In one aspect of the invention, a downhole tool string component comprises a tubular body with a first and a second tool joint adapted to connect to adjacent tool string components, and a central bore adapted to pass drilling mud between the joints. A sleeve circumferentially disposed about an outer surface of the tubular body. The sleeve is rigidly attached to the outer surface at first and second sleeve ends and forming at least three stabilizer blades. A nuclear source and at least one nuclear detector are disposed within a gap formed between the inner surface of the sleeve and the outer surface of the tubular body.