An FPGA-based data acquisition system for directional dark matter detection

Directional dark matter detection is a powerful tool in the search for dark matter. Low-pressure gas TPCs are commonly used for directional detection, and dark-matter-induced recoils are $\sim$mm long. These tracks can be reconstructed by micropatterned readouts. Because large detector volumes are needed, a cost-effective data acquisition system capable of scaling to large channel counts (10$^5$ or 10$^6$) is required. The Directional Recoil Identification From Tracks (DRIFT) collaboration has pioneered the use of TPCs for directional detection. We employ a negative ion gas with drift speed comparable to the electron drift speed in liquid argon (LAr). We aim to use electronics developed for million-channel readouts in large LAr neutrino detectors. We have built a prototype Micromegas-based directional detector with 10$^3$ channels. A FPGA-based back-end system (BE) receives a 12\,Gbps data stream from eight ASIC-based front-end boards (FE), each with 128 detector channels. The BE buffers 3$\mu$s of pretrigger data for all channels in DRAM, and streams triggered data to a host PC. We will describe the system architecture and present preliminary measurements from the DAQ.