Τρίτη, 11 Νοεμβρίου 2008

'Super-microscope' opens at Isis -The world's newest "super microscope

The world's newest "super microscope" is fired up and ready to go.
http://news.bbc.co.uk/2/hi/science/nature/7686622.stm
The £200m second target station 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. But what does that actually mean? Well, if you're a physicist curious to see how matter behaves when no-one is looking, then Isis is your private snoop. If you're an engineer trying to make the hydrogen car a working reality, then Isis is your genie. World leader Want to see how spiders spin silk stronger than steel? Or peer into a newborn baby's lungs as they take their first breath? Isis will grant your wishes - and you get more than three. Up to 40 different experiments can run side by side, now that the second target station "Isis 2" is open. No wonder that physicists from across the globe will be flying in to seek an audience with the oracle, which resides at the Rutherford Appleton Laboratory, at Harwell Science and Innovation Campus. Their areas of interest stretch the breadth of the Universe - from the darkest corners of quantum mechanics, to the supermarket shelf. Theory geeks searching for the elusive "Boson peak" will stand side-by-side with a Dutch group who are studying cheese. Both groups have turned to neutron scattering as a powerful tool for examining their materials at the atomic level - the positioning, spacing, and the forces between the individual atoms. This Airbus wing is an example of Isis' everyday applications"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. "And you're not just taking a snapshot - you can watch how this changes over time, with temperature, or any other variable. "You're not just sending a postcard; you're making a little video story." The first target station, Isis 1, has exceeded all expectations since it opened in 1984. It has answered fundamental questions - about magnetism at the atomic level, or the properties of "Buckyballs" - synthetic carbon molecules, once hailed as the great hope of nanotechnology. But equally, it has solved "everyday" problems - the causes of railway crashes, or the most economic way to make fabric softener.
New frontiers
The second target station will open new frontiers - soft condensed matter, bio-molecular sciences, and advanced materials.
SPYING ON ATOMS
"Throughout the 90s, it became apparent that there was some science that we just couldn't do with Isis 1," said Andrew Taylor. "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." The new target station supplies these. 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. At its core is a lump of tungsten metal the size of a packet of biscuits - the "target" - into which pulses of protons are fired at 84% of the speed of light. The target radiates neutrons like a discoball scatters light - 20,000 million million per second. Surrounding it is a ring of colour-coded bunkers, inside which scientists place their samples - be they toothpaste or turbine blades. Their silk is as strong as steel - but how do spiders do it? Isis can help. Each bunker houses a different experimental tool for imaging matter.
The neutrons are like pinballs fired into the sample, cannoning off the atoms inside and spraying out on to a detector. By recording the angles they pop out, scientists can plot the atomic structure of the sample material, without breaking it open, or cutting it up. And whereas other high-resolution microscopy techniques only scratch the surface of a material, Isis can give a cross sectional view of the material in its natural state. Take a pint of beer. To watch the individual alcohol molecules flirting with different water molecules, you need to observe them in the aqueous environment. Spiders and silkworms spin their silk from liquid precursors - creating fibres far stronger than anything we humans can synthesise artificially. So how do they do it? Scientists from the Oxford Silk Group have been using Isis 1 to measure the properties of the liquid silk ingredients. Isis 2 is equipped with more powerful experiments, which will reveal how the silk recipe is stored and prepared.

Δεν υπάρχουν σχόλια: