1. 1 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Hg Microwave Ion Clock Technologies for Fundamental Physics in Space John Prestage JPL, Pasadena In Lab: Sang Chung Thanh Le Robert Tjoelker Eric Burt Rob Thompson Nan Yu John Prestage Flight Design: Armond Matevosian Saverio D’Agostino Eric Archer Larry Epp Paul MacNeal Talso Chui John Prestage Lamp Exciter Electronics: William Riley

2. 2 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Space Clock Outline 2-3 kg atomic clock,10 -16 stability for under $10M Technology Overview Compact physics package layout Reliability for in-space operation Magnetic Design, Shielding Factors Mechanical design for launch vibration

3. 3 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 AAA Battery USO Flights Topex Grace Mars Global Surveyor Cassini New Horizons (Pluto)

4. 4 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Space-Based Clocks (LEO, MEO) ** Graphic 01020304050607080 Mass of Atomic Clock (kg) 1E-16 1E-15 1E-14 1E-13 GPS Cs GLONASS Cs GPS Rb (  10 -13 /day drift) H-Masers NASA/SAO ESA JPL Ion Clock (Prototype) Galileo Passive H-Maser Aces H-Maser (ISS) GP-A H-Maser Galileo Rb (10 -13 /day drift) ** Only Atomic Clock to leave Earth Orbit was a pair of Rb clocks on Cassini-Huygens Probe for Doppler Winds measurement in Atmosphere of Titan GALILEO Atomic Clocks

5. 5 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 No Lasers, No Cryogenics, No Microwave cavities No Light Shift ! No gas load, not a gas ‘flow-thru‘ architecture, no consumables 10 6 -10 7 199 Hg + trapped ions Clock Transition: 40,507,347,996.8 Hz No wall collisions, high Q line State selection via optical pumping from 202 Hg + ; 1-2 photons/s scattered Plasma UV light source is radiation tolerant, PMT’s have flown many times. Ion Shuttling from Quad to Multi-pole, “Reversible, lossless atomic beam” Ions are buffer-gas (Ne) cooled to ~300K Very low tempco - 0.1C temp change only pulls frequency by ~6x10 -17 Hg microwave Ion clock Physics Overview

6. 6 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Clock stability to 10 -15 in 1 liter physics package Sealed Tube operation with no active pumps (no power required) for more than 2 years, no degradation of signal size. Breadboard Liter Clock Results

7. 7 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Ultra-high vacuum leads to ultra-high Q ~4x10 -13 /  Cryogenic Cavity With cryogenic local oscillator, will deliver 3x10 -14 / 

8. 8 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 ~4x10 -13 /  Ultra-high vacuum leads to ultra-high Q With quartz USO, will eliminate Dick effect degradation with modified trap architecture See: Local Oscillator Induced Degradation of Medium –Term Stability in Passive Atomic Frequency Standards, Dick, Prestage, Greenhall, Maleki

9. 9 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Physics Package Design Summary Mass of package shown ~1 kg w/ Ti tube, 2 layers Mu-metal, Mg baseplate, 4 FS lens,.. Trap layout same size as lab breadboard, Optical system collection ~ 2x improved, Additional outer shield + electronics will add 1-2 kg.

10. 10 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Alumina Ceramic VUV Sapphire to Titanium Seal 450 C Rated Trap rods Electron Emitter ~ 1 mA @ 1-2 Watts heater Titanium-Titanium Welds Titanium- Titanium Weld Tantalum Tubes - Molybdenum Wires Sealed Tube uses getters to maintain Vacuum (No Consumables) d(T)T=200CT=350CT=450CT=550C E a =1 eV1~600~7500~75000 E a =5 eV O 2 on Fe 1~10 14 ~10 19 ~10 24 Bake-Out de-gas rate is exponential

11. 11 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Getter Reservoir 50 grams >50 years Estimated Lifetime (from typical outgassing and measurable leak rates)  100 yrs/gram of getter material Huygens/Cassini MS used Titanium, Molybdenum getter material Getter Pumping used in prototype demo (~3 years with no degradation of ion signal)

12. 12 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Tube Materials for 400 C Bakeout Improve vacuum 1000-fold Ultra-clean vacuum is essential for clock stability and tube lifetime. Ion lifetime limited by residual gases, eg., Hg + + H 2 O  Hg + H 2 O + Gettering action not diminished by presence of weak Hg vapor. Time (in hours)

13. 13 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 …Optical Design…

14. 14 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Designed, Fabricated Ovenized Hg Lamp exciter following GPS Rb technology. UV Light Source – 202 Hg Lamp Lamp Holder (Indium Solder) Hg Lamp Al Oven Shell G10 Thermal Standoff

15. 15 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Sapphire bulb material for longer lifetime UV Sterilization/ Water purification Industry uses high power Hg UV Lamps (~185 nm Ozone production) Bulb Lifetime Problem Identified: Hg reacts with glass SiO 2 to form HgO Light level falls, Hg leaves the vapor, shortens bulb life Sapphire Material will extend bulb lifetime by 2-4 Conclusion: Build bulbs from Sapphire

16. 16 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 ….Magnetic Design…. Mount Tube through 2 shields and coil 3 layer shields, each 0.020” thick

17. 17 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Reference Magnetic Field (Quantization Axis for Microwave polarization) Transverse magnetic field allows Doppler-free probe of Clock and Zeeman transitions Inherently Low magnetic field sensitivity (35x less than Rb) H1.4 GHz + (2764 Hz/G 2 )B 2 Rb6.8 GHz + (574 Hz/G 2 )B 2 Cs9.2 GHz + (427 Hz/G 2 )B 2 Hg + 40.5 GHz + (97 Hz/G 2 )B 2

18. 18 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Shielding Factor and Frequency Shift 1 gauss external pulls frequency ~ 10 -15 - Measure μ for real single layer shield (μ de-rated from 80K to 20K) - Enter shields layout in Maxwell field simulator - Apply 1G (80A/m) field along each of 3 axes - Determine SF = H ext / H in - Single layer Shield Factor ~

19. 19 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Shielding Factor and Frequency Shift - Can estimate frequency shift at any position inside shields - μ adjusted from 80K to 20K - B C-field = 50 mGauss - Apply 1G (80A/m) field along each of 3 axes - Determine frequency shift vs position (Plotted at right) More useful calculation is the clock frequency shift when external field (1 Gauss) is applied 5x10 -16 These directions are perpendicular to reference field This leakage is parallel to reference field

20. 20 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 …Vibration Design and Test…

21. 21 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Completed Physics Package Vibration Modal Analysis for TRL 6 vib spec Modal analysis ~3000 mesh points to find resonant frequencies, all above 200 Hz Loads are based generic random vibration level, 9.2 G rms Equivalent quasi-static loads  G peak  100 G’s Factors of safety  Yield factor of safety is 1.25  Ultimate factor of safety is 1.40 FrequencyRandom Axis(Hz)Level X,Y,Z 2050 +3 db/octave 505000.10 g 2 /Hz 500 2000- 6 db/octave Overall Level9.2 g rms

22. 22 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Serial Number Cathode Radiant Sensitivity mA/W Anode Radiant Sensitivity A/W Anode Drak Current nA Vibration Test Level Date of Manufacture Pass/Fail AU0045 O R 66.9 59.0 96.6 62.3 0.02 0.03 from 2.3 to 9.2 Before 1999Pass AU0713 O R 28.1 29.6 444 333 0.08 0.12 from 2.3 to 13.8 Aug 2001Pass AU0653 O R 58.2 55.1 338 266 0.10 1.40 (Unstable ?) from 2.3 to 18.4 Aug 2001Pass ? JQ1843 O R 62.9 61.7 922 1036 0.14 0.15 from 2.3 to 9.2 Aug 2001Pass JQ1845 O R 62.5 63.2 931 1083 0.18 0.36 from 2.3 to 13.8 Aug 2001Pass JQ1851 O R 65.7 65.2 925 1077 0.04 0.07 from 2.3 to 18.4 Aug 2001Pass O: Original Data R: Retest Data R6354 R7154 Shake Test for UV Photo-Multiplier Tubes

23. 23 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Summary - Ion Space Clock Teamed with flight engineers (JPL, GPS) to design small Ion clock for in-vacuum operation and vibration hardening __________________________________________________________________________________________________ Tube design based on other space vacuum tubes with 10+ years life ___________________________________________________________________________________________________ Lamp lifetime expected to exceed 10 years with VUV sapphire bulb material ___________________________________________________________________________________________________ 10 -15 stability in (2-3 kg) small package feasible (1 ns at ~ 2 weeks autonomous TK)

24. 24 Quantum to Cosmos: Fundamental Physics in Space for the Next Decade, Airlie Center, VA 2008 Thermal base with indium heat conduction at ~60 C Two turn inductive exciter coil, 1 Amp at ~200 Mhz Lighting Industry uses cylindrical coil exciter Plasma deposition and Ion thruster industries use planar coil plasma exciter. Creates uniform plasma region Hybrid Planar-Cylindrical Coil ICP, Inductively Coupled Plasma Lamp In vacuum operation, temperature rises to 170 C, higher than in-air optimum by 70 C