Abstract: An apparatus and method for curing radiation curable material includes a lamp unit providing radiation in a converging beam directed toward a focal plane and forming a curing zone at a curing position for receiving the curable material. The lamp unit is mounted in a boot member having a spiral external thread for engaging a spiral internal thread on the wall of a housing chamber for receiving the boot member. The engagement of the threads is such that rotation of the boot member controllably varies the intensity of radiation in the curing zone by changing the distance between the radiation outlet of the lamp unit and the curing position. The curing zone may be an elongated band such that rotation of the boot member also provides angular adjustment of the elongated band relative to a curing path for the curable material. The boot member may include internal cooling passages and these passages may contain overlapping light baffles blocking the escape of harmful radiation.