University of York scientists in solar 'first'
Posted on 30 June 2006
A group, headed by Professor Greg Tallents, of the University's Department of Physics, has become the first to directly measure, in the laboratory, the opacity of plasma material found halfway towards the centre of the sun.
The discovery will help to refine predictions of solar output, its potential impact on the earth’s climate and its effect on the magnetic field (the magnetosphere) that protects the planet from high energy particles from outer space. Changes in the magnetosphere can also affect radio signals around the earth's surface and radio communication between earth and spacecraft.
Direct measurements of the opacity of hot dense material will greatly help in understanding the radiation outflow from the sun and other stars
Professor Greg Tallents
Details of the work, which was funded by a £400,000 grant from the Engineering and Physical Sciences Research Council (EPSRC), will be published in the US journal Physical Review Letters.
Hot, dense plasma emits huge quantities of radiation, so the scientists had to identify a source for the opacity measurement that could 'outshine' the plasma.
The group led by Professor Tallents used an extreme ultra-violet laser as the radiation source and created the hot dense plasma using another infra-red laser beam. The transmission of the extreme ultra-violet beam through an infra-red laser heated target comprising plastic and a thin layer of iron enabled the iron opacity to be measured and compared with computer code simulations.
Professor Tallents said: "Direct measurements of the opacity of hot dense material will greatly help in understanding the radiation outflow from the sun and other stars. Up till now, solar opacity at the relevant conditions has always been calculated using largely unchecked theoretical calculations."
Measurements of the opacity of hot dense material will also help the development of free-electron lasers that will produce intense laser light at very short wavelengths. They will have a wide range of applications including the determination of the structure of biological molecules.
Notes to editors:
- The work was carried out at the Central Laser Facility, Rutherford Appleton Laboratory in Oxfordshire with funding from the United Kingdom Engineering and Physical Sciences Research Council and £180,000 worth of experimental time funded by the Council for the Central Laboratory of the Research Councils.
- The York Plasma group has worked on optimising and understanding extreme ultra-violet lasers for many years. The record shortest wavelength 'saturated' laser was achieved in an experiment involving Greg Tallents and Geoff Pert from the group in the late 1990s.
- The work
is to be published in the US journal Physical Review Letters on 30 June
2006 as follows:
- Opacity measurements of a hot iron plasma using an
x-ray laser
M H Edwards, D S Whittaker, P Mistry, N Booth, G J Pert, G J Tallents, Department of Physics, University of York, York, YO10 5DD, U.K. B Rus, T Mocek, M Koslovà, Department of X-ray Lasers, PALS Research Centre, Institute of Physics, Academy of Sciences of the Czech Republic, 182 21 Prague 8, Czech Republic C McKenna, A Delserieys, C L S Lewis, School of Mathematics and Physics, The Queen's University of Belfast, Belfast BT7 1NN, UK M Notley, D Neely, Rutherford Appleton Laboratory, Chilton Didcot, Oxfordshire OX11 0QX, UK
- Opacity measurements of a hot iron plasma using an
x-ray laser