The PTB’s caesium fountain atomic
clock will be 10x more accurate than
standard caesium atomic clocks
currently defining time worldwide.
At the center of the instrument,
caesium atoms are trapped and
cooled by 6 laser beams in a vacu-
um to be accelerated vertically and
to fall back down again.
During their flight an internal oscil-
lation is excited to achieve a pace-
maker of great accuracy.

[s] ‘The SECOND is the duration
of 9 192 631 770 periods of the
radiation corresponding to the
transition between the two hyperfine
levels of the ground state of the
caesium 133 atom.’