Design and first experience of the prototype pixel layers for the ALICE FoCal

Abstract

The University of Bergen is involved in developing two calorimeters: the pixel section of the Electromagnetic Forward Calorimeter for the ALICE Upgrade to be installed during LS3 for data-taking in the period 2029–2032 and the Digital Tracking Calorimeter for the proton Computed Tomography prototype. Both designs utilize pixel sensors and require a reliable connection to the readout which is positioned approximately 5 meters away. Furthermore, the structural design of these calorimeters calls for a compact layer assembly. This paper provides the strategies deployed to meet these critical requirements, focusing on the implementation of the chip-on-flex assembly, and the ultrasonic welding techniques. It further describes other design considerations essential for maintaining good signal integrity. Finally, it gives insight into the experiences and challenges faced while working with the prototypes, both in the laboratory and test beam setups.