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Simulating charge transport to understand the spectral response of swept charge devices

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dc.contributor.author Athiray, P. S
dc.contributor.author Sreekumar, P
dc.contributor.author Narendranath, S
dc.contributor.author Gow, J. P. D
dc.date.accessioned 2020-11-17T14:17:33Z
dc.date.available 2020-11-17T14:17:33Z
dc.date.issued 2015-11
dc.identifier.citation Astronomy & Astrophysics, Vol. 583, A97 en_US
dc.identifier.issn 0004-6361
dc.identifier.uri http://prints.iiap.res.in/handle/2248/7135
dc.description Open Access © ESO http://dx.doi.org/10.1051/0004-6361/201526426 en_US
dc.description.abstract Context. Swept Charge Devices (SCD) are novel X-ray detectors optimized for improved spectral performance without any demand for active cooling. The Chandrayaan-1 X-ray Spectrometer (C1XS) experiment onboard the Chandrayaan-1 spacecraft used an array of SCDs to map the global surface elemental abundances on the Moon using the X-ray fluorescence (XRF) technique. The successful demonstration of SCDs in C1XS spurred an enhanced version of the spectrometer on Chandrayaan-2 using the next-generation SCD sensors. Aims. The objective of this paper is to demonstrate validation of a physical model developed to simulate X-ray photon interaction and charge transportation in a SCD. The model helps to understand and identify the origin of individual components that collectively contribute to the energy-dependent spectral response of the SCD. Furthermore, the model provides completeness to various calibration tasks, such as generating spectral matrices (RMFs – redistribution matrix files), estimating efficiency, optimizing event selection logic, and maximizing event recovery to improve photon-collection efficiency in SCDs. Methods. Charge generation and transportation in the SCD at different layers related to channel stops, field zones, and field-free zones due to photon interaction were computed using standard drift and diffusion equations. Charge collected in the buried channel due to photon interaction in different volumes of the detector was computed by assuming a Gaussian radial profile of the charge cloud. The collected charge was processed further to simulate both diagonal clocking read-out, which is a novel design exclusive for SCDs, and event selection logic to construct the energy spectrum. Results. We compare simulation results of the SCD CCD54 with measurements obtained during the ground calibration of C1XS and clearly demonstrate that our model reproduces all the major spectral features seen in calibration data. We also describe our understanding of interactions at different layers of SCD that contribute to the observed spectrum. Using simulation results, we identify the origin of different spectral features and quantify their contributions. en_US
dc.language.iso en en_US
dc.publisher EDP Sciences en_US
dc.subject X-rays: general en_US
dc.subject Instrumentation: detectors en_US
dc.subject Methods: numerical en_US
dc.title Simulating charge transport to understand the spectral response of swept charge devices en_US
dc.type Article en_US


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