The TOSCA incoherent inelastic neutron spectrometer: progress and results

The back-scattering part (phase I) of the new incoherent inelastic neutron spectrometer, TOSCA, replacing the old TFXA, has been successfully installed at the ISIS pulsed neutron spallation source. The results, owing to the much larger detector area, show a significant enhancement of the counting rate and an improvement of the resolution. In spring 2000, the forward scattering bank (phase II) will be completed and, during the final installation, the whole instrument will be moved from the present 12 m primary flight path to 17 m. This will result in a large improvement of the overall resolution (from 2-3% to 1-1.5% of the energy transfer). A chopper will be added in order to avoid neutron frame overlap and to reduce the fast neutron background. In addition, TOSCA will have a diffraction capability.