Smart Rocks and Wireless Communication System for Real-Time Monitoring and Mitigation of Bridge Scour -- A Proof-of-Concept Study

This study aims to integrate commercial measurement and communication components into a scour monitoring system with magnets or electronics embedded in smart rocks, and evaluate and improve its performance in laboratory and field conditions for the movement of smart rocks. Properly-designed smart rocks were found to be automatically rolled into the very bottom of a scour hole and can give critical information about the maximum scour depth and effectiveness of rip-rap mitigation strategies. Four types of smart rock technologies were investigated in this proof-of-concept phase of study, including passive with embedded magnets, active with magneto-inductive communication, active with controllable magnet rotation, and active with acoustic communication. Their performances were evaluated against three criteria: 1) movement accuracy within 0.5 m, 2) transmission distance between 5 and 30 m, and 3) at least one measurement every 15 minutes. Test results demonstrated that the proposed smart rocks are cost-effective, viable technologies for bridge scour monitoring

Manipulation of Ca+ Ions in Penning Traps

The long term aim of this work is to study the suitability of using laser cooled Ca+ ions in Penning traps as the basic components of a quantum computer. A great deal of progress in the field of quantum computing has been made in recent years with laser cooled ions stored in radio frequency ion traps. Building a useful quantum computer with trapped ions is however extremely challenging. Penning traps offer some possible benefits over radio frequency traps. They also create some additional difficulties. The potential advantages and disadvantages of Penning traps are discussed throughout the thesis. We show that we are able to overcome the problems associated with laser cooling in Penning traps, and have trapped single ions for extended periods of time. Pairs of Ca+ ions have been aligned along the axis of a Penning trap, and have been optically resolved. A novel Penning trap array based on PCB boards has been developed. A prototype was built and tested, along with the electronics required to shuttle ions between different sub-traps. Ions have been shuttled a distance of 10 mm in 2.5 μs. A return trip efficiency of up to 75% was seen. A quantum effect – J-state mixing caused by large magnetic fields – has been observed for the first time in single atomic ions. The magnetic field causes a forbidden [Delta]J = 2 transition to become weakly allowed. This effect is of general interest in atomic physics, and is also very relevant for quantum computation studies. A quantitative prediction of the magnitude of the J-mixing effect has been derived theoretically. This is compared to experimental data, and is found to be in excellent qualitative and good quantitative agreement

Dosimetry of Photon and Proton MRI Guided Radiotherapy Beams using Silicon Array Dosimeters

The integration of online magnetic resonance imaging (MRI) with photon and pro-ton radiotherapy has potential to overcome the soft tissue contrast limitations of the current standard of care kV-image guided radiotherapy in some challenging treat-ment sites. By directly visualising soft tissue targets and organs at risk, removing the dependence on surrogates for image guidance, it is expected there will be a decrease in the geometric uncertainties related to daily patient setup. This new approach to image guided radiotherapy presents unique challenges due to the permanent mag-netic field of the integrated MRI unit. The trajectory of charged particles including dose depositing secondary electrons are perturbed by the magnetic field, adding to the challenge of calculating the patient dosimetry and validating the calculation with measurement as is standard practice in radiotherapy. The magnetic field may also effect the operation and response of radiation detectors and a method of accurately characterising the influence of the magnetic field on detector response and operation is required. This thesis reports progress made towards real time high spatial resolution dosime-try of photon and proton MRI guided radiotherapy beams using novel monolithic silicon detectors designed at the Centre for Medical Radiation Physics (CMRP). One challenge in experimentally characterising the magnetic field effects on a radiation detectors operation is how to perform dosimetry measurements with and without a magnetic field of varying strength and orientation from a single radiation source as this is not feasible on existing MRI linacs with a permanent magnetic field of fixed strength. A bespoke semi-portable magnet device was developed to meet this need. The device employs an adjustable iron yoke and focusing cones to vary the magnetic field of the central volume, a 0.3 T field can be achieved for volume to 10 x 10 x 10 cm3 and up to a 1.2 T for a volume of at least 3 x 3 x 3 cm3. The device is de-signed to be used with a clinical linear accelerator in both inline and perpendicular magnetic field orientations to meet the challenge of detector characterisation. The performance of the magnetic field generated by the device was within ±2 % of finite element modelling predictions of all configurations tested