A rubidium standard or rubidium atomic clock is a

frequency standard A frequency standard is a stable oscillator used for frequency calibration or reference. A frequency standard generates a fundamental frequency with a high degree of accuracy and precision. Harmonics of this fundamental frequency are used to p ...

in which a specified

hyperfine transition In atomic physics, hyperfine structure is defined by small shifts in otherwise degenerate energy levels and the resulting splittings in those energy levels of atoms, molecules, and ions, due to electromagnetic multipole interaction between the nuc ...

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no kn ...

s in rubidium-87 atoms is used to control the output frequency.

Synopsis

The Rb standard is the most inexpensive, compact, and widely produced

atomic clock An atomic clock is a clock that measures time by monitoring the resonant frequency of atoms. It is based on atoms having different energy levels. Electron states in an atom are associated with different energy levels, and in transitions betwee ...

, used to control the frequency of

television station A television station is a set of equipment managed by a business, organisation or other entity, such as an amateur television (ATV) operator, that transmits video content and audio content via radio waves directly from a transmitter on the earth ...

s, cell phone base stations, in test equipment, and

global navigation satellite system A satellite navigation or satnav system is a system that uses satellites to provide autonomous geo-spatial positioning. It allows satellite navigation devices to determine their location (longitude, latitude, and altitude/elevation) to high pr ...

s like

GPS The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...

. Commercial rubidium clocks are less accurate than

caesium atomic clock The caesium standard is a primary frequency standard in which the photon absorption by transitions between the two hyperfine ground states of caesium-133 atoms is used to control the output frequency. The first caesium clock was built by Louis ...

s, which serve as primary frequency standards, so the rubidium clock is a secondary frequency standard. All commercial rubidium frequency standards operate by disciplining a

crystal oscillator A crystal oscillator is an electronic oscillator circuit that uses a piezoelectric crystal as a frequency-selective element. The oscillator frequency is often used to keep track of time, as in quartz wristwatches, to provide a stable cloc ...

to the rubidium hyperfine transition of 6.8 GHz (). The intensity of light from a rubidium

discharge lamp Gas-discharge lamps are a family of artificial light sources that generate light by sending an electric discharge through an ionization, ionized gas, a plasma (physics), plasma. Typically, such lamps use a noble gas (argon, neon, krypton, and ...

that reaches a

photodetector Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation. There is a wide variety of photodetectors which may be classified by mechanism of detection, such as photoelectric or photochemical effects, or ...

through a resonance cell will drop by about 0.1% when the rubidium vapor in the resonance cell is exposed to

microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ran ...

power near the transition frequency. The crystal oscillator is stabilized to the rubidium transition by detecting the light dip while sweeping an RF

synthesizer A synthesizer (also spelled synthesiser) is an electronic musical instrument that generates audio signals. Synthesizers typically create sounds by generating waveforms through methods including subtractive synthesis, additive synthesis and ...

(referenced to the crystal) through the transition frequency.

References

Bibliography

Stanford Research Systems documentation on the PRS10 frequency standard
* * {{FS1037C

External links

* ttp://www.npl.co.uk/server.php?show=ConWebDoc.1727 Secondary Representation of the SI Second
PTB "Unit of Time"

NPL Rubidium Fountain
Electronics standards Atomic clocks Rubidium

Synopsis

See also

References

Bibliography

External links