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Recently, the first direct detection of the long-searched low-lying isomeric first excited state of 229Th could be realized via its internal conversion decay branch, which confirms the isomer's existence and lays the foundation for precise studies of its decay parameters, in particular its half-life and excitation energy. Follow-up studies confirmed the theoretically expected lifetime reduction by...
We recently reported a 5×10−17 level frequency comparison of two 40Ca+ optical clocks, one of which has fractional frequency uncertainty of 3.4×10−17, limited by the BBR effect. Here we present progress towards a 40Ca+ optical clock with uncertainty at the 10−18 level. The differential static scalar polarizability Δα0 of the 40Ca+ ion clock transition is obtained by precisely measuring the “magic”...
We describe China Area Positioning System (CAPS) to transfer Time and Frequency between ground and space using a round-trip link via a transparent transponder onboard a satellite. The purpose is generation of navigation signals from ground, which appear to come from a non-physical “virtual” on-board clock, and its time modulation being close to UTC at the satellite transponder output. The system is...
Introduction of tensile stress via localized Joule heating has yielded some of the highest metal MEMS resonator Q's measured to date, as high as 48,919 for a 12-MHz ruthenium micromechanical clamped-clamped beam (‘CC-beam'). The high Q's continue into the VHF range, with Q's of 7,202 and 4,904 at 61 and 70 MHz, respectively. These marks are substantially higher than the 6,000 at 10 MHz and 300 at...
For the first time, this paper demonstrates the cancellation of nonlinear response in weakly coupled resonators. It has been observed that by working in the region where the mechanical nonlinearity of the resonators and the electrical nonlinearity of the electrostatic coupling cancel, the output current amplitudes are increased by 4x while the trend of vibration amplitude variation upon stiffness...
This paper presents the effect of elastic anharmonicity in AlN film on the nonlinear performance of extensional AlN resonators. Elastic energy distribution is tailored through dispersion engineering of the waveguide to avoid boundary-induced nonlinearities and enable the study of the elastic anharmonicity contribution on the amplitude-frequency (A-f) characteristic. A 97MHz resonator with a Q of ∼2,250...
We discuss theoretically the new concept of dual phononic and photonic (phoxonic) crystal for sensing the light and sound velocities of fluidic analytes. We show that such a structure can support cavity modes with well confinement of both electromagnetic and acoustic fields with high quality factors. These modes give rise to peaks or dips in the transmission spectrum that are sensitive to both the...
This work investigates design criteria for an array of polymer-coated shear-horizontal surface acoustic wave sensors for detection of aromatic compounds directly in groundwater and wastewater. In addition to the sensitivity and selectivity issues, coating stability in water and long-term repeatability of the sensor response have been investigated. The compounds used in designing the coating have been...
We present a unique lateral bulk resonance mode with a lateral strain profile that resembles a shirt button that we transduce piezoelectrically in a MEMS disk resonator. This button-like (BL) mode offers the 3-fold benefits of (1) intrinsic feedthrough cancellation using fully-differential transduction, (2) strong piezoelectric coupling from the associated strain profile, and (3) higher quality (Q)...
We present a novel composite comprised of piezoelectric PMN-PT nanoparticles embedded in a SU8 polymer matrix that can be spin coated on any substrate to realize acoustic resonators and transducers. High Overtone Bulk Acoustic Resonators (HBARs) are fabricated using this novel composite on a low acoustic loss silicon substrate. Initial experimental results yield piezoelectric coefficient (d33) as...
The Allan variance is the key measure for stability analysis, a fundamental tool to establish the performances of atomic clocks, which are often critical elements in many applications, such as global navigation satellite systems (GNSS). In some applications, only frequency measurements with numerous missing data are available. Because of missing data, the resulting Allan variance can be dramatically...
Clock ensembles are at the core of many applications in which precise time or frequency is required. The widely used time scale algorithms need cumbersome modifications when clocks can be potentially faulty. Fault-tolerant clock synchronization algorithms from distributed systems allow to build time scales without the need of special detection systems for anomalous behavior of the clocks. We present...
The article presents research results on predicting the deviations for UTC(AOS) timescale realized on the basis of hydrogen maser by means of GMDH type neural network. Input data are prepared in the form of two time series (TS1 and TS2). Time series TS1 is built on the basis of values of comparison between the UTC(AOS) timescale with a clock realizing this scale, and values of deviations determined...
In the early 1980s, it was common to hear that Rb atomic clocks were limited to Sy(τ) = 10−11/τ1/2 at best, and that their ultimate frequency stability could never be better than low-parts of 10−13. Twenty-first century Rb clocks put the lie to those pronouncements. Today, it is not uncommon for vapor-cell clocks to exhibit short-term stabilities at low-parts of 10−13/τ1/2, and ultimate stability...
This paper presents the results of the ESA funded C-MAC activity, started mid-2015 and currently in the assembly and testing phase. The objective of the activity is to develop an innovative and low-cost ceramic-based physics package (PP) for ultra-low power miniature atomic clocks (MACs) with flat form factor for future portable devices (GNSS receiver, smartphone, tablet, laptop, etc.) and high-end...
We apply an innovative method called Optically-Detected Spin-Echo to measure the intrinsic coherence relaxation time in the buffer-gas vapor cell of a Rb atomic clock [1]. This method suppresses the influence of static-magnetic-field-gradients across the cell which is a source of relaxation processes. Such studies are of interest for high-performance Rb atomic clocks, where both intrinsic population...
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