Status Report on Time and Frequency Activities at KRISS Taeg Yong Kwon Center for Time and Frequency, Division of Physical Metrology Korea Research Institute of Standards and Science (KRISS)

Better Standards, Better Life 2 KRISS Activities Timescale & Time Transfer Generation of UTC(KRIS) and TA(KRIS) Clocks comparison with TWSTFT Clocks comparison with GNSS Microwave frequency standard Atomic fountain clock Optical frequency standard Optical lattice clock using Ytterbium (Yb) Optical frequency combs Calibration and Dissemination

Better Standards, Better Life 3 Generation and Maintenance of UTC(KRIS) and TA(KRIS)  KRISS Timescale generated by using 5 Cs clocks and 4 H-masers Auxiliary Output Generator (Datum, AOG110) RF Distribution Amp. Pulse Distribution Amp. KSFUTC(KRIS) 1 PPS5 MHz Dual Mixer Time Difference Measurement System (Timing Sol, TSC 2000) Ext. 5 MHz BIPM TCP/IP Other Clocks 5 MHz UTC(KRIS) KSF H Maser TWSTFT GPS Time Transfer Receiver GPS PC Communication Satellite

Better Standards, Better Life 4 Dual system

Better Standards, Better Life GNSS Antennas (Ashtech Z12T, PolaRX2e, PolaRX3e, Euro-80, TTR6 etc.) 2. JCSAT-1B VSAT: Ф1.8 m (Asia Link: Stopped) 3. Eutelsat 172A: Ф1.8 m (Asia Link): ongoing 4. AM2: Ф2.4 m (Europe Link): ongoing 5. Time Transfer Equipment in Laboratory 4 5 Time Transfer Systems 5

Better Standards, Better Life 6 Atomic fountain frequency standard  Cs & Rb double fountain as the second fountain at KRISS. (111)-configuration Ramsey signal measured without magnetic shields in 2011

Better Standards, Better Life 분야 연구내용 Design of Magnetic shields and C-field coil

Better Standards, Better Life 8 Low Distributed Cavity phase Cs-Rb MW cavity Cs cavity end cap Rb cavity end cap Cs cavity body Cs-Rb cavity end cap Rb cavity body Cs cavity feeding waveguide Rb cavity feeding waveguide  Frequency shift due to DCP Biggest uncertainty source of atomic fountain Low DCP cavity proposed by  Prof. Kurt Gibble (Penn. State University)  NPL, KRISS: introduce the new-type cavity design and fabrication of a MW cavity system for Cs and Rb atoms x3 H0H0 Conventional cavity New-type cavity by Prof. Kurt Gibble Conventional New type

Better Standards, Better Life 9 CSO local oscillator developed in collaboration with the Univ. of Western Australia Preliminary results Realization of an Ultra-Stable Local Oscillator Using an Ultra-Low Vibration Pulse-Tube Cryocooler (2011 ~ 2013) Under test in UWA To be installed at KRISS in September, 2013 Under test in UWA To be installed at KRISS in September, ×10 10 s

Better Standards, Better Life 10 Future New Definition of the “Second” Microwave clock (Cs) to Optical clock (e.g. Yb…) can greatly reduce the clock uncertainty ! Toward ~ accuracy Yb Optical Lattice Clock

Better Standards, Better Life 11 Photo of Yb optical lattice clock system MOT Super-cavity Optical comb

Better Standards, Better Life 광시계분야 연구내용 Effectu (Hz) Linear lattice ac Stark shift5.8 Hyper polarizability0.03 Second order Zeeman0.2 Gravitational shift0.1 Blackbody radiation shift0.2 Collisional shift2.7 Total Yb6.4 Yb optical lattice clock: uncertainty 1.2 × Uncertainty evaluation in 2011

Better Standards, Better Life 13 Improvement of clock laser Short term Mid term Long term

Better Standards, Better Life 14 Improvement of lasers  399 nm laser injection locking of 2 lasers with the stabilized master laser  399 nm, 556 nm laser frequency stabilization: side lock to peak lock  repumping laser 4 repumping lasers replaced by a single 1389 nm laser  lattice laser stabilized to an optical comb  Atomic beam shutter

Better Standards, Better Life 15 increase the optical lattice depth 2011(retro type) 2012(build-up cavity type) U=U 0 Potential depth U ≈ 4U 0 Potential depth Build-up cavity

Better Standards, Better Life 16 30MHz band pass filter 759nm counter Phase detector Attenuator Analog PID Ti:sapphire 759nm lattice laser, Reference cavity APD DDSH-maser Stabilization of lattice laser nm laser: stabilized to an internal cavity Stabilized to an optical comb

Better Standards, Better Life 17 Re-estimation of uncertainty (ongoing) Uncertainty below 1× expected in the very near future!

Better Standards, Better Life 18 5 MHz, 5 kW  Broadcasting of Time Signal (call sign: HLA)  Time service through internet NTP time server at KRISS Dissemination of the Korea Standard Time

Better Standards, Better Life 19 Calibration and Test Service 19 service categories Remote site 1 Remote site 2 KRISS server Internet or modem Calibration system Remote calibration system

Better Standards, Better Life 20 Maintenance of the CIPM MRA at KRISS  1 st Peer review: Feb CMC review (2004)  2 nd peer review : Mar nd round CMC review (2008)  KRISS CMC for 19 service categories  CMC published in the KCDB website in 2009  3 rd peer review April 24 ~ 26, 2012 In the process of CMC review for publication

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