Radon backgrounds in the DEAP-1 liquid-argon-based Dark Matter detector

Abstract

The DEAP-1 \SI{7}{kg} single phase liquid argon scintillation detector was operated underground at SNOLAB in order to test the techniques and measure the backgrounds inherent to single phase detection, in support of the \mbox{DEAP-3600} Dark Matter detector. Backgrounds in DEAP are controlled through material selection, construction techniques, pulse shape discrimination and event reconstruction. This report details the analysis of background events observed in three iterations of the DEAP-1 detector, and the measures taken to reduce them. The ${}^{222}$Rn decay rate in the liquid argon was measured to be between 16 and \SI{26}{\micro\becquerel\per\kilogram}. We found that the background spectrum near the region of interest for Dark Matter detection in the DEAP-1 detector can be described considering events from three sources: radon daughters decaying on the surface of the active volume, the expected rate of electromagnetic events misidentified as nuclear recoils due to inefficiencies in the pulse shape discrimination, and leakage of events from outside the fiducial volume due to imperfect position reconstruction. These backgrounds statistically account for all observed events, and they will be strongly reduced in the DEAP-3600 detector due to its higher light yield and simpler geometry.

References in corpus (1)

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Cited by in corpus (15)

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• Results from a Calibration of XENON100 Using a Source of Dissolved Radon-220
• Design and construction of a new detector to measure ultra-low radioactive-isotope contamination of argon
• Application of the TPB Wavelength Shifter to the DEAP-3600 Spherical Acrylic Vessel Inner Surface
• DEAP-3600 Dark Matter Search
• Some properties of dark matter field in the complex octonion space
• Improving Photoelectron Counting and Particle Identification in Scintillation Detectors with Bayesian Techniques
• Measurement of ambient radon progeny decay rates and energy spectra in liquid argon using the MicroBooNE detector
• Technique for Surface Background Rejection in Liquid Argon Dark Matter Detectors using Layered Wavelength-Shifting and Scintillating Thin Films
• Preliminary test results of LAr prototype detector
• Search for Dark Matter with Liquid Argon and Pulse Shape Discrimination: Results from DEAP-1 and Status of DEAP-3600