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Title: Monte Carlo simulation of the resolution volume for the SEQUOIA spectrometer

  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
DOE Contract Number:
Resource Type:
Resource Relation:
Conference: QENS-WINS 2014, Autrans, France, 20140512, 20140516
Country of Publication:
United States

Citation Formats

Granroth, Garrett E. Monte Carlo simulation of the resolution volume for the SEQUOIA spectrometer. United States: N. p., 2015. Web.
Granroth, Garrett E. Monte Carlo simulation of the resolution volume for the SEQUOIA spectrometer. United States.
Granroth, Garrett E. 2015. "Monte Carlo simulation of the resolution volume for the SEQUOIA spectrometer". United States. doi:.
title = {Monte Carlo simulation of the resolution volume for the SEQUOIA spectrometer},
author = {Granroth, Garrett E},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2015,
month = 1

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  • Simulation of an inelastic scattering experiment, with a sample and a large pixilated detector, usually requires days of time because of finite processor speeds. We report simulations on an SNS (Spallation Neutron Source) instrument, SEQUOIA, that reduce the time to less than 2 hours by using parallelization and the resources of the TeraGrid. SEQUOIA is a fine resolution (∆E/Ei ~ 1%) chopper spectrometer under construction at the SNS. It utilizes incident energies from Ei = 20 meV to 2 eV and will have ~ 144,000 detector pixels covering 1.6 Sr of solid angle. The full spectrometer, including a 1-D dispersivemore » sample, has been simulated using the Monte Carlo package McStas. This paper summarizes the method of parallelization for and results from these simulations. In addition, limitations of and proposed improvements to current analysis software will be discussed.« less
  • It is proposed to build an inverse geometry spectrometer to provide extremely high energy resolution (0.2 {mu}eV FWHM, elastic) at the Long Wavelength Target Station (LWTS) at SNS. The design employs mica analyzers in close to backscattering geometry (final neutron wavelength of 20 Angstroms). Analytical calculations and Monte Carlo simulations (using the McStas package) have been used to optimize the layout of individual components and to estimate the instrument performance. This design requires a long initial guide section of 63 m from moderator to sample in order to achieve the timing resolution necessary for the desired {Delta}{omega}. The LWTS willmore » provide the high flux of long wavelength neutrons at the requisite pulse rate required by the spectrometer design. The resolution of this spectrometer lies between that routinely achieved by spin echo techniques and the design goal of the high power target station backscattering spectrometer. Covering this niche in energy resolution will allow systematic studies over the large dynamic range required by many disciplines. Molecular biology, for example, often requires systematic studies of many similar molecules under slightly different conditions, requiring a large range of energy/timing resolutions for optimum study.« less
  • A Monte Carlo simulation of dynode statistics has been used to generate multiphotoelectron distributions to compare with actual photomultiplier resolution results. In place of Poission of Polya statistics, in this novel approach, the basis for the simulation is an experimentally determined single electron response. The relevance of this method to the study of intrinsic line widths of scintillators is discussed.
  • The study of texture and grain boundary misorientation in multiphase materials has been greatly benefited from the recent automation of the electron back-scattered diffraction (EBSD) technique. With this technique, each phase in a multiphase material can be individually sampled and analyzed. This is of great significance and interest in the study of thin films, inclusions and multiphase alloys. Spatial resolution, which depends on experimental conditions such as beam energy and specimen tilt, and the material being studied, is critical in order to determine the orientation of different phases in multiphase materials. The Monte Carlo (MC) method has been effectively usedmore » to investigate spatial resolution in single phase materials. In this paper, the MC simulation is modified and applied to two-phase geometries, specifically an Al/Au specimen, and a 750 nm thick Au film on a SiO{sub 2} substrate.« less