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The U.S. Naval Observatory has an ongoing program to develop atomic fountains for eventual incorporation into the USNO Master Clock. The fountains are being constructed to provide a stable frequency reference which will allow for rapid characterization of drift of masers in our clock ensemble. In support of this goal we are using rubidium to exploit the small cold-collision frequency shift. We report...
Sr-atoms are of special interest for an optical frequency standard since a large number of atoms can be cooled down efficiently to ultra-low temperatures in a magneto-optical trap (MOT) [1]. The ultra-narrow line on the forbidden 1S0 → 3P0 transition of 87Sr (3P0 natural lifetime is approx. 100 s), and the ability to interrogate Sr atoms in a perturbation free dipole trap [2] promise un-precedented...
Three hydrogen masers were put into operation at the earth station of Chinese positioning system four years ago. We have made many physical and electronics improvement on these hydrogen masers for improving the long-term performance. The hydrogen maser's size is 110cm(high)*54cm(width)*73cm(depth). It weighs 250kg.By performance comparing with each other. we may choose the best one as a frequency...
National Institute of Information Communications Technology (NICT) has been developing a Cesium atomic fountain primary frequency standard. In order to achieve the high stability as the frequency standard, we have made efforts to improve the signal to noise (SN) ratio of the signal. The frequency stability is 2×10−12/τ1/2 presently. This report presents the current status of the development of NICT...
A single indium ion stored in a radio-frequency trap and laser-cooled to a temperature below 1 mK is a promising candidate for an optical frequency standard of exceptionally high accuracy and stability. Probing the 5s21S0 - 5s5p 3P0 transition of 115In+ at λ = 237 nm with a natural linewidth of 0.8 Hz by a laser with a sub-Hertz linewidth can lead to an accuracy of 10−18 after several days of averaging...
The research project on the CPT maser was aimed to study the feasibility of the clock and to investigate its stability capabilities. We realized a CPT maser prototype and we tested all its main components: the physical package, the optical and the electronic systems. Electronics and laser noises are well controlled in our apparatus and the measured Allan deviation at 1s is quite close to the expected...
Optimization of Single Phase Unidirectional Transducers (SPUDT) is main problem in thedesign of low-loss SAW filters. Here we deal with Distributed Acoustic Reflection Transducers, each elementary cell (one wavelength) of that includes not more than one “hot”electrode and/or one, two, three or four grounded electrodes [1]. For assembling the input andoutput SPUDTs we use more than ten different cell...
The cold atom space clock PHARAO is under industrial construction since two years. It will be one of the two atomic clocks of the ESA supported ACES mission which will fly on an external pallet of the European module Columbus of the International Space Station. The goal of PHARAO is the study and utilization of a laser cooled cesium clock in microgravity environment. Two models of the clock will be...
An optical clock based upon a single mercury ion in a radio-frequency trap has the potential for both high stability and high accuracy. The systematic uncertainty of this frequency standard is limited by contributions due to two types of external fields. The clock has previously been operated with a magnetic bias field that destabilizes dark states that limit the rates of laser cooling and state detection...
An optical frequency standard is operated at PTB where the frequency of a laser is stabilized to the intercombination transition (λ ≈ 657 nm) in laser cooled Ca atoms. Previously the uncertainty resulting from the residual velocity of the cold atoms at 3 mK limited the fractional uncertainty to 2 × 10−14. We now apply a novel method for producing ultra-cold atoms (λ ≈ 10 µK). The frequency of the...
Recent progress in the development of high-accuracy optical frequency standards has resulted in some of these standards now achieving better stabilities than the caesium fountain microwave standard [1]. In parallel with this, the development of femtosecond lasers with pulse repetition rates that can be referenced to microwave standards, coupled with extensive broadening of the femtosecond pulse spectrum...
We present the realisation of a compact and high-performance Rubidium atomic frequency standard under development for space applications. The clock comprises a compact frequency-stabilised diode laser head for optical pumping of a lamp-removed industrial Rb clock module, in order to exploit the advantages of laser optical pumping for optimised short-term stability. We obtain typical signal contrasts...
The ACES project aims at operating ultra stable clocks on board the International Space Station ISS and comparing them to ground clocks located all around the world. The expected performance of ACES space clocks (frequency stability and accuracy at 10−16 level) and of the dedicated microwave link (time stability better than 10 ps over 1 day) will be of great interest for time & frequency metrology...
The use of GPS Carrier Phase (CP) techniques is now widely accepted as an inexpensive and easy to use method to compare time and frequencies over long distances. A collaboration between the Astronomical Institute of the University of Bern (AIUB) and the Swiss Federal Office of Metrology and Accreditation (METAS) has produced a dedicated Geodetic Time Transfer Terminal (GeTT-Terminal) which was the...
The researches of Two Way Satellite Time and Frequency Transfer (TWSTFT) at TL are very active in the recent years. In Asia Pacific Rim region, TL has joined the Asia-Pacific networks (being organized and sponsored by CRL) since June 2000, and performed the C-band experiments of NML(Australia)-TL and NIST(USA)-TL from September 2002 to April 2003. Moreover, the Ku-band TWSTFT experiments of CRL-TL,...
The WAAS, EGNOS, MSAS, and SNAS GPS-Augmentation Systems bridge the gap between the military applications of GPS and the needs of the civil aviation navigation community. These USA, Europe, and Asian systems consist of a network of differential GPS ground stations, using principally the Inmarsat-3 geo-synchronous satellite constellation as the means of relaying the differential corrections to the...
The time transfer precision of the GPS common-view method with single-channel C/A code receivers has become inadequate for an international time comparison network because of the advances made in atomic clock technology. NICT has been developing carrier-phase time transfer software with geodetic receivers to enable more precise time transfer technology. This paper describes the details of this software...
The use of entangled states can provide an increased sensitivity in quantum-limited spectroscopic measurements, leading to an uncertainty that is inversely proportional to the number of particles instead of the usual square-law dependence [1].
Accuracy of resonator phase noise measurement systems in a passive method depends on the stability of the excitation source. Good accuracy over a quite large frequency range is needed because of the various resonant frequencies of the resonators studied. In this paper, Direct Digital Synthesis solution is investigated as excitation source of measurement bench. Various stability measurements on this...
The total jitter of a signal can be found directly by integrating the sideband spectrum as it appears on a spectrum analyser. If there are any significant spur components, these can be included in the calculation of total RMS jitter if they are identified and corrected in power level according to the spectrum analyser resolution bandwidth. The jitter amplitude PDF (Probability Density Function) can...
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