Renseignements généraux

Nº de série

S/O

Nº de partie

1

Nombre total de parties

1

Ou

S/O

Brevets

S/O

Description générale

METAL, INCUDING ALUMINUM & BRASS/ SYNTHETIC, INCLUDING PLASTICS & PHENOLIC (DEFLECTORS), ADHESIVE TAPE

Dimensions

Remarque : Cette information reflète la taille générale pour l’entreposage et ne représente pas nécessairement les véritables dimensions de l’objet.

Longueur

324,0 cm

Largeur

84,0 cm

Hauteur

189,0 cm

Épaisseur

S/O

Poids

S/O

Diamètre

S/O

Volume

S/O

Lexique

Groupe

Métrologie

Catégorie

Divers

Sous-catégorie

S/O

Fabricant

Ou

NRC

Pays

Canada

État/province

Ontario

Ville

Ottawa

Contexte

Pays

Canada

État/province

Ontario

Période

1958-1965

Canada

THIS WAS THE 1ST CAESIUM BASED CLOCK BUILT IN CANADA & THE 2ND IN THE WORLD, IT PROVIDED CANADA'S MASTER TIME SIGNAL FOR 7 YEARS. IT WAS REPLACED BY NRC'S 2ND CBRA IN 1965, WHICH WITH ATOMIC CLOCKS IN THE U.S., BRITAIN, SWITZERLAND & JAPAN WAS USED TO REDEFINE THE SECOND, & WAS ACCURATE TO BETTER THAN 1 PT IN 10 10 SEC. This clock, known as CS1, was built in 1957/58 and by 1961 the NRC scientists in the Time Frequency Division at NRC had learned enough about its performance and had compared the results with the standard time provided by the astronomers at the Dominion Observatory long enough to know this clock was more accurate and more stable than the rotation of the Earth. The DO had provided the official time for all of Canada from 1905. In 1961 it was decided that this clock would replace the DO as the official source of time but the DO continued to monitor the Earth's rotation until 1970. The gradual difference in time between CS 1 and the astronomical determined time was compared and resulted in the occasional addition of a leap second at the end of some years. The Earth is slowing down at an irregular rate which is not desirable for a time standard (Ref. 6).

Fonction

A PRECISE TIME INTERVAL MEASURING INSTRUMENT, USED TO CHECK THE ACCURACY OF HIGH PRECISION CRYSTAL CLOCKS & TO PROVIDE THE MASTER TIME SIGNAL FOR CANADA. TIME IS MAINTAINED BY A CAESIUM BEAM RESONANCE APPARATUS.

Technique

THIS WAS THE 2ND CAESIUM CLOCK DEVELOPED IN THE WORLD, BUILT AT NRC 1956-1958TO PROVIDE THE PRECISE TIME INTERVAL MEASUREMENTS REQUIRED IN SCIENTIFIC WORK; NEITHER ASTRONOMICAL OBSERVATIONS NOR MAN-MADE CLOCKS WERE SUFFICIENTLY ACCURATE. THE CBRA USES THE MAGNETIC DIPOLE RESONANCE OF THE CAESIUM ATOM. Cesium clocks work because the outer electrons in a cesium atom are normally in one of two very stable energy levels. However, if a cloud of cesium atoms is heated to 350 K (about 77 C) and a magnetic field is applied, the electrons shift their energy state and if passed through a microwave cavity the atoms can be separated. The ones of with exactly the right energy are allowed to pass through the cavity and stimulates an oscillator where the activity is measured. The oscillator frequency counts off the precise number of cycles required to define a second. The accuracy of CS 1 was 1 second in about 3,000 years (Ref. 6).

Notes sur la région

Inconnu

Détails

Marques

NONE APPARENT, save handwritten markings on various component pieces, at junctions, etc. Several tags with handwritten notes are attached to this piece.

Manque

CAESIUM BEAM APPARATUS APPEARS COMPLETE BUT WOULD HAVE BEEN USED WITH BANKS OF ELECTRICAL APPARATUS INCLUDING POWER SUPPLIES, FREQUENCY COUNTERS ETC.

Fini

METALLIC FRAME/ GREY PAINTED PARTS/ MULTICOLOURED SYNTHETIC

Décoration

S/O