A laser with little divergence Lasers can emit highly divergent beams of energy For example, a CO2 laser can emit a 1 2 mrad divergent beam (1 mrad = 1 milliradian = 1 millimeter divergence per 1 meter traveled), and an ND: YAG laser can emit a 1 2-25 mrad beam
Lead bricks were placed around the radioactive source so that the escaping gamma rays would be limited to a collimated beam rather than filling the lab.