Upgrade of the ATLAS Liquid Argon Calorimeters for the High-Luminosity LHC

TL;DR

This paper discusses the challenges faced by the ATLAS liquid argon calorimeters at the HL-LHC due to increased luminosity and outlines upgrade plans, including potential FCal replacement and high-granularity timing detectors, to maintain performance.

Contribution

It provides an overview of the upgrade strategies for the ATLAS liquid argon calorimeters in response to HL-LHC conditions, including technical assessments and proposed solutions.

Findings

Increased ionization load affects FCal performance.

Potential FCal replacement considered to mitigate issues.

High-granularity timing detectors under investigation.

Abstract

The increased particle flux at the high luminosity phase of the Large Hadron Collider (HL-LHC), with instantaneous luminosities of up to 7.5 times the original design value, will have an impact on many sub-systems of the ATLAS detector. This contribution highlights the particular impacts on the ATLAS liquid argon calorimeter system, together with an overview of the various upgrade plans leading up to the HL-LHC. The higher luminosities are of particular importance for the forward calorimeters (FCal), where the expected increase in the ionization load poses a number of problems that can degrade the FCal performance such as beam heating and space-charge effects in the liquid argon gaps and high-voltage drop due to increased current drawn over the current-limiting resistors. A proposed FCal replacement as a way to counter some of these problems is weighed against the risks associated with the replacement. To further mitigate the effects of increased pile-up, the installation of a high-granularity timing detector at the front face of each end-cap cryostat is also currently under consideration. Several different sensor technologies and layouts are being investigated.