1. 1 Maryvonne De JésusIlias/N3/WG5 meeting Neutron studies in Edelweiss “Suite” Valencia (Espana)15/04/2005

2. 2 Plan Germanium nuclear recoil angular distribution in Geant 3 Rock spectra propagation with Geant 3 and MCNPX

3. 3 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 TALYS A.J. Koning, S. Hilaire and M. Duijvestijn, TALYS: Comprehensive nuclear reaction modeling Proceedings of the International Conference on Nuclear Data for Science and Technology - ND2004 Sep. 26 - Oct. 1, Santa Fe, USA, to be published Proper reference to the optical model parameters for germanium A.J. Koning and J.P. Delaroche Local and global nucleon optical models from 1 keV to 200 MeV Nuclear Physics A 713 (2003) 231-310) Correction :

4. 4 Modification in the SUBROUTINE COLISN IF (KZI.eq.32) call MYCANG

5. 5 Edelweiss-I neutron calibration with 232 Cf Simulation with modified Geant-321  Ratio Data/Simulation [15, 200 ] keV : 1.5  Data vs. simulation : good agreement in the nuclear recoil spectra

6. 6 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/cm 3  Neutron flux in lab reevaluated ( G.Chardin et al IDM 2002 ) En > 2 MeV :  1.6x10 -6 n/s/cm 2 -Spectrum calculated by R.Lemrani with code SOURCES : Neutron production in the rock :  1.133x10e -7 n/s/cm 3 Rock composition introduced in Geant 3 Measured rock composition : Density :  =2.65 g/cm 3

7. 7 Geometries for simulations with geant3 : LabRock Air or PE Plane geometry

8. 8 Results : LSM Geometry with scatterring LSM Geometry without scatterringPlane Geometry LSM Geometry with scatterring MCNPX V.Chazal SOURCES Geant 3 MCNPX V.Chazal SOURCES Geant 3 MCNPX V.Chazal SOURCES Geant 3

9. 9 FLuxx10 -6 >1 MeV>2 MeV LSM DirectGeant 3V.Ch0.620.41 SOURCES0.310.17 MCNPXSOURCES0.380.23 LSM TotalGeant 3V.Ch1.571.05 SOURCES0.810.44 MCNPXSOURCES0.480.27 PLANEGeant3V.Ch0.960.70 SOURCES0.620.35 MCNPXSOURCES0.400.24 Plane + 60 cm polyethylene : reduction factor of ~ 15000  ~ 13x10 -10 Results :

10. 10 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.