https://www.sciencedaily.com/releases/2018/05/180524081605.htm

Scientists at Osaka University discovered a novel particle acceleration mechanism called 'Micro-bubble implosion,' in which super-high energy hydrogen ions (relativistic protons) are emitted at the moment when bubbles shrink to atomic size through the irradiation of hydrides with micron-sized spherical bubbles by ultraintense laser pulses. Their research results were published in Scientific Reports.

The group led by Masakatsu Murakami has reported an astonishing physical phenomenon: when shrinking matter to the unprecedented high level, with density comparable to matter the size of a sugar cube weighing more than 100 kg, high-energy protons are emitted from the positively-charged nanoscale clusters, a world first. Usually, an acceleration distance of several tens to hundreds of meters is necessary for conventional accelerators to generate such huge energy.