Optically pumped rubidium as a frequency standard at 196 THz

The performance of 196.0-THz (1529-nm) DFB lasers frequency-locked to absorption lines of a rubidium vapor optically pumped at 384.2 THz (780.2 nm) is studied. The absorption profiles of the pumped vapor are measured under various conditions and compared with theoretical predictions. A bright resonance resulting from the cascade of two cycling transitions is characterized both experimentally and theoretically. The measured frequency stability of a DFB laser frequency-locked to this line reaches a level of 2×10^-10 for an averaging time of 100 s when compared to a similar laser locked to an acetylene line     

Environmental factors and hydrogen maser frequency stability

It is necessary to have a complete understanding of the environmental sensitivities of cavity-tuned hydrogen masers to obtain optimum frequency stability and to avoid common-mode frequency fluctuations. Measurements of environmental sensitivities (temperature, relative humidity, atmospheric pressure, line voltage and magnetic field) made at the National Institute of Standards and Technology have demonstrated that the frequency stability of a cavity-tuned, active hydrogen maser is not significantly degraded if the maser is operated in a moderately controlled environment. Under these conditions, common-mode frequency fluctuations caused by the observed environmental factors also are negligible.     

Research in creating a fountain type frequency standard

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.     

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.     

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.     

Incorporating data from a primary frequency standard into a timescale

It is difficult to combine data from a primary frequency standard with the time-difference measurements that are usually used as input to most time scales because a primary standard usually operates only occasionally on an irregular schedule and because the fundamental output of a primary frequency standard is a frequency rather than a time, and there is often no natural way of inserting this kind of datum into the scale in a manner that is statistically robust. We will present a new time-scale algorithm that seeks to address these problems. We call this frequency-based algorithm AF1, by analogy with the time-based algorithm AT1 that has been used at NIST for many years. Unlike AT1 in which frequency is simply a parameter that specifies how the time of a clock evolves between measurements, however, the frequency of each clock is a fundamental parameter in AF1. This change in focus provides a natural way for incorporating data from a primary frequency standard into the ensemble. We will present the details of the algorithm and results using data from our primary frequency standard, NIST-7     

Temperature fluctuations in a solid-nitrogen cooled secondary frequency standard

Liquid helium and liquid nitrogen are commonly used as coolants for highly frequency stable oscillators. In this paper, we present the use of solid nitrogen as an alternative coolant. Solid nitrogen solidifies near 52 K under vacuum and we show that the temperature fluctuations in the solid are an order of magnitude lower than in the liquid. This has the advantage of reducing the temperature control requirements necessary to limit temperature induced frequency fluctuations in cryogenic microwave resonator-oscillators.     

A transportable working frequency standard

Summary The use of GSVCh standard reference frequency signals transmitted by radio, in combination with transportable RÉCh radio broadcasting stations, can play a decisive role in maintaining consistency and accuracy in frequency measurements under any operating conditions of radio engineering equipment, as confirmed by the results of experimental operation, certification, and confirmation of the transportable working frequency standard at VNIIFTRI.Translated from Izmeritel'naya Tekhnika, No. 9, pp. 91–93, September, 1974.     

High-power free-electron maser with frequency multiplication operating in a shortwave part of the millimeter wave range

The possibility of using frequency multiplication in order to obtain high-power short-wavelength radiation from a free-electron maser (FEM) with a Bragg resonator has been studied. Preliminary experiments with an LIU-3000 (JINR) linear induction accelerator demonstrate the operation of a frequency-multiplying FEM at megawatt power in the 6- and 4-mm wave bands on the second and third harmonic, respectively.     

9.9Tc as a dosimetric standard

Translated from Izmeritel'naya Tekhnika, No. 3, pp. 46–47, March, 1989.