Tsinghua University, Beijing, People's Republic of China
The particle detector array (KM2A) of Large High Altitude Air Shower Observatory (LHAASO) project consists of 5631 electron and 1221 muon detection units over 1.2 square km area. To reconstruct the incident angle of cosmic ray, sub-nanosecond time synchronization must be achieved. The White Rabbit (WR) protocol is applied for its high synchronization precision, automatic delay compensation and intrinsic high band-width data transmit capability. This paper describes the design of a sub-nanosecond timing and data acquisition endpoint for KM2A. It works as a FMC mezzanine mounted on detector specific front-end electronic boards and provides the WR synchronized clock and timestamp. The endpoint supports EtherBone protocol for remote monitor and firmware update. Moreover, a hardware UDP engine is integrated in the FPGA to pack and transmit raw data from detector electronics to readout network. Preliminary test demonstrates a timing precision of 29ps (RMS) and a timing accuracy better than 100ps (RMS).
* The authors are with Key Laboratory of Particle and Radiation Imaging, Department of Engineering Physics, Tsinghua University, Beijing, China, 100084
* pwb.thu@gmail.com
