Ensuring a successful TPC production Design Quality Assurance (QA) Quality Control (QC) Sven

Hypothetical Failure Scenarios As magnetic field is turned on four of the TPC instantly fail. Cause: Ferromagnetic screws used to secure field cage resistors in last four TPCs, after we ran out of other screws. Actual problem: design stage - no clear agreement on exactly which screws to use. During phase II, as luminosity increases, gas purity deteriorates. We find we need slightly higher drift velocity and HV to get a good signal. Three of the TPCs spark at the new setting and can no longer be used. Cause: Rough specs on three individual field cage ring. Actual problem: QC procedure did not specify passing criteria for spark testing of field cage. Only nominal field value used. QA did not specify visual inspection of rings. Three of the TPCs have a lower signal. We have to flow more gas to recover, and run out of funds, due to the expensive gas vendor at KEK. Cause: there is food grease on three Kapton shields. Log reveals these three TPCs were assembled by one particular student. Actual problems: QC: Did not measure outgassing of all final field cages. QA: Did not prescribe use of gloves. Such failures are very typical in experimental HEP(!) Minimize or avoid through careful Design – what do build Quality Assurance (QA) – how to build Quality Control (QC) – how to test

Design: All aspects of design should be Agreed on – shown in production meeting Approved – by all three Ph.D.s: Igal, Peter, Sven Documented – on Wiki Exact design specification (shop drawing, design file, part number, web page link or similar) Date approved, and by whom QA/QC procedure is part of design, must also be agreed on, approved, and documented We did some rough documentation of prototype design here: https://wiki.phys.hawaii.edu/bin/view/BEAST/TechnicalDocumentation Need more detailed page for production

Quality Assurance (QA) We need written instructions for how to build each part There should be a checklist on a printed piece of paper, where people checks off each production step, put initials, and date There can be multiple people signing off Example (rough) for FE DAQ boards: Procure circuit board from vendor A Vendor B loads components Send to LBNL for chip loading Glue chip with epoxy of type TBD Wire bond Ultrasonic cleaning Ship back to Hawaii Characterize FE chip Assemble onto field cage structure As the TPCs get integrated, the QA/QC sheet for all parts get put into a common folder (one folder per TPC) There can be separate levels of sheets. For instance, characterizing FE chip may get a separate QA sheet with more detail. And one top-level sheet per TPC.

Quality Control (QC) We need written instructions for how to test each part There should be a checklist on a printed piece of paper, where people checks off each test step, put initials, a few key summary tests results, date, location of test data Detailed test data should go into a common location on dcube server [As the TPCs get integrated, the QA/QC sheet for all parts get put into a common folder (one folder per TPC)

Final Comment What you just heard may sounds pedantic But, such steps were crucial for construction of complex detectors systems in the past. E.g. ATLAS pixel detector If production is well documented, you can often figure out cause of failures by studying the log books carefully, and correct procedures in time If not well documented, failure is likely