Interestingly, the bipolar output of the amplifier of the CHIO sent (and splitted) to check correlation on the channel 15 of the ADC CHIO (or on channel 29 of the ADC MUST2) provides a much better resolution (about 10%) than the one obtained using the unipolar output that we were looking since then (about 20% resolution).
This can be understood by the fact that the bipolar signal from the spectroscopic amplifier filters the baseline fluctuation by deriving the unipolar signal.
On the attached PID plot, it is easy to see the improvment. On the other hand, the beam spot extends also at lower channels and covers part of the other lines.
Since the unipolar signal will have some negative part (undershoot), it is possible for pile-up signals to arrive on top of this negative part and end up with lower energy.
With numexo, the energies extracted from the digitized signals, this undershoot issue is not visible. |