

    African Journals Online (AJOL)

    30 juin 2012 ... With the emergence of rare-earth doped fibers, and especially double-clad fibers, there is a renewed ... continuous signal in a rare-earth doped fiber amplifier can generate high enough intensities to ..... signal continu dans les fibres dopées aux terres rares génère des intensités élevées qui donnent lieu à ...

  17. Theoretical and numerical simulation of the saturation of the stimulated Raman scattering instability that occurs in laser-plasma interaction

    International Nuclear Information System (INIS)

    Fouquet, T.

    2007-01-01

    In this work we present 2 important results. First, for a relatively moderate laser lighting (I*λ 2 ≅ 10 14 Wμm 2 /cm 2 ), cavitation appears in Langmuir decay instability (LDI) whenever the plasma wavelength is above a certain limit. Secondly, in the case of an inhomogeneous plasma there is an increase of the Raman reflectivity in presence of LDI for a plasma density profile that was initially smooth. This work is divided into 5 chapters. The first chapter is dedicated to parametric instabilities especially Raman instability and Langmuir decay instability. The equations that govern these instabilities as well as their numerical solutions are presented in the second chapter. The third chapter deals with the case of a mono-dimensional plasma with homogenous density. The saturation of the Raman instability in a mono-dimensional plasma with inhomogeneous density is studied in the fourth chapter. The last chapter is dedicated to bi-dimensional simulations for various types of laser beams

  18. Effect of the laser incoherence on some parametric instabilities

    International Nuclear Information System (INIS)

    Berge, L.; Rousseaux, C.

    1994-01-01

    This study is devoted to the laser finite band with effects on the stimulated Raman and Brillouin backscattering, and to the laser spatial incoherence upon the growth of the filamentation instability. The possible reduction of the latter instabilities initiated by a loss of beam coherence is more particularly investigated in the context of the intending Mega joule laser facility. (authors). 15 refs

  19. ASPEN: A fully kinetic, reduced-description particle-in-cell model for simulating parametric instabilities

    International Nuclear Information System (INIS)

    Vu, H.X.; Bezzerides, B.; DuBois, D.F.

    1999-01-01

    A fully kinetic, reduced-description particle-in-cell (RPIC) model is presented in which deviations from quasineutrality, electron and ion kinetic effects, and nonlinear interactions between low-frequency and high-frequency parametric instabilities are modeled correctly. The model is based on a reduced description where the electromagnetic field is represented by three separate temporal envelopes in order to model parametric instabilities with low-frequency and high-frequency daughter waves. Because temporal envelope approximations are invoked, the simulation can be performed on the electron time scale instead of the time scale of the light waves. The electrons and ions are represented by discrete finite-size particles, permitting electron and ion kinetic effects to be modeled properly. The Poisson equation is utilized to ensure that space-charge effects are included. The RPIC model is fully three dimensional and has been implemented in two dimensions on the Accelerated Strategic Computing Initiative (ASCI) parallel computer at Los Alamos National Laboratory, and the resulting simulation code has been named ASPEN. The authors believe this code is the first particle-in-cell code capable of simulating the interaction between low-frequency and high-frequency parametric instabilities in multiple dimensions. Test simulations of stimulated Raman scattering, stimulated Brillouin scattering, and Langmuir decay instability are presented

  20. Widely tunable multiwavelength Brillouin-erbium fiber laser with triple Brillouin-shift wavelength spacing

    Science.gov (United States)

    Al-Mansoori, M. H.; Al-Sheriyani, A.; Younis, M. A. A.; Mahdi, M. A.

    2018-03-01

    In this paper, we demonstrate a widely tunable multiwavelength Brillouin-erbium fiber laser (MBEFL) having a wavelength spacing of 0.25 nm (triple Brillouin-shift wavelength spacing). The proposed laser structure overcomes the need for Brillouin pump wavelength to be closed to the self-lasing cavity modes region. The laser exhibits a wide tuning range of 40 nm (from 1530 nm to 1570 nm) at Brillouin pump and 980 nm pump powers of 25 mW and 350 mW, respectively. Four stable output channels are produced within this wavelength range with all the channels having a peak output power greater than 1.58 mW. The laser has the potential to be used as a multiwavelength laser source for dense wavelength division multiplexing communication.

  1. Distributed Brillouin fiber optic strain monitoring applications in advanced composite materials

    Science.gov (United States)

    Bastianini, Filippo; Cargnelutti, Mario; Di Tommaso, Angelo; Toffanin, Massimo

    2003-08-01

    Composite materials based on glass, carbon and aramid fibers have many advantages such as fast application, lightweight and corrosion resistance, and are widely diffused for manufacturing of tanks, pipings and for restoration, upgrade and seismic retrofit of structures and historical heritage. As several questions regarding long term durability of composite strengthenings remains still unsolved, monitoring of strain and temperature is strongly recommended, respectively to assess proper load transfer and no glass phase transition of the polymeric matrix. In this research work strain and temperature distributed sensing trough Brillouin scattering in single-mode optical fibers was used in different tests in order to understand the influence of different fiber coatings and embedding techniques. Pressure tests were performed on a GFRP piping with inhomogeneous strengthening layout and Brillouin strain data were compared with conventional strain gages. A smart CFRP material has been also developed and evaluated in a seismic retrofit application on an historical building dated 1500 that was seriously damaged in the earthquake of 1997. The developed embedding technique has been demonstrated successful to obtain fiber-optic smart composites with low optical losses, and the data comparison between Brillouin and resistive strain gauges confirms Brillouin technique is very effective for composite monitoring.

  2. Multiwavelength ytterbium-Brillouin random Rayleigh feedback fiber laser

    Science.gov (United States)

    Wu, Han; Wang, Zinan; Fan, Mengqiu; Li, Jiaqi; Meng, Qingyang; Xu, Dangpeng; Rao, Yunjiang

    2018-03-01

    In this letter, we experimentally demonstrate the multiwavelength ytterbium-Brillouin random fiber laser for the first time, in the half-open cavity formed by a fiber loop mirror and randomly distributed Rayleigh mirrors. With a cladding-pumped ytterbium-doped fiber and a long TrueWave fiber, the narrow linewidth Brillouin pump can generate multiple Brillouin Stokes lines with hybrid ytterbium-Brillouin gain. Up to six stable channels with a spacing of about 0.06 nm are obtained. This work extends the operation wavelength of the multiwavelength Brillouin random fiber laser to the 1 µm band, and has potential in various applications.

  3. On stimulated scattering of laser light in inertial fusion energy targets

    Energy Technology Data Exchange (ETDEWEB)

    Nikolic, Lj [National Inst. for Fusion Science, The Graduate Univ. for Advanced Studies, Toki, Gifu (Japan); Skoric, M.M. [Vinca Inst. of Nuclear Sciences, Belgrade (Yugoslavia); Ishiguro, S. [National Inst. for Fusion Science, Theory and Computer Simulation Center, Toki, Gifu (Japan); Sato, T. [JAMSTEC, Earth Simulator Center, Yokohama, Kanagawa (Japan)

    2002-11-01

    Propagation of a laser light through regions of an underdense plasma is an active research topic in laser fusion. In particular, a large effort has been invested in studies of stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) which can reflect laser energy and produce energetic particles to preheat a fusion energy target. Experiments, theory and simulations agree on a complex interplay between various laser-plasma instabilities. By particle-in-cell simulations of an underdense electron-plasma, we have found, apart from the standard SRS, a strong backscattering near the electron plasma frequency at densities beyond the quarter critical. This novel instability, recognized in recent experiments as stimulated laser scattering on a trapped electron-acoustic mode (SEAS), is absent from a classical theory of laser-parametric instabilities. A parametric excitation of SEAS instability, is explained by a three-wave resonant decay of the incident laser light into a standing backscattered wave and a slow trapped electron acoustic wave ({omega} < {omega}{sub p}). Large SEAS pulsations, eventually suppressed by relativistic heating of electrons, are observed in our simulations. This phenomenon seems relevant to future hohlraum target and fast ignition experiments. (author)

  4. 3.05 kW monolithic fiber laser oscillator with simultaneous optimizations of stimulated Raman scattering and transverse mode instability

    Science.gov (United States)

    Yang, Baolai; Zhang, Hanwei; Shi, Chen; Tao, Rumao; Su, Rongtao; Ma, Pengfei; Wang, Xiaolin; Zhou, Pu; Xu, Xiaojun; Lu, Qisheng

    2018-01-01

    We report a high power monolithic ytterbium-doped fiber laser oscillator with an output power of 3.05 kW, which is achieved by simultaneous optimizations of the stimulated Raman scattering (SRS) and transverse mode instability (TMI). The optimizations of the SRS are designed and utilized in the construction of the fiber laser oscillator, while the TMI threshold is optimized with the study of the dependence of TMI threshold on the pump distribution. In the fiber laser oscillator, the TMI threshold is enhanced by ˜30% when the counter-pump scheme is employed instead of the co-pump scheme. By applying bidirectional-pump scheme and appropriately distributing the pump power, the TMI threshold is further enhanced and the monolithic fiber laser oscillator achieves an output power of 3.05 kW with near diffraction limited beam quality.

  5. Electron acoustic waves and parametric instabilities in a 4-component relativistic quantum plasma with Thomas-Fermi distributed electrons

    Science.gov (United States)

    Ikramullah, Ahmad, Rashid; Sharif, Saqib; Khattak, Fida Younus

    2018-01-01

    The interaction of Circularly Polarized Electro-Magnetic (CPEM) waves with a 4-component relativistic quantum plasma is studied. The plasma constituents are: relativistic-degenerate electrons and positrons, dynamic degenerate ions, and Thomas-Fermi distributed electrons in the background. We have employed the Klein-Gordon equations for the electrons as well as for the positrons, while the ions are represented by the Schrödinger equation. The Maxwell and Poisson equations are used for electromagnetic waves. Three modes are observed: one of the modes is associated with the electron acoustic wave, a second mode at frequencies greater than the electron acoustic wave mode could be associated with the positrons, and the third one at the lowest frequencies could be associated with the ions. Furthermore, Stimulated Raman Scattering (SRS), Modulational, and Stimulated Brillouin Scattering (SBS) instabilities are studied. It is observed that the growth rates of both the SRS and SBS instabilities decrease with increase in the quantum parameter of the plasma. It is also observed that the scattering spectra in both the SRS and SBS get restricted to very small wavenumber regions. It is shown that for low amplitude CPEM wave interaction with the quantum plasma, the positron concentration has no effect on the SRS and SBS spectra. In the case of large amplitude CPEM wave interaction, however, one observes spectral changes with varying positron concentrations. An increase in the positron concentration also enhances the scattering instability growth rates. Moreover, the growth rate first increases and then decreases with increasing intensity of the CPEM wave, indicating an optimum value of the CPEM wave intensity for the growth of these scattering instabilities. The modulational instability also shows dependence on the quantum parameter as well as on the positron concentration.

  6. Temperature dependence of Brillouin frequency shift in polymers controlled by plasticization effect

    Science.gov (United States)

    Minakawa, Kazunari; Koike, Kotaro; Du, Qiming; Hayashi, Neisei; Koike, Yasuhiro; Mizuno, Yosuke; Nakamura, Kentaro

    2015-04-01

    The temperature-dependence coefficient of Brillouin frequency shift (BFS) in perfluorinated graded-index polymer optical fibers is known to change drastically, because of the glass transition, at a certain critical temperature (Tc), above which the BFS becomes more sensitive to temperature. In this paper, we demonstrate that the Tc value can be adjusted by varying the dopant concentration, which is originally used to form the graded-index profile in the core region. Furthermore, we show that the temperature sensitivity of the BFS is enhanced in the presence of dopant probably because the temperature sensitivity of Young's modulus is increased. The results indicate a big potential of the temperature sensors based on Brillouin scattering with an extremely high sensitivity in a specific desired temperature range.

  7. Measurement of Laser Plasma Instability (LPI) Driven Light Scattering from Plasmas Produced by Nike KrF Laser

    Science.gov (United States)

    Oh, Jaechul; Weaver, J. L.; Phillips, L.; Obenschain, S. P.; Schmitt, A. J.; Kehne, D. M.; Serlin, V.; Lehmberg, R. H.; McLean, E. A.; Manka, C. K.

    2010-11-01

    With short wavelength (248 nm), large bandwidth (1˜3 THz), and ISI beam smoothing, Nike KrF laser provides unique research opportunities and potential for direct-drive inertial confinement fusion. Previous Nike experiments observed two plasmon decay (TPD) driven signals from CH plasmas at the laser intensities above ˜2x10^15 W/cm^2 with total laser energies up to 1 kJ of ˜350 ps FWHM pulses. We have performed a further experiment with longer laser pulses (0.5˜4.0 ns FWHM) and will present combined results of the experiments focusing on light emission data in spectral ranges relevant to the Raman (SRS) and TPD instabilities. Time- or space-resolved spectral features of TPD were detected at different viewing angles and the absolute intensity calibrated spectra of thermal background were used to obtain blackbody temperatures in the plasma corona. The wave vector distribution in k-space of the participating TPD plasmons will be also discussed. These results show promise for the proposed direct-drive designs.

  8. S-band multi-wavelength Brillouin-Raman fiber laser utilizing fiber Bragg grating and Raman amplifier in the ring cavity

    Science.gov (United States)

    Anwar, Nur Elina; Ahmad Hambali, N. A. M.; Sohaimi, M. Syazwan; M. Shahimin, M.; A. Wahid, M. H.; Yusof, N. Roshidah; Malek, A. Zakiah

    2015-08-01

    This paper is focusing on simulation and analyzed of S-band multi-wavelength Brillouin-Raman fiber laser performance utilizing fiber Bragg grating and Raman amplifier in ring cavity by using Optisystem software. Raman amplifieraverage power model is employed for signal amplification. This laser system is operates in S-band wavelength region due to vast demanding on transmitting the information. Multi-wavelength fiber lasers based on hybrid Brillouin-Raman gain configuration supported by Rayleigh scattering effect have attracted significant research interest due to its ability to produced multi-wavelength signals from a single light source. In multi-wavelength Brillouin-Raman fiber, single mode fiber is utilized as the nonlinear gain medium. From output results, 90 % output coupling ratio has ability to provide the maximum average output power of 43 dBm at Brillouin pump power of 20 dBm and Raman pump power of 14 dBm. Furthermore, multi-wavelength Brillouin-Raman fiber laser utilizing fiber Bragg grating and Raman amplifier is capable of generated 7 Brillouin Stokes signals at 1480 nm, 1510 nm and 1530 nm.

  9. The electromagnetic Brillouin precursor in one-dimensional photonic crystals

    NARCIS (Netherlands)

    Uitham, R.; Hoenders, B. J.

    2008-01-01

    We have calculated the electromagnetic Brillouin precursor that arises in a one-dimensional photonic crystal that consists of two homogeneous slabs which each have a single electron resonance. This forerunner is compared with the Brillouin precursor that arises in a homogeneous double-electron

  10. Viscoelasticity of amyloid plaques in transgenic mouse brain studied by Brillouin microspectroscopy and correlative Raman analysis

    Directory of Open Access Journals (Sweden)

    Sara Mattana

    2017-11-01

    Full Text Available Amyloidopathy is one of the most prominent hallmarks of Alzheimer’s disease (AD, the leading cause of dementia worldwide, and is characterized by the accumulation of amyloid plaques in the brain parenchyma. The plaques consist of abnormal deposits mainly composed of an aggregation-prone protein fragment, β-amyloid 1-40/1-42, into the extracellular matrix. Brillouin microspectroscopy is an all-optical contactless technique that is based on the interaction between visible light and longitudinal acoustic waves or phonons, giving access to the viscoelasticity of a sample on a subcellular scale. Here, we describe the first application of micromechanical mapping based on Brillouin scattering spectroscopy to probe the stiffness of individual amyloid plaques in the hippocampal part of the brain of a β-amyloid overexpressing transgenic mouse. Correlative analysis based on Brillouin and Raman microspectroscopy showed that amyloid plaques have a complex structure with a rigid core of β-pleated sheet conformation (β-amyloid protein surrounded by a softer ring-shaped region richer in lipids and other protein conformations. These preliminary results give a new insight into the plaque biophysics and biomechanics, and a valuable contrast mechanism for the study and diagnosis of amyloidopathy.

  11. Viscoelasticity of amyloid plaques in transgenic mouse brain studied by Brillouin microspectroscopy and correlative Raman analysis

    Science.gov (United States)

    Mattana, Sara; Caponi, Silvia; Tamagnini, Francesco; Fioretto, Daniele; Palombo, Francesca

    2017-01-01

    Amyloidopathy is one of the most prominent hallmarks of Alzheimer’s disease (AD), the leading cause of dementia worldwide, and is characterized by the accumulation of amyloid plaques in the brain parenchyma. The plaques consist of abnormal deposits mainly composed of an aggregation-prone protein fragment, β-amyloid 1-40/1-42, into the extracellular matrix. Brillouin microspectroscopy is an all-optical contactless technique that is based on the interaction between visible light and longitudinal acoustic waves or phonons, giving access to the viscoelasticity of a sample on a subcellular scale. Here, we describe the first application of micromechanical mapping based on Brillouin scattering spectroscopy to probe the stiffness of individual amyloid plaques in the hippocampal part of the brain of a β-amyloid overexpressing transgenic mouse. Correlative analysis based on Brillouin and Raman microspectroscopy showed that amyloid plaques have a complex structure with a rigid core of β-pleated sheet conformation (β-amyloid) protein surrounded by a softer ring-shaped region richer in lipids and other protein conformations. These preliminary results give a new insight into the plaque biophysics and biomechanics, and a valuable contrast mechanism for the study and diagnosis of amyloidopathy. PMID:29151920

  12. Experimental investigation of two-dimensional critical surface structure, stimulated Raman scattering, and two-plasmon decay instability. Annual report, January 1, 1981-April 30, 1982

    International Nuclear Information System (INIS)

    Wong, A.Y.; Eggleston, D.L.; Tanikawa, T.; Qian, S.J.

    1982-11-01

    Experimental observations of the space and time evolution of resonantly enhanced electrostatic electric fields and plasma density in cylindrical geometry demonstrate the development of two-dimensional caviton structure when an initial density perturbation is imposed on the plasma in the direction perpendicular to the driver field. This two-dimensional structure is observed after the development of profile modification and grows on the ion time scale. The existence of a large azimuthal electric field component is an observational signature of two-dimensional structure. Enhanced electric field maxima are found to be azimuthally correlated with the density minima. Both the density cavities and electric field peaks exhibit increased azimuthal location with the growth of two-dimensional structure. The two-dimensional development exhibits a strong dependence on both perturbation wavenumber and driver power. The related theoretical literature is reviewed and numerical, analytical, and qualitative hybrid models for a driven, two-dimensional, inhomogeneous plasma are presented. Preliminary work is presented in the following additional areas: weak magnetic field effects on critical surface physics, optical measurements of fast electron production, two-dimensional effects in microwave-plasma interactions, Langmuir wave trapping, stimulated Raman scattering and two-plasmon decay instability

  13. Temperature and molecular-weight dependences of acoustic behaviors of polystyrene studied using Brillouin spectroscopy

    Science.gov (United States)

    Oh, Soo Han; Lee, Byoung Wan; Ko, Jae-Hyeon; Lee, Hyeonju; Park, Jaehoon; Ko, Young Ho; Kim, Kwang Joo

    2017-04-01

    The acoustic properties of three polystyrene polymers with different molecular weights were investigated as a function of temperature by using Brillouin light scattering. The longitudinal sound velocity showed a change in the slope, which depended on the molecular weight, at the glass transition temperature. The absorption coefficient exhibited a maximum above the glass transition temperature, and the maximum temperature became higher as the molecular weight was increased. Comparison with previous acoustic studies on polystyrene indicate that a substantial frequency dispersion caused by strong coupling between the longitudinal acoustic waves and the segmental motions exists in the high-temperature range.

  14. Probing microscopic mechanical properties of hard tissues with Brillouin spectroscopy

    Science.gov (United States)

    Meng, Zhaokai; Yakovlev, Vladislav V.

    2015-02-01

    Mechanical properties of hard tissues play an important role in understanding underlying biological structures, as well as assessing the quality of artificial bone replacement materials. In this study, we employed Brillouin spectroscopy as a non-invasive approach to probe the microscopic elasticity of hard tissues, such as bones. Brillouin spectra were collected using a background free virtually imaged phased array spectrometer. As a reference, Raman spectra were also acquired for each imaging point. Experimental results reveal a positive correlation between the local concentration of the mineral content and the corresponding tissue stiffness, assessed through a Brillouin shift.

  15. Fabry-Perot spectrometer for high resolution light scattering investigations

    International Nuclear Information System (INIS)

    Deniz, K.U.; Parvathanathan, P.S.; Paranjpe, A.S.

    1976-01-01

    A Fabry-Perot spectrometer designed specially for carrying out Brillouin scattering experiment is described in detail. The instrument has free spectral range in the domain of frequencies 1 - 10 GHz and resolution widths in the range of 30 MHz - 3 GHz. The signal to noise ratio has been improved by a factor of about 10 3 by : (1) cooling the photomultiplier detector and (2) the use of magnetic defocussing techniques. With the use of a single frequency laser source, accurate determination of Brillouin frequency shifts and of Brillouin line shapes can be made with this spectrometer. Some preliminary results obtained with a few simple liquids, are discussed. (author)

  16. A Brillouin smart FRP material and a strain data post processing software for structural health monitoring through laboratory testing and field application on a highway bridge

    Science.gov (United States)

    Bastianini, Filippo; Matta, Fabio; Galati, Nestore; Nanni, Antonio

    2005-05-01

    Strain and temperature sensing obtained through frequency shift evaluation of Brillouin scattered light is a technology that seems extremely promising for Structural Health Monitoring (SHM). Due to the intrinsic distributed sensing capability, Brillouin can measure the deformation of any individual segment of huge lengths of inexpensive single-mode fiber. In addition, Brillouin retains other typical advantages of Fiber Optic Sensors (FOS), such as harsh environment durability and interference rejection. Despite these advantages, the diffusion of Brillouin for SHM is constrained by different factors, such as the high equipment cost, the commercial unavailability of specific SHM oriented fiber products and even some prejudices on the required sensitivity performances. In the present work, a complete SHM pilot application was developed, installed and successfully operated during a diagnostic load test on the High Performance Steel (HPS) bridge A6358 located at the Lake of the Ozarks (Miller County, MO, USA). Four out of five girders were extensively instrumented with a "smart" Glass Fiber Reinforced Polymer (GFRP) tape having embedded fibers for strain sensing and thermal compensation. Data collected during a diagnostic load test were elaborated through a specific post-processing software, and the strain profiles retrieved were compared to traditional strain gauges and theoretical results based on the AASHTO LRFD Bridge Design Specifications for structural assessment purposes. The excellent results obtained confirm the effectiveness of Brillouin SHM systems for the monitoring of real applications.

  17. Saturation of Backward Stimulated Scattering of a Laser Beam in the Kinetic Regime

    International Nuclear Information System (INIS)

    Yin, L.; Albright, B. J.; Bowers, K. J.; Daughton, W.; Rose, H. A.

    2007-01-01

    Stimulated Raman (SRS) and Brillouin scattering (SBS) are examined in the kinetic regime using particle-in-cell simulations. Wave front bowing of electron-plasma waves (ion-acoustic waves) from trapped particle nonlinear frequency shift is observed in the SRS (SBS) regime for the first time. Self-focusing from trapped particle modulational instability (TPMI) is shown to occur in 2D and 3D SRS simulations. The key physics of SRS saturation is identified as a combination of wave front bowing, TPMI, and self-focusing: Bowing marks the beginning of SRS saturation and self-focusing terminates SRS. Ion-acoustic wave bowing also contributes to SBS saturation. Velocity diffusion by transverse modes and rapid loss of hot electrons in regions of small transverse extent formed from self-focusing dissipate wave energy and increase Landau damping, despite trapping that reduces Landau damping initially

  18. Experimental analysis of thermo-acoustic instabilities in a generic gas turbine combustor by phase-correlated PIV, chemiluminescence, and laser Raman scattering measurements

    Science.gov (United States)

    Arndt, Christoph M.; Severin, Michael; Dem, Claudiu; Stöhr, Michael; Steinberg, Adam M.; Meier, Wolfgang

    2015-04-01

    A gas turbine model combustor for partially premixed swirl flames was equipped with an optical combustion chamber and operated with CH4 and air at atmospheric pressure. The burner consisted of two concentric nozzles for separately controlled air flows and a ring of holes 12 mm upstream of the nozzle exits for fuel injection. The flame described here had a thermal power of 25 kW, a global equivalence ratio of 0.7, and exhibited thermo-acoustic instabilities at a frequency of approximately 400 Hz. The phase-dependent variations in the flame shape and relative heat release rate were determined by OH* chemiluminescence imaging; the flow velocities by stereoscopic particle image velocimetry (PIV); and the major species concentrations, mixture fraction, and temperature by laser Raman scattering. The PIV measurements showed that the flow field performed a "pumping" mode with varying inflow velocities and extent of the inner recirculation zone, triggered by the pressure variations in the combustion chamber. The flow field oscillations were accompanied by variations in the mixture fraction in the inflow region and at the flame root, which in turn were mainly caused by the variations in the CH4 concentration. The mean phase-dependent changes in the fluxes of CH4 and N2 through cross-sectional planes of the combustion chamber at different heights above the nozzle were estimated by combining the PIV and Raman data. The results revealed a periodic variation in the CH4 flux by more than 150 % in relation to the mean value, due to the combined influence of the oscillating flow velocity, density variations, and CH4 concentration. Based on the experimental results, the feedback mechanism of the thermo-acoustic pulsations could be identified as a periodic fluctuation of the equivalence ratio and fuel mass flow together with a convective delay for the transport of fuel from the fuel injector to the flame zone. The combustor and the measured data are well suited for the validation of

  19. Centrifugal instability in the regime of fast rotation

    Science.gov (United States)

    Gueroult, R.; Rax, J. M.; Fisch, N. J.

    2017-08-01

    Centrifugal instability, which stems from a difference between the azimuthal angular drift velocity of ions and electrons, is studied in the limit of fast rotation for which ions can rotate up to twice as fast as electrons. As the angular velocity approaches the so-called Brillouin limit, the growth rate for the centrifugal instability in a collisionless solid-body rotating plasma increases markedly and is proportional to the azimuthal mode number. For large wavenumbers, electron inertia effects set in and lead to a cut-off. Interestingly, conditions for the onset of this instability appear to overlap with the operating conditions envisioned for plasma mass separation devices.

  20. Neutron scattering from an imperfect flux-line lattice

    International Nuclear Information System (INIS)

    Brandt, E.H.

    1978-01-01

    The diffraction of neutrons from the imperfect vortex lattice of a type-II superconductor is investigated. It is found that flux pinning leads not only to a broadening of the Bragg reflections but also to diffuse scattering into the first Brillouin zone, which at high fields exceeds Bragg scattering

  1. Experimental observation of stochastic, periodic, and localized light structures in a brillouin cavity system

    Science.gov (United States)

    Ding, Yingchun; Feng, Qi; Zhang, Bin; Liu, Zhongxuan; Tang, Xin; Lin, Chengyou; Chen, Zhaoyang

    2017-06-01

    It has been an important research subject to find new nonlinear optical phenomena. In this paper, we report the experimental observation of stochastic, periodic, and localized light structures in a super long single-mode standard fiber with external optical feedback provided by the fiber end. The end facet reflection provides an analogous Fabry-Perot stimulated Brillouin resonator cavity. By increasing the pump power to exceed stimulated Brillouin scattering threshold, we observed light structures exhibiting extremely rich temporal-pulse characteristics that had never been reported in literature before, including supercontinuum background generation, the localization of periodic optical structure formation, fission, and compression. These optical structures are of period-doubling distribution and have different recurrence rates. What is more interesting is that we have observed sets of low frequency bipolar cycle-pulse trains that is often seen in the electrical field and hardly seen in pure optical system. Real-time specification of dynamical temporal regimes of laser operation may bring new insight into rich underlying nonlinear physics of practical fiber cavity systems. Therefore, some new nonlinear optical phenomena have been observed.

  2. Brillouin distributed temperature sensing system for monitoring of submarine export cables of off-shore wind farms

    Science.gov (United States)

    Marx, Benjamin; Rath, Alexander; Kolm, Frederick; Schröder, Andreas; Buntebarth, Christian; Dreß, Albrecht; Hill, Wieland

    2016-05-01

    For high-voltage cables, the maximum temperature of the insulation must never be exceeded at any location and at any load condition. The local temperatures depend not only on the cable design and load history, but also on the local thermal environment of the cable. Therefore, distributed temperature monitoring of high-voltage cables is essential to ensure the integrity of the cable at high load. Especially, the load of the export cables of wind farms varies strongly in dependence on weather conditions. In this field study, we demonstrate the measurement performance of a new, robust Brillouin distributed temperature sensing system (Brillouin-DTS). The system is based on spontaneous Brillouin scattering and does not require a fibre loop. This is essential for long submarine high-voltage cables, where normally no loop can be formed in the seabed. It is completely passively cooled and does not contain any moving or wearing parts. The instrument is dedicated for use in industrial and other rough environments. With a measuring time below 10 min, the temperature resolution is better than 1 °C for distances up to 50 km. In the field study, the submarine export cable of an off-shore wind farm has been monitored. The temperature profile of the export cable shows several hot spots, mostly located at cable joints, and also several cold spots.

  3. Brillouin optical correlation domain analysis in composite material beams

    DEFF Research Database (Denmark)

    Stern, Yonatan; London, Yosef; Preter, Eyal

    2017-01-01

    with optical fiber sensors. In this work, we report high-resolution distributed Brillouin sensing over standard fibers that are embedded in composite structures. A phase-coded, Brillouin optical correlation domain analysis (B-OCDA) protocol was employed, with spatial resolution of 2 cm and sensitivity of 1 °K......) estimating the stiffness and Young’s modulus of a composite beam; and (c) distributed strain measurements across the surfaces of a model wing of an unmanned aerial vehicle. The measurements are supported by the predictions of structural analysis calculations. The results illustrate the potential added values...

  4. Development of in situ Brillouin spectroscopy at high pressure and high temperature with synchrotron radiation and infrared laser heating system: Application to the Earth's deep interior

    Science.gov (United States)

    Murakami, Motohiko; Asahara, Yuki; Ohishi, Yasuo; Hirao, Naohisa; Hirose, Kei

    2009-05-01

    Seismic wave velocity profiles in the Earth provide one of the strongest constraints on structure, mineralogy and elastic properties of the Earth's deep interior. Accurate sound velocity data of deep Earth materials under relevant high-pressure and high-temperature conditions, therefore, are essential for interpretation of seismic data. Such information can be directly obtained from Brillouin scattering measurement. Here we describe an in situ Brillouin scattering system for measurements at high pressure and high temperature using a laser heated diamond anvil cell and synchrotron radiation for sample characterization. The system has been used with single-crystal and polycrystalline materials, and with glass and fluid phase. It provided high quality sound velocity and elastic data with X-ray diffraction data at high pressure and/or high temperature. Those combined techniques can potentially offer the essential information for resolving many remaining issues in mineral physics.

  5. Quantum-Chemical Calculation and Visualization of the Vibrational Modes of Graphene in Different Points of the Brillouin Zone.

    Science.gov (United States)

    Lebedieva, Tetiana; Gubanov, Victor; Dovbeshko, Galyna; Pidhirnyi, Denys

    2015-12-01

    Different notations of graphene irreducible representations and optical modes could be found in the literature. The goals of this paper are to identify the correspondence between available notations, to calculate the optical modes of graphene in different points of the Brillouin zone, and to compare them with experimental data obtained by Raman and coherent anti-Stokes Raman scattering (CARS) spectroscopy. The mechanism of the resonance enhancement of vibration modes of the molecules adsorbed on graphene in CARS experiments is proposed. The possibility of appearance of the discrete breathing modes is discussed.

  6. Beyond the random phase approximation: Stimulated Brillouin backscatter for finite laser coherence times

    International Nuclear Information System (INIS)

    Korotkevich, Alexander O.; Lushnikov, Pavel M.; Rose, Harvey A.

    2015-01-01

    We developed a linear theory of backward stimulated Brillouin scatter (BSBS) of a spatially and temporally random laser beam relevant for laser fusion. Our analysis reveals a new collective regime of BSBS (CBSBS). Its intensity threshold is controlled by diffraction, once cT c exceeds a laser speckle length, with T c the laser coherence time. The BSBS spatial gain rate is approximately the sum of that due to CBSBS, and a part which is independent of diffraction and varies linearly with T c . The CBSBS spatial gain rate may be reduced significantly by the temporal bandwidth of KrF-based laser systems compared to the bandwidth currently available to temporally smoothed glass-based laser systems

  7. Dynamics of ponderomotive self-focusing and periodic bursts of stimulated Brillouin backscattering in plasmas

    International Nuclear Information System (INIS)

    Andreev, N.E.; Gorbunov, L.M.; Tarakanov, S.V.; Zykov, A.I.

    1993-01-01

    The space--time evolution of ponderomotive self-focusing of electromagnetic beams in a plasma is investigated. The quasineutral, hydrodynamic plasma response to the ponderomotive force is considered. The set of coupled quasioptic and acoustic equations is solved both analytically and numerically for slab and cylindrical beams. It is shown that the transient process of self-focusing has the form of a nonlinear wave propagating along the beam axis from boundary into the interior of a plasma with velocity considerably higher than the ion-sound velocity. Mutual dynamics of self-focusing and stimulated Brillouin backscattering (SBBS) is computed. It is shown that self-focusing results in the high intensity periodical bursts of SBBS. However, the time average level of scattered radiation is quite low

  8. Robust, Brillouin Active Embedded Fiber-Is-The-Sensor System in Smart Composite Structures

    Science.gov (United States)

    Yu, Chung

    1996-01-01

    Extensive review of our proposed sensing scheme, based mainly on the forward Guided Acoustic Wave Brillouin Scattering (GAWBS) with backward stimulated Brillouin scattering (sBs) as an auxiliary scheme for system fault tolerance has been completed during this project period. This preliminary study is conducted for a number of reasons. The most significant reasons lie in the essential capability of the system to measure temperature and pressure. These two measurands have been proposed to be sensed by sBs in our proposal. Temperature and pressure/strain are important measurands in structural monitoring, so that the effectiveness of sensing by sBs needs to be further examined. It has been pointed out initially that sBs shift will be dependent on temperature and pressure/strain simultaneously. The shift versus temperature or strain is linear. Now, the question is how can these two measurands be separated when sBs is used to sense an environment, in which both temperature and strain are changing simultaneously. Typical sBs shift plotted versus strain and varying temperature is shown in Fig. 1. As is clear, a fiber initially stressed will relax with rising temperature. This is verified by a displacement to the right with rising temperature of the sBs shift vs strain curves in the figure. A way to circumvent this ambiguity is by employing two fibers, one pre-stressed and the other is a free fiber. The latter will measure temperature and subtracting data in the latter fiber from those of the former will give us net strain readings. This is a laborious approach, since it involves the use of two identical fibers, and this is hard to accomplish, especially when many sensors are needed. Additional multiplexing of the data stream for data subtraction becomes a necessity.

  9. Brillouin Distributed Fiber Sensors: An Overview and Applications

    Directory of Open Access Journals (Sweden)

    C. A. Galindez-Jamioy

    2012-01-01

    Full Text Available A review focused on real world applications of Brillouin distributed fiber sensors is presented in this paper. After a brief overview of the theoretical principles, some works to face the two main technical challenges (large dynamic range and higher spatial resolution are commented. Then an overview of some real and on-field applications is done.

  10. Kinetic study of Raman instability in inhomogeneous plasma through semi-Lagrangian Vlasov numerical simulations; Etude cinetique de l'instabilite Raman en plasma inhomogene par simulation numerique Vlasov semi-lagrangienne

    Energy Technology Data Exchange (ETDEWEB)

    Albrecht-Marc, M

    2005-09-15

    This thesis deals with the numerical simulation of Raman instability through optical mixing in the field of inertial confinement fusion. We have used a semi-Lagrangian Vlasov-Maxwell code allowing a fine description in phase space of the effects of this type of plasma instabilities (likely to occur in future machines like LMJ and NIF). We have showed, both in homogeneous and inhomogeneous profiles, the effect of the convective amplification of the probe wave that induces weak turbulence in plasma. It is associated with a non-linear shift in frequency and in wave-vector of the scattered modes, due to kinetic effects. All this is a preliminary phase of the plasma. Moreover, both forward Raman or Brillouin scatterings have been taken into account. Eventually, we have been able to detect in various conditions low frequency (below the plasma frequency) electronic modes (KEEN) appearing through parametric coupling with other waves already present in the plasma. This work is divided into 3 parts: 1) models for laser-plasma interaction, 2) Raman scattering, optical mix and wave beat, and 3) analysis of the results of simulation.

  11. Anomalous thermal expansion, negative linear compressibility, and high-pressure phase transition in ZnAu2(CN) 4 : Neutron inelastic scattering and lattice dynamics studies

    Science.gov (United States)

    Gupta, Mayanak K.; Singh, Baltej; Mittal, Ranjan; Zbiri, Mohamed; Cairns, Andrew B.; Goodwin, Andrew L.; Schober, Helmut; Chaplot, Samrath L.

    2017-12-01

    We present temperature-dependent inelastic-neutron-scattering measurements, accompanied by ab initio calculations of the phonon spectra and elastic properties as a function of pressure to quantitatively explain an unusual combination of negative thermal expansion and negative linear compressibility behavior of ZnAu2(CN) 4 . The mechanism of the negative thermal expansion is identified in terms of specific anharmonic phonon modes that involve bending of the -Zn-NC-Au-CN-Zn- linkage. The soft phonon at the L point at the Brillouin zone boundary quantitatively relates to the high-pressure phase transition at about 2 GPa. The ambient pressure structure is also found to be close to an elastic instability that leads to a weakly first-order transition.

  12. Brillouin microspectroscopy of nanostructured biomaterials: photonics assisted tailoring mechanical properties

    Science.gov (United States)

    Meng, Zhaokai; Jaiswal, Manish K.; Chitrakar, Chandani; Thakur, Teena; Gaharwar, Akhilesh K.; Yakovlev, Vladislav V.

    2016-03-01

    Developing new biomaterials is essential for the next-generation of materials for bioenergy, bioelectronics, basic biology, medical diagnostics, cancer research, and regenerative medicine. Specifically, recent progress in nanotechnology has stimulated the development of multifunctional biomaterials for tissue engineering applications. The physical properties of nanocomposite biomaterials, including elasticity and viscosity, play key roles in controlling cell fate, which underlines therapeutic success. Conventional mechanical tests, including uniaxial compression and tension, dynamic mechanical analysis and shear rheology, require mechanical forces to be directly exerted onto the sample and therefore may not be suitable for in situ measurements or continuous monitoring of mechanical stiffness. In this study, we employ spontaneous Brillouin spectroscopy as a viscoelasticity-specific probing technique. We utilized a Brillouin spectrometer to characterize biomaterial's microscopic elasticity and correlated those with conventional mechanical tests (e.g., rheology).

  13. Magnetic scattering experiments

    International Nuclear Information System (INIS)

    Vettier, C.

    2001-01-01

    We discuss the relative use of neutrons and X-rays as scattering tools to probe the magnetic properties of materials. Neutron diffraction experiments continue to be the most appropriate tool to determine the magnetic structure of bulk solids. Synchrotron X-ray experiments are and will be used to investigate selectively the magnetic behaviour of different chemical species and/or electronic shells in magnetic systems. There exist some grey areas where the two probes can be used depending on the scientific problem under investigation. In particular, neutrons allow very accurate measurements of magnetic form factors, but X-rays provide a separation of the orbital momentum contribution to magnetisation. Comparisons between X-rays and neutrons studies of magnetism at surfaces are presented. Finally, one can anticipate that only inelastic neutron scattering experiments will allow the observation of magnetic excitations across the whole Brillouin zone

  14. Optimizing signal collection efficiency of the VIPA-based Brillouin spectrometer

    Directory of Open Access Journals (Sweden)

    Zhaokai Meng

    2015-07-01

    Full Text Available Brillouin spectroscopy is an emerging tool for microscopic optical imaging as it allows for noninvasive and direct assessment of the viscoelastic properties of materials. Recent advances of background-free confocal Brillouin spectrometer allows investigators to acquire the Brillouin spectra for turbid samples as well as transparent ones. However, due to strong signal loss induced by the imperfect optical setup, the Brillouin photons are usually immersed in background noise. In this report, we proposed and experimentally demonstrated multiple approaches to enhance the signal collection efficiency. A signal enhancement by > 4 times can be observed, enabling observation of ultra-weak signals.

  15. Two-color Brillouin ring laser gyro with gyro-compassing capability.

    Science.gov (United States)

    Raab, M; Quast, T

    1994-09-15

    We investigated the gyro-compassing capability of a Brillouin ring laser gyro set up in a two-color operation. Two counterpropagating pump lasers initiated two Brillouin ring lasers on different resonances of a fiber-optic ring resonator cavity, which excluded the mutual intracavity interaction between both counterpropagating Brillouin lasers. Additionally minimizing the external feedback channels of the individual Brillouin lasers allowed for high-resolution measurements, e.g., the horizontal component of the Earth's rotation rate (10.0 degrees /h at Uberlingen, Germany, which corresponded to a beat frequency of 6.85 Hz).

  16. Scattering tensors and optical transitions in Si and Ge

    CSIR Research Space (South Africa)

    Kunert, HW

    2012-08-01

    Full Text Available and L high symmetry points and the highest maximum of the valence band (VB) in the Brillouin zone of Oh7 space group symmetry are determined. The elements of El-Ph scattering tensors are linear combinations of the Clebsch-Gordon coefficients (CGC...

  17. Carpal instability

    International Nuclear Information System (INIS)

    Schmitt, R.; Froehner, S.; Coblenz, G.; Christopoulos, G.

    2006-01-01

    This review addresses the pathoanatomical basics as well as the clinical and radiological presentation of instability patterns of the wrist. Carpal instability mostly follows an injury; however, other diseases, like CPPD arthropathy, can be associated. Instability occurs either if the carpus is unable to sustain physiologic loads (''dyskinetics'') or suffers from abnormal motion of its bones during movement (''dyskinematics''). In the classification of carpal instability, dissociative subcategories (located within proximal carpal row) are differentiated from non-dissociative subcategories (present between the carpal rows) and combined patterns. It is essential to note that the unstable wrist initially does not cause relevant signs in standard radiograms, therefore being ''occult'' for the radiologic assessment. This paper emphasizes the high utility of kinematographic studies, contrast-enhanced magnetic resonance imaging (MRI) and MR arthrography for detecting these predynamic and dynamic instability stages. Later in the natural history of carpal instability, static malalignment of the wrist and osteoarthritis will develop, both being associated with significant morbidity and disability. To prevent individual and socio-economic implications, the handsurgeon or orthopedist, as well as the radiologist, is challenged for early and precise diagnosis. (orig.)

  18. High-resolution, on-chip RF photonic signal processor using Brillouin gain shaping and RF interference.

    Science.gov (United States)

    Choudhary, Amol; Liu, Yang; Morrison, Blair; Vu, Khu; Choi, Duk-Yong; Ma, Pan; Madden, Stephen; Marpaung, David; Eggleton, Benjamin J

    2017-07-19

    Integrated microwave photonics has strongly emerged as a next-generation technology to address limitations of conventional RF electronics for wireless communications. High-resolution RF signal processing still remains a challenge due to limitations in technology that offer sub-GHz spectral resolution, in particular at high carrier frequencies. In this paper, we present an on-chip high-resolution RF signal processor, capable of providing high-suppression spectral filtering, large phase shifts and ns-scale time delays. This was achieved through tailoring of the Brillouin gain profiles using Stokes and anti-Stokes resonances combined with RF interferometry on a low-loss photonic chip with strong opto-acoustic interactions. Using an optical power of <40 mW, reconfigurable filters with a bandwidth of ~20 MHz and an extinction ratio in excess of 30 dB are synthesized. Through the concept of vector addition of RF signals we demonstrate, almost an order of magnitude amplification in the phase and delay compared to devices purely based upon the slow-light effect of Brillouin scattering. This concept allows for versatile and power-efficient manipulation of the amplitude and phase of RF signals on a photonic chip for applications in wireless communications including software defined radios and beam forming.

  19. The effect of signal to noise ratio on accuracy of temperature measurements for Brillouin lidar in water

    Science.gov (United States)

    Liang, Kun; Niu, Qunjie; Wu, Xiangkui; Xu, Jiaqi; Peng, Li; Zhou, Bo

    2017-09-01

    A lidar system with Fabry-Pérot etalon and an intensified charge coupled device can be used to obtain the scattering spectrum of the ocean and retrieve oceanic temperature profiles. However, the spectrum would be polluted by noise and result in a measurement error. To analyze the effect of signal to noise ratio (SNR) on the accuracy of measurements for Brillouin lidar in water, the theory model and characteristics of SNR are researched. The noise spectrums with different SNR are repetitiously measured based on simulation and experiment. The results show that accuracy is related to SNR, and considering the balance of time consumption and quality, the average of five measurements is adapted for real remote sensing under the pulse laser conditions of wavelength 532 nm, pulse energy 650 mJ, repetition rate 10 Hz, pulse width 8 ns and linewidth 0.003 cm-1 (90 MHz). Measuring with the Brillouin linewidth has a better accuracy at a lower temperature (15 °C), based on the classical retrieval model we adopt. The experimental results show that the temperature error is 0.71 °C and 0.06 °C based on shift and linewidth respectively when the image SNR is at the range of 3.2 dB-3.9 dB.

  20. Single-frequency pulsed Brillouin-thulium fiber laser at 2 µm with nonlinear polarization rotation and active phase modulation

    Science.gov (United States)

    Wang, Xiong; Lv, Haibin; Zhou, Pu; Wu, Weijun; Wang, Xiaolin; Xiao, Hu; Liu, Zejin

    2014-10-01

    We present a single-frequency (SF) pulsed fiber laser at 2 µm based on stimulated Brillouin scattering in a thulium-doped fiber laser. The effective feedback of the fiber laser is quite weak to induce pulse operation. Nonlinear polarization rotation and active phase modulation are employed to compress the pulse width and stabilize the pulse train. This SF pulsed Brillouin-thulium fiber laser (BTFL) can generate a stable pulse train with a repetition rate of ˜310 kHz and a pulse width of ˜200 ns. The repetition rate of the pulse train can be adjusted by controlling the cavity length, and the pulse width can be tuned between 200 and 500 ns. The central wavelength locates at 1971.58 nm with an optical signal-to-noise ratio of more than 40 dB, and the linewidth is about 6 MHz. This is the first demonstration of the SF pulsed BTFL as far as we know.

  1. Optimization of the Brillouin operator on the KNL architecture

    Science.gov (United States)

    Dürr, Stephan

    2018-03-01

    Experiences with optimizing the matrix-times-vector application of the Brillouin operator on the Intel KNL processor are reported. Without adjustments to the memory layout, performance figures of 360 Gflop/s in single and 270 Gflop/s in double precision are observed. This is with Nc = 3 colors, Nv = 12 right-hand-sides, Nthr = 256 threads, on lattices of size 323 × 64, using exclusively OMP pragmas. Interestingly, the same routine performs quite well on Intel Core i7 architectures, too. Some observations on the much harderWilson fermion matrix-times-vector optimization problem are added.

  2. Rayleigh-Brillouin spectrum in special relativistic hydrodynamics

    International Nuclear Information System (INIS)

    Garcia-Perciante, A. L.; Garcia-Colin, L. S.; Sandoval-Villalbazo, A.

    2009-01-01

    In this paper we calculate the Rayleigh-Brillouin spectrum for a relativistic simple fluid according to three different versions available for a relativistic approach to nonequilibrium thermodynamics. An outcome of these calculations is that Eckart's version predicts that such spectrum does not exist. This provides an argument to question its validity. The remaining two results, which differ one from another, do provide a finite form for such spectrum. This raises the rather intriguing question as to which of the two theories is a better candidate to be taken as a possible version of relativistic nonequilibrium thermodynamics. The answer will clearly require deeper examination of this problem.

  3. Brillouin-zone database on the Bilbao Crystallographic Server.

    Science.gov (United States)

    Aroyo, Mois I; Orobengoa, Danel; de la Flor, Gemma; Tasci, Emre S; Perez-Mato, J Manuel; Wondratschek, Hans

    2014-03-01

    The Brillouin-zone database of the Bilbao Crystallographic Server (http://www.cryst.ehu.es) offers k-vector tables and figures which form the background of a classification of the irreducible representations of all 230 space groups. The symmetry properties of the wavevectors are described by the so-called reciprocal-space groups and this classification scheme is compared with the classification of Cracknell et al. [Kronecker Product Tables, Vol. 1, General Introduction and Tables of Irreducible Representations of Space Groups (1979). New York: IFI/Plenum]. The compilation provides a solution to the problems of uniqueness and completeness of space-group representations by specifying the independent parameter ranges of general and special k vectors. Guides to the k-vector tables and figures explain the content and arrangement of the data. Recent improvements and modifications of the Brillouin-zone database, including new tables and figures for the trigonal, hexagonal and monoclinic space groups, are discussed in detail and illustrated by several examples.

  4. Neutron scattering at structural phase transformations

    International Nuclear Information System (INIS)

    Plakida, N.M.

    1982-01-01

    The specific fractures of neutron scattering cross sections on crystal lattices at structural phase transformations are considered in the lecture. The analysis of the elastic and inelastic scattering is carried out at different transformations (ordering type, displacement type incommensurable transformations). The experimental study on some transitions are given as an example, namely, transformation at the Brillouin zone edge in cubic perovskite. RbCaF 3 transformation in a quasiunidimensional ferroelectrics CsH 2 PO 4 and CsD 2 PO 4 , phase transformation into an incommensurable phase in diphenyl

  5. Inelastic neutron scattering from glass formers

    International Nuclear Information System (INIS)

    Buchenau, U.

    1997-01-01

    Neutron spectra below and above the glass transition temperature show a pronounced difference between strong and fragile glass formers in Angell's fragility scheme. The strong anharmonic increase of the inelastic scattering with increasing temperature in fragile substances is absent in the strongest glass former SiO 2 . That difference is reflected in the temperature dependence of Brillouin sound velocities above the glass transition. Coherent inelastic neutron scattering data indicate a mixture of sound waves and local modes at the low frequency boson peak. A relation between the fragility and the temperature dependence of the transverse hypersound velocity at the glass temperature is derived. (author)

  6. Diffuse Neutron Scattering of the High Temperature Phase of Fe3O4

    OpenAIRE

    Siratori , K.; Ishii , Y.; Morii , Y.; Funahashi , S.; Yanase , A.

    1997-01-01

    Diffuse neutron scattering is observed for the high temperature phase of magnetite, Fe3O4, in an extended range in the (001) and (011) plane of the Brillouin zone. Contours of scattered intensity shows a characteristic pattern, discs in the (100) plane around the Γ points, spheres around the X points, etc. The intensity of this diffuse scattering increases with decreasing temperature down to the Verwey point and is attributed to the lattice distortion induced by charge fluctuation in the B si...

  7. FINANCIAL INSTABILITY AND POLITICAL INSTABILITY

    Directory of Open Access Journals (Sweden)

    Ionescu Cristian

    2012-12-01

    Full Text Available There is an important link between the following two variables: financial instability and political instability. Often, the link is bidirectional, so both may influence each other. This is way the lately crisis are becoming larger and increasingly complex. Therefore, the academic environment is simultaneously talking about economic crises, financial crises, political crises, social crises, highlighting the correlation and causality between variables belonging to the economic, financial, political and social areas, with repercussions and spillover effects that extend from one area to another. Given the importance, relevance and the actuality of the ones described above, I consider that at least a theoretical analysis between economic, financial and political factors is needed in order to understand the reality. Thus, this paper aims to find links and connections to complete the picture of the economic reality.

  8. Spectrum of ballooning instabilities in a stellarator

    International Nuclear Information System (INIS)

    Cooper, W.A.; Singleton, D.B.; Dewar, R.L.

    1995-08-01

    The recent revival of interest in the application of the 'ballooning formalism' to low-frequency plasma instabilities has prompted a comparison of the Wentzel-Brillouin-Kramers (WKB) ballooning approximation with an (in principle) exact normal mode calculation for a three-dimensional plasma equilibrium. Semiclassical quantization, using the ideal magnetohydrodynamic (MHD) ballooning eigenvalue to provide a local dispersion relation, is applied to a ten-field period stellarator test case. Excellent qualitative agreement, and good quantitative agreement is found with predictions from the TERPSICHORE code for toroidal mode numbers from 1 to 14 and radial mode numbers from 0 to 2. The continuum bands predicted from three-dimensional WKB theory are too narrow to resolve. (author) 3 figs., 24 refs

  9. Quantum Rabi model in the Brillouin zone with ultracold atoms

    Science.gov (United States)

    Felicetti, Simone; Rico, Enrique; Sabin, Carlos; Ockenfels, Till; Koch, Johannes; Leder, Martin; Grossert, Christopher; Weitz, Martin; Solano, Enrique

    2017-01-01

    The quantum Rabi model describes the interaction between a two-level quantum system and a single bosonic mode. We propose a method to perform a quantum simulation of the quantum Rabi model, introducing an implementation of the two-level system provided by the occupation of Bloch bands in the first Brillouin zone by ultracold atoms in tailored optical lattices. The effective qubit interacts with a quantum harmonic oscillator implemented in an optical dipole trap. Our realistic proposal allows one to experimentally investigate the quantum Rabi model for extreme parameter regimes, which are not achievable with natural light-matter interactions. When the simulated wave function exceeds the validity region of the simulation, we identify a generalized version of the quantum Rabi model in a periodic phase space.

  10. High-pressure Brillouin study on methane hydrate

    CERN Document Server

    Sasaki, S; Suwa, I; Kume, T; Shimizu, H

    2002-01-01

    Acoustic velocities and adiabatic elastic constants of structure I of methane hydrate (MH) have been determined as a function of pressure up to 0.6 GPa at 23 deg. C by the high-pressure Brillouin spectroscopy developed for a single molecular crystal. The pressure dependence of the acoustic velocities of MH is very similar to that of ice-Ih except for the longitudinal acoustic (LA) velocity. The value of the LA velocity along the (100) direction of MH at 0.02 GPa is 3.63 km s sup - sup 1 which is about 7% lower than the average of the LA velocities in the ice-Ih phase at -35.5 deg. C and atmospheric pressure.

  11. Time gated phase-correlation distributed Brillouin fibre sensor

    Science.gov (United States)

    Denisov, Andrey; Soto, Marcelo A.; Thévenaz, Luc

    2013-05-01

    A random access distributed Brillouin fibre sensor is presented, based on phase modulation using a pseudo-random bit sequence (PRBS) together with time gating. The standard phase-correlation technique is known to show a noise level increasing linearly with the number of measured points due to weak gratings generated randomly along the whole sensing fibre. Here we show how intensity modulated pump and time gated detection significantly improve the signal-tonoise ratio (SNR) of the system with no impact on the spatial resolution. A measurement with 1.1 cm spatial resolution over 3.3 km is demonstrated, representing 300'000 equivalent points. The limitations of the proposed technique are discussed through the paper.

  12. Reflectivity of stimulated back scattering in a homogeneous-slab medium in the case of negligible pump-wave damping

    International Nuclear Information System (INIS)

    Cho, G.S.; Cho, B.H.

    1981-01-01

    As to the backscatter instability which is one of nonlinear three-wave resonant interactions, the reflectivity(r) in the case of homogeneous-slab medium is calculated, assuming all the three wavepackets negligible damping caused by medium. The expression has turned out such that r = tanh 2 KAsub(p)L, where K, Asub(p), and L are the constant coupling coefficient, the constant pump-wave amplitude, and the thickness of the medium engaged in the interaction each. When this result is interpreted in terms of the stimulated Brillouin back-scattering in a so-called underdense plasma in controlled fusion, we find the reflectivity twice as large as that by others in the limit of large pump-wave damping, and unfitting to former experiments in the independence on the incident laser-light intensity. We see the incompatibility rise chiefly from neglecting the damping of pump-wave in the plasma. In contrast to the former results by others in the limit of large pump-wave damping, our result might be regarded as that for cases of negligible pump-wave damping, in general stimulated back-scattering phenomena. (author)

  13. Ignition target and laser-plasma instabilities

    International Nuclear Information System (INIS)

    Laffite, S.; Loiseau, P.

    2010-01-01

    For the first time indirect drive ignition targets have been designed with the constraint of limiting laser-plasma instabilities. The amplification of these instabilities is directly proportional to the luminous flux density, it means to the sizes of the focal spots too. This study shows that increasing the sizes of the focal spots does not reduce linear amplification gains in a proportional way because the global optimization of the target implies changes in hydrodynamical conditions that in turn have an impact on the value of the amplification gain. The design of the target is a 2-step approach: the first step aims at assuring a uniform irradiation and compression of the target. The first step requires information concerning the laser focusing spots, the dimensions of the hohlraum, the inert gas contained in it, the materials of the wall. The second step is an optimization approach whose aim is to reduce the risk of laser-plasmas instabilities. This optimization is made through simulations of the amplification gains of stimulated Raman and Brillouin backscattering. This method has allowed us to design an optimized target for a rugby-shaped hohlraum. (A.C.)

  14. Bi-Directional Brillouin Optical Time Domain Analyzer System for Long Range Distributed Sensing.

    Science.gov (United States)

    Guo, Nan; Wang, Liang; Wang, Jie; Jin, Chao; Tam, Hwa-Yaw; Zhang, A Ping; Lu, Chao

    2016-12-16

    We propose and experimentally demonstrate a novel scheme of bi-directional Brillouin time domain analyzer (BD-BOTDA) to extend the sensing range. By deploying two pump-probe pairs at two different wavelengths, the Brillouin frequency shift (BFS) distribution over each half of the whole fiber can be obtained with the simultaneous detection of Brillouin signals in both channels. Compared to the conventional unidirectional BOTDA system of the same sensing range, the proposed BD-BOTDA scheme enables distributed sensing with a performance level comparable to the conventional one with half of the sensing range and a spatial resolution of 2 m, while maintaining the Brillouin signal-to-noise ratio (SNR) and the BFS uncertainty. Based on this technique, we have achieved distributed temperature sensing with a measurement range of 81.9 km fiber at a spatial resolution of 2 m and BFS uncertainty of ~0.44 MHz without introducing any complicated components or schemes.

  15. Simulation of simultaneously obtaining ocean temperature and salinity using dual-wavelength Brillouin lidar

    International Nuclear Information System (INIS)

    Yu, Yin; Ma, Yong; Li, Hao; Huang, Jun; Fang, Yu; Liang, Kun; Zhou, Bo

    2014-01-01

    A method for simultaneously obtaining the ocean temperature and salinity based on dual-wavelength Brillouin lidar is proposed in this letter. On the basis of the relationships between the temperature and salinity and the Brillouin shifts, a retrieval model for retrieving the temperature and salinity is established. By using the retrieval model, the ocean temperature and salinity can be simultaneously obtained through the Brillouin shifts. Simulation based on dual-wavelength Brillouin lidar is also carried out for verification of the accuracy of the retrieval model. Results show that the errors of the retrieval model for temperature and salinity are ±0.27 °C and ±0.33‰. (letter)

  16. Collective Excitations in Liquid Hydrogen Observed by Coherent Neutron Scattering

    DEFF Research Database (Denmark)

    da Costa Carneiro, Kim; Nielsen, M.; McTague, J. P.

    1973-01-01

    Coherent scattering of neutrons by liquid parahydrogen shows the existence of well-defined collective excitations in this liquid. Qualitative similarity with the scattering from liquid helium is found. Furthermore, in the range of observed wave vectors, 0.7 Å-1 ≤κ≤3.1 Å-1, extending from the firs...... through the third Brillouin zones in the solid, S(κ,ω) is remarkably similar to the scattering law expected from a polycrystal. For κ≤2.3 Å-1 the observed spectra satisfy the one-phonon sum rule with mean square displacement 〈u2〉=1.0 Å2....

  17. White-light parametric instabilities in plasmas.

    Science.gov (United States)

    Santos, J E; Silva, L O; Bingham, R

    2007-06-08

    Parametric instabilities driven by partially coherent radiation in plasmas are described by a generalized statistical Wigner-Moyal set of equations, formally equivalent to the full wave equation, coupled to the plasma fluid equations. A generalized dispersion relation for stimulated Raman scattering driven by a partially coherent pump field is derived, revealing a growth rate dependence, with the coherence width sigma of the radiation field, scaling with 1/sigma for backscattering (three-wave process), and with 1/sigma1/2 for direct forward scattering (four-wave process). Our results demonstrate the possibility to control the growth rates of these instabilities by properly using broadband pump radiation fields.

  18. Thermodynamical instabilities under strong magnetic fields

    Science.gov (United States)

    Chen, Y. J.

    2017-03-01

    The thermodynamical instabilities of low densities in the n p matter and n p e matter are studied within several relativistic nuclear models under some values of magnetic fields. The results are compared between each other and the effects of the symmetry energy slope at saturation density on the instability are investigated. The instability regions can exhibit bands due to the presence of Landau levels for very strong magnetic fields of the order of 1017 G, while for weaker magnetic fields, the bands are replaced by many diffused or scattered pieces. It also shows that the proton fraction in the inner crust of neutron stars may be complex under strong magnetic fields.

  19. Controlling Stimulated Brillouin/Raman Scattering in High Power Fiber Lasers

    Science.gov (United States)

    2017-08-09

    fiber amplifier archetype . 26 Approved for public release. Distribution is unlimited. The fiber was coiled on a 65 cm diameter aluminum spool with...compare to bulk silica [7] and the gB for the Yb- and P2O5-doped silica was 4.3x reduced [12] compared to literature values. A 2x reduction can be...glass interface. Other efficiency metrics for free-space fiber amplifiers that are found in the literature include efficiency with respect to the

  20. Application of Coupled-Wave Wentzel-Kramers-Brillouin Approximation to Ground Penetrating Radar

    Directory of Open Access Journals (Sweden)

    Igor Prokopovich

    2017-12-01

    Full Text Available This paper deals with bistatic subsurface probing of a horizontally layered dielectric half-space by means of ultra-wideband electromagnetic waves. In particular, the main objective of this work is to present a new method for the solution of the two-dimensional back-scattering problem arising when a pulsed electromagnetic signal impinges on a non-uniform dielectric half-space; this scenario is of interest for ground penetrating radar (GPR applications. For the analytical description of the signal generated by the interaction of the emitted pulse with the environment, we developed and implemented a novel time-domain version of the coupled-wave Wentzel-Kramers-Brillouin approximation. We compared our solution with finite-difference time-domain (FDTD results, achieving a very good agreement. We then applied the proposed technique to two case studies: in particular, our method was employed for the post-processing of experimental radargrams collected on Lake Chebarkul, in Russia, and for the simulation of GPR probing of the Moon surface, to detect smooth gradients of the dielectric permittivity in lunar regolith. The main conclusions resulting from our study are that our semi-analytical method is accurate, radically accelerates calculations compared to simpler mathematical formulations with a mostly numerical nature (such as the FDTD technique, and can be effectively used to aid the interpretation of GPR data. The method is capable to correctly predict the protracted return signals originated by smooth transition layers of the subsurface dielectric medium. The accuracy and numerical efficiency of our computational approach make promising its further development.

  1. Modal instabilities in very large mode area rod fiber amplifiers

    DEFF Research Database (Denmark)

    Jørgensen, Mette Marie; Hansen, Kristian Rymann; Laurila, Marko

    with the finite element method to allow complex micro structured fibers to be considered. Thereby the modal instability threshold is estimated for very large mode area fiber amplifiers of various photonic crystal fiber designs. Experimentally the modal instability threshold for very large mode area fiber......Optical fiber amplifiers have gained increased scientific and commercial interest due to high output powers with easy operation and maintenance. The main advantages of fiber amplifiers are good thermal properties, due to a large surface/volume ratio, excellent beam quality and stability [1]. Very...... large core fiber areas are highly desirable to mitigate various nonlinear processes, such as Kerr, four-wave mixing, Raman, and Brillouin effects. It is difficult to scale up the core area without going into a multi-moded regime. Microstructured fiber technology has allowed core diameters of 60...

  2. Polygonal instabilities

    Science.gov (United States)

    Labousse, Matthieu

    2015-11-01

    The interaction of a vortex with a free surface is encountered in a series of experiments, the hydraulic jump, the hydraulic bump, the toroidal Leidenfrost experiment. All these experiments share in common an unstable configuration in which azimuthal perturbations give rise to polygonal patterns. We propose a unified theoretical framework to model the emergence of this instability by investigating the stability of a liquid torus with a poloidal motion. As simple as it is, we show that the model retains the necessary ingredients to account for the experimental observations. In this talk, I will first describe the model and compare it to the existing data. However this model is purely inviscid and reaches its limits when being applied to relatively moderate Reynolds flows. So in a second part, I will present a recent experimental and theoretical investigation in which polygonal patterns are now driven by Marangoni flows. To our great surprise, it extends the range of validity of the initial proposed framework, much more than initially expected.

  3. Fiber amplifiers under thermal loads leading to transverse mode instability

    DEFF Research Database (Denmark)

    Johansen, Mette Marie; Hansen, Kristian Rymann; Alkeskjold, Thomas Tanggaard

    2014-01-01

    Transverse mode instability (TMI) in rare-earth doped fiber amplifiers operating above an average power threshold is caused by intermodal stimulated thermal Rayleigh scattering due to quantum defect heating. We investigate thermally induced longitudinal waveguide perturbations causing power trans...

  4. Applications of phase conjugate mirror to Thomson scattering diagnostics (invited)

    International Nuclear Information System (INIS)

    Hatae, T.; Naito, O.; Nakatsuka, M.; Yoshida, H.

    2006-01-01

    A high performance phase conjugate mirror based on stimulated Brillouin scattering (SBS-PCM) has been applied to the Thomson scattering system in the JT-60U tokamak for the first time in order to improve the measurement performance. A SBS-PCM realized a high reflectivity of 95% at a high input power of 145 W (2.9 J, 50 Hz). Using the SBS-PCM, two methods have been developed to increase the intensity of scattered light. For the first method, we have developed a new optical design to provide a double-pass scattering method with the SBS-PCM. A laser beam passing through the plasma is reflected by the SBS-PCM. The reflected beam passes the plasma again along the same path by means of the phase conjugation of the optically nonlinear stimulated Brillouin scattering process. The double-pass Thomson scattering method using the SBS-PCM has demonstrated an increase of the scattered light by a factor of 1.6 compared with the single-pass scattering method in JT-60U. A multipass Thomson scattering method in which the laser beam can be confined between a couple of SBS-PCMs is also proposed. It is estimated that the multipass scattering method generates the scattered light more than several times as large as that of the single-pass scattering method. For the second method, a high-average-power yttrium aluminum garnet (Nd:YAG) laser system has been developed using the SBS-PCM. The SBS-PCM effectively compensated thermal degradation at two amplifier lines, and the average power was increased by a factor of >8 from 45 W (1.5 J, 30 Hz) to 373 W (7.46 J, 50 Hz). A Nd:YAG laser (5 J, 100 Hz) for the edge Thomson scattering in International Thermonuclear Experimental Reactor (ITER) has been designed based on the result

  5. Decay instability of a whistler in a plasma

    International Nuclear Information System (INIS)

    Tewari, D.P.; Sharma, R.R.

    1982-01-01

    The parametric instabilities of a high power whistler in a high density plasma possess large growth rate when the scattered sideband is an electrostatic lower hybrid mode. The efficient channels of decay include oscillating two stream instability, nonlinear Landau damping and resonant decay involving ion acoustic and ion cyclotron modes. The processes of nonlinear scattering, i.e., the ones possessing whistler sidebands are relatively less significant. (author)

  6. Non-local effect in Brillouin optical time-domain analyzer based on Raman amplification

    International Nuclear Information System (INIS)

    Jia Xinhong; Rao Yunjiang; Wang Zinan; Zhang Weili; Ran Zengling; Deng Kun; Yang Zixin

    2012-01-01

    Compared with conventional Brillouin optical time-domain analyzer (BOTDA), the BOTDA based on Raman amplification allows longer sensing range, higher signal-to-noise ratio and higher measurement accuracy. However, the non-local effect induced by pump depletion significantly restricts the probe optical power injected to sensing fiber, thereby limiting the further extension for sensing distance. In this paper, the coupled equations including the interaction of probe light, Brillouin and Raman pumps are applied to the study on the non-local characteristics of BOTDA based on Raman amplification. The results show that, the system error induced by non-local effect worsens with increased powers of probe wave and Raman pump. The frequency-division-multiplexing (cascading the fibers with various Brillouin frequency shifts) and time-division-multiplexing (modulating both of the Brillouin pump and probe lights) technologies are efficient approaches to suppress the non-local effect, through shortening the effective interaction range between Brillouin pump and probe lights. (authors)

  7. Detection of sinkhole formation via Brillouin Optical-Fiber Time-Domain Reflectrometry (BOTDR)

    Science.gov (United States)

    Linker, R.; Klar, A.

    2009-04-01

    Sinkholes have been considered a major natural hazard in the Dead Sea region since their apparition more than 15 year ago. Although these sinkholes develop slowly over several months, they collapse very suddenly without any warning signs, which makes them especially dangerous to both people and infrastructures. The most commonly accepted mechanism for sinkholes formation in the Dead Sea area is dissolving of salt in subsurface layers. As a result of salt dissolution, the load that was carried originally by the salt layers is transferred to the other soil layers. When this load exceeds the layers' holding capacity, collapse occurs. Throughout this load-transfer process, small mechanical deformations must develop in the soil and the present study investigates the use of Brillouin Optical-Fiber Time-Domain Reflectrometry (BOTDR) for detecting these changes. BOTDR uses the Brillouin-scattering of the light along the optic fiber to estimate the temperature or strain profile in the fiber in a distributed manner. Following temperature compensation, such a system allows for nearly-continuous distributed monitoring of strains over distances of tens of kilometers with a spatial resolution of about 1 meter. In the present study, an analytical solution of the strains that develop in the soil due to sinkhole development was used to simulate the BOTDR signals that would be produced by an optic fiber buried one meter below the soil surface. These simulated "ideal" signals were corrupted artificially to account for the actual spatial resolution of the signal analyzer and random measurement errors. In addition, BOTDR signals due to above-surface disturbances (400kg loading and rain) that were obtained experimentally, were superimposed to the simulated signals. Three thousands BOTDR signals were generated with sinkhole radii and depths ranging from 1.5 to 4.0m and from 10 to 30m, respectively. These signals were subjected to wavelet decomposition and the most informative wavelet

  8. Raman sidescatter instability in a nonuniform plasma

    International Nuclear Information System (INIS)

    Mostrom, M.A.

    1977-01-01

    In the various laser-fusion concepts, an intense electromagnetic wave (the laser) must propagate through an under-dense plasma region where it could decay, via the stimulated Raman instability, into a Langmuir plasma wave and a scattered electromagnetic wave. This process could, therefore, scatter a significant fraction of the laser energy before it could be deposited in the plasma. A density gradient, in the direction of laser incidence, localizes the instability to a narrow resonance zone where the local plasma wave frequency approximately equals the difference-frequency between the incident and scattered electromagnetic waves. The narrowness of this zone can strongly inhibit the growth of back- or oblique-scattered electromagnetic waves since they quickly propagate out of their resonance region; however, the density gradient has a much weaker effect on side-scattered waves (which propagate perpendicular to the density gradient) since they remain in their resonance zone until refraction bends them out or they exit through the side of the finite diameter laser beam. Thus, we place particular emphasis on evaluating, in a manner valid for the side scattered electromagnetic waves (which are at their turning point), the level of exponentiation at which the growth is linearly saturated due to convection of the waves out of their resonance zone. We also determine the general nature and propagation of the scattered electromagnetic waves and obtain approximate values for the resonance zone size and the time required for the above saturation

  9. Characterization of red blood cells (RBCs) using dual Brillouin/Raman micro-spectroscopy

    Science.gov (United States)

    Meng, Zhaokai; Bustamante-Lopez, Sandra C.; Yakovlev, Vladislav V.; Meissner, Kenith E.

    2016-04-01

    Erythrocytes, or red blood cells, transport oxygen to and carbon dioxide from the body's tissues and organs. Red blood cell mechanical properties are altered in a number of diseases such as sickle cell anaemia and malaria. Additionally, mechanically modified red blood cell ghosts are being considered as a long-term, biocompatible carrier for drug delivery and for blood analyte sensing. Brillouin spectroscopy enables viscoelastic characterization of samples at the microscale. In this report, Brillouin spectroscopy is applied to characterize the mechanical properties of red blood cells and red blood cell ghosts.

  10. Determination of the elastic constants of portlandite by Brillouin spectroscopy

    KAUST Repository

    Speziale, S.

    2008-10-01

    The single crystal elastic constants Cij and the shear and adiabatic bulk modulus of a natural portlandite (Ca(OH)2) crystal were determined by Brillouin spectroscopy at ambient conditions. The elastic constants, expressed in GPa, are: C11 = 102.0(± 2.0), C12 = 32.1(± 1.0), C13 = 8.4(± 0.4), C14 = 4.5(± 0.2), C33 = 33.6(± 0.7), C44 = 12.0(± 0.3), C66 = (C11-C12)/2 = 35.0(± 1.1), where the numbers in parentheses are 1σ standard deviations. The Reuss bounds of the adiabatic bulk and shear moduli are K0S = 26.0(± 0.3) GPa and G0 = 17.5(± 0.4) GPa, respectively, while the Voigt bounds of these moduli are K0S = 37.3(± 0.4) GPa and G0 = 24.4(± 0.3) GPa. The Reuss and Voigt bounds for the aggregate Young\\'s modulus are 42.8(± 1.0) GPa and 60.0(± 0.8) GPa respectively, while the aggregate Poisson\\'s ratio is equal to 0.23(± 0.01). Portlandite exhibits both large compressional elastic anisotropy with C11/C33 = 3.03(± 0.09) equivalent to that of the isostructural hydroxide brucite (Mg(OH)2), and large shear anisotropy with C66/C44 = 2.92(± 0.12) which is 11% larger than brucite. The comparison between the bulk modulus of portlandite and that of lime (CaO) confirms a systematic linear relationship between the bulk moduli of brucite-type simple hydroxides and the corresponding NaCl-type oxides. © 2008 Elsevier Ltd. All rights reserved.

  11. Residual strain sensor using Al-packaged optical fiber and Brillouin optical correlation domain analysis.

    Science.gov (United States)

    Choi, Bo-Hun; Kwon, Il-Bum

    2015-03-09

    We propose a distributed residual strain sensor that uses an Al-packaged optical fiber for the first time. The residual strain which causes Brillouin frequency shifts in the optical fiber was measured using Brillouin optical correlation domain analysis with 2 cm spatial resolution. We quantified the Brillouin frequency shifts in the Al-packaged optical fiber by the tensile stress and compared them for a varying number of Al layers in the optical fiber. The Brillouin frequency shift of an optical fiber with one Al layer had a slope of 0.038 MHz/με with respect to tensile stress, which corresponds to 78% of that for an optical fiber without Al layers. After removal of the stress, 87% of the strain remained as residual strain. When different tensile stresses were randomly applied, the strain caused by the highest stress was the only one detected as residual strain. The residual strain was repeatedly measured for a time span of nine months for the purpose of reliability testing, and there was no change in the strain except for a 4% reduction, which is within the error tolerance of the experiment. A composite material plate equipped with our proposed Al-packaged optical fiber sensor was hammered for impact experiment and the residual strain in the plate was successfully detected. We suggest that the Al-packaged optical fiber can be adapted as a distributed strain sensor for smart structures, including aerospace structures.

  12. Elastic and anharmonic properties of pyridinium tetrafluoroborate ([C{sub 5}NH{sub 6}]{sup +}[BF{sub 4}]{sup -{identical_to}}PyBF{sub 4}): light scattering study of the phase transitions at various pressures

    Energy Technology Data Exchange (ETDEWEB)

    Ecolivet, C.; Beaufils, S.; Girard, A. [Groupe Matiere Condensee et Materiaux - UMR CNRS 6626, Universite de Rennes 1, Rennes (France); Czarnecki, P.; Wasicki, J.; Bobrowicz-Sarga, L. [Institute of Physics, Adam Mickiewicz University, Poznan (Poland)

    2001-07-30

    The vibrational properties of pyridinium tetrafluoroborate crystals were studied by means of Brillouin scattering at atmospheric pressure, Raman scattering and neutron diffraction under high pressure. It is shown that the elastic properties strongly reflect the molecular anisotropy of the pyridinium ions. The compressibility obtained from the Brillouin scattering study is in reasonable agreement with the results from neutron crystallography under pressure. Brillouin spectra reveal a small quasielastic component at room temperature, which is described by a coupled-susceptibilities formalism applied to the longitudinal mode and a relaxation mode. The mode Grueneisen parameters for all three phases that are found are determined from the pressure and temperature dependence of the Raman spectra and from neutron experiments. (author)

  13. Localization of the interband transitions in the bulk of the Brillouin zone of III–V compound crystals

    Energy Technology Data Exchange (ETDEWEB)

    Sobolev, V. V., E-mail: sobolev@uni.udm.ru; Perevoshchikov, D. A. [Udmurt State University (Russian Federation)

    2016-05-15

    The localization of the transitions in the bulk of the Brillouin zone that form the main structures in the spectra of the imaginary part of the permittivity in the range up to ~7 eV for III–V semiconductors (AlSb, GaSb, InSb, and InAs) is determined using electron density functional theory. It is established that intense transitions occur not only in the vicinity of the high-symmetry axes of the Brillouin zone, but also in some specific large volumes of the irreducible part of the Brillouin zone.

  14. Influence of Stimuled Raman Scattering on Transmitted Optical Signal in WDM System

    Directory of Open Access Journals (Sweden)

    Ján Ružbarský

    2015-12-01

    Full Text Available Paper is focused on simulations behavior of signals in high-speed networks. Huge amount of transmitted information and increase in transmission speed create unwanted events in optical fiber. The main influences comprise effects such as: stimulated Raman scattering and stimulated Brillouin scattering. This paper is focused only on Raman scattering. For transmitting a signal through optical fiber one needs to select an appropriate wavelength. This is one of goals the experiment in this article. Signals were transmitted accordance with Dense Wavelength Division Multiplexing (DWDM and spacing among channels 100GHz.

  15. Magnetic interactions and Onsager reaction field from paramagnetic diffuse neutron scattering

    CERN Document Server

    Hohlwein, D

    2002-01-01

    Magnetic interaction parameters can be deduced from the diffuse scattering distribution using a mean-field theory. However, this theory is only valid at quite high temperatures. We introduce into the theory an additional parameter for the Onsager reaction field. Diffuse scattering data of the antiferromagnetic model system MnF sub 2 are used to refine the additional parameter as a function of temperature. The Onsager parameter is also calculated by integrating the diffuse scattering in the Brillouin zone. We show that this parameter correctly describes the deviation from the mean-field theory over a large temperature range, from 1.06 to 2.4 T sub N. (orig.)

  16. Magnetic interactions and Onsager reaction field from paramagnetic diffuse neutron scattering

    International Nuclear Information System (INIS)

    Hohlwein, D.

    2002-01-01

    Magnetic interaction parameters can be deduced from the diffuse scattering distribution using a mean-field theory. However, this theory is only valid at quite high temperatures. We introduce into the theory an additional parameter for the Onsager reaction field. Diffuse scattering data of the antiferromagnetic model system MnF 2 are used to refine the additional parameter as a function of temperature. The Onsager parameter is also calculated by integrating the diffuse scattering in the Brillouin zone. We show that this parameter correctly describes the deviation from the mean-field theory over a large temperature range, from 1.06 to 2.4 T N . (orig.)

  17. Joint Instability and Osteoarthritis

    Directory of Open Access Journals (Sweden)

    Darryl Blalock

    2015-01-01

    Full Text Available Joint instability creates a clinical and economic burden in the health care system. Injuries and disorders that directly damage the joint structure or lead to joint instability are highly associated with osteoarthritis (OA. Thus, understanding the physiology of joint stability and the mechanisms of joint instability-induced OA is of clinical significance. The first section of this review discusses the structure and function of major joint tissues, including periarticular muscles, which play a significant role in joint stability. Because the knee, ankle, and shoulder joints demonstrate a high incidence of ligament injury and joint instability, the second section summarizes the mechanisms of ligament injury-associated joint instability of these joints. The final section highlights the recent advances in the understanding of the mechanical and biological mechanisms of joint instability-induced OA. These advances may lead to new opportunities for clinical intervention in the prevention and early treatment of OA.

  18. Study of a non-ideal liquid mixture in the hydrodynamic regime. Rayleigh-Brillouin spectra, sound propagation and damping in the CH3CN-CCl4 system at the azeotropic composition

    International Nuclear Information System (INIS)

    Sassi, Paola; D'Elia, Valerio; Cataliotti, Rosario Sergio

    2003-01-01

    The hydrodynamic behaviour in the GHz frequency region has been analzsed for the non-ideal CH 3 CN-CCl 4 liquid mixture around the azeotropic composition. Rayleigh-Brillouin spectra have been measured as a function of temperature and composition, at fixed value of transferred wave vector in the 90 deg. scattering geometry, and also at different scattering angles to study dispersion with frequency of the spectral observables. These measurements have been complemented by those of refractive index, density and viscosity at the same temperatures and mole fraction values. Very interesting behaviour of the classic Brillouin spectral observables, such as the hypersonic propagation speeds and the acoustic absorption coefficients, has been revealed near the azeotropic composition of the mixture at the investigated temperatures, namely 15 deg. C, 25 deg. C, 40 deg. C and 60 deg. C. These effects have been interpreted at the light of the Mountain and Deutch theory of binary solutions and the forecast behaviour of the intermolecular forces around the azeotropic point composition of these very different molecular liquids

  19. Research on distributed strain separation technology of fiber Brillouin sensing system combining an electric power optical fiber cable

    Science.gov (United States)

    Lei, Yuqing; Chen, Xi; Li, Jihui; Tong, Jie

    2013-12-01

    Brillouin-based optical fiber sensing system has been taken more and more attentions in power transmission line in recent years. However, there exists a temperature cross sensitivity problem in sensing system. Hence, researching on strain separation technology of fiber brillouin sensing system is an urgent requirement in its practical area. In this paper, a real-time online distributed strain separation calculation technology of fiber Brillouin sensing combining an electric power optical fiber cable is proposed. The technology is mainly composed of the Brillouin temperature-strain distributed measurement system and the Raman temperature distributed measurement system. In this technology, the electric power optical fiber cable is a special optical phase conductor (OPPC); the Brillouin sensing system uses the Brillouin optical time domain analysis (BOTDA) method. The optical unit of the OPPC includes single-mode and multimode fibers which can be used as sensing channel for Brillouin sensing system and Raman sensing system respectively. In the system networking aspect, the data processor of fiber Brillouin sensing system works as the host processor and the data processor of fiber Raman sensing system works as the auxiliary processor. And the auxiliary processor transfers the data to the host processor via the Ethernet interface. In the experiment, the BOTDA monitoring system and the Raman monitoring system work on the same optical unit of the OPPC simultaneously; In the data processing aspect, the auxiliary processor of Raman transfers the temperature data to the host processor of Brillouin via the Ethernet interface, and then the host processor of Brillouin uses the temperature data combining itself strain-temperature data to achieve the high sampling rate and high-precision strain separation via data decoupling calculation. The data decoupling calculation is achieved through the interpolation, filtering, feature point alignment, and the singular point prediction

  20. Electrically tunable Brillouin fiber laser based on a metal-coated single-mode optical fiber

    Directory of Open Access Journals (Sweden)

    S.M. Popov

    Full Text Available We explore tunability of the Brillouin fiber laser employing Joule heating. For this purpose, 10-m-length of a metal-coated single-mode optical cavity fiber has been directly included into an electrical circuit, like a conductor wire. With the current up to ∼3.5 A the laser tuning is demonstrated over a spectrum range of ∼400 MHz. The observed laser line broadening up to ∼2 MHz is explained by frequency drift and mode-hoping in the laser caused by thermal noise. Keywords: Brillouin fiber laser, Metal-coated optical fiber, Laser tuning, Fiber sensors

  1. Evaluating biomechanical properties of murine embryos using Brillouin microscopy and optical coherence tomography

    Science.gov (United States)

    Raghunathan, Raksha; Zhang, Jitao; Wu, Chen; Rippy, Justin; Singh, Manmohan; Larin, Kirill V.; Scarcelli, Giuliano

    2017-08-01

    Embryogenesis is regulated by numerous changes in mechanical properties of the cellular microenvironment. Thus, studying embryonic mechanophysiology can provide a more thorough perspective of embryonic development, potentially improving early detection of congenital abnormalities as well as evaluating and developing therapeutic interventions. A number of methods and techniques have been used to study cellular biomechanical properties during embryogenesis. While some of these techniques are invasive or involve the use of external agents, others are compromised in terms of spatial and temporal resolutions. We propose the use of Brillouin microscopy in combination with optical coherence tomography (OCT) to measure stiffness as well as structural changes in a developing embryo. While Brillouin microscopy assesses the changes in stiffness among different organs of the embryo, OCT provides the necessary structural guidance.

  2. Brillouin Corrosion Expansion Sensors for Steel Reinforced Concrete Structures Using a Fiber Optic Coil Winding Method

    Directory of Open Access Journals (Sweden)

    Xingjun Lv

    2011-11-01

    Full Text Available In this paper, a novel kind of method to monitor corrosion expansion of steel rebars in steel reinforced concrete structures named fiber optic coil winding method is proposed, discussed and tested. It is based on the fiber optical Brillouin sensing technique. Firstly, a strain calibration experiment is designed and conducted to obtain the strain coefficient of single mode fiber optics. Results have shown that there is a good linear relationship between Brillouin frequency and applied strain. Then, three kinds of novel fiber optical Brillouin corrosion expansion sensors with different fiber optic coil winding packaging schemes are designed. Sensors were embedded into concrete specimens to monitor expansion strain caused by steel rebar corrosion, and their performance was studied in a designed electrochemical corrosion acceleration experiment. Experimental results have shown that expansion strain along the fiber optic coil winding area can be detected and measured by the three kinds of sensors with different measurement range during development the corrosion. With the assumption of uniform corrosion, diameters of corrosion steel rebars were obtained using calculated average strains. A maximum expansion strain of 6,738 με was monitored. Furthermore, the uniform corrosion analysis model was established and the evaluation formula to evaluate mass loss rate of steel rebar under a given corrosion rust expansion rate was derived. The research has shown that three kinds of Brillouin sensors can be used to monitor the steel rebar corrosion expansion of reinforced concrete structures with good sensitivity, accuracy and monitoring range, and can be applied to monitor different levels of corrosion. By means of this kind of monitoring technique, quantitative corrosion expansion monitoring can be carried out, with the virtues of long durability, real-time monitoring and quasi-distribution monitoring.

  3. Diffuse scattering

    Energy Technology Data Exchange (ETDEWEB)

    Kostorz, G. [Eidgenoessische Technische Hochschule, Angewandte Physik, Zurich (Switzerland)

    1996-12-31

    While Bragg scattering is characteristic for the average structure of crystals, static local deviations from the average lattice lead to diffuse elastic scattering around and between Bragg peaks. This scattering thus contains information on the occupation of lattice sites by different atomic species and on static local displacements, even in a macroscopically homogeneous crystalline sample. The various diffuse scattering effects, including those around the incident beam (small-angle scattering), are introduced and illustrated by typical results obtained for some Ni alloys. (author) 7 figs., 41 refs.

  4. Hydrodynamic instabilities in inertial fusion

    International Nuclear Information System (INIS)

    Hoffman, N.M.

    1994-01-01

    This report discusses topics on hydrodynamics instabilities in inertial confinement: linear analysis of Rayleigh-Taylor instability; ablation-surface instability; bubble rise in late-stage Rayleigh-Taylor instability; and saturation and multimode interactions in intermediate-stage Rayleigh-Taylor instability

  5. Brillouin spectroscopy reveals changes in muscular viscoelasticity in Drosophila POMT mutants

    Science.gov (United States)

    Meng, Zhaokai; Baker, Ryan; Panin, Vladislav M.; Yakovlev, Vladislav V.

    2015-03-01

    Muscular dystrophy (MD) is a group of muscle diseases that induce weakness in skeletal muscle and cause progressive muscle degeneration. The muscular mechanical properties (i.e., viscoelasticity), however, have not been thoroughly examined before and after MD. On the other hand, Brillouin spectroscopy (BS) provides a non-invasive approach to probing the local sound speed within a small volume. Moreover, recent advances in background-free Brillouin spectroscopy enable investigators to imaging not only transparent samples, but also turbid ones. In this study, we investigated the mechanical properties of muscles while employing Drosophila model of dystroglycanopathies, human congenital muscular dystrophies resulting from abnormal glycosylation of alphadystroglycan. Specifically, we analyzed larval abdominal muscles of Drosophila with mutations in protein Omannosyltransferase (POMT) genes. As a comparison, we have also examined muscular tissues dissected from wildtype Drosophila. The Brillouin spectra were obtained by a background free VIPA (virtually imaged phased array) spectrometer described in the previous report. As a reference, the Raman spectra were also acquired for each test. Our current results indicated that POMT defects cause changes in muscle elasticity, which suggests that muscular dystrophy conditions may be also associated with abnormalities in muscle elastic properties.

  6. Instability of vortex pair leapfrogging

    DEFF Research Database (Denmark)

    Tophøj, Laust; Aref, Hassan

    2013-01-01

    )]10.1088/0143-0807/21/3/310 determined by numerical experiments that leapfrogging is linearly unstable for σ2 stable for larger α. Here we derive a linear system of equations governing small perturbations of the leapfrogging motion. We show that symmetry-breaking perturbations are essentially governed by a 2D...... linear system with time-periodic coefficients and perform a Floquet analysis. We find transition from linearly unstable to stable leapfrogging at α = φ2 ≈ 0.381966, where is the golden ratio. Acheson also suggested that there was a sharp transition between a "disintegration" instability mode, where two...... pairs fly off to infinity, and a "walkabout" mode, where the vortices depart from leapfrogging but still remain within a finite distance of one another. We show numerically that this transition is more gradual, a result that we relate to earlier investigations of chaotic scattering of vortex pairs [L...

  7. Neutrino beam plasma instability

    Indian Academy of Sciences (India)

    We derive relativistic fluid set of equations for neutrinos and electrons from relativistic Vlasov equations with Fermi weak interaction force. Using these fluid equations, we obtain a dispersion relation describing neutrino beam plasma instability, which is little different from normal dispersion relation of streaming instability.

  8. Light-scattering study of the glass transition in lubricants

    Science.gov (United States)

    Alsaad, M. A.; Winer, W. O.; Medina, F. D.; Oshea, D. C.

    1977-01-01

    The sound velocity of four lubricants has been measured as a function of temperature and pressure using Brillouin scattering. A change in slope of the velocity as a function of temperature or pressure allowed the determination of the glass transition temperature and pressure. The glass transition data were used to construct a phase diagram for each lubricant. The data indicate that the glass transition temperature increased with pressure at a rate which ranged from 120 to 200 C/GPa. The maximum pressure attained was 0.69 GPa and the temperature range was from 25 to 100 C.

  9. Experimental study of the saturation of parametric instabilities in the conditions of an inertial fusion plasma

    International Nuclear Information System (INIS)

    Michel, D.T.

    2010-09-01

    This work presents the results of 3 series of experiments carried on the 2 French nanosecond multi-kilo-joule laser facilities: LULI 2000 and LIL (Laser Integration Line - that is a prototype of the future LMJ quadruplets). 2 issues have been tackled: first, the influence of the wavelength (second or third harmonic) on the saturation levels of Brillouin and Raman reflectivities and secondly, the laser smoothing and the imprint reduction through the use of a low-density foam layer. The first series of experiments has enabled us to get Brillouin backscattering rates in identical saturation regimes for the 2 frequencies: 2ω and 3ω. Hydrodynamic simulations and the interpretation of experimental results have shown that for both frequencies the laser-plasma conditions in which the instability develops are quite similar. In the second series of experiments we have shown that the saturation process that most limits the amplitude of the Electron Plasma Wave is the Langmuir decay instability (LDI). A low-density foam is efficient to reduce the imprint and if the foam ionization is supersonic, there is no risk to create a shock that could pre-heat the target core. A foam thickness of 500 μm for a density of 10 mg/cm 3 is efficient for a laser power of 10 14 W/cm 2 . (A.C.)

  10. MRI of shoulder instability

    Energy Technology Data Exchange (ETDEWEB)

    Steinbach, Lynne S. [University of California San Francisco, 505 Parnassus, Suite M392, San Francisco, CA 94143-0628 (United States)], E-mail: lynne.steinbach@radiology.ucsf.edu

    2008-10-15

    The most unstable joint in the body, the glenohumeral joint is subject to many insults including microinstability, subluxation and dislocation. During the last two decades, MRI has allowed for direct visualization of many of the lesions related to instability, aiding in diagnosis as well as therapeutic planning and follow-up. This article reviews the use of MRI for shoulder instability and describes the different types of lesions associated with this disorder. Topics include technical considerations, the use of MR arthrography, normal anatomy and variants, labral and glenohumeral ligament pathology, and osseous lesions related to instability.

  11. Spondylolisthesis and Posterior Instability

    International Nuclear Information System (INIS)

    Niggemann, P.; Beyer, H.K.; Frey, H.; Grosskurth, D.; Simons, P.; Kuchta, J.

    2009-01-01

    We present the case of a patient with a spondylolisthesis of L5 on S1 due to spondylolysis at the level L5/S1. The vertebral slip was fixed and no anterior instability was found. Using functional magnetic resonance imaging (MRI) in an upright MRI scanner, posterior instability at the level of the spondylolytic defect of L5 was demonstrated. A structure, probably the hypertrophic ligament flava, arising from the spondylolytic defect was displaced toward the L5 nerve root, and a bilateral contact of the displaced structure with the L5 nerve root was shown in extension of the spine. To our knowledge, this is the first case described of posterior instability in patients with spondylolisthesis. The clinical implications of posterior instability are unknown; however, it is thought that this disorder is common and that it can only be diagnosed using upright MRI

  12. Spondylolisthesis and Posterior Instability

    Energy Technology Data Exchange (ETDEWEB)

    Niggemann, P.; Beyer, H.K.; Frey, H.; Grosskurth, D. (Privatpraxis fuer Upright MRT, Koeln (Germany)); Simons, P.; Kuchta, J. (Media Park Klinik, Koeln (Germany))

    2009-04-15

    We present the case of a patient with a spondylolisthesis of L5 on S1 due to spondylolysis at the level L5/S1. The vertebral slip was fixed and no anterior instability was found. Using functional magnetic resonance imaging (MRI) in an upright MRI scanner, posterior instability at the level of the spondylolytic defect of L5 was demonstrated. A structure, probably the hypertrophic ligament flava, arising from the spondylolytic defect was displaced toward the L5 nerve root, and a bilateral contact of the displaced structure with the L5 nerve root was shown in extension of the spine. To our knowledge, this is the first case described of posterior instability in patients with spondylolisthesis. The clinical implications of posterior instability are unknown; however, it is thought that this disorder is common and that it can only be diagnosed using upright MRI.

  13. Quasiresonant scattering

    International Nuclear Information System (INIS)

    Hategan, Cornel; Comisel, Horia; Ionescu, Remus A.

    2004-01-01

    The quasiresonant scattering consists from a single channel resonance coupled by direct interaction transitions to some competing reaction channels. A description of quasiresonant Scattering, in terms of generalized reduced K-, R- and S- Matrix, is developed in this work. The quasiresonance's decay width is, due to channels coupling, smaller than the width of the ancestral single channel resonance (resonance's direct compression). (author)

  14. Streaming gravity mode instability

    International Nuclear Information System (INIS)

    Wang Shui.

    1989-05-01

    In this paper, we study the stability of a current sheet with a sheared flow in a gravitational field which is perpendicular to the magnetic field and plasma flow. This mixing mode caused by a combined role of the sheared flow and gravity is named the streaming gravity mode instability. The conditions of this mode instability are discussed for an ideal four-layer model in the incompressible limit. (author). 5 refs

  15. Effect of acoustic waveguide properties on the Brillouin gain spectrum in multi-mode fibers

    Science.gov (United States)

    Ke, Wei-Wei; Wang, Xiao-Jun; Tang, Xuan

    2015-02-01

    With a recent developed mode-coupling model, the Brillouin gain spectra (BGS) of multi-mode fibers (MMF) are investigated and compared with the corresponding experiment. It is found that the calculation results are coincident well with the experiment data. Furthermore, the BGS are found to be very sensitive to the index fluctuation. Such phenomenon is demonstrated by introducing a small index hump or dip in the center of the fiber core. And it can be explained by that the index fluctuation may influence the acoustic mode greatly.

  16. Deformation of Brillouin gain spectrum shape caused by strain varying linearly with respect to time

    Science.gov (United States)

    Naruse, Hiroshi; Komatsu, Ayako; Tateda, Mitsuhiro

    2015-09-01

    The shape of the Brillouin gain spectrum (BGS) that is produced in an optical fiber undergoing strain varying linearly with respect to time, which is a typical example of temporally non-uniform strain, is theoretically derived through an analysis similar to that by which the BGS under spatially non-uniform strain would be derived. The BGS shape that is theoretically derived agrees well with the shape experimentally observed. The characteristics of the BGS deformation and strain measurement error under the temporally linear strain are discussed based on their similarity to the BGS shape derived under spatially linear strain.

  17. Proton scattering from unstable nuclei {sup 20}O, {sup 30}S, {sup 34}Ar: experimental study and models; Diffusion de protons sur les noyaux instables {sup 20}O, {sup 30}S, {sup 34}Ar: etude experimentale et developpement de modeles

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Elias [Institut de Physique Nucleaire, CNRS - IN2P3, Universite Paris - Sud, 91406 Orsay Cedex (France)

    2000-01-28

    Elastic and inelastic proton scattering from the unstable nuclei {sup 20}O, {sup 30}S and {sup 34}Ar were measured in inverse kinematics at the Grand Accelerateur National d'Ions Lourds. Secondary beams of {sup 20}O at 43 MeV/A, {sup 30}S at 53 MeV/A and {sup 34}Ar at 47 MeV/A impinged on a (CH{sub 2}){sub n} target. Recoiling protons were detected in the silicon strip array MUST. Energies and angular distributions of the first 2{sup +} and 3{sup -} states were measured. A phenomenological analysis yields values of the deformation parameters {beta}{sub 2} and {beta}{sub 3} of 0.55 (6) and 0.35 (5) for {sup 20}O, 0.32 (3) and 0.22 (4) for {sup 30}S, 0.27 (2) and 0.39 (3) for {sup 34}Ar, respectively, and allows the extraction of the ratio of neutron to proton transition matrix elements (M{sub n}/M{sub p})/(N/Z) for 2{sup +} states: 2.35 (37) for {sup 20}O, 0.93 (20) for {sup 30}S and 1.35 (28) for {sup 34}Ar. Therefore the proton rich nuclei {sup 30}S and {sup 34}Ar show a 2{sup +} excitation of isoscalar character whereas the excitation of {sup 20}O is of isovector character. In order to perform a microscopic analysis of the data, we have developed a QRPA model, using three Skyrme interaction: SIII, SG2, SLy4. This model reproduces measured B(EL) values for the oxygen, sulfur and argon isotopic chains, whereas RPA calculations, which do not take pairing into account, underestimate these values. In the case of the QRPA model the energies of the first 2{sup +} state are overestimated by about 1 MeV, but the evolution along the isotopic chains is well reproduced. (M{sub n}/M{sub p})/(N/Z) ratios for the first 2{sup +} state deduced from the microscopic analysis using QRPA are 1.98 for {sup 20}O, 1.05 for {sup 30}S and 1.00 for {sup 34}Ar, in agreement with the conclusions of the phenomenological analysis. However important discrepancies are observed between the two types of analysis for other isotopes, in particular neutron rich argon and sulfur nuclei. (author)

  18. Nonlinear optical absorption and stimulated Mie scattering in metallic nanoparticle suspensions.

    Science.gov (United States)

    He, Guang S; Law, Wing-Cheung; Baev, Alexander; Liu, Sha; Swihart, Mark T; Prasad, Paras N

    2013-01-14

    The nonlinear optical properties of four metallic (Au-, Au/Ag-, Ag-, and Pt-) nanoparticle suspensions in toluene have been studied in both femtosecond and nanosecond regimes. Nonlinear transmission measurements in the femtosecond laser regime revealed two-photon absorption (2PA) induced nonlinear attenuation, while in the nanosecond laser regime a stronger nonlinear attenuation is due to both 2PA and 2PA-induced excited-state absorption. In the nanosecond regime, at input pump laser intensities above a certain threshold value, a new type of stimulated (Mie) scattering has been observed. Being essentially different from all other well known molecular (Raman, Brillouin) stimulated scattering effects, the newly observed stimulated Mie scattering from the metallic nanoparticles exhibits the features of no frequency shift and low pump threshold requirement. A physical model of induced Bragg grating initiated by the backward Mie scattering from metallic nanoparticles is proposed to explain the gain mechanism of the observed stimulated scattering effect.

  19. Scattering theory

    International Nuclear Information System (INIS)

    Sitenko, A.

    1991-01-01

    This book emerged out of graduate lectures given by the author at the University of Kiev and is intended as a graduate text. The fundamentals of non-relativistic quantum scattering theory are covered, including some topics, such as the phase-function formalism, separable potentials, and inverse scattering, which are not always coverded in textbooks on scattering theory. Criticisms of the text are minor, but the reviewer feels an inadequate index is provided and the citing of references in the Russian language is a hindrance in a graduate text

  20. Parametric decay instabilities in ECR heated plasmas

    International Nuclear Information System (INIS)

    Porkolab, M.

    1982-01-01

    The possibility of parametric excitation of electron Bernstein waves and low frequency ion oscillations during ECR heating at omega/sub o/ approx. = l omega/sub ce/, l = 1,2 is examined. In particular, the thresholds for such instabilities are calculated. It is found that Bernstein waves and lower hybrid quasi-modes have relatively low homogeneous where T/sub e/ approx. = T/sub i/. Thus, these processes may lead to nonlinear absorption and/or scattering of the incident pump wave. The resulting Bernstein waves may lead to either more effective heating (especially during the start-up phase) or to loss of microwave energy if the decay waves propagate out of the system before their energy is absorbed by particles. While at omega/sub o/ = omega/sub UH/ the threshold is reduced due to the WKB enhancement of the pump wave, (and this instability may be important in tokamaks) in EBT's and tandem mirrors the instability at omega /sub o/ greater than or equal to 2 omega/sub ce/ may be important. The instability may persist even if omega > 2 omega/sub ce/ and this may be the case during finite beta depression of the magnetic field in which case the decay waves may be trapped in the local magnetic well so that convective losses are minimized. The excited fluctuations may lead to additional scattering of the ring electrons and the incident microwave fields. Application of these calculations to ECR heating of tokamaks, tandem mirrors, and EBT's will be examined

  1. Critical scattering

    International Nuclear Information System (INIS)

    Stirling, W.G.; Perry, S.C.

    1996-01-01

    We outline the theoretical and experimental background to neutron scattering studies of critical phenomena at magnetic and structural phase transitions. The displacive phase transition of SrTiO 3 is discussed, along with examples from recent work on magnetic materials from the rare-earth (Ho, Dy) and actinide (NpAs, NpSb, USb) classes. The impact of synchrotron X-ray scattering is discussed in conclusion. (author) 13 figs., 18 refs

  2. Critical scattering

    Energy Technology Data Exchange (ETDEWEB)

    Stirling, W.G. [Liverpool Univ., Dep. of Physics, Liverpool (United Kingdom); Perry, S.C. [Keele Univ. (United Kingdom). Dept. of Physics

    1996-12-31

    We outline the theoretical and experimental background to neutron scattering studies of critical phenomena at magnetic and structural phase transitions. The displacive phase transition of SrTiO{sub 3} is discussed, along with examples from recent work on magnetic materials from the rare-earth (Ho, Dy) and actinide (NpAs, NpSb, USb) classes. The impact of synchrotron X-ray scattering is discussed in conclusion. (author) 13 figs., 18 refs.

  3. Parametric instability of a nonuniform plasma near a linear focus

    Energy Technology Data Exchange (ETDEWEB)

    Arkhipenko, V.I.; Budnikov, V.N.; Gusakov, E.Z.; Romanchuk, I.A.; Simonchik, L.V.

    1985-02-01

    Parametric instability l ..-->.. l'+s resulting in anomalous reflection of oblique Langmuir waves in a two-dimensionally nonuniform plasma is studied experimentally and theoretically. The experimental results confirm the theoretical prediction that for low input powers, the instability consists in the spatial amplification of ion-sound noise. The scattered signal is found to rise abruptly for spatial gains s> or approx. =10/sup 4/ because the threshold for absolute instability l ..-->.. l'+s is approached. The absolute instability saturates due to depletion of the pump wave, which is almost completely reflected. A mechanism for the generation of cascade parametric turbulence spectra is identified which is specific to nonuniform plasmas.

  4. Generation of high-power few-cycle lasers via Brillouin-based plasma amplification

    Science.gov (United States)

    Zhang, Z. M.; Zhang, B.; Hong, W.; Deng, Z. G.; Teng, J.; He, S. K.; Zhou, W. M.; Gu, Y. Q.

    2017-11-01

    Strong coupling stimulated Brillouin backscattering (sc-SBS) in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers. Here, we report on a new regime of brillouin-based plasma amplification, producing an amplified pulse with a duration of 5 fs and unfocused intensity of 6 × 1017 W/cm2. The results are obtained from 2D particle-in-cell simulations, using two circularly polarized pump and seed pulse with Gaussian transverse profile, both at an intensity of 2.74 × 1016 W/cm2, counter-propagating in a 0.3nc plasma. The significant compression of amplified seed is achieved as a result of sc-SBS amplification as well as additional compression by the interplay between self-phase modulation and negative group delay dispersion. We show that the amplified seed retains high beam qualities since the filamentation can be prevented due to the fast compression. This scheme may pave the way for few-cycle laser pulses to reach exawatt or even zetawatt regime.

  5. Fingerprints of dynamical instabilities

    International Nuclear Information System (INIS)

    Chomaz, Ph.; Colonna, M.; Guarnera, A.

    1993-01-01

    It is explained why any reduced descriptions, such as mean field approximation, are stochastic in nature. It is shown that the introduction of this stochastic dynamics leads to a predictive theory in a statistical sens whatever the individual trajectories are characterized by the occurrence of bifurcations, instabilities or phase transitions. Concerning nuclear matter, the spinodal instability is discussed. In such a critical situation, the possibility to replace the stochastic part of the collision integral in the Boltzmann-Langevin model by the numerical noise associated with the finite number of test particles in ordinary BUU treatment is studied. It is shown that the fingerprints of these instabilities are kept during the evolution because of the relatively long recombination time compared with the typical time scales imposed by the Coulomb repulsion and the possible collective expansion. (author) 5 refs., 12 figs

  6. Instability and star evolution

    International Nuclear Information System (INIS)

    Mirzoyan, L.V.

    1981-01-01

    The observational data are discussed which testify that the phenomena of dynamical instability of stars and stellar systems are definite manifestations of their evolution. The study of these phenomena has shown that the instability is a regular phase of stellar evolution. It has resulted in the recognition of the most important regularities of the process of star formation concerning its nature. This became possible due to the discovery in 1947 of stellar associations in our Galaxy. The results of the study of the dynamical instability of stellar associations contradict the predictions of classical hypothesis of stellar condensation. These data supplied a basis for a new hypothesis on the formation of stars and nebulae by the decay of superdense protostars [ru

  7. Causes of genome instability

    DEFF Research Database (Denmark)

    Langie, Sabine A S; Koppen, Gudrun; Desaulniers, Daniel

    2015-01-01

    , genome instability can be defined as an enhanced tendency for the genome to acquire mutations; ranging from changes to the nucleotide sequence to chromosomal gain, rearrangements or loss. This review raises the hypothesis that in addition to known human carcinogens, exposure to low dose of other......Genome instability is a prerequisite for the development of cancer. It occurs when genome maintenance systems fail to safeguard the genome's integrity, whether as a consequence of inherited defects or induced via exposure to environmental agents (chemicals, biological agents and radiation). Thus...... chemicals present in our modern society could contribute to carcinogenesis by indirectly affecting genome stability. The selected chemicals with their mechanisms of action proposed to indirectly contribute to genome instability are: heavy metals (DNA repair, epigenetic modification, DNA damage signaling...

  8. Optimization of interaction conditions for efficient short laser pulse amplification by stimulated Brillouin scattering in the strongly coupled regime

    Czech Academy of Sciences Publication Activity Database

    Chiaramello, M.; Riconda, C.; Amiranoff, F.; Fuchs, J.; Grech, M.; Lancia, L.; Marquès, J.-R.; Vinci, T.; Weber, Stefan A.

    2016-01-01

    Roč. 23, č. 7 (2016), s. 1-11, č. článku 072103. ISSN 1070-664X R&D Projects: GA MŠk LQ1606; GA MŠk EF15_008/0000162 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:68378271 Keywords : plasmas Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.115, year: 2016

  9. Investigation of Laser Beam Combining and Clean-Up via Seeded Stimulated Brillouin Scattering in Multimode Optical Fibers

    National Research Council Canada - National Science Library

    Choi, Bryan

    2000-01-01

    .... Beam combining in multimode fibers via SBS is being considered as a method of combining low power laser beams into a single beam having higher power and superior spatial coherence for applications...

  10. Signatures of the self-similar regime of strongly coupled stimulated brillouin scattering for efficient short laser pulse amplification

    Czech Academy of Sciences Publication Activity Database

    Lancia, L.; Giribono, A.; Vassura, L.; Chiaramello, M.; Riconda, C.; Weber, Stefan A.; Castan, A.; Chatelain, A.; Frank, A.; Gangolf, T.; Quinn, M.N.; Fuchs, J.; Marqués, J.-R.

    2016-01-01

    Roč. 116, č. 7 (2016), 1-5, č. článku 075001. ISSN 0031-9007 R&D Projects: GA MŠk EF15_008/0000162; GA MŠk ED1.1.00/02.0061 EU Projects: European Commission(XE) 284464 - LASERLAB-EUROPE Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162; ELI Beamlines(XE) CZ.1.05/1.1.00/02.0061 Institutional support: RVO:68378271 Keywords : light-pulses * compression * plasmas * Raman Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 8.462, year: 2016

  11. Stimulated Brillouin Scattering (SBS) Suppression and Long Delivery Fibers at the Multikilowatt Level with Chirped Seed Lasers

    Science.gov (United States)

    2017-03-16

    the Multikilowatt Level with Chirped Seed Lasers by Jeffrey O White, Mark Harfouche, John Edgecumbe, Naresh Satyan, George Rakuljic, and Amnon...Suppression and Long Delivery Fibers at the Multikilowatt Level with Chirped Seed Lasers by Jeffrey O White Sensors and Electron Devices Directorate, ARL...Fibers at the Multikilowatt Level with Chirped Seed Lasers 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S

  12. Light scattering studies of solids and atomic vapors

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, T.C.

    1978-09-01

    The general technique of light scattering and luminescence was used to study the properties of a number of material systems. First, multi-phonon resonant Raman scattering up to four phonons in GaSe and one- and two-phonon resonant Raman scattering in the mixed GaS/sub x/Se/sub 1-x/ crystals with x < or = 0.23 were investigated. Second, the observation of one-phonon resonant Raman scattering in HfS/sub 2/ is reported. The result is used to determine the position of the direct gap of HfS/sub 2/. Third, the first observation of the ..pi..-polarized one-magnon luminescence sideband of the /sup 4/T/sub lg/ (/sup 4/G) ..-->.. /sup 6/A/sub lg/(/sup 6/S) excitonic transition in antiferromagnetic MnF/sub 2/ is presented. An effective temperature of the crystal is deduced from the simultaneously observed anti-Stokes sideband emission. Multi-magnon (< or = 7) excitonic luminescence sidebands were also observed in MnF/sub 2/, KMnF/sub 2/, and RbMnF/sub 3/ using pulsed excitation and detection. A simple model based on two-ion local exchange is proposed to explain the results qualitatively. Fourth, the first observation of two-magnon resonant Raman scattering in MnF/sub 2/ around the magnon sidebands is reported. A simple theoretical description explains the experimental observations. Fifth, a detailed theory of exciton-exciton interaction in MnF/sub 2/ is developed to explain and to predict the experimental results on two-exciton absorption, high level excitation, and exciton--exciton scattering. Sixth, Brillouin scattering was used to obtain the five independent elastic constants of the layered compound GaSe. The results show clear elastic anisotropy of the crystal. Resonant Brillouin scattering near the absorption edge was also studied, but no resonant enhancement was found. Seventh, two-photon parametric scattering in sodium vapor was studied. Phase matching angles and scattering cross sections are calculated for a given set of experimental conditions.

  13. Buneman instability and Pierce instability in a collisionless bounded plasma

    International Nuclear Information System (INIS)

    Iizuka, Satoru; Saeki, Koichi; Sato, Noriyoshi; Hatta, Yoshisuke

    1983-01-01

    A systematic experiment is performed on the Buneman instability and the Pierce instability in a bounded plasma consisting of beam electrons and stationary ions. Current fluctuations are confirmed to be induced by the Buneman instability. On the other hand, the Pierce instability gives rise to a current limitation. The phenomena are well explained by Mikhailovskii's theory taking account of ion motion in a bounded plasma. (author)

  14. Neutrino beam plasma instability

    Indian Academy of Sciences (India)

    Abstract. We derive relativistic fluid set of equations for neutrinos and electrons from relativistic. Vlasov equations with Fermi weak interaction force. Using these fluid equations, we obtain a dis- persion relation describing neutrino beam plasma instability, which is little different from normal dispersion relation of streaming ...

  15. Elbow joint instability

    DEFF Research Database (Denmark)

    Olsen, Bo Sanderhoff; Henriksen, M G; Søjbjerg, Jens Ole

    1994-01-01

    The effect of simultaneous ulnar and radial collateral ligament division on the kinematics of the elbow joint is studied in a cadaveric model. Severance of the anterior part of the ulnar collateral ligament and the annular ligament led to significant elbow joint instability in valgus and varus...

  16. Structural and Material Instability

    DEFF Research Database (Denmark)

    Cifuentes, Gustavo Cifuentes

    This work is a small contribution to the general problem of structural and material instability. In this work, the main subject is the analysis of cracking and failure of structural elements made from quasi-brittle materials like concrete. The analysis is made using the finite element method. Three...

  17. Atlantooccipital instability. Case report.

    Science.gov (United States)

    Finney, H L; Roberts, T S

    1978-04-01

    A patient is presented who had neck pain and transient episodes of visual-field defect followed by unconsciousness when he hyperextended his neck. Radiographic examination revealed atlantooccipital instability on flexion and extension views. Treatment by fusion of the occiput to C-2 resulted in relief of symptoms.

  18. The role of cell body density in ruminant retina mechanics assessed by atomic force and Brillouin microscopy

    Science.gov (United States)

    Weber, Isabell P.; Yun, Seok Hyun; Scarcelli, Giuliano; Franze, Kristian

    2017-12-01

    Cells in the central nervous system (CNS) respond to the stiffness of their environment. CNS tissue is mechanically highly heterogeneous, thus providing motile cells with region-specific mechanical signals. While CNS mechanics has been measured with a variety of techniques, reported values of tissue stiffness vary greatly, and the morphological structures underlying spatial changes in tissue stiffness remain poorly understood. We here exploited two complementary techniques, contact-based atomic force microscopy and contact-free Brillouin microscopy, to determine the mechanical properties of ruminant retinae, which are built up by different tissue layers. As in all vertebrate retinae, layers of high cell body densities (‘nuclear layers’) alternate with layers of low cell body densities (‘plexiform layers’). Different tissue layers varied significantly in their mechanical properties, with the photoreceptor layer being the stiffest region of the retina, and the inner plexiform layer belonging to the softest regions. As both techniques yielded similar results, our measurements allowed us to calibrate the Brillouin microscopy measurements and convert the Brillouin shift into a quantitative assessment of elastic tissue stiffness with optical resolution. Similar as in the mouse spinal cord and the developing Xenopus brain, we found a strong correlation between nuclear densities and tissue stiffness. Hence, the cellular composition of retinae appears to strongly contribute to local tissue stiffness, and Brillouin microscopy shows a great potential for the application in vivo to measure the mechanical properties of transparent tissues.

  19. Electron Scattering

    International Nuclear Information System (INIS)

    Li, Xiaodong; Lee, Kyong Sei; Shaw, J.J.; Bahri, C.

    1990-01-01

    Electron scattering is one of the best probes available to us to probe the nucleus. It has revealed to us, with unprecedented accuracy, the charge and current distributions of nuclei. It has provided us with positive evidence for meson exchange currents. It was used to 'discover' the quark and it revealed to us that nucleons may be modified in the nuclear environment (EMC Effect). In short, electron scattering has revolutionized the study of nuclear physics. Several recent developments will insure that electron beams which will soon become availabe at CEBAF, Bates and elsewhere will make high-precision coincidence experiments possible. As the technology is becoming available, we are just beginning to exploit polarization degrees of freedom in our experiments. In this paper, we will introduce the formalism of electron scattering, review what we have learned in the past and look ahead toward the future

  20. Tracking Code for Microwave Instability

    International Nuclear Information System (INIS)

    Heifets, S.; SLAC

    2006-01-01

    To study microwave instability the tracking code is developed. For bench marking, results are compared with Oide-Yokoya results [1] for broad-band Q = 1 impedance. Results hint to two possible mechanisms determining the threshold of instability

  1. Compton scattering

    Energy Technology Data Exchange (ETDEWEB)

    Botto, D.J.; Pratt, R.H.

    1979-05-01

    The current status of Compton scattering, both experimental observations and the theoretical predictions, is examined. Classes of experiments are distinguished and the results obtained are summarized. The validity of the incoherent scattering function approximation and the impulse approximation is discussed. These simple theoretical approaches are compared with predictions of the nonrelativistic dipole formula of Gavrila and with the relativistic results of Whittingham. It is noted that the A/sup -2/ based approximations fail to predict resonances and an infrared divergence, both of which have been observed. It appears that at present the various available theoretical approaches differ significantly in their predictions and that further and more systematic work is required.

  2. Experimental observation of parametric instabilities at laser intensities relevant for shock ignition

    Czech Academy of Sciences Publication Activity Database

    Cristoforetti, G.; Colaïtis, A.; Antonelli, L.; Atzeni, S.; Baffigi, F.; Batani, D.; Barbato, F.; Boutoux, G.; Dudžák, Roman; Koester, P.; Krouský, Eduard; Labate, L.; Nicolaï, P.; Renner, Oldřich; Skoric, M.; Tikhonchuk, V.; Gizzi, L.A.

    2017-01-01

    Roč. 117, č. 3 (2017), č. článku 35001. ISSN 0295-5075 R&D Projects: GA MŠk(CZ) LC528; GA MŠk LM2010014; GA MŠk EF15_008/0000162 EU Projects: European Commission(XE) 633053 - EUROfusion Grant - others:EU - ICT(XE) COST Action IC1208; ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:61389021 ; RVO:68378271 Keywords : laser intensity regime * Stimulated Brillouin Scattering (SBS) * Stimulated Raman Scattering (SRS) * Two-Plasmon Decay (TPD) Subject RIV: BL - Plasma and Gas Discharge Physics; BL - Plasma and Gas Discharge Physics (FZU-D) OBOR OECD: Fluids and plasma physics (including surface physics); Fluids and plasma physics (including surface physics) (FZU-D) Impact factor: 1.957, year: 2016 https:// doi . org /10.1209/0295-5075/117/35001

  3. Acoustic and relaxation behaviors of polydimethylsiloxane studied by using brillouin and dielectric spectroscopies

    Science.gov (United States)

    Lee, Byoung Wan; Ko, Jae-Hyeon; Park, Jaehoon; Shin, Dong-Myeong; Hwang, Yoon-Hwae

    2016-04-01

    The temperature dependences of the acoustic properties and the dielectric relaxation times of polydimethylsiloxane were investigated by using high-resolution Brillouin and broadband dielectric spectroscopies. The longitudinal sound velocity showed a large increase upon approaching the glass transition temperature while the acoustic absorption coefficient exhibited a maximum at ~263 K. Comparison of these results with previous ultrasonic data revealed a substantial frequency dispersion of the acoustic properties of this silicone-based elastomer. The relaxation times derived from the acoustic absorption peaks were consistent with the temperature dependence of the dielectric relaxation time of the structural a process, indicating a strong coupling between the acoustic waves and the segmental motions of the main chains.

  4. Temperature Dependence of the Rayleigh Brillouin Spectrum Linewidth in Air and Nitrogen.

    Science.gov (United States)

    Liang, Kun; Xu, Jiaqi; Zhang, Peng; Wang, Yuanqing; Niu, Qunjie; Peng, Li; Zhou, Bo

    2017-06-26

    The relation between spontaneous Rayleigh Brillouin (SRB) spectrum linewidth, gas temperature, and pressure are analyzed at the temperature range from 220 to 340 K and the pressure range from 0.1 to 1 bar, covering the stratosphere and troposphere relevant for the Earth's atmosphere and for atmospheric Lidar missions. Based on the analysis, a model retrieving gas temperature from directly measured linewidth is established and the accuracy limitations are estimated. Furthermore, some experimental data of air and nitrogen are used to verify the accuracy of the model. As the results show, the retrieved temperature shows good agreement with the reference temperature, and the absolute difference is less than 3 K, which indicates that this method provides a fruitful tool in satellite retrieval to extract the gaseous properties of atmospheres on-line by directly measuring the SRB spectrum linewidth.

  5. Tunable and reconfigurable multi-tap microwave photonic filter based on dynamic Brillouin gratings in fibers.

    Science.gov (United States)

    Sancho, J; Primerov, N; Chin, S; Antman, Y; Zadok, A; Sales, S; Thévenaz, L

    2012-03-12

    We propose and experimentally demonstrate new architectures to realize multi-tap microwave photonic filters, based on the generation of a single or multiple dynamic Brillouin gratings in polarization maintaining fibers. The spectral range and selectivity of the proposed periodic filters is extensively tunable, simply by reconfiguring the positions and the number of dynamic gratings along the fiber respectively. In this paper, we present a complete analysis of three different configurations comprising a microwave photonic filter implementation: a simple notch-type Mach-Zehnder approach with a single movable dynamic grating, a multi-tap performance based on multiple dynamic gratings and finally a stationary grating configuration based on the phase modulation of two counter-propagating optical waves by a common pseudo-random bit sequence (PRBS).

  6. Instability and internet design

    Directory of Open Access Journals (Sweden)

    Sandra Braman

    2016-09-01

    Full Text Available Instability - unpredictable but constant change in one’s environment and the means with which one deals with it - has replaced convergence as the focal problem for telecommunications policy in general and internet policy in particular. Those who designed what we now call the internet during the first decade of the effort (1969-1979, who in essence served simultaneously as its policy-makers, developed techniques for coping with instability of value for network designers today and for those involved with any kind of large-scale sociotechnical infrastructure. Analysis of the technical document series that was medium for and record of that design process reveals coping techniques that began with defining the problem and went on to include conceptual labour, social practices, and technical approaches.

  7. Orphans and political instability.

    Science.gov (United States)

    Breuning, Marijke; Ishiyama, John

    2011-01-01

    This study investigates the security implications of growing orphan populations, particularly in Sub-Saharan Africa. Little has been written about the security implications of this especially vulnerable group of children. Are growing orphan populations associated with increases in political instability as has been suggested? Using data from several sources, we employ regression analysis to test whether Sub-Saharan African countries with larger proportions of orphans and those with increasing orphan populations experience higher rates of political instability. We find that the increase in the orphan population is related to an increasing incidence of civil conflict, but do not find a similar relationship for the proportion of orphans. In addition, we find that the causes of orphanhood matter. We conclude that increases in orphan populations (rather than simple proportions) are destabilizing. We suggest possible avenues for mediating the security risks posed by growing orphan populations.

  8. State Instability and Terrorism

    Science.gov (United States)

    2010-01-01

    security, heterosexual relationships and goods and services. Although prisons constitute a very controlled social structure to begin with, it is...closely although the NBRM model fits slightly better. The Vuong test preferred the ZINB model over the NBRM (p<.0000). This suggests that I ought to...then, it is preferred because it allows me to examine the effects of instability within-country only. This is the purest test of the 109 concept

  9. Instability of gravitating sphalerons

    International Nuclear Information System (INIS)

    Boschung, P.; Brodbeck, O.; Moser, F.; Straumann, N.; Volkov, M.

    1994-01-01

    We prove the instability of the gravitating regular sphaleron solutions of the SU(2) Einstein-Yang-Mills-Higgs system with a Higgs doublet, by studying the frequency spectrum of a class of radial perturbations. With the help of a variational principle we show that there exist always unstable modes. Our method has the advantage that no detailed knowledge of the equilibrium solution is required. It does, however, not directly apply to black holes

  10. Relativistic centrifugal instability

    Science.gov (United States)

    Gourgouliatos, Konstantinos N.; Komissarov, Serguei S.

    2018-03-01

    Near the central engine, many astrophysical jets are expected to rotate about their axis. Further out they are expected to go through the processes of reconfinement and recollimation. In both these cases, the flow streams along a concave surface and hence, it is subject to the centrifugal force. It is well known that such flows may experience the centrifugal instability (CFI), to which there are many laboratory examples. The recent computer simulations of relativistic jets from active galactic nuclei undergoing the process of reconfinement show that in such jets CFI may dominate over the Kelvin-Helmholtz instability associated with velocity shear (Gourgouliatos & Komissarov). In this letter, we generalize the Rayleigh criterion for CFI in rotating fluids to relativistic flows using a heuristic analysis. We also present the results of computer simulations which support our analytic criterion for the case of an interface separating two uniformly rotating cylindrical flows. We discuss the difference between CFI and the Rayleigh-Taylor instability in flows with curved streamlines.

  11. Instability of warped discs

    Science.gov (United States)

    Doǧan, S.; Nixon, C. J.; King, A. R.; Pringle, J. E.

    2018-01-01

    Accretion discs are generally warped. If a warp in a disc is too large, the disc can `break' apart into two or more distinct planes, with only tenuous connections between them. Further if an initially planar disc is subject to a strong differential precession, then it can be torn apart into discrete annuli that precess effectively independently. In previous investigations, torque-balance formulae have been used to predict where and when the disc breaks into distinct parts. In this work, focusing on discs with Keplerian rotation and where the shearing motions driving the radial communication of the warp are damped locally by turbulence (the `diffusive' regime), we investigate the stability of warped discs to determine the precise criterion for an isolated warped disc to break. We find and solve the dispersion relation, which in general yields three roots. We provide a comprehensive analysis of this viscous-warp instability and the emergent growth rates and their dependence on disc parameters. The physics of the instability can be understood as a combination of (1) a term which would generally encapsulate the classical Lightman-Eardley instability in planar discs (given by ∂(νΣ)/∂Σ condition acting on the diffusion of the warp amplitude given in simplified form by ∂(ν2|ψ|)/∂|ψ| < 0. We discuss our findings in the context of discs with an imposed precession, and comment on the implications for different astrophysical systems.

  12. Collective spin excitations in the singlet-correlated band model: a comparison with resonant inelastic x-ray scattering

    International Nuclear Information System (INIS)

    Eremin, M V; Shigapov, I M; Thuy, Ho Thi Duyen

    2013-01-01

    We analyse the spin excitations near the optimal doping of superconducting layered cuprates taking into account both the local and the itinerant spin components self-consistently. The obtained expression allows us to reproduce well the basic features of the resonant inelastic x-ray scattering and neutron scattering data experiments using a reasonable set of tight-binding parameters corresponding to the angle-resolved photoemission spectroscopy data. We also find that the spin excitation branch along the (0,0) − (0,π) symmetry direction in the first Brillouin zone shows a splitting at T c . Possible experiments for verification of that prediction are briefly discussed. (paper)

  13. Scattering theory

    International Nuclear Information System (INIS)

    Friedrich, Harald

    2013-01-01

    Written by the author of the widely acclaimed textbook. Theoretical Atomic Physics Includes sections on quantum reflection, tunable Feshbach resonances and Efimov states. Useful for advanced students and researchers. This book presents a concise and modern coverage of scattering theory. It is motivated by the fact that experimental advances have shifted and broadened the scope of applications where concepts from scattering theory are used, e.g. to the field of ultracold atoms and molecules, which has been experiencing enormous growth in recent years, largely triggered by the successful realization of Bose-Einstein condensates of dilute atomic gases in 1995. In the present treatment, special attention is given to the role played by the long-range behaviour of the projectile-target interaction, and a theory is developed, which is well suited to describe near-threshold bound and continuum states in realistic binary systems such as diatomic molecules or molecular ions. The level of abstraction is kept as low as at all possible, and deeper questions related to mathematical foundations of scattering theory are passed by. The book should be understandable for anyone with a basic knowledge of nonrelativistic quantum mechanics. It is intended for advanced students and researchers, and it is hoped that it will be useful for theorists and experimentalists alike.

  14. Scattering theory

    CERN Document Server

    Friedrich, Harald

    2016-01-01

    This corrected and updated second edition of "Scattering Theory" presents a concise and modern coverage of the subject. In the present treatment, special attention is given to the role played by the long-range behaviour of the projectile-target interaction, and a theory is developed, which is well suited to describe near-threshold bound and continuum states in realistic binary systems such as diatomic molecules or molecular ions. It is motivated by the fact that experimental advances have shifted and broadened the scope of applications where concepts from scattering theory are used, e.g. to the field of ultracold atoms and molecules, which has been experiencing enormous growth in recent years, largely triggered by the successful realization of Bose-Einstein condensates of dilute atomic gases in 1995. The book contains sections on special topics such as near-threshold quantization, quantum reflection, Feshbach resonances and the quantum description of scattering in two dimensions. The level of abstraction is k...

  15. Neutron scattering

    International Nuclear Information System (INIS)

    1991-02-01

    The annual report on hand gives an overview of the research work carried out in the Laboratory for Neutron Scattering (LNS) of the ETH Zuerich in 1990. Using the method of neutron scattering, it is possible to examine in detail the static and dynamic properties of the condensed material. In accordance with the multidisciplined character of the method, the LNS has for years maintained a system of intensive co-operation with numerous institutes in the areas of biology, chemistry, solid-state physics, crystallography and materials research. In 1990 over 100 scientists from more than 40 research groups both at home and abroad took part in the experiments. It was again a pleasure to see the number of graduate students present, who were studying for a doctorate and who could be introduced into the neutron scattering during their stay at the LNS and thus were in the position to touch on central ways of looking at a problem in their dissertation using this modern experimental method of solid-state research. In addition to the numerous and interesting ways of formulating the questions to explain the structure, nowadays the scientific programme increasingly includes particularly topical studies in connection with high temperature-supraconductors and materials research

  16. Radiation Induced Genomic Instability

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, William F.

    2011-03-01

    Radiation induced genomic instability can be observed in the progeny of irradiated cells multiple generations after irradiation of parental cells. The phenotype is well established both in vivo (Morgan 2003) and in vitro (Morgan 2003), and may be critical in radiation carcinogenesis (Little 2000, Huang et al. 2003). Instability can be induced by both the deposition of energy in irradiated cells as well as by signals transmitted by irradiated (targeted) cells to non-irradiated (non-targeted) cells (Kadhim et al. 1992, Lorimore et al. 1998). Thus both targeted and non-targeted cells can pass on the legacy of radiation to their progeny. However the radiation induced events and cellular processes that respond to both targeted and non-targeted radiation effects that lead to the unstable phenotype remain elusive. The cell system we have used to study radiation induced genomic instability utilizes human hamster GM10115 cells. These cells have a single copy of human chromosome 4 in a background of hamster chromosomes. Instability is evaluated in the clonal progeny of irradiated cells and a clone is considered unstable if it contains three or more metaphase sub-populations involving unique rearrangements of the human chromosome (Marder and Morgan 1993). Many of these unstable clones have been maintained in culture for many years and have been extensively characterized. As initially described by Clutton et al., (Clutton et al. 1996) many of our unstable clones exhibit persistently elevated levels of reactive oxygen species (Limoli et al. 2003), which appear to be due dysfunctional mitochondria (Kim et al. 2006, Kim et al. 2006). Interestingly, but perhaps not surprisingly, our unstable clones do not demonstrate a “mutator phenotype” (Limoli et al. 1997), but they do continue to rearrange their genomes for many years. The limiting factor with this system is the target – the human chromosome. While some clones demonstrate amplification of this chromosome and thus lend

  17. Study of microwave instability

    International Nuclear Information System (INIS)

    Heifets, S.; Chao, A.

    1996-12-01

    The microwave instability is usually described by linearizing Vlasov equation in the angle-action variables I, φ and assuming that the interaction of azimuthal harmonics ρ n (I) of the distribution function ρ is weak. The argument implied here is that the Hamiltonian flow smears out particles over invariant tori characterized by the action variables, and the remaining azimuthal dependence of the distribution function is small. Indeed, such an approach successfully describes bunch spectrum and the threshold of the microwave instability. However, recently there have been interesting observations of bunch centroid and bunch shape oscillations above instability threshold at LEP and the damping ring at SLAC. There are also indicates that the oscillations sometimes occur in localized region in the longitudinal coordinate instead of affecting the entire longitudinal distribution as one expects by an action-angle analysis. In this paper the authors describe an alternative approach to the problem of bunch stability using decomposition of the Fokker-Plank equation in the system of nonlinear equations for the moments of the distribution function. In particular, this approach allows them to avoid the conventional action-angle decomposition. The physical quantities they are interested in, the moments, are expressed in the Cartesian z - δ phase space. To close the infinite hierarchy of moments equations, the authors assume that higher order correlations are small. Although both the action-angle and the Cartesian languages must be equivalent before truncation, they may have different speed of convergence depending on the problem being studied. It is hoped that Cartesian expansion approach would converge faster for the cases corresponding to those observed recently above threshold. The recent experimental observations made them interested in it again. This note is a progress report of their work

  18. Instability of warped discs

    Science.gov (United States)

    Doǧan, S.; Nixon, C. J.; King, A. R.; Pringle, J. E.

    2018-05-01

    Accretion discs are generally warped. If a warp in a disc is too large, the disc can `break' apart into two or more distinct planes, with only tenuous connections between them. Further, if an initially planar disc is subject to a strong differential precession, then it can be torn apart into discrete annuli that precess effectively independently. In previous investigations, torque-balance formulae have been used to predict where and when the disc breaks into distinct parts. In this work, focusing on discs with Keplerian rotation and where the shearing motions driving the radial communication of the warp are damped locally by turbulence (the `diffusive' regime), we investigate the stability of warped discs to determine the precise criterion for an isolated warped disc to break. We find and solve the dispersion relation, which, in general, yields three roots. We provide a comprehensive analysis of this viscous-warp instability and the emergent growth rates and their dependence on disc parameters. The physics of the instability can be understood as a combination of (1) a term that would generally encapsulate the classical Lightman-Eardley instability in planar discs (given by ∂(νΣ)/∂Σ < 0) but is here modified by the warp to include ∂(ν1|ψ|)/∂|ψ| < 0, and (2) a similar condition acting on the diffusion of the warp amplitude given in simplified form by ∂(ν2|ψ|)/∂|ψ| < 0. We discuss our findings in the context of discs with an imposed precession, and comment on the implications for different astrophysical systems.

  19. High beta tokamak instabilities

    International Nuclear Information System (INIS)

    Bateman, G.

    1977-01-01

    Theoretical predictions using the ideal MHD model indicable that large-scale ballooning modes should appear when the average beta is raised about 1 to 2% in present-day tokamak geometries or 5 to 10% in more optimized geometries. The onset of instability is predicted to be sudden and the behavior of ballooning modes to be strikingly different from the saw-tooth and Mirnov oscillations experimentally observed at low beta. Conditions close to the predicted onset were achieved in ORMAK with no noticeable change in plasma behavior. Experiments are planned for the ISX tokamak to test the beta limit. 15 references, 3 figures

  20. Evaporation and Antievaporation Instabilities

    Directory of Open Access Journals (Sweden)

    Andrea Addazi

    2017-10-01

    Full Text Available We review (antievaporation phenomena within the context of quantum gravity and extended theories of gravity. The (antievaporation effect is an instability of the black hole horizon discovered in many different scenarios: quantum dilaton-gravity, f ( R -gravity, f ( T -gravity, string-inspired black holes, and brane-world cosmology. Evaporating and antievaporating black holes seem to have completely different thermodynamical features compared to standard semiclassical black holes. The purpose of this review is to provide an introduction to conceptual and technical aspects of (antievaporation effects, while discussing problems that are still open.

  1. Observations of parametric instabilities in long-scalelength plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, E.M.; Max, C.E.; Phillion, D.W.; Turner, R.E.; Estabrooke, K.; Laskinski, B.; Kruer, W.L.; Mead, W.C.

    1983-03-22

    This paper is organized in the following manner. In the second section we discussed absorption; the dependence of scattered light signatures of parametric instabilities occurring at n/sub e/ less than or equal to n/sub c//4 on corona size is shown in section three; and evidence for suprathermal electron production in these long-scale length plasmas is presented in section four. The results and conclusions are finally summarized in section five.

  2. Resonant Drag Instabilities in protoplanetary disks: the streaming instability and new, faster-growing instabilities

    Science.gov (United States)

    Squire, Jonathan; Hopkins, Philip F.

    2018-04-01

    We identify and study a number of new, rapidly growing instabilities of dust grains in protoplanetary disks, which may be important for planetesimal formation. The study is based on the recognition that dust-gas mixtures are generically unstable to a Resonant Drag Instability (RDI), whenever the gas, absent dust, supports undamped linear modes. We show that the "streaming instability" is an RDI associated with epicyclic oscillations; this provides simple interpretations for its mechanisms and accurate analytic expressions for its growth rates and fastest-growing wavelengths. We extend this analysis to more general dust streaming motions and other waves, including buoyancy and magnetohydrodynamic oscillations, finding various new instabilities. Most importantly, we identify the disk "settling instability," which occurs as dust settles vertically into the midplane of a rotating disk. For small grains, this instability grows many orders of magnitude faster than the standard streaming instability, with a growth rate that is independent of grain size. Growth timescales for realistic dust-to-gas ratios are comparable to the disk orbital period, and the characteristic wavelengths are more than an order of magnitude larger than the streaming instability (allowing the instability to concentrate larger masses). This suggests that in the process of settling, dust will band into rings then filaments or clumps, potentially seeding dust traps, high-metallicity regions that in turn seed the streaming instability, or even overdensities that coagulate or directly collapse to planetesimals.

  3. Atlantooccipital instability in Down syndrome.

    Science.gov (United States)

    Rosenbaum, D M; Blumhagen, J D; King, H A

    1986-06-01

    Atlantooccipital instability is an uncommon and usually lethal result of major trauma. Nontraumatic cases of instability at this site are rare. We report the findings in two children with Down syndrome who have striking atlantooccipital subluxation demonstrated on flexion and extension radiographs. Since there is increasing radiologic evaluation of cervical spine stability in patients with Down syndrome who wish to participate in athletic activities, the status of the atlantooccipital joint needs careful assessment, especially after cervical fusion for C1-C2 instability.

  4. Three-dimensional Langmuir wave instabilities in type III solar radio bursts

    International Nuclear Information System (INIS)

    Bardwell, S.; Goldman, M.V.

    1976-01-01

    Assuming that type III solar radio bursts are associated with electron streams moving at about c/3, Langmuir waves should be strongly excited. We have studied all of the Langmuir-wave linear parametric instabilities excited in cylindrical symmetry by an electron-stream--driven Langmuir wave-pump propagating along the stream axis. Included in this unified homogeneous treatment are induced backscattering off ions, the oscillating two-stream instability, and a new ''stimulated modulational instability,'' previously unconsidered in this context. Near a few solar radii, the latter two deposit Langmuir wave energy into a forward-scattering cone about the stream axis. It is concluded that the linear stage of the forward-scattering instabilities involves transfer of energy to Langmuir waves which remain in resonance with the stream, and therefore probably do not prevent rapid depletion of the electron stream due to quasilinear plateau formation at these distances from the Sun

  5. Nonlinear turbulence theory and simulation of Buneman instability

    International Nuclear Information System (INIS)

    Yoon, P. H.; Umeda, T.

    2010-01-01

    In the present paper, the weak turbulence theory for reactive instabilities, formulated in a companion paper [P. H. Yoon, Phys. Plasmas 17, 112316 (2010)], is applied to the strong electron-ion two-stream (or Buneman) instability. The self-consistent theory involves quasilinear velocity space diffusion equation for the particles and nonlinear wave kinetic equation that includes quasilinear (or induced emission) term as well as nonlinear wave-particle interaction term (or a term that represents an induced scattering off ions). We have also performed one-dimensional electrostatic Vlasov simulation in order to benchmark the theoretical analysis. Under the assumption of self-similar drifting Gaussian distribution function for the electrons it is shown that the current reduction and the accompanying electron heating as well as electric field turbulence generation can be discussed in a self-consistent manner. Upon comparison with the Vlasov simulation result it is found that quasilinear wave kinetic equation alone is insufficient to account for the final saturation amplitude. Upon including the nonlinear scattering term in the wave kinetic equation, however, we find that a qualitative agreement with the simulation is recovered. From this, we conclude that the combined quasilinear particle diffusion plus induced emission and scattering (off ions) processes adequately account for the nonlinear development of the Buneman instability.

  6. Transmission properties in a photonic crystal with a Dirac-like point located at the Brillouin zone center

    Science.gov (United States)

    Gao, H.; Zhou, Y.; Zhao, L.; Wei, G.

    2017-11-01

    Light transmission properties of a two-dimensional dielectric photonic crystal (PC) with a Dirac-like point located at the Brillouin zone center are studied. The results show that at the Dirac-like point, the transmittance remains constant rather than inversely varying with the PC's thickness, that is, this transmission does not follow the pseudo-diffusive phenomenon. Moreover, since the PC with a Dirac point at the Brillouin zone center can mimic zero index material (ZIM), transmittance of a real homogeneous ZIM layer is also theoretically investigated. Invariant transmittance is obtained again and the constant transmittance at the Dirac-like point is confirmed. Physical mechanisms of the pseudo-diffusive transmission as well as the constant transmission are both analyzed. It is found that the Dirac point is a critical state between band gaps and transmission bands, where the wave vector takes a complex number. It is the imaginary part of the wave vector which causes the decrease of the transmittance. While at the Dirac-like point at the center of the Brillouin zone, an additional flat band makes the Dirac point frequency fall into a transmission band where the wave vector is a real number, therefore the transmittance does not display any decrease tendency.

  7. Characterization of 'strong-fragile' behaviour of glass-forming aqueous solutions by neutron scattering

    CERN Document Server

    Branca, C; Galli, G; Magazù, S; Maisano, G; Migliardo, F

    2002-01-01

    Neutron-scattering measurements have been performed on trehalose/H sub 2 O and sucrose/H sub 2 O mixtures by using the spectrometer MIBEMOL at the Laboratoire Leon Brillouin (LLB, Saclay) as a function of temperature and concentration. In order to characterize the different rigidities of both the disaccharide/H sub 2 O mixtures, we have evaluated the R sub 1 (T sub g) parameter connected to the 'strong-fragile' classification of the systems according to Angell's nomenclature. (orig.)

  8. Rigorous coupled-wave analysis of electromagnetic scattering from lamellar grating with defects.

    Science.gov (United States)

    Watanabe, Koki; Pištora, Jaromír; Nakatake, Yoshimasa

    2011-12-05

    This paper proposes a spectral-domain approach to the electromagnetic scattering problem of lamellar grating with defects. The fields in imperfectly periodic structures have continuous spectra in the wavenumber space, and the main problem of the spectral-domain approach is connected to the discretization scheme on the wavenumber. The present approach introduces the pseudo-periodic Fourier transform to consider the discretization scheme in the Brillouin zone. This transformation also makes it possible to apply the conventional grating formulations to the problems of imperfectly periodic structures. The present formulation is based on the rigorous coupled-wave analysis with the help of pseudo-periodic Fourier transform.

  9. Experimental determination of the berilium phonon spectra using inelastic neutro scattering

    International Nuclear Information System (INIS)

    Sirota, N.N.; Bulat, I.A.

    1976-01-01

    A study has been made of in elastic scattering of cold neutrons with energies between 0.0022 and 0.00523 eV by polycrystalline beryllium and restoration of its phonon spectrum. The specimen studied is a block of polycrystalline beryllium. In the case of beryllium the averaging of coherent effects upon scattering on a thick specimen takes place as a result of multiple internal Bragg-type reflections of neutrons which undergo inelastic scattering with absorption of phonons. The thickness of the spheric averaging layer for Esub(6) = 0.00523 eV is almost equal to the maximum dimension of the Brillouin band. The phonon spectrum of beryllium for three mean energies used of incident neutrons has been demonstrated. The phonon spectrum of beryllium, measured for the first time, is of interest for quantitative calculations of a number of its physical properties

  10. Neutron scattering in the proximate quantum spin liquid α-RuCl3

    Science.gov (United States)

    Banerjee, Arnab; Yan, Jiaqiang; Knolle, Johannes; Bridges, Craig A.; Stone, Matthew B.; Lumsden, Mark D.; Mandrus, David G.; Tennant, David A.; Moessner, Roderich; Nagler, Stephen E.

    2017-06-01

    The Kitaev quantum spin liquid (KQSL) is an exotic emergent state of matter exhibiting Majorana fermion and gauge flux excitations. The magnetic insulator α-RuCl3 is thought to realize a proximate KQSL. We used neutron scattering on single crystals of α-RuCl3 to reconstruct dynamical correlations in energy-momentum space. We discovered highly unusual signals, including a column of scattering over a large energy interval around the Brillouin zone center, which is very stable with temperature. This finding is consistent with scattering from the Majorana excitations of a KQSL. Other, more delicate experimental features can be transparently associated with perturbations to an ideal model. Our results encourage further study of this prototypical material and may open a window into investigating emergent magnetic Majorana fermions in correlated materials.

  11. Theoretical and numerical simulation of the saturation of the stimulated Raman scattering instability that occurs in laser-plasma interaction; Modelisation theorique et numerique de la saturation de l'instabilite de diffusion Raman stimulee se developpant dans l'interaction laser-plasma

    Energy Technology Data Exchange (ETDEWEB)

    Fouquet, T

    2007-01-15

    In this work we present 2 important results. First, for a relatively moderate laser lighting (I*{lambda}{sup 2} {approx_equal} 10{sup 14} W{mu}m{sup 2}/cm{sup 2}), cavitation appears in Langmuir decay instability (LDI) whenever the plasma wavelength is above a certain limit. Secondly, in the case of an inhomogeneous plasma there is an increase of the Raman reflectivity in presence of LDI for a plasma density profile that was initially smooth. This work is divided into 5 chapters. The first chapter is dedicated to parametric instabilities especially Raman instability and Langmuir decay instability. The equations that govern these instabilities as well as their numerical solutions are presented in the second chapter. The third chapter deals with the case of a mono-dimensional plasma with homogenous density. The saturation of the Raman instability in a mono-dimensional plasma with inhomogeneous density is studied in the fourth chapter. The last chapter is dedicated to bi-dimensional simulations for various types of laser beams.

  12. Hemispherical Brillouin zone imaging of a diamond-type biological photonic crystal

    Science.gov (United States)

    Wilts, Bodo D.; Michielsen, Kristel; De Raedt, Hans; Stavenga, Doekele G.

    2012-01-01

    The brilliant structural body colours of many animals are created by three-dimensional biological photonic crystals that act as wavelength-specific reflectors. Here, we report a study on the vividly coloured scales of the diamond weevil, Entimus imperialis. Electron microscopy identified the chitin and air assemblies inside the scales as domains of a single-network diamond (Fd3m) photonic crystal. We visualized the topology of the first Brillouin zone (FBZ) by imaging scatterometry, and we reconstructed the complete photonic band structure diagram (PBSD) of the chitinous photonic crystal from reflectance spectra. Comparison with calculated PBSDs indeed showed a perfect overlap. The unique method of non-invasive hemispherical imaging of the FBZ provides key insights for the investigation of photonic crystals in the visible wavelength range. The characterized extremely large biophotonic nanostructures of E. imperialis are structurally optimized for high reflectance and may thus be well suited for use as a template for producing novel photonic devices, e.g. through biomimicry or direct infiltration from dielectric material. PMID:22188768

  13. Instabilities in electromagnetic quasilevitation.

    Science.gov (United States)

    Spragg, Kirk; Letout, Sebastien; Ernst, R; Sneyd, Alfred; Fautrelle, Yves

    2014-05-01

    We investigate free-surface instabilities occurring in various industrial processes involving liquid metal. Of particular interest is the behavior of the free surface of a pool of liquid metal when it is submitted to an alternating magnetic field. Experimentally, we study the effect of a vertical alternating medium-frequency magnetic field on an initially circular pool. We observe various types of behavior according to magnetic field amplitude, e.g., axisymmetric deformations, azimuthal mode structures, slow radial oscillation of the pool perimeter, and random rotation of the pool around its center. Drop rotation could be attributed to nonsymmetric shape deformations. The effect of oxidation leads to drastic changes in pool behavior. The experimental results are then compared to a linear stability analysis of the free surface of a circular liquid drop.

  14. Posterolateral elbow joint instability

    DEFF Research Database (Denmark)

    Olsen, Bo Sanderhoff; Søjbjerg, Jens Ole; Nielsen, K K

    1998-01-01

    Thirty-five osteoligamentous elbows were included in a study on the kinematics of posterolateral elbow joint instability during the pivot shift test (PST) before and after separate ligament cuttings in the lateral collateral ligament complex (LCLC). Division of the annular ligament or the lateral...... ulnar collateral ligament caused no laxity during the PST. Division of the lateral collateral ligament caused maximal laxity of 4 degrees and 23 degrees during forced PST in valgus and external rotation (supination), respectively. Cutting of the LCLC at the ulnar or the humeral insertion was necessary...... for any PST stressed elbow joint laxity to occur. Total division of the LCLC induced a maximal laxity of 7.9 degrees and 37 degrees during forced PST in valgus and external rotation (supination), respectively. This study suggests the lateral collateral ligament to be the primary soft tissue constraint...

  15. Cinerama sickness and postural instability

    NARCIS (Netherlands)

    Bos, J.E.; Ledegang, W.D.; Lubeck, A.J.A.; Stins, J.F.

    2013-01-01

    Motion sickness symptoms and increased postural instability induced by motion pictures have been reported in a laboratory, but not in a real cinema. We, therefore, carried out an observational study recording sickness severity and postural instability in 19 subjects before, immediately and 45 min

  16. Cohabitation and Children's Family Instability

    Science.gov (United States)

    Kelly Raley, R.; Wildsmith, Elizabeth

    2004-01-01

    This study estimates how much children's family instability is missed when we do not count transitions into and out of cohabitation, and examines early life course trajectories of children to see whether children who experience maternal cohabitation face more family instability than children who do not. Using data from the 1995 National Survey of…

  17. Nonlinear theory of drift instability

    International Nuclear Information System (INIS)

    Hatori, T.

    1981-01-01

    In this chapter, we review recent works on the analytical and numerical analysis for the nonlinear evolution of drift instabilities. Only the case of a coherent wave is considered. Contributions to the turbulence theory for drift instabilities are already presented in Chapter 4. (author)

  18. Internal rotor friction instability

    Science.gov (United States)

    Walton, J.; Artiles, A.; Lund, J.; Dill, J.; Zorzi, E.

    1990-01-01

    The analytical developments and experimental investigations performed in assessing the effect of internal friction on rotor systems dynamic performance are documented. Analytical component models for axial splines, Curvic splines, and interference fit joints commonly found in modern high speed turbomachinery were developed. Rotor systems operating above a bending critical speed were shown to exhibit unstable subsynchronous vibrations at the first natural frequency. The effect of speed, bearing stiffness, joint stiffness, external damping, torque, and coefficient of friction, was evaluated. Testing included material coefficient of friction evaluations, component joint quantity and form of damping determinations, and rotordynamic stability assessments. Under conditions similar to those in the SSME turbopumps, material interfaces experienced a coefficient of friction of approx. 0.2 for lubricated and 0.8 for unlubricated conditions. The damping observed in the component joints displayed nearly linear behavior with increasing amplitude. Thus, the measured damping, as a function of amplitude, is not represented by either linear or Coulomb friction damper models. Rotordynamic testing of an axial spline joint under 5000 in.-lb of static torque, demonstrated the presence of an extremely severe instability when the rotor was operated above its first flexible natural frequency. The presence of this instability was predicted by nonlinear rotordynamic time-transient analysis using the nonlinear component model developed under this program. Corresponding rotordynamic testing of a shaft with an interference fit joint demonstrated the presence of subsynchronous vibrations at the first natural frequency. While subsynchronous vibrations were observed, they were bounded and significantly lower in amplitude than the synchronous vibrations.

  19. Mitigating the effects of the gain-dependence of the Brillouin line-shape on dynamic BOTDA sensing methods.

    Science.gov (United States)

    Motil, Avi; Davidi, Roy; Hadar, Raanan; Tur, Moshe

    2017-09-18

    It has been recently shown that in stimulated Brillouin amplification (pulsed pump & CW probe) the line-shape of the normalized logarithmic Brillouin Gain Spectrum (BGS) broadens with increasing gain. Most pronounced for short pump pulses, a linewidth increase of ~3 MHz (~1.5 MHz) per dB of additional gain was observed for a pump pulse width of 15 ns (30 ns), respectively. This gain-dependency of the shape of the BGS compromises the accuracy of the otherwise attractive, highly dynamic and distributed slope-assisted BOTDA techniques, where measurand-induced gain variations of a single probe, are converted to strain/temperature values through a calibration factor that depends on the line-shape of the BGS. A previously developed technique with built-in compensation for Brillouin gain variations, namely: the Ratio Double Slope-Assisted BOTDA (RDSA-BOTDA) method, where both slopes of the BGS are interrogated, fails to meet this new challenge of the gain-induced shape dependence of the BGS, resulting, for instance, in significant measurement errors of ~5% per dB of gain change for a 15 ns pump pulse. Here, we propose and demonstrate an extension of the RDSA-BOTDA method, which now offers immunity also to Brillouin gain-dependent line-shape variations. Requiring a prior characterization of the gain-induced line-shape dependency of the fiber and pump-pulse-width in use, this mitigation technique takes advantage of the fact that the sum of the measured logarithmic gains at judiciously chosen two fixed frequency points of the BGS can be used to determine the local peak gain, via a pre-established calibration curve. Based on the deduced correct peak gain, its associated BGS shape can now be used in the application of the previously introduced RDSA-BOTDA technique to obtain error-free results, independent of the gain dependence of the line-shape. The proposed technique has been successfully put to test in an experiment, involving a RDSA-BOTDA measurement of a fiber segment

  20. Fermi Liquid Instabilities in the Spin Channel

    International Nuclear Information System (INIS)

    Wu, Congjun

    2010-01-01

    We study the Fermi surface instabilities of the Pomeranchuk type in the spin triplet channel with high orbital partial waves (F l a (l > 0)). The ordered phases are classified into two classes, dubbed the α and β-phases by analogy to the superfluid 3 He-A and B-phases. The Fermi surfaces in the α-phases exhibit spontaneous anisotropic distortions, while those in the β-phases remain circular or spherical with topologically non-trivial spin configurations in momentum space. In the α-phase, the Goldstone modes in the density channel exhibit anisotropic overdamping. The Goldstone modes in the spin channel have nearly isotropic underdamped dispersion relation at small propagating wavevectors. Due to the coupling to the Goldstone modes, the spin wave spectrum develops resonance peaks in both the α and β-phases, which can be detected in inelastic neutron scattering experiments. In the p-wave channel β-phase, a chiral ground state inhomogeneity is spontaneously generated due to a Lifshitz-like instability in the originally nonchiral systems. Possible experiments to detect these phases are discussed.

  1. Penrose process, superradiance, and ergoregion instabilities

    Science.gov (United States)

    Vicente, Rodrigo; Cardoso, Vitor; Lopes, Jorge C.

    2018-04-01

    Superradiant scattering is a radiation enhancement process that takes place in many contexts, and which has recently found exciting applications in astrophysics and particle physics. In the framework of curved spacetime physics, it has been associated with the classical Penrose process for particles. Superradiance is usually also associated with bosonic fields around geometries with ergoregions and horizons. These notions are in clear tension however: the Penrose process occurs for horizonless geometries, and particles are composed of fermions. Here, we resolve the tension in its different aspects, by showing that (i) superradiance occurs for self-interacting fermions on flat spacetime. (ii) Superradiance occurs also for horizonless geometries, where it leads to an ergoregion instability. Ultracompact, horizonless geometries will usually respond with echoes of growing amplitude, until rotational (or electrostatic) energy is extracted from the object. (iii) The Fourier-domain analysis leads to absence of superradiance when horizons are not present. We elucidate why this analysis fails to give meaningful results. (iv) Finally, we show that superradiant, ergoregion instabilities have a particle analog of similar growth timescales and which can power the formation of a structure outside a compact, rotating star.

  2. Fermi Liquid Instabilities in the Spin Channel

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Congjun; /Santa Barbara, KITP; Sun, Kai; Fradkin, Eduardo; /Illinois U., Urbana; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-03-16

    We study the Fermi surface instabilities of the Pomeranchuk type in the spin triplet channel with high orbital partial waves (F{sub l}{sup a} (l > 0)). The ordered phases are classified into two classes, dubbed the {alpha} and {beta}-phases by analogy to the superfluid {sup 3}He-A and B-phases. The Fermi surfaces in the {alpha}-phases exhibit spontaneous anisotropic distortions, while those in the {beta}-phases remain circular or spherical with topologically non-trivial spin configurations in momentum space. In the {alpha}-phase, the Goldstone modes in the density channel exhibit anisotropic overdamping. The Goldstone modes in the spin channel have nearly isotropic underdamped dispersion relation at small propagating wavevectors. Due to the coupling to the Goldstone modes, the spin wave spectrum develops resonance peaks in both the {alpha} and {beta}-phases, which can be detected in inelastic neutron scattering experiments. In the p-wave channel {beta}-phase, a chiral ground state inhomogeneity is spontaneously generated due to a Lifshitz-like instability in the originally nonchiral systems. Possible experiments to detect these phases are discussed.

  3. Electron Parametric Instabilities Driven by Relativistically Intense Laser Light in Plasma

    Science.gov (United States)

    Barr, H. C.; Mason, P.; Parr, D. M.

    1999-08-01

    A unified treatment of electron parametric instabilities driven by ultraintense laser light in plasma is described. It is valid for any intensity, polarization, plasma density, and scattering geometry. The method is applied to linearly polarized light in both underdense plasma and overdense plasma accessible by self-induced transparency. New options arise which are hybrids of stimulated Raman scattering, the two plasmon decay, the relativistic modulational and filamentation instabilities, and stimulated harmonic generation. There is vigorous growth over a wide range of wave numbers and harmonics.

  4. Dynamical Instability and Soliton Concept

    International Nuclear Information System (INIS)

    Kartavenko, V.G.

    1994-01-01

    The problem of dynamical instability and clustering (stable fragments formation) in a breakup of excited nuclear systems are considered from the points of view of the soliton concept. It is noted that the volume (spinodal) instability can be associated with nonlinear terms, and the surface (Rayleigh-Taylor type) instability, with the dispersion terms in the evolution equations. The spinodal instability and the Rayleigh-Taylor instability may compensate each other and lead to stable quasi-soliton type objects. The simple analytical model is presented to illustrate this physical picture. The time evolution of an initially compressed cold nuclear system is analysed in the framework of the inverse mean-field method. It is demonstrated that the nonlinearity and dispersion terms of the evolution equations can lead to clusterization in the final channel. 8 p

  5. Instability of ties in compression

    DEFF Research Database (Denmark)

    Buch-Hansen, Thomas Cornelius

    2013-01-01

    exact instability solutions are complex to derive, not to mention the extra complexity introducing dimensional instability from the temperature gradients. Using an inverse variable substitution and comparing an exact theory with an analytical instability solution a method to design tie...... the temperature gradient between the outer and the inner wall, which results in critical increase of the bending moments in the ties. Since the ties are loaded by combined compression and moment forces, the loadbearing capacity is derived from instability equilibrium equations. Most of them are iterative, since......-connectors in cavity walls was developed. The method takes into account constraint conditions limiting the free length of the wall tie, and the instability in case of pure compression which gives an optimal load bearing capacity. The model is illustrated with examples from praxis....

  6. Beam instability Workshop - plenary sessions

    International Nuclear Information System (INIS)

    2001-01-01

    The purpose of this workshop was to provide a review of the mechanisms of limiting beam instabilities, their cures, including feedback, and beam measurement for synchrotron radiation light sources. 12 plenary sessions took place whose titles are: 1) challenging brilliance and lifetime issues with increasing currents; 2) limiting instabilities in multibunch; 3) experience from high currents in B factories; 4) longitudinal dynamics in high intensity/bunch; 5) Transverse instabilities for high intensity/bunch; 6) working group introduction from ESRF experience; 7) impedance modelling: simulations, minimization; 8) report on the broadband impedance measurements and modelling workshop; 9) feedback systems for synchrotron light sources; 10) beam instabilities diagnostics; 11) harmonic cavities: the pros and cons; and 12) experimental study of fast beam-ion instabilities at PLS. This document gathers the 12 articles that were presented during these sessions

  7. Electron/electron acoustic instability

    International Nuclear Information System (INIS)

    Gary, S.P.

    1987-01-01

    The electron acoustic wave becomes a normal mode of an unmagnetized collisionless plasma in the presence of two electron components with similar densities, but strongly disparate temperatures. The characteristic frequency of this mode is the plasma frequency of the cooler electron component. If these two electron components have a relative drift speed several times the thermal speed of the cooler component, the electron/electron acoustic instability may arise. This paper describes the parametric dependences of the threshold drift speed and maximum growth rate of this instability, and compares these with the same properties of the electron/ion acoustic instability. Under the condition of zero current, the electron/ion acoustic instability typically has the lower threshold drift speed, so that observation of the electron/electron acoustic instability is a strong indication of the presence of an electrical current in the plasma

  8. Neutron scattering. Lectures

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2012-07-01

    The following topics are dealt with: Neutron scattering in contemporary research, neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)

  9. Neutron scattering. Lectures

    International Nuclear Information System (INIS)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner

    2012-01-01

    The following topics are dealt with: Neutron scattering in contemporary research, neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)

  10. Instability timescale for the inclination instability in the solar system

    Science.gov (United States)

    Zderic, Alexander; Madigan, Ann-Marie; Fleisig, Jacob

    2018-04-01

    The gravitational influence of small bodies is often neglected in the study of solar system dynamics. However, this is not always an appropriate assumption. For example, mutual secular torques between low mass particles on eccentric orbits can result in a self-gravity instability (`inclination instability'; Madigan & McCourt 2016). During the instability, inclinations increase exponentially, eccentricities decrease (detachment), and orbits cluster in argument of perihelion. In the solar system, the orbits of the most distant objects show all three of these characteristics (high inclination: Volk & Malhotra (2017), detachment: Delsanti & Jewitt (2006), and argument of perihelion clustering: Trujillo & Sheppard (2014)). The inclination instability is a natural explanation for these phenomena.Unfortunately, full N-body simulations of the solar system are unfeasible (N ≈ O(1012)), and the behavior of the instability depends on N, prohibiting the direct application of lower N simulations. Here we present the instability timescale's functional dependence on N, allowing us to extrapolate our simulation results to that appropriate for the solar system. We show that ~5 MEarth of small icy bodies in the Sedna region is sufficient for the inclination instability to occur in the outer solar system.

  11. Kinetic-MHD simulations of gyroresonance instability driven by CR pressure anisotropy

    Science.gov (United States)

    Lebiga, O.; Santos-Lima, R.; Yan, H.

    2018-02-01

    The transport of cosmic rays (CRs) is crucial for the understanding of almost all high-energy phenomena. Both pre-existing large-scale magnetohydrodynamic (MHD) turbulence and locally generated turbulence through plasma instabilities are important for the CR propagation in astrophysical media. The potential role of the resonant instability triggered by CR pressure anisotropy to regulate the parallel spatial diffusion of low-energy CRs (≲ 100 GeV) in the interstellar and intracluster medium of galaxies (ISM and ICM) has been showed in previous theoretical works. This work aims to study the gyroresonance instability via direct numerical simulations, in order to access quantitatively the wave-particle scattering rates. For this we employ a 1D PIC-MHD code to follow the growth and saturation of the gyroresonance instability. We extract from the simulations the pitch-angle diffusion coefficient Dμμ produced by the instability during the linear and saturation phases, and a very good agreement (within a factor of 3) is found with the values predicted by the quasilinear theory (QLT). Our results support the applicability of the QLT for modeling the scattering of low-energy CRs by the gyroresonance instability in the complex interplay between this instability and the large-scale MHD turbulence.

  12. Kinetic-MHD simulations of gyroresonance instability driven by CR pressure anisotropy

    Science.gov (United States)

    Lebiga, O.; Santos-Lima, R.; Yan, H.

    2018-05-01

    The transport of cosmic rays (CRs) is crucial for the understanding of almost all high-energy phenomena. Both pre-existing large-scale magnetohydrodynamic (MHD) turbulence and locally generated turbulence through plasma instabilities are important for the CR propagation in astrophysical media. The potential role of the resonant instability triggered by CR pressure anisotropy to regulate the parallel spatial diffusion of low-energy CRs (≲100 GeV) in the interstellar and intracluster medium of galaxies has been shown in previous theoretical works. This work aims to study the gyroresonance instability via direct numerical simulations, in order to access quantitatively the wave-particle scattering rates. For this, we employ a 1D PIC-MHD code to follow the growth and saturation of the gyroresonance instability. We extract from the simulations the pitch-angle diffusion coefficient Dμμ produced by the instability during the linear and saturation phases, and a very good agreement (within a factor of 3) is found with the values predicted by the quasi-linear theory (QLT). Our results support the applicability of the QLT for modelling the scattering of low-energy CRs by the gyroresonance instability in the complex interplay between this instability and the large-scale MHD turbulence.

  13. Functional Instability of the Ankle Joint: Etiopathogenesis

    Directory of Open Access Journals (Sweden)

    Aydan ÖRSÇELİK

    2016-09-01

    Full Text Available Ankle sprain is one of the most common sports injuries. Chronic ankle instability is a common complication of ankle sprains. Two causes of chronic ankle instability are mechanical instability and functional instability. It is important to understand functional instability etiopathogenesis of the ankle joint in order to guide diagnosis and treatment. This article aims to understand the etiopathogenesis of functional ankle instability.

  14. Urethral morphology and bladder instability.

    Science.gov (United States)

    Hausegger, K A; Fotter, R; Sorantin, E; Schmidt, P

    1991-01-01

    In order to calculate the relationship between Spinning top urethra (STU) and bladder instability 160 voiding cystourethrogramms (VCU), performed in 102 girls, have been analysed retrospectively. 28 girls had STU, 16 of those had bladder instability as well (57%). We could not find the highly positive correlation between unstable bladder and STU as reported by other authors, although there was a statistically positive correlation between STU and bladder instability. However the confidence interval was very broad (38%-75%). We conclude that bladder instability may contribute to STU but cannot render the etiological explanation for all cases. STU seems to be a polyetiological sign. In our opinion only the combination of STU and bladder instability has a diagnostic impact, since several therapeutical concepts are available in cases of bladder instability. The finding of STU in the VCU should alert the examiner's attention to functional disorders of the lower urinary tract. If no instability can be found, STU should be considered to be a normal variant.

  15. Urethral morphology and bladder instability

    Energy Technology Data Exchange (ETDEWEB)

    Hausegger, K.A.; Fotter, R.; Sorantin, E. (Graz Univ. (Austria). Radiologische Klinik); Schmidt, P. (Rehabilitationszentrum, Schallerbach (Austria))

    1991-05-01

    In order to calculate the relationship between Spinning top urethra (STU) and bladder instability 160 voiding cystourethrogramms (VCU), performed in 102 girls, have been analysed retrospectively. 28 girls had STU, 16 of those had bladder instability as well (57%). We could not find the highly positive correlation between unstable bladder and STU as reported by other authors, although there was a statistically positive correlation between STU and bladder instability. However the confidence interval was very broad (38%-75%). We conclude that bladder instability may contribute to STU but cannot render the etiological explanation for all cases. STU seems to be a polyetiological sign. In our opinion only the combination of STU and bladder instability has a diagnostic impact, since several therapeutical concepts are available in cases of bladder instability. The finding of STU in the VCU should alert the examiner's attention to functional disorders of the lower urinary tract. If no instability can be found, STU should be considered to be a normal variant. (orig.).

  16. Genetic instability in human tumors.

    Science.gov (United States)

    Raptis, Stavroula; Bapat, Bharati

    2006-01-01

    Genetic, or genomic, instability refers to a series of observed spontaneous genetic changes occurring at an accelerated rate in cell populations derived from the same ancestral precursor. This is far from a new finding, but is one that has increasingly gained more attention in the last decade due to its plausible role(s) in tumorigenesis. The majority of genetic alterations contributing to the malignant transformation are seen in growth regulatory genes, and in genes involved in cell cycle progression and arrest. Genomic instability may present itself through alterations in the length of short repeat stretches of coding and non-coding DNA, resulting in microsatellite instability. Tumors with such profiles are referred to as exhibiting a mutator phenotype, which is largely a consequence of inactivating mutations in DNA damage repair genes. Genomic instability may also, and most commonly, results from gross chromosomal changes, such as translocations or amplifications, which lead to chromosomal instability. Telomere length and telomerase activity, important in maintaining chromosomal structure and in regulating a normal cell's lifespan, have been shown to have a function in both suppressing and facilitating malignant transformation. In addition to such direct sequence and structural changes, gene silencing through the hypermethylation of promoter regions, or increased gene expression through the hypomethylation of such regions, together, form an alternative, epigenetic mechanism leading to instability. Emerging evidence also suggests that dietary and environmental agents can further modulate the contribution of genetic instability to tumorigenesis. Currently, there is still much debate over the distinct classes of genomic instability and their specific roles in the initiation of tumor formation, as well as in the progressive transition to a cancerous state. This review examines the various molecular mechanisms that result in this genomic instability and the potential

  17. The Laboratoire Léon Brillouin, the French National Neutron Facility

    International Nuclear Information System (INIS)

    Alba-Simionesco, C.; Visticot, J.P.; Menelle, A.

    2013-01-01

    The Laboratoire Léon Brillouin is a French research infrastructure supported jointly by the Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA) and the Centre National de la Recherche Scientifique (CNRS); it constructs and operates spectrometers around Orphée, a 14 MW reactor operated by the CEA since 1980. The three missions of this national large scale facility are to perform research in its own scientific programs, to promote the use of diffraction and neutron spectroscopy, to welcome and assist experimentalists, subsequently ensuring training and education, and providing access for industrial partners. As a service institute the LLB makes its facilities and expertise available to visiting scientists from France and foreign countries. Every year, about 500 researchers from France (70%) and other countries (30%) visit the LLB and perform their experiments on the 20 operational spectrometers. About 450 experiments selected by a scientific review committee are performed annually. These activities are enduring and complementary to international centers, such as the Institute Laue-Langevin or the future European Spallation Source in Sweden, and cooperation programs with other national centers. As a national facility, its management of beam time is quite flexible, allowing more tests, thoughts and discussions between beginners and experts, the exploration of new areas or experiment preparation, and access to industrial partners. The exceptional situation of the LLB in the southwest of Paris, in the scientific centre of Saclay, nearby faculties, engineering schools and other large scale facilities, such the synchrotron Soleil, promotes external contacts and discussions, and stimulates new collaborations. New objectives in research are at the centre of the instrumental development program CAP2015. The goal of this program is the modernization or construction of nearly half of the laboratory's instruments by 2015, accounting for the needs of the

  18. Sheared Electroconvective Instability

    Science.gov (United States)

    Kwak, Rhokyun; Pham, Van Sang; Lim, Kiang Meng; Han, Jongyoon

    2012-11-01

    Recently, ion concentration polarization (ICP) and related phenomena draw attention from physicists, due to its importance in understanding electrochemical systems. Researchers have been actively studying, but the complexity of this multiscale, multiphysics phenomenon has been limitation for gaining a detailed picture. Here, we consider electroconvective(EC) instability initiated by ICP under pressure-driven flow, a scenario often found in electrochemical desalinations. Combining scaling analysis, experiment, and numerical modeling, we reveal unique behaviors of sheared EC: unidirectional vortex structures, its size selection and vortex propagation. Selected by balancing the external pressure gradient and the electric body force, which generates Hagen-Poiseuille(HP) flow and vortical EC, the dimensionless EC thickness scales as (φ2 /UHP)1/3. The pressure-driven flow(or shear) suppresses unfavorably-directed vortices, and simultaneously pushes favorably-directed vortices with constant speed, which is linearly proportional to the total shear of HP flow. This is the first systematic characterization of sheared EC, which has significant implications on the optimization of electrodialysis and other electrochemical systems.

  19. Bidirectional optical scattering facility

    Data.gov (United States)

    Federal Laboratory Consortium — Goniometric optical scatter instrument (GOSI)The bidirectional reflectance distribution function (BRDF) quantifies the angular distribution of light scattered from a...

  20. Modification of the collective Thomson scattering radiometer in the search for parametric decay on TEXTOR

    DEFF Research Database (Denmark)

    Nielsen, Stefan Kragh; Salewski, Mirko; Bongers, W.

    2012-01-01

    Strong scattering of high-power millimeter waves at 140 GHz has been shown to take place in heating and current-drive experiments at TEXTOR when a tearing mode is present in the plasma. The scattering signal is at present supposed to be generated by the parametric decay instability. Here we descr...

  1. Atlantoaxial instability in Down's syndrome.

    OpenAIRE

    Collacott, R A

    1987-01-01

    The radiographs and clinical evaluations of 90 children with Down’s syndrome were reassessed after an interval of 5 years in a study of atlantoaxial instability (AAI) at the Derbyshire Children’s Hospital and Infirmary, Derby, UK.

  2. Summary of longitudinal instabilities workshop

    Energy Technology Data Exchange (ETDEWEB)

    Chasman, R.

    1976-01-01

    A five-day ISABELLE workshop on longitudinal instabilities was held at Brookhaven, August 9-13, 1976. About a dozen outside accelerator experts, both from Europe and the U.S.A., joined the local staff for discussions of longitudinal instabilities in ISABELLE. An agenda of talks was scheduled for the first day of the workshop. Later during the week, a presentation was given on the subject ''A more rigorous treatment of Landau damping in longitudinal beam instabilities''. A few progress meetings were held in which disagreements regarding calculations of coupling impedances were clarified. A summary session was held on the last day. Heavy emphasis was put on single bunched beam instabilities in the microwave region extending above the cut-off frequency of the ISABELLE vacuum chamber.

  3. Predicting Catastrophic BGP Routing Instabilities

    National Research Council Canada - National Science Library

    Nguyen, Lien

    2004-01-01

    .... Currently, this critical function is performed by the Border Gateway Protocol (BGP) version 4 RF01771. Like all routing protocols, BGP is vulnerable to instabilities that reduce its effectiveness...

  4. Genomic instability and radiation effects

    International Nuclear Information System (INIS)

    Christian Streffer

    2007-01-01

    Complete text of publication follows. Cancer, genetic mutations and developmental abnormalities are apparently associated with an increased genomic instability. Such phenomena have been frequently shown in human cancer cells in vitro and in situ. It is also well-known that individuals with a genetic predisposition for cancer proneness, such as ataxia telangiectesia, Fanconi anaemia etc. demonstrate a general high genomic instability e.g. in peripheral lymphocytes before a cancer has developed. Analogous data have been found in mice which develop a specific congenital malformation which has a genetic background. Under these aspects it is of high interest that ionising radiation can increase the genomic instability of mammalian cells after exposures in vitro an in vivo. This phenomenon is expressed 20 to 40 cell cycles after the exposure e.g. by de novo chromosomal aberrations. Such effects have been observed with high and low LET radiation, high LET radiation is more efficient. With low LET radiation a good dose response is observed in the dose range 0.2 to 2.0 Gy, Recently it has been reported that senescence and genomic instability was induced in human fibroblasts after 1 mGy carbon ions (1 in 18 cells are hit), apparently bystander effects also occurred under these conditions. The instability has been shown with DNA damage, chromosomal aberrations, gene mutation and cell death. It is also transferred to the next generation of mice with respect to gene mutations, chromosomal aberrations and congenital malformations. Several mechanisms have been discussed. The involvement of telomeres has gained interest. Genomic instability seems to be induced by a general lesion to the whole genome. The transmission of one chromosome from an irradiated cell to an non-irradiated cell leads to genomic instability in the untreated cells. Genomic instability increases mutation rates in the affected cells in general. As radiation late effects (cancer, gene mutations and congenital

  5. Highly sensitive distributed birefringence measurements based on a two-pulse interrogation of a dynamic Brillouin grating

    Science.gov (United States)

    Soto, Marcelo A.; Denisov, Andrey; Angulo-Vinuesa, Xabier; Martin-Lopez, Sonia; Thévenaz, Luc; Gonzalez-Herraez, Miguel

    2017-04-01

    A method for distributed birefringence measurements is proposed based on the interference pattern generated by the interrogation of a dynamic Brillouin grating (DBG) using two short consecutive optical pulses. Compared to existing DBG interrogation techniques, the method here offers an improved sensitivity to birefringence changes thanks to the interferometric effect generated by the reflections of the two pulses. Experimental results demonstrate the possibility to obtain the longitudinal birefringence profile of a 20 m-long Panda fibre with an accuracy of 10-8 using 16 averages and 30 cm spatial resolution. The method enables sub-metric and highly-accurate distributed temperature and strain sensing.

  6. Wentzel-Kramers-Brillouin solution of cut-off frequency for horizontal shear (SH) waves in various inhomogeneous thin films

    Science.gov (United States)

    Cao, Xiaoshan; Shi, Junping; Jin, Feng

    2013-01-01

    The Wentzel-Kramers-Brillouin method is employed to study the cut-off frequencies of the horizontal shear waves in a freestanding functionally graded piezoelectric-piezomagnetic material film with the electrically and magnetically open boundary conditions. An analytical solution, which could be used in analyzing the problems of various functionally graded materials, is proven to have high precision by analytical analysis and a numerical example. The results reveal that the set of cut-off frequencies is a series of approximate arithmetic progressions. A theoretical foundation based on the relationship between the cut-off frequencies and the materials' gradient property is established for nondestructive evaluation.

  7. Simulation of nanowire tunneling transistors: From the Wentzel-Kramers-Brillouin approximation to full-band phonon-assisted tunneling

    Science.gov (United States)

    Luisier, Mathieu; Klimeck, Gerhard

    2010-04-01

    Nanowire band-to-band tunneling field-effect transistors (TFETs) are simulated using the Wentzel-Kramers-Brillouin (WKB) approximation and an atomistic, full-band quantum transport solver including direct and phonon-assisted tunneling (PAT). It is found that the WKB approximation properly works if one single imaginary path connecting the valence band (VB) and the conduction band (CB) dominates the tunneling process as in direct band gap semiconductors. However, PAT is essential in Si and Ge nanowire TFETs where multiple, tightly-coupled, imaginary paths exist between the VB and the CB.

  8. Separated-pair independent particle model and the generalized Brillouin theorem: ab initio calculations on the dissociation of polyatomic molecules

    Energy Technology Data Exchange (ETDEWEB)

    Sundberg, Kenneth Randall [Iowa State Univ., Ames, IA (United States). Dept. of Electrical and Computer Engineering

    1976-01-01

    A method is developed to optimize the separated-pair independent particle (SPIP) wave function; it is a special case of the separated-pair theory obtained by using two-term natural expansions of the geminals. The orbitals are optimized by a theory based on the generalized Brillouin theorem and iterative configuration interaction (CI) calculations in the space of the SPIP function and its single excitations. The geminal expansion coefficients are optimized by serial 2 x 2 CI calculations. Formulas are derived for the matrix elements. An algorithm to implement the method is presented, and the work needed to evaluate the molecular integrals is discussed.

  9. Microsatellite instability in bladder cancer

    DEFF Research Database (Denmark)

    Gonzalez-Zulueta, M; Ruppert, J M; Tokino, K

    1993-01-01

    Somatic instability at microsatellite repeats was detected in 6 of 200 transitional cell carcinomas of the bladder. Instabilities were apparent as changes in (GT)n repeat lengths on human chromosome 9 for four tumors and as alterations in a (CAG)n repeat in the androgen receptor gene on the X...... or larger (> 2 base pairs) alterations in repeat length. All six tumors were low stage (Ta-T1), suggesting that these alterations can occur early in bladder tumorigenesis....

  10. Microsatellite instability in hematological malignancies

    OpenAIRE

    Maletzki, Claudia; Stier, Saskia; Linnebacher, Michael

    2013-01-01

    The genome of colorectal carcinomas displaying pronounced microsatellite instability codes for an extraordinarily high number of mutated proteins that elicit tumor-specific cellular immune responses. We have recently demonstrated that leukemic cells are also vulnerable to T cells specific for tumor-associated antigens produced in the context of microsatellite instability. This finding extends our understanding of secondary and therapy-related leukemogenesis, linking it to the mutual interacti...

  11. Beam Instabilities in Hadron Synchrotrons

    CERN Document Server

    Métral, E; Bartosik, H; Biancacci, N; Buffat, X; Esteban Muller, J F; Herr, W; Iadarola, G; Lasheen, A; Li, K; Oeftiger, A; Pieloni, T; Quartullo, D; Rumolo, G; Salvant, B; Schenk, M; Shaposhnikova, E; Tambasco, C; Timko, H; Zannini, C; Burov, A; Banfi, D; Barranco, J; Mounet, N; Boine-Frankenheim, O; Niedermayer, U; Kornilov, V; White, S

    2016-01-01

    Beam instabilities cover a wide range of effects in particle accelerators and they have been the subjects of intense research for several decades. As the machines performance was pushed new mechanisms were revealed and nowadays the challenge consists in studying the interplays between all these intricate phenomena, as it is very often not possible to treat the different effects separately. The aim of this paper is to review the main mechanisms, discussing in particular the recent developments of beam instability theories and simulations.

  12. Waves and instabilities in plasmas

    International Nuclear Information System (INIS)

    Chen, L.

    1987-01-01

    The contents of this book are: Plasma as a Dielectric Medium; Nyquist Technique; Absolute and Convective Instabilities; Landau Damping and Phase Mixing; Particle Trapping and Breakdown of Linear Theory; Solution of Viasov Equation via Guilding-Center Transformation; Kinetic Theory of Magnetohydrodynamic Waves; Geometric Optics; Wave-Kinetic Equation; Cutoff and Resonance; Resonant Absorption; Mode Conversion; Gyrokinetic Equation; Drift Waves; Quasi-Linear Theory; Ponderomotive Force; Parametric Instabilities; Problem Sets for Homework, Midterm and Final Examinations

  13. History of shoulder instability surgery.

    Science.gov (United States)

    Randelli, Pietro; Cucchi, Davide; Butt, Usman

    2016-02-01

    The surgical management of shoulder instability is an expanding and increasingly complex area of study within orthopaedics. This article describes the history and evolution of shoulder instability surgery, examining the development of its key principles, the currently accepted concepts and available surgical interventions. A comprehensive review of the available literature was performed using PubMed. The reference lists of reviewed articles were also scrutinised to ensure relevant information was included. The various types of shoulder instability including anterior, posterior and multidirectional instability are discussed, focussing on the history of surgical management of these topics, the current concepts and the results of available surgical interventions. The last century has seen important advancements in the understanding and treatment of shoulder instability. The transition from open to arthroscopic surgery has allowed the discovery of previously unrecognised pathologic entities and facilitated techniques to treat these. Nevertheless, open surgery still produces comparable results in the treatment of many instability-related conditions and is often required in complex or revision cases, particularly in the presence of bone loss. More high-quality research is required to better understand and characterise this spectrum of conditions so that successful evidence-based management algorithms can be developed. IV.

  14. Neutron scattering. Lectures

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2010-07-01

    The following topics are dealt with: Neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)

  15. Neutron scattering. Lectures

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2013-07-01

    The following topics are dealt with: Neutron sources, symmetry of crystals, nanostructures investigated by small-angle neutron scattering, structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic neutron scattering, strongly correlated electrons, polymer dynamics, applications of neutron scattering. (HSI)

  16. Neutron scattering. Lectures

    International Nuclear Information System (INIS)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner

    2010-01-01

    The following topics are dealt with: Neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)

  17. Neutron scattering. Lectures

    International Nuclear Information System (INIS)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner

    2013-01-01

    The following topics are dealt with: Neutron sources, symmetry of crystals, nanostructures investigated by small-angle neutron scattering, structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic neutron scattering, strongly correlated electrons, polymer dynamics, applications of neutron scattering. (HSI)

  18. Outline of Neutron Scattering Formalism

    OpenAIRE

    Berk, N. F.

    1993-01-01

    Neutron scattering formalism is briefly surveyed. Topics touched upon include coherent and incoherent scattering, bound and free cross-sections, the Van Hove formalism, magnetic scattering, elastic scattering, the static approximation, sum rules, small angle scattering, inelastic scattering, thermal diffuse scattering, quasielastic scattering, and neutron optics.

  19. Mars’ Growth Stunted by an Early Giant Planet Instability

    Science.gov (United States)

    Clement, Matthew; Kaib, Nathan A.; Raymond, Sean N.; Walsh, Kevin J.

    2017-10-01

    Many dynamical aspects of the solar system can be explained by the outer planets experiencing a period of orbital instability. Though often correlated with a perceived delayed spike in the lunar cratering record known as the Late Heavy Bombardment (LHB), recent work suggests that this event may have occurred during the epoch of terrestrial planet formation. Though current simulations of terrestrial accretion can reproduce many observed qualities of the solar system, replicating the small mass of Mars requires modification to standard planet formation models. Here we use direct numerical simulations to show that an early instability in the outer solar system regularly yields properly sized Mars analogues. In 80% of simulations, we produce a Mars of the appropriate mass. Our most successful outcomes occur when the terrestrial planets evolve 10 million years (Myr), and accrete several Mars sized embryos in the Mars forming region before the instability takes place. Mars is left behind as a stranded embryo, while the remainder of these bodies are either ejected from the system or scattered towards the inner solar system where they deliver water to Earth. An early giant planet instability can thus replicate both the inner and outer solar system in a single model.

  20. Neutron scattering. Lectures

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2010-07-01

    The following topics are dealt with: Neutron sources, neutron properties and elastic scattering, correlation functions measured by scattering experiments, symmetry of crystals, applications of neutron scattering, polarized-neutron scattering and polarization analysis, structural analysis, magnetic and lattice excitation studied by inelastic neutron scattering, macromolecules and self-assembly, dynamics of macromolecules, correlated electrons in complex transition-metal oxides, surfaces, interfaces, and thin films investigated by neutron reflectometry, nanomagnetism. (HSI)

  1. Neutron scattering. Lectures

    International Nuclear Information System (INIS)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner

    2010-01-01

    The following topics are dealt with: Neutron sources, neutron properties and elastic scattering, correlation functions measured by scattering experiments, symmetry of crystals, applications of neutron scattering, polarized-neutron scattering and polarization analysis, structural analysis, magnetic and lattice excitation studied by inelastic neutron scattering, macromolecules and self-assembly, dynamics of macromolecules, correlated electrons in complex transition-metal oxides, surfaces, interfaces, and thin films investigated by neutron reflectometry, nanomagnetism. (HSI)

  2. On Kelvin-Helmholtz instability in superfluids

    International Nuclear Information System (INIS)

    Volovik, G.E.

    2002-01-01

    The problem of the Kelvin-Helmholtz (KH) instability in superfluids is discussed. The classical KH instability and the KH instability in superfluids at low temperature are considered. The results of experimental observations of such instabilities at the interface between superfluid 3 He-A and superfluid 3 He-B are analyzed. The causes of the disagreement of values for the instability threshold obtained by means of the Kelvin Helmholtz criterion and the modified Landau criterion are discussed [ru

  3. Observation of soft phonon mode in TbFe3(BO3)4 by inelastic neutron scattering

    Science.gov (United States)

    Pavlovskiy, M. S.; Shaykhutdinov, K. A.; Wu, L. S.; Ehlers, G.; Temerov, V. L.; Gudim, I. A.; Shinkorenko, A. S.; Podlesnyak, A.

    2018-02-01

    The phonon dispersion in terbium iron borate TbFe3(BO3)4 has been measured by inelastic neutron scattering in a temperature range 180 Brillouin zone (Λ point) at temperatures T ⪆TS , in full agreement with theoretical calculations. The TA soft mode undergoes considerable broadening at the Λ point near the transition temperature that can be attributed to the anharmonic interference between transverse acoustic and optical modes.

  4. Optical scattering noise in high Q fiber ring resonators and its effect on optoelectronic oscillator phase noise.

    Science.gov (United States)

    Saleh, Khaldoun; Merrer, Pierre-Henri; Llopis, Olivier; Cibiel, Gilles

    2012-02-15

    Nonlinear phenomena occurring in an optical fiber ring resonator featuring ultrahigh Q factor are experimentally studied. The laser is locked onto the resonator, and the optical power induced in the resonator is controlled. The onset of the first stimulated Brillouin scattering wave occurs at an optical input power as low as -9 dBm in these resonators. When the resonator is used as the frequency reference device in an optoelectronic oscillator (OEO), it has been found that these parasitic signals mix with the OEO signal and degrade its phase noise. More than 20 dB improvement of the OEO phase noise has been demonstrated by limiting these nonlinear optical effects.

  5. Direct time integration of Maxwell's equations in linear dispersive media with absorption for scattering and propagation of femtosecond electromagnetic pulses

    Science.gov (United States)

    Joseph, Rose M.; Hagness, Susan C.; Taflove, Allen

    1991-01-01

    The initial results for femtosecond pulse propagation and scattering interactions for a Lorentz medium obtained by a direct time integration of Maxwell's equations are reported. The computational approach provides reflection coefficients accurate to better than 6 parts in 10,000 over the frequency range of dc to 3 x 10 to the 16th Hz for a single 0.2-fs Gaussian pulse incident upon a Lorentz-medium half-space. New results for Sommerfeld and Brillouin precursors are shown and compared with previous analyses. The present approach is robust and permits 2D and 3D electromagnetic pulse propagation directly from the full-vector Maxwell's equations.

  6. Inelastic neutron scattering in the spin wave energy gap of the polydomain γ-Mn(12%Ge) alloy

    International Nuclear Information System (INIS)

    Jankowska-Kisielinska, J.; Mikke, K.

    1999-01-01

    The subject of the present experiment was the investigation of the inelastic neutron scattering (INS) for energy transfers lower than and close to the energy gap of the spin wave spectrum for long wavelengths. The aim was a search for the excitations at the magnetic Brillouin zone (MBZ) boundary in polydomain Mn(12%Ge) alloy. The present measurements were performed by a 3-axis spectrometer at Maria Reactor at IEA in Swierk. We observed the INS in the polydomain Mn(12%Ge) alloy for energies smaller than and close to the energy gap value of the spin wave spectrum at room temperature. The observed intensity can be treated as a sum of intensity of neutrons scattered on spin waves around magnetic Brillouin zone centre and that of neutrons scattered on fluctuations at the zone boundary. The intensity of both components for energies 2-6 MeV was found to be of the same order. For higher energies spin waves around magnetic zone centre dominate. (author)

  7. Temperature extraction in Brillouin optical time-domain analysis sensors using principal component analysis based pattern recognition.

    Science.gov (United States)

    Azad, Abul Kalam; Khan, Faisal Nadeem; Alarashi, Waled Hussein; Guo, Nan; Lau, Alan Pak Tao; Lu, Chao

    2017-07-10

    We propose and experimentally demonstrate the use of principal component analysis (PCA) based pattern recognition to extract temperature distribution from the measured Brillouin gain spectra (BGSs) along the fiber under test (FUT) obtained by Brillouin optical time domain analysis (BOTDA) system. The proposed scheme employs a reference database consisting of relevant ideal BGSs with known temperature attributes. PCA is then applied to the BGSs in the reference database as well as to the measured BGSs so as to reduce their size by extracting their most significant features. Now, for each feature vector of the measured BGS, we determine its best match in the reference database comprised of numerous reduced-size feature vectors of the ideal BGSs. The known temperature attribute corresponding to the best-matched BGS in the reference database is then taken as the extracted temperature of the measured BGS. We analyzed the performance of PCA-based pattern recognition algorithm in detail and compared it with that of curve fitting method. The experimental results validate that the proposed technique can provide better accuracy, faster processing speed and larger noise tolerance for the measured BGSs. Therefore, the proposed PCA-based pattern recognition algorithm can be considered as an attractive method for extracting temperature distributions along the fiber in BOTDA sensors.

  8. A self-consistent trapping model of driven electron plasma waves and limits on stimulated Raman scatter

    International Nuclear Information System (INIS)

    Rose, Harvey A.; Russell, David A.

    2001-01-01

    A Vlasov equation based model is used to determine various regimes of electron plasma wave response to a source appropriate to stimulated scatter in a laser hot spot. It incorporates trapped particle effects such as the standard nonlinear frequency shift, extended beyond the weak regime, and a reduction of damping a la Zakharov and Karpman [V. E. Zakharov and V. I. Karpman, JETP 16, 351 (1963)]. The results are consistent with those of Holloway and Dorning [J. P. Holloway and J. J. Dorning, Phys. Rev. A 44, 3856 (1991)] for small amplitude Bernstein-Greene-Kruskal modes. This leads to the prediction that as long as kλ D ≥0.53 for a background Maxwellian distribution function, e.g., a 5 keV plasma with n e /n c ≤0.075, anomalously large backward stimulated Raman scatter can be excluded. A similar analysis leads to density limits on stimulated Brillouin scatter

  9. Advantages of using gyrotron scattering for alpha particle diagnostics

    International Nuclear Information System (INIS)

    Woskoboinikow, P.P.; Cohn, D.R.; Machuzak, J.S.; Myer, R.C.; Rhee, R.Y.

    1987-07-01

    Millimeter-wave gyrotron collective Thomson scattering can be an effective diagnostic technique for the study of alpha particle behavior in ignited plasmas. The measurement of alpha particle density, velocity distribution, and alpha particle induced plasma instabilities can be accomplished with both spatial and temporal resolution. Advantages include long pulse operation which can make possible very high signal to noise ratios and use of millimeter waves which maximizes the Doppler shifted scattered signal in WHz -1 and makes possible scattering angles up to 180 0 . Extraordinary mode scattering at approximately 60 and 200 GHz would be used in TFTR and CIT respectively, and 140 GHz ordinary mode scattering in JET. 8 refs., 1 fig

  10. Radiation-induced chromosomal instability

    Energy Technology Data Exchange (ETDEWEB)

    Ritter, S. [GSI, Biophysics, Darmstadt (Germany)

    1999-03-01

    Recent studies on radiation-induced chromosomal instability in the progeny of exposed mammalian cells were briefly described as well as other related studies. For the analysis of chromosomal damage in clones, cells were seeded directly after exposure in cell well-dish to form single cell clones and post-irradiation chromosome aberrations were scored. Both exposure to isoeffective doses of X-ray or 270 MeV/u C-ions (13 keV/{mu}m) increased the number of clones with abnormal karyotype and the increase was similar for X-ray and for C-ions. Meanwhile, in the progeny of cells for mass cultures, there was no indication of a delayed expression of chromosomal damage up to 40 population doublings after the exposure. A high number of aberrant cells were only observed directly after exposure to 10.7 MeV/u O-ions, i.e. in the first cycle cells and decreased with subsequent cell divisions. The reason for these differences in the radiation-induced chromosomal instability between clonal isolates and mass culture has not been clarified. Recent studies indicated that genomic instability occurs at a high frequency in the progeny of cells irradiated with both sparsely and densely ionizing radiation. Such genomic instability is thought likely to increase the risk of carcinogenesis, but more data are required for a well understanding of the health risks resulting from radiation-induced delayed instability. (M.N.)

  11. Instabilities and soot formation in spherically expanding, high pressure, rich, iso-octane-air flames

    Energy Technology Data Exchange (ETDEWEB)

    Lockett, R D [School of Engineering and Mathematical Sciences, City University, Northampton Square, London EC1V OHB (United Kingdom)

    2006-07-15

    Flame instabilities, cellular structures and soot formed in high pressure, rich, spherically expanding iso-octane-air flames have been studied experimentally using high speed Schlieren cinematography, OH fluorescence, Mie scattering and laser induced incandescence. Cellular structures with two wavelength ranges developed on the flame surface. The larger wavelength cellular structure was produced by the Landau-Darrieus hydrodynamic instability, while the short wavelength cellular structure was produced by the thermal-diffusive instability. Large negative curvature in the short wavelength cusps caused local flame quenching and fracture of the flame surface. In rich flames with equivalence ratio {phi} > 1.8, soot was formed in a honeycomb-like structure behind flame cracks associated with the large wavelength cellular structure induced by the hydrodynamic instability. The formation of soot precursors through low temperature pyrolysis was suggested as a suitable mechanism for the initiation of soot formation behind the large wavelength flame cracks.

  12. Hund's Induced Fermi-Liquid Instabilities and Enhanced Quasiparticle Interactions

    Science.gov (United States)

    de'Medici, Luca

    2017-04-01

    Hund's coupling is shown to generally favor, in a doped half-filled Mott insulator, an increase in the compressibility culminating in a Fermi-liquid instability towards phase separation. The largest effect is found near the frontier between an ordinary and an orbitally decoupled ("Hund's") metal. The increased compressibility implies an enhancement of quasiparticle scattering, thus favoring other possible symmetry breakings. This physics is shown to happen in simulations of the 122 Fe-based superconductors, possibly implying the relevance of this mechanism in the enhancement of the critical temperature for superconductivity.

  13. Pierce instability and bifurcating equilibria

    International Nuclear Information System (INIS)

    Godfrey, B.B.

    1981-01-01

    The report investigates the connection between equilibrium bifurcations and occurrence of the Pierce instability. Electrons flowing from one ground plane to a second through an ion background possess a countable infinity of static equilibria, of which only one is uniform and force-free. Degeneracy of the uniform and simplest non-uniform equilibria at a certain ground plan separation marks the onset of the Pierce instability, based on a newly derived dispersion relation appropriate to all the equilibria. For large ground plane separations the uniform equilibrium is unstable and the non-uniform equilibrium is stable, the reverse of their stability properties at small separations. Onset of the Pierce instability at the first bifurcation of equilibria persists in more complicated geometries, providing a general criterion for marginal stability. It seems probable that bifurcation analysis can be a useful tool in the overall study of stable beam generation in diodes and transport in finite cavities

  14. Microsatellite instability in bladder cancer

    DEFF Research Database (Denmark)

    Gonzalez-Zulueta, M; Ruppert, J M; Tokino, K

    1993-01-01

    Somatic instability at microsatellite repeats was detected in 6 of 200 transitional cell carcinomas of the bladder. Instabilities were apparent as changes in (GT)n repeat lengths on human chromosome 9 for four tumors and as alterations in a (CAG)n repeat in the androgen receptor gene on the X...... chromosome for three tumors. Single locus alterations were detected in three tumors, while three other tumors revealed changes in two or more loci. In one tumor we found microsatellite instability in all five loci analyzed on chromosome 9. The alterations detected were either minor 2-base pair changes...... or larger (> 2 base pairs) alterations in repeat length. All six tumors were low stage (Ta-T1), suggesting that these alterations can occur early in bladder tumorigenesis....

  15. Kinetic theory of tearing instability

    International Nuclear Information System (INIS)

    Hazeltine, R.D.; Dobrott, D.; Wang, T.S.

    1975-01-01

    The guiding-center kinetic equation with Fokker-Planck collision term is used to study, in cylindrical geometry, a class of dissipative instabilities of which the classical tearing mode is an archetype. Variational solution of the kinetic equation obviates the use of an approximate Ohm's law or adiabatic assumption, as used in previous studies, and it provides a dispersive relation which is uniformly valid for any ratio of wave frequency to collision frequency. One result of using the rigorous collision operator is the prediction of a new instability. This instability, driven by the electron temperature gradient, is predicted to occur under the long mean-free path conditions of present tokamak experiments, and has significant features in common with the kink-like oscillations observed in such experiments

  16. Telomere dysfunction and chromosome instability

    Energy Technology Data Exchange (ETDEWEB)

    Murnane, John P., E-mail: jmurnane@radonc.ucsf.edu [Department of Radiation Oncology, University of California San Francisco, 2340 Sutter Street, San Francisco, CA 94143-1331 (United States)

    2012-02-01

    The ends of chromosomes are composed of a short repeat sequence and associated proteins that together form a cap, called a telomere, that keeps the ends from appearing as double-strand breaks (DSBs) and prevents chromosome fusion. The loss of telomeric repeat sequences or deficiencies in telomeric proteins can result in chromosome fusion and lead to chromosome instability. The similarity between chromosome rearrangements resulting from telomere loss and those found in cancer cells implicates telomere loss as an important mechanism for the chromosome instability contributing to human cancer. Telomere loss in cancer cells can occur through gradual shortening due to insufficient telomerase, the protein that maintains telomeres. However, cancer cells often have a high rate of spontaneous telomere loss despite the expression of telomerase, which has been proposed to result from a combination of oncogene-mediated replication stress and a deficiency in DSB repair in telomeric regions. Chromosome fusion in mammalian cells primarily involves nonhomologous end joining (NHEJ), which is the major form of DSB repair. Chromosome fusion initiates chromosome instability involving breakage-fusion-bridge (B/F/B) cycles, in which dicentric chromosomes form bridges and break as the cell attempts to divide, repeating the process in subsequent cell cycles. Fusion between sister chromatids results in large inverted repeats on the end of the chromosome, which amplify further following additional B/F/B cycles. B/F/B cycles continue until the chromosome acquires a new telomere, most often by translocation of the end of another chromosome. The instability is not confined to a chromosome that loses its telomere, because the instability is transferred to the chromosome donating a translocation. Moreover, the amplified regions are unstable and form extrachromosomal DNA that can reintegrate at new locations. Knowledge concerning the factors promoting telomere loss and its consequences is

  17. Inelastic neutron scattering study of the Cs5H3(SO4)4 x 0.5H2O crystal and its deuterated analog

    International Nuclear Information System (INIS)

    Lushnikov, S.G.; Gvasaliya, S.N.; Belushkin, A.V.; Natcaniec, I.; Smirnov, L.S.; Dolbinina, V.V.; Shuvalov, L.A.

    1999-01-01

    Complete text of publication follows. Cs 5 H 3 (SO 4 ) 4 x 0.5H 2 O (PCTS) is a representative of superprotonic crystals, which have a dynamically disordered network of partially occupied hydrogen bonds in the high-temperature phase. Recent investigation of these crystals by Brillouin light scattering and neutron scattering revealed the isotopic effect: the disappearance of the high temperature phase transition in deuturated PCTS compound - Cs 5 D 3 (SO 4 ) 4 x 0.5D 2 O (DPCTS) [1]. For continuation these studies in the low temperature phase the inelastic neutron scattering (INS) was used. Experiments were carried out on NERA spectrometer (JINR, Dubna) on powdered samples of PCTS and DOTCS in the temperature range 20 - 30 K. The difference of diffraction spectra of PCTS and DPCTS with a different deuterium content was observed. Dependence of inelastic neutron scattering spectra versus deuterium concentration at different temperatures is discussed. (author)

  18. Political instability and illegal immigration.

    Science.gov (United States)

    Campos, J E; Lien, D

    1995-01-01

    "Economic theory suggests that transnational migration results from the push-pull effect of wage differentials between host and source countries. In this paper, we argue that political instability exacerbates the migration flow, with greater instability leading to relatively larger flows. We conclude then that an optimal solution to the illegal immigration problem requires proper coordination of immigration and foreign policies by the host country. A narrow preoccupation with tougher immigration laws is wasteful and may be marginally effective." Emphasis is on the United States as a host country. excerpt

  19. Stringy bounces and gradient instabilities

    CERN Document Server

    Giovannini, Massimo

    2017-01-01

    Bouncing solutions are obtained from a generally covariant action characterized by a potential which is a nonlocal functional of the dilaton field at two separated space-time points. Gradient instabilities are shown to arise in this context but they are argued to be nongeneric. After performing a gauge-invariant and frame-invariant derivation of the evolution equations of the fluctuations, a heuristic criterium for the avoidance of pathological instabilities is proposed and corroborated by a number of explicit examples that turn out to be compatible with a quasi-flat spectrum of curvature inhomogeneities for typical wavelengths larger than the Hubble radius.

  20. Helical instability in film blowing process: Analogy to buckling instability

    Science.gov (United States)

    Lee, Joo Sung; Kwon, Ilyoung; Jung, Hyun Wook; Hyun, Jae Chun

    2017-12-01

    The film blowing process is one of the most important polymer processing operations, widely used for producing bi-axially oriented film products in a single-step process. Among the instabilities observed in this film blowing process, i.e., draw resonance and helical motion occurring on the inflated film bubble, the helical instability is a unique phenomenon portraying the snake-like undulation motion of the bubble, having the period on the order of few seconds. This helical instability in the film blowing process is commonly found at the process conditions of a high blow-up ratio with too low a freezeline position and/or too high extrusion temperature. In this study, employing an analogy to the buckling instability for falling viscous threads, the compressive force caused by the pressure difference between inside and outside of the film bubble is introduced into the simulation model along with the scaling law derived from the force balance between viscous force and centripetal force of the film bubble. The simulation using this model reveals a close agreement with the experimental results of the film blowing process of polyethylene polymers such as low density polyethylene and linear low density polyethylene.

  1. Algebraic scattering theory and heavy ion scattering

    International Nuclear Information System (INIS)

    Allen, L.J.; Amos, K.; Berge, L.; Fiedeldey, H.

    1993-01-01

    Algebraic scattering theory is used to analyze elastic scattering cross-sections from heavy ion collisions. Collisions epitomized by strong absorption lead to algebraic potentials that can be described by simple exponential forms. But for collisions that are 'transparent', while asymptotically the algebraic potentials are exponential, their actual form (for low 1-values) is quite complex. 7 refs., 4 figs

  2. Implementation of the multireference Brillouin-Wigner and Mukherjee's coupled cluster methods with non-iterative triple excitations utilizing reference-level parallelism

    Czech Academy of Sciences Publication Activity Database

    Bhaskaran-Nair, Kiran; Brabec, Jiří; Apra, E.; van Dam, H. J. J.; Pittner, Jiří

    2012-01-01

    Roč. 137, č. 9 (2012), 094112 ISSN 0021-9606 R&D Projects: GA ČR GAP208/11/2222 Institutional support: RVO:61388955 Keywords : multireference methods * molecular applications * Brillouin-Wogner Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.164, year: 2012

  3. Application of Coupled-Wave Wentzel-Kramers-Brillouin Approximation to Ground Penetrating Radar

    OpenAIRE

    Igor Prokopovich; Alexei Popov; Lara Pajewski; Marian Marciniak

    2017-01-01

    This paper deals with bistatic subsurface probing of a horizontally layered dielectric half-space by means of ultra-wideband electromagnetic waves. In particular, the main objective of this work is to present a new method for the solution of the two-dimensional back-scattering problem arising when a pulsed electromagnetic signal impinges on a non-uniform dielectric half-space; this scenario is of interest for ground penetrating radar (GPR) applications. For the analytical description of the s...

  4. Neutron scattering from fractals

    DEFF Research Database (Denmark)

    Kjems, Jørgen; Freltoft, T.; Richter, D.

    1986-01-01

    The scattering formalism for fractal structures is presented. Volume fractals are exemplified by silica particle clusters formed either from colloidal suspensions or by flame hydrolysis. The determination of the fractional dimensionality through scattering experiments is reviewed, and recent small...

  5. Elastic magnetic electron scattering

    International Nuclear Information System (INIS)

    Sick, I.

    1985-01-01

    The paper surveys the field of elastic magnetic electron scattering. Magnetic scattering as a configuration analyzer; magnetic form factors of high multipole order; absolute spectroscopic factors; and non-nucleonic constituents; are all discussed. (U.K.)

  6. Size effects on cavitation instabilities

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2006-01-01

    In metal-ceramic systems the constraint on plastic flow leads to so high stress triaxialities that cavitation instabilities may occur. If the void radius is on the order of magnitude of a characteristic length for the metal, the rate of void growth is reduced, and the possibility of unstable cavi...... as the void grows to a size well above the characteristic material length....

  7. Modulational instability of nematic phase

    Indian Academy of Sciences (India)

    2014-02-08

    Feb 8, 2014 ... We numerically observe the effect of homogeneous magnetic field on the modulation- ally stable case ... irrespective of the magnetic field effect the uniaxial and biaxial nematic phases show modulational instability. ..... [13] J Kronjager, C Becker, P S Panahi, K Bongs and K Sengstock, Phys. Rev. Lett. 105 ...

  8. Parametric instabilities in magnetized plasmas

    International Nuclear Information System (INIS)

    Sanuki, H.; Schmidt, G.

    1976-02-01

    A theory is developed for parametric instabilities driven by a finite wavenumber general pump wave. This formalism is applied to describe lower hybrid decay into electromagnetic modes. A separate treatment is given for the all electrostatic wave case using the physically more transparent particle drift equations. In particular, the purely growing mode is studied

  9. Cinerama sickness and postural instability.

    Science.gov (United States)

    Bos, Jelte E; Ledegang, Wietse D; Lubeck, Astrid J A; Stins, John F

    2013-01-01

    Motion sickness symptoms and increased postural instability induced by motion pictures have been reported in a laboratory, but not in a real cinema. We, therefore, carried out an observational study recording sickness severity and postural instability in 19 subjects before, immediately and 45 min after watching a 1 h 3D aviation documentary in a cinema. Sickness was significantly larger right after the movie than before, and in a lesser extent still so after 45 min. The average standard deviation of the lateral centre of pressure excursions was significantly larger only right afterwards. When low-pass filtered at 0.1 Hz, lateral and for-aft excursions were both significantly larger right after the movie, while for-aft excursions then remained larger even after 45 min. Speculating on previous findings, we predict more sickness and postural instability in 3D than in 2D movies, also suggesting a possible, but yet unknown risk for work-related activities and vehicle operation. Watching motion pictures may be sickening and posturally destabilising, but effects in a cinema are unknown. We, therefore, carried out an observational study showing that sickness then is mainly an issue during the exposure while postural instability is an issue afterwards.

  10. Faraday instability in deformable domains

    International Nuclear Information System (INIS)

    Pucci, G.

    2013-01-01

    Hydrodynamical instabilities are usually studied either in bounded regions or free to grow in space. In this article we review the experimental results of an intermediate situation, in which an instability develops in deformable domains. The Faraday instability, which consists in the formation of surface waves on a liquid experiencing a vertical forcing, is triggered in floating liquid lenses playing the role of deformable domains. Faraday waves deform the lenses from the initial circular shape and the mutual adaptation of instability patterns with the lens boundary is observed. Two archetypes of behaviour have been found. In the first archetype a stable elongated shape is reached, the wave vector being parallel to the direction of elongation. In the second archetype the waves exceed the response of the lens border and no equilibrium shape is reached. The lens stretches and eventually breaks into fragments that have a complex dynamics. The difference between the two archetypes is explained by the competition between the radiation pressure the waves exert on the lens border and its response due to surface tension.

  11. Waves and instabilities in plasmas

    CERN Document Server

    Chen Liu

    1987-01-01

    The topics covered in these notes are selective and tend to emphasize more on kinetic-theory approaches to waves and instabilities in both uniform and non-uniform plasmas, students are assumed to have some basic knowledge of plasma dynamics in terms of single-particle and fluid descriptions.

  12. Lending sociodynamics and economic instability

    Science.gov (United States)

    Hawkins, Raymond J.

    2011-11-01

    We show how the dynamics of economic instability and financial crises articulated by Keynes in the General Theory and developed by Minsky as the Financial Instability Hypothesis can be formalized using Weidlich’s sociodynamics of opinion formation. The model addresses both the lending sentiment of a lender in isolation as well as the impact on that lending sentiment of the behavior of other lenders. The risk associated with lending is incorporated through a stochastic treatment of loan dynamics that treats prepayment and default as competing risks. With this model we are able to generate endogenously the rapid changes in lending opinion that attend slow changes in lending profitability and find these dynamics to be consistent with the rise and collapse of the non-Agency mortgage-backed securities market in 2007/2008. As the parameters of this model correspond to well-known phenomena in cognitive and social psychology, we can both explain why economic instability has proved robust to advances in risk measurement and suggest how policy for reducing economic instability might be formulated in an experimentally sound manner.

  13. Electron scattering from tetrahydrofuran

    International Nuclear Information System (INIS)

    Fuss, M C; Sanz, A G; García, G; Muñoz, A; Oller, J C; Blanco, F; Do, T P T; Brunger, M J; Almeida, D; Limão-Vieira, P

    2012-01-01

    Electron scattering from Tetrahydrofuran (C 4 H 8 O) was investigated over a wide range of energies. Following a mixed experimental and theoretical approach, total scattering, elastic scattering and ionization cross sections as well as electron energy loss distributions were obtained.

  14. Magnetic photon scattering

    International Nuclear Information System (INIS)

    Lovesey, S.W.

    1987-05-01

    The report reviews, at an introductory level, the theory of photon scattering from condensed matter. Magnetic scattering, which arises from first-order relativistic corrections to the Thomson scattering amplitude, is treated in detail and related to the corresponding interaction in the magnetic neutron diffraction amplitude. (author)

  15. Instability of counter-rotating stellar disks

    Science.gov (United States)

    Hohlfeld, R. G.; Lovelace, R. V. E.

    2015-09-01

    We use an N-body simulation, constructed using GADGET-2, to investigate an accretion flow onto an astrophysical disk that is in the opposite sense to the disk's rotation. In order to separate dynamics intrinsic to the counter-rotating flow from the impact of the flow onto the disk, we consider an initial condition in which the counter-rotating flow is in an annular region immediately exterior the main portion of the astrophysical disk. Such counter-rotating flows are seen in systems such as NGC 4826 (known as the "Evil Eye Galaxy"). Interaction between the rotating and counter-rotating components is due to two-stream instability in the boundary region. A multi-armed spiral density wave is excited in the astrophysical disk and a density distribution with high azimuthal mode number is excited in the counter-rotating flow. Density fluctuations in the counter-rotating flow aggregate into larger clumps and some of the material in the counter-rotating flow is scattered to large radii. Accretion flow processes such as this are increasingly seen to be of importance in the evolution of multi-component galactic disks.

  16. Singlet and triplet instability theorems

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, Tomonori; Hirata, So, E-mail: sohirata@illinois.edu [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan)

    2015-09-21

    A useful definition of orbital degeneracy—form-degeneracy—is introduced, which is distinct from the usual energy-degeneracy: Two canonical spatial orbitals are form-degenerate when the energy expectation value in the restricted Hartree–Fock (RHF) wave function is unaltered upon a two-electron excitation from one of these orbitals to the other. Form-degenerate orbitals tend to have isomorphic electron densities and occur in the highest-occupied and lowest-unoccupied molecular orbitals (HOMOs and LUMOs) of strongly correlated systems. Here, we present a mathematical proof of the existence of a triplet instability in a real or complex RHF wave function of a finite system in the space of real or complex unrestricted Hartree–Fock wave functions when HOMO and LUMO are energy- or form-degenerate. We also show that a singlet instability always exists in a real RHF wave function of a finite system in the space of complex RHF wave functions, when HOMO and LUMO are form-degenerate, but have nonidentical electron densities, or are energy-degenerate. These theorems provide Hartree–Fock-theory-based explanations of Hund’s rule, a singlet instability in Jahn–Teller systems, biradicaloid electronic structures, and a triplet instability during some covalent bond breaking. They also suggest (but not guarantee) the spontaneous formation of a spin density wave (SDW) in a metallic solid. The stability theory underlying these theorems extended to a continuous orbital-energy spectrum proves the existence of an oscillating (nonspiral) SDW instability in one- and three-dimensional homogeneous electron gases, but only at low densities or for strong interactions.

  17. Anomalous resonance-radiation energy-transfer rate in a scattering dispersive medium

    International Nuclear Information System (INIS)

    Shekhtman, V.L.

    1992-01-01

    This paper describes a generalization of the concept of group velocity as an energy-transfer rate in a dispersive medium with complex refractive index when the polaritons, which are energy carriers, undergo scattering, in contrast to the classical concept of the group velocity of free polaritons (i.e., without scattering in the medium). The concept of delay time from quantum multichannel-scattering, theory is used as the fundamental concept. Based on Maxwell's equations and the new mathematical Φ-function method, a consistent conceptual definition of group velocity in terms of the ratio of the coherent-energy flux density to the coherent-energy density is obtained for the first time, and a critical analysis of the earlier (Brillouin) understanding of energy-transfer rate is given in the light of radiation-trapping theory and the quantum theory of resonance scattering. The role of generalized group velocity is examined for the interpretation of the phenomenon of multiple resonance scattering, or radiation diffusion. The question of causality for the given problem is touched upon; a new relationship is obtained, called the microcausality condition, which limits the anomalous values of group velocity by way of the indeterminacy principle and the relativistic causality principle for macroscopic time intervals directly measurable in experiment, whereby attention is focused on the connection of the given microcausality condition and the well-known Wigner inequality for the time delay of spherical waves. 22 refs

  18. Method to map one-dimensional electronic wave function by using multiple Brillouin zone angle resolved photoemission

    Directory of Open Access Journals (Sweden)

    Dong-Wook Lee

    2010-10-01

    Full Text Available Angle resolved photoemission spectroscopy (ARPES is a powerful tool to investigate electronic structures in solids and has been widely used in studying various materials. The electronic structure information by ARPES is obtained in the momentum space. However, in the case of one-dimensional system, we here show that we extract the real space information from ARPES data taken over multiple Brillouin zones (BZs. Intensities in the multiple BZs are proportional to the photoemission matrix element which contains information on the coefficient of the Bloch wave function. It is shown that the Bloch wave function coefficients can be extracted from ARPES data, which allows us to construct the real space wave function. As a test, we use ARPES data from proto-typical one-dimensional system SrCuO2 and construct the real space wave function.

  19. Macro-Economic Instability and Crime

    OpenAIRE

    Guillaumont, Patrick; Puech, Frédéric

    2011-01-01

    This paper adds to the literature on the economic determinants of crime by examining the impact of macro-economic instability. Instability increases the frustration level of individuals and incites them to smooth their income by using illegal earnings. Results from a panel of developed and developing countries for the period 1980-97 suggests that macro-economic instability had a significant impact on crime, both homicide and robbery. However, homicide and robbery do not react to instability i...

  20. Kelvin-Helmholtz instability with mixing zone

    International Nuclear Information System (INIS)

    Chong-Techer, R.

    2008-01-01

    This thesis is part of the FATHER experiment and the analyze of the hydrodynamical instabilities which appear during the mixing of two liquids of same volume mass with shearing speed in the mixing zone. The aim is to understand the possible influence of a Kelvin-Helmholtz hydrodynamical instability with mixing zone, compared to classical Kelvin-Helmholtz instability with interface and with theoretical results of Rayleigh-Taylor instability. (A.L.B.)

  1. Nonlinear behavior of the radiative condensation instability

    International Nuclear Information System (INIS)

    McCarthy, D.; Drake, J.F.

    1991-01-01

    An investigation of the nonlinear behavior of the radiative condensation instability is presented in a simple one-dimensional magnetized plasma. It is shown that the radiative condensation is typically a nonlinear instability---the growth of the instability is stronger once the disturbance reaches finite amplitude. Moreover, classical parallel thermal conduction is insufficient by itself to saturate the instability. Radiative collapse continues until the temperature in the high density condensation falls sufficiently to reduce the radiation rate

  2. A general approach to optomechanical parametric instabilities

    International Nuclear Information System (INIS)

    Evans, M.; Barsotti, L.; Fritschel, P.

    2010-01-01

    We present a simple feedback description of parametric instabilities which can be applied to a variety of optical systems. Parametric instabilities are of particular interest to the field of gravitational-wave interferometry where high mechanical quality factors and a large amount of stored optical power have the potential for instability. In our use of Advanced LIGO as an example application, we find that parametric instabilities, if left unaddressed, present a potential threat to the stability of high-power operation.

  3. BOOK REVIEW: Instabilities in a confined plasma

    Science.gov (United States)

    Glasser, A. H.

    1999-05-01

    This is a large and important work by one of the leading Russian contributors to this subject. It covers topics of central importance to magnetic fusion energy research with a breadth, depth and clarity not found elsewhere. It is intended as a reference book and guide to the original literature for serious practitioners of the field. The book is divided into 8 large parts, listed below, and further subdivided into 31 chapters. The preface states, ``A need was identified to summarize the large amount of information on the topic of instabilities. This information is scattered throughout many papers on certain special subjects on the theory of toroidal-plasma instabilities. This book aims to treat it from a unified point of view.'' This is a good description of the aims and approach. The range of topics is large and the treatment deep and thorough. This is often accomplished by assuming considerable knowledge on the part of the reader, most appropriate for mature researchers in the field. The pace is fast. The requisite background includes extensive knowledge of a wide range of physics, ordinary and partial differential equations, integral equations, differential geometry and special functions. The preface also states, ``The author starts with the fundamental principles, so that no special knowledge of plasma physics is necessary before reading the book. It will therefore be useful for researchers, postgraduates, high-school teachers and students specializing in plasma physics and controlled fusion.'' In the opinion of this reviewer, that may be overly ambitious. The terse approach, characteristic of the whole book, as well as the steep price, would make it rather challenging for such an audience. For example, in the opening chapter, `General results of equilibrium theory', the properties of non-orthogonal, curvilinear co-ordinates are stated tersely without much explanation or derivation, more as a review than a first presentation. It is common for physics students

  4. Observation of Parametric Instability in Advanced LIGO.

    Science.gov (United States)

    Evans, Matthew; Gras, Slawek; Fritschel, Peter; Miller, John; Barsotti, Lisa; Martynov, Denis; Brooks, Aidan; Coyne, Dennis; Abbott, Rich; Adhikari, Rana X; Arai, Koji; Bork, Rolf; Kells, Bill; Rollins, Jameson; Smith-Lefebvre, Nicolas; Vajente, Gabriele; Yamamoto, Hiroaki; Adams, Carl; Aston, Stuart; Betzweiser, Joseph; Frolov, Valera; Mullavey, Adam; Pele, Arnaud; Romie, Janeen; Thomas, Michael; Thorne, Keith; Dwyer, Sheila; Izumi, Kiwamu; Kawabe, Keita; Sigg, Daniel; Derosa, Ryan; Effler, Anamaria; Kokeyama, Keiko; Ballmer, Stefan; Massinger, Thomas J; Staley, Alexa; Heinze, Matthew; Mueller, Chris; Grote, Hartmut; Ward, Robert; King, Eleanor; Blair, David; Ju, Li; Zhao, Chunnong

    2015-04-24

    Parametric instabilities have long been studied as a potentially limiting effect in high-power interferometric gravitational wave detectors. Until now, however, these instabilities have never been observed in a kilometer-scale interferometer. In this Letter, we describe the first observation of parametric instability in a gravitational wave detector, and the means by which it has been removed as a barrier to progress.

  5. Multifragmentation: Surface instabilities or statistical decay

    International Nuclear Information System (INIS)

    Moretto, L.G.; Tso, K.; Delis, D.; Colonna, N.; Wozniak, G.J.

    1992-11-01

    Boltzmann-Nordheim-Vlasov calculations show multifragmentation that seems to originate from surface instabilities. These instabilities are traced to a sheet instability caused by the proximity interaction. Experimental data, on the other hand, suggest that multifragmentation may be dominated by phase space

  6. Multifragmentation: surface instabilities or statistical decay?

    International Nuclear Information System (INIS)

    Moretto, L.G.; Tso, K.; Delis, D.; Colonna, N.; Wozniak, G.J.

    1993-01-01

    Boltzmann-Nordheim-Vlasov calculations show multifragmentation that seems to originate from surface instabilities. These instabilities are traced to a sheet instability caused by the proximity interaction. Experimental data, on the other hand, suggest that multifragmentation may be dominated by phase space. (author)

  7. Multifragmentation: surface instabilities or statistical decay

    Energy Technology Data Exchange (ETDEWEB)

    Moretto, L.G.; Tso, K.; Delis, D.; Colonna, N.; Wozniak, G.J. (Lawrence Berkeley Lab., Berkeley, CA (United States). Nuclear Science Div.)

    1993-01-01

    Boltzmann-Nordheim-Vlasov calculations show multifragmentation that seems to originate from surface instabilities. These instabilities are traced to a sheet instability caused by the proximity interaction. Experimental data, on the other hand, suggest that multifragmentation may be dominated by phase space. (author).

  8. Multifragmentation: Surface instabilities or statistical decay?

    Science.gov (United States)

    Moretto, L. G.; Tso, K.; Delis, D.; Colonna, N.; Wozniak, G. J.

    Boltzmann-Nordheim-Vlasov calculations show multifragmentation that seems to originate from surface instabilities. These instabilities are traced to a sheet instability caused by the proximity interaction. Experimental data, on the other hand, suggest that multifragmentation may be dominated by phase space.

  9. Multifragmentation: Surface instabilities or statistical decay

    Energy Technology Data Exchange (ETDEWEB)

    Moretto, L.G.; Tso, K.; Delis, D.; Colonna, N.; Wozniak, G.J.

    1992-11-01

    Boltzmann-Nordheim-Vlasov calculations show multifragmentation that seems to originate from surface instabilities. These instabilities are traced to a sheet instability caused by the proximity interaction. Experimental data, on the other hand, suggest that multifragmentation may be dominated by phase space.

  10. Drying paint: from micro-scale dynamics to mechanical instabilities

    Science.gov (United States)

    Goehring, Lucas; Li, Joaquim; Kiatkirakajorn, Pree-Cha

    2017-04-01

    Charged colloidal dispersions make up the basis of a broad range of industrial and commercial products, from paints to coatings and additives in cosmetics. During drying, an initially liquid dispersion of such particles is slowly concentrated into a solid, displaying a range of mechanical instabilities in response to highly variable internal pressures. Here we summarize the current appreciation of this process by pairing an advection-diffusion model of particle motion with a Poisson-Boltzmann cell model of inter-particle interactions, to predict the concentration gradients in a drying colloidal film. We then test these predictions with osmotic compression experiments on colloidal silica, and small-angle X-ray scattering experiments on silica dispersions drying in Hele-Shaw cells. Finally, we use the details of the microscopic physics at play in these dispersions to explore how two macroscopic mechanical instabilities-shear-banding and fracture-can be controlled. This article is part of the themed issue 'Patterning through instabilities in complex media: theory and applications.'

  11. Gravitational instability in higher dimensions

    Science.gov (United States)

    Gibbons, Gary; Hartnoll, Sean A.

    2002-09-01

    We explore a classical instability of spacetimes of dimension D>4. First, we consider static solutions: generalized black holes and brane world metrics. The dangerous mode is a tensor mode on an Einstein base manifold of dimension D-2. A criterion for instability is found for the generalized Schwarzschild, AdS-Schwarzschild and topological black hole spacetimes in terms of the Lichnerowicz spectrum on the base manifold. Secondly, we consider perturbations in time-dependent solutions: Generalized dS and AdS. Thirdly we show that, subject to the usual limitations of a linear analysis, any Ricci flat spacetime may be stabilized by embedding into a higher dimensional spacetime with cosmological constant. We apply our results to pure AdS black strings. Finally, we study the stability of higher dimensional ``bubbles of nothing.''

  12. Feedback control of resistive instabilities

    International Nuclear Information System (INIS)

    White, R.B.; Rutherford, P.H.; Furth, H.P.; Park, W.; Chen, L.

    1985-12-01

    Resistive instabilities are responsible for much of the global behavior and the determination of the possible domains of operation of tokamaks. Their successful control could have definite advantages, even making available new regimes of operation. Elimination of sawtoothing might allow operation with higher currents and more peaked current profiles, with q on axis well below unity. In this work different feedback schemes are explored. Simple analytical derivations of the effects of local heating and current drive feedback are presented. Although control of modes with m greater than or equal to 2 is fairly straightforward, the control of the m = 1 mode is more difficult because of its proximity to ideal instability. The most promising scheme utilizes high energy trapped particles. 20 refs., 3 figs

  13. Nonlinear evolution of drift instabilities

    International Nuclear Information System (INIS)

    Lee, W.W.; Krommes, J.A.; Oberman, C.R.; Smith, R.A.

    1984-01-01

    The nonlinear evolution of collisionless drift instabilities in a shear-free magnetic field has been studied by means of gyrokinetic particle simulation as well as numerical integration of model mode-coupling equations. The purpose of the investigation is to identify relevant nonlinear mechanisms responsible for the steady-state drift wave fluctuations. It is found that the saturation of the instability is mainly caused by the nonlinear E x B convection of the resonant electrons and their associated velocity space nonlinearity. The latter also induces energy exchange between the competing modes, which, in turn, gives rise to enhanced diffusion. The nonlinear E x B convection of the ions, which contributes to the nonlinear frequency shift, is also an important ingredient for the saturation

  14. Fluctuations and Instability in Sedimentation

    KAUST Repository

    Guazzelli, Élisabeth

    2011-01-21

    This review concentrates on the fluctuations of the velocities of sedimenting spheres, and on the structural instability of a suspension of settling fibers. For many years, theoretical estimates and numerical simulations predicted the fluctuations of the velocities of spheres to increase with the size of the container, whereas experiments found no such variation. Two ideas have increased our understanding. First, the correlation length of the velocity fluctuations was found experimentally to be 20 interparticle separations. Second, in dilute suspensions, a vertical variation in the concentration due to the spreading of the front with the clear fluid can inhibit the velocity fluctuations. In a very dilute regime, a homogeneous suspension of fibers suffers a spontaneous instability in which fast descending fiber-rich columns are separated by rising fiber-sparse columns. In a semidilute regime, the settling is hindered, more so than for spheres. © 2011 by Annual Reviews. All rights reserved.

  15. Modulational instability of coupled waves

    International Nuclear Information System (INIS)

    McKinstrie, C.J.; Bingham, R.

    1989-01-01

    The collinear propagation of an arbitrary number of finite-amplitude waves is modeled by a system of coupled nonlinear Schroedinger equations; one equation for each complex wave amplitude. In general, the waves are modulationally unstable with a maximal growth rate larger than the modulational growth rate of any wave alone. Moreover, waves that are modulationally stable by themselves can be driven unstable by the nonlinear coupling. The general theory is then applied to the relativistic modulational instability of two laser beams in a beat-wave accelerator. For parameters typical of a proposed beat-wave accelerator, this instability can seriously distort the incident laser pulse shapes on the particle-acceleration time scale, with detrimental consequences for particle acceleration

  16. Electromagnetic theory of the radiative Pierce instability

    International Nuclear Information System (INIS)

    Klochkov, D.N.; Rukhadze, A.A.

    1997-01-01

    A study is made of the radiative Pierce instability of a relativistic electron beam propagating in a waveguide in the presence of an infinitely strong magnetic field. The perturbation theory is used to find the growth rates and conditions of instability over a broad range of the beam current. It is shown that, under the Pierce boundary conditions, the instability is Raman in nature, and there is no current threshold for the instability. This allows the instability saturation level to be accurately determined from the condition for the violation of the Cherenkov resonance and the radiation efficiency to be estimated

  17. Instability of colliding metastable strings

    Energy Technology Data Exchange (ETDEWEB)

    Hiramatsu, Takashi [Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics; Eto, Minoru [Yamagata Univ. (Japan). Dept. of Physics; Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics; Ookouchi, Yutaka [Kyoto Univ. (Japan). Dept. of Physics; Kyoto Univ. (Japan). The Hakubi Center for Advanced Research

    2013-04-15

    We investigate the collision dynamics of two metastable strings which can be viewed as tube-like domain walls with winding numbers interpolating a false vacuum and a true vacuum. We find that depending on the relative angle and speed of two strings, instability of strings increases and the false vacuum is filled out by rapid expansion of the strings or of a remnant of the collision.

  18. Symmetric instability of monsoon flows

    OpenAIRE

    Krishnakumar, V.; Lau, K.-M.

    2011-01-01

    Using a zonally symmetric multi-level moist linear model, we have examined the possibility of symmetric instability in the monsoon region. Stability analyses with a zonally symmetric model using monthly ECMWF (Jan – Dec) zonal basic flows revealed both unstable as well as neutral modes. In the absence of cumulus heating, the linear stability of the monsoon flow changes dramatically with the emergence of many unstable modes in the month of May and lasting through August; whereas with the inclu...

  19. Laser driven hydrodynamic instability experiments

    International Nuclear Information System (INIS)

    Remington, B.A.; Weber, S.V.; Haan, S.W.; Kilkenny, J.D.; Glendinning, S.G.; Wallace, R.J.; Goldstein, W.H.; Wilson, B.G.; Nash, J.K.

    1993-01-01

    An extensive series of experiments has been conducted on the Nova laser to measure hydrodynamic instabilities in planar foils accelerated by x-ray ablation. Single mode experiments allow a measurement of the fundamental growth rates from the linear well into the nonlinear regime. Two-mode foils allow a first direct observation of mode coupling. Surface-finish experiments allow a measurement of the evolution of a broad spectrum of random initial modes

  20. Combustion instability modeling and analysis

    Energy Technology Data Exchange (ETDEWEB)

    Santoro, R.J.; Yang, V.; Santavicca, D.A. [Pennsylvania State Univ., University Park, PA (United States); Sheppard, E.J. [Tuskeggee Univ., Tuskegee, AL (United States). Dept. of Aerospace Engineering

    1995-12-31

    It is well known that the two key elements for achieving low emissions and high performance in a gas turbine combustor are to simultaneously establish (1) a lean combustion zone for maintaining low NO{sub x} emissions and (2) rapid mixing for good ignition and flame stability. However, these requirements, when coupled with the short combustor lengths used to limit the residence time for NO formation typical of advanced gas turbine combustors, can lead to problems regarding unburned hydrocarbons (UHC) and carbon monoxide (CO) emissions, as well as the occurrence of combustion instabilities. The concurrent development of suitable analytical and numerical models that are validated with experimental studies is important for achieving this objective. A major benefit of the present research will be to provide for the first time an experimentally verified model of emissions and performance of gas turbine combustors. The present study represents a coordinated effort between industry, government and academia to investigate gas turbine combustion dynamics. Specific study areas include development of advanced diagnostics, definition of controlling phenomena, advancement of analytical and numerical modeling capabilities, and assessment of the current status of our ability to apply these tools to practical gas turbine combustors. The present work involves four tasks which address, respectively, (1) the development of a fiber-optic probe for fuel-air ratio measurements, (2) the study of combustion instability using laser-based diagnostics in a high pressure, high temperature flow reactor, (3) the development of analytical and numerical modeling capabilities for describing combustion instability which will be validated against experimental data, and (4) the preparation of a literature survey and establishment of a data base on practical experience with combustion instability.

  1. Kinetic instabilities in plasmas: from electromagnetic fluctuations to collisionless shocks

    International Nuclear Information System (INIS)

    Ruyer, Charles

    2014-01-01

    Collisionless shocks play a major role in powerful astrophysical objects (e.g., gamma-ray bursts, supernova remnants, pulsar winds, etc.), where they are thought to be responsible for non-thermal particle acceleration and radiation. Numerical simulations have shown that, in the absence of an external magnetic field, these self-organizing structures originate from electromagnetic instabilities triggered by high-velocity colliding flows. These Weibel-like instabilities are indeed capable of producing the magnetic turbulence required for both efficient scattering and Fermi-type acceleration. Along with rapid advances in their theoretical understanding, intense effort is now underway to generate collisionless shocks in the laboratory using energetic lasers. In a first part we study the (w,k)-resolved electromagnetic thermal spectrum sustained by a drifting relativistic plasma. In particular, we obtain analytical formulae for the fluctuation spectra, the latter serving as seeds for growing magnetic modes in counterstreaming plasmas. Distinguishing between sub-luminal and supra-luminal thermal fluctuations, we derived analytical formulae of their respective spectral contributions. Comparisons with particle-in-cell (PIC) simulations are made, showing close agreement in the sub-luminal regime along with some discrepancy in the supra-luminal regime. Our formulae are then used to estimate the saturation time of the Weibel instability of relativistic pair plasmas. Our predictions are shown to match 2-D particle-in-cell (PIC) simulations over a three-decade range in flow energy. We then develop a predictive kinetic model of the nonlinear phase of the Weibel instability induced by two counter-streaming, symmetric and non-relativistic ion beams. This self consistent, fully analytical model allows us to follow the evolution of the beams' properties up to a stage close to complete isotropization and thus to shock formation. Its predictions are supported by 2D and 3D particle

  2. Hydrodynamic instabilities in miscible fluids

    Science.gov (United States)

    Truzzolillo, Domenico; Cipelletti, Luca

    2018-01-01

    Hydrodynamic instabilities in miscible fluids are ubiquitous, from natural phenomena up to geological scales, to industrial and technological applications, where they represent the only way to control and promote mixing at low Reynolds numbers, well below the transition from laminar to turbulent flow. As for immiscible fluids, the onset of hydrodynamic instabilities in miscible fluids is directly related to the physics of their interfaces. The focus of this review is therefore on the general mechanisms driving the growth of disturbances at the boundary between miscible fluids, under a variety of forcing conditions. In the absence of a regularizing mechanism, these disturbances would grow indefinitely. For immiscible fluids, interfacial tension provides such a regularizing mechanism, because of the energy cost associated to the creation of new interface by a growing disturbance. For miscible fluids, however, the very existence of interfacial stresses that mimic an effective surface tension is debated. Other mechanisms, however, may also be relevant, such as viscous dissipation. We shall review the stabilizing mechanisms that control the most common hydrodynamic instabilities, highlighting those cases for which the lack of an effective interfacial tension poses deep conceptual problems in the mathematical formulation of a linear stability analysis. Finally, we provide a short overview on the ongoing research on the effective, out of equilibrium interfacial tension between miscible fluids.

  3. Hydrodynamic instabilities in miscible fluids.

    Science.gov (United States)

    Truzzolillo, Domenico; Cipelletti, Luca

    2018-01-24

    Hydrodynamic instabilities in miscible fluids are ubiquitous, from natural phenomena up to geological scales, to industrial and technological applications, where they represent the only way to control and promote mixing at low Reynolds numbers, well below the transition from laminar to turbulent flow. As for immiscible fluids, the onset of hydrodynamic instabilities in miscible fluids is directly related to the physics of their interfaces. The focus of this review is therefore on the general mechanisms driving the growth of disturbances at the boundary between miscible fluids, under a variety of forcing conditions. In the absence of a regularizing mechanism, these disturbances would grow indefinitely. For immiscible fluids, interfacial tension provides such a regularizing mechanism, because of the energy cost associated to the creation of new interface by a growing disturbance. For miscible fluids, however, the very existence of interfacial stresses that mimic an effective surface tension is debated. Other mechanisms, however, may also be relevant, such as viscous dissipation. We shall review the stabilizing mechanisms that control the most common hydrodynamic instabilities, highlighting those cases for which the lack of an effective interfacial tension poses deep conceptual problems in the mathematical formulation of a linear stability analysis. Finally, we provide a short overview on the ongoing research on the effective, out of equilibrium interfacial tension between miscible fluids.

  4. Study of three-mode parametric instability

    International Nuclear Information System (INIS)

    Liang Fengchao; Zhao Chunnong; Gras, Slawomir; Ju Li; Blair, D G

    2010-01-01

    The effect of parametric instability in advanced interferometric gravitational wave detectors is a potential problem for their proper operation. Great efforts have been made to study the onset of parametric instabilities and to find ways to control them. Here we present an experimental design for studying parametric instability in a 72 m cavity with suspended high quality fused silica mirrors. With 5 W input power and 20 kW circulation power inside the cavity, it is predicted that parametric instability will occur. The resonant condition of parametric instability can be met by thermally tuning the radius of curvature of a test mass. We will present simulation results of parametric gains for different radii of curvature of a test mass. The simulation results will provide the basis for designing the thermal tuning and observation parametric instability experiments. This will provide a test bed for studying parametric instability and its control for next generation detectors.

  5. Introduction to neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, W.E. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1996-11-01

    We give here an introduction to the theoretical principles of neutron scattering. The relationship between scattering- and correlation-functions is particularly emphasized. Within the framework of linear response theory (justified by the weakness of the basic interaction) the relation between fluctuation and dissipation is discussed. This general framework explains the particular power of neutron scattering as an experimental method. (author) 4 figs., 4 refs.

  6. Mechanical spectra of glass-forming liquids. II. Gigahertz-frequency longitudinal and shear acoustic dynamics in glycerol and DC704 studied by time-domain Brillouin scattering

    DEFF Research Database (Denmark)

    Klieber, Christoph; Hecksher, Tina; Pezeril, Thomas

    2013-01-01

    This paper presents and discusses the temperature and frequency dependence of the longitudinal and shear viscoelastic response at MHz and GHz frequencies of the intermediate glass former glycerol and the fragile glass former tetramethyl-tetraphenyl-trisiloxane (DC704). Measurements were performed...... of the shear acoustic relaxation time agrees well with literature data for dielectric measurements. In DC704, combining the new data with data from measurements obtained previously by piezo-ceramic transducers yields figures showing the longitudinal and shear sound velocities at frequencies from mHz to GHz...

  7. Elastic scattering phenomenology

    Energy Technology Data Exchange (ETDEWEB)

    Mackintosh, R.S. [The Open University, School of Physical Sciences, Milton Keynes (United Kingdom)

    2017-04-15

    We argue that, in many situations, fits to elastic scattering data that were historically, and frequently still are, considered ''good'', are not justifiably so describable. Information about the dynamics of nucleon-nucleus and nucleus-nucleus scattering is lost when elastic scattering phenomenology is insufficiently ambitious. It is argued that in many situations, an alternative approach is appropriate for the phenomenology of nuclear elastic scattering of nucleons and other light nuclei. The approach affords an appropriate means of evaluating folding models, one that fully exploits available empirical data. It is particularly applicable for nucleons and other light ions. (orig.)

  8. Quantum theory of scattering

    CERN Document Server

    Wu Ta You

    1962-01-01

    This volume addresses the broad formal aspects and applications of the quantum theory of scattering in atomic and nuclear collisions. An encyclopedic source of pioneering work, it serves as a text for students and a reference for professionals in the fields of chemistry, physics, and astrophysics. The self-contained treatment begins with the general theory of scattering of a particle by a central field. Subsequent chapters explore particle scattering by a non-central field, collisions between composite particles, the time-dependent theory of scattering, and nuclear reactions. An examinati

  9. Customized finite difference Maxwell solver for elimination of numerical Cherenkov instability in EM-PIC code

    Science.gov (United States)

    Yu, Peicheng; Li, Fei; Dalichaouch, Thamine; Fiuza, Frederico; Decyk, Viktor; Davidson, Asher; Tableman, Adam; An, Weiming; Tsung, Frank; Fonseca, Ricardo; Lu, Wei; Vieira, Jorge; Silva, Luis; Mori, Warren

    2016-10-01

    we present a finite-difference-time-domain (FDTD) Maxwell solver for the particle-in-cell (PIC) algorithm, which is customized to effectively eliminate the numerical Cerenkov instability (NCI) which arises when a plasma (neutral or non-neutral) relativistically drifts on a grid when using the PIC algorithm. We control the EM dispersion curve in the direction of the plasma drift of a FDTD Maxwell solver by using a customized higher order finite difference operator for the spatial derivative along the direction of the drift (1& circ; direction). We show that this eliminates the main NCI modes with moderate | k1 | , while keeps additional main NCI modes well outside the range of physical interest with higher | k1 | . These main NCI modes can be easily filtered out along with first spatial aliasing NCI modes which are also at the edge of the fundamental Brillouin zone. The customized solver has the possible advantage of improved parallel scalability because it can be easily partitioned along 1& circ; which typically has many more cells than other directions for the problems of interest.

  10. Detection of 2-mm-long strained section in silica fiber using slope-assisted Brillouin optical correlation-domain reflectometry

    Science.gov (United States)

    Lee, Heeyoung; Mizuno, Yosuke; Nakamura, Kentaro

    2018-02-01

    Slope-assisted Brillouin optical correlation-domain reflectometry is a single-end-access distributed Brillouin sensing technique with high spatial resolution and high-speed operation. We have recently discovered its unique feature, that is, strained or heated sections even shorter than nominal resolution can be detected, but its detailed characterization has not been carried out. Here, after experimentally characterizing this “beyond-nominal-resolution” effect, we show its usefulness by demonstrating the detection of a 2-mm-long strained section along a silica fiber. We also demonstrate the detection of a 5-mm-long heated section along a polymer optical fiber. The lengths of these detected sections are smaller than those of the other demonstrations reported so far.

  11. Modes of storage ring coherent instabilities

    International Nuclear Information System (INIS)

    Wang, J.M.

    1986-12-01

    Longitudinal impedance in a beam and various modes of longitudinal coherent instabilities are discussed. The coasting beam coherent instability, microwave instability, and single-bunch longitudinal coherent instabilities are considered. The Vlasov equation is formulated, and a method of solving it is developed. The synchrotron modes are treated, which take the possible bunch shape distortion fully into consideration. A method of treating the synchrotron mode coupling in the case of a small bunch is discussed which takes advantage of the fact that only a few of the synchrotron modes can contribute in such a case. The effect of many bunches on the coherent motion of the beam and the longitudinal symmetric coupled bunch modes are discussed. The transverse impedance is then introduced, and the transverse coasting beam instability is discussed. Various bunched beam instabilities are discussed, including both single bunch instabilities and coupled bunch instabilities. The Vlasov equation for transverse as well as longitudinal motion of particles is introduced as well as a method of solving it within a linear approximation. Head-tail modes and short bunch instabilities and strong coupling instabilities in the long bunch case are covered

  12. Modes of storage ring coherent instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J.M.

    1986-12-01

    Longitudinal impedance in a beam and various modes of longitudinal coherent instabilities are discussed. The coasting beam coherent instability, microwave instability, and single-bunch longitudinal coherent instabilities are considered. The Vlasov equation is formulated, and a method of solving it is developed. The synchrotron modes are treated, which take the possible bunch shape distortion fully into consideration. A method of treating the synchrotron mode coupling in the case of a small bunch is discussed which takes advantage of the fact that only a few of the synchrotron modes can contribute in such a case. The effect of many bunches on the coherent motion of the beam and the longitudinal symmetric coupled bunch modes are discussed. The transverse impedance is then introduced, and the transverse coasting beam instability is discussed. Various bunched beam instabilities are discussed, including both single bunch instabilities and coupled bunch instabilities. The Vlasov equation for transverse as well as longitudinal motion of particles is introduced as well as a method of solving it within a linear approximation. Head-tail modes and short bunch instabilities and strong coupling instabilities in the long bunch case are covered. (LEW)

  13. Regularization of instabilities in gravity theories

    Science.gov (United States)

    Ramazanoǧlu, Fethi M.

    2018-01-01

    We investigate instabilities and their regularization in theories of gravitation. Instabilities can be beneficial since their growth often leads to prominent observable signatures, which makes them especially relevant to relatively low signal-to-noise ratio measurements such as gravitational wave detections. An indefinitely growing instability usually renders a theory unphysical; hence, a desirable instability should also come with underlying physical machinery that stops the growth at finite values, i.e., regularization mechanisms. The prototypical gravity theory that presents such an instability is the spontaneous scalarization phenomena of scalar-tensor theories, which feature a tachyonic instability. We identify the regularization mechanisms in this theory and show that they can be utilized to regularize other instabilities as well. Namely, we present theories in which spontaneous growth is triggered by a ghost rather than a tachyon and numerically calculate stationary solutions of scalarized neutron stars in these theories. We speculate on the possibility of regularizing known divergent instabilities in certain gravity theories using our findings and discuss alternative theories of gravitation in which regularized instabilities may be present. Even though we study many specific examples, our main point is the recognition of regularized instabilities as a common theme and unifying mechanism in a vast array of gravity theories.

  14. Production of (3/2) ω0 light by the two-plasmon decay instability

    International Nuclear Information System (INIS)

    Villeneuve, D.M.; Baldis, H.A.; Walsh, C.J.

    1985-01-01

    Measurements of the emission of (3/2) ω 0 light from CO 2 laser plasma interactions are described. The target was an underdense preformed plasma with a relatively long density scalelength. Comparisons are made between the (3/2) ω 0 emission and the spectrum of plasma waves driven by the two-plasmon decay instability as measured by Thomson scattering techniques. The spectrum of (3/2) ω 0 light is shown as a function of scattering angle and compared with the relevant theories. Strong modulation of the spectrum was seen and is ascribed to the production of short-wavelength ion waves by the plasma waves

  15. Continuous Transition between Brillouin-Wigner and Rayleigh-Schrödinger Perturbation Theory, Generalized Bloch Equation, and Hilbert Space Multireference Coupled Cluster

    Czech Academy of Sciences Publication Activity Database

    Pittner, Jiří

    2003-01-01

    Roč. 118, č. 24 (2003), s. 10876-10889 ISSN 0021-9606 R&D Projects: GA MŠk OC D23.001; GA ČR GA203/99/D009; GA AV ČR IAA4040108 Institutional research plan: CEZ:AV0Z4040901 Keywords : continuous transition * Brillouin-Wigner * Rayleigh-Schrödinger Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.950, year: 2003

  16. Microbunch Instability Theory and Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Stupakov, G.

    2005-01-26

    Over the last years there have been several reports of quasiperiodic bursts of coherent synchrotron radiation (CSR) in electron rings in the microwave and far-infrared range. The observations were made on synchrotron radiation light sources which include the Synchrotron Ultraviolet Radiation Facility SURF II [1], the VUV ring at the National Synchrotron Light Source at BNL [2, 3], second generation light sources MAX-I [4], BESSY II [5], and ALS [6]. General features of those observations can be summarized as follows. Above a threshold current, there is a strongly increased radiation of the beam in the range of wavelengths shorter than the bunch length, {lambda} < {sigma}{sub 2}. At large currents, this radiation is observed as a sequence of random bursts. In the bursting regime, intensity of the radiation scales approximately as square of the number of particles in the bunch, indicating a coherent nature of the phenomenon. It is generally accepted that the source of this radiation is related to the microbunching of the beam arising from development of a microwave instability caused by the coherent synchrotron radiation of the beam. A relativistic electron beam moving in a circular orbit in free space can radiate coherently if the wavelength of the synchrotron radiation exceeds the length of the bunch. In accelerators coherent radiation of the bunch is usually suppressed by the shielding effect of the conducting walls of the vacuum chamber [7-9], which gives an exponential cutoff of wavelengths greater than a certain threshold. However, an initial density fluctuation with a characteristic length much shorter than the shielding threshold would radiate coherently. If the radiation reaction force is such that it results in the growth of the initial fluctuation one can expect an instability that leads to micro-bunching of the beam and an increased coherent radiation at short wavelengths. A possibility of CSR instability was pointed out in Refs. [10, 11].

  17. Laser driven hydrodynamic instability experiments

    International Nuclear Information System (INIS)

    Remington, B.A.; Weber, S.V.; Haan, S.W.; Kilkenny, J.D.; Glendinning, S.G.; Wallace, R.J.; Goldstein, W.H.; Wilson, B.G.; Nash, J.K.

    1992-01-01

    We have conducted an extensive series of experiments on the Nova laser to measure hydrodynamic instabilities in planar foils accelerated by x-ray ablation. Single mode experiments allow a measurement of the fundamental growth rates from the linear well into the nonlinear regime; multimode foils allow an assessment of the degree of mode coupling; and surface-finish experiments allow a measurement of the evolution of a broad spectrum of random initial modes. Experimental results and comparisons with theory and simulations are presented

  18. Sheet Beam Klystron Instability Analysis

    International Nuclear Information System (INIS)

    Bane, K.

    2009-01-01

    Using the principle of energy balance we develop a 2D theory for calculating growth rates of instability in a two-cavity model of a sheet beam klystron. An important ingredient is a TE-like mode in the gap that also gives a longitudinal kick to the beam. When compared with a self-consistent particle-in-cell calculation, with sheet beam klystron-type parameters, agreement is quite good up to half the design current, 65 A; at full current, however, other, current-dependent effects come in and the results deviate significantly

  19. Dynamic Instability of Barlike Modes

    Science.gov (United States)

    Durisen, Richard H.; Pickett, Brian K.; Bate, Matthew R.; Imamura, James N.; Brandl, Andreas; Sterzik, Michael F.

    Numerical simulations during the 1980's established that prompt binary formation (or ``fission'') through dynamic growth of barlike modes is aborted by gravitational torques. Because these instabilities may occur during star formation and because their outcome over long times is still uncertain, we have combined various linear analyses with simulations by hydrodynamics codes to refine our understanding. We show that it is in fact the torques which cause nonlinear saturation of the mode amplitude. Excellent agreement for the early nonlinear phase is obtained using radically different hydrodynamics codes. However, the ultimate outcome is sensitive to assumptions about dissipative heating and is also somewhat code-dependent.

  20. Risk bubbles and market instability

    Science.gov (United States)

    Marsili, Matteo; Raffaelli, Giacomo

    2006-10-01

    We discuss a simple model of correlated assets capturing the feedback effects induced by portfolio investment in the covariance dynamics. This model predicts an instability when the volume of investment exceeds a critical value. Close to the critical point the model exhibits dynamical correlations very similar to those observed in real markets. Maximum likelihood estimates of the model's parameter for empirical data indeed confirms this conclusion. We show that this picture is confirmed by the empirical analysis for different choices of the time horizon.

  1. Neutron scattering from fractals

    DEFF Research Database (Denmark)

    Kjems, Jørgen; Freltoft, T.; Richter, D.

    1986-01-01

    -angle neutron scattering studies of the variation with aggregation rate are presented. These results allow a very detailed comparison to be made with the theoretical scattering curves. Preliminary incoherent inelastic data on the low-frequency dynamics of hydroxylated silica particle aggregates show a clear...

  2. Modelling Hyperboloid Sound Scattering

    DEFF Research Database (Denmark)

    Burry, Jane; Davis, Daniel; Peters, Brady

    2011-01-01

    The Responsive Acoustic Surfaces workshop project described here sought new understandings about the interaction between geometry and sound in the arena of sound scattering. This paper reports on the challenges associated with modelling, simulating, fabricating and measuring this phenomenon using...... both physical and digital models at three distinct scales. The results suggest hyperboloid geometry, while difficult to fabricate, facilitates sound scattering....

  3. Inelastic Neutron Scattering and Molecular Dynamics Determination of the Interaction Potential in Liquid CD4

    International Nuclear Information System (INIS)

    Guarini, E.; Barocchi, F.; Sampoli, M.; Venturi, G.; Bafile, U.

    2007-01-01

    Anisotropic interactions of liquid CD 4 are studied in detail by comparison of inelastic neutron Brillouin scattering data with molecular dynamics simulations using up to four different models of the methane site-site potential. We demonstrate that the experimental dynamic structure factor S(Q,ω) acts as a highly discriminating quantity for possible interaction schemes. In particular, the Q evolution of the spectra enables a selective probing of the short- and medium-range features of the anisotropic potentials. We show that the preferential configuration of methane dimers at liquid densities can thus be discerned by analyzing the orientation-dependent model potential curves, in light of the experimental and simulation results

  4. Probing the pairing symmetry of the iron pnictides with electronic Raman scattering

    Energy Technology Data Exchange (ETDEWEB)

    Boyd, G.R.

    2010-04-29

    An important issue in the study of the iron-arsenic based superconductors is the symmetry of the superconducting gap, a problem complicated by multiple gaps on different Fermi surface sheets. Electronic Raman scattering is a flexible bulk probe which allows one in principle to determine gap magnitudes and test for gap nodes in different regions of the Brillouin zone by employing different photon polarization states. Here we calculate the clean Raman intensity for A{sub 1g}, B{sub 1g} and B{sub 2g} polarizations, and discuss the peak structures and low-energy power laws which might be expected for several popular models of the superconducting gap in these systems.

  5. Transverse Instabilities in the Fermilab Recycler

    Energy Technology Data Exchange (ETDEWEB)

    Prost, L.R.; Burov, A.; Shemyakin, A.; Bhat, C.M.; Crisp, J.; Eddy, N.; /Fermilab

    2011-07-01

    Transverse instabilities of the antiproton beam have been observed in the Recycler ring soon after its commissioning. After installation of transverse dampers, the threshold for the instability limit increased significantly but the instability is still found to limit the brightness of the antiprotons extracted from the Recycler for Tevatron shots. In this paper, we describe observations of the instabilities during the extraction process as well as during dedicated studies. The measured instability threshold phase density agrees with the prediction of the rigid beam model within a factor of 2. Also, we conclude that the instability threshold can be significantly lowered for a bunch contained in a narrow and shallow potential well due to effective exclusion of the longitudinal tails from Landau damping.

  6. Delayed chromosomal instability induced by DNA damage

    International Nuclear Information System (INIS)

    Morgan, W.F.; Marder, B.A.; Day, J.P.

    1994-01-01

    Cellular exposure to DNA damaging agents rapidly results in a dose dependent increase in chromosomal breakage and gross structural chromosomal rearrangements. Over recent years, evidence has been accumulating indicating genomic instability can manifest multiple generations after cellular exposure to physical and chemical DNA damaging agents. Genomic instability manifests in the progeny of surviving cells, and has been implicated in mutation, gene application, cellular transformation, and cell killing. To investigate chromosome instability following DNA damage, we have used fluorescence in situ hybridization to detect chromosomal rearrangements in a human/hamster somatic hybrid cell line following exposure to ionizing radiation. Delayed chromosomal instability was detected when multiple populations of uniquely arranged metaphases were observed in clonal isolates raised from single cells surviving X-irradiation many generations after exposure. At higher radiation doses, chromosomal instability was observed in a relatively high frequency of surviving clones and, in general, those clones showed delayed chromosome instability also showed reduced survival as measured by colony forming ability

  7. Mode-locking via dissipative Faraday instability.

    Science.gov (United States)

    Tarasov, Nikita; Perego, Auro M; Churkin, Dmitry V; Staliunas, Kestutis; Turitsyn, Sergei K

    2016-08-09

    Emergence of coherent structures and patterns at the nonlinear stage of modulation instability of a uniform state is an inherent feature of many biological, physical and engineering systems. There are several well-studied classical modulation instabilities, such as Benjamin-Feir, Turing and Faraday instability, which play a critical role in the self-organization of energy and matter in non-equilibrium physical, chemical and biological systems. Here we experimentally demonstrate the dissipative Faraday instability induced by spatially periodic zig-zag modulation of a dissipative parameter of the system-spectrally dependent losses-achieving generation of temporal patterns and high-harmonic mode-locking in a fibre laser. We demonstrate features of this instability that distinguish it from both the Benjamin-Feir and the purely dispersive Faraday instability. Our results open the possibilities for new designs of mode-locked lasers and can be extended to other fields of physics and engineering.

  8. Introductory theory of neutron scattering

    International Nuclear Information System (INIS)

    Gunn, J.M.F.

    1986-12-01

    The paper comprises a set of six lecture notes which were delivered to the summer school on 'Neutron Scattering at a pulsed source', Rutherford Laboratory, United Kingdom, 1986. The lectures concern the physical principles of neutron scattering. The topics of the lectures include: diffraction, incoherent inelastic scattering, connection with the Schroedinger equation, magnetic scattering, coherent inelastic scattering, and surfaces and neutron optics. (UK)

  9. How does political instability affect economic growth?

    OpenAIRE

    Aisen, Ari; Veiga, Francisco José

    2011-01-01

    The purpose of this paper is to empirically determine the effects of political instability on economic growth. Using the system-GMM estimator for linear dynamic panel data models on a sample covering up to 169 countries, and 5-year periods from 1960 to 2004, we find that higher degrees of political instability are associated with lower growth rates of GDP per capita. Regarding the channels of transmission, we find that political instability adversely affects growth by lowering the rates of pr...

  10. Jeans instability in a viscoelastic fluid

    International Nuclear Information System (INIS)

    Janaki, M. S.; Chakrabarti, N.; Banerjee, D.

    2011-01-01

    The well known Jeans instability is studied for a viscoelastic gravitational fluid using generalized hydrodynamic equations of motions. It is found that the threshold for the onset of instability appears at higher wavelengths in a viscoelastic medium. Elastic effects playing a role similar to thermal pressure are found to lower the growth rate of the gravitational instability. Such features may manifest themselves in matter constituting dense astrophysical objects.

  11. Proton scattering on unstable nuclei: study of {sup 40}S(p,p`) and {sup 43}Ar(p,p`) reactions, development of detection system MUST; Diffusion de protons par des noyaux instables: Etudes des reactions {sup 40}S(p,p`) et {sup 43}Ar(p,p`), developpement du systeme de detection MUST

    Energy Technology Data Exchange (ETDEWEB)

    Marechal, F

    1998-02-06

    We measured for the first time the elastic and inelastic proton scattering on the {sup 40}S unstable nucleus. The experiment was performed in inverse kinematics at the NSCL AT Michigan State University with a {sup 40}S secondary beam bombarding a CH{sub 2} target at 30 MeV/A. We obtained the elastic scattering angular distribution and two points of the inelastic distribution to the first 2{sup +} excited state found to be located at 860{+-}90 KeV. With a coupled channel analysis, the {beta}{sub 2} quadrupolar deformation parameter is found to be equal to 0.35{+-}0.05. This value can be compared to 0.28{+-}0.02 obtained by coulomb excitation. A macroscopic analysis allowed us to extract the neutron and proton transition matrix element ratio M{sub n}/M{sub p} which is equal to 1.88{+-}0.38. This value, greater than N/Z, could indicate an isovector effect in the first 2{sup +} state excitation which could be due to a difference between the neutron and proton vibrations. The microscopic analysis gives the possibility to test the densities and the transition densities to the first 2{sup +} state. The calculated densities for the {sup 40}S nucleus show a neutron skin. However the microscopic analysis yields a M{sub n}/M{sub p} ratio of 1.40{+-}0.20. A similar elastic and inelastic proton scattering experiment allowed us to get a deformation parameter of 0.25{+-}0.03 for the {sup 43}Ar nucleus. To develop the study of direct reactions induced by radioactive beams at GANIL, we have developed and built, in collaboration with the CEA-Saclay and the CEA-Bruyeres, the new detector MUST.It is based on the silicon strip technology, and is dedicated to the measurement of recoiling light particles emitted in these reactions. The results obtained with a {sup 40}Ar beam at 77 Me V/A, have shown the good performances of the detector for the particle identification as well as for the resolutions, and allow us to consider now a large experimental programme concerning these direct

  12. Instability of asymmetric shaft system

    Science.gov (United States)

    Srinath, R.; Sarkar, Abhijit; Sekhar, A. S.

    2016-02-01

    In the present work, parametric instability of asymmetric shaft mounted on bearings is studied. Towards this end, four different models of increasing complexity are studied. The equations corresponding to these models are formulated in the inertial reference frame. These equations involve a periodically varying coefficient. This is similar to classical Mathieu equation but in a multi-degree of freedom context. As such, under suitable parameter combination these systems result in growing oscillation amplitudes or instability. For wider generalization, the equations and results are presented in a non-dimensional form. The unstable parameter regimes are found using the Floquet theory and perturbation methods. These results are also corroborated with existing results in the literature. The nature of the stability boundary and its dependence on various system parameters is discussed in elaborate detail. The stability boundary can be used to determine unstable operating speed ranges for different asymmetric shaft cross-sections. Further, material, geometry and bearing selection guidelines for ensuring stable operations can be inferred from these results.

  13. Damage-induced tensile instability

    International Nuclear Information System (INIS)

    Hult, J.

    1975-01-01

    The paper presents a unified description of ductile and brittle rupture phenomena in structural components under tensile loading with particular emphasis on creep rupture. Two structural elements are analyzed in detail: 1) the uniform tensile bar subject to a Heaviside history of tensile force and superimposed such loadings, i.e. staircase histories, and 2) the thinwalled spherical pressure vessel subject to a Heaviside history of internal pressure. For both these structures the conditions for instantaneous as well as delayed rupture are analysed. It is shown that a state of mechanical instability will be reached at a certain load or after a certain time. The cases of purely ductile rupture and purely brittle fracture are identified as two limiting cases of this general instability phenomenon. The Kachanov-Rabotnov damage law implies that a structural component will fail in tension only when it has reached a state of complete damage, i.e. zero load carrying capacity. The extended law predicts failure at an earlier stage of the deterioration process and is therefore more compatible with experimental observation. Further experimental support is offered by predictions for staircase loading histories, both step-up and step-down type. The presented damage theory here predicts strain histories which are in closer agreement with test data than predictions based on other phenomenological theories

  14. Option price and market instability

    Science.gov (United States)

    Baaquie, Belal E.; Yu, Miao

    2017-04-01

    An option pricing formula, for which the price of an option depends on both the value of the underlying security as well as the velocity of the security, has been proposed in Baaquie and Yang (2014). The FX (foreign exchange) options price was empirically studied in Baaquie et al., (2014), and it was found that the model in general provides an excellent fit for all strike prices with a fixed model parameters-unlike the Black-Scholes option price Hull and White (1987) that requires the empirically determined implied volatility surface to fit the option data. The option price proposed in Baaquie and Cao Yang (2014) did not fit the data during the crisis of 2007-2008. We make a hypothesis that the failure of the option price to fit data is an indication of the market's large deviation from its near equilibrium behavior due to the market's instability. Furthermore, our indicator of market's instability is shown to be more accurate than the option's observed volatility. The market prices of the FX option for various currencies are studied in the light of our hypothesis.

  15. The Chemistry of Beer Instability

    Science.gov (United States)

    Stewart, Graham G.

    2004-07-01

    Compared to most other alcoholic beverages, beer is unique because it is unstable when in the final package. This instability can be divided into biological and nonbiological instability. Nonbiological stability of beer involves a wide range of chemical processes and can be considered in a number of categories: physical, flavor, light, foam, and gushing. It is the balance between flavanoid polyphenols (tannoids) and sensitive proteins that specifically combine with polyphenols to form haze that largely dictates physical stability. The flavor stability of beer primarily depends on the oxygen concentration of packaged beer but is influenced by all stages of the brewing process. Foam stability in a glass of beer reflects the quality of the beverage. The backbone of foam is hydrophobic polypeptides. Novel brewing processes such as high-gravity brewing result in a disproportionate loss of these polypeptides and have a negative effect on the foam stability of the resulting beer. Beer is light sensitive, especially in the 350 500 nm range. Beer exposed to this wavelength range in clear or green glass containers quickly develop nauseous skunky-like off-flavors resulting from the formation of 3-methyl-2-butene-1-thiol. Methods of enhancing all of these types of beer stability are discussed.

  16. Instabilities in the plasma focus

    International Nuclear Information System (INIS)

    Kaeppeler, H.J.

    1975-03-01

    The plasma focus was studied by many research teams in view of a possible approach to controlled thermonuclear fusion. Though it is questionable whether the plasma focus will ever lead to a fusion reactor, it nevertheless constitutes a strong source of neutron, X- and gamma radiation for simulating fusion reactor conditions. Furthermore, the plasma focus yields very high temperatures (10 7 K) and densities (> 10 19 cm -3 ) and thus provides interesting conditions for the study of high density plasmas. This review paper starts with a description of the compression stage of the focussing plasma, using a snow-plough model. It is shown that sophisticated MHD calculations substantiate the snowplough theory, but are not suited to describe the phenomena in the final compressed stage. For this purpose, a particle-in-cell calculation is employed, yielding a beam-beam collision model for the neutron production. Experimental evidence indicates that neutron production is associated with the appearence of m = O instabilities and is the direct result of collisions between anomalously accelerated ions. One of the mechanisms of ion acceleration are strong local electric fields. Another possible mechanism can bee seen in beam-plasma instabilities caused by runaway electrons. The analytical derivation of the dispersion relation for plasma focus conditions including runaway effect is discussed (orig.) [de

  17. Adhesional instabilities and gecko locomotion

    Science.gov (United States)

    Williams, John A.

    2015-01-01

    Geckos possess a remarkable ability to run rapidly on both walls and ceilings and in recent years the mechanisms that underlie this facility have come under close scrutiny. It is now generally agreed that one of the principal mechanisms of adhesion relies on the action of van der Waal forces acting between the final extremely fine structure of the gecko toe and the underlying substrate. High speed video analysis shows that adhesive contact is both made and broken in intervals of less than 20 ms and this suggests that the mechanism of detachment is one of adhesive instability rather than steady-state peeling. By considering the gecko seta/spatula as a Euler-Bernoulli cantilever it is possible to model this instability in non-dimensional terms and thus to test the analysis at a much larger scale with more conventional engineering materials. When applied to the scale and material combination appropriate to a gecko spatula, the predicted critical load, of around 10 nN, is close to values that have been observed using and AFM cantilever and a single detached spatula.

  18. Adhesional instabilities and gecko locomotion

    International Nuclear Information System (INIS)

    Williams, John A

    2015-01-01

    Geckos possess a remarkable ability to run rapidly on both walls and ceilings and in recent years the mechanisms that underlie this facility have come under close scrutiny. It is now generally agreed that one of the principal mechanisms of adhesion relies on the action of van der Waal forces acting between the final extremely fine structure of the gecko toe and the underlying substrate. High speed video analysis shows that adhesive contact is both made and broken in intervals of less than 20 ms and this suggests that the mechanism of detachment is one of adhesive instability rather than steady-state peeling. By considering the gecko seta/spatula as a Euler–Bernoulli cantilever it is possible to model this instability in non-dimensional terms and thus to test the analysis at a much larger scale with more conventional engineering materials. When applied to the scale and material combination appropriate to a gecko spatula, the predicted critical load, of around 10 nN, is close to values that have been observed using and AFM cantilever and a single detached spatula. (paper)

  19. Electromagnetic theory of the radiative Pierce instability

    International Nuclear Information System (INIS)

    Klochkov, D.N.; Rukhadze, A.A.

    1997-01-01

    The radiative Pierce instability of a relativistic electron beam in a waveguide stabilized by an infinite strong magnetic field is considered. the increment and conditions for instability development in a wide interval of the beam currents are determined on the basis of the perturbation theory. It is shown that the instability has always the Raman character and is threshold less in current for the Pierce boundary conditions. It permits sufficiently strictly to define the instability saturation level from breaking the resonance condition and to estimate the radiation efficiency

  20. Size-effects on cavitation instabilities

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2005-01-01

    In metal-ceramic systems the constraint on plastic flow leads to so high stress triaxialities that cavitation instabilities may occur. If the void radius is on the order of magnitude of a characteristic length for the metal, the rate of void growth is reduced, and the possibility of unstable cavity...... triaxiality, where cavitation instabilities are predicted by conventional plasticity theory, such instabilities are also found for the nonlocal theory, but the effects of gradient hardening delay the onset of the instability. Furthermore, in some cases the cavitation stress reaches a maximum and then decays...

  1. Analysis of fluid structural instability in water

    International Nuclear Information System (INIS)

    Piccirillo, N.

    1997-02-01

    Recent flow testing of stainless steel hardware in a high pressure/high temperature water environment produced an apparent fluid-structural instability. The source of instability was investigated by studying textbook theory and by performing NASTRAN finite element analyses. The modal analyses identified the mode that was being excited, but the flutter instability analysis showed that the design is stable if minimal structural damping is present. Therefore, it was suspected that the test hardware was the root cause of the instability. Further testing confirmed this suspicion

  2. Fringe instability in constrained soft elastic layers.

    Science.gov (United States)

    Lin, Shaoting; Cohen, Tal; Zhang, Teng; Yuk, Hyunwoo; Abeyaratne, Rohan; Zhao, Xuanhe

    2016-11-04

    Soft elastic layers with top and bottom surfaces adhered to rigid bodies are abundant in biological organisms and engineering applications. As the rigid bodies are pulled apart, the stressed layer can exhibit various modes of mechanical instabilities. In cases where the layer's thickness is much smaller than its length and width, the dominant modes that have been studied are the cavitation, interfacial and fingering instabilities. Here we report a new mode of instability which emerges if the thickness of the constrained elastic layer is comparable to or smaller than its width. In this case, the middle portion along the layer's thickness elongates nearly uniformly while the constrained fringe portions of the layer deform nonuniformly. When the applied stretch reaches a critical value, the exposed free surfaces of the fringe portions begin to undulate periodically without debonding from the rigid bodies, giving the fringe instability. We use experiments, theory and numerical simulations to quantitatively explain the fringe instability and derive scaling laws for its critical stress, critical strain and wavelength. We show that in a force controlled setting the elastic fingering instability is associated with a snap-through buckling that does not exist for the fringe instability. The discovery of the fringe instability will not only advance the understanding of mechanical instabilities in soft materials but also have implications for biological and engineered adhesives and joints.

  3. Systems and methods for controlling flame instability

    KAUST Repository

    Cha, Min Suk

    2016-07-21

    A system (62) for controlling flame instability comprising: a nozzle (66) coupled to a fuel supply line (70), an insulation housing (74) coupled to the nozzle, a combustor (78) coupled to the nozzle via the insulation housing, where the combustor is grounded (80), a pressure sensor (82) coupled to the combustor and configured to detect pressure in the combustor, and an instability controlling assembly coupled to the pressure sensor and to an alternating current power supply (86), where, the instability controlling assembly can control flame instability of a flame in the system based on pressure detected by the pressure sensor.

  4. Radiation-induced instability of human genome

    International Nuclear Information System (INIS)

    Ryabchenko, N.N.; Demina, Eh.A.

    2014-01-01

    A brief review is dedicated to the phenomenon of radiation-induced genomic instability where the increased level of genomic changes in the offspring of irradiated cells is characteristic. Particular attention is paid to the problems of genomic instability induced by the low-dose radiation, role of the bystander effect in formation of radiation-induced instability, and its relationship with individual radiosensitivity. We believe that in accordance with the paradigm of modern radiobiology the increased human individual radiosensitivity can be formed due to the genome instability onset and is a significant risk factor for radiation-induced cancer

  5. Review of two-phase instabilities

    International Nuclear Information System (INIS)

    Kang, Han Ok; Seo, Han Ok; Kang, Hyung Suk; Cho, Bong Hyun; Lee, Doo Jeong

    1997-06-01

    KAERI is carrying out a development of the design for a new type of integral reactors. The once-through helical steam generator is important design features. The study on designs and operating conditions which prevent flow instability should precede the introduction of one-through steam generator. Experiments are currently scheduled to understand two-phase instability, evaluate the effect of each design parameter on the critical point, and determine proper inlet throttling for the prevention of instability. This report covers general two-phase instability with review of existing studies on this topics. The general classification of two phase flow instability and the characteristics of each type of instability are first described. Special attention is paid to BWR core flow instability and once-through steam generator instability. The reactivity feedback and the effect of system parameters are treated mainly for BWR. With relation to once-through steam generators, the characteristics of convective heating and dryout point oscillation are first investigated and then the existing experimental studies are summarized. Finally chapter summarized the proposed correlations for instability boundary conditions. (author). 231 refs., 5 tabs., 47 figs

  6. Phase space evolution in linear instabilities

    Science.gov (United States)

    Pantellini, F. G. E.; Burgess, D.; Schwartz, S. J.

    1994-12-01

    A simple and powerful way to investigate the linear evolution of particle distribution functions in kinetic instabilities in a homogeneous collisionless plasma is presented. The method can be applied to any kind of instability, provided the characteristics (growth rate, frequency, wave vector, and polarization) of the mode are known and can also be used to estimate the amplitude of the waves at the end of the linear phase of growth. Two didactic examples are used to illustrate the versatility of the technique: the Alfvén Ion Cyclotron (AIC) instability, which is electromagnetic, and the Electron Ion Cyclotron (EIC) instability, which is electrostatic.

  7. On the instability regime of the rotating Kerr spacetime to massive scalar perturbations

    International Nuclear Information System (INIS)

    Hod, Shahar

    2012-01-01

    The instability of rotating Kerr black holes due to massive scalar perturbations is investigated. It is well known that a bosonic field impinging on a Kerr black hole can be amplified as it scatters off the hole. This superradiant scattering occurs for frequencies in the range ω< mΩ, where Ω is the angular frequency of the black hole and m is the azimuthal harmonic index of the mode. If the incident field has a non-zero rest mass, μ, then the mass term effectively works as a mirror, reflecting the scattered wave back towards the black hole. The wave may bounce back and forth between the black hole and some turning point amplifying itself each time. This may lead to a dynamical instability of the system, a phenomena known as a “black-hole bomb”. In this work we provide a bound on the instability regime of rotating Kerr spacetimes. In particular, we show that Kerr black holes are stable to massive perturbations in the regime μ⩾√(2)mΩ.

  8. Studies of central interactions of Si ions at 14.5 x A GeV/c in Au and Cu

    International Nuclear Information System (INIS)

    Eiseman, S.E.; Etkin, A.; Foley, K.J.; Hackenburg, R.W.; Longacre, R.S.; Love, W.A.; Morris, T.W.; Platner, E.D.; Saulys, A.C.; Lindenbaum, S.J.; Chan, C.S.; Kramer, M.A.; Zhao, K.; Hallman, T.J.; Madansky, L.; Bonner, B.E.; Buchanan, J.A.; Chiou, C.N.; Clement, J.M.; Corcoran, M.D.; Kruk, J.W.; Mutchler, G.S.; Nessi-Tedaldi, F.; Nessi, M.; Roberts, J.B.

    1990-01-01

    Understanding the growth and saturation of parametric instabilities in laser-produced plasmas requires knowledge of the nonlinear properties of the instabilities and their interaction with each other. Nonlinear behavior of parametric instabilities, which are usually associated with unique optical features, have been evidenced in numerous experiments on a variety of laser facilities. We will discuss four examples of nonlinear behavior in laser-produced plasmas: nonlinear stimulated Brillouin scattering spectra, suppression of stimulated Raman scattering by stimulated Brillouin scattering, the parametric decay instability and the onset of turbulence, and the transition to ''bursting'' behavior of the two-plasmon decay instability. We also discuss experiments that demonstrate the nonlinear effects which occur as a consequence. 49 refs

  9. Laser and Plasma Parameters for Laser Pulse Amplification by Stimulated Brillouin Backscattering in the Strong Coupling Regime

    Science.gov (United States)

    Gangolf, Thomas; Blecher, Marius; Bolanos, Simon; Lancia, Livia; Marques, Jean-Raphael; Cerchez, Mirela; Prasad, Rajendra; Aurand, Bastian; Loiseau, Pascal; Fuchs, Julien; Willi, Oswald

    2017-10-01

    In the ongoing quest for novel techniques to obtain ever higher laser powers, plasma amplification has drawn much attention, benefiting from the fact that a plasma can sustain much higher energy densities than a solid state amplifier. As a plasma process, Stimulated Brillouin Backscattering in the strong coupling regime (sc-SBS) can be used to transfer energy from one laser pulse (pump) to another (seed), by a nonlinear ion oscillation forced by the pump laser. Here, we report on experimental results on amplification by sc-SBS using the ARCTURUS Ti:Sapphire multi-beam laser system at the University of Duesseldorf, Germany. Counter-propagating in a supersonic Hydrogen gas jet target, an ultrashort seed pulse with a pulse duration between 30 and 160 fs and an energy between 1 and 12 mJ was amplified by a high-energy pump pulse (1.7 ps, 700 mJ). For some of the measurements, the gas was pre-ionized with a separate laser pulse (780 fs, 460 mJ). Preliminary analysis shows that the amplification was larger for the longer seed pulses, consistent with theoretical predictions.

  10. Volume 15. Neutron scattering

    International Nuclear Information System (INIS)

    Kostorz, G.

    1979-01-01

    This volume of the Treatise on Materials Science and Technology shows how neutron scattering methods can be used to obtain important information on materials, by guiding the reader through the principles and describing recent applications. Materials scientists, but also solid state physicists, physical chemists, and metallurgists interested in this field, will find a completely referenced survey of the ''classical topics'' of neutron scattering and a more detailed presentation of methods and techniques that are more specifically related to materials science. After a brief review of the general principles in the first chapter, subsequent chapters concentrate on particular methods and problems. The techniques used in neutron crystallography are presented, and selected applications of nuclear and magnetic scattering are discussed. The measurement of phonons, their role in phase transformations, and their behavior in the presence of crystal defects are considered, and quasi-elastic scattering is given detailed treatment. The methods of small-angle scattering and diffuse scattering have been developed to a considerable perfection in recent years and are presented in detail. The structure and dynamics of hydrogen dissolved in metals and the conformation and dynamics of polymers are two outstanding subjects to which neutron scattering has contributed so much in recent years that separate chapters are devoted to covering these fields. Finally, the choice of the appropriate materials is also becoming increasingly crucial in the design and construction of neutron spectrometers. Therefore, the last chapter deals with special materials problems in neutron devices

  11. The electrostatic ion-cyclotron instability-a two-dimensional potential relaxation instability

    DEFF Research Database (Denmark)

    Popa, G.; Schrittwieser, R.; Juul Rasmussen, Jens

    1985-01-01

    An experimental investigation shows that the electrostatic ion-cyclotron instability, driven by an electron current to a positively biased collector, is accompanied by strong coherent two-dimensional fluctuations of the plasma potential in front of the collector. These results suggest that this i...... that this instability evolves like a two-dimensional potential relaxation instability....

  12. Manipulating scattering features by metamaterials

    Directory of Open Access Journals (Sweden)

    Lu Cui

    2016-01-01

    Full Text Available We present a review on manipulations of electromagnetic scattering features by using metamaterials or metasurfaces. Several approaches in controlling the scattered fields of objects are presented, including invisibility cloaks and radar illusions based on transformation optics, carpet cloak using gradient metamaterials, dc cloaks, mantle cloaks based on scattering cancellation, “skin” cloaks using phase compensation, scattering controls with coding/programmable metasurfaces, and scattering reductions by multilayered structures. Finally, the future development of metamaterials on scattering manipulation is predicted.

  13. Shoulder instability in professional football players.

    Science.gov (United States)

    Leclere, Lance E; Asnis, Peter D; Griffith, Matthew H; Granito, David; Berkson, Eric M; Gill, Thomas J

    2013-09-01

    Shoulder instability is a common problem in American football players entering the National Football League (NFL). Treatment options include nonoperative and surgical stabilization. This study evaluated how the method of treatment of pre-NFL shoulder instability affects the rate of recurrence and the time elapsed until recurrence in players on 1 NFL team. Retrospective cohort. Medical records from 1980 to 2008 for 1 NFL team were reviewed. There were 328 players included in the study who started their career on the team and remained on the team for at least 2 years (mean, 3.9 years; range, 2-14 years). The history of instability prior to entering the NFL and the method of treatment were collected. Data on the occurrence of instability while in the NFL were recorded to determine the rate and timing of recurrence. Thirty-one players (9.5%) had a history of instability prior to entering the NFL. Of the 297 players with no history of instability, 39 (13.1%) had a primary event at a mean of 18.4 ± 22.2 months (range, 0-102 months) after joining the team. In the group of players with prior instability treated with surgical stabilization, there was no statistical difference in the rate of recurrence (10.5%) or the timing to the instability episode (mean, 26 months) compared with players with no history of instability. Twelve players had shoulder instability treated nonoperatively prior to the NFL. Five of these players (41.7%) had recurrent instability at a mean of 4.4 ± 7.0 months (range, 0-16 months). The patients treated nonoperatively had a significantly higher rate of recurrence (P = 0.02) and an earlier time of recurrence (P = 0.04). The rate of contralateral instability was 25.8%, occurring at a mean of 8.6 months. Recurrent shoulder instability is more common in NFL players with a history of nonoperative treatment. Surgical stabilization appears to restore the rate and timing of instability to that of players with no prior history of instability.

  14. Virtual neutron scattering experiments

    DEFF Research Database (Denmark)

    Overgaard, Julie Hougaard; Bruun, Jesper; May, Michael

    2016-01-01

    We describe how virtual experiments can be utilized in a learning design that prepares students for hands-on experiments at large-scale facilities. We illustrate the design by showing how virtual experiments are used at the Niels Bohr Institute in a master level course on neutron scattering....... In the last week of the course, students travel to a large-scale neutron scattering facility to perform real neutron scattering experiments. Through student interviews and survey answers, we argue, that the virtual training prepares the students to engage more fruitfully with experiments by letting them focus...

  15. Virtual neutron scattering experiments

    DEFF Research Database (Denmark)

    Overgaard, Julie Hougaard; Bruun, Jesper; May, Michael

    2017-01-01

    We describe how virtual experiments can be utilized in a learning design that prepares students for hands-on experiments at large-scale facilities. We illustrate the design by showing how virtual experiments are used at the Niels Bohr Institute in a master level course on neutron scattering....... In the last week of the course, students travel to a large-scale neutron scattering facility to perform real neutron scattering experiments. Through student interviews and survey answers, we argue, that the virtual training prepares the students to engage more fruitfully with experiments by letting them focus...

  16. Turbulent mixing induced by Richtmyer-Meshkov instability

    Science.gov (United States)

    Krivets, V. V.; Ferguson, K. J.; Jacobs, J. W.

    2017-01-01

    Richtmyer-Meshkov instability is studied in shock tube experiments with an Atwood number of 0.7. The interface is formed in a vertical shock tube using opposed gas flows, and three-dimensional random initial interface perturbations are generated by the vertical oscillation of gas column producing Faraday waves. Planar Laser Mie scattering is used for flow visualization and for measurements of the mixing process. Experimental image sequences are recorded at 6 kHz frequency and processed to obtain the time dependent variation of the integral mixing layer width. Measurements of the mixing layer width are compared with Mikaelian's [1] model in order to extract the growth exponent θ where a fairly wide range of values is found varying from θ ≈ 0.2 to 0.6.

  17. CT investigation of instability of the shoulder joint

    International Nuclear Information System (INIS)

    Grasshoff, H.; Buhtz, C.; Gellerich, I.; Knorre, C. v.; Medizinische Akademie, Magdeburg

    1991-01-01

    CT is able to demonstrate the predisposing factors for recurrent und posttraumatic subluxation of the shoulder . In addition to demonstrating bony changes in the glenoid (Bankart lesion) and in the humeral head (Hill-Sachs lesion), CT can measure the degree of retroversion of the glenoid and torsion of the humerus. Measurements on 17 shoulders with habitual and 24 shoulders with recurrent posttraumatic subluxation showed low values for glenoid retriversion as compared with a control group. Particulary patients with habitual anterior subluxation frequently showed anteversion of the glenoid. Measurements of humeral torsion showed wide scatter amongst all groups, indicating wide biological variability. The results were compared with those published in the literature and the indications and limitations of CT for the investigation of shoulder instability are discussed. (orig.) [de

  18. RADIATIVE RAYLEIGH-TAYLOR INSTABILITIES

    International Nuclear Information System (INIS)

    Jacquet, Emmanuel; Krumholz, Mark R.

    2011-01-01

    We perform analytic linear stability analyses of an interface separating two stratified media threaded by a radiation flux, a configuration relevant in several astrophysical contexts. We develop a general framework for analyzing such systems and obtain exact stability conditions in several limiting cases. In the optically thin, isothermal regime, where the discontinuity is chemical in nature (e.g., at the boundary of a radiation pressure-driven H II region), radiation acts as part of an effective gravitational field, and instability arises if the effective gravity per unit volume toward the interface overcomes that away from it. In the optically thick a diabaticregime where the total (gas plus radiation) specific entropy of a Lagrangian fluid element is conserved, for example at the edge of radiation pressure-driven bubble around a young massive star, we show that radiation acts like a modified equation of state and derive a generalized version of the classical Rayleigh-Taylor stability condition.

  19. Instabilities in coaxial rotating jets

    Science.gov (United States)

    Ivanic, Tanja; Foucault, Eric; Pecheux, Jean; Gilard, Virginie

    2000-12-01

    The aim of this study is the characterization of the cylindrical mixing layer resulting from the interaction of two coaxial swirling jets. The experimental part of this study was performed in a cylindrical water tunnel, permitting an independent rotation of two coaxial jets. The rotations are generated by means of 2×36 blades localized in two swirling chambers. As expected, the evolution of the main instability modes presents certain differences compared to the plane-mixing-layer case. Experimental results obtained by tomography showed the existence of vortex rings and streamwise vortex pairs in the near field region. This method also permitted the observation of the evolution and interaction of different modes. PIV velocity measurements realized in the meridian plans and the plans perpendicular to the jet axis show that rotation distorts the typical top-hat axial velocity profile. The transition of the axial velocity profile from jet-like into wake-like is also observed.

  20. Chromosomal instability determines taxane response

    DEFF Research Database (Denmark)

    Swanton, C.; Nicke, B.; Schuett, M.

    2009-01-01

    Microtubule-stabilizing (MTS) agents, such as taxanes, are important chemotherapeutics with a poorly understood mechanism of action. We identified a set of genes repressed in multiple cell lines in response to MTS agents and observed that these genes are overexpressed in tumors exhibiting...... chromosomal instability (CIN). Silencing 22/50 of these genes, many of which are involved in DNA repair, caused cancer cell death, suggesting that these genes are involved in the survival of aneuploid cells. Overexpression of these "CIN-survival'' genes is associated with poor outcome in estrogen receptor......-positive breast cancer and occurs frequently in basal-like and Her2-positive cases. In diploid cells, but not in chromosomally unstable cells, paclitaxel causes repression of CIN-survival genes, followed by cell death. In the OV01 ovarian cancer clinical trial, a high level of CIN was associated with taxane...

  1. Parametric instabilities in inhomogeneous plasma

    International Nuclear Information System (INIS)

    Nicholson, D.R.

    1975-01-01

    The nonlinear coupling of three waves in a plasma is considered. One of the waves is assumed large and constant; its amplitude is the parameter of the parametric instability. The spatial-temporal evolution of the other two waves is treated theoretically, in one dimension, by analytic methods and by direct numerical integration of the basic equations. Various monotonic forms of inhomogeneity are considered; agreement with previous work is found and new results are established. Nonmonotonic inhomogeneities are considered, in the form of turbulence and, as a model problem, in the form of a simple sinusoidal modulation. Relatively small amounts of nonmonotonic inhomogeneity, in the presence of a linear density gradient, are found to destabilize the well-known convective saturation, absolute growth occurring instead. (U.S.)

  2. Instability of expanding bacterial droplets.

    Science.gov (United States)

    Sokolov, Andrey; Rubio, Leonardo Dominguez; Brady, John F; Aranson, Igor S

    2018-04-03

    Suspensions of motile bacteria or synthetic microswimmers, termed active matter, manifest a remarkable propensity for self-organization, and formation of large-scale coherent structures. Most active matter research deals with almost homogeneous in space systems and little is known about the dynamics of strongly heterogeneous active matter. Here we report on experimental and theoretical studies on the expansion of highly concentrated bacterial droplets into an ambient bacteria-free fluid. The droplet is formed beneath a rapidly rotating solid macroscopic particle inserted in the suspension. We observe vigorous instability of the droplet reminiscent of a violent explosion. The phenomenon is explained in terms of continuum first-principle theory based on the swim pressure concept. Our findings provide insights into the dynamics of active matter with strong density gradients and significantly expand the scope of experimental and analytic tools for control and manipulation of active systems.

  3. Ion instabilities in the Hall plasma

    International Nuclear Information System (INIS)

    Gordeev, A.V.; Grechina, A.V.

    1992-01-01

    Instabilities of the Hall plasma are investigated to study the properties of plasma with small ion number per unit length, taking into account ion dynamics and electron mass finiteness. The availability of a universal mechanism resulting in a high two-stream instability with maximum increment of (ω Hi ω He ) 1/2 order is shown

  4. Cultural diversity, economic development and societal instability

    Science.gov (United States)

    Nettle, D.; Grace, J.B.; Choisy, M.; Cornell, H.V.; Guegan, J.-F.; Hochberg, M.E.

    2007-01-01

    Background. Social scientists have suggested that cultural diversity in a nation leads to societal instability. However, societal instability may be affected not only by within-nation on ?? diversity, but also diversity between a nation and its neighbours or ?? diversity. It is also necessary to distinguish different domains of diversity, namely linguistic, ethnic and religious, and to distinguish between the direct effects of diversity on societal instability, and effects that are mediated by economic conditions. Methodology/Principal Findings. We assembled a large cross-national dataset with information on ?? and ?? cultural diversity, economic conditions, and indices of societal instability. Structural equation modeling was used to evaluate the direct and indirect effects of cultural diversity on economics and societal stability. Results show that different type and domains of diversity have interacting effects. As previously documented, linguistic ?? diversity has a negative effect on economic performance, and we show that it is largely through this economic mechanism that it affects societal instability. For ?? diversity, the higher the linguistic diversity among nations in a region, the less stable the nation. But, religious ?? diversity has the opposite effect, reducing instability, particularly in the presence of high linguistic diversity. Conclusions. Within-nation linguistic diversity is associated with reduced economic performance, which, in turn, increases societal instability. Nations which differ linguistically from their neighbors are also less stable. However, religious diversity between, neighboring nations has the opposite effect, decreasing societal instability.

  5. Heuristic Explanation of Journal Bearing Instability

    Science.gov (United States)

    1982-05-01

    A fluid-filled journal bearing is viewed as a powerful pump circulating fluid around the annular space between the journal and the bearing. A small...other simple explanations of journal - bearing instability. It is shown that for non-cavitating long bearings the hypothesis predicts instability onset

  6. Direct observation of nonequilibrium electroosmotic instability

    NARCIS (Netherlands)

    Rubinstein, S.M.; Manukyan, G.; Staicu, A.D.; Rubinstein, I.; Zaltzman, B.; Lammertink, Rob G.H.; Mugele, Friedrich Gunther; Wessling, Matthias

    2008-01-01

    We present a visualization of the predicted instability in ionic conduction from a binary electrolyte into a charge selective solid. This instability develops when a voltage greater than critical is applied to a thin layer of copper sulfate flanked by a copper anode and a cation selective membrane.

  7. The short circuit instability in protoplanetary disks

    DEFF Research Database (Denmark)

    Hubbard, A.; McNally, C.P.; Mac Low, M.M.

    2013-01-01

    We introduce a magneto-hydrodynamic instability which occurs, among other locations, in the inner, hot regions of protoplanetary disks, and which alters the way in which resistive dissipation of magnetic energy into heat proceeds. This instability can be likened to both an electrical short circui...

  8. Plasma instabilities in high electric fields

    DEFF Research Database (Denmark)

    Morawetz, K.; Jauho, Antti-Pekka

    1994-01-01

    expression is derived for the nonequilibrium dielectric function epsilon(K, omega). For certain values of momenta K and frequency omega, Imepsilon(K, omega) becomes negative, implying a plasma instability. This new instability exists only for strong electric fields, underlining its nonequilibrium origin....

  9. Partnership Instability, School Readiness, and Gender Disparities

    Science.gov (United States)

    Cooper, Carey E.; Osborne, Cynthia A.; Beck, Audrey N.; McLanahan, Sara S.

    2011-01-01

    Trends in family formation during the past several decades have increased children's exposure to mothers' partnership instability, defined as an entrance into or exit from a coresidential union or a dating partnership. Instability, in turn, is associated with negative outcomes for children and adolescents. This study uses data from the Fragile…

  10. On viscoelastic instability in polymeric filaments

    DEFF Research Database (Denmark)

    Rasmussen, Henrik Koblitz; Hassager, Ole

    1999-01-01

    The 3D Lagrangian Integral Method is used to simulate the effects of surface tension on the viscoelastic end-plate instability, occuring in the rapid extension of some polymeric filaments between parallel plates. It is shovn that the surface tension delays the onset of the instability. Furthermore...

  11. Experimental study of the Richtmyer-Meshkov instability induced by a Mach 3 shock wave

    International Nuclear Information System (INIS)

    BP Puranik; JG Oakley; MH Anderson; R Bonaazza

    2003-01-01

    OAK-B135 An experimental investigation of a shock-induced interfacial instability (Richtmyer-Meshkov instability) is undertaken in an effort to study temporal evolution of interfacial perturbations in the late stages of development. The experiments are performed in a vertical shock tube with a square cross-section. A membraneless interface is prepared by retracting a sinusoidally shaped metal plate initially separating carbon dioxide from air, with both gases initially at atmospheric pressure. With carbon dioxide above the plate, the Rayleigh-Taylor instability commences as the plate is retracted and the amplitude of the initial sinusoidal perturbation imposed on the interface begins to grow. The interface is accelerated by a strong shock wave (M=3.08) while its shape is still sinusoidal and before the Kelvin-Helmhotz instability distorts it into the well known mushroom-like structures; its initial amplitude to wavelength ratio is large enough that the interface evolution enters its nonlinear stage very shortly after shock acceleration. The pre-shock evolution of the interface due to the Rayleigh-Taylor instability and the post-shock evolution of the interface due to the Richtmyer-Meshkov instability are visualized using planar Mie scattering. The pre-shock evolution of the interface is carried out in an independent set of experiments. The initial conditions for the Richtmyer-Meshkov experiment are determined from the pre-shock Rayleigh-Taylor growth. One image of the post-shock interface is obtained per experiment and image sequences, showing the post-shock evolution of the interface, are constructed from several experiments. The growth rate of the perturbation amplitude is measured and compared with two recent analytical models of the Richtmyer-Meshkov instability

  12. FIRE HOSE INSTABILITY DRIVEN BY ALPHA PARTICLE TEMPERATURE ANISOTROPY

    Energy Technology Data Exchange (ETDEWEB)

    Matteini, L.; Schwartz, S. J. [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Hellinger, P. [Astronomical Institute, CAS, Prague (Czech Republic); Landi, S. [Dipartimento di Fisica e Astronomia, Università di Firenze, Firenze (Italy)

    2015-10-10

    We investigate properties of a solar wind-like plasma, including a secondary alpha particle population exhibiting a parallel temperature anisotropy with respect to the background magnetic field, using linear and quasi-linear predictions and by means of one-dimensional hybrid simulations. We show that anisotropic alpha particles can drive a parallel fire hose instability analogous to that generated by protons, but that, remarkably, can also be triggered when the parallel plasma beta of alpha particles is below unity. The wave activity generated by the alpha anisotropy affects the evolution of the more abundant protons, leading to their anisotropic heating. When both ion species have sufficient parallel anisotropies, both of them can drive the instability, and we observe the generation of two distinct peaks in the spectra of the fluctuations, with longer wavelengths associated to alphas and shorter ones to protons. If a non-zero relative drift is present, the unstable modes propagate preferentially in the direction of the drift associated with the unstable species. The generated waves scatter particles and reduce their temperature anisotropy to a marginally stable state, and, moreover, they significantly reduce the relative drift between the two ion populations. The coexistence of modes excited by both species leads to saturation of the plasma in distinct regions of the beta/anisotropy parameter space for protons and alpha particles, in good agreement with in situ solar wind observations. Our results confirm that fire hose instabilities are likely at work in the solar wind and limit the anisotropy of different ion species in the plasma.

  13. Electron scattering from pyrimidine

    International Nuclear Information System (INIS)

    Colmenares, Rafael; Fuss, Martina C; García, Gustavo; Oller, Juan C; Muñoz, Antonio; Blanco, Francisco; Almeida, Diogo; Limão-Vieira, Paulo

    2014-01-01

    Electron scattering from pyrimidine (C 4 H 4 N 2 ) was investigated over a wide range of energies. Following different experimental and theoretical approaches, total, elastic and ionization cross sections as well as electron energy loss distributions were obtained.

  14. LIDAR Thomson scattering

    International Nuclear Information System (INIS)

    1991-07-01

    This collection contains 21 papers on the application and development of LIDAR (Light Detection and Ranging) Thomson scattering techniques for the determination of spatially resolved electron temperature and density in magnetic confinement experiments, particularly tokamaks. Refs, figs and tabs

  15. Applied electromagnetic scattering theory

    CERN Document Server

    Osipov, Andrey A

    2017-01-01

    Besides classical applications (radar and stealth, antennas, microwave engineering), scattering and diffraction are enabling phenomena for some emerging research fields (artificial electromagnetic materials or metamaterials, terahertz technologies, electromagnetic aspects of nano-science). This book is a tutorial for advanced students who need to study diffraction theory. The textbook gives fundamental knowledge about scattering and diffraction of electromagnetic waves and provides some working examples of solutions for practical high-frequency scattering and diffraction problems. The book focuses on the most important diffraction effects and mechanisms influencing the scattering process and describes efficient and physically justified simulation methods - physical optics (PO) and the physical theory of diffraction (PTD) - applicable in typical remote sensing scenarios. The material is presented in a comprehensible and logical form, which relates the presented results to the basic principles of electromag...

  16. Magnetic electron scattering

    International Nuclear Information System (INIS)

    Peterson, G.A.

    1989-01-01

    We briefly review some of the motivations, early results, and techniques of magnetic elastic and inelastic electron-nucleus scattering. We then discuss recent results, especially those acquired at high momentum transfers. 50 refs., 19 figs

  17. Gravitational Bhabha scattering

    International Nuclear Information System (INIS)

    Santos, A F; Khanna, Faqir C

    2017-01-01

    Gravitoelectromagnetism (GEM) as a theory for gravity has been developed similar to the electromagnetic field theory. A weak field approximation of Einstein theory of relativity is similar to GEM. This theory has been quantized. Traditional Bhabha scattering, electron–positron scattering, is based on quantized electrodynamics theory. Usually the amplitude is written in terms of one photon exchange process. With the development of quantized GEM theory, the scattering amplitude will have an additional component based on an exchange of one graviton at the lowest order of perturbation theory. An analysis will provide the relative importance of the two amplitudes for Bhabha scattering. This will allow an analysis of the relative importance of the two amplitudes as the energy of the exchanged particles increases. (paper)

  18. Treatment of the subject of tearing instability

    International Nuclear Information System (INIS)

    Paris, P.C.

    1977-07-01

    A simple approach is taken to the mechanics of potential instability associated with the steady tearing portion of J-Integral R-curves. The analysis is developed from simple examples of structural component (or test specimen) configurations with cracks, examining their instability possibilities individually, in order to draw more general conclusions about elastic-plastic cracking instability as contrasted to linear-elastic behavior. Finally, an attempt is made to model a more local cleavage-like instability for material in the fracture process zone just ahead of a crack tip. Results are then presented of a testing program which clearly demonstrates the appropriateness of the tearing instability analysis and which illustrates its broad potential for future application, as well as presenting guidelines for its further development. The material selected for analysis was Ni-Cr-Mo-V rotor steel

  19. Role of microsatellite instability in colon cancer

    Directory of Open Access Journals (Sweden)

    M. Yu. Fedyanin

    2012-01-01

    Full Text Available Coloncancer is among leading causes of cancer morbidity and mortality both inRussiaand worldwide. Development of molecular biology lead to decoding of carcinogenesis and tumor progression mechanisms. These processes require accumulation of genetic and epigenetic alterations in a tumor cell.Coloncancer carcinogenesis is characterized by mutations cumulation in genes controlling growth and differentiation of epithelial cells, which leads to their genetic instability. Microsatellite instability is a type of genetic instability characterized by deterioration of mismatch DNA repair. This leads to faster accumulation of mutations in DNA. Loss of mismatch repair mechanism can easily be diagnosed by length of DNA microsatellites. These alterations are termed microsatellite instability. They can be found both in hereditary and sporadic colon cancers. This review covers the questions of microsatellite instability, its prognostic and predictive value in colon cancer.

  20. Gravitational waves from instabilities in relativistic stars

    International Nuclear Information System (INIS)

    Andersson, Nils

    2003-01-01

    This paper provides an overview of stellar instabilities as sources of gravitational waves. The aim is to put recent work on secular and dynamical instabilities in compact stars in context, and to summarize the current thinking about the detectability of gravitational waves from various scenarios. As a new generation of kilometre length interferometric detectors is now coming online this is a highly topical theme. The review is motivated by two key questions for future gravitational-wave astronomy: are the gravitational waves from various instabilities detectable? If so, what can these gravitational-wave signals teach us about neutron star physics? Even though we may not have clear answers to these questions, recent studies of the dynamical bar-mode instability and the secular r-mode instability have provided new insights into many of the difficult issues involved in modelling unstable stars as gravitational-wave sources. (topical review)