Some Q&A Results
The testing of silicon detectors are performed in a probe station housed in a
cleantent in Los Alamos National Laboratory.
Figue Fig.4
The strip detectors on the inner barrel and the outer barrel have very similar structure.
The individual strip or pad currents in the respective strip or pad detectors
are on the order of 1 nA. We require the individual strip or pad leakage
currents in an acceptable detector to be lower than 10 nA. The characteristic
of capacitance vs voltage
of individual strips indicates a full depletion around 20 to 25 Volts,
and the alpha-source test indicates a full depletion around 35 Volts. The
leakage current in the outer guard ring is quite high, and the one in the inner
guard ring is lower than 7 uA. The outer guard ring is floated during
operation and the leakage current in the inner guard ring for an
acceptable detector is required to be lower than 15 uA.
The C/V and alpha-source tests indicate a full depletion around 40 Volts.
We require the depletion voltage for an acceptable detector as determined
from 1/C^2 plot at 1 MHz to be lower than 35 Volts.
Figue Fig.5
The last figure of this poster shows the characteristic of individual strip
currents vs voltage for a silicon detector with high interstrip resistance.
We require the interstrip resistance
for an acceptable detector to be larger than 100 MOhm.
Figue Fig.6
We use a beta-source stand to measure the additional cross talk in a pad
detector induced by double metal design (see the poster in this section by
Sangyeol Kim of Yonsei University, Korea). The measured cross talk is lower
than 3%, which is acceptable for the performance requirement of the MVD
endcaps.
Figure 5: C/V test of depletion voltage.
Figure 6: I/V responses in individual strip with low and high
interstrip resistance.
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