BornAgain ≻ git-develop ≻ Documentation ≻ Reference ≻ Simulation model ≻ Common settings ≻ Background

Poisson background

To add a Poisson background to a Simulation instance, use

bg = ba.PoissonBackground()
simulation.setBackground(bg)

In this case, the output intensity is randomly distributed around the exact value with discrete Poisson statistics.

The lower the intensity of the probing beam, the lower the signal-to-noise ratio.

Constant background

To add a constant background to a Simulation instance, use

bg = ba.ConstantBackground(1e3)
simulation.setBackground(bg)

Special cases

Specular simulation:

Background is applied before the reflectivity is normalized, so the background value will also be divided by the probe beam intensity.

Depth probe simulation:

Background is not supported.

Examples

Examples/specular/Background.py

Examples/scatter2d/Background.py

Scattering intensity

The script below shows how to add different types of background in the context of a GISAXS simulation of cylindrical particles on substrate.

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#!/usr/bin/env python3
"""
Cylinder form factor in DWBA with background/noise
"""
import bornagain as ba
from bornagain import ba_plot as bp, deg, nm


def get_sample():
    from bornagain import std_samples
    return std_samples.cylinders()


def get_simulation(sample, background):
    beam = ba.Beam(1e6, 0.1*nm, 0.2*deg)
    n = 100
    detector = ba.SphericalDetector(n, 0., 2*deg, n, 0., 2*deg)
    simulation = ba.ScatteringSimulation(beam, sample, detector)
    simulation.setBackground(background)
    return simulation


def simulate(background, title):
    sample = get_sample()
    simulation = get_simulation(sample, background)
    result = simulation.simulate()
    result.setTitle(title)
    return result


if __name__ == '__main__':    
    results = [
        simulate(ba.ConstantBackground(1e1), "Constant background"),
        simulate(ba.PoissonBackground(), "Poisson noise"),
    ]    
    bp.plot_to_row(results, log_range=5)
    bp.plt.show()
auto/Examples/scatter2d/Background.py