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Los Alamos National Laboratory Research Quarterly, Fall 2002
A Modular Neutron Detector
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A Modular Neutron Detector

Computer Rendering of Detection Cells

Illustration of an eight cell detector showing: lids with lithium undercoating, a polyethylene body, modified spark plug, spherical positive electrode, and the lithium-coated detection-cell dish

A computer rendering of two argon-filled detection cells in an eight-cell detector. The high-energy neutrons emitted by plutonium are moderated to lower energies by the detector's polyethylene body so that they can be more readily absorbed by a cell's lithium coating. Nuclear reactions in the lithium produce tritons and alpha particles, about half of which penetrate the coating and ionize the cell's argon gas, producing electrons and positively charged ions. A radial electric field draws electrons to the spherical positive electrode and ions to the cell's negatively biased metal surfaces. The electron flow produces a current pulse, which is the detection signal.

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