FPGA based data read-out system of the Belle II pixel detector

The upgrades of the Belle experiment and the KEKB accelerator aim to increase the data set of the experiment by a factor 50. This will be achieved by increasing the luminosity of the accelerator which requires a significant upgrade of the detector. A new pixel detector based on DEPFET technology will be installed to handle the increased reaction rate and provide better vertex resolution. One of the features of the DEPFET detector is a long integration time of 20~μs , which increases detector occupancy up to 3%. The detector will generate about 22 GB/s of data. An FPGA-based two-level read-out system, the Data Handling Hub, was developed for the Belle II pixel detector. The system consists of 40 read-out and eight controller modules. All modules are built in μTCA form factor using Xilinx Virtex-6 FPGA and can utilize up to 4 GB DDR3 RAM. The system was successfully tested in the beam test at DESY in January 2014. The functionality and the architecture of the Belle II Data Handling Hybrid system as well as the performance of the system during the beam test are presented in the paper.