NEUTRON ATTENUATION CORRECTIONS FOR THE PARIS-EDINBURGH HIGH PRESSURE CELL. W.G.Marshall^*, R.J.Nelmes^*, J.S.Loveday^*, J.M.Besson^#. S.Klotz^# and G.Hamel^@. ^*Department of Physics and Astronomy, The University of Edinburgh, Edinburgh, EH9 3JZ, U.K.; ^#Physique des Milieux Condenses (CNRS URA 782), Universite P. et M. Curie, 4 Place Jussieu, Paris, France; ^@Departement des Hautes Pressions, Universite P. et M. Curie, 4 Place, Jussieu, Paris, France.

For data collected using the Paris-Edinburgh cell and time-of-flight neutron diffraction, it is important that accurate attenuation corrections are applied if reliable structural and thermal parameters are to be obtained. Because a direct measurement of the cell attenuation is time-consuming and can be made for only a limited number of sample/cell configurations, the approach followed has been one of performing a direct, first principles, calculation.

Direct calculation of the cell attenuation is a non-trivial problem: in general the attenuation is a function of not only the anvil and sample material, but also the neutron wavelength and the scattering angle. The results of a number of detailed experimental tests of the calculations, including direct measurements of the attenuation using a sample of vanadium, will be presented.

As a result of this effort, it is now possible to carry out, with confidence, full structural refinements of the high-quality diffraction data collected using the Paris-Edinburgh cell at pressures up to 25 GPa. This will be illustrated with results from a number of recent studies which rely heavily upon the accuracy of the attenuation calculations.