def change_the_g(self, g):
# funzione che in base alla posizione del cristallo su cui cade il
# fotone gli cambia il g relativamente alla curvatura del cristallo
raggio = math.sqrt (self.photon.r[0]**2 + self.photon.r[1]**2)
delta_angle = (self.xtal.rho-raggio ) * self.xtal.curvature
gtheta = self.xtal.gtheta + delta_angle
return Physics.spherical2cartesian(norm(g),self.xtal.gphi, gtheta)
def g_needed(self, order=1):
###############################################
local_xtal_g = self.change_the_g(self.xtal.g)
#lgn=Physics.normalize(local_xtal_g)
local_xtal_gphi = Physics.atan2(local_xtal_g[1], local_xtal_g[0])
###############################################
"""Calculates the reciprocal lattice vector that a photon needs to be
scattered by a known crystal with planes oriented in a particular
direction that is already known"""
#When the energy is too low the returned value is None.
if self.photon.knorm < self.xtal.gnorm*order: return None
# For the calculation see the notes of 09/07/2004 modified the 12/07/04
A = (self.photon.k[0]*math.cos(local_xtal_gphi)+self.photon.k[1]*math.sin(local_xtal_gphi))
B = self.photon.k[2]
C = self.xtal.gnorm/2.
#A = (self.photon.k[0]*math.cos(self.xtal.gphi)+self.photon.k[1]*math.sin(self.xtal.gphi))
#B = self.photon.k[2]
#C = self.xtal.gnorm/2.
if abs(A)<=EPSILON:
# B can't be 0 together with A unless gnorm=0, so this function should be almost safe
# The result can be otained with the calculation in the else block
# but this is faster and common (is the case of paraxial photons).
if abs(C/B)>1.: return None
else:
theta=math.acos(-C/B)
else:
A2B2=A**2+B**2
BC=B*C
# Two solutions, but only one satisfies the Laue equation
Mean=-BC/A2B2
try:
Delta=A*math.sqrt(A2B2-C**2)/A2B2
except ValueError:
return None
cosp, cosm = Mean+Delta, Mean-Delta
thp, thm = math.acos(cosp), math.acos(cosm)
sinp, sinm = math.sin(thp), math.sin(thm)
checkp = abs(A*sinp + B*cosp + C)
checkm = abs(A*sinm + B*cosm + C)
# Da ricontrollare
if checkp<checkm:
theta=thp
else:
theta=thm
return Physics.spherical2cartesian(self.xtal.gnorm, local_xtal_gphi, theta)