Development and Preliminary Operation of 87Rb Continuously Running Atomic Fountain Clock at NTSC

Abstract

An atomic clock with excellent long-term stability is important for maintaining the Local Atomic Time (TA(k)). The 87 Rb atomic fountain clock has the potential to fulfill these characteristics. It is required to operate continuously, similar to commercial cesium beam clocks and hydrogen masers. This paper describes the design and preliminary operation results of an 87 Rb atomic fountain continuous clock ( 87 RFCC) developed at the National Time Service Center (NTSC) of the Chinese Academy of Sciences. We adopted some improved design aspects and suppressed Majorana effect and microwave leakage to enhance the clock’s stability. Its continuous operation has been improved owing to the advantages of the high-reliability optical system and servo high-resolution offset generator (HROG) algorithm. We presented an algorithm for the 5 MHz/1 PPS signal output of the 87 RFCC through the HROG. The 87 RFCC exhibited a frequency stability of 1.91×10 -13 τ -1/2 , reaching 4.7×10 -16 at 200000 s. We referenced the 1 PPS output signal to the UTC(NTSC) and obtained the relative phase fluctuation of the 87 RFCC, which was within ±1.75 ns for approximately 90 days. We estimated the preliminary drift of the 87 RFCC relative to the UTC(NTSC) for three different periods at 0.000019±0.00148 ns/d/d, 0.00119±0.00182 ns/d/d, and -0.00155±0.00060 ns/d/d and discussed the results. During the 90-day evaluation period, although the frequency of the 87 RFCC relative to the UTC(NTSC) had changed, it still exhibited a low drift compared to cesium beam clocks and hydrogen masers, which highlights its potential for excellent long-term stability. The 87 RFCC investigated here has the potential to improve the local time scale.

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