Speaker
Description
The inner tracker of the ATLAS detector will be replaced by a silicon-based completely new inner tracker (ITk) for the Phase 2 of the CERN LHC (HL-LHC). The silicon strip detector covers the volume 40<R<100 cm in radial and |z|<300 cm in longitudinal directions. The silicon sensors for the detector will be fabricated on n+-on-p 6-inch wafer technology, for the total of 22 thousand wafers. Intensive studies were carried out on the final prototype sensors ATLAS17LS fabricated by Hamamatsu Photonics. The charge collection properties were examined using penetrating 90Sr \beta-rays and ALIBAVA fast readout system for the miniature sensors of 1cm×1cm in area. The samples were irradiated by protons in the 28 MeV Birmingham cyclotron, 70 MeV CYRIC at Tohoku University and 24 GeV CERN-PS, and by neutrons at Ljubljana TRIGA reactor up to 2×10^{15} neq/cm2 fluence. The change in the charge collection with fluence was found to be similar to the previous prototype ATLAS12, and acceptable for ITk. The sensors with two active thicknesses 300 \mu m (standard) and 240 \mu m (thin) were compared and difference in the small charge collection after irradiation between them was observed to be in the operation bias voltage range up to 500 V. This was also verified by the studies of the changes in the charge collection as a function of the depth measured by an edge-TCT technique. Some samples were also irradiated with gammas up to 2 MGy, and the full depletion voltage was found to decrease with the dose, indicating acceptor removal caused by 60Co irradiation. In summary, the ATLAS17LS design and fabrication technology have been verified for implementation in the ITk. We are in the stage of sensor pre-production with the first sensors scheduled to be delivered at the end of 2019.
| Submission declaration | Original and unpublished |
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