Add example for polarized reflectometry

Examples/python/simulation/ex06_Reflectometry/BasicPolarizedReflectometry.py

+"""
+An example of computing reflectivity on a
+magnetized sample.
+"""
+
+import bornagain as ba
+from bornagain import deg, angstrom
+
+
+def get_sample():
+    """
+    Defines sample and returns it
+    """
+
+    # creating materials
+    m_ambient = ba.MaterialBySLD("Ambient", 0.0, 0.0)
+    m_layer_mat = ba.MaterialBySLD("Layer", 1e-4, 1e-8,
+                                   ba.kvector_t(0.0, 1e8, 0.0))
+    m_substrate = ba.MaterialBySLD("Substrate", 7e-5, 2e-6)
+
+    # creating layers
+    ambient_layer = ba.Layer(m_ambient)
+    layer = ba.Layer(m_layer_mat, 10)
+    substrate_layer = ba.Layer(m_substrate)
+
+    # creating multilayer
+    multi_layer = ba.MultiLayer()
+    multi_layer.addLayer(ambient_layer)
+    multi_layer.addLayer(layer)
+    multi_layer.addLayer(substrate_layer)
+
+    return multi_layer
+
+
+def get_simulation(scan_size=500):
+    """
+    Defines and returns a specular simulation.
+    """
+    simulation = ba.SpecularSimulation()
+    scan = ba.AngularSpecScan(1.54 * angstrom, scan_size,
+                              0.0 * deg, 5.0 * deg)
+    simulation.setScan(scan)
+    return simulation
+
+
+def run_simulation(polarization=ba.kvector_t(0.0, 1.0, 0.0),
+                   analyzer=ba.kvector_t(0.0, 1.0, 0.0)):
+    """
+    Runs simulation and returns its result.
+    """
+    sample = get_sample()
+    simulation = get_simulation()
+
+    # adding polarization and analyzer operator
+    simulation.setBeamPolarization(polarization)
+    simulation.setAnalyzerProperties(analyzer, 1.0, 0.5)
+
+    simulation.setSample(sample)
+    simulation.runSimulation()
+    return simulation.result()
+
+
+def plot(pp, mm):
+    from matplotlib import pyplot as plt
+
+    ba.plot_simulation_result(pp, postpone_show=True)
+    plt.semilogy(mm.axis(), mm.array())
+    plt.legend(['Up-Up', 'Down-Down'],
+               loc='upper right')
+
+    plt.show()
+
+
+if __name__ == '__main__':
+    results_pp = run_simulation(ba.kvector_t(0.0, 1.0, 0.0),
+                                ba.kvector_t(0.0, 1.0, 0.0))
+    results_mm = run_simulation(ba.kvector_t(0.0, -1.0, 0.0),
+                                ba.kvector_t(0.0, -1.0, 0.0))
+    plot(results_pp, results_mm)