High speed imaging using a capacitive division technique

The charge division technique is a simple concept used in photon-counting imaging detectors to determine one or two-dimensional event coordinates by location of the centroid of the charge cloud generated in the detector. Traditional devices, such as the resistive anode and wedge-and-strip anode, utilize resistive and geometric methods respectively to implement this technique, enabling them to achieve reasonably good spatial resolution at moderate event rates using a low electronic channel count. We describe the Capacitive Division Image Readout (C-DIR), a simple method of implementing charge division readout with major performance advantages and which is simple and economical to construct. C-DIR utilizes three elements; (i) a resistive layer providing event charge localization and DC signal current return path, (ii) a dielectric substrate which provides electrical isolation from the detector voltages and capacitively couples the event transient signal to the third element, (iii) an array of capacitively coupled electrodes which divides the signal among several charge measurement nodes. The purely capacitive signal paths have high bandwidth and present a low capacitive load to the preamplifiers, allowing an unprecedented combination of excellent event time and spatial resolution. We present simulations and experimental results demonstrating the performance advantages of the device and discuss various readout design alternatives, optimized electronics and potential applications. (C) 2011 Elsevier B.V. All rights reserved.