Short Term Frequency Stability Tests of Two Cryogenic Sapphire Oscillators

Watabe, K.; Hartnett, John G.; Locke, Clayton R.; Santarelli, Giorgio; Yanagimachi, Shinya; Shimazaki, Takeshi; Ikegami, Takeshi; Ohshima, Shinichi

doi:10.1143/jjap.45.9234

Cited by 18 publications

(12 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The characteristics of our liquid-helium cooled CSOs is briefly reviewed below [8]. Three high quality (HEMEX grade) sapphire crystals from Crystal Systems were cut and polished cylindrically with a height of 30 mm and a diameter of 50 mm ( Fig.1(a)), and are used as electromagnetic resonators.…”

Section: Nmij Cryogenic Sapphire Oscillators Using Liquid Heliummentioning

confidence: 99%

“…The crystal2 was used for the cryoCSO1. The loaded Q-factor and coupling on the primary reflection port were re-measured to be Q L =5×10 8 and β 1 * =0.51, respectively. The incident power on the resonator and modulation index were set to 100 μW and 0.2 rad, respectively.…”

Section: First Cryocso (Cryocso1)mentioning

confidence: 99%

“…The Allan deviation of the frequency stability for the single CSO1 is shown as a gray dotted line in Fig. 3(b) [8]. For the longer term frequency stability evaluation (τ > 1000 s), a hydrogen maser (HM) was used as a reference, whose specified Allan deviation is shown as a black dotted line in Fig.…”

Section: First Cryocso (Cryocso1)mentioning

confidence: 99%

See 2 more Smart Citations

Autonomous cryogenic sapphire oscillators employing low vibration pulse-tube cryocoolers at NMIJ

Ikegami¹,

Watabe²,

Yanagimachi³

et al. 2016

J. Phys.: Conf. Ser.

Self Cite

View full text Add to dashboard Cite

Abstract. Two liquid-helium-cooled cryogenic sapphire-resonator oscillators (CSOs), have been modified to operate using cryo-refrigerators and low-vibration cryostats. The Allan deviation of the first CSO was evaluated to be better than 2×10-15 for averaging times of 1 s to 30 000 s, which is better than that of the original liquid helium cooled CSO. The Allan deviation of the second CSO is better than 4×10 -15 from 1 s to 6 000 s averaging time. IntroductionCryogenic sapphire oscillators (CSOs) are still the most frequency-stable oscillator operating in the microwave frequency region [1]. Their frequency stability, expressed as Allan standard deviation, reaches a few times 10 -16 over averaging times of 1 s to 1 000 s. This short-term stability cannot be obtained in any commercial device, for example, in BVA OCXOs or hydrogen masers.Recently, the cesium atomic-fountain primary frequency standards, when limited by a quantum projection noise, have a short-term frequency stability approaching a few times 10 -14 . In order to avoid the influence of the Dick effect (the degradation of frequency stability due to dead time), a more stable local oscillator than obtainable in commercially available devices is required. Thus CSOs have been successfully implemented as local oscillators for such frequency standards [2], [3].On the other hand, the development of optical atomic clocks is rapid and their frequency stability and uncertainty approaches 10 -18 . In near future, the redefinition of the unit of time, the "second," is expected [4]. One purpose of optical clocks is the improvement of the international timescale, TAI (International Atomic Time). The uncertainty of TAI has been determined by a balance of the frequency stabilities between primary frequency standards (currently Cs atomic fountains), time comparison methods (GPS or two-way satellite time transfer), and local oscillators (LOs, currently, hydrogen masers), to the current value of about 3×10 -16 . Because primary frequency standards (current Cs atomic fountains, and optical clocks in future) do not operate continuously over years, better LOs to replace the current hydrogen masers will be necessary. The LO should be stable enough to keep good time and phase, even when a primary standard stops operating and hence it cannot calibrate the LO during those periods. If stable LOs are successfully developed that can operate continuously without phase jumps over many years, they can be calibrated with the best optical clocks and can be

show abstract

Section: Nmij Cryogenic Sapphire Oscillators Using Liquid Heliummentioning

confidence: 99%

Section: First Cryocso (Cryocso1)mentioning

confidence: 99%

See 1 more Smart Citation

Autonomous cryogenic sapphire oscillators employing low vibration pulse-tube cryocoolers at NMIJ

Ikegami¹,

Watabe²,

Yanagimachi³

et al. 2016

J. Phys.: Conf. Ser.

Self Cite

View full text Add to dashboard Cite

show abstract

“…11,12 At least 20 prototypes of such oscillator have been implemented for primary metrology and physical experiments, [13][14][15][16] in which the sapphire is cooled in a large liquid-He Dewar flask. The liquid He requires refilling every 3-4 weeks, and also senses the atmospheric pressure.…”

Section: Introductionmentioning

confidence: 99%

New-generation of cryogenic sapphire microwave oscillators for space, metrology, and scientific applications

Giordano

Grop

Dubois

et al. 2012

Review of Scientific Instruments

View full text Add to dashboard Cite

This article reports on the characterization of cryogenic sapphire oscillators (CSOs), and on the first test of a CSO in a real field installation, where ultimate frequency stability and continuous operation are critical issues, with no survey. Thanks to low-vibration liquid-He cryocooler design, Internet monitoring, and a significant effort of engineering, these oscillators could bridge the gap from an experiment to a fully reliable machine. The cryocooler needs scheduled maintenance every 2 years, which is usual for these devices. The direct comparison of two CSOs demonstrates a frequency stability of 5 × 10 −16 for 30 s ≤ τ ≤ 300 s integration time, and 4.5 × 10 −15 at 1 day (1 × 10 −14 typical). Two prototypes are fully operational, codenamed ELISA and ULISS. ELISA has been permanently installed the new deep space antenna station of the European Space Agency in Malargüe, Argentina, in May 2012. ULISS is a transportable version of ELISA, modified to fit in a small van (8.5 m 2 footprint). Installation requires a few hours manpower and 1 day of operation to attain full stability. ULISS, intended for off-site experiments and as a technology demonstrator, and has successfully completed two long-distance travels.

show abstract

“…Cryogenic sapphire oscillators have been deployed to a number of frequency standards labs [5], [6] and have facilitated atomic fountain clocks reaching a performance limited only by quantum projection noise [7]. Since most atomic fountain clocks [8] have significant dead time in their interrogation cycle, simply due to the fact that they are pulsed devices where one has to wait until the detection process is finished before the next cloud of cold atoms is launched, it is impossible to avoid influences of the Dick effect [9]- [12].…”

mentioning

confidence: 99%

Ultra-Low Vibration Pulse-Tube Cryocooler Stabilized Cryogenic Sapphire Oscillator With ${\hbox{10}}^{-16}$ Fractional Frequency Stability

Hartnett

Nand

2010

IEEE Trans. Microwave Theory Techn.

Self Cite

View full text Add to dashboard Cite

Abstract-A low maintenance long-term operational cryogenic sapphire oscillator has been implemented at 11.2 GHz using an ultra-low-vibration cryostat and pulse-tube cryocooler. It is currently the world's most stable microwave oscillator employing a cryocooler. Its performance is explained in terms of temperature and frequency stability. The phase noise and the Allan deviation of frequency fluctuations have been evaluated by comparing it to an ultra-stable liquid-helium cooled cryogenic sapphire oscillator in the same laboratory. Assuming both contribute equally, the Allan deviation evaluated for the cryocooled oscillator is σy ≈ 1 × 10 −15 τ −1/2 for integration times 1 < τ < 10 s with a minimum σy = 3.9 × 10 −16 at τ = 20 s. The long term frequency drift is less than 5 × 10 −14 /day. From the measured power spectral density of phase fluctuations the single side band phase noise can be represented by L φ (f ) = 10

show abstract

Short Term Frequency Stability Tests of Two Cryogenic Sapphire Oscillators

Cited by 18 publications

References 16 publications

Autonomous cryogenic sapphire oscillators employing low vibration pulse-tube cryocoolers at NMIJ

Autonomous cryogenic sapphire oscillators employing low vibration pulse-tube cryocoolers at NMIJ

New-generation of cryogenic sapphire microwave oscillators for space, metrology, and scientific applications

Ultra-Low Vibration Pulse-Tube Cryocooler Stabilized Cryogenic Sapphire Oscillator With ${\hbox{10}}^{-16}$ Fractional Frequency Stability

Contact Info

Product

Resources

About