# NIST Primary Frequency Standards and the Realization of the SI Second

@article{Lombardi2007NISTPF, title={NIST Primary Frequency Standards and the Realization of the SI Second}, author={M. Lombardi and T. Heavner and S. Jefferts}, journal={NCSLI Measure}, year={2007}, volume={2}, pages={74 - 89} }

Abstract: As the base unit of time interval, the second holds a place of preeminence in the world of metrology. Time interval, and its reciprocal, frequency, can be measured with more resolution and less uncertainty than any of the other physical quantities. The precise realization of the second was made possible by the development of frequency standards based on the energy transitions of atoms, an event that not only revolutionized the science of timekeeping, but also forever changed many… Expand

#### 53 Citations

Realization and characterization of optical frequency standards

- Chemistry
- 2013

During the Ph.D. Course I worked on the realization and the characterization of an ytterbium optical frequency standard. Since year 2000, it is possible using optical frequency comb to directly and… Expand

Optical frequency transfer via telecommunication fiber links for metrological applications

- Materials Science
- 2014

This thesis reports on the characterization of ultra-stable optical frequency transfer via long-haul telecommunication fiber links. Optical frequencies like this are provided by stable laser systems… Expand

Atomic Clocks

- 2015

In atomic clocks, the frequency of the oscillator is determined by the energy difference between two quantum mechanical states in atoms, ions or molecules. This transition energy depends only on… Expand

Digital instrumentation for the measurement of high spectral purity signals

- Engineering
- 2017

Improvements on electronic technology in recent years have allowed the application of digital techniques in time and frequency metrology where low noise and high accuracy are required, yielding… Expand

Atomic clocks: A brief history and current status of research in India

- Physics
- 2014

Frequency corresponding to the energy difference between designated levels of an atom provides precise reference for making a universally accurate clock. Since the middle of the 20th century till… Expand

Frequency Transfer Techniques and Applications in Fiber Optic Communication Systems

- Engineering
- 2013

Modern society is dependent on communications and the developments of these increases constantly through a seemingly endless demand for communication services and thereby synchronization and time.… Expand

Coherence Time of Rabi Oscillations of Cold Atoms

- 2013

Ultracold atoms, also described as “matter waves”, stand at the base of two Nobel prizes in the last 15 years. During the same time, two other Nobel prizes were given for quantum optics. The… Expand

Atomic physics with vapor-cell clocks

- Chemistry
- 2012

The most widely used atomic frequency standards (or clocks) are based on the microwave resonant frequencies of optically pumped vapors of alkali-metal atoms in glass cells filled with buffer gas.… Expand

Double-resonance studies on compact, high-performance rubidium cell frequency standards

- Chemistry
- 2013

This thesis presents experimental studies on continuous-wave (CW) laser-microwave double-resonance (DR) spectroscopy and metrology in rubidium (87Rb) vapor cells in view of new high-performance,… Expand

Advanced laser frequency stabilisation systems for mobile strontium optical lattice clocks

- Physics
- 2020

Strontium optical lattice clocks have undergone vast developments in the past decade with world leading frequency stability and uncertainty records. Now, a lot of scientists are moving from… Expand

#### References

SHOWING 1-10 OF 84 REFERENCES

The metrology of time

- Computer Science, Biology
- Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
- 2005

The evolution of the measuring of time, current state-of-the-art measures and future challenges are explained. Expand

SPECTRAL LINES AS FREQUENCY STANDARDS

- Physics, Medicine
- Annals of the New York Academy of Sciences
- 1952

Although the problems involved in the design of accurate and reliable frequency and time standards are somewhat different, these two topics will be dealt with together since a clock can be used as a frequencyStandard while a frequency standard by itself will not read time. Expand

Standards of Time and Frequency at the Outset of the 21st Century

- Medicine
- Science
- 2004

After 50 years of development, microwave atomic clocks based on cesium have achieved fractional uncertainties below 1 part in 1015, a level unequaled in all of metrology. The past 5 years have seen… Expand

The Measurement of Time: Time, Frequency and the Atomic Clock

- Physics
- 2001

This book provides an in-depth and comprehensive survey of the current state-of-the-art of the international atomic timescale and its underpinning relationship to practical and legal timescales. The… Expand

Improvements in Atomic Cesium Beam Frequency Standards at the National Bureau of Standards

- Mathematics
- 1970

The National Bureau of Standards Frequency Standard, NBS-III, a cesium beam with a 3.66-meter interaction region, has been in operation since 1963. The last published (1966) accuracy capability for… Expand

Time and frequency measurement at NIST: the first 100 years

- Engineering
- Proceedings of the 2001 IEEE International Frequncy Control Symposium and PDA Exhibition (Cat. No.01CH37218)
- 2001

During this, the NIST Centennial Year, I look back on the first 100 years and summarize NIST work on time and frequency measurement, a topic of some prominence from the early years of the… Expand

The Performance and Capability of Cesium Beam Frequency Standards at the National Bureau of Standards

- Mathematics
- 1966

NBS II, the older of the two cesium atomic beam frequency standards which are used alternatively as the United States Frequency Standard, has been operating for more than five years. The contribution… Expand

Cesium Primary Frequency References

- Physics, Chemistry
- 2004

Primary frequency standards with stated inaccuracies of δf/f~10 -15 or slightly better are in use today in several national timing laboratories. These standards, which are the most accurate in the… Expand

Operation of the NIST-F1 caesium fountain primary frequency standard with a maser ensemble, including the impact of frequency transfer noise

- Environmental Science
- 2005

The operation of a caesium fountain primary frequency standard is greatly influenced by the characteristics of two other important facilities. The first is a stable frequency reference and the second… Expand

Accuracy Evaluation and Stability of the NBS Primary Frequency Standards

- Materials Science
- 1974

The National Bureau of Standards has two primary standards for frequency and the unit of time. They are both cesium devices and are designated NBS-4 and NBS-5. The design of NBS-5 is discussed in… Expand