Captinnov
CONTEXT:
CERN's Large Hadron Collider (LHC) is the world's highest energy accelerator for the study of particle physics. It accelerates proton beams within a 27 km underground ring. In 2024-2026, the LHC will be optimized for High Luminosity LHC (LH-LHC): when the ATLAS detector (one of the LHC's detectors) will be upgraded in 2025 to Phase II, a brand new all-silicon internal trajectograph will replace the old one. The latter is a key element for the study of the Standard Model and discoveries in the physics of supersymmetry.
HL-LHC will operate at a five times higher luminosity (5 − 7 × 1034cm−2 s−1). The detectors will have to handle higher particle densities leading to higher occupancies in the detector components and higher radiation levels. The number of events per collision will increase from around 25 to up to 140−200 (depending on the luminosity) events per collision. Tracking systems of the detectors at HL-LHC are built to cope with this increased particle multiplicity. A very fine granularity is needed to resolve nearby tracks. Since the time between bunch crossing is 25ns, detectors and electronics with fast response time and on-detector pipelined memories to store the data from each collision, until a level-one trigger decision is made, are required. Inner detectors are also required to survive a harsh radiation environment with particle fluxes of between 1013 and 1014 equivalent 1 MeV neutrons/cm2 /yr and they are designed in order to continue working for at least 10 years. The pixel detector will comprise the five innermost layers, and will be instrumented with new sensor and readout electronics technologies to improve the tracking performance and cope with the HL-LHC environment. The total surface area of silicon in the new pixel system could measure up to 14 m2. All components of the new ITK are currently under progress and validation. A detailed organization with an industrial and distributed approach has been realized for the construction of such a large-scale detector, in order to guarantee a uniform quality and match the schedule.
CAPTINNOV: A KEY TOOL ATLAS ITK PIXEL QUALITY CONTROL AND QUALITY INSURANCE:
A major investment of IJC Lab has been done for silicon pixel technology development and especially targeted for major HEP projects like the ATLAS pixel new ITK construction. A new 80 m2 ISO7 class clean room has been constructed and delivered early February 2020 after eight month work. The clean room is housing the SignatoneTM P2IO probe-station and a full chain of modern equipment for pixel module characterization and development.
A collaborative consortium has been created within the ITK IN2P3 Groups and especially inside the Paris-Saclay-cluster site (IJC Lab-LPNHE-CEA/IRFU). The construction of such a large scale ATLAS detector is considered as the main task of ATLAS IJC Lab team; this operation requires an industrial and distributed approach and inhouse modern infrastructure like Captinnov plateform. The procedures following at each step of the production chain are carefully studied and be will following a rigorous quality control survey of all the metrology tasks. Sensor-chip interconnection options are being evaluated in collaboration with industrial partners to identify reliable technologies when employing very thin (150 μm to 400μm) pixel devices. While the CERN-RD53 Collaboration is developing the new readout chip, the pixel off-detector readout electronics will be implemented in the framework of the general ATLAS trigger and DAQ system.
The pixel modules are first assembled in the laboratory and bonded to the flex readout system using state of the art wire bonding machine. In order to quickly identify and possibly correct module problems a full electrical test is done just after the bonding. After the gluing and flex bonding operation, modules will follow the Quality Control chain in our laboratories. Low voltage bias will be supplied to modules including a silicon pixel sensor detector bump-bonded to its ITKpixV1 readout chip. The bump bonding operation is sub-treated in specialized industrial companies. Assembled modules are continuously evaluated according defined criteria included in an established list of metrology tests. Modules will be systematically submitted to thermal cycles and X- Ray gun will be used to measure the channel pixel hit-map efficiency.
The quality assurance for the final modules is crucial. A peculiarity that has to be taken into account for pixel modules is the difficulty to replace them once they are integrated into the final mechanical structures. For this reason the test procedures to qualify each single module are very demanding in terms of defect finding and reliability. Single module is evaluated in the different stages of the production chain, and it is foreseen to use a complex system to continuously readout a batch of modules while thermal stresses, similar to the real ATLAS Tracker operating conditions, are being applied.
TO GO FURTHER:
To reach the ultimate physics goals in terms of new particle discovery and pushing further the actual knowledge in particle physics understanding especially in high scale energies and supersymmetry predictions, ATLAS has launched a very large challenging technical program by building a new particle tracker. The goal of the ATLAS ITK project is to address the complex tracker construction project in a collaborative effort as well as federating the different teams of P2IO active on the subject to share and put beneficially in common our expertise. The project cover, three laboratories in the Paris Cluster (IJC Lab, LPNHE, CEA IRFU). Our three production centers have, as much as possible, identical state of the art equipment, high class clean room and common software procedures. In addition, our results from qualification procedures at all stages are stored in a central common database, to allow monitoring of the production quality and quick feed- back to production centers. P2IO-Captinnov probe station is considered a master tool for module production and gives our team the opportunity to have an important and visible position inside the ATLAS ITK international collaboration.
