Prof. M. Zahangir Kabir Profile

Prof. M. Zahangir Kabir

Assistant Professor at Concordia Univ

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Author

Publications (9)

Proceedings Article | 4 April 2022 Presentation

Energy resolution of amorphous selenium detectors: conventional vs unipolar charge sensing

Ahmet Camlica, Denny Lee, Hyunsuk Jang, M. Zahangir Kabir, Karim Karim

Proceedings Volume PC12031, PC120310G (2022) https://doi.org/10.1117/12.2613030

KEYWORDS: Sensors, Selenium, Photon counting, Electric field sensors, Spatial resolution, Time metrology, Surgery, Spectroscopy, Spectroscopes, Single photon

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Proceedings Article | 16 March 2020 Paper

Performance of amorphous selenium-based unipolar charge sensing detector for photon counting x-ray imaging

Ahmet Camlica, Denny Lee, Hyunsuk Jang, Salman Arnab, Yuan Fang, M. Kabir, Karim Karim

Proceedings Volume 11312, 113120G (2020) https://doi.org/10.1117/12.2550318

KEYWORDS: Sensors, Electrodes, Signal detection, Photon counting, Selenium, Photoresistors, Electric field sensors, Near field, X-ray imaging, Photodetectors

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Proceedings Article | 19 March 2010 Paper

Investigation of ghosting recovery techniques and mechanisms in multilayer selenium x-ray detector structures under low bias

S. Mahmood, M. Kabir, O. Tousignant, J. Greenspan, M. Mokam

Proceedings Volume 7622, 762216 (2010) https://doi.org/10.1117/12.844034

KEYWORDS: X-rays, Electrons, X-ray detectors, Sensors, Metals, Selenium, Photoresistors, Electrodes, Mammography, X-ray imaging

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Proceedings Article | 14 March 2009 Paper

Ghosting and its recovery mechanisms in multilayer selenium detectors for mammography

S. Mahmood, M. Kabir, O. Tousignant, H. Mani

Proceedings Volume 7258, 725860 (2009) https://doi.org/10.1117/12.812261

KEYWORDS: X-rays, Sensors, Electrons, X-ray detectors, Photoresistors, Mammography, Selenium, X-ray imaging, Electric field sensors, Electrodes

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Proceedings Article | 18 March 2008 Paper

Modeling of dark current and ghosting in multilayer amorphous selenium x-ray detectors

M. Kabir, F. Manouchehri, S. Mahmood, V. Devabhaktuni, O. Tousignant, H. Mani, J. Greenspan, P. Botka

Proceedings Volume 6913, 69133U (2008) https://doi.org/10.1117/12.770697

KEYWORDS: X-rays, Sensors, X-ray detectors, Electrons, Data modeling, Photoresistors, X-ray imaging, Metals, Electric field sensors, Electrodes

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A theoretical model for describing the bias-dependent transient behavior of dark current in multilayer amorphous selenium (a-Se) detectors has been developed by solving the trapping rate equations and Poisson's equation in the a-Se layer. The transient dark currents in these detectors are measured and the proposed dark model is compared with the measured data. The model shows a very good agreement with the experimental results. It has been found that the dark current is mainly controlled by the Schottky emission of holes from the metal/a-Se contact. The space charge build-up due to the hole injection and trapping in the blocking layer reduces the internal field at the metal/a-Se interface of positive side and thus the dark current eventually is limited by the space charge. It has been found that the electric fields at the metal contacts reduce to 20-30% of the applied field (applied voltage/thickness). The comparison of the model with the experimental data estimates some important properties (e.g., trap center concentrations, space charges, and effective barrier heights) of the blocking layers of the multilayer detectors. The dependence of the X-ray sensitivity of multilayer a-Se X-ray imaging detectors on repeated X-ray exposures is studied by considering accumulated trapped charges and their effects (trap filling, recombination, electric field profile, electric field dependent electron-hole pair creation), the carrier transport in the blocking layers, X-ray induced metastable deep trap center generations, and the effects of dark current. We simultaneously solve the continuity equations for both holes and electrons, trapping rate equations, and the Poisson's equation across the photoconductor for a step X-ray exposure by the Backward Euler finite difference method. The theoretical model shows a very good agreement with the experimental relative sensitivity versus cumulative X-ray exposure characteristics. The electric field distribution across the multilayer detector and the dark current density under repeated exposures are also estimated.

Proceedings Article | 20 April 2005 Paper

Ghosting mechanisms in a-Se based direct conversion x-ray image sensors

M. Zahangir Kabir, M. Yunus, S. Kasap, Olivier Tousignant, Habib Mani, Philippe Gauthier

Proceedings Volume 5745, (2005) https://doi.org/10.1117/12.594692

KEYWORDS: X-rays, X-ray detectors, Sensors, X-ray imaging, Electrons, Photoresistors, Image sensors, Electric field sensors, Electrodes, Data modeling

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Proceedings Article | 6 May 2004 Paper

Dependence of x-ray sensitivity of direct conversion x-ray detectors on x-ray exposure and exposure history

Mohammad Kabir, Mohammad Yunus, Safa Kasap

Proceedings Volume 5368, (2004) https://doi.org/10.1117/12.535546

KEYWORDS: X-rays, X-ray detectors, Sensors, Photoresistors, X-ray imaging, Chest, Electrons, Electrodes, Image sensors, Electric field sensors

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Proceedings Article | 5 June 2003 Paper

Charge transport and trapping-limited sensitivity and resolution of pixellated x-ray image detectors

Mohammad Kabir, Safa Kasap

Proceedings Volume 5030, (2003) https://doi.org/10.1117/12.479947

KEYWORDS: Electrodes, X-rays, Sensors, Modulation transfer functions, Photoresistors, X-ray detectors, Electrons, Image resolution, Composites, X-ray imaging

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Proceedings Article | 3 May 2002 Paper

Dependence of the DQE of photoconductive x-ray detectors on charge transport and trapping

Mohammad Kabir, Safa Kasap

Proceedings Volume 4682, (2002) https://doi.org/10.1117/12.465590

KEYWORDS: Sensors, X-rays, Photoresistors, Quantum efficiency, X-ray detectors, Medical imaging, Signal attenuation, Interference (communication), Physics, CRTs

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Showing 5 of 9 publications

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