1. Use of Cosmic-Ray Neutron Data in Nuclear Threat Detection and Other Applications: Hydrology +
Neutron Monitor Community Workshop—Honolulu, Hawaii
October 24-25, 2015
Paul Goldhagen
Physicist National Urban Security Technology Laboratory Science and Technology Directorate

2. Hydrology Zreda, Desilets, et al., Univ. of Arizona, Sandia Natl. Lab.
Measure soil water, snow, biomass using cosmogenic neutrons
Previously elusive scale, tens of hectares, 10 – 60 cm deep
Same principal as Am-Be soil moisture gauges: water moderates / thermalizes evaporation (MeV) neutrons
Use moderated (and bare) neutron detectors to measure rates of 1 – 1000 eV slowing-down neutrons (and thermals)
Over 200 probes in use
COSMOS network in U.S. (NSF); networks in other countries
Thermal-neutron rate depends on soil composition
Normalize using neutron monitor rate; best if nearby (U.S.)
COSMOS: Cosmic Ray Soil Moisture Observing System
Understand spectrum using MCNP6.

3. Cosmic-ray neutron spectrum
Thermal
High energy
Slowing-down region ~1/E
Evaporation

4. Cosmic-ray neutron surface moisture probe
M. Zreda, Third COSMOS workshop, 2012

5. What is sensed
M. Zreda, Third COSMOS workshop, 2012

6. Hydrology Zreda, Desilets, et al., Univ. of Arizona, Sandia Natl. Lab.
Measure soil water, snow, biomass using cosmogenic neutrons
Previously elusive scale, tens of hectares, 10 – 60 cm deep
Same principal as Am-Be soil moisture gauges: water moderates / thermalizes evaporation (MeV) neutrons
Use moderated (and bare) neutron detectors to measure rates of 1 – 1000 eV slowing-down neutrons (and thermals)
Over 200 probes in use
COSMOS network in U.S. (NSF); networks in other countries
Thermal-neutron rate depends on soil composition
Normalize using neutron monitor rate; best if nearby (U.S.)
COSMOS: Cosmic Ray Soil Moisture Observing System
Understand spectrum using MCNP6.

7. Cosmic-ray probe locations (2012)
2012: 123 probes : >200 probes
M. Zreda, Third COSMOS workshop, 2012

8. Hydrology Zreda, Desilets, et al., Univ. of Arizona, Sandia Natl. Lab.
Measure soil water, snow, biomass using cosmogenic neutrons
Previously elusive scale, tens of hectares, 10 – 60 cm deep
Same principal as Am-Be soil moisture gauges: water moderates / thermalizes evaporation (MeV) neutrons
Use moderated (and bare) neutron detectors to measure rates of 1 – 1000 eV slowing-down neutrons (and thermals)
Over 200 probes in use
COSMOS network in U.S. (NSF); networks in other countries
Thermal-neutron rate depends on soil composition
Normalize using neutron monitor rate; best if nearby (U.S.)
COSMOS: Cosmic Ray Soil Moisture Observing System
Understand spectrum using MCNP6.

9. Another group of other applications of cosmic-ray neutron data

10. Production of cosmogenic radionuclides
Cosmic-ray neutrons create cosmogenic radionuclides in the air and ground
Atmospheric tracers (7Be)
Geological dating (10Be,14C, 36Cl, …)
Background for neutron activation measurements
Source terms require knowledge of cosmic-ray neutron spectrum and intensity
For shorter half-life nuclides, intensity requires neutron monitor data
DS2002 resolution of Hiroshima neutron dosimetry discrepancy
Measurements of neutron activation nuclides in Hiroshima samples (36Cl, 60Co, 63Ni, 152Eu) seemed high at large distances. Actually caused by cosmic-ray neutron background.