Summary and Conclusions of the First DESY Test Beam User Workshop

On October 5/6, 2017, DESY hosted the first DESY Test Beam User Workshop [1] which took place in Hamburg. Fifty participants from different user communities, ranging from LHC (ALICE, ATLAS, CMS, LHCb) to FAIR (CBM, PANDA), DUNE, Belle-II, future linear colliders (ILC, CLIC) and generic detector R&D presented their experiences with the DESY II Test Beam Facility, their concrete plans for the upcoming years and a first estimate of their needs for beam time in the long-term future beyond 2025. A special focus was also on additional improvements to the facility beyond its current capabilities

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

Quality studies of silicon-sensor assemblies using electroless nickel/gold under-bump-metallurgy (UBM) for the pixel detector of the ATLAS experiment

This paper is about my summer student time in 2015 at CERN. I will describe my work as being a member of the ATLAS pixel group and present my results of the measurements I have done there

Detection and Identification of Electrons and Photons - Applications in the ATLAS Experiment, for the ATLAS ITk Detector and at the DESY II Test Beam

It is important to exploit particle detectors for the detection and identification of electrons and photons in the best possible way, as it is adressed in this thesis by discussing three different application examples of precisely measuring electrons and photons at high-energy physics andtest beam experiments.Firstly, the optimization of the photon identification within the ATLAS detector at the LHCis investigated. Appropriate selection criteria are needed to efficiently discriminate prompt photons steming from the hard-scattering collision process from photons originating from hadronic jet decays. Systematic studies for the use of a multivariate optimization with a Boosted Decision Tree are presented and compared to the currently used rectangular cut approach.Secondly, the planned Inner Tracker (ITk) as an upgrade of the ATLAS detector for the HL-LHC is discussed. The focus of the investigations lies on the support structures foreseen for the silicon sensor modules, the petal core. The thermo-mechanical characterization of the petal is investigated using infrared thermography, dual-phase CO2 cooling and geometrical metrology, proving a well-performing design of the local support structure within the ITk detector specifications.Finally, measurements with multi-GeV electrons at the DESY II Test Beam Facility are presented to investigate the potential of the Material Budget Imaging technique. This technique aims to reconstruct the material distribution of samples by measuring the deflection angles of traversing electrons with the high-resolution EUDET-type beam telescopes exploiting the underlying effect of multiple Coulomb scattering. The results in terms of the determination of the characteristic radiation length of several materials as well as the two-dimensional material budget image of complex composite structures are shown

Detection and Identification of Electrons and Photons - Applications in the ATLAS Experiment, for the ATLAS ITk Detector and at the DESY II Test Beam

It is important to exploit particle detectors for the detection and identification of electrons and photons in the best possible way, as it is adressed in this thesis by discussing three different application examples of precisely measuring electrons and photons at high-energy physics andtest beam experiments.Firstly, the optimization of the photon identification within the ATLAS detector at the LHCis investigated. Appropriate selection criteria are needed to efficiently discriminate prompt photons steming from the hard-scattering collision process from photons originating from hadronic jet decays. Systematic studies for the use of a multivariate optimization with a Boosted Decision Tree are presented and compared to the currently used rectangular cut approach.Secondly, the planned Inner Tracker (ITk) as an upgrade of the ATLAS detector for the HL-LHC is discussed. The focus of the investigations lies on the support structures foreseen for the silicon sensor modules, the petal core. The thermo-mechanical characterization of the petal is investigated using infrared thermography, dual-phase CO2 cooling and geometrical metrology, proving a well-performing design of the local support structure within the ITk detector specifications.Finally, measurements with multi-GeV electrons at the DESY II Test Beam Facility are presented to investigate the potential of the Material Budget Imaging technique. This technique aims to reconstruct the material distribution of samples by measuring the deflection angles of traversing electrons with the high-resolution EUDET-type beam telescopes exploiting the underlying effect of multiple Coulomb scattering. The results in terms of the determination of the characteristic radiation length of several materials as well as the two-dimensional material budget image of complex composite structures are shown

Material budget imaging with multi-GeV electrons - calibration and applications for 2D material scanning

Abstract. The technique of material budget imaging (MBI) uses multi-GeV electrons to directly measure the material budget $\epsilon= x/X_0$ of a material with thickness $x$ and its radiation length $X_0$. The beam particles are deflected by multiple Coulomb scattering and the deflection angle distribution is centered at zero with a width depending on the traversed material. Hence, a reconstruction of kink angles using individual electron trajectories measured in high resolution beam telescopes allows to estimate the material budget by applying appropiate models of multiple scattering theory, such as the Highland formula. Measurements at the DESY II testbeam were performed with various materials in terms of thickness and type for a calibration of the MBI technique. The material budget is an important quantity for the design of high-energy particle detectors. Therefore, the material budget of unknown materials can be experimentally measured as well as complex material distributions can be imaged in 2D

Application of material budget imaging for the design of the ATLAS ITk strip detector

The technique of material budget imaging (MBI) allows to experimentally assess the material budget $\epsilon = x/X_0$ of a material with thickness $x$ and its radiation length $X_0$. Here, multi-GeV electrons from a test beam facility such as the DESY-II test beam are used. This novel technique exploits the fact that the beam particles are deflected by multiple Coulomb scattering following a distribution of the deflection angle with a center at zero and a width depending on the traversed material. By reconstructing the individual kink angles from the measured particle trajectories in a high resolution beam telescope, the material budget can be extracted by applying appropriate models of multiple scattering theory, such as the Highland formula.On the one hand, various materials with known material budgets were measured to calibrate the MBI technique and study also different systematic effects such as the beam telescope’s acceptance and the variation of the beam energy. On the other hand, a number of material samples planned in the design of the local support structures of the new ATLAS Inner Tracker (ITk) strip detector were investigated to extract the according radiation length values not known beforehand.This paper shows therefore the potential of the MBI technique to give an input for the design of high-energy particle detectors by providing experimentally measured numbers of the radiation length for various material compounds with not a-priori known $X_0$ values

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