Polarized SANS

This example shows how to simulate polarized SANS with BornAgain, using the Born Approximation.

The main difference between simulating GISAS and SAS in BornAgain is the presence of only a single layer in the multilayer object. This triggers the software to calculate the differential scattering cross section in the Born Approximation:

multiLayer = ba.MultiLayer()
multiLayer.addLayer(solvent_layer)

The rest of the example script hereafter contains nothing new compared to the previous examples. A sample with a magnetic core-shell particle is constructed. Beam and detector are setup to detect the spin-flip scattering channel and the result of this simulation is plotted as usual.

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#!/usr/bin/env python3
"""
Simple example demonstrating how polarized SANS experiments can be
simulated with BornAgain.
"""

import bornagain as ba
from bornagain import ba_plot as bp, deg, nm, R3


def get_sample():
    """
    Returns a sample with a magnetic core-shell particle in a solvent.
    """

    # Define materials
    magnetic_field = R3(0, 1e7, 0)
    material_Core = ba.RefractiveMaterial("Core", 6e-06, 2e-08,
                                           magnetic_field)
    material_Shell = ba.RefractiveMaterial("Shell", 1e-07, 2e-08)
    material_Solvent = ba.RefractiveMaterial("Solvent", 5e-06, 0)

    # Define form factors
    ff_1 = ba.Sphere(10*nm)
    ff_2 = ba.Sphere(12*nm)

    # Define particles
    particle_1 = ba.Particle(material_Core, ff_1)
    particle_1_position = R3(0, 0, 2*nm)
    particle_1.setParticlePosition(particle_1_position)
    particle_2 = ba.Particle(material_Shell, ff_2)

    # Define core shell particles
    particle = ba.CoreAndShell(particle_2, particle_1)

    # Define particle layouts
    layout = ba.ParticleLayout()
    layout.addParticle(particle)
    layout.setTotalParticleSurfaceDensity(0.01)

    # Define layers
    layer = ba.Layer(material_Solvent)
    layer.addLayout(layout)

    # Define sample
    sample = ba.MultiLayer()
    sample.addLayer(layer)

    return sample


def get_simulation(sample):
    """
    Returns a polarized SANS simulation
    """
    n = bp.simargs['n']

    # Beam from above (perpendicular to sample):
    beam = ba.Beam(1, 0.4*nm, ba.Direction(90*deg, 0))

    # Detector opposite to source:
    detPos = 2000  # distance from sample center to detector in mm
    detWid = 500  # detector width in mm
    detector = ba.RectangularDetector(n, detWid, n, detWid)
    detector.setPerpendicularToDirectBeam(detPos, detWid/2, detWid/2)

    beam.setPolarization(R3(0, 1, 0))
    detector.setAnalyzer(R3(0, -1, 0), 1, 0.5)

    return ba.ScatteringSimulation(beam, sample, detector)


if __name__ == '__main__':
    bp.parse_args(sim_n=200, units=ba.Coords_QSPACE)
    sample = get_sample()
    simulation = get_simulation(sample)
    result = simulation.simulate()
    bp.plot_simulation_result(result)
Examples/scatter2d/PolarizedSANS.py