Heidelberg 2022 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 95: Pixel Detectors 3

T 95.6: Vortrag

Donnerstag, 24. März 2022, 17:30–17:45, T-H26

Challenges of offset calibration in irradiated modules of the Pixel Vertex Detector at the Belle II experiment — •Maria Konstantinova and Arthur Bolz — DESY Hamburg

The Pixel Vertex Detector (PXD) is situated as the innermost subdetector of the Belle II experiment at the SuperKEKB collider in Japan. Each PXD module includes a matrix of 192'000 pixels based on the Depleted P-channel Field-Effect Transistor (DEPFET) technology. The matrices are read out in rolling shutter mode such that 1000 channels are digitized in parallel by four custom Drain Current Digitizer (DCD) ASICs. For a consistent response to transversing charged particles during operation, homogeneous pedestal currents must be subtracted for each pixel to obtain as much room as possible for analogue-to-digital conversion of the signal current. Therefore, a narrow pedestal spread is achieved by adding a 2-bit DAC offset current to every pixel. The offset currents show non-linear behaviour which is dependent on the hardware architecture and may change during module operation in a harsh radiation environment in the interaction region. In this talk those effects are analyzed and the challenges they pose to a good offset calibration of PXD are discussed.