Patent Number: 
Section: claims

1. An apparatus comprising:a chemical neutron emitter;a neutron shield having an aperture, at least one of the neutron shield and the chemical neutron emitter arranged for linear movement through a position that aligns the chemical neutron emitter with the aperture of the neutron shield; anda control unit that controls the movement of at least one of the chemical neutron emitter and the neutron shield to chop a neutron beam emitted from the chemical neutron emitter with the neutron shield. 2. The apparatus of claim 1, wherein:the chemical neutron emitter is fixed in position;the neutron shield is arranged for linear movement with respect to the chemical neutron emitter; andthe control unit controls linear movement of the neutron shield. 3. The apparatus of claim 2, wherein the neutron shield is arranged to oscillate linearly with respect to the chemical neutron emitter. 4. The apparatus of claim 1, further comprising:wherein the neutron shield is fixed in position;wherein the chemical neutron emitter is arranged for linear movement with respect to the neutron shield; andthe control unit controls linear movement of the chemical neutron emitter. 5. The apparatus of claim 4, further comprising:a platform, wherein the chemical neutron emitter is attached to the platform, the platform structured for linear movement with respect to the neutron shield; andwherein the control unit that controls the linear movement of the chemical neutron emitter moves the platform. 6. The apparatus of claim 5, wherein the platform is structured to oscillate linearly with respect to the neutron shield. 7. The apparatus of claim 4, wherein the control unit includes circuitry structured to regulate motion of the chemical neutron emitter or the neutron shield at a selected frequency. 8. The apparatus of claim 1, wherein the apparatus includes:a processing unit arranged to process signals collected in response to generation of neutrons from the aperture in a borehole; anda communications unit to transmit results from the processing unit. 9. The apparatus of claim 1, wherein the chemical neutron emitter includes one or more radioactive isotopes. 10. A method comprising:generating neutrons from a chemical neutron emitter; andlinearly moving one or more of the chemical neutron emitter or a neutron shield through a position at which an aperture of the neutron shield is aligned with the chemical neutron emitter to pass neutrons output through the aperture. 11. The method of claim 10, wherein linearly moving includes moving the neutron shield with the chemical neutron emitter fixed or linearly moving the chemical neutron emitter with the neutron shield fixed. 12. The method of claim 10, wherein linearly moving includes an oscillatory linear motion. 13. The method of claim 10, wherein linearly moving includes moving with a selected frequency of movement. 14. The method of claim 10, wherein linearly moving includes moving with a selected variation of frequency of movement. 15. The method of claim 10, further comprising:analyzing signals from generating the pulses of neutrons output in a borehole; anddirecting a drilling-based operation in response to analyzing the signals. 16. An apparatus comprising:a neutron shield having an aperture;a chemical neutron emitter arranged to move through a position that aligns the chemical neutron emitter with the aperture of the neutron shield; anda control unit that controls the movement of the chemical neutron emitter to chop a neutron beam emitted from the chemical neutron emitter with the neutron shield. 17. An apparatus of claim 16, wherein the apparatus includes a backstop partially encircling the chemical neutron emitter, the backstop disposed between the chemical neutron emitter and neutron shield. 18. The apparatus of claim 16, wherein the chemical neutron emitter is rotatable such that the chemical neutron emitter is operatively aligned with the aperture at one angular region in a rotation of the chemical neutron emitter. 19. The apparatus of claim 16, wherein the chemical neutron emitter includes one or more radioactive isotopes. 20. The apparatus of claim 16, wherein the chemical neutron emitter is rotatable with the neutron shield surrounding the chemical neutron emitter such that the chemical neutron emitter is operatively aligned with the aperture at one angular region in each rotation of the chemical neutron emitter. 21. The apparatus of claim 20, further comprising:a platform, wherein the chemical neutron emitter is attached to the platform, the platform structured to rotate with respect to the neutron shield; andwherein the control unit that controls movement of the chemical neutron emitter moves the platform. 22. The apparatus of claim 16, wherein the control unit includes circuitry to regulate motion of the chemical neutron emitter at a selected frequency. 23. The apparatus of claim 16, wherein the apparatus includes:a processing unit arranged to process signals collected in response to generation of neutrons from the aperture in a borehole; anda communications unit to transmit results from the processing unit. 24. A method comprising:generating neutrons from a chemical neutron emitter; andmoving the chemical neutron emitter through a position at which an aperture of a neutron shield is aligned with the chemical neutron emitter to pass pulses of neutrons output through the aperture. 25. The method of claim 24, wherein the neutron shield is fixed in position. 26. The method of claim 24, wherein moving the chemical neutron emitter comprises moving the chemical neutron emitter in a rotational motion. 27. The method of claim 24, wherein moving the chemical neutron emitter comprises moving with a selected frequency of movement. 28. The method of claim 24, wherein moving the chemical neutron emitter comprises moving with a selected variation of frequency of movement. 29. The method of claim 24, further comprising:analyzing signals from generating the pulses of neutrons output in a borehole; anddirecting a drilling-based operation in response to analyzing the signals.