1. Swiss Light Source, Paul Scherrer Institut, CH 5232 Villigen PSI, Switzerland.
2. Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, UK.
3. ISIS Facility, RAL, Oxfordshire OX11 0QX, UK.
4. Diamond Light Source Limited, Oxfordshire OX11 0DE, UK.