1. Supermirror polarizer and beam simulations
Christopher Crawford (UKy)
NPDGamma Collaboration Meeting
ORNL,

2. Outline
McStas simulations of beam profile
Characterization of SM polarizer by Swiss Neutronics
Analysis of FP12 statistics

3. FnPB supermirror polarizer
Fe/Si on boron float glass, no Gd
m = critical angle n = channels
r = 9.6 m radius of curvature
l = 40 cm length
d = 0.3mm vane thickness
T=25.8% transmission
P=95.3% polarization
N=2.2£1010 n/s output flux (chopped)
simulations using
McStas / ROOT ntuple

4. McStas Simulations

5. Transmission Comparison
Presented at collab, mtg.
34% -> 26%
Transmission
Changes:
Fe/Si coating
No Gd undercoat
No line of sight

6. Transmission

7. Comparison of optimal stats. vs. open pedestal
after
chopper,
pedestal

8. Comparison of optimal stats. vs. open pedestal
after
chopper,
pedestal

9. Polarization Comparison
Presented at collab, mtg.
95.6%
Polarization
Changes:
Fe/Si coating
No Gd undercoat
No line of sight

10. Polarization Comparison
Presented at collab, mtg.
95.6% -> 95.3%
Polarization
Changes:
Fe/Si coating
No Gd undercoat
No line of sight

11. Neutron Flux vs. wavelength, position in vane
from polarimetry MRI proposal

12. Polarization vs. wavelength, position in vane

13. Neutron flux vs. Λ, Θx

14. Polarization vs. Λ, Θx

15. Beam profile before and after Smpol
horizontal
vertical
after

16. Beam profile at 1st lead wall

17. Beam profile at 2nd lead wall

18. Beam profile at LH2 target

19. Horizontal profile vs. dist. from SMpol

20. Vertical profile vs. dist. from SMpol

21. SM polarizer characterization by Swiss Neutronics at PSI

22. Specifications from SNAG
Waviness

23. Individual Vanes – 2

24. Individual Vanes – 6

25. Individual Vanes – 10

26. Individual Vanes – 14

27. Individual Vanes – 19

28. Individual Vanes – 22

29. Individual Vanes – 26

30. Individual Vanes – 26R

31. Reflectivity profile use in McStas simulations
R+, P

32. Reflectivity profile use in McStas simulations
R+, P

33. Transmission measurement at PSI

34. Polarization measurement at PSI

35. Polarization measurement data

36. Measurement of Flux at FP12
Americo Salas Bacci, et al.
Technical Note #3

37. LANSCE FP12 Neutron Flux Measurement
Americo Salas Bacci,
Technical Note #3

38. LANSCE FP12 Neutron Flux – Electronics

39. Fission Chamber energy spectrum
from
Americo

40. LANSCE FP12 Neutron Flux – Electronics

41. Comparison of statistics at LANSCE FP12
Calculation based on: David’s estimate , Americo’s note , and Gericke, NIMA (2009)
2.68x107 n/s cm2 neutron flux at 100 μA, measured with FC
3.5” collimator, 87.6 μA proton current
4966 runs (after cut) x 104/20 Hz
0.88 (air) x 0.90 (Al) x 0.88 (glass) x (3He) transmission
0.60 capture in LH2 x geom. factor
0.53 pol. 3He x SF eff. / (1+0.25) bkg. dilution
δA = 1.9 x from above vs x RMS width in A
Comparison of raw counts vs. above estimate?