Optimisation of pixel modules for the ATLAS inner tracker at the high-luminosity LHC

The Large Hadron Collider and its pre-accelerator complex will be upgraded in three steps to allow for the high luminosity phase. A factor of ten times more data will be collected in this period by facilitating the increased instantaneous luminosity being seven times as large as the original design value. A new inner tracker system is in preparation for the ATLAS detector in view of the high luminosity phase to start operation around 2026. This all silicon tracker relies on various innovative technologies to cope with the severe challenges arising from the increased luminosity. The pixel detector employs a new readout chip to decrease the pixel size to a fifth of the pixel size of the present generation to be able to disentangle all tracks in the high multiplicity environment close to the interaction point. Thanks to their reduced power dissipation and high charge collection efficiency after irradiation, thin planar n-in-p pixel sensors are ideally suited to cope with the expected unprecedented radiation damage. TCAD simulations are being performed to optimise the sensor layout for the new pixel cell size of 50x50um2. In this study, charge collection efficiency, electronic noise and electrical field properties are investigated both before and after irradiation. The RD53A prototype readout chip is used to build modules based on the proposed thin planar n-in-p sensors. The performance of different sensor designs is assessed by analysing data from various test-beam campaigns. The effects of storage time at room temperature for the ITk pixel detector during maintenance periods are reproduced on real modules. Pixel detector modules built with sensors of 100-150um thickness are characterised with testbeam measurements. The charge collection and hit efficiencies are compared before and after annealing at room temperature up to one year

Apparatus and Its Uses: ‘Ecologising' Diffraction As A Materialist-Epistemological Practice

This paper addresses the problem of how to 'do' theory without implying “that theorizing is outside the world” (Barad & Gandorfer, 2021, p. 16) by elaborating a particular, ecological use of the apparatus. Tracing Foucault’s use of the dispositif (Foucault, [1977] 1980, p. 194), I argue that his key invention is identifying the generative capacity of the apparatus in terms of its constraints, which coincide with its situatedness as part of the world. By diffractively reading this invention through Barad’s posthumanist use of the apparatus, their agential realist practice of diffraction is re-iterated as a specifically 'ecologising' technique. Rather than following Barad in grounding this technique ontologically, Foucault’s “author-function” (Foucault 1969) leads me to ground such theorising an ongoing, materialist-epistemological engagement with the environment

Semi-classical spin dynamics of the antiferromagnetic Heisenberg model on the kagome lattice

We investigate the dynamical properties of the classical antiferromagnetic Heisenberg model on the kagome lattice using a combination of Monte Carlo and molecular dynamics simulations. We find that frustration induces a distribution of timescales in the cooperative paramagnetic regime (i.e. far above the onset of coplanarity), as recently reported experimentally in deuterium jarosite. At lower temperature, when the coplanar correlations are well established, we show that the weath- ervane loop fluctuations control the system relaxation : the time distribution observed at higher temperatures splits into two distinct timescales associated with fluctuations in the plane and out of the plane of coplanarity. The temperature and wave vector dependences of these two components are qualitatively consistent with loops diffusing in the entropically dominated free energy landscape. Numerical results are discussed and compared with the $O(N)$ model and recent experiments for both classical and quantum realizations of the kagome magnets.Comment: 18 pages, 14 figure

Valuations on the character variety: Newton polytopes and Residual Poisson Bracket

We study the space of measured laminations ML on a closed surface from the valuative point of view. We introduce and study a notion of Newton polytope for an algebraic function on the character variety. We prove for instance that trace functions have unit coefficients at the extremal points of their Newton polytope. Then we provide a definition of tangent space at a valuation and show how the Goldman Poisson bracket on the character variety induces a symplectic structure on this valuative model for ML. Finally we identify this symplectic space with previous constructions due to Thurston and Bonahon.Comment: 25 pages, 7 figure

« Malthus in, Malthus out? »

In this paper, we analyse the world model which represents the most ambitious attempt yet to bring together six great forecasts comprising population, resource depletion, food supply, capital investment, pollution and space. We wish to show on the one hand that the model has serious limitations and, on the other, that many different conclusions can be arrived at with this kind of study.

The WFIRST Galaxy Survey Exposure Time Calculator

This document describes the exposure time calculator for the Wide-Field Infrared Survey Telescope (WFIRST) high-latitude survey. The calculator works in both imaging and spectroscopic modes. In addition to the standard ETC functions (e.g. background and S/N determination), the calculator integrates over the galaxy population and forecasts the density and redshift distribution of galaxy shapes usable for weak lensing (in imaging mode) and the detected emission lines (in spectroscopic mode). The source code is made available for public use.Comment: 44 pages. The current C source code and version history can be found at http://www.tapir.caltech.edu/~chirata/web/software/space-etc/ ; IPAC maintains a web interface at http://wfirst-web.ipac.caltech.edu/wfDepc/wfDepc.js