HIGH INTENSITY, PULSED THERMAL NEUTRON SOURCE

• US 3,778,627 A
• Filed: 04/17/1973
• Issued: 12/11/1973
• Est. Priority Date: 04/17/1973
• Status: Expired due to Term

• Current Assignee: John M. Carpenter
• Original Assignee: John M. Carpenter
• Inventors: Carpenter, John M.
• Primary Examiner(s): Lawrence, James W.
• Assistant Examiner(s): Grigsby, T. N.
• Application Number:
  US05/351,893
• Time in Patent Office: 238 Days
• Field of Search: 250/499,500,501,502,518,393
• US Class Current: 376/192
• CPC Class Codes: G21G 4/02 Neutron sources
• CPC Class Codes: H05H 3/06 Generating neutron beams targets for producing nuclear reactions H05H6/00; neutron sources G21G4/02

Abstract

This invention relates to a high intensity, pulsed thermal neutron source comprising a neutron-producing source which emits pulses of fast neutrons, a moderator block adjacent to the fast neutron source, a reflector block which encases the fast neutron source and the moderator block and has a thermal neutron exit port extending therethrough from the moderator block, and a neutron energy-dependent decoupling reflector liner covering the interior surfaces of the thermal neutron exit port and surrounding all surfaces of the moderator block except the surface viewed by the thermal neutron exit port.

Claims

1. A high-intensity, pulsed thermal neutron source comprising a neutron-producing source which emits pulses of fast neutrons;

a moderator block adjacent to the fast neutron source;

a reflector block encasing said fast neutron source and said moderator block, said reflector block having a thermal neutron exit port extending therethrough from said moderator block; and

a neutron-energydependent decoupling reflector liner covering the interior surfaces of said port and all surfaces of said moderator block except the moderator surface viewed by said thermal neutron exit port.

2. The thermal neutron source according to claim 1 wherein said neutron-energy-dependent decoupling reflector liner comprises a material which will capture and absorb neutrons having energies below the decoupling energy and transmit neutrons having energies at or above said decoupling energy, said decoupling energy being related to that energy to which said reflector block will slow down said fast neutrons in a time less than the response time of said moderator block.

3. The thermal neutron source according to claim 2 wherein said decoupling energy is that energy to which said reflector block will slow down said fast neutrons in 15 Mu sec.

4. The thermal neutron source according to claim 1 wherein said reflector block comprises a material having a high density of deuterons.

5. The thermal neutron source according to claim 1 wherein said reflector block comprises a material selected from the group consisting of beryllium, heavy water and heavy metal deuterides.

6. The thermal neutron source according to claim 1 wherein said moderator block comprises a material having a high density of protons.

7. The thermal neutron source according to claim 6 wherein said moderator block is selected from the group consisting of polyethylene, water, non-gaseous methane, non-gaseous ammonia, liquid hydrogen and heavy metal hydrides.

8. The thermal neutron source according to claim 1 wherein said neutron-energy-dependent decoupling reflector liner comprises a material having a high capture cross section for absorption of low-energy neutrons.

9. The thermal neutron source according to claim 8 wherein said neutron-energy-dependent decoupling reflector liner is selected from the group consisting of cadmium and gadolinium.

10. A pulsed thermal neutron source capable of emitting high-intensity thermal neutron pulses of about 30 Mu SEC pulse width comprising a neutron-producing source which emits pulses of fast neutrons;

a polyethylene moderator block adjacent to the fast neutron source;

a beryllium reflector block encasing said fast neutron source and said polyethylene moderator block, said beryllium reflector block having a thermal neutron exit port extending therethrough from said polyethylene moderator block; and

a cadmium neutron-energy-dependent decoupling reflector liner covering the interior surfaces of said port and all surfaces of said polyethylene moderator block except the moderator surface viewed by said thermal neutron exit port.

11. The thermal neutron source according to claim 10 wherein said fast neutron source comprises a spallation target material capable of emitting pulses of fast neutrons upon interaction with energetic pulsed proton beams, and wherein said beryllium reflector block has a proton beam entry port extending therethrough from said spallation target material.

12. The thermal neutron source according to claim 11 wherein said spallation target material comprises a material selected from the group consisting of U238 and lead-bismuth eutectic.

13. The thermal neutron source according to claim 12 wherein said fast neutron source comprises U238 impinged upon by 0.5 GeV pulsed proton beams.

14. The thermal neutron source according to claim 10 wherein said fast neutron source, said moderator block, said neutron-energy-dependent decoupling reflector liner and said thermal neutron exit port are arranged so that the path of said thermal neutron pulses emerging from said moderator block is essentially at right angles to a line intersecting said fast neutron source and said moderator block.