arXiv subjects

J. Fernandez-Tejero

Publications and source records attributed to J. Fernandez-Tejero.

6 recordsLinked to original sources

arXiv2026

Gamma irradiation of ATLAS18 ITk strip sensors affected by static charge

Construction of the new all-silicon ITk, developed by the ATLAS collaboration to be able to track charged particles produced at the HL- LHC, started in 2021 and is expected to continue until 2028. The ITk detector will include ~18,000 highly segmented and radiation hard n+-in-p silicon strip sensors, which are being manufactured by HPK. Upon their delivery, the ATLAS ITk strip sensor collaboration performs detailed measurements of sensors to monitor quality of all fabricated pieces. QC electrical tests include IV and CV tests, full strip tests, and a measurement of the long-term stability of the sensor leakage current. While most sensors demonstrate excellent performance during QC testing, we have nevertheless observed that a number of sensors from several production batches failed the electrical tests. Accumulated data indicates a strong correlation between observed electrical test failures and high electrostatic charge measured on the sensor surface during initial reception tests. This electrostatic charge enhances the risk of "Local trapped charge" events during manufacturing, shipping, and handling procedures, resulting in failed electrical QC tests. In the presented study, we have investigated whether the TID expected in the real experiment can effectively resolve early breakdown or low interstrip isolation caused by the electrostatic charge. Selected charge-affected sensors were irradiated with gamma rays from a 60Co source for a number of TID values. The results of this study indicate that the negative effects of the electrostatic charge on the critical sensors characteristics disappear after a very small amount of an accumulated TID, which actually corresponds to one or two days in the experiment. This finding gives us confidence in mitigating the issue of electrostatic charge during the operation of the ITk strip sensors in the real experiment.

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arXiv2026

Summary of quality control (QC) of ATLAS18 production ITk strip sensors

To address the demanding operational requirements of the High-Luminosity upgrade of the Large Hadron Collider (HL-LHC), the ATLAS experiment is replacing its current Inner Detector with a new all-silicon Inner Tracker (ITk). The ITk will feature an active area of 165 m2, with its outer tracking layers populated by approximately 18,000 ATLAS18 n+-in-p silicon strip sensors. The silicon sensors, available in eight geometries tailored to two barrel and six endcap types, respectively, are designed to tolerate fluences of up to 1.6 x 10^15 neq/cm2 and ionizing doses of 66 Mrad. A comprehensive, multi-year Quality Control (QC) program is underway across multiple international institutes to evaluate these ITk strip sensors for mechanical and electrical conformity. The QC process includes IV/CV characterization, full strip tests, long-term current stability monitoring, visual inspection, and metrology tests. To manage the high throughput of about 500 sensors per month, the collaboration has implemented standardized test procedures, software packages for data monitoring and integrity checks, unified data formats, and automated analysis tools. The standardization ensures consistent pass/fail evaluation and centralized data handling that enables effective identification of trends and anomalies at all sites during the production. This contribution presents an overview of the ITk strip sensor production and QC framework, along with key findings throughout the whole production, such as charge-up of sensors, stability of the leakage currents, nonrecoverable IV breakdown, and low inter-strip isolation within wafers. It provides insights into sensor yield, quality trends, and reviews specific case studies, such as p-stop doping non-uniformity. Over 91% of the production, totaling over 590 batches, were tested and accepted. Six batches were rejected. These account for 2.8% of the total tested sensors.

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arXiv2024

Evolution of the electrical characteristics of the ATLAS18 ITk strip sensors with HL-LHC radiation exposure range

The objective of the study is to evaluate the evolution of the performance of the new ATLAS Inner-Tracker (ITk) strip sensors as a function of radiation exposure, to ensure the proper operation of the upgraded detector during the lifetime of the High-Luminosity Large Hadron Collider (HL-LHC). Full-size ATLAS ITk Barrel Short-Strip (SS) sensors with final layout design, ATLAS18SS, have been irradiated with neutrons and gammas, to confirm the results obtained with prototypes and miniature sensors during the development phase. The irradiations cover a wide range of fluences and doses that ITk will experience, going from 1e13 neq/cm2 and 0.49 Mrad, to 1.6e15 neq/cm2 and 80 Mrad. The split irradiation enables a proper combination of fluence and dose values of the HL-LHC, including a 1.5 safety factor. A complete electrical characterization of the key sensor parameters before and after irradiation is presented, studying the leakage current, bulk capacitance, single-strip and inter-strip characteristics. The results confirm the fulfilment of the ATLAS specifications throughout the whole experiment. The study of a wide range of fluences and doses also allows to obtain detailed results, such as the frequency dependence of the bulk capacitance measurements for highly irradiated sensors, or the evolution of the punch-through protection and inter-strip resistance with radiation.

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arXiv2023

Setups for eliminating static charge of the ATLAS18 strip sensors

Construction of the new all-silicon Inner Tracker (ITk), developed by the ATLAS collaboration for the High Luminosity LHC, started in 2020 and is expected to continue till 2028. The ITk detector will include 18,000 highly segmented and radiation hard n+-in-p silicon strip sensors (ATLAS18), which are being manufactured by Hamamatsu Photonics. Mechanical and electrical characteristics of produced sensors are measured upon their delivery at several institutes participating in a complex Quality Control (QC) program. The QC tests performed on each individual sensor check the overall integrity and quality of the sensor. During the QC testing of production ATLAS18 strip sensors, an increased number of sensors that failed the electrical tests was observed. In particular, IV measurements indicated an early breakdown, while large areas containing several tens or hundreds of neighbouring strips with low interstrip isolation were identified by the Full strip tests, and leakage current instabilities were measured in a long-term leakage current stability setup. Moreover, a high surface electrostatic charge reaching a level of several hundreds of volts per inch was measured on a large number of sensors and on the plastic sheets, which mechanically protect these sensors in their paper envelopes. Accumulated data indicates a clear correlation between observed electrical failures and the sensor charge-up. To mitigate the above-described issues, the QC testing sites significantly modified the sensor handling procedures and introduced sensor recovery techniques based on irradiation of the sensor surface with UV light or application of intensive flows of ionized gas. In this presentation, we will describe the setups implemented by the QC testing sites to treat silicon strip sensors affected by static charge and evaluate the effectiveness of these setups in terms of improvement of the sensor performance.

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arXiv2022

A Starry Byte -- proton beam measurements of single event upsets and other radiation effects in ABCStar ASIC Versions 0 and 1 for the ITk strip tracker

Single Event Effects (SEEs) - predominately bit-flips in electronics caused by particle interactions - are a major concern for ASICs operated in high radiation environments such as ABCStar ASICs, which are designed to be used in the future ATLAS ITk strip tracker. The chip design is therefore optimised to protect it from SEEs by implementing triplication techniques such as Triple Modular Redundancy (TMR). In order to verify the radiation protection mechanisms of the chip design, the cross-section for Single Event Upsets (SEUs), a particular class of SEEs, is measured by exposing the chip to high-intensity particle beams while monitoring it for observed SEUs. This study presents the setup, the performed measurements, and the results from SEU tests performed using the latest version of the ABCStar ASIC (ABCStar V1) using a 480 MeV proton beam.

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arXiv2021

Mapping the in-plane electric field inside irradiated diodes

A significant aspect of the Phase-II Upgrade of the ATLAS detector is the replacement of the current Inner Detector with the ATLAS Inner Tracker (ITk). The ATLAS ITk is an all-silicon detector consisting of a pixel tracker and a strip tracker. Sensors for the ITk strip tracker have been developed to withstand the high radiation environment in the ATLAS detector after the High Luminosity Upgrade of the Large Hadron Collider at CERN, which will significantly increase the rate of particle collisions and resulting particle tracks. During their operation in the ATLAS detector, sensors for the ITk strip tracker are expected to accumulate fluences up to 1.6 x 10^15 n_eq/cm^2 (including a safety factor of 1.5), which will significantly affect their performance. One characteristic of interest for highly irradiated sensors is the shape and homogeneity of the electric field inside its active area. For the results presented here, diodes with edge structures similar to full size ATLAS sensors were irradiated up to fluences comparable to those in the ATLAS ITk strip tracker and their electric fields mapped using a micro-focused X-ray beam (beam diameter 2x3 μm^2). This study shows the extension and shape of the electric field inside highly irradiated diodes over a range of applied bias voltages. Additionally, measurements of the outline of the depleted sensor areas allow a comparison of the measured leakage current for different fluences with expectations for the corresponding active areas.

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