A 0.3nV/root Hz Input-Referred-Noise Analog Front-End for Weakly-Interacting-Massive-Particles (WIMPs) Acoustic Sensing in Bubbles-Chamber Detectors

The Mosca-B-Detector (Materia OSCura a Bolle, dark matter bubble detector) is a geyser bubble chamber based on a superheated C 3 F 8 volume in a closed vessel which aims to detect Dark Matter Weakly Interacting Massive Particles (WIMPs). When a particle interacts with the fluorine atoms, energy is released in small volume that acts as a nucleation site, producing a bubble and an acoustic signal, which are sensed by means of a set of ultrasound sensors and high-speed cameras. Each event, detected by threshold crossing approach, presents a specific acoustic signature (signal amplitude, duration and bandwidth) that can be used to separate the involved particles from background noise and thus detects an eventual WIMP interaction. However, the very low event rate (few events/day) along with weak signal amplitude (10 0 - 10 1 μV 0-PEAK range) and small intrinsic sensor noise (2.3 nV/√Hz), forces strong constraints on the electronics noise to maximize the sensitivity of the detector to weak signals (thus minimizing false negatives/missed detections). This work presents the design of a 45 dB 0.3 nV/√Hz Input Referred Noise analog front-end specifically dedicated to acoustic particle detection applications. The final 0.2 dB Noise Figure allows to set a 7-sigma threshold as low as 14 μV (input-referred), thus allowing to observe the weakest events and thus maximize the detector sensitivity.