PURPOSE: To always detect the occurrence of collision only by mounting and detaching an attachment part by mechanically detecting that the attachment part is mounted while leaving the number of connector contacts to those of conventional ones intact, by providing a means for sending a signal showing that the attachment part is mounted to a sequence means and displaying that the attachment part is mounted.

CONSTITUTION: When no applicator 9 is mounted, a limit switch 32 takes such a state that a movable contact is present on the side of an NC. When the contact of the movable part of a collimator head 3 is detected by a contact detector 10, a switch 13 is opened and a relay 22 becomes a usual state by this and a signal showing 'occurrence of collision' is sent to an interlock circuit 15. When the applicator 9 is mounted, a cam 31 moves the movable contact of the limit switch 32 toward the NC, and the switch 13 and a normally closed contact type switch 14 for detecting the collision of the applicator 19 are connected in series. As a result, even when either one of the switches 13, 14 is opened, the relay 22 becomes a usual state and the signal showing 'the occurrence of collision' is sent to the interlock circuit.