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Evaluation of the TAI Scale Interval Using an Optical Clock

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Evaluation of the TAI Scale Interval Using an Optical Clock Evaluation of the TAI scale interval using an optical clock National Institute of Information and Communications Technology (NICT) Space-Time Standards Laboratory T. Ido H. Hachisu, N. Nemitz, F. Nakagawa, T. Gotoh, Y. Hanado 1 Optical – microwave hybrid time scale using Sr lattice clock 2 Time scale NICT institute k BIPM H-Maser EAL UTC(k) (ensemble) >400 clocks Local adjustment Ensemble 18 clocks TAI Cs (or Rb) fountains PMS adjustment adjustment leap second UTC(NICT) UTC UT + 9h Interval of UTC-UTC(k) Generating a real signal is 5 DAYS in Circular T Japan Standard Time (JST) in institute k (BIPM monthly report) 3 Optical clocks utilized for time scale NICT institute k BIPM UTC(k) H-Maser EAL >400 clocks adjustment (~1e-13) Cs (or Rb) fountains TAI PMS adjustment adjustment (~1e-15) leap second ? UTC(NICT) UTC UT Japan Standard Time (JST) PMS: Phase micro stepper 4 How much clocks deviate from linear drift? Allan variance (= two sample variance) is insensitive to constant frequency difference. ↓ Raise the # of variance. Three sample variance (Hadamard variance) is insensitive to constant difference of frequency drift rate. 3-sample variance （Hadamard variance) 푀−2 푁−3 1 1 푦 푖 + 2 − 2푦 푖 + 1 + 푦(푖) 2 = 푥 푖 + 3 − 3푥 푖 + 2 6 푀 − 2 6 푁 − 3 휏2 푖=1 푁=1 + 3푥 푖 + 1 − 푥 푖 5 Advantage of “optical” steering 1 Operation • 104 s of operation is sufficient • Short term fluctuation of HM may be to evaluate the scale unit of a compensated by an optical clock. -16 HM at mid-10 level • Not necessary to operate all the time. once in a week for 3 hours INTERMITTENT Evaluation of a HM for 6 monthsby Sr and UTC(NICT) 104 s measurement ) 1.15 -12 evaluation by UTC(NICT) evaluation by Sr clock 1.10 1.05 1×10-13 1.00 0.95 6 months Fractional frequency (x10 0.90 57450 57480 57510 57540 57570 57600 57630 57660 MJD 7 Evaluation of one-month mean TAI scale interval by Sr y(HM) Effects Uncertainty (10-17) 7 days Sr systematic 6 Gravity 2.2 Hydrogen maser deterministic 25 stochastic (dead 18 1 month time) t Phase 5 measurement UTC-UTC(NICT) link 26 (30 days average) Sr frequency 40 (CIPM 2017) (uSrep) Total 57 (40 w/o uSrep) 8 Result: Evaluation of TAI scale interval by Sr Sr standard frequency: 429 228 004 229 873.0 Hz (2017 CIPM#) 9 History of TAI scale interval (evaluated by Cs or Rb fountains) 2012～2018 (7 years) • Error less than 1×10-15 in most of time 40 ) • BIPM manually tunes TAI -16 20 referring primary (Cs) and secondary (Rb) microwave standards validated by CCTF- 0 WG -20 • Only those in PTB and SYRTE routinely evaluate these days -40 (Difficulties in regular Change in frequency offset to be added TAI fractional frequency (x10 frequency fractional TAI to free mean time scale (EAL) operations?) -60 56000 56500 57000 57500 58000 58500 59000 修正ユリウス日 10 Evaluation of TAI scale interval Table 2: Estimate of d by the BIPM based on all PSFS measurements identified to be used for TAI steering over the period MJD58304-58694, and corresponding uncertainties. Period of estimation d u 58664-58694 0.67x10**-15 0.21x10**-15 (2019 JUN 30 - 2019 JUL 30) PTB-CS1, Cs2: not fountain, but Cs beam Circular T (Aug, 2019) NICT-Sr1 provides the least u = 2.8×10-16 Normally, fountains in PTB report with the smallest u = 0.2～0.3 (×10-16) TAI calibration using optical lattice clocks • Working group in CCTF validates frequency standards which can be usable to calibrate the one second of TAI. Optical lattice clocks accepted by CCTF working group SYRTE-Sr2 & SrB NICT-Sr1 NIST-Yb1 INRIM-Yb1 Test 2014/10 (10d) 2016/04～09 2017/11～ calibration 2015/06(20d) (30dX6) 2018/06 (check using 2016/03(10d） 2018/02 (30dX8) past data) 2016/05(15d) (30d) WG validation 2017/02 2018/11 2019/02 2019/11 “on-time” 2018/12 2018/12 N/A N/A calibration 2019/01 2019/02 2019/07 12 TAI calibrations provided by optical clocks NICT-Sr1 detected the upward deviation of TAI frequency 2012～2018年 (7年間) • Latest two points of Various CsF NICT-Sr1 reflect the 40 NICT-Sr1 ) NIST-Yb1 manual adjustment of -16 Based on #CCTF2015 SYRTE-Sr2 TAI by BIPM, which Cs 20 SYRTE-SrB fountains don’t show clearly 0 • These data may demonstrate the -20 advantage of optical Based on #CCTF2017 clocks over fountains. -40 →Another driving TAI fractional frequency (x10 frequency fractional TAI TAI算出時に使用する自由平均時に対する調整値 － 6520×10-16 force to the -60 redefinition of the 56000 56500 57000 57500 58000 58500 second 修正ユリウス日 13 Search: Highlights BIPM 2019 https://www.bipm.org/cc/PARTNERS/Allowed/2019_October/PRES03-M.MILTON_Highlights_from_the_work__of_the_BIPM_Scientific_and_Technical_Secretariat.pdf https://www.bipm.org/cc/PARTNERS/Allowed/2019_October/PRES03-M.MILTON_Highlights_from_the_work__of_the_BIPM_Scientific_and_Technical_Secretariat.pdf Summary • Opt. –MW hybrid timescale generated in real time for half a year, demonstrated stably and accurately • Optical clocks started contributions to maintain UTC, which is social time employed in society. First application of optical clocks to our daily life 16 17 Particularly, strong contribution to the work presented here Team Sr: H. Hachisu, N. Nemitz Time scale: F. Nakagawa Y. Hanado Result: Evaluation of TAI scale interval by Sr Sr standard frequency: 429 228 004 229 873.0 Hz (2017 CIPM#) Optically steered time scale TA(Sr) • No external reference • Reference to compare with: UTC, TT(BIPM16) 20 What do we need to reach the redefinition of the SI second? 21 Prediction of the timeline for redefinition of the second 3 clocks −18 ∆휈푖/휈푖~10 Uncertainties ~ two order of magnitude better than Cs 3 comparisons agreements of the same optical clocks in −18 ∆휈푖/휈푖 < 5 × 10 different institutes 3 clocks Continuity with present definition: independent measurements −16 ∆휈푖/휈푖 < 3 × 10 w.r.t. three independent Cs primary clocks Regular contribution to TAI Measurement reports covering at least ten days 2 ratio comparisons Locally available frequency ratios in >2 laboratories agree among 5 transitions −18 (Yb/Sr, Yb+/Sr, Hg/Sr, Al+/Sr, In+/Sr) ∆ 휈푖/휈푗 / 휈푖/휈푗 < 5 × 10 CCTF CGPM CCTF CGPM CGPM 2017 2018 2020 2022 2025 2026 2030 CCTF Strategy Document, Annex 1 (Towards a new definition of the second in the SI, F. Riehle) 22 Steering by intermittent operation of Sr lattice clock: “Opt. –mwave hybrid time scale” • HM frequency and drift rate Phase micro Source osc. calibrated by Sr stepper T_Sr (HM) (PMS) • Adjustment of PMS offset frequency every 4 hours f(HM) based on Sr • No servo to reduce the time offset UTC-T_Sr • Based on our frequency* obtained in 2015 Intermittent operation more than once a week for 104 s continued *429 228 004 229 872.97 Hz (Hachisu et al., Appl. Phys. B 34, 123 (2017)) … 873.2 Hz (CIPM2015) → … 873.0 Hz (CCTF WGFS, Jun 2017) 23 Steering Linear drift estimation interval: T=25days Number of OFS operation in T : N+1 >4 (once per week or more frequently) One HM free evolution time: DT = T/N 24 Comparison against UTC & TT(BIPM16) TA(Sr)-TT(BIPM16) • Clearly detect the frequency offset of UTC • Phase difference against TA(Sr)-UTC TT(BIPM16) < 1ns after 5months TT(BIPM16)-UTC • Stability 4e-16 @ 20 days H. Hachisu et al., Sci. Rep. 8, 4243 (2018) 25 Japan Standard Time (JST) 26 Commercial Cs clock & H maser (a) Commercial Cs clock 9.2GHz Noisy, but no drift time (b) Hydrogen maser 1.42GHz Less (short-time) noise, but drifty time JST employed only Cs clocks before 2006. But since 2006, Cs and H-maser have been combined to get better stability in short term too. 27 JST generation Synthesizing Atomic clocks JST 18 Cs 3 HM Time, frequency adjustment Ｈメーザ Phase micro 1PPS ＨメーザHM 3 to 1 stepper generation Source oscillator multiplexer - Cs clock Averaging + in software HM frequency was steered to ensemble of 18 Cs clock 28 Time scale NICT institute k BIPM H-Maser EAL UTC(k) (ensemble) >400 clocks Local adjustment Ensemble 18 clocks TAI Cs (or Rb) fountains PMS adjustment adjustment leap second UTC(NICT) UTC UT + 9h Interval of UTC-UTC(k) Generating a real signal is 5 DAYS in Circular T Japan Standard Time (JST) in institute k (BIPM monthly report) 29 JST : Time scale generation Timescale Clocks for generating UTC(NICT) : The behavior of UTC(NICT) : Cs 5071A : 18 (ensemble timescale) | UTC – UTC(NICT) | < 20 ns. Anritsu H-Masers : 1(source) + 2(backup) Stability ~ 2E-15 @ 10-30d. 2013 2014 2015 2016 2017 40 4 20 2 0 0 Accuracy [UTC-UTC(NICT)]/ns -20 -2 freq. correction (1e-15) correction freq. conservative: 5e-14 (employed for calibration service) -40 -4 Standard deviation: <4e-14 manual frequency correction 56000 56500 57000 57500 58000 24hours, 7days a week MJD 30 JST Kobe sub-station in becoming ready Distributed generation of JST HM Cs (5071A) • Kobe sub-station is scheduled to begin time-keeping in June 2018 Kobe) (ns) Kobe) • 2 H-maser & 5 Cs clocks - • Primary purpose is a backup of Koganei HQ against disasters Koganei ( SD=2.0ns (JST has never stopped in more than SD=6.7ns 40 years) T D Time (day) Operation mode: 1. Copy of Koganei HQ 2. Independent operation 3. JST as an ensemble of all clocks operated in 4 stations 31 80 ns / 0.6 year = 4 × 10-15 32 Application of optical clocks toward real-time generation of a time scale Tetsuya Ido Space-Time Standards Laboratory National Institute of Information and Communications Technology Japan 33 Dissemination service of Japan Standard Time JST Generation and measurement system satellite H maser calibratio International Optical n comparison frequency PFS Cs clocks JST standards Radio wave(JJY) Telephone NTP Provision to Calibration dissemination service time stamp service service TAA TSA アナログ回線 光電話回線 Via GPS インター ネット Time stamp UTC 12:10:35 NICT Carry-in （5, 10MHz） 電波時計用 中継器 34 Secondary representation of the second (SRS) Frequency combs proposed in late 90s easily provide coherent link of optical frequency to (microwave) SI second.
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