Beam divergence

By default, the incident beam is perfectly monochromatic and collimated. Here we show how to set finite distributions of wavelengths and of grazing angles.

  • The wavelength follows a log-normal distribution around the mean value of 0.1 nm with a scale parameter equal to $0.1$.
  • Both incident angles follow a Gaussian distribution around the average values $\alpha_i = 0.2 ^{\circ}$ and $\varphi_i = 0^{\circ}$, respectively and $\sigma_{\alpha_i} = \sigma_{\varphi_i} = 0.1^{\circ}$.

First, the distributions should be defined:

distr_lambda = ba.DistributionLogNormal(0.1*nm, 0.1, 5, 2)
distr_alpha = ba.DistributionGaussian(0.2*deg, 0.1*deg, 5, 2)
distr_phi = ba.DistributionGaussian(0, 0.1*deg, 5, 2)

Then the distributions are to be applied to the simulation object in the following way:

simulation = ba.ScatteringSimulation(...)
simulation.addParameterDistribution(role, distribution)

The role is a special object itself, indicating which parameter is distributed. There are three roles:

role_wavelength = ba.ParameterDistribution.BeamWavelength
role_grazing_angle = ba.ParameterDistribution.BeamGrazingAngle
role_azimuthal_angle = ba.ParameterDistribution.BeamAzimuthalAngle

Distributions are passed to the simulation together with their role:

simulation.addParameterDistribution(role_wavelength, distr_lambda)
simulation.addParameterDistribution(role_grazing_angle, distr_alpha)
simulation.addParameterDistribution(role_azimuthal_angle, distr_phi)

Example

The DWBA simulation example is shown for a standard sample model:

  • The sample is composed of monodisperse cylinders deposited on a substrate.
  • The cylinders are dilute and distributed at random, hence there is no interference between scattered waves.

Real-space model

Intensity image

auto/Examples/scatter2d/BeamDivergence.py