Radiation tolerance and annealing studies of silicon sensors for the CMS HGCAL

by Leena Diehl (CERN)

Wednesday 27 Mar 2024, 11:00 → 12:00 Europe/Zurich

32/1-A24 (CERN)

To face the higher levels of radiation due to the10-fold increase in integrated luminosity during the High-Luminosity LHC, the CMS detector will replace the current endcap calorimeters with the new High-Granularity Calorimeter (HGCAL). It will facilitate the use of particle-flow calorimetry with its unprecedented transverse and longitudinal readout/trigger segmentation, with more than 6M readout channels. The electromagnetic section as well as the high-radiation regions of the hadronic section of the HGCAL will be equipped with silicon pad sensors, covering a total area of 620m². Fluences up to 10¹⁶ n_eq/cm² and doses up to 1.5MGy are expected.

The sensors are processed on novel 8-inch p-type wafers with an active thickness of 300𝜇𝑚, 200𝜇𝑚 and 120𝜇𝑚 and cut into hexagonal shapes for optimal use of the wafer area and tiling.  With each main sensor several small sized test structures are hosted on the wafers, used for quality assurance and radiation hardness tests. In order to investigate the radiation-induced bulk damage, these sensors have been irradiated with neutrons up to the highest fluences. 

In this seminar, the electrical characterisation and charge collection measurements of the irradiated silicon diodes will be presented. The most recent measurements were conducted with the a new setup, constructed with support of the EP R&D programme and the EP-DT SSD group. The study focuses on the isothermal annealing behaviour of the bulk material at various temperatures. The results can be used to optimise the HGCAL layout and to establish an operating and annealing scenario for HGCAL.

EPDT_Seminar-3.pdf