Abstract
For the high luminosity upgrade of the Large Hadron Collider (HL-LHC), the instantaneous luminosity is expected to reach unprecedented values, resulting in about 200 proton-proton interactions in a typical bunch crossing. To cope with the resultant increase in occupancy, bandwidth and radiation damage, the ATLAS Inner Detector will be replaced by an all-silicon system, the Inner Tracker (ITk). The innermost part of ITk will consist of a state-of-the-art pixel detector, with an active area of about 14 m2, which will provide tracking capability up to |η|=4. Detector requirements in terms of radiation hardness and occupancy, as well as thermal performance depend strongly on the distance from the interaction region. Therefore, the innermost layer will feature 3D silicon sensors, due to their inherent radiation hardness and low power consumption, while the remaining layers will employ planar silicon sensors with thickness ranging from 100 μm to 150 μm. All hybrid detector modules will be read out by novel ASICs, implemented in 65 nm CMOS technology and thinned to 150 μm, which will be connected to the silicon sensors using bump bonding. With the recent arrival of the first readout chip prototype, the RD53A chip, prototype modules are being built to study sensor and chip properties, thermal performance, as well as bump bonding yield in lab measurements and beam test campaigns. Irradiation studies are ongoing. The report will present latest results from the module characterization measurements both before and after irradiation.
Highlights
Two types of pixel sensors are developed to balance the required radiation tolerance, varying across the detector volume, with the production costs
The RD53 collaboration is developing a new type of FE chip for the ATLAS and CMS experiments at the HL-LHC [2] based on 65 nm CMOS technology
The HL-LHC is an important opportunity for high energy physics research, but the detector upgrade is necessary to cope with the radiation environment over the long data taking time
Summary
Two types of pixel sensors are developed to balance the required radiation tolerance, varying across the detector volume, with the production costs. The production process is technically much more complex and expensive than in the case of planar sensors. For the ITk upgrade, the 3D sensor has been developed for use in the innermost layer, while the planar one will be used in the other parts. The thickness of both types is small compared to previous generation pixel detectors, being 150 μm or 100 μm. The final choice will be made based on studies of tracking performance The performance of these sensors has been evaluated for different values of the thickness and pixel size.
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