def test_Sand_radiation_constant(self):
        # value from S. Lee: Accelerator Physics, 2nd ed., eq (4.5)
        # convert from GeV^3 to eV^3
        self.assertAlmostEqual(self.electron.C_gamma, 8.846e-5 / (1e9)**3, delta=1e-35,
                               msg='Electron: wrong radiation constant')