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import unittest
import numpy as np
import scipy.stats
#import matplotlib.pyplot as plt
from chroma.geometry import Solid, Geometry, Surface, Material
from chroma.loader import create_geometry_from_obj
from chroma.make import sphere
from chroma.sim import Simulation
from chroma.demo.optics import vacuum
from chroma.event import Photons, SURFACE_DETECT
from chroma.tools import enable_debug_on_crash
class TestReemission(unittest.TestCase):
def testBulkReemission(self):
'''Test bulk reemission
Start a bunch of monoenergetic photons at the center of a wavelength-
shifting sphere, forcing reemission, and check that the final
wavelength distribution matches the wls spectrum.
'''
nphotons = 1e5
# set up detector -- a sphere of 'scintillator' surrounded by a
# detecting sphere
scint = Material('scint')
scint.set('refractive_index', 1)
scint.set('absorption_length', 1.0)
scint.set('scattering_length', 1e7)
scint.set('reemission_prob', 1)
x = np.arange(0,1000,10)
norm = scipy.stats.norm(scale=50, loc=600)
pdf = 10 * norm.pdf(x)
cdf = norm.cdf(x)
scint.reemission_cdf = np.array(zip(x, cdf))
detector = Surface('detector')
detector.set('detect', 1)
world = Geometry(vacuum)
world.add_solid(Solid(sphere(1000), vacuum, vacuum, surface=detector))
world.add_solid(Solid(sphere(500), scint, vacuum))
w = create_geometry_from_obj(world, update_bvh_cache=False)
sim = Simulation(w, geant4_processes=0)
# initial photons -- isotropic 250 nm at the origin
pos = np.tile([0,0,0], (nphotons,1)).astype(np.float32)
dir = np.random.rand(nphotons, 3).astype(np.float32) * 2 - 1
dir /= np.sqrt(dir[:,0]**2 + dir[:,1]**2 + dir[:,2]**2)[:,np.newaxis]
pol = np.zeros_like(pos)
t = np.zeros(nphotons, dtype=np.float32)
wavelengths = np.ones(nphotons).astype(np.float32) * 250
photons = Photons(pos=pos, dir=dir, pol=pol, t=t, wavelengths=wavelengths)
# run simulation and extract final wavelengths
event = sim.simulate([photons], keep_photons_end=True).next()
mask = (event.photons_end.flags & SURFACE_DETECT) > 0
final_wavelengths = event.photons_end.wavelengths[mask]
# compare wavelength distribution to scintillator's reemission pdf
hist, edges = np.histogram(final_wavelengths, bins=x)
print 'detected', hist.sum(), 'of', nphotons, 'photons'
hist_norm = 1.0 * hist / (1.0 * hist.sum() / 1000)
pdf /= (1.0 * pdf.sum() / 1000)
chi2 = scipy.stats.chisquare(hist_norm, pdf[:-1])[1]
print 'chi2 =', chi2
# show histogram comparison
#plt.figure(1)
#width = edges[1] - edges[0]
#plt.bar(left=edges, height=pdf, width=width, color='red')
#plt.bar(left=edges[:-1], height=hist_norm, width=width)
#plt.show()
self.assertTrue(chi2 > 0.75)
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