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n _TOF EAR2 Simulation Studies

n _TOF EAR2 Simulation Studies. N_TOF Collaboration Meeting I.Bergstrom , J.Mann , J.Vollaire , C.Weiss , T.Zhang , V.Vlachoudis 28-30 Nov 2012. Geometry. Detailed Geometry C.Weiss I. Bergstrom J. Volaire J. Mann T. Zhang. Spallation Target. Neutron moderator Beam pipe layout

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n _TOF EAR2 Simulation Studies

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  1. n_TOF EAR2 Simulation Studies N_TOF Collaboration Meeting I.Bergstrom, J.Mann, J.Vollaire, C.Weiss, T.Zhang, V.Vlachoudis 28-30 Nov 2012

  2. Geometry • Detailed Geometry • C.Weiss • I. Bergstrom • J. Volaire • J. Mann • T. Zhang

  3. Spallation Target • Neutron moderator • Beam pipe layout • Fluence and resolution estimation • Dose to electronics • Optimization of the neutron target for future upgrade • Determination of neutron gain by shifting the vertical pipe to neutron maximum • Activation calculation of the present spallation target, container for a possible decommissioning in 2018 Neutron pipe Moderator Spallation target Container

  4. Neutron Fluence Maximum Gain: 27 (keV Region) Reference for EAR1 : FLUKA Simulations with fission collimator (d = 8 cm) C.Weiss

  5. Neutron Moderator • Simulations have been performed for a setup: • Without additional moderator at the bottom of the neutron tube • With Moderator at the bottom of the tube: Polyethylene (dmin = 1 cm) C.Weiss

  6. Resolution in comparison with EAR1 Neutron Fluence is reduced by about 32 % if a Moderator in this form isused * C. Coceva et al., NIMA 489 (2002) 346-356 C.Weiss

  7. Future target for 2018 • A more optimized target would require to cut the lead at Dz=16.5cm • Gain in flux ×2-4(Vertical flight path) • Loss of 20% in horizontal flight path • Gain in resolution since top surface is flat • Correct positioning of vertical neutron pipe would give an additional gain 10-20% Incompatible with the present target/layout. Will delay considerably the project! T.Zhang

  8. 1st Collimator, Magnet & Shielding • Introduction of 1st collimator: • Shaping the beam • Background reduction in ISR • Magnet protection • Permanent magnet • Field intensity needed • Dose (degradation of magnet) Permanent Magnet Additional Shielding For ISR 1st Collimator

  9. Magnet pmax = 1.205 [GeV/c] protons B = 0.2 [T] Possible Position for a magnet: Assumed magnet length: l = 1 [m] C.Weiss

  10. ISR Shielding • Dose reduction in ISR tunnel • Permanent work place< 0.5 mSv/h • Non-permanent work place< 2.5 mSv/h • Lot’s of constraints: • Keeping the existing crane • Amount of shielding • Existing cables/piping • n_TOF PS-line controls • Numerous shielding options have been evaluated • Introduction of 1st collimator Crane level ISR tunnel Existing Shielding

  11. Dose in ISR tunnel Default layout Safety factor ×3 & Future targetNot INCLUDED! With additional shielding + collimator I.Bergstrom

  12. 1stCollimator Test of various 1st collimators andimpact on the total neutron fluencein the experimental area  Chosen  No Collimator • Collimator: • 1m long made of iron • Internal diameter 190mm • Z=7 m from center of target I.Bergstrom

  13. Second Collimator, EAR, Neutron Dump • 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

  14. Background in EAR2 • 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

  15. Prompt dose rate (30 cm collimator) FLUKA geometry of the bunker Prompt dose – 30 cm collimator + new target (x3 intensity) Extra wall (30 cm collimator) J.Vollaire

  16. Dose due to skyshine (1 y operation) J.Vollaire

  17. Residual dose rate and air activation 5 min cooling time • Checking if activation of the beam dump in the EAR2 area could be a problem for access and additional measures are required • Irradiation cycle (very conservative) : • 5 consecutive years • 30 cm collimator(100 % of the time) • 9 Months with 1.59 109 n/sentering the area • Air activation is found negligible 8 hours 7 days J.Vollaire

  18. Summary A large amount of calculation has been performed, mainly focused on the facility and RP issues (thanks to Ida, Cristina, Joachim, Tian, Jonn) Pending Calculations • Magnet Sm-Co evaluation of the 60Co production • Air activation in the access gallery • Dose to earth, needed for RP during excavation • 1st and 2ndCollimator optimization • Materials of collimator and surrounding elements • Exchangeable setups Capture, Fission and Electronic testing • EAR-2 Background optimization (w/o samples and detectors) • Neutron dump backscattering, respecting the max weight of the dump imposed by Civil Engineering • “g-flash” from fast neutron on 2ndcollimator

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