Power supply cable Charge injection 3 channels readout (external cables to the scope) 3 channels readout (internal cables) Set up for reading two cards

3 channels readout Charge Injection Testing one card at a time Reading one card 3 channels connected Output signals are reasonable The quality of the output signal improves when the grounds of the input and output cables were connected inside the box Same for both cards Grounds of input and output cables are connected

Testing one card at a time with one channel connected – signal recorded from main channel Long tail Ringing/oscillations in the tail

Long tail, oscillations reduced when the grounds of the input and output inside the box are connected Gain is also increased Testing one card at a time with one channel connected – signal recorded main channel

Testing one card at a time with two channels connected – signals recorded from main channel

Testing one card at a time with three channels connected – signal recorded from main channel

Reasonable signal recorded from bottom card (card 1), but with bad oscillations Very bad oscillations on top card (card 2) Signals in the two cards do not behave in the same manner

Summary of current status Can read one channel from one card Signal quality improves when the grounds of cables for the input and output inside the shielding box were connected With this configuration, signals in the main channel are reasonable in terms of time response and gain, even when the neighbour channels are connected When both cards are connected, signals from one card has a long tail and the other with significant oscillations.

Work to do: To investigate the problem when two cards are connected To investigate possible injection from pulse generator into the ground Other observations: As soon as pulse generator is connected to the shielding box, there is a potential difference around the box (ie. the potential is not homogeneous across the box). The pulse generator seems to disturb the ground potential. The pulse generator was set to have a 50ohm impedance. A signal is observed at the ground pin once the pulse generator is connected.