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Title: Measurement of high-energy neutron flux above ground utilizing a spallation based multiplicity technique

Cosmogenic high-energy neutrons are a ubiquitous, difficult to shield, poorly measured background. Above ground the high-energy neutron energy-dependent flux has been measured, with significantly varying results. Below ground, high-energy neutron fluxes are largely unmeasured. Here we present a reconstruction algorithm to unfold the incident neutron energy-dependent flux measured using the Multiplicity and Recoil Spectrometer (MARS), simulated test cases to verify the algorithm, and provide a new measurement of the above ground high-energy neutron energy-dependent flux with a detailed systematic uncertainty analysis. Uncertainty estimates are provided based upon the measurement statistics, the incident angular distribution, the surrounding environment of the Monte Carlo model, and the MARS triggering efficiency. Quantified systematic uncertainty is dominated by the assumed incident neutron angular distribution and surrounding environment of the Monte Carlo model. The energy-dependent neutron flux between 90 MeV and 400 MeV is reported. Between 90 MeV and 250 MeV the MARS results are comparable to previous Bonner sphere measurements. Over the total energy regime measured, the MARS result are located within the span of previous measurements. Lastly, these results demonstrate the feasibility of future below ground measurements with MARS.
Authors:
 [1] ;  [2] ;  [3] ;  [4]
  1. Univ. of California, Berkeley, CA (United States). Dept. of Nuclear Engineering
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Nuclear and Chemical Sciences Division
  3. Sandia National Lab. (SNL-CA), Livermore, CA (United States). Radiation and Nuclear Detection Systems
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Nuclear Science Division
Publication Date:
Report Number(s):
SAND-2016-6353J; SAND-2017-0536J
Journal ID: ISSN 0018-9499; 643448; TRN: US1701258
Grant/Contract Number:
AC04-94AL85000; NA0000979; AC5-07NA27344
Type:
Accepted Manuscript
Journal Name:
IEEE Transactions on Nuclear Science
Additional Journal Information:
Journal Volume: 63; Journal Issue: 6; Journal ID: ISSN 0018-9499
Publisher:
IEEE
Research Org:
Sandia National Lab. (SNL-CA), Livermore, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA) Nuclear Science and Security Consortium (NSSC)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; cosmogenic neutrons; high-energy neutron spectroscopy; neutrons; energy measurement; particle measurements; spectroscopy; detectors; Monte Carlo methods
OSTI Identifier:
1340509
Alternate Identifier(s):
OSTI ID: 1361647