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EMU machine

A look inside an instrument that sees the nanoverse: Meet Emu

ANSTO’s Emu is not a native animal, although it is fast and exotic like its namesake. Emu is a high resolution backscattering spectrometer, that is expected to open up a new ultrasensitive ‘energy window’ for researchers and industry. 

Read a quick Q & A with the Emu instrument team.

A new animation has just been released that explains how the state-of-the-art instrument works.

The power of the technology is its ability to observe atomic interactions—such as the diffusion of hydrogen or water molecules or the ways molecules rearrange themselves in polymers.  It can detect the phenomena of quantum tunnelling and the changes to the nuclear spin of particles in a magnetic field.

For an instrument that detects incredibly small amounts of energy, it requires a very large space, 25 square metres in ANSTO’s Neutron Guide Hall. It is located near 12 other instruments that use neutrons from the OPAL research reactor. This large, complex instrument is ultrasensitive and precise enough to detect motion in the nanoverse, such as the vibrations of individual atoms.

Emu can measure minutely small energy shifts in a world governed by quantum mechanical effects.

“The distinctive feature of backscattering instruments is their ability to determine the energy transfer of neutrons with a very high resolution, “explainedGail Iles, who with Alice Klapproth and the construction project leader Nicolas de Souza, is one of the three Instrument Scientists on Emu.

It also belongs to a group known as spectrometers. They are used to measure

ANSTO has three other instruments that are used for inelastic neutron scattering, Taipan, Sika and the cold neutron time-of-flight spectrometer, Pelican.

“The choice of instrument is determined by the scientific question to be answered,” said Iles.

Animation of new EMU instrument
Measuring  25 square metres, ANSTO's new Emu instrument  is ultrasensitive and precise enough to detect vibrations of individual atoms.

“The selection of a neutron beam instrument depends on the energy transfer range and the momentum of interest.”

Emu’s conceptual design was completed in early 2010. It is in the process of being commissioned, which means that ANSTO will soon be accepting proposals for research. 

Emu is funded as part of the Australian Government Super-Science Initiative.

ANSTO’s neutron instruments are named after Australian and overseas fauna.

A quick Q & A with the Emu instrument team

How long did it take, in all, to construct and test? When do you expect full commissioning?

Construction lasted 5 years and the hot commissioning licence was granted on 16 March 2015.  We expect the commissioning process to last for approximately 12 months.

This is an incredibly complex instrument. Once it is operational and commissioned, it is difficult to maintain?

Maintenance of the instrument should be minimal during the first years of operation.  All components have been specifically chosen and rated to operate for at least 5-10 years without failure.

Is the extreme sensitivity due to the sophistication of the technology?

The sensitivity comes from the technique itself – ‘backscattering’.  The neutrons we want are reflected back at close to 180° by single-crystals of silicon wafers.  Whilst the reflection is simple enough, having the crystals in the correct place presented significant technological challenges.  For example, the steel backing plates were cast relatively simply, however, owing to their parabolic curvature, the Si wafers have to be glued and then air compressed onto these steel plates using uniform pressure pistons.  The entire rig to attach the crystals was built in house and Colin Hobman has shown great dedication to the project by gluing every single Si wafer onto the plates.  That’s over 500 wafers!

Does it have to be this complex, to outsmart nature? A stratagem required to capture fleeting energy exchanges?

In a word, yes.  That reflection back at about 180° is a condition that only ~10% of the scattered neutrons fulfil which essentially means we are throwing away 90% of our signal.  However, this is what gives us our very high resolution, and that is precisely what we need to observe these very small energy transfers.

Are there many instruments in the world that can measure energy at these levels?

There are 10 backscattering spectrometers in the world.  IN16 (Grenoble, France), upon which Emu was based, has since been remodelled into the newer IN16B, in full user operation.  The ILL also houses IN10 and IN13 which are both backscattering instruments.  The other backscattering instruments are HFBS (NIST, USA), SPHERES (FRM-II, Germany), IRIS and OSIRIS (ISIS, UK), BASIS (ORNL, USA) and MARS (PSI, Switzerland).

Do you expect international users?

Absolutely! Once EMU enters full user service in early 2016, it will join the existing suite of instruments available at the Bragg Institute for user experiments, and this is of course open to both international and national users.

There is a significant amount of mathematical calculation involved with these techniques. Is there software do this?

Emu will utilise MANTID, software already used at Oak Ridge National Laboratory (USA) and ISIS (UK).  Both ORNL and ISIS are spallation sources (i.e. the neutrons arrive in pulses) and this software project was designed to assist users when travelling between sites to use a similar interface when operating the instrument and handling the data.  With such highly specialised scientific instruments it is not uncommon for equipment to have completely individual software, often developed by the instrument scientists themselves, however, there is more of a drive to create more uniform software solutions for the future.

Can you clarify how backscattering addresses relatively slow nuclear motion?

Backscattered neutrons are those that have been scattered by slow motions of different kinds.  These slow motions captured in this energy window may come from certain molecular groups rotating at the end of a long chain, for example.  Or the motion may come from very slow lattice vibrations, or from the spin of nuclei.  Specific examples would be the motion of polymer chains or diffusion processes e.g. in ion conductors. Whilst EMU has an energy resolution of 1µeV and an energy range of +/- 28µeV, Pelican (the time-of-flight instrument) has energy resolutions of ~100µeV whilst the triple-axis instruments have an energy resolution of ~1meV.

µeV = microelectron volts