Readout System for ePixHR X-ray Detectors: A Framework and Case Study

Abstract

LCLS-II, a Free Electron Laser (FEL) X-ray light source, started operations at SLAC National lab in 2020. This new machine will produce X-ray pulses with a repetition rate up to 1,000,000 times per second. To take advantage of its high pulse rate, detectors and readout systems that can operate at the same frequency and cope with the generated data volumes are being developed. In this paper, we present the readout system for the first generation of ePixHR high rate detectors including the first readout ASIC, namely, ePixHR10k, the first prototype of this family. This system aims at sustaining readout rates higher than 5,000 frames per second for the matrix of the ePixHR10k sensor/ASIC module (288 rows x 384 columns and 2 bytes per pixel). The proposed electronic system uses an FPGA to perform data capture and transmission to a host computer. The firmware is developed using a custom public library called SURF where building blocks such as ASIC register access, high speed communication links, protocols for data stream, and register configuration exist. The user interface uses a companion framework called ROGUE, which implements the software modules for the elements that exist in SURF. Initial results from X-ray tests using Fe55 source are presented.