User added to our systems on Tue Jan 21 2025
# z_c=rho**2/(2*R) # except ZeroDivisionError: # z_c=0 phi = self.k*z_c - psi # leave k out, retarded reference frame return {'w':w, 'psi':psi, 'absE':absE, 'phi':phi, 'R':R} def dphidz(self, z, rho):