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  • 1. AIP Bi-Annual Postgraduate Conference 7th – 8th September 2001 Anapana Ridge, 38 Gilchrist Road, LESMURDIE WA Book of Abstracts Edited by Dr. Christine Creagh Murdoch University 1
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  • 3. Gravitational wave background from coalescing binary black holes Xing-Jiang Zhu ( or Supervisor: Prof. David Blair Gravitational wave group, UWA Abstract: Gravitational waves, ripples in the curvature of space-time, are predicted by Einstein’s theory of general relativity. Strong evidences for their existence have come from astronomical observations of the orbital decay of binary pulsars. The first unambiguous direct detection of gravitational waves is expected in a few years with the advent of advanced interferometric detectors. A stochastic gravitational wave background signal can be produced by a cosmological population of astrophysical sources distributed throughout the Universe. This work considers the gravitational wave background signal produced by inspiraling binary black hole systems, expected to be one of the most energetic emitters of gravitational waves. This signal is important as it could provide information on the average properties and distribution of black holes throughout the cosmos. It could also mask the much sought primordial signal from the earliest epochs of the Universe. In this talk I firstly introduce gravitational wave sources and detectors before discussing the concept of an astrophysical gravitational wave background signal. I finish by presenting recent published results on the background signal from coalescing binary black hole systems. 3
  • 4. Three-mode opto-acoustic parametric interaction in a coupled optical cavity Xu Chen ( Supervisors: Chunnong Zhao, Li Ju, David Blair Gravity group, University of Western Australia Abstract: Advanced laser interferometric gravitational wave detectors require high optical power in order to improve the coupling between the gravitational wave signal and the optical field. However, interferometers with high density optical fields suffer the possibility of three-mode opto-acoustic parametric instabilities. The three-mode parametric interactions can be considered as a scattering process between two optical modes and an acoustic mode. The mirror with an acoustic resonator frequency scatters the high power incident light into upper and lower sidebands. If the frequency different between two optical modes is equal to the mirror acoustic resonant frequency, it can cause an amplification of the acoustic mode and cause the gravitation detectors to go out of operation. My study is investigating three-mode parametric interactions on a tabletop experiment with a coupled cavity (a membrane in the middle of a simple cavity). The tabletop experiment provides a test bed for three-mode parametric interaction. By studying these exciting new interactions, we can build an opto-acoustic parametric amplifier which will amplify sound with light. 4
  • 5. Quantum Mechanics? No Dice! Bruce M Hartley ( Supervisor : Winthrop Professor Ian McArthur Field Theory and Quantum Gravity Research Group University of Western Australia Abstract: For over eighty years the standard model of quantum theory has been that of the Copenhagen School. It is based on the Bohr model of the atom, the wave nature of particles proposed by de Broglie, the uncertainly relationships of Heisenberg, and Planck and Einstein’s quantisation of the electromagnetic field. A statistical interpretation of measurement developed, which precluded the ability to track particles. Yet there was a competing proposal based on a similar picture of atomic phenomena but with the ability to track particles and which doesn’t conflict with any experimental data. This deterministic interpretation was proposed by deBroglie in the 1920s and developed by Bohm from the 1950s. It is based on the Schrödinger equation and is now known as Bohmian Mechanics and is an alternative to the Copenhagen interpretation. It is considered, by its adherents, as the most complete expression of atomic quantum theory. It has recently been applied in the analysis of the basic physical observations which underlie the concept of quantisation of the electromagnetic field into photons. The analysis shows that, in a deterministic framework, photon quantisation is unnecessary for interpreting the key experiments of the photoelectric effect and Compton scatter. I will describe the how the de Broglie Bohm picture of quantum mechanics is derived from solutions of the Schrödinger Equation by introducing a new potential and how that is used to track particle. I will use the double slit experiment to illustrate the concepts of quantum potential and the tracking of particles. The key concept of quantum potential has as yet no physical interpretation. I will make a physically consistent conjecture for an interpretation, based on electromagnetic fields in atomic interactions. I will then propose a method of testing this conjecture using numerical modelling. 5
  • 6. Roberts Linkage as a very low frequency suspension and control element in 3rd generation gravitational wave detectors Siddartha S Verma ( Supervisors: Prof. David G. Blair, Assoc. Prof. Chunnong Zhao, Assoc. Prof. Li Ju, Research Australian International Gravitational Research Center (AIGRC) School of Physics, UWA Abstract: Next generation gravitational wave detectors are aiming for very low frequency stage operation. While advanced second generation instruments are limited to greater than 10 Hz operation, third generation projects are aiming to access the frequency region between 1 Hz to 10 Hz. To achieve sensitivity in this regime requires even lower frequency suspension and control stages than offered in current instruments. Here we demonstrate a Roberts linkage vibration isolation stage which may benefit such projects. It emulates a very low frequency pendulum in a compact stage, and has the added benefit of allowing low frequency position control using electrically controlled thermal expansion of its suspension wires. This method attenuates the seismic translational noise through actuation. We show here that using multiple parallel wires and a thermal offset the radiative response time can be increased, and that the corner frequency in the frequency response of the vibration isolation stage can be raised to 100 mHz or more. 6
  • 7. Excitation of spin waves in a magnetic nano-stripe array by direct injection of microwave currents using a coplanar probe. Crosby Chang ( Supervisor: Dr. Mikhail Kostylev Condensed Matter Group School of Physics, University of Western Australia Abstract: Magnetic nano-stripe (MNS) arrays show promising technological applications in microwave filtering, delay, and magnetic memory storage. One way to characterise the dynamic magnetic properties of magnetic materials is by performing ferromagnetic resonance (FMR) experiments. The non-uniform spin wave modes (SSWMs) in thin magnetic films and nanostructures provide important information about their magnetic properties. Very often they are lacking in the recorded FMR spectra for symmetry reasons. In this work, we perform FMR experiments on a MNS array using a new method; by direct injection of microwave currents into the MNS array using Picoprobe®, which is a sub-millimetre sized microwave coplanar probe. The probe we used has a ground-signal -ground tip width of 400 microns. The probe is mounted on a high precision translation stage with 3 degrees of translation freedom and 1 degree of rotation freedom. A custom-made probe station has been made to house the translation stage, substrate holder, electromagnets, and a digital microscope. Probe motion is monitored using the microscope, and probe contact onto the MNS array is established by measuring the DC resistance across the probe tips. These ensure good contact and parallelism of the probe tip with the MNS array. In contrast with the ‘traditional’ microstrip method, our coplanar probe method is able to efficiently excite non-uniform standing spin wave modes (SSWMs) with odd symmetry in the MNS array. We propose that this is due to confinement of real microwave currents along the nano-stripes which induce a non-uniform microwave magnetic field, and which in turn, couples efficiently with the non-uniform SSWMs with odd symmetry. The proposed method is quick and allows easy spatial mapping of magnetic properties with resolution down to 100 microns, which is the tip size of the smallest commercially available Picoprobe®. 7
  • 8. Generation of 103.75 GHz CW Source with 5.10-16 Frequency Instability Using Cryogenic Sapphire Oscillators Romain Bara ( Supervisors: Michael E. Tobar Fellow IEEE, Eugene N. Ivanov, Jean-Michel Le Floch, FSM / School of Physics, University of Western Australia Abstract: Precise frequency generation is important for a variety of applications including radar, telecommunications, positioning and navigation system, geodesy and time keeping, tests of fundamental physics and radio astronomy. So far, signals with short-term fractional frequency instability of a few parts in 1016 have been generated at microwave frequencies only. This was achieved either with classical oscillators based on sapphire loaded cavity resonators cooled to liquid helium temperature, termed “sapphire clocks” or “cryogenic sapphire oscillators” (CSO), or via the use of mode-locked laser technology by extracting high order harmonics of pulse repetition rate from a femtosecond pulse train referenced to an ultra-stable laser. We report on the generation of millimeter wave signals with frequency instability of a few parts in 1016. Such performance was achieved at 103.750 GHz by frequency multiplication of two nominally identical 12.969 GHz oscillators based on liquid helium cooled sapphire dielectric resonators. The multiplication stages were shown to only add a small amount of noise at averaging times less than 10 seconds, resulting in a minimum of frequency instability of 5x10-16 at 20 seconds averaging time. Such ultra-stable signal sources operating at frequencies of 100 GHz are very important for many applications including high frequency radio astronomy. We demonstrate that the excellent fractional frequency stability of a typical microwave CSO can be transferred to frequencies above 100 GHz by means of direct frequency multiplication. 8
  • 9. Designing a Macroscopic Phonon Laser using Cryogenic Sapphire Microwave Resonators Warrick Farr ( Supervisors: Mike Tobar, Jean-Michel le Floch, Eugene Ivanov EQUS, UWA Abstract: Optical lasers have become ubiquitous in the last 50 years. If we consider phonons as analogues of photons we may wonder why the phonon laser is not so common. In this work we investigate a possible technique for creating a macroscopic phonon laser and report on computer simulations and experiments so far completed. In a conventional optical laser the first step is the pumping process, where the electrons in the active medium e.g. crystals or gas, are pumped from the ground state into an excited state in order to create a population inversion. These electrons decay, and give off photons as spontaneous emission. Using positive feedback these photons create additional coherent photons through stimulated emission. Which is outputted as a laser beam. In an analogue to optical lasers, phonons can also be amplified. Our proposed technique is to arrange two cylindrical sapphire resonators to interact with each other. By changing the distance between them we can tune the relative frequency between the 0th and 1st order microwave modes. This gives a tunable two level system. By pumping the higher frequency 1 st order microwave mode with an external microwave signal to create a population inversion. Brillouin scattering processes will create spontaneous phonons at the frequency of the difference between the microwave modes. If we can tune the microwave modes, we can then tune the phonons to a frequency which is resonant with the mechanical system. This creates positive feedback on the two level system, which will continue to create additional phonons due to stimulated emission, which results in a phonon laser. For my PhD, we aim to build a phonon laser using sapphire crystals. The first step is completing simulations of the crystal two level system. In the simulations we investigate the influences on the cavity setup such as; crystal separation, mode number or temperature. These simulations clearly prove the theoretical feasibility of the phonon laser. 9
  • 10. Glancing angle deposition: Technique for the fabrication of arrays of nanostructures Nikola Radevski ( Supervisors: David Parlevliet and Christine Creagh Murdoch University Physics and Nanotechnology Research Group Abstract: Glancing angle deposition (Glad) is a physical vapour deposition (PVD) technique used to fabricate three-dimensional columnar nanostructures by taking advantage of atomic shadowing (Deniz & Lad, 2011; Zhao, Ye, Wang, & Lu, 2003; Kennedy & Brett, 2004; Hawkeye & Brett, 2007). The technique was first reported in 1959 (Liu, et al., 1999) and combines substrate rotation with oblique angle of incidence to sculpt various microstructure thin films (Robbie, Beydaghyan, Brown, Dean, Adams, & Buzea, 2004). The deposition of thin films requires a material to undergo a phase change from vapour above the substrate to a solid on the substrate (Hawkeye & Brett, 2007). This process is achieved by thermal evaporation, electron beam evaporation or sputtering techniques. Glad is capable of growing a variety of complex nanostructure morphologies (Robbie, Beydaghyan, Brown, Dean, Adams, & Buzea, 2004) by manipulating the angle of incidence and substrate rotation. Glad enables the growth of columnar structured thin films in: shorter periods of time, with few material restrictions, and with lower costs (Robbie, Beydaghyan, Brown, Dean, Adams, & Buzea, 2004). These are key concerns of solar cell research. Many of the structures fabricated using Glad cannot be achieved using other deposition techniques (Robbie, Beydaghyan, Brown, Dean, Adams, & Buzea, 2004) and a wide range of materials, insulators, metals and semi-conductors, can be used to fabricate the nanostructures with the technique (Robbie, Beydaghyan, Brown, Dean, Adams, & Buzea, 2004). Deniz, D., & Lad, R. J. (2011). Temperature threshold for nanorod structuring of metal and oxide films by glancing angle deposition. American Vacuum Society , 1 - 6. Hawkeye, M. M., & Brett, M. J. (2007). Glancing angle deposition: Fabrication, properties, and applications of micro- and nanostructured thin films. American Institute of Physics , 1317 - 1334. Kennedy, S. R., & Brett, M. J. (2004). Advanced techniques for the fabrication of square spiral photonic crystals by glancing angle deposition. American Vacuum Society , 1184 - 1190. Liu, F., Umlor, M. T., Shen, L., Weston, J., Eads, W., Barnard, J. A., et al. (1999). The growth of nanoscale structured iron films by glancing angle deposition. American Institute of Physics , 5486 - 5488. Robbie, K., Beydaghyan, G., Brown, T., Dean, C., Adams, J., & Buzea, C. (2004). Ultrahigh vacuum glancing angle deposition system for thin films with controlled three-dimensional nanoscale structure. American Institute of Physics, 1089 - 1097. Zhao, Y. -P., Ye, D. -X., Wang, G. -C., & Lu, T. -M. (2003). Designing Nanostructures by Glancing Angle Deposition. SPIE , 59 - 73. 10
  • 11. Study on the Effect of Substrate and Gold catalyst thickness on Characteristics of PPECVD Grown Silicon Nanowires Nicholas Michael William Wyatt ( Supervisors: Zhong-Tao Jiang, Christine Creagh and David Parlevliet Murdoch University Physics and Nanotechnology Research Group Abstract: The purpose of the study was to examine the effect of changing catalyst thickness and substrate on the crystal structure of silicon nano-wires and investigate the impact upon the electronic structure. Various characterisation techniques were employed to investigate the; degree of crystallinity and crystal structure, silicon bonding, oxide phases present on the surface and the binding energies on the core electrons (2p and 2s orbital) in the silicon. The silicon nanowires were grown by Pulsed Plasma Enhanced Chemical Vapour Deposition on stainless steel, crystalline silicon and indium tin oxide coated glass with a gold catalyst coating. The wire diameter was approximately linearly related to the catalyst thickness. The catalyst thicknesses used were 20 nm, 40 nm, 110 nm, 160 nm and 200 nm. The mean diameters were 104.8- 184.55 nm with an average standard distribution of 39.86 nm. There appeared to be significant changes in both crystal and electronic structure, although dramatic changes in crystal structure did not necessarily correspond to large changes in electronic structure and vice versa. All samples were found to have crystalline cored SiNW with oxides and amorphous silicon present on the surface. Evidence of SiO2 and Si-O-Si on the sample surface was found. Surface oxide varied strongly with gold catalyst thickness. The amount of surface oxide seemed directly related to the shifts in binding energy of the core silicon photoelectrons except for the nanowires on the indium tin oxide substrate using 160 nm thickness of gold catalyst. The gold binding energy on valence and 4f orbital electrons changed significantly for the indium tin oxide substrate samples grown with 110 and 160 nm of gold catalyst. There is evidence to suggest that the gold was deposited or the indium reacting differently for these samples before the nanowires were grown. Multiple crystalline phases of silicon and silicon oxide were found and varied heavily with substrate and catalyst thickness. The crystallite size varied strongly with catalyst thickness and was very similar for the nanowires grown on stainless steel and silicon. 11
  • 12. Determining the Migration Pattern of an Extinct Australian Diprotodon using Strontium Isotopes Lynette Howearth ( Supervisors: Drs Marjan Zadnik, Robert Loss, Gavin Prideaux and David Nelson The John De Laeter Centre for Isotope Research, Department of Imaging and Applied Physics, Curtin University, Perth Abstract: Strontium (Sr) isotopic data of enamel cores from an 80,000-year-old fossilised diprotodon incisor have been obtained using data acquired with a thermal ionization mass spectrometer. Although the extinct rhinoceros-sized diprotodon, Diprotodon optatum, was one of the most widespread Pleistocene marsupials that lived throughout most of Australia before the last ice age, little is known of its migratory behaviour. However, migration patterns are being reconstructed with the use of isotopic and elemental ratios from the tooth enamel since teeth retain information about the environmental and physiological conditions present at the time of their formation. Strontium, lead, oxygen and carbon isotopic analyses are being correlated and compared with analysis of rocks, soil, vegetation and kangaroo teeth collected from the Pilbara region where the fossilised diprotodon was found. Early results indicate that the animal spent portions of its life in at least two different geological settings and that the time period recorded by one tooth documents less than one full year. Illustrator: Vince Wathen 12
  • 13. Impact-parameter convergent close-coupling approach to antiproton collisions with atomic hydrogen and helium I. B. Abdurakhmanov ( A. S. Kadyrov, D. Fursa, and I. Bray ARC Centre for Antimatter-Matter Studies, Curtin University, GPO Box U1987, Perth 6845, Australia Abstract: A fully quantum-mechanical close-coupling approach to antiproton-atom collisions is developed [1] along the lines of the convergent-close-coupling approach to electron-atom scattering. The approach starts from the exact three-body Schr¨odinger equation for the scattering wave function and leads to coupled-channel Lippmann-Schwinger equations for the transition amplitudes in the impact-parameter representation. In addition to providing information on the heavy particle scattering, the approach allows one to investigate the differential electron ejection. With these the total and fully differential cross sections can be calculated. A method is applied to calculate integrated excitation and ionization cross sections for hydrogen and helium targets. Fully differential cross sections for the antiproton-impact ionization of hydrogen are also calculated [2]. References [1] I. B. Abdurakhmanov, A. S. Kadyrov, I. Bray, and A. T. Stelbovics, J. Phys. B 44, 075204 (2011). [2] I. B. Abdurakhmanov, A. S. Kadyrov, I. Bray, and A. T. Stelbovics, J. Phys. B 44, 165203 (2011). 13
  • 14. Convergent close-coupling calculations for positron-magnesium scattering Jeremy Savage ( Supervisors: Dmitry Fursa and Igor Bray ARC Centre for Antimatter-Matter Studies Curtin University, GPO Box U1987, Perth, WA 6845, Australia Abstract: The CCC method has been extensively tested for electron-atom scattering from various targets including alkaline-earth atoms. It has also been applied successfully to positron scattering from hydrogen, helium, and noble gases. In this work we apply the single-centre CCC approach to positron scattering from magnesium, a pseudo-two-electron target. In the CCC method the change from incident electron to incident positron requires a simple reversal of projectile sign and dropping projectile-atom exchange, with no further changes to the code. Conceptually the method is particularly simple; computationally the problem becomes very different to electronatom scattering. For incident positron energies above target atom ionisation potential (7.6 eV) the total ionisation cross section (TICS) obtained in the CCC method provides an accurate estimate of the sum of direct ionisation and positronium formation. The incident energy region between the positronium formation and ionisation thresholds (0.8—7.6 eV) proved to be problematic for the single-centre approach. At these energies the positronium formation channels are open but the positive energy pseudostates that model the break-up are closed. As a result a lack of convergence was found in this energy range. For low incident energies where positronium formation channels are closed (below 0.8 eV) the CCC method provides an accurate estimate of elastic scattering cross sections. In this case the virtual positronium formation channels which play an important role in describing the scattering can be modelled via large close-coupling expansion. States with angular momentum of up to l=14 were required for convergence. At these low positron energies a p-wave resonance centred at approximately 0.17 eV. A similar prediction has been made by Mitroy (2007) at 0.1 eV. Detailed convergence studies have been conducted to verify the accuracy of our results, and the reason for the discrepancy between resonance predictions remains unclear. Currently we are approaching the positron-magnesium scattering problem using the two-centre CCC method that has recently been developed and extensively tested for positron-helium scattering by Utamuratov (2010). 14
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  • 16. Synthesis and evaluation of AAO-PHEMA nano-composite. Nurshahidah Ali ( Supervisors: Dr Gerrard Eddy Poinern, Dr. Zhong Tao Jiang, Professor Pritam Singh Murdoch Applied Nanotechnology Research Group Abstract: Anodic aluminium oxide (AAO) membrane has in the last decade attracted enormous attention because of the ease of its preparation and regularity of the pores obtained. It is also one of the only systems that can be engineered at the nano level using macroscopic parameters. Porous AAO membranes are considered to be the most suitable host materials for the fabrication of polymer nanowires and nanotubes. More recently, composite materials of AAO membrane are being synthesised for application as biodevices to analyse hereditary diseases and as implants with enhanced bone bonding capability. Organic and inorganic nano-composite materials are of particular interest because the fabrication of these two components at the nanoscale level often exhibit physical and chemical properties that vary greatly from their individual constituents. In this novel project, we are aiming to develop and evaluate an efficient nano-composite of AAOPHEMA (poly-hydroxyethylmethacrylate) for potential cell attachment. PHEMA is a non-toxic, non-antigenic polymer with good biocompatibility. It is used for several medical applications such as contact lenses and drug delivery systems. This study aims to alter the surface properties hence chemical and structural composition of the AAO membrane and examine if the addition of PHEMA results in significant effects on cellular growth. AAO-PHEMA nano-composite membranes were prepared by dip coating. Investigations into the structural and chemical properties of the nano-composite were carried out using field emission scanning electron microscopy (FE-SEM), Fourier Transmission Infra Red (FT-IR) spectroscopy and X-Ray Photoelectron Spectroscopy (XPS). Variable interfacial bonding structure can be achieved with different methods of preparation which in turn, would affect cellular attachment. 16