Probing soil moisture

Transcription

1 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

2 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 ( [2] The Clay Research Group (

3 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 ( [2] The Clay Research Group (

4 Can neutrons of the cosmic radiation primary (high energetic) nucleus be used to probe the moisture content of the soil?

5 Can neutrons of the cosmic radiation primary (high energetic) nucleus be used to probe the moisture content of the soil? (dry) soil water

6 Can neutrons of the cosmic radiation primary (high energetic) nucleus be used to probe the moisture content of the soil? (dry) soil water

7 Can neutrons of the cosmic radiation primary (high energetic) nucleus be used to probe the moisture content of the soil? (dry) soil water

8 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

9 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?

10 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

11 The cosmic neutron spectrum 4

12 The cosmic neutron spectrum Σ: 150 pro (m 2 s) 4

13 The cosmic neutron spectrum Base Spectrum

14 The cosmic neutron spectrum Elastic Scattering 2

15 The cosmic neutron spectrum Elastic Scattering 2

16 The cosmic neutron spectrum Thermal E = O(k B 300K) 2

17 The cosmic neutron spectrum Thermal E = O(k B 300K) 2

18 Neutron spectra examples 100 % water 1 % water 6

19 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

20 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

21 Intensity [A.U.] Relative Intensity Neutron spectra for different humidities (with thermal neutron cutoff) 21% vol moisture 20 C 20 C 30 C 30 C 35 C 38 C 8

22 Intensity [A.U.] Relative Intensity Neutron spectra for different humidities (with thermal neutron cutoff) 21% vol moisture 20 C 20 C 30 C 30 C 35 C 38 C 8

23 Intensity [A.U.] Intensity [A.U.] Neutron spectra of a simulated Detector all neutrons 100 % vol. water 1 % vol. water only surface scattered 9

24 Range distribution of scattered neutrons range D 10 68% quantile 95% quantile radial distance [m]

25 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

26 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

27 Outlook Understand data collected by actual in-the-field measurements (Neutron Monitor) (Moisture Sensor Array) Think of: How should a detector look like? 13

28 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

29 Backup Slides

30 Altitude [m] Example Paths Neutron scattered off the ground Neutron scattered in water

31 Example Cross Section [JANIS 3.4]