GRASansP: Graphical Reduction and Analysis SANS Program

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GRASansP Graphical Reduction and Analysis SANS
Program
by Charles Dewhurst Institut Laue
Langevin Grenoble France

• Data Reduction Using GRASansP at ILL
• (and other Neutron sources)
• Examples 2D SANS data
• - SANS from ferromagnetic samples
• - Small-angle diffraction
• (vortex lattice, gratings, ordered nano-particle
  arrays)
• D22 New fast 2D Multidetector
• - construction, characteristics data handling

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GRASansP What do you want to do with your SANS
data?

• Isotropic (1D) SANS data
• Background subtraction
• Transmission correction (including T vs.
  scattering angle)
• Masking
• Calibration to known standard
• Detector efficiency correction
• Solid angle corrections
• Flux vs. Collimation corrections
• Data reduction, most commonly want I vs. q
• Model fitting to scattering curve

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GRASansP What do you want to do with your SANS
data?

• Anisotropic (2D) SANS data
• all of the above
• Data reduction, I vs. q, y (angle around
  detector), qx, qy
• Sectors, Boxes, Strips, Ellipses, etc. to select
  or mask regions
• of interest of the 2D data
• Direct analysis of the 2D data
• e.g. Fitting to 2D Bragg peaks, cos2 variation of
  I vs. q, y for magnetic scattering,
  shear-aligned polymers, superconducting vortex
  lattice,
• colloidal nano-particle crystals etc.

Bragg Peaks Vortex Lattice in Superconductors
Magnetic Scattering
G-SANS Reflectivity
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GRASansP What do you want to do with your SANS
data?

• What about 3D SANS data? i.e. 2D data
  varying sample conditions.
• - Time resolved and kinetic studies (also
  re-group and average frames).
• - SANS crystallography (rocking curves of
  Bragg peaks).
• - Temperature, Pressure, Magnetic Field, ..etc.
  etc.
• - Generally, many individual measurements that
  combine to make
• a single larger experiment.
• - Want to cross-reference 2D data as a function
  of some 3rd data dimension.

Critical magnetic scattering as fn. of q and
temperature
Rocking curves of Bragg peaks
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GRASansP

• GRASansP attempts to provide a comprehensive
  suite of 2D data manipulation and analysis tools
• Pixel-by-pixel manipulation of multidetector
  data
• - If required, 1D scattering curves (e.g. I vs.
  q) are calculated as a final reduction step
• No intermediate temporary analysis files
• Selective use of multidetector data
• Sectors, Strips, Box Ellipse analysis masks
• Data correction
• Subtraction of backgrounds
• Transmission corrections
• Masking
• Calibration to known standards
• Detector efficiency correction
• Detector dead-time corrections
• Geometry corrections (solid angle, transmission
  vs. scattering angle)
• Flux-Collimation scaling

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GRASansP

• All the expected aspects of a modern-style
  application

• Instrument Tools
• Instrument Parameters
• Measurement Setup tool
• Raw data parameters

• File Tools
• Open, Close, Save Projects
• Import / Export 1D 2D data
• Graphics Export Print

• Display Tools
• Plot type
• Color
• Contours
• Smoothing
• Movie

• Data Tools
• Customizable workspaces
• Raw data tools
• File listings
• Data organisation
• Normalisation options.

• Analysis Tools
• Beam centre Transmission calculators
• Averaging Radial Aziumthal.
• Magnetic Scattering (Ancos2).
• 1D curve fitting to reduced data.
• 2D peak fitting to multidetector data.
• 3D Box Sector Sums over worksheet depth.

User Modules
User Fit Functions
Grasp-Script
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Data and Analysis Tools
Display Options
Data Control
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GRASansP Calibrations, Solid Angle and
Geometrical Corrections
Water calibration measurement (or some other
flat-scatterer) Detector _at_1.4m
Flat-detector and pixel solid angle corrections
Sample transmission as fn. of scattering angle
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D22 SANS _at_ ILL Roland May, Charles Dewhurst,
Bruno Demé
D22
D22
ORTF
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D22 New fast Multidetector

• Construction Design Characteristics
• - 2MHz total count rate
• - Achieved by 128 individual linear position
• sensitive tubes
• - Each tube 8 mm Ø
• - small dead volume between tubes
• - predetermined resolution in x
• - High gas pressure allowed by materials
  geometry
• - 15 Bar He3
• - Gas pressure quenching gas determine
• linear resolution to some extent
• - Tension 1500 V
• - Dead time 1 x 10-6 seconds / tube

Designed Built by Roland May, Bruno
Guerard, ILL Detector Group and D22 team
Assembling the tubes
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D22 New fast Multidetector
The Rolls-Royce of SANS detectors ?
gt5Km of cable
Lifting into position
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D22 New fast Multidetector

• Characteristics
• Measured rates up to 3MHz with no significant
  aliasing
• 4.5 MHz misaddressing problems the
  electronics falls over!
• Resolution
• x 8mm determined by the tube size and spacing
• y 5 6 mm data is subsequently software
  re-binned to 8mm
• Under normal resolution conditions see no
  modulation as
• the beam is scanned across the detector.
• Can see a small oscillation 10 in
  over-collimated conditions
• Efficiency Gold foil flux measurements,
  Calibrated monitor measurements relative to the
  detector indicate a total efficiency of
• 75 _at_ 4.5Å
• 66 _at_ 10Å (70 old detector)
• 61 _at_ 24Å (75 )

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D22 New fast Multidetector Calibration
Linearity
Raw data
Tweaked Raw data
2cm 5cm spaced slits in Cd mask
Small non-linearity in tube amplifiers at the ends
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D22 New fast Multidetector Calibration
Linearity
Raw data
Tweaked Raw data
Silver Behenate
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D22 New fast Multidetector Spatial
Resolution
Bragg peaks from a polymer-diffraction
grating d2545Å, q2.47x10-3Å-1
Rocking curves measured as a function of small
detector translations i.e. lt 1pixel show
negligible differences in position and intensity
Scanning a fine over-collimated beam over the
detector does show a small (15) modulation in
measured intensity
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GRASansP Summary

• Analysis of Data from
• ILL - D22
• - D11
• - D16
• PSI - SANS I
• - SANS II
• HMI - V4
• NIST - NG7
• Petten - SANS

Available for
Runtime code is licence free compiled
Matlab m-code is the source Matlab code
Website www.ill.fr/lss/grasp/