[1] West Xray Solut, 405 Whirlowdale Rd, Sheffield S11 9NF, S Yorkshire, England
[2] Oxford Instruments Ind Anal, Abingdon OX13 5QX, Oxon, England
[3] Vienna Univ Technol, Atominst, A-1020 Vienna, Austria
[4] Open Univ, Fac Sci, Milton Keynes MK7 6AA, Bucks, England
[5] Flemish Inst Technol Res VITO, B-2400 Mol, Belgium