Title
RRL ammonia absorption frequency standard
Authors
Radio Research Laboratories
Date of Issue
1955-12
Device Type
frequency
Operating Principle
cell
Reference Species
ammonia
Quantum Transition
inversion
J=3, K=3
Reference Frequency
23 870 127 750 (260) Hz
Fabrication Source
noncommercial
Host Institution
Radio Research Laboratories
Status Timeline
Design: 1953, development starts
Operational: 1955-12, a prototype is reported as completed
Technical Design aspects: size, design etc.
The output of a 102.3 kHz quartz oscillator was multiplied to produce a 23,870 MHz microwave signal. RRL used a source-modulation method: a 50 kHz modulation signal was applied to the helix of a travelling-wave tube, slightly frequency-modulating the microwave signal. Changes in the signal transmitted through the sealed ammonia absorption tube were then detected and used to determine the centre of the absorption line.
The ammonia was sealed in an absorption tube approximately 4 m long, forming part of a K-band waveguide.
Technical specifications: stability, precision
Accuracy: initially about 2E-7, improved by 1957 toward approximately 3E-9
Modification History
1957: the modulation/discrimination system and microwave-power control were refined to reduce errors in determining the centre of the absorption line
Usage History
By 1956 the ammonia absorption line was being used to measure the frequency of the RRL's standard quartz oscillator. The stated objective was a high-accuracy, long-term-stable atomic frequency standard suitable for practical use in the standard-frequency broadcasting service.
Product
nagatake1956
RRL1957FiveYears
Identifiers
https://libra.unine.ch/handle/20.500.14713/100579