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BTOF demonstrator/mechanics meeting
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Description
https://ucsc.zoom.us/j/98299273347?pwd=HHm9tGM6hD7aZaIVWWaF16ueAT3gVu.1
Quick recap
The meeting focused on updates and discussions regarding the TOF (Time of Flight) sensor project, including quality assurance (QA) processes, sensor specifications, and assembly procedures. Simone Mazza reported that their technical lead had returned from vacation and was working on test PIM assembly with a new full jig for assembly and suction cups. The team discussed a critical issue about dead channels in the sensors, with John suggesting collaboration with physics working groups to define acceptable efficiency losses. Satoshi shared information about Hamamatsu's planned QA measurements including IV curves and capacitance measurements for all channels before dicing, though the team discussed the importance of conducting measurements after dicing to better reflect final sensor performance. The group agreed on the need to develop a detailed specification document for the sensors, similar to what was done for other components, to ensure consistency and quality control. Rachid emphasized the importance of defining bulk resistivity requirements in contracts with Hamamatsu to ensure uniform sensor performance across batches. The team also discussed yield requirements, with conflicting information about whether 20% or 60% spare sensors were needed, and agreed to address this in upcoming collaboration meetings.
Next steps
- Simone Mazza: Order a new version of the interposer stavelet with stiffeners to improve rigidity and act as a shim for the sensor.
- Simone Mazza: Work on the initial draft of the ITP (Inspection Test Plan) document for the stavelet assembly, to be discussed at the collaboration meeting.
- Satoshi: Summarize and share the QA/QC information from Hamamatsu regarding sensor measurements, including details about dicing method (diamond vs. laser) and possibility of measurements after dicing.
- Satoshi: Visit Hamamatsu Photonics next week and ask about the dicing method, resistivity requirements, and the 64x1 (half) sensor option.
- Surabhi: Send around an example of a specification document (e.g., for CIPMs or crystals) to the group.
- Elke: Initiate the development of a specification document for the sensors to be used with Hamamatsu, to be discussed at the collaboration meeting.
- Satoshi: Check and clarify the yield and spare sensor requirements (e.g., 20% vs. 60% spare) with Koji.
- Rachid: Contact Jean-Paul to discuss the organization and frequency of meetings regarding the thermal model and cooling impacts.
- Simone Mazza: Provide Satoshi with a list of desired sensor permutations for characterization.
- Satoshi: Bring some sensors to Simone Mazza at the next opportunity (Glasgow meeting).
- TOF Group: Assign a lead person to take responsibility for the task of defining and studying the impact of dead channels, with the goal of deciding by the end of the collaboration meeting.
- Simone Mazza / TOF Group: Interact with the tracking working group (at the July workfest) to define criteria and get help with studies on the impact of dead channels.
Summary
PIM Testing Progress Update
Simone Mazza reported that their technical person was on vacation for a week but has now returned, and they are back on track with PIM testing. The team has assembled a full jig for assembly with suction cups and plans to order an improved interposer stavelet with stiffeners that can also serve as a sensor shim. The discussion concluded with Simone Mazza noting that reviewer comments, particularly regarding mechanical fabrication and dead channel issues, need addressing through simulation results.
Dead Channels Impact Discussion
Simone Mazza raised concerns about the impact of dead channels in their detector, noting that losing one channel could result in losing a significant millimeter-by-centimeter region, potentially requiring zero tolerance for dead channels. John suggested working with physics working groups to define acceptable efficiency loss criteria, particularly for tracking and background rejection requirements that might include TOF hits. The group agreed to coordinate with tracking experts and working groups, with John mentioning an upcoming workfest at the July working group meeting where more people could help address these questions.
Sensor Collaboration and QC Planning
The team discussed organizing a final collaboration session and identified the need for a lead person to focus on workforce arrangements, with Kentaro suggested as a potential candidate. Simone Mazza explained sensor behavior with different pitch sizes and outlined a QC procedure where wire bonds could be removed if one or two channels stop working before mounting, though this might not be possible after potting. Satoshi shared information about Hamamatsu's planned QC measurements during mass production, including IV curve and AC measurements of all channels and visual inspection of all sensors before shipping.
Sensor Quality Assurance Strategies
Satoshi discussed quality assurance strategies for sensor measurements, particularly focusing on post-dicing testing. Rachid recommended testing only a sample (25%) from each batch rather than all sensors to avoid unnecessary time consumption, suggesting a database approach to compare results between Hamamatsu and their facility. Satoshi plans to visit Hamamatsu Photonics next week to inquire about their dicing process and discuss implementing capacitance measurements on single channels. Simone Mazza mentioned they would prepare questions for Satoshi's upcoming Hamamatsu visit regarding 64x1 half sensors.
Inspection Test Plan Discussion
The team discussed the inspection test plan (ITP) for the project, with Simone Mazza reporting initial work on the tablet-specific plan while noting that separate plans are needed for sensors, FPC, electronics, ASICs, and mechanics. Rachid emphasized the importance of defining bulk resistivity requirements for silicon sensors in contracts with Hamamatsu to ensure consistent performance across batches. Elke proposed creating a specification document for sensors following established project procedures, which Satoshi agreed to, and Surabhi committed to sharing examples of similar documents. The team also discussed yield requirements, with clarification that a 60% spare rate refers to the total production rather than just sensor yield, and Simone Mazza noted that assembly process losses could reach 20% beyond the sensor yield.
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