Strategy for TKR tower environmental test without a full set of flight cables

1. Strategy for TKR tower environmental test without a full set of flight cables MRB Meeting – 13 july 2005

2. Description and reference documentation • Description of nonconformance • TKR towers assembly, test and env-test without a full set of flight cables • Occurrences • TKR towers 7-8-9. Current cables delivery schedule will very likely extend the issue to the remainder of the TKR production (towers 10-11-12-13-14) • Root cause • Flight cables not available to cope with TKR assembly and test schedule • Consequence • Full tower read-out is not assured and is dependent on power-cycles to randomly re-establish connection with idle layers. Complexity increases with number of missing cables • Standard CPT cannot be applied – test procedure must be redefined • A strategy for towers assembly and test must be agreed, taking into account cable delivery, towers assembly and test schedule • Reference NCR List • NCR 530: twr7 non std configuration • NCR 540: twr8 non std configuration • NCR 541: twr9 non std configuration • NCR 543: twr7 layerX7 readout failure • NCR 417 (closed) – annex 1: MCM GTFE reset issue

3. Missing cable impact on tower readout • MCM design features: • the left-hand GTRC sends the hard reset only to GTFE chips 0 through 11, while the right-hand GTRC sends the hard reset only to GTFE chips 12 through 23 (see NCR417-annex1) • when a cable is missing, the GTRC reset input is not terminated and the hard reset to the GTFEs can be held active and cause the chips to be stuck on (see NCR417-annex 2) • readout of the 12 chips closer to a missing cable is not assured • most of the time an unpredictable number of power cycles put the reset line in the correct state and all the GTFE chips on an MCM can be read • some layers might not be reset at all (as in tower7-layerX7) • different power cycles reset different layers, so the chance to reset all the 9 layers connected to a tower cable with the same power cycle is small • when a tower is missing more than 2 cables, resetting all the layers with the same power cycle becomes almost impossible

4. Detailed tower status • Tower 7 • 2 cables missing (C5, C6) • sides (-X), (-Y) with 1 cable • CPT at INFN-Pisa successful. All layers could be read in steps at the expense of several power cycles to overcome reset issue • CPT at Alenia after VIB incomplete: layer X7 could not be properly reset and read with any number of power cycles • 1st CPT in vacuum: all layers could be read after 1st power cycle, tower will not be switched OFF during TVAC to avoid reset problem at power-up • Tower 8 • 4 cables missing (C3, C5, C6, C7) • side (-Y) with NO cable • sides (-X), (+Y) with 1 cable • CPT at INFN-Pisa incomplete: 9 layers on (-Y) side could not be read • Sidewalls in place and alignment performed • Tower 9 • 6 cables missing (C0, C1, C3, C5, C6, C7) • sides (+X), (-Y) side with NO cable • sides (-X), (+Y) with 1 cable • No CPT performed yet • Sidewalls in place and alignment performed

5. Parlex cable status • Pioneer cables will not be available before end of august • Towers env-test schedule in Alenia cannot be re-negotiated • Towers 8,9,10,11 will not have a complete flight (F) set. Assuming delivery dates in the chart are maintained for pink cables: • Tower 8 complete set with: • C7-142 (F/NF as per current MRB, Parlex) • an EGSE-C3 (NF, SLAC?) • a purple C6 (NF, Pisa) • Tower 9 complete set with: • C1-17 (F/NF as per current MRB, Pisa) • C6-97 (F/NF as per current MRB, Parlex) • a purple C0 (NF, SLAC/Pisa), C7 (NF, Pisa) • an EGSE C3 (NF, SLAC?) • Towers 10,11 complete set with yellow C1 and purple C6, C7 • cables for both towers MUST be at Pisa by 7/25: the last useful time to install both tower cables to match env-test is during tower 11 assembly, that cannot start before 7/22 • Tower2 12-13-14: • assemble complete new set • backup non-flight cable MUST be available at start of tower assembly in case new cables do not make it in time

6. Corrective actions – strategy 1 (preferred) • Install ALL available flight cables AND complete set with non-flight cables • Do not use solithane to allow future removal of sidewalls for cable replacement • Pros: • Full tower read-out assured, standard test procedures • 1st set of cables could be installed with the tower in the assembly jig, as foreseen in the assembly procedure (at least for tower 10 and beyond) • early full test of the tower to detect any anomaly • any repair (e.g. tray replacement/repair) is much easier than a repair on a tower with sidewalls • Cons: • Minimal risk of damage during cable replacement • 9 towers built • 70 cable installations + 11 cables removed and reinstalled or replaced + 16 cables partly demated and remated (tray repairs) • 2 pin damaged on cable omnetics connectors (pins were most likely already cracked) • 1 tray-SSD hit and damaged during cable assembly (twr4) • 1 tray-SSD hit with no consequence during a cable removal (twr3) • Few screws might loose torque during VIB test • Comment: • Cables are meant to be mated and demated by definition • TKR records show that this can be done with controlled risk

7. Corrective actions – strategy 2 (backup) • Install at least 1 flight cable per side and perform environmental tests in such configuration • Pros: • No risk for extra cables assembly and disassembly • Cons: • Need to redefine test procedure to cope with schedule and feasibility of the test • High risk of running a blind env-test for several layers • The only anomalies found in TVAC became evident only when operating and reading out the tower in vacuum • tower1-NCR430, required replacement of a mid tray • tower7-NCR544, noise anomaly with temperature, to be investigated • Unpredictable test schedule • Installing cables at the very last moment has negative impacts on tower assembly schedule (as already happening now) • it’s hard to plan activities and people commitment • any accident needing repair would be detected late and repair would cause env-test slip • Comment: • Current cable delivery schedule does not assure we will have at least 1 flight cable per side: • we might have to install NF cables anyway to be able to run TVAC • it would too late to gather and install a full completion of a cable set with NF cables  we would face the cons of both strategies (NF cables, awkward test procedure, cable replacement)

8. Modified test flow with missing cables Due to unpredictable delays from the required power cycles, it is strongly recommended to give-up the redundancy of the full CPT suite and just perform the following iterative test (enough to assess TKR functionality): • find a configuration with a reasonable nb of working layers by power-cycling the system and running the following new script at each power-up: • power-up & register test: • issue a GTCC reset • configures the layers to be read w/o the missing cables • execute a register load and read-back on a mask register for each GTFE and display the list of failed layers • Configure failed layers to be read with 12 layers on the connected cable (TBD) • for a chosen configuration of working layers perform the following: • Noise&gain (TE301) • to be run in two steps as GTCC event buffer limitation and TE301 time optimization allow testing a maximum of 5 layers in parallel with a cable missing • Strip noise occupancy (noisy channels search – TE302) • Repeat steps 1 and 2 until all layers have been tested Note: even choosing strategy 1 we might be in this situation for some towers due to limited number of non-flight cables