Ing. Marcela Mikeštíková, Ph.D.
The Inner Tracker (ITk) is a new all-silicon tracking detector developed for the ATLAS experiment, which will measure the tracks of charged particles produced at the HL-LHC accelerator. FZU participates in the ITk project since its very beginning, dominantly by testing of silicon strip sensors (it is needed to test ~4500 radiation-resistant End-Cap (EC) silicon strip sensors which represents half of all EC silicon strip sensors produced under the ATLAS ITk project), but also by covering irradiation, testbeam, and off-detector services activities in terms of personnel and material.
The Inner Tracker (ITk) is a new all-silicon tracking detector developed for the ATLAS experiment, which will measure the tracks of charged particles produced at the HL-LHC accelerator. FZU participates in the ITk project since its very beginning, dominantly by testing of silicon strip sensors (it is needed to test ~4500 radiation-resistant End-Cap (EC) silicon strip sensors which represents half of all EC silicon strip sensors produced under the ATLAS ITk project), but also by covering irradiation, testbeam, and off-detector services activities in terms of personnel and material.
Development of silicon strip sensors that will be able to operate for 10 years in a harsh radiation environment expected at the HL-LHC took several years [1]. This effort was finished in 2020 by the start of pre-production testing, which at FZU included Quality Control (QC) testing of MAIN sensors (visual inspection and capture, metrology measurements, current-voltage and capacitance-voltage tests, full-strip tests, and measurement of leakage current stability) and Quality Assurance (QA) measurements of irradiated testchips. The pre-production phase of the project was finished by qualification of the individual testing sites, when our Laboratory for testing or semiconductor particle detectors qualified as the first ITk strip sensor QC testing site in the world, but to fulfill this commitment, a brand new Laboratory for Testing Silicon Particle Detectors with a total area of 52 m² had to be built at the Institute of Physics (Fig. 1, 2). The cleanliness level of the laboratory is ISO 7 according to the ISO 14644-1 standard, and the laboratory also meets the requirements for protection against damage to laboratory equipments or tested samples by electrostatic discharge.
Moreover, our FZU group in collaboration with UJP Praha, a.s. is also qualified for irradiation of ITk strip components by 60Co source (Fig. 5). Since the end of 2021, when the production testing started, we have measured nearly 3000 MAIN sensors and 120 QA testchips, and a total of 570 sensor QA structures were irradiated by 60Co source in 24 irradiation campaigns [2]. The MAIN sensors tested at FZU are continuously being distributed to the ITk institutes involved in assembly of ITk strip modules worldwide, while the samples irradiated by the 60Co source are shipped either to JSI Ljubljana for neutron irradiation or directly to testing sites. The distribution includes vacuum packaging of the sensors and the preparation of suitable mechanical, humidity, and ESD protection.
Besides of the testing of ITk strip sensors, our FZU research group is intensively participating also in ITk strip testbeam campaigns (testing of ITk strip detectors with high-energy beams of charged particles) and in irradiation of ITk strip sensors and detectors by 24 GeV protons produced at CERN IRRAD facility (Fig. 4). In 2023 we have also designed and built a new moving stage for precise positioning of tested devices with non-trivial dimensions and weight into the beam of charged particles (Fig. 3, 6, 7).
Development of new radiation hard semiconductor sensors
Besides of the ATLAS ITk project, our research group focuses also on development and testing of the new radiation hard semiconductor sensors that will be able to operate in radiation conditions expected for Future Circular Collider (TIDs above 1E9 Gy and total fluences around 1E18 1 MeV neq/cm2). These activities are being coordinated mainly by the newly established collaboration DRD3 - R&D on Semiconductor Detectors, within which we are active in most of the working groups, with special interest being put on LGAD sensors [3], wide bandgap materials (GaN, SiC), and radiation damage characterization [4]. Our investigations of LGAD sensors using SiC material is based on close collaboration with Onsemi company located in Rožnov pod Radhoštěm.
[1] M. Mikestikova et al., Electrical characterization of surface properties of the ATLAS17LS sensors after neutron, proton and gamma irradiation, Nucl. Instrum. Methods Phys. Res. A 983, (2020) 164456. DOI
[2] M. Mikestikova et al., ATLAS ITk strip sensor quality control procedures and testing site qualification, J. Instrum 17, (2022) C12013. DOI
[3] G. Lastovicka-Medin et al., Linking laser-induced and self-induced signals in double trench isolated LGADs: Implications for signal anomalies in interpad region, Nucl. Instrum. Methods Phys. Res. A 1066, (2024) 169635. DOI
[4] M. Mikestikova et al., The study of gamma-radiation induced displacement damage in n+-in-p silicon diodes, Nucl. Instrum. Methods Phys. Res. A 1064, (2024) 169432. (DOI)