Summary and Conclusions
- Several of the chips in the commissioning HDIs had problems.
These HDIs were not nearly of production quality.
The quality control must be greatly improved.
- For the working chips, measurements of gains, offsets and noise
were in general agreement
with expectations based on measurements performed
on individual test
chips at Pavia and elsewhere.
- Some of the chip problems that we observed were intermittent and/or
additional problems developed with time. It will be hard to weed
out chips with intermittent problems, but an effort must be made
to do this before attaching HDIs to the silicon. Burn-in should help.
- We believe that there may very well be a problem with location
9 (chip ID 2 on the p-side) on the H1 hybrids. If this is not
resolved, we fear that the performance of 15% of the channels on
the z-side of layers 1 and 2 will be compromised at some level.
- We observed a type of problem (No response to Q-inject)
that we had never seen on rad soft chips. Channels with this problem
do not respond to charge injection, but they are not completely dead
since they fire on noise at very low threshold. These channels do
not appear to respond to LED scans either.
- One chip stopped working after bonding. At this moment
we cannot say whether this was due to infant mortality or to
a handling accident.
- A region of very high noise developed on the detector after mounting
in the commissioning box. A visual inspection showed no obvious damage,
but again this could have been caused by handling.
- Time constraints on online calibrations at PEP II will likely prevent
us from extracting offsets from threshold scans performed
by firing one channel at a time. There are systematic shifts
in both gain and threshold measurements when the measurements are
performed firing more than one channel at a time. This requires
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