Here is the somewhat delayed description of the problems encountered with the testbeam data from last run. In the analysis we have done so far, we have not identified any DAQ related problems in the ADC's used with the Phobos detector. We did find some bad ADC channels which had a significant tail on the pedestal on the negative side. This was found during the run but all we did was verify that it was a bad ADC channel and not a bad detector channel. We have also studied some interesting common-mode noise problems where the whole detector (or certain subsections) have correlated changes in their pedestals. This analysis ended with the conclusions that the detector seemed to be working well, the efficiency was decent, and the pulse-sharing seemed to occur only over a very narrow range between pads.

The primary on-line diagnostics needed for the Phobos detector in the Camac ADC's is a histogram of the signals (preferably pedestal subtracted) for each pad as well as a 2-D histogram of the signal on each pad versus the sum of the signals on the surrounding pads.

For the telescope, we had much greater problems. First, there were some selected runs where the pedestal was quite broad. We have not done a full systematic check so I can't tell how prevalent this problem was. The biggest problem was events in which the data for part of the telescope appears to be identical to the previous event. We have only looked at data separated by sensor, not by individual VA1 chips. When a particular sensor fails, there is a very high probability that all higher number sensors are bad. This is why we believe that the problem was some timing mis-match in the read-out. We also had a problem that a significant fraction of the strips in the section of sensor#1 that we were using were not giving signals, only pedestals. Finally, there is a very strange problem with sensor #3. When we look at sensor #'s 1, 2, and 5 (the Y planes), we see excellent alignment. When we look at sensor #'s 4 and 6, we also see good agreement after we correct for the fact that sensor #4 has 100 micron strips (all others are 50 microns). However, if we try to correlate sensor #3 with sensor #4 or #6 or with a line fitted to the two, we see a big discrepancy. The effect is that a change in the hit strip on sensor #3 deviates from the change in projected distance at sensor #3. The deviation depends roughly linearly on the location on sensor #3. This suggests that the sensor had a different strip pitch or that it was rotated, or both. We have looked at the data in various ways and have not yet found a good explanation. We continue working on this problem.

We need several on-line diagnostics for the telescope, starting with a histogram of the signals on each sensor with pedestal subtraction (a 2-D plot with signals versus channel number). Then, we need plots of one sensor versus the others in the same orientation (X vs X and Y vs Y) but here we need to find the peak and plot peak positions. Finally, we need a check for the repeated data problem. The last check is to find tracks and fit a line.