Upgrade of the ALICE ITS detector

A Large Ion Collider Experiment (ALICE) has been conceived and constructed as a heavy-ion experiment at the LHC. During LHC Runs 1 and 2, it has produced a wide range of physics results using all collision systems available at the LHC. In order to best exploit new physics opportunities opening up with the upgraded LHC and new detector technologies, the experiment has undergone a major upgrade during the LHC Long Shutdown 2 (2019–2022). This comprises the move to continuous readout, the complete overhaul of core detectors, as well as a new online event processing farm with a redesigned online-offline software framework. These improvements will allow to record Pb-Pb collisions at rates up to 50 kHz, while ensuring sensitivity for signals without a triggerable signature.

Section: Component Production Detector Assembly and Commissioning On ...mentioning

confidence: 99%

ALICE upgrades during the LHC Long Shutdown 2

Acharya,

Acosta Hernandez,

Adamová

et al. 2024

“…In past few years, CMOS Monolithic Active Pixel Sensors (MAPS) have widely demonstrated to meet the requirements of tracking detectors as a viable alternative to hybrid pixels in high-energy physics experiments [1][2][3]. Since the spatial density of particle collisions expected in near-future high-energy physics experiments will dramatically increase, silicon detectors are requested to provide also precise time information to perform an accurate reconstruction of tracks [4,5], particle identification [6] or as beam-induced background mitigation technique (see, for instance, ref.…”

Section: Introductionmentioning

confidence: 99%

First results on monolithic CMOS detector with internal gain

Follo,

Gioachin,

Ferrero

et al. 2024

In this paper we report on a set of characterisations carried out on the first monolithic LGAD prototype integrated in a customised 110 nm CMOS process having a depleted active volume thickness of 48 μm. This prototype is formed by a pixel array where each pixel has a total size of 100 μm× 250 μm and includes a high-speed front-end amplifier. After describing the sensor and the electronics architecture, both laboratory and in-beam measurements are reported and described. Optical characterisations performed with an IR pulsed laser setup have shown a sensor internal gain of about 2.5. With the same experimental setup, the electronic jitter was found to be between 50 ps and 150 ps, depending on the signal amplitude. Moreover, the analysis of a test beam performed at the Proton Synchrotron (PS) T10 facility of CERN with 10 GeV/c protons and pions indicated that the overall detector time resolution is in the range of 234 ps to 244 ps. Further TCAD investigations, based on the doping profile extracted from C(V) measurements, confirmed the multiplication gain measured on the test devices. Finally, TCAD simulations were used to tune the future doping concentration of the gain layer implant, targeting sensors with a higher avalanche gain. This adjustment is expected to enhance the timing performance of the sensors of the future productions, in order to cope with the high event rate expected in most of the near future high-energy and high-luminosity physics experiments, where the time resolution will be essential to disentangle overlapping events and it will also be crucial for Particle IDentification (PID).

“…Recently, the detector system was replaced by a second, digital-only version (ITS2), based on the ALPIDE Monolithic Active Pixel Sensors (MAPS). In this new design, a higher intrinsic spatial resolution of 5 μm is achieved [1], owing to the high granularity of the 50 μm thick sensors, the low material budget (0.35% x/X 0 for the inner layers) and the proximity to the interaction point (23 mm for the innermost layer). Even though the ITS2 detector is very lightweight, the active silicon part of the sensor represents only 15% of the total material budget [2].…”

mentioning

confidence: 99%

Testbeam performance results of bent ALPIDE monolithic active pixel sensors in view of the ALICE Inner Tracking System 3

Blidaru¹

2022

The ALICE Inner Tracking System has been recently upgraded to a full silicon detector consisting entirely of monolithic active pixel sensors, arranged in seven concentric layers around the LHC beam pipe. Further ahead, during the LHC Long Shutdown 3, the ALICE collaboration is planning to replace the three innermost layers of this new ITS with a novel vertex detector. The proposed design features wafer-scale, ultra-thin, truly cylindrical MAPS. The new sensors will be thinned down to 20–40 µm, featuring a material budget of less than 0.05% x/X 0 per layer, unprecedented low, and will be arranged concentrically around the beam pipe, as close as 18 mm from the interaction point. Anticipating the first prototypes in the new 65 nm CMOS technology node, an active R&D programme is underway to test the response to bending of existing 50 µm thick ALPIDE sensors. A number of such chips were successfully bent, even below the targeted innermost radius, without signs of mechanical damage, while retaining their full electrical functionality in laboratory tests. The curved detectors were subsequently tested during particle beam campaigns, where their particle detection performance was assessed. In this contribution, testbeam highlights from the data analysis of bent ALPIDE sensors, will be presented. It was proved that the current ALPIDE produced in the 180 nm CMOS technology retains its properties after bending. The results show an inefficiency that is generally below 10−4, independent of the inclination and position of the impinging beam with respect to the sensor surface. This encouraging outcome proves that the use of curved MAPS is an exciting possibility for future silicon detector designs, as not only the sensor can survive the bending exercise mechanically, but the enticing attributes that make it attractive for use in the inner tracking layers are comparable to the flat state.