Gamma-metrics

Thomas L Atwell

Clinton LaMar Lingren

James Francis Miller

Raymond J Proctor

Chris A Isaacson

Andrew H Smith

Richard Louis Conwell

Chaur-Ming Shyu

James P Stronski

Richard A Ackermann

Ernesto A Corte

In a bulk material analyzer in which bulk material is received in an activation region between a pair of neutron sources laterally disposed on one side of the activation region for emitting neutrons for bombarding the bulk material within the activation region to cause gamma-rays to be emitted from the bombarded bulk material and a pair of gamma-ray detectors laterally disposed on another side of the activation region for detecting gamma-rays emitted from the bulk material, a primary neutron moderator is disposed about the neutron sources for reducing the velocity of the emitted neutrons; and a secondary neutron moderator is disposed about the primary neutron moderator for further reducing the velocity of the neutrons and is further disposed adjacent the lateral edges of the activation region for channeling and reflecting the neutrons into the activation region. The two gamma-ray detectors are disposed toward opposite lateral edges of the activation region, with each detector being skewed so that a portion of each detector that is closer to the edge of the activation region toward which the detector is disposed than to the lateral center of the activation region is disposed closer to a plane passing laterally through the center of the activation region than is another portion of each detector that is closer to the lateral center of the activation region than to the edge of the activation region toward which the detector is disposed. Spatial compensators are disposed adjacent the same side of the activation region as the detectors for reflecting neutrons toward the activation region at a greater density toward opposite lateral edges of the activation region than toward the center of the activation region. Bladders containing a liquid primary neutron moderating material that expands and contracts with temperature variations, such as heavy water, are tightly packed within a compartment for maintaining a substantial quantity of the liquid material between the neutron sources and the activation region notwithstanding thermal contraction of the liquid material; and a resilient compressible foam is disposed about the bladders for enabling the tight packing of the liquid material to be maintained notwithstanding expansion and contraction of the liquid material.

Enhancement of measurement accuracy in bulk material analyzer

A bulk material analyzer of the type in which the bulk material is transported through the material analyzer assembly on a conveyor belt between at least one radiation source and at least one radiation detector, includes a plurality of lower and upper modules that contain radiation shielding material and are so shaped as to define a passageway for the conveyor belt between the upper modules and the lower modules when the upper modules are placed on the lower modules. A primary centrally located lower module also includes the radiation sources and a primary centrally located upper module also includes the radiation detectors. Some of the outwardly located modules contain less radiation shielding material. The radiation shielding material includes a plurality of personally portable blocks. The conveyor belt is supported by compressed air passed through central upper wails in the outwardly located lower modules. The lower modules contain alignment members on upward facing surfaces thereof and the upper modules contain alignment members on downward facing surfaces thereof that are complementary to the alignment members on the upward facing surfaces in order to enable the upper modules to be accurately placed on the lower modules. The lower modules each include a central upper wall bounded by outwardly inclined inner side walls to define a trough for accommodating passage through the passageway of a conveyor belt having a contour corresponding to the trough. The container includes apertures disposed beneath at least part of the passageway, and includes conduits leading to the apertures from a port adapted to be connected to a source of compressed air so that the conveyor belt can be at least partially supported by compressed air while passing through the passageway.

Modularized assembly for bulk material analyzer

A calibration block is used for calibrating a bulk material analyzer that has an activation region in which bulk material is received for analysis and a chute for passing the bulk material through the activation region. The block is dimensioned to be of almost the same cross-sectional size as the interior of the chute and extends both above and below the activation region when inserted in the chute. The calibration block is manufactured by (a) providing a mixture of known materials of known proportions that do not chemically react with each other, including a bonding agent; (b) homogenizing the mixture to make a thick paste in which the known materials are bound without segregation of known materials that have different densities; (c) molding the homogeneous mixture into the shape of a block having predetermined dimensions; and (d) solidifying the molded mixture to provide the calibration block. Alternative processes for manufacturing the calibration block utilize compaction and sintering techniques instead of a bonding agent. The measurement system of the bulk material analyzer is calibrated in accordance with measurements made while the calibration block is in the chute. One embodiment of the calibration block includes a plurality of uniformly distributed holes extending through the block for receiving insertions of a known quantity of a unique known material.

Bulk material analyzer calibration block

A complete PGNAA bulk material analyzer is self contained in a sealed and air conditioned housing. Bulk material is channeled by an open-ended vertical chute having a one-foot-by-three-foot cross-sectional dimension through an activation region between three neutron sources and two gamma ray detectors. The sources are symmetrically disposed on one of the three-foot long sides of the chute from one end of such side to the other. The detectors are symmetrically disposed on the opposite side of the chute between positions opposing the positions of the sources on the one side of the chute. The chute is dimensioned to enable free flow of various bulk materials. It handles coal of up to a top size of four inches and with typical surface moisture contents and agglomeration characteristics. The relative disposition of the sources and detectors results in the measurements being independent of the lateral distribution of the bulk material within the chute. The signals produced by the detectors are continuously processed by signal processing equipment sealed within a separate compartment in the container to provide periodic measurements of the elemental content of the bulk material channeled through the activation region. A measurement of the bulk material channeled through the activation region during each periodic measurement interval is processed over several measurement intervals with the periodic elemental content measurements to provide weighted average measurements of the elemental content of bulk material over time periods representing average lots of the bulk material.

Self-contained, on-line, real-time bulk material analyzer

Growing community of inventors

La Jolla, CA, United States of America

Thomas L Atwell