Abstract: A socket for receiving a radiation source, such as a luminous source, having a base, the base having at least one groove-shaped depression thereon, the socket having a bottom portion defining a receptacle for receiving the base; a pair of walls extending upwardly from the bottom portion and being spaced apart from each other so as to receive the base therebetween; at least one of the walls having at least one protuberance which projects inwardly of the socket toward the other of the walls; the at least one protuberance being receivable in a corresponding groove-shaped depression in the base so as to guide and retain the base in the socket; the socket and the base being shiftable relative to each other along an axis, wherein the at least one protuberance and the groove-shaped depression extend in a direction substantially parallel to the axis.