CdTe/CdZnTe pixellated radiation detector

The work in this thesis is focused on the study of CdTe/CdZnTe pixellated detectors. During this research, three main aspects have been covered in the development and application of these detectors. These broadly describe the fabrication process, characterisation of energy spectrum and imaging performance, and application of these detectors in industrial X-ray tomography. The first topic to be discussed in detail is the fabrication process of CZT pixellated detectors. This is a process that involves many steps, such as cutting the sample, cleaning the substrate, writing a masking pattern with e-beam lithography, photolithography, cleaning the surface using oxygen ash, metallisation and removing the resin in the development stage. However, these stages were grouped into three major steps to give a clearer image on what was going on throughout the fabrication process. They are grouped as sample preparation, pixellated structure deposition and sample passivation. The dry ash processing had been carried out in the James Watt Nano Fabrication Centre at Glasgow University. The motivation for the development of the dry ash process was to reduce the level of leakage current on the surface of the device so that a good energy spectrum resolution could be obtained. The research showed that a passivation technique using a layer of SiN as well as an oxygen plasma oxidation layer provided low leakage current in the pixel and lower interpixel leakage current. A good performance in energy spectrum was achieved after performing passivation. The FWHM of Co-57 is 10.78 keV where energy resolution is 8.8%. The second area covered in this thesis is the energy spectrum and imaging performance of pixellated CdTe Timepix detector. Two pitches of pixel have been studied namely, 110 µm pitch and 55 µm pitch. The work on characterisations has been performed with polychromatic and monoenergetic beams of X-rays. In both the Counting mode and ToT (Time over Threshold) mode it was discovered that there were large effects on performance due to charge sharing and fluorescence. In terms of image quality the result of MTF was found to be as expected, around half the contrast transfer (30%) recorded for 110 µm compared to 55 µm pixel detector at 4 lp/mm. Another field of interest explored was the defect factor. For this to be achieved studies had been performed in positive and negative bias of CdTe Timepix detector. The results showed that the presence of defects in the material affects the performance of the energy resolution of CdTe Timepix detector. The third area covered in this thesis was the study of CdTe Timepix detector for use in Industrial X-ray tomography. To give the sensor the best performance it could offer in capturing images for industrial use, work had been carried to optimise the technique for producing good quality images. The hardware setup involved the careful alignment all of the components of the system and the introduction of a collimator. In addition the sofware software it dealt with the flat field correction, noise filter and data projection algorithm. The results show that the CdTe Timepix detector can be used as a good detector for X-ray tomography. Here, the 3D of volume rendering studies had been performed to a pencil as a sample and voltage regulator. The result of the pencil image in volume rendering showed that CdTe Timepix detector had successfully provided good image for different density profile of material (paint coating, wooden and carbon). Not only that, another important finding besides the excellent image produced was that the effect of beam hardening, ring artifact and metal shrank artifact in tomogram of voltage regulator had been eliminated successfully

Development of a distillation column scanning apparatus using gamma-ray tomography

Process column and reactor scanning apparatus are process diagnostics instrumentation and is required to be brought to the plant and used by specialized personnel. Radioisotope gauges have been used for this type of measurements for more than 50 years, and is still widely used. Data is normally recorded for subsequent off-line analysis. Often multiple measurements are carried out in a scan for instance by manually lowering a source down one side of a vessel and a detector down the other to build up a vertical density profile. A trained operator can then easily interpret this signature and provide information on the state of the process as well as the process vessel

Smart bus terminal using infrared identification

Significant increase in vehicles inside city areas results in adding more troubles to that section of citizens using public transportation network as their primary source of travelling. This specific section of society is a victim of this rapid growing traffic volume and causing a huge waste of time due to not having proper information of required bus current position. The problem results in not only wasting of time but also mentally unhappy and tensed citizens. Nowadays, passengers want to get the clear information of their desired buses at station, like the position and estimated time of arrival of bus etc. The implementation of Intelligent Transportation Systems (ITS) nowadays has developed to the incredible extent. This system is proved that is to be very useful not only in the safety purpose but also it eases to any users. The combination with infrared can use to monitor and identify the location of certain bus and present it the information to the bus passenger on LCD at terminal by using the simulation. The tag and the reader of the infrared devices are wirelessly connected and control station can authorize not only to monitor the bus but can also identify the particular of the bus such as bus registration number and bus company names

Automatic gate sensors

Advancement in technology is a live of example of this concept. As it is too difficult for a common man to think earlier that can a gate could be opened automatically without any manual work. Also the types included in this system are vast in market. So the technological advancement is required to combine all such features in a single system. Also the system should be easily operatable by any beginner or any incoherent person. It also provides security as it’s the major requirement from any gate by any user, without security the system is of no use. So, security is also a non-comprisable feature of this system. One more problem related to gate is that the user should be reliable on others also the security feature can be compromised due to innumerable reasons that occur related to humans. First gate introduced was completely manual and humans were completely required to open such gates. Then came the next system used on toll booths that opened the gate after the click of the operator over switch. Later came the system that only recognized any type of moving vehicle and then opened the gate using the system, IR detector was used in this type of system. The next system used in the type was the system that only allowed the authorized user the access and opened the gate required to be opened for the unauthorized user. The main task of this system is to reduce manual work and bring technological advancement in the society. At last the system with some modifications from the above system was introduced like opening of gate by mobile application rather than opening it manually. This helps in reducing maximum of the physical work. The cost expenditure on machine is one time which is bearable whereas the cost expenditure on human is recurring and increases with time

Stability test for NaI(TI) scintillation detector

The objective of this endeavor is to present a brief description of a stability test performed on a NaI(TI) scintillation detector to determine its most suitable operating voltage range. The Chi-square test is used to check the reliability of the data obtained. Some test results are included

Advance data logging software for gamma-ray scanning technology

Gamma-ray scanning is a non-destructive testing method based on gamma-ray absorption principle. It is currently used in oil refineries, gas processing plants, chemical, petrochemical and oleo-chemicals installation. The technique provides a visible representation of the true nature of the operating characteristics of a process column and identifies internal damage while the column is in operation [1,5]. Meanwhile, Vasquez et al. [2] had developed a scintillator detector system for gamma-ray scanning of industrial distillation columns. They applied CsI(TI) counter as detector instead of commercial NaI(TI) counter for gamma-ray and Co-60 sealed source as a gamma-ray emitter. The system has been used to scan a simulated model of a tray-type distillation column. A comparison results of gamma-ray scan on a simulated column using NaI(TI) and Cs(TI) counters have been made. The results showed that Cs(TI) detector presented similar profiles of column as NaI(TI) detector. However, the efficiency of Cs(TI) was 3% and is considered lower compared to that of NaI(TI) (30%). Overall, the Cs(TI) detector can be alternatively used for gamma-ray scanning technique

Image fusion of dual-modal tomography (electrical capacitance and optical) for solid/gas flow

The paper presents a novel method of combining dual modality electrical capacitance and optical tomography for applications in monitoring and investigating solid/gas ow. The objective of this method is to obtain a good quality image of the full-scale concentration distribution of solid/gas ow. A new image reconstruction algo- rithm fused the dual modality images is developed and evaluated

Dual modality tomography: the image analysis of forward problem

The paper presents the novel idea in process tomography which is the combination of dual modality; electrical capacitance and optical tomography for monitoring solid/gas flow measurement. Dual Modality Tomography (DMT) system consists of eight electrodes of capacitance sensor and 16 pairs of optical sensor in one sensor plane. The data obtained from both sensors were inseries transfer to PC with control and triggered by data acquisition system. The data obtained from both sensors will then be reconstructed into image using Linear Back Projection or Iterative Reconstruction Algorithm. In this project, the DMT produces an image fusion, which is developed based on the adjustment of pixel values and the detection region of pixel images reconstruction between capacitance and optical tomography sensor. Series of error analyses will determine the feasibility of the DMT sensors to perform as an instrument in solid flow visualization

Introduction to gamma-ray transmission tomography

Conventional gamma ray computed tomography methods measure the attenuation of an incident beam that travels in a straight path through an object. The incident beam is partially absorbed and scattered in the object of interest, with the remaining transmitted radiation traveling in a straight line to the detector. This is the principle of gamma -ray transmission tomography. The amount of attenuation is related to the atomic number of the phases distributed in the object, as well as their density distributions. As with radiography, access to both side s of the structure is required. Any changes in the transmitted intensity to the adjacent detector will reflect the change s of the mass per unit area of the material