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PINS workshop

PINS workshop. Brookhaven, April 6-7, 2006. VITESS – Simulations for the HYSPEC polarization options. U. Filges, P. Allenspach, J.Stahn Paul Scherrer Institute (PSI), Switzerland. Introduction. PINS workshop Brookhaven , April 6-7, 2006. MC- packages.

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PINS workshop

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  1. PINS workshop Brookhaven, April 6-7, 2006 VITESS – Simulations for the HYSPEC polarization options U. Filges, P. Allenspach, J.Stahn Paul Scherrer Institute (PSI), Switzerland

  2. Introduction PINS workshop Brookhaven, April 6-7, 2006 MC- packages • - the programs VITESS and McStas are used at PSI • VITESS 2.6 contains several different polarizer • components like a polarizing bender or He-3 polarizer • presently McStas doesn’t include polarizer components content of presentation - cross-check/intercomparison (between VITESS and NISP) to the HYSPEC supermirror transmission polarizer option - S- bender polarizer configuration for the reflected neutron beam - wedge-bender polarizer configuration for the transmitted neutron beam

  3. HYSPEC - Supermirror-bender transmission polarizer PINS workshop Brookhaven, April 6-7, 2006 starting point was a cross-check/intercomparison between the NISP and VITESS packages setup of the transmission polarizer horizontal profiles of the neutron intensity at the detector for 3.7, 10 and 20 meV I.Zaliznyak et al. Physica B 356 (2005) 150-155

  4. Main values of VITESS setup PINS workshop Brookhaven, April 6-7, 2006 source size 2x2 cm; Dl/l = 1 % distance source – upstream collimator: 40 cm upstream collimator: 20 minutes; dimension: 2x12x15 cm (WxHxL) distance source – bender: 55 cm bender configuration: dimension 2x12x5 cm; r=500cm; 80 Si-blades coated with m=3 ð R=77% (spin up) and m=1 (spin down); distance source – detector: 450 cm

  5. Energy 3.7 meV with q=0.3º PINS workshop Brookhaven, April 6-7, 2006 theta q– tilt angle between collimator and bender axes • differences: absorption of Si-wavers ; using different reflectivity curves

  6. Energy 10 meV with q=0.1º PINS workshop Brookhaven, April 6-7, 2006 • very small differences in the shape of the reflected beam

  7. Energy 20 meV with q=0º PINS workshop Brookhaven, April 6-7, 2006 • small differences in the shape and scaling factor for the transmitted neutron beam

  8. Influence of Reflectivity on the Detector Profile PINS workshop Brookhaven, April 6-7, 2006

  9. Detector Profiles for E = 25 meV PINS workshop Brookhaven, April 6-7, 2006 • very complicated to split reflected and transmitted beam (also for higher theta)

  10. Dependency of the Detector Profile from the Sample Size PINS workshop Brookhaven, April 6-7, 2006 Conclusion cross-check shows a very good agreement separation of spin up and spin down neutrons over a big energy range is very complicated presently defuse scattering and waviness of supermirrors are not included comparison of spin up neutron beam for different sample sizes

  11. S-shaped Supermirror Bender PINS workshop Brookhaven, April 6-7, 2006 spin up and spin down neutrons will be measured subsequently each useful neutron makes two reflections transmitted neutron beam will be absorbed in a gadolinium layer (approx 50 mm) behind supermirror layer right-curved supermirror bender upstream collimator left-curved supermirror bender

  12. VITESS setup for the S-Bender configuration PINS workshop Brookhaven, April 6-7, 2006 source size 2x2 cm; Dl/l = 1 % distance source – upstream collimator: 40 cm upstream collimator: 20 minutes; dimension: 2x12x15 cm (WxHxL) distance source – bender: 55 cm bender configuration: dimension 2x12x10 cm; r1=500 cm; r2=-500 cm; 80 Si-blades coated with m=3 ð R=77% (spin up) and m=0.1 (spin down); distance source – detector: 450 cm

  13. Detector profiles for 3.7 and 15 meV PINS workshop Brookhaven, April 6-7, 2006 tilt angle: 0.3°in both cases

  14. Detector profiles for 20 and 25 meV PINS workshop Brookhaven, April 6-7, 2006 tilt angle: 0.3°in both cases

  15. Detector profile without Gadolinium PINS workshop Brookhaven, April 6-7, 2006 Conclusion no contamination fixed tilt angle qfor the full energy range from 3.7 to 25 meV disadvantage: polarization efficiency; some loss in intensity; factor 4 ð but present setup notoptimized on intensity

  16. Wedge-shaped supermirror Bender PINS workshop Brookhaven, April 6-7, 2006 spin up and spin down neutrons will be measured subsequently increasing of the acceptance angle through wedge shape of the Si-waver transmitted neutron beam will be measured – reflected neutron beam will be absorbed by the downstream collimator wedge-shaped supermirror bender downstream collimator upstream collimator

  17. VITESS setup for thewedge-supermirrror bender configuration PINS workshop Brookhaven, April 6-7, 2006 source size 2x2 cm; Dl/l = 1 % distance source – upstream collimator: 40 cm upstream collimator: 20 minutes; dimension: 2x12x15 cm (WxHxL) distance source – bender: 55 cm bender configuration: dimension 2x12x10 cm; r=500 cm; 80 Si-blades coated with m=3 ð R=77% (spin up) and m=0.1 (spin down); each Si-plate: width at entry side 0.25 mm – width at exit side 0.28 mm (curved wedge) downstream collimator: 10 minutes distance source – detector: 450 cm

  18. Detector profiles for 3.7 and 10 meV PINS workshop Brookhaven, April 6-7, 2006 - S-bender has been tilted with 0.2°in both cases

  19. Detector profiles for 20 and 25 meV PINS workshop Brookhaven, April 6-7, 2006 - S-bender has been tilted with 0.2°in both cases

  20. Improvement of the Detector Profile for Higher Energies PINS workshop Brookhaven, April 6-7, 2006 Conclusion Small contamitaions in the low energy range (up to 20 meV) also fixed tilt angle qfor the full energy range from 3.7 to 25 meV polarization efficiency higher as S-bender configuration ð present setup notoptimized on intensity/contaminations in the higher energy range >20 meV supermirror coating for spin up neutrons was increased to m=4

  21. Summary PINS workshop Brookhaven, April 6-7, 2006 cross-check shows a good agreement between the MC-packages NISP and VITESS analysis of simultaneously measured spin up/spin down neutrons can be sophisticated subsequent measurement of the spin states covers a big energy range with very good polarization – especially using the S-bender configuration certainly the polarization efficiency can be improved for the supermirror S-Bender and wedge bender configurations

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