Organic-scintillator compton gamma ray telescope
First Claim
1. A Compton telescope-type gamma-ray imaging apparatus (20) including a plurality of scintillators (28), said device comprising:
- a chassis, said chassis including at least three discrete layers (24) spaced-apart from one another and supported in an aligned, generally parallel orientation;
at least one gamma ray detector operatively disposed in each said layer (24);
each said gamma ray detector comprising a plurality of scintillator pixels (28);
said gamma ray detectors on at least two of said layers (24) including organic scintillator pixels (28), said organic scintillator pixels (28) each including a unitary volume of scintillator material having at least three semiconductor-based high-gain photodetectors (30) mounted thereon and configured to determine the (x,y) position and total energy deposited by a gamma ray collision inside the respective said organic scintillator pixel (28).
1 Assignment
0 Petitions
Accused Products
Abstract
Apparatus and methods for imaging sources of gamma rays with a large area, comparatively low-cost Compton telescope (20). The Compton telescope (20) uses multiple layers (24) of low-cost organic solid plastic or liquid scintillator, arranged in large arrays of identical scintillator pixels (28). Photodiodes, avalanche photodiodes (30), or solid-state photomultipliers are used to read out the fluorescent pulses from scintillator pixels (28). Multiple scintillator pixels (28) are multiplexed into a few fast digitizers (80) and a few fast FPGA programmable digital microprocessors (78). Selection rule methods are presented for processing multiple near-simultaneous gamma ray collisions within the Compton telescope (28) to identify trackable events that yield gamma ray image data of interest. A calibration method achieves improved energy resolution along with (x,y) position information in pixels (28) made of organic scintillator materials with multiple photodetectors (30). Synchronization trigger signals are used from a pulsed neutron source (58) to maximize the signal-to-background ratio for prompt gamma neutron activation analysis (PGNAA) of objects at greater than 2 meters range, where such trigger signals are based on the estimated range to PGNAA sources and neutron time-of-flight.
-
Citations
25 Claims
-
1. A Compton telescope-type gamma-ray imaging apparatus (20) including a plurality of scintillators (28), said device comprising:
-
a chassis, said chassis including at least three discrete layers (24) spaced-apart from one another and supported in an aligned, generally parallel orientation; at least one gamma ray detector operatively disposed in each said layer (24); each said gamma ray detector comprising a plurality of scintillator pixels (28); said gamma ray detectors on at least two of said layers (24) including organic scintillator pixels (28), said organic scintillator pixels (28) each including a unitary volume of scintillator material having at least three semiconductor-based high-gain photodetectors (30) mounted thereon and configured to determine the (x,y) position and total energy deposited by a gamma ray collision inside the respective said organic scintillator pixel (28). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
-
-
17. A method of operating a Compton telescope-type gamma-ray imaging apparatus (20) including plural scintillators (28), said method comprising the steps of:
-
supporting at least three discrete layers (24) of gamma ray detectors in spaced-apart generally parallel alignment;
each said gamma ray detector including a plurality of substantially identical scintillator pixels (28);forming a plurality of the scintillator pixels (28) in at least two of the layers (24) from an organic scintillator material composition; and individually calibrating at least one organic scintillator pixel (28) to improve its (x,y) position and energy resolution characteristics, said calibrating step including correcting the energy measurement from at least one organic scintillator pixel (28). - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25)
-
Specification