Showing papers by "Richard C. Lanza published in 2015"

SiPM response to long and intense light pulses

Abstract: Recently Silicon Photomultipliers (SiPMs) have become well recognized as the detector of choice for various applications which demand good photon number resolution and time resolution of short weak light pulses in the nanosecond time scale. In the case of longer and more intensive light pulses, SiPM performance gradually degrades due to dark noise, afterpulsing, and non-instant cell recovering. Nevertheless, SiPM benefits are expected to overbalance their drawbacks in applications such as X-ray cargo inspection using Scintillation-Cherenkov detectors and accelerator beam loss monitoring with Cherenkov fibres, where light pulses of a microsecond time scale have to be detected with good amplitude and timing resolution in a wide dynamic range of 105–106. This report is focused on transient characteristics of a SiPM response on a long rectangular light pulse with special attention to moderate and high light intensities above the linear dynamic range. An analytical model of the transient response and an initial consideration of experimental results in comparison with the model are presented.

High speed, low dose, intelligent X-ray cargo inspection

Abstract: The security market requirements for high throughput rail cargo radiography inspection systems include better than 5 mm line pair imaging resolution, penetration beyond 400 mm steel equivalent, scan speeds of up to 60 km/h, material discrimination (four groups of Z) in 100 % of cargo at speeds reaching 45 km/h, low dose and small radiation exclusioi zone. In order to achieve these requirements, which cannot be met t conventional dual energy radiography systems, a team lead by RadiaBeam Technologies, LLC (RBT) has initiated a research into new radiography methods and imaging detector materials with the goal of developing an Adaptive Railroad Cargo Inspection System (ARCIS). The ARCIS technical concept relies on linac-based, adaptive, ramped energy source of packets of short X-ray pulses sampled by a new type of fast X-ray detectors with rapid hardware processing for intelligent linac control, and advanced radiography image processing and material discrimination analysis. The following ARCIS key enabling technologies overcome the limitations of the conventional dual energy interlaced cargo inspection systems: • Multi-energy material discrimination in a single scan line provided by packets of short pulses from an X-ray source with end-point energy ramp up (> 1 MHz rate of energy switching); • Real-time intelligent setting of packet's maximum energy depend on X-ray attenuation in cargo; • Fast Scintillation-Cherenkov detectors with reduced sensitivity to scatter radiation; • Detector readout with Silicon Photomultiplier (SiPM) provides time-resolving of short X-ray pulses; • Self-control adaptive dynamic adjustment of SiPM responsivity in detector channel for increased dynamic range.

Engineering upgrades to the accelerator-based in-situ materials surveillance diagnostic on Alcator C-Mod

Abstract: This paper presents an overview of the engineering upgrades being made to optimize the AIMS diagnostic on the Alcator C-Mod tokamak, a novel, particle accelerator-based diagnostic that can nondestructively measure the evolution of material surface compositions inside magnetic fusion devices. Three major AIMS subsystems are presented: the RFQ deuteron accelerator; the particle detectors; and the Alcator C-Mod tokamak. The combined results of the upgrades will enable AIMS to routinely map critical plasma-material interaction quantities, such as net erosion/redeposition and fusion fuel retention, over large areas of PFC surfaces between plasma shots and after the run day.