Using the calibration system one gap in one octant of a station was pulsed at various amplitudes and the response of channels not connected to strips in that gap, both in the same octant and other octants of that station, were observed. At the nominal calibration pulse amplitude (DAC = 0x40) no apprecaible cross talk can be seen at the resolution of these plots. But at the maximum aplitude (0xff corresponding to about 10 volts into 100 ohms) some cross talk in other planes in different gaps of the same octant is seen. I estimate the level of that cross talk to be 2% or less. Note that since the preamps saturate somewhere near or below an amplitude of 0x80 that when calculating the fractional cross talk one has to take into account that the reponse in the pulsed strips is lowered by a factor of two or three by this saturation at the largest DAC value of 0xff. For DAC = 0x40 there is not such saturation. At DAC = 0x80 there may still be a little saturation.
The graphs below show the ADC values for each strip connected to a certain half-chassis with the four time samples for each strip shown. The approximate response to the pulse can be seen as the difference between the highest ADC value (near 1800) and the lowest ADC value (about 700 ADC counts lower for DAC = 0x40). Remember that the positive pulses from the calibration system (or from real hits) lower the ADC counts from the pedestal value near 1800 counts.
These plots show the response of octants that were not pulsed in the same station as the gap & octant that was pulsed. They show little or no cross talk to planes that are not in the same octant as was pulsed.
Mike Leitch (leitch@lanl.gov)