PINS workshop
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Transcript of PINS workshop
PINS workshopPINS workshop
VITESS – Simulations for the HYSPEC polarization options
Brookhaven, April 6-7, 2006
U. Filges, P. Allenspach, J.Stahn Paul Scherrer Institute (PSI), Switzerland
Introduction
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
PINS workshopBrookhaven, 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
PINS workshopBrookhaven, April 6-7, 2006
HYSPEC - Supermirror-bender transmission polarizer
starting point was a cross-check/intercomparison between the NISP and VITESS packages
I.Zaliznyak et al. Physica B 356 (2005) 150-155
setup of the transmission polarizer
horizontal profiles of the neutron intensity at the detector for
3.7, 10 and 20 meV
PINS workshopBrookhaven, April 6-7, 2006 Main values of VITESS setup
source size 2x2 cm; = 1 %
upstream collimator: 20 minutes; dimension: 2x12x15 cm (WxHxL)
distance source – upstream collimator: 40 cm
distance source – bender: 55 cm
bender configuration: dimension 2x12x5 cm; r=500cm; 80 Si-blades coated with m=3 R=77% (spin up) and m=1 (spin down);
distance source – detector: 450 cm
Energy 3.7 meV with =0.3ºPINS workshopBrookhaven, April 6-7, 2006
-20 -15 -10 -5 0 5 10 15 20-2.0x104
0.0
2.0x104
4.0x104
6.0x104
8.0x104
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1.2x105
1.4x105
VITESS - E = 3.7 meV º supermirror-transmission bender configuration
total neutrons spin up neutrons spin down neutrons
Inte
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Detector x [cm]
theta – tilt angle between collimator and bender axes
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Detector x [cm]
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total neutrons
spin up neutrons
spin down neutrons
NISP - E = 3.7 meV º supermirror-transmission bender configuration
- differences: absorption of Si-wavers ; using different reflectivity curves
PINS workshopBrookhaven, April 6-7, 2006
-20 -15 -10 -5 0 5 10 15 20-2.0x104
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2.0x104
4.0x104
6.0x104
8.0x104
1.0x105
1.2x105
1.4x105
VITESS - E = 10 meV º supermirror-transmission bender configuration
total neutrons spin up neutrons spin down neutrons
Inte
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Detector x [cm]
-20 -15 -10 -5 0 5 10 15 20
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NISP - E = 10 meV º supermirror-transmission bender configuration
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Detector x [cm]
total neutrons spin up neutrons spin down neutrons
- very small differences in the shape of the reflected beam
Energy 10 meV with =0.1º
PINS workshopBrookhaven, April 6-7, 2006 Energy 20 meV with =0º
-20 -15 -10 -5 0 5 10 15 20
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NISP - E = 20 meV º supermirror-transmission bender configuration
Inte
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total neutrons spin up neutrons spin down neutrons
- small differences in the shape and scaling factor for the transmitted neutron beam
-20 -15 -10 -5 0 5 10 15 20-2.0x104
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2.0x104
4.0x104
6.0x104
8.0x104
1.0x105
1.2x105
1.4x105
1.6x105
1.8x105
VITESS - E = 20 meV º supermirror-transmission bender configuration
total neutrons spin up neutrons spin down neutrons
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Detector x [cm]
PINS workshopBrookhaven, April 6-7, 2006
Influence of Reflectivity on the Detector Profile
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NISP - E = 20 meV º supermirror-transmission bender configuration
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Detector x [cm]
total neutrons spin up neutrons spin down neutrons
-15 -10 -5 0 5 10 15-2.0x104
0.0
2.0x104
4.0x104
6.0x104
8.0x104
1.0x105
1.2x105
1.4x105
1.6x105
1.8x105
2.0x105
neutron total spin up neutrons R=90% spin down neutrons spin up neutrons R=77 %
VITESS - E = 20 meV .2º supermirror-transmission bender configuration R=90%
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Detector x [cm]
PINS workshopBrookhaven, April 6-7, 2006 Detector Profiles for E = 25 meV
-20 -15 -10 -5 0 5 10 15 20-2.0x104
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4.0x104
6.0x104
8.0x104
1.0x105
1.2x105
VITESS - E = 25 meV º supermirror-transmission bender configuration
total neutrons spin up neutrons spin down neutrons
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Detector x [cm]
- very complicated to split reflected and transmitted beam (also for higher theta)
-20 -15 -10 -5 0 5 10 15 20-2.0x104
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2.0x104
4.0x104
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VITESS - E = 25 meV .1º supermirror-transmission bender configuration
total neutrons spin up neutrons spin down neutrons
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Detector x [cm]
PINS workshopBrookhaven, April 6-7, 2006
Dependency of the Detector Profile from the Sample Size
Conclusion
separation of spin up and spin down neutrons over a big energy range is very complicated
cross-check shows a very good agreement
presently defuse scattering and waviness of supermirrors are not included
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1.0 2.0 x 2.0 cm
0.5 x 0.5 cm
3.0 x 5.0 cm
VITESS - E=20 meV .2º BNL-Bender configuration
comparison of different sample sizes - spin up neutrons
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Detector x [cm]
comparison of spin up neutron beam for
different sample sizes
PINS workshopBrookhaven, April 6-7, 2006 S-shaped Supermirror Bender
spin up and spin down neutrons will be measured subsequently
transmitted neutron beam will be absorbed in a gadolinium layer (approx 50 m) behind supermirror layer
each useful neutron makes two reflections
upstream collimator right-curved supermirrorbender
left-curved supermirrorbender
PINS workshopBrookhaven, April 6-7, 2006
VITESS setup for the S-Bender configuration
source size 2x2 cm; = 1 %
upstream collimator: 20 minutes; dimension: 2x12x15 cm (WxHxL)
distance source – upstream collimator: 40 cm
distance source – bender: 55 cm
bender configuration: dimension 2x12x10 cm; r1=500 cm; r2=-500 cm; 80 Si-blades coated with m=3 R=77% (spin up) and m=0.1 (spin down);
distance source – detector: 450 cm
PINS workshopBrookhaven, April 6-7, 2006 Detector profiles for 3.7 and 15 meV
tilt angle: 0.3in both cases
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1x104
2x104
3x104
4x104
5x104
6x104VITESS - E=15 meV .3º S-Bender configuration
total neutrons spin up neutrons spin down neutrons
Inte
nsity
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Detector x [cm]
-15 -10 -5 0 5 10 15
0
1x104
2x104
3x104
4x104
5x104
6x104VITESS - E=3.7 meV .3º S-Bender configuration
total neutrons spin up neutrons spin down neutrons
Inte
nsity
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Detector x [cm]
PINS workshopBrookhaven, April 6-7, 2006 Detector profiles for 20 and 25 meV
-15 -10 -5 0 5 10 15
0.0
5.0x103
1.0x104
1.5x104
2.0x104
2.5x104VITESS - E=25 meV .3º S-Bender configuration
total neutrons spin up neutrons spin down neutrons
Inte
nsity
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Detector x [cm]
-15 -10 -5 0 5 10 15
0.0
2.0x103
4.0x103
6.0x103
8.0x103
1.0x104
1.2x104
VITESS - E=20 meV .3º S-Bender configuration
total neutrons spin up neutrons spin down neutrons
Inte
nsity
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Detector x [cm]
tilt angle: 0.3in both cases
PINS workshopBrookhaven, April 6-7, 2006 Detector profile without Gadolinium
Conclusion
fixed tilt angle for the full energy range from 3.7 to 25 meV
no contamination
disadvantage: polarization efficiency; some loss in intensity; factor 4
but present setup not optimized on
intensity
-10 -5 0 5 10
0.0
2.0x104
4.0x104
6.0x104
8.0x104
1.0x105
1.2x105
1.4x105
1.6x105
1.8x105
2.0x105VITESS - E=15 meV .3º S-Bender configuration without GD
total neutrons spin up neutrons spin down neutrons
Inte
nsity
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Detector x [cm]
PINS workshopBrookhaven, April 6-7, 2006
Wedge-shaped supermirror Bender
spin up and spin down neutrons will be measured subsequently
transmitted neutron beam will be measured – reflected neutron beam will be absorbed by the downstream collimator
increasing of the acceptance angle through wedge shape of the Si-waver
upstream collimator downstream collimator
wedge-shaped supermirrorbender
PINS workshopBrookhaven, April 6-7, 2006
VITESS setup for thewedge-supermirrror bender configuration
source size 2x2 cm; = 1 %
upstream collimator: 20 minutes; dimension: 2x12x15 cm (WxHxL)
distance source – upstream collimator: 40 cm
distance source – bender: 55 cm
bender configuration: dimension 2x12x10 cm; r=500 cm;80 Si-blades coated with m=3 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)
distance source – detector: 450 cm
downstream collimator: 10 minutes
PINS workshopBrookhaven, April 6-7, 2006 Detector profiles for 3.7 and 10 meV
- S-bender has been tilted with 0.2in both cases
-10 -5 0 5 10
0
1x104
2x104
3x104
4x104
5x104
6x104
7x104
8x104VITESS - E=10 meV .2º wedge-bender configuration
total neutrons spin up neutrons spin down neutrons
Inte
nsity
[arb
. uni
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Detector x [cm]
-10 -5 0 5 10
0
1x104
2x104
3x104
4x104
5x104
6x104
7x104
8x104VITESS - E=10 meV .2º wedge-bender configuration
total neutrons spin up neutrons spin down neutrons
Inte
nsity
[arb
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ts]
Detector x [cm]
PINS workshopBrookhaven, April 6-7, 2006
Detector profiles for 20 and 25 meV
- S-bender has been tilted with 0.2in both cases
-10 -5 0 5 10
0
1x104
2x104
3x104
4x104
5x104
6x104
VITESS - E=25 meV .2º wedge-bender configuration
total neutrons spin up neutrons spin down neutrons
Inte
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ty [
arb
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Detector x [cm]
-10 -5 0 5 10
0.0
5.0x103
1.0x104
1.5x104
2.0x104
2.5x104
3.0x104
3.5x104VITESS - E=20 meV .2º wedge-bender configuration
total neutrons spin up neutrons spin down neutrons
Inte
nsity
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Detector x [cm]
PINS workshopBrookhaven, April 6-7, 2006
Improvement of the Detector Profile for Higher Energies
Conclusion
also fixed tilt angle for the full energy range from 3.7 to 25 meV
Small contamitaions in the low energy range (up to 20 meV)
polarization efficiency higher as S-bender configuration
present setup not optimized on intensity/contaminations in the higher
energy range >20 meVsupermirror coating for spin up neutrons
was increased to m=4
-10 -5 0 5 10
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1x104
2x104
3x104
4x104
5x104
6x104VITESS - E=25 meV .2º wedge-bender configuration m= 4
total neutrons spin up neutrons spin down neutrons
Inte
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Detector x [cm]
PINS workshopBrookhaven, April 6-7, 2006 Summary
subsequent measurement of the spin states covers a bigenergy range with very good polarization – especiallyusing the S-bender configuration
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
certainly the polarization efficiency can be improved for the supermirror S-Bender and wedge bender configurations