Patent ID: 7285772

Claim:
A logging tool ( 20 ) for underground formations surrounding a borehole ( 14 ), comprising: an elongated body ( 21 ) along a major axis; a collar ( 22 ) disposed peripherally around said body ( 21 ) having a collar wall defined by an inner and an outer surface; a radiation emitting source ( 201 ) arranged to illuminate the earth formation ( 16 ) surrounding the borehole; at least one radiation detecttor ( 211 ) arranged to detect radiation reflected by the earth formation resulting from illumination by the source ( 201 ); at least one source collimation window ( 202 ) and one detector collimation window ( 212 ) through which the earth formation is illuminated and radiation is detected; at least one radiation shield positioned so as to eliminate patasitic radiation that has not traversed the outer collar and is located between said emitting radiation source and said radiation detector, said radiation shield having a length along the axis that is less than 80% of the distance between said emitting radiation source ( 201 ) and said radiation detector ( 211 ).