Title
Swiss atomic clock with ammonia masers
Authors
LSRH
Oscilloquartz
Date of Issue
1958
Device Type
clock
Operating Principle
maser
Reference Species
ammonia
Quantum Transition
inversion
J=3, K=3
Reference Frequency
23 870 MHz
Fabrication Source
noncommercial
Host Institution
LSRH
Status Timeline
Commissioned: 1957-05 by the Swiss Chamber of Horology for the Brussels World's Fair (Kartaschoff 1958)
Development: 1957, masers and most electronic assemblies designed at the LSRH (Recherches au LSRH)
Construction: 1957–1958, built in eight months by Ebauches S.A., Département Oscilloquartz, under LSRH direction; final assembly and adjustment at the LSRH (Kartaschoff 1958; Recherches au LSRH)
Shipped: 1958-03-18, by truck from the LSRH to Brussels (Guye 1958)
Exhibited: 1958-04-17–1958-10-19, assembled on site in the Swiss pavilion, Exposition Universelle et Internationale de Bruxelles (Guye 1958; Recherches au LSRH)
Technical Design aspects: size, design etc.
Configuration: two ammonia beam masers in parallel for mutual control, with microwave superheterodyne receivers and frequency-comparison equipment, in a five-bay cabinet (Kartaschoff 1958; Berger 1958)
Weight: about 600 kg, dividable into two parts for transport (Kartaschoff 1958); about 370 kg per Recherches au LSRH
Electronics: about 250 vacuum tubes in the whole ensemble, some 200 in the molecular standard; no transistors (Recherches au LSRH; Berger 1958)
Beam source: nozzle of many fine parallel channels; thermal velocity about 600 m/s (Kartaschoff 1958; Berger 1958)
State selection: electrostatic Stark-effect focuser, parallel wires on a cylinder at about 15 000 V, in Pyrex vessels with liquid-air cooling jackets (Kartaschoff 1958)
Cavity: critically coupled twin resonators, about 15 cm, thermostated, in anodized aluminium enclosures with thermal insulation; Magic-T coupler to a common receiver (Kartaschoff 1958)
Vacuum: 1E-5 mm Hg by water-cooled oil diffusion pumps over a 0.1 mm Hg rotary-pump forevacuum; liquid-air cold traps; ammonia purified by freezing, 2 l reserve (Kartaschoff 1958)
Comparison chain: auxiliary oscillator 8 500.756 kHz multiplied ×2808; quartz clock with 100 kHz Y-cut bar; readout by gated decade counters (Kartaschoff 1958; Berger 1958)
Technical specifications: stability, precision
Precision: 1E-10 as a complete atomic clock (molecular standard + quartz clock), about 1/100 000 s per day (Berger 1958; Guye 1958; Kartaschoff 1958)
Reproducibility: ±1E-10 (±2.4 Hz) (Kartaschoff 1958)
Line Q: 1E7 (Kartaschoff 1958)
cavity Q: 1E4 (Kartaschoff 1958)
Modification History
After the exhibit the ammonia frequency standard was returned to LSRH, while the quartz clock was sold by Ebauches S.A., Département Oscilloquartz
Usage History
Atomic clock built in eight months for the Swiss watch industry's exhibit at the 1958 Brussels World's Fair. Two ammonia beam masers, running roughly every fifteen days, calibrated a quartz clock that drove a Favag master clock and a two-metre universal dial in the Swiss pavilion. Designed at the LSRH in Neuchâtel and built by Ebauches S.A., it was the first Swiss atomic clock shown to the public; after the fair the ensemble was dispersed and the maser standard returned to the LSRH.
Product
kartaschoff1958
berger1958
guye1958
RecherchesAuLSRH
Identifiers
https://libra.unine.ch/handle/20.500.14713/99857