[Paper Review] Electronics and DAQ for the CHIPS Experiment

D. van Eijk|arXiv (Cornell University)|May 17, 2018

Astrophysics and Cosmic Phenomena2 references3 citations

TL;DR

This paper presents a low-cost, modular electronics and data acquisition (DAQ) system for the CHIPS neutrino detector, a 5-kiloton proof-of-concept water-Cherenkov detector using 6,400 3-inch PMTs. It employs two DAQ schemes—KM3NeT-inspired for standard PMTs and microDAQ for refurbished NEMO3 PMTs—using White Rabbit timing, event building via BeagleBone, and optical fiber transmission, enabling efficient 10 μs spill-triggered data collection with sub-nanosecond timing accuracy for neutrino oscillation studies at a fraction of conventional detector costs.

ABSTRACT

CHIPS (CHerenkov detectors In mine PitS ) is a novel neutrino detector concept, aimed at building megaton water-Cherenkov neutrino detectors in a flexible and cheap way, while yielding science results comparable and contributing to conventional long-baseline neutrino experiments. In the summer of 2018, a 5 kiloton proof-of-principle detector will be installed in a disused water-filled mine pit located in the NuMI neutrino beamline path in Minnesota, USA. The submerged cylindrical detector volume is 25 meters in diameter and 10 meter tall and is surrounded by light-tight liners. All inside walls are covered with PMT holding structures. CHIPS will use thousands of 3-inch PMTs to detect neutrinos interacting in the high-purity water in the detector volume. The focus of the (poster) presentation at the NuPhys2017 conference was on DAQ and electronics for the CHIPS experiment.

Motivation & Objective

• To develop a cost-effective, scalable electronics and DAQ system for megaton-scale water-Cherenkov neutrino detectors.
• To enable precise timing and signal reconstruction using low-cost, modular components for both new and refurbished PMTs.
• To demonstrate feasibility of a $200k/kiloton detector cost, significantly lower than conventional $2–10M/kiloton water-Cherenkov detectors.
• To support high-precision measurements of neutrino oscillation parameters (δCP, θ13, θ23) using a compact, modular detector in a mine pit.

Proposed method

• The CHIPS detector uses 6,400 3-inch PMTs—5,500 Hamamatsu R12199-02 and 900 refurbished NEMO3 PMTs—mounted on detector planes covering the inner walls of a 25 m diameter, 10 m tall cylindrical volume.
• Each detector plane processes signals from 30 PMTs using a Central Logic Board (CLB) that computes time-over-threshold (ToT) values.
• A separate microDAQ system is used for the refurbished NEMO3 PMTs, integrating a microprocessor board with the same form factor as the PMT base to enable full signal shape reconstruction via time-delay buffers.
• ToT data from 16 PMTs per plane are sent to a BeagleBone board for event building, which communicates with higher-level fanout boards via standard Ethernet CAT cables.
• Both DAQ systems use White Rabbit technology to provide a 10 MHz clock reference and absolute timing via a pulse-per-second (PPS) signal for sub-nanosecond synchronization.
• Data acquisition is restricted to 10 μs NuMI beam spills to suppress cosmic ray backgrounds, with all data transmitted to shore via optical fibers using coarse wavelength division multiplexing (CWDM).

Experimental results

Research questions

• RQ1 Can a modular, low-cost DAQ system achieve the required timing precision and dynamic range for neutrino detection using standard and refurbished PMTs?
• RQ2 What is the feasibility of using a hybrid DAQ architecture combining KM3NeT-style and microDAQ readout for different PMT types in a single detector?
• RQ3 How effectively can White Rabbit-based timing and synchronization be implemented in a large-scale, water-immersed detector environment?
• RQ4 To what extent can the use of refurbished PMTs reduce overall detector cost without compromising data quality or timing resolution?
• RQ5 Can the system achieve sufficient trigger efficiency and data throughput during short 10 μs beam spills to enable precision measurements of δCP and mixing angles?

Key findings

• The CHIPS detector concept achieves a projected cost of $200k/kiloton, significantly lower than the $2–10M/kiloton for conventional water-Cherenkov detectors.
• The DAQ system successfully processes ToT signals from 30 PMTs per plane using a Central Logic Board (CLB) in a water-tight enclosure, ensuring robustness in the submerged environment.
• The microDAQ system enables full signal shape reconstruction for refurbished NEMO3 PMTs using time-delay buffers on a compact, PMT-base-compatible microprocessor board.
• White Rabbit technology provides sub-nanosecond timing accuracy via a 10 MHz clock and PPS signal, ensuring precise synchronization across the entire detector array.
• Event building is performed efficiently on BeagleBone boards, which aggregate data from 16 PMTs per plane and forward it via standard Ethernet cables.
• Data acquisition is restricted to 10 μs beam spills, minimizing cosmic background, and all data are transmitted to shore using optical fibers with coarse wavelength division multiplexing (CWDM).