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Title: Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

Abstract

Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm{sup 2} to 20 × 20 mm{sup 2}. This increase in brightness has the potential to translate to an increase of beam intensity at the instruments’ sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxesmore » in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. A first effort was undertaken to group decoupled moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.« less

Authors:
; ; ; ;  [1]
  1. Instrument and Source Division, Oak Ridge National Laboratory, P.O. Box 2008, MS6466, Oak Ridge, Tennessee 37831 (United States)
Publication Date:
OSTI Identifier:
22597968
Resource Type:
Journal Article
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 87; Journal Issue: 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0034-6748
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ACCELERATORS; BEAMS; BRIGHTNESS; BURNOUT; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; CYLINDRICAL CONFIGURATION; GEV RANGE 01-10; HYDROGEN; MODERATORS; NEUTRON EMISSION; NEUTRON SOURCES; NEUTRONS; ORNL; PEAKS; PROTONS; PULSES; SPALLATION; TIN SULFIDES

Citation Formats

Gallmeier, F. X., E-mail: gallmeierfz@ornl.gov, Lu, W., Riemer, B. W., Zhao, J. K., Herwig, K. W., and Robertson, J. L. Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station. United States: N. p., 2016. Web. doi:10.1063/1.4953612.
Gallmeier, F. X., E-mail: gallmeierfz@ornl.gov, Lu, W., Riemer, B. W., Zhao, J. K., Herwig, K. W., & Robertson, J. L. Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station. United States. https://doi.org/10.1063/1.4953612
Gallmeier, F. X., E-mail: gallmeierfz@ornl.gov, Lu, W., Riemer, B. W., Zhao, J. K., Herwig, K. W., and Robertson, J. L. Wed . "Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station". United States. https://doi.org/10.1063/1.4953612.
@article{osti_22597968,
title = {Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station},
author = {Gallmeier, F. X., E-mail: gallmeierfz@ornl.gov and Lu, W. and Riemer, B. W. and Zhao, J. K. and Herwig, K. W. and Robertson, J. L.},
abstractNote = {Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm{sup 2} to 20 × 20 mm{sup 2}. This increase in brightness has the potential to translate to an increase of beam intensity at the instruments’ sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. A first effort was undertaken to group decoupled moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.},
doi = {10.1063/1.4953612},
url = {https://www.osti.gov/biblio/22597968}, journal = {Review of Scientific Instruments},
issn = {0034-6748},
number = 6,
volume = 87,
place = {United States},
year = {2016},
month = {6}
}

Works referencing / citing this record:

Conceptual design of CHESS, a new direct-geometry inelastic neutron spectrometer dedicated to studying small samples
journal, March 2018