I think this would be easier and faster as 

```python
def calc_ebins(self):
    """ Calculate the energy value for each channel."""
    channels = self.channels = np.asarray(self.channels, float)
    self.Ebin = self.calib_E_fit[0] + (self.calib_E_fit[1]*channels) + (self.calib_E_fit[2]*channels**2)
```