Transmission electron microscopy is used to investigate the spatial arrangement of the small gas bubbles produced in copper by 16 keV proton irradiation at 300 K to a high dose. The irradiation parameters have been chosen to match those of earlier studies of helium bubble structure in copper at 300 K. In what is a new result for hydrogen bubbles it is found that the bubble structure can be characterised as an fcc superlattice with principal axes aligned with those of the host matrix. The bubble array exhibits a much wider range of bubble sizes and many more structural defects than are evident in the corresponding helium gas bubble superlattice. For bubbles with diameter ~ 2 run a bubble lattice constant, a 1, of ~ 12 nm is found for the hydrogen case compared with a 1 ~ 7 nm for the helium case. There is evidence to suggest that hydrogen bubbles may move apart as they grow. Even within the same grain there are well-defined separated regions in which the average bubble size is much greater than that in the surrounding matrix. These larger bubbles are faceted and are commonly elongated along particular crystallographic directions.