Development, characterization and operation of the DCDB, the front-end readout chip for the pixel vertex detector of the future BELLE-II experiment

The BELLE-II detector is the upgrade of its predecessor named BELLE at KEK research centre in Tsukuba, Japan, which was successfully used in the past to find evidence for CP violating decays. The upgraded SuperKEKB accelerator is specified to produce a luminosity of 8 x 10 high 35 cm high -2 s high -1. Consequently, the BELLE-II detector and particularly the innermost pixel vertex detector (PXD) suffers from enormous occupancy due to background events. Coping with this harsh environment while providing the required physics performance results in tough specifications for the front-end readout electronics. The PXD pixel detector system is based on the DEPFET technology. DEPFET transistors combine particle detection and signal amplification within one device. The DCDB chip is developed to sample and digitize signals from these transistors while complying with the specifications of BELLE-II. The presented work illustrates the chip’s features and describes its implementation process. The device is comprehensively characterized using an individually developed test environment. The obtained results are presented. The DCDB’s ability to serve as a readout device for particle physics applications is demonstrated by its successful operation within a DEPFET detector prototype system. Highlights are a decay spectrum measurement using Cd-109 and the successful operation in a beam test experiment at CERN.