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| Independent Time Scale TA(NIM), Which is Steered by NIM5 Cesium Fountain Clock |
| GAO Yuan1,GAO Xiao-xun1,ZHANG Ai-min1,WANG Wei-bo1, NING Da-yu1,LIU Nian-feng1,WANG Ping1,LIN Ping-wei1,CHEN Wei-liang1,LI Tian-chu1,HUANG Yan2 |
1.National Institute of Metrology, Beijing 100013, China
2.Beijing Institute of Metrology, Beijing 100013, China |
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Abstract TA (NIM) is an independent atomic time scale. It is steered by a primary frequency standard that is NIM5 cesium fountain clock. The reference clock of TA (NIM) is an active hydrogen maser, which is measured and calibrated by the primary frequency standard periodically. A time scale algorithm can predict future frequency of the hydrogen maser, compensate frequency difference between the prediction and the calibration, and estimate the maser’s frequency when NIM5 fountain is not operational, in order to keep the frequency of TA(NIM) the same as the frequency of NIM5 fountain as much as possible. TA(NIM) began test run from August, 2007 and started to run formally from June, 2008. Data in recent more than one year show that TA(NIM) runs continuously, its time deviation (5 days) relative to TAI is 1.2 ns,and its frequency offset relative to TAI is 2.0×10-15.
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［1］李天初,等. NIM4#激光冷却-铯原子喷泉钟—新一代国家时间频率基准［J］.计量学报, 2004, 25(3): 193－197.
［2］BIPM. Circular T ［EB/OL］. http://www.bipm.org/jsp/en/TimeFtp.jsp?TypePub=publication. |
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2011, Vol. 32 
