The High Voltage Feedthroughs for the ATLAS Liquid Argon Calorimeters

The purpose, design specifications, construction techniques, and testing methods are described for the high voltage feedthrough ports and filters of the ATLAS Liquid Argon calorimeters. These feedthroughs carry about 5000 high voltage wires from a room-temperature environment (300 K) through the cryostat walls to the calorimeters cells (89 K) while maintaining the electrical and cryogenic integrity of the system. The feedthrough wiring and filters operate at a maximum high voltage of 2.5 kV without danger of degradation by corona discharges or radiation at the Large Hadron Collider

Construction, assembly and tests of the ATLAS electromagnetic barrel calorimeter

The construction and assembly of the two half barrels of the ATLAS central electromagnetic calorimeter and their insertion into the barrel cryostat are described. The results of the qualification tests of the calorimeter before installation in the LHC ATLAS pit are given

Stochastic modelling of air pollution impacts on respiratory infection risk

The impact of air pollution on people’s health and daily activities in China has recently aroused much attention. By using stochastic differential equations, variation in a 6 year long time series of air quality index (AQI) data, gathered from air quality monitoring sites in Xi’an from 15 November 2010 to 14 November 2016 was studied. Every year the extent of air pollution shifts from being serious to not so serious due to alterations in heat production systems. The distribution of such changes can be predicted by a Bayesian approach and the Gibbs sampler algorithm. The intervals between changes in a sequence indicate when the air pollution becomes increasingly serious. Also, the inflow rate of pollutants during the main pollution periods each year has an increasing trend. This study used a stochastic SEIS model associated with the AQI to explore the impact of air pollution on respiratory infections. Good fits to both the AQI data and the numbers of influenza-like illness cases were obtained by stochastic numerical simulation of the model. Based on the model’s dynamics, the AQI time series and the daily number of respiratory infection cases under various government intervention measures and human protection strategies were forecasted. The AQI data in the last 15 months verified that government interventions on vehicles are effective in controlling air pollution, thus providing numerical support for policy formulation to address the haze crisis

New numerical tools to study waves and instabilities of flowing plasmas

Studying plasma waves and instabilities is an indispensable part of present thermonuclear fusion and astrophysical magnetohydrodynamics (MHD). Up till recently, spectral analysis was mostly restricted to static plasmas. However, the assumption of a static plasma is unrealistic not only for astrophysical but also for modern fusion research. Plasmas with flow have been shown to have spectra essentially different from those of static plasmas [Phys. Rev. Lett. 84 (2000) 2865].\ud \ud We present two new numerical tools for spectral studies of plasmas with flow. The first one, a program called FINESSE (Finite Element Solver for Stationary Equilibria), computes equilibria of non-static plasmas for a variety of fusion and astrophysical configurations (tokamaks, solar loops, solar winds, etc.).\ud \ud Ideal and resistive spectra of the computed equilibria are studied with another tool, a program called PHOENIX. In PHOENIX, the large-scale generalized eigenproblems are solved with the recently proposed iterative Jacobi–Davidson method [SIAM J. Matrix Anal. Appl. 17 (1996) 401].\ud \ud Our numerical examples show how FINESSE and PHOENIX can be used to study the effect of the poloidal flows on Toroidal Alfvén Eigenmodes

FINESSE: axisymmetric MHD equilibria with flow

The FINESSE code (finite element solver for stationary equilibria) computes axisymmetric magnetohydrodynamic equilibria in poloidal elliptic flow regimes for a variety of astrophysical and laboratory plasma configurations. The obtained equilibria are accurate and are used to study the spectral characteristics of such flowing equilibria. The nonlinear partial differential equation for the poloidal magnetic flux is solved in a weak form via Picard iteration, resulting in a large-scale linear problem. The algebraic Bernoulli equation for the poloidal Alfvén Mach number is solved with a nonlinear root finder. Converged solutions are obtained by iterating on these two equations