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Maryvonne De Jésus

Ilias/N3/WG5 meeting

Neutron studies in Edelweiss

“Suite”

Valencia (Espana) 15/04/2005

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Plan

• Germanium nuclear recoil angular distribution in Geant 3

• Rock spectra propagation with Geant 3 and MCNPX

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Angular distribution with Geant 321

Code THALYS used to calculate differential cross sections in the CM with Koning-Delaroche set of parameters and spherical nuclei (O. Bersillon , private communication :Proper reference to the code TALYSA.J. Koning, S. Hilaire and M. Duijvestijn, TALYS: Comprehensive nuclear reaction modelingProceedings of the International Conference on Nuclear Data for Science and Technology - ND2004Sep. 26 - Oct. 1, Santa Fe, USA, to be publishedProper reference to the optical model parameters for germaniumA.J. Koning and J.P. DelarocheLocal and global nucleon optical models from 1 keV to 200 MeVNuclear Physics A 713 (2003) 231-310)

Correction :

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Modification in the SUBROUTINE COLISNIF (KZI.eq.32) call MYCANG

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Edelweiss-I neutron calibration with 232Cf

Simulation with modified Geant-321

Ratio Data/Simulation [15 , 200 ] keV : 1.5

Data vs. simulation : good agreement in the nuclear recoil spectra

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Propagation of neutrons through the LSM rock :Geant3 and MCNPX

Initial rock spetra :

- Spectrum calculated by V.Chazal (Astroparticle Phys.9 (1996)163-172 )

Neutron production in the rock : 1.143x10e-7 n/s/cm3

Neutron flux in lab reevaluated(G.Chardin et al IDM 2002 )

En > 2 MeV : 1.6x10-6 n/s/cm2

-Spectrum calculated by R.Lemrani with code SOURCES :

Neutron production in the rock : 1.133x10e-7 n/s/cm3

Rock composition introduced in Geant 3

Measured rock composition :LSM H C O Na Mg Al Si P K Ca Ti Mn Fe

% mass

Rock 1 6 49 0,44 0,84 2,6 7 0,064 0,21 31 0,07 0,03 1,9

Density : =2.65 g/cm3

% mass

Rock 1 49.3 0.8 2.6 7 31 1,9

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Geometries for simulations with geant3 :

LabRock

Air or PE

Plane geometry

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Results : LSM Geometry with scatterring

LSM Geometry without scatterring Plane Geometry

LSM Geometry with scatterring

MCNPX

V.ChazalSOURCES

Geant 3

MCNPX

V.ChazalSOURCES

Geant 3

MCNPX

V.ChazalSOURCES

Geant 3

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FLux x10-6 >1 MeV >2 MeV

LSM Direct Geant 3 V.Ch 0.62 0.41

SOURCES 0.31 0.17

MCNPX SOURCES 0.38 0.23

LSM Total Geant 3 V.Ch 1.57 1.05

SOURCES 0.81 0.44

MCNPX SOURCES 0.48 0.27

PLANE Geant3 V.Ch 0.96 0.70

SOURCES 0.62 0.35

MCNPX SOURCES 0.40 0.24

Plane + 60 cm polyethylene : reduction factor of ~ 15000 ~ 13x10-10

Results :

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Summary and outlook

- Relatively good agreement between the 2 codes G3 and MCNP-Continue code comparisons to understand the remaining discrepancies-Propagate the lab n spetrum through EDW-1 and EDW-II geometries to get correct nuclear recoil spectra for Germanium .