Reflectivity sample component

[yxqd]

This is a python based sample component. The sample is a 2D surface with a center at (0,0,0), a norm along y axis, and a size in the xz-plane (size_x, size_z). The neutron will be scattered according to a reflectivity curve R(Q), which will be given as a python function, where Q is a numpy array.

Implementation (hint: use the "monitor" component as the starting point)

• Propagate neutron to the xz-plane (note: the "monitor" component has a function to propagate neutrons to xy-plane. easy to adapt that)
• Filter out neutrons that are not in within the size limit of the sample, and those propagate backward
• Calculate the Q value as v2k 2vy
• Calculate reflectivity using R(Q)
• Change the velocity of neutrons that are scattered by the sample to (vx, -vy, vz)
• Multiply the probability of scattered neutrons by reflectivity

Test:

• Create a simple test case to check
  • neutron from above
  • neutron from below
  • neutron parallel to the surface
  • neutron already passed the surface

[yxqd]

Test is not fully done yet. @Fahima-Islam, could you please pick this up when you got time? Thanks