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  • 1
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    Ultra-stable Hg(+) trapped ion frequency standard (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: We report the development of a fieldable frequency standard based on Hg-199(+) ions confined in a hybrid r.f./dc linear ion trap. This trap permits storage of large numbers of ions with reduced susceptibility to the second-order Doppler effect caused by the r.f. confining fields. A 160 mHz wide atomic resonance line for the 40.5 GHz clock transition is used to steer the output of a 5 MHz crystal oscillator to obtain a stability of 2 x 10 exp -15 for 24,000 s averaging times. For longer averaging intervals, measurements are limited by instabilities in available hydrogen maser frequency standards. Measurements with 37 mHz linewidth for the Hg(+) clock transition demonstrate that the inherent stability for this frequency standard is at least as good as 1 x 10 exp -15.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Journal of Modern Optics (ISSN 0950-0340); 39; 2; p. 221-232.
    Format: text
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  • 2
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    Cryo-Cooled Sapphire Oscillator for the Cassini Ka-Band Experiment (1997)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: We present features for an ultra-stable sapphire cryogenic oscillator which has been designed to support the Cassini Ka-band Radio Science experiment. The design of this standard is new in several respects. It is cooled by a commercial cryocooler instead of liquid cryogens to increase operating time, and it uses a technology to adjust the temperature turn-over point to extend the upper operating temperature limit and to enable construction of multiple units with uniform operating characteristics. Objectives are 3 x 10(exp -15) stability for measuring times 1 second less than or equal to (tau) less than or equal to 100 seconds, phase noise of -85 dBc/Hz from offset frequencies of 1 Hz to 1000 Hz at 10 GHz carrier frequency, and a one year continuous operating period.
    Keywords: Instrumentation and Photography
    Type: Proceedings of the Workshop on the Scientific Applications of Clocks in Space; 127-129; NASA/CR-97-112594
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    NASA TECHNICAL REPORTS
  • 3
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    Ultra-stable performance of the superconducting cavity maser (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Recent measurements on the superconducting cavity maser (SCM) oscillator show frequency stability of parts in 10 exp 15 for times from 1 to 1000 sec. Phase noise of approximately -80 dB/f-cubed was also measured. This short- and mid-term performance is believed to be better than that of any known microwave oscillator. In particular, stability at a measuring time of 1 sec is 10 times better than that of a hydrogen maser, and phase noise at 8 GHz is more than 20 dB below that of the best multiplied quartz crystal oscillators. Substantial technical improvements have been made to eliminate frequency instability due to operational parameters. They are temperature, pump frequency, pump power, pump frequency polarization, temperature gradient, coupling strength, and output VSWR. Either the parameter was stabilized or the coefficient which couples the parameter to the operating frequency was minimized. A frequency pulling coil has been implemented and tested to enable the SCM to be slaved to a hydrogen maser with a time constant of approximately 50 sec. This combination would allow the excellent long term performance of the hydrogen maser to be improved by the newly available short term performance of the SCM.
    Keywords: LASERS AND MASERS
    Type: IEEE Transactions on Instrumentation and Measurement (ISSN 0018-9456); 40; 174-177
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  • 4
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    Linear ion trap based atomic frequency standard (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: In order to develop a trapped ion-based fieldable frequency standard with stability 1 x 10 to the -13th/sq rt tau for averaging times tau greater than 10,000 s, a hybrid RF/DC linear ion trap was developed which permits storage of large numbers of ions with reduced susceptibility to the second-order Doppler effect caused by the RF confining fields. The authors have confined Hg-199(+) ions in this trap and have measured very high Q transitions with good SNRs. In preliminary measurements they obtained stabilities of 1.6 x 10 to the -13th/sq rt tau (tau between 50 and 800 s) with a 160-mHz wide atomic resonance linewidth and a signal-to-noise ratio of 40 for each measurement cycle. Atomic resonance lines as narrow as 30 mHz on the 40.5-GHz clock transition have been measured with no appreciable reduction in the ion signal. A stability of 7 x 10 to the -14th/sq rt tau is made possible by the signal-to-noise and line Q of this measured transition. Analysis of fundamental sources of frequency instability indicates that a long-term stability of 2 x 10 to the -16th is feasible for this device with existing technology for tau = 10 to the 6th s or more.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: IEEE Transactions on Instrumentation and Measurement (ISSN 0018-9456); 40; 132-136
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  • 5
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    Measurement and analysis of a microwave oscillator stabilized by a sapphire dielectric ring resonator for ultra-low noise (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Phase-noise measurements are presented for a microwave oscillator whose frequency is stabilized by a whispering-gallery sapphire ring resonator with Q of 200,000. This mode involves little metallic conduction and allows nearly full use of the very low dielectric loss in sapphire. Several mode families have been identified, in good agreement with frequency calculations. For a 5-cm wheel resonator in a 7.6-cm container, Q values above 100,000 were found at room temperature for all of the modes in this sequence. Coupling Q-values for these same modes ranged from 10,000 (n = 5) to 100,000 (n = 10) for a WR112 waveguide port at the center of the cylinder wall of the containing can. Phase noise measurements for a transistor oscillator locked to the n = 10 (7.84-GHz) mode showed a 1/f cubed dependence for low offset frequencies, and a value of L(f) = -55 dB/Hz at an offset of 10 Hz from the carrier.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control (ISSN 0885-3010); 37; 339-346
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  • 6
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    Microwave applications and characterization of the microwave properties of high temperature superconducting films (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The development by NASA JPL of high-temperature superconductors (HTSs) for use in microwave circuit elements is discussed. The synthesis of HTS films and characterization of their microwave absorption are reviewed. Applications to cryogenic low-noise receivers, spacecraft microwave systems, and low-noise oscillators are considered.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
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  • 7
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    New ion trap for atomic frequency standard applications (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A novel linear ion trap that permits storage of a large number of ions with reduced susceptibility to the second-order Doppler effect caused by the radio frequency (RF) confining fields has been designed and built. This new trap should store about 20 times the number of ions a conventional RF trap stores with no corresponding increase in second-order Doppler shift from the confining field. In addition, the sensitivity of this shift to trapping parameters, i.e., RF voltage, RF frequency, and trap size, is greatly reduced.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: The Telecommunications and Data Acquisition Report; p 58-63
    Format: application/pdf
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  • 8
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    Zero-crossing detector with sub-microsecond jitter and crosstalk (1990)
    In:  Other Sources
    Details
    Publication Date: 2013-08-29
    Description: A zero-crossing detector (ZCD) was built and tested with a new circuit design which gives reduced time jitter compared to previous designs. With the new design, time jitter is reduced for the first time to a value which approaches that due to noise in the input amplifying stage. Additionally, with fiber-optic transmission of the output signal, crosstalk between units has been eliminated. The measured values are in good agreement with circuit noise calculations and approximately ten times lower than that for ZCD's presently installed in the JPL test facility. Crosstalk between adjacent units was reduced even more than the jitter.
    Keywords: PHYSICS (GENERAL)
    Type: The 22nd Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting; p 269-282
    Format: text
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  • 9
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    Ultra-stable Hg(+) trapped ion frequency standard (1990)
    In:  Other Sources
    Details
    Publication Date: 2013-08-29
    Description: A fieldable trapped ion frequency standard based on Hg-199(+) ions confined in a hybrid rf/dc linear ion trap is developed. This trap permits storage of large numbers of ions with reduced susceptibility to the second-order Doppler effect caused by the rf confining fields. In preliminary measurements a stability of 2 to 3 x 10(exp -15) was obtained for 10000 second averaging times. These measurements were carried out with a 120 mHz wide atomic resonance line for the 40.5 GHz clock transition with a second order Doppler shift from the rf trapping field of 6 x 10(exp -13).
    Keywords: PHYSICS (GENERAL)
    Type: The 22nd Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting; p 171-185
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  • 10
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    Operational parameters for the superconducting cavity maser (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Tests of the superconducting cavity maser (SCM) ultra-stable frequency source have been made for the first time using a hydrogen maser for a frequency reference. In addition to characterizing the frequency stability, the sensitivity of the output frequency to several crucial parameters was determined for various operating conditions. Based on this determination, the refrigeration and thermal control systems of the SCM were modified. Subsequent tests showed substantially improved performance, especially at the longest averaging times.
    Keywords: LASERS AND MASERS
    Type: The Telecommunications and Data Acquisition Report; p 64-71
    Format: application/pdf
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