Design of a 32-channel NIM TDC module based on single FPGA for the μSR spectrometer prototype at the China Spallation Neutron Source

The design of an experimental muon source (EMuS) at the China Spallation Neutron Source (CSNS) has been underway for muon spin rotation, relaxation and resonance (μSR) experiments since 2007. A 128-channel μSR spectrometer prototype is also being developed. We have successfully developed a 32-channel time-to-digital converter (TDC) electronic readout unit module for the μSR spectrometer prototype. It receives timing signals from four front-end electronics (FEEs) and communicates with them. Moreover, it is a standard NIM module with a single field-programmable gate array-based design that meets the following requirements for μSR experiments: a low dead time, an instantaneous high count rate, a relatively long measurement duration, a relatively high resolution, and multiple channel-compatibility. By incorporating look-up tables (LUTs), placement constraints and area constraints, the routing skew of all TDC channels is reduced to less than 4 ps. Furthermore, Gigabit Ethernet data transmission has been incorporated in anticipation of more channels being added in the future.