A gamma-ray imager for arms control
Ascertaining the number of warheads on a missile-delivery systems by a remote, nonvisual inspection may be desirable in some arms-control verification scenarios. A gamma-ray imaging system (GRIS) has been developed to inspect for nuclear warheads by imaging the highly penetrating gamma-radiation emitted by radioactive materials integral to warheads. Such an image may be used to obtain the missile loadout. The authors describe the GRIS's operating principles and capabilities, present data, and discuss the advantages and disadvantages of such a system for arms control. They also present field results where GRIS was used on an emplaced Peacekeeper missile. Improvements to GRIS in light of the field trial results are presented.<<ETX>>
The LANL prototype Compton gamma-ray imager: design and image reconstruction techniques
Today we face serious threats from radiological dispersion devices, improvised nuclear devices, and unsecured nuclear materials. Detectors which are currently used to detect and characterize these radioactive materials (or the radioactive materials within larger assemblies) suffer from large background rates. In addition, these detectors have only minimal ability to localize the position of the source without the use of mechanical collimators - which reduce efficiency. Imaging detectors using the Compton scattering process have the potential to provide greatly improved sensitivity through their ability to reject off-source background by localizing the source. We are developing a prototype device using readily available detector systems to explore Compton imaging technology. Our aim is to build a proof-of-concept device to study the Compton technology and to benchmark simulation efforts that will guide development of larger, more efficient devices that would be needed for deployment in the field. Here we discuss the concept of our detector design and results from Monte Carlo simulations of our prototype detector. We present an extension of an imaging technique used for gamma-ray astronomy to near-field sources
Gas Scintillation Drift Chambers with Wave Shifter Read-Out for Hard X-Ray Astronomy
A major improvement in hard X-ray and gamma ray astrophysics could be provided by high pressure xenon time projection chambers where gas scintillation is used both for the measurement of the time of interaction and for the detection of the extracted electrons. This allows three dimensional imaging of naturally complex events (photoelectric interaction with escape photon, Compton scatter, and pair production). We propose a novel read-out system based on wave shifter fibers which is well suited to the high pressures and large areas required of a hard X-ray telescope. We compute expected performances, outline potential problems and describe our experimental effort to solve these problems.