铯束原子频率标准装置测量不确定度的分析

时间计量已经广泛地用于现代科学技术的各个方面,并且用于对其它物理量的间接测量之中,因而作为时间频率量值传递系统中的一级频标——铯束原子频率标准不确定度分析就显的尤为重要。本文介绍了用铯束原子频率标准装置测量不确定度的评定过程,并给出了计算过程及表达方式。     

Modern tools for accurate gas flow measurements

Measurement Techniques -     

A new design of a diffused laser light optically pumped small cesium beam frequency standard

A new set-up of a small Cs clock has been successfully experimentally tested. The short-term stability (2x10(-12)) and the long-term stability (3.5x10(-13) for a day sample time) have been measured. Only one laser is needed without any frequency shift device. The light frequency shift caused by diffuse light was calculated and measured.     

Systematic shift uncertainty evaluation of IEN CSF1 primary frequency standard

We report a preliminary systematic shift uncertainty evaluation of our cesium fountain and of the first comparison with the NIST-F1 clock of the National Institute of Standard and Technology (NIST) with a two way satellite comparison system. The stability of the time scale UTC (IEN), (generated with a commercial Cs beam) is insufficient to allow evaluation of systematic shifts by conventional techniques; therefore, the accuracy evaluation of the fountain was accomplished using mainly fast differential techniques, resulting in an overall uncertainty of 3/spl times/10/sup -15/.     

Cryogenic dual-mode resonator for a fly-wheel oscillator for a caesium frequency standard

A dual-mode, sapphire-loaded cavity (SLC) resonator has been designed and optimized with the aid of finite element software. The resonance frequency was designed to be near the frequency of a Cs atomic frequency standard. Experimental tests are shown to agree very well with calculations. The difference frequency of two differently polarized modes is shown to be a highly sensitive temperature sensor in the 50 to 80 K temperature range. We show that an oscillator based on this resonator has the potential to operate with fractional frequency instability below 10/sup -14/ for measurement times of 1 to 100 seconds. This is sufficient to operate an atomic clock at the quantum projection noise limit.     

Estimating the total error for a distributed group standard for time and frequency

Studies have been made on the systematic and random errors in the group frequency and time scale for a distributed group standard for the units of time and frequency. A new approach has been devised for calculating the total error of secondary standards. __________ Translated from Izmeritel’naya Tekhnika, No. 6, pp. 24–26, June, 2008.     

Hydrogen maser as a quantum frequency standard

Conclusions The main factors limiting the frequency stability of a hydrogen maser over long periods are magnetic field drift, error in the compensation setting, and inconstancy in bulb temperature. Future researches will be directed to raising the long term stability with continuous operation. We have developed a hydrogen maser with automatic magnetic field stabilization, with an improved frequency modulator that introduces very little Q change, and with a thermostatic cavity. In six months of preliminary tests the systematic frequency drift has been zero from day to day within 10^–13. Atomic clocks of this type may be recommended as working time reference standards.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 29–32, November, 1972.     

原子频标频率漂移率测试系统

针对铷原子频标的日漂移率的测试需求,采用时差法设计日频率漂移率检测装置。该装置通过多路分频器,将被测频标1 MHz、5 MHz、10 MHz信号分频为标准1PPS信号。GPIB接口控制时间间隔计数器测量时差数据并传输给计算机,计算测量结果。装置自动化程度高、工作稳定,实现对多台铷原子频标日频率漂移率的自动化测量。     

Optimized scheme of a rubidium all-optical frequency standard

A new approach to the creation of a quantum frequency standard based on the phenomenon of coherent population trapping is proposed, which employs linearly polarized radiation and involves signal discrimination at the absorption maximum.     

Development of a cesium atomic fountain frequency standard

We report on the development of a cesium atomic fountain frequency standard at the Korea Research Institute of Standards and Science (KRISS). Cesium atoms were launched upwards by using an optical moving molasses method after they were cooled in a magnetooptical trap. The temperature of launched atoms was about 2.5 /spl mu/K. From our cesium atomic fountain, we were able to observe Ramsey fringes of 1 Hz linewidth on the 9.2 GHz clock transition of cesium atoms.     

Resonator tuning accuracy in an automatic frequency tuning system for a passive hydrogen frequency standard

An automatic tuning system for a cavity in a passive hydrogen frequency standard is considered, which uses the excitation signal with phase modulation. Numerical and experimental tests have shown that the performance of this system is dependent on the extent of spectrum distortion resulting from the signal and asymmetry of the resonance curve in the UHF cavity.     

Pragmatic software tools for water reuse evaluation in a factory

The optimal use of process water becomes increasingly important since natural water resources are heavily solicited by a growing economy. Two steps can be considered in the process water optimization. A first step is the inventory of the different process streams in the process water network. Pure mathematical modeling of a dynamic water network is extremely complicated and expensive. As an approximation, the use of a steady-state network node model within commercial software is accepted to set up a water balance. Sophisticated software tools are available but common solver software may offer an alternative. A second step is the water “pinch” which searches for an optimal use of process water by combining sources and sinks, taking into account contaminant concentrations of process streams. Sophisticated pinch software can be applied but it is also possible to implement a simplified combinatory approach. Such approach can be pragmatically programmed in e.g., Visual Basic. Such tool allows for a first evaluation of the complex combinatory sources–sinks problem, enabling a low cost and easy-to-handle first interpretation of possible water-reuse opportunities. This could stimulate a further enhanced analysis with more advanced software tools and therefore promote a sustainable use of process water in the industrialized world.     

SIS junctions with frequency dependent damping for a programmableJosephson voltage standard

Experimental and computational results on programmable Josephson junction array (JJA) chips based on superconductor-insulator-superconductor (SIS) junctions are presented. Implications of circuit design and fabrication process on the performance are discussed. We introduce a method to decrease the attenuation of the pump microwave. Different designs are compared, suggesting that 1 V chips operating at the third constant voltage step with 70 GHz pump frequency can be produced with our process