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Resolution effects in TOF Reflectometry

In the following reflectometry example, each scan point has a distribution of $q_z$ values.

The constructor

ba.DistributionGaussian(0., 1., 25, 2.)

specifies a Gaussian distribution with mean 0, standard deviation 1, 25 sampling points, and a cut-off at 2 sigma. For other distributions (besides Gaussian), see distributions.

The statements

scan = ba.QzScan(qzs)
scan.setVectorResolution(distr, dq)

take arrays qzs and dq as arguments. These arrays must have the same length n. For each scan point (i=0,..,n-1), the $q_z$ values have a Gaussian distribution with mean qzs[i] and dq[i].

TOF simulation without resolution effects

TOF simulation with $dq = 0.03\,q$

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#!/usr/bin/env python3
"""
An example of defining reflectometry instrument
for time of flight experiment. In this example
we will use purely qz-defined beam,
without explicitly specifying
incident angle or a wavelength.
Additionally we will set pointwise resolution
to the scan.
Note that these approaches work with SLD-based
materials only.
"""
import numpy as np
import bornagain as ba
from bornagain import ba_plot as bp, std_samples


def get_sample():
    return std_samples.alternating_layers()


def get_simulation(sample):
    """
    Defines and returns specular simulation
    with a qz-defined beam
    """
    n = bp.simargs['n']

    qzs = np.linspace(0.01, 1, n)  # qz-values
    dq = 0.03*qzs
    distr = ba.DistributionGaussian(0., 1., 25, 2.)

    scan = ba.QzScan(qzs)
    scan.setVectorResolution(distr, dq)

    return ba.SpecularSimulation(scan, sample)


if __name__ == '__main__':
    bp.parse_args(sim_n=500)
    sample = get_sample()
    simulation = get_simulation(sample)
    result = simulation.simulate()
    bp.plot_simulation_result(result)
Examples/specular/TOFRWithResolution.py