Erlangen 2026 – wissenschaftliches Programm
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T: Fachverband Teilchenphysik
T 55: Silicon Detectors VI
T 55.4: Vortrag
Mittwoch, 18. März 2026, 17:00–17:15, KH 01.022
Investigation of X-ray-induced effects and resulting high backside currents in DePFET pixel sensors for the Belle II experiment — Florian Bernlochner, Jochen Dingfelder, and •Georgios Giakoustidis — University of Bonn, Bonn, Germany
For the Belle II experiment at KEK (Tsukuba, Japan) the KEKB accelerator was upgraded to deliver e+e− collisions at a center-of-mass energy of ECM = 10.58 GeV and it has reached a record-breaking instantaneous luminosity of 5.1·1034 cm−2s−1 in December 2024. During the so-called Long Shutdown 1 (LS1) the innermost part of the Belle II detector, the initially descoped PiXel Detector (PXD1) with 20 modules, based on Depleted P-channel Field Effect Transistor (DePFET) technology, was replaced by a fully-populated, two-layer PXD with 40 modules. As the detector closest to the experiment’s interaction region, the PXD is most exposed to radiation from the accelerator. Throughout the operation of the PXD1 a steady increase of backside current with irradiation was observed in several modules. Doping-profile measurements and electric field simulations show that this is a consequence of (partially) shorted guard rings at the backside leading to high electric fields and avalanche current multiplication. In this contribution, irradiation studies investigating both the X-ray-induced effects in DePFET sensors and the resulting high backside currents will be presented.
Keywords: DEPFET; PXD; Belle II; SuperKEKB