Writing in Britain and Ireland, c. 400 to c. 800

No abstract available

Experimental Study and Empirical Modelling of Long Term Annealing of the ATLAS18 Sensors

In order to continue the program of the LHC, the accelerator will be upgraded to the HL-LHC, which will have a design luminosity 10e3 cm^2 s^-1, an order of magnitude greater than the present machine. In order to meet the occupancy and radiation hardness requirements resulting from this increase in luminosity, the present ATLAS tracking detector must be replaced. The ATLAS Collaboration is constructing a new central tracking system based completely on silicon sensors. The system comprises an inner pixel detector, a barrel strip detector and an endcap strip detector. In order to satisfy the radiation hardness requirements we have developed a new n-in-p sensor design. Extensive studies have shown that it results in detectors which comfortably reach the required end-of-life performance. The latest sensor layouts prepared for preproduction, known as ATLAS18, implement this design. However, as well as knowing the performance after a given irradiation fluence, operational considerations require an understanding of the time development of the annealing, and resulting variation of the collected charge, of irradiated detectors at different temperatures. This requirement results from the fact that there are various proposed temperature profiles for the operation of the detector over the expected lifetime of 14 years. Here we describe the measurement of charge collection performance as a function of irradiated fluence and long term annealing time. We also describe a semi-empirical model based on these measurements which allows us to predict the end-of-life charge collection as a function of the temperature profile during operation of the detector. The use of the model to study the effect of annealing on the strip detector at a radius of 40 cm and an integrated irradiation fluence of 16e14 MeV neutron equiv. is presented. This methodology can be applied to other regions of the detector, such as the pixels

ATLAS ITk strip sensor quality assurance tests and results of ATLAS18 pre-production sensors

Towards the high luminosity (HL) operation of the Large Hadron Collider (LHC), the inner tracking system of the ATLAS detector is replaced by a fully silicon-based inner tracker (ITk). Its outer region consists of 17,888 $n^+$-in-$p$ silicon strip sensors. In order to confirm key properties of the production sensors as well as to establish a solid workflow of quality inspection and monitoring of the various sensor properties, about 5\% of the total strip sensors were produced in 2020 as a pre-production run. As a quality assurance (QA) program, irradiation of dedicated QA test pieces was periodically performed. The fluences of proton, neutron and $\gamma$-ray irradiations were up to $1.6 \times 10^{15}$ 1-MeV neutrons$/\mathrm{cm}^2$ and 0.66 MGy, which are equivalent to the maximum expected radiation fluences at the HL-LHC operation with a safety factor of 1.5. Results from 154 QA test pieces demonstrated high quality of the strip sensors through the pre-production. Detailed understanding of post-irradiated strip sensors was acquired, and the procedures of irradiation and post-irradiation QA testing were fully established. Consequently, the 3.8-year project of the strip sensor production for the ATLAS ITk detector was initiated in July 2021

Analysis of the Quality Assurance results from the initial part of production of the ATLAS18 ITk strip sensors

The production of strip sensors for the ATLAS Inner Tracker (ITk) started in 2021. Since then, a Quality Assurance (QA) program has been carried out continuously, by using specific test structures, in parallel to the Quality Control (QC) inspection of the sensors. The QA program consists of monitoring sensor-specific characteristics and the technological process variability, before and after the irradiation with gammas, neutrons, and protons. After two years, half of the full production volume has been reached and we present an analysis of the parameters measured as part of the QA process. The main devices used for QA purposes are miniature strip sensors, monitor diodes, and the ATLAS test chip, which contains several test structures. Such devices are tested by several sites across the collaboration depending on the type of samples (non-irradiated components or irradiated with protons, neutrons, or gammas). The parameters extracted from the tests are then uploaded to a database and analyzed by Python scripts. These parameters are mainly examined through histograms and time-evolution plots to obtain parameter distributions, production trends, and meaningful parameter-to-parameter correlations. The purpose of this analysis is to identify possible deviations in the fabrication or the sensor quality, changes in the behavior of the test equipment at different test sites, or possible variability in the irradiation processes. The conclusions extracted from the QA program have allowed test optimization, establishment of control limits for the parameters, and a better understanding of device properties and fabrication trends. In addition, any abnormal results prompt immediate feedback to the vendor

Open Letter to The American Association for the Advancement of Science

This is an open letter concerning the recent launch of the new open access journal, Science Advances. In addition to the welcome diversification in journal choices for authors looking for open access venues, there are many positive aspects of Science Advances: its broad STEM scope, its interest in cross-disciplinary research, and the offering of fee waivers. While we welcome the commitment of the Association to open access, we are also deeply concerned with the specific approach. Herein, we outline a number of suggestions that are in line with both the current direction that scholarly publishing is taking and the needs expressed by the open access community, which this journal aims to serve