M. Celli 1 , D. Colognesi 1 , S. F. Parker 2 , V. Rossi-Albertini 3 , F. Sacchetti 4 , J. Tomkinson 2 , and M. Zoppi 1 (

1. Science with TOSCA: The principles of molecular transitions Virtual level Excited molecular levels Ground level E0=p02/2m=incoming neutron energy E1=p12/2m=scattered neutron energy = E0- E1 =energy transfer Q= p0-p1 = momentum transfer THE NEUTRON SPECTROMETER TOSCA M. Celli1, D. Colognesi1, S. F. Parker2, V. Rossi-Albertini3, F. Sacchetti4, J. Tomkinson2, and M. Zoppi1 (zoppi@ifac.cnr.it) 1IFAC-CNR (IT); 2ISIS - R.A.L. (UK); 3ISM-CNR (IT); 4Dip.to di Fisica and INFM, Univ. di Perugia (IT) View of TOSCA-II showing detector banks for forward and backward scattering. The TOSCA project (http://www.ifac.cnr.it/tosca/tosca-main.htm) The final version of the high-resolution crystal analyser spectrometer, TOSCA, has been built, installed and operated at the ISIS pulsed neutron source (Rutherford Appleton Laboratory, Chilton, Didcot, UK) as a joint project of Consiglio Nazionale delle Ricerche (Italy) and Rutherford Appleton Laboratory (UK). TOSCA is mainly intended for molecular vibrational spectroscopy but will have also some general diffraction capability with elastic detectors in forward and backward scattering (0.02-2 nm in d-plane spacing). The instrument, placed 17 m apart from the neutron water moderator, makes possible to measure inelastic neutron scattering in a large energy transfer range ω=(5-1000) meV, with a relative energy-resolution of about Δω/ω=1-2% in the whole interval of ω. It has replaced both the old TFXA, removed in spring 1998, and subsequently, a prototypical version of TOSCA (TOSCA-I) which was incorporated into the final version of TOSCA (TOSCA-II) in spring 2000. The advantage over its two predecessors is both in detected flux and energy resolution. TFXA and TOSCA-I, which were placed 12 m apart from the neutron moderator, included two and ten back-scattering detector modules, respectively and showed a Δω/ω of 3-4% and 2-2.5%, respectively. In addition, dowstream of the TOSCA spectrometer, the INES (Italian Neutron Experimental Station) experimental and test facility will be built. This experimental station will be initially equipped with a multi-purpose time-of-flight neutron diffractometer whose construction should be completed during the current year (2004). The modular instrument design, the large blockhouse, and the ample sample space will allow INES to be used for a large variety of different applications ranging from powder diffraction, to archaeometric measurements, to neutron detector testing. TOSCA-II detection geometry: the yellow arrow represents all the scattered neutrons, the black plate is the graphite analyser, the yellow block is the Be filter and the white arrow stands for the monocromatic neutrons detected by the 3He tubes. TOSCA-II inelastic spectra from potassium hydrogen phtalate at 20 K. The fully protonated sample is reported as blue line, while the red line represents a selectively deuterated one. Missing peaks clearly indicate two hydrogen bond modes.