In recent years, high resolution x-ray detection systems have been used extensively in a variety of scientific fields such as protein crystallography, x-ray fluorescence analysis of substances (XRF), and particle physics studies. X-ray incidents are sensed and their energy measured by means of a semiconductor detector readout system. Each x-ray incident on a semiconductor diode creates electron-hole pairs which are transferred to the readout system and are then converted to a digital signal. X-ray energies vary greatly depending on the application. For instance, protein crystallography commonly uses x-rays with energy of around 12KeV. Small-angle x-ray scattering (SAXS) which is used in the Stanford Synchrotron Radiation Laboratory (SSRL) uses x-rays with energies of 8KeV and below. XRF applications generally employ a wide range of x-rays with energies as low as 200eV. The resolution of x-ray detection systems depend highly on the noise of the readout electronics. In order to be able to detect low energy levels, the noise of the readout system must be low. The goal of this project is to reduce the minimum noise level using new circuit techniques. A survey of literature on x-ray detector systems shows that current x-ray detector systems have a minimum noise of about 100ENC. Hopefully, this thesis will be able to reduce the noise of the readout system to below 50ENC.
Integrated Circuits Lab
Center for Integrated Systems
Stanford University