Speaker
Description
The Photon Detection Systems of the DUNE Far Detectors (FD-HV and FD-VD) use large SiPM arrays read out by low-noise, discrete-component amplifiers operating in liquid argon. Signals are transmitted to warm electronics either electrically (in FD-HD and in FD-VD membrane modules) or optically (in FD-VD cathode modules). The warm readout board, DAPHNE, interfaces with all these cold electronics variants, performing signal digitization, online triggering, filtering and data transfer, using an FPGA SoM. This contribution presents the design, implementation, and test results of the complete readout chain, highlighting challenges and solutions for achieving low-noise, high-performance signal acquisition in a cryogenic environment.
Summary (500 words)
The Photon Detection System (PDS) of the Deep Underground Neutrino Experiment (DUNE) Far Detectors plays a crucial role in the precise reconstruction of neutrino interactions by capturing scintillation light produced in liquid argon (LAr). Two distinct detector modules – the Horizontal Drift (FD-HD) and Vertical Drift (FD-VD) – use X-ARAPUCA light traps with large arrays of Silicon Photomultipliers (SiPMs) as photodetectors.
These SiPM arrays, configured in a passive ganging arrangement, are read out by custom-designed, low-noise discrete-component amplifiers that operate reliably in the cryogenic environment of LAr at 87 K. Despite an input capacitance of up to tens of nF and a power budget of a few mW per channel, the amplifiers provide a S/N ratio greater than 5, a dynamic range from single photon up to 2000 photons, and a rise time below 100 ns.
Signal transmission from the cold amplifiers to the warm electronics depends on the specific PDS configuration. In the FD-HD and the membrane modules of the FD-VD, electrical transmission is used with shielded twisted-pair cables. In contrast, the FD-VD cathode modules, operating at about 300 kV from the ground potential, must employ an optical transmission scheme, both for signals (Signal-over-Fiber, SoF) and power (Power-over-Fiber, PoF). This dual approach addresses the unique geometry and grounding constraints of the different detector designs while maintaining high signal integrity and operating in a cryogenic environment.
All PDS signal paths converge at a common warm interface: the DAPHNE board. DAPHNE is designed to accommodate the diverse cold electronics configurations with a flexible and scalable architecture based on mezzanine boards for additional signal conditioning or optical-to-analog conversion. DAPHNE also houses the 14-bit digitization chips (AFE5808) operating at 62.5 Msps. Digital processing is based on the Kria K26 Zynq Ultrascale+ System-on-Module (SoM), which performs multiple key functions: AFE chips interface, data filtering, triggering, signal metadata calculation, packet creation, and data transmission to the back-end data acquisition (DAQ) system via high-speed 10 Gbps links.
The design and implementation of the entire readout chain – from cryogenic front-end electronics to warm digital processing – have involved careful optimization to meet the demanding requirements of noise performance, signal fidelity, power consumption, and reliability in a challenging cryogenic environment. This contribution presents a detailed overview of the system and its design choices, together with test results from lab setups and integrated system tests at the CERN Neutrino Platform facilities, demonstrating the performance of the full PDS readout chain.
Through its reliable and high-performance readout electronics, the DUNE PDS will provide a critical component for enabling precision timing and calorimetric measurements in one of the leading neutrino experiments of the near future.
