WO2005022197A2 - Procedes et appareils de detection et de localisation de matieres dangereuses - Google Patents

Procedes et appareils de detection et de localisation de matieres dangereuses Download PDF

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Publication number
WO2005022197A2
WO2005022197A2 PCT/US2004/022926 US2004022926W WO2005022197A2 WO 2005022197 A2 WO2005022197 A2 WO 2005022197A2 US 2004022926 W US2004022926 W US 2004022926W WO 2005022197 A2 WO2005022197 A2 WO 2005022197A2
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Prior art keywords
ofthe
source
detector
location
hazardous source
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PCT/US2004/022926
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English (en)
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WO2005022197A3 (fr
Inventor
Arkady Pittel
Sergey Liberman
Michael Partensky
Stanislav Elektrov
Niyaz Khusnatdinov
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Radioact Corporation
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Publication of WO2005022197A2 publication Critical patent/WO2005022197A2/fr
Publication of WO2005022197A3 publication Critical patent/WO2005022197A3/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/167—Measuring radioactive content of objects, e.g. contamination
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T7/00—Details of radiation-measuring instruments

Definitions

  • detectors that are sensitive to the specific source ofthe hazardous material. These detectors provide information relating to the intensity ofthe hazardous source relative to a background intensity. However, typical detectors cannot determine precise positional information about the hazardous material. An operator using a mobile detector can locate a hazardous source by measuring an intensity at a starting location and navigating the detector in the direction of maximum intensity levels. This process can require extensive time and cannot be practically implemented, especially over large detection areas.
  • FIG. 1 illustrates a block diagram of a system for locating a hazardous source according to one embodiment ofthe invention.
  • FIG. 2 A illustrates the position of a plurality of detectors in a detector array relative to a location of an isotropic source of radiation.
  • FIG. 2B illustrates the position of a plurality of detectors in a detector array relative to the location of a non-isotropic source of radiation.
  • FIG. 2C illustrates the position of a plurality of detectors in a detector array relative to another location of a non-isotropic source of radiation.
  • FIG. 2D illustrates the position of a plurality of detectors in a detector array including a faulty detector relative to a location of an isotropic source of radiation.
  • FIG. 3 illustrates a top view of a vehicle including four detectors in a detector array relative to a truck carrying an isotropic source of radiation.
  • FIG. 4 illustrates a flowchart of a process of locating a hazardous source using an array of fixed detectors.
  • FIG. 5 illustrates a block diagram of a system for locating a hazardous source according to one embodiment ofthe invention.
  • FIG. 6 illustrates the path of a detector relative to a location of a non-isotropic source of radiation.
  • FIG. 7 illustrates a flowchart of a process of locating a hazardous source using a portable detector.
  • FIG. 8 illustrates a flowchart of a process of locating a hazardous source using a detector array having both fixed and portable detectors .
  • FIG. 9 illustrates a table of radioactive isotopes and their corresponding activities in units of intensity per mass.
  • FIG. 10A illustrates a simulated display showing the location of an isotropic source of radiation that was determined using a three detector array.
  • FIG. 10B illustrates a simulated display showing the location of an isotropic source of radiation that was determined using a five detector array.
  • FIGS. 11 A-l IC illustrate the flux distributions from a source of radiation located in the center of square shielded boxes that each have a different thickness.
  • FIG. 12A illustrates the position of a plurality of detectors relative to the location of a source within a shielded container.
  • FIG. 12B graphically illustrates the half-value layer for different materials as a function of energy.
  • FIG. 13 A illustrates the position of an array of detectors relative to the location of a source of radiation.
  • FIG. 13B illustrates the position of a first array of detectors and a second array of detectors relative to the location of a source of radiation.
  • FIG. 14 illustrates an operational mode of software display showing the location of a non-isotropic source of radiation that was determined using a six-detector array.
  • FIG. 15A illustrates a simulated display showing the location of a non-isotropic source of radiation that was determined using a four detector array.
  • FIG. 15B illustrates a simulated display showing the location of a non-isotropic source of radiation that was determined using a six detector array.
  • the "hazardous sources” can be various toxic substances including radioactive particles and gamma or neutron radiation.
  • sources of radiation When a radiation source emits gamma or neutron radiation, the emissions are referred to as "sources of radiation", hi some embodiments, the radiation source is an isotropic source. In these embodiments, the radiation propagates symmetrically in "radial" directions if scattering is ignored. It is assumed that weather conditions, wind, and convection have a very small impact on the gamma-rays. Therefore, the anisotropy ofthe radiation distribution is mostly predetermined by the geometry ofthe source and anisotropy due to shielding and natural obstructions.
  • a hazardous source or a "source of hazardous material” is a diffused chemical or biological substance. Chemical agents or bacteria can diffuse through the atmosphere. They are substantially affected by the movement ofthe air, not only due to the weather, but also due to the movement ofthe sources and/or the detectors. Thus, the anisotropy ofthe source as well as the direction of dispersion ofthe hazardous materials depends heavily on environmental and geographical conditions. Additional parameters, such as the type of propagation media (air, water, etc.), the velocity ofthe propagation media in three directions, geographical details, etc., all must be considered to monitor hazardous plumes in real time.
  • the additional parameters such as the velocity ofthe media, must be monitored and updated at suitable intervals to recalculate the position ofthe hazardous source in real time.
  • the hazardous source in the case of diffused particles is a plume rather than a specific point with X and Y coordinates as is a case with gamma and neutron radiation.
  • the apparatus includes one or more fixed or movable detectors that detect a property of a hazardous source from three or more different locations.
  • the property ofthe source could be an intensity ofthe hazardous source relative to a background intensity.
  • a combination of fixed detectors or movable detectors can be positioned at the three or more different locations.
  • a portable detector can acquire measurements at the three or more different locations.
  • Each detector includes a detection zone.
  • the detector's "detection zone” is defined herein to mean the volume of space in three dimensions or the area in two dimensions in which the detector can detect the hazardous source.
  • a hazardous source that is outside a detector's detection (sensitivity) zone cannot be detected by the detector.
  • the detection zone ofthe detector is also a function ofthe intensity ofthe source.
  • three detectors are positioned at three different locations having known sets of coordinates.
  • the three detectors constitute a detector array.
  • the three detectors are also positioned so that each of their detection zones overlaps the location ofthe hazardous source.
  • a minimum of three detectors or three different measurement locations is used to determine the intensity and the location ofthe source in two-dimensions.
  • a minimum of four or more detectors can provide redundancy and can improve the sensitivity and range ofthe system.
  • the number of detectors in the detector array is dynamically changeable. For example, detectors can be added to or subtracted from the detector array in real time.
  • the detector array generates signals that are related to a detected property ofthe source.
  • the signals can have unique signal strengths depending on the location and the sensitivity of each ofthe detectors.
  • the signals generated by each ofthe detectors can have unique strengths, even if each ofthe detectors is identical and each detector is located an equal distance from the source.
  • the signals generated by the detectors have a statistical distribution and the same fixed detector can generate signals having different values during different measurement periods.
  • the sets of coordinates of each ofthe detectors are either known or can be ascertained using a GPS receiver or another coordinate locating system.
  • the intensity and the location ofthe hazardous source can be determined by correlating the known sets of coordinates with the signals generated by each detector by using an algorithm.
  • FIG. 1 illustrates a block diagram of a system 100 for locating a hazardous source according to one embodiment ofthe invention.
  • the system 100 includes an array of detectors including a first detector 102, a second detector 104, and a third detector 106. Additional detectors 108 can be added to the detector array depending on the requirements ofthe system 100 including the number of hazardous sources to be located.
  • One or more ofthe detectors 102, 104, 106, 108 can be fixed or portable depending on the configuration ofthe system 100.
  • Each ofthe detectors 102, 104, 106, 108 communicates with a processor 110 through a plurality of communication links 112, 114, 116, 118.
  • the array of detectors 102, 104, 106, 108 communicates with the processor 110 through a single communication link.
  • the communication links 112, 114, 116, 118 between the array of detectors 102, 104, 106, 108 and the processor 110 can be wired or wireless and can include wired or wireless Ethernet, standard RS485, 1 2 C, or any other suitable communication protocol.
  • the processor 110 can include a computer, a microcontroller, a Field Programmable Gate Array (FPGA), or any digital processor.
  • the system 100 can include more than one processor 110 including redundant processors 110 that are positioned in the same or different locations, hi one embodiment, the processor 110 is a distributed processor that can be located in remote locations or within one or more ofthe detectors 102, 104, 106, 108.
  • the detectors 102, 104, 106, 108 can be elements in a redundant detector array
  • an array of detectors functions together in a single detector unit to localize the source.
  • a redundant detector array can increase the sensitivity and reliability of detecting a hazardous source by detecting the source with multiple detectors having overlapping detection zones.
  • the RDA increases the reliability ofthe system because it can compensate for a malfunctioning detector in the array. This compensation is described in more detail herein.
  • the number of detectors in the RDA is dynamically changeable depending on the requirements ofthe system.
  • an array of detectors includes three or more detectors that are installed in any location within a structure, such as a toll plaza, a border crossing, an airport, a bus/train station, a theater, or a stadium. A minimum of three detectors is used to localize a hazardous source in two-dimensions.
  • a display 120 including a graphical user interface (GUI) communicates with the processor 110 through a communication link 122.
  • An input device 124 such as a microphone, a keyboard, a keypad, a mouse, a trackball, a touchpad, or a digitizer communicates input signals to the processor through a communication link 126.
  • the input signals activate the system 100 and or program any required input parameters into the processor 110.
  • the display 120 can include a cathode ray tube (CRT) display, a liquid crystal display (LCD) display, a light emitting diode (LED) display, a plasma display, a projector or any other graphical display.
  • CTR cathode ray tube
  • LCD liquid crystal display
  • LED light emitting diode
  • plasma display a projector or any other graphical display.
  • one or more portable devices 128 such as a personal digital assistant (PDA), a pager, a cellular telephone, a palmtop computer, or a laptop computer also communicates with the processor 110.
  • the portable device 128 can receive and display data from the processor 110 relating to the detection, identification, quantification, localization, and tracking of biological, chemical, combustible, explosive, nuclear and radiological sources.
  • a communication link 130 between the processor 110 and the portable device 128 can be wireless.
  • the processor 110 includes a receiver 132 that receives signals from the array of detectors 102, 104, 106, 108.
  • the receiver 132 communicates the received signals to a microprocessor 134.
  • the microprocessor 134 analyzes the received signals and generates data that is related to the detection, identification, quantification, localization, and tracking of a hazardous source.
  • the microprocessor 134 can determine the intensity and the location of one or more hazardous sources based on a best fit to a physical model algorithm. The algorithms used to determine the intensity and the location of the one or more sources are described in detail herein.
  • the processor 110 includes a microprocessor 134 that communicates the intensity and location data to a transmitter 136 that is located within the processor 110.
  • the processor 110 transmits the intensity and location data to the display/GUI 124 though the communication link 122 to be displayed to an operator.
  • the processor 110 can also transmit the data to the portable device 128 through the communication link 130.
  • a first responder equipped with the portable device 128 can receive information relating to the detection, identification, quantification, localization, and tracking ofthe source.
  • the detectors 102, 104, 106, 108 in the array can each include various subsystems.
  • the first detector 102 can include one or more sensors or detectors that detect properties of various sources.
  • a radiation sensor 140 detects the presence of gamma, beta, alpha, and neutron radiation.
  • a chemical sensor 142 detects the presence of chemical agents such as nerve agents.
  • a biological sensor 144 detects the presence of biological agents such as anthrax.
  • An explosive sensor 146 detects the presence of incendiaries or explosives such as C-4,
  • each ofthe detectors 102, 104, 106, 108 in the detector array include the same or different sets of sensors depending on the configuration ofthe system 100.
  • the localization of radiological sources is' described in detail herein, but the same principles apply to the localization of biological, chemical, incendiary, or controlled substances.
  • additional parameters such as the velocity and the direction ofthe wind, including speed and direction of local air perturbations, could be added to an algorithm to determine the intensity and the location ofthe chemical plume.
  • the system 100 can also include one or more additional portable detectors (not shown) that can be mounted in backpacks or in vehicles.
  • the portable detectors can generate signals that are transmitted to the processor 110 to improve the sensitivity and range ofthe system and to increase the accuracy ofthe determination ofthe intensity and the location ofthe source.
  • Each ofthe sensors 140, 142, 144, 146 can detect a presence of a hazardous material and can sample/count particles ofthe radiation or detect a concentration ofthe hazardous material from a specific known location.
  • the sensors 140, 142, 144, 146 communicate sensor data to a controller 148.
  • the controller 148 generates signals by processing the sensor data.
  • the signals are related to the intensity ofthe hazardous material relative to a background intensity.
  • the signals are sent to a transmitter 150.
  • the transmitter 150 communicates the signals to the processor 110 through the communication link 112.
  • the sensor signals generated by at least one ofthe detectors 102, 104, 106, 108 are used to determine one or more of a location ofthe source, a velocity of a moving source, a direction ofthe moving source, an intensity ofthe source, and an identity ofthe source.
  • One or more ofthe detectors 102, 104, 106, 108 can also include a GPS receiver 152 that communicates the location coordinates of each detector 102, 104, 106, 108 to the controller 148.
  • the first detector 102 can include a GPS receiver 152 that communicates the location coordinates ofthe first detector 102 to the controller 148.
  • the GPS receiver 152 can also communicate the location coordinates ofthe first detector 102 to the processor 110 through the communication link 112.
  • the GPS receiver 152 is located remotely from the first detector 102 and communicates the location coordinates ofthe first detector 102 to the controller 148 and/or the processor 110.
  • a radio-frequency identification (RF-ID) system can also be used to determine the coordinates ofthe first detector 102.
  • the location coordinates of the first detector 102 can also be determined by using an image recognition system having cameras that record the location ofthe first detector 102 relative to its surroundings. Other systems for determining the coordinates ofthe detectors can also be used.
  • RFID radio-frequency identification
  • the first detector 102 can also include a camera 154 that is connected to the controller 148.
  • the camera 154 can be a digital camera or a video camera including a zoom lens.
  • the camera 154 can be integrated into a closed circuit television (CCTV) system.
  • the camera 154 is mounted on a movable platform.
  • the movable platform can pan or tilt the camera 154.
  • the controller 148 controls the position ofthe camera 154 based on the determined location ofthe source.
  • one or more cameras 154 can be located remotely from the first detector 102.
  • the processor 110 can generate a signal that adjusts positions ofthe one or more cameras 154 based on the determined location ofthe source.
  • FIG. 2A illustrates the position 200 of a plurality of detectors 202, 204, 206, 208, 210 in a detector array relative to a location 212 of an isotropic source 214 of radiation.
  • the array of detectors 202, 204, 206, 208, 210 are positioned so that the detection zones 222, 224, 226, 228, 230 of at least three ofthe detectors 202, 204, 206, 208, 210 partially overlap the location 212 of the isotropic source 214.
  • the detectors 202, 204, 206, 208, 210 can be elements in a redundant detector array (RDA).
  • the RDA architecture provides increased sensitivity and range of detection, improved finding and tracking of moving hazardous sources, a reduction in the occurrence of false alarms, the ability to locate hazardous sources within shielded enclosures and improved accuracy in the determination ofthe intensity and the location ofthe hazardous sources.
  • the isotropic source 214 is located within the detection zones 222, 224, 226, 228, 230 of at least three ofthe detectors 202, 204, 206, 208, 210.
  • the array of detectors 202, 204, 206, 208, 210 can detect a property ofthe hazardous source which can include an intensity of radiation relative to a background radiation or a chemical/biological plume that is emanating from the source 214.
  • Each ofthe detectors 202, 204, 206, 208, 210 generates signals relating to a detected property ofthe source 214. The strength ofthe signals depends on the sensitivity and position of each ofthe detectors 202, 204, 206, 208, 210.
  • the intensity/of radiation from an isotropic source 214 of radiation decreases according to the equation I ⁇ MR 1 , where R is the distance from the source 214 to each ofthe detectors 202, 204, 206, 208, 210.
  • R is the distance from the source 214 to each ofthe detectors 202, 204, 206, 208, 210.
  • the detectors 202, 204, 206, 208, 210 overlap the location 212 ofthe source 214.
  • the placement ofthe detectors 202, 204, 206, 208, 210 depends on the sensitivity ofthe individual detectors, the topology ofthe detection area, and the spatial distribution ofthe detection zone of each detector
  • the processor 110 (FIG. 1) first determines whether each ofthe detectors 202, 204, 206, 208, 210 is functioning properly by receiving signals from the detectors 202, 204, 206, 208, 210 that are related to background radiation from the earth and the atmosphere. The processor can also determine if one or more ofthe detectors 202, 204, 206, 208, 210 are detecting the presence of a hazardous material. One or more ofthe detectors 202, 204, 206, 208, 210 is considered to be malfunctioning if it outputs a zero or other reading over a specified time period that is substantially outside ofthe specification.
  • the processor 110 stores information relating to any malfunctioning detector(s), excludes data from such detector(s) from consideration, and compensates for the malfunction by using data from the adjacent working detectors.
  • the processor 110 also provides a notification ofthe malfunctioning detector(s) so that they can be repaired or replaced without disruption to the overall system. In this scenario, the accuracy of the determined location and intensity ofthe source 214 can be decreased.
  • a source 214 that is present within the detection zones 222, 224, 226, 228, 230 of at least three ofthe detectors 202, 204, 206, 208, 210 can be located in two dimensions.
  • a source 214 that is present within the detection zones 222, 224, 226, 228, 230 of at least four ofthe detectors 202, 204, 206, 208, 210 can be located in three dimensions.
  • the processor 110 receives signals from the detectors 202, 204, 206, 208, 210 that are related to the detection of a property ofthe source 214. In FIG. 2A, the peak intensity ofthe radiation from the source 214 is in zone C when the hazardous material is emanating from an isotropic source.
  • Signals generated by the detectors 202, 204, 206, 208, 210 can be transmitted to the processor 110 in coded digital format.
  • the processor 110 generates data that indicates the intensity and the location 212 ofthe source 214 of radiation.
  • Correlating the coordinates ofthe detectors 202, 204, 206, 208, 210 with the signals that are generated by the detectors 202, 204, 206, 208, 210 generates the data by using an algorithm.
  • the algorithm can include but is not limited to a least squares fit algorithm, a combinatorial algorithm, a system of linear equations, and a non-linear regression algorithm. Examples of algorithms used for processing the signals generated by the detectors 202, 204, 206, 208, 210 are discussed herein.
  • the source 214 is assumed to be an isotropic point source.
  • An example of locating a non- isotropic source will be discussed herein with reference to FIG. 2B. It is assumed that all ofthe detectors 202, 204, 206, 208, 210 have the same isotropic sensitivity.
  • the system 100 can deploy detectors having different isotropic sensitivities as long as the different characteristics of each ofthe detectors are known.
  • the average number of counts per unit time detected by each detector is inversely proportional to the square ofthe distance between each detector and the radiation source. This can be expressed as follows:
  • A is a known constant that characterizes the sensitivity ofthe detector
  • ,- and j ⁇ - are the known coordinates ofthe z ' -th detector, /is the unknown intensity ofthe source of radiation, and and Fare the unknown coordinates ofthe source in two dimensions.
  • A is a known constant that characterizes the sensitivity ofthe detector
  • x h y ⁇ , and z,- are the known coordinates ofthe z ' -th detector
  • / is the unknown intensity ofthe source of radiation
  • X, Y, and Z are the unknown coordinates ofthe source of radiation in three dimensions.
  • a minimum of four detectors at different locations or a minimum of four measurements at four different locations are required to determine the intensity and the location ofthe source in three dimensions, hi the case in which more than four measurements are available, an over-defined system of equations exists and the precision ofthe source localization can be increased using a least squares fit or other mathematical model.
  • A/C (l/l) *(X 2 -2 *X *x i + x 2 +Y 2 -2 *Y *y l + y 2 ) ,
  • N 1 , 2, ...N, and N is the number of detectors.
  • a linearization method is used to solve for /, X, and Y.
  • the z ' -th equation is subtracted from the (z'-l)th equation and the first equation is subtracted from the last equation. This yields a system of equations as follows:
  • This system of equations is linear with respect to the unknowns /, X, and Y.
  • the system of equations can be solved precisely if it contains three or more equations.
  • a system of equations having more than three equations can be solved using a least squares fit if the determinant ofthe system is not zero.
  • the term "precisely" is used herein in a mathematical sense.
  • each ofthe known and measured parameters have certain errors associated with them. For example, there can be errors in determining the sets of coordinates for each detector. There can also be statistical fluctuations in the readings/counts (Q from the detectors. However, as the number of detectors increases, the number of equations also increases. Solving an over-defined system of equations using a least squares fit can reduce the impact ofthe measurement errors and the detector coordinate errors.
  • the equation used to define the relationship between the detector measurements and the source is as follows:
  • C is the mean number of counts reported by the detector
  • S is the known sensitivity ofthe detector
  • / is the unknown intensity ofthe source
  • Tis the integration time
  • R is the distance between the source and the detector.
  • the number of counts typically has a Poisson distribution.
  • the number of counts can be assumed to have a Gaussian distribution when the number of counts is significantly large. In this case, the distribution sigma is numerically equal to the square root ofthe mean value ofthe number of counts.
  • a large number of detectors N can detect a large number of sources K with the restriction that K is less than or equal to N/3 in two-dimensions.
  • This embodiment uses non-linear regression algorithms to solve a large system of non-linear equations for positioning hazardous sources.
  • C is the average number of counts measured at each z ' -th detector
  • (x are the coordinates ofthe z ' -th detector
  • (X k , Y k ) are the coordinates ofthe /c-th source
  • /* is the intensity ofthe k-th source
  • a t is a known constant that characterizes the sensitivity of each z ' -th detector and is determined through a calibration measurement.
  • the parameter A can be calibrated and tabulated for each isotope and stored in a lookup table for each detector. The use of spectral detectors is discussed in more detail herein.
  • the sets of coordinates ofthe detectors can be either fixed or variable.
  • the sets of coordinates can be generated by GPS or other positioning systems.
  • the system can also integrate multiple fixed or moving detectors each measuring multiple samples of radiation from different coordinate locations. Increasing the number of detectors and increasing the number of measurements provides improved response and accuracy ofthe system.
  • a statistical regression analysis for the least square fit for an over-defined system of quadratic functions is performed to estimate parameters ofthe system. Finding the optimum parameters involves computing the sum ofthe squared residuals for one set of parameter values and then adding a small variation to the parameter values and re-computing the sum of squared residuals to determine the effect ofthe parameter values on the sum ofthe squared residuals. By dividing the difference between the original and new sum of squared residual values by the amount that the parameter was altered, an approximate partial derivative with respect to the parameter is determined. This partial derivative is used to decide the manner in which to alter the value ofthe parameter for the next iteration.
  • the Poisson distribution is commonly used to model the number of random occurrences of some phenomenon in a specified unit of space or time. For example, the probability of detecting n events per unit time for an absolutely random source of radiation can be described by a Poisson distribution. For n that is much greater than one, the probability can be approximated using a Gaussian distribution:
  • This equation describes the distribution of particles that arrive at the detector. This is the standard Gaussian distribution, where ⁇ n> is an average number of particles that arrive at detector, and ⁇ is standard deviation. In one embodiment, a Poisson distribution is used for low counts of n particles.
  • P(n) is the probability that n particles arrive at the counter/detector during some period of time. The time period can be any pre-defined interval of time. The value of ⁇ n> is an average value estimated over the same pre-defined interval of time.
  • the Gaussian distribution describes only random processes. A source of radiation that emits a steady flux of particles arriving at the detector is assumed to be random.
  • Radioactive atoms do tend to decay independently even though they are very close to each other. As the number of particles increases then the Gaussian distribution becomes narrower. At low fluxes of particles, the deviation from the average number of particles can be significant:
  • FIG. 2B illustrates the position 200' of a plurality of detectors 202, 204, 206, 208, 210 in a detector array relative to the location 216 of a non-isotropic source 218 of radiation.
  • the non-isotropic source 218 of radiation can be moving or stationary relative to the detectors 202, 204, 206, 208, 210.
  • the detectors 202, 204, 206, 208, 210 are positioned so that the detection zones 222, 224, 226, 228, 230 of at least three ofthe detectors 202, 204, 206, 208, 210 partially overlap the location 216 ofthe non-isotropic source 218 of hazardous material.
  • Each ofthe detectors 202, 204, 206, 208, 210 in the detector array generates signals relating to a detected property ofthe non-isotropic source 218 of hazardous material.
  • the strength ofthe signals depends on the sensitivity and position of each ofthe detectors 202, 204, 206, 208, 210.
  • the energy distribution from the source 218 is not isotropic and tnerelore, the maximum energy level reaching the detectors is skewed, and the location ofthe source 218 is more difficult to determine.
  • d the thickness ofthe shielded container
  • ⁇ y 2 is a parameter that characterizes the distance over which the intensity is decreased by one-half.
  • the processor 110 (FIG. 1) first determines whether each ofthe detectors 202, 204, 206, 208, 210 is functioning properly by receiving signals from the detectors 202, 204, 206, 208, 210 that are related to background radiation from the earth and the atmosphere. The processor can also determine if one or more ofthe detectors 202, 204, 206, 208, 210 are detecting the presence of a hazardous material. One or more ofthe detectors 202, 204, 206, 208, 210 is considered to be malfunctioning if it outputs a zero or other reading over a specified time period that is substantially outside ofthe specification.
  • the processor 110 stores information relating to any malfunctioning detector(s), excludes data from such detector(s) from consideration, and compensates for the malfunction by using data from the adjacent working detectors.
  • the processor 110 also provides a notification ofthe malfunctioning detector(s) so that they can be repaired or replaced without disruption to the overall system. In this scenario, the accuracy of the determined location and intensity ofthe source 218 can be decreased.
  • the processor 110 receives signals from the detectors 202, 204, 206, 208, 210 that are related to the detection of a property ofthe source 218 of hazardous material.
  • the peak intensity ofthe radiation from the source 218 of hazardous material is in zone B when the hazardous material is emanating from the non-isotropic source.
  • the sensitivity ofthe various detectors as well as the strength ofthe signals from adjacent detectors can be used to determine the characteristics ofthe anisotropy.
  • the processor 110 can still accurately determine the intensity and the location ofthe source 218 by correlating the signals from the detectors 202, 204, 206, 208, 210 and the known coordinates ofthe detectors 202, 204, 206, 208, 210 using an algorithm.
  • an algorithm In order to determine the intensity and the location ofthe non-isotropic source i ⁇ , enougn radiation must reach the detectors to be detected and the radiation energy flux must be quasi-evenly distributed. An increased number of measurements from many different locations can improve the convergence ofthe algorithm as well improve the sensitivity and range ofthe system 100 (FIG. 1).
  • the algorithm can include a least squares fit algorithm, a combinatorial algorithm, a system of linear equations, a non-linear regression algorithm, and/or any combination of these as previously described.
  • FIG. 2C illustrates the position 200" of a plurality of detectors 202, 204, 206, 208, 210 in a detector array relative to another location 220 of a non-isotropic source 218 of radiation.
  • the non-isotropic source 218 of radiation can be moving or stationary relative to the detectors 202, 204, 206, 208, 210.
  • the detectors 202, 204, 206, 208, 210 are positioned so that the detection zones 222, 224, 226, 228, 230 of at least three ofthe detectors 202, 204, 206, 208, 210 partially overlap the location 220 ofthe non-isotropic source 218 of radiation.
  • FIG. 2C also illustrates that a moving non-isotropic source 218 that has moved behind a row of omni-directional detectors 202, 204, 206, 208, 210 can still be localized by the system 100.
  • Each ofthe detectors 202, 204, 206, 208, 210 generates signals relating to a detected property ofthe non-isotropic source 218 of radiation. The strength ofthe signals depends on the sensitivity and position of each ofthe detectors 202, 204, 206, 208, 210.
  • the processor 110 receives the signals from the detectors 202, 204, 206, 208, 210 that are related to the detection ofthe source 218 of radiation. The peak intensity ofthe radiation from the source 218 is in zone B.
  • the sensitivity ofthe various detectors as well as the strength ofthe signals from adjacent detectors can be used to determine the characteristics ofthe anisotropy and the intensity and location ofthe source 218.
  • FIG. 2D illustrates the position 250 of a plurality of detectors 252, 254, 256, 258, 260, 262, 264 in a detector array including a faulty detector 258 relative to a location 266 of an isotropic source 268 of radiation.
  • the isotropic source 268 of radiation can be moving or stationary relative to the detectors 252, 254, 256, 258, 260, 262, 264.
  • the detectors 252, 254, 256, 258, 260, 262, 264 are positioned so that the detection zones 272, 274, 276, 280, 282, 284 of at least three ofthe detectors 252, 254, 256, 258, 260, 262, 264 partially overlap the location 266 ofthe isotropic source 268 of radiation.
  • FIG. 2D illustrates that the detection zone of a malfunctioning detector 258 can be covered by the detection zones 276, 280 of adjacent detectors 256, 260 in the detector array when the malfunctioning detector 258 fails.
  • the detection zones 276, 280 ofthe adjacent detectors 256, 260 sufficiently overlap to compensate for the malfunctioning detector 258.
  • the coverage from the adjacent detectors 276, 280 is somewhat compromised and can affect the accuracy ofthe localization ofthe source. At least three measurements from at least three different locations are still required to determine the intensity and location ofthe source 268 in two dimensions.
  • Each ofthe functioning detectors 252, 254, 256, 260, 262, 264 in the detector array generates signals relating to a detected property ofthe isotropic source 268.
  • the strength ofthe signals depends on the sensitivity and position of each ofthe detectors 252, 254, 256, 260, 262, 264.
  • the processor 110 receives the signals from the detectors 252, 254, 256, 260, 262, 264 that are related to the detection ofthe source 268.
  • the peak intensity ofthe radiation from the source 268 is in zone D.
  • the malfunctioning detector 258 is located adjacent to the area of peak energy distribution from the source 268.
  • the system 100 can still determine the intensity and the location ofthe source 268 by correlation the signals from the functioning detectors 252, 254, 256, 260, 262, 264 and the known coordinates ofthe functioning detectors 252, 254, 256, 260, 262, 264 using an algorithm.
  • FIG 3 illustrates a top view 285 of a vehicle 286 including four detectors 287, 288, 289, 290 in a detector array relative to a truck 291 carrying an isotropic source 292 of radiation.
  • the body 293 ofthe truck 291 can create some anisotropy and the engine 294 ofthe truck 291 can create significant anisotropy ofthe source 292. It is assumed for this example that the source 292 is isotropic and that any anisotropy caused by the vehicle 295 that is partially between the truck 291 and the vehicle 295 is insignificant.
  • the vehicle 286 can be an emergency vehicle such as a police car or another first responder vehicle.
  • the detectors 287, 288, 289, 290 are positioned on the four corners ofthe vehicle 286.
  • the detectors 287, 288, 289, 290 are fixed relative to each other and the vehicle
  • the truck 291 containing the isotropic source 292 is moving relative to the vehicle 286.
  • the detection zones 296, 297, 298, 299 ofthe detectors 287, 288, 289, 290 overlap the source 292 contained in the truck 291.
  • 287, 288, 289, 290 are continually monitoring the area for hazardous materials.
  • the coordinates ofthe detectors 287, 288, 289, 290 are determined in real-time using a GPS receiver located in the vehicle 286.
  • the detectors 287, 288, 289, 290 detect a property of the source 292 and generate signals that are transmitted to a processor that is located in the vehicle 286.
  • the processor determines the intensity, the location, the velocity and the direction ofthe source 292 by correlating the coordinates ofthe detectors 287, 288, 289, 290 and the signals generated by the detectors 287, 288, 289, 290 using an algorithm.
  • the processor can also determine the identity and mass of the source 564. The use of spectral detectors is discussed in more detail herein with reference to
  • the processor generates data that is transmitted to a display located in the vehicle 286.
  • the data can be transmitted to other emergency vehicles in the area (not shown) or command control center, and processors at those locations can determine the location ofthe source 292 relative to those emergency vehicles.
  • the processor in another emergency vehicle determines the location ofthe source 292 relative to that emergency vehicle by first determining the position ofthe vehicle 286 relative to that emergency vehicle, and then by using the data generated by the processor that indicates the location ofthe source 292 relative to the vehicle 286.
  • the occupants in the vehicle 286 can view the position ofthe source 292 relative to the vehicle 286 in approximately real-time, whether the truck 291 is moving or is stationary relative to the vehicle 286.
  • FIG. 4 illustrates a flow chart 300 of a process of locating a source of hazardous material using an array of fixed detectors.
  • the processor 110 (FIG. 1) initializes a non-linear regression module.
  • the processor 110 begins to receive data from the array of fixed detectors to determine how many detectors are online.
  • the processor 110 configures the non-linear regression algorithm by loading the number of detectors into the algorithm along with the parameters of each detector, such as the known sets of coordinates of each detector and the sensitivity of each detector. The algorithm is re-compiled with the known parameters.
  • the signals (readings/counts) from each ofthe detectors in the array of fixed detectors are loaded into the non-linear regression module.
  • the processor 110 executes the non-linear regression algorithm and generates data that indicates the intensity and the location ofthe source.
  • the data is sent to the main program where it can be processed further or displayed on a graphical user interface (GUI) or transmitted to a personal digital assistant (PDA), pager, cellular telephone, etc.
  • GUI graphical user interface
  • PDA personal digital assistant
  • the GUI can display the locations ofthe detectors and the calculated location and intensity ofthe source in real-time.
  • a seventh step 314 the processor 110 determines whether any ofthe signals from the detectors have changed. For example, signals from the detectors that have changed can indicate that the source is not stationary. If the signals from the detectors have not changed, the intensity and the location o the source that is determined by the processor 110 in the fifth step
  • step 316 the non-linear regression module is closed.
  • the system includes a detector that has changed locations
  • the new set of coordinates for that detector is loaded into the algorithm in the third step 306.
  • the signals generated by the detector at the new location are loaded into the non-linear regression module described in the fourth step 308.
  • FIG. 5 illustrates a block diagram of a system 400 for locating a source of hazardous material according to one embodiment ofthe invention.
  • the system 400 includes a detector 402 that is movable or portable. Additional fixed or portable detectors can be added depending on the requirements ofthe system 400 including the number of sources of hazardous materials to be located.
  • the detector 402 communicates with a processor 404 through a wireless communication link 406.
  • the processor 404 can include a computer, a microcontroller, a Field Programmable Gate Array (FPGA), or any digital processor.
  • the processor 404 is integrated with the detector 402 into a single portable unit.
  • the single portable unit can be carried in a backpack or integrated into an emergency vehicle.
  • the detector 402 can be positioned at various locations to detect the source from the various locations.
  • the detection zone ofthe detector 402 must overlap the source at each ofthe various detector locations in order to calculate the intensity and the position information ofthe source.
  • An increased number of detector locations can increase the sensitivity and reliability of detecting the source of hazardous material by providing more detector signals than necessary and generating an over-defined system of equations.
  • a minimum of three detector signals each from a different location is used to localize a source of hazardous material in two dimensions.
  • a minimum of four detector signals each from a different location is used to localize a source in three dimensions. Increasing the number of detector signals from different locations provides increased reliability, improved measurement precision, and increased accuracy in the localization ofthe source.
  • a display 408 including a graphical user interface (GUI) communicates with the processor 404 through a communication link 410.
  • An input device 412 such as a keyboard, communicates input signals to the processor 404 through a communication link 414. The input signals from the input device 412 initialize the system 400 and program any required input parameters into the processor 404.
  • the processor 404 includes a receiver 416 that receives signals from the detector 402.
  • the receiver 416 communicates the received signals to a microprocessor 418.
  • the microprocessor 418 analyzes the received signals and generates data that indicates the intensity and the location ofthe source of hazardous material.
  • the microprocessor 418 can determine the location of one or more sources of hazardous materials based on a best fit to a physical model algorithm. The algorithms used to determine the location ofthe one or more sources are described in detail herein.
  • the microprocessor 418 communicates the data to a transmitter 420.
  • the transmitter 420 transmits the data to the display 408 through the communication link 410.
  • the transmitter 420 can also transmit the data to a display 422 that is integrated with the detector 402 or to a portable device 424 through the wireless communication link 406.
  • a first responder equipped with the portable device 424 can receive information relating to the intensity and the location of the source of hazardous material.
  • the processor 404 can also communicate with at least one camera 426 through the communication link 406.
  • the camera 426 can be a digital camera or a video camera including a zoom lens.
  • the camera 426 can be integrated into a closed circuit television (CCTV) system.
  • the camera 426 is mounted on a movable platform.
  • the movable platform can pan or tilt the camera 426.
  • the processor 404 controls the position ofthe camera 426 based on the determined location ofthe source of hazardous material.
  • the detector 402 can include various subsystems.
  • the detector 402 can include one or more sensors or detectors that detect properties of various sources of hazardous materials.
  • the sensors can include one or more of a radiation sensor 430, a chemical sensor 432, a biological sensor 434, and an explosive sensor 436.
  • Other sensors can be added that can detect the presence of vapor and particles of contraband substances, such as narcotics.
  • the system 400 can also include one or more additional portable detectors (not shown) that can be mounted in backpacks or in vehicles.
  • the portable detectors can generate signals that are transmitted to the processor 404 to improve the sensitivity and range ofthe system and to increase the accuracy ofthe determination ofthe intensity and the location ofthe source ofthe hazardous material.
  • Each ofthe sensors 430, 432, 434, 436 can detect a presence of a hazardous material and can detect an intensity ofthe radiation relative to a background radiation or concentration of the hazardous material.
  • the sensors 430, 432, 434, 436 communicate sensor data to a controller
  • the controller 438 generates signals by processing the sensor data.
  • the signals are related to the intensity ofthe hazardous material relative to a background intensity.
  • the signals are sent to a transmitter 440.
  • the transmitter 440 communicates the signals to the processor 404 through the communication link 406.
  • the sensor signals generated by the detector 402 from the various locations can be used to determine the location ofthe source, an intensity ofthe source, and an identity ofthe source. In general, a single first responder can locate only stationary hazardous sources.
  • the detector 402 can also include a GPS receiver 442 that communicates a set of location coordinates ofthe detector 402 to the controller 438.
  • the GPS receiver 442 can also communicate the set of location coordinates ofthe detector 402 to the processor 438 through the communication link 406.
  • the GPS receiver 402 can be located remotely from the detector 402 and can communicate the set of location coordinates ofthe detector 402 to the controller 438 and/or the processor 404.
  • a radio-frequency identification (RF-JD) system can also be used to determine the set of coordinates ofthe detector 402. Other systems for determining the coordinates ofthe detectors can also be used.
  • the detector 402 includes a portable device 444 such as a personal digital assistant (PDA), a pager, a cellular telephone, a palmtop computer, or a laptop computer that can be used to display data or input system parameters.
  • the portable device 444 can receive and display data from the processor 404 relating to the detection, identification, quantification, localization, and tracking ofthe hazardous sources.
  • the detector 402 can also include a receiver 446 that receives data from the processor 404.
  • FIG. 6 illustrates the path 500 ofthe detector 402 (FIG. 5) relative to a location 502 of an isotropic source 504 of radiation.
  • the isotropic source 504 is located in a plastic trash container 506 which does not create any significant anisotropy.
  • FIG. 6 describes locating an isotropic source 504, the system 400 can also determine the intensity and the location of a non- isotropic source, which could be created by shielding an isotropic source. Determining the location of a non-isotropic source is described in more detail herein.
  • the 402 reaches at least three or more ofthe known locations 508, 510, 512, 514, 516, 518 in order to determine the intensity and the location ofthe source in two dimensions.
  • the detection zone must overlap the source at four or more locations 508, 510, 512, 514, 516, 518 in order to determine the intensity and the location ofthe source 504 in three dimensions. As the number of measurement locations increases, so to does the accuracy of determining the intensity and the location ofthe source.
  • the increase in the number of measurement locations also provides increased sensitivity and range of detection; improved finding and tracking of moving hazardous sources, which is possible when several first responders/detectors are sampling the sources concurrently; a reduction in the occurrence of false alarms; the ability to locate hazardous sources within shielded enclosures; and improved accuracy in the measurement ofthe intensity ofthe hazardous sources.
  • the isotropic source 504 of hazardous material is located within the detection zone ofthe detector 402 (FIG. 5) at four different measurement locations 512, 514, 516, 518.
  • the detector 402 cannot detect the property ofthe source 504 from two ofthe measurement locations 508, 510 because the detection zone ofthe detector 402 does not overlap the source 504 from those locations 508, 510.
  • the detector 402 generates signals from each of the known measurement locations 512, 514, 516, 518 relating to a detected property ofthe source 504 of hazardous material. The strength ofthe signals depends on the sensitivity and the specific location ofthe detector 402 relative to the source 504.
  • the processor 404 (FIG. 5) first determines whether the detector 402 is functioning properly by receiving signals from the detector 402 that are related to background radiation from the earth and the atmosphere. The processor can also determine if the detector 402 is detecting the presence of a hazardous material.
  • the GPS receiver 442 determines the set of coordinates for the detector 402 at the first location 508. The detector 402 attempts to detect a property of the source 504 at the first location 508 during a first time period. The detector 402 detects only background radiation because the distance between the first location 508 and the source 504 is too great.
  • the detector 402 is then moved to the second location 510. The detector 402 attempts to detect a property ofthe source 504 at the second location 510 during a second time period. The detector 402 detects only background radiation because the distance between the second location 510 and the source 504 is too great.
  • the detector 402 is then moved to the third location 512 and attempts to detect a property ofthe source 504 at the third location 512 during a third time period.
  • the detector 402 detects a property ofthe source 504 from the third location 512 and generates detector signals that are communicated to the processor 404.
  • the set of coordinates ofthe third location 512, as well as the third time period including the start and end times, and the detector signals are loaded into an algorithm executing on the processor 404.
  • the detector 402 is then moved to the fourth 514, fifth 516, and sixth locations 518 and measurements/readings are taken at each of those locations 514, 516, 518.
  • the sets of coordinates for each ofthe fourth 514, fifth 516, and sixth locations 518, as well as the time periods ofthe measurements at those locations, and the detector signals are loaded into an algorithm executing on the processor 404.
  • the processor 404 generates data that indicates the intensity and the location ofthe source 504 of hazardous material.
  • the data is generated by correlating the coordinates ofthe detector locations 512, 514, 516, 518 with the signals that are generated by the detector 402 by using an algorithm.
  • the algorithm can include a least squares fit algorithm, a combinatorial algorithm, a system of linear equations, a non-linear regression algorithm, and/or a combination of algorithms.
  • the data generated by the processor 404 can be displayed on a portable device 524, such as a PDA.
  • the data can include the intensity and the location ofthe source 504.
  • the portable device 524 displays a replicated path 500' including the replicated locations 508', 510', 512', 513', 516', 518' having coordinates that were determined using the GPS receiver 442 (FIG. 5).
  • the portable device 524 also displays the calculated location 526 ofthe source 504 relative to the replicated path 500 ' .
  • Multiple stationary sources can be resolved given enough samples from the moving first responder 520 with detector 402 and GPS system. For K sources at least N detection locations/samples are required, where K is less than N/3 in two dimensions. For each source there must be at least three detection locations with overlapping sensitivity zones with hazardous source inside.
  • the portable device 524 can display the velocity and direction ofthe moving source only when the source is moving significantly slower than the first responder 520. Otherwise, the case ofthe moving source is unresolved mathematically.
  • the data from more than one first responder 520 can be input into the same algorithm for localization and identification of hazardous sources. When more then three detectors/responders are used, the case of moving sources can be resolved. [0113] Multiple moving sources can be resolved given enough first responders 520 with detectors 402 and GPS systems. For K sources at least N detectors are required, where K is less than N/3 in two dimensions. For each source there must be at least three detectors with overlapping sensitivity zones at any given time.
  • FIG. 7 illustrates a flowchart 600 of a process of locating a source of hazardous material using a portable detector.
  • the processor 404 (FIG. 5) initializes a non-linear regression module.
  • the processor 404 begins to receive signals from the detector 402 and data from a GPS receiver relating to the position ofthe detector 402.
  • the processor 404 receives signals from the detector 402 that indicate the presence of a hazardous material, the coordinates ofthe detector 402 during the measurement, and the time of the measurement.
  • the processor 404 configures the non-linear regression algorithm by loading the number of sample measurements taken by the detector 402 into the algorithm along with the parameters ofthe detector 402 such as the known sets of coordinates of each measurement location. The algorithm is then re-compiled with the known parameters.
  • step 608 the signals (readings/counts) from the detector 402 at each measurement location are loaded into the non-linear regression module.
  • the processor 404 executes the non-linear regression algorithm and generates data that indicates the intensity and the location ofthe source.
  • the data is sent to the main program where it can be processed further or displayed on a graphical user interface (GUI) or transmitted to a personal digital assistant (PDA), pager, cellular telephone, etc.
  • GUI graphical user interface
  • PDA personal digital assistant
  • the GUI can display the locations ofthe detector and the calculated location and intensity ofthe source in real-time.
  • a seventh step 614 the processor 404 determines whether any ofthe signals from the detector 402 have changed. If the signals from the detector 402 have not changed, the intensity and the location ofthe source that is determined by the processor 404 in the fifth step 610 are used. In an eighth step 616, the non-linear regression module is closed.
  • FIG. 8 illustrates a flowchart 620 of a process of locating a source of hazardous material using a detector array having both fixed and portable detectors.
  • the processor initializes a non-linear regression module
  • the processor begins to receive signals from the fixed and portable detectors in the detector array and data from a GPS receiver relating to the position ofthe fixed and portable detectors.
  • the processor receives signals from the fixed and portable detectors that indicate the presence of a hazardous material, the coordinates ofthe fixed and portable detectors taken during the measurements, and the time ofthe measurements.
  • the processor configures the non-linear regression algorithm by loading the number of sample measurements taken by the portable detectors and the measurements taken by the fixed detectors into the algorithm along with the parameters of the detectors such as the known sets of coordinates of each measurement location and the time of each measurement. The algorithm is then re-compiled with the known parameters.
  • the signals (readings/counts) from the fixed and portable detectors at each measurement location are loaded into the non-linear regression module.
  • the processor executes the non-linear regression algorithm and generates data that indicates the intensity and the location ofthe source.
  • the data is sent to the main program where it can be processed further or displayed on a graphical user interface (GUI) or transmitted to a personal digital assistant (PDA), pager, cellular telephone, etc.
  • GUI graphical user interface
  • PDA personal digital assistant
  • the GUI can display the locations ofthe detector and the calculated location and intensity ofthe source in real-time.
  • a seventh step 634 the processor determines whether any ofthe signals from any ofthe fixed or portable detectors have changed. If the signals from the detectors have not changed, the intensity and the location ofthe source that is determined by the processor in the fifth step 630 are used. In an eighth step 636, the non-linear regression module is closed.
  • the new signals from those detectors are loaded into the non-linear regression module described in the fourth step 628. If the portable detectors have changed locations, the new sets of coordinates for the portable detectors are loaded into the algorithm in the third step 626. The signals generated by the portable detectors at the coordinates ofthe new locations are loaded into the non-linear regression module described in the fourth step 628. This loop continues by loading new coordinates and new signals from the fixed and portable detectors and updating the changing location ofthe source.
  • FIG. 9 illustrates a table 640 of radioactive isotopes 642 and their co ⁇ esponding activities 644 in units of intensity per mass.
  • the table 640 also illustrates the energy 646 for each isotope at the major intensity line and the energy 648 for each isotope at additional intensity lines.
  • the mass of the isotope is important for determining the level of a radiological threat.
  • the mass of isotope can be calculated by dividing the determined intensity ofthe located isotope by a known activity ofthe isotope from a unit of mass of that isotope as illustrated in the table 640 of FIG. 9.
  • the identification ofthe isotope is determined by using state-of-the-art radioactive detectors having spectral response.
  • the spectral detectors can identify the isotope based on the spectral response.
  • the activity A of each isotope can be calibrated for each detector and the results for each isotope are tabulated and stored in a lookup table for each spectral detector.
  • RDAs redundant detector array
  • each detector is subject to inherent random statistical fluctuations ofthe number of counts and there is no correlation between readings from multiple detectors.
  • there is a strong correlation between readings from multiple detectors in the presence of a radioactive source as follows:
  • Corr(z) IT C j (x)C 2 (y - x)C 3 (z - y + x)dxdy .
  • An alarm signal from an array of detectors is more reliable and prevents false alarms that can occur from a single detector.
  • An array of detectors also minimizes system down time in case of a malfunctioning detector.
  • Detectors in the array can be positioned in any configuration.
  • the system can signal security cameras to pan/tilt zoom on a suspected target containing a source of hazardous material.
  • the images from the camera can be used for facial recognition or license plate recognition.
  • additional capabilities ofthe command-control system can be activated to verify whether the signal emanates from, a stationary or moving source.
  • Image recognition as well as detectors that are repositioned can be used to determine whether the source is stationary or moving.
  • the source location can be correlated between the two detection methods. This provides improved filtering of a background radiation level from the presence and movement ofthe radioactive materials in the vicinity ofthe detectors.
  • the performance ofthe detector array can be fully simulated by knowing the characteristics ofthe detectors and their topological/geographical placement.
  • the system can be tuned between heightened security and lowest false alarm rate by increasing or decreasing the number of detectors and changing the locations ofthe detectors. For example, positioning a detector array in a vertical plane (Z-axis) in addition to the horizontal plane (X-Y-axes) provides the capability to resolve the location ofthe hazardous source in three dimensions.
  • FIG. 10A illustrates a simulated display 650 showing the location 652 of an isotropic source 654 of radiation that was determined using a three-detector array 656.
  • the simulated display 650 can be presented on a PDA, laptop, CRT display, monitor, LCD display, LED display, cellular telephone, or any other type of graphical display.
  • the isotropic source 654 is a radiation source of l,000microCurie.
  • the location 652 ofthe radiation source is shown as a shaded square box.
  • the three-detector array 656 includes a first 658, a second 660, and a third detector 662 that are positioned in a triangular configuration.
  • the simulated display 650 illustrates the location ofthe source 654 relative to the locations ofthe first 658, the second 660, and the third detector 662.
  • the simulated display 650 also illustrates the ten measurement samples 664 from the three-detector a ⁇ ay 656.
  • the right side ofthe simulated display 650 illustrates the number of sensors 666, the integration time 668 in seconds, the detector sensitivity 670 for the three-detector a ⁇ ay 656, and the number of measurements 672 that are used in the calculation ofthe intensity and the location 652 ofthe source 654.
  • the simulated display 650 also illustrates the determined location 674 ofthe source 654 and the intensity 676 ofthe source 654.
  • the known sets of coordinates 678 ofthe three- detector a ⁇ ay 656 and the average number of counts 680 for the tliree detectors 658, 660, 662 are also displayed.
  • the system of three equations is solved for the ten samples having a Gaussian distribution of events.
  • the simulated display 650 also illustrates the calculated coordinates 682 ofthe source 654 based on the signals from the three-detector a ⁇ ay 656 and the known coordinates ofthe three detectors 658, 660, 662.
  • the calculated intensity 684 ofthe source 654 is also displayed.
  • the ten sample measurements 664 from the three detectors 658, 660, 662 are somewhat highly dispersed around the location 652 ofthe source 654 due to the minimum number of detectors 658, 660, 662 used in the calculation.
  • FIG. 10B illustrates a simulated display 700 showing the location 702 of an isotropic source 704 of radiation that was determined using a five-detector a ⁇ ay 706.
  • the isotropic source 704 is a radiation source of lOmicroCurie.
  • the location 702 ofthe radiation source is shown as a shaded square box.
  • the five-detector a ⁇ ay 706 includes a first 708, a second 710, a third detector 712, a fourth detector 714, and a fifth detector 716 that are positioned in a straight line configuration.
  • the simulated display 700 illustrates the location 702 ofthe source 704 relative to the locations ofthe detectors 708, 710, 712, 714, 716.
  • the simulated display 700 also illustrates the ten measurement samples 718 from the five-detector a ⁇ ay 706.
  • the right side ofthe simulated display 700 illustrates the number of detectors 720, the integration time 722 in seconds, the detector sensitivity 724 for the five-detector a ⁇ ay 706, and the number of measurements 726 that are used in the calculation ofthe intensity and the location 702 ofthe source 704.
  • the simulated display 700 also illustrates the determined location 728 ofthe source 704 and the intensity 730 ofthe source 704.
  • the simulated display 700 also illustrates the calculated coordinates 728 ofthe source 704 based on the signals from the five-detector a ⁇ ay 706 and the known coordinates ofthe five detectors 708, 710, 712, 714, 716.
  • the calculated intensity 730 of the source 704 is also displayed.
  • 710, 712, 714, 716 are closely grouped around the location 702 ofthe source 704 due to the increased number of detectors 708, 710, 712, 714, 716 used in the calculation as compared to the minimum number of detectors 658, 660, 662 illustrated in FIG. 10A.
  • the present invention can determine the location and the intensity of a non-isotropic source of radiation.
  • the energy flux from the non-isotropic source should be quasi-evenly distributed.
  • FIGS. 11A-1 IC illustrate the energy flux distributions 750, 750', 750" from a source 752 of radiation located in the center of square shielded boxes 754, 756, 758 that each have a different thickness.
  • the energy flux distributions 750, 750', 750" are measured from a radius often meters from the source 752.
  • FIG. 11 A illustrates that when the anisotropy k is equal to two, the shape ofthe energy flux distribution 750 is distorted compared to the energy flux distribution of an isotopic source.
  • the distortion is due to the significant thickness ofthe walls ofthe shielded box 754.
  • An apparatus according to the invention can still resolve the location ofthe source 752 because the shape ofthe energy flux distribution 750 is quasi-evenly distributed.
  • FIG. 1 IB illustrates that when the anisotropy k is equal to one, the shape ofthe energy flux distribution 750' is less distorted compared to the energy flux distribution 750 shown in FIG. 11 A. As expected, the reduced distortion is due to the reduced thickness ofthe walls ofthe shielded box 756.
  • An apparatus according to the invention can resolve the location ofthe source 752 because the shape ofthe energy flux distribution 750' is quasi-evenly distributed.
  • FIG. 11C illustrates that when the anisotropy k is equal to two-thirds, the shape ofthe energy flux distribution 750" is even less distorted compared to the energy flux distribution 750' shown in FIG. 1 IB. As expected, the reduced distortion is due to the reduced thickness of the walls ofthe shielded box 758. The walls ofthe shielded box 758 provide significantly reduced shielding compared with the shielded box 754 and the energy flux distribution 750" is almost an isotropic distribution.
  • the energy flux distribution from a shielded source can be any shape due to the specific type of shielding and/or due to natural obstacles such as buildings.
  • the apparatus first applies a non-linear regression algorithm to the data from all ofthe available detectors/measurement samples and uses an isotropic model ofthe energy distribution. If an alarm condition is found due to one or more ofthe detectors generating strong signals, but the source location is undefined or is obviously inco ⁇ ect (for example, by comparing the determined location with closed circuit television (CCTV) monitoring or other means), another algorithm is used having a mathematical model that assumes a non-isotropic flux distribution.
  • CCTV closed circuit television
  • One such algorithm utilizes a "piece-wise" non-isotropic model for a limited number of detectors in the detector a ⁇ ay, e.g., three detectors at a time.
  • the model is quasi-isotropic or isotropic for certain sections/pieces ofthe detector a ⁇ ay. All combinations of detector a ⁇ ays of three (sub-a ⁇ ays of three) are analyzed for localization ofthe source. The sub-a ⁇ ays having the most consistent solutions are used in the algorithm to determine the location o the source.
  • the number of sub-a ⁇ ays can be limited by grouping the detectors/samples according to their proximity to each other to provide a na ⁇ ow detection "beam" towards the source.
  • FIG. 12A illustrates the position 760 of a plurality of detectors 761 , 762, 763, 764, 765, 766, 767, 768 relative to the location 770 of a source 772 within a shielded container 774.
  • the energy flux distribution 776 from the source 772 has an irregular shape due to the significant shielding from the shielded container 774.
  • the shielded container 774 is a lead "pig" having a na ⁇ ow channel 778 that leads to a small exit hole 780.
  • a detector a ⁇ ay includes the plurality of detectors 761, 762, 763, 764, 765, 766, 767, 768.
  • the detector a ⁇ ay consists ofthe portable detector obtaining measurement samples at various locations as described with reference to FIG. 6.
  • the detectors 763, 764, 765 are combined to create a sub-a ⁇ ay 782 that is within the energy flux distribution 776 ofthe source 772.
  • the detector signals generated by the sub-a ⁇ ay 782 can be used to localize the source 772. Detector signals from other sub-a ⁇ ays consisting of combinations ofthe other detectors 761, 762, 766, 767, 768 can yield inaccurate results.
  • the system initially analyzes the signals from the entire detector a ⁇ ay including the plurality of detectors 761, 762, 763, 764, 765, 766, 767, 768. The determination ofthe intensity and the location ofthe source 772 is either not found or an inco ⁇ ect solution is calculated.
  • the system divides the detectors 761, 762, 763, 764, 765, 766, 767, 768 into groups of sub- a ⁇ ays.
  • the groups of sub-a ⁇ ays can include a minimum of three detectors to locate a source in two dimensions.
  • the system can group the detectors based on their proximity to each other, hi this example, the sub-a ⁇ ay 782 provides the best solution.
  • the propagation media for radiation can create a more complex energy flux distribution.
  • the attenuation rate includes an additional exponential decay factor and the intensity / can be expressed as: j — o r 2 '
  • ⁇ /2 is the decay length, and is illustrated in FIG. 12B for different materials.
  • the propagation media is air
  • the value ofthe decay length ⁇ is practically infinite and the exponential factor can be disregarded.
  • the attenuation ofthe radiation decays according to the inverse square ofthe distance to the source.
  • determining the position ofthe source can still be accomplished. In this case and in other cases in which the decay function is unknown, the determination ofthe location ofthe source can be resolved in a general sense as described below.
  • FIG. 12B graphically illustrates the half-value layer 790 for different materials as a function of energy.
  • the different materials include water 792, concrete 794, iron 796 and lead 798.
  • the degree of attenuation ofthe radiation depends on the properties ofthe specific material.
  • the decay function is a certain (unknown) function of distance,/(
  • FIG. 13 A illustrates the position 800 of an a ⁇ ay 802 of detectors 804, 806, 808, relative to the location 810 of a source 812 of radiation.
  • the detectors 804, 806, 808 in the detector a ⁇ ay 802 form a right triangle with side 814 equal to a distance a.
  • the detectors 804, 806, 808 are positioned at the vertices ofthe triangle. The coordinates of each ofthe detectors are known. In other embodiments, the detectors 804, 806, 808 can be positioned to form non- right triangles.
  • the detectors 804, 806, 808 detect a property ofthe source 812 and generate a first, a second, and a third signal that are related to the detected property. Assuming that a is small relative to the distance from the source 812 to the detector 804, the differences between the sample counts ofthe detectors 804, 806, 808 can be given by:
  • additional detector a ⁇ ays each having three detectors that form additional triangles can be positioned proximate to the detector a ⁇ ay. Additional angles that represent a direction ofthe hazardous source relative to a direction of each ofthe additional triangles can be determined. The additional angles can be used to increase an accuracy ofthe determined direction ofthe hazardous source relative to the detector a ⁇ ay.
  • FIG. 13B illustrates the position 800' of a first a ⁇ ay 802 of detectors 804, 806, 808 and a second a ⁇ ay 820 of detectors 822, 824, 826 relative to the location 810 of a source 812 of radiation.
  • Adding the second triangular a ⁇ ay 820 at a fixed distance from the first triangular a ⁇ ay 802 allows the system to triangulate the location 810 ofthe source 812 by resolving the coordinates ofthe intersection ofthe lines 828 and 830. This is accomplished by knowing the distance between the first triangular a ⁇ ay 802 and the second triangular array 820 as well as the angles between each ofthe a ⁇ ays 802, 820 and the source 812. Additional triangular detector a ⁇ ays can be positioned to increase an accuracy ofthe determined direction ⁇ and the location
  • this approach can be also used for resolving a source with an anisotropic distribution of radiation.
  • this approach does not require the decay function to be isotropic.
  • the only restriction is that the angular variation ofthe energy flux must be smooth compared to the r-dependence in the spatial limits ofthe triangular a ⁇ ay.
  • a sector-wise anisotropy (for instance, due to the complete shielding of radiation in certain directions and insignificant shielding in other directions) can easily obey these conditions.
  • the angular distribution of radiation can be modeled by just two beams in two different directions.
  • the doted lines 828, 830 represent two directions obtained from the equation above for tan( ⁇ ).
  • the first implementation allows resolution of location coordinates and intensity ofthe source by using the flux distribution with a decay function that is inversely proportional to the square ofthe distance from the source ("square of distance decay" approach).
  • the second implementation uses a ⁇ ays of three detectors to find the direction (angle) to the source, and is independent of any specific decay function and only requires that the energy flux function to be smooth ("decay independent" approach).
  • anisotropic sources in FIGS. 11A-1 IC as well as in simulations illustrated in FIGS. 15A and 15B, it is assumed that the square shielded boxes creating anisotropic sources are in vacuum, so that the r-dependence outside the boxes is known.
  • the flux outside ofthe shielded boxes is determined by box geometry and material, position ofthe radiation source inside the box, the thickness ofthe walls ofthe box, the orientation ofthe box, and is inversely proportional to the square ofthe distance from the source.
  • the "square of distance decay" is adequate for finding anisotropic sources, while in other cases, especially with very strong anisotropy, or when the piece-wise isotropy cannot be found for a sub-a ⁇ ay of three detectors, or when the media outside the source is not vacuum or air, direction finding using an a ⁇ ay of three detectors can be used.
  • FIG. 14 illustrates an operational mode of software display 850 showing the location 852 of a non-isotropic source 854 of radiation that was determined using a six-detector a ⁇ ay.
  • the six detector a ⁇ ay includes a first 856, a second 858, a third 860, a fourth 862, a fifth 864, and a sixth detector 866 having known coordinates.
  • the six detector a ⁇ ay can also consist of a portable detector that obtains measurements at six different locations having known coordinates.
  • the right side ofthe operational display 850 illustrates the total number of sensors 868 in the a ⁇ ay at the last measurement (the number of sensors can vary as detectors can come into the a ⁇ ay and leave the a ⁇ ay in real time depending on their proximity to the source), the selected detector that has its characteristics displayed 870, the integration time 872 in seconds, the quantum efficiency ofthe selected detector 874, and the number of measurements 876 that are used in the calculation ofthe intensity and the location 852 ofthe source 854.
  • the display 850 also illustrates the determined location 878 ofthe first source 854 and the intensity/activity 880 ofthe first source 854 found.
  • the display 850 can show the determined location 882 of other sources and their activity 884 provided there are enough detectors in the area.
  • the isotope type 886 and the mass 888 ofthe source can also be displayed on the display 850.
  • FIG. 15A illustrates a simulated display 900 showing the location 902 of a non- isotropic source 904 of radiation that was determined using a four-detector a ⁇ ay.
  • the four detector a ⁇ ay includes a first 906, a second 908, a third 910 and a fourth detector 912 that are positioned in a square configuration.
  • the simulated display 900 can be presented on a PDA, laptop, CRT display, monitor, LCD display, LED display, cellular telephone, or any other type of graphical display.
  • the non-isotropic source 904 is a radiation source of 88.0milliCurie.
  • the location 902 ofthe radiation source 904 is shown as a shaded square box.
  • any information about anisotropy ofthe source can be used in the model, such as information about the shape ofthe shielded container.
  • a customized fitting-function that describes anisotropy can be used to locate an anisotropic source in such cases.
  • These customized functions could contain additional parameters and might require additional detectors in the a ⁇ ay to resolve the location ofthe sources.
  • the shape ofthe shielded container or the type of anisotropy caused by natural obstacles, in general is unknown in most practical situations. Therefore, the fitting function cannot be constructed.
  • other techniques can be used such as dynamically self-adjusting sub-a ⁇ ays to make use of piece-wise isotropic sections ofthe source energy flux and the application of different algorithms for processing data from those sub-a ⁇ ays.
  • the simulated display 900 illustrates the location 902 ofthe non-isotropic source 904 relative to the locations ofthe first 906, the second 908, the third 910 and the fourth detector 912.
  • the simulated display 900 also illustrates the locations ofthe measurements 914 from the four-detector a ⁇ ay.
  • the right side ofthe simulated display 900 illustrates the number of sensors 916, the integration time 918 in seconds, the quantum efficiency ofthe detectors 920, and the number of measurements 922 that are used in the calculation ofthe intensity and the location 902 ofthe source 904.
  • the simulated display 900 also illustrates the determined location 924 of the source 904 and the intensity/activity 926 ofthe source 904.
  • the simulated display 900 can also illustrate other parameters, such as the type of shielding material 928 and the thickness 930 ofthe shielding material.
  • the radiation source 904 is positioned in the middle of a shielded square box (not shown).
  • the system can simulate a container having a known shape with shielded walls having different thickness 930 that are fabricated from different materials 928 (i.e. lead, steel).
  • An angular orientation 932 ofthe shielded box relative to a horizontal plane ofthe detector a ⁇ ay can also be displayed.
  • the system of four equations and three unknowns is solved for the ten samples having a Gaussian distribution of events. This is an over-defined system of equations as previously described.
  • the simulated display 900 also illustrates the calculated coordinates 934 ofthe source 904 based on the signals from the four-detector a ⁇ ay and the known coordinates of the four detectors 906, 908, 910, and 912.
  • the calculated intensity 936 ofthe source 904 is also displayed.
  • FIG. 15B illustrates a simulated display 950 showing the location 952 of a non- isotropic source 954 of radiation that was determined using a six detector a ⁇ ay.
  • the six detector a ⁇ ay includes a first 956, a second 958, a third 960, a fourth 962, a fifth 964, and a sixth detector 966 that are positioned in a rectangular configuration.
  • the non-isotropic source 954 is a radiation source of 88.0milliCurie.
  • the location 952 ofthe radiation source is shown as a shaded square box.
  • any infonnation about the anisotropy ofthe source is used in the model. For example, information about the shape ofthe shielded container or whether the anisotropy is weak could be used to create a more accurate mathematical model.
  • the simulated display 950 illustrates the location 952 ofthe source 954 relative to the locations ofthe detectors 956, 958, 960, 962, 964, 966.
  • the simulated display 950 also illustrates the ten measurement samples 968 from the six-detector a ⁇ ay.
  • the right side ofthe simulated display 950 illustrates the number of sensors 970, the integration time 972 in seconds, the quantum efficiency ofthe detectors 974, and the number of measurements 976 that are used in the calculation ofthe intensity and the location 952 ofthe source 954.
  • the simulated display 950 also illustrates the determined location 978 ofthe source 954 and the intensity/activity 980 ofthe source 954.
  • the simulated display 950 can also illustrate other parameters, such as the type of shielding material 982 and the thickness 984 ofthe shielding material.
  • the radiation source 954 is positioned in the middle of a shielded square box (not shown).
  • the system can simulate a container with shielded walls having different thickness 984 that are fabricated from different materials 982 (i.e. lead, steel).
  • An angular orientation 986 ofthe shielded box relative to a horizontal plane ofthe detector a ⁇ ay can also be displayed.
  • the model can use a fitting function that utilizes information about the source, such as the shape ofthe shielded container.
  • the over-defined system of six equations is solved for the ten samples having a Gaussian distribution of events.
  • the simulated display 950 also illustrates the calculated coordinates 988 ofthe source 954 based on the signals from the six-detector a ⁇ ay and the known coordinates ofthe six detectors 956, 958, 960, 962, 964, 966.
  • the calculated intensity 990 ofthe source 954 is also displayed.
  • FIG. 15A and FIG. 15B illustrate cases in which the radiological materials produce a semi-isotropic and slightly asymmetrical distribution of energy flux emitted from a square box having a uniform wall thickness as described with reference to FIGS. 11A-1 IC.
  • these non-isotropic sources can be assumed to be approximately isotropic sources. The intensity and location can still be found in the cases in which the source is actually non- isotropic but the energy flux distribution is only slightly anisotropic and still significantly symmetrical.

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Abstract

L'invention concerne un procédé et un appareil qui permettent de déterminer une intensité et un emplacement d'une source de matières dangereuses. L'appareil comprend une mosaïque de détecteurs comprenant au moins trois détecteurs placés à trois ou plusieurs emplacements différents, les coordonnées des différents emplacements étant connus. Au moins trois détecteurs parmi la mosaïque de détecteurs présentent des zones de détection qui recouvrent partiellement l'emplacement de la source de matières dangereuses. La mosaïque de détecteurs détecte une propriété de la source de matières dangereuses et émet des signaux se rapportant à la propriété détectée. Un processeur reçoit les signaux émis par la mosaïque de détecteurs et génère des données indiquant l'intensité et l'emplacement de la source de matières dangereuses en corrélant les ensembles connus de coordonnées aux signaux émis par la mosaïque de détecteurs au moyen d'un algorithme.
PCT/US2004/022926 2003-07-18 2004-07-16 Procedes et appareils de detection et de localisation de matieres dangereuses WO2005022197A2 (fr)

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US6913287B2 (en) * 2003-08-27 2005-07-05 Kenneth Leitner Snowmobile elevation mechanism
GB2424704A (en) * 2005-03-31 2006-10-04 Bil Solutions Ltd Monitoring radioactive emissions
FR2991781A1 (fr) * 2012-06-12 2013-12-13 Irsn Procede de cartographie en temps reel d'une distribution de photons dans un site
FR2991782A1 (fr) * 2012-06-12 2013-12-13 Irsn Procede de localisation d'au moins une source d'emission de photons
EP2074442B1 (fr) * 2006-09-27 2014-12-03 Create Technologies Limited Mesure de la radiation
WO2018146358A1 (fr) 2017-02-10 2018-08-16 Consejo Superior De Investigaciones Cientificas (Csic) Système et procédé d'identification volumétrique et isotopique de répartitions de scènes radioactives
JP2019148597A (ja) * 2013-08-23 2019-09-05 エステーエムイー ソシエテ デ テクニーク アン ミリウ イオニゾン 携帯端末を用いて環境の３ｄトポグラフィおよび放射能をモデリングするためのモデリング方法、コンピュータプログラム、デジタルデータ媒体、携帯端末
CN112205991A (zh) * 2020-10-14 2021-01-12 成都理工大学 一种x光机阳极足跟效应修正的方法
CN113447974A (zh) * 2021-06-28 2021-09-28 上海交通大学 一种放射源强度三维分布的估计方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6913287B2 (en) * 2003-08-27 2005-07-05 Kenneth Leitner Snowmobile elevation mechanism
GB2424704A (en) * 2005-03-31 2006-10-04 Bil Solutions Ltd Monitoring radioactive emissions
EP2074442B1 (fr) * 2006-09-27 2014-12-03 Create Technologies Limited Mesure de la radiation
FR2991782A1 (fr) * 2012-06-12 2013-12-13 Irsn Procede de localisation d'au moins une source d'emission de photons
WO2013186231A1 (fr) * 2012-06-12 2013-12-19 Institut De Radioprotection Et De Surete Nucleaire Procede de cartographie en temps reel d'une distribution de photons dans un site
WO2013186239A3 (fr) * 2012-06-12 2014-02-20 Institut De Radioprotection Et De Surete Nucleaire Procede de localisation d'au moins une source d'emission de photons
FR2991781A1 (fr) * 2012-06-12 2013-12-13 Irsn Procede de cartographie en temps reel d'une distribution de photons dans un site
JP2015526702A (ja) * 2012-06-12 2015-09-10 アンスティテュ ド ラディオプロテクシオン エ ド スルテ ニュクレエール サイトにおいて光子分布をリアルタイムにマッピングする方法
US9678228B2 (en) 2012-06-12 2017-06-13 Institut De Radioprotection Et De Surete Nuclaire Method of real-time mapping of a distribution of photons in a site
JP2019148597A (ja) * 2013-08-23 2019-09-05 エステーエムイー ソシエテ デ テクニーク アン ミリウ イオニゾン 携帯端末を用いて環境の３ｄトポグラフィおよび放射能をモデリングするためのモデリング方法、コンピュータプログラム、デジタルデータ媒体、携帯端末
WO2018146358A1 (fr) 2017-02-10 2018-08-16 Consejo Superior De Investigaciones Cientificas (Csic) Système et procédé d'identification volumétrique et isotopique de répartitions de scènes radioactives
US11022705B2 (en) 2017-02-10 2021-06-01 Consejo Superior De Investigaciones Cientificas (Csic) System and method for the volumetric and isotopic identification of radiation distribution in radioactive surroundings
CN112205991A (zh) * 2020-10-14 2021-01-12 成都理工大学 一种x光机阳极足跟效应修正的方法
CN113447974A (zh) * 2021-06-28 2021-09-28 上海交通大学 一种放射源强度三维分布的估计方法
CN113447974B (zh) * 2021-06-28 2022-07-19 上海交通大学 一种放射源强度三维分布的估计方法

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