TheLartians
commented
6 years ago The idea is to define the initial field u0 as the appropriate scalar field from your source.
To define a beam traveling at an small angle alpha in the xz plane, you would multiply a phase factor exp(-ikx sin(alpha)) to the beam's initial profile.
For example, the following script defines, propagates and plots a gaussian beam traveling downwards at an angle of 0.1 degrees in a perfectly reflective box.
from pypropagate import *
settings = presets.settings.create_paraxial_wave_equation_settings() # stores simulation parameters s = settings.symbols # shortcut to relevant parameters
s = settings.symbols # shortcut to relevant parameters
# define the initial condition as a 1D gaussian profile propagating at a small angle
angle = -0.1*units.degrees
phase_shift = pc.exp(-1j*s.k*pc.sin(angle)*s.x) # phase shift resulting from the rotation
gaussian_profile = pc.exp(-s.x**2/(2*(10*units.nm)**2))
s.u0 = gaussian_profile * phase_shift
s.n = 1 # free-space propagation
s.u_boundary = 0 # reflective boundary condition
settings.simulation_box.set((100*units.nm,100*units.nm,0.1*units.mm),(1024,1024,2000)) # set simulation boxphysical and voxel size
settings.wave_equation.set_energy(100*units.keV) # set photon energy
propagator = propagators.FiniteDifferences2D(settings) # initialize propagation algorithm
field = propagator.run_slice()[:,:] # propagate and store the resulting 2D field
plot(field) # plot resultAs for documentation, I've finally uploaded the complete thesis covering the mathematical theory behind PyPropagate and also many more examples.
Free to ask if you need any more support.
I am trying to simulate a thin film on top of a substrate layer interacting with an x-ray plane wave source at a shallow angle (<2°) but none of the examples explain how to customize the source in anyway outside of the energy. I tried to figure it out myself by looking through the source code but that part is not really commented and as far as I can tell the few examples are the complete documentation so I have to ask some stupid questions.
Thanks in advance