arXiv subjects

Alessandro La Rosa

Publications and source records attributed to Alessandro La Rosa.

15 recordsLinked to original sources

arXiv2023

Three-dimensional calculations of the inductive coupling between radio-frequency waves and plasma in the drivers of the SPIDER device

This work documents the initial 3D calculations to simulate the coupling between radio-frequency (RF) waves and plasma in discharges of the SPIDER device. Axisymmetric 3D calculations in the plasma domain alone compare well against equivalent 2D cases. A model of SPIDER driver, the cylindrical chamber where the plasma is heated by the RF drive, is then defined including the metallic parts of the Faraday shield, insulator and vacuum layer up to the RF winding (not included in the calculation domain). Estimates of the power share in the different parts are obtained using experimental conditions and plasma data. The results are sensitive to the particular geometry of the driver and the temperature of the Faraday shield, but generally agree with the experimental knowledge. The ratio between total delivered power and plasma absorbed power is found, depending on the plasma parameters, in the range 30--45\%

physics.plasm-ph↗

arXiv2023

Gain layer degradation study after neutron and proton irradiations in Low Gain Avalanche Diodes

The high-luminosity upgrade of the ATLAS and CMS experiments includes dedicated sub-detectors to perform the time-stamping of minimum ionizing particles (MIPs). These detectors will be exposed up to fluences in the range of 1.5 - 2.5e15 neq/cm2 at the end of their lifetime and, Low Gain Avalanche Diode (LGAD) has been chosen as their baseline detection technology. To better understand the performance of LGAD detectors in these environments, a gain layer degradation study after neutron and proton irradiations up to a fluence of 1.5e15 neq/cm2 was performed. LGADs manufactured at Hamamatsu Photonics (HPK) and Centro Nacional de Microelectrónica (CNM-IMB) were chosen for this study and, a comparison in the gain layer degradation after exposure to reactor neutrons at the Jozef Stefan Institute (JSI) in Ljubjana and 24 GeV/c protons at the CERN-PS is presented here.

physics.ins-det↗

arXiv2021

The Upgrade of the CMS Tracker at HL-LHC

In the high luminosity scenario of the LHC (HL-LHC), which will bring the instantaneous luminosity up to 7.5\,$\times$\,$10^{34}$\,cm$^{-2}$s$^{-1}$, ATLAS and CMS will need to operate at up to 200 interactions per 25\,ns beam crossing and reaching up to 4000\,fb$^{-1}$ of integrated luminosity. To achieve their physics goals the experiments will need to improve the tracking and vertexing capability and the ability to selectively trigger on specific physics events at reasonable thresholds. The upgrade of the CMS Tracker requires designing new inner and outer tracking detectors to cope with the increased luminosity and to implement first trigger level functionality. This paper describes the new layout and the technological choices together with some highlights of research and development activities.

physics.ins-det↗

arXiv2020

The CMS Outer Tracker for the High Luminosity LHC upgrade

The High Luminosity Large Hadron Collider (HL-LHC) at CERN is expected to collide protons at a centre-of-mass energy of 14\,TeV and to reach the unprecedented peak instantaneous luminosity of 5\,$-$\,7.5\,x\,$10^{34}$\,cm$^{-2}$s$^{-1}$ with an average number of pileup events of 140\,$-$\,200. This will allow the ATLAS and CMS experiments to collect integrated luminosities up to 3000\,$-$\,4000\,fb$^{-1}$ during the project lifetime. To cope with this extreme scenario the CMS detector will be substantially upgraded before starting the HL-LHC, with a plan known as CMS Phase-2 upgrade. The CMS Tracker detector will have to be replaced in order to fully exploit the delivered luminosity and cope with the demanding operating conditions. The new detector will provide robust tracking as well as input for the first level trigger. This paper is focused on the replacement of the CMS Outer Tracker system, describing the new layout and the technological choices together with some highlights of module assembly and quality assurance aspects.

physics.ins-det↗

arXiv2018

TCAD simulations of pixel sensors for the ATLAS ITk upgrade and performance of annealed planar pixel modules

For the high luminosity phase of the Large Hadron Collider to start operation around 2026, a major upgrade of the ATLAS Inner Tracker (ITk) is in preparation. Thanks to their low power dissipation and high charge-collection efficiency after irradiation, thin planar pixel modules are the baseline option to instrument all, except for the innermost layer of the pixel detector. To optimise the sensor layout for a pixel cell size of $50\times50\,μm^2$, TCAD simulations are being performed. Charge-collection efficiency, electronic noise and electrical-field properties are investigated. A radiation-damage model is employed in TCAD simulations to estimate the performance before- and after irradiation. The impact of storage time at room temperature for the ITk pixel detector during maintenance periods are estimated using sensors irradiated up to a fluence of 5$\times10^{15}\,$n$_\text{eq}$/cm$^2$. Pixel sensors of $100-150\,μm$ thickness, interconnected to FE-I4 read-out chips with pixel dimensions of $50\times250\,μm^2$, are characterised using the testbeam facilities at the CERN-SPS and DESY. The charge-collection and hit efficiencies are compared before and after annealing at room temperature for up to one year.

physics.ins-det↗

arXiv2018

Characterisation of novel thin n-in-p planar pixel modules for the ATLAS Inner Tracker upgrade

In view of the high luminosity phase of the LHC (HL-LHC) to start operation around 2026, a major upgrade of the tracker system for the ATLAS experiment is in preparation. The expected neutron equivalent fluence of up to 2.4 * 1e16 1 MeV neq./cm2 at the innermost layer of the pixel detector poses the most severe challenge. Thanks to their low material budget and high charge collection efficiency after irradiation, modules made of thin planar pixel sensors are promising candidates to instrument these layers. To optimise the sensor layout for the decreased pixel cell size of 50 * 50 μm2, TCAD device simulations are being performed to investigate the charge collection efficiency before and after irradiation. In addition, sensors of 100-150 μm thickness, interconnected to FE-I4 read-out chips featuring the previous generation pixel cell size of 50 * 250 μm2, are characterised with testbeams at the CERN-SPS and DESY facilities. The performance of sensors with various designs, irradiated up to a fluence of 1 * 1e16 neq./cm2, is compared in terms of charge collection and hit efficiency. A replacement of the two innermost pixel layers is foreseen during the lifetime of HL-LHC. The replacement will require several months of intervention, during which the remaining detector modules cannot be cooled. They are kept at room temperature, thus inducing an annealing. The performance of irradiated modules will be investigated with testbeam campaigns and the method of accelerated annealing at higher temperatures.

physics.ins-det↗

arXiv2017

Performance of irradiated thin n-in-p planar pixel sensors for the ATLAS Inner Tracker upgrade

The ATLAS collaboration will replace its tracking detector with new all silicon pixel and strip systems. This will allow to cope with the higher radiation and occupancy levels expected after the 5-fold increase in the luminosity of the LHC accelerator complex (HL-LHC). In the new tracking detector (ITk) pixel modules with increased granularity will implement to maintain the occupancy with a higher track density. In addition, both sensors and read-out chips composing the hybrid modules will be produced employing more radiation hard technologies with respect to the present pixel detector. Due to their outstanding performance in terms of radiation hardness, thin n-in-p sensors are promising candidates to instrument a section of the new pixel system. Recently produced and developed sensors of new designs will be presented. To test the sensors before interconnection to chips, a punch-through biasing structure has been implemented. Its design has been optimized to decrease the possible tracking efficiency losses observed. After irradiation, they were caused by the punch-through biasing structure. A sensor compatible with the ATLAS FE-I4 chip with a pixel size of 50x250 $\mathrmμ$m$^{2}$, subdivided into smaller pixel implants of 30x30 $\mathrmμ$m$^{2}$ size was designed to investigate the performance of the 50x50 $\mathrmμ$m$^{2}$ pixel cells foreseen for the HL-LHC. Results on sensor performance of 50x250 and 50x50 $\mathrmμ$m$^{2}$ pixel cells in terms of efficiency, charge collection and electric field properties are obtained with beam tests and the Transient Current Technique.

physics.ins-det↗

arXiv2017

Optimization of thin n-in-p planar pixel modules for the ATLAS upgrade at HL-LHC

The ATLAS experiment will undergo around the year 2025 a replacement of the tracker system in view of the high luminosity phase of the LHC (HL-LHC) with a new 5-layer pixel system. Thin planar pixel sensors are promising candidates to instrument the innermost region of the new pixel system, thanks to the reduced contribution to the material budget and their high charge collection efficiency after irradiation. The sensors of 50-150 $μ$m thickness, interconnected to FE-I4 read-out chips, have been characterized with radioactive sources and beam tests. In particular active edge sensors have been investigated. The performance of two different versions of edge designs are compared: the first with a bias ring, and the second one where only a floating guard ring has been implemented. The hit efficiency at the edge has also been studied after irradiation at a fluence of $10^{15}$ \neqcm. Highly segmented sensors will represent a challenge for the tracking in the forward region of the pixel system at HL-LHC. In order to reproduce the performance of 50x50 $μ$m$^2$ pixels at high pseudo-rapidity values, FE-I4 compatible planar pixel sensors have been studied before and after irradiation in beam tests at high incidence angles with respect to the short pixel direction. Results on the hit efficiency in this configuration are discussed for different sensor thicknesses.

physics.ins-det↗

arXiv2016

Characterization of Novel Thin N-in-P Planar Pixel Modules for the ATLAS Inner Tracker Upgrade

The ATLAS experiment will undergo a major upgrade of the tracker system in view of the high luminosity phase of the LHC (HL-LHC) to start operation in 2026. The most severe challenges are to be faced by the innermost layers of the pixel detector which will have to withstand a radiation fluence of up to $1.4\times10^{16}\,$n$_\text{eq}$/cm$^{2}$. Thin planar pixel modules are promising candidates to instrument these layers, thanks to the small material budget and their high charge collection efficiency after irradiation. Sensors of $100-200\,μ$m thickness, interconnected to FE-I4 read-out chips, are characterized with radioactive sources as well as testbeams at the CERN-SPS and DESY. The performance of sensors irradiated up to a fluence of $5\times 10^{15}\,$n$_\text{eq}$/cm$^{2}$ is compared in terms of charge collection and hit efficiency. Highly segmented sensors are a challenge for the tracking in the forward region of the pixel system at the HL-LHC. To reproduce the performance of $50$x$50\,μ$m$^2$ pixels at high pseudo-rapidities, FE-I4 compatible planar pixel sensors are studied before and after irradiation in beam tests at high incidence angle ($80^\circ$) with respect to the short pixel direction. Results on cluster shape and hit efficiency will be shown.

physics.ins-det↗

arXiv2016

The ATLAS Insertable B-Layer: from construction to operation

The ATLAS Insertable B-Layer (IBL) is the innermost layer of pixel detectors, and was installed in May 2014 at a radius of 3.3 cm from the beam axis, between the existing Pixel detector and a new smaller radius beam-pipe. The new detector, built to cope with high radiation and occupancy, is the first large scale application of 3D sensors and CMOS 130 nm technology. The IBL detector construction was completed within about two years (2012-2014), and the key features and challenges met during the IBL project are presented, as well as its commissioning and operational experience at the LHC.

physics.ins-det↗

arXiv2016

Irradiation induced effects in the FE-I4 front-end chip of the ATLAS IBL detector

The ATLAS Insertable B-Layer (IBL) detector was installed into the ATLAS experiment in 2014 and has been in operation since 2015. During the first year of IBL data taking an increase of the low voltage currents associated with the FE-I4 front-end chip was observed and this increase was traced back to the radiation damage in the chip. The dependence of the current on the total-ionising dose and temperature has been tested with X-ray and proton irradiations and will be presented in this paper together with the detector operation guidelines.

physics.ins-det↗

arXiv2015

ATLAS Pixel Detector: Operational Experience and Run-1 to Run-2 Transition

The Pixel Detector of the ATLAS experiment has shown excellent performance during the whole Run-1 of LHC. Taking advantage of the long shutdown, the detector was extracted from the experiment and brought to surface, to equip it with new service quarter panels, to repair modules and to ease installation of a new innermost layer, the Insertable B-Layer (IBL). An overview of the operational experience, the refurbishing of the Pixel Detector and of the IBL project as well as the experience in its construction, integration and commissioning are described.

physics.ins-det↗

arXiv2013

Selected results from the static characterization of edgeless n-on-p planar pixel sensors for ATLAS upgrades

In view of the LHC upgrade for the High Luminosity Phase (HL-LHC), the ATLAS experiment is planning to replace the Inner Detector with an all-Silicon system. The n-on-p technology represents a valid solution for the modules of most of the layers, given the significant radiation hardness of this option and the reduced cost. There is also the demand to reduce the inactive areas to a minimum. The ATLAS LPNHE Paris group and FBK Trento started a collaboration for the development on a novel n-on-p edgeless planar pixel design, based on the deep-trench process which can cope with all these demands. This paper reports selected results from the electrical characterization, both before and after irradiation, of test structures from the first production batch.

physics.ins-det↗

arXiv2011

ATLAS IBL: a challenging first step for ATLAS Upgrade at the sLHC

With the LHC collecting data at 7 TeV, plans are already advancing for a series of upgrades leading eventually to about five times the LHC design luminosity some 10 years from now in the High Luminosity LHC (HL-LHC) project. The upgrades for ATLAS detector will be staged in preparation for HL-LHC. The first upgrade for the Pixel Detector will be the construction of a new pixel layer, which will be installed during the first shutdown of the LHC machine foreseen in 2013-14. The new detector, called the Insertable B-Layer (IBL) will be installed between the existing Pixel Detector and a new, smaller radius beam-pipe at the radius of 3.2 cm. The IBL will require the development of several new technologies to cope with increased radiation and pixel occupancy and also to improve the physics performance through reduction of the pixel size and more stringent material budget. Two different and promising Silicon sensor technologies (planar n-in-n and 3D) are currently under investigation for the IBL. An overview of the IBL module design and the qualification for these sensor technologies are presented in this proceeding. This proceeding also summarizes the improvements expected to the ATLAS detector at the HL-LHC.

physics.ins-det↗

arXiv2011

Characterization and Performance of Silicon n-in-p Pixel Detectors for the ATLAS Upgrades

The existing ATLAS Tracker will be at its functional limit for particle fluences of 10^15 neq/cm^2 (LHC). Thus for the upgrades at smaller radii like in the case of the planned Insertable B-Layer (IBL) and for increased LHC luminosities (super LHC) the development of new structures and materials which can cope with the resulting particle fluences is needed. N-in-p silicon devices are a promising candidate for tracking detectors to achieve these goals, since they are radiation hard, cost efficient and are not type inverted after irradiation. A n-in-p pixel production based on a MPP/HLL design and performed by CiS (Erfurt, Germany) on 300 μm thick Float-Zone material is characterised and the electrical properties of sensors and single chip modules (SCM) are presented, including noise, charge collection efficiencies, and measurements with MIPs as well as an 241Am source. The SCMs are built with sensors connected to the current the ATLAS read-out chip FE-I3. The characterisation has been performed with the ATLAS pixel read-out systems, before and after irradiation with 24 GeV/c protons. In addition preliminary testbeam results for the tracking efficiency and charge collection, obtained with a SCM, are discussed.

physics.ins-det↗