共查询到20条相似文献,搜索用时 15 毫秒
1.
Szymaniec K Chalupczak W Weyers S Wynands R 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2007,54(9):1721-1722
We describe a situation where a varying collisional frequency shift in cesium fountain primary frequency standards can be misinterpreted as a power-dependent shift. This misinterpretation may affect analyses of fountains test-operated at multiple pi/2 microwave pulse areas. Such tests are typically performed in the search for microwave- and cavity-related systematic frequency biases. 相似文献
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Dudle G Mileti G Joyet A Fretel E Berthoud P Thomann P 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2000,47(2):438-442
We report on the primary frequency standard now under construction at the Observatoire de Neuchatel (ON). The design is based on a continuous fountain of laser-cooled cesium atoms, which combines two advantages: the negligible contribution of collisions to the inaccuracy and the absence of stability degradation caused by aliasing effects encountered in pulsed operation. The design is reviewed with special emphasis on the specific features of a continuous fountain, namely the source, the microwave cavity (TE(021) mode), and the microwave modulation scheme. The possible sources of frequency biases and their expected contributions to the error budget are discussed. Based on present data, an accuracy in the low 10(-15) range and a short-term stability of 7.10(-14) are attainable simultaneously under the same operating conditions. 相似文献
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Jingbiao Chen 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(9):1685-1688
An experimental scheme to simulate the Blackbody radiation (BBR) frequency shift with carbon dioxide (CO2) laser in cesium fountain frequency standard is proposed. The alternative (ac) electric field from a CO2 laser with 10.6 microm wavelength causes the similar ac Stark shift of the clock transition frequency, but with much higher intensity than BBR power intensity at about room temperature. This scheme provides a simple, new method for measuring the BBR frequency shift in fountain clock. It provides the possibility to explain the difference of BBR shifts in Cs fountain clocks between two measurement methods. 相似文献
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Jingbiao Chen 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(9):1685-1688
An experimental scheme to simulate the blackbody radiation (BBR) frequency shift with carbon dioxide (CO/sub 2/) laser in cesium fountain frequency standard is proposed. The alternative (ac) electric field from a CO/sub 2/ laser with 10.6 /spl mu/m wavelength causes the similar ac Stark shift of the clock transition frequency, but with much higher intensity than BBR power intensity at about room temperature. This scheme provides a simple, new method for measuring the BBR frequency shift in fountain clock. It provides the possibility to explain the difference of BBR shifts in Cs fountain clocks between two measurement methods. 相似文献
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Domnin Yu. S. Elkin G. A. Novoselov A. V. Baryshev V. N. Kopylov L. N. Malyshev Yu. M. Pal’chikov V. G. 《Measurement Techniques》2005,48(1):16-23
Results of research aimed at creating a new generation of quantum frequency standards, i.e., a cesium fountain, are presented. Measurement data for controlling and detecting cold atoms are analyzed. The possibility of cooling cesium atoms to a level of the order of 2 µK is demonstrated by experiment.Translated from Izmeritelnaya Tekhnika, No. 1, pp. 18–23, January, 2005. 相似文献
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Taeg Yong Kwon Ho Seong Lee Sung Hoon Yang Sang Eon Park 《IEEE transactions on instrumentation and measurement》2003,52(2):263-266
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. 相似文献
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We calculate the shift in velocity of an ion trapped on a vortex, line in He II when, in addition to a dc electric field directed along the line, an ac field is applied perpendicular to the line. We employ a model of the ion on a line first introduced by Ohmi and Usui and used by them to calculate the dc mobility. The ion drift velocity in the presence of the ac field exhibits a nearly flat plateau as a function of dc field and a canted dip as a function of frequency. The present calculation differs in some details from the earlier one and permits a more reliable estimate of the change in velocity.This work is supported in part by two grants from the National Science Foundation: DMR 72-03221 A01 and GH-34890. 相似文献
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Daphna G Enzer William M Klipstein 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(9):1564-1569
We characterize the light shift in the interaction region of a laser-cooled frequency standard and demonstrate an approach for its mitigation without the use of mechanical shutters. The light shift is confirmed to be below 10-15 and expected to be orders of magnitude lower. This technique makes use of a master-slave laser configuration where cutting the injection power to a slave laser causes it to lase at its free-running wavelength, often two or more nanometers off from the atomic resonance. 相似文献
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Enzer D.G. Klipstein W.M. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(9):1564-1569
We characterize the light shift in the interaction region of a laser-cooled frequency standard and demonstrate an approach for its mitigation without the use of mechanical shutters. The light shift is confirmed to be below 10/sup -15/ and expected to be orders of magnitude lower. This technique makes use of a master-slave laser configuration where cutting the injection power to a slave laser causes it to lase at its free-running wavelength, often two or more nanometers off from the atomic resonance. 相似文献
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Jefferts SR Shirley JH Ashby N Burt EA Dick GJ 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2005,52(12):2314-2321
We discuss the implications of using high-power microwave tests in a fountain frequency standard to measure the frequency bias resulting from distributed cavity-phase shifts. We develop a theory which shows that the frequency bias from distributed cavity phase depends on the amplitude of the microwave field within the cavity. The dependence leads to the conclusion that the frequency bias associated with the distributed cavity phase is typically both misestimated and counted twice within the error budget of fountain frequency standards. 相似文献
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Gupta AS Popovic D Walls FL 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2000,47(2):475-479
The paper describes a new approach to synthesizing the Cs hyperfine frequency of 9.192 GHz that is designed to be sufficiently rugged for use in space, specifically for the Primary Atomic Reference Clock in Space (PARCS) planned for the International Space Station, as well as ground applications. This new approach requires no narrow band filters or frequency multiplication, and the primary source of cooling is conduction. Instead of frequency multiplication, it uses a custom regenerative divider stage followed by two commercial binary dividers and several mixing stages. A fractional frequency step of 2x10(-17) is achieved by mixing the output of a 48-bit numerically controlled oscillator with the microwave signal. Preliminary tests on the new synthesizer design indicate an internal fractional frequency stability of 1x10(-15) at 10 s and 1x10 (-18) at 1 d, dominated by the daily room temperature variations. The phase and amplitude noise are similar to our previous designs that used frequency multiplication and narrow band filters. The temperature coefficient is less than 0.2 ps/K. 相似文献
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Weyers S Bauch A Hubner U Schroder R Tamm C 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2000,47(2):432-437
At the Physikalisch-Technische Bundesanstalt (PTB), an atomic caesium fountain was constructed. Ramsey fringes with a full width at half maximum (FWHM) of 0.86 Hz were obtained by launching the atoms to a height of 83 cm above the cooling region (40 cm above the microwave cavity center). A first measurement of the homogeneity of the magnetic flux density yields 0.33 nT (rms), only 0.16% of the mean value of 0.205 muT used in normal operation. The inherent elementary noise contributions of the fountain and of a thermal beam atomic clock are compared in some detail. 相似文献
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《International Journal of Impact Engineering》2002,27(3):317-341
We discuss the modeling of the coefficient of restitution as a function of the incoming velocity in elasto-plastic collisions with normal frictionless impact, and compare the results from nonlinear finite-element analysis to those of two recent normal force displacement models: One by Thornton (ASME J. Appl. Mech. 64 (1997) 383) and one by Vu-Quoc and Zhang (Proc. R. Soc. London, Ser. A 455 (1999) 4013) which is the displacement-driven counterpart of the force-driven model proposed by Vu-Quoc, Zhang, and Lesburg (ASME. J. Appl. Mech. 67 (2000) 363). The resulting values of the coefficient of restitution are also compared to those from the model proposed in Stronge (in: R.C. Batra, A.K. Mal, G.P. MacSithigh (Eds.), Impact Waves and Fractures, ASME AMD 205 (1995) 351). The relationships among the coefficient of restitution, the incoming velocity, the collision time, the contact force/displacement, the normal pressure distribution are presented and discussed. These results establish the better accuracy provided by the model proposed by Vu-Quoc, Zhang, and Lesburg, when compared to previously proposed models. 相似文献
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Jinquan Deng 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2001,48(6):1657-1661
One of the most important physical processes occurring in Rb frequency standards is the light shift, which depends strongly on the intensity and the optical frequency detuning of the pumping light. This paper presents a method to compensate the light shift by means of two-laser pumping. The two-laser pumping schemes will also improve the signal-to-noise ratio, because almost all atoms can be pumped to the desired state 相似文献