Abstract: A method and system for treating internal surface material overlying the interior of a tubular a substrate, and more particularly, to a system for ablating contaminates and other unwanted material from an internal surface 52 using a pulsed laser beam (38). The system includes three main sub-systems: a back end (30), a work head (100), and an umbilical tube (31) to protect conduits communicating between the back end (30) and the work head (100). The back end (30) includes heavy and bulky equipment such as a laser (32), chiller (4), pressurized air source (70), suction system (84), waste containment system (82), and electric power source (78). A conveyance such as a trailer (17) may enclose the back end (30) to make it transportable. The work head (100) includes a propeller driven rotating mirror assembly (380), and a lens assembly (520). During operation, the work head (100) is inserted in the tube or pipe and the laser (32) activated.