U. Soldevila

A double-sided, shield-less stave prototype for the ATLAS Upgrade strip tracker for the High Luminosity LHC

A detailed description of the integration structures for the barrel region of the silicon strips tracker of the ATLAS Phase-II upgrade for the upgrade of the Large Hadron Collider, the so-called High Luminosity LHC (HL-LHC), is presented. This paper focuses on one of the latest demonstrator prototypes recently assembled, with numerous unique features. It consists of a shortened, shield-less, and double sided stave, with two candidate power distributions implemented. Thermal and electrical performances of the prototype are presented, as well as a description of the assembly procedures and tools.

A double-sided silicon micro-strip Super-Module for the ATLAS Inner Detector upgrade in the High-Luminosity LHC

The ATLAS experiment is a general purpose detector aiming to fully exploit the discovery potential of the Large Hadron Collider (LHC) at CERN. It is foreseen that after several years of successful data-taking, the LHC physics programme will be extended in the so-called High-Luminosity LHC, where the instantaneous luminosity will be increased up to 5 × 1034 cm−2 s−1. For ATLAS, an upgrade scenario will imply the complete replacement of its internal tracker, as the existing detector will not provide the required performance due to the cumulated radiation damage and the increase in the detector occupancy. The current baseline layout for the new ATLAS tracker is an all-silicon-based detector, with pixel sensors in the inner layers and silicon micro-strip detectors at intermediate and outer radii. The super-module is an integration concept proposed for the strip region of the future ATLAS tracker, where double-sided stereo silicon micro-strip modules are assembled into a low-mass local support structure. An electrical super-module prototype for eight double-sided strip modules has been constructed. The aim is to exercise the multi-module readout chain and to investigate the noise performance of such a system. In this paper, the main components of the current super-module prototype are described and its electrical performance is presented in detail.

Radiation-hard silicon for LH-LHC trackers

In order to harvest the maximum physics potential of the CERN Large Hadron Collider (LHC), it is foreseen to significantly increase the LHC luminosity by upgrading the LHC towards the HL-LHC (High Luminosity LHC), also known as sLHC. The final upgrade (Phase-II) will mean unprecedented radiation levels, exceeding the LHC fluences by roughly an order of magnitude. Due to the radiation damage limitations of the silicon sensors presently used, the physics experiments will require new tracking detectors for HL-LHC operation. All-silicon central trackers are being studied in ATLAS, CMS and LHCb, with extremely radiation hard silicon sensors to be employed on the innermost layers. Within the CERN RD50 Collaboration, a massive R&D programme is underway across experimental boundaries to develop silicon sensors with sufficient radiation tolerance. We will present results of several detector technologies and silicon materials at radiation levels corresponding to HL-LHC fluences.

Characterisation of strip silicon detectors for the ATLAS Phase-II Upgrade with a micro-focused X-ray beam

The planned HL-LHC (High Luminosity LHC) in 2025 is being designed to maximise the physics potential through a sizable increase in the luminosity up to 61034 cm−2s−1. A consequence of this increased luminosity is the expected radiation damage at 3000 fb−1 after ten years of operation, requiring the tracking detectors to withstand fluences to over 11016 1 MeV neq/cm2. In order to cope with the consequent increased readout rates, a complete re-design of the current ATLAS Inner Detector (ID) is being developed as the Inner Tracker (ITk).Two proposed detectors for the ATLAS strip tracker region of the ITk were characterized at the Diamond Light Source with a 3 μm FWHM 15 keV micro focused X-ray beam. The devices under test were a 320 μm thick silicon stereo (Barrel) ATLAS12 strip mini sensor wire bonded to a 130 nm CMOS binary readout chip (ABC130) and a 320 μm thick full size radial (end-cap) strip sensor - utilizing bi-metal readout layers - wire bonded to 250 nm CMOS binary readout chips (ABCN-25).A resolution better than the inter strip pitch of the 74.5 μm strips was achieved for both detectors. The effect of the p-stop diffusion layers between strips was investigated in detail for the wire bond pad regions.Inter strip charge collection measurements indicate that the effective width of the strip on the silicon sensors is determined by p-stop regions between the strips rather than the strip pitch.

Functional and performance evaluation of low-resistance strip sensors for beam-loss event protection

A new technological solution to improve the beam-loss protection of silicon strip sensors used in large High Energy Physics experiments is presented. In the current ATLAS-SCT, sensors have Punch-Through protection (PTP) structures included to develop low impedance from the strip to the bias ring in case large voltages exceed some threshold that could damage the strip coupling capacitance. Previous studies show that the high strip resistance limits the beneficial effect of full PTP structures to the area near the structures. In our approach, we extend the PTP protection to the full active area of the sensor by lowering the strip resistance. This is achieved by the addition of a conductive layer connected along the whole strip implant. Strip sensors with different PTP structures, varying the p-stop strip isolation width and the distance between the strip to the bias ring, have been designed and fabricated using our technology proposal, together with standard sensors. Electrical characterization include general performance sensor tests (IV, CV, Rinterstrip, Cinterstrip, Ccoupling) and pulse formation tests to show that sensor performance is not compromised due to the technological modification. Besides, Punch-through DC static measurements and laser-based performance studies have been done to demonstrate the effectiveness of our proposal.

Studies on charge collection of p-type silicon detectors under neutron irradiation expected for Super-LHC

The existing technology used in the ATLAS Tracker is at the limit for performances of 10 years of running at a LHC peak luminosity of 1034 cm-2s-1. The operation under an upgraded luminosity of 1035 cm-2s-1 (Super-LHC) will imply a corresponding increase of the radiation dose. The expected dose for the inner detector tracker at the Super-LHC is up to 1 × 1016 equivalent neutron cm-2 in comparison with a dose of 1 × 1015 equivalent neutron cm-2 at the LHC after the envisaged 10 years of operation. So, the classic concept of p-on-n silicon microstrip detector as used in the current Semiconductor Tracker (SCT) in ATLAS needs to be abandoned for the Super-LHC. Investigations with n-on-p silicon sensors are showing arguments in favor of implementing these technologies in harsh radiation environment as the Super-LHC. This paper reports about studies with p-type sensors undergoing high radiation doses of neutrons in terms of their charge collection efficiency. A significant contribution to the radiation damage to the sensors in the tracker volume is due to backscattered neutrons so it is important to know the sensor performance under this kind of irradiation. Microstrip sensors from two different suppliers have been tested and a new analogue acquisition system called ALIBAVA system has been used to carry out the measurements.

Measurement of the Lambda_b lifetime and mass in the ATLAS experiment

Aad, G.; et al., [Unknown]; Aben, R.; Beemster, L.J.; Bentvelsen, S.; Berglund, E.; Bobbink, G.J.; Bos, K.; Boterenbrood, H.; Colijn, A.P.; de Jong, P.; de Nooij, L.; Deluca, C.; Deviveiros, P.O.; Doxiadis, A.D.; Ferrari, P.; Garitaonandia, H.; Geerts, D.A.A.; Gosselink, M.; Hartjes, F.; Hessey, N.P.; Igonkina, O.; Kayl, M.S.; Klous, S.; Kluit, P.; Koffeman, E.; Lee, H.; Lenz, T.; Linde, F.; Luijckx, G.; Massaro, G.; Mechnich, J.; Mussche, I.; Ottersbach, J.P.; Pani, P.; Rijpstra, M.; Ruckstuhl, N.; Ta, D.; Tsiakiris, M.; Turlay, E.; van der Deijl, P.C.; van der Geer, R.; van der Graaf, H.; van der Leeuw, R.; van der Poel, E.; van Vulpen, I.; Verkerke, W.; Vermeulen, J.C.; Vranjes Milosavljevic, M.; Vreeswijk, M.A measurement of the Λb lifetime and mass in the decay channel Λ 0 b → J/ψ(μ+μ−)Λ0(pπ−) is presented. The analysis uses a signal sample of about 2200 Λb and Λ̄ 0 b decays that are reconstructed in 4.9 fb −1 of ATLAS pp collision data collected in 2011 at the LHC center-of-mass energy of 7 TeV. A simultaneous mass and decay time maximum likelihood fit is used to extract the Λb lifetime and mass. They are measured to be τΛb = 1.449± 0.036(stat)± 0.017(syst) ps and mΛb = 5619.7± 0.7(stat)± 1.1(syst) MeV. ar X iv :1 20 7. 22 84 v3 [ he pex ] 2 0 A pr 2 01 3 Measurement of the Λ0b lifetime and mass in the ATLAS experiment The ATLAS Collaboration (Dated: May 2, 2014) A measurement of the Λb lifetime and mass in the decay channel Λ 0 b → J/ψ(μ+μ−)Λ0(pπ−) is presented. The analysis uses a signal sample of about 2200 Λb and Λ̄ 0 b decays that are reconstructed in 4.9 fb−1 of ATLAS pp collision data collected in 2011 at the LHC center-of-mass energy of 7 TeV. A simultaneous mass and decay time maximum likelihood fit is used to extract the Λb lifetime and mass. They are measured to be τΛb = 1.449± 0.036(stat)± 0.017(syst) ps and mΛb = 5619.7± 0.7(stat)± 1.1(syst) MeV.

Silicon detectors for the SLHC recent RD50 results

It is foreseen to significantly increase the luminosity of the Large Hadron Collider (LHC) at CERN around 2018 by upgrading the LHC towards the SLHC (Super-LHC). Due to the radiation damage to the silicon detectors used, the physics experiment will require new tracking detectors for SLHC operation. All-silicon central trackers are being studied in ATLAS, CMS and LHCb, with extremely radiation hard silicon sensors on the innermost layers. The radiation hardness of these new sensors must surpass the one of LHC detectors by roughly an order of magnitude. Within the CERN RD50 collaboration, a massive R&D program is underway to develop silicon sensors with sufficient radiation tolerance. Among the R&D topics are gaining a deeper understanding of the microscopic defects created by radiation, testing new detector materials such as Czochralski Silicon instead of Float-Zone material, and studying planar p-type sensors that will not experience radiation-induced type-inversion. Another field of activity is the development of new sensor technologies like 3D silicon detectors especially designed for the extreme radiation levels of the innermost layers of SLHC experiments. We will report on the recent results obtained by RD50 from tests of several detector technologies and silicon materials at radiation levels corresponding to SLHC fluences. Based on these results, we will give recommendations for the silicon detectors to be used at the different radii of SLHC tracking systems.