A micro-sample prepared by processing with an ion beam is extracted by a probe and, in this state, a voltage is applied across the probe and a micro-sample holder by a circuit for sending electric current to probe. A mounting segment is adjacent the first end of the connector member. A control system, which may include a programmable computer, controls the motion of the variable carving head. The optical fiber includes a defect substantially surrounded by the cladding, the defect increasing a coupling coefficient between the first core and the second core. An exit duct portion of the combustor forms a sliding joint with a downstream turbine vane assembly and has at least two discrete sheet metal walls fastened to the sheet metal combustor wall at a common intersection region.