Jakob Haidl ; Christian Kiesling

2016
LMU Munich

Abstract: The Super-KEKB accelerator at the KEK high energy research center in Tsukuba, Japan will provide a 40 times higher luminosity. To cope with this high luminosity the Belle detector is improved to Belle II, which includes the integration of a two layer DEPFET Pixel Detector (PXD) resulting in a higher vertex resolution. The task of the read-out electronics is to process the high data rate of the PXD. To fulfill these requirements, three different types of ASICs were designed. The foremost of them called Drain Current Digitizer (DCD) converts the drain currents of the DEPFET pixel sensors into digital code. Since the PXD will be equipped with 160 DCDs, automatic testing of the chips is needed. Analog to digital transfer curves are an appropriate tool for error recognition and optimization of the digitization process within the DCD. A detailed description of different defect types and their origins will be presented. Particular attention is paid to the missing code error, which arises from a transistor mismatch in the DCD, as it is still a prototype version. On this basis an optimization routine is developed, which compensates defects by an adjustment of settings. In an exemplary optimization, the number of channels containing missing codes is reduced to 6.25 %, at a combined defect number of 8.2 %. Finally, a fast routine speeding up the characterization time by a factor of ∼ 90 is proposed.

Note: Presented on 07 04 2016
Note: MSc