Physics
- 2D electron gas at LaAlO3/SrTiO3 interface
- Study response of silicon on insulator (SOI) microdosimeter to low energy ions of Galactic Cosmic Rays "
- Radiation protection of Australian astronauts: New materials for space suite and their investigation at HIMAC using microdosimetry (Space Medicine)
- Response of multiple microdosimeter system – The Octobox to PuBe neutron source
- Radiation protection of Australian astronauts: New materials for space suite and their investigation at HIMAC using microdosimetry (Space Medicine)
- Mixed gamma/neutron field in-vivo dosimetry using Metal-Oxide Semiconductor Field-Effect Transistor for Accelerator-Based Boron Neutron Capture Therapy
- Development of innovative detector for Diffused Alpha Radiaion Therapy (DaRT)
- Range verification of ions and protons in particle therapy: DMG detector Monte Carlo simulations
Project description
Despite intensive research, the two-dimensional electron gas (2DEG) interfacial conductivity between insulating perovskite oxides SrTiO3 (STO) and LaAlO3 (LAO) is not understood. There is no universally agreed upon theory able to account for diverse properties of 2DEG. Some of these properties include semiconductor-like field-effect control of conductivity, tunable superconductivity, and ferromagnetism. This project will explore the origin and related properties, which can be controlled, with a view of possible applications.
Project description
Space environments present a dangerous environment for both astronauts and electrical equipment in terms of radiation damage. At the altitude of the ISS, the main radiation sources are Galactic Cosmic Rays (GCR), made up of approximately 87% protons, 12% alpha particles and 1% heavy ions (e.g. C, O, Ne, Si, Fe) with a large energy spectrum, up to hundreds of GeV/u. Although heavier ions’ abundance is much lower than protons and alpha particles, their high LET can cause significant damage to electronics and lead to radiobiological effects to the astronauts. Microdosimetry is an extremely useful technique, used for dosimetry in unknown mixed radiation fields typical of space and aviation, as well as in hadron therapy [1]. In this project, the response of a Mushroom silicon microdosimeter with 3D sensitive volumes (SVs) developed by CMRP [2] to different low energy ions (Ne-20, Ti-48, Fe-56) will be investigated to understand dose received by astronauts during Extra Vehicular Activities (EVA). Experiments will be performed at Department of Nuclear Physics in the Research School of Physics and Engineering at the Australian National University (ANU), Canberra. The project will lead to several publications.
Research
Centre for Medical Radiation Physics
Principal supervisor
Principal supervisor
Project description
Nowadays, it is becoming increasingly important when space exploration encompassing a broad range of human and robotic missions including missions to Moon, Mars and beyond. Spacecraft and astronauts are exposed to a variety of penetrating energetic radiation in space which have adverse effects on astronauts and microelectronic devices. There are three naturally occurring sources of particle radiation in space including: trapped radiation, Galactic Cosmic Rays (GCR) and Solar Particle Events (SPEs). A very stringent requirement on the optimization process of the cost-effective spacecraft design is necessary as well as radiobiological/microdosimetry experiments aiming to measure the relative biological effectiveness (RBE) of heavy ions are urgently needed to benchmark the current models. Microdosimetry is an extremely useful technique, used for dosimetry in unknown mixed radiation fields typical of space and aviation, as well as in hadron therapy [1]. By measuring the microdosimetric spectra of a radiation field, the dose equivalent, H and the quality factor, Q can be obtained. This study will involve testing different novel shielding materials for spacecraft and spacesuit using 3D Mushroom microdosimeter. The experiments will be carried out at Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. Geant4 simulation will be performed to optimise the shielding design and to compare with experimental results. This work is a continuing strong project at CMRP and will lead to several publications.
Research
Centre for Medical Radiation Physics
Principal supervisor
Principal supervisor
Project description
An important need in neutron dosimetry for radiation protection is a dosimeter with an energy independent response over a broad energy range. Such dosimeters are of great importance for nuclear accident and military dosimetry. The dosimeter should be reliable and capable to provide dose rate and total neutron dose equivalent in a mixed gamma-neutron radiation field. Neutron detection with silicon detectors is usually performed indirectly with the assistance of a converter material that converts neutrons into charged particles. The material selected for the converter is usually dependent on the neutron energy under consideration. For thermal neutrons, B-10 can be used to convert thermal neutrons to alpha particles and recoil Li-7 nuclei. For fast neutrons, a hydrogenous material such as polyethylene (PE) can be used to convert fast neutrons to protons through elastic scattering reactions. Microdosimetry is a very useful technique, used for dosimetry in unknown mixed radiation fields generated from neutrons. The Centre for Medical Radiation Physics (CMRP), at the University of Wollongong, Australia, has successfully developed SOI microdosimeter (Bridge and Mushroom microdosimeters) [1, 2]. They were successfully used for relative biological effectiveness (RBE) studies in proton and heavy ion therapy and for dose equivalent evaluation for radiation protection [3, 4]. However, due to a relatively small sensitive area of the developed sensors, they cannot be used efficiently for real time dosimetry in low dose rate radiation environments such as aviation and space, and reactor site. The CMRP has developed a new microdosimetry system, named Octobox, which allows multiple microdosimeters to be connected together while restricting electronic noise to levels typical of a single microdosimeter. This study will involve characterisation of the Octobox with PuBe 14 MeV neutron sources at CSIRO, ANSTO. The Octobox will be covered with different thicknesses of polyethylene converter to study neutron detection efficiency. This work will demonstrate ability of microdosimeter to measure in neutron field and will lead to a good publication.
Research
Centre for Medical Radiation Physics
Principal supervisor
Principal supervisor
Project description
Nowadays, it is becoming increasingly important when space exploration encompassing a broad range of human and robotic missions including missions to Moon, Mars and beyond. Spacecraft and astronauts are exposed to a variety of penetrating energetic radiation in space which have adverse effects on astronauts and microelectronic devices. There are three naturally occurring sources of particle radiation in space including: trapped radiation, Galactic Cosmic Rays (GCR) and Solar Particle Events (SPEs). A very stringent requirement on the optimization process of the cost-effective spacecraft design is necessary as well as radiobiological/microdosimetry experiments aiming to measure the relative biological effectiveness (RBE) of heavy ions are urgently needed to benchmark the current models. Microdosimetry is an extremely useful technique, used for dosimetry in unknown mixed radiation fields typical of space and aviation, as well as in hadron therapy [1]. By measuring the microdosimetric spectra of a radiation field, the dose equivalent, H and the quality factor, Q can be obtained. This study will involve testing different novel shielding materials for spacecraft and spacesuit using 3D Mushroom microdosimeter. The experiments will be carried out at Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. Geant4 simulation will be performed to optimise the shielding design and to compare with experimental results. This work is a continuing strong project at CMRP and will lead to several publications.
Research
Centre for Medical Radiation Physics
Principal supervisor
Principal supervisor
Project description
Boron Neutron Capture Therapy (BNCT) is a biologically-guided form of external beam radiotherapy, and an interdisciplinary approach to treat the most complex and challenging tumours by location and radioresistance. It is based on an injection of a drug carrying 10B and neutron irradiation. Due to thermal neutron capture (NC) in 10B, high LET α particle and recoiled 7Li nuclei with a few µm penetration range are emitted and constitute to the main source of dose in a tumour. Each BNCT system has its specific neutron energy spectrum extending from thermal to fast neutron (FN) range of up to a few MeV as well as γ contamination. Since the cross-section for NC is the highest for thermal neutrons, to reach deeper tumours epithermal neutrons are used to be thermalised within the patient at depth of the tumour. Production of epithermal neutron beam requires sophisticated moderation assembly [1, 2] and therefore, QA tools to measure the fluence and quality of the neutron beam entering the patient are crucial [3, 4]. At CMRP, we proposed a disposable, miniature semiconductor detector Metal Oxide Field Oxide Transistor (MOSFET) with different converters for in-vivo dosimetry of components of the BNCT epithermal neutron beam. MOSFET is attractive particularly due to its low voltage or passive operation; possibility sensitivity adjustment by biasing the gate during irradiation and/or thickness of the gate oxide (sensitive volume (SV)); small size of 0.6x0.8x0.35 mm3; ability for on-line readout or immediately after irradiation. Two converters were proposed above MOSFET - 10B and polyethylene (PE) as well as no converter geometry to measure fluence of thermal/epithermal neutrons, fast neutrons (FN), and γ components, respectively. This project will involve Geant4 simulations of the MOSFET response covered with 10B, polyethylene and without converter irradiated with epithermal neutron beam typical for accelerator based BNCT in free-air geometry and on the surface of a spherical water phantom.
Research
Centre for Medical Radiation Physics
Principal supervisor
Principal supervisor
Project description
Alpha particles are highly lethal to cancerous cells, creating complex double-strand DNA breaks. Only a few hits to the cell nucleus are required to kill the cancer cell. Diffusing alpha-emitters radiation therapy (DaRT) is a new brachytherapy method utilizing alpha particles to treat solid tumors with interstitial implantable radioactive sources of 224Ra which continually release 220Rn, 216Po and 212Pb atoms from their surface [1]. The atoms disperse inside the tumor, delivering a high dose through their alpha and beta decays. These atoms disperse a considerable distance from the 224Ra source in the tumor, leading to the formation of a high dose alpha radiation region [2]. Alpha emitting atoms which get out of the tumour enter the blood system and disperse in the entire body delivering a very low dose to most organs and reduced damage to the immediate vicinity of the tumor [1]. In traditional photon based brachytherapy, development of detectors for in vivo real time absorbed dose Quality Assurance (QA) is extremely important for improvement of clinical outcome [3, 4, 5] and is paramount for success of this technology. In DaRT, QA is more complicated as on top of in vivo absorbed dose measurements, understanding of Radiobiological Efficiency (RBE) of mixed alpha, beta radiation field is required. No in vivo real time QA for RBE and dose monitoring is available currently for DaRT. Development of such a system will accelerate clinical implementation of DaRT technology. Microdosimetry is a useful method to obtain the dose equivalent of any mixed radiation field, without prior knowledge of type of charged particles and their spectra. Regional microdosimetry is based on measuring the ionizing energy deposited in a micron sized volume with similar dimensions to biological cells. The deposition of energy, E, event by event in such a volume is called the lineal energy deposition (y): y=E/(<l>), where E is the energy deposited in a micron sized SV with a mean chord length <l> and the spectrum of stochastic events f(y) for all primary and secondary charged particles. The Centre for Medical Radiation Physics (CMRP), University of Wollongong, Australia, under leadership of Dist. Professor Anatoly Rozenfeld originated the concept of silicon microdosimetry from 1996 and since then, many successful development of silicon on insulator microdosimeters were carried out [6]. This project will focus on the development of innovative microdosimeter and instrumentation for DaRT QA and implementation in clinical studies with 224Ra source. Projects is in collaboration with St George Cancer Care Centre, Prince of Wales Hospital (POWH) and Alpha Tau company.
Research
Centre for Medical Radiation Physics
Principal supervisor
Principal supervisor
Project description
"Range/energy verification of protons and ions is important quality assurance in particle therapy. Small error in range can lead to underdosing of tumour or damage of organ at risk (OAR) which is often close to the tumour. Currently used range verification systems are based on multiple transmission ionization chambers which are bulky and expensive (https://www.iba-dosimetry.com/product/zebra/). CMRP recently proposed the silicon strip detector –dose magnifying glass (DMG) for proton range verification in a PMMA phantom that provide submillimetre spatial resolution [Debrot et al, 2018]. Project will lead to development of the phantom with embedded silicon strip detector with 256 channels or 512 channels and implementation to clinical practice. The same system will be used for temporal and spatial verification for pencil beam scanning (PBS) in the same phantom. Dual functionality of the system using the same DMG is a task to be solved by student. Development of multichannel readout system and software including graphic display is a part of this project. Experiments will be carried out at proton therapy facility in the USA (Mayo clinic or/and Florida University Proton therapy centre) and with one of the industrial company.
Research
Centre for Medical Radiation Physics