Bonn 2020 – scientific programme

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T: Fachverband Teilchenphysik

T 13: Pixel detectors I

T 13.3: Talk

Monday, March 30, 2020, 17:00–17:15, H-HS XIV

Charge Calibration and Crosstalk Measurements with RD53A Assemblies — •Georgios Giakoustidis — Physikalisches Institut, Universität Bonn, Nussallee 12, 53115 Bonn, Germany

The RD53 collaboration designed a new prototype hybrid pixel readout chip using the 65 nm CMOS technology for the High-Luminosity LHC upgrade. Thinner silicon sensors chosen to cope with the prospective high radiation levels in ATLAS require lower threshold of the readout electronics making the tunings more challenging. Thus, calibration of the charge injection circuitry of RD53A assemblies with different sensor geometries was conducted using the precise TDC method. At low thresholds crosstalk becomes more perceptible and should be considered for the final sensor design selection. Therefore RD53A assemblies with sensors of different pixel structure and geometries were tested by injecting artificial charge to neighbouring pixels in various patterns.

Events of cluster size one and two are analysed, leading to a transfer function with slope of (10.37 ± 0.10) e/DAC and offset of (180 ± 60) e. Calibration results for different thresholds showed no significant difference. Assemblies with the same pixel geometry between the sensor and the readout chip exhibited crosstalk of about 1%, whereas 7% to 16% crosstalk was observed for assemblies with geometry mismatch.

Since no significant differences observed between charge calibration of different RD53A assemblies and thresholds, the final transfer function is of global use. A sensor with a non-matching pixel geometry to the readout chip is not ideal for the RD53A. Sensors with smaller implants reduce the crosstalk levels by 30%.