ION ACCUMULATION
With this experiment, PTB metrolo-
gists sought to redefine the kilogram
by tying it to the atomic mass unit.
The setup creates metal mass arti-
facts by accumulating bismuth ions
inside a collector and counting them
by measuring the electrical current
required to neutralize the ions.
Because the required measurement
precision can’t be reached in due
time, however, the experiment will
be discontinued.