Design and implementation of an x-ray colour detection system using the Medipix3RX

Abstract

In this work the design and implementation of an x-ray imager system is presented. The design features a direct x-ray detection scheme by making use of a hybrid pixel detector (Medipix3RX). Taking advantage of the capabilities of the Medipix3RX, such as a high resolution, zero dead-time, single photon detection, charge-sharing mode and colour mode. The imager has a better resolution and higher sensitivity compared to using traditional indirect detection schemes. A detailed description of the design process and implementation of the system is presented, which consists of a vacuum chamber containing the sensor, an electronic board for temperature management, conditioning and readout of the sensor and a data processing unit which also handles network connection and communication with clients by acting as a server. A field programmable gate array (FPGA) device is used to implement the readout protocol for the Medipix3RX. Apart from the readout, the FPGA can perform complex image processing functions such as histogram, profiling and image compression at high speeds. The temperature of the sensor is monitored and controlled through a PID algorithm making use of a Peltier cooler, improving the energy resolution and response stability of the sensor. Without implementing data compression techniques, the system is capable of transferring 680 profiles/s or 240 images/s in a continuous mode. A detailed analysis of equalization procedures and tests for all the operation modes of the sensor are presented in this work. Different equalization methods were tested, such as using electronic noise, injected pulses and x-ray photons to perform the equalization. The results of the trade-off of equalization time versus energy resolution are analysed and discussed. One of the tested applications of the system is as an x-ray beam position monitor (XBPM) device for synchrotron light source experiments. The XBPM allows a non-destructive real time measurement of the beam position, size and intensity. A Kapton foil is placed in the beam path scattering radiation towards a pinhole camera setup that allows the sensor to obtain an image of the beam. By using profiles of the synchrotron x-ray beam, high frequency movement of the beam position can be studied. Experiments testing the characteristics of the Medipix3RX are shown in this work. The colour mode capability and its limitations were tested and found to be able to recognize elements by their characteristic x-ray fluorescence. The Medipix3RX dependence to temperature was measured, showing the necessity of controlling the sensor's temperature.

Date of Award	1 Aug 2018
Original language	English
Awarding Institution	The University of Manchester
Supervisor	David Foster (Supervisor) & Roelof Van Silfhout (Supervisor)