| 摘要 |
<p>Apparatus for locating a discontinuity in the medium surrounding a test bore comprises: a probe having an axially extending tubular housing environmentally sealed at each end; an omnidirectional radiation source associated with the housing; a radiation detector and a radiation absorbing plug associated with teh housing and arranged so that the plug is interposed between the source and the detector; an electrical cable passing through an end of the housing for operating the detector; a shield removably mounted on the housing in an axial position that overlies the detector, comprising a cylindrical metallic sleeve having means defining a radiation transparent window that extends axially along the sleeve and circumferentially up to 180 degrees of arc; and means for rotating at least the shield so as to indicate the angular position of the transparent window with respect to a reference.</p> |
