{HEAD ~ the temperature controller} is configured to control {TAIL ~ the electric current} supplied to the heater so that the first trap unit is maintained within a temperature range which is at or above the melting point and below the boiling point of the debris and within which a reaction rate at which the debris reacts with the etching gas and the gaseous reaction product is generated is less than a reaction rate at which the gaseous reaction product is decomposed and the debris is deposited, and 
{ HEAD ~ the temperature controller } is configured to control { TAIL ~ the electric current } supplied to the heater so that the first trap unit is maintained within a temperature range which is at or above the melting point and below the boiling point of the debris and within which a reaction rate at which the debris reacts with the etching gas and the gaseous reaction product is generated is less than a reaction rate at which the gaseous reaction product is decomposed and the debris is deposited , and
HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH