Method and apparatus for a directional neutron detector which discriminates neutrons from gamma rays

A method for detecting a particle in an energy range of interest and for discriminating between the particle and background radiation, the method comprising the steps of:

• connecting a scintillating medium to a plurality of photomultipliers, the scintillating medium being in the form of a plurality of types of optical fibers which transmit light pulses in different portions of the electromagnetic spectrum, which are arranged substantially contiguously along at least a first direction, the first direction being essentially perpendicular to a length dimension of the optical fibers, and which are arranged in an alternating pattern, in which contiguous optical fibers are of different types;
• optically coupling a filtering means to each of said photomultipliers, each of which filtering means allows only light photons from a different one of said portions of the electromagnetic spectrum to be incident on the respective photomultiplier;
• using the photomultipliers to detect photons caused by ionization in the scintillating medium and to provide output signals upon the detection of photons;
• processing said photomultiplier output signals to determine whether a detected photon is indicative of a particle in the energy range of interest.

A method for detecting a particle in an energy range of interest and for discriminating between the particle and background radiation, the method comprising the steps of:

• providing a scintillating medium between two photomultipliers, the scintillating medium being in the form of a plurality of optical fibers, the optical fibers being arranged substantially contiguously along at least a first direction, the first direction being essentially perpendicular to a length dimension of the optical fibers, each of the optical fibers having a first end and an opposing second end, each of which said optical fibers emit light pulses only in a higher portion of the electromagnetic spectrum or only in a lower portion of the electromagnetic spectrum, with contiguous ones of the optical fibers emitting light pulses only in the higher portion of the electromagnetic spectrum alternating with optical fibers which emit photons only in the lower portion of the electromagnetic spectrum;
• connecting a filtering means to a first photomultiplier tube which allows only light pulses in the lower portion of the electromagnetic spectrum to be incident on the said first photomultiplier;
• connecting a filtering means to a second photomultiplier tube which allows only light pulses in the higher portion of the electromagnetic spectrum to be incident on the said second photomultiplier;
• producing output signals from the first and second photomultipliers when photons are incident thereon;
• processing said photomultiplier output signals to determine whether a detected photon is indicative of a particle in the energy range of interest.

A directional neutron-gamma ray discrimination detector, comprising:

• (a) one or more plastic scintillator fibers of a first type which emits light photons having wavelengths within a first region of the electromagnetic spectrum in response to the incidence thereon of neutrons and/or gamma rays;
• (b) one or more plastic scintillator fibers of a second type which emits light photons having wavelengths within a second region of the electromagnetic spectrum in response to the incidence thereon of neutrons and/or gamma rays;
• (c) each of said first-type fibers and second-type fibers having a first end and an opposing second end and a lengthwise dimension extending therebetween;
• (d) said first-type fibers and said second-type fibers being substantially contiguous to one another in a direction substantially perpendicular to said lengthwise dimension thereof, with said first-type fibers alternating with said second-type fibers such that first-type fibers are contiguous only with second-type fibers and second-type fibers are contiguous only with first-type fibers;
• (e) first and second photomultipliers optically coupled to the same end of all of said first-type fibers and said second-type fibers for selectively producing signals in response to light photons emitted by said first-type fibers and said second-type fibers, respectively;
• and
• (f) means for processing the signals from said first and second photomultipliers to identity signals resulting from neutrons incident on the other end of said fibers in directions generally parallel to the lengthwise direction of said fibers and to discriminate against signals resulting from neutrons incident on said fibers in other directions or from gamma rays.

A directional neutron detector, comprising:

• (a) one or more plastic scintillator fibers of a first type which emits light photons having wavelengths within a first region of the electromagnetic spectrum in response to the incidence thereon of neutrons and/or gamma rays;
• (b) one or more plastic scintillator fibers of a second type which emits light photons having wavelengths within a second region of the electromagnetic spectrum in response to the incidence thereon of neutrons and/or gamma rays;
• (c) each of said first-type fibers and second-type fibers having a first end and an opposing second end and a lengthwise dimension extending therebetween;
• (d) said first-type fibers and said second-type fibers being substantially contiguous to one another in a direction substantially perpendicular to said lengthwise dimension thereof, with said first-type fibers alternating with said second-type fibers such that first-type fibers are contiguous only with second-type fibers and second-type fibers are contiguous only with first-type fibers;
• (e) each of said first-type fibers and said second-type fibers being sensitive to neutrons within the range of from about 0.5 MeV-8 MeV;
• and
• (f) each of said fibers having a dimension in said substantially perpendicular direction that is small relative to the range therein of Compton scattering electrons resulting from interactions with said fibers of gamma rays having energies within said energy range of sensitivity.