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School of Physical, Environmental and Mathematical Sciences |
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Research Interests:
Advanced Materials
Personal Website: http://www.pems.adfa.edu.au/~htimmers
I am a physicist and a Senior Lecturer of the University of New South Wales at the Australian Defence Force Academy in Canberra, Australia.
My areas of expertise are nuclear physics, ion beam analysis and material science. Recent work has included studies of thin film semiconductors, the development of position-sensitive gas ionisation detectors, measurements of ion-stopping in matter and experiments to determine the role of neutron-transfer in nuclear fusion reactions. I teach officers and officer cadets at the Academy, lead the development of a facility for radioisotope implantation and supervise postgraduate students.
Before my present appointment I carried out research projects at the GSI Research Institute in Darmstadt, the University of Munich, the University of Liverpool, New York State University, the Italian Nuclear Research Laboratories in Padua and the Australian National University in Canberra. My Diplomarbeit (MSc thesis) focused on shape-changes of atomic nuclei induced by rapid rotation and centrifugal stress. In my PhD project I demonstrated experimentally how the internal structure of nuclei can affect the process of nuclear fusion. As a postdoctoral researcher I developed detection techniques for ion beam analysis and studied ion-material interactions.
I have a strong research
background in nuclear physics and
I am active in collaborative projects
dealing with fusion dynamics
and scattering and the sensitive
technique of elastic recoil detection
(ERD) as applied to the quantitative
compositional depth-profiling of
materials and thin films. I am
responsible for the operation and continuing development of the
joint UNSW@ADFA/ANU 155 keV
radioisotope implanter which uses
a versatile negative ion source.
Implanted radioactive probes are
employed to study the microscopic
properties of materials via
ultra-sensitive, hyperfine interaction
spectroscopy techniques such
as perturbed angular correlation
(PAC) and NMR on oriented nuclei
(NMRON).
Most recently, I became involved in two
separate collaborative projects
that exploit the ability to detect
very dilute concentrations of
radioisotopes. The first of these uses
radioisotope tracing to monitor
sediment transport in large river
basins and local forests. The second
project measures the dynamics of
wear debris shedding from knee
prostheses with the unprecedented
accuracy of rare isotope tracing and
accelerator mass spectrometry.
Characterization of III-V
semiconductors with ion beam
analysis and radioisotope probes
Dr Heiko Timmers, with Dr S. Shrestha,
Dr S. Butcher, Dr M. Wintrebert-
Fouquet, Prof. A. Byrne,
Prof. R. Vianden & Dr W. Zeitz
The increasing demand for wireless
communications systems requires
faster transistor operating speeds.
For many applications, high power,
high temperature operation is
also needed. The fundamental
physical properties of the group
III-nitrides GaN and InN suggest
that they should outperform Si,
and also GaAs, in high-frequency
applications. InN is expected to
provide the highest operating
frequencies while still at high
power. In collaboration with
Macquarie University in Sydney
and others the growth of GaN and
InN films is developed to achieve
quality material for commercial
applications. High precision analysisof the film composition is achieved
using Elastic Recoil Detection (ERD)
analysis. In addition, in order to
study the role of defects and to
test important processing steps,
radioisotopes are implanted into
GaN and InN. The subsequent decay
of these probes is then observed
with Perturbed Angular Correlation
(PAC) spectroscopy.
Elastic recoil detection analysis of
materials
Dr Heiko Timmers with Prof. R. Elliman& Dr T. Weijers
Elastic Recoil Detection (ERD) analysis is an ion beam analysis technique which enables the quantitative compositional depthprofiling of materials and thin films. In contrast to Rutherford backscattering (RBS) spectrometry, with ERD analysis an individual depth-profile can be resolved for each chemical element. With very heavy ion projectile beams the sensitivity can be extended to span the periodic table. In order to improve the efficacy of ERD analysis, new design concepts for gas-ionisation detectors have been designed and tested.
Fusion dynamics and scattering
Dr Heiko Timmers with Dr M. Dasgupta & Prof. D. Hinde
The relative motion of two nuclei
colliding at energies spanning the
Coulomb barrier is coupled to other
degrees of freedom of this binary
system with the consequence that
the binary system encounters a
distribution of potential barriers
rather than a single barrier. While
barrier distributions can be probed
in fusion experiments, it has been
shown in this work that some
information about the barrier
distribution may also be obtained
with measurements of quasi-elastic
and elastic scattering. Experiments
on the system 40Ca+96Zr suggest
that multi-neutron transfer may play
an important role in the fusion of
heavy systems, as has long been
postulated. Quasi-elastic scattering
measurements are performed to
test this postulate. The results are
relevant to the laboratory synthesis
of super heavy elements.
New approaches to
measurements of stopping forces
Dr Heiko Timmers with Dr T. Weijers & Dr H. Whitlow
In collaboration with the University of Lund in Sweden the stopping forces for heavy ions in matter are measured applying new approaches in order to achieve more reliable results than currently available.
Radioisotope tracing of sediment
transport
Dr Heiko Timmers & Dr Wayne
Hutchison with Assoc. Prof. Jacky
Croke, Dr Chris Thompson &
Dr J. Fernandez-Niello
Sediment transport along rivers and creeks is an important environmental issue. In this work we have established measurement facilities in the School to quantify sediment transport using the radioisotopes Cs-137, Pb-210 and Be-7. Experiments in progress are relevant to the Fitzroy river basin and local ACT forest management.
Rare isotopes as tracers of
prosthesis debris
Dr Heiko Timmers & Dr Laura Gladkis
with Assoc. Prof. P. Smith, Dr J. Scarvell & Dr J. Fernandez-Niello.
The incidence of knee replacement surgery in Australia (~ 30,000 per year) is rising annually by about 10%. The established bearing material for knee prostheses is ultrahigh molecular weight polyethylene (UHMWPE) which is superior to any other. However, particulate wear debris delaminating from the UHMWPE component causes an inflammatory reaction that breaks down the bone, unfastens the prosthesis and can result in severe pain. Due to increasing life expectancy, many patients need several surgical interventions over their lifetime. Knee replacement surgery costs typically $15,000, imposing a high annual burden of half a billion dollars on the Australian health budget. In this project, we measure the dynamics of wear debris shedding from UHMWPE in knee prostheses with the unprecedented accuracy of rare isotope tracing and accelerator mass spectrometry.
A meeting of the cross-disciplinary Advanced Materials/TORU/ANU collaboration which applies nuclear techniques of analysis to wear phenomena in knee prostheses.
L to R: Dr Jennie Scarvell, Dr Laura Gladkis, Dr Heiko Timmers, Dr Fernandez-Niello, Assoc. Prof. Paul Smith.
PhD Opportunities and Scholarships
Further information concerning scholarships at: http://www.unsw.adfa.edu.au/pems/student/pgrescourses.html
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Dr Wolf Dietrich Zeitz (Visiting Fellow), |
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I am currently involved in teaching the following courses:
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Recent Publications
Journals - refereed
Amos, K. J., Croke, J. C., Timmers, H., Thompson, C. & Owens, P. N., The application of Caesium-137 measurements to investigate floodplain deposition in a large semi-arid catchment in Queensland, Australia, submitted to Earth Surface Processes and Landforms.
Butcher, K. S. A., Fernandes, A. J., Chen, P.P.-T., Wintrebert-Fouquet, M., Timmers, H., Shrestha, S. K., Hirshy, H., Perks, R .M. & Usher, B. F., 2007, The nature of nitrogen related point defects in common forms of InN, Journal of Applied Physics, 101(12), 123702-1-123702-11.
Chen, P. P., Butcher, K. S. A., Wintrebert-
Fouquet, M., Wuhrer, R., Phillips, M. R.,
Prince, K. E., Timmers, H., Shrestha, S.
K. & Usher, B., 2006, Apparent bandgap
shift in InN films grown by remoteplasma-
enhanced CVD, Journal of
Crystal Growth, 288(2), 241-246
Shrestha, S. K. & Timmers, H., 2006, The optimum heavy ion beam for the compositional analysis of indium nitride films, Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions With Materials and Atoms, 249(1-2), 257-260.
Timmers, H., Butcher, K. S. A., Shrestha, S.
K., Chen, P. P., Wintrebert-Fouquet, M.& Dogra, R., 2006, Compositional and
structural characterization of indium
nitride using swift ions, Journal of
Crystal Growth, 288(2), 236-240.
Weijers-Dall, T. D. M., Timmers, H., Stenström, K., Persson, P., Pergjegjaj, A., Wang, X., Graczyk, M., Osipowicz, T., Ren, M. Q., O’Connor, D. J. & Whitlow, H. J., 2006, Measurements of the stopping forces for heavy ions in Ge, Ag and Au using novel ‘polka-dot’ detectors, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 251(2), 352-360.
Conference abstract
Amos, K. J., Croke, J. C., Timmers, H. &
Thompson, C. T., 2007, Investigating
floodplain deposition in a large semiarid
Australian river using Caesium-137,
Abstract, EGU Conference.
- Member of the DPG (German Institute of Physics)
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2007- present Member of the UNSW@ADFA Ethics Committee