Use of Cosmic-Ray Neutron Data in Nuclear Threat Detection and Other Applications Neutron Monitor Community Workshop—Honolulu, Hawaii October 24-25, 2015 Paul Goldhagen Physicist National Urban Security Technology Laboratory Science and Technology Directorate National Urban Security Technology Laboratory (formerly, Environmental Measurements Laboratory) . DHS Government lab in New York City Science and Technology Directorate . ~30 people . Established 1947, AEC- DOE - DHS . HASL - EML - NUSTL . Support to emergency responders . Long history of fallout and radiation measurements . 35 years of neutron spectrometry Paul Goldhagen Uses of cosmic-ray neutron data 2 Overview . Cosmic rays and cosmic-ray-induced (cosmogenic) neutrons . Variation of cosmic particle intensity in the atmosphere . Cosmic rays and cosmogenic neutrons on Earth affect: . Nuclear threat detection for homeland/national security . Measurements for nuclear treaty verification . Microelectronics reliability (single-event upsets) . Radiation dose to airplane crews/passengers (and everyone) . Hydrology measurements . Production of cosmogenic radionuclides – atmospheric tracers, geological dating, background for neutron activation . Calculations and measurements of cosmic-ray neutron spectra . Importance of neutron monitor data Paul Goldhagen Uses of cosmic-ray neutron data 3 Cosmic rays in Earth’s atmosphere electrons/positrons photons neutrons protons mesons muons Paul Goldhagen Uses of cosmic-ray neutron data 4 Cosmic-ray-induced neutrons in the atmosphere . Cosmic rays: energetic atomic nuclei from space . Protons (90%), He ions (9%), heavier ions (1%); No neutrons . Collision with atmosphere cascades of all kinds of particles, including neutrons (and protons, mesons, muons, photons, electrons) . Two kinds / sources . Galactic (GCR) – continual, high energy, dominate effects . Solar – sporadic (~1 GLE/y), high rates for hours, lower energy, affect GCR . GCR-induced neutrons dominate radiation effects in the atmosphere from airplane altitudes to the ground . Rates depend on air pressure, magnetic latitude, solar activity, and nearby materials . Materials can scatter, absorb, moderate, regenerate neutrons . Effects depend on neutron energy distribution Paul Goldhagen Uses of cosmic-ray neutron data 5 GCR neutron rates in the atmosphere depend on . Altitude or air pressure - Shielding by air . Big effect, but calculable, measured, well known . Neutron rate at 10,000 ft. = 11 rate at sea level . Barometric pressure changes can change rate >50% at sea level . Latitude - Shielding by geomagnetic field . Calculable, measured . Effect increases with altitude . Rate at poles / equator 8 at 20 km, 3.3 at 9 km, 2 at sea level . Solar activity - magnetic field of solar wind . Not calculable, measured by neutron monitors . ~11-year sunspot cycle: Radiation min at sunspot max . Effect increases with geomagnetic latitude & altitude . Solar modulation >2 (polar) at 20 km, <30% at sea level Paul Goldhagen Uses of cosmic-ray neutron data 6 Neutron monitor Raw count rate count rate and barometric pressure during super-storm Sandy 760 Newark neutron monitor 12 days in 2012 Pressure-corrected rate Neutron count rate (counts/sec) Pressure Pressure (mm-Hg) 712 Paul Goldhagen Uses of cosmic-ray neutron data 7 Effect of air pressure (elevation) Log scale ) 500 Fremont Pass, CO -1 (11,300 ft) s Leadville, CO (10,300 ft) -2 300 (m 200 Mt. Washington, NH > 10 MeV > 10 (6,250 ft) E 100 Neutron flux decreases exponentially with increasing 50 air pressure Yorktown Heights, NY Houston, TX Neutron Flux, 30 700 800 900 1000 Atmospheric Depth (g cm-2) Paul Goldhagen Uses of cosmic-ray neutron data 8 Effect of geomagnetic field (latitude) /h) 4 Calculated Count Rate (10 Measured Paul Goldhagen Uses of cosmic-ray neutron data 9 Solar activity changes Paul Goldhagen Uses of cosmic-ray neutron data 10 Sunspot number and GCR flux Paul Goldhagen Uses of cosmic-ray neutron data 11 Solar modulation of cosmic-ray neutron flux Daily neutron monitor rate in Delaware Paul Goldhagen Uses of cosmic-ray neutron data 12 Uses of cosmic-ray neutron data Paul Goldhagen Uses of cosmic-ray neutron data Radiation detection to find nuclear threats . DHS, DOE, and DoD fund programs to improve detection of hidden nuclear devices and fissile materials . Primary method is radiation detection . Passive detection – detect gamma rays emitted by uranium and gammas and neutrons emitted by plutonium . Active interrogation: use pulsed incident radiation; detect neutrons and rays from induced fission of HEU as well as Pu . To find hidden materials, detectors must be sensitive enough to detect / measure background radiation . Passive gamma detection: Low-E rays easily shielded; variable background from common radioactive materials; nuisance alarms from medical treatments, commercial sources Paul Goldhagen Uses of cosmic-ray neutron data 14 Neutron detection for homeland/national security . Neutrons are a signature of fissile materials . Plutonium emits neutrons – spontaneous fission of 240Pu . Common radioactive materials don’t . Passive neutron detection . Far fewer nuisance alarms for neutrons than for gamma rays . Neutrons are harder to shield than gamma rays . Active interrogation: use pulsed incident radiation; detect neutrons and rays from induced fission of HEU as well as Pu . To find hidden materials, detectors must be sensitive enough to detect / measure background . The background for neutron detection is neutrons produced by cosmic rays Paul Goldhagen Uses of cosmic-ray neutron data 15 Need to understand background neutrons Background rate in deployed detectors can and must be measured, but need to understand background in advance to: . Design new, better detection systems . Improve signal/background; reduce nuisance alarms . Test and compare developmental detection systems . Deal with rapidly varying position-dependent background . Mobile standoff detection in cities – varying shielding from buildings . Searching ships . For some applications, can’t measure background, must calculate it . For some applications, cosmogenic neutrons are the signal Paul Goldhagen Uses of cosmic-ray neutron data 16 Background radiation algorithm development . DHS DNDO TAR funded LANL, NUSTL, UD to calculate the cosmic-ray neutron background everywhere on Earth. UD: Primary CR spectrum, directional geomagnetic cutoffs, atmosphere . LANL: coding, normalization, transport, solar modulation . NUSTL: Benchmark measurements of cosmogenic neutron energy spectra in airplane and on ground at various locations . MCNP6 calculations: cosmic source, method, results, version 2.0 . n, p, , spectra on 2054 point global grid at ground and 10 altitudes . Directional n, spectra on ground; altitude scaling to location of interest . Agreement with NUSTL measurements . Date (corresponding to NM data) is an input. To be valid in future, calculations require ongoing neutron monitor data Supported by the US Department of Homeland Security, Domestic Nuclear Detection Office, under competitively awarded contract/IAA HSHQDC-12-X-00251. Paul Goldhagen Uses of cosmic-ray neutron data 17 MCNP6 cosmic source option . Built-in spectra Description of SDEF keywords. Keyword Values Description . Historic (PRL / Lal, 1980) . Modern (UoD / Clem, 2006) [-]cr All cosmic particles [-]ch Cosmic protons only [-]ca Cosmic alphas only PAR . SDEF card [-]c7014 Cosmic nitrogen only . PAR keyword enhanced [-]c14028 Cosmic silicon only [-]c26056 Cosmic iron only . New keyword DAT . New keyword LOC (Clem) M Month (1-12) DAT D Day (1-31) Y Year (4 digit) . Benchmarking LAT Latitude (-90 to 90; S to N) . NASA ER-2 flights LOC LNG Longitude (-180 to 180; W to E) ALT Altitude (km) . NUSTL Long Dwell / Goldhagen Garrett McMath and Gregg McKinney LANL, Nuclear Engineering & Nonproliferation Division Paul Goldhagen Uses of cosmic-ray neutron data 18 Cosmic-ray neutron spectrum on the ground Livermore, CA - Nov 2006 20 ) Measured -1 Calculated sec with geomagnetic field -2 in the atmosphere m 10 /dE ( /dE E d 0 10-8 10-6 10-4 10-2 100 102 104 Neutron Energy (MeV) Paul Goldhagen Uses of cosmic-ray neutron data 19 2 Ways to plot neutron spectra dΦ/dE vs E Same data EdΦ/dE vs E ) -1 104 30 MeV Flux -1 2 ) s 10 -1 proportional -2 s -2 to area (m 0 20 10 (m under curve /dE . /dE -2 . d 10 10-4 E·d 10 10-6 Differential Flux, Differential 10-8 0 10-8 10-6 10-4 10-2 100 102 104 10-8 10-6 10-4 10-2 100 102 104 Neutron Energy (MeV) Neutron Energy (MeV) Paul Goldhagen Uses of cosmic-ray neutron data 20 Cosmic-ray neutron spectrum 20 Evaporation ) Measured -1 High energy Calculated sec -2 Thermal m 10 /dE ( E d Slowing-down region ~1/E 0 10-8 10-6 10-4 10-2 100 102 104 Neutron Energy (MeV) Paul Goldhagen Uses of cosmic-ray neutron data 21 NUSTL measurements . NUSTL has measured the energy spectrum of cosmic-ray neutrons on: . Airplanes . Ground . Ships Components of NUSTL’s new neutron spectrometer Paul Goldhagen Uses of cosmic-ray neutron data 22 Measurement on the ground Livermore, CA - Nov 2006 Paul Goldhagen Uses of cosmic-ray neutron data 23 2 Ways to plot neutron spectra dΦ/dE vs E Same data EdΦ/dE vs E ) -1 104 30 MeV Flux -1 2 ) s 10 -1 proportional -2 s -2 to area (m 0 20 10 (m under curve /dE . /dE -2 . d 10 10-4 E·d 10 10-6 Differential Flux, Differential 10-8 0 10-8 10-6 10-4 10-2 100 102 104 10-8 10-6 10-4 10-2 100 102 104 Neutron Energy (MeV) Neutron Energy (MeV) Paul Goldhagen Uses of cosmic-ray neutron data 24 Measurements on these container ships SS Lurline 826 ft 22,221