RETRIEVABLE RADIATION SOURCE CARRIER

摘要

A retrievable radiation source carrier assembly for a logging while drilling tool is disclosed. The carrier includes a solid rod or member of high strength and low elastic modulus that connects the housings of at least two radiation sources. In a preferred embodiment, the carrier includes a sheath of high performance thermoplastic that covers the rod from the upper source to the lower source. The sheath provides the carrier with a smooth outer surface and a substantially constant diameter that resists the accumulation of mud particulate buildup thereon. The sheath also provides a low friction surface which allows improved ease of insertion and removal of the radiation source carrier into and from the internal source passageway of the LWD tool. In another preferred embodiment, the source carrier's end cap disposed above the upper source is provided with a drilling fluid path that provides drilling fluid pressure equalization between the interior of the LWD tool and the source passageway in which the carrier assembly is placed. The pressure equalization path includes a gravity trap for substantially preventing particulates found in the drilling fluid from entering the source passageway and settling around the source carrier assembly.