U622490.pdf (74.65 MB)
X-ray imaging and spectroscopy with charge coupled devices.
thesisposted on 2015-11-19, 09:17 authored by David H. Lumb
Recent advances in X-ray astronomy which have been obtained by the employment of imaging detectors are noted. The application of several types of devices to imaging at the focal plane of future space-borne X-ray telescopes is reviewed, and the Charge Coupled Device (CCD) is shown to be competitive with other imaging spectrometers. A review of some important principles of CCD operation and fabrication is presented. A description of the apparatus used for the experimental measurements performed for this work is presented. An investigation into the optimum bias levels of the output amplifier is described. The various contributions of different noise sources are assessed, and it is shown that in good quality CCD imagers, when operated in a cooled slow-scan mode, the noise of the output transistors is the dominant noise source. An analysis of different signal processing amplifiers is presented, and measures to maximise the signal-to-noise ratio are highlighted. Contrary to original expectations, the CCD X-ray energy resolution is shown not to be determined by the electronic noise alone. The processes of signal charge collection are considered, and it is shown that the diffusion of charge from a field-free region in the substrate causes partial charge events to be recorded. The measurement of the amount of charge detected for different device structures and X-ray energies is seen to be in good agreement with the predictions of the theoretical model. Changes to the CCD architecture to alleviate the degrading effects of diffusion are discussed, and the likely performance of future generations of X-ray imaging CCD's in astronomical applications is examined.
Date of award1983-01-01
Author affiliationPhysics and Astronomy
Awarding institutionUniversity of Leicester