Varian Associates pre-production rubidium-vapor frequency standard
date: label: date made
content: 1960
name: label: maker
content: Varian Associates
notes: label: Description
content: Varian, Inc. pre-production rubidium-vapor frequency standard, enclosed in metal frame, with two components in separate small metal cases.
label: Description
content: In this accession (no. 1980.0511), the pre-production (.01) and production (.02) model frequency standards show the intermediate and final instruments in the process of developing the rubidium-vapor absorption frequency standard from a laboratory apparatus into a commercially viable, production-line "atomic clock."
label: Description
content: History and basic principles
label: Description
content: Object ID no. 1980.0511.01 is one of the two pre-production models of an atomic absorption clock that Varian, Associates delivered to NASA’s Jet Propulsion Laboratory in October 1960 for use in tracking space vehicles. It employs many standard commercial components (e.g., power supply, modulation oscillator). Consequently it is far less compact than Object ID no. 1980.0511.02, the V-4700A production model put on the market a year later.
label: Description
content: Earlier devices in the development employed sodium in the absorption cell, but it was concluded that the optimum atom for an absorption clock was rubidium, an element similar to sodium and cesium, lying between them in atomic weight. For its commercial models, Varian adopted rubidium.
label: Description
content: Brief description of an atomic clock
label: Description
content: Electromagnetic waves of very specific and consistent frequencies can induce atoms to fluctuate between two energy states, and by measuring that frequency we can determine the “tick” of an atomic clock. A second in a cesium clock, for example, is defined as 9,192,631,770.0 cycles of the frequency that causes the cesium atom to jump between those states. Different atoms “tick” at different rates – strontium atoms tick about 10,000 times faster than cesium atoms – but all atoms of a given element tick at the same rate, making atomic clocks much more consistent than clocks based on macroscopic objects such as pendulums or quartz crystals.
label: Description
content: (Ref: Steven Jefferts, physicist, National Institute of Standards and Technology)
label: Description
content: There are different types of atomic clocks, the principle behind all of them remains the same. The major difference is associated with the element used and the means of detecting when the energy level changes. The various types of atomic clocks include:
label: Description
content: •Cesium atomic clocks employ a beam of cesium atoms. The clock separates cesium atoms of different energy levels by magnetic field.
label: Description
content: •Hydrogen atomic clocks maintain hydrogen atoms at the required energy level in a container with walls of a special material so that the atoms don't lose their higher energy state too quickly.
label: Description
content: •Rubidium atomic clocks, the simplest and most compact of all, use a glass cell of rubidium gas that changes its absorption of light at the optical rubidium frequency when the surrounding microwave frequency is just right.
label: Description
content: For additional background information go to:
label: Description
content: http://www.nist.gov/pml/div688/timekeeping.cfm
label: Description
content: http://science.howstuffworks.com/atomic-clock.htm
setName: label: See more items in
content: Medicine and Science: Modern Physics
creditLine: label: Credit Line
content: Transfer from National Aeronautics and Space Administration, Jet Propulsion Laboratory
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1980.0511.01
label: accession number
content: 1980.0511
label: catalog number
content: 1980.0511.01
objectType: label: Object Name
content: Frequency Standard, Rubidium Vapor
physicalDescription: label: Physical Description
content: metal; plastic (overall material)
label: Measurements
content: overall: 29 1/2 in x 23 in x 21 1/8 in; 74.93 cm x 58.42 cm x 53.6575 cm