A buffer-free concept bubble chamber for PICO dark matter searches

Abstract

In this paper, we report on the successful operation at Drexel University of the PICO collaboration's first C${}_3$F${}_8$ buffer-free prototype fluorocarbon bubble chamber. Previous PICO bubble chambers have produced world-leading WIMP search results with fluorocarbon target fluids, separated from the steel bellows by a buffer layer of water. Surface tension effects at the jar walls and liquid-liquid interface lead to a class of background events which have nuclear-recoil-like acoustic signatures and thus contaminate the WIMP-like signal region in analysis. Thus new bubble chambers are to be constructed "right-side-up", meaning that the jar of C${}_3$F${}_8$ is above the bellows with no water inside the inner vessel. The Drexel Bubble Chamber (DBC), runs successfully at and below the nuclear recoil thresholds used by PICO for WIMP searches, including thresholds as low as 1.19 keV. We have demonstrated sensitivity to ${}^{137}$Cs gammas and spontaneous fission neutrons from ${}^{244}$Cm, and acoustic alpha discrimination is demonstrated to be possible although the observed rate of alpha decays is very low. Position reconstruction from stereoscopic imaging allows for basic analysis cuts for calibration data. The successful construction and operation of this prototype confirm the effectiveness of the right-side-up design, which will be used in future dark matter searches such as PICO-40L and PICO-500.

arXiv commentFor v2: figures updated for clarity and readability, some text updated with better explanations and references added. Results unchanged For v3: Bibliography formatting updated

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Cited by in corpus (7)

• Direct Detection of Dark Matter -- APPEC Committee Report
• Data-Driven Modeling of Electron Recoil Nucleation in PICO C${}_3$F${}_8$ Bubble Chambers
• The role of small scale experiments in the direct detection of dark matter
• Low-threshold response of a scintillating xenon bubble chamber to nuclear and electronic recoils
• A direct test of Auger cascade induced nucleation from heavy element contamination in C${}_3$F${}_8$ bubble chambers
• SBC-SNOLAB scintillation system and SiPM implementation for dark matter searches
• Small scale direct dark matter search experiments