Status Report on Time and Frequency Activities at National Physical Laboratory India

Transcription

1 Status Report on Time and Frequency Activities at National Physical Laboratory India (TCTF 2015) Ashish Agarwal *, S. Panja. P. Arora, P. Thorat, S. De, S. Yadav, P. Kandpal, M. P. Olaniya, S S Rajput, A Sen Gupta * ashish@nplindia.org 1

2 Major activities Time generation & dissemination Calibration services Major Activities Cesium fountain frequency standards Ytterbium ion optical clock Rubidium Atomic Clock for Space

3 Time Scale Major activities Generation and maintenance of UTC (NPLI) Time transfer using GNSS Time transfer using TWSTFT Dissemination Dissemination by Telephone Time broadcast (Teleclock), and NTP server. Cs Fountain Frequency Standard Frequency evaluation and international inter-comparison of the first Cs Fountain. Development of the second Cs Fountain Rubidium Atomic Clock Development of Space Clock. Development of glass bulbs and cells. Optical Frequency Standards Development of single trapped Yb + ion standard. Calibration Services Atomic Clocks (Rb & Cs Freq Standards), Time Interval Counter, Hour Meter, Teleclocks, GPS timing receivers and Stopwatch. Providing traceability to IRNSS time scale.

4 Time Scale and Time Transfer Links Five Cesium clocks 1 2 UTC (NPLI) Hydrogen maser Accurate to few ns Time transfer via satellite links Antenna systems

5 UTC (NPLI) and UTCr (NPLI) UTC (NPLI) and UTCr (NPLI) in Last One Year October 2014 September2015 UTC-UTC (NPLI) UTC-UTCr(NPLI) MJD

6 UTC(PTB)-UTC (NPLI), ns Typical TWSTFT Results on the Eu-Asia Network April 2014 November 2014 MJD

7 Time Dissemination Teleclock Service Internet Time Service Domain name: time.npli.in

8 NPLI Cesium Fountain Physics Package (0,0,1) geometry for cooling, trapping and launching. Two anti-helmholtz coils generate a field gradient of 9 G/cm at the center of the trap at 5A of current. Three pairs of rectangular Helmholtz coils. Two detection beams, one of 10 mm x 10 mm; another of 5mm X 10mm. Large area (10 mm 2 ) photodiodes for detection. Overall vacuum ~ 6 x Torr with two 55 l/sec ion pumps.

9 NPLI Cesium Fountain Optical Set Up Cooling laser is locked to the crossover peak of the F = 4 F = 4, 5 transition Repump laser is locked to the F = 3 F = 4 transition. Total five AOMs are used. Four in double pass configuration. Four horizontal cooling beams with FWHM of 22mm and two vertical cooling beams and two detection beams with FWHM of 15mm are produced. Polarization maintaining single mode fibers are used to transport the beams to physics package Five relay based mechanical shutters are used to block laser beams to prevent light-shift.

10 International intercomparison 2 x CSF1(PTB)-CSF(NPLI) 2 x CSF2(SU)-CSF(NPLI) TWSTFT TWSTFT 1 GPS PPP 1 GPS PPP Frequency Difference 0-1 Frequency Difference ,419 56,424 56,429 56,434 56,439 MJD -2 56,419 56,424 56,429 56,434 56,439 MJD Frequency offset (CsF-UTC) X 1e MJD

11 Fractional frequency difference between TAI and SI second Frequency offset (X 1e-15) IT CsF1 IT CsF2 NICT CsF1 NIST F1 PTB CsF1 PTB CsF2 NPL CsF2 NPL CsF1 NPLI CsF1 SYTRE FO1 SYTRE FO MJD

12 Progress in development of 2 nd Cs Fountain Design features: (1, 1,1) geometry for cooling and launching to reduce light shifts. Optical pumping to enhance the S/N ratio. Four-feed cavity design to reduce phase shifts. Better estimation of systematic shifts. Improved accuracy and stability

13 New Apex Metrology Laboratory Front View Side View

14 Single Trapped Ytterbium Ion Optical Standard repump 1 Paul Trap Energy levels of 171 Yb + 4f 13 5d6s 1 D[3/2] 3/ f 13 5d6s 3 D[3/2] 1/2 1 4f 14 6p 2 P 1/2 1 0 atom ion Continuum 4f 14 5d 2 D 3/ nm 760 nm (quadrupole ) nm 4 4f 14 6s6p 1 P nm 6s 2 4f 13 2 F 7/2 3 4f 14 6s 2 1 S nm 4f 14 6s 2 S 1/2 1 0

15 Ion Trap:

16 Ultra high vacuum chamber: Turbo pump Ti:sublimation pump Imaging port - Non-magnetic SS - Inner surface electro-polished - Vacuum ~10-12 mbar All metal valve Ion gauge Feedthrough for ion trap Feedthrough for compensation electrodes Ytterbium-oven

17 Status of the Lasers and Optics Lasers Stabilization Light source Mounts & optics Photoionization : 399 nm nm Laser cooling : nm 935 nm 760 nm 10 MHz ~10 MHz ~10 MHz 20 MHz 20 MHz Clock : 467 nm < 1 Hz nm 935 & 760 nm Frequency locking 399 nm

18 Development of Rubidium Atomic Clock Frequency Stability (1 s) 9 x (10 s) 5 x (100 s) 2 x 10-12

19 Rubidium Filling System

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21 Rubidium Lamp

22 Courtesy : ISRO

23 Calibration Services UTC Traceability to the Time scale of the Indian Regional Navigational Satellite System (IRNSS) using all in view GPS P3. Soon a dedicated TWSTFT link with IRNSS time scale will be established. We are providing Calibration Services to Test & Calibration Labs in India for the calibration of Rb & Cs Atomic Clocks, Time Interval Counters, Hour meters, Teleclocks, GPS receivers and Stop watches Synchronization of pan-india Information Technology network of Government of India

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25 Thank You for your Attention!