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Robert Tjoelker

Researcher

About

Bio

Robert L. Tjoelker was born in 1958 in Bellingham, WA. He received degrees in architecture, physics, and mathematics from the University of Washington in Seattle and the Ph.D degree in physics from Harvard University, Cambridge, MA for a precision comparison of the proton and antiproton mass. He is involved in numerous time and frequency science, research and development, and engineering activities that include the development of practical high-stability mercury trapped ion frequency standards, state-of-the-art clocks and timing, and reference distribution systems. His group leads and is responsible for the JPL Frequency Standards Test Laboratory, the NASA Deep Space Network Frequency and Timing System, and frequency and timing technology development, implementation, and characterization for the Deep Space Network and spaceflight.

Education

  • Ph.D. in Physics, Harvard University, Cambridge, MA; November 1990
  • Dissertation: "Antiprotons in a Penning Trap: A New Measurement of the Inertial Mass"
  • M.S. in Physics, University of Washington, Seattle, WA; November 1985
  • B.S. in Physics, University of Washington, Seattle, WA; June 1984
  • B.S. in Mathematics, University of Washington, Seattle, WA; June 1984
  • B.A. Magna cum Laude, in Architecture, University of Washington, Seattle, WA; June 1980

Research Interests

  • Frequency and Timing: Science, Technology, Engineering, and Systems.
  • Atomic Frequency Standards and Clocks
  • Trapped Ion Frequency Standards and Mass Spectroscopy
  • Frequency and Time Metrology
  • Precision Measurements and Fundamental Atomic Physics

Experience

Professional Experience

NASA Jet Propulsion Laboratory (1990 - Present)

  • Principal Member of Technical Staff ( 2002-present)
  • NASA SCAN Ion Clock Technology Maturation Lead (2020-present)
  • Co-Investigator: Deep Space Atomic Clock (DSAC) Technology Demonstration Mission (2011-2021).
  • Technical Group Supervisor; Section 335 (1999-2019)
    • Frequency & Timing Advanced Instrument Development Group 335E
  • Frequency and Timing System Engineer (SE), NASA Deep Space Network, (2003-2020)
  • IND Frequency & Timing Work Area & Task Manager (1998-2020)
  • Project Element Manager, Frequency & Timing Laboratory, Section 335, (1998-1999)
  • Time and Frequency Research Staff (1990-1998)

European Laboratory for Particle Physics (CERN) - Geneva, Switzerland;

  • CERN Associate Scientist and Harvard Traveling Scholar (1988-1990).

Harvard University; Cambridge, MA; Research Assistant; Dept. of Physics (1987-1990)

University of Washington; Seattle, WA; Research Assistant; Dept. of Physics (1985-1987)

Research Community Service

1997-2022 Technical Program Committee(TPC), IEEE Frequency Control Symposium.

2014-2021 Planning Commitee, ION Precise Time and Time Interval (PTTI) Meeting.

1998- 2013 Executive Committee, Precise Time and Time Interval (PTTI) Applications Meeting.

1997- 2022 United States Study Group 7, ITU-R (International Telecommunications Union).

2010 General Chair, 2010 IEEE Frequency Control Symposium.

2005 Technical Program Chair, 2005 Joint IEEE Frequency Control Symposium & PTTI Meeting.

2004 TPC Vice-Chair, Group 3, 2004 Joint IEEE Frequency Control Symposium & UFFC Meeting.

2003 TPC Vice-Chair, Group 3, 2003 Joint IEEE Frequency Control Symposium & EFTF Meeting.

2003, 2004 Chair, JPL Division Principal Promotion Advisory Board (PPAB).

Member in the IEEE (Institute of Electectrical and Electronics Engineers), ION (Institute of Navigation), and the APS (American Physical Society). Presenter of multiple tutorials in the area of Atomic Frequency Standards, Clocks, and Timekeeping.

Achievements

Awards & Recognitions

  • Professional Society and External Organization Awards | IEEE | Fellow (2023)
  • NASA Award | Exceptional Engineering Achievement Medal | For exceptional achievement in the design, development, and delivery of ultra precise clocks and frequency systems for NASA's Deep Space Network, the Navy, and space applications. (2019)
  • Professional Society and External Organization Awards | Institute of Navigation (ION) Precise Time & Time Interval (PTTI) | Distinguished Service Award (2018)
  • NASA Award | Group Achievement Award | "DSS-26 Delivery Team" (2017)
  • NASA Award | Group Achievement Award | "Photonic Frequency Distribution Development Team" (2015)
  • NASA Award | Space Technology Mission Directorate (STMD) | Groundbreaker Award (2015)
  • NASA Award | Group Achievement Award | "MSL Project Operations Team" (2013)
  • NASA Award | Group Achievement Award | SCaN Space Ion Clock Technology Development Team" (2012)
  • NASA Award | Major Space Act Award | "High Resolution and Low Cost Optical Link Stabilizing Technology" (2012)
  • NASA Award | Group Achievement Award | "Mercury-201 Trapped Ion Clock Development Team" (2010)
  • NASA Award | Group Achievement Award | "DSN Frequency Reference Subsystem Development Team" (2010)
  • NASA Award | Space Act Award | "Coherent Frequency Reference Generation System for the NASA DSN" (2009)
  • NASA Award | Group Achievement Award | "for Master Clock and Timing System Development Team” (2006)
  • NASA Award | Space Act Award | “Master Clock & Time Distribution System for the NASA Deep Space Network” (2005)
  • NASA Award | Space Act Award | “Stabilized Reference Frequency Distribution for Radio Science with the Cassini Spacecraft and the Deep Space Network” (2004)
  • NASA Award | Group Achievement Award | "for Cassini Radio Science Ground System Development Team" (2004)
  • JPL Principal Designation | 335E - Frequency And Timing Advanced Instrument Development (2002)
  • NASA Award | Space Act Award | "Multi-purpose Time Analyer and Monitor for the Deep Space Network Time Synchronization" (2002)
  • NASA Award | Group Achievement Award | “for Frequency & Timing Monitor and Control Upgrade Team" (2002)
  • NASA Award | Group Achievement Award | “for exceptional contributions to the development of the linear ion trap frequency standard" (1995)
  • Professional Society and External Organization Awards | NIST | National Research Council NIST Fellowship (1990)
  • Professional Society and External Organization Awards | University of Washington | Paul M. Higgs-Frederick A. Osborn Prize (1984)

Publications

  1. Next Generation High Stability, Long-Life Mercury Ion Clocks for Ground and Space Applications; Eric Tardiff, Michael Toennies, Anatoliy Savchenkov, Jamie McKelvy, Vladimir Iltchenko, Daphna Enzer, Andrey Matsko, Eric Burt, and Robert Tjoelker; Proceedings of the 2024 ION Precise Time and Time Interval (PTTI), Long Beach, CA, January 22-24, 2024.
  2. DSAC and next generation high stability, long life trapped mercury ion frequency standards; E.A. Burt, T.A. Ely, and R.L. Tjoelker; 9th Symposium on Frequency Standards and Metrology, Kingscliff Australia, October 16-20, 2023.
  3. Deep Space Atomic Clock Technology Demonstration Mission Results; Todd Ely, John Prestage, Robert Tjoelker, Eric Burt, Angela Dorsey, Daphna Enzer, Randy Herrera, Da Kuang, David Murphy, David Robison, Gabriella Seal, Jeffrey Stuart, Rabi Wang, and Jill Seubert; 2022 IEEE Aerospace Conference (AERO), March 2022.
  4. Demonstration of a trapped-ion atomic clock in space; Burt, E. A., Prestage, J. D., Tjoelker, R. L., Enzer, D. G., Kuang, D., Murphy, D. W., Robison, D. E., Seubert, J. M., Wang, R. T., & Ely, T. A.; Nature, 595(7865), 43–47, (2021).
  5. Integrated physics package of micro-mercury trapped ion clock with 10-14 level frequency stability; Thai M. Hoang, Sang K. Chung, Thanh Le, John D. Prestage, Lin Yi, Robert L. Tjoelker, Sehyun Park, Sung-Jin Park, Gary Eden, Chris Holland, and Nan Yu; Appl. Phys. Lett. 119, 044001 (2021).
  6. Stabilized photonic links for space applications; Shouhua Huang, Robert Tjoelker, Wei Zhang, and Andrey Matsko; Applied Optics Vol. 60, Issue 12, pp. 3487-3491 (2021) , https://doi.org/10.1364/AO.419890.
  7. Demonstration of a mercury trapped ion clock prototype, Thai M. Hoang, Sang K. Chung, Thanh Le, John D. Prestage, Lin Yi, Robert L. Tjoelker, Nan Yu, Sehyun Park, Sung-Jin Park, Gary Eden, and Chris Holland; 2021 Joint IEEE Frequency Control Symposium and European Frequency and Time Forum, July, 2021.
  8. A Low SWaP-C prototype Ka-band Frequency Synthesizer for Atomic Clocks; Michael O Toennies, Lin Yi, Eric A. Burt and Robert L. Tjoelker; 2018 Proc. IEEE Frequency Control Symposium, Squaw Valley, NV; May 2018.
  9. Miniaturized and Low Power Mercury Microwave Ion Clock; Gurpreet Kaur Gulati, Sang Chung, Thanh Le, John Prestage, Lin Yi, Robert Tjeolker, Nan Yu, Chris Holland; 2018 Proc. IEEE Frequency Control Symposium, Squaw Valley, NV; May 2018.
  10. Using the Deep Space Atomic Clock for Navigation and Science; T. A. Ely, E. A. Burt, J.D. Prestage, J.S Seubert, and R. L. Tjoelker; IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (TUFFC), accepted for publication and front cover, May 2018.
  11. Drifts and Environmental Disturbances in Atomic Clock Subsystems: Quantifying Local Oscillator, Control Loop, & Ion Resonance Interactions; D. G. Enzer, W. A. Diener, D. W. Murphy, S. R. Rao, and R. L. Tjoelker; IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (TUFFC), Vol. 64, No. 3, March 2017.
  12. Mercury Ion Clock for a NASA Technology Demonstration Mission; R.L. Tjoelker, J.D. Prestage, E. A. Burt, P. Chen, Y. Chong, S. Chung, W. Diener, T. Ely, D. Enzer, H. Mojaradi, C. Okino, M. Pauken, D. Robison, B. Swenson, B. Tucker, R. Wang; IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (TUFFC), Vol. 63, No. 7, July 2016.
  13. JPL Ultrastable Trapped Ion Atomic Frequency Standards; E. Burt, L. Yi, B. Tucker, R. Hamell, and R.L. Tjoelker; IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (TUFFC), Vol. 63, No. 7, July 2016.
  14. Paradigm for Predicting How Local-Oscillator Drift-Rate and Other Environmental Disturbance Impact Atomic Clock Output; Daphna G. Enzer, William A. Diener, David W. Murphy, Shanti R. Rao, and Robert L. Tjoelker; 2016 IEEE Frequency Control Symposium, New Orleans, LA; May 9-12, 2016.
  15. Mercury Lamp Studies in Support of Trapped Ion Frequency Standards; Lin Yi, Eric A. Burt and Robert L. Tjoelker; 2015 Joint IEEE Frequency Control Symposium and European Frequency and Time Forum, Denver, CO; April 13-16, 2015.
  16. Next Generation JPL Ultra-stable Trapped Ion Atomic Clocks; Eric Burt, Lin Yi, Blake Tucker, Robert Hamell, and Robert Tjoelker, JPL; Scott Crane and Ken Senior, NRL; 2015 Joint IEEE Frequency Control Symposium and European Frequency and Time Forum, Denver, CO; April 13-16, 2015.
  17. Deep Space Atomic Clock (DSAC) Development for a NASA Technology Demonstration Mission; R.L. Tjoelker, et al; 2014 ION PTTI, Boston, MA Dec 2014; and 2015 Joint IEEE Frequency Control Symposium and European Frequency and Time Forum, Denver, CO; April 13-16, 2015.
  18. (invited) Ultra-Stable RF-Over-Fiber Transport in NASA Antennas, Phased Arrays and Radars; Kam Lau, George Lutes, Robert L. Tjoelker; Journal of Lightwave Technology, Vol. 32, No. 20, pp. 3440-3451, Oct 15, 2014.
  19. Next generation JPL ultra-stable trapped ion atomic clocks; Eric Burt, Blake Tucker, Kameron Larsen, Robert Hamell, and Robert Tjoelker; Proc. of the 2013 Precise Time and Time Interval Systems and Applications Meeting, ION PTTI 2013, Bellevue, WA December 2-5, 2013.
  20. Sub-mm Scale Fiber Guided Deep/Vacuum Ultra-Violet Optical Source for Trapped Mercury Ion Clocks; Lin Yi, Eric A. Burt, Shouhua Huang, Robert L. Tjoelker; Proc. of the 2013 Precise Time and Time Interval Systems and Applications Meeting, ION PTTI 2013, Bellevue, WA Dec. 2-5, 2013.
  21. The Deep Space Atomic Clock Mission; Todd A. Ely, Timothy Koch, Da Kuang, Karen Lee, David Murphy, John Prestage, Robert Tjoelker, Jill Seubert; Proceeding published 2013.
  22. The Deep Space Atomic Clock: Ushering in a New Paradigm for Radio Navigation and Science; Todd Ely, Jill Seubert, John Prestage, and Robert Tjoelker; AAS 13-325 (2013).
  23. Progress Towards a Dual-Isotope Trapped Mercury Ion Atomic Clock: Further Studies of Background Gas Pressure shifts; L. Yi, S. Taghavi-Larigani, E.A. Burt, R.L. Tjoelker; Proc. 2012 International Frequency Control Symposium, Baltimore Md; May 21-24, 2012.
  24. JPL Activities in Preparation for the ACES Mission; R.L. Tjoelker, E.A. Burt, W. Diener, D. Enzer, J.D. Prestage, N. Yu; EFTF, Gothenburg, Sweden, April 2012.
  25. Mercury Atomic Frequency Standards for Space Based Navigation and Timekeeping; R.L Tjoelker, E. A. Burt, S. Chung, R.L. Hamell,, J.D. Prestage, B. Tucker, P. Cash, R. Lutwak; Proc. 2011 PTTI ; Long Beach, CA, Nov 2011.
  26. Stabilized Photonic Links for Deep Space Tracking, Navigation, and Radio Science Applications; S. Huang and R.L Tjoelker; Proc. 2011 PTTI ; Long Beach, CA, Nov 2011.
  27. High Q Miniature Sapphire Acoustic Resonator; R. Wang, R.L. Tjoelker; Proc. 2010 International Frequency Control Symposium, Newport Beach, CA; June 2-4, 2010.
  28. Background Gas Induced Frequency Shifts in a 201Hg+ Trapped Ion Clock; S. Taghavi-Larigani, E.A. Burt, R.L. Tjoelker; Proc. 2010 International Frequency Control Symposium, Newport Beach, CA; June 2-4, 2010.
  29. High Q Miniature Sapphire Acoustic Resonator; R. Wang and R.L. Tjoelker; Proc. of the 2010 IEEE IFCS, Newport Beach, CA (2010).
  30. Background Gas Induced Frequency Shifts in a 201Hg+ Trapped Ion Atomic Frequency Standards; S. Taghavi-Larigani, E. Burt, R.L. Tjoelker; Proc. of the 2010 IEEE IFCS, Newport Beach, CA (2010).
  31. Repetitive Interrogation of 2-Level Quantum Systems; J. Prestage, E. Burt, S. Chung, R. Tjoelker, and N. Yu; Proc. of the 2010 IEEE IFCS, Newport Beach, CA (2010).
  32. A new trapped ion clock based on 201Hg+; E.A. Burt, S. Taghavi-Larigani, and R.L. Tjoelker; IEEE Transactions on UFFC 57, 629-635 (2010).
  33. High-resolution spectroscopy of 201Hg+:a sensitive probe of nuclear structure and the hyperfine anomaly;
  34. E.A. Burt, S. Taghavi-Larigani, and R.L. Tjoelker; Phys. Rev. A 79, 062506 (2009).
  35. Miniature Sapphire Acoustic Resonator; R. Wang, G.J. Dick, R. L. Tjoelker; Proc. of the 2009 Joint IEEE Frequency Control Symposium and European Frequency and Time Forum, Besancon, France; April 2009.
  36. A New Trapped Ion Clock Based On 201Hg+; E.A. Burt, S. Taghavi-Larigani, S.N. Lea, J.D. Prestage, and R.L. Tjoelker; Proc. of the 2009 Joint IEEE Frequency Control Symposium and European Frequency and Time Forum, Besancon, France; April 2009.
  37. Time and Frequency Activities at the Jet Propulsion Laboratory; R.L. Tjoelker; 40th Ann. Precise Time and Time Interval (PTTI) Planning Meeting ; Reston, VA; Dec 1-4, 2008.
  38. Coherent Frequency Reference Generation in the NASA Deep Space Network; B. Tucker, J. Lauf, J. Gonzalez, R. Hamell, W. Diener, and R.L. Tjoelker; Proc. of the 40th Ann. Precise Time and Time Interval (PTTI) Planning Meeting ; Reston, VA; Dec 1-4, 2008.
  39. A Dual- Isotope Mercury Ion Clock to Search Variation in Fundamental Constants; E. Burt, S. N. Lea, J.D. Prestage, S. Taghavi, and R. L. Tjoelker; Proc. of the Seventh Symposium on Frequency Standards and Metrology (FSM), Monterey, CA, October 2008.
  40. Compensated Multi-pole Mercury Trapped Ion Frequency Standard and Stability Evaluation of Systematic Effects; E. Burt, J.D. Prestage, S. Taghavi, and R.L. Tjoelker; Proc. of the Seventh Symposium on Frequency Standards and Metrology (FSM), Monterey, CA, October 2008.
  41. Stability Evaluation of Systematic Effects in a Compensated Multi-pole Mercury Trapped Ion Frequency Standards; E. Burt, S. Taghavi, J.D. Prestage, and R. L. Tjoelker; Proc. of the 2008 International Frequency Control Symposium, Honolulu, Hawaii, May 19-21, 2008.
  42. A Compensated Multi-pole Linear Ion Trap Mercury Frequency Standard for Ultra-Stable Timekeeping; E. Burt, W. Diener, and R. L. Tjoelker; IEEE Transactions UFFC, TUFFC 55, 2586 (2008).
  43. “Time and Frequency Activities at the Jet Propulsion Laboratory”; R.L. Tjoelker; Proc. of 39th Ann. Precise Time and Time Interval (PTTI) Meeting; Long Beach, California; Nov 26-29, 2007.
  44. Prospects for Ultra-Stable time keeping with sealed vacuum operation in Multi-pole Linear Ion Trap Standards; E. Burt and R. L. Tjoelker; Proc. of 39th Ann. Precise Time and Time Interval (PTTI) Planning Meeting ; Long Beach, California; Nov 26-29, 2007.
  45. Stable Photonic Links for Frequency and Time Transfer in the DSN and Antenna Arrays; M. Calhoun, S. Huang, R. Tjoelker; Proceedings of the IEEE, Special Issue, Vol 95, No. 10, pp. 1931-1946, October 2007.
  46. Voltage Controlled Sapphire Oscillator: Design, Development, and Preliminary Performance; R. Wang, G.J. Dick, R. Tjoelker; IPN Progress Report 42-170, August 15, 2007.
  47. Long Term Measurements of JPL’s Compensated Multi-pole Linear Ion Trap Standard at the 10-16 Level; E. Burt, W. Diener, R. Tjoelker; Proc. of the 2007 Joint IEEE Frequency Control Symposium and European Frequency and Time Forum, Geneva, Switzerland, May 2007.
  48. Frequency Standards Stability Analyzer for the Deep Space Network; C.A. Greenhall, A. Kirk, and R.L. Tjoelker, IPN Progress Report 42-169, May 15, 2007.
  49. Master Clock and Time Signal Distribution System; R. Tjoelker, M. Calhoun, P. Kuhnle, R. Sydnor, J. Lauf; NASA Tech Briefs, May 2007.
  50. Stabilized Photonic Links for Frequency and Time Transfer in Antenna Arrays; S. Huang, R. L. Tjoelker; Proc. of the 38th Annual Precise Time and Time Interval Meeting (PTTI), Reston, VA; December 2006.
  51. Sub-10-16 Frequency Stability in the JPL Multi-pole Linear Ion Trap Standard; E. Burt, D.G. Enzer, R.T. Wang, W.A. Diener, and R.L. Tjoelker; Proceedings of the 38th Annual Precise Time and Time Interval Meeting (PTTI), Reston, VA; December 2006.
  52. A Multi-Channel Stability Analyzer for Frequency Standards in the Deep Space Network; C. Greenhall, A. Kirk, R.L. Tjoelker; Proceedings of the 38th Annual Precise Time and Time Interval Meeting (PTTI), Reston, VA; December 2006.
  53. All Photonic Link and Local Oscillator Synthesis Architecture for High Performance Antenna Arraying; R.L. Tjoelker, S. Huang, M. Tu; RTD Poster & Annual Report, November 2006.
  54. Master Clock and Time Distribution System for the NASA Deep Space Network: Part I; R.L. Tjoelker, M. Calhoun, P.F. Kuhnle, J. Lauf, R.L. Sydnor; IPN Progress Report 42-167, November 15, 2006.
  55. All Photonic Link for High Performance Antenna Arraying; S. Huang, R.L. Tjoelker; IPN Progress Report 42-167, November 15, 2006.
  56. Sub 10-16 Frequency Stability in Multipole Linear Ion Trap Standards: Reduction of Number Dependent Sensitivity; E. Burt, R.L. Tjoelker; IPN Progress Report 42-166, August 15, 2006.
  57. Optical Links and RF Distribution for Antenna Arrays; S. Huang, M. Calhoun, and R.L. Tjoelker; Proc. of the 2006 IFCS, Miami, FL; June 5-7, 2006.
  58. Progress Report for a New Cryogenic Sapphire Oscillator; R. Wang, J. Dick, and R. L.Tjoelker; Proc. of the 2006 IFCS, Miami, FL; June 5-7, 2006.
  59. Characterization and Reduction of Number Dependent Sensitivity in Multipole Linear Ion Trap Standards (LITS); E. Burt and R.L. Tjoelker; Proc. of the 2005 Joint PTTI / IFCS, Vancouver, Canada; Aug 29-31, 2005.
  60. Clocks and Timing in the NASA Deep Space Network; J. Lauf, M. Calhoun, J. Gonzalez, W. Diener, P. Kuhnle, B. Tucker, C. Kirby, and R.L. Tjoelker; Proc. of the 2005 Joint PTTI / IFCS, Vancouver, Canada; Aug 29-31, 2005.
  61. A High Performance Frequency Standard and Distribution System for Cassini Ka-Band Experiment; R.T. Wang, M.D. Calhoun, A. Kirk, W. Diener, G.J. Dick, R.L. Tjoelker; Proc. of the 2005 Joint PTTI / IFCS, Vancouver, Canada; Aug 29-31, 2005.
  62. Design and Progress Report for Compact Cryocooled Sapphire Oscillator “VCSO”; G. J. Dick, R.T. Wang, and R.L. Tjoelker; in Proc. of the 2005 Joint PTTI / IFCS, Vancouver, Canada; Aug 29-31, 2005.
  63. Various Buffer Gas Experiments in a small Mercury Ion Clock for Space Use; S. Chung, J.D. Prestage, R. Tjoelker, L. Maleki; Proc. of the 59th Ann. Symp. On Frequency Control and UFFC, Montreal, Quebec, Canada; Aug 24-27, 2004.
  64. Master Clock and Time Distribution System for the NASA Deep Space Network; J. Lauf, M. Calhoun, P. Kuhnle, R. Sydnor, and R.L Tjoelker; Proc. of the 35th Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting, San Diego, CA, Dec. 2003.
  65. One Liter Ion Clock: New Capability for Spaceflight Applications; J.D. Prestage, M. Beach, S. Chung, R. Hamell, T. Le, L. Maleki, and R.L. Tjoelker; Proc. Of the 35th Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting, San Diego, CA, Dec. 2003.
  66. Stability Measurements of a JPL Multi-pole Mercury Trapped Ion Freuqency Standard at the USNO; R.L. Tjoelker, J.D. Prestage, P.A. Koppang, T.B.Swanson; Proc. of the 2003 Joint Meeting of the 17th EFTF and 58th Ann. Symp. On Frequency Control, Tampa, FL; May 5-8, 2003.
  67. One-Liter Hg Ion Clock for Space and Ground Applications; J.D. Prestage, S. Chung, T. Le, M. Beach, L. Maleki, and R.L. Tjoelker; Proc. of the 2003 Joint Meeting of the 17th EFTF and 58th Ann. Symp. On Frequency Control, Tampa, FL; May 5-8, 2003.
  68. Probing Magnetic Field Effects in 12-Pole Linear Ion Trap Frequency Standards; E. Burt, J.D. Prestage, and R.L. Tjoelker; Proc. of the 56th Annual Symp.on Frequency Control, New Orleans, LA; May 27-29, 2002.
  69. Stability Measurements Between Two Mercury LITE 12-Pole Clocks; J.D. Prestage, E. Burt, S. Chung, L. Maleki, and R.L. Tjoelker: Proc. of the 56th Annual Symp.on Frequency Control, New Orleans, LA; May 27-29, 2002.
  70. Mercury Trapped Ion Frequency Standard For the Global Positioning System; R.L.Tjoelker, E. Burt, S. Chung, R. Glaser, R. Hamell, L. Lim, L. Maleki, J.D. Prestage, N. Raouf, T. Radey, C. Sepulveda, G. Sprague, B. Tucker, and B. Young; 33nd Ann. Precise Time and Time Interval (PTTI) Systems and Applications Mtg, Long Beach, CA, Nov 27-29, 2001.
  71. Mercury Trapped Ion Frequency Standard For Space Applications; R.L.Tjoelker, E. Burt, S. Chung, R. Glaser, R. Hamell, L. Maleki, J.D. Prestage, N. Raouf, T. Radey, G. Sprague, B. Tucker, and B. Young: Proc. of the 2001 Symp. on Frequency Standards and Metrology, St. Andrews, Scotland, United Kingdom; September 9-14, 2001.
  72. Recent Developments in Microwave Ion Clocks; John D. Prestage, Robert L. Tjoelker, Lute Maleki; in Topics in Applied Physics 79, Frequency Measurement and Control, A.N. Luiten (Ed.), Springer-Verlag Berlin Heidelberg 2001, pp. 195-211 (2001)
  73. Multi-purpose Time Analyzer and Monitor for Deep Space Network Time Synchronization; J. Gonzalez jr., M. Calhoun, S. Cole, and R.L. Tjoelker; 32nd Annual Precise Time and Time Interval (PTTI) Systems and Applications Mtg., Reston, VA, Nov. 28-30, 2000.
  74. Stabilized Reference Frequency Distribution for Radio Science with the Cassini Spacecraft and the Deep Space Network; M. Calhoun, R. Wang, A. Kirk, W. Diener, G.J. Dick, and R.L. Tjoelker; 32nd Annual Precise Time and Time Interval (PTTI) Systems and Applications Mtg., Reston, VA Nov. 28-30, 2000.
  75. Mercury Ion clock Based on a Linear Multi-pole Ion Trap; J.D. Prestage, R. L. Tjoelker, and L. Maleki; TMO Progress Report, 42-143, November 15, 2000.
  76. Nan Yu, et. al. , Proceedings of the clock synchronization workshop, Pasadena (2000).
  77. Nitrogen Buffer Gas Experiments in Mercury Trapped Ion Frequency Standards; R.L. Tjoelker, W. Diener, A. Kirk, L. Maleki, J.D. Prestage, B. Young; Proc. of the 54th Annual Symp.on Frequency Control, Kansas City, MO; June 7-9, 2000.
  78. Mercury Ion Atomic Clock Based on a 12-pole Linear Trap; J.D. Prestage, R.L. Tjoelker, B. Young, L. Maleki; Proc. of the 54th Annual Symp.on Frequency Control, Kansas City, MO; June 7-9, 2000.
  79. Improved Timekeeping Using Advanced Trapped Ion Clocks; R.L. Tjoelker, J.D. Prestage, L. Maleki: Proc. of 31th Ann. Precise Time and Time Interval (PTTI) Planning Meeting ; Dana Point, California; Dec. 5-7, 1999.
  80. Higher Pole Linear Traps For Atomic Clock Applications; J.D. Prestage, R.L. Tjoelker, L. Maleki; 13th European Frequency and Time Forum, Besancon, France, April 13-16, 1999.
  81. Precise Clock Solutions Using Carrier Phase from GPS Receivers in the International GPS Service; J.F. Zumberge, D.C. Jefferson, D.A. Stowers, R.L. Tjoelker, and L. E. Young; Proc. of 30th Ann. Precise Time and Time Interval (PTTI) Planning Meeting ; Reston, Virginia; December 1-3, 1998.
  82. Hg+ Frequency Standards; J.D. Prestage, R.L. Tjoelker, L. Maleki; Proc. of the International Conference on Trapped Charged Particles and Fundamental Physics, Monterey, California Aug 31-Sept. 4, 1998.
  83. Cryo-cooled Sapphire Oscillator; Rabi T. Wang, G. John Dick, and Robert L. Tjoelker; Proc. of the CPEM, Washington D.C. July 1998.
  84. Cryo-cooled Sapphire Oscillator with Ultra-High Stability; G. John Dick, Rabi T. Wang, and Robert L. Tjoelker; Proc. of the 52th Annual Symp.on Frequency Control, Pasadena, CA June 1998.
  85. Radio Frequency Measurements of Cloud Size in a Linear Ion Trap; J.D. Prestage, R.L. Tjoelker, L. Maleki; Proc. of the 51th Annual Symp.on Frequency Control, Orlando, Florida June 1997.
  86. Development of a Mercury Ion Frequency Standard; R.L. Tjoelker, C. Bricker, W. Diener, R.L. Hammel, A. Kirk, P. Kuhnle, L. Maleki, J.D. Prestage, D. Santiago, D. Seidel, D.A. Stowers, R.L. Sydnor, T. Tucker; NASA Tech Briefs, Vol. 21, No. 3, pp.112, March 1997.
  87. The JPL Hg+ Extended Linear Ion Trap Frequency Standard: Status, Stability, and Accuracy Prospects; R.L. Tjoelker, J.D. Prestage, L. Maleki; Proc. of 28th Ann. Precise Time and Time Interval (PTTI) Planning Meeting , December 3-5, 1996.
  88. Ion-Atom Cold Collisions and Atomic Clocks; J. D. Prestage, L. Maleki, and R.L. Tjoelker; Proc. of the Workshop on Scientific Applications of Clocks in Space, JPL Pub 97-15, pp 153-162, Nov. 7-8, 1996
  89. GPS Synchronization of the JPL Linear Ion Trap Relative to an Ensemble of Hydrogen Masers; L.E. Young, D. Jefferson, S.M. Lichten, R.L. Tjoelker, L. Maleki; Proc. of the 50th Annual Symp.on Frequency Control, Honolulu, Hawaii June 5-7, 1996.
  90. A Mercury Ion Frequency Standard Engineering Prototype for the NASA Deep Space Network; R.L. Tjoelker, C. Bricker, W. Diener, R.L. Hamell, A. Kirk, P. Kuhnle, L. Maleki, J.D. Prestage, D. Santiago, D. Seidel, D.A. Stowers, R.L. Sydnor, T. Tucker; Proc. of the 50th Annual Symp.on Frequency Control, Honolulu, Hawaii June 5-7, 1996.
  91. Record Atomic Frequency Standard Stability With Mercury in a Linear Ion Trap; R. L. Tjoelker, J. D. Prestage, and L. Maleki; NASA/JPL Telecommunications and Data Acquisition (TDA) Progress Report 42-126, Aug. 15, 1996, pg 1-7.
  92. (Invited) Trapped Ion Frequency Standards; R. L. Tjoelker; Bull Am. Phys. Soc., 41, 404 (1996).
  93. Atomic Clocks and Variations of the Fine Structure Constant; J.D. Prestage, R. L. Tjoelker, and L. Maleki; Physical Review Letters, 74, 3511, (1995).
  94. (Invited) Record Frequency Stability with Mercury in a Linear Ion Trap; R.L. Tjoelker, J.D. Prestage, L. Maleki; Proc. of the 1995 Symp. on Frequency Standards and Metrology, Woods Hole, Massachusetts October 11-15, 1995.
  95. Progress Report on the Improved Linear Ion Trap Physics Package: J. D. Prestage, R. L. Tjoelker, G. J. Dick, and L. Maleki; Proc. 49th Ann. Symp. Freq. Control, San Francisco, California, pp. 82-85, June 1995.
  96. A Hg+ Linear Trapped Ion Frequen­cy Stan­dard for the USNO; R.L. Tjoelker, J.D. Prestage, L. Maleki; Proc. of the 49th Annual Symp. on Freq. Control, San Francisco, California, May 31-June 2, 1995.
  97. Atomic Clock Tests and for Variations of the Fine Structure Constant; J.D. Prestage, R.L. Tjoelker, L. Maleki;
  98. Proc. de 30th Recontres de Moriond, Villars-Sur-Ollon, Switzerland, Jan 21-28, 1995.
  99. Recent Stability Comparisons Between the JPL Hg+ Trapped Ion Frequen­cy Stan­dards; R.L.Tjoelker, J.D.Prestage, G.J.Dick, L.Maleki; Proc. of the 48th Annual Symp. on Frequency Control, Boston, MA, pp. 739-743, June 1-3, 1994.
  100. Hg+ Trapped Ion Frequency Standard with the Superconducting Cavity Maser; Oscillator as L.O.; J.D Prestage, R.L. Tjoelker, G.J. Dick, and L. Maleki; IEEE Transactions on Instrument and Measurement 42, April (1993).
  101. Improved Linear Ion Trap; J.D. Prestage, R.L. Tjoelker, G.J. Dick, L. Maleki; Proc. of the 47th Annual Symp. on Frequency Control, pp.144-147, (1993).
  102. Doppler Sideband Spectra for Hg+ Ions in a Linear Ion Trap; J.D. Prestage, R.L. Tjoelker, G.J. Dick, L. Maleki; Proc. of the 47th Annual Symp. on Frequency Control, pp.148-154, (1993).
  103. (Invited) Long Term Stability of Hg+ Trapped Ion Frequency Standards; R.L. Tjoelker, G.J. Dick, and L. Maleki, J.D. Prestage; Proc. of the 47th Annual Symp. on Frequency Control, pp.132-138, (1993).
  104. Ultra-Stable Hg+ Trapped Ion Frequency Standard; J.D Prestage, R.L. Tjoelker, G.J. Dick, and L. Maleki; Journal of Modern Optics 39, No. 2, 221-232, (1992).
  105. Hg+ Trapped Ion Frequency Standard with the Superconducting Cavity Maser Oscillator as Local Oscillator; J.D. Prestage, R.L. Tjoelker, G.J. Dick, and L. Maleki; Proc. of the 46th Annual Symp. on Frequency Control, pp. 58-63, (1992).
  106. A High-Performance Hg+ Trapped Ion Frequency Standard; J.D. Prestage, R.L. Tjoelker, G.J. Dick, and L. Maleki; JPL Telecom. and Data Acquisition (TDA) Progress Report 42-108, Oct-Dec 1991, pp. 10-18, February 15, 1992.
  107. Criteria for Ultrastable Operation of the Trapped Ion Frequency Standard; R.L. Tjoelker, J.D. Prestage, L. Maleki; JPL Telecom. and Data Acquisition (TDA) Progress Report 42-108, Oct-Dec 1991, pp. 19-30, February 15, 1992.
  108. A superconducting solenoid system which cancels fluctua­tions in the ambient magnetic field; G.Gabrielse, J. Tan, L.A. Orozco, S.L. Rolston, C.H. Tseng, and R.L. Tjoelker; Journal of Magnetic Resonance 91, 564-572 (1991).
  109. Thousand-fold improvement in the measured antiproton mass; G.Gabrielse, X. Fei, L.A. Orozco, R.L. Tjoelker, T.A. Trainor, J. Haas, H. Kalinowsky, and W. Kells; Physical Review Letters 65, 1317 (1990).
  110. (Invited Paper) Cryogenic antiprotons: a 1000‑fold improvement in their measured mass; G.Gabrielse, X. Fei, W. Jhe, L.A. Orozco, J. Tan, R.L. Tjoelker, J. Haas, H. Kalinowsky, T.A. Trainor, and W. Kells; in Atomic Physics XII (1990).
  111. Cooling and slowing of trapped antiprotons below 100 mev; G.Gabrielse, X. Fei, L.A. Orozco, R.L. Tjoelker, T.A. Trainor, J. Haas, H. Kalinowsky, and W. Kells; Physical Review Letters 63, 1360 (1989).
  112. Barkas effect observed with antiprotons and protons; G.Gabrielse, X. Fei, L.A. Orozco, S.L. Rolston, R.L. Tjoelker, T.A. Trainor, J. Haas, H. Kalinowsky, and W. Kells; Physical Review A 40, 481 (1989).
  113. First capture of antiprotons in an ion trap: progress toward a precision mass measurement and antihydrogen; G.Gabrielse, X. Fei, L. Haarsma, S.L. Rolston, R. Tjoelker, T.A. Trainor, H. Kalinowsky, J. Haas, and W. Kells; Physica Scripta T22, 36 (1988).
  114. First capture of antiprotons in a Penning trap: a kiloelectronvolt source; G.Gabrielse, X. Fei, K. Helmerson, S.L. Rolston, R. Tjoelker, T.A. Trainor, H. Kalinowsky, J. Haas, and W. Kells; Physical Review Letters 57, 2504 (1986).
  115. First antiprotons in an ion trap; G.Gabrielse, X. Fei, K. Helmerson, S.L. Rolston, R.L. Tjoelker, T.A. Trainor, H. Kalinowsky, J. Haas, and W. Kells; in Laser Spectroscopy VIII, ed. by W. Persson and S. Svanberg, (Springer‑Verlag, New York, 1987), p.22.
  116. Prospects for experiments with trapped antiprotons; G.Gabrielse, K. Helmerson, R.L. Tjoelker, X. Fei, T.A. Trainor, W. Kells, and H. Kalinowsky; Proc. of the first workshop on antimatter physics at low energy, ed. by B.E. Bonner, L.S. Pinsky (Fermilab, Batavia 1986), p.211.

DISSERTATION ARTICLES:

  1. Antiprotons in a Penning Trap: A New Measurement of the Inertial Mass; R. L. Tjoelker, PhD Dissertation, Harvard University, November 1990.
  2. Extremely Cold Antiprotons; G. Gabrielse, Scientific American, pp. 78-89, December 1992.
  3. Antiprotons Cooled to 4K and Weighed in a Penning Trap; in Search and Discovery, Physics Today, pp. 17-20, July 1990.
  4. Antiproton Trapping; in Physics Watch, Discover, pp. 32-33, July 1989.

PATENTS

  1. Eric A. Burt, Robert L. Hamell, Blake C. Tucker, Kameron Larsen, and Robert L. Tjoelker; US Patent 9766593, 2017 - Mercury trapped ion frequency standard for ultra-stable reference applications,
  2. Lin Yi, Shouhua Huang, Eric A. Burt, and Robert L. Tjoelker; US Patent 9,372,299, 2016 - Hollow-Core Fiber lamp for Mercury Ion Clocks, Micro-Plasma Studies, and Applications,
  3. Eric A. Burt, Shervin Taghavi, and Robert Tjoelker; US Patent 8,026,768, 2011 - A 201Hg+ co-magnetometer for 199Hg+ trapped ion space atomic clocks,