Claims
- 1. A nuclear magnetic resonance apparatus, comprising:
- an antenna for inducing a radio frequency magnetic field in materials to be analyzed and for detecting nuclear magnetic resonance signals from said materials; and
- a magnet for inducing a static magnetic field in said materials, said magnet formed from an electrically conductive permanent magnet material, said magnet assembled from electrically isolated blocks where boundaries between adjacent ones of said blocks are oriented to substantially interrupt flow of eddy currents induced in said magnet by said radio frequency field and wherein said blocks each have a thickness calculated to provide a predetermined minimum value of quality factor for said antenna.
- 2. The apparatus as defined in claim 1 wherein said eddy currents are induced by said radio frequency magnetic field.
- 3. The apparatus as defined in claim 1 wherein said electrically conductive permanent magnet material comprises powder having a maximum particle size with respect to a frequency of said radio frequency magnetic field so as to substantially prevent intragranular power loss of said radio frequency magnetic field.
- 4. The apparatus as defined in claim 1 wherein said electrically conductive magnet material comprises a powder bonded by a non-conductive material comprising polymeric resin.
- 5. The apparatus as defined in claim 1 wherein said electrically conductive material comprises Samarium-Cobalt.
- 6. The apparatus as defined in claim 1 wherein said electrically conductive magnet material comprises Neodymium-Iron-Boron.
- 7. The apparatus as defined in claim 1 wherein said antenna comprises a transversal dipole antenna disposed on an exterior surface of said magnet, and said boundaries are substantially parallel to said longitudinal axis and perpendicular to a principal magnetic field direction of said antenna.
- 8. The apparatus as defined in claim 1 wherein said antenna comprises a transversal dipole antenna disposed on an exterior surface of said magnet, and said boundaries are substantially perpendicular to said longitudinal axis.
- 9. The apparatus as defined in claim 1 wherein said antenna comprises a longitudinal dipole antenna, and said boundaries are substantially parallel to said longitudinal axis and extend radially outward from said longitudinal axis.
- 10. A nuclear magnetic resonance well logging apparatus, comprising:
- an antenna for inducing a radio frequency magnetic field in earth formations surrounding said apparatus and for detecting nuclear magnetic resonance signals from said earth formations; and
- a magnet for inducing a static magnetic field within said earth formations, said magnet formed from an electrically conductive permanent magnet material, said magnet material having a maximum particle size with respect to a frequency of said radio frequency magnetic field to substantially prevent intragranular power loss of said radio frequency magnetic field, said magnet assembled from electrically isolated blocks of said magnet material where boundaries between adjacent ones of said blocks are oriented to substantially interrupt flow of eddy currents in said magnet.
- 11. The apparatus as defined in claim 10 wherein said eddy currents are induced by said radio frequency magnetic field.
- 12. The apparatus as defined in claim 10 wherein each of said blocks has a thickness calculated to provide a minimum value of quality factor for said antenna.
- 13. The well logging apparatus as defined in claim 10 wherein said electrically conductive magnet material comprises powdered magnetic material bonded by a non-conductive material comprising polymeric resin.
- 14. The well logging apparatus as defined in claim 10 wherein said electrically conductive magnet material comprises Samarium-Cobalt.
- 15. The well logging apparatus as defined in claim 10 wherein said electrically conductive magnet material comprises Neodymium-Iron-Boron.
- 16. The well logging apparatus as defined in claim 10 wherein said magnet comprises a cylinder having substantially uniform magnetization along a longitudinal axis of said cylinder and a magnetization direction substantially perpendicular to said longitudinal axis, said antenna comprises a transversal dipole antenna disposed on an exterior surface of said magnet, and said boundaries are substantially parallel to said longitudinal axis and substantially perpendicular to a principal magnetic field direction of said antenna.
- 17. The well logging apparatus as defined in claim 10 wherein said magnet comprises a cylinder having substantially uniform magnetization along a longitudinal axis of said cylinder and a magnetization direction substantially perpendicular to said longitudinal axis, said antenna comprises a transversal dipole antenna disposed on an exterior surface of said magnet, and said boundaries are substantially perpendicular to said longitudinal axis.
- 18. The well logging apparatus as defined in claim 10 wherein said magnet comprises a cylinder having substantially uniform magnetization along a longitudinal axis of said cylinder and a magnetization direction substantially perpendicular to said longitudinal axis, said antenna comprises a longitudinal dipole antenna, and said boundaries are substantially parallel to said longitudinal axis and extend substantially radially outward from said longitudinal axis.
- 19. A nuclear magnetic resonance sensing apparatus, comprising:
- an antenna for inducing a radio frequency magnetic field in materials to be analyzed and for detecting nuclear magnetic resonance signals from said materials; and
- a magnet for inducing a static magnetic field within said materials, said magnet formed from a powdered, electrically conductive magnetic material and a non-conductive bonding agent, said powdered magnetic material having a maximum grain size to substantially prevent intragranular power loss of said radio frequency magnetic field.
- 20. The apparatus as defined in claim 19 wherein said powdered magnetic material comprises Samarium-Cobalt.
- 21. The apparatus as defined in claim 19 wherein said maximum grain size is about 50 microns corresponding to a frequency of said radio frequency magnetic field of about 0.5 MHz.
- 22. The apparatus as defined in claim 19 wherein said powdered magnetic material comprises Neodymium-Iron-Boron.
- 23. The apparatus as defined in claim 19 wherein said bonding agent comprises a polymeric resin.
- 24. The apparatus as defined in claim 19 wherein a proportion of said powdered, electrically conductive magnetic material in said magnet is selected to provide a predetermined electrical conductivity of said magnet, whereby a predetermined value of quality factor for said antenna is determined.
Parent Case Info
This is a continuation-in-part of Ser. No. 08/740,825 filed on Nov. 4, 1996.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
5621324 |
Ota et al. |
Apr 1997 |
|
Foreign Referenced Citations (1)
Number |
Date |
Country |
2 141 236 |
Dec 1984 |
GBX |
Non-Patent Literature Citations (1)
Entry |
Proceedings of the Fourth International Workshop on Rare Earth-Cobalt Permanent Magnets and their Applications, May 22-24 1979 Japan. |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
740825 |
Nov 1996 |
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