A heavy ion beam in an accelerator is like a crowd of people shoving each other with elbows: the more people, the wider the crowd. Charged particles repel each other, and at currents above a few microamps the beam spreads and loses its shape. For light particles this is tolerable, but for heavy ones, such as gold ions, the problem is acute: they fly slowly, and the shoving has time to ruin the beam.
The authors took an existing multi-stage accelerator and changed the voltages on its stages. Previously, the field only accelerated the ions; now it simultaneously compresses the beam, just as a glass lens focuses light. The result is a column that both accelerates and focuses. For gold ions at an energy of 64 keV, they managed to push the current to 100 microamps — more than ten times the previous limit while keeping the beam narrow.
This approach suits a variety of tasks, from measuring plasma parameters in future fusion reactors to implanting ions into materials and working with heavy molecules. Instead of building a new accelerator, you can simply retune an old one, and heavy ions will fly in a dense beam, like a column that doesn't scatter along the way.
A current of 100 microamps of gold ions is about 6×$10^{14}$ ions per second. If each ion were a grain of sand, this flow would fill a bucket in a minute.