The ABC130 barrel module prototyping programme for the ATLAS strip tracker

For the Phase-II Upgrade of the ATLAS Detector, its Inner Detector, consisting of silicon pixel, silicon strip and transition radiation sub-detectors, will be replaced with an all new 100 % silicon tracker, composed of a pixel tracker at inner radii and a strip tracker at outer radii. The future ATLAS strip tracker will include 11,000 silicon sensor modules in the central region (barrel) and 7,000 modules in the forward region (end-caps), which are foreseen to be constructed over a period of 3.5 years. The construction of each module consists of a series of assembly and quality control steps, which were engineered to be identical for all production sites. In order to develop the tooling and procedures for assembly and testing of these modules, two series of major prototyping programs were conducted: an early program using readout chips designed using a 250 nm fabrication process (ABCN-25) and a subsequent program using a follow-up chip set made using 130 nm processing (ABC130 and HCC130 chips). This second generation of readout chips was used for an extensive prototyping program that produced around 100 barrel-type modules and contributed significantly to the development of the final module layout. This paper gives an overview of the components used in ABC130 barrel modules, their assembly procedure and findings resulting from their tests.Comment: 82 pages, 66 figure

The silicon strip detector of the ATLAS Inner Tracker: from individual sensing units to multi-module petal structures

Nowadays particle detector technology is taking big steps forwards and new devices dedicated to particle physics show very high performance. Particularly the semi-conductor detectors have advanced significantly and are used for tracking purposes in the A Toroidal LHC ApparatuS (ATLAS) experiment at CERN thanks to their excellent spacial resolution: the compact size of the silicon and its high granularity allow to reach a precision measurement of few tens of microns.This thesis is focused on the upgrade of the ATLAS tracking detector required for the High Luminosity Large Hadron Collider (HL-LHC), starting in 2027. The HL-LHC foresees an integrated luminosity of L = 3000 fb−1, which comes with an unprecedented rate of proton collisions, with a pile-up of 〈η〉= 200, and very high radiation doses. As the current inner detector has not been designed for the HL-LHC environmental conditions, an all-silicon Inner Tracker (ITk) will take its place during Phase-II upgrade of the ATLAS experiment.The ITk strip endcap sub-detector is the main topic of this PhD project. The investigation covers the assembly of silicon strip endcap modules and their loading on a local support structure. The building and loading procedures are presented as well as results of quality control (QC) tests carried out on prototyping components to establish their working performance and the fulfillment of the specifications. This work provides the procedure optimization in order to achieve the requirements imposed by the collaboration.Results on prototyping components, such as a fully electrical module and a semi-electrical petal, both built and tested at DESY, are presented. They are followed by tests on an electrical petal performed at low temperature with the evaporative CO2cooling technique. The QC tests carried out on all prototypes have demonstrated that they have been properly assembled and are fully functional. Moreover they fulfill the respective requirements validating therefore the components design and the building methods

Performance study of dual-phase CO2{}_2 cooling on the example of the ATLAS ITk strip end-cap detector

The technique of evaporative CO${}_2$ cooling is one of the standard cooling options for high-energy particle detectors, such as the new ATLAS Inner Tracker (ITk) for the planned high-luminosity upgrade of the LHC by 2026. The advantages of CO${}_2$ are a high latent heat transfer at reasonable flow parameters, a low viscosity which allows to use small diameter cooling pipes with a low pressure drops, a well-suited temperature range for detector cooling between ＋25 and −40 °C and being an environment friendly alternative to many other currently used coolants. When comparing with a monophase coolant, the operation in the dual-phase regime comes with several parameters influencing the cooling performance.This paper contains the results of experimental studies performed to understand these influencing factors. For this, prototype structures from the ITk strip detector end-cap were used, like bare local support structures (‘cores’) or fully loaded structures (‘petals’). Here, the design is optimized to guarantee a good heat transfer between the silicon strip modules glued on the surface and the embedded titanium cooling pipe with the CO${}_2$ coolant. Systematic investigations on the thermal performance using infrared thermography are used to study the influence of dual-phase CO${}_2$ cooling parameters such as the orientation of CO${}_2$ flow. Moreover, the dependence of the pressure drop as a key parameter for the cooling performance on the applied heat load or the selected mass flow rate is investigated

Performance tests of dual-phase CO2{}_2 cooling for particle detectors

Evaporative CO${}_2$ cooling is becoming a popular cooling solution for large-scale, high-energy particle detectors, such as the new ATLAS Inner Tracker (ITk) for the high-luminosity upgrade of the LHC. CO${}_2$ offers a high latent heat transfer at reasonable flow parameters and is an environment friendly alternative to many other coolants currently used. This cooling technique is used to investigate the thermal performance of prototypes from the ITk strip detector produced at DESY. The strip end-cap local support structure, called petal core, is designed to allow a good heat transfer between silicon strip modules glued on its surface and the embedded titanium cooling pipe. Studies on the thermal properties using infrared thermography have been performed to analyse the heat dissipation path which allows also to detect eventual imperfections in the assembly as part of the quality control strategy. A similaranalysis was executed on a petal loaded with electrical modules to study the heat generation due to active components and its dissipation for each module under different CO${}_2$ conditions

Small-pad resistive Micromegas for operation at very high rates

We present the development of resistive Micromegas with O(mm$^2$) pad readout aiming at precision tracking in high rate environment without efficiency loss up to few MHz/cm$^2$.Characterization and performance studies of the detector have been carried out by means of radioactive sources, X-Rays, cosmic rays and test beam data. Gain has been measured as a function of amplification and drift electric fields, under low and high irradiation fluxes.Measurements of the detector efficiency, cluster multiplicity, cluster size and spatial resolution using test beam data will be reported

The ABC130 barrel module prototyping programme for the ATLAS strip tracker

For the Phase-II Upgrade of the ATLAS Detector [1], its Inner Detector, consisting of silicon pixel, silicon strip and transition radiation sub-detectors, will be replaced with an all new 100% silicon tracker, composed of a pixel tracker at inner radii and a strip tracker at outer radii. The future ATLAS strip tracker will include 11,000 silicon sensor modules in the central region (barrel) and 7,000 modules in the forward region (end-caps), which are foreseen to be constructed over a period of 3.5 years. The construction of each module consists of a series of assembly and quality control steps, which were engineered to be identical for all production sites. In order to develop the tooling and procedures for assembly and testing of these modules, two series of major prototyping programs were conducted: an early program using readout chips designed using a 250 nm fabrication process (ABCN-250) [2,2] and a subsequent program using a follow-up chip set made using 130 nm processing (ABC130 and HCC130 chips). This second generation of readout chips was used for an extensive prototyping program that produced around 100 barrel-type modules and contributed significantly to the development of the final module layout. This paper gives an overview of the components used in ABC130 barrel modules, their assembly procedure and findings resulting from their tests