Neutron Irradiation and Electrical Characterisation of the First 8" Silicon Pad Sensor Prototypes for the CMS Calorimeter Endcap Upgrade

TL;DR

This paper reports on neutron irradiation tests and electrical characterization of 8-inch silicon pad sensors developed for the CMS high-granularity calorimeter upgrade, demonstrating their radiation hardness and electrical performance post-irradiation.

Contribution

It presents the first neutron irradiation and electrical testing of 8-inch silicon sensors for the CMS calorimeter upgrade, advancing sensor qualification methods.

Findings

Sensors maintained electrical integrity after irradiation

Detailed procedures for neutron irradiation and testing are documented

Results support the radiation hardness of the sensors for HL-LHC conditions

Abstract

As part of its HL-LHC upgrade program, the CMS collaboration is replacing its existing endcap calorimeters with a high-granularity calorimeter (CE). The new calorimeter is a sampling calorimeter with unprecedented transverse and longitudinal readout for both electromagnetic and hadronic compartments. Due to its compactness, intrinsic time resolution, and radiation hardness, silicon has been chosen as active material for the regions exposed to higher radiation levels. The silicon sensors are fabricated as 20 cm (8") wide hexagonal wafers and are segmented into several hundred pads which are read out individually. As part of the sensor qualification strategy, 8" sensor irradiation with neutrons has been conducted at the Rhode Island Nuclear Science Center (RINSC) and followed by their electrical characterisation in 2020-21. The completion of this important milestone in the CE's R&D program is documented in this paper and it provides detailed account of the associated infrastructure and procedures. The results on the electrical properties of the irradiated CE silicon sensors are presented.