Plasma detection from $U_{loop}$

This is a quick plasma start and end detection from the peaks in the derivative of the $U_{loop}$ signal. This procedure is run as soon as possible in order to provide the information on plasma existance to other routines.

The processing is done only beyond the CD system activation time (to prevent thyristor noise from e.g. the $B_t$ system)

Estimate $\frac{d U_{loop}}{dt}$ by a second order Savitzky-Golay 1. derivative filter.

The plasma starts when the $U_{loop}$ decreases significantly for the first (index 0) time.

The plasma ends when the $U_{loop}$ increases significantly for the last (index -1) time.