In 1919 Ernest Rutherford reported a very important discovery, the significance of which was not lost on Breit and Tuve. The collision of an alpha particle with an atom of nitrogen produced an atom of oxygen and one of hydrogen. It was the transmutation of one element into another, a scientific goal dating from the earliest alchemy. This opened an astounding new field of research, but, despite its primordial fascination, one that proceeded very slowly because the process was very rare and required large numbers of alpha particles to produce a single event.

Rutherford had speculated openly about replacing the tiny flux of particles from a radioactive source with a relatively gigantic stream of alphas or other particles, certainly including protons, that had been accelerated through an electric potential of millions of volts. Typical kinetic energies of alpha particles were of the order of millions of electron volts (MeV), and laboratory gas discharges could produce copious numbers of ions. The combination of a source of ions and an accelerating potential opened possibilities that allowed one to imagine all manner of experiments. Tuve and Breit wanted to build such a voltage source and accelerate ions with it.

Fleming persuaded them to do the work at DTM. In taking this risky step, which was precipitated by Tuve considering doing it at Rutherford's laboratory, he was following Andrew Carnegie's original dictum of identifying competent scientists and supporting them.