Tests of large charge injection with external capacitorMarcus, Mutsumi
PurposeCharge injection tests with an external capacitor were
performed to investigate crosstalk between strips on SSDs, channels on GTFE
analog circuits when large charge events issued.
MethodWe used a full ladder - miniMCM test system. A 2.2 pF capacitor
was attached to the end of the strip #96, the opposite side of the ladder from
the readout electronics. A test pulse with a step function was sent to the
capacitor and hit strip data was read out repeatedly. We scanned trigger
acknowledge delay from the rising time of the calibration strobe pulse, and
investigated the development of hit pattern (crosstalk) during the
Charge injections by external capacitor: 2.2pF * 40mV = 88fCExternal
charges which corresponds to 88 fC were injected to the strip #96 via the
external capacitor. The channels #0--#383 were connected to the strips on the
ladder. The channels #384--#447 were opened. The figure below shows the time
dependence of the hit pattern. We see that 3 adjacent strips of #96 were
affected by injection charge. The right panel is the magnification of the left
panel around the strip #96. The unit of TACK_DELAY is a clock cycle [/50ns].
The TOT for the signal is about 2500 * 50ns = 125us, which is a little longer
than that in LAT-TD-01090 p.18, 80us, but would not differ so largely. We can
also see that the noise level is a little high around the edges of the
detector, channels #0 and #383.
Charge injection by external capacitor: 2.2pF * 400mV = 880fCExternal
charges which corresponds to 880 fC were injected to the strip #96 via an
external capacitor. The TOT for the signal is about 3000 * 50ns = 150us, which
is consistent with that in LAT-TD-01090 p.18.
Another sample of test results: charge injection by internal calibration
system and external capacitorTo check the test system, internal
calibration pulses of about 1 MIP are injected to the strips #48, #112, #176,
#240, #304, #368, #432 simultaneously with the external pulse. We see that the
TOT for 1 MIP is about 160*50ns = 8us.
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Jul 28 12:10:23 PDT 2004