US4622467A
Expired / Lapsed
US
⏱️ 0.0 years remaining
System for mapping radioactive specimens
Assignee: California Institute of Technology
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Filing: 1984-12-17
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Granted: 1986-11-11
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Expires: 2004-12-17
Abstract
Abstract A system for mapping radioactive specimens comprises an avalanche counter, an encoder, pre-amplifier circuits, sample and hold circuits and a programmed computer. The parallel plate counter utilizes avalanche event counting over a large area with the ability to locate radioactive sources in two dimensions. When a beta ray, for example, enters a chamber, an ionization event occurs and the avalanche effect multiplies the event and results in charge collection on the anode surface for a limited period of time before the charge leaks away. The encoder comprises a symmetrical array of planar conductive surfaces separated from the anode by a dielectric material. The encoder couples charge currents, the amplitudes of which define the relative position of the ionization event. The amplitude of coupled current, delivered to pre-amplifiers, defines the location of the event.
Inventors
- 👤 Roy J. Britten
- 👤 Eric H. Davidson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 23:40
CPC Classifications
H; H01; H01J; H01J47/00; H01J47/14
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
333 words
An apparatus for detecting radioactive sources on a test specimen, the apparatus comprising: a counter having a gas filled chamber, said chamber being formed by an electrically conductive planar window and a parallel semiconductive surface spaced from said window, and adapted for having an electric field imposed within said chamber by a voltage differential between said window and said semiconductive surface; an encoder surface spaced from said semiconductive surface and having geometrically arrayed elements thereon for receiving an electrical charge induced on said elements by an ion avalanche occurring within said chamber in response to entry of a radioactive particle into said chamber; a dielectric layer between said semiconductive surface and said encoder surface, said semiconductive surface forming a coating on one side of said layer and said arrayed elements forming a coating on the opposite side of said layer; means for coupling each said element to a row wire and to a column wire which are electrically isolated from each other whereby a preselected fraction of coupled charge current is transferred to each wire defining an element, the amplitude of the respective transferred charge fraction depending upon the location of the charge current relative to the element; a plurality of charge sensitive integrating amplifiers, one such amplifier being connected to each row wire, respectively, and one such amplifier being connected to each column wire, respectively; a plurality of sample and hold circuits, each of such circuits being connected to a respective one of said amplifiers for selectively sampling and holding an analog signal created by said induced electrical charge; means controlling said sample and hold circuits for selectively holding said analog signal when the summed output of all said sample and hold circuits exceeds a predefined threshhold level; and means for converting each said analog signal into a corresponding digital signal and for calculating the location of each corresponding induced electrical charge on said encoder surface based on the relative amplitude of each analog signal on respective row wires and column wires.
Claim 2
Independent Claim
333 words
An apparatus for detecting radioactive sources on a test specimen, the apparatus comprising: a counter having a gas filled chamber, said chamber being formed by an electrically conductive planar window and a parallel semiconductive surface spaced from said window, and adapted for having an electric field imposed within said chamber by a voltage differential between said window and said semiconductive surface; an encoder surface spaced from said semiconductive surface and having geometrically arrayed elements thereon for receiving an electrical charge induced on said elements by an ion avalanche occurring within said chamber in response to entry of a radioactive particle into said chamber; a dielectric layer between said semiconductive surface and said encoder surface, said semiconductive surface forming a coating on one side of said layer and said arrayed elements forming a coating on the opposite side of said layer; means for coupling each said element to a row wire and to a column wire which are electrically isolated from each other whereby a preselected fraction of coupled charge current is transferred to each wire defining an element, the amplitude of the respective transferred charge fraction depending upon the location of the charge current relative to the element; a plurality of charge sensitive integrating amplifiers, one such amplifier being connected to each row wire, respectively, and one such amplifier being connected to each column wire, respectively; a plurality of sample and hold circuits, each of such circuits being connected to a respective one of said amplifiers for selectively sampling and holding an analog signal created by said induced electrical charge; means controlling said sample and hold circuits for selectively holding said analog signal when the summed output of all said sample and hold circuits exceeds a predefined threshhold level; and means for converting each said analog signal into a corresponding digital signal and for calculating the location of each corresponding induced electrical charge on said encoder surface based on the relative amplitude of each analog signal on respective row wires and column wires.
Claim 3
Dependent Claim
58 words
The apparatus recited in claim 1 wherein said arrayed elements comprise at least thirty six substantially square elements of equal dimensions, each such element being spaced equally from all adjacent elements by a distance less than the lateral dimension of each element-the total area occupied by said arrayed elements being greater than the area of said test specimen.
Claim 4
Dependent Claim
34 words
The apparatus recited in claim 1 wherein said arrayed elements comprise a plurality of perpendicular, regularly spaced electrically insulated conductors, each such conductor being separated from adjacent parallel conductors by a selected electrical impedance.
Claim 5
Dependent Claim
35 words
The apparatus recited in claim 3 further comprising a plurality of integrating amplifiers connected to said electrical impedances at regularly spaced intervals dependent upon the desired radioactive source detection resolution and signal to noise ratio.
Claim 6
Independent Claim
100 words
A system for locating, mapping and displaying radioactive sources on a test specimen; the system comprising: counter means for detecting radioactive events by producing corresponding ion avalanche effects; encoder means for defining the detected events in the form of induced electrical charges at a location corresponding to the position of the event on the test specimen; mapping means for producing analog electrical signals corresponding to said induced electrical charges, calculating the location of said induced electrical charges based on the relative amplitudes of said analog electrical signals, and displaying an image of each detected event on a defined geometrical array.
Claim 7
Independent Claim
100 words
A system for locating, mapping and displaying radioactive sources on a test specimen; the system comprising: counter means for detecting radioactive events by producing corresponding ion avalanche effects; encoder means for defining the detected events in the form of induced electrical charges at a location corresponding to the position of the event on the test specimen; mapping means for producing analog electrical signals corresponding to said induced electrical charges, calculating the location of said induced electrical charges based on the relative amplitudes of said analog electrical signals, and displaying an image of each detected event on a defined geometrical array.
Claim 8
Dependent Claim
89 words
The system recited in claim 5 wherein the counter means comprises: an electrically conductive planar window, a dielectric layer having a semiconductive surface parallel to and spaced from said window to form a chamber between said window and said semiconductive surface, means for sealing said chamber, a gas mixture of selected constituent gases contained within said chamber, and means for applying for electric field of selected magnitude across said chamber, said window being in a state of radial tension that may be selectively varied for assuring substantial flatness thereof.
Claim 9
Dependent Claim
75 words
The system recited in claim 5 wherein the encoder means comprises: a plurality of geometrically arrayed electrically conductive elements arranged symmetrically on a common planar surface; a matrix of conducting wires arranged in substantially equal pluralities of rows and columns, each such row being associated with a selected plurality of elements and each such column being associated with a selected plurality of elements whereby a selected row and column define one and only one element.
Claim 10
Dependent Claim
15 words
The encoder system recited in claim 7 wherein each said element is square in shape.
Claim 11
Dependent Claim
28 words
The encoder system recited in claim 7 wherein said means for coupling each element to a row wire and each element to a column wire comprises respective capacitors.
Claim 12
Dependent Claim
139 words
The system recited in claim 5 wherein the encoder means comprises: a matrix of conducting paths arranged symmetrically on a common planar surface whereby to define a plurality of row paths and a plurality of columm paths, the respective pluralities of paths being each connected to selected terminals of a voltage divider network, a first plurality of charge sensitive integrating amplifiers respectively connected to equally spaced points along said row paths network and a second plurality of charge sensitive integrating amplifiers respectively connected to equally spaced points along said column path network, means for coupling discrete electrical charge current only to those conducting paths within relative proximity to said discrete current, whereby the relative amplitude of the charge current delivered to amplifiers in each of said first and second pluralities defines the location of each discrete electrical charge current.
Claim 13
Dependent Claim
110 words
The system recited in claim 5 wherein the mapping means comprises: a plurality of charge sensitive integrating amplifiers, one such amplifier being connected to each row wire, respectively, and one such amplifier being connected to each column wire, respectively; a plurality of sample and hold circuits, each of such circuits being connected to a respective one of said amplifiers for selectively sampling and holding the output signal thereof; means controlling said sample and hold circuits for selectively holding said output signal when the summed output of all said signal and hold circuits exceeds a predefined threshhold level; and means for converting each said analog signal into a corresponding digital signal.
Claim 14
Dependent Claim
33 words
The system recited in claim 11 further comprising means for analyzing said digital signals and for displaying the relative count and positions of corresponding radioactive events on an array simulation of said counter.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-11-10 | 1990-05-12 | 1990-11-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-11-10 | 1994-05-12 | 1994-11-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-11-10 | 1998-05-12 | 1998-11-11 | $7700.00 | Window Closed / Lapsed |