40m tower that houses the particle accelerator( during a cleaning and maintenance
operation). The accelerator (the centrol column of metal) rises over 20
metres and can generate 15 million volts.
The Heavy Ion Accelerator
speeding particles to probe the nature of matter
heavy ion accelerator is a towering device that speeds up charged atoms
to 10% of the speed of light. These speeding 'bullets' can then be used
for a range of studies, including some high powered materials science.
Ion Accelerator (or 14 UD accelerator) is one of the world's largest Van
de Graaff generators (much like you would have seen at high school only
larger, see below for a comparison). It's housed in a 40 metre-tall, steel
and cement tower, and is used to generate enormous voltages of 15 million
volts and more. This voltage is used to accelerate charged particles (ions)
to 10% the speed of light. This is sufficient to overcome the strong electrostatic
repulsion between atomic nuclei (which are positively charged so they
repel), allowing the study of one of the fundamental but least understood
forces - the strong nuclear force.
The Particle Accelerator supplies high energy ions for a variety of purposes
ranging from studies on the structure of the nucleus, interactions between
nuclei, materials science, global climate change, bio-medicine and archaeology.
it: The accelerator is operated by the Department
of Nuclear Physics (part of the Research School of Physical Sciences
and Engineering). It was commissioned in 1974 and has been constantly
upgraded since then. Now it forms a part of the Department's Heavy-Ion
Accelerator Facility, Australia's top nuclear physics laboratory. The
Facility attracts some of the world's top scientists.
How does it work: To investigate the secrets of the nuclei of atoms
you need to get them close enough so that they feel the strong nuclear
force which only acts at short distances (one trillionth of a mm). The
only way to achieve this is by striking them with other nuclei travelling
with enormous energy. The accelerator is a machine that provides nuclei
with such high energies.
The 14 UD accelerator works on the same principle as a Van de Graaff generator
that you might have used in high school. The high school version is basically
a metal sphere supported by a plastic tube. Inside the tube is a rubber
belt that runs up and down in a closed loop. As the belt turns it generates
a static electrical charge which is transferred to the metal sphere. Hold
a piece of metal close to the sphere and you can observe a powerful spark
jumping from the sphere to the metal. This is the same process of building
up a charge by scuffing your feet on the carpet and then touching someone
The ANU's Van de Graaff generator is a bit more powerful. Instead of the
rubber belt it contains three chains of nylon and stainless steel pellets.
Each chain is over 20 metres long and whirs around at speeds over 50 km/hr.
This generates electrical voltages in excess of 15 million volts. Working
with such enormous voltages is tricky. The entire generator is housed
in a massive steel tank filled with high-pressured, insulating sulphur
Running down through the centre of the accelerator is an evacuated tube
through which charged particles travel. Negative ions (negatively charged
atoms) are injected into the top of the accelerator. They are accelerated
(pulled) towards the positive terminal (positioned half way down). Here
the speeding particles pass through a thin carbon foil which strips away
the electrons around the nucleus. The atom is now positively charged and
is repelled away from the positive terminal to the bottom of the accelerator
gaining further energy.
A beam of speeding nuclei emerges from the bottom of the accelerator for
use in a range of investigations. Magnets steer the beam of nuclei into
one of several beam lines, each equipped with different devices and detectors
for different experiments.
Many of the beamlines are involved in studies of the nucleus. One beam
line passes through a second accelerator, a superconducting LINAC, which
further increases the energy of the particles. These nuclei are travelling
fast enough to fuse with heavier nuclei, providing a window into the sub-atomic
world of the nucleus.
area of research that uses the speeding bullets being produced by the
particle accelerator is materials science. There are two broad areas of
materials science being pursued:
So the accelerator
is actually only one component in a long line of sophisticated devices
that together make up the Heavy Ion Facility.
information: ANU Department of Nuclear Physics: Accelerator