Title
RRL ammonia maser
Alternative Title
AM-1
Authors
Radio Research Laboratories
Date of Issue
1959-09
Device Type
frequency
Operating Principle
maser
Reference Species
ammonia
Quantum Transition
inversion
J=3, K=3
Reference Frequency
23 870 128 809 (7) Hz
Fabrication Source
noncommercial
Host Institution
Radio Research Laboratories
Status Timeline
Development: 1956, After observing Japan’s first ammonia-maser oscillation in Koichi Shimoda’s laboratory at the University of Tokyo, Yoshikazu Saburi rapidly assembled an oscillation-type ammonia standard at RRL (Harada 2012).
First oscillation: 1957-01, with an initial accuracy of 3E-9 (Harada 2012)
Development: 1957-1959, the maser was progressively improved, eventually reaching an accuracy of 1E-10 (Harada 2012)
Operational: 1959-09, the ammonia maser entered use as a primary frequency standard for JJY; continuous long-range measurements began around this time (RRL 1960; Harada 2012)
Technical Design aspects: size, design etc.
A beam of ammonia molecules passed through an octupole electrostatic focuser, which selected molecules in the appropriate upper inversion state, and then entered a microwave resonant cavity where stimulated emission produced self-sustained oscillation. The octupole focuser consisted of eight steel rods, 2 mm in diameter and 38 cm long (Saburi and Kobayashi 1960).
The maser was contained in a brass cylindrical vacuum vessel about 17 cm in diameter and 75 cm long (Saburi and Kobayashi 1960).
The beam source was a 6 mm-diameter effuser containing about 150 stainless-steel tubes, each 0.2 mm in diameter and 5 mm long (Saburi and Kobayashi 1960).
The frequency-standard experiments used a 12 cm-long cylindrical TM₀₁₃ cavity, longitudinally slotted for fine tuning, with approximately 8 mm entrance and exit apertures (Saburi and Kobayashi 1960).
Technical specifications: stability, precision
Stability: 2E-10, over 30 hours of operation (Saburi and Kobayashi 1960).
Later assessments: Harada (2012) reports “accuracy” (確度) improving from 3E-9 to 1E-10; Nakagiri (1992) gives ±2E-10, termed “precision” in the text and “frequency reproducibility” in the chronology. Whether the later figures describe stability or frequency-setting performance is not established.
Usage History
From September 1959, AM-1 was used as a primary frequency standard for JJY, providing a reference for measuring and regulating the frequency of the Japanese standard radio transmission. Systematic long-term measurements against JJY were carried out from October 1959.
Product
saburi1960
harada2012
RadioResearchLaboratoriesJapan1960
Identifiers
https://libra.unine.ch/handle/20.500.14713/100592