Modular design of long narrow scintillating cells for ILC detector

The experimental results for the narrow scintillating elements with effective area about 20 cm{sup 2} are reported. The elements were formed from the single piece of scintillator and were read out via wavelength shifting fibers with the MRS (Metal/Resistor/Semiconductor) photodiodes on both ends of each fiber. The formation of the cells from the piece of scintillator by using grooves is discussed. The cell performance was tested using the radioactive source by measuring the PMT current and a single rate after amplifier and discrimination with threshold at about three photo electrons in each channel and quad coincidences (double coincidences between sensors on each fiber and double coincidences between two neighboring fibers). This result is of high importance for large multi-channel systems, i.e. module may be used as an active element for calorimeter or muon system for the design of the future electron-positron linear collider detector because cell effective area can be smoothly enlarged or reduced (to 4 cm{sup 2} definitely)

An Array of Spherically Dimpled Scintillating Cells for an Integrated Readout Layer

The CALICE collaboration is developing calorimetry for particle flow algorithm (PFA) based detectors. To measure particle shower development, a finely segmented calorimeter optimized for PFA must consist of millions of channels. A scintillator-based calorimeter with cells of size 30 x 30 x 3 mm³ readout with silicon photo-multipliers (SiPMs) in situ shows great promise. The construction and assembly challenges of a highly segmented scintillator-SiPM calorimeter could be greatly reduced with full integration of the readout electronics into active calorimeter layers. An integrated readout layer (IRL) comprised of a multi-channel electronics board instrumented with SiPMs paired to a solid uniform array of scintillator cells would eliminate much of the labor intensive production associated with the fiber readout cells. We discuss the development and performance of injection molded polystyrene arrays of 2x2 dimpled scintillator cells with a thickness of 3 mm and cell area of about 900 mm². The spherically dimpled cells ensure uniformity of response for a SiPM positioned at the center of the cell. The performance of an array of molded cells is compared to an array of cells uniformly machined from a solid sheet of polyvinyltolulene cast scintillator with 3 mm thickness. To improve the performance of the molded array the cell dimple depth was optimized. The light output, uniformity, and cross talk of the molded and machined cells irradiated with a Sr-90 source and measured with a SiPM in current mode are reported. Plans for initial particle beam tests of the complete IRL are also discussed

Adaptive windowing in contrast-enhanced intravascular ultrasound imaging

Intravascular ultrasound (IVUS) is one of the most commonly-used interventional imaging techniques and has seen recent innovations which attempt to characterize the risk posed by atherosclerotic plaques. One such development is the use of microbubble contrast agents to image vasa vasorum, fine vessels which supply oxygen and nutrients to the walls of coronary arteries and typically have diameters less than 200 µm. The degree of vasa vasorum neovascularization within plaques is positively correlated with plaque vulnerability. Having recently presented a prototype dual-frequency transducer for contrast agent-specific intravascular imaging, here we describe signal processing approaches based on minimum variance (MV) beamforming and the phase coherence factor (PCF) for improving the spatial resolution and contrast-to-tissue ratio (CTR) in IVUS imaging. These approaches are examined through simulations, phantom studies, ex vivo studies in porcine arteries, and in vivo studies in chicken embryos. In phantom studies, PCF processing improved CTR by a mean of 4.2 dB, while combined MV and PCF processing improved spatial resolution by 41.7%. Improvements of 2.2 dB in CTR and 37.2% in resolution were observed in vivo. Applying these processing strategies can enhance image quality in conventional B-mode IVUS or in contrast-enhanced IVUS, where signal-to-noise ratio is relatively low and resolution is at a premium