overall: 10 1/2 in x 18 5/8 in x 19 in; 26.67 cm x 47.3075 cm x 48.26 cm
Object Name:
Frequency Standard, Rubidium Vapor
Date made:
1961
Description:
Varian Associates V-4700A rubidium-vapor frequency standard, serial no. 20: chassis with front panel, for rack mounting.
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."
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). Object ID no. 1980.0511.02, the V-4700A production model put on the market a year later, was far more compact than the pre-production model.
Brief description of an atomic clock
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.
(Ref: Steven Jefferts, physicist, National Institute of Standards and Technology)
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:
•Cesium atomic clocks employ a beam of cesium atoms. The clock separates cesium atoms of different energy levels by magnetic field.
•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.
•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.
For additional background information go to:
http://www.nist.gov/pml/div688/timekeeping.cfm
http://science.howstuffworks.com/atomic-clock.htm
Location:
Currently not on view
Credit Line:
Transfer from National Aeronautics and Space Administration, Jet Propulsion Laboratory
