def nb0(self):
        """
        On-axis beam density :math:`n_{b,0}`.
        """
        return self.N_e / ( (2*_np.pi)**(3/2) * self.sig_r**2 * self.sig_xi)
def nb0(self):
        """
        On-axis beam density :math:`n_{b,0}`.
        """
        return self.N_e / ( (2*_np.pi)**(3/2) * self.sig_r**2 * self.sig_xi)
def nb0 ( self ) : return self . N_e / ( ( 2 * _np . pi ) ** ( 3 / 2 ) * self . sig_r ** 2 * self . sig_xi )
On-axis beam density :math:`n_{b,0}`.
On - axis beam density : math : n_ { b 0 } .