95 research outputs found
Microchannel avalanche photodiode with wide linearity range
Design and physical operation principles of new microchannel avalanche
photodiode (MC APD) with gain up to 10^5 and linearity range improved an order
of magnitude compared to known similar devices. A distinctive feature of the
new device is a directly biased p-n junction under each pixel which plays role
of an individual quenching resistor. This allows increasing pixel density up to
40000 per mm^2 and making entire device area sensitive.Comment: Submitted to Journal of Technical Physic
A New Low-Noise Avalanche Photodiode With Micro-Pixel Structure
A new design of the avalanche photodiodes with an array of micro-pixel p-n-junctions was developed on base of metal-oxide-silicon
structure. The thermal oxide layer of 1000A thickness contains tunnel oxide regions with about 25A thickness. The device exhibits a noise
factor ~ 4 at a high multiplication factor (M~10000). A high space uniformity of sensitivity was found for gain of M~ 1000
Hadron calorimeter with MAPD readout in the NA61/SHINE experiment
The modular hadron calorimeter with micro-pixel avalanche photodiodes readout
for the NA61/SHINE experiment at the CERN SPS is presented. The calorimeter
consists of 44 independent modules with lead-scintillator sandwich structure.
The light from the scintillator tiles is captured by and transported with
WLS-fibers embedded in scintillator grooves. The construction provides a
longitudinal segmentation of the module in 10 sections with independent MAPD
readout. MAPDs with pixel density of /mm ensure good linearity of
calorimeter response in a wide dynamical range. The performance of the
calorimeter prototype in a beam test is reported
Performance of a plastic scintillator developed using styrene monomer polymerization
This paper presents a newly developed plastic scintillator produced in
collaboration with Turkiye Energy, Nuclear and Mineral Research Agency
(TENMAK). The scintillator is manufactured using thermal polymerization of
commercially available styrene monomer. The absorption spectrum of the
scintillator exhibited two absorption bands at 225 nm and 340 nm, with an
absorption edge observed at 410 nm. The wavelength of the emitted light was
measured in the range of 400-800 nm, with a maximum intensity at 427 nm.
Monoenergetic electrons from the 137Cs source were used to evaluate the
characteristics of the new scintillator, particularly its light yield. As the
light readout the MAPD-3NM type silicon photomultiplier array (4 x 4) with an
active area of 15 x 15 mm2, assembled using single MAPDs with an active area of
3.7 x 3.7 mm2, was used. The light yield of the scintillator was determined to
be 6134 photons/MeV. In addition, the efficiency of the scintillator for gamma
rays with an energy of 662 keV was found to be approximately 1.8 %. A CmBe
neutron source was employed to evaluate its fast neutron detection performance.
However, neutron/gamma discrimination using pulse shape discrimination (charge
integration) method was not observed. The results demonstrate the potential of
a newly produced plastic scintillator for various applications, particularly in
radiation monitoring and detection systems.Comment: 7 pages, 7 figure
Altered Retinoic Acid Metabolism in Diabetic Mouse Kidney Identified by 18O Isotopic Labeling and 2D Mass Spectrometry
Numerous metabolic pathways have been implicated in diabetes-induced renal injury, yet few studies have utilized unbiased systems biology approaches for mapping the interconnectivity of diabetes-dysregulated proteins that are involved. We utilized a global, quantitative, differential proteomic approach to identify a novel retinoic acid hub in renal cortical protein networks dysregulated by type 2 diabetes.Total proteins were extracted from renal cortex of control and db/db mice at 20 weeks of age (after 12 weeks of hyperglycemia in the diabetic mice). Following trypsinization, (18)O- and (16)O-labeled control and diabetic peptides, respectively, were pooled and separated by two dimensional liquid chromatography (strong cation exchange creating 60 fractions further separated by nano-HPLC), followed by peptide identification and quantification using mass spectrometry. Proteomic analysis identified 53 proteins with fold change >or=1.5 and p<or=0.05 after Benjamini-Hochberg adjustment (out of 1,806 proteins identified), including alcohol dehydrogenase (ADH) and retinaldehyde dehydrogenase (RALDH1/ALDH1A1). Ingenuity Pathway Analysis identified altered retinoic acid as a key signaling hub that was altered in the diabetic renal cortical proteome. Western blotting and real-time PCR confirmed diabetes-induced upregulation of RALDH1, which was localized by immunofluorescence predominantly to the proximal tubule in the diabetic renal cortex, while PCR confirmed the downregulation of ADH identified with mass spectrometry. Despite increased renal cortical tissue levels of retinol and RALDH1 in db/db versus control mice, all-trans-retinoic acid was significantly decreased in association with a significant decrease in PPARbeta/delta mRNA.Our results indicate that retinoic acid metabolism is significantly dysregulated in diabetic kidneys, and suggest that a shift in all-trans-retinoic acid metabolism is a novel feature in type 2 diabetic renal disease. Our observations provide novel insights into potential links between altered lipid metabolism and other gene networks controlled by retinoic acid in the diabetic kidney, and demonstrate the utility of using systems biology to gain new insights into diabetic nephropathy
Application of Silicon Photomultipliers to Positron Emission Tomography
Historically, positron emission tomography (PET) systems have been based on scintillation crystals coupled to photomultipliers tubes (PMTs). However, the limited quantum efficiency, bulkiness, and relatively high cost per unit surface area of PMTs, along with the growth of new applications for PET, offers opportunities for other photodetectors. Among these, small-animal scanners, hybrid PET/MRI systems, and incorporation of time-of-flight information are of particular interest and require low-cost, compact, fast, and magnetic field compatible photodetectors. With high quantum efficiency and compact structure, avalanche photodiodes (APDs) overcome several of the drawbacks of PMTs, but this is offset by degraded signal-to-noise and timing properties. Silicon photomultipliers (SiPMs) offer an alternative solution, combining many of the advantages of PMTs and APDs. They have high gain, excellent timing properties and are insensitive to magnetic fields. At the present time, SiPM technology is rapidly developing and therefore an investigation into optimal design and operating conditions is underway together with detailed characterization of SiPM-based PET detectors. Published data are extremely promising and show good energy and timing resolution, as well as the ability to decode small scintillator arrays. SiPMs clearly have the potential to be the photodetector of choice for some, or even perhaps most, PET systems
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