Monte Carlo simulation for adaptive optics

Transcription

1 Monte Carlo simulation for adaptive optics R. Valicu 1, P. Böni 1,3, J. Stahn 2, U. Filges 2, T. Panzner 2, Y. Bodenthin 2, M. Schneider 2,3, C.Schanzer 3 1 Physik-Department E21, James-Franck-Strasse, D Garching, Germany 2 Paul Scherrer Institut, Villigen PSI, Switzerland 3 SwissNeutronics AG, Bruehlstrasse 28, CH-5313 Klingnau, Switzerland

2 Overview Motivation and goals New McStas component Simulations for 1 -dimensional focusing Prototype development, possible performance Performed experiment Applications

3 Motivation and goals to significantly increase the neutron flux well defined beam characteristics gain factor in intensity of over 30 compared to linear guides for small samples to obtain a focal point in the sub mm range for elastic and inelastic scattering on very small samples to reduce the scattering background during the extreme environment experiments: magnetic fields, high pressure

4 Adaptive optics a) guide actuators possibility to align the focal point on tiny samples b) focal point adaptation of beam size to the sample size optimization of the divergence of the neutron beam with respect to the sample c) Adjust curvature of tapered guide by means of actuators change focal length of the device

5 New McStas component -different wall thickness -truly curved -different curvature for each wall -transparent, absorbing or reflecting inner or outer walls

6 Shift in x direction (mm) Initial simulations f out l w in h in = distance from the exit of guide to second focal point = length of the guide = width at entrance of the guide = height at entrance of the guide Above parameters define the height and width at exit of the guide xshift First simulation parameters f out = 250 mm l = 500 mm w in = 35 mm h in = 120 mm fout (m) One dimensional variation of f out in x-direction - perpendicular to the beam axis in horizontal direction

7 Results for different distances Entrance FRM II Neutron Optics Group

8 Results for different distances Exit FRM II Neutron Optics Group

9 Results for different distances 50 mm from exit FRM II Neutron Optics Group

10 Results for different distances 150 mm from exit FRM II Neutron Optics Group

11 Results for different distances 250 mm from exit FRM II Neutron Optics Group

12 Results for different distances 300 mm from exit FRM II Neutron Optics Group

13 Results for different distances 350 mm from exit FRM II Neutron Optics Group

14 Results for different distances 400 mm from exit FRM II Neutron Optics Group

15 Results for different distances 500 mm from exit FRM II Neutron Optics Group

16 Intensity (a.u.) Intensity (a.u.) FWHM (mm) Intenstiy (a.u.) One dimensional simulations λ = 5 Å 5x10 6 4x10 6 3x10 6 2x10 6 m6 m3 m1 Intensity increases with increasing m value of the coating due to reflection of neutrons with higher angle of incidence 1x x10 5 cuts through the PSD for various d 8.0x x x x X (cm) X (cm) 1m 2m 4m 7m Variation of d (distance guide-entrance): divergence of incoming neutrons is changed 9x10 4 8x10 4 7x10 4 6x10 4 5x10 4 4x10 4 3x10 4 2x10 4 Intensity FWHM d (m)

17 Simulations for various f out Variation of f out requires change in curvature of guide PSD detectors in focal point f out = 50 mm f out = 100 mm λ = 5 Å f out (mm) x shift (mm) f out = 200 mm f out = 400 mm f out = 300 mm f out = 500 mm

18 Intenstiy (a.u.) Intenstiy (a.u.) Intensity (a.u.) FWHM (mm) Simulations for various f out λ = 5 Å 1.6x x x x x x x x x X (cm) fout0.05 fout0.25 fout x x x x x x x x x x x x x x X (deg) divfout0.05 divfout0.25 divfout0.5 2x10 5 1x10 5 1x10 5 1x10 5 1x10 5 1x10 5 9x10 4 Intensity FWHM 8x Observation for decreasing f out : Example: f out = 100 mm: -increase in intensity - FWHM = 6 mm -increase of curvature of mirror - flux: neutrons cm-2 s-1 -decrease of width of beam (FWHM) fout(m) Applications: -at PSI: -at FRM II: - RITA - TOFTOF (see poster for details) - DMC - MIRA

19 Development of prototype Details: Poster of M. Schneider h fout Prototype: w d L coating on one side one point to press defined curvature

20 One reflecting side h fout Maintain position of focal point: w d L push mirror on one side vary angle of rotation of tangenta with respect to optical axis of device a 1, x 1 Shift in x direction is correlated with rotation angle a 2, x 2 F

21 Experiment: Beam line SINQ transversal scan rotation a detector Parallel beam: 1mm slits Rotation angle of mirror: deg 2θ-scan: 0-3 deg Detector at 230 mm from mirror beam FRM II Neutron Optics Group slits 1mm

22 Experimental setup rotation a do match movement x rotation a do not match movement x F scan scan for different translation reflected beams appear at the same position on detector for different translation reflected beams appear at different position on detector

23 Counts Counts Counts Counts Experimental results 2 (deg.) rotation a (deg.) rotation a = 0.6 deg. transversal position transversal position transversal detector scan (mm) transversal detector scan (mm) rotation matches x-shift of 2 mm for rotation angle 0.6 deg rotation a = 0.72 deg. transversal position transversal position Conclusions: - one focal point observed - the parabolic shape confirmed rotation a = 0.48 deg. transversal position transversal position transversal detector scan (mm) rotation a = 0.8 deg. transversal position transversal position transversal detector scan (mm)

24 device tilting angle [deg] device tilting angle [deg] Possible aplications bend beam away from primary beam by tilting component f out = 0.3m, length = 0.5m, m = 3 and 6, d=1m m = m = primary beam reflected beam E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E primary beam reflected beam intensity [a.u.] 5.680E E E E E E E E divergence of the neutrons [deg] reflected beam divergence of the neutrons [deg] MACS beamline at NIST re-design of focusing linearly tapered guide

25 Acknowledgements Stimulus Programm

26 device tilting angle [deg] Conclusions h fout w d L m = primary beam reflected beam intensity [a.u.] 5.680E E E E E E E E divergence of the neutrons [deg]