Several new particle types were
discovered with the cloud chamber in the 1940s.
Donald A. Glaser (Nobel Prize 1960), who had made his
thesis work with Carl Anderson (who discovered the
positron using the cloud chamber, Nobel Prize 1936)
and studied particles using the cloud chamber, was
thinking of how to improve observations of rare
particles. The cloud chamber had two important
limitations. Because of the low density of the gas
very few interactions occured in the visible part of
the chamber. The rate with which the chamber could be
operated was slow and could not be used together with
the new accelerators being constructed in the 1950s
where particle bursts came every few seconds.