Speaker
Description
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 (fluences above $1e14 n_{eq}/cm^2$) will be equipped with silicon pad sensors, covering a total area of 620$m^2$). Fluences up to $1e16 n_{eq}/cm^2$ and doses up to 1.5MGy are expected. The whole HGCAL will normally operate at -35°C in order to mitigate the effects of radiation damage.
The sensors are processed on novel 8-inch p-type wafers with an active thickness of $300\mu m$, $200\mu $m and $120\mu$m 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 at JSI (Jožef Stefan Institute, Ljubljana) to fluences between 2e15 and $1.5e16 n_{eq}/cm^2$.
In this talk the electrical characterisation and charge collection measurements of the irradiated silicon diodes will be presented. The study focuses on the isothermal annealing behaviour of the bulk material at temperatures of 6.5°C, 20°C and 60°C. The results have been used to optimize the layout of the silicon modules in HGCAL and are being used to evaluate the annealing possibilities for HGCAL during year-end technical stops and long HL-LHC shutdowns at around 0°C.
| Type of presentation (in-person/online) | in-person presentation |
|---|---|
| Type of presentation (scientific results or project proposal) | Presentation on scientific results |
