Science.gov

Sample records for frequency stability measurement

  1. 47 CFR 2.1055 - Measurements required: Frequency stability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Measurements required: Frequency stability. 2... Certification § 2.1055 Measurements required: Frequency stability. (a) The frequency stability shall be measured...) Frequency measurements shall be made at the extremes of the specified temperature range and at intervals...

  2. The measurement of frequency and frequency stability of precision oscillators

    NASA Technical Reports Server (NTRS)

    Allan, D. W.

    1974-01-01

    The specification and performance of precision oscillators is discussed as a very important topic to the owners and users of these oscillators. This paper presents at the tutorial level some convenient methods of measuring the frequencies of precision oscillators -- giving advantages and disadvantages of these methods. Further it is shown that by processing the data from the frequency measurements in certain ways, one may be able to state more general characteristics of the oscillators being measured. The goal in this regard is to allow the comparisons of different manufacturers' specifications and more importantly to help assess whether these oscillators will meet the standard of performance the user may have in a particular application.

  3. Frequency stability measurement of a transfer-cavity-stabilized diode laser by using an optical frequency comb

    NASA Astrophysics Data System (ADS)

    Uetake, S.; Matsubara, K.; Ito, H.; Hayasaka, K.; Hosokawa, M.

    2009-10-01

    We report results of frequency stability measurements of an extended cavity diode laser (ECDL) whose frequency is stabilized by a non-evacuated scanning transfer cavity. The transfer cavity is locked to a commercial frequency stabilized helium-neon laser. Frequency stability is measured by use of an optical frequency comb. The environmental perturbations (variations of temperature, air pressure, and humidity) are also simultaneously measured. The observed frequency drift of the ECDL is well explained by environmental perturbations. An atmospheric pressure variation, which is difficult to control with a non-evacuated cavity, is mainly affected to the frequency stability. Thus we put the cavity into a simple O-ring sealed (non-evacuated) tube. With this simple O-ring sealed tube, the frequency drift is reduced by a factor of 3, and the Allan variance reaches a value of 2.4×10-10, corresponds to the frequency stability of 83 kHz, at the average time of 3000 s. Since the actual frequency drift is well estimated by simultaneous measurement of the ambient temperature, pressure, and humidity, a feed-forward compensation of frequency drifts is also feasible in order to achieve a higher frequency stability with a simple non-evacuated transfer cavity.

  4. 47 CFR 2.1055 - Measurements required: Frequency stability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... not more than 10° centigrade through the range. A period of time sufficient to stabilize all of the... incorporating heater type crystal oscillators to be used in mobile stations, for which type acceptance is first... from a cold start and the elapsed time necessary for the frequency to stabilize within the...

  5. 47 CFR 2.1055 - Measurements required: Frequency stability.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... not more than 10° centigrade through the range. A period of time sufficient to stabilize all of the... incorporating heater type crystal oscillators to be used in mobile stations, for which type acceptance is first... from a cold start and the elapsed time necessary for the frequency to stabilize within the...

  6. 47 CFR 2.1055 - Measurements required: Frequency stability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... not more than 10° centigrade through the range. A period of time sufficient to stabilize all of the... incorporating heater type crystal oscillators to be used in mobile stations, for which type acceptance is first... from a cold start and the elapsed time necessary for the frequency to stabilize within the...

  7. Frequency stability review

    NASA Technical Reports Server (NTRS)

    Greenhall, C. A.

    1987-01-01

    Certain aspects of the description and measurement of oscillator stability are treated. Topics covered are time and frequency deviations, Allan variance, the zero-crossing counter measurement technique, frequency drift removal, and the three-cornered hat.

  8. Laser Frequency Stabilization

    NASA Technical Reports Server (NTRS)

    Donelan, Darsa; Mueller, Guido; Thorpe, James; Livas, Jeffrey

    2011-01-01

    Laser ranging and interferometry are essential technologies allowing for many astounding new spacebased missions such as the Laser Interferometer Space Antenna (LISA) to measure gravitational radiation emitted from distant super massive black hole mergers or distributed aperture telescopes with unprecedented angular resolution in the NIR or visible regime. The requirements on laser frequency noise depend on the residual motion and the distances between the spacecraft forming the interferometer. The intrinsic frequency stability of commercial lasers is several orders of magnitude above these requirements. Therefore, it is necessary for lasers to be stabilized to an ultrastable frequency reference so that they can be used to sense and control distances between spacecraft. Various optical frequency references and frequency stabilization schemes are considered and investigated for the applicability and usefulness for space-based interferometry missions.

  9. Frequency standard stability for Doppler measurements on-board the shuttle

    NASA Technical Reports Server (NTRS)

    Harton, P. L.

    1974-01-01

    The short and long term stability characteristics of crystal and atomic standards are described. Emphasis is placed on crystal oscillators because of the selection which was made for the shuttle baseline and the complexities which are introduced by the shuttle environment. Attention is given, first, to the definitions of stability and the application of these definitions to the shuttle system and its mission. Data from time domain measurements are used to illustrate the definitions. Results of a literature survey to determine environmental effects on frequency reference sources are then presented. Finally, methods of standard frequency dissemination over radio frequency carriers are noted as a possible means of measuring absolute accuracy and long term stability characteristics during on one way Doppler equipment.

  10. Wavemeter measurements of frequency stability of an injection seeded alexandrite laser for pressure and temperature lidar

    NASA Technical Reports Server (NTRS)

    Prasad, C. R.; Schwemmer, G. K.; Korb, C. L.

    1992-01-01

    The GSFC pressure-temperature lidar is a differential absorption lidar operating in the oxygen A band absorption region (760 to 770 nm), and utilizes two tunable pulsed alexandrite lasers. For obtaining temperature measurements with an accuracy of less than or = 1 K, it has been determined that the stability of the online laser frequency over a period of time corresponding to a set of measurements, 0.1 to 30 min, has to be better than +/- 0.002/cm. In addition, the requirements on laser spectral bandwidth and spectral purity are less than or = 0.02/cm and greater than or = 99.9 percent, respectively. Injection seeding with a stabilized AlGaAs diode laser was used to achieve the required frequency stability and spectral bandwidth. A high resolution Fizeau wavemeter was employed to determine the frequency stability of the pulsed alexandrite laser and determine its bandwidth, mode structure. We present the results of measurements of the frequency stability and the spectrum of the injection seeded alexandrite laser.

  11. Stabilized radio frequency quadrupole

    DOEpatents

    Lancaster, H.D.; Fugitt, J.A.; Howard, D.R.

    1984-12-25

    Disclosed is a long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator. 5 figs.

  12. Stabilized radio frequency quadrupole

    DOEpatents

    Lancaster, Henry D.; Fugitt, Jock A.; Howard, Donald R.

    1984-01-01

    A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

  13. The Autonomous Cryocooled Sapphire Oscillator: A Reference for Frequency Stability and Phase Noise Measurements

    NASA Astrophysics Data System (ADS)

    Giordano, V.; Grop, S.; Fluhr, C.; Dubois, B.; Kersalé, Y.; Rubiola, E.

    2016-06-01

    The Cryogenic Sapphire Oscillator (CSO) is the microwave oscillator which feature the highest short-term stability. Our best units exhibit Allan deviation σy (τ) of 4.5x10-16 at 1s, ≈ 1.5x10-16 at 100 s ≤ t ≤ 5,000 s (floor), and ≤ 5x10-15 at one day. The use of a Pulse-Tube cryocooler enables full two year operation with virtually no maintenance. Starting with a short history of the CSO in our lab, we go through the architecture and we provide more details about the resonator, the cryostat, the oscillator loop, and the servo electronics. We implemented three similar oscillators, which enable the evaluation of each with the three- cornered hat method, and provide the potential for Allan deviation measurements at parts of 10-17 level. One of our CSOs (ULISS) is transportable, and goes with a small customized truck. The unique feature of ULISS is that its σy (τ) can be validated at destination by measuring before and after the roundtrip. To this extent, ULISS can be regarded as a traveling standard of frequency stability. The CSOs are a part of the Oscillator IMP project, a platform dedicated to the measurement of noise and short-term stability of oscillators and devices in the whole radio spectrum (from MHz to THz), including microwave photonics. The scope spans from routine measurements to the research on new oscillators, components, and measurement methods.

  14. Stability of the translocation frequency following whole-body irradiation measured in rhesus monkeys

    NASA Technical Reports Server (NTRS)

    Lucas, J. N.; Hill, F. S.; Burk, C. E.; Cox, A. B.; Straume, T.

    1996-01-01

    Chromosome translocations are persistent indicators of prior exposure to ionizing radiation and the development of 'chromosome painting' to efficiently detect translocations has resulted in a powerful biological dosimetry tool for radiation dose reconstruction. However, the actual stability of the translocation frequency with time after exposure must be measured before it can be used reliably to obtain doses for individuals exposed years or decades previously. Human chromosome painting probes were used here to measure reciprocal translocation frequencies in cells from two tissues of 8 rhesus monkeys (Macaca mulatta) irradiated almost three decades previously. Six of the monkeys were exposed in 1965 to whole-body (fully penetrating) radiation and two were unexposed controls. The primates were irradiated as juveniles to single doses of 0.56, 1.13, 2.00, or 2.25 Gy. Blood lymphocytes (and skin fibroblasts from one individual) were obtained for cytogenetic analysis in 1993, near the end of the animals' lifespans. Results show identical dose-response relationships 28 y after exposure in vivo and immediately after exposure in vitro. Because chromosome aberrations are induced with identical frequencies in vivo and in vitro, these results demonstrate that the translocation frequencies induced in 1965 have not changed significantly during the almost three decades since exposure. Finally, our emerging biodosimetry data for individual radiation workers are now confirming the utility of reciprocal translocations measured by FISH in radiation dose reconstruction.

  15. A method for using a time interval counter to measure frequency stability

    NASA Technical Reports Server (NTRS)

    Greenhall, C. A.

    1987-01-01

    It is shown how a commercial time interval counter can be used to measure the relative stability of two signals that are offset in frequency and mixed down to a beat note of about 1 Hz. To avoid the dead-time problem, the counter is set up to read the time interval between each beat note upcrossing and the next pulse of a 10 Hz reference pulse train. The actual upcrossing times are recovered by a simple algorithm whose outputs can be used for computing residuals and Allan variance. A noise floor-test yielded a delta f/f Allan deviation of 1.3 times 10 to the minus 9th power/tau relative to the beat frequency.

  16. Developing Stabilized Lasers, Measuring their Frequencies, demoting the Metre, inventing the Comb, and further consequences

    NASA Astrophysics Data System (ADS)

    Hall, John L.

    2010-02-01

    Michelson's 1907 proposal to define the SI Metre in terms of an optical wavelength was realized only in 1960, based on a ^86Krypton discharge lamp. The same year saw the cw HeNe laser arrive and a future redefinition based on laser technology assured. Separation in the late 60's of the laser's gain and spectral-reference-gas functions led to unprecedented levels of laser frequency stability and reproducibility. In addition to HeNe:CH4 system at 3392 nm and HeNe:I2 at 633 nm, systems at 514 nm and 10600 nm were studied. Absolute frequency measurement became the holy grail and some NBS team experiences will be shared. We measured both frequency and wavelength in 1972, and so obtained a speed of light value, improved 100-fold in accuracy. During the next decade, the NBS value of c was confirmed by other national labs, and frequency metrology was extended to the 473 THz (633 nm) Iodine-based wavelength standard. This frequency to ˜10 digit accuracy was obtained in 1983, thus setting the stage for redefining the SI Metre. By consensus choice the value 299 792 458 m/s was adopted for the speed of light, effectively reducing the Metre to a derived SI quantity. Knowledge of the frequency of the particular laser being utilized was controlled by International intercomparisons, but the need for a fast and accurate means to make these laser frequency measurements was obvious. Creative proposals by H"ansch and by Chebotayev were to use ultra-fast repetitive pulses to create an ``Optical Comb,'' but it was years before any technical basis existed to implement their Fourier dreams. Finally, in 1999 the last needed capability was demonstrated -- continuum production at 100 MHz rates and non-destructive power levels. By May 2000 phase-locked combs were operational in both Garching and Boulder, substantially accelerated by their collaborative interactions. Within 18 months all the known proposed ``optical frequency standards'' had been accurately measured via Comb techniques. )

  17. Optical Frequency Stabilization and Optical Phase Locked Loops: Golden Threads of Precision Measurement

    SciTech Connect

    Taubman, Matthew S.

    2013-07-01

    Stabilization of lasers through locking to optical cavities, atomic transitions, and molecular transitions has enabled the field of precision optical measurement since shortly after the invention of the laser. Recent advances in the field have produced an optical clock that is orders of magnitude more stable than those of just a few years prior. Phase locking of one laser to another, or to a frequency offset from another, formed the basis for linking stable lasers across the optical spectrum, such frequency chains exhibiting progressively finer precision through the years. Phase locking between the modes within a femtosecond pulsed laser has yielded the optical frequency comb, one of the most beautiful and useful instruments of our time. This talk gives an overview of these topics, from early work through to the latest 1E-16 thermal noise-limited precision recently attained for a stable laser, and the ongoing quest for ever finer precision and accuracy. The issues of understanding and measuring line widths and shapes are also studied in some depth, highlighting implications for servo design for sub-Hz line widths.

  18. Frequency measuring system using mirror gap stabilized Fabry-Perot interferometer

    NASA Astrophysics Data System (ADS)

    Nishimiya, Nobuo; Yamaguchi, Yoko; Ohrui, Yoshinobu; Suzuki, Masao

    2004-02-01

    The mirror gap of a Fabry-Perot interferometer was stabilized with two laser diodes; one locked to the line frequency 385 243 555.14445 MHz of the F=3←1 in 5 D3/2←5 S1/2 ( 87Rb) and the other to the 385 284 566.3663 MHz of the F=4←2 in 5 D5/2←5 S1/2 ( 87Rb) [Opt. Commun. 102 (1993) 432]. The length of the mirror gap was adjusted to generate the zero-cross points simultaneously at both of the two line positions. The fringe signals obtained from an interferometer thus stabilized can be used as frequency markers having accuracies of the order of 10 10 depending on the finesse of the interferometer used. Based on measurement using Cs D1 hyperfine lines reported by Udem et al. [Phys. Rev. Lett. 82 (1999) 3568], the uncertainty of markers in the region 50 THz apart from the reference lines is ±5 MHz.

  19. Absolute frequency measurement of an acetylene stabilized laser using a selected single mode from a femtosecond fiber laser comb.

    PubMed

    Ryu, Han Young; Lee, Sung Hun; Lee, Won Kyu; Moon, Han Seb; Suh, Ho Suhng

    2008-03-01

    We performed an absolute frequency measurement of an acetylene stabilized laser utilizing a femtosecond injection locking technique that can select one component among the fiber laser comb modes. The injection locking scheme has all the fiber configurations. Femtosecond comb lines of 250 MHz spacing based on the fiber femtosecond laser were used for injection locking of a distributed feedback (DFB) laser operating at 1542 nm as a frequency reference. The comb injected DFB laser serves as a selection filter of optical comb modes and an amplifier for amplification of the selected mode. The DFB laser injection locked to the desired comb mode was used to evaluate the frequency stability and absolute frequency measurement of an acetylene stabilized laser. The frequency stability of the acetylene stabilized laser was measured to be 1.1 x 10(-12) for a 1 s averaging time, improving to 6.9 x 10(-14) after 512 s. The absolute frequency of the laser stabilized on the P(16) transition of (13)C(2)H(2) was measured to be 194 369 569 385.7 kHz.

  20. Laser frequency stabilization for LISA

    NASA Technical Reports Server (NTRS)

    Mueller, Guido; McNamara, Paul; Thorpe, Ira; Camp, Jordan

    2005-01-01

    The requirement on laser frequency noise in the Laser Interferometer Space Antenna (LISA) depends on the velocity and our knowledge of the position of each spacecraft of the interferometer. Currently it is assumed that the lasers must have a pre-stabilized frequency stability of 30Hz/square root of Hz over LISA'S most sensitive frequency band (3 mHz - 30 mHz). The intrinsic frequency stability of even the most stable com- mercial lasers is several orders of magnitude above this level. Therefore it is necessary to stabilize the laser frequency to an ultra-stable frequency reference which meets the LISA requirements. The baseline frequency reference for the LISA lasers are high finesse optical cavities based on ULE spacers. We measured the stability of two ULE spacer cavities with respect to each other. Our current best results show a noise floor at, or below, 30 Hz/square root of Hz above 3 mHz. In this report we describe the experimental layout of the entire experiment and discuss the limiting noise sources.

  1. Accurate displacement-measuring interferometer with wide range using an I2 frequency-stabilized laser diode based on sinusoidal frequency modulation

    NASA Astrophysics Data System (ADS)

    Vu, Thanh-Tung; Higuchi, Masato; Aketagawa, Masato

    2016-10-01

    We propose the use of the sinusoidal frequency modulation technique to improve both the frequency stability of an external cavity laser diode (ECLD) and the measurement accuracy and range of a displacement-measuring interferometer. The frequency of the ECLD was modulated at 300 kHz by modulating the injection current, and it was locked to the b21 hyperfine component of the transition 6-3, P(33), 127I2 (633 nm) by the null method. A relative frequency stability of 6.5  ×  10-11 was achieved at 100 s sampling time. The stabilized ECLD was then utilized as a light source for an unbalanced Michelson interferometer. In the interferometer, the displacement and direction of the target mirror can be determined using a Lissajous diagram based on two consecutive and quadrant-phase harmonics of the interference signal. Generally, the measurement range of the interferometer by the proposed method is limited by the modulation index and the signal-to-noise ratio of the harmonics. To overcome this drawback, suitable consecutive harmonic pairs were selected for the specific measurement ranges to measure the displacement. The displacements determined in the specific ranges by the proposed method were compared with those observed by a commercial capacitive sensor. From the comparison, the proposed method has high precision to determine the displacement. The measurement range was also extended up to 10 m by selecting a suitable modulation index and suitable consecutive pairs of harmonics.

  2. Biomechanical evaluation of oversized drilling technique on primary implant stability measured by insertion torque and resonance frequency analysis

    PubMed Central

    Santamaría-Arrieta, Gorka; Brizuela-Velasco, Aritza; Fernández-González, Felipe J.; Chávarri-Prado, David; Chento-Valiente, Yelko; Solaberrieta, Eneko; Diéguez-Pereira, Markel; Yurrebaso-Asúa, Jaime

    2016-01-01

    Background This study evaluated the influence of implant site preparation depth on primary stability measured by insertion torque and resonance frequency analysis (RFA). Material and Methods Thirty-two implant sites were prepared in eight veal rib blocks. Sixteen sites were prepared using the conventional drilling sequence recommended by the manufacturer to a working depth of 10mm. The remaining 16 sites were prepared using an oversize drilling technique (overpreparation) to a working depth of 12mm. Bone density was determined using cone beam computerized tomography (CBCT). The implants were placed and primary stability was measured by two methods: insertion torque (Ncm), and RFA (implant stability quotient [ISQ]). Results The highest torque values were achieved by the conventional drilling technique (10mm). The ANOVA test confirmed that there was a significant correlation between torque and drilling depth (p<0.05). However, no statistically significant differences were obtained between ISQ values at 10 or 12 mm drilling depths (p>0.05) at either measurement direction (cortical and medullar). No statistical relation between torque and ISQ values was identified, or between bone density and primary stability (p >0.05). Conclusions Vertical overpreparation of the implant bed will obtain lower insertion torque values, but does not produce statistically significant differences in ISQ values. Key words:Implant stability quotient, overdrilling, primary stability, resonance frequency analysis, torque. PMID:27398182

  3. Laser-frequency stabilization using forward scattering

    NASA Astrophysics Data System (ADS)

    Fellman, T.; Lindberg, Å.; Ståhlberg, B.

    1994-12-01

    Frequency stabilization of a single-mode dye laser is demonstrated using a simple magneto-optical forward scattering method. The dye laser was locked to the 2p4-3ss2, λ = 633 nm neon transition. Heterodyne beat-frequency measurements against a127I2-He-Ne meter standard laser showed a frequency stability of a few MHz.

  4. A proposed far-field method for frequency-stability measurements on the DSS 13 beam-waveguide antenna

    NASA Technical Reports Server (NTRS)

    Otoshi, T. Y.

    1991-01-01

    A method for measuring the frequency stability of the beam-waveguide (BWG) antenna at Deep Space Station 13 is presented. This method is relatively inexpensive and primarily utilizes equipment that is already available. Another desirable feature of the method is that a far-field signal will be used for the measurement. In concert with the goal of employing new technology developments, a fiber optic system will be used at 12 GHz to carry a reference antenna signal to the BWG antenna Ku-band test-package location in the pedestal room.

  5. Stabilized radio-frequency quadrupole

    DOEpatents

    Lancaster, H.D.; Fugitt, J.A.; Howard, D.R.

    1982-09-29

    A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

  6. External laser frequency stabilizer

    SciTech Connect

    Hall, J.L.; Hansch, T.W.

    1987-10-13

    A frequency transducer for controlling or modulating the frequency of a light radiation system is described comprising: a source of radiation having a predetermined frequency; an electro-optic phase modulator for receiving the radiation and for changing the phase of the radiation in proportion to an applied error voltage; an acousto-optic modulator coupled to the electro-optic modulator for shifting the frequency of the output signal of the electro-optic modulator; a signal source for providing an error voltage representing undesirable fluctuations in the frequency of the light radiation; a first channel including a fast integrator coupled between the signal source and the input circuit of the electro-optic modulator; a second channel including a voltage controlled oscillator coupled between the signal source and the acousto-optic modulator; and a network including an electronic delay circuit coupled between the first and second channels for matching the delay of the acousto-optic modulator.

  7. FREQUENCY STABILIZING SYSTEM

    DOEpatents

    Kerns, Q.A.; Anderson, O.A.

    1960-05-01

    An electronic control circuit is described in which a first signal frequency is held in synchronization with a second varying reference signal. The circuit receives the first and second signals as inputs and produces an output signal having an amplitude dependent upon rate of phase change between the two signals and a polarity dependent on direction of the phase change. The output may thus serve as a correction signal for maintaining the desired synchronization. The response of the system is not dependent on relative phase angle between the two compared signals. By having practically no capacitance in the circuit, there is minimum delay between occurrence of a phase shift and a response in the output signal and therefore very fast synchronization is effected.

  8. 47 CFR 24.135 - Frequency stability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Frequency stability. 24.135 Section 24.135... SERVICES Narrowband PCS § 24.135 Frequency stability. (a) The frequency stability of the transmitter shall be maintained within ±0.0001 percent (±1 ppm) of the center frequency over a temperature variation...

  9. 47 CFR 24.135 - Frequency stability.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 2 2011-10-01 2011-10-01 false Frequency stability. 24.135 Section 24.135... SERVICES Narrowband PCS § 24.135 Frequency stability. (a) The frequency stability of the transmitter shall be maintained within ±0.0001 percent (±1 ppm) of the center frequency over a temperature variation...

  10. 47 CFR 24.235 - Frequency stability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Frequency stability. 24.235 Section 24.235... SERVICES Broadband PCS § 24.235 Frequency stability. The frequency stability shall be sufficient to ensure that the fundamental emission stays within the authorized frequency block....

  11. 47 CFR 24.235 - Frequency stability.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 2 2011-10-01 2011-10-01 false Frequency stability. 24.235 Section 24.235... SERVICES Broadband PCS § 24.235 Frequency stability. The frequency stability shall be sufficient to ensure that the fundamental emission stays within the authorized frequency block....

  12. 47 CFR 24.235 - Frequency stability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 2 2014-10-01 2014-10-01 false Frequency stability. 24.235 Section 24.235... SERVICES Broadband PCS § 24.235 Frequency stability. The frequency stability shall be sufficient to ensure that the fundamental emission stays within the authorized frequency block....

  13. 47 CFR 24.135 - Frequency stability.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 false Frequency stability. 24.135 Section 24.135... SERVICES Narrowband PCS § 24.135 Frequency stability. (a) The frequency stability of the transmitter shall be maintained within ±0.0001 percent (±1 ppm) of the center frequency over a temperature variation...

  14. 47 CFR 101.507 - Frequency stability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequency stability. 101.507 Section 101.507... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.507 Frequency stability. The frequency...% for each DEMS User Station transmitter. The frequency stability in the 24,250-25,250 MHz bands must...

  15. 47 CFR 101.507 - Frequency stability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequency stability. 101.507 Section 101.507... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.507 Frequency stability. The frequency...% for each DEMS User Station transmitter. The frequency stability in the 24,250-25,250 MHz bands must...

  16. 47 CFR 24.135 - Frequency stability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 2 2014-10-01 2014-10-01 false Frequency stability. 24.135 Section 24.135... SERVICES Narrowband PCS § 24.135 Frequency stability. (a) The frequency stability of the transmitter shall be maintained within ±0.0001 percent (±1 ppm) of the center frequency over a temperature variation...

  17. 47 CFR 101.507 - Frequency stability.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequency stability. 101.507 Section 101.507... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.507 Frequency stability. The frequency...% for each DEMS User Station transmitter. The frequency stability in the 24,250-25,250 MHz bands must...

  18. 47 CFR 24.135 - Frequency stability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Frequency stability. 24.135 Section 24.135... SERVICES Narrowband PCS § 24.135 Frequency stability. (a) The frequency stability of the transmitter shall be maintained within ±0.0001 percent (±1 ppm) of the center frequency over a temperature variation...

  19. 47 CFR 24.235 - Frequency stability.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 false Frequency stability. 24.235 Section 24.235... SERVICES Broadband PCS § 24.235 Frequency stability. The frequency stability shall be sufficient to ensure that the fundamental emission stays within the authorized frequency block....

  20. 47 CFR 24.235 - Frequency stability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Frequency stability. 24.235 Section 24.235... SERVICES Broadband PCS § 24.235 Frequency stability. The frequency stability shall be sufficient to ensure that the fundamental emission stays within the authorized frequency block....

  1. Compact stabilized semiconductor laser for frequency metrology.

    PubMed

    Liang, Wei; Ilchenko, Vladimir S; Eliyahu, Danny; Dale, Elijah; Savchenkov, Anatoliy A; Seidel, David; Matsko, Andrey B; Maleki, Lute

    2015-04-10

    We report on the development of a frequency modulatable 795 nm semiconductor laser based on self-injection locking to a high-quality-factor whispering-gallery-mode microresonator. The laser is characterized by residual amplitude modulation below -80  dB and frequency noise better than 300  Hz/Hz(1/2) at offset frequencies ranging from 100 Hz to 10 MHz. The frequency modulation speed and span of the laser exceed 1 MHz and 4 GHz, respectively. Locking of the laser to the Doppler-free saturated absorption resonance of the (87)Rb D1 line is demonstrated and relative frequency stability better than 10(-12) is measured for integration time spanning from 1 s to 1 day. The architecture demonstrated in this study is suitable for the realization of frequency modulatable lasers at any wavelength.

  2. 47 CFR 27.54 - Frequency stability.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 false Frequency stability. 27.54 Section 27.54 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES Technical Standards § 27.54 Frequency stability. The frequency stability shall...

  3. 47 CFR 27.54 - Frequency stability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Frequency stability. 27.54 Section 27.54 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES Technical Standards § 27.54 Frequency stability. The frequency stability shall...

  4. 47 CFR 27.54 - Frequency stability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 2 2014-10-01 2014-10-01 false Frequency stability. 27.54 Section 27.54 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES Technical Standards § 27.54 Frequency stability. The frequency stability shall...

  5. 47 CFR 27.54 - Frequency stability.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 2 2011-10-01 2011-10-01 false Frequency stability. 27.54 Section 27.54 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES Technical Standards § 27.54 Frequency stability. The frequency stability shall...

  6. 47 CFR 27.54 - Frequency stability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Frequency stability. 27.54 Section 27.54 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES Technical Standards § 27.54 Frequency stability. The frequency stability shall...

  7. 47 CFR 22.863 - Frequency stability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Frequency stability. 22.863 Section 22.863...-Ground Radiotelephone Service Commercial Aviation Air-Ground Systems § 22.863 Frequency stability. The frequency stability of equipment used under this subpart shall be sufficient to ensure that,...

  8. 47 CFR 22.863 - Frequency stability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 2 2013-10-01 2013-10-01 false Frequency stability. 22.863 Section 22.863...-Ground Radiotelephone Service Commercial Aviation Air-Ground Systems § 22.863 Frequency stability. The frequency stability of equipment used under this subpart shall be sufficient to ensure that,...

  9. 47 CFR 22.863 - Frequency stability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 2 2014-10-01 2014-10-01 false Frequency stability. 22.863 Section 22.863...-Ground Radiotelephone Service Commercial Aviation Air-Ground Systems § 22.863 Frequency stability. The frequency stability of equipment used under this subpart shall be sufficient to ensure that,...

  10. 47 CFR 22.863 - Frequency stability.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 2 2011-10-01 2011-10-01 false Frequency stability. 22.863 Section 22.863...-Ground Radiotelephone Service Commercial Aviation Air-Ground Systems § 22.863 Frequency stability. The frequency stability of equipment used under this subpart shall be sufficient to ensure that,...

  11. 47 CFR 22.863 - Frequency stability.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 2 2012-10-01 2012-10-01 false Frequency stability. 22.863 Section 22.863...-Ground Radiotelephone Service Commercial Aviation Air-Ground Systems § 22.863 Frequency stability. The frequency stability of equipment used under this subpart shall be sufficient to ensure that,...

  12. Absolute distance measurement by multi-heterodyne interferometry using a frequency comb and a cavity-stabilized tunable laser.

    PubMed

    Wu, Hanzhong; Zhang, Fumin; Liu, Tingyang; Balling, Petr; Qu, Xinghua

    2016-05-20

    In this paper, we develop a multi-heterodyne system capable of absolute distance measurement using a frequency comb and a tunable diode laser locked to a Fabry-Perot cavity. In a series of subsequent measurements, numerous beat components can be obtained by downconverting the optical frequency into the RF region with multi-heterodyne interferometry. The distances can be measured via the mode phases with a series of synthetic wavelengths. The comparison with the reference interferometer shows an agreement within 1.5 μm for the averages of five measurements and 2.5 μm for the single measurement, which is at the 10-8 relative precision level. PMID:27411152

  13. Laser Frequency Stabilization for GRACE-II

    NASA Technical Reports Server (NTRS)

    Folkner, W. M.; deVine, G.; Klipstein, W. M.; McKenzie, K.; Shaddock, D.; Spero, R.; Thompson, R.; Wuchenich, D.; Yu, N.; Stephens, M.; Leitch, J.; Davis, M.; deCino, J.; Pace, C.; Pierce, R.

    2010-01-01

    The GRACE mission monitors changes in the Earth's gravity field by measuring changes in the distance between spacecraft induced by that changing field. The distance variation is measured with a microwave ranging system with sub-micron accuracy. The ranging measurement accuracy is limited by the signal-to-noise ratio and by the frequency stability of the microwave signal referenced to an ultra-stable oscillator (USO). For GRACE-2 a laser ranging system is envisioned with accuracy better than the GRACE microwave ranging system. A laser ranging system easily provides an improved signal-to-noise ratio over the microwave system. Laser frequency stability better than the GRACE USO stability has been demonstrated in several laboratories using thermally stabilized optical cavities. We are developing a space-qualifiable optical cavity and associated optics and electronics for use on GRACE-2 to provide a stable frequency reference for the laser ranging system. Two breadboard units have been developed and tested for performance and ability to survive launch and orbit environments. A prototype unit is being designed using lessons learned from tests of the breadboard units.

  14. 47 CFR 90.539 - Frequency stability.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequency stability. 90.539 Section 90.539... MOBILE RADIO SERVICES Regulations Governing the Licensing and Use of Frequencies in the 763-775 and 793-805 MHz Bands § 90.539 Frequency stability. Transmitters designed to operate in 769-775 MHz and...

  15. 47 CFR 90.213 - Frequency stability.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Frequency stability. 90.213 Section 90.213... MOBILE RADIO SERVICES General Technical Standards § 90.213 Frequency stability. (a) Unless noted elsewhere, transmitters used in the services governed by this part must have a minimum frequency...

  16. 47 CFR 90.539 - Frequency stability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Frequency stability. 90.539 Section 90.539... MOBILE RADIO SERVICES Regulations Governing the Licensing and Use of Frequencies in the 763-775 and 793-805 MHz Bands § 90.539 Frequency stability. Transmitters designed to operate in 769-775 MHz and...

  17. 47 CFR 90.213 - Frequency stability.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequency stability. 90.213 Section 90.213... MOBILE RADIO SERVICES General Technical Standards § 90.213 Frequency stability. (a) Unless noted elsewhere, transmitters used in the services governed by this part must have a minimum frequency...

  18. 47 CFR 90.213 - Frequency stability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequency stability. 90.213 Section 90.213... MOBILE RADIO SERVICES General Technical Standards § 90.213 Frequency stability. (a) Unless noted elsewhere, transmitters used in the services governed by this part must have a minimum frequency...

  19. 47 CFR 90.539 - Frequency stability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequency stability. 90.539 Section 90.539... MOBILE RADIO SERVICES Regulations Governing the Licensing and Use of Frequencies in the 758-775 and 788-805 MHz Bands § 90.539 Frequency stability. Transmitters designed to operate in 769-775 MHz and...

  20. 47 CFR 5.101 - Frequency stability.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 1 2011-10-01 2011-10-01 false Frequency stability. 5.101 Section 5.101...) Technical Standards and Operating Requirements § 5.101 Frequency stability. An applicant must propose to use a frequency tolerance that would confine emissions within the band of operation, unless...

  1. 47 CFR 5.101 - Frequency stability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Frequency stability. 5.101 Section 5.101...) Technical Standards and Operating Requirements § 5.101 Frequency stability. An applicant must propose to use a frequency tolerance that would confine emissions within the band of operation, unless...

  2. 47 CFR 90.213 - Frequency stability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequency stability. 90.213 Section 90.213... MOBILE RADIO SERVICES General Technical Standards § 90.213 Frequency stability. (a) Unless noted elsewhere, transmitters used in the services governed by this part must have a minimum frequency...

  3. 47 CFR 90.539 - Frequency stability.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Frequency stability. 90.539 Section 90.539... MOBILE RADIO SERVICES Regulations Governing the Licensing and Use of Frequencies in the 763-775 and 793-805 MHz Bands § 90.539 Frequency stability. Transmitters designed to operate in 769-775 MHz and...

  4. 47 CFR 5.101 - Frequency stability.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 1 2013-10-01 2013-10-01 false Frequency stability. 5.101 Section 5.101... Operating Requirements § 5.101 Frequency stability. Experimental Radio Service licensees shall ensure that transmitted emissions remain within the authorized frequency band under normal operating conditions:...

  5. 47 CFR 90.213 - Frequency stability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Frequency stability. 90.213 Section 90.213... MOBILE RADIO SERVICES General Technical Standards § 90.213 Frequency stability. (a) Unless noted elsewhere, transmitters used in the services governed by this part must have a minimum frequency...

  6. 47 CFR 90.539 - Frequency stability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequency stability. 90.539 Section 90.539... MOBILE RADIO SERVICES Regulations Governing the Licensing and Use of Frequencies in the 763-775 and 793-805 MHz Bands § 90.539 Frequency stability. Transmitters designed to operate in 769-775 MHz and...

  7. 47 CFR 87.133 - Frequency stability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Frequency stability. 87.133 Section 87.133... Technical Requirements § 87.133 Frequency stability. (a) Except as provided in paragraphs (c), (d), and (f) of this section, the carrier frequency of each station must be maintained within these...

  8. 47 CFR 5.101 - Frequency stability.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 1 2014-10-01 2014-10-01 false Frequency stability. 5.101 Section 5.101... Operating Requirements § 5.101 Frequency stability. Experimental Radio Service licensees shall ensure that transmitted emissions remain within the authorized frequency band under normal operating conditions:...

  9. 47 CFR 5.101 - Frequency stability.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 1 2012-10-01 2012-10-01 false Frequency stability. 5.101 Section 5.101...) Technical Standards and Operating Requirements § 5.101 Frequency stability. An applicant must propose to use a frequency tolerance that would confine emissions within the band of operation, unless...

  10. Operational frequency stability of rubidium and cesium frequency standards

    NASA Technical Reports Server (NTRS)

    Lavery, J. E.

    1973-01-01

    The frequency stabilities under operational conditions of several commercially available rubidium and cesium frequency standards were determined from experimental data for frequency averaging times from 10 to the 7th power s and are presented in table and graph form. For frequency averaging times between 10 to the 5th power and 10 to the 7th power s, the rubidium standards tested have a stability of between 10 to the minus 12th power and 5 x 10 to the minus 12th power, while the cesium standards have a stability of between 2 x 10 to the minus 13th power and 5 x 10 to the minus 13th power.

  11. 47 CFR 101.507 - Frequency stability.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Frequency stability. 101.507 Section 101.507 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES 24 GHz Service and Digital Electronic Message Service § 101.507 Frequency stability. The...

  12. 47 CFR 101.507 - Frequency stability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Frequency stability. 101.507 Section 101.507 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES 24 GHz Service and Digital Electronic Message Service § 101.507 Frequency stability. The...

  13. Providing hydrogen maser timing stability to orbiting VLBI radio telescope observations by post-measurement compensation of linked frequency standard imperfections

    NASA Technical Reports Server (NTRS)

    Springett, James C.

    1994-01-01

    Orbiting VLBI (OVLBI) astronomical observations are based upon measurements acquired simultaneously from ground-based and earth-orbiting radio telescopes. By the mid-1990s, two orbiting VLBI observatories, Russia's Radioastron and Japan's VSOP, will augment the worldwide VLBI network, providing baselines to earth radio telescopes as large as 80,000 km. The challenge for OVLBI is to effectuate space to ground radio telescope data cross-correlation (the observation) to a level of integrity currently achieved between ground radio telescopes. VLBI radio telescopes require ultrastable frequency and timing references in order that long term observations may be made without serious cross-correlation loss due to frequency source drift and phase noise. For this reason, such instruments make use of hydrogen maser frequency standards. Unfortunately, space-qualified hydrogen maser oscillators are currently not available for use on OVLBI satellites. Thus, the necessary long-term stability needed by the orbiting radio telescope may only be obtained by microwave uplinking a ground-based hydrogen maser derived frequency to the satellite. Although the idea of uplinking the frequency standard intrinsically seems simple, there are many 'contaminations' which degrade both the long and short term stability of the transmitted reference. Factors which corrupt frequency and timing accuracy include additive radio and electronic circuit thermal noise, slow or systematic phase migration due to changes of electronic circuit temporal operating conditions (especially temperature), ionosphere and troposphere induced scintillations, residual Doppler-incited components, and microwave signal multipath propagation. What is important, though, is to realize that ultimate stability does not have to be achieved in real-time. Instead, information needed to produce a high degree of coherence in the subsequent cross-correlation operation may be derived from a two-way coherent radio link, recorded and later

  14. Intermode beat stabilized laser with frequency pulling.

    PubMed

    Yokoyama, S; Araki, T; Suzuki, N

    1994-01-20

    A frequency-stabilized two-mode He-Ne laser has been developed. The intermode beat frequency of the experimental laser was approximately 600 MHz for a 25-cm cavity. The laser frequency in which the mode stands is pulled to the center of the gain curve (frequency pulling). The degree of pulling depends on where the longitudinal modes stand in the broadened gain curve. Beat frequency is thereby changed periodically of the order of hundreds of kilohertz with respect to cavity expansion. The frequency pulling was effectively used for frequency stabilization of the laser. The standing position of the longitudinal mode lights was locked in the gain curve by controlling the change of intermode beat frequency. A microwave mixer was applied to extract the frequency change of the intermode beat. Excellent frequency stability (10(10) for the laser oscillation and 10(6) for the beat frequency) was attained. The polarization orthogonality of the proposed laser was superior to that of Zeeman lasers.

  15. The influence of fixation in formalin on the measurement of stability of implants using resonance frequency analysis and Periotest M®: a study in a dog.

    PubMed

    Doi, Kazuya; Kajihara, Shiho; Morita, Koji; Makihara, Yusuke; Okada, Shinsuke; Akagawa, Yasumasa

    2014-01-01

    Resonance frequency analysis (RFA) and Periotest® have been widely used to evaluate measurements of the stability of implants in clinical studies and animal experiments. In animals, these measurements are often made after bone has been fixed in formalin. However, it is not yet clear how this fixation influences RFA and Periotest®, and our aim was to clarify this using the implant stability quotient (ISQ) and Periotest® value (PTV). Six titanium implants were placed, 3 into each femur, of one male dog (a beagle/labrador cross). After 2 months blocks of bone were harvested, each block containing 3 implants, and were fixed in 10% neutral formalin. Measurements were made before fixation (time 0) then at 4h, and 1, 7, 14, 21, and 28 days. ISQ values of 6 implants were evaluated 3 times on the short and long axes, as were PTV. ISQ ranged from 67.5 to 79.3 and tended to increase with time. ISQ at 7-28 days were significantly higher than that at time 0. PTV ranged from -7.7 to -7.8 and did not differ significantly among fixation times. These results suggest that fixation of bony tissue in formalin might affect ISQ, so it might be preferable to measure ISQ during the early stages of fixation.

  16. Improved low frequency stability of bolometric detectors

    SciTech Connect

    Wilbanks, T.; Devlin, M.; Lange, A.E. . Dept. of Physics); Sato, S. . Dept. of Physics); Beeman, J.W.; Haller, E.E. . Center for Advanced Materials)

    1990-04-01

    The authors have developed an AC bridge readout system that greatly improves the low-frequency stability of bolometric detectors. The readout can be implemented with a simple circuit appropriate for use in space applications. Using a matched pair of detectors in the readout, the authors have achieved system noise within a factor of two of the fundamental noise limit of the detectors at frequencies as low as 10 mHz. The low frequency stability of the readout system allows slower, more sensitive detectors to be used in many applications, and facilitates observing strategies that are well-suited to space-borne observations.

  17. Frequency stabilization of algaas lasers

    SciTech Connect

    Ohtsu, M.; Tsuchida, H.; Tako, T.

    1982-01-01

    Performances of semiconductor lasers have been remarkably improved by the demand of the optical communications industry. Recently, a single longitudinal mode, CW oscillation at room temperature has been realized. The price of each laser has been reduced as low as $250. These lasers are mostly oscillated in the near-infrared, and the coherent lights of 0.83 micrometers and 1.3-1.6 micrometers in wavelengths are obtained by AlGaAs lasers and InGaAsP lasers, respectively. Since few number of other kind of lasers oscillates in these wavelength regions, these semiconductor lasers could be conveniently used not only in optical communications but in many fields of application, e.g., laser spectroscopy, optical pumping, frequency and length standards, laser radar, air-borne gyroscope, etc.

  18. Frequency stabilization by synchronization of Duffing oscillators

    NASA Astrophysics Data System (ADS)

    Zanette, Damián H.

    2016-07-01

    We present analytical and numerical results on the joint dynamics of two coupled Duffing oscillators with nonlinearity of opposite signs (hardening and softening). In particular, we focus on the existence and stability of synchronized oscillations where the frequency is independent of the amplitude. In this regime, the amplitude-frequency interdependence (a-f effect) —a noxious consequence of nonlinearity, which jeopardizes the use of micromechanical oscillators in the design of time-keeping devices— is suppressed. By means of a multiple time scale formulation, we find approximate conditions under which frequency stabilization is achieved, characterize the stability of the resulting oscillations, and compare with numerical solutions to the equations of motion.

  19. Stabilizing Microwave Frequency of a Photonic Oscillator

    NASA Technical Reports Server (NTRS)

    Maleki, Lute; Yu, Nan; Tu, Meirong

    2006-01-01

    A scheme for stabilizing the frequency of a microwave signal is proposed that exploits the operational characteristics of a coupled optoelectronic oscillator (COEO) and related optoelectronic equipment. An essential element in the scheme is a fiber mode-locked laser (MLL), the optical frequency of which is locked to an atomic transition. In this scheme, the optical frequency stability of the mode-locked laser is transferred to that of the microwave in the same device. Relative to prior schemes for using wideband optical frequency comb to stabilize microwave signals, this scheme is simpler and lends itself more readily to implementation in relatively compact, rugged equipment. The anticipated development of small, low-power, lightweight, highly stable microwave oscillators based on this scheme would afford great benefits in communication, navigation, metrology, and fundamental sciences. COEOs of various designs, at various stages of development, in some cases called by different names, have been described in a number of prior NASA Tech Briefs articles. A COEO is an optoelectronic apparatus that generates both short (picosecond) optical pulses and a steady microwave signal having an ultrahigh degree of spectral purity. The term "coupled optoelectronic" in the full name of such an apparatus signifies that its optical and electronic oscillations are coupled to each other in a single device. The present frequency-stabilization scheme is best described indirectly by describing the laboratory apparatus used to demonstrate it. The apparatus (see figure) includes a COEO that generates a comb-like optical spectrum, the various frequency components of which interfere, producing short optical pulses. This spectrum is centered at a nominal wavelength of 1,560 nm. The spectrum separation of this comb is about 10 GHz, as determined primarily by the length of an optical loop and the bandpass filter in the microwave feedback loop. The optical loop serves as microwave resonator

  20. Scientific applications of frequency-stabilized laser technology in space

    NASA Technical Reports Server (NTRS)

    Schumaker, Bonny L.

    1990-01-01

    A synoptic investigation of the uses of frequency-stabilized lasers for scientific applications in space is presented. It begins by summarizing properties of lasers, characterizing their frequency stability, and describing limitations and techniques to achieve certain levels of frequency stability. Limits to precision set by laser frequency stability for various kinds of measurements are investigated and compared with other sources of error. These other sources include photon-counting statistics, scattered laser light, fluctuations in laser power, and intensity distribution across the beam, propagation effects, mechanical and thermal noise, and radiation pressure. Methods are explored to improve the sensitivity of laser-based interferometric and range-rate measurements. Several specific types of science experiments that rely on highly precise measurements made with lasers are analyzed, and anticipated errors and overall performance are discussed. Qualitative descriptions are given of a number of other possible science applications involving frequency-stabilized lasers and related laser technology in space. These applications will warrant more careful analysis as technology develops.

  1. A phase-stabilized carbon nanotube fiber laser frequency comb.

    PubMed

    Lim, Jinkang; Knabe, Kevin; Tillman, Karl A; Neely, William; Wang, Yishan; Amezcua-Correa, Rodrigo; Couny, François; Light, Philip S; Benabid, Fetah; Knight, Jonathan C; Corwin, Kristan L; Nicholson, Jeffrey W; Washburn, Brian R

    2009-08-01

    A frequency comb generated by a 167 MHz repetition frequency erbium-doped fiber ring laser using a carbon nanotube saturable absorber is phase-stabilized for the first time. Measurements of the in-loop phase noise show an integrated phase error on the carrier envelope offset frequency of 0.35 radians. The carbon nanotube fiber laser comb is compared with a CW laser near 1533 nm stabilized to the nu(1) + nu(3) overtone transition in an acetylene-filled kagome photonic crystal fiber reference, while the CW laser is simultaneously compared to another frequency comb based on a Cr:Forsterite laser. These measurements demonstrate that the stability of a GPS-disciplined Rb clock is transferred to the comb, resulting in an upper limit on the locked comb's frequency instability of 1.2 x 10(-11) in 1 s, and a relative instability of <3 x 10(-12) in 1 s. The carbon nanotube laser frequency comb offers much promise as a robust and inexpensive all-fiber frequency comb with potential for scaling to higher repetition frequencies.

  2. Frequency stability of maser oscillators operated with cavity Q. [hydrogen and rubidium masers

    NASA Technical Reports Server (NTRS)

    Tetu, M.; Tremblay, P.; Lesage, P.; Petit, P.; Audoin, C.

    1982-01-01

    The short term frequency stability of masers equipped with an external feedback loop to increase the cavity quality factor was studied. The frequency stability of a hydrogen and a rubidium maser were measured and compared with theoretical evaluation. It is shown that the frequency stability passes through an optimum when the cavity Q is varied. Long term fluctuations are discussed and the optimum mid term frequency stability achievably by small size active and passive H-masers is considered.

  3. Cryogenic masers. [frequency stability and design parameters

    NASA Technical Reports Server (NTRS)

    Berlinsky, A. J.; Hardy, W. N.

    1982-01-01

    Various factors affecting the frequency stability of hydrogen masers are described and related to maser design parameters. The long-term frequency stability of a hydrogen maser is limited by the mechanical stability of the cavity, and the magnitudes of the wall relaxation, spin exchange, and recombination rates which affect the Q of the line. Magnetic resonance studies of hydrogen atoms at temperatures below 1 K and in containers coated with liquid helium films demonstrated that cryogenic masers may allow substantial improvements in all of these parameters. In particular the thermal expansion coefficients of most materials are negligible at 1 K. Spin exchange broadening is three orders of magnitude smaller at 1 K than at room temperature, and the recombination and wall relaxation rates are negligible at 0.52 K where the frequency shift due to the 4 He-coated walls of the container has a broad minimum as a function of temperature. Other advantages of the helium-cooled maser result from the high purity, homogeneity, and resilence of helium-film-coated walls and the natural compatibility of the apparatus with helium-cooled amplifiers.

  4. Trajectory of frequency stability in typical development

    PubMed Central

    Irimia, Andrei; Jeste, Shafali S.

    2015-01-01

    Introduction This work explores a feature of brain dynamics, metastability, by which transients are observed in functional brain data. Metastability is a balance between static (stable) and dynamic (unstable) tendencies in electrophysiological brain activity. Furthermore, metastability is a theoretical mechanism underlying the rapid synchronization of cell assemblies that serve as neural substrates for cognitive states, and it has been associated with cognitive flexibility. While much previous research has sought to characterize metastability in the adult human brain, few studies have examined metastability in early development, in part because of the challenges of acquiring adequate, noise free continuous data in young children. Methods To accomplish this endeavor, we studied a new method for characterizing the stability of EEG frequency in early childhood, as inspired by prior approaches for describing cortical phase resets in the scalp EEG of healthy adults. Specifically, we quantified the variance of the rate of change of the signal phase (i.e., frequency) as a proxy for phase resets (signal instability), given that phase resets occur almost simultaneously across large portions of the scalp. We tested our method in a cohort of 39 preschool age children (age = 53 ± 13.6 months). Results We found that our outcome variable of interest, frequency variance, was a promising marker of signal stability, as it increased with the number of phase resets in surrogate (artificial) signals. In our cohort of children, frequency variance decreased cross-sectionally with age (r = −0.47, p = 0.0028). Conclusions EEG signal stability, as quantified by frequency variance, increases with age in preschool age children. Future studies will relate this biomarker with the development of executive function and cognitive flexibility in children, with the overarching goal of understanding metastability in atypical development. PMID:25501709

  5. Polarimetric optical fiber sensor using a frequency stabilized semiconductor laser

    SciTech Connect

    Tsuchida, H.; Mitsuhashi, Y.; Ishihara, S. )

    1989-05-01

    The authors discuss the performance of a polarimetric optical fiber sensor for remote temperature measurement improved by the use of a frequency stabilized semiconductor laser. The temperature change is measured from the phase delay between two orthogonally polarized modes in a polarization maintaining fiber. The sensor output signal is demodulated utilizing direct modulation of the laser frequency. The center frequency of the modulated laser is locked to a Fabry-Perot interferometer by controlling the injection current. The minimum detectable temperature change is evaluated experimentally to be less than 0.005{sup 0}C, which is seven times smaller than that obtained with the freerunning laser.

  6. Laser frequency stabilization using bichromatic crossover spectroscopy

    SciTech Connect

    Jeong, Taek; Seb Moon, Han

    2015-03-07

    We propose a Doppler-free spectroscopic method named bichromatic crossover spectroscopy (BCS), which we then use for the frequency stabilization of an off-resonant frequency that does not correspond to an atomic transition. The observed BCS in the 5S{sub 1/2} → 5P{sub 1/2} transition of {sup 87}Rb is related to the hyperfine structure of the conventional saturated absorption spectrum of this transition. Furthermore, the Doppler-free BCS is numerically calculated by considering all of the degenerate magnetic sublevels of the 5S{sub 1/2} → 5P{sub 1/2} transition in an atomic vapor cell, and is found to be in good agreement with the experimental results. Finally, we successfully achieve modulation-free off-resonant locking at the center frequency between the two 5S{sub 1/2}(F = 1 and 2) → 5P{sub 1/2}(F′ = 1) transitions using a polarization rotation of the BCS. The laser frequency stability was estimated to be the Allan variance of 2.1 × 10{sup −10} at 1 s.

  7. Stabilized Fiber-Optic Distribution of Reference Frequency

    NASA Technical Reports Server (NTRS)

    Calhoun, Malcolm; Tjoelker, Robert; Diener, William; Dick, G. John; Wang, Rabi; Kirk, Albert

    2003-01-01

    An optoelectronic system distributes a reference signal of low noise and highly stabilized phase and frequency (100 MHz) from an atomic frequency standard to a remote facility at a distance up to tens of kilometers. The reference signal is transmitted to the remote station as amplitude modulation of an optical carrier signal propagating in an optical fiber. The stabilization scheme implemented in this system is intended particularly to suppress phase and frequency fluctuations caused by vibrations and by expansion and contraction of the optical fiber and other components in diurnal and seasonal heating and cooling cycles. The system (see figure) comprises several subsystems, the main one being (1) a hydrogen-maser or linear-ion-trap frequency standard in an environmentally controlled room in a signal-processing center (SPC), (2) a stabilized fiber-optic distribution assembly (SFODA), (3) a compensated sapphire oscillator (CSO) in an environmentally controlled room in the remote facility, (4) thermally stabilized distribution amplifiers and cabling from the environmentally controlled room to end users, and (5) performance- measuring equipment.

  8. Frequency-stabilization of mode-locked laser-based photonic microwave oscillator

    NASA Technical Reports Server (NTRS)

    Yu, Nan; Tu, Meirong; Salik, Ertan; Maleki, Lute

    2005-01-01

    In this paper, we will describe our recent phase-noise measurements of photonic microwave oscillators. We will aslo discuss our investigation of the frequency stability link between the optical and microwave frequencies in the coupled oscillator.

  9. Frequency stabilization for mobile satellite terminals via LORAN

    NASA Technical Reports Server (NTRS)

    Ernst, Gregory J.; Kee, Steven M.; Marquart, Robert C.

    1990-01-01

    Digital satellite communication systems require careful management of frequency stability. Historically, frequency stability has been accomplished by continuously powered, high cost, high performance reference oscillators. Today's low cost mobile satellite communication equipment must operate under wide ranging environmental conditions, stabilize quickly after application of power, and provide adequate performance margin to overcome RF link impairments unique to the land mobile environment. Methods for frequency stabilization in land mobile applications must meet these objectives without incurring excessive performance degradation. A frequency stabilization scheme utilizing the LORAN (Long Range Navigation) system is presented.

  10. Full stabilization of a microresonator-based optical frequency comb.

    PubMed

    Del'Haye, P; Arcizet, O; Schliesser, A; Holzwarth, R; Kippenberg, T J

    2008-08-01

    We demonstrate control and stabilization of an optical frequency comb generated by four-wave mixing in a monolithic microresonator with a mode spacing in the microwave regime (86 GHz). The comb parameters (mode spacing and offset frequency) are controlled via the power and the frequency of the pump laser, which constitutes one of the comb modes. Furthermore, generation of a microwave beat note at the comb's mode spacing frequency is demonstrated, enabling direct stabilization to a microwave frequency standard.

  11. Long-term laser frequency stabilization using fiber interferometers

    SciTech Connect

    Kong, Jia; Lucivero, Vito Giovanni; Jiménez-Martínez, Ricardo; Mitchell, Morgan W.

    2015-07-15

    We report long-term laser frequency stabilization using only the target laser and a pair of 5 m fiber interferometers, one as a frequency reference and the second as a sensitive thermometer to stabilize the frequency reference. When used to stabilize a distributed feedback laser at 795 nm, the frequency Allan deviation at 1000 s drops from 5.6 × 10{sup −8} to 6.9 × 10{sup −10}. The performance equals that of an offset lock employing a second, atom-stabilized laser in the temperature control.

  12. Frequency stabilization of a high power argon laser.

    NASA Technical Reports Server (NTRS)

    Hohimer, J. P.; Tittel, F. K.; Kelly, R. C.

    1972-01-01

    A technique for frequency stabilizing a high power, single frequency argon laser is described which offers certain advantages over those that have already been reported. This system is capable of maintaining a relative short term frequency stability of the order of plus or minus two parts in one billion and a long term stability (2 hr) of about plus or minus five parts in one billion for the 5145-A line at a power level of 750 mW. This short and long term stability is achieved by means of a multiple feedback loop composed of an optical cavity discriminator which is stabilized against an iodine vapor absorption line.

  13. Frequency stabilization of diode-laser-pumped solid state lasers

    NASA Technical Reports Server (NTRS)

    Byer, Robert L.

    1988-01-01

    The goal of the NASA Sunlite program is to fly two diode-laser-pumped solid-state lasers on the space shuttle and while doing so to perform a measurement of their frequency stability and temporal coherence. These measurements will be made by combining the outputs of the two lasers on an optical radiation detector and spectrally analyzing the beat note. Diode-laser-pumped solid-state lasers have several characteristics that will make them useful in space borne experiments. First, this laser has high electrical efficiency. Second, it is of a technology that enables scaling to higher powers in the future. Third, the laser can be made extremely reliable, which is crucial for many space based applications. Fourth, they are frequency and amplitude stable and have high temporal coherence. Diode-laser-pumped solid-state lasers are inherently efficient. Recent results have shown 59 percent slope efficiency for a diode-laser-pumped solid-state laser. As for reliability, the laser proposed should be capable of continuous operation. This is possible because the diode lasers can be remote from the solid state gain medium by coupling through optical fibers. Diode lasers are constructed with optical detectors for monitoring their output power built into their mounting case. A computer can actively monitor the output of each diode laser. If it sees any variation in the output power that might indicate a problem, the computer can turn off that diode laser and turn on a backup diode laser. As for stability requirements, it is now generally believed that any laser can be stabilized if the laser has a frequency actuator capable of tuning the laser frequency as far as it is likely to drift in a measurement time.

  14. Diode laser frequency stabilization using a low cost, low finesse Fabry-Perot cavity

    NASA Astrophysics Data System (ADS)

    Hastings, Hannah; Jaber, Noura B.; Piatt, Georgia; Gregoric, Vincent C.; Carroll, Thomas J.; Noel, Michael W.

    2016-05-01

    Our lab employs low cost, low finesse Fabry-Perot cavities to stabilize the frequency of diode lasers used in ultra-cold Rydberg atom experiments. To characterize the stability of this technique, we perform a self-heterodyne linewidth measurement. For comparison, we also measure the linewidth when using a saturated absorption spectrometer to provide frequency stability. This work is supported by the National Science Foundation under Grants No. 1205895 and No. 1205897.

  15. Better Stability with Measurement Errors

    NASA Astrophysics Data System (ADS)

    Argun, Aykut; Volpe, Giovanni

    2016-06-01

    Often it is desirable to stabilize a system around an optimal state. This can be effectively accomplished using feedback control, where the system deviation from the desired state is measured in order to determine the magnitude of the restoring force to be applied. Contrary to conventional wisdom, i.e. that a more precise measurement is expected to improve the system stability, here we demonstrate that a certain degree of measurement error can improve the system stability. We exemplify the implications of this finding with numerical examples drawn from various fields, such as the operation of a temperature controller, the confinement of a microscopic particle, the localization of a target by a microswimmer, and the control of a population.

  16. Stability measures in arid ecosystems

    NASA Astrophysics Data System (ADS)

    Nosshi, M. I.; Brunsell, N. A.; Koerner, S.

    2015-12-01

    Stability, the capacity of ecosystems to persist in the face of change, has proven its relevance as a fundamental component of ecological theory. Here, we would like to explore meaningful and quantifiable metrics to define stability, with a focus on highly variable arid and semi-arid savanna ecosystems. Recognizing the importance of a characteristic timescale to any definition of stability, our metrics will be focused scales from annual to multi-annual, capturing different aspects of stability. Our three measures of stability, in increasing order of temporal scale, are: (1) Ecosystem resistance, quantified as the degree to which the system maintains its mean state in response to a perturbation (drought), based on inter-annual variability in Normalized Difference Vegetation Index (NDVI). (2) An optimization approach, relevant to arid systems with pulse dynamics, that models vegetation structure and function based on a trade off between the ability to respond to resource availability and avoid stress. (3) Community resilience, measured as species turnover rate (β diversity). Understanding the nature of stability in structurally-diverse arid ecosystems, which are highly variable, yields theoretical insight which has practical implications.

  17. The JPL Hg(sup +) Extended Linear Ion Trap Frequency Standard: Status, Stability, and Accuracy Prospects

    NASA Technical Reports Server (NTRS)

    Tjoelker, R. L.; Prestage, J. D.; Maleki, L.

    1996-01-01

    Microwave frequency standards based on room temperature (sup 199)Hg(sup +) ions in a Linear Ion Trap (LITS) presently achieve a Signal to Noise and line Q inferred short frequency stability. Long term stability has been measured for averaging intervals up to 5 months with apparent sensitivity to variations in ion number/temperature limiting the flicker floor.

  18. Atomic frequency standards for ultra-high-frequency stability

    NASA Technical Reports Server (NTRS)

    Maleki, L.; Prestage, J. D.; Dick, G. J.

    1987-01-01

    The general features of the Hg-199(+) trapped-ion frequency standard are outlined and compared to other atomic frequency standards, especially the hydrogen maser. The points discussed are those which make the trapped Hg-199(+) standard attractive: high line Q, reduced sensitivity to external magnetic fields, and simplicity of state selection, among others.

  19. Methods and apparatus for broadband frequency comb stabilization

    DOEpatents

    Cox, Jonathan A; Kaertner, Franz X

    2015-03-17

    Feedback loops can be used to shift and stabilize the carrier-envelope phase of a frequency comb from a mode-locked fibers laser or other optical source. Compared to other frequency shifting and stabilization techniques, feedback-based techniques provide a wideband closed-loop servo bandwidth without optical filtering, beam pointing errors, or group velocity dispersion. It also enables phase locking to a stable reference, such as a Ti:Sapphire laser, continuous-wave microwave or optical source, or self-referencing interferometer, e.g., to within 200 mrad rms from DC to 5 MHz. In addition, stabilized frequency combs can be coherently combined with other stable signals, including other stabilized frequency combs, to synthesize optical pulse trains with pulse durations of as little as a single optical cycle. Such a coherent combination can be achieved via orthogonal control, using balanced optical cross-correlation for timing stabilization and balanced homodyne detection for phase stabilization.

  20. Time, Frequency and Physical Measurement.

    ERIC Educational Resources Information Center

    Hellwig, Helmut; And Others

    1978-01-01

    Describes several developments in atomic clocks and frequency standards pointing out the feasibility and practicality in adopting a unified standard of time and frequency to replace other base standards of length, mass, and temperature. (GA)

  1. Chromium:forsterite laser frequency comb stabilization and development of portable frequency references inside a hollow optical fiber

    NASA Astrophysics Data System (ADS)

    Thapa, Rajesh

    We have made significant accomplishments in the development of portable frequency standard inside hollow optical fibers. Such standards will improve portable optical frequency references available to the telecommunications industry. Our approach relies on the development of a stabilized Cr:forsterite laser to generate the frequency comb in the near-IR region. This laser is self referenced and locked to a CW laser which in turn is stabilized to a sub-Doppler feature of a molecular transition. The molecular transition is realized using a hollow core fiber filled with acetylene gas. We finally measured the absolute frequency of these molecular transitions to characterize the references. In this thesis, the major ideas, techniques and experimental results for the development and absolute frequency measurement of the portable frequency references are presented. A prism-based Cr:forsterite frequency comb is stabilized. We have effectively used the prism modulation along with power modulation inside the cavity in order to actively stabilize the frequency comb. We have also studied the carrier-envelope-offset frequency (f0) dynamics of the laser and its effect on laser stabilization. A reduction of f0 linewidth from ˜2 MHz to ˜20 kHz has also been observed. Both our in-loop and out-of-loop measurements of the comb stability showed that the comb is stable within a part in 1011 at 1-s gate time and is currently limited by our reference signal. In order to develop this portable frequency standard, saturated absorption spectroscopy is performed on the acetylene v1 + v3 band near 1532 nm inside different kinds of hollow optical fibers. The observed linewidths are a factor 2 narrower in the 20 mum fiber as compared to 10 mum fiber, and vary from 20-40 MHz depending on pressure and power. The 70 mum kagome fiber shows a further reduction in linewidth to less than 10 MHz. In order to seal the gas inside the hollow optical fiber, we have also developed a technique of splicing the

  2. 47 CFR 87.71 - Frequency measurements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Frequency measurements. 87.71 Section 87.71... Operating Requirements and Procedures Operating Requirements § 87.71 Frequency measurements. A licensed operator must measure the operating frequencies of all land-based transmitters at the following times:...

  3. 47 CFR 74.762 - Frequency measurements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Frequency measurements. 74.762 Section 74.762... Booster Stations § 74.762 Frequency measurements. (a) The licensee of a low power TV station, a TV translator, or a TV booster station must measure the carrier frequencies of its output channel as often...

  4. 47 CFR 74.762 - Frequency measurements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency measurements. 74.762 Section 74.762... Booster Stations § 74.762 Frequency measurements. (a) The licensee of a low power TV station, a TV translator, or a TV booster station must measure the carrier frequencies of its output channel as often...

  5. 47 CFR 74.762 - Frequency measurements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Frequency measurements. 74.762 Section 74.762... Booster Stations § 74.762 Frequency measurements. (a) The licensee of a low power TV station, a TV translator, or a TV booster station must measure the carrier frequencies of its output channel as often...

  6. 47 CFR 87.71 - Frequency measurements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Frequency measurements. 87.71 Section 87.71... Operating Requirements and Procedures Operating Requirements § 87.71 Frequency measurements. A licensed operator must measure the operating frequencies of all land-based transmitters at the following times:...

  7. 47 CFR 87.71 - Frequency measurements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Frequency measurements. 87.71 Section 87.71... Operating Requirements and Procedures Operating Requirements § 87.71 Frequency measurements. A licensed operator must measure the operating frequencies of all land-based transmitters at the following times:...

  8. 47 CFR 87.71 - Frequency measurements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Frequency measurements. 87.71 Section 87.71... Operating Requirements and Procedures Operating Requirements § 87.71 Frequency measurements. A licensed operator must measure the operating frequencies of all land-based transmitters at the following times:...

  9. 47 CFR 74.762 - Frequency measurements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency measurements. 74.762 Section 74.762... Booster Stations § 74.762 Frequency measurements. (a) The licensee of a low power TV station, a TV translator, or a TV booster station must measure the carrier frequencies of its output channel as often...

  10. Frequency stabilization of a single-frequency Q-switched Tm:YAG laser by using injection seeding technique.

    PubMed

    Zhang, Yunshan; Gao, Chunqing; Gao, Mingwei; Zheng, Yan; Wang, Lei; Wang, Ran

    2011-07-20

    A stable single-frequency Q-switched Tm:YAG laser was demonstrated. The laser was injection seeded by a monolithic nonplanar ring oscillator laser utilizing the ramp-hold-fire technique. The measurements of the output parameters were presented. This paper focused on investigation of the frequency stability of the injection-seeded laser, which was measured by optical heterodyne technique. A method used to restrict the frequency jitter of the laser was discussed. The fluctuation of the laser frequency was reduced from 2.36 MHz (rms) to 1.07 MHz (rms) in 1 h by optimizing the voltage of the piezoelectric translator. PMID:21772412

  11. Frequency stabilization of a single-frequency Q-switched Tm:YAG laser by using injection seeding technique.

    PubMed

    Zhang, Yunshan; Gao, Chunqing; Gao, Mingwei; Zheng, Yan; Wang, Lei; Wang, Ran

    2011-07-20

    A stable single-frequency Q-switched Tm:YAG laser was demonstrated. The laser was injection seeded by a monolithic nonplanar ring oscillator laser utilizing the ramp-hold-fire technique. The measurements of the output parameters were presented. This paper focused on investigation of the frequency stability of the injection-seeded laser, which was measured by optical heterodyne technique. A method used to restrict the frequency jitter of the laser was discussed. The fluctuation of the laser frequency was reduced from 2.36 MHz (rms) to 1.07 MHz (rms) in 1 h by optimizing the voltage of the piezoelectric translator.

  12. A method of minimizing the frequency stabilization sensitivity for four frequency differential laser gyro

    NASA Astrophysics Data System (ADS)

    Yang, Jianqiang; Zhu, Yong; Luo, Yun; Jiang, Tian

    2010-10-01

    The frequency stabilization error is an important error source to limit the precision of four frequency differential ring laser gyro (DILAG) in navigation application. Different from the traditional technology mainly related to frequency stabilization circuits design, this paper introduces a new method to solve the problem. The method can essentially minimize the frequency stabilization sensitivity of DILAG, by applying an outer longitudinal magnetic field to the gain region of DILAG. Through adjusting the value of magnetic field to make the frequency splitting equal to the Faraday splitting, the minimum frequency stabilization sensitivity of DILAG will be available. The physics mechanism and mathematic model of this method are analyzed and set up. Concrete steps to realize the method are given in detail. Experimental results have verified its validity and it can decrease the startup drift. Hence, this new method can improve the performance of DILAG, which will be helpful to navigation application.

  13. Stabilization of two frequency combs with a small relative fceo jitter using diode laser injection locking

    NASA Astrophysics Data System (ADS)

    Chun, Byung Jae; Kim, Young-Jin; Kim, Seung-Woo

    2016-03-01

    We report a novel stabilization method for two frequency combs with a small relative fceo jitter using a selected single optical mode out of a frequency comb. This proposed method is intended to stabilize optical frequencies which generated by two different optical combs with immunity to environmental disturbance, frequency drift and fluctuation with time so as to enhance the measuring performance of dual comb based spectroscopy and distance measurement. A single comb mode is selected out using a composite optical filtering and diode laser injection locking. The selected optical frequency yields a narrow relative linewidth less than 1 Hz and the frequency stability of 1.58×10-17 at 10 s averaging time. By using this, we generated heterodyned beat signal between generated optical frequency and another comb to stabilize relative fceo using phase lock-in control which adjust driving frequency of acousto-optic modulator. As a result of feedback control, the relative jitter is well stabilized down to 1.06×10-15 at 10 s averaging time. This highly stable frequency instability of two combs can perform to enhance the measuring resolution, accuracy and repeatability for dual comb based spectroscopy and distance metrology.

  14. Frequency difference stabilization in dual-frequency laser by stress-induced birefringence closed-loop control.

    PubMed

    Li, Jiyang; Niu, Yanxiong; Niu, Haisha

    2016-06-01

    The frequency difference of dual-frequency lasers is increasingly becoming an area of focus in research. The stabilization of beat frequency is of significance in fields such as synthetic wavelength and shows great potential in precise measurement. In this paper, a novel device based on stress-induced birefringence closed-loop control is proposed. Experiments are carried out on a dual-frequency He-Ne Zeeman-birefringence laser with the output mirror sealed in the opposite direction. The results show that the device is capable of controlling the frequency difference variation in 1.3%, in a convenient and highly cost-effective way, and it can increase the quantity of frequency difference, which is crucial to the application of precise measurement through dual-frequency lasers.

  15. Frequency-tunable Pre-stabilized Lasers for LISA via Sideband-locking

    NASA Technical Reports Server (NTRS)

    Livas, Jeffrey C.; Thorpe, James I.; Numata, Kenji; Mitryk, Shawn; Mueller, Guido; Wand, Vinzenz

    2008-01-01

    Laser frequency noise mitigation is one of the most challenging aspects of the LISA interferometric measurement system. The unstabilized frequency fluctuations must be suppressed by roughly twelve orders of magnitude in order to achieve stability sufficient for gravitational wave detection. This enormous suppression will be achieved through a combination of stabilization and common-mode rejection. The stabilization component will itself be achieved in two stages: pre-stabilization to a local optical cavity followed by arm-locking to some combination of the inter-spacecraft distances. In order for these two stabilization stages to work simultaneously, the lock-point of the pre-stabilization loop must be frequency tunable. The current baseline stabilization technique, locking to an optical cavity, does not provide tunability between cavity resonances, which are typically spaced by 100s of MHz. Here we present a modification to the traditional Pound-Drever-Hall cavity locking technique that allows the laser to be locked to a cavity resonance with an adjustable frequency offset. This technique requires no modifications to the optical cavity itself, thus preserving the stability of the frequency reference. We present measurements of the system performance and demonstrate that we can meet implement the first two stages of stabilization.

  16. Frequency-dependence stabilizes competitive interactions among four annual plants.

    PubMed

    Harpole, W Stanley; Suding, Katharine N

    2007-12-01

    It is the combination of large fitness differences and strong stabilizing mechanisms that often constitute niche-based explanations for species abundance patterns. Despite the importance of this assumption to much of community ecology, empirical evidence is surprisingly limited. Empirical tests are critical because many abundance patterns are also consistent with neutral-based alternatives (that assume no fitness differences or stabilization). We quantified interactions of four annual grassland species in two-species mixtures at varying frequencies. We found evidence of strong negative frequency-dependent stabilization, where scaled population growth rates increased with decreasing frequency for all four species. There was also a consistent competitive hierarchy among these species indicative of strong fitness differences that, in most cases, suggested potential competitive exclusion despite the observed strong stabilization.

  17. Advanced two-way satellite frequency transfer by carrier-phase and carrier-frequency measurements

    NASA Astrophysics Data System (ADS)

    Fujieda, Miho; Gotoh, Tadahiro; Amagai, Jun

    2016-06-01

    Carrier-phase measurement is one of the ways to improve the measurement resolution of two-way satellite frequency transfer. We introduce two possible methods for carrier-phase measurement: direct carrier-phase detection identified by Two-Way Carrier-Phase (TWCP) and the use of carrier-frequency information identified by Two-Way Carrier Frequency (TWCF). We performed the former using an arbitrary waveform generator and an analog-to-digital sampler and the latter using a conventional modem. The TWCF measurement using the modem had a resolution of 10-13 and the result agreed with that obtained by GPS carrier-phase frequency transfer in a 1500 km baseline. The measurement accuracy may have been limited by the poor frequency resolution of the modem; however, the TWCF measurement was able to improve the stability of conventional two-way satellite frequency transfer. Additionally, we show that the TWCP measurement system has the potential to achieve a frequency stability of 10-17.

  18. Frequency-Tunable Pre-stabilized lasers for LISA via Stabilized Lasers for LISA via Sideband Locking

    NASA Technical Reports Server (NTRS)

    Livas, Jeffrey; Thorpe, James Ira; Numata, K.

    2008-01-01

    This viewgraph presentation discusses a major potential source of noise for the Laser Interferometer Space Antenna (LISA) that is the laser frequency noise and the proposed mechanism to suppress the unstabilized frequency fluctuations. These fluctuations must be suppresed by about 12 orders of magnitude to achieve a stability that is sufficient for the detection of gravitational waves. This presentation reviews present a modification to the traditional cavity locking technique that allows the laser to be locked to a cavity resonance with an adjustable frequency offset. This presentation also discusses measurements of the system stability, demonstrating that the pre-stabilization level satisfies LISA requirements and a demonstration of a phase-lock loop which utilizes the tunable sideband locking technique as a pre-stabilization stage.

  19. Robust frequency stabilization of multiple spectroscopy lasers with large and tunable offset frequencies.

    PubMed

    Nevsky, A; Alighanbari, S; Chen, Q-F; Ernsting, I; Vasilyev, S; Schiller, S; Barwood, G; Gill, P; Poli, N; Tino, G M

    2013-11-15

    We have demonstrated a compact, robust device for simultaneous absolute frequency stabilization of three diode lasers whose carrier frequencies can be chosen freely relative to the reference. A rigid ULE multicavity block is employed, and, for each laser, the sideband locking technique is applied. A small lock error, computer control of frequency offset, wide range of frequency offset, simple construction, and robust operation are the useful features of the system. One concrete application is as a stabilization unit for the cooling and trapping lasers of a neutral-atom lattice clock. The device significantly supports and improves the clock's operation. The laser with the most stringent requirements imposed by this application is stabilized to a line width of 70 Hz, and a residual frequency drift less than 0.5 Hz/s. The carrier optical frequency can be tuned over 350 MHz while in lock.

  20. An atomic magnetometer with autonomous frequency stabilization and large dynamic range

    SciTech Connect

    Pradhan, S. E-mail: pradhans75@gmail.com; Poornima,; Dasgupta, K.; Mishra, S.; Behera, R.

    2015-06-15

    The operation of a highly sensitive atomic magnetometer using elliptically polarized resonant light is demonstrated. It is based on measurement of zero magnetic field resonance in degenerate two level systems using polarimetric detection. The transmitted light through the polarimeter is used for laser frequency stabilization, whereas reflected light is used for magnetic field measurement. Thus, the experimental geometry allows autonomous frequency stabilization of the laser frequency leading to compact operation of the overall device and has a preliminary sensitivity of <10 pT/Hz{sup 1/2} @ 1 Hz. Additionally, the dynamic range of the device is improved by feedback controlling the bias magnetic field without compromising on its sensitivity.

  1. An atomic magnetometer with autonomous frequency stabilization and large dynamic range.

    PubMed

    Pradhan, S; Mishra, S; Behera, R; Poornima; Dasgupta, K

    2015-06-01

    The operation of a highly sensitive atomic magnetometer using elliptically polarized resonant light is demonstrated. It is based on measurement of zero magnetic field resonance in degenerate two level systems using polarimetric detection. The transmitted light through the polarimeter is used for laser frequency stabilization, whereas reflected light is used for magnetic field measurement. Thus, the experimental geometry allows autonomous frequency stabilization of the laser frequency leading to compact operation of the overall device and has a preliminary sensitivity of <10 pT/Hz(1/2) @ 1 Hz. Additionally, the dynamic range of the device is improved by feedback controlling the bias magnetic field without compromising on its sensitivity. PMID:26133825

  2. An atomic magnetometer with autonomous frequency stabilization and large dynamic range.

    PubMed

    Pradhan, S; Mishra, S; Behera, R; Poornima; Dasgupta, K

    2015-06-01

    The operation of a highly sensitive atomic magnetometer using elliptically polarized resonant light is demonstrated. It is based on measurement of zero magnetic field resonance in degenerate two level systems using polarimetric detection. The transmitted light through the polarimeter is used for laser frequency stabilization, whereas reflected light is used for magnetic field measurement. Thus, the experimental geometry allows autonomous frequency stabilization of the laser frequency leading to compact operation of the overall device and has a preliminary sensitivity of <10 pT/Hz(1/2) @ 1 Hz. Additionally, the dynamic range of the device is improved by feedback controlling the bias magnetic field without compromising on its sensitivity.

  3. Precise Stabilization of the Optical Frequency of WGMRs

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Matsko, Andrey; Matsko, Andrey; Yu, Nan; Maleki, Lute; Iltchenko, Vladimir

    2009-01-01

    Crystalline whispering gallery mode resonators (CWGMRs) made of crystals with axial symmetry have ordinary and extraordinary families of optical modes. These modes have substantially different thermo-refractive constants. This results in a very sharp dependence of differential detuning of optical frequency on effective temperature. This frequency difference compared with clock gives an error signal for precise compensation of the random fluctuations of optical frequency. Certain crystals, like MgF2, have turnover points where the thermo-refractive effect is completely nullified. An advantage for applications using WGMRs for frequency stabilization is in the possibility of manufacturing resonators out of practically any optically transparent crystal. It is known that there are crystals with negative and zero thermal expansion at some specific temperatures. Doping changes properties of the crystals and it is possible to create an optically transparent crystal with zero thermal expansion at room temperature. With this innovation s stabilization technique, the resultant WGMR will have absolute frequency stability The expansion of the resonator s body can be completely compensated for by nonlinear elements. This results in compensation of linear thermal expansion (see figure). In three-mode, the MgF2 resonator, if tuned at the turnover thermal point, can compensate for all types of random thermal-related frequency drift. Simplified dual-mode method is also available. This creates miniature optical resonators with good short- and long-term stability for passive secondary frequency ethalon and an active resonator for active secondary frequency standard (a narrowband laser with long-term stability).

  4. Accurate frequency noise measurement of free-running lasers.

    PubMed

    Schiemangk, Max; Spiessberger, Stefan; Wicht, Andreas; Erbert, Götz; Tränkle, Günther; Peters, Achim

    2014-10-20

    We present a simple method to accurately measure the frequency noise power spectrum of lasers. It relies on creating the beat note between two lasers, capturing the corresponding signal in the time domain, and appropriately postprocessing the data to derive the frequency noise power spectrum. In contrast to methods already established, it does not require stabilization of the laser to an optical reference, i.e., a second laser, to an optical cavity or to an atomic transition. It further omits a frequency discriminator and hence avoids bandwidth limitation and nonlinearity effects common to high-resolution frequency discriminators.

  5. Stabilized Lasers and Precision Measurements.

    ERIC Educational Resources Information Center

    Hall, J. L.

    1978-01-01

    Traces the development of stabilized lasers from the Massachusetts Institute of Technology passive-stabilization experiments of the early 1960s up through the current epoch of highly stabilized helium-neon and carbon dioxide and continuous wave dye lasers. (Author/HM)

  6. Heterodyne laser instantaneous frequency measurement system

    DOEpatents

    Wyeth, Richard W.; Johnson, Michael A.; Globig, Michael A.

    1989-01-01

    A heterodyne laser instantaneous frequency measurement system is disclosed. The system utilizes heterodyning of a pulsed laser beam with a continuous wave laser beam to form a beat signal. The beat signal is processed by a controller or computer which determines both the average frequency of the laser pulse and any changes or chirp of th frequency during the pulse.

  7. Heterodyne laser instantaneous frequency measurement system

    DOEpatents

    Wyeth, Richard W.; Johnson, Michael A.; Globig, Michael A.

    1990-01-01

    A heterodyne laser instantaneous frequency measurement system is disclosed. The system utilizes heterodyning of a pulsed laser beam with a continuous wave laser beam to form a beat signal. The beat signal is processed by a controller or computer which determines both the average frequency of the laser pulse and any changes or chirp of the frequency during the pulse.

  8. Frequency Control Performance Measurement and Requirements

    SciTech Connect

    Illian, Howard F.

    2010-12-20

    Frequency control is an essential requirement of reliable electric power system operations. Determination of frequency control depends on frequency measurement and the practices based on these measurements that dictate acceptable frequency management. This report chronicles the evolution of these measurements and practices. As technology progresses from analog to digital for calculation, communication, and control, the technical basis for frequency control measurement and practices to determine acceptable performance continues to improve. Before the introduction of digital computing, practices were determined largely by prior experience. In anticipation of mandatory reliability rules, practices evolved from a focus primarily on commercial and equity issues to an increased focus on reliability. This evolution is expected to continue and place increased requirements for more precise measurements and a stronger scientific basis for future frequency management practices in support of reliability.

  9. Frequency stabilization of laser diodes in an aggressive thermal environment

    NASA Astrophysics Data System (ADS)

    Minch, J. R.; Walther, F. G.; Savage, S.; Plante, A.; Scalesse, V.

    2015-03-01

    Mobile free-space laser communication systems must reconcile the requirements of low size, weight, and power with the ability to both survive and operate in harsh thermal and mechanical environments. In order to minimize the aperture size and amplifier power requirements of such systems, communication links must exhibit performance near theoretical limits. Such performance requires laser transmitters and receiver filters and interferometers to maintain frequency accuracy to within a couple hundred MHz of the design frequency. We demonstrate an approach to achieving high frequency stability over wide temperature ranges by using conventional DFB lasers, tuned with TEC and current settings, referenced to an HCN molecular frequency standard. A HCN cell absorption line is scanned across the TEC set-point to adjust the DFB laser frequency. Once the center of the line is determined, the TEC set-point is offset as required to obtain frequency agility. To obtain large frequency offsets from an HCN absorption line, as well as continuous laser source operation, a second laser is offset from the reference laser and the resulting beat tone is detected in a photoreceiver and set to the desired offset using a digital frequency-locked loop. Using this arrangement we have demonstrated frequency accuracy and stability of better than 8 MHz RMS over an operational temperature range of 0ºC to 50º C, with operation within minutes following 8 hour soaks at -40º C and 70º C.

  10. Diode-laser frequency stabilization based on the resonant Faraday effect

    NASA Technical Reports Server (NTRS)

    Wanninger, P.; Valdez, E. C.; Shay, T. M.

    1992-01-01

    The authors present the results of a method for frequency stabilizing laser diodes based on the resonant Faraday effects. A Faraday cell in conjunction with a polarizer crossed with respect to the polarization of the laser diode comprises the intracavity frequency selective element. In this arrangement, a laser pull-in range of 9 A was measured, and the laser operated at a single frequency with a linewidth less than 6 MHz.

  11. Apparatus for measuring high frequency currents

    NASA Technical Reports Server (NTRS)

    Hagmann, Mark J. (Inventor); Sutton, John F. (Inventor)

    2003-01-01

    An apparatus for measuring high frequency currents includes a non-ferrous core current probe that is coupled to a wide-band transimpedance amplifier. The current probe has a secondary winding with a winding resistance that is substantially smaller than the reactance of the winding. The sensitivity of the current probe is substantially flat over a wide band of frequencies. The apparatus is particularly useful for measuring exposure of humans to radio frequency currents.

  12. Review of the frequency stabilization of TEA CO2 laser oscillators

    NASA Technical Reports Server (NTRS)

    Willetts, David V.

    1987-01-01

    Most applications of TEA CO2 lasers in heterodyne radar systems require that the transmitter has a high degree of frequency stability. This ensures good Doppler resolution and maximizes receiver sensitivity. However, the environment within the device is far from benign with fast acoustic and electrical transients being present. Consequently the phenomena which govern the frequency stability of pulsed lasers are quite different from those operative in their CW counterparts. This review concentrates on the mechanisms of chirping within the output pulse; pulse to pulse frequency drift may be eliminated by frequency measurement and correction on successive pulses. It emerges that good stability hinges on correct cavity design. The energy-dependent laser-induced frequency sweep falls dramatically as mode diameter is increased. Thus, it is necessary to construct resonators with good selectivity for single mode operation while having a large spot size.

  13. A long-term frequency stabilized deep ultraviolet laser for Mg+ ions trapping experiments

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Yuan, W. H.; Deng, K.; Deng, A.; Xu, Z. T.; Qin, C. B.; Lu, Z. H.; Luo, J.

    2013-12-01

    As many precision laser spectroscopy experiments require frequency stabilized lasers, development of long-term stabilized lasers is of great interest. In this work, we report long-term frequency stabilization of a 280 nm deep ultraviolet laser to a high precision wavemeter with digital servo control such that the long-term drift of the laser frequency was greatly reduced. Long-term laser frequency drift was measured with a fiber frequency comb system over 8 h. After locking, the maximum drift rate of the 280 nm laser was lowered from 576 MHz/h to 6.4 MHz/h. With proper environment control of the wavemeter, the maximum drift rate of the 280 nm laser was further lowered to less than 480 kHz/h. The locked laser system was successfully used in a Mg+ ions trapping experiment, which was also discussed in this work.

  14. A long-term frequency stabilized deep ultraviolet laser for Mg+ ions trapping experiments.

    PubMed

    Zhang, J; Yuan, W H; Deng, K; Deng, A; Xu, Z T; Qin, C B; Lu, Z H; Luo, J

    2013-12-01

    As many precision laser spectroscopy experiments require frequency stabilized lasers, development of long-term stabilized lasers is of great interest. In this work, we report long-term frequency stabilization of a 280 nm deep ultraviolet laser to a high precision wavemeter with digital servo control such that the long-term drift of the laser frequency was greatly reduced. Long-term laser frequency drift was measured with a fiber frequency comb system over 8 h. After locking, the maximum drift rate of the 280 nm laser was lowered from 576 MHz/h to 6.4 MHz/h. With proper environment control of the wavemeter, the maximum drift rate of the 280 nm laser was further lowered to less than 480 kHz/h. The locked laser system was successfully used in a Mg(+) ions trapping experiment, which was also discussed in this work.

  15. 47 CFR 87.71 - Frequency measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Frequency measurements. 87.71 Section 87.71 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES AVIATION SERVICES Operating Requirements and Procedures Operating Requirements § 87.71 Frequency measurements. A...

  16. 47 CFR 74.762 - Frequency measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency measurements. 74.762 Section 74.762 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES EXPERIMENTAL RADIO... Booster Stations § 74.762 Frequency measurements. (a) The licensee of a low power TV station, a...

  17. Precision frequency measurements with interferometric weak values

    NASA Astrophysics Data System (ADS)

    Starling, David J.; Dixon, P. Ben; Jordan, Andrew N.; Howell, John C.

    2010-12-01

    We demonstrate an experiment which utilizes a Sagnac interferometer to measure a change in optical frequency of 129 ± 7 kHz/Hz with only 2 mW of continuous-wave, single-mode input power. We describe the measurement of a weak value and show how even higher-frequency sensitivities may be obtained over a bandwidth of several nanometers. This technique has many possible applications, such as precision relative frequency measurements and laser locking without the use of atomic lines.

  18. Amplitude Frequency Response Measurement: A Simple Technique

    ERIC Educational Resources Information Center

    Satish, L.; Vora, S. C.

    2010-01-01

    A simple method is described to combine a modern function generator and a digital oscilloscope to configure a setup that can directly measure the amplitude frequency response of a system. This is achieved by synchronously triggering both instruments, with the function generator operated in the "Linear-Sweep" frequency mode, while the oscilloscope…

  19. Molecular laser stabilization at low frequencies for the LISA mission

    SciTech Connect

    Argence, B.; Halloin, H.; Jeannin, O.; Prat, P.; Turazza, O.; Vismes, E. de; Auger, G.; Plagnol, E.

    2010-04-15

    We have developed a 532 nm iodine stabilized laser system that may be suitable for the LISA mission (Laser Interferometer Space Antenna) or other future spaceborne missions. This system is based on an externally frequency-doubled Nd:YAG laser source and uses the molecular transfer spectroscopy technique for the frequency stabilization. This technique has been optimized for LISA: compactness (less than 1.1x1.1 m{sup 2}), vacuum compatibility, ease of use and initialization, minimization of the number of active components (acousto-optic modulators are both used for frequency shifting and phase modulating the pump beam). By locking on the a{sub 10} hyperfine component of the R(56)32-0 transition, we find an Allan standard deviation ({sigma}) of 3x10{sup -14} at 1 s and {sigma}<2x10{sup -14} for 20 s{<=}{tau}{<=}10{sup 3} s. In terms of linear spectral density, this roughly corresponds to a stability better than 30 Hz/{radical}(Hz) between 10{sup -2} and 1 Hz with a stability decrease close to 1/f below 10 mHz.

  20. A compact laser head with high-frequency stability for Rb atomic clocks and optical instrumentation

    SciTech Connect

    Affolderbach, Christoph; Mileti, Gaetano

    2005-07-15

    We present a compact and frequency-stabilized laser head based on an extended-cavity diode laser. The laser head occupies a volume of 200 cm{sup 3} and includes frequency stabilization to Doppler-free saturated absorption resonances on the hyperfine components of the {sup 87}Rb D{sub 2} lines at 780 nm, obtained from a simple and compact spectroscopic setup using a 2 cm{sup 3} vapor cell. The measured frequency stability is {<=}2x10{sup -12} over integration times from 1 s to 1 day and shows the potential to reach 2x10{sup -13} over 10{sup 2}-10{sup 5} s. Compact laser sources with these performances are of great interest for applications in gas-cell atomic frequency standards, atomic magnetometers, interferometers and other instruments requiring stable and narrow-band optical sources.

  1. Low Frequency Vibration Energy Harvesting using Diamagnetically Stabilized Magnet Levitation

    NASA Astrophysics Data System (ADS)

    Palagummi, Sri Vikram

    Over the last decade, vibration-based energy harvesting has provided a technology push on the feasibility of self-powered portable small electronic devices and wireless sensor nodes. Vibration energy harvesters in general transduce energy by damping out the environmentally induced relative emotion through either a cantilever beam or an equivalent suspension mechanism with one of the transduction mechanisms, like, piezoelectric, electrostatic, electromagnetic or magnetostrictive. Two major challenges face the present harvesters in literature, one, they suffer from the unavoidable mechanical damping due to internal friction present in the systems, second, they cannot operate efficiently in the low frequency range (< 10 Hz), when most of the ambient vibrational energy is in this low frequency broadband range. Passive and friction free diamagnetically stabilized magnet levitation mechanisms which can work efficiently as a vibration energy harvester in the low frequency range are discussed in this work. First, a mono-stable vertical diamagnetic levitation (VDL) based vibration energy harvester (VEH) is discussed. The harvester consists of a lifting magnet (LM), a floating magnet (FM) and two diamagnetic plates (DPs). The LM balances out the weight of the FM and stability is brought about by the repulsive effect of the DPs, made of pyrolytic graphite. Two thick cylindrical coils, placed in grooves which are engraved in the DPs, are used to convert the mechanical energy into electrical energy. Experimental frequency response of the system is validated by the theoretical analysis which showed that the VEH works in a low frequency range but sufficient levitation gap was not achieved and the frequency response characteristic of the system was effectively linear. To overcome these challenges, the influence of the geometry of the FM, the LM, and the DP were parametrically studied to assess their effects on the levitation gap, size of the system and the natural frequency. For

  2. Optical Frequency Measurements Relying on a Mid-Infrared Frequency Standard

    NASA Astrophysics Data System (ADS)

    Rovera, G. Daniele; Acef, Ouali

    Only a small number of groups are capable of measuring optical frequencies throughout the world. In this contribution we present some of the underlying philosophy of such frequency measurement systems, including some important theoretical hints. In particular, we concentrate on the approach that has been used with the BNM-LPTF frequency chain, where a separate secondary frequency standard in the mid-infrared has been used. The low-frequency section of the chain is characterized by a measurement of the phase noise spectral density Sφ at 716GHz.Most of the significant measurements performed in the last decade are briefly presented, together with a report on the actual stability and reproducibility of the CO2/ OsO4 frequency standard.Measuring the frequency of an optical frequency standard by direct comparison with the signal available at the output of a primary frequency standard (usually between 5MHz and 100MHz) requires a multiplication factor greater than 107. A number of possible configurations, using harmonic generation, sum or difference frequency generation, have been proposed and realized in the past [1,2,3,4,5,6] and in more recent times [7]. A new technique, employing a femtosecond laser, is presently giving its first impressive results [8].All of the classical frequency chains require a large amount of manpower, together with a great deal of simultaneously operating hardware. This has the consequence that only a very few systems are actually in an operating condition throughout the world.

  3. Transient stability assessment by pattern recognition in the frequency domain

    SciTech Connect

    Ostojic, D.R. ); Heydt, G.T. . School of Electrical Engineering)

    1991-02-01

    This paper presents pattern recognition methodology which utilizes spectral monitoring of electromechanical oscillations to assess the transient stability of interconnected power systems. The proposed frequency domain approach permits definitive recognition of unstable dynamic modes. This is used to design an adaptive linear classifier which, in the developmental implementation virtually eliminates both false dismissals, and false alarms. The result is an accurate and reliable decision-making system which performs transient stability monitoring and assessment in real-time. Production computer code has not yet been implemented, but it is expected that the cited performance in developmental tests will be duplicated.

  4. Laser frequency stabilization by dual arm locking for LISA

    SciTech Connect

    Sutton, Andrew; Shaddock, Daniel A.

    2008-10-15

    The Laser Interferometer Space Antenna (LISA) will be the first dedicated space based gravitational wave detector. LISA will consist of a triangular formation of spacecraft, forming an interferometer with 5x10{sup 6} km long arms. Annual length variations of the interferometer arms prevent exact laser frequency noise cancellation. Despite prestabilization to an optical cavity the expected frequency noise is many orders of magnitude larger than the required levels. Arm locking is a feedback control method that will further stabilize the laser frequency by referencing it to the 5x10{sup 6} km arms. Although the original arm locking scheme produced a substantial noise reduction, the technique suffered from slowly decaying start-up transients and excess noise at harmonic frequencies of the inverse round-trip time. Dual arm locking, presented here, improves on the original scheme by combining information from two interferometer arms for feedback control. Compared to conventional arm locking, dual arm locking exhibits significantly reduced start-up transients, no noise amplification at frequencies within the LISA signal band, and more than 50 fold improvement in noise suppression at low frequencies. In this article we present a detailed analysis of the dual arm locking control system and present simulation results showing a noise reduction of 10 000 at a frequency of 10 mHz.

  5. Acoustic frequency combs for carrier-envelope phase stabilization.

    PubMed

    Borchers, Bastian; Lücking, Fabian; Steinmeyer, Günter

    2014-02-01

    A method for improved performance of feed-forward carrier-envelope phase stabilization in amplified laser sources is presented and experimentally demonstrated. The phase stabilization scheme is applicable for a broad range of repetition rates spanning from subhertz to 100 kHz. The method relies on driving an acousto-optic frequency shifter by few-cycle transients. The phase of these transients suitably controls the grating phase of the generated index grating inside the shifter material. This approach removes beam pointing as well as amplitude noise issues observed in continuously driven feed-forward schemes. The synthesis of these gratings can be understood as the acoustic equivalent of mode-locking or acoustic frequency combs. PMID:24487861

  6. Influence of absorption on stability of terahertz difference frequency generation.

    PubMed

    Huang, Nan; Liu, Hongjun; Sun, Qibing; Wang, Zhaolu; Li, Shaopeng; Han, Jing

    2016-01-20

    This work presents numerical studies of the stability feature of terahertz difference frequency generation (THz-DFG) with a ZnGeP(2) crystal using two pump wavelengths. We found that the maximum output of a THz wave is located in the unstable output region because of the competitive equilibrium between the absorption and the gain. Furthermore, the output stability is dependent on the pump stability. Different from the results at the pump wavelength of 9.588 μm, there is neither an appropriate stable output region nor gain saturation region at the pump wavelength of 1.064 μm for a larger absorption coefficient. This work demonstrates that the stable output region of the THz wave is difficult to obtain when the pump absorption is excessively large in DFG. PMID:26835915

  7. Ultrashort pulse Cr4+:YAG laser for high precision infrared frequency interval measurements

    PubMed Central

    Alcock, A. J.; Ma, P.; Poole, P. J.; Chepurov, S.; Czajkowski, A.; Bernard, J. E.; Madej, A. A.; Fraser, J. M.; Mitchell, I. V.; Sorokina, I. T.; Sorokin, E.

    2010-01-01

    A cavity stabilized, SESAM mode-locked Cr4+:YAG laser capable of generating sub-100 fs pulses has been developed. Locking the 130-MHz pulse repetition frequency to that of a hydrogen maser-referenced frequency synthesizer provides a 30-nm wide frequency comb for the 1530-nm wavelength region. In conjunction with a pair of acetylene stabilized, external cavity diode lasers, this laser provides a high precision measurement tool for the determination of acetylene transition frequencies. PMID:19498916

  8. B-chromosome frequency stability in Prochilodus lineatus (Characiformes, Prochilodontidae).

    PubMed

    Voltolin, Tatiana Aparecida; Senhorini, José Augusto; Oliveira, Claudio; Foresti, Fausto; Bortolozzi, Jehud; Porto-Foresti, Fabio

    2010-03-01

    The genus Prochilodus includes individuals ranging in size from medium to large, being highly relevant for commercial and subsistence fishing. Prochilodus species have a diploid number of 2n = 54 chromosomes and up to seven supernumerary (B) microchromosomes. Previous research has shown that B frequency increased drastically in the Mogi-Guaçu river population of Prochilodus lineatus in the early 1980s, whereas it remained about constant in the 1990s. Here we analyses B frequency in this population during the 2003-2007 period and have found that frequency has not changed significantly since 1987, and that these B chromosomes do not show the intra-individual variation in number that characterized them in the 1980s. This indicates that these B chromosomes have been neutralized, after their invasion, through their mitotic stabilization. PMID:19882308

  9. A high-performance frequency stability compact CPT clock based on a Cs-Ne microcell.

    PubMed

    Boudot, Rodolphe; Liu, Xiaochi; Abbé, Philippe; Chutani, Ravinder; Passilly, Nicolas; Galliou, Serge; Gorecki, Christophe; Giordano, Vincent

    2012-11-01

    This paper reports on a compact table-top Cs clock based on coherent population trapping (CPT) with advanced frequency stability performance. The heart of the clock is a single buffer gas Cs-Ne microfabricated cell. Using a distributed feedback (DFB) laser resonant with the Cs D1 line, the contrast of the CPT signal is found to be maximized around 80°C, a value for which the temperature dependence of the Cs clock frequency is canceled. Advanced techniques are implemented to actively stabilize the clock operation on a zero-light-shift point. The clock frequency stability is measured to be 3.8 × 10(-11) at 1 s and well below 10(-11) until 50,000 s. These results demonstrate the possibility to develop high-performance chip-scale atomic clocks using vapor cells containing a single buffer gas. PMID:23192824

  10. 5 W frequency stabilized 976 nm tapered diode lasers

    NASA Astrophysics Data System (ADS)

    Friedmann, Patrick; Gilly, Jürgen; Moritz, Stefan; Ostendorf, Ralf; Kelemen, Márc T.

    2008-02-01

    More and more applications, like tunable frequency doubling of diode lasers for blue-green outputs, non linear spectroscopy, or pump laser sources for fiber lasers necessitate diffraction-limited tunable narrow linewidths and high output powers in the multiwatt regime. For these applications, tapered lasers based on a tapered amplifier with gain-guided design can be used in an external cavity set up to guarantee both - frequency stabilization and tunability. We have realized frequency stabilized high-power ridge-waveguide tapered diode lasers with more than 4W of cw output power. These low modal gain, single quantum well InGaAs/AlGaAs devices emitting between 920nm and 1064nm were grown by molecular beam epitaxy. Tapered single emitters consist of an index-guided ridge section and a gain-guided taper section with an overall length of 3.5mm. The taper angle was 6°. With a high-reflectivity coating on the rear facet and an antireflection coating on the front facet more than 10W of output power have been demonstrated. To optimize the beam quality at higher output power the two different sections have been operated by different operation currents. For this purpose the tapered diodes have been mounted p-side down on structured submounts. For wavelength tunability and frequency stabilization the tapered diodes, provided with AR coatings on both facets, have been used in external cavity setup in Littrow configuration. The influence of the different operation currents on the electrooptical and beam characteristics has been carefully investigated in detail. Within this operation mode a nearly diffraction limited behavior up to 5W has been established.

  11. A model for the synchronous machine using frequency response measurements

    SciTech Connect

    Bacalao, N.J.; Arizon, P. de; Sanchez L., R.O.

    1995-02-01

    This paper presents new techniques to improve the accuracy and velocity for the modeling of synchronous machines in stability and transient studies. The proposed model uses frequency responses as input data, obtained either directly from measurements or calculated from the available data. The new model is flexible as it allows changes in the detail in which the machine can be represented, and it is possible to partly compensate for the numerical errors incurred when using large integration time steps. The model can be used in transient stability and electromagnetic transient studies as secondary arc evaluation, load rejections and sub-synchronous resonance.

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

    PubMed

    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. PMID:25167146

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

    PubMed

    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.

  14. Frequency stabilization via the mixed mode in three mode HeNe lasers

    SciTech Connect

    Ellis, J D; Joo, K; Buice, E S; Spronck, J W; Munnig Schmidt, R H

    2010-02-05

    This paper describes a three mode HeNe laser frequency stabilization technique using the mixed mode frequency to obtain a fractional frequency stability of 2 x 10{sup -11}. The mixed mode frequency occurs due to optical nonlinear interactions with the adjacent modes at each of the three modes. In precision displacement interferometry systems, the laser source frequency must be stabilized to provide an accurate conversion ratio between phase change and displacement. In systems, such as lithography applications, which require high speed, high accuracy and low data age uncertainty, it is also desirable to avoid periodic nonlinearities, which reduces computation time and errors. One method to reduce periodic nonlinearity is to spatially separate the measurement and reference beams to prevent optical mixing, which has been shown for several systems. Using spatially separated beams and the proper optical configuration, the interferometer can be fiber fed, which can increase the interferometer's stability by reducing the number of beam steering optical elements. Additionally, as the number of measurement axes increases, a higher optical power from the laser source is necessary.

  15. Nonlinear Trivelpiece-Gould Waves: Frequency, Functional Form, and Stability

    NASA Astrophysics Data System (ADS)

    Dubin, Daniel H. E.

    2015-11-01

    This poster considers the frequency, spatial form, and stability, of nonlinear Trivelpiece- Gould (TG) waves on a cylindrical plasma column of length L and radius rp, treating both traveling and standing waves, and focussing on the regime of experimental interest in which L/rp >> 1. In this regime TG waves are weakly dispersive, allowing strong mode-coupling between Fourier harmonics. The mode coupling implies that linear theory for such waves is a poor approximation even at fairly small amplitudes, and nonlinear theories that include only a small number of harmonics (such as 3-wave parametric resonance theory) fail to fully capture the stability properties of the system. We find that nonlinear standing waves suffer jumps in their functional form as their amplitude is varied continuously. The jumps are caused by nonlinear resonances between the standing wave and nearly linear waves whose frequencies and wave numbers are harmonics of the standing wave. Also, the standing waves are found to be unstable to a multi-wave version of 3-wave parametric resonance, with an amplitude required for instability onset that is much larger than expected from three wave theory. For traveling wave, linearly stability is found for all amplitudes that could be studied, in contradiction to 3-wave theory. Supported by National Science Foundation Grant PHY-1414570, Department of Energy Grants DE-SC0002451and DE-SC0008693.

  16. Current trends to measure implant stability.

    PubMed

    Swami, Vasanthi; Vijayaraghavan, Vasantha; Swami, Vinit

    2016-01-01

    Implant stability plays a critical role for successful osseointegration. Successful osseointegration is a prerequisite for functional dental implants. Continuous monitoring in an objective and qualitative manner is important to determine the status of implant stability. Implant stability is measured at two different stages: Primary and secondary. Primary stability comes from mechanical engagement with cortical bone. Secondary stability is developed from regeneration and remodeling of the bone and tissue around the implant after insertion and affected by the primary stability, bone formation and remodelling. The time of functional loading is dependent upon the implant stability. Historically the gold standard method to evaluate stability were microscopic or histologic analysis, radiographs, however due to invasiveness of these methods and related ethical issues various other methods have been proposed like cutting torque resistance, reverse torque analysis, model analysis etc. It is, therefore, of an utmost importance to be able to access implant stability at various time points and to project a long term prognosis for successful therapy. Therefore this review focuses on the currently available methods for evaluation of implant stability.

  17. Frequency stabilization in nonlinear MEMS and NEMS oscillators

    DOEpatents

    Lopez, Omar Daniel; Antonio, Dario

    2014-09-16

    An illustrative system includes an amplifier operably connected to a phase shifter. The amplifier is configured to amplify a voltage from an oscillator. The phase shifter is operably connected to a driving amplitude control, wherein the phase shifter is configured to phase shift the amplified voltage and is configured to set an amplitude of the phase shifted voltage. The oscillator is operably connected to the driving amplitude control. The phase shifted voltage drives the oscillator. The oscillator is at an internal resonance condition, based at least on the amplitude of the phase shifted voltage, that stabilizes frequency oscillations in the oscillator.

  18. Dynamics of microresonator frequency comb generation: models and stability

    NASA Astrophysics Data System (ADS)

    Hansson, Tobias; Wabnitz, Stefan

    2016-06-01

    Microresonator frequency combs hold promise for enabling a new class of light sources that are simultaneously both broadband and coherent, and that could allow for a profusion of potential applications. In this article, we review various theoretical models for describing the temporal dynamics and formation of optical frequency combs. These models form the basis for performing numerical simulations that can be used in order to better understand the comb generation process, for example helping to identify the universal combcharacteristics and their different associated physical phenomena. Moreover, models allow for the study, design and optimization of comb properties prior to the fabrication of actual devices. We consider and derive theoretical formalisms based on the Ikeda map, the modal expansion approach, and the Lugiato-Lefever equation. We further discuss the generation of frequency combs in silicon resonators featuring multiphoton absorption and free-carrier effects. Additionally, we review comb stability properties and consider the role of modulational instability as well as of parametric instabilities due to the boundary conditions of the cavity. These instability mechanisms are the basis for comprehending the process of frequency comb formation, for identifying the different dynamical regimes and the associated dependence on the comb parameters. Finally, we also discuss the phenomena of continuous wave bi- and multistability and its relation to the observation of mode-locked cavity solitons.

  19. Frequency Stability of 1X10(sup -13) in a compensated Saphirre Oscillator Operating Above 77K

    NASA Technical Reports Server (NTRS)

    Dick, G. John; Santiago, David G.; Wang, Rabi T.

    1996-01-01

    We report on tests of a compensated saphirre oscillator (CS) which shows frequency-stable operation at temperatures above 77k.The frequency stability for this oscillator shows an apparent flicker floor of 7.5X10(sup -14) for measuring times between 3 and 10 seconds, and stability is better than 2X10(sup -13) for all measuring times between 10 and 100 seconds... Frequency sensitivities os the microwave sapphire resonator to temperature and temperature rate have been characterized, and a careful analysis of several aspects of the ac frequency-lock.

  20. Stability and noise spectra of relative Loran-C frequency comparisons

    NASA Technical Reports Server (NTRS)

    Proverbio, E.; Quesada, V.; Simoncini, A.

    1973-01-01

    Relative comparisons of Loran-C frequency transmissions between the master station of Catanzaro (Simeri Crichi) and the X, Z slave stations of Estartit (Spain) and Lampedusa (Italy) are carrying out by the GG LORSTA monitor station of the Mediterranean Sea Loran-C chain. These comparisons are able to emphasize the relative and, under certain conditions, the absolute rate of the emitting standard frequencies of the slave stations and some relevant statistical properties of the Loran-C Method for frequency transmission and time synchronization. The stability of each Loran-C frequency standard transmission is subject to perturbations, more or less known, due to the propagation medium and other causes. Following the Allan (1966) method for data processing, the performance of the relative rate of frequency of the transmissions of the X, Z slave stations are described calculating the standard deviation of a set of N frequency measurements from its mean averaged during sampling times. This standard deviation is designated as the measure of the stability of the Loran-C frequency transmission.

  1. Fast phase stabilization of a low frequency beat note for atom interferometry.

    PubMed

    Oh, E; Horne, R A; Sackett, C A

    2016-06-01

    Atom interferometry experiments rely on the ability to obtain a stable signal that corresponds to an atomic phase. For interferometers that use laser beams to manipulate the atoms, noise in the lasers can lead to errors in the atomic measurement. In particular, it is often necessary to actively stabilize the optical phase between two frequency components of the beams. Typically this is achieved using a time-domain measurement of a beat note between the two frequencies. This becomes challenging when the frequency difference is small and the phase measurement must be made quickly. The method presented here instead uses a spatial interference detection to rapidly measure the optical phase for arbitrary frequency differences. A feedback system operating at a bandwidth of about 10 MHz could then correct the phase in about 3 μs. This time is short enough that the phase correction could be applied at the start of a laser pulse without appreciably degrading the fidelity of the atom interferometer operation. The phase stabilization system was demonstrated in a simple atom interferometer measurement of the (87)Rb recoil frequency. PMID:27370424

  2. Fast phase stabilization of a low frequency beat note for atom interferometry.

    PubMed

    Oh, E; Horne, R A; Sackett, C A

    2016-06-01

    Atom interferometry experiments rely on the ability to obtain a stable signal that corresponds to an atomic phase. For interferometers that use laser beams to manipulate the atoms, noise in the lasers can lead to errors in the atomic measurement. In particular, it is often necessary to actively stabilize the optical phase between two frequency components of the beams. Typically this is achieved using a time-domain measurement of a beat note between the two frequencies. This becomes challenging when the frequency difference is small and the phase measurement must be made quickly. The method presented here instead uses a spatial interference detection to rapidly measure the optical phase for arbitrary frequency differences. A feedback system operating at a bandwidth of about 10 MHz could then correct the phase in about 3 μs. This time is short enough that the phase correction could be applied at the start of a laser pulse without appreciably degrading the fidelity of the atom interferometer operation. The phase stabilization system was demonstrated in a simple atom interferometer measurement of the (87)Rb recoil frequency.

  3. A frequency-domain transient stability criterion for normal contingencies

    SciTech Connect

    Marceau, R.J.; Rizzi, J.C.; Mailhot, R.

    1995-08-01

    In a previous paper, a simple frequency-domain stability criterion was proposed for networks near the stability limit subjected to a 3-phase fault with no loss of line. The criterion can be summarized as follows: if a system is stable, the phase angle of the Fourier transform of a network`s transient voltage response exhibits a clockwise polar plot behavior at all buses (i.e. for increasing frequency); if the system is unstable, it exhibits a counterclockwise behavior in at least one location. Though these results are of interest, the criterion would be of greater practical use in mechanizing dynamic security analysis if it could be extended to the types of contingencies actually used in security analysis, namely normal contingencies. Normal contingencies are commonly defined as the loss of any element in a power system, either spontaneously or preceded by a fault, and such changes in topology impact post-contingency steady-state voltages in addition to their transient behavior. The present paper shows how such cases can be treated, thereby extending the applicable range of the criterion to normal contingencies.

  4. Single frequency and wavelength stabilized near infrared laser source for water vapor DIAL remote sensing application

    NASA Astrophysics Data System (ADS)

    Chuang, Ti; Walters, Brooke; Shuman, Tim; Losee, Andrew; Schum, Tom; Puffenberger, Kent; Burnham, Ralph

    2015-02-01

    Fibertek has demonstrated a single frequency, wavelength stabilized near infrared laser transmitter for NASA airborne water vapor DIAL application. The application required a single-frequency laser transmitter operating at 935 nm near infrared (NIR) region of the water vapor absorption spectrum, capable of being wavelength seeded and locked to a reference laser source and being tuned at least 100 pm across the water absorption spectrum for DIAL on/off measurements. Fibertek is building a laser transmitter system based on the demonstrated results. The laser system will be deployed in a high altitude aircraft (ER-2 or UAV) to autonomously perform remote, long duration and high altitude water vapor measurements.

  5. The correction of vibration in frequency scanning interferometry based absolute distance measurement system for dynamic measurements

    NASA Astrophysics Data System (ADS)

    Lu, Cheng; Liu, Guodong; Liu, Bingguo; Chen, Fengdong; Zhuang, Zhitao; Xu, Xinke; Gan, Yu

    2015-10-01

    Absolute distance measurement systems are of significant interest in the field of metrology, which could improve the manufacturing efficiency and accuracy of large assemblies in fields such as aircraft construction, automotive engineering, and the production of modern windmill blades. Frequency scanning interferometry demonstrates noticeable advantages as an absolute distance measurement system which has a high precision and doesn't depend on a cooperative target. In this paper , the influence of inevitable vibration in the frequency scanning interferometry based absolute distance measurement system is analyzed. The distance spectrum is broadened as the existence of Doppler effect caused by vibration, which will bring in a measurement error more than 103 times bigger than the changes of optical path difference. In order to decrease the influence of vibration, the changes of the optical path difference are monitored by a frequency stabilized laser, which runs parallel to the frequency scanning interferometry. The experiment has verified the effectiveness of this method.

  6. A discussion of dynamic stability measurement techniques

    NASA Technical Reports Server (NTRS)

    Johnson, W.

    1975-01-01

    Techniques for the measurement of the dynamic stability of linear systems are discussed. Particular attention is given to an analysis of the errors in the procedures, and to methods for calculating the system damping from the data. The techniques discussed include: transient decay, moving block analysis, spectral analysis, random decrement signatures, transfer function analysis, and parameter identification methods. The special problems of rotorcraft dynamic stability testing are discussed.

  7. Precision measurements and applications of femtosecond frequency combs

    NASA Astrophysics Data System (ADS)

    Jones, R. Jason

    2002-05-01

    The merging of femtosecond (fs) laser physics with the field of optical f requency metrology over recent years has had a profound impact on both di sciplines. Precision control of the broad frequency bandwidth from fs la sers has enabled new areas of exploration in ultrafast physics and revolu tionized optical frequency measurement and precision spectroscopy. Most recently, the transition frequency of the length standard at 514.7 nm,^ 127I2 P(13) 43-0 a3 has been measured in our lab with an improvement of more than 100 times in precision. Interesting molecular dynamics and s tructure are being explored using absolute frequency map of molecular tra nsitions over a large wavelength range. The iodine transition at 532 nm h as been used to establish an optical atomic clock with a fs comb providin g both an RF standard with stability comparable to the best atomic clocks and millions of optical frequencies across the visible and near IR spect rum, each stable to the Hz level. Work is presently underway to directly compare the iodine optical clocks at JILA with the Hg and Ca optical cloc ks currently being refined at NIST via a direct optical fiber link. A wi dely tunable single frequency laser in combination with a fs comb has bee n employed to realize an optical frequency synthesizer. Frequency combs of two independent ultrafast lasers have been coherently locked, enablin g several different avenues of application such as synthesis of arbitrary waveforms, coherent control of quantum systems, and coherent anti-Stokes Raman scattering microscopy. This talk will review these recent accompl ishments from our lab and discuss plans for further improving the control and precision of fs laser based measurements. te

  8. High Precision Noise Measurements at Microwave Frequencies

    SciTech Connect

    Ivanov, Eugene; Tobar, Michael

    2009-04-23

    We describe microwave noise measurement system capable of detecting the phase fluctuations of rms amplitude of 2{center_dot}10{sup -11} rad/{radical}(Hz). Such resolution allows the study of intrinsic fluctuations in various microwave components and materials, as well as precise tests of fundamental physics. Employing this system we discovered a previously unknown phenomenon of down-conversion of pump oscillator phase noise into the low-frequency voltage fluctuations.

  9. Stability of similarity measurements for bipartite networks

    PubMed Central

    Liu, Jian-Guo; Hou, Lei; Pan, Xue; Guo, Qiang; Zhou, Tao

    2016-01-01

    Similarity is a fundamental measure in network analyses and machine learning algorithms, with wide applications ranging from personalized recommendation to socio-economic dynamics. We argue that an effective similarity measurement should guarantee the stability even under some information loss. With six bipartite networks, we investigate the stabilities of fifteen similarity measurements by comparing the similarity matrixes of two data samples which are randomly divided from original data sets. Results show that, the fifteen measurements can be well classified into three clusters according to their stabilities, and measurements in the same cluster have similar mathematical definitions. In addition, we develop a top-n-stability method for personalized recommendation, and find that the unstable similarities would recommend false information to users, and the performance of recommendation would be largely improved by using stable similarity measurements. This work provides a novel dimension to analyze and evaluate similarity measurements, which can further find applications in link prediction, personalized recommendation, clustering algorithms, community detection and so on. PMID:26725688

  10. 47 CFR 73.1540 - Carrier frequency measurements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Carrier frequency measurements. 73.1540 Section... measurements. (a) The carrier frequency of each AM and FM station and the visual carrier frequency and the... departure limits. (c) The primary standard of frequency for radio frequency measurements is the...

  11. 47 CFR 73.1540 - Carrier frequency measurements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Carrier frequency measurements. 73.1540 Section... measurements. (a) The carrier frequency of each AM and FM station and the visual carrier frequency and the... departure limits. (c) The primary standard of frequency for radio frequency measurements is the...

  12. Local vs. global redundancy - trade-offs between resilience against cascading failures and frequency stability

    NASA Astrophysics Data System (ADS)

    Plietzsch, A.; Schultz, P.; Heitzig, J.; Kurths, J.

    2016-05-01

    When designing or extending electricity grids, both frequency stability and resilience against cascading failures have to be considered amongst other aspects of energy security and economics such as construction costs due to total line length. Here, we compare an improved simulation model for cascading failures with state-of-the-art simulation models for short-term grid dynamics. Random ensembles of realistic power grid topologies are generated using a recent model that allows for a tuning of global vs local redundancy. The former can be measured by the algebraic connectivity of the network, whereas the latter can be measured by the networks transitivity. We show that, while frequency stability of an electricity grid benefits from a global form of redundancy, resilience against cascading failures rather requires a more local form of redundancy and further analyse the corresponding trade-off.

  13. Engineering stabilizer measurements in circuit QED: I

    NASA Astrophysics Data System (ADS)

    Chou, Kevin; Blumoff, Jacob; Reagor, M.; Axline, C.; Brierley, R.; Nigg, S.; Reinhold, P.; Heeres, R.; Wang, C.; Sliwa, K.; Narla, A.; Hatridge, M.; Jiang, L.; Devoret, M. H.; Girvin, S. M.; Schoekopf, R. J.

    Quantum error correction based on stabilizer codes has emerged as an attractive approach towards building a practical quantum information processor. One requirement for such a device is the ability to perform hardware efficient measurements on registers of qubits. We demonstrate a new protocol to realize such multi-qubit measurements. A key feature of our approach is that it enables arbitrary stabilizer measurements to be selected in software, and requires a relatively small number of buses, ancillae, and control lines. This allows for a minimally complex sample realizing a simple dispersive hamiltonian while maintaining a high degree of decoupling between our fixed-tuned qubits. We experimentally implement these measurements in 3D circuit QED using transmon qubits coupled to a common bus resonator. In this first of two talks, we introduce our 3D cQED system and describe the protocol for measuring n-qubit parities of a three qubit register. We acknowledge funding from ARO.

  14. Femtosecond frequency comb measurement of absolute frequencies and hyperfine coupling constants in cesium vapor

    SciTech Connect

    Stalnaker, Jason E.; Mbele, Vela; Gerginov, Vladislav; Fortier, Tara M.; Diddams, Scott A.; Hollberg, Leo; Tanner, Carol E.

    2010-04-15

    We report measurements of absolute transition frequencies and hyperfine coupling constants for the 8S{sub 1/2}, 9S{sub 1/2}, 7D{sub 3/2}, and 7D{sub 5/2} states in {sup 133}Cs vapor. The stepwise excitation through either the 6P{sub 1/2} or 6P{sub 3/2} intermediate state is performed directly with broadband laser light from a stabilized femtosecond laser optical-frequency comb. The laser beam is split, counterpropagated, and focused into a room-temperature Cs vapor cell. The repetition rate of the frequency comb is scanned and we detect the fluorescence on the 7P{sub 1/2,3/2{yields}}6S{sub 1/2} branches of the decay of the excited states. The excitations to the different states are isolated by the introduction of narrow-bandwidth interference filters in the laser beam paths. Using a nonlinear least-squares method we find measurements of transition frequencies and hyperfine coupling constants that are in agreement with other recent measurements for the 8S state and provide improvement by 2 orders of magnitude over previously published results for the 9S and 7D states.

  15. Extreme low frequency acoustic measurement system

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A. (Inventor); Zuckerwar, Allan J. (Inventor)

    2013-01-01

    The present invention is an extremely low frequency (ELF) microphone and acoustic measurement system capable of infrasound detection in a portable and easily deployable form factor. In one embodiment of the invention, an extremely low frequency electret microphone comprises a membrane, a backplate, and a backchamber. The backchamber is sealed to allow substantially no air exchange between the backchamber and outside the microphone. Compliance of the membrane may be less than ambient air compliance. The backplate may define a plurality of holes and a slot may be defined between an outer diameter of the backplate and an inner wall of the microphone. The locations and sizes of the holes, the size of the slot, and the volume of the backchamber may be selected such that membrane motion is substantially critically damped.

  16. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Frequency range of measurements. 18.309 Section... MEDICAL EQUIPMENT Technical Standards § 18.309 Frequency range of measurements. (a) For field strength measurements: Frequency band in which device operates (MHz) Range of frequency measurements Lowest...

  17. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 1 2012-10-01 2012-10-01 false Frequency range of measurements. 18.309 Section... MEDICAL EQUIPMENT Technical Standards § 18.309 Frequency range of measurements. (a) For field strength measurements: Frequency band in which device operates (MHz) Range of frequency measurements Lowest...

  18. Lysogen stability is determined by the frequency of activity bursts from the fate-determining gene.

    PubMed

    Zong, Chenghang; So, Lok-hang; Sepúlveda, Leonardo A; Skinner, Samuel O; Golding, Ido

    2010-11-30

    The ability of living cells to maintain an inheritable memory of their gene-expression state is key to cellular differentiation. Bacterial lysogeny serves as a simple paradigm for long-term cellular memory. In this study, we address the following question: in the absence of external perturbation, how long will a cell stay in the lysogenic state before spontaneously switching away from that state? We show by direct measurement that lysogen stability exhibits a simple exponential dependence on the frequency of activity bursts from the fate-determining gene, cI. We quantify these gene-activity bursts using single-molecule-resolution mRNA measurements in individual cells, analyzed using a stochastic mathematical model of the gene-network kinetics. The quantitative relation between stability and gene activity is independent of the fine details of gene regulation, suggesting that a quantitative prediction of cell-state stability may also be possible in more complex systems. PMID:21119634

  19. Microcalorimetric Measurements of Hydrogen Peroxide Stability

    NASA Technical Reports Server (NTRS)

    Davis, Dennis D.; Hornung, Steven D.; Baker, Dave L.

    1999-01-01

    Recent interest in propellants with nontoxic reaction products has led to a resurgence of interest in hydrogen peroxide for various propellant applications. Because hydrogen peroxide is sensitive to contaminants and materials interactions, stability and shelf life are issues. A relatively new, ultrasensitive heat measurement technique, isothermal microcalorimetry, is being used at the White Sands Test Facility to monitor the decomposition of hydrogen peroxide at near ambient temperatures. Isothermal microcalorimetry measures the beat flow from a reaction vessel into a surrounding heat sink. In these applications, microcalorimetry is approximately 1,000 times more sensitive than accelerating rate calorimetry or differential scanning calorimetry for measuring thermal events. Experimental procedures have been developed for the microcalorimetric measurement of the ultra-small beat effects caused by incompatible interactions of hydrogen peroxide. The decomposition rates of hydrogen peroxide at the picomole/sec/gram level have been measured showing the effects of stabilizers and peroxide concentration. Typical measurements are carried out at 40 C over a 24-hour period, This paper describes a method for the conversion of the heat flow measurements to chemical reaction rates based on thermochemical considerations. The reaction rates are used in a study of the effects of stabilizer levels on the decomposition of propellant grade hydrogen peroxide.

  20. Operational stability of rubidium and cesium frequency standards. [analysis of equipment performance at NASA tracking stations

    NASA Technical Reports Server (NTRS)

    Lavery, J. E.

    1972-01-01

    In the course of testing various rubidium and cesium frequency standards under operational conditions for use in NASA tracking stations, about 55 unit-years of relative frequency measurements for averaging times from 10 to 10 to the 7th power have been accumulated at Goddard Space Flight Center (GSFC). Statistics on the behavior of rubidium and cesium standards under controlled laboratory conditions have been published, but it was not known to what extent the lesser controlled environments of NASA tracking stations affected the performance of the standards. The purpose of this report is to present estimates of the frequency stability of rubidium and cesium frequency standards under operational conditions based on the data accumulated at GSFC.

  1. Engineering stabilizer measurements in circuit QED: II

    NASA Astrophysics Data System (ADS)

    Blumoff, Jacob; Chou, Kevin; Reagor, M.; Axline, C.; Brierly, R.; Nigg, S.; Reinhold, P.; Heeres, R.; Wang, C.; Sliwa, K.; Narla, A.; Hatridge, M.; Jiang, L.; Devoret, M. H.; Girvin, S. M.; Schoelkopf, R. J.

    Quantum error correction based on stabilizer codes has emerged as an attractive approach towards building a practical quantum information processor. One requirement for such a device is the ability to perform hardware efficient measurements on registers of qubits. We demonstrate a new protocol to realize such multi-qubit measurements. A key feature of our approach is that it enables arbitrary stabilizer measurements to be selected in software, and requires a relatively small number of buses, ancillae, and control lines. This allows for a minimally complex sample realizing a simple dispersive hamiltonian while maintaining a high degree of decoupling between our fixed-tuned qubits. We experimentally implement these measurements in 3D circuit QED using transmon qubits coupled to a common bus resonator. In the second of two talks, we present a full characterization of the algorithm describing the outcome dependent projections via quantum process tomography. We acknowledge funding from ARO.

  2. Estimating Gait Stability: Asymmetrical Loading Effects Measured Using Margin of Stability and Local Dynamic Stability.

    PubMed

    Worden, Timothy A; Beaudette, Shawn M; Brown, Stephen H M; Vallis, Lori Ann

    2016-01-01

    Changes to intersegmental locomotor control patterns may affect body stability. Our study aimed to (a) characterize upper body dynamic stability in response to the unilateral addition of mass to the lower extremity and (b) evaluate the efficacy of 2 different stability measures commonly used in the literature to detect resulting symmetrical step pattern modifications across the weighted segments (spatial) and between epochs of the gait cycle (temporal). Young adults walked on a treadmill while unloaded or with weights applied unilaterally to their foot, shank, or thigh. Both margin of stability and local dynamic stability (LDS) estimates detected similar trends of distal segment weighting resulting in more unstable upper body movement compared to proximal weighting; however only LDS detected anteroposterior changes in upper body stability over time.

  3. Frequency stability of GPS NAVSTAR block 1 and block 2 on-orbit clocks

    NASA Technical Reports Server (NTRS)

    Mccaskill, Thomas B.; Reid, Wilson G.; Buisson, James A.; Warren, Hugh E.

    1992-01-01

    Analysis of the frequency stability of the on-orbit NAVSTAR clocks os performed by the Naval Research Laboratory. The frequency stability is presented for sample times of one day to 30 days. Composite frequency stability profiles are presented for Block 1 and Block 2 NAVSTAR clocks. Several NAVSTAR cesium clocks show frequency stabilities of a few parts in 1 x 10(exp 14) for long sample times. Time-domain noise-process analysis shows the dominant noise type to be white frequency noise for sample times of one to ten days. The non-stationary stochastic behavior of one of the cesium clocks, illustrated by its frequency stability history, shows that the frequency stability is not always time-invariant.

  4. Stabilization of a self-referenced, prism-based, Cr:forsterite laser frequency comb using an intracavity prism

    SciTech Connect

    Tillman, Karl A.; Thapa, Rajesh; Knabe, Kevin; Wu Shun; Lim, Jinkang; Washburn, Brian R.; Corwin, Kristan L.

    2009-12-20

    The frequency comb from a prism-based Cr:forsterite laser has been frequency stabilized using intracavity prism insertion and pump power modulation. Absolute frequency measurements of a CW fiber laser stabilized to the P(13) transition of acetylene demonstrate a fractional instability of {approx}2x10{sup -11} at a 1 s gate time, limited by a commercial Global Positioning System (GPS)-disciplined rubidium oscillator. Additionally, absolute frequency measurements made simultaneously using a second frequency comb indicate relative instabilities of 3x10{sup -12} for both combs for a 1 s gate time. Estimations of the carrier-envelope offset frequency linewidth based on relative intensity noise and the response dynamics of the carrier-envelope offset to pump power changes confirm the observed linewidths.

  5. Mechanical monolithic sensor for low frequency seismic noise measurement

    NASA Astrophysics Data System (ADS)

    Acernese, Fausto; De Rosa, Rosario; Giordano, Gerardo; Romano, Rocco; Barone, Fabrizio

    2007-10-01

    This paper describes a mechanical monolithic sensor for geophysical applications developed at the University of Salerno. The instrument is basically a monolithic tunable folded pendulum, shaped with precision machining and electric-discharge-machining, that can be used both as seismometer and, in a force-feedback configuration, as accelerometer. The monolithic mechanical design and the introduction of laser interferometric techniques for the readout implementation make it a very compact instrument, very sensitive in the low-frequency seismic noise band, with a very good immunity to environmental noises. Many changes have been produced since last version (2006), mainly aimed to the improvement of the mechanics and of the optical readout of the instrument. In fact, we have developed and tested a prototype with elliptical hinges and mechanical tuning of the resonance frequency together with a new laser optical lever and laser interferometer readout system. The theoretical sensitivity curve for both laser optical lever and laser interferometric readouts, calculated on the basis of suitable theoretical models, shows a very good agreement with the experimental measurements. Very interesting scientific result is that the measured natural resonance frequency of the instrument is ~ 70mHz with a Q ~ 140 in air without thermal stabilization, demonstrating the feasibility of a monolithic FP sensor with a natural resonance frequency of the order of 5 mHz with a more refined mechanical tuning.

  6. Mechanical monolithic horizontal sensor for low frequency seismic noise measurement

    NASA Astrophysics Data System (ADS)

    Acernese, Fausto; Giordano, Gerardo; Romano, Rocco; De Rosa, Rosario; Barone, Fabrizio

    2008-07-01

    This paper describes a mechanical monolithic horizontal sensor for geophysical applications developed at the University of Salerno. The instrument is basically a monolithic tunable folded pendulum, shaped with precision machining and electric discharge machining, that can be used both as seismometer and, in a force-feedback configuration, as accelerometer. The monolithic mechanical design and the introduction of laser interferometric techniques for the readout implementation makes it a very compact instrument, very sensitive in the low frequency seismic noise band, with a very good immunity to environmental noises. Many changes have been produced since last version (2007), mainly aimed to the improvement of the mechanics and of the optical readout of the instrument. In fact, we have developed and tested a prototype with elliptical hinges and mechanical tuning of the resonance frequency together with a laser optical lever and a new laser interferometer readout system. The theoretical sensitivity curve for both laser optical lever and laser interferometric readouts, evaluated on the basis of suitable theoretical models, shows a very good agreement with the experimental measurements. Very interesting scientific result is the measured natural resonance frequency of the instrument of 70mHz with a Q =140 in air without thermal stabilization. This result demonstrates the feasibility of a monolithic folded pendulum sensor with a natural resonance frequency of the order of millihertz with a more refined mechanical tuning.

  7. Ionospheric calibration for single frequency altimeter measurements

    NASA Astrophysics Data System (ADS)

    Schreiner, William S.; Born, George H.

    1993-08-01

    This report investigates the potential of using Global Positioning System (GPS) data and a model of the ionosphere to supply a measure of the sub-satellite Total Electron Current (TEC) of the required accuracy (10 TECU rms) for the purpose of calibrating single frequency radar altimeter measurements. Since climatological (monthly mean) models are known to be in error by as much as 50 percent, this work focused on the Parameterized Real-Time Ionospheric Specification Model (PRISM) which has the capability to improve model accuracy by ingesting (adjusting to) in situ ionospheric measurements. A set of globally distributed TEC measurements were generated using GPS data and were used as input to improve the accuracy of the PRISM model. The adjusted PRISM TEC values were compared to TOPEX dual frequency TEC measurements (which are considered truth) for a number of TOPEX sub-satellite tracks. The adjusted PRISM values generally compared to the TOPEX measurements within the 10 TECU accuracy requirements when the sub-satellite track passed within 300 to 400 km of the GPS TEC data or when the track passed through a night time ionosphere. However, when the sub-satellite points were greater than 300 to 400 km away from the GPS TEC data or when a local noon ionosphere was sampled, the adjusted PRISM values generally differed by greater than 10 TECU rms with data excursions from the TOPEX TEC measurements of as much as 40 TECU (an 8 cm path delay error at K band). Therefore, it can be concluded from this analysis that an unrealistically large number of GPS stations would be needed to predict sub-satellite TEC at the 10 TECU level in the day time ionosphere using a model such as PRISM. However, a technique currently being studied at the Jet Propulsion Laboratory (JPL) may provide a means of supplying adequate TEC data to meet the 10 TECU ionospheric correction accuracy when using a realistic number of ionospheric stations. This method involves using global GPS TEC data to

  8. Ionospheric calibration for single frequency altimeter measurements

    NASA Technical Reports Server (NTRS)

    Schreiner, William S.; Born, George H.

    1993-01-01

    This report investigates the potential of using Global Positioning System (GPS) data and a model of the ionosphere to supply a measure of the sub-satellite Total Electron Current (TEC) of the required accuracy (10 TECU rms) for the purpose of calibrating single frequency radar altimeter measurements. Since climatological (monthly mean) models are known to be in error by as much as 50 percent, this work focused on the Parameterized Real-Time Ionospheric Specification Model (PRISM) which has the capability to improve model accuracy by ingesting (adjusting to) in situ ionospheric measurements. A set of globally distributed TEC measurements were generated using GPS data and were used as input to improve the accuracy of the PRISM model. The adjusted PRISM TEC values were compared to TOPEX dual frequency TEC measurements (which are considered truth) for a number of TOPEX sub-satellite tracks. The adjusted PRISM values generally compared to the TOPEX measurements within the 10 TECU accuracy requirements when the sub-satellite track passed within 300 to 400 km of the GPS TEC data or when the track passed through a night time ionosphere. However, when the sub-satellite points were greater than 300 to 400 km away from the GPS TEC data or when a local noon ionosphere was sampled, the adjusted PRISM values generally differed by greater than 10 TECU rms with data excursions from the TOPEX TEC measurements of as much as 40 TECU (an 8 cm path delay error at K band). Therefore, it can be concluded from this analysis that an unrealistically large number of GPS stations would be needed to predict sub-satellite TEC at the 10 TECU level in the day time ionosphere using a model such as PRISM. However, a technique currently being studied at the Jet Propulsion Laboratory (JPL) may provide a means of supplying adequate TEC data to meet the 10 TECU ionospheric correction accuracy when using a realistic number of ionospheric stations. This method involves using global GPS TEC data to

  9. Measurement of microresonator frequency comb coherence by spectral interferometry.

    PubMed

    Webb, K E; Jang, J K; Anthony, J; Coen, S; Erkintalo, M; Murdoch, S G

    2016-01-15

    We experimentally investigate the spectral coherence of microresonator optical frequency combs. Specifically, we use a spectral interference method, typically used in the context of supercontinuum generation, to explore the variation of the magnitude of the complex degree of first-order coherence across the full comb bandwidth. We measure the coherence of two different frequency combs and observe wholly different coherence characteristics. In particular, we find that the observed dynamical regimes are similar to the stable and unstable modulation instability regimes reported in previous theoretical studies. Results from numerical simulations are found to be in good agreement with experimental observations. In addition to demonstrating a new technique to assess comb stability, our results provide strong experimental support for previous theoretical analyses. PMID:26766693

  10. Optimization of A 2-Micron Laser Frequency Stabilization System for a Double-Pulse CO2 Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Chen, Songsheng; Yu, Jirong; Bai, Yingsin; Koch, Grady; Petros, Mulugeta; Trieu, Bo; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

    2010-01-01

    A carbon dioxide (CO2) Differential Absorption Lidar (DIAL) for accurate CO2 concentration measurement requires a frequency locking system to achieve high frequency locking precision and stability. We describe the frequency locking system utilizing Frequency Modulation (FM), Phase Sensitive Detection (PSD), and Proportional Integration Derivative (PID) feedback servo loop, and report the optimization of the sensitivity of the system for the feed back loop based on the characteristics of a variable path-length CO2 gas cell. The CO2 gas cell is characterized with HITRAN database (2004). The method can be applied for any other frequency locking systems referring to gas absorption line.

  11. Unprecedented long-term frequency stability with a microwave resonator oscillator.

    PubMed

    Grop, Serge; Schafer, Wolfgang; Bourgeois, Pierre-Yves; Kersale, Yann; Oxborrow, Mark; Rubiola, Enrico; Giordano, Vincent

    2011-08-01

    This article reports on the long-term frequency stability characterization of a new type of cryogenic sapphire oscillator using an autonomous pulse-tube cryocooler as its cold source. This new design enables a relative frequency stability of better than 4.5 x 10(-15) over one day of integration. To the best of our knowledge, this represents the best long-term frequency stability ever obtained with a signal source based on a macroscopic resonator.

  12. Are gait variability and stability measures influenced by directional changes?

    PubMed Central

    2014-01-01

    Background Many gait variability and stability measures have been proposed in the literature, with the aim to quantify gait impairment, degree of neuro-motor control and balance disorders in healthy and pathological subjects. These measures are often obtained from lower trunk acceleration data, typically acquired during rectilinear gait, but relevant experimental protocols and data processing techniques lack in standardization. Since directional changes represent an essential aspect of gait, the assessment of their influence on such measures is essential for standardization. In addition, their investigation is needed to evaluate the applicability of these measures in laboratory trials and in daily life activity analysis. A further methodological aspect to be standardized concerns the assessment of the sampling frequency, which could affect stability measures. The aim of the present study was hence to assess if gait variability and stability measures are affected by directional changes, and to evaluate the influence of sampling frequency of trunk acceleration data on the results. Methods Fifty-one healthy young adults performed a 6-minute walk test along a 30 m straight pathway, turning by 180 deg at each end of the pathway. Nine variability and stability measures (Standard deviation, Coefficient of variation, Poincaré plots, maximum Floquet multipliers, short-term Lyapunov exponents, Recurrence quantification analysis, Multiscale entropy, Harmonic ratio and Index of harmonicity) were calculated on stride duration and trunk acceleration data (acquired at 100 Hz and 200 Hz) coming from straight walking windows and from windows including both straight walking and the directional change. Results Harmonic ratio was the only measure that resulted to be affected by directional changes and sampling frequency, decreasing with the presence of a directional change task. HR was affected in the AP and V directions for the 200 Hz, but only in AP direction for the 100 Hz group

  13. Time delay measurement in the frequency domain

    SciTech Connect

    Durbin, Stephen M.; Liu, Shih -Chieh; Dufresne, Eric M.; Li, Yuelin; Wen, Haidan

    2015-08-06

    Pump–probe studies at synchrotrons using X-ray and laser pulses require accurate determination of the time delay between pulses. This becomes especially important when observing ultrafast responses with lifetimes approaching or even less than the X-ray pulse duration (~100 ps). The standard approach of inspecting the time response of a detector sensitive to both types of pulses can have limitations due to dissimilar pulse profiles and other experimental factors. Here, a simple alternative is presented, where the frequency response of the detector is monitored versus time delay. Measurements readily demonstrate a time resolution of ~1 ps. Improved precision is possible by simply extending the data acquisition time.

  14. Time delay measurement in the frequency domain

    DOE PAGESBeta

    Durbin, Stephen M.; Liu, Shih -Chieh; Dufresne, Eric M.; Li, Yuelin; Wen, Haidan

    2015-08-06

    Pump–probe studies at synchrotrons using X-ray and laser pulses require accurate determination of the time delay between pulses. This becomes especially important when observing ultrafast responses with lifetimes approaching or even less than the X-ray pulse duration (~100 ps). The standard approach of inspecting the time response of a detector sensitive to both types of pulses can have limitations due to dissimilar pulse profiles and other experimental factors. Here, a simple alternative is presented, where the frequency response of the detector is monitored versus time delay. Measurements readily demonstrate a time resolution of ~1 ps. Improved precision is possible bymore » simply extending the data acquisition time.« less

  15. Time delay measurement in the frequency domain

    PubMed Central

    Durbin, Stephen M.; Liu, Shih-Chieh; Dufresne, Eric M.; Li, Yuelin; Wen, Haidan

    2015-01-01

    Pump–probe studies at synchrotrons using X-ray and laser pulses require accurate determination of the time delay between pulses. This becomes especially important when observing ultrafast responses with lifetimes approaching or even less than the X-ray pulse duration (∼100 ps). The standard approach of inspecting the time response of a detector sensitive to both types of pulses can have limitations due to dissimilar pulse profiles and other experimental factors. Here, a simple alternative is presented, where the frequency response of the detector is monitored versus time delay. Measurements readily demonstrate a time resolution of ∼1 ps. Improved precision is possible by simply extending the data acquisition time. PMID:26289282

  16. Long term frequency stability analysis of the GPS NAVSTAR 6 Cesium clock

    NASA Technical Reports Server (NTRS)

    Mccaskill, T. B.; Stebbins, S.; Carson, C.; Buisson, J.

    1982-01-01

    Time domain measurements, taken between the NAVSTAR 6 Spacecraft Vehicle (SV) and the Vandenberg Global Positioning System (GPS) Monitor Site, by a pseudo random noise receiver, were collected over an extended period of time and analyzed to estimate the long term frequency stability of the NAVSTAR 6 onboard frequency standard, referenced to the Vandenberg MS frequency standard. The technique employed separates the clock offset from the composite signal by first applying corrections for equipment delays, ionospheric delay, tropospheric delay, Earth rotation and the relativistic effect. The data are edited and smoothed using the predicted SV ephemeris to calculate the geometric delay. Then all available passes from each of the four GPS monitor stations, are collected at 1-week intervals and used to calculate the NAVSTAR orbital elements. The procedure is then completed by subtracting the corrections and the geometric delay, using the final orbital elements, from the composite signal, thus leaving the clock offset and random error.

  17. A tunable Doppler-free dichroic lock for laser frequency stabilization

    NASA Astrophysics Data System (ADS)

    Singh, Vivek; Tiwari, V. B.; Mishra, S. R.; Rawat, H. S.

    2016-08-01

    We propose and demonstrate a laser frequency stabilization scheme which generates a dispersion-like tunable Doppler-free dichroic lock (TDFDL) signal. This signal offers a wide tuning range for lock point (i.e. zero-crossing) without compromising on the slope of the locking signal. The method involves measurement of magnetically induced dichroism in an atomic vapour for a weak probe laser beam in the presence of a counter-propagating strong pump laser beam. A simple model is presented to explain the basic principles of this method to generate the TDFDL signal. The spectral shift in the locking signal is achieved by tuning the frequency of the pump beam. The TDFDL signal is shown to be useful for locking the frequency of a cooling laser used for magneto-optical trap (MOT) for 87 Rb atoms.

  18. Stabilizing low frequency beam motion in the Tevatron

    SciTech Connect

    Ranjbar, V.H.; /Fermilab

    2005-05-01

    A feed back orbit stabilization system is being developed using a set of BPMS and existing Tevatron corrector magnets to stabilize beam motion up to 50 microns below 25 Hz. The construction of this system is described and the stability limits and magnitude of beam motion reduction is explored.

  19. Optical wire guided lumpectomy: frequency domain measurements

    NASA Astrophysics Data System (ADS)

    Dayton, A. L.; Keränen, V. T.; Prahl, S. A.

    2009-02-01

    In practice, complete removal of the tumor during a lumpectomy is difficult; the published rates of positive margins range from 10% to 50%. A spherical lumpectomy specimen with tumor directly in the middle may improve the success rate. A light source placed within the tumor may accomplish this goal by creating a sphere surrounding the tumor that can serve as a guide for resection. In an optical phantom and a prophylactic mastectomy specimen, sinusoidally modulated light within the medium was collected by optical fiber(s) at fixed distance(s) from the source and used to measure the optical properties. These optical properties were then used to calculate the distance the light had traveled through the medium. The fiber was coupled to an 830nm diode laser that was modulated at 100, 200 and 300 MHz. A handheld optical probe collected the modulated light and a network analyzer measured the phase lag. This data was used to calculate the distance the light traveled from the emitting fiber tip to the probe. The optical properties were μa = 0.004mm-1 and μ1s = 0.38mm-1 in the phantom. The optical properties for the tissue were μa = 0.005mm-1 and μ1s = 0.20mm-1. The prediction of distance from the source was within 4mm of the actual distance at 30mm in the phantom and within 3mm of the actual distance at 25mm in the tissue. The feasibility of a frequency domain system that makes measurements of local optical properties and then extrapolates those optical properties to make measurements of distance with a separate probe was demonstrated.

  20. Lasic -Cavity-enhanced molecular iodine laser frequency stabilization for space projects

    NASA Astrophysics Data System (ADS)

    Turazza, Oscar; Acef, O.; Auger, G.; Halloin, H.; Duburck, F.; Plagnol, E.; Holleville, D.; Dimarcq, N.; Binetruy, P.; Brillet, A.; Lemonde, P.; Devismes, E.; Prat, P.; Lours, M.; Tuckey, P.; Argence, B.

    We present work in progress at SYRTE, APC and ARTEMIS aiming at stabilizing the frequency of a Nd:YAG laser using saturated absorption spectroscopy of molecular iodine 127I2. The novel design of the LASIC project allows for robustness and compacity while achieving high-performance phase noise suppression. The project is a follow-up of the laser stabilization work started at Artemis and continued at APC. The use of a low-finesse bow-tie optical cavity around the iodine absorber, combined with an adapted high-frequency modulation of the laser phase -NICE-OHMS technique-yields shot-noise limited saturated absorption signals with cavity-enhanced signal-to-noise ratios. Residual fractional frequency instability in terms of Allan Std. Deviation is expected below 10-14 @1s integration time and down to 10-15 over several hours. The compact iodine / cavity design, and performance well above LISA requirements make this project an interesting candidate for the space-based Gravitational Waves detector. We discuss the scientific background and outline of this project within the LISA framework, as well as its potential impact on other stringent technical requirements of the LISA project (e.g. U.S.O. clock-stability, arm-length measurements. . . ). We also present other possible applications for space projects involving interferometry, laser ranging or onboard ultrastable oscillators.

  1. Ionospheric calibration for single frequency altimeter measurements

    NASA Astrophysics Data System (ADS)

    Schreiner, William S.; Born, George H.; Markin, Robert E.

    1994-03-01

    This study is a preliminary analysis of the effectiveness (in terms of altimeter calibration accuracy) of various ionosphere models and the Global Positioning System (GPS) to calibrate single frequency altimeter height measurements for ionospheric path delay. In particular, the research focused on ingesting GPS Total Electron Content (TEC) data into the physical Parameterized Real-Time Ionospheric Specification Model (PRISM), which estimates the composition of the ionosphere using independent empirical and physical models and has the capability of adjusting to additional ionospheric measurements. Two types of GPS data were used to adjust the PRISM model: GPS receiver station data mapped from line-of-sight observations to the vertical at the point of interest and a grid map (generated at the Jet Propulsion Laboratory) of GPS derived TEC in a sun-fixed longitude frame. The adjusted PRISM TEC values, as well as predictions by the International Reference Ionosphere (IRI-90), a climatological (monthly mean) model of the ionosphere, were compared to TOPEX dual-frequency TEC measurements (considered as truth) for a number of TOPEX sub-satellite tracks. For a 13.6 GHz altimeter, a Total Electron Content (TEC) of 1 TECU 10(exp 16) electrons/sq m corresponds to approximately 0.218 centimeters of range delay. A maximum expected TEC (at solar maximum or during solar storms) of 10(exp 18) electrons/sq m will create 22 centimeters of range delay. Compared with the TOPEX data, the PRISM predictions were generally accurate within the TECU when the sub-satellite track of interest passed within 300 to 400 km of the GPS TEC data or when the track passed through a night-time ionosphere. If neither was the case, in particular if the track passed through a local noon ionosphere, the PRISM values differed by more than 10 TECU and by as much as 40 TECU. The IRI-90 model, with no current ability to unseat GPS data, predicted TEC to a slightly higher error of 12 TECU. The performance of

  2. Ionospheric calibration for single frequency altimeter measurements

    NASA Technical Reports Server (NTRS)

    Schreiner, William S.; Born, George H.; Markin, Robert E.

    1994-01-01

    This study is a preliminary analysis of the effectiveness (in terms of altimeter calibration accuracy) of various ionosphere models and the Global Positioning System (GPS) to calibrate single frequency altimeter height measurements for ionospheric path delay. In particular, the research focused on ingesting GPS Total Electron Content (TEC) data into the physical Parameterized Real-Time Ionospheric Specification Model (PRISM), which estimates the composition of the ionosphere using independent empirical and physical models and has the capability of adjusting to additional ionospheric measurements. Two types of GPS data were used to adjust the PRISM model: GPS receiver station data mapped from line-of-sight observations to the vertical at the point of interest and a grid map (generated at the Jet Propulsion Laboratory) of GPS derived TEC in a sun-fixed longitude frame. The adjusted PRISM TEC values, as well as predictions by the International Reference Ionosphere (IRI-90), a climatological (monthly mean) model of the ionosphere, were compared to TOPEX dual-frequency TEC measurements (considered as truth) for a number of TOPEX sub-satellite tracks. For a 13.6 GHz altimeter, a Total Electron Content (TEC) of 1 TECU 10(exp 16) electrons/sq m corresponds to approximately 0.218 centimeters of range delay. A maximum expected TEC (at solar maximum or during solar storms) of 10(exp 18) electrons/sq m will create 22 centimeters of range delay. Compared with the TOPEX data, the PRISM predictions were generally accurate within the TECU when the sub-satellite track of interest passed within 300 to 400 km of the GPS TEC data or when the track passed through a night-time ionosphere. If neither was the case, in particular if the track passed through a local noon ionosphere, the PRISM values differed by more than 10 TECU and by as much as 40 TECU. The IRI-90 model, with no current ability to unseat GPS data, predicted TEC to a slightly higher error of 12 TECU. The performance of

  3. Long-path atmospheric measurements using dual frequency comb measurements

    NASA Astrophysics Data System (ADS)

    Waxman, Eleanor; Cossel, Kevin; Truong, Gar-Wing; Giorgetta, Fabrizio; Swann, William; Coddington, Ian; Newbury, Nathan

    2016-04-01

    The dual frequency comb spectrometer is a new tool for performing atmospheric trace gas measurements. This instrument is capable of measuring carbon dioxide, methane, and water with extremely high resolution in the region between 1.5 and 2.1 microns in the near-IR. It combines the high resolution of a laboratory-based FTIR instrument with the portability of a long-path DOAS system. We operate this instrument at path lengths of a few kilometers, thus bridging the spatial resolution of in-situ point sensors and the tens of square kilometer footprints of satellites. This spatial resolution is ideal for measuring greenhouse gas emissions from cities. Here we present initial long-path integrated column measurements of the greenhouse gases water, carbon dioxide, and methane in an urban environment. We present a time series with 5 minute time resolution over a 2 kilometer path in Boulder, Colorado at the urban-rural interface. We validate this data via a comparison with an in-situ greenhouse gas monitor co-located along the measurement path and show that we agree well on the baseline concentration but that we are significantly less sensitive to local point source emission that have high temporal variability, making this instrument ideal for measurements of average city-wide emissions. We additionally present progress towards measurements over an 11 kilometer path over downtown Boulder to measure the diurnal flux of greenhouse gases across the city.

  4. 47 CFR 74.562 - Frequency monitors and measurements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency monitors and measurements. 74.562... Auxiliary Stations § 74.562 Frequency monitors and measurements. The licensee shall ensure that the STL, ICR... accomplished by appropriate frequency measurement techniques and consideration of the transmitter emissions....

  5. Dynamic frequency-noise spectrum measurement for a frequency-swept DFB laser with short-delayed self-heterodyne method.

    PubMed

    Zhou, Qian; Qin, Jie; Xie, Weilin; Liu, Zhangweiyi; Tong, Yitian; Dong, Yi; Hu, Weisheng

    2015-11-01

    We proposed and experimentally demonstrated a short-delayed self-heterodyne method with 15.5m delay to get a large-frequency-range laser frequency-noise spectrum over 10Hz to 50 MHz, and an averaging approach to extract the intrinsic frequency noise of a frequency-swept laser. With these two techniques, dynamic frequency-noise spectrum of a frequency-swept DFB laser when free running and servo-controlled are both measured. This measurement method permits accurate and insightful investigation of laser stability.

  6. Chronic alcohol self-administration in monkeys shows long-term quantity/frequency categorical stability

    PubMed Central

    Baker, Erich J.; Farro, Jonathan; Gonzales, Steven; Helms, Christa; Grant, Kathleen A.

    2014-01-01

    Background The current criteria for alcohol use disorders (AUD) do not include consumption (quantity/frequency) measures of alcohol intake, in part due to the difficulty of these measures in humans. Animal models of ethanol self-administration have been fundamental in advancing our understanding of the neurobiological basis of (AUD) and can address quantity/frequency measures with accurate measurements over prolonged periods of time. The non-human primate (NHP) model of voluntary oral alcohol self-administration has documented both binge drinking and drinking to dependence and can be used to test the stability of consumption measures over time. Methods and Results Here, an extensive set of alcohol intakes (g/kg/day) was analyzed from a large multi-cohort population of Rhesus (Macaca mulatta) monkeys (n=31). Daily ethanol intake was uniformly distributed over chronic (12 months) access for all animals. Underlying this distribution of intakes were subpopulations of monkeys that exhibited distinctive clustering of drinking patterns, allowing us to categorically define very heavy drinking (VHD), heavy drinking (HD), binge drinking (BD), and low drinking (LD). These categories were stable across the 12-month assessed by the protocol, but exhibited fluctuations when examined at shorter intervals. Conclusions The establishment of persistent drinking categories based on quantity/frequency suggests that consumption variables can be used to track long-term changes in behavioral, molecular or physiochemical mechanisms related to our understanding of diagnosis, prevention, intervention and treatment efficacies. PMID:25421519

  7. Frequency stability and offset locking of a laser-diode-pumped Nd:YAG monolithic nonplanar ring oscillator

    NASA Technical Reports Server (NTRS)

    Kane, Thomas J.; Nilsson, Alan C.; Byer, Robert L.

    1987-01-01

    The frequency stability of laser-diode-pumped, monolithic Nd:YAG solid-state unidirectional nonplanar ring oscillators was studied by heterodyne measurements. CW single-axial- and transverse-mode power of 25 mW at 1064 nm was obtained at a slope efficiency of 19 percent. Two independent oscillators were offset-locked at 17 MHz with frequency fluctuations of less than + or - 40 kHz for periods of 8 min.

  8. Sexual Frequency and the Stability of Marital and Cohabiting Unions

    ERIC Educational Resources Information Center

    Yabiku, Scott T.; Gager, Constance T.

    2009-01-01

    Prior research found that lower sexual frequency and satisfaction were associated with higher rates of divorce, but little research had examined the role of sexual activity in the dissolution of cohabiting unions. We drew upon social exchange theory to hypothesize why sexual frequency is more important in cohabitation: (a) cohabitors' lower costs…

  9. Experimental Investigation of Hexagon Stability in Two Frequency Forced Faraday Waves

    NASA Astrophysics Data System (ADS)

    Ding, Yu; Umbanhowar, Paul

    2003-03-01

    We have conducted experiments on a deep layer of silicone oil vertically oscillated with an acceleration a(t) = Am sin(m ω t + φ_m) + An sin(n ω t + φ_n). The stability of hexagonal surface wave patterns is investigated as a function of the overall acceleration, the ratio m:n, and the phase of the two rationally related driving frequencies. When the ratio A_m/An is chosen so the system is near a co-dimension two point, the stability of hexagons above onset is determined by the acceleration amplitude and the relative phase. Recent results by Porter and Silver (J. Porter and M. Silber, Phys. Rev. Lett. 084501, 2002) predicts that the range of pattern stability above onset as a function of acceleration is determined by cos(Φ), where Φ = π/4 - m φn / 2- n φm /2. We have tested this prediction for a number of m:n ratios and for various values of the dimensionless damping coefficient γ. We find that the patterns exhibit the predicted functional dependence on s(Φ) but with an additional phase offset. We measure the phase offset as a function of m:n and γ for varying frequency ω and fluid viscosity 5 cS <= ν <= 30 cS.

  10. Effect of power frequency harmonics on magnetic field measurements.

    PubMed

    Isokorpi, J; Rautee, J; Keikko, T; Korpinen, L

    2000-03-01

    This paper presents a study of the effect of harmonic frequencies on magnetic field measurements. We introduced magnetic field meters in a known magnetic field of different frequencies: power frequency (50 Hz) as well as 3rd (150 Hz) and 5th (250 Hz) harmonic frequencies. Two magnetic field levels (0.25 A and 2.5 A) were used. A Helmholtz coil was applied to generate an exact magnetic field. The difference between the measurement results at harmonic frequencies and at power frequency was analyzed using the t-test for matched pairs. The test results show significant differences (P< or =0.01) for 13 out of 28 tests carried out, which is probably due to a curved frequency response near the power frequency. It is, therefore, essential to consider harmonic frequencies in magnetic field measurements in practice.

  11. On-chip multi spectral frequency standard replication by stabilizing a microring resonator to a molecular line

    NASA Astrophysics Data System (ADS)

    Zektzer, Roy; Stern, Liron; Mazurski, Noa; Levy, Uriel

    2016-07-01

    Stabilized laser lines are highly desired for myriad of applications ranging from precise measurements to optical communications. While stabilization can be obtained by using molecular or atomic absorption references, these are limited to specific frequencies. On the other hand, resonators can be used as wide band frequency references. Unfortunately, such resonators are unstable and inaccurate. Here, we propose and experimentally demonstrate a chip-scale multispectral frequency standard replication operating in the spectral range of the near IR. This is obtained by frequency locking a microring resonator (MRR) to an acetylene absorption line. The MRR consists of a Si3N4 waveguides with microheater on top of it. The thermo-optic effect is utilized to lock one of the MRR resonances to an acetylene line. This locked MRR is then used to stabilize other laser sources at 980 nm and 1550 nm wavelength. By beating the stabilized laser to another stabilized laser, we obtained frequency instability floor of 4 ×10-9 at around 100 s in terms of Allan deviation. Such stable and accurate chip scale sources are expected to serve as important building block in diverse fields such as communication and metrology.

  12. A new measure for upright stability.

    PubMed

    Honarvar, Mohammad Hadi; Nakashima, Motomu

    2014-01-22

    The control of balance is a primary objective in most human movements. In many cases, research or practice, it is essential to quantitatively know how good the balance is at a body posture or at every moment during a task. In this paper we suggest a new measure for postural upright stability which assigns a value to a body state based on the probability of avoiding a fall initiation from that state. The balance recovery problem is solved for a population sample using a strength database, and the probability of successfully maintaining the balance is found over the population and called the probability of recovery (PoR). It, therefore, describes an attribute of a body state: how possible the control of balance is, or how safe being at that state is. We also show the PoR calculated for a 3-link body model for all states on a plane, compare it to that found using a 2-link model, and compare it to a conventional metric: the margin of stability (MoS). It is shown, for example, that MoS may be very low at a state from which most of the people will be able to easily control their balance.

  13. Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies.

    PubMed

    Jackson, Michael; Zink, Lyndon R

    2015-01-01

    The generation and subsequent measurement of far-infrared radiation has found numerous applications in high-resolution spectroscopy, radio astronomy, and Terahertz imaging. For about 45 years, the generation of coherent, far-infrared radiation has been accomplished using the optically pumped molecular laser. Once far-infrared laser radiation is detected, the frequencies of these laser emissions are measured using a three-laser heterodyne technique. With this technique, the unknown frequency from the optically pumped molecular laser is mixed with the difference frequency between two stabilized, infrared reference frequencies. These reference frequencies are generated by independent carbon dioxide lasers, each stabilized using the fluorescence signal from an external, low pressure reference cell. The resulting beat between the known and unknown laser frequencies is monitored by a metal-insulator-metal point contact diode detector whose output is observed on a spectrum analyzer. The beat frequency between these laser emissions is subsequently measured and combined with the known reference frequencies to extrapolate the unknown far-infrared laser frequency. The resulting one-sigma fractional uncertainty for laser frequencies measured with this technique is ± 5 parts in 10(7). Accurately determining the frequency of far-infrared laser emissions is critical as they are often used as a reference for other measurements, as in the high-resolution spectroscopic investigations of free radicals using laser magnetic resonance. As part of this investigation, difluoromethane, CH2F2, was used as the far-infrared laser medium. In all, eight far-infrared laser frequencies were measured for the first time with frequencies ranging from 0.359 to 1.273 THz. Three of these laser emissions were discovered during this investigation and are reported with their optimal operating pressure, polarization with respect to the CO2 pump laser, and strength. PMID:26709957

  14. Characterizing Far-infrared Laser Emissions and the Measurement of Their Frequencies.

    PubMed

    Jackson, Michael; Zink, Lyndon R

    2015-12-18

    The generation and subsequent measurement of far-infrared radiation has found numerous applications in high-resolution spectroscopy, radio astronomy, and Terahertz imaging. For about 45 years, the generation of coherent, far-infrared radiation has been accomplished using the optically pumped molecular laser. Once far-infrared laser radiation is detected, the frequencies of these laser emissions are measured using a three-laser heterodyne technique. With this technique, the unknown frequency from the optically pumped molecular laser is mixed with the difference frequency between two stabilized, infrared reference frequencies. These reference frequencies are generated by independent carbon dioxide lasers, each stabilized using the fluorescence signal from an external, low pressure reference cell. The resulting beat between the known and unknown laser frequencies is monitored by a metal-insulator-metal point contact diode detector whose output is observed on a spectrum analyzer. The beat frequency between these laser emissions is subsequently measured and combined with the known reference frequencies to extrapolate the unknown far-infrared laser frequency. The resulting one-sigma fractional uncertainty for laser frequencies measured with this technique is ± 5 parts in 10(7). Accurately determining the frequency of far-infrared laser emissions is critical as they are often used as a reference for other measurements, as in the high-resolution spectroscopic investigations of free radicals using laser magnetic resonance. As part of this investigation, difluoromethane, CH2F2, was used as the far-infrared laser medium. In all, eight far-infrared laser frequencies were measured for the first time with frequencies ranging from 0.359 to 1.273 THz. Three of these laser emissions were discovered during this investigation and are reported with their optimal operating pressure, polarization with respect to the CO2 pump laser, and strength.

  15. (87)Rb-stabilized 375-MHz Yb:fiber femtosecond frequency comb.

    PubMed

    Schratwieser, Thomas C; Balskus, Karolis; McCracken, Richard A; Farrell, Carl; Leburn, Christopher G; Zhang, Zhaowei; Lamour, Tobias P; Ferreiro, Teresa I; Marandi, Alireza; Arnold, Aidan S; Reid, Derryck T

    2014-05-01

    We report a fully stabilized 1030-nm Yb-fiber frequency comb operating at a pulse repetition frequency of 375 MHz. The comb spacing was referenced to a Rb-stabilized microwave synthesizer and the comb offset was stabilized by generating a super-continuum containing a coherent component at 780.2 nm which was heterodyned with a (87)Rb-stabilized external cavity diode laser to produce a radio-frequency beat used to actuate the carrier-envelope offset frequency of the Yb-fiber laser. The two-sample frequency deviation of the locked comb was 235 kHz for an averaging time of 50 seconds, and the comb remained locked for over 60 minutes with a root mean squared deviation of 236 kHz.

  16. A digital frequency stabilization system of external cavity diode laser based on LabVIEW FPGA

    NASA Astrophysics Data System (ADS)

    Liu, Zhuohuan; Hu, Zhaohui; Qi, Lu; Wang, Tao

    2015-10-01

    Frequency stabilization for external cavity diode laser has played an important role in physics research. Many laser frequency locking solutions have been proposed by researchers. Traditionally, the locking process was accomplished by analog system, which has fast feedback control response speed. However, analog system is susceptible to the effects of environment. In order to improve the automation level and reliability of the frequency stabilization system, we take a grating-feedback external cavity diode laser as the laser source and set up a digital frequency stabilization system based on National Instrument's FPGA (NI FPGA). The system consists of a saturated absorption frequency stabilization of beam path, a differential photoelectric detector, a NI FPGA board and a host computer. Many functions, such as piezoelectric transducer (PZT) sweeping, atomic saturation absorption signal acquisition, signal peak identification, error signal obtaining and laser PZT voltage feedback controlling, are totally completed by LabVIEW FPGA program. Compared with the analog system, the system built by the logic gate circuits, performs stable and reliable. User interface programmed by LabVIEW is friendly. Besides, benefited from the characteristics of reconfiguration, the LabVIEW program is good at transplanting in other NI FPGA boards. Most of all, the system periodically checks the error signal. Once the abnormal error signal is detected, FPGA will restart frequency stabilization process without manual control. Through detecting the fluctuation of error signal of the atomic saturation absorption spectrum line in the frequency locking state, we can infer that the laser frequency stability can reach 1MHz.

  17. System and method for tuning adjusting the central frequency of a laser while maintaining frequency stabilization to an external reference

    NASA Technical Reports Server (NTRS)

    Livas, Jeffrey (Inventor); Thorpe, James I. (Inventor); Numata, Kenji (Inventor)

    2011-01-01

    A method and system for stabilizing a laser to a frequency reference with an adjustable offset. The method locks a sideband signal generated by passing an incoming laser beam through the phase modulator to a frequency reference, and adjusts a carrier frequency relative to the locked sideband signal by changing a phase modulation frequency input to the phase modulator. The sideband signal can be a single sideband (SSB), dual sideband (DSB), or an electronic sideband (ESB) signal. Two separate electro-optic modulators can produce the DSB signal. The two electro-optic modulators can be a broadband modulator and a resonant modulator. With a DSB signal, the method can introduce two sinusoidal phase modulations at the phase modulator. With ESB signals, the method can further drive the optical phase modulator with an electrical signal with nominal frequency OMEGA(sub 1) that is phase modulated at a frequency OMEGA(sub 2)

  18. Thermal Noise Limit in Frequency Stabilization of Lasers with Rigid Cavities

    NASA Technical Reports Server (NTRS)

    Numata, Kenji; Kemery, Amy; Camp, Jordan

    2005-01-01

    We evaluated thermal noise (Brownian motion) in a rigid reference cavity Used for frequency stabilization of lasers, based on the mechanical loss of cavity materials and the numerical analysis of the mirror-spacer mechanics with the direct application of the fluctuation dissipation theorem. This noise sets a fundamental limit for the frequency stability achieved with a rigid frequency-reference cavity of order 1 Hz/rtHz at 10mHz at room temperature. This level coincides with the world-highest level stabilization results.

  19. Thermal Noise Limit in Frequency Stabilization of Lasers with Rigid Cavities

    NASA Technical Reports Server (NTRS)

    Numata, Kenji; Kemery, Amy; Camp, Jordan

    2004-01-01

    We evaluated thermal noise (Brownian motion) in a rigid reference cavity used for frequency stabilization of lasers, based on the mechanical loss of cavity materials and the numerical analysis of the mirror-spacer mechanics with t.he direct application of the fluctuation dissipation theorem. This noise sets a fundamental limit for the frequency stability achieved with a rigid frequency- reference cavity of order 1 Hz/square root Hz(0.01 Hz/square root Hz) at 10 mHz (100 Hz) at room temperature. This level coincides with the world-highest level stabilization results.

  20. Thermal-noise limit in the frequency stabilization of lasers with rigid cavities.

    PubMed

    Numata, Kenji; Kemery, Amy; Camp, Jordan

    2004-12-17

    We evaluate thermal noise (Brownian motion) in a rigid reference cavity used for frequency stabilization of lasers, based on the mechanical loss of cavity materials and the numerical analysis of the mirror-spacer mechanics with the direct application of the fluctuation dissipation theorem. This noise sets a fundamental limit for the frequency stability achieved with a rigid frequency-reference cavity of order 1 Hz/ square root Hz (0.01 Hz/ square root Hz) at 10 mHz (100 Hz) at room temperature. This level coincides with the world-highest level stabilization results. PMID:15697887

  1. Frequency-stabilized limit-cycle dynamics of an optically injected semiconductor laser

    NASA Astrophysics Data System (ADS)

    AlMulla, Mohammad; Liu, Jia-Ming

    2014-07-01

    Limit-cycle dynamics are self-sustained oscillations that arise in man-made nonlinear systems and in nature. In an optically injected semiconductor laser, limit-cycle oscillations can reach a frequency ten times the relaxation resonance frequency of the solitary semiconductor laser. To stabilize such oscillations, complicated circuitry is often used. Here, we demonstrate limit-cycle oscillations of inherently stable frequencies. By properly choosing the operating conditions, three distinct types of stable-frequency oscillation points are defined.

  2. COMPONENTS OF LASER SYSTEMS AND STABILITY PROBLEMS: High-frequency CO2 waveguide with optothermal and optogalvanic stabilization of the radiation frequency and power

    NASA Astrophysics Data System (ADS)

    Anufriev, É. V.; Biryulin, V. P.; Gerasimchuk, A. G.; Kornilov, S. T.; Ovechkin, V. A.; Ostreĭkovskiĭ, I. V.; Protsenko, E. D.

    1988-08-01

    Optothermal and optogalvanic stabilization of a CO2 waveguide laser with selective and nonselective resonators and with hf excitation of the active medium was investigated. The optothermal method ensured stability of the average signal frequency amounting to 3×10-10 τ -1/2, whereas the stability achieved by the optogalvanic method was 1.5×10-9 τ -1/2 for averaging times of 0.01 <= τ <= 10 s. The optogalvanic method ensured that the power of a laser with resonators of different types was stable to within 0.2%.

  3. Frequency stabilization of an optically pumped far-infrared laser to the harmonic of a microwave synthesizer.

    PubMed

    Danylov, A A; Light, A R; Waldman, J; Erickson, N

    2015-12-10

    Measurements of the frequency stability of a far-infrared molecular laser have been made by mixing the harmonic of an ultrastable microwave source with a portion of the laser output signal in a terahertz (THz) Schottky diode balanced mixer. A 3 GHz difference-frequency signal was used in a frequency discriminator circuit to lock the laser to the microwave source. Comparisons of the short- and long-term laser frequency stability under free-running and locked conditions show a significant improvement with locking. Short-term frequency jitter was reduced by an order of magnitude, from approximately 40 to 4 kHz, and long-term drift was reduced by more than three orders of magnitude, from approximately 250 kHz to 80 Hz. The results, enabled by the efficient Schottky diode balanced mixer downconverter, demonstrate that ultrastable microwave-based frequency stabilization of THz optically pumped lasers (OPLs) will now be possible at frequencies extending well above 4.0 THz.

  4. Frequency stabilization of an optically pumped far-infrared laser to the harmonic of a microwave synthesizer.

    PubMed

    Danylov, A A; Light, A R; Waldman, J; Erickson, N

    2015-12-10

    Measurements of the frequency stability of a far-infrared molecular laser have been made by mixing the harmonic of an ultrastable microwave source with a portion of the laser output signal in a terahertz (THz) Schottky diode balanced mixer. A 3 GHz difference-frequency signal was used in a frequency discriminator circuit to lock the laser to the microwave source. Comparisons of the short- and long-term laser frequency stability under free-running and locked conditions show a significant improvement with locking. Short-term frequency jitter was reduced by an order of magnitude, from approximately 40 to 4 kHz, and long-term drift was reduced by more than three orders of magnitude, from approximately 250 kHz to 80 Hz. The results, enabled by the efficient Schottky diode balanced mixer downconverter, demonstrate that ultrastable microwave-based frequency stabilization of THz optically pumped lasers (OPLs) will now be possible at frequencies extending well above 4.0 THz. PMID:26836876

  5. Fixation Stability Measurement Using Two Types of Microperimetry Devices

    PubMed Central

    Liu, Hongting; Bittencourt, Millena G.; Sophie, Raafay; Sepah, Yasir J.; Hanout, Mostafa; Rentiya, Zubir; Annam, Rachel; Scholl, Hendrik P. N.; Nguyen, Quan Dong

    2015-01-01

    Purpose We compared the fixation stability measurements obtained with two microperimeters, the Micro Perimeter 1 (MP-1) and the Spectral OCT/SLO (OCT/SLO), in subjects with and without maculopathies. Methods A total of 41 eyes with no known ocular diseases and 45 eyes with maculopathies were enrolled in the study. Both eyes of each participant had a 20-second fixation test using the MP-1 and OCT/SLO. The bivariate contour ellipse area (BCEA) was used for fixation stability evaluation. Results In the normal group, BCEA was 2.93 ± 0.32 log minarc2 on OCT/SLO and 2.89 ± 0.30 log minarc2 on MP-1. In the maculopathy group, BCEA was 3.05 ± 0.41 log minarc2 on OCT/SLO and 3.15 ± 0.46 log minarc2 on MP-1. There was no statistically significant difference between the BCEA measured by OCT/SLO and by MP-1 in both groups. A moderate correlation was found between the two devices (r = 0.45, P < 0.001). The sample size during the fixation test was 535.5 ± 14.6 pairs of coordinates in the normal group and 530.7 ± 14.9 pairs in the maculopathy group with MP-1, while it was 72.3 ± 6.9 and 59.9 ± 10.1, respectively, with OCT/SLO. This was due to different tracking frequencies between the two microperimeters. Conclusion Fixation stability assessment yields similar results using the OCT/SLO and MP-1. A major difference in sampling rate between the two microperimeters does not significantly affect BCEA measurements. Translational Relevance Fixation stability assessments are comparable and interchangeable between the OCT/SLO and the MP-1. PMID:25774329

  6. Planar-waveguide external cavity laser stabilization for an optical link with 10(-19) frequency stability.

    PubMed

    Clivati, Cecilia; Mura, Alberto; Calonico, Davide; Levi, Filippo; Costanzo, Giovanni A; Calosso, Claudio E; Godone, Aldo

    2011-12-01

    We stabilized the frequency of a compact planar-waveguide external cavity laser (ECL) on a Fabry-Perot cavity (FPC) through a Pound-Drever-Hall scheme. The residual frequency stability of the ECL is 10(-14), comparable to the stability achievable with a fiber laser (FL) locked to an FPC through the same scheme. We set up an optical link of 100 km, based on fiber spools, that reaches 10(-19) relative stability, and we show that its performances using the ECL or FL are comparable. Thus ECLs could serve as an excellent replacement for FLs in optical links where cost-effectiveness and robustness are important considerations. PMID:23443694

  7. Monolithic device for modelocking and stabilization of frequency combs.

    PubMed

    Lee, C-C; Hayashi, Y; Silverman, K L; Feldman, A; Harvey, T; Mirin, R P; Schibli, T R

    2015-12-28

    We demonstrate a device that integrates a III-V semiconductor saturable absorber mirror with a graphene electro-optic modulator, which provides a monolithic solution to modelocking and noise suppression in a frequency comb. The device offers a pure loss modulation bandwidth exceeding 5 MHz and only requires a low voltage driver. This hybrid device provides not only compactness and simplicity in laser cavity design, but also small insertion loss, compared to the previous metallic-mirror-based modulators. We believe this work paves the way to portable and fieldable phase-coherent frequency combs.

  8. ATS-6 - Radio Frequency Interference Measurement Experiment

    NASA Technical Reports Server (NTRS)

    Henry, V. F.

    1975-01-01

    The frequency band from 5.925 to 6.425 GHz is served by fixed satellites and by terrestrial microwave links. There is a possibility of microwave links pointed at the horizon causing interference to the uplinks of domestic and international communications satellites sharing the same frequency band. A mathematical model has been derived for predicting the fields at geostationary orbit based on the known characteristics and known distribution of the terrestrial microwave relay system. The Applications Technology Satellite-6 (ATS-6) is sensitive to signals in the range of 10 dBW radiated in the direction of the satellite. Signals in the range of 10-30 dBW have been recorded over various parts of the United States.

  9. Elimination of frequency noise from groundwater measurements

    SciTech Connect

    Chien, Y.M.; Bryce, R.W.; Strait, S.R.; Yeatman, R.A.

    1986-04-01

    Groundwater response to atmospheric fluctuation can be effectively removed from downhole-pressure records using the systematic approach. The technique is not as successful for removal of earth tides, due to a probable discrepancy between the actual earth tide and the theoretical earth tide. The advantage of the systematic technique is that a causative relationship is established for each component of the pressure response removed. This concept of data reduction is easily understood and well accepted. The disadvantage is that a record of the stress causing the pressure fluctuation must be obtained. This may be done by monitoring or synthesizing the stress. Frequency analysis offers a simpler way to eliminate the undesirable hydrologic fluctuations from the downhole pressure. Frequency analysis may prove to be impractical if the fluctuations being removed have broadband characteristics. A combination of the two techniques, such as eliminating the atmospheric effect with the systematic method and the earth-tide fluctuations with the frequency method, is the most effective and efficient approach.

  10. Laser frequency stabilization using a dispersive line shape induced by Doppler Effect.

    PubMed

    Wang, Qing; Qi, Xianghui; Liu, Shuyong; Yu, Jiachen; Chen, Xuzong

    2015-02-01

    We report a simple and robust Doppler-free spectroscopic technique to stabilize a laser frequency to the atomic transition. By employing Doppler Effect on the atomic beam, we obtained a very stable dispersive signal with a high signal-to-noise ratio and no Doppler-background, which served as an error signal to electronically stabilize a laser frequency without modulation. For validating the performance of this technique, we locked a DFB laser to the (133)Cs D2 line and observed an efficient suppression of the frequency noise and a long-term reduction of the frequency drifts in a laboratory environment.

  11. Laser frequency stabilization using a dispersive line shape induced by Doppler Effect.

    PubMed

    Wang, Qing; Qi, Xianghui; Liu, Shuyong; Yu, Jiachen; Chen, Xuzong

    2015-02-01

    We report a simple and robust Doppler-free spectroscopic technique to stabilize a laser frequency to the atomic transition. By employing Doppler Effect on the atomic beam, we obtained a very stable dispersive signal with a high signal-to-noise ratio and no Doppler-background, which served as an error signal to electronically stabilize a laser frequency without modulation. For validating the performance of this technique, we locked a DFB laser to the (133)Cs D2 line and observed an efficient suppression of the frequency noise and a long-term reduction of the frequency drifts in a laboratory environment. PMID:25836158

  12. On-orbit frequency stability analysis of the GPS NAVSTAR 8 rubidium clock and NAVSTARS 9 and 10 cesium clocks. Memorandum report, January-December 1985

    SciTech Connect

    Buisson, J.A.; Largay, M.M.

    1987-09-17

    This report describes the on-orbit frequency stability performance analysis of the Global Positioning System (GPS) NAVSTAR 8 rubidium clock and the NAVSTARs 9 and 10 cesium clocks. Time-domain measurements, taken from three GPS monitor sites and from the United States Naval Observatory (USNO), were analyzed to determine the short and long-term frequency-stability performance of the NAVSTAR clocks. The data presented include measurements from 1985.

  13. Emulsification by high frequency ultrasound using piezoelectric transducer: formation and stability of emulsifier free emulsion.

    PubMed

    Kaci, Messaouda; Meziani, Smail; Arab-Tehrany, Elmira; Gillet, Guillaume; Desjardins-Lavisse, Isabelle; Desobry, Stephane

    2014-05-01

    Emulsifier free emulsion was developed with a new patented technique for food and cosmetic applications. This emulsification process dispersed oil droplets in water without any emulsifier. Emulsions were prepared with different vegetable oil ratios 5%, 10% and 15% (v/v) using high frequency ultrasounds generated by piezoelectric ceramic transducer vibrating at 1.7 MHz. The emulsion was prepared with various emulsification times between 0 and 10h. Oil droplets size was measured by laser granulometry. The pH variation was monitored; electrophoretic mobility and conductivity variation were measured using Zêtasizer equipment during emulsification process. The results revealed that oil droplets average size decreased significantly (p<0.05) during the first 6h of emulsification process and that from 160 to 1 μm for emulsions with 5%, 10% and from 400 to 29 μm for emulsion with 15% of initial oil ratio. For all tested oil ratios, pH measurement showed significant decrease and negative electrophoretic mobility showed the accumulation of OH(-) at oil/water interface leading to droplets stability in the emulsion. The conductivity of emulsions showed a decrease of the ions quantity in solution, which indicated formation of positive charge layer around OH(-) structure. They constitute a double ionic layer around oil particles providing emulsion stability. This study showed a strong correlation between turbidity measurement and proportion of emulsified oil. PMID:24315670

  14. 47 CFR 73.1540 - Carrier frequency measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 73.1540 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... measurements. (a) The carrier frequency of each AM and FM station and the visual carrier frequency and the difference between the visual carrier and the aural carrier or center frequency of each TV and Class A...

  15. Intermediate term frequency measurements with the HP computing counter in the USNO clock time system

    NASA Technical Reports Server (NTRS)

    Winkler, G. M. R.

    1972-01-01

    High precision frequency measurements with various integration times can be made with conventional counters by using variable gate times. The Hewlett-Packard (HP) computing counter allows such measurements over a wide range of frequencies and measurement times. This instrument can also convert period measurements into frequency by means of its arithmetic capabilities: The program library contains programs to facilitate frequency stability measurements in the most direct and convenient way. This method was used as the basis for all time scale computations, until requirements for highest resolution justified the development of an automatic data acquisition system. The phase measurements are now being made with the HP computing counter (with time interval plug-in unit) under program control from the HP System Programmer.

  16. Stability improvement of an operational two-way satellite time and frequency transfer system

    NASA Astrophysics Data System (ADS)

    Huang, Yi-Jiun; Fujieda, Miho; Takiguchi, Hiroshi; Tseng, Wen-Hung; Tsao, Hen-Wai

    2016-04-01

    To keep national time accurately coherent with coordinated universal time, many national metrology institutes (NMIs) use two-way satellite time and frequency transfer (TWSTFT) to continuously measure the time difference with other NMIs over an international baseline. Some NMIs have ultra-stable clocks with stability better than 10-16. However, current operational TWSTFT can only provide frequency uncertainty of 10-15 and time uncertainty of 1 ns, which is inadequate. The uncertainty is dominated by the short-term stability and the diurnals, i.e. the measurement variation with a period of one day. The aim of this work is to improve the stability of operational TWSTFT systems without additional transmission, bandwidth or increase in signal power. A software-defined receiver (SDR) comprising a high-resolution correlator and successive interference cancellation associated with open-loop configuration as the TWSTFT receiver reduces the time deviation from 140 ps to 73 ps at averaging time of 1 h, and occasionally suppresses diurnals. To study the source of the diurnals, TWSTFT is performed using a 2  ×  2 earth station (ES) array. Consequently, some ESs sensitive to temperature variation are identified, and the diurnals are significantly reduced by employing insensitive ESs. Hence, the operational TWSTFT using the proposed SDR with insensitive ESs achieves time deviation to 41 ps at 1 h, and 80 ps for averaging times from 1 h to 20 h.

  17. Development of an automatic frequency measurement system for RF linear accelerator magnetrons

    NASA Astrophysics Data System (ADS)

    Cha, Sungsu; Kim, Yujong; Lee, Byeong-No; Joo, Youngwoo; Lee, Soo Min; Lee, Byung Cheol; Cha, Hyungki; Lee, Seung Hyun; Park, Hyung Dal; Song, Ki Beak

    2015-06-01

    An X-band [9300 MHz] magnetron frequency measurement system was developed for the electron linear accelerators at the Korean Atomic Energy Research Institute (KAERI). The measurement and the display of the RF frequency during the accelerator operation time is a crucial factor for continuous operation for two key reasons. Firstly, if the RF frequency of the magnetron is not known, then the amount of frequency tuning cannot be known, and the appropriate RF power cannot be supplied to the accelerating-structure. Second, values including the accelerating-structure's coolingwater temperature setting, the solenoid-magnet's cooling-water temperature setting, and the tuning of the source's (magnetron's) frequency can be undertaken because the RF frequency is used as the reference. A key component of the accelerator is the accelerating-structure. The volume of the accelerating-structure changes according to the environment's temperature; there, the resonance frequency of the accelerating-structure varies. When the resonance frequency of the accelerator is changed, the output becomes unstable, and a low beam energy is obtained. Accordingly, was developed a magnetron frequency-measuring device in order to stabilize the accelerator's operation. The results of the test demonstrate that the measurement's accurate up to 100 kHz, which enables the provision of an accurate RF power to the accelerating -structure. In this paper, we discuss the RF frequency measurement system for the magnetron to enable a more stable accelerator operation in a linac.

  18. An inkjet vision measurement technique for high-frequency jetting

    SciTech Connect

    Kwon, Kye-Si Jang, Min-Hyuck; Park, Ha Yeong; Ko, Hyun-Seok

    2014-06-15

    Inkjet technology has been used as manufacturing a tool for printed electronics. To increase the productivity, the jetting frequency needs to be increased. When using high-frequency jetting, the printed pattern quality could be non-uniform since the jetting performance characteristics including the jetting speed and droplet volume could vary significantly with increases in jet frequency. Therefore, high-frequency jetting behavior must be evaluated properly for improvement. However, it is difficult to measure high-frequency jetting behavior using previous vision analysis methods, because subsequent droplets are close or even merged. In this paper, we present vision measurement techniques to evaluate the drop formation of high-frequency jetting. The proposed method is based on tracking target droplets such that subsequent droplets can be excluded in the image analysis by focusing on the target droplet. Finally, a frequency sweeping method for jetting speed and droplet volume is presented to understand the overall jetting frequency effects on jetting performance.

  19. Effect of master oscillator stability over pulse repetition frequency on hybrid semiconductor mode-locked laser

    NASA Astrophysics Data System (ADS)

    Castro Alves, D.; Abreu, Manuel; Cabral, Alexandre; Rebordão, J. M.

    2015-04-01

    Semiconductor mode-locked lasers are a very attractive laser pulse source for high accuracy length metrology. However, for some applications, this kind of device does not have the required frequency stability. Operating the laser in hybrid mode will increase the laser pulse repetition frequency (PRF) stability. In this study it is showed that the laser PRF is not only locked to the master oscillator but also maintains the same level of stability of the master oscillator. The device used in this work is a 10 mm long mode-locked asymmetrical cladding single section InAs/InP quantum dash diode laser emitting at 1580 nm with a pulse repetition frequency of ≈4.37 GHz. The laser nominal stability in passive mode (no external oscillator) shows direct dependence with the gain current and the stability range goes from 10-4 to 10-7. Several oscillators with different stabilities were used for the hybrid-mode operation (with external oscillator) and the resulting mode-locked laser stability compared. For low cost oscillators with low stability, the laser PRF stability achieves a value of 10-7 and for higher stable oscillation source (such as oven controlled quartz oscillators (OXCO)) the stability can reach values up to 10-12 (τ =1 s).

  20. Method of detecting system function by measuring frequency response

    DOEpatents

    Morrison, John L.; Morrison, William H.; Christophersen, Jon P.; Motloch, Chester G.

    2013-01-08

    Methods of rapidly measuring an impedance spectrum of an energy storage device in-situ over a limited number of logarithmically distributed frequencies are described. An energy storage device is excited with a known input signal, and a response is measured to ascertain the impedance spectrum. An excitation signal is a limited time duration sum-of-sines consisting of a select number of frequencies. In one embodiment, magnitude and phase of each frequency of interest within the sum-of-sines is identified when the selected frequencies and sample rate are logarithmic integer steps greater than two. This technique requires a measurement with a duration of one period of the lowest frequency. In another embodiment, where selected frequencies are distributed in octave steps, the impedance spectrum can be determined using a captured time record that is reduced to a half-period of the lowest frequency.

  1. Laser Frequency Stabilization and Control through Offset Sideband Locking to Optical Cavities

    NASA Technical Reports Server (NTRS)

    Thorpe, James I.; Livas, J.; Numata, K.

    2008-01-01

    We describe a class of techniques whereby a laser frequency can be stabilized to a fixed optical cavity resonance with an adjustable offset, providing a wide tuning range for the central frequency. These techniques require only minor modifications to the standard Pound-Drever-Hall locking techniques and have the advantage of not altering the intrinsic stability of the frequency reference. In a laboratory investigation the sideband techniques were found to perform equally well as the standard, non-tunable Pound-Drever-Hall technique, each providing more than four decades of frequency noise suppression over the free-running noise. An application of a tunable system as a pre-stabilization stage in a phase-lock loop is also presented with the combined system achieving a frequency noise suppression of nearly twelve orders of magnitude.

  2. Frequency stabilization in injection controlled pulsed CO2 lasers

    NASA Technical Reports Server (NTRS)

    Menzies, Robert T.; Ancellet, Gerard M.

    1987-01-01

    Longitudinal mode selection by injection has been demonstrated as a viable technique for tailoring a TEA-CO2 laser with pulse energies of a Joule or greater to fit the requirements of a coherent lidar transmitter. Once reliable generation of single-longitudinal-mode (SLM) pulses is obtained, one can study the intrapulse frequency variation and attempt to determine the sources of frequency sweeping, or chirp. These sources include the effect of the decaying plasma, the thermal gradient due to the energy dissipation associated with the laser mechanism itself, and the pressure shift of the center frequency of the laser transition. The use of the positive-branch unstable resonator as an efficient means of coupling a discharge with transverse spatial dimensions of the order of centimeters to an optical cavity mode introduces another concern: namely, what can be done to emphasize transverse mode discrimination in an unstable resonator cavity while maintaining high coupling efficiency. These issues are briefly discussed in the paper, and representative experimental examples are included.

  3. Low-Frequency Measurements of the CMB Spectrum

    SciTech Connect

    Kogut, A.; Bensadoun, M.; De Amici, Giovanni; Levin, S.; Limon,M.; Smoot, George F.; Sironi, G.; Bersanelli, M.; Bonelli, G.

    1989-10-01

    As part of an extended program to characterize the spectrum of the cosmic microwave background (CMB) at low frequencies, we have performed multiple measurements from a high-altitude site in California. On average, these measurements suggest a CMB temperature slightly lower than measurements at higher frequencies. Atmospheric conditions and the encroachment of civilization are now significant limitations from our present observing site. In November 1989, we will make new measurements from the South Pole Amundsen-Scott Station at frequencies 0.82, 1.5, 2.5, 3.8, 7.5, and 90 GHz. We discuss recent measurements and indicate improvements possible from a polar observing site.

  4. FROM STABLE LASERS TO OPTICAL-FREQUENCY CLOCKS:. Merging the UltraFast and the UltraStable, for a New Epoch of Optical Frequency Measurements, Standards, & Applications

    NASA Astrophysics Data System (ADS)

    Hall, J. L.; Ye, J.; Ma, L.-S.; Peng, J.-L.; Notcutt, M.; Jost, J. D.; Marian, A.

    2002-04-01

    This is a report on behalf of the World Team of Stable Laser and Optical Frequency Measurement Enthusiasts, even if most detailed illustrations draw mainly from our work at JILA. Specifically we trace some of the key ideas that have led from the first stabilized lasers, to frequency measurement up to 88 THz using frequency chains, revision of the Definition of the Metre, extension of coherent frequency chain technology into the visible, development of a vast array of stabilized lasers, and finally the recent explosive growth of direct frequency measurement capability in the visible using fs comb techniques. We present our recent work showing a Molecular Iodine-based Optical Clock which delivers, over a range of time scales, rf output at a stability level basically equivalent to the RF stability prototype, the Hydrogen Maser. We note the bifurcation between single-ion-based clocks - likely to be the stability/reproducibility ultimate winners in the next generation - and simpler systems based on gas cells, which can have impressive stabilities but may suffer from a variety of reproducibility-limiting processes. Active Phase-Lock synchronization of independent fs lasers allows sub-fs timing control. Copies of related works in our labs may be found/obtained at our website .

  5. 47 CFR 74.465 - Frequency monitors and measurements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency monitors and measurements. 74.465 Section 74.465 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... Broadcast Stations § 74.465 Frequency monitors and measurements. The licensee of a remote pickup station...

  6. 47 CFR 78.113 - Frequency monitors and measurements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency monitors and measurements. 78.113 Section 78.113 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES CABLE TELEVISION RELAY SERVICE Technical Regulations § 78.113 Frequency monitors and measurements....

  7. 47 CFR 74.162 - Frequency monitors and measurements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency monitors and measurements. 74.162 Section 74.162 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... Broadcast Stations Technical Operation and Operators § 74.162 Frequency monitors and measurements....

  8. 47 CFR 74.662 - Frequency monitors and measurements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency monitors and measurements. 74.662 Section 74.662 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... Auxiliary Stations § 74.662 Frequency monitors and measurements. The licensee of a television...

  9. 47 CFR 74.1262 - Frequency monitors and measurements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Frequency monitors and measurements. 74.1262 Section 74.1262 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... Translator Stations and FM Broadcast Booster Stations § 74.1262 Frequency monitors and measurements. (a)...

  10. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 1 2014-10-01 2014-10-01 false Frequency range of measurements. 18.309 Section 18.309 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL INDUSTRIAL, SCIENTIFIC, AND MEDICAL EQUIPMENT Technical Standards § 18.309 Frequency range of measurements. (a) For field...

  11. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 1 2011-10-01 2011-10-01 false Frequency range of measurements. 18.309 Section 18.309 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL INDUSTRIAL, SCIENTIFIC, AND MEDICAL EQUIPMENT Technical Standards § 18.309 Frequency range of measurements. (a) For field...

  12. 47 CFR 18.309 - Frequency range of measurements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 1 2013-10-01 2013-10-01 false Frequency range of measurements. 18.309 Section 18.309 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL INDUSTRIAL, SCIENTIFIC, AND MEDICAL EQUIPMENT Technical Standards § 18.309 Frequency range of measurements. (a) For field...

  13. Measurement of soil water content with dielectric dispersion frequency

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Frequency domain reflectometry (FDR) is an inexpensive and attractive methodology for repeated measurements of soil water content (SWC). Although there are some known measurement limitations for dry soil and sand, a fixed-frequency method is commonly employed using commercially available FDR probes....

  14. 47 CFR 74.162 - Frequency monitors and measurements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency monitors and measurements. 74.162 Section 74.162 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... Broadcast Stations Technical Operation and Operators § 74.162 Frequency monitors and measurements....

  15. 47 CFR 78.113 - Frequency monitors and measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency monitors and measurements. 78.113 Section 78.113 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES CABLE TELEVISION RELAY SERVICE Technical Regulations § 78.113 Frequency monitors and measurements....

  16. 47 CFR 74.465 - Frequency monitors and measurements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency monitors and measurements. 74.465 Section 74.465 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... Broadcast Stations § 74.465 Frequency monitors and measurements. The licensee of a remote pickup station...

  17. 47 CFR 74.662 - Frequency monitors and measurements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency monitors and measurements. 74.662 Section 74.662 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... Auxiliary Stations § 74.662 Frequency monitors and measurements. The licensee of a television...

  18. 47 CFR 74.162 - Frequency monitors and measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency monitors and measurements. 74.162 Section 74.162 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... Broadcast Stations Technical Operation and Operators § 74.162 Frequency monitors and measurements....

  19. 47 CFR 74.1262 - Frequency monitors and measurements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency monitors and measurements. 74.1262 Section 74.1262 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... Translator Stations and FM Broadcast Booster Stations § 74.1262 Frequency monitors and measurements. (a)...

  20. 47 CFR 74.562 - Frequency monitors and measurements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency monitors and measurements. 74.562 Section 74.562 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... Auxiliary Stations § 74.562 Frequency monitors and measurements. The licensee shall ensure that the STL,...

  1. 47 CFR 74.562 - Frequency monitors and measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency monitors and measurements. 74.562 Section 74.562 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... Auxiliary Stations § 74.562 Frequency monitors and measurements. The licensee shall ensure that the STL,...

  2. 47 CFR 78.113 - Frequency monitors and measurements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Frequency monitors and measurements. 78.113 Section 78.113 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES CABLE TELEVISION RELAY SERVICE Technical Regulations § 78.113 Frequency monitors and measurements....

  3. 47 CFR 74.1262 - Frequency monitors and measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency monitors and measurements. 74.1262 Section 74.1262 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... Translator Stations and FM Broadcast Booster Stations § 74.1262 Frequency monitors and measurements. (a)...

  4. 47 CFR 74.662 - Frequency monitors and measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency monitors and measurements. 74.662 Section 74.662 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... Auxiliary Stations § 74.662 Frequency monitors and measurements. The licensee of a television...

  5. 47 CFR 74.465 - Frequency monitors and measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Frequency monitors and measurements. 74.465 Section 74.465 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES... Broadcast Stations § 74.465 Frequency monitors and measurements. The licensee of a remote pickup station...

  6. Measuring Postural Stability: Strategies For Signal Acquisition And Processing

    NASA Astrophysics Data System (ADS)

    Riedel, Susan A.; Harris, Gerald F.

    1987-01-01

    A balance platform was used to collect postural stability data from 60 children, approximately half of whom have been diagnosed with cerebral palsy. The data was examined with respect to its frequency content, resulting in an improved strategy for frequency estimation. With a reliable assessment of the frequency domain characteristics, the signal stationarity could then be examined. Significant differences in signal stationarity were observed when the epoch length was changed, as well as between the normal and cerebral palsy populations.

  7. Time and frequency measuring metrological equipment in the USSR

    NASA Technical Reports Server (NTRS)

    Uljanov, Adolph A.

    1990-01-01

    The complex of the means of providing time and frequency traceability in the USSR includes the system of time and frequency standards of the National Time and Frequency Calibration Service, time and frequency transfer facilities and local time and frequency standards. Control on measurement correctness is performed by the All-Union State Standard calibration service. The hardware of most of the above-mentioned systems is provided by the instruments developed by our institute. A common scientific and technological approach allowed us to create a unified system of time-frequency equipment composed of widely used serial instruments, sets, automated systems and complexes. Primary frequency standards of different classes, time and frequency references and instruments are based on the unified system. CH1-70 hydrogen frequency standard and its CH1-70A, CH1-80 modifications are used in the group time and frequency standards. Measuring time and data processing techniques, and also instrumentation specifications on the results of 10-year operation are given. The existing system provides time-frequency measurements with 2 times 10(exp -13) plus or minus 1 times 10(exp -14) accuracy.

  8. Pump-induced carrier envelope offset frequency dynamics and stabilization of an Yb-doped fiber frequency comb

    NASA Astrophysics Data System (ADS)

    Zhao, Jian; Li, Wen-Xue; Yang, Kang-Wen; Shen, Xu-Ling; Bai, Dong-Bi; Chen, Xiu-Liang; Zeng, He-Ping

    2014-12-01

    In this paper, we demonstrate a carrier envelope phase-stabilized Yb-doped fiber frequency comb seeding by a nonlinear-polarization-evolution (NPE) mode-locked laser at a repetition rate of 60 MHz with a pulse duration of 191 fs. The pump-induced carrier envelope offset frequency (f0) nonlinear tuning is discussed and further explained by the spectrum shift of the laser pulse. Through the environmental noise suppression, the drift of the free-running f0 is reduced down to less than 3 MHz within an hour. By feedback control on the pump power with a self-made phase-lock loop (PLL) electronics the carrier envelope offset frequency is well phase-locked with a frequency jitter of 85 mHz within an hour.

  9. Exploring the Frequency Stability Limits of Whispering Gallery Mode Resonators for Metrological Applications

    NASA Technical Reports Server (NTRS)

    Chembo, Yanne K.; Baumgartel, Lukas; Grudinin, Ivan; Strekalov, Dmitry; Thompson, Robert; Yu, Nan

    2012-01-01

    Whispering gallery mode resonators are attracting increasing interest as promising frequency reference cavities. Unlike commonly used Fabry-Perot cavities, however, they are filled with a bulk medium whose properties have a significant impact on the stability of its resonance frequencies. In this context that has to be reduced to a minimum. On the other hand, a small monolithic resonator provides opportunity for better stability against vibration and acceleration. this feature is essential when the cavity operates in a non-laboratory environment. In this paper, we report a case study for a crystalline resonator, and discuss the a pathway towards the inhibition of vibration-and acceleration-induced frequency fluctuations.

  10. Frequency stability requirements for two way range rate tracking

    NASA Technical Reports Server (NTRS)

    Reinhardt, V.

    1975-01-01

    Accuracy limitations to two way range rate Doppler tracking due to master (reference) oscillator frequency instabilities are discussed. Theory is developed to treat both the effects of random and nonrandom oscillator instabilities. The nonrandom instabilities treated are drift, environmental effects, and coherent phase modulation. The effects of random instabilities on range rate accuracy are shown to be describable in terms of sigma y (2, T, tau). For the typical noise processes encountered in precision oscillators, range rate error is related to the more familiar sigma y (tau) and script L (f). Three examples are discussed to show how to determine range rate error from given sigma y (tau) or script L (f) curves, and approximations are developed to simplify the treatment of complex systems. An error analysis of range determined from rate data is also given.

  11. Hybrid nanolaminate dielectrics engineered for frequency and bias stability

    NASA Astrophysics Data System (ADS)

    Sahoo, S. K.; Patel, R. P.; Wolden, C. A.

    2013-08-01

    Metal-insulator-metal capacitors were fabricated from hybrid alumina-silicone nanolaminates deposited by plasma-enhanced chemical vapor deposition. These two materials have complementary properties that produce dielectrics that are exceptionally stable with respect to frequency and dc bias. 50% alumina-silicone nanolaminates displayed low dielectric loss (tan δ = 0.04) and a negligible quadratic voltage coefficient (α = 7 ppm/V2). Both of these values are exceptionally improved over the properties of the individual components. This performance was achieved in 165 nm thick films that provide both high specific capacitance (30 nF/cm2) and extremely low leakage (˜10-9 A/cm2 at 1 MV/cm).

  12. Note: Directly measuring the direct digital synthesizer frequency chirp-rate for an atom interferometer

    SciTech Connect

    Tao, Juan-Juan; Zhou, Min-Kang E-mail: zmk@hust.edu.cn; Zhang, Qiao-Zhen; Cui, Jia-Feng; Duan, Xiao-Chun; Shao, Cheng-Gang; Hu, Zhong-Kun E-mail: zmk@hust.edu.cn

    2015-09-15

    During gravity measurements with Raman type atom interferometry, the frequency of the laser used to drive Raman transition is scanned by chirping the frequency of a direct digital synthesizer (DDS), and the local gravity is determined by precisely measuring the chip rate α of DDS. We present an effective method that can directly evaluate the frequency chirp rate stability of our DDS. By mixing a pair of synchronous linear sweeping signals, the chirp rate fluctuation is precisely measured with a frequency counter. The measurement result shows that the relative α instability can reach 5.7 × 10{sup −11} in 1 s, which is neglectable in a 10{sup −9} g level atom interferometry gravimeter.

  13. A new way to measure the electron cyclotron frequency

    NASA Astrophysics Data System (ADS)

    Palmer, F. L.

    1993-03-01

    A method is described for using spin flips to measure the 0 to 1 cyclotron transition frequency of a single electron in a Penning trap. Detection can be accomplished with magnetic bottles of 10 T/m2 or less, thereby greatly reducing the thermal broadening of the cyclotron line. This method complements a recently published technique for measuring the anomaly frequency, making a more precise measurement of the electron anomaly ratio possible.

  14. Active frequency stabilization of a 1.062-micron, Nd:GGG, diode-laser-pumped nonplanar ring oscillator to less than 3 Hz of relative linewidth

    NASA Technical Reports Server (NTRS)

    Day, T.; Gustafson, E. K.; Byer, R. L.

    1990-01-01

    Results are presented on the frequency stabilization of two diode-laser-pumped ring lasers that are independently locked to the same high-finesse interferometer. The relative frequency stability is measured by locking the lasers one free spectral range apart and observing the heterodyne beat note. The resultant beat note width of 2.9 Hz is consistent with the theoretical system noise-limited linewidth and is approximately 20 times that expected for shot-noise-limited performance.

  15. Improvement in medium long-term frequency stability of the integrating sphere cold atom clock

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    The medium-long term frequency stability of the integrating sphere cold atom clock was improved.During the clock operation, Rb atoms were cooled and manipulated using cooling light diffusely reflected by the inner surface of a microwave cavity in the clock. This light heated the cavity and caused a frequency drift from the resonant frequency of the cavity. Power fluctuations of the cooling light led to atomic density variations in the cavity's central area, which increased the clock frequency instability through a cavity pulling effect. We overcame these limitations with appropriate solutions. A frequency stability of 3.5E-15 was achieved when the integrating time ? increased to 2E4 s.

  16. A 100Mbps coherent optical link demonstration using frequency stabilized solid state lasers

    NASA Technical Reports Server (NTRS)

    Chen, CHIEN-C.; Arbel, Dalia; Win, Moe Z.

    1992-01-01

    The design, implementation, and performance evaluation of a 100Mbps binary phase shift keying (BPSK) coherent optical link using frequency stabilized solid state lasers is described. In this demonstration, the transmitted data is binary phase modulated at 100Mbps using an external resonant cavity phase modulator. At the receiving end, the signal is detected using a balanced heterodyne detector. An auxiliary frequency tracking loop (FTL) is used to help the initial frequency acquisition before handing over to the carrier phase tracking loop. The FTL is implemented using a delay line discriminator, and the detected frequency error is fed back to the local oscillator laser to close the tracking loop. Phase coherent reception is achieved by synchronizing the carrier phase using a Costas tracking loop. The demonstration showed that a high data rate phase coherent optical link can be implemented using frequency stabilized solid state lasers.

  17. A 100Mbps coherent optical link demonstration using frequency stabilized solid state lasers

    NASA Astrophysics Data System (ADS)

    Chen, Chien-C.; Arbel, Dalia; Win, Moe Z.

    1992-06-01

    The design, implementation, and performance evaluation of a 100Mbps binary phase shift keying (BPSK) coherent optical link using frequency stabilized solid state lasers is described. In this demonstration, the transmitted data is binary phase modulated at 100Mbps using an external resonant cavity phase modulator. At the receiving end, the signal is detected using a balanced heterodyne detector. An auxiliary frequency tracking loop (FTL) is used to help the initial frequency acquisition before handing over to the carrier phase tracking loop. The FTL is implemented using a delay line discriminator, and the detected frequency error is fed back to the local oscillator laser to close the tracking loop. Phase coherent reception is achieved by synchronizing the carrier phase using a Costas tracking loop. The demonstration showed that a high data rate phase coherent optical link can be implemented using frequency stabilized solid state lasers.

  18. Application of sub-Doppler DAVLL to laser frequency stabilization in atomic cesium.

    PubMed

    Su, Dian-Qiang; Meng, Teng-Fei; Ji, Zhong-Hua; Yuan, Jin-Peng; Zhao, Yan-Ting; Xiao, Lian-Tuan; Jia, Suo-Tang

    2014-10-20

    We achieve laser frequency stabilization by a simple technique based on sub-Doppler dichroic atomic vapor laser lock (DAVLL) in atomic cesium. The technique that combines saturated-absorption spectroscopy and Zeeman splitting of hyperfine structures allows us to obtain a modulation-free dispersion-like error signal for frequency stabilization. For the error signal, the dependence of peak-to-peak amplitude and the slope at the zero-crossing point on the magnetic field is studied by simulation and experiment. Based on the result, we obtain an available sub-Doppler DAVLL error signal with high sensitivity to the frequency drift by selecting an appropriate strength of the magnetic field. Ultimately, the fluctuation of the locked laser frequency is confined to below 0.5 MHz in a long term, exhibiting efficient suppression of frequency noise. PMID:25402788

  19. Frequency stabilization of ambience-isolated internal-mirror He-Ne lasers by thermoelectric-cooling thermal compensation

    NASA Astrophysics Data System (ADS)

    Saha, Asit; Pal, Nikhil; Saha, Tapash; Ghorui, M. K.; Chatterjee, Prasanta

    2016-08-01

    An approach for frequency stabilization of an ambience-isolated internal-mirror He-Ne laser (632.8 nm) utilizing temperature control of the laser tube with Peltier thermoelectric coolers is demonstrated. Measurements indicate that there are an optimal temperature (23 °C) and an optimal discharge current (5.5 mA) of laser tube for which the laser light power is separately maximized. To prevent the effect of fluctuation of discharge current on the laser stability, an adjustable current source is designed and fabricated so that the current is set to be optimal (5.50 ± 0.01 mA). To isolate the laser tube from the environment, the laser metallic box connected to two Peltier thermoelectric coolers is surrounded by two thermal and acoustic insulator shells. The laser has two longitudinal modes very often. Any change in the frequency of longitudinal modes at the optimal temperature is monitored by sampling the difference of longitudinal modes' intensities. Therefore, using a feedback mechanism, the current of thermoelectric coolers is so controlled that the frequency of modes stays constant on the gain profile of the laser. The frequency stability is measured equal to 1.17 × 10-9 (˜2700×) for less than 1 min and 2.57 × 10-9 (˜1200×) for more than 1 h.

  20. Dielectric measurements of selected ceramics at microwave frequencies

    NASA Technical Reports Server (NTRS)

    Dahiya, J. N.; Templeton, C. K.

    1994-01-01

    Dielectric measurements of strontium titanate and lead titanate zirconate ceramics are conducted at microwave frequencies using a cylindrical resonant cavity in the TE(sub 011) mode. The perturbations of the electric field are recorded in terms of the frequency shift and Q-changes of the cavity signal. Slater's perturbation equations are used to calculate e' and e" of the dielectric constant as a function of temperature and frequency.

  1. Low data rate coherent optical link demonstration using frequency stabilized solid state lasers

    NASA Technical Reports Server (NTRS)

    Chen, CHIEN-C.; Win, Moe Z.; Marshall, William K.; Lesh, James R.

    1991-01-01

    A low data rate laboratory heterodyne link demonstration operating at 1.06 micron using frequency stabilized Nd:YAG lasers was implemented. The data was modulated onto the optical carrier at 100 kbps using binary pulse position modulation. Phase coherent reception was achieved by closing the receiver phase tracking loop around the piezo-electric and temperature-tuned local oscillator laser. Initial frequency acquisition was accomplished by linearly scanning the LO frequency over the uncertainty range while a combined frequency and phase tracking loop searches for a lock indicator signal. The link performance was experimentally evaluated and compared to the theoretical predictions.

  2. Using Frequency Noise Feedback to Improve Stability in Extended Cavity Diode Lasers

    NASA Astrophysics Data System (ADS)

    Pugh, Mckinley; Durfee, Dallin

    2016-03-01

    We are developing a feedback system to stabilize extended cavity diode lasers using frequency noise. In other literature, amplitude noise has been used to predict and prevent mode hops. We've found, however, that amplitude noise only correlates to an impending mode hop when the laser is locked to a frequency reference. We have found evidence that the amplitude noise is generated from more fundamental frequency noise by the lock feedback. We therefore propose a way to use frequency noise directly to generate a signal to predict and prevent mode hops.

  3. Dominant side in single-leg stance stability during floor oscillations at various frequencies

    PubMed Central

    2014-01-01

    Background We investigated lateral dominance in the postural stability of single-leg stance with anteroposterior floor oscillations at various frequencies. Methods Thirty adults maintained a single-leg stance on a force platform for 20 seconds per trial. Trials were performed with no oscillation (static condition) and with anteroposterior floor oscillations (2.5-cm amplitude) at six frequencies: 0.25, 0.5, 0.75, 1.0, 1.25 and 1.5 Hz (dynamic condition). A set of three trials was performed on each leg in each oscillation frequency in random order. The mean speed of the center of pressure in the anteroposterior direction (CoPap) was calculated as an index of postural stability, and frequency analysis of CoPap sway was performed. Footedness for carrying out mobilizing activities was assessed with a questionnaire. Results CoPap speed exponentially increased as oscillation frequency increased in both legs. The frequency analysis of CoPap showed a peak <0.3 Hz at no oscillation. The frequency components at 0.25-Hz oscillation included common components with no oscillation and those at 1.5-Hz oscillation showed the maximum amplitude among all conditions. Postural stability showed no significant difference between left- and right-leg stance at no oscillation and oscillations ≤1.25 Hz, but at 1.5-Hz oscillation was significantly higher in the right-leg stance than in the left-leg stance. For the lateral dominance of postural stability at individual levels, the lateral difference in postural stability at no oscillation was positively correlated with that at 0.25-Hz oscillation (r = 0.51) and negatively correlated with that at 1.5-Hz oscillation (r = -0.53). For 70% of subjects, the dominant side of postural stability was different at no oscillation and 1.5-Hz oscillation. In the subjects with left- or right-side dominance at no oscillation, 94% or 38% changed their dominant side at 1.5-Hz oscillation, with a significant difference between these percentages. In

  4. Measurement of core electrical parameters at ultrahigh and microwave frequencies

    SciTech Connect

    Rau, R.N.; Wharton, R.P.

    1982-11-01

    The Electromagnetic Propagation Tool (EPT) has demonstrated that the electrical conductivity and dielectric permittivity of rocks at microwave frequencies are different from those at low frequencies. These differences are helpful in determining the properties of the rocks and the fluids they contain and thus contribute to improved formation evaluation. Electrical parameters of rocks are found generally complex. A technique has been developed for measuring the complex dielectric permittivity, conductivity, and magnetic permeability over a range of frequencies in the ultrahigh frequency (UHF) and microwave frequency bands (100 MHz to 2.0 GHz). The sample core constitutes the dielectric of a coaxial transmission-line sample holder. With an S-parameter setup, two-port S-parameter measurements are made. The complex constituent parameters (epsilon', epsilon'', sigma, ..mu..) of the core samples then are computed from the S-parameters. Measurements on bulk water of various salinities demonstrate the salinity dependence of the dielectric constant (epsilon'/epsilon /SUB o/ ) of water at high salinities. The total measured loss is separated into a conductivity loss (sigma) and a dielectric loss (epsilon''/epsilon /SUB O/ ), since the frequency dependence of conductivity loss is well-known. Computed conductivity of bulk water shows little dispersion and is in good agreement with measured low-frequency (400-Hz) values.

  5. Stabilizing soliton-based multichannel transmission with frequency dependent linear gain-loss

    NASA Astrophysics Data System (ADS)

    Chakraborty, Debananda; Peleg, Avner; Nguyen, Quan M.

    2016-07-01

    We report several major theoretical steps towards realizing stable long-distance multichannel soliton transmission in Kerr nonlinear waveguide loops. We find that transmission destabilization in a single waveguide is caused by resonant formation of radiative sidebands and investigate the possibility to increase transmission stability by optimization with respect to the Kerr nonlinearity coefficient γ. Moreover, we develop a general method for transmission stabilization, based on frequency dependent linear gain-loss in Kerr nonlinear waveguide couplers, and implement it in two-channel and three-channel transmission. We show that the introduction of frequency dependent loss leads to significant enhancement of transmission stability even for non-optimal γ values via decay of radiative sidebands, which takes place as a dynamic phase transition. For waveguide couplers with frequency dependent linear gain-loss, we observe stable oscillations of soliton amplitudes due to decay and regeneration of the radiative sidebands.

  6. Particle simulation on radio frequency stabilization of flute modes in a tandem mirror. I. Parallel antenna

    SciTech Connect

    Kadoya, Y.; Abe, H.

    1988-04-01

    A two- and one-half-dimensional electromagnetic particle code (PS2M) (H. Abe and S. Nakajima, J. Phys. Soc. Jpn. 53, xxx (1987)) is used to study how an electric field applied parallel to the magnetic field affects the radio frequency stabilization of flute modes in a tandem mirror plasma. The parallel electric field E/sub parallel/ perturbs the electron velocity v/sub parallel/ parallel to the magnetic field and also induces a perpendicular magnetic field perturbation B/sub perpendicular/. The unstable growth of the flute mode in the absence of such a radio frequency electric field is first studied as a basis for comparison. The ponderomotive force originating from the time-averaged product is then shown to stabilize the flute modes. The stabilizing wave power threshold, the frequency dependency, and the dependence on delchemically bondE/sub parallel/chemically bond all agree with the theoretical predictions.

  7. Constant frequency pulsed phase-locked loop measuring device

    NASA Technical Reports Server (NTRS)

    Yost, William T. (Inventor); Kushnick, Peter W. (Inventor); Cantrell, John H. (Inventor)

    1993-01-01

    A measuring apparatus is presented that uses a fixed frequency oscillator to measure small changes in the phase velocity ultrasonic sound when a sample is exposed to environmental changes such as changes in pressure, temperature, etc. The invention automatically balances electrical phase shifts against the acoustical phase shifts in order to obtain an accurate measurement of electrical phase shifts.

  8. Long-term frequency stabilization system for external cavity diode laser based on mode boundary detection

    NASA Astrophysics Data System (ADS)

    Xu, Zhouxiang; Huang, Kaikai; Jiang, Yunfeng; Lu, Xuanhui

    2011-12-01

    We have realized a long-term frequency stabilization system for external cavity diode laser (ECDL) based on mode boundary detection method. In this system, the saturated absorption spectroscopy was used. The current and the grating of the ECDL were controlled by a computer-based feedback control system. By checking if there are mode boundaries in the spectrum, the control system determined how to adjust current to avoid mode hopping. This procedure was executed periodically to ensure the long-term stabilization of ECDL in the absence of mode hops. This diode laser system with non-antireflection coating had operated in the condition of long-term mode-hop-free stabilization for almost 400 h, which is a significant improvement of ECDL frequency stabilization system.

  9. Multipoint joint time and frequency dissemination in delay-stabilized fiber optic links.

    PubMed

    Śliwczyński, Ł; Krehlik, P

    2015-03-01

    This paper presents the system for dissemination of both the RF frequency (e.g., 5, 10, or 100 MHz) and time (pulse per second) signals using an actively tapped fiber-optic link with electronic stabilization of the propagation delay. In principle several nodes for accessing the time/frequency signals may be added without the degradation of the dissemination in the main link. We are discussing the algorithm of determining the propagation delay from the local end of the link to the access node that is required for calibration of the time dissemination. Performed analysis shows that the uncertainty of the time calibration at the access node may in practice be dominated by the dependence of the propagation delay of the receivers on impinging optical powers and is only weakly affected by the distance between the local and access modules. The uncertainty is, however, still low, being only about two times higher compared with the calibration uncertainty of the main link. Experimental results performed on several spooled fibers show that the accuracy of described calibration procedures, expressed as a difference from the results of direct measurement, is not worse than 35 ps. PMID:25768810

  10. Intelligent two-loop time-division-multiplexing (TDM) optical frequency stabilization system for multichannel communications

    NASA Astrophysics Data System (ADS)

    Li, Aiguo; Wu, Deming; Xie, Linzhen

    1995-04-01

    A channel spacing frequency stabilization system for optical frequency-division-multiplexing communications is reported. Considering variable environmental condition and device aging effects, we have designed two loops in the system using a Fabry-perot interferometer as a frequency reference. One loop is a fine-tuning one, which is a time-division-multiplexing frequency stabilization scheme adjusting the driving currents of all the transmitter. The other loop is a rough-tuning one, which is a series of newly designed digital temperature controllers in which microprocessors and electrical oscillation circuits rather than Wheatstone bridge- circuits are used to detect the temperature error signal in order to reduce laser operating temperature dependence on the environmental conditions and there are RS-232 interfaces for communications with the first loop.

  11. Chip Scale Atomic Resonator Frequency Stabilization System With Ultra-Low Power Consumption for Optoelectronic Oscillators.

    PubMed

    Zhao, Jianye; Zhang, Yaolin; Lu, Haoyuan; Hou, Dong; Zhang, Shuangyou; Wang, Zhong

    2016-07-01

    We present a long-term chip scale stabilization scheme for optoelectronic oscillators (OEOs) based on a rubidium coherent population trapping (CPT) atomic resonator. By locking a single mode of an OEO to the (85)Rb 3.035-GHz CPT resonance utilizing an improved phase-locked loop (PLL) with a PID regulator, we achieved a chip scale frequency stabilization system for the OEO. The fractional frequency stability of the stabilized OEO by overlapping Allan deviation reaches 6.2 ×10(-11) (1 s) and  ∼ 1.45 ×10 (-11) (1000 s). This scheme avoids a decrease in the extra phase noise performance induced by the electronic connection between the OEO and the microwave reference in common injection locking schemes. The total physical package of the stabilization system is [Formula: see text] and the total power consumption is 400 mW, which provides a chip scale and portable frequency stabilization approach with ultra-low power consumption for OEOs. PMID:26529751

  12. Frequency stabilization of a semiconductor laser using an external phase modulator.

    PubMed

    Tsuchida, H; Iwasaki, T

    1992-01-01

    A Ti:LiNbO(3) waveguide phase modulator is used as an external frequency stabilizer to reduce the linewidth of an AlGaAs semiconductor laser. A ring interferometer is used as a frequency discriminator, and a wideband servo controller (dc to 30 MHz) is constructed in which feed-forward control of the external phase modulator is combined with feedback control of the injection current. A linewidth of 45 kHz is obtained. PMID:19784226

  13. Development of a Frequency-Stabilized Mid-Infrared External Cavity-Qcl Cavity Ringdown Spectrometer

    NASA Astrophysics Data System (ADS)

    Gibson, Bradley M.; McCall, Benjamin J.

    2014-06-01

    External cavity quantum cascade lasers (EC-QCLs) provide significantly enhanced wavelength tunability while maintaining the high output powers of traditional QCLs throughout the mid-infrared portion of the spectrum. However, the inclusion of wavelength-selective moving parts allows vibrational and acoustic noise to be coupled into the laser as frequency and power noise. This can be particularly troublesome for cavity-enhanced spectroscopy, as attempts to increase vibrational isolation may interfere with stable cavity alignment. Here, we discuss our efforts to improve the frequency stability of our EC-QCL while maintaining tunability and consistent cavity alignment. A mid-infrared hollow silica waveguide is used to vibrationally isolate the laser from the cavity while maintaining alignment. To further increase frequency stability, the laser is side-of-fringe locked to an uncoated solid germanium etalon. Tunability is maintained by incrementing the angle of incidence upon the etalon using a piezo-driven mirror. Angle of incidence tuning and automated periodic re-locking are managed using a BeagleBone Black development board. This allows us to maintain essentially continuous frequency tuning between 1140-1220 wn while stabilizing the laser's frequency to within 30 MHz. Other mid-infrared frequencies could easily be accessed by swapping QCL chips.

  14. Real-Time Stability Margin Measurements for X-38 Robustness Analysis

    NASA Technical Reports Server (NTRS)

    Bosworth, John T.; Stachowiak, Susan J.

    2005-01-01

    A method has been developed for real-time stability margin measurement calculations. The method relies on a tailored-forced excitation targeted to a specific frequency range. Computation of the frequency response is matched to the specific frequencies contained in the excitation. A recursive Fourier transformation is used to make the method compatible with real-time calculation. The method was incorporated into the X-38 nonlinear simulation and applied to an X-38 robustness test. X-38 stability margins were calculated for different variations in aerodynamic and mass properties over the vehicle flight trajectory. The new method showed results comparable to more traditional stability analysis techniques, and at the same time, this new method provided coverage that is more complete and increased efficiency.

  15. Mode-resolved frequency comb interferometry for high-accuracy long distance measurement

    NASA Astrophysics Data System (ADS)

    van den Berg, Steven. A.; van Eldik, Sjoerd; Bhattacharya, Nandini

    2015-09-01

    Optical frequency combs have developed into powerful tools for distance metrology. In this paper we demonstrate absolute long distance measurement using a single femtosecond frequency comb laser as a multi-wavelength source. By applying a high-resolution spectrometer based on a virtually imaged phased array, the frequency comb modes are resolved spectrally to the level of an individual mode. Having the frequency comb stabilized against an atomic clock, thousands of accurately known wavelengths are available for interferometry. From the spectrally resolved output of a Michelson interferometer a distance is derived. The presented measurement method combines spectral interferometry, white light interferometry and multi-wavelength interferometry in a single scheme. Comparison with a fringe counting laser interferometer shows an agreement within <10-8 for a distance of 50 m.

  16. Mode-resolved frequency comb interferometry for high-accuracy long distance measurement

    PubMed Central

    van den Berg, Steven. A.; van Eldik, Sjoerd; Bhattacharya, Nandini

    2015-01-01

    Optical frequency combs have developed into powerful tools for distance metrology. In this paper we demonstrate absolute long distance measurement using a single femtosecond frequency comb laser as a multi-wavelength source. By applying a high-resolution spectrometer based on a virtually imaged phased array, the frequency comb modes are resolved spectrally to the level of an individual mode. Having the frequency comb stabilized against an atomic clock, thousands of accurately known wavelengths are available for interferometry. From the spectrally resolved output of a Michelson interferometer a distance is derived. The presented measurement method combines spectral interferometry, white light interferometry and multi-wavelength interferometry in a single scheme. Comparison with a fringe counting laser interferometer shows an agreement within <10−8 for a distance of 50 m. PMID:26419282

  17. Measurement of background translocation frequencies in individuals with clones

    SciTech Connect

    Wade, M.J.

    1996-08-01

    In the leukemia case the unseparated B and T lymphocytes had a high translocation frequency even after 0.0014, respectively. After purging all clones from the data, the translocation frequencies for Bio 8 and Bio 23 were 0.00750.0014 and 0.0073 metaphases were scored for chromosomal aberrations,, specifically reciprocal translocations, using fluorescence in situ hybridization (FISH). Metaphase spreads were used from two healthy, unexposed individuals (not exposed to radiation, chemotherapy or radiotherapy) and one early B- precursor acute lymphocytic leukemia (ALL) patient (metaphase spreads from both separated T lymphocytes and unseparated B and T lymphocytes were scored). All three individuals had an abnormally high translocation frequency. The high translocation frequencies resulted from clonal expansion of specific translocated chromosomes. I show in this thesis that by purging (discounting or removing) clones from the data of unexposed individuals, one can obtain true background translocation frequencies. In two cases, Bio 8 and Bio 23, the measured translocation frequency for chromosomes 1, 2 and 4 was 0.0124 purging all of the clones from the data. This high translocation frequency may be due to a low frequency of some clones and may not be recognized. The separated T lymphocytes had a higher translocation frequency than expected.

  18. Computational study of ion cyclotron frequency stabilization of the m = 1 interchange mode in mirror geometry

    SciTech Connect

    Myra, J.R.; D'Ippolito, D.A.; Francis, G.L.

    1987-01-01

    A cylindrical plasma model is used to study the stabilizing effect of electromagnetic ion cyclotron frequency range (ICRF) waves on the m = 1 magnetohydrodynamic interchange mode. The fast wave eigenmodes of the column and the near-field antenna pattern are calculated numerically for a diffuse plasma profile when ..omega..>..cap omega../sub i/. The resulting ponderomotive force and sideband contributions to global interchange stability are then determined using a rigid shift trial function. For far-field stabilization it is verified that the direct ponderomotive and sideband contributions cancel exactly as the conducting wall supporting the fast wave eigenmode moves out to infinity. The near-field stabilization effect is related numerically to the driven k/sub parallel/ spectrum of the waves and their radial profiles. The numerical model is employed to calculate threshold ICRF wave amplitudes for the stabilization experiments in the Phaedrus tandem mirror (Phys. Rev. Lett. 51, 1955 (1983)).

  19. Cold denaturation as a tool to measure protein stability.

    PubMed

    Sanfelice, Domenico; Temussi, Piero Andrea

    2016-01-01

    Protein stability is an important issue for the interpretation of a wide variety of biological problems but its assessment is at times difficult. The most common parameter employed to describe protein stability is the temperature of melting, at which the populations of folded and unfolded species are identical. This parameter may yield ambiguous results. It would always be preferable to measure the whole stability curve. The calculation of this curve is greatly facilitated whenever it is possible to observe cold denaturation. Using Yfh1, one of the few proteins whose cold denaturation occurs at neutral pH and low ionic strength, we could measure the variation of its full stability curve under several environmental conditions. Here we show the advantages of gauging stability as a function of external variables using stability curves.

  20. Enabling coherent control of trapped ions with economical multi-laser frequency stabilization technology

    NASA Astrophysics Data System (ADS)

    Lybarger, Warren Emanuel, Jr.

    A phase-locked scanning stability transfer cavity (SSTC) for transferring the absolute frequency stability of an iodine referenced He-Ne (master) laser to three otherwise uncalibrated (slave) lasers (at 844, 1033, & 1092 nm) of a trapped-Sr+ quantum information processing (QIP) apparatus is described. When locked, the 422 nm frequency-doubled Doppler-cooling laser exhibits an error of <1 MHz RMS for several hours, and similar stability is achieved with the other slave lasers. When unlocked, each slave laser drifts by a large fraction (or more) of the corresponding transition linewidth in minutes, thus making reliable laser cooling, ion state readout, and execution of QIP algorithms practically infeasible. The SSTC makes coherent control of Sr+ possible by addressing this problem, and the QIP apparatus is now sufficiently stable for single user operation. New single-ion experimental capabilities include ground state cooling, high-fidelity Rabi flopping, Ramsey interferometry, and sympathetic cooling of 88Sr+( 86Sr+) with 86Sr+( 88Sr+). A 2.5 msec coherence time has been achieved with the optical quoit encoded in a |5 2S 1/2> ↔ |4 2D5/2> quadrupole transition, a precision measurement of the isotope shift of the qubit transition in 86Sr+ relative to 88Sr+ is reported, and a single-ion heating rate consistent with results throughout the trapped-ion community is reported. The SSTC is simple to implement, uses no custom optics, and it has a higher scanning rate than previously demonstrated SSTC's. Phase-locked SSTC's are shown to have an advantage over the more common displacement-locked SSTC in the low finesse regime, and they are an attractive alternative to passively stable but complex optical references and diode lasers designed to address the same problem. The SSTC is useful in spectroscopic applications with other ion species, atoms, and molecules, in general. An appendix is dedicated to describing in detail an advanced trapped-ion quantum processor concept

  1. Wideband Doppler frequency shift measurement and direction ambiguity resolution using optical frequency shift and optical heterodyning.

    PubMed

    Lu, Bing; Pan, Wei; Zou, Xihua; Yan, Xianglei; Yan, Lianshan; Luo, Bin

    2015-05-15

    A photonic approach for both wideband Doppler frequency shift (DFS) measurement and direction ambiguity resolution is proposed and experimentally demonstrated. In the proposed approach, a light wave from a laser diode is split into two paths. In one path, the DFS information is converted into an optical sideband close to the optical carrier by using two cascaded electro-optic modulators, while in the other path, the optical carrier is up-shifted by a specific value (e.g., from several MHz to hundreds of MHz) using an optical-frequency shift module. Then the optical signals from the two paths are combined and detected by a low-speed photodetector (PD), generating a low-frequency electronic signal. Through a subtraction between the specific optical frequency shift and the measured frequency of the low-frequency signal, the value of DFS is estimated from the derived absolute value, and the direction ambiguity is resolved from the derived sign (i.e., + or -). In the proof-of-concept experiments, DFSs from -90 to 90 kHz are successfully estimated for microwave signals at 10, 15, and 20 GHz, where the estimation errors are lower than ±60  Hz. The estimation errors can be further reduced via the use of a more stable optical frequency shift module.

  2. Stability measurements of the radio science system at the 34-m high-efficiency antennas

    NASA Technical Reports Server (NTRS)

    Pham, T. T.; Breidenthal, J. C.; Peng, T. K.; Abbate, S. F.; Rockwell, S. T.

    1993-01-01

    From 1991 to 1993 the fractional frequency stability of the operational Radio Science System was measured at DSS's 15, 45, and 65. These stations are designed to have the most stable uplink and downlink equipment in the Deep Space Network (DSN). Some measurements were performed when the antenna was moving and the frequency was ramped. The stability, including contributions of all elements in the station except for the antenna and the hydrogen maser, was measured to be 0.3 to 1.3 x 10(exp -15) when the frequency was fixed, and 0.6 to 6.0 x 10(exp -15) when the frequency was ramped (sample interval, 1000 sec). Only one measurement out of fifteen exceeded specification. In all other cases, when previous measurements on the antenna and the hydrogen maser were added, a total system stability requirement of 5.0 x 10(exp -15) as met. In addition, ambient temperature was found to cause phase variation in the measurements at a rate of 5.5 deg of phase per deg C.

  3. Arbitrary frequency stabilization of a diode laser based on visual Labview PID VI and sound card output

    NASA Astrophysics Data System (ADS)

    Feng, Guo-Sheng; Wu, Ji-Zhou; Wang, Xiao-Feng; Zheng, Ning-Xuan; Li, Yu-Qing; Ma, Jie; Xiao, Lian-Tuan; Jia, Suo-Tang

    2015-10-01

    We report a robust method of directly stabilizing a grating feedback diode laser to an arbitrary frequency in a large range. The error signal, induced from the difference between the frequency measured by a wavelength meter and the preset target frequency, is fed back to the piezoelectric transducer module of the diode laser via a sound card in the computer. A visual Labview procedure is developed to realize a feedback system. In our experiment the frequency drift of the diode laser is reduced to 8 MHz within 25 min. The robust scheme can be adapted to realize the arbitrary frequency stabilization for many other kinds of lasers. Project supported by the National Basic Research Program of China (Grant No. 2012CB921603), the Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (Grant No. IRT13076), the Major Research Plan of the National Natural Science Foundation of China (Grant No. 91436108), the National Natural Science Foundation of China (Grant Nos. 61378014, 61308023, 61378015, and 11434007), the Fund for Fostering Talents in Basic Science of the National Natural Science Foundation of China (Grant No. J1103210), the New Teacher Fund of the Ministry of Education of China (Grant No. 20131401120012), and the Natural Science Foundation for Young Scientists of Shanxi Province, China (Grant No. 2013021005-1).

  4. Frequency-dependent viscoelasticity measurement by atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Yang, Nan; Wong, Kenneth Kar Ho; de Bruyn, John R.; Hutter, Jeffrey L.

    2009-02-01

    We demonstrate a new technique for investigating viscoelastic properties of soft materials using the atomic force microscope. A small oscillatory voltage is added to the deflection signal of the atomic force microscope causing a vertical oscillatory sample motion. Monitoring the amplitude and phase of this motion allows determination of the viscous and elastic moduli of the sample as a function of frequency during contact imaging. This technique is applied to suspended poly(vinyl alcohol) nanofibers and poly(vinyl alcohol) hydrogels, giving results similar to those measured using traditional static methods. However, the moduli of both the fibers and the hydrogels show a significant frequency dependence. The Young's modulus of the fibers increases with frequency, while for the viscoelastic hydrogels, the storage modulus dominates the mechanical response at low frequency whereas the loss modulus dominates at high frequency.

  5. Surface-polymer stabilized liquid crystals with dual-frequency control.

    PubMed

    Minasyan, Amalya; Galstian, Tigran

    2013-08-01

    Dual-frequency control liquid crystal (LC) and thin reactive mesogen (RM) films, cast on internal surfaces of cell substrate, are used to build surface polymer stabilized structures. Electric field of high frequency is used to orient the LC molecules by the negative dielectric torque prior to the photopolymerization of RM films. Electro-optic characterization results show that the contrasts of light scatter modulation and polarization dependence are noticeably improved by the dual-frequency control. However, there is no significant shortening in the full cycle duration of excitation-relaxation-excitation.

  6. UHF FM receiver having improved frequency stability and low RFI emission

    DOEpatents

    Lupinetti, Francesco

    1990-02-27

    A UHF receiver which converts UHF modulated carrier signals to baseband video signals without any heterodyne or frequency conversion stages. A bandpass filter having a fixed frequency first filters the signals. A low noise amplifier amplifies the filtered signal and applies the signal through further amplification stages to a limited FM demodulator circuit. The UHF signal is directly converted to a baseband video signal. The baseband video signal is clamped by a clamping circuit before driving a monitor. Frequency stability for the receivers is at a theoretical maximum, and interference to adjacent receivers is eliminated due to the absence of a local oscillator.

  7. Surface-polymer stabilized liquid crystals with dual-frequency control.

    PubMed

    Minasyan, Amalya; Galstian, Tigran

    2013-08-01

    Dual-frequency control liquid crystal (LC) and thin reactive mesogen (RM) films, cast on internal surfaces of cell substrate, are used to build surface polymer stabilized structures. Electric field of high frequency is used to orient the LC molecules by the negative dielectric torque prior to the photopolymerization of RM films. Electro-optic characterization results show that the contrasts of light scatter modulation and polarization dependence are noticeably improved by the dual-frequency control. However, there is no significant shortening in the full cycle duration of excitation-relaxation-excitation. PMID:23913090

  8. Frequency-noise measurements of optical frequency combs by multiple fringe-side discriminator.

    PubMed

    Coluccelli, Nicola; Cassinerio, Marco; Gambetta, Alessio; Laporta, Paolo; Galzerano, Gianluca

    2015-11-09

    The frequency noise of an optical frequency comb is routinely measured through the hetherodyne beat of one comb tooth against a stable continuous-wave laser. After frequency-to-voltage conversion, the beatnote is sent to a spectrum analyzer to retrive the power spectral density of the frequency noise. Because narrow-linewidth continuous-wave lasers are available only at certain wavelengths, heterodyning the comb tooth can be challenging. We present a new technique for direct characterization of the frequency noise of an optical frequency comb, requiring no supplementary reference lasers and easily applicable in all spectral regions from the terahertz to the ultraviolet. The technique is based on the combination of a low finesse Fabry-Perot resonator and the so-called "fringe-side locking" method, usually adopted to characterize the spectral purity of single-frequency lasers, here generalized to optical frequency combs. The effectiveness of this technique is demonstrated with an Er-fiber comb source across the wavelength range from 1 to 2 μm.

  9. Frequency-noise measurements of optical frequency combs by multiple fringe-side discriminator.

    PubMed

    Coluccelli, Nicola; Cassinerio, Marco; Gambetta, Alessio; Laporta, Paolo; Galzerano, Gianluca

    2015-01-01

    The frequency noise of an optical frequency comb is routinely measured through the hetherodyne beat of one comb tooth against a stable continuous-wave laser. After frequency-to-voltage conversion, the beatnote is sent to a spectrum analyzer to retrive the power spectral density of the frequency noise. Because narrow-linewidth continuous-wave lasers are available only at certain wavelengths, heterodyning the comb tooth can be challenging. We present a new technique for direct characterization of the frequency noise of an optical frequency comb, requiring no supplementary reference lasers and easily applicable in all spectral regions from the terahertz to the ultraviolet. The technique is based on the combination of a low finesse Fabry-Perot resonator and the so-called "fringe-side locking" method, usually adopted to characterize the spectral purity of single-frequency lasers, here generalized to optical frequency combs. The effectiveness of this technique is demonstrated with an Er-fiber comb source across the wavelength range from 1 to 2 μm. PMID:26548900

  10. Frequency-noise measurements of optical frequency combs by multiple fringe-side discriminator

    PubMed Central

    Coluccelli, Nicola; Cassinerio, Marco; Gambetta, Alessio; Laporta, Paolo; Galzerano, Gianluca

    2015-01-01

    The frequency noise of an optical frequency comb is routinely measured through the hetherodyne beat of one comb tooth against a stable continuous-wave laser. After frequency-to-voltage conversion, the beatnote is sent to a spectrum analyzer to retrive the power spectral density of the frequency noise. Because narrow-linewidth continuous-wave lasers are available only at certain wavelengths, heterodyning the comb tooth can be challenging. We present a new technique for direct characterization of the frequency noise of an optical frequency comb, requiring no supplementary reference lasers and easily applicable in all spectral regions from the terahertz to the ultraviolet. The technique is based on the combination of a low finesse Fabry-Perot resonator and the so-called “fringe-side locking” method, usually adopted to characterize the spectral purity of single-frequency lasers, here generalized to optical frequency combs. The effectiveness of this technique is demonstrated with an Er-fiber comb source across the wavelength range from 1 to 2 μm. PMID:26548900

  11. Constant strain frequency sweep measurements on granite rock.

    PubMed

    Haller, Kristian C E; Hedberg, Claes M

    2008-02-15

    Like many materials, granite exhibits both nonlinear acoustic distortion and slow nonequilibrium dynamics. Measurements to date have shown a response from both phenomena simultaneously, thus cross-contaminating the results. In this Letter, constant strain frequency sweep measurements eliminate the slow dynamics and, for the first time, permit evaluation of nonlinearity by itself characterized by lower resonance frequencies and a steeper slope. Measurements such as these are necessary for the fundamental understanding of material dynamics, and for the creation and validation of descriptive models.

  12. Improvement of Space Shuttle Main Engine Low Frequency Acceleration Measurements

    NASA Technical Reports Server (NTRS)

    Stec, Robert C.

    1999-01-01

    The noise floor of low frequency acceleration data acquired on the Space Shuttle Main Engines is higher than desirable. Difficulties of acquiring high quality acceleration data on this engine are discussed. The approach presented in this paper for reducing the acceleration noise floor focuses on a search for an accelerometer more capable of measuring low frequency accelerations. An overview is given of the current measurement system used to acquire engine vibratory data. The severity of vibration, temperature, and moisture environments are considered. Vibratory measurements from both laboratory and rocket engine tests are presented.

  13. Continuous cardiac output measurement - Aspects of Doppler frequency analysis

    NASA Technical Reports Server (NTRS)

    Mackay, R. S.; Hechtman, H. B.

    1975-01-01

    From the suprasternal notch blood flow velocity in the aorta can be measured non-invasively by a Doppler probe. Integration over systole after frequency analysis gives a measure of stroke volume if a separate diameter observation is incorporated. Frequency analysis by a zero crossing counter or by a set of parallel phaselock loops was less effective than a set of bandpass filters. Observations on dogs, baboons and humans before and after exercise or surgery suggest the indications to be useful. Application to judging heart failure by the effect of introducing a volume load is indicated. Changes in output also are measured in freely moving subjects.

  14. Optimal Load Control via Frequency Measurement and Neighborhood Area Communication

    SciTech Connect

    Zhao, CH; Topcu, U; Low, SH

    2013-11-01

    We propose a decentralized optimal load control scheme that provides contingency reserve in the presence of sudden generation drop. The scheme takes advantage of flexibility of frequency responsive loads and neighborhood area communication to solve an optimal load control problem that balances load and generation while minimizing end-use disutility of participating in load control. Local frequency measurements enable individual loads to estimate the total mismatch between load and generation. Neighborhood area communication helps mitigate effects of inconsistencies in the local estimates due to frequency measurement noise. Case studies show that the proposed scheme can balance load with generation and restore the frequency within seconds of time after a generation drop, even when the loads use a highly simplified power system model in their algorithms. We also investigate tradeoffs between the amount of communication and the performance of the proposed scheme through simulation-based experiments.

  15. Longitudinal Frequency and Stability of Family Contact in Institutional and Community Living

    ERIC Educational Resources Information Center

    Stancliffe, Roger J.; Lakin, K. Charlie

    2006-01-01

    We examined the frequency and stability of family contact with long-term institutional residents during a major deinstitutionalization project. Movers relocated to community accommodation between Assessments 1 (baseline) and 2. Stayers remained institutionalized. We investigated family contact longitudinally over four annual assessments. There was…

  16. Frequency noise induced by fiber perturbations in a fiber-linked stabilized laser

    NASA Technical Reports Server (NTRS)

    Pang, YI; Hamilton, Jeffrey J.; Richard, Jean-Paul

    1992-01-01

    The effects of acoustic perturbations on an optical fiber that links a stabilized laser to its reference cavity are studied. An extrapolation indicates that 69 dB of acoustic noise impinging on a 1-m segment of the 10-m fiber contribute frequency noise at the level of 1 Hz/(Hz)1/2 in the 1100-2100-Hz band.

  17. Measurements and Predictions of High Frequency Ambient Noise

    NASA Astrophysics Data System (ADS)

    Holden, Andrew

    2004-11-01

    A great deal has been published on ambient noise. Most of this has covered (a) omni directional levels, and (b) the vertical and horizontal directivity of shipping noise at low frequencies. There is some published material on the vertical directivity of wind generated noise at lower frequencies, but very little at higher frequencies. In order to study wind generated ambient noise at higher frequencies, work has recently started using a small planar array from QinetiQ Bincleaves. As well as measurements, a model called CANARY has been written to predict ambient noise vertical directivity and array responses to this noise. This paper contains some comparisons between CANARY predictions and (a) previous measured vertical directivity data at 4.5 kHz, (b) measured omni-directional data, and (c) initial analysis of the planar array measurements. The paper shows the nature of the ambient noise vertical structure at higher frequencies and that the CANARY predictions are in good agreement with the measurements.

  18. An improved offset generator developed for Allan deviation measurement of ultra stable frequency standards

    NASA Technical Reports Server (NTRS)

    Hamell, Robert L.; Kuhnle, Paul F.; Sydnor, Richard L.

    1992-01-01

    Measuring the performance of ultra stable frequency standards such as the Superconducting Cavity Maser Oscillator (SCMO) necessitates improvement of some test instrumentation. The frequency stability test equipment used at JPL includes a 1 Hz Offset Generator to generate a beat frequency between a pair of 100 MHz signals that are being compared. The noise floor of the measurement system using the current Offset Generator is adequate to characterize stability of hydrogen masers, but it is not adequate for the SCMO. A new Offset Generator with improved stability was designed and tested at JPL. With this Offset Generator and a new Zero Crossing Detector, recently developed at JPL, the measurement flow was reduced by a factor of 5.5 at 1 second tau, 3.0 at 1000 seconds, and 9.4 at 10,000 seconds, compared against the previous design. In addition to the new circuit designs of the Offset Generator and Zero Crossing Detector, tighter control of the measurement equipment environment was required to achieve this improvement. The design of this new Offset Generator are described, along with details of the environment control methods used.

  19. Western Wind and Solar Integration Study Phase 3 – Frequency Response and Transient Stability

    SciTech Connect

    Miller, N. W.; Shao, M.; Pajic, S.; D'Aquila, R.

    2014-12-01

    Power system operators and utilities worldwide have concerns about the impact of high-penetration wind and solar generation on electric grid reliability (EirGrid 2011b, Hydro-Quebec 2006, ERCOT 2010). The stability of North American grids under these conditions is a particular concern and possible impediment to reaching future renewable energy goals. Phase 3 of the Western Wind and Solar Integration Study (WWSIS-3) considers a 33% wind and solar annual energy penetration level that results in substantial changes to the characteristics of the bulk power system, including different power flow patterns, different commitment and dispatch of existing synchronous generation, and different dynamic behavior of wind and solar generation. WWSIS-3 evaluates two specific aspects of fundamental frequency system stability: frequency response and transient stability.

  20. 47 CFR 2.1055 - Measurements required: Frequency stability.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... broadcast transmitters) and any heating element cycling normally occurring at each ambient temperature level... transmitter keying (except for broadcast transmitters) and any heating element cycling at the nominal...

  1. Frequency stabilization of spin-torque-driven oscillations by coupling with a magnetic nonlinear resonator

    SciTech Connect

    Kudo, Kiwamu Suto, Hirofumi; Nagasawa, Tazumi; Mizushima, Koichi; Sato, Rie

    2014-10-28

    The fundamental function of any oscillator is to produce a waveform with a stable frequency. Here, we show a method of frequency stabilization for spin-torque nano-oscillators (STNOs) that relies on coupling with an adjacent nanomagnet through the magnetic dipole–dipole interaction. It is numerically demonstrated that highly stable oscillations occur as a result of mutual feedback between an STNO and a nanomagnet. The nanomagnet acts as a nonlinear resonator for the STNO. This method is based on the nonlinear behavior of the resonator and can be considered as a magnetic analogue of an optimization scheme in nanoelectromechanical systems. The oscillation frequency is most stabilized when the nanomagnet is driven at a special feedback point at which the feedback noise between the STNO and resonator is completely eliminated.

  2. Stability measurements of PPL atmospheric pressure arc

    SciTech Connect

    Roquemore, L.; Zweben, S.J.; Wurden, G.A.

    1997-12-31

    Experiments on the stability of atmospheric pressure arcs have been started at PPL to understand and improve the performance of arc furnaces used for processing applications in metallurgy and hazardous waste treatment. Previous studies have suggested that the violent instabilities in such arcs may be due to kink modes. A 30 kW, 500 Amp CW DC experimental arc furnace was constructed with a graphite cathode and a molten steel anode. The arc plasma is diagnosed with 4000 frames/sec digital camera, Hall probes, and voltage and current monitors. Under certain conditions, the arc exhibits an intermittent helical instability, with the helix rotating at {approx}600 Hz. The nature of the instability is investigated. A possible instability mechanism is the self-magnetic field of the arc, with saturation occurring due to inhomogeneous heating in a helical arc. The effect of external DC and AC magnetic fields on the instability is investigated. Additionally, arc deflection due to external transverse magnetic field is investigated. The deflection angle is found to be proportional to the applied field, and is in good agreement with a simple model of the {rvec J} x {rvec b} force on the arc jet.

  3. Low-frequency sound absorption measurements in air

    NASA Technical Reports Server (NTRS)

    Zuckerwar, A. J.; Meredith, R. W.

    1984-01-01

    Thirty sets of sound absorption measurements in air at a pressure of 1 atmosphere are presented at temperatures from 10 C to 50 C, relative humidities from 0 to 100 percent, and frequencies from 10 to 2500 Hz. The measurements were conducted by the method of free decay in a resonant tube having a length of 18.261 m and bore diameter of 0.152 m. Background measurements in a gas consisting of 89.5 percent N2 and 10.5 percent Ar, a mixture which has the same sound velocity as air, permitted the wall and structural losses of the tube to be separated from the constituent absorption, consisting of classical rotational and vibrational absorption, in the air samples. The data were used to evaluate the vibrational relaxation frequencies of N2 and/or O2 for each of the 30 sets of meteorological parameters. Over the full range of humidity, the measured relaxation frequencies of N2 in air lie between those specified by ANSI Standard S1.26-1978 and those measured earlier in binary N2H2O mixtures. The measured relaxation frequencies could be determined only at very low values of humidity, reveal a significant trend away from the ANSI standard, in agreement with a prior investigation.

  4. Measuring terrestrial radio frequency interference at orbit altitudes

    NASA Technical Reports Server (NTRS)

    Bayol, M. E.; Locke, P. A.

    1973-01-01

    An experiment has been designed to measure and characterize the effect of man-made interference on satellite receivers at orbital altitudes. The experiment, as designed, requires dedicated hardware on a spacecraft of specified orbit and will measure (within the frequency range from 400 MHz to 12.4 GHz) peak levels of interference in cells dimensioned in space, time, and frequency. The experiment will provide data indicative of some of the statistical characteristics of interference levels at satellite orbital altitudes and will provide designers of satellite communications links with new facilities for the prediction and prevention of interference problems.

  5. Stabilizing carrier-envelope offset frequency of a femtosecond laser using heterodyne interferometry.

    PubMed

    Zhang, Xiaosheng; Wu, Guanhao; Hu, Minghao; Xiong, Shilin

    2016-09-15

    We propose a time-domain fceo stabilization method of a femtosecond laser using heterodyne interferometry. A femtosecond pulse train that is delayed by a spatial delay line interferes with the original pulse train. The phase difference between heterodyne interference signals extracted from different spectral regions is used to stabilize the relative position of the two pulse trains; then the heterodyne interference phase is used to stabilize the carrier-envelope offset frequency fceo. The experimental results show that, after being stabilized, the relative Allan deviations of fceo are 1.0×10-9 at 0.5 s and 4.6×10-10 at 50 s. PMID:27628376

  6. Feasibility demonstration of a variable frequency driver-microwave transient regression rate measurement system. [for solid propellant combustion response

    NASA Technical Reports Server (NTRS)

    Strand, L. D.; Mcnamara, R. P.

    1976-01-01

    The feasibility of a system capable of rapidly and directly measuring the low-frequency (motor characteristics length bulk mode) combustion response characteristics of solid propellants has been investigated. The system consists of a variable frequency oscillatory driver device coupled with an improved version of the JPL microwave propellant regression rate measurement system. The ratio of the normalized regression rate and pressure amplitudes and their relative phase are measured as a function of varying pressure level and frequency. Test results with a well-characterized PBAN-AP propellant formulation were found to compare favorably with the results of more conventional stability measurement techniques.

  7. Frequency shift measurement in shock-compressed materials

    DOEpatents

    Moore, D.S.; Schmidt, S.C.

    1984-02-21

    A method is disclosed for determining molecular vibrational frequencies in shock-compressed transparent materials. A single laser beam pulse is directed into a sample material while the material is shock-compressed from a direction opposite that of the incident laser beam. A Stokes beam produced by stimulated Raman scattering is emitted back along the path of the incident laser beam, that is, in the opposite direction to that of the incident laser beam. The Stokes beam is separated from the incident beam and its frequency measured. The difference in frequency between the Stokes beam and the incident beam is representative of the characteristic frequency of the Raman active mode of the sample. Both the incident beam and the Stokes beam pass perpendicularly through the stock front advancing through the sample, thereby minimizing adverse effects of refraction.

  8. Frequency shift measurement in shock-compressed materials

    DOEpatents

    Moore, David S.; Schmidt, Stephen C.

    1985-01-01

    A method for determining molecular vibrational frequencies in shock-compressed transparent materials. A single laser beam pulse is directed into a sample material while the material is shock-compressed from a direction opposite that of the incident laser beam. A Stokes beam produced by stimulated Raman scattering is emitted back along the path of the incident laser beam, that is, in the opposite direction to that of the incident laser beam. The Stokes beam is separated from the incident beam and its frequency measured. The difference in frequency between the Stokes beam and the incident beam is representative of the characteristic frequency of the Raman active mode of the sample. Both the incident beam and the Stokes beam pass perpendicularly through the shock front advancing through the sample, thereby minimizing adverse effects of refraction.

  9. Measurement of the Fundamental Thermal Noise Limit in a Cryogenic Sapphire Frequency Standard Using Bimodal Maser Oscillations

    SciTech Connect

    Benmessai, Karim; Kersale, Yann; Giordano, Vincent; Creedon, Daniel Lloyd; Tobar, Michael Edmund; Bourgeois, Pierre-Yves

    2008-06-13

    We report observations of the Schawlow-Townes noise limit in a cryogenic sapphire secondary frequency standard. The effect causes a fundamental limit to the frequency stability, and was measured through the novel excitation of a bimodal maser oscillation of a Whispering Gallery doublet at 12.04 GHz. The beat frequency of 10 kHz between the oscillations enabled a sensitive probe for this measurement of fractional frequency instability of 10{sup -14}{tau}{sup -1/2} with only 0.5 pW of output power.

  10. Swept frequency technique for dispersion measurement of microstrip lines

    NASA Technical Reports Server (NTRS)

    Lee, R. Q.

    1986-01-01

    Microstrip lines used in microwave integrated circuits are dispersive. Because a microstrip line is an open structure, the dispersion can not be derived with pure TEM, TE, or TM mode analysis. Dispersion analysis has commonly been done using a spectral domain approach, and dispersion measurement has been made with high Q microstrip ring resonators. Since the dispersion of a microstrip line is fully characterized by the frequency dependent phase velocity of the line, dispersion measurement of microstrip lines requires the measurement of the line wavelength as a function of frequency. In this paper, a swept frequency technique for dispersion measurement is described. The measurement was made using an automatic network analyzer with the microstrip line terminated in a short circuit. Experimental data for two microstrip lines on 10 and 30 mil Cuflon substrates were recorded over a frequency range of 2 to 20 GHz. Agreement with theoretical results computed by the spectral domain approach is good. Possible sources of error for the discrepancy are discussed.

  11. Measuring ionospheric electron density using the plasma frequency probe

    SciTech Connect

    Jensen, M.D.; Baker, K.D. )

    1992-02-01

    During the past decade, the plasma frequency probe (PFP) has evolved into an accurate, proven method of measuring electron density in the ionosphere above about 90 km. The instrument uses an electrically short antenna mounted on a sounding rocket that is immersed in the plasma and notes the frequency where the antenna impedance is large and nonreactive. This frequency is closely related to the plasma frequency, which is a direct function of free electron concentration. The probe uses phase-locked loop technology to follow a changing electron density. Several sections of the plasma frequency probe circuitry are unique, especially the voltage-controlled oscillator that uses both an electronically tuned capacitor and inductor to give the wide tuning range needed for electron density measurements. The results from two recent sounding rocket flights (Thunderstorm II and CRIT II) under vastly different plasma conditions demonstrate the capabilities of the PFP and show the importance of in situ electron density measurements of understanding plasma processes. 9 refs.

  12. Frequency Domain Magnetic Measurements from Kilohertz to Gigahertz

    NASA Astrophysics Data System (ADS)

    Gregg, John F.

    "......we applied much prolonged labor on investigating the magnetical forces; so wonderful indeed are they, compared with the forces in all other minerals, surpassing even the virtues of all bodies around us. Nor have we found this labor idle or unfruitful; since daily in our experimenting new unexpected properties came to light."William Gilbert, De Magnete, 1600Abstract. This review deals with practical aspects of making frequency-domain measurements of magnetic susceptibility and magnetic losses from 200 kHz up to 10 GHz. It sets out the types of measurement concerned, distinguishing resonant from nonresonant phenomena. The techniques available are categorized according to suitability for the different frequency regimes and types of investigation. Practical recipes are provided for undertaking such experiments across the entire frequency range. Marginal oscillator spectrometry is discussed which is applicable across the whole frequency range. Different instruments are presented, and particular emphasis is placed on designs which function on the Robinson principle. Analysis of oscillation condition and signal-to-noise performance is dealt with, also sample considerations such as filling factor. Practical circuits are presented and their merits and demerits evaluated. Layout and radio-frequency design considerations are dealt with. Ultrahigh/microwave frequency marginal oscillator spectrometry is given special treatment and several practical designs are given. The essentials of good microwave design are emphasized. A general discussion of resonant structures is included which treats multiple layer coil design, slow wave line structures, stripline and cavities. Unusual cavity designs such as the rhumbatron are treated. Use of striplines with microwave marginal spectrometry is described and compared with conventional network-analysis techniques. The use of parameter matrices for high-frequency analysis is alluded to. Some details of good construction practice are

  13. Newton algorithm for fitting transfer functions to frequency response measurements

    NASA Technical Reports Server (NTRS)

    Spanos, J. T.; Mingori, D. L.

    1993-01-01

    In this paper the problem of synthesizing transfer functions from frequency response measurements is considered. Given a complex vector representing the measured frequency response of a physical system, a transfer function of specified order is determined that minimizes the sum of the magnitude-squared of the frequency response errors. This nonlinear least squares minimization problem is solved by an iterative global descent algorithm of the Newton type that converges quadratically near the minimum. The unknown transfer function is expressed as a sum of second-order rational polynomials, a parameterization that facilitates a numerically robust computer implementation. The algorithm is developed for single-input, single-output, causal, stable transfer functions. Two numerical examples demonstrate the effectiveness of the algorithm.

  14. Absolute molecular transition frequencies measured by three cavity-enhanced spectroscopy techniques

    NASA Astrophysics Data System (ADS)

    Cygan, A.; Wójtewicz, S.; Kowzan, G.; Zaborowski, M.; Wcisło, P.; Nawrocki, J.; Krehlik, P.; Śliwczyński, Ł.; Lipiński, M.; Masłowski, P.; Ciuryło, R.; Lisak, D.

    2016-06-01

    Absolute frequencies of unperturbed 12C16O transitions from the near-infrared (3-0) band were measured with uncertainties five-fold lower than previously available data. The frequency axis of spectra was linked to the primary frequency standard. Three different cavity enhanced absorption and dispersion spectroscopic methods and various approaches to data analysis were used to estimate potential systematic instrumental errors. Except for a well established frequency-stabilized cavity ring-down spectroscopy, we applied the cavity mode-width spectroscopy and the one-dimensional cavity mode-dispersion spectroscopy for measurement of absorption and dispersion spectra, respectively. We demonstrated the highest quality of the dispersion line shape measured in optical spectroscopy so far. We obtained line positions of the Doppler-broadened R24 and R28 transitions with relative uncertainties at the level of 10-10. The pressure shifting coefficients were measured and the influence of the line asymmetry on unperturbed line positions was analyzed. Our dispersion spectra are the first demonstration of molecular spectroscopy with both axes of the spectra directly linked to the primary frequency standard, which is particularly desirable for the future reference-grade measurements of molecular spectra.

  15. Distributed dynamic strain measurement using optical frequency-domain reflectometry.

    PubMed

    Zhou, Da-Peng; Chen, Liang; Bao, Xiaoyi

    2016-08-20

    Distributed dynamic strain measurement based on optical frequency-domain reflectometry is proposed. The technique makes use of the wide scanning range of a tunable laser source in a short sweeping time, and subdivides the overall spectrum into narrower frequency windows. The advantage of subdividing the laser spectral range is to improve the measurement uncertainty induced by the laser wavelength difference between repeated scans. The noise-limited dynamic strain resolution is investigated experimentally, indicating that a minimum detectable strain is less than 200 nε for a spatial resolution of 20 cm. By measuring the subdivided spectral shifts in the time sequence along the sensing fiber, the dynamic strain can be properly quantified over a 30 m measurement range for a highest sampling rate of up to 50 Hz. PMID:27556996

  16. Carrier-envelope offset frequency stabilization in a femtosecond optical parametric oscillator without nonlinear interferometry.

    PubMed

    Balskus, Karolis; Fleming, Melissa; McCracken, Richard A; Zhang, Zhaowei; Reid, Derryck T

    2016-03-01

    By exploiting the correlation between changes in the wavelength and the carrier-envelope offset frequency (f(CEO)) of the signal pulses in a synchronously pumped optical parametric oscillator, we show that f(CEO) can be stabilized indefinitely to a few megahertz in a 333 MHz repetition-rate system. Based on a position-sensitive photodiode, the technique is easily implemented, requires no nonlinear interferometry, has a wide capture range, and is compatible with feed-forward techniques that can enable f(CEO) stabilization at loop bandwidths far exceeding those currently available to OPO combs. PMID:26974092

  17. High-bandwidth transfer of phase stability through a fiber frequency comb.

    PubMed

    Scharnhorst, Nils; Wübbena, Jannes B; Hannig, Stephan; Jakobsen, Kornelius; Kramer, Johannes; Leroux, Ian D; Schmidt, Piet O

    2015-07-27

    We demonstrate phase locking of a 729 nm diode laser to a 1542 nm master laser via an erbium-doped-fiber frequency comb, using a transfer-oscillator feedforward scheme which suppresses the effect of comb noise in an unprecedented 1.8 MHz bandwidth. We illustrate its performance by carrying out coherent manipulations of a trapped calcium ion with 99 % fidelity even at few-μs timescales. We thus demonstrate that transfer-oscillator locking can provide sufficient phase stability for high-fidelity quantum logic manipulation even without pre-stabilization of the slave diode laser. PMID:26367634

  18. Frequency stabilization of a single mode terahertz quantum cascade laser to the kilohertz level.

    PubMed

    Danylov, Andriy A; Goyette, Thomas M; Waldman, Jerry; Coulombe, Michael J; Gatesman, Andrew J; Giles, Robert H; Goodhue, William D; Qian, Xifeng; Nixon, William E

    2009-04-27

    A simple analog locking circuit was shown to stabilize the beat signal between a 2.408 THz quantum cascade laser and a CH(2)DOH THz CO(2) optically pumped molecular laser to 3-4 kHz (FWHM). This is approximately a tenth of the observed long-term (t approximately sec) linewidth of the optically pumped laser showing that the feedback loop corrects for much of the mechanical and acoustic-induced frequency jitter of the gas laser. The achieved stability should be sufficient to enable the use of THz quantum cascade lasers as transmitters in short-range coherent transceivers.

  19. Scaling laws for the intrapulse frequency stability of an injection mode selected TEA CO2 laser

    NASA Astrophysics Data System (ADS)

    Willetts, D. V.; Harris, M. R.

    1983-05-01

    Heterodyne measurements of the intrapulse frequency behavior of an injection mode selected TEA CO2 laser are presented. The frequency rose as the square of time at a rate varying linearly with energy and strongly dependent on spot size. These results are in accordance with a laser induced medium perturbative (LIMP) model, which allows the chirp in any TEA laser system to be predicted.

  20. Event group importance measures for top event frequency analyses

    SciTech Connect

    1995-07-31

    Three traditional importance measures, risk reduction, partial derivative, nd variance reduction, have been extended to permit analyses of the relative importance of groups of underlying failure rates to the frequencies of resulting top events. The partial derivative importance measure was extended by assessing the contribution of a group of events to the gradient of the top event frequency. Given the moments of the distributions that characterize the uncertainties in the underlying failure rates, the expectation values of the top event frequency, its variance, and all of the new group importance measures can be quantified exactly for two familiar cases: (1) when all underlying failure rates are presumed independent, and (2) when pairs of failure rates based on common data are treated as being equal (totally correlated). In these cases, the new importance measures, which can also be applied to assess the importance of individual events, obviate the need for Monte Carlo sampling. The event group importance measures are illustrated using a small example problem and demonstrated by applications made as part of a major reactor facility risk assessment. These illustrations and applications indicate both the utility and the versatility of the event group importance measures.

  1. Variable optical attenuator with a polymer-stabilized dual-frequency liquid crystal.

    PubMed

    Wu, Yung-Hsun; Liang, Xiao; Lu, Yan-Qing; Du, Fang; Lin, Yi-Hsin; Wu, Shin-Tson

    2005-07-10

    A transmission-type variable optical attenuator (VOA) based on a polymer-stabilized dual-frequency liquid crystal (PSDFLC) is demonstrated at gamma = 1.55 microm. The VOA is highly transparent in the voltage-off state but scatters light in the voltage-on state. By using a birefringent beam displacer incorporated with half-wave plates, we can obtain a VOA that is polarization independent and that exhibits a 31 dB dynamic range. The polymer networks and dual-frequency effect together reduce the response time (rise + decay) of a 16 microm PSDFLC cell to 30 ms at room temperature and at a voltage of 24 Vrms.

  2. ELISA: a cryocooled 10 GHz oscillator with 10(-15) frequency stability.

    PubMed

    Grop, S; Bourgeois, P Y; Bazin, N; Kersalé, Y; Rubiola, E; Langham, C; Oxborrow, M; Clapton, D; Walker, S; De Vicente, J; Giordano, V

    2010-02-01

    This article reports the design, the breadboarding, and the validation of an ultrastable cryogenic sapphire oscillator operated in an autonomous cryocooler. The objective of this project was to demonstrate the feasibility of a frequency stability of 3x10(-15) between 1 and 1000 s for the European Space Agency deep space stations. This represents the lowest fractional frequency instability ever achieved with cryocoolers. The preliminary results presented in this paper validate the design we adopted for the sapphire resonator, the cold source, and the oscillator loop.

  3. Atmospheric range correction for two-frequency SLR measurements

    NASA Astrophysics Data System (ADS)

    Wijaya, Dudy D.; Brunner, Fritz K.

    2011-09-01

    It has been widely known that the use of two-frequency Satellite Laser Ranging (SLR) system is limited by stringent precision requirements of the range measurements and the proper atmospheric model. Owing to the stringent requirements, this SLR system is impractical for the current requirement of SLR measurements within the framework of global geodetic observing system (GGOS). If in the future this stringent requirement could be met, this SLR system would be an attractive tool to reduce atmospheric propagation effects of SLR and would be of great benefit for the next generation of GGOS design. To anticipate possible future developments of the two-frequency SLR systems, we have developed a new atmospheric correction formula for the two-frequency SLR measurements. The new formula eliminates the total atmospheric density effect including its gradient and provides two terms to calculate the curvature effect and the water vapor distribution effect. While the curvature effect can be calculated by an accurate model, the required information about the water vapor distribution along the propagation path can be calculated using previous developments of optical delay modeling or alternatively using results from microwave measurements. Theoretical simulations using the two-frequency systems of the Graz and TIGO-Concepción stations shows that the new formula completely reduces all propagation effects at any elevation angle above 3° with an accuracy better than 1 mm. However, the required precision for the difference of the two-frequency SLR measurements, i.e. better than 45 μm for a single epoch, exceeds the capability of the current state of the art SLR systems.

  4. Highly precise stabilization of intracavity prism-based Er:fiber frequency comb using optical-microwave phase detector.

    PubMed

    Zhang, Shuangyou; Wu, Jiutao; Leng, Jianxiao; Lai, Shunnan; Zhao, Jianye

    2014-11-15

    In this Letter, we demonstrate a fully stabilized Er:fiber frequency comb by using a fiber-based, high-precision optical-microwave phase detector. To achieve high-precision and long-term phase locking of the repetition rate to a microwave reference, frequency control techniques (tuning pump power and cavity length) are combined together as its feedback. Since the pump power has been used for stabilization of the repetition rate, we introduce a pair of intracavity prisms as a regulator for carrier-envelope offset frequency, thereby phase locking one mode of the comb to the rubidium saturated absorption transition line. The stabilized comb performs the same high stability as the reference for the repetition rate and provides a residual frequency instability of 3.6×10(-13) for each comb mode. The demonstrated stabilization scheme could provide a high-precision comb for optical communication, direct frequency comb spectroscopy.

  5. Monolithic CEO-stabilization scheme-based frequency comb from an octave-spanning laser

    NASA Astrophysics Data System (ADS)

    Zi-Jiao, Yu; Hai-Nian, Han; Yang, Xie; Hao, Teng; Zhao-Hua, Wang; Zhi-Yi, Wei

    2016-04-01

    We demonstrate a carrier-envelope phase-stabilized octave-spanning oscillator based on the monolithic scheme. A wide output spectrum extending from 480 nm to 1050 nm was generated directly from an all-chirped mirror Ti:sapphire laser. After several improvements, the carrier-envelope offset (CEO) beat frequency accessed nearly 60 dB under a resolution of 100 kHz. Using a feedback system with 50-kHz bandwidth, we compressed the residual phase noise to 55 mrad (integrated from 1 Hz to 1 MHz) for the stabilized CEO, corresponding to 23-as timing jitter at the central wavelength of 790 nm. This is, to the best of our knowledge, the smallest timing jitter achieved among the existing octave-spanning laser based frequency combs. Project supported by the National Basic Research Program of China (Grant No. 2012CB821304) and the National Natural Science Foundation of China (Grant Nos. 11078022 and 61378040).

  6. Stability Diagrams for Paul Ion Traps Driven by Two-Frequencies.

    PubMed

    Possa, Gabriela C; Roncaratti, Luiz F

    2016-07-14

    In this paper, we present and discuss stability diagrams for Paul traps driven by two ac voltages. In contrast to a typical Paul trap, here we suggest a secondary ac voltage whose frequency is twice the frequency of the primary one. The ratio between their amplitudes can be used to expand the region of stability and to access different states of motion of trapped ions. This provides a further mechanism to trap, cool, and manipulate single ions and also to improve the experimental framework where ion clouds and crystals can be prepared and controlled. Such approach opens the possibility of designing more sophisticated trapping architectures, leading to a wide variety of applications on ion trap research and mass analysis techniques.

  7. Efficient carrier-envelope offset frequency stabilization through gain modulation via stimulated emission.

    PubMed

    Karlen, Lauriane; Buchs, Gilles; Portuondo-Campa, Erwin; Lecomte, Steve

    2016-01-15

    A novel scheme for intracavity control of the carrier-envelope offset (CEO) frequency of a 100 MHz mode-locked Er:Yb:glass diode-pumped solid-state laser (DPSSL) based on the modulation of the laser gain via stimulated emission of the excited Er(3+) ions is demonstrated. This method allows us to bypass the ytterbium system few-kHz low-pass filter in the f(CEO) stabilization loop and thus to push the phase lock bandwidth up to a limit close to the relaxation oscillations frequency of the erbium system. A phase lock bandwidth above 70 kHz has been achieved with the fully stabilized laser, leading to an integrated phase noise [1 Hz-1 MHz] of 120 mrad. PMID:26766718

  8. Measurement of formant frequencies and bandwidths in singing.

    PubMed

    Schutte, H K; Miller, D G; Svec, J G

    1995-09-01

    That singers under certain circumstances adjust the articulation of the vocal tract (formant tuning) to enhance acoustic output is both apparent from measurements and understood in theory. The precise effect of a formant on an approaching (retreating) harmonic as the latter varies in frequency during actual singing, however, is difficult to isolate. In this study variations in amplitude of radiated sound components as well as supraglottal and subglottal (esophageal) pressures accompanying the vibrato-related sweep of voice harmonics were used as a basis for estimating the effective center frequencies and bandwidths of the first and second formants. PMID:8541972

  9. Frequency stabilization to a molecular line of a diode-pumped Er{endash}Yb laser at 1533-nm wavelength

    SciTech Connect

    Taccheo, S.; Longhi, S.; Pallaro, L.; Laporta, P.; Svelto, C.; Bava, E.

    1995-12-01

    Two identical diode-pumped bulk Er:Yb:glass lasers, operating at 1533-nm wavelength, have been locked independently to the {ital P}(13) vibrational{endash}rotational line of an acetylene molecule. A long-term frequency stability over a 4-h period of better than 1.5 MHz and a short-term laser linewidth narrower than 50 kHz have been obtained by measurement of the beat note between the two lasers. {copyright} {ital 1995 Optical Society of America.}

  10. Frequency measures of behavior for assistive technology and rehabilitation.

    PubMed

    Merbitz, C

    1996-01-01

    Documenting assistive technology outcomes has grown in importance, but outcome measurement remains problematic. A new approach uses natural science measures and a model (selectionism) from the field of Behavior Analysis. Selectionism defines behaviors by their effects (functional performance) and the environment (including technology) within which they occur, and explicitly treats variation in patterns of behavior over time for individuals (intervention effects). Its basic metric is frequency of behaviors (count per unit time) which is similar to robust engineering measures like centimeters, grams, and seconds. This approach eliminates many of the problems inherent to more traditional psychometrics. Selectionism based on frequencies also provides an empirical structure or taxonomy to organize efforts and outcomes, unified by the notion of fluency. Composite behaviors are combinations of smaller component behaviors that are required for performance of the composite. A frequency above which a component behavior is readily retained, generalized, and recruited into the more complex composite behavior is called fluency; thus individuals fluent on the critical components easily and efficiently demonstrate the composite. This model suggests that when assistive technology interventions raise component behavior frequencies to fluent levels, they will be integrated usefully into an individual's life. This selectionistic approach has been used successfully in the field of education. It has the added benefit of not only empirically defining measurable outcomes, but also of providing useful ongoing measurement of change during treatment. This paper briefly describes this "Precision Measurement" strategy and its data-driven feedback process and makes suggestions for further research and development efforts. The method provides a basis for better documentation, control, and outcomes of assistive technology and related interventions. PMID:10163930

  11. Mid frequency shallow water fine-grained sediment attenuation measurements.

    PubMed

    Holland, Charles W; Dosso, Stan E

    2013-07-01

    Attenuation is perhaps the most difficult sediment acoustic property to measure, but arguably one of the most important for predicting passive and active sonar performance. Measurement techniques can be separated into "direct" measurements (e.g., via sediment probes, sediment cores, and laboratory studies on "ideal" sediments) which are typically at high frequencies, O(10(4)-10(5)) Hz, and "indirect" measurements where attenuation is inferred from long-range propagation or reflection data, generally O(10(2)-10(3)) Hz. A frequency gap in measurements exists in the 600-4000 Hz band and also a general acknowledgement that much of the historical measurements on fine-grained sediments have been biased due to a non-negligible silt and sand component. A shallow water measurement technique using long range reverberation is critically explored. An approximate solution derived using energy flux theory shows that the reverberation is very sensitive to depth-integrated attenuation in a fine-grained sediment layer and separable from most other unknown geoacoustic parameters. Simulation using Bayesian methods confirms the theory. Reverberation measurements across a 10 m fine-grained sediment layer yield an attenuation of 0.009 dB/m/kHz with 95% confidence bounds of 0.006-0.013 dB/m/kHz. This is among the lowest values for sediment attenuation reported in shallow water.

  12. Implicit attitude measures: consistency, stability, and convergent validity.

    PubMed

    Cunningham, W A; Preacher, K J; Banaji, M R

    2001-03-01

    In recent years, several techniques have been developed to measure implicit social cognition. Despite their increased use, little attention has been devoted to their reliability and validity. This article undertakes a direct assessment of the interitem consistency, stability, and convergent validity of some implicit attitude measures. Attitudes toward blacks and whites were measured on four separate occasions, each 2 weeks apart, using three relatively implicit measures (response-window evaluative priming, the Implicit Association Test, and the response-window Implicit Association Test) and one explicit measure (Modern Racism Scale). After correcting for interitem inconsistency with latent variable analyses, we found that (a) stability indices improved and (b) implicit measures were substantially correlated with each other, forming a single latent factor. The psychometric properties of response-latency implicit measures have greater integrity than recently suggested.

  13. Stabilized chip-scale Kerr frequency comb via a high-Q reference photonic microresonator.

    PubMed

    Lim, Jinkang; Huang, Shu-Wei; Vinod, Abhinav K; Mortazavian, Parastou; Yu, Mingbin; Kwong, Dim-Lee; Savchenkov, Anatoliy A; Matsko, Andrey B; Maleki, Lute; Wong, Chee Wei

    2016-08-15

    We stabilize a chip-scale Si3N4 phase-locked Kerr frequency comb via locking the pump laser to an independent stable high-Q reference microresonator and locking the comb spacing to an external microwave oscillator. In this comb, the pump laser shift induces negligible impact on the comb spacing change. This scheme is a step toward miniaturization of the stabilized Kerr comb system as the microresonator reference can potentially be integrated on-chip. Fractional instability of the optical harmonics of the stabilized comb is limited by the microwave oscillator used for a comb spacing lock below 1 s averaging time and coincides with the pump laser drift in the long term. PMID:27519068

  14. Stabilized chip-scale Kerr frequency comb via a high-Q reference photonic microresonator

    NASA Astrophysics Data System (ADS)

    Lim, Jinkang; Huang, Shu-Wei; Vinod, Abhinav K.; Mortazavian, Parastou; Yu, Mingbin; Kwong, Dim-Lee; Savchenkov, Anatoliy A.; Matsko, Andrey B.; Maleki, Lute; Wong, Chee Wei

    2016-08-01

    We stabilize a chip-scale Si3N4 phase-locked Kerr frequency comb via locking the pump laser to an independent stable high-Q reference microresonator and locking the comb spacing to an external microwave oscillator. In this comb, the pump laser shift induces negligible impact on the comb spacing change. This scheme is a step towards miniaturization of the stabilized Kerr comb system as the microresonator reference can potentially be integrated on-chip. Fractional instability of the optical harmonics of the stabilized comb is limited by the microwave oscillator used for comb spacing lock below 1 s averaging time and coincides with the pump laser drift in the long term.

  15. High-frequency electric field measurement using a toroidal antenna

    DOEpatents

    Lee, Ki Ha

    2002-01-01

    A simple and compact method and apparatus for detecting high frequency electric fields, particularly in the frequency range of 1 MHz to 100 MHz, uses a compact toroidal antenna. For typical geophysical applications the sensor will be used to detect electric fields for a wide range of spectrum starting from about 1 MHz, in particular in the frequency range between 1 to 100 MHz, to detect small objects in the upper few meters of the ground. Time-varying magnetic fields associated with time-varying electric fields induce an emf (voltage) in a toroidal coil. The electric field at the center of (and perpendicular to the plane of) the toroid is shown to be linearly related to this induced voltage. By measuring the voltage across a toroidal coil one can easily and accurately determine the electric field.

  16. Time-frequency representation measurement based on temporal Fourier transformation

    NASA Astrophysics Data System (ADS)

    Suen, Yifan; Xiao, Shaoqiu; Hao, Sumin; Zhao, Xiaoxiang; Xiong, Yigao; Liu, Shenye

    2016-10-01

    We propose a new scheme to physically realize the short-time Fourier transform (STFT) of chirped optical pulse using time-lens array that enables us to get time-frequency representation without using FFT algorithm. The time-lens based upon the four-wave mixing is used to perform the process of temporal Fourier transformation. Pump pulse is used for both providing the quadratic phase and being the window function of STFT. The idea of STFT is physically realized in our scheme. Simulations have been done to investigate performance of the time-frequency representation scheme (TFRS) in comparison with STFT using FFT algorithm. Optimal measurement of resolution in time and frequency has been discussed.

  17. Frequency spectrum analysis for spectrum stabilization in airborne gamma-ray spectrometer.

    PubMed

    Zeng, Guoqiang; Tan, Chengjun; Ge, Liangquan; Zhang, Qingxian; Gu, Yi

    2014-02-01

    Abnormal multi-crystal spectral drifts often can be observed when power on the airborne gamma-ray spectrometer. Currently, these spectral drifts of each crystal are generally eliminated through manual adjustment, which is time-consuming and labor-ineffective. To realize this quick automatic spectrum stabilization of multi-crystal, a frequency spectrum analysis method for natural gamma-ray background spectrum is put forward in this paper to replace traditional spectrum stabilization method used characteristic peak. Based on the polynomial fitting of high harmonics in frequency spectrum and gamma-ray spectral drift, it calculates overall spectral drift of natural gamma-ray spectrum and adjusts the gain of spectrometer by this spectral drift value, thus completing quick spectrum stabilization in the power on stage of spectrometer. This method requires no manual intervention and can obtain the overall spectral drift value automatically under no time-domain pre-processing to the natural gamma-ray spectra. The spectral drift value calculated by this method has an absolute error less than five channels (1024 resolution) and a relative error smaller than 0.80%, which can satisfy the quick automatic spectrum stabilization requirement when power on the airborne gamma-ray spectrometer instead of manual operation.

  18. Suppressing interfering scattered signals in swept-frequency radar measurements by using frequency domain Wiener filtering

    NASA Technical Reports Server (NTRS)

    Weissman, David E.; Staton, Leo D.

    1991-01-01

    A novel approach to the reduction of scattered, interfering signals that corrupt measurements of the signal backscattered from radar targets of interest is being developed. It is being explored with sphere measurements in an indoor microwave radar range. This method is based on the concept of Wiener filtering (which minimizes the difference between the signal plus noise and the desired signal in the time domain). In contrast to the traditional Wiener filter, in which the time domain error between two sequences are minimized, the approach reported uses the frequency domain phasor amplitudes of a swept frequency signal. It minimizes the difference (least-mean-square-magnitude) between the signal-plus-noise and the signal complex phasors, across the entire spectrum.

  19. Development of a frequency-domain electromagnetic scattering measurement system

    NASA Astrophysics Data System (ADS)

    Oh, Kenneth K.

    1993-12-01

    This thesis describes the development of a system for measuring frequency-domain scattered fields in the Transient Electromagnetic Scattering Range at the Naval Postgraduate School. The new system employs a stepped-frequency CW waveform and utilizes an HP-8510B network analyzer as an RF front-end and a coherent receiver. A pair of AEL H1498 antennas was installed to cover a frequency range of 2 GHz to 18 GHz. An HP-82300C BASIC Language Processor was installed on a COMPAQ Deskpro-386 PC, and an HP-BASIC program was developed for remote control of the HP-8510B with data acquisition over the HPIB bus. A post-processing algorithm was created using MatLab for background subtraction, calibration, and deconvolution. A set of RCS measurements was made using various size spheres, and the postprocessing outputs were compared to computed values. Good agreement between these measurements and computed data indicates excellent accuracy of the measurement system and valid operations of the postprocessing algorithm.

  20. Influence of Speed Governors of Hydropower Stations on Frequency Stabilization of Fixed-Speed Wind Farm

    NASA Astrophysics Data System (ADS)

    AL Jowder, Fawzi A. Rahman

    2013-05-01

    This paper uses a small power system, consisting of two hydropower stations and a fixed-speed wind farm as sources of power, to study the influence of type of speed governor of hydropower stations on the frequency stabilization of the fixed-speed wind farm. As an example, two types of speed governors are selected which are (1) mechanical-hydraulic speed governor and (2) electrical-hydraulic speed governor. Rest of the speed governors can be also examined following the same methodology presented in the research. Two transfer functions, which correspond to the two speed governors, are developed for each hydropower station. The overall transfer function of the test power system is developed, and different study cases are presented. The frequency response analysis of the different transfer functions is used to compare the two speed governors based on their ability to stabilize the frequency deviation of the fixed-speed wind resulting from electrical or mechanical disturbances in the power systems. Time-domain simulations under a mechanical disturbance, represented by a wind gust, and an electrical disturbance, represented by three-phase to ground fault, are performed to validate the results of the frequency response analysis.

  1. Relative efficiency of ambiguous vs. directly measured haplotype frequencies.

    PubMed

    Schaid, Daniel J

    2002-11-01

    Haplotypes are useful for both fine-mapping of susceptibility loci and evaluation of sequence variation at multiple sites along a chromosome. However, they are difficult to directly measure over long stretches of DNA in diploid organisms. Consequently, multiple genetic markers are typically measured, without linkage phase information, giving rise to a subject's diplotype. From diplotype data, haplotypes are often inferred by pedigree information, or treated as partially missing data when haplotype frequencies are estimated among unrelated subjects. This latter ambiguity can increase the variance of the estimated haplotype frequencies. Douglas et al. ([2001] Nat. Genet. 28:361-364) recently quantified the relative efficiency of estimating haplotype frequencies from the diplotypes of unrelated subjects, relative to directly measured haplotypes via somatic cell hybrids (conversion technology), and demonstrated that unknown linkage phase can lead to a large loss of efficiency. However, their results were based on linkage equilibrium among marker loci, which may not be realistic for closely linked markers. We extend their relative efficiency calculations by several aspects: 1) allowance for linkage disequilbrium (LD) among marker loci; 2) evaluation of different patterns of LD; and 3) evaluation of nuclear families with and without parents. We show that although the loss in efficiency of haplotype frequencies among unrelated subjects decreases as LD increases to its maximum value, the general conclusions of Douglas et al. ([2001] Nat. Genet. 28:361-364) hold true for a variety of LD patterns and magnitudes. However, our results also demonstrate that trios of parents+one child are highly efficient for haplotype frequency estimation, that additional children offer little information, and that siblings without parents can be grossly inefficient. Genet. Epidemiol. 23:426-443, 2002. PMID:12432508

  2. Direct measurements of the frequency-dependent dielectrophoresis force.

    PubMed

    Wei, Ming-Tzo; Junio, Joseph; Ou-Yang, H Daniel

    2009-01-01

    Dielectrophoresis (DEP), the phenomenon of directed motion of electrically polarizable particles in a nonuniform electric field, is promising for applications in biochemical separation and filtration. For colloidal particles in suspension, the relaxation of the ionic species in the shear layer gives rise to a frequency-dependent, bidirectional DEP force in the radio frequency range. However, quantification methods of the DEP force on individual particles with the pico-Newton resolution required for the development of theories and design of device applications are lacking. We report the use of optical tweezers as a force sensor and a lock-in phase-sensitive technique for analysis of the particle motion in an amplitude modulated DEP force. The coherent detection and sensing scheme yielded not only unprecedented sensitivity for DEP force measurements, but also provided a selectivity that clearly distinguishes the pure DEP force from all the other forces in the system, including electrophoresis, electro-osmosis, heat-induced convection, and Brownian forces, all of which can hamper accurate measurements through other existing methods. Using optical tweezers-based force transducers already developed in our laboratory, we have results that quantify the frequency-dependent DEP force and the crossover frequency of individual particles with this new experimental method. PMID:19693384

  3. Ionospheric Coherence Bandwidth Measurements in the Lower VHF Frequency Range

    NASA Astrophysics Data System (ADS)

    Suszcynsky, D. M.; Light, M. E.; Pigue, M. J.

    2015-12-01

    The United States Department of Energy's Radio Frequency Propagation (RFProp) experiment consists of a satellite-based radio receiver suite to study various aspects of trans-ionospheric signal propagation and detection in four frequency bands, 2 - 55 MHz, 125 - 175 MHz, 365 - 415 MHz and 820 - 1100 MHz. In this paper, we present simultaneous ionospheric coherence bandwidth and S4 scintillation index measurements in the 32 - 44 MHz frequency range collected during the ESCINT equatorial scintillation experiment. 40-MHz continuous wave (CW) and 32 - 44 MHz swept frequency signals were transmitted simultaneously to the RFProp receiver suite from the Reagan Test Site at Kwajalein Atoll in the Marshall Islands (8.7° N, 167.7° E) in three separate campaigns during the 2014 and 2015 equinoxes. Results show coherence bandwidths as small as ~ 1 kHz for strong scintillation (S4 > 0.7) and indicate a high degree of ionospheric variability and irregularity on 10-m spatial scales. Spread-Doppler clutter effects arising from preferential ray paths to the satellite due to refraction off of isolated density irregularities are also observed and are dominant at low elevation angles. The results are compared to previous measurements and available scaling laws.

  4. Frequency effects on the stability of a journal bearing for periodic loading

    NASA Technical Reports Server (NTRS)

    Vijayaraghavan, D.; Brewe, D. E.

    1991-01-01

    The stability of a journal bearing is numerically predicted when a unidirectional periodic external load is applied. The analysis is performed using a cavitation algorithm, which mimics the Jakobsson-Floberg and Olsson (JFO) theory by accounting for the mass balance through the complete bearing. Hence, the history of the film is taken into consideration. The loading pattern is taken to be sinusoidal and the frequency of the load cycle is varied. The results are compared with the predictions using Reynolds boundary conditions for both film rupture and reformation. With such comparisons, the need for accurately predicting the cavitation regions for complex loading patterns is clearly demonstrated. For a particular frequency of loading, the effects of mass, amplitude of load variation and frequency of journal speed are also investigated. The journal trajectories, transient variations in fluid film forces, net surface velocity and minimum film thickness, and pressure profiles are also presented.

  5. Stability of Low-Frequency Residual Hearing in Patients Who Are Candidates for Combined Acoustic Plus Electric Hearing

    ERIC Educational Resources Information Center

    Yao, Wai Na; Turner, Christopher W.; Gantz, Bruce J.

    2006-01-01

    The purpose of this study was to investigate the stability over time of low-frequency auditory thresholds to better determine if the new technique of using a short-electrode cochlear implant that preserves residual low-frequency acoustic hearing can be a long-term solution for those with severe-to-profound hearing loss at high frequencies. The…

  6. Longitudinal measurement invariance, stability and change of anger and cynicism.

    PubMed

    Hakulinen, Christian; Jokela, Markus; Keltikangas-Järvinen, Liisa; Merjonen, Päivi; Raitakari, Olli T; Hintsanen, Mirka

    2014-06-01

    Anger and hostility are key concepts in behavioral medicine, but little is known about their stability over life course. A sample of 3,074 individuals from six age groups (aged 15-30 at the baseline) were selected from a population-based study to examine longitudinal measurement invariance, stability and change in anger and cynicism from early to middle adulthood over 15 years. Cynicism, a facet of hostility, and anger were measured 4 times in 1992, 1997, 2001 and 2007. Final longitudinal measurement invariance models achieved partial strict measurement invariance, indicating good measurement consistency over time. Rank-order stability of anger and cynicism was found to be moderate. Mean levels of anger and cynicism decreased over time, but in anger the decline was faster among women. The variance of anger and cynicism also increased over time, but in cynicism the rate of change was higher among men. Altogether, anger and cynicism show measurement invariance and moderate stability from early adulthood to middle adulthood.

  7. Frequency response measurements of integrated-optic electrodes

    SciTech Connect

    Hugenberg, K.F; Sargis, P.D.; McConaghy, C.F.

    1994-07-01

    The frequency response of electro-optic waveguides can be determined using a variety of testing methods. In this paper, we compare and contrast three measurement techniques used to test our LiNbO{sub 3} devices for improving packages and electrode designs. Each method is described and accompanied by typical results and the experimental setup. Finally, we summarize the advantages and disadvantages of each method.

  8. Microstrip antenna modeling and measurement at high frequencies

    SciTech Connect

    Bevensee, R.M.

    1986-04-30

    This report addresses the task C(i) of the Proposal for Microstrip Antenna Modeling and Measurement at High Frequencies by the writer, July 1985. The task is: Assess the advantages and disadvantages of the three computational approaches outlined in the Proposal, including any difficulties to be resolved and an estimate of the time required to implement each approach. The three approaches are (1) Finite Difference, (2) Sommerfeld-GTD-MOM, and (3) Surface Intergral Equations - MOM. These are discussed in turn.

  9. Technique for Performing Dielectric Property Measurements at Microwave Frequencies

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B.; Jackson, Henry W.

    2010-01-01

    A paper discusses the need to perform accurate dielectric property measurements on larger sized samples, particularly liquids at microwave frequencies. These types of measurements cannot be obtained using conventional cavity perturbation methods, particularly for liquids or powdered or granulated solids that require a surrounding container. To solve this problem, a model has been developed for the resonant frequency and quality factor of a cylindrical microwave cavity containing concentric cylindrical samples. This model can then be inverted to obtain the real and imaginary dielectric constants of the material of interest. This approach is based on using exact solutions to Maxwell s equations for the resonant properties of a cylindrical microwave cavity and also using the effective electrical conductivity of the cavity walls that is estimated from the measured empty cavity quality factor. This new approach calculates the complex resonant frequency and associated electromagnetic fields for a cylindrical microwave cavity with lossy walls that is loaded with concentric, axially aligned, lossy dielectric cylindrical samples. In this approach, the calculated complex resonant frequency, consisting of real and imaginary parts, is related to the experimentally measured quantities. Because this approach uses Maxwell's equations to determine the perturbed electromagnetic fields in the cavity with the material(s) inserted, one can calculate the expected wall losses using the fields for the loaded cavity rather than just depending on the value of the fields obtained from the empty cavity quality factor. These additional calculations provide a more accurate determination of the complex dielectric constant of the material being studied. The improved approach will be particularly important when working with larger samples or samples with larger dielectric constants that will further perturb the cavity electromagnetic fields. Also, this approach enables the ability to have a

  10. Stability of continuous-time quantum filters with measurement imperfections

    NASA Astrophysics Data System (ADS)

    Amini, H.; Pellegrini, C.; Rouchon, P.

    2014-07-01

    The fidelity between the state of a continuously observed quantum system and the state of its associated quantum filter, is shown to be always a submartingale. The observed system is assumed to be governed by a continuous-time Stochastic Master Equation (SME), driven simultaneously by Wiener and Poisson processes and that takes into account incompleteness and errors in measurements. This stability result is the continuous-time counterpart of a similar stability result already established for discrete-time quantum systems and where the measurement imperfections are modelled by a left stochastic matrix.

  11. Long-path Atmospheric Measurements Using Dual Frequency Comb Spectroscopy

    NASA Astrophysics Data System (ADS)

    Cossel, K.; Truong, G. W.; Waxman, E.; Baumann, E.; Giorgetta, F.; Rieker, G. B.; Sinclair, L.; Swann, W.; Coddington, I.; Newbury, N.

    2015-12-01

    Dual frequency comb (DFC) spectroscopy is a new technique that combines broad spectral bandwidth, high spectral resolution, rapid data acquisition, and high sensitivity. In addition, unlike standard Fourier-transform spectroscopy, it has an almost ideal instrument lineshape function and does not require recalibration. These features make DFC spectroscopy well suited for accurate measurements of multiple species simultaneously. We have recently demonstrated DFC-based open-path measurements of several greenhouse gases in the 1.6-1.67 μm (6250-6000 cm-1) spectral region with 2 km of path length [Rieker et al, 2014]. This initial demonstration used laboratory-based lasers and achieved a sensitivity of 2.3 ppbv for CH4, 1 ppmv for CO2, and <1 ppmv for H2O and HDO with 5 minute measurement times. We are currently developing a portable system that will cover a wider spectral region (about 1.3-2.1 μm or 7700-4750 cm-1) with improved sensitivity. In this talk, we will provide an introduction to dual frequency comb spectroscopy and then discuss ongoing improvements to the open-path system. G. B. Rieker, F. R. Giorgetta, W. C. Swann, J. Kofler, A. M. Zolot, L. C. Sinclair, E. Baumann, C. Cromer, G. Petron, C. Sweeney, P. P. Tans, I. Coddington, and N. R. Newbury (2014), Frequency-comb-based remote sensing of greenhouse gases over kilometer air paths, Optica, 1(5), 290-298.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Measuring absolute frequencies beyond the GPS limit via long-haul optical frequency dissemination.

    PubMed

    Clivati, Cecilia; Cappellini, Giacomo; Livi, Lorenzo F; Poggiali, Francesco; de Cumis, Mario Siciliani; Mancini, Marco; Pagano, Guido; Frittelli, Matteo; Mura, Alberto; Costanzo, Giovanni A; Levi, Filippo; Calonico, Davide; Fallani, Leonardo; Catani, Jacopo; Inguscio, Massimo

    2016-05-30

    Global Positioning System (GPS) dissemination of frequency standards is ubiquitous at present, providing the most widespread time and frequency reference for the majority of industrial and research applications worldwide. On the other hand, the ultimate limits of the GPS presently curb further advances in high-precision, scientific and industrial applications relying on this dissemination scheme. Here, we demonstrate that these limits can be reliably overcome even in laboratories without a local atomic clock by replacing the GPS with a 642-km-long optical fiber link to a remote primary caesium frequency standard. Through this configuration we stably address the 1S0-3P0 clock transition in an ultracold gas of 173Yb, with a precision that exceeds the possibilities of a GPS-based measurement, dismissing the need for a local clock infrastructure to perform beyond-GPS high-precision tasks. We also report an improvement of two orders of magnitude in the accuracy on the transition frequency reported in literature. PMID:27410109

  14. Measuring absolute frequencies beyond the GPS limit via long-haul optical frequency dissemination.

    PubMed

    Clivati, Cecilia; Cappellini, Giacomo; Livi, Lorenzo F; Poggiali, Francesco; de Cumis, Mario Siciliani; Mancini, Marco; Pagano, Guido; Frittelli, Matteo; Mura, Alberto; Costanzo, Giovanni A; Levi, Filippo; Calonico, Davide; Fallani, Leonardo; Catani, Jacopo; Inguscio, Massimo

    2016-05-30

    Global Positioning System (GPS) dissemination of frequency standards is ubiquitous at present, providing the most widespread time and frequency reference for the majority of industrial and research applications worldwide. On the other hand, the ultimate limits of the GPS presently curb further advances in high-precision, scientific and industrial applications relying on this dissemination scheme. Here, we demonstrate that these limits can be reliably overcome even in laboratories without a local atomic clock by replacing the GPS with a 642-km-long optical fiber link to a remote primary caesium frequency standard. Through this configuration we stably address the 1S0-3P0 clock transition in an ultracold gas of 173Yb, with a precision that exceeds the possibilities of a GPS-based measurement, dismissing the need for a local clock infrastructure to perform beyond-GPS high-precision tasks. We also report an improvement of two orders of magnitude in the accuracy on the transition frequency reported in literature.

  15. High-resolution frequency measurement method with a wide-frequency range based on a quantized phase step law.

    PubMed

    Du, Baoqiang; Dong, Shaofeng; Wang, Yanfeng; Guo, Shuting; Cao, Lingzhi; Zhou, Wei; Zuo, Yandi; Liu, Dan

    2013-11-01

    A wide-frequency and high-resolution frequency measurement method based on the quantized phase step law is presented in this paper. Utilizing a variation law of the phase differences, the direct different frequency phase processing, and the phase group synchronization phenomenon, combining an A/D converter and the adaptive phase shifting principle, a counter gate is established in the phase coincidences at one-group intervals, which eliminates the ±1 counter error in the traditional frequency measurement method. More importantly, the direct phase comparison, the measurement, and the control between any periodic signals have been realized without frequency normalization in this method. Experimental results show that sub-picosecond resolution can be easily obtained in the frequency measurement, the frequency standard comparison, and the phase-locked control based on the phase quantization processing technique. The method may be widely used in navigation positioning, space techniques, communication, radar, astronomy, atomic frequency standards, and other high-tech fields.

  16. A linewidth-narrowed and frequency-stabilized dye laser for application in laser cooling of molecules.

    PubMed

    Dai, D P; Xia, Y; Yin, Y N; Yang, X X; Fang, Y F; Li, X J; Yin, J P

    2014-11-17

    We demonstrate a robust and versatile solution for locking the continuous-wave dye laser for applications in laser cooling of molecules which need linewidth-narrowed and frequency-stabilized lasers. The dye laser is first stabilized with respect to a reference cavity by Pound-Drever-Hall (PDH) technique which results in a single frequency with the linewidth 200 kHz and short-term stabilization, by stabilizing the length of the reference cavity to a stabilized helium-neon laser we simultaneously transfer the ± 2 MHz absolute frequency stability of the helium-neon laser to the dye laser with long-term stabilization. This allows the dye laser to be frequency chirped with the maximum 60 GHz scan range while its frequency remains locked. It also offers the advantages of locking at arbitrary dye laser frequencies, having a larger locking capture range and frequency scanning range to be implemented via software. This laser has been developed for the purpose of laser cooling a molecular magnesium fluoride beam.

  17. A linewidth-narrowed and frequency-stabilized dye laser for application in laser cooling of molecules.

    PubMed

    Dai, D P; Xia, Y; Yin, Y N; Yang, X X; Fang, Y F; Li, X J; Yin, J P

    2014-11-17

    We demonstrate a robust and versatile solution for locking the continuous-wave dye laser for applications in laser cooling of molecules which need linewidth-narrowed and frequency-stabilized lasers. The dye laser is first stabilized with respect to a reference cavity by Pound-Drever-Hall (PDH) technique which results in a single frequency with the linewidth 200 kHz and short-term stabilization, by stabilizing the length of the reference cavity to a stabilized helium-neon laser we simultaneously transfer the ± 2 MHz absolute frequency stability of the helium-neon laser to the dye laser with long-term stabilization. This allows the dye laser to be frequency chirped with the maximum 60 GHz scan range while its frequency remains locked. It also offers the advantages of locking at arbitrary dye laser frequencies, having a larger locking capture range and frequency scanning range to be implemented via software. This laser has been developed for the purpose of laser cooling a molecular magnesium fluoride beam. PMID:25402105

  18. Automated Performance Characterization of DSN System Frequency Stability Using Spacecraft Tracking Data

    NASA Technical Reports Server (NTRS)

    Pham, Timothy T.; Machuzak, Richard J.; Bedrossian, Alina; Kelly, Richard M.; Liao, Jason C.

    2012-01-01

    This software provides an automated capability to measure and qualify the frequency stability performance of the Deep Space Network (DSN) ground system, using daily spacecraft tracking data. The results help to verify if the DSN performance is meeting its specification, therefore ensuring commitments to flight missions; in particular, the radio science investigations. The rich set of data also helps the DSN Operations and Maintenance team to identify the trends and patterns, allowing them to identify the antennas of lower performance and implement corrective action in a timely manner. Unlike the traditional approach where the performance can only be obtained from special calibration sessions that are both time-consuming and require manual setup, the new method taps into the daily spacecraft tracking data. This new approach significantly increases the amount of data available for analysis, roughly by two orders of magnitude, making it possible to conduct trend analysis with good confidence. The software is built with automation in mind for end-to-end processing. From the inputs gathering to computation analysis and later data visualization of the results, all steps are done automatically, making the data production at near zero cost. This allows the limited engineering resource to focus on high-level assessment and to follow up with the exceptions/deviations. To make it possible to process the continual stream of daily incoming data without much effort, and to understand the results quickly, the processing needs to be automated and the data summarized at a high level. Special attention needs to be given to data gathering, input validation, handling anomalous conditions, computation, and presenting the results in a visual form that makes it easy to spot items of exception/ deviation so that further analysis can be directed and corrective actions followed.

  19. Automated Performance Characterization of DSN System Frequency Stability Using Spacecraft Tracking Data

    NASA Technical Reports Server (NTRS)

    Pham, Timothy T.; Machuzak, Richard J.; Bedrossian, Alina; Kelly, Richard M.; Liao, Jason C.

    2012-01-01

    This software provides an automated capability to measure and qualify the frequency stability performance of the Deep Space Network (DSN) ground system, using daily spacecraft tracking data. The results help to verify if the DSN performance is meeting its specification, therefore ensuring commitments to flight missions; in particular, the radio science investigations. The rich set of data also helps the DSN Operations and Maintenance team to identify the trends and patterns, allowing them to identify the antennas of lower performance and implement corrective action in a timely manner. Unlike the traditional approach where the performance can only be obtained from special calibration sessions that are both time-consuming and require manual setup, the new method taps into the daily spacecraft tracking data. This new approach significantly increases the amount of data available for analysis, roughly by two orders of magnitude, making it possible to conduct trend analysis with good confidence. The software is built with automation in mind for end-to-end processing. From the inputs gathering to computation analysis and later data visualization of the results, all steps are done automatically, making the data production at near zero cost. This allows the limited engineering resource to focus on high-level assessment and to follow up with the exceptions/deviations. To make it possible to process the continual stream of daily incoming data without much effort, and to understand the results quickly, the processing needs to be automated and the data summarized at a high level. Special attention needs to be given to data gathering, input validation, handling anomalous conditions, computation, and presenting the results in a visual form that makes it easy to spot items of exception/deviation so that further analysis can be directed and corrective actions followed.

  20. Development of Modulator Pulse Stability Measurement Device and Test Results at SLAC

    SciTech Connect

    Huang, C.; Burkhart, C.; Kemp, M.; Morris, B.; Beukers, T.; Ciprian, R.; Nguyen, M.; /SLAC

    2011-08-19

    In this paper, the development of a pulse stability measurement device is presented. The measurement accuracy is better than 250uV, about 4.2ppm of a typical 60V input pulse. Pulse signals up to +/- 80V peak can be measured. The device works together with an oscilloscope. The primary function of the measurement device is to provide a precision offset, such that variations in the flattop of the modulator voltage pulse can be accurately resolved. The oscilloscope records the difference between the pulse flattop and the reference for a series of waveforms. The scope math functions are utilized to calculate the rms variations over the series. The frequency response of the device is characterized by the measured cutoff frequency of about 6.5MHz. In addition to detailing the design and calibration of the precision pulse stability device, measurements of SLAC line-type linac modulators and recently developed induction modulators will be presented. Factors affecting pulse stability will be discussed.

  1. A New Measure of Reading Habit: Going Beyond Behavioral Frequency

    PubMed Central

    Schmidt, Fabian T. C.; Retelsdorf, Jan

    2016-01-01

    Reading habit is considered an important construct in reading research as it serves as a significant predictor of reading achievement. However, there is still no consensus on how to best measure reading habit. In recent research, it has mostly been measured as behavioral frequency; this approach neglects the fact that repeated behavior does not cover the broad content of habitual behavior—such as automaticity and the expression of one’s identity. In this study, we aimed to adapt a 10-item scale on the basis of the Self-Report Habit Index by Verplanken and Orbell (2003) that is comprehensive but still economical for measuring reading habit. It was tested by drawing on a sample of N = 1,418 upper secondary school students. The scale showed good psychometric properties and the internal and external validity was supported. Moreover, the scale predicted reading achievement and decoding speed over and above reading frequency. The implications of an elaborated but still economical way of measuring reading habit are discussed giving new impetus on research on reading habit, challenging conventional approaches of traditional measures.

  2. A New Measure of Reading Habit: Going Beyond Behavioral Frequency.

    PubMed

    Schmidt, Fabian T C; Retelsdorf, Jan

    2016-01-01

    Reading habit is considered an important construct in reading research as it serves as a significant predictor of reading achievement. However, there is still no consensus on how to best measure reading habit. In recent research, it has mostly been measured as behavioral frequency; this approach neglects the fact that repeated behavior does not cover the broad content of habitual behavior-such as automaticity and the expression of one's identity. In this study, we aimed to adapt a 10-item scale on the basis of the Self-Report Habit Index by Verplanken and Orbell (2003) that is comprehensive but still economical for measuring reading habit. It was tested by drawing on a sample of N = 1,418 upper secondary school students. The scale showed good psychometric properties and the internal and external validity was supported. Moreover, the scale predicted reading achievement and decoding speed over and above reading frequency. The implications of an elaborated but still economical way of measuring reading habit are discussed giving new impetus on research on reading habit, challenging conventional approaches of traditional measures. PMID:27660619

  3. A New Measure of Reading Habit: Going Beyond Behavioral Frequency

    PubMed Central

    Schmidt, Fabian T. C.; Retelsdorf, Jan

    2016-01-01

    Reading habit is considered an important construct in reading research as it serves as a significant predictor of reading achievement. However, there is still no consensus on how to best measure reading habit. In recent research, it has mostly been measured as behavioral frequency; this approach neglects the fact that repeated behavior does not cover the broad content of habitual behavior—such as automaticity and the expression of one’s identity. In this study, we aimed to adapt a 10-item scale on the basis of the Self-Report Habit Index by Verplanken and Orbell (2003) that is comprehensive but still economical for measuring reading habit. It was tested by drawing on a sample of N = 1,418 upper secondary school students. The scale showed good psychometric properties and the internal and external validity was supported. Moreover, the scale predicted reading achievement and decoding speed over and above reading frequency. The implications of an elaborated but still economical way of measuring reading habit are discussed giving new impetus on research on reading habit, challenging conventional approaches of traditional measures. PMID:27660619

  4. Note: Precise phase and frequency comparator based on direct phase-time measurements

    NASA Astrophysics Data System (ADS)

    Prochazka, Ivan; Panek, Petr; Kodet, Jan

    2014-12-01

    We are reporting on the design, performance, and application results of a phase and frequency comparator based on the direct phase-time measurement using a high performance event timer. The advantages of this approach are the simple implementation, a broad frequency range, and the clear interpretation of the measured results. Primarily we analyzed the background instability of the instrument in a common-clock test when a 200 MHz clock signal was connected to both inputs and the noise bandwidth was kept at 5 Hz by a preprocessing of the measured data. The results show that the Allan deviation of the background instability follows 4 × 10-14/τ for a wide range of averaging intervals from 0.1 s up to 104 s. These results are better than background instability of commercially available state-of-the-art instruments based on the phase difference multiplication. Finally the instrument was used for comparison of two H-masers. This experiment proofed that one of possible applications is a comparison of low-noise highly stable frequency sources and measurement of their frequency stability in the time-domain. The noise background of the instrument was negligible for averaging intervals longer than 100 ms.

  5. On the measurement of frequency and of its sample variance with high-resolution counters

    SciTech Connect

    Rubiola, Enrico

    2005-05-15

    A frequency counter measures the input frequency {nu} averaged over a suitable time {tau}, versus the reference clock. High resolution is achieved by interpolating the clock signal. Further increased resolution is obtained by averaging multiple frequency measurements highly overlapped. In the presence of additive white noise or white phase noise, the square uncertainty improves from {sigma}{sub {nu}}{sup 2}{proportional_to}1/{tau}{sup 2} to {sigma}{sub {nu}}{sup 2}{proportional_to}1/{tau}{sup 3}. Surprisingly, when a file of contiguous data is fed into the formula of the two-sample (Allan) variance {sigma}{sub y}{sup 2}({tau})=E{l_brace}(1/2)(y{sub k+1}-y{sub k}){sup 2}{r_brace} of the fractional frequency fluctuation y, the result is the modified Allan variance mod {sigma}{sub y}{sup 2}({tau}). But if a sufficient number of contiguous measures are averaged in order to get a longer {tau} and the data are fed into the same formula, the results is the (nonmodified) Allan variance. Of course interpretation mistakes are around the corner if the counter internal process is not well understood. The typical domain of interest is the the short-term stability measurement of oscillators.

  6. Stability of the Medial Olivocochlear Reflex as Measured by Distortion Product Otoacoustic Emissions

    PubMed Central

    Abdala, Carolina

    2015-01-01

    Purpose The purpose of this study was to assess the repeatability of a fine-resolution, distortion product otoacoustic emission (DPOAE)–based assay of the medial olivocochlear (MOC) reflex in normal-hearing adults. Method Data were collected during 36 test sessions from 4 normal-hearing adults to assess short-term stability and 5 normal-hearing adults to assess long-term stability. DPOAE level and phase measurements were recorded with and without contralateral acoustic stimulation. MOC reflex indices were computed by (a) noting contralateral acoustic stimulation-induced changes in DPOAE level (both absolute and normalized) at fine-structure peaks, (b) recording the effect as a vector difference, and (c) separating DPOAE components and considering a component-specific metric. Results Analyses indicated good repeatability of all indices of the MOC reflex in most frequency ranges. Short- and long-term repeatability were generally comparable. Indices normalized to a subject's own baseline fared best, showing strong short- and long-term stability across all frequency intervals. Conclusions These results suggest that fine-resolution DPOAE-based measures of the MOC reflex measured at strategic frequencies are stable, and natural variance from day-to-day or week-to-week durations is small enough to detect between-group differences and possibly to monitor intervention-related success. However, this is an empirical question that must be directly tested to confirm its utility. PMID:25320951

  7. Calculated and Measured Air and Soil Freeze-Thaw Frequencies.

    NASA Astrophysics Data System (ADS)

    Baker, Donald G.; Ruschy, David L.

    1995-10-01

    Freeze-thaw frequencies calculated by eight different counting methods were compared using daily maximum and minimum temperatures from eight north-central United States National Weather Service (NWS) stations. These frequencies were also compared to those obtained using hourly air temperature data from six of the same NWS stations. In addition, the calculated frequencies were compared to measured freeze-thaw frequencies at several depths in a bare soil and a sod-covered soil at the University of Minnesota St. Paul campus climatological observatory.The necessary acceptance of the idealized daily heating cycle when using daily maximum and minimum air temperature data resulted in a higher occurrence of calculated freeze-thaw events than those obtained with hourly data; one method gave 23% more freeze-thaw events with the daily maximum and minimum temperatures.With the freeze-thaw phenomenon centered upon those months in which the mean temperature hovers near O°C, a bimodal frequency occurs at the northern stations (October and April, as at International Falls, Minnesota, and November and March at Fargo, North Dakota), while in warmer climates the bimodal characteristic is replaced by a single-peak frequency in January as at Sedalia and West Plains, Missouri.In the comparison between the calculated freeze-thaw frequencies based on daily maximum and minimum values and the hourly temperature measurements at several heights between the surface and the temperature shelter at the climatological observatory, it was found that the annual total frequencies increased as the height above the surface decreased. For the shallowest height above the surface there was an approximate 13% increase over those measured in the shelter with hourly temperature data.The annual total frequencies of the calculated freeze-thaw events obtained with the daily maximum and minimum temperature measurements in the shelter approximated those actually occurring at the 1-cm depth in a bare soil at the

  8. STABILITY MEASUREMENTS ON CORED CABLES IN NORMAL AND SUPERFLUID HELIUM

    SciTech Connect

    GHOSH,A.K.; SAMPSON,W.B.; KIM,S.W.; LEROY,D.; OBERLI,L.R.; WILSON,M.N.

    1998-05-10

    The relative stability of LHC type cables has been measured by the direct heating of one of the individual strands with a short duration current pulse. The minimum energy required to initiate a quench has been determined for a number of cables which have a central core to increase the effective inter-strand cross-over resistance. Experiments were performed in both normal helium at 4.4 K and superfluid at 1.9 K. Conductors in general are less stable at the lower temperature when measured at the same fraction of critical current. Results show that the cored-cables, even when partially filled with solder or with a porous-metal filler exhibit a relatively low stability at currents close to the critical current. It is speculated that the high inter-strand electrical and thermal resistance inherent in these cables may effect the stability at high currents.

  9. Stability measurements on cored cables in normal and superfluid helium

    SciTech Connect

    Ghosh, A.K.; Sampson, W.B.; Kim, S.W.; Leroy, D.; Oberli, L.R.; Wilson, M.N.

    1998-07-01

    The relative stability of LHC type cables has been measured by the direct heating of one of the individual strands with a short duration current pulse. The minimum energy required to initiate a quench has been determined for a number of cables which have a central core to increase the effective inter-strand cross-over resistance. Experiments were performed in both normal helium at 4.4 K and superfluid at 1.9 K. Conductors in general are less stable at the lower temperature when measured at the same fraction of critical current. Results show that the cored-cables, even when partially filled with solder or with a porous-metal filler exhibit a relatively low stability at currents close to the critical current. It is speculated that the high inter-strand electrical and thermal resistance inherent in these cables may effect the stability at high currents.

  10. Integrated wideband optical frequency combs with high stability and their application in microwave photonic filters

    NASA Astrophysics Data System (ADS)

    Sun, Wenhui; Wang, Sunlong; Zhong, Xin; Liu, Jianguo; Wang, Wenting; Tong, Youwan; Chen, Wei; Yuan, Haiqing; Yu, Lijuan; Zhu, Ninghua

    2016-08-01

    An integrated wideband optical frequency comb (OFC) based on a semiconductor quantum dot laser is realized with high stability. The OFC module is packaged in our lab. A circuit which is designed to provide a low-ripple current and control the temperature regards as a servo system to enhance the stability of the OFC. The frequency stability of the OFC is 2.7×10-9 (Allan Variance). The free spectral range (FSR) of the OFC is 40 GHz and the number of comb lines is up to 55. The flatness of the OFC over span of 4 nm can be limited to 0.5 dB. Negative coefficients microwave photonic filters with multiple taps are generated based on the proposed OFC. For the 10 taps microwave photonic filter, the pass-band at 8.74 GHz has a 3 dB bandwidth of 630 MHz with 16.58 dB side-lobe suppression. Compared with the published microwave photonic filters, the proposed system is more stable, of more compact structures, and of less power consumption.

  11. Vibration frequency measurement using a local multithreshold technique.

    PubMed

    Ferrer, Belen; Espinosa, Julian; Roig, Ana B; Perez, J; Mas, D

    2013-11-01

    In this paper, we demonstrate the use of a video camera for measuring the frequency of small-amplitude vibration movements. The method is based on image acquisition and multilevel thresholding and it only requires a video camera with high enough acquisition rate, not being necessary the use of targets or auxiliary laser beams. Our proposal is accurate and robust. We demonstrate the technique with a pocket camera recording low-resolution videos with AVI-JPEG compression and measuring different objects that vibrate in parallel or perpendicular direction to the optical sensor. Despite the low resolution and the noise, we are able to measure the main vibration modes of a tuning fork, a loudspeaker and a bridge. Results are successfully compared with design parameters and measurements with alternative devices.

  12. Dynamics of suspended microchannel resonators conveying opposite internal fluid flow: Stability, frequency shift and energy dissipation

    NASA Astrophysics Data System (ADS)

    Zhang, Wen-Ming; Yan, Han; Jiang, Hui-Ming; Hu, Kai-Ming; Peng, Zhi-Ke; Meng, Guang

    2016-04-01

    In this paper, the dynamics of suspended microchannel resonators which convey internal flows with opposite directions are investigated. The fluid-structure interactions between the laminar fluid flow and oscillating cantilever are analyzed by comprehensively considering the effects of velocity profile, flow viscosity and added flowing particle. A new model is developed to characterize the dynamic behavior of suspended microchannel resonators with the fluid-structure interactions. The stability, frequency shift and energy dissipation of suspended microchannel resonators are analyzed and discussed. The results demonstrate that the frequency shifts induced by the added flowing particle which are obtained from the new model have a good agreement with the experimental data. The steady mean flow can cause the frequency shift and influence the stability of the dynamic system. As the flow velocity reaches the critical value, the coupled-mode flutter occurs via a Hamiltonian Hopf bifurcation. The perturbation flow resulted from the vibration of the microcantilever leads to energy dissipation, while the steady flow does not directly cause the damping which increases with the increasing of the flow velocity predicted by the classical model. It can also be found that the steady flow firstly changes the mode shape of the cantilever and consequently affects the energy dissipation.

  13. Stability and natural frequency of nonspherical mode of an encapsulated microbubble in a viscous liquid

    NASA Astrophysics Data System (ADS)

    Liu, Yunqiao; Wang, Qianxi

    2016-06-01

    The dynamics of encapsulated microbubbles (EMBs) subject to an ultrasound wave have wide and important medical applications, including sonography, drug delivery, and sonoporation. The nonspherical shape oscillation of an EMB, termed as shape modes, is one of the core mechanisms of these applications and therefore its natural frequency is a fundamentally important parameter. Based on the linear stability theory, we show that shape modes of an EMB in a viscous Newtonian liquid are stable. We derive an explicit expression for the natural frequency of shape modes, in terms of the equilibrium radius of an EMB, and the parameters of the external liquid, coating, and internal gases. The expression is validated by comparing to the numerical results obtained from the dynamic equations of shape modes of an EMB. The natural frequency of shape modes shifts appreciably due to the viscosity of the liquid, and this trend increases with the mode number. The significant viscous effects are due to the no-slip condition for the liquid flow at the surface of an EMB. Our results show that when subject to an acoustic wave, the shape instability for an EMB is prone to appear if 2ωk/ωd = n, where ωk is the natural frequency of shape modes, ωd is the driving frequency of the acoustic wave, and n is a natural number. The effects of viscosity on the natural frequency is thus critical in setting the driving frequency of ultrasound to avoid or activate shape modes of EMBs, which should be considered in the applications of medical ultrasound.

  14. Low frequency motion measurement and control of spacecrafts and satellites

    NASA Astrophysics Data System (ADS)

    Acernese, F.; Giordano, G.; Romano, R.; Barone, F.

    2015-04-01

    This paper describes a new mechanical application of the Watt-linkage for the development and implementation of mono-axial sensors aimed to low frequency motion measurement and control of spacecrafts and satellites. The basic component of these sensors is the one dimensional UNISA Folded Pendulum mechanical sensor, developed for ground-based applications, whose unique features are due to a very effective optimization of the effects of gravitational force on the folded pendulum mechanical components, that allowed the design and implementation of FP sensors compact (< 20 cm), light (< 300 g), scalable, tunable resonance frequency < 200mHz), with large band (10-6 Hz - 100Hz), high quality factor (Q > 15000 in vacuum at 1Hz), with good immunity to environmental noises and sensitivity, guaranteed by an integrated laser optical readout, and fully adaptable to the specific requirements of the application. In this paper we show how to extend the application of ground-based FP also to space, in absence of gravity, still keeping all the above interesting features and characteristics that make this class of sensors very effective in terms of large band, especially in the low frequency, sensitivity and long term reliability. Preliminary measurements on a prototype confirm the feasibility, showing also that very good performances can be relatively easily obtained.

  15. Study on technology of high-frequency pulsed magnetic field strength measurement.

    PubMed

    Chen, Yi-Mei; Liu, Zhi-Peng; Yin, Tao

    2012-01-01

    High-frequency transient weak magnetic field is always involved in researches about biomedical engineering field while common magnetic-field sensors cannot work properly at frequencies as high as MHz. To measure the value of MHz-level weak pulsed magnetic-field strength accurately, this paper designs a measurement and calibration method for pulsed magnetic-field. In this paper, a device made of Nonferromagnetic material was independently designed and applied to pulsed magnetic field measurement. It held an accurately relative position between the magnetic field generating coil and the detecting coil. By applying a sinusoidal pulse to the generator, collecting the induced electromotive force of the detector, the final magnetic field strength was worked out through algorithms written in Matlab according to Faraday's Law. Experiments were carried out for measurement and calibration. Experiments showed that, under good stability and consistency, accurate measurement of magnetic-field strength of a sinepulse magnetic-field can be achieved, with frequency at 0.5, 1, 1.5 MHz and strength level at micro-Tesla. Calibration results carried out a measuring relative error about 2.5%.

  16. The optical frequency method of distance measurement with sub-nanometer resolution

    NASA Astrophysics Data System (ADS)

    Cip, Ondrej; Petru, Frantisek; Lazar, Josef

    2005-02-01

    We present design and experimental setup for direct transformation of the relative change of distances in measuring arm of the Michelson interferometer to relative changes of the resonant optical-frequency of Fabry-Perot (F.-P.) resonator. The method consists of a mechanical coupled moving system of the corner cube mirror of the interferometer measuring arm with one of the mirrors of F.-P. resonator. A piezoelectric transducer (PZT) with elongation 10 microns approximately drives that moving system. An external tunable laser source at 633 nm wavelength provides identification of one of the resonant optical frequency of F.-P. resonator by the frequency locking mechanism with synchronous detection technique in the servo loop feedback. Because the definition of the meter unit is based on iodine stabilized He-Ne laser, then the optical frequency of the locked tunable laser is frequency compared with He-Ne-I2 laser by the heterodyne optical mixing. A fast high-resolution counter counts the resultant radio-frequency signal as a product of the optical mixing. Measured frequency values and values of interference phase acquired by the interferometer are simultaneously sampled step by step for each elongation position of PZT element. We used that experimental setup for the testing process where a verification of scale-linearity of Michelson interferometer with total resolution 0,3 nm is investigated. The experimental data achieved by F.-P. resonator during such a way shows the absolute uncertainty better than 0,08 nm for the relative distance change 1.5 microns. We verified the scale-linearity of Michelson interferometer to +/-1,0 nm limit.

  17. Postural stability index is a more valid measure of stability than equilibrium score.

    PubMed

    Chaudhry, Hans; Findley, Thomas; Quigley, Karen S; Ji, Zhiming; Maney, Miriam; Sims, Tiffany; Bukiet, Bruce; Foulds, Richard

    2005-01-01

    Researchers, therapists, and physicians often use equilibrium score (ES) from the Sensory Organization Test, a key test in the NeuroCom EquiTest System (a dynamic posturography system) to assess stability. ES reflects the overall coordination of the visual, proprioceptive, and vestibular systems for maintaining standing posture. In our earlier article, we proposed a new measure of anterior-posterior (A-P) postural stability called the Postural Stability Index (PSI), which accounts for more biomechanical aspects than ES. This article showed that PSI provides a clinically important adjunct to ES. In the present article, we show that PSI can provide an acceptable index even if a person falls during the trial, whereas ES assigns a zero score for any fall. We also show that PSI decreases as ankle stiffness increases, which is intuitive, while ES exhibits the opposite behavior. Ankle stiffness is generally recognized as an indicator of postural stability. These results suggest that PSI is a more valid measure of A-P stability than ES. PMID:16320149

  18. Low frequency azimuthal stability of the ionization region of the Hall thruster discharge. II. Global analysis

    SciTech Connect

    Escobar, D.; Ahedo, E.

    2015-10-15

    The linear stability of the Hall thruster discharge is analysed against axial-azimuthal perturbations in the low frequency range using a time-dependent 2D code of the discharge. This azimuthal stability analysis is spatially global, as opposed to the more common local stability analyses, already afforded previously (D. Escobar and E. Ahedo, Phys. Plasmas 21(4), 043505 (2014)). The study covers both axial and axial-azimuthal oscillations, known as breathing mode and spoke, respectively. The influence on the spoke instability of different operation parameters such as discharge voltage, mass flow, and thruster size is assessed by means of different parametric variations and compared against experimental results. Additionally, simplified models are used to unveil and characterize the mechanisms driving the spoke. The results indicate that the spoke is linked to azimuthal oscillations of the ionization process and to the Bohm condition in the transition to the anode sheath. Finally, results obtained from local and global stability analyses are compared in order to explain the discrepancies between both methods.

  19. Stabilization of Neoclassical Tearing Modes in Tokamaks by Radio Frequency Current Drive

    SciTech Connect

    La Haye, R. J.

    2007-09-28

    Resistive neoclassical tearing modes (NTMs) will be the principal limit on stability and performance in the ITER standard scenario as the resulting islands break up the magnetic surfaces that confine the plasma. Drag from rotating island-induced eddy current in the resistive wall can also slow the plasma rotation, produce locking to the wall, and cause loss of high confinement H-mode and disruption. The NTMs are maintained by helical perturbations to the pressure-gradient driven 'bootstrap' current. Thus, this is a high beta instability even at the modest beta for ITER. A major line of research on NTM stabilization is the use of radio frequency (rf) current drive at the island rational surface. While large, broad current drive from lower hybrid waves has been shown to be stabilizing (COMPASS-D), most research is directed to small, narrow current drive from electron cyclotron waves (ECCD); ECCD stabilization and/or preemptive prevention is successful in ASDEX Upgrade, DIII-D and JT-60U, for example, with as little as a few percent of the total plasma current if the ECCD is kept sufficiently narrow so that the peak off-axis ECCD is comparable to the local bootstrap current.

  20. Injection seeding of a Q-switched alexandrite laser: Study of frequency stabilization

    NASA Technical Reports Server (NTRS)

    Brown, Lamarr A.

    1992-01-01

    AlGaAs diode lasers were used to injection seed a pulsed Q-switched alexandrite laser which produces a narrowband of radiation. Injection seeding is a method for achieving linewidths of less than 500 mega-Hz in the output of the broadband, tunable solid state laser. When the laser was set at a current of 59.8 milli-A and a temperature of 14.04 C, the wavelength was 767.6 nano-m. The Q-switched alexandrite laser was injection seeded and frequency stabilization was studied. The linewidth requirement was met, but the stability requirement was not due to drifting in the feedback voltage. Improvements on injection seeding should focus on increasing the feedback voltage to the laser diode, filtering the laser diode by using temperature controlled narrowband filters, and the use of diamond (SiC) grating placed inside the alexandrite laser's resonator cavity.

  1. Accurate and fast fiber transfer delay measurement based on phase discrimination and frequency measurement

    NASA Astrophysics Data System (ADS)

    Dong, J. W.; Wang, B.; Gao, C.; Wang, L. J.

    2016-09-01

    An accurate and fast fiber transfer delay measurement method is demonstrated. As a key technique, a simple ambiguity resolving process based on phase discrimination and frequency measurement is used to overcome the contradiction between measurement accuracy and system complexity. The system achieves a high measurement accuracy of 0.2 ps with a 0.1 ps measurement resolution and a large dynamic range up to 50 km as well as no dead zone.

  2. The ATS-F radio frequency interference measurement experiment

    NASA Technical Reports Server (NTRS)

    Henry, V. F.

    1973-01-01

    The technical objectives of the uplink interference tests and measurements to be performed during this experiment are set forth as the determination of the integrated interference power from all 6-GHz terrestrial sources sharing the common carrier band with the RF field of view of the ATS-F satellite; the establishment of practical limits of receiver antenna gain-to-noise temperature ratios for satellites sharing the common 6-GHz carrier band; and the determination of the geographical and frequency distribution of 6-GHz terrestrial sources sharing the common carrier band. A brief description of the RF interference measurement system with some details on its hardware and subsystems is included. The performance characteristics of the mission and a measurement program are discussed.

  3. Frequency-Rank Distributions

    ERIC Educational Resources Information Center

    Brookes, Bertram C.; Griffiths, Jose M.

    1978-01-01

    Frequency, rank, and frequency rank distributions are defined. Extensive discussion on several aspects of frequency rank distributions includes the Poisson process as a means of exploring the stability of ranks; the correlation of frequency rank distributions; and the transfer coefficient, a new measure in frequency rank distribution. (MBR)

  4. Contribution of thermal noise to frequency stability of rigid optical cavity via Hertz-linewidth lasers

    SciTech Connect

    Notcutt, Mark; Ma, L.-S.; Ludlow, Andrew D.; Foreman, Seth M.; Ye Jun; Hall, John L.

    2006-03-15

    We perform detailed studies of state-of-the-art laser stabilization to high finesse optical cavities, revealing fundamental mechanical thermal noise-related length fluctuations. We compare the frequency noise of lasers tightly locked to the resonances of a variety of rigid Fabry-Perot cavities of differing lengths and mirror substrate materials. The results are in agreement with the theoretical model proposed in K. Numata, A. Kemery, and J. Camp [Phys. Rev. Lett. 93, 250602 (2004)]. The results presented here on the fundamental limits of FP references will impact planning and construction of next generation ultrastable optical cavities.

  5. Gain, phase and frequency stability of DSS-42 and DSS-43 vor Voyage Uranus encounter

    NASA Technical Reports Server (NTRS)

    Cha, A. G.; Levy, R.

    1986-01-01

    Theoretically rigorous definitions are derived of such parameters as RF signal path length, phase delay, and phase/frequency stability in a Cassegrainian antenna applicable to a narrow bandwidth channel, as well as algorithms for evaluating these parameters. This work was performed in support of the Voyager spacecraft encounter with Uranus in January 1986. The information was needed to provide Voyager/Uranus radio science researchers with a rotational basis for deciding the best strategy to operate the three antennas involved during the crucial 5-hour occultation period of the encounter. Such recommendations are made at the end of the article.

  6. Variable optical attenuator with a polymer-stabilized dual-frequency liquid crystal

    NASA Astrophysics Data System (ADS)

    Wu, Yung-Hsun; Liang, Xiao; Lu, Yan-Qing; Du, Fang; Lin, Yi-Hsin; Wu, Shin-Tson

    2005-07-01

    A transmission-type variable optical attenuator (VOA) based on a polymer-stabilized dual-frequency liquid crystal (PSDFLC) is demonstrated at lambda=1.55 μm. The VOA is highly transparent in the voltage-off state but scatters light in the voltage-on state. By using a birefringent beam displacer incorporated with half-wave plates, we can obtain a VOA that is polarization independent and that exhibits a 31 dB dynamic range. The polymer networks and dual-frequency effect together reduce the response time (rise + decay) of a 16 μm PSDFLC cell to 30 ms at room temperature and at a voltage of 24 Vrms.

  7. Variable optical attenuator with a polymer-stabilized dual-frequency liquid crystal.

    PubMed

    Wu, Yung-Hsun; Liang, Xiao; Lu, Yan-Qing; Du, Fang; Lin, Yi-Hsin; Wu, Shin-Tson

    2005-07-10

    A transmission-type variable optical attenuator (VOA) based on a polymer-stabilized dual-frequency liquid crystal (PSDFLC) is demonstrated at gamma = 1.55 microm. The VOA is highly transparent in the voltage-off state but scatters light in the voltage-on state. By using a birefringent beam displacer incorporated with half-wave plates, we can obtain a VOA that is polarization independent and that exhibits a 31 dB dynamic range. The polymer networks and dual-frequency effect together reduce the response time (rise + decay) of a 16 microm PSDFLC cell to 30 ms at room temperature and at a voltage of 24 Vrms. PMID:16045229

  8. Noninvasive measurement of conductivity anisotropy at larmor frequency using MRI.

    PubMed

    Lee, Joonsung; Song, Yizhuang; Choi, Narae; Cho, Sungmin; Seo, Jin Keun; Kim, Dong-Hyun

    2013-01-01

    Anisotropic electrical properties can be found in biological tissues such as muscles and nerves. Conductivity tensor is a simplified model to express the effective electrical anisotropic information and depends on the imaging resolution. The determination of the conductivity tensor should be based on Ohm's law. In other words, the measurement of partial information of current density and the electric fields should be made. Since the direct measurements of the electric field and the current density are difficult, we use MRI to measure their partial information such as B1 map; it measures circulating current density and circulating electric field. In this work, the ratio of the two circulating fields, termed circulating admittivity, is proposed as measures of the conductivity anisotropy at Larmor frequency. Given eigenvectors of the conductivity tensor, quantitative measurement of the eigenvalues can be achieved from circulating admittivity for special tissue models. Without eigenvectors, qualitative information of anisotropy still can be acquired from circulating admittivity. The limitation of the circulating admittivity is that at least two components of the magnetic fields should be measured to capture anisotropic information.

  9. Characterization of Low-Frequency Combustion Stability of the Fastrac Engine

    NASA Technical Reports Server (NTRS)

    Rocker, Marvin; Jones, Preston (Technical Monitor)

    2002-01-01

    A series of tests were conducted to measure the combustion performance of the Fastrac engine thrust chamber. During mainstage, the thrust chamber exhibited no large-amplitude chamber pressure oscillations that could be identified as low-frequency combustion instability or 'chug'. However, during start-up and shutdown, the thrust chamber very briefly exhibited large-amplitude chamber pressure oscillations that were identified as chug. These instabilities during start-up and shutdown were regarded as benign due to their brevity. Linear models of the thrust chamber and the propellant feed systems were formulated for both the thrust chamber component tests and the flight engine tests. These linear models determined the frequency and decay rate of chamber pressure oscillations given the design and operating conditions of the thrust chamber and feed system. The frequency of chamber pressure oscillations determined from the model closely matched the frequency of low-amplitude, low-frequency chamber pressure oscillations exhibited in some of the later thrust chamber mainstage tests. The decay rate of the chamber pressure oscillations determined from the models indicated that these low-frequency oscillations were stable. Likewise, the decay rate, determined from the model of the flight engine tests indicated that the low-frequency chamber pressure oscillations would be stable.

  10. Frequency-response method for determination of dynamic stability characteristics of airplanes with automatic controls

    NASA Technical Reports Server (NTRS)

    Greenberg, Harry

    1947-01-01

    A frequency-response method for determining the critical control-gearing and hunting oscillations of airplanes with automatic pilots is presented. The method is graphical and has several advantages over the standard numerical procedure based on Routh's discriminant. The chief advantage of the method is that direct use can be made of the measured response characteristics of the automatic pilot. This feature is especially useful in determining the existence, amplitude, and frequency of the hunting oscillations that may be present when the automatic pilot has nonlinear dynamic characteristics. Several examples are worked out to illustrate the application of the frequency-response method in determining the effect of automatic-pilot lag or lead on critical control gearing and in determining the amplitude and frequency hunting. It is shown that the method may be applied to the case of a control geared to airplane motions about two axes.

  11. Frequency Stability of 1X10(sup -13) in a Compensated Sapphire Oscillator Operating Above 77 K

    NASA Technical Reports Server (NTRS)

    Santiago, D. G.; Dick, G. J.; Wang, R. T.

    1996-01-01

    We report on a frequency-stable temperature compensated sapphire oscillator (CSO) at temperatures above 77 K. Previously, high stability in sapphire oscillators had only been obtained with liquid helium cooling.

  12. Viscometer for low frequency, low shear rate measurements

    NASA Technical Reports Server (NTRS)

    Berg, R. F.; Moldover, M. R.

    1986-01-01

    A computer-controlled torsion-oscillator viscometer with low 0.5 Hz frequency and very low 0.05/s shear rate is designed to precisely study shear-sensitive fluids such as microemulsions, gels, polymer solutions and melts, colloidal solutions undergoing coagulation, and liquid mixtures near critical points. The viscosities are obtained from measurements of the logarithmic decrement of an underdriven oscillator. The viscometer is found to have a resolution of 0.2 percent when used with liquid samples and a resolution of 0.4 percent when used with a dense gaseous sample. The design is compatible with submillikelvin temperature control.

  13. Technique for Performing Dielectric Property Measurements at Microwave Frequencies

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B. (Inventor); Jackson, Henry W. (Inventor)

    2014-01-01

    A method, system, apparatus, and computer readable medium has been provided with the ability to obtain a complex permittivity dielectric or a complex permeability micron of a sample in a cavity. One or more complex-valued resonance frequencies f(sub m) of the cavity, wherein each f(sub m) is a measurement, are obtained. Maxwell's equations are solved exactly for dielectric, and/or micron, using the f(sub m) as known quantities, thereby obtaining the dielectric and/or micron of the sample.

  14. On frequency and efficiency measurements in counting experiments

    NASA Astrophysics Data System (ADS)

    Rotondi, Alberto

    2010-02-01

    The methods for the evaluation of the uncertainties in the frequency and the efficiency in counting experiments are re-examined. It is shown that the confidence intervals, obtained from inverting test acceptance regions with pivotal variables and including the Continuity Correction (CC), give in many cases intervals with coverage and width comparable to those of some more sophisticated methods in use. The Poisson counting with and without background (known or measured) and with acceptance effects, as well as the efficiency determination through binomial counting are considered in detail. Most of the proposed formulae are simple and could substitute the standard textbook ones used by the physicists in their daily practice.

  15. Measurements of the frequency spectrum of transition radiation

    NASA Technical Reports Server (NTRS)

    Cherry, M. L.; Mueller, D.

    1977-01-01

    We report a measurement of the frequency spectrum of X-ray transition radiation. X rays were generated by electrons of 5 and 9 GeV in radiators of multiple polypropylene foils, and detected in the range 4 to 30 keV with a calibrated single-crystal Bragg spectrometer. The experimental results closely reproduce the features of the theoretically predicted spectrum. In particular, the pronounced interference pattern of multifoil radiators and the expected hardening of the radiation with increasing foil thickness are clearly observed. The overall intensity of the radiation is somewhat lower than predicted by calculations.

  16. Resonance Frequency of Optical Microbubble Resonators: Direct Measurements and Mitigation of Fluctuations

    PubMed Central

    Cosci, Alessandro; Berneschi, Simone; Giannetti, Ambra; Farnesi, Daniele; Cosi, Franco; Baldini, Francesco; Nunzi Conti, Gualtiero; Soria, Silvia; Barucci, Andrea; Righini, Giancarlo; Pelli, Stefano

    2016-01-01

    This work shows the improvements in the sensing capabilities and precision of an Optical Microbubble Resonator due to the introduction of an encaging poly(methyl methacrylate) (PMMA) box. A frequency fluctuation parameter σ was defined as a score of resonance stability and was evaluated in the presence and absence of the encaging system and in the case of air- or water-filling of the cavity. Furthermore, the noise interference introduced by the peristaltic and the syringe pumping system was studied. The measurements showed a reduction of σ in the presence of the encaging PMMA box and when the syringe pump was used as flowing system. PMID:27589761

  17. Low noise buffer amplifiers and buffered phase comparators for precise time and frequency measurement and distribution

    NASA Technical Reports Server (NTRS)

    Eichinger, R. A.; Dachel, P.; Miller, W. H.; Ingold, J. S.

    1982-01-01

    Extremely low noise, high performance, wideband buffer amplifiers and buffered phase comparators were developed. These buffer amplifiers are designed to distribute reference frequencies from 30 KHz to 45 MHz from a hydrogen maser without degrading the hydrogen maser's performance. The buffered phase comparators are designed to intercompare the phase of state of the art hydrogen masers without adding any significant measurement system noise. These devices have a 27 femtosecond phase stability floor and are stable to better than one picosecond for long periods of time. Their temperature coefficient is less than one picosecond per degree C, and they have shown virtually no voltage coefficients.

  18. Resonance Frequency of Optical Microbubble Resonators: Direct Measurements and Mitigation of Fluctuations.

    PubMed

    Cosci, Alessandro; Berneschi, Simone; Giannetti, Ambra; Farnesi, Daniele; Cosi, Franco; Baldini, Francesco; Nunzi Conti, Gualtiero; Soria, Silvia; Barucci, Andrea; Righini, Giancarlo; Pelli, Stefano

    2016-01-01

    This work shows the improvements in the sensing capabilities and precision of an Optical Microbubble Resonator due to the introduction of an encaging poly(methyl methacrylate) (PMMA) box. A frequency fluctuation parameter σ was defined as a score of resonance stability and was evaluated in the presence and absence of the encaging system and in the case of air- or water-filling of the cavity. Furthermore, the noise interference introduced by the peristaltic and the syringe pumping system was studied. The measurements showed a reduction of σ in the presence of the encaging PMMA box and when the syringe pump was used as flowing system. PMID:27589761

  19. Resonance Frequency of Optical Microbubble Resonators: Direct Measurements and Mitigation of Fluctuations.

    PubMed

    Cosci, Alessandro; Berneschi, Simone; Giannetti, Ambra; Farnesi, Daniele; Cosi, Franco; Baldini, Francesco; Nunzi Conti, Gualtiero; Soria, Silvia; Barucci, Andrea; Righini, Giancarlo; Pelli, Stefano

    2016-08-31

    This work shows the improvements in the sensing capabilities and precision of an Optical Microbubble Resonator due to the introduction of an encaging poly(methyl methacrylate) (PMMA) box. A frequency fluctuation parameter σ was defined as a score of resonance stability and was evaluated in the presence and absence of the encaging system and in the case of air- or water-filling of the cavity. Furthermore, the noise interference introduced by the peristaltic and the syringe pumping system was studied. The measurements showed a reduction of σ in the presence of the encaging PMMA box and when the syringe pump was used as flowing system.

  20. Resilience, reactivity and variability: A mathematical comparison of ecological stability measures.

    PubMed

    Arnoldi, J-F; Loreau, M; Haegeman, B

    2016-01-21

    In theoretical studies, the most commonly used measure of ecological stability is resilience: ecosystems asymptotic rate of return to equilibrium after a pulse-perturbation -or shock. A complementary notion of growing popularity is reactivity: the strongest initial response to shocks. On the other hand, empirical stability is often quantified as the inverse of temporal variability, directly estimated on data, and reflecting ecosystems response to persistent and erratic environmental disturbances. It is unclear whether and how this empirical measure is related to resilience and reactivity. Here, we establish a connection by introducing two variability-based stability measures belonging to the theoretical realm of resilience and reactivity. We call them intrinsic, stochastic and deterministic invariability; respectively defined as the inverse of the strongest stationary response to white-noise and to single-frequency perturbations. We prove that they predict ecosystems worst response to broad classes of disturbances, including realistic models of environmental fluctuations. We show that they are intermediate measures between resilience and reactivity and that, although defined with respect to persistent perturbations, they can be related to the whole transient regime following a shock, making them more integrative notions than reactivity and resilience. We argue that invariability measures constitute a stepping stone, and discuss the challenges ahead to further unify theoretical and empirical approaches to stability.

  1. Established time series measure occurrence and frequency of episodic events.

    NASA Astrophysics Data System (ADS)

    Pebody, Corinne; Lampitt, Richard

    2015-04-01

    Established time series measure occurrence and frequency of episodic events. Episodic flux events occur in open oceans. Time series making measurements over significant time scales are one of the few methods that can capture these events and compare their impact with 'normal' flux. Seemingly rare events may be significant on local scales, but without the ability to measure the extent of flux on spatial and temporal scales and combine with the frequency of occurrence, it is difficult to constrain their impact. The Porcupine Abyssal Plain Sustained Observatory (PAP-SO) in the Northeast Atlantic (49 °N 16 °W, 5000m water depth) has measured particle flux since 1989 and zooplankton swimmers since 2000. Sediment traps at 3000m and 100 metres above bottom, collect material year round and we have identified close links between zooplankton and particle flux. Some of these larger animals, for example Diacria trispinosa, make a significant contribution to carbon flux through episodic flux events. D. trispinosa is a euthecosome mollusc which occurs in the Northeast Atlantic, though the PAP-SO is towards the northern limit of its distribution. Pteropods are comprised of aragonite shell, containing soft body parts excepting the muscular foot which extends beyond the mouth of the living animal. Pteropods, both live-on-entry animals and the empty shells are found year round in the 3000m trap. Generally the abundance varies with particle flux, but within that general pattern there are episodic events where significant numbers of these animals containing both organic and inorganic carbon are captured at depth and therefore could be defined as contributing to export flux. Whether the pulse of animals is as a result of the life cycle of D. trispinosa or the effects of the physics of the water column is unclear, but the complexity of the PAP-SO enables us not only to collect these animals but to examine them in parallel to the biogeochemical and physical elements measured by the

  2. An ultralow noise preamplifier for low frequency noise measurements.

    PubMed

    Cannatà, Gianluca; Scandurra, Graziella; Ciofi, Carmine

    2009-11-01

    Low frequency noise measurements are among the most sensitive tools for the investigation of the quality and of the reliability of semiconductor devices. The sensitivity that can be obtained depends on the background noise of the low noise preamplifier coupled to the device under test (DUT) that, at very low frequencies, is dominated by flicker noise. The low frequency noise produced by the DUT, on the other end, is very often the most interesting signal to be detected and analyzed. In this work we propose a very simple topology for the realization of a general purpose low noise preamplifier whose noise performances, at very low frequencies (below 10 Hz), are significantly better than those that can be obtained by the most popular commercial instrumentation. Indeed, a gain of 80 dB with a pass band extending from a few tens of mHz up to a few kHz with an equivalent input voltage noise as low as 14 nV/square root(Hz) (100 mHz), 1.4 nV/square root(Hz) (1 Hz), 1.0 nV/square root(Hz) (10 Hz), and 0.8 nV/square root(Hz) (1 kHz) are consistently obtained by using quite standard electronic components and with no need for trimming and/or calibration steps. Moreover, the junction field-effect transistor input stage of the amplifier is characterized by an equivalent input current noise below 4 fA/square root(Hz) in the entire bandwidth, resulting in negligible background noise degradation for DUT impedances in excess of 100 kohms. PMID:19947746

  3. Stabilization and feedback control of weak measurement monitored quantum oscillators

    NASA Astrophysics Data System (ADS)

    Uys, Hermann; Du Toit, Pieter; Burd, Shaun; Konrad, Thomas

    2016-05-01

    We study feedback control of quantum oscillators, monitored through periodic weak measurement. By implementing reversals of measurement perturbations based on a Bayesian estimate of the state dynamics, we demonstrate suppressed measurement noise leading to greater oscillator stability and improved quantum feedback control. The work in this paper was supported in part by the National Research Foundation of South Africa through Grant No. 93602 as well as an award by the United States Airforce Office of Scientific Research, Award No. FA9550-14-1-0151.

  4. On-board telemetry of emitted sounds from free-flying bats: compensation for velocity and distance stabilizes echo frequency and amplitude.

    PubMed

    Hiryu, Shizuko; Shiori, Yu; Hosokawa, Tatsuro; Riquimaroux, Hiroshi; Watanabe, Yoshiaki

    2008-09-01

    To understand complex sensory-motor behavior related to object perception by echolocating bats, precise measurements are needed for echoes that bats actually listen to during flight. Recordings of echolocation broadcasts were made from flying bats with a miniature light-weight microphone and radio transmitter (Telemike) set at the position of the bat's ears and carried during flights to a landing point on a wall. Telemike recordings confirm that flying horseshoe bats (Rhinolophus ferrumequinum nippon) adjust the frequency of their sonar broadcasts to compensate for echo Doppler shifts. Returning constant frequency echoes were maintained at the bat's reference frequency +/-83 Hz during flight, indicating that the bats compensated for frequency changes with an accuracy equivalent to that at rest. The flying bats simultaneously compensate for increases in echo amplitude as target range becomes shorter. Flying bats thus receive echoes with both stabilized frequencies and stabilized amplitudes. Although it is widely understood that Doppler-shift frequency compensation facilitates detection of fluttering insects, approaches to a landing do not involve fluttering objects. Combined frequency and amplitude compensation may instead be for optimization of successive frequency modulated echoes for target range estimation to control approach and landing.

  5. Dream recall frequency: impact of prospective measures and motivational factors.

    PubMed

    Zadra, Antonio; Robert, Geneviève

    2012-12-01

    Significant individual differences exist in dream recall frequency (DRF) but some variance is likely attributable to instrument choice in measuring DRF. Three hundred and fifty eight participants estimated their weekly DRF and recorded their dreams in either a narrative log (n = 165) or checklist log (n = 193) for 2-5 weeks. There was an early peak in DRF within the first week of both types of prospective logs after which DRF remained relatively stable. Although the two groups did not differ in their estimated DRF, significantly fewer dreams were reported per week on the narrative logs and only checklist logs yielded significantly higher DRF than participants' questionnaire estimates. The interactions between DRF measures did not vary across groups with low, medium or high baseline levels of DRF. Keeping a dream log does not necessarily increase DRF and narrative logs' time consuming nature can impact subjects' motivation to report all of their dreams over time.

  6. A precise measurement of the B^0 meson oscillation frequency

    NASA Astrophysics Data System (ADS)

    Aaij, R.; Abellán Beteta, C.; Adeva, B.; Adinolfi, M.; Affolder, A.; Ajaltouni, Z.; Akar, S.; Albrecht, J.; Alessio, F.; Alexander, M.; Ali, S.; Alkhazov, G.; Alvarez Cartelle, P.; Alves, A. A., Jr.; Amato, S.; Amerio, S.; Amhis, Y.; An, L.; Anderlini, L.; Anderson, J.; Andreassi, G.; Andreotti, M.; Andrews, J. E.; Appleby, R. B.; Aquines Gutierrez, O.; Archilli, F.; d'Argent, P.; Artamonov, A.; Artuso, M.; Aslanides, E.; Auriemma, G.; Baalouch, M.; Bachmann, S.; Back, J. J.; Badalov, A.; Baesso, C.; Baldini, W.; Barlow, R. J.; Barschel, C.; Barsuk, S.; Barter, W.; Batozskaya, V.; Battista, V.; Bay, A.; Beaucourt, L.; Beddow, J.; Bedeschi, F.; Bediaga, I.; Bel, L. J.; Bellee, V.; Belloli, N.; Belyaev, I.; Ben-Haim, E.; Bencivenni, G.; Benson, S.; Benton, J.; Berezhnoy, A.; Bernet, R.; Bertolin, A.; Bettler, M.-O.; van Beuzekom, M.; Bien, A.; Bifani, S.; Billoir, P.; Bird, T.; Birnkraut, A.; Bizzeti, A.; Blake, T.; Blanc, F.; Blouw, J.; Blusk, S.; Bocci, V.; Bondar, A.; Bondar, N.; Bonivento, W.; Borghi, S.; Borsato, M.; Bowcock, T. J. V.; Bowen, E.; Bozzi, C.; Braun, S.; Britsch, M.; Britton, T.; Brodzicka, J.; Brook, N. H.; Buchanan, E.; Bursche, A.; Buytaert, J.; Cadeddu, S.; Calabrese, R.; Calvi, M.; Calvo Gomez, M.; Campana, P.; Campora Perez, D.; Capriotti, L.; Carbone, A.; Carboni, G.; Cardinale, R.; Cardini, A.; Carniti, P.; Carson, L.; Carvalho Akiba, K.; Casse, G.; Cassina, L.; Castillo Garcia, L.; Cattaneo, M.; Cauet, Ch.; Cavallero, G.; Cenci, R.; Charles, M.; Charpentier, Ph.; Chefdeville, M.; Chen, S.; Cheung, S.-F.; Chiapolini, N.; Chrzaszcz, M.; Cid Vidal, X.; Ciezarek, G.; Clarke, P. E. L.; Clemencic, M.; Cliff, H. V.; Closier, J.; Coco, V.; Cogan, J.; Cogneras, E.; Cogoni, V.; Cojocariu, L.; Collazuol, G.; Collins, P.; Comerma-Montells, A.; Contu, A.; Cook, A.; Coombes, M.; Coquereau, S.; Corti, G.; Corvo, M.; Couturier, B.; Cowan, G. A.; Craik, D. C.; Crocombe, A.; Cruz Torres, M.; Cunliffe, S.; Currie, R.; D'Ambrosio, C.; Dall'Occo, E.; Dalseno, J.; David, P. N. Y.; Davis, A.; De Aguiar Francisco, O.; De Bruyn, K.; De Capua, S.; De Cian, M.; De Miranda, J. M.; De Paula, L.; De Simone, P.; Dean, C.-T.; Decamp, D.; Deckenhoff, M.; Del Buono, L.; Déléage, N.; Demmer, M.; Derkach, D.; Deschamps, O.; Dettori, F.; Dey, B.; Di Canto, A.; Di Ruscio, F.; Dijkstra, H.; Donleavy, S.; Dordei, F.; Dorigo, M.; Dosil Suárez, A.; Dossett, D.; Dovbnya, A.; Dreimanis, K.; Dufour, L.; Dujany, G.; Dupertuis, F.; Durante, P.; Dzhelyadin, R.; Dziurda, A.; Dzyuba, A.; Easo, S.; Egede, U.; Egorychev, V.; Eidelman, S.; Eisenhardt, S.; Eitschberger, U.; Ekelhof, R.; Eklund, L.; El Rifai, I.; Elsasser, Ch.; Ely, S.; Esen, S.; Evans, H. M.; Evans, T.; Falabella, A.; Färber, C.; Farley, N.; Farry, S.; Fay, R.; Ferguson, D.; Fernandez Albor, V.; Ferrari, F.; Ferreira Rodrigues, F.; Ferro-Luzzi, M.; Filippov, S.; Fiore, M.; Fiorini, M.; Firlej, M.; Fitzpatrick, C.; Fiutowski, T.; Fohl, K.; Fol, P.; Fontana, M.; Fontanelli, F.; C. Forshaw, D.; Forty, R.; Frank, M.; Frei, C.; Frosini, M.; Fu, J.; Furfaro, E.; Gallas Torreira, A.; Galli, D.; Gallorini, S.; Gambetta, S.; Gandelman, M.; Gandini, P.; Gao, Y.; García Pardiñas, J.; Garra Tico, J.; Garrido, L.; Gascon, D.; Gaspar, C.; Gauld, R.; Gavardi, L.; Gazzoni, G.; Gerick, D.; Gersabeck, E.; Gersabeck, M.; Gershon, T.; Ghez, Ph.; Gianì, S.; Gibson, V.; Girard, O. G.; Giubega, L.; Gligorov, V. V.; Göbel, C.; Golubkov, D.; Golutvin, A.; Gomes, A.; Gotti, C.; Grabalosa Gándara, M.; Graciani Diaz, R.; Granado Cardoso, L. A.; Graugés, E.; Graverini, E.; Graziani, G.; Grecu, A.; Greening, E.; Gregson, S.; Griffith, P.; Grillo, L.; Grünberg, O.; Gui, B.; Gushchin, E.; Guz, Yu.; Gys, T.; Hadavizadeh, T.; Hadjivasiliou, C.; Haefeli, G.; Haen, C.; Haines, S. C.; Hall, S.; Hamilton, B.; Han, X.; Hansmann-Menzemer, S.; Harnew, N.; Harnew, S. T.; Harrison, J.; He, J.; Head, T.; Heijne, V.; Heister, A.; Hennessy, K.; Henrard, P.; Henry, L.; Hernando Morata, J. A.; van Herwijnen, E.; Heß, M.; Hicheur, A.; Hill, D.; Hoballah, M.; Hombach, C.; Hulsbergen, W.; Humair, T.; Hussain, N.; Hutchcroft, D.; Hynds, D.; Idzik, M.; Ilten, P.; Jacobsson, R.; Jaeger, A.; Jalocha, J.; Jans, E.; Jawahery, A.; Jing, F.; John, M.; Johnson, D.; Jones, C. R.; Joram, C.; Jost, B.; Jurik, N.; Kandybei, S.; Kanso, W.; Karacson, M.; Karbach, T. M.; Karodia, S.; Kecke, M.; Kelsey, M.; Kenyon, I. R.; Kenzie, M.; Ketel, T.; Khanji, B.; Khurewathanakul, C.; Kirn, T.; Klaver, S.; Klimaszewski, K.; Kochebina, O.; Kolpin, M.; Komarov, I.; Koopman, R. F.; Koppenburg, P.; Kozeiha, M.; Kravchuk, L.; Kreplin, K.; Kreps, M.; Krocker, G.; Krokovny, P.; Kruse, F.; Krzemien, W.; Kucewicz, W.; Kucharczyk, M.; Kudryavtsev, V.; K. Kuonen, A.; Kurek, K.; Kvaratskheliya, T.; Lacarrere, D.; Lafferty, G.; Lai, A.; Lambert, D.; Lanfranchi, G.; Langenbruch, C.; Langhans, B.; Latham, T.; Lazzeroni, C.; Le Gac, R.; van Leerdam, J.; Lees, J.-P.; Lefèvre, R.; Leflat, A.; Lefrançois, J.; Lemos Cid, E.; Leroy, O.; Lesiak, T.; Leverington, B.; Li, Y.; Likhomanenko, T.; Liles, M.; Lindner, R.; Linn, C.; Lionetto, F.; Liu, B.; Liu, X.; Loh, D.; Longstaff, I.; Lopes, J. H.; Lucchesi, D.; Lucio Martinez, M.; Luo, H.; Lupato, A.; Luppi, E.; Lupton, O.; Lusardi, N.; Lusiani, A.; Machefert, F.; Maciuc, F.; Maev, O.; Maguire, K.; Malde, S.; Malinin, A.; Manca, G.; Mancinelli, G.; Manning, P.; Mapelli, A.; Maratas, J.; Marchand, J. F.; Marconi, U.; Marin Benito, C.; Marino, P.; Marks, J.; Martellotti, G.; Martin, M.; Martinelli, M.; Martinez Santos, D.; Martinez Vidal, F.; Martins Tostes, D.; Massafferri, A.; Matev, R.; Mathad, A.; Mathe, Z.; Matteuzzi, C.; Mauri, A.; Maurin, B.; Mazurov, A.; McCann, M.; McCarthy, J.; McNab, A.; McNulty, R.; Meadows, B.; Meier, F.; Meissner, M.; Melnychuk, D.; Merk, M.; Michielin, E.; Milanes, D. A.; Minard, M.-N.; Mitzel, D. S.; Molina Rodriguez, J.; Monroy, I. A.; Monteil, S.; Morandin, M.; Morawski, P.; Mordà, A.; Morello, M. J.; Moron, J.; Morris, A. B.; Mountain, R.; Muheim, F.; Müller, D.; Müller, J.; Müller, K.; Müller, V.; Mussini, M.; Muster, B.; Naik, P.; Nakada, T.; Nandakumar, R.; Nandi, A.; Nasteva, I.; Needham, M.; Neri, N.; Neubert, S.; Neufeld, N.; Neuner, M.; Nguyen, A. D.; Nguyen, T. D.; Nguyen-Mau, C.; Niess, V.; Niet, R.; Nikitin, N.; Nikodem, T.; Novoselov, A.; O'Hanlon, D. P.; Oblakowska-Mucha, A.; Obraztsov, V.; Ogilvy, S.; Okhrimenko, O.; Oldeman, R.; Onderwater, C. J. G.; Osorio Rodrigues, B.; Otalora Goicochea, J. M.; Otto, A.; Owen, P.; Oyanguren, A.; Palano, A.; Palombo, F.; Palutan, M.; Panman, J.; Papanestis, A.; Pappagallo, M.; Pappalardo, L. L.; Pappenheimer, C.; Parkes, C.; Passaleva, G.; Patel, G. D.; Patel, M.; Patrignani, C.; Pearce, A.; Pellegrino, A.; Penso, G.; Pepe Altarelli, M.; Perazzini, S.; Perret, P.; Pescatore, L.; Petridis, K.; Petrolini, A.; Petruzzo, M.; Picatoste Olloqui, E.; Pietrzyk, B.; Pilař, T.; Pinci, D.; Pistone, A.; Piucci, A.; Playfer, S.; Plo Casasus, M.; Poikela, T.; Polci, F.; Poluektov, A.; Polyakov, I.; Polycarpo, E.; Popov, A.; Popov, D.; Popovici, B.; Potterat, C.; Price, E.; Price, J. D.; Prisciandaro, J.; Pritchard, A.; Prouve, C.; Pugatch, V.; Puig Navarro, A.; Punzi, G.; Qian, W.; Quagliani, R.; Rachwal, B.; Rademacker, J. H.; Rama, M.; Rangel, M. S.; Raniuk, I.; Rauschmayr, N.; Raven, G.; Redi, F.; Reichert, S.; Reid, M. M.; dos Reis, A. C.; Ricciardi, S.; Richards, S.; Rihl, M.; Rinnert, K.; Rives Molina, V.; Robbe, P.; Rodrigues, A. B.; Rodrigues, E.; Rodriguez Lopez, J. A.; Rodriguez Perez, P.; Roiser, S.; Romanovsky, V.; Romero Vidal, A.; W. Ronayne, J.; Rotondo, M.; Rouvinet, J.; Ruf, T.; Ruiz Valls, P.; Saborido Silva, J. J.; Sagidova, N.; Sail, P.; Saitta, B.; Salustino Guimaraes, V.; Sanchez Mayordomo, C.; Sanmartin Sedes, B.; Santacesaria, R.; Santamarina Rios, C.; Santimaria, M.; Santovetti, E.; Sarti, A.; Satriano, C.; Satta, A.; Saunders, D. M.; Savrina, D.; Schael, S.; Schiller, M.; Schindler, H.; Schlupp, M.; Schmelling, M.; Schmelzer, T.; Schmidt, B.; Schneider, O.; Schopper, A.; Schubiger, M.; Schune, M.-H.; Schwemmer, R.; Sciascia, B.; Sciubba, A.; Semennikov, A.; Sergi, A.; Serra, N.; Serrano, J.; Sestini, L.; Seyfert, P.; Shapkin, M.; Shapoval, I.; Shcheglov, Y.; Shears, T.; Shekhtman, L.; Shevchenko, V.; Shires, A.; Siddi, B. G.; Silva Coutinho, R.; Silva de Oliveira, L.; Simi, G.; Sirendi, M.; Skidmore, N.; Skwarnicki, T.; Smith, E.; Smith, E.; Smith, I. T.; Smith, J.; Smith, M.; Snoek, H.; Sokoloff, M. D.; Soler, F. J. P.; Soomro, F.; Souza, D.; Souza De Paula, B.; Spaan, B.; Spradlin, P.; Sridharan, S.; Stagni, F.; Stahl, M.; Stahl, S.; Stefkova, S.; Steinkamp, O.; Stenyakin, O.; Stevenson, S.; Stoica, S.; Stone, S.; Storaci, B.; Stracka, S.; Straticiuc, M.; Straumann, U.; Sun, L.; Sutcliffe, W.; Swientek, K.; Swientek, S.; Syropoulos, V.; Szczekowski, M.; Szczypka, P.; Szumlak, T.; T'Jampens, S.; Tayduganov, A.; Tekampe, T.; Teklishyn, M.; Tellarini, G.; Teubert, F.; Thomas, C.; Thomas, E.; van Tilburg, J.; Tisserand, V.; Tobin, M.; Todd, J.; Tolk, S.; Tomassetti, L.; Tonelli, D.; Topp-Joergensen, S.; Torr, N.; Tournefier, E.; Tourneur, S.; Trabelsi, K.; Tran, M. T.; Tresch, M.; Trisovic, A.; Tsaregorodtsev, A.; Tsopelas, P.; Tuning, N.; Ukleja, A.; Ustyuzhanin, A.; Uwer, U.; Vacca, C.; Vagnoni, V.; Valenti, G.; Vallier, A.; Vazquez Gomez, R.; Vazquez Regueiro, P.; Vázquez Sierra, C.; Vecchi, S.; van Veghel, M.; Velthuis, J. J.; Veltri, M.; Veneziano, G.; Vesterinen, M.; Viaud, B.; Vieira, D.; Vieites Diaz, M.; Vilasis-Cardona, X.; Vollhardt, A.; Volyanskyy, D.; Voong, D.; Vorobyev, A.; Vorobyev, V.; Voß, C.; de Vries, J. A.; Waldi, R.; Wallace, C.; Wallace, R.; Walsh, J.; Wandernoth, S.; Wang, J.; Ward, D. R.; Watson, N. K.; Websdale, D.; Weiden, A.; Whitehead, M.; Wilkinson, G.; Wilkinson, M.; Williams, M.; Williams, M. P.; Williams, M.; Williams, T.; Wilson, F. F.; Wimberley, J.; Wishahi, J.; Wislicki, W.; Witek, M.; Wormser, G.; Wotton, S. A.; Wright, S.; Wyllie, K.; Xie, Y.; Xu, Z.; Yang, Z.; Yu, J.; Yuan, X.; Yushchenko, O.; Zangoli, M.; Zavertyaev, M.; Zhang, L.; Zhang, Y.; Zhelezov, A.; Zhokhov, A.; Zhong, L.; Zhukov, V.; Zucchelli, S.

    2016-07-01

    The oscillation frequency, Δ m_d, of B^0 mesons is measured using semileptonic decays with a D^- or D^{*-} meson in the final state. The data sample corresponds to 3.0fb^{-1} of pp collisions, collected by the LHCb experiment at centre-of-mass energies √{s} = 7 and 8 TeV. A combination of the two decay modes gives Δ m_d = (505.0 ± 2.1 ± 1.0) ns^{-1}, where the first uncertainty is statistical and the second is systematic. This is the most precise single measurement of this parameter. It is consistent with the current world average and has similar precision.

  7. Application of frequency combs in the measurement of the refractive index of air

    SciTech Connect

    Zhang, J.; Lu, Z. H.; Menegozzi, B.; Wang, L. J.

    2006-08-15

    We report a new method in the precision measurement of the refractive index of air using a highly unbalanced Michelson interferometer with a femtosecond optical frequency comb as the light source. Standard dry air is filled into a 30 m multipass cell, serving as the long arm of the interferometer, while a short arm acts as the reference path. Both time and frequency domain interferograms are recorded to measure the refractive index of air. The deviation of our experimental results with Edlen's formula is 1.4x10{sup -9} at 800 nm. Our experiment has a standard error of 5.2x10{sup -9} at fixed parameters (pressure and temperature). This is achieved by putting the multipass cell into a temperature-stabilized box, and also by locking the interferometer path length with a He-Ne laser. We achieved a temperature stabilization of 0.8 mK for 25 h. This corresponds to 0.4 {mu}m multipass cell length change. The locking of the He-Ne interferometer enables us to achieve 7 nm path-length change outside the multipass cell. Combined with accurate measurement of temperature and pressure, we were able to achieve an accuracy of 7.7x10{sup -9}.

  8. Measurement of Resonant Frequencies and Modes of Freestanding Nanoparticle Monolayers

    NASA Astrophysics Data System (ADS)

    Kanjanaboos, Pongsakorn; Lin, Xiao-Min; Jaeger, Heinrich; Guest, Jeffrey

    2012-02-01

    We recently showed that freestanding membranes of ligated nanoparticles can be assembled in a one-step drying-mediated process [1]. These 10nm thin membranes can stretch over holes up to 100 microns in diameter and are supported by a substrate only along their outer edge, thereby freely suspending of the order of 100 million close-packed particles [2]. Previous work has focused on quasi-static mechanical properties [1-3]. Here we present the first investigation of the full dynamic response of freely suspended nanoparticle membranes, utilizing a high frequency laser interferometer with picometer sensitivity. This instrument allows us to rapidly measure the dynamical properties of freestanding nanoparticle monolayers for the first time including resonant frequencies, quality factors, and images of different modes.[4pt] [1] Klara E. Mueggenburg et al., ``Elastic membranes of close-packed nanoparticle arrays,'' Nature Materials 6, 656-660 (2007). [0pt] [2] Jinbo He et al., ``Fabrication and Mechanical properties of large-scale freestanding nanoparticle membranes,'' Small 6, 1449-1456 (2010).[0pt] [3] Pongsakorn Kanjanaboos et al., ``Strain Patterning and Direct Measurement of Poisson's Ratio in Nanoparticle Monolayer Sheets,'' Nano Letters 11, 2567-2571 (2011).

  9. Transportable cavity-stabilized laser system for optical carrier frequency transmission experiments.

    PubMed

    Parker, B; Marra, G; Johnson, L A M; Margolis, H S; Webster, S A; Wright, L; Lea, S N; Gill, P; Bayvel, P

    2014-12-10

    We report the design and performance of a transportable laser system at 1543 nm, together with its application as the source for a demonstration of optical carrier frequency transmission over 118 km of an installed dark fiber network. The laser system is based around an optical reference cavity featuring an elastic mounting that bonds the cavity to its support, enabling the cavity to be transported without additional clamping. The cavity exhibits passive fractional frequency insensitivity to vibration along the optical axis of 2.0×10(-11)  m(-1) s(2). With active fiber noise cancellation, the optical carrier frequency transmission achieves a fractional frequency instability, measured at the user end, of 2.6×10(-16) at 1 s, averaging down to below 3×10(-18) after 20,000 s. The fractional frequency accuracy of the transfer is better than 3×10(-18). This level of performance is sufficient for comparison of state-of-the-art optical frequency standards and is achieved in an urban fiber environment.

  10. Tunable mechanical monolithic sensor with interferometric readout for low frequency seismic noise measurement

    NASA Astrophysics Data System (ADS)

    Acernese, F.; De Rosa, R.; Giordano, G.; Romano, R.; Barone, F.

    2008-03-01

    This paper describes a mechanical monolithic sensor for geophysical applications developed at the University of Salerno. The instrument is basically a monolithic tunable folded pendulum, shaped with precision machining and electric-discharge-machining, that can be used both as seismometer and, in a force-feedback configuration, as accelerometer. The monolithic mechanical design and the introduction of laser interferometric techniques for the readout implementation make it a very compact instrument, very sensitive in the low-frequency seismic noise band, with a very good immunity to environmental noises. Many changes have been produced since last version (2007), mainly aimed to the improvement of the mechanics and of the optical readout of the instrument. In fact, we have developed and tested a prototype with elliptical hinges and mechanical tuning of the resonance frequency together with a laser optical lever and a new laser interferometer readout system. The theoretical sensitivity curve both for both laser optical lever and laser interferometric readouts, evaluated on the basis of suitable theoretical models, shows a very good agreement with the experimental measurements. Very interesting scientific result, for example, is that the measured natural resonance frequency of the instrument is 70 mHz with a Q = 140 in air without thermal stabilization, demonstrating the feasibility of a monolithic FP sensor with a natural resonance frequency of the order of mHz with a more refined mechanical tuning. Results on the readout system based on polarimetric homodyne Michelson interferometer is discussed.

  11. Fast stabilization of a CO{sub 2} laser for a frequency standard at 10 {mu}m

    SciTech Connect

    Pisani, M.Q.; Sassi, M.P.; Zucco, M.

    1994-12-31

    A CO{sub 2} laser has been frequency stabilized to an OsO{sub 4} transition with a control bandwidth of 10 kHz. The obtained spectral purity of the laser is 100 Hz. The realization of very accurate frequency standards and experiments of high resolution spectroscopy in the 10 {mu}m region are made possible by this source.

  12. Frequency measurement of THz waves by electro-optic sampling using Mach-Zehnder-modulator-based flat comb generator

    NASA Astrophysics Data System (ADS)

    Morohashi, Isao; Kirigaya, Mayu; Kaneko, Yuta; Katayama, Ikufumi; Sakamoto, Takahide; Sekine, Norihiko; Kasamatsu, Akifumi; Hosako, Iwao

    2016-02-01

    In the recent progress in terahertz (THz) devices, various kinds of source devices, such as resonant tunneling diodes, quantum cascade lasers and so forth, have been developed. Frequency measurement of THz radiations, which can operate in high speed and at room-temperature, is important for development of high-performance THz source devices. Recently, frequency measurement using optical combs are demonstrated by several groups. In these techniques, modelocked lasers (MLLs) are used for optical comb source, so that phase-locking techniques are required in order to stabilize the repetition frequency of the MLLs. On the other hand, a modulator-based optical comb generator has high accuracy and stability in the comb spacing, which is comparable to that of microwave signal driving the modulator. Thus it is suitable for frequency measurement of THz waves. In this paper, we demonstrated frequency measurement of THz waves using a Mach-Zehnder-modulator-based flat comb generator (MZ-FCG). The frequency measurement was carried out by an electro-optic (EO) sampling method, where an optical two-tone signal extracted from the optical comb generated by the MZ-FCG was used for the probe light. A 100 GHz signal generated by a W-band frequency multiplier and the probe beam collinearly traveled through an EO crystal, and beat signals between them were measured by a combination of a balanced photodetector and a spectrum analyzer. As a result, frequency measurement of the 100 GHz wave was successfully demonstrated, in which the linewidth of the beat signal was less than 1 Hz.

  13. Measurement of ciliary beat frequency using Doppler optical coherence tomography

    PubMed Central

    Lemieux, Bryan T.; Chen, Jason J.; Jing, Joseph; Chen, Zhongping; Wong, Brian J.F.

    2015-01-01

    1. Introduction Measuring ciliary beat frequency (CBF) is a technical challenge and difficult to perform in vivo. Doppler optical coherence tomography (D-OCT) is a mesoscopic non-contact imaging modality that provides high-resolution tomographic images and detects micromotion simultaneously in living tissues. Here we use D-OCT to measure CBF in ex vivo tissue as the first step toward translating this technology to clinical use. 2. Methods Fresh ex vivo samples of rabbit tracheal mucosa were imaged using both D-OCT and phase-contrast microscopy (n = 5). The D-OCT system was designed and built to specification in our lab (1310 nm swept source vertical-cavity surface-emitting laser (VCSEL), 6 μm axial resolution). The samples were placed in culture and incubated at 37°C. A fast Fourier transform was performed on the D-OCT signal recorded on the surface of the samples to gauge CBF. High-speed digital video of the epithelium recorded via phase-contrast microscopy was analyzed to confirm the CBF measurements. 3. Results The D-OCT system detected Doppler signal at the epithelial layer of ex vivo rabbit tracheal samples suggestive of ciliary motion. CBF was measured at 9.36 ± 1.22 Hz using D-OCT and 9.08 ± 0.48 Hz using phase-contrast microscopy. No significant differences were found between the two methods (p ≫ 0.05). 4. Conclusions D-OCT allows for the quantitative measurement of CBF without the need to resolve individual cilia. Furthermore, D-OCT technology can be incorporated into endoscopic platforms that allow clinicians to readily measure CBF in the office and provide a direct measurement of mucosal health. PMID:26136399

  14. 0. 04 Hz relative optical-frequency stability in a 1. 5. mu. m distributed-Bragg-reflector (DBR) laser

    SciTech Connect

    Ishida, O.; Toba, H. ); Tohmori, Y. )

    1989-12-01

    The optical frequency of a 1.5 {mu}m distributed-Bragg-reflector (DBR) laser is stabilized against that of a master laser by heterodyne-type frequency locking with a phase-locked loop (PLL). Despite its wide linewidth of 16 MHz, stable PLL operation with an optical hold-in range of 26 GHz is realized, and residual frequency fluctuations are reduced to 0.04 Hz at an averaging time of 500 s. The combination of DBR laser and PLL is, therefore, suitable for future frequency-controlled light sources. The offset error from the settled frequency caused by the band-limited beat spectrum is also discussed.

  15. Atomic vapor cells for chip-scale atomic clocks with improved long-term frequency stability.

    PubMed

    Knappe, S; Gerginov, V; Schwindt, P D D; Shah, V; Robinson, H G; Hollberg, L; Kitching, J

    2005-09-15

    A novel technique for microfabricating alkali atom vapor cells is described in which alkali atoms are evaporated into a micromachined cell cavity through a glass nozzle. A cell of interior volume 1 mm3, containing 87Rb and a buffer gas, was made in this way and integrated into an atomic clock based on coherent population trapping. A fractional frequency instability of 6 x 10(-12) at 1000 s of integration was measured. The long-term drift of the F=1, mF=0-->F=2, mF=0 hyperfine frequency of atoms in these cells is below 5 x 10(-11)/day.

  16. Short-term stability improvements of an optical frequency standard based on free Ca atoms

    NASA Astrophysics Data System (ADS)

    Sherman, Jeff; Oates, Chris

    2010-03-01

    Compared to optical frequency standards featuring trapped ions or atoms in optical lattices, the strength of a standard using freely expanding neutral calcium atoms is not ultimate accuracy but rather short-term stability and experimental simplicity. Recently, a fractional frequency instability of 4 x10-15 at 1 second was demonstrated for the Ca standard at 657 nm [1]. The short cycle time (˜2 ms) combined with only a moderate interrogation duty cycle (˜15 %) is thought to introduce excess, and potentially critically limiting technical noise due to the Dick effect---high-frequency noise on the laser oscillator is not averaged away but is instead down-sampled by aliasing. We will present results of two strategies employed to minimize this effect: the reduction of clock laser noise by filtering the master clock oscillator through a high-finesse optical cavity [2], and an optimization of the interrogation cycle to match our laser's noise spectrum.[4pt] [1] Oates et al., Optics Letters, 25(21), 1603--5 (2000)[0pt] [2] Nazarova et al., J. Opt. Soc. Am. B, 5(10), 1632--8 (2008)

  17. Gigahertz frequency comb offset stabilization based on supercontinuum generation in silicon nitride waveguides.

    PubMed

    Klenner, Alexander; Mayer, Aline S; Johnson, Adrea R; Luke, Kevin; Lamont, Michael R E; Okawachi, Yoshitomo; Lipson, Michal; Gaeta, Alexander L; Keller, Ursula

    2016-05-16

    Silicon nitride (Si3N4) waveguides represent a novel photonic platform that is ideally suited for energy efficient and ultrabroadband nonlinear interactions from the visible to the mid-infrared. Chip-based supercontinuum generation in Si3N4 offers a path towards a fully-integrated and highly compact comb source for sensing and time-and-frequency metrology applications. We demonstrate the first successful frequency comb offset stabilization that utilizes a Si3N4 waveguide for octave-spanning supercontinuum generation and achieve the lowest integrated residual phase noise of any diode-pumped gigahertz laser comb to date. In addition, we perform a direct comparison to a standard silica photonic crystal fiber (PCF) using the same ultrafast solid-state laser oscillator operating at 1 µm. We identify the minimal role of Raman scattering in Si3N4 as a key benefit that allows to overcome the fundamental limitations of silica fibers set by Raman-induced self-frequency shift. PMID:27409927

  18. Measurement of bone conduction levels for high frequencies.

    PubMed

    Lenhardt, Martin L; Richards, Douglas G; Madsen, Alan G; Goldstein, Barbara A; Shulman, Abraham; Guinta, Robert

    2002-01-01

    For assessment of safety, it is necessary to measure the maximum possible force exerted by a bone conduction device coupled to the human head. Calibration of bone conduction hearing aids and vibrators in the audiometric range is based on measurement of acceleration and force using an artificial mastoid. Extending the measurement to the high audio range was accomplished using a live head. To assess safety of the UltraQuiet tinnitus treatment system, as an example, acceleration was measured from 5 to 20 kHz on a live human head as compared with calibrated levels at 6 kHz on an artificial mastoid and the live head. Using head acceleration and anchoring it to established calibration levels is a means of establishing clinical safety. Stimulation in the high audio frequencies at low levels was found to be safe. In contrast, stimulation with ultrasound requires more energy (approximately 75-90 dB re 6 kHz), which may increase the risk of damage to the car.

  19. Measurement of tumor oxygenation using new frequency domain phosphorometers.

    PubMed

    Wilson, David F; Vinogradov, Sergei A; Dugan, Benjamin W; Biruski, Dubravko; Waldron, Lee; Evans, Sydney A

    2002-05-01

    Oxygen dependent quenching of phosphorescence allows for non-invasive measurements of oxygen in tissue. We have designed and constructed a novel multi-frequency instrument for measurement of phosphorescence lifetimes and developed algorithms for determining the distribution of oxygen (oxygen histogram) in the microvasculature of tissue with good temporal resolution (Vinogradov et al., 2002, Compar. Biochem. A, these proceedings). This technology, in combination with a new water soluble near infra red phosphor (Oxyphor G2), was used to examine the oxygenation of subcutaneous Q7 tumors grown on the flank of Buffalo rats and their response to giving the rats oxygen or carbogen to breathe. Phosphorescence was measured using excitation at 635 nm and emission at >700 nm (the phosphorescence maximum is near 800 nm). The excitation and collection light guides were placed on the surface of the skin of the anesthetized animals separated by approximately 0.8 cm. A 6 x 6 or 7 x 7 grid (approx. 4 cm x 4 cm) was drawn on the flank and oxygen histograms were measured in each square, providing 'images' of the oxygen distribution in the tissue. This procedure determines the tissue oxygen distribution at each position in the grid. Regions of relative hypoxia (associated with the tumor) can be readily localized and the extent of hypoxia quantitatively evaluated.

  20. Using Accelerometer and Gyroscopic Measures to Quantify Postural Stability

    PubMed Central

    Alberts, Jay L.; Hirsch, Joshua R.; Koop, Mandy Miller; Schindler, David D.; Kana, Daniel E.; Linder, Susan M.; Campbell, Scott; Thota, Anil K.

    2015-01-01

    Context Force platforms and 3-dimensional motion-capture systems provide an accurate method of quantifying postural stability. Substantial cost, space, time to administer, and need for trained personnel limit widespread use of biomechanical techniques in the assessment of postural stability in clinical or field environments. Objective To determine whether accelerometer and gyroscope data sampled from a consumer electronics device (iPad2) provide sufficient resolution of center-of-gravity (COG) movements to accurately quantify postural stability in healthy young people. Design Controlled laboratory study. Setting Research laboratory in an academic medical center. Patients or Other Participants A total of 49 healthy individuals (age = 19.5 ± 3.1 years, height = 167.7 ± 13.2 cm, mass = 68.5 ± 17.5 kg). Intervention(s) Participants completed the NeuroCom Sensory Organization Test (SOT) with an iPad2 affixed at the sacral level. Main Outcome Measure(s) Primary outcomes were equilibrium scores from both systems and the time series of the angular displacement of the anteroposterior COG sway during each trial. A Bland-Altman assessment for agreement was used to compare equilibrium scores produced by the NeuroCom and iPad2 devices. Limits of agreement was defined as the mean bias (NeuroCom − iPad) ± 2 standard deviations. Mean absolute percentage error and median difference between the NeuroCom and iPad2 measurements were used to evaluate how closely the real-time COG sway measured by the 2 systems tracked each other. Results The limits between the 2 devices ranged from −0.5° to 0.5° in SOT condition 1 to −2.9° to 1.3° in SOT condition 5. The largest absolute value of the measurement error within the 95% confidence intervals for all conditions was 2.9°. The mean absolute percentage error analysis indicated that the iPad2 tracked NeuroCom COG with an average error ranging from 5.87% to 10.42% of the NeuroCom measurement across SOT conditions. Conclusions The i

  1. Spherical aberration standards and measurement system stability over time

    NASA Astrophysics Data System (ADS)

    Compertore, David; Ignatovich, Filipp; Marcus, Michael

    2015-10-01

    A Shack-Hartmann wave-front sensor system has been used to measure a set of plano-convex lenses at two different times, separated by almost 2 years. The plano-convex lenses were selected to cover a range of powers and apertures relevant to intraocular lenses, and were measured at two different orientations. The results demonstrate the high temporal stability of the measurement system, as well as of the glass standard. In addition, both times the effective focal lengths of the standards were measured using a NIST traceable nodal slide bench, and the center thicknesses were measured using low-coherence interferometer. The spherical aberration and the effective focal length results are analyzed for statistically significant changes. The results are also compared to the Zemax models of the standards.

  2. The stability of H/V spectral ratios from noise measurements in Armutlu Peninsula (Turkey)

    NASA Astrophysics Data System (ADS)

    Livaoǧlu, Hamdullah; Irmak, T. Serkan; Caka, Deniz; Yavuz, Evrim; Lühr, B. G.; Woith, H.; Tunç, B.; Baris, S.

    2016-04-01

    The horizontal to vertical spectral ratio (H/V) method has been successfully using in order to estimate the fundamental resonance frequency of the sedimentary cover, its thickness and amplification factor since at least 3 decades. There are numerous studies have been carried out on the stability of the H/V spectral ratios. Almost all studies showed that fundamental frequency is stable even measurements are repeated at different times. From this point of view, the results will show us an approach whether the stations are suitable for accurate estimate of earthquake studies and engineering purposes or not. Also we want to see if any effects of the amplification factor changing on the seismograms for Armutlu Seismic Network (ARNET) even though seismic stations are established far away from cultural noise and located on hard rock sites. It has been selected one hour recorded data of all stations during the most stationary times. The amplification and resonant frequency variations of H/V ratio were calculated to investigate temporal stability in time. There is a total harmony in fundamental frequencies values and H/V spectral ratio values in time-lagged periods. Some stations shows secondary minor peaks in high frequency band due to a shallow formation effect or cultural noises around. In the east side of the area ILYS station shows amplitude peak in lower fundamental frequency band from expected. This could compose a high amplification in lower frequencies and so that yield less reliable results in local earthquakes studies. By the experimental results from ambient noise analysis, it could be worked up for relocation of one station.

  3. Transient Stability and Frequency Response of the US Western Interconnection Under Conditions of High Wind and Solar Generation

    SciTech Connect

    Miller, Nicholas W.; Shao, Miaolei; Pajic, Slobodan; D'Aquila, Robert; Clark, Kara

    2014-11-13

    The addition of large amounts of wind and solar generation to bulk power systems that are traditionally subject to operating constraints set by transient stability and frequency response limitations is the subject of considerable concern in the industry. The US Western Interconnection (WI) is expected to experience substantial additional growth in both wind and solar generation. These plants will, to some extent, displace large central station thermal generation, both coal and gas-fired, which have traditionally helped maintain stability. This paper reports the results of a study that investigated the transient stability and frequency response of the WI with high penetrations of wind and solar generation. The main goals of this work were to (1) create a realistic, baseline model of the WI, (2) test selected transient stability and frequency events, (3) investigate the impact of large amounts of wind and solar generation, and (4) examine means to improve performance.

  4. Transient Stability and Frequency Response of the US Western Interconnection under conditions of High Wind and Solar Generation

    SciTech Connect

    Clark, Kara; Miller, Nicholas W.; Shao, Miaolei; Pajic, Slobodan; D'Aquila, Robert

    2015-04-15

    Adding large amounts of wind and solar generation to bulk power systems that are traditionally subject to operating constraints set by transient stability and frequency response limitations is the subject of considerable concern in the industry. The US Western Interconnection (WI) is expected to experience substantial additional growth in both wind and solar generation. These plants will, to some extent, displace large central station thermal generation, both coal and gas-fired, which have traditionally helped maintain stability. Our paper reports the results of a study that investigated the transient stability and frequency response of the WI with high penetrations of wind and solar generation. Moreover, the main goals of this work were to (1) create a realistic, baseline model of the WI, (2) test selected transient stability and frequency events, (3) investigate the impact of large amounts of wind and solar generation, and (4) examine means to improve performance.

  5. Modulation-free laser frequency stabilization to a saturated sub-Doppler spectral line in a transversal magnetic field

    NASA Astrophysics Data System (ADS)

    Okubo, Sho; Iwakuni, Kana; Hasegawa, Taro

    2012-09-01

    We demonstrate frequency stabilization of a modulation-free laser to a saturated absorption spectral line of atoms in a transversal magnetic field. This stabilization scheme has been proposed for wide capture range in comparison with the dichroic atomic vapor laser lock (DAVLL) scheme and demonstrated for a Doppler-broadened spectral line in J. Opt. Soc. Am. B, 26, 1216 (2009). In this paper, a 1083-nm external-cavity laser diode is frequency-stabilized to the sub-Doppler spectral line of helium transition (23S1,mJ=0↔23P0). Even though the error signal shape strongly depends on the pump beam polarization, the stabilized frequency is expected to be insensitive to the pump beam polarization.

  6. Precise measurement of dielectric properties at frequencies from 1 kHz to 100 MHz

    NASA Astrophysics Data System (ADS)

    Kakimoto, Akira; Etoh, Akihiro; Hirano, Kaoru; Nonaka, Satoshi

    1987-02-01

    This paper describes an improved apparatus to measure dielectric constants and dissipation factors using a resonance technique. The measurements can be made rapidly and accurately without appreciable systematic error in the wide frequency range from 1 kHz to 100 MHz. This apparatus uses the half power-gap variation method or the half power-varying gap-immersion method for solid-plate specimens and the solid-plate displacement method for liquid specimens. The electrode system is 30 mm in diameter and has a shield ring to avoid the edge capacitance effect, guards against surface current leakage, and variable air capacitors to set the electrode gap at any arbitrary value. To detect a very small power loss, the resonance voltages in circuits with Q≂100 are stabilized to -86 dB at a constant ambient temperature. We use phase detectors so that the electrode gap and the voltage at resonance can easily be read from the digital panel meter and the digital voltmeter. No corrections are necessary even at a high frequency of 100 MHz. The accuracy of measurements made using the half power-varying gap-immersion method is within 0.2% for the dielectric constant and 3% for the dissipation factor without marked degradation over the entire frequency range.

  7. Frequency stabilization of the zero-phonon line of a quantum dot via phonon-assisted active feedback

    SciTech Connect

    Hansom, Jack; Schulte, Carsten H. H.; Matthiesen, Clemens; Stanley, Megan J.; Atatüre, Mete

    2014-10-27

    We report on the feedback stabilization of the zero-phonon emission frequency of a single InAs quantum dot. The spectral separation of the phonon-assisted component of the resonance fluorescence provides a probe of the detuning between the zero-phonon transition and the resonant driving laser. Using this probe in combination with active feedback, we stabilize the zero-phonon transition frequency against environmental fluctuations. This protocol reduces the zero-phonon fluorescence intensity noise by a factor of 22 by correcting for environmental noise with a bandwidth of 191 Hz, limited by the experimental collection efficiency. The associated sub-Hz fluctuations in the zero-phonon central frequency are reduced by a factor of 7. This technique provides a means of stabilizing the quantum dot emission frequency without requiring access to the zero-phonon emission.

  8. Frequency stabilization of a 1083 nm fiber laser to {sup 4}He transition lines with optical heterodyne saturation spectroscopies

    SciTech Connect

    Gong, W.; Peng, X. Li, W.; Guo, H.

    2014-07-15

    Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable {sup 4}He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to its flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10{sup −12}@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.

  9. Frequency stabilization of a 1083 nm fiber laser to 4He transition lines with optical heterodyne saturation spectroscopies

    NASA Astrophysics Data System (ADS)

    Gong, W.; Peng, X.; Li, W.; Guo, H.

    2014-07-01

    Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable 4He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to its flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10-12@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.

  10. An approach to measure wheelchair stability. Concept and benefits.

    PubMed

    Stefanov, Dimitar H; Pasco, Damien

    2014-01-01

    Wheelchair stability is dependent on user's body characteristics that can shift significantly the original center of mass in the cases of limb amputation, severe skeletal deformities or obesity. The center of gravity may change with the installation of additional devices such as oxygen cylinders or ventilators on the wheelchair. Therefore, quantitative evaluation and prediction of the behavior of the user-wheelchair system in a variety of static and dynamic situations is essential for user's safety and for the optimal tuning of the human-wheelchair system. In this paper we discuss an approach for wheelchair stability assessment that only requires two inclinations and weight measurements. We also discuss the algorithm associated to the procedure based on the use of the reaction forces in the contact points of the wheels measured by the load cells. Further, the paper includes an analysis of the influence of the errors in measurement of the input parameters on the output results and demonstrates that the proposed approach possesses high accuracy. The advantage of the proposed approach is the use of a reliable procedure based on three simple steps and five weight measurements with four independent load scales which may lead to the design of an affordable and accurate measurement system.

  11. On-orbit frequency stability analysis of the GPS NAVSTAR-1 quartz clock and the NAVSTARs-6 and -8 rubidium clocks

    NASA Technical Reports Server (NTRS)

    Mccaskill, T. B.; Buisson, J. A.; Reid, W. G.

    1984-01-01

    An on-orbit frequency stability performance analysis of the GPS NAVSTAR-1 quartz clock and the NAVSTARs-6 and -8 rubidium clocks is presented. The clock offsets were obtained from measurements taken at the GPS monitor stations which use high performance cesium standards as a reference. Clock performance is characterized through the use of the Allan variance, which is evaluated for sample times of 15 minutes to two hours, and from one day to 10 days. The quartz and rubidium clocks' offsets were corrected for aging rate before computing the frequency stability. The effect of small errors in aging rate is presented for the NAVSTAR-8 rubidium clock's stability analysis. The analysis includes presentation of time and frequency residuals with respect to linear and quadratic models, which aid in obtaining aging rate values and identifying systematic and random effects. The frequency stability values were further processed with a time domain noise process analysis, which is used to classify random noise process and modulation type.

  12. Measuring amplitudes of harmonics and combination frequencies in variable stars

    NASA Astrophysics Data System (ADS)

    Bellinger, E. P.; Wysocki, D.; Kanbur, S. M.

    2016-05-01

    Discoveries of RR Lyrae and Cepheid variable stars with multiple modes of pulsation have increased tremendously in recent years. The Fourier spectra of these stars can be quite complicated due to the large number of combination frequencies that can exist between their modes. As a result, light- curve fits to these stars often suffer from undesirable ringing effects that arise from noisy observations and poor phase coverage. These non-physical overfitting artifacts also occur when fitting the harmonics of single-mode stars. Here we present a new method for fitting light curves that is much more robust against these effects. We prove that the amplitude measurement problem is very difficult (NP-hard) and provide a heuristic algorithm for solving it quickly and accurately.

  13. Spectroscopic measurements of high frequency plasma in supercritical carbon dioxide

    SciTech Connect

    Maehara, T.; Mukasa, S.; Takemori, T.; Watanabe, T.; Kurokawa, K.; Toyota, H.; Nomura, S.; Kawashima, A.; Iwamae, A.

    2009-03-15

    Spectroscopic measurements of high frequency (hf) plasma were performed under high pressure conditions (5 and 7 MPa) and supercritical (sc) CO{sub 2} conditions (8-20 MPa). Temperature evaluated from C{sub 2} Swan bands (d {sup 3}{pi}{sub g}{yields}a {sup 3}{pi}{sub u}) increased from 3600 to 4600 K with an increase in pressure. The first observation of broadening and shifting of the O I line profile (3p {sup 5} P{sub 3,2,1}{yields}3s {sup 5} S{sub 2}{sup 0}) of hf plasma under sc CO{sub 2} conditions was carried out. However, the origin of broadening and the shifting cannot be understood because the present theory explaining them is not valid for such high pressure conditions.

  14. Measurement of the Bs0-Bs0 oscillation frequency.

    PubMed

    Abulencia, A; Acosta, D; Adelman, J; Affolder, T; Akimoto, T; Albrow, M G; Ambrose, D; Amerio, S; Amidei, D; Anastassov, A; Anikeev, K; Annovi, A; Antos, J; Aoki, M; Apollinari, G; Arguin, J-F; Arisawa, T; Artikov, A; Ashmanskas, W; Attal, A; Azfar, F; Azzi-Bacchetta, P; Azzurri, P; Bacchetta, N; Bachacou, H; Badgett, W; Barbaro-Galtieri, A; Barnes, V E; Barnett, B A; Baroiant, S; Bartsch, V; Bauer, G; Bedeschi, F; Behari, S; Belforte, S; Bellettini, G; Bellinger, J; Belloni, A; Ben Haim, E; Benjamin, D; Beretvas, A; Beringer, J; Berry, T; Bhatti, A; Binkley, M; Bisello, D; Blair, R E; Blocker, C; Blumenfeld, B; Bocci, A; Bodek, A; Boisvert, V; Bolla, G; Bolshov, A; Bortoletto, D; Boudreau, J; Boveia, A; Brau, B; Bromberg, C; Brubaker, E; Budagov, J; Budd, H S; Budd, S; Burkett, K; Busetto, G; Bussey, P; Byrum, K L; Cabrera, S; Campanelli, M; Campbell, M; Canelli, F; Canepa, A; Carlsmith, D; Carosi, R; Carron, S; Casal, B; Casarsa, M; Castro, A; Catastini, P; Cauz, D; Cavalli-Sforza, M; Cerri, A; Cerrito, L; Chang, S H; Chapman, J; Chen, Y C; Chertok, M; Chiarelli, G; Chlachidze, G; Chlebana, F; Cho, I; Cho, K; Chokheli, D; Chou, J P; Chu, P H; Chuang, S H; Chung, K; Chung, W H; Chung, Y S; Ciljak, M; Ciobanu, C I; Ciocci, M A; Clark, A; Clark, D; Coca, M; Compostella, G; Convery, M E; Conway, J; Cooper, B; Copic, K; Cordelli, M; Cortiana, G; Crescioli, F; Cruz, A; Cuenca Almenar, C; Cuevas, J; Culbertson, R; Cyr, D; DaRonco, S; D'Auria, S; D'Onofrio, M; Dagenhart, D; de Barbaro, P; De Cecco, S; Deisher, A; De Lentdecker, G; Dell'Orso, M; Delli Paoli, F; Demers, S; Demortier, L; Deng, J; Deninno, M; De Pedis, D; Derwent, P F; Di Giovanni, G P; Di Ruzza, B; Dionisi, C; Dittmann, J R; DiTuro, P; Dörr, C; Donati, S; Donega, M; Dong, P; Donini, J; Dorigo, T; Dube, S; Ebina, K; Efron, J; Ehlers, J; Erbacher, R; Errede, D; Errede, S; Eusebi, R; Fang, H C; Farrington, S; Fedorko, I; Fedorko, W T; Feild, R G; Feindt, M; Fernandez, J P; Field, R; Flanagan, G; Flores-Castillo, L R; Foland, A; Forrester, S; Foster, G W; Franklin, M; Freeman, J C; Frisch, H J; Furic, I; Gallinaro, M; Galyardt, J; Garcia, J E; Garcia Sciveres, M; Garfinkel, A F; Gay, C; Gerberich, H; Gerdes, D; Giagu, S; Giannetti, P; Gibson, A; Gibson, K; Ginsburg, C; Giokaris, N; Giolo, K; Giordani, M; Giromini, P; Giunta, M; Giurgiu, G; Glagolev, V; Glenzinski, D; Gold, M; Goldschmidt, N; Goldstein, J; Gomez, G; Gomez-Ceballos, G; Goncharov, M; González, O; Gorelov, I; Goshaw, A T; Gotra, Y; Goulianos, K; Gresele, A; Griffiths, M; Grinstein, S; Grosso-Pilcher, C; Group, R C; Grundler, U; Guimaraes da Costa, J; Gunay-Unalan, Z; Haber, C; Hahn, S R; Hahn, K; Halkiadakis, E; Hamilton, A; Han, B-Y; Han, J Y; Handler, R; Happacher, F; Hara, K; Hare, M; Harper, S; Harr, R F; Harris, R M; Hatakeyama, K; Hauser, J; Hays, C; Heijboer, A; Heinemann, B; Heinrich, J; Herndon, M; Hidas, D; Hill, C S; Hirschbuehl, D; Hocker, A; Holloway, A; Hou, S; Houlden, M; Hsu, S-C; Huffman, B T; Hughes, R E; Huston, J; Incandela, J; Introzzi, G; Iori, M; Ishizawa, Y; Ivanov, A; Iyutin, B; James, E; Jang, D; Jayatilaka, B; Jeans, D; Jensen, H; Jeon, E J; Jindariani, S; Jones, M; Joo, K K; Jun, S Y; Junk, T R; Kamon, T; Kang, J; Karchin, P E; Kato, Y; Kemp, Y; Kephart, R; Kerzel, U; Khotilovich, V; Kilminster, B; Kim, D H; Kim, H S; Kim, J E; Kim, M J; Kim, S B; Kim, S H; Kim, Y K; Kirsch, L; Klimenko, S; Klute, M; Knuteson, B; Ko, B R; Kobayashi, H; Kondo, K; Kong, D J; Konigsberg, J; Korytov, A; Kotwal, A V; Kovalev, A; Kraan, A; Kraus, J; Kravchenko, I; Kreps, M; Kroll, J; Krumnack, N; Kruse, M; Krutelyov, V; Kuhlmann, S E; Kusakabe, Y; Kwang, S; Laasanen, A T; Lai, S; Lami, S; Lammel, S; Lancaster, M; Lander, R L; Lannon, K; Lath, A; Latino, G; Lazzizzera, I; LeCompte, T; Lee, J; Lee, J; Lee, Y J; Lee, S W; Lefèvre, R; Leonardo, N; Leone, S; Levy, S; Lewis, J D; Lin, C; Lin, C S; Lindgren, M; Lipeles, E; Liss, T M; Lister, A; Litvintsev, D O; Liu, T; Lockyer, N S; Loginov, A; Loreti, M; Loverre, P; Lu, R-S; Lucchesi, D; Lujan, P; Lukens, P; Lungu, G; Lyons, L; Lys, J; Lysak, R; Lytken, E; Mack, P; MacQueen, D; Madrak, R; Maeshima, K; Maki, T; Maksimovic, P; Malde, S; Manca, G; Margaroli, F; Marginean, R; Marino, C; Martin, A; Martin, V; Martínez, M; Maruyama, T; Mastrandrea, P; Matsunaga, H; Mattson, M E; Mazini, R; Mazzanti, P; McFarland, K S; McIntyre, P; McNulty, R; Mehta, A; Menzemer, S; Menzione, A; Merkel, P; Mesropian, C; Messina, A; von der Mey, M; Miao, T; Miladinovic, N; Miles, J; Miller, R; Miller, J S; Mills, C; Milnik, M; Miquel, R; Mitra, A; Mitselmakher, G; Miyamoto, A; Moggi, N; Mohr, B; Moore, R; Morello, M; Movilla Fernandez, P; Mülmenstädt, J; Mukherjee, A; Muller, Th; Mumford, R; Murat, P; Nachtman, J; Naganoma, J; Nahn, S; Nakano, I; Napier, A; Naumov, D; Necula, V; Neu, C; Neubauer, M S; Nielsen, J; Nigmanov, T; Nodulman, L; Norniella, O; Nurse, E; Ogawa, T; Oh, S H; Oh, Y D; Okusawa, T; Oldeman, R; Orava, R; Osterberg, K; Pagliarone, C; Palencia, E; Paoletti, R; Papadimitriou, V; Paramonov, A A; Parks, B; Pashapour, S; Patrick, J; Pauletta, G; Paulini, M; Paus, C; Pellett, D E; Penzo, A; Phillips, T J; Piacentino, G; Piedra, J; Pinera, L; Pitts, K; Plager, C; Pondrom, L; Portell, X; Poukhov, O; Pounder, N; Prakoshyn, F; Pronko, A; Proudfoot, J; Ptohos, F; Punzi, G; Pursley, J; Rademacker, J; Rahaman, A; Rakitin, A; Rappoccio, S; Ratnikov, F; Reisert, B; Rekovic, V; van Remortel, N; Renton, P; Rescigno, M; Richter, S; Rimondi, F; Ristori, L; Robertson, W J; Robson, A; Rodrigo, T; Rogers, E; Rolli, S; Roser, R; Rossi, M; Rossin, R; Rott, C; Ruiz, A; Russ, J; Rusu, V; Saarikko, H; Sabik, S; Safonov, A; Sakumoto, W K; Salamanna, G; Saltó, O; Saltzberg, D; Sanchez, C; Santi, L; Sarkar, S; Sartori, L; Sato, K; Savard, P; Savoy-Navarro, A; Scheidle, T; Schlabach, P; Schmidt, E E; Schmidt, M P; Schmitt, M; Schwarz, T; Scodellaro, L; Scott, A L; Scribano, A; Scuri, F; Sedov, A; Seidel, S; Seiya, Y; Semenov, A; Sexton-Kennedy, L; Sfiligoi, I; Shapiro, M D; Shears, T; Shepard, P F; Sherman, D; Shimojima, M; Shochet, M; Shon, Y; Shreyber, I; Sidoti, A; Sinervo, P; Sisakyan, A; Sjolin, J; Skiba, A; Slaughter, A J; Sliwa, K; Smith, J R; Snider, F D; Snihur, R; Soderberg, M; Soha, A; Somalwar, S; Sorin, V; Spalding, J; Spezziga, M; Spinella, F; Spreitzer, T; Squillacioti, P; Stanitzki, M; Staveris-Polykalas, A; St Denis, R; Stelzer, B; Stelzer-Chilton, O; Stentz, D; Strologas, J; Stuart, D; Suh, J S; Sukhanov, A; Sumorok, K; Sun, H; Suzuki, T; Taffard, A; Takashima, R; Takeuchi, Y; Takikawa, K; Tanaka, M; Tanaka, R; Tanimoto, N; Tecchio, M; Teng, P K; Terashi, K; Tether, S; Thom, J; Thompson, A S; Thomson, E; Tipton, P; Tiwari, V; Tkaczyk, S; Toback, D; Tokar, S; Tollefson, K; Tomura, T; Tonelli, D; Tönnesmann, M; Torre, S; Torretta, D; Tourneur, S; Trischuk, W; Tsuchiya, R; Tsuno, S; Turini, N; Ukegawa, F; Unverhau, T; Uozumi, S; Usynin, D; Vaiciulis, A; Vallecorsa, S; Varganov, A; Vataga, E; Velev, G; Veramendi, G; Veszpremi, V; Vidal, R; Vila, I; Vilar, R; Vine, T; Vollrath, I; Volobouev, I; Volpi, G; Würthwein, F; Wagner, P; Wagner, R G; Wagner, R L; Wagner, W; Wallny, R; Walter, T; Wan, Z; Wang, S M; Warburton, A; Waschke, S; Waters, D; Wester, W C; Whitehouse, B; Whiteson, D; Wicklund, A B; Wicklund, E; Williams, G; Williams, H H; Wilson, P; Winer, B L; Wittich, P; Wolbers, S; Wolfe, C; Wright, T; Wu, X; Wynne, S M; Yagil, A; Yamamoto, K; Yamaoka, J; Yamashita, T; Yang, C; Yang, U K; Yang, Y C; Yao, W M; Yeh, G P; Yoh, J; Yorita, K; Yoshida, T; Yu, G B; Yu, I; Yu, S S; Yun, J C; Zanello, L; Zanetti, A; Zaw, I; Zetti, F; Zhang, X; Zhou, J; Zucchelli, S

    2006-08-11

    We present the first precise measurement of the Bs0-Bs0 oscillation frequency Deltams. We use 1 fb-1 of data from pp collisions at sqrts=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. The sample contains signals of 3600 fully reconstructed hadronic Bs decays and 37,000 partially reconstructed semileptonic Bs decays. We measure the probability as a function of proper decay time that the Bs decays with the same, or opposite, flavor as the flavor at production, and we find a signal consistent with Bs0-Bs0 oscillations. The probability that random fluctuations could produce a comparable signal is 0.2%. Under the hypothesis that the signal is due to Bs0-Bs0 oscillations, we measure Deltams=17.31(-0.18)+0.33(stat)+/-0.07(syst) ps-1 and determine |Vtd/Vts|=0.208(-0.002)+0.001(expt)-0.006(+0.008)(theor).

  15. Measurement of the Bs0-Bs0 oscillation frequency.

    PubMed

    Abulencia, A; Acosta, D; Adelman, J; Affolder, T; Akimoto, T; Albrow, M G; Ambrose, D; Amerio, S; Amidei, D; Anastassov, A; Anikeev, K; Annovi, A; Antos, J; Aoki, M; Apollinari, G; Arguin, J-F; Arisawa, T; Artikov, A; Ashmanskas, W; Attal, A; Azfar, F; Azzi-Bacchetta, P; Azzurri, P; Bacchetta, N; Bachacou, H; Badgett, W; Barbaro-Galtieri, A; Barnes, V E; Barnett, B A; Baroiant, S; Bartsch, V; Bauer, G; Bedeschi, F; Behari, S; Belforte, S; Bellettini, G; Bellinger, J; Belloni, A; Ben Haim, E; Benjamin, D; Beretvas, A; Beringer, J; Berry, T; Bhatti, A; Binkley, M; Bisello, D; Blair, R E; Blocker, C; Blumenfeld, B; Bocci, A; Bodek, A; Boisvert, V; Bolla, G; Bolshov, A; Bortoletto, D; Boudreau, J; Boveia, A; Brau, B; Bromberg, C; Brubaker, E; Budagov, J; Budd, H S; Budd, S; Burkett, K; Busetto, G; Bussey, P; Byrum, K L; Cabrera, S; Campanelli, M; Campbell, M; Canelli, F; Canepa, A; Carlsmith, D; Carosi, R; Carron, S; Casal, B; Casarsa, M; Castro, A; Catastini, P; Cauz, D; Cavalli-Sforza, M; Cerri, A; Cerrito, L; Chang, S H; Chapman, J; Chen, Y C; Chertok, M; Chiarelli, G; Chlachidze, G; Chlebana, F; Cho, I; Cho, K; Chokheli, D; Chou, J P; Chu, P H; Chuang, S H; Chung, K; Chung, W H; Chung, Y S; Ciljak, M; Ciobanu, C I; Ciocci, M A; Clark, A; Clark, D; Coca, M; Compostella, G; Convery, M E; Conway, J; Cooper, B; Copic, K; Cordelli, M; Cortiana, G; Crescioli, F; Cruz, A; Cuenca Almenar, C; Cuevas, J; Culbertson, R; Cyr, D; DaRonco, S; D'Auria, S; D'Onofrio, M; Dagenhart, D; de Barbaro, P; De Cecco, S; Deisher, A; De Lentdecker, G; Dell'Orso, M; Delli Paoli, F; Demers, S; Demortier, L; Deng, J; Deninno, M; De Pedis, D; Derwent, P F; Di Giovanni, G P; Di Ruzza, B; Dionisi, C; Dittmann, J R; DiTuro, P; Dörr, C; Donati, S; Donega, M; Dong, P; Donini, J; Dorigo, T; Dube, S; Ebina, K; Efron, J; Ehlers, J; Erbacher, R; Errede, D; Errede, S; Eusebi, R; Fang, H C; Farrington, S; Fedorko, I; Fedorko, W T; Feild, R G; Feindt, M; Fernandez, J P; Field, R; Flanagan, G; Flores-Castillo, L R; Foland, A; Forrester, S; Foster, G W; Franklin, M; Freeman, J C; Frisch, H J; Furic, I; Gallinaro, M; Galyardt, J; Garcia, J E; Garcia Sciveres, M; Garfinkel, A F; Gay, C; Gerberich, H; Gerdes, D; Giagu, S; Giannetti, P; Gibson, A; Gibson, K; Ginsburg, C; Giokaris, N; Giolo, K; Giordani, M; Giromini, P; Giunta, M; Giurgiu, G; Glagolev, V; Glenzinski, D; Gold, M; Goldschmidt, N; Goldstein, J; Gomez, G; Gomez-Ceballos, G; Goncharov, M; González, O; Gorelov, I; Goshaw, A T; Gotra, Y; Goulianos, K; Gresele, A; Griffiths, M; Grinstein, S; Grosso-Pilcher, C; Group, R C; Grundler, U; Guimaraes da Costa, J; Gunay-Unalan, Z; Haber, C; Hahn, S R; Hahn, K; Halkiadakis, E; Hamilton, A; Han, B-Y; Han, J Y; Handler, R; Happacher, F; Hara, K; Hare, M; Harper, S; Harr, R F; Harris, R M; Hatakeyama, K; Hauser, J; Hays, C; Heijboer, A; Heinemann, B; Heinrich, J; Herndon, M; Hidas, D; Hill, C S; Hirschbuehl, D; Hocker, A; Holloway, A; Hou, S; Houlden, M; Hsu, S-C; Huffman, B T; Hughes, R E; Huston, J; Incandela, J; Introzzi, G; Iori, M; Ishizawa, Y; Ivanov, A; Iyutin, B; James, E; Jang, D; Jayatilaka, B; Jeans, D; Jensen, H; Jeon, E J; Jindariani, S; Jones, M; Joo, K K; Jun, S Y; Junk, T R; Kamon, T; Kang, J; Karchin, P E; Kato, Y; Kemp, Y; Kephart, R; Kerzel, U; Khotilovich, V; Kilminster, B; Kim, D H; Kim, H S; Kim, J E; Kim, M J; Kim, S B; Kim, S H; Kim, Y K; Kirsch, L; Klimenko, S; Klute, M; Knuteson, B; Ko, B R; Kobayashi, H; Kondo, K; Kong, D J; Konigsberg, J; Korytov, A; Kotwal, A V; Kovalev, A; Kraan, A; Kraus, J; Kravchenko, I; Kreps, M; Kroll, J; Krumnack, N; Kruse, M; Krutelyov, V; Kuhlmann, S E; Kusakabe, Y; Kwang, S; Laasanen, A T; Lai, S; Lami, S; Lammel, S; Lancaster, M; Lander, R L; Lannon, K; Lath, A; Latino, G; Lazzizzera, I; LeCompte, T; Lee, J; Lee, J; Lee, Y J; Lee, S W; Lefèvre, R; Leonardo, N; Leone, S; Levy, S; Lewis, J D; Lin, C; Lin, C S; Lindgren, M; Lipeles, E; Liss, T M; Lister, A; Litvintsev, D O; Liu, T; Lockyer, N S; Loginov, A; Loreti, M; Loverre, P; Lu, R-S; Lucchesi, D; Lujan, P; Lukens, P; Lungu, G; Lyons, L; Lys, J; Lysak, R; Lytken, E; Mack, P; MacQueen, D; Madrak, R; Maeshima, K; Maki, T; Maksimovic, P; Malde, S; Manca, G; Margaroli, F; Marginean, R; Marino, C; Martin, A; Martin, V; Martínez, M; Maruyama, T; Mastrandrea, P; Matsunaga, H; Mattson, M E; Mazini, R; Mazzanti, P; McFarland, K S; McIntyre, P; McNulty, R; Mehta, A; Menzemer, S; Menzione, A; Merkel, P; Mesropian, C; Messina, A; von der Mey, M; Miao, T; Miladinovic, N; Miles, J; Miller, R; Miller, J S; Mills, C; Milnik, M; Miquel, R; Mitra, A; Mitselmakher, G; Miyamoto, A; Moggi, N; Mohr, B; Moore, R; Morello, M; Movilla Fernandez, P; Mülmenstädt, J; Mukherjee, A; Muller, Th; Mumford, R; Murat, P; Nachtman, J; Naganoma, J; Nahn, S; Nakano, I; Napier, A; Naumov, D; Necula, V; Neu, C; Neubauer, M S; Nielsen, J; Nigmanov, T; Nodulman, L; Norniella, O; Nurse, E; Ogawa, T; Oh, S H; Oh, Y D; Okusawa, T; Oldeman, R; Orava, R; Osterberg, K; Pagliarone, C; Palencia, E; Paoletti, R; Papadimitriou, V; Paramonov, A A; Parks, B; Pashapour, S; Patrick, J; Pauletta, G; Paulini, M; Paus, C; Pellett, D E; Penzo, A; Phillips, T J; Piacentino, G; Piedra, J; Pinera, L; Pitts, K; Plager, C; Pondrom, L; Portell, X; Poukhov, O; Pounder, N; Prakoshyn, F; Pronko, A; Proudfoot, J; Ptohos, F; Punzi, G; Pursley, J; Rademacker, J; Rahaman, A; Rakitin, A; Rappoccio, S; Ratnikov, F; Reisert, B; Rekovic, V; van Remortel, N; Renton, P; Rescigno, M; Richter, S; Rimondi, F; Ristori, L; Robertson, W J; Robson, A; Rodrigo, T; Rogers, E; Rolli, S; Roser, R; Rossi, M; Rossin, R; Rott, C; Ruiz, A; Russ, J; Rusu, V; Saarikko, H; Sabik, S; Safonov, A; Sakumoto, W K; Salamanna, G; Saltó, O; Saltzberg, D; Sanchez, C; Santi, L; Sarkar, S; Sartori, L; Sato, K; Savard, P; Savoy-Navarro, A; Scheidle, T; Schlabach, P; Schmidt, E E; Schmidt, M P; Schmitt, M; Schwarz, T; Scodellaro, L; Scott, A L; Scribano, A; Scuri, F; Sedov, A; Seidel, S; Seiya, Y; Semenov, A; Sexton-Kennedy, L; Sfiligoi, I; Shapiro, M D; Shears, T; Shepard, P F; Sherman, D; Shimojima, M; Shochet, M; Shon, Y; Shreyber, I; Sidoti, A; Sinervo, P; Sisakyan, A; Sjolin, J; Skiba, A; Slaughter, A J; Sliwa, K; Smith, J R; Snider, F D; Snihur, R; Soderberg, M; Soha, A; Somalwar, S; Sorin, V; Spalding, J; Spezziga, M; Spinella, F; Spreitzer, T; Squillacioti, P; Stanitzki, M; Staveris-Polykalas, A; St Denis, R; Stelzer, B; Stelzer-Chilton, O; Stentz, D; Strologas, J; Stuart, D; Suh, J S; Sukhanov, A; Sumorok, K; Sun, H; Suzuki, T; Taffard, A; Takashima, R; Takeuchi, Y; Takikawa, K; Tanaka, M; Tanaka, R; Tanimoto, N; Tecchio, M; Teng, P K; Terashi, K; Tether, S; Thom, J; Thompson, A S; Thomson, E; Tipton, P; Tiwari, V; Tkaczyk, S; Toback, D; Tokar, S; Tollefson, K; Tomura, T; Tonelli, D; Tönnesmann, M; Torre, S; Torretta, D; Tourneur, S; Trischuk, W; Tsuchiya, R; Tsuno, S; Turini, N; Ukegawa, F; Unverhau, T; Uozumi, S; Usynin, D; Vaiciulis, A; Vallecorsa, S; Varganov, A; Vataga, E; Velev, G; Veramendi, G; Veszpremi, V; Vidal, R; Vila, I; Vilar, R; Vine, T; Vollrath, I; Volobouev, I; Volpi, G; Würthwein, F; Wagner, P; Wagner, R G; Wagner, R L; Wagner, W; Wallny, R; Walter, T; Wan, Z; Wang, S M; Warburton, A; Waschke, S; Waters, D; Wester, W C; Whitehouse, B; Whiteson, D; Wicklund, A B; Wicklund, E; Williams, G; Williams, H H; Wilson, P; Winer, B L; Wittich, P; Wolbers, S; Wolfe, C; Wright, T; Wu, X; Wynne, S M; Yagil, A; Yamamoto, K; Yamaoka, J; Yamashita, T; Yang, C; Yang, U K; Yang, Y C; Yao, W M; Yeh, G P; Yoh, J; Yorita, K; Yoshida, T; Yu, G B; Yu, I; Yu, S S; Yun, J C; Zanello, L; Zanetti, A; Zaw, I; Zetti, F; Zhang, X; Zhou, J; Zucchelli, S

    2006-08-11

    We present the first precise measurement of the Bs0-Bs0 oscillation frequency Deltams. We use 1 fb-1 of data from pp collisions at sqrts=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. The sample contains signals of 3600 fully reconstructed hadronic Bs decays and 37,000 partially reconstructed semileptonic Bs decays. We measure the probability as a function of proper decay time that the Bs decays with the same, or opposite, flavor as the flavor at production, and we find a signal consistent with Bs0-Bs0 oscillations. The probability that random fluctuations could produce a comparable signal is 0.2%. Under the hypothesis that the signal is due to Bs0-Bs0 oscillations, we measure Deltams=17.31(-0.18)+0.33(stat)+/-0.07(syst) ps-1 and determine |Vtd/Vts|=0.208(-0.002)+0.001(expt)-0.006(+0.008)(theor). PMID:17026163

  16. Correction of Single Frequency Altimeter Measurements for Ionosphere Delay

    NASA Technical Reports Server (NTRS)

    Schreiner, William S.; Markin, Robert E.; Born, George H.

    1997-01-01

    This study is a preliminary analysis of the accuracy of various ionosphere models to correct single frequency altimeter height measurements for Ionospheric path delay. In particular, research focused on adjusting empirical and parameterized ionosphere models in the parameterized real-time ionospheric specification model (PRISM) 1.2 using total electron content (TEC) data from the global positioning system (GPS). The types of GPS data used to adjust PRISM included GPS line-of-sight (LOS) TEC data mapped to the vertical, and a grid of GPS derived TEC data in a sun-fixed longitude frame. The adjusted PRISM TEC values, as well as predictions by IRI-90, a climatotogical model, were compared to TOPEX/Poseidon (T/P) TEC measurements from the dual-frequency altimeter for a number of T/P tracks. When adjusted with GPS LOS data, the PRISM empirical model predicted TEC over 24 1 h data sets for a given local time to with in a global error of 8.60 TECU rms during a midnight centered ionosphere and 9.74 TECU rms during a noon centered ionosphere. Using GPS derived sun-fixed TEC data, the PRISM parameterized model predicted TEC within an error of 8.47 TECU rms centered at midnight and 12.83 TECU rms centered at noon. From these best results, it is clear that the proposed requirement of 3-4 TECU global rms for TOPEX/Poseidon Follow-On will be very difficult to meet, even with a substantial increase in the number of GPS ground stations, with any realizable combination of the aforementioned models or data assimilation schemes.

  17. Radio Frequency (RF) Attenuation Measurements of the Space Shuttle Vehicle

    NASA Technical Reports Server (NTRS)

    Scully, R. C.; Kent, B. M.; Kempf, D. R.; Johnk, R. T.

    2006-01-01

    Following the loss of Columbia, the Columbia Accident Investigation Board (CAIB) provided recommendations to be addressed prior to Return To Flight (RTF). As a part of CAIB Recommendation 3.4.1 - Ground Based Imagery, new C-band and X-band radars were added to the array of ground-based radars and cameras already in-situ at Kennedy Space Center. Because of higher power density considerations and new operating frequencies, the team of Subject Matter Experts (SMEs) assembled to investigate the technical details of introducing the new radars recommended a series of radio frequency (RF) attenuation tests be performed on the Space Shuttle vehicle to establish the attenuation of the vehicle outer mold line structure with respect to its external RF environment. Because of time and complex logistical constraints, it was decided to split the test into two separate efforts. The first of these would be accomplished with the assistance of the Air Force Research Laboratory (AFRL), performing RF attenuation measurements on the aft section of OV-103 (Discovery) while in-situ in Orbiter Processing Facility (OPF) 3, located at Kennedy Space Center. The second would be accomplished with the assistance of the National Institute of Standards and Technology (NIST) and the electromagnetic interference (EMI) laboratory out of the Naval Air Warfare Center, Patuxent River, Maryland (PAX River), performing RF attenuation measurements on OV-105 (Endeavour) in-situ inside the Space Shuttle Landing Facility (SLF) hangar, also located at Kennedy Space Center. This paper provides a summary description of these efforts and their results.

  18. Examination of Balance Measures Produced by the Biodex Stability System

    PubMed Central

    Arnold, Brent L.; Schmitz, Randy J.

    1998-01-01

    Objective: Our purpose was to establish normal patterns and relationships of stability using the Biodex Stability System. Design and Setting: The design of this study used both nonexperimental and quasi-experimental methods. All testing was performed in a university sports medicine laboratory. Subjects: Nineteen healthy subjects (8 males, 11 females, age = 24.4 ± 4.2 years; wt = 70.5 ± 20 kg; ht = 171.2 ± 11.7 cm) with no history of lower extremity injury participated in this study. Measurements: For data analysis, the medial/lateral stability index (MLSI), anterior/posterior stability index (APSI), overall stability index (OSI), and time-in-balance scores were recorded. Results: Multiple regression revealed that APSI and MLSI significantly contributed to the OSI, with the APSI accounting for 95% of the OSI variance. Additionally, the percentage of time spent between 0° and 5° from level was significantly greater than the time spent between 6° and 10°, 11° and 15°, and 16° and 20°. Furthermore, the percentage of time spent between 6° and 10° was significantly greater than the time spent between 16° and 20°. Conclusions: These data suggest that uninjured individuals spent the majority of the time balanced within 0° to 5° from level and progressively less time at greater angles. Additionally, the data suggest that the OSI is very closely related to the APSI and receives a relatively small contribution from the MLSI. Because of this small contribution, if the clinician is interested in both anterior-posterior and medial-lateral motions, it may be best to use the MLSI and APSI separately rather than the OSI. PMID:16558529

  19. Precise Measurement of ^{40}CaH^{+} Vibrational Transition Frequency

    NASA Astrophysics Data System (ADS)

    Kajita, Masatoshi; Abe, Minori

    2013-06-01

    Small number of molecular ions in a linear trap can be sympathetically cooled with atomic ions and form a string crystal at the position, where the electric field is zero. Molecular ions in a strinc crystal are advantageous to measure the transition frequencies without Stark shift induced by the trap electric field, but it is required to localize small number of molecular ions in a single quantum state. ^{40}CaH^{+} molecular ion is advantageous to solve this problem, because (1) molecular ion with rotational constant of 141 GHz is localized in the vibrational-rotational ground state when the surrounding temperature is lower than 10 K, and (2) there is no hyperfine splitting in the J=0 state. In this presentation, we porpose to measure the ^{40}CaH^{+} X^{1}% Σ( v,N,F,M) =(0,0,1/2,±1/2) → (v_{u},0,1/2,±1/2) (v_{u}=1,2,3,,,) transition with the uncertainty lower than 10^{-16}. With these transitions, Zeeman shift is less than 10^{-16}/G (given by the slight dependence of schielding effect by electron cloud on the vibrational state) and electric quadrupole shift is zero because of F=1/2. The J=0→0 transition is one-photon forbidden, and it can be observed also by Raman transition using two lasers. Stark shift induced by Raman lasers actually dominates the measurement uncertainty. When v=0→1 transition is observed using Raman lasers in the 6000-15000 /cm, Stark shift with saturation power is of the order of 1.5×10^{-14} and it is higher for overtone transitions. With the following Raman laser frequencies, total Stark shift induced by two Raman lasers is zero. v=0→1 24527 /cm and 23079 /cm v=0→2 24600 /cm and 21745 /cm v=0→3 26237 /cm and 22017 /cm v=0→4 25354 /cm and 19814 /cm The ^{40}CaH^{+} X^{1}Σ( v,N,F,M) =(0,0,1/2,±1/2) →(v_{u},0,1/2,±1/2) (v_{u}=1,2,3,,,) transition can be measured with the uncertainty lower than 10^{-16}, and it is useful to test the variation in the proton-to-electron mass ratio.

  20. Stabilization and Low-Frequency Oscillation of Capillary Bridges with Modulated Acoustic Radiation Pressure

    NASA Technical Reports Server (NTRS)

    Marston, Philip L.; Marr-Lyon, Mark J.; Morse, S. F.; Thiessen, David B.

    1996-01-01

    In the work reported here it is demonstrated that acoustic radiation pressure may be used in simulated low gravity to produce stable bridges significantly beyond the Rayleigh limit with S as large as 3.6. The bridge (PDMS mixed with a dense liquid) has the same density as the surrounding water bath containing an ultrasonic standing wave. Modulation was first used to excite specific bridge modes. In the most recent work reported here the shape of the bridge is optically sensed and the ultrasonic drive is electronically adjusted such that the radiation stress distribution dynamically quenches the most unstable mode. This active control simulates passive stabilization suggested for low gravity. Feedback increases the mode frequency in the naturally stable region since the effective stiffness of the mode is increased.

  1. Dual-axis vapor cell for simultaneous laser frequency stabilization on disparate optical transitions

    SciTech Connect

    Jayakumar, Anupriya Plotkin-Swing, Benjamin; Jamison, Alan O.; Gupta, Subhadeep

    2015-07-15

    We have developed a dual-axis ytterbium (Yb) vapor cell and used it to simultaneously address the two laser cooling transitions in Yb at wavelengths 399 nm and 556 nm, featuring the disparate linewidths of 2π × 29 MHz and 2π × 182 KHz, respectively. By utilizing different optical paths for the two wavelengths, we simultaneously obtain comparable optical densities suitable for saturated absorption spectroscopy for both the transitions and keep both the lasers frequency stabilized over several hours. We demonstrate that by appropriate control of the cell temperature profile, two atomic transitions differing in relative strength across a large range of over three orders of magnitude can be simultaneously addressed, making the device adaptable to a variety of spectroscopic needs. We also show that our observations can be understood with a simple theoretical model of the Yb vapor.

  2. Accurate absolute reference frequencies from 1511 to 1545 nm of the {nu}{sub 1}+{nu}{sub 3} band of {sup 12}C{sub 2}H{sub 2} determined with laser frequency comb interval measurements

    SciTech Connect

    Madej, Alan A.; Alcock, A. John; Czajkowski, Andrzej; Bernard, John E.; Chepurov, Sergei

    2006-10-15

    Absolute frequency measurements, with uncertainties as low as 2 kHz (1x10{sup -11}), are presented for the {nu}{sub 1}+{nu}{sub 3} band of {sup 12}C{sub 2}H{sub 2} at 1.5 {mu}m (194-198 THz). The measurements were made using cavity-enhanced, diode-laser-based saturation spectroscopy. With one laser system stabilized to the P(16) line of {sup 13}C{sub 2}H{sub 2} and a system stabilized to the line in {sup 12}C{sub 2}H{sub 2} whose frequency was to be determined, a Cr:YAG laser-based frequency comb was employed to measure the frequency intervals. The systematic uncertainty is notably reduced relative to that of previous studies, and the region of measured lines has been extended. Improved molecular constants are obtained.

  3. Innovative frequency measurement technique used in the design of a single channel frequency to digital converter ASIC

    NASA Astrophysics Data System (ADS)

    Ramalingam, Neranjen; Varadan, Vijay K.; Varadan, Vasundara V.

    1996-09-01

    The frequency to digital converter (FDC) is an application specific integrated circuit. The chip has been designed to handle one input channel but can easily be expanded to handle multiple channels of frequencies. The channel is capable of measuring frequencies from 100 Hz to 100 kHz. The power consumption of the chip is very low. The frequency measurement accuracy is better than 0.1 percent. The conversion rate per channel is 100 samples/second which can be carried too. The chip has a built-in test equipment to verify its operation. It is able to generate frequencies like 8 Mhz, 4Mhz, 2Mhz and 1Mhz which can be fed as optional clock frequencies depending on the accuracy desired. The FDC chip can be interfaced to a 16 bit bus. To meet these stringent specifications of the FDC chip an innovative frequency measurement technique has been devised called the hybrid technique of frequency measurement. The technique proves to be very accurate and it is found that by varying the sampling rate the range of input frequencies over which this accuracy can be achieved also changes. The specifications are particularly strict so that it is possible to use the chip for any military application for which a very reliable operation is demanded. The FDC chip is hence ideal for control and guidance purposes. The chip has wide ranging applications. In conjunction with sensors such as accelerometers it can be used to design smart sensors. The chip can play a vital role in engine controllers and in pressure measurements using vibrating type transducers. Sometimes to isolate transducers, the output is converted to frequency and isolation is achieved using opto-isolators; then by measuring the frequency using this chip this can be converted to digital information.

  4. 47 CFR 15.33 - Frequency range of radiated measurements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... level of radiated emissions within the frequency range 9 kHz to 30 MHz, such as a CB receiver or a device designed to conduct its radio frequency emissions via connecting wires or cables, e.g., a carrier... used in the device, without going below 9 kHz (25 MHz for CB receivers), up to the frequency shown...

  5. 47 CFR 15.33 - Frequency range of radiated measurements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... level of radiated emissions within the frequency range 9 kHz to 30 MHz, such as a CB receiver or a device designed to conduct its radio frequency emissions via connecting wires or cables, e.g., a carrier... used in the device, without going below 9 kHz (25 MHz for CB receivers), up to the frequency shown...

  6. 47 CFR 15.33 - Frequency range of radiated measurements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... level of radiated emissions within the frequency range 9 kHz to 30 MHz, such as a CB receiver or a device designed to conduct its radio frequency emissions via connecting wires or cables, e.g., a carrier... used in the device, without going below 9 kHz (25 MHz for CB receivers), up to the frequency shown...

  7. 47 CFR 15.33 - Frequency range of radiated measurements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... level of radiated emissions within the frequency range 9 kHz to 30 MHz, such as a CB receiver or a device designed to conduct its radio frequency emissions via connecting wires or cables, e.g., a carrier... used in the device, without going below 9 kHz (25 MHz for CB receivers), up to the frequency shown...

  8. 47 CFR 15.33 - Frequency range of radiated measurements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 5000. Above 1000 5th harmonic of the highest frequency or 40 GHz, whichever is lower. (2) A... below 10 GHz: to the tenth harmonic of the highest fundamental frequency or to 40 GHz, whichever is... harmonic of the highest fundamental frequency or to 100 GHz, whichever is lower. (3) If the...

  9. Fully stabilized optical frequency comb with sub-radian CEO phase noise from a SESAM-modelocked 1.5-µm solid-state laser.

    PubMed

    Schilt, Stephane; Bucalovic, Nikola; Dolgovskiy, Vladimir; Schori, Christian; Stumpf, Max C; Di Domenico, Gianni; Pekarek, Selina; Oehler, Andreas E H; Südmeyer, Thomas; Keller, Ursula; Thomann, Pierre

    2011-11-21

    We report the first full stabilization of an optical frequency comb generated from a femtosecond diode-pumped solid-state laser (DPSSL) operating in the 1.5-μm spectral region. The stability of the comb is characterized in free-running and in phase-locked operation by measuring the noise properties of the carrier-envelope offset (CEO) beat, of the repetition rate, and of a comb line at 1558 nm. The high Q-factor of the semiconductor saturable absorber mirror (SESAM)-modelocked 1.5-µm DPSSL results in a low-noise CEO-beat, for which a tight phase lock can be much more easily realized than for a fiber comb. Using a moderate feedback bandwidth of only 5.5 kHz, we achieved a residual integrated phase noise of 0.72 rad rms for the locked CEO, which is one of the smallest values reported for a frequency comb system operating in this spectral region. The fractional frequency stability of the CEO-beat is 20‑fold better than measured in a standard self-referenced commercial fiber comb system and contributes only 10(-15) to the optical carrier frequency instability at 1 s averaging time.

  10. Ka-Band Atmospheric Phase Stability Measurements in Goldstone, CA; White Sands, NM; and Guam

    NASA Technical Reports Server (NTRS)

    Zemba, Michael J.; Morse, Jacquelynne Rose; Nessel, James A.

    2014-01-01

    As spacecraft communication links are driven to higher frequencies (e.g. Ka-band) both by spectrum congestion and the appeal of higher data rates, the propagation phenomena at these frequencies must be well characterized for effective system design. In particular, the phase stability of a site at a given frequency will govern whether or not the site is a practical location for an antenna array, particularly if uplink capabilities are desired. Propagation studies to characterize such phenomena must be done on a site-by-site basis due to the wide variety of climates and weather conditions at each ground terminal. Accordingly, in order to statistically characterize the atmospheric effects on Ka-Band links, site test interferometers (STIs) have been deployed at three of NASA's operational sites to directly measure each site's tropospheric phase stability. Using three years of results from these experiments, this paper will statistically characterize the simultaneous atmospheric phase noise measurements recorded by the STIs deployed at the following ground station sites: the Goldstone Deep Space Communications Complex near Barstow, CA; the White Sands Ground Terminal near Las Cruces, NM; and the Guam Remote Ground Terminal on the island of Guam.

  11. Laser noise measurement techniques and applications of femtosecond encoding in the frequency domain

    NASA Astrophysics Data System (ADS)

    Scott, Ryan Patrick

    This dissertation investigates mode-locked laser noise measurement techniques, the concept and measurement of a laser's noise transfer function, and then two applications of spectral encoding of optical pulses. The one application is optical code division multiple access (O-CDMA) and the other is optical arbitrary waveform generation (OAWG). The relationship between source stability, encoding, and overall system performance in O-CDMA is also discussed. Techniques for making sensitive and high-dynamic-range measurements of laser amplitude and envelope phase noise (timing jitter) in the frequency domain at the shot-noise limit are described. The short term stability of a Kerr-lens modelocked (KLM) Ti:sapphire laser is shown to be close to that of the precision crystal oscillators used in its characterization. The amplitude and envelope phase noise of a KLM Ti:sapphire laser are shown to depend directly on the pump laser amplitude stability. The sensitivity of this process is described by a noise transfer function (NTF) which represents the magnitude of the amplitude-to-amplitude modulation and amplitude-to-phase modulation conversion gain of the pump-induced amplitude and phase noise, respectively. A spectral phase-encoded time-spreading (SPECTS) O-CDMA testbed is described. The testbed employs a fiber-pigtailed, bulk-optics arrangement that utilizes a two-dimensional spatial light phase modulator for encoding multiple channels. The time-gated SPECTS O-CDMA receiver is composed of a nonlinear optical loop mirror (NOLM) and a nonlinear thresholder Experimentally measured performance is compared to numerical simulations. Finally, an optical frequency comb with 20-GHz spacing is shaped by an integrated silica arrayed-waveguide grating (AWG) pair to produce optical waveforms with high fidelity. Characterization of both the intensity and phase of the crafted opitical fields is accomplished with cross-correlation frequency-resolved optical gating (XFROG) which has been

  12. High frequency strain measurements with fiber Bragg grating sensors

    NASA Astrophysics Data System (ADS)

    Koch, J.; Angelmahr, M.; Schade, W.

    2015-05-01

    In recent years fiber Bragg grating sensors gained interest in structural health monitoring and concepts for smart structures. They are small, lightweight, and immune to electromagnetic interference. Using multiplexing techniques, several sensors can be addressed by a single fiber. Therefore, well-established structures and materials in industrial applications can be easily equipped with fiber optical sensors with marginal influence on their mechanical properties. In return, critical components can be monitored in real-time, leading to reduced maintenance intervals and a great reduction of costs. Beside of generally condition monitoring, the localization of failures in a structure is a desired feature of the condition monitoring system. Detecting the acoustic emission of a sudden event, its place of origin can be determined by analyzing the delay time of distributed sensor signals. To achieve high localization accuracies for the detection of cracks, breaks, and impacts high sampling rates combined with the simultaneous interrogation of several fiber Bragg grating sensors are required. In this article a fiber Bragg grating interrogator for high frequency measurements up to the megahertz range is presented. The interrogator is based on a passive wavelength to intensity conversion applying arrayed waveguide gratings. Light power fluctuations are suppressed by a differential data evaluation, leading to a reduced signal-to-noise ratio and a low strain detection limit. The measurement system is used to detect, inter alia, wire breaks in steel wire ropes for dockside cranes.

  13. Velocity field measurements on high-frequency, supersonic microactuators

    NASA Astrophysics Data System (ADS)

    Kreth, Phillip A.; Ali, Mohd Y.; Fernandez, Erik J.; Alvi, Farrukh S.

    2016-05-01

    The resonance-enhanced microjet actuator which was developed at the Advanced Aero-Propulsion Laboratory at Florida State University is a fluidic-based device that produces pulsed, supersonic microjets by utilizing a number of microscale, flow-acoustic resonance phenomena. The microactuator used in this study consists of an underexpanded source jet that flows into a cylindrical cavity with a single, 1-mm-diameter exhaust orifice through which an unsteady, supersonic jet issues at a resonant frequency of 7 kHz. The flowfields of a 1-mm underexpanded free jet and the microactuator are studied in detail using high-magnification, phase-locked flow visualizations (microschlieren) and two-component particle image velocimetry. These are the first direct measurements of the velocity fields produced by such actuators. Comparisons are made between the flow visualizations and the velocity field measurements. The results clearly show that the microactuator produces pulsed, supersonic jets with velocities exceeding 400 m/s for roughly 60 % of their cycles. With high unsteady momentum output, this type of microactuator has potential in a range of ow control applications.

  14. The Interannual Stability of Cumulative Frequency Distributions for Convective System Size and Intensity

    NASA Technical Reports Server (NTRS)

    Mohr, Karen I.; Molinari, John; Thorncroft, Chris D,

    2010-01-01

    The characteristics of convective system populations in West Africa and the western Pacific tropical cyclone basin were analyzed to investigate whether interannual variability in convective activity in tropical continental and oceanic environments is driven by variations in the number of events during the wet season or by favoring large and/or intense convective systems. Convective systems were defined from TRMM data as a cluster of pixels with an 85 GHz polarization-corrected brightness temperature below 255 K and with an area at least 64 km 2. The study database consisted of convective systems in West Africa from May Sep for 1998-2007 and in the western Pacific from May Nov 1998-2007. Annual cumulative frequency distributions for system minimum brightness temperature and system area were constructed for both regions. For both regions, there were no statistically significant differences among the annual curves for system minimum brightness temperature. There were two groups of system area curves, split by the TRMM altitude boost in 2001. Within each set, there was no statistically significant interannual variability. Sub-setting the database revealed some sensitivity in distribution shape to the size of the sampling area, length of sample period, and climate zone. From a regional perspective, the stability of the cumulative frequency distributions implied that the probability that a convective system would attain a particular size or intensity does not change interannually. Variability in the number of convective events appeared to be more important in determining whether a year is wetter or drier than normal.

  15. Two-Stage System Based on a Software-Defined Radio for Stabilizing of Optical Frequency Combs in Long-Term Experiments

    PubMed Central

    Čížek, Martin; Hucl, Václav; Hrabina, Jan; Šmíd, Radek; Mikel, Břetislav; Lazar, Josef; Číp, Ondřej

    2014-01-01

    A passive optical resonator is a special sensor used for measurement of lengths on the nanometer and sub-nanometer scale. Astabilized optical frequency comb can provide an ultimate reference for measuring the wavelength of a tunable laser locked to the optical resonator. If we lock the repetition and offset frequencies of the comb to a high-grade radiofrequency (RF) oscillator its relative frequency stability is transferred from the RF to the optical frequency domain. Experiments in the field of precise length metrology of low-expansion materials are usually of long-term nature so it is required that the optical frequency comb stay in operation for an extended period of time. The optoelectronic closed-loop systems used for stabilization of combs are usually based on traditional analog electronic circuits processing signals from photodetectors. From an experimental point of view, these setups are very complicated and sensitive to ambient conditions, especially in the optical part, therefore maintaining long-time operation is not easy. The research presented in this paper deals with a novel approach based on digital signal processing and a software-defined radio. We describe digital signal processing algorithms intended for keeping the femtosecond optical comb in a long-time stable operation. This need arose during specialized experiments involving measurements of optical frequencies of tunable continuous-wave lasers. The resulting system is capable of keeping the comb in lock for an extensive period of time (8 days or more) with the relative stability better than 1.6 × 10−11. PMID:24448169

  16. The Problem of the Instrument Stabilization During Hydrographic Measurements

    NASA Astrophysics Data System (ADS)

    Felski, Andrzej; Naus, Krzysztof; Wąż, Mariusz

    2016-06-01

    Performing any measurement on watercraft is connected with many additional difficulties caused by the sea-environment. The most important is the problem of spatial stabilization of measurement systems, which are usually fastened to craft body. As soon as usually these measurement are executed during the move of the craft additional question is the accuracy of execution the planed trajectory. This is a problem for all investigators, especially when system use spatially configured beams of any antennas or other sensors, regardless is it receiving or transmitting one. Different aspects of these question are the subject of research activity of Institute of Navigation and Maritime Hydrography of Polish Naval Academy. In this paper the review of works executed in last years are presented.

  17. Method of detecting system function by measuring frequency response

    NASA Technical Reports Server (NTRS)

    Morrison, John L. (Inventor); Morrison, William H. (Inventor); Christophersen, Jon P. (Inventor)

    2012-01-01

    Real-time battery impedance spectrum is acquired using a one-time record. Fast Summation Transformation (FST) is a parallel method of acquiring a real-time battery impedance spectrum using a one-time record that enables battery diagnostics. An excitation current to a battery is a sum of equal amplitude sine waves of frequencies that are octave harmonics spread over a range of interest. A sample frequency is also octave and harmonically related to all frequencies in the sum. The time profile of this signal has a duration that is a few periods of the lowest frequency. The voltage response of the battery, average deleted, is the impedance of the battery in the time domain. Since the excitation frequencies are known and octave and harmonically related, a simple algorithm, FST, processes the time record by rectifying relative to the sine and cosine of each frequency. Another algorithm yields real and imaginary components for each frequency.

  18. Method of detecting system function by measuring frequency response

    DOEpatents

    Morrison, John L.; Morrison, William H.; Christophersen, Jon P.

    2012-04-03

    Real-time battery impedance spectrum is acquired using a one-time record. Fast Summation Transformation (FST) is a parallel method of acquiring a real-time battery impedance spectrum using a one-time record that enables battery diagnostics. An excitation current to a battery is a sum of equal amplitude sine waves of frequencies that are octave harmonics spread over a range of interest. A sample frequency is also octave and harmonically related to all frequencies in the sum. The time profile of this signal has a duration that is a few periods of the lowest frequency. The voltage response of the battery, average deleted, is the impedance of the battery in the time domain. Since the excitation frequencies are known and octave and harmonically related, a simple algorithm, FST, processes the time record by rectifying relative to the sine and cosine of each frequency. Another algorithm yields real and imaginary components for each frequency.

  19. Beamline stability measurements with a stretched wire system in the FFTB

    SciTech Connect

    Assmann, R.; Salsberg, C.; Montag, C.

    1996-09-01

    Beamline stability is of great importance for future linear colliders where tolerances generally are in the micron to sub-micron range. A stretched wire system in the sealed FFTB tunnel at SLAC was used to monitor beamline motion with a sub-micron resolution. In future linear colliders low frequency changes of the beamline alignment (< 0.1 Hz) lead to untolerable quasistatical misalignments and betatron oscillations. Since it requires time to correct those errors, it is very important to determine how often corrections are needed. The authors present the measurements, discuss the systematics of the stretched wire system and compare the observations with the ATL-model for ground motion.

  20. Assessment of Osstell ISQ’s reliability for implant stability measurement: A cross-sectional clinical study

    PubMed Central

    Herrero-Climent, Mariano; Santos-García, Rocio; Jaramillo-Santos, Reyes; Romero-Ruiz, Manuel M.; Fernández-Palacin, Ana; Lázaro-Calvo, Pedro; Bullón, Pedro

    2013-01-01

    Resonance frequency analysis (RFA) allows assess implant stability by measuring implant oscillation frequency on the bone. RFA is an objective and non-invasive method for implant stability measurement, although scarce evidence has been provided so far on its reliability. Objectives: Assess the Osstell ISQ system’s reliability (i.e., its measurement reproducibility and repeatability) by means of the intraclass correlation coefficient (ICC) as statistical method. Study Desing: Implants stability registers were completed by means of Osstell ISQ on 85 implants on 23 patients. Six measurements were completed on each implant by means of two different SmartPegs (types I and II); that is, three consecutive measurements with each transducer. Results: Average ISQ was 72.40, 72.22 and 72.79, and 72.06, 72.59 and 72.82 in the first, second, and third measurements with SmartPegs I and II, respectively. Equal values or differences below three ISQ points were observed in 52.9% and 62.4% of the cases with SmartPegs I and II, respectively. The intraclass correlation coefficient was 0.97 for both SmartPegs, and repeatability and reproducibility also reached 0.97 for both SmartPegs. Conclusions: The RFA system Osstell ISQ presents almost perfect repeatability and reproducibility after intraclass correlation coefficient analysis. Osstell ISQ measurements are highly reliable regarding reproducibility. Therefore, one measurement proves enough. Key words:Dental implants, RFA, ISQ, implant stability, Osstell. PMID:24121909

  1. Frequency-stabilized Yb:fiber comb with a tapered single-mode fiber

    NASA Astrophysics Data System (ADS)

    Yang, Xie; Hai-Nian, Han; Long, Zhang; Zi-Jiao, Yu; Zheng, Zhu; Lei, Hou; Li-Hui, Pang; Zhi-Yi, Wei

    2016-04-01

    We demonstrate a stable Yb:fiber frequency comb with supercontinuum generation by using a specially designed tapered single-mode fiber, in which a spectrum spanning from 500 nm to 1500 nm is produced. The carrier-envelope offset signal of the Yb:fiber comb is measured with a signal-to-noise ratio of more than 40 dB and a linewidth narrower than 120 kHz. The repetition rate and carrier-envelope offset signals are simultaneously phase locked to a microwave reference frequency. Project supported by the National Basic Research Program of China (973 Program) (Grant No. 2012CB821304) and the National Natural Science Foundation of China (Grant No. 61378040).

  2. Long-term frequency and amplitude stability of a solid-nitrogen-cooled, continuous wave THz quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Danylov, Andriy A.; Waldman, Jerry; Light, Alexander R.; Goyette, Thomas M.; Giles, Robert H.; Qian, Xifeng; Chandrayan, Neelima; Goodhue, William D.; Nixon, William E.

    2012-02-01

    Operational temperature increase of CW THz QCLs to 77 K has enabled us to employ solid nitrogen (SN2) as the cryogen. A roughing pump was used to solidify liquid nitrogen and when the residual vapor pressure in the nitrogen reservoir reached the pumping system's minimum pressure the temperature equilibrated and remained constant until all the nitrogen sublimated. The hold time compared to liquid helium has thereby increased approximately 70-fold, and at a greatly reduced cost. The milliwatt CW QCL was at a temperature of approximately 60 K, dissipating 5 W of electrical power. To measure the long-term frequency, current, and temperature stability, we heterodyned the free-running 2.31 THz QCL with a CO2 pumped far-infrared gas laser line in methanol (2.314 THz) in a corner-cube Schottky diode and recorded the IF frequency, current and temperature. Under these conditions the performance characteristics of the QCL, which will be reported, exceeded that of a device mounted in a mechanical cryocooler.

  3. Self-mixing vibration measurement using emission frequency sinusoidal modulation

    NASA Astrophysics Data System (ADS)

    Tao, Yufeng; Wang, Ming; Guo, Dongmei; Hao, Hui; Liu, Qiang

    2015-04-01

    In this paper, a simplified phase demodulation scheme is applied to recover vibration trail on a laser self-mixing interferometer for noncontact vibration measurement. The emission of semiconductor laser diode is modulated by injecting sinusoidal wave, and corresponding interference signal is a quasi-sinusoid wave. The vibration mathematical model for semiconductor laser diode is theoretically educed from basic self-mixing theory, the variation of target is converted into phase information. The simulation of demodulation algorithm and standard deviation are presented and the reconstructed waveform displays a desirable consistence with various moving trails. Following the principle, a minimum experimental system is established and position variation of the target mirror driven by voltage signal is translated into phase shifts, feedback is controlled at weak level during experiment, Fourier transform is implemented to analyze phase information. The comparisons of both amplitude and velocity with a Germany Doppler vibrometer are performed to testify vibration model, the error of proposed demodulation method is less than 30 nm and achieve a high accuracy in vibration frequency. The experimental results indicate the traditional phase technology can be applied on complex optical power signal after adaption providing a feasible application prospects in industrial and scientific situation with an inexpensive semiconductor laser.

  4. Spectroscopic Measurements of Radio Frequency Plasmas in Supercritical Fluids

    SciTech Connect

    Maehara, Tsunehiro; Iwamae, Atsushi; Kawashima, Ayato

    2010-10-29

    Spectroscopic measurements of radio frequency (rf) plasma were performed under high pressure CO{sub 2} conditions (5 and 7 MPa) and supercritical (sc)CO{sub 2} conditions (8-20 MPa). The temperatures evaluated from C{sub 2} Swan bands increased from 3600 K to 4600 K with increasing pressure. The broadening and shifting of the O I line profile ({approx}777 nm) of rf plasma was observed under scCO{sub 2} conditions. The width of the line profile increased with increasing pressure. The reason for the broadening and shifting is still unclear because the present theory used to explain them is not valid for such high pressure conditions. Further, the broadening of the Ar I line profile ({approx}811.5 nm) in rf plasmas was observed under atmospheric Ar (0.1 MPa), high pressure Ar conditions (1-4 MPa), and scAr condition (5 MPa); the observation of the O I line profile in CO{sub 2} plasmas is difficult in this pressure range owing to its weak intensity therein. Similar to the case of the O I line in CO{sub 2} plasmas, the reason for the broadening of the Ar I line profile at 5 MPa is unclear.

  5. Avoiding nuclear war, Confidence-building measures for crisis stability

    SciTech Connect

    Borawski, J.; Goodby, J.E.

    1986-01-01

    Confidence-building measures (CBMs) may offer one way out of the contemporary arms control morass. Instead of focusing on limiting the number and types of weaponry, CBMs are designed to control how, when, where, and why military activities are employed. By clarifying military intentions and regulating the operations of military forces in times of both crisis and calm, CBMs can help diminish the opportunities for war arising from surprise attack or from miscalculation, accident, or failure of communication. This volume assembles CBM experts from government and academia to assess the utility of CBMs in a wide variety of areas. CONTENTS: Foreword; Prologue; Introduction; The World of CBMs; The Accidents Measures Agreement; Avoiding Incidents at Sea; The Stockholm CDE Conference; CBMs in the UN Setting; Soviet Views of CBMs; Beyond the Hotline: Controlling a Nuclear Crisis; CBMs for Stabilizing the Strategic Nuclear Competition; Risk Reduction and Crisis Prevention; An East-West Center for Military Cooperation; The Limits of Confidence.

  6. Polarization switching detection method using a ferroelectric liquid crystal for dichroic atomic vapor laser lock frequency stabilization techniques.

    PubMed

    Dudzik, Grzegorz; Rzepka, Janusz; Abramski, Krzysztof M

    2015-04-01

    We present a concept of the polarization switching detection method implemented for frequency-stabilized lasers, called the polarization switching dichroic atomic vapor laser lock (PSDAVLL) technique. It is a combination of the well-known dichroic atomic vapor laser lock method for laser frequency stabilization with a synchronous detection system based on the surface-stabilized ferroelectric liquid crystal (SSFLC).The SSFLC is a polarization switch and quarter wave-plate component. This technique provides a 9.6 dB better dynamic range ratio (DNR) than the well-known two-photodiode detection configuration known as the balanced polarimeter. This paper describes the proposed method used practically in the VCSEL laser frequency stabilization system. The applied PSDAVLL method has allowed us to obtain a frequency stability of 2.7×10⁻⁹ and a reproducibility of 1.2×10⁻⁸, with a DNR of detected signals of around 81 dB. It has been shown that PSDAVLL might be successfully used as a method for spectra-stable laser sources.

  7. Linearized blade row compression component model. Stability and frequency response analysis of a J85-3 compressor

    NASA Technical Reports Server (NTRS)

    Tesch, W. A.; Moszee, R. H.; Steenken, W. G.

    1976-01-01

    NASA developed stability and frequency response analysis techniques were applied to a dynamic blade row compression component stability model to provide a more economic approach to surge line and frequency response determination than that provided by time-dependent methods. This blade row model was linearized and the Jacobian matrix was formed. The clean-inlet-flow stability characteristics of the compressors of two J85-13 engines were predicted by applying the alternate Routh-Hurwitz stability criterion to the Jacobian matrix. The predicted surge line agreed with the clean-inlet-flow surge line predicted by the time-dependent method to a high degree except for one engine at 94% corrected speed. No satisfactory explanation of this discrepancy was found. The frequency response of the linearized system was determined by evaluating its Laplace transfer function. The results of the linearized-frequency-response analysis agree with the time-dependent results when the time-dependent inlet total-pressure and exit-flow function amplitude boundary conditions are less than 1 percent and 3 percent, respectively. The stability analysis technique was extended to a two-sector parallel compressor model with and without interstage crossflow and predictions were carried out for total-pressure distortion extents of 180 deg, 90 deg, 60 deg, and 30 deg.

  8. Laser Frequency Stabilization for Coherent Lidar Applications using Novel All-Fiber Gas Reference Cell Fabrication Technique

    NASA Technical Reports Server (NTRS)

    Meras, Patrick, Jr.; Poberezhskiy, Ilya Y.; Chang, Daniel H.; Levin, Jason; Spiers, Gary D.

    2008-01-01

    Compact hollow-core photonic crystal fiber (HC-PCF)gas frequency reference cell was constructed using a novel packaging technique that relies on torch-sealing a quartz filling tube connected to a mechanical splice between regular and hollow-core fibers. The use of this gas cell for laser frequency stabilization was demonstrated by locking a tunable diode laser to the center of the P9 line from the (nu)1+(nu)3 band of acetylene with RMS frequency error of 2.06 MHz over 2 hours. This effort was performed in support of a task to miniaturize the laser frequency stabilization subsystem of JPL/LMCT Laser Absorption Spectrometer (LAS) instrument.

  9. Theoretical and experimental analysis of high-power frequency-stabilized semiconductor master oscillator power-amplifier system.

    PubMed

    Ji, Encai; Liu, Qiang; Nie, Mingming; Fu, Xing; Gong, Mali

    2016-04-10

    We present a compact high-power 780 nm frequency-stabilized diode laser with a power of as high as 2.825 W, corresponding to an estimated overall efficiency of 38.5%. The tapered amplifier (TPA) gain was about 24.5 dB, which was basically consistent with the simulation results. The beam quality factor was M2<1.72. The core feature of the system was stabilizing the frequency of the narrowband semiconductor TPA system with the matured saturated absorption spectrum technique. The laser frequency was stabilized against mode hops for a period of >4200  s with a frequency fluctuation around 6.7×10-10 within 1 s of the observation period, and the linewidth was no more than 0.95 MHz. The laser performance indicates that the current frequency-stabilized semiconductor laser has great potential in certain conditions that require several watts of output power. PMID:27139853

  10. Using optical soliton stability for magnetic field measurement

    NASA Astrophysics Data System (ADS)

    Şchiopu, IonuÅ£ Romeo; ǎgulinescu, Andrei, Dr; Marinescu, Andrei

    2015-02-01

    In this paper we propose a novel optical method for measuring the circular magnetic field. In practice, many situations may appear in which there are difficulties in measuring the magnetic field, as inside coils, motors etc., where the magnetic field lines are circular or elliptical. The proposed method, applied for measuring the current on high voltage lines, strongly benefits from the advantages that it offers as compared to classical solutions based on the inductive principle. Some of the advantages of optoelectronic and optic measurement methods have a real importance. These advantages consist in: avoiding the use of energy intensive materials (Cu, Fe etc.), reducing the weight of the measuring system, reducing at the minimum the fire danger due to the use of paper-oil insulation in high voltage devices etc. The novelty of our proposed method consists in using the electromagnetic radiation in ultrashort pulses, having a relatively large frequency band and a much improved resistance to external perturbations, for measuring the circular magnetic field generated from the current of high voltage lines, inside power transformers or high power motors.

  11. Study of V-OTDR stability for dynamic strain measurement in piezoelectric vibration

    NASA Astrophysics Data System (ADS)

    Ren, Meiqi; Lu, Ping; Chen, Liang; Bao, Xiaoyi

    2016-09-01

    In a phase-sensitive optical-time domain reflectometry (Φ-OTDR) system, the challenge for dynamic strain measurement lies in large intensity fluctuations from trace to trace. The intensity fluctuation caused by stochastic characteristics of Rayleigh backscattering sets detection limit for the minimum strength of vibration measurement and causes the large measurement uncertainty. Thus, a trace-to-trace correlation coefficient is introduced to quantify intensity fluctuation of Φ-OTDR traces and stability of the sensor system theoretically and experimentally. A novel approach of measuring dynamic strain induced by various driving voltages of lead zirconate titanate (PZT) in Φ-OTDR is also demonstrated. Piezoelectric vibration signals are evaluated through analyzing peak values of fast Fourier transform spectra at the fundamental frequency and high-order harmonics based on Bessel functions. High trace-to-trace correlation coefficients varying from 0.824 to 0.967 among 100 measurements are obtained in experimental results, showing the good stability of our sensor system, as well as small uncertainty of measured peak values.

  12. Study of Ф-OTDR stability for dynamic strain measurement in piezoelectric vibration

    NASA Astrophysics Data System (ADS)

    Ren, Meiqi; Lu, Ping; Chen, Liang; Bao, Xiaoyi

    2016-06-01

    In a phase-sensitive optical-time domain reflectometry (Φ-OTDR) system, the challenge for dynamic strain measurement lies in large intensity fluctuations from trace to trace. The intensity fluctuation caused by stochastic characteristics of Rayleigh backscattering sets detection limit for the minimum strength of vibration measurement and causes the large measurement uncertainty. Thus, a trace-to-trace correlation coefficient is introduced to quantify intensity fluctuation of Φ-OTDR traces and stability of the sensor system theoretically and experimentally. A novel approach of measuring dynamic strain induced by various driving voltages of lead zirconate titanate (PZT) in Φ-OTDR is also demonstrated. Piezoelectric vibration signals are evaluated through analyzing peak values of fast Fourier transform spectra at the fundamental frequency and high-order harmonics based on Bessel functions. High trace-to-trace correlation coefficients varying from 0.824 to 0.967 among 100 measurements are obtained in experimental results, showing the good stability of our sensor system, as well as small uncertainty of measured peak values.

  13. Measurement of carbonaceous aerosol with different sampling configurations and frequencies

    NASA Astrophysics Data System (ADS)

    Cheng, Y.; He, K.-B.

    2015-07-01

    A common approach for measuring the mass of organic carbon (OC) and elemental carbon (EC) in airborne particulate matter involves collection on a quartz fiber filter and subsequent thermal-optical analysis. Although having been widely used in aerosol studies and in PM2.5 (fine particulate matter) chemical speciation monitoring networks in particular, this measurement approach is prone to several types of artifacts, such as the positive sampling artifact caused by the adsorption of gaseous organic compounds onto the quartz filter, the negative sampling artifact due to the evaporation of OC from the collected particles and the analytical artifact in the thermal-optical determination of OC and EC (which is strongly associated with the transformation of OC into char OC and typically results in an underestimation of EC). The presence of these artifacts introduces substantial uncertainties to observational data on OC and EC and consequently limits our ability to evaluate OC and EC estimations in air quality models. In this study, the influence of sampling frequency on the measurement of OC and EC was investigated based on PM2.5 samples collected in Beijing, China. Our results suggest that the negative sampling artifact of a bare quartz filter could be remarkably enhanced due to the uptake of water vapor by the filter medium. We also demonstrate that increasing sampling duration does not necessarily reduce the impact of positive sampling artifact, although it will enhance the analytical artifact. Due to the effect of the analytical artifact, EC concentrations of 48 h averaged samples were about 15 % lower than results from 24 h averaged ones. In addition, it was found that with the increase of sampling duration, EC results exhibited a stronger dependence on the charring correction method and, meanwhile, optical attenuation (ATN) of EC (retrieved from the carbon analyzer) was more significantly biased by the shadowing effect. Results from this study will be useful for the

  14. Dynamic characterization and single-frequency cancellation performance of SMASH (SMA actuated stabilizing handgrip)

    NASA Astrophysics Data System (ADS)

    Pathak, Anupam; Brei, Diann; Luntz, Jonathan; LaVigna, Chris; Kwatny, Harry

    2008-03-01

    In urban combat environments where it is common to have unsupported firing positions, wobble significantly decreases shooting accuracy reducing mission effectiveness and soldier survivability. The SMASH (SMA Stabilizing Handgrip) has been developed to cancel wobble using antagonistic SMA actuators which reduce weight and size relative to conventional actuation, but lead to interesting control challenges. This paper presents the specification and design of the SMA actuation system for the SMASH platform along with experimental validation of the actuation and cancellation authority on the benchtop and on an M16 platform. Analytical dynamic weapon models and shooter experiments were conducted to define actuation frequency and amplitude specifications. The SMASH, designed to meet these, was experimentally characterized from the bounding quasi-static case up to the 3 Hz range, successfully generating the +/-2 mm amplitude requirement. To effectively cancel wobble it is critical to produce the proper output functional shape which is difficult for SMA due to inherent nonlinearities, hysteresis, etc. Three distinct electrical heating input functions (square, ramp, and preheat) were investigated to shape the actuator output to produce smooth sinusoidal motion. The effect of each of these functions on the cancellation response of the SMASH applied to the M16 platform was experimentally studied across the wobble range (1-3 Hz) demonstrating significant cancellation, between 50-97% depending on the smoothing function and frequency. These results demonstrate the feasibility of a hand-held wobble cancellation device providing an important foundation for future work in overall system optimization and the development of physically based feed-forward signals for closed-loop control.

  15. Statistical precision and sensitivity of measures of dynamic gait stability.

    PubMed

    Bruijn, Sjoerd M; van Dieën, Jaap H; Meijer, Onno G; Beek, Peter J

    2009-04-15

    Recently, two methods for quantifying a system's dynamic stability have been applied to human locomotion: local stability (quantified by finite time maximum Lyapunov exponents, lambda(S-stride) and lambda(L-stride)) and orbital stability (quantified as maximum Floquet multipliers, MaxFm). Thus far, however, it has remained unclear how many data points are required to obtain precise estimates of these measures during walking, and to what extent these estimates are sensitive to changes in walking behaviour. To resolve these issues, we collected long data series of healthy subjects (n=9) walking on a treadmill in three conditions (normal walking at 0.83 m/s (3 km/h) and 1.38 m/s (5 km/h), and walking at 1.38 m/s (5 km/h) while performing a Stroop dual task). Data series from 0.83 and 1.38 m/s trials were submitted to a bootstrap procedure and paired t-tests for samples of different data series lengths were performed between 0.83 and 1.38 m/s and between 1.38 m/s with and without Stroop task. Longer data series led to more precise estimates for lambda(S-stride), lambda(L-stride), and MaxFm. All variables showed an effect of data series length. Thus, when estimating and comparing these variables across conditions, data series covering an equal number of strides should be analysed. lambda(S-stride), lambda(L-stride), and MaxFm were sensitive to the change in walking speed while only lambda(S-stride) and MaxFm were sensitive enough to capture the modulations of walking induced by the Stroop task. Still, these modulations could only be detected when using a substantial number of strides (>150). PMID:19135478

  16. Effect of milking frequency on DHI performance measures.

    PubMed

    Smith, J W; Ely, L O; Graves, W M; Gilson, W D

    2002-12-01

    Increasing production by increasing milking frequency (MF) is a management option available to dairy producers. This study examined effects of MF and interactions with region and herd size on measures of herd performance. Dairy Herd Improvement (DHI) Holstein herd summary records (n = 10,754, 10,550, and 10,438) for the years 1998, 1999, and 2000 were classified by MF: two times a day (2X) milking vs three times a day (3X); herd size: small (< 250 cows) and large (> or = 250 cows); and region: North and South. Percentage of herds milking 3X by year were 7.0, 6.7, and 7.1. Rolling herd average milk production was 16, 16, and 15% higher for herds milking 3X than herds milking 2X for the respective years. Herds milking 3X in the North region outproduced herds milking 3X in the South region. Milk fat and protein percentages were lower for herds milking 3X during all 3 yr. Differences in energy-corrected milk production between herds milking 3X and herds milking 2X were 14.5, 13.4, and 13.4% during the respective 3 yr as a result of lower component percentages for herds milking 3X. Herds milking 3X had more days open and higher actual calving intervals than herds milking 2X. Services per pregnancy for herds breeding primarily by artificial insemination were higher for herds milking 3X than for herds milking 2X. Somatic cell scores and weighted somatic cell counts were lower for herds milking 3X than herds milking 2X. Herds milking 3X had a higher percentage of somatic cell scores in the low range (0 to 3) and a lower percentage in the high range (7 to 9). Mean percentages of cows entering and leaving the herd were higher for herds milking 3X during all 3 yr.

  17. Precision frequency synthesizing sources with excellent time/frequency performances

    NASA Technical Reports Server (NTRS)

    Zhou, Liren; Lin, Hai

    1994-01-01

    Precision frequency synthesizing sources are needed in the time / frequency measuring system, atomic frequency standards, telemetry, communication, and radar systems. This kind of frequency synthesizing source possesses high frequency accuracy and excellent long term and short term frequency stability. Several precision frequency synthesizing sources developed by Beijing Institute of Radio Metrology and Measurement (BIRMM) which have been successfully applied to the time / frequency measuring system, atomic frequency standards system, and radar system are described. In addition, the working principle, implementation approach, and the main technical specifications of the frequency synthesizing sources are also given.

  18. Quantitative Measurement of the Doppler Shift at an Ultrasonic Frequency

    ERIC Educational Resources Information Center

    Nerbun, R. C.; Leskovec, R. A.

    1976-01-01

    Discussed is a Doppler shift laboratory experiment for an introductory college physics course. Ultrasonic transducers and a digital phase detector circuit "black box" are used to overcome room noise and "standing waves" and to produce an observable frequency shift. (SL)

  19. Scaling, stability and distribution of the high-frequency returns of the IBEX35 index

    NASA Astrophysics Data System (ADS)

    Suárez-García, Pablo; Gómez-Ullate, David

    2013-03-01

    In this paper we perform a statistical analysis of the high-frequency returns of the IBEX35 Madrid stock exchange index. We find that its probability distribution seems to be stable over different time scales, a stylized fact observed in many different financial time series. However, an in-depth analysis of the data using maximum likelihood estimation and different goodness-of-fit tests rejects the Lévy-stable law as a plausible underlying probabilistic model. The analysis shows that the Normal Inverse Gaussian distribution provides an overall fit for the data better than any of the other subclasses of the family of Generalized Hyperbolic distributions and certainly much better than the Lévy-stable laws. Furthermore, the right (resp. left) tail of the distribution seems to follow a power-law with exponent α≈4.60 (resp. α≈4.28). Finally, we present evidence that the observed stability is due to temporal correlations or non-stationarities of the data.

  20. Frequency stabilization of single layer graphene oscillators through optical injection locking

    NASA Astrophysics Data System (ADS)

    Houri, Samer; Cartamil Bueno, Santiago; Venstra, Warner

    Single layer graphene (SLG) drum resonators offer exciting prospects as experimental testbeds for nonlinear dynamics. Recently, photo-thermal induced feedback effects leading to self-oscillations in graphene have been demonstrated. In this paper we examine the phase jitter of self-oscillating SLG, and the means to improve the frequency stability through optical injection locking. The resonator consists of an SLG on top of a 10 micron diameter circular cavity with a cavity depth of 750 nm. By shining a 10 mW He-Ne laser the drum enters a regime of photo-thermally induced self-oscillation. The oscillating SLG suffers from a significant phase noise that can be directly observed in the time domain as random walk of the oscillation period. By applying a lock tone to the oscillator through the application of a modulated blue laser (405 nm), the SLG motion is then phase locked to the applied tone with more than an order of magnitude improvement in its coherence time. The injection locking is also studied as a function of lock signal detuning and power. Presenting author.