Status of the prototype Pulsed Photonuclear Assessment (PPA) inspection system
The Idaho National Laboratory, in collaboration with Idaho State University's Idaho Accelerator Center and the Los Alamos National Laboratory, continues to develop the Pulsed Photonuclear Assessment (PPA) technique for shielded nuclear material detection in large volume configurations, such as cargo containers. In recent years, the Department of Homeland Security has supported the development of a prototype PPA cargo inspection system. This PPA system integrates novel neutron and gamma-ray detectors for nuclear material detection along with a complementary and unique gray scale, density mapping component for significant shield material detection. This paper will present the developmental status of the prototype system, its detection performance using several INL Calibration Pallets, and planned enhancements to further increase its nuclear material detection capability.
Feasibility of prompt correlated counting from photon interrogation of concealed nuclear materials
We describe new Monte Carlo codes for the simulation of coincident counts, both real and accidental, originating from photonuclear and photoatomic events in nuclear, and non-nuclear, materials. The codes perform fully analog simulation of all secondary neutrons, and photons, emitted by photonuclear, and photoatomic, events. Separate algorithms are then used to simulate the accidental coincidences. These new codes have been applied to a realistic measurement scenario. Two possible techniques for minimizing the detection of accidental coincidences are then analyzed: pulse-shape discrimination and detector lead shielding. The results showed that the use of lead-shielded liquid scintillation detectors with pulse-shape discrimination is a promising technique for the detection of actinides in shielded configurations by minimizing accidental counts. The data acquisition time for this approach would be on the order of 1 min or less for the measurement scenario considered here.
Microwave source with enhanced radiation power based on orbitron MASERs
We have proposed the design of high power microwave source in a vacuum tube based on the theory of negative mass instability. The proposed source does not operate based on a slow-wave structure but instead makes use of accelerated charged particles. In our structure, an electron emitter injects the charged particles into to the cavity. Emitted particles move around the anode, which leads to electron acceleration and emission of electromagnetic waves with a specific frequency. In this paper, we have enhanced the output power and frequency of microwave source by variation of particles initial energy and the number of anodes incorporating their specific arrangement and applied voltages. Working at room temperature, compactness, wide bandwidth, and tunability of output frequency are among the advantages of the proposed source.