Patent Number: 
Section: claims

1. An apparatus for providing a signal indicative of a property of an earth formation, the apparatus comprising:a carrier configured to be conveyed through a borehole penetrating the earth formation;a neutron source disposed on the carrier and configured to emit neutrons into the earth formation;a radiation detector disposed on the carrier and configured to detect radiation from the earth formation due to interaction of emitted neutrons with the earth formation and to provide the signal indicative of the property; anda radiation detector neutron shield configured to shield the radiation detector from emitted neutrons that did not interact with the earth formation;wherein the radiation detector shield comprises a glass ceramic material having a plurality of nano-crystallites, each nano-crystallite in the plurality having a periodic crystal structure with a diameter or dimension that is less than 1000 nm that includes Li and/or Boron and a rare-earth element that have positions in the periodic crystal structure of each nano-crystallite. 2. The apparatus according to claim 1, wherein the radiation detector shield defines an opening configured to admit the radiation from the earth formation due to interaction of emitted neutrons with the earth formation. 3. The apparatus according to claim 1, further comprising:downhole electronics disposed on the carrier, coupled to the radiation detector and configured to process the signal indicative of the property to estimate the property; anda downhole electronics neutron shield configured to shield the downhole electronics from neutrons emitted by the neutron source;wherein the downhole electronics shield comprises a glass ceramic material having a plurality of nano-crystallites, each nano-crystallite in the plurality having a periodic crystal structure with a diameter or dimension that is less than 1000 nm and includes a rare-earth element that has positions in the periodic crystal structure of each nano-crystallite. 4. The apparatus according to claim 3, wherein at least one of the detector neutron shield and the downhole electronics neutron shield comprises a plurality of sections. 5. The apparatus according to claim 4, where the plurality of sections is connected by at least one of an adhesive and a mechanical fastener. 6. The apparatus according to claim 1, wherein the radiation detector comprises a neutron detector. 7. The apparatus according to claim 1, wherein the radiation detector comprises a gamma-ray detector. 8. The apparatus according to claim 1, wherein the property is porosity and/or density. 9. The apparatus according to claim 1, wherein the glass ceramic material comprises a composition of 10B, 6Li and rare-earth oxides, Sm2O3, Er2O3, Yb2O3, Nd2O3. 10. The apparatus according to claim 1, wherein the glass ceramic material comprises a composition of a natural B and rare-earth oxides, Sm2O3, Er2O3, Yb2O3, and Nd2O3. 11. The apparatus according to claim 1, wherein the glass ceramic material comprises a composition of 10B and rare-earth oxides, Sm2O3, Er2O3, Yb2O3, Nd2O3. 12. The apparatus according to claim 1, wherein the radiation detector neutron shield comprises an electrical penetration for electrically connecting an electrical conductor to the radiation detector. 13. The apparatus according to claim 1, wherein the carrier comprises at least one of a drill string, coiled tubing, a slickline and a wireline. 14. A method for providing a signal indicative of a property of an earth formation, the method comprising:conveying a carrier through a borehole penetrating the earth formation;emitting neutrons into the earth formation using a neutron source disposed on the carrier;detecting radiation from the earth formation due to interaction of emitted neutrons with the earth formation using a radiation detector configured to provide a signal indicative of the property;shielding the radiation detector from emitted neutrons that did not interact with the earth formation using a radiation detector neutron shield, wherein the radiation detector shield comprises a glass ceramic material having a plurality of nano-crystallites, each nano-crystallite in the plurality having a periodic crystal structure with a diameter or dimension that is less than 1000 nm that includes Li and/or B and a rare-earth element that have positions in the periodic crystal structure of each nano-crystallite. 15. The method according to claim 14, further comprising shielding downhole electronics disposed on the carrier and coupled to the radiation detector from neutrons emitted by the neutron source using a downhole electronics neutron shield, the downhole electronics neutron shield comprising a glass ceramic material having a glass ceramic material that includes a plurality of nano-crystallites, each nano-crystallite in the plurality having a periodic crystal structure with a diameter or dimension that is less than 1000 nm and includes a rare-earth element that has positions in the periodic crystal structure of each nano-crystallite. 16. The method according to claim 14, wherein the glass ceramic material comprises a composition of 10B, 6Li and rare-earth oxides, Sm2O3, Er2O3, Yb2O3, Nd2O3. 17. The method according to claim 14, wherein the glass ceramic material comprises a composition of a natural B and rare-earth oxides, Sm2O3, Er2O3, Yb2O3, and Nd2O3. 18. The method according to claim 14, wherein the glass ceramic material comprises a composition of 10B and rare-earth oxides, Sm2O3, Er2O3, Yb2O3, Nd2O3.