資料８－Ａ

Commission A (Electromagnetic Metrology) Activity Report
March 2009 - July 2009

1. Activities in the field of electromagnetic metrology
At National Metrology Institute of Japan (National Institute of Advanced
Industrial Science and Technology), research and developments related with thetime and frequency field are performed by three sections. Time Standards Section isoperating the cesium atomic fountain frequency standard, NMIJ-F1, with theuncertainty of 4x10-15. The second fountain frequency standard, NMIJ-F2, is being
developed with the target uncertainty of 10-16 level. Wavelength Standards Section
has achieved the absolute frequency measurement of the clock transition of Ybatoms with the uncertainty of 5x10-14, and also collaborated with a group at theUniversity of Tokyo and the University of Electro-Communications to evaluate theabsolute frequency of the 87Sr optical lattice clock developed by the University ofTokyo. These results were reported to the CCL-CCTF Frequency Standards
Working Group meeting held on the begging of June 2009. Frequency Measurement
Systems Section is performing research and developments for precise time keeping,dissemination of standards, and traceability.
Standards related with electromagnetic waves are performed at Electricity andMagnetism Division and Electromagnetic Waves Division. The former division isdealing with standards such as electric current, magnetic resistance, and power ofelectric power lines. The later division is performing research on power standards,
noise standards, attenuation standards, and impedance standards. The antenna
calibration for precise measurement is also performed at the same division.
At National Institute of Information and Communications Technology, researchand developments related with time and frequency are currently conducted by theSpace-Time Standards Group of the New Generation Network Research Center. The
objectives of this group are to establish standards and reference of space and timeas the fundamental basis for various fields of activities in science, engineering, andsocial activities, and to provide easy access to these foundations from wide range ofcommunities. Single ion trap system of the Ca+ ion and optical lattice system of Sr
atoms are currently developed to evaluate the accurate clock transition frequencies.
The Electromagnetic Compatibility Group of the Applied Electromagnetic Research

1Center is performing various research related with EMC problems which include
standards of electromagnetic measurement methods and calibrations.
At University of Electro-Communications, a stable transfer system for frequency
standard signals by using optical fiber has been developed and was used to evaluate
the absolute frequency of the clock transition of 87Sr atoms. At Kyoto University,
developments of small size trap systems for multiple ions of Yb+ and Ba+ ions arebeing performed. At Yokohama National University, software GNSS/GPS receiversystems for common view time and frequency transfer are being developed. AtTokyo Metropolitan University, developments of small size atomic oscillator arebeing performed. An experimental system with 85Rb has been developed and verygood performance of long interval frequency stability was demonstrated. A low
phase noise crystal oscillator system with the performance of -120dBc/Hz@1Hz has
also been developed.

2. International meetings
18th meeting of the CCTF (Consultive Committee for Time and Frequency) was
held for two days from June 4, 2009, at BIPM in Sevres, France. Before the main
meeting, second meeting of the CCL-CCTF Frequency Standards Working Group(June 2) and eighth meeting of representatives of laboratories contributing to TAI(June 3) were also held. During these meetings, various fields relating with timeand frequency were discussed. Due to the recent rapid developments of the opticalfrequency standards, optical clocks are now considered to be superior to the best
primary cesium clocks with respect to stability and accuracy. For the possible new
definition of the second, it was emphasized that the strategic cooperation andimprovements of the time and frequency transfer methods are necessary.
The 26th meeting of the CCEM was also held at the Pavillon du Mail in BIPM
on 12 and 13 March 2009. The CCEM working groups met during the days before
the CCEM meeting. The main WGs are the WGLF and the GTRF. The CCEM WG
on radio frequency quantities is the GTRF. The major topic in the meetings was themanagement of Key Comparisons of miscellaneous electric and electromagnetic
quantities, namely power, attenuation, impedance and so on, to keep theCalibration and Measurement Capabilities (CMC) registered in the BIPM databaseof Appendix-C which were important to be used to show the equivalency andconformity of the national metrology standards made by the National Metrology
Institute (NMI) of each country.

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