RRL double-beam ammonia maser

Radio Research Laboratories

Title

Authors

Radio Research Laboratories

Date of Issue

1960-07

Device Type

frequency

Operating Principle

maser

Reference Species

ammonia

Quantum Transition

inversion

J=3, K=2

Reference Frequency

22 834 185 037 (5) Hz

Frequency relative to the US atomic standard (NPM radio signal transmitted from Hawaii). The standard deviation reflected not only the stability of the maser but also the comparison chain (Saburi et al. 1962).

Fabrication Source

noncommercial

Host Institution

Radio Research Laboratories

Technical Design aspects: size, design etc.

Two ammonia molecular-beam sources and electrostatic focusers were arranged symmetrically on opposite sides of a centrally located resonant cavity. The double-beam geometry increased the effective molecular-beam intensity required for oscillation on the weaker 3–2 transition and strongly reduced frequency shifts caused by the travelling-wave effect (Saburi et al. 1962).

Each octopole focuser comprised eight steel rods, 2 mm in diameter and 37 cm long, arranged on a 10 mm circumference and operated at up to approximately 13 kV. Each 6 mm beam effuser contained approximately 150 stainless-steel capillary tubes, 0.2 mm internal diameter and 5 mm long (Saburi et al. 1962).

The copper cylindrical resonant cavity operated in the TM011 mode, was 12 cm long, had approximately 8 mm beam apertures, and had a Q of about 6,000. Longitudinal slots permitted fine mechanical tuning by squeezing the cavity (Saburi et al. 1962).

Two oil-diffusion pumps and liquid-nitrogen trapping provided the vacuum system. Under operating conditions the tank pressure remained around the 1E-6 mmHg range, and oscillation could be maintained satisfactorily for more than ten hours (Saburi et al. 1962).

Technical specifications: stability, precision

Resettability: expected to be a few parts in 1E-11 (Saburi et al. 1962).

Short-term frequency stability: relative beat-frequency variations of less than a few times 1E-11, peak-to-peak, with one-second observations (Saburi et al. 1962).

Later reported “accuracy”: 2E-11 (Nakagiri 1992); 5E-11 (Harada 2012). These may summarize the frequency-setting performance discussed by Saburi et al. 1962; their equivalence to the reported resettability is not established.

Usage History

First oscillation: 1959 (Nakagiri 1992)

Operational: 1960-07, used to regulate the Japanese disseminated standard frequency (Nakagiri 1992)

Primary standard: 1961-09-01, formally adopted as the primary frequency standard for the disseminated standard frequency, replacing the previous UT2-based reference (Nakagiri 1992)

Product

saburi1962a

saburi1962

nakagiri1992

harada2012

Identifiers

https://libra.unine.ch/handle/20.500.14713/100593