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Published January 2012 | Published
Journal Article Open

Design and operation of the wide angular-range chopper spectrometer ARCS at the Spallation Neutron Source

Abstract

The wide angular-range chopper spectrometer ARCS at the Spallation Neutron Source (SNS) is optimized to provide a high neutron flux at the sample position with a large solid angle of detector coverage. The instrument incorporates modern neutron instrumentation, such as an elliptically focused neutron guide, high speed magnetic bearing choppers, and a massive array of ^3He linear position sensitive detectors. Novel features of the spectrometer include the use of a large gate valve between the sample and detector vacuum chambers and the placement of the detectors within the vacuum, both of which provide a window-free final flight path to minimize background scattering while allowing rapid changing of the sample and sample environment equipment. ARCS views the SNS decoupled ambient temperature water moderator, using neutrons with incident energy typically in the range from 15 to 1500 meV. This range, coupled with the large detector coverage, allows a wide variety of studies of excitations in condensed matter, such as lattice dynamics and magnetism, in both powder and single-crystal samples. Comparisons of early results to both analytical and Monte Carlo simulation of the instrument performance demonstrate that the instrument is operating as expected and its neutronic performance is understood. ARCS is currently in the SNS user program and continues to improve its scientific productivity by incorporating new instrumentation to increase the range of science covered and improve its effectiveness in data collection.

Additional Information

© 2012 American Institute of Physics. Received 14 July 2011; accepted 4 January 2012; published online 31 January 2012. The ARCS project was only made possible by the support of numerous colleagues at the SNS, Caltech and the IDT members. In particular, expert design work was provided by K. Shaw and S. Howard, outstanding support for neutronic calculations by E. Iverson, and excellent project management by P. Albertson and B. Thibadeau. Many essential discussions were held with J. Ankner, J. Carpenter, G. Ehlers, G. Granroth, M. Hagen, and K. Herwig.We acknowledge T. Kelley for his work on creating the early version of the reduction software, and M. Aivazis for his guidance on software architecture and design. We thank D. Mikkelson, R. Mikkelson, and A. Schultz for developing the ISAW handling of ARCS data. A. Kolesnikov graciously provided the idea and sample for the C4H2I2S measurement. Data for the liquid 4He measurement were provided by S. Diallo, R. Azuah and H. Glyde. Data for the FeSi single crystal measurements were provided by O. Delaire. ARCS was supported by the DOE under Grant No. DE-FG02-01ER45950. ORNL/SNS is managed by UT-Battelle, LLC, for the DOE under Contract No. DE-AC05-00OR22725. Research at the SNS was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, DOE.

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August 19, 2023
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