Probing soil moisture by cosmic ray induced neutron showers U. Schmidt AG Dubbers Ruprecht-Karls-Universität Heidelberg 19. März 2014 in collaboration with: Martin Schrön Helmholtz Center for Environmental Research Leipzig
Present: The measurement of moisture via satellite remote sensing (optical, microwave) [1] [2] via local techniques (electrical resistivity, capacitance, etc) (even neutrons ) 1 [1] ESA SMOS (http://www.esa.int/our_activities/observing_the_earth/smos/horn_of_africa_drought_seen_from_space) [2] The Clay Research Group (http://www.theclayresearchgroup.org/images/ert.jpg)
Present: The measurement of moisture via satellite remote sensing (optical, microwave) No (affordable) technique in between [1] via local techniques (electrical resistivity, capacitance, etc) (even neutrons ) [2] 1 [1] ESA SMOS (http://www.esa.int/our_activities/observing_the_earth/smos/horn_of_africa_drought_seen_from_space) [2] The Clay Research Group (http://www.theclayresearchgroup.org/images/ert.jpg)
Can neutrons of the cosmic radiation primary (high energetic) nucleus be used to probe the moisture content of the soil?
Can neutrons of the cosmic radiation primary (high energetic) nucleus be used to probe the moisture content of the soil? (dry) soil water
Can neutrons of the cosmic radiation primary (high energetic) nucleus be used to probe the moisture content of the soil? (dry) soil water
Can neutrons of the cosmic radiation primary (high energetic) nucleus be used to probe the moisture content of the soil? (dry) soil water
Can neutrons of the cosmic radiation primary (high energetic) nucleus be used to probe the moisture content of the soil? D D (dry) soil water
Can neutrons of the cosmic radiation primary (high energetic) nucleus be used to probe the moisture content of the soil? range? D intensity? soil scattering & energy dependence?
Why a Monte Carlo simulation? Neutrons are difficult to detect moderator [thickness depends on energy] detector (absorber) just counts with bad energy and angular resolution 3
The cosmic neutron spectrum 4
The cosmic neutron spectrum Σ: 150 pro (m 2 s) 4
The cosmic neutron spectrum Base Spectrum
The cosmic neutron spectrum Elastic Scattering 2
The cosmic neutron spectrum Elastic Scattering 2
The cosmic neutron spectrum Thermal E = O(k B 300K) 2
The cosmic neutron spectrum Thermal E = O(k B 300K) 2
Neutron spectra examples 100 % water 1 % water 6
Intensity [A.U.] Relative Intensity Neutron spectra for soil of different moisture (with thermal neutron cutoff) 0% 5% 0% 5%15% 25% 99% 15% 25% 35% 70% 99% 7
Intensity [A.U.] Relative Intensity Neutron spectra for soil of different moisture (with thermal neutron cutoff) 0% 5% 0% 5%15% 25% 99% 15% 25% 35% 70% 99% 7
Intensity [A.U.] Relative Intensity Neutron spectra for different humidities (with thermal neutron cutoff) 21% vol moisture 0% @ 20 C 50% @ 20 C 50% @ 30 C 100% @ 30 C 100% @ 35 C 100% @ 38 C 8
Intensity [A.U.] Relative Intensity Neutron spectra for different humidities (with thermal neutron cutoff) 21% vol moisture 0% @ 20 C 50% @ 20 C 50% @ 30 C 100% @ 30 C 100% @ 35 C 100% @ 38 C 8
Intensity [A.U.] Intensity [A.U.] Neutron spectra of a simulated Detector all neutrons 100 % vol. water 1 % vol. water only surface scattered 9
Range distribution of scattered neutrons range D 10 68% quantile 95% quantile radial distance [m]
Range of the cosmic neutron probe Radius of 68% of the neutrons (Q 0.68 ) Radius of 95% of the neutrons (Q 0.95 ) 11
Concluding Cosmic ray induced neutrons provide a probe for soil moisture [If the detector is well suited for 10 ev to 100 kev] [and other more easy to determine - influences are known] especially for slight changes at low moisture in a radius of about 70 meters at Q 0.68 12
Outlook Understand data collected by actual in-the-field measurements (Neutron Monitor) (Moisture Sensor Array) Think of: How should a detector look like? 13
Probing soil moisture by cosmic ray induced neutron showers - fin- Thank you U. Schmidt AG Dubbers Ruprecht-Karls-Universität Heidelberg in collaboration with: Martin Schrön Helmholtz Center for Environmental Research Leipzig
Backup Slides
Altitude [m] Example Paths Neutron scattered off the ground Neutron scattered in water
Example Cross Section [JANIS 3.4]