1. Large Colimator Study EAR2 Christina Weiss, CERN

2. Introduction 26. February 2015n_TOF Analysis Group Meeting, CERN2  INTC approved proposals for measurements with large collimator in EAR2: 1.STEFF: CERN-INTC-2014-004 ; INTC-P-405 2.26Al: CERN-INTC-2014-006 ; INTC-P-406  Count-rate estimations where performed with n/cm 2 from EAR2 proposal, for samples: 1.STEFF( 235 U): 50 mm in diameter 2.26Al: 50 x 60 mm 2, tilted in the beam  Study for large collimator for EAR2.

3. 2 nd Collimator Geometries under Study 26. February 2015n_TOF Analysis Group Meeting, CERN3 Smallest aperture for all geometries: r = 30 mm. Geometries: Scoring at 2 m from the floor in EAR2 (STEFF nominal sample position). Straight ConicalDouble ConicalFunnel

4. Study Approach 26. February 2015n_TOF Analysis Group Meeting, CERN4 1.Study profile and flux with transport program from Vasilis – geometrical transport. 2.Choose best geometries. 3.FLUKA simulations for photon and neutron background impinging on NaI detectors of STEFF.

5. Results from Particle Transport Program 26. February 2015n_TOF Analysis Group Meeting, CERN5

6. Cone Collimator from EAR2 Proposal 26. February 2015n_TOF Analysis Group Meeting, CERN6 Initial simulations for EAR2, these results are included in the proposal for EAR2!

7. Present Collimator in EAR2 26. February 2015n_TOF Analysis Group Meeting, CERN7 Existing collimator in EAR2!

8. Conical Geometry 26. February 2015n_TOF Analysis Group Meeting, CERN8

9. Double Conical Geometry 26. February 2015n_TOF Analysis Group Meeting, CERN9

10. Cone Geometry 26. February 2015n_TOF Analysis Group Meeting, CERN10

11. Straight Geometry 26. February 2015n_TOF Analysis Group Meeting, CERN11

12. In Comparison to EAR1 26. February 2015n_TOF Analysis Group Meeting, CERN12 Best Profile

13. Beam Profile - cummulative 26. February 2015n_TOF Analysis Group Meeting, CERN13 Highest Flux

14. Total Flux for different Geometries 26. February 2015n_TOF Analysis Group Meeting, CERN14

15. Total Flux for different Geometries 26. February 2015n_TOF Analysis Group Meeting, CERN15

16. Conclusions from Transport Program 26. February 2015n_TOF Analysis Group Meeting, CERN16 Best beam profile with conical geometry. Highest flux with double conical geometry.

17. FLUKA Simulations 26. February 2015n_TOF Analysis Group Meeting, CERN17

18. Introduction 26. February 2015n_TOF Analysis Group Meeting, CERN18 Neutron beam above the target as primary beam in the simulations. No ‘in-beam’ material implemented in the simulations. Conical and double conical geometry for 2 nd collimator. Materials: -1 m B-PE (5%) -2 m stainless steel Materials already available. Conical Double Conical

19. Introduction 26. February 2015n_TOF Analysis Group Meeting, CERN19 For STEFF: Closest ‘sensitive’ detector are NaI at ~ 30 cm from the beam center. Scoring of neutron and photon spectra impinging on the ‘NaI detectors’. Shielding elements removed (Pb after 2 nd coll., B4C + B-PE + Pb before the dump).

20. Neutron Flux 26. February 2015n_TOF Analysis Group Meeting, CERN20

21. Neutron Background @ STEFF-NaI 26. February 2015n_TOF Analysis Group Meeting, CERN21

22. Neutron Background @ STEFF-NaI 26. February 2015n_TOF Analysis Group Meeting, CERN22 x 5 x 1.5

23. Photon Background @ STEFF-NaI 26. February 2015n_TOF Analysis Group Meeting, CERN23

24. Photon Background @ STEFF-NaI 26. February 2015n_TOF Analysis Group Meeting, CERN24 x 3.3

25. Beam Profile (Conical), different Times 26. February 2015n_TOF Analysis Group Meeting, CERN25 Asymmetric shape for high-energy beam profile

26. Beam Profile (Conical) at 2 m Height 26. February 2015n_TOF Analysis Group Meeting, CERN26

27. Beam Profile (Conical) at 1 m Height 26. February 2015n_TOF Analysis Group Meeting, CERN27

28. Conclusions 26. February 2015n_TOF Analysis Group Meeting, CERN28 Best beam profile with conical geometry. Highest flux with double conical geometry. Less background with double conical geometry. ?Which geometry and aperture shall we choose?

29. Beam Profiles 26. February 2015n_TOF Analysis Group Meeting, CERN29

30. Thank you for your attention.

31. High-Energy Beam Profile at 2 m Height 26. February 2015n_TOF Analysis Group Meeting, CERN31 Vacuum chamber above the target