Complex sentence: At a conference at Cambridge on beta particles and gamma rays in 1928, Chadwick met Geiger again, who brought with him a new model of his Geiger counter, which had been improved by his post-doctoral student Walther Müller.
Split into simpler sentences: At a conference at Cambridge on beta particles and gamma rays in 1928, Chadwick met Geiger again. Geiger had brought with him a new model of his Geiger counter, which had been improved by his post-doctoral student Walther Müller.