Scanning instrument
A scanning apparatus for measuring the attenuation of radiation passing from a radiation source along a radiation path to a radiation detector includes a source of radiation; at least one radiation detector capable of detecting radiation emitted by the source a data processor associated with the at least one radiation detector for calculating a property of material present in a linear radiation path between the source and the at least one detector; and a spacer arranged between the source and the at least one detector. The spacer defines a space which is capable of excluding water and having an average density which is less than 1 gcm −3 . The provision of a spacer in the radiation path enables more radiation to be passed along the radiation path because water can be replaced with a material which is less attenuating to radiation.
1. A sub-sea pipeline scanning apparatus for measuring the attenuation of gamma radiation passing from a source of gamma radiation along a radiation path through a sub-sea pipeline to a radiation detector comprising:
a) the source of gamma radiation;
b) the radiation detector, which is capable of detecting gamma radiation emitted by said source and passed through the sub-sea pipeline,
wherein the sub-sea pipeline scanning apparatus is configured to rotate the source and the at least one radiation detector around the sub-sea pipeline while maintaining the source and the at least one radiation detector in a fixed relationship to each other;
c) a data processor associated with said at radiation detector configured to calculate a property of a material present in a linear radiation path between said source and said radiation detector;
wherein said sub-sea pipeline scanning apparatus further comprises:
a first spacer mounted in a fixed relationship with respect to the source and positioned, between the source and the sub-sea pipeline to be scanned; and
a second spacer mounted in a fixed relationship with respect to the radiation detector and positioned, between the radiation detector and the sub-sea pipeline;
wherein said first and second spacers are rotatable around the sub-sea pipeline with the source and the radiation detector, and said first and second spacers each define a space which is capable of excluding water and have an average density which is less than 1 gcm −3 .
2. The scanning apparatus according to claim 1 , wherein the first and/or second spacer has an average density <0.75 gcm −3 .
3. The scanning apparatus according to claim 2 , wherein the first and/or second spacer comprises a shell enclosing a vacuum or a gas.
4. The scanning apparatus according to claim 2 , wherein a proportion of the volume of the first and/or second spacer is filled by a solid foamed material.
5. The scanning apparatus according to claim 2 , wherein the first and/or second spacer comprises a shell which is impervious to water.
6. The scanning apparatus according to claim 2 , further comprising removable weights for adjusting a trim of the scanning apparatus when underwater.
7. The scanning apparatus according to claim 2 , wherein each of the first and second spacers are formed from a plurality of spacer portions which are adapted to engage each other to form the first and second spacers, wherein the first and second spacers each fill a greater volume than any of the separate spacer portions.
8. The scanning apparatus according to claim 1 , wherein the first and/or second spacer comprises a shell enclosing a vacuum or a gas.
9. The scanning apparatus according to claim 1 , wherein a proportion of the volume of the first and/or second spacer is filled by a solid foamed material.
10. The scanning apparatus according to claim 1 , wherein the first and/or second spacer comprises a shell which is impervious to water.
11. The scanning apparatus according to claim 10 , wherein said shell is rigid or flexible.
12. The scanning apparatus according to claim 1 , wherein the first and/or second spacer comprises a buoyancy material.
13. The scanning apparatus according to claim 1 , further comprising removable weights for adjusting a trim of the scanning apparatus when underwater.
14. The scanning apparatus according to claim 1 , wherein each of the first and second spacers are formed from a plurality of spacer portions which are adapted to engage each other to form the first and/or second spacer, wherein the first and second spacers each fill a greater volume than any of the separate spacer portions.