![]() ![]() Improvements in the stability performance and reduced mass and volume make the H-maser competitive in modern scientific research applications.Ī typical stability performance of 10 −15 to 10 −16 per day has been reached for the traditional design and a better than 1 × 10 −16 has been demonstrated in the laboratory ( Figure 1). H-maser-related studies performed world-wide demonstrated its applications in the fields of time-keeping, the deep space network (DSN), and the very long base line interferometry (VLBI) network for radio astronomy and geophysics, as well as the global navigation satellite system (GNSS) and others. The H-maser experiments originated in an effort to develop a device that proved four features : 1) a narrow resonance line 2) a reduced broadening of the line due to some effects 3) a reduced first-order Doppler shift and 4)a favorable signal-to-noise ratio. ![]() The H-maser dates back to the 1960s or even earlier. Tables 1– 3 demonstrate the best performance of the H-maser for a τ value of approximately 10 3. Comparisons of the frequency stability performance of the H-maser to those of the Cesium beam tube and Rubidium frequency standards are reported in Refs. ![]() The accuracy and stability performance of the H-maser are mainly limited by factors such as the relaxation time, thermal noise, wall shift, second-order Doppler shift, and second order Zeeman effect, depending on the particular design. The stability of the frequency output of the H-maser is typically a few parts in 10 15 for an average time interval, τ, of the order of 10 3–10 5 s. The frequency accuracy of the H-maser is approximately 1 × 10 −12, which is not sufficient for a primary frequency standard compared to the 1 × 10 −13 accuracy of the Cesium beam standard. The H-maser is larger in volume than the other two frequency standards. We also review some of its fields of application. Rather than focusing only on comparing the H-maser to the other two well-developed atomic frequency standards namely, the cesium beam atomic frequency and rubidium frequency standards, this review discusses the frequency accuracy and stability performance, the volume and mass weight for particular applications, and the power consumption of the H-maser. The hydrogen microwave amplification by stimulated emission of radiation (H-maser) is an atomic frequency standard widely used in ground and on-board-based settings. Along with upgrades to the frequency stability performance of the H-maser, improved knowledge of the world has also been reported. H-maser is one of three well-developed microwave atomic frequency standards and is widely used worldwide in both ground and on-board-based settings. A variety of H-maser designs have been developed for the demands of space science applications, including the deep space network (DSN) and the gravity probe (GP) experiment. Since 1960, when the first hydrogen frequency standard, the microwave amplification by stimulated emission of radiation (maser), was developed in the laboratory of Norman Ramsey at Harvard University, the performance of its frequency stability and technique development have been closely related to scientific research. 2School of Materials Science and Engineering, Shanghai University, Shanghai, China.1Laboratory of Time & Frequency Technology Research, Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, China. ![]() Jiayu Dai 1*, Tiexin Liu 1, Yong Cai 1, Zhichun Chen 1 and Qi Li 1,2 ![]()
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