SCT and TRT Performance from Cosmic Ray Runs

The ATLAS SCT and TRT detectors have been integrated into one barrel and two end-cap parts. Cosmic ray runs of the combined detectors are used to study the individual and combined detector integration and performance. This has taken place both in the surface building (SR1) and after installation in the ATLAS cavern. This article focuses on the most resent results, which includes timing in and synchronisation procedures, noise studies as well as initial efficiency, tracking and alignment results

Coherent laser cooling with trains of ultrashort laser pulses

We propose to extend coherent laser cooling from narrow-band to broad-band transitions by using trains of ultrashort broadband pulses. We study analytically two possible methods to reduce the momentum spread of a distribution by several units of photon momentum in a single spontaneous emission lifetime. We report on numerical simulations of one-dimensional laser cooling of a two-level system with realistic parameters. The technique introduced here is of high interest for efficient laser cooling of fast species with short lifetime such as positronium

The detector control system for the ATLAS semiconductor tracker assembly phase

The ATLAS Semiconductor Tracker (SCT) consists of 4088 silicon microstrip modules, with a total of 6.3 million readout channels. These are arranged into 4 concentric barrel layers and 2 endcaps of 9 disks each. The coherent and safe operation of the SCT during commissioning and subsequent operation is an essential task of the Detector Control System (DCS). The main building blocks of the SCT DCS, the cooling system, the power supplies and the environmental system, are described. First results from DCS testing are presented

Radiation hard 3D silicon pixel sensors for use in the ATLAS detector at the HL-LHC

The High Luminosity LHC (HL-LHC) upgrade requires the planned Inner Tracker (ITk) of the ATLAS detector to tolerate extremely high radiation doses. Specifically, the innermost parts of the pixel system will have to withstand radiation fluences above 1 × 1016 neqcm-2. Novel 3D silicon pixel sensors offer a superior radiation tolerance compared to conventional planar pixel sensors, and are thus excellent candidates for the innermost parts of the ITk. This paper presents studies of 3D pixel sensors with pixel size 50 × 50 μm2 mounted on the RD53A prototype readout chip. Following a description of the design and fabrication steps, Test Beam results are presented for unirradiated as well as heavily irradiated sensors. For particles passing at perpendicular incidence, it is shown that average efficiencies above 96% are reached for sensors exposed to fluences of 1 × 1016 neqcm-2 when biased to 80 V.publishedVersio

Charged-particle multiplicities in pppp interactions at s\sqrt{s} = 900 GeV measured with the ATLAS detector at the LHC

The first measurements from proton-proton collisions recorded with the ATLAS detector at the LHC are presented. Data were collected in December 2009 using a minimum-bias trigger during collisions at a centre-of-mass energy of 900 GeV. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity, and the relationship between mean transverse momentum and charged-particle multiplicity are measured for events with at least one charged particle in the kinematic range |eta|500 MeV. The measurements are compared to Monte Carlo models of proton-proton collisions and to results from other experiments at the same centre-of-mass energy. The charged-particle multiplicity per event and unit of pseudorapidity at eta = 0 is measured to be 1.333 +/- 0.003 (stat.) +/- 0.040 (syst.), which is 5-15% higher than the Monte Carlo models predict.publishedVersio

Radiation hardness of MALTA2 monolithic CMOS imaging sensors on Czochralski substrates

MALTA2 is the latest full-scale prototype of the MALTA family of Depleted Monolithic Active Pixel Sensors (DMAPS) produced in Tower Semiconductor 180 nm CMOS sensor imaging technology. In order to comply with the requirements of high energy physics (HEP) experiments, various process modifications and front-end changes have been implemented to achieve low power consumption, reduce random telegraph signal (RTS) noise, and optimise the charge collection geometry. Compared to its predecessors, MALTA2 targets the use of a high-resistivity, thick Czochralski (Cz) substrates in order to demonstrate radiation hardness in terms of detection efficiency and timing resolution up to 3 × 1015 1 MeV neq/cm2 with backside metallisation to achieve good propagation of the bias voltage. This manuscript shows the results that were obtained with non-irradiated and irradiated MALTA2 samples on Cz substrates from the CERN SPS test beam campaign from 2021 to 2023 using the MALTA telescope

Novel 3D Pixel Sensors for the Upgrade of the ATLAS Inner Tracker

The ATLAS experiment will undergo a full replacement of its inner detector to face the challenges posed by the High Luminosity upgrade of the Large Hadron Collider (HL-LHC). The new Inner Tracker (ITk) will have to deal with extreme particle fluences. Due to its superior radiation hardness the 3D silicon sensor technology has been chosen to instrument the innermost pixel layer of ITk, which is the most exposed to radiation damage. Three foundries (CNM, FBK, and SINTEF), have developed and fabricated novel 3D pixel sensors to meet the specifications of the new ITk pixel detector. These are produced in a single-side technology on either Silicon On Insulator (SOI) or Silicon on Silicon (Si-on-Si) bonded wafers by etching both n- and p-type columns from the same side. With respect to previous generations of 3D sensors they feature thinner active substrates and smaller pixel cells of 50 × 50 and 25 × 100 µm2. This paper reviews the main design and technological issues of these novel 3D sensors, and presents their characterization before and after exposure to large radiation doses close to the one expected for the innermost layer of ITk. The performance of pixel modules, where the sensors are interconnected to the recently developed RD53A chip prototype for HL-LHC, has been investigated in the laboratory and at beam tests. The results of these measurements demonstrate the excellent radiation hardness of this new generation of 3D pixel sensors that enabled the project to proceed with the pre-production for the ITk tracker.publishedVersio

Performance of the MALTA Telescope

MALTA is part of the Depleted Monolithic Active Pixel sensors designed in Tower 180nm CMOS imaging technology. A custom telescope with six MALTA planes has been developed for test beam campaigns at SPS, CERN, with the ability to host several devices under test. The telescope system has a dedicated custom readout, online monitoring integrated into DAQ with realtime hit map, time distribution and event hit multiplicity. It hosts a dedicated fully configurable trigger system enabling to trigger on coincidence between telescope planes and timing reference from a scintillator. The excellent time resolution performance allows for fast track reconstruction, due to the possibility to retain a low hit multiplicity per event which reduces the combinatorics. This paper reviews the architecture of the system and its performance during the 2021 and 2022 test beam campaign at the SPS North Area

Preliminary results of 3D-DDTC pixel detectors for the ATLAS upgrade

Presented at: 9th International Conference on Large Scale Applications and Radiation Hardness of Semiconductor Detectors - RD09. Florence, Italy, 30 September - 2 October 20093D Silicon sensors fabricated at FBK-irst with the Double-side Double Type Column (DDTC) approach and columnar electrodes only partially etched through p-type substrates were tested in laboratory and in a 1.35 Tesla magnetic field with a 180GeV pion beam at CERN SPS. The substrate thickness of the sensors is about 200μm, and different column depths are available, with overlaps between junction columns (etched from the front side) and ohmic columns (etched from the back side) in the range from 110μm to 150μm. The devices under test were bump bonded to the ATLAS Pixel readout chip (FEI3) at SELEX SI (Rome, Italy). We report leakage current and noise measurements, results of functional tests with Am241 γ-ray sources, charge collection tests with Sr90 β-source and an overview of preliminary results from the CERN beam test.publishedVersio