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EAR2 Collimator Simulations

EAR2 Collimator Simulations. Ida Bergstrom Vasilis Vlachoudis 12 Feb 2013. Simulations for the Experimental Area. Preliminary study of Collimator Capture Fission setup EAR-2 Background Neutron dump External wall Shielding for the EAR2 walls and beam dump Study of dose due to skyshine

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EAR2 Collimator Simulations

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  1. EAR2 Collimator Simulations Ida Bergstrom Vasilis Vlachoudis 12 Feb 2013

  2. Simulations for the Experimental Area • Preliminary study of Collimator • Capture • Fission setup • EAR-2 Background • Neutron dump • External wall • Shielding for the EAR2 walls and beam dump • Study of dose due to skyshine • Study of residual dose rate and air activation Neutron Dump External Wall ExperimentalArea 2nd Collimator As shown on last CB meeting

  3. Background in EAR2 (CB meeting status) • Beam profile and background in the area for fission setup (worst case) • WARNING: • 1st and 2nd collimator are not optimized • Beam dump is not optimizedfor back-scattering Non-optimized!4-5 ordersof magnitude As shown on last CB meeting

  4. Background Sources Epithermal • Background: • Thermal & Epithermal: • 50% from collimator • 50% from dump • Fast: • - 100% from collimator • Both are not optimized Factor ×2 Fast

  5. Collimator Profile Borated Poly Iron Beam Profile 4 1 Sample Pb Target Flux 2 3 Radius Direct – Full View  Contributes to the Plateau/Flat Direct – Partial View  Contributes to Halo Indirect Hitting collimator gap  Major contribution to Background Indirect Hitting front face of collimator  Minor contribution to Background

  6. Collimator setup tested Cylindrical Borated-Poly Iron Copper Copper Copper Conical – closing Gap follows focusing lines Borated-Poly Iron Conical – opening Gap follows: 1st part focusing lines 2nd part defocusing Borated-Poly Iron

  7. Capture Collimator setup Design Parameters: • Flat radius 1.5 cm • Maximum halo radius ~3.5 cm 6 different setups: • Cylindrical • Conical focusing (Closing) • Conical like hour-glass (Opening) • w/o Copper inset 3 different energies: • 1 eV (Thermal) • 1 keV (Epithermal) • 1 MeV (Fast) Scoring • Profile from 1m to 2m after collimator WARNING: plots are integrated in time. No real discrimination on energy due to TOF

  8. Capture Neutron fluence @1keV Cylindrical Closing Opening 1m 2m

  9. Capture Profile (1eV, 1keV, 1MeV) 1 keV 1 keV 1 MeV 1 eV

  10. Fission Collimator setup Design Parameters: • Flat radius 4.0 cm • Maximum halo radius 5.0 cm 6 different setups: • Cylindrical • Conical focusing (Closing) • Conical like hour-glass (Opening) • w/o Copper inset 3 different energies: • 1 eV (Thermal) • 1 keV (Epithermal) • 1 MeV (Fast) Scoring • Profile from 1m to 2m after collimator WARNING: plots are integrated in time. No real discrimination on energy due to TOF

  11. Fission Neutron fluence @1keV Cylindrical Closing Opening 1m 2m

  12. Fission Profile (1eV, 1keV, 1MeV) 1 keV 1 keV 1 MeV 1 eV

  13. Conclusions: General Background Sources: • Thermal & Epithermal : ~50-50% collimator – dumpDump not studied for the moment.However backscattering can be more easily shielded than what comes out of the collimator • Fast: ~100% from the collimator Collimator Important Factors: • Spatially integrated Neutron Flux • Beam profile (Flat or not) • Neutron Background Copper inset seems improves slightly (÷2) the background in all cases.More pronounced in the fast, MeV range

  14. Conclusions: Capture Comments: • Difficult to design a proper “Open” layout due to: • Short distance (18 m) • Extended source (Pb target) • Small required beam profile • Note: In EAR1 Capture integrated flux is 3-5 times smaller than Fission integrated flux over the same capture radius! therefore even the “Open” layout will gives the same increase of flux in EAR2 vs EAR1 (when comparing both capture setups)

  15. Conclusions: Fission Comments: • Fission detectors are inside the beam, therefore background conditions are not so critical. • “Open” gives a Gaussian like profile when trying to limit the maximum profile to less than 7.5 cm in radius

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