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from Geant4 import *
import g4py.ezgeom
import g4py.NISTmaterials
import g4py.ParticleGun
import pyublas
import numpy as np
from chroma.event import Photons, Vertex
try:
import G4chroma
except:
# Try building the module
import subprocess
import sys, os
module_dir = os.path.split(os.path.realpath(__file__))[0]
print >>sys.stderr, 'Compiling G4chroma.so...'
retcode = subprocess.call('g++ -o \'%s/G4chroma.so\' -shared \'%s/G4chroma.cc\' -fPIC `geant4-config --cflags --libs` `python-config --cflags --libs --ldflags` -lboost_python' % (module_dir, module_dir), shell=True)
assert retcode == 0
import G4chroma
class G4Generator(object):
def __init__(self, material, seed=None):
"""Create generator to produce photons inside the specified material.
material: chroma.geometry.Material object with density,
composition dict and refractive_index.
composition dictionary should be
{ element_symbol : fraction_by_weight, ... }.
seed: int, *optional*
Random number generator seed for HepRandom. If None, generator
is not seeded.
"""
if seed is not None:
HepRandom.setTheSeed(seed)
g4py.NISTmaterials.Construct()
g4py.ezgeom.Construct()
self.physics_list = G4chroma.ChromaPhysicsList()
gRunManager.SetUserInitialization(self.physics_list)
self.particle_gun = g4py.ParticleGun.Construct()
self.world_material = self.create_g4material(material)
g4py.ezgeom.SetWorldMaterial(self.world_material)
g4py.ezgeom.ResizeWorld(100*m, 100*m, 100*m)
self.world = g4py.ezgeom.G4EzVolume('world')
self.world.CreateBoxVolume(self.world_material, 100*m, 100*m, 100*m)
self.world.PlaceIt(G4ThreeVector(0,0,0))
self.tracking_action = G4chroma.PhotonTrackingAction()
gRunManager.SetUserAction(self.tracking_action)
gRunManager.Initialize()
# preinitialize the process by running a simple event
self.generate_photons([Vertex('e-', (0,0,0), (1,0,0), 0, 1.0)])
def create_g4material(self, material):
g4material = G4Material('world_material', material.density * g / cm3,
len(material.composition))
# Add elements
for element_name, element_frac_by_weight in material.composition.items():
g4material.AddElement(G4Element.GetElement(element_name, True),
element_frac_by_weight)
# Set index of refraction
prop_table = G4MaterialPropertiesTable()
# Reverse entries so they are in ascending energy order rather
# than wavelength
energy = list((2*pi*hbarc / (material.refractive_index[::-1,0] * nanometer)).astype(float))
values = list(material.refractive_index[::-1, 1].astype(float))
prop_table.AddProperty('RINDEX', energy, values)
# Load properties
g4material.SetMaterialPropertiesTable(prop_table)
return g4material
def _extract_photons_from_tracking_action(self):
n = self.tracking_action.GetNumPhotons()
pos = np.zeros(shape=(n,3), dtype=np.float32)
pos[:,0] = self.tracking_action.GetX()
pos[:,1] = self.tracking_action.GetY()
pos[:,2] = self.tracking_action.GetZ()
dir = np.zeros(shape=(n,3), dtype=np.float32)
dir[:,0] = self.tracking_action.GetDirX()
dir[:,1] = self.tracking_action.GetDirY()
dir[:,2] = self.tracking_action.GetDirZ()
pol = np.zeros(shape=(n,3), dtype=np.float32)
pol[:,0] = self.tracking_action.GetPolX()
pol[:,1] = self.tracking_action.GetPolY()
pol[:,2] = self.tracking_action.GetPolZ()
wavelengths = self.tracking_action.GetWavelength().astype(np.float32)
t0 = self.tracking_action.GetT0().astype(np.float32)
return Photons(pos, dir, pol, wavelengths, t0)
def generate_photons(self, vertices):
"""Use GEANT4 to generate photons produced by propagating `vertices`.
Args:
vertices: list of event.Vertex objects
List of initial particle vertices.
Returns:
photons: event.Photons
Photon vertices generated by the propagation of `vertices`.
"""
photons = None
for vertex in vertices:
self.particle_gun.SetParticleByName(vertex.particle_name)
mass = G4ParticleTable.GetParticleTable().FindParticle(vertex.particle_name).GetPDGMass()
total_energy = vertex.ke*MeV + mass
self.particle_gun.SetParticleEnergy(total_energy)
self.particle_gun.SetParticlePosition(G4ThreeVector(*vertex.pos)*m)
self.particle_gun.SetParticleMomentumDirection(G4ThreeVector(*vertex.dir).unit())
self.particle_gun.SetParticleTime(vertex.t0*s)
self.tracking_action.Clear()
gRunManager.BeamOn(1)
if photons is None:
photons = self._extract_photons_from_tracking_action()
else:
photons += self._extract_photons_from_tracking_action()
return photons
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