Operation Totem status, the British government restarted its own development effort, which was given the cover name "High Explosive Research". The first British atomic bomb was tested in Operation Hurricane at the Montebello Islands in Western Australia on 3 October 1952. The main purpose of the trial was to determine the acceptable limit on the amount of plutonium-240 which could be present in a bomb. The plutonium used in the original Hurricane device was produced in the nuclear reactor at Windscale, but the Windscale Piles did not have anything like the capacity to provide sufficient material for the British government's planned weapons
Atomic clock of using atomic transitions to measure time was suggested by Lord Kelvin in 1879. Magnetic resonance, developed in the 1930s by Isidor Rabi, became the practical method for doing this. In 1945, Rabi first publicly suggested that atomic beam magnetic resonance might be used as the basis of a clock. The first atomic clock was an ammonia absorption line device at 23870.1 MHz built in 1949 at the U.S. National Bureau of Standards (NBS, now NIST). It was less accurate than existing quartz clocks, but served to demonstrate the concept. The first accurate atomic clock, a caesium standard based on