Detector Sensitivity

Transcription

1 Monte-Carlo Simulations on the Detector Sensitivity to Cosmic-Ray nduced Neutron Showers U. Schmidt AG Dubbers Physikalisches Institut Ruprecht-Karls-Universität Heidelberg COSMOS Workshop, 7th of May 2014 in collaboration with: Martin Schrön Helmholtz Center for Environmental Research Leipzig

2 Neutron Detector Research in Heidelberg Large Area High Resolution 1

3 Stacked Solid State Detectors 2

4 Large Area Detector - Segment With Cover Without Cover strips wires 4

5 Neutron Detector Simulation Neutrons GEM ch 2 Li α GEM ch 1 5 Energy (MeV)

6 Neutron Soil Simulation Neutrons 6

7 Neutron Soil Simulation air N 2, O 2 biomass H 2 O + (CH 2 ) Neutrons water soil H 2 O SiO 2 Al 2 O 3 6

8 Why a Monte Carlo simulation? moderator [thickness depends on energy] detector (absorber) just counts ( with bad energy and angular resolution) 8

9 The cosmic neutron spectrum [1] [1] Gordon, M.S.; Goldhagen, P.:, Measurement of the Flux and Energy Spectrum of Cosmic-Ray Induced Neutrons on the Ground, 9 Nuclear Science, IEEE Transactions on, Vol 51, Issue 6 (2004)

10 The cosmic neutron spectrum Σ: 150 pro (m 2 s) [1] 9 [1] Gordon, M.S.; Goldhagen, P.:, Measurement of the Flux and Energy Spectrum of Cosmic-Ray Induced Neutrons on the Ground, Nuclear Science, IEEE Transactions on, Vol 51, Issue 6 (2004)

11 The cosmic neutron spectrum Nuclear resonances primary Base Spectrum [1]

12 The cosmic neutron spectrum Elastic Scattering [1] 2

13 The cosmic neutron spectrum Elastic Scattering [1] 2

14 The cosmic neutron spectrum Thermal [1] E = O(k B 300K) 2

15 The cosmic neutron spectrum Thermal [1] E = O(k B 300K) 2

16 Important Reactions Type of scattering: Thermal Elastic Inelastic Evaporation [1] Absorption Absorption 11

17 Example Cross Section [JANIS 3.4] 12

18 Altitude [m] Example Paths Neutron scattered off the ground Neutron scattered in water 13 color: hue scaled by logarithmic energy of the neutron

19 Example Paths 900 Neutrons scattered off the ground into air 14

20 Neutron analytical spectrum 15

21 Neutron spectra examples 100 % water 0 % water 16 Reverse engineered fom Sato and Niita (Rev. )

22 Intensity [A.U.] Neutron spectra for soil of different moisture (with thermal neutron cutoff) 0% 0% 5% 35% 99% 5% 10% 15% 25% 35% 99% 17

23 Intensity [A.U.] Neutron spectra for soil of different moisture (with thermal neutron cutoff) 0% 5% 35% 99% operating range for possible detector 17

24 Intensity [A.U.] Neutron spectra for different humidities (with thermal neutron cutoff) 20 C 20 C 26 C 32 C 18 10% vol moisture

25 Intensity [A.U.] Neutron spectra for different plant heights (with thermal neutron cutoff) No plants 0.25 m plants 0.5 m plants 0.75 m plants 1.00 m plants 1.50 m plants 19 10% vol moisture

26 Depth distribution of the cosmic neutron probe 20 10% vol moisture

27 Depth distribution of the cosmic neutron probe max depth mean depth 21

28 Intensity [A.U.] Intensity [A.U.] Neutron spectra of a simulated Detector 100 % vol. water 1 % vol. water all neutrons only surface scattered 22

29 Intensity [A.U.] Intensity [A.U.] Neutron spectra of a simulated Detector 100 % vol. water 1 % vol. water all neutrons only surface scattered 22

30 Range distribution of scattered neutrons range D 23 70% quantile 90% quantile radial distance [m]

31 Range of the cosmic neutron probe range D 90% neutron radius 70% neutron radius 50% neutron radius 24

32 Range of the cosmic neutron probe range D 90% neutron radius 70% neutron radius 50% neutron radius 20 C 20 C 26 C 32 C 25

33 Test: Detector propagating over interface Rover driving water soil 10% vol 26

34 Test: Detector propagating over interface Rover driving water soil 10% vol 26

35 Concluding [Boron solid state detectors may be an alternative] [Tailor the detector for the optimal neutron energy range] Monte Carlo Simulations should be used to model geometries to answer some of this week s questions Actual results in disagreement with established Like: footprint varies with soil moisture 2e-folding footprint is approximately 150 m 27

36 Monte-Carlo Simulations on the Detector Sensitivity to cosmic ray induced neutron showers - finopen for discussion U. Schmidt AG Dubbers Physikalisches Institut Ruprecht-Karls-Universität Heidelberg in collaboration with: Martin Schrön Helmholtz Center for Environmental Research Leipzig

37 Backup Slides

38 Range-quantiles of neutrons for different moistures

39 Intensity distribution of a neutron source in water Data: Caswell, R.S. et al: Attenuation of 14.1 MeV Neutrons in water Nuclear Sci. and Eng. 2, 143 (1957)