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Title: Modeling of photocurrent and lag signals in amorphous selenium x-ray detectors

A mathematical model for transient photocurrent and lag signal in x-ray imaging detectors has been developed by considering charge carrier trapping and detrapping in the energy distributed defect states under exponentially distributed carrier generation across the photoconductor. The model for the transient and steady-state carrier distributions and hence the photocurrent has been developed by solving the carrier continuity equation for both holes and electrons. The residual (commonly known as lag signal) current is modeled by solving the trapping rate equations considering the thermal release and trap filling effects. The model is applied to amorphous selenium (a-Se) detectors for both chest radiography and mammography. The authors analyze the dependence of the residual current on various factors, such as x-ray exposure, applied electric field, and temperature. The electron trapping and detrapping mostly determines the residual current in a-Se detectors. The lag signal is more prominent in chest radiographic detector than in mammographic detectors. The model calculations are compared with the published experimental data and show a very good agreement.
Authors:
;  [1]
  1. Department of Electrical and Computer Engineering, Concordia University, 1455 Blvd. de Maisonneuve West, Montreal, Quebec H3G 1M8 (Canada)
Publication Date:
OSTI Identifier:
22479711
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films; Journal Volume: 33; Journal Issue: 4; Other Information: (c) 2015 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; BIOMEDICAL RADIOGRAPHY; CHEST; MAMMARY GLANDS; MATHEMATICAL MODELS; SELENIUM; SIGNALS; SIMULATION; X RADIATION