Patent Number: 059828382
Section: claims

1. A portable pulsed neutron detection system for detection of specific elements in an object, comprising: a manually transportable probe, said probe having a pulsed neutron generator and at least one gamma ray detector;  a controller operably connected to said pulsed neutron generator for varying the intensity and pulse characteristics of said pulsed neutron generator so as to emit a beam of neutrons from said generator;  a data acquisition system operably connected to said at least one gamma ray detector for collecting data measured by said detector; and,  means to analyze said data corresponding to fast neutron reactions, thermal neutron reactions and activation neutron reactions to determine the chemical composition of said object.  a cylindrical housing containing said neutron generator and said at least one gamma ray detector;  shielding material separating said gamma ray detector and said neutron generator. 2. The system of claim 1 wherein said probe is further comprised of: 3. The system of claim 2 wherein said shielding is lead. 4. The system of claim 2 wherein said shielding is bismuth. 5. The system of claim 2 wherein said shielding is positioned around said at least one gamma ray detector about 235 degrees. 6. The system of claim 2 wherein said probe is encased in a stainless steel cylindrical housing. 7. The system of claim 1 wherein said at least one gamma ray detector is bismuth germanate. 8. The system of claim 1 wherein said at least one gamma ray detector is gadolinium orthosilicate. 9. The system of claim 1 wherein said data acquisition system further comprises a computer to process signals supplied by said at least one gamma ray detector. 10. The system of claim 9 wherein said computer generates a fitted spectrum of gamma rays at each energy channel by the equation: EQU f[i]=.SIGMA..sub.k c.sub.k *m.sub.k [i]+.alpha.*bg[i] 11. The system of claim 10 wherein said m.sub.k [i]'s are determined by measuring the spectrum of a sample containing only one chemical element. 12. The system of claim 10 wherein said coefficients c.sub.k and .alpha. are determined by the least squares method, minimizing the general X.sup.2 equation: EQU X.sup.2 =.SIGMA..sub.i (y.sub.i -f[i]).sup.2 /.sigma..sub.i.sup.2 13. The system of claim 1 wherein said controller separates pulses from said neutron generator by between 85 and 90 microseconds. 14. The system of claim 1 wherein said pulsed neutron generator is a deuterium-tritium neutron generator. 15. The system of claim 1 wherein said generator emits neutrons at about 14 MeV. 16. The system of claim 1 wherein said generator produces pulses between about 10 kHz and 14 kHz. 17. The system of claim 1 wherein said at least one gamma ray detector measures fast neutron reactions, thermal neutron reactions and activation neutron reactions.