Dr Andrew Smith
Senior Principal Research Scientist, ANSTO
Who do you work for?
I work for the Australian Nuclear Science and Technology Organisation, which is known as ANSTO, a Federal Government laboratory like CSIRO but not quite so large. There are about 1000 people working at ANSTO, which is based in Southern Sydney.
ANSTO is home to Australia’s only nuclear reactor – OPAL – which, by law, is not used to generate nuclear power. Instead, OPAL is used to produce radio-pharmaceuticals ̶ that is, radioactive drugs used in medicine for treatment and for diagnosis. OPAL is also used to produce beams of neutrons used as powerful probes of matter in science and in industry. OPAL is also used to ‘transmute’ silicon, transforming it for use in integrated circuits, particularly for use in digital cameras.
But, as the name suggests, ANSTO manages other nuclear-based scientific equipment and technologies besides the nuclear reactor. I work within the Institute for Environmental Research at ANSTO, where we have two linear particle accelerators: one is called ANTARES, the Australian National Tandem for Applied Research, which uses voltages as high as 10 million volts (10 MV) to accelerate charged particles. The other is called STAR and is a smaller 2 MV machine. We are currently building the Centre for Accelerator Science at ANSTO, where these machines will be joined by two more new machines: 6 MV and 1 MV tandem accelerators. We will also have a new suite of laboratories for all the physical and chemical samples processing we have to do to get our samples ready for measurement on the accelerators.
What does your job involve?
When I am asked this question I normally answer: “I count atoms for a living”. While this is perfectly true, it is perhaps not very informative! I am trained as physicist and the technique I use at ANSTO is called Accelerator Mass Spectrometry, or AMS for short. It also just happens to be my initials!
AMS uses particle accelerators as extremely sensitive mass spectrometers. After suitable sample preparation, we place our samples in an ion source, where the atoms and molecules in the samples are ionised. This means they are given an electric charge so that they can be accelerated. Once the ion beam emerges from the ion source we use magnetic and electric fields to separate the particles on the basis of their mass, charge and energy. As the beam of particles finally enters the detector at the end of the beam line we can identify the individual atoms from which it is comprised – and count them, one by one. So, as you might imagine, this is a very sensitive analytic technique.
But this probably doesn’t help you understand my job. The atoms that we count by AMS are rather rare ones – mostly what we call ‘cosmogenic radionuclides’. This means that they have been naturally produced by cosmic rays or by their energetic secondary particles. I will explain this next.
Unlike electromagnetic radiation, cosmic ‘rays’ aren’t really rays at all. They are energetic particles originating in Outer Space from distant events such as supernovae explosions. The Earth has always been bombarded by cosmic radiation and always will be. What kinds of particles make up cosmic rays? About 89% of cosmic rays are simple protons (hydrogen nuclei), 10% are alpha particles (helium nuclei) and the remaining 1% are the nuclei of heavier elements, as well as energetic electrons.
Because all these particles have an electric charge, they are deflected by magnetic fields, such as those they encounter as they cross the solar system before they impact upon the Earth’s atmosphere. Then they collide with the nuclei of atoms of gases in our atmosphere, causing nuclear reactions. The products of these nuclear reactions are called secondary particles. The cosmic rays and the energetic secondary particles lose energy by collisions in the atmosphere or in the surface of the Earth. In these collisions, radioisotopes (radioactive isotopes of different elements) are produced.
The isotopes of any given element always have the same number of protons but different numbers of neutrons in their nuclei. The atoms of radioactive isotopes have an unstable nucleus. Since it is unstable, the nucleus ‘decays’ (breaks down), producing more stable nuclei and emitting radioactive radiation in the process. These reactions are called nuclear reactions. (In chemical reactions the nuclei of the atoms of the reactants are not changed.) The amount of time it takes for a given mass of a radioactive material to decay to half of that original mass is called the ‘half-life’ of the isotope.
A good example of a radioisotope produced in this way is ‘radiocarbon’, which physicists represent as 14C (carbon-14). Atoms of this isotope of carbon have 6 protons and 8 neutrons in their nucleus. Their relative mass is 14 amu.
The carbon-14 isotope is very rare. Almost all carbon atoms (99%) are the 12C isotope; they have 6 protons and 6 neutrons in their nucleus and a relative mass of 12 amu. The remaining 1% of carbon atoms are slightly heavier. Almost all of these atoms are the 13C isotope, which have 6 protons and 7 neutrons in their nucleus and a relative mass of 13. Only a very, very small fraction (about 1 in a million million) of carbon atoms are the heavier 14C isotope.
The extra neutron in the nucleus of carbon-14 atoms makes these nuclei unstable. The half-life of radiocarbon is 5 730 years. This makes it a very useful tool for archaeologist and anthropologists for dating suitable material over the last 50 000 years or so. But radiocarbon is also a very useful tracer for many other geophysical processes. These include studying the carbon cycle and learning about the Earth’s past climate and the factors that have forced climate change in the past. These signals are found in many natural archives such as sediments, corals, tree rings and ice cores.
So, one of the activities that my job has involved is the study of cosmogenic radionuclides in ice sheets, using AMS. This has meant that I have travelled to Antarctica on three occasions. I first went there for three months in the summer of 1997-1998 to study methane trapped in the upper part of the ice sheet (the ‘firn’). I then went for a further three months in 2005-2006, again to study methane, but deeper in the ice. My last expedition was for two weeks in February 2012, which was part of a long-term study to use the cosmogenic radionuclides 7Be (half-life 53.28 days) and 10Be (half-life 1.39 million years) to learn more about how the Sun’s energy output has varied in past times.
These methane projects are aimed at gaining a better understanding of the natural and anthropogenic (human) sources of methane, the second-most important greenhouse gas after carbon dioxide.
This work is very important because it adds to our understanding of past climate change and those forces that have caused climate change in the past.
What do you enjoy most about your job?
Everything! My job is fantastically varied so there is never a dull moment. I was lucky enough to be involved in the design of ANTARES from the beginning, and that meant a lot of fundamental physics and very specialised engineering, computing and electronics. This type of work continues to today, and soon we will have two new complicated machines to debug and develop into AMS tools: for both routine measurements and to develop new isotopes and new applications.
Each day I work with experts in a variety of fields, such as archaeology, anthropology, marine science, oceanography, biology, space science, environmental science and climate science; to name a few. As well as working alongside scientists who are recognised leaders in their fields and learning all sorts of interesting facts about our planet, I also have my own research interests and students.
What has been one of your recent achievements?
One that springs to mind is the development of a new device for producing tiny samples for radiocarbon measurement; we call this the ‘laser-heated micro furnace’. Even though ANSTO has always been at the forefront of radiocarbon measurement in samples containing very little carbon, it became challenging dealing with the very small amounts of carbon extracted from bubbles in ice cores – even when counting atoms! We needed a new way of producing the graphite, used in the ion source, from this carbon. My approach was to miniaturise the reaction chamber and to use a focused infrared laser beam to heat an iron catalyst to 600ºC to initiate the reaction. An infrared thermometer is used to determine the temperature of the catalyst by measuring the black-body radiation.
View the Catalyst story about Andrew, which was filmed when Andrew was nominated for the Australian Museum’s Eureka people’s Choice Awards in 2009.
What do you hope to do in the future?
There are lots of interesting things on the horizon. Early 2014 we should receive delivery of the new 1 MV accelerator, and later that year the new 6 MV accelerator. These will both keep me busy! I am also excited about our new sample preparation laboratory, as this will have a special walk-in freezer in which we can manage ice cores and expand our ice-related science activities. I am also going on another expedition May-June 2014, but this time to the Arctic – the Summit of Greenland! Not only will this be an adventure in itself but it will also yield a lot of new samples and exciting science.
What are some of the other benefits of your job?
As you have seen, my job is very varied so that is a benefit in itself. I have the opportunity to meet scientists at the forefront of their fields and to work with them on science that is sometimes ground- breaking. I travel a lot to international conferences and for field work.
Also, ANSTO is also a great place to work as we have football fields, tennis, squash and volleyball courts, a 25 m pool, a gymnasium as well as running and cycling tracks in the surrounding bushland. We get plenty of exercise at ANSTO!
What training did you have for this job?
Firstly a good mark in Year 12! In Years 11 and 12 I studied advanced Science and Mathematics, along with Geography and English.
On finishing school I went straight to the University of NSW where I was enrolled in an undergraduate Science degree; I did an extra (fourth) Honours year in Physics. During my undergraduate days I worked as a vacation student in three of the physics research laboratories; this not only earned me money but taught me many valuable skills.
After graduating, I worked for one of these laboratories as a ‘technical officer’ and during this time I built a small 0.2 MV accelerator that was used for ion beam implantation. After spending a few years building this machine, and acquiring new, practical skills I decided that I would like to use it for something, so I enrolled in a post-graduate degree, developing a novel electrostatic lens for my thesis dissertation. I finally graduated with a Doctor of Philosophy (PhD) in Physics.
What is your advice to students?
My advice to students is to never stop learning. School is just the first step. There is an entire Universe out there and we don’t know very much about it all. Never lose your sense of wonder and curiosity.