Acknowledgements

The authors would like to thank F.McDevitt, A.Meikle and F.Doherty for technical support and all those at the ISIS, CERN PS and PSI facilities during the irradiation runs. One of us (R.Bates) gratefully acknowledges the support received through a CASE postgraduate studentship from RAL. The results obtained within the RD8 collaboration are from work partly funded by PPARC (UK), INFN (Italy), and the BMFD (Germany).