Abstract
During the so-called Phase-2 Upgrade, the CMS experiment at CERN will undergo significant improvements to cope with the 10-fold luminosity increase of the High Luminosity LHC (HL-LHC) era. Especially the forward calorimetry will suffer from very high radiation levels and intensified pileup in the detectors. For this reason, the CMS collaboration is designing a High Granularity Calorimeter (HGCAL) to replace the existing endcap calorimeters. It features unprecedented transverse and longitudinal segmentation for both electromagnetic (CE-E) and hadronic (CE-H) compartments. The CE-E and a large fraction of CE-H will consist of a sandwich structure with silicon as active detector material. This paper presents an overview of the ongoing sensor development for the HGCAL and highlights important design features and measurement techniques. The design and layout of an 8-inch silicon sensor prototype is shown. The hexagonal sensors consist of 235 pads, each with an area of about 1 cm2. Furthermore, Synopsys TCAD simulations regarding the high voltage stability of the sensors for different geometric parameters are performed. Finally, two different IV characterisation methods are compared on the same sensor.
Highlights
: During the so-called Phase-2 Upgrade, the CMS experiment at CERN will undergo significant improvements to cope with the 10-fold luminosity increase of the High Luminosity LHC
The forward calorimetry will suffer from very high radiation levels and intensified pileup in the detectors
This paper presents an overview of the ongoing sensor development for the High Granularity Calorimeter (HGCAL) and highlights important design features and measurement techniques
Summary
Sensors in the endcap with lower radial distance to the interaction point receive a higher fluence in comparison to sensors with higher radial distance. The full depletion voltage of a p-type silicon sensor will increase. The sensors need to be operated at higher voltage in comparison to unirradiated sensors For this project, the sensors are planned to be operated at 800 V after 3000 fb−1 but should be designed to withstand 1 kV. A hexagonal sensor contains many individual cells, which are mostly smaller hexagons with an area of either 0.5 cm or about 1.0 cm. Two of the hexagonal cells are divided into an inner small hexagon and a surrounding area. The former is to facilitate calibration with minimumionizing particles. As there is no common biasing grid for all cells of the whole sensor, each pad has to be biased individually
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