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Sample records for on-board atomic clock

  1. Improved spacecraft radio science using an on-board atomic clock: application to gravitational wave searches

    CERN Document Server

    Tinto, Massimo; Prestage, John D; Armstrong, J W

    2008-01-01

    Recent advances in space-qualified atomic clocks (low-mass, low power-consumption, frequency stability comparable to that of ground-based clocks) can enable interplanetary spacecraft radio science experiments at unprecedented Doppler sensitivities. The addition of an on-board digital receiver would allow the up- and down-link Doppler frequencies to be measured separately. Such separate, high-quality measurements allow optimal data combinations that suppress the currently-leading noise sources: phase scintillation noise from the Earth's atmosphere and Doppler noise caused by mechanical vibrations of the ground antenna. Here we provide a general expression for the optimal combination of ground and on-board Doppler data and compute the sensitivity such a system would have to low-frequency gravitational waves (GWs). Assuming a plasma scintillation noise calibration comparable to that already demonstrated with the multi-link CASSINI radio system, the space-clock/digital-receiver instrumentation enhancements would ...

  2. The Long-term Performance Analysis for On-board Atomic Clocks of BDS

    OpenAIRE

    WANG Yupu; LÜ Zhiping; Wang, Ning

    2017-01-01

    BeiDou Navigation Satellite System (BDS) has begun to provide regional services since the end of 2012. It plays an important role in analyzing the long-term performance of BDS satellite clocks in evaluating the performance of the whole system, determining and predicting satellite clock bias (SCB) etc. Precise satellite clock data products derived from multi-satellite orbit determination are used to conduct the performance analysis of BDS satellite clocks. Specifically, the characteristics of ...

  3. The Long-term Performance Analysis for On-board Atomic Clocks of BDS

    Directory of Open Access Journals (Sweden)

    WANG Yupu

    2017-02-01

    Full Text Available BeiDou Navigation Satellite System (BDS has begun to provide regional services since the end of 2012. It plays an important role in analyzing the long-term performance of BDS satellite clocks in evaluating the performance of the whole system, determining and predicting satellite clock bias (SCB etc. Precise satellite clock data products derived from multi-satellite orbit determination are used to conduct the performance analysis of BDS satellite clocks. Specifically, the characteristics of SCB data are discussed by using a proposed modified median absolute deviation (MAD to preprocess original SCB data. Long-term variations of satellite clocks' phase, frequency, frequency drift and model noise level are analyzed based on the quadratic polynomial SCB model. Frequency stability of BDS satellite clocks is calculated and discussed based on Overlapping Hadamard Variance. Periodicity of BDS SCB is analyzed by using spectral analysis method. Integrating the above mentioned discussions and corresponding experiment results, the long-term performance of BDS satellite clocks is relatively comprehensively evaluated and analyzed. In addition, some valuable conclusions are obtained. For example, in the aspects of noise characteristics and clock drift, the performance of MEO satellite clocks is the best, followed by the IGSO satellite clocks, and the GEO satellite clocks' performance is the worst. The average values of noise level and frequency drift of BDS satellite clocks are respectively 0.677 ns and 1.922×10-18. There are also obvious periodic terms in BDS SCB data derived from multi-satellite orbit determination and their primary periods are approximate equal or one-half to the corresponding satellite orbit periods. The average value of frequency stability of BDS satellite clocks is 1.484×10-13.

  4. Optical atomic clocks

    CERN Document Server

    Poli, N; Gill, P; Tino, G M

    2014-01-01

    In the last ten years extraordinary results in time and frequency metrology have been demonstrated. Frequency-stabilization techniques for continuous-wave lasers and femto-second optical frequency combs have enabled a rapid development of frequency standards based on optical transitions in ultra-cold neutral atoms and trapped ions. As a result, today's best performing atomic clocks tick at an optical rate and allow scientists to perform high-resolution measurements with a precision approaching a few parts in $10^{18}$. This paper reviews the history and the state of the art in optical-clock research and addresses the implementation of optical clocks in a possible future redefinition of the SI second as well as in tests of fundamental physics.

  5. History of early atomic clocks

    Energy Technology Data Exchange (ETDEWEB)

    Ramsey, N.F. [Harvard Univ., Cambridge, MA (United States). Lyman Lab. of Physics

    2005-06-01

    This review of the history of early atomic clocks includes early atomic beam magnetic resonance, methods of separated and successive oscillatory fields, microwave absorption, optical pumping and atomic masers. (author)

  6. Microchip-Based Trapped-Atom Clocks

    CERN Document Server

    Vuletic, Vladan; Schleier-Smith, Monika H

    2011-01-01

    This is a chapter of a recently published book entitled Atom Chips, edited by Jakob Reichel and Vladan Vuletic. The contents of this chapter include: Basic Principles; Atomic-Fountain versus Trapped-Atom Clocks; Optical-Transition Clocks versus Microwave Clocks; Clocks with Magnetically Trapped Atoms--Fundamental Limits and Experimental Demonstrations; Readout in Trapped-Atom Clocks; and Spin Squeezing.

  7. Stochastic models for atomic clocks

    Science.gov (United States)

    Barnes, J. A.; Jones, R. H.; Tryon, P. V.; Allan, D. W.

    1983-01-01

    For the atomic clocks used in the National Bureau of Standards Time Scales, an adequate model is the superposition of white FM, random walk FM, and linear frequency drift for times longer than about one minute. The model was tested on several clocks using maximum likelihood techniques for parameter estimation and the residuals were acceptably random. Conventional diagnostics indicate that additional model elements contribute no significant improvement to the model even at the expense of the added model complexity.

  8. Collisionally induced atomic clock shifts and correlations

    Energy Technology Data Exchange (ETDEWEB)

    Band, Y. B.; Osherov, I. [Departments of Chemistry and Electro-Optics and the Ilse Katz Center for Nano-Science, Ben-Gurion University, Beer-Sheva 84105 (Israel)

    2011-07-15

    We develop a formalism to incorporate exchange symmetry considerations into the calculation of collisional frequency shifts for atomic clocks using a density-matrix formalism. The formalism is developed for both fermionic and bosonic atomic clocks. Numerical results for a finite-temperature {sup 87}Sr {sup 1}S{sub 0} (F=9/2) atomic clock in a magic wavelength optical lattice are presented.

  9. Laser controlled atom source for optical clocks

    Science.gov (United States)

    Kock, Ole; He, Wei; Świerad, Dariusz; Smith, Lyndsie; Hughes, Joshua; Bongs, Kai; Singh, Yeshpal

    2016-11-01

    Precision timekeeping has been a driving force in innovation, from defining agricultural seasons to atomic clocks enabling satellite navigation, broadband communication and high-speed trading. We are on the verge of a revolution in atomic timekeeping, where optical clocks promise an over thousand-fold improvement in stability and accuracy. However, complex setups and sensitivity to thermal radiation pose limitations to progress. Here we report on an atom source for a strontium optical lattice clock which circumvents these limitations. We demonstrate fast (sub 100 ms), cold and controlled emission of strontium atomic vapours from bulk strontium oxide irradiated by a simple low power diode laser. Our results demonstrate that millions of strontium atoms from the vapour can be captured in a magneto-optical trap (MOT). Our method enables over an order of magnitude reduction in scale of the apparatus. Future applications range from satellite clocks testing general relativity to portable clocks for inertial navigation systems and relativistic geodesy.

  10. Could Atomic clocks be affected by neutrinos?

    CERN Document Server

    Hanafi, Hanaa

    2016-01-01

    An atomic clock is a clock device that uses an electronic transition frequency of the electromagnetic spectrum of atoms as a frequency standard in order to derive a time standard since time is the reciprocal of frequency. If the electronic transition frequencies are in an "optical region", we are talking in this case about optical atomic clocks. If they are in an "microwave region" these atomic clocks are made of the metallic element cesium so they are called Cesium atomic clocks. Atomic clocks are the most accurate time and frequency standards known despite the different perturbations that can affect them, a lot of researches were made in this domain to show how the transitions can be different for different type of perturbations..Since atomic clocks are very sensitive devices, based on coherent states (A coherent state tends to loose coherence after interacting). One question can arise (from a lot of questions) which is why cosmic neutrinos are not affecting these clocks? The answer to this question requir...

  11. Atomic clocks with suppressed blackbody radiation shift

    CERN Document Server

    Yudin, V I; Okhapkin, M V; Bagayev, S N; Tamm, Chr; Peik, E; Huntemann, N; Mehlstaubler, T E; Riehle, F

    2011-01-01

    We develop a nonstandard concept of atomic clocks where the blackbody radiation shift (BBRS) and its temperature fluctuations can be dramatically suppressed (by one to three orders of magnitude) independent of the environmental temperature. The suppression is based on the fact that in a system with two accessible clock transitions (with frequencies $\

  12. Cesium Atomic Fountain Clocks at NMIJ

    Science.gov (United States)

    2010-11-01

    Wynands and S. Weyers, 2005, “Atomic fountain clocks,” Metrologia , 42, S64-S79. [2] M. Takamoto, F. L. Hong, R. Higashi, et al., 2005, “An optical...beam of laser-cooled cesium atoms,” Physical Review, A 60, R4241-R4244. [13] V. Gerginov, N. Nemitz, S. Weyers, et al., 2010, “Uncertainty evaluation of the caesium fountain clock PTB-CSF2,” Metrologia , 47, 65-79.

  13. Using Atomic Clocks to Detect Gravitational Waves

    CERN Document Server

    Loeb, Abraham

    2015-01-01

    Atomic clocks have recently reached a fractional timing precision of $<10^{-18}$. We point out that an array of atomic clocks, distributed along the Earth's orbit around the Sun, will have the sensitivity needed to detect the time dilation effect of mHz gravitational waves (GWs), such as those emitted by supermassive black hole binaries at cosmological distances. Simultaneous measurement of clock-rates at different phases of a passing GW provides an attractive alternative to the interferometric detection of temporal variations in distance between test masses separated by less than a GW wavelength, currently envisioned for the eLISA mission.

  14. Sagnac interferometry with a single atomic clock

    CERN Document Server

    Stevenson, R; Bishop, T; Lesanovsky, I; Fernholz, T

    2015-01-01

    We theoretically discuss an implementation of a Sagnac interferometer with cold atoms. In contrast to currently existing schemes our protocol does not rely on any free propagation of atoms. Instead it is based on superpositions of fully confined atoms and state-dependent transport along a closed path. Using Ramsey sequences for an atomic clock, the accumulated Sagnac phase is encoded in the resulting population imbalance between two internal (clock) states. Using minimal models for the above protocol we analytically quantify limitations arising from atomic dynamics and finite temperature. We discuss an actual implementation of the interferometer with adiabatic radio-frequency potentials that is inherently robust against common mode noise as well as phase noise from the reference oscillator.

  15. Satellite virtual atomic clock with pseudorange difference function

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Satellite atomic clocks are the basis of GPS for the control of time and frequency of navigation signals. In the Chinese Area Positioning System (CAPS), a satellite navigation system without the satellite atomic clocks onboard is successfully developed. Thus, the method of time synchronization based on satellite atomic clocks in GPS is not suitable. Satellite virtual atomic clocks are used to implement satellite navigation. With the satellite virtual atomic clocks, the time at which the signals are transmitted from the ground can be delayed into the time that the signals are transmitted from the satellites and the pseudorange measuring can be fulfilled as in GPS. Satellite virtual atomic clocks can implement the navigation, make a pseudorange difference, remove the ephemeris error, and improve the accuracy of navigation positioning. They not only provide a navigation system without satellite clocks, but also a navigation system with pseudorange difference.

  16. Laser Cooled Atomic Clocks in Space

    Science.gov (United States)

    Thompson, R. J.; Kohel, J.; Klipstein, W. M.; Seidel, D. J.; Maleki, L.

    2000-01-01

    The goals of the Glovebox Laser-cooled Atomic Clock Experiment (GLACE) are: (1) first utilization of tunable, frequency-stabilized lasers in space, (2) demonstrate laser cooling and trapping in microgravity, (3) demonstrate longest 'perturbation-free' interaction time for a precision measurement on neutral atoms, (4) Resolve Ramsey fringes 2-10 times narrower than achievable on Earth. The approach taken is: the use of COTS components, and the utilization of prototype hardware from LCAP flight definition experiments. The launch date is scheduled for Oct. 2002. The Microgravity Science Glovebox (MSG) specifications are reviewed, and a picture of the MSG is shown.

  17. Designing Zeeman slower for strontium atoms - towards optical atomic clock

    CERN Document Server

    Bober, Marcin; Gawlik, Wojciech

    2010-01-01

    We report on design and construction of a Zeeman slower for strontium atoms which will be used in an optical atomic clock experiment. The paper describes briefly required specifications of the device, possible solutions, and concentrates on the chosen design. The magnetic field produced by the built Zeeman slower has been measured and compared with the simulations. The system consisting of an oven and Zeeman slower are designed to produce an atomic beam of 10-12 s-1 flux and final velocity of ~30 m/s.

  18. Designing Zeeman slower for strontium atoms - towards optical atomic clock

    OpenAIRE

    Bober, Marcin; Zachorowski, Jerzy; Gawlik, Wojciech

    2010-01-01

    We report on design and construction of a Zeeman slower for strontium atoms which will be used in an optical atomic clock experiment. The paper describes briefly required specifications of the device, possible solutions, and concentrates on the chosen design. The magnetic field produced by the built Zeeman slower has been measured and compared with the simulations. The system consisting of an oven and Zeeman slower are designed to produce an atomic beam of 10-12 s-1 flux and final velocity of...

  19. Atomic fountains and optical clocks at SYRTE: status and perspectives

    CERN Document Server

    Abgrall, M; De Sarlo, L; Guéna, J; Laurent, Ph; Coq, Y Le; Targat, R Le; Lodewyck, J; Lours, M; Rosenbusch, P; Rovera, D; Bize, S

    2015-01-01

    In this article, we report on the work done with the LNE-SYRTE atomic clock ensemble during the last 10 years. We cover progress made in atomic fountains and in their application to timekeeping. We also cover the development of optical lattice clocks based on strontium and on mercury. We report on tests of fundamental physical laws made with these highly accurate atomic clocks. We also report on work relevant to a future possible redefinition of the SI second.

  20. Miniaturized optical system for atomic fountain clock

    Institute of Scientific and Technical Information of China (English)

    Lü De-Sheng; Qu Qiu-Zhi; Wang Bin; Zhao Jian-Bo; Li Tang; Liu Liang; Wang Yu-Zhu

    2011-01-01

    Using modularized components, we have built a miniaturized optical system for 87Rb atomic fountain clock that is fitted on an 80 cm × 60 cm optical breadboard. Compared with the conventional optical setup on the table, our system is more compact, more robust and miniaturized. Taking advantage of this system, laser beams are transmitted through eight optical fibre patch cords from the optical breadboard to an ultra high vacuum system. This optical setup has operated for five months in our fountain system and required no alignment.

  1. Miniature Optical Atomic Clock: Stabilization of a Kerr Comb Oscillator

    CERN Document Server

    Savchenkov, A A; Liang, W; Ilchenko, V S; Byrd, J; Matsko, A B; Seidel, D; Maleki, L

    2013-01-01

    Mechanical clocks consist of a pendulum and a clockwork that translates the pendulum period to displayed time. The most advanced clocks utilize optical transitions in atoms in place of the pendulum and an optical frequency comb generated by a femtosecond laser as the clockwork. The comb must be stabilized at two points along its frequency spectrum: one with a laser to lock a comb line to a transition in the atom, and another through self referencing to stabilize the frequency interval between the comb lines. This approach requires advanced techniques, so optical atomic clocks are currently laboratory devices in specialized labs. In this paper we leverage unique properties of Kerr comb oscillators for realization of optical atomic clocks in miniature form factors. In particular, we describe a clock based on D1 transition of 87Rb that fits in the palm of the hand, and can be further miniaturized to chip scale.

  2. Remote atomic clock synchronization via satellites and optical fibers

    CERN Document Server

    Piester, D; Fujieda, M; Feldmann, T; Bauch, A

    2011-01-01

    In the global network of institutions engaged with the realization of International Atomic Time (TAI), atomic clocks and time scales are compared by means of the Global Positioning System (GPS) and by employing telecommunication satellites for two-way satellite time and frequency transfer (TWSTFT). The frequencies of the state-of-the-art primary caesium fountain clocks can be compared at the level of 10e-15 (relative, 1 day averaging) and time scales can be synchronized with an uncertainty of one nanosecond. Future improvements of worldwide clock comparisons will require also an improvement of the local signal distribution systems. For example, the future ACES (atomic clock ensemble in space) mission shall demonstrate remote time scale comparisons at the uncertainty level of 100 ps. To ensure that the ACES ground instrument will be synchronized to the local time scale at PTB without a significant uncertainty contribution, we have developed a means for calibrated clock comparisons through optical fibers. An un...

  3. Hunting for topological dark matter with atomic clocks

    CERN Document Server

    Derevianko, A

    2013-01-01

    The cosmological applications of atomic clocks so far have been limited to searches of the uniform-in-time drift of fundamental constants. In this paper, we point out that a transient in time change of fundamental constants can be induced by dark matter objects that have large spatial extent, and are built from light non-Standard Model fields. The stability of this type of dark matter can be dictated by the topological reasons. We point out that correlated networks of atomic clocks, some of them already in existence, can be used as a powerful tool to search for the topological defect dark matter, thus providing another important fundamental physics application to the ever-improving accuracy of atomic clocks. During the encounter with a topological defect, as it sweeps through the network, initially synchronized clocks will become desynchronized. Time discrepancies between spatially-separated clocks are expected to exhibit a distinct signature, encoding defect's space structure and its interaction strength wit...

  4. The quantum beat principles and applications of atomic clocks

    CERN Document Server

    Major, F

    2007-01-01

    This work attempts to convey a broad understanding of the physical principles underlying the workings of these quantum-based atomic clocks, with introductory chapters placing them in context with the early development of mechanical clocks and the introduction of electronic time-keeping as embodied in the quartz-controlled clocks. While the book makes no pretense at being a history of atomic clocks, it nevertheless takes a historical perspective in its treatment of the subject. Intended for nonspecialists with some knowledge of physics or engineering, The Quantum Beat covers a wide range of salient topics relevant to atomic clocks, treated in a broad intuitive manner with a minimum of mathematical formalism. Detailed descriptions are given of the design principles of the rubidium, cesium, hydrogen maser, and mercury ion standards; the revolutionary changes that the advent of the laser has made possible, such as laser cooling, optical pumping, the formation of "optical molasses," and the cesium "fountain" stand...

  5. Ultrastable optical clock with two cold-atom ensembles

    Science.gov (United States)

    Schioppo, M.; Brown, R. C.; McGrew, W. F.; Hinkley, N.; Fasano, R. J.; Beloy, K.; Yoon, T. H.; Milani, G.; Nicolodi, D.; Sherman, J. A.; Phillips, N. B.; Oates, C. W.; Ludlow, A. D.

    2017-01-01

    Atomic clocks based on optical transitions are the most stable, and therefore precise, timekeepers available. These clocks operate by alternating intervals of atomic interrogation with the 'dead' time required for quantum state preparation and readout. This non-continuous interrogation of the atom system results in the Dick effect, an aliasing of frequency noise from the laser interrogating the atomic transition. Despite recent advances in optical clock stability that have been achieved by improving laser coherence, the Dick effect has continually limited the performance of optical clocks. Here we implement a robust solution to overcome this limitation: a zero-dead-time optical clock that is based on the interleaved interrogation of two cold-atom ensembles. This clock exhibits vanishingly small Dick noise, thereby achieving an unprecedented fractional frequency instability assessed to be for an averaging time τ in seconds. We also consider alternate dual-atom-ensemble schemes to extend laser coherence and reduce the standard quantum limit of clock stability, achieving a spectroscopy line quality factor of Q > 4 × 1015.

  6. The First Atomic Clock Program: NBS, 1947-1954

    Science.gov (United States)

    1985-12-03

    clock was being brought into operation, Lyons’ group would gladly have sacrificed something in Q for the convience of carrying the frequency...divider, while the use of small, solid samples raised hopes of a n-ortable clock. Finally, when, late in 1954 it became clear that Townes’ own "atomic

  7. Hunting for dark matter with GPS and atomic clocks

    Science.gov (United States)

    Derevianko, Andrei

    2015-05-01

    Atomic clocks are arguably the most accurate scientific instruments ever build. Modern clocks are astonishing timepieces guaranteed to keep time within a second over the age of the Universe. The cosmological applications of atomic clocks so far have been limited to searches of the uniform-in-time drift of fundamental constants. We point out that a transient in time change of fundamental constants (translating into clocks being sped up or slowed down) can be induced by dark matter objects that have large spatial extent, and are built from light non-Standard Model fields. The stability of this type of dark matter can be dictated by the topological reasons. We argue that correlated networks of atomic clocks, such as atomic clocks onboard satellites of the GPS constellation, can be used as a powerful tool to search for the topological defect dark matter. In other words, one could envision using GPS as a 50,000 km-aperture dark-matter detector. Similar arguments apply to terrestrial networks of atomic clocks. Details:

  8. Experimental constraint on dark matter detection with optical atomic clocks

    Science.gov (United States)

    Wcisło, P.; Morzyński, P.; Bober, M.; Cygan, A.; Lisak, D.; Ciuryło, R.; Zawada, M.

    2016-12-01

    The total mass density of the Universe appears to be dominated by dark matter. However, beyond its gravitational interactions at the galactic scale, little is known about its nature1. Several proposals have been advanced in recent years for the detection of dark matter2-4. In particular, a network of atomic clocks could be used to search for transient indicators of hypothetical dark matter5 in the form of stable topological defects; for example, monopoles, strings or domain walls6. The clocks become desynchronized when a dark-matter object sweeps through the network. This pioneering approach5 requires a comparison between at least two distant optical atomic clocks7-9. Here, by exploiting differences in the susceptibilities of the atoms and the cavity to the fine-structure constant10,11, we show that a single optical atomic clock12 is already sensitive to dark-matter events. This implies that existing optical atomic clocks13,14 can serve as a global topological-defect dark-matter observatory, without any further developments in experimental apparatus or the need for long phase-noise-compensated optical-fibre links15. Using optical atomic clocks, we explored a new dimension of astrophysical observations by constraining the strength of atomic coupling to hypothetical dark-matter cosmic objects. Under the conditions of our experiments, the degree of constraint was found to exceed the previously reported limits16 by more than three orders of magnitude.

  9. Improvement of an Atomic Clock using Squeezed Vacuum

    DEFF Research Database (Denmark)

    Kruse, I.; Lange, K; Peise, Jan;

    2016-01-01

    , the vacuum noise restricts the precision of the interferometer to the standard quantum limit (SQL). Here, we propose and experimentally demonstrate a novel clock configuration that surpasses the SQL by squeezing the vacuum in the empty input state. We create a squeezed vacuum state containing an average of 0.......75 atoms to improve the clock sensitivity of 10000 atoms by 2.05+0.34−0.37  dB. The SQL poses a significant limitation for today’s microwave fountain clocks, which serve as the main time reference. We evaluate the major technical limitations and challenges for devising a next generation of fountain clocks......Since the pioneering work of Ramsey, atom interferometers are employed for precision metrology, in particular to measure time and to realize the second. In a classical interferometer, an ensemble of atoms is prepared in one of the two input states, whereas the second one is left empty. In this case...

  10. Geophysical applicability of atomic clocks: direct continental geoid mapping

    CERN Document Server

    Bondarescu, Ruxandra; Hetényi, György; Boschi, Lapo; Jetzer, Philippe; Balakrishna, Jayashree; 10.1111/j.1365-246X.2012.05636.x

    2012-01-01

    The geoid is the true physical figure of the Earth, a particular equipotential surface of the gravity field of the Earth that accounts for the effect of all subsurface density variations. Its shape approximates best (in the sense of least squares) the mean level of oceans, but the geoid is more difficult to determine over continents. Satellite missions carry out distance measurements and derive the gravity field to provide geoid maps over the entire globe. However, they require calibration and extensive computations including integration, which is a non-unique operation. Here we propose a direct method and a new tool that directly measures geopotential differences on continents using atomic clocks. General Relativity Theory predicts constant clock rate at sea level, and faster (resp. slower) clock rate above (resp. below) sea level. The technology of atomic clocks is on the doorstep of reaching an accuracy level in clock rate that is equivalent to 1 cm in determining equipotential surface (including geoid) he...

  11. The quantum beat the physical principles of atomic clocks

    CERN Document Server

    Major, F G

    1998-01-01

    One of the indicators of the level of technological development of a society has been, throughout history, the precision of clocks it was able to build. This book examines the physical principles underlying the workings of clocks--from the earliest mechanical clocks to the present-day sophisticated clocks based on the properties of individual atoms. Intended for non-specialists with some knowledge of physics or engineering,the book treats the material in a broad intuitive manner, with a minimum of mathematical formalism. The presentation covers a broad range of salient topics relevant to the measurement of frequency and time intervals. The main focus is on electronic time-keeping: clocks based on quartz crystal oscillators and, at greater length, atomic clocks based on quantum resonance in rubidium, cesium, and hydrogen atoms, and, more recently, mercury ions. The book treats the revolutionary changes that the optical laser has wrought on atomic standards through laser cooling and optical pumping, and it disc...

  12. Atomic Clocks and Variations of the FIne Structure Constant

    Science.gov (United States)

    Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

    1995-01-01

    We describe a new test for possible variations of the fine structure constant alpha by comparisons of rates between clocks based on hyperfine transitions in alkali atoms with different atomic number Z. H-maser, Cs, and Hg(+) clocks have a different dependence on alpha via relativistic contributions of order (Z-alpha)(sup 2). Recent H-maser vs Hg(+) clock comparison data improve laboratory limits on a time variation by 100-fold to give dot-alpha less than or equal to 3.7 x 10(exp -14)/yr. Future laser cooled clocks (Be(+), Rb, Cs, Hg(+), etc.), when compared, will yield the most sensitive of all tests for dot-alpha/alpha.

  13. 0.75 atoms improve the clock signal of 10,000 atoms

    DEFF Research Database (Denmark)

    Kruse, I.; Lange, K.; Peise, Jan

    2017-01-01

    Since the pioneering work of Ramsey, atom interferometers are employed for precision metrology, in particular to measure time and to realize the second. In a classical interferometer, an ensemble of atoms is prepared in one of the two input states, whereas the second one is left empty. In this case.......75 atoms to improve the clock sensitivity of 10,000 atoms by 2.05 dB. The SQL poses a significant limitation for today's microwave fountain clocks, which serve as the main time reference. We evaluate the major technical limitations and challenges for devising a next generation of fountain clocks based...... on atomic squeezed vacuum....

  14. Tests of Local Position Invariance Using Continuously Running Atomic Clocks

    Science.gov (United States)

    2013-01-22

    principle) and that nongravitational measurements should be independent of the velocity of the freely falling reference frame (local Lorentz invariance...be independent of the clock composition, for example. Violation of LPI may manifest itself in an anomalous gravitational redshift of an atomic clock... violating parameters β1 and β2, the relative frequencies should vary with the gravitational potential as (ν/ν)1,2 = (β1 − β2)U/c2. (2) *steven.peil

  15. The Rubidium Atomic Clock and Basic Research

    Science.gov (United States)

    2007-12-10

    photodetector . (Chip-scale clock image from ref. 14.) 38 November 2007 Physics Today www.physicstoday.org an all-optical fashion:13 The laser field is...spectroscopy, laser chemistry, atmospheric propagation and beam control, LIDAR /LADAR remote sensing; solar cell and array testing and evaluation, battery

  16. Phase locking a clock oscillator to a coherent atomic ensemble

    CERN Document Server

    Kohlhaas, R; Cantin, E; Aspect, A; Landragin, A; Bouyer, P

    2015-01-01

    The sensitivity of an atomic interferometer increases when the phase evolution of its quantum superposition state is measured over a longer interrogation interval. In practice, a limit is set by the measurement process, which returns not the phase, but its projection in terms of population difference on two energetic levels. The phase interval over which the relation can be inverted is thus limited to the interval $[-\\pi/2,\\pi/2]$; going beyond it introduces an ambiguity in the read out, hence a sensitivity loss. Here, we extend the unambiguous interval to probe the phase evolution of an atomic ensemble using coherence preserving measurements and phase corrections, and demonstrate the phase lock of the clock oscillator to an atomic superposition state. We propose a protocol based on the phase lock to improve atomic clocks under local oscillator noise, and foresee the application to other atomic interferometers such as inertial sensors.

  17. Searching for dark matter with optical atomic clocks

    CERN Document Server

    Wcislo, Piotr; Bober, Marcin; Cygan, Agata; Lisak, Daniel; Ciurylo, Roman; Zawada, Michal

    2016-01-01

    One of the most fundamental questions of modern physics is the existence of yet unknown forms of matter and interactions. The total mass density of the Universe appears to be dominated by some hypothetical dark matter (DM). However, beyond its gravitational interaction at galactic scale, little is known about the DM nature and properties. One possibility is that it has a form of stable topological defects built from light scalar fields which, for nonzero DM-SM coupling, would result in transient variations of fundamental constants. Optical atomic clocks, highly sensitive to variations of the fine-structure constant, seem to be natural candidates for such searches. Here we demonstrate the first experimental constraint on the strength of transient DM-SM coupling determined with optical atomic clocks. Instead of measuring the phase difference between two distant clocks we determine a common component of their readouts. We show that our constraint, even for one-day measurement, greatly exceeds previous laboratory...

  18. Heisenberg-limited atom clocks based on entangled qubits.

    Science.gov (United States)

    Kessler, E M; Kómár, P; Bishof, M; Jiang, L; Sørensen, A S; Ye, J; Lukin, M D

    2014-05-16

    We present a quantum-enhanced atomic clock protocol based on groups of sequentially larger Greenberger-Horne-Zeilinger (GHZ) states that achieves the best clock stability allowed by quantum theory up to a logarithmic correction. Importantly the protocol is designed to work under realistic conditions where the drift of the phase of the laser interrogating the atoms is the main source of decoherence. The simultaneous interrogation of the laser phase with a cascade of GHZ states realizes an incoherent version of the phase estimation algorithm that enables Heisenberg-limited operation while extending the coherent interrogation time beyond the laser noise limit. We compare and merge the new protocol with existing state of the art interrogation schemes, and identify the precise conditions under which entanglement provides an advantage for clock stabilization: it allows a significant gain in the stability for short averaging time.

  19. Evaluating and Minimizing Distributed Cavity Phase Errors in Atomic Clocks

    CERN Document Server

    Li, Ruoxin

    2010-01-01

    We perform 3D finite element calculations of the fields in microwave cavities and analyze the distributed cavity phase errors of atomic clocks that they produce. The fields of cylindrical cavities are treated as an azimuthal Fourier series. Each of the lowest components produces clock errors with unique characteristics that must be assessed to establish a clock's accuracy. We describe the errors and how to evaluate them. We prove that sharp structures in the cavity do not produce large frequency errors, even at moderately high powers, provided the atomic density varies slowly. We model the amplitude and phase imbalances of the feeds. For larger couplings, these can lead to increased phase errors. We show that phase imbalances produce a novel distributed cavity phase error that depends on the cavity detuning. We also design improved cavities by optimizing the geometry and tuning the mode spectrum so that there are negligible phase variations, allowing this source of systematic error to be dramatically reduced.

  20. The fission time scale measured with an atomic clock

    NARCIS (Netherlands)

    Kravchuk, VL; Wilschut, HW; Hunyadi, M; Kopecky, S; Lohner, H; Rogachevskiy, A; Siemssen, RH; Krasznahorkay, A; Hamilton, JH; Ramayya, AV; Carter, HK

    2003-01-01

    We present a new direct method of measuring the fission absolute time scale using an atomic clock based on the lifetime of a vacancy in the atomic K-shell. We studied the reaction Ne-20 + Th-232 -> O-16 + U-236* at 30 MeV/u. The excitation energy of about 115 MeV in such a reaction is in the range w

  1. Atomic clocks as a tool to monitor vertical surface motion

    CERN Document Server

    Bondarescu, Ruxandra; Lundgren, Andrew; Hetényi, György; Houlié, Nicolas; Jetzer, Philippe; Bondarescu, Mihai

    2015-01-01

    Atomic clock technology is advancing rapidly, now reaching stabilities of $\\Delta f/f \\sim 10^{-18}$, which corresponds to resolving $1$ cm in equivalent geoid height over an integration timescale of about 7 hours. At this level of performance, ground-based atomic clock networks emerge as a tool for monitoring a variety of geophysical processes by directly measuring changes in the gravitational potential. Vertical changes of the clock's position due to magmatic, volcanic, post-seismic or tidal deformations can result in measurable variations in the clock tick rate. As an example, we discuss the geopotential change arising due to an inflating point source (Mogi model), and apply it to the Etna volcano. Its effect on an observer on the Earth's surface can be divided into two different terms: one purely due to uplift and one due to the redistribution of matter. Thus, with the centimetre-level precision of current clocks it is already possible to monitor volcanoes. The matter redistribution term is estimated to b...

  2. 2e-18 total uncertainty in an atomic clock

    CERN Document Server

    Nicholson, T L; Hutson, R B; Marti, G E; Bloom, B J; McNally, R L; Zhang, W; Barrett, M D; Safronova, M S; Strouse, G F; Tew, W L; Ye, J

    2014-01-01

    The pursuit of better atomic clocks has advanced many research areas, providing better quantum state control, new insights in quantum science, tighter limits on fundamental constant variation, and improved tests of relativity. The record for the best stability and accuracy is currently held by optical lattice clocks. This work takes an important step towards realizing the full potential of a many-particle clock with a state-of-the-art stable laser. Here, we achieve fractional stability of 2.2e-16 at 1 s by using seconds-long coherent interrogations of our clock transition in a low-density system not limited by atomic interactions. With this better stability, we perform a new accuracy evaluation of our clock, improving many systematic uncertainties that limited our previous measurements, such as the lattice ac Stark and blackbody radiation (BBR) shifts. For the lattice ac Stark systematic, we identify the lattice laser frequency where the scalar and tensor components of the shift cancel, allowing for state ind...

  3. Synchronization of Active Atomic Clocks via Quantum and Classical Channels

    CERN Document Server

    Roth, Alexander

    2016-01-01

    Superradiant lasers based on atomic ensembles exhibiting ultra-narrow optical transitions can emit light of unprecedented spectral purity and may serve as active atomic clocks. We consider two frequency-detuned active atomic clocks, which are coupled in a cascaded setup, i.e. as master & slave lasers, and study the synchronization of the slave to the master clock. In a setup where both atomic ensembles are coupled to a common cavity mode such synchronization phenomena have been predicted by Xu et al. [Phys. Rev. Lett. 113, 154101 (2014)] and experimentally observed by Weiner et al. [arXiv:1503.06464 (2015)]. Here we demonstrate that synchronization still occurs in cascaded setups but exhibits distinctly different phase diagrams. We study the characteristics of synchronization in comparison to the case of coupling through a common cavity. We also consider synchronization through a classical channel where light of the master laser is measured phase sensitively and the slave laser is injection locked by feed...

  4. Synchronization of active atomic clocks via quantum and classical channels

    Science.gov (United States)

    Roth, Alexander; Hammerer, Klemens

    2016-10-01

    Superradiant lasers based on atomic ensembles exhibiting ultranarrow optical transitions can emit light of unprecedented spectral purity and may serve as active atomic clocks. We consider two frequency-detuned active atomic clocks, which are coupled in a cascaded setup, i.e., as master and slave lasers, and study the synchronization of the slave to the master clock. In a setup where both atomic ensembles are coupled to a common cavity mode, such synchronization phenomena have been predicted by Xu et al. [M. Xu, D. A. Tieri, E. C. Fine, J. K. Thompson, and M. J. Holland, Phys. Rev. Lett. 113, 154101 (2014)., 10.1103/PhysRevLett.113.154101] and experimentally observed by Weiner et al. (J. M. Weiner et al., arXiv:1503.06464). Here we demonstrate that synchronization still occurs in cascaded setups but exhibits distinctly different phase diagrams. We study the characteristics of synchronization in comparison to the case of coupling through a common cavity. We also consider synchronization through a classical channel where light of the master laser is measured phase sensitively and the slave laser is injection locked by feedback and compare to the results achievable by coupling through quantum channels.

  5. Gravitational wave detection with optical lattice atomic clocks

    CERN Document Server

    Kolkowitz, Shimon; Langellier, Nicholas; Lukin, Mikhail D; Walsworth, Ronald L; Ye, Jun

    2016-01-01

    We propose a space-based gravitational wave detector consisting of two spatially separated, drag-free satellites sharing ultra-stable optical laser light over a single baseline. Each satellite contains an optical lattice atomic clock, which serves as a sensitive, narrowband detector of the local frequency of the shared laser light. A synchronized two-clock comparison between the satellites will be sensitive to the effective Doppler shifts induced by incident gravitational waves (GWs) at a level competitive with other proposed space-based GW detectors, while providing complementary features. The detected signal is a differential frequency shift of the shared laser light due to the relative velocity of the satellites, rather than a phase shift arising from the relative satellite positions, and the detection window can be tuned through the control sequence applied to the atoms' internal states. This scheme enables the detection of GWs from continuous, spectrally narrow sources, such as compact binary inspirals, ...

  6. Optical lattice clock with Strontium atoms; Horloge a reseau optique a atomes de strontium

    Energy Technology Data Exchange (ETDEWEB)

    Baillard, X

    2008-01-15

    This thesis presents the latest achievements regarding the optical lattice clock with Strontium atoms developed at LNE-SYRTE. After a review of the different types of optical clocks that are currently under development, we stress on the concept of optical lattice clock which was first imagined for Sr{sup 87} using the {sup 1}S{sub 0} {yields} {sup 3}P{sub 0} transition. We exhibit the features of this atom, in particular the concept of magic wavelength for the trap, and the achievable performances for this kind of clock. The second part presents the experimental aspects, insisting particularly on the ultra-stable laser used for the interrogation of the atoms which is a central part of the experiment. Among the latest improvements, an optical pumping phase and an interrogation phase using a magnetic field have been added in order to refine the evaluation of the Zeeman effect. Finally, the last part presents the experimental results. The last evaluation of the clock using Sr{sup 87} atoms allowed us to reach a frequency accuracy of 2.6*10{sup -15} and a measurement in agreement with the one made at JILA (Tokyo university) at the 10{sup -15} level. On another hand, thanks to recent theoretical proposals, we made a measurement using the bosonic isotope Sr{sup 88} by adapting the experimental setup. This measurement represents the first evaluation for this type of clock, with a frequency accuracy of 7*10{sup -14}. (author)

  7. Development of a compact cold-atom atomic clock based on coherent population trapping

    Science.gov (United States)

    Blanshan, Eric M.

    Field-grade atomic clocks capable of primary standard performance in compact physics packages would be of significant value in a variety of applications ranging from network synchronization and secure communications to GPS hold-over and inertial navigation. A cold-atom coherent population trapping (CACPT) clock featuring laser-cooled atoms and pulsed Ramsey interrogation is a strong candidate for this technology if the principal frequency shifts can be controlled and the performance degradation associated with miniaturization can be overcome. In this thesis, research focused on the development of this type of compact atomic clock is presented. To address the low atom numbers obtained in small cold-atom sources, experiments were performed in which an atomic beam was decelerated with bichromatic stimulated laser forces and loaded into a mm-scale magneto-optical trap, increasing the atom number by a factor of 12.5. A CACPT clock using the high-contrast lin||lin optical interrogation technique was developed and achieved a stability of 7 x 10-13 after one hour of integration. Doppler shifts in the clock are explained using a simple kinematic model and canceled by interrogating the atoms with a counter-propagating CPT configuration. Finally, a thorough characterization of the AC-stark effect in lin||lin CPT was performed. Observed shifts are explained in terms of contributions from coherent CPT-generating couplings and population transfer effects caused by optical pumping from incoherent light. Measurements are compared with existing and new theoretical treatments, and a laser configuration is identified that reduces clock drift from light shifts to less than 10-14 for the current system.

  8. Improvement of an Atomic Clock using Squeezed Vacuum

    DEFF Research Database (Denmark)

    Kruse, I.; Lange, K; Peise, Jan

    2016-01-01

    Since the pioneering work of Ramsey, atom interferometers are employed for precision metrology, in particular to measure time and to realize the second. In a classical interferometer, an ensemble of atoms is prepared in one of the two input states, whereas the second one is left empty. In this case......, the vacuum noise restricts the precision of the interferometer to the standard quantum limit (SQL). Here, we propose and experimentally demonstrate a novel clock configuration that surpasses the SQL by squeezing the vacuum in the empty input state. We create a squeezed vacuum state containing an average of 0...

  9. Generating and probing entangled states for optical atomic clocks

    Science.gov (United States)

    Braverman, Boris; Kawasaki, Akio; Vuletic, Vladan

    2016-05-01

    The precision of quantum measurements is inherently limited by projection noise caused by the measurement process itself. Spin squeezing and more complex forms of entanglement have been proposed as ways of surpassing this limitation. In our system, a high-finesse asymmetric micromirror-based optical cavity can mediate the atom-atom interaction necessary for generating entanglement in an 171 Yb optical lattice clock. I will discuss approaches for creating, characterizing, and optimally utilizing these nonclassical states for precision measurement, as well as recent progress toward their realization. This research is supported by DARPA QuASAR, NSF, and NSERC.

  10. Clock Technology Development in the Laser Cooling and Atomic Physics (LCAP) Program

    Science.gov (United States)

    Seidel, Dave; Thompson, R. J.; Klipstein, W. M.; Kohel, J.; Maleki, L.

    2000-01-01

    This paper presents the Laser Cooling and Atomic Physics (LCAP) program. It focuses on clock technology development. The topics include: 1) Overview of LCAP Flight Projects; 2) Space Clock 101; 3) Physics with Clocks in microgravity; 4) Space Clock Challenges; 5) LCAP Timeline; 6) International Space Station (ISS) Science Platforms; 7) ISS Express Rack; 8) Space Qualification of Components; 9) Laser Configuration; 10) Clock Rate Comparisons: GPS Carrier Phase Frequency Transfer; and 11) ISS Model Views. This paper is presented in viewgraph form.

  11. Ultra-stable optical clock with two cold-atom ensembles

    CERN Document Server

    Schioppo, M; McGrew, W F; Hinkley, N; Fasano, R J; Beloy, K; Yoon, T H; Milani, G; Nicolodi, D; Sherman, J A; Phillips, N B; Oates, C W; Ludlow, A D

    2016-01-01

    Atomic clocks based on optical transitions are the most stable, and therefore precise, timekeepers available. These clocks operate by alternating intervals of atomic interrogation with dead time required for quantum state preparation and readout. This non-continuous interrogation of the atom system results in the Dick effect, an aliasing of frequency noise of the laser interrogating the atomic transition. Despite recent advances in optical clock stability achieved by improving laser coherence, the Dick effect has continually limited optical clock performance. Here we implement a robust solution to overcome this limitation: a zero-dead-time optical clock based on the interleaved interrogation of two cold-atom ensembles. This clock exhibits vanishingly small Dick noise, thereby achieving an unprecedented fractional frequency instability of $6 \\times 10^{-17} / \\sqrt{\\tau}$ for an averaging time $\\tau$ in seconds. We also consider alternate dual-atom-ensemble schemes to extend laser coherence and reduce the stan...

  12. Compact atomic clock prototype based on coherent population trapping

    Directory of Open Access Journals (Sweden)

    Danet Jean-Marie

    2014-01-01

    Full Text Available Toward the next generations of compact atomic clocks, clocks based on coherent population trapping (CPT offer a very interesting alternative. Thanks to CPT, a quantum interfering process, this technology has made a decisive step in the miniaturization direction. Fractional frequency stability of 1.5x10-10 at 1 s has been demonstrated in commercial devices of a few cm3. The laboratory prototype presented here intends to explore what could be the ultimate stability of a CPT based device. To do so, an original double-Λ optical scheme and a pulsed interrogation have been implemented in order to get a good compromise between contrast and linewidth. A study of two main sources of noise, the relative intensity and the local oscillator (LO noise, has been performed. By designing simple solutions, it led to a new fractional frequency limitation lower than 4x10-13 at 1 s integration. Such a performance proves that such a technology could rival with classical ones as double resonance clocks.

  13. Atomic clocks: A brief history and current status of research in India

    Indian Academy of Sciences (India)

    Poonam Arora; Amrita Awasthi; Vattikonda Bharath; Aishik Acharya; Suchi Yadav; Aashish Agarwal; Amitava Sen Gupta

    2014-02-01

    Frequency corresponding to the energy difference between designated levels of an atom provides precise reference for making a universally accurate clock. Since the middle of the 20th century till now, there have been tremendous efforts in the field of atomic clocks making time the most accurately measured physical quantity. National Physical Laboratory India (NPLI) is the nation’s timekeeper and is developing an atomic fountain clock which will be a primary frequency standard. The fountain is currently operational and is at the stage of complete frequency evaluation. In this paper, a brief review on atomic time along with some of the recent results from the fountain clock will be discussed.

  14. Making optical atomic clocks more stable with $10^{-16}$ level laser stabilization

    CERN Document Server

    Jiang, Y Y; Lemke, N D; Fox, R W; Sherman, J A; Ma, L -S; Oates, C W

    2011-01-01

    The superb precision of an atomic clock is derived from its stability. Atomic clocks based on optical (rather than microwave) frequencies are attractive because of their potential for high stability, which scales with operational frequency. Nevertheless, optical clocks have not yet realized this vast potential, due in large part to limitations of the laser used to excite the atomic resonance. To address this problem, we demonstrate a cavity-stabilized laser system with a reduced thermal noise floor, exhibiting a fractional frequency instability of $2 \\times 10^{-16}$. We use this laser as a stable optical source in a Yb optical lattice clock to resolve an ultranarrow 1 Hz transition linewidth. With the stable laser source and the signal to noise ratio (S/N) afforded by the Yb optical clock, we dramatically reduce key stability limitations of the clock, and make measurements consistent with a clock instability of $5 \\times 10^{-16} / \\sqrt{\\tau}$.

  15. The dynamic Allan Variance IV: characterization of atomic clock anomalies.

    Science.gov (United States)

    Galleani, Lorenzo; Tavella, Patrizia

    2015-05-01

    The number of applications where precise clocks play a key role is steadily increasing, satellite navigation being the main example. Precise clock anomalies are hence critical events, and their characterization is a fundamental problem. When an anomaly occurs, the clock stability changes with time, and this variation can be characterized with the dynamic Allan variance (DAVAR). We obtain the DAVAR for a series of common clock anomalies, namely, a sinusoidal term, a phase jump, a frequency jump, and a sudden change in the clock noise variance. These anomalies are particularly common in space clocks. Our analytic results clarify how the clock stability changes during these anomalies.

  16. Precision Excited State Lifetime Measurements for Atomic Parity Violation and Atomic Clocks

    Science.gov (United States)

    Sell, Jerry; Patterson, Brian; Gearba, Alina; Snell, Jeremy; Knize, Randy

    2016-05-01

    Measurements of excited state atomic lifetimes provide a valuable test of atomic theory, allowing comparisons between experimental and theoretical transition dipole matrix elements. Such tests are important in Rb and Cs, where atomic parity violating experiments have been performed or proposed, and where atomic structure calculations are required to properly interpret the parity violating effect. In optical lattice clocks, precision lifetime measurements can aid in reducing the uncertainty of frequency shifts due to the surrounding blackbody radiation field. We will present our technique for precisely measuring excited state lifetimes which employs mode-locked ultrafast lasers interacting with two counter-propagating atomic beams. This method allows the timing in the experiment to be based on the inherent timing stability of mode-locked lasers, while counter-propagating atomic beams provides cancellation of systematic errors due to atomic motion to first order. Our current progress measuring Rb excited state lifetimes will be presented along with future planned measurements in Yb.

  17. High accuracy measure of atomic polarizability in an optical lattice clock

    OpenAIRE

    Sherman, J. A.; Lemke, N. D.; Hinkley, N.; Pizzocaro, M.; Fox, R. W.; Ludlow, A. D.; Oates, C. W.

    2011-01-01

    Despite being a canonical example of quantum mechanical perturbation theory, as well as one of the earliest observed spectroscopic shifts, the Stark effect contributes the largest source of uncertainty in a modern optical atomic clock through blackbody radiation. By employing an ultracold, trapped atomic ensemble and high stability optical clock, we characterize the quadratic Stark effect with unprecedented precision. We report the ytterbium optical clock's sensitivity to electric fields (suc...

  18. Atomic clock using coherent population trapping in a cesium cell: frequency stability and limitations

    Science.gov (United States)

    Mejri, Sinda; Tricot, Francois; Danet, Jean-Marie; Yun, Peter; De Clercq, Emeric; Guerandel, Stephane

    2016-06-01

    Toward the next generation of compact devices, atomic clocks based on coherent population trapping (CPT) offer a very interesting alternative. We present a review of our studies on the short and mid term stability of a compact high performance atomic clock based on CPT in view of portable applications.

  19. Searching for dilaton dark matter with atomic clocks

    CERN Document Server

    Arvanitaki, Asimina; Van Tilburg, Ken

    2014-01-01

    We propose an experiment to search for ultralight scalar dark matter (DM) with dilatonic interactions. Such couplings can arise for the dilaton as well as for moduli and axion-like particles in the presence of CP violation. Ultralight dilaton DM acts as a background field that can cause tiny but coherent oscillations in Standard Model parameters such as the fine structure constant and the proton-electron mass ratio. These minute variations can be detected through precise frequency comparisons of atomic clocks. Our experiment extends current searches for drifts in fundamental constants to the well-motivated high-frequency regime. Our proposed setups can probe scalars lighter than 10^-15 eV with discovery potential of dilatonic couplings as weak as 10^-11 times the strength of gravity, improving current equivalence principle bounds by up to 8 orders of magnitude. We point out potential 10^4 sensitivity enhancements with future optical and nuclear clocks, as well as possible signatures in gravitational wave dete...

  20. Towards a Re-definition of the Second Based on Optical Atomic Clocks

    CERN Document Server

    Riehle, Fritz

    2015-01-01

    The rapid increase in accuracy and stability of optical atomic clocks compared to the caesium atomic clock as primary standard of time and frequency asks for a future re-definition of the second in the International System of Units (SI). The status of the optical clocks based on either single ions in radio-frequency traps or on neutral atoms stored in an optical lattice is described with special emphasis of the current work at the Physikalisch-Technische Bundesanstalt (PTB). Besides the development and operation of different optical clocks with estimated fractional uncertainties in the 10^-18 range, the supporting work on ultra-stable lasers as core elements and the means to compare remote optical clocks via transportable standards, optical fibers, or transportable clocks is reported. Finally, the conditions, methods and next steps are discussed that are the prerequisites for a future re-definition of the second.

  1. Frequency Stability of Atomic Clocks Based on Coherent Population Trapping Resonance in 85Rb

    Institute of Scientific and Technical Information of China (English)

    LIU Lu; GUO Tao; DENG Ke; LIU Xin-Yuan; CHEN Xu-Zong; WANG Zhong

    2007-01-01

    An atomic clock system based on coherent population trapping (CPT) resonance in 85Rb is reported, while most past works about the CPT clock are in 87Rb. A new modulation method (full-hyperfine-frequency-splitting modulation) is presented to reduce the effect of light shift to improve the frequency stability of the CPT clock in 85Rb. The experimental results show that the short-term frequency stability of the CPT clock in 85Rb is in the order of 10-10/s and the long-term frequency stability can achieve 1.5 × 10-11 /80000s, which performs as well as 87Rb in CPT resonance. This very good frequency stability performance associated with the low-cost and low-power properties of 85Rb indicates that an atomic clock based on CPT in 85 Rb should be a promising candidate for making the chip scale atomic clock.

  2. Decreasing the uncertainty of atomic clocks via real-time noise distinguish

    CERN Document Server

    Dong, Richang; Wei, Rong; Wang, Wenli; Zou, Fan; Du, Yuanbo; Chen, Tingting; Wang, Yuzhu

    2016-01-01

    The environmental perturbation on atoms is the key factor restricting the performance of atomic frequency standards, especially in long term scale. In this letter, we demonstrate a real-time noise distinguish operation of atomic clocks. The operation improves the statistical uncertainty by about an order of magnitude of our fountain clock which is deteriorated previously by extra noises. The frequency offset bring by the extra noise is also corrected. The experiment proves the real-time noise distinguish operation can reduce the contribution of ambient noises and improve the uncertainty limit of atomic clocks.

  3. A Compact Microchip-Based Atomic Clock Based on Ultracold Trapped Rb Atoms

    CERN Document Server

    Farkas, Daniel M; Anderson, Dana Z

    2009-01-01

    We propose a compact atomic clock based on ultracold Rb atoms that are magnetically trapped near the surface of an atom microchip. An interrogation scheme that combines electromagnetically-induced transparency (EIT) with Ramsey's method of separated oscillatory fields can achieve atomic shot-noise level performance of 10^{-13}/sqrt(tau) for 10^6 atoms. The EIT signal can be detected with a heterodyne technique that provides noiseless gain; with this technique the optical phase shift of a 100 pW probe beam can be detected at the photon shot-noise level. Numerical calculations of the density matrix equations are used to identify realistic operating parameters at which AC Stark shifts are eliminated. By considering fluctuations in these parameters, we estimate that AC Stark shifts can be canceled to a level better than 2*10^{-14}. An overview of the apparatus is presented with estimates of duty cycle and power consumption.

  4. Hyperfine-induced quadrupole moments of alkali-metal atom ground states and their implications for atomic clocks

    CERN Document Server

    Derevianko, Andrei

    2016-01-01

    Spherically-symmetric ground states of alkali-metal atoms do not posses electric quadrupole moments. However, the hyperfine interaction between nuclear moments and atomic electrons distorts the spherical symmetry of electronic clouds and leads to non-vanishing atomic quadrupole moments. We evaluate these hyperfine-induced quadrupole moments using techniques of relativistic many-body theory and compile results for Li, Na, K, Rb, and Cs atoms. For heavy atoms we find that the hyperfine-induced quadrupole moments are strongly (two orders of magnitude) enhanced by correlation effects. We further apply the results of the calculation to microwave atomic clocks where the coupling of atomic quadrupole moments to gradients of electric fields leads to clock frequency uncertainties. We show that for $^{133}$Cs atomic clocks, the spatial gradients of electric fields must be smaller than $30 \\, \\mathrm{V}/\\mathrm{cm}^2$ to guarantee fractional inaccuracies below $10^{-16}$.

  5. Enhancing coherence in molecular spin qubits via atomic clock transitions

    Science.gov (United States)

    Shiddiq, Muhandis; Komijani, Dorsa; Duan, Yan; Gaita-Ariño, Alejandro; Coronado, Eugenio; Hill, Stephen

    2016-03-01

    Quantum computing is an emerging area within the information sciences revolving around the concept of quantum bits (qubits). A major obstacle is the extreme fragility of these qubits due to interactions with their environment that destroy their quantumness. This phenomenon, known as decoherence, is of fundamental interest. There are many competing candidates for qubits, including superconducting circuits, quantum optical cavities, ultracold atoms and spin qubits, and each has its strengths and weaknesses. When dealing with spin qubits, the strongest source of decoherence is the magnetic dipolar interaction. To minimize it, spins are typically diluted in a diamagnetic matrix. For example, this dilution can be taken to the extreme of a single phosphorus atom in silicon, whereas in molecular matrices a typical ratio is one magnetic molecule per 10,000 matrix molecules. However, there is a fundamental contradiction between reducing decoherence by dilution and allowing quantum operations via the interaction between spin qubits. To resolve this contradiction, the design and engineering of quantum hardware can benefit from a ‘bottom-up’ approach whereby the electronic structure of magnetic molecules is chemically tailored to give the desired physical behaviour. Here we present a way of enhancing coherence in solid-state molecular spin qubits without resorting to extreme dilution. It is based on the design of molecular structures with crystal field ground states possessing large tunnelling gaps that give rise to optimal operating points, or atomic clock transitions, at which the quantum spin dynamics become protected against dipolar decoherence. This approach is illustrated with a holmium molecular nanomagnet in which long coherence times (up to 8.4 microseconds at 5 kelvin) are obtained at unusually high concentrations. This finding opens new avenues for quantum computing based on molecular spin qubits.

  6. Light-Shifts of an Integrated Filter-Cell Rubidium Atomic Clock

    Science.gov (United States)

    2015-05-25

    rubidium atomic clock and basic research, Phys. Today , 60(11), 33-39 (2007). 2. R. T. Dupuis, T. J. Lynch, and J. R. Vaccaro, Rubidium frequency...AEROSPACE REPORT NO. TOR-2015-02236 Light-Shifts of an Integrated Filter-Cell Rubidium Atomic Clock May 25, 2015 James C. Camparo...COVERED - 4. TITLE AND SUBTITLE Light-Shifts of an Integrated Filter-Cell Rubidium Atomic Clock 5a. CONTRACT NUMBER FA8802-14-C-0001 5b

  7. Demonstration of a Dual Alkali Rb/Cs Atomic Fountain Clock

    CERN Document Server

    Guéna, J; Laurent, Ph; Abgrall, M; Rovera, D; Lours, M; Santarelli, G; Tobar, M E; Bize, S; Clairon, A; 10.1109/TUFFC.2010.1461

    2013-01-01

    We report the operation of a dual Rb/Cs atomic fountain clock. 133Cs and 87Rb atoms are cooled, launched, and detected simultaneously in LNE-SYRTE's FO2 double fountain. The dual clock operation occurs with no degradation of either the stability or the accuracy. We describe the key features for achieving such a simultaneous operation. We also report on the results of the first Rb/Cs frequency measurement campaign performed with FO2 in this dual atom clock configuration, including a new determination of the absolute 87Rb hyperfine frequency.

  8. A New Generation of Atomic Clocks: Accuracy and Stability at the 10^{-18} Level

    CERN Document Server

    Bloom, B J; Williams, J R; Campbell, S L; Bishof, M; Zhang, X; Zhang, W; Bromley, S L; Ye, J

    2013-01-01

    The exquisite control exhibited over quantum states of individual particles has revolutionized the field of precision measurement, as exemplified by the most accurate atomic clock realized in single trapped ions. Whereas many-atom lattice clocks have shown advantages in measurement precision over trapped-ion clocks, their accuracy has remained 20 times worse. Here we demonstrate, for the first time, that a many-atom system achieves accuracy (6x10^{-18}) better than a single ion-based clock, with vastly reduced averaging times (3000 s). This is the first time a single clock has achieved the best performance in all three key ingredients necessary for consideration as a primary standard - stability, reproducibility, and accuracy. This work paves the way for future experiments to integrate many-body quantum state engineering into the frontiers of quantum metrology, creating exciting opportunities to advance precision beyond the standard quantum limit. Improved frequency standards will have impact to a wide range ...

  9. A VLBI experiment using a remote atomic clock via a coherent fibre link

    Science.gov (United States)

    Clivati, Cecilia; Ambrosini, Roberto; Artz, Thomas; Bertarini, Alessandra; Bortolotti, Claudio; Frittelli, Matteo; Levi, Filippo; Mura, Alberto; Maccaferri, Giuseppe; Nanni, Mauro; Negusini, Monia; Perini, Federico; Roma, Mauro; Stagni, Matteo; Zucco, Massimo; Calonico, Davide

    2017-02-01

    We describe a VLBI experiment in which, for the first time, the clock reference is delivered from a National Metrology Institute to a radio telescope using a coherent fibre link 550 km long. The experiment consisted of a 24-hours long geodetic campaign, performed by a network of European telescopes; in one of those (Medicina, Italy) the local clock was alternated with a signal generated from an optical comb slaved to a fibre-disseminated optical signal. The quality of the results obtained with this facility and with the local clock is similar: interferometric fringes were detected throughout the whole 24-hours period and it was possible to obtain a solution whose residuals are comparable to those obtained with the local clock. These results encourage further investigation of the ultimate VLBI performances achievable using fibre dissemination at the highest precision of state-of-the-art atomic clocks.

  10. A VLBI experiment using a remote atomic clock via a coherent fibre link

    Science.gov (United States)

    Clivati, Cecilia; Ambrosini, Roberto; Artz, Thomas; Bertarini, Alessandra; Bortolotti, Claudio; Frittelli, Matteo; Levi, Filippo; Mura, Alberto; Maccaferri, Giuseppe; Nanni, Mauro; Negusini, Monia; Perini, Federico; Roma, Mauro; Stagni, Matteo; Zucco, Massimo; Calonico, Davide

    2017-01-01

    We describe a VLBI experiment in which, for the first time, the clock reference is delivered from a National Metrology Institute to a radio telescope using a coherent fibre link 550 km long. The experiment consisted of a 24-hours long geodetic campaign, performed by a network of European telescopes; in one of those (Medicina, Italy) the local clock was alternated with a signal generated from an optical comb slaved to a fibre-disseminated optical signal. The quality of the results obtained with this facility and with the local clock is similar: interferometric fringes were detected throughout the whole 24-hours period and it was possible to obtain a solution whose residuals are comparable to those obtained with the local clock. These results encourage further investigation of the ultimate VLBI performances achievable using fibre dissemination at the highest precision of state-of-the-art atomic clocks. PMID:28145451

  11. An atomic clock with $1\\times 10^{-18}$ room-temperature blackbody Stark uncertainty

    CERN Document Server

    Beloy, K; Phillips, N B; Sherman, J A; Schioppo, M; Lehman, J; Feldman, A; Hanssen, L M; Oates, C W; Ludlow, A D

    2014-01-01

    The Stark shift due to blackbody radiation (BBR) is the key factor limiting the performance of many atomic frequency standards, with the BBR environment inside the clock apparatus being difficult to characterize at a high level of precision. Here we demonstrate an in-vacuum radiation shield that furnishes a uniform, well-characterized BBR environment for the atoms in an ytterbium optical lattice clock. Operated at room temperature, this shield enables specification of the BBR environment to a corresponding fractional clock uncertainty contribution of $5.5 \\times 10^{-19}$. Combined with uncertainty in the atomic response, the total uncertainty of the BBR Stark shift is now $1\\times10^{-18}$. Further operation of the shield at elevated temperatures enables a direct measure of the BBR shift temperature dependence and demonstrates consistency between our evaluated BBR environment and the expected atomic response.

  12. Loading of a fountain clock with an enhanced Low-Velocity Intense Source of atoms

    CERN Document Server

    Dobrev, Georgi; Weyers, Stefan

    2016-01-01

    We present experimental work for improved atom loading in the optical molasses of a caesium fountain clock, employing a low-velocity intense source of atoms (LVIS) [Lu et al., Phys. Rev. Lett. 77, 3331 (1996)], which we modified by adding a "dark" state pump laser. With this modification the atom source has a mean flux of $4 \\times 10^{8}$ atoms/s at a mean atom velocity of $8.6$ m/s. Compared to fountain operation using background gas loading, we achieved a significant increase of the loaded and detected atom number by a factor of 40. Operating the fountain clock with a total number of detected atoms $N_{\\mathrm{at}}=2.9 \\times 10^6$ in the quantum projection noise-limited regime, a frequency instability $\\sigma_y\\left(1\\text{s}\\right)=2.7 \\times 10^{-14}$ was demonstrated.

  13. Testing spatial α-variation with optical atomic clocks based on highly charged ions

    Directory of Open Access Journals (Sweden)

    Berengut J. C.

    2013-08-01

    Full Text Available We review recent works illustrating the potential use of highly charged ions as the basis of optical atomic clocks of exceptional accuracy and very high sensitivity to variation of the fine structure constant, α. The tendency towards large transition energies in highly charged ions can be overcome using level crossings, which allow transitions between different orbitals to be within the range of usual lasers. We present simple scaling laws that demonstrate reduced systematics that could be realised in highly charged ion clocks. Such clocks could allow us to corroborate astronomical studies that suggest a spatial gradient in values of α across the Universe.

  14. Determination of a high spatial resolution geopotential model using atomic clock comparisons

    OpenAIRE

    Lion, Guillaume; Panet, Isabelle; Wolf, Peter; Guerlin, Christine; Bize, Sébastien; Delva, Pacôme

    2016-01-01

    Recent technological advances in optical atomic clocks are opening new perspectives for the direct determination of geopotential differences between any two points at a centimeter-level accuracy in geoid height. However, so far detailed quantitative estimates of the possible improvement in geoid determination when adding such clock measurements to existing data are lacking. We present a first step in that direction with the aim and hope of triggering further work and efforts in this emerging ...

  15. Modeling and Estimation of Stationary and Non-stationary Noises of Rubidium Atomic Clock

    Directory of Open Access Journals (Sweden)

    Deepak Mishra,

    2014-07-01

    Full Text Available Noise estimation of atomic clock is one of the important research areas in the field of atomic clock development and application. Most of the atomic clocks are having random-stochastic noises and periodic noises due to temperature variation. Random-stochastic noises have a well identified signature in time domain but periodic noises are difficult to analyze in time domain. However, in this paper, an effort is made to identify and analyze the deterministic trends of both random-stochastic noises and periodic noises due to variation in temperature using an alternate approach of least-squares normalized-error (LSNE regression algorithm. A MATLAB based application with graphical user interface (GUI is developed to estimate and analyze random-stochastic noises and periodic noises and re-estimate the stability of rubidium atomic clock after removing these noises from the raw phase data. The estimation of stationary noises are done using Allan variance from time domain data and noise profile is calculated using curve fit method. The estimation of periodic noises due to temperature variation is carried in frequency domain through spurious analysis of the frequency data of atomic clock.

  16. The magneto-optical effect of cold atoms in an integrating sphere for atomic clock and optical magnetometer

    CERN Document Server

    Wan, Jinyin; Meng, Yanling; Xiao, Ling; Liu, Peng; Wang, Xiumei; Wang, Yaning; Liu, Liang

    2014-01-01

    We investigate the magneto-optical effect of cold atoms in an integrating sphere both experimentally and theoretically. The dependence of magneto-optical rotation angle on the biased magnetic field, the probe light intensity, and the probe light detuning are investigated. The probe light background is blocked and the shot noise is strongly suppressed. This detection scheme may provide a new approach for high contrast cold atom clock and cold atom optical magnetometer.

  17. NAVEX - A Space Shuttle Experiment with Atomic Clocks

    Science.gov (United States)

    1982-12-01

    for synchronization will be clock transportations. In cooperation with our national time institute ’ Physikalisch -Technische Bundesanstalt’ (FTB...Einwegentfernungsrnessung" Nachrichtentechniskh Zeitschrift 29 (1976) H. 9, S. 673-677. [41 Tschiesche, H, : Experiment zur "Syllchronisation und Ein

  18. Near-Heisenberg-limited atomic clocks in the presence of decoherence.

    Science.gov (United States)

    Borregaard, J; Sørensen, A S

    2013-08-30

    The ultimate stability of atomic clocks is limited by the quantum noise of the atoms. To reduce this noise it has been suggested to use entangled atomic ensembles with reduced atomic noise. Potentially this can push the stability all the way to the limit allowed by the Heisenberg uncertainty relation, which is denoted the Heisenberg limit. In practice, however, entangled states are often more prone to decoherence, which may prevent reaching this performance. Here we present an adaptive measurement protocol that in the presence of a realistic source of decoherence enables us to get near-Heisenberg-limited stability of atomic clocks using entangled atoms. The protocol may thus realize the full potential of entanglement for quantum metrology despite the detrimental influence of decoherence.

  19. The Potential of Continuous, Local Atomic Clock Measurements for Earthquake Prediction and Volcanology

    CERN Document Server

    Bondarescu, Mihai; Jetzer, Philippe; Lundgren, Andrew

    2015-01-01

    Modern optical atomic clocks along with the optical fiber technology currently being developed can measure the geoid, which is the equipotential surface that extends the mean sea level on continents, to a precision that competes with existing technology. In this proceeding, we point out that atomic clocks have the potential to not only map the sea level surface on continents, but also look at variations of the geoid as a function of time with unprecedented timing resolution. The local time series of the geoid has a plethora of applications. These include potential improvement in the predictions of earthquakes and volcanoes, and closer monitoring of ground uplift in areas where hydraulic fracturing is performed.

  20. Testing General Relativity and Alternative Theories of Gravity with Space-based Atomic Clocks and Atom Interferometers

    CERN Document Server

    Bondarescu, Ruxandra; Jetzer, Philippe; Angélil, Raymond; Saha, Prasenjit; Lundgren, Andrew

    2015-01-01

    The successful miniaturisation of extremely accurate atomic clocks and atom interferometers invites prospects for satellite missions to perform precision experiments. We discuss the effects predicted by general relativity and alternative theories of gravity that can be detected by a clock, which orbits the Earth. Our experiment relies on the precise tracking of the spacecraft using its observed tick-rate. The spacecraft's reconstructed four-dimensional trajectory will reveal the nature of gravitational perturbations in Earth's gravitational field, potentially differentiating between different theories of gravity. This mission can measure multiple relativistic effects all during the course of a single experiment, and constrain the Parametrized Post-Newtonian Parameters around the Earth. A satellite carrying a clock of fractional timing inaccuracy of $\\Delta f/f \\sim 10^{-16}$ in an elliptic orbit around the Earth would constrain the PPN parameters $|\\beta -1|, |\\gamma-1| \\lesssim 10^{-6}$. We also briefly revi...

  1. Hg-201 (+) CO-Magnetometer for HG-199(+) Trapped Ion Space Atomic Clocks

    Science.gov (United States)

    Burt, Eric A. (Inventor); Taghavi, Shervin (Inventor); Tjoelker, Robert L. (Inventor)

    2011-01-01

    Local magnetic field strength in a trapped ion atomic clock is measured in real time, with high accuracy and without degrading clock performance, and the measurement is used to compensate for ambient magnetic field perturbations. First and second isotopes of an element are co-located within the linear ion trap. The first isotope has a resonant microwave transition between two hyperfine energy states, and the second isotope has a resonant Zeeman transition. Optical sources emit ultraviolet light that optically pump both isotopes. A microwave radiation source simultaneously emits microwave fields resonant with the first isotope's clock transition and the second isotope's Zeeman transition, and an optical detector measures the fluorescence from optically pumping both isotopes. The second isotope's Zeeman transition provides the measure of magnetic field strength, and the measurement is used to compensate the first isotope's clock transition or to adjust the applied C-field to reduce the effects of ambient magnetic field perturbations.

  2. Double-resonance spectroscopy in Rubidium vapour-cells for high performance and miniature atomic clocks

    Science.gov (United States)

    Gharavipour, M.; Affolderbach, C.; Kang, S.; Mileti, G.

    2017-01-01

    We report our studies on using microwave-optical double-resonance (DR) spectroscopy for a high-performance Rb vapour-cell atomic clock in view of future industrial applications. The clock physics package is very compact with a total volume of only 0.8 dm3. It contains a recently in-house developed magnetron-type cavity and a Rb vapour cell. A homed-made frequency-stabilized laser system with an integrated acousto-optical-modulator (AOM) - for switching and controlling the light output power- is used as an optical source in a laser head (LH). The LH has the overall volume of 2.5 dm3 including the laser diode, optical elements, AOM and electronics. In our Rb atomic clock two schemes of continuous-wave DR and Ramsey-DR schemes are used, where the latter one strongly reduces the light-shift effect by separation of the interaction of light and microwave. Applications of the DR clock approach to more radically miniaturized atomic clocks are discussed.

  3. Atomic clock with nuclear transition: current status in TU Wien

    OpenAIRE

    Kazakov, G. A.; Schreitl, M.; Winkler, G.; Sterba, J. H.; Steinhauser, G; Schumm, T.

    2011-01-01

    The nucleus of 229Thorium presents a unique isomer state of very low energy and long lifetime, current estimates are around 7.8 eV and seconds to hours respectively. This nuclear transitions therefore is a promising candidate for a novel type of frequency standard and several groups worldwide have set out to investigate this system. Our aim is to construct a "solid state nuclear clock", i.e. a frequency standard where Thorium ions are implanted into Calciumfluoride crystals transparent in vac...

  4. Hyperfine-induced electric dipole contributions to the electric octupole and magnetic quadrupole atomic clock transitions

    CERN Document Server

    Dzuba, V A

    2016-01-01

    Hyperfine-induced electric dipole contributions may significantly increase probabilities of otherwise very weak electric octupole and magnetic quadrupole atomic clock transitions (e.g. transitions between $s$ and $f$ electron orbitals). These transitions can be used for exceptionally accurate atomic clocks, quantum information processing and search for dark matter. They are very sensitive to new physics beyond the Standard Model, such as temporal variation of the fine structure constant, the Lorentz invariance and Einstein equivalence principle violation. We formulate conditions under which the hyperfine-induced electric dipole contribution dominates. Due to the hyperfine quenching the electric octupole clock transition in $^{173}$Yb$^+$ is two orders of magnitude stronger than that in currently used $^{171}$Yb$^+$. Some enhancement is found in $^{143}$Nd$^{13+}$, $^{149}$Pm$^{14+}$, $^{147}$Sm$^{14+}$, and $^{147}$Sm$^{15+}$ ions.

  5. Clock Technology Development for the Laser Cooling and Atomic Physics (LCAP) Program

    Science.gov (United States)

    Klipstein, W. M.; Thompson, R. J.; Seidel, D. J.; Kohel, J.; Maleki, L.

    1998-01-01

    The Time and Frequency Sciences and Technology Group at Jet Propulsion Laboratory (JPL) has developed a laser cooling capability for flight and has been selected by NASA to support the Laser-Cooling and Atomic Physics (LCAP) program. Current work in the group includes design and development for tee two laser-cooled atomic clock experiments which have been selected for flight on the International Space Station.

  6. A high-performance Raman-Ramsey Cs vapor cell atomic clock

    Science.gov (United States)

    Abdel Hafiz, Moustafa; Coget, Grégoire; Yun, Peter; Guérandel, Stéphane; de Clercq, Emeric; Boudot, Rodolphe

    2017-03-01

    We demonstrate a high-performance coherent-population-trapping (CPT) Cs vapor cell atomic clock using the push-pull optical pumping technique in the pulsed regime, allowing the detection of high-contrast and narrow Ramsey-CPT fringes. The impact of several experimental parameters onto the clock resonance and short-term fractional frequency stability, including the laser power, the cell temperature, and the Ramsey sequence parameters, has been investigated. We observe and explain the existence of a slight dependence on laser power of the central Ramsey-CPT fringe line-width in the pulsed regime. We report also that the central fringe line-width is commonly narrower than the expected Ramsey line-width given by 1 / ( 2 T R ) , with TR the free-evolution time, for short values of TR. The clock demonstrates a short-term fractional frequency stability at the level of 2.3 × 10 - 13 τ - 1 / 2 up to 100 s averaging time, mainly limited by the laser amplitude modulation noise. Comparable performances are obtained in the conventional continuous wave regime, with the use of an additional laser power stabilization setup. The pulsed interaction allows to reduce significantly the clock frequency sensitivity to laser power variations, especially for high values of TR. This pulsed CPT clock, ranking among the best microwave vapor cell atomic frequency standards, could find applications in telecommunication, instrumentation, defense or satellite-based navigation systems.

  7. DFB-ridge laser diodes at 894 nm for Cesium atomic clocks

    Science.gov (United States)

    von Bandel, N.; Garcia, M.; Lecomte, M.; Larrue, A.; Robert, Y.; Vinet, E.; Driss, O.; Parrilaud, O.; Krakowski, M.; Gruet, F.; Matthey, R.; Mileti, G.

    2016-02-01

    Time and frequency applications are in need of high accuracy and high stability clocks. Optically pumped compact industrial Cesium atomic clocks are a promising approach that could satisfy these demands. However, the stability of these clocks relies, among others, on the performances of the laser diodes that are used. This issue has led the III-V Lab to commit to the European Euripides-LAMA project that aims to provide competitive compact optical Cesium clocks for ground applications. This work will provide key experience for further space technology qualification. III-V Lab is in charge of the design, fabrication and reliability of Distributed-Feedback diodes (DFB) at 894 nm (D1 line of Cesium) and 852 nm (D2 line). LTF-Unine is in charge of their spectral characterisation. The use of D1 line for pumping will provide simplified clock architecture compared to the D2 line pumping thanks to simpler atomic transitions and a larger spectral separation between lines in the 894 nm case. Also, D1 line pumping overcomes the issue of unpumped "idle states" that occur with D2 line. The modules should provide narrow linewidth (= 10 Hz and 109 Hz2/Hz @ f >= 10 Hz.

  8. Atomic fountain clock with very high frequency stability employing a pulse-tube-cryocooled sapphire oscillator.

    Science.gov (United States)

    Takamizawa, Akifumi; Yanagimachi, Shinya; Tanabe, Takehiko; Hagimoto, Ken; Hirano, Iku; Watabe, Ken-ichi; Ikegami, Takeshi; Hartnett, John G

    2014-09-01

    The frequency stability of an atomic fountain clock was significantly improved by employing an ultra-stable local oscillator and increasing the number of atoms detected after the Ramsey interrogation, resulting in a measured Allan deviation of 8.3 × 10(-14)τ(-1/2)). A cryogenic sapphire oscillator using an ultra-low-vibration pulse-tube cryocooler and cryostat, without the need for refilling with liquid helium, was applied as a local oscillator and a frequency reference. High atom number was achieved by the high power of the cooling laser beams and optical pumping to the Zeeman sublevel m(F) = 0 employed for a frequency measurement, although vapor-loaded optical molasses with the simple (001) configuration was used for the atomic fountain clock. The resulting stability is not limited by the Dick effect as it is when a BVA quartz oscillator is used as the local oscillator. The stability reached the quantum projection noise limit to within 11%. Using a combination of a cryocooled sapphire oscillator and techniques to enhance the atom number, the frequency stability of any atomic fountain clock, already established as primary frequency standard, may be improved without opening its vacuum chamber.

  9. The Physics of Miniature Atomic Clocks: 0-0 Versus "End" Transitions

    Science.gov (United States)

    Post, Amber; Jau, Yuan-Yu; Kuzma, Nicholas; Happer, William

    2003-05-01

    The majority of traditional atomic-clock designs are based on the 0-0 hyperfine transition of a Cs 133 atom. We are currently investigating the advantages of operating a miniature optical atomic clock using the "end" transitions, e.g. connecting states |f=1, mf =+/-1> and |f=2, mf=+/-2> in 87Rb. In our paper we present extensive new measurements of relevant relaxation rates, such as those due to spin-exchange collisions, buffer-gas pressure shifts, Carver Rates and others, which ultimately determine the choices of an operating regime for the miniature optical atomic clock. The relationship between these rates is non-trivial: for example, using higher laser power will increase polarization and reduce the spin-exchange rate [1], but it can simultaneously increase the linewidth due to the optical pumping rate. The dependence of these and other relaxation rates on the cell size, temperature, pressure, a choice of buffer gas, and other parameters will be reported. Based on these measured rates, our modeling can be used to predict the transition linewidths, signal-to-noise ratios and thus the stability of the clock in different operating regimes. The trade-off between the stability of the clock and the desired small cell size and low power consumption needs to be carefully considered in order to optimize our design. In our experiments we used optical, microwave, and radio-frequency excitation to study hyperfine and Zeeman resonance lines in heated glass cells containing pure-isotope alkali-metal vapor and buffer gasses (N2, Ar, He, etc.) at low (0 - 10 G) magnetic fields. Simultaneous use of light, microwave and radio-frequency fields allowed us to calibrate surrounding magnetic fields by observing the corresponding shifts of the resonance, thus leading us to a quantitative understanding of our system. [1] S. Appelt, A. B. Baranga, A. R. Young, W. Happer, Phys. Rev. A 59, 2078 (1999).

  10. Cold Atom Clocks, Precision Oscillators and Fundamental Tests

    CERN Document Server

    Bize, S; Abgrall, M; Cacciapuoti, L; Clairon, A; Gruenert, J; Laurent, P; Lemonde, P; Maksimovic, I; Mandache, C; Marion, H; Dos Santos, F P; Rosenbusch, P; Santarelli, G; Sortais, Y; Vian, C; Zhang, S; Salomon, C; Luiten, A N; Tobar, M E; Laurent, Ph.

    2003-01-01

    We describe two experimental tests of the Equivalence Principle that are based on frequency measurements between precision oscillators and/or highly accurate atomic frequency standards. Based on comparisons between the hyperfine frequencies of 87Rb and 133Cs in atomic fountains, the first experiment constrains the stability of fundamental constants. The second experiment is based on a comparison between a cryogenic sapphire oscillator and a hydrogen maser. It tests Local Lorentz Invariance. In both cases, we report recent results which improve significantly over previous experiments.

  11. Blackbody radiation shift in the Sr optical atomic clock

    CERN Document Server

    Safronova, M S; Safronova, U I; Kozlov, M G; Clark, Charles W

    2012-01-01

    We evaluated the static and dynamic polarizabilities of the 5s^2 ^1S_0 and 5s5p ^3P_0^o states of Sr using the high-precision relativistic configuration interaction + all-order method. Our calculation explains the discrepancy between the recent experimental 5s^2 ^1S_0 - 5s5p ^3P_0^o dc Stark shift measurement \\Delta \\alpha = 247.374(7) a.u. [Middelmann et. al, arXiv:1208.2848 (2012)] and the earlier theoretical result of 261(4) a.u. [Porsev and Derevianko, Phys. Rev. A 74, 020502R (2006)]. Our present value of 247.5 a.u. is in excellent agreement with the experimental result. We also evaluated the dynamic correction to the BBR shift with 1 % uncertainty; -0.1492(16) Hz. The dynamic correction to the BBR shift is unusually large in the case of Sr (7 %) and it enters significantly into the uncertainty budget of the Sr optical lattice clock. We suggest future experiments that could further reduce the present uncertainties.

  12. Resolved Atomic Interaction Sidebands in an Optical Clock Transition

    Science.gov (United States)

    2011-06-24

    interrogated by a linearly polarized laser with bare Rabi frequency B and detuning from the atomic resonance . The Pauli exclusion principle forces...are populated. The population of transverse modes is accounted for as a renormalization of the interaction parameter. The interaction part of the

  13. Magnetic field-induced spectroscopy of forbidden optical transitions with application to lattice-based optical atomic clocks.

    Science.gov (United States)

    Taichenachev, A V; Yudin, V I; Oates, C W; Hoyt, C W; Barber, Z W; Hollberg, L

    2006-03-01

    We develop a method of spectroscopy that uses a weak static magnetic field to enable direct optical excitation of forbidden electric-dipole transitions that are otherwise prohibitively weak. The power of this scheme is demonstrated using the important application of optical atomic clocks based on neutral atoms confined to an optical lattice. The simple experimental implementation of this method--a single clock laser combined with a dc magnetic field--relaxes stringent requirements in current lattice-based clocks (e.g., magnetic field shielding and light polarization), and could therefore expedite the realization of the extraordinary performance level predicted for these clocks. We estimate that a clock using alkaline-earth-like atoms such as Yb could achieve a fractional frequency uncertainty of well below 10(-17) for the metrologically preferred even isotopes.

  14. Microfabricated rubidium vapour cell with a thick glass core for small-scale atomic clock applications

    Science.gov (United States)

    Pétremand, Y.; Affolderbach, C.; Straessle, R.; Pellaton, M.; Briand, D.; Mileti, G.; de Rooij, N. F.

    2012-02-01

    This paper presents a new fabrication method to manufacture alkali reference cells having dimensions larger than standard micromachined cells and smaller than glass-blown ones, for use in compact atomic devices such as vapour-cell atomic clocks or magnetometers. The technology is based on anodic bonding of silicon and relatively thick glass wafers and fills a gap in cell sizes and technologies available up to now: on one side, microfabrication technologies with typical dimensions ≤ 2 mm and on the other side, classical glass-blowing technologies for typical dimensions of about 6-10 mm or larger. The fabrication process is described for cells containing atomic Rb and spectroscopic measurements (optical absorption spectrum and double resonance) are reported. The analysis of the bonding strength of our cells was performed and shows that the first anodic bonding steps exhibit higher bonding strengths than the later ones. The spectroscopic results show a good quality of the cells. From the double-resonance signals, we predict a clock stability of ≈3 × 10-11 at 1 s of integration time, which compares well to the performance of compact commercial Rb atomic clocks.

  15. Al-free active region laser diodes at 894 nm for compact Cesium atomic clocks

    Science.gov (United States)

    Von Bandel, N.; Bébé Manga Lobé, J.; Garcia, M.; Larrue, A.; Robert, Y.; Vinet, E.; Lecomte, M.; Drisse, O.; Parillaud, O.; Krakowski, M.

    2015-03-01

    Time-frequency applications are in need of high accuracy and high stability clocks. Compact industrial Cesium atomic clocks optically pumped is a promising area that could satisfy these demands. However, the stability of these clocks relies, among others, on the performances of laser diodes that are used for atomic pumping. This issue has led the III-V Lab to commit to the European Euripides-LAMA project that aims to provide competitive compact optical Cesium clocks for earth applications. This work will provide key experience for further space technology qualification. We are in charge of the design, fabrication and reliability of Distributed-Feedback diodes (DFB) at 894nm (D1 line of Cesium) and 852nm (D2 line). The use of D1 line for pumping will provide simplified clock architecture compared to D2 line pumping thanks to simpler atomic transitions and larger spectral separation between lines in the 894nm case. Also, D1 line pumping overcomes the issue of unpumped "dark states" that occur with D2 line. The modules should provide narrow linewidth (<1MHz), very good reliability in time and, crucially, be insensitive to optical feedback. The development of the 894nm wavelength is grounded on our previous results for 852nm DFB. Thus, we show our first results from Al-free active region with InGaAsP quantum well broad-area lasers (100μm width, with lengths ranging from 2mm to 4mm), for further DFB operation at 894nm. We obtained low internal losses below 2cm-1, the external differential efficiency is 0.49W/A with uncoated facets and a low threshold current density of 190A/cm², for 2mm lasers at 20°C.

  16. Microfabricated vapor cells filled with a cesium dispensing paste for miniature atomic clocks

    Science.gov (United States)

    Maurice, V.; Rutkowski, J.; Kroemer, E.; Bargiel, S.; Passilly, N.; Boudot, R.; Gorecki, C.; Mauri, L.; Moraja, M.

    2017-04-01

    A method for filling alkali vapor cells with cesium from a dispensing paste is proposed and its compliance with miniature atomic clock applications is evaluated. The paste is an organic-inorganic composition of cesium molybdate, zirconium-aluminum powder, and a hybrid organic-inorganic binder. It is compatible with collective deposition processes such as micro-drop dispensing, which can be done under ambient atmosphere at the wafer-level. After deposition and sealing by anodic bonding, cesium is released from the consolidated paste through local heating with a high power laser. Linear absorption signals have been observed over one year in several cells, showing a stable atomic density. For further validation of this technology for clock applications, one cell has been implemented in a coherent population trapping clock setup to monitor its frequency stability. A fractional frequency aging rate around -4.4 × 10-12 per day has been observed, which is compliant with a clock frequency instability below 1 × 10-11 at one day integration time. This filling method can drastically reduce the cost and the complexity of alkali vapor cell fabrication.

  17. Collective non-equilibrium spin exchange in cold alkaline-earth atomic clocks

    Science.gov (United States)

    Acevedo, Oscar Leonardo; Rey, Ana Maria

    2016-05-01

    Alkaline-earth atomic (AEA) clocks have recently been shown to be reliable simulators of two-orbital SU(N) quantum magnetism. In this work, we study the non-equilibrium spin exchange dynamics during the clock interrogation of AEAs confined in a deep one-dimensional optical lattice and prepared in two nuclear levels. The two clock states act as an orbital degree of freedom. Every site in the lattice can be thought as populated by a frozen set of vibrational modes collectively interacting via predominantly p-wave collisions. Due to the exchange coupling, orbital state transfer between atoms with different nuclear states is expected to happen. At the mean field level, we observe that in addition to the expected suppression of population transfer in the presence of a large magnetic field, that makes the single particle levels off-resonance, there is also an interaction induced suppression for initial orbital population imbalance. This suppression resembles the macroscopic self-trapping mechanism seen in bosonic systems. However, by performing exact numerical solutions and also by using the so-called Truncated Wigner Approximation, we show that quantum correlations can significantly modify the mean field suppression. Our predictions should be testable in optical clock experiments. Project supported by NSF-PHY-1521080, JILA-NSF-PFC-1125844, ARO, AFOSR, and MURI-AFOSR.

  18. A compact microchip atomic clock based on all-optical interrogation of ultra-cold trapped Rb atoms

    Science.gov (United States)

    Farkas, D. M.; Zozulya, A.; Anderson, D. Z.

    2010-12-01

    We propose a compact atomic clock that uses all-optical interrogation of ultra-cold Rb atoms that are magnetically trapped near the surface of an atom microchip. The interrogation scheme, which combines electromagnetically induced transparency with Ramsey's method of separated oscillatory fields, can achieve an atomic shot-noise-level performance better than 10^{-13}/sqrt{tau} for 106 atoms. A two-color Mach-Zehnder interferometer can detect a 100-pW probe beam at the optical shot-noise level using conventional photodetectors. This measurement scheme is nondestructive and therefore can be used to increase the operational duty cycle by reusing the trapped atoms for multiple clock cycles. Numerical calculations of the density matrix equations are used to identify realistic operating parameters at which AC Stark shifts are eliminated. By considering fluctuations in these parameters, we estimate that AC Stark shifts can be canceled to a level better than 2×10-14. An overview of the apparatus is presented with estimates of cycle time and power consumption.

  19. Testing general relativity and alternative theories of gravity with space-based atomic clocks and atom interferometers

    Directory of Open Access Journals (Sweden)

    Bondarescu Ruxandra

    2015-01-01

    Full Text Available The successful miniaturisation of extremely accurate atomic clocks and atom interferometers invites prospects for satellite missions to perform precision experiments. We discuss the effects predicted by general relativity and alternative theories of gravity that can be detected by a clock, which orbits the Earth. Our experiment relies on the precise tracking of the spacecraft using its observed tick-rate. The spacecraft’s reconstructed four-dimensional trajectory will reveal the nature of gravitational perturbations in Earth’s gravitational field, potentially differentiating between different theories of gravity. This mission can measure multiple relativistic effects all during the course of a single experiment, and constrain the Parametrized Post-Newtonian Parameters around the Earth. A satellite carrying a clock of fractional timing inaccuracy of Δ f / f ∼ 10−16 in an elliptic orbit around the Earth would constrain the PPN parameters |β − 1|, |γ − 1| ≲ 10−6. We also briefly review potential constraints by atom interferometers on scalar tensor theories and in particular on Chameleon and dilaton models.

  20. Limits on gravitational Einstein Equivalence Principle violation from monitoring atomic clock frequencies during a year

    CERN Document Server

    Dzuba, V A

    2016-01-01

    Sun's gravitation potential at earth varies during a year due to varying Earth-Sun distance. Comparing the results of very accurate measurements of atomic clock transitions performed at different time in the year allows us to study the dependence of the atomic frequencies on the gravitational potential. We examine the measurement data for the ratio of the frequencies in Hg$^+$ and Al$^+$ clock transitions and absolute frequency measurements (with respect to caesium frequency standard) for Dy, Sr, H, hyperfine transitions in Rb and H, and obtain significantly improved limits on the values of the gravity related parameter of the Einstein Equivalence Principle violating term in the Standard Model Extension Hamiltonian $c_{00} = (3.0 \\pm 5.7) \\times 10^{-7}$ and the parameter for the gravity-related variation of the fine structure constant $\\kappa_{\\alpha} = (-5.3 \\pm 10) \\times 10^{-8}$.

  1. Microwave lensing frequency shift of the PHARAO laser-cooled microgravity atomic clock

    Science.gov (United States)

    Peterman, Phillip; Gibble, Kurt; Laurent, Phillipe; Salomon, Christophe

    2016-04-01

    We evaluate the microwave lensing frequency shift of the microgravity laser-cooled caesium clock PHARAO. We find microwave lensing frequency shifts of δν/ν  =  11  ×  10-17 to 13  ×  10-17, larger than the shift of typical fountain clocks. The shift has a weak dependence on PHARAO parameters, including the atomic temperature, size of the atomic cloud, detection laser intensities, and the launch velocity. We also find the lensing frequency shift to be insensitive to selection and detection spatial inhomogeneities and the expected low-frequency vibrations. We conservatively assign a nominal microwave lensing frequency uncertainty of  ±4  ×  10-17.

  2. Limits on gravitational Einstein equivalence principle violation from monitoring atomic clock frequencies during a year

    Science.gov (United States)

    Dzuba, V. A.; Flambaum, V. V.

    2017-01-01

    The Sun's gravitational potential at Earth varies during a year due to varying Earth-Sun distance. Comparing the results of very accurate measurements of atomic clock transitions performed at different times in the year allows us to study the dependence of the atomic frequencies on the gravitational potential. We examine the measurement data for the ratio of the frequencies in Hg+ and Al+ clock transitions and absolute frequency measurements (with respect to the caesium frequency standard) for Dy, Sr, H, hyperfine transitions in Rb and H and obtain significantly improved limits on the values of the gravity-related parameter of the Einstein equivalence principle violating term in the electron sector of the Standard Model extension Hamiltonian c00=(-3.0 ±5.7 )×10-7 and the parameter for the gravity-related variation of the fine structure constant κα=(-5.3 ±10 )×10-8.

  3. Highly charged ions for atomic clocks, quantum information, and search for α variation.

    Science.gov (United States)

    Safronova, M S; Dzuba, V A; Flambaum, V V; Safronova, U I; Porsev, S G; Kozlov, M G

    2014-07-18

    We propose 10 highly charged ions as candidates for the development of next generation atomic clocks, quantum information, and search for α variation. They have long-lived metastable states with transition wavelengths to the ground state between 170-3000 nm, relatively simple electronic structure, stable isotopes, and high sensitivity to α variation (e.g., Sm(14+), Pr(10+), Sm(13+), Nd(10+)). We predict their properties crucial for the experimental exploration and highlight particularly attractive systems for these applications.

  4. Delivering pulsed and phase stable light to atoms of an optical clock

    CERN Document Server

    Falke, Stephan; Sterr, Uwe; Lisdat, Christian

    2011-01-01

    In optical clocks, transitions of ions or neutral atoms are interrogated using pulsed ultra-narrow laser fields. Systematic phase chirps of the laser or changes of the optical path length during the measurement cause a shift of the frequency seen by the interrogated atoms. While the stabilization of cw-optical links is now a well established technique even on long distances, phase stable links for pulsed light pose additional challanges and have not been demonstrated so far. In addition to possible temperature or pressure drift of the laboratory, which may lead to a Doppler shift by steadily changing the optical path length, the pulsing of the clock laser light calls for short settling times of stabilization locks. Our optical path length stabilization uses retro-reflected light from a mirror that is fixed with respect to the interrogated atoms and synthetic signals during the dark time. Length changes and frequency chirps are compensated for by the switching AOM. For our strontium optical lattice clock we ha...

  5. Controlling the magnetic field sensitivity of atomic clock states by microwave dressing

    CERN Document Server

    Sárkány, L; Hattermann, H; Fortágh, J

    2014-01-01

    We demonstrate control of the differential Zeeman shift between clock states of ultracold rubidium atoms by means of non-resonant microwave dressing. Using the dc-field dependence of the microwave detuning, we suppress the first and second order differential Zeeman shift in magnetically trapped $^{87}$Rb atoms. By dressing the state pair 5S$_{1/2} F= 1, m_F = -1$ and $F= 2, m_F = 1$, a residual frequency spread of <0.1 Hz in a range of 100 mG around a chosen magnetic offset field can be achieved. This is one order of magnitude smaller than the shift of the bare states at the magic field of the Breit-Rabi parabola. We further identify double magic points, around which the clock frequency is insensitive to fluctuations both in the magnetic field and the dressing Rabi frequency. The technique is compatible with chip-based cold atom systems and allows the creation of clock and qubit states with reduced sensitivity to magnetic field noise.

  6. Optical lattice clock with strontium atoms: a second generation of cold atom clocks; Horloge a reseau optique au strontium: une 2. generation d'horloges a atomes froids

    Energy Technology Data Exchange (ETDEWEB)

    Le Targat, R

    2007-07-15

    Atomic fountains, based on a microwave transition of Cesium or Rubidium, constitute the state of the art atomic clocks, with a relative accuracy close to 10{sup -16}. It nevertheless appears today that it will be difficult to go significantly beyond this level with this kind of device. The use of an optical transition, the other parameters being unchanged, gives hope for a 4 or 5 orders of magnitude improvement of the stability and of the relative uncertainty on most systematic effects. As for motional effects on the atoms, they can be controlled on a very different manner if they are trapped in an optical lattice instead of experiencing a free ballistic flight stage, characteristic of fountains. The key point of this approach lies in the fact that the trap can be operated in such a way that a well chosen, weakly allowed, J=0 {yields} J=0 clock transition can be free from light shift effects. In this respect, the strontium atom is one of the most promising candidate, the 1S{sub 0} {yields} 3P{sub 0} transition has a natural width of 1 mHz, and several other easily accessible transitions can be used to efficiently laser cool atoms down to 10 {mu}K. This thesis demonstrates the experimental feasibility of an optical lattice clock based on the strontium atom, and reports on a preliminary evaluation of the relative accuracy with the fermionic isotope {sup 87}Sr, at a level of a few 10{sup -15}. (author)

  7. A highly miniaturized vacuum package for a trapped ion atomic clock

    Energy Technology Data Exchange (ETDEWEB)

    Schwindt, Peter D. D., E-mail: pschwin@sandia.gov; Jau, Yuan-Yu; Partner, Heather; Casias, Adrian; Wagner, Adrian R.; Moorman, Matthew; Manginell, Ronald P. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Kellogg, James R.; Prestage, John D. [Jet Propulsion Laboratory, Pasadena, California 91109 (United States)

    2016-05-15

    We report on the development of a highly miniaturized vacuum package for use in an atomic clock utilizing trapped ytterbium-171 ions. The vacuum package is approximately 1 cm{sup 3} in size and contains a linear quadrupole RF Paul ion trap, miniature neutral Yb sources, and a non-evaporable getter pump. We describe the fabrication process for making the Yb sources and assembling the vacuum package. To prepare the vacuum package for ion trapping, it was evacuated, baked at a high temperature, and then back filled with a helium buffer gas. Once appropriate vacuum conditions were achieved in the package, it was sealed with a copper pinch-off and was subsequently pumped only by the non-evaporable getter. We demonstrated ion trapping in this vacuum package and the operation of an atomic clock, stabilizing a local oscillator to the 12.6 GHz hyperfine transition of {sup 171}Y b{sup +}. The fractional frequency stability of the clock was measured to be 2 × 10{sup −11}/τ{sup 1/2}.

  8. Inner-shell magnetic dipole transition in Tm atom as a candidate for optical lattice clocks

    CERN Document Server

    Sukachev, D; Tolstikhina, I; Kalganova, E; Vishnyakova, G; Khabarova, K; Tregubov, D; Golovizin, A; Sorokin, V; Kolachevsky, N

    2016-01-01

    We consider a narrow magneto-dipole transition in the $^{169}$Tm atom at the wavelength of $1.14\\,\\mu$m as a candidate for a 2D optical lattice clock. Calculating dynamic polarizabilities of the two clock levels $[\\text{Xe}]4f^{13}6s^2 (J=7/2)$ and $[\\text{Xe}]4f^{13}6s^2 (J=5/2)$ in the spectral range from $250\\,$nm to $1200\\,$nm, we suggest the "magic" wavelength for the optical lattice at $807\\,$nm. Frequency shifts due to black-body radiation (BBR), the van der Waals interaction, the magnetic dipole-dipole interaction and other effects which can perturb the transition frequency are calculated. The transition at $1.14\\,\\mu$m demonstrates low sensitivity to the BBR shift corresponding to $8\\times10^{-17}$ in fractional units at room temperature which makes it an interesting candidate for high-performance optical clocks. The total estimated frequency uncertainty is less than $5 \\times 10^{-18}$ in fractional units. By direct excitation of the $1.14\\,\\mu$m transition in Tm atoms loaded into an optical dipole ...

  9. Quantum noise limited interferometric measurement of atomic noise: towards spin squeezing on the Cs clock transition

    CERN Document Server

    Oblak, D; Tittel, W; Vershovski, A K; Sørensen, J L; Petrov, P G; Alzar, C L G; Polzik, E S; Oblak, Daniel; Mikkelsen, Jens K.; Tittel, Wolfgang; Vershovski, Anton K.; Sorensen, Jens L.; Petrov, Plamen G.; Alzar, Carlos L. Garrido; Polzik, Eugene S.

    2003-01-01

    We investigate theoretically and experimentally a nondestructive interferometric measurement of the state population of an ensemble of laser cooled and trapped atoms. This study is a step towards generation of (quasi-) spin squeezing of cold atoms targeted at the improvement of the Caesium clock performance beyond the limit set by the quantum projection noise of atoms. We propose a protocol for the sequence of operations required to generate and utilize spin squeezing for the improved microwave clock performance via a quantum nondemolition measurement (qnd) on the probe light. We calculate the phase shift and the quantum noise of a near resonant optical probe pulse propagating through a cloud of cold 133Cs atoms. We analyze the figure of merit for a qnd measurement of the collective quasi-spin and show that it can be expressed simply as a product of the ensemble optical depth and the probability of the spontaneous emission caused by the off-resonant probe light. In the experimental part we report on the preli...

  10. Status of the atomic fountain clock at the National Research Council of Canada

    Science.gov (United States)

    Beattie, S.; Alcock, J.; Jian, B.; Gertsvolf, M.; Bernard, J.

    2016-06-01

    Despite the rapid advances in optical frequency standards, caesium fountain clocks retain a critical role as the most accurate primary frequency standards available. At the National Research Council Canada, we are working to develop a second generation caesium fountain clock. Work is currently underway to improve several systems of FCs1, such as the laser system and microwave local oscillator, which will be incorporated into its refurbished version, FCs2. In addition, we have added an optical pumping stage which has increased the detected atom number by over a factor of six. In collaboration with the National Physical Laboratory (NPL), we are planning on replacing the physics package of FCs1. We will report on several recent improvements to FCs1, along with our progress in the development of FCs2.

  11. Composite pulses in Hyper-Ramsey spectroscopy for the next generation of atomic clocks

    Science.gov (United States)

    Zanon-Willette, T.; Minissale, M.; Yudin, V. I.; Taichenachev, A. V.

    2016-06-01

    The next generation of atomic frequency standards based on an ensemble of neutral atoms or a single-ion will provide very stringent tests in metrology, applied and fundamental physics requiring a new step in very precise control of external systematic corrections. In the proceedings of the 8th Symposium on Frequency Standards and Metrology, we present a generalization of the recent Hyper-Ramsey spectroscopy with separated oscillating fields using composites pulses in order to suppress field frequency shifts induced by the interrogation laser itself. Sequences of laser pulses including specific selection of phases, frequency detunings and durations are elaborated to generate spectroscopic signals with a strong reduction of the light-shift perturbation by off resonant states. New optical clocks based on weakly allowed or completely forbidden transitions in atoms, ions, molecules and nuclei will benefit from these generalized Ramsey schemes to reach relative accuracies well below the 10-18 level.

  12. Composite pulses in Hyper-Ramsey spectroscopy for the next generation of atomic clocks

    CERN Document Server

    Zanon-Willette, T; Yudin, V I; Taichenachev, A V

    2016-01-01

    The next generation of atomic frequency standards based on an ensemble of neutral atoms or a single-ion will provide very stringent tests in metrology, applied and fundamental physics requiring a new step in very precise control of external systematic corrections. In the proceedings of the 8th Symposium on Frequency Standards and Metrology, we present a generalization of the recent Hyper-Ramsey spectroscopy with separated oscillating fields using composites pulses in order to suppress field frequency shifts induced by the interrogation laser itself. Sequences of laser pulses including specific selection of phases, frequency detunings and durations are elaborated to generate spectroscopic signals with a strong reduction of the light-shift perturbation by off resonant states. New optical clocks based on weakly allowed or completely forbidden transitions in atoms, ions, molecules and nuclei will benefit from these generalized Ramsey schemes to reach relative accuracies well below the 10$^{-18}$ level.

  13. Automatic compensation of magnetic field for a rubidium space cold atom clock

    Science.gov (United States)

    Lin, Li; Jingwei, Ji; Wei, Ren; Xin, Zhao; Xiangkai, Peng; Jingfeng, Xiang; Desheng, Lü; Liang, Liu

    2016-07-01

    When the cold atom clock operates in microgravity around the near-earth orbit, its performance will be affected by the fluctuation of magnetic field. A strategy is proposed to suppress the fluctuation of magnetic field by additional coils, whose current is changed accordingly to compensate the magnetic fluctuation by the linear and incremental compensation. The flight model of the cold atom clock is tested in a simulated orbital magnetic environment and the magnetic field fluctuation in the Ramsey cavity is reduced from 17 nT to 2 nT, which implied the uncertainty due to the second order Zeeman shift is reduced to be less than 2×10-16. In addition, utilizing the compensation, the magnetic field in the trapping zone can be suppressed from 7.5 μT to less than 0.3 μT to meet the magnetic field requirement of polarization gradients cooling of atoms. Project supported by the Ministry of Science and Technology of China (Grant No. 2013YQ09094304), the Youth Innovation Promotion Association, Chinese Academy of Sciences, and the National Natural Science Foundation of China (Grant Nos. 11034008 and 11274324).

  14. Role of the multipolar black-body radiation shifts in the atomic clocks at the 10-18 uncertainty level

    Indian Academy of Sciences (India)

    B K Sahoo

    2014-08-01

    We present here an overview of the role of the multipolar black-body radiation (BBR) shifts in the single ion atomic clocks to appraise the anticipated 10-18 uncertainty level. With an attempt to use the advanced technologies for reducing the instrumental uncertainties at the unprecedented low, it is essential to investigate contributions from the higher-order systematics to achieve the ambitious goal of securing the most precise clock frequency standard. In this context, we have analysed contributions to the BBR shifts from the multipolar polarizabilities in a few ion clocks.

  15. Determination of a high spatial resolution geopotential model using atomic clock comparisons

    Science.gov (United States)

    Lion, G.; Panet, I.; Wolf, P.; Guerlin, C.; Bize, S.; Delva, P.

    2017-01-01

    Recent technological advances in optical atomic clocks are opening new perspectives for the direct determination of geopotential differences between any two points at a centimeter-level accuracy in geoid height. However, so far detailed quantitative estimates of the possible improvement in geoid determination when adding such clock measurements to existing data are lacking. We present a first step in that direction with the aim and hope of triggering further work and efforts in this emerging field of chronometric geodesy and geophysics. We specifically focus on evaluating the contribution of this new kind of direct measurements in determining the geopotential at high spatial resolution (≈ 10 km). We studied two test areas, both located in France and corresponding to a middle (Massif Central) and high (Alps) mountainous terrain. These regions are interesting because the gravitational field strength varies greatly from place to place at high spatial resolution due to the complex topography. Our method consists in first generating a synthetic high-resolution geopotential map, then drawing synthetic measurement data (gravimetry and clock data) from it, and finally reconstructing the geopotential map from that data using least squares collocation. The quality of the reconstructed map is then assessed by comparing it to the original one used to generate the data. We show that adding only a few clock data points (less than 1% of the gravimetry data) reduces the bias significantly and improves the standard deviation by a factor 3. The effect of the data coverage and data quality on the results is investigated, and the trade-off between the measurement noise level and the number of data points is discussed.

  16. Determination of a high spatial resolution geopotential model using atomic clock comparisons

    Science.gov (United States)

    Lion, G.; Panet, I.; Wolf, P.; Guerlin, C.; Bize, S.; Delva, P.

    2017-06-01

    Recent technological advances in optical atomic clocks are opening new perspectives for the direct determination of geopotential differences between any two points at a centimeter-level accuracy in geoid height. However, so far detailed quantitative estimates of the possible improvement in geoid determination when adding such clock measurements to existing data are lacking. We present a first step in that direction with the aim and hope of triggering further work and efforts in this emerging field of chronometric geodesy and geophysics. We specifically focus on evaluating the contribution of this new kind of direct measurements in determining the geopotential at high spatial resolution (≈ 10 km). We studied two test areas, both located in France and corresponding to a middle (Massif Central) and high (Alps) mountainous terrain. These regions are interesting because the gravitational field strength varies greatly from place to place at high spatial resolution due to the complex topography. Our method consists in first generating a synthetic high-resolution geopotential map, then drawing synthetic measurement data (gravimetry and clock data) from it, and finally reconstructing the geopotential map from that data using least squares collocation. The quality of the reconstructed map is then assessed by comparing it to the original one used to generate the data. We show that adding only a few clock data points (less than 1% of the gravimetry data) reduces the bias significantly and improves the standard deviation by a factor 3. The effect of the data coverage and data quality on the results is investigated, and the trade-off between the measurement noise level and the number of data points is discussed.

  17. Improved limits on interactions of low-mass spin-0 dark matter from atomic clock spectroscopy

    Science.gov (United States)

    Stadnik, Y. V.; Flambaum, V. V.

    2016-08-01

    Low-mass (sub-eV) spin-0 dark matter particles, which form a coherently oscillating classical field ϕ =ϕ0cos(mϕt ) , can induce oscillating variations in the fundamental constants through their interactions with the standard model sector. We calculate the effects of such possible interactions, which may include the linear interaction of ϕ with the Higgs boson, on atomic and molecular transitions. Using recent atomic clock spectroscopy measurements, we derive limits on the linear interaction of ϕ with the Higgs boson, as well as its quadratic interactions with the photon and light quarks. For the linear interaction of ϕ with the Higgs boson, our derived limits improve on existing constraints by up to 2-3 orders of magnitude.

  18. Dependence of microwave-excitation signal parameters on frequency stability of caesium atomic clock

    Science.gov (United States)

    Petrov, A. A.; Davydov, V. V.; Vologdin, V. A.; Zalyotov, D. V.

    2015-11-01

    New scheme of the microwave - excitation signal for the caesium atomic clock is based on method of direct digital synthesis. The theoretical calculations and experimental research showed decrease step frequency tuning by several orders and improvement the spectral characteristics of the output signal of frequency synthesizer. A range of generated output frequencies is expanded, and the possibility of detuning the frequency of the neighboring resonance of spectral line that makes it possible to adjust the C-field in quantum frequency standard is implemented. Experimental research of the metrological characteristics of the quantum frequency standard on the atoms of caesium - 133 with new design scheme of the microwave - excitation signal showed improvement in daily frequency stability on 1.2*10-14.

  19. Effects of variation of fundamental constants from Big Bang to atomic clocks

    Science.gov (United States)

    Flambaum, Victor

    2004-05-01

    Theories unifying gravity with other interactions suggest temporal and spatial variation of the fundamental "constants" in expanding Universe. I discuss effects of variation of the fine structure constant, strong interaction, quark mass and gravitational constant. The measurements of these variations cover the lifespan of the Universe from few minutes after Big Bang to the present time and give controversial results. There are some hints for the variations in Big Bang nucleosynthesis, quasar absorption spectra and Oklo natural nuclear reactor data. A very promising method to search for the variation of the fundamental constants consists in comparison of different atomic clocks. A billion times enhancement of the variation effects happens in transitions between accidentally degenerate atomic energy levels.

  20. Improved limits on interactions of low-mass spin-0 dark matter from atomic clock spectroscopy

    CERN Document Server

    Stadnik, Y V

    2016-01-01

    Low-mass (sub-eV) spin-0 dark matter particles, which form a coherently oscillating classical field $\\phi = \\phi_0 \\cos(m_\\phi t)$, can induce oscillating variations in the fundamental constants through their interactions with the Standard Model sector. We calculate the effects of such possible interactions, which may include the linear interaction of $\\phi$ with the Higgs boson, on atomic and molecular transitions. Using recent atomic clock spectroscopy measurements, we derive new limits on the linear interaction of $\\phi$ with the Higgs boson, as well as its quadratic interactions with the photon and light quarks. For the linear interaction of $\\phi$ with the Higgs boson, our derived limits improve on existing constraints by up to $2-3$ orders of magnitude.

  1. Microfabricated cells for chip-scale atomic clock based on coherent population trapping: Fabrication and investigation

    Directory of Open Access Journals (Sweden)

    S.V. Ermak

    2015-03-01

    Full Text Available A universal method for fabrication of miniature cells for frequency standards and quantum magnetometers containing 87Rb atoms in the atmosphere of inert gas neon based on integrated technologies is considered. The results of experimental studies of coherent population trapping signals observed for a series of cells which provided recovery of vapors of an alkali metal from the rubidium dichromate salt with the help of laser radiation are presented. The coherent population trapping signals with a typical linewidth of 2–3 kHz and a signal-to-noise ratio of 1500 in the 1-Hz bandwidth were observed, which allows one to provide a relative frequency stability of atomic clock of 10−11 at 100 s.

  2. Effects of getters on hermetically sealed micromachined cesium-neon cells for atomic clocks

    Science.gov (United States)

    Hasegawa, M.; Chutani, R. K.; Boudot, R.; Mauri, L.; Gorecki, C.; Liu, X.; Passilly, N.

    2013-05-01

    The wafer-level integration technique of PageWafer® (SAES Getters’ solution for getter film integration into wafer to wafer bonded devices) has been tested in hermetically sealed miniature glass-Si-glass cells filled with Cs and Ne, e.g. for microelectromechanical systems (MEMS) atomic clock applications. Getter effects on the cell atmosphere are analyzed by quadruple mass spectroscopy and coherent population trapping (CPT) spectroscopy. The quadruple mass spectroscopy revealed that the residual gases (H2, O2, N2 and CO2) that are attributed to anodic bonding process are drastically reduced by the getter films while desirable gases such as Ne seem to remain unaffected. The impurity pressure in the getter-integrated cells was measured to be less than 4 × 10-2 mbar, i.e. pressure 50 times lower than the one measured in the cells without getter (2 mbar). Consequently, the atmosphere of the getter-integrated cells is much more pure than that of the getter-free cells. CPT signals obtained from the getter-integrated cells are stable and are, in addition, similar to each other within a cell batch, suggesting the strong potential of applications of this getter film and especially for its wafer-level integration to MEMS atomic clocks and magnetometers.

  3. A Technology Demonstration Experiment for Laser Cooled Atomic Clocks in Space

    Science.gov (United States)

    Klipstein, W. M.; Kohel, J.; Seidel, D. J.; Thompson, R. J.; Maleki, L.; Gibble, K.

    2000-01-01

    We have been developing a laser-cooling apparatus for flight on the International Space Station (ISS), with the intention of demonstrating linewidths on the cesium clock transition narrower than can be realized on the ground. GLACE (the Glovebox Laser- cooled Atomic Clock Experiment) is scheduled for launch on Utilization Flight 3 (UF3) in 2002, and will be mounted in one of the ISS Glovebox platforms for an anticipated 2-3 week run. Separate flight definition projects funded at NIST and Yale by the Micro- gravity Research Division of NASA as a part of its Laser Cooling and Atomic Physics (LCAP) program will follow GLACE. Core technologies for these and other LCAP missions are being developed at JPL, with the current emphasis on developing components such as the laser and optics subsystem, and non-magnetic vacuum-compatible mechanical shutters. Significant technical challenges in developing a space qualifiable laser cooling apparatus include reducing the volume, mass, and power requirements, while increasing the ruggedness and reliability in order to both withstand typical launch conditions and achieve several months of unattended operation. This work was performed at the Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration.

  4. Generalized Collective States and Their Role in a Collective State Atomic Interferometer and Atomic Clock

    CERN Document Server

    Sarkar, Resham; Fang, Renpeng; Tu, Yanfei; Shahriar, Selim M

    2014-01-01

    We investigate the behavior of an ensemble of N non-interacting, identical atoms, excited by a laser with a wavelength of $\\lambda$. In general, the i-th atom sees a Rabi frequency $\\Omega_i$, an initial position dependent laser phase $\\phi_i$, and a motion induced Doppler shift of $\\delta_i$. When $\\Omega_i=\\Omega$ and $\\delta_i=\\delta$ for all atoms, the system evolves into a superposition of (N+1) symmetric collective states (SCS), independent of the values of $\\phi_i$. If $\\phi_i=\\phi$ for all atoms, these states simplify to the well-known Dicke collective states. When $\\Omega_i$ or $\\delta_i$ is distinct for each atom, the system evolves into a superposition of SCS as well as asymmetric collective states (ACS). For large N, the number of ACS's $(2^N-N-1)$ is far greater than that of the SCS. We show how to formulate the properties of all the collective states under various non-idealities, and use this formulation to understand the dynamics thereof. For the case where $\\Omega_i=\\Omega$ and $\\delta_i=\\delt...

  5. Explaining atomic clock behavior in a gravitational field with only 1905 Relativity

    CERN Document Server

    Hidalgo-Gato, Rafael A Valls

    2010-01-01

    Supported only in the two 1905 Einstein's papers on Relativity and a very rigid respect for the historical context, an analysis is done of the derivation of the universal mass-energy relationship. It is found, contrary to the today accepted Physics knowledge, that a body's Rest Mass measures its Potential Energy in the 1905 context. After emphasizing the difference between 1905 Relativity (1905R) and Special Relativity (SR), the developing of a 1905R relativistic gravity is started for a small mass m material point moving in the central gravitational field of a great mass M one. A formula for the rest mass m_0 as a function of its distance r from M is obtained. Finally, those results are applied to an atomic clock in a gravitational field, reaching a factor to obtain the clock time rate change very close to the GR one. The factors from 1905R and GR are compared, emphasizing the absent of a singularity in 1905R. In the conclusions, a new road for the development of a 1905R relativistic mechanics is declared, r...

  6. Measurement of the magnetic field profile in the atomic fountain clock FoCS-2 using Zeeman spectroscopy

    CERN Document Server

    Laurent, Devenoges; André, Stefanov; Antoine, Jallageas; Jacques, Morel; Thomas, Südmeyer; Pierre, Thomann

    2016-01-01

    We report the evaluation of the second order Zeeman shift in the continuous atomic fountain clock FoCS-2. Because of the continuous operation and its geometrical constraints, the methods used in pulsed fountain are not applicable. We use here time-resolved Zeeman spectroscopy to probe the magnetic field profile in the clock. The pulses of ac magnetic excitation allow us to measure the Zeeman frequency with spatial resolution and to evaluate the Zeeman shift with an uncertainty smaller than 10E-16 in relative units.

  7. How ticks an atomic clock? Realization of the second from 1955 until today; Wie tickt eine Atomuhr? Realisierung der Sekunde von 1955 bis heute

    Energy Technology Data Exchange (ETDEWEB)

    Bauch, Andreas [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany). Arbeitsgruppe ' Zeituebertragung' ; Weyers, Stefan [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany). Arbeitsgruppe ' Zeitnormale' ; Peik, Ekkehard [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany). Fachbereich ' Zeit und Frequenz'

    2016-06-15

    In this paper the principle of the atomic clock on the base of the hyperfine-structure transition in {sup 133}Cs is described. Additional further developments in the definition of the second on the base of optical clocks are considered. (HSI)

  8. Ultrastable laser system for spectroscopy of the 1S0-3P0 clock transition in Sr atoms

    Science.gov (United States)

    Berdasov, O. I.; Gribov, A. Yu.; Belotelov, G. S.; Pal'chikov, V. G.; Strelkin, S. A.; Khabarova, K. Yu.; Kolachevsky, N. N.; Slyusarev, S. N.

    2017-06-01

    A laser system with a spectral linewidth less than 1 Hz for spectroscopy of the 1S0-3P0 clock transition in strontium atoms has been demonstrated. A semiconductor laser emitting at a wavelength of 698 nm was stabilised to an external high-finesse Fabry-Perot cavity with vibration and temperature compensation near the zero expansion point. After laser cooling to a temperature below 3 μK, 88Sr atoms were loaded into an optical lattice at a magic wavelength of 813 nm. The laser system was used to characterise the 88Sr clock transition by magnetically induced spectroscopy. The resonance spectral width was determined to be 130 ± 17 Hz, which corresponds to a quality factor of 3 × 1012.

  9. A low phase noise microwave frequency synthesis for a high-performance cesium vapor cell atomic clock.

    Science.gov (United States)

    François, B; Calosso, C E; Danet, J M; Boudot, R

    2014-09-01

    We report the development, absolute phase noise, and residual phase noise characterization of a 9.192 GHz microwave frequency synthesis chain devoted to be used as a local oscillator in a high-performance cesium vapor cell atomic clock based on coherent population trapping (CPT). It is based on frequency multiplication of an ultra-low phase noise 100 MHz oven-controlled quartz crystal oscillator using a nonlinear transmission line-based chain. Absolute phase noise performances of the 9.192 GHz output signal are measured to be -42, -100, -117 dB rad(2)/Hz and -129 dB rad(2)/Hz at 1 Hz, 100 Hz, 1 kHz, and 10 kHz offset frequencies, respectively. Compared to current results obtained in a state-of-the-art CPT-based frequency standard developed at LNE-SYRTE, this represents an improvement of 8 dB and 10 dB at f = 166 Hz and f = 10 kHz, respectively. With such performances, the expected Dick effect contribution to the atomic clock short term frequency stability is reported at a level of 6.2 × 10(-14) at 1 s integration time, that is a factor 3 higher than the atomic clock shot noise limit. Main limitations are pointed out.

  10. Atomic clocks based on extened-cavity diode laser in multimode operation

    Science.gov (United States)

    Yim, Sin; Cho, D.

    2011-05-01

    We demonstrated the possibilities to develope an atomic clock based on coherent population trapping (CPT) without using a local oscillator and a modulator. Instead of using a modulator, we use two modes from a single extended-cavity diode laser in multimode operation. Two different types of feedback system are applied to stabilize a difference frequency between the two modes and eliminate the need for an extra frequency modulation. In the first type, we employ an electronic feedback using dispersion of the CPT resonance as an error signal. The two modes are phase locked with reference to a dispersion signal from a CPT resonance of 85Rb at 3.036 GHz ground hyperfine splitting. We use D1 transition at 794.8 nm with lin ⊥lin polarizations to obtain large-contrast CPT signal. Allan deviation of the beat frequency between the two modes is 1 ×10-10 at 200-s integration time. In the second type, we employ optoelectronic feedback to construct an opto-electronic oscillator (OEO). In an OEO, the beating signal between two modes is recovered by a fast photodiode, and its output is amplified and fed back to the laser diode by using a direct modulation of an injection current. When the OEO loop is closed, oscillation frequency depends on variations of the loop length. In order to stabilize an OEO loop length and thereby its oscillation frequency, CPT cell is inserted to play a role of microwave band pass filter. Allan deviation of the CPT-stabilized OEO is 2 ×10-10 at 100-s integration time.

  11. Optimizing passive quantum clocks

    Science.gov (United States)

    Mullan, Michael; Knill, Emanuel

    2014-10-01

    We describe protocols for passive atomic clocks based on quantum interrogation of the atoms. Unlike previous techniques, our protocols are adaptive and take advantage of prior information about the clock's state. To reduce deviations from an ideal clock, each interrogation is optimized by means of a semidefinite program for atomic state preparation and measurement whose objective function depends on the prior information. Our knowledge of the clock's state is maintained according to a Bayesian model that accounts for noise and measurement results. We implement a full simulation of a running clock with power-law noise models and find significant improvements by applying our techniques.

  12. One single trapped and laser cooled radium ion: Towards an all-optical atomic clock

    Energy Technology Data Exchange (ETDEWEB)

    Versolato, Oscar; Wansbeek, Lotje; Willmann, Lorenz; Timmermans, Rob; Jungmann, Klaus [KVI, University of Groningen (Netherlands)

    2008-07-01

    One single trapped radium ion is an ideal candidate for an all-optical frequency standard (*clock*). This system provides a long coherence time and tractable systematics. If the ion is laser cooled to the Lamb-Dicke regime, first order Doppler shifts are eliminated. Ultra-narrow transitions in radium ions provide an excellent basis for such a high stability clock, using commercially available semiconductor lasers in the visible regime. In certain odd isotopes of radium, the nuclear electric quadrupole shift is absent. Further, the radium ion is an excellent candidate for a high sensitivity experiment to search for a time variation of the finestructure constant.

  13. Precision Clock Evaluation Facility

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Tests and evaluates high-precision atomic clocks for spacecraft, ground, and mobile applications. Supports performance evaluation, environmental testing,...

  14. Accuracy budget of the 88Sr optical atomic clocks at KL FAMO

    Science.gov (United States)

    Radzewicz, Czesław; Bober, Marcin; Morzyński, Piotr; Cygan, Agata; Lisak, Daniel; Bartoszek-Bober, Dobrosława; Masłowski, Piotr; Ablewski, Piotr; Zachorowski, Jerzy; Gawlik, Wojciech; Ciuryło, Roman; Zawada, Michał

    2016-08-01

    This paper presents a detailed accuracy budget of two independent strontium optical lattice clocks at the National Laboratory FAMO (KL FAMO) probed with a single shared ultra-narrow laser. The combined instability of the two frequency standards was 7× {10}-17 after 105s of averaging.

  15. Dynamic polarizabilities and related properties of clock states of ytterbium atom

    CERN Document Server

    Dzuba, V A

    2009-01-01

    We carry out relativistic many-body calculations of the static and dynamic dipole polarizabilities of the ground $6s^2 ^1S_0$ and the first excited $6s6p ^3P^o_0$ states of Yb. With these polarizabilities, we compute several properties of Yb relevant to optical lattice clocks operating on the $6s^2 ^1S_0 - 6s6p ^3P^o_0$ transition. We determine (i) the first four {\\em magic} wavelengths of the laser field for which the frequency of the clock transition is insensitive to the laser intensity. While the first magic wavelength is known, we predict the second, the third and the forth magic wavelengths to be 551 nm, 465 nm, and 413 nm. (ii) We reevaluate the effect of black-body radiation on the frequency of the clock transition, the resulting clock shift at $T=300 \\mathrm{K}$ being $-1.41(17)$ Hz. (iii) We compute long-range interatomic van der Waals coefficients (in a.u.) $C_6(6s^2 ^1S_0 +6s^2 ^1S_0) = 1909(160)$, $C_6(6s^2 ^1S_0 + 6s6p ^3P_0) =2709(338) $, and $C_6(6s6p ^3P_0 + 6s6p ^3P_0) =3886(360) $. Finally,...

  16. Optical clock networks

    Science.gov (United States)

    Riehle, Fritz

    2017-01-01

    Within the last decade, optical atomic clocks have surpassed the best cesium clocks, which are used to realize the unit of time and frequency, in terms of accuracy and stability by about two orders of magnitude. When remote optical atomic clocks are connected by links without degradation in the clock signals, an optical clock network is formed, with distinct advantages for the dissemination of time, geodesy, astronomy and basic and applied research. Different approaches for time and frequency transfer in the microwave and optical regime, via satellites and free-space links, optical fibre links, or transportable optical atomic clocks, can be used to form a hybrid clock network that may allow a future redefinition of the unit of time based on an optical reference transition.

  17. A CPT-based Cs vapor cell atomic clock with a short-term fractional frequency stability of 3 x 10-13 τ-1/2

    Science.gov (United States)

    Abdel Hafiz, Moustafa; Liu, Xiaochi; Guérandel, Stéphane; De Clercq, Emeric; Boudot, Rodolphe

    2016-06-01

    This article reports on the development and short-term fractional frequency stability of a continuous-regime (CW) Cs vapor cell atomic clock based on coherent population trapping (CPT). The push-pull optical pumping technique is used to increase the number of atoms that participate to the clock transition, yielding a typical CPT resonance contrast of 25% for a CPT linewidth of about 450 Hz. The clock short-term fractional frequency stability is measured to be 3 x 10-13 τ-1/2 up to 100 seconds averaging time, in correct agreement with the signal-to-noise ratio limit. The mid-term frequency stability results are currently mainly limited by laser power effects. The detection of high-contrast narrow Raman-Ramsey fringes is demonstrated with this setup by making the atoms interact with a light pulse sequence.

  18. A New Rb Lamp Exciter Circuit for Rb atomic clocks and Studies on Transition from Ring to Red mode

    CERN Document Server

    Singh, Savita; Saxena, G M

    2010-01-01

    In this paper we describe the development of novel RF exciter circuit for electrode less Rb lamp. The lamp exciter circuit is a RF oscillator with a a new configuration operating at 60 to 65 MHz frequency with 3 to 4 watt power. The Rb lamp is used in exciting the ground state hyperfine transitions in Rb atom in a glass cell placed inside a tuned microwave cavity, As the frequency of these hyperfine transitions is very stable it is used in the development of Rb atomic clock by phase locking the oven controlled crystal oscillator (OCXO) to this atomic transition frequency. The details of the Rb lamp exciter are presented in the paper.The Lamp is ideally operated in ring mode as in this mode the linewidth is narrow and there is no self reversal. However, high temperature and RF excitation power may drive the Rb lamp to red mode which gives rise to line broadening and self reversal. It is the experience that mode change from ring to red deteriorates the atomic signal strength and S/N. In this paper the reasons o...

  19. Formulation of geopotential difference determination using optical-atomic clocks onboard satellites and on ground based on Doppler cancellation system

    Science.gov (United States)

    Shen, Ziyu; Shen, Wen-Bin; Zhang, Shuangxi

    2016-08-01

    In this study, we propose an approach for determining the geopotential difference using high-frequency-stability microwave links between satellite and ground station based on Doppler cancellation system. Suppose a satellite and a ground station are equipped with precise optical-atomic clocks (OACs) and oscillators. The ground oscillator emits a signal with frequency fa towards the satellite and the satellite receiver (connected with the satellite oscillator) receives this signal with frequency fb which contains the gravitational frequency shift effect and other signals and noises. After receiving this signal, the satellite oscillator transmits and emits, respectively, two signals with frequencies fb and fc towards the ground station. Via Doppler cancellation technique, the geopotential difference between the satellite and the ground station can be determined based on gravitational frequency shift equation by a combination of these three frequencies. For arbitrary two stations on ground, based on similar procedures as described above, we may determine the geopotential difference between these two stations via a satellite. Our analysis shows that the accuracy can reach 1 m2 s- 2 based on the clocks' inaccuracy of about 10-17 (s s-1) level. Since OACs with instability around 10-18 in several hours and inaccuracy around 10-18 level have been generated in laboratory, the proposed approach may have prospective applications in geoscience, and especially, based on this approach a unified world height system could be realized with one-centimetre level accuracy in the near future.

  20. Atomic clock with a nuclear transition: solid state approach at TU Wien

    CERN Document Server

    Kazakov, G A; Winkler, G; Sterba, J H; Steinhauser, G; Schumm, T

    2011-01-01

    The nucleus of 229Thorium presents a unique isomer state of very low energy and long lifetime, current estimates are around 7.8 eV and seconds to hours respectively. This nuclear transitions therefore is a promising candidate for a novel type of frequency standard and several groups worldwide have set out to investigate this system. Our aim is to construct a "solid state nuclear clock", i.e. a frequency standard where Thorium ions are implanted into Calciumfluoride crystals transparent in vacuum ultraviolet range. As a first step towards an accurate determination of the exact energy and lifetime of this isomer state we perform low-resolution fluorescent spectroscopic measurements.

  1. Stable clocks and general relativity

    CERN Document Server

    Will, C M

    1995-01-01

    We survey the role of stable clocks in general relativity. Clock comparisons have provided important tests of the Einstein Equivalence Principle, which underlies metric gravity. These include tests of the isotropy of clock comparisons (verification of local Lorentz invariance) and tests of the homogeneity of clock comparisons (verification of local position invariance). Comparisons of atomic clocks with gravitational clocks test the Strong Equivalence Principle by bounding cosmological variations in Newton's constant. Stable clocks also play a role in the search for gravitational radiation: comparision of atomic clocks with the binary pulsar's orbital clock has verified gravitational-wave damping, and phase-sensitive detection of waves from inspiralling compact binaries using laser interferometric gravitational observatories will facilitate extraction of useful source information from the data. Stable clocks together with general relativity have found important practical applications in navigational systems s...

  2. Compact Yb$^+$ optical atomic clock project: design principle and current status

    CERN Document Server

    Lacroûte, Clément; Bourgeois, Pierre-Yves; Millo, Jacques; Saleh, Khaldoun; Bigler, Emmanuel; Boudot, Rodolphe; Giordano, Vincent; Kersalé, Yann

    2016-01-01

    We present the design of a compact optical clock based on the $^2S_{1/2} \\rightarrow ^2D_{3/2}$ 435.5 nm transition in $^{171}$Yb$^+$. The ion trap will be based on a micro-fabricated circuit, with surface electrodes generating a trapping potential to localize a single Yb ion a few hundred $\\mu$m from the electrodes. We present our trap design as well as simulations of the resulting trapping pseudo-potential. We also present a compact, multi-channel wavelength meter that will permit the frequency stabilization of the cooling, repumping and clear-out lasers at 369.5 nm, 935.2 nm and 638.6 nm needed to cool the ion. We use this wavelength meter to characterize and stabilize the frequency of extended cavity diode lasers at 369.5 nm and 638.6 nm.

  3. Quantum theory of atomic clocks and gravito-inertial sensors: an update

    Energy Technology Data Exchange (ETDEWEB)

    Antoine, Ch [Equipe de Relativite Gravitation et Astrophysique, LERMA, UMR 8112, CNRS-Observatoire de Paris, Universite Pierre et Marie Curie, 4 place Jussieu, 75005 Paris (France); Borde, Ch J [Equipe de Relativite Gravitation et Astrophysique, LERMA, UMR 8112, CNRS-Observatoire de Paris, Universite Pierre et Marie Curie, 4 place Jussieu, 75005 Paris (France)

    2003-04-01

    In the framework of the ABCD{xi} formulation of atom optics and with an adequate modelization of the beam splitters, we establish an exact analytical phase shift expression for atom interferometers. This result is valid for a time-dependent external Hamiltonian at most quadratic in position and momentum operators and is expressed in terms of coordinates and momenta of the wave packet centres at the interaction vertices only. As a specific application, the case of atom gyrometers and accelerometers is presented in detail.

  4. Active optical clock

    Institute of Scientific and Technical Information of China (English)

    CHEN JingBiao

    2009-01-01

    This article presents the principles and techniques of active optical clock, a special laser combining the laser physics of one-atom laser, bad-cavity gas laser, super-cavity stabilized laser and optical atomic clock together. As a simple example, an active optical clock based on thermal strontium atomic beam shows a quantum-limited linewidth of 0.51 Hz, which is insensitive to laser cavity-length noise, and may surpass the recorded narrowest 6.7 Hz of Hg ion optical clock and 1.5 Hz of very recent optical lattice clock. The estimated 0.1 Hz one-second instability and 0.27 Hz uncertainty are limited only by the rela-tivistic Doppler effect, and can be improved by cold atoms.

  5. Ra{sup +} ion trapping - atomic parity violation measurement and an optical clock

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, Amita; Dijck, Elwin A.; Nunez Portela, Mayerlin; Valappol, Nivedya; Boell, Oliver; Jungmann, Klaus; Onderwater, Cornelis G. G.; Schlesser, Sophie; Timmermans, Rob G.E.; Willmann, Lorenz; Wilschut, Hans W. [University of Groningen, FWN, Groningen (Netherlands)

    2014-07-01

    A single trapped Ra{sup +} ion has an excellent potential for a precision measurement of the Weinberg mixing angle at low momentum transfer and testing thereby the electroweak running. The absolute frequencies of the transition 7s {sup 2}S{sub 1/2}-7d{sup 2}D{sub 3/2} at wavelength 828 nm have been determined in {sup 212*214}Ra{sup +} to better than 19 MHz with laser spectroscopy on small samples of ions trapped in a linear Paul trap at the online facility TRIμP of KVI. The measurement of the Weinberg angle requires the localization of the ion within a fraction of an optical wavelength. The current experiments are focused on trapping and laser spectroscopy on a single Ba{sup +} as a precursor for Ra{sup +}. Work towards single ion trapping of Ra{sup +}, including the preparation of an offline {sup 223}Ra source is in progress. Most elements of the setup for single Ra+ ion parity measurement are also well suited for realizing a most stable optical clock.

  6. Single-Ion Atomic Clock with 3×10(-18) Systematic Uncertainty.

    Science.gov (United States)

    Huntemann, N; Sanner, C; Lipphardt, B; Tamm, Chr; Peik, E

    2016-02-12

    We experimentally investigate an optical frequency standard based on the (2)S1/2(F=0)→(2)F7/2(F=3) electric octupole (E3) transition of a single trapped (171)Yb+ ion. For the spectroscopy of this strongly forbidden transition, we utilize a Ramsey-type excitation scheme that provides immunity to probe-induced frequency shifts. The cancellation of these shifts is controlled by interleaved single-pulse Rabi spectroscopy, which reduces the related relative frequency uncertainty to 1.1×10(-18). To determine the frequency shift due to thermal radiation emitted by the ion's environment, we measure the static scalar differential polarizability of the E3 transition as 0.888(16)×10(-40)  J m(2)/V(2) and a dynamic correction η(300  K)=-0.0015(7). This reduces the uncertainty due to thermal radiation to 1.8×10(-18). The residual motion of the ion yields the largest contribution (2.1×10(-18)) to the total systematic relative uncertainty of the clock of 3.2×10(-18).

  7. Simple-design ultra-low phase noise microwave frequency synthesizers for high-performing Cs and Rb vapor-cell atomic clocks

    Energy Technology Data Exchange (ETDEWEB)

    François, B. [FEMTO-ST, CNRS, Université de Franche-Comté, 26 chemin de l’Epitaphe, 25030 Besançon (France); INRIM, Strada delle Cacce 91, 10135 Torino (Italy); Calosso, C. E.; Micalizio, S. [INRIM, Strada delle Cacce 91, 10135 Torino (Italy); Abdel Hafiz, M.; Boudot, R. [FEMTO-ST, CNRS, Université de Franche-Comté, 26 chemin de l’Epitaphe, 25030 Besançon (France)

    2015-09-15

    We report on the development and characterization of novel 4.596 GHz and 6.834 GHz microwave frequency synthesizers devoted to be used as local oscillators in high-performance Cs and Rb vapor-cell atomic clocks. The key element of the synthesizers is a custom module that integrates a high spectral purity 100 MHz oven controlled quartz crystal oscillator frequency-multiplied to 1.6 GHz with minor excess noise. Frequency multiplication, division, and mixing stages are then implemented to generate the exact output atomic resonance frequencies. Absolute phase noise performances of the output 4.596 GHz signal are measured to be −109 and −141 dB rad{sup 2}/Hz at 100 Hz and 10 kHz Fourier frequencies, respectively. The phase noise of the 6.834 GHz signal is −105 and −138 dB rad{sup 2}/Hz at 100 Hz and 10 kHz offset frequencies, respectively. The performances of the synthesis chains contribute to the atomic clock short term fractional frequency stability at a level of 3.1 × 10{sup −14} for the Cs cell clock and 2 × 10{sup −14} for the Rb clock at 1 s averaging time. This value is comparable with the clock shot noise limit. We describe the residual phase noise measurements of key components and stages to identify the main limitations of the synthesis chains. The residual frequency stability of synthesis chains is measured to be at the 10{sup −15} level for 1 s integration time. Relevant advantages of the synthesis design, using only commercially available components, are to combine excellent phase noise performances, simple-architecture, low-cost, and to be easily customized for signal output generation at 4.596 GHz or 6.834 GHz for applications to Cs or Rb vapor-cell frequency standards.

  8. Simple-design ultra-low phase noise microwave frequency synthesizers for high-performing Cs and Rb vapor-cell atomic clocks.

    Science.gov (United States)

    François, B; Calosso, C E; Abdel Hafiz, M; Micalizio, S; Boudot, R

    2015-09-01

    We report on the development and characterization of novel 4.596 GHz and 6.834 GHz microwave frequency synthesizers devoted to be used as local oscillators in high-performance Cs and Rb vapor-cell atomic clocks. The key element of the synthesizers is a custom module that integrates a high spectral purity 100 MHz oven controlled quartz crystal oscillator frequency-multiplied to 1.6 GHz with minor excess noise. Frequency multiplication, division, and mixing stages are then implemented to generate the exact output atomic resonance frequencies. Absolute phase noise performances of the output 4.596 GHz signal are measured to be -109 and -141 dB rad(2)/Hz at 100 Hz and 10 kHz Fourier frequencies, respectively. The phase noise of the 6.834 GHz signal is -105 and -138 dB rad(2)/Hz at 100 Hz and 10 kHz offset frequencies, respectively. The performances of the synthesis chains contribute to the atomic clock short term fractional frequency stability at a level of 3.1 × 10(-14) for the Cs cell clock and 2 × 10(-14) for the Rb clock at 1 s averaging time. This value is comparable with the clock shot noise limit. We describe the residual phase noise measurements of key components and stages to identify the main limitations of the synthesis chains. The residual frequency stability of synthesis chains is measured to be at the 10(-15) level for 1 s integration time. Relevant advantages of the synthesis design, using only commercially available components, are to combine excellent phase noise performances, simple-architecture, low-cost, and to be easily customized for signal output generation at 4.596 GHz or 6.834 GHz for applications to Cs or Rb vapor-cell frequency standards.

  9. Optical Lattice Clocks

    Science.gov (United States)

    Oates, Chris

    2012-06-01

    Since they were first proposed in 2003 [1], optical lattice clocks have become one of the leading technologies for the next generation of atomic clocks, which will be used for advanced timing applications and in tests of fundamental physics [2]. These clocks are based on stabilized lasers whose frequency is ultimately referenced to an ultra-narrow neutral atom transition (natural linewidths magic'' value so as to yield a vanishing net AC Stark shift for the clock transition. As a result lattice clocks have demonstrated the capability of generating high stability clock signals with small absolute uncertainties (˜ 1 part in 10^16). In this presentation I will first give an overview of the field, which now includes three different atomic species. I will then use experiments with Yb performed in our laboratory to illustrate the key features of a lattice clock. Our research has included the development of state-of-the-art optical cavities enabling ultra-high-resolution optical spectroscopy (1 Hz linewidth). Together with the large atom number in the optical lattice, we are able to achieve very low clock instability (< 0.3 Hz in 1 s) [3]. Furthermore, I will show results from some of our recent investigations of key shifts for the Yb lattice clock, including high precision measurements of ultracold atom-atom interactions in the lattice and the dc Stark effect for the Yb clock transition (necessary for the evaluation of blackbody radiation shifts). [4pt] [1] H. Katori, M. Takamoto, V. G. Pal'chikov, and V. D. Ovsiannikov, Phys. Rev. Lett. 91, 173005 (2003). [0pt] [2] Andrei Derevianko and Hidetoshi Katori, Rev. Mod. Phys. 83, 331 (2011). [0pt] [3] Y. Y. Jiang, A. D. Ludlow, N. D. Lemke, R. W. Fox, J. A. Sherman, L.-S. Ma, and C. W. Oates, Nature Photonics 5, 158 (2011).

  10. New On-board Microprocessors

    Science.gov (United States)

    Weigand, R.

    Two new processor devices have been developed for the use on board of spacecrafts. An 8-bit 8032-microcontroller targets typical controlling applications in instruments and sub-systems, or could be used as a main processor on small satellites, whereas the LEON 32-bit SPARC processor can be used for high performance controlling and data processing tasks. The ADV80S32 is fully compliant to the Intel 80x1 architecture and instruction set, extended by additional peripherals, 512 bytes on-chip RAM and a bootstrap PROM, which allows downloading the application software using the CCSDS PacketWire pro- tocol. The memory controller provides a de-multiplexed address/data bus, and allows to access up to 16 MB data and 8 MB program RAM. The peripherals have been de- signed for the specific needs of a spacecraft, such as serial interfaces compatible to RS232, PacketWire and TTC-B-01, counters/timers for extended duration and a CRC calculation unit accelerating the CCSDS TM/TC protocol. The 0.5 um Atmel manu- facturing technology (MG2RT) provides latch-up and total dose immunity; SEU fault immunity is implemented by using SEU hardened Flip-Flops and EDAC protection of internal and external memories. The maximum clock frequency of 20 MHz allows a processing power of 3 MIPS. Engineering samples are available. For SW develop- ment, various SW packages for the 8051 architecture are on the market. The LEON processor implements a 32-bit SPARC V8 architecture, including all the multiply and divide instructions, complemented by a floating-point unit (FPU). It includes several standard peripherals, such as timers/watchdog, interrupt controller, UARTs, parallel I/Os and a memory controller, allowing to use 8, 16 and 32 bit PROM, SRAM or memory mapped I/O. With on-chip separate instruction and data caches, almost one instruction per clock cycle can be reached in some applications. A 33-MHz 32-bit PCI master/target interface and a PCI arbiter allow operating the device in a plug-in card

  11. Are atomic clocks slowing down? Possible connection between the quantum and the cosmos: A feasible experimental test of objective realism

    CERN Document Server

    Ramanathan, R

    2014-01-01

    An alternative to the current accepted model of expanding universe is presented. The proposal is anchored in the objective realist, stochastic formulation of quantum mechanics wherein the Planck constant plays the role of a diffusion constant which need not be an universal constant for all epochs. This underlying noise is charecterised by a very high initial value of the Planck constant which gradually decreased over the epochs gone by, finally reaching its present value .It is this decrease in the strength of the Planck constant that causes a spectral red shift with the passage of time .The compatibility of this proposal with some cosmological data is shown.Feasible spectroscopic measurement of a specific spectral line frequency done over a period of a few years can decisively either validate or invalidate the proposal in a terrestrially bound experiment. This proposal predicts a slowing down of atomic clocks by nearly 2. 10^-18 s with respect to every preceding second. A positive experimental outcome will v...

  12. Improved limit on a temporal variation of mp/me from comparisons of Yb+ and Cs atomic clocks.

    Science.gov (United States)

    Huntemann, N; Lipphardt, B; Tamm, Chr; Gerginov, V; Weyers, S; Peik, E

    2014-11-21

    Accurate measurements of different transition frequencies between atomic levels of the electronic and hyperfine structure over time are used to investigate temporal variations of the fine structure constant α and the proton-to-electron mass ratio μ. We measure the frequency of the (2)S1/2→(2)F7/2 electric octupole (E3) transition in (171)Yb(+) against two caesium fountain clocks as f(E3)=642,121,496,772,645.36  Hz with an improved fractional uncertainty of 3.9×10(-16). This transition frequency shows a strong sensitivity to changes of α. Together with a number of previous and recent measurements of the (2)S1/2→(2)D3/2 electric quadrupole transition in (171)Yb(+) and with data from other elements, a least-squares analysis yields (1/α)(dα/dt)=-0.20(20)×10(-16)/yr and (1/μ)(dμ/dt)=-0.5(1.6)×10(-16)/yr, confirming a previous limit on dα/dt and providing the most stringent limit on dμ/dt from laboratory experiments.

  13. Stable 85Rb micro vapour cells: fabrication based on anodic bonding and application in chip-scale atomic clocks

    Science.gov (United States)

    Su, Juan; Deng, Ke; Guo, Deng-Zhu; Wang, Zhong; Chen, Jing; Zhang, Geng-Min; Chen, Xu-Zong

    2010-11-01

    We describe the microfabrication of 85Rb vapour cells using a glass-silicon anodic bonding technique and in situ chemical reaction between rubidium chloride and barium azide to produce Rb. Under controlled conditions, the pure metallic Rb drops and buffer gases were obtained in the cells with a few mm3 internal volumes during the cell sealing process. At an ambient temperature of 90 °C the optical absorption resonance of 85Rb D1 transition with proper broadening and the corresponding coherent population trapping (CPT) resonance, with a signal contrast of 1.5% and linewidth of about 1.7 kHz, have been detected. The sealing quality and the stability of the cells have also been demonstrated experimentally by using the helium leaking detection and the after-9-month optoelectronics measurement which shows a similar CPT signal as its original status. In addition, the physics package of chip-scale atomic clock (CSAC) based on the cell was realized. The measured frequency stability of the physics package can reach to 2.1 × 10-10 at one second when the cell was heated to 100 °C which proved that the cell has the quality to be used in portable and battery-operated devices.

  14. An analytic technique for statistically modeling random atomic clock errors in estimation

    Science.gov (United States)

    Fell, P. J.

    1981-01-01

    Minimum variance estimation requires that the statistics of random observation errors be modeled properly. If measurements are derived through the use of atomic frequency standards, then one source of error affecting the observable is random fluctuation in frequency. This is the case, for example, with range and integrated Doppler measurements from satellites of the Global Positioning and baseline determination for geodynamic applications. An analytic method is presented which approximates the statistics of this random process. The procedure starts with a model of the Allan variance for a particular oscillator and develops the statistics of range and integrated Doppler measurements. A series of five first order Markov processes is used to approximate the power spectral density obtained from the Allan variance.

  15. 星载原子钟数据预处理的方法研究%Research on the Methods of Preprocessing the Satellite-Borne Atomic Clocks Data

    Institute of Scientific and Technical Information of China (English)

    李斌; 杨富春; 江峻毅

    2015-01-01

    Satellite-borne atomic clocks data preprocessing is the basis of atomic clocks performance analysis and clock forecasting,phase and frequency of data conversion and abnormal data analysis and processing methods are used to preprocess the clocks data, these methods can effectively guarantee the re-liability of the clocks data.%星载原子钟的数据预处理是进行原子钟性能分析和钟差预报的前提,本文主要利用相位数据和频率数据的转换和异常数据的分析处理方法对原子钟数据进行了预处理,有效的保证了数据的可靠性。

  16. The ac stark shift and space-borne rubidium atomic clocks

    Science.gov (United States)

    Formichella, V.; Camparo, J.; Sesia, I.; Signorile, G.; Galleani, L.; Huang, M.; Tavella, P.

    2016-11-01

    Due to its small size, low weight, and low power consumption, the Rb atomic frequency standard (RAFS) is routinely the first choice for atomic timekeeping in space. Consequently, though the device has very good frequency stability (rivaling passive hydrogen masers), there is interest in uncovering the fundamental processes limiting its long-term performance, with the goal of improving the device for future space systems and missions. The ac Stark shift (i.e., light shift) is one of the more likely processes limiting the RAFS' long-term timekeeping ability, yet its manifestation in the RAFS remains poorly understood. In part, this comes from the fact that light-shift induced frequency fluctuations must be quantified in terms of the RAFS' light-shift coefficient and the output variations in the RAFS' rf-discharge lamp, which is a nonlinear inductively-couple plasma (ICP). Here, we analyze the light-shift effect for a family of 10 on-orbit Block-IIR GPS RAFS, examining decade-long records of their on-orbit frequency and rf-discharge lamp fluctuations. We find that the ICP's light intensity variations can take several forms: deterministic aging, jumps, ramps, and non-stationary noise, each of which affects the RAFS' frequency via the light shift. Correlating these light intensity changes with RAFS frequency changes, we estimate the light-shift coefficient, κLS, for the family of RAFS: κLS = -(1.9 ± 0.3) × 10-12/%. The 16% family-wide variation in κLS indicates that while each RAFS may have its own individual κLS, the variance of κLS among similarly designed RAFS can be relatively small. Combining κLS with our estimate of the ICP light intensity's non-stationary noise, we find evidence that random-walk frequency noise in high-quality space-borne RAFS is strongly influenced by the RAFS' rf-discharge lamp via the light shift effect.

  17. Phase Coherent Link of an Atomic Clock to a Self-Referenced Microresonator Frequency Comb

    CERN Document Server

    Del'Haye, Pascal; Fortier, Tara; Beha, Katja; Cole, Daniel C; Yang, Ki Youl; Lee, Hansuek; Vahala, Kerry J; Papp, Scott B; Diddams, Scott A

    2015-01-01

    The counting and control of optical cycles of light has become common with modelocked laser frequency combs. But even with advances in laser technology, modelocked laser combs remain bulk-component devices that are hand-assembled. In contrast, a frequency comb based on the Kerr-nonlinearity in a dielectric microresonator will enable frequency comb functionality in a micro-fabricated and chip-integrated package suitable for use in a wide-range of environments. Such an advance will significantly impact fields ranging from spectroscopy and trace gas sensing, to astronomy, communications, atomic time keeping and photonic data processing. Yet in spite of the remarkable progress shown over the past years, microresonator frequency combs ("microcombs") have still been without the key function of direct f-2f self-referencing and phase-coherent frequency control that will be critical for enabling their full potential. Here we realize these missing elements using a low-noise 16.4 GHz silicon chip microcomb that is coher...

  18. Optical Clocks and Relativity

    Science.gov (United States)

    Chou, C. W.; Hume, D. B.; Rosenband, T.; Wineland, D. J.

    2010-09-01

    Observers in relative motion or at different gravitational potentials measure disparate clock rates. These predictions of relativity have previously been observed with atomic clocks at high velocities and with large changes in elevation. We observed time dilation from relative speeds of less than 10 meters per second by comparing two optical atomic clocks connected by a 75-meter length of optical fiber. We can now also detect time dilation due to a change in height near Earth’s surface of less than 1 meter. This technique may be extended to the field of geodesy, with applications in geophysics and hydrology as well as in space-based tests of fundamental physics.

  19. First Results of the GPS.DM Observatory: Search for Dark Matter and Exotic Physics with Atomic Clocks and GPS Constellation

    Science.gov (United States)

    Roberts, Benjamin; Blewitt, Geoff; Dailey, Conner; Pospelov, Maxim; Rollings, Alex; Sherman, Jeff; Williams, Wyatt; Derevianko, Andrei; GPS. DM Collaboration

    2017-01-01

    Despite the overwhelming cosmological evidence for the existence of dark matter, and the considerable effort of the scientific community over decades, there is no evidence for dark matter in terrestrial experiments. The GPS.DM observatory uses the existing GPS constellation as a 50,000 km-aperture sensor array, analysing the satellite and terrestrial atomic clock data for exotic physics signatures. In particular, the collaboration searches for evidence of transient variations of fundamental constants correlated with the Earth's galactic motion through the dark matter halo. There already exists more than 10 years of good clock timing data that can be used in the search. This type of search is particularly sensitive to exotic forms of dark matter, such as topological defects. Supported by the NSF.

  20. The Saga of Light-Matter Interaction and Magneto-optical Effects Applications to Atomic Magnetometry, Laser-cooled Atoms, Atomic Clocks, Geomagnetism, and Plant Bio-magnetism

    Science.gov (United States)

    Corsini, Eric P.

    The quest to expand the limited sensorial domain, in particular to bridge the inability to gauge magnetic fields near and far, has driven the fabrication of remedial tools. The interaction of ferromagnetic material with a magnetic field had been the only available technique to gauge that field for several millennium. The advent of electricity and associated classical phenomena captured in the four Maxwell equations, were a step forward. In the early 1900s, the model of quantum mechanics provided a two-way leap forward. One came from the newly understood interaction of light and matter, and more specifically the three-way coupling of photons, atoms' angular momenta, and magnetic field, which are the foundations of atomic magnetometry. The other came from magnetically sensitive quantum effects in a fabricated energy-ladder form of matter cooled to a temperature below that of the energy steps; these quantum effects gave rise to the superconducting quantum interference device (SQUID). Research using atomic magnetometers and SQUIDs has resulted in thousands of publications, text books, and conferences. The current status in each field is well described in Refs. [48,49,38,42] and all references therein. In this work we develop and investigate techniques and applications pertaining to atomic magnetometry. [Full text: eric.corsini gmail.com].

  1. A HBAR-oscillator-based 4.596~GHz frequency source: Application to a coherent population trapping Cs vapor cell atomic clock

    CERN Document Server

    Daugey, Thomas; Martin, Gilles; Boudot, Rodolphe

    2015-01-01

    This article reports on the design and characterization of a high-overtone bulk acoustic wave resonator (HBAR)-oscillator-based 4.596~GHz frequency source. A 2.298~GHz signal, generated by an oscillator constructed around a thermally-controlled two-port AlN-sapphire HBAR resonator with a Q-factor of 24000 at 68$^{\\circ}$C, is frequency multiplied by 2 to 4.596~GHz, half of the Cs atom clock frequency. The temperature coefficient of frequency (TCF) of the HBAR is measured to be $-23$~ppm/$^{\\circ}$C at 2.298~GHz. The measured phase noise of the 4.596~GHz source is $-105$~dBrad$^2$/Hz at 1~kHz offset and $-150$~dBrad$^2$/Hz at 100~kHz offset. The 4.596~GHz output signal is used as a local oscillator (LO) in a laboratory-prototype Cs microcell-based coherent population trapping (CPT) atomic clock. The signal is stabilized onto the atomic transition frequency by tuning finely a voltage-controlled phase shifter (VCPS) implemented in the 2.298~GHz HBAR-oscillator loop, preventing the need for a high-power-consuming...

  2. Stability Analysis of the In-Orbit Satellite Atomic Clocks%GPS在轨卫星原子钟的稳定性分析

    Institute of Scientific and Technical Information of China (English)

    李长会; 闫国锋

    2012-01-01

    导航卫星星载原子钟的相位或频率数据,作为导航系统应用研究的基础,将直接影响导航系统时间尺度建立以及定位的精度和准确性.本文针对由IGS官网提供的四种GPS卫星钟的钟差数据,采用修正阿伦方差进行了稳定性分析,得到了一些有益的结论.%As the application research basis of navigation system, the phase or frequency data of in - orbit satellite atomic clocks directly affect the precision and accuracy of navigation system. This paper analyzes the stability of four types of data of GPS satellite a-tomic clocks which is provided by the official website of IGS using Allan variance method and reaches some beneficial conclusions.

  3. On-Board GPS Clock Monitoring for Signal Integrity

    Science.gov (United States)

    2010-11-01

    Dyke, K. Kovach , J. Kraemer, J. Lavrakas, J. P. Fernow, J. Reese, and N. Attallah, 2003, “GPS Integrity Failure Modes and Effects Analysis,” in...California, USA (Institute of Navigation, Alexandria, Virginia), pp. 689-703. [9] K. Van Dyke, K. Kovach , J. Lavrakas, and B. Carroll, 2004

  4. A high-overtone bulk acoustic wave resonator-oscillator-based 4.596 GHz frequency source: Application to a coherent population trapping Cs vapor cell atomic clock

    Energy Technology Data Exchange (ETDEWEB)

    Daugey, Thomas; Friedt, Jean-Michel; Martin, Gilles; Boudot, Rodolphe [FEMTO-ST, CNRS, UFC, 26 chemin de l’Epitaphe 25030 Besançon Cedex (France)

    2015-11-15

    This article reports on the design and characterization of a high-overtone bulk acoustic wave resonator (HBAR)-oscillator-based 4.596 GHz frequency source. A 2.298 GHz signal, generated by an oscillator constructed around a thermally controlled two-port aluminum nitride-sapphire HBAR resonator with a Q-factor of 24 000 at 68 °C, is frequency multiplied by 2–4.596 GHz, half of the Cs atom clock frequency. The temperature coefficient of frequency of the HBAR is measured to be −23 ppm/ °C at 2.298 GHz. The measured phase noise of the 4.596 GHz source is −105 dB rad{sup 2}/Hz at 1 kHz offset and −150 dB rad{sup 2}/Hz at 100 kHz offset. The 4.596 GHz output signal is used as a local oscillator in a laboratory-prototype Cs microcell-based coherent population trapping atomic clock. The signal is stabilized onto the atomic transition frequency by tuning finely a voltage-controlled phase shifter implemented in the 2.298 GHz HBAR-oscillator loop, preventing the need for a high-power-consuming direct digital synthesis. The short-term fractional frequency stability of the free-running oscillator is 1.8 × 10{sup −9} at one second integration time. In locked regime, the latter is improved in a preliminary proof-of-concept experiment at the level of 6.6 × 10{sup −11} τ{sup −1/2} up to a few seconds and found to be limited by the signal-to-noise ratio of the detected CPT resonance.

  5. Employee on Boarding Process Automation

    Directory of Open Access Journals (Sweden)

    Khushboo Nalband

    2017-03-01

    Full Text Available On boarding, also known as organizational socialization, plays a vital role in building the initial relationship between an organization and an employee. It also contributes to an employees’ satisfaction, better performance and greater organizational commitment thus increasing an employees’ effectiveness and productivity in his/her role. Therefore, it is essential that on boarding process of an organization is efficient and effective to improve new employees’ retention. Generally this on boarding process is done manually which is time consuming and monotonous. To enhance this process, the proposed solution automates the on boarding or joining process. It will enable HR, ADMINISTRATOR and IT to complete this process by robot which will automatically perform the actions taken to complete the on boarding process. To complete this process direct access is given to applications, where as in automation, robot will perform all the actions taken to complete the process, which is a secured way to access applications. This will thus improve the timeframe and efficiency to complete the on boarding or joining process.

  6. Colloquium: Physics of optical lattice clocks

    CERN Document Server

    Derevianko, Andrei

    2010-01-01

    Recently invented and demonstrated, optical lattice clocks hold great promise for improving the precision of modern timekeeping. These clocks aim at the 10^-18 fractional accuracy, which translates into a clock that would neither lose or gain a fraction of a second over an estimated age of the Universe. In these clocks, millions of atoms are trapped and interrogated simultaneously, dramatically improving clock stability. Here we discuss the principles of operation of these clocks and, in particular, a novel concept of "magic" trapping of atoms in optical lattices. We also highlight recently proposed microwave lattice clocks and several applications that employ the optical lattice clocks as a platform for precision measurements and quantum information processing.

  7. Progress of the ~(87)Rb Fountain Clock

    Institute of Scientific and Technical Information of China (English)

    ZHOU Zi-Chao; WEI Rong; SHI Chun-Yan; LV De-Sheng; LI Tang; WANG Yu-Zhu

    2009-01-01

    A fountain atomic clock based on cold ~(87)Rb atoms has been in operation in our laboratory for several months.We therefore report the design of the rubidium fountain clock including its physical package,optical system and daily operation.Ramsey fringes have been attained with the signal to noise ratio of about 100.

  8. 航天器铷钟的一种精密控温系统%A Precise Temperature Control System for Spacecraft Rubidium Atomic Clock

    Institute of Scientific and Technical Information of China (English)

    李国强; 耿利寅; 童叶龙

    2011-01-01

    研究了一种应用于航天器的高精度、高稳定度的温度控制系统:使用热敏电阻作为温度传感器;采用多级控温策略,核心级采用基于径向基函数(Radial Basis Function,RBF)神经网络比例、积分、微分(PID)控制算法,非核心级采用积分分离式PID算法;采用脉宽调制(PWM)控制作为控制方式。以航天器铷钟作为控制对象,通过铷钟模拟件的热平衡试验,验证了高精度控温系统的控制效果。试验结果表明:核心级施加RBF神经网络PID控制时,稳态控温精度优于±0.08℃;内热源阶跃冲击或外热流正弦扰动下,其温度波动%The paper shows a high-precision and high-stability temperature control system for spacecraft,which uses thermistor as sensor.The system control strategy is step-by-step,using RBF-based nenral network PID control for core stage,using integral separation PID control for others;and using pulse width modulation(PWM) as control mode.The system's performance is verified through thermal balance test of rubidium atomic clock simulator.Test results are shown as follows.When the core stage is controlled by nerval network PID control,its temperature change can be within ±0.08℃ in steady case;when it is disturbed by internal heat source or orbit heat flux,the core stage's temperature change can be within ±0.1℃ and the temperature stability is ±0.1℃/day.The temperature control system can be applied in precision temperature control for spacecraft atomic clock and high-resolution camera.

  9. Entangling the lattice clock: Towards Heisenberg-limited timekeeping

    CERN Document Server

    Weinstein, Jonathan D; Derevianko, Andrei

    2009-01-01

    We present a scheme for entangling the atoms of an optical lattice to reduce the quantum projection noise of a clock measurement. The divalent clock atoms are held in a lattice at a ``magic'' wavelength that does not perturb the clock frequency -- to maintain clock accuracy -- while an open-shell J=1/2 ``head'' atom is coherently transported between lattice sites via the lattice polarization. This polarization-dependent ``Archimedes' screw'' transport at magic wavelength takes advantage of the vanishing vector polarizability of the scalar, J=0, clock states of bosonic isotopes of divalent atoms. The on-site interactions between the clock atoms and the head atom are used to engineer entanglement and for clock readout.

  10. A quantum network of clocks

    Science.gov (United States)

    Kómár, P.; Kessler, E. M.; Bishof, M.; Jiang, L.; Sørensen, A. S.; Ye, J.; Lukin, M. D.

    2014-08-01

    The development of precise atomic clocks plays an increasingly important role in modern society. Shared timing information constitutes a key resource for navigation with a direct correspondence between timing accuracy and precision in applications such as the Global Positioning System. By combining precision metrology and quantum networks, we propose a quantum, cooperative protocol for operating a network of geographically remote optical atomic clocks. Using nonlocal entangled states, we demonstrate an optimal utilization of global resources, and show that such a network can be operated near the fundamental precision limit set by quantum theory. Furthermore, the internal structure of the network, combined with quantum communication techniques, guarantees security both from internal and external threats. Realization of such a global quantum network of clocks may allow construction of a real-time single international time scale (world clock) with unprecedented stability and accuracy.

  11. Analysis of the performance of hydrogen maser clocks at the ...

    African Journals Online (AJOL)

    Cilence

    clock characteristics have a direct influence on precision and accuracy of the ..... Generation Atomic Fountain Clock at NIST', Proceedings of the 2004 IEEE International ... Plag H-P, Altamimi Z, Bettadpur S, Beutler G, Beyerle G, Cazenve A, ...

  12. 铯原子喷泉钟均匀C场的实现%A realization of uniform C field in caesium atomic fountain clock

    Institute of Scientific and Technical Information of China (English)

    吴长江; 管勇; 陈江; 张辉; 阮军; 张首刚

    2011-01-01

    C场均匀度是影响铯原子喷泉钟性能的重要因素。为了消除漏磁等对磁场均匀度的影响,加入补偿线圈,通过用最小二乘法计算,逐次得出补偿线圈的个数、位置与电流。实验表明:计算数据与实验结果吻合,得到c场不均匀性小于2nT、长度达48cm的均匀区。%The performance of the caesium atomic fountain clock is affected by the uniformity of the C field. In order to compensate the uneven magnetic field caused by the leakage in magnetic shielding region, compensation coils are introduced and the number, position and current of the coils are calculated by the least square methgd. The experimental results agree with the theoretical prediction and an uniform magnetic-field of 48 cm with a fluctuation of less than 2 nT is obtained.

  13. 基于动态阿伦方差的北斗星载原子钟特性分析%Analysis of Characteristics of BDS On-board Atomic Clocks Based on Dynamic AllanVariance

    Institute of Scientific and Technical Information of China (English)

    李铸洋; 米科峰; 周培元

    2016-01-01

    针对传统的阿伦方差等评价手段无法实现对星载原子钟进行动态性能评估的缺陷,将动态阿伦方差引入到BDS星载原子钟的监测和评估中.采用BDS多星定轨卫星钟差产品,基于动态阿伦方差算法对BDS原子钟在轨性能进行了研究,并利用BDS星地双向无线电时间比对钟差数据对其结果进行了对比和验证.实验结果表明,动态阿伦方差算法可以实现对BDS星载原子钟动态特性的有效评估,BDS原子钟的万秒稳定度的量级基本为在10-14,但是随着时间有一定的变化.

  14. Detector Data Simulation and Filtering Strategy for the European Laser Timing (ELT) Experiment On-board ACES

    Science.gov (United States)

    Bamann, Christoph; Schlicht, Anja; Hugentobler, Urs; Pühl, Magdalena

    2015-04-01

    Due to the rapid progress of frequency standards in the optical domain and increasingly demanding applications in metrology and fundamental physics studies, accuracy requirements on frequency and time transfer are continuously increasing. Most present satellite based clock comparison systems work in the microwave domain and are based on GPS and TWSTFT (Two-Way Satellite Time and Frequency Transfer). Recently, systems such as LASSO (LAser Synchronization from a Stationary Orbit) and T2L2 (Time Transfer by Laser Link) promised even better performance in the optical domain. In 2016 the ESA mission ACES (Atomic Clock Ensemble in Space) will bring a new generation of atomic clocks into the microgravity environment of the ISS, which will distribute a stable and accurate time base. In the frame of this mission an optical link called ELT (European Laser Timing) is presently under study, which is subject of our work. The on-board hardware of ELT consists of a corner cube retro-reflector (CCR), a single-photon avalanche diode (SPAD), and an event timer connected to the ACES time scale. The SPAD detects laser pulses fired towards the payload and the CCR reflects these pulses back to the ground station. The detection dates are recorded in the ACES time scale, while the two-way time of flight can be used for precise ranging. Consequently, time transfer and clock analysis can be performed based on data triplets comprising the time of transmission of a laser pulse, its time of reception at the ELT-detector and its time of reception back at the station-detector. We present simulations of these triplets based on simple ISS orbits including preset attitude and accurate Earth orientation data. In addition, we consider experimentally derived detector, reflector, and background noise characteristics as well as simulations of the ACES clocks. The ELT data center, which will be hosted by our institution, will have to extract the data triplets from the large amount of noisy detector dates

  15. 欧洲空间原子钟组ACES 与超高精度时频传递技术新进展%Advances in Atomic Clock Ensemble in Space of Europe and Ultraprecise Time and Frequency Transfer

    Institute of Scientific and Technical Information of China (English)

    杨文可; 孟文东; 韩文标; 谢勇辉; 任晓乾; 胡小工; 董文丽

    2016-01-01

    高精度时间频率的产生和超高精度时频信号的传递是现代物理学、天文学和计量科学的基础。空间原子钟组计划(Atomic Clock Ensemble in Space, ACES)是由欧洲空间局实施的基于国际空间站(International Space Station, ISS)微重力环境下的新型空间微波原子钟实验验证项目。概要介绍ACES项目基本情况,重点介绍ACES项目的主要科学和技术目标,围绕科学目标而形成的ACES 组成结构,并梳理涉及的关键技术,特别介绍了ACES 将应用的超高精度时频传递技术,为我国自主研究并实现相关空间时间频率系统及其应用提供参考。最后简述了我国正在建设的空间站时频系统主要情况和实施计划。%One of the foundations for the development of modern physics, astronomy and metrology is the generation, transfer and measurement of high precision time frequency signals. As a space mission for the study of high precision time frequency signals, Atomic Clock Ensemble in Space, or ACES, sponsored by European Space Agency to launch in 2017 or later, will take advantage of the excellent stability performance of microwave atomic clocks in a microgravity environment. One clock using laser-cooled Cs atoms working together with one hydrogen maser clock are planned to be placed onboard the International Space Station in hope to produce a frequency standard with both accuracy and stability reaching the level of 10−16. A microwave link along with a laser link will be set up between ACES and ground atomic clocks distributed around the world for high precision comparison and transfer. Various basic researches will benefit from a high precision space atomic clock such as the verification of Einstein’s general relativity, detection of possible time variability of certain fundamental constants in physics, as well as brand new applications such as relativistic gravity and GNSS remote sensing. This paper reviews and summarizes the

  16. First observation of the strongly forbidden transition {sup 1}S{sub 0} - {sup 3}P{sub 0} in Strontium, for an atomic clock with trapped atoms; Premiere observation de la transition fortement interdite {sup 1}S{sub 0} - {sup 3}P{sub 0} du strontium, pour une horloge optique a atomes pieges

    Energy Technology Data Exchange (ETDEWEB)

    Courtillot, I

    2003-11-01

    This thesis reports the first results towards the realization of an optical clock using trapped strontium atoms. This set up would combine advantages of the different approaches commonly used to develop an atomic frequency standard. The first part describes the cold atoms source which is implemented. A magneto-optical trap operating on the {sup 1}S{sub 0}-{sup 1}P{sub 1} transition at 461 nm is loaded from an atomic beam decelerated by a Zeeman slower. The 461 nm laser is obtained by sum-frequency mixing in a potassium titanyl phosphate (KTP) crystal. The second part is devoted to the different stages developed to achieve the direct excitation of the {sup 1}S{sub 0}-{sup 3}P{sub 0} clock transition in {sup 87}Sr. This line has a theoretical natural width of 10{sup -3} Hz. Before this detection, we obtained an estimate of the resonance frequency by measuring absolute frequencies of several allowed optical transitions. (author)

  17. Performances evaluation of the PHARAO atomic fountain: participation to the study of the PHARAO space clock; Evaluation des performances de la fontaine atomique PHARAO, participation a l'etude de l'horloge spatiale PHARAO

    Energy Technology Data Exchange (ETDEWEB)

    Abgrall, M

    2003-01-01

    The performances of an atomic frequency standard depend drastically on the observation time of the atoms. The interrogation of laser cooled atoms allows to obtain about half a second interaction time in a fountain geometry. This duration could be much more varied in absence of gravity, and would allow a better trade-off between stability and accuracy. The application of this principle is the aim of the PHARAO project, that should attend to the ACES mission planned in 2006 onboard the International Space Station. The first part of this thesis deals with the cold Cs{sup 133} PHARAO fountain. This clock stems from the transformation of a space clock prototype previously tested in microgravity. A detailed evaluation of the whole frequency shifts has been carried out, reaching a 7.7 10{sup -16} accuracy and a 1.7 10{sup -13}{tau}{sup -1/2} short term stability. These values are obtained for 4 10{sup 5} detected atoms, that provides a good stability-accuracy trade-off. This transportable fountain, built at BNM-SYRTE, has been operating at MPQ in Munich (Germany). The collaboration between the 2 laboratories gave a {approx} 10 improvement factor on the measurement accuracy (1.8 10{sup -14}) for the 1S - 2S two photons hydrogen transition. In a second part of this thesis, we present the characterisation of 2 elements of the PHARAO space clock: the construction of a standard extended cavity laser and the test of the phase symmetry between the two interrogating areas of the space cavity. (author)

  18. Body Clock

    Institute of Scientific and Technical Information of China (English)

    刘洪毓

    2000-01-01

    “Body clocks” are biological methods of controling body activities.Every living thing has one. In humans, a body clock controls normal periods of sleeping and waking. It controls the time swhen you are most likely to feel pain.Eating, sleeping and exercising at about the same time each day will help keep body activities normal. But changes in your life, a new job, for example, destroy the balance and thus cause health problems.

  19. Distinction between Clock and Time, and a Suggested Experiment with Different Types of Clocks in GPS

    Science.gov (United States)

    Smarandache, Florentin

    2013-03-01

    The clock is an instrument for measuring the time, instrument that may not run perfectly (accurately) under certain conditions (like, say, in strong electromagnetic field, in strong gravitational field, in extremely high or low temperature, pressure, etc.), but this does not mean that time itself runs slower or faster as Einstein's Theory of Relativity asserts. We are referring to an absolute time, i.e. time measured not with respect to ether or non-ether, but with respect to an absolute mathematical reference frame. Several types of clocks could run at a more slowly rate in a moving frame of reference than other types of clocks; it depends on the construction material and functioning principle of each type of clock. Relativists say that ``gravity slows time''. This is incorrect, since actually gravity slows today's types of clocks. And one type of clock is slowed more or less than another type of clock. Not only gravity but other (electric, magnetic, etc.) fields or various medium composition elements or structures may slow or accelerate clocks that are in that medium. The clocks used today in the satellites for the GPS necessitate a correction with respect to the Earth clocks. But in the future, when new types of clocks will be built based on different construction material and functioning principle, the correction of the GPS clocks would be different. In order to make the distinction between ``clock'' and ``time'', we suggest a Experiment # 1 with different types of clocks for the GPS clocks, in order to prove that the resulted dilation and contraction factors are different from those obtained with today's cesium atomic clock.

  20. Feasibility of an optical fiber clock

    Science.gov (United States)

    Ilinova, Ekaterina; Babb, James F.; Derevianko, Andrei

    2017-09-01

    We explore the feasibility of a fiber clock, i.e., a compact, high-precision, optical lattice atomic clock based on atoms trapped inside a hollow-core optical fiber. Such a setup offers an intriguing potential both for a substantially increased number of interrogated atoms (and thereby an improved clock stability) and for miniaturization. We evaluate the sensitivity of the 1S0-3P0 clock transition in Hg and other divalent atoms to the fiber inner core surface at nonzero temperatures. The Casimir-Polder interaction induced 1S0-3P0 transition frequency shift is calculated for the atom inside the hollow capillary as a function of atomic position, capillary material, and geometric parameters. For Hg atoms on the axis of a silica capillary with inner radius ≥15 μ m and optimally chosen thickness d ˜1 μ m , the atom-surface interaction induced 1S0-3P0 clock transition frequency shift can be kept on the level δ ν /νHg˜10-19 . We also estimate the atom loss and heating due to collisions with the buffer gas, lattice intensity noise induced heating, spontaneous photon scattering heating, and residual birefringence induced frequency shifts.

  1. On-board Data Mining

    Science.gov (United States)

    Tanner, Steve; Stein, Cara; Graves, Sara J.

    Networks of remote sensors are becoming more common as technology improves and costs decline. In the past, a remote sensor was usually a device that collected data to be retrieved at a later time by some other mechanism. This collected data were usually processed well after the fact at a computer greatly removed from the in situ sensing location. This has begun to change as sensor technology, on-board processing, and network communication capabilities have increased and their prices have dropped. There has been an explosion in the number of sensors and sensing devices, not just around the world, but literally throughout the solar system. These sensors are not only becoming vastly more sophisticated, accurate, and detailed in the data they gather but they are also becoming cheaper, lighter, and smaller. At the same time, engineers have developed improved methods to embed computing systems, memory, storage, and communication capabilities into the platforms that host these sensors. Now, it is not unusual to see large networks of sensors working in cooperation with one another. Nor does it seem strange to see the autonomous operation of sensorbased systems, from space-based satellites to smart vacuum cleaners that keep our homes clean and robotic toys that help to entertain and educate our children. But access to sensor data and computing power is only part of the story. For all the power of these systems, there are still substantial limits to what they can accomplish. These include the well-known limits to current Artificial Intelligence capabilities and our limited ability to program the abstract concepts, goals, and improvisation needed for fully autonomous systems. But it also includes much more basic engineering problems such as lack of adequate power, communications bandwidth, and memory, as well as problems with the geolocation and real-time georeferencing required to integrate data from multiple sensors to be used together.

  2. Short-term GNSS satellite clock stability

    Science.gov (United States)

    Griggs, E.; Kursinski, E. R.; Akos, D.

    2015-08-01

    Global Navigation Satellite System (GNSS) clock stability is characterized via the modified Allan deviation using active hydrogen masers as the receiver frequency reference. The high stability of the maser reference allows the GNSS clock contribution to the GNSS carrier phase variance to be determined quite accurately. Satellite clock stability for four different GNSS constellations are presented, highlighting the similarities and differences between the constellations as well as satellite blocks and clock types. Impact on high-rate applications, such as GNSS radio occultation (RO), is assessed through the calculation of the maximum carrier phase error due to clock instability. White phase noise appears to dominate at subsecond time scales. However, while we derived the theoretical contribution of white phase modulation to the modified Allan deviation, our analysis of the GNSS satellite clocks was limited to 1-200 s time scales because of inconsistencies between the subsecond results from the commercial and software-defined receivers. The rubidium frequency standards on board the Global Positioning System (GPS) Block IIF, BeiDou, and Galileo satellites show improved stability results in comparison to previous GPS blocks for time scales relevant to RO. The Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS) satellites are the least stable of the GNSS constellations in the short term and will need high-rate corrections to produce RO results comparable to those from the other GNSS constellations.

  3. Atoms

    Institute of Scientific and Technical Information of China (English)

    刘洪毓

    2007-01-01

    Atoms(原子)are all around us.They are something like the bricks (砖块)of which everything is made. The size of an atom is very,very small.In just one grain of salt are held millions of atoms. Atoms are very important.The way one object acts depends on what

  4. Optical lattice clocks and frequency comparison

    Energy Technology Data Exchange (ETDEWEB)

    Katori, Hidetoshi; Takano, Tetsushi; Takamoto, Masao, E-mail: katori@amo.t.u-tokyo.ac.jp [Department of Applied Physics, University of Tokyo, Tokyo (Japan); CREST, Japan Science and Technology Agency, Saitama (Japan)

    2011-01-10

    We consider designs of optical lattice clocks in view of the quantum statistics, relevant atomic spins, and atom-lattice interactions. The first two issues lead to two optimal constructions for the clock: a one-dimensional (1D) optical lattice loaded with spin-polarized fermions and a 3D optical lattice loaded with bosons. By taking atomic multipolar interactions with the lattice fields into account, an 'atomic motion insensitive' wavelength is proposed to provide a precise definition of the 'magic wavelength'. We then present a frequency comparison of these two optical lattice clocks: spin-polarized fermionic {sup 87}Sr and bosonic {sup 88}Sr prepared in 1D and 3D optical lattices, respectively. Synchronous interrogations of these two optical lattice clocks by the same probe laser allowed canceling out its frequency noise as a common mode noise to achieve a relative stability of 3x10{sup -17} for an averaging time of {tau} = 350 s. The scheme, therefore, provides us with a powerful means to investigate intrinsic uncertainty of the clocks regardless of the probe laser stability. We discuss prospects of the synchronous operation of the clocks on the measurement of the geoid height difference and on the search of constancy of fundamental constants.

  5. Noise in state of the art clocks and their impact for fundamental physics

    Science.gov (United States)

    Maleki, L.

    2001-01-01

    In this paper a review of the use of advanced atomic clocks in testing the fundamental physical laws will be presented. Noise sources of clocks will be discussed, together with an outline their characterization based on current models. The paper will conclude with a discussion of recent attempts to reduce the fundamental, as well as technical noise in atomic clocks.

  6. Synthetic Spin-Orbit Coupling in an Optical Lattice Clock

    Science.gov (United States)

    Wall, Michael L.; Koller, Andrew P.; Li, Shuming; Zhang, Xibo; Cooper, Nigel R.; Ye, Jun; Rey, Ana Maria

    2016-01-01

    We propose the use of optical lattice clocks operated with fermionic alkaline-earth atoms to study spin-orbit coupling (SOC) in interacting many-body systems. The SOC emerges naturally during the clock interrogation, when atoms are allowed to tunnel and accumulate a phase set by the ratio of the "magic" lattice wavelength to the clock transition wavelength. We demonstrate how standard protocols such as Rabi and Ramsey spectroscopy that take advantage of the sub-Hertz resolution of state-of-the-art clock lasers can perform momentum-resolved band tomography and determine SOC-induced s -wave collisions in nuclear-spin-polarized fermions. With the use of a second counterpropagating clock beam, we propose a method for engineering controlled atomic transport and study how it is modified by p - and s -wave interactions. The proposed spectroscopic probes provide clean and well-resolved signatures at current clock operating temperatures.

  7. Magic Wavelengths for Terahertz Clock Transitions

    OpenAIRE

    Zhou, Xiaoji; Xu, Xia; Chen, Xuzong; Chen, Jingbiao

    2010-01-01

    Magic wavelengths for laser trapping of boson isotopes of alkaline-earth Sr, Ca and Mg atoms are investigated while considering terahertz clock transitions between the $^{3}P_{0}, ^{3}P_{1}, ^{3}P_{2}$ metastable triplet states. Our calculation shows that magic wavelengths of trapping laser do exist. This result is important because those metastable states have already been used to realize accurate clocks in the terahertz frequency domain. Detailed discussions for magic wavelength for teraher...

  8. Internal Clock Drift Estimation in Computer Clusters

    Directory of Open Access Journals (Sweden)

    Hicham Marouani

    2008-01-01

    Full Text Available Most computers have several high-resolution timing sources, from the programmable interrupt timer to the cycle counter. Yet, even at a precision of one cycle in ten millions, clocks may drift significantly in a single second at a clock frequency of several GHz. When tracing the low-level system events in computer clusters, such as packet sending or reception, each computer system records its own events using an internal clock. In order to properly understand the global system behavior and performance, as reported by the events recorded on each computer, it is important to estimate precisely the clock differences and drift between the different computers in the system. This article studies the clock precision and stability of several computer systems, with different architectures. It also studies the typical network delay characteristics, since time synchronization algorithms rely on the exchange of network packets and are dependent on the symmetry of the delays. A very precise clock, based on the atomic time provided by the GPS satellite network, was used as a reference to measure clock drifts and network delays. The results obtained are of immediate use to all applications which depend on computer clocks or network time synchronization accuracy.

  9. Lego clocks: building a clock from parts.

    Science.gov (United States)

    Brunner, Michael; Simons, Mirre J P; Merrow, Martha

    2008-06-01

    A new finding opens up speculation that the molecular mechanism of circadian clocks in Synechococcus elongatus is composed of multiple oscillator systems (Kitayama and colleagues, this issue, pp. 1513-1521), as has been described in many eukaryotic clock model systems. However, an alternative intepretation is that the pacemaker mechanism-as previously suggested-lies primarily in the rate of ATP hydrolysis by the clock protein KaiC.

  10. Gender Quotas on Board of Directors

    DEFF Research Database (Denmark)

    Smith, Nina

    2013-01-01

    on the grounds of economic efficiency. Furthermore, in most countries a limited number of women are qualified to join boards of directors, and it is not clear from the evidence to date on the operation of quotas whether they will lead to a better pool of female candidates in the medium and long term.......Beside arguments of fairness and equal opportunities, it is often argued that gender diversity on boards of directors may improve firm performance, but the empirical results are mixed and often negative. Based on the available research, gender quotas on boards of directors cannot be justified...

  11. Frequency comparison of optical lattice clocks beyond the Dick limit

    Science.gov (United States)

    Takamoto, Masao; Takano, Tetsushi; Katori, Hidetoshi

    2011-05-01

    The supreme accuracy of atomic clocks relies on the universality of atomic transition frequencies. The stability of a clock, meanwhile, measures how quickly the clock's statistical uncertainties are reduced. The ultimate measure of stability is provided by the quantum projection noise, which improves as 1/√N by measuring N uncorrelated atoms. Quantum projection noise limited stabilities have been demonstrated in caesium clocks and in single-ion optical clocks, where the quantum noise overwhelms the Dick effect attributed to local oscillator noise. Here, we demonstrate a synchronous frequency comparison of two optical lattice clocks using 87Sr and 88Sr atoms, respectively, for which the Allan standard deviation reached 1 × 10-17 in an averaging time of 1,600 s by cancelling out the Dick effect to approach the quantum projection noise limit. The scheme demonstrates the advantage of using a large number (N ~ 1,000) of atoms in optical clocks and paves the way to investigating the inherent uncertainties of clocks and relativistic geodesy on a timescale of tens of minutes.

  12. 47 CFR 80.1179 - On-board repeater limitations.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false On-board repeater limitations. 80.1179 Section... On-board repeater limitations. When an on-board repeater is used, the following limitations must be met: (a) The on-board repeater antenna must be located no higher than 3 meters (10 feet) above...

  13. Optical Clocks in Space

    CERN Document Server

    Schiller, S; Nevsky, A; Koelemeij, J C J; Wicht, A; Gill, P; Klein, H A; Margolis, H S; Mileti, G; Sterr, U; Riehle, F; Peik, E; Tamm, C; Ertmer, W; Rasel, E; Klein, V; Salomon, C; Tino, G M; Lemonde, P; Holzwarth, R; Hänsch, T W; Tamm, Chr.

    2007-01-01

    The performance of optical clocks has strongly progressed in recent years, and accuracies and instabilities of 1 part in 10^18 are expected in the near future. The operation of optical clocks in space provides new scientific and technological opportunities. In particular, an earth-orbiting satellite containing an ensemble of optical clocks would allow a precision measurement of the gravitational redshift, navigation with improved precision, mapping of the earth's gravitational potential by relativistic geodesy, and comparisons between ground clocks.

  14. SAS wave experiment on board Magion 4

    Directory of Open Access Journals (Sweden)

    J. Błęcki

    Full Text Available A short description of the SAS (subsatellite analyser of spectra wave experiment on board the Magion-4 subsatellite is given. We present first measurements of the magnetic-field fluctuations in the frequency range 32–2000 Hz obtained in the magnetotail during the disturbed period at the magnetopause and in the polar cusp.

  15. Faculty Members on Boards of Trustees

    Science.gov (United States)

    Ehrenberg, Ronald G.; Patterson, Richard W.; Key, Andrew V.

    2013-01-01

    During the 2011-12 academic year, a group of faculty and student researchers at the Cornell Higher Education Research Institute (CHERI) gathered information on which public and private institutions had faculty members on boards of trustees and obtained the names of the faculty members serving in these roles. In April and May 2012, the authors…

  16. Women on boards and firm performance

    NARCIS (Netherlands)

    Lückerath – Rovers, M.

    2013-01-01

    This study investigates the financial performance of Dutch companies both with and without women on their boards. The analysis extends earlier methods used in research by Catalyst (The bottom line: corporate performance and women’s representation on boards, 2007) and McKinsey (Women matter. Gender d

  17. Women on boards and firm performance

    NARCIS (Netherlands)

    M. Lückerath-Rovers (Mijntje)

    2013-01-01

    textabstractThis study investigates the financial performance of Dutch companies both with and without women on their boards. The analysis extends earlier methods used in research by Catalyst (The bottom line: corporate performance and women's representation on boards, 2007) and McKinsey (Women matt

  18. Superradiance on the milliHertz linewidth strontium clock transition

    CERN Document Server

    Norcia, Matthew A; Cline, Julia R K; Thompson, James K

    2016-01-01

    Today's best atomic clocks are limited by frequency noise on the lasers used to interrogate the atoms. A proposed solution to this problem is to create a superradiant laser using an optical clock transition as its gain medium. This laser would act as an active atomic clock, and would be highly immune to the fluctuations in reference cavity length that limit today's best lasers. Here, we demonstrate and characterize superradiant emission from the mHz linewidth clock transition in an ensemble of laser-cooled $^{87}$Sr atoms trapped within a high-finesse optical cavity. We measure a collective enhancement of the emission rate into the cavity mode by a factor of more than 10,000 compared to independently radiating atoms. We also demonstrate a method for seeding superradiant emission and observe interference between two independent transitions lasing simultaneously. We use this interference to characterize the relative spectral properties of the two lasing sub-ensembles.

  19. Hanle Detection for Optical Clocks

    Directory of Open Access Journals (Sweden)

    Xiaogang Zhang

    2015-01-01

    Full Text Available Considering the strong inhomogeneous spatial polarization and intensity distribution of spontaneous decay fluorescence due to the Hanle effect, we propose and demonstrate a universe Hanle detection configuration of electron-shelving method for optical clocks. Experimental results from Ca atomic beam optical frequency standard with electron-shelving method show that a designed Hanle detection geometry with optimized magnetic field direction, detection laser beam propagation and polarization direction, and detector position can improve the fluorescence collection rate by more than one order of magnitude comparing with that of inefficient geometry. With the fixed 423 nm fluorescence, the improved 657 nm optical frequency standard signal intensity is presented. The potential application of the Hanle detection geometry designed for facilitating the fluorescence collection for optical lattice clock with a limited solid angle of the fluorescence collection has been discussed. The Hanle detection geometry is also effective for ion detection in ion optical clock and quantum information experiments. Besides, a cylinder fluorescence collection structure is designed to increase the solid angle of the fluorescence collection in Ca atomic beam optical frequency standard.

  20. MODIS On-board Blackbody Performance

    Science.gov (United States)

    Xiong, Xiaoxiong; Chen, N.; Wu, A.; Wenny, B.; Dodd, J.

    2008-01-01

    Currently, there are two MODIS instruments operated on-orbit: one on-board the Terra spacecraft launched in December 1999 and the other on-board the Aqua spacecraft launched in May 2002. MODIS is a scanning radiometer that has 16 thermal emissive bands (TEBs) in the MWIR and LWIR regions. The remaining spectral bands are in the VISINIR and SWIR regions. The TEBs have a total of 160 detectors (10 detectors per band), which are calibrated on-orbit using an on-board blackbody (BB). MODIS TEB calibration is performed via a quadratic algorithm with its linear calibration coefficients updated on a scan-by-scan basis using each detector's response to the BB. The offset and nonlinear terms of the quadratic calibration equation are stored in a look-up table (LUT). The LUT parameters are derived from pre-launch calibration and updated on-orbit from BB observations, as needed. Typically, the BB is set at a fixed temperature. Periodically, a warm-up and cool-down activity is performed, which enables the BB temperature to be varied from instrument ambient up to 315K. The temperature of the BB is measured each scan using 12 thermistors, which were fully characterized pre-launch with reference to the NIST temperature scale. This paper describes MODIS on-board BB operational activities and performance. The TEB detector response (short-term stability and long-term changes) and noise characterization results derived from BB observations and their impact on the TEB calibration uncertainty are also presented.

  1. A Feminist Framework for Nurses on Boards.

    Science.gov (United States)

    Sundean, Lisa J; Polifroni, E Carol

    Nurses' knowledge, skills, and expertise uniquely situate them to contribute to health care transformation as equal partners in organizational board governance. The Institute of Medicine, the 10,000 Nurses on Boards Coalition, and a growing number of nurse and health care scholars advocate nurse board leadership; however, nurses are rarely appointed as voting board members. When no room is made for nurses to take a seat at the table, the opportunity is lost to harness the power of nursing knowledge for health care transformation and social justice. No philosophical framework underpins the emerging focus on nurse board leadership. The purpose of this article is to add to the extant nursing literature by suggesting feminism as a philosophical framework for nurses on boards. Feminism contributes to the knowledge base of nursing as it relates to the expanding roles of nurses in health care transformation, policy, and social justice. Furthermore, a feminist philosophical framework for nurses on boards sets the foundation for new theory development and validates ongoing advancement of the nursing profession.

  2. Frequency Ratio of ${}^{199}$Hg and ${}^{87}$Sr Optical Lattice Clocks beyond the SI Limit

    CERN Document Server

    Yamanaka, Kazuhiro; Ushijima, Ichiro; Takamoto, Masao; Katori, Hidetoshi

    2015-01-01

    We report on a frequency ratio measurement of a ${}^{199}$Hg-based optical lattice clock referencing a ${}^{87}$Sr-based clock. Evaluations of lattice light shift, including atomic-motion-dependent shift, enable us to achieve a total systematic uncertainty of $7.2 \\times 10^{-17}$ for the Hg clock. The frequency ratio is measured to be $\

  3. Stability Transfer between Two Clock Lasers Operating at Different Wavelengths for Absolute Frequency Measurement of Clock Transition in 87Sr

    CERN Document Server

    Yamaguchi, A; Nagano, S; Li, Y; Ishijima, H; Hachisu, H; Kumagai, M; Ido, T; 10.1143/APEX.5.022701

    2012-01-01

    We demonstrated transferring the stability of one highly stable clock laser operating at 729 nm to another less stable laser operating at 698 nm. The two different wavelengths were bridged using an optical frequency comb. The improved stability of the clock laser at 698 nm enabled us to evaluate the systematic frequency shifts of the Sr optical lattice clock with shorter averaging time. We determined the absolute frequency of the clock transition 1S0 - 3P0 in 87Sr to be 429 228 004 229 873.9 (1.4) Hz referenced to the SI second on the geoid via International Atomic Time (TAI).

  4. Realization of a time-scale with an optical clock

    CERN Document Server

    Grebing, C; Dörscher, S; Häfner, S; Gerginov, V; Weyers, S; Lipphardt, B; Riehle, F; Sterr, U; Lisdat, C

    2015-01-01

    Optical clocks are not only powerful tools for prime fundamental research, but are also deemed for the re-definition of the SI base unit second as they surpass the performance of caesium atomic clocks in both accuracy and stability by more than an order of magnitude. However, an important obstacle in this transition has so far been the limited reliability of the optical clocks that made a continuous realization of a time-scale impractical. In this paper, we demonstrate how this dilemma can be resolved and that a time-scale based on an optical clock can be established that is superior to one based on even the best caesium fountain clocks. The paper also gives further proof of the international consistency of strontium lattice clocks on the $10^{-16}$ accuracy level, which is another prerequisite for a change in the definition of the second.

  5. GPS Composite Clock Analysis

    OpenAIRE

    Wright, James R.

    2008-01-01

    The GPS composite clock defines GPS time, the timescale used today in GPS operations. GPS time is illuminated by examination of its role in the complete estimation and control problem relative to UTC/TAI. The phase of each GPS clock is unobservable from GPS pseudorange measurements, and the mean phase of the GPS clock ensemble (GPS time) is unobservable. A new and useful observability definition is presented, together with new observability theorems, to demonstrate explicitly that GPS time is...

  6. Orbitography for next generation space clocks

    CERN Document Server

    Duchayne, Loïc; Wolf, Peter

    2007-01-01

    Over the last decade of the 20th century and the first few years of the 21st, the uncertainty of atomic clocks has decreased by about two orders of magnitude, passing from the low 10^-14 to below 10^-16, in relative frequency . Space applications in fundamental physics, geodesy, time/frequency metrology, navigation etc... are among the most promising for this new generation of clocks. Onboard terrestrial or solar system satellites, their exceptional frequency stability and accuracy makes them a prime tool to test the fundamental laws of nature, and to study gravitational potentials and their evolution. In this paper, we study in more detail the requirements on orbitography compatible with operation of next generation space clocks at the required uncertainty based on a completely relativistic model. Using the ACES (Atomic Clock Ensemble in Space) mission as an example, we show that the required accuracy goal can be reached with relatively modest constraints on the orbitography of the space clock, much less str...

  7. Energy storage on board of railway vehicles

    Energy Technology Data Exchange (ETDEWEB)

    Steiner, M.; Scholten, J. [Bombardier Transportation, Mannheim (Germany)

    2004-07-01

    The proposed energy storage on board of a Railway vehicle leads to a big step in the reduction of consumed energy. Up to 30% energy saving are expected in a light rail vehicle, at the same time reducing the peak power demand drastically. In addition, with the energy storage an operation without catenary could become reality, which was successfully demonstrated with the prototype light rail vehicle driving with switched off pantograph. This prototype vehicle is in passenger operation since September 2003, the implemented software is optimised on energy savings and first experience is very promising. (authors)

  8. Legal Time of the Republic of Colombia and its international traceability using the Cesium Atomic Clock - Time and Frequency National Standard

    Science.gov (United States)

    Hernández Forero, Liz Catherine; Bahamón Cortés, Nelson

    2017-06-01

    Around the world, there are different providers of timestamp (mobile, radio or television operators, satellites of the GPS network, astronomical measurements, etc.), however, the source of the legal time for a country is either the national metrology institute or another designated laboratory. This activity requires a time standard based on an atomic time scale. The International Bureau of Weights and Measures (BIPM) calculates a weighted average of the time kept in more than 60 nations and produces a single international time scale, called Coordinated Universal Time (UTC). This article presents the current time scale that generates Legal Time for the Republic of Colombia produced by the Instituto Nacional de Metrología (INM) using the time and frequency national standard, a cesium atomic oscillator. It also illustrates how important it is for the academic, scientific and industrial communities, as well as the general public, to be synchronized with this time scale, which is traceable to the International System (SI) of units, through international comparisons that are made in real time.

  9. Clocked combustor can array

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Won-Wook; McMahan, Kevin Weston; Srinivasan, Shiva Kumar

    2017-01-17

    The present application provides a clocked combustor can array for coherence reduction in a gas turbine engine. The clocked combustor can array may include a number of combustor cans positioned in a circumferential array. A first set of the combustor cans may have a first orientation and a second set of the combustor cans may have a second orientation.

  10. Clocked combustor can array

    Science.gov (United States)

    Kim, Won-Wook; McMahan, Kevin Weston; Srinivasan, Shiva Kumar

    2017-01-17

    The present application provides a clocked combustor can array for coherence reduction in a gas turbine engine. The clocked combustor can array may include a number of combustor cans positioned in a circumferential array. A first set of the combustor cans may have a first orientation and a second set of the combustor cans may have a second orientation.

  11. Prototype of the DLR Operational Composite Clock: Methods and Test Cases

    Science.gov (United States)

    2009-11-01

    Study of Time Scale Algorithms,” Metrologia , 28, 57-63. [2] R. Jones and P. Tryon, 1983, “Estimating Time From Atomic Clocks,” Journal of Research of...L. Galleani and P. Tavella, 2008, “Detection and identification of atomic clock anomalies,” Metrologia , 45, 127-133. [16] C. Zucca and P

  12. Gender balance on boards: Stakeholders identification

    Directory of Open Access Journals (Sweden)

    Pilar de Luis Carnicer

    2011-12-01

    Full Text Available Recent Spanish law and regulations have turned gender balance on Boards of Directors into a necessary element to manage in companies. The aim of this paper is to identify the stakeholders demanding such gender balance to companies, according to the Methodology of Mitchell et al. (1997 and Agle et al. (1999. The results sugest the shareholders are the most important group, so it seems that the financial goals continue being a priority. But we also observe that the Government is perceived as a very important stakeholder. Despite managers acknowledge the Government has a lot of power, its importance is explained by urgency and legitimacy attributes. This fact makes us doubting about the effectiveness of any development of a compulsory law, beyond the current one.

  13. High-Performance Coherent Population Trapping Clock with Polarization Modulation

    Science.gov (United States)

    Yun, Peter; Tricot, François; Calosso, Claudio Eligio; Micalizio, Salvatore; François, Bruno; Boudot, Rodolphe; Guérandel, Stéphane; de Clercq, Emeric

    2017-01-01

    We demonstrate a vapor-cell atomic-clock prototype based on a continuous-wave interrogation and double-modulation coherent population trapping (DM-CPT) technique. The DM-CPT technique uses a synchronous modulation of polarization and the relative phase of a bichromatic laser beam in order to increase the number of atoms trapped in a dark state, i.e., a nonabsorbing state. The narrow resonance, observed in the transmission of a Cs vapor cell, is used as a narrow frequency discriminator in an atomic clock. A detailed characterization of the CPT resonance versus numerous parameters is reported. A short-term fractional-frequency stability of 3.2 ×10-13τ-1 /2 up to a 100-s averaging time is measured. These performances are more than one order of magnitude better than industrial Rb clocks and are comparable to those of the best laboratory-prototype vapor-cell clocks. The noise-budget analysis shows that the short- and midterm frequency stability is mainly limited by the power fluctuations of the microwave used to generate the bichromatic laser. These preliminary results demonstrate that the DM-CPT technique is well suited for the development of a high-performance atomic clock, with the potential compact and robust setup due to its linear architecture. This clock could find future applications in industry, telecommunications, instrumentation, or global navigation satellite systems.

  14. The Space Optical Clock project: status and perspectives

    Science.gov (United States)

    Schiller, Stephan; Tino, Guglielmo M.; Sterr, Uwe; Lemonde, Pierre; Görlitz, Axel; Salomon, Christophe

    The Space Optical Clocks project aims at operating lattice clocks on the ISS for tests of funda-mental physics and for providing high-accuracy comparisons of future terrestrial optical clocks. A pre-phase-A study (2007-10), funded partially by ESA and DLR, includes the implementa-tion of several optical lattice clock systems using Strontium and Ytterbium as atomic systems and their characterization. Subcomponents of clock demonstrators with the added specification of transportability and using techniques that are suitable for later space use, such as all-solid-state lasers, low power consumption, and compact dimensions, have been developed and are being validated. The talk will give a brief overview over the achieved results and outline future developments.

  15. Resetting Biological Clocks

    Science.gov (United States)

    Winfree, Arthur T.

    1975-01-01

    Reports on experiments conducted on two biological clocks, in organisms in the plant and animal kingdoms, which indicate that biological oscillation can be arrested by a single stimulus of a definite strength delivered at the proper time. (GS)

  16. Resetting Biological Clocks

    Science.gov (United States)

    Winfree, Arthur T.

    1975-01-01

    Reports on experiments conducted on two biological clocks, in organisms in the plant and animal kingdoms, which indicate that biological oscillation can be arrested by a single stimulus of a definite strength delivered at the proper time. (GS)

  17. On-board measurements of exhaust (OBM); On-Board Messungen von Abgas (OBM)

    Energy Technology Data Exchange (ETDEWEB)

    Heinze, H.E.

    1997-06-18

    The European Union intends to introduce on-board diagnosis of car exhaust emissions (OBD) from 2000, i.e. emission control by monitoring the various exhaust-relevant components of a motor car by an on-board computer. OBD is already in use in the USA (OBD I) and will be replaced by OBD step by step from 1995. In the present project, two systems by Messrs. WWU GmbH, Hamburg, will be investigated for the components CO and HC. For this purpose, comparative measurements with a FTIR spectrometer (SESAM = System for Emission Sampling and Measurement) are made using an exhaust dynamometer. (orig.) [Deutsch] Zur weiteren Verminderung der Emissionen schaedlicher Abgase aus Kraftfahrzeugen ist es in der Europaeischen Union vorgesehen, ab dem Jahre 2000 die On-Board Diagnose (OBD) einzufuehren. Darunter versteht man ein System zur Emissionskontrolle durch die Ueberwachung der Funktionsfaehigkeit der einzelnen abgasrelevanten Bauteile eines Kraftfahrzeugs durch den Fahrzeugcomputer. In den USA gibt es schon laenger eine erste Form der OBD fuer Pkw (OBD I), die ab dem Modelljahr 1995 schrittweise durch die weitergehende OBD II abgeloest wird. In diesem Vorhaben sollen zwei NDIR-Geraete der Firma WWU GmbH, Hamburg, auf ihre Eignung fuer den OBM-Einsatz ueberprueft werden, zunaechst nur fuer die Komponenten CO und HC. Dazu werden Vergleichsmessungen mit einem FTIR-Spektrometer (SESAM=System for Emission Sampling and Measurement) an einem Pkw auf dem Abgasrollenpruefstand durchgefuehrt. (orig.)

  18. The Chemical and Educational Appeal of the Orange Juice Clock

    Science.gov (United States)

    Kelter, Paul B.; Carr, James D.; Johnson, Tanya; Mauricio Castro-Acuña, Carlos

    1996-12-01

    characterized by seeing educational possibilities in so many things, created a modified version of the clock, with the atomic numbers of the elements representing the hours in the day (see Fig. 2) in his internationally popular workshops. Due largely to Talesnick's efforts, the orange juice clock is a standard demonstration in many chemistry programs and presentations. Figure 2.Irwin Talesnick represents the hours of the day by the corresponding elements in his clock. The Procedure This can be done as a demonstration or as an activity, although at about 10 per clock, expense does become an issue. There are no unusual safety precautions with this demonstration. We know of no accidents that have occurred with the orange juice clock. The demonstration requires: a single AA-cell battery-operated wall clock with a sweep-second hand a medium-sized beaker (600 mL is fine) enough orange juice or other electrolyte mixture or solution to fill the beaker about 2/3 full (tap water often works fine!) a 20-30-cm magnesium strip, coiled at one end or wrapped around a popsicle stick a 20-30-cm copper strip, coiled at one end alligator clips to connect the strips to the battery terminals on the clock a stand against which to lean the setup The demonstration is put together as shown in Figure 3. Connect the magnesium to the "-" contact of the clock and the copper to the "+" contact. Immerse the other ends of the strips into the solution. The clock will start to tick within a few seconds. If it does not work within a short period of time, check that the strips are well connected to the battery terminals, are hooked to the proper poles, and are not touching each other. The clock should keep reasonably close time (in orange juice) for a couple of days, or until the magnesium is nearly completely oxidized. Figure 3.A schematic of the orange juice clock seup. Video of orange juice clock. In video, the copper electrode is on the left and the magnesium electrode is on the right. Video was filmed and

  19. Detection of weak frequency jumps for GNSS onboard clocks.

    Science.gov (United States)

    Huang, Xinming; Gong, Hang; Ou, Gang

    2014-05-01

    In this paper, a weak frequency jump detection method is developed for onboard clocks in global navigation satellite systems (GNSS). A Kalman filter is employed to facilitate the onboard real-time processing of atomic clock measurements, whose N-step prediction residuals are used to construct the weak frequency jump detector. Numerical simulations show that the method can successfully detect weak frequency jumps. The detection method proposed in this paper is helpful for autonomous integrity monitoring of GNSS satellite clocks, and can also be applied to other frequency anomalies with an appropriately modified detector.

  20. General relativistic effects in quantum interference of "clocks"

    CERN Document Server

    Zych, Magdalena; Costa, Fabio; Brukner, Časlav

    2016-01-01

    Quantum mechanics and general relativity have been each successfully tested in numerous experiments. However, the regime where both theories are jointly required to explain physical phenomena remains untested by laboratory experiments, and is also not fully understood by theory. This contribution reviews recent ideas for a new type of experiments: quantum interference of "clocks", which aim to test novel quantum effects that arise from time dilation. "Clock" interference experiments could be realised with atoms or photons in near future laboratory experiments.

  1. Frequency ratios of Sr, Yb and Hg based optical lattice clocks and their applications

    CERN Document Server

    Takamoto, Masao; Das, Manoj; Nemitz, Nils; Ohkubo, Takuya; Yamanaka, Kazuhiro; Ohmae, Noriaki; Takano, Tetsushi; Akatsuka, Tomoya; Yamaguchi, Atsushi; Katori, Hidetoshi

    2015-01-01

    This article describes the recent progress of optical lattice clocks with neutral strontium ($^{87}$Sr), ytterbium ($^{171}$Yb) and mercury ($^{199}$Hg) atoms. In particular, we present frequency comparison between the clocks locally via an optical frequency comb and between two Sr clocks at remote sites using a phase-stabilized fibre link. We first review cryogenic Sr optical lattice clocks that reduce the room-temperature blackbody radiation shift by two orders of magnitude and serve as a reference in the following clock comparisons. Similar physical properties of Sr and Yb atoms, such as transition wavelengths and vapour pressure, have allowed our development of a compatible clock for both species. A cryogenic Yb clock is evaluated by referencing a Sr clock. We also report on a Hg clock, which shows one order of magnitude less sensitivity to blackbody radiation, while its large nuclear charge makes the clock sensitive to the variation of fine-structure constant. Connecting all three types of clocks by an o...

  2. Method of Enhancing On-Board State Estimation Using Communication Signals

    Science.gov (United States)

    Anzalone, Evan J. (Inventor); Chuang, Jason C. H. (Inventor)

    2015-01-01

    A method of enhancing on-board state estimation for a spacecraft utilizes a network of assets to include planetary-based assets and space-based assets. Communication signals transmitted from each of the assets into space are defined by a common protocol. Data is embedded in each communication signal transmitted by the assets. The data includes a time-of-transmission for a corresponding one of the communication signals and a position of a corresponding one of the assets at the time-of-transmission. A spacecraft is equipped to receive the communication signals, has a clock synchronized to the space-wide time reference frame, and has a processor programmed to generate state estimates of the spacecraft. Using its processor, the spacecraft determines a one-dimensional range from itself to at least one of the assets and then updates its state estimates using each one-dimensional range.

  3. 40 CFR 86.005-17 - On-board diagnostics.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 18 2010-07-01 2010-07-01 false On-board diagnostics. 86.005-17... Petroleum Gas-Fueled and Methanol-Fueled Heavy-Duty Vehicles § 86.005-17 On-board diagnostics. (a) General... “Road Vehicles-Diagnostics on Controller Area Network (CAN)—Part 4: Requirements for...

  4. 47 CFR 90.423 - Operation on board aircraft.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Operation on board aircraft. 90.423 Section 90... PRIVATE LAND MOBILE RADIO SERVICES Operating Requirements § 90.423 Operation on board aircraft. (a) Except... after September 14, 1973, under this part may be operated aboard aircraft for air-to-mobile, air-to-base...

  5. Evaluation of Long Term Performance of Continuously Running Atomic Fountains

    Science.gov (United States)

    2014-05-28

    Observatory (USNO). These fountains are used as continuous clocks in the manner of commercial caesium beams and hydrogen masers for the purpose of improved...clock, rubidium fountain, operational atomic fountain (Some figures may appear in colour only in the online journal) 1. Introduction: beyond caesiums ...and masers The performance of atomic clocks has improved more than seven orders of magnitude since the first caesium clock was demonstrated by Essen

  6. On-board processing of video image sequences

    DEFF Research Database (Denmark)

    Andersen, Jakob Dahl; Chanrion, Olivier Arnaud; Forchhammer, Søren

    2008-01-01

    of the mission is to study transient luminous events (TLE) above severe thunderstorms: the sprites, jets and elves. Other atmospheric phenomena are also studied including aurora, gravity waves and meteors. As part of the ASIM Phase B study, on-board processing of data from the cameras is being developed...... and evaluated. On-board there are six video cameras each capturing images of 1024times1024 pixels of 12 bpp at a frame rate of 15 fps, thus totalling 1080 Mbits/s. In comparison the average downlink data rate for these images is projected to be 50 kbit/s. This calls for efficient on-board processing to select...... and compress the data. Algorithms for on-board processing of the image data are presented as well as evaluation of the performance. The main processing steps are event detection, image cropping and image compression. The on-board processing requirements are also evaluated....

  7. On clocks and clouds

    Directory of Open Access Journals (Sweden)

    M. K. Witte

    2013-09-01

    Full Text Available Cumulus clouds exhibit a life cycle that consists of: (a the growth phase (increasing size, most notably in the vertical direction; (b the mature phase (growth ceases; any precipitation that develops is strongest during this period; and (c the dissipation phase (cloud dissipates because of precipitation and/or entrainment; no more dynamical support. Although radar can track clouds over time and give some sense of the age of a cloud, most aircraft in situ measurements lack temporal context. We use large eddy simulations of trade wind cumulus cloud fields from cases during the Barbados Oceanographic and Meteorological Experiment (BOMEX and Rain In Cumulus over the Ocean (RICO campaigns to demonstrate a potential cumulus cloud "clock". We find that the volume-averaged total water mixing ratio rt is a useful cloud clock for the 12 clouds studied. A cloud's initial rt is set by the subcloud mixed-layer mean rt and decreases monotonically from the initial value due primarily to entrainment. The clock is insensitive to aerosol loading, environmental sounding and extrinsic cloud properties such as lifetime and volume. In some cases (more commonly for larger clouds, multiple pulses of buoyancy occur, which complicate the cumulus clock by replenishing rt. The clock is most effectively used to classify clouds by life phase.

  8. Analysis of Atom-Interferometer Clocks

    Science.gov (United States)

    2014-01-21

    particle has been mostly ignored [3]. But in recent years it has appeared in the literature with claims that the redshift of the Compton oscillation... literature it has been claimed that ω0 does not correspond to a physical oscillation, with the points being made that it is not Doppler shifted to an...Peters, and S. Chu, Nature (London) 463, 926 (2010). [5] P. Catillon, N. Cue, M. J. Gaillard, R. Genre , M. Gouanère, R. G. Kirsch, J. C. Poizat, J

  9. Relativistic quantum clocks

    CERN Document Server

    Lock, Maximilian P E

    2016-01-01

    The conflict between quantum theory and the theory of relativity is exemplified in their treatment of time. We examine the ways in which their conceptions differ, and describe a semiclassical clock model combining elements of both theories. The results obtained with this clock model in flat spacetime are reviewed, and the problem of generalizing the model to curved spacetime is discussed, before briefly describing an experimental setup which could be used to test of the model. Taking an operationalist view, where time is that which is measured by a clock, we discuss the conclusions that can be drawn from these results, and what clues they contain for a full quantum relativistic theory of time.

  10. The circadian clock goes genomic.

    Science.gov (United States)

    Staiger, Dorothee; Shin, Jieun; Johansson, Mikael; Davis, Seth J

    2013-06-24

    Large-scale biology among plant species, as well as comparative genomics of circadian clock architecture and clock-regulated output processes, have greatly advanced our understanding of the endogenous timing system in plants.

  11. SRC: Smart Reminder Clock

    Science.gov (United States)

    Kasim, Shahreen; Hafit, Hanayanti; Leong, Tan Hua; Hashim, Rathiah; Ruslai, Husni; Jahidin, Kamaruzzaman; Syafwan Arshad, Mohammad

    2016-11-01

    Nowadays, some people facing the problem to wake up in the morning. This was result to absence of the classes, meetings, and even exams. The aim of this project is to develop an android application that can force the user to wake up. The method used in this application are pedometer and Short Message Service (SMS) function. This application need the user to take their smartphone and walk about 10 steps to disable it, when the alarm clock is activated. After that, when the alarm clock was rang, this alarm application has automatically send a message to the users’ friends or parents phone to wake them up.

  12. Gravitomagnetism, clocks and geometry

    CERN Document Server

    Tartaglia, A

    2001-01-01

    New techniques to evaluate the clock effect using light are described. These are based on the flatness of the cylindrical surface containing the world lines of the rays constrained to move on circular trajectories about a spinning mass. The effect of the angular momentum of the source is manifested in the fact that inertial observers must be replaced by local non rotating observers. Starting from this an exact formula for circular trajectories is found. Numerical estimates for the Earth environment show that light would be a better probe than actual clocks to evidence the angular momentum influence. The advantages of light in connection with some principle experiments are shortly reviewed.

  13. The absolute frequency of the 87Sr optical clock transition

    DEFF Research Database (Denmark)

    Campbell, Gretchen K.; Ludlow, Andrew D.; Blatt, Sebastian;

    2008-01-01

    The absolute frequency of the 1S0–3P0 clock transition of 87Sr has been measured to be 429 228 004 229 873.65 (37) Hz using lattice-confined atoms, where the fractional uncertainty of 8.6 × 10-16 represents one of the most accurate measurements of an atomic transition frequency to date. After a d...... is made possible using a femtosecond laser based optical frequency comb to phase coherently connect the optical and microwave spectral regions and by a 3.5 km fibre transfer scheme to compare the remotely located clock signals....

  14. Decamp Clock Board Firmware

    Energy Technology Data Exchange (ETDEWEB)

    Vicente, J. de; Castilla, J.; Martinez, G.

    2007-09-27

    Decamp (Dark Energy Survey Camera) is a new instrument designed to explore the universe aiming to reveal the nature of Dark Energy. The camera consists of 72 CCDs and 520 Mpixels. The readout electronics of DECam is based on the Monsoon system. Monsoon is a new image acquisition system developed by the NOAO (National Optical Astronomical Observatory) for the new generation of astronomical cameras. The Monsoon system uses three types of boards inserted in a Eurocard format based crate: master control board, acquisition board and clock board. The direct use of the Monsoon system for DECam readout electronics requires nine crates mainly due to the high number of clock boards needed. Unfortunately, the available space for DECam electronics is constrained to four crates at maximum. The major drawback to achieve such desired compaction degree resides in the clock board signal density. This document describes the changes performed at CIEMAT on the programmable logic of the Monsoon clock board aiming to meet such restricted space constraints. (Author) 5 refs.

  15. Cyclotomic quantum clock

    CERN Document Server

    Rosu, H C

    2003-01-01

    In the wake of our recent work on cyclotomic effects in quantum phase locking [M. Planat and H. C. Rosu, Phys. Lett. A 315, 1 (2003)], we briefly discuss here a cyclotomic extension of the Salecker and Wigner quantum clock. We also hint on a possible cyclotomic structure of time at the Planck scales

  16. XMM instrument on-board software maintenance concept

    Science.gov (United States)

    Peccia, N.; Giannini, F.

    1994-01-01

    While the pre-launch responsibility for the production, validation and maintenance of instrument on-board software traditionally lies with the experimenter, the post-launch maintenance has been the subject of ad hoc arrangements with the responsibility shared to different extent between the experimenter, ESTEC and ESOC. This paper summarizes the overall design and development of the instruments on-board software for the XMM satellite, and describes the concept adopted for the maintenance of such software post-launch. The paper will also outline the on-board software maintenance and validation facilities and the expected advantages to be gained by the proposed strategy. Conclusions with respect to adequacy of this approach will be presented as well as recommendations for future instrument on-board software developments.

  17. Advanced On Board Inert Gas Generation System (OBBIGS) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Valcor Engineering Corporation proposes to develop an advanced On Board Inert Gas Generation System, OBIGGS, for aircraft fuel tank inerting to prevent hazardous...

  18. An Algorithm for the Detection of the Frequency Jumps in Space Clocks

    Science.gov (United States)

    2010-11-01

    Tavella, 2008, “Detection and identification of atomic clock anomalies,” Metrologia , 45, 127-133. [4] L. Galleani, 2008, “Detection of changes in clock...noise using the time–frequency spectrum,” Metrologia , 45, 143-153. [5] I. Sesia, L. Galleani, and P. Tavella, 2007, “Implementation of the Dynamic

  19. Relativity and Al^+ Optical Clocks

    Science.gov (United States)

    Chou, Chin-Wen; Hume, David B.; Wineland, David J.; Rosenband, Till

    2010-03-01

    We have constructed an optical clock based on quantum logic spectroscopy of an Al+ ion that has a fractional frequency inaccuracy of 8.6x10-18. The frequency of the ^1S0^3P0 clock transition is compared to that of a previously constructed Al^+ optical clock with a statistical measurement uncertainty of 7.0x10-18. The two clocks exhibit a relative stability of 2.8x10-15&-1/2circ;, and a fractional frequency difference of -1.8x10-17, consistent with the accuracy limit of the older clock. By comparing the frequencies of the clocks, we have observed relativistic effects, such as time dilation due to velocities less than 10 m/s and the gravitational red shift from a 0.33 m height change of one of the clocks.

  20. 40 CFR 86.1806-04 - On-board diagnostics.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 19 2010-07-01 2010-07-01 false On-board diagnostics. 86.1806-04..., and Complete Otto-Cycle Heavy-Duty Vehicles § 86.1806-04 On-board diagnostics. This § 86.1806-04... alternative to SAE J1850. (iii) ISO 15765-4.3:2001 “Road Vehicles-Diagnostics on Controller Area Network...

  1. A Miniature Cold-Atom Frequency Standard

    CERN Document Server

    Shah, Vishal; Stoner, Rick; Vuletic, Vladan; Lutwak, Robert

    2011-01-01

    Atomic sensors employing cold-atom technology enable unprecedented accuracy and resolution for next generation atomic clocks, magnetometers, gravimeters, and gyroscopes. To date, however, the size and complexity of cold atom systems have prevented their deployment in practical applications outside of large research laboratories. Here we demonstrate a low power, palm-top, and fully integrated cold atom system that functions as an atomic clock with a stability of 2 parts in 10^11 at 1s. This work demonstrates the feasibility of developing compact, robust, and portable devices based on laser cooled atoms.

  2. Detecting negative ions on board small satellites

    Science.gov (United States)

    Lepri, S. T.; Raines, J. M.; Gilbert, J. A.; Cutler, J.; Panning, M.; Zurbuchen, T. H.

    2017-04-01

    Recent measurements near comets, planets, and their satellites have shown that heavy ions, energetic neutral atoms, molecular ions, and charged dust contain a wealth of information about the origin, evolution, and interaction of celestial bodies with their space environment. Using highly sensitive plasma instruments, positively charged heavy ions have been used to trace exospheric and surface composition of comets, planets, and satellites as well as the composition of interplanetary and interstellar dust. While positive ions dominate throughout the heliosphere, negative ions are also produced from surface interactions. In fact, laboratory experiments have shown that oxygen released from rocky surfaces is mostly negatively charged. Negative ions and negatively charged nanograins have been detected with plasma electron analyzers in several different environments (e.g., by Cassini and Rosetta), though more extensive studies have been challenging without instrumentation dedicated to negative ions. We discuss an adaptation of the Fast Imaging Plasma Spectrometer (FIPS) flown on MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) for the measurement of negatively charged particles. MESSENGER/FIPS successfully measured the plasma environment of Mercury from 2011 until 2015, when the mission ended, and has been used to map multiple ion species (H+ through Na+ and beyond) throughout Mercury's space environment. Modifications to the existing instrument design fits within a 3U CubeSat volume and would provide a low mass, low power instrument, ideal for future CubeSat or distributed sensor missions seeking, for the first time, to characterize the contribution of negative particles in the heliospheric plasmas near the planets, moons, comets, and other sources.

  3. Round the clock librarianship

    OpenAIRE

    1995-01-01

    The concept of Round the Clock Librarianship (ROCLOLIB) is one such opportunity of terminal and critical importance to librarians, which helps people (clients) in general and reassures them about the professional commitment and devotedness of librarians. Although the concept is old, it is an exercise here to analyse its importance for the overall image and status of the practice/occupation. The chapter discusses the proposal of opening Libraries for 24 Hours. It also points out the reasons fo...

  4. Highly charged ions as a basis of optical atomic clockwork of exceptional accuracy.

    Science.gov (United States)

    Derevianko, Andrei; Dzuba, V A; Flambaum, V V

    2012-11-02

    We propose a novel class of atomic clocks based on highly charged ions. We consider highly forbidden laser-accessible transitions within the 4f(12) ground-state configurations of highly charged ions. Our evaluation of systematic effects demonstrates that these transitions may be used for building exceptionally accurate atomic clocks which may compete in accuracy with recently proposed nuclear clocks.

  5. Quantum Repeaters and Atomic Ensembles

    DEFF Research Database (Denmark)

    Borregaard, Johannes

    that can exist between remote quantum systems called entanglement. These correlations are exploited to detect eavesdroppers and construct unconditionally secure communication channels, enhance the sensitivity in various metrology schemes and construct powerful quantum computers, which can solve extremely...... a previous protocol, thereby enabling fast local processing, which greatly enhances the distribution rate. We then move on to describe our work on improving the stability of atomic clocks using entanglement. Entanglement can potentially push the stability of atomic clocks to the so-called Heisenberg limit...... and allows for near-Heisenberg limited stability of atomic clocks. Furthermore, we describe how the operation of a clock can be altered to gain an exponential improvement of the stability even without entanglement. In the next part of the thesis, we describe our work on a novel type of heralded quantum gates...

  6. On-Board Mining in the Sensor Web

    Science.gov (United States)

    Tanner, S.; Conover, H.; Graves, S.; Ramachandran, R.; Rushing, J.

    2004-12-01

    On-board data mining can contribute to many research and engineering applications, including natural hazard detection and prediction, intelligent sensor control, and the generation of customized data products for direct distribution to users. The ability to mine sensor data in real time can also be a critical component of autonomous operations, supporting deep space missions, unmanned aerial and ground-based vehicles (UAVs, UGVs), and a wide range of sensor meshes, webs and grids. On-board processing is expected to play a significant role in the next generation of NASA, Homeland Security, Department of Defense and civilian programs, providing for greater flexibility and versatility in measurements of physical systems. In addition, the use of UAV and UGV systems is increasing in military, emergency response and industrial applications. As research into the autonomy of these vehicles progresses, especially in fleet or web configurations, the applicability of on-board data mining is expected to increase significantly. Data mining in real time on board sensor platforms presents unique challenges. Most notably, the data to be mined is a continuous stream, rather than a fixed store such as a database. This means that the data mining algorithms must be modified to make only a single pass through the data. In addition, the on-board environment requires real time processing with limited computing resources, thus the algorithms must use fixed and relatively small amounts of processing time and memory. The University of Alabama in Huntsville is developing an innovative processing framework for the on-board data and information environment. The Environment for On-Board Processing (EVE) and the Adaptive On-board Data Processing (AODP) projects serve as proofs-of-concept of advanced information systems for remote sensing platforms. The EVE real-time processing infrastructure will upload, schedule and control the execution of processing plans on board remote sensors. These plans

  7. An Innovative On-Board Computer for Space Robot

    Institute of Scientific and Technical Information of China (English)

    WEI Ran; JIN Ming-he; XIA Jin-jun; LIU Hong

    2007-01-01

    In this paper an on-board computer system for the first Chinese Intelligent Space Robotic System was presented. A fault tolerance design on on-board computer (OBC) was proposed that allows commercial-off-theshelf (COTS) devices to be incorporated into dual processing modules of on-board computer. The processing module is composed of 32-bit ARM RISC processor and other COTS devices. This innovative approach deeply relies on light weight/low cost equipment development using commercial miniaturized parts and non-space qualified technologies. As well as, a set of fault handling mechanisms was implemented in the computer system. The on-board software was organized around a set of processes that communicate between each other through a routing process.The qualification experiment shows that the fault tolerant on-board computer has excellent data processing capability and is enough to meet the demanding of the extremely tight constraints on mass, volume, power consumption and space environmental conditions.

  8. Frequency shift due to blackbody radiation in a cesium atomic fountain and improvement of the clock performances; Deplacement de frequence du au rayonnement du corps noir dans une fontaine atomique a cesium et amelioration des performances de l'horloge

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, S

    2004-07-01

    FO1 was the first caesium fountain primary frequency standard in the world. The most recent evaluation in 2002 before improvement reached an accuracy of 1*10{sup -15} when operated with optical molasses. Working as an extremely precise and stable instrument, FO1 has contributed to fundamental physics and technical measurements: - Frequency comparison between Cs and Rb fountains over an interval of 5 years sets an upper limit for a possible variation of the fine structure constant as |alpha/alpha| < 2*10{sup -15}/y. The resolution is about 5 times better than the previous test in our laboratory. The projected accuracy of the space clock PHARAO is 1*10{sup -16}. We confirmed its Ramsey cavity performance by testing the phase difference between the two interaction zones in FO1. The measured temperature T dependent frequency shift of the Cs clock induced by the blackbody radiation field is given as nu(T)=154(6)*10{sup -6}*(T/300){sup 4}[1+{epsilon}(T/300){sup 2}] Hz with the theoretical value {epsilon} = 0,014. The obtained accuracy represents a 3 times improvement over the previous measurement by the PTB group. Some improvements have been carried out on FO1. The new FO1 version works directly with optical molasses loaded by a laser slowed atomic beam. The application of the adiabatic passage method to perform the state selection allows us to determine the atom number dependent frequency shifts due to the cold collision and cavity pulling effects at a level of of 10{sup -16}. Recently, the obtained frequency stability is 2,8*10{sup -14}*{tau}{sup -1/2} for about 4*10{sup 6} detected atoms. The accuracy is currently under evaluation, the expected value is a few times 10{sup -16}. (author)

  9. Circadian clocks and breast cancer

    OpenAIRE

    Blakeman, Victoria; Jack L. Williams; Meng, Qing-Jun; Streuli, Charles H

    2016-01-01

    Circadian clocks respond to environmental time cues to coordinate 24-hour oscillations in almost every tissue of the body. In the breast, circadian clocks regulate the rhythmic expression of numerous genes. Disrupted expression of circadian genes can alter breast biology and may promote cancer. Here we overview circadian mechanisms, and the connection between the molecular clock and breast biology. We describe how disruption of circadian genes contributes to cancer via multiple mechanisms, an...

  10. Radium single-ion optical clock

    CERN Document Server

    Versolato, O O; Jungmann, K; Timmermans, R G E; Willmann, L; Wilschut, H W

    2011-01-01

    We explore the potential of the electric quadrupole transitions $7s\\,^2S_{1/2}$ - $6d\\,^2D_{3/2}$, $6d\\,^2D_{5/2}$ in radium isotopes as single-ion optical frequency standards. The frequency shifts of the clock transitions due to external fields and the corresponding uncertainties are calculated. Several competitive $^A$Ra$^+$ candidates with $A=$ 223 - 229 are identified. In particular, we show that the transition $7s\\,^2S_{1/2}\\,(F=2,m_F=0)$ - $6d\\,^2D_{3/2}\\,(F=0,m_F=0)$ at 828 nm in $^{223}$Ra$^+$, with no linear Zeeman and electric quadrupole shifts, stands out as a relatively simple case, which could be exploited as a compact, robust, and low-cost atomic clock operating at a fractional frequency uncertainty of $10^{-17}$. With more experimental effort, the $^{223,225,226}$Ra$^+$ clocks could be pushed to a projected performance reaching the $10^{-18}$ level.

  11. Position and orientation inference via on-board triangulation.

    Science.gov (United States)

    Advani, Madhu; Weile, Daniel S

    2017-01-01

    This work proposes a new approach to determine the spatial location and orientation of an object using measurements performed on the object itself. The on-board triangulation algorithm we outline could be implemented in lieu of, or in addition to, well-known alternatives such as Global Positioning System (GPS) or standard triangulation, since both of these correspond to significantly different geometric pictures and necessitate different hardware and algorithms. We motivate the theory by describing situations in which on-board triangulation would be useful and even preferable to standard methods. The on-board triangulation algorithm we outline involves utilizing dumb beacons which broadcast omnidirectional single frequency radio waves, and smart antenna arrays on the object itself to infer the direction of the beacon signals, which may be used for onboard calculation of the position and orientation of the object. Numerical examples demonstrate the utility of the method and its noise tolerance.

  12. CSAC Characterization and Its Impact on GNSS Clock Augmentation Performance

    Science.gov (United States)

    Fernández, Enric; Calero, David; Parés, M. Eulàlia

    2017-01-01

    Chip Scale Atomic Clocks (CSAC) are recently-developed electronic instruments that, when used together with a Global Navigation Satellite Systems (GNSS) receiver, help improve the performance of GNSS navigation solutions in certain conditions (i.e., low satellite visibility). Current GNSS receivers include a Temperature Compensated Cristal Oscillator (TCXO) clock characterized by a short-term stability (τ = 1 s) of 10−9 s that leads to an error of 0.3 m in pseudorange measurements. The CSAC can achieve a short-term stability of 2.5 × 10−12 s, which implies a range error of 0.075 m, making for an 87.5% improvement over TCXO. Replacing the internal TCXO clock of GNSS receivers with a higher frequency stability clock such as a CSAC oscillator improves the navigation solution in terms of low satellite visibility positioning accuracy, solution availability, signal recovery (holdover), multipath and jamming mitigation and spoofing attack detection. However, CSAC suffers from internal systematic instabilities and errors that should be minimized if optimal performance is desired. Hence, for operating CSAC at its best, the deterministic errors from the CSAC need to be properly modelled. Currently, this modelling is done by determining and predicting the clock frequency stability (i.e., clock bias and bias rate) within the positioning estimation process. The research presented in this paper aims to go a step further, analysing the correlation between temperature and clock stability noise and the impact of its proper modelling in the holdover recovery time and in the positioning performance. Moreover, it shows the potential of fine clock coasting modelling. With the proposed model, an improvement in vertical positioning precision of around 50% with only three satellites can be achieved. Moreover, an increase in the navigation solution availability is also observed, a reduction of holdover recovery time from dozens of seconds to only a few can be achieved. PMID:28216600

  13. CSAC Characterization and Its Impact on GNSS Clock Augmentation Performance

    Directory of Open Access Journals (Sweden)

    Enric Fernández

    2017-02-01

    Full Text Available Chip Scale Atomic Clocks (CSAC are recently-developed electronic instruments that, when used together with a Global Navigation Satellite Systems (GNSS receiver, help improve the performance of GNSS navigation solutions in certain conditions (i.e., low satellite visibility. Current GNSS receivers include a Temperature Compensated Cristal Oscillator (TCXO clock characterized by a short-term stability (τ = 1 s of 10−9 s that leads to an error of 0.3 m in pseudorange measurements. The CSAC can achieve a short-term stability of 2.5 × 10−12 s, which implies a range error of 0.075 m, making for an 87.5% improvement over TCXO. Replacing the internal TCXO clock of GNSS receivers with a higher frequency stability clock such as a CSAC oscillator improves the navigation solution in terms of low satellite visibility positioning accuracy, solution availability, signal recovery (holdover, multipath and jamming mitigation and spoofing attack detection. However, CSAC suffers from internal systematic instabilities and errors that should be minimized if optimal performance is desired. Hence, for operating CSAC at its best, the deterministic errors from the CSAC need to be properly modelled. Currently, this modelling is done by determining and predicting the clock frequency stability (i.e., clock bias and bias rate within the positioning estimation process. The research presented in this paper aims to go a step further, analysing the correlation between temperature and clock stability noise and the impact of its proper modelling in the holdover recovery time and in the positioning performance. Moreover, it shows the potential of fine clock coasting modelling. With the proposed model, an improvement in vertical positioning precision of around 50% with only three satellites can be achieved. Moreover, an increase in the navigation solution availability is also observed, a reduction of holdover recovery time from dozens of seconds to only a few can be achieved.

  14. A Light Clock Satisfying the Clock Hypothesis of Special Relativity

    Science.gov (United States)

    West, Joseph

    2007-01-01

    The design of the FMEL, a floor-mirrored Einstein-Langevin "light clock", is introduced. The clock provides a physically intuitive manner to calculate and visualize the time dilation effects for a spatially extended set of observers (an accelerated "frame") undergoing unidirectional acceleration or observers on a rotating cylinder of constant…

  15. Development of a strontium optical lattice clock for space applications

    Science.gov (United States)

    Singh, Yeshpal

    2016-07-01

    With timekeeping being of paramount importance for modern life, much research and major scientific advances have been undertaken in the field of frequency metrology, particularly over the last few years. New Nobel-prize winning technologies have enabled a new era of atomic clocks; namely the optical clock. These have been shown to perform significantly better than the best microwave clocks reaching an inaccuracy of 1.6x10-18 [1]. With such results being found in large lab based apparatus, the focus now has shifted to portability - to enable the accuracy of various ground based clocks to be measured, and compact autonomous performance - to enable such technologies to be tested in space. This could lead to a master clock in space, improving not only the accuracy of technologies on which modern life has come to require such as GPS and communication networks. But also more fundamentally, this could lead to the redefinition of the second and tests of fundamental physics including applications in the fields of ground based and satellite geodesy, metrology, positioning, navigation, transport and logistics etc. Within the European collaboration, Space Optical Clocks (SOC2) [2-3] consisting of various institutes and industry partners across Europe we have tried to tackle this problem of miniaturisation whilst maintaining stability, accuracy (5x10-17) and robustness whilst keeping power consumption to a minimum - necessary for space applications. We will present the most recent results of the Sr optical clock in SOC2 and also the novel compact design features, new methods employed and outlook. References [1] B. J. Bloom, T. L. Nicholson, J. R. Williams, S. L. Campbell, M. Bishof, X. Zhang, W. Zhang, S. L. Bromley, and J. Ye, "An optical lattice clock with accuracy and stability at the 10-18 level," Nature 506, 71-75 (2014). [2] S. Schiller et al. "Towards Neutral-atom Space Optical Clocks (SOC2): Development of high-performance transportable and breadboard optical clocks and

  16. Clocks and cardiovascular function

    Science.gov (United States)

    McLoughlin, Sarah C.; Haines, Philip; FitzGerald, Garret A.

    2016-01-01

    Circadian clocks in central and peripheral tissues enable the temporal synchronization and organization of molecular and physiological processes of rhythmic animals, allowing optimum functioning of cells and organisms at the most appropriate time of day. Disruption of circadian rhythms, from external or internal forces, leads to widespread biological disruption and is postulated to underlie many human conditions, such as the incidence and timing of cardiovascular disease. Here, we describe in vivo and in vitro methodology relevant to studying the role of circadian rhythms in cardiovascular function and dysfunction PMID:25707279

  17. A mixed relaxed clock model

    Science.gov (United States)

    2016-01-01

    Over recent years, several alternative relaxed clock models have been proposed in the context of Bayesian dating. These models fall in two distinct categories: uncorrelated and autocorrelated across branches. The choice between these two classes of relaxed clocks is still an open question. More fundamentally, the true process of rate variation may have both long-term trends and short-term fluctuations, suggesting that more sophisticated clock models unfolding over multiple time scales should ultimately be developed. Here, a mixed relaxed clock model is introduced, which can be mechanistically interpreted as a rate variation process undergoing short-term fluctuations on the top of Brownian long-term trends. Statistically, this mixed clock represents an alternative solution to the problem of choosing between autocorrelated and uncorrelated relaxed clocks, by proposing instead to combine their respective merits. Fitting this model on a dataset of 105 placental mammals, using both node-dating and tip-dating approaches, suggests that the two pure clocks, Brownian and white noise, are rejected in favour of a mixed model with approximately equal contributions for its uncorrelated and autocorrelated components. The tip-dating analysis is particularly sensitive to the choice of the relaxed clock model. In this context, the classical pure Brownian relaxed clock appears to be overly rigid, leading to biases in divergence time estimation. By contrast, the use of a mixed clock leads to more recent and more reasonable estimates for the crown ages of placental orders and superorders. Altogether, the mixed clock introduced here represents a first step towards empirically more adequate models of the patterns of rate variation across phylogenetic trees. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’. PMID:27325829

  18. High-performance coherent population trapping clock with polarization modulation

    CERN Document Server

    Yun, Peter; Calosso, Claudio Eligio; Micalizio, Salvatore; François, Bruno; Boudot, Rodolphe; Guérandel, Stéphane; de Clercq, Emeric

    2016-01-01

    We demonstrate a vapor cell atomic clock prototype based on continuous-wave (CW) interrogation and double-modulation coherent population trapping (DM-CPT) technique. The DM-CPT technique uses a synchronous modulation of polarization and relative phase of a bi-chromatic laser beam in order to increase the number of atoms trapped in a dark state, i.e. a non-absorbing state. The narrow resonance, observed in transmission of a Cs vapor cell, is used as a narrow frequency discriminator in an atomic clock. A detailed characterization of the CPT resonance versus numerous parameters is reported. A short-term frequency stability of $3.2 \\times 10^{-13} \\tau^{-1/2}$ up to 100 s averaging time is measured. These performances are more than one order of magnitude better than industrial Rb clocks and comparable to those of best laboratory-prototype vapor cell clocks. The noise budget analysis shows that the short and mid-term frequency stability is mainly limited by the power fluctuations of the microwave used to generate ...

  19. Bijlagen visie on-board-monitoring in de binnenvaart

    NARCIS (Netherlands)

    Verbeek, R.P.; Harmsen, J.; Mensch, P. van

    2015-01-01

    In deze memo zijn de resultaten gepresenteerd van een analyse naar de impact van verschillende opties voor het vergroenen van de binnenvaart. In deze analyse zijn de volgende maatregelen opgenomen:  Vervroegd vervangen van de motor om in 2025 te voldoen aan CCRII;  Installeren van een On Board Mon

  20. Real-time Java for on-board systems

    Science.gov (United States)

    Cechticky, V.; Pasetti, A.

    2002-07-01

    The Java language has several attractive features but cannot at present be used in on-board systems primarily because it lacks support for hard real-time operation. This shortcoming is in being addressed: some suppliers are already providing implementations of Java that are RT-compliant; Sun Microsystem has approved a formal specification for a real-time extension of the language; and an independent consortium is working on an alternative specification for real-time Java. It is therefore expected that, within a year or so, standardized commercial implementations of real-time Java will be on the market. Availability of real-time implementations now opens the way to its use on-board. Within this context, this paper has two objectives. Firstly, it discusses the suitability of Java for on-board applications. Secondly, it reports the results of an ESA study to port a software framework for on-board control systems to a commercial real-time version of Java.

  1. Quantum Repeaters and Atomic Ensembles

    DEFF Research Database (Denmark)

    Borregaard, Johannes

    a previous protocol, thereby enabling fast local processing, which greatly enhances the distribution rate. We then move on to describe our work on improving the stability of atomic clocks using entanglement. Entanglement can potentially push the stability of atomic clocks to the so-called Heisenberg limit......, which is the absolute upper limit of the stability allowed by the Heisenberg uncertainty relation. It has, however, been unclear whether entangled state’s enhanced sensitivity to noise would prevent reaching this limit. We have developed an adaptive measurement protocol, which circumvents this problem...... based on atomic ensembles....

  2. Clocks around Sgr A*

    CERN Document Server

    Angélil, Raymond

    2014-01-01

    The S stars near the Galactic centre and any pulsars that may be on similar orbits, can be modelled in a unified way as clocks orbiting a black hole, and hence are potential probes of relativistic effects, including block-hole spin. The high eccentricities of many S stars mean that relativistic effects peak strongly around pericentre; for example, orbit precession is not a smooth effect but almost a kick at pericentre. We argue that concentration around pericentre will be an advantage when analysing redshift or pulse-arrival data to measure relativistic effects, because cumulative precession will be drowned out by Newtonian perturbations from other mass in the Galactic-centre region. Wavelet decomposition may be a way to disentangle relativistic effects from Newton perturbations. Assuming a plausible model for Newtonian perturbations on S2, relativity appears to be strongest in a two-year interval around pericentre, in wavelet modes of timescale approximately 6 months.

  3. Clock Genes in Glia Cells

    Science.gov (United States)

    Chi-Castañeda, Donají

    2016-01-01

    Circadian rhythms are periodic patterns in biological processes that allow the organisms to anticipate changes in the environment. These rhythms are driven by the suprachiasmatic nucleus (SCN), the master circadian clock in vertebrates. At a molecular level, circadian rhythms are regulated by the so-called clock genes, which oscillate in a periodic manner. The protein products of clock genes are transcription factors that control their own and other genes’ transcription, collectively known as “clock-controlled genes.” Several brain regions other than the SCN express circadian rhythms of clock genes, including the amygdala, the olfactory bulb, the retina, and the cerebellum. Glia cells in these structures are expected to participate in rhythmicity. However, only certain types of glia cells may be called “glial clocks,” since they express PER-based circadian oscillators, which depend of the SCN for their synchronization. This contribution summarizes the current information about clock genes in glia cells, their plausible role as oscillators and their medical implications. PMID:27666286

  4. Testing the Gravitational Redshift with Atomic Gravimeters?

    CERN Document Server

    Wolf, Peter; Bordé, Christian J; Reynaud, Serge; Salomon, Christophe; Cohen-Tannoudji, Claude

    2011-01-01

    Atom interferometers allow the measurement of the acceleration of freely falling atoms with respect to an experimental platform at rest on Earth's surface. Such experiments have been used to test the universality of free fall by comparing the acceleration of the atoms to that of a classical freely falling object. In a recent paper, M\\"uller, Peters and Chu [Nature {\\bf 463}, 926-929 (2010)] argued that atom interferometers also provide a very accurate test of the gravitational redshift (or universality of clock rates). Considering the atom as a clock operating at the Compton frequency associated with the rest mass, they claimed that the interferometer measures the gravitational redshift between the atom-clocks in the two paths of the interferometer at different values of gravitational potentials. In the present paper we analyze this claim in the frame of general relativity and of different alternative theories, and conclude that the interpretation of atom interferometers as testing the gravitational redshift ...

  5. Cooling of rubidium atoms in pulsed diffuse laser light

    Institute of Scientific and Technical Information of China (English)

    Cheng Hua-Dong; Wang Xu-Cheng; Xiao Ling; Zhang Wen-Zhuo; Liu Liang; Wang Yu-Zhu

    2011-01-01

    This paper reports an experiment on laser cooling of 87Rb atoms in pulsed diffuse light, which is the key step towards a compact cold atom clock. It deduces an empirical formula to simulate the pulse cooling process based on the loading of cold atoms in cooling time and the loss in the dead time, which is in agreement with the experimental data. The formula gives a reference to select the parameters for the cold atom clock.

  6. Improved Short-Term Clock Prediction Method for Real-Time Positioning

    Directory of Open Access Journals (Sweden)

    Yifei Lv

    2017-06-01

    Full Text Available The application of real-time precise point positioning (PPP requires real-time precise orbit and clock products that should be predicted within a short time to compensate for the communication delay or data gap. Unlike orbit correction, clock correction is difficult to model and predict. The widely used linear model hardly fits long periodic trends with a small data set and exhibits significant accuracy degradation in real-time prediction when a large data set is used. This study proposes a new prediction model for maintaining short-term satellite clocks to meet the high-precision requirements of real-time clocks and provide clock extrapolation without interrupting the real-time data stream. Fast Fourier transform (FFT is used to analyze the linear prediction residuals of real-time clocks. The periodic terms obtained through FFT are adopted in the sliding window prediction to achieve a significant improvement in short-term prediction accuracy. This study also analyzes and compares the accuracy of short-term forecasts (less than 3 h by using different length observations. Experimental results obtained from International GNSS Service (IGS final products and our own real-time clocks show that the 3-h prediction accuracy is better than 0.85 ns. The new model can replace IGS ultra-rapid products in the application of real-time PPP. It is also found that there is a positive correlation between the prediction accuracy and the short-term stability of on-board clocks. Compared with the accuracy of the traditional linear model, the accuracy of the static PPP using the new model of the 2-h prediction clock in N, E, and U directions is improved by about 50%. Furthermore, the static PPP accuracy of 2-h clock products is better than 0.1 m. When an interruption occurs in the real-time model, the accuracy of the kinematic PPP solution using 1-h clock prediction product is better than 0.2 m, without significant accuracy degradation. This model is of practical

  7. Simulating Future GPS Clock Scenarios with Two Composite Clock Algorithms

    Science.gov (United States)

    2010-11-01

    Alexandria, Virginia), pp. 223-242. [8] C. A. Greenhall, 2007, “A Kalman filter clock ensemble algorithm that admits measurement noise,” Metrologia ...43, S311-S321. [9] J. A. Davis, C. A. Greenhall, and P. W. Stacey, 2005, “A Kalman filter clock algorithm for use in the presence of flicker frequency modulation noise,” Metrologia , 42, 1-10.

  8. p-Wave cold collisions in a Yb lattice clock

    CERN Document Server

    Lemke, N D; von Stecher, J; Sherman, J A; Rey, A M; Oates, C W

    2011-01-01

    State-of-the-art optical clocks with neutral atoms employ an optical lattice to tightly confine the atoms, enabling high-resolution spectroscopy and the potential for high-accuracy timekeeping. Interrogating many atoms simultaneously facilitates high measurement precision, but also yields high atomic density and the potential for cold collisions. To suppress these atom-atom interactions, the use of ultracold, spin-polarized fermions was proposed to exploit the Fermi suppression of s-wave collisions while freezing out higher-wave contributions. However, small collision shifts have been measured in Sr and Yb. For Sr, the shifts were attributed to s-wave interactions enabled by excitation inhomogeneity. Here, we report definitive experimental evidence and a quantitative theoretical treatment of p-wave collisions in Yb. We also demonstrate a novel suppression of the collisional frequency shift utilizing strong interactions in a two-dimensional optical lattice. Understanding these interactions and dynamics for two...

  9. Circadian clock components in the rat neocortex

    DEFF Research Database (Denmark)

    Rath, Martin Fredensborg; Rohde, Kristian; Fahrenkrug, Jan

    2013-01-01

    The circadian master clock of the mammalian brain resides in the suprachiasmatic nucleus (SCN) of the hypothalamus. At the molecular level, the clock of the SCN is driven by a transcriptional/posttranslational autoregulatory network with clock gene products as core elements. Recent investigations...... have shown the presence of peripheral clocks in extra-hypothalamic areas of the central nervous system. However, knowledge on the clock gene network in the cerebral cortex is limited. We here show that the mammalian clock genes Per1, Per2, Per3, Cry1, Cry2, Bmal1, Clock, Nr1d1 and Dbp are expressed...

  10. On board aircrew dosimetry with a semiconductor spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Spurny, F.; Daschev, T

    2002-07-01

    Radiation fields on board aircraft contain particles with energies up to a few hundred MeV. Many instruments have been tested to characterise these fields. This paper presents the results of studies on the use of an Si diode spectrometer to characterise the on board field. During a Czech Airlines flight from Prague to New York it was possible to register the effects of an intense solar flare, (ground level even, GLE 60), which occurred on 15 April 2001. It was found that the number of deposition events registered was increased by about 70% and the dose in Si by a factor of 2.0 when compared with the presence of galactic cosmic rays alone. Directly measured data are interpreted with respect to on-earth reference field calibration (photons, CERN high-energy particles); it was found that this approach leads to encouraging results and should be followed up. (author00.

  11. Harmonic distortions measured on board of a maritime vessel

    Science.gov (United States)

    Zburlea, Elena; Dordea, Stefan

    2016-12-01

    Measurements where performed on four channels by means of an autonomous equipment (galvanic separated and not supplied from the ship's mains) performed on board of some maritime transport vessels, inside the Port of Constanţa aquatorium. Distorted voltages where state in the distribution panels. The sources of those distortions are the switching power supplies of the electric drives. The novelty of our work states in performing those measurements during the inside port maneuvers, when the operating time of each electric equipment is non definable. Harmonic distortions caused by the switching power converters lower the Power Factor. There is no better manner to find out the main distortions sources on board of a maritime transport vessel than to perform the measurements directly, on each location.

  12. ON BOARD OF SHIPS THERMAL ENERGY RECOVERY CONDITIONS

    Directory of Open Access Journals (Sweden)

    Beazit ALI

    2016-12-01

    Full Text Available In the paper are presented at first the energy recovery conditions used at the moment on board of ships and the restrictions which do not allow the achievement of higher recovery ratios. The authors suggest a new type of recovery plant by vaporization of water by means of expansion and they show its advantages in the considerably increase of energy recovery ratio from burnt gases from the cooling water of marine engine

  13. Virtualizing Super-Computation On-Board Uas

    Science.gov (United States)

    Salami, E.; Soler, J. A.; Cuadrado, R.; Barrado, C.; Pastor, E.

    2015-04-01

    Unmanned aerial systems (UAS, also known as UAV, RPAS or drones) have a great potential to support a wide variety of aerial remote sensing applications. Most UAS work by acquiring data using on-board sensors for later post-processing. Some require the data gathered to be downlinked to the ground in real-time. However, depending on the volume of data and the cost of the communications, this later option is not sustainable in the long term. This paper develops the concept of virtualizing super-computation on-board UAS, as a method to ease the operation by facilitating the downlink of high-level information products instead of raw data. Exploiting recent developments in miniaturized multi-core devices is the way to speed-up on-board computation. This hardware shall satisfy size, power and weight constraints. Several technologies are appearing with promising results for high performance computing on unmanned platforms, such as the 36 cores of the TILE-Gx36 by Tilera (now EZchip) or the 64 cores of the Epiphany-IV by Adapteva. The strategy for virtualizing super-computation on-board includes the benchmarking for hardware selection, the software architecture and the communications aware design. A parallelization strategy is given for the 36-core TILE-Gx36 for a UAS in a fire mission or in similar target-detection applications. The results are obtained for payload image processing algorithms and determine in real-time the data snapshot to gather and transfer to ground according to the needs of the mission, the processing time, and consumed watts.

  14. Who nominates the board? - Implications on board diversity and turnover

    OpenAIRE

    Viskari, Milla

    2014-01-01

    This thesis assesses whether the type of nomination poses implications on board diversity in terms of age, gender, nationality and education, as well as turnover on a Finnish and Swedish data. The existing research on director selection and especially nomination committees is rather limited, and thus the research aims at contributing to the topic. The reviewed time period concerns 2008 to 2012, and altogether 55 Finnish and 55 Swedish public companies are included in the study, thus resul...

  15. Einstein's Clocks and Langevin's Twins

    CERN Document Server

    Weinstein, Galina

    2012-01-01

    In 1905 Einstein presented the Clock Paradox and in 1911 Paul Langevin expanded Einstein's result to human observers, the "Twin Paradox." I will explain the crucial difference between Einstein and Langevin. Einstein did not present the so-called "Twin Paradox." Later Einstein continued to speak about the clock paradox. Einstein might not have been interested in the question: what happens to the observers themselves. The reason for this could be the following; Einstein dealt with measurement procedures, clocks and measuring rods. Einstein's observers were measuring time with these clocks and measuring rods. Einstein might not have been interested in so-called biology of the observers, whether these observers were getting older, younger, or whether they have gone any other changes; these changes appeared to be out of the scope of his "Principle of relativity" or kinematics. The processes and changes occurring within observers seemed to be good for philosophical discussions. Later writers criticized Einstein's c...

  16. A scheme for implementing quantum clock synchronization algorithm in cavity QED

    Institute of Scientific and Technical Information of China (English)

    Wu Qin-Qin; Kuang Le-Man

    2006-01-01

    In this paper, we propose a scheme for implementing the quantum clock synchronization (QCS) algorithm in cavity quantum electrodynamic (QED) formalism. Our method is based on three-level ladder-type atoms interacting with classical and quantized cavity fields. Atom-qubit realizations of three-qubit and four-qubit QCS algorithms are explicitly presented.

  17. Spin-orbit coupled fermions in an optical lattice clock

    CERN Document Server

    Kolkowitz, S; Bothwell, T; Wall, M L; Marti, G E; Koller, A P; Zhang, X; Rey, A M; Ye, J

    2016-01-01

    Engineered spin-orbit coupling (SOC) in cold atom systems can aid in the study of novel synthetic materials and complex condensed matter phenomena. Despite great advances, alkali atom SOC systems are hindered by heating from spontaneous emission, which limits the observation of many-body effects. Here we demonstrate the use of optical lattice clocks (OLCs) to engineer and study SOC with metrological precision and negligible heating. We show that clock spectroscopy of the ultra-narrow transition in fermionic 87Sr represents a momentum- and spin-resolved in situ probe of the SOC band structure and eigenstates, providing direct access to the SOC dynamics and control over lattice band populations, internal electronic states, and quasimomenta. We utilize these capabilities to study Bloch oscillations, spin-momentum locking, and van Hove singularities in the transition density of states. Our results lay the groundwork for the use of OLCs to probe novel SOC phases including magnetic crystals, helical liquids, and to...

  18. High accuracy correction of blackbody radiation shift in an optical lattice clock

    CERN Document Server

    Middelmann, Thomas; Lisdat, Christian; Sterr, Uwe

    2012-01-01

    We have determined the frequency shift that blackbody radiation is inducing on the $5s^2$ $^1$S$_0$ -- $5s5p$ $^3$P$_0$ clock transition in strontium. Previously its uncertainty limited the uncertainty of strontium lattice clocks to $1\\times10^{-16}$. Now the uncertainty associated to the black body radiation shift correction translates to $5\\times 10^{-18}$ relative frequency uncertainty at room temperature. Our evaluation is based on a measurement of the differential dc-polarizability of the two clock states and on a modeling of the dynamic contribution using this value and experimental data for other atomic properties.

  19. Simulation of the clock framework of Gaia

    CERN Document Server

    Castaneda, J; Portell, J; García-Berro, E; Luri, X; Castaneda, Javier; Gordo, Jose P.; Portell, Jordi; Garcia-Berro, Enrique; Luri, Xavier

    2005-01-01

    Gaia will perform astrometric measurements with an unprecedented resolution. Consequently, the electronics of the Astro instrument must time tag every measurement with a precision of a few nanoseconds. Hence, it requires a high stability clock signal, for which a Rb-type spacecraft master clock has been baselined. The distribution of its signal and the generation of clock subproducts must maintain these high accuracy requirements. We have developed a software application to simulate generic clock frameworks. The most critical clock structures for Gaia have also been identified, and its master clock has been parameterised.

  20. Molecular mechanisms underlying the Arabidopsis circadian clock.

    Science.gov (United States)

    Nakamichi, Norihito

    2011-10-01

    A wide range of biological processes exhibit circadian rhythm, enabling plants to adapt to the environmental day-night cycle. This rhythm is generated by the so-called 'circadian clock'. Although a number of genetic approaches have identified >25 clock-associated genes involved in the Arabidopsis clock mechanism, the molecular functions of a large part of these genes are not known. Recent comprehensive studies have revealed the molecular functions of several key clock-associated proteins. This progress has provided mechanistic insights into how key clock-associated proteins are integrated, and may help in understanding the essence of the clock's molecular mechanisms.

  1. 40 CFR 85.2207 - On-board diagnostics test standards.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 18 2010-07-01 2010-07-01 false On-board diagnostics test standards... Warranty Short Tests § 85.2207 On-board diagnostics test standards. (a) (b) A vehicle shall fail the on-board diagnostics test if it is a 1996 or newer vehicle and the vehicle connector is missing, has...

  2. 49 CFR 395.15 - Automatic on-board recording devices.

    Science.gov (United States)

    2010-10-01

    ... certifying that the design of the automatic on-board recorder has been sufficiently tested to meet the... 49 Transportation 5 2010-10-01 2010-10-01 false Automatic on-board recording devices. 395.15... OF SERVICE OF DRIVERS § 395.15 Automatic on-board recording devices. (a) Applicability and...

  3. Calibration strategies for the LAD instrument on-board LOFT

    CERN Document Server

    Pacciani, Luigi; Argan, Andrea; Barret, Didier; Bozzo, Enrico; Feroci, Marco; Fraser, George W; Herder, Jan-Willem den; Pohl, Martin; Schmid, Christian; Tenzer, Chris; Vacchi, Andrea; Walton, Dave; Zampa, Gianluigi; Zane, Silvia

    2012-01-01

    The Scientific objectives of the LOFT mission, e.g., the study of the Neutron Star equation of state and of the Strong Gravity, require accurate energy, time and flux calibration for the 500k channels of the SDD detectors, as well as the knowledge of the detector dead-time and of the detector response with respect to the incident angle of the photons. We report here the evaluations made to asses the calibration issues for the LAD instrument. The strategies for both ground and on-board calibrations, including astrophysical observations, show that the goals are achievable within the current technologies.

  4. On-board image compression for the RAE lunar mission

    Science.gov (United States)

    Miller, W. H.; Lynch, T. J.

    1976-01-01

    The requirements, design, implementation, and flight performance of an on-board image compression system for the lunar orbiting Radio Astronomy Explorer-2 (RAE-2) spacecraft are described. The image to be compressed is a panoramic camera view of the long radio astronomy antenna booms used for gravity-gradient stabilization of the spacecraft. A compression ratio of 32 to 1 is obtained by a combination of scan line skipping and adaptive run-length coding. The compressed imagery data are convolutionally encoded for error protection. This image compression system occupies about 1000 cu cm and consumes 0.4 W.

  5. Circadian clocks, epigenetics, and cancer

    KAUST Repository

    Masri, Selma

    2015-01-01

    The interplay between circadian rhythm and cancer has been suggested for more than a decade based on the observations that shift work and cancer incidence are linked. Accumulating evidence implicates the circadian clock in cancer survival and proliferation pathways. At the molecular level, multiple control mechanisms have been proposed to link circadian transcription and cell-cycle control to tumorigenesis.The circadian gating of the cell cycle and subsequent control of cell proliferation is an area of active investigation. Moreover, the circadian clock is a transcriptional system that is intricately regulated at the epigenetic level. Interestingly, the epigenetic landscape at the level of histone modifications, DNA methylation, and small regulatory RNAs are differentially controlled in cancer cells. This concept raises the possibility that epigenetic control is a common thread linking the clock with cancer, though little scientific evidence is known to date.This review focuses on the link between circadian clock and cancer, and speculates on the possible connections at the epigenetic level that could further link the circadian clock to tumor initiation or progression.

  6. Circadian clock proteins and immunity.

    Science.gov (United States)

    Curtis, Anne M; Bellet, Marina M; Sassone-Corsi, Paolo; O'Neill, Luke A J

    2014-02-20

    Immune parameters change with time of day and disruption of circadian rhythms has been linked to inflammatory pathologies. A circadian-clock-controlled immune system might allow an organism to anticipate daily changes in activity and feeding and the associated risk of infection or tissue damage to the host. Responses to bacteria have been shown to vary depending on time of infection, with mice being more at risk of sepsis when challenged ahead of their activity phase. Studies highlight the extent to which the molecular clock, most notably the core clock proteins BMAL1, CLOCK, and REV-ERBα, control fundamental aspects of the immune response. Examples include the BMAL1:CLOCK heterodimer regulating toll-like receptor 9 (TLR9) expression and repressing expression of the inflammatory monocyte chemokine ligand (CCL2) as well as REV-ERBα suppressing the induction of interleukin-6. Understanding the daily rhythm of the immune system could have implications for vaccinations and how we manage infectious and inflammatory diseases. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. Fast and Adaptive Lossless On-Board Hyperspectral Data Compression System for Space Applications

    Science.gov (United States)

    Aranki, Nazeeh; Bakhshi, Alireza; Keymeulen, Didier; Klimesh, Matthew

    2009-01-01

    Efficient on-board lossless hyperspectral data compression reduces the data volume necessary to meet NASA and DoD limited downlink capabilities. The techniques also improves signature extraction, object recognition and feature classification capabilities by providing exact reconstructed data on constrained downlink resources. At JPL a novel, adaptive and predictive technique for lossless compression of hyperspectral data was recently developed. This technique uses an adaptive filtering method and achieves a combination of low complexity and compression effectiveness that far exceeds state-of-the-art techniques currently in use. The JPL-developed 'Fast Lossless' algorithm requires no training data or other specific information about the nature of the spectral bands for a fixed instrument dynamic range. It is of low computational complexity and thus well-suited for implementation in hardware, which makes it practical for flight implementations of pushbroom instruments. A prototype of the compressor (and decompressor) of the algorithm is available in software, but this implementation may not meet speed and real-time requirements of some space applications. Hardware acceleration provides performance improvements of 10x-100x vs. the software implementation (about 1M samples/sec on a Pentium IV machine). This paper describes a hardware implementation of the JPL-developed 'Fast Lossless' compression algorithm on a Field Programmable Gate Array (FPGA). The FPGA implementation targets the current state of the art FPGAs (Xilinx Virtex IV and V families) and compresses one sample every clock cycle to provide a fast and practical real-time solution for Space applications.

  8. Metabolic regulation of circadian clocks.

    Science.gov (United States)

    Haydon, Michael J; Hearn, Timothy J; Bell, Laura J; Hannah, Matthew A; Webb, Alex A R

    2013-05-01

    Circadian clocks are 24-h timekeeping mechanisms, which have evolved in plants, animals, fungi and bacteria to anticipate changes in light and temperature associated with the rotation of the Earth. The current paradigm to explain how biological clocks provide timing information is based on multiple interlocking transcription-translation negative feedback loops (TTFL), which drive rhythmic gene expression and circadian behaviour of growth and physiology. Metabolism is an important circadian output, which in plants includes photosynthesis, starch metabolism, nutrient assimilation and redox homeostasis. There is increasing evidence in a range of organisms that these metabolic outputs can also contribute to circadian timing and might also comprise independent circadian oscillators. In this review, we summarise the mechanisms of circadian regulation of metabolism by TTFL and consider increasing evidence that rhythmic metabolism contributes to the circadian network. We highlight how this might be relevant to plant circadian clock function.

  9. Types for X10 Clocks

    Directory of Open Access Journals (Sweden)

    Francisco Martins

    2011-10-01

    Full Text Available X10 is a modern language built from the ground up to handle future parallel systems, from multicore machines to cluster configurations. We take a closer look at a pair of synchronisation mechanisms: finish and clocks. The former waits for the termination of parallel computations, the latter allow multiple concurrent activities to wait for each other at certain points in time. In order to better understand these concepts we study a type system for a stripped down version of X10. The main result assures that well typed programs do not run into the errors identified in the X10 language reference, namely the ClockUseException. The study will open, we hope, doors to a more flexible utilisation of clocks in the X10 language.

  10. Synchronous clock stopper for microprocessor

    Science.gov (United States)

    Kitchin, David A. (Inventor)

    1985-01-01

    A synchronous clock stopper circuit for inhibiting clock pulses to a microprocessor in response to a stop request signal, and for reinstating the clock pulses in response to a start request signal thereby to conserve power consumption of the microprocessor when used in an environment of limited power. The stopping and starting of the microprocessor is synchronized, by a phase tracker, with the occurrences of a predetermined phase in the instruction cycle of the microprocessor in which the I/O data and address lines of the microprocessor are of high impedance so that a shared memory connected to the I/O lines may be accessed by other peripheral devices. The starting and stopping occur when the microprocessor initiates and completes, respectively, an instruction, as well as before and after transferring data with a memory. Also, the phase tracker transmits phase information signals over a bus to other peripheral devices which signals identify the current operational phase of the microprocessor.

  11. On-board aircrew dosimetry using a semiconductor spectrometer

    CERN Document Server

    Spurny, F

    2002-01-01

    Radiation fields on board aircraft contain particles with energies up to a few hundred MeV. Many instruments have been tested to characterise these fields. This paper presents the results of studies on the use of an Si diode spectrometer to characterise these fields. The spectrometer has been in use since spring 2000 on more than 130 return flights to monitor and characterise the on-board field. During a Czech Airlines flight from Prague to New York it was possible to register the effects of an intense solar flare, (ground level event, GLE 60), which occurred on 15 April 2001. It was found that the number of deposition events registered was increased by about 70% and the dose in Si by a factor of 2.0 when compared with the presence of galactic cosmic rays alone. Directly measured data are interpreted with respect to on-earth reference field calibration (photons, CERN high-energy particles); it was found that this approach leads to encouraging results and should be followed up. (7 refs).

  12. Hard X-ray Detector (HXD) on Board Suzaku

    CERN Document Server

    Takahashi, T; Endo, M; Endo, Y; Ezoe, Y; Fukazawa, Y; Hamaya, M; Hirakuri, S; Hong, S; Horii, M; Inoue, H; Isobe, N; Itoh, T; Iyomoto, N; Kamae, T; Kasama, D; Kataoka, J; Kato, H; Kawaharada, M; Kawano, N; Kawashima, K; Kawasoe, S; Kishishita, T; Kitaguchi, T; Kobayashi, Y; Kokubun, M; Kotoku, J; Kouda, M; Kubota, A; Kuroda, Y; Madejski, G; Makishima, K; Masukawa, K; Matsumoto, Y; Mitani, T; Miyawaki, R; Mizuno, T; Mori, K; Mori, M; Murashima, M; Murakami, T; Nakazawa, K; Niko, H; Nomachi, M; Okada, Y; Ohno, M; Oonuki, K; Ota, N; Ozawa, H; Sato, G; Shinoda, S; Sugiho, M; Suzuki, M; Taguchi, K; Takahashi, H; Takahashi, I; Takeda, S; Tamura, K; Tamura, T; Tanaka, T; Tanihata, C; Tashiro, M; Terada, Y; Tominaga, S; Uchiyama, Y; Watanabe, S; Yamaoka, K; Yanagida, T; Yonetoku, D

    2006-01-01

    The Hard X-ray Detector (HXD) on board Suzaku covers a wide energy range from 10 keV to 600 keV by combination of silicon PIN diodes and GSO scintillators. The HXD is designed to achieve an extremely low in-orbit back ground based on a combination of new techniques, including the concept of well-type active shield counter. With an effective area of 142 cm^2 at 20 keV and 273 cm2 at 150 keV, the background level at the sea level reached ~1x10^{-5} cts s^{-1} cm^{-2} keV^{-1} at 30 keV for the PI N diodes, and ~2x10^{-5} cts s^{-1} cm^{-2} keV^{-1} at 100 keV, and ~7x10^{-6} cts s^{-1} cm^{-2} keV^{-1} at 200 keV for the phoswich counter. Tight active shielding of the HXD results in a large array of guard counters surrounding the main detector parts. These anti-coincidence counters, made of ~4 cm thick BGO crystals, have a large effective area for sub-MeV to MeV gamma-rays. They work as an excellent gamma-ray burst monitor with limited angular resolution (~5 degree). The on-board signal-processing system and th...

  13. Digital signal processing techniques for on-board processing satellites

    Science.gov (United States)

    Kwan, Ching Chung

    1990-08-01

    In on-board processing satellite systems in which frequency division multiple access (FDMA)/signal channel per carrier (SCPC) access schemes are employed, transmultiplexers are required for the frequency demultiplexing of the SCPC signals. Digital techniques for the implementation of the transmultiplexer for such application were examined. The signal processing in the transmultiplexer operations involved many parameters which could be optimized in order to reduce the hardware complexity while satisfying the level of performance required of the system. An approach for the assessment of the relationship between the various parameters and the system performance was devised, which allowed hardware requirement of practical system specifications to be estimated. For systems involving signals of different bandwidths, a more flexible implementation of the transmultiplexer is required and two computationally efficient methods, the DFT convolution and analysis/synthesis filter bank, were investigated. These methods gave greater flexibility to the input frequency plan of the transmultiplexer, at the expense of increased computational requirements. Filters were then designed to exploit specific properties of the flexible transmultiplexer methods, resulting in considerable improvement in their efficiencies. Hardware implementation of the flexible transmultiplexer was considered and an efficient multiprocesser architecture in combination with parallel processing software algorithms for the signal processing operations were designed. Finally, an experimental model of the payload for a land-mobile satellite system proposal, T-SAT, was constructed using general-purpose digital signal processors and the merits of the on-board processing architecture were demonstrated.

  14. On-Orbit Performance of MODIS On-Board Calibrators

    Science.gov (United States)

    Xiong, X.; Che, N.; Chiang, K.; Esposito, J.; Barnes, William; Guenther, B.; Zukor, Dorothy J. (Technical Monitor)

    2001-01-01

    The Terra MODIS (Moderate Resolution Imaging Spectroradiometer) was launched on December 18, 1999 and acquired the first scene data on February 24, 2000. It has 36 spectral bands covering spectral range from 0.41 to 14.2 microns and provides spatial resolutions of 250 (2 bands), 500 (5 bands), and 1000 m at Nadir. The instrument on-orbit calibration and characterization are determined and monitored through the use of a number of on-board calibrators (OBC). Radiometric calibration for the reflective solar bands (B1-B19, B26), from VIS (visible) to SWIR (short wavelength infrared) (0.41 to 2.1 microns), uses a Spectralon (tm) solar diffuser (SD) and a solar diffuser stability monitor (SDSM). For the thermal emissive bands (B20-B25, B27-B36), from MWIR (medium wavelength infrared) to LWIR (long wavelength infrared) (3.75 to 14.2 micron), a V-grooved flat panel blackbody is used. The instrument spectral for the VIS to SWIR bands and spatial co-registration characterizations for all bands are monitored on-orbit by the spectral radiometric calibration assembly (SRCA). In this report, we discuss the application and performance of the key MODIS on-board calibrators and their impacts on the instrument system calibration and characterization.

  15. The SXI telescope on board EXIST: scientific performances

    CERN Document Server

    Natalucci, L; Campana, S; Caraveo, P; Della Ceca, R; Grindlay, J E; Panessa, F; Pareschi, G; Ramsey, B; Tagliaferri, G; Ubertini, P; Villa, G

    2009-01-01

    The SXI telescope is one of the three instruments on board EXIST, a multiwavelength observatory in charge of performing a global survey of the sky in hard X-rays searching for Supermassive Black Holes. One of the primary objectives of EXIST is also to study with unprecedented sensitivity the most unknown high energy sources in the Universe, like high redshift GRBs, which will be pointed promptly by the Spacecraft by autonomous trigger based on hard X-ray localization on board. The recent addition of a soft X-ray telescope to the EXIST payload complement, with an effective area of ~950 cm2 in the energy band 0.2-3 keV and extended response up to 10 keV will allow to make broadband studies from 0.1 to 600 keV. In particular, investigations of the spectra components and states of AGNs and monitoring of variability of sources, study of the prompt and afterglow emission of GRBs since the early phases, which will help to constrain the emission models and finally, help the identification of sources in the EXIST hard...

  16. The Soft X-ray Imager on board EXIST

    CERN Document Server

    Natalucci, L; Panessa, F; Ubertini, P; Tagliaferri, G; Della Ceca, R; Ghisellini, G; Pareschi, G; Villa, G; Caraveo, P; Fiorini, M; Uslenghi, M; Grindlay, J E; Ramsey, B

    2010-01-01

    The Soft X-ray Imager (SXI) is one of the three instruments on board EXIST, a multi-wavelength observatory in charge of performing a global survey of the sky in hard X-rays searching for Super-massive Black Holes (Grindlay & Natalucci, these Proceedings). One of the primary objectives of EXIST is also to study with unprecedented sensitivity the most unknown high energy sources in the Universe, like high redshift GRBs, which will be pointed promptly by the Spacecraft by autonomous trigger based on hard X-ray localization on board. The presence of a soft X-ray telescope with an effective area of about 950cm2 in the energy band 0.2-3 keV and extended response up to 10 keV will allow to make broadband studies from 0.1 to 600 keV. In particular, investigations of the spectra components and states of AGNs and monitoring of variability of sources, study of the prompt and afterglow emission of GRBs since the early phases, which will help to constrain the emission models and finally, help the identification of sou...

  17. Modeling and Simulation Reliable Spacecraft On-Board Computing

    Science.gov (United States)

    Park, Nohpill

    1999-01-01

    The proposed project will investigate modeling and simulation-driven testing and fault tolerance schemes for Spacecraft On-Board Computing, thereby achieving reliable spacecraft telecommunication. A spacecraft communication system has inherent capabilities of providing multipoint and broadcast transmission, connectivity between any two distant nodes within a wide-area coverage, quick network configuration /reconfiguration, rapid allocation of space segment capacity, and distance-insensitive cost. To realize the capabilities above mentioned, both the size and cost of the ground-station terminals have to be reduced by using reliable, high-throughput, fast and cost-effective on-board computing system which has been known to be a critical contributor to the overall performance of space mission deployment. Controlled vulnerability of mission data (measured in sensitivity), improved performance (measured in throughput and delay) and fault tolerance (measured in reliability) are some of the most important features of these systems. The system should be thoroughly tested and diagnosed before employing a fault tolerance into the system. Testing and fault tolerance strategies should be driven by accurate performance models (i.e. throughput, delay, reliability and sensitivity) to find an optimal solution in terms of reliability and cost. The modeling and simulation tools will be integrated with a system architecture module, a testing module and a module for fault tolerance all of which interacting through a centered graphical user interface.

  18. Mercury Atomic Frequency Standards for Space Based Navigation and Timekeeping

    Science.gov (United States)

    Tjoelker, R. L.; Burt, E. A.; Chung, S.; Hamell, R. L.; Prestage, J. D.; Tucker, B.; Cash, P.; Lutwak, R.

    2012-01-01

    A low power Mercury Atomic Frequency Standard (MAFS) has been developed and demonstrated on the path towards future space clock applications. A self contained mercury ion breadboard clock: emulating flight clock interfaces, steering a USO local oscillator, and consuming approx 40 Watts has been operating at JPL for more than a year. This complete, modular ion clock instrument demonstrates that key GNSS size, weight, and power (SWaP) requirements can be achieved while still maintaining short and long term performance demonstrated in previous ground ion clocks. The MAFS breadboard serves as a flexible platform for optimizing further space clock development and guides engineering model design trades towards fabrication of an ion clock for space flight.

  19. Mercury Atomic Frequency Standards for Space Based Navigation and Timekeeping

    Science.gov (United States)

    Tjoelker, R. L.; Burt, E. A.; Chung, S.; Hamell, R. L.; Prestage, J. D.; Tucker, B.; Cash, P.; Lutwak, R.

    2012-01-01

    A low power Mercury Atomic Frequency Standard (MAFS) has been developed and demonstrated on the path towards future space clock applications. A self contained mercury ion breadboard clock: emulating flight clock interfaces, steering a USO local oscillator, and consuming approx 40 Watts has been operating at JPL for more than a year. This complete, modular ion clock instrument demonstrates that key GNSS size, weight, and power (SWaP) requirements can be achieved while still maintaining short and long term performance demonstrated in previous ground ion clocks. The MAFS breadboard serves as a flexible platform for optimizing further space clock development and guides engineering model design trades towards fabrication of an ion clock for space flight.

  20. A circadian clock in Saccharomyces cerevisiae

    NARCIS (Netherlands)

    Eelderink-Chen, Zheng; Mazzotta, Gabriella; Sturre, Marcel; Bosman, Jasper; Roenneberg, Till; Merrow, Martha

    2010-01-01

    Circadian timing is a fundamental biological process, underlying cellular physiology in animals, plants, fungi, and cyanobacteria. Circadian clocks organize gene expression, metabolism, and behavior such that they occur at specific times of day. The biological clocks that orchestrate these daily

  1. The NIST 27 Al+ quantum-logic clock

    Science.gov (United States)

    Leibrandt, David; Brewer, Samuel; Chen, Jwo-Sy; Hume, David; Hankin, Aaron; Huang, Yao; Chou, Chin-Wen; Rosenband, Till; Wineland, David

    2016-05-01

    Optical atomic clocks based on quantum-logic spectroscopy of the 1 S0 3 P0 transition in 27 Al+ have reached a systematic fractional frequency uncertainty of 8 . 0 ×10-18 , enabling table-top tests of fundamental physics as well as measurements of gravitational potential differences. Currently, the largest limitations to the accuracy are second order time dilation shifts due to the driven motion (i.e., micromotion) and thermal motion of the trapped ions. In order to suppress these shifts, we have designed and built new ion traps based on gold-plated, laser-machined diamond wafers with differential RF drive, and we have operated one of our clocks with the ions laser cooled to near the six mode motional ground state. We present a characterization of the time dilation shifts in the new traps with uncertainties near 1 ×10-18 . Furthermore, we describe a new protocol for clock comparison measurements based on synchronous probing of the two clocks using phase-locked local oscillators, which allows for probe times longer than the laser coherence time and avoids the Dick effect. This work is supported by ARO, DARPA, and ONR.

  2. Single-transistor-clocked flip-flop

    Science.gov (United States)

    Zhao, Peiyi; Darwish, Tarek; Bayoumi, Magdy

    2005-08-30

    The invention provides a low power, high performance flip-flop. The flip-flop uses only one clocked transistor. The single clocked transistor is shared by the first and second branches of the device. A pulse generator produces a clock pulse to trigger the flip-flop. In one preferred embodiment the device can be made as a static explicit pulsed flip-flop which employs only two clocked transistors.

  3. BMAL1 and CLOCK, two essential components of the circadian clock, are involved in glucose homeostasis.

    Directory of Open Access Journals (Sweden)

    R Daniel Rudic

    2004-11-01

    Full Text Available Circadian timing is generated through a unique series of autoregulatory interactions termed the molecular clock. Behavioral rhythms subject to the molecular clock are well characterized. We demonstrate a role for Bmal1 and Clock in the regulation of glucose homeostasis. Inactivation of the known clock components Bmal1 (Mop3 and Clock suppress the diurnal variation in glucose and triglycerides. Gluconeogenesis is abolished by deletion of Bmal1 and is depressed in Clock mutants, but the counterregulatory response of corticosterone and glucagon to insulin-induced hypoglycaemia is retained. Furthermore, a high-fat diet modulates carbohydrate metabolism by amplifying circadian variation in glucose tolerance and insulin sensitivity, and mutation of Clock restores the chow-fed phenotype. Bmal1 and Clock, genes that function in the core molecular clock, exert profound control over recovery from insulin-induced hypoglycaemia. Furthermore, asynchronous dietary cues may modify glucose homeostasis via their interactions with peripheral molecular clocks.

  4. Light and the human circadian clock

    NARCIS (Netherlands)

    Roenneberg, Till; Kantermann, Thomas; Juda, Myriam; Vetter, Céline; Allebrandt, Karla V

    2013-01-01

    The circadian clock can only reliably fulfil its function if it is stably entrained. Most clocks use the light-dark cycle as environmental signal (zeitgeber) for this active synchronisation. How we think about clock function and entrainment has been strongly influenced by the early concepts of the

  5. Light and the human circadian clock

    NARCIS (Netherlands)

    Roenneberg, Till; Kantermann, Thomas; Juda, Myriam; Vetter, Céline; Allebrandt, Karla V

    2013-01-01

    The circadian clock can only reliably fulfil its function if it is stably entrained. Most clocks use the light-dark cycle as environmental signal (zeitgeber) for this active synchronisation. How we think about clock function and entrainment has been strongly influenced by the early concepts of the f

  6. Synthetic dimensions and spin-orbit coupling with an optical clock transition

    CERN Document Server

    Livi, L F; Diem, M; Franchi, L; Clivati, C; Frittelli, M; Levi, F; Calonico, D; Catani, J; Inguscio, M; Fallani, L

    2016-01-01

    We demonstrate a novel way of synthesizing spin-orbit interactions in ultracold quantum gases, based on a single-photon optical clock transition coupling two long-lived electronic states of two-electron $^{173}$Yb atoms. By mapping the electronic states onto effective sites along a synthetic "electronic" dimension, we have engineered synthetic fermionic ladders with tunable magnetic fluxes. We have detected the spin-orbit coupling with fiber-link-enhanced clock spectroscopy and directly measured the emergence of chiral edge currents, probing them as a function of the magnetic field flux. These results open new directions for the investigation of topological states of matter with ultracold atomic gases.

  7. Cryogenic optical lattice clocks with a relative frequency difference of $1\\times 10^{-18}$

    CERN Document Server

    Ushijima, Ichiro; Das, Manoj; Ohkubo, Takuya; Katori, Hidetoshi

    2014-01-01

    Time and frequency are the most accurately measurable quantities, providing foundations for science and modern technologies. The accuracy relies on the SI (Syst\\'eme International) second that refers to Cs microwave clocks with fractional uncertainties at $10^{-16}$. Recent revolutionary progress of optical clocks aims to achieve $1\\times 10^{-18}$ uncertainty, which however has been hindered by long averaging-times or by systematic uncertainties. Here, we demonstrate optical lattice clocks with $^{87}$Sr atoms interrogated in a cryogenic environment to address the blackbody radiation-induced frequency-shift, which remains the primary source of clocks' uncertainties and has initiated vigorous theoretical and experimental investigations. The quantum-limited stability for $N \\sim 1,000$ atoms allows investigation of the uncertainties at $2\\times 10^{-18}$ in two hours of clock operation. After 11 measurements performed over a month, the two cryo-clocks agree to within $(-1.1\\pm 1.6)\\times 10^{-18}$. Besides its...

  8. Biological clocks: riding the tides.

    Science.gov (United States)

    de la Iglesia, Horacio O; Johnson, Carl Hirschie

    2013-10-21

    Animals with habitats in the intertidal zone often display biological rhythms that coordinate with both the tidal and the daily environmental cycles. Two recent studies show that the molecular components of the biological clocks mediating tidal rhythms are likely different from the phylogenetically conserved components that mediate circadian (daily) rhythms.

  9. A generalized gravitomagnetic clock effect

    CERN Document Server

    Hackmann, Eva

    2014-01-01

    In General Relativity the rotation of a gravitating body like the Earth influences the motion of orbiting test particles or satellites in a non-Newtonian way. This causes e.g. a precession of the orbital plane, known as the Lense-Thirring effect, and a precession of the spin of a gyroscope, known as the Schiff effect. Here we discuss a third effect, first introduced by Cohen and Mashhoon, called the gravitomagnetic clock effect. It describes the difference in proper time of counter revolving clocks after a revolution of $2\\pi$. For two clocks on counter rotating equatorial circular orbits around the Earth the effect is about $10^{-7}$ seconds per revolution, which is quite large. We introduce a general relativistic definition of the gravitomagnetic clock effect which is valid for arbitrary pairs of orbits. This includes rotations in the same direction and different initial conditions, which is crucial if the effect can be detected with existing satellites or with payloads on non-dedicated missions. We also de...

  10. Status of UHECR detector KLYPVE on-board the ISS

    Science.gov (United States)

    Klimov, Pavel; Garipov, Gali; Khrenov, Boris; Yashin, Ivan; Panasyuk, Mikhail; Tkachev, Leonid; Sharakin, Sergey; Zotov, Mikhail; Churilo, Igor; Markov, Alexander

    A preliminary project of the KLYPVE detector of ultra high energy cosmic rays (UHECR) on board the International Space Station (ISS) was developed in Lomonosov Moscow State University Skobeltsyn Institute of Nuclear Physics in cooperation with RSC “Energia”. The main scientific aims of the mission are measurements of the primary particles energy spectrum, their arrival directions and a search for large and small scale anisotropy (including point sources) in the energy region above the Greisen-Zatsepin-Kuzmin cut-off. Various types of optical systems, photo detectors, mechanical structures and multiple issues related to transportation and accommodation on the Russian Segment of the ISS were considered. Recent development of KLYPVE is made in close cooperation with the JEM-EUSO collaboration in order to improve the detector parameters such as field of view, angular and energy resolution, energy threshold. Current status of the project is presented in the report.

  11. TSP-Based Generic Payload On-Board Software

    Science.gov (United States)

    Arberet, P.; Metge, J.-J.; Gras, O.; Crespo, A.

    2009-05-01

    The paper address the contect and rationale for deciding to develop a TSP-based solution for payload on-board software, highly generic and reusable, project named LVCUGEN. Then it describes the key design issues and the associated architectual achievements obtained at the end of development phase of LVCUGEN. It provides some inputs on the way to instantiate the developed framework in the scope of deployment of the solution on a target-project. Last, the paper presents the status of the project and the forthcoming activities, also open issues, still to be performed. Some perspectives are provided in particular the selection of the first space program targeted for deployment of the solution.

  12. Novel satellite transport protocol with on-board spoofing proxy

    Institute of Scientific and Technical Information of China (English)

    Liu Jiong; Cao Zhigang; Wang Jinglin

    2006-01-01

    As a result of the exponential growing rate of worldwide Internet usage, satellite systems are required to support broadband Internet applications. The transmission control protocol (TCP) which is widely used in the Internet, performs very well on wired networks. However, in the case of satellite channels, due to the delay and transmission errors, TCP performance degrades significantly and bandwidth of satellite links can not be fully utilized. To improve the TCP performance, a new idea of placing a TCP spoofing proxy in the satellite is considered. A Novel Satellite Transport Protocol (NSTP) which takes advantage of the special properties of the satellite channel is also proposed. By using simulation, as compared with traditional TCPs, the on-board spoofing proxy integrated with the special transport protocol can significantly enhance throughput performance on the high BER satellite link, the time needed to transfer files and the bandwidth used in reverse path are sharply reduced.

  13. DAMPE silicon tracker on-board data compression algorithm

    CERN Document Server

    Dong, Yifan; Qiao, Rui; Peng, Wenxi; Fan, Ruirui; Gong, Ke; Wu, Di; Wang, Huanyu

    2015-01-01

    The Dark Matter Particle Explorer (DAMPE) is an upcoming scientific satellite mission for high energy gamma-ray, electron and cosmic rays detection. The silicon tracker (STK) is a sub detector of the DAMPE payload with an excellent position resolution (readout pitch of 242um), which measures the incident direction of particles, as well as charge. The STK consists 12 layers of Silicon Micro-strip Detector (SMD), equivalent to a total silicon area of 6.5m$^2$. The total readout channels of the STK are 73728, which leads to a huge amount of raw data to be dealt. In this paper, we focus on the on-board data compression algorithm and procedure in the STK, which was initially verified by cosmic-ray measurements.

  14. Why so few Women on Boards of Directors?

    DEFF Research Database (Denmark)

    Smith, Nina; Parrotta, Pierpaolo

    2015-01-01

    hypotheses on female board representation that we denote the female-led hypothesis, the tokenism hypothesis, and the pipeline hypothesis, respectively. We find evidence rejecting the female-led hypothesis. Firms with a female chairperson on the board of directors tend to have significantly fewer other...... nonemployee-elected female board members. We also find clear evidence of a tokenism behavior in Danish companies. The likelihood of enlarging the share of non-employee-elected female board members is significantly smaller if one, two, or more women have sat on the board of directors. Finally, the pipeline......This paper analyzes the determinants of women’s representation on boards of directors based on a panel of all privately owned or listed Danish firms with at least 50 employees observed during the period 1998–2010. We focus on the directors who are not elected by the employees and test three...

  15. Cosmic Rays Induced Background Radiation on Board of Commercial Flights

    CERN Document Server

    Pinilla, S; Núñez, L A

    2015-01-01

    The aim of this work is to determine the total integrated flux of cosmic radiation which a commercial aircraft is exposed to along specific flight trajectories. To study the radiation background during a flight and its modulation by effects such as altitude, latitude, exposure time and transient magnetospheric events, we perform simulations based on Magnetocosmics and CORSIKA codes, the former designed to calculate the geomagnetic effects on cosmic rays propagation and the latter allows us to simulate the development of extended air showers in the atmosphere. In this first work, by considering the total flux of cosmic rays from 5 GeV to 1 PeV, we obtained the expected integrated flux of secondary particles on board of a commercial airplane during the Bogot\\'a-Buenos Aires trip by point-to-point numerical integration.

  16. Neutral atmosphere composition from SOIR measurements on board Venus Express

    Science.gov (United States)

    Mahieux, A.; Drummond, R.; Wilquet, V.; Vandaele, A. C.; Federova, A.; Belyaev, D.; Korablev, O.; Villard, E.; Montmessin, F.; Bertaux, J.-L.

    2009-04-01

    The SOIR instrument performs solar occultation measurements in the IR region (2.2 - 4.3 m) at a resolution of 0.12 cm-1, the highest on board Venus Express. It combines an echelle spectrometer and an AOTF (Acousto-Optical Tunable Filter) for the order selection [1,2]. The wavelength range probed by SOIR allows a detailed chemical inventory of the Venus atmosphere above the cloud layer with an emphasis on vertical distribution of the gases. Measurements of HDO, H2O, HCl, HF, CO and CO2 vertical profiles have been routinely performed, as well as those of their isotopologues [3,4]. We will discuss the improvements introduced in the analysis algorithm of the SOIR spectra. This discussion will be illustrated by presenting new results of retrievals of minor constituents of the Venus mesosphere, in terms of vertical profiles and geographical distribution. CO2 is the major constituent of the Venus atmosphere and was therefore observed in many solar occultations, leading to a good geographical coverage, although limited by the geometry of the orbit. Depending on the abundance of the absorbing isotopologue and on the intensity of the band measured, we will show that the SOIR instrument is able to furnish CO2 vertical profiles ranging typically from 65 to 150 km, reaching in some conditions 185 km altitude. This information is important in the frame of compiling, in collaboration with other teams, a new Venus Atmosphere Model. 1. A. Mahieux, S. Berkenbosch, R. Clairquin, D. Fussen, N. Mateshvili, E. Neefs, D. Nevejans, B. Ristic, A. C. Vandaele, V. Wilquet, D. Belyaev, A. Fedorova, O. Korablev, E. Villard, F. Montmessin and J.-L. Bertaux, "In-Flight performance and calibration of SPICAV SOIR on board Venus Express", Applied Optics 47 (13), 2252-65 (2008). 2. D. Nevejans, E. Neefs, E. Van Ransbeeck, S. Berkenbosch, R. Clairquin, L. De Vos, W. Moelans, S. Glorieux, A. Baeke, O. Korablev, I. Vinogradov, Y. Kalinnikov, B. Bach, J.-P. Dubois and E. Villard, "Compact high

  17. Advanced on-board electric vehicle charger. Final report

    Energy Technology Data Exchange (ETDEWEB)

    None

    1979-12-31

    The design and development of an on-board charger power module for use in electric vehicles is described. The module operates at 20KHz in a series resonant, half bridge configuration. Circuit design trade-offs, module performance, and solutions to the problems of acoustic noise, maintaining high power factor, circuit protection and operating reliability are discussed. The power module operates from a single phase, 240 V, 50/60 Hz utility line. Average power factor is 0.90; efficiency at maximum power output is 86%. The module is rated to charge a bank consisting of 20 Exide EV-106 batteries (60 cells) to an end voltage of 2.42 V/cell. Physically, the module weighs less than 17 Kg. Projected manufacturing cost at the thousand unit level is $394.00 (1978 dollars).

  18. Challenge of lightning detection with LAC on board Akatsuki spacecraft

    Science.gov (United States)

    Takahashi, Yukihiro; Sato, Mitsutero; Imai, Masataka; Yair, Yoav; Fischer, Georg; Aplin, Karen

    2016-04-01

    Even after extensive investigations with spacecraft and ground-based observations, there is still no consensus on the existence of lightning in Venus. It has been reported that the magnetometer on board Venus Express detected whistler mode waves whose source could be lightning discharge occurring well below the spacecraft. On the other hand, with an infrared sensor, VIRTIS of Venus Express, does not show the positive indication of lightning flashes. In order to identify the optical flashes caused by electrical discharge in the atmosphere of Venus, at least, with an optical intensity of 1/10 of the average lightning in the Earth, we built a high-speed optical detector, LAC (Lightning and Airglow Camera), on board Akatsuki spacecraft. The unique performance of the LAC compared to other instruments is the high-speed sampling rate at 32 us interval for all 32 pixels, enabling us to distinguish the optical lightning flash from other pulsing noises. Though, unfortunately, the first attempt of the insertion of Akatsuki into the orbit around Venus failed in December 2010, the second one carried out in December 7 in 2015 was quite successful. We checked out the condition of the LAC on January 5, 2016, and it is healthy as in 2010. Due to some elongated orbit than that planned originally, we have umbra for ~30 min to observe the lightning flash in the night side of Venus every ~10 days, starting on April 2016. Here we would report the instrumental status of LAC and the preliminary results of the first attempt to observe optical lightning emissions.

  19. MicroCameras and Photometers (MCP) on board TARANIS satellite

    Science.gov (United States)

    Farges, Thomas; Blanc, Elisabeth; Hébert, Philippe; Le Mer-Dachard, Fanny; Ravel, Karen; Gaillac, Stéphanie

    2017-04-01

    TARANIS (Tool for the Analysis of Radiations from lightNings and Sprites) is a CNES micro satellite. Its main objective is to study impulsive transfers of energy between the Earth atmosphere and the space environment. It will be sun-synchronous at an altitude of 700 km. It will be launched from end-2018 for at least 2 years. Its payload is composed of several electromagnetic instruments in different wavelengths (from gamma-rays to radio waves including optical). TARANIS instruments are currently in calibration and qualification phase. The purpose of this poster is to present the MicroCameras and Photometers (MCP) scientific objectives and the sensor design, to show the performances of this instrument using the recent characterization, and at last to promote its products. The MicroCameras, developed by Sodern, are dedicated to the spatial description of TLEs and their parent lightning. They are able to differentiate sprite and lightning thanks to two narrow bands ([757-767 nm] and [772-782 nm]) that provide simultaneous pairs of images of an Event. Simulation results of the differentiation method will be shown. After calibration and tests, the MicroCameras are now delivered to CNES for integration on the payload. The Photometers, developed by Bertin Technologies, will provide temporal measurements and spectral characteristics of TLEs and lightning. There are key instrument because of their capability to detect on-board TLEs and then switch all the instruments of the scientific payload in their high resolution acquisition mode. Photometers use four spectral bands in the [170-260 nm], [332-342 nm], [757-767 nm] and [600-900 nm] and have the same field of view as cameras. The on-board TLE detection algorithm remote-controlled parameters have been tuned before launch using the electronic board and simulated or real events waveforms. The Photometers are now in the calibration and test phase. They will be delivered for integration in mid-2017.

  20. Corporate sponsored education initiatives on board the ISS

    Science.gov (United States)

    Durham, Ian T.; Durham, Alyson S.; Pawelczyk, James A.; Brod, Lawrence B.; Durham, Thomas F.

    1999-01-01

    This paper proposes the creation of a corporate sponsored ``Lecture from Space'' program on board the International Space Station (ISS) with funding coming from a host of new technology and marketing spin-offs. This program would meld existing education initiatives in NASA with new corporate marketing techniques. Astronauts in residence on board the ISS would conduct short ten to fifteen minute live presentations and/or conduct interactive discussions carried out by a teacher in the classroom. This concept is similar to a program already carried out during the Neurolab mission on Shuttle flight STS-90. Building on that concept, the interactive simulcasts would be broadcast over the Internet and linked directly to computers and televisions in classrooms worldwide. In addition to the live broadcasts, educational programs and demonstrations can be recorded in space, and marketed and sold for inclusion in television programs, computer software, and other forms of media. Programs can be distributed directly into classrooms as an additional presentation supplement, as well as over the Internet or through cable and broadcast television, similar to the Canadian Discovery Channel's broadcasts of the Neurolab mission. Successful marketing and advertisement can eventually lead to the creation of an entirely new, privately run cottage industry involving the distribution and sale of educationally related material associated with the ISS that would have the potential to become truly global in scope. By targeting areas of expertise and research interest in microgravity, a large curriculum could be developed using space exploration as a unifying theme. Expansion of this concept could enhance objectives already initiated through the International Space University to include elementary and secondary school students. The ultimate goal would be to stimulate interest in space and space related sciences in today's youth through creative educational marketing initiatives while at the

  1. Unraveling the circadian clock in Arabidopsis.

    Science.gov (United States)

    Wang, Xiaoxue; Ma, Ligeng

    2013-02-01

    The circadian clock is an endogenous timing system responsible for coordinating an organism's biological processes with its environment. Interlocked transcriptional feedback loops constitute the fundamental architecture of the circadian clock. In Arabidopsis, three feedback loops, the core loop, morning loop and evening loop, comprise a network that is the basis of the circadian clock. The components of these three loops are regulated in distinct ways, including transcriptional, post-transcriptional and posttranslational mechanisms. The discovery of the DNA-binding and repressive activities of TOC1 has overturned our initial concept of its function in the circadian clock. The alternative splicing of circadian clock-related genes plays an essential role in normal functioning of the clock and enables organisms to sense environmental changes. In this review, we describe the regulatory mechanisms of the circadian clock that have been identified in Arabidopsis.

  2. Circadian clock, cell cycle and cancer

    Directory of Open Access Journals (Sweden)

    Cansu Özbayer

    2011-12-01

    Full Text Available There are a few rhythms of our daily lives that we are under the influence. One of them is characterized by predictable changes over a 24-hour timescale called circadian clock. This cellular clock is coordinated by the suprachiasmatic nucleus in the anterior hypothalamus. The clock consist of an autoregulatory transcription-translation feedback loop compose of four genes/proteins; BMAL1, Clock, Cyrptochrome, and Period. BMAL 1 and Clock are transcriptional factors and Period and Cyrptochrome are their targets. Period and Cyrptochrome dimerize in the cytoplasm to enter the nucleus where they inhibit Clock/BMAL activity.It has been demonstrate that circadian clock plays an important role cellular proliferation, DNA damage and repair mechanisms, checkpoints, apoptosis and cancer.

  3. Atom gravimeters and gravitational redshift

    CERN Document Server

    Wolf, Peter; Borde, Christian J; Reynaud, Serge; Salomon, Christophe; Cohen-Tannoudji, Claude; 10.1038/nature09340

    2010-01-01

    In a recent paper, H. Mueller, A. Peters and S. Chu [A precision measurement of the gravitational redshift by the interference of matter waves, Nature 463, 926-929 (2010)] argued that atom interferometry experiments published a decade ago did in fact measure the gravitational redshift on the quantum clock operating at the very high Compton frequency associated with the rest mass of the Caesium atom. In the present Communication we show that this interpretation is incorrect.

  4. Ultra-stable clock laser system development towards space applications

    Science.gov (United States)

    Świerad, Dariusz; Häfner, Sebastian; Vogt, Stefan; Venon, Bertrand; Holleville, David; Bize, Sébastien; Kulosa, André; Bode, Sebastian; Singh, Yeshpal; Bongs, Kai; Rasel, Ernst Maria; Lodewyck, Jérôme; Le Targat, Rodolphe; Lisdat, Christian; Sterr, Uwe

    2016-09-01

    The increasing performance of optical lattice clocks has made them attractive for scientific applications in space and thus has pushed the development of their components including the interrogation lasers of the clock transitions towards being suitable for space, which amongst others requires making them more power efficient, radiation hardened, smaller, lighter as well as more mechanically stable. Here we present the development towards a space-compatible interrogation laser system for a strontium lattice clock constructed within the Space Optical Clock (SOC2) project where we have concentrated on mechanical rigidity and size. The laser reaches a fractional frequency instability of 7.9 × 10-16 at 300 ms averaging time. The laser system uses a single extended cavity diode laser that gives enough power for interrogating the atoms, frequency comparison by a frequency comb and diagnostics. It includes fibre link stabilisation to the atomic package and to the comb. The optics module containing the laser has dimensions 60 × 45 × 8 cm3 and the ultra-stable reference cavity used for frequency stabilisation with its vacuum system takes 30 × 30 × 30 cm3. The acceleration sensitivities in three orthogonal directions of the cavity are 3.6 × 10-10/g, 5.8 × 10-10/g and 3.1 × 10-10/g, where g ≈ 9.8 m/s2 is the standard gravitational acceleration.

  5. GPS/GLONASS Combined Precise Point Positioning with Receiver Clock Modeling.

    Science.gov (United States)

    Wang, Fuhong; Chen, Xinghan; Guo, Fei

    2015-06-30

    Research has demonstrated that receiver clock modeling can reduce the correlation coefficients among the parameters of receiver clock bias, station height and zenith tropospheric delay. This paper introduces the receiver clock modeling to GPS/GLONASS combined precise point positioning (PPP), aiming to better separate the receiver clock bias and station coordinates and therefore improve positioning accuracy. Firstly, the basic mathematic models including the GPS/GLONASS observation equations, stochastic model, and receiver clock model are briefly introduced. Then datasets from several IGS stations equipped with high-stability atomic clocks are used for kinematic PPP tests. To investigate the performance of PPP, including the positioning accuracy and convergence time, a week of (1-7 January 2014) GPS/GLONASS data retrieved from these IGS stations are processed with different schemes. The results indicate that the positioning accuracy as well as convergence time can benefit from the receiver clock modeling. This is particularly pronounced for the vertical component. Statistic RMSs show that the average improvement of three-dimensional positioning accuracy reaches up to 30%-40%. Sometimes, it even reaches over 60% for specific stations. Compared to the GPS-only PPP, solutions of the GPS/GLONASS combined PPP are much better no matter if the receiver clock offsets are modeled or not, indicating that the positioning accuracy and reliability are significantly improved with the additional GLONASS satellites in the case of insufficient number of GPS satellites or poor geometry conditions. In addition to the receiver clock modeling, the impacts of different inter-system timing bias (ISB) models are investigated. For the case of a sufficient number of satellites with fairly good geometry, the PPP performances are not seriously affected by the ISB model due to the low correlation between the ISB and the other parameters. However, the refinement of ISB model weakens the

  6. Improved frequency measurement of the $^1S_{0}$-$^3P_{0}$ clock transition in $^{87}$Sr using the Cs fountain clock at NMIJ as a transfer oscillator

    CERN Document Server

    Tanabe, Takehiko; Kobayashi, Takumi; Takamizawa, Akifumi; Yanagimachi, Shinya; Ikegami, Takeshi; Suzuyama, Tomonari; Inaba, Hajime; Okubo, Sho; Yasuda, Masami; Hong, Feng-Lei; Onae, Atsushi; Hosaka, Kazumoto

    2015-01-01

    We performed an absolute frequency measurement of the $^1S_{0}$-$^3P_{0}$ transition in $^{87}$Sr with a fractional uncertainty of $1.2 \\times 10^{-15}$, which is less than one third that of our previous measurement. A caesium fountain atomic clock was used as a transfer oscillator to reduce the uncertainty of the link between a strontium optical lattice clock and the SI second. The absolute value of the transition frequency is 429 228 004 229 873.56(49) Hz.

  7. Magnetic-dipole transitions in highly charged ions as a basis of ultraprecise optical clocks.

    Science.gov (United States)

    Yudin, V I; Taichenachev, A V; Derevianko, A

    2014-12-05

    We evaluate the feasibility of using magnetic-dipole (M1) transitions in highly charged ions as a basis of an optical atomic clockwork of exceptional accuracy. We consider a range of possibilities, including M1 transitions between clock levels of the same fine-structure and hyperfine-structure manifolds. In highly charged ions these transitions lie in the optical part of the spectra and can be probed with lasers. The most direct advantage of our proposal comes from the low degeneracy of clock levels and the simplicity of atomic structure in combination with negligible quadrupolar shift. We demonstrate that such clocks can have projected fractional accuracies below the 10^{-20}-10^{-21} level for all common systematic effects, such as blackbody radiation, Zeeman, ac-Stark, and quadrupolar shifts.

  8. Entanglement of quantum clocks through gravity.

    Science.gov (United States)

    Castro Ruiz, Esteban; Giacomini, Flaminia; Brukner, Časlav

    2017-03-21

    In general relativity, the picture of space-time assigns an ideal clock to each world line. Being ideal, gravitational effects due to these clocks are ignored and the flow of time according to one clock is not affected by the presence of clocks along nearby world lines. However, if time is defined operationally, as a pointer position of a physical clock that obeys the principles of general relativity and quantum mechanics, such a picture is, at most, a convenient fiction. Specifically, we show that the general relativistic mass-energy equivalence implies gravitational interaction between the clocks, whereas the quantum mechanical superposition of energy eigenstates leads to a nonfixed metric background. Based only on the assumption that both principles hold in this situation, we show that the clocks necessarily get entangled through time dilation effect, which eventually leads to a loss of coherence of a single clock. Hence, the time as measured by a single clock is not well defined. However, the general relativistic notion of time is recovered in the classical limit of clocks.

  9. Physical Layer Ethernet Clock Synchronization

    Science.gov (United States)

    2010-11-01

    42 nd Annual Precise Time and Time Interval (PTTI) Meeting 77 PHYSICAL LAYER ETHERNET CLOCK SYNCHRONIZATION Reinhard Exel , Georg...5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES...Austrian Academy of Sciences Viktor Kaplan StraÃe 2, A-2700 Wiener Neustadt, Austria 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING

  10. Inertial Frames and Clock Rates

    CERN Document Server

    Kak, Subhash

    2012-01-01

    This article revisits the historiography of the problem of inertial frames. Specifically, the case of the twins in the clock paradox is considered to see that some resolutions implicitly assume inertiality for the non-accelerating twin. If inertial frames are explicitly identified by motion with respect to the large scale structure of the universe, it makes it possible to consider the relative inertiality of different frames.

  11. Researchers Discover Plants Biological Clock

    Institute of Scientific and Technical Information of China (English)

    王全良

    1996-01-01

    Scientists who created glow-in-the-dark plants by shooting up seedlingswith firefly DNA have identified the first biological clock gene in plants. Discovery of the timepiece gene, which controls such biological rhythmsas daily leaf movements and proe openings, flower-blooming schedules andphotosynthesis cycles, could lead to a host of applications in ornamental horti-culture, agriculture and even human health. Many researchers believe that

  12. Microresonator Frequency Comb Optical Clock

    Science.gov (United States)

    2014-07-22

    Number Microresonator frequency comb optical clock Block 13: Supplementary Note © 2014 . Published in Optica , Vol. Ed. 0 1, (1) (2014), (, (1). DoD...Oscillators. http://dx.doi.org/10.1364/ OPTICA .1.000010 1. INTRODUCTION Optical frequency combs enable extraordinary measurement precision and accuracy...1, No. 1 / July 2014 / Optica 10 deviation for 1 s averaging is completely dominated by the Rb reference, and the microcomb contribution is only ɚ

  13. Cellular circadian clocks in mood disorders.

    Science.gov (United States)

    McCarthy, Michael J; Welsh, David K

    2012-10-01

    Bipolar disorder (BD) and major depressive disorder (MDD) are heritable neuropsychiatric disorders associated with disrupted circadian rhythms. The hypothesis that circadian clock dysfunction plays a causal role in these disorders has endured for decades but has been difficult to test and remains controversial. In the meantime, the discovery of clock genes and cellular clocks has revolutionized our understanding of circadian timing. Cellular circadian clocks are located in the suprachiasmatic nucleus (SCN), the brain's primary circadian pacemaker, but also throughout the brain and peripheral tissues. In BD and MDD patients, defects have been found in SCN-dependent rhythms of body temperature and melatonin release. However, these are imperfect and indirect indicators of SCN function. Moreover, the SCN may not be particularly relevant to mood regulation, whereas the lateral habenula, ventral tegmentum, and hippocampus, which also contain cellular clocks, have established roles in this regard. Dysfunction in these non-SCN clocks could contribute directly to the pathophysiology of BD/MDD. We hypothesize that circadian clock dysfunction in non-SCN clocks is a trait marker of mood disorders, encoded by pathological genetic variants. Because network features of the SCN render it uniquely resistant to perturbation, previous studies of SCN outputs in mood disorders patients may have failed to detect genetic defects affecting non-SCN clocks, which include not only mood-regulating neurons in the brain but also peripheral cells accessible in human subjects. Therefore, reporters of rhythmic clock gene expression in cells from patients or mouse models could provide a direct assay of the molecular gears of the clock, in cellular clocks that are likely to be more representative than the SCN of mood-regulating neurons in patients. This approach, informed by the new insights and tools of modern chronobiology, will allow a more definitive test of the role of cellular circadian clocks

  14. On-Board Visual Tracking with Unmanned Aircraft System (UAS)

    CERN Document Server

    Qadir, Ashraf; Semke, William

    2012-01-01

    This paper presents the development of a real time tracking algorithm that runs on a 1.2 GHz PC/104 computer on-board a small UAV. The algorithm uses zero mean normalized cross correlation to detect and locate an object in the image. A kalman filter is used to make the tracking algorithm computationally efficient. Object position in an image frame is predicted using the motion model and a search window, centered at the predicted position is generated. Object position is updated with the measurement from object detection. The detected position is sent to the motion controller to move the gimbal so that the object stays at the center of the image frame. Detection and tracking is autonomously carried out on the payload computer and the system is able to work in two different methods. The first method starts detecting and tracking using a stored image patch. The second method allows the operator on the ground to select the interest object for the UAV to track. The system is capable of re-detecting an object, in t...

  15. Women on boards of directors and corporate philanthropic disaster response

    Institute of Scientific and Technical Information of China (English)

    Ming Jia; Zhe Zhang

    2012-01-01

    In this study we conduct firm-level analysis of the impact of women in the boardroom on corporate philanthropic disaster response(CPDR).We propose that CPDR contains agency costs and that female directors are more likely to restrain the associated agency costs of CPDR.We predict a negative relationship between the ratio of women on boards of directors(WoBs) and philanthropic contribution,which is weaker in firms with political connections and stronger in firms with better-developed institutional environments.Data was collected from the philanthropic responses to the Wenchuan earthquake on May 12,2008 of privately-owned listed Chinese firms.The results support the hypothesized negative relationship,which is found to be weaker in firms with political connections.However,marketization-related factors do not significantly moderate this relationship.These results indicate that CPDR contains agency costs and that female directors do not facilitate the corporate donation process,but rather evaluate the benefits and restrain the associated agency costs.

  16. Medical emergencies on board commercial airlines: is documentation as expected?

    Science.gov (United States)

    Sand, Michael; Morrosch, Stephan; Sand, Daniel; Altmeyer, Peter; Bechara, Falk G

    2012-12-12

    The purpose of this study was to perform a descriptive, content-based analysis on the different forms of documentation for in-flight medical emergencies that are currently provided in the emergency medical kits on board commercial airlines. Passenger airlines in the World Airline Directory were contacted between March and May 2011. For each participating airline, sample in-flight medical emergency documentation forms were obtained. All items in the sample documentation forms were subjected to a descriptive analysis and compared to a sample "medical incident report" form published by the International Air Transport Association (IATA). A total of 1,318 airlines were contacted. Ten airlines agreed to participate in the study and provided a copy of their documentation forms. A descriptive analysis revealed a total of 199 different items, which were summarized into five sub-categories: non-medical data (63), signs and symptoms (68), diagnosis (26), treatment (22) and outcome (20). The data in this study illustrate a large variation in the documentation of in-flight medical emergencies by different airlines. A higher degree of standardization is preferable to increase the data quality in epidemiologic aeromedical research in the future.

  17. On-board neural processor design for intelligent multisensor microspacecraft

    Science.gov (United States)

    Fang, Wai-Chi; Sheu, Bing J.; Wall, James

    1996-03-01

    A compact VLSI neural processor based on the Optimization Cellular Neural Network (OCNN) has been under development to provide a wide range of support for an intelligent remote sensing microspacecraft which requires both high bandwidth communication and high- performance computing for on-board data analysis, thematic data reduction, synergy of multiple types of sensors, and other advanced smart-sensor functions. The OCNN is developed with emphasis on its capability to find global optimal solutions by using a hardware annealing method. The hardware annealing function is embedded in the network. It is a parallel version of fast mean-field annealing in analog networks, and is highly efficient in finding globally optimal solutions for cellular neural networks. The OCNN is designed to perform programmable functions for fine-grained processing with annealing control to enhance the output quality. The OCNN architecture is a programmable multi-dimensional array of neurons which are locally connected with their local neurons. Major design features of the OCNN neural processor includes massively parallel neural processing, hardware annealing capability, winner-take-all mechanism, digitally programmable synaptic weights, and multisensor parallel interface. A compact current-mode VLSI design feasibility of the OCNN neural processor is demonstrated by a prototype 5 X 5-neuroprocessor array chip in a 2-micrometers CMOS technology. The OCNN operation theory, architecture, design and implementation, prototype chip, and system applications have been investigated in detail and presented in this paper.

  18. The ALTCRISS project on board the International Space Station

    CERN Document Server

    Casolino, M; Minori, M; Picozza, P; Fuglesang, C; Galper, A; Popov, A; Benghin, V; Petrov, V M; Nagamatsu, A; Berger, T; Reitz, G; Durante, M; Pugliese, M; Roca, V; Cucinotta, L Sihver F; Semones, E; Shavers, M; Guarnieri, V; Lobascio, C; Castagnolo, D; Fortezza, R

    2007-01-01

    The Altcriss project aims to perform a long term survey of the radiation environment on board the International Space Station. Measurements are being performed with active and passive devices in different locations and orientations of the Russian segment of the station. The goal is to perform a detailed evaluation of the differences in particle fluence and nuclear composition due to different shielding material and attitude of the station. The Sileye-3/Alteino detector is used to identify nuclei up to Iron in the energy range above 60 MeV/n. Several passive dosimeters (TLDs, CR39) are also placed in the same location of Sileye-3 detector. Polyethylene shielding is periodically interposed in front of the detectors to evaluate the effectiveness of shielding on the nuclear component of the cosmic radiation. The project was submitted to ESA in reply to the AO in the Life and Physical Science of 2004 and data taking began in December 2005. Dosimeters and data cards are rotated every six months: up to now three lau...

  19. An atomic clockwork using phase dependent energy shifts

    CERN Document Server

    De Munshi, D; Mukherjee, M

    2011-01-01

    A frequency stabilized laser referenced to an unperturbed atomic two level system acts as the most accurate clock with femtosecond clock ticks. For any meaningful use, a Femtosecond Laser Frequency Comb (FLFC) is used to transfer the atomic clock accuracy to electronically countable nanosecond clock ticks. Here we propose an alternative clockwork based on the phenomenon that when an atomic system is slowly evolved in a cyclic path, the atomic energy levels gather some phase called the geometric phase. This geometric phase dependent energy shift has been used here to couple the two frequency regimes in a phase coherent manner. It has also been shown that such a technique can be implemented experimentally, bypassing the highly involved setup of a FLFC.

  20. A quantum many-body spin system in an optical lattice clock

    CERN Document Server

    Martin, M J; Swallows, M D; Zhang, X; Benko, C; von-Stecher, J; Gorshkov, A V; Rey, A M; Ye, Jun

    2013-01-01

    Strongly interacting quantum many-body systems are fundamentally compelling and ubiquitous in science. However, their complexity generally prevents exact solutions of their dynamics. Precisely engineered ultracold atomic gases are emerging as a powerful tool to unravel these challenging physical problems. Here we present a new laboratory for the study of many-body effects: strongly interacting two-level systems formed by the clock states in ${}^{87}$Sr, which are used to realize a neutral atom optical clock that performs at the highest level of optical-atomic coherence and with precision near the limit set by quantum fluctuations. Our measurements of the collective spin evolution reveal signatures of many-body dynamics, including beyond-mean-field effects. We derive a many-body Hamiltonian that describes the experimental observation of severely distorted lineshapes, atomic spin coherence decay, density-dependent frequency shifts, and correlated quantum spin noise. These investigations open the door to explori...

  1. Comparing a mercury optical lattice clock with microwave and optical frequency standards

    CERN Document Server

    Tyumenev, R; Bilicki, S; Bookjans, E; Targat, R Le; Lodewyck, J; Nicolodi, D; Coq, Y Le; Abgrall, M; Guéna, J; De Sarlo, L; Bize, S

    2016-01-01

    In this paper we report the evaluation of an optical lattice clock based on neutral mercury down to a relative uncertainty of $1.7\\times 10^{-16}$. Comparing this characterized frequency standard to a Cs atomic fountain we determine the absolute frequency of the $^1S_0 \\rightarrow \\phantom{}^3P_0$ transition of $^{199}$Hg as $\

  2. The Implementation of E1 Clock Recovery

    Directory of Open Access Journals (Sweden)

    Wang Ziyu

    2016-01-01

    Full Text Available Clock transform and recovery is of significant importance in microwave TDM service, and it is always extracted from the E1 line data stream in most cases. However, intrinsically uncertain delay and jitter caused by packet transmission of E1 data information, may lead to the indexes of the data recovery clock exceed the clock performance template. Through analysis of the E1 clock indexes and measuring methods, this paper proposes a new clock recovery method. The method employs two buffers, the first RAM is used as a buffer to deduct excess information, and the second FIFO is used as a buffer to recovery the clock and data. The first buffer has a feedback from the second one, and is able to actively respond to changes in the data link and requests from the second one. The test results validate the effectiveness of the method, and the corresponding scheme is also valuable for the other communication systems.

  3. The circadian clock coordinates ribosome biogenesis.

    Directory of Open Access Journals (Sweden)

    Céline Jouffe

    Full Text Available Biological rhythms play a fundamental role in the physiology and behavior of most living organisms. Rhythmic circadian expression of clock-controlled genes is orchestrated by a molecular clock that relies on interconnected negative feedback loops of transcription regulators. Here we show that the circadian clock exerts its function also through the regulation of mRNA translation. Namely, the circadian clock influences the temporal translation of a subset of mRNAs involved in ribosome biogenesis by controlling the transcription of translation initiation factors as well as the clock-dependent rhythmic activation of signaling pathways involved in their regulation. Moreover, the circadian oscillator directly regulates the transcription of ribosomal protein mRNAs and ribosomal RNAs. Thus the circadian clock exerts a major role in coordinating transcription and translation steps underlying ribosome biogenesis.

  4. Optical to microwave clock frequency ratios with a nearly continuous strontium optical lattice clock

    CERN Document Server

    Lodewyck, Jérôme; Bookjans, Eva; Robyr, Jean-Luc; Shi, Chunyan; Vallet, Grégoire; Targat, Rodolphe Le; Nicolodi, Daniele; Coq, Yann Le; Guéna, Jocelyne; Abgrall, Michel; Rosenbusch, Peter; Bize, Sébastien

    2016-01-01

    Optical lattice clocks are at the forefront of frequency metrology. Both the instability and systematic uncertainty of these clocks have been reported to be two orders of magnitude smaller than the best microwave clocks. For this reason, a redefinition of the SI second based on optical clocks seems possible in the near future. However, the operation of optical lattice clocks has not yet reached the reliability that microwave clocks have achieved so far. In this paper, we report on the operation of a strontium optical lattice clock that spans several weeks, with more than 80% uptime. We make use of this long integration time to demonstrate a reproducible measurement of frequency ratios between the strontium clock transition and microwave Cs primary and Rb secondary frequency standards.

  5. First results from the RAPID imaging energetic particle spectrometer on board Cluster

    Directory of Open Access Journals (Sweden)

    B. Wilken

    Full Text Available The advanced energetic particle spectrometer RAPID on board Cluster can provide a complete description of the relevant particle parameters velocity, V , and atomic mass, A, over an energy range from 30 keV up to 1.5 MeV. We present the first measurements taken by RAPID during the commissioning and the early operating phases. The orbit on 14 January 2001, when Cluster was travelling from a perigee near dawn northward across the pole towards an apogee in the solar wind, is used to demonstrate the capabilities of RAPID in investigating a wide variety of particle populations. RAPID, with its unique capability of measuring the complete angular distribution of energetic particles, allows for the simultaneous measurements of local density gradients, as reflected in the anisotropies of 90° particles and the remote sensing of changes in the distant field line topology, as manifested in the variations of loss cone properties. A detailed discussion of angle-angle plots shows considerable differences in the structure of the boundaries between the open and closed field lines on the nightside fraction of the pass and the magnetopause crossing. The 3 March 2001 encounter of Cluster with an FTE just outside the magnetosphere is used to show the first structural plasma investigations of an FTE by energetic multi-spacecraft observations.

    Key words. Magnetospheric physics (energetic particles, trapped; magnetopause, cusp and boundary layers; magnetosheath

  6. Molecular Mechanisms Underlying the Arabidopsis Circadian Clock

    OpenAIRE

    Nakamichi, Norihito

    2011-01-01

    A wide range of biological processes exhibit circadian rhythm, enabling plants to adapt to the environmental day–night cycle. This rhythm is generated by the so-called ‘circadian clock’. Although a number of genetic approaches have identified >25 clock-associated genes involved in the Arabidopsis clock mechanism, the molecular functions of a large part of these genes are not known. Recent comprehensive studies have revealed the molecular functions of several key clock-associated proteins. Thi...

  7. The Square Light Clock and Special Relativity

    Science.gov (United States)

    Galli, J. Ronald; Amiri, Farhang

    2012-01-01

    A thought experiment that includes a square light clock is similar to the traditional vertical light beam and mirror clock, except it is made up of four mirrors placed at a 45[degree] angle at each corner of a square of length L[subscript 0], shown in Fig. 1. Here we have shown the events as measured in the rest frame of the square light clock. By…

  8. A Mathematical Model of the Liver Circadian Clock Linking Feeding and Fasting Cycles to Clock Function

    OpenAIRE

    Aurore Woller; Hélène Duez; Bart Staels; Marc Lefranc

    2016-01-01

    To maintain energy homeostasis despite variable energy supply and consumption along the diurnal cycle, the liver relies on a circadian clock synchronized to food timing. Perturbed feeding and fasting cycles have been associated with clock disruption and metabolic diseases; however, the mechanisms are unclear. To address this question, we have constructed a mathematical model of the mammalian circadian clock, incorporating the metabolic sensors SIRT1 and AMPK. The clock response to various tem...

  9. Probing Many-Body Interactions in an Optical Lattice Clock (Preprint)

    Science.gov (United States)

    2013-10-23

    9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine energy levels of a caesium atom. Since then, the accuracy...as meter, volt and ampere. Thanks to the development of laser trapping and cooling techniques [1, 2], the best caesium standards have reached an...accuracy of one part in 1016. However, caesium clocks are limited by the fact that they are based on atomic transitions in the microwave domain. Because

  10. Superradiance on the mHz linewidth clock transition in 87Sr

    Science.gov (United States)

    Norcia, Matthew; Winchester, Matthew; Cline, Julia; Thompson, James

    2016-05-01

    In this talk, I will discuss our recent experimental explorations of superradiant emission from the mHz linewidth clock transition in an ensemble of cold 87 Sr atoms confined within a high-finesse optical cavity. Recent proposals suggest that superradiant lasers based on such dipole-forbidden transitions in alkaline earth atoms could achieve linewidths below the current state of the art, with reduced sensitivity to environmental perturbations.

  11. Laser Cooling of Lanthanides: from Optical Clocks to Quantum Simulators

    Directory of Open Access Journals (Sweden)

    Golovizin A.

    2015-01-01

    Full Text Available We discuss current progress in laser cooling of lanthanides (Er, Yb, Dy, Tm etc. focusing on applications. We describe some important peculiarities taking Thulium atom as an example: Two stage laser cooling, trapping in an optical lattice, anisotropic interactions and spectroscopy of narrow transitions. Specific level structure and presence of magic wavelengths make ultracold Thulium a favorable candidate for optical clock applications. On the other hand, abundance of Feshbach resonances allow to tune interactions in ultracold gases and thus reach quantum degeneracy. It opens intriguing perspectives for novel quantum simulators employing dipole-dipole interactions in an optical lattice.

  12. Song I-Yeong's Armillary Clock

    Science.gov (United States)

    Kim, Sang Hyuk; Lee, Yong Sam

    In 1669 (the 10th year of the reign of King Hyeonjong), Song I-Yeong (宋以穎, 1619-1692), who was a professor of astronomy at Gwansanggam (Bureau of Astronomy), developed the armillary clock which uses the weight power system of an alarm clock. The armillary clock is a unique astronomical clock that combines the traditional armillary sphere of Joseon and the principle of a Western alarm clock. Song I-Yeong's armillary clock was repaired in 1687-1688 according to the records, and since then not much is known about the history of the armillary clock. After many years, in the early 1930s which was the Japanese colonial era, Inchon (仁村) Kim Seong-Su (金性洙, 1891-1955) purchased the armillary clock at the Insa-dong antique street and donated to the Korea University Museum of the present time (designated as National Treasure No. 230 in 1985). Currently, the armillary clock is not in operation because some of the parts are damaged or lost.

  13. Clock genes, pancreatic function, and diabetes.

    Science.gov (United States)

    Vieira, Elaine; Burris, Thomas P; Quesada, Ivan

    2014-12-01

    Circadian physiology is responsible for the temporal regulation of metabolism to optimize energy homeostasis throughout the day. Disturbances in the light/dark cycle, sleep/wake schedule, or feeding/activity behavior can affect the circadian function of the clocks located in the brain and peripheral tissues. These alterations have been associated with impaired glucose tolerance and type 2 diabetes. Animal models with molecular manipulation of clock genes and genetic studies in humans also support these links. It has been demonstrated that the endocrine pancreas has an intrinsic self-sustained clock, and recent studies have revealed an important role of clock genes in pancreatic β cells, glucose homeostasis, and diabetes.

  14. Experimenting an optical second with strontium lattice clocks

    CERN Document Server

    Targat, R Le; Coq, Y Le; Zawada, M; Guéna, J; Abgrall, M; Gurov, M; Rosenbusch, P; Rovera, D G; Nagórny, B; Gartman, R; Westergaard, P G; Tobar, M E; Lours, M; Santarelli, G; Clairon, A; Bize, S; Laurent, P; Lemonde, P; Lodewyck, J

    2013-01-01

    Progress in realizing the SI second had multiple technological impacts and enabled to further constraint theoretical models in fundamental physics. Caesium microwave fountains, realizing best the second according to its current definition with a relative uncertainty of 2-4x10^(-16), have already been superseded by atomic clocks referenced to an optical transition, both more stable and more accurate. Are we ready for a new definition of the second? Here we present an important step in this direction: our system of five clocks connects with an unprecedented consistency the optical and the microwave worlds. For the first time, two state-of-the-art strontium optical lattice clocks are proven to agree within their accuracy budget, with a total uncertainty of 1.6x10^(-16). Their comparison with three independent caesium fountains shows a degree of reproducibility henceforth solely limited at the level of 3.1x10^(-16) by the best realizations of the microwave-defined second.

  15. Tomographic reconstruction of storm time RC ion distribution from ENA images on board multiple spacecraft

    Science.gov (United States)

    Ma, Shu-Ying; Yan, Wei-Nan; Xu, Liang

    2015-11-01

    A quantitative retrieval of 3-D distribution of energetic ions as energetic neutral atoms (ENA) sources is a challenging task. In this paper the voxel computerized tomography (CT) method is initially applied to reconstruct the 3-D distribution of energetic ions in the magnetospheric ring current (RC) region from ENA emission images on board multiple spacecraft. To weaken the influence of low-altitude emission (LAE) on the reconstruction, the LAE-associated ENA intensities are corrected by invoking the thick-target approximation. To overcome the divergence in iteration due to discordant instrument biases, a differential ENA voxel CT method is developed. The method is proved reliable and advantageous by numerical simulation for the case of constant bias independent of viewing angle. Then this method is implemented with ENA data measured by the Two Wide-angle Imaging Neutral-atom Spectrometers mission which performs stereoscopic ENA imaging. The 3-D spatial distributions and energy spectra of RC ion flux intensity are reconstructed for energies of 4-50 keV during the main phase of a major magnetic storm. The retrieved ion flux distributions seem to correspond to an asymmetric partial RC, located mainly around midnight favoring the postmidnight with L = 3.5-7.0 in the equatorial plane. The RC ion distributions with magnetic local time depend on energy, with major equatorial flux peak for lower energy located east of that for higher energy. In comparison with the ion energy spectra measured by Time History of Events and Macroscale Interactions during Substorms-D satellite flying in the RC region, the retrieved spectrum from remotely sensed ENA images are well matched with the in situ measurements.

  16. Test of Special Relativity Using a Fiber Network of Optical Clocks.

    Science.gov (United States)

    Delva, P; Lodewyck, J; Bilicki, S; Bookjans, E; Vallet, G; Le Targat, R; Pottie, P-E; Guerlin, C; Meynadier, F; Le Poncin-Lafitte, C; Lopez, O; Amy-Klein, A; Lee, W-K; Quintin, N; Lisdat, C; Al-Masoudi, A; Dörscher, S; Grebing, C; Grosche, G; Kuhl, A; Raupach, S; Sterr, U; Hill, I R; Hobson, R; Bowden, W; Kronjäger, J; Marra, G; Rolland, A; Baynes, F N; Margolis, H S; Gill, P

    2017-06-02

    Phase compensated optical fiber links enable high accuracy atomic clocks separated by thousands of kilometers to be compared with unprecedented statistical resolution. By searching for a daily variation of the frequency difference between four strontium optical lattice clocks in different locations throughout Europe connected by such links, we improve upon previous tests of time dilation predicted by special relativity. We obtain a constraint on the Robertson-Mansouri-Sexl parameter |α|≲1.1×10^{-8}, quantifying a violation of time dilation, thus improving by a factor of around 2 the best known constraint obtained with Ives-Stilwell type experiments, and by 2 orders of magnitude the best constraint obtained by comparing atomic clocks. This work is the first of a new generation of tests of fundamental physics using optical clocks and fiber links. As clocks improve, and as fiber links are routinely operated, we expect that the tests initiated in this Letter will improve by orders of magnitude in the near future.

  17. Autonomous Defensive Space Control via On-Board Artificial Neural Networks

    Science.gov (United States)

    2007-04-01

    AUTONOMOUS DEFENSIVE SPACE CONTROL VIA ON-BOARD ARTIFICIAL NEURAL NETWORKS Michael T. Manor, Major, USAF April 2007...TITLE AND SUBTITLE Sutonomous Defensive Space Control via On-Board Artificial Neural Networks 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM...11 HOW ARTIFICIAL NEURAL NETWORKS WORK

  18. Reliability analysis and design of on-board computer system for small stereo mapping satellite

    Institute of Scientific and Technical Information of China (English)

    马秀娟; 曹喜滨; 马兴瑞

    2002-01-01

    The on-board computer system for a small satellite is required to be high in reliability, light in weight, small in volume and low in power consumption. This paper describes the on-board computer system with the advantages of both centralized and distributed systems, analyzes its reliability, and briefs the key techniques used to improve its reliability.

  19. Human intestinal circadian clock: expression of clock genes in colonocytes lining the crypt.

    Science.gov (United States)

    Pardini, L; Kaeffer, B; Trubuil, A; Bourreille, A; Galmiche, J-P

    2005-01-01

    Biological clock components have been detected in many epithelial tissues of the digestive tract of mammals (oral mucosa, pancreas, and liver), suggesting the existence of peripheral circadian clocks that may be entrainable by food. Our aim was to investigate the expression of main peripheral clock genes in colonocytes of healthy humans and in human colon carcinoma cell lines. The presence of clock components was investigated in single intact colonic crypts isolated by chelation from the biopsies of 25 patients (free of any sign of colonic lesions) undergoing routine colonoscopy and in cell lines of human colon carcinoma (Caco2 and HT29 clone 19A). Per-1, per-2, and clock mRNA were detected by real-time RT-PCR. The three-dimensional distributions of PER-1, PER-2, CLOCK, and BMAL1 proteins were recorded along colonic crypts by immunofluorescent confocal imaging. We demonstrate the presence of per-1, per-2, and clock mRNA in samples prepared from colonic crypts of 5 patients and in all cell lines. We also demonstrate the presence of two circadian clock proteins, PER-1 and CLOCK, in human colonocytes on crypts isolated from 20 patients (15 patients for PER-1 and 6 for CLOCK) and in colon carcinoma cells. Establishing the presence of clock proteins in human colonic crypts is the first step toward the study of the regulation of the intestinal circadian clock by nutrients and feeding rhythms.

  20. Atomic frequency standard relativistic Doppler shift experiment

    Science.gov (United States)

    Peters, H. E.; Reinhardt, V. S.

    1974-01-01

    An experiment has been performed to measure possible space anisotropy as it would effect the frequency of a cesium atomic beam standard clock in a laboratory on earth due to motion relative to external coordinate frames. The cesium frequency was measured as a function of orientation with respect to an atomic hydrogen maser standard. Over a period of 34 days 101 measurements were made. The results are consistent with a conclusion that no general orientation dependance attributable to spacial anisotropy was observed. It is shown that both the airplane clock results, and the null results for the atomic beam clock, are consistent with Einstein general or special relativity, or with the Lorentz transformations alone.

  1. Gravitational Wave Detection with Single-Laser Atom Interferometers

    Science.gov (United States)

    Yu, Nan; Tinto, Massimo

    2011-01-01

    A new design for a broadband detector of gravitational radiation relies on two atom interferometers separated by a distance L. In this scheme, only one arm and one laser are used for operating the two atom interferometers. The innovation here involves the fact that the atoms in the atom interferometers are not only considered as perfect test masses, but also as highly stable clocks. Atomic coherence is intrinsically stable, and can be many orders of magnitude more stable than a laser.

  2. Horloge à réseau optique à atomes de Strontium

    OpenAIRE

    2008-01-01

    This thesis presents the latest achievements regarding the optical lattice clock with Strontium atoms developed at LNE-SYRTE. After a review of the different types of optical clocks that are currently under development, we stress on the concept of optical lattice clock which was first imagined for 87Sr using the 1S0 - 3P0 transition. We exhibit the features of this atom, in particular the concept of magic wavelength for the trap, and the achievable performances for this kind of clock. The sec...

  3. Uncertainty principle in larmor clock

    Institute of Scientific and Technical Information of China (English)

    QIAO Chuan; REN Zhong-Zhou

    2011-01-01

    It is well known that the spin operators of a quantum particle must obey uncertainty relations.We use the uncertainty principle to study the Larmor clock.To avoid breaking the uncertainty principle,Larmor time can be defined as the ratio of the phase difference between a spin-up particle and a spin-down particle to the corresponding Larmor frequency.The connection between the dwell time and the Larmor time has also been confirmed.Moreover,the results show that the behavior of the Larmor time depends on the height and width of the barrier.

  4. Clock genes, chronotypes and diseases

    Directory of Open Access Journals (Sweden)

    Bogdan I. Voinescu

    2009-08-01

    Full Text Available Many common diseases in humans (such as cancer, heart disease, diabetes mellitus orpsychiatric disorders, such as depression seem to be linked to disruptions of circadian cycles and toclock genes variation. It is unlikely that such diseases to be caused by a genetic variation within a singlegene. They must be influenced by complex interactions among multiple genes, as well as environmentaland lifestyle factors. Therefore, it is important to understand how the resulting perturbations in ourcircadian biology could affect our physiological processes and susceptibility to disease. Associationsbetween the polymorphisms of the main components of the circadian molecular clock, circadian type(also known as diurnal preference or chronotype and diseases are presented.

  5. Gigabit Ethernet Asynchronous Clock Compensation FIFO

    Science.gov (United States)

    Duhachek, Jeff

    2012-01-01

    Clock compensation for Gigabit Ethernet is necessary because the clock recovered from the 1.25 Gb/s serial data stream has the potential to be 200 ppm slower or faster than the system clock. The serial data is converted to 10-bit parallel data at a 125 MHz rate on a clock recovered from the serial data stream. This recovered data needs to be processed by a system clock that is also running at a nominal rate of 125 MHz, but not synchronous to the recovered clock. To cross clock domains, an asynchronous FIFO (first-in-first-out) is used, with the write pointer (wprt) in the recovered clock domain and the read pointer (rptr) in the system clock domain. Because the clocks are generated from separate sources, there is potential for FIFO overflow or underflow. Clock compensation in Gigabit Ethernet is possible by taking advantage of the protocol data stream features. There are two distinct data streams that occur in Gigabit Ethernet where identical data is transmitted for a period of time. The first is configuration, which happens during auto-negotiation. The second is idle, which occurs at the end of auto-negotiation and between every packet. The identical data in the FIFO can be repeated by decrementing the read pointer, thus compensating for a FIFO that is draining too fast. The identical data in the FIFO can also be skipped by incrementing the read pointer, which compensates for a FIFO draining too slowly. The unique and novel features of this FIFO are that it works in both the idle stream and the configuration streams. The increment or decrement of the read pointer is different in the idle and compensation streams to preserve disparity. Another unique feature is that the read pointer to write pointer difference range changes between compensation and idle to minimize FIFO latency during packet transmission.

  6. Circadian molecular clock in lung pathophysiology.

    Science.gov (United States)

    Sundar, Isaac K; Yao, Hongwei; Sellix, Michael T; Rahman, Irfan

    2015-11-15

    Disrupted daily or circadian rhythms of lung function and inflammatory responses are common features of chronic airway diseases. At the molecular level these circadian rhythms depend on the activity of an autoregulatory feedback loop oscillator of clock gene transcription factors, including the BMAL1:CLOCK activator complex and the repressors PERIOD and CRYPTOCHROME. The key nuclear receptors and transcription factors REV-ERBα and RORα regulate Bmal1 expression and provide stability to the oscillator. Circadian clock dysfunction is implicated in both immune and inflammatory responses to environmental, inflammatory, and infectious agents. Molecular clock function is altered by exposomes, tobacco smoke, lipopolysaccharide, hyperoxia, allergens, bleomycin, as well as bacterial and viral infections. The deacetylase Sirtuin 1 (SIRT1) regulates the timing of the clock through acetylation of BMAL1 and PER2 and controls the clock-dependent functions, which can also be affected by environmental stressors. Environmental agents and redox modulation may alter the levels of REV-ERBα and RORα in lung tissue in association with a heightened DNA damage response, cellular senescence, and inflammation. A reciprocal relationship exists between the molecular clock and immune/inflammatory responses in the lungs. Molecular clock function in lung cells may be used as a biomarker of disease severity and exacerbations or for assessing the efficacy of chronotherapy for disease management. Here, we provide a comprehensive overview of clock-controlled cellular and molecular functions in the lungs and highlight the repercussions of clock disruption on the pathophysiology of chronic airway diseases and their exacerbations. Furthermore, we highlight the potential for the molecular clock as a novel chronopharmacological target for the management of lung pathophysiology.

  7. Arabidopsis circadian clock and photoperiodism: time to think about location

    OpenAIRE

    Imaizumi, Takato

    2009-01-01

    Plants possess a circadian clock that enables them to coordinate internal biological events with external daily changes. Recent studies in Arabidopsis revealed that tissue specific clock components exist and that the clock network architecture also varies within different organs. These findings indicate that the makeup of circadian clock(s) within a plant is quite variable. Plants utilize the circadian clock to measure day-length changes for regulating seasonal responses, such as flowering. T...

  8. Legionella on board trains: effectiveness of environmental surveillance and decontamination

    Directory of Open Access Journals (Sweden)

    Quaranta Gianluigi

    2012-08-01

    Full Text Available Abstract Background Legionella pneumophila is increasingly recognised as a significant cause of sporadic and epidemic community-acquired and nosocomial pneumonia. Many studies describe the frequency and severity of Legionella spp. contamination in spa pools, natural pools, hotels and ships, but there is no study analysing the environmental monitoring of Legionella on board trains. The aims of the present study were to conduct periodic and precise environmental surveillance of Legionella spp. in water systems and water tanks that supply the toilet systems on trains, to assess the degree of contamination of such structures and to determine the effectiveness of decontamination. Methods A comparative pre-post ecological study was conducted from September 2006 to January 2011. A total of 1,245 water samples were collected from plumbing and toilet water tanks on passenger trains. The prevalence proportion of all positive samples was calculated. The unpaired t-test was performed to evaluate statistically significant differences between the mean load values before and after the decontamination procedures; statistical significance was set at p ≤ 0.05. Results In the pre-decontamination period, 58% of the water samples were positive for Legionella. Only Legionella pneumophila was identified: 55.84% were serogroup 1, 19.03% were serogroups 2–14 and 25.13% contained both serogroups. The mean bacterial load value was 2.14 × 103 CFU/L. During the post-decontamination period, 42.75% of water samples were positive for Legionella spp.; 98.76% were positive for Legionella pneumophila: 74.06% contained serogroup 1, 16.32% contained serogroups 2–14 and 9.62% contained both. The mean bacterial load in the post-decontamination period was 1.72 × 103 CFU/L. According to the t-test, there was a statistically significant decrease in total bacterial load until approximately one and a half year after beginning the decontamination programme (p

  9. Frequency shifts in an optical lattice clock due to magnetic-dipole and electric-quadrupole transitions.

    Science.gov (United States)

    Taichenachev, A V; Yudin, V I; Ovsiannikov, V D; Pal'chikov, V G; Oates, C W

    2008-11-01

    We report a hitherto undiscovered frequency shift for forbidden J = 0-->J = 0 clock transitions excited in atoms confined to an optical lattice. These shifts result from magnetic-dipole and electric-quadrupole transitions, which have a spatial dependence in an optical lattice that differs from that of the stronger electric-dipole transitions. In combination with the residual translational motion of atoms in an optical lattice, this spatial mismatch leads to a frequency shift via differential energy level spacing in the lattice wells for ground state and excited state atoms. We estimate that this effect could lead to fractional frequency shifts as large as 10(-16), which might prevent lattice-based optical clocks from reaching their predicted performance levels. Moreover, these effects could shift the magic wavelength in lattice clocks in three dimensions by as much as 100 MHz, depending on the lattice configuration.

  10. Global synchronization of parallel processors using clock pulse width modulation

    Science.gov (United States)

    Chen, Dong; Ellavsky, Matthew R.; Franke, Ross L.; Gara, Alan; Gooding, Thomas M.; Haring, Rudolf A.; Jeanson, Mark J.; Kopcsay, Gerard V.; Liebsch, Thomas A.; Littrell, Daniel; Ohmacht, Martin; Reed, Don D.; Schenck, Brandon E.; Swetz, Richard A.

    2013-04-02

    A circuit generates a global clock signal with a pulse width modification to synchronize processors in a parallel computing system. The circuit may include a hardware module and a clock splitter. The hardware module may generate a clock signal and performs a pulse width modification on the clock signal. The pulse width modification changes a pulse width within a clock period in the clock signal. The clock splitter may distribute the pulse width modified clock signal to a plurality of processors in the parallel computing system.

  11. Fast Clock Recovery for Digital Communications

    Science.gov (United States)

    Tell, R. G.

    1985-01-01

    Circuit extracts clock signal from random non-return-to-zero data stream, locking onto clock within one bit period at 1-gigabitper-second data rate. Circuit used for synchronization in opticalfiber communications. Derives speed from very short response time of gallium arsenide metal/semiconductor field-effect transistors (MESFET's).

  12. Temperature influences in receiver clock modelling

    Science.gov (United States)

    Wang, Kan; Meindl, Michael; Rothacher, Markus; Schoenemann, Erik; Enderle, Werner

    2016-04-01

    In Precise Point Positioning (PPP), hardware delays at the receiver site (receiver, cables, antenna, …) are always difficult to be separated from the estimated receiver clock parameters. As a result, they are partially or fully contained in the estimated "apparent" clocks and will influence the deterministic and stochastic modelling of the receiver clock behaviour. In this contribution, using three years of data, the receiver clock corrections of a set of high-precision Hydrogen Masers (H-Masers) connected to stations of the ESA/ESOC network and the International GNSS Service (IGS) are firstly characterized concerning clock offsets, drifts, modified Allan deviations and stochastic parameters. In a second step, the apparent behaviour of the clocks is modelled with the help of a low-order polynomial and a known temperature coefficient (Weinbach, 2013). The correlations between the temperature and the hardware delays generated by different types of antennae are then analysed looking at daily, 3-day and weekly time intervals. The outcome of these analyses is crucial, if we intend to model the receiver clocks in the ground station network to improve the estimation of station-related parameters like coordinates, troposphere zenith delays and ambiguities. References: Weinbach, U. (2013) Feasibility and impact of receiver clock modeling in precise GPS data analysis. Dissertation, Leibniz Universität Hannover, Germany.

  13. A circadian clock in Saccharomyces cerevisiae

    NARCIS (Netherlands)

    Eelderink-Chen, Zheng; Mazzotta, Gabriella; Sturre, Marcel; Bosman, Jasper; Roenneberg, Till; Merrow, Martha

    2010-01-01

    Circadian timing is a fundamental biological process, underlying cellular physiology in animals, plants, fungi, and cyanobacteria. Circadian clocks organize gene expression, metabolism, and behavior such that they occur at specific times of day. The biological clocks that orchestrate these daily cha

  14. A clock synchronization skeleton based on RTAI

    NARCIS (Netherlands)

    Huang, Y.; Visser, P.M.; Broenink, Johannes F.

    2006-01-01

    This paper presents a clock synchronization skeleton based on RTAI (Real Time Application Interface). The skeleton is a thin layer that provides unified but extendible interfaces to the underlying operating system, the synchronization algorithms and the upper level applications in need of clock

  15. "Molecular Clock" Analogs: A Relative Rates Exercise

    Science.gov (United States)

    Wares, John P.

    2008-01-01

    Although molecular clock theory is a commonly discussed facet of evolutionary biology, undergraduates are rarely presented with the underlying information of how this theory is examined relative to empirical data. Here a simple contextual exercise is presented that not only provides insight into molecular clocks, but is also a useful exercise for…

  16. A Mathematical Model of the Liver Circadian Clock Linking Feeding and Fasting Cycles to Clock Function

    Directory of Open Access Journals (Sweden)

    Aurore Woller

    2016-10-01

    Full Text Available To maintain energy homeostasis despite variable energy supply and consumption along the diurnal cycle, the liver relies on a circadian clock synchronized to food timing. Perturbed feeding and fasting cycles have been associated with clock disruption and metabolic diseases; however, the mechanisms are unclear. To address this question, we have constructed a mathematical model of the mammalian circadian clock, incorporating the metabolic sensors SIRT1 and AMPK. The clock response to various temporal patterns of AMPK activation was simulated numerically, mimicking the effects of a normal diet, fasting, and a high-fat diet. The model reproduces the dampened clock gene expression and NAD+ rhythms reported for mice on a high-fat diet and predicts that this effect may be pharmacologically rescued by timed REV-ERB agonist administration. Our model thus identifies altered AMPK signaling as a mechanism leading to clock disruption and its associated metabolic effects and suggests a pharmacological approach to resetting the clock in obesity.

  17. A Mathematical Model of the Liver Circadian Clock Linking Feeding and Fasting Cycles to Clock Function.

    Science.gov (United States)

    Woller, Aurore; Duez, Hélène; Staels, Bart; Lefranc, Marc

    2016-10-18

    To maintain energy homeostasis despite variable energy supply and consumption along the diurnal cycle, the liver relies on a circadian clock synchronized to food timing. Perturbed feeding and fasting cycles have been associated with clock disruption and metabolic diseases; however, the mechanisms are unclear. To address this question, we have constructed a mathematical model of the mammalian circadian clock, incorporating the metabolic sensors SIRT1 and AMPK. The clock response to various temporal patterns of AMPK activation was simulated numerically, mimicking the effects of a normal diet, fasting, and a high-fat diet. The model reproduces the dampened clock gene expression and NAD(+) rhythms reported for mice on a high-fat diet and predicts that this effect may be pharmacologically rescued by timed REV-ERB agonist administration. Our model thus identifies altered AMPK signaling as a mechanism leading to clock disruption and its associated metabolic effects and suggests a pharmacological approach to resetting the clock in obesity.

  18. Single electron relativistic clock interferometer

    Science.gov (United States)

    Bushev, P. A.; Cole, J. H.; Sholokhov, D.; Kukharchyk, N.; Zych, M.

    2016-09-01

    Although time is one of the fundamental notions in physics, it does not have a unique description. In quantum theory time is a parameter ordering the succession of the probability amplitudes of a quantum system, while according to relativity theory each system experiences in general a different proper time, depending on the system's world line, due to time dilation. It is therefore of fundamental interest to test the notion of time in the regime where both quantum and relativistic effects play a role, for example, when different amplitudes of a single quantum clock experience different magnitudes of time dilation. Here we propose a realization of such an experiment with a single electron in a Penning trap. The clock can be implemented in the electronic spin precession and its time dilation then depends on the radial (cyclotron) state of the electron. We show that coherent manipulation and detection of the electron can be achieved already with present day technology. A single electron in a Penning trap is a technologically ready platform where the notion of time can be probed in a hitherto untested regime, where it requires a relativistic as well as quantum description.

  19. Tectonic blocks and molecular clocks

    Science.gov (United States)

    2016-01-01

    Evolutionary timescales have mainly used fossils for calibrating molecular clocks, though fossils only really provide minimum clade age constraints. In their place, phylogenetic trees can be calibrated by precisely dated geological events that have shaped biogeography. However, tectonic episodes are protracted, their role in vicariance is rarely justified, the biogeography of living clades and their antecedents may differ, and the impact of such events is contingent on ecology. Biogeographic calibrations are no panacea for the shortcomings of fossil calibrations, but their associated uncertainties can be accommodated. We provide examples of how biogeographic calibrations based on geological data can be established for the fragmentation of the Pangaean supercontinent: (i) for the uplift of the Isthmus of Panama, (ii) the separation of New Zealand from Gondwana, and (iii) for the opening of the Atlantic Ocean. Biogeographic and fossil calibrations are complementary, not competing, approaches to constraining molecular clock analyses, providing alternative constraints on the age of clades that are vital to avoiding circularity in investigating the role of biogeographic mechanisms in shaping modern biodiversity. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’. PMID:27325840

  20. Three errors in the article:" The OPERA neutrino velocity result and the synchronisation of clocks, "

    CERN Document Server

    Besida, Olivier

    2011-01-01

    We found three mistakes in the article " The OPERA neutrino velocity result and the synchronisation of clocks" by Contaldi \\cite{Contaldi}. First, the definition of the angle of the latitude in the geoid description leads to a prolate spheroid (rugby ball shape) instead of an oblate spheroid with the usual equatorial flattening. Second, Contaldi forgot a cosine of the latitude in the centripetal contribution term. And last but not least, a profound conceptual mistake was done in believing that an atomic clock or any timekeeper apparatus was carried in a journey by car or plane between CERN and Gran Sasso; instead of that atomic clocks are continuously resynchronized through a GPS device, and the variation of the potential term applies only for the neutrino travel itself. Thus instead of a $\\Delta t \\approx 30ns $ correction claimed by the author in a travel of 12 hours plus 4 days at rest for an atomic clock, we have found a time correction only for the neutrino itself $\\Delta t=3.88 \\, 10^{-16} s$! That mean...

  1. A low maintenance Sr optical lattice clock

    CERN Document Server

    Hill, Ian R; Bowden, William; Bridge, Elizabeth M; Donnellan, Sean; Curtis, E Anne; Gill, Patrick

    2016-01-01

    We describe the Sr optical lattice clock apparatus at NPL with particular emphasis on techniques used to increase reliability and minimise the human requirement in its operation. Central to this is a clock-referenced transfer cavity scheme for the stabilisation of cooling and trapping lasers. We highlight several measures to increase the reliability of the clock with a view towards the realisation of an optical time-scale. The clock contributed 502 hours of data over a 25 day period (84% uptime) in a recent measurement campaign with several uninterrupted periods of more than 48 hours. An instability of $2\\times10^{-17}$ was reached after $10^5$ s of averaging in an interleaved self-comparison of the clock.

  2. Cost and Precision of Brownian Clocks

    CERN Document Server

    Barato, Andre C

    2016-01-01

    Brownian clocks are biomolecular networks that can count time. A paradigmatic example are proteins that go through a cycle thus regulating some oscillatory behaviour in a living system. Typically, such a cycle requires free energy often provided by ATP hydrolysis. We investigate the relation between the precision of such a clock and its thermodynamic costs. For clocks driven by a constant thermodynamic force, a given precision requires a minimal cost that diverges as the uncertainty of the clock vanishes. In marked contrast, we show that a clock driven by a periodic variation of an external protocol can achieve arbitrary precision at arbitrarily low cost. This result constitutes a fundamental difference between processes driven by a fixed thermodynamic force and those driven periodically. As a main technical tool, we map a periodically driven system with a deterministic protocol to one subject to an external protocol that changes in stochastic time intervals, which simplifies calculations significantly. In th...

  3. Developing an "atomic clock" for fission lifetime measurements

    NARCIS (Netherlands)

    Wilschut, H.W.E.M.; Kravchuk, V.

    2004-01-01

    The relevance of measuring fission lifetimes of hot nuclei is briefly discussed. It is shown that K X-ray emission prior to fission can be used to measure fission lifetimes. The preparation of the K-shell hole, the simultaneous nuclear excitation, and the analysis of the X-ray spectra is described.

  4. PHARAO: A Space Clock with Cold Cesium Atoms

    Science.gov (United States)

    1996-12-01

    Fundamental Tests. [z] R. Vessot et al. 1980, Physical Review Letters , 45, 2081. IS] R. Vessot 1993, Proceedings of the 28th Moriond Conference. [4...World Scientific, Singapore), pp. 49-59. [6] M. Kasevich, E. Riis, S. Chu, and R. de Voe 1989, Physical Review Letters , 63, 612. 171 A. Clairon, C...Salomon, S. Guellati, and W. Phillips 1991, Europhysical Letters, 16, 165. [a] K Gibble, and S. Chu 1993, Physical Review Letters , 70, 177. [g] B

  5. An Atomic Clock with 10 (exp -18) Instability

    Science.gov (United States)

    2013-09-13

    Parker, Metrologia 47, 1 10 (2010). 6. T. Rosenband et al., Science 319, 1808 1812 (2008). 7. C. W. Chou, D. B. Hume , J. C. J. Koelemeij, D. J. Wineland...W. Chou, D. B. Hume , T. Rosenband, D. J. Wineland, Science 329, 1630 1633 (2010). 27. D. Kleppner, Phys. Today 59, 10 (2006). 28. S. Schiller et al...for financial support; D. Hume for experimental assistance; and T. Fortier and S. Diddams for femtosecond optical frequency comb measurements

  6. Imaging the Mott Insulator Shells using Atomic Clock Shifts

    OpenAIRE

    Campbell, Gretchen K.; Mun, Jongchul; Boyd, Micah; Medley, Patrick; Leanhardt, Aaron E.; Marcassa, Luis; Pritchard, David E.; Ketterle, Wolfgang

    2006-01-01

    Microwave spectroscopy was used to probe the superfluid-Mott Insulator transition of a Bose-Einstein condensate in a 3D optical lattice. Using density dependent transition frequency shifts we were able to spectroscopically distinguish sites with different occupation numbers, and to directly image sites with occupation number n=1 to n=5 revealing the shell structure of the Mott Insulator phase. We use this spectroscopy to determine the onsite interaction and lifetime for individual shells.

  7. Developing an "atomic clock" for fission lifetime measurements

    NARCIS (Netherlands)

    Wilschut, H.W.E.M.; Kravchuk, V.

    2004-01-01

    The relevance of measuring fission lifetimes of hot nuclei is briefly discussed. It is shown that K X-ray emission prior to fission can be used to measure fission lifetimes. The preparation of the K-shell hole, the simultaneous nuclear excitation, and the analysis of the X-ray spectra is described.

  8. Raman transitions between hyperfine clock states in a magnetic trap

    CERN Document Server

    Naber, J B; Hubert, T; Spreeuw, R J C

    2016-01-01

    We present our experimental investigation of an optical Raman transition between the magnetic clock states of $^{87}$Rb in an atom chip magnetic trap. The transfer of atomic population is induced by a pair of diode lasers which couple the two clock states off-resonantly to an intermediate state manifold. This transition is subject to destructive interference of two excitation paths, which leads to a reduction of the effective two-photon Rabi-frequency. Furthermore, we find that the transition frequency is highly sensitive to the intensity ratio of the diode lasers. Our results are well described in terms of light shifts in the multi-level structure of $^{87}$Rb. The differential light shifts vanish at an optimal intensity ratio, which we observe as a narrowing of the transition linewidth. We also observe the temporal dynamics of the population transfer and find good agreement with a model based on the system's master equation and a Gaussian laser beam profile. Finally, we identify several sources of decoheren...

  9. HTML 5 Displays for On-Board Flight Systems

    Science.gov (United States)

    Silva, Chandika

    2016-01-01

    During my Internship at NASA in the summer of 2016, I was assigned to a project which dealt with developing a web-server that would display telemetry and other system data using HTML 5, JavaScript, and CSS. By doing this, it would be possible to view the data across a variety of screen sizes, and establish a standard that could be used to simplify communication and software development between NASA and other countries. Utilizing a web- approach allowed us to add in more functionality, as well as make the displays more aesthetically pleasing for the users. When I was assigned to this project my main task was to first establish communication with the current display server. This display server would output data from the on-board systems in XML format. Once communication was established I was then asked to create a dynamic telemetry table web page that would update its header and change as new information came in. After this was completed, certain minor functionalities were added to the table such as a hide column and filter by system option. This was more for the purpose of making the table more useful for the users, as they can now filter and view relevant data. Finally my last task was to create a graphical system display for all the systems on the space craft. This was by far the most challenging part of my internship as finding a JavaScript library that was both free and contained useful functions to assist me in my task was difficult. In the end I was able to use the JointJs library and accomplish the task. With the help of my mentor and the HIVE lab team, we were able to establish stable communication with the display server. We also succeeded in creating a fully dynamic telemetry table and in developing a graphical system display for the advanced modular power system. Working in JSC for this internship has taught me a lot about coding in JavaScript and HTML 5. I was also introduced to the concept of developing software as a team, and exposed to the different

  10. Extended Coherence Time on the Clock Transition of Optically Trapped Rubidium

    DEFF Research Database (Denmark)

    Kleine Büning, G.; Will, J.; Ertmer, W.

    2011-01-01

    Optically trapped ensembles are of crucial importance for frequency measurements and quantum memories but generally suffer from strong dephasing due to inhomogeneous density and light shifts. We demonstrate a drastic increase of the coherence time to 21 s on the magnetic field insensitive clock...... transition of 87Rb by applying the recently discovered spin self-rephasing [C. Deutsch et al., Phys. Rev. Lett. 105, 020401 (2010)]. This result confirms the general nature of this new mechanism and thus shows its applicability in atom clocks and quantum memories. A systematic investigation of all relevant...... frequency shifts and noise contributions yields a stability of 2.4×10-11τ-1/2, where τ is the integration time in seconds. Based on a set of technical improvements, the presented frequency standard is predicted to rival the stability of microwave fountain clocks in a potentially much more compact setup....

  11. Limitations of long term stability in a coherent population trapping Cs clock

    CERN Document Server

    Kozlova, Olga; Guérandel, Stéphane; de Clercq, Emeric

    2013-01-01

    Vapor cell atomic clocks exhibit reduced frequency stability for averaging time between about one hundred and a few thousand seconds. Here we report a study on the impact of the main parameters on the mid-to-long term instability of a buffer-gas vapor cell Cs clock, based on coherent population trapping (CPT). The CPT signal is observed on the Cs D1 line transmission, using a double $\\Lambda$ scheme and a Ramsey interrogation technique. The effects on the clock frequency of the magnetic field, the cell temperature, and the laser intensities are reported. We show in particular that the laser intensity shift is temperature dependent. Along with the laser intensity ratio and laser polarization properties, this is one of the most important parameters.

  12. Microwave-clock timescale with instability on order of 10-17

    Science.gov (United States)

    Peil, Steven; Swanson, Thomas B.; Hanssen, James; Taylor, Jennifer

    2017-06-01

    The fundamental limits of atomic fountains as operational clocks are considered. Four rubidium fountains in operation at the US Naval Observatory for over 5.5 years have demonstrated unprecedented long-term stability for continuously running clocks (Peil et al 2014 Metrologia 51 263-9, Peil et al 2016 J. Phys.: Conf. Ser. 723 012004). With only these rubidium fountains, a post-processed timescale can be created that demonstrates superior long-term performance to any individual clock by compensating for occasional frequency steps. By comparing to the world’s primary standards we demonstrate instability of this rubidium fountain timescale reaching the mid 10-17’s and zero drift at the level of 1.3  ×  10-19 d-1. We discuss fundamental limits due to common mode behaviour or individual fountain performance that cannot be corrected.

  13. Circadian clocks are designed optimally

    CERN Document Server

    Hasegawa, Yoshihiko

    2014-01-01

    Circadian rhythms are acquired through evolution to increase the chances for survival by synchronizing to the daylight cycle. Reliable synchronization is realized through two trade-off properties: regularity to keep time precisely, and entrainability to synchronize the internal time with daylight. Since both properties have been tuned through natural selection, their adaptation can be formalized in the framework of mathematical optimization. By using a succinct model, we found that simultaneous optimization of regularity and entrainability entails inherent features of the circadian mechanism irrespective of model details. At the behavioral level we discovered the existence of a dead zone, a time during which light pulses neither advance nor delay the clock. At the molecular level we demonstrate the role-sharing of two light inputs, phase advance and delay, as is well observed in mammals. We also reproduce the results of phase-controlling experiments and predict molecular elements responsible for the clockwork...

  14. Half Swing Clocking Scheme at 45nm

    Directory of Open Access Journals (Sweden)

    Sakshi Verma,

    2014-01-01

    Full Text Available Achievement of high processor speed with low power consumption is an elemental factor in processor technology, especially for hand-held devices. The need for low power has caused a major paradigm shift where power dissipation has become a important consideration as performance and area. In CMOS circuits, dynamic power consumption is proportional to the transition frequency, capacitance, and square of supply voltage. Consequentially, lowering supply voltage delivers significant power savings compromising the speed of processor. Large portion of the total power is consumed in the clocking circuitry in embedded processor technology. So clock power can be reduced using half swing of clock scheme which will cut down the power dissipation and minimum speed degradation. In Digital circuits by using double-edge triggered flip flops (DETFFs, the clock frequency can be significantly reduced ideally, in half while preserving the rate of data processing. Using lower clock frequency may translate into considerable power savings for the clocked portions of a circuit, including the clock distribution network and flip-flops. The designing is based on 45nm process technology.

  15. The molecular clock as a metabolic rheostat.

    Science.gov (United States)

    Perelis, M; Ramsey, K M; Bass, J

    2015-09-01

    Circadian clocks are biologic oscillators present in all photosensitive species that produce 24-h cycles in the transcription of rate-limiting metabolic enzymes in anticipation of the light-dark cycle. In mammals, the clock drives energetic cycles to maintain physiologic constancy during the daily switch in behavioural (sleep/wake) and nutritional (fasting/feeding) states. A molecular connection between circadian clocks and tissue metabolism was first established with the discovery that 24-h transcriptional rhythms are cell-autonomous and self-sustained in most tissues and comprise a robust temporal network throughout the body. A major window in understanding how the clock is coupled to metabolism was opened with discovery of metabolic syndrome pathologies in multi-tissue circadian mutant mice including susceptibility to diet-induced obesity and diabetes. Using conditional transgenesis and dynamic metabolic testing, we have pinpointed tissue-specific roles of the clock in energy and glucose homeostasis, with our most detailed understanding of this process in endocrine pancreas. Here, we review evidence for dynamic regulation of insulin secretion and oxidative metabolic functions by the clock transcription pathway to regulate homeostatic responses to feeding and fasting. These studies indicate that clock transcription is a determinant of tissue function and provide a reference for understanding molecular pathologies linking circadian desynchrony to metabolic disease.

  16. On-Board Engine Exhaust Particulate Matter Sensor for HCCI and Conventional Diesel Engines

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Matt; Matthews, Ron

    2011-09-30

    The goal of the research was to refine and complete development of an on-board particulate matter (PM) sensor for diesel, DISI, and HCCI engines, bringing it to a point where it could be commercialized and marketed.

  17. Advanced Hybrid On-Board Data Processor - SpaceCube 2.0 Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Develop advanced on-board processing to meet the requirements of the Decadal Survey missions: advanced instruments (hyper-spectral, SAR, etc) require advanced...

  18. Noise and sleep on board vessels in the Royal Norwegian Navy

    OpenAIRE

    Erlend Sunde; Magne Bratveit; Stale Pallesen; Bente Elisabeth Moen

    2016-01-01

    Previous research indicates that exposure to noise during sleep can cause sleep disturbance. Seamen on board vessels are frequently exposed to noise also during sleep periods, and studies have reported sleep disturbance in this occupational group. However, studies of noise and sleep in maritime settings are few. This study's aim was to examine the associations between noise exposure during sleep, and sleep variables derived from actigraphy among seamen on board vessels in the Royal Norwegian ...

  19. The SpaceCube Family of Hybrid On-Board Science Data Processors: An Update

    Science.gov (United States)

    Flatley, T.

    2012-12-01

    SpaceCube is an FPGA based on-board hybrid science data processing system developed at the NASA Goddard Space Flight Center (GSFC). The goal of the SpaceCube program is to provide 10x to 100x improvements in on-board computing power while lowering relative power consumption and cost. The SpaceCube design strategy incorporates commercial rad-tolerant FPGA technology and couples it with an upset mitigation software architecture to provide "order of magnitude" improvements in computing power over traditional rad-hard flight systems. Many of the missions proposed in the Earth Science Decadal Survey (ESDS) will require "next generation" on-board processing capabilities to meet their specified mission goals. Advanced laser altimeter, radar, lidar and hyper-spectral instruments are proposed for at least ten of the ESDS missions, and all of these instrument systems will require advanced on-board processing capabilities to facilitate the timely conversion of Earth Science data into Earth Science information. Both an "order of magnitude" increase in processing power and the ability to "reconfigure on the fly" are required to implement algorithms that detect and react to events, to produce data products on-board for applications such as direct downlink, quick look, and "first responder" real-time awareness, to enable "sensor web" multi-platform collaboration, and to perform on-board "lossless" data reduction by migrating typical ground-based processing functions on-board, thus reducing on-board storage and downlink requirements. This presentation will highlight a number of SpaceCube technology developments to date and describe current and future efforts, including the collaboration with the U.S. Department of Defense - Space Test Program (DoD/STP) on the STP-H4 ISS experiment pallet (launch June 2013) that will demonstrate SpaceCube 2.0 technology on-orbit.; ;

  20. Iterative quantum algorithm for distributed clock synchronization

    Institute of Scientific and Technical Information of China (English)

    Wang Hong-Fu; Zhang Shou

    2012-01-01

    Clock synchronization is a well-studied problem with many practical and scientific applications.We propose an arbitrary accuracy iterative quantum algorithm for distributed clock synchronization using only three qubits.The n bits of the time difference △ between two spatially separated clocks can be deterministically extracted by communicating only O(n) messages and executing the quantum iteration process n times based on the classical feedback and measurement operations.Finally,we also give the algorithm using only two qubits and discuss the success probability of the algorithm.

  1. CMOS Law-jitter Clock Driver Design

    OpenAIRE

    2012-01-01

    [ANGLÈS] Design of a low-jitter, low-phase noise clock driver in 40 nm CMOS technology. The work is in the field of analog integrated circuit (IC) design in nanometer CMOS technologies. [CASTELLÀ] Diseño de un circuito integrado "clock driver" de bajo jitter y bajo ruido de fase en tecnología CMOS 40 nm. El trabajo se contextualiza en el campo del diseño de circuitos integrados analógicos en tecnologías CMOS nanométricas. [CATALÀ] Disseny d'un circuit "clock driver" de baix jitter i bai...

  2. Light clocks in strong gravitational fields

    CERN Document Server

    Punzi, Raffaele; Wohlfarth, Mattias N R

    2009-01-01

    We argue that the time measured by a light clock operating with photons rather than classical light requires a refinement of the standard clock postulate in general relativity. In the presence of a gravitational field, already the one-loop quantum corrections to classical Maxwell theory affect light propagation and the construction of observers' frames of reference. Carefully taking into account these kinematic effects, a concise geometric expression for the time shown by a light clock is obtained. This result has far-reaching implications for physics in strong gravitational fields.

  3. Sleep: the sound of a local alarm clock.

    Science.gov (United States)

    Adamantidis, Antoine R

    2015-01-05

    Besides the master clock located in the suprachiasmatic nucleus (SCN) of the brain, additional clocks are distributed across the central nervous system and the body. The role of these 'secondary' clocks remains unclear. A new study shows that the lack of an internal clock in histamine neurons profoundly perturbs sleep. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Transcripts from the Circadian Clock: Telling Time and Season

    NARCIS (Netherlands)

    K. Brand (Karl)

    2011-01-01

    textabstractWe all know it when we wake mere moments before an alarm clock is scheduled to wake us: our body clock made the alarm clock redundant. This phenomenon is driven by an endogenous timer known as the biological, or circadian clock. Each revolution of the Earth about its own axis produces pe

  5. Circadian and Circalunar Clock Interactions in a Marine Annelid

    Directory of Open Access Journals (Sweden)

    Juliane Zantke

    2013-10-01

    Full Text Available Life is controlled by multiple rhythms. Although the interaction of the daily (circadian clock with environmental stimuli, such as light, is well documented, its relationship to endogenous clocks with other periods is little understood. We establish that the marine worm Platynereis dumerilii possesses endogenous circadian and circalunar (monthly clocks and characterize their interactions. The RNAs of likely core circadian oscillator genes localize to a distinct nucleus of the worm’s forebrain. The worm’s forebrain also harbors a circalunar clock entrained by nocturnal light. This monthly clock regulates maturation and persists even when circadian clock oscillations are disrupted by the inhibition of casein kinase 1δ/ε. Both circadian and circalunar clocks converge on the regulation of transcript levels. Furthermore, the circalunar clock changes the period and power of circadian behavior, although the period length of the daily transcriptional oscillations remains unaltered. We conclude that a second endogenous noncircadian clock can influence circadian clock function.

  6. Deregulated expression of circadian clock and clock-controlled cell cycle genes in chronic lymphocytic leukemia.

    Science.gov (United States)

    Rana, Sobia; Munawar, Mustafa; Shahid, Adeela; Malik, Meera; Ullah, Hafeez; Fatima, Warda; Mohsin, Shahida; Mahmood, Saqib

    2014-01-01

    Circadian rhythms are endogenous and self-sustained oscillations of multiple biological processes with approximately 24-h rhythmicity. Circadian genes and their protein products constitute the molecular components of the circadian oscillator that form positive/negative feedback loops and generate circadian rhythms. The circadian regulation extends from core clock genes to various clock-controlled genes that include various cell cycle genes. Aberrant expression of circadian clock genes, therefore, may lead to genomic instability and accelerated cellular proliferation potentially promoting carcinogenesis. The current study encompasses the investigation of simultaneous expression of four circadian clock genes (Bmal1, Clock, Per1 and Per2) and three clock-controlled cell cycle genes (Myc, Cyclin D1 and Wee1) at mRNA level and determination of serum melatonin levels in peripheral blood samples of 37 CLL (chronic lymphocytic leukemia) patients and equal number of age- and sex-matched healthy controls in order to indicate association between deregulated circadian clock and manifestation of CLL. Results showed significantly down-regulated expression of Bmal1, Per1, Per2 and Wee1 and significantly up-regulated expression of Myc and Cyclin D1 (P circadian clock genes can lead to aberrant expression of their downstream targets that are involved in cell proliferation and apoptosis and hence may result in manifestation of CLL. Moreover, shift-work and low melatonin levels may also contribute in etiology of CLL by further perturbing of circadian clock.

  7. Analysis of the blackbody-radiation shift in an ytterbium optical lattice clock

    Science.gov (United States)

    Xu, Yi-Lin; Xu, Xin-Ye

    2016-10-01

    We accurately evaluate the blackbody-radiation shift in a 171Yb optical lattice clock by utilizing temperature measurement and numerical simulation. In this work. three main radiation sources are considered for the blackbody-radiation shift, including the heated atomic oven, the warm vacuum chamber, and the room-temperature vacuum windows. The temperatures on the outer surface of the vacuum chamber are measured during the clock operation period by utilizing seven calibrated temperature sensors. Then we infer the temperature distribution inside the vacuum chamber by numerical simulation according to the measured temperatures. Furthermore, we simulate the temperature variation around the cold atoms while the environmental temperature is fluctuating. Finally, we obtain that the total blackbody-radiation shift is -1.289(7) Hz with an uncertainty of 1.25 × 10-17 for our 171Yb optical lattice clock. The presented method is quite suitable for accurately evaluating the blackbody-radiation shift of the optical lattice clock in the case of lacking the sensors inside the vacuum chamber. Project supported by the National Key Basic Research and Development Program of China (Grant No. 2012CB821302), the National Natural Science Foundation of China (Grant No. 11134003), the National High Technology Research and Development Program of China (Grant No. 2014AA123401), and the Shanghai Excellent Academic Leaders Program of China (Grant No. 12XD1402400).

  8. A New Design of Clock Synchronization Algorithm

    Directory of Open Access Journals (Sweden)

    Jingmeng Liu

    2014-05-01

    Full Text Available The introduction of Ethernet makes the distributed network system more flexible and efficient, but it also makes nodes which are far apart from each other unable to work in the same time basis due to the long distance. This is not allowed for the high performance requirements of the system synchronization, such as high-precision multiaxis machining system. This paper presents a high-precision network clock synchronization algorithm, namely, optimal PI clock servo, which imposes a PI controller in order to compensate for the clock drift of each network node. Then a simulation platform established by the toolbox TrueTime is used to verify the stability of the algorithm and compare it with the clock synchronization algorithm of EtherCAT. The results show that the new synchronization algorithm has higher synchronization precision and faster convergence rate.

  9. Programmable Clock Waveform Generation for CCD Readout

    Energy Technology Data Exchange (ETDEWEB)

    Vicente, J. de; Castilla, J.; Martinez, G.; Marin, J.

    2006-07-01

    Charge transfer efficiency in CCDs is closely related to the clock waveform. In this paper, an experimental framework to explore different FPGA based clock waveform generator designs is described. Two alternative design approaches for controlling the rise/fall edge times and pulse width of the CCD clock signal have been implemented: level-control and time-control. Both approaches provide similar characteristics regarding the edge linearity and noise. Nevertheless, dissimilarities have been found with respect to the area and frequency range of application. Thus, while the time-control approach consumes less area, the level control approach provides a wider range of clock frequencies since it does not suffer capacitor discharge effect. (Author) 8 refs.

  10. The Mechanics of Mechanical Watches and Clocks

    CERN Document Server

    Du, Ruxu

    2013-01-01

    "The Mechanics of Mechanical Watches and Clocks" presents historical views and mathematical models of mechanical watches and clocks. Although now over six hundred years old, mechanical watches and clocks are still popular luxury items that fascinate many people around the world. However few have examined the theory of how they work as presented in this book. The illustrations and computer animations are unique and have never been published before. It will be of significant interest to researchers in mechanical engineering, watchmakers and clockmakers, as well as people who have an engineering background and are interested in mechanical watches and clocks. It will also inspire people in other fields of science and technology, such as mechanical engineering and electronics engineering, to advance their designs. Professor Ruxu Du works at the Chinese University of Hong Kong, China. Assistant Professor Longhan Xie works at the South China University of Technology, China.

  11. Draper Clock-Synchronization Protocol in SAL

    Data.gov (United States)

    National Aeronautics and Space Administration — In 1973, Daly, Hpokins, and McKenna (from Draper Lab.) presented a fault-tolerant digital clocking system at the FTCS conference. This is probably one of the first...

  12. Turning Back the Aging Clock -- in Mice

    Science.gov (United States)

    ... 164250.html Turning Back the Aging Clock -- in Mice Elderly rodents treated with cellular therapy regained lost fur, became ... 2017 THURSDAY, March 23, 2017 (HealthDay News) -- Aging mice became more youthful following a new cellular therapy ...

  13. Circadian clock circuitry in colorectal cancer.

    Science.gov (United States)

    Mazzoccoli, Gianluigi; Vinciguerra, Manlio; Papa, Gennaro; Piepoli, Ada

    2014-04-21

    Colorectal cancer is the most prevalent among digestive system cancers. Carcinogenesis relies on disrupted control of cellular processes, such as metabolism, proliferation, DNA damage recognition and repair, and apoptosis. Cell, tissue, organ and body physiology is characterized by periodic fluctuations driven by biological clocks operating through the clock gene machinery. Dysfunction of molecular clockworks and cellular oscillators is involved in tumorigenesis, and altered expression of clock genes has been found in cancer patients. Epidemiological studies have shown that circadian disruption, that is, alteration of bodily temporal organization, is a cancer risk factor, and an increased incidence of colorectal neoplastic disease is reported in shift workers. In this review we describe the involvement of the circadian clock circuitry in colorectal carcinogenesis and the therapeutic strategies addressing temporal deregulation in colorectal cancer.

  14. Micro Mercury Ion Clock (MMIC) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Demonstrate micro clock based on trapped Hg ions with more than 10x size reduction and power; Fractional frequency stability at parts per 1014 level, adequate for...

  15. Modeling circadian clocks: From equations to oscillations

    National Research Council Canada - National Science Library

    Gonze, Didier

    2011-01-01

    ... (such as light and temperature) is greatly helped by mathematical modeling. In the present paper we review some mathematical models for circadian clocks, ranging from abstract, phenomenological models to the most detailed molecular models...

  16. PTTI 2030 - System Applications of Advanced Clocks

    Science.gov (United States)

    2010-11-01

    while you enjoy the freedom of hands-free driving. 42 nd Annual Precise Time and Time Interval (PTTI) Meeting 587 PLATE TECTONICS ...MONITORING Ultra-stable clocks have been recognized for some time as great tools to calibrate plate movement on the earth’s crust. In combination...position after a seismic event. The addition of multiple clocks to a worldwide monitoring system has allowed improved accuracy of these measurements

  17. Reduced Kalman Filters for Clock Ensembles

    Science.gov (United States)

    Greenhall, Charles A.

    2011-01-01

    This paper summarizes the author's work ontimescales based on Kalman filters that act upon the clock comparisons. The natural Kalman timescale algorithm tends to optimize long-term timescale stability at the expense of short-term stability. By subjecting each post-measurement error covariance matrix to a non-transparent reduction operation, one obtains corrected clocks with improved short-term stability and little sacrifice of long-term stability.

  18. Zebrafish circadian clocks: cells that see light.

    Science.gov (United States)

    Tamai, T K; Carr, A J; Whitmore, D

    2005-11-01

    In the classical view of circadian clock organization, the daily rhythms of most organisms were thought to be regulated by a central, 'master' pacemaker, usually located within neural structures of the animal. However, with the results of experiments performed in zebrafish, mammalian cell lines and, more recently, mammalian tissues, this view has changed to one where clock organization is now seen as being highly decentralized. It is clear that clocks exist in the peripheral tissues of animals as diverse as Drosophila, zebrafish and mammals. In the case of Drosophila and zebrafish, these tissues are also directly light-responsive. This light sensitivity and direct clock entrainability is also true for zebrafish cell lines and early-stage embryos. Using luminescent reporter cell lines containing clock gene promoters driving the expression of luciferase and single-cell imaging techniques, we have been able to show how each cell responds rapidly to a single light pulse by being shifted to a common phase, equivalent to the early day. This direct light sensitivity might be related to the requirement for light in these cells to activate the transcription of genes involved in DNA repair. It is also clear that the circadian clock in zebrafish regulates the timing of the cell cycle, demonstrating the wide impact that this light sensitivity and daily rhythmicity has on the biology of zebrafish.

  19. Adipose Clocks: Burning the Midnight Oil.

    Science.gov (United States)

    Henriksson, Emma; Lamia, Katja A

    2015-10-01

    Circadian clocks optimize the timing of physiological processes in synchrony with daily recurring and therefore predictable changes in the environment. Until the late 1990s, circadian clocks were thought to exist only in the central nervous systems of animals; elegant studies in cultured fibroblasts and using genetically encoded reporters in Drosophila melanogaster and in mice showed that clocks are ubiquitous and cell autonomous. These findings inspired investigations of the advantages construed by enabling each organ to independently adjust its function to the time of day. Studies of rhythmic gene expression in several organs suggested that peripheral organ clocks might play an important role in optimizing metabolic physiology by synchronizing tissue-intrinsic metabolic processes to cycles of nutrient availability and energy requirements. The effects of clock disruption in liver, pancreas, muscle, and adipose tissues support that hypothesis. Adipose tissues coordinate energy storage and utilization and modulate behavior and the physiology of other organs by secreting hormones known as "adipokines." Due to behavior- and environment-driven diurnal variations in supply and demand for chemical and thermal energy, adipose tissues might represent an important peripheral location for coordinating circadian energy balance (intake, storage, and utilization) over the whole organism. Given the complexity of adipose cell types and depots, the sensitivity of adipose tissue biology to age and diet composition, and the plethora of known and yet-to-be-discovered adipokines and lipokines, we have just begun to scratch the surface of understanding the role of circadian clocks in adipose tissues.

  20. A Miniature Wide Band Atomic Magnetometer

    Science.gov (United States)

    2011-12-01

    atomic magnetometer CSAC – Chip scale atomic clock DAC – Digital to Analog Converter DARPA – Defense Advanced Research Projects Agency DBR...Finally, the heater frequencies must not beat with the Laser servo’s modulation. Heater amplifiers This circuit is essentially an audio power...amplifier for the heater waveforms. The heater waveforms are made on the DAC board and then amplified in this circuit. The heater PCB consists of 4

  1. A new on-board imaging treatment technique for palliative and emergency treatments in radiation oncology

    Energy Technology Data Exchange (ETDEWEB)

    Held, Mareike

    2016-03-23

    This dissertation focuses on the use of on-board imaging systems as the basis for treatment planning, presenting an additional application for on-board images. A clinical workflow is developed to simulate, plan, and deliver a simple radiation oncology treatment rapidly, using 3D patient scans. The work focuses on an on-line dose planning and delivery process based on on-board images entirely performed with the patient set up on the treatment couch of the linear accelerator. This potentially reduces the time between patient simulation and treatment to about 30 minutes. The basis for correct dose calculation is the accurate image gray scale to tissue density calibration. The gray scale, which is defined in CT Numbers, is dependent on the energy spectrum of the beam. Therefore, an understanding of the physics characteristics of each on-board system is required to evaluate the impact on image quality, especially regarding the underlying cause of image noise, contrast, and non-uniformity. Modern on-board imaging systems, including kV and megavoltage (MV) cone beam (CB) CT as well as MV CT, are characterized in terms of image quality and stability. A library of phantom and patient CT images is used to evaluate the dose calculation accuracy for the on-board images. The dose calculation objective is to stay within 5% local dose differences compared to standard kV CT dose planning. The objective is met in many treatment cases. However, dose calculation accuracy depends on the anatomical treatment site. While on-board CT-based treatments of the head and extremities are predictable within 5% on all systems, lung tissue and air cavities may create local dose discrepancies of more than 5%. The image quality varies between the tested units. Consequently, the CT number-to-density calibration is defined independently for each system. In case of some imaging systems, the CT numbers of the images are dependent on the protocol used for on-board imaging, which defines the imaging dose

  2. Optical atomic phase reference and timing.

    Science.gov (United States)

    Hollberg, L; Cornell, E H; Abdelrahmann, A

    2017-08-06

    Atomic clocks based on laser-cooled atoms have made tremendous advances in both accuracy and stability. However, advanced clocks have not found their way into widespread use because there has been little need for such high performance in real-world/commercial applications. The drive in the commercial world favours smaller, lower-power, more robust compact atomic clocks that function well in real-world non-laboratory environments. Although the high-performance atomic frequency references are useful to test Einstein's special relativity more precisely, there are not compelling scientific arguments to expect a breakdown in special relativity. On the other hand, the dynamics of gravity, evidenced by the recent spectacular results in experimental detection of gravity waves by the LIGO Scientific Collaboration, shows dramatically that there is new physics to be seen and understood in space-time science. Those systems require strain measurements at less than or equal to 10(-20) As we discuss here, cold atom optical frequency references are still many orders of magnitude away from the frequency stability that should be achievable with narrow-linewidth quantum transitions and large numbers of very cold atoms, and they may be able to achieve levels of phase stability, ΔΦ/Φtotal ≤ 10(-20), that could make an important impact in gravity wave science.This article is part of the themed issue 'Quantum technology for the 21st century'. © 2017 The Author(s).

  3. Optical atomic phase reference and timing

    Science.gov (United States)

    Hollberg, L.; Cornell, E. H.; Abdelrahmann, A.

    2017-06-01

    Atomic clocks based on laser-cooled atoms have made tremendous advances in both accuracy and stability. However, advanced clocks have not found their way into widespread use because there has been little need for such high performance in real-world/commercial applications. The drive in the commercial world favours smaller, lower-power, more robust compact atomic clocks that function well in real-world non-laboratory environments. Although the high-performance atomic frequency references are useful to test Einstein's special relativity more precisely, there are not compelling scientific arguments to expect a breakdown in special relativity. On the other hand, the dynamics of gravity, evidenced by the recent spectacular results in experimental detection of gravity waves by the LIGO Scientific Collaboration, shows dramatically that there is new physics to be seen and understood in space-time science. Those systems require strain measurements at less than or equal to 10-20. As we discuss here, cold atom optical frequency references are still many orders of magnitude away from the frequency stability that should be achievable with narrow-linewidth quantum transitions and large numbers of very cold atoms, and they may be able to achieve levels of phase stability, ΔΦ/Φtotal ≤ 10-20, that could make an important impact in gravity wave science. This article is part of the themed issue 'Quantum technology for the 21st century'.

  4. Gated Clock Implementation of Arithmetic Logic Unit (ALU

    Directory of Open Access Journals (Sweden)

    Dr. Neelam R. Prakash

    2013-05-01

    Full Text Available Low power design has emerged as one of the challenging area in today’s ASIC (Application specific integrated circuit design. With continuous decrease in transistor size, power density is increasing and there is an urgent need for reduction in total power consumption. Clock gating is one most effective technique for low power synchronous circuit design. Clock gating technique in low power design is used to reduce the dynamic power consumption. Clock signal in a synchronous circuit is used for synchronization only and hence does not carry any important information. Since clock is applied to each block of a synchronous circuit, and clock switches for every cycle, clock power is the major part of dynamic power consumption in synchronous circuits. Clock gating is a well known technique to reduce clock power. In clock gating clock to an idle block is disabled. Thus significant amount of power consumption is reduced by employing clock gating. In this paper an ALU design is proposed employing Gated clock for its operation. Design simulation has been performed on Xilinx ISE design suite, and power calculation is done by Xilinx Xpower analyzer. Results show that approximately 17% of total clock power consumption is reduced by gated clock implementation.

  5. DESIGN OF TWO-PHASE SINUSOIDAL POWER CLOCK AND CLOCKED TRANSMISSION GATE ADIABATIC LOGIC CIRCUIT

    Institute of Scientific and Technical Information of China (English)

    Wang Pengjun; Yu Junjun

    2007-01-01

    First the research is conducted on the design of the two-phase sinusoidal power clock generator in this paper. Then the design of the new adiabatic logic circuit adopting the two-phase sinusoidal power clocks-Clocked Transmission Gate Adiabatic Logic (CTGAL) circuit is presented. This circuit makes use of the clocked transmission gates to sample the input signals, then the output loads are charged and discharged in a fully adiabatic manner by using bootstrapped N-Channel Metal Oxide Semiconductor (NMOS) and Complementary Metal Oxide Semiconductor (CMOS) latch structure.Finally, with the parameters of Taiwan Semiconductor Manufacturing Company (TSMC) 0.25 μm CMOS device, the transient energy consumption of CTGAL, Bootstrap Charge-Recovery Logic (BCRL)and Pass-transistor Adiabatic Logic (PAL) including their clock generators is simulated. The simulation result indicates that CTGAL circuit has the characteristic of remarkably low energy consumption.

  6. Optimized geometries for future generation optical lattice clocks

    CERN Document Server

    Krämer, Sebastian; Ritsch, Helmut

    2015-01-01

    Atoms trapped in magic wavelength optical lattices provide a Doppler- and collision-free dense ensemble of quantum emitters ideal for fast high precision spectroscopy and thus they are the basis of the best optical clock setups to date. Despite the minute optical dipole moments the inherent long range dipole-dipole interactions in such lattices at high densities generate measurable line shifts, increased dephasing and modified decay rates. We show that these effects can be resonantly enhanced or suppressed depending on lattice constant, geometry and excitation procedure. While these interactions generally limit the accuracy and precision of Ramsey spectroscopy, under optimal conditions collective effects can be exploited to yield zero effective shifts and long dipole lifetimes for a measurement precision beyond a noninteracting ensemble. In particular, 2D lattices with a lattice constant below the optical wavelength feature an almost ideal performance.

  7. Testing Lorentz Invariance with Laser-Cooled Cesium Atomic Frequency Standards

    Science.gov (United States)

    Klipstein, William M.

    2004-01-01

    This slide presentation reviews the Lorentz invariance testing during the proposed PARCS experiment. It includes information on the primary atomic reference clock in space (PARCS), cesium, laser cooling, and the vision for the future.

  8. Circadian clock feedback cycle through NAMPT-mediated NAD+ biosynthesis.

    Science.gov (United States)

    Ramsey, Kathryn Moynihan; Yoshino, Jun; Brace, Cynthia S; Abrassart, Dana; Kobayashi, Yumiko; Marcheva, Biliana; Hong, Hee-Kyung; Chong, Jason L; Buhr, Ethan D; Lee, Choogon; Takahashi, Joseph S; Imai, Shin-Ichiro; Bass, Joseph

    2009-05-01

    The circadian clock is encoded by a transcription-translation feedback loop that synchronizes behavior and metabolism with the light-dark cycle. Here we report that both the rate-limiting enzyme in mammalian nicotinamide adenine dinucleotide (NAD+) biosynthesis, nicotinamide phosphoribosyltransferase (NAMPT), and levels of NAD+ display circadian oscillations that are regulated by the core clock machinery in mice. Inhibition of NAMPT promotes oscillation of the clock gene Per2 by releasing CLOCK:BMAL1 from suppression by SIRT1. In turn, the circadian transcription factor CLOCK binds to and up-regulates Nampt, thus completing a feedback loop involving NAMPT/NAD+ and SIRT1/CLOCK:BMAL1.

  9. Body weight, metabolism and clock genes

    Directory of Open Access Journals (Sweden)

    Zanquetta Melissa M

    2010-08-01

    Full Text Available Abstract Biological rhythms are present in the lives of almost all organisms ranging from plants to more evolved creatures. These oscillations allow the anticipation of many physiological and behavioral mechanisms thus enabling coordination of rhythms in a timely manner, adaption to environmental changes and more efficient organization of the cellular processes responsible for survival of both the individual and the species. Many components of energy homeostasis exhibit circadian rhythms, which are regulated by central (suprachiasmatic nucleus and peripheral (located in other tissues circadian clocks. Adipocyte plays an important role in the regulation of energy homeostasis, the signaling of satiety and cellular differentiation and proliferation. Also, the adipocyte circadian clock is probably involved in the control of many of these functions. Thus, circadian clocks are implicated in the control of energy balance, feeding behavior and consequently in the regulation of body weight. In this regard, alterations in clock genes and rhythms can interfere with the complex mechanism of metabolic and hormonal anticipation, contributing to multifactorial diseases such as obesity and diabetes. The aim of this review was to define circadian clocks by describing their functioning and role in the whole body and in adipocyte metabolism, as well as their influence on body weight control and the development of obesity.

  10. Direct laser cooling Al+ ions optical clocks

    CERN Document Server

    Zhang, J; Luo, J; Lu, Z H

    2016-01-01

    Al$^+$ ions optical clock is a very promising optical frequency standard candidate due to its extremely small blackbody radiation shift. It has been successfully demonstrated with indirect cooled, quantum-logic-based spectroscopy technique. Its accuracy is limited by second-order Doppler shift, and its stability is limited by the number of ions that can be probed in quantum logic processing. We propose a direct laser cooling scheme of Al$^+$ ions optical clocks where both the stability and accuracy of the clocks are greatly improved. In the proposed scheme, two Al$^+$ ions traps are utilized. The first trap is used to trap a large number of Al$^+$ ions to improve the stability of the clock laser, while the second trap is used to trap a single Al$^+$ ions to provide the ultimate accuracy. Both traps are cooled with a continuous wave 167 nm laser. The expected clock laser stability can reach $9.0\\times10^{-17}/\\sqrt{\\tau}$. For the second trap, in addition to 167 nm laser Doppler cooling, a second stage pulsed ...

  11. Performance analysis of different organic Rankine cycle configurations on board liquefied natural gas-fuelled vessels

    DEFF Research Database (Denmark)

    Baldasso, Enrico; Andreasen, Jesper Graa; Meroni, Andrea

    2017-01-01

    Gas-fuelled shipping is expected to increase significantly in the coming years. Similarly, much effort is devoted to the study of waste heat recovery systems to be implemented on board ships. In this context, the organic Rankine cycle (ORC) technology is considered one of the most promising...... solutions. The ORC favorably compares to the steam Rankine cycle because of its simple layout and high efficiency, achievable by selecting a working fluid with desirable properties. This paper aims at assessing the fuel savings attainable by implementing ORC units on board vessels powered by liquefied...

  12. Evolutionary links between circadian clocks and photoperiodic diapause in insects.

    Science.gov (United States)

    Meuti, Megan E; Denlinger, David L

    2013-07-01

    In this article, we explore links between circadian clocks and the clock involved in photoperiodic regulation of diapause in insects. Classical resonance (Nanda-Hamner) and night interruption (Bünsow) experiments suggest a circadian basis for the diapause response in nearly all insects that have been studied. Neuroanatomical studies reveal physical connections between circadian clock cells and centers controlling the photoperiodic diapause response, and both mutations and knockdown of clock genes with RNA interference (RNAi) point to a connection between the clock genes and photoperiodic induction of diapause. We discuss the challenges of determining whether the clock, as a functioning module, or individual clock genes acting pleiotropically are responsible for the photoperiodic regulation of diapause, and how a stable, central circadian clock could be linked to plastic photoperiodic responses without compromising the clock's essential functions. Although we still lack an understanding of the exact mechanisms whereby insects measure day/night length, continued classical and neuroanatomical approaches, as well as forward and reverse genetic experiments, are highly complementary and should enable us to decipher the diverse ways in which circadian clocks have been involved in the evolution of photoperiodic induction of diapause in insects. The components of circadian clocks vary among insect species, and diapause appears to have evolved independently numerous times, thus, we anticipate that not all photoperiodic clocks of insects will interact with circadian clocks in the same fashion.

  13. Susceptibility of Redundant Versus Singular Clock Domains Implemented in SRAM-Based FPGA TMR Designs

    Science.gov (United States)

    Berg, Melanie D.; LaBel, Kenneth A.; Pellish, Jonathan

    2016-01-01

    We present the challenges that arise when using redundant clock domains due to their clock-skew. Radiation data show that a singular clock domain (DTMR) provides an improved TMR methodology for SRAM-based FPGAs over redundant clocks.

  14. Sugars, the clock and transition to flowering

    Directory of Open Access Journals (Sweden)

    Mohammad Reza eBolouri Moghaddam

    2013-02-01

    Full Text Available Sugars do not only act as source of energy, but they also act as signals in plants. This mini review summarizes the emerging links between sucrose-mediated signaling and the cellular networks involved in flowering time control and defense. Cross-talks with gibberellin (GA and jasmonate (JA signaling pathways are highlighted. The circadian clock fulfills a crucial role at the heart of cellular networks and the bilateral relation between sugar signaling and the clock is discussed. It is proposed that important factors controlling plant growth (DELLAs, PIFs, invertases and trehalose- 6-phosphate or T6P might fulfill central roles in the transition to flowering as well. The emerging concept of ‘sweet immunity’, modulated by the clock, might at least partly rely on a sucrose-specific signaling pathway that needs further exploration.

  15. Quantum clock: A critical discussion on spacetime

    CERN Document Server

    Burderi, Luciano; Iaria, Rosario

    2016-01-01

    We critically discuss the measure of very short time intervals. By means of a Gedankenexperiment, we describe an ideal clock based on the occurrence of completely random events. Many previous thought experiments have suggested fundamental Planck-scale limits on measurements of distance and time. Here we present a new type of thought experiment, based on a different type of clock, that provide further support for the existence of such limits. We show that the minimum time interval $\\Delta t$ that this clock can measure scales as the inverse of its size $\\Delta r$. This implies an uncertainty relation between space and time: $\\Delta r$ $\\Delta t$ $> G \\hbar / c^4$; where G, $\\hbar$ and c are the gravitational constant, the reduced Planck constant, and the speed of light, respectively. We outline and briefly discuss the implications of this uncertainty conjecture.

  16. Models of the Primordial Standard Clock

    CERN Document Server

    Chen, Xingang; Wang, Yi

    2014-01-01

    Oscillating massive fields in the primordial universe can be used as Standard Clocks. The ticks of these oscillations induce features in the density perturbations, which directly record the time evolution of the scale factor of the primordial universe, thus if detected, provide a direct evidence for the inflation scenario or the alternatives. In this paper, we construct a full inflationary model of primordial Standard Clock and study its predictions on the density perturbations. This model provides a full realization of several key features proposed previously. We compare the theoretical predictions from inflation and alternative scenarios with the Planck 2013 temperature data on Cosmic Microwave Background (CMB), and identify a statistically marginal but interesting candidate. We discuss how future CMB temperature and polarization data, non-Gaussianity analysis and Large Scale Structure data may be used to further test or constrain the Standard Clock signals.

  17. Biogeographic calibrations for the molecular clock.

    Science.gov (United States)

    Ho, Simon Y W; Tong, K Jun; Foster, Charles S P; Ritchie, Andrew M; Lo, Nathan; Crisp, Michael D

    2015-09-01

    Molecular estimates of evolutionary timescales have an important role in a range of biological studies. Such estimates can be made using methods based on molecular clocks, including models that are able to account for rate variation across lineages. All clock models share a dependence on calibrations, which enable estimates to be given in absolute time units. There are many available methods for incorporating fossil calibrations, but geological and climatic data can also provide useful calibrations for molecular clocks. However, a number of strong assumptions need to be made when using these biogeographic calibrations, leading to wide variation in their reliability and precision. In this review, we describe the nature of biogeographic calibrations and the assumptions that they involve. We present an overview of the different geological and climatic events that can provide informative calibrations, and explain how such temporal information can be incorporated into dating analyses.

  18. Sample-Clock Phase-Control Feedback

    Science.gov (United States)

    Quirk, Kevin J.; Gin, Jonathan W.; Nguyen, Danh H.; Nguyen, Huy

    2012-01-01

    To demodulate a communication signal, a receiver must recover and synchronize to the symbol timing of a received waveform. In a system that utilizes digital sampling, the fidelity of synchronization is limited by the time between the symbol boundary and closest sample time location. To reduce this error, one typically uses a sample clock in excess of the symbol rate in order to provide multiple samples per symbol, thereby lowering the error limit to a fraction of a symbol time. For systems with a large modulation bandwidth, the required sample clock rate is prohibitive due to current technological barriers and processing complexity. With precise control of the phase of the sample clock, one can sample the received signal at times arbitrarily close to the symbol boundary, thus obviating the need, from a synchronization perspective, for multiple samples per symbol. Sample-clock phase-control feedback was developed for use in the demodulation of an optical communication signal, where multi-GHz modulation bandwidths would require prohibitively large sample clock frequencies for rates in excess of the symbol rate. A custom mixedsignal (RF/digital) offset phase-locked loop circuit was developed to control the phase of the 6.4-GHz clock that samples the photon-counting detector output. The offset phase-locked loop is driven by a feedback mechanism that continuously corrects for variation in the symbol time due to motion between the transmitter and receiver as well as oscillator instability. This innovation will allow significant improvements in receiver throughput; for example, the throughput of a pulse-position modulation (PPM) with 16 slots can increase from 188 Mb/s to 1.5 Gb/s.

  19. Secure and self-stabilizing clock synchronization in sensor networks

    NARCIS (Netherlands)

    Hoepman, J.H.; Larsson, A.; Schiller, E.M.; Tsigas, P.

    2007-01-01

    In sensor networks, correct clocks have arbitrary starting offsets and nondeterministic fluctuating skews. We consider an adversary that aims at tampering with the clock synchronization by intercepting messages, replaying intercepted messages (after the adversary's choice of delay), and capturing no

  20. Unusual Maths clock or Reverse Traveling Salesman Problem

    Directory of Open Access Journals (Sweden)

    Valerij F. Ochkov

    2014-01-01

    Full Text Available The article discusses some of the mathematical problem, attached to the clock. We show how to use the clock in the classroom for mathematics to illustrate some mathematical problems 

  1. Ultracold photodissociation and progress towards a molecular lattice clock with 88 Sr

    Science.gov (United States)

    Lee, Chih-Hsi; McGuyer, Bart; McDonald, Mickey; Apfelback, Florian; Grier, Andrew; Zelevinsky, Tanya

    2016-05-01

    Techniques originally developed for the construction of atomic clocks can be adapted to the study of ultracold molecules, with applications ranging from studies of ultracold chemistry to searches for new physics. We present recent experimental results involving studies of fully quantum state-resolved photodissociation of 88 Sr2 molecules, as well as progress toward building a molecular clock. First, our system has allowed for precise, quantum state-resolved photodissociation studies, revealing not only excellent control over quantum states but also a more accurate way to describe the photodissociation of diatomic molecules and access ultracold chemistry. Second, the molecular clock will allow us to search for a possible time variation of the proton-electron mass ratio. The ``oscillator'' of such a molecular clock would consist of the frequency difference between two lasers driving a two-photon Raman transition between deeply and intermediately-bound rovibrational levels in the electronic ground state. Accomplishing this task requires exploring several research directions, including the precision spectroscopy of bound states and developing tools for the control and minimization of differential lattice light shifts.

  2. Clocking Scheme for Switched-Capacitor Circuits

    DEFF Research Database (Denmark)

    Steensgaard-Madsen, Jesper

    1998-01-01

    A novel clocking scheme for switched-capacitor (SC) circuits is presented. It can enhance the understanding of SC circuits and the errors caused by MOSFET (MOS) switches. Charge errors, and techniques to make SC circuits less sensitive to them are discussed.......A novel clocking scheme for switched-capacitor (SC) circuits is presented. It can enhance the understanding of SC circuits and the errors caused by MOSFET (MOS) switches. Charge errors, and techniques to make SC circuits less sensitive to them are discussed....

  3. The Large Water-Clock of Amphiaraeion

    Science.gov (United States)

    Theodossiou, E.; Manimanis, V. N.; Katsiotis, M.; Mantarakis, P.

    2010-07-01

    A very well preserved ancient water-clock exists at the Amphiaraeion, in Oropos, Greece. The Amphiaraeion, sanctuary of the mythical oracle and deified healer Amphiaraus, was active from the pre-classic period until the 5th Century A.D. In such a place the measurement of time, both day and night, was a necessity. Therefore, time was kept with both a conical sundial and a water-clock in the shape of a fountain, which, according to the archaeologists, dates to the 4th Century B.C.

  4. Determination of the thermal radiation effect on an optical strontium lattice clock; Bestimmung des Einflusses thermischer Strahlung auf eine optische Strontium-Gitteruhr

    Energy Technology Data Exchange (ETDEWEB)

    Middelmann, Thomas

    2013-05-31

    Optical clocks have the potential to be 100 times more accurate than current best cesium atomic clocks within a fraction of the averaging time. This corresponds to a fractional uncertainty of the clock frequency on the level of 10{sup -18} and requires highaccuracy knowledge of systematic frequency shifts, such that they can be avoided or corrected for. In strontium optical lattice clocks an ensemble of ultracold strontium atoms is confined in an optical lattice, to allow for spectroscopy of the reference transition 5s{sup 2} {sup 1}S{sub 0}-5s5p {sup 3}P{sub 0} in the Lamb-Dicke regime. The by far largest systematic frequency shift of the strontium clock transition is caused by its high sensitivity to blackbody radiation (BBR). The knowledge of the resulting frequency shift limited the achievable clock uncertainty to about 1 x 10{sup -16}. In this thesis for the first time an experimental approach was followed, to determine the sensitivity of the strontium clock transition to blackbody radiation. At an environmental temperature of 300 K the resulting frequency shift corresponds to 2.277 8(23) Hz. The achieved uncertainty contributes with 5 x 10{sup -18} to the fractional systematic uncertainty of the clock frequency. The determination is based on a precision measurement of the difference of static polarizabilities of the two clock states {Delta}{alpha}{sub dc} = {alpha}(5s5p {sup 3}P{sub 0})-{alpha}(5s{sup 2} {sup 1}S{sub 0}) = 4.078 73(11) x 10{sup -39} Cm{sup 2} /V. For this the de Stark shift of the clock transition has been measured in the accurately known electric field of a precision plate capacitor, which has been developed in this work. The attained static polarizability difference {Delta}{alpha}{sub dc} corresponds to the first term of a power series of the sensitivity to BBR. Higher orders are accumulated as dynamic part of the BBR shift. Which has been modelled using {Delta}{alpha}{sub dc} and experimental data for other atomic properties. To

  5. Frequency standards based on ultracold atoms in tests of general relativity, navigation and gravimetry

    Science.gov (United States)

    Khabarova, K. Yu.; Kudeyarov, K. S.; Kolachevsky, N. N.

    2017-06-01

    Research and development in the field of optical clocks based on ultracold atoms and ions have enabled the relative uncertainty in frequency to be reduced down to a few parts in 1018. The use of novel, precise frequency comparison methods opens up new possibilities for basic research (sensitive tests of general relativity, a search for a drift of fundamental constants and a search for ‘dark matter’) as well as for state-of-the-art navigation and gravimetry. We discuss the key methods that are used in creating precision clocks (including transportable clocks) based on ultracold atoms and ions and the feasibility of using them in resolving current relativistic gravimetry issues.

  6. New technologies for fire suppression on board naval craft, FiST

    NARCIS (Netherlands)

    Rahm, M.; Hiltz, J.; Wal, R. van der; Hertzberg, T.; Lindström, J.

    2014-01-01

    For three years Canada, Sweden and the Netherlands have been investigating new technologies for fire suppression on board naval crafts within the FiST project. The project has focused on a number of technologies. These included the evaluation of water based fire suppression systems and in particular

  7. Spacecube: A Family of Reconfigurable Hybrid On-Board Science Data Processors

    Science.gov (United States)

    Flatley, Thomas P.

    2015-01-01

    SpaceCube is a family of Field Programmable Gate Array (FPGA) based on-board science data processing systems developed at the NASA Goddard Space Flight Center (GSFC). The goal of the SpaceCube program is to provide 10x to 100x improvements in on-board computing power while lowering relative power consumption and cost. SpaceCube is based on the Xilinx Virtex family of FPGAs, which include processor, FPGA logic and digital signal processing (DSP) resources. These processing elements are leveraged to produce a hybrid science data processing platform that accelerates the execution of algorithms by distributing computational functions to the most suitable elements. This approach enables the implementation of complex on-board functions that were previously limited to ground based systems, such as on-board product generation, data reduction, calibration, classification, eventfeature detection, data mining and real-time autonomous operations. The system is fully reconfigurable in flight, including data parameters, software and FPGA logic, through either ground commanding or autonomously in response to detected eventsfeatures in the instrument data stream.

  8. On-board conversion of methanol to dimethyl ether as an alternative diesel fuel

    Energy Technology Data Exchange (ETDEWEB)

    Armbruster, H.; Heinzelmann, G.; Struis, R.; Stucki, S. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    The catalytic dehydration of methanol to dimethyl ether was investigated for application on-board a methanol fuelled vehicle. Several catalysts have been tested in a fixed bed reactor. Our approach is to develop a small and efficient reactor converting liquid MeOH under pressure and at low reaction temperatures. (author) 2 figs., 5 refs.

  9. Processor breadboard for on-board RFI detection and mitigation in MetOp-SG radiometers

    DEFF Research Database (Denmark)

    Skou, Niels; Kristensen, Steen S.; Kovanen, Arhippa;

    2015-01-01

    that the next generation MetOp satellites must include some kind of RFI detection and mitigation system at Ku band. This paper describes a breadboard processor that detects and mitigates RFI on-board the satellite. Thus cleaned data can be generated in real time, and following suitable integration, downloaded...

  10. The Application of a Mixed General/Special Purpose Hardware in On-Board SATSAT Processing

    NARCIS (Netherlands)

    Bierens, L.H.J.

    1998-01-01

    In SATSAR huge amounts of data are involved corresponding to data rates of 100 to 1000 Mbits/s. The communication system and the intermediate storage on-board the satellite must handle this increasing amount of data as well. Furthermore, ground stations must process, broadcast and archive the SAR da

  11. Survivability of chilled water networks on board ships when using dincs

    NARCIS (Netherlands)

    Smit, C.S.

    2012-01-01

    Fast reaction is required when a chilled water distribution network on board a naval ship is damaged. Without immediate isolation of the leakage area, all water supply is lost soon, with immense consequences for the ship’s operational state. The only solution for that is using an automated recovery

  12. On-Board File Management and Its Application in Flight Operations

    Science.gov (United States)

    Kuo, N.

    1998-01-01

    In this paper, the author presents the minimum functions required for an on-board file management system. We explore file manipulation processes and demonstrate how the file transfer along with the file management system will be utilized to support flight operations and data delivery.

  13. 75 FR 739 - Use of Additional Portable Oxygen Concentrator Devices on Board Aircraft

    Science.gov (United States)

    2010-01-06

    ... manner to add two more POC devices, Delphi Medical Systems' RS-00400 and Invacare Corporation's XPO2, to... documentation of the devices to the Department of Transportation's Docket Management System. That documentation... Aviation Regulation 106--Rules for Use of Portable Oxygen Concentrator Systems on Board...

  14. Forbush decrease effects on radiation dose received on-board aeroplanes.

    Science.gov (United States)

    Lantos, P

    2005-01-01

    Doses received on-board aeroplanes during deep Forbush decreases (FDs) have been recently measured and published. Using an operational model of dose calculation, the effects on aviation dose of the FDs observed from 1981 to 2003 using neutron monitors are studied and a simplified method to estimate dose variations from galactic cosmic ray variations during FDs is derived.

  15. THE DEVELOPMENT OF METHOD AND ON-BOARD DEVICES FOR COLLISION AVOIDANCE WHEN OVERTAKING

    Directory of Open Access Journals (Sweden)

    Podryhalo, M.

    2013-06-01

    Full Text Available A method for improving the safety of overtaking maneuver by using the on-board collision avoidance system, which has an increased assessment reliability of safety of vehicles overtaking that move in the same direction is offered. The proposed system takes into account the main factors that affect the overtaking maneuver.

  16. Evaluation of the on-board module building cotton harvest systems

    Science.gov (United States)

    The "on-board" module building systems from Case IH (Module Express 625 [ME 625]) and a system under final testing by John Deere (7760) represent the most radical change in the seed cotton handling and harvest system since the module builder was introduced over 30 years ago. The Module Express 625 c...

  17. Incorporate design of on-board network and inter-satellite network

    Science.gov (United States)

    Li, Bin; You, Zheng; Zhang, Chenguang

    2005-11-01

    In satellite, Data transferring is very important and must be reliable. This paper first introduced an on-board network based on Control Area Network (CAN). As a kind of field bus, CAN is simple and reliable, and has been tested by previous flights. In this paper, the CAN frame is redefined, including the identifier and message data, the addresses for source and destination as well as the frame types. On-board network provides datagram transmission and buffer transmission. Data gram transmission is used to carry out TTC functions, and buffer transmission is used to transfer mass data such as images. Inter-satellite network for satellite formation flying is not designed individually. It takes the advantage of TCP/IP model and inherits and extends on-board network protocols. The inter-satellite network includes a linkage layer, a network layer and a transport layer. There are 8 virtual channels for various space missions or requirements and 4 kinds of services to be selected. The network layer is designed to manage the whole net, calculate and select the route table and gather the network information, while the transport layer mainly routes data, which correspondingly makes it possible for communication between each two nodes. Structures of the linkage frame and transport layer data segment are similar, thus there is no complex packing and unpacking. At last, this paper gives the methods for data conversion between the on-board network and the inter-satellite network.

  18. Immunometabolism: Is it under the eye of the clock?

    OpenAIRE

    Early, James O.; Curtis, Anne M.

    2016-01-01

    Molecular clocks allow an organism to track time of day, providing the means to anticipate and respond to the daily changes within the environment. In mammals the molecular clock consists of a network of proteins that form auto-regulatory feedback loops that drive rhythms in physiology and behavior. In recent times the extent to which the molecular clock controls key metabolic and immune pathways has begun to emerge. For example, the main clock protein BMAL1 has been linked to mitochondrial m...

  19. Circadian clocks - the fall and rise of physiology

    NARCIS (Netherlands)

    Roenneberg, Till; Merrow, Martha

    2005-01-01

    Circadian clocks control the daily life of most light-sensitive organisms- from cyanobacteria to humans. Molecular processes generate cellular rhythmicity, and cellular clocks in animals coordinate rhythms through interaction ( known as coupling). This hierarchy of clocks generates a complex, simila

  20. MICROBIOLOGICAL EFFECTS OF ON-BOARD FISHING VESSEL HANDLING IN MERLUCCIUS MERLUCCIUS

    Directory of Open Access Journals (Sweden)

    P. Serratore

    2011-01-01

    Full Text Available The purpose of the present study was to determine the impact of different manipulation techniques applied on board fishing vessel, on the microbiological quality of the flesh of European hake (Merluccius merluccius during storage at +3°C ± 1°C for a time (T of 10 days after landing (T1-T10. Samples of fish were taken from a fishing vessel of the Adriatic Sea and from one of the Tyrrhenian Sea, treated on-board under different icing conditions: 1 a low ice/product weight ratio and 2 an optimal ice/product weight ratio, up to 1:3 (3. Spoilage bacteria as Total Bacterial Count (TBC and specific spoilage bacteria as Sulphide Producing Bacteria (SPB were enumerated in fish flesh as Colony Forming Units (CFU/g on Plate Count Agar and Lyngby Agar at 20°C for 3-5 days. TBC of the Adriatic fishes (gutted on-board resulted 103 UFC/g at T1-T6, and 104-105 at T10, whereas TBC of the Tyrrhenian fishes (not gutted on-board resulted 10-102 UFC/g at T2- T3, 103 at T6, and 104-105 at T10. SPB resulted 10- 102 UFC/g at T1-T6, and 103- 104 at T10, with absolute values higher in the Adriatic fishes, in respect with the Tyrrhenian fishes, and in the low icing conditions in respect with the optimal icing condition. At the experimented condition, the lowering of the microbiological quality of fish flesh during storage, seems to be more dependent on the gutting versus not gutting on-board practice rather than on the low versus optimal icing treatment.

  1. Atom interferometry and the Einstein equivalence principle

    CERN Document Server

    Wolf, Peter; Bordé, Christian J; Reynaud, Serge; Salomon, Christophe; Cohen-Tannoudji, Clande

    2011-01-01

    The computation of the phase shift in a symmetric atom interferometer in the presence of a gravitational field is reviewed. The difference of action-phase integrals between the two paths of the interferometer is zero for any Lagrangian which is at most quadratic in position and velocity. We emphasize that in a large class of theories of gravity the atom interferometer permits a test of the weak version of the equivalence principle (or universality of free fall) by comparing the acceleration of atoms with that of ordinary bodies, but is insensitive to that aspect of the equivalence principle known as the gravitational redshift or universality of clock rates.

  2. The salient features of the clock

    DEFF Research Database (Denmark)

    Ebbesen, Toke Riis

    2005-01-01

    of functional semiotics is explained in short terms and then further demonstrated in the analysis of a basic mechanical alarm clock. On this ground, the digital watch and digital design products in general are characterised and three possible avenues for the interpretation of the interactive possibilities...

  3. Circadian clocks: Omnes viae Romam ducunt.

    Science.gov (United States)

    Roenneberg, T; Merrow, M

    2000-10-19

    The circadian clock in all organisms is so intimately linked to light reception that it appears as if evolution has simply wired a timer into the mechanism that processes photic information. Several recent studies have provided new insights into the role of light input pathways in the circadian system of Arabidopsis.

  4. The mammalian retina as a clock

    Science.gov (United States)

    Tosini, Gianluca; Fukuhara, Chiaki

    2002-01-01

    Many physiological, cellular, and biochemical parameters in the retina of vertebrates show daily rhythms that, in many cases, also persist under constant conditions. This demonstrates that they are driven by a circadian pacemaker. The presence of an autonomous circadian clock in the retina of vertebrates was first demonstrated in Xenopus laevis and then, several years later, in mammals. In X. laevis and in chicken, the retinal circadian pacemaker has been localized in the photoreceptor layer, whereas in mammals, such information is not yet available. Recent advances in molecular techniques have led to the identification of a group of genes that are believed to constitute the molecular core of the circadian clock. These genes are expressed in the retina, although with a slightly different 24-h profile from that observed in the central circadian pacemaker. This result suggests that some difference (at the molecular level) may exist between the retinal clock and the clock located in the suprachiasmatic nuclei of hypothalamus. The present review will focus on the current knowledge of the retinal rhythmicity and the mechanisms responsible for its control.

  5. Radium single-ion optical clock

    NARCIS (Netherlands)

    Versolato, O. O.; Wansbeek, L. W.; Jungmann, K.; Timmermans, R. G. E.; Willmann, L.; Wilschut, H. W.

    2011-01-01

    We explore the potential of the electric quadrupole transitions $7s\\,^2S_{1/2}$ - $6d\\,^2D_{3/2}$, $6d\\,^2D_{5/2}$ in radium isotopes as single-ion optical frequency standards. The frequency shifts of the clock transitions due to external fields and the corresponding uncertainties are calculated.

  6. Circadian clock proteins in prokaryotes: hidden rhythms?

    Directory of Open Access Journals (Sweden)

    Maria eLoza-Correa

    2010-12-01

    Full Text Available Circadian clock genes are vital features of eukaryotes that have evolved such that organisms can adapt to our planet’s rotation in order to anticipate the coming day or night as well as unfavorable seasons. This circadian clock uses oscillation as a timekeeping element. However, circadian clock mechanisms exist also in prokaryotes. The circadian clock of Cyanobacteria is well studied. It is regulated by a cluster of three genes: kaiA, kaiB and kaiC. In this review, we will discuss the circadian system in cyanobacteria, and provide an overview and up-dated phylogenetic analysis of prokaryotic organisms that contain the main circadian genes. It is evident that the evolution of the kai genes has been influenced by lateral transfers but further and deeper studies are needed to get an in depth understanding of the exact evolutionary history of these genes. Interestingly, Legionella pneumophila an environmental bacterium and opportunistic human pathogen that parasitizes protozoa in fresh water environments also contains kaiB and kaiC, but their functions are not known. All of the residues described for the biochemical functions of the main pacemaker KaiC in Synechoccous elongates are also conserved in the L. pneumophila KaiC protein.

  7. Biochemical basis for the biological clock

    Science.gov (United States)

    Morre, D. James; Chueh, Pin-Ju; Pletcher, Jake; Tang, Xiaoyu; Wu, Lian-Ying; Morre, Dorothy M.

    2002-01-01

    NADH oxidases at the external surface of plant and animal cells (ECTO-NOX proteins) exhibit stable and recurring patterns of oscillations with potentially clock-related, entrainable, and temperature-compensated period lengths of 24 min. To determine if ECTO-NOX proteins might represent the ultradian time keepers (pacemakers) of the biological clock, COS cells were transfected with cDNAs encoding tNOX proteins having a period length of 22 min or with C575A or C558A cysteine to alanine replacements having period lengths of 36 or 42 min. Here we demonstrate that such transfectants exhibited 22, 36, or 40 to 42 h circadian patterns in the activity of glyceraldehyde-3-phosphate dehydrogenase, a common clock-regulated protein, in addition to the endogenous 24 h circadian period length. The fact that the expression of a single oscillatory ECTO-NOX protein determines the period length of a circadian biochemical marker (60 X the ECTO-NOX period length) provides compelling evidence that ECTO-NOX proteins are the biochemical ultradian drivers of the cellular biological clock.

  8. Internal clock formulation of quantum mechanics

    Science.gov (United States)

    Małkiewicz, Przemysław; Miroszewski, Artur

    2017-08-01

    The basic tenet of the present work is the assumption of the lack of external and fixed time in the Universe. This assumption is best embodied by general relativity, which replaces the fixed space-time structure with the gravitational field, which is subject to dynamics. The lack of time does not imply the lack of evolution but rather brings to the forefront the role of internal clocks which are some largely arbitrary internal degrees of freedom with respect to which the evolution of timeless systems can be described. We take this idea seriously and try to understand what it implies for quantum mechanics when the fixed external time is replaced by an arbitrary internal clock. We put the issue in a solid, mathematically rigorous framework. We find that the dynamical interpretation of a quantum state of a timeless system depends on the employed internal clock. In particular, we find that the continuous spectra of well-known dynamical observables like the position of a free particle on the real line may turn discrete if measured in unusual clocks. We discuss the meaning of our result for attempts at quantization of global gravitational degrees of freedom.

  9. Circadian clocks - from genes to complex behaviour

    NARCIS (Netherlands)

    Roenneberg, Till; Merrow, Martha

    1999-01-01

    Circadian clocks control temporal structure in practically all organisms and on all levels of biology, from gene expression to complex behaviour and cognition. Over the last decades, research has begun to unravel the physiological and, more recently, molecular mechanisms that underlie this endogenou

  10. Circadian Clocks in the Immune System.

    Science.gov (United States)

    Labrecque, Nathalie; Cermakian, Nicolas

    2015-08-01

    The immune system is a complex set of physiological mechanisms whose general aim is to defend the organism against non-self-bodies, such as pathogens (bacteria, viruses, parasites), as well as cancer cells. Circadian rhythms are endogenous 24-h variations found in virtually all physiological processes. These circadian rhythms are generated by circadian clocks, located in most cell types, including cells of the immune system. This review presents an overview of the clocks in the immune system and of the circadian regulation of the function of immune cells. Most immune cells express circadian clock genes and present a wide array of genes expressed with a 24-h rhythm. This has profound impacts on cellular functions, including a daily rhythm in the synthesis and release of cytokines, chemokines and cytolytic factors, the daily gating of the response occurring through pattern recognition receptors, circadian rhythms of cellular functions such as phagocytosis, migration to inflamed or infected tissue, cytolytic activity, and proliferative response to antigens. Consequently, alterations of circadian rhythms (e.g., clock gene mutation in mice or environmental disruption similar to shift work) lead to disturbed immune responses. We discuss the implications of these data for human health and the areas that future research should aim to address.

  11. Using circadian entrainment to find cryptic clocks

    NARCIS (Netherlands)

    Eelderink-Chen, Zheng; Olmedo, Maria; Bosman, Jasper; Merrow, Martha

    2015-01-01

    Three properties are most often attributed to the circadian clock: a ca. 24-h free-running rhythm, temperature compensation of the circadian rhythm, and its entrainment to zeitgeber cycles. Relatively few experiments, however, are performed under entrainment conditions. Rather, most chronobiology pr

  12. Current Status of the Molecular Clock Hypothesis

    Science.gov (United States)

    Hermann, Gilbert

    2003-01-01

    Molecular genetics is a rapidly changing field with new developments almost from day to day. One interesting hypothesis that has come from everyone's ability to sequence proteins and/or genes is that of the molecular clock. This hypothesis postulates that homologous sequences of DNA and thus macro molecules evolve at a constant and invariable rate…

  13. Clock Synchronization for Multihop Wireless Sensor Networks

    Science.gov (United States)

    Solis Robles, Roberto

    2009-01-01

    In wireless sensor networks, more so generally than in other types of distributed systems, clock synchronization is crucial since by having this service available, several applications such as media access protocols, object tracking, or data fusion, would improve their performance. In this dissertation, we propose a set of algorithms to achieve…

  14. The Atomic and Nuclear Physics of Atomic EDMs

    Science.gov (United States)

    Chupp, Timothy

    2016-09-01

    Atomic Electric-Dipole-Moment (EDM) measurements employ low-energy atomic and precision-measurement techniques to measure the effects of elementary particle forces that affect the distribution of charge and mass in the nucleus, which is probed by the atomic electrons. Experiments and their interpretation strongly overlap atomic and nuclear physics in the experimental and theoretical problems presented. On the experimental side, the atomic EDM couples to electric fields while the magnetic dipole moment couples to magnetic fields requiring exquisite control and characerization of the magnetic fields. Measuring the tiny frequency shifts requires clock-comparisons and a large signal-to-noise ratio for frequency resolution much smaller than the linewidths, which are lmitied by observation times. To address the experimental challenges, I will discuss systematic effects related to magnetic fields and techniques of magnetometry and co-magntometery as well as optical pumping and related techniques that enhance signal-to-noise. I will also address the interpretation of atomic EDMs in terms of a set of low-energy parameters that relate to effective-field-theory coefficients, and I will empshaize the need for improved calculations from both atomic-theory and nuclear theory.

  15. Pineal clock gene oscillation is disturbed in Alzheimer's disease, due to functional disconnection from the "master clock".

    NARCIS (Netherlands)

    Wu, Y.-H.; Fischer, D.F.; Kalsbeek, A.; Garidou-Boof, M.-L.; Vliet, J. van der; Heijningen, C. van; Liu, R.-Y.; Zhou, J.-N.; Swaab, D.F.

    2006-01-01

    The suprachiasmatic nucleus (SCN) is the "master clock" of the mammalian brain. It coordinates the peripheral clocks in the body, including the pineal clock that receives SCN input via a multisynaptic noradrenergic pathway. Rhythmic pineal melatonin production is disrupted in Alzheimer's disease (AD

  16. Real-Time On-Board Airborne Demonstration of High-Speed On-Board Data Processing for Science Instruments (HOPS)

    Science.gov (United States)

    Beyon, Jeffrey Y.; Ng, Tak-Kwong; Davis, Mitchell J.; Adams, James K.; Bowen, Stephen C.; Fay, James J.; Hutchinson, Mark A.

    2015-01-01

    The project called High-Speed On-Board Data Processing for Science Instruments (HOPS) has been funded by NASA Earth Science Technology Office (ESTO) Advanced Information Systems Technology (AIST) program since April, 2012. The HOPS team recently completed two flight campaigns during the summer of 2014 on two different aircrafts with two different science instruments. The first flight campaign was in July, 2014 based at NASA Langley Research Center (LaRC) in Hampton, VA on the NASA's HU-25 aircraft. The science instrument that flew with HOPS was Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) CarbonHawk Experiment Simulator (ACES) funded by NASA's Instrument Incubator Program (IIP). The second campaign was in August, 2014 based at NASA Armstrong Flight Research Center (AFRC) in Palmdale, CA on the NASA's DC-8 aircraft. HOPS flew with the Multifunctional Fiber Laser Lidar (MFLL) instrument developed by Excelis Inc. The goal of the campaigns was to perform an end-to-end demonstration of the capabilities of the HOPS prototype system (HOPS COTS) while running the most computationally intensive part of the ASCENDS algorithm real-time on-board. The comparison of the two flight campaigns and the results of the functionality tests of the HOPS COTS are presented in this paper.

  17. Comparing a mercury optical lattice clock with microwave and optical frequency standards

    Science.gov (United States)

    Tyumenev, R.; Favier, M.; Bilicki, S.; Bookjans, E.; Le Targat, R.; Lodewyck, J.; Nicolodi, D.; Le Coq, Y.; Abgrall, M.; Guéna, J.; De Sarlo, L.; Bize, S.

    2016-11-01

    In this paper we report the evaluation of an optical lattice clock based on neutral mercury with a relative uncertainty of 1.7× {10}-16. Comparing this characterized frequency standard to a 133Cs atomic fountain we determine the absolute frequency of the {}1{{{S}}}0\\to {}3{{{P}}}0 transition of 199Hg as {ν }{Hg}=1128 575 290 808 154.62 {Hz}+/- 0.19 {Hz}({statistical})+/- 0.38 {Hz} (systematic), limited solely by the realization of the SI second. Furthermore, by comparing the mercury optical lattice clock to a 87Rb atomic fountain, we determine for the first time to our knowledge the ratio between the 199Hg clock transition and the 87Rb ground state hyperfine transition. Finally we present a direct optical to optical measurement of the 199Hg/87Sr frequency ratio. The obtained value of {ν }{Hg}/{ν }{Sr} = 2.629 314 209 898 909 15 with a fractional uncertainty of 1.8× {10}-16 is in excellent agreement with a similar measurement obtained by Yamanaka et al (2015 Phys. Rev. Lett. 114 230801). This makes this frequency ratio one of the few physical quantities agreed upon by different laboratories to this level of uncertainty. Frequency ratio measurements of the kind reported in this paper have a strong impact for frequency metrology and fundamental physics as they can be used to monitor putative variations of fundamental constants.

  18. Clock measurements to improve the geopotential determination

    Science.gov (United States)

    Lion, Guillaume; Panet, Isabelle; Delva, Pacôme; Wolf, Peter; Bize, Sébastien; Guerlin, Christine

    2017-04-01

    Comparisons between optical clocks with an accuracy and stability approaching the 10-18 in term of relative frequency shift are opening new perspectives for the direct determination of geopotential at a centimeter-level accuracy in geoid height. However, so far detailed quantitative estimates of the possible improvement in geoid determination when adding such clock measurements to existing data are lacking. In this context, the present work aims at evaluating the contribution of this new kind of direct measurements in determining the geopotential at high spatial resolution (10 km). We consider the Massif Central area, marked by smooth, moderate altitude mountains and volcanic plateaus leading to variations of the gravitational field over a range of spatial scales. In such type of region, the scarcity of gravity data is an important limitation in deriving accurate high resolution geopotential models. We summarize our methodology to assess the contribution of clock data in the geopotential recovery, in combination with ground gravity measurements. We sample synthetic gravity and disturbing potential data from a spherical harmonics geopotential model, and a topography model, up to 10 km resolution; we also build a potential control grid. From the synthetic data, we estimate the disturbing potential by least-squares collocation. Finally, we assess the quality of the reconstructed potential by comparing it to that of the control grid. We show that adding only a few clock data reduces the reconstruction bias significantly and improves the standard deviation by a factor 3. We discuss the role of different parameters, such as the effect of the data coverage and data quality on these results, the trade-off between the measurement noise level and the number of data, and the optimization of the clock data network.

  19. Maximum likelihood molecular clock comb: analytic solutions.

    Science.gov (United States)

    Chor, Benny; Khetan, Amit; Snir, Sagi

    2006-04-01

    Maximum likelihood (ML) is increasingly used as an optimality criterion for selecting evolutionary trees, but finding the global optimum is a hard computational task. Because no general analytic solution is known, numeric techniques such as hill climbing or expectation maximization (EM), are used in order to find optimal parameters for a given tree. So far, analytic solutions were derived only for the simplest model--three taxa, two state characters, under a molecular clock. Four taxa rooted trees have two topologies--the fork (two subtrees with two leaves each) and the comb (one subtree with three leaves, the other with a single leaf). In a previous work, we devised a closed form analytic solution for the ML molecular clock fork. In this work, we extend the state of the art in the area of analytic solutions ML trees to the family of all four taxa trees under the molecular clock assumption. The change from the fork topology to the comb incurs a major increase in the complexity of the underlying algebraic system and requires novel techniques and approaches. We combine the ultrametric properties of molecular clock trees with the Hadamard conjugation to derive a number of topology dependent identities. Employing these identities, we substantially simplify the system of polynomial equations. We finally use tools from algebraic geometry (e.g., Gröbner bases, ideal saturation, resultants) and employ symbolic algebra software to obtain analytic solutions for the comb. We show that in contrast to the fork, the comb has no closed form solutions (expressed by radicals in the input data). In general, four taxa trees can have multiple ML points. In contrast, we can now prove that under the molecular clock assumption, the comb has a unique (local and global) ML point. (Such uniqueness was previously shown for the fork.).

  20. Suppression of Clock Shifts at Magnetic-Field-Insensitive Transitions

    Science.gov (United States)

    Arnold, K. J.; Barrett, M. D.

    2016-10-01

    We show that it is possible to significantly reduce rank 2 tensor shifts of a clock transition by operating at a judiciously chosen magnetic-field-insensitive point. In some cases shifts are almost completely eliminated making the transition an effective J =0 to J =0 candidate. This significantly improves the feasibility of a recent proposal for clock operation with large ion crystals. For such multi-ion clocks, geometric constraints and selection rules naturally divide clock operation into two categories based on the orientation of the magnetic field. We discuss the limitations imposed on each type and how calibrations might be carried out for clock operation.

  1. Suppression of clock shifts at field-insensitive transitions

    CERN Document Server

    Arnold, Kyle J

    2016-01-01

    We show that it is possible to significantly reduce quadrupole and tensor polarizability shifts of a clock transition by operating at a judiciously chosen field-insensitive point. In some cases shifts are almost completely eliminated making the transition an effective J = 0 to J = 0 candidate. This significantly improves the feasibility of a recent proposal for clock operation with large ion crystals. For such multi-ion clocks, geometric constraints and selection rules naturally divide clock operation into two categories based on the orientation of the magnetic field. We discuss the limitations imposed on each type and how calibrations might be carried out for clock operation.

  2. USING THE INFORMATION OF ON-BOARD DIAGNOSTIC SYSTEMS IN DETERMINING THE TECHNICAL STATE OF THE LOCOMOTIVE

    Directory of Open Access Journals (Sweden)

    B. Ye. Bodnar

    2008-12-01

    Full Text Available The issues of increase of efficiency of information processing by оn-board systems of diagnostics of locomotives are considered. The examples of information processing by the on-board system of diagnostics of electric locomotives DE1 are presented. The suggestions on improvement of systematization and processing of information by on-board systems of diagnostics are given.

  3. Surveillance study of vector species on board passenger ships, Risk factors related to infestations

    Directory of Open Access Journals (Sweden)

    Hatzoglou Chrissi

    2008-03-01

    Full Text Available Abstract Background Passenger ships provide conditions suitable for the survival and growth of pest populations. Arthropods and rodents can gain access directly from the ships' open spaces, can be carried in shiploads, or can be found on humans or animals as ectoparasites. Vectors on board ships may contaminate stored foods, transmit illness on board, or, introduce diseases in new areas. Pest species, ship areas facilitating infestations, and different risk factors related to infestations were identified in 21 ferries. Methods 486 traps for insects and rodents were placed in 21 ferries. Archives of Public Health Authorities were reviewed to identify complaints regarding the presence of pest species on board ferries from 1994 to 2004. A detail questionnaire was used to collect data on ship characteristics and pest control practices. Results Eighteen ferries were infested with flies (85.7%, 11 with cockroaches (52.3%, three with bedbugs, and one with fleas. Other species had been found on board were ants, spiders, butterflies, beetles, and a lizard. A total of 431 Blattella germanica species were captured in 28 (9.96% traps, and 84.2% of them were nymphs. One ship was highly infested. Cockroach infestation was negatively associated with ferries in which Hazard Analysis Critical Control Point system was applied to ensure food safety on board (Relative Risk, RR = 0.23, p = 0.03, and positively associated with ferries in which cockroaches were observed by crew (RR = 4.09, p = 0.007, no cockroach monitoring log was kept (RR = 5.00, p = 0.02, and pesticide sprays for domestic use were applied by crew (RR = 4.00, p = 0.05. Cockroach infested ships had higher age (p = 0.03. Neither rats nor mice were found on any ship, but three ferries had been infested with a rodent in the past. Conclusion Integrated pest control programs should include continuing monitoring for a variety of pest species in different ship locations; pest control measures should be more

  4. Cold Atom Source Containing Multiple Magneto-Optical Traps

    Science.gov (United States)

    Ramirez-Serrano, Jaime; Kohel, James; Kellogg, James; Lim, Lawrence; Yu, Nan; Maleki, Lute

    2007-01-01

    An apparatus that serves as a source of a cold beam of atoms contains multiple two-dimensional (2D) magneto-optical traps (MOTs). (Cold beams of atoms are used in atomic clocks and in diverse scientific experiments and applications.) The multiple-2D-MOT design of this cold atom source stands in contrast to single-2D-MOT designs of prior cold atom sources of the same type. The advantages afforded by the present design are that this apparatus is smaller than prior designs.

  5. Molecular-clock methods for estimating evolutionary rates and timescales.

    Science.gov (United States)

    Ho, Simon Y W; Duchêne, Sebastián

    2014-12-01

    The molecular clock presents a means of estimating evolutionary rates and timescales using genetic data. These estimates can lead to important insights into evolutionary processes and mechanisms, as well as providing a framework for further biological analyses. To deal with rate variation among genes and among lineages, a diverse range of molecular-clock methods have been developed. These methods have been implemented in various software packages and differ in their statistical properties, ability to handle different models of rate variation, capacity to incorporate various forms of calibrating information and tractability for analysing large data sets. Choosing a suitable molecular-clock model can be a challenging exercise, but a number of model-selection techniques are available. In this review, we describe the different forms of evolutionary rate heterogeneity and explain how they can be accommodated in molecular-clock analyses. We provide an outline of the various clock methods and models that are available, including the strict clock, local clocks, discrete clocks and relaxed clocks. Techniques for calibration and clock-model selection are also described, along with methods for handling multilocus data sets. We conclude our review with some comments about the future of molecular clocks.

  6. Arabidopsis circadian clock and photoperiodism: time to think about location.

    Science.gov (United States)

    Imaizumi, Takato

    2010-02-01

    Plants possess a circadian clock that enables them to coordinate internal biological events with external daily changes. Recent studies in Arabidopsis revealed that tissue-specific clock components exist and that the clock network architecture also varies within different organs. These findings indicate that the makeup of circadian clock(s) within a plant is quite variable. Plants utilize the circadian clock to measure day-length changes for regulating seasonal responses, such as flowering. To ensure that flowering occurs under optimum conditions, the clock regulates diurnal CONSTANS (CO) expression. Subsequently, CO protein induces FLOWERING LOCUS T (FT) expression which leads to flowering. It is emerging that both CO and FT expression are intricately controlled by groups of transcription factors with overlapping functions. Copyright 2009 Elsevier Ltd. All rights reserved.

  7. A Faster Algorithm for Solving One-Clock Priced Timed Games

    DEFF Research Database (Denmark)

    Hansen, Thomas Dueholm; Ibsen-Jensen, Rasmus; Miltersen, Peter Bro

    2012-01-01

    previously known time bound for solving one-clock priced timed games was 2^(O(n^2+m)), due to Rutkowski. For our improvement, we introduce and study a new algorithm for solving one-clock priced timed games, based on the sweep-line technique from computational geometry and the strategy iteration paradigm from...... the algorithmic theory of Markov decision processes. As a corollary, we also improve the analysis of previous algorithms due to Bouyer, Cassez, Fleury, and Larsen; and Alur, Bernadsky, and MadhusudanWe present a construction of log-depth formulae for various threshold functions based on atomic threshold gates...... in this setting that is efficient and actively secure against a constant fraction of corrupted parties, a long standing open problem. Finally, we show a negative result on usage of our scheme for pseudorandom secret sharing as defined by Cramer, Damgård and Ishai...

  8. Light-shift elimination in Generalized Hyper-Ramsey quantum clocks

    CERN Document Server

    Zanon-Willette, Thomas; Arimondo, Ennio

    2015-01-01

    We present a new generation of quantum clocks absolutely free from ac Stark-shift based on generalized hyper-Ramsey resonances with separated oscillating fields. Sequences of composite laser pulses with specific selection of phases, frequency detunings and durations are combined to generate a very efficient and robust frequency locking signal with a perfect elimination of the light-shift from off resonant states. Laser phase-step modulations during interactions with electromagnetic fields are applied in order to decouple the unperturbed frequency measurement from the laser's intensity. The frequency lock point is protected against laser pulse area fluctuations and errors in potentially applied frequency shift compensations. Quantum clocks based on weakly allowed or completely forbidden optical transitions in atoms, ions, molecules and nuclei will benefit from these hyper-stable laser frequency stabilization schemes to reach relative accuracies well below the 10$^{-18}$ level.

  9. Probe light-shift elimination in generalized hyper-Ramsey quantum clocks

    Science.gov (United States)

    Zanon-Willette, T.; de Clercq, E.; Arimondo, E.

    2016-04-01

    We present an interrogation scheme for the next generation of quantum clocks to suppress frequency shifts induced by laser probing fields that are themselves based on generalized hyper-Ramsey resonances. Sequences of composite laser pulses with a specific selection of phases, frequency detunings, and durations are combined to generate a very efficient and robust frequency locking signal with an almost perfect elimination of the light shift from off-resonant states and to decouple the unperturbed frequency measurement from the laser's intensity. The frequency lock point generated from synthesized error signals using either π /4 or 3 π /4 laser phase steps during the intermediate pulse is tightly protected against large laser-pulse area variations and errors in potentially applied frequency shift compensations. Quantum clocks based on weakly allowed or completely forbidden optical transitions in atoms, ions, molecules, and nuclei will benefit from these hyperstable laser frequency stabilization schemes to reach relative accuracies below the 10-18 level.

  10. Comparison of Two Independent Sr Optical Clocks with 1*10^-17 Stability at 10^3 s

    CERN Document Server

    Nicholson, T L; Williams, J R; Bloom, B J; Bishof, M; Swallows, M D; Campbell, S L; Ye, J

    2012-01-01

    Many-particle optical lattice clocks have the potential for unprecedented measurement precision and stability due to their low quantum projection noise (QPN). However, this potential has so far never been realized because clock stability has been limited by frequency noise of optical local oscillators. By synchronously probing two 87Sr lattice systems using a laser with a thermal noise floor of 1*10^-15, we remove classically correlated laser noise from the inter-comparison, but this approach does not improve the stability of an independent clock. With an improved optical oscillator that has a 1*10^-16 thermal noise floor, we demonstrate an order of magnitude improvement over the best reported independent clock stability, achieving a record fractional instability of 1*10^-17 in 1000 s of averaging time for synchronous or asynchronous comparisons. This result is within a factor of 2 of the combined QPN limit for a 160 ms probe time with ~10^3 atoms in each clock. We further demonstrate that even at this high p...

  11. Scientific goals achievable with radiation monitor measurements on board gravitational wave interferometers in space

    Science.gov (United States)

    Grimani, C.; Boatella, C.; Chmeissani, M.; Fabi, M.; Finetti, N.; Lobo, A.; Mateos, I.

    2012-06-01

    Cosmic rays and energetic solar particles constitute one of the most important sources of noise for future gravitational wave detectors in space. Radiation monitors were designed for the LISA Pathfinder (LISA-PF) mission. Similar devices were proposed to be placed on board LISA and ASTROD. These detectors are needed to monitor the flux of energetic particles penetrating mission spacecraft and inertial sensors. However, in addition to this primary use, radiation monitors on board space interferometers will carry out the first multipoint observation of solar energetic particles (SEPs) at small and large heliolongitude intervals and at very different distances from Earth with minor normalization errors. We illustrate the scientific goals that can be achieved in solar physics and space weather studies with these detectors. A comparison with present and future missions devoted to solar physics is presented.

  12. Testing of the on-board attitude determination and control algorithms for SAMPEX

    Science.gov (United States)

    McCullough, Jon D.; Flatley, Thomas W.; Henretty, Debra A.; Markley, F. Landis; San, Josephine K.

    1993-02-01

    Algorithms for on-board attitude determination and control of the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) have been expanded to include a constant gain Kalman filter for the spacecraft angular momentum, pulse width modulation for the reaction wheel command, an algorithm to avoid pointing the Heavy Ion Large Telescope (HILT) instrument boresight along the spacecraft velocity vector, and the addition of digital sun sensor (DSS) failure detection logic. These improved algorithms were tested in a closed-loop environment for three orbit geometries, one with the sun perpendicular to the orbit plane, and two with the sun near the orbit plane - at Autumnal Equinox and at Winter Solstice. The closed-loop simulator was enhanced and used as a truth model for the control systems' performance evaluation and sensor/actuator contingency analysis. The simulations were performed on a VAX 8830 using a prototype version of the on-board software.

  13. On-board fuel conversion: Dimethyl ether from methanol for compression ignition engines

    Energy Technology Data Exchange (ETDEWEB)

    Armbruster, H.; Stucki, S.

    2002-03-01

    One example of an on-board fuel conversion system is the fumigation of dimethyl ether. In this concept, a fraction of the methanol used as fuel is catalytically converted on-board to DME and water. The rate-determining step of the catalytic reaction with {gamma}-Al{sub 2}O{sub 3} as a catalyst is found to be the reaction of adsorbed intermediates; mass transfer is limited by Knudsen diffusivity. Providing DME for fumigation in a 180 kW engine will require approx. 0,7 kg of catalyst. The transient behavior of a pilot fixed-bed reactor has been estimated using simplified models, which show that the cold start should be manageable in less than one minute. This is an acceptable time for cold-starting an engine in heavy-duty vehicles. (author)

  14. Sensor network architecture for intelligent high-speed train on-board monitoring

    Institute of Scientific and Technical Information of China (English)

    Xiao-fan WU; Chun CHEN; Jia-jun BU; Gang CHEN

    2011-01-01

    The China's high-speed railway is experiencing a rapid growth.Its operating mileage and the number of operating trains will exceed 45000 km and 1500 trains by 2015,respectively.During the long range and constant high-speed operation,the high-speed trains have extremely complex and varied work conditions.Such a situation creates a huge demand for high-speed train on-board monitoring.In this paper,architecture for high-speed train on-board monitoring sensor network is proposed.This architecture is designed to achieve the goals of reliable sensing,scalable data transporting,and easy management.The three design goals are realized separately.The reliable sensing is achieved by deploying redundant sensor nodes in the same components.Then a hierarchal transporting scheme is involved to meet the second goal.Finally,an electronic-tag based addressing method is introduced to solve the management problem.

  15. Integrated extension board for on-board computer (OBDH) of SSETI ESEO satellite

    Science.gov (United States)

    Cichocki, Andrzej; Graczyk, Rafal

    2008-01-01

    This paper holds an information about an extension module for Single Board Computer (MIP405), which is the heart of On-board Data Handling Module (OBDH) of student Earth's microsatellite - SSETI ESEO. OBDH is a PC104 stack of four boards electrically connected and mechanically fixed. On-Board Computer is a key subsystem to the mission success - it is responsible for distribution of control signals to each module of the spacecraft. It is also expected to gather critical data for an appropriate mission progress, implementation of a part of algorithms used for satellite stabilization and orbit control and, at last, processing telecommands. Since whole system should meet spaceborne application requirements, it must be exceptionally reliable.

  16. An on-board near-optimal climb-dash energy management

    Science.gov (United States)

    Weston, A. R.; Cliff, E. M.; Kelley, H. J.

    1982-01-01

    On-board real time flight control is studied in order to develop algorithms which are simple enough to be used in practice, for a variety of missions involving three dimensional flight. The intercept mission in symmetric flight is emphasized. Extensive computation is required on the ground prior to the mission but the ensuing on-board exploitation is extremely simple. The scheme takes advantage of the boundary layer structure common in singular perturbations, arising with the multiple time scales appropriate to aircraft dynamics. Energy modelling of aircraft is used as the starting point for the analysis. In the symmetric case, a nominal path is generated which fairs into the dash or cruise state. Feedback coefficients are found as functions of the remaining energy to go (dash energy less current energy) along the nominal path.

  17. On-board near-optimal climb-dash energy management

    Science.gov (United States)

    Weston, A. R.; Cliff, E. M.; Kelley, H. J.

    1983-01-01

    On-board real time flight control is studied in order to develop algorithms which are simple enough to be used in practice, for a variety of missions involving three dimensional flight. The intercept mission in symmetric flight is emphasized. Extensive computation is required on the ground prior to the mission but the ensuing on-board exploitation is extremely simple. The scheme takes advantage of the boundary layer structure common in singular perturbations, arising with the multiple time scales appropriate to aircraft dynamics. Energy modelling of aircraft is used as the starting point for the analysis. In the symmetric case, a nominal path is generated which fairs into the dash or cruise state.

  18. High-Speed On-Board Data Processing for Science Instruments

    Science.gov (United States)

    Beyon, Jeffrey Y.; Ng, Tak-Kwong; Lin, Bing; Hu, Yongxiang; Harrison, Wallace

    2014-01-01

    A new development of on-board data processing platform has been in progress at NASA Langley Research Center since April, 2012, and the overall review of such work is presented in this paper. The project is called High-Speed On-Board Data Processing for Science Instruments (HOPS) and focuses on a high-speed scalable data processing platform for three particular National Research Council's Decadal Survey missions such as Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS), Aerosol-Cloud-Ecosystems (ACE), and Doppler Aerosol Wind Lidar (DAWN) 3-D Winds. HOPS utilizes advanced general purpose computing with Field Programmable Gate Array (FPGA) based algorithm implementation techniques. The significance of HOPS is to enable high speed on-board data processing for current and future science missions with its reconfigurable and scalable data processing platform. A single HOPS processing board is expected to provide approximately 66 times faster data processing speed for ASCENDS, more than 70% reduction in both power and weight, and about two orders of cost reduction compared to the state-of-the-art (SOA) on-board data processing system. Such benchmark predictions are based on the data when HOPS was originally proposed in August, 2011. The details of these improvement measures are also presented. The two facets of HOPS development are identifying the most computationally intensive algorithm segments of each mission and implementing them in a FPGA-based data processing board. A general introduction of such facets is also the purpose of this paper.

  19. Energy management systems on board of electric vehicles, based on power electronics

    OpenAIRE

    Guidi, Giuseppe

    2009-01-01

    The core of any electric vehicle (EV) is the electric drive train, intended as the energy conversion chain from the energy tank (typically some kind of rechargeable battery) to the electric motor that converts the electrical energy into the mechanical energy needed for the vehicle motion.The need for on-board electrical energy storage is the factor that has so far prevented pure electric vehicles from conquering significant market share. In fact electrochemical batteries, which are currently ...

  20. Increasing the object recognition distance of compact open air on board vision system

    Science.gov (United States)

    Kirillov, Sergey; Kostkin, Ivan; Strotov, Valery; Dmitriev, Vladimir; Berdnikov, Vadim; Akopov, Eduard; Elyutin, Aleksey

    2016-10-01

    The aim of this work was developing an algorithm eliminating the atmospheric distortion and improves image quality. The proposed algorithm is entirely software without using additional hardware photographic equipment. . This algorithm does not required preliminary calibration. It can work equally effectively with the images obtained at a distances from 1 to 500 meters. An algorithm for the open air images improve designed for Raspberry Pi model B on-board vision systems is proposed. The results of experimental examination are given.