November 11, 2008

Scientists Welcome New ‘Super-Microscope’ At Isis

The world's newest "super microscope" at Isis in Oxfordshire will allow scientists to see things 10,000 times thinner than a human hair.

The machine is known as a pulsed neutron source. And now that the second target station "Isis 2" is open, up to 40 different experiments can run side by side.

Physicists from around the world are flying in to seek an audience with the oracle, which resides at the Rutherford Appleton Laboratory, at Harwell Science and Innovation Campus.

"Essentially, it's a giant camera," says Andrew Taylor, the Director of Isis, which is owned and operated by the Science and Technology Facilities Council (STFC).

"Let's do a simple experiment - take your Biro pen and bend it. What do you see? One side stretches and the other contracts - the individual atoms are getting closer or further apart.

"Now imagine your pen is the turbine blade of a Rolls Royce jet engine - operating under vast mechanical and thermal stresses.

"Isis allows you to measure these stresses, and see how they alter the spacing between each individual atom of the turbine," Taylor said.

Since opening in 1984, the first target station, Isis 1, has exceeded all expectations.

So far, it has answered fundamental questions of nanotechnology such as magnetism at the atomic level, and the properties of "Buckyballs" - synthetic carbon molecules, once hailed as the great hope.

But scientists agree it has also solved "everyday" problems like the causes of railway crashes, or the most economic way to make fabric softener.

However, the unveiling of the second target station will open new frontiers such as soft condensed matter, bio-molecular sciences, and advanced materials.

Taylor said throughout the 90s, it became apparent that there was some science that we just couldn't do with Isis 1.

"We wanted to look at polymers, surfactants, aggregates - these things have got structures bigger than just a few tenths of angstroms.

"Bigger molecules need neutrons which are matched to their structure - longer wavelength neutrons."

He says the new target station supplies all of these and more. It also has a greater flux (flow of neutrons per second) allowing greater control of intensity, and quicker experiments - ideal if you are a researcher visiting from Japan for just three days of beam time.

A small lump of tungsten metal is at its core, making up the "target" into which pulses of protons are fired at 84% of the speed of light.

The target radiates neutrons 20,000 million per second. Surrounding it is a ring of color-coded bunkers where scientists place their samples - be they toothpaste or turbine blades. And each bunker houses a different experimental tool for imaging matter.

The neutrons are fired into the sample, cannoning off the atoms inside and spraying out on to a detector.

Scientists can then record the angles in which they pop out, plotting the atomic structure of the sample material without breaking it open or cutting it up.

Isis can also give a cross sectional view of the material in its natural state, whereas other high-resolution microscopy techniques only scratch the surface of a material.

For instance, with a pint of beer, to watch the individual alcohol molecules reacting with different water molecules, you need to observe them in the aqueous environment.

Scientists from the Oxford Silk Group have been using Isis 1 to measure the properties of the liquid silk ingredients that spiders and silkworms spin"”fibers far stronger than anything we humans can synthesize artificially.

But Isis 2 is equipped with more powerful experiments, which will reveal how the silk recipe is stored and prepared.

Meanwhile, on a global scale, the new target station will help Isis to compete with other neutron sources that include the Institut Laue-Langevin (ILL), Grenoble, France, which uses a continuous nuclear reactor as its neutron source, and the Spallation Neutron Source (SNS), in Oak Ridge, Tennessee, US, which is based on Isis technology, only with higher beam powers.

There are other types of super-microscopes within eyesight of Isis, such as the Diamond synchrotron light source, which uses highly focused beams of X-rays to probe deep into the basic structure of matter and materials.

But Taylor says Isis can do some things that Diamond just cannot.

"We see matter in a different way," Taylor explains. "Neutrons see the nucleus of the atom. X-rays see the electrons. And that means that neutrons see the hydrogens. X-rays don't."

"Take uranium hydride," he said. "Uranium's got 92 electrons and hydrogen has one. The X-rays have no idea where the hydrogen is.

"But neutrons see the hydrogen and uranium nuclei with equal magnitude."

Therefore, if you're an engineer trying to make the hydrogen car a working reality, then Isis is your answer.


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