College Park, Maryland      June 6 - 10 , 2004

W3-A8: Breakout session for VISION, an neutron vibrational spectrometer for SNS

J.Z. Larese (Chemistry Department,, University of Tennessee; Oak Ridge National Laboratory), B.S. Hudson (Chemistry Department, Syracuse University), L.L. Daemen (LANSCE, Los Alamos National Laboratory)

At this breakout discussion we will discuss the VISION project, a neutron vibrational spectrometer for the SNS. We encourage all interested participants of the ACNS to attend. At the breakout session we will provide information on the purpose, performance and status of the VISION project in the form of a short presentation. VISION has been designated by SNS as one of the viable instruments for inclusion in the first target station instrument suite. We will follow the informational segment with a town meeting or round table discussion to address community inclusion, outreach and participation by members of the neutron community. We will close with a brief team meeting to discuss and develop a strategy to move the project into the next (design and engineering) phase and to discuss funding and technical issues that are relevant to the project at the time of the ACNS meeting. Several members of the VISION team will be called upon to give a brief highlight of the types of science possible with such an instrument.

There is a need in the United States for a state-of-the-art neutron scattering instrument for vibrational spectroscopy to investigate the structure and dynamics of condensed matter systems by the simultaneous use of elastic diffraction and moderate resolution (1-2% DE/E) inelastic scattering over a broad energy transfer range. The use of neutron vibrational spectroscopy (NVS) is growing at a significant rate in Europe thanks to the second-generation instrument TOSCA at ISIS, the spallation neutron source at the Rutherford-Appleton Laboratory in England. We propose to design a next generation, time of flight (TOF) spectrometer named, VISION, which is not an acronym, to investigate a vast array of molecular dynamics and structure. Under optimal conditions this instrument will - have a throughput two orders of magnitude greater than TOSCA –currently the best instrument in the field; - cover an energy transfer range of 0-500 meV (0-4000 cm-1 ); - have a 1-2% energy resolution while simultaneously enabling diffraction studies for structural characterization; - offer a wide range of sample environments (low temperature, high-pressure, flow cell, thermal analysis, etc). Our approach will incorporate neutron techniques developed during the decade since TFXA and TOSCA were first designed and built. This includes improved supermirror technology, parametrically matched crystal analyzer–helium gas detectors, efficient electronics for high rate data acquisition, high-performance data analysis algorithms, novel moderator concepts, as well as the use of (by now) well-developed Monte Carlo software for neutron optics and instrument design and optimization. The flux available at SNS will enable for the first time time-resolved vibrational measurements at a neutron source. Proposals to form an Instrument Design Team (IDT) and a subsequent proposal describing the scientific background for VISION have been presented to the Spallation Neutron Source (SNS) Experimental Facilities Advisory Committee (EFAC) and have been positively received. (EFAC has enthusiastically endorsed the science case presented by the IDT and a beamline position for installation and construction of VISION has been identified by SNS.) We are confident that VISION’s broader impact will be that an entirely new segment of users will be brought into the U.S. neutron community. This is exemplified by the extraordinary expansion in recent years of the community of scientists in the United Kingdom and the European Union using TOSCA at ISIS. Indeed, TOSCA is now routinely oversubscribed by a factor of 1.5 to 2. The demand for beam time is so great that only a few days per year are available to investigate novel applications. Furthermore, the VISION instrument will introduce a new generation of students and researchers to the use of neutron vibrational spectroscopy in the study of new materials and a wide range of engineering problems, especially those materials that have interesting structure and dynamics on the nanometer length scale and topics of commercial importance. VISION will substantially expand the range and flexibility of neutron investigations in in the United States. It will open new and fruitful directions for studies of atomic and molecular dynamics and structure in condensed matter.

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