Real-Time Pulse Processing on the Time-Division Multiplex Readout Electronics of the Transition Edge Sensor for the Line Emission Mapper (LEM)

We are developing a real-time X-ray pulse processor for the Line Emission Mapper (LEM) mission, a NASA X-ray probe concept for imaging and spectroscopy in the 0.2 to 2 keV range. The main detector is a hybrid Transition Edge Sensor (TES) array with a 33' outer array with “Hydra” multiplexing and a 7' × 7' inner subarray. The ∼4,000 TES sensors are read out using time-division multiplexing (TDM) technology. We are developing room-temperature digital readout electronics based on laboratory TDM electronics, where all X-ray pulses are processed in real-time to reduce the size of the data transmission. The process includes pulse triggering, grading, extraction, and optimal filtering performed in the FPGA of the TDM column electronics. In this paper we describe the real-time pulse processing firmware for a LEM flight-like prototype electronics and demonstrate count rate capability. We also demonstrate that it provides identical performance compared to conventional offline pulse-processing.