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

Journal Article · · IEEE Transactions on Nuclear Science
 [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
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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.
Research Organization:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Sandia National Laboratories (SNL-CA), Livermore, CA (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA); USDOE National Nuclear Security Administration (NNSA) Nuclear Science and Security Consortium (NSSC)
Grant/Contract Number:
AC04-94AL85000; AC52-07NA27344; NA0000979
OSTI ID:
1340509
Alternate ID(s):
OSTI ID: 1513114
OSTI ID: 1361647
OSTI ID: 1458482
Report Number(s):
LLNL-JRNL--695883; SAND--2016-6353J; SAND--2017-0536J; 643448
Journal Information:
IEEE Transactions on Nuclear Science, Journal Name: IEEE Transactions on Nuclear Science Journal Issue: 6 Vol. 63; ISSN 0018-9499
Publisher:
IEEECopyright Statement
Country of Publication:
United States
Language:
English

Figures / Tables (7)

Fig. 1(p. 3)figure Fig. 1
TABLE I(p. 3)table TABLE I
Fig. 2(p. 5)figure Fig. 2
Fig. 3(p. 5)figure Fig. 3
Fig. 4(p. 5)figure Fig. 4
Fig. 5(p. 5)figure Fig. 5
Fig. 5(p. 5)figure Fig. 5

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Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
Monte Carlo methods
cosmogenic neutrons
detectors
energy measurement
high-energy neutron spectroscopy
neutrons
particle measurements
spectroscopy