Minutes Run IIB Silicon General Meeting,
These minutes can be found at:
ü News / Status George / Marcel
ü Layer 0 Studies Kazu Hanagaki
ü General Grounding Issues and Implications Marvin Johnson
ü Status of Database definition Eckhard von Toerne
News/Status (George, Marcel)
o A revised version of the outer layer sensor specifications (http://d0server1.fnal.gov/projects/run2b/Silicon/www/smt2b/Documentation/Minutes/silicon_spec_layer2_5_v5.doc) and a letter (http://d0server1.fnal.gov/projects/run2b/Silicon/www/smt2b/Documentation/Minutes/HPK_feedback.doc) has been forwarded to procurement, so the order for the outer layer sensors has effectively been released. This is the single largest procurement of the Run IIb silicon project.
o Irradiated foils were sent to Fermilab on 18 April and were to be counted by Vernon Cupps at the Radionuclide Analysis Lab here at Fermilab this week.
o There will be a meeting at the University of Washington on May 5 and 6 primarily focusing on grounding for the inner layers
o Burn in test stand partial Operational Readiness Clearance is working its way through the hi-rise
Layer 0 Studies (Kazu)
o Kazu summarized the results of his recent grounding studies of the layer 0 prototype module. Details can be viewed at http://d0server1.fnal.gov/projects/run2b/Silicon/www/smt2b/Documentation/Minutes/May01_03.ppt or http://d0server1.fnal.gov/projects/run2b/Silicon/www/smt2b/Documentation/Minutes/May01_03.pdf
the best circumstances a S/N ratio of 11 is obtained on the bench with a layer
0 module. The design goal aims for a S/N greater than 12 before irradiation.
Noise levels are demonstrated to be strongly dependent upon the details of the
grounding. The best performance is observed when only the hybrid is grounded.
When only the sensors are grounded the noise is extremely high. This points to
the importance of a low inductance connection. An interesting study which
corroborates the importance of the low inductance connection was clearly
demonstrated when Kazu added additional ground wires to the hybrid ground
connection, varying the number of wires and their length. The implications of
these observations for the inner layers will be explored at the
General Grounding Issues and Implications (Marvin)
o Marvin reported on his interpretation of numerous observations made on CFT and SMT readout of the detectors at DAB. His scanned presentation can be found at http://d0server1.fnal.gov/projects/run2b/Silicon/www/smt2b/Documentation/Minutes/Marvins_smt_cft_noise.pdf . Some of Marvin’s observations are:
o SVX oscillations are observed after the preamp reset in the SMT, CFT and CPS resulting in pedestal variations of a few counts for the SMT
o All channels have a similar response; the SVX2 chip is not ground referenced. As such is the case, the most likely culprit for this effect is a bounce in the ground.
o The CFT sees a similar effect in the SIFT readout (discriminator readout).
o Preamp reset is probably not the only signal that the SVX is sensitive to in this fashion, it just happens to be phase locked so that we directly notice the impact of the ground shift in this case.
o CFT readout has also suffers from split pedestals in alternating ticks. This looks like a harmonic of RF/4, and Marvin suspect that this is also attributable to ground bounce. As a consequence, there is a significant behavior of the CFT occupancy as function of tick number.
o The concern (with respect to the Run IIb SMT project) is that the current design ties the analog and digital grounds together, so the current design may also be sensitive to these problems (although there are certainly significant differences between the SVX 2 and the SVX 4 which may reduce the sensitivity to this issue)
o Marvin emphasized that it is good practice to separate analog and digital grounds, but this would require more layers in the hybrid, making the hybrid more challenging to fabricate to specs and increasing costs. The design of the digital cable would also have to be modified to accommodate this separation of grounds.
o An Analog Front End Board for the CFT has been modified to change the inductance between the analog and digital ground, to attempt to reduce this effect (and verify the interpretation), and that AFE board has been installed on the platform. Studies performed in the near future should provide additional insights
o Andrei reviewed a study on the SVX4 response after preamp reset, which showed evidence of significant shift for the pipeline immediately after the reset, but the shift had settled after three pipeline cells. Additional checks will be performed.
o Bob pointed out that the QA document specifies that the CV curves should have V measured to 350 V. He requested that the measurements be limited to 300 V due to specs on the matrix. Since the depletion voltage for these sensors is well below 300 V, this did not seem to be an unreasonable modification.
o Bob reported that he still sees the unusual frequency dependence of the interstrip capacitance measurements (with a peak around 1kHz), and he suspect that he will see the same thing on all HPK sensors. He has seen the effect on an ELMA sensor and on HPK baby sensor 59.
o Bob measured a 5 pF silver mica capacitor and it did not exhibit this behavior. He suspects that it may be an interaction between the LCR meter and the sensor.
o Sergey reported similar difficulties in measuring interstrip capacitance, but this observation has not been reproducible at Fermilab (on HPK sensor) or in Zuerich (on a baby sensor).
Status of Database Definition (Eckhard)
o Eckhard reported on meeting with Stu, Stan and Vladimir. They discussed plans for handling data, and recommend that the output from the sensor test stands (running LabView) be put into a web readable directory, and that python scripts be used to transfer the information from that directory to the Oracle database, and the online support group would be responsible for generating the python scripts and the Oracle database support.
o The online data group expressed a preference to avoid web interfaces for data input due to difficulties of data parsing.
o Eckhard is still leaning towards an EXCEL spreadsheet format for the output from the sensor test stands, and he was asked for a definitive proposal for format of the sensor data by next week.
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