Speaker
Description
ALICE 3 is an innovative experiment that will be installed at the LHC during Long Shutdown 4, replacing the current ALICE detector, and will operate in Run 5 (2036-2041). The new apparatus will be equipped with compact silicon-based timing detector to provide an excellent electron identification capability up to 500 MeV/c and $\pi/K$ separation up to 2 GeV/c over a wide rapidity range. The Time-Of-Flight system will be composed by two barrel layers, the inner and the outer, and a forward one, based on state-of-the-art sensors with a required time resolution below 20 ps. The sensors will also need to withstand the expected irradiation levels, up to $10^{13}\ \mathrm{MeVn_{eq}/cm^2}$ in the forward TOF.
In this context lies the development of Low Gain Avalanche Diodes (LGADs) prototype in CMOS technology, featuring an internal gain layer beneath the collection electrode. This sensors are characterized by a 48 $\mu$m active volume and a particularly fast integrated front-end amplifier. Recent studies conducted within our $\text{R&D}$ program on standard LGAD prototypes have demonstrated that the time resolutions required by the ALICE 3 experiment can indeed be achieved by reducing the sensor thickness. However, the development of CMOS-LGAD sensors allows the integration of both the sensor and the electronics within a single substrate. This approach not only simplifies the system but also significantly reduces production costs, while maintaining the desired performance.
The first CMOS-LGAD prototypes with moderate gain were devoleped from an $\text{R&D}$ program carried out by ALICE and INFN ARCADIA introducing a gain layer in the CMOS Monolithic Active Pixel Sensors produced by LFoundry in the 110nm technology. The characterization was performed both in the laboratory, using a pulsed 1054 nm laser to estimate the electronic jitter contribution, and in several test-beam campaigns at the CERN Proton Synchrotron with 10 GeV/c proton and pion beams to evaluate the overall time resolution. The measured jitter was found to be about 30-35 ps, while the time resolution of the devices with the highest gain is about 75 ps at room temperature. An overview of the current state of the $\text{R&D}$ and future plans aimed at achieving the time resolutions required by the ALICE 3 experiment will be presented. In particular, this contribution will discuss the performance in terms of time resolution as a function of the sensor temperature, as well as the in-pixel efficiency.