Time and Frequency Activities at KRISS

Transcription

1 Time and Frequency Activities at KRISS Dai-Hyuk Yu Center for Time and Frequency, Division of Physical Metrology Korea Research Institute of Standards and Science (KRISS)

2 Time and Frequency Transfer (GNSS) Receivers of GNSS time transfer at KRISS Ashtech Z12-T: 2 sets (master Rx) Multi-ch. P-code/PPP Septentrio PolaRx3e: 1 set Multi-ch. P-code/PPP GPS & GLONASS Piktime TTS4: 1 set Multi-ch. P-code/PPP GPS & GLONASS & Galileo Dicom GTR51: 1 set Multi-ch. P-code/PPP GPS & GLONASS & Galileo Asia link VSAT GNSS Antennas Asia-EU link VSAT Study on GLONASS PPP by using the Bernese new antenna tower new experimental room

3 Time and Frequency Transfer (TWSTFT) Two Way Satellite Time and Frequency Transfer Asia link via Eutelsat-172A KRISS NICT TL SATRE modem & SDR supplied by TL Asia-Europe link vis AM22 PTB - KRISS, NIM, NTST, VNIIFTRI Study on Improvement of carrier phase measurement

4 KRISS-F1 Cs & Rb double fountain as the second fountain at KRISS. (111)-configuration Cs fountain Contributes to TAI Improves UTC(KRIS) Gives the best Cs SI second and its uncertainty to Yb optical lattice clock Rb fountian Secondary representation of the SI second Precision measurement of clock transition frequency with respect to Cs fountain

5 New laser system based on DBR lasers M M AOM 3 Downward beam Detection (F g =3) AOM 2 M Upward beam TA AOM 4 Detection (F g =4) M AOM 6 Repumping DBR AOM 1 AOM 5 MTS ECDL MTS DBR

6 Short-term stability with DBR master laser Intensity noise Frequency noise Signal-to-noise ratio H-maser: σσ yy 1 ss ~ Detection laser (DBR): σσ yy 11 ss ~

7 Simple precision phase transient analyzer Interferometer (IF) switch CSO 11.2GHz 100 MHz Synthesizer 9 GHz SSB 9.1 GHz Voltage controlled RF attenuator MHz KRISS-F1(Cs) Downconverter 800 MHz DDS MHz MHz 100 MHz DDS2 Reference 100kHz Reference Signal Lock-in amplifier 100kHz Digital lock-in amplifier

8 Analysis and optimization of IF switch ~ 92.6 MHz φφ SSSS φφ LLLL 100 MHz LO 9 GHz phase deviation (µrad) φφ LLLL + φφ SSSS VCO V bias 1.0 Vdc 2.0 Vdc 2.2 Vdc 2.5 Vdc 3.0 Vdc time (ms) φφ SSSS ττ = aa 1 sin 2ττ + aa 2 sin 4ττ+aa 3 sin 6ττ+aa 4 sin 8ττ φφ LLLL ττ = constant Frequency error due to SW:

9 Microwave leakage shift Frequency differences between with and without IF switch Fractional frequency difference (10-15 ) Measurment fitted with A n sin(n π/2) Ramsey pulse area (π/2) Frequency shift due to microwave leakage for π/2 pulse:

10 Yb Optical Lattice Clock: Improvements Clock laser linewidth and jitter: ~1 Hz Increasing coherence of atom Reducing short-term stability Better uncertainty evaluation Lattice depth : ~2500 E r Higher cavity finesse Better extinction ratio of linear pol. of lattice Better uncertainty evaluation from latticeinduced shift BBR environment New Laboratory drift RT < 0.3 o C Black-coating inside UHV chamber

11 Lattice parameters & Spectrums Thin film polarizer R=99.5 % R = 98.8 % Lattice Input P= 900 mw of 759 nm Build-up factor > 66 w 0 ~ 100 mm 70 E r < Lattice Trap < 2500 E r View port T=99.7 % w 0 ~ 100 mm 2200 E r Dichroic mirror R=99.8 % R = 99.8

12 Rabi Oscillation Rabi spectrum T=80 ms, FWHM~ 8 Hz

13 Cancellation of collisional shift! γ= 0.23 (4.9 µk) γ = 0.15 (3.9 µk) γ = 0.15 (3.9 µk) Pulse area Inhomogeneity Frac. shift Frac. uncertainty 0.6π π over-π pulse + small inhomogeneity cancel the collisional frequency shift S. Lee et al. New J. Phys. 18, (2016)

14 Atomic gravimeter Atomic gravimeter Absolute gravimeter with high sensitivity using atomic coherence Physical constant measurement Gravitational constant G, fine-structure constant a Test of general relativity Testing of equivalence principle, measurement of gravitational redshift and gravitational wave Other Applications Inertial sensor for navigation Precision measurement of geoid watt balance project Investigation of under ground structure and resource T height 0 time I II Laser pulse T I II

15 Physics package and magnetic shields

16 Gravitational acceleration g shots average data T = 44 ms T = 46 ms T = 48 ms T = 50 ms N 2 /N T Sensitivity is limited by vibration noise 0.40 gg = g = α/k eff Oct (Lunar) Sweeping rate α (Hz/s) aa kk eeeeee (Δφφ = 0 independent of T) g (µgal) Nov 20 Nov 22 Nov 24 Nov 26 Nov 28 Nov MJD

17 Sensitivity improvements 0.60 Single shot data 0.60 Single shot data N 2 /N T N 2 /N T Sweeping rate α (MHz/s) gg = 0.30 aa kk eeeeee gg = aa kk eeeeee Sweeping rate α (MHz/s)

18 Miniature Atomic Clock Potential applications in civil and military industries Information and communications, navigation, GPS, smart grid, satellite, timing devices, sensor watching, etc. Target performance Stability 1s Volume 25 cm 3, Power consumption 125 mw Physics package CPT resonance curves Clock transition

19 Dissemination of the Korea Standard Time Broadcasting of Time Signal (call sign: HLA) 5 MHz, 5 kw Time service through internet NTP time server at KRISS 260 million/day

20 LF Station in Korea Project: 2015~2019 Signal: KST + Information (public, commercial?) Carrier frequency: 65 khz 500 km Reference and Control station Transmitting station Synchronization with UTC(KRIS)

21 Test Station Spec. Place: ~Center of Korea Peninsula Antenna height: 132 m Carrier Frequency 65 khz Transmitter Power: 50 ~ 100 kw Expected operation: early 2018

22 Design of Test Bed Antenna Antenna type: umbrella Antenna angle: about 40 degrees Antenna shape Polarization: isotropic TLE length: about 66 m Number of TLE: about 16 Vertical characteristics Horizontal characteristics

23 Workshop on Optical Clocks Workshop on Optical Clocks and Related Applications ( ~23) - Host: KRISS & INRIM(Italy) - Date: 22~23 July Venue: KRISS in Daejeon - Participants: 68 (Foreign 36, Korean 32) - Invited Talk: 15 - Poster Presentation: 14 - Lab Tour

24 Thank you