Development of Pixel Modules for the Belle II Detector

The future Belle II experiment at the SuperKEKB accelerator will improve the current understanding of flavor physics by increasing the recorded data set fiftyfold; allowing high precision measurements of CKM parameters and measurements of rare decays. The experiment will feature 2 layers of ultra-thin DEPFET pixel modules close to the interaction point to increase the vertex resolution while coping with an instantaneous luminosity 40 times higher than the previous Belle experiment. A DEPFET is a DEpleted P-channel Field Effect Transistor. Charge collected in the depleted bulk drifts into a potential minimum below the transistor gate and modulates the drain current, which is processed by two ASICs, the DCD and DHP. In this thesis the protptype ASICs for Belle II were characterized with an emphasis on the Drain Current Digitizer (DCD). To ensure data quality during the experiment runtime of Belle II, the radiation hardness and temperature stability of the DCD was investigated. With characterized ASICs, small and large Belle II prototype sensors were evaluated and used to investigate system performance. Sensor measurements were performed using a laser system with in-pixel resolution, radioactive sources and high energy electron beams at the DESY beam test facility

Effects of gamma irradiation on DEPFET pixel sensors for the Belle II experiment

For the Belle II experiment at KEK (Tsukuba, Japan) the KEKB accelerator was upgraded to deliver a 40 times larger instantaneous luminosity than before, which requires an increased radiation hardness of the detector components. As the innermost part of the Belle II detector, the pixel detector (PXD), based on DEPFET (DEpleted P-channel Field Effect Transistor) technology, is most exposed to radiation from the accelerator. An irradiation campaign was performed to verify that the PXD can cope with the expected amount of radiation. We present the results of this measurement campaign in which an X-ray machine was used to irradiate a single PXD half-ladder to a total dose of 266 kGy. The half-ladder is from the same batch as the half-ladders used for Belle II. According to simulations, the total accumulated dose corresponds to 7–10 years of Belle II operation. While individual components have been irradiated before, this campaign is the first full system irradiation. We discuss the effects on the DEPFET sensors, as well as the performance of the front-end electronics. In addition, we present efficiency studies of the half-ladder from beam tests performed before and after the irradiation

High-voltage pixel detectors in commercial CMOS technologies for ATLAS, CLIC and Mu3e experiments

High-voltage particle detectors in commercial CMOS technologies are a detector family that allows implementation of low-cost, thin and radiation-tolerant detectors with a high time resolution. In the R/D phase of the development, a radiation tolerance of 10 15 n eq = cm 2 , nearly 100% detection ef fi ciency and a spatial resolution of about 3 μ m were demonstrated. Since 2011 the HV detectors have fi rst applications: the technology is presently the main option for the pixel detector of the planned Mu3e experiment at PSI (Switzerland). Several prototype sensors have been designed in a standard 180 nm HV CMOS process and successfully tested. Thanks to its high radiation tolerance, the HV detectors are also seen at CERN as a promising alternative to the standard options for ATLAS upgrade and CLIC. In order to test the concept, within ATLAS upgrade R/D, we are currently exploring an active pixel detector demonstrator HV2FEI4; also implemented in the 180 nm HV proces