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import unittest
import numpy as np
from chroma.geometry import Solid, Geometry
from chroma.make import box
from chroma.sim import Simulation
from chroma.optics import water_wcsim
from chroma.event import Photons
import histogram
from histogram.root import rootify
import ROOT
ROOT.gROOT.SetBatch(1)
class TestRayleigh(unittest.TestCase):
def setUp(self):
self.cube = Geometry(water_wcsim)
self.cube.add_solid(Solid(box(100,100,100), water_wcsim, water_wcsim))
self.cube.pmtids = [0]
self.cube.build(use_cache=False)
self.sim = Simulation(self.cube, geant4_processes=0)
nphotons = 100000
pos = np.tile([0,0,0], (nphotons,1)).astype(np.float32)
dir = np.tile([0,0,1], (nphotons,1)).astype(np.float32)
pol = np.zeros_like(pos)
phi = np.random.uniform(0, 2*np.pi, nphotons).astype(np.float32)
pol[:,0] = np.cos(phi)
pol[:,1] = np.sin(phi)
t = np.zeros(nphotons, dtype=np.float32)
wavelengths = np.empty(nphotons, np.float32)
wavelengths.fill(400.0)
self.photons = Photons(pos=pos, dir=dir, pol=pol, t=t, wavelengths=wavelengths)
def testAngularDistributionPolarized(self):
# Fully polarized photons
self.photons.pol[:] = [1.0, 0.0, 0.0]
photons_end = self.sim.simulate([self.photons], keep_photons_end=True, max_steps=1).next().photons_end
aborted = (photons_end.flags & (1 << 31)) > 0
self.assertFalse(aborted.any())
# Compute the dot product between initial and final dir
rayleigh_scatters = (photons_end.flags & (1 << 4)) > 0
cos_scatter = (self.photons.dir[rayleigh_scatters] * photons_end.dir[rayleigh_scatters]).sum(axis=1)
theta_scatter = np.arccos(cos_scatter)
h = histogram.Histogram(bins=100, range=(0, np.pi))
h.fill(theta_scatter)
h = rootify(h)
# The functional form for polarized light should be
# (1 + \cos^2 \theta)\sin \theta according to GEANT4 physics
# reference manual.
f = ROOT.TF1("pol_func", "[0]*(1+cos(x)**2)*sin(x)", 0, np.pi)
h.Fit(f)
self.assertGreater(f.GetProb(), 1e-3)
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