CERN Accelerating science

Article
Title Gamma irradiation of ATLAS18 ITk strip sensors affected by static charge
Author(s)

Mikestikova, M (Rez, Nucl. Phys. Inst.) ; Fadeyev, V (UC, Santa Cruz, Inst. Part. Phys.) ; Federicova, P (Rez, Nucl. Phys. Inst.) ; Tejero, J Fernandez (Simon Fraser U. ; TRIUMF) ; Fleta, C (Barcelona, Inst. Microelectron.) ; Gallus, P (Charles U.) ; Jessiman, C (Carleton U.) ; Keller, J (Carleton U.) ; Klein, C (Carleton U.) ; Koffas, T (Carleton U.) ; Kroll, J (Rez, Nucl. Phys. Inst.) ; Kvasnicka, J (Rez, Nucl. Phys. Inst.) ; Staats, E (Carleton U.) ; Tuma, P (Rez, Nucl. Phys. Inst.) ; Ullan, M (Barcelona, Inst. Microelectron.) ; Unno, Y (KEK, Tsukuba)

Publication 2024
Number of pages 6
In: PoS VERTEX2023 (2024) 026
In: 32nd International Workshop on Vertex Detectors (VERTEX 2023), Sestri Levante, Italy, 16 - 20 Oct 2023, pp.026
DOI 10.22323/1.448.0026
Subject category Detectors and Experimental Techniques
Accelerator/Facility, Experiment CERN LHC ; ATLAS
Abstract Construction of the new all-silicon Inner Tracker (ITk), developed by the ATLAS collaboration to be able to track charged particles produced at the High-Luminosity LHC, started in 2021 and is expected to continue until 2028. The ITk detector will include  18,000 highly segmented and radiation hard n$^+$-in-p silicon strip sensors, which are being manufactured by Hamamatsu Photonics. Upon their delivery, the ATLAS ITk strip sensor collaboration performs detailed measurements of sensors to monitor quality of all fabricated pieces. QC electrical tests include current-voltage (IV) and capacitance-voltage (CV) tests, full strip tests, and a measurement of the long-term stability of the sensor leakage current. While most sensors demonstrate excellent performance during QC testing, we have nevertheless observed that a number of sensors from several production batches failed the electrical tests. Accumulated data indicates a strong correlation between observed electrical test failures and high electrostatic charge measured on the sensor surface during initial reception tests. This electrostatic charge enhances the risk of "Local trapped charge" events during manufacturing, shipping, and handling procedures, resulting in failed electrical QC tests. To mitigate the above-described issues, the QC testing institutes modified the sensor handling procedures and introduced sensor recovery techniques. Despite the implementation of various recovery techniques, it is still possible that some affected sensors will not be identified by the sensor QC testing, or that "Local trapped charge" events could occur in later manipulation stages of the sensor. In the presented study, we have investigated whether the total ionizing dose (TID) expected in the real experiment can effectively resolve early breakdown or low interstrip isolation caused by the electrostatic charge. Selected charge-affected sensors were irradiated with gamma rays from the $^{60}$Co source for a number of TID values. The results of this study indicate that the negative effects of the electrostatic charge on the critical sensors characteristics disappear after a very small amount of an accumulated TID, which actually corresponds to one or two days in the experiment. This finding gives us confidence in mitigating the issue of electrostatic charge during the operation of the ITk strip sensors in the real experiment.
Copyright/License © 2023-2024 The authors (License: CC-BY-NC-ND-4.0)

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