ATLAS Pixels

The ATLAS tracker upgrade activities towards the High Luminosity LHC are ramping up. IFAE counts with space in the white and grey rooms to carry out the assembly and characterization of modules. Last year, a new climate chamber capable of reaching -70oC was acquired to perform the thermal tests of the ITk (and HGTD) modules. The wire-bonding and gluing processes were optimized with different prototypes which were then used to validate the testing process. These tests include: electrical tests, device communication and tuning, tests with radiation sources, monitoring of various relevant parameters and the logging of data into the databases. The preproduction of the innermost pixel modules (called triplets) has been launched and the first prototype was assembled and tested at IFAE. Eleven other modules will be fabricated during the pre-production early in 2024. The production of about 130 modules will be started in 2025 and it is expected to take about 1.5 years to complete. P. Fernandez, J. Carlotto, N. Kakoty and S. Terzo are participating in the activities.

As part of the HL-LHC upgrade the ATLAS experiment a new High Granularity Timing Detector (HGTD) will be installed in ATLAS between the forward and central calorimeters, covering the region of 2.4<|𝛈|<4.0. HGTD will precisely measure the time associated with the tracks that reach the detector using LGAD sensors, a technology first developed in Barcelona (CNM). During 2023 IFAE fabricated about 40 modules, including 3 that were the first to pass the thermal cycling requirements of the experiment. In parallel, the groups continued improving Alvin, the HGTD module readout system developed at IFAE and used for device characterization in various labs and also fundamental for the testbeam DAQ at CERN and DESY. In parallel the group has advanced the hybridization process of HGTD, which has been fully developed at IFAE, producing more than 100 hybrids during 2023 with the ALTIROC2 and ALTIROC3 ASICs and various LGAD sensors. P. Fernandez, M. Chmeissani, J. Pinol and S. Terzo are participating in the activities. Finally, R. Casanova has participated in the design of the final version of the readout ASICs for HGTD, ALTIROC-A.

Depleted Monolithic Active Pixel Sensors (DMAPS) integrate both sensor and front-end electronics on a single substrate, avoiding the complicated sensor to chip interconnection process. Modern CMOS technologies allow a good radiation tolerance which draws a lot of interest as an alternative solution for tracking detectors in High Energy Physics (HEP). Furthermore, recently DMAPS are being explored for timing measurements. IFAE has been working on DAMPS timing, building up from an initial MiniCactus chip that was shown to deliver about 65 ps resolution. IFAE, together with IRFU (France), designed a new prototype using LFoundry 150 nm HV technology: the mini-CACTUS-V2 chip. This chip targets an improved jitter and recovery time which has been validated in post simulation. The chip was submitted in October 2023 and is expected by the first part of 2024. Y. Gan and R. Casanova are working on these monolithic devices. A designed monolithic photon counting detector submitted in 2022, H2M, was received in 2023. This ASIC was fabricated with a 65 nm CMOS process. First tests were successful and showed a correct operation of the device. More exhaustive tests are on-going.