Abstract
This article describes the event detection system of the NEXT-White detector, a 5 kg high pressure xenon TPC with electroluminescent amplification, located in the Laboratorio Subterráneo de Canfranc (LSC), Spain. The detector is based on a plane of photomultipliers (PMTs) for energy measurements and a silicon photomultiplier (SiPM) tracking plane for offline topological event filtering. The event detection system, based on the SRS-ATCA data acquisition system developed in the framework of the CERN RD51 collaboration, has been designed to detect multiple events based on online PMT signal energy measurements and a coincidence-detection algorithm. Implemented on FPGA, the system has been successfully running and evolving during NEXT-White operation. The event detection system brings some relevant and new functionalities in the field. A distributed double event processor has been implemented to detect simultaneously two different types of events thus allowing simultaneous calibration and physics runs. This special feature provides constant monitoring of the detector conditions, being especially relevant to the lifetime and geometrical map computations which are needed to correct high-energy physics events. Other features, like primary scintillation event rejection, or a double buffer associated with the type of event being searched, help reduce the unnecessary data throughput thus minimizing dead time and improving trigger efficiency.
Highlights
NEXT-White [1] is the phase one of NEXT-100 [2], an experiment to measure the neutrino double beta decay
The experiment has been operating since the end of 2016 at the Laboratorio Subterráneo de Canfranc (LSC) in Spain and will end its data-taking and be replaced by NEXT-100, during 2021
The NEXT-White detector, being a demonstrator of the 100 kg scale NEXT-100 detector, is needed to prove all the technical solutions that will be implemented in the later detector
Summary
NEXT-White [1] is the phase one of NEXT-100 [2], an experiment to measure the neutrino double beta decay. While other xenon experiments (EXO [3], KamLAND-Zen [4]) have an approach of large exposures at the cost of losing energy resolution (and background rejection potential), the HPGXe TPC technology has demonstrated an excellent energy resolution (1% FWHM at the Q value of the double beta decay [5]) and an impressive topological rejection factor thanks to the relatively low density of the xenon gas and to the tracking system with SiPMs [6] These two tools provide a very low background index in the region of interest near Qββ, a fundamental parameter for generation detectors. The double circular buffer can be prioritized for a type of event reducing dead time for this selected event, generally, physics data versus calibration data
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